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Area of Circles So far, we've been looking at areas of triangles and rectangles and trapezoids. Shapes with straight edges and angles and corners. Well, it was fun while it lasted, but we're done with all that business. Time to get a little less square and a little more well-rounded. We know what a circle is. We know what area is. Need we say more? Uh, probably. A circle doesn't have any straight lines. It's just a never-ending curve that goes around and around. That being the case, there's no such thing as a base and height. They just don't exist for circles. But if they don't exist, how can we find the area of a circle? Nooo! Okay, so it isn't that terrible. If we don't have a base and a height, what do we have to work with? As we know, a circle is described by its radius r, which is the distance from the center of the circle to its edge. As it turns out, the area of a circle can be given by the formula A = πr2, where π is the never ending irrational number that we can estimate as 3.14. We wish it were key lime, but that might just be too much to hope for. After all, pies are round, but pi r squared. What is the area of a circle with a radius of 3 cm? To find the area of a circle, we only need to know the radius. After that, just apply the formula for the area of a circle. A = πr2 A = π(3 cm)2 A = 9π cm2 ≈ 28.3 cm2 A ship malfunction causes a circular oil spill that covers 4.52 square miles of the ocean. What is the length across the entire oil spill? Even in unfortunate situations such as these, we can still use the formula A = πr2 when dealing with the area of a circle. A = πr2 4.52 miles2 = πr2 r2 = 1.44 miles2 r = 1.2 miles Since the radius is the distance from the edge to the center, we need to multiply it by 2 so that it reaches from one side of the oil spill to the other. The distance across the entire oil spill is 2 × 1.2 miles = 2.4 miles. In addition to the radius, another term to describe a circle is the diameter d, which is twice the length of the radius. The diameter goes all the way across the circle, through its center, kind of like a belt. But you knew that. The pizza guy from Inconvenient Pizzas, Inc. might ask you whether you want a 6-inch pizza (if you're hungry), a 12-inch pizza (if you're really hungry), or even an 18-inch pizza (if you're a hungry hungry hippo). These inches are the diameter of the pizza you are ordering. Even though you only have the diameter, you can still figure out the area. Though with Inconvenient, you can't be sure what you order is what you get. The perimeter of a circle (called the circumference C) can also be used to find the area. In general, as long as we can find the radius of a circle r, we can find the area. We can convert diameter into radius (just divide d by 2 to get r) and circumference into radius (use the formula C = 2πr and isolate for r). Then, we just have to use the formula A = πr2 to solve for area. Easier than a piece of π, right? Aliens have arrived! You could have sworn you heard a weird humming during the night and some strange chatter outside. Sure enough, they've made a mark on your farm in the form of a crop circle with a diameter of exactly 6 kilometers. What is the area of the crop circle? We know that the diameter of the circle is 6 km, which means the radius of the circle is d⁄2 or 3 km. As long as we know the radius of a circle, we can find its area faster than the speed of light using our trusty area formula. A = πr2 A = π(3 km)2 A = 9π ≈ 28.3 km2 The area of the crop circle with a diameter of 6 km is 9π or about 28.3 km2. We can also find the areas of portions of circles (called sectors) as long as we know central angle of the sector. For instance, a semicircle is a sector with a central angle of 180° (or π radians) and its area is half that of a circle with the same radius. We can generalize this for all sectors and come up with two formulas (depending on whether the central angle of the sector, θ, is in degrees or radians). A = θ⁄360° × πr2 A = θ⁄2π × πr2
In meteorology, a cloud is an aerosol comprising a visible mass of minute liquid droplets or frozen crystals, both of which are made of water or various chemicals. The droplets or particles are suspended in the atmosphere above the surface of a planetary body. On Earth, clouds are formed by the saturation of air in the homosphere (which includes the troposphere, stratosphere, and mesosphere). The air may be cooled to its dew point by a variety of atmospheric processes or it may gain moisture (usually in the form of water vapor) from an adjacent source. Nephology is the science of clouds which is undertaken in the cloud physics branch of meteorology. Cloud types in the troposphere, the atmospheric layer closest to Earth’s surface, have Latin names due to the universal adaptation of Luke Howard’s nomenclature. It was formally proposed in December 1802 and published for the first time the following year. It became the basis of a modern international system that classifies these tropospheric aerosols into five physical forms and three altitude levels or tages. These physical types, in approximate ascending order of convective activity, include stratiform sheets, cirriform wisps and patches, stratocumuliform layers (mainly structured as rolls, ripples, and patches), cumuliform heaps and tufts, and very large cumulonimbiform heaps that often show complex structure. The physical forms are cross-classified by altitude levels to produce ten basic genus-types or genera. Some of these basic types are common to more than one form or more than one tage, as illustrated in the stratocumuliform and cumuliform columns of the classification table below. Most genera can be divided into species, some of which are common to more than one genus. These can be subdivided into varieties, some of which are common to more than one genus or species. Cirriform clouds that form higher up in the stratosphere and mesosphere have common names for their main types, but are sub-classified alpha-numerically rather than with the elaborate system of Latin names given to cloud types in the troposphere. They are relatively uncommon and are mostly seen in the polar regions of Earth. Clouds have been observed in the atmospheres of other planets and moons in the Solar System and beyond. However, due to their different temperature characteristics, they are often composed of other substances such as methane, ammonia, and sulfuric acid as well as water. The origin of the term cloud can be found in the old English clud or clod, meaning a hill or a mass of rock. Around the beginning of the 13th century, it was extended as a metaphor to include rain clouds as masses of evaporated water in the sky because of the similarity in appearance between a mass of rock and a cumulus heap cloud. Over time, the metaphoric term replaced the original old English weolcan to refer to clouds in general. Ancient cloud studies were not made in isolation, but were observed in combination with other weather elements and even other natural sciences. In about 340 BC the Greek philosopher Aristotle wrote Meteorologica, a work which represented the sum of knowledge of the time about natural science, including weather and climate. For the first time, precipitation and the clouds from which precipitation fell were called meteors, which originate from the Greek word meteoros, meaning ‘high in the sky’. From that word came the modern term meteorology, the study of clouds and weather. Meteorologica was based on intuition and simple observation, but not on what is now considered the scientific method. Nevertheless, it was the first known work that attempted to treat a broad range of meteorological topics. The magazine De Mundo (attributed to Pseudo-Aristotle) noted: Cloud is a vaporous mass, concentrated and producing water. Rain is produced from the compression of a closely condensed cloud, varying according to the pressure exerted on the cloud; when the pressure is slight it scatters gentle drops; when it is great it produces a more violent fall, and we call this a shower, being heavier than ordinary rain, and forming continuous masses of water falling over earth. Snow is produced by the breaking up of condensed clouds, the cleavage taking place before the change into water; it is the process of cleavage which causes its resemblance to foam and its intense whiteness, while the cause of its coldness is the congelation of the moisture in it before it is dispersed or rarefied. When snow is violent and falls heavily we call it a blizzard. Hail is produced when snow becomes densified and acquires impetus for a swifter fall from its close mass; the weight becomes greater and the fall more violent in proportion to the size of the broken fragments of cloud. Such then are the phenomena which occur as the result of moist exhalation. Several years after Aristotle’s book, his pupil Theophrastus put together a book on weather forecasting called The Book of Signs. Various indicators such as solar and lunar halos formed by high clouds were presented as ways to forecast the weather. The combined works of Aristotle and Theophrastus had such authority they became the main influence in the study of clouds, weather and weather forecasting for nearly 2000 years. After centuries of speculative theories about the formation and behavior of clouds, the first truly scientific studies were undertaken by Luke Howard in England and Jean-Baptiste Lamarck in France. Howard was a methodical observer with a strong grounding in the Latin language and used his background to classify the various tropospheric cloud types during 1802. He believed that the changing cloud forms in the sky could unlock the key to weather forecasting. Lamarck had worked independently on cloud classification the same year and had come up with a different naming scheme that failed to make an impression even in his home country of France because it used unusual French names for cloud types. His system of nomenclature included twelve categories of clouds, with such names as (translated from French) hazy clouds, dappled clouds and broom-like clouds. By contrast, Howard used universally accepted Latin, which caught on quickly after it was published in 1803. As a sign of the popularity of the naming scheme, the German dramatist and poet Johann Wolfgang von Goethe composed four poems about clouds, dedicating them to Howard. An elaboration of Howard’s system was eventually formally adopted by the International Meteorological Conference in 1891. Howard’s original system established three physical categories or forms based on appearance and process of formation: cirriform (mainly detached and wispy), cumuliform or convective (mostly detached and heaped, rolled, or rippled), and non-convective stratiform (mainly continuous layers in sheets). These were cross-classified into lower and upper tages. Cumuliform clouds forming in the lower level were given the genus name cumulus from the Latin word for heap, while low stratiform clouds took the genus name stratus from the Latin word for a flattened or spread out sheet. Cirriform clouds were identified as always upper level and given the genus name cirrus from the Latin for hair. From this genus name, the prefix cirro- was derived and attached to the names of upper level cumulus and stratus, yielding the names cirrocumulus, and cirrostratus. In addition to these individual cloud types; Howard added two names to designate cloud systems consisting of more than one form joined together or located in very close proximity. Cumulostratus described large cumulus clouds blended with stratiform layers in the lower or upper levels. The term nimbus, taken from the Latin word for rain cloud, was given to complex systems of cirriform, cumuliform, and stratiform clouds with sufficient vertical development to produce significant precipitation, and it came to be identified as a distinct nimbiform physical category. In 1840, German meteorologist Ludwig Kaemtz added stratocumulus to Howard’s canon as a mostly detached low-tage genus of limited convection. It was defined as having cumuliform and stratiform characteristics integrated into a single layer (in contrast to cumulostratus which was deemed to be composite in nature and could be structured into more than one layer). This led to the recognition of a stratocumuliform physical category that included rolled and rippled clouds classified separately from the more freely convective heaped cumuliform clouds. During the mid 1850s, Emilien Renou, director of the Parc Saint-Maur and Montsouris observatories, began work on an elaboration of Howard’s classifications that would lead to the introduction during the 1870s of a newly defined middle tage . Clouds in this altitude range were given the prefix alto- derived from the Latin word altum pertaining to height above the low-level clouds. This resulted in the genus name altocumulus for mid-level cumuliform and stratocumuliform types and altostratus for stratiform types in the same altitude range. In 1880, Philip Weilbach, secretary and librarian at the Art Academy in Copenhagen, and like Luke Howard, an amateur meteorologist, unsuccessfully proposed an alternative to Howard’s classification. However, he also proposed and had accepted by the permanent committee of the International Meteorological Organization (IMO), a forerunner of the present-day World Meteorological Organization (WMO), the designation of a new free-convective vertical or multi-tage genus type, cumulonimbus (heaped rain cloud), which would be distinct from cumulus and nimbus and identifiable by its often very complex structure (frequently including a cirriform top and what are now recognized as multiple accessory clouds), and its ability to produce thunder. With this addition, a canon of ten tropospheric cloud genera was established that came to be officially and universally accepted. Howard’s cumulostratus was not included as a distinct type, having effectively been reclassified into its component cumuliform and stratiform genus types already included in the new canon. In 1890, Otto Jesse revealed the discovery and identification of the first clouds known to form above the troposphere. He proposed the name noctilucent which is Latin for night shining. Because of the extremely high altitudes of these clouds in what is now known to be the mesosphere, they could become illuminated by the a sun’s rays when the sky was nearly dark after sunset and before sunrise. Three years later, Henrik Mohn revealed a similar discovery of nacreous clouds in what is now considered the stratosphere. In 1896, the first cloud atlas sanctioned by the IMO was produced by Teisserenc de Borte based on collaborations with Hugo H. Hildebrandsson. The latter had become the first researcher to use photography for the study and classification of clouds in 1879. Alternatives to Howard’s classification system were proposed throughout the 19th century. Heinrich Dove of Germany and Elias Loomis of the United States came up with other schemes in 1828 and 1841 respectively, but neither met with international success. Additional proposals were made by Andre Poey (1863), Clemment Ley (1894), and H.H. Clayton (1896), but their systems, like earlier alternative schemes, differed too much from Howard’s to have any success beyond the adoption of some secondary cloud types. However, Clayton’s idea to formalize the division of clouds by their physical structures into cirriform, stratiform, “flocciform” (stratocumuliform) and cumuliform (with the later addition of cumulonimbiform), eventually found favor as an aid in the analysis of satellite cloud images. A further modification of the genus classification system came when an IMC commission for the study of clouds put forward a refined and more restricted definition of the genus nimbus which was effectively reclassified as a stratiform cloud type. It was then renamed nimbostratus (flattened or spread out rain cloud) and published with the new name in the 1932 edition of the International Atlas of Clouds and of States of the Sky. This left cumulonimbus as the only nimbiform type as indicated by its root-name. On April 1, 1960, the first successful weather satellite, TIROS-1 (Television Infrared Observation Satellite), was launched from Cape Canaveral, Florida by the National Aeronautics and Space Administration (NASA) with the participation of The US Army Signal Research and Development Lab, RCA, the US Weather Bureau, and the US Naval Photographic Center. During its 78-day mission, it relayed thousands of pictures showing the structure of large-scale cloud regimes, and proved that satellites could provide useful surveillance of global weather conditions from space. In 1976, the United Kingdom Department of Industry published a modification of the international cloud classification system adapted for satellite cloud observations. It was co-sponsored by NASA and showed a change in name of the nimbiform type to cumulonimbiform, although the earlier name and original meaning pertaining to all rain clouds can still be found in some classifications. Clouds can be divided into five physical forms based on physical structure and process of formation. These forms are commonly used for the purpose of satellite analysis. They are given below in approximate ascending order of instability or convective activity. Non-convective stratiform clouds appear in stable airmass conditions and, in general, have flat sheet-like structures that can form at any altitude in the troposphere. Very low stratiform cloud results when advection fog is lifted above surface level during breezy conditions. The stratiform group is divided by altitude range into the genera cirrostratus (high-tage), altostratus (middle-tage), stratus (low-tage), and nimbostratus (multi-tage). Cirriform clouds are generally of the genus cirrus and have the appearance of detached or semi-merged filaments. They form at high tropospheric altitudes in air that is mostly stable with little or no convective activity, although denser patches may occasionally show buildups caused by limited high-level convection where the air is partly unstable. Clouds of this structure have both cumuliform and stratiform characteristics in the form of rolls, ripples, or patches. They generally form as a result of limited convection in an otherwise mostly stable airmass topped by an inversion layer. If the inversion layer is absent or higher in the troposphere, increased convective activity may cause the cloud layers to develop tops in the form of turrets consisting of embedded cumuliform buildups. The stratocumuliform group is divided into layered cirrocumulus (high-tage), layered altocumulus (middle-tage), and stratocumulus (low-tage). Cumuliform clouds generally appear in isolated heaps or tufts. They are the product of localized but generally free-convective lift where there are no inversion layers in the atmosphere to limit vertical growth. In general, small cumuliform clouds tend to indicate comparatively weak instability. Larger cumuliform types are a sign of moderate to strong atmospheric instability and convective activity. Depending on their vertical size, clouds of the cumulus genus-type may be low-level single-tage or multi-tage with moderate to towering vertical extent. Tufted altocumulus and cirrocumulus genera in the middle and high tages are also considered cumuliform because they have a more detached heaped structure than their layered stratocumuliform variants. The largest free-convective clouds comprise the genus cumulonimbus which are multi-tage because of their towering vertical extent. They occur in highly unstable air and often have complex structures that include cirriform tops and multiple accessory clouds. Genus types are commonly grouped by tage for the purpose of cloud atlases, surface weather observations and weather maps. These maps are produced from information in the international synoptic code (or SYNOP) that is transmitted at regular intervals by professionally trained staff at major weather stations. The base-height range for each tage that is cross-classified with the physical forms varies depending on the latitudinal geographical zone. A consensus exists as to the designation of high, middle, and low tages, the makeup of the basic canon of ten cloud genera that results from the cross-classifications, and the tage designations of non-vertical genus types. Clouds with significant vertical extent occupy more than one tage and are commonly, but not always, treated as a separate group or sub-group, or given separate descriptions within the context of the standard tages. The standard tages and genus-types are summarised below in approximate descending order of the altitude at which each is normally based. Multi-tage clouds with significant vertical extent are separately listed and summarised in approximate ascending order of instability or convective activity. Clouds of the high tage form at altitudes of 3,000 to 7,600m (10,000 to 25,000ft) in the polar regions, 5,000 to 12,200m (16,500 to 40,000ft) in the temperate regions and 6,100 to 18,300m (20,000 to 60,000ft) in the tropical region. All cirriform clouds are classified as high and thus constitute a single genus cirrus (Ci). Stratocumuliform and stratiform clouds in the high tage carry the prefix cirro-, yielding the respective genus names cirrocumulus (Cc) and cirrostratus (Cs). When comparatively low-resolution satellite images of high clouds are analized without supporting data from direct human observations, it becomes impossible to distinguish between individual genus types which are then collectively identified as cirrus-type. Non-vertical clouds in the middle tage are prefixed by alto-, yielding the genus names altocumulus (Ac) and altostratus (As). These clouds can form as low as 2,000m (6,500ft) above surface at any latitude, but may be based as high as 4,000m (13,000ft) near the poles, 7,000m (23,000ft) at mid latitudes, and 7,600m (25,000ft) in the tropics. As with high clouds, it is not always possible to distinguish between individual genera using satellite photography alone. Without the addition of human observations, these clouds are usually collectively identified as ‘middle-type’ on satellite images. Low-tage clouds are found from near surface up to 2,000m (6,500ft). Genus types in this tage either have no prefix or carry one that refers to a characteristic other than altitude. These clouds have low to middle-tage bases that form anywhere from near surface to about 2,400m (8,000ft) and tops that can extend into the high tage. The term vertical is often used in connection with this group and is useful for distinguishing between clouds of moderate, deep, and towering vertical extent. However this term is sometimes restricted to upward-growing free-convective cumuliform and cumulonimbiform genera to the exclusion of deep stratiform clouds. The terms multi-level or multi-tage are sometimes used instread for very thick or tall cloud types including nimbostratus to avoid the association of ‘vertical’ with free-convective cumuliform only. Alternatively, some classifications do not recognize a vertical or multi-tage designation for any genus types and include all vertical free-convective cumuliform and cumulonimbiform genera with the low-tage clouds. Nimbostratus and some cumulus in this group usually achieve moderate or deep vertical extent, but without towering structure. However, with sufficient airmass instability, upward-growing cumuliform clouds can grow to high towering proportions. Although genus types with vertical extent are often considered a single group, the International Civil Aviation Organization (ICAO) further distinguishes towering vertical clouds as a separate group or sub-group. It is specified that these very large cumuliform and cumulonimbiform types must be identified by their standard names or abbreviations in all aviation observations (METARS) and forecasts (TAFS) to warn pilots of possible severe weather and turbulence. When towering vertical types are considered separately, they comprise the aforementioned cumulonimbus genus and one cumulus subtype, cumulus congestus (Cu con), which is designated towering cumulus (Tcu) by ICAO. There is no stratiform type in this group because by definition, even very thick stratiform clouds cannot have towering vertical structure, although nimbostratus may be accompanied by embedded towering cumuliform or cumulonimbiform types. These clouds are sometimes classified separately from the other vertical or multi-tage types because of their ability to produce severe turbulence. Genus types are commonly divided into subtypes called species that indicate specific structural details which can vary according to the stability and windshear characteristics of the atmosphere at any given time and location. Despite this hierarchy, a particular species may be a subtype of more than one genus, especially if the genera are of the same physical form and are differentiated from each other mainly by altitude or tage. Some species can even be subtypes of genera that are each of different physical forms. The species types are grouped below according to the physical forms and genera with which each is normally associated. The forms, genera, and species are listed in approximate ascending order of instability or convective activity. Of the stratiform group, high-level cirrostratus comprises two species. Cirrostratus nebulosus has a rather diffuse appearance lacking in structural detail. Cirrostratus fibratus is a species made of semi-merged filaments that are transitional to or from cirrus. Mid-level altostratus and multi-level nimbostratus always have a flat or diffuse appearance and are therefore not subdivided into species. Low-tage stratus is of the species nebulosus except when broken up into ragged sheets of stratus fractus (see below). Cirriform clouds have three non-convective species that can form in mostly stable airmass conditions. Cirrus fibratus comprise filaments that may be straight, wavy, or occasionally twisted by non-convective wind shear. The species uncinus is similar but has upturned hooks at the ends. Cirrus spissatus appear as opaque patches that can show light grey shading. Stratocumuliform genus-types (cirrocumulus, altocumulus, and stratocumulus) that appear in mostly stable air have two species each that can form in the high, middle, or low tages of the troposphere. The stratiformis species normally occur in extensive sheets or in smaller patches where there is only minimal convective activity. Clouds of the lenticularis species tend to have lens-like shapes tapered at the ends. They are most commonly seen as orographic mountain-wave clouds, but can occur anywhere in the troposphere where there is strong wind shear combined with sufficient airmass stability to maintain a generally flat cloud structure. The species fractus shows variable instability because it can be a subdivision of genus-types of different physical forms that have different stability characteristics. This subtype can be in the form of ragged but mostly stable stratiform sheets (stratus fractus) or small ragged cumuliform heaps with somewhat greater instability (cumulus fractus). When they form at low altitudes, stratiform and cumuliform genus-types can be torn up into shreds by brisk low level winds that create mechanical turbulence against the ground. Fractus clouds can form in precipitation at low altitudes, with or without brisk or gusty winds. They are closely associated with precipitating cloud systems of considerable vertical and sometimes horizontal extent, so they are also classified as accessory clouds under the name pannus (see section on supplementary features). These species are subdivisions of genus types that occur in partly unstable air. The species castellanus appears when a mostly stable stratocumuliform or cirriform layer becomes disturbed by localized areas of airmass instability. This results in the formation of cumuliform buildups arising from a common stratiform base. Castellanus resembles the turrets of a castle when viewed from the side, and can be found with stratocumuliform genera at any tropospheric altitude level and with limited-convective patches of high-tage cirrus. Clouds of the more detached tufted floccus species are subdivisions of genus-types which may be cirriform or cumuliform in overall structure. They are sometimes seen with cirrus, and with tufted cirrocumulus, and altocumulus. However floccus clouds are not generally found in the low tage, an altitude range where their place is taken by clouds of the cumulus genus. More general airmass instability in the troposphere tends to produce clouds of the more freely convective cumulus genus type, whose species are mainly indicators of degrees of atmospheric instability and resultant vertical development of the clouds. A cumulus cloud initially forms in the low tage as a cloudlet of the species humilis that shows only slight vertical development. If the air becomes more unstable, the cloud tends to grow vertically into the species mediocris, then congestus, the tallest cumulus species. With highly unstable atmospheric conditions, large cumulus may continue to grow into cumulonimbus calvus (essentially a very tall congestus cloud that produces thunder), then ultimately into the species capillatus when supercooled water droplets at the top of the cloud turn into ice crystals giving it a cirriform appearance. Genus and species types are further subdivided into varieties whose names can appear after the species name to provide a fuller description of a cloud. Some cloud varieties are not restricted to a specific tage or form, and can therefore be common to more than one genus or species. All cloud varieties fall into one of two main groups. One group identifies the opacities of particular low and middle tage cloud structures and comprises the varieties translucidus (thin translucent), perlucidus (thick opaque with translucent breaks), and opacus (thick opaque). These varieties are always identifiable for cloud genera and species with variable opacity. All three are associated with the stratiformis species of altocumulus and stratocumulus. However, only two varieties are seen with altostratus and stratus nebulosus whose uniform structures prevent the formation of a perlucidus variety. Opacity-based varieties are not applied to high-tage clouds because they are always translucent, or in the case of cirrus spissatus, always opaque. Similarly, these varieties are also not associated with moderate and towering vertical clouds because they are always opaque. A second group describes the occasional arrangements of cloud structures into particular patterns that are discernible by a surface-based observer (cloud fields usually being visible only from a significant altitude above the formations). These varieties are not always present with the genera and species with which they are otherwise associated, but only appear when atmospheric conditions favor their formation. Intortus and vertebratus varieties occur on occasion with cirrus fibratus. They are respectively filaments twisted into irregular shapes, and those that are arranged in fishbone patterns, usually by uneven wind currents that favor the formation of these varieties. The variety radiatus is associated with cloud rows of a particular type that appear to converge at the horizon. It is sometimes seen with the fibratus and uncinus species of cirrus, the stratiformis species of altocumulus and stratocumulus, the mediocris and sometimes humilis species of cumulus, and with the genus altostratus. Another variety, duplicatus (closely spaced layers of the same type, one above the other), is sometimes found with cirrus of both the fibratus and uncinus species, and with altocumulus and stratocumulus of the species stratiformis and lenticularis. The variety undulatus (having a wavy undulating base) can occur with any clouds of the species stratiformis or lenticularis, and with altostratus. It is only rarely observed with stratus nebulosus. The variety lacunosus is caused by localized downdrafts that create circular holes in the form of a honeycomb or net. It is occasionally seen with cirrocumulus and altocumulus of the species stratiformis, castellanus, and floccus, and with stratocumulus of the species stratiformis and castellanus. It is possible for some species to show combined varieties at one time, especially if one variety is opacity-based and the other is pattern-based. An example of this would be a layer of altocumulus stratiformis arranged in seemingly converging rows separated by small breaks. The full technical name of a cloud in this configuration would be altocumulus stratiformis radiatus perlucidus, which would identify respectively its genus, species, and two combined varieties. Supplementary features and accessory clouds are not further subdivisions of cloud types below the species and variety level. Rather, they are either hydrometeors or special cloud formations with their own Latin names that form in association with certain cloud genera, species, and varieties. Supplementary features, whether in the form of clouds or precipitation, are directly attached to the main genus-cloud. Accessory clouds, by contrast, are generally detached from the main cloud. One group of supplementary features are not actual cloud formations, but precipitation that falls when water droplets or ice crystals that make up visible clouds have grown too heavy to remain aloft. Virga is a feature seen with clouds producing precipitation that evaporates before reaching the ground, these being of the genera cirrocumulus, altocumulus, altostratus, nimbostratus, stratocumulus, cumulus, and cumulonimbus. When the precipitation reaches the ground without completely evaporating, it is designated as the feature praecipitatio. This normally occurs with altostratus opacus, which can produce widespread but usually light precipitation, and with thicker clouds that show significant vertical development. Of the latter, upward-growing cumulus mediocris produces only isolated light showers, while downward growing nimbostratus is capable of heavier, more extensive precipitation. Towering vertical clouds have the greatest ability to produce intense precipitation events, but these tend to be localized unless organized along fast-moving cold fronts. Showers of moderate to heavy intensity can fall from cumulus congestus clouds. Cumulonimbus, the largest of all cloud genera, has the capacity to produce very heavy showers. Low stratus clouds usually produce only light precipitation, but this always occurs as the feature praecipitatio due to the fact this cloud genus lies too close to the ground to allow for the formation of virga. Incus is the most type-specific supplementary feature, seen only with cumulonimbus of the species capillatus. A cumulonimbus incus cloud top is one that has spread out into a clear anvil shape as a result of rising air currents hitting the stability layer at the tropopause where the air no longer continues to get colder with increasing altitude. The mamma feature forms on the bases of clouds as downward-facing bubble-like protuberances caused by localized downdrafts within the cloud. It is also sometimes called mammatus, an earlier version of the term used before a standardization of Latin nomenclature brought about by the World Meterorological Organization during the 20th century. The best-known is cumulonimbus with mammatus, but the mamma feature is also seen occasionally with cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus. A tuba feature is a cloud column that may hang from the bottom of a cumulus or cumulonimbus. A newly formed or poorly organized column might be comparatively benign, but can quickly intensify into a funnel cloud or tornado. An arcus feature is a roll cloud with ragged edges attached to the lower front part of cumulus congestus or cumulonimbus that forms along the leading edge of a squall line or thunderstorm outflow. A large arcus formation can have the appearance of a dark menacing arch. There are some arcus-like clouds that form as a consequence of interactions with specific geographical features rather than with a parent cloud. Perhaps the strangest geographically specific cloud of this type is the Morning Glory, a rolling cylindrical cloud that appears unpredictably over the Gulf of Carpentaria in Northern Australia. Associated with a powerful “ripple” in the atmosphere, the cloud may be “surfed” in glider aircraft. It has been officially suggested that roll clouds of this type that are not attached to a parent cloud be reclassified as a new species of stratocumulus, possibly with the Latin name volutus. Supplementary cloud formations detached from the main cloud are known as accessory clouds. The heavier precipitating clouds, nimbostratus, towering cumulus (cumulus congestus), and cumulonimbus typically see the formation in precipitation of the pannus feature, low ragged clouds of the genera and species cumulus fractus or stratus fractus. After the pannus types, the remaining accessory clouds comprise formations that are associated mainly with upward-growing cumuliform and cumulonimbiform clouds of free convection. Pileus is a cap cloud that can form over a cumulonimbus or large cumulus cloud, whereas a velum feature is a thin horizontal sheet that sometimes forms like an apron around the middle or in front of the parent cloud. Under conditions of strong atmospheric wind shear and instability, wave-like undulatus formations may break into regularly spaced crests. This variant has no separate WMO Latin designation, but is sometimes known informally as a KelvinHelmholtz (wave) cloud. This phenomenon has also been observed in cloud formations over other planets and even in the sun’s atmosphere. It has been formally suggested that this wave cloud be classified as a supplementary feature, possibly with the Latin name fluctus. Another wave-like cloud feature that is distinct from the variety undulatus has been given the Latin name asperatus. It has been recommended for formal classification as a supplementary feature using its suggested Latin name. A circular fall-streak hole occasionally forms in a thin layer of supercooled altocumulus or cirrocumulus. Fall streaks consisting of virga or wisps of cirrus are usually seen beneath the hole as ice crystals fall out to a lower altitude. This type of hole is usually larger than typical lacunosus holes, and a formal recommendation has been made to classify it as a supplementary feature, possibly with the Latin name cavus. Clouds initially form in clear air or become clouds when fog rises above surface level. The genus of a newly formed cloud is determined mainly by air mass characteristics such as stability and moisture content. If these characteristics change over time, the genus tends to change accordingly. When this happens, the original genus is called a mother cloud. If the mother cloud retains much of its original form after the appearance of the new genus, it is termed a genitus cloud. One example of this is stratocumulus cumulogenitus, a stratocumulus cloud formed by the partial spreading of a cumulus type when there is a loss of convective lift. If the mother cloud undergoes a complete change in genus, it is considered to be a mutatus cloud. It has been officially recommended that the genitus category be expanded to include certain types that do not originate from pre-existing clouds or as the result of any natural atmospheric processes. Among vertically developed clouds, these may include flammagenitus for cumulus congestus or cumulonimbus that are formed by large scale fires or volcanic eruptions. Smaller low-tage “pyrocumulus” or “fumulus” clouds formed by contained industrial activity could be classified as cumulus homogenitus. Contrails formed from the exhaust of aircraft flying in the high tage can persist and spread into formations resembling any of the high cloud genus-types. These variants have no special WMO designations, but are sometimes given the faux-Latin name Aviaticus. Persistent contrails have been identified as candidates for possible inclusion in the genitus category as cirrus, cirrostratus, or cirrocumulus homogenitus Stratocumulus clouds can be organized into “fields” that take on certain specially classified shapes and characteristics. In general, these fields are more discernible from high altitudes than from ground level. They can often be found in the following forms: These patterns are formed from a phenomenon known as a Krmn vortex which is named after the engineer and fluid dynamicist Theodore von Krmn,. When wind driven clouds are forced through a mountain range, or when ocean wind driven clouds encounter a high elevation island, they can begin to circle the mountain or high land mass. They can form at any altitude in the troposphere and are not restricted to any particular cloud type. Air can become saturated as a result of being cooled to its dew point or by having moisture added from an adjacent source. Adiabatic cooling occurs when one or more of three possible lifting agents – cyclonic/frontal, convective, or orographic causes air containing invisible water vapor to rise and cool to its dew point, the temperature at which the air becomes saturated. The main mechanism behind this process is adiabatic cooling. If the air is cooled to its dew point and becomes saturated, it normally sheds vapor it can no longer retain, which condenses into cloud. Water vapor in saturated air is normally attracted to condensation nuclei such as dust and salt particles that are small enough to be held aloft by normal circulation of the air. Frontal and cyclonic lift occur when stable air is forced aloft at weather fronts and around centers of low pressure.Warm fronts associated with extratropical cyclones tend to generate mostly cirriform and stratiform clouds over a wide area unless the approaching warm airmass is unstable, in which case cumulus congestus or cumulonimbus clouds will usually be embedded in the main precipitating cloud layer.Cold fronts are usually faster moving and generate a narrower line of clouds which are mostly stratocumuliform, cumuliform, or cumulonimbiform depending on the stability of the warm air mass just ahead of the front. Another agent is the convective upward motion of air caused by daytime solar heating at surface level. Airmass instability allows for the formation of cumuliform clouds that can produce showers if the air is sufficiently moist. On comparatively rare occasions, convective lift can be powerful enough to penetrate the tropopause and push the cloud top into the stratosphere. A third source of lift is wind circulation forcing air over a physical barrier such as a mountain (orographic lift). If the air is generally stable, nothing more than lenticular cap clouds will form. However, if the air becomes sufficiently moist and unstable, orographic showers or thunderstorms may appear. Along with adiabatic cooling that requires a lifting agent, there are three major non-adiabatic mechanisms for lowering the temperature of the air to its dew point. Conductive, radiational, and evaporative cooling require no lifting mechanism and can cause condensation at surface level resulting in the formation of fog. There are several main sources of water vapor that can be added to the air as a way of achieving saturation without any cooling process: Water or moist ground, precipitation or virga, and transpiration from plants Although the local distribution of clouds can be significantly influenced by topography, the global prevalence of cloud cover tends to vary more by latitude. It is most prevalent globally in and along low pressure zones of surface atmospheric convergence which encircle the Earth close to the equator and near the 50th parallels of latitude in the northern and southern hemispheres. The adiabatic cooling processes that lead to the creation of clouds by way of lifting agents are all associated with convergence; a process that involves the horizontal inflow and accumulation of air at a given location, as well as the rate at which this happens. Near the equator, increased cloudiness is due to the presence of the low-pressure Intertropical Convergence Zone (ITCZ) where very warm and unstable air promotes mostly cumuliform and cumulonimbiform clouds. Clouds of virtually any type can form along the mid-latitude convergence zones depending on the stability and moisture content of the air. These extratropical convergence zones are occupied by the polar fronts where air masses of polar origin meet and clash with those of tropical or subtropical origin. This leads to the formation of weather-making extratropical cyclones composed of cloud systems that may be stable or unstable to varying degrees according to the stability characteristics of the various airmasses that are in conflict. Divergence is the opposite of convergence. In the Earth’s atmosphere, it involves the horizontal outflow of air from the upper part of a rising column of air, or from the lower part of a subsiding column often associated with an area or ridge of high pressure. Cloudiness tends to be least prevalent near the poles and in the subtropics close to the 20th parallels, north and south. The latter are sometimes referred to as the horse latitudes. The presence of a large-scale high-pressure subtropical ridge on each side of the equator reduces cloudiness at these low latitudes. Similar patterns also occur at higher latitudes in both hemispheres. The luminance or brightness of a cloud is determined by how light is reflected, scattered, and transmitted by the cloud’s particles. Its brightness may also be affected by the presence of haze or photometeors such as halos and rainbows. In the troposphere, dense, deep clouds exhibit a high reflectance (70% to 95%) throughout the visible spectrum. Tiny particles of water are densely packed and sunlight cannot penetrate far into the cloud before it is reflected out, giving a cloud its characteristic white color, especially when viewed from the top. Cloud droplets tend to scatter light efficiently, so that the intensity of the solar radiation decreases with depth into the gases. As a result, the cloud base can vary from a very light to very-dark-grey depending on the cloud’s thickness and how much light is being reflected or transmitted back to the observer. High thin tropospheric clouds reflect less light because of the comparatively low concentration of constituent ice crystals or supercooled water droplets which results in a slightly off-white appearance. However, a thick dense ice-crystal cloud appears brilliant white with pronounced grey shading because of its greater reflectivity. As a tropospheric cloud matures, the dense water droplets may combine to produce larger droplets. If the droplets become too large and heavy to be kept aloft by the air circulation, they will fall from the cloud as rain. By this process of accumulation, the space between droplets becomes increasingly larger, permitting light to penetrate farther into the cloud. If the cloud is sufficiently large and the droplets within are spaced far enough apart, a percentage of the light that enters the cloud is not reflected back out but is absorbed giving the cloud a darker look. A simple example of this is one’s being able to see farther in heavy rain than in heavy fog. This process of reflection/absorption is what causes the range of cloud color from white to black. Striking cloud colorations can be seen at any altitude, with the color of a cloud usually being the same as the incident light. During daytime when the sun is relatively high in the sky, tropospheric clouds generally appear bright white on top with varying shades of grey underneath. Thin clouds may look white or appear to have acquired the color of their environment or background. Red, orange, and pink clouds occur almost entirely at sunrise/sunset and are the result of the scattering of sunlight by the atmosphere. When the sun is just below the horizon, low-etage clouds are gray, middle clouds appear rose-colored, and high-etage clouds are white or off-white. Clouds at night are black or dark grey in a moonless sky, or whitish when illuminated by the moon. They may also reflect the colors of large fires, city lights, or auroras that might be present. A cumulonimbus cloud that appears to have a greenish/bluish tint is a sign that it contains extremely high amounts of water; hail or rain which scatter light in a way that gives the cloud a blue color. A green colorization occurs mostly late in the day when the sun is comparatively low in the sky and the incident sunlight has a reddish tinge that appears green when illuminating a very tall bluish cloud. Supercell type storms are more likely to be characterized by this but any storm can appear this way. Coloration such as this does not directly indicate that it is a severe thunderstorm, it only confirms its potential. Since a green/blue tint signifies copious amounts of water, a strong updraft to support it, high winds from the storm raining out, and wet hail; all elements that improve the chance for it to become severe, can all be inferred from this. In addition, the stronger the updraft is, the more likely the storm is to undergo tornadogenesis and to produce large hail and high winds. Yellowish clouds may be seen in the troposphere in the late spring through early fall months during forest fire season. The yellow color is due to the presence of pollutants in the smoke. Yellowish clouds caused by the presence of nitrogen dioxide are sometimes seen in urban areas with high air pollution levels. The role of tropospheric clouds in regulating weather and climate remains a leading source of uncertainty in projections of global warming. This uncertainty arises because of the delicate balance of processes related to clouds, spanning scales from millimeters to planetary. Hence, interactions between large-scale weather events (synoptic meteorology) and clouds becomes difficult to represent in global models. The complexity and diversity of clouds, as outlined above, adds to the problem. On the one hand, white-colored cloud tops promote cooling of Earth’s surface by reflecting short-wave radiation from the sun. Most of the sunlight that reaches the ground is absorbed, warming the surface, which emits radiation upward at longer, infrared, wavelengths. At these wavelengths, however, water in the clouds acts as an efficient absorber. The water reacts by radiating, also in the infrared, both upward and downward, and the downward long-wave radiation results in some warming at the surface. This is analogous to the greenhouse effect of greenhouse gases and water vapor. High-tage genus-types particularly show this duality with both short-wave albedo cooling and long-wave greenhouse warming effects. On the whole though, ice-crystal clouds in the upper troposphere tend to favor net warming. However, the cooling effect is dominant with mid-level and low clouds made of very small water droplets with an average radius of about 0.002mm (0.00008in)., especially when they form in extensive sheets that block out more of the sun. Small-droplet aerosols are not good at absorbing long-wave radiation reflected back from Earth, so there is a net cooling with almost no long-wave effect. This effect is particularly pronounced with low clouds that form over water. Measurements taken by NASA indicate that on the whole, the effects of low and middle tage clouds that tend to promote cooling are outweighing the warming effects of high layers and the variable outcomes associated with or vertically developed clouds. Low and vertical heaps of cumulus, towering cumulus, and cumulonimbus are made of larger water droplets ranging in radius from 0.005 to about 0.015mm. Nimbostratus cloud droplets can also be quite large, up to 0.015mm radius. These larger droplets associated with vertically developed clouds are better able to trap the long-wave radiation thus mitigating the cooling effect to some degree. However, these large often precipitating clouds are variable or unpredictable in their overall effect because of variations in their concentration, distribution, and vertical extent. As difficult as it is to evaluate the effects of current cloud cover characteristics on climate change, it is even more problematic to predict the outcome of this change with respect to future cloud patterns and events. As a consequence, much research has focused on the response of low and vertical clouds to a changing climate. Leading global models can produce quite different results, however, with some showing increasing low-tage clouds and others showing decreases. Polar stratospheric clouds show little variation in structure and are limited to a single very high range of altitude of about 15,00025,000m (49,20082,000ft), so they are not classified into tages, genus types, species, or varieties in the manner of tropospheric clouds. Instead, the classification is alpha-numeric and is based on chemical makeup rather than variations in physical appearance. Polar stratospheric clouds form in the lowest part of the stratosphere during the winter, at the altitude and during the season that produces the coldest temperatures and therefore the best chances of triggering condensation caused by adiabatic cooling. They are typically very thin with an undulating cirriform appearance. Moisture is scarce in the stratosphere, so nacreous and non-nacreous cloud at this altitude range is rare and is usually restricted to polar regions in the winter where the air is coldest. Polar mesospheric clouds form at a single extreme altitude range of about 80 to 85km (50 to 53mi) and are consequently not classified into more than one tage. They are given the Latin name noctilucent because of their illumination well after sunset and before sunrise. They typically have a bluish or silvery white coloration that can resemble brightly illuminated cirrus. Noctilucent clouds may occasionally take on more of a red or orange hue. They are not common or widespread enough to have a significant effect on climate. However, an increasing frequency of occurrence of noctilucent clouds since the 19th century may be the result of climate change.An alpha-numeric classification is used to identify variations in physical appearance. Polar mesospheric clouds are the highest in the atmosphere and form near the top of the mesosphere at about ten times the altitude of tropospheric high clouds. From ground level, they can occasionally be seen illuminated by the sun during deep twilight. Ongoing research indicates that convective lift in the mesosphere is strong enough during the polar summer to cause adiabatic cooling of small amount of water vapour to the point of saturation. This tends to produce the coldest temperatures in the entire atmosphere just below the mesopause. These conditions result in the best environment for the formation of polar mesospheric clouds. There is also evidence that smoke particles from burnt-up meteors provide much of the condensation nuclei required for the formation of noctilucent cloud. Distribution in the mesosphere is similar to the stratosphere except at much higher altitudes. Because of the need for maximum cooling of the water vapor to produce noctilucent clouds, their distribution tends to be restricted to polar regions of Earth. A major seasonal difference is that convective lift from below the mesosphere pushes very scarce water vapor to higher colder altitudes required for cloud formation during the respective summer seasons in the northern and southern hemispheres. Sightings are rare more than 45 degrees south of the north pole or north of the south pole. Cloud cover has been seen on most other planets in the solar system. Venus’s thick clouds are composed of sulfur dioxide and appear to be almost entirely stratiform. They are arranged in three main layers at altitudes of 45 to 65km that obscure the planet’s surface and can produce virga. No embedded cumuliform types have been identified, but broken stratocumuliform wave formations are sometimes seen in the top layer that reveal more continuous layer clouds underneath. On Mars, noctilucent, cirrus, cirrocumulus and stratocumulus composed of water-ice have been detected mostly near the poles. Water-ice fogs have also been detected on this planet. Both Jupiter and Saturn have an outer cirriform cloud deck composed of ammonia, an intermediate stratiform haze-cloud layer made of ammonium hydrosulfide, and an inner deck of cumulus water clouds. Embedded cumulonimbus are known to exist near the Great Red Spot on Jupiter. The same category-types can be found covering Uranus, and Neptune, but are all composed of methane. Saturn’s moon Titan has cirrus clouds believed to be composed largely of methane. The CassiniHuygens Saturn mission uncovered evidence of polar stratospheric clouds and a fluid cycle on Titan, including lakes near the poles and fluvial channels on the surface of the moon. Some planets outside the solar system are known to have atmospheric clouds. In October 2013, the detection of high altitude optically thick clouds in the atmosphere of exoplanet Kepler-7b was announced, and, in December 2013, also in the atmospheres of GJ 436 b and GJ 1214 b. Read the original: Cloud – Wikipedia
Malta Teacher Resources Find Malta educational ideas and activities Showing 1 - 20 of 80 resources In this online interactive reading comprehension learning exercise, students respond to 25 multiple choice questions about Christopher Marlowe's The Jew of Malta. Students may submit their answers to be scored. In this online interactive literature learning exercise, students respond to 3 short answer and essay questions about Christopher Marlowe's The Jew of Malta. Students may check some of their answers online. Students work in small groups to create a topographic map of Malta. They must include labeled line drawings of bordering countries and bodies of water. Students use salt and flour clay to make Malta three dimensional, showing the nearest mountains and the major body of water surrounding Malta. This is the first of a series of lessons at this link. Seven chapters of the book "Malta" are covered in this series. New Review Introduction to the European Union What is the purpose of the European Union, and what institutions and countries comprise it? Check out this resource in which class members participate in a student-led WebQuest activity designed to offer an overview of the European Union. They will then work in groups to design travel brochures on assigned countries from the European Union. In this online interactive geography quiz worksheet, students examine the the a map and chart as they try to name all of the Mediterranean Islands represented in 4 minutes. Students study the make-up of compound words. In this compound words lesson, students work as a class to brainstorm a list of compound words and then draw pictures on a piece of paper to represent each part of the compound words. Students read an article on the British Empire. In this ESL instructional activity, students explore the British Empire from the 1600's, then work in small groups to complete several activities that reinforce the information learned in the reading. High schoolers research island formation, plot locations on a map and make an analysis of why some islands are formed where they are. In this everyday editing worksheet, young scholars correct grammatical mistakes in a short paragraph about Malta. The errors range from punctuation, capitalization, grammar, and spelling. New Review The Cold War Take your instruction on the Cold War to the next level by having learners participate in a group role-playing exercise, working to convey pertinent information and illustrate the intense anxiety related to this time period in the United States. New Review Arctic Food Chain Explore the food chains that support Arctic ecosystems. A class discussion on interdependence and the different roles plants and animals play in ecosystems provides students with the knowledge to complete a worksheet asking them to create food chains involving a variety of Arctic life. To further engage students in the activity, consider assigning each child an Arctic plant or animal and having the class arrange and rearrange themselves into food chains. This resource would fit perfectly into a unit investigating the different types of ecosystems found around the world. New Review Land of the Midnight Sun From days of 24 hour sunlight, to endless nights that last for days, the Arctic is a very unique place to live. Examine the seasonal changes that occur in the northern-most reaches of the globe and the impact they have on the plants and animals living there. The included worksheet offers a number of different opportunities for learners to demonstrate their understanding of this unique region. This lesson would fit nicely in either a unit on ecosystems or weather and climate in an upper-elementary science class. New Review Bar Charts & Pie Charts Learn about life in the Arctic while practicing how to graph and interpret data with this interdisciplinary lesson. Starting with a whole group data-gathering exercise, students are then given a worksheet on which they analyze and create bar and pie graphs involving information about Arctic animals. This lesson is perfect for tying together a math unit on representing data and a science exploration of Arctic ecosystems. New Review Shapes Investigate the properties of three-dimensional figures with this Arctic-themed math lesson plan. Beginning with a class discussion about different types of solid figures present in the classroom, young mathematicians are then given a two-sided worksheet asking them to draw 3-D shapes, identify their parts, and create cubes from a series of nets. Though the lesson plan does not provide any detailed information about the Arctic, it is does provide a fun change of pace to a geometry unit in the upper-elementary grades. New Review Take 6 Investigate the various properties of the number six with this elementary math lesson. From simple addition, subtraction, multiplication, and division problems to the creation of hexagonal tessellations, this lesson covers all aspects of this simple number. As a lesson, this would best fit in a geometry unit introducing hexagons, but the included worksheet could also stand alone as an option for early finishers. What is the difference between the, a, and an?Designed for upper-intermediate English language pupils, this two-page packet could be used with less-advanced learners as well. Common rules are outlined and learners study when to use definite, indefinite, and zero articles. Finally, at the end of page two, they complete a practice opportunity by 26 fill-in-the-blank spaces. How are definite and indefinite articles used in the English language? Beginning English speakers review a, an, the, and the zero article with this two-page document. After reviewing common rules, examples, and exceptions (there are many!), learners complete one fill-in-the-blank exercise where they must choose which article best completes each sentence. Answers are provided. Discuss The Supper at Emmaus by Michelangelo with your eager sixth graders. While the painting does depict a religious scene, it is a great way to show how cultural context can be reflected in art. Viewers will learn about Michelangelo, the setting in the painting, and use the chiaroscuro technique to enhance a painting of their own. Working in partners, scholars each build a two-digit number by taking 10-stacks and single cubes from bags and coloring them on a chart (provided). They then compare numbers and determine which is greater. Together, they calculate the difference between the larger and smaller numbers. Using academic language is emphasized: "greater than," "less than," and "the difference." An assessment rubric is included. Learners construct a model of the hydrologic cycle, and observe that water is an element of a cycle in the natural environment. They explain how the hydrologic cycle works and why it is important, and compare the hydrologic cycle to other cycles found in nature. This is one of the most thoroughly thought-through, one-period lesson plans I've ever come across!
Head-related transfer function \|\|This article provides insufficient context for those unfamiliar with the subject. Learn how and when to remove this template message) (October 2009) (\| A head-related transfer function (HRTF) is a response that characterizes how an ear receives a sound from a point in space; a pair of HRTFs for two ears can be used to synthesize a binaural sound that seems to come from a particular point in space. It is a transfer function, describing how a sound from a specific point will arrive at the ear (generally at the outer end of the auditory canal). Some consumer home entertainment products designed to reproduce surround sound from stereo (two-speaker) headphones use HRTFs. Some forms of HRTF-processing have also been included in computer software to simulate surround sound playback from loudspeakers. Humans have just two ears, but can locate sounds in three dimensions – in range (distance), in direction above and below, in front and to the rear, as well as to either side. This is possible because the brain, inner ear and the external ears (pinna) work together to make inferences about location. This ability to localize sound sources may have developed in humans and ancestors as an evolutionary necessity, since the eyes can only see a fraction of the world around a viewer, and vision is hampered in darkness, while the ability to localize a sound source works in all directions, to varying accuracy, regardless of the surrounding light. Humans estimate the location of a source by taking cues derived from one ear (monaural cues), and by comparing cues received at both ears (difference cues or binaural cues). Among the difference cues are time differences of arrival and intensity differences. The monaural cues come from the interaction between the sound source and the human anatomy, in which the original source sound is modified before it enters the ear canal for processing by the auditory system. These modifications encode the source location, and may be captured via an impulse response which relates the source location and the ear location. This impulse response is termed the head-related impulse response (HRIR). Convolution of an arbitrary source sound with the HRIR converts the sound to that which would have been heard by the listener if it had been played at the source location, with the listener's ear at the receiver location. HRIRs have been used to produce virtual surround sound. [example needed] The HRTF is the Fourier transform of HRIR. The HRTF is also sometimes known as the anatomical transfer function (ATF). HRTFs for left and right ear (expressed above as HRIRs) describe the filtering of a sound source (x(t)) before it is perceived at the left and right ears as xL(t) and xR(t), respectively. The HRTF can also be described as the modifications to a sound from a direction in free air to the sound as it arrives at the eardrum. These modifications include the shape of the listener's outer ear, the shape of the listener's head and body, the acoustic characteristics of the space in which the sound is played, and so on. All these characteristics will influence how (or whether) a listener can accurately tell what direction a sound is coming from. How HRTF works The associated mechanism varies between individuals, as their head and ear shapes differ. HRTF describes how a given sound wave input (parameterized as frequency and source location) is filtered by the diffraction and reflection properties of the head, pinna, and torso, before the sound reaches the transduction machinery of the eardrum and inner ear (see auditory system). Biologically, the source-location-specific prefiltering effects of these external structures aid in the neural determination of source location), particularly the determination of the source's elevation (see vertical sound localization). Linear systems analysis defines the transfer function as the complex ratio between the output signal spectrum and the input signal spectrum as a function of frequency. Blauert (1974; cited in Blauert, 1981) initially defined the transfer function as the free-field transfer function (FFTF). Other terms include free-field to eardrum transfer function and the pressure transformation from the free-field to the eardrum. Less specific descriptions include the pinna transfer function, the outer ear transfer function, the pinna response, or directional transfer function (DTF). The transfer function H(f) of any linear time-invariant system at frequency f is: - H(f) = Output(f) / Input(f) One method used to obtain the HRTF from a given source location is therefore to measure the head-related impulse response (HRIR), h(t), at the ear drum for the impulse Δ(t) placed at the source. The HRTF H(f) is the Fourier transform of the HRIR h(t). Even when measured for a "dummy head" of idealized geometry, HRTF are complicated functions of frequency and the three spatial variables. For distances greater than 1 m from the head, however, the HRTF can be said to attenuate inversely with range. It is this far field HRTF, H(f, θ, φ), that has most often been measured. At closer range, the difference in level observed between the ears can grow quite large, even in the low-frequency region within which negligible level differences are observed in the far field. HRTFs are typically measured in an anechoic chamber to minimize the influence of early reflections and reverberation on the measured response. HRTFs are measured at small increments of θ such as 15° or 30° in the horizontal plane, with interpolation used to synthesize HRTFs for arbitrary positions of θ. Even with small increments, however, interpolation can lead to front-back confusion, and optimizing the interpolation procedure is an active area of research. In order to maximize the signal-to-noise ratio (SNR) in a measured HRTF, it is important that the impulse being generated be of high volume. In practice, however, it can be difficult to generate impulses at high volumes and, if generated, they can be damaging to human ears, so it is more common for HRTFs to be directly calculated in the frequency domain using a frequency-swept sine wave or by using maximum length sequences. User fatigue is still a problem, however, highlighting the need for the ability to interpolate based on fewer measurements. The head-related transfer function is involved in resolving the Cone of Confusion, a series of points where ITD and ILD are identical for sound sources from many locations around the "0" part of the cone. When a sound is received by the ear it can either go straight down the ear into the ear canal or it can be reflected off the pinnae of the ear, into the ear canal a fraction of a second later. The sound will contain many frequencies, so therefore many copies of this signal will go down the ear all at different times depending on their frequency (according to reflection, diffraction, and their interaction with high and low frequencies and the size of the structures of the ear.) These copies overlap each other, and during this, certain signals are enhanced (where the phases of the signals match) while other copies are canceled out (where the phases of the signal do not match). Essentially, the brain is looking for frequency notches in the signal that correspond to particular known directions of sound. If another person's ears were substituted, the individual would not immediately be able to localize sound, as the patterns of enhancement and cancellation would be different from those patterns the person's auditory system is used to. However, after some weeks, the auditory system would adapt to the new head-related transfer function. The inter-subject variability in the spectra of HRTFs has been studied through cluster analyses. Assessing the variation through changes between the person's ear, we can limit our perspective with the degrees of freedom of the head and its relation with the spatial domain. Through this, we eliminate the tilt and other co-ordinate parameters that add complexity. For the purpose of calibration we are only concerned with the direction level to our ears, ergo a specific degree of freedom. Some of the ways in which we can deduce an expression to calibrate the HRTF are: - Localization of sound in Virtual Auditory space - HRTF Phase synthesis - HRTF Magnitude synthesis A basic assumption in the creation of a virtual auditory space is that if the acoustical waveforms present at a listener’s eardrums are the same under headphones as in free field, then the listener’s experience should also be the same. Typically, sounds generated from headphones appear to originate from within the head. In the virtual auditory space, the headphones should be able to “externalize” the sound. Using the HRTF, sounds can be spatially positioned using the technique described below. Let x1(t) represent an electrical signal driving a loudspeaker and y1(t) represent the signal received by a microphone inside the listener’s eardrum. Similarly, let x2(t) represent the electrical signal driving a headphone and y2(t) represent the microphone response to the signal. The goal of the virtual auditory space is to choose x2(t) such that y2(t) = y1(t). Applying the Fourier transform to these signals, we come up with the following two equations: - Y1 = X1LFM, and - Y2 = X2HM, where L is the transfer function of the loudspeaker in the free field, F is the HRTF, M is the microphone transfer function, and H is the headphone-to-eardrum transfer function. Setting Y1 = Y2, and solving for X2 yields - X2 = X1LF/H. By observation, the desired transfer function is - T= LF/H. Therefore, theoretically, if x1(t) is passed through this filter and the resulting x2(t) is played on the headphones, it should produce the same signal at the eardrum. Since the filter applies only to a single ear, another one must be derived for the other ear. This process is repeated for many places in the virtual environment to create an array of head-related transfer functions for each position to be recreated while ensuring that the sampling conditions are set by the Nyquist criteria. There is less reliable phase estimation in the very low part of the frequency band, and in the upper frequencies the phase response is affected by the features of the pinna. Earlier studies also show that the HRTF phase response is mostly linear and that listeners are insensitive to the details of the interaural phase spectrum as long as the interaural time delay (ITD) of the combined low-frequency part of the waveform is maintained. This is the modeled phase response of the subject HRTF as a time delay, dependent on the direction and elevation. A scaling factor is a function of the anthropometric features. For example, a training set of N subjects would consider each HRTF phase and describe a single ITD scaling factor as the average delay of the group. This computed scaling factor can estimate the time delay as function of the direction and elevation for any given individual. Converting the time delay to phase response for the left and the right ears is trivial. The HRTF phase can be described by the ITD scaling factor. This is in turn is quantified by the anthropometric data of a given individual taken as the source of reference. For a generic case we consider β as a sparse vector that represents the subject’s anthropometric features as a linear superposition of the anthropometric features from the training data (y' = βT X), and then apply the same sparse vector directly on the scaling vector H. We can write this task as a minimization problem, for a non-negative shrinking parameter λ: From this, ITD scaling factor value H' is estimated as: where The ITD scaling factors for all persons in the dataset are stacked in a vector H ∈ RN, so the value Hn corresponds to the scaling factor of the n-th person. We solve the above minimization problem using Least Absolute Shrinkage and Selection Operator (LASSO). We assume that the HRTFs are represented by the same relation as the anthropometric features. Therefore, once we learn the sparse vector β from the anthropometric features, we directly apply it to the HRTF tensor data and the subject’s HRTF values H' given by: where The HRTFs for each subject are described by a tensor of size D × K, where D is the number of HRTF directions and K is the number of frequency bins. All Hn,d,k corresponds to all the HRTFs of the training set are stacked in a new tensor H ∈ RN×D×K, so the value Hn,d,k corresponds to the k-th frequency bin for dth HRTF direction of the n-th person. Also H'd,k corresponds to kth frequency for every d-th HRTF direction of the synthesized HRTF. Recordings processed via an HRTF, such as in a computer gaming environment (see A3D, EAX and OpenAL), which approximates the HRTF of the listener, can be heard through stereo headphones or speakers and interpreted as if they comprise sounds coming from all directions, rather than just two points either side of the head. The perceived accuracy of the result depends on how closely the HRTF data set matches the characteristics of one's own ears. - 3D sound reconstruction - Binaural recording - Dummy head recording - Environmental audio extensions - Sound Retrieval System - Sound localization - Transfer function - Daniel Starch (1908). Perimetry of the localization of sound. State University of Iowa. p. 35 ff. - Begault, D.R. (1994) 3D sound for virtual reality and multimedia. AP Professional. - So, R.H.Y., Leung, N.M., Braasch, J. and Leung, K.L.(2006) A low cost, Non-individualized surround sound system based upon head-related transfer functions. An Ergonomics study and prototype development. Applied Ergonomics, 37, pp. 695–707. - Blauert, J. (1997) Spatial hearing: the psychophysics of human sound localization. MIT Press. - Hofman, Paul M.; Van Riswick, JG; Van Opstal, AJ (September 1998). "Relearning sound localization with new ears" (PDF). Nature Neuroscience. 1 (5): 417–421. doi:10.1038/1633. PMID 10196533. - So, R.H.Y., Ngan, B., Horner, A., Leung, K.L., Braasch, J. and Blauert, J. (2010) Toward orthogonal non-individualized head-related transfer functions for forward and backward directional sound: cluster analysis and an experimental study. Ergonomics, 53(6), pp.767-781. - Carlile,S (1996). "Virtual Auditory Space and Applications". Austin, TX, Springer. - Tashev, Ivan (2014). "HRTF PHASE SYNTHESIS VIA SPARSE REPRESENTATION OF ANTHROPOMETRIC FEATURES". Information Technology and Applications Workshop,San Diego, CA, USA, Conference paper: 1–5. doi:10.1109/ITA.2014.6804239. - Bilinski,Piotr; Ahrens, Jens; Thomas, Mark R.P; Tashev, Ivan; Platt,John C (2014). "HRTF MAGNITUDE SYNTHESIS VIA SPARSE REPRESENTATION OF ANTHROPOMETRIC FEATURES". IEEE ICASSP, Florence, Italy: 4468–4472. doi:10.1109/ICASSP.2014.6854447.
Trigonometry: Circles and Angles In this circle and angel activity, students identify angles that correspond to a point on the unit circle. They give their solution in both degrees and radians. This two-page activity contains 20 problems. 3 Views 29 Downloads Special Triangles and the Unit Circle Calculate exact trigonometric values using the angles of special right triangles. Beginning with a review of the unit circle and trigonometric functions, class members use their knowledge of special right triangles to find the value of... 11th - 12th Math CCSS: Designed Basic Trigonometry and Radians A fabulous set of examples and problems that introduce basic trigonometry concepts, this packet is set apart by the care it takes to integrate both radians and degrees into the material. After defining radians, the author demonstrates... 9th - 12th Math CCSS: Adaptable New Review Special Right Triangles and Right Triangle Trigonometry Right triangles are so special! Use special right triangles to discover the trigonometric ratios. Pairs construct special right triangles and find the values of the ratios of the sides. In the process, they discover the ratios stay the... 9th - 11th Math CCSS: Adaptable Trigonometric Functions: The Unit Circle This comprehensive problem and note set walks the class through a large part of simplifying trigonometric expressions using the unit circle and identities. From identifying angles to applying appropriate trigonometric ratios, problems... 10th - 12th Math CCSS: Adaptable Measure Angles in Standard Position Using the Coordinate Plane The mechanics of measuring angles is a skill that is often taken for granted in an upper-level math class. This clear and detailed video presentation bridges the gap between identifying angles in geometry, and using their unit-circle... 5 mins 9th - 12th Math CCSS: Designed
The centroid of an area is the coordinates of the geometric centre. It is calculated from the area’s geometry and is represented in coordinate form (xc, yc). Centroids of basic shapes can be intuitive, such as the centre of a circle. Centroids of basic shapes are widely known and published. These can be used to find the centroid of composite areas or areas made up of basic shapes. Centroids of complex or arbitrary shapes can be found using the integration method of calculus. - Skill level: Other People Are Reading Things you need - Graph paper - Calculator (optional) Draw the figure to scale on graph paper. Identify the basic shapes that make up the figure and indicate these shapes on the drawing using dotted lines at the boundaries. The basic shapes are rectangle, triangle, circle, trapezoid, circle, quarter-circular area, semicircular area, quarter-elliptical area, semielliptical area, semi-parabolic area, parabolic area, parabolic spandrel, general spandrel and circular sector. Label each basic shape with numbers starting with 1(1, 2, 3, ... , n,). Label all the important dimensions. Define an X axis and Y axis on your graph paper. A convenient location of the graph origin point (0,0) is the lower left-hand corner of the figure. Let the centroid coordinates of the whole figure be defined as (xc, yc). Let the area of each basic shape be defined as An. Let n be the number used to label the basic shapes in Step 1. Locate and mark the centroids of each basic shape using the equations found in the resources. Determine the coordinates of each centroid location relative to the origin of the graph. Let the centroid coordinates for each basic shape be defined as (xn, yn). Calculate the X coordinate of the figure’s centroid (xc) using the following equation: xc = ?xnAn ??An ? indicates finite summation. The help clarify, this equation can be represented as follows: xc = (x1A1 + x2A2 + x3A3 +...+ xnAn) ?(A1 + A2 + A3 +...+ An) Calculate the Y coordinate of the figure’s centroid (yc) using the following equation: yc = ?ynAn ??An The help clarify, this equation can be represented as follows: yc = (y1A1 + y2A2 + y3A3 +...+ ynAn) ?(A1 + A2 + A3 +...+ An) Check your math. Mark the centroid of the figure (xc, yc) on your sketch. It should lie near the centre of the area. Tips and warnings - Use the link in Resources or an engineering reference manual to obtain basic shape centroid equations. - The areas of voids are considered negative areas in the above equations. An example of a void is a hole in a circle. - 20 of the funniest online reviews ever - 14 Biggest lies people tell in online dating sites - Hilarious things Google thinks you're trying to search for
This project, in which the Instituto de Astrofísica de Canarias (IAC) is collaborating, has made a map with 300 galaxies close to the Milky Way, which they have classified on the basis of the way the stars are moving, rather than using the morphological classification used until now. The results of this work were recently published in the journal Nature Astronomy. The objects within galaxies have two basic types of motions: orbiting around the galaxy center in a regular organized disc, or in orbits oriented at random without a clear direction of rotation. If we imagined that galaxies behave in the same way as the Solar System we could think that as the objects move further away from the center their orbital velocities decrease. However, this is not necessarily the case for galaxies, as there are several factors that affect the rotational velocity of these objects, such as the dimensions of the galaxy, the gravitational pull of other galaxies, and the quantity of dark matter in a given galaxy. An international team of astrophysicists, among them IAC and Universidad de La Laguna researcher Jesús Falcón Barroso, coordinator of the CALIFA (Calar Alto Legacy Integral Field Area survey) at the IAC who is one of the authors of the article published in Nature Astronomy, has collected data from 600 galaxies in the neighborhood of the Milky Way with the Potsday Multiple Aperture Spectrophotometer (PMAS) on the 3.6m telescope at the Calar Alto Observatory (Almería, Spain). As part of this catalog, the scientists have made velocity maps of 300 galaxies showing the movements of their stars. In this way, they have defined three different groups among the sets of stellar orbits, which they have called “cold orbits” “warm orbits” and “hot orbits,” the latter typical of stars with random motions. When they analyzed the data they showed that circular orbits are frequent in lower mass galaxies, while the “hot orbits” are more often found in galaxies with higher mass. In addition, they have found quite a number of “warm orbits,” greater than that previously expected for this type of galaxies. Using these maps of stellar motions one can obtain a lot of information about the history of the formation of these galaxies. They evolve and grow over thousands of millions of years, merging with other galaxies. Those which have absorbed other smaller galaxies generally have thin rotating discs, while when two galaxies with similar masses merge an elliptical galaxy is formed, in which the orbits are arranged in random directions. Measuring the orbits in the galaxies analyzed allows us to distinguish between disc galaxies (with colder orbits) and elliptical galaxies (with hotter orbits) even when this difference cannot be detected when using images alone. This implies that by measuring the stellar orbits the researchers will be able to determine if the galaxy we observe is the result of the internal evolution of an isolated object, a relatively calm series of mergers with smaller objects, or the product of a violent merger. CALIFA, which with its 300 galaxy sample has become one of the biggest archives of data on galaxy dynamics up to now is the “first study to propose a scheme of galaxy classification based on the orbital distribution of their stars, which is different from the classical Hubble diagram, based on morphological classification,” explains Falcón Barroso. This researcher also acknowledges that the results of this study “present some problems for current theories of formation and evolution of galaxies.” This new classification has been carefully prepared to produce a representative sample that will help astronomers to make models of the evolution of galaxies, and show whether their simulations produce valid predictions. Reference: “The stellar orbit distribution in present-day galaxies inferred from the CALIFA survey” by Ling Zhu, Glenn van de Ven, Remco van den Bosch, Hans-Walter Rix, Mariya Lyubenova, Jesús Falcón-Barroso, Marie Martig, Shude Mao, Dandan Xu, Yunpeng Jin, Aura Obreja, Robert J. J. Grand, Aaron A. Dutton, Andrea V. Macciò, Facundo A. Gómez, Jakob C. Walcher, Rubén García-Benito, Stefano Zibetti and Sebastian F. Sánchez, 1 January 2018, Nature Astronomy. Be the first to comment on "CALIFA Survey Helps Update the Classification of Galaxies"
Information Sheets – Types of Hearing Loss Deaf Children Australia provides information sheets for deaf and hard of hearing children and young people and their families on a range of subjects. Information Sheets are copied onto pages in plain text so they are able be translated in your web browser. To translate a page, please use the yellow Translate tab at the bottom right of the screen. To download an information sheet in PDF format, click the PDF button and save the file. Hearing losses may be located in the external, middle or inner ear or in a mixture of all three places. Damage to any part of the external, middle or inner ear can cause a hearing loss. The different types of hearing loss are: Conductive Hearing Loss If there is a problem in the external or middle ear, a conductive hearing loss exists. This means sound is not being conducted properly to the inner ear. Common causes of conductive hearing loss are: · wax in the external ear; · fluid in the middle ear; · a hole or tear (perforation) in the eardrum; · improper development of the outer or middle ear; · damage to the small bones in the middle ear; · an infection in the middle ear; or · a blockage in the Eustachian tube meaning that air cannot move into the middle ear. Conductive hearing losses do not cause the hearing to be lost completely but there is a loss of volume. Sounds may be quiet but there is no distortion. Sometimes this is from too much fluid in the middle ear which means the three small bones cannot vibrate properly. This is sometimes called “glue ear.” If a child has repeated ear infections, these may cause more permanent damage to the inner ear. Sensorineural Hearing Loss (SNHL or nerve deafness) If a problem occurs in the inner ear or auditory nerve, the hearing loss is sensorineural. Some people call this “nerve deafness.” With this type of deafness, there are problems with the cochlear or the nerve which carries sound to the brain Sensorineural losses can range from mild to profound. Both the volume and clarity of sound are affected. Sound may be heard but it may be distorted. What causes a sensorineural hearing loss? Common causes of sensorineural hearing loss in young children are: · certain pre-natal infections · lack of oxygen during birth · genetic factors · use of some certain drugs · premature birth What are the genetic causes of hearing loss? There are an increasing number of genetic causes of hearing loss being identified. For investigation into possible genetic causes of a hearing loss, contact: The Paediatric Hearing Loss Investigation Clinic Monash Medical Centre, Clayton Ph: 03 9594 6666 Genetic Health Services Murdoch Children’s Research Institute 10th Floor, Royal Children’s Hospital Flemington Rd, Parkville Ph: 03 8 341 6201 Fax: 03 8341 6390 Genetic Services of WA Princess Margaret Hospital for Children Roberts Rd, Subiaco, WA. 6008 Ph: 08 9340 8828 Ph: 08 9340 1525 Fax: 08 9340 7058 The Royal Melbourne Hospital Genetic Services visits Hobart, Launceston and the North West. Queensland Clinical Genetics Services Royal Children’s Hospital Back Road, Bramston Terrace Entrance Herston Qld Ph: 07 3636 1686 Fax: 07 3253 1987 Mater Children’s Hospital Ph: 07 3840 8195 New South Wales Royal North Shore Centre for Genetic Education St Leonards 2065 Ph: 02 9926 7324 Fax: 02 9906 7529 Department of Medical Genetics Level 2 Sydney Children’s Hospital High St Randwick 2031 Ph: 02 9382 1704
Neutron stars are the densest known objects after the black holes found in the universe. They are highly compressed cores of giant stars that are formed after their death as a result of a supernova. The level of their compression is so high that mass equivalent to the sun is fitted into the size of a city. How Neutron Stars Are Formed? The life of a neutron star begins with the death of a giant star. Stars that are about 10 times heavier than our Sun end their life in a most violent and energetic explosion called a supernova. Supernova occurs because the dying star has consumed all of its nuclear fuel and its nuclear fusion ceases. After the ceasing of nuclear fusion, there is no way for a star to fight-off the gravitational collapse. The sudden gravitational collapse causes a star to go supernova. During a supernova, the remaining core of a star goes further into gravitational collapse and reaches a level that subatomic particles in atoms of the core lose the battle. The electrons and protons are squeezed together to form neutrons in the remaining core. The process goes until the core gets around 90% neutrons by mass. The core of a dying star has now converted into a neutron star at this stage. Properties of Neutron Stars Density – Neutron stars are one of the most bizarre objects found in our universe. One of the most important properties for which they are known is their incredible density; around 1017 kg/m3. They are so dense that if you bring a spoonful matter of a neutron star on the Earth, it will weigh around 1 billion tons. Furthermore, if you drop that spoon of neutron star matter on the Earth, it will just pass through the Earth without getting blocked. Gravity – The gravity of a neutron star is tremendous as compared to any object in our universe except the black holes. They have gravity around 2 billion times more as compared to our Earth. They get such tremendous gravity due to their ultra-compactness. Magnetic Field – Much like density and gravity, neutron stars have also got the strongest magnetic field. The magnetic field of any neutron star is more than a trillion times powerful than the Earth’s magnetic field. Due to this reason, they are called the universe’s most strong magnets. Types of Neutron Stars There are various types of neutron stars in our universe that are categorized according to their properties. The two most common types of neutron stars are pulsars and magnetars. Pulsar – They are much similar to ordinary neutron stars except that they emit pulses of matter that are accelerated to nearly the speed of light and high energy electromagnetic radiations. The particle and radiations are emitted in pulses due to the rotation of neutron stars. Scientists have even found a way to use pulsars for the navigation of spaceships in the future. Magnetar – Magnetars are the type of neutrons stars whose magnetic field is more than a thousand times stronger than an ordinary neutron star. They are the universe’s most powerful magnets whose magnetic field is so powerful that it disintegrates the atoms that surround it. Furthermore, the crust of neutron stars is the strongest material in our universe. But the magnetic field of magnetars can tear its own crust; the process is known as starquake. Magnetars under starquake release more energy in 0.1 seconds that our Sun releases in 100,000 years. - Astronomers have discovered 2,000 neutron stars in our universe to date. - When two neutrons stars collide with each other, a massive explosion is resulted, called a kilonova. Kilonova results in the formation of gold and other heavier elements that couldn’t be formed in an ordinary supernova. - There are some neutron stars that couldn’t be categorized yet due to their periodic conversion between a pulsar and a magnetar.
LOG10E Math. LOG2E Math. PI Math. SQRT2 Math. NaN Number. ISBN: Decrement -- The -- operator expects an lvalue operand. It converts the value of the operand to a number, subtracts 1, and assigns the decremented value back to the operand. When used before the operand, it decrements and returns the decremented value. When used after the operand, it decrements the operand but returns the undecremented value. When used after its operand, no line break is allowed between the operand and the operator. A bit is set in the result if the corresponding bit is set in one or both of the operands. For example, 0x 0x00FF evaluates to 0x12FF. Exclusive OR means that either operand one is true or operand two is true, but not both. It operates by reversing all bits in the operand. Relational expressions always evaluate to a boolean value, and that value is often used to control the flow of program execution in if, while, and for statements see Chapter 5. Both operators accept operands of any type, and both return true if their operands are the same and false if they are different. Be sure you understand the differences between these assignment, equality, and strict equality operators, and be careful to use the correct one when coding! This makes it easy to remember that! An object is equal to itself, but not to any other object. If two distinct objects have the same number of properties, with the same names and values, they are still not equal. Two arrays that have the same elements in the same order are not equal to each other. The NaN value is never equal to any other value, including itself! To check whether a value x is NaN, use x! NaN is the only value of x for which this expression will be true. If one value is 0 and the other is -0, they are also equal. If the strings differ in length or content, they are not equal. Two strings may have the same meaning and the same visual appearance, but still be encoded using different sequences of bit values. See String. If they refer to different objects they are not equal, even if both objects have identical properties. Infinity is larger than any number other than itself, and -Infinity is smaller than any number other than itself. If either operand is or converts to NaN, then the comparison operator always returns false. This rule can cause confusing results if you do not expect it. Result is 3. Result is "12". Numeric comparison. Result is false. String comparison. Result is true. It expects a right-side operand that is an object. It evaluates to true if the left-side value is the name of a property of the right-side object. The operator evaluates to true if the left-side object is an instance of the right-side class and evaluates to false otherwise. If it finds it, then o is an instance of f or of a superclass of f and the operator returns true. These operators are described in the subsections that follow. If one or both of these operands is false, it returns false. The falsy values are false, 4. Thus, the right-side operand of instanceof should be a function. Here are examples: null, undefined, 0, -0, NaN, and "". All other values, including all objects, are truthy. If both operands are truthy, the operator returns a truthy value. Otherwise, one or both operands must be falsy, and the operator returns a falsy value. This operator starts by evaluating its first operand, the expression on its left. On the other hand, if the value on the left is truthy, then the overall value of the expression depends on the value on the right-hand side. If the value on the right is truthy, then the overall value must be truthy, and if the value on the right is falsy, then the overall value must be falsy. In the code above, the variable p is set to null, and the expression p. Whether those side effects occur depends on the value of the left-hand side. Despite the somewhat complex way that this operator actually works, it is most commonly used as a simple Boolean algebra operator that works on truthy and falsy values. If one or both operands is truthy, it returns a truthy value. If both operands are falsy, it returns a falsy value. If that is not defined use a hard-coded constant. Its purpose is to invert the boolean value of its operand. For example, if x is truthy! If x is falsy, then! This means that! As a unary operator,! It starts by evaluating its first operand, the expression on its left. If the value of this first operand is truthy, it returns that truthy value. Otherwise, it evaluates its second operand, the expression on its right, and returns the value of that expression. It expects its right-side operand to be an arbitrary value of any type. The value of an assignment expression is the value of the right-side operand. Although assignment expressions are usually quite simple, you may sometimes see the value of an assignment expression used as part of a larger expression. The assignment operator has right-to-left associativity, which means that when multiple assignment operators appear in an expression, they are evaluated from right to left. For numeric operands, it performs addition and assignment; for string operands, it performs concatenation and assignment. Table lists them all. In the second it is evaluated twice. The two cases will differ only if a includes side effects such as a function call or an increment operator. If you find yourself using eval , you should think carefully about whether you really need to use it. The subsections below explain the basic use of eval and then explain two restricted versions of it that have less impact on the optimizer. If it successfully parses the string, then it evaluates the code and returns the value of the last expression or statement in the string or undefined if the last expression or statement had no value. If the string throws an exception, the eval propagates that expression. The key thing about eval when invoked like this is that it uses the variable environment of the code that calls it. That is, it looks up the values of variables and defines new variables and functions in the same way that local code does. If a function defines a local variable x and then calls eval "x" , it will obtain the value of the local variable. Note that the string of code you pass to eval must make syntactic sense on its ownï¿½ you cannot use it to paste code fragments into a function. It makes no sense to write eval "return;" , for example, because return is only legal within functions, and the fact that the evaluated string uses the same variable environment as the calling function does not make it part of that function. Any other callï¿½an indirect callï¿½uses the global object as its variable environment and cannot read, write, or define local variables or functions. As noted at the beginning of this section, it is rare to truly need to evaluate a string of code. But if you do find it necessary, you are more likely to want to do a global eval than a local eval. Before IE9, IE differs from other browsers: it does not do a global eval when eval is invoked by a different name. But IE does define a global function named execScript that executes its string argument as if it were a top-level script. Unlike eval , however, execScript always returns null. This means that in strict mode, evaluated code can query and set local variables, but it cannot define new variables or functions in the local scope. You are not allowed to overwrite the eval function with a new value. This operator is sometimes written? Because this operator has three operands, the first goes before the? The first operand is evaluated and interpreted as a boolean. If the value of the first operand is truthy, then the second operand is evaluated, and its value is returned. Otherwise, if the first operand is falsy, then the third operand is evaluated and its value is returned. Only one of the second and third operands is evaluated, never both. Its value is a string that specifies the type of the operand. Otherwise, delete attempts to delete the specified lvalue. Not all properties can be deleted, however: some built-in core and client-side properties are immune from deletion, and user-defined variables declared with the var statement cannot be deleted. Functions defined with the function statement and declared function parameters cannot be deleted either. Outside of strict mode, no exception occurs in these cases and delete simply returns false to indicate that the operand could not be deleted. This sort of statement was shown in Chapter 4. Assignment statements are one major category of expression statements. Thus, it is almost always used as a statement, rather than as part of a larger expression: delete o. For example: alert greeting ; window. These statements define identifiers variable and function names that can be used elsewhere in your program and assign values to those identifiers. First, it does not end with a semicolon. The primitive statements within the block end in semicolons, but the block itself does not. Second, the lines inside the block are indented relative to the curly braces that enclose them. This is optional, but it makes the code easier to read and understand. The subsections that follow explain the var statement and the function statement, but do not cover variables and functions comprehensively. It can also be used in statement form. The function name is followed by a comma-separated list of parameter names in parentheses. These identifiers can be used within the body of the function to refer to the argument values passed when the function is invoked. Instead, they are associated with the new function object for execution when the function is invoked. Note that the curly braces are a required part of the function statement. Unlike statement blocks used with while loops and other statements, a function body requires curly braces, even if the body consists of only a single statement. If o already has an own noninherited property named x, then the assignment simply changes the value of this existing property. Otherwise, the assignment creates a new property named x on the object o. If o previously inherited the property x, that inherited property is now hidden by the newly created own property with the same name. Property assignment examines the prototype chain to determine whether the assignment is allowed. If o inherits a read-only property named x, for example, then the assignment is not allowed. If the assignment is allowed, however, it always creates or sets a property in the original object and never modifies the prototype chain. This section explains the things that can go wrong when you query or set a property. It is not an error to query a property that does not exist. If the property x is not found as an own property or an inherited property of o, the property access expression o. The null and undefined values have no properties, and it is an error to query properties of these values. Attempting to set a property on null or undefined also causes a TypeError, of course. Attempts to set properties on other values do not always succeed, either: some properties are read-only and cannot be set, and some objects do not allow the addition of new properties. In strict mode, any failed attempt to set a property throws a TypeError exception. The rules that specify when a property assignment succeeds and when it fails are intuitive but difficult to express concisely. See the defineProperty method, however, for an exception that allows configurable read-only properties to be set. If p does not already exist on o, and if there is no setter method to call, then p must be added to o. But if o is not extensible, then no new properties can be defined on it. Its single operand should be a property access expression. Surprisingly, delete does not operate on the value of the property but on the property itself: delete book. The delete operator only deletes own properties, not inherited ones. To delete an inherited property, you must delete it from the prototype object in which it is defined. Doing this affects every object that inherits from that prototype. A delete expression evaluates to true if the delete succeeded or if the delete had no effect such as deleting a nonexistent property. Though it will remove configurable properties of nonextensible objects. Certain properties of built-in objects are nonconfigurable, as are properties of the global object created by variable declaration and function declaration. In strict mode, attempting to delete a nonconfigurable property causes a TypeError. You can do this with the in operator, with the hasOwnProperty and propertyIsEnumerable methods, or simply by querying the property. The in operator expects a property name as a string on its left side and an object on its right. It returns true only if the named property is an own property and its enumerable attribute is true. Certain built-in properties are not enumerable. It runs the body of the loop once for each enumerable property own or inherited of the specified object, assigning the name of the property to the loop variable. The return value of the setter method is ignored. Accessor properties do not have a writable attribute as data properties do. If it has only a getter method, it is a read-only property. And if it has only a setter method, it is a write-only property something that is not possible with data properties and attempts to read it always evaluate to undefined. Note that no colon is used to separate the name of the property from the functions that access that property, but that a comma is still required after the function body to separate the method from the next method or data property. So the getter method for the r property can refer to the x and y properties as this. Accessor properties are inherited, just as data properties are, so you can use the object p defined above as a prototype for other points. The next section shows how to add accessor properties to existing objects. In ECMAScript 3, there is no way to set these attributes: all properties created by ECMAScript 3 programs are writable, enumerable, and configurable, and there is no way to change this. For the purposes of this section, we are going to consider getter and setter methods of an accessor property to be property attributes. Thus, we can say that a property has a name and four attributes. The four attributes of a data property are value, writable, enumerable, and configurable. So the four attributes of an accessor property are get, set, enumerable, and configurable. The ECMAScript 5 methods for querying and setting the attributes of a property use an object called a property descriptor to represent the set of four attributes. A property descriptor object has properties with the same names as the attributes of the property it describes. Thus, the property descriptor object of a data property has properties named value, writable, enumerable, and configurable. And the descriptor for an accessor property has get and set properties instead of value and writable. The writa ble, enumerable, and configurable properties are boolean values, and the get and set properties are function values, of course. To obtain the property descriptor for a named property of a specified object, call Object. To query the attributes of inherited properties, you must explicitly traverse the prototype chain see Object. Note that this method alters an existing own property or creates a new own property, but it will not alter an inherited property. If you want to create or modify more than one property at a time, use Object. The first argument is the object that is to be modified. The second argument is an object that maps the names of the properties to be created or modified to the property descriptors for those properties. It relies on the fact that Object. The other reasons that these methods might throw TypeError have to do with the attributes themselves. The writable attribute governs attempts to change the value attribute. And the configurable attribute governs attempts to change the other attributes and also specifies whether a property can be deleted. The rules are not completely straightforward, however. It is possible to change the value of a nonwritable property if that property is configurable, for example. Also, it is possible to change a property from writable to nonwritable even if that property is nonconfigurable. Here are the complete rules. Calls to Object. You can change the value of a property that is configurable but nonwritable, however because that would be the same as making it writable, then changing the value, then converting it back to nonwritable. Example included an extend function that copied properties from one object to another. That function simply copied the name and value of the properties and ignored their attributes. Furthermore, it did not copy the getter and setter methods of accessor properties, but simply converted them into static data properties. Example shows a new version of extend that uses Object. Rather than being written as a function, this version is defined as a new Object method and is added as a nonenumerable property to Object. We learned there that the first argument to that method is the prototype object for the newly created object. This method also accepts a second optional argument, which is the same as the second argument to Object. If you pass a set of property descriptors to Object. The names of each of these methods begin and end with double underscores to indicate that they are nonstandard methods. These nonstandard methods are not documented in the reference section. The subsections that follow explain what these attributes do and where possible how to query and set them. The prototype attribute is set when an object is created. Objects created with new use the value of the prototype property of their constructor function as their prototype. And objects created with Object. There is no equivalent function in ECMAScript 3, but it is often possible to determine the prototype of an object o using the expression o. Objects created with a new expression usually inherit a constructor property that refers to the constructor function used to create the object. And, as described above, constructor functions have a prototype property that specifies the prototype for objects created using that constructor. Note that objects created by object literals or by Object. Thus, constructor. To determine whether one object is the prototype of or is part of the prototype chain of another object, use the isPrototypeOf method. To find out if p is the prototype of o write p. Create an object with that prototype. The default toString method inherited from Object. The tricky part is that many objects inherit other, more useful toString methods, and to invoke the correct version of toString , we must do so indirectly, using the Function. Example defines a function that returns the class of any object you pass it. Numbers, strings, and booleans behave like objects when the toString method is invoked on them, and the function includes special cases for null and undefined. Objects created through built-in constructors such as Array and Date have class attributes that match the names of their constructors. Host objects typically have meaningful class attributes as well, though this is implementation-dependent. Objects created through object literals or by Object. In ECMAScript 3, all built-in and user-defined objects are implicitly extensible, and the extensibility of host objects is implementation defined. In ECMAScript 5, all built-in and user-defined objects are extensible unless they have been converted to be nonextensible, and the extensibility of host objects is again implementation defined. ECMAScript 5 defines functions for querying and setting the extensibility of an object. To determine whether an object is extensible, pass it to Object. To make an object nonextensible, pass it to Object. Note that there is no way to make an object extensible again once you have made it nonextensible. Also note that calling preventExtensions only affects the extensibility of the object itself. If new properties are added to the prototype of a nonextensible object, the nonextensible object will inherit those new properties. The extensible object attribute is often used in conjunction with the configurable and writable property attributes, and ECMAScript 5 defines functions that make it easy to set these attributes together. This means that new properties cannot be added to the object, and existing properties cannot be deleted or configured. Existing properties that are writable can still be set, however. There is no way to unseal a sealed object. You can use Object. If the object has accessor properties with setter methods, these are not affected and can still be invoked by assignment to the property. Use Object. It is important to understand that Object. If you want to thoroughly lock down an object, you probably need to seal or freeze the objects in the prototype chain as well. These functions use the JSON data interchange format. Objects, arrays, strings, finite numbers, true, false, and null are supported and can be serialized and restored. NaN, Infinity, and -Infinity are serialized to null. Date objects are serialized to ISO-formatted date strings see the Date. Function, RegExp, and Error objects and the undefined value cannot be serialized or restored. If a property value cannot be serialized, that property is simply omitted from the stringified output. Both JSON. Complete documentation for these functions is in the reference section. These customized versions of the toString method are documented in the reference section. See Array. The purpose of this method is to return a localized string representation of the object. The Date and Number classes define customized versions of toLocaleString that attempt to format numbers, dates, and times according to local conventions. Array defines a toLocaleString method that works like toString except that it formats array elements by calling their toLocale String methods instead of their toString methods. If this method exists on the object to be serialized, it is invoked, and the return value is serialized, instead of the original object. Array literal syntax allows an optional trailing comma, so [,,] has only two elements, not three. Another way to create an array is with the Array constructor. This form of the Array constructor can be used to preallocate an array when you know in advance how many elements will be required. We then assigned values at indexes 1, 2, and 3. The length property of the array changed as we did so: a. All indexes are property names, but only property names that are integers between 0 and ï¿½1 are indexes. All arrays are objects, and you can create properties of any name on them. If you use properties that are array indexes, however, arrays have the special behavior of updating their length property as needed. Note that you can index an array using numbers that are negative or that are not integers. When you do this, the number is converted to a string, and that string is used as the property name. Since the name is not a non-negative integer, it is treated as a regular object property, not an array index. Also, if you index an array with a string that happens to be a non-negative integer, it behaves as an array index, not an object property. The same is true if you use a floating-point number that is the same as an integer: a[ This is just as true for arrays as it is for objects: 7. You can use this syntax to both read and write the value of an element of an array. No element at this index. No property with this name. Since arrays are objects, they can inherit elements from their prototype. If an array does inherit elements or use getters and setters for elements, you should expect it to use a nonoptimized code path: the time to access an element of such an array would be similar to regular object property lookup times. Normally, the length property of an array specifies the number of elements in the array. If the array is sparse, the value of the length property is greater than the number of elements. Sparse arrays can be created with the Array constructor or simply by assigning to an array index larger than the current array length. In order to maintain this invariant, arrays have two special behaviors. Delete all elements. Length is 5, but no elements, like new Array 5 You can also set the length property of an array to a value larger than its current value. Doing this does not actually add any new elements to the array, it simply creates a sparse area at the end of the array. Make the length property readonly. Similarly, if you make an array element nonconfigurable, it cannot be deleted. If it cannot be deleted, then the length property cannot be set to less than the index of the nonconfigurable element. You can also use the push method to add one or more values to the end of an array: 7. Note that using delete on an array element does not alter the length property and does not shift elements with higher indexes down to fill in the gap that is left by the deleted property. If you delete an element from an array, the array becomes sparse. As we saw above, you can also delete elements from the end of an array simply by setting the length property to the new desired length. Arrays have a pop method it works with push that reduces the length of an array by 1 but also returns the value of the deleted element. There is also a shift method which goes with unshift to remove an element from the beginning of an array. Unlike delete, the shift method shifts all elements down to an index one lower than their current index. Finally, splice is the general-purpose method for inserting, deleting, or replacing array elements. It alters the length property and shifts array elements to higher or lower indexes as needed. If this is not the case, you should test the array elements before using them. This loop assigns enumerable property names including array indexes to the loop variable one at a time. Implementations typically iterate array elements in ascending order, but this is not guaranteed. In particular, if an array has both object properties and array elements, the property names may be returned in the order they were created, 7. ECMAScript 5 defines a number of new methods for iterating array elements by passing each one, in index order, to a function that you define. To access a value in an array of arrays, simply use the operator twice. For example, suppose the variable matrix is an array of arrays of numbers. Every element in matrix[x] is an array of numbers. To access a particular number within this array, you would write matrix[x][y]. As usual, complete details can be found under Array in the client-side reference section. You can specify an optional string that separates the elements in the resulting string. If no separator string is specified, a comma is used. To sort an array into some order other than alphabetical, you must pass a comparison function as an argument to sort. This function decides which of its two arguments should appear first in the sorted array. If the first argument should appear before the second, the comparison function should return a number less than zero. If the first argument should appear after the second in the sorted array, the function should return a number greater than zero. And if the two values are equivalent i. Since the comparison functions are used only once, there is no need to give them names. If any of these arguments is itself an array, then it is the array elements that are concatenated, not the array itself. Note, however, that concat does not recursively flatten arrays of arrays. Its two arguments specify the start and end of the slice to be returned. The returned array contains the element specified by the first argument and all subsequent elements up to, but not including, the element specified by the second argument. If only one argument is specified, the returned array contains all elements from the start position to the end of the array. If either argument is negative, it specifies an array element relative to the last element in the array. An argument of -1, for example, specifies the last element in the array, and an argument of -3 specifies the third from last element of the array. Note that slice does not modify the array on which it is invoked. Unlike slice and concat , splice modifies the array on which it is invoked. Note that splice and slice have very similar names but perform substantially different operations. Elements of the array that come after the insertion or deletion point have their indexes increased or decreased as necessary so that they remain contiguous with the rest of the array. The second argument specifies the number of elements that should be deleted from spliced out of the array. If this second argument is omitted, all array elements from the start element to the end of the array are removed. These arguments may be followed by any number of additional arguments that specify elements to be inserted into the array, starting at the position specified by the first argument. Instead of being inserted into the array one at a time, arguments are inserted all at once as with the splice method. This means that they appear in the resulting array in the same order in which they appeared in the argument list. Had the elements been inserted one at a time, their order would have been reversed. For an array, this method converts each of its elements to a string calling the toString methods of its elements, if necessary and outputs a comma-separated list of those strings. Note that the output does not include square brackets or any other sort of delimiter around the array value. For example: [1,2,3]. It converts each array element to a string by calling the toLocaleString method of the element, and then it concat- enates the resulting strings using a locale-specific and implementation-defined separator string. The subsections below describe these methods. Before we cover the details, however, it is worth making some generalizations about these ECMAScript 5 array methods. First, most of the methods accept a function as their first argument and invoke that function once for each element or some elements of the array. If the array is sparse, the function you pass is not invoked for nonexistent elements. In most cases, the function you supply is invoked with three arguments: the value of the array element, the index of the array element, and the array itself. Often, you only need the first of these argument values and can ignore the second and third values. Most of the ECMAScript 5 array methods that accept a function as their first argument accept an optional second argument. If specified, the function is invoked as if it is a method of this second argument. That is, the second argument you pass becomes the value of the this keyword inside of the function you pass. The return value of the function you pass is important, but different methods handle the return value in different ways. If you pass a function to these methods, that function may modify the array, of course. As described above, you pass the function as the first argument to forEach. That is, there is no equivalent of the break statement you can use with a regular for loop. If you need to terminate early, you must throw an exception, and place the call to forEach within a try block. The following code defines a foreach function that calls the forEach method within such a try block. If the function passed to foreach throws foreach. For the map method, however, the function you pass should return a value. Note that map returns a new array: it does not modify the array it is invoked on. If that array is sparse, the returned array will be sparse in the same way: it will have the same length and the same missing elements. The function you pass to it should be predicate: a function that returns true or false. The predicate is invoked just as for forEach and map. If the return value is true, or a value that converts to true, then the element passed to the predicate is a member of the subset and is added to the array that will become the return value. Note that both every and some stop iterating array elements as soon as they know what value to return. Note also that by mathematical convention, every returns true and some returns false when invoked on an empty array. The first is the function that performs the reduction operation. The task of this reduction function is to somehow combine or reduce two values into a single value, and to return that reduced value. In the examples above, the functions combine two values by adding them, multiplying them, and choosing the largest. The second optional argument is an initial value to pass to the function. Functions used with reduce are different than the functions used with forEach and map. The familiar value, index, and array values are passed as the second, third, and fourth arguments. The first argument is the accumulated result of the reduction so far. On the first call to the function, this first argument is the initial value you passed as the second argument to reduce. On subsequent calls, it is the value returned by the previous invocation of the function. In the first example above, the reduction function is first called with arguments 0 and 1. It adds these and returns 1. It is then called again with arguments 1 and 2 and it returns 3. This final value, 15, becomes the return value of reduce. You may have noticed that the third call to reduce above has only a single argument: there is no initial value specified. When you invoke reduce like this with no initial value, it uses the first element of the array as the initial value. This means that the first call to the reduction function will have the first and second array elements as its first and second arguments. In the sum and product examples above, we could have omitted the initial value argument. Calling reduce on an empty array with no initial value argument causes a TypeError. If you call it with only one valueï¿½either an array with one element and no initial value or an empty array and an initial valueï¿½it simply returns that one value without ever calling the reduction function. The optional initial value argument takes its place. See the Function. It is worth noting that the every and some methods described above perform a kind of array reduction operation. They differ from reduce , however, in that they terminate early when possible, and do not always visit every array element. The examples shown so far have been numeric for simplicity, but reduce and reduce Right are not intended solely for mathematical computations. Consider the union function from Example The first argument is the value to search for. The second argument is optional: it specifies the array index at which to begin the search. If this argument is omitted, indexOf starts at the beginning and lastIndexOf starts at the end. Negative values are allowed for the second argument and are treated as an offset from the end of the array, as they are for the splice method: a value of ï¿½1, for example, specifies the last element of the array. The following function searches an array for a specified value and returns an array of all matching indexes. 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Inflation is the rate at which the general level of prices for goods and services is rising and subsequently purchasing power is falling. Central banks attempt to limit inflation and avoid deflation, in order to keep the economy running smoothly. It is not one international institution such as The United Nations (UN) that has a specific mechanism for controlling inflation on an international level. However, the UN does have agencies, such as the International Monetary Fund (IMF) and the World Bank, that work with member countries to promote economic stability and growth, which can help to mitigate inflation. Additionally, the UN may make recommendations or provide assistance to member countries experiencing high inflation through its various economic and social development programs. Central banks use a variety of tools to control inflation. The most common methods include setting interest rates. Central banks can raise interest rates to make borrowing more expensive, which can slow down economic growth and reduce inflationary pressures. Further, central banks can buy or sell government securities to control the money supply and influence interest rates. They too can change the number of reserves that commercial banks are required to hold, which can affect the amount of money that banks have available to lend. In addition, central banks can communicate their future policy actions, to help shape expectations and influence the behaviour of consumers, businesses, and investors. And the last method open to the central banks is to create new money and use it to buy financial assets such as government bonds, lower long-term interest rates and increase the money supply otherwise known as Quantitative Easing. Each central bank has its own monetary policy, which is the set of tools they use to achieve its goals, such as controlling inflation, stabilizing the currency, and promoting economic growth. Central banks do not necessarily coordinate their interest rate decisions with each other, as each country has its own unique economic conditions and policy goals. However, they may take into account the monetary policy actions of other major central banks when making their own decisions. For example, if the Federal Reserve (the central bank of the United States) raises interest rates, it could put upward pressure on interest rates in other countries, and other central banks may take that into account when deciding on their own interest rate policy. Additionally, central banks may coordinate their actions during times of financial crisis to provide liquidity and stability to the global financial system. The use of central banks to control inflation and stabilize the economy is a relatively modern development. The concept of a central bank can be traced back to the late 17th century, with the establishment of the Bank of Sweden in 1668, but the modern central banking system as we know it today has been in place for over a century. The Federal Reserve System, the central bank of the United States, was established in 1913 and since then many other countries have followed suit and established their own central banks. The use of monetary policy tools such as setting interest rates and open market operations to control inflation and stabilize the economy also has a relatively short history. These tools were first developed in the 1930s and 1940s and have been refined and expanded over time. It’s worth noting that different central banks use different monetary policy tools and they may have different policy objectives and frameworks, but overall the system has been in place for more than a century. The goal of central banks is generally to maintain low and stable inflation, but the target rate can vary depending on the country and the specific central bank. In some countries, the target rate is zero inflation, meaning that prices are stable and not rising. In other countries, the target rate is a low but positive rate of inflation, typically around 2%. Achieving zero inflation can be difficult and may have negative consequences for the economy. Zero inflation can lead to deflation, which is a sustained decrease in the general price level of goods and services. Deflation can lead to lower economic growth, as consumers and businesses may delay spending and invest in anticipation of lower prices in the future. Additionally, zero inflation can make it more difficult for central banks to stimulate economic growth by cutting interest rates, as interest rates cannot be negative. For these reasons, many central banks aim for a target rate of low but positive inflation, which allows for some flexibility in monetary policy and can help to avoid the negative consequences of deflation. One example of bad inflation in history is the hyperinflation that occurred in Germany in the early 1920s. After World War I, Germany was required to pay large reparations to the victorious Allied powers. To finance these payments, the German government printed large amounts of money, leading to a rapid increase in the money supply. This, coupled with other economic and political factors, led to a period of hyperinflation in which prices for goods and services increased at an extremely rapid pace. At its worst, prices were doubling every few days, and the German currency, the mark, became practically worthless. People would carry wheelbarrows of money to buy basic goods, and salaries were paid multiple times a day to keep up with the inflation. This period of hyperinflation had a devastating effect on the German economy and society, leading to widespread poverty, unemployment, and social unrest. It also contributed to the rise of the Nazi party and the eventual collapse of the Weimar Republic. Hyperinflation is an extreme example of bad inflation, it’s a rare but severe form of inflation that can have a destructive effect on an economy and society. It can be caused by a variety of factors such as war, political instability, or monetary mismanagement. Inflation was not a major factor in the stock market crash of 1929 and the subsequent Great Depression in the United States. The crash was primarily caused by a combination of factors, including speculative excesses in the stock market, a lack of regulation in the financial sector, and underlying structural issues in the economy. Before the crash, the economy was booming, driven by new technologies, increased productivity, and a rising stock market. However, many stocks were overvalued and there were widespread speculative activities in the market. When the market began to decline in late 1929, many investors panicked and began selling, leading to a downward spiral in stock prices. The depression was exacerbated by a number of factors, including the collapse of the banking system and the contraction of credit, along with the failure of policies and institutions that were supposed to provide stability. The Federal Reserve, the central bank of the United States, was criticized for not doing enough to stem the crisis and for allowing the money supply to shrink. Inflation was not a major problem during the Great Depression, on the contrary, the economy was characterized by deflation, a sustained decrease in the general price level of goods and services. Due to the contraction of the money supply, decrease in demand and decrease in production, prices dropped significantly, making it harder for the economy to recover and for individuals to pay off their debts. Deflation is a sustained decrease in the general price level of goods and services. This means that the purchasing power of money increases, as the same amount of money can buy more goods and services than before. Deflation can occur when there is a decrease in the money supply, a decrease in demand for goods and services, or an increase in production. Deflation can be harmful to an economy, as it can lead to lower economic growth and higher unemployment. When prices are falling, consumers and businesses may delay spending and invest in anticipation of lower prices in the future. This can lead to a decrease in demand, which can cause businesses to cut back on production and lay off workers. As unemployment increases, consumer spending decreases, creating a vicious cycle of decreasing demand, production and employment. Additionally, deflation can make it more difficult for central banks to stimulate economic growth by cutting interest rates, as interest rates cannot be negative. It can also make it harder for individuals and businesses to pay off their debts, as the value of the debt increases as prices fall. In summary, deflation is the opposite of inflation, it is a sustained decrease in the general price level of goods and services and can have negative effects on an economy, such as lower economic growth and higher unemployment. One historical example of deflation is the Great Depression of the 1930s. The Great Depression was a severe economic downturn that began in 1929 and lasted for more than a decade. A decline in economic activity, high unemployment, and a decrease in the general price level of goods and services characterised it. During the Great Depression, the money supply contracted and demand for goods and services decreased, leading to a decrease in prices. This deflation made it harder for individuals and businesses to pay off their debts, as the value of their debt increased as prices fell. Additionally, as prices fell, businesses cut back on production and laid off workers, leading to high unemployment. The deflation of the Great Depression was further exacerbated by the failure of policies and institutions that were supposed to provide stability, such as the Federal Reserve, the central bank of the United States, which was criticized for not doing enough to stem the crisis and for allowing the money supply to shrink. The Great Depression was a global phenomenon and many other countries experienced deflation and economic decline as well, leading to a severe contraction of global trade and a decline in living standards. It is considered one of the worst economic depressions in history, with a severe and long-lasting impact on the economy and society of many countries. The Great Depression was eventually brought to an end by a combination of government policies and the onset of World War II. One of the key policy responses to the Great Depression was the implementation of massive government spending programs, such as the New Deal in the United States. These programs put money into the hands of consumers and businesses, helping to boost demand and stimulate economic growth. Additionally, governments around the world adopted expansionary monetary policies, such as increasing the money supply and lowering interest rates, to try to stimulate economic activity. The onset of World War II also played a major role in ending the Great Depression. The massive government spending on the war effort led to a significant increase in economic activity, as businesses ramped up production to meet the needs of the military. The war also led to the employment of millions of people, which helped to decrease unemployment. It’s worth noting that the recovery from the Great Depression was not immediate, it took time and some countries recovered faster than others. Additionally, not all the policies implemented were successful, some were even criticised for not being effective enough or for making the situation worse. The Great Depression was a complex event with multiple causes and solutions, it serves as a reminder of the importance of economic stability and the need for effective policies to mitigate the effects of severe economic downturns.
Rectilinear motion: motion along a straight line is called rectilinear motion curvilinear motion: for non uniform motion. Motion taking a straight line path is what's known as rectilinear motion the rectilinear motion graph what is uniform motion angular motion definition. Examples on uniform rectilinear motion ex 1: if a car reaches a velocity of 72 km/hr in 10s which h has started from rest , calculate: (i) the acceleration. Do physics online rectilinear motion with a uniform acceleration predict observe explain exercise 1 take an a4 sheet of paper and a heavy object (cricket ball, basket ball, brick, book, etc. Uniform rectilinear motion for particle in uniform rectilinear motion, the acceleration is zero and the velocity is constant x x vt x x vt dx v dt v dt dx x t. exercise 1: rectilinear motion rectilinear motion essay problem 112 sample problem 113 uniform rectilinear-motion uniformly accelerated. Exercise 1: rectilinear motion uniformly accelerated rectilinear motion and newton’s law of momentum equations to use (remember to keep track of units). Collection of essays at the 2011 international congress on newton’s law tells us that a body will in fact continue its uniform rectilinear motion if it. Motion in one dimension (rectilinear motion) the motion along a straight line is known as rectilinear motion the important parameters required to study the motion along a straight line are position, displacement, velocity, and acceleration. Solving dynamics problems in maple (rectilinear motion) 30 struggling with equations of motion and kinematic. Linear motion (also called rectilinear motion) the linear motion can be of two types: uniform linear motion with constant velocity or zero acceleration. Linear motion described in distance-time graphs and velocity-time graphsthe equations of motion are given in linear motion : uniform acceleration [disp. A problem on rectilinear motion in a car i drew the velocity-time graph describing the motion of the if the car travels with uniform velocity for a time. Conclusion linear motion is movement in a straight line in one direction from science 413 at australian institute of applied sciences or be non uniform. Rectilinear motion with a uniform acceleration, rectilinear motion with a uniform acceleration to start our study of howard zinn essay questions. Essays are written for different purposes and for different occasions so uniform linear motion with constant velocity (also called rectilinear motion. Lab conclusion - acceleration topics: velocity physics lab report uniform rectilinear motion teacher: patrick popular essays earth space essay. Fhsst physics/rectilinear motion/equations of motion from wikibooks, open books for an open world rectilinear motion equations of motion. Uniformly accelerating motion refers to a state of motion that accelerates at a constant rate in a single direction gravity is an example of uniform acceleration an object in free fall accelerates. Rectilinear motion is another name for straight-line motion or bodies experiencing rectilinear (straight-line) motion essays miscellaneous sports. What is the equation of the uniform rectilinear motion what are some examples of rectilinear motion a freely falling body a car moving along a straight road. Uniform relativistic acceleration benjamin knorr june 19 since we will only consider rectilinear motion in one element gives also the metric for a uniform. Concerning the rectilinear motion of a free point acted on by absolute forces p 76] uniform force, or which acts. Linear motion, also called uniform motion or rectilinear motion, motion in one spatial dimension according to newton’s first law (also known as the principle of inertia), a body with no net force acting on it will either remain at rest or continue to move with uniform speed in a straight line, according to its initial condition of motion. Abstract the purpose of this experiment, was to prove the concept of the uniform linear motion by using an air track with this, we demonstrated the impulse and change in momentum, the conservation of energy and the linear motion. Because rectilinear motion takes place in one straight line, examples include a train following a straight set of tracks, a baseball thrown in a gravity-free vacuum or a penny that someone drops from.
Python \| Output using print() function Python print() function prints the message to the screen or any other standard output device. print(value(s), sep= ' ', end = '\n', file=file, flush=flush) - value(s) : Any value, and as many as you like. Will be converted to string before printed - sep=’separator’ : (Optional) Specify how to separate the objects, if there is more than one.Default :’ ‘ - end=’end’: (Optional) Specify what to print at the end.Default : ‘\n’ - file : (Optional) An object with a write method. Default :sys.stdout - flush : (Optional) A Boolean, specifying if the output is flushed (True) or buffered (False). Default: False Return Type: It returns output to the screen. Though it is not necessary to pass arguments in the print() function, it requires an empty parenthesis at the end that tells python to execute the function rather calling it by name. Now, let’s explore the optional arguments that can be used with the print() function. String literals in python’s print statement are primarily used to format or design how a specific string appears when printed using the print() function. - \n : This string literal is used to add a new blank line while printing a statement. - “” : An empty quote (“”) is used to print an empty line. GeeksforGeeks is best for DSA Content. end= ” ” statement The end keyword is used to specify the content that is to be printed at the end of the execution of the print() function. By default, it is set to “\n”, which leads to the change of line after the execution of print() statement. Example: Python print() without new line GeeksForGeeks is the best platform for DSA content GeeksForGeeks is the best platform for DSA content**Welcome to GFG The I/Os in python are generally buffered, meaning they are used in chunks. This is where flush comes in as it helps users to decide if they need the written content to be buffered or not. By default, it is set to false. If it is set to true, the output will be written as a sequence of characters one after the other. This process is slow simply because it is easier to write in chunks rather than writing one character at a time. To understand the use case of the flush argument in the print() function, let’s take an example. Imagine you are building a countdown timer, which appends the remaining time to the same line every second. It would look something like below: The initial code for this would look something like below; So, the above code adds text without a trailing newline and then sleeps for one second after each text addition. At the end of the countdown, it prints Start and terminates the line. If you run the code as it is, it waits for 3 seconds and abruptly prints the entire text at once. This is a waste of 3 seconds caused due to buffering of the text chunk as shown below: Though buffering serves a purpose, it can result in undesired effects as shown above. To counter the same issue, the flush argument is used with the print() function. Now, set the flush argument as true and again see the results. The print() function can accept any number of positional arguments. To separate these positional arguments , keyword argument “sep” is used. note: As sep , end , flush , file are keyword arguments their position does not change the result of code. Contrary to popular belief, the print() function doesn’t convert the messages into text on the screen. These are done by lower-level layers of code, that can read data(message) in bytes. The print() function is an interface over these layers, that delegates the actual printing to a stream or file-like object. By default, the print() function is bound to sys.stdout through the file argument. Example: Python print() to file Example : Using print() function in Python GeeksForGeeks x = 5 GFG Python@GeeksforGeeks
Overview of Comparative Advantage Example The following example of Comparative Advantage provides an overview of the most popular comparative advantages. Comparative Advantage can be defined as a firm’s or the organization’s comparative advantage: its ability to produce service or goods compared to another firm or entity at a lower cost of opportunity. Economist David Ricardo was the one who first coined the terminology of comparative advantage. According to his theory, the country should specialize in what they enjoy this advantage and should import in which the country lacks or is behind. Examples of Comparative Advantage in the real world (With Excel Template) Let’s take an example to understand the calculation of Comparative Advantage in the real world in a better manner. Below are a few examples of Comparative Advantages: Comparative Advantage Example – #1 Consider 2 countries (the United States and the United Kingdom) that use input such as labor to produce 2 different goods: cloth and wine. In the United Kingdom, 1 hour of labor can produce either 20 wines or 10 cloths. In the United States, 1 hour of labor can produce either 30 wines or 30 cloths. You are required to determine how should each country make optimize the use of labor, that is, by producing the good in which they have a comparative advantage. One can note that the US has an absolute advantage in either producing Wine or cloth compared with the United Kingdom. With one labor hour, it’s either 30 units of cloth or its 30 units of wine. From this, one can conclude that the United States has an absolute advantage. In order to determine the comparative advantage, we shall determine the opportunity cost of wine and cloth for both countries. For the United Kingdom: - Opportunity Cost of 1 wine = ½ unit of cloth - Opportunity Cost of 1 cloth = 2 units of wine For the United States: - Opportunity Cost of 1 wine = 1 unit of cloth - Opportunity Cost of 1 cloth = 1 unit of wine From above, we can see that the opportunity cost of producing 1 cloth in the United States is less than the United Kingdom, and the opportunity cost of producing 1 wine in the United Kingdom is less than the United States, hence from this we can conclude that the United States has a comparative advantage in producing cloth and United Kingdom has a comparative advantage in producing wine. Comparative Advantage Example – #2 Company A produces cars and bikes, and similarly, their rival company B does. However, Company B dominates in terms of producing both products. Company A claims it has a comparative advantage in producing cars over company B. Based on the below table, you are required to justify the company’s A claim. As mentioned in the problem statement, Company B indeed has an absolute advantage in producing either car or bike when compared with Company A. In order to determine the comparative advantage, we shall determine the opportunity cost of car and bike for both the firms. For Company A: - Opportunity Cost of 1 car = 2.5 unit of bike - Opportunity Cost of 1 bike = 0.40 unit of a car For Company B: - Opportunity Cost of 1 car = 2 unit of bike - Opportunity Cost of 1 bike = 0.50 unit of a car It can be observed that Company A’s opportunity cost of producing a car in place of the bike is more than the Company’s B and hence the claim made by Company A that has a comparative advantage in making a car is incorrect and rather it has a comparative advantage in producing bike. Comparative Advantage Example – 3 Below is the comparative advantage summary of PQR country and XYZ country : For Country PQR: - Opportunity Cost of 1 Smartphone = 20 unit of Beer - Opportunity Cost of 1 Beer = 0.05 units of Smartphone For Country XYZ: - Opportunity Cost of 1 Smartphone = 25 unit of Beer - Opportunity Cost of 1 Beer = 0.04 units of Smartphone Determine which country will trade for which product and given that smartphone that can be produced by using equal scare resources when both countries decide to apply a comparative advantage technique. The comparative advantage for smartphones lies with country PQR, and the comparative advantage for Beer lies with Country XYZ. And if there is free trade and both the countries decide to use the comparative advantage technique, then company XYZ should import smartphones, and Company PQR should import Beer which shall increase the available quantity of both the products. Comparative Advantage Example – 4 JP Morgan uses two web-based applications for booking their trades for fixed income securities and reports, which are FISCO and IMPACT. Both are used in different regions. One is used for the EMEA region, and another one is used for the North America Region. The management has been seeing that the following are the outputs. The management of the company is looking to either switch the system into one or use one system for one type of product. You are required to advise the management as to which system should be more preferred and for which type of product or should combine all into one system? As mentioned in the problem statement, IMPACT indeed has an absolute advantage in booking either Bond or Repos when compared with FISCO as it takes lesser time. In order to determine the comparative advantage, we shall determine the opportunity cost of booking Bond and Repo for both the web-based system. - Opportunity Cost of booking bond trade = 2.5 mins of Booking Repo - Opportunity Cost of booking Repo trade = 0.40 units of Booking Bond Trade - Opportunity Cost of booking bond trade = 2.0 mins of Booking Repo - Opportunity Cost of booking Repo trade = 0.50 units of Booking Bond Trade Since FISCO takes less time in comparison to IMPACT for booking bond trade, the same should be used to book Bond trade, whereas Repo trade should be booked in IMPACT as it takes less time to compare to FISCO. Comparative advantage can be said a theory that is based on the concept of relativity. If a company or country is relatively better at producing or making a particular product, it should make that product and should ignore anything else. As such, comparative advantage can be considered as an important concept in global trade, and that’s the reason for several countries to concentrate on trying to make or to produce certain services or goods more efficiently when compared to other countries. This has been a guide to the Comparative Advantage Example. Here we discuss the top 4 practical Comparative Advantage Example in the real world with an explanation and downloadable excel template. You can also go through our other suggested articles to learn more –
INSTRUCTIONS: click the "Open in Cocalc" link on the upper right to make the 3d graphics display. You may have to refresh your browser once or twice to load everything. Keep scrolling down until you reach the last frame, which says "The End." A conic section, or "conic", is a curve obtained by intersecting a plane with a right circular cone. Let be the angle between the cone's axis and any line that lies in the cone (a "generator"), and let be the angle between the cone's axis and the plane. (The plane is viewed "edge-on" in the figure.) The shape of the conic depends on these angles, and whether or not the plane intersects the vertex of the cone. If the plane intersects the vertex the conic is "singular"; it is an isolated point if , two intersecting lines if , or one line "counted twice" if . If the plane does not intersect the vertex the conic is "smooth". A smooth conic is an ellipse if , a hyperbola if , or a parabola if . I'll concentrate on the smooth conics. Below are some pictures. To rotate a picture select it then move the mouse holding down the left mouse button. Enlarge the picture with the mouse wheel on a PC, or "shrink or enlarge" finger motions on a mac. All the 3d pictures work better if one rotates and enlarges them. The ellipse has two special points called foci. Dandelin constructed them by placing spheres inside the cone so that each sphere is tangent to the plane at a point, and tangent to the cone along a circle that is perpendicular to the axis of the cone. (To see that this always possible, put very small spheres inside the cone then inflate them until they are in the right position.) The foci are the points where the spheres touch the plane. The foci of the ellipse have a special distance-to-foci property: The sum of the distances from the foci to the point is the same for every point on the ellipse. In the figure the purple length plus the green length is constant. The hyperbola also has two foci, constructed in a similar way using Dandelin's spheres. The foci of the hyperbola have a special distance-to-foci property: The difference of the distances from the foci to the point is the same for every point on the hyperbola. In the figure, the purple length minus the green length is constant The parabola has one special point, its focus, plus a directrix, which is a special line. As before, Dandelin constructed them by placing a sphere inside the cone, tangent to both the plane and the cone. The sphere is tangent to the plane at the focus and tangent to the cone along a circle. This circle lies in a plane that is perpendicular to the axis of the cone -- the green plane in the figure. The intersection of this plane with the plane containing the parabola is the directrix. The parabola's focus and directrix have a distance-to-focus property The distance from the focus to equals the distance from to the directrix, for every point on the parabola. In the figure the purple length equals the green length. Of course the distance to the directrix is measured along a perpendicular to the directrix. The ancients knew these distance-to-foci properties and an easy corollary: Conic-section-shaped mirrors reflect light (sound, radio waves, ...) in a special way. Ellipse: light (black line) leaving one focus reflects into the other focus. Hyperbola: light (black line) traveling toward one focus reflects toward the other focus. Parabola: light (black line) perpendicular to the directrix (green line) reflects into the focus The reflection properties follow immediately from the fact that the tangent lines (blue) bisect the obvious angles in the following figures. The proof is based on the distance-to-focus property of the ellipse, which will be proved below. The proofs for the other conics are similar. It's enough to show that the angle bisector (blue line) intersects the ellipse only at one point, . Let be any other point on the blue line. Extend the segment to so the lengths of the green segments are equal and are collinear. The blue line bisects so triangles are congruent (side-angle-side). cannot be on the ellipse because the sum of the distances are not equal. Here is our hero, Germinal Pierre Dandelin (1794-1847), Belgian soldier and professor of engineering. His proof uses a simple property of circles and tangent lines. If and are tangent to a circle at and then the lengths The same is true of spheres: if and are tangent to a sphere at and then In the figure the yellow point is on the ellipse. The red points are foci. Each line segment (red or purple) connecting the yellow point to a focus is tangent to the corresponding sphere at the focus because the segment lies in the plane and the plane is tangent to the sphere at the focus. The spheres are tangent to the cone along the green and purple circles. The green and purple segments connecting the yellow point to the circles lie in the cone. The cone is tangent to the spheres, so the segments connecting the yellow point to the circles are tangent to the spheres at the green and purple points where the segments meet the circles. Therefore, because they are tangent to the same sphere, both green segments have the same length, and both purple segments have the same length. Thus the purple length plus the green length is the same as the distance in the figure between the green point on the green circle and the purple point on the purple circle, along the line segment connecting these points in the cone. The cone, spheres, and circles are rotationally symmetric around the cone's axis, so the length of this line segment is the same no matter where the yellow point is located on the ellipse. In other words, (purple length) + (green length) is constant. The proof is similar to the proof for the ellipse. In the figure the red points are foci, the yellow point is on the hyperbola, each spheres is tangent to the cone along a green or purple circle. The green segments connecting the yellow point to the focus and green circle have equal length. The purple segment connecting yellow point to the other focus has the same length as the green-and-purple segment connecting the yellow point to the purple point on the purple circle. The difference in the distances, yellow point-on-hyperbola to foci, equals the length of the segment, green point to purple point, connecting the circles. This length is just the distance between the circles, measured along a line in the cone, so it doesn't depend on the location of the yellow point. Thus the difference beween the distances to the foci does not depend on where the yellow point is located on the hyperbola. = angle between the cone's axis and any cone generator "green" = the green segment connecting parabola to circle "black" = black segment, "blue" = segment Thus their lengths (blue), (green), (black) satisfy (blue) = (black) = (green) (blue) = (green) A picture showing the blue and black lines translated to the x-z plane so the black line coincides with the cone's axis. The blue plane is parallel to the tangent plane along the purple generator.
The foundation of all economic theory lies with “supply” and “demand.” Supply is the number of goods or services available to be sold, and demand is the number people willing to buy. The price of goods and services is determined at the intersection point where supply equals demand. Too much supply, not enough demand Think about a store owner with items left unsold. When the supply of a product increases, but demand stays the same, the retailer may reduce the price, hoping to increase demand for the product (and sell through their remaining inventory). It’s important to understand that the price of a product moves in the opposite direction to the supply available. When supply goes up, price goes down. More demand, not enough supply The opposite is true for demand: If there’s not enough supply to meet the demand, the price usually increases. For example, if an influencer posts a positive review of a product, this can increase the demand for that produce with followers. This could lead to an increase in the price of the product, as demand increases and available products become scarce. Price moves in the same direction as the demand for the product. When demand goes up, price also goes up. How does this impact everyday life? 1. Pricing of goods and services: This is best seen during end-of-season sales — when a retailer’s supply exceeds demand. For example, a clothing store has a number of winter coats left in March, as the weather becomes warmer. To sell off leftover inventory, the retailer will often reduce prices, driving demand for the lower-priced coats. Alternately, if something popular is rare or more difficult to find, like a limited edition designer handbag, the scarcity of that handbag, will drive premium pricing. 2. Job opportunities: The theory of supply and demand can also be found in the job market. If demand for a particular skill increases, but the supply of that skilled labour is in short supply, the ability to secure a job or request higher wages may be more favourable. For example, in 2022, wages for scientific and technical jobs — those that require higher levels of education and specialized training — were double that of hospitality and food services on average. 3. Housing market: Supply and demand also affects the housing market and directly impacts price. When there is a short supply of houses on the market and demand for those houses is high, the prices often rise and may even cause a bidding war. This is what’s referred to as a seller’s market because sellers can obtain more money for their home. When the supply of houses on the market exceeds demand, prices tend to drop in order to sell. This is called a buyer’s market. 4. Stock market: While it’s not the only factor that influences a stock or other security’s price, the financial market is highly driven by supply and demand. An increased demand for a particular security can lead to an increase in the price of that security, and a lack of demand can lead to a price decline. 5. Product availability: Supply and demand also impact product availability on store shelves, as manufacturers use the demand to determine the supply they are willing to produce. If demand rises unexpectedly, like during the pandemic, the available inventory can be depleted. If supply exceeds what consumers want to purchase, excess inventory remains, and a brand may reduce or discontinue making an item. Supply and demand are the bedrock on which economies are built; they shape the prices of goods and services, influence production decisions, and guide markets. As markets change, supply and demand will remain an essential compass, guiding consumers through the labyrinth of choice and opportunity. This article is intended as general information only and is not to be relied upon as constituting legal, financial or other professional advice. A professional advisor should be consulted regarding your specific situation. Information presented is believed to be factual and up-to-date but we do not guarantee its accuracy and it should not be regarded as a complete analysis of the subjects discussed. All expressions of opinion reflect the judgment of the authors as of the date of publication and are subject to change. No endorsement of any third parties or their advice, opinions, information, products or services is expressly given or implied by Royal Bank of Canada or any of its affiliates.
Why does space have structure? Why does our universe have not only stars, but galaxies and galactic clusters? Researchers recently identified 234 potential proto-clusters: candidates for early galactic clusters from when the universe was just 3 billion years old that may help solve this astrophysical mystery. Top image: An all-sky map of the universe in submillimeter wavelengths, with a bright band marking the dust of the Milky Way and black dots marking proto-cluster candidates. Credit: ESA/the Planck Collaboration/ H. Dole/D. Guéry/G. Hurier/IAS/University Paris-Sud/CNRS/CNES Galaxy clusters are vast cosmic structures containing galaxies, huge clouds of dust, and dark matter we primarily identify through its gravitational impact. We have theories for how galaxy clusters evolve — most involving initial gravity fluctuations, dark matter, and a really long time provided nothing nasty like turbulence gets in the way — but what we lack is good observations of proto-clusters to show us what the universe looked like while it was young. Unlike the challenges of seeing the first few moments of time, this is made slightly easier in that galaxies didn't start evolving until the first few billion years after the Big Bang. That may have just changed with new observations from a pair of space telescopes. How did the universe evolve to have great clusters of galaxies? Image credit: ESA The observations come from a pair of European Space Agency space telescopes: Planck, a microwave observatory, and Herschel, the only space observatory to cover wavelengths from far infrared to sub-millimetre. The Planck observatory's primary mission is to observe the Cosmic Microwave Background radiation, prying out secrets of the early universe. In an all-sky survey, researchers identified roughly 200 extra-luminous objects in Planck's data, objects that date back to the first three billion years after the Big Bang. While bothersome foreground noise for cosmological research, these objects were perfect targets for Herschel to make follow-up observations in greater detail. Planck all-sky map in 545 GHz; proto-cluster candidates identified with black dots, with insets of Herschel observations contoured by galaxy density. Image credit: ESA/the Planck Collaboration/ H. Dole/D. Guéry/G. Hurier/IAS/University Paris-Sud/CNRS/CNES This is early research so far — the team is still making observations to pin down distances, luminosities, and ages — but it looks like these may be the earliest proto-clusters, groupings that one day evolved into the galactic clusters we observe around us now. If confirmed, these proto-clusters are a half-billion years older than the next-oldest observed galaxy cluster, and may bring us new insights into how the structures first formed. Even with just preliminary data, what they have found is surprising: the objects are young galaxies producing stars hundreds to 1.5 thousand times faster than star production in our modern Milky Way. Lead author on the study Hervé Dole explains: "Finding so many intensely star-forming, dust galaxies in such concentrated groups was a huge surprise. We think this is a missing piece of cosmological structure formation." It was an exciting, chaotic time for our universe: stars, galaxies, and clusters all forming at the same time, and we really don't know exactly what was going on. It's going to take a lot more work to verify these proto-cluster candidates are what we think they are, and even more to understand how the new and future observations of them will impact galactic cluster formation theories, but that's what makes this so exciting: It's another reminder that this is a vast, mysterious universe and we have so much more to learn. Even after we get a handle on galaxy clusters, we still aren't sure what to make of the potential higher-order organization of clusters yet... Read more: The Herschel view of the dominant mode of galaxy growth from z = 4 to the present day by C. Schreiber, M. Pannella, D. Elbaz, M. Béthermin, H. Inami, M. Dickinson, B. Magnelli, T. Wang, H. Aussel, E. Daddi et al. in Astronomy and Astrophysics 575, A74 (2015). Press releases by ESA and NASA
Strategies to Calculate National Income Disclaimer: This work has been submitted by a student. This is not an example of the work written by our professional academic writers. You can view samples of our professional work here. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of UK Essays. Published: Tue, 17 Oct 2017 There are several ways to calculate national income. The most commonly methods used are product, income and expenditure approach. The product method is also called the output method using Gross National Product or GNP. These output for example are mineral, forestry and agricultural outputs. However only the final goods are considered in the national income. Fundamentally, GNP is the total value of all final goods and services. The goods and services have to be produced within the border of the country in a particular year, plus income earned by its citizens. Which include income of those located abroad regardless of their location. The data used to assess GNP include the manufacturing of tangible goods for example automotive, machinery and agricultural product and the intangible services for example education and healthcare. Note that GNP does not include the services used to produce manufactured goods because their value is included in the price of the finished product. However, GNP does include the depreciation and the indirect business taxes for example sales tax. The formula for GNP is: Gross National Product = Consumption + Government Expenditures + Investments + Exports + Foreign Production by Foreign Companies – Domestic Production by The difference between GNP and GDP (Gross Domestic Product) is that GNP includes the value of products made by the country’s citizens and companies from overseas. GDP only accounts for products made within a country’s borders. The income approach by using the Gross National Income or GNI is the sum of a nation’s gross domestic product (GDP) plus net income received from overseas. Gross national income (GNI) is defined as the sum of value added by all producers who are residents in a nation, plus any product taxes (minus subsidies) but do not include in the output production. The expenditures approach (expenditure = Y), the product approach is the Gross Domestic Product or GDP. Gross Domestic Product or also called GDP is the market value of all final goods and services produced within a country in a given period of time (Mankiw, 2013). GDP is one of the primarily indicators used to measure the well-being of a country’s economic condition. National Output = National Expenditure (Aggregate Demand) = National Income The Expenditure Method – aggregate demand (AD) The GDP equation approach GDP = consumption + investment + (government spending) + (exports – imports) Y : Income C: Household spending I: Capital Investment spending G: Government spending X: Exports of Goods and Services M: Imports of Goods and Services In the circumstance of Income Method – adding together factor incomes GDP is the sum of the incomes earned over the production of goods and services. Gross Domestic product = Income from people in jobs and in self-employment (by factor incomes) + Profits of private + sector businesses + Rent income from the ownership of land 2.1Move over, GDP: How should you measure a country’s value? Generally, Gross Domestic Product (GDP) measures the value of output produced within the domestic boundaries of a country over a period of time. A sustainable increase in real GDP means there is a sustained increase in the output of goods and services in the economy. However, GDP ignores to include the quality of life. The limitations of GDP are that it ignores the quality of life, it take too lightly illegal markets, and overestimates the negative external factors. The quality of life is used to measure the overall well-being of individuals and societies. It is also should not be confused with standard of living base on income. Instead, the quality of life should include education, employment, physical and mental health, etc. It is related with the human right, freedom of speech, making choices and live in harmony. Adequate welfare is the goal towards good health, happiness, and prosperity of a person. For example, while Russia and Saudi Arabia are an oil-rich countries most of its people live in poverty, meaning they have a low quality of life because they lack basic human needs such as food and shelter. The United States of America however has the most comprehensive healthcare in the world yet have low life expectancy. Using GDP alone is not an adequate measure of welfare. Using Social Progress Index (SPI) we can measure domestic output and income, as well as health and happiness of a person. 2.2Guest Post: Counting Brazil’s Gross National Happiness Setting happiness, as the ultimate goal, involves in the best encompassing measure. According to some people the happiness of one person depends primarily on family, friends, work satisfaction and activities. Even though income does play a major role. Unfortunately, society-wide happiness as assessed via surveys does not change much over time. Understanding the different level of well-being is important for understanding choices made by individuals and policymakers which is the government. It is impossible for GDP cannot measure the quality of the environment. Having higher real GDP does not mean people have a better quality of life if the air, water, and other resources are polluted. GDP does not reflect how production contributes to the quality of people’s lives. Its only measures how much output a country produces. 2.3The Rise of the Intangible Economy: U.S GDP Counts R&D, Artistic Creation Gross domestic product and its related concepts (such as real GDP, per capita GDP, and per capita real GDP) are incomplete measures of a country’s standard of living. There are many productive activities that are not included in GDP because it only measures output produced and sold in legal markets. It does not include productive activity that does not have a market transaction. GDP concepts are only useful in measuring a country’s output, income, and standard of living, There are many other aspects of life that are not considered in the calculation of GDP that include happiness, environmental, and health. GDP only measures the output produced and sold in legal markets. It does not include productive activity that does not have a market transaction. Honestly, all data have their limitations. Though GDP data are not perfect measures of the quality of life in a country, it is still useful in determining the standard of living. 2.4The good and the bad of China’s Growth China’s economy grew at the slowest rate for the first quarter of the year, raising fears that the government will miss its 2014 growth target of 7.5%. Gross domestic product (GDP) increased by 7.4% compared with the same period a year earlier, for the following 7.7% growth in the fourth quarter of 2013. Chinese government are trying to target 7.5% of GDP this year (2014). According to the National Bureau of Statistics data, it was the slowest rate of growth for second largest economy in the world since the third quarter of 2012, however faster than the 7.2% increase predicted by some economists. The slowing growth rate raised stimulus package from the China government in order to cushion the economic slowdown prompted by the rebalancing of China economy. The package was to boost growth adding support to the small and medium enterprises. The representation of the percentage worsened when the first three months of 2014 are compared with the final three months of 2013 with the growth slowing down to 1.4% from 1.8%. On a separate data showed that Chinese economy was dependable on investment. The expenditure comprise of building, infrastructure plant and equipment already reached 40% of its GDP. Relatively, an improved measurement of the latest economic momentum should have further eased fears that the country is facing economic slowdown. This is because the Chinese economy is likely to decline further more as the total liabilities on China Banking System reached $15 Trillion during this period. The government is trying to increase the domestic consumption due to export demand warming and infrastructure investment possibly bottoming out, subsequently a sharp slowdown could be avoided. However, the latest data is not suggesting forthcoming need for a massive government intervention and China will continue with this path of reform. 2.5Does size matter? China poised to overtake US as world’s largest economy in 2014 The gross domestic product (GDP) is one the primary indicators used to measure the condition of a country’s economy and this include China. The GDP is increasingly criticized for its failure to adequate measure the standard of living. In my view, the criticism is seemed right. With its recent GDP growth at 7.4% it hardly capable to measure the overall living standard of its citizens. Though China has the largest population in the its GDP (gross domestic product) has grown faster compare to the United States as the main global player in the astonishing global economy. Even though the report of the GDP is an essential measurement, it is not the best indicator of their citizens’ standard of living. Despite the increase in GDP growth poverty in China is becoming a problematic when it comes to improving standards of living. In the affair of a slowing economy and unwarranted political moment of rising criticism of one party state, China socioeconomic discrepancy is has risen concern. Though China’s growth declined to 7.4%, it still remains a global economic powerhouse. The government regulations rely heavily on investments both domestically and internationally for sustainability. China’s economic growth emphasis on increasing the economy domestically. GDP figures ignore the impact of declining standard of living. This because high GDP data are achieved at the expense of environmental degradation for example more pollution and congestion. Resulting with the very low standard of living. China GDP doesn’t take into account black economy or the illegal such as piracy, prostitution, drugs etc. into account. 2.6The Rise of the Intangible Economy: U.S GDP Counts R&D, Artistic Creation Intangible assets which include computer software, research and development (R&D), intellectual property, workforce training, and spending to promote the innovative creativity of firms. Recently, intangibles assets are consider a key driver of the competitiveness of United States of America economic growth and sustainability. The Bureau of Economic Analysis (BEA) specifies the important of intangible assets can be in terms of its impact on the nation’s economy. Transforming from the current method of gross domestic product (GDP), which currently a category that includes under assets as buildings, structures, equipment and tools. In particular, the focused on the role of talent and intellectual property as the intangible assets most important to future economic development. The new GDP revisions not only for the changes but also due to the fact that they are expected to instantly add about 3% to the overall size of U.S.A GDP. The significant biggest change to the GDP methodology will be the insertion of R&D as a capital investment. The changes will have a swelling effect. This new method will make corporate profits rich and assertive, as companies will no longer need to calculate the net of R&D after depreciation as a cost. Whenever we calculate the value of an investment in a new building, we rely on the market price of the land, labor, and the material it takes to construct it. However, research and development and artistic originals are not commodities. 2.7Boundary problems: America has changed the way it measures GDP This explanation of GDP is necessarily, it only described the principle of the concept. The easiest way of understanding GDP is as the total of all production of goods and services. In the economy this transaction is associated with money changes hands. Excluding in certain organized business of barter transactions which are counted as income for individuals or corporations. GDP usually does not include transactions in which no money changes hands. The exercise of associating wealth and prosperity with GDP is completely vulnerable. Wealth, is the total of all resources belonging to a country or individual citizen. We can say that a change in wealth is equal to the amount of wealth being created and the amount being destroyed or used up. 2.8World Bank chief economist on future of India’s economy India is Asia’s third largest economy has annual growth rate is below 5%. It has been weighed down by high inflation, weak currency and a decrease in Foreign Direct Investment (FDI). According to the Indian Chief Economic Advisor, overall the fundamentals of the economy are resilient. However, India economy has been relatively under the weather and there are two big challenges to overcome. The first is the poor corporate governance. This due to lake of urgency in decision making, the bureaucracy is extremely troublesome. It is not easy to change the culture over the last 60 years. The second is India need a better infrastructure. This is reasonably possible to accomplish and India needs to improve its infrastructure between five to 10 years. The prospect will be vast if only both governance and infrastructure can be improved within this period of time. When crisis occur, people will begin to take extra precautions. In order to have a full potential growth, India will need a governance overhaul. Nevertheless India has its own unique strengths for example India’s intellectual citizen, technical and engineering skill workers are countless. The motivation behind its high intellectual resource is the fact that as an emerging economy, India after Independence invested excessively in higher education. That is why there is the large Indian presence in Silicon Valley which makes about half the professional immigration to the US consists of Indians. The other strength is labour. In the past, labour resources was difficult to mobilize in the global market. With the modern technology the biggest global break through which is also a factor behind the global crisis the global labour market is gradually becoming a common pool and utilized in this is moving global economy. It shows the level of surplus labour engaged in agriculture sectors. However the major stumbling block is the poor infrastructure. China has successfully used their new small towns effectively. India can follow this concept to string of new small towns because the property is much cheaper. The Indian government has to come with a solution on how to deliver basic infrastructure and law and order. Inflation in India has occurred in at the early stages of development and that was between 2003 and 2011, India was growing at an average of 8%. In 2008, inflation was close to 10% and that is going to make the economy hurt even more. 2.9Thai GDP Growth Slows as Unrest Increases Rate-Cut Pressure According to the Bloomberg, the Thailand state planning agency today cut its 2014 GDP growth forecast to 3% to 4% from a range of 4% to 5%. Thailand GDP was mostly came from the services sectors, while agriculture and other industry hardly contributed. The economy slowed due to the weak demand from the domestic and meanwhile the exports were slow-moving. Thailand economy grew at the slowest pace in two years last quarter since the political unrest hurt local demand and tourism. Political tensions has weakened the private consumption, investment, and government spending during this time worsened. This result reflected mainly when the Thailand government became unfocussed by political pressure and staggered by legal challenges. The economic viewpoint is subject to unusually high of uncertainty. After antigovernment protests worsened in November 2013. The Thailand government dissolved the parliament in December to scheduled national elections for 2 February. This situation cause more tension and restrictions on its reliability and capability to borrow, spend, or make policy decisions. 2.10Singapore Raises 2013 GDP Growth Forecast on Manufacturing According to the Bloomberg, Singapore’s Gross domestic product (GDP) expanded an annualized 1.3% last quarter from the previous three months, compared with a 1% decline earlier. This is due to profiting from the monetary stimulus aided by the U.S. Federal Reserve’s extension as global risks remain from budgetary bickering in Washington and a promising recovery in the Europe. Singapore GDP grew 5.8% in the three months through September from a year earlier, compared with an earlier estimate of a 5.1% expansion. Being the world’s busiest container ports, Singapore has remained vulnerable to fluctuations in external demand for manufactured goods even as the government boosts financial services and tourism to cut reliance on the exports. For many years, especially since 1929 nations have associated economic growth with progress and sustainability. Economic and income growth is an increase in the production and consumption of goods and services, and is indicated by increasing Gross Domestic Product (GDP). GDP, therefore, has become the standard measure of economic progress. Even though it was only intended as a macroeconomic accounting tool. The disadvantage with GDP is that it does not separate costs from benefits. It simply adds them together under the heading of economic activity. GDP is a good measure of income size and nothing else. At the individual level, economic activity is required for wellbeing, but the relationship becomes very weak after a surprisingly low per capita GDP is derived. GDP does not shows about how income and wealth are distributed among the people. Cite This Work To export a reference to this article please select a referencing stye below:
In the coming years, many ground-based and space-based telescopes will commence operations and collect their first light from cosmic sources. This next-generation of telescopes is not only expected to see farther into the cosmos (and hence, farther back in time), they are also expected to reveal new things about the nature of our Universe, its creation and its evolution. One of these instruments is the Extremely Large Telescope, an optical telescope that is overseen by the European Southern Observatory. Once it is built, the ELT will be the largest ground-based telescope in the world. Construction began in May of 2017, and the ESO recently released a video that illustrates what it will look like when it is complete. The question how life began on Earth has always been a matter of profound interest to scientists. But just as important as how life emerged is the question of when it emerged. In addition to discerning how non-living elements came together to form the first living organisms (a process known as abiogenesis), scientists have also sought to determine when the first living organisms appeared on Earth. Ever since the first exoplanet was confirmed in 1992, astronomers have found thousands of worlds beyond our Solar System. With more and more discoveries happening all the time, the focus of exoplanet research has begun to slowly shift from exoplanet discovery to exoplanet characterization. Essentially, scientists are now looking to determine the composition of exoplanets to determine whether or not they could support life. In recent years, the number of confirmed extra-solar planets has risen exponentially. As of the penning of the article, a total of 3,777 exoplanets have been confirmed in 2,817 star systems, with an additional 2,737 candidates awaiting confirmation. What’s more, the number of terrestrial (i.e. rocky) planets has increased steadily, increasing the likelihood that astronomers will find evidence of life beyond our Solar System. Unfortunately, the technology does not yet exist to explore these planets directly. As a result, scientists are forced to look for what are known as “biosignatures”, a chemical or element that is associated with the existence of past or present life. According to a new study by an international team of researchers, one way to look for these signatures would be to examine material ejected from the surface of exoplanets during an impact event. As they indicate in their study, most efforts to characterize exoplanet biospheres have focused on the planets’ atmospheres. This consists of looking for evidence of gases that are associated with life here on Earth – e.g. carbon dioxide, nitrogen, etc. – as well as water. As Cataldi told Universe Today via email: “We know from Earth that life can have a strong impact on the composition of the atmosphere. For example, all the oxygen in our atmosphere is of biological origin. Also, oxygen and methane are strongly out of chemical equilibrium because of the presence of life. Currently, it is not yet possible to study the atmospheric composition of Earth-like exoplanets, however, such a measurement is expected to become possible in the foreseeable future. Thus, atmospheric biosignatures are the most promising way to search for extraterrestrial life.” However, Cataldi and his colleagues considered the possibility of characterizing a planet’s habitability by looking for signs of impacts and examining the ejecta. One of the benefits of this approach is that ejecta escapes lower gravity bodies, such as rocky planets and moons, with the greatest ease. The atmospheres of these types of bodies are also very difficult to characterize, so this method would allow for characterizations that would not otherwise be possible. And as Cataldi indicated, it would also be complimentary to the atmospheric approach in a number of ways: “First, the smaller the exoplanet, the more difficult it is to study its atmosphere. On the contrary, smaller exoplanets produce larger amounts of escaping ejecta because their surface gravity is lower, making ejecta from smaller exoplanet easier to detect. Second, when thinking about biosignatures in impact ejecta, we think primarily of certain minerals. This is because life can influence the mineralogy of a planet either indirectly (e.g. by changing the composition of the atmosphere and thus allowing new minerals to form) or directly (by producing minerals, e.g. skeletons). Impact ejecta would thus allow us to study a different sort of biosignature, complementary to atmospheric signatures.” Another benefit to this method is the fact that it takes advantage of existing studies that have examined the impacts of collisions between astronomical objects. For instance, multiple studies have been conducted that have attempted to place constraints on the giant impact that is believed to have formed the Earth-Moon system 4.5 billion years ago (aka. the Giant Impact Hypothesis). While such giant collisions are thought to have been common during the final stage of terrestrial planet formation (lasting for approximately 100 million years), the team focused on impacts of asteroidal or cometary bodies, which are believed to occur over the entire lifetime of an exoplanetary system. Relying on these studies, Cataldi and his colleagues were able to create models for exoplanet ejecta. As Cataldi explained, they used the results from the impact cratering literature to estimate the amount of ejecta created. To estimate the signal strength of circumstellar dust disks created by the ejecta, they used the results from debris disk (i.e. extrasolar analogues of the Solar System’s Main Asteroid Belt) literature. In the end, the results proved rather interesting: “We found that an impact of a 20 km diameter body produces enough dust to be detectable with current telescopes (for comparison, the size of the impactor that killed the dinosaurs 65 million years ago is though to be around 10 km). However, studying the composition of the ejected dust (e.g. search for biosignatures) is not in the reach of current telescopes. In other words, with current telescopes, we could confirm the presence of ejected dust, but not study its composition.” In short, studying material ejected from exoplanets is within our reach and the ability to study its composition someday will allow astronomers to be able to characterize the geology of an exoplanet – and thus place more accurate constraints on its potential habitability. At present, astronomers are forced to make educated guesses about a planet’s composition based on its apparent size and mass. Unfortunately, a more detailed study that could determine the presence of biosignatures in ejecta is not currently possible, and will be very difficult for even next-generation telescopes like the James Webb Space Telescope (JWSB) or Darwin. In the meantime, the study of ejecta from exoplanets presents some very interesting possibilities when it comes to exoplanet studies and characterization. As Cataldi indicated: “By studying the ejecta from an impact event, we could learn something about the geology and habitability of the exoplanet and potentially detect a biosphere. The method is the only way I know to access the subsurface of an exoplanet. In this sense, the impact can be seen as a drilling experiment provided by nature. Our study shows that dust produced in an impact event is in principle detectable, and future telescopes might be able to constrain the composition of the dust, and therefore the composition of the planet.” In the coming decades, astronomers will be studying extra-solar planets with instruments of increasing sensitivity and power in the hopes of finding indications of life. Given time, searching for biosignatures in the debris around exoplanets created by asteroid impacts could be done in tandem with searchers for atmospheric biosignatures. With these two methods combined, scientists will be able to say with greater certainty that distant planets are not only capable of supporting life, but are actively doing so! In the course of discovering planets beyond our Solar System, astronomers have found some truly interesting customers! In addition to “Super-Jupiters” (exoplanets that are many times Jupiter’s mass) a number of “Hot Jupiters” have also been observed. These are gas giants that orbit closely to their stars, and in some cases, these planets have been found to be so hot that they could melt stone or metal. This has led to the designation “ultra-hot Jupiter”, the hottest of which was discovered last year. But now, according to a recent study made by an international team of astronomers, this planet is hot enough to turn metal into vapor. It is known as KELT-9b, a gas giant located 650 light-years from Earth that has atmospheric temperatures so hot – over 4,000 °C (7,232 °F) – it can vaporize iron and titanium! The study which describes their findings – “Atomic iron and titanium in the atmosphere of the exoplanet KELT-9b” – recently appeared in the scientific journal Nature. For the sake of their study, the team sought to place constraints on the chemical composition of an ultra-hot Jupiter since these planets straddle the boundary between gas giants and stars and could help astronomers learn more about exoplanet formation history. To do this, they selected KELT-9b, which was originally discovered in 2017 by astronomers using the Kilodegree Extremely Little Telescope(s) (KELT) survey. Like all ultra-hot Jupiters, this planet orbits very close to its star – 30 times closer than the Earth’s distance from the Sun – and has a orbital period of 36 hours. As a result, it experiences surface temperatures in excess of 4,000 °C (7,232 °F), making it hotter than many stars. Based on this, Dr. Hoeijmakers and his colleagues conducted a theoretical study that predicted the presence of iron vapor in the planet’s atmosphere. As Kevin Heng, a professor at the UNIBE and a co-author on the study, explained in a recent UNIGE press release: “The results of these simulations show that most of the molecules found there should be in atomic form, because the bonds that hold them together are broken by collisions between particles that occur at these extremely high temperatures.” To test this prediction, the team relied on data from the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-North or HARPS-N) spectrograph during a single transit of the exoplanet. During a transit, light from the star can been seen filtering through the atmosphere, and examining this light with a spectrometer can reveal things about the atmosphere’s chemical composition. What they found were strong indications of not only singly-ionized atomic iron but singly-ionized atomic titanium, which has a significantly higher melting point – 1670 °C (3040 °F) compared to 1250 °C (2282 °F). As Hoeijmakers explained, “With the theoretical predictions in hand, it was like following a treasure map, and when we dug deeper into the data, we found even more.” In addition to revealing the composition of a new class of ultra-hot Jupiter, this study has also presented astronomers with something of a mystery. For example, scientists believe that many planets have evaporated due to being in a tight orbit with a bright star in the same way that KELT-9b is. And, as their study indicates, the star’s radiation is breaking down heavy transition metals like iron and titanium. Although KELT-9b is probably too massive to ever totally evaporate, this new study demonstrates the strong impact that stellar radiation has on the composition of a planet’s atmosphere. On cooler gas giants, elements like iron and titanium are believed to take the form of gaseous oxides or dust particles, which are difficult to detect. But in the case of KELT-9b, the fact that these elements are in atomized form makes them highly detectable. As David Ehrenreich, the principal investigator with the UNIGE’s FOUR ACES team and a co-author on the study, concluded,“This planet is a unique laboratory to analyze how atmospheres can evolve under intense stellar radiation.” Looking ahead, the team’s study also predicts that it should be possible to observe gaseous atomic iron in the planet’s atmosphere using current telescopes. In short, astronomers need not wait for next-generation telescopes in order to study this unique planetary laboratory, which can teach astronomers much about the process of exoplanet formation. And in by learning more about the formation of gas giants in other star systems, astronomers are likely to gain vital clues as to how our own Solar System formed and evolved. Who knows? Perhaps our own Jupiter was hot at one time, and lost mass before it migrating to its current position. Or perhaps Mercury is the burnt-out husk of a once giant planet that lost its gaseous layers. As the study of exoplanets is teaching us, such strange things are known to happen in this Universe! The mission recently started science operations (on July 25th, 2018) and is expected to transmit its first collection of data back to Earth this month. But before that, the planet-hunting telescope took a series of images that featured a recently-discovered comet known as C/2018 N1. These images helped demonstrate the satellite’s ability to collect images over a broad region of the sky – which will be critical when it comes to finding exoplanets. As the name would suggest, the TESS mission is designed to search for planets around distant stars using the Transit Method (aka. Transit Photometry). For this method, distant stars are monitored for periodic dips in brightness, which are indications that a planet is passing in front of the star (aka. transiting) relative to the observer. From these dips, astronomers are able to estimate a planet’s size and orbital period. This method remains the most effective and popular means for finding exoplanets, accounting for 2,951 of the 3,774 confirmed discoveries made to date. To test its instruments before it began science operations, TESS took images of C/2018 N1 over a short period near the end of the mission’s commissioning phase – which occurred over the course of 17 hours on July 25th. The comet that it managed to capture, C/2018 N1, was discovered by NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) satellite on June 29th. This comet is located about 48 million km (29 million mi) from Earth in the southern constellation Piscis Austrinus. In these pictures, which were compiled into a video (shown below), the comet is seen as a bright dot against a background of stars and other objects. As it moves across the frame (from right to left), the comet’s tail can be seen extending to the top of the frame, and gradually changes direction as the comet glides across the field of view. The images also reveal a considerable amount of astronomical activity in the background. For instance, image processing causes the stars to shift between white and black, which highlights some variable stars visible in the images. These are stars that change brightness as a result of pulsation, rapid rotation, or being eclipsed by a binary neighbor. A number of Solar System asteroids are also visible as small white dots moving across the field of view. Last, but not least, some stray light that was reflected from Mars is also visible near the end of the video. This light appears as a faint broad arc that moves across the middle section of the frame, from left to right. This effect was due to the fact that Mars was at its brightest at the time since it was near opposition (i.e. at the closest point in its orbit to Earth). These images showcase the capabilities of the TESS mission, even though they only show a fraction of the instrument’s active field of view. In the coming weeks and months, TESS science team will continue to fine-tune the spacecraft’s performance as it searches for extra-solar planets. As noted, it is expected that TESS will find thousands of planets in our galaxy, vastly increasing our knowledge of exoplanets and the kinds of worlds that exist beyond our Solar System! And be sure to check out the video of the images TESS captured, courtesy of NASA’s Goddard Space Flight Center: The James Webb Space Telescope is like the party of the century that keeps getting postponed. Due to its sheer complexity and some anomalous readings that were detected during vibration testing, the launch date of this telescope has been pushed back many times – it is currently expected to launch sometime in 2021. But for obvious reasons, NASA remains committed to seeing this mission through. Once deployed, the JWST will be the most powerful space telescope in operation, and its advanced suite of instruments will reveal things about the Universe that have never before been seen. Among these are the atmospheres of extra-solar planets, which will initially consist of gas giants. In so doing, the JWST will refine the search for habitable planets, and eventually begin examining some potential candidates. The JWST will be doing this in conjunction with the Transiting Exoplanet Survey Satellite (TESS), which deployed to space back in April of 2018. As the name suggests, TESS will be searching for planets using the Transit Method (aka. Transit Photometry), where stars are monitored for periodic dips in brightness – which are caused by a planet passing in front of them relative to the observer. Some of Webb’s first observations will be conducted through the Director’s Discretionary Early Release Science program – a transiting exoplanet planet team at Webb’s science operation center. This team is planning on conducting three different types of observations that will provide new scientific knowledge and a better understanding of Webb’s science instruments. As Jacob Bean of the University of Chicago, a co-principal investigator on the transiting exoplanet project, explained in a NASA press release: “We have two main goals. The first is to get transiting exoplanet datasets from Webb to the astronomical community as soon as possible. The second is to do some great science so that astronomers and the public can see how powerful this observatory is.” As Natalie Batalha of NASA Ames Research Center, the project’s principal investigator, added: “Our team’s goal is to provide critical knowledge and insights to the astronomical community that will help to catalyze exoplanet research and make the best use of Webb in the limited time we have available.” For their first observation, the JWST will be responsible for characterizing a planet’s atmosphere by examining the light that passes through it. This happens whenever a planet transits in front of a star, and the way light is absorbed at different wavelengths provides clues as to the atmosphere’s chemical composition. Unfortunately, existing space telescopes have not had the necessary resolution to scan anything smaller than a gas giant. The JWST, with its advanced infrared instruments, will examine the light passing through exoplanet atmospheres, split it into a rainbow spectrum, and then infer the atmospheres’ composition based on which sections of light are missing. For these observations, the project team selected WASP-79b, a Jupiter-sized exoplanet that orbits a star in the Eridanus constellation, roughly 780 light-years from Earth. The team expects to detect and measure the abundances of water, carbon monoxide, and carbon dioxide in WASP-79b, but is also hoping to find molecules that have not yet been detected in exoplanet atmospheres. For their second observation, the team will be monitoring a “hot Jupiter” known as WASP-43b, a planet which orbits its star with a period of less than 20 hours. Like all exoplanets that orbit closely to their stars, this gas giant is tidally-locked – where one side is always facing the star. When the planet is in front of the star, astronomers are only able to see its cooler backside; but as it orbits, the hot day-side slowly comes into view. By observing this planet for the entirety of its orbit, astronomers will be able to observe those variations (known as a phase curve) and use the data to map the planet’s temperature, clouds, and atmospheric chemistry. This data will allow them to sample the atmosphere to different depths and obtain a more complete picture of the planet’s internal structure. As Bean indicated: “We have already seen dramatic and unexpected variations for this planet with Hubble and Spitzer. With Webb we will reveal these variations in significantly greater detail to understand the physical processes that are responsible.” For their third observation, the team will be attempting to observe a transiting planet directly. This is very challenging, seeing as how the star’s light is much brighter and therefore obscures the faint light being reflected off the planet’s atmosphere. One method for addressing this is to measure the light coming from a star when the planet is visible, and again when it disappears behind the star. By comparing the two measurements, astronomers can calculate how much light is coming from the planet alone. This technique works best for very hot planets that glow brightly in infrared light, which is why they selected WASP-18b for this observation – a hot Jupiter that reaches temperatures of around 2,900 K (2627 °C; 4,800 °F). In the process, they hope to determine the composition of the planet’s smothering stratosphere. In the end, these observations will help test the abilities of the JWST and calibrate its instruments. The ultimate goal will be to examine the atmospheres of potentially-habitable exoplanets, which in this case will include rocky (aka. “Earth-like”) planets that orbit low mass, dimmer red dwarf stars. In addition to being the most common star in our galaxy, red dwarfs are also believed to be the most likely place to find Earth-like planets. “TESS should locate more than a dozen planets orbiting in the habitable zones of red dwarfs, a few of which might actually be habitable. We want to learn whether those planets have atmospheres and Webb will be the one to tell us. The results will go a long way towards answering the question of whether conditions favorable to life are common in our galaxy.” The James Webb Space Telescope will be the world’s premier space science observatory once deployed, and will help astronomers to solve mysteries in our Solar System, study exoplanets, and observe the very earliest periods of the Universe to determine how its large-scale structure evolved over time. For this reason, its understandable why NASA is asking that the astronomical community be patient until they are sure it will deploy successfully. When the payoff is nothing short of ground-breaking discoveries, it’s only fair that we be willing to wait. In the meantime, be sure to check out this video about how scientists study exoplanet atmospheres, courtesy of the Space Telescope Science Institute: The gas/ice giant Uranus has long been a source of mystery to astronomers. In addition to presenting some thermal anomalies and a magnetic field that is off-center, the planet is also unique in that it is the only one in the Solar System to rotate on its side. With an axial tilt of 98°, the planet experiences radical seasons and a day-night cycle at the poles where a single day and night last 42 years each. Thanks to a new study led by researchers from Durham University, the reason for these mysteries may finally have been found. With the help of NASA researchers and multiple scientific organizations, the team conducted simulations that indicated how Uranus may have suffered a massive impact in its past. Not only would this account for the planet’s extreme tilt and magnetic field, it would also explain why the planet’s outer atmosphere is so cold. “Uranus spins on its side, with its axis pointing almost at right angles to those of all the other planets in the solar system. This was almost certainly caused by a giant impact, but we know very little about how this actually happened and how else such a violent event affected the planet.” To determine how a giant impact would affect Uranus, the team conducted a suite of smoothed particle hydrodynamics (SPH) simulations, which were also used in the past to model the giant impact that led to the formation of the Moon (aka. the Giant Impact Theory). All told, the team ran more than 50 different impact scenarios using a high-powered computer to see if it would recreate the conditions that shaped Uranus. In the end, the simulations confirmed that Uranus’ tilted position was caused by a collision with a massive object (between two and three Earth masses) that took place roughly 4 billion years ago – i.e. during the formation of the Solar System. This was consistent with a previous study that indicated that an impact with a young proto-planet made of rock and ice could have been responsible for Uranus’ axial tilt. “Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today,” said Kegerries. In addition, the simulations answered a fundamental questions about Uranus that was raised in response to previous studies. Essentially, scientists have wondered how Uranus could retain its atmosphere after a violent collision, which would have theoretically blown off its out layers of hydrogen and helium gas. According to the team’s simulations, this was most likely because the impact struck a grazing a blow on Uranus. This would have been enough to alter Uranus’ tilt, but was not strong enough to remove its outer atmosphere. In addition, their simulations indicated that the impact could have jettisoned rock and ice into orbit around the planet. This could then have coalesced to form the planet’s inner satellites and altered the rotation of any pre-existing moons already in orbit around Uranus. Last, but not least, the simulations offered a possible explanation for how Uranus got its off-center magnetic field and its thermal anomalies. In short, the impact could have created molten ice and lopsided lumps of rock inside the planet (thus accounting for its magnetic field). It could have also created a thin shell of debris near the edge of the planet’s ice layer which would have trapped internal heat, which could explain why Uranus’ outer atmosphere experiences extremely cold temperatures of -216 °C (-357 °F). Beyond helping astronomers to understand Uranus, one of the least-understood planets in the Solar System, the study also has implications when it comes to the study of exoplanets. So far, most of the planets discovered in other star systems have been comparable in size and mass to Uranus. As such, the researchers hope their findings will shed light on these planet’s chemical compositions and explain how they evolved. As Dr. Luis Teodoro – of the BAER Institute and NASA Ames Research Center – and one of the co-authors on the paper, said, “All the evidence points to giant impacts being frequent during planet formation, and with this kind of research we are now gaining more insight into their effect on potentially habitable exoplanets.” In the coming years, additional missions are planned to study the outer Solar System and the giant planets. These studies will not only help astronomers understand how our Solar System evolved, they could also tell us what role gas giants play when it comes to habitability.
One of the most widely known instructional design model is the Dick and Carey model. Since 1968, several versions of this model have been developed (Dick & Carey, 2004). Throughout the time Dick and Carey model had been modified and can be used in business now. Nowadays, Dick and Carey model is still used and has helped shape other models like Kirkpatrick model. Another important model is called Diamond Model, created by Robert Diamond. It is specially formed for institutions of higher education and provides a great example of a team work. The author believed that cooperation between different types of people will bring fruitful results at the end. A lot of visual materials are used in this model and it distinguishes this pattern from others. Dick and Carey model could be called a macro-level model because it covers the whole design task and gives detailed steps that will help to achieve a goal. Although Diamond model is more flexible, it helps to find the most appropriate solution for a particular situation. Using own ideas and methods to achieve a goal will provoke a person to create new solutions and approaches. Diamond model stimulates a person to think “out-of-box”, to ignore traditional solutions or methods, and it requires analyzing a current social situation, being realistic and being able to solve a problem on your own. Get this EXCLUSIVE benefits for FREE Outline (on demand) Instructional design model consists of the reductionist model of breaking instructions into smaller elements. It comprises 9 stages, starting with identifying goals and ending with summative evaluation. At the first stage, it is necessary to identify instructional goals. It is important to understand what the goal of the instruction is and what learners will be able to do at the end. The second stage refers to conducting the instructional analysis. It determines skills and knowledge required for students to do the instruction. Next stage is identifying entry behaviors. It distinguishes skills that students will bring to the learning task. Writing performance objectives deal with interpreting the needs and targets into specific objectives. The fifth stage is called Developing Criterion-Reference Test Items and it focuses on developing prerequisites for learning new skills and identifying how to check students` results and, at this time, provide these results to them (Gustafson, 2002).Another stage is an instructional Strategy. It determines what kind of activities student should follow to achieve the goal (giving examples, practice, feedback, pretest, memorization etc.).The seventh stage is to develop and select instructional materials. It works with types of materials that are necessary to use (printed, media etc.).Developing and conducting Formative Evaluation means to improve instructional materials and to make them effective for as many students as possible. And the last stage determines the summative evaluation. The task is to understand how effective the system was in whole and whether students achieved their goals. In comparison to instructional design model, the Diamond model includes only 5 stages: 1) defining the need to change 2) determining aims and results 3) identifying instructions and assessments that will help to achieve the goal 4) fulfillment of the goal using assessments 5) revision of a result and desired outcome. In this model, stages are not so clear written and explained because students should have the possibility to decide on their own what needs to be done to achieve the goal. Also, this model includes two Phases and each Phase incorporates with some stages in Dick and Carey Model. Phase I consists of project selection and design (Diamond, 1989). These stages are mentioned in Dick and Carey Model till the fifth stage. The difference is that Dick and Carey Model is more detailed so the first phase in that model consists of more steps. Phase II contains production, implementation and evaluation that corresponds to last 5 stages in Dick and Carey Model (Diamond, 1989). The difference is in another formulation of instructions, but the meaning remains the same. Also in Dick and Carey model, all stages are described more elaborated and it gives step-by-step instructions what should be done. The similarity of these two models is that each of them has an objective plan for students but different steps are used to achieve goals. Dick and Carey model can be called as an organized model. It gives students definite instructions how to achieve their goals. The Diamond model emphasizes on spontaneous decisions of a student and gives some instructions, but they are not so detailed. A student has the only general idea about instructions and he decides on his own what methods or actions are needed for getting the desired result. The advantage of Dick and Carey model is that it provides detailed instructions to a student so he can successfully finish the task. In Diamond, model student should use his own ideas and there is a possibility that the task will not be finished or will be finished partially because of the lack of ideas. In addition, Dick and Carey model can be used for large or small audiences of a different age, while Diamond model is preferably for students of higher educational institutions and big groups of people. Although in Dick and Carey model learners don’t consider the current social situation and it can be a problem to achieve the goal. In Diamond model daily situation is over thought and took into attention, so this model could be called more flexible. In order to fulfill all steps in Diamond model, you don’t need to spend too much time, but finishing Dick and Carey model will take a great deal of time because of many steps to follow. Also, each level in this model is difficult to understand and students need a careful and appropriate explanation. In Diamond model all steps are clearer and more accessible, so students will not have problems with understanding. In Diamond model people work in teams and it has a good influence on the result and on people in a whole, while Dick and Carey’s model implies single work that doesn’t train teamwork skills. Both models are goal-directed but the difference is that in Diamond model students can change their actions within the task depending on the situation, while Dick and Carey’s model instructions are not so flexible and students are able to change something only after finishing the task. At the same time, Diamond model provokes creative and innovative decisions, while Dick and Carey’s model is based on the traditional boundaries. Another point is that according to Diamond model many visual materials can be used, so it helps a student to get information quicker. Dick and Carey model is usually used without any diagrams or graphics and can cause some difficulties in realizing the task or situation. At the end of the task, all students will reach their goals but this will be achieved with the help of different methods. Dick and Carey’s model seems to be easier for students because it is clear, detailed and easy to follow. Diamond model is more difficult and demanding. That is why this model is likely to be used in higher educational institutions than schools. There are a lot of advantages and disadvantages of each model that could significantly influence on the educator`s choice. Using this or that method depends on many factors starting from the age of the audience and ending with the current social situation in a particular area. The task of an educator is to choose the appropriate model for his audience and make everything possible to help students achieve their goals. \|Benefits of Technology to the Society\|\|People Change Management\|
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To search, use the text box at the bottom of the book. Click a search result to be taken to that chapter or section of the book (note you may need to scroll down to get to the result). View Full Student FAQs 11.4 Vapor Pressure - To know how and why the vapor pressure of a liquid varies with temperature. Nearly all of us have heated a pan of water with the lid in place and shortly thereafter heard the sounds of the lid rattling and hot water spilling onto the stovetop. When a liquid is heated, its molecules obtain sufficient kinetic energy to overcome the forces holding them in the liquid and they escape into the gaseous phase. By doing so, they generate a population of molecules in the vapor phase above the liquid that produces a pressure—the vapor pressureThe pressure created over a liquid by the molecules of a liquid substance that have enough kinetic energy to escape to the vapor phase. of the liquid. In the situation we described, enough pressure was generated to move the lid, which allowed the vapor to escape. If the vapor is contained in a sealed vessel, however, such as an unvented flask, and the vapor pressure becomes too high, the flask will explode (as many students have unfortunately discovered). In this section, we describe vapor pressure in more detail and explain how to quantitatively determine the vapor pressure of a liquid. Evaporation and Condensation Because the molecules of a liquid are in constant motion, we can plot the fraction of molecules with a given kinetic energy (KE) against their kinetic energy to obtain the kinetic energy distribution of the molecules in the liquid (Figure 11.13 "The Distribution of the Kinetic Energies of the Molecules of a Liquid at Two Temperatures"), just as we did for a gas (Figure 10.19 "The Wide Variation in Molecular Speeds Observed at 298 K for Gases with Different Molar Masses"). As for gases, increasing the temperature increases both the average kinetic energy of the particles in a liquid and the range of kinetic energy of the individual molecules. If we assume that a minimum amount of energy (E0) is needed to overcome the intermolecular attractive forces that hold a liquid together, then some fraction of molecules in the liquid always has a kinetic energy greater than E0. The fraction of molecules with a kinetic energy greater than this minimum value increases with increasing temperature. Any molecule with a kinetic energy greater than E0 has enough energy to overcome the forces holding it in the liquid and escape into the vapor phase. Before it can do so, however, a molecule must also be at the surface of the liquid, where it is physically possible for it to leave the liquid surface; that is, only molecules at the surface can undergo evaporation (or vaporization)The physical process by which atoms or molecules in the liquid phase enter the gas or vapor phase., where molecules gain sufficient energy to enter a gaseous state above a liquid’s surface, thereby creating a vapor pressure. Figure 11.13 The Distribution of the Kinetic Energies of the Molecules of a Liquid at Two Temperatures Just as with gases, increasing the temperature shifts the peak to a higher energy and broadens the curve. Only molecules with a kinetic energy greater than E0 can escape from the liquid to enter the vapor phase, and the proportion of molecules with KE > E0 is greater at the higher temperature. To understand the causes of vapor pressure, consider the apparatus shown in Figure 11.14 "Vapor Pressure". When a liquid is introduced into an evacuated chamber (part (a) in Figure 11.14 "Vapor Pressure"), the initial pressure above the liquid is approximately zero because there are as yet no molecules in the vapor phase. Some molecules at the surface, however, will have sufficient kinetic energy to escape from the liquid and form a vapor, thus increasing the pressure inside the container. As long as the temperature of the liquid is held constant, the fraction of molecules with KE > E0 will not change, and the rate at which molecules escape from the liquid into the vapor phase will depend only on the surface area of the liquid phase. Figure 11.14 Vapor Pressure (a) When a liquid is introduced into an evacuated chamber, molecules with sufficient kinetic energy escape from the surface and enter the vapor phase, causing the pressure in the chamber to increase. (b) When sufficient molecules are in the vapor phase for a given temperature, the rate of condensation equals the rate of evaporation (a steady state is reached), and the pressure in the container becomes constant. As soon as some vapor has formed, a fraction of the molecules in the vapor phase will collide with the surface of the liquid and reenter the liquid phase in a process known as condensationThe physical process by which atoms or molecules in the vapor phase enter the liquid phase. (part (b) in Figure 11.14 "Vapor Pressure"). As the number of molecules in the vapor phase increases, the number of collisions between vapor-phase molecules and the surface will also increase. Eventually, a steady state will be reached in which exactly as many molecules per unit time leave the surface of the liquid (vaporize) as collide with it (condense). At this point, the pressure over the liquid stops increasing and remains constant at a particular value that is characteristic of the liquid at a given temperature. The rates of evaporation and condensation over time for a system such as this are shown graphically in Figure 11.15 "The Relative Rates of Evaporation and Condensation as a Function of Time after a Liquid Is Introduced into a Sealed Chamber". Figure 11.15 The Relative Rates of Evaporation and Condensation as a Function of Time after a Liquid Is Introduced into a Sealed Chamber The rate of evaporation depends only on the surface area of the liquid and is essentially constant. The rate of condensation depends on the number of molecules in the vapor phase and increases steadily until it equals the rate of evaporation. Equilibrium Vapor Pressure Two opposing processes (such as evaporation and condensation) that occur at the same rate and thus produce no net change in a system, constitute a dynamic equilibriumA state in which two opposing processes occur at the same rate, thus producing no net change in the system.. In the case of a liquid enclosed in a chamber, the molecules continuously evaporate and condense, but the amounts of liquid and vapor do not change with time. The pressure exerted by a vapor in dynamic equilibrium with a liquid is the equilibrium vapor pressureThe pressure exerted by a vapor in dynamic equilibrium with its liquid. of the liquid. If a liquid is in an open container, however, most of the molecules that escape into the vapor phase will not collide with the surface of the liquid and return to the liquid phase. Instead, they will diffuse through the gas phase away from the container, and an equilibrium will never be established. Under these conditions, the liquid will continue to evaporate until it has “disappeared.” The speed with which this occurs depends on the vapor pressure of the liquid and the temperature. Volatile liquidsA liquid with a relatively high vapor pressure. have relatively high vapor pressures and tend to evaporate readily; nonvolatile liquidsA liquid with a relatively low vapor pressure. have low vapor pressures and evaporate more slowly. Although the dividing line between volatile and nonvolatile liquids is not clear-cut, as a general guideline, we can say that substances with vapor pressures greater than that of water (Table 11.4 "Surface Tension, Viscosity, Vapor Pressure (at 25°C Unless Otherwise Indicated), and Normal Boiling Points of Common Liquids") are relatively volatile, whereas those with vapor pressures less than that of water are relatively nonvolatile. Thus diethyl ether (ethyl ether), acetone, and gasoline are volatile, but mercury, ethylene glycol, and motor oil are nonvolatile. The equilibrium vapor pressure of a substance at a particular temperature is a characteristic of the material, like its molecular mass, melting point, and boiling point (Table 11.4 "Surface Tension, Viscosity, Vapor Pressure (at 25°C Unless Otherwise Indicated), and Normal Boiling Points of Common Liquids"). It does not depend on the amount of liquid as long as at least a tiny amount of liquid is present in equilibrium with the vapor. The equilibrium vapor pressure does, however, depend very strongly on the temperature and the intermolecular forces present, as shown for several substances in Figure 11.16 "The Vapor Pressures of Several Liquids as a Function of Temperature". Molecules that can hydrogen bond, such as ethylene glycol, have a much lower equilibrium vapor pressure than those that cannot, such as octane. The nonlinear increase in vapor pressure with increasing temperature is much steeper than the increase in pressure expected for an ideal gas over the corresponding temperature range. The temperature dependence is so strong because the vapor pressure depends on the fraction of molecules that have a kinetic energy greater than that needed to escape from the liquid, and this fraction increases exponentially with temperature. As a result, sealed containers of volatile liquids are potential bombs if subjected to large increases in temperature. The gas tanks on automobiles are vented, for example, so that a car won’t explode when parked in the sun. Similarly, the small cans (1–5 gallons) used to transport gasoline are required by law to have a pop-off pressure release. Figure 11.16 The Vapor Pressures of Several Liquids as a Function of Temperature The point at which the vapor pressure curve crosses the P = 1 atm line (dashed) is the normal boiling point of the liquid. Note the Pattern Volatile substances have low boiling points and relatively weak intermolecular interactions; nonvolatile substances have high boiling points and relatively strong intermolecular interactions. The exponential rise in vapor pressure with increasing temperature in Figure 11.16 "The Vapor Pressures of Several Liquids as a Function of Temperature" allows us to use natural logarithms to express the nonlinear relationship as a linear one.For a review of natural logarithms, refer to Essential Skills 6 in Section 11.9 "Essential Skills 6". where ln P is the natural logarithm of the vapor pressure, ΔHvap is the enthalpy of vaporization, R is the universal gas constant [8.314 J/(mol·K)], T is the temperature in kelvins, and C is the y-intercept, which is a constant for any given line. A plot of ln P versus the inverse of the absolute temperature (1/T) is a straight line with a slope of −ΔHvap/R. Equation 11.1, called the Clausius–Clapeyron equationA linear relationship that expresses the nonlinear relationship between the vapor pressure of a liquid and temperature: ln where is pressure, is the heat of vaporization, is the universal gas constant, is the absolute temperature, and C is a constant. The Clausius–Clapeyron equation can be used to calculate the heat of vaporization of a liquid from its measured vapor pressure at two or more temperatures., can be used to calculate the ΔHvap of a liquid from its measured vapor pressure at two or more temperatures. The simplest way to determine ΔHvap is to measure the vapor pressure of a liquid at two temperatures and insert the values of P and T for these points into Equation 11.2, which is derived from the Clausius–Clapeyron equation: Conversely, if we know ΔHvap and the vapor pressure P1 at any temperature T1, we can use Equation 11.2 to calculate the vapor pressure P2 at any other temperature T2, as shown in Example 6. The experimentally measured vapor pressures of liquid Hg at four temperatures are listed in the following table: From these data, calculate the enthalpy of vaporization (ΔHvap) of mercury and predict the vapor pressure of the liquid at 160°C. (Safety note: mercury is highly toxic; when it is spilled, its vapor pressure generates hazardous levels of mercury vapor.) Given: vapor pressures at four temperatures Asked for: ΔHvap of mercury and vapor pressure at 160°C A Use Equation 11.2 to obtain ΔHvap directly from two pairs of values in the table, making sure to convert all values to the appropriate units. B Substitute the calculated value of ΔHvap into Equation 11.2 to obtain the unknown pressure (P2). A The table gives the measured vapor pressures of liquid Hg for four temperatures. Although one way to proceed would be to plot the data using Equation 11.1 and find the value of ΔHvap from the slope of the line, an alternative approach is to use Equation 11.2 to obtain ΔHvap directly from two pairs of values listed in the table, assuming no errors in our measurement. We therefore select two sets of values from the table and convert the temperatures from degrees Celsius to kelvins because the equation requires absolute temperatures. Substituting the values measured at 80.0°C (T1) and 120.0°C (T2) into Equation 11.2 gives B We can now use this value of ΔHvap to calculate the vapor pressure of the liquid (P2) at 160.0°C (T2): Using the relationship eln x = x, we have At 160°C, liquid Hg has a vapor pressure of 4.21 torr, substantially greater than the pressure at 80.0°C, as we would expect. The vapor pressure of liquid nickel at 1606°C is 0.100 torr, whereas at 1805°C, its vapor pressure is 1.000 torr. At what temperature does the liquid have a vapor pressure of 2.500 torr? As the temperature of a liquid increases, the vapor pressure of the liquid increases until it equals the external pressure, or the atmospheric pressure in the case of an open container. Bubbles of vapor begin to form throughout the liquid, and the liquid begins to boil. The temperature at which a liquid boils at exactly 1 atm pressure is the normal boiling pointThe temperature at which a substance boils at a pressure of 1 atm. of the liquid. For water, the normal boiling point is exactly 100°C. The normal boiling points of the other liquids in Figure 11.16 "The Vapor Pressures of Several Liquids as a Function of Temperature" are represented by the points at which the vapor pressure curves cross the line corresponding to a pressure of 1 atm. Although we usually cite the normal boiling point of a liquid, the actual boiling point depends on the pressure. At a pressure greater than 1 atm, water boils at a temperature greater than 100°C because the increased pressure forces vapor molecules above the surface to condense. Hence the molecules must have greater kinetic energy to escape from the surface. Conversely, at pressures less than 1 atm, water boils below 100°C. Typical variations in atmospheric pressure at sea level are relatively small, causing only minor changes in the boiling point of water. For example, the highest recorded atmospheric pressure at sea level is 813 mmHg, recorded during a Siberian winter; the lowest sea-level pressure ever measured was 658 mmHg in a Pacific typhoon. At these pressures, the boiling point of water changes minimally, to 102°C and 96°C, respectively. At high altitudes, on the other hand, the dependence of the boiling point of water on pressure becomes significant. Table 11.5 "The Boiling Points of Water at Various Locations on Earth" lists the boiling points of water at several locations with different altitudes. At an elevation of only 5000 ft, for example, the boiling point of water is already lower than the lowest ever recorded at sea level. The lower boiling point of water has major consequences for cooking everything from soft-boiled eggs (a “three-minute egg” may well take four or more minutes in the Rockies and even longer in the Himalayas) to cakes (cake mixes are often sold with separate high-altitude instructions). Conversely, pressure cookers, which have a seal that allows the pressure inside them to exceed 1 atm, are used to cook food more rapidly by raising the boiling point of water and thus the temperature at which the food is being cooked. Note the Pattern As pressure increases, the boiling point of a liquid increases and vice versa. Table 11.5 The Boiling Points of Water at Various Locations on Earth \|Place\|\|Altitude above Sea Level (ft)\|\|Atmospheric Pressure (mmHg)\|\|Boiling Point of Water (°C)\| \|Mt. Everest, Nepal/Tibet\|\|29,028\|\|240\|\|70\| \|Dead Sea, Israel/Jordan\|\|−1312\|\|799\|\|101.4\| Use Figure 11.16 "The Vapor Pressures of Several Liquids as a Function of Temperature" to estimate the following. - the boiling point of water in a pressure cooker operating at 1000 mmHg - the pressure required for mercury to boil at 250°C Given: data in Figure 11.16 "The Vapor Pressures of Several Liquids as a Function of Temperature", pressure, and boiling point Asked for: corresponding boiling point and pressure A To estimate the boiling point of water at 1000 mmHg, refer to Figure 11.16 "The Vapor Pressures of Several Liquids as a Function of Temperature" and find the point where the vapor pressure curve of water intersects the line corresponding to a pressure of 1000 mmHg. B To estimate the pressure required for mercury to boil at 250°C, find the point where the vapor pressure curve of mercury intersects the line corresponding to a temperature of 250°C. - A The vapor pressure curve of water intersects the P = 1000 mmHg line at about 110°C; this is therefore the boiling point of water at 1000 mmHg. - B The vertical line corresponding to 250°C intersects the vapor pressure curve of mercury at P ≈ 75 mmHg. Hence this is the pressure required for mercury to boil at 250°C. Use the data in Figure 11.16 "The Vapor Pressures of Several Liquids as a Function of Temperature" to estimate the following. - the normal boiling point of ethylene glycol - the pressure required for diethyl ether to boil at 20°C. - 450 mmHg Because the molecules of a liquid are in constant motion and possess a wide range of kinetic energies, at any moment some fraction of them has enough energy to escape from the surface of the liquid to enter the gas or vapor phase. This process, called vaporization or evaporation, generates a vapor pressure above the liquid. Molecules in the gas phase can collide with the liquid surface and reenter the liquid via condensation. Eventually, a steady state is reached in which the number of molecules evaporating and condensing per unit time is the same, and the system is in a state of dynamic equilibrium. Under these conditions, a liquid exhibits a characteristic equilibrium vapor pressure that depends only on the temperature. We can express the nonlinear relationship between vapor pressure and temperature as a linear relationship using the Clausius–Clapeyron equation. This equation can be used to calculate the enthalpy of vaporization of a liquid from its measured vapor pressure at two or more temperatures. Volatile liquids are liquids with high vapor pressures, which tend to evaporate readily from an open container; nonvolatile liquids have low vapor pressures. When the vapor pressure equals the external pressure, bubbles of vapor form within the liquid, and it boils. The temperature at which a substance boils at a pressure of 1 atm is its normal boiling point. - The equilibrium vapor pressure of a liquid depends on the temperature and the intermolecular forces present. - The relationship between pressure, enthalpy of vaporization, and temperature is given by the Clausius-Clapeyron equation. Using vapor pressure at two temperatures to calculate Δ H vap What is the relationship between the boiling point, vapor pressure, and temperature of a substance and atmospheric pressure? What is the difference between a volatile liquid and a nonvolatile liquid? Suppose that two liquid substances have the same molecular mass, but one is volatile and the other is nonvolatile. What differences in the molecular structures of the two substances could account for the differences in volatility? An “old wives’ tale” states that applying ethanol to the wrists of a child with a very high fever will help to reduce the fever because blood vessels in the wrists are close to the skin. Is there a scientific basis for this recommendation? Would water be as effective as ethanol? Why is the air over a strip of grass significantly cooler than the air over a sandy beach only a few feet away? If gasoline is allowed to sit in an open container, it often feels much colder than the surrounding air. Explain this observation. Describe the flow of heat into or out of the system, as well as any transfer of mass that occurs. Would the temperature of a sealed can of gasoline be higher, lower, or the same as that of the open can? Explain your answer. What is the relationship between the vapor pressure of a liquid and - its temperature? - the surface area of the liquid? - the pressure of other gases on the liquid? - its viscosity? At 25°C, benzene has a vapor pressure of 12.5 kPa, whereas the vapor pressure of acetic acid is 2.1 kPa. Which is more volatile? Based on the intermolecular interactions in the two liquids, explain why acetic acid has the lower vapor pressure. Acetylene (C2H2), which is used for industrial welding, is transported in pressurized cylinders. Its vapor pressure at various temperatures is given in the following table. Plot the data and use your graph to estimate the vapor pressure of acetylene at 293 K. Then use your graph to determine the value of ΔHvap for acetylene. How much energy is required to vaporize 2.00 g of acetylene at 250 K? T (K) 145 155 175 200 225 250 300 P (mmHg) 1.3 7.8 32.2 190 579 1370 5093 The following table gives the vapor pressure of water at various temperatures. Plot the data and use your graph to estimate the vapor pressure of water at 25°C and at 75°C. What is the vapor pressure of water at 110°C? Use these data to determine the value of ΔHvap for water. T (°C) 0 10 30 50 60 80 100 P (mmHg) 4.6 9.2 31.8 92.6 150 355 760 The ΔHvap of carbon tetrachloride is 29.8 kJ/mol, and its normal boiling point is 76.8°C. What is its boiling point at 0.100 atm? The normal boiling point of sodium is 883°C. If ΔHvap is 97.4 kJ/mol, what is the vapor pressure (in millimeters of mercury) of liquid sodium at 300°C? An unknown liquid has a vapor pressure of 0.860 atm at 63.7°C and a vapor pressure of 0.330 atm at 35.1°C. Use the data in Table 11.6 "Melting and Boiling Points and Enthalpies of Fusion and Vaporization for Selected Substances" in Section 11.5 "Changes of State" to identify the liquid. An unknown liquid has a boiling point of 75.8°C at 0.910 atm and a boiling point of 57.2°C at 0.430 atm. Use the data in Table 11.6 "Melting and Boiling Points and Enthalpies of Fusion and Vaporization for Selected Substances" in Section 11.5 "Changes of State" to identify the liquid. If the vapor pressure of a liquid is 0.850 atm at 20°C and 0.897 atm at 25°C, what is the normal boiling point of the liquid? If the vapor pressure of a liquid is 0.799 atm at 99.0°C and 0.842 atm at 111°C, what is the normal boiling point of the liquid? The vapor pressure of liquid SO2 is 33.4 torr at −63.4°C and 100.0 torr at −47.7 K. - What is the ΔHvap of SO2? - What is its vapor pressure at −24.5 K? - At what temperature is the vapor pressure equal to 220 torr? The vapor pressure of CO2 at various temperatures is given in the following table: T (°C) −120 −110 −100 −90 P (torr) 9.81 34.63 104.81 279.5 - What is ΔHvap over this temperature range? - What is the vapor pressure of CO2 at −70°C? - At what temperature does CO2 have a vapor pressure of 310 torr? vapor pressure at 273 K is 3050 mmHg; ΔHvap = 18.7 kJ/mol, 1.44 kJ ΔHvap = 28.9 kJ/mol, n-hexane ΔHvap = 7.81 kJ/mol, 36°C
HERE AGAIN IS THE THEOREM of the previous Lesson: What, then, will be the case if two squares are not in the same ratio as two square numbers? What if one square is twice the size of another? 2 and 1 are not both square numbers. What must we say about the ratio of the sides? The sides do not have the same ratio as two natural numbers. One side is not any multiple of the other, any part of it, or parts of it. Language is incapable of expressing how they are related. We say that those sides are incommensurable. Problem 1. If one square is three times the size of another square, then a) are their sides commensurable or incommensurable? To see the answer, pass your mouse over the colored area. Incommensurable. The squares are in the ratio 3 to 1, and 3 and 1 are not both square numbers. b) if the side of one square is a multiple of one-eighth of an inch, could No. Those sides have no common measure. c) if one side is so many millionths of an inch, could the other side also d) if one side is a multiple of any unit fraction, could the other side also e) Will those sides have the same ratio as two natural numbers? That is, f) If one side is a rational number of units, could the other side also be No. They cannot both be rational, because if they were, they would have a common measure. (Lesson 9.) g) Can you express the ratio of those sides? Problem 2. How will we know when straight lines are incommensurable? The squares on them are not in the same ratio as square numbers. a) If two squares are to one another as 9 is to 20, do their sides have a No. 9 and 20 are not both square numbers. b) If two squares are to one another as 9 is to 25, do their sides have a The smaller side is three fifths of the larger. Problem 4. Let a square be 10 square meters. a) Does that square have a common measure with 1 square meter? Yes. 10 and 1 are natural numbers. b) Will its side have a common measure with 1 meter? No. 10 and 1 are not both square numbers. c) Will its side be a rational number of meters? No. The side has no common measure with 1 meter. a) If one square is four ninths of another square, is its side a fraction of Yes. 4 and 9 are square numbers. b) If one square is four fifths of another square, is its side a fraction of No. 4 and 5 are not both square numbers. Could both sides be a rational number of centimeters? No. The square drawn on the diagonal That two magnitudes could be incommensurable was first realized by Pythagoras in the 6th century B.C. To see what Pythagoras saw, consider the square ABCD on the left: On the right, we have joined three equal squares, making a square four times as large. Let us now cut each of those four equal squares in half: Then EDBF is itself as square, and it is composed of four of those equal halves. ABCD is composed of two of them. Therefore EDBF is twice as large as ABCD. Now, DB is called the diagonal of the square whose side is AB. Problem 6. Are the diagonal DB and the side AB commensurable or incommensurable? Incommensurable. The squares on them are in the ratio 2 : 1, and 2 is not a square number. The student should know that this discovery -- The diagonal and side of a square are incommensurable -- was a landmark in the history of mathematics. It drove home the distinction between geometry and arithmetic; between what is continuous, namely length, and what is discrete: the names of the ratios of numbers. We are about to see that it led to the invention of what are now called irrational numbers. Pythagoras realized that since the diagonal and side are not in the same ratio as two natural numbers, he could not say how they were related. He said that their relationship was "without a name." That has been called mathematics first logical crisis. Nevertheless, knowledge of a square figure is still rational: The square drawn on the diagonal is twice the square on the side. This suggests that the fundamental magnitude is not length but area. Area --the figure itself -- is what is geometrically real. Multiples that meet? Consider two magnitudes of the same kind, a and b. Then if multiples of them meet, that is, if a multiple of a is equal to a multiple of b, then those magnitudes are commensurable -- they have the same ratio as two natural numbers. If four a's, for example, are equal to three b's, then that implies the ratio of a to b, namely a is three fourths of b. (Lesson 3.) On the other hand, if a and b were incommensurable, then their multiples would never meet, no matter how far they might be extended. Multiples of the diagonal and side of a square will never meet. A multiple of one will never be equal to a multiple of the other. Problem 7. Since any two lengths could be measured with a ruler, and we always get a rational number, what sense does it make to say that two lengths are incommensurable? Since lengths are continuous, with no units to count, we always have the problem of measuring exactly. Measurement is limited not only by the fineness of the measuring instrument, but also by the fineness of our eyes to see its readings. two lengths do, or do not, have a common measure, we mean as determined logically, not with rulers. a) Again, what is the ratio that natural numbers have to one another? One number is a multiple of the other, a part of it, or parts of it; or a mixture of those. Express the following ratios: b) Are magnitudes necessarily in the same ratio as natural numbers? No. We cannot always express their relationship in words. c) Therefore, what do we mean by the "ratio" of two magnitudes? ? ? ? The new theory of proportions That magnitudes can be incommensurable completely upsets the theory of proportions. For if the square on AB is twice the square on CD, if they are in the ratio 2 : 1, then the lengths AB, CD are incommensurable; 2 is not a square number. And if the square on EF is also twice the square on GH, then EF, GH are also incommensurable -- yet we expect that whatever ratio AB has to CD, EF will have it to GH. We expect, proportionally, AB is to CD in the same ratio as EF is to GH. But according to the definition of natural numbers being "in the same ratio," that will make no sense, because AB is not any multiple of CD, any part of it or any parts of it Yet we can see that they have the same relationship. Therefore we must create a new definition of "in the same ratio," one that will be applicable to incommensurable magnitudes. We will not present the new definition here. Seeing the need for it -- namely the discovery of incommensurables -- is the climax of our present study. Seeing the need for a new definition of "in the same ratio" was mathematics first logical crisis, and it has always marked the beginning of advanced mathematics. Please make a donation to keep TheMathPage online. Copyright © 2016 Lawrence Spector Questions or comments?
This is a comprehensive collection of free printable math worksheets for fourth grade, organized by topics such as addition, subtraction, mental math, place value, multiplication, division, long division, factors, measurement, fractions, and decimals. They are randomly generated, printable from your browser, and include the answer key. Short Division Worksheets, 4th Grade Math Worksheets, Division Games, Addition Worksheets, Phonics Worksheets, Printable Worksheets, Math Facts, Free Stuff. Calendar Worksheets. Divided 3 digit numbers by 1 digit, using the long division methods. These division sums have remainders! Free math learning material for advanced students or for extra. Division with remainders worksheet for 4th grade children. This is a math PDF printable activity sheet with several exercises. It has an answer key attached on the second page. This worksheet is a supplementary fourth grade resource to help teachers, parents and children at home and in school. Math worksheets on division. Suitable PDF printable division worksheets for children in the following grades: 2nd grade, 3rd grade, 4th grade, 5th grade, 6th grade and 7th grade. Worksheets cover the following division topics: introduction to division, division with pictures, division of fruits, division of single digits, division of multiples. Your students will take the next step to becoming math pros with these fourth grade division worksheets and printables! Now that your students are familiar with the basics of division, put their skills to the test with word problems, puzzles, drills, and other interactive activities. Welcome to our Math Multiplication Worksheets for 4th graders. Here you will find our selection of printable 4th grade multiplication worksheets which will help your child learn to multiply a range of numbers up to 4 digits by a single digit. The Individual Division Fact 4 (A) Math Worksheet from the Division Worksheets Page at Math-Drills.com.. Fractions Worksheets Grade 6, 4th Grade Math Worksheets, Free Printable Math Worksheets, Kids Worksheets, Free Printables, Multiplication Facts, Multiplication Practice Sheets, Array Worksheets, Perimeter Worksheets. Preschool Assessment Printable - Color By Division. 4th Grade Math Long Division. Division Printable Worksheets For 4th Grade. Character Traits Reading Passages. math expressions grade 4 worksheets. 4th Grade Computation Test. Modal Verbs Exercises Advanced Level PDF. Spelling And Reading Worksheets. Our division worksheets are free to download, easy to use, and very flexible. These division worksheets are a great resource for children in Kindergarten, 1st Grade, 2nd Grade, 3rd Grade, 4th Grade, and 5th Grade. Click here for a Detailed Description of all the Division Worksheets. Free Division worksheets without remainder and with remainder for 2nd grade, 3rd grade, 4th grade and 5th grade. This is a collection of our 4th grade multiplication and division worksheets and teaching resources. You'll save time making your own resources by using these products. You can go through the collection below. It includes various types of activities for your students such as coloring pages, mystery pictures, classic wo. Math Skills Worksheets. This page contains only a partial index of the math skills worksheets on S.T.W. Full Website Index. View the complete index of all Math, ELA, Spelling, Phonics, Grammar, Science, and Social Studies worksheets found on this website. The best free 4th grade math worksheets are available for you as the media to test your grade 4 students’ skill in several math exercises.There are division, fraction, counting coin, and other Math problems for 4 th grade provided in these worksheets. Use these worksheets posted below to test your children’s ability in math! To ace math division, they need practice and that's what we provide here in a fun and easy manner. These free printable division worksheets are perfect for teachers, homeschooling mothers, parents who are looking for something different from their monotonous curriculum. These free printable math worksheets for kids form as math help. Math Division Worksheets 4th Grade Math Worksheets Sixth Grade Math Printable Math Worksheets Fourth Grade Math Worksheet For Class 2 Math Pages Homeschool Math Homeschooling.. Grade 5 Math Worksheets, Free Printable Math Worksheets, Fractions Worksheets, Math Blocks, Maths Puzzles, Word Problems 3rd Grade, Math Sheets. What others are saying.Free 3rd Grade Division Worksheets Pictures - 3rd Grade Math Worksheet For Kids. 3rd Grade Division Worksheets For Download. 3rd Grade Division Worksheets To Download. 3rd Grade Division Worksheets To Printable To. 3rd Grade Division Worksheets For You. 3rd Grade Division Worksheets. 1st Grade 2nd Grade 3rd Grade 4th Grade 5th Grade.Division Worksheets Printable Long Division Worksheets 4th Grade The Best Facts F Fun For Graders Common Core And Multiplication Pdf Word Problems Decimal With Remainders.
Astronomers from The University of Western Australia’s node of the International Centre for Radio Astronomy Research (ICRAR) have developed a new way to study star formation in galaxies from the dawn of time to today. “Stars can be thought of as enormous nuclear-powered processing plants,” said lead researcher Dr Sabine Bellstedt, from ICRAR. “They take lighter elements like hydrogen and helium, and, over billions of years, produce the heavier elements of the periodic table that we find scattered throughout the Universe today. “The carbon, calcium and iron in your body, the oxygen in the air you breathe, and the silicon in your computer all exist because a star created these heavier elements and left them behind,” Bellstedt said. “Stars are the ultimate element factories in the Universe.” Understanding how galaxies formed stars billions of years ago requires the very difficult task of using powerful telescopes to observe galaxies many billions of light-years away in the distant Universe. However, nearby galaxies are much easier to observe. Using the light from these local galaxies, astronomers can forensically piece together the history of their lives (called their star-formation history). This allows researchers to determine how and when they formed stars in their infancy, billions of years ago, without struggling to observe galaxies in the distant Universe. Traditionally, astronomers studying star formation histories assumed the overall metallicity—or amount of heavy elements—in a galaxy doesn’t change over time. But when they used these models to pinpoint when stars in the Universe should have formed, the results didn’t match up with what they were seeing through their telescopes. “The results not matching up with our observations is a big problem,” Bellstedt said. “It tells us we’re missing something.” “That missing ingredient, it turns out, is the gradual build-up of heavy metals within galaxies over time.” Using a new algorithm to model the energy and wavelengths of light coming from almost 7000 nearby galaxies, the researchers succeeded in reconstructing when most of the stars in the Universe formed—in agreement with telescope observations for the first time. The designer of the new code—known as ProSpect—is Associate Professor Aaron Robotham from ICRAR’s University of Western Australia node. “This is the first time we’ve been able to constrain how the heavier elements in galaxies change over time based on our analysis of these 7000 nearby galaxies,” Robotham said. “Using this galactic laboratory on our own doorstep gives us lots of observations to test this new approach, and we’re very excited that it works. “With this tool, we can now dissect nearby galaxies to determine the state of the Universe and the rate at which stars form and mass grows at any stage over the past 13 billion years. “It’s absolutely mind-blowing stuff.” This work also confirms an important theory about when most of the stars in the Universe formed. “Most of the stars in the Universe were born in extremely massive galaxies early on in cosmic history—around three to four billion years after the Big Bang,” Bellstedt said. “Today, the Universe is almost 14 billion years old, and most new stars are being formed in much smaller galaxies.” Based on this research, the next challenge for the team will be to expand the sample of galaxies being studied using this technique, in an effort to understand when, where and why galaxies die and stop forming new stars. Bellstedt and Robotham, along with colleagues from Australia, the UK and the United States, are reporting their results in the scientific journal the Monthly Notices of the Royal Astronomical Society. From: International Centre for Radio Astronomy Research (ICRAR)
The foundation of many areas of Mathematics emerged from the brilliant nation of India. Vedic Math Sutras or Indian Mathematics commenced around 1200 BC and lasted up the later part of the 18th century until modern technology and methods took over. Important contributions were made in this area by scholars like Aryabhatta, Brahmagupta, Bhaskara II, Varahamiriha. The concept of zero as a number, negative numbers, the decimal system, and a lot more find their roots in Vedic mathematics. The concept of Trigonometry, the sine and the cosine also developed further, thanks to this interesting subject. Read about the advantages of learning Vedic Maths, here. This article will help you learn and apply the first and the most crucial Vedic Maths Sutra- The Ekadhikena Purvena. The Genesis of Vedic Maths All ancient and medieval works were composed in Sanskrit and it usually contained sutras (rules) which aided students with memorization. It was also followed by a prose commentary section that provided detailed justification of all problems. The oldest mathematical document is the BAKSHALI MANUSCRIPT discovered in 1881 in modern- day Pakistan which is stated to be likely from the 7th century CE. We will now have a look at the very first of these 16 sutras. This sutra is called the Ekadhikena Purvena. Vedic Maths Sutra 1- Ekadhikena Purvena The term ‘Ekadhikena Purvena’ means- ‘by one more than the previous one.’ Ekhadhikina Purvena is a method useful for finding the squares of numbers and special divisions like 1 divided by a number for eg: 19, 29, etc. Using the conventional method, it is difficult to divide 1 by numbers ending with 9 like 19, 29, 39. This is so because some of these are prime numbers and thus cannot be factorized. To reduce such tedious tasks as well as mistakes we apply the sutra Ekadhikena Purvena. Method 1 – Going from left to right Suppose we take 1 divided by 29, 1 being the numerator here and 19 being the denominator (1/19). For the denominator 29, the Purva or the first digit of the number is 1. Hence, the Ekadhikena Purvena for this i.e one more than the previous will be Now we will be using 3 as the denominator for the division purpose i.e 1/29 = 1/30 yet they are not equal - Divide 1 by 3 and it will give a quotient of 0 and 1 as the remainder. - Now, the quotient and remainder are collectively 10. Divide 10 by 3. This gives a quotient of 3 and a remainder of 1. When we are writing these numbers it will appear something like this: - Again, we divide 13 by 3. This will give us a quotient of 4 and a remainder of 1. - Similarly, we continue the same process till we get the same quotient and remainder we found at the very first. This means the Quotient is 0 and remainder is 1. And our final answer will be the series written in black. Once you grasp the concept, it becomes easy to divide such numbers. Method 2. – Go right to left This is also the Ekhdikena Purvena. The difference here is just that we use the 3 for the multiplication process instead of division. - We will start by taking the number 6 (considering this was the last number in the division process given above) and multiply it by 3. This gives 18. - Now write 8 on the left side of 6(now that our process is from right to left) and carry forward the 1. - Now multiply 8 by 3(as 3 is our Purva for the division) by 8 and add 1 which gives 25. - Again, write on the left of 8 in the series and carry forward the 2. - Continue this process. Keep doing this till you get your desired number or the same pair of quotients and remainder is obtained as earlier. Our final answer is our series written in black. Let us take another example to be clear with our concepts: We will now take 38/59. This can be approximated as 38/60 and can be further written as 3.8/6. We will be following method 1. - So our numerator is 3.8 and denominator is 6. This gives us a quotient of 6 and remainder as 2. - Now as our quotient and remainder are collectively 26 dividing it by 6 gives a quotient of 4 and remainder of 2. - Keep writing it in a series so that you don’t forget it. - Now divide 24 by 6. This gives you a quotient of 4 and a remainder of 0. - Continue the series until you get the desired number. WHEN THE NUMERATOR IS GREATER THAN THE DENOMINATOR Suppose we have to divide the number 12345 by 39. In the previous methods, the numerator and denominator had an equal number of digits. Here, however, the numerator is greater than the denominator. Hence we need to apply a different method. This can be a little tricky but it is fun when understood. - Let us take 12345 divided by 29. This is approximated to 12345/30 = 1234.5/3 - For the first division, we will simply divide 12 by 3. This gives us a quotient of 4 and a remainder of 0. - Now we still have 3 digits (34.5) left in the original dividend which is 123.45. - Therefore we will now add 4 (from our series) to 3 (the first digit from the original divisor) which gives us 7. - Now divide this 7 by 3 which will give us a quotient of 2 and a remainder of 1. - Again add the quotient (2) which the next digit in the original dividend which is 4. This gives us 6. Now append the remainder 1 from the series with 6. - Hence the next number to be divided by 3 is 16. This gives the quotient as 5 and the remainder as 1. - Again add the quotient 5 from the series to the next remaining digit 5. This will give us 10. Now append the remainder 1 to it. In this case, we put 1 in the ten’s place while adding, so instead of 11+1=12 we will get 11+10=20. - So now we divide 20 by 3. This gives us a quotient of 6 and a remainder of 2. - From here onwards the division takes place normally as we did in Method 1. These Vedic Math methods are quite helpful even in this modern day and age. Learn them with a little patience and then perform calculations in seconds!
ELA: KINDERGARTEN - GRADE 12 LITERACY: GRADES 6 - 12 RH.9-10.1. Cite specific textual evidence to support analysis of primary and secondary sources, attending to such features as the date and origin of the information. The Secret Life of the American Gossip Girl So in first period today, Chloe told Brianna that she liked Mark…but Brianna told Stephanie that Chloe looooved Mark, then Stephanie told Jake who told Ross who is best friends with Mark… Sound familiar? All of this drama is due to a misinterpretation of a primary source: Chloe’s original statement. All of the rumors spread following this statement are considered secondary sources, secondhand information reporting on the original event. Knowing the difference is essential in analyzing a text, and may even help you keep some friends when the school soap opera begins. Teach With Shmoop Tag! You're it. The links in this section will take you straight to the standard-aligned assignments tagged in Shmoop's teaching guides. That's right, we've done the work. You just do the clickin... Teaching Guides Using this Standard Pretty Little Lesson Let’s say you’re writing on an important historical event, like the 2000’s Thumb Wrestling Championship . If you reference in your analysis, a speech given by the previous year’s thumb war champ, then that would be primary. But, if you also reference a text such as Oscar Villalon’s “The Way of the Thumb” (2007)ii, about winning strategies and tactics in this audacious sport, then that would be secondary. Think of it as how far removed the source is from the action; if someone creates, is present for, or reports on the action first-hand as it’s happening, then they are a primary source. However, if someone writes a criticism or commentary on any of the historically reported information, then it is a secondary source because it’s once removed from the original information. How I Met Your Paper The difference between the two kinds of documents is why the little bit on the end of the standard is important, “attending to such features as the date and origin of the information,” showing that you know which is which and can discuss the sources correctly. Once you’ve sorted out your sources, it’s time to analyze them or break them down in order to determine what they mean and why they matter. Don’t forget our favorite part: cite text evidence! You need to cite specific portions of the text that support your analysis or interpretation of the text or the subject. Referencing the text doesn’t ever go away for the rest of your educational days; you should write a poem about it, then reference your own poem in an essay about primary and secondary sources—it would blow your teacher’s mind. - Shmoop tip of the day: Keeping colored sticky notes when reading multiple documents is like having a life vest on in the middle of the ocean; you have to keep your head above the flood of information. Tracking what’s what in this way can be a boon to your sanity… and to your analysis. The Primary Diaries Still not sure about what’s what? There are several ways to conquer this textual shortcoming. Original stuff (no posers), such as art of any mode, speeches, letters, autobiographies= primary, the epicenter of the knowledge explosion. People who like to talk about the original works by quoting it, alluding to it, referencing it, analyzing it= secondary, in the wake of the knowledge. Don’t let yourself get confused in the aftermath of the big info bang. Quiz QuestionsHere's an example of a quiz that could be used to test this standard. Synthesize the following documents and answer the questions that follow. Lincoln's Gettysburg Address, given November 19, 1863 on the battlefield near Gettysburg, Pennsylvania, USA “Four score and seven years ago, our fathers brought forth upon this continent a new nation: conceived in liberty, and dedicated to the proposition that all men are created equal. Now we are engaged in a great civil war ... testing whether that nation, or any nation so conceived and so dedicated ... can long endure. We are met on a great battlefield of that war. We have come to dedicate a portion of that field as a final resting place for those who here gave their lives that this nation might live. It is altogether fitting and proper that we should do this. But, in a larger sense, we cannot dedicate ... we cannot consecrate ... we cannot hallow this ground. The brave men, living and dead, who struggled here have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember, what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us ... that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion ... that we here highly resolve that these dead shall not have died in vain ... that this nation, under God, shall have a new birth of freedom ... and that government of the people ... by the people ... for the people ... shall not perish from this earth.” March 6, 2012 Lincoln’s short speech to the soldiers at Gettysburg was given shortly after he pushed through a limited proclamation, emancipating slaves in confederate states. Thus, it is no coincidence that the chin-strap bearded President uses trendy words like “liberty” and “freedom” to get everyone’s attention and conveniently remind them of why they were there. Almost everyone knows the first line, “Four score and seven years ago,” though it isn’t just when your grandma was born; this is when the Declaration of Independence was written. Lincoln is throwing back to 87 years prior to that moment, speaking to a half illiterate crowd about the founding documents in order to prove his point about rights for all men. I’m sure if he had the opportunity to throw this little presentation into a PowerPoint and give out candy for a pop quiz, he would have, but since he was in the middle of a battlefield with tired, hungry, and scantly bathed men he had to keep it brief and to the point; they weren’t dying for giggles. There was a reason for the many already dead and the many soon to be; Abe was just being honest. This does sound a bit like any rousing battle speech in a movie given before the slow-motion deaths with some really nice instrumental music behind it, but Lincoln was the American Classic. There are some anti-Lincoln commentaries out there. Many believe Lincoln was a liar and a hypocrite at these words; they claim that the speech was a dedication for only those fighting for his cause of a united nation, and therefore mocked the Southern states’ fallen soldiers. The last lines of his speech beg the question of whether he was truly giving a loaded address or if he was attempting to state that these men have died and will die in the name of government for its own sake (for the people, by the people, yadda yadda…). The jury on Lincoln’s rep is currently out with many in the anti-Abe camp hoping to sully his good name as it is ingrained Americana. Perhaps a break from the hatred and a look at the man’s breadth of work would be in order. - Teaching The Columbian Exchange: Quotation Analysis: American Exceptionalism - Teaching The Columbian Exchange: Primary Sources: Smallpox and the Aztecs - Teaching the French & Indian War: Document-Based Activity: Diplomacy and the Iroquois Half King - Teaching the French & Indian War: Image-Based Activity: The Death of General Wolfe - Teaching The Gilded Age: Discussion/Writing Assignment: Re-Thinking Pullman Town - Teaching The Great Depression: Graphing Activity: Depression Statistics - Teaching The Great Depression: Quotation Analysis: The Psychology of Depression - Teaching The Great Depression: Primary Sources: Dust Bowl Migration - Teaching The Great Depression: Debate Huey Long’s Share the Wealth Plan - Teaching The Great Depression: Oral History Activity: Memories of the Depression - Teaching the American Revolution: Writing Activity: What's Up with Whatley? - Teaching the American Revolution: Writing Activity: Who's in Charge Here, Anyway? - Teaching the American Revolution: Image Analysis: Was the American Revolution Picturesque? - Teaching the American Revolution: Statistical Analysis: Setting British Policy - Teaching The Jacksonian Era: Bloody Deeds of General Jackson - The Korean War: Korean War Activity: Quotation Analysis/Writing Assignment: Reasons for Fighting in Korea - The Korean War: Korean War Activity: Document Analysis: General MacArthur on the Korean War - The Korean War: Korean War Activity: Image Analysis: Political Cartoons from the Korea War - Teaching the Civil War: Article and Discussion: Gettysburg—Did Lee Walk Right Into It? - Teaching the Civil War: Document-Based Essay: Lincoln and Slavery - Teaching the Civil War: Image and Document Analysis/Writing Assignment: Soldiers' Letters Home - Teaching the Civil War: Image Analysis: Civil War Uniforms - Teaching Causes of the Civil War: Image Analysis: Cartoons with a Cause - Teaching Causes of the Civil War: Primary Source Analysis: Slavery as a Positive Good - Teaching Causes of the Civil War: Decoding Quotations: Lincoln’s Views on Slavery - Teaching the Executive Branch & Presidents: Image Analysis: Cultivating a Presidential Image - Teaching FDR's New Deal: Statistical Analysis: Was the New Deal a Success? - Teaching the Spanish-American War: Document-Based Writing Assignment: Self-Interest and Idealism in American Foreign Policy - Teaching the Spanish-American War: Document and Image Analysis: Yellow Journalism - Teaching the Spanish-American War: Document Analysis: The American Anti-Imperialist League - Teaching Abolitionism: Document Analysis: Was the Constitution a Pro-Slavery Document? - Teaching Abolitionism: Document Analysis: The Appeal of David Walker - Teaching Abolitionism: Document Analysis/Writing Exercise: Incidents in the Life of a Slave Girl - Teaching Abolitionism: Writing/Illustrating Assignment: The Caning of Charles Sumner - Teaching Transcontinental Railroad: Document Analysis: Theodore Judah's Proposal
Both are programming processes whereas OOP stands for “Object Oriented Programming” and POP stands for “Procedure Oriented Programming”. Both are programming languages that use high-level programming to solve a problem but using different approaches. These approaches in technical terms are known as programming paradigms. A programmer can take different approaches to write a program because there’s no direct approach to solve a particular problem. This is where programming languages come to the picture. A program makes it easy to resolve the problem using just the right approach or you can say ‘paradigm’. Object-oriented programming and procedure-oriented programming are two such paradigms. What is Object Oriented Programming (OOP)? OOP is a high-level programming language where a program is divided into small chunks called objects using the object-oriented model, hence the name. This paradigm is based on objects and classes. - Object – An object is basically a self-contained entity that accumulates both data and procedures to manipulate the data. Objects are merely instances of classes. - Class – A class, in simple terms, is a blueprint of an object which defines all the common properties of one or more objects that are associated with it. A class can be used to define multiple objects within a program. The OOP paradigm mainly eyes on the data rather than the algorithm to create modules by dividing a program into data and functions that are bundled within the objects. The modules cannot be modified when a new object is added restricting any non-member function access to the data. Methods are the only way to assess the data. Objects can communicate with each other through same member functions. This process is known as message passing. This anonymity among the objects is what makes the program secure. A programmer can create a new object from the already existing objects by taking most of its features thus making the program easy to implement and modify. What is Procedure Oriented Programming (POP)? POP follows a step-by-step approach to break down a task into a collection of variables and routines (or subroutines) through a sequence of instructions. Each step is carried out in order in a systematic manner so that a computer can understand what to do. The program is divided into small parts called functions and then it follows a series of computational steps to be carried out in order. It follows a top-down approach to actually solve a problem, hence the name. Procedures correspond to functions and each function has its own purpose. Dividing the program into functions is the key to procedural programming. So a number of different functions are written in order to accomplish the tasks. Initially, all the computer programs are procedural or let’s say, in the initial stage. So you need to feed the computer with a set of instructions on how to move from one code to another thereby accomplishing the task. As most of the functions share global data, they move independently around the system from function to function, thus making the program vulnerable. These basic flaws gave rise to the concept of object-oriented programming which is more secure. Difference between OOP and POP OOP stands for Object-oriented programming and is a programming approach that focuses on data rather than the algorithm, whereas POP, short for Procedure-oriented programming, focuses on procedural abstractions. In OOP, the program is divided into small chunks called objects which are instances of classes, whereas in POP, the main program is divided into small parts based on the functions. - Accessing Mode Three accessing modes are used in OOP to access attributes or functions – ‘Private’, ‘Public’, and ‘Protected’. In POP, on the other hand, no such accessing mode is required to access attributes or functions of a particular program. The main focus is on the data associated with the program in case of OOP while POP relies on functions or algorithms of the program. In OOP, various functions can work simultaneously while POP follows a systematic step-by-step approach to execute methods and functions. - Data Control In OOP, the data and functions of an object act like a single entity so accessibility is limited to the member functions of the same class. In POP, on the other hand, data can move freely because each function contains different data. OOP is more secure than POP, thanks to the data hiding feature which limits the access of data to the member function of the same class, while there is no such way of data hiding in POP, thus making it less secure. - Ease of Modification New data objects can be created easily from existing objects making object-oriented programs easy to modify, while there’s no simple process to add data in POP, at least not without revising the whole program. OOP follows a bottom-up approach for designing a program, while POP takes a top-down approach to design a program. Commonly used OOP languages are C++, Java, VB.NET, etc. Pascal and Fortran are used by POP. OOP vs. POP \|OOP takes a bottom-up approach in designing a program.\|\|POP follows a top-down approach.\| \|Program is divided into objects depending on the problem.\|\|Program is divided into small chunks based on the functions.\| \|Each object controls its own data.\|\|Each function contains different data.\| \|Focuses on security of the data irrespective of the algorithm.\|\|Follows a systematic approach to solve the problem.\| \|The main priority is data rather than functions in a program.\|\|Functions are more important than data in a program.\| \|The functions of the objects are linked via message passing.\|\|Different parts of a program are interconnected via parameter passing.\| \|Data hiding is possible in OOP.\|\|No easy way for data hiding.\| \|Inheritance is allowed in OOP.\|\|No such concept of inheritance in POP.\| \|Operator overloading is allowed.\|\|Operator overloading is not allowed.\| \|C++, Java.\|\|Pascal, Fortran.\| - A program is nothing but a set of step-by-step instructions that only a computer can understand so that it can come up with a solution. There are different approaches to do that, which in technical term, are referred to as programming paradigms. - OOP and POP are such high-level programming paradigms that use different approaches to create a program to solve a particular problem in the less time possible. - The idea is to solve complicated tasks using programming with less code. While an object-oriented program depends mainly upon data rather than the algorithm, a procedure-oriented program follows a step-by-step approach to solve a problem. - OOP, of course, has a little edge over POP on many fronts such as data security, ease of use, accessibility, operator overloading, and more. - Difference Between Biometric Authentication and Password - January 23, 2021 - Difference Between Neuroevolution and Deep Learning - January 23, 2021 - Difference Between Citrucel and Metamucil - January 22, 2021
Evidence for Dark Matter Edited by StephWrites, Jen Moreau What is Dark Matter The universe is constituted by matter and energy. Visible matter is everything we can touch and see. However, in the last years, the scientific community has found that this is less than 20% of the entire mass of the universe. The rest of the mass seems to be made of two substances named dark matter and dark energy. Dark matter emanates and absorbs no light consequently; it is not visible. However, dark matter gravitational influence on the visible matter can be perceived. Galaxies are held together by dark matter, and this determines the location where galaxies meet in clusters and filaments. Recently, dark energy was identified and apparently it generates pressure that affects gravity and produces the expansion of the universe to go faster. Apparently, dark matter is 84.5% of the total mass in the universe, while dark energy plus dark matter represent 95.1% of total mass "energy content". The most extensively admitted hypothesis on the form for dark matter says that it is constituted by Weakly Interacting Massive Particles (WIMPs) that interact only across gravity and the weak force. There are currently different experiments to uncover dark matter particles through non-gravitational ways, but no dark matter particle has been decisively detected by these means. Driven by the lack of decisive detection of dark matter, a minority of astronomers claim for various changes in the standard laws of general relativity. They try to account for the observations without referring the additional matter. Who discovered it? Astronomers started to examine the spectra of galaxies in the early 1900s. Thanks to that, they were able to define the speed of stars as a function of their distance from the galactic center. This is known as a galactic rotation curve. The majority of galaxies have a bright center which can be seen in normal light, but it reduces as you take distance from the center. This means that most of the stars are situated close to the center of a Galaxy. One would imagine stars distant from the center to travel much more slowly than stars near the center. That's what happens in our solar system; Earth orbits the Sun much more rapidly than Pluto. Max Wolf and Vesto Slipher did an experiment where they measured the rotation curve of the Andromeda Galaxy in 1914. Through their observations, they discovered that it was flat which meant that stars moved at the same speed despite their position from the galactic center. A hypothesis is that Andromeda is surrounded by dark matter so that its mass is not clustered in the center. By the 1950s radio observations of both the Andromeda Galaxy and our own Milky Way Galaxy exhibited similarly flat rotation curves. The results showed that the stars and the gas of any dark nebulae were orbiting the galaxies at parallel speeds. It can either be that galaxies held important dark matter, or that our comprehension of gravity was not right. In 1922, the first to propose the existence of dark matter was Jacobus Kapteyn. In 1932, Jan Oort also hypothesized the presence of it. However, Fritz Zwicky made the first official inference about the presence of dark matter in 1933. The astrophysicist of the California Institute of Technology (Caltech), used the virial theorem to the Coma cluster of galaxies and made deductions about invisible mass. Zwicky estimated the cluster's total mass based on the movement of galaxies approaching its edge. After comparing this mass approximation to one that was based on the number of galaxies and total brightness of the cluster, he discovered that there was about 400 times more mass than anticipated. Something extra was required because the gravity of the visible galaxies in the cluster would be far too small for such fast orbits. This is known as the "missing mass problem". He suggested that there must be some non-visible form of matter which would offer enough of the mass and gravity to keep the cluster together. Evidences of Dark Matter As the support for dark matter theory increased, astronomers realized that there was a challenging issue. If our gravitational theories were right, dark matter must be far more abundant than luminous matter both in galaxies and among galactic clusters. Assuming this dark matter consisted of things like dark nebulae, their existence should be measurable by the light they absorb. If there is so much dark matter, it must not only be obscure, but it must not absorb light either; it couldn't just be a regular matter that is cold and dark. It was due to this assumption that many astronomers examined the legitimacy of Newtonian gravity. By the 1980s several alternative gravitational models appeared. These models worked well for dwarf galaxies, but they did pretty badly with things like galactic clusters. Dark matter models had their complications, but they corresponded more readily with observations. In general, scientists know more about what dark matter is not rather than what it is. However, they do have a few thoughts about what it could be. Scientists have found other methods to explore dark matter because they can't see it directly, like looking at a shadow and making a reasonable guess about what's producing the shadow. Astronomers use indirect ways to study dark matter, by instance, gravitational lensing is a way scientists use indirectly to learn about it. A gravitational lens is described as a distribution of matter between a distant light source and an observer that is able of bending the light from the source as the light goes towards the observer. This effect is known as gravitational lensing. By measuring the alteration geometry, the mass of the intervening cluster can be calculated. In the cases where this process has been completed, the mass-to-light ratios obtained, correspond to the dynamical dark matter measurements of clusters. After Zwicky's early interpretations, no other supporting studies suggested that the mass to light ratio was anything other than unity. Then, 40 years later, Vera Rubin and Kent Ford at the Department of Terrestrial Magnetism at the Carnegie Institution of Washington presented discoveries based on a new sensitive spectrograph. It could measure the velocity curve of edge-on spiral galaxies better than it had ever been achieved before. They said that most stars in spiral galaxies orbit at about the same speed, which showed that their mass densities were similar. This result proposes that either Newtonian gravity is not universal or that, conservatively, upwards of 50 percent of the mass of galaxies was delimited in the relatively dark matter. Rubin insisted skeptically that the observations were accurate. Little by little other astronomers started to support her work and until it became common to say that most galaxies were influenced by dark matter. Some exceptions were the galaxies with mass-to-light ratios near to that of stars. In time, many observations have been registered that do point out the presence of dark matter in various parts of the cosmos. Observational evidence for dark matter has been gathered over the decades to the point that today most astrophysicists accept its existence. As a result, dark matter is one of the leading aspects considered in the investigation of structures of galactic scale and larger. Classification of dark matter Dark matter is classified into cold, warm and hot categories. These categories refer to how far corresponding objects moved due to arbitrary motions in the early universe before they decelerated as a result of cosmic expansion. While larger fluctuations are unaffected, early density fluctuations smaller than this length get washed out as particles spread from over-dense to under-dense regions. For that reason, this length sets a minimum scale for later structure formation. The categories are set in comparison to the size of a protogalaxy: dark matter particles are classified as: - Cold: much smaller than a protogalaxy. - Warm: similar size. - Hot: much larger. Finally, data from the Large Hadron Collider (the world's largest and most powerful particle accelerator located underneath the France-Switzerland border) is being examined in search of missing energy like a mark of new weakly interacting particles that may be linked to dark matter. We could say that all the methods to study dark matter, such as direct detection in dedicated laboratory experiments, indirect detection in the cosmic radiation, and searches at particle accelerators will sooner or later find more answers about the place where our world exists, the Universe. Referencing this Article If you need to reference this article in your work, you can copy-paste the following depending on your required format: APA (American Psychological Association) Evidence for Dark Matter. (2017). In ScienceAid. Retrieved May 16, 2022, from https://scienceaid.net/Evidence_for_Dark_Matter MLA (Modern Language Association) "Evidence for Dark Matter." ScienceAid, scienceaid.net/Evidence_for_Dark_Matter Accessed 16 May 2022. Chicago / Turabian ScienceAid.net. "Evidence for Dark Matter." Accessed May 16, 2022. https://scienceaid.net/Evidence_for_Dark_Matter. Categories : Astronomy Recent edits by: StephWrites
Missing Numbers Multiplication [B] This Missing Numbers Multiplication [B] worksheet also includes: - Answer Key - Join to access all included materials In this multiplication instructional activity, students fill in the missing number to solve a total of 24 problems; answers are included on page 2. 3 Views 5 Downloads - Activities & Projects - Graphics & Images - Lab Resources - Learning Games - Lesson Plans - Primary Sources - Printables & Templates - Professional Documents - Study Guides - Writing Prompts - AP Test Preps - Lesson Planet Articles - Interactive Whiteboards - All Resource Types - Show All See similar resources: Patterns in the Multiplication Table Explore patterns in the multiplication table in order to deepen your third graders' understanding of this essential skill. Implement this activity as a whole-class lesson, allowing students to work in pairs or small groups to support... 3rd - 4th Math CCSS: Designed I Have...Who Has...Multiplication Game Get the whole class involved in practicing their multiplication facts with this fun collaborative activity. With each child given a card containing both a product and an unrelated multiplication sentence, the activity begins as the child... 3rd - 6th Math CCSS: Adaptable Catch the Monkeys Multiplication Game Young mathematicians master their multiplication facts with the help of this fun math game. As they roll a die and move around the included game board, children must identify the missing factor for each multiplication sentence they land... 3rd - 4th Math CCSS: Adaptable Numbers in a Multiplication Table Identifying patterns is a crucial skill for all mathematicians, young and old. Explore the multiplication table with your class, using patterns and symmetry to teach about square numbers, prime numbers, and the commutative and identity... 3rd - 5th Math CCSS: Designed Find Missing Elements in Growing Patterns Combine prior learning about function rules and shape patterns in the third video of this nine-part series. Given a sequence of numbers, tables are used to identify and extend patterns in order to determine specific missing elements.... 6 mins 3rd - 5th Math CCSS: Designed
Pie charts are common visualizations that can be used to display parts of a whole as slices of a circle. They are very useful when trying to show relativity between pieces of data such as which slices are smaller or larger or to show a majority. When pie charts should not be used - If the data does not add up to a whole (100%) - If there are too many data points - If the data is spread across a time period What makes a good pie chart - Distinct slice colors - Clear labeling that is not too large - A reasonable amount of slices; no more than seven - Accurate data; slices should add up to the whole (100%) Example of a pie chart This is a good example of a pie chart that follows the basic rules and displays a clear message about the data to the viewer. Since the data about popularity of programming languages was collected as percentages, or parts of a whole, the pie chart was a great option to show what languages are most commonly used and how they compare against each other. It also does not have too many slices that overcrowd the whole chart and make it difficult to read. The labeling is also clear with a distinct set of colors to differentiate between each data point. An alternative chart that could be used to visualize the popularity of programming languages could be a bar graph to show how each language stacks up overall. It’s weird seeing Python as the top programming language when Stockton and many other colleges specialize in Java and C++ more.
On Earth, scientists can observe weather patterns, and more importantly can predict them, through the use of tens of thousands of weather observatories scattered around the globe. Up in the space surrounding Earth -- a space that seethes with its own space weather made of speeding charged particles and constantly changing magnetic fields that can impact satellites – there are only a handful of spacecraft to watch for solar and magnetic storms. The number of observatories has been growing over the last six years, however. Today these spacecraft have begun to provide the first multipoint measurements to better understand space weather events as they move through space, something impossible to track with a single spacecraft. Helping to anchor that team of spacecraft is a NASA mission called THEMIS (Time History of Events and Macroscale Interactions during Substorms). THEMIS launched on Feb. 17, 2007, with five nearly identical spacecraft nestled inside a Delta II rocket. Simply orchestrating how to expel each of the five satellites without unbalancing the rocket was an engineering tour de force – but it was only the preamble. Over time, each spacecraft moved into formation to fly around Earth in a highly-elliptical orbit that would have them travelling through all parts of Earth's space weather environment, a giant magnetic bubble called the magnetosphere. With five different observatories, scientists could watch space weather unfold in a way never before possible. In its sixth year in space, scientific papers using THEMIS data helped highlight a number of crucial details about what causes space weather events in this complex system. "Scientists have been trying to understand what drives changes in the magnetosphere since the 1958 discovery by James Van Allen that Earth was surrounded by rings of radiation," says David Sibeck, project scientist for THEMIS at NASA's Goddard Space Flight Center in Greenbelt, Md. "Over the last six years, in conjunction with other key missions such as Cluster and the recently launched Van Allen Probes to study the radiation belts, THEMIS has dramatically improved our understanding of the magnetosphere." Since that 1958 discovery, observations of the radiation belts and near Earth space have shown that in response to different kinds of activity on the sun, energetic particles can appear almost instantaneously around Earth, while in other cases they can be wiped out completely. Electromagnetic waves course through the area too, kicking particles along, pushing them ever faster, or dumping them into the Earth’s atmosphere. The bare bones of how particles and waves interact have been described, but with only one spacecraft traveling through a given area at a time, it's impossible to discern what causes the observed changes during any given event. "Trying to understand this very complex system over the last 40 years has been quite difficult," says Vassilis Angelopoulos, the principal investigator for THEMIS at the University of California in Los Angeles (UCLA). "But very recently we have learned how even small variations in the solar wind – which buffets Earth's space environment at a million miles an hour -- can sometimes cause extreme responses, causing more particles to arrive or to be lost." An artist's concept of the THEMIS spacecraft orbiting around Earth. Credit: NASANear Earth, THEMIS has now traveled through more than 50 solar storms that caused particles in the outer radiation belts to either increase or decrease in number. Historically, it has been difficult for scientists to find commonalities between such occurrences and discover what, if anything consistently caused an enhancement or a depletion. With so many events to study, however, and a more global view of the system from several spacecraft working together – including, in this case, ground based observations and NOAA's GOES (Geostationary Operational Environment Satellites) and POES (Polar Operational Environmental Satellites) data in addition to THEMIS data – a team of scientists led by Drew Turner at UCLA could better characterize what processes caused which results. Turner's group recently presented evidence linking specific kinds of electromagnetic waves in space – waves that are differentiated based on such things as their frequencies, whether they interact with ions or electrons, and whether they move along or across the background magnetic fields – to different effects. Chorus waves, so called because when played through an amplifier they sound like a chorus of singing birds, consistently sped up particles, leading to an increase in particle density. On the other hand, two types of waves known as hiss and EMIC (Electromagnetic Ion Cyclotron) waves occurred in those storms that showed particle depletion. Turner also observed that when incoming activity from the sun severely pushed in the boundaries of the magnetosphere this, too, led to particle drop outs, or sudden losses throughout the system. Such information is helpful to those attempting to forecast changes in the radiation belts, which if they swell too much can encompass many of our spacecraft. Another group has a paper in print in 2013 based on 2008 data from the five THEMIS spacecraft in conjunction with three of NOAA's GOES (Geostationary Operational Environmental Satellites) spacecraft, and the ESA/NASA Cluster mission. Led by Michael Hartinger at the University of Michigan in Ann Arbor, this group compared observations at the bow shock where the supersonic solar wind brakes to flow around the magnetosphere to what happens inside the magnetosphere. They found that instabilities drive perturbations in the solar wind particles streaming towards the bow shock and that these perturbations can be correlated with another type of magnetized wave – ULF (ultra low frequency) waves -- inside the magnetosphere. ULF waves, in turn, are thought to be important for changes in the radiation belts. "The interesting thing about this paper is that it shows how the magnetosphere actually gets quite a bit of energy from the solar wind, even by seemingly innocuous rotations in the magnetic field," says Angelopoulos. "People hadn't realized that you could get waves from these types of events, but there was a one-to-one correspondence. One THEMIS spacecraft saw an instability at the bow shock and another THEMIS spacecraft then saw the waves closer to Earth." Since all the various waves in the magnetosphere are what can impart energy to the particles surrounding Earth, knowing just what causes each kind of wave is yet another important part of the space weather puzzle. A third interesting science paper from THEMIS's sixth year focused on features originating even further upstream in the solar wind. Led by Galina Korotova at IZMIRAN in Troitsk, Russia, this work made use of THEMIS and GOES data to observe the magnetosphere boundary, the magnetopause. The researchers addressed how seemingly small perturbations in the solar wind can have large effects near Earth. Wave-particle interactions in the solar wind in the turbulent region upstream from the bow shock act as a gate valve, dramatically changing the bow shock orientation and strength directly in front of Earth, an area that depends critically on the magnetic field orientation. The extreme bow shock variations cause undulations throughout the magnetopause, which, launch pressure perturbations that may in turn energize particles in the Van Allen radiation belts. All of this recent work helps illuminate the nitty gritty details of how seemingly small changes in a system can lead to large variations in the near-Earth space environment where so many important technologies – including science, weather, GPS and communications satellites all reside. Much of this work was based on data from when all five spacecraft were orbiting Earth. Beginning in the fall of 2010, however, two of the THEMIS spacecraft were moved over the course of nine months to observe the environment around the moon. These two satellites were renamed ARTEMIS (Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun). In their new position, the two ARTEMIS spacecraft spend 80% of their time directly observing the solar wind, offering a vantage point on this area outside our magnetosphere that is quite close to home. The THEMIS spacecraft continue to work at their original levels of operation and all the instruments function highly effectively. With their current positioning and the ability to work in conjunction with other nearby spacecraft, scientists look forward to the stream of data yet to come. "What we have with THEMIS and ARTEMIS and the Van Allen Probes, is a whole constellation we are developing in near-Earth space," says Turner. "It's crucial for developing our forecasting ability and getting a better sense of the system as a whole." THEMIS is the fifth medium-class mission under NASA's Explorer Program, which was conceived to provide frequent flight opportunities for world-class scientific investigations from space within the Heliophysics and Astrophysics science areas. The Explorers Program Office at Goddard manages this NASA-funded mission. The University of California, Berkeley's Space Sciences Laboratory and Swales Aerospace in Beltsville, Md., built the THEMIS probes.
Difference between FDMA, TDMA and CDMA 1. Frequency Division Multiple Access (FDMA) : FDMA is a type of channelization protocol. In this bandwidth is divided into various frequency bands. Each station is allocated with band to send data and that band is reserved for particular station for all the time which is as follows : Figure – FDMA The frequency bands of different stations are separated by small band of unused frequency and that unused frequency bands are called as guard bands that prevents the interference of stations. It is like access method in data link layer in which data link layer at each station tells its physical layer to make a band pass signal from the data passed to it. The signal is created in the allocated band and there is no physical multiplexer at the physical layer. 2. Time Division Multiple Access (TDMA) : TDMA is the channelization protocol in which bandwidth of channel is divided into various stations on the time basis. There is a time slot given to each station, the station can transmit data during that time slot only which is as follows : Figure – TDMA Each station must aware of its beginning of time slot and the location of the time slot. TDMA requires synchronization between different stations. It is type of access method in the data link layer. At each station data link layer tells the station to use the allocated time slot. 3. Code Division Multiple Access (CDMA) : In CDMA, all the stations can transmit data simultaneously. It allows each station to transmit data over the entire frequency all the time. Multiple simultaneous transmissions are separated by unique code sequence. Each user is assigned with a unique code sequence. Figure – CDMA In the above figure, there are 4 stations marked as 1, 2, 3 and 4. Data assigned with respective stations as d1, d2, d3 and d4 and the code assigned with respective stations as c1, c2, c3 and c4. Difference between FDMA, CDMA and TDMA : \|FDMA stands for Frequency Division Multiple Access.\|\|TDMA stands for Time Division Multiple Access.\|\|CDMA stands for Code Division Multiple Access.\| \|In this, sharing of bandwidth among different stations takes place.\|\|In this, only the sharing of time of satellite transponder takes place.\|\|In this, there is sharing of both i.e. bandwidth and time among different stations takes place.\| \|There is no need of any codeword.\|\|There is no need of any codeword.\|\|Codeword is necessary.\| \|In this, there is only need of guard bands between the adjacent channels are necessary.\|\|In this, guard time of the adjacent slots are necessary.\|\|In this, both guard bands and guard time are necessary.\| \|Synchronization is not required.\|\|Synchronization is required.\|\|Synchronization is not required.\| \|The rate of data is low.\|\|The rate of data is medium.\|\|The rate of data is high.\| \|Mode of data transfer is continuous signal.\|\|Mode of data transfer is signal in bursts.\|\|Mode of data transfer is digital signal.\| \|It is little flexible.\|\|It is moderate flexible.\|\|It is highly flexible.\|
School-Wide Strategies for Managing... A service of www.interventioncentral.org Mathematics instruction is a lengthy, incremental process that spans all grade levels. As children begin formal schooling in kindergarten, they develop 'number sense', an intuitive understanding of foundation number concepts and relationships among numbers. A central part of number sense is the student's ability to internalize the number line as a precursor to performing mental arithmetic. As students progress through elementary school, they must next master common math operations (addition, subtraction, multiplication, and division) and develop fluency in basic arithmetic combinations ('math facts'). In later grades, students transition to applied, or 'word', problems that relate math operations and concepts to real-world situations. Successful completion of applied problems requires that the student understand specialized math vocabulary, identify the relevant math operations needed to solve the problem while ignoring any unnecessary information also appearing in that written problem, translate the word problem from text format into a numeric equation containing digits and math symbols, and then successfully solve. It is no surprise, then, that there are a number of potential blockers to student success with applied problems, including limited reading decoding and comprehension skills, failure to acquire fluency with arithmetic combinations (math facts), and lack of proficiency with math operations. Deciding what specific math interventions might be appropriate for any student must therefore be a highly individualized process, one that is highly dependent on the student's developmental level and current math skills, the requirements of the school district's math curriculum, and the degree to which the student possesses or lacks the necessary auxiliary skills (e.g., math vocabulary, reading comprehension) for success in math. Here are some wide-ranging classroom (Tier I RTI) ideas for math interventions that extend from the primary through secondary grades. Applied Problems: Encourage Students to Draw to Clarify Understanding (Van Essen & Hamaker, 1990; Van Garderen,2006). Making a drawing of an applied, or 'word', problem is one easy heuristic tool that students can use to help them to find the solution. An additional benefit of the drawing strategy is that it can reveal to the teacher any student misunderstandings about how to set up or solve the word problem. To introduce students to the drawing strategy, the teacher hands out a worksheet containing at least six word problems. The teacher explains to students that making a picture of a word problem sometimes makes that problem clearer and easier to solve. The teacher and students then independently create drawings of each of the problems on the worksheet. Next, the students show their drawings for each problem, explaining each drawing and how it relates to the word problem. The teacher also participates, explaining his or her drawings to the class or group. Then students are directed independently to make drawings as an intermediate problem-solving step when they are faced with challenging word problems. NOTE: This strategy appears to be more effective when used in later, rather than earlier, elementary grades. Math Computation: Two Ideas to Jump-Start Active Academic Responding (Skinner, Pappas & Davis, 2005). Research shows that when teachers use specific techniques to motivate their classes to engage in higher rates of active and accurate academic responding, student learning rates are likely to go up. Here are two ideas to accomplish increased academic responding on math tasks. First, break longer assignments into shorter assignments with performance feedback given after each shorter 'chunk' (e.g., break a 20-minute math computation worksheet task into 3 seven minute assignments). Breaking longer assignments into briefer segments also allows the teacher to praise struggling students more frequently for work completion and effort, providing an additional 'natural' reinforcer. Second, allow students to respond to easier practice items orally rather than in written form to speed up the rate of correct responses. Math Homework: Motivate Students Through Reinforcers, Interesting Assignments, Homework Planners, and Self-Monitoring (Bryan & Sullivan-Burstein, 1998). Improve students' rate of homework completion and quality by using reinforcers, motivating 'real-life' assignments, a homework planner, and student self-monitoring. (1) Reinforcers: Allow students to earn a small reward (e.g., additional free time) when they turn in all homework assignments for the week. (2) 'Real-life' Assignments: Make homework meaningful by linking concepts being taught to students' lives. In a math lesson on estimating area, for example, give students the homework task of calculating the area of their bedroom and estimating the amount of paint needed to cover the walls. (3) Homework Planner: Teach students to use a homework planner to write down assignments, organize any materials (e.g., worksheets) needed for homework, transport completed homework safely back to school, and provide space for parents and teachers to communicate about homework via written school-home notes. (4) Student Self-Monitoring: Direct students to chart their homework completion each week. Have students plot the number of assignments turned in on-time in green, assignments not turned in at all in red, and assignments turned in late in yellow. Math Instruction: Consolidate Student Learning During Lecture Through the Peer-Guided Pause (Hawkins, & Brady, 1994). During large-group math lectures, teachers can help students to retain more instructional content by incorporating brief Peer Guided Pause sessions into lectures. Students are trained to work in pairs. At one or more appropriate review points in a lecture period, the instructor directs students to pair up to work together for 4 minutes. During each Peer Guided Pause, students are given a worksheet that contains one or more correctly completed word or number problems illustrating the math concept(s) covered in the lecture. The sheet also contains several additional, similar problems that pairs of students work cooperatively to complete, along with an answer key. Student pairs are reminded to (a) monitor their understanding of the lesson concepts; (b) review the correctly math model problem; (c) work cooperatively on the additional problems, and (d) check their answers. The teacher can direct student pairs to write their names on the practice sheets and collect them as a convenient way to monitor student understanding. Math Instruction: Maintain a Supportive Atmosphere for Classroom "Math Talk" (Cooke & Adams, 1998). Teachers can promote greater student 'risk-taking' in mathematics learning when they cultivate a positive classroom atmosphere for math discussions while preventing peers from putting each other down. The teacher models behavioral expectations for open, interactive discussions, praises students for their class participation and creative attempts at problem-solving, and regularly points out that incorrect answers and misunderstandings should be celebrated—as they often lead to breakthroughs in learning. The teacher uses open-ended comments (e.g., "What led you to that answer?") as tools to draw out students and encourage them to explore and apply math concepts in group discussion. Students are also encouraged in a supportive manner to evaluate each other's reasoning. However, the teacher intervenes immediately to prevent negative student comments or 'put-downs' about peers. As with any problem classroom behavior, a first offense requires that the student meet privately with the instructor to discuss teacher expectations for positive classroom behavior. If the student continues to put down peers, the teacher imposes appropriate disciplinary consequences. Math Instruction: Unlock the Thoughts of Reluctant Students Through Class Journaling (Baxter, Woodward & Olson, 2005). Students can effectively clarify their knowledge of math concepts and problem-solving strategies through regular use of class 'math journals'. Journaling is a valuable channel of communication about math issues for students who are unsure of their skills and reluctant to contribute orally in class. At the start of the year, the teacher introduces the journaling assignment, telling students that they will be asked to write and submit responses at least weekly to teacherposed questions. At first, the teacher presents 'safe' questions that tap into the students' opinions and attitudes about mathematics (e.g., 'How important do you think it is nowadays for cashiers in fast-food restaurants to be able to calculate in their head the amount of change to give a customer?"). As students become comfortable with the journaling activity, the teacher starts to pose questions about the students' own mathematical thinking relating to specific assignments. Students are encouraged to use numerals, mathematical symbols, and diagrams in their journal entries to enhance their explanations. The teacher provides brief written comments on individual student entries, as well as periodic oral feedback and encouragement to the entire class on the general quality and content of class journal responses. Regular math journaling can prod students to move beyond simple 'rote' mastery of the steps for completing various math problems toward a deeper grasp of the math concepts that underlie and explain a particular problem solving approach. Teachers will find that journal entries are a concrete method for monitoring student understanding of more abstract math concepts. To promote the quality of journal entries, the teacher might also assign them an effort grade that will be calculated into quarterly math report card grades. Math Review: Teach Effective Test-Preparation Strategies (Hong, Sas, & Sas, 2006). A comparison of the methods that high and low-achieving math students typically use to prepare for tests suggests that struggling math students need to be taught (1) specific test-review strategies and (2) time-management and self-advocacy skills. Among review-related strategies, deficient test-takers benefit from explicit instruction in how to take adequate in-class notes; to adopt a systematic method to review material for tests (e.g., looking over their notes each night, rereading relevant portions of the math text, reviewing handouts from the teacher, etc.), and to give themselves additional practice in solving problems (e.g., by attempting all homework items, tackling additional problems from the text book, and solving problems included in teacher handouts). Deficient test-takers also require pointers in how to allocate and manage their study time wisely, to structure their study environment to increase concentration and reduce distractions, as well as to develop 'self advocacy' skills such as seeking additional help from teachers when needed. Teachers can efficiently teach effective test-preparation methods as a several-session whole-group instructional module. Math Vocabulary: Preteach, Model, and Use Standard Math Terms (Chard, D., n.d.). Three strategies can help students to learn essential math vocabulary: preteaching key vocabulary items, modeling those vocabulary words, and using only universally accepted math terms in instruction. (1) Preteach key math vocabulary. Math vocabulary provides students with the language tools to grasp abstract mathematical concepts and to explain their own reasoning. Therefore, do not wait to teach that vocabulary only at 'point of use'. Instead, preview relevant math vocabulary as a regular a part of the 'background' information that students receive in preparation to learn new math concepts or operations. (2) Model the relevant vocabulary when new concepts are taught. Strengthen students' grasp of new vocabulary by reviewing a number of math problems with the class, each time consistently and explicitly modeling the use of appropriate vocabulary to describe the concepts being taught. Then have students engage in cooperative learning or individual practice activities in which they too must successfully use the new vocabulary—while the teacher provides targeted support to students as needed. (3) Ensure that students learn standard, widely accepted labels for common math terms and operations and that they use them consistently to describe their math problem-solving efforts. Armendariz, F., & Umbreit, J. (1999). Using active responding to reduce disruptive behavior in a general education classroom. Journal of Positive Behavior Interventions, 1(3), 152-158. Baxter, J. A., Woodward, J., & Olson, D. (2005). Writing in mathematics: An alternative form of communication for academically low-achieving students. Learning Disabilities Research & Practice, 20(2), 119–135. Bryan, T., & Sullivan-Burstein, K. (1998). Teacher-selected strategies for improving homework completion. Remedial & Special Education, 19, 263-275. From Jim Wright: Intervention Ideas for MATHEMATICS 9/26/08 11:53 AM http://www.jimwrightonline.com/php/interventionista/interventionista_intv_list.php?prob_type=MATHEMATICS&print_status=YES Page 5 of 5 Carnine, D. (1997). Instructional design in mathematics for students with learning disabilities. Journal of Learning Disabilities, 30, 130-141. Caron, T. A. (2007). Learning multiplication the easy way. The Clearing House, 80, 278-282. Chard, D. (n.d..) Vocabulary strategies for the mathematics classroom. Retrieved November 23, 2007, from Cooke, L B. & Adams, V. M. (1998). Encouraging "math talk" in the classroom. Middle School Journal, 29(5), 35-40. Hawkins, J., & Brady, M. P. (1994). The effects of independent and peer guided practice during instructional pauses on the academic performance of students with mild handicaps. Education & Treatment of Children, 17 (1), 1-28. Hong, E., Sas, M., & Sas, J. C. (2006). Test-taking strategies of high and low mathematics achievers. Journal of Educational Research, 99(3), 144-155. Lambert, M. C., Cartledge, G., Heward, W. L., & Lo, Y. (2006). Effects of response cards on disruptive behavior and academic responding during math lessons by fourth-grade urban students. Journal of Positive Behavior Interventions, 8(2), 88-99. Montague, M. (1997). Cognitive strategy instruction in mathematics for students with learning disabilities. Journal of Learning Disabilities, 30, 164-177. Montague, M., Warger, C., & Morgan, T. H. (2000). Solve it! Strategy instruction to improve mathematical problem solving.. Learning Disabilities Research & Practice, 15, 110-116. Pólya, G. (1957). How to solve it (2nd ed.). Princeton University Press: Princeton, N.J. Rhymer, K. N., Skinner, C. H., Jackson, S., McNeill, S., Smith, T., & Jackson, B. (2002). The 1-minute explicit timing intervention: The influence of mathematics problem difficulty. Journal of Instructional Psychology, 29(4), 305-311. Skinner, C. H., Pappas, D. N., & Davis, K. A. (2005). Enhancing academic engagement: Providing opportunities for responding and influencing students to choose to respond. Psychology in the Schools, 42, 389-403. Van Essen, G., & Hamaker, C. (1990). Using self-generated drawings to solve arithmetic word problems. Journal of Educational Research, 83, 301-312. Van Garderen, D. (2006). Spatial visualization, visual imagery, and mathematical problem solving of students with varying abilities. Journal of Learning Disabilities, 39, 496-506. Williams, K. M. (2003). Writing about the problem solving process to improve problem-solving performance. Mathematics Teacher, 96(3), 185-187. Woodward, J. (2006). Developing automaticity in multiplication facts integrating strategy instruction with timed practice drills. Learning Disability Quarterly, 29, 269-289. Zrebiec Uberti, H., Mastropieri, M. A., & Scruggs, T. E. (2004). Check it off: Individualizing a math algorithm for students with disabilities via self-monitoring checklists. Intervention in School and Clinic, 39, 269-275.
Asteroid impact avoidance comprises the methods by which near-Earth objects (NEO) on a potential collision course with Earth could be diverted away, preventing destructive impact events. An impact by a sufficiently large asteroid or other NEOs would cause, depending on its impact location, massive tsunamis or multiple firestorms, and an impact winter caused by the sunlight-blocking effect of large quantities of pulverized rock dust and other debris placed into the stratosphere. A collision 66 million years ago between the Earth and an object approximately 10 kilometres (6 miles) wide is thought to have produced the Chicxulub crater and triggered the Cretaceous–Paleogene extinction event that is understood by the scientific community to have caused the extinction of all non-avian dinosaurs. While the chances of a major collision are low in the near term, it is a near-certainty that one will happen eventually unless defensive measures are taken. Astronomical events—such as the Shoemaker-Levy 9 impacts on Jupiter and the 2013 Chelyabinsk meteor, along with the growing number of objects on the Sentry Risk Table—have drawn renewed attention to such threats. The popularity of the 2021 movie Don't Look Up helped to raise awareness of the possibility of avoiding NEOs. In 2016, a NASA scientist warned that the Earth is unprepared for such an event. In April 2018, the B612 Foundation reported "It's 100 percent certain we'll be hit by a devastating asteroid, but we're not 100 percent sure when." Also in 2018, physicist Stephen Hawking, in his final book, Brief Answers to the Big Questions, considered an asteroid collision to be the biggest threat to the planet. Several ways of avoiding an asteroid impact have been described. Nonetheless, in March 2019, scientists reported that asteroids may be much more difficult to destroy than thought earlier. In addition, an asteroid may reassemble itself due to gravity after being disrupted. In May 2021, NASA astronomers reported that 5 to 10 years of preparation may be needed to avoid a virtual impactor based on a simulated exercise conducted by the 2021 Planetary Defense Conference. According to expert testimony in the United States Congress in 2013, NASA would require at least five years of preparation before a mission to intercept an asteroid could be launched. In June 2018, the US National Science and Technology Council warned that the United States was unprepared for an asteroid impact event, and developed and released the "National Near-Earth Object Preparedness Strategy Action Plan" to better prepare. Most deflection efforts for a large object require from a year to decades of warning, allowing time to prepare and carry out a collision avoidance project, as no known planetary defense hardware has yet been developed. It has been estimated that a velocity change of just 3.5/t × 10−2 m·s−1 (where t is the number of years until potential impact) is needed to successfully deflect a body on a direct collision trajectory. In addition, under certain circumstances, much smaller velocity changes are needed. For example, it was estimated there was a high chance of 99942 Apophis swinging by Earth in 2029 with a 10−4 probability of passing through a 'keyhole' and returning on an impact trajectory in 2035 or 2036. It was then determined that a deflection from this potential return trajectory, several years before the swing-by, could be achieved with a velocity change on the order of 10−6 ms−1. An impact by a 10 kilometres (6.2 mi) asteroid on the Earth has historically caused an extinction-level event due to catastrophic damage to the biosphere. There is also the threat from comets entering the inner Solar System. The impact speed of a long-period comet would likely be several times greater than that of a near-Earth asteroid, making its impact much more destructive; in addition, the warning time is unlikely to be more than a few months. Impacts from objects as small as 50 metres (160 ft) in diameter, which are far more common, are historically extremely destructive regionally (see Barringer crater). Finding out the material composition of the object is also helpful before deciding which strategy is appropriate. Missions like the 2005 Deep Impact probe and the Rosetta spacecraft, have provided valuable information on what to expect. REP. STEWART: ... are we technologically capable of launching something that could intercept [an asteroid]? ... DR. A'HEARN: No. If we had spacecraft plans on the books already, that would take a year ... I mean a typical small mission ... takes four years from approval to start to launch ... Efforts in asteroid impact prediction have concentrated on the survey method. The 1992 NASA-sponsored Near-Earth-Object Interception Workshop hosted by Los Alamos National Laboratory evaluated issues involved in intercepting celestial objects that could hit Earth. In a 1992 report to NASA, a coordinated Spaceguard Survey was recommended to discover, verify and provide follow-up observations for Earth-crossing asteroids. This survey was expected to discover 90% of these objects larger than one kilometer within 25 years. Three years later, another NASA report recommended search surveys that would discover 60–70% of short-period, near-Earth objects larger than one kilometer within ten years and obtain 90% completeness within five more years. In 1998, NASA formally embraced the goal of finding and cataloging, by 2008, 90% of all near-Earth objects (NEOs) with diameters of 1 km or larger that could represent a collision risk to Earth. The 1 km diameter metric was chosen after considerable study indicated that an impact of an object smaller than 1 km could cause significant local or regional damage but is unlikely to cause a worldwide catastrophe. The impact of an object much larger than 1 km diameter could well result in worldwide damage up to, and potentially including, extinction of the human species. The NASA commitment has resulted in the funding of a number of NEO search efforts, which made considerable progress toward the 90% goal by 2008. However the 2009 discovery of several NEOs approximately 2 to 3 kilometers in diameter (e.g. 2009 CR2, 2009 HC82, 2009 KJ, 2009 MS and 2009 OG) demonstrated there were still large objects to be detected. United States Representative George E. Brown Jr. (D-CA) was quoted as voicing his support for planetary defense projects in Air & Space Power Chronicles, saying "If some day in the future we discover well in advance that an asteroid that is big enough to cause a mass extinction is going to hit the Earth, and then we alter the course of that asteroid so that it does not hit us, it will be one of the most important accomplishments in all of human history." Because of Congressman Brown's long-standing commitment to planetary defense, a U.S. House of Representatives' bill, H.R. 1022, was named in his honor: The George E. Brown, Jr. Near-Earth Object Survey Act. This bill "to provide for a Near-Earth Object Survey program to detect, track, catalogue, and characterize certain near-Earth asteroids and comets" was introduced in March 2005 by Rep. Dana Rohrabacher (R-CA). It was eventually rolled into S.1281, the NASA Authorization Act of 2005, passed by Congress on December 22, 2005, subsequently signed by the President, and stating in part: The U.S. Congress has declared that the general welfare and security of the United States require that the unique competence of NASA be directed to detecting, tracking, cataloguing, and characterizing near-Earth asteroids and comets in order to provide warning and mitigation of the potential hazard of such near-Earth objects to the Earth. The NASA Administrator shall plan, develop, and implement a Near-Earth Object Survey program to detect, track, catalogue, and characterize the physical characteristics of near- Earth objects equal to or greater than 140 meters in diameter in order to assess the threat of such near-Earth objects to the Earth. It shall be the goal of the Survey program to achieve 90% completion of its near-Earth object catalogue (based on statistically predicted populations of near-Earth objects) within 15 years after the date of enactment of this Act. The NASA Administrator shall transmit to Congress not later than 1 year after the date of enactment of this Act an initial report that provides the following: (A) An analysis of possible alternatives that NASA may employ to carry out the Survey program, including ground-based and space-based alternatives with technical descriptions. (B) A recommended option and proposed budget to carry out the Survey program pursuant to the recommended option. (C) Analysis of possible alternatives that NASA could employ to divert an object on a likely collision course with Earth. The result of this directive was a report presented to Congress in early March 2007. This was an Analysis of Alternatives (AoA) study led by NASA's Program Analysis and Evaluation (PA&E) office with support from outside consultants, the Aerospace Corporation, NASA Langley Research Center (LaRC), and SAIC (amongst others). See also Improving impact prediction. The Minor Planet Center in Cambridge, Massachusetts has been cataloging the orbits of asteroids and comets since 1947. It has recently been joined by surveys that specialize in locating the near-Earth objects (NEO), many (as of early 2007) funded by NASA's Near Earth Object program office as part of their Spaceguard program. One of the best-known is LINEAR that began in 1996. By 2004 LINEAR was discovering tens of thousands of objects each year and accounting for 65% of all new asteroid detections. LINEAR uses two one-meter telescopes and one half-meter telescope based in New Mexico. The Catalina Sky Survey (CSS) is conducted at the Steward Observatory's Catalina Station, located near Tucson, Arizona, in the United States. It uses two telescopes, a 1.5-meter (60-inch) f/2 telescope on the peak of Mount Lemmon, and a 68-cm (27-inch) f/1.7 Schmidt telescope near Mount Bigelow (both in the Tucson, Arizona area). In 2005, CSS became the most prolific NEO survey surpassing Lincoln Near-Earth Asteroid Research (LINEAR) in total number of NEOs and potentially hazardous asteroids discovered each year since. CSS discovered 310 NEOs in 2005, 396 in 2006, 466 in 2007, and in 2008 564 NEOs were found. Spacewatch, which uses a 90 centimeter telescope sited at the Kitt Peak Observatory in Arizona, updated with automatic pointing, imaging, and analysis equipment to search the skies for intruders, was set up in 1980 by Tom Gehrels and Robert S. McMillan of the Lunar and Planetary Laboratory of the University of Arizona in Tucson, and is now being operated by McMillan. The Spacewatch project has acquired a 1.8 meter telescope, also at Kitt Peak, to hunt for NEOs, and has provided the old 90-centimeter telescope with an improved electronic imaging system with much greater resolution, improving its search capability. Other near-Earth object tracking programs include Near-Earth Asteroid Tracking (NEAT), Lowell Observatory Near-Earth-Object Search (LONEOS), Campo Imperatore Near-Earth Object Survey (CINEOS), Japanese Spaceguard Association, and Asiago-DLR Asteroid Survey. Pan-STARRS completed telescope construction in 2010, and it is now actively observing. The Asteroid Terrestrial-impact Last Alert System, now in operation, conducts frequent scans of the sky with a view to later-stage detection on the collision stretch of the asteroid orbit. Those would be much too late for deflection, but still in time for evacuation and preparation of the affected Earth region. Another project, supported by the European Union, is NEOShield, which analyses realistic options for preventing the collision of a NEO with Earth. Their aim is to provide test mission designs for feasible NEO mitigation concepts. The project particularly emphasises on two aspects. "Spaceguard" is the name for these loosely affiliated programs, some of which receive NASA funding to meet a U.S. Congressional requirement to detect 90% of near-Earth asteroids over 1 km diameter by 2008. A 2003 NASA study of a follow-on program suggests spending US$250–450 million to detect 90% of all near-Earth asteroids 140 meters and larger by 2028. NEODyS is an online database of known NEOs. The B612 Foundation is a private nonprofit foundation with headquarters in the United States, dedicated to protecting the Earth from asteroid strikes. It is led mainly by scientists, former astronauts and engineers from the Institute for Advanced Study, Southwest Research Institute, Stanford University, NASA and the space industry. As a non-governmental organization it has conducted two lines of related research to help detect NEOs that could one day strike the Earth, and find the technological means to divert their path to avoid such collisions. The foundation's goal had been to design and build a privately financed asteroid-finding space telescope, Sentinel, which was to be launched in 2017–2018. However the project was cancelled in 2015. Had the Sentinel's infrared telescope been parked in an orbit similar to that of Venus, it would have helped identify threatening NEOs by cataloging 90% of those with diameters larger than 140 metres (460 ft), as well as surveying smaller Solar System objects. Data gathered by Sentinel would have helped identify asteroids and other NEOs that pose a risk of collision with Earth, by being forwarded to scientific data-sharing networks, including NASA and academic institutions such as the Minor Planet Center. The foundation also proposes asteroid deflection of potentially dangerous NEOs by the use of gravity tractors to divert their trajectories away from Earth, a concept co-invented by the organization's CEO, physicist and former NASA astronaut Ed Lu. Orbit@home intends to provide distributed computing resources to optimize search strategy. On February 16, 2013, the project was halted due to lack of grant funding. However, on July 23, 2013, the orbit@home project was selected for funding by NASA's Near Earth Object Observation program and was to resume operations sometime in early 2014. As of July 13, 2018, the project is offline according to its website. The Large Synoptic Survey Telescope, currently under construction, is expected to perform a comprehensive, high-resolution survey starting in the early 2020s. On November 8, 2007, the House Committee on Science and Technology's Subcommittee on Space and Aeronautics held a hearing to examine the status of NASA's Near-Earth Object survey program. The prospect of using the Wide-field Infrared Survey Explorer was proposed by NASA officials. WISE surveyed the sky in the infrared band at a very high sensitivity. Asteroids that absorb solar radiation can be observed through the infrared band. It was used to detect NEOs, in addition to performing its science goals. It is projected that WISE could detect 400 NEOs (roughly two percent of the estimated NEO population of interest) within the one-year mission. NEOSSat, the Near Earth Object Surveillance Satellite, is a microsatellite launched in February 2013 by the Canadian Space Agency (CSA) that will hunt for NEOs in space. Furthermore Near-Earth Object WISE (NEOWISE), an extension of the WISE mission, started in September 2013 (in its second mission extension) to hunt asteroids and comets close to the orbit of Earth. Research published in the March 26, 2009 issue of the journal Nature, describes how scientists were able to identify an asteroid in space before it entered Earth's atmosphere, enabling computers to determine its area of origin in the Solar System as well as predict the arrival time and location on Earth of its shattered surviving parts. The four-meter-diameter asteroid, called 2008 TC3, was initially sighted by the automated Catalina Sky Survey telescope, on October 6, 2008. Computations correctly predicted that it would impact 19 hours after discovery and in the Nubian Desert of northern Sudan. A number of potential threats have been identified, such as 99942 Apophis (previously known by its provisional designation 2004 MN4), which in 2004 temporarily had an impact probability of about 3% for the year 2029. Additional observations revised this probability down to zero. The ellipses in the diagram on the right show the predicted position of an example asteroid at closest Earth approach. At first, with only a few asteroid observations, the error ellipse is very large and includes the Earth. Further observations shrink the error ellipse, but it still includes the Earth. This raises the predicted impact probability, since the Earth now covers a larger fraction of the error region. Finally, yet more observations (often radar observations, or discovery of a previous sighting of the same asteroid on archival images) shrink the ellipse revealing that the Earth is outside the error region, and the impact probability is near zero. For asteroids that are actually on track to hit Earth the predicted probability of impact continues to increase as more observations are made. This similar pattern makes it difficult to differentiate between asteroids that will only come close to Earth and those that will actually hit it. This in turn makes it difficult to decide when to raise an alarm as gaining more certainty takes time, which reduces time available to react to a predicted impact. However, raising the alarm too soon has the danger of causing a false alarm and creating a Boy Who Cried Wolf effect if the asteroid in fact misses Earth. Various collision avoidance techniques have different trade-offs with respect to metrics such as overall performance, cost, failure risks, operations, and technology readiness. There are various methods for changing the course of an asteroid/comet. These can be differentiated by various types of attributes such as the type of mitigation (deflection or fragmentation), energy source (kinetic, electromagnetic, gravitational, solar/thermal, or nuclear), and approach strategy (interception, rendezvous, or remote station). Strategies fall into two basic sets: Fragmentation and delay. Fragmentation concentrates on rendering the impactor harmless by fragmenting it and scattering the fragments so that they miss the Earth or are small enough to burn up in the atmosphere. Delay exploits the fact that both the Earth and the impactor are in orbit. An impact occurs when both reach the same point in space at the same time, or more correctly when some point on Earth's surface intersects the impactor's orbit when the impactor arrives. Since the Earth is approximately 12,750 km in diameter and moves at approx. 30 km per second in its orbit, it travels a distance of one planetary diameter in about 425 seconds, or slightly over seven minutes. Delaying, or advancing the impactor's arrival by times of this magnitude can, depending on the exact geometry of the impact, cause it to miss the Earth. Collision avoidance strategies can also be seen as either direct, or indirect and in how rapidly they transfer energy to the object. The direct methods, such as nuclear explosives, or kinetic impactors, rapidly intercept the bolide's path. Direct methods are preferred because they are generally less costly in time and money. Their effects may be immediate, thus saving precious time. These methods would work for short-notice and long-notice threats, and are most effective against solid objects that can be directly pushed, but in the case of kinetic impactors, they are not very effective against large loosely aggregated rubble piles. Indirect methods, such as gravity tractors, attaching rockets or mass drivers, are much slower. They require traveling to the object, changing course up to 180 degrees for space rendezvous, and then taking much more time to change the asteroid's path just enough so it will miss Earth. Many NEOs are thought to be "flying rubble piles" only loosely held together by gravity, and a typical spacecraft sized kinetic-impactor deflection attempt might just break up the object or fragment it without sufficiently adjusting its course. If an asteroid breaks into fragments, any fragment larger than 35 meters across would not burn up in the atmosphere and itself could impact Earth. Tracking the thousands of buckshot-like fragments that could result from such an explosion would be a very daunting task, although fragmentation would be preferable to doing nothing and allowing the originally larger rubble body, which is analogous to a shot and wax slug, to impact the Earth. In Cielo simulations conducted in 2011–2012, in which the rate and quantity of energy delivery were sufficiently high and matched to the size of the rubble pile, such as following a tailored nuclear explosion, results indicated that any asteroid fragments, created after the pulse of energy is delivered, would not pose a threat of re-coalescing (including for those with the shape of asteroid Itokawa) but instead would rapidly achieve escape velocity from their parent body (which for Itokawa is about 0.2 m/s) and therefore move out of an earth-impact trajectory. Initiating a nuclear explosive device above, on, or slightly beneath, the surface of a threatening celestial body is a potential deflection option, with the optimal detonation height dependent upon the composition and size of the object. It does not require the entire NEO to be vaporized to mitigate an impact threat. In the case of an inbound threat from a "rubble pile," the stand off, or detonation height above the surface configuration, has been put forth as a means to prevent the potential fracturing of the rubble pile. The energetic neutrons and soft X-rays released by the detonation, which do not appreciably penetrate matter, are converted into thermal heat upon encountering the object's surface matter, ablatively vaporizing all line of sight exposed surface areas of the object to a shallow depth, turning the surface material it heats up into ejecta, and, analogous to the ejecta from a chemical rocket engine exhaust, changing the velocity, or "nudging", the object off course by the reaction, following Newton's third law, with ejecta going one way and the object being propelled in the other. Depending on the energy of the explosive device, the resulting rocket exhaust effect, created by the high velocity of the asteroid's vaporized mass ejecta, coupled with the object's small reduction in mass, would produce enough of a change in the object's orbit to make it miss the Earth. A Hypervelocity Asteroid Mitigation Mission for Emergency Response (HAMMER) has been proposed. If the object is very large but is still a loosely-held-together rubble pile, a solution is to detonate one or a series of nuclear explosive devices alongside the asteroid, at a 20-meter (66 ft) or greater stand-off height above its surface, so as not to fracture the potentially loosely-held-together object. Providing that this stand-off strategy was done far enough in advance, the force from a sufficient number of nuclear blasts would alter the object's trajectory enough to avoid an impact, according to computer simulations and experimental evidence from meteorites exposed to the thermal X-ray pulses of the Z-machine. In 1967, graduate students under Professor Paul Sandorff at the Massachusetts Institute of Technology were tasked with designing a method to prevent a hypothetical 18-month distant impact on Earth by the 1.4-kilometer-wide (0.87 mi) asteroid 1566 Icarus, an object that makes regular close approaches to Earth, sometimes as close as 16 lunar distances. To achieve the task within the timeframe and with limited material knowledge of the asteroid's composition, a variable stand-off system was conceived. This would have used a number of modified Saturn V rockets sent on interception courses and the creation of a handful of nuclear explosive devices in the 100-megaton energy range—coincidentally, the same as the maximum yield of the Soviets' Tsar Bomba would have been if a uranium tamper had been used—as each rocket vehicle's payload. The design study was later published as Project Icarus which served as the inspiration for the 1979 film Meteor. A NASA analysis of deflection alternatives, conducted in 2007, stated: Nuclear standoff explosions are assessed to be 10–100 times more effective than the non-nuclear alternatives analyzed in this study. Other techniques involving the surface or subsurface use of nuclear explosives may be more efficient, but they run an increased risk of fracturing the target NEO. They also carry higher development and operations risks. In the same year, NASA released a study where the asteroid Apophis (with a diameter of around 300 metres or 1,000 feet) was assumed to have a much lower rubble pile density (1,500 kg/m3 or 100 lb/cu ft) and therefore lower mass than it is now known to have, and in the study, it is assumed to be on an impact trajectory with Earth for the year 2029. Under these hypothetical conditions, the report determines that a "Cradle spacecraft" would be sufficient to deflect it from Earth impact. This conceptual spacecraft contains six B83 physics packages, each set for their maximum 1.2-megatonne yield, bundled together and lofted by an Ares V vehicle sometime in the 2020s, with each B83 being fuzed to detonate over the asteroid's surface at a height of 100 metres or 330 feet ("1/3 of the objects diameter" as its stand-off), one after the other, with hour-long intervals between each detonation. The results of this study indicated that a single employment of this option "can deflect NEOs of [100–500 metres or 330–1,640 feet diameter] two years before impact, and larger NEOs with at least five years warning". These effectiveness figures are considered to be "conservative" by its authors, and only the thermal X-ray output of the B83 devices was considered, while neutron heating was neglected for ease of calculation purposes. In 2011, the director of the Asteroid Deflection Research Center at Iowa State University, Dr. Bong Wie (who had published kinetic impactor deflection studies previously), began to study strategies that could deal with 50-to-500-metre-diameter (200–1,600 ft) objects when the time to Earth impact was less than one year. He concluded that to provide the required energy, a nuclear explosion or other event that could deliver the same power, are the only methods that can work against a very large asteroid within these time constraints. This work resulted in the creation of a conceptual Hypervelocity Asteroid Intercept Vehicle (HAIV), which combines a kinetic impactor to create an initial crater for a follow-up subsurface nuclear detonation within that initial crater, which would generate a high degree of efficiency in the conversion of the nuclear energy that is released in the detonation into propulsion energy to the asteroid. A similar proposal would use a surface-detonating nuclear device in place of the kinetic impactor to create the initial crater, then using the crater as a rocket nozzle to channel succeeding nuclear detonations. At the 2014 NASA Innovative Advanced Concepts (NIAC) conference, Wie and his colleagues stated that "we have the solution, using our baseline concept, to be able to mitigate the asteroid-impact threat, with any range of warning." For example, according to their computer models, with a warning time of 30 days, a 300-metre-wide (1,000 ft) asteroid would be neutralized[vague] by using a single HAIV, with less than 0.1% of the destroyed object's mass potentially striking Earth, which by comparison would be more than acceptable.[further explanation needed] As of 2015, Wie has collaborated with the Danish Emergency Asteroid Defence Project (EADP), which ultimately intends to crowdsource sufficient funds to design, build, and store a non-nuclear HAIV spacecraft as planetary insurance. For threatening asteroids too large and/or too close to Earth impact to effectively be deflected by the non-nuclear HAIV approach, nuclear explosive devices (with 5% of the explosive yield than those used for the stand-off strategy) are intended to be swapped in, under international oversight, when conditions arise that necessitate it. Following the 1994 Shoemaker-Levy 9 comet impacts with Jupiter, Edward Teller proposed, to a collective of U.S. and Russian ex-Cold War weapons designers in a 1995 planetary defense workshop meeting at Lawrence Livermore National Laboratory (LLNL), that they collaborate to design a one-gigaton nuclear explosive device, which would be equivalent to the kinetic energy of a one-kilometer-diameter (0.62 mi) asteroid. The theoretical one-gigaton device would weigh about 25–30 tons, light enough to be lifted on the Energia rocket. It could be used to instantaneously vaporize a one-kilometre (0.62 mi) asteroid, divert the paths of ELE-class asteroids (greater than 10 kilometres or 6.2 miles in diameter) within short notice of a few months. With one year of notice, and at an interception location no closer than Jupiter, it could also deal with the even rarer short period comets that can come out of the Kuiper belt and transit past Earth orbit within two years.[clarification needed] For comets of this class, with a maximum estimated diameter of 100 kilometers (62 mi), Chiron served as the hypothetical threat. In 2013, the related National Laboratories of the US and Russia signed a deal that includes an intent to cooperate on defense from asteroids. An April 2014 GAO report notes that the NNSA is retaining canned sub assemblies (CSAs—nuclear secondary stages) in an indeterminate state pending a senior-level government evaluation of their use in planetary defense against earthbound asteroids." In its FY2015 budget request, the NNSA noted that the nine-megaton B53 component disassembly was "delayed", leading some observers to conclude they might be the warhead CSAs being retained for potential planetary defense purposes.[failed verification] The impact of a massive object, such as a spacecraft or even another near-Earth object, is another possible solution to a pending NEO impact. An object with a high mass close to the Earth could be sent out into a collision course with the asteroid, knocking it off course. When the asteroid is still far from the Earth, a means of deflecting the asteroid is to directly alter its momentum by colliding a spacecraft with the asteroid. A NASA analysis of deflection alternatives, conducted in 2007, stated: Non-nuclear kinetic impactors are the most mature approach and could be used in some deflection/mitigation scenarios, especially for NEOs that consist of a single small, solid body. The European Space Agency (ESA) is studying the preliminary design of two space missions for ~2020, named AIDA (formerly Don Quijote), and if flown, they would be the first intentional asteroid deflection mission. ESA's Advanced Concepts Team has also demonstrated theoretically that a deflection of 99942 Apophis could be achieved by sending a simple spacecraft[when?] weighing less than one ton to impact against the asteroid. During a trade-off study one of the leading researchers[who?] argued that a strategy called 'kinetic impactor deflection' was more efficient than others.[dubious ] The European Union's NEOShield-2 Mission is also primarily studying the Kinetic Impactor mitigation method. The principle of the kinetic impactor mitigation method is that the NEO or Asteroid is deflected following an impact from an impactor spacecraft. The principle of momentum transfer is used, as the impactor crashes into the NEO at a very high velocity of 10 km/s (36,000 km/h; 22,000 mph) or more. The momentum of the impactor is transferred to the NEO, causing a change in velocity and therefore making it deviate from its course slightly. As of mid-2021, the modified AIDA mission has been approved. The NASA Double Asteroid Redirection Test (DART) kinetic impactor spacecraft was launched in November 2021. The goal is to impact Dimorphos (nicknamed Didymoon), the 180-meter (590 ft) minor-planet moon of near-Earth asteroid 65803 Didymos. The impact will occur in October 2022 when Didymos is relatively close to Earth, allowing Earth-based telescopes and planetary radar to observe the event. The result of the impact will be to change the orbital velocity and hence orbital period of Dimorphos, by a large enough amount that it can be measured from Earth. This will show for the first time that it is possible to change the orbit of a small 200-meter (660 ft) asteroid, around the size most likely to require active mitigation in the future. The second part of the AIDA mission–the ESA HERA spacecraft–has been approved by ESA member states in October 2019. It would reach the Didymos system in 2027 and measure both the mass of Dimorphos and the precise effect of the impact on that body, allowing much better extrapolation of the AIDA mission to other targets. Main article: Gravity tractor Another alternative to explosive deflection is to move the asteroid slowly over time. A small but constant amount of thrust accumulates to deviate an object sufficiently from its course. Edward T. Lu and Stanley G. Love have proposed using a massive unmanned spacecraft hovering over an asteroid to gravitationally pull the asteroid into a non-threatening orbit. Though both objects are gravitationally pulled towards each other, the spacecraft can counter the force towards the asteroid by, for example, an ion thruster, so the net effect would be that the asteroid is accelerated towards the spacecraft and thus slightly deflected from its orbit. While slow, this method has the advantage of working irrespective of the asteroid's composition or spin rate; rubble pile asteroids would be difficult to deflect by means of nuclear detonations, while a pushing device would be difficult or inefficient to mount on a fast-rotating asteroid. A gravity tractor would likely have to spend several years beside the asteroid to be effective. A NASA analysis of deflection alternatives, conducted in 2007, stated: "Slow push" mitigation techniques are the most expensive, have the lowest level of technical readiness, and their ability to both travel to and divert a threatening NEO would be limited unless mission durations of many years to decades are possible. Main article: Ion-beam shepherd Another "contactless" asteroid deflection technique has been proposed by C. Bombardelli and J. Peláez from the Technical University of Madrid. The method involves the use of a low-divergence ion thruster pointed at the asteroid from a nearby hovering spacecraft. The momentum transmitted by the ions reaching the asteroid surface produces a slow-but-continuous force that can deflect the asteroid in a similar way as the gravity tractor, but with a lighter spacecraft. H. J. Melosh with I. V. Nemchinov proposed deflecting an asteroid or comet by focusing solar energy onto its surface to create thrust from the resulting vaporization of material. This method would first require the construction of a space station with a system of large collecting, concave mirrors similar to those used in solar furnaces. Orbit mitigation with highly concentrated sunlight is scalable to achieving the predetermined deflection within a year even for a global-threatening body without prolonged warning time. Such a hastened strategy may become topical in the case of late detection of a potential hazard, and also, if required, in providing the possibility for some additional action. Conventional concave reflectors are practically inapplicable to the high-concentrating geometry in the case of a giant shadowing space target, which is located in front of the mirrored surface. This is primarily because of the dramatic spread of the mirrors' focal points on the target due to the optical aberration when the optical axis is not aligned with the Sun. On the other hand, the positioning of any collector at a distance to the target much larger than its size does not yield the required concentration level (and therefore temperature) due to the natural divergence of the sunrays. Such principal restrictions are inevitably at any location regarding the asteroid of one or many unshaded forward-reflecting collectors. Also, in the case of secondary mirrors use, similar to the ones found in Cassegrain telescopes, would be prone to heat damage by partially concentrated sunlight from primary mirror. In order to remove the above restrictions, V.P. Vasylyev proposed to apply an alternative design of a mirrored collector – the ring-array concentrator. This type of collector has an underside lens-like position of its focal area that avoids shadowing of the collector by the target and minimizes the risk of its coating by ejected debris. Provided the sunlight concentration ~ 5 × 103 times, a surface irradiance of around 4-5 MW/m2 leads to a thrusting effect ~ 103 N. Intensive ablation of the rotating asteroid surface under the focal spot will lead to the appearance of a deep "canyon", which can contribute to the formation of the escaping gas flow into a jet-like one. This may be sufficient to deflect a 0.5-km asteroid within several months and no addition warning period, only using ring-array collector size ~ 0.5 of asteroid diameter. For such a prompt deflection of the larger NEOs, 1.3-2.2 km, the required collector sizes are comparable to the target diameter. In the case of a longer warning time, the required size of the collector may be significantly decreased. A mass driver is an (automated) system on the asteroid to eject material into space thus giving the object a slow steady push and decreasing its mass. A mass driver is designed to work as a very low specific impulse system, which in general uses a lot of propellant, but very little power. The idea is that when using local material as propellant, the amount of propellant is not as important as the amount of power, which is likely to be limited. Attaching any spacecraft propulsion device would have a similar effect of giving a push, possibly forcing the asteroid onto a trajectory that takes it away from Earth. An in-space rocket engine that is capable of imparting an impulse of 106 N·s (E.g. adding 1 km/s to a 1000 kg vehicle), will have a relatively small effect on a relatively small asteroid that has a mass of roughly a million times more. Chapman, Durda, and Gold's white paper calculates deflections using existing chemical rockets delivered to the asteroid. Such direct force rocket engines are typically proposed to use highly-efficient electrically powered spacecraft propulsion, such as ion thrusters or VASIMR. Main article: Asteroid laser ablation Similar to the effects of a nuclear device, it is thought possible to focus sufficient laser energy on the surface of an asteroid to cause flash vaporization / ablation to create either in impulse or to ablate away the asteroid mass. This concept, called asteroid laser ablation was articulated in the 1995 SpaceCast 2020 white paper "Preparing for Planetary Defense", and the 1996 Air Force 2025 white paper "Planetary Defense: Catastrophic Health Insurance for Planet Earth". Early publications include C. R. Phipps "ORION" concept from 1996, Colonel Jonathan W. Campbell's 2000 monograph "Using Lasers in Space: Laser Orbital Debris Removal and Asteroid Deflection", and NASA's 2005 concept Comet Asteroid Protection System (CAPS). Typically such systems require a significant amount of power, such as would be available from a Space-Based Solar Power Satellite. Another proposal is the Phillip Lubin's DE-STAR proposal: Carl Sagan, in his book Pale Blue Dot, expressed concern about deflection technology, noting that any method capable of deflecting impactors away from Earth could also be abused to divert non-threatening bodies toward the planet. Considering the history of genocidal political leaders and the possibility of the bureaucratic obscuring of any such project's true goals to most of its scientific participants, he judged the Earth at greater risk from a man-made impact than a natural one. Sagan instead suggested that deflection technology be developed only in an actual emergency situation. All low-energy delivery deflection technologies have inherent fine control and steering capability, making it possible to add just the right amount of energy to steer an asteroid originally destined for a mere close approach toward a specific Earth target. According to former NASA astronaut Rusty Schweickart, the gravitational tractor method is controversial because, during the process of changing an asteroid's trajectory, the point on the Earth where it could most likely hit would be slowly shifted across different countries. Thus, the threat for the entire planet would be minimized at the cost of some specific states' security. In Schweickart's opinion, choosing the way the asteroid should be "dragged" would be a tough diplomatic decision. Analysis of the uncertainty involved in nuclear deflection shows that the ability to protect the planet does not imply the ability to target the planet. A nuclear explosion that changes an asteroid's velocity by 10 meters/second (plus or minus 20%) would be adequate to push it out of an Earth-impacting orbit. However, if the uncertainty of the velocity change was more than a few percent, there would be no chance of directing the asteroid to a particular target. Asteroid or comet impacts are a common subgenre of disaster fiction, and such stories typically feature some attempt—successful or unsuccessful—to prevent the catastrophe, most of which involve trying to destroy or explosively redirect an object. The warheads would explode at a distance of one-third of the NEO's diameter and each detonation's X and gamma rays and neutrons would turn part of the NEO's surface into an expanding plasma to generate a force to deflect the asteroid. ((cite web)): CS1 maint: archived copy as title (link) ((cite web)): CS1 maint: archived copy as title (link)
1. 1850-1864 : Taiping Rebellion led by Hong Xiuquan. He worked for reforms to abolish private property, share communal wealth, free education for all, end the system of concubine, and create equality between men and women. He wound up capturing Nanjing, but it was put down by the British and the French. 2. During the Second Opium War in 1860, the allegiance of European imperialist occupied the Chinese capital of Peking (Beijing). The Old Summer Palace, the Qing Chinese equivalent of a national museum, was looted and subsequently burnt down. 3. British started selling Opium to the Chinese to make a profit and eventually try to gain power over them by getting the Chinese addicted. This eventually leads to the Opium War. 1. During the 1700s, a joint-stock company called the British East India Company was chartered by Queen Elizabeth I of England. The company’s main objective was to make a profit for shareholders by exploiting the abundant natural resources and gaining access to the markets in India. 2. To do this, the British East India Company successfully used “divide and conquer” tactics to increase their control over entire regions of the Indian subcontinent. This strategy entailed fanning the flames of religious division between native Muslim and Hindu groups, and taking advantage of the political rivalries that existed between local native rulers. 3. By the 1830s, the British government had taken over control of the East India Company. Under British rule, native customs such as sati, the ritual suicide of a wife after her husband’s death, were banned. The British built schools and railroads, and missionaries spread Christianity. 4. British held most of the political and economic power and they used this to restrict Indian-owned industries including cotton textiles. This led to a loss of self-sufficiency for many locals and, in the late 1800s, India experienced a severe famine. 1. The incomes of the members of the population who work for the imperialist are very small. If one discounts the amount paid to the overseas managers, goods bought at the “company store,” and the housing furnished by the company, the total is minute. 2. Nutritionally, the underdeveloped country’s workers are frequently worse off after the imperialist country’s intervention. Although bulkier food is eaten because the employer wants a more productive worker, the diet is often deficient nutritionally. Political 1. Resentment against the British mounted in the mid-1800s. In southern India, the British and the French allied with opposed political factions to extract Indian goods for their domestic uses. A strong sense of nationalism began to take hold. In 1857, Indian Sepoys came to believe that the cartridges of their rifles were greased with pork and beef fat. This was important because to use the cartridges, the user had to bite off the ends. 2. This was a religious concern for Hindu and Muslim Sepoys who were forbidden to eat these meats. This led to the Sepoy Mutiny when 85 soldiers refused to use the cartridges. The soldiers were jailed by the British and on May 10, 1857 the Sepoys marched to Delhi. Once there, they were joined by other soldiers and eventually the captured the city. 3. The Sepoy Mutiny spread to much of northern India, sparking an intense battle between British forces and the Indian soldiers. It took the East India Company more than one year to regain control. However, the event weakened Britain’s political position. Growing nationalism led to the founding of the Indian National Congress in 1885 and then to the Muslim League in 1906. 1. Self-Strengthening Movement: an attempt to restore value, and as implied by the name strength, to the weakened country through the application of Western technology and learning. Students, at home and those sent abroad, studied Western thought, languages, and science. Factories, shipyards, and arsenals were based on Western models. 2. The actual partitioning of the Empire was only prevented by the fact that the Great Powers were too evenly matched for any one of them to be able to steal a march on the others. Instead they extorted concessions, “unequal treaties” and extra-territorial rights from the weak Chinese Government. Great Britain had led the way by actually going to war with China to force her to accept imports of Indian opium. 1. In the North African dependencies of the declining Turkish Empire France and Germany intrigued and counter-intrigued, twice coming to the verge of war; in Persia and Afghanistan, still nominally independent, Britain and Russia worked against one another for effective control. 2. In South Africa the opening up of the Transvaal goldfields and the Kimberley diamond mines led to an influx of British adventurers whose interests clashed with those of the Boer settlers; backing them up, the Imperial Government was drawn into war in 1899, and achieved a not very glorious victory two years later. 1. British held most of the political and economic power and they used this to restrict Indian-owned industries including cotton textiles. This led to a loss of self-sufficiency for many locals and, in the late 1800s, India experienced a severe famine. 2. The British had a more-or-less hands-off policy when it came to religious and social customs in India. However, British missionaries increased during the imperial era, with hopes to spread Western Christianity. Many of the British officials working in India were racist, impacting the political climate. Many Indians who worked with British officials for administrative purposes were portrayed as disloyal or deceitful to their Indian brethren by the British. 1. By dividing African territory across tribal and established boundaries, the Euros trapped previous enemies within the new political units created by the Berlin Conference and left those previous warring factions to get along with their old enemies and their new ones (Euros) at the same time. The slaughter in Rwanda and Burundi a few years ago (mid-90’s) was a direct result of the 1884-85 Berlin Conference. Enemies within the same territory simply revived an old struggle and killed 600,000 people in the process. 1. Chinese cultural and art no longer had great influence worldwide. Westerner people started to appreciate their own culture and art, Japan turned completely western. People started to appreciate western stuff more than Chinese, from culture, to art, to fashion, to ideology, to everything. Chinese were discriminated throughout the whole world, even till today. Their collective spirits are no longer shared their traditions and customs are often attack under prejudices. 2. Before the rise of 19th century imperialism, China was viewed by western people and most people of the world as the dreamland. People around the globe praised their society and values, then suddenly after they were beaten down by the western military might, they turned into nothing. 1. Educationally, the workers are taught such “crucial” items as free enterprise economics. The nature of this set-up gives rise to a very small group of local wealthy opportunists who have a vested interest in maintaining the status quo. This group uses whatever type of government (monarchy, dictatorship, fascism) that will keep it in power to repress the masses. 2. The U.S. supports these governments that suppress all popular movements for social and national liberation, which allows the stifling of economic and social development and therefore continued exploitation. Another result of this is that the top leaders of the underdeveloped countries spend money extremely wastefully on their own pleasures. Of course, a lot has to be spent to keep the military and inner police force of these dictators. 1. India became increasingly valuable to British interests after a railway network was built there. The railroads were used to transport raw products from the inner parts of the Indian sub-continent to the ports. Manufactured goods made at the ports would be transported back to the inner zones. Nearly all the materials used in manufacturing were produced on plantations, including tea, cotton, opium and coffee. 2. The British would ship opium to China in exchange for tea that was sold in England. The trade goods had an enormous impact on Indian politics. The 1850s Crimean War, for example, cut off supplies of Russian exports to Scotland. The exports of products in the Indian province of Bengal increased. The U.S. Civil War boosted cotton production in India. The British further replaced India’s political aristocracy with a bureaucratic military adept at maintaining law and order. This led to a reduction in fiscal overheads, leaving a larger share of national product available to the British while simultaneously stripping self-governance rights and natural products from the Indian people. 1. Opium had been grown in Asia for hundreds of years. The Chinese emperor outlawed opium distribution in 1729. British traders had been smuggling in small amounts of Indian-grown opium for years. With the British need for trading revnue from China becoming dire, the British East India Company increasingly turned a blind eye to opium smuggling. (The British government granted the British East India Company a monopoly on British trade in and out of India). 2. When China tried to stop in the illegal opium trading in 1839, British traders manipulated the situation so that the British sent warships into the harbor at Canton and easily vanquished Chinese forces. While opium still remained illegal, the Chinese were forced to open additional ports to western traders. Opium began flooding into the country, and addiction became a chronic problem. Government officials, soldiers, and many citizens became addicts. Again, China tried to stem the tide. Again, British traders generated a pretext for a military attack. After the British won the second Opium War in 1860, China was forced to legalize opium (and make other concessions). 3. Addiction worsened throughout China. Workers and peasants fell to the drug. China’s opium problem came as the country was sinking into a slow but severe decline. Its once-vaunted economic, technological and political structures were collapsing. So the Chinese began growing opium, and soon dwarfed India’s output. British trading profits in opium declined, and moral opposition to the practice grew at home. Finally, about 1910, the British government stopped the repugnant trade. Cite this page SPICE Chart on Imperialism. (2016, Mar 07). Retrieved from https://studymoose.com/spice-chart-on-imperialism-essay
Super-Earths – planets that are up to 10 times more massive than Earth — might play billiards with planetary systems. New simulations suggest that if a super-Earth existed in our own solar system, say between Venus and the Earth, far more asteroids would collide with us. But that isn’t necessarily a bad thing, if the timing is right. Understanding the effect of these massive planets on others nearby could help direct the search for life on exoplanets. Given that our galaxy is overrun with Super-Earths, Jeremy Smallwood at the University of Nevada and his colleagues set out to discover what their effect might be on neighbouring worlds, and what role one might play in a planet’s habitability. They ran simulations of the inner solar system’s formation, shuffling the theoretical super-Earth around. They discovered that a super-Earth closer to the sun than we are would increase the number of asteroid impacts on our planet, while a super-Earth outside Earth’s orbit would have the opposite effect. Why? A super-Earth near our sun would causes an asteroid’s orbit to stretch out, making a collision with Earth more likely. A Game of Goldilocks It may seem that the system with fewer asteroid impacts would be more conducive to life – but many astronomers argue the opposite. “Asteroid collisions are thought to be destructive for life – that was definitely true for the dinosaurs,” says Smallwood’s PhD advisor Rebecca Martin. “But they are also essential for life.” Take Earth’s climate as an example. When our planet first formed, its orbit was eccentric – it might zip close to the sun for a short period and then spend long stretches of time in the cold outer regions of the solar system. But asteroid impacts helped to dampen these eccentricities and making our planet’s orbit more circular, making the climate more stable. Astronomers also argue that the building blocks of life, like water, arrived on the first asteroids. In fact, the Earth’s water is a chemical match for the asteroid belt’s water, says Sean Raymond at the University of Bordeaux. Asteroids also might have sent heavier elements – like the iron that runs through our veins – toward the early Earth as well. Some scientists even suggest that life itself could have hitched a lift on these early asteroids, jumping from one planet to the next. Still an asteroid impact is a double-edged sword. A large impact might sterilise a planet, leaving it inhospitable for years to come. Raymond says that a planet needs a balance between too many asteroid impacts and too few. Smallwood calls this idea a new “goldilocks zone” for habitability. Still, if astronomers discovered two exoplanetary systems – one where a super-Earth orbited inside that of a planet like our own, and one where a super-Earth orbited outside an Earth-like planet’s orbit – Smallwood would search for life in the first system. Sure, he’s taking a chance that the planet might be sterile. But the other world might not have received the necessary ingredients for life in the first place. Read more: The five best exoplanets in the galaxy to check for alien life
The tidal force is an apparent force that stretches a body towards the center of mass of another body due to a gradient (difference in strength) in gravitational field from the other body; it is responsible for the diverse phenomena, including tides, tidal locking, breaking apart of celestial bodies and formation of ring systems within Roche limit, and in extreme cases, spaghettification of objects. It arises because the gravitational force exerted on one body by another is not constant across its parts: the nearest side is attracted more strongly than the farthest side. It is this difference that causes a body to get stretched. Thus, the tidal force is also known as the differential force, as well as a secondary effect of the gravitational force. In celestial mechanics, the expression "tidal force" can refer to a situation in which a body or material (for example, tidal water) is mainly under the gravitational influence of a second body (for example, the Earth), but is also perturbed by the gravitational effects of a third body (for example, the Moon). The perturbing force is sometimes in such cases called a tidal force (for example, the perturbing force on the Moon): it is the difference between the force exerted by the third body on the second and the force exerted by the third body on the first. When a body (body 1) is acted on by the gravity of another body (body 2), the field can vary significantly on body 1 between the side of the body facing body 2 and the side facing away from body 2. Figure 2 shows the differential force of gravity on a spherical body (body 1) exerted by another body (body 2). These so-called tidal forces cause strains on both bodies and may distort them or even, in extreme cases, break one or the other apart. The Roche limit is the distance from a planet at which tidal effects would cause an object to disintegrate because the differential force of gravity from the planet overcomes the attraction of the parts of the object for one another. These strains would not occur if the gravitational field were uniform, because a uniform field only causes the entire body to accelerate together in the same direction and at the same rate. Effects of tidal forces In the case of an infinitesimally small elastic sphere, the effect of a tidal force is to distort the shape of the body without any change in volume. The sphere becomes an ellipsoid with two bulges, pointing towards and away from the other body. Larger objects distort into an ovoid, and are slightly compressed, which is what happens to the Earth's oceans under the action of the Moon. The Earth and Moon rotate about their common center of mass or barycenter, and their gravitational attraction provides the centripetal force necessary to maintain this motion. To an observer on the Earth, very close to this barycenter, the situation is one of the Earth as body 1 acted upon by the gravity of the Moon as body 2. All parts of the Earth are subject to the Moon's gravitational forces, causing the water in the oceans to redistribute, forming bulges on the sides near the Moon and far from the Moon. When a body rotates while subject to tidal forces, internal friction results in the gradual dissipation of its rotational kinetic energy as heat. In the case for the Earth, and Earth's Moon, the loss of rotational kinetic energy results in a gain of about 2 milliseconds per century. If the body is close enough to its primary, this can result in a rotation which is tidally locked to the orbital motion, as in the case of the Earth's moon. Tidal heating produces dramatic volcanic effects on Jupiter's moon Io. Stresses caused by tidal forces also cause a regular monthly pattern of moonquakes on Earth's Moon. Tidal forces contribute to ocean currents, which moderate global temperatures by transporting heat energy toward the poles. It has been suggested that in addition to other factors, harmonic beat variations in tidal forcing may contribute to climate changes. However, no strong link has been found to date. Tidal effects become particularly pronounced near small bodies of high mass, such as neutron stars or black holes, where they are responsible for the "spaghettification" of infalling matter. Tidal forces create the oceanic tide of Earth's oceans, where the attracting bodies are the Moon and, to a lesser extent, the Sun. Tidal forces are also responsible for tidal locking, tidal acceleration, and tidal heating. Tides may also induce seismicity. For a given (externally generated) gravitational field, the tidal acceleration at a point with respect to a body is obtained by vectorially subtracting the gravitational acceleration at the center of the body (due to the given externally generated field) from the gravitational acceleration (due to the same field) at the given point. Correspondingly, the term tidal force is used to describe the forces due to tidal acceleration. Note that for these purposes the only gravitational field considered is the external one; the gravitational field of the body (as shown in the graphic) is not relevant. (In other words, the comparison is with the conditions at the given point as they would be if there were no externally generated field acting unequally at the given point and at the center of the reference body. The externally generated field is usually that produced by a perturbing third body, often the Sun or the Moon in the frequent example-cases of points on or above the Earth's surface in a geocentric reference frame.) Tidal acceleration does not require rotation or orbiting bodies; for example, the body may be freefalling in a straight line under the influence of a gravitational field while still being influenced by (changing) tidal acceleration. By Newton's law of universal gravitation and laws of motion, a body of mass m at distance R from the center of a sphere of mass M feels a force , equivalent to an acceleration , where is a unit vector pointing from the body M to the body m (here, acceleration from m towards M has negative sign). Consider now the acceleration due to the sphere of mass M experienced by a particle in the vicinity of the body of mass m. With R as the distance from the center of M to the center of m, let ∆r be the (relatively small) distance of the particle from the center of the body of mass m. For simplicity, distances are first considered only in the direction pointing towards or away from the sphere of mass M. If the body of mass m is itself a sphere of radius ∆r, then the new particle considered may be located on its surface, at a distance (R ± ∆r) from the centre of the sphere of mass M, and ∆r may be taken as positive where the particle's distance from M is greater than R. Leaving aside whatever gravitational acceleration may be experienced by the particle towards m on account of m's own mass, we have the acceleration on the particle due to gravitational force towards M as: Pulling out the R2 term from the denominator gives: The Maclaurin series of is which gives a series expansion of: The first term is the gravitational acceleration due to M at the center of the reference body , i.e., at the point where is zero. This term does not affect the observed acceleration of particles on the surface of m because with respect to M, m (and everything on its surface) is in free fall. When the force on the far particle is subtracted from the force on the near particle, this first term cancels, as do all other even-order terms. The remaining (residual) terms represent the difference mentioned above and are tidal force (acceleration) terms. When ∆r is small compared to R, the terms after the first residual term are very small and can be neglected, giving the approximate tidal acceleration (axial) for the distances ∆r considered, along the axis joining the centers of m and M: When calculated in this way for the case where ∆r is a distance along the axis joining the centers of m and M, is directed outwards from to the center of m (where ∆r is zero). Tidal accelerations can also be calculated away from the axis connecting the bodies m and M, requiring a vector calculation. In the plane perpendicular to that axis, the tidal acceleration is directed inwards (towards the center where ∆r is zero), and its magnitude is (axial) in linear approximation as in Figure 2. The tidal accelerations at the surfaces of planets in the Solar System are generally very small. For example, the lunar tidal acceleration at the Earth's surface along the Moon-Earth axis is about 1.1 × 10−7 g, while the solar tidal acceleration at the Earth's surface along the Sun-Earth axis is about 0.52 × 10−7 g, where g is the gravitational acceleration at the Earth's surface. Hence the tide-raising force (acceleration) due to the Sun is about 45% of that due to the Moon. The solar tidal acceleration at the Earth's surface was first given by Newton in the Principia. - "On the tidal force", I. N. Avsiuk, in "Soviet Astronomy Letters", vol. 3 (1977), pp. 96–99. - See p. 509 in "Astronomy: a physical perspective", M. L. Kutner (2003). - R Penrose (1999). The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics. Oxford University Press. p. 264. ISBN 0-19-286198-0. - Thérèse Encrenaz; J -P Bibring; M Blanc (2003). The Solar System. Springer. p. 16. ISBN 3-540-00241-3. - R. S. MacKay; J. D. Meiss (1987). Hamiltonian Dynamical Systems: A Reprint Selection. CRC Press. p. 36. ISBN 0-85274-205-3. - Rollin A Harris (1920). The Encyclopedia Americana: A Library of Universal Knowledge. 26. Encyclopedia Americana Corp. pp. 611–617. - "The Tidal Force \| Neil deGrasse Tyson". www.haydenplanetarium.org. Retrieved 2016-10-10. - "Millennial Climate Variability: Is There a Tidal Connection?". - "Hungry for Power in Space". New Scienctist. New Science Pub. 123: 52. 23 September 1989. Retrieved 14 March 2016. - "Inseparable galactic twins". ESA/Hubble Picture of the Week. Retrieved 12 July 2013. - The Admiralty (1987). Admiralty manual of navigation. 1. The Stationery Office. p. 277. ISBN 0-11-772880-2., Chapter 11, p. 277 - Newton, Isaac (1729). The mathematical principles of natural philosophy. 2. p. 307. ISBN 0-11-772880-2., Book 3, Proposition 36, Page 307 Newton put the force to depress the sea at places 90 degrees distant from the Sun at "1 to 38604600" (in terms of g), and wrote that the force to raise the sea along the Sun-Earth axis is "twice as great", i.e. 2 to 38604600, which comes to about 0.52 × 10−7 g as expressed in the text. - Gravitational Tides by J. Christopher Mihos of Case Western Reserve University - Audio: Cain/Gay – Astronomy Cast Tidal Forces – July 2007. - Gray, Meghan; Merrifield, Michael. "Tidal Forces". Sixty Symbols. Brady Haran for the University of Nottingham. - "Pau Amaro Seoane MODEST working group 4 "Tidal disruption of a star by a massive black hole"". Retrieved 2013-05-30. - Myths about Gravity and Tides by Mikolaj Sawicki of John A. Logan College and the University of Colorado. - Tidal Misconceptions by Donald E. Simanek
Travel topics > Cultural attractions > Historical travel > Military tourism > World War II > Pacific War Western accounts generally consider the war to have started with the Pearl Harbor attack of December 1941. Chinese accounts date it from Japan's invasion of central China in July 1937, or even their expansion into Manchuria in 1931. The war ended with Japanese surrender in August, 1945; an important factor was that the first, and so far the only, atomic bombs used in warfare had just been detonated over Hiroshima and Nagasaki. - See also: Japanese colonial empire Japan began to expand in the late 19th century, annexing Okinawa in 1879, then defeating China in the 1894-95 First Sino-Japanese War, annexing Taiwan and the Liaodong Peninsula, and forcing China to give up its influence over its vassal state Korea. In the same period, the US became more active in the Pacific, taking over the Philippines in 1898 after a war with Spain, and annexing Hawaii and Guam. Various European powers also expanded their holdings or influence in the region. Japan won a war against the Russian Empire in 1905, the first time in centuries that a non-European power defeated a European one. Once the Russians were out of their way, they annexed Korea outright in 1910. Japan was part of the Allies during World War I, and would thus gain more territory from the defeated Central Powers following the end of that war in 1918, including the former German concessions in Shandong, China. Such attempts by Japan would later result in the May Fourth Movement, which is further described in our article on early 20th century Chinese history. There was a faction fight among the Japanese high command in the late 30s; they all agreed that expanding the empire was a fine idea, but how? Should they "Strike North", expand into Mongolia and Siberia and fight only the Russians, or "Strike South" which would mean fighting the US, the British Empire, and other colonial powers — the French, Dutch and Portuguese? The Imperial Way Faction (皇道派), which supported an invasion of Soviet Union, even tried a coup (the February 26 Incident) in 1936, but that failed. Striking north was tried, but in 1939 the Soviets gave Japanese forces a thorough thrashing at the Battle of Kalkhin Gol in Mongolia. After that, Japan concentrated on striking south. In the last juncture, we can only sacrifice everything and resist to the end. Only with the determination to sacrifice everything can we fight for ultimate victory. If (the war) is treated with hesitation and uncertainty or selfish momentary ease, this will lead our nation to an catastrophic irreversible situation. —Chiang Kai-shek, Speech at Lushan, just after the Marco Polo Bridge incident Japan acquired considerable influence in Manchuria when they defeated the Russians; in particular they took over administration of the profitable Russian-built railway. Then in 1931 they staged the Mukden Incident; Japanese troops bombed part of the railway, the attack was blamed on Chinese forces, and that gave Japan a pretext to occupy Manchuria, setting up a puppet state called Manchukuo. Japan invaded central China in 1937 after the Marco Polo Bridge Incident, where nearby Japanese troops attacked after a request to search for an alleged missing Japanese soldier was refused by Chinese forces. Japanese forces soon managed to occupy much of eastern China, including the then-capital Nanjing. This invasion turned out to be a disaster for both sides. The Chinese were fighting an invader with far better armament and training, making do with whatever weapons their allies could send (many of them World War I surplus), enduring some spectacularly vicious oppression, and taking enormous numbers of casualties — over ten million military and civilian deaths, far more than any other nation except the Soviet Union. Moreover, they were disunited; some factions of the Nationalists (Kuomintang) were sometimes more interested in fighting the Communists than in battling Japan; ex-warlord units were less trusted and received less equipment by Chiang Kai-shek's faction, despite their gallantry at war. Despite all that, the Chinese Army (run by the Nationalists with American advisors) managed to give the Japanese a remarkably hard time. Japanese planners thought they could take all of China in three months, leave a small force to hold it, and move most of their armies elsewhere. Actually, it took them three months just to take Shanghai and in eight years of fighting, 1937-1945, they never managed to take more than about half of China. The Chinese Army fought on through the entire war, often retreating but always at a cost to the enemy. Chinese guerrillas and saboteurs — Nationalist, Communist and independent — harassed the Japanese everywhere. Roughly half of the total Japanese ground forces were tied down in China throughout the war, including troops they had planned to use elsewhere. All the Allied land victories in the Pacific War were partly due to Chinese tenacity. American, British and Dutch sanctions were imposed on Japan after the invasion of China; those, in particular restrictions on oil imports, were the main reason Japan gave for going to war with those nations. The Western powers also sent supplies to China via the Burma Road. The Soviet Union and America also sent volunteer air force units to support China, with the American one based in Yunnan being known as the renowned "Flying Tigers". Japan joins the world war \|“\|\|Yesterday, December 7th, 1941 — a date which will live in infamy — the United States of America was suddenly and deliberately attacked by naval and air forces of the Empire of Japan.\|\|”\| —US President Franklin D. Roosevelt, December 8, 1941 Meanwhile, World War II in Europe began with the German invasion of Poland in September 1939, and became more complex when Germany invaded the Soviet Union in June 1941. The conflict became global in December 1941, when Japan attacked Pearl Harbor, other US bases in the Pacific, the Philippines, and British possessions such as Hong Kong, Burma and Malaya. The United States and the entire British Empire immediately declared war on Japan, and Germany declared war on the US. The Soviet Union did not declare war on Japan until after the end of the war in Europe. After that, Japan proceeded to invade and occupy much of Southeast Asia and parts of Oceania; they even managed to bomb the city of Darwin in Australia. By the middle of 1943, virtually all of Southeast Asia had been conquered by Japan, with the colonial powers of the United Kingdom, France, the Netherlands, Portugal and the United States all having suffered humiliating defeats at the hands of the Japanese. The Japanese took effective control of some areas without fighting. The Vichy government in France, essentially a German puppet regime, ordered French administrators in French Indochina (now Vietnam, Laos and Cambodia) to co-operate with Japan, and most did. Thailand, the only country in Southeast Asia not colonized by Western powers, remained nominally independent but was forced to dance to the Japanese tune. Japan was able to establish military bases in these countries and to freely move troops and supplies through them. Japanese propaganda claimed they were driving out Western imperialists, leading an "Asia for Asians" movement, and this got them some support; countries such as India had both pro-Japanese and pro-Allied movements. Subhas Chandra Bose, the leader of the pro-Japanese Indian National Army (INA), is still widely regarded as a national hero in India. In many areas, this was also divided along ethnic lines; in Malaya, at least initially, the Japanese were welcomed by many ethnic Malays and Indians, but opposed by most ethnic Chinese. In China both the Kuomintang and the Communists opposed Japan, but they were sometimes more interested in fighting each other. Everywhere, the local political movements were jockeying for control and trying to use the war to gain independence and/or domestic political influence for the time after the war. Japanese rule in the occupied territories was brutal, and by the end of the war, the Japanese had lost the support of much of the local population who initially supported them (e.g. Burmese independence hero Aung San). In the occupied areas, Japanese troops engaged in mass rapes, massacres and pillaging, with the Nanjing Massacre of 1937-38 being the most notorious. Many women from China, Korea and other occupied areas were forced to serve as "comfort women", sex slaves in Japanese military brothels. The Japanese also performed inhumane experiments on captive locals from the occupied territories, the most famous being Unit 731 in Manchuria (listed below), though other similar units existed throughout the occupied territories. They also treated prisoners of war very badly; perhaps the most famous incidents were the "Bataan death march" and the Bridge on the River Kwai, but there were many others. As retribution for their role in resisting Japanese rule in China, the ethnic Chinese — both in China and in Southeast Asia — were singled out for the harshest treatment; in all the occupied territories, they were rounded up for "screening" by the Japanese, and the unfortunate ones who were identified (often arbitrarily) as anti-Japanese were brought to remote locations and shot. The tide turns The Japanese suffered two important naval defeats at the hands of the Americans in mid-1942, the Battle of the Coral Sea in May and the Battle of Midway in June. These were the first naval battles in history fought mainly by aircraft carriers which never came within sight of each other. The Americans were intercepting Japanese communication, and had broken many Japanese codes, which was an advantage in both battles. At Midway they surprised the Japanese by destroying their aircraft carriers when the planes were away on a bombing raid. The battle not only destroyed most regular aircraft carriers of the Imperial Japanese Navy, but also killed a number of elite Japanese naval aviators, a catastrophe for Japanese forces. Two land campaigns, both starting in mid-1942 and lasting until early 1943, also went badly for Japan. In what is now Papua New Guinea, a mainly Australian force gave them their first defeat on land at Milne Bay then, in a hard-fought campaign, drove them back along the Kokoda Track. Meanwhile the Americans took the island of Guadalcanal after a prolonged and intense fight, allowing them to defend their supply and communication lines to Australia and New Zealand, and to create a forward base for island-hopping toward Japan. These Allied victories marked the turning point in the Pacific War. After that the ANZACs (Australia and New Zealand Army Corps) continued the New Guinea campaign and invaded the Solomon Islands, while the British re-took Burma with the help of the Chinese, and reopened the Burma Road to supply Chinese forces. The Japanese had spread their forces too thinly in China, and the Chinese were able to counterattack and reclaim some of the occupied territories. The Americans re-took the Philippines and captured a series of islands across the Pacific, including some like Guam and Wake Island that Japan had taken from them in the first months of the war. At sea, Japan was defeated repeatedly by the Americans, with some Commonwealth help. The Battle of Leyte Gulf was the largest naval battle of the war; it took place during the invasion of the Philippines, and was a major Allied victory. When they took the Mariana Islands, the "Great Marianas Turkey Shoot" saw over 550 Japanese aircraft destroyed, while America only lost about 120 aircraft. End of the war In early 1945 the US won fierce battles in Okinawa and Iwo Jima and occupied those islands, putting them in position to bomb or invade the Japanese home islands. Having by then won the naval part of the war, they also bombarded Japanese cities with their ships. Japan tried desperation tactics such as sending kamikaze (named after a series of two typhoons that sank the invading Mongol fleet in the 13th century) pilots on suicide missions to crash planes full of explosives into American ships, but even that did not make a large difference. The invasion never took place. The Americans dropped the first (and to date only) atomic bombs to be used in actual combat on Hiroshima on 6 August 1945, followed by Nagasaki on 9 August 1945; on the same day the Soviet Union invaded Manchuria. Japan surrendered unconditionally to the Allies on 15 August 1945, bringing World War II to an end. Following the surrender, Japan was occupied by the Americans and forced to give up all its colonies, and abolished its military. While the Emperor remained on his throne, many political and military leaders were indicted in the International Military Tribunal for the Far East, and many were sentenced to death. The Americans also imposed a new pacifist constitution on Japan, forbidding it from establishing a military, and turning it into a democratic constitutional monarchy. However, when the Cold War began, the American occupiers established the National Police Reserve, a paramilitary organization that would later develop into the Japan Self-Defense Forces, the de-facto military of the country. Taiwan and Manchuria were returned to China, though the Chinese Civil War would resume following the Japanese surrender, eventually resulting in victory for the Communists in the mainland, and the Nationalists being forced to retreat to Taiwan, which continues to be governed separately to this day. Korea regained its independence, but would be split into communist North Korea and capitalist South Korea, leading up to the Korean War. The Americans would eventually leave mainland Japan in 1952, though the American military continues to maintain several bases in different parts of the country. Okinawa was only returned to Japan in 1972, though the United States continues to maintain a strong military presence there. The Western colonial powers also got their colonies back, but the war had galvanised many nationalist movements, which were to come of age in the years to come and eventually lead to the independence of the colonies. The first was the Philippines, where American rule ended in 1946; the largest was the end of the British Raj in 1947, which became the modern countries of India, Pakistan and later Bangladesh. The Indochina Wars were a brutal example of lingering national and ideological conflict in Asia. Hong Kong and Macau would eventually be given back to China in the 1990s but part of the agreement between China and the former colonial powers stipulates a "one country two systems" arrangement that makes both act like independent countries in some regards. A few Japanese soldiers, isolated in various jungles, did not know the war had ended and fought on. The last two surrendered in 1974, one on the Philippine island of Lubang and the other on Indonesia's Morotai Island. Many places that were sites of battles, atrocities or other wartime activities can be visited. There are also many museums with exhibits wholly or partly related to this war. - 1 Darwin Military Museum. Darwin was an important staging point for Australian and American forces during the war, and would be the only Australian city that was subject to Japanese bombing raids. The museum houses exhibits about the bombing of Darwin. - 2 Australian War Memorial. Located in Canberra, the memorial also includes a military museum dedicated to the memory of Australian soldiers who fought in various wars including both world wars. See Chinese Revolutions for background. - 3 Jiaozhuanghu Tunnel Warfare Site Museum (焦庄户地道战遗址纪念馆) (Shunyi District, Beijing). A 23-kilometer network of underground tunnels built by residents of Jiaozhuanghu Village in the 1940s during the Japanese occupation of Beijing. The tunnels were used by Chinese resistance fighters to evade capture and launch attacks on Japanese forces. An 830-meter section of the tunnels is open to the public. - 4 Marco Polo Bridge/Lugou Bridge (卢沟桥) (Fengtai District, Beijing). The location of the Marco Polo Bridge Incident, which was used as the casus belli by the Japanese for the second Sino-Japanese War. - 5 Memorial of Famous Generals in the War of Resistance Against Japanese Agression (抗战名将纪念馆) (Haidian District, Beijing). Dedicated to the dozens of prominent Chinese generals who fought the Japanese duriung the Second Sino-Japanese War. - 6 Museum of the War of Chinese People's Resistance Against Japanese Aggression (中国人民抗日战争纪念馆) (Fengtai District, Beijing). The largest museum in China about the Second Sino-Japanese War. The museum is inside the Wanping Fortress, a Ming-era fortress next to the Lugou Bridge (or Marco Polo Bridge), which was the site of the Marco Polo Bridge Incident - a battle between Chinese and Japanese forces in July 1937 that led directly to the outbreak of full-scale war between the two nations. The fortress was fired upon during the battle and shell-holes are still visible today. - 7 Pingbei Sino-Japanese War Martyrs Memorial Park (平北抗日烈士纪念园) (Yanqing District, Beijing). Dedicated to the many Chinese soldiers who died fighting the Japanese in the Pingbei region (a vast region which includes northern Beijing and northern Hebei Province). Inside the park is the Pingbei Sino-Japanese War Museum (平北抗日战争纪念馆), which displays around 200 photographs and artefacts. The "temporary capital" of China during World War II, after Nanjing had fallen to the Japanese. Despite numerous attempts by the Japanese to take it, Chinese resistance in the inland areas was much fiercer than the Japanese expected, and though it was heavily bombed, Chongqing managed to avoid Japanese occupation for the duration of the war. - 8 Chiang Kai-Shek's Mount Huang residence (黄山蒋介石官邸, 蒋介石旧军事总部 Chiang Kai-Shek's old military headquarters) (Chongqing). When Chongqing was the capital of China during World War II, Jiang Jieshi (Chiang Kai-Shek) established his military headquarters up in the mountains above Chongqing. As a result the Japanese bombers never found it, and it is now a museum, preserved as it was during the war. There are many buildings in the beautiful compound and you can visit his work room with the motto over his desk "all officials must serve the people" (in free translation), his bedroom, and his meeting room, and sit in his chair where he negotiated with the American advisers, with his American-educated wife usually to his left. The residence is usually referred to as Chiang Kai-Shek's Mount Huang (or Huangshan) residence in order to distinguish it from Chiang's other official residences (he had no less than four official residences in Chongqing alone). Together with the other buildings in the compound, the residence forms part of the Chongqing Sino-Japanese War Sites Museum (重庆抗战遗址博物馆). - 9 Chongqing Flying Tigers Museum (重庆飞虎队展览馆, 重庆友好飞虎队展览馆, 重庆飞虎队陈列馆) (Chongqing). A privately-run museum about the Flying Tigers - a group of volunteer American fighter pilots who fought the Japanese from 1941 to 1942 as part of the Chinese air force. - 10 Former Site of Eighth Route Army Chongqing Office (八路军驻重庆办事处旧址) (Chongqing). The Eighth Route army was a group army formed from the Red Army in 1937 after the Communists and the Nationalists agreed to stop fighting each other and form the Second United Front against Japan. It was nominally part of the national army led by Chiang Kai-Shek, but commanded by the Chinese Communist Party. The army had several offices throughout China to faciliate communications with the Nationalist authorites, including this one in Chongqing. - 11 Former Site of US Embassy in Chongqing (重庆美国大使馆旧址) (Chongqing). The US embassy operated at this site from 1942 to 1946. In 2019, the former embassy site was reopened to the public as a museum. There are exhibitions about the wartime alliance between the US and China. - 12 Jianchuan Museum Cluster (建川博物馆聚落) (Chongqing). This is the Chongqing branch of the museum group established by the industrialist Fan Jianchuan in Chengdu. It consists of eight separate museums built inside a series of World War II bomb shelters. Some of the museums are primarily about the war, including the Museum of the No. 1 Ordnance Factory, the Sino-Japanese War Relics Museum, and the Weapons Development History Museum. - 13 Joseph Stilwell Residence (史迪威故居, 史迪威将军旧居, 重庆史迪威博物馆 Stillwell Museum) (Chongqing). Not far from Red Rock Village is the former residence and office of General Joseph W. ("Vinegar Joe") Stilwell, who headed American operations in China during the Anti-Japanese War. Stilwell is an impressive person, not only for his leadership ability but also for his understanding of China and Chinese culture (he could write in Chinese with a brush). His former residence is a 1930s modernist house with great views overlooking the Yangtze river. The main level is set up as it was during Stilwell's tenure. The lower level is filled with photos and bilingual descriptions of the Chinese front during the Second World War. - 14 Liziba Park (李子坝公园, 李子坝抗战遗址公园 Liziba Sino-Japanese War Relics Park) (Chongqing). On the banks of the Jialing River, this is a newly developed park housing many original and relocated historical buildings when Chongqing was China's wartime capital. It includes old bank buildings, government offices and the residences of local warlords. Some military pillboxes are also preserved here. - 15 Song Qingling's former residence (Soong Ching-ling's former residence 宋庆龄故居, 宋庆龄旧居) (Chongqing). This was Song Qingling's (Song Qing-ling's) residence from the period of the Second World War when Japan occupied much of China and Chongqing was the temporary capital. It also served as the headquarters of the China Defense League, an organisation that Song Qingling founded to help raise funds and procure supplies for the war effort in Communist-controlled areas of the country. - 16 Nanjing Massacre Memorial (侵华日军南京大屠杀遇难同胞纪念馆) (Nanjing). Commemorates the late 1937 slaughter of a huge number of civilians in and around Nanjing by the invading Japanese army. - 17 Nanjing Memorial Hall to Aviation Martyrs Killed in the War of Resistance Against Japan (南京抗日航空烈士纪念馆, Nanjing Anti-Japanese Aviation Martyrs Memorial Hall) (Nanjing). Dedicated to all those who fought and died during the aerial battles that were fought against the Japanese during the Second World War. The memorial hall is close to a cemetery where around 3500 aviation martyrs are buried, including 870 from China, 2197 from the US, 237 from the Soviet Union and 2 from Korea. - 18 Nanjing Non-Government Museum of the War of Resistance Against Japan (南京民间抗日战争博物馆) (Nanjing). A privately-run museum dedicated to the Second Sino-Japanese War. - 19 Former site of Japanese Shinto shrine (日本神社旧址) (Nanjing). Built in 1939 by the Imperial Japanese Army during their occupation of the city. The shrine, officially known as the Nanjing Shrine (南京神社), was one of the largest Shinto shrines the Japanese built on Chinese soil. It was also one of the very few that was not demolished after the war. Today the site is being used as an activity centre for retired Communist Party cadres, so you might not be able to enter the building, but viewing it from the outside should be okay. - 20 John Rabe's former residence (拉贝旧居，拉贝故居, 拉贝与国际安全区纪念馆 John Rabe and International Safety Zone Memorial Hall) (Nanjing). John Rabe (1882-1950) was a German businessman and Nazi party member who is widely celebrated in China for his efforts to protect civilians during the Japanese occupation. This house was his residence from 1932 to 1938. It is now a museum dedicated to telling the story of Rabe's life and the Nanjing International Safety Zone that he helped to establish and which is credited with saving thousands of lives. - 21 Liji Alley Comfort Station Site (利济巷慰安所旧址) (Nanjing). The term 'comfort station' was a euphemism used by the Japanese army in World War II to refer to a brothel where so-called 'comfort women' were held captive and forced to render sexual services to Japanese soldiers. This particular comfort station was one of the largest in Asia. It is now a museum run by the Nanjing Massacre Memorial Hall. Entry is by appointment only. Visitors are required to make an appointment at least one day before visiting and cannot visit more than twice a month or more than 10 times a year. Due to the adult content of the exhibitions, children are not permitted inside the building. - 22 Shanghai Songhu Memorial Hall for the War of Resistance Against Japanese Aggression (上海淞沪抗战纪念馆) (Baoshan District, Shanghai). Commemorates the Battle of Shanghai, one of the largest and bloodiest battles of the Second Sino-Japanese War. - 23 Sihang Warehouse Battle Memorial (上海四行仓库抗战纪念馆) (Zhabei District, Shanghai). The Sihang Warehouse is a historic warehouse on the north bank of Suzhou Creek. It was built in 1931 by four banks, hence the literal name of the warehouse is the 'Four Banks Warehouse'. In 1937, the warehouse became a flashpoint in the latter stages of the Battle of Shanghai. At that time, it was being used as the headquarters of the 88th Division of the National Revolutionary Army. The division was preparing to retreat to the city's hinterland, but left one battalion behind at the warehouse in order to buy time for the retreat and also to demonstrate to the international community the determination of the Chinese people to resist the Japanese. The battalion successfully defended the warehouse for about 6 days before eventually retreating to the International Concession, where they were promptly disarmed and arrested by British troops acting under pressure from the Japanese. Part of the warehouse is now a museum about the Defence of Sihang Warehouse and the Battle of Shanghai. - 24 Chinese "Comfort Women" History Museum (中国“慰安妇”历史博物馆) (French Concession, Shanghai). A museum about the women who were forced into sexual slavery by the Japanese army during the Second World War. - 25 Shanghai Jewish Refugees Museum (上海犹太难民纪念馆) (Hongkou District, Shanghai). The museum is at the site of what used to be the Ohel Moishe Synagogue. The synagogue was built in 1928 by Russian Jews and was one of the principal places of worship for Jewish refugees in Shanghai during the Second World War. - 26 9.18 Memorial Museum (“九•一八”历史博物馆, 9.18 History Museum) (Shenyang). Dedicated to the Mukden Incident, which is usually referred to as the '9.18 Incident' in Chinese. At 22:30 on 18 September 1931, a bomb exploded beside the Japanese-run railway line near Shenyang. The Japanese had actually planted the bomb themselves, but the Chinese were blamed, giving the Japanese an excuse to invade and occupy the whole of the northeast of China. Shenyang was the epicenter of that invasion, so it is most appropriate that the museum for the '9.18 Incident', as it is known, is in Shenyang next to the spot where the explosion occurred. The museum, as one would expect, depicts the incident from a Chinese perspective. It is not for the faint of heart because it unflinchingly displays the atrocities of war. Only the main descriptions are available in English, but it's enough to follow the course of events. The pictures and exhibits speak for themselves, anyway. - 27 Former Site of Shenyang Military Tribunal for the Trial of Japanese War Criminals (中国审判日本战犯法庭旧址陈列馆) (Shenyang). 36 Japanese war criminals were publicly tried and prosecuted at this site between June 9th and July 20th, 1956. The site is now a museum. - 28 Shenyang World War II Allied Prisoners Camp Site Museum (二战盟军战俘集中营旧址陈列馆) (Shenyang). From 1942 to 1945, around 1500 soldiers from six different countries were interned by the Japanese at this POW camp in Shenyang. The site is now a museum. Information is provided in both Chinese and English. - 29 Former Residence of Zhou Enlai (周恩来故居) (Wuchang District, Wuhan). CCP statesman Zhou Enlai lived here with his wife for four months in 1938 while helping to coordinate the war against Japan. The residence has been fully restored and is open to the public. - 30 Former Site of Eighth Route Army Wuhan Office (八路军武汉办事处旧址纪念馆, Memorial Museum of Wuhan Office of Chinese Eighth Route Army) (Jiang'an District, Wuhan). The Eighth Route Army was a Communist-controlled army unit nominally subordinate to the Kuomintang-led Chinese national army during the Second World War. The army's former office in Wuhan is now a museum with exhibits relating to the war. - 31 Former Site of New Fourth Army Hankou Headquarters (汉口新四军军部旧址纪念馆) (Jiang'an District, Wuhan). The New Fourth Army was the second of the two major Communist-controlled army units that fought during the Second World War. The New Fourth Army's former headquarters is just around the corner from the former site of the Eighth Route Army Wuhan Office, so the two sites are probably best visited together. - 32 Shimen Peak Memorial Park (石门峰纪念公园) (Hongshan District, Wuhan). The park is divided into several sections, one of which is the Wuhan War of Resistance Memorial Park (武汉抗战纪念园), which commemorates the heroes of the war against Japan and is located next to the Cemetery for Air Force Matrys Who Defended Greater Wuhan (保卫大武汉中国空军英烈墓园). On Shimen Peak Road (石门峰路), just outside the park's main entrance, you will find the Museum of the Hubei Soldiers and Citizens War of Resistance Against Japan (湖北军民抗战博物馆), which has exhibits about the war in Hubei. - 33 Wuhan Art Museum (武汉美术馆), 2 Baohua Street, Jiang'an District (江岸区保华街2号) (Jiang'an District, Wuhan). The museum is housed inside the former Jincheng Bank. The building was used as a military headquarters by the Japanese during their occupation of the city. - 34 Yaojiashan Scenic Area (姚家山风景区, Mount Yaojia Scenic Area) (Huangpi District, Wuhan). A tourist resort in a scenic mountain village. The village played an important role in the Second World War, being the site of a base for the Fifth Division of the New Fourth Army. The old army office has been preserved as a heritage site and there is a museum nearby. - 35 Zhongshan Park (中山公园) (Jianghan District, Wuhan). On the left side of the Sun Yat-Sen statue is a building where Japanese forces stationed in Hubei formally surrended to the Chinese government in 1945. The building is now a museum dedicated to the event. - 36 Zhongshan Warship Museum (武汉市中山舰博物馆) (Jiangxia District, Wuhan). This museum, near the right bank of the Yangtze in the far southwestern suburbs of Wuhan, commemorates a naval battle that happened here, hundreds of miles from the sea, in October 1938. Sunk by the Japanese air force - just three years before the Pearl Harbor attack on the US fleet - the Chinese warship Zhongshan was raised from the bottom of the Yangzte in 1997, restored, and is now displayed in this museum's main hall. Adjacent are exhibits on the history of the ship, as well as the process of its lifting from the river bottom and its restoration. On the top of a hill across the small lake from the museum is a memorial to the 25 sailors, including the ship's captain, who found their watery grave in the Yangtze, far from their hometowns on Fujian's northern coast. The lake is surrounded by sculptures commemorating various aspects of the Battle of Wuhan in 1938, as well as of the city's eventual liberation after the surrender of Japan in 1945. Various other exhibits of military and patriotic nature, such as a sampling of PLA's older weaponry, can be seen here as well. - 37 Eighth Route Army Xi'an Office Museum (八路军西安办事处纪念馆) (Xi'an). From 1937 to 1946, this site served as the Communist Eighth Route Army's official liason office for coordinating communications with the Nationalist authorities in Xi'an. - 38 Sanqin Museum of the War of Resistance Against Japanese Aggression (三秦抗战纪念馆) (Xi'an). A museum about the Second World War in Shaanxi Province (Sanqin is an old name for Shaanxi). Xi'an Incident sites Chinese politics in the 1930s were complex. The Nationalists under Chiang Kai Shek were nominally in charge, but in several areas local warlords held the real power, some ethnic minority areas were de facto independent, and the Communists held other regions (see Long March). The strength of a political group was measured not mainly by how many votes it could get, but rather by how many divisions it could put in the field. Yang Hucheng was the warlord of Shaanxi, the province whose capital is Xi'an. Chang Hsüeh-liang (Zhang Xueliang) was the "Young Marshal" whose family had ruled Manchuria. The Japanese assassinated his father (the "Old Marshal") in 1928, and took over the region in 1931; he retreated into central China, bringing an army. Both were nominally subordinate to Chiang, and he ordered them to attack the Communists. Instead they arrested him and held him until he agreed to co-operate with the Communists against the Japanese. - 39 Huaqing Pool (华清池) (Xi'an). A hot spring villa in Xi'an where Chiang was held. - 40 General Yang Hucheng's Zhiyuan Villa (杨虎城将军止园别墅) (Xi'an). One of two heritage properties administered by the Xi'an Incident Museum (西安事变纪念馆). the other being General Zhang Xueliang's Official Residence (listed below). The property has been restored to appears as it did in 1930s and has exhibitions about General Yang Hucheng and his role in the Xi'an Incident. - 41 General Zhang Xueliang's Official Residence (张学良将军公馆, General Chang Hsüeh-liang's Official Residence) (Xi'an). The Xi'an Incident Museum's main exhibition halls are at this site. - 42 Unit 731 Museum. A museum in Harbin located in a former bio-chemical weapons testing facility built by the Japanese and used to perform experiments on Chinese citizens and POWs. After the war, the Americans agreed to cover up their actions and grant immunity from prosecution to the scientists involved in exchange for being granted exclusive access to the data, as they feared that the data would end up in the hands of the Soviet Union, and many of those scientists ended up having successful careers in academia. - 43 Burial site of laborers killed in Basuo during the Japanese occupation of Hainan (日军侵琼八所死难劳工遗址) (Dongfang, Hainan). During their occupation of Hainan Island, the Japanese army used forced labor to complete several infrastructure projects, including the Daguang Dam, the Shilu Iron Ore Mine and the railway line connecting the mine to the ports in Basuo and Sanya. At first the Japanese mainly relied on Chinese labor but later they began importing POWs that they had captured in Southeast Asia, including POWs who originally hailed from Australia, Canada, Britain and other allied countries. Conditions for the laborers were extremely brutal. Only 6000 of the more than 30,000 laborers survived. Many of the dead are buried here at this site. In 2013, the old prison buildings from the Basuo POW Camp Site were controversially moved here from their original location about 500 meters away. Free. - 44 Changsha. The site of four separate battles between the Chinese and Japanese in 1939, 1941, 1942 and 1944. The first of those was the first significant victory scored by the Chinese over the Japanese during World War II. The Japanese were only able to capture Changsha on their fourth attempt in 1944. One of the battlefields has been preserved at the Yingzhushan War of Resistance Site Park (影珠山抗战遗址公园) about 70km northeast of downtown Changsha. One can also visit war memorials, graves and former military buildings at the Yuelu Mountain National Scenic Area (岳麓山国家重点风景名胜区) in the western part of the city. - 45 Kunming Flying Tigers Museum. This commemorates a group of volunteer American fighter pilots who fought in China. Kunming was their main base. Some of their other bases included Huaihua, Guilin, Liuzhou and Chongqing. These cities also have their own museums dedicated to the Flying Tigers. - 46 National Cemetery to the Fallen of World War II (国殇墓园) (Tengchong, Yunnan). War cemetery with the graves of thousands of Chinese Nationalist soldiers, as well as 19 American soldiers, who died in a 1944 battle in which the Chinese were victorious and managed to reclaim Tengchong from the occupying Japanese. - 47 Khalkhin Gol. Site of a battle in 1939 in which the Soviets demolished a large Japanese force. This turned Japanese thinking away from expansion into Mongolia and Siberia; instead they adopted a "strike south" strategy which led directly to Pearl Harbor and their attacks in Southeast Asia. - 48 Burma Road. This road ran from Western China into Burma (now Myanmar) and connected to Assam in Eastern India as well. It was built by the Chinese in the late 1930s, upgraded by the Americans later, and used throughout the war. - 49 Sandakan Memorial Park. This memorial in the Malaysian city of Sandakan was built at the site of a former Japanese POW prison camp with funding from the Australian government to commemorate the Allied POWs who lost their lives during the Sandakan Death Marches. Only 6 people out of several thousand survived the march, and only because those 6 managed to escape. Incidentally, all 6 survivors were Australian. - 50 The Battlebox, 2 Cox Terrace, Singapore 179622. A former British military bunker and command centre which served as the headquarters for the British forces in Malaya during the Malayan Campaign. It was here that Lieutenant-General Arthur E. Percival met with his senior officers and made the decision to surrender to the Japanese. It has been converted to a museum dedicated to the Malayan Campaign, and a re-enactment of how it functioned during the war. - 51 Changi Museum. A former POW camp-turned-museum has information about the Japanese occupation of Singapore and what life was like in the POW camp. It focuses on the general history and conditions as well as containing personal accounts and artifacts donated by former prisoners. It has a replica of the Changi Chapel that was built by Australian POWs in captivity; the original was dismantled and moved to Canberra after the war, where it now stands in the Royal Military College, Duntroon. You can also see replicas of the Changi murals, Christian murals that were painted by British POW Stanley Warren while in capitvity; the original murals are located in a military airbase and off limits to the general public. - 52 Civilian War Memorial. Monument commemorating the local civilians who lost their lives during the Japanese occupation. The remains of many unidentified victims are buried under the memorial. - 53 Ford Motor Factory, 351 Upper Bukit Timah Road, Singapore 588192. A former factory of American automobile manufacturer Ford, and the first motor vehicle factory to be opened in Southeast Asia. This is also the site where the British lieutenant-general Arthur E. Percival surrendered unconditionally to Japanese general Tomoyuki Yamashita on 15 February 1942, thus ending the Malayan Campaign. It was also used by the Japanese to produce military vehicles during the occupation. It has now been converted to a museum dedicated to life in Singapore during the Japanese occupation. The boardroom in which the surrender took place has also been reconstructed for viewing. - 54 Fort Siloso. One of four British forts on what was then the island of Pulau Blakang Mati, today known as Sentosa. It is the only one of the four to have been restored as a tourist attraction, and contains the remnants of some British artillery guns, as well as interactive displays and a re-enactment of the unconditional surrender of the British forces to the Japanese. - 55 Labrador Nature Reserve. The site of numerous British artillery gun emplacements during World War II. Today, you can see the remains of those gun emplacements, numerous pillboxes, and a network of underground tunnels that were used to store ammunition and move them to the gun emplacements. free. - 56 Reflections at Bukit Chandu, 31K Pepys Road, Singapore 118458, ✉ RBC@nhb.gov.sg. An interpretive centre of the Battle of Pasir Panjang, one of the fiercest battles in the Malayan Campaign that pitted the Malay Regiment (today the Royal Malay Regiment, the most decorated regiment in the Malaysian Army) against the Japanese. - 57 Syonan Jinja. A Shinto shrine built by the occupying Japanese in Singapore (which they re-named Syonan-to) in 1942, located at MacRitchie Reservoir, and destroyed after the Japanese surrender on 15th August 1945. The ruins of the shrine still exist, but are now in the middle of the jungle with no footpaths leading there, making it very hard to find. - 58 Syonan Chureito. A memorial built by Australian POWs to honour the Japanese war dead during World War II, with a smaller memorial behind that to commemorate the Allied war dead. Both memorials were torn down following the Japanese surrender, and today, only the road and stairs leading up to the memorial, as well as two pedestals at the bottom of the stairs, survive. A television transmission tower now occupies the former memorial site. - 59 Pearl Harbor. Site of the bombing in Western Honolulu that caused the United States to enter the war. - 60 The National WWII Museum, New Orleans, ☏ . Museum commemorating the American war effort in both theatres of World War II, with interactive displays that aim to re-create the battlefield experience for visitors. - 61 MacArthur Memorial, 198 Bank St; Norfolk, Virginia, ☏ , fax: . Tu-Sa 10AM-5PM; Su 11AM-5PM. Museum dedicated to the life of Douglas MacArthur, the general who led U.S. forces to victory over the Japanese in the Philippines, and was appointed Supreme Commander of the Allied Forces. His grave is located within the museum. The last non-president to have been granted a U.S. state funeral. Free. - 62 , ☏ (reservations). Tours available Th-Sa at 12:45PM (allow 1½ hours). Not all dates and times may be available. No public access Su-We. This memorial honors 320 individuals (including 200 young African American men) who were killed in a munitions accident during World War II while loading munitions and bombs onto ships bound for the Pacific Rim. Following the explosion many of the enlisted men refused to work, resulting in the Navy's largest mutiny trial and eventually helping to push the US Armed Forces to desegregate. The memorial is located on an active military base and as a result reservations must be made at least two weeks in advance and all visitors must be US citizens or permanent residents. Reservations can be made by calling or via an online reservation form. All visitors are shuttled to the memorial from John Muir National Historic Site in nearby Martinez. - 63 Aleutian World War II National Historic Area (Visitor Center located on the apron of the Dutch Harbor airport), ☏ . Year round, but May-October offer the best access. This site is the remains of one of four WWII era forts constructed to defend Dutch Harbor against a potential Japanese attack. The visitor center is free, however, a Land Use Permit must be obtained to visit the historic site on Mount Ballyhoo. Free. A number of sites in the US commemorate the internment of Japanese-Americans during the war. - 64 Manzanar Internment Camp. The largest internment camp in the United States where approximately 110,000 Japanese-Americans and Japanese nationals living in the United States during the war were forced to live after being ordered to leave their homes. This museum contains information about the camp, the experiences of those who were forced to live here, and life after the war. - 65 WWII Japanese American Internment Museum. A former internment camp turned into a museum to educate people about the lives of Japanese-Americans at the Rohwer Relocation Center. - 66 Topaz Museum. The Topaz Relocation Center (internment camp) housed over 11,000 Japanese-Americans. Because people were moved here before it was finished, internees were actually hired to build the wire fences to pen themselves in. - 68 Wake Island. This US-controlled island was taken by Japan shortly after Pearl Harbor and held by them throughout the war. There are ruins of Japanese fortifications, a monument for the American defenders who put up a stiff fight despite being badly outnumbered and outgunned, and a monument for a group of 98 POWs executed by the Japanese. Today the island is a US military base, off limits for most visitors. - 69 Henderson Airfield (HIR IATA). The Japanese began constructing an airfield in May 1942 in Honiara on Guadalcanal. Knowing that if they completed it, they'd be able to both isolate Australia from its allies and launch potentially devastating attacks, America quickly moved to take control of the airfield. It took six months to secure the airfield, after which the Americans finished construction on it and used it to launch attacks on other islands. Henderson Airfield was later expanded to become the international airport of the Solomon Islands, so of course it can be visited. Other sites around the airport include Bloody Ridge (where America defended against the Japanese), the Gifu (named after the city by the same name, it was a Japanese post attacked by the US), Mount Austin (used by the Japanese to get a full view of the airfield in their plan to retake it), as well as memorials for both the Americans and Japanese that fought here. - 70 Betio Island. Within a few days of Pearl Harbor, the Japanese took the Gilbert Islands, then a British colony, now part of the independent nation Kiribati. America's first attack on Japanese forces occurred in Butaritari, in the Gilberts, shortly after that. In late 1943, the Allies came to oust Japan from the islands, which by then had been heavily fortified. Betio Island in Tarawa was the site of the Battle of Tarawa, considered to be one of the bloodiest battles of the war. While war relics can be found on multiple islands throughout Kiribati, Betio Island is where the main battle took place and also where the most remains. Visitors can see tanks, bunkers, shipwrecks, guns, and memorials built by the Japanese, Americans, and Australians and New Zealanders. - 71 Kokoda Track. An important battle line in Papua New Guinea, between Australia and Japan, it is now a trekking destination, especially for Australians. - 72 Command Ridge (Nauru). During World War II, Nauru was occupied by the Japanese from August 1942 until their surrender at the tail end of the war in the wake of three years of near-continuous Allied air raids. Today, rusting relics from this era are scattered throughout the island — disused Japanese pillboxes line the shore every couple of kilometres, and old cannons can be seen along roadsides barely hidden by forest or even in plain sight between homes. However, for those who want a firsthand look at Nauru's WWII history, Command Ridge (Nauruan: Janor) is the place to go. As the island's highest point, rising to an elevation of 63 m above sea level, it was a natural lookout point for the occupiers. Today you'll find a bevy of old artillery emplacements (including a pair of six-barrel antiaircraft guns still pointed skyward), the ruins of a prison complex used to hold interned Nauruan natives (who were treated brutally by the Japanese) as well as five members of the Australian military captured during the invasion, and — most impressive of all — the former communications center, now open for any visitors to enter. The interior is not well lit, but bring in a lantern or torch and you'll still be able to make out faded Japanese writing on the walls. - 73 War in the Pacific National Historical Park. On Guam, but part of the US national park system since Guam is an American territory. The park honors all those who fought in the Pacific, not just on Guam and not just Americans. Guam was taken by the Japanese early in the war and retaken by the US in 1944. - 74 Gizo. Located on Ghizo Island, Gizo evokes the memories of vivid fighting in WWII. It is nowadays a tourist centre and some wrecks can be found underwater, including the Toa Maru. - 75 Corregidor Island. Established as an American fort to defend Manila from naval attacks, it fell to the Japanese in 1942, and was liberated in 1945. This is where General MacArthur left and uttered his most famous line "I shall return", a promise he fulfilled in 1944. - 76 Capas. A largely rural municipality housing Camp O'Donnell, an American military camp turned into a POW camp where the infamous Bataan Death March in 1942 ended. Two memorial shrines dedicated to the American and Filipino prisoners of war who suffered and died under the hands of the Japanese are erected here, and two abandoned railroad stations where the prisoners were unloaded have been turned into museums and memorials. The exact number of prisoners on the march is unknown; estimates range from 6,000 to 18,000. - 77 Coron. This town in Palawan Province has excellent wreck diving; the US Navy sank about a dozen Japanese ships in shallow water nearby in 1944. - 78 MacArthur Landing Memorial National Park. This is where General McArthur landed on his return to the country in 1944; it is in Palo municipality on Leyte Island, near Tacloban. - 79 Camp Pangatian. A former American military camp turned into a POW camp by the Japanese, it is the site of the raid at Cabanatuan, a major engagement of the liberation of the Philippines in 1945. The camp, now a shrine, is northeast of Cabanatuan city (then a rural area) in Nueva Ecija province. - 80 Okinawa Peace Park and Himeyuri Monument. The site of one of the most brutal and bloody battles of the war, Okinawa island has many war remnants and memorials. Outside of Japan, Okinawa is often viewed as the first battle on Japanese soil. However, like the other Pacific Islands, Okinawa was also colonized territory so the local population was not fully trusted by the Japanese and often treated as expendable. With the Americans being obvious enemies and the Japanese not being complete allies, the question on many Okinawans' minds was not "How am I going to survive?" but "How do I want to die?". The museums here show the war from a uniquely Okinawan perspective, including life for citizens, students and military. It also depicts well how they were mistreated by both the Japanese and the Americans during and after the war. The Peace Park and the Himeyuri Monument in Itoman are the best places to learn about the battle, but remnants and reminders of the war can be found throughout the island. - 81 Iwo Jima. Another group of islands close to Japan, scene of some extremely fierce fighting. An image of victorious US Marines raising the Stars and Stripes there is quite famous. US Military Tours has exclusive rights to the island and only US citizens who are members of the Iwo Jima Association of America, WWII veterans, or WWII prisoners of war are eligible to join the tours. - 82 Chiran Peace Museum for Kamikaze Pilots. As the war approached the home islands, the desperate Japanese began sending out young men to fly aircraft packed with explosives into American ships. The museum is located in Chiran over the former spot where the tokko pilots (known abroad as kamikaze pilots) were trained and flew from. The museum contains information about the pilots, artifacts and letters from them, and recovered kamikaze planes. - 83 Hiroshima Peace Park and Memorial Museum. Hiroshima was the first place in the world to be attacked with an atomic bomb. The museum shows how devastating the bomb was to the city and the effects it had on the people from the immediate aftermath to the present day. - 84 [dead link] Nagasaki Atomic Bomb Museum and Peace Memorial Hall. Museums that are on the site where the atomic bomb was dropped on August 9, 1945. The Nagasaki bombing led to Japanese surrender and is also noted as the last place to have an atomic bomb dropped on it. - 85 Yasukuni Shrine (靖國神社 Yasukuni-jinja), 3-1-1 Kudan-kita, ☏ . A controversial shrine to Japan's war dead, housing the souls of some 2.5 million people killed in Japan's wars — including numerous Taiwanese and Koreans, and controversially, convicted war criminals executed by the Allies. Often visited by Japanese politicians, drawing sharp criticisms from neighbours China and South Korea in the process. If you choose to visit, consider keeping it a secret from your Chinese or Korean friends. There are also many other sites that commemorate parts of the war. - The 86 US Marine Corps Memorial at Arlington, Virginia, depicts the famous scene of the raising of the (American) flag on Iwo Jima, whose history is told by the movie Flags of our Fathers directed by Clint Eastwood. One of the soldiers involved, Ira Hayes, is commemorated in a fine song by Johnny Cash. - 87 US National Museum of the Pacific War. In Fredericksburg (Texas), home town of Admiral Chester Nimitz who commanded US forces in part of the Pacific, this is a large museum complex with many exhibits. - 88 Bank Kerapu. There is a small war memorial and museum in the former Bank Kerapu building in Kota Bharu, Malaysia, which served as a secret police station during the Japanese occupation; it might not merit a special trip but is worth visiting if you are in Kota Bharu. - There are Commonwealth War Cemeteries in Taukkyan, Thanbyuzayat, Kranji, Taiping, Labuan, Sai Wan, Kanchanaburi, Imphal, Chennai and Yokohama as well as an American War Cemetery in Manila, in which many of the Allied war dead are buried. While some sources claim Chinese communist forces contributed little to the Pacific War, Chinese law enacted in 2019 criminalizes the denial of officially-endorsed heroes and martyrs, in addition with defamation lawsuits. - World War I - Holocaust remembrance - World War II in Europe - World War II in Africa - Japanese colonial empire - Industrialization of the United States for non-military US history of the 1930s and 40s - Long March - Nuclear tourism
The reason we know today just how much ice is melting in Greenland and Antarctica is because of a pair of satellites, launched in 2002 by NASA and the German Research Centre for Geosciences (GFZ). Now, they are set to be replaced by a more modern duo. A SpaceX Falcon 9 rocket blasted off at 3:47pm (7:47pm GMT) Tuesday from Vandenberg Air Force Base in California, hoisting into orbit the spacecraft known as GRACE-FO, a follow-on to the prior, 15-year mission known as the Gravity Recovery and Climate Experiment (GRACE). How to measure water from space? Two satellites, each the size of a car, will circle the Earth at a distance of 137 miles (220 kilometres) from each other. They will be flying about 310 miles (490 kilometres) above the Earth for the next five years. According to the laws of physics, the slightest variation in mass on Earth modifies the pull of gravity on satellites. When the lead satellite passes over a mountain, it will get slightly farther from its twin for a few instants because of the extra mass in this area and a slightly stronger pull of gravity. These slight variations in distance will be constantly recorded by the spacecraft, because each shift signals a change in mass on the planet underneath. The satellites use a monthly reference point, because unless there is an earthquake or other unusual event, only water has the capacity to change that fast. Water always has mass, whether it is in the form of liquid, solid, or gas. When ice melts, the oceans' mass rises. When it rains a lot in a certain region, the volume of the aquifers mounts. The satellites will pick this up, and the data will show that the mass in a certain area was higher than it was in the prior month, or year. That is how the GRACE-FO satellites will establish a map of the water on Earth, every 30 days, showing which areas have more and which have less, whether above or below ground. They operate with a precision equivalent to a change of 0.4 inches (one centimetre) in water height across areas of about 211 miles (340 kilometres) in diameter. What is the point? The prior mission, GRACE, allowed scientists to gain an understanding of how much ice Greenland was losing. It was more than they thought, based on ground-observations. From 2002 to 2016, 280 gigatons of ice melted each year, which led to a sea level rise of 0.8 millimetres. The satellites were also able to track just how much ice Antarctica was losing, and produced colourful maps that showed losses in red and gains in blue. The map of California showed plenty of red when it was struck by a massive drought in recent years, and scientists and policymakers were about to calculate how low the water table was falling. Meanwhile, other parts of the globe such as the Okavango Delta in Botswana saw water reserves mount from 2002 to 2016 due to heavy rains. Renewing the mission will allow scientists to continue to track trends in sea level rise, glacial and ice melt, and the drying up of certain aquifers. "Water is critical to every aspect of life on Earth - for health, for agriculture, for maintaining our way of living," said Michael Watkins, GRACE-FO science lead and director of NASA's Jet Propulsion Laboratory in Pasadena, California. "You can't manage it well until you can measure it." NASA has spent $430 million on the mission, and the Germans have invested EUR 77 million (about $90 million).
Suppose and are right triangles and share another congruent angle. By the Angle-Angle Similarity Theorem, these triangles are similar. As a result, corresponding sides are proportional. In fact, the ratio between corresponding sides is constant. For example, The second proportion yields trigonometric ratios — ratios that relate the side lengths of one right triangle. Namely, the tangent of is defined asBecause proportions of all corresponding sides can be written, there are trigonometric ratios that relate all pairs of the three sides of a triangle. A trigonometric ratio relates two side lengths of a right triangle. The three most notable are sine, cosine, and tangent. Consider the right triangle As drawn, is the hypotenuse of The remaining sides can be named relative to the marked angle Because is next to it is called the adjacent side. Similarly, because lies across from it is called the opposite side. Sine, cosine, and tangent of are defined as follows. Trigonometric ratios can be used to determine unknown side lengths in right triangles. Determine sine, cosine, and tangent of the angle To begin we need to determine the triangle's sides relative to The side across from the right angle is always the hypotenuse. The side next to is the adjacent side and the side across it is the opposite side. Thus, Now that the sides are known, we can use the definition of sine to determine its value. It follows that the sum of the measures of and is Therefore, they are complementary angles. The sine and cosine ratios of complementary angles have a special relationship. To explore this, the three sides in the triangle will be labeled and The definitions of sine and cosine can be applied as follows. It can be seen that and This is true for all pairs of complementary angles. If an acute angle is named its complementary angle can be written Thus, the relationship can be written as follows.
24/7 writing help on your phone The basic economic problem of scarcity refers to the situation in which finite factor inputs are insufficient to produce goods and services to satisfy infinite human wants. It is incontrovertible and irrefutable that all societies face the basic problem of scarcity due to limited resources and unlimited wants. Scarcity makes it necessary for us to make the most of what we have. In trying to obtain the highest level of satisfaction from available resources, good or rational choices have to be made. The concept of choice applies to all decision-making units. We are continually uncovering new wants and demands. Scarcity implies that not all of society’s goals can be pursued simultaneously, as the many different kinds of resources (production factors) are available only in limited amounts. The various factors of production refer to the inputs used in the production of goods and services. They are divided into four broad categories: land, labour, capital and entrepreneurship. Labour refers to human effort-physical and mental-which is directed to the production of goods and services. Normally the labour force of a country consists of everyone of the working age (14-64), and this form of resource is largely dictated and governed by the demographic distribution within the country (or any other geographical entity), and is therefore restricted by dependency ratio. Land refers to all the productive resources supplied by nature, and various aspects of such a form of resource are limited and exhaustible. Capital is a man-made resource used in the production of goods and services, which includes machines, tools, and buildings. The production capacity of a country therefore, is dependent on the amount of capital the country possesses. Entrepreneurship is a human resource that is separate from labour. An entrepreneur is one that performs the functions of organizing and managing the factors of production, of innovating new products and ways of production and he takes the risks of being in business. Without entrepreneurship, virtually no business organisation can operate. However, such a form of human resource depends on amount of talented people capable of generating innovative ideas. It is generally understood that the self-interested nature of economic agents compels them to make rational decisions and choices to maximise utility and welfare. The basic assumption of Economics is that all decision-making units make rational choices. Rational choices maximize the well-being of economic agents. Rational choices are made by different decision-making units to maximize different objectives. To obtain the highest level of satisfaction, a rational decision must be made. This decision has to be an optimal one. Assuming rational behaviour on the part of decision-making units, this optimal choice must be the one that chooses the most desirable alternative among the possibilities that the available resources permit. These decision-making units include household, firms and the government. The figure above shows a PPC (production possibility curve). A production possibility curve is a graph that shows the maximum attainable combinations of output that can be produced in an economy within a specific period of time, when all the available resources are fully and efficiently employed, at a given state of technology. The PPC is a economic framework that can be used to illustrate concepts of scarcity, choices and opportunity costs. All the points on the PPC represent productive efficient levels of production. Scarcity is illustrated, therefore, by the unattainable combinations outside the PPC as well as the fact that society has to choose between combinations of the two goods as resources cannot be used to produce all at the same time, and the combinations of goods (such as amount od capital and consumer goods in the case of the PPC above) the economy eventually chooses depends on its priorities). The downward (negative) sloping gradient of the PPC also illustrates the concept of opportunity cost. To choose to have more of one good means having to give up some of the other good, given that the limited resources have been fully and efficiently employed (increased output of one product in turn causes the out put of the other product to fall due to limited resources and scarcity) Economic agents employ several analytical tools to make rational choices. They take into account the opportunity costs and often make decisions based on the marginalist principle. Every time a choice is made, an opportunity cost is incurred. Opportunity cost refers to the real cost in terms of the next best alternative that has to be forgone, and it arises due to the fact that the resources available to meet the unlimited wants are limited so that not all of the wants can be fully satisfied. An economic agent, therefore, has to make a decision based on his current priorities and sacrifice the next best alternative. Economics, as mentioned before, is about making rational/optimal choices. Economic choices are made at the margin. The margin is the edge or border where we must decide whether to take one more step or to produce one more unit of a particular good or whether to use one more unit of a particular resource. Rational decisions are made at the margin involve weighing up marginal costs and marginal benefits. Generally, economic agents are compelled to continue producing a particular type of good until the marginal cost is equals to the marginal benefit (ie the production of one additional unit would mean that the marginal costs would outweigh the benefits). In conclusion, due to the fact that resources are high limited, all societies face the problem of scarcity and hence have to make decisions like a household does. A society has to decide what and how much to produce, how to produce and for whom to produce. Firstly, the society must decide what goods it is going to produce (and hence what not to produce). Such choices usually take the form of more of one thing and less of the other (i.e. it needs to choose the composition of total output. Secondly, most goods can be produced by a variety of methods, and a society must decide on the methods of production to be adopted. Thirdly, the total output needs to be distributed among members of the society, and the society therefore needs to consider how it can distribute its goods. Therefore, we can conclusively assert that the basic economic problem of scarcity compels economic agents to make rational decisions (such as choosing the composition of total output) to maximize total profit and to comply with their current priorities. 👋 Hi! I’m your smart assistant Amy! Don’t know where to start? Type your requirements and I’ll connect you to an academic expert within 3 minutes.get help with your assignment
Chapter 1 Outline As a whole, this chapter was meant to depict the differences in the creation of cultures in the Americas and the changes that took place in these cultures after the Europeans arrived. Beginning with the formation and shaping of the continents, and then leading into the Ice Age, the authors described the theories of how people came to the Americas. The most common belief is that they crossed a land bridge connecting Siberia to Alaska, which does not exist currently, and came into North America. They then spread across the Americas after the glaciers of the Ice Age melted. After beginning to cultivate corn, the cultures of Latin and South America began developing and societies such the Incas of the western coast of South America and the Aztecs of Mexico could now be found. The native peoples of North America were less developed, for they preferred to live nomadically rather than agriculturally. The majority of the natives were polytheistic, at least before the European appearance. Upon the Spaniards’ arrival, the American Indians were found as a fairly civilized people who possessed ridiculously large amounts of gold and goods. And so, in the name of their country and in the name of religion, the Spanish conquered the Incas of South America and the Aztecs of Mexico. The natives were conquered with relative ease, for the guns and diseases of the Europeans were far greater than the Native Americans could withstand. Soon, more Spanish conquistadores arrived, exploring the newly conquered lands and converting the natives to Christianity. It was the Roman Catholic mission that was to become the main establishment in the colonies, and in the name of the Church, many of these “missionaries” adopted the practice of slavery as well as other brutalities. The Spanish conquistadores forever changed the fate of the Americas the moment Christopher Columbus landed on the shores of the West Indies. But this fate was not all together good, for while the Spanish brought over new animals, new culture, new laws, new religion, and new language onto a large amount of native civilizations, they also had a hand in bringing slavery to the Americas, they brought over diseases that condemned the biologically susceptible natives, and they severed the contact the natives had with their original cultures. Chapter 1 Vocab Aztecs The Aztecs were a Native American Empire who lived in Mexico. Their capital was Tenochtitlan. They worshipped everything around them especially the sun. Cortes conquered them in 1521. Pueblo Indians The Pueblo Indians lived in the Southwestern United States. They built extensive irrigation systems to water their primary crop, which was corn. Their houses were multi-storied buildings made of adobe. Joint Stock Companies These were developed to gather the savings from the middle class to support finance colonies. Ex. London Company and Plymouth Company. Spanish Armada "Invincible" group of ships sent by King Philip II of Spain to invade England in 1588; Armada was defeated by smaller, more maneuverable English "sea dogs" in the Channel; marked the beginning of English naval dominance and fall of Spanish dominance. Conquistadores Spanish explorers that invaded Central and South America for it's riches during the 1500's. In doing so they conquered the Incas, Aztecs, and other Native Americans of the area. Eventually they intermarried these tribes. Renaissance After the Middle Ages there was a rebirth of culture in Europe where art and science were developed. It was during this time of enrichment that America was discovered. Canadian Shield Geological shape of North America; 10 million years ago it held the northeast corner of North America in place and eventually was the first part of North America to come above sea level. Christopher Columbus An Italian navigator who was funded by the Spanish monarchy to find a passage to the Far East. He is given credit for discovering the "New World," even though at his death he believed he had made it to India. He made four voyages to the "New World." The first sighting of land was on October 12, 1492, and three other journeys until the time of his death in 1503. Hernan Cortes He was a Spanish explorer who conquered the Native American civilization of the Aztecs in 1519 in what is now Mexico. Treaty of Tordesillas In 1494 Spain and Portugal were disputing the lands of the new world, so the Spanish went to the Pope, and he divided the land of South America for them. Spain got the vast majority, the west, and Portugal got the east. “By the time Europeans arrived in America in 1492, perhaps 54 million people inhabited the two American continents. Over the centuries they split into countless tribes, evolved more than 2,000 languages, and developed many diverse religions, cultures, and ways of life.” (Pg. 6) “Unlike the Europeans, who would soon arrive with the presumption that humans had dominion over the earth and with the technologies to alter the very face of the land, the Native Americans had neither the desire nor the means to manipulate nature aggressively.” (Pg. 10) “Europe provided the markets, the capital, and the technology; Africa furnished the labor; and the New World offered its raw materials, especially its precious metals and its soil for the cultivation of sugar cane. For Europeans as well as for Africans and Native Americans, the world after 1492 would never be the same, for better or worse.” (Pg. 14) “During the Indians’ millennia of isolation in the Americas, most of the Old World’s killer maladies had disappeared from among them. But generations of freedom from those illnesses had also wiped out protective antibodies. Devoid of natural resistance to Old World sicknesses, Indians died in droves.” (Pg. 15) “It [the encomienda system] allowed the government to “commend,” or give, Indians to certain colonists in return for the promise to try to Christianize them. In all but name, it was slavery.” (Pg. 17) “Moctezuma treated Cortes hospitably at first, but soon the Spaniards’ hunger for gold and power exhausted their welcome. ‘They thirsted mightily for gold; they stuffed themselves with it; they starved for it; they lusted for it like pigs,’ said one Aztec.” (Pg. 20) “The Spanish invaders did indeed kill, enslave, and infect countless natives, but they also erected a colossal empire, sprawling from California and Florida to Tierra del Fuego. They grafted their culture laws, religions, and language onto a wide array of native societies, laying the foundations for a score of Spanish-speaking nations.” (Pg. 23) Chapter 2 Outline Chapter two of The American Pageant focuses on the first colonies in America. The first English settlement established was Jamestown in 1606. After arriving, the settlers of Jamestown struggled mightily to survive. They were not used to having to capture their own food and produce everything that they needed. The settlers had decided to return home when Lord de la Warr arrived. He was sent by the English government to be the new leader of Jamestown. Under the strong leadership of de la Warr, the settlement was able to survive and eventually prosper. The settlement was greatly helped by John Rolfe, who perfected his method for growing tobacco. This led to a rush of tobacco growing across Virginia. Around the time that the settlement had begun to prosper was when problems with the local Indians arose. After several decades of losing land to the settlers, the Powhatan Indians attacked Jamestown in 1622. The attack left 347 settlers dead and caused the Virginia Company to declare war upon any hostile Indians. A second Anglo-Powhatan War erupted in 1644 as once again the Indians attempted to drive the settlers out. The Indians were defeated in 1646 and banned from their ancestral lands. Settling America continued as Lord Baltimore founded Maryland in 1634. He not only wanted to reap the financial benefits of having a colony, but wanted to create a refuge for Catholics like himself. More settlers arrived in Carolina in 1670. They brought with them slaves and the Barbados Slave Code. Caroline officially adopted the code in 1696 and Carolina would serve as a staging area for slavery that would eventually take hold of North America. The colonists in Carolina needed cheap labor and decided to make an alliance with the Savannah Indians. The Savannah Indians would capture members of rival tribes and give them to the colonists as slaves. When the Savannah Indians decided to end the alliance in 1707 and leave, the colonists massacred the majority of the tribe. To replace the Indian slaves, the colonists in Carolina purchased slaves from West Africa. These slaves were excellent rice-growers and had a lot of experience. The Tuscarora Indians angered by the loss of their land, attacked North Carolina settlements in 1711. Aided by colonists from South Carolina, the Tuscaroras were badly defeated. Most were sold into slavery while the rest were left alone. The colony of Georgia was formally founded in 1733. Named after King George II, it was intended to serve as a buffer to protect the valuable Carolinas. Virginia Company: Founded to find gold and a more direct route to India, financed the journey to America and helped build Jamestown. Iroquois Confederacy: Powerful group of tribes made up of Mohawks, Oneidas, Cayugas, and Senecas. Slave Codes: Provided rules of slavery, denied slaves basic fundamental rights, and gave their owners permission to treat them as they saw fit. Lord De la Warr: Englishman who came to America in 1610. Helped Jamestown survive and fought Indians. Royal Charter: Document given to the founders of a colony by the monarch that allows for special privileges and establishes a general relationship. Page 29: “Once ashore in Virginia, the settlers died by the dozens from disease, malnutrition, and starvation. Ironically, the woods rustled with game and the rivers flopped with fish, but the greenhorn settlers, many of them self-styled ‘gentlemen’ unaccustomed to fending for themselves, wasted valuable time grubbing for nonexistent gold when they should have been gathering provisions.” Page 30: “But the Indians, pressed by the land-hungry whites and ravaged by European diseases, struck back in 1622. A series of Indian attacks left 347 settlers dead, including John Rolfe. In response the Virginia Company issued new orders calling for ‘a perpetual war without peace or truce,’ one that would prevent the Indians ‘from being any longer a people.’ Periodic punitive raids systematically reduced the native population and drove the survivors ever farther westward.” Page 32: “John Rolfe, the husband of Pocahontas, became father of the tobacco industry and an economic savior of the Virginia colony. By 1612 he had perfected methods of raising and curing the pungent weed, eliminating much of the bitter tang. Soon the European demand for tobacco was nearly insatiable. A tobacco rush swept over Virginia, as crops were planted in the streets of Jamestown and even between the numerous graves. So exclusively did the colonists concentrate on planting the yellow leaf that at first they had to import some of their foodstuffs. Colonists who had once hungered for food now hungered for land, ever more land on which to plant ever more tobacco. Relentlessly, they pressed the frontier of settlement up the river valleys to the west, abrasively edging against the Indians.” Page 34: “Lord Baltimore, a canny soul, permitted unusual freedom of worship at the outset. He hoped that he would thus purchase toleration for his own fellow worshipers. But the heavy tide of Protestants threatened to submerge the Catholics and place severe restrictions on them, as in England. Faced with disaster, the Catholics of Maryland threw their support behind the famed Act of Toleration, which was passed in 1649 by the local representative assembly.” Page 37: “In 1707 the Savannah Indians decided to end their alliance with the Carolinians and to migrate to the backcountry of Maryland and Pennsylvania, where a new colony founded by Quakers under William Penn promised better relations between whites and Indians. But the Carolinians determined to “thin” the Savannahs before they could depart. A series of bloody raids all but annihilated the Indian tribes of coastal Carolina by 1710.” Main Idea: The main idea of Chapter two is that whenever settlers and Indians lived close to each other, they could not get along. At the very first settlement of Jamestown, the settler and Indians could not coexist. This also occurred in the Carolinas, where after a short period of harmony, the settlers slaughtered the Indians. The failure to coexist was due to the settlers’ tendency of continuously taking land which drove the Indians to violence. Review Outline Chapter 3 – Settling the Northern Colonies The Puritan religion was formed by a group of people who wanted to “purify” King Henry VIII’s Anglican Church in the 1530’s, and Puritan Separatists (extremists now known as the “pilgrims”) were kicked out of England and forced to migrate to the New World. The Separatists arrived in New England, signed the Mayflower Compact, which later became an influence on the Constitution, and lost 60% of their population to the first winter. Another colony was formed in Massachusetts by another group of Puritans with a royal charter, and John Winthrop was elected governor. The Bay Colony extended suffrage to all adult male Puritans. Rules in the Bay Colony were very puritanical as the Puritans were a God-fearing people with a very unpleasant concept of Hell. These rules were generally obeyed, but religious dissenters like Quakers, Anne Hutchinson, and Roger Williams were persecuted. These people fled to the colony of Rhode Island, which acquired a royal charter in 1644. The English Colonies spread out quickly as colonies like Connecticut, New Haven, Maine, and New Hampshire were founded. Unfortunately, this expansion brought them into direct conflict with Native Americans, resulting in wars such as the Pequot War, which ended in a Puritan annihilation of the natives, and King Philip’s War, a desperate attack by neighboring tribes that was also a failure. While old England was wrapped up in Civil Wars, the colonies banded together to form the heavily-Puritan New England Confederation in 1643. When King Charles II was restored to the throne, he revoked the charter of insolent Massachusetts and granted charters to Connecticut and Rhode Island. Further British attempts to control the colonies came in the form of the Dominion of New England, headed by Sir Edmund Andros, who instated heavy taxes, enforced the Navigation Laws, and restricted local democratic meeting. The Dominion was toppled by the Glorious Revolution in England, which raised William and Mary to the throne. The Dutch West India Company bought Manhattan Island and set up the colony of New Netherland there. New England was hostile to its new neighbors, New Sweden and New Netherland, and the Dutch were kicked out of New Netherland, renamed New York, by the British army. Meanwhile, the Quaker William Penn set up Pennsylvania, the first of the Middle Colonies. Pennsylvania was tolerant of religious diversity and kind to the Native Americans, it was against slavery and it had relaxed naturalization laws. The Middle Colonies, which later included New York, New Jersey, and Delaware, were very fertile and had a high output of grain. As Americans became more prosperous, they began to realize that they were not merely surviving, but truly thriving. Mayflower Compact – A contract signed by the white male Separatists aboard the Mayflower agreeing that they would set up a democratic government. Navigation Laws – A set of English Laws restricting colonial trade with countries other than England. These laws were defied through smuggling and were often the focus of colonial dissatisfaction with British rule. New England Confederation – Made up of the Bay Colony, Plymouth Colony, Connecticut Colony, and New Haven Colony. Purpose was to defend New England against its enemies in the absence of British Troops (which were fighting Civil Wars in England). King Phillip’s War – A massive attack of neighboring tribes against New England led by Metacom. Although the Native Americans lost the war, they destroyed over fifty Puritan settlements and halted westward expansion for decades. Charles II – An English King restored to the throne after the English Civil War. He revoked Massachusetts’s charter and gave charters to Connecticut and Rhode Island. “The Pilgrims’ first winter of 1620-1621 took a grisly toll. Only 44 out of the 102 survived. At one time only 7 were well enough to lay the dead in their frosty graves. Yet when the Mayflower sailed back to England in the spring, not a single one of the courageous band of Separatists left. As one of them wrote, ‘it is not with us as with other men, whom small things can discourage.’” (45) “When Charles II was restored to the English Throne in 1660, the royalists and their Church of England allies were once more firmly in the saddle. Puritan hopes of eventually purifying the old English church withered. Worse, Charles II was determined to take an active, aggressive hand in the management of the colonies… As a slap at Massachusetts, Charles II gave rival Connecticut in 1662 a sea-to-sea charter grant, which legalized the squatter settlements. The very next year, the outcasts in Rhode Island received a new charter, which gave kingly sanction to the most religiously tolerant government yet devised in America. A final and crushing blow fell on the stiff necked Bay Colony in 1684, when its precious charter was revoked by the London authorities.” (53) “Residues remained of Charles II’s effort to assert tighter administrative control over his empire. More English officials – judges, clerks, customs officials – now staffed courts and strolled the wharves of English America. Many were incompetent, corrupt hacks who knew little and cared less about American affairs. Appointed by influential patrons in far-off England, they blocked, by their very presence, the rise of local leaders to positions of political power. Aggrieved Americans viewed them with mounting contempt as the eighteenth century wore on.” (55) The Days of the Dutch on the Hudson were numbered, for the English regarded them as intruders. In 1664, after the imperially ambitious Charles II had granted the area to his brother, the Duke of York, a strong English squadron appeared off the decrepit defenses of New Amsterdam. A fuming Peter Stuyvesant, short of all munitions except courage, was forced to surrender without firing a shot. New Amsterdam was thereupon renamed New York, in honor of the Duke of York… With the removal of this foreign wedge, the English banner now waved triumphantly over a solid stretch of territory from Maine to the Carolinas.” (57-58) “By the time Franklin arrived in the City of Brotherly Love, the American Colonies were themselves ‘coming to life’. Population was growing robustly. Transportation and communication were improving. The British, for the most part, continued their hands off policies, leaving the colonists to fashion their own governments, run their own churches, and develop networks of intercolonial trade. As people and products crisscrossed the colonies with increasing frequency and in increasing volume, Americans began to realize that – far removed from Mother England – they were not merely surviving, but truly thriving. The Plymouth Colony and its sister colonies were founded to allow Puritans the freedom to worship without persecution from the Anglican Church. Religious dissent in these intolerant colonies led to the foundation of other colonies like Rhode Island and Pennsylvania. The New England colonies were hard pressed for survival and banded together in the New England Confederation, the first step toward continental unity. The Middle Colonies of New York and Pennsylvania established themselves as much more tolerant than the New England Colonies, and had fertile valleys in which they could grow a lot of grain. The English Colonies in the New World were very successful by the 18th Century. Ch. 4 Outline Settlement in the Chesapeake Bay -- located in modern day Virginia -- was harsh at first. There was terrible diseases that the English settlers were not immune to such as malaria and typhoid. In addition, male immigrants outnumbered females 6 to 1 which resulted in very slow family growth. However, the Chesapeake Bay was a very fertile region with flat lands and rivers which were perfect for tobacco growth. As southern farms grew, they needed more a larger source of labor. This resulted in an immigration of indentured servants who gained freedom after a few years of service. The "head-right system" allowed for masters to receive 50 acres of land if they pay for the voyage of their servants. As a result of unhappy planters that were pushed to the outskirts of the colony in search of land and threatened with Indian attacks, an uprising known as Bacon's Rebellion occurred. Led by Nathaniel Bacon, these small planters rebelled against Virginia's Governor Berkley -- especially because of his friendly Indian policy -- causing chaos in the colony. The South -- particularly Virginia -- began importing African slaves in larger numbers by the 1680s; mostly as result of better wages in England. A greater importation of slaves resulted in a growing slave culture that contributed to American culture. This can be seen in the development of Gullah -- a mixture of English and several African languages -- and jazz. In the 1700's the social structure of the South widened as a result of slave importation creating a wealthy planter class. In New England, conditions were much better for the settlers. On average, New Englanders lived 10 years longer than those in England. In addition, settlers usually immigrated with their families which resulted in greater population growth. However, the New England soil was filled with stones and many of the rivers were short and fast; this caused New Englanders to look for work as traders, fisherman and shipbuilders. Slavery was introduced early in New England settlement, but it never flourished as a result of a society not centered around agriculture like in the South. The New England society was based around their Puritan beliefs which was reflected by western settlements created by New Englanders. As a result of colonial expansion and the pass of time, the Puritan religion began to dampen down. In order to enter the Church, individuals had to profess conversion -- the claim that they witnessed God's grace and they deserved admittance into the Church. As a result of a decrease in membership the Half-Way Covenant was created; this arrangement allowed for unconverted individuals to receive baptism, but not full membership. Chapter 5 Outline This chapter primarily features the economic opportunity, arts, and religion of the colonies. The main occupation of the time was farming, though fishing and merchantry were also common in the North. The most respected members of society were clerics, physicians, and jurists, while the lowest members were African slaves and indentured servants. During this time, the First Great Awakening occurred, notable for being the first mass movement in American history. There were many different sects of Protestant Christianity in colonial America, notably the Anglican, Congregational, Calvinist, and Methodist churches. Arts also flourished in colonial America, mainly in the forms of literature and painting. Benjamin Franklin and Thomas Paine were great writers of the time while John Trumbull, Charles Wilson Peale, Benjamin West, and John Singleton Copley were notable painters. From all of the opportunity of the American colonies came immigrants, mostly Scots-Irish and Germans. These groups fled from religious persecution, economic oppression, and war. The Germans’ Lutheran faith increased religious diversity even more. None were more accepting of these newcomers than the Quakers of Pennsylvania, thus many Germans and Scots-Irish felt welcome in the Middle colonies. With these beginnings of cultural mixing, America started to form its unique multicultural American national identity unlike anything known in Europe.
Hybrid Electric VehiclesEdit Hybrid Electric Vehicles (HEVs) are a cross between an electric car and an internal-combustion car. They combine the electric motor and battery of an electric car with a small internal-combustion engine. The electric motor receives power from the batteries which are charged by the internal-combustion engine batteries as needed. The Hybrid separates itself from electric vehicles by its much greater range. Unlike electric vehicles, which are typically limited to 130 km between charges, HEVs can run until both the batteries and gasoline are depleted, giving it a substantially greater range. The electric motor tends to run at lower speeds, while the internal combustion engine is used at higher speeds and to charge the batteries when they are depleted. Also, because the internal-combustion engine charges the batteries, HEVs don't need to be plugged in as electric vehicles do. Compared to a typical internal-combustion vehicle, the main advantage an HEV provides is increased fuel efficiency. This leads to fewer emissions and fuel savings. In particular, HEVs excel in their fuel efficiency over internal-combustion vehicles in city driving. The electric motor tends to be more efficient in dealing with the frequent acceleration and deceleration. This is partly because HEVs are able to capture some of the power lost during breaking. This is done by reversing the engine and charging the batteries. This leads to even greater fuel savings over internal-combustion vehicles. When stopped completely, HEVs can shut off their engine automatically, conserving energy, while internal-combustion vehicles (ICVs) continue to run unless the driver manually switches them off. One feature of HEVs and EVs which is both advantageous and, at the same time, a safety concern is their lack of noise. When operating their electric motor (typically at low speeds), HEVs are much quieter than their ICV counterparts. Quieter vehicles are typically desirable because they reduce noise pollution, an expensive transportation externality. The problem is that pedestrians are accustomed to the noise of internal-combustion vehicles. Pedestrians rely on the noise generated by vehicles to warn them that they are nearby. The lack of noise generated by slow moving HEVs presents a concern for pedestrian safety. The U.S. Congress enacted the Pedestrian Safety Enhancement Act which includes a minimum sound requirement for motor vehicles. Manufacturers have begun adding vehicle noise and warning sounds to help protect pedestrians. The primary market for HEVs includes economically and environmentally conscious consumers who are looking to reduce emissions and save on fuel but do not want to be confined to the limitations of electric vehicles. Most HEVs are smaller vehicles and so the market revolves around drivers willing to drive compact cars. This trend has been changing, however, with the development of hybrid SUVs. Due to the higher cost of HEVs over ICVs, the market tends to include higher income drivers. Also, because HEVs are relatively new, fewer used HEVs are available on the market. This restricts the market further to those willing to purchase new, or nearly new, vehicles. The success of HEVs in the market is largely dependent on the price of gasoline and the prevalence of environmental concerns. This can be seen by looking at the history of HEVs sales in comparison to gasoline prices. As oil prices rise, the fuel savings from driving HEVs also increases. As seen in the 1970s however, a sustained period of high oil prices is needed for HEVs to capture sufficient market share. In Encyclopedia of Energy, German discusses new vehicle purchasers lack of concern for the cost of fuel. Often, the short term savings of ICVs win out over the possible long term fuel savings of HEVs. One problem HEVs have encountered in trying to establish their market share is that manufactures continue to make enough improvements to ICVs. The improvements limit the benefits of HEVs. As concerns about fuel efficiency rise, manufactures produce more fuel efficient ICVs. If fuel prices drop, no action is necessary from manufacturers as consumers will continue to purchase ICVs. The internal combustion engine continues to win out because the "incremental advantages [of HEVs] are less than the cost of switching infrastructure." HEVs were not new to the U.S. in 1999 as the sales data seems to suggest. In fact, their origins go back all the way to 1905. At that time, American engineer H. Piper came up with the concept of a hybrid vehicle. His motivation was an increase in performance. His hybrid electric vehicle could accelerate to 40 km/h in 10 seconds while internal-combustion vehicles of the time were requiring 30 seconds. Although this was a drastic improvement, the internal-combustion engine caught up by the time Piper received his patent. A major disadvantage of the gasoline engine was the requirement to start by crank. Once Piper received his patent, this barrier had been overcome and the internal-combustion vehicle went on to dominate the market. Some electric vehicles had been developed around the same time as Piper with the help of electricity pioneers like Edison and Tesla. Like EVs today, the major drawback was the battery technology which greatly limited the vehicles' range. However, this originally was less of a concern due to the limited road infrastructure between cities. The range was sufficient for city driving. As roads began to expand, though, the internal-combustion vehicle made its run. The heavy batteries required for EVs weighed them down. Adding additional batteries had diminishing returns because of the extra weight. Hybrid's had to rely on mechanical means of switching between the electric and gas motors. This was complex and less efficient than today's HEVs which have computers optimizing and controlling its operations. Until the oil crisis in the mid-1970s, the gasoline car went virtually unchallenged by electric vehicles. With gasoline prices relatively low, oil plentiful, and with existing dominance over the market, gasoline cars were not threatened. Improvements in power and efficiency further helped to prevent any potential competitors from entering the market. In the 1970s, with the oil crises causing gas prices to rise, a brief opening appeared for alternative vehicles. Wouk discusses his own attempts at bringing an HEV during this time. His model was able to achieve much higher fuel efficiency and seemed to be on for manufacturing. However, the crisis was too short-lived and once oil was readily available again, funding for alternative vehicles such as his declined. The oil crises did bring about the Energy Policy and Conservation Act (EPCA) requiring new fuel efficiency standards. HEVs such as Wouk's immediately met these standards but automakers had until 1985 to comply with their ICVs. This allowed them sufficient time to improve ICVs and left little chance for alternative vehicles to enter the market. Nearly 20 years later, President Clinton makes a deal with major U.S automakers. Instead of raising CAFE (Corporate Average Fuel Economy) standards, the deal requires GM, Ford and Chrysler to establish a "Supercar." The program would combine government and corporate money in the development of an 80 miles per gallon vehicle. The biggest problem with the deal was this somewhat arbitrary milestone of 80mpg. The goal was attainable, but required automakers to use very light, and therefore expensive, materials. The automakers were successful in developing an 80mpg vehicle, but due to its enormous expense, it was simply not marketable to the public. Perhaps a more modest goal would have produced a marketable vehicle which was still drastically more fuel efficient than ICVs of the time. Nevertheless, the Supercar program did help spur innovation in the alternative vehicle industry. Several years later, Toyota and Honda rolled out their hybrid vehicles, first in Japan. Their cars achieved more modest fuel efficiency than the Supercar but still double the average ICV. The Japanese market was also more suited to an HEV. With higher gasoline prices, higher density driving and culture more accustomed to compact cars, Toyota and Honda saw success in their home market. Driver demand for vehicle performance was also less than in the U.S. Both companies worked to adapt their hybrid technology to suit the U.S. market. Beginning as early as 1999, but primarily in 2000, Americans began purchasing HEVs. Innovation in HEV TechnologyEdit Technological innovations in the last 100 years has made all types of vehicles safer, faster, more efficient and cheaper. HEVs are no exception. They have greatly benefited from technological breakthroughs between the Piper HEV of 1905 and Toyota's Prius of the 1990s. A difficulty of early 20th century hybrids was the mechanical method of switching between electric and internal-combustion power. This had to be controlled mechanically, whereas today's hybrids are controlled by tiny microcomputers. In fact, even ICV's systems are computer controlled. The implementation of computers into HEVs allows for optimal control between the two power sources. An area which has seen less advancement and continues to be a limiting factor in HEVs is battery technology. Although batteries in today's hybrids are certainly an improvement over previous models, they have improved at a much slower pace than other vehicle technologies. The batteries continue to add substantial weight to the vehicles and are greatly limited in their capacity. As mentioned earlier, the great weight of the batteries means a non-trivial amount of energy must be taken from all the batteries to transport the weight of the additional battery. Policy and Market in the Birth of HEVsEdit Initially, HEVs served a niche market, appealing to the economically and environmentally conscious community. As the technology has improved and HEVs have become more popular, the market has expanded. Initially, HEVs were compact cars in order to be as fuel efficient as possible. However, as HEVs have looked to expand and gain more of the market share from ICVs, manufacturers have begun developing larger HEV models. One can now buy SUV hybrids, proving that the hybrid is no longer restricted its initial niche market. EVs on the other hand, are limited in their range and require charging stations. Although they pose some advantages of HEVs, their limitations cause them to primarily serve a niche market where electricity is cheap, readily available and distances are short. Drivers in this market must have a high value on reduced emissions and smaller need for driving long distances. Additionally, EVs require extra infrastructure such as charging stations to be readily available. In contrast, HEVs are able to capture some of the ICV market because they don't require additional infrastructure and have fewer limitations. The Energy Policy and Conservation Act of 1975 was legislation during the oil crisis of the 1970s which contained new requirements aimed at improving fuel economy. The act imposed new fuel efficiency standards on automakers, but allowed manufacturers 10 years to comply. Similar policies such as the Corporate Average Fuel Economy standards would appear to be helpful in encouraging alternative vehicles. By creating stricter fuel efficiency standards, new vehicle types may be able to capture a share of the market if gasoline cars cannot keep up. Car manufacturers may decide to invest additional capital in alternative vehicles. On the other hand, the policies require car manufacturers to improve the fuel economy of their ICVs or to stop producing them. Demand for ICVs is not affected by the policies and therefore, manufacturers go ahead with improving the fuel efficiency. This has the effect of reducing the net benefit which HEVs provide over ICVs. With more efficient ICVs on the market, the fuel savings provided by HEVs is reduced. It's possible that the cost of ICVs could rise as well if manufacturers passed on this additional cost. However, policy such as CAFE causes a reduction in price for high efficiency vehicles as manufacturers encourage their sales to offset the low efficiency vehicles. This further hurts the market for HEVs. President Clinton took alternative approach to increasing fuel economy standards by agreeing to a deal with major American automakers to develop an 80mpg Supercar. The program had some benefits but ultimately, didn't directly lead to the development of a domestic HEV due to the high cost of the Supercar materials. Growth and Maturity of HEVsEdit As can been seen in the quantitative analysis below, hybrid electric vehicle sales in the US experienced a very rapid lifecycle. If we consider 1999 the birth of HEV sales in the US, maturity occurred just 8 years later. The birthing years encompass roughly the first 4 years. Most government tax incentives occurred during the rapid grown between 2004 and 2007. During this time, various tax deductions were available at a national and state level. The monetary incentives, however, seem to have played little role in the growth of HEVs. One possible explanation including that dealers may have factored these incentives into their prices, leaving the consumer with little or no net benefit. More likely, was the influence of the economy, especially fuel prices. The rise in fuel prices around the country between 2004 and 2008 likely played a significant role in the growth of HEVs. The decline of fuel prices between 2008 and 2009 and the recession correspond to the decline in HEV sales. However, HEV sales continued to decline even as fuel prices steadily rose between 2010 and 2012. Perhaps this suggests that HEVs matured in 2007? Although fuel prices rose between 2009 and 2012, the American economy was still in recession, influencing sales of all vehicles. Consumers that absolutely need a vehicle will continue to buy, but will be less likely to pay the additional upfront cost necessary to purchase a HEV. The infrastructure for HEVs is certainly not going away. Unlike past transportation modes which have seen rapid decline after their maturity, HEVs will likely experience slower decline after maturity. This can be seen in the data since 2007. Modes such as railroads, which saw their tracks being removed and highways built instead, experienced rapid decline. As long as highways continue to be used and energy is of concern, HEVs will likely remain an alternative to the internal-combustion vehicle. The most likely scenario to contribute to a more rapid decline of HEVs, would be improvements to electric vehicles or discovery of a new energy source. Battery technology has seen little improvement in 100 years. If that were to change, EVs may experience growth, leading to the further decline of HEVs. In any case, the last 100 years are a pretty clear indication that the internal-combustion vehicle is not going away anytime soon. Data and AnalysisEdit U.S. Hybrid Electric Vehicle SalesEdit Data Source: National Transportation Statistics Data Source: National Transportation Statistics \|Year\|\|HEV Vehicles Sold\|\|Predicted Sales\| \|Adjusted R Square\|\|0.968150733\| \|'\|\|Coefficients\|\|Standard Error\|\|t Stat\|\|P-value\|\|Lower 95%\|\|Upper 95%\|\|Lower 95.0%\|\|Upper 95.0%\| \|X Variable 1\|\|1.199158717\|\|0.062700327\|\|19.12523876\|\|8.6304E-10\|\|1.061156228\|\|1.337161205\|\|1.061156228\|\|1.337161205\| The following model was used to predict HEV sales S(t) = K/[1+exp(-b(t-t0)] S(t) is the status measure, (HEV sales traveled) t is time (years), t0 is the inflection time (year in which 1/2 K is achieved), K is saturation status level, b is a coefficient. K and b are to be estimated The regression equation derived is: In completing the regression, a K value of 352863 was used. This value represents the HEV market maturing in 2007. Whether this is the case or not is difficult to determine. Since 2007, HEV sales in the U.S. have been on the decline. The recession certainly has been a factor in this. What remains in question is whether HEV will begin to climb again and reach a higher peak, or whether 2007 will remain the peak. Factors such as the economy and gas prices will certainly influence this. Since no one can say with certainty where future gas prices will go, it's difficult to say with certainty that the HEV market has peaked. If gas prices skyrocket, HEV sales will certainly increase, but their decline may also be sped up by a drop in fuel prices. The trend now puts HEV sales on a slow, but steady decline. This regression model assumes that 2007 was the peak of HEV sales in the U.S.. Alternative vehicles as a whole are still in the birthing phase. If HEVs continue to decline, other alternative vehicles are likely to step up and experience growth. Due to the relatively slow decline since 2007, however, HEVs may make a comeback. Only time will tell. The regression resulted in an R-squared value of 0.9708 and t-statistic of 19.125. An R-squared value close to 1.0 and t-statistic as high as possible are desirable. A b-value was estimated in order to achieve the most desirable fit, and therefore, the best R-squared and t-statistic values. Analysis of the curve shows that the model originally underestimates sales, then overestimates during the growth period before tapering off in 2007 for the mature phase. Unlike the real data, the model does not predict the decline after the peak in 2007. Also, the t-naught value was chosen based on the 2007 peak and the slope between years 2004 and 2005. T-naught represents half of the peak which occurs between '04 and '05. Although HEV sales can be volatile due to the various influencing factors such as fuel prices, tax credits, regulations and the economy all changing, the data between birth in 1999 and maturity in 2007 represents a fairly consistent S-curve of transportation modes. Since 2007, the decline has been somewhat different and HEVs may reach a higher peak in years to come which would greatly influence the model. However, due to the nature of growth between 1999 and 2007, the model was able to generate a fairly good fit. As data from future years comes out, the model will continue to be modified. - Wouk, V (1997). Hybrid Electric Vehicles, SCIENTIFIC AMERICAN-AMERICAN EDITION - German, J. M. (2004). Hybrid Electric Vehicles, Encyclopedia of Energy, 3, 197–213. - The Library of Congress (http://thomas.loc.gov/cgi-bin/query/z?c111:S.841.IS:) - National Transportation Statistics (http://www.bts.gov/publications/national_transportation_statistics/html/table_01_19.html) - Chan, C. C. (2002). The state of the art of electric and hybrid vehicles. Proceedings of the IEEE, 90(2), 247–275. doi:10.1109/5.989873 - David Diamond, The impact of government incentives for hybrid-electric vehicles: Evidence from US states, Energy Policy, Volume 37, Issue 3, March 2009, Pages 972-983, ISSN 0301-4215, 10.1016/j.enpol.2008.09.094. (http://www.sciencedirect.com/science/article/pii/S0301421508005466)
I. BEFORE 1556 From their first appearance in the history of the world the Germans represented the principle of unchecked individualism, as opposed to the Roman principle of an all-embracing authority. German history in the Middle Ages was strongly influenced by two opposing principles: universalism and individualism. After Arminius had fought for German freedom in the Teutoburg Forest the idea that the race was entitled to be independent gradually became a powerful factor in its historical development. This conception first took form when the Germanic states grew out of the Roman Empire. Even Theodoric the Great thought of uniting the discordant barbarian countries with the aid of the leges gentium into a great confederation of the Mediterranean. Although in these Mediterranean countries the Roman principle finally prevailed, being that of a more advanced civilization, still the individualistic forces which contributed to found these states were not wasted. By them the world-embracing empire of Rome was overthrown and the way prepared for the national principle. It was not until after the fall of the Western Empire that a great Frankish kingdom became possible and the Franks, no longer held in check by the Roman Empire, were able to draw together the tribes of the old Teutonic stock and to lay the foundation of a German empire. Before this the Germanic tribes had been continually at variance; no tie bound them together; even the common language failed to produce unity. On the other hand, the so-called Lautverschiebung, or shifting of the consonants, in German, separated the North and South Germans. Nor was German mythology a source of union, for the tribal centres of worship rather increased the already existing particularism. The Germans had not even a common name. Since the eighth century most probably the designations Franks and Frankish extended beyond the boundaries of the Frankish tribe. It was not, however, until the ninth century that the expression theodisk (later German Deutsch), signifying "popular," or "belonging to people" made its appearance and a great stretch of time divided this beginning from the use of the word as a name of the nation. The work of uniting Germany was not begun by a tribe living in the interior but by one on the outskirts of the country. The people called Franks suddenly appear in history in the third century. They represented no single tribe, but consisted of a combination of Low and High German tribes. Under the leadership of Clovis (Chlodwig) the Franks overthrew the remains of the Roman power in Gaul and built up the Frankish state on a Germano-Romanic foundation. The German tribes were conquered one after another and colonized in the Roman manner. Large extents of territory were marked out as belonging to the king, and on these military colonies were founded. The commanders of these military colonies gradually became administrative functionaries, and the colonies themselves grew into peaceful agricultural village communities. For a long time political expressions, such as Hundreds, recalled the original military character of the people. From that time the Frankish ruler became the German overlord, but the centrifugal tendency of the Germanic tribes reacted against this sovereignty as soon as the Merovingian Dynasty began slowly to decline, owing to internal feuds. In each of the tribes after this the duke rose to supremacy over his fellow tribesmen. From the seventh century the tribal duke became an almost independent sovereign. These ducal states originated in the supreme command of large bodies of troops, and then in the administration of large territories by dukes. At the same time the disintegration was aided by the bad administration of the counts, the officials in charge of the territorial districts (Gau), who were no longer supervised by the central authority. But what was most disastrous was that an unruly aristocracy sought to control all the economical interests and to exercise arbitrary powers over politics. These sovereign nobles had become powerful through the feudal system, a form of government which gave to medieval Germany its peculiar character. Caesar in his day found that it was customary among the Gauls for a freeman, the "client," voluntarily to enter into a relation of dependence on a "senior." This surrender (commendatio) took place in order to obtain the protection of the lord or to gain the usufruct of land. From this Gallic system of clientship there developed, in Frankish times, the conception of the "lord's man" (homagium or hominium), who by an oath swore fealty to his suzerain and became a vassus, or gasindus, or homo. The result of the growth of this idea was that finally there appeared, throughout the kingdom, along with royalty, powerful territorial lords with their vassi or vassalli, as their followers were called from the eighth century. The vassals received as fief (beneficium) a piece of land of which they enjoyed the use for life. The struggle of the Franks with the Arabs quickened the development of the feudal system, for the necessity of creating an army of horsemen then became evident. Moreover the poorer freemen, depressed in condition by the frequent wars, could not be required to do service as horsemen, a duty that could only be demanded from the vassals of the great landowners. In order to force these territorial lords to do military service fiefs were granted from the already existing public domain, and in their turn the great lords granted part of these fiefs to their retainers. Thus the Frankish king was gradually transformed from a lord of the land and people to a feudal lord over the beneficiaries directly and indirectly dependent upon him by feudal tenure. By the end of the ninth century the feudal system had bound together the greater part of the population. While in this way the secular aristocracy grew into a power, at the same time the Church was equally strengthened by feudalism. The Christian Church during this era — a fact of the greatest importance — was the guardian of the remains of classical culture. With this culture the Church was to endow the Germans. Moreover it was to bring them a great fund of new moral conceptions and principles, much increase in knowledge, and skill in art and handicrafts. The well-knit organization of the Church, the convincing logic of dogma, the grandeur of the doctrine of salvation, the sweet poetry of the liturgy, all these captured the understanding of the simple-minded but fine-natured primitive German. It was the Church, in fact, that first brought the exaggerated individualism of the race under control and developed in it gradually, by means of asceticism, those social virtues essential to the State. The country was converted to Christianity very slowly for the Church had here a difficult problem to solve, namely, to replace the natural conception of life by an entirely different one that appeared strange to the people. The acceptance of the Christian name and ideas was at first a purely mechanical one, but it became an inner conviction. No people has shown a more logical or deeper comprehension of the organization and saving aims of the Christian Church. None has exhibited a like devotion to the idea of the Church nor did any people contribute more in the Middle Ages to the greatness of the Church than the German. In the conversion of Germany much credit is due the Irish and Scotch, but the real founders of Christianity in Germany are the Anglo-Saxons, above all St. Boniface. Among the early missionaries were: St. Columbanus, the first to come to the Continent (about 583), who laboured in Swabia; Fridolin, the founder of Saeckingen; Pirminius, who established the monastery of Reichenau in 724; and Gallus (d. 645), the founder of St. Gall. The cause of Christianity was furthered in Bavaria by Rupert of Worms (beginning of the seventh century), Corbinian (d. 730), and Emmeram (d. 715). The great organizer of the Church of Bavaria was St. Boniface. The chief herald of the Faith among the Franks was the Scotchman, St. Kilian (end of the seventh century); the Frisians received Christianity through Willibrord (d. 739). The real Apostle of Germany was St. Boniface, whose chief work was in Central Germany and Bavaria. Acting in conjunction with Rome he organized the German Church, and finally in 755 met the death of a martyr at the hands of the Frisians. After the Church had thus obtained a good foothold it soon reached a position of much importance in the eyes of the youthful German peoples. By grants of land the princes gave it an economic power which was greatly increased when many freemen voluntarily became dependents of these new spiritual lords; thus, besides the secular territorial aristocracy, there developed a second power, that of the ecclesiastical princes. Antagonism between these two elements was perceptible at an early date. Pepin sought to remove the difficulty by strengthening the Frankish Church and placing between the secular and spiritual lords the new Carlovingian king, who, by the assumption of the title Dei gratia, obtained a somewhat religious character. The Augustinian conception of the Kingdom of God early influenced the Frankish State; political and religious theories unconsciously blended. The union of Church and State seemed the ideal which was to be realized. Each needed the other; the State needed the Church as the only source of real order and true education; the Church needed for its activities the protection of the secular authority. In return for the training in morals and learning that the Church gave, the State granted it large privileges, such as: the privilegium fori or freedom from the jurisdiction of the State; immunity, that is exemption from taxes and services to the State, from which gradually grew the right to receive the taxes of the tenants residing on the exempt lands and the right to administer justice to them; further, release from military service; and, finally, the granting of great fiefs that formed the basis of the later ecclesiastical sovereignties. The reverse of this picture soon became apparent; the ecclesiastics to whom had been given lands and offices in fief became dependent on secular lords. Thus the State at an early date had a share in the making of ecclesiastical laws, exercised the right of patronage, appointed to dioceses, and soon undertook, especially in the time of Charles Martel, the secularization of church lands. Consequently the question of the relation of Church and State soon claimed attention; it was the most important question in the history of the German Middle Ages. Under the first German emperor this problem seemed to find its solution. Real German history begins with Charlemagne (768-814). The war with the Saxons was the most important one he carried on, and the result of this struggle, of fundamental importance for German history, was that the Saxons were brought into connexion with the other Germanic tribes and did not fall under Scandinavian influence. The lasting union of the Franks, Saxons, Frisians, Thuringians, Hessians, Alamanni, and Bavarians, that Charlemagne effected, formed the basis of a national combination which gradually lost sight of the fact that it was the product of compulsion. From the time of Charlemagne the above-named German tribes lived under Frankish constitution retaining their own old laws, the leges barbarorum, which Charlemagne codified. Another point of importance for German development was that Charlemagne fixed the boundary between his domain and the Slavs, including the Wends, on the farther side of the Elbe and Saale Rivers. It is true that Charlemagne did not do all this according to a deliberate plan, but mainly in the endeavour to win these related Germanic peoples over to Christianity. Charlemagne's German policy, therefore, was not a mere brute conquest, but a union which was to be strengthened by the ties of morality and culture to be created by the Christian religion. The amalgamation of the ecclesiastical with the secular elements that had begun in the reign of Pepin reached its completion under Charlemagne. The fact that Pepin obtained papal approval of his kingdom strengthened the bond between the Church and the Frankish kingdom. The consciousness of being the champion of Christianity against the Arabs, moreover, gave to the King of the Franks the religious character of the predestined protectors of the Church; thus he attained a position of great importance in the Kingdom of God. Charlemagne was filled with these ideas; like St. Augustine he hated the supremacy of the heathen empire. The type of God's Kingdom to Charlemagne and his councillors was not the Roman Empire but the Jewish theocracy. This type was kept in view when Charlemagne undertook to give reality to the Kingdom of God. The Frankish king desired like Solomon to be a great ecclesiastical and secular potentate, a royal priest. He was conscious that his conception of his position as the head of the Kingdom of God, according to the German ideas, was opposed to the essence of Roman Caesarism, and for reason he objected to being crowned emperor by the Pope on Christmas Day, 800. On this day the Germanic idea of the Kingdom of God, of which Charlemagne was the representative, bowed to the Roman idea, which regards Rome as its centre, Rome the seat of the old empire and the most sacred place of the Christian world. Charlemagne when emperor still regarded himself as the real leader of the Church. Although in 774 he confirmed the gift of his father to the Roman res publica, nevertheless he saw to it that Rome remained connected with the Frankish State; in return it had a claim to Frankish protection. He even interfered in dogmatic questions. Charlemagne looked upon the revived Roman Empire from the ancient point of view inasmuch as he greatly desired recognition by the Eastern Empire. He regarded his possession of the empire as resulting solely from his own power, consequently he himself crowned his son Louis. Yet on the other hand he looked upon his empire only as a Christian one, whose most noble calling it was to train up the various races within its borders to the service of God and thus to unify them. The empire rapidly declined under his weak and nerveless son, Louis the Pious (814-40). The decay was hastened by the prevailing idea that this State was the personal property of the sovereign, a view that contained the germ of constant quarrels and necessitated the division of the empire when there were several sons. Louis sought to prevent the dangers of such division by the law of hereditary succession published in 817, by which the sovereign power and the imperial crown were to be passed to the oldest son. This law was probably enacted through the influence of the Church, which maintained positively this unity of the supreme power and the Crown, as being in harmony with the idea of the Kingdom of God, and as besides required by the hierarchical economy of the church organization. When Louis had a fourth son, by his second wife, Judith, he immediately set aside the law of partition of 817 for the benefit of the new heir. An odious struggle broke out between father and sons, and among the sons themselves. In 833 the emperor was captured by his sons at the battle of Luegenfeld (field of lies) near Colmar. Pope Gregory IV was at the time in the camp of the sons. The demeanour of the pope and the humiliating ecclesiastical penance that Louis was compelled to undergo at Soissons made apparent the change that had come about since Charlemagne in the theory of the relations of Church and State. Gregory's view that the Church was under the rule of the representative of Christ, and that it was a higher authority, not only spiritually but also substantially, and therefore politically, had before this found learned defenders in France. In opposition to the oldest son Lothair, Louis and Pepin, sons of Louis the Pious, restored the father to his throne (834), but new rebellions followed, when the sons once more grew dissatisfied. In 840 the emperor died near Ingelheim. The quarrels of the sons went on after the death of the father, and in 841 Lothair was completely defeated near Fontenay (Fontanetum) by Louis the German and Charles the Bald. The empire now fell apart, not from the force of national hatreds, but in consequence of the partition now made and known as the Treaty of Verdun (August, 843), which divided the territory between the sons of Louis the Pious: Lothair, Louis the German (843-76), and Charles the Bald, and which finally resulted in the complete overthrow of the Carlovingian monarchy. As the imperial power grew weaker, the Church gradually raised itself above the State. The scandalous behaviour of Lothair II, who, divorced himself from his lawful wife in order to marry his concubine, brought deep disgrace on his kingdom. The Church however, now an imposing and well-organized power, sat in judgment on the adulterous king. When Lothair II died, his uncles divided his possessions between them; by the Treaty of Ribemont (Mersen), Lorraine, which lay between the East Frankish Kingdom of Louis the German and the West Frankish Kingdom of Charles the Bald, was assigned to the East Frankish Kingdom. In this way a long-enduring boundary was definitely drawn between the growing powers of Germany and France. By a curious chance this boundary coincided almost exactly with the linguistic dividing line. Charles the Fat (876-87), the last son of Louis the German, united once more the entire empire. But according to old Germanic ideas the weak emperor forfeited his sovereignty by his cowardice when the dreaded Northmen appeared before Paris on one of their frequent incursions into France, and by his incapacity as a ruler. Consequently the Eastern Franks made his nephew Arnulf (887-99) king. This change was brought about by a revolt of the laity against the bishops in alliance with the emperor. The danger of Norman invasion Arnulf ended once and for all by his victory in 891 at Louvain on the Dyle. In the East also he was victorious after the death (894) of Swatopluk, the great King of Moravia. The conduct of some of the great nobles forced him to turn for aid to the bishops; supported by the Church, he was crowned emperor at Rome in 896. Theoretically his rule extended over the West Frankish Kingdom, but the sway of his son, Louis the Child (899-911), the last descendant of the male line of the German Carlovingians, was limited entirely to the East Frankish Kingdom. Both in the East and West Frankish Kingdoms, in this era of confusion, the nobility grew steadily stronger, and freemen in increasing numbers became vassals in order to escape the burdens that the State laid on them; the illusion of the imperial title could no longer give strength to the empire. Vassal princes like Guido and Lamberto of Spoleto, and Berengar of Friuli, were permitted to wear the diadem of the Caesars. As the idea of political unity declined, that of the unity of the Church increased in power. The Kingdom of God, which the royal priest, Charlemagne, by his overshadowing personality had, in his own opinion, made a fact, proved to be an impossibility. Church and State, which for a short time were united in Charlemagne, had, as early as the reign of Louis the Pious, become separated. The Kingdom of God was now identified with the Church. Pope Nicholas I asserted that the head of the one and indivisible Church could not be subordinate to any secular power, that only the pope could rule the Church, that it was obligatory on princes to obey the pope in spiritual things, and finally that the Carlovingians had received their right to rule from the pope. This grand idea of unity, this all-controlling sentiment of a common bond, could not be annihilated even in these troubled times when the papacy was humiliated by petty Italian rulers. The idea of her unity gave the Church the strength to raise herself rapidly to a position higher than that of the State. From the age of St. Boniface the Church in the East Frankish Kingdom had direct relations with Rome, while numerous new churches and monasteries gave her a firm hold in this region. At an early date the Church here controlled the entire religious life and, as the depositary of all culture, the entire intellectual life. She had also gained frequently decisive influence over German economic life, for she disseminated much of the skill and many of the crafts of antiquity. Moreover the Church itself had grown into an economic power in the East Frankish Kingdom. Piety led many to place themselves and their lands under the control of the Church. There was also in this period a change in social life that was followed by important social consequences. The old militia composed of every freeman capable of bearing arms went to pieces, because the freemen constantly decreased in number. In its stead there arose a higher order in the State, which alone was called on for military service. In this chaotic era the German people made no important advance in civilization. Nevertheless the union that had been formed between Roman and German elements and Christianity prepared the way for a development of the East Frankish Kingdom in civilization from which great results might be expected. At the close of the Carlovingian period the external position of the kingdom was a very precarious one. The piratic Northmen boldly advanced far into the empire; Danes and Slavs continually crossed its borders; but the most dangerous incursions were those of the Magyars, who in 907 brought terrible suffering upon Bavaria; in their marauding expeditions they also ravaged Saxony, Thuringia, and Swabia. It was then that salvation came from the empire itself. The weak authority of the last of the Carlovingians, Louis the Child, an infant in years, fell to pieces altogether, and the old ducal form of government revived in the several tribes. This was in accordance with the desires of the people. In these critical times the dukes sought to save the country; still they saw clearly that only a union of all the duchies could successfully ward off the danger from without; the royal power was to find its entire support in the laity. Once more, it is true, the attempt was made by King Conrad I (911-18) to make the Church the basis of the royal power, but the centralizing clerical policy of the king was successfully resisted by the subordinate powers. Henry I (919-36) was the free choice of the lay powers at Fritzlar. On the day he was elected the old theory of the State as the personal estate of the sovereign was finally done away with, and the Frankish realm was transformed into a German one. The manner of his election made plain to Henry the course to be pursued. It was necessary to yield to the wish of the several tribes to have their separate existence with a measure of self-government under the imperial power recognized. Thus the duchies were strengthened at the expense of the Crown. The fame of Henry I was assured by his victory over the Magyars near Merseburg (933). By regaining Lorraine, that had been lost during the reign of Conrad, he secured a bulwark on the side towards France that permitted the uninterrupted consolidation of his realm. The same result was attained on other frontiers by his successful campaigns against the Wends and Bohemians. Henry's kingdom was made up of a confederation of tribes, for the idea of a "King of the Germans" did not yet exist. It was only as the "Holy Roman Empire of the German Nation" that Germany could develop from a union of German tribes to a compact nation. As supporters of the supreme power, as vassals of the emperor, the Germans were united. This imperial policy was continued by Otto I, the Great (936-73). During his long reign Otto sought to found a strong central power in Germany, an effort at once opposed by the particularistic powers of Germany, who took advantage of disputes in the royal family. Otto proved the necessity of a strong government by his victory over the Magyars near Augsburg (955), one result of which was the reestablishment of the East Mark. After this he was called to Rome by John XII, who had been threatened by Berengarius II of Italy, and by making a treaty that secured to the imperial dignity a share in the election of the pope, he attained the imperial crown, 2 February, 962. It was necessary for Otto to obtain imperial power in order to carry out his politico-ecclesiastical policy. His intention was to make the Church an organic feature of the German constitution. This he could only do if the Church was absolutely under his control, and this could not be attained unless the papacy and Italy were included within the sphere of his power. The emperor's aim was to found his royal power among the Germans, who were strongly inclined to particularism, upon a close union of Church and State. The Germans had now revived the empire and had freed the papacy from its unfortunate entanglement with the nobility of the city of Rome. The papacy rapidly regained strength and quickly renewed the policy of Nicholas I. By safeguarding the unity of the Church of Western Europe the Germans protected both the peaceful development of civilization, which was dependent upon religion, and the progress of culture which the Church spread. Thus the Germans, in union with the Church, founded the civilization of Western Europe. For Germany itself the heroic age of the medieval emperors was a period of progress in learning. The renaissance of antiquity during the era of the Ottos was hardly more than superficial. Nevertheless it denoted a development in learning, throughout ecclesiastical in character, in marked contrast to the tendencies in the same age of the grammarian Wilgard at Ravenna, who sought to revive not only the literature of ancient times, but also the ideas of antiquity, even when they opposed Christian ideas. Germany now boldly assumed the leadership of Western Europe and thus prevented any other power from claiming the supremacy. Moreover the new empire sought to assert its universal character in France, as well as in Burgundy and Italy. Otto also fixed his eyes on Lower Italy, which was in the hands of the Greeks, but he preferred a peaceful policy with Byzantium. He therefore married his son Otto II, in 972, to the Greek Princess Theophano. Otto II (973-83) and his son Otto III (983-1002) firmly upheld the union with the Church inaugurated by Otto I. Otto II aimed at a great development of his power along the Mediterranean; these plans naturally turned his mind from a national German policy. His campaign against the Saracens, however, came to a disastrous end in Calabria in 982, and he did not long survive the calamity. His romantic son sought to bring about a complete revival of the ancient empire, the centre of which was to be Rome, as in ancient times. There, in union with the pope, he wished to establish the true Kingdom of God. The pope and the emperor were to be the wielders of a power one and indivisible. This idealistic policy, full of vague abstractions, led to severe German losses in the east, for the Poles and Hungarians once more gained their independence. In Italy Arduin of Ivrea founded a new kingdom; naturally enough the Apennine Peninsula revolted against the German imperial policy. Without possession of Italy, however, the empire was impossible, and the blessings of the Ottonian theory of government were now manifest. The Church became the champion of the unity and legitimacy of the empire. After the death of Otto III and the collapse of imperialism the Church raised Henry II (1002-24) to the throne. Henry, reviving the policy of Otto I which had been abandoned by Otto III, made Germany and the German Church the basis of his imperial system; he intended to rule the Church as Otto I had done. In 1014 he defeated Arduin and thus attained the Imperial crown. The sickly ruler, whose nervousness caused him to take up projects of which he quickly tired, did his best to repair the losses of the empire on its eastern frontier. He was not able, however, to defeat the Polish King Boleslaw II: all he could do was to strengthen the position of the Germans on the Elbe River by an alliance with the Lusici, a Slavonic tribe. Towards the end of his reign a bitter dispute broke out between the emperor and the bishops. At the Synod of Seligenstadt, in 1023, Archbishop Aribo of Mainz, who was an opponent of the Reform of Cluny, made an appeal to the pope without the permission of the bishop. This ecclesiastical policy of Aribo's would have led in the end to the founding of a national German Church independent of Rome. The greater part of the clergy supported Aribo, but the emperor held to the party of reform. Henry, however, did not live to see the quarrel settled. With Conrad II (1024-39) began the sway of the Franconian (Salian) emperors. The sovereigns of this line were vigorous, vehement, and autocratic rulers. Conrad had natural political ability and his reign is the most flourishing era of medieval imperialism. The international position of the empire was excellent. In Italy Conrad strengthened the German power, and his relations with King Canute of Denmark were friendly. Internal disputes kept the Kingdom of Poland from becoming dangerous; moreover, by regaining Lusatia the Germans recovered the old preponderance against the Poles. Important gains were also made in Burgundy, whereby the old Romanic states, France and Italy, were for a long time separated and the great passes of the Alps controlled by the Germans. The close connexion with the empire enabled the German population of north-western Burgundy to preserve its nationality. Conrad had also kept up the close union of the State with the Church and had maintained his authority over the latter. He claimed for himself the same right of ruling the Church that his predecessors had exercised, and like them appointed bishops and abbots; he also reserved to himself the entire control of the property of the Church. Conrad's ecclesiastical policy, however, lacked definiteness; he failed to understand the most important interests of the Church, nor did he grasp the necessity of reform. Neither did he do anything to raise the papacy, discredited by John XIX and Benedict IX, from its dependence on the civil rulers of Rome. The aim of his financial policy was economic emancipation from the Church; royal financial officials took their place alongside of the ministeriales, or financial agents, of the bishops and monasteries. Conrad sought to rest his kingdom in Germany on these royal officials and on the petty vassals. In this way the laity was to be the guarantee of the emperor's independence of the episcopate. As he pursued the same methods in Italy, he was able to maintain an independent position between the bishops and the petty Italian despots who were at strife with one another. Thus the ecclesiastical influence in Conrad's theory of government becomes less prominent. This statesmanlike sovereign was followed by his son, the youthful Henry III (1039-56). Unlike his father Henry had a good education; he had also been trained from an early age in State affairs. He was a born ruler and allowed himself to be influenced by no one; to force of character and courage he added a strong sense of duty. His foreign policy was at first successful. He established the suzerainty of the empire over Hungary, without, however, being always able to maintain it; Bohemia also remained a dependent state. The empire gained a dominant position in Western Europe, and a sense of national pride was awakened in the Germans that opened the way for a national spirit. But the aim of these national aspirations, the hegemony in Western Europe, was a mere phantom. Each time an emperor went to Italy to be crowned that country had to be reconquered. Even at this very time the imperial supremacy was in great danger from the threatened conflict between the imperial and the sacerdotal power, between Church and State. The Church, the only guide on earth to salvation, had attained dominion over mankind, whom it strove to wean from the earthly and to lead to the spiritual. The glaring contrast between the ideal and the reality awoke in thousands the desire to leave the world. A spirit of asceticism, which first appeared in France, took possession of many hearts. As early as the era of the first Saxon emperors the attempt was made to introduce the reform movement of Cluny into Germany, and in the reign of Henry III this reform had become powerful. Henry himself laid much more stress than his predecessors on the ecclesiastical side of his royal position. His religious views led him to side with the men of Cluny. The great mistake of his ecclesiastical policy was the belief that it was possible to promote this reform of the Church by laying stress on his suzerain authority. He repeatedly called and presided over synods and issued many decisions in Church affairs. His fundamental mistake, the thought that he could transform the Church in the manner desired by the party of reform and at the same time maintain his dominion over it, was also evident in his relations with the papacy. He sought to put an end to the disorder at Rome, caused by the unfortunate schism, by the energetic measure of deposing the three contending popes and raising Clement II to the Apostolic See. Clement crowned him emperor and made him Patrician of Rome. Thus Henry seemed to have regained the same control over the Church that Otto had exercised. But the papacy, purified by the elevated conceptions of the party of reform and freed by Henry from the influence of the degenerate Roman aristocracy, strove to be absolutely independent. The Church was now to be released from all human bonds. The chief aims of the papal policy were the celibacy of the clergy, the presentation of ecclesiastical offices by the Church alone, and the attainment by these means of as great a centralization as possible. Henry had acted with absolute honesty in raising the papacy, but he did not intend that it should outgrow his control. Sincerely pious, he was convinced of the possibility and necessity of complete accord between empire and papacy. His fanciful policy became an unpractical idealism. Consequently the monarchical power began rapidly to decline in strength. Hungary regained freedom, the southern part of Italy was held by the Normans, and the Duchy of Lorraine, already long a source of trouble, maintained its hostility to the king. By the close of the reign of Henry III discontent was universal in the empire, thus permitting a growth of the particularistic powers, especially of the dukes. When Henry III died Germany had reached a turning-point in its history. His wife Agnes assumed the regency for their four-year-old son, Henry IV (1056-1106), and at once showed her incompetence for the position by granting the great duchies to opponents of the crown. She also sought the support of the lesser nobility and thus excited the hatred of the great princes. A conspiracy of the more powerful nobles, led by Archbishop Anno (Hanno) of Cologne, obtained possession of the royal child by a stratagem at Kaiserswert and took control of the imperial power. Henry IV, however, preferred the guidance of Adalbert, Archbishop of Bremen, who was able for the moment to give the governmental policy a more national character. Thus in 1063 he restored German influence over Hungary, and the aim of his internal policy was to strengthen the central power. At the Diet of Tribur, 1066, however, he was overthrown by the particularists, but the king by now was able to assume control for himself. In the meantime the papacy had been rapidly advancing towards absolute independence. The Curia now extended the meaning of simony to the granting of an ecclesiastical office by a layman and thus demanded an entire change in the conditions of the empire and placed itself in opposition to the imperial power. The ordinances passed in 1059 for the regulation of the papal elections excluded all imperial rights in the same. Conditions in Italy grew continually more unfavourable for the empire. The chief supporters of the papal policy were the Normans, over whom the pope claimed feudal suzerainty. The German bishops also yielded more and more to the authority of Rome; the Ottonian theory of government was already undermined. The question was now raised: In the Kingdom of God on earth who is to rule, the emperor or the pope? In Rome this question had long been settled. The powerful opponent of Henry, Gregory VII, claimed that the princes should acknowledge the supremacy of the Kingdom of God, and that the laws of God should be everywhere obeyed and carried out. The struggle which now broke out was in principle a conflict concerning the respective rights of the empire and the papacy. But the conflict soon shifted from the spiritual to the secular domain; at last it became a conflict for the possession of Italy, and during the struggle the spiritual and the secular were often confounded. Henry was not a match for the genius of Gregory. He was courageous and intelligent and, though of a passionate nature, fought with dogged obstinacy for the rights of his monarchical power. But Gregory as the representative of the reform movement in the Church, demanding complete liberty for the Church, was too powerful for him. Aided by the inferior nobility, Henry sought to make himself absolute. The particularistic powers, however, insisted upon the maintenance of the constitutional limits of the monarchy. The revolt of the Saxons against the royal authority was led both by spiritual and secular princes, and it was not until after many humiliations that Henry was able to conquer them in the battle on the Unstrut (1075). Directly after this began his conflict with the papacy. The occasion was the appointment of an Archbishop of Milan by the emperor without regard to the election already held by the ecclesiastical party. Gregory VII at once sent a threatening letter to Henry. Angry at this, Henry had the deposition of the pope declared at the Synod of Worms, 24 January, 1076. Gregory now felt himself released from all restraint and excommunicated the emperor. On 16 October, 1076, the German princes decided that the pope should pronounce judgment on the king and that unless Henry were released from excommunication within a year and a day he should lose his crown. Henry now sought to break the alliance between the particularists and the pope by a clever stroke. The German princes he could not win back to his cause, but he might gain over the pope. By a penitential pilgrimage he forced the pope to grant him absolution. Henry appealed to the priest, and Gregory showed his greatness. He released the king from the ban, although by so doing he injured his own interests, which required that he should keep his agreement to act in union with the German princes. Thus the day of Canossa (2 and 3 February, 1077) was a victory for Henry. It did not, however, mean the coming of peace, for the German confederates of the pope did not recognize the reconciliation at Canossa, and elected Duke Rudolf of Swabia as king at Forchheim, 13 March, 1077. A civil war now broke out in Germany. After long hesitation Gregory finally took the side of Rudolf and once more excommunicated Henry. Soon after this however, Rudolf lost both throne and life in the battle of Hohenmoelsen not far from Merseburg. Henry now abandoned his policy of absolutism, recognizing its impracticability. He returned to the Ottonian theory of government, and the German episcopate, which was embittered by the severity of the ecclesiastical administration of Rome, now came over to the side of the king. Relying upon this strife within the Church, Henry caused Gregory to be deposed by a synod held at Brixen and Guibert of Ravenna to be elected pope as Clement III. Accompanied by this pope, he went to Rome and was crowned emperor there in 1084. Love for the rights of the Church drove the great Gregory into exile where he soon after died. After the death of his mighty opponent Henry was more powerful than the particularists who had elected a new rival king, Herman of Luxembourg. In 1090 Henry went again to Italy to defend his rights against the two powerful allies of the papacy, the Normans in the south and the Countess Matilda of Tuscany in the north. While he was in Italy his own son Conrad declared himself king in opposition to him. Overwhelmed by this blow, Henry remained inactive in Italy, and it was not until 1097 that he returned to Germany. No reconciliation had been effected between him and Pope Urban II. In Germany Henry sought to restore internal peace, and this popular policy intensified the particularism of the princes. In union with these the king's son, young Henry, rebelled against his father. The pope supported the revolt, and the emperor was unable to cope with so many opponents. In 1105 he abdicated. After this he once more asserted his rights, but death soon closed (1106) this troubled life filled with so many thrilling and tragic events. To Henry should be ascribed the credit of saving the monarchy from the threatened collapse. He has been called the most brilliant representative of the German laity in the early Middle Ages. During his reign began the development, so fruitful in results, of the German cities. Henry V (1106-25) also adopted the policy of the Ottos. In the numerous discussions of the right of investiture men of sober judgment insisted, as did the emperor, that the latter could not give up the right of the investiture of his vassal bishops with the regalia, that a distinction must be made between the spiritual and secular power of the bishops. The pope now made the strange proposal that the emperor should give up the investiture and the pope the regalia. This proposal to strip the Church of secular power would have led to a revolution in Germany. Not only would the bishops have been unwilling to give up their position as ruling princes, but many nobles, as well as vassals of the Church, would have rebelled. The storm of dissatisfaction which in 1111 broke out in Rome obliged the pope to annul the prohibition of investiture. It was soon seen to be impossible to carry out the permission so granted, and the conflict regarding investitures began again. The ecclesiastical party was again joined by the German princes antagonistic to the emperor, and the imperial forces soon suffered defeats on the Rhine and in Saxony. Consequently the papal party gained ground again in Germany, and the majority of the bishops fell away from Henry. Notwithstanding this he went, in 1116, to Italy to claim the imperial feudal estates of the Countess Matilda, who had died, and to confiscate her freehold property. This action naturally made more difficult the relations between pope and emperor, and in spite of the universal weariness the conflict began anew. The influence of the German secular princes had now to be reckoned with, for at this time certain families of the secular nobility commenced to claim hereditary power and appeared as hereditary dynasties with distinct family names and residences. It was in the age of the Franconian emperors that the dynastic families of the German principalities were founded. These princes acted as an independent power in settling the disagreement between emperor and pope. Callistus II was ready for peace; in 1122 an agreement was reached and the concordat was proclaimed at the Synod of Worms. In this the pope agreed that in Germany the election of bishops should take place according to canonical procedure in the presence of the king or his representative, and that the bishop-elect should then be invested by the king with the sceptre as a symbol of the regalia. In Germany this investiture was to precede the ecclesiastical consecration, in Italy and Burgundy it was to follow it. The emperor therefore retained all his influence in the appointment to vacant dioceses, and as secular princes the bishops were responsible to him. Not withstanding this the Concordat of Worms was a defeat for the imperial claims, for the papacy that had been hitherto a subordinate power had now become a power of at least equal rank. It was now entirely free from the control of the German Crown and held an independent position, deriving its dignity wholly from God. The emperor, on the contrary, received his dignity from the papacy. The talented, but intriguing and deceitful, king had greatly strengthened the anti-imperial tendency in all Western Europe. During the great investiture conflict the other kings had freed themselves completely from the suzerainty of the emperor. The pope was the guarantee of their independence, and he had become the representative of the whole of Christendom, while the imperial dignity had lost the attribute of universality. The way was now open to the pope to become the umpire over kings and nations. There was now a truce in the conflict between pope and emperor. Only a minor question had been settled, but the conflict had awakened the intellects of men, and on both sides a voluminous controversial literature appeared. The assertion was now made that the Christian conception of the papacy was not realized by existing conditions. There were also other manifestations of independent thought. The Crusades opened a new world of ideas; historical writing made rapid progress, and art ventured upon new forms in architecture. Commerce and travel increased through the active intercourse with Italy, a state of affairs beneficial to the growth of the cities. Germany grew in civilization although it did not reach the same level of culture which Italy and France had then attained. Henry V died childless, and his nephew, Duke Frederick of Swabia, the representative of the most powerful ruling family in the empire, hoped to be his successor. The clergy, led by Archbishop Adalbert of Mainz, however, feared that Frederick would continue the ecclesiastical policy of the Franconian emperors, and they succeeded in defeating him as a candidate. At Mainz the majority of the princes voted for Lothair of Supplinburg (1125-37); thus the electors disregarded any hereditary right to the throne. The Hohenstaufen brothers, Frederick and Conrad, did not yield the crown to Lothair without a struggle. The Hohenstaufen family was in possession of the crownlands belonging to the inheritance of the Franconian emperors, and a long struggle ensued over these territories. Lothair's suzerainty was for a while in a very critical position; the Hohenstaufen power increased to such an extent that in 1127 its abettors ventured to proclaim Conrad king. In the end, however, Lothair conquered. A courageous man, but one somewhat inclined to hasty action, he was able to maintain the claims of the empire against Bohemia, Poland, and Denmark. As a statesman, however, Conrad was less aggressive. He allowed the schism of 1130, when Innocent II and Anacletus Il contended for the Holy See, to pass by without turning the temporal weakness of the papacy to the benefit of the empire. After a delay Lothair finally recognized Innocent as pope and brought him to Rome. Here Lothir was crowned emperor in 1133; but the Curia did not agree to his demand for the restoration of the old right of investiture. However, he received the domains of the Countess Matilda as a fief from the pope and thus laid the foundation of the strong position of the house of Welf (Guelph) in Central Europe. In the meantime the two Hohenstaufen brothers were defeated, and Lothair was now able (1136), without fear of an uprising in Germany, to go to Rome for a second time. The object of this further campaign in Italy was to defeat King Roger of Sicily, the protector of the antipope, but the success of the imperial army was only temporary. Differences of opinion as to imperial and papal rights in lower Italy and Sicily endangered at times the good understanding between the two great powers. The emperor grew ill and died on the way home, and after his death the vigorous Roger united all lower Italy, with the exception of Benevento, into a kingdom that held an unrivalled position in Europe for its brilliant and strangely mixed culture. In the struggle between the papacy and the empire this Sicilian kingdom was before long to take an important part. The political policy of the Church was directed by its distrust of the aims of the Saxon dynasty in lower Italy; consequently by a bold stroke it brought about the election of Conrad III (1138-52), the Hohenstaufen Duke of Franconia, passing over Duke Henry the Proud, ruler of Saxony and Bavaria, and a descendant of Duke Welf (Guelph). The new king demanded from Henry the surrender of the Saxon duchy. Although after a long struggle the double Duchy of Bavaria-Saxony was dissolved, yet the Saxon duchy that was given by the treaty of 1142 to young Henry the Lion, son of Henry the Proud, continued a menace to the Hohenstaufen rule. Conrad was not able to put an end to the disorders in his realm, and the respect felt for the empire on the eastern frontier declined; neither was he able to assert his power in Italy. Yet all these troubles did not prevent his yielding to the fiery eloquence of St. Bernard of Clairvaux and joining the Second Crusade. This crusade, the success of which had been promised by St. Bernard and the pope, failed completely. When Conrad returned home, broken in spirit, he was confronted by the danger of a formidable rising of the Welfs. In 1152 he died. During his reign the intellectual results of the Crusades began to show themselves. Men's imaginations had been stimulated and led them away from traditional medieval sentiment. The world was seized by a romantic impulse and the conception of the Crusades, developed first among the Romanic nations, gave a Romanic colouring to the civilization and morals of the age. For a long time German knighthood, in particular, was characterized by Romanic ideas and manners. When the new king, Frederick I Barbarossa (1152-90), ascended the throne his German kingdom seemed on the verge of disintegration, and he sought to strengthen his power by a journey through all parts of his realms. Contrary to the policy pursued by his predecessor, he exerted himself to settle the strife between the Welf (Guelph) and Hohenstaufen parties. He wanted to strengthen the Welf power to such extent as to make it evident that this party's interests coincided with those of the Crown. Besides, Saxony, Henry the Lion received also the Duchy of Bavaria which had been taken from his father Henry the Proud. As secular protector of the Church, Frederick came to an agreement with the pope in regard to the latter's adversaries, the citizens of Rome and King Roger of Sicily. The imperial policy of Frederick was one of vast schemes which he could only carry out when he had a firm footing in Italy. But in Italy the city republics had arisen, and these had entirely cast off his suzerainty. Not realizing the power of resistance of the free communities, Frederick wanted to force the cities to recognize the supremacy of the empire. In case the pope should interfere in the dispute, Frederick was resolved not to permit his intervention in secular affairs. Frederick was filled with an ideal conception of his position as emperor. He believed that the Germans were destined in the history of the world to exercise universal rule. It was this idea, however, that exasperated the Italians and aroused their hatred. Frederick could only carry out this universal policy if Italy were his, and the question of its possession led to renewed struggles between Church and State. When Frederick went to Rome to be crowned emperor in 1155, most of the Italian cities paid their homage to him. On his return home Bavaria was restored in fief to Henry the Lion, the East Mark (later Austria) being first detached from the duchy. This led in the course of time to a development of the mark that proved of great importance for the future history of the empire. Frederick's policy was, in the main, not to interfere with the rights of the German princes as long as they obeyed the laws of the empire. The spiritual princes he attached closely to himself. The most powerful bishops of this period, Rainald of Cologne, Christian of Mainz, and Wichmann of Magdeburg, supported the imperial party. The majority of the bishops looked upon Frederick as a protection against the encroachments of Rome and of the secular rulers. The emperor sought, by strengthening his dynastic power, to make himself independent of both the ecclesiastical and temporal princes; to carry out this policy he depended on his inferior civil officials (Ministerialen), who were still serfs, and from whom was hereafter to come the important military nobility. Thus Frederick prepared the way for the flourishing period of chivalry, which was to give its signature to the time now at hand. A romantic, knightly culture arose; poetry flourished; yet the love lyrics of the age often expounded unhealthy views of morals and marriage. Nevertheless, the movement did not penetrate very deep, and the common people remained uncorrupted. Moreover, poetry was not wasted on artificial love songs; Wolfram von Eschenbach had the courage to attempt great problems; Walther von der Vogelweide was the herald of German imperialism. Art undertook to solve great questions, and began to draw its themes from life. Scientific learning, however, had not made equal progress; the time of apprenticeship was not yet passed, while in France and Italy Scholasticism had already shown itself creative. In 1158 Frederick made a second campaign in Italy that closed with the sack of Milan, the subjugation of Italy, and the flight of Pope Alexander III to France. When, however, the rest of Europe sided with the lawful pope, the defeat of the emperor was assured, for the papacy, when supported by all other countries, could not be coerced by Frederick. The emperor's third campaign in Italy (1162-64) ended in the failure of his lower Italian policy, and the outbreak of the plague destroyed the more promising prospects of the fourth expedition. In the fifth campaign (1174) occurred the memorable defeat near Legnano which opened the eyes of the emperor to the necessity of a treaty of peace. In 1177 he made peace with the pope at Venice, and recognized Alexander III, whom he had so obstinately opposed. The papacy had victoriously defended its equality with the empire. In Germany Frederick was obliged to take steps against the violent proceedings of Henry the Lion. The insubordinate Guelph was deposed and his fiefs divided, Bavaria being given to Otto of Wittelsbach. By the repeated allotment of these lands Frederick in reality helped to break up the empire, and when in 1184 he betrothed his son Henry to Constance, the heiress of the Norman kingdom, he prepared the way for new complications. Frederick took part in the Third Crusade in order that the highest power of Christendom might actively fight against the infidel. He was drowned in Asia Minor, 10 June, 1190; and was, at his death, a popular hero. He had greatly strengthened the feeling of the Germans that they were one great people, though a really national empire was at the time quite out of the question; the achievement of unity was prevented by the international character of intellectual, and partly of social, life. Frederick's son, Henry VI (1190-97), meant to establish a world power along the Mediterranean. His schemes were opposed by a Saxon-Guelphic combination headed by Richard the Lion-Hearted of England, and also by the German princes, who strove to hinder the increase of the royal power aimed at by Henry. The capture of Richard in 1192 dissolved the league of princes and led to peace with the House of Guelph. In 1194 Henry succeeded in conquering Sicily, and it now seemed as though his imperialistic schemes would gain the day; nevertheless they failed owing to the opposition of the German princes and the pope. When Henry died in 1197 the countries of Western Europe had already taken a stand against the all-embracing schemes of the German emperor. Germany was threatened by the horrors of a civil war. All the anti-national forces were active. Instead of the crown going to Frederick, son of Henry, who was at Naples, Archbishop Adolph of Cologne sought, by means of the electoral rights of the princes, to obtain it for the son of Henry the Lion, Otto IV (1198-1215). But the Hohenstaufen party anticipated this scheme by securing the election of the popular Duke Philip of Swabia (1198-1208). For the first time the question now arose, which of the princes have the right to vote? The number of electors had not, so far, been defined, yet as early as the election of Lothair and Conrad only the princes had voted, and the right of the Archbishops of Mainz to preside at the election was clearly admitted. Not much later the opinion prevailed that only six ruling princes were entitled to act as electors: the three Rhenish Archbishops, the Rhenish Palsgrave, the Duke of Saxony, and the Margrave of Brandenburg; to these was added in the course of time the King of Bohemia. The "Sachsenspiegel" (compilation of Saxon law, c. 1230) caused this view to prevail. At the time of the double election of Otto and Philip the policy pursued by the German princes was a purely selfish one. The energetic Innocent III, who was then pope, claimed the right of deciding the dispute and adjudged the crown to Otto. Thus the latter for a time gained the advantage over Philip. In this conflict the German princes changed sides whenever it seemed to their interest. Archbishop Adolph of Cologne, who had carried the election of Otto, finally fell away from him. Philip gained in authority, and after the successful battle near Wassenberg in 1206 he would have overcome Otto and his ally the papacy, had he not been murdered at Bamberg in 1208 by Otto of Wittelsbach. Otto IV was now universally acknowledged king. He had promised the pope to give up his claim to the domains of the Countess Matilda of Tuscany and to grant the free election of bishops. But when at Rome he refused to carry out these promises. However, the pope, though displeased, crowned him emperor in 1209. But when Otto after this wished to revive the imperial claims to Naples, the pope excommunicated him (1210). In the meantime the supreme position of the empire had become so important a matter that foreign princes meddled in German politics. The great conflict between Philip II Augustus of France and John of England was reflected in the contest between the Guelphs and the Hohenstaufens in Germany. Protected by the French and the pope, Frederick II (1212-50) came to Germany and was crowned at Mainz. The coalition of the English and the Guelphs was broken by the French at the battle of Bouvines (1214), yet Otto kept up the struggle for his rights until his death in 1218. The long conflict had greatly impaired the strength of the Hohenstaufen line; both the imperial and the Hohenstaufen domains had been squandered, and the German princes had become conscious of their power. Like his father, Frederick II made Italy the centre of his policy; but at the same time he intended to keep the control of Germany in his own hands, as the imperial power was connected with this country and he must draw the soldiers needed for his Italian projects from Germany. In order to maintain peace in Germany and to secure the aid of the German princes for his Italian policy Frederick made great concessions to the ecclesiastical princes in the "Confoederatio cum principibus ecclesiasticis" (1220) and to the secular princes in the "Statutum in favorem principum" (1232). These two laws became the basis of an aristocratic constitution for the German Empire. They both contained a large number of separate ordinances, which taken together might serve as a secure basis for the future sovereignty of the local princes. In these statutes the expression landesherr (lord of the land) occurs for the first time. In this era Germany was cut up into a large number of territorial sovereignties, consisting of the ecclesiastical territories, the duchies, which, however, were no longer tribal duchies, the margravates, among which the North Mark ruled by Albert the Bear was one of the most important, the palatinates, the countships, and the independent domains of those who had risen from landed proprietors to landed sovereigns. In addition to these were the districts ruled directly by the king through imperial wardens. What Frederick sought to get by favouring the princes he obtained. He had no real interest in Germany, which was at first ruled by the energetic Engelbert, Archbishop of Cologne; after 1220 he visited it only once. It was to him an appendage of Sicily. Frederick's Italian policy threatened the papacy, and he strove by concessions to avert a conflict with the pope. The highly talented, almost learned, emperor was far in advance of his age; an autocratic ruler, he created in lower Italy the first modern state; but by his care for Italy he overstrained the resources of the empire. This brought advantages to the neighbouring Kingdoms of France, and England, now long independent powers, as well as to Hungary, Poland, and the Scandinavian countries. The conflict between the sacerdotal power and the empire had aided the independent development of the states of Western Europe. The possession of Italy and the vow to go on a crusade regulated Frederick's relations with the Curia. In 1212 he was crowned emperor. Repeatedly urged to undertake the promised crusade, and finally excommunicated because he failed to do so, the emperor obtained successes in the East in 1227-29, contrary to the wishes of the pope. The silent acknowledgment of these successes by the Curia was a victory for Frederick. A rebellion headed by his son Henry was quickly crushed, but the confederates of Henry, the Lombards, assumed a threatening attitude. The emperor was able to bring order out of the confusion in Germany by the policy of yielding to the princes. About the same time began Frederick's struggle with the Lombards and Pope Gregory IX (1227-41). The German princes loyally upheld the emperor, consequently, upon the pope's death, the victory seemed to belong to the imperial party. Innocent IV (1243-54), however, renewed the struggle and from Lyons excommunicated the emperor, whose position now became a serious one. In Germany his son Conrad was obliged to contend with the pretenders, Heinrich Raspe of Thuringia and William of Holland. In Italy, though, conditions seemed favourable, but just at this juncture Frederick died (13 December, 1250), and with his death ended the struggle for the world sovereignty. The year 1250 marks an era of extraordinary change in Germany. The romance of chivalry passed away, and new forces directed the life of the nation. On account of the extraordinary economic changes the population rapidly increased; the majority of the people were peasants, and this class was rising, but compared with nobles and ecclesiastics the peasants had no weight politically. The important factor of the new era was the municipality, and its development was the beginning of a purely German policy. The glamour of the imperial idea had vanished, men now took their stand on facts and realities. Education found its way among laymen, and it developed with trade. New markets were opened for commerce. The new commercial settlements received "city charters" under the royal cross. The merchants in these settlements needed craftsmen, and these latter from the twelfth century formed themselves into guilds, thus making a new political unit. Councils elected by the cities strove to set aside the former lords of the cities, especially the bishops on the Rhine. In vain the Hohenstaufen rulers supported the bishops against the independence of the towns, but the government in the cities could no longer be put down. In order to protect their rights some of the cities formed alliances, such as the confederation of the Rhenish towns, that was formed as early as the period of the Great Interregnum in order to guard the public peace. These confederations promised to become dangerous opponents of the territorial lords, but such alliances did not become general and, divided among themselves without mutual support, the smaller confederations of towns succumbed to the united princely power. The growth of the towns brought about the ruin of the system of trade by barter or in kind; the rise of the capitalistic system of commerce at once affected German views of life. Up to this time almost wholly absorbed in the supernatural, henceforth the Germans took more interest in worldly things. Unconditional renunciation of the world came to an end, and men grew more matter-of-fact and practical. This change in the German way of thinking was aided by the opposition that sprang up in the towns between the citizens and the former lords of the territory, often the bishops and their clergy. Here and there the influence of the city on the views of the clergy manifested itself. The Dominicans and Franciscans, at least, taught their doctrines in language quite intelligible to the people. The rise of the cities was also of importance in the social life of the day, for the principle, "City air gives freedom" (Stadtluft macht frei), created an entirely new class of freemen. Under the last of the Hohenstaufens the beginnings of a national culture began to appear. Latin had fallen into disuse, and German become the prevailing written language. For the first time Germany felt that she was a nation. This soon brought many Germans into opposition to the Church. In the conflict between the papacy and the empire the former often seemed the opponent of nationalism, and bitterness was felt, not against the idea of the Church, but against its representative. The Germans still remained deeply religious, as was made evident by the German mystics. The most valuable result of this strengthening of the national feeling was the conquest of what is now the eastern part of the present German Empire. Henry I had sought to attain this end, but it was not until the thirteenth century that it was accomplished, largely by the energy of the Teutonic Order. The Marks of Brandenburg, Pomerania, Prussia, and Silesia were colonized by Germans in a manner that challenges admiration, and German influence advanced as far as the Gulf of Finland. The centres of German civilization in these districts were the Premonstratensian and Cistercian monasteries. This extraordinary success was won by Germans in an era when the imperial government seemed ready to go to pieces. It was the period of the Great Interregnum (1256-73). We find traces of internal chaos as early as the reign of Frederick's son, Conrad IV (1250-54), and the confusion grew worse in the reign of William of Holland, and after him during the nominal reigns of Richard of Cornwall and Alfonso of Castile. At the same time Bohemia rapidly advanced in power under Ottocar II and became a dangerous element for the domestic and foreign policy of Germany. It was Pope Gregory X who restored order in Germany. To carry out his projects in the Holy Land peace must be secured in Western Europe. He therefore commissioned the electoral princes, who now appear for the first time, to elect a new king. In 1273 the princes chose Rudolf of Hapsburg (1273-91), a man of no great family resources. Meantime the imperial power had fallen into decay; the imperial estates had been squandered; there were no imperial taxes; and the old method of obtaining soldiers for the service of the empire had broken down. Rudolf saw how necessary the possession of crown-lands was for the imperial authority, his aim being to create a dynastic force. Ottocar II, King of Bohemia, sought to induce the Curia to object to the election of Rudolf, but the Curia had quickly come to terms with Rudolf concerning conditions in Italy. After his election he demanded from Ottocar the return of the imperial fiefs, and the refusal of the latter led to a war (1276) in which, on the plain called the Marchfeld, Ottocar lost both life and crown. This victory gave Rudolf secure possession of the Austrian provinces. As the German king was not permitted to retain vacant fiefs, he evaded this law by granting Austria, Styria, Carniola, and Lusatia in fief to his sons Albert and Rudolf; in this way the power of the family was greatly increased. Not even Rudolf thought of strengthening the kingly power by constitutional means. He decided to protect the public peace but did not entirely succeed in this. His policy was always influenced by the circumstances of the moment: at one time he favoured the princes, at another the cities; consequently he was never more than half successful. His only great achievement was that he secured for his family a position in Eastern Europe that was destined to give it importance in the future. Rudolf's successor was Adolf of Nassau (1292-98), not his son Albert, as he had desired. The policy of the new sovereign was to weaken Austria, his natural opponent. Like Rudolf he recognized the necessity of obtaining possessions for his family, for which he tried to lay a foundation in Thuringia. Adolf's success against Frederick the Degenerate of Thuringia caused the electoral princes to incline to Albert. In a battle near Goellheim, fought between Albert and Adolf, Albert, aided by Adolf's numerous enemies, defeated the king, who was killed. Albert I of Austria, a very able but morose man (1298-1308), was filled with a boundless ambition for power. Without regard for the rights of others, he enforced the recognition of his own rights in his duchy. He desired to preserve the public peace in Germany and opposed the cruel persecution of the Jews customary at this time. He also wished to reorganize the imperial lands, which were to be regained in such a way as to provide a connecting link between the territories of the Hapsburgs in the east and those in the west. If his lands were thus united he would be a match for the strongest of the territorial princes; but the latter opposed this scheme. Albert also roused the anger of the ecclesiastical electors by combining with King Philip IV of France against Boniface VIII, who had not recognized Albert. Boniface now declared his intention of summoning Albert before his tribunal for the murder of Adolf. Supported by the cities, Albert contended successfully with the Rhenish electors, but after a while, in order to carry out his plans for the aggrandizement of his family, he came to terms with the pope, and this put an end to the opposition of these electors. The only opponent of his dynastic schemes now to be dreaded was Wenceslaus II of Bohemia; but the Przemysl line soon died out, and Albert at once claimed their lands and gave them to his son Rudolf as a fief. Before he could carry out his designs on Thuringia he was murdered by John of Swabia, called Johannes Parricida. According to legend, the tyranny of his rule in Switzerland led to a great struggle for freedom on the part of the confederated Swiss. The aim pursued by Albert was always the same: by making Austria powerful to force the other sovereign princes to acknowledge his suzerainty and thus to make the crown hereditary in his family. It is, therefore, not a matter of surprise that after his death the electors decided to select a less mighty prince. Archbishop Baldwin of Trier managed the matter so skillfully that his brother Henry of Luxembourg (Lützelburg) was chosen (1308-13). A man of gentle, amiable character, Henry was full of visionary enthusiasm, but withal he was a man of energy; consequently he was soon very popular. By birth he was in sympathy with the French. German interests concerned him less. Italy had a great fascination for him; he was ambitious to receive the imperial crown, to be the first after a long interregnum. Clement V had recognized him. The Ghibelline party in Italy greeted him with joy. At first he sought to hold a neutral position in the quarrels of the Italian parties, but this proved to be impossible. The Guelphs, led by King Robert of Naples, began to oppose him. When Henry thereupon wished to attack Naples, the old conflict with the Church again broke out, but death suddenly ended his imperial dreams. Henry's only successful act was the marriage of his son John with the heiress of Bohemia, Elizabeth, the sister of Wenceslaus III; for Germany his reign proved of no advantage. The election of his son John to succeed him was impossible, and the Luxembourg party chose Louis the Bavarian (1314-47) in opposition to Frederick the Fair (1314-30). There was a double election, each of the candidates being elected by one party, and a civil war broke out, confined, however, mainly to the partisans of the two Houses of Wittelsbach and Hapsburg. The struggle was ended by the capture of Frederick at the battle of Mühldorf (1322); after this Louis was universally recognized. While this conflict was going on the old strife between Church and State again broke out. At the time of the double election John XXII claimed the rights of an administrator of the country. He asserted that no king chosen by the electors could exercise authority before the pope had given his approval. This over-straining of the papal claims roused a dissatisfaction which continually grew and to which were already added complaints of the worldliness of the Church. The Minorites placed at the disposal of the king eloquent preachers to denounce the worldliness of the papacy, which had rejected as heretical the Franciscan teaching concerning the poverty of Christ and the Apostles. In 1324 Louis was excommunicated because he had not obeyed the papal command to lay down his authority. To this Louis made a sharp reply in the proclamation of Sachsenhausen, in which he denied the claims of the pope and at the same time defended the teaching concerning poverty upheld by the Franciscans. In the conflict with the pope, who supported the candidature of Charles IV of France for the imperial throne, the German cities and the German episcopate, the latter led by Baldwin of Trier, were virtually a unit on the side of Louis. Even the death of Frederick the Fair did not produce a reconciliation with the Curia. It was at this juncture that the writings of the Franciscans, Michael of Cesena and William of Occam began to exert their influence. The spirit of revolution in the Church is shown by the "Defensor Pacis" of Marsilius of Padua, a professor of Paris who went to the Court of Louis the Bavarian. In this the medieval papal ecclesiastical system is attacked. The intellectual ferment enabled Louis to undertake an expedition to Rome. He had been invited to enter Italy by the magnates of northern Italy, especially by the Visconti of Milan and the Scala of Verona. The city of Rome received him with joy, and he was the first German king to receive the imperial crown from the Roman commonwealth which had always regarded itself as the source of all sovereignty. But the fickle populace soon drove him away; the means at his command were too small to carry out the old imperial policy. Again Italy was lost. Notwithstanding the lack of success in Italy, Germany in the main held to Louis, who had been excommunicated again. It was now evident that papal interdicts had largely lost their terrors; the civil communities frequently paid no attention to them, and in some places ecclesiastics were forced, notwithstanding the prohibition, to say Mass. The growth of a worldly spirit in the Church began to undermine respect for it, and Germany was the first country to turn against the ideals of the Middle Ages. Sects opposed to sacerdotalism appeared; mysticism tended to make the soul independent in its progress towards God, without, however, rejecting the sacraments, as was done by some in this era. Yet, unintentionally, mysticism strengthened the tendency to deny the absolute necessity of the intercessory office of the Church. Moreover, mysticism gave a national cast to German religious life, for the intellectual leaders of mysticism, Ekkehard, Suso, and Tauler, wrote and preached in German. The chief strength of this religious movement was among the citizens of the towns. In the conflict between Church and State the cities sided with the emperor, but they were not yet strong enough without assistance to maintain the authority of a German emperor. Consequently, the position taken by the German princes was decisive for Louis. As he meant to carry on a dynastic policy, as his predecessors had done, he soon came into conflict with these princes, and, in order to be stronger than his opponents, he sought to establish friendly relations with the pope. But although Louis could resolve on vigorous action, yet he lacked the necessary persistence. He was not an able man, nor one of much intellectual power. He tried to make a good impression on every one; as a consequence, he failed with all parties. He opened negotiations with the Curia, but the intrigues of Philip VI of France kept the two parties from concluding peace. This led Louis to take the side of Edward III of England at the beginning of the war between the French and English for the succession to the French throne. This stand won more general sympathy for Louis in Germany. The electors were also influenced by public opinion when they declared at Rense in 1338 that a legitimate German emperor could be created only by their votes; a king so chosen needed no papal recognition, and the pope, by crowning the German king, only gave him the imperial title. Louis was also declared to be entirely without blame in the dispute with the Curia. When Edward III appeared before Louis at Coblenz and the latter appointed him imperial vicar for the territories beyond the Rhine, the emperor had reached the zenith of his power. Nevertheless the fickle Louis, because he hoped, through the mediation of the King of France, to be reconciled with the Curia and to secure the support of the latter for his schemes to aggrandize his family, allied himself with the French in 1341. Instead of peace a worse estrangement with the papal court was the result. With the consent of the emperor, Margaret Maultasch of Tyrol, who had married John of Luxembourg (Lützelburg), had divorced herself without awaiting the papal decision and married the emperor's son, Louis of Brandenburg. The Luxembourg party at once had recourse to Clement VI. Louis was excommunicated in 1346, and Charles IV of Moravia (1347-78) was, with the help of the pope, chosen German king by five of the electors under humiliating conditions. At first Louis had strong support from the German cities, but his unexpected death secured universal recognition for Charles. Henceforth for nearly a hundred years the Luxembourg-Bohemian dynasty held the throne. The king set up by the Wittelsbach party, Guenther of Schwarzburg, could make no headway against the adroit policy of Charles IV. In 1347 Germany was ravaged by the Black Death; the Jews were immediately accused of poisoning the wells, and a frightful persecution followed. In the midst of the confusion the country was traversed by bands of Flagellants, and these "penitents" were often full of hostility to the Church. While in Italy Petrarch and Cola di Rienzi revived the dream of the universal dominion of the Eternal City, Charles IV regarded Italian affairs with the eyes of a political realist. The Italians said that he went to Rome (1355) to secure the imperial crown like a merchant going to a fair. In Germany Charles sought to settle the election to the crown at the Diets of Nuremberg and Metz in 1356, and he issued the Golden Bull, which was the first attempt to put into writing the more important stipulations of the imperial constitution. Above all, the Bull was intended to regulate the election of the king, and defined what princes should have the electoral vote. The electoral college was to consist of the three Archbishops of Mainz, Trier, and Cologne; the Count Palatine of the Rhine, the Duke of Saxony (Sachsen-Wittenberg), and the Margrave of Brandenburg; to this number was added later the King of Bohemia. The electors were granted special privileges; besides the royal rights (regalia) and those of taxation and coinage, they received the privilegium de non evocando, that is, their subjects could not be summoned before the court of another jurisdiction, not even before an imperial one. The royal authority was to find in the electors who were scattered throughout the empire a support against the many petty princes. Other articles of the Golden Bull were to guard the rights of the local princes against their vassals and subjects, especially against the cities. Nothing is said of the share of the pope in the election of the king; the one chosen by the majority of the electors was to be the king. Only the coronation as emperor was left to the pope. The Golden Bull remained the most important part of the fundamental law of the Holy Roman Empire. Learning flourished under the rule of Charles, who was a scholar among his contemporaries. He was surrounded by highly educated men, one of whom was John of Neumarkt, the head of his chancelry. His interest being almost entirely in Bohemia, he showed his care for the advancement of learning chiefly in this country and founded there, 7 April, 1348, the University of Prague. Charles held steadfastly to Catholicism and Christian Scholasticism. But this did not prevent him from carrying on policies independent of the pope. In reorganizing the imperial chancelry he encouraged the use of German in the imperial documents and thus assured the victory of the national tongue over Latin. By this action he gave German learning an independent standing. Charles also furthered the interests of the empire in various other directions. He did not, indeed, overthrow the power of the princes, which had grown strong during the several hundred years of its existence, but he sought by the maintenance of internal peace to preserve his supreme power. To promote the foreign interests of Germany he desired to liberate the papacy from its connexion with France and to persuade the pope to return from Avignon to Rome. Gregory went back to Rome, but the Babylonian Captivity was to be followed by the Great Schism. In the meantime, Charles had largely increased the territorial possession of his family; the Marks of Brandenburg, Lusatia, and Silesia came into his hands. By marriage he hoped to obtain for his son, and thus for his dynasty, both Hungary and Poland. Thus for a time the House of Luxembourg threatened to crash out the Hapsburgs. In two directions only Charles's adroit agreements and diplomatic skill failed of success. The Swiss Confederation seceded more and more completely from the empire, and the cities by their leagues established for themselves an independent position in the empire. Towards the end of his life he secured the election of his son Wenceslaus as German king. Wenceslaus (1378-1400) reigned without the confirmation of the defenceless pope of that time. The German crown was no longer dependent on the papacy. Other questions far more important than this were now brought into the foreground by the Great Schism. There was a continually growing clamour, which could not be suppressed, for the reform of the Church in its head and members. The demand for reform had infused new life into the whole conception of the Church, and the leaders of this movement still held to Catholic dogmas. The most difficult task of the new king, and one he did not shirk, was to put an end to the schism. He sided with Rome and supported Urban VI while France, at the head of the Romanic countries, upheld Clement VII. Wenceslaus, however, took no energetic action in ecclesiastical affairs; the internal disorder in Germany did not permit it, for here the confederations of princes, knights, and the cities, struggled with one another. In 1381 the confederation of the Rhenish cities formed a coalition with the league of the Swabian cities and sought with considerable success to obtain the adherence of other Swabian towns and of those of North Germany. Thus strengthened, the cities wished to share in the government of the empire; this desire was opposed by the princes who in military force were superior to the cities. The attempts of the rulers of Austria to overthrow the Swiss confederates failed, but in Germany the army of the Swabian League suffered a crushing defeat in 1388 near Doeffingen. After this Wenceslaus changed his policy and sided with the princes. Confederations of the cities were forbidden. Owing to their lack of union the cities succumbed in this contest for political independence and the territorial princes were the conquerors. The quick-tempered, irascible king sought to strengthen his hold on his hereditary provinces by protecting himself against the other ruling princes, but in this he was not successful. A government by favouritism of the worst kind began which excited the anger of the nobility and the clergy. A dispute with the Archbishop of Prague led to the murder, by the king's command, of the archbishop's vicar-general, John of Pomuk, and this caused open rebellion. In 1394 the nobles with Jost, Margrave of Moravia, as their leader, took the king prisoner; he was soon set free at the instance of the German princes, but his release did not do away with the rule of the nobility in Bohemia. In this era of confusion no attempt was made to oppose the repeated incursions (1388) of Charles VI of France into Germany. Wenceslaus looked on inactively when the French king undertook to carry out a scheme for putting an end to the schism by securing the success of the Avignon pope by a bold stroke; but in 1392 Charles VI became insane, and his plans were brought to nought. The waning influence of the German Empire was everywhere perceptible and called forth universal indignation. The king's lack of capacity for government led the majority of the electors to form a league for the protection of the interests of the country. Soon after this the three episcopal electors chose Ruprecht, Count Palatine of the Rhine, as King of Germany (1400-10). As only a part of the electors joined in this choice Ruprecht was never more than a pretender, and although he was an ambitious and capable man he never succeeded in uniting the empire. Ruprecht hoped to gain popularity by restoring German influence in northern Italy, and by securing the imperial crown to prove himself the legal sovereign. As Ruprecht had no money, his expedition to Italy was inglorious, and its failure had a bad effect on his position in Germany. Even his final recognition by the pope, who had for a long time held to the Luxembourg dynasty, his faithful supporters, did little to aid Ruprecht's cause, and his throne began to totter. In 1405 Archbishop Johann of Mainz combined the princes against Ruprecht in the League of Marbach which, however, accomplished next to nothing. In the question of the schism Ruprecht supported Boniface IX. As King of the Germans Ruprecht was a failure. During the laxity of government that followed his death the German conquests in the eastern part of the empire were in danger of being lost. A new factor had appeared in history, the Kingdom of Poland. All this time the confusion in the affairs of the Church had continued to grow worse, and it was now proposed to put an end to the schism by means of a council. The cardinals of the two rival popes called a council at Pisa which deposed Popes Gregory XII and Benedict XIII and elected Alexander V, but Gregory and Benedict could still count on some supporters, and the world thus saw three popes. The greater part of Germany held to the new pope, Alexander V, but the party of the Count Palatine and of the Bishop of Trier held to Gregory. A period of utter confusion and great distress of conscience followed; all the relations of life suffered, the political by no means the least. In Germany the troubles led to a double election; Sigismund of Luxembourg, King of Hungary, the brother of Wenceslaus was elected (1410-37), as was also Jost, Margrave of Moravia. Jost withdrew, and Wenceslaus resigned the government to Sigismund, who in 1411 was generally recognized as emperor. The impotence of the last reign convinced the electors, who had chosen Margrave Jost for reasons of Church politics, that a king who had not large territorial power could accomplish nothing. Consequently they dropped their opposition to Sigismund. The latter's life before his election had been a very eventful one. He had married the daughter and heiress of Louis the Great of Hungary, and had been crowned king of that country in 1387. In the war between Hungary and the Turks he had been completely defeated by Sultan Bajazet; after this he had to contend with a dangerous rebellion in Hungary. Sigismund was talented, eloquent, witty, and exceedingly ambitious; he was inclined to visionary schemes, but he honestly desired to relieve the woeful troubles of his time. In his hereditary dominions, to which Hungary was now added, there was great disorder. Yet notwithstanding this he succeeded in bringing together the great councils of Constance and Basle. Ambition led him to attempt to settle the difficulties in which the Church was involved, but he was also impelled by political considerations. He hoped that a council would aid him in suppressing the religious troubles kindled in his hereditary kingdom of Bohemia by John Hus. It was not zeal for the Church, however, which inspired his interest in the council, as is evident from the general bent of his mind. For with all his interest in literature and learning, Sigismund scrupulously avoided involving himself in theological difficulties; moreover he took pleasure in denouncing the faults of the clergy. Nevertheless it was Sigismund's energy that held together the great council at Constance. It was certainly not his fault that many were not satisfied with the result of this and the following council. The forcible interference of the Council of Constance in the religious difficulties of Bohemia and the burning of John Hus were injurious to Sigismund's dynastic interests, and not in accordance with his political schemes. In Bohemia and Moravia the Hussites at once strove to prevent the king from taking possession of these countries; and it, especially in Bohemia, was a violent religious and national outbreak. The king was held directly responsible for the burning of the national hero and saint. Fanatical hordes led by Ziska repeatedly overthrew Sigismund's army in his crusade against the Hussites, and the storm spread over the adjacent provinces of the empire. Bavaria, Franconia, Saxony, and Silesia were terribly devastated. The imperial government broke down completely. The selfishness of the cities prevented the reform of the German military system, even after its necessity had been proved by further successes of the Hussites. In 1427 an imperial law for the levying of a war-tax was laid before the Diet at Frankfurt, but it was never carried out. In addition to the troubles in Bohemia, Sigismund's already insecure position was made more precarious by a fresh invasion of Hungary by the Turks. The only help he received was from Duke Albert V of Austria, his son-in-law and the prospective heir of the great inheritance of the Luxembourg possessions. The jealousy among the German states prevented common action against both foes. Sigismund's chief ambition, after the reunion and reformation of the Church, to unite all the nations of Western Europe in a war against the Turks, became more and more hopeless. The defeat of the Hussites appeared equally impossible, and negotiations were opened with them, peace being finally arranged at Basle. Sigismund induced the pope to weaken in his attitude towards the conciliar theory, and especially to the Council of Basle which was to deal with the Hussite difficulties. To gain his point he had gone to Rome, where he was crowned emperor in 1433. Even in Bohemia where the existing anarchy had been increased by a new religious quarrel, where the moderate Calixtines had obtained a decisive victory over the Taborites under Procopius the Great in 1434, the need of peace grew more and more intense. The year previous to this, 1433, a commission of the Council of Basle had made a number of concessions to the Hussites in the Compact of Basle or of Prague; among these was the granting of the Cup to the laity. On the basis of the Compact a peace was agreed to, which was followed by the recognition (1436) of Sigismund as king in Bohemia. When this was attained Sigismund seemed to lose all concern for the reform of the Church and empire in which before he had shown so keen and active an interest. He can hardly be blamed for the boundless selfishness and jealousy of the princes repeatedly wrecked the work of reform; and the whole responsibility for the scanty gains for the empire achieved during his reign should not be laid on his shoulders. Only two of his measures were to have permanent existence: the transfer of the Mark of Brandenburg to the Hohenzollerns, and the granting of electoral Saxony to the House of Wettin. The great councils passed without bringing the fervently desired reform. Great changes were witnessed in these assemblies. At Basle the pope was regarded simply as a representative of the Church, and the superiority of the council over the pope was openly declared. In 1433 Procopius had been allowed to enter Basle at the head of his heretical followers and to set forth his opinions before the assembled members of the council without molestation. At Basle opinions which were signs of a revolutionary movement in the Church repeatedly appeared. In character this council differed entirely from all earlier ones; the excitement was so great that tumults and brawls occurred. Contrary to the wishes of Rome the council remained at Basle; the fear was that if it were transferred to Italian soil the work of reform would be forgotten. Yet the honest intentions of the majority of the members cannot be doubted. In the end the pope was victorious, and the council was transferred to Ferrara. Some of the members remained at Basle and the spectacle of a conciliar schism was offered to the world. In this troubled era Albert II (1438-39), Duke of Austria, was chosen emperor. The electors recognized the fact that the centre of gravity of the empire now lay towards the east. Albert, member of the Hapsburg family, had not put himself forward as a candidate, and the electors probably selected him through fear that the important and necessary eastern territories might fall away from the empire. Before he could come to Western Germany Albert, a rough soldier, died during a campaign against the Turks. The election now went to the head of the Hapsburg family, the inert and indolent Frederick III, who, as King of the Romans, was Frederick IV (1440-93). During his reign the work of reform in the empire fell completely into abeyance. He too was obliged to face the difficulties in the Church. The electors had decided to remain neutral in the dispute between the pope and the Council of Basle, but this neutrality had been broken, inasmuch as the Diet of Mainz in 1439 accepted the reform decree of Basle, with exception of the assertion of the superiority of the council over the pope. Henceforth bishops and abbots were to be elected canonically, but the king had the right to secure the election of suitable persons by negotiation. Papal reservations and annates were abolished. The Council of Basle, however, held firm]y to its exaggerated conception of the powers of a council, and its members wished to establish the dogma of conciliar superiority by deposing Pope Eugene IV. In this dispute the electors remained neutral. The reform of the Church was more and more lost sight of by the Council of Basle in its struggle with the pope. Frederick, who was appealed to by both Rome and Basle, at first remained neutral; then he proposed the calling of a new council to reunite divided Christianity. Western Europe gradually turned again to the rightful pope, and the pope elected at Basle, Felix V, received but slight recognition. For a time the German attitude of neutrality was maintained, but after a while Frederick gave the impulse to the universal recognition of Pope Eugene. This was brought about by Aeneas Sylvius, later Pius II, an adroit diplomat who was able to influence the king and the leading princes. An agreement was made with Rome in the Concordat of Vienna (1448) in which the Curia made but trifling concessions, while the question of reform received scant consideration. From now on the Synod of Basle, transferred to Lausanne, had only a shadowy existence. The Curia, although sorely pressed, had once more conquered. The general anxiety to avoid a new schism in the Church had far more to do with the settlement of these ecclesiastical troubles than the interference of Frederick. Moreover Frederick showed his lack of skill in other ways. In 1444 the Swiss at the battle of St. Jakob on the Birs, not far from Basle, by their extraordinary courage defeated his French mercenaries, called Armagnacs, and thus frustrated his schemes for restoring the control of the Hapsburgs over the Swiss League. In spite of the constant disorders in the empire and the frequent wars, Frederick never wavered in his belief in the future greatness of the Hapsburg dynasty. It was this confidence that in 1452 led him to Rome, where he was crowned emperor by the pope, the last German king to be crowned at Rome. Directly afterwards came the capture of Constantinople by the Turks, which obliged the emperor to take up arms for the defence of the eastern frontier of his realm. Yet he could neither maintain peace within the empire nor its most important rights. Luxembourg and the possessions of the Wittelsbach family in the Netherlands fell into the hands of Burgundy, the Poles annexed West Prussia, and the remnant of the Teutonic Order in East Prussia was obliged to recognize the suzerainty of the Polish king. Thus the Germanizing influences that had been at work for centuries in what is now the eastern part of the German Empire were destroyed. The complete breakdown of the power of the empire called forth the demand that the emperor should be either deposed or have a coadjutor, but the lack of harmony among the electors prevented any change. The clamour for internal reform grew louder, but nothing was done except to enact laws for the maintenance of the public peace. During this confusion Frederick's position in his hereditary possessions became very precarious. The Czechs had held the preponderating power in Bohemia ever since the time of the Hussite troubles and now elected George of Podiebrad as king. The Hungarians also chose a ruler for themselves, electing the hero of the wars with the Turks, Matthias I Corvinus. Matthias soon overthrew the Bohemian king, and in 1487 apparently intended to form a great kingdom by uniting the eastern German provinces with the Bohemian, Moravian, and Hungarian territories. Important changes also occurred in the northern part of Germany. The Counts of Holstein, who had carried the German nationality into the northern territory of what is now Germany, had received Schleswig as early as 1386 in fief from Denmark; the two provinces, Holstein and Schleswig, soon grew together. After the death of the last Count of Holstein, King Christian of Denmark was in 1460 elected duke by Schleswig and Holstein. In this way he became a prince of the empire, a point of importance in the near future. This was afterwards to influence the position of the Baltic countries and the German interests there. For centuries the centre of the empire had been in the south, and Germany had no maritime interests. In this case also, as in the Germanization of the east, self-help was the means of attaining the desired end. The Hanseatic League, a union of German mercantile guilds, rapidly extended from Cologne to Reval on the Gulf of Finland. From the middle of the thirteenth century the chief towns of the League were Luebeck and Hamburg. German commerce flourished on all waters, for the members of the League carried the fame of their country across all the seas surrounding the Europe of that day. It is in fact a striking phenomenon that the national feeling was invigorated, while the strength of the empire was weakened by the division into so many petty sovereignties. The Hanseatic League maintained its ascendency in the Baltic as late as the fifteenth and sixteenth centuries. At the same time a great power threatened to spring up in the west. By peaceful agreement Charles the Bold, Duke of Burgundy (1467-77), attempted to secure Frederick's consent to his election as King of the Romans and to the elevation of his possessions to the rank of an independent kingdom. But all these ambitious plans came to an end upon the death of Charles at the battle of Nancy in 1477. The duke's possessions fell to Louis XI of France, while Maximilian, son of the Emperor Frederick and son-in-law of Charles the Bold, hastened to the Netherlands, which he secured for himself (1479) by the brilliant battle at Guinegate. He was not, however, able to make himself master of Burgundy and Artois. Moreover, Flanders was not willing to submit to the new regime and it was not until 1489 that it was completely subdued. Somewhat later, on the death of Matthias Corvinus in 1490, Maximilian's energetic action gained for his dynasty the future possession of Hungary and Bohemia, while at the same time he reunited the Tyrol with Austria. Consequently when the old emperor died, all looked to the knightly hero Maximilian for the restoration of the empire. Thus the outlook was by no means unfavourable at the time Maximilian I (1493-1519) ascended the throne. There were even indications of a healthier condition of internal affairs. The Swabian League, made up of the free cities and of the knights, sought, especially in 1486, to effect an adjustment of those interests of the different estates which most threatened the existence of the empire. Another favourable sign was the rapid development in civilization and culture of the several principalities. No less promising was the decision of the electors, now that the imperial authority had shown its entire impotence to check further decentralization. Turbulent agitation for reform in the cities was another important indication in the same direction. Maximilian tried by vigorous reforms to win the good will of the cities, the aid of which would be essential to him in the expected war with France, but the obstacles to be overcome before reforms could be introduced seemed steadily to increase. The most serious difficulty was and remained the antagonism between the interests of the empire and those of the princes. Maximilian, with his dynastic resources, which were made up of very heterogeneous elements, was not able to overcome these opposing forces. Thus the Diet of Worms in 1495 could not do much to promote reform on account of the opposing interests of the ruling princes, the free knights of the empire, and the imperial cities. At this diet the "Universal Pacification of the Empire" was proclaimed. All private wars were forbidden. An Imperial Chamber was established as a perpetual supreme court for the maintenance of the public peace, and the appointments to it were made by the emperor and the Estates of the empire. So many matters, however, were turned over to this court that it was condemned to inactivity from the outset. Nor was the Imperial Chamber able to promote the public peace, as it lacked all power of enforcing its decrees. Order in the empire could not be attained until the subordinate rulers became strong enough to exercise a vigorous police power in their territories. Maximilian had only agreed to the establishment of this court on condition that a general imperial tax, "the common penny," and military help against France and the Turks should be promised him. Concessions of a very different character had also been demanded by the ruling princes from the king. The powerful Archbishop of Mainz, Berthold of Henneberg, was the first to express the opinion that the administration of the empire should be placed in the hands of the electors, without, however, doing away with the monarchy. This proposition of the Diet of Worms was rejected by Maximilian. Five years later, however, when the promised financial and military aid was not forthcoming, he consented to the appointment of a permanent Imperial Council at Nuremberg. If this council had maintained an active existence for any length of time the king would have become a mere puppet. But after two years the royal power proved strong enough to break down the unnatural limitations imposed on it by the Estates. During these constitutional struggles within the empire the hostile feeling between France and Germany continued to grow. France, now greatly increased in power, wished to gain a firm foothold in the Italian peninsula, and put forward claims to Naples and Milan. Thus began the long struggle of the Hapsburg dynasty with France for the possession of Italy. Maximilian was unable to checkmate the Italian schemes of the French king. In the end Maximilian even changed his policy, for, in order to gain assistance against Venice, he allied himself with France. Yet even now he reaped no laurels in Italy. In the Swabian war also, which the Swiss confederated cantons carried on against the Swabian League, his intervention was unsuccessful. As a matter of fact Maximilian was obliged, in the Treaty of Basle (1501), to acknowledge the independence of the Swiss Confederation. In the course of these wars the Swiss had become enthusiastic soldiers, and after this Switzerland could furnish or refuse entire armies of mercenaries, in this way attaining European importance in the great struggle of the Hapsburgs with France. The work of reform in the empire, however, came to a complete standstill on account of these unsuccessful foreign undertakings. The only permanent result of all these efforts was the Imperial Chamber. The course of history could not be reversed: the territorial development of the separate states had been too logical to allow its reversal. A strengthening of the central administration, the preliminary condition for a reform of the empire, was no longer possible. In 1508 Maximilian had assumed the title of "Elected Roman Emperor," thus proclaiming that the imperial dignity was independent of papal confirmation. Restlessly active, he staked everything on the success of those foreign policies that would strengthen his royal power. It was for this reason that he finally returned to his earlier course of action and joined the Holy League against France. The brilliant success of Francis I over the Swiss at Marignano (1515) forced Maximilian to agree to a peace by which the French received Milan, and Venice obtained Verona. In the meantime various imperial diets again took up the question of reform, but the whole reform movement failed entirely, and the separate states gained a complete victory over the central administration. At Maximilian's death practically nothing had been accomplished for the constitution of the empire. Political and cultural life followed the course of development we have described, the foci being in the several states. Among these states the most prominent were the electoral principalities, which had been granted special honours and privileges by the Golden Bull. The three Rhenish electors were the most important political personages. Saxony was much increased in size by the addition of Meissen. It would have become the leading state of northern Germany had not its territories been divided in 1485 between the Albertine and Ernestine branches of the ruling family. The Electoral Mark of Brandenburg, acquire in 1417 by the Hohenzollerns, was still in the beginnings of its growth. The Hussite wars had almost entirely estranged Bohemia from the empire. The Palatinate of the Rhine, always a home of culture, was still one of its centres. The Duchies of Brunswick-Lueneburg and Bavaria were also prominent. In 1495 the able Counts of Wirtemberg (Würtemberg) received Countship of Swabia, which was raised to a duchy. Baden grew into a principality more slowly. More rapid was the development of Hesse, whose sovereigns under the title of Landgraves, were soon to come into prominence. The future of the empire depended on these minor states. The empire lacked imperial civil officials, imperial taxes, an imperial army, a general and systematized administration of imperial justice, while in these subordinate states there arose a defined government, a centralization of the civil officials, a systematic administration of law. This is also true of Maxmilian's hereditary possessions, the Austrian provinces. The leaders of progress in this respect also were the imperial cities, in which intellectual life began to flourish. In art they produced an Albrecht Durer and the two Holbeins. A darker side, however, was not lacking to this brilliant city life. Bloody outbreaks were often caused by a restless proletariat. Dissatisfaction was also rife among the free knights of the empire who had lost their former importance in consequence of the change in the military system, which had again made infantry the decisive element in battle. Moreover discontent was at work among the peasantry. The knights became robber-knights and highwaymen. Though banned by the empire, Franz von Sickingen, without authority, carried on war with the city of Worms. The economic changes had even more ruinous consequences for the peasantry. The age of discovery, of the growth of commerce, and of the great inventions, is also the age in which capital made its appearance as the great power of the world. There was a change in the value of money which brought severe suffering upon the peasantry which was despised and politically without rights, especially in the thickly populated southern part of Germany. Communistic writings appeared, which discussed the position of the peasants. The unrest increased in Franconia, Swabia, and on the upper Rhine, and revolts occurred. It was proposed to found a communistic kingdom of God and all hopes were placed on a strong emperor. Mixed with these desires was the expectation of a thorough reform of ecclesiastical affairs concerning which dissatisfaction was loudly expressed. The social-religious restlessness continually increased. The period of political confusion had not passed by without leaving its impress on the German character. The brilliant exterior of life covered but thinly the brutality within. There was widespread evidence of the lack of morality in domestic life, of barbarity in the administration of justice, and of inhumanity in war. Loyalty to the Church continually decreased, although a rich and voluminous religious literature had been disseminated by the art of printing. Great preachers, like Geiler von Kaysersberg at Strasburg, also appeared at this time. The Brethren of the Common Life took for their ideal the abnegation of the world. But all this failed to prevent the decline of the authoritative influence of the Church on the life of the people. The Great Schism had severely shaken the position of the papacy. The common people were estranged from the Church. A craving for religious self-help arose, and religious movements antagonistic to the Church won large followings. German learning loosened the bond that up to then had united it to theology. A new intellectual movement disputed the dominance of Scholasticism at the universities. Nicholas of Cusa, Æneas Sylvius, and Gregor von Heimburg prepared the way for Humanism. The medieval ideals having apparently lost their attraction, men turned to others, which advocated the world and its pleasures in opposition to self-abnegation, and instead of medieval universalism preached the freedom of the individual. In the second half of the fifteenth century Italian Humanism entered Germany in order to break down here as it had done in Italy the absolute domination of the ecclesiastical conception of the world. But Humanism in Germany assumed an entirely different form. In Germany the end sought was not beauty of form in learning, art, and life; here it manifested, rather, a practical, pedagogical, and, finally, religious tendency. Aided by the art of printing, humanism by its delight in experiment and induction, roused other sciences to fresh life, such as the science of history and especially the natural sciences. Individualism, moreover, strengthened the national sentiment and was a powerful force in overthrowing medieval universalism, and in putting an end to the ideal of the medieval world, the universality of the Kingdom of God. At the close of Maximilian's reign the signs of the times were undoubtedly very threatening, yet closer investigation shows that the Christian idea was still powerful. Notwithstanding the turning away of many from the Church, there were still men in Germany who were filled with this idea. These men did not conceal from themselves the necessity of genuine moral reform. The same power and intensity of Christian feeling that had built the great cathedrals in the later Middle Ages was still alive in the more serious minded part of the nation. Only the elect few carried these feelings over into the succeeding age, and with them the certain expectation of the reform of the Church from within. POTTHAST, Bibliotheca historica medii oevi (2nd ed., 1896); DAHLMANN AND WAITZ, Quellenkunde der deutschen Geschichte, 7th ed., edited by BRANDENBURG (1905—); WATTENBACH, Deutschlands Geschichtsquellen im Mittelalter bis zur Mitte des XIII. Jahrh.: Vol. I in 7th ed., edited by DUEMMLER AND TRAUBE (1904); Vol. II in 6th ed. (1894); LORENZ, Deutschlands Geschichtsquellen im Mittelalter seit der Mitte des XIII. Jahrh. (3rd ed., 1886-87); VILDHAUT, Handbuch der Quellenkunde zur deutschen Geschichte; Vol. I, to the fall of the Hohenstaufens (1898; 2nd ed., 1906); Vol. Il, from the fall of the Hohenstaufens to the rise of Humanism (1900); Mon. Germ. Hist., (Hanover and Berlin, 1826—); Script. rerum Germanicarum (in usum scholarum) ex Mon. Germ. Hist. recusi (Hanover, 1840) contains revised texts; Die Geschichtschreiber der deutsches Vorzeit in deutscher Bearbeitung (Berlin, 1849—), 2nd complete ed., edited by WATTENBACH (Leipzig, 1884—); JAFFE, Bibliotheca rerum Germanicarum (6 vols., Berlin, 1864-73), mainly letters of the Carlovingian age; BOEHMER, Fontes rerum Germanicarum, Geschictsquellen Deutschlands (Stuttgart, 1843-68); IDEM, Regesta imperii, a collection, from Boehmer's various works, of imperial records from the time of the Carlovingians up into the fourteenth century, revised and continued to 1410, some parts already published; Die Chroniken der deutschen Staedte vom XIV. bis ins XVI Jahrh. (Leipzig, 1862—), I-XXVIII; ALTMANN AND BERNHEIM, Ausgewaehlte Urkunden zur Erlaeuterung der Verfassungsgeschichte Deutschlands im Mittelalter (2nd ed., Berlin, 1895); VON BELOW AND KEUTGEN, Ausgeschichte Urkunden zur deutschen Verfassungsgeschichte, Vol. I: Urkunden zur staedtischen Verfassung (Berlin, 1899); ZEUMER, Quellensammlung zur Geschichte der deutschen Reichsverfassung im Mittelalter und Neuzeit (Leipzig, 1904); VON GIESEBRECHT, Geschichte der deutschen Kaiserzeit (5th ed., Leipzig, 1881-90), I-III; (2nd ed., 1877), IV; (Leipzig, 1895), VI; VON ZWIEDINECK-SUEDENHORTST, ed., Bibliothek deutscher Geschichte (Stuttgart, 1876—); NITZSCH, Geschichte des deutschen Volkes bis zum Augsburger Religionsfrieden, ed. MATTHAEI from the literary remains and lectures of NITZSCH (2nd ed., Leipzig, 1892), III; GEBHARD ed., Handbuch der deutschen Geschichte (2nd ed., Stuttgart, 1902), II; LAMPRECHT, Deutsche Geschichte (Berlin, 1891-96), VI; Vols. I-Il in 3rd ed. (1902); Vols. III-V, Pt. I in 2nd ed. (1895-96); LINDNER, Geschichte des deutschen Volkes (Stuttgart, 1894), II; LOSERTH, Geschichte des spaeteren Mittelalters 1197-1429 (Munich, 1903); in VON BELOW AND MEINECKE eds., Handbuch der mittelalterlichen und neueren Geschichte (Munich, 1903—), in publication; HENNE AM RHYN, Kulturgeschichte des deutschen Volkes (3rd ed., Berlin, 1898); STEINHAUSEN, Geschichte der deutschen Kultur (Leipzig, 1904); GRUPP, Kulturgeschichte des Mittelalters (Paderborn, 1908), II, Vol. III not yet published; WAITZ, Deutsche Verfassungsgeschichte (Kiel and Berlin, 1844—), VIII; SCHROEDER, Lehrbuch der deutschen Rechtsgeschichte (4th ed., Leipzig, 1902); VON INAMA-STERNEGG, Deutsche Wirtschaftsgeschichte (Leipzig, 1879-1901), IV; LAMPRECHT, Deutsches Wirtschaftsleben im Mittelalter (Leipzig, 1886), IV; SOMMERLAD, Die wirtschaftliche Taetigkeit der Kirche in Deutschland, Vol. I, In der naturalwirtschaftlichen Zeit bis auf Karl den Grossen (Leipzig, 1900); HAUCK, Kirchengeschichte Deutschlands (Protestant), Vols. I-IV (Leipzig, 1887-1903); Vols. I and III (4th ed., 1904); Vol. II (2nd ed., 1898). II. FROM 1556 TO 1618 After the death of Maximilian I the two great competitors for the imperial crown were Francis I of France and Charles, Maximilian's grandson. Notwithstanding the opposition of Leo X and the alienation of French sympathies, the choice of the electors fell on Charles (28 June, 1519), who was crowned as Charles V at Aachen, on 23 October, 1520, and by Clement VII at Bologna, on 23 February, 1530. In January, 1521, he opened the Diet of Worms and his administration of the Holy Roman Empire lasted until his abdication. In 1556 Charles V resigned the imperial throne. This act implied a serious break in the continuity of the political and religious history of the German people. Charles's reign had lasted for more than a generation, but only an insignificant part of it had been devoted to Germany. His attention had been mainly given to the Netherlands, to Spain, and to the wars with France and the Turks. Consequently from 1520 the defection from the Church had made more and more rapid headway, in spite of the emperor's prohibitory edicts issued at the Diet of Worms (1521) and at the Diet of Augsburg (1530), and shortly after 1540 this apostasy threatened to affect the whole of Germany. At the same time the separatist tendencies of the ruling princes increased in strength. It was not until towards the end of his reign that Charles took measures to check the princes of the empire. By the war in Gelderland (1543), the deposition of the Archbishop of Cologne (1547), and the Smalkaldic War (1546-47), he succeeded in bringing the triumphant career of Protestantism to a standstill, thus saving the greater part of western and southern Germany to Catholicism. Driven from these territories Protestantism overran, during the following decades, the Bavarian and Bohemian-Austrian provinces in the south-east. But even there it was not able to maintain itself. On the other hand, Charles did not succeed in forcing the princes to return to their proper position in the empire and to subordination to the emperor. The most important of the princes were the rulers of the northern states; these were in no wise affected by Charles's military successes, as he did not push his operations as far as northern Germany. The Dukes of Saxon and Bavaria also, who were friendly to Charles and took part in his campaigns, suffered no curtailment of their power. The partial failure of Charles determined the future development of the empire, the basis of which was laid down in the recess of the Imperial Diet of 1555. By it, in the so-called Religious Peace of Augsburg, Germany was divided between the Catholics and the adherents of the Augsburg Confession, and the territorial princes were practically made the political arbiters of the empire. The principle, cujus regio, ejus religio, was recognized. The Imperial Chamber (Reichskammergericht) was subjected to the influence of the Estates of the empire. In the newly instituted system of administration by "circles" also, the control of the emperor was no longer permitted. Further, the permanent council of administration (Reichsdeputationstag), an organ of centralization developed in 1558 from the system of "circles," was summoned and presided over by the Elector of Mainz as chancellor of the empire and not by the emperor. Economical and judicial legislation devolved on the separate states. At the Diet of Speyer (1570) the princes annulled the supreme authority of the emperor in military matters. These events implied not only a change in the government of the empire, so that it was controlled by the electors and not by the emperor, but the empire itself became almost a shadow incapable of great administrative actions. Its constitutional powers waned; diets were seldom convoked (only ten up to 1618), the decisions of the Imperial Chamber were not carried out, the administration by "circles" did not take root. The empire failed just as signally, as a European power, in maintaining its interests during the great wars of the reign of Philip II in Western Europe, an exception being the Pacification of Cologne (1579), which sought to restore order in the Netherlands, but to which little heed was paid. Not even the boundaries of the empire were maintained. From about 1580 the Spaniards and Dutch established themselves in the Rhine provinces and Emden, and Spain sought in addition to obtain Alsace. France entangled as many of the south-western sections of the empire as possible in its intrigues, especially the city of Strasburg. James I of England married his daughter to the Elector Palatine. On the Baltic coast the Swedes, Russians, and Poles despoiled the Germans of the more distant territories colonized by them, while the Danes settled in the south-west corner of the Baltic. At the same time the Dutch overthrew the economic supremacy of the Hanseatic League in the Baltic Sea and German Ocean. On the Danube the Hapsburgs were compelled to buy an armistice with the Turks by the payment of tribute. The blame for the helpless condition of the empire rested principally on the reigning princes. They took no interest in its affairs, not because they were lacking in German sentiment, but because the horizon of their ideas was still too restricted, and because either they gave little thought to politics or their attention was absorbed by the details of administration within their own dominions. The governmental organization of their principalities was still very imperfect. The conservation and gradual development of their territories engrossed the energies of the princes, especially of the most powerful among them, the Elector Augustus of Saxony (1553-86) and Duke Albert V of Bavaria (1550-89). They, therefore, avoided war above all things. The only alliance among them that had any stability at that time, the "Landsberg League" of southern Germany (1556-90), had, for its sole object, the maintenance of peace. The emperors of this period, Ferdinand I (1556-64), Maximilian II (1564-76), Rudolf II (1576-1612), and Matthias (1612-19), not only failed to arouse the princes to a more intelligent treatment of the affairs of the empire, but by their own policy they encouraged the princes to pursue purely personal ends. For, unlike Charles V who had ruled a world-empire, his successors governed territories, the political importance of which barely exceeded that of the majority of German states, and which only surpassed these latter in extent. Accordingly, as none of them were men of pre-eminent ability, their political aims were narrow, their need of peace urgent, and their credit inadequate, while the credit of the western powers had largely developed since the time of Charles V. Moreover they had harder conditions to face in their own dominions than the other princes. Most of their territories were in the eastern part of Europe where, from the end of the fifteenth century, the landed petty nobles, who formed a large class, opposed with ever-increasing success the progress of the commonalty and the introduction of orderly administration under the control of the sovereign. With this inferior nobility in the dominions of the German Hapsburgs, the Protestants, who attracted to themselves all the opposing elements, made common cause. Thus the emperors were by degrees so harassed in their family possessions that, towards the end of Rudolf's reign, the power fell into the hands of the nobility, and Matthias, though advised by his able minister Cardinal Klesl, was hardly able to maintain his authority. In the period from 1556 to 1618 the only general movement in the inner politics of the empire, and one that caused important changes in the relative influence of the German rulers, namely, the endeavour to place the ecclesiastical principalities in the hands of the younger sons of reigning princes, was entirely due to the desire of these princes to increase their territories. The ecclesiastical domains in the eastern provinces of Germany were few and insignificant, whereas in the north-west as well as throughout the west and south they were numerous, some being large in extent and of great importance. With exception of the territorially powerful Diocese of Münster and the small diocese of Hildesheim, those in the east and north came under the control of Protestant princes as "administrators" to the aggrandizement of the Houses of Wettin, Hohenzollern, and Guelph. In this way these territories were made ripe for secularization. Bavarian princes became Bishops of Cologne and Hildesheim, which were, thereby, saved from the fate that befell the others. These measures quickened the process of consolidation by which the territories of a few dynastic houses in northern Germany steadily grew in extent, the result being of considerable importance in the future political development of Germany. On the other hand, the attempts of the princes to annex the spiritual principalities of southern Germany failed. Protestantism entered these territories at a later date and with less force than it had in those of northern Germany. Consequently the ecclesiastical lands in the south had more power of resistance than those in the north, while the princes were weaker, because their number was large and their possessions all small, excepting what belonged to the Austrian Hapsburgs on the Upper Rhine and perhaps also the territory belonging to Würtemberg. In these circumstances the Ecclesiastical Reservation (Reservatum Ecclesiasticum), adopted at the instance of the Catholics in the Recess of the Imperial Diet of 1555, proved an effective precautionary measure in southern Germany. It provided that any bishop or abbot who turned Protestant could not take advantage of the rule cujus regio, ejus religio, but must resign. The chief opponents of the ecclesiastical principalities in southern Germany were the representatives of the House of Wittelsbach, rulers of the Palatinates and of Bavaria. Prominent because of their noble descent, the Elector Palatine being in fact the ranking temporal elector, they were all poor in land. The branch that ruled the Palatinate of Neuburg acquired a heritage on the Lower Rhine by marrying into the ducal House of Cleves-Juelich, which was becoming extinct. The other branches sought to extend their domains at the expense of their neighbours. What decided the predominance of the Catholics in the south was the result of two movements which settled the question whether the Protestants, in spite of the successes in 1543-47 of Charles V, were finally to seize Cologne and the whole country of the Lower Rhine and from these centres crush the Catholics of southern Germany. In the first of these contests, the "Cologne War" (1582-84), which arose from the apostasy of Archbishop Gebhard Truchsess, the last Archbishop of Cologne who was not a Bavarian, the Catholics were successful. In the second, the contest over the Cleves-Juelich succession on the extinction of the native ducal family, the inheritance, it is true, passed to Protestant rulers, the Palatines of Neuburg and the Hohenzollerns; but of these the Neuburg line became Catholic in 1612, so that the danger was dispelled once more. As a consequence the Catholic Church gained sufficient time, after the Council of Trent, to accomplish gradually the reconversion of the greater part of southern and western Germany, especially since Bavaria in the south, and Münster as well as Cologne in the west, remained faithful to it. The political consequence of the Catholic victory in the south-west was that this part of the empire, in contrast to the northern sections, continued to be split up into many principalities. This caused a constant state of unrest among the reigning princes and the nobles of the empire in south-western Germany. The electors palatine, especially, were dissatisfied with their fortunes. They pursued within the empire a policy of hostility to the Catholics and to the imperial house that became more and more reckless with each succeeding decade. Moreover they were in league with France and other foreign countries. In accordance with this policy they turned from the Lutheran to the Calvinistic faith and put themselves at the head of all the discontented elements in the empire. Up to 1591 their aim was to bring about a union of all the German Protestant princes, including the Lutheran, for the purpose of enforcing the claims of Protestantism in south-western Germany. Even Saxony eventually took part in these negotiations. At the same time Calvinism also penetrated surreptitiously into central Germany (the so-called Crypto-Calvinisin). But in 1592 a complete revulsion took place in Saxony. After that, the only remaining adherents of the palatine princes in central Germany were a few petty reigning princes and counts of that section. One of them, Christian of Anhalt, appears actually to have guided the policies of the Electorate of the Palatinate from 1592-1620. After sixteen years more of persistent urging, a few princes of south-western Germany joined the palatine princes in 1608 to form the "Protestant Union." Their value as allies, however, was in inverse ratio to their historical fame. The hopes of foreign succour that the palatine princes had entertained also proved vain; in 1609 the Netherlands concluded an armistice with Spain; in 1610 Henry IV of France was assassinated. In their disappointment the Calvinists brought the entire machinery of the empire to a standstill by breaking up the Imperial Diet in 1613. In their freebooting temper the party was ready to snatch at whatsoever spoil presented itself. The Calvinistic party was, nevertheless, too weak to inflict any serious harm. The Lutherans, under the leadership of Saxony, drew back more and more. The Catholics, led by Bavaria, maintained a purely defensive attitude. The revival of religious life among them made but slow progress, despite the strenuous exertions of the Bavarian rulers, of the Hapsburgs, and of individual bishops, of whom the Bishop of Würzburg, Julius Echter of Mespelbrunn, was the most prominent, and of the Jesuits. The situation was in no wise altered by the fact that in 1598 Maximilian I succeeded to the sovereignty of Bavaria. He surpassed all the German princes of that period in ability and energy, and in the course of a few years he made Bavaria the most powerful of the German states. But he was prudent, peaceable, and above all intent on the internal improvement of his principality. Only on one occasion did he offer a decided opposition to the Calvinistic party; in 1607 he seized Donauwörth, which had persecuted its Catholic inhabitants. The Catholic League, which he organized in 1609 to offset the Protestant Union, was of a purely defensive nature. Thus, in spite of unrest, the peace of the empire was apparently not in immediate danger at the beginning of the seventeenth century. Its impotence, however, was most clearly manifested in its economic and intellectual life. Under Charles V the German mercantile instinct had made the mistake of giving itself largely to the profitable business of money transactions with governments. This was no longer lucrative, but the self-control necessary for the more arduous gains of industrial enterprises now hardly existed. Moreover, political conditions made commerce timid. The free cities of the empire, the centres of mercantile life, had lost the support of the imperial power. The princes were either hostile to them or still biased by their economic views of land and agriculture. Furthermore, the extent of the several principalities was too small to form the basis of commercial undertakings while customs duties closed their frontiers. Foreign competition was already proving a superior force; commerce and manufacture, with the prosperity of which the growth of great states seems universally bound up, were at the point of collapse in Germany. Intellectual life was in an equally discouraging state. Almost without knowing it the nation had been divided by the Reformation into two religious camps, and a large part of it had accepted a wholly different faith. The thoughts of the people were being concentrated more and more on this one fact. They were encouraged in this by the princes who had derived from the schism great advantages in position and possessions, and also by the clergy on either side. The still insurmountable prejudice of the Lutherans of northern Germany against Catholics can be traced to the sermons of their preachers in the sixteenth century. From an entirely different point of view the Jesuits exhorted the Catholics to have as little as possible to do with Protestants. Sectarian strife controlled all minds. Thereby the common consciousness of nationality was just as obscured in the people as it was dulled in the princes by political selfishness. III. FROM 1618 TO 1713 (1) 1618 to 1648 The political life of the German nation was quickened into fresh activity by the strong character of several princes who in their respective states took up almost simultaneously the fight against the preponderating power of the petty landed nobility. Those among these princes who made their mark on German history were Ferdinand II of Austria, Gustavus Adolphus of Sweden, and, a generation later, Frederick William of Brandenburg, called the Great Elector. In 1617 Frederick II was chosen by his family, on account of the vigour he had shown as ruler of Styria, to be the associate and successor of Matthias. No sooner had the nobles felt Ferdinand's strong hand than they revolted in Bohemia, where they were most rebellious (1618). As Ferdinand did not have at his disposal the means to suppress it vigorously, the rebellion spread to the Danubian provinces, where it was supported by the rulers of Transylvania. When Matthias died (1619) the insurgents, through the mediation of Christian of Anhalt, went to the extreme of raising the head of the Union, Frederick V of Palatinate, to the throne of Bohemia (August, 1619), in order to obtain the help of the German Protestants. At the same time, however, Ferdinand was chosen emperor by the electors, whereupon Maximilian of Bavaria and the Elector of Saxony promised to fight on his side. The issue at stake was the existence of the Hapsburg dynasty. The struggle was carried on chiefly by troops of the two Wittelsbach lines and the Elector Palatine was defeated by the Duke of Bavaria on 8 November, 1620, at the battle of the White Mountain (Weissenberg) before the gates of Prague. Ferdinand II followed up his victory vigorously and from 1621 to 1628 established a new basis of political administration in his dominions. The multiplicity of heterogeneous Hapsburg territories, bound together almost solely by dynastic unity, was to be replaced by a compact Austrian state. This was to be founded on a system of government based on one official language, the German, on uniformity of administrative principles, on the profession of the Catholic faith by the entire population, and on the steady support of the reigning house by a body of great landed proprietors whose states were made up of the confiscated lands of the landed petty nobility. These great landowners, established in the various dominions of the Hapsburgs and free from separatist traditions, were to represent the principle of a single state as against the peoples of the several provinces. The consequences of this change of system were soon felt all over Europe. The scheme had in view the organization of so extensive a state that the united Austrian dominion must needs become one of the great powers of Europe. Hitherto great countries had developed only in Western Europe, namely Spain and France. Their fields of conflict were Italy and Burgundy. Now, however, a strong power was rising on the borders of central Europe, which appeared to have unlimited room for expansion in the territories of eastern Europe. By means of its dynastic connexion with Spain it was as well a menace to France. As early as 1623 Austria and Spain supported each other in Switzerland; in 1628 Ferdinand by his power as emperor protected the interests of Spain in the War of the Mantuan Succession. As a result France became the natural enemy of Austria from the very beginning. It was for this reason that the empire first became interested in the issue of the war in Bohemia. The greater portion of its territory lay between France and Austria. In the paralyzed condition of the empire a war between these two great countries would have to be fought out on imperial territory. It was remarkable that the clouds of war so quickly gathered. For the states of western Europe were, first of all, hampered by internal troubles and by their relations to one another, while the Hapsburgs were occupied at home. Even Maximilian of Bavaria, after the battle of the White Mountain, expected to bring the war to a speedy end by overcoming Christian of Anhalt and a few other adherents of the fugitive Elector Palatine. In order to bring the old Wittelsbach family feud to a final settlement, to seize the Upper Palatinate by way of war indemnity, and to secure the transfer of the electoral dignity from the palatine to the Bavarian line of the house Maximilian occupied the entire Palatinate. But war once kindled in the empire could not be confined within limits, and it spread slowly but steadily (see THIRTY YEARS WAR). Too much inflammable material had been accumulated by the discontent of the petty princes of the empire, by the religious animosities, by the lack of employment that resulted from the economic decline, and by the occupation of the border provinces by foreign powers. Whenever Maximilian gained a victory his enemies with very little trouble enlisted fresh hosts of mercenaries; the Netherlands furnished the money. Very soon he was obliged to send his army into north-western Germany; thus the war continued to spread. Two events of the years 1624-29 increased animosities and, finally, in 1630, gave the struggle an international character. (a) The historical development of the German Hapsburgs had led to so close a connexion between their dynastic power in their own dominions and the imperial authority that the recovery of the former immediately filled Ferdinand with the ambition to restore the latter. When he drove the Elector Palatine out of Bohemia he had also outlawed him as a prince of the empire. Now that the territories in the empire occupied by Maximilian of Bavaria were growing in extent and the war was becoming more general throughout Germany, Ferdinand could hardly avoid assuming its direction. He had not the necessary funds for such an undertaking, because of the persistently blundering economic administration of Austria. But, he accepted Wallenstein's offer to maintain an army for him. Wallenstein was ambitious to be invested, as the head of an army, with extraordinary powers both military and diplomatic. He was a genius as an organizer and a remarkable man, but a condottiere rather than a statesman. Nevertheless the emperor placed him (1625) at the head of an army. Wallenstein did not act in conjunction with Maximilian's troops; moreover, he showed little respect either for the historically established relation between emperor and princes, or for the position of the latter in the empire. He quartered his troops in the territories of the princes, levied heavy contributions from their subjects and treated these sovereigns themselves with arrogance, while at the same time he was not a general who rapidly achieved decisive results. The blind jealousy that had animated the princes against Charles V was now directed against Ferdinand. Once more the complaint resounded that the emperor was placing on them "the yoke of brutal servitude," was making himself "monarch" of the empire, and an autocrat. (b) Maximilian followed up the victory of the Bavarian and imperial forces by restoring Catholicism in the Upper Palatinate. The Catholics demanded the restitution of the small territories in southern Germany of which they had been despoiled since 1550, despite the Reservatum ecclesiasticum. Furthermore, overestimating their success in the field, they sought to regain the dioceses in northern Germany that had passed under Protestant administration. The emperor was impelled by his political interests to enforce the claims for restitution in the south, since this would greatly weaken the Würtemberg dynasty, which was an obstacle to the extension of the Hapsburg power in Swabia. In addition he also authorized the reclamation of the bishoprics of northern Germany in the district of the Elbe and at the mouth of the Weser, in order to place them in the hands of an Austrian archduke. Accordingly he issued the Edict of Restitution of 1629. The Calvinistic party of the Palatinate had been totally defeated, and now Lutheranism was in danger of being confined to a comparatively narrow territory split up into detached districts by Catholic ecclesiastical principalities. On this account all the Protestant states of the empire were filled with distrust and resentment, although ill-prepared to take up arms in self-defence. Cardinal Richelieu had, meanwhile, overthrown the Huguenots in France and had laid plans to strengthen the French power in Europe by the occupation of desirable positions in upper Italy as well as in Lorraine and on German soil. He saw a menace to his schemes in the growth of the imperial power in the empire and in Ferdinand's interference in the War of the Mantuan Succession. He reminded the princes that Framoe had formerly protected their liberties, impressed them with its peace-loving character, and urged them, especially Maximilian of Bavaria, to refuse to elect the emperor's son King of the Romans and to demand the dismissal of Wallenstein (1629-30). While he thus sought to deprive the emperor of his commander-in-chief and his main army, Richelieu also used every means to induce Gustavus Adolphus, King of Sweden, to invade the empire. The appearance of Wallenstein on the Baltic coast and the invasion of the ecclesiastical principalities on the Elbe by the Catholics disturbed the ambitious King of Sweden. He was the ablest of all the princes who, in the first half of the seventeenth century, sustained the authority of the sovereign against the encroachments of the petty nobility in central and eastern Europe. After a speedily won success in Sweden itself, he set about the task of conquering all the territories on the Baltic in which the princes still suffered the inferior nobles to do as they pleased, thereby securing also for Sweden the control of this sea and a place as one of the great powers. If the Hapsburgs should accomplish their plans for the restoration of Catholicism the schemes of Gustavus Adolphus would be completely frustrated. For, in order to control all the lands on the Baltic and to sever permanently the German provinces of this region from the empire, he must unite them in an organic political system and civilization; this would be impossible unless all of them were separated in religion from the greater part of the rest of Europe by professing Lutheranism. In the summer of 1630 the king landed in Pomerania; in August the emperor sacrificed Wallenstein to the princes. The success of Richelieu's intrigues and of the invasion of Gustavus Adolphus appeared more alarming at first than the outcome warranted. They did not cause the dynastic power of the Hapsburgs to totter. Gustavus Adolphus was killed at Lützen (1632); his finest troops, the mainstay of his strength, were annihilated at Nördlingen (1634). Thereafter the Swedes could achieve only ephemeral successes by means of a few bold but spasmodic excursions from the coast into the interior of the empire. Years passed before Richelieu was able to replace the army of Gustavus Adolphus by French troops. During the Swedish invasion he had occupied (1630-34) the whole of Lorraine and the region between the Moselle and the Upper Rhine. After the battle of Nördlingen he openly declared war against the emperor (1635), but he did not venture far beyond the Rhine. Within the empire the first successes of the Swedes led to a reconciliation between Maximilian and the emperor, while the continued occupation of German soil by the Swedes and the French declaration of war after Richelieu's assurances of peace influenced most of the other princes to ally themselves again with the emperor, Saxony leading the way. There was a burst of patriotic indignation, such as had not been known for a long time; men were again ready to sacrifice their interests to those of the empire. In the Peace of Prague (1635) emperor and princes agreed upon the future organization of the empire. This treaty made allowances both for the historical development of the empire and its necessities: the enforcement of the Edict of Restitution was suspended, the autonomy of the Austrian dominions, of Bavaria, and of the great states of northern Germany was recognized, and the exercise of the imperial authority, in so far as it extended to internal affairs, was confined to the smaller territories of the west and south. On the other hand, the administration by "circles" was to be revived and perfected. Against foreign foes all pledged themselves to act in common, no one desired any further separate leagues. In case of war a consolidated imperial army was to enter the field. As early as 1635 the offensive was taken against France and the Swedes. In 1636 Ferdinand III was elected King of the Romans; he was emperor 1637-57. Thus the political unity of the German nation, sorely as it had suffered from the weakness of the imperial authority, the excessive growth of separatism, and the religious schism, stood the test in the hour of danger. However, its resources, seriously weakened after a struggle of twenty years, were not adequate to carry out the compact made at Prague and to relieve the distress of the empire at one stroke; Austria, in particular, was not equal to its task. It was found impossible to drive the enemy by force out of the empire and to move all the estates to unite with the emperor. For the protection of the frontiers had been neglected and the individual states allowed to cultivate relations with foreign countries too long to permit the attainment of these ends. In western Germany the Landgravate of Hesse became a supporter of the French, while the young Frederick William, Elector of Brandenburg, who had succeeded to his electorate in the latter part of 1640, concluded an armistice with the Swedes. From 1640 on Richelieu was finally able to send French armies into Germany. The inadequacy of the services that Austria rendered the empire and the support it gave the Spaniards, who were hated throughout Germany, reawakened distrust in the emperor. Moreover economic conditions in the German states, after nearly a century of gradual decline, and the ravages since 1621 of the soldiery, became each year more pitiful. The need for rest excluded every other consideration. Even the antagonistic religious parties began to long for peace. The smaller estates of the empire felt no interest in the war and demanded peace at any price with the foreign enemies; even the greater ones, becoming gradually exhausted, declared themselves neutral. In conjunction with the emperor, and even without him, they negotiated for peace at Münster and Osnabrück with France and Sweden, whose influence thereby naturally became much more powerful. But the consciousness that they were parts of the empire did not again die out. A dim perception that Austria in its development as a great power partly belonged largely to eastern Europe had deepened the conviction, which was encouraged by France, that the interests of the empire and Austria were not absolutely identical, that the policy of the one need not of necessity be the policy of the other, and that the empire had needs of its own which should be safeguarded by the estates. In order to meet these exigencies the estates claimed, on behalf of the empire, the right to seek the protection of other great powers as well as of the emperor, so as to find support in all emergencies either on one side or the other. Some declared that these needs were, above all, the restoration and maintenance of peace, and the preservation of the independence of the different estates of the empire, and of the varied forms of German governmental administration as opposed to the centralization of other countries. The Bishop of Würzburg, John Philip of Schönborn, the most active representative of the inferior estates, was strongly imbued with these principles. These views were officially recognized by the peace of Westphalia (1648). To procure the evacuation of Germany by the foreign armies France was indemnified by that part of Alsace that belonged to Austria, and Sweden by the territories at the mouths of the Oder and the Weser. The great possessions gained by Austria in Bohemia and in the countries on the Danube were not touched, but it agreed to cease supporting Spain. Within the empire everyone was restored to his own possessions and his own rights. At the same time, however, the possessions of the German princes having military resources were enlarged in such manner that the balance of power was maintained among them. To do this the lands of decadent principalities, especially the lands of the bishoprics of northern Germany which were ready for secularization, were allotted to them. The consolidation of northern Germany into an ever decreasing number of states thus made another great advance, as was evidenced by the fact that towards the end of the war even the much divided possessions of the Guelphs in the north-west were combined to a large extent, like those of the other north German dynasties, under a single government. An attempt was made to assure the mutual recognition of the new territorial boundaries by establishing complete equality between Protestants and Catholics. The Catholics were satisfied with a slight enlargement of their possessions over those they held in the year 1618, the year taken as the standard being 1624, and the Calvinistic Confession was recognized. The new order of things was protected, as regards the emperor, by proclaiming the sovereignty of the princes of the empire, by restoring to them the right to make alliances, and by making France and Sweden the guarantors of the execution of the treaty. As against these two powers, however, it was most inadequately secured; the disturbances in the south-west, it is true, were suppressed, but the division of that region into small states was maintained, and its development thereby impeded. The result was that the frontier bordering on France was ill-protected, while the occupation of the lands at the mouths of the Oder and Weser by the Swedes was a perennial danger to northern Germany. (2) 1648 to 1673 Frightful as had been the devastation of property and loss of life, the conclusion of peace did not find a ruined people. Both in political affairs and in the advance of civilization the war had brought about the renewal of national vigour. In most of the states the governments gave themselves to arduous work. Some commercial centres gradually revived, and by untiring energy the agriculture of northern Germany recovered its working power. Intellectual life also reawakened and grew apace. In jurisprudence, political science, education, the perfecting of the German language, and poetry, a succession of scholars, by a constantly increasing mastery of form and matter, produced a series of great works. The study of these works during the next two decades matured the all-embracing genius of Leibniz (1646-1716). France, which reached the height of its literary culture in the following generation, was the teacher of Germany, and Catholicism derived especial advantage from the influence of France. The reputation of Catholicism rapidly increased, and it soon exerted a powerful force of attraction over many high-minded Protestants in Germany which eventually led them into the Church. Around Schönborn especially, who in 1647 had become Archbishop of Mainz and chancellor of the empire, was gathered a circle of Catholics, converts, and well-intentioned Protestants, among the latter Leibniz. From Schönborn emanated an influence that permeated the entire intellectual life of Germany. In the domain of politics Catholic hopes were founded on the military successes of Austria and Bavaria, which had shown themselves the strongest of the German states, on the efforts of Schönborn to infuse life into the administration by "circles," and on his attempt to form alliances among the princes with the ultimate aim of bringing about a general confederation of the estates. Schönborn desired, by means of such a general confederation, to make Germany under his own leadership independent of the favour of the great powers. Although this confederation was to be peaceful in character and could consequently only become a second grade power, he even hoped to make of it a means of establishing a balance of power in Europe between France and Austria, such as some Italians had sought to make of their country in the preceding century. Schönborn's policy was most successful in 1657-58, when Ferdinand III died without leaving an heir who had attained his majority and had been elected King of the Romans, thus giving France an opportunity to attempt to dictate the succession to the imperial crown. Schönborn, however, secured its bestowal upon another Hapsburg, Leopold I (1658-1705); at the same time he united a large number of princes in the Confederation of the Rhine (Rheinbund), which looked for support to France. Still more powerful but not more advantageous for Germany was the influence exercised on the course of events by another reigning prince, Frederick William of Brandenburg, the Great Elector. His contemporaries looked upon him only as the most turbulent of the rulers in the empire. His chief object was the aggrandizement of Brandenburg to the eastward of the Elbe, but in the Peace of Westphalia he had been compensated by new territories in western Germany. Dissatisfied with this arrangement he openly avowed that as the greater part of his dominion bordered on eastern Europe, he, like Austria and even more unscrupulously, did not consider the interests of Germany as identical with those of Brandenburg. When Sweden declared war on Poland in 1655 he took part on the side of the former country with all his resources. In 1658 the new emperor joined forces with him to drive Sweden out of Germany. In order to be more certain of the aid of the imperial troops Frederick William, at the election of the emperor, brought it about that Austria was required to renew its pledges not to support Spain, at which France was preparing to strike the final blow. This threatened Germany once more with serious danger, for France, after forcing Spain into concluding the Peace of the Pyrenees in 1659, in 1660 dictated peace on the Baltic at Oliva and Copenhagen on such terms that Sweden was protected against any diminution of its territories. Then when the Turks, after a long truce, renewed their advance on Vienna in 1662 France forced auxiliaries on Austria as soon as the latter began to offer a sturdy defence. Consequently, after the first victories, Leopold preferred to come to a secret understanding with the Turks at Vasvár (1664). France interfered in every quarrel among the states of the empire. Aided by the personal charm of its young king Louis XIV, who had assumed the government in 1661, France appeared to have obtained a dominant influence in Germany such as Charles V had formerly held in Italy. What it had vainly striven to gain by war France now acquired during ten years of peace. Apparently in all parts of the empire, including Austria, there was a continually growing need of peace. The subsidies that Louis poured into the exchequers of the impecunious princes, who were just beginning to devise a rational system of taxation, were intended to fetter them. The upper classes in Germany surrendered themselves completely to the influence of French culture and customs. Moreover, French statecraft, economic policy, and military system, which presented to the princes an example of effective administrative organisation, all promised to place Germany more and more under the spell of its western neighbour. The Houses of Guelph and Wittelsbach and the rulers of Saxony allowed themselves to be won over by France. In 1667-68 Louis was able to place a check upon the Elector of Brandenburg, and also upon Austria, the dynastic line of which was now reduced to one person, and threatened to become extinct like that of Spain. Although the Peace of Westphalia led the Germans to take France as a model, yet in many unseen ways it prepared the emancipation of Germany. The national consciousness became quickened in proportion as intellectual life reawakened, and the national spirit once more found a voice. The princes gradually drew back from France, and its friendship was only seriously sought by the House of Wittelsbach. When de Lionne, Louis's adviser in foreign affairs, warned him not to carry out his purpose of attacking the Netherlands until he was sure of the sympathy of the more important German princes, all the efforts of the able French diplomats did not avail to obtain this assurance. Louis, nevertheless, advanced against the Dutch, and a storm of popular indignation broke out in Germany which carried along with it the German princes, with the exception of the Wittelsbach line. In 1674 the empire declared war against France. This was the signal for a war of forty years duration, which was divided into three periods. In the first the advantages of efficient generals, well-trained troops, and abundant means were all on the side of France. The contingents of the German princes formed a motley body; in 1675 the Elector of Brandenburg withdrew, and marched into Pomerania against the Swedes. In addition, the allies of the emperor, the Netherlands and Spain, proved inefficient. Only a few isolated exploits, such as the battle of Fehrbellin (1675), revived the fame of German military prowess. In 1679 peace was made between the empire and France at Nimwegen. Louis, however, overestimated his success. On the one hand he calculated on detaching the Elector of Brandenburg permanently from the German cause by compelling him in 1660, to restore all the territory won from the Swedes and then to enter into an alliance with France that would reduce him almost to feudatory dependence. On the other hand, after peace had been signed, France seized various strips of territory on the western frontier of Germany (called the "Reunions"), this unwarranted procedure culminating in the occupation of Strasburg (1781). Such conduct, however, only stimulated the patriotic indignation of the small western states (Alliance of Laxenburg, 1682), while at the same time the rising generation in the larger principalities, including the territories of the Wittelsbach line, was rallying enthusiastically around the emperor for the Turkish war. The repulse of the Turks at the siege of Vienna (1683), followed by the glorious recovery of Hungary, gave a new, impulse to Austria's political power. With the increase of French interference in German affairs (succession to the Palatinate, 1685; election of the Bishop of Cologne, 1688), German resistance to Louis, in which Brandenburg joined, became unanimous. Louis retorted by renewing war. Although Austria was still engaged in the struggle with the Turks, the military forces of the two sides were almost even. The Margrave Louis William of Baden organized the troops of the small south-western states of Germany in an efficient manner. Austria found in Eugene of Savoy a general and statesman who, in a position similar to Wallenstein's, far surpassed the latter in genius and character. Moreover, the emperor found in England a far more efficient ally than the Netherlands had been. Both sides brought larger and larger armies into the field, until each of them maintained 400,000 men. By the Peace of Ryswick (1697) Louis restored part of the territory of which he had robbed the empire. Austria, by the brilliant victory of Zenta (1697), drove the Turks completely out of Hungary and Transylvania (Treaty of Carlowitz, 1699). The death of the last Spanish Hapsburg (1700) caused a fresh outbreak of the war as early as 1701. This time Austria was able to employ most of its forces against France, England being again the ally of the empire. The allied powers won brilliant victories, some jointly, some separately (Blenheim, 1704, Ramillies and Turin, 1706, Oudenarde, 1708, Malplaquet, 1709). By straining its powers to the utmost France bettered its position after 1709. During the course of the war Austria changed rulers twice, Joseph I reigning 1705-11, Charles VI, 1711-40. After Charles VI ascended the throne England deserted Austria. By the Treaties of Rastatt and Baden in 1713-14 France retained only Alsace out of all its conquests on the German frontier. Meanwhile Austria, which had once more become embroiled with the Turks, again defeated the latter, and imposed terms at the Peace of Passarowitz in 1718 that were extremely favourable to Austrian trade in the Levant. At the same time a war was raging between Russia and Sweden, and the princes of northern Germany took advantage of it to drive Sweden completely out of Germany (treaty of Stockholm between Sweden and Hanover in 1719; between Sweden and Prussia in 1720). By the victories over the Turks and by its opposition to Louis XIV the Austrian monarchy became in the fullest sense a great power, while France effected no substantial extension of its frontiers. In this way the plans of Ferdinand II were realized and secured for a long period. But at the same time Ferdinand's successors allowed the imperial power and the reorganization of the empire to decline. In the reign of Leopold I the Diet had, indeed, become a permanent body at Ratisbon from 1663, and the empire took part as a whole in all three periods of the war. The contemporary sovereign princes, however, were interested chiefly in the political development of the separate states. Their policies were based on the centralizing and absolutist principles of the government of Louis XIV. These principles were susceptible of application to the individual principalities, but not to the empire, which, by its very nature, was federal and parliamentary. The empire could never have the same bureaucratic form of administration that the separate principalities had now received, nor could it be organized on a fiscal basis similar to theirs. Consequently Austria, Prussia, which had become a kingdom in 1701, and the other larger German states detached themselves more and more from the empire. Some ruling houses, dissatisfied with the smallness of their territories, which did not admit of extension, were disposed, at the beginning of the new century, to seek new countries. The Elector of Saxony, belonging to the Wettin line, accepted the crown of Poland (1697), while the main branch of the Guelphs ascended the throne of England (1714). The branch of the House of Wittelsbach that ruled Bavaria aspired to the crown of Spain, or at least to the sovereignty of the Spanish Netherlands. When foiled in this they made an alliance with France in 1701; this doomed them to an unfruitful, separatist policy in their territories. Even among the people the conception of imperial unity no longer obtained. It is true that the nation made steady progress towards intellectual unity, as the development of its written language improved. Moreover between 1660 and 1690 the patriotic sentiment of the nation showed itself plainly, but it grew weak again at the very moment that was decisive for a constitutional policy. For the people took but little interest in the aims of the last period of war, the struggle over the Spanish succession while at the same time the entire organic life of a nation was undergoing a vital crisis. Economically the country made but little progress because its resources were too much exhausted and the constant wars permitted no recuperation. Consequently the social organization of the nation, in particular, lost its elasticity; the nobility became arrogant, the middle class decayed, the bureaucracy grew overweening and excluded all others from participation in state affairs. During this period the Germans made no effort to secure national unity. Under these circumstances, notwithstanding the German victories, foreign countries affected in large measure German politics. France continued to be the guaranteeing power. Two other great powers, England and Russia, had considerable influence, the former on Hanover, with which it was connected by a common dynasty, the other on all the German states on the Baltic, especially Prussia. Catholicism lost its preponderance once more owing both to the renewed decay of political and national life in Germany and to the decline of France. At the beginning of the eighteenth century its progress lay in the field of art, especially in that of architecture. In Vienna and the capitals of the spiritual and temporal lords of southern Germany many architecturally striking buildings were erected; among the great architects and fresco painters of the period were Hildebrand, Prändauer, Fischer of Erlach, Neumann, and the brothers Asam. Protestantism, however, led in learning, as was exemplified by the professors of the University of Halle, Thomasius, Christian Wolff, Francke. Moreover, the close relations of England to Germany now began to make themselves felt, and German Protestantism found in England a powerful and progressive intellectual aid that Sweden had not been able to afford. IV. FROM 1713 TO 1848 (1) 1713 to 1763 Many petty differences were still left unsettled in 1713, many an ambition was as yet unrealized. In Germany as well as in the rest of Europe questions remained to be settled by diplomatic negotiations, but swords were sheathed. The people had an intense desire for peace. The industrial classes longed to emerge from the miserable hand-to-mouth existence which had been theirs for so many years, to rise again to the profitable exercise of trades and commerce, and to accumulate capital for larger undertakings. For several decades to come they were obliged to work without visible results. But the strenuous effort produced the will and the strength necessary to achieve the phenomenal economic progress of the German people in the nineteenth century. The prevailing tendency among the princes and nobility was towards the voluptuous enjoyment of the social and artistic pleasures of life, which they gratified by the erection of magnificent buildings and by gorgeous court ceremonials; examples of the indulgence of such tastes were the rulers of Saxony Augustus II (1694-1733) and Augustus III (1733-63), the latter being also King of Poland; Maximilian II Emanuel of Bavaria (1679-1726); Eberhard Louis (1677-1733) and Charles Eugene (1737-93) of Würtemberg. Men of higher aims were Maximilian III Joseph of Bavaria (1745-77), and, among the bishops, especially those of the Schönborn family. In the interior development of the states the princes sought to complete the reorganization of their territories according to the French absolutist and bureaucratic model, as: the introduction of state officials into local government, the collection of taxes in coin and a money basis for trade, the augmentation of the standing armies, repression of the privileges of the nobility, and the extinction of parliamentary and corporative rights. To perfect such a system both persistent and steady effort was needed; the majority of states fell short in this respect. In Hanover the nobles gradually recovered control of the government; in Austria a perilous state of political inertia set in under Charles I. Frederick William I of Prussia (1713-40) was the only sovereign who carried out the work of economic reconstruction with energy. The ideal state which the statesmen of the age of Louis XIV sought to attain, an ideal impracticable in larger countries, was to a great extent realized in Prussia. Small as was Prussia's territory and backward as it was in civilization, it grew, nevertheless, into a power influential out of all proportion to the size of its population and area, thanks to the high efficiency of the administration, to the utilization of all resources for the benefit of the state, and to the unflagging energy of the king himself. Shortly after 1740 Prussia was able to maintain a standing army of more than 100,000 men ready for war, and with this army it could turn the scale in a conflict between the equally balanced forces of the great countries. In 1740 Frederick II, the Great, succeeded to the throne of Prussia. In the period just passed Austria and France had exhausted themselves in a war begun in 1733 over issues that had not been settled in 1713, namely, the Polish Succession, and the right of France to Lorraine. By the Peace of Vienna in 1738 France obtained Lorraine; Austria, moreover in 1739 lost Belgrad to the Turks. Soon after Frederick's accession in Prussia, the Emperor Charles VI died, leaving a daughter, Maria Theresa (1740-80). France and Bavaria took up arms to prevent her coming to the throne of Austria; this was in direct violation of the promises made to Charles when these countries recognized the Pragmatic Sanction. At the instigation of France the electors chose Charles Albert of Bavaria emperor under the title of Charles VII (1742-45). Frederick the Great took full advantage of Maria Theresa's difficulties; he occupied Silesia and, upon her refusal to surrender it, concluded an alliance with France and Bavaria; the wars that followed upon this were the War of the Austrian Succession (1740-48), the First Silesian War (1740-42), and the Second Silesian War (1744-45). Impaired in strength during the weak government of Charles VI, Austria seemed ready to fall to pieces under the force of the shock. But the hesitation of Frederick the Great, the aid of England, Austria's ally after 1742, and above all Maria Theresa's political energy and inspiriting personality helped Austria to withstand the shock. Silesia, it is true, was not recovered, but Maria Theresa kept all the other provinces and in 1745 her husband, Francis I, was elected emperor. She found in Kaunitz a most valuable guide in matters of foreign policy and a wise assistant in the direction of home affairs. The internal administration was steadily perfected in imitation of Prussia, the army was reorganized by Daun, Laudon, and Lacy. Further, by the new alliance between the three great European powers, Austria, France and Russia, Austria was once more established in a commanding position in Europe. However, Frederick, with the aid of England as ally, prevented the consequences of these measures from becoming immediately apparent. In 1756 he made a fresh attack on Austria while England simultaneously went to war with France for the purpose of acquiring the latter's colonies. The ensuing struggle was the Seven Years War, which exposed the weak points of the schemes of Kaunitz and especially the decline in the military strength of France before their excellences could be turned to use. Moreover Maria Theresa, by summoning as empress the French to enter the country, stifled in the princes all feeling of obligation to the empire, while Frederick by his victory over the French at Rossbach (1757) became a national hero despite the unpopularity of Prussia. In addition, the sturdy resistance that the Prussian king offered to the three powers, even though he failed of victory, made an impression on the political world in Prussia's favour no less great in results than were the consequences in northern Germany of his alliance with England. (2) 1761 to 1815 After the Treaty of Hubertusburg (1763) Prussia was not only an independent state, it had as well an independent policy. From this time on the rest of northern Germany also became alienated from Austria and southern Germany. These states now received an impulse from England such as they had never had from the empire and Central Europe, for England in this period was rapidly advancing in commerce, industries, and intellectual life, and exhibited an energetic and far-seeing political policy. The mining of the coal and ore deposits in the Rhenish-Westphalian district and in Silesia was undertaken on a large scale, the number of factories increased, the Hanseatic towns took advantage of the American Declaration of Independence to establish transoceanic trade relations that were pregnant with rich results for the future of German commerce, while agriculture east of the Elbe adopted larger methods involving the use of capital in order to develop export trade in grain with England. In addition to Halle other universities in northern Germany became noted as centres of intellectual life; among these were Göttingen, founded in 1737, which had the historians and writers on political science, Schlözer and Spittler, as professors, and Königsberg, where Kant and Kraus taught. Most of the precursors of the classical age of German poetry, as Klopstock and Lessing, were North Germans, so were many of the writers of the Storm and Stress (Sturm und Drang) period. And although Goethe and Schiller, the great poets of the classic era, were South Germans, yet they made their homes in the north, the centre from which their influence was exerted being the Court of Weimar. Herder and the two Humboldts were Prussians. The Romantic School also under the leadership of North Germans, the Schlegels, Hardenberg, Tieck, Schleiermacher, developed around two northern cities, Berlin and Jena. It was through the intellectual ascendancy exerted by northern Germany that Denmark and Holland were brought almost completely within the sphere of German culture. From north-western Germany proceeded the chief influences that in a periodical press created German public opinion (Schlözer's criticisms on contemporary politics in his "Staatsanzeigen," the political writings of Gentz), and encouraged the sense of nationality (Möser, Count Stolberg). It was in this part of Germany that Freiherr vom Stein received his early education and his training in official life. The relatively large area of the states of northern Germany, the result of the last two hundred and fifty years of political evolution, encouraged intellectual progress and was in turn promoted thereby. For the first time northern Germany undertook to outstrip southern Germany in development; along with this, however, the Protestant states once more took the lead of the Catholic states. It is true that southern Germany immediately strove to compete with northern Germany, but the division of the former section into so many small principalities paralyzed commerce and retarded intellectual progress and the development of industries. Joseph II, joint-ruler with Maria Theresa from 1760 and sole ruler of Austria from 1780 to 1790, desired to remedy this disintegration by annexing Bavaria to Austria and by extending the Austrian power in Swabia and on the Upper Rhine. The latter result he desired to attain by making the city of Constance a great emporium of trade between Italy and Germany. In Austria he set on foot far-reaching projects of reform. On the non-material side he and other rulers strove to infuse new strength into the intellectual and civilizing influence of Catholicity as opposed to Protestantism. Catholicity in southern Germany, which remained closely in touch with French intellectual life, suffered from the paralyzing influence of French rationalism and its destructive critical tendencies. The champions of the Church, foremost among them being the Prince-Abbot Martin Gerbert of St. Blasien, gave it a more national basis again and infused into it a more positive spirit. But they failed, almost without exception, to renounce in principle the rationalistic movement; this failure led many men, as Joseph II, and Wessenberg, into grievous errors. Progress in southern Germany depended ultimately upon progress in Austria. Not only, however, did all the political plans for Germany of Joseph II break down before the opposition of Frederick the Great, as shown in the War of the Bavarian Succession (1778-79) and in the league of princes formed by Frederick against Joseph (1785), but towards the end of Joseph's reign serious revolutionary movements sprang up against him even in his own dominions. A complete reversal of the relative strength of northern and southern Germany seemed imminent. Nevertheless northern Germany did not fully utilize the pre-eminence it had obtained in intellectual progress. In spirit Frederick the Great was not in sympathy with recent developments. The English political system rested on principles differing widely from French absolutism, the methods and aims of which Frederick, following in his father's footsteps, clung to tenaciously. He even carried these somewhat further, especially in regard to economic administration. Taken altogether his political achievements were the greatest and most effective development of the French system. After 1763 by the annexation of West Prussia, obtained through the First Partition of Poland in 1722, he extended his dominions in the district of the Oder and Weichsel Rivers, and by adopting the policy of Catherine II of Russia he secured for his kingdom a strong position among the states of Eastern Europe. Moreover he declared his intention to give special weight to the eastern or Prussian part of his monarchy by making its nobility, the Junker, his principal instruments both in the military and civil administration. From the time of their arrival in these districts these nobles had been trained to fight and to colonize. The impulse towards a united northern Germany could in this era only come from Frederick the Great, the middle class of north-western Germany had not as yet made itself felt. In 1786 Frederick died, whereupon Prussia's prestige declined once more. Bereft of a strong political stimulus the intellectual life of Germany, both north and south, took on a cosmopolitan and purely humanitarian character. Even the outbreak of the French Revolution at first produced in Germany not progress but a shock. The ideas of 1789 were greeted with approval, but when the Revolution became radical in 1792 and involved Germany in war, the people, craving peaceful development, without exception rejected it. Austria, reorganized by Leopold II (1790-92), took up again under Thugut, prime-minister of Francis II, who was Francis I of Austria (1792-1835), the policy of expansion initiated by Joseph II. Thugut, however, preferred to make conquests in Italy rather than in southern Germany, and Napoleon's victories in 1796 compelled him to desist even from these (Treaty of Campo-Formio, 1797). The princes of southern Germany, being left to themselves, now turned to the French government and by humble supplication obtained from it the aggrandizement of their territories at the expense of the ecclesiastical rulers whose dominions were to be secularized. At the Congress of Rastatt (1797-99) France was willing to grant their petitions, but Russia, England, and Austria brought the congress to a premature end by renewing the war with France. Previous to this, in 1792, Prussia had joined Austria in taking up arms against the French Revolution. At he Treaty of Basle (1795), however, it had deserted Austria and, influenced by French diplomacy, disclosed for the first time its ambition to become the ruling power of northern Germany, to annex Hanover and to carry out the secularization of ecclesiastical lands. But Frederick the Great's successors, Frederick William II (1786-97) and Frederick William III (1797-1840), were men of little energy. Moreover at the Second (1793) and Third (1795) Partitions of Poland Prussia had assumed more Polish territory than it could assimilate; its administrative resources, unable to bear the strain put upon them, were paralyzed. Thus the end of the eighteenth century left Germany in complete disorder. South-western Germany, brought into constant contact with France by active commercial relations, now manifested a desire for comprehensive and efficient political organization. For, by the impetuosity with which the French Revolution preached the principle of nationality and the rights of the individual in the State, the German mind had again become accessible to national ideas and strong political convictions. From the beginning of the nineteenth century the Romantic School extolled the glories of German nationality and the empire, and the younger generation of officials in the several states, especially in Prussia, promoted drastic measures of reform. Napoleon, as the instrument of the times, contributed to the realization of these ideals. Defeating Austria again, both in 1800 (Treaty of Luneville, 1801), and in 1805 (Treaty of Presburg), Napoleon proceeded to make a new distribution of German territory. By the Treaty of Luneville he annexed the left bank of the Rhine to France. By the partition compacts with Prussia and Bavaria in 1802 and by the Imperial Delegates Enactment of 1803, he secularized such ecclesiastical states as still existed, and in 1805-06 he abolished the rest of the decadent petty principalities in the south, including the domains of the free knights of the empire and of the free cities. He was to retain only three territorial divisions in southern Germany: Bavaria, Würtemberg, and Baden. These his creative genius built up into secondary states, similar to those of northern Germany both in area and in their capacity for internal development. The South Germans had at last a clear course for renewed progress. Napoleon hoped thereby to put them under lasting obligation to France; in 1806 he bound them, as well as the central German states, more strongly to himself by the Confederation of the Rhine (Rheinbund). In the abolition of the small principalities he gave the death-blow to the Holy Roman Empire, which ceased to exist, 6 August, 1806. The administration and economic condition of the secondary states now rapidly improved, but, contrary to Napoleon's expectations, the sympathies of their inhabitants did not turn to France. Napoleon then overthrew Prussia at the battles of Jena and Auerstädt (1806) and by the Treaty of Tilsit (1807) left to Prussia only its original provinces between the Elbe and the Russian frontier. After this, by means of far-reaching, liberal reforms instituted under the enlightened guidance of Freiherr vom Stein aided by Gneisenau and Scharnhorst, both state and army in Prussia became stronger and more progressive than ever before. In all the German lands on the right bank of the Rhine the educated classes were full of fervid patriotism, and in Austria and Prussia as well the people bore the foreign yoke with impatience. In 1809 a national war against Napoleon broke out in Austria. The Tyrolese under Hofer made a heroic struggle, and Archduke Charles won a victory over the French at Aspern. It is true that Napoleon, notwithstanding all this, finally maintained his ascendancy (Treaty of Schoenbrunn, also called of Vienna, 1809), and Austria, thereafter, by the advice of Metternich, who was prime-minister from 1809 to 1848, adopted a policy of inaction. Pursuing an opposite course, the Prussian people rose in a body in 1813 after Napoleon's disastrous campaign in Russia. This revolt Napoleon did not succeed in crushing; on the contrary, he himself was now defeated in the Wars of Liberation by the coalition of Russia, Austria, Prussia, and England. The interior of Germany, the true home of Teutonic national life, had been forced almost completely into the background during the eighteenth century by Austria and Prussia. During the Napoleonic era it advanced materially in influence as a result of the formation of the secondary states and the growth of national political opinions. Nevertheless Austria and Prussia re-established their military ascendancy over the interior during the Wars of Liberation. In the Treaties of Paris (1814) and at the Congress of Vienna (1814-15) efforts were made to do justice to both of these circumstances. Under Metternich's guidance Austria reached the climax of its power at the Congress of Vienna. It became the leading state in Europe, but at the same time it made the Danube and the territory east of the Alps the centres of its power and withdrew completely from southern Germany. Prussia, now likewise recognized as a great power and a leading state of Germany, received, on condition of surrendering a part of its Polish possessions, a strong position in the extreme north-west, but it did not attain the hegemony of northern Germany. The Napoleonic system of secondary states was ratified and amplified, as in the four kingdoms of Bavaria, Würtemberg, Hanover, and Saxony, etc. It was hoped that this settlement would be permanent since it was founded on the joint liability of all the European states, a principle recognized by the Vienna Congress and the maintenance of which was guaranteed both by Prussia and Austria. Moreover the political rivalry between the different faiths was supposed to have been overcome, since of the great powers Austria was Catholic and Prussia Protestant, and both were now on friendly terms. By the award of many Catholic districts to Protestant sovereigns Catholicity had, it is true, sustained great losses in central Germany, Würtemberg being one-third, Baden two-thirds and Prussia almost one-half Catholic. It was thought, however, that none of these states, not even Prussia, could be able thereafter to retain an entirely Protestant character. Moreover Catholicity gained greater influence over the minds of men owing to the Romantic movement and the spread of anti-revolutionary ideas. Metternich, continuing the policy decided upon in 1548 and 1635, committed himself to the following programme: to give a new guarantee to the reawakened national feeling by establishing a German Confederation; that each German state must belong to the Confederation, though without prejudice to its autonomy; that the primary object of the Confederation was to be the defence of the independence and stability of Germany against external foes as well as against revolutionary agitation; but it was also to be allowed to develop into a confederated state by gradually enlarging its authority over the internal affairs of the individual states, such as commerce, economic administration civil and constitutional law. The organ of this confederation was to be a permanent assembly composed of plenipotentiaries appointed by the reigning princes, as in the Imperial Diet prior to 1806. This body was authorized to enact fundamental laws for the Confederation and to organize its administrative machinery (Federal Acts of the Congress of Vienna, 9 June, 1815). (3) 1815 to 1848 The Federal Diet was in session from 1816 to 1848 and again from 1850 to 1866 without, however, enacting any fundamental laws or creating any administrative machinery. The only result of the deliberations was a fuller and more detailed but not a more definite statement of the problems to be solved by the confederation (Final Federal Act of Vienna, 1820), and this in spite of Metternich's pressure for the working out of these problems. Prussia and the secondary states opposed all progress in the work of the Diet. Even Metternich was no longer really in earnest about it. In the autumn of 1815 he had concluded the Holy Alliance with the Czar and the King of Prussia and had thereby bound himself to a common policy with the great powers of Eastern Europe, the three countries Russia, Austria, and Prussia being then called the eastern powers. This policy, in view of the possibility of revolutionary agitation, opposed the national and constitutional current of the times. Moreover, as Premier of Austria, Metternich's course had to be directed by the fact that, after the troubles of the reign of Joseph II and the losses sustained in war during the last twenty-five years, the country stood in need of absolute rest. Austria kept its people from all foreign commercial competition and in politics avoided contact with foreign nations. Consequently its policy within the confederation was restricted substantially to the safeguarding of its own interests. Between 1815 and 1848 Prussia and the secondary states also devoted themselves exclusively to the solution of problems within their own boundaries. Up to 1848 Germany witnessed the most complete autonomy of the individual states in its entire history. The need of national unity was once more entirely ignored. In most of the secondary states much was done to improve the administration and the economic policy. Prussia, the self-reliance of which had been still further intensified by the Wars of Independence waged against Napoleon, completed the reforms that had been started in the period before 1815, although not in the German national spirit of their authors but rather in accordance with antiquated Prussian ideas. Even the new western provinces were as far as possible subjected to the old Prussian law as well as the old Prussian ecclesiastical policy and methods of government. At the University of Berlin, founded in 1909 by William von Humboldt, Hegel raised the Prussian conception of the state, filled with the spirit of Protestantism and rooted in absolutism, to the dignity of a philosophical system. He gave this position to the state as the highest and all-controlling form of society. Nevertheless the individual German states had clearly passed the limit of their capacity for organization. Routine dominated state administration. A well-trained but arrogant bureaucracy seized control of the government in Prussia as well in the secondary states and while it carried to excess the traditional political principles, yet it did not enforce them with the firm hand of the rulers of an earlier era. This was especially the case in the conflict concerning mixed marriage in the fourth decade of the century when the Prussian government arrested Archbishop Droste-Vischering of Cologne as an "insubordinate servant of the state" (1837). Its weakness was also plainly shown when the people of western and southern Germany objected to the interfering supervision of the government officials. The middle class was indebted to Metternich for more than thirty years of uninterrupted peace, during which he protected it from all disturbances both at home and abroad, and they owed to Prussia laws more favourable to commerce than had ever before existed. These were the moderately protective Prussian customs law of 1818 and the founding (1833) of the customs-union (Zollverein), which made a commercial unit of Prussia, central and southern Germany. Now for the first time the exertions of the commercial classes during the eighteenth century brought forth ample fruit, and Germany regained the financial ability to undertake large commercial enterprises. Important industries flourished and traffic was increased many-fold, while the middle class gained a clearer perception of the influence of foreign and domestic policies on economic conditions. The leaders (Hansemann, Mevissen, and von der Heydt) in the manufacturing district of the Lower Rhine, the most promising region in Germany from an economic point of view, were ready as early as 1840 to guide the fortunes of Prussia, provided they could obtain political rights. Holding radical views in politics and religion, they adopted also the political demands of their intellectual kinsmen in France, the Liberals: the creation of a constitutional parliament and the remodelling of the body politic in accordance with their social and economic principles. As Prussia like Austria had not granted its subjects a constitution, the struggle of these men for influence was conducted under difficulties. Their efforts, however, were aided by the existence of constitutional government in some of the smaller states since 1819, whereby a number of men, mostly university professors, were enabled in the several Diets to attack the bureaucratic administrations. These men were also Liberals, but their primary demand was the substitution of popular government for that of the bureaucracy; the leaders were Rotteck and Welcker of Baden; and of the moderates, Dahlmann. As early as 1837 matters came to a crisis in Hanover, while in Baden the contest lasted from 1837 to 1844. In answer to the opposition they called forth the Liberals raised the battle-cry of national unity, claiming that union would be the strongest guarantee of civic liberty. Their programme, as well as the appeal to the moral feeling of the people made by many of their leaders, aroused universal sympathy. As champions both of the principle of national unity and of economic and social progress, they hoped soon to be able to lead the entire people in a struggle against the reactionary administrations of the individual states. The latter, blinded by their particularistic prejudices, did not rally their forces to meet the threatening attack. As early as the forties differences on politico-economic questions weakened the customs-union between Prussia and the states of southern Germany. Metternich had repeatedly urged that Austria become a member of the customs-union. But it now appeared that the social and economic differences, always existing between Austria and the rest of Germany, had been so accentuated by the selfish policy pursued by Austria since 1815 that a strong opposition to its entering the customs-union came from within Austria itself. The position of the Catholic Church also became critical. The expectations of the Congress of Vienna had not been realized. Catholicity, it is true, owing to the splendid abilities of a number of men, partly the sons of the Church and partly converts, exercised a leading influence in the field of political sciences (Haller, Adam Müller, Frederick von Schlegel, Görres, Jarcke, Radowitz), in history (Buchholtz, Hurter), in art (Cornelius, Overbeck, Veit), and in theology (Möhler, Döllinger, Kuhn, Hefele). But in actual political life and in connexion with the life of the masses it fared ill. The bureaucratic state administration so fettered the Catholic Church that it was hardly able to stir, while Liberalism, for the most part anti-Catholic, threatened to place a gulf between the Church and the people. The deep piety of the people, however, was manifested both in 1844, on the occasion of the pilgrimage to Trier, and in the rejection of German Catholicism (1844-46). The attempt, however, to build up a Christian and anti-revolutionary party in conjunction with a few conservative Protestants (the two von Gerlachs, and the periodical "Politisches Wochenblatt" in Berlin; Görres and his circle of friends in Munich), on the basis of Haller's political teaching, was unpopular and altogether out of sympathy with the actual politico-social and politico-economic development of the nation. Nevertheless a few courageous politicians attacked at the same time the bureaucratic administration and Liberalism; thus Görres published his "Athanasius" in 1837, and founded with friends the periodical "Historisch-politische Blätter" in 1838; others were Andlaw and Buss in Baden, Kuhn and Hefele in Würtemberg, Moritz Lieber in Nassau. In Bavaria the Catholics were represented by the Abel ministry (1837-47). In Austria Metternich favoured them. V. FROM 1848 TO 1871 The wide-spread political agitation in Western Europe, which from 1846 had been undermining the foundations of the system of government established by the Congress of Vienna, culminated in Germany in March, 1848. The reigning princes, unprepared for the emergency, turned the governments over to the Liberals and ordered elections for a German Parliament on the basis of universal suffrage. Austria and Prussia, in addition, now granted constitutions to their peoples and, besides the national, summoned local parliaments. On 18 May the German National Parliament was opened at Frankfurt, Heinrich von Gagern presiding. Archduke Johann of Austria was elected provisional imperial administrator. The success of Liberalism was apparently complete, the individual existence of the separate states practically annulled, and the establishment of a constitutional German national State, as opposed to the development as a confederation, seemed assured. The only difficult question was, apparently, how Prussia was to be "merged" into Germany. However, as Frederick William IV of Prussia (1840-61) had expressed his sympathy with German unity, while the Liberals were prepared to make it as easy as possible for Prussia, as the head of the customs-union and the leading Protestant power in Germany, to surrender its individuality as a state, and were ready to offer to Prussia the hereditary imperial crown, the Parliament made light of this obstacle. Austria, rent by grievous national dissensions, seemed ready to step aside of its own accord. In the autumn of 1848, however, the situation became complicated. The draft of a new constitution made by the Liberals awakened the distrust of the Catholics by its provisions regarding the Church and the schools. At the suggestion of the Pius Association () of Mainz, the Catholics flooded the Parliament with petitions, while in October the Catholic societies assembled at Mainz and the German bishops at Würzburg. The Liberals gave way but conditions remained strained. The great mass of Catholics repudiated the proposed settlement of the German question in the "Little German" (Kleindeutsche) sense, which advocated the exclusion of Austria from German and the conferring of the imperial dignity upon Prussia; they demanded that Austria should remain part of Germany and should be its leader. This was called the "Great German" (Grossdeutsche) view. Simultaneously a radical reaction broke out against the Liberals. Liberalism stood for ethical and political progress only, not for social progress; nevertheless it had received the support of the labouring classes, who were impoverished by the recent industrial development but not ready to become a political organization, because of the Liberal opposition to the existing state of things. Now that the Parliament did nothing to better their condition they flocked to the standards of radical agitators. Before the spring of 1849 repeated disturbances resulted, especially in Southern Germany; furthermore Radicalism obtained a majority in the constitutional assembly of Berlin. The Liberals were not able to make any headway against this movement. Prussian troops had to re-establish the authority of the state, and in the interim the reigning princes had also regained confidence. Austria, now under the leadership of Schwarzenberg (Francis Joseph having been emperor since November, 1848), declared in December, 1848, that it would not suffer itself to be forced out of Germany. The Catholic agitation as well as the politico-economic movements were in Austria's favour. The industrial classes of Southern Germany, inspired by the fear that Prussia would adopt free-trade, desired to secure a politico-economic alliance with Austria, while the great merchants of the Hanseatic cities preferred for the field of their commercial operations Germany with Austria included, an area extending from the Baltic Sea to the Levant, to the lesser Germany alone. Having imposed a constitution on his kingdom in December, 1848, the King of Prussia refused to accept the imperial crown at the hands of the Frankfurt Parliament (April, 1849). Maximilian II of Bavaria (1848-64), by a strange recourse to the ideas of the seventeenth century, advocated a union of the secondary states, which in conjunction with Prussia but not in subjection to it, should control the policy of Germany (the "Triad"). In May, 1848, the Frankfort Parliament came to an inglorious end. An attempt was made immediately afterwards by Prussia with the aid of the Liberals and the secondary states to agree on a German constitution maintaining the federal principle (The Union, Diet of Erfurt, 1850), and to form merely an offensive and defensive alliance with Austria; this was foiled by Austria. But although Austria forced Prussia to yield in the negotiations at Olmütz in December, 1850, it failed to effect either the renewal of the German Confederation under conditions that would strengthen itself or to gain admission to the customs-union. The German Diet, still unreformed, resumed its deliberations in 1851, while by the treaty of February, 1853 (Februarvertrag) the negotiations for Austria's entrance into the customs-union were postponed for six years. Austria and Prussia neutralized each other's influence and nothing was done, either in the customs-union or in the Diet. Consequently the central states, Saxony and Bavaria, von Beust being prime-minister in Saxony and von der Pfordten of Bavaria, regarded themselves as the balance of power. Maximilian II summoned to Catholic Munich Liberal and Protestant professors, nicknamed the "Northern Lights, in order to win the public opinion of all Germany for his "Triad" project. Both of the great powers strove to secure the support of the German press. The failure to secure German unity once more gave the bureaucracy of the individual states the control. It was, however, no longer able to check the growth of democratic ideas among the people, and the masses were more and more influenced by the political and social movement of the times. In 1849-50 Liberalism underwent defeat; it then changed its programme and pursued chiefly economic aims. These were attained partly by founding countless politico-economic associations, such as consumers' leagues, unions of dealers in raw products, and loan associations (Schulze-Delitzsch); partly, and more largely, by controlling the use of capital on a large scale. During the fifties the representatives of great capital were able, by founding large joint-stock banks, principally for the purpose of building railroads and of financing mining enterprises, to attain a leading position in German economic life. The large landed proprietors of the Prussian provinces east of the Elbe had also in 1848 formed an economic, the Conservative, party. They watched over agrarian interests and also aimed at restoring the old Prussian-Protestant character of the Prussian monarchy, and the absolute sovereignty of the king. For a time incompetent leadership hindered their growth. On the other hand the Catholic movement soon spread among the people, though it did not constitute as yet an organized political party. The Catholics, undeceived at last as to the true character of Liberalism, but without entering into relations with the Conservatives, devoted themselves chiefly to the interests of the suffering masses whose social and economic needs had interested Radicalism merely as a pretext for agitation, and who had been neglected by the other parties. Thus arose the organization of journeymen's unions (Gesellenvereine) by Kolping of farmers' associations by Schorlermer-Alst, and the attempts to solve the labour question, which was taken up especially by Ketteler and Jörg. At the same time the Catholics fought against the restoration of Protestant supremacy in Prussia ("Catholic Fraction," 1852, Mallinckrodt, the Reichenspergers), and in the South-West against the unwarranted control of the Church by the bureaucracy. The beginnings of Socialism resembled those of the Catholic movement. The feeling of a community of interests awoke in the labouring classes; but it was not until about 1864 that Lassalle utilized this sentiment for political purposes. Throughout the fifties and sixties the Liberals retained the lead. As early as 1859 they deemed the time propitious for seeking to attain again to political power, without, however, any such revolutionary disturbances as in 1848. The decline of Austria's influence since Schwarzenberg's death (1852) encouraged them. In the Crimean War the temporizing policy of Austria, which offended Russia and did not satisfy the western powers, brought upon that country a serious diplomatic defeat, while in the Italian war it suffered military disaster. In both cases Austria had opposed Napoleon III who by these wars laid the foundation of his prestige in Europe. The growth of large commercial enterprises in Germany widened the breach between it and Austria so that in 1859 the latter was obliged to consent to a further postponement of its admission into the customs-union. In ecclesiastical politics Austria sought to satisfy the "Great German" aspirations of the Catholics of southern and western Germany by signing the Concordat (1855). Würtemberg and Baden also negotiated with Rome on the subject of a Concordat; but when, in 1859, Austria was defeated they relinquished the project. Austria's discomfiture in 1859 and its failure to form an alliance with Prussia against Napoleon, greatly excited public opinion in Germany, for the impression prevailed that Germany was menaced by France. The Liberals took advantage of this to renew their agitation for the union of Germany into a single constitutional state. In 1860 the Grand Duke Frederick of Baden (1852-1907), whose land was exposed to the attacks of France, entrusted the Liberals with the ministry of Baden. In 1861 the Liberals undertook to force parliamentary government upon Prussia so as to obviate all further opposition on the part of the king to the creation of a consolidated German state. They encountered, indeed, an obstinate resistance from King William I (1861-88), but the prevailing antagonism between the bureaucracy and the people caused the sympathies of almost the entire German nation to be enlisted on the side of the Liberals. The smaller states, becoming anxious, proposed reforms, leading to greater unity, in the constitution of the German Confederation. Austria, where since 1860 von Schmerling had been prime minister, also made advances to the Liberals in order to strengthen its position in Germany (Austrian Constitution, 1861; congress of the princes at Frankfurt, 1863). However, the appointment of Bismarck to the presidency of the Prussian ministry in the autumn of 1862, and the political organization in 1864 of Socialism by Lassalle, again checked the rising tide of Liberalism as early as 1863-64. This was followed by Bismarck's determination to settle once and for all with the sword the antagonism existing since 1848 in German affairs between Prussia and Austria. As Prussian envoy to the Federal Diet in the fifties Bismarck had observed the instability of the lesser German states and the decline of Austria's strength, as well as the methods of Napoleon, especially the use the latter made of the principle of nationalities; but he was also able to see that since 1860 Napoleon's star was on the wane. To a certain extent he appropriated Napoleon's views in order that Prussia might reap the fruits of what the French emperor had sown in Europe. At the same time he preserved an independent judgment so as to fit his measures to German conditions and proved that his genius contained greater qualities and more elements of success. In the Danish War (1864), fought to settle whether Schleswig and Holstein belonged to Denmark or Germany, he forced the Austrian minister of foreign affairs, Rechberg, to adopt his policy. He then manoeuvred Austria into a position of diplomatic isolation in Europe and, after forming an alliance with Italy, made a furious attack upon Austria in 1866. After two weeks of war Austria was completely defeated at Königgrätz (3 July), and by the middle of July Prussia had occupied all Germany. In the meanwhile Napoleon had intervened. Bismarck put him off with unmeaning, verbal concessions, and in like manner pacified the German Liberals whose continued opposition might hinder the carrying out of his solution of the question of German unity. He then concluded with Austria the Treaty of Prague (23 August, 1866) which partook of the nature of a compromise. Austria separated itself entirely from Germany, the South German states were declared internationally independent, Prussia was recognized as the leader of North Germany, while Hanover, Hesse-Cassel (Electoral Hesse), Hesse-Nassau, Schleswig-Holstein, and Frankfurt were directly annexed to Prussia, and preliminaries were arranged for the adoption of a federal constitution by the still-existing North German states. The constitution of the North-German Confederation, established, 1 July, 1867, was framed by Bismarck so that the federal development of German constitutional law should be guarded, thus the constitution was adopted by treaties with the several sovereign princes, the autonomy of the individual states was assured, and a federal council (Bundesrat) was to be the representative of the various governments. The necessary unity of the government was guaranteed (1) by endowing Prussia with large authority in administration, giving it especially the command of the army and direction of diplomatic relations; (2) by assigning foreign affairs, formation of the army, economic interests, traffic and means of communication to the authority of the confederation, the competence of which was to be gradually enlarged (the model here taken being the Federal Acts of the Congress of Vienna of 1815); (3) by creating the Reichstag (Parliament), elected by universal, direct and equal suffrage, as the exponent of the national desire for unity. In the years immediately following the Reichstag passed laws regulating the administration of justice. Bismarck considered the absence from the confederation of the South German states to be merely temporary. As early as August, 1866, he had secretly made sure of their co-operation in case of war. In 1867 he re-established the customs-union with them; politico-economic questions of common interest were, in future, to be laid before the Reichstag of the North German Confederation which, for this purpose, was to be complemented by delegates from Southern Germany so as to constitute a customs parliament. In all other respects he left diplomatic relations with the states of South Germany in statu quo. Attempts on their part to found a southern confederation failed. In like manner Bismarck postponed as long as possible the accounting with France in regard to the unification of Germany, although he foresaw that such an accounting was unavoidable. At a conference held in London, in 1867, he secured the neutralization of Luxembourg. In 1868 he desired to secure a resolution in favour of national unity from the customs parliament. To attain this he relied on the economic progress which, in consequence of the gradual unification of Germany, continually grew more marked and caused a complete change in a Liberal direction in the legislation on social and economic questions, and in that on the administration of law, both in the North German Confederation and Bavaria. Illustrations of these more liberal changes are: the organization of the postal system by Henry Stephan; introduction of freedom of trade and the right to reside in any part of Germany; enactment of the penal code, 1870. Notwithstanding these results of the efforts towards union, the opposition, led by Ludwig Windthorst, succeeded in obtaining a majority against him. On 19 July, 1870, war broke out with France, the cause being the candidature of Prince Leopold of Hohenzollern for the Spanish throne. Napoleon had not been able to secure the help of Austria and Italy; furthermore, his army was not prepared for war. Bismarck, on the contrary, fanned to white heat the national enthusiasm of Germany. The German armies quickly crossed the Rhine, and gained a firm footing on the other side by a rapid succession of victories at Weissenburg, Wörth, and the Heights of Spicheren. The main French army under Bazaine was defeated at Metz and shut up inside the city, 14-18 August. The army of relief under MacMahon was defeated at Sedan, 1-2 September. The war became a series of Strasburg fell, 28 September; Metz, 27 October; and Paris, not until 28 January. Meanwhile Gambetta had organized a national militia, 600,000 strong, which, in conjunction with the remains of the standing army, harassed and obstructed the Germans on the Loire and in the North-West from October to January. On 10 May, 1871, by the Peace of Frankfurt, Alsace-Lorraine was restored to Germany as an imperial territory (Reichsland). The southern states had already joined the Confederation, which had become the German Empire (with an area of 208,748 sq. miles). The Constitution of the North German Confederation was adopted, with the reservation of certain privileges in favour of Bavaria and Würtemberg. The Constitution was proclaimed 16-20 April, 1871, Prussia being entitled to 17 of the 58 votes in the Bundesrat or Federal Council, and to 236 of the 397 deputies in the Reichstag or Imperial Parliament. William I assumed the title of "German Emperor" at Versailles, 18 January, 1871; the office was made hereditary. VI. THE NEW GERMAN EMPIRE A development that had been in progress for many centuries and had been attended by many complications had practically reached its culmination; the political union of the Germans in a single body politic, without any relinquishment of the federal principle, so far as the relations among the ruling houses were concerned, had been accomplished, advantage being taken of the popular movement towards the unification of the several States into one organic whole. Austria had been excluded from Germany, the political consolidation of Northern Germany was almost complete, and Prussia's economic superiority over the south had been established beyond question. For while Southern and Central Germany (with the exception of Saxony and Nassau), as well as Hanover, experienced an increase in population of only about 22 to 36 per cent between 1830 and 1880, that of Prussia grew about 60 per cent; and nearly all the coal and ore deposits of Germany were located within the borders of the latter kingdom. Withal, during the ensuing years the united people did not devote themselves exclusively to peaceful pursuits. It is true these received great attention; German commercial and economic interests throughout the world were developed; uniformity was established in weights and measures (1872), coinage (1875), the administration of justice (1879); the laws of the empire were codified; and after a short time close attention was also given to social problems. On the other hand, military preparations (September, 1874), in case France should renew the war, were pushed forward with increasing zeal. Furthermore, the old internal feuds among the religious creeds and parties were resumed with greater passion than ever in consequence of the proclamation of the dogma of Infallibility and of the organization of the Centre party. In all this Bismarck was the leader, while the Liberals constituted the government party (see KULTURKAMPF). It was not until 1875 that there was any degree of tranquillity and stability. Bismarck recognized that he was lessening the extraordinary esteem in which he was held by the whole world, by his excessive intimidation of France. Moreover, the defeat in France of the Royalists and Catholics by the Radicals and Protestants freed him from apprehension of danger from that quarter. Russia having been estranged from the empire by his anti-French policy, Bismarck sought the friendship of Austria-Hungary. In 1879 he brought about an alliance with Austria, which, when joined by Italy in 1883, became the Triple Alliance, which still subsists — the league of the great powers of Central Europe. He re-established better relations with Russia by means of the secret treaty with that country in 1887. The election of Leo XIII, the "pope of peace" (1878), disposed Bismarck to come to an understanding with the Catholic Church. But as a preliminary condition he demanded either that the centre party be dissolved or that it become a government party. At the same time he contemplated sweeping changes in internal politics. The Liberal ascendancy, beginning in 1871, had been responsible for the inauguration of an excessive number of economic undertakings, resulting in the financial depression of 1873; in political finance it brought about an almost complete stagnation in the development of the systems of taxation both of the empire and the component states; in social politics it had led to a rapid increase in the ranks of the Social Democrats, who after Lassalle's death had become under Bebel and Liebknecht an international party, in which numerous anarchistic elements were blended. In 1875 there had been a fusion of the Lassalle and Bebel factions; the Gotha programme was drawn up; at the elections of 1877 they scored their first important success. Liberalism had also failed completely in its opposition to the Centre; the latter party had so grown that it controlled more than a quarter of the votes in the Reichstag. Bismarck determined to restrict once more the influence of the Liberals in domestic politics. The transformation of the Conservative faction from an old-Prussian party of landed proprietors into a German Agrarian party (1876) made it capable of further development and useful as a support for Bismarck. He purposed forming a majority by combining this Conservative party with the moderate National Liberals (under Bennigsen and Miquel), while at the same time, the Centre party having refused to disband, there was the possibility of forming a majority of the Conservatives and the Centre. Between 1876 and 1879 to organize the administration of the empire, the Reichstag created, subordinate to the chancellor, who under the Constitution was the only responsible official, the following imperial authorities or secretariats of State: Ministry for Foreign Affairs, Imperial Home Office, Imperial Ministry of Justice, Imperial Treasury, Administration of Imperial Railways, Imperial Post Office, Imperial Admiralty, Secretariat for the Colonies (1907). A number of non-political departments were also established, in part under the various secretaries of State, the chief of which was the Imperial Insurance Department; military affairs were placed under the Prussian Minister of War. In 1879 the imperial territory of Alsace-Lorraine was granted autonomy, though this was of a limited character. In 1878, after the attempts made by Hoedel and Nobiling on the life of William I, Bismarck carried out temporary measures for the suppression of Social Democratic agitation, e.g., the Socialist Law forbidding all Social Democratic organizations and newspapers. In the following year, encouraged by the increase in the sense of national unity due above all to the growth of German commerce and industry, he effected the financial and economic-political reform, his battle cry being: "Protection for German Labour!" Small protective duties were imposed upon agricultural and industrial imports, and a tariff for revenue only on colonial wares. The proceeds of both duties were to constitute the chief revenue of the empire, but of these only 130 million marks were to go to the imperial treasury, the rest being divided among the federal states, in return for which the latter, by means of federal contributions (Matrikularbeiträge), were to make good the contingent deficits of the empire. During the eighties the duties on agricultural products were gradually raised (especially in 1887), besides which several profitable indirect taxes, e.g., on brandy, tobacco, and stamps, were sanctioned, in order to meet the growing expenditures of the empire. In 1881 an imperial message to the Reichstag announced the inauguration of a policy of social reform in favour of the working classes. Between 1881 and 1889 the compulsory insurance of working-men against sickness, accident, disability, and old age was provided for by legislation. This was Bismarck's greatest achievement in domestic politics. The empire was now for the first time made the centre of the civil interests of the Germans, who up to this time had been occupied chiefly with the doings of their restive states, the management of Church and school having been retained by these. Bismarck, now at the zenith of the second creative period of his life, conceived the idea of organizing labour insurance on the basis of the community of interests of those engaged in the same work. By this means he proposed to establish in the empire self-government in social politics, which would equal in importance the local self-government of communities subordinated to the individual states, and which would complement the establishment of universal suffrage by educating the people for the administration of public affairs. Bismarck also gave his support to the great German commercial interests which insisted upon the acquisition of colonies; in 1884 South-West Africa, Kamerun, and Togo were acquired; in 1885-86 German East Africa, German New Guinea, and the Bismarck Archipelago. He even went so far as to risk being embroiled with England, although it was an inviolable fundamental principle of his policy not to encroach on that country's privileges. It appeared as if Bismarck, though he had grown up under wholly different conditions and had been schooled in wholly different ideas, entered into the spirit of the democratic German of the future, with its world-wide commerce and its world-wide economic interests. But the first step taken, he retreated. He did not carry out his scheme of co-operative organization. It was in the fight against the growth of the German democratic tendencies within the empire that he exhausted his strength in the eighties. Domestic peace was promoted in Germany by the final though belated close of the Kulturkampf (1886-87); the beneficial effects of this were greatly lessened by the severity and violence of the measures with which Bismarck had begun (1885-86) to break up the national movement of the Prussian Poles, which was the consequence of constantly increasing prosperity and a rise of a middle class among them. Exile, efforts to suppress the Polish language, the expenditure of State funds to colonize Poland with German peasants were the means used. Incapable of respecting political parties and working in harmony with them, he became involved in incessant parliamentary contests with them. Particularly the demands of the Government for an increase in the strength of the army, which was levied by general conscription, brought him into conflict with the Centre and the Left, because of his insistence that the appropriation for army purposes should be made for a period of seven years, instead of for one year, according to the Constitution, or for the term of a parliament. Bitter quarrels also marked the debates on social questions, because Bismarck refused to agree to state protection of workmen, though he had conceded state insurance. The political parties, all of which had been organized before the creation of the empire, now began to adapt themselves to new conditions, to cast aside issues resulting from the division of Germany into separate states, and to alter their positions to conform to new points of view; but their development was seriously hampered by these conflicts. In 1879 the Liberals had resigned the presidency of the Reichstag in consequence of the adoption of financial and tariff reform. The president was now chosen from the Conservatives, marking the Conservative era of the empire, which down to the present time has been uninterrupted with the exception of the supremacy of the Centre from 1895 to 1906. After their fall from power, the Liberals repeatedly split into factions according to their differences of opinion on commercial policy. The most important section, the National Liberal party, was reorganized in 1884 by Miquel. It became reconciled with Bismarck and regained some seats in the Reichstag, but not its former power. The Conservatives energetically took up the demands for the protection of the working classes. Eventually the Agrarian element among them got the upper hand. They failed, however, to attract into their ranks the smaller middle class, i.e., the small retail traders who had combined to resist the great industrial interests; nor did they win over the officials of the civil service, nor the Christian Socialists among their Evangelical constituents. Consequently, small parties sprang up in the west and south of Germany that were fundamentally Conservative in character but had no connexion with the great Conservative party. The attempt that von Kleist-Retzow made to found a Protestant party of the Centre in the hope of winning over the heir to the throne, Prince William, to its cause, was frustrated by Bismarck's intrigues, by which the prince was alienated from the Conservatives. The Centre maintained its strength and directed its attention to social politics in the empire and to the school question in the individual states. It became the leading party in the Reichstag, represented by Hitze and von Hertling. In 1890 the "People's Union for Catholic Germany" (Volksverein für das katholische Deutschland) was founded. The Social Democrats, prevented by the Socialist Law from agitating their cause publicly, kept up their strength by secret recruitment. By dissolving the Reichstag in 1887, Bismarck secured the most favourable electoral results that had ever fallen to his lot, inasmuch as an overwhelming majority of Conservatives and National Liberals (so-called Kartell-Reichstag) was returned. But he was unable to work harmoniously even with this majority. (2) From 1888 to 1909 In 1888 William I died. Frederick III, the hope of the Liberals, followed him to the grave in ninety-nine days, and the reign of William II began. The youthful and able ruler wished to make Germany as speedily as possible a sharer in the world's commerce. He realized that, to attain this end, internal tranquillity was as necessary as external peace. He dismissed Bismarck in March 1890 and replaced him by Caprivi (1890-94). Then he saw to it that the all but unanimous desire of the Reichstag to complete the compulsory insurance legislation by comprehensive factory legislation was satisfied. An international conference for the protection of working men was held, March, 1890, and a supplementary law (Gewerbsordnungs-Novelle) was passed 1 June, 1891. He moderated the repressive measures against the Poles. He intended to give the Catholics a guarantee that the national schools would continue to be Christian by the proposed National School Law in 1892, but withdrew the bill when the Liberals assumed a hostile attitude, and his pacific aims were thwarted. In foreign affairs he came to an understanding with England in regard to the difficulties that had arisen from the colonial expansion of Germany, e.g., the exchange of Zanzibar for Heligoland in 1890. In the interests of peace likewise he succeeded in concluding commercial treaties with Austria, Italy, Russia, and several smaller states, by lowering the agricultural duties which had become very high. With France he sought to establish relations that were at least free from bitterness. Because of its sovereignty over the Balkans and the East, he devoted special attention to Germany's political relations to Turkey. For he saw that these countries were the best markets for German trade. But trouble soon began. The emperor's autocratic proclivities and his sudden changes of opinion aroused bitter criticism among the people. The new Army Bill of 1893, which proposed to reduce the period of military service to two years, was well-meant on his part, but was so badly managed that it brought him into collision with the Centre (Dissolution of the Reichstag, 1893). On the other hand, the commercial treaties, which were opposed by the agricultural party, got the emperor into difficulties with the Conservatives. In 1895 the Reichstag turned a deaf ear to his demands for renewal of sharp repressive measures against agitations that were "hostile to the state" (the so-called "Umsturzvorlage"). His views subsequently became liberalized, his following being recruited mainly from the commercial, industrial, and intellectual classes (Krupp, Ballin, Harnack). The success of the emperor's policy during the next few years dispelled the clouds of opposition, especially as Caprivi's successor, Chlodwig Hohenlohe (1894-1901), was a man of astute and conciliatory nature, while in Count Posadowsky, Secretary of State for Home Affairs, the emperor had the support of an extremely competent and energetic man. Germany became Turkey's chief counsellor. The maintenance of friendly relations with the rapidly developing United States of America, despite the opposition of their economical interests and isolated instances of friction between officers, strengthened public confidence in the international situation. By the occupation of Kiao-chau in 1898, Germany secured a footing in Eastern Asia, while the partition of the Samoan Islands and the acquisition of the Carolines (1898-9) gave her a much-desired increase of stations in the Pacific. The German transatlantic merchant marine held for a long period the record for the race across the Atlantic, and, even in Africa and Asia, Germany promised to become a very serious rival of England. The last decade of the nineteenth century was a period of exceptional prosperity throughout the country. From forty-one millions in 1871, the population increased to sixty millions in 1905. The increased national well-being will be realized from the fact that at present the gross value of the agricultural produce amounts to some $3,525,000,000, and of the industrial output to about $8,460,000,000. In 1871, two-thirds of the population still lived in the country, whereas in 1900 54.3 per cent lived in towns of more than 2000 inhabitants, and in 1905 19 per cent lived in cities of more than 100,000 inhabitants. In the agricultural districts, however, conditions continued to be healthy — 31 per cent being cultivated by peasants, 24 per cent being held in large estates, and the remainder in lots of less than 20 hectares (roughly 50 acres). The woodland area still includes one-fourth of the total area. During this period the national standard of living became more luxurious; revolutionary and anarchistic tendencies began appreciably to disappear. The whole nation was seized by a burning tendency towards the formation of new associations, a spirit to which we owe the foundation of the Catholic People's Union (der Volksverein: members in 1908, 600,000), the Farmers' League (1908: 300,000 members), the free (Socialistic) guilds (1908: over 750,000 members), the Christian Endeavour guilds (1908: over 200,000 members), etc. In Parliament, the great political parties (Conservatives, National Liberals, and the Centre) drew closer together; the presidency devolved on the Centre in consequence of its numerical preponderance and the ability of its leaders. In 1899, the constantly recurring conflict between the Crown and the Reichstag on the subject of appropriations for military expenditure was settled by an agreement on the part of the legislative assembly to vote supplies henceforth for the parliamentary period, which had been increased from three to five years in 1888. Among the important measures passed were the completion of the unified legal codes (1896) and the Naval Acts (1898, 1901), which had in view the raising of Germany to a maritime power of the first rank. In 1902 the resolution to restore the high protective duties on agricultural products was passed in the face of the bitter opposition maintained by the Social Democrats for many months (Tariff Bills, on the basis of which the commercial treaties were renewed in 1905). Prussia's project of constructing a canal through her own territory from the Oder to the Rhine met with obstinate resistance, not indeed in the Reichstag, but in the Prussian Diet (rejected in 1899, approved in 1903). In the midst of this era of prosperity Bismarck died (1898). In foreign politics, however, there came a change for the worse after England's subjugation of the Boers. Under Edward VII, Great Britain forced Germany back from almost all the positions which she had recently occupied. Meanwhile, William II devoted himself to a line of policy calculated to win temporary favour (journey to Jerusalem, 1898; intervention in the Chinese complications, 1900; landing in Tangier, 1905). Prince Buelow, who replaced Hohenlohe in 1900, was unable to stem the ebbing tide. In the Moroccan controversy between Germany and France, Germany, who appealed to an international conference (at Algeciras, 1906), suffered a severe rebuff. By his efforts to separate Austria and Italy from the Triple Alliance and by his ententes with the other Powers of Europe, Edward VII isolated his rival (1907, Triple-Entente between England, Russia, and France). Buelow's Polish policy, which was more drastic even than Bismarck's (cf. the Expropriation Act of 1908), resulted only in disappointments without effectually checking the Polish disturbances. In 1907, owing in part to the financial crisis in America, Germany's commercial prosperity markedly declined. Favoured by the customs tariff, agriculture alone continued to flourish. The revenue of the empire decreased with the commercial profits. At the same time the rising of the Herreros in South-Western Africa in 1904 called for large unforeseen expenditures, while the troubled aspect of the foreign situation necessitated a tremendous increase in the outlay on armaments (cf. Naval statutes of 1908. The "ordinary" expenditure in 1907 was 2329 millions of marks; National debt in 1873: 1800 millions, and in 1908, 4400 millions of marks.) One attempt after another was made at fiscal reform [1904, relaxation of the Franckenstein clause; 1906, 150 million marks ($35,250,000) yearly taxes were voted; in 1908-09, 500 millions were demanded by the government], but the government is still carried on with a deficit. Thorough recovery has been prevented by the renewed violent dissensions in the nation by party spirit (since 1892) and the clash of opposing ideals. The coalition, which had formed the majority during the nineties, broke up in 1903. Its most important factor was the Centre, the number of whose seats in the Reichstag and supporters in the constituencies remained stationary even during the period of its parliamentary ascendancy. Therein lay its weakness, since meanwhile its allies, the official Liberal and Conservative parties, gained ground. The Liberals gained in consequence of a movement towards concentration among the Liberals of the Left soon after the beginning of the century (Fusion of the Liberal of the Left, 1906), and of a reconciliation between the National Liberals and the Liberals of the Left by means of a "Young Liberal" movement in their ranks. The Conservatives, who had been growing as a party almost uninterruptedly since 1876, especially after the founding of the "Farmers' League" in 1893, gained by gradually invading the agrarian territory in the west and south-west. Up to 1906, the Protestant League, founded in 1886, maintained a fanatical agitation amongst the populace to frustrate the endeavours of the Catholics, directed through the Centre, to secure recognition of their equal rights as citizens in the public life of the nation. Yielding to this agitation, first the National Liberals then the Conservatives dissociated themselves from the Centre. Despite its utmost efforts, the Centre failed in 1906 to secure the repeal of the remainder of the Kulturkampf Laws, except to the extent of the two paragraphs of the Jesuit law (i.e., the expulsion clauses). Furthermore, the so-called "toleration bills," in which the Centre strove by imperial legislation to fix the minimum of rights to be conceded to Catholics in the separate states, although repeatedly presented to the Reichstag after 1900, always met with defeat. When, in 1906, the Christian character of the national schools was finally established by statute in Prussia after an interval of 13 years, the Government drafted the bill in accordance with the wishes of the Conservatives and the National Liberals, and left to the Centre only the right of voting for it. Another important factor in bringing about the cleavage between the parties was the spread among the wealthier classes, both Liberal and Conservative, of a strong feeling of opposition to further social legislation. This feeling found an outlet in the formation of influential syndicates, and was most bitterly directed against the Centre, as the principal promoter of social remedial measures. An open breach between the parties took place on the question of a relatively insignificant colonial budget. The Government immediately disowned the Centre, and dissolved the Reichstag (13 December, 1906). Since then the situation has been very complicated. As a result of the elections the Centre retained its former voting strength, but was isolated. The Government formed a new coalition, called "the Block," consisting of the Conservatives and the united Liberal party — the Liberals of the Left had hitherto been in opposition. In this it relied on the feelings of hostility towards the Centre which animated the Protestants and the propertied classes. When the administration, however, made concessions to Liberal principles (extension of the right of association, partial repeal of the stock exchange legislation, promise to introduce popular suffrage into Prussia), the Conservatives, after some hesitation, decided to oppose the Government so again sought an alliance with the Centre. They are stronger than the Liberals, but the sympathies of the Government and of the Anti-Catholic portion of the population will help the Liberals in their contests with the Conservatives. The quarrel amongst the civil parties prevents the further loss of parliamentary seats by the Social Democrats, whose voting power has been steadily increasing since 1890 (in 1907 they cast 3,259,000 votes, 29 per cent of the total, although they won only forty-three seats in the Reichstag as compared with eighty-one in 1903). It also prevents the reconstruction of the programme of the Socialists, many of whom — especially in South Germany — favour a peaceful transformation of society. The difference of opinions existing among the Socialist party was clearly evidenced by the violent quarrel between the opposing sections at the Dresden Convention in 1903. The position of the Government in view of its relations with the parties is at present (Jan., 1909) not very favourable. The administrative organization of the empire hardly suffices. Besides, the shock given to the power of the emperor in November, 1908, in consequence of the popular resentment of his personal interference in politics as revealed in the "Daily Telegraph" interview, has not served to strengthen the Government. On the other hand, its prestige was greatly enhanced by the re-establishment of German influence in international politics, owing to its firm support of Austria-Hungary in the Balkan crisis (1908-9). It has put an end to the isolation of Germany, strengthened the bonds of the Triple Alliance, and promises to result in a rapprochement with Russia. In dealing with the present situation of German Catholicism, relations between Church and State must be separated from the question of the civic rights of the German Catholics. The authorities of the Church and State work together in a spirit of mutual benevolence, the chief credit for which is due to Cardinal Kopp, since 1886 Prince-Bishop of Breslau. Ecclesiastically speaking, Germany is divided into 5 archbishoprics, 14 suffragan and 6 exempt bishoprics, 3 Apostolic vicariates, and 2 Apostolic prefectures. The clergy are trained for the most part by 15 theological university or lyceum faculties (the most recently established being at Strasburg, 1902), a smaller number in seminaries. Ecclesiastical affairs are not regulated by the empire but by the individual state. In Prussia they rest on the Bull "De Salute Animarum" and the explanatory brief "Quod de Fidelium" of 1821 (although the promise of land endowment for the bishoprics has not been kept), on the constitution of 1850, and on the laws of 1886-87 regulating ecclesiastical polity. In Würtemberg, they rest on the Statute of 1862, in Baden on the Statutes of 1860, in Bavaria on the Concordat of 1817, which has not actually been enforced and which consequently creates a state of legal uncertainty. In these divisions of the empire, the Church has the rights of a privileged corporation. In the Kingdom of Saxony and in Saxe-Weimar, all ecclesiastical ordinances and appointments, even those issued from Rome, as well as the erection of new churches, etc., are subject to the approval of the Government. Appeal to Rome is forbidden. In the other small Thuringian states, and in Brunswick and Mecklenburg, the Catholics even recently had to submit their parochial affairs to the authority of the Protestant pastors, and in part Catholics even now pay tithes to the Protestant pastors for this unsought-for service. The building of churches and establishment of schools are also subject to galling restrictions. The bishops are elected by the cathedral chapters, except in Bavaria (where they are chosen by agreement between the Government and Rome); in the Upper Rhenish church province, in Osnabrück, and in Hildesheim, the Irish method of election obtains; elsewhere exists the customary submission of a list of candidates to the Government. The establishment of convents is everywhere subject to the approval of the State. In Würtemberg and Baden only female orders are allowed; in Saxony and the smaller Protestant States only nursing sisterhoods. Jesuit institutions are not permitted anywhere. The primary schools are mostly denominational, but are neutral in Baden, in part of Bavaria, and in two provinces of Prussia. They are founded by the State and by the communities, but the local pastors supervise the religious instruction and are generally the local school inspectors. The system of intermediate and higher schools for boys is undenominational almost without exception, and is under either state or municipal control; the schools for girls are mostly under private and denominational management, being largely conducted by nuns. The civil marriage ceremony takes precedence of the religious by an imperial law of 1875; divorce is regulated by the civil code. For Catholic couples separation a mensâ et thoro may be granted. Charitable relief work is admirably regulated and carefully stimulated by the focusing of charitable impulses in the Charitasverband (Charity Organization Society), founded at Freiburg in 1897. It is working more and more in harmony with social relief work. There is a large number of religious societies; the throngs who assist at all religious festivals are impressive, and the numbers who receive the sacraments are gratifying. Pilgrimages are numerously attended, the most famous place of pilgrimage in Prussia being Kevelaer, in Bavaria Altötting. Considerable anxiety is inspired by the prevalence of Social Democracy in certain districts, and by the irreligious indifference of the rising generation of the propertied classes. The civil status of Catholics is not so good. Of the 60,641,272 inhabitants of Germany in 1905, about 36.00 per cent were Catholic (in 1900 only 36.1 per cent as compared with 36.2 per cent in 1871). At present, as formerly, unity infuses life into the Catholic Church. The Catholics are splendidly organized (for politics by the Centre and in sociological respect by the Christian guilds and by Volksverein). They are making persistent efforts to secure equal recognition in public life (cf. the agitation afoot in Prussia since 1890 in favour of equal rights for Catholics; the so-called "Self-examination Movement" throughout the empire, that is to say, the general investigation into the injustices suffered by Catholics in the educational and economical life of the country). Recently, the number of Catholic pupils in the intermediate and higher schools has increased, but only on the humanistic side. Their representation in the poly-technic schools as well as in the student bodies at the universities continues to be weak, out of all proportion to those of the other communions. Only in isolated instances are the leading positions in the states and communities filled by Catholics. No Prussian state minister, and only one state secretary is Catholic. Their share in the public wealth does not at all correspond with their numerical strength. JANSEN, Geschichte des deutschen Volkes, IV-VIII; RITTER, Deutsche Geschichte im Zeitalter der Gegenreformation und des 30-jahrigen Krieges, III; ERDMANNSDOERFFER, Deutsche Geschichte vom Westfaelischen Frieden bis zur Regierungsantritt Friedrichs des Grossen, II; IMMICH, Geschichte des europaeischen Staatensystems von 1660 bis 1789: KOSER, Friedrich der Grosse (1903-04), II; ARNETH, Geschichte der Maria Theresia (1863-79), X; HEIGEL, Deutsche Geschichte vom Tod Friedrichs d. Gr. bis zur Aufloesung des Reichs (1899), I; TREITSCHKE, Deutsche Geschichte im XIX. Jahrhundert (1879-94), V, goes to 1848; SYBEL, Begruendung des Deutschen Reichs durch Kaiser Wilhelm I (1889-94), VII; FRIEDJUNG, Geschichte Oesterreichs von 1848 bis 1859 (1908), I; IDEM, Der Kampf um die Vorherrschaft in Deutschland 1859-1866 (1908), II; LORENZ, Wilhelm I, und die Begruedung des Deutschen Reichs (1902), I; MARCKS, Wilhelm I, (1905); LENZ, Bismarck; BISMARCK, Gedanken und Erinnerungen (1898), II; Denkwuerdigkeiten des Fuersten Chlodwig zu Hohenlohe-Schillingsfuerst (1906), II; EGELHAAF, Deutsche Geschichte seit dem Frankfurter Frieden (1908), I; LABORD, Das Staatsrecht des Deutschen Reichs (1901), IV; Publications of the Bureau of Imperial Statistics (Kaiserl. Statistisch. Amt.); BRUECK-KIPLING, Geschichte der kath. Kirche im Deutschland im XIX. Jahrh. (1887-1908), IV. I. FROM OLDEST PRE-CHRISTIAN PERIOD TO 800 A.D. There are no written monuments before the eighth century. The earliest written record in any Germanic language, the Gothic translation of the Bible by Bishop Ulfilas, in the fourth century, does not belong to German literature. It is known from Tacitus that the ancient Germans had an unwritten poetry, which among them supplied the place of history. It consisted of hymns in honour of gods, or songs commemorative of the deeds of heroes. Such hymns were sung in chorus on solemn occasions, and were accompanied by dancing; their verse form was alliteration. There were also songs, not choric, but sung by minstrels before kings or nobles, songs of praise, besides charms and riddles. During the great period of the migrations poetic activity received a fresh impulse. New heroes, like Attila (Etzel), Theodoric (Dietrich), and Ermanric (Ermanrich), came upon the scene; their exploits were confused by tradition with those of older heroes, like Siegfried. Mythic and historic elements were strangely mingled, and so arose the great saga cycles, which later on formed the basis of the national epics. Of all these the Nibelungen saga became the most famous, and spread to all Germanic tribes. Here the most primitive legend of Siegfried's death was combined with the historical destruction of the Burgundians by the Huns in 435, and affords a typical instance of saga-formation. Of all this pagan poetry hardly anything has survived. The collection that Charlemagne caused to be made of the old heroic lays has perished. All that is known are the "Merseburger Zaubersprüche," two songs of enchantment preserved in a manuscript of the tenth century, and the famous "Hildebrandslied," an epic fragment narrating an episode of the Dietrich saga, the tragic combat between father and son. It was written down after 800 by two monks of Fulda, on the covers of a theological manuscript. The evidence afforded by these fragments, as well as such literature as the "Beowulf" and the "Edda," seems to indicate that the oldest German poetry was of considerable extent and of no mean order of merit. II. THE OLD HIGH GERMAN PERIOD (c. 800-1050). CHRISTIANITY AND ITS INFLUENCE Between the years 500 and 700 occurred the High German soundshifting, which divided the dialects of the South, High German, from those of the North, Low German. The history of German literature is henceforth mainly concerned with High German monuments. In fact, until the close of the Middle Ages Southern Germany occupies the leading place in literary production. The Goths, the first Germanic tribe to be converted, embraced Christianity in the form of Arianism. But they soon gave way to the Franks, who became the dominant people, and the conversion of their king, Clovis, to Christianity, in 496, was of decisive importance. The conversion of Germany, vigorously carried on since the eighth century by Irish and Anglo-Saxon missionaries, notably by St. Boniface (d. 755), was completed when Charlemagne (d. 814) forced the heathen Saxons to submit to his rule and to be baptized, and united all the German tribes under his sway. Under him and his successors Christianity was firmly established. The clergy became the representatives of learning; the newly established monasteries and their schools, above all those of Fulda and St. Gall, were the centres of culture. The language of the Church was Latin, but preaching and instruction had to be carried on in the vernacular. The prose literature that arose to serve this purpose is only of linguistic interest. The poetry that developed during this period was wholly Christian in character. Examples are the "Wessobrunner Gebet" and the "Muspilli," the latter an alliterative poem on the destruction of the world; both date from the ninth century. The Church, naturally, opposed the old heathen songs and strove to supplant them by Christian poems. Thus arose the Old Saxon epic, the "Heliand," which was composed between 822 and 840 by an unknown poet, at the suggestion of King Louis the Pious. It is written in Low German and is the last great poem in alliterative verse. The story of the Redeemer is here told from a thoroughly German point of view, Christ being conceived as a mild but powerful chief, and His disciples as vassals or thanes. The same subject is treated in the "Evangelienbuch" of Otfried, a monk of Weissenburg, the first German poet known by name. It was completed about 868 and dedicated to Louis the German. While not possessing the literary merit of the "Heliand," it is of the greatest importance because it definitely introduces into German poetry the principle of rhyme, already familiar from the Latin church hymns. Rhyme was also used by the unknown author of the "Ludwigslied" to celebrate the victory of Louis III over the Northmen at Saucourt (881). This is the only song of the period not purely religious in character, though its author was probably a cleric. During the ninth and tenth centuries German poetry fell into neglect; at the courts of the Saxon (919-1024) and Franconian emperors (1024-1125) and in the monasteries the Latin language was almost exclusively cultivated, and thus a body of Latin poetry arose, of which the tenth-century "Waltharius" (Waltharilied) of Ekkehard, a monk of St. Gall (d. 973), the "Ruodlieb" (1030), and the "Ecbasis Captivi" (c. 940) are the most noteworthy examples. The "Waltharilied" relates an old Burgundian saga and is thoroughly German in spirit, while the "Ecbasis" is the oldest medieval beast epic that we possess. The Latin dramas of the nun Roswitha (Hrotsvitha) hardly belong to German literature. The great master of German prose in this period was Notker III, surnamed Labeo (about 952-1022), the head of the convent-school of St. Gall. His translations from Boethius, Aristotle, Marcianus Capella, and especially of the Psalter, are the best examples of German prose until the fourteenth century. III. THE PERIOD OF CHIVALRY AND THE CRUSADES (1050-1300). MIDDLE HIGH GERMAN POETRY In the eleventh century, under the influence of the reform movement that emanated from the Burgundian monastery of Cluny, a spirit of stern asceticism begins to dominate in literature. The Church in its struggle with the emperors turned again to the people, to carry through the reforms of Gregory VII, and although the poets of the beginning of this period were almost exclusively clerics, they at least wrote in German. The literature which they produced consists mainly of rhymed versions of Biblical stories and other sacred themes, and is represented by Ezzo's "Lay of the Miracles of Christ," Williram's paraphrase of the Canticle of Canticles (both c. 1060), and the poems of Frau Ava. Some of the best poetry of this time was inspired by devotion to the Blessed Virgin, as for instance the "Driu Liet von der Maget" by a Bavarian priest named Wernher (c. 1170). In these songs the characteristic German trend towards mysticism is unmistakable. A most noteworthy product of the age is the half legendary "Annolied," a poem in praise of Archbishop Anno II of Cologne (d. 1075). The "Kaiserchronik" (c. 1150), a bulky poem narrating the story of the world, presents a strange medley of legendary and historic lore. The bitter hostility of the ascetic spirit to the worldly life finds expression in the scathing satire of Heinrich von Melk (c. 1160). But asceticism was losing ground; under the influence of the Crusades the prestige of the knightly caste was steadily rising. A compromise with the secular spirit became imperative, and the clerical poets, to keep their audiences and meet the competition of the gleemen, now had recourse to worldly subjects. For their models they turned to France. A priest named Lamprecht composed the "Alexanderlied" (c. 1130), while a priest of Ratisbon, named Konrad, wrote the "Rolandslied" (c. 1135). In both cases the authors drew from French originals. The minstrels began once more to come to the front, and a number of popular epics date from this period. Among these "König Rother" (c. 1160) is conspicuous. Its subject is an old Germanic saga, and the role which the Orient, Constantinople in this case, plays therein shows the influence of the Crusades. Still more noticeable is this fondness for the Orient in "Herzog Ernst" (c. 1190), where the historical hero, Duke Ernest II of Swabia (d. 1030), is represented as a pilgrim to the Holy Land and the subject of marvellous adventures in the Far East. From this period dates also the first German beast epic, "Reinhart Fuchs," by Heinrich der Glichesaere (c. 1170). The rule of the Hohenstaufens (1138-1254) marks the first great classic era of German literature. Many causes contributed to bring about a great literary revival. The Crusades instilled new fervour into religious life. Many thousands of German knights followed King Conrad III in the crusade of 1145-47. They were brought into contact on the one hand with the Orient and its wealth of stories and marvels, and on the other with their more cultured French neighbours, whose polished customs and manners they adopted with avidity. Chivalry, an institution essentially Romance in origin and spirit, was thus raised to predominance in the social life of the age. The cultivation of poetry passed chiefly into its hands; the clergy ceased to be the sole purveyors of learning and culture. The poets of this period are, as a rule, of knightly rank. Many of the poorer knights depended on the generosity of princely patrons, such as the landgraves of Thuringia or the dukes of Austria. The only kinds of poetry cultivated in this epoch were the epic and the lyric, and the former was either courtly or popular. Form received the most careful attention; versification was regulated by the strictest rules; the classic Middle High German, is extremely elegant. This classic poetry was essentially a poetry of caste, and conformed absolutely to the ideals of courtly society. Brilliant as it was, it was mainly a poetry of translation and adaptation. The courtly epic deals almost exclusively with foreign subjects; its models were derived mostly from France. The subject most in favour was the matière de Bretagne, the legends clustering around King Arthur and the Round Table, with which that of the Holy Grail had been combined. This subject was made especially popular by the versions of the French trouvere, Chrestien de Troyes, who exerted great influence on the German courtly epic. Chivalry and the cult of woman are the leading motifs of this poetry. The court epic was introduced into Germany by Heinrich von Veldeke, a knight of the Lower Rhineland, whose "Eneit" (c. 1175-86), based on a French model, treats the story of Æneas in thoroughly medieval and chivalric spirit. The court epic was transplanted to Upper Germany by the Swabian, Hartmann von Aue (d. about 1215). In his "Erec" he introduced the Arthurian romance into German literature; his "Iwein" is from the same cycle; his "Gregorius" is an ascetic version of the Oedipus story. His best-known work is "Der arme Heinrich," which, as a purely German story of womanly devotion, occupies a unique position among the creations of the courtly poets — greatest of these poets is Wolfram von Eachenbach (d. about 1220), whose chief work is his "Parzival," the story of the simpleton who overcomes doubt and temptation and ultimately becomes King of the Holy Grail. As in Goethe's "Faust," we have here the story of a human soul. To the cycle of Grail-romances belong also the so-called "Titurel" fragments, while Wolfram's last work "Willehalm," is a historical legend which, however, remained incomplete. Opposed to Wolfram in spirit is his great rival, Gottfried von Strasburg, whose "Tristan" (c. 1210) is a glorification of sensual love and of somewhat dubious morality. With Gottfried the court epic reached its highest development; with him excessive artificiality begins to appear, and soon this species of poetry declines rapidly. The succeeding poets, in trying to imitate the great masters just mentioned, fall into tedious diffuseness, and their epics too often become a meaningless string of adventures. Rudolf of Ems (d. 1254) and Konrad von Würzburg (d. 1287) are the most gifted among these epigones. The former is the author of narrative poems like "Der gute Gerhard" and "Barlaam und Josaphat," an old Buddhistic legend in Christian form. The latter wrote a bulky epic on the Trojan War, for which he used the French romance of Benoit de Sainte-More as a model. Far more meritorious are his shorter romances, like "Herzemaere" and "Engelhard." His "Goldene Schmiede" is a poem in honour of the Blessed Virgin. Thoroughly independent of courtly influence is the powerful and realistic poem "Meier Helmbrecht," a tragic village story written by a Bavarian priest named Wernher der Gärtner (c. 1250). By the side of the courtly romances developed the popular epic. On the basis of old songs still current among the people, arose about 1200 in Austria the great German epic, the "Nibelungenlied," telling of Siegfried's death at the hands of Hagen and Kriemhild's fearful vengeance. The author is unknown, though he was probably of knightly rank. The poem is in strophic form, and, though the subject is primitively Germanic, the influence of chivalry and Christianity is throughout apparent. In Austria arose also, but little later, the "Gudrunlied," a story of the North Sea, telling of Gudrun's loyal devotion to her betrothed lover, King Herwig of Seeland. Of far less interest are the other popular epics, which also date from the beginning of the thirteenth century; they are mostly related to the saga-cycle concerning Dietrich von Bern. The most notable are the "Rosengarten," "Alpharts Tod," "Laurin," "Eckenlied," and "Rabenschlacht." Three other epics, "Ortnit," "Hugdietrich," and "Wolfdietrich," take their subjects from the Langobardic saga-cycle; in them the influence of the Crusades is very noticeable. Lyric poetry also flourished brilliantly in this period. Lyric poetry of a popular kind seems to have existed in Austrian territory long before the Romance influence came in from the North-west; but it was under this Romance influence that the lyric attained its characteristic form. Minne, i.e., the conventional cult of woman, is the leading motif, but other times, religious or political, are not wanting, and the Spruch, a poem of gnomic or sententious character, was also in great favour. Most of the minnesingers were of knightly rank. Tradition mentions Heinrich von Veldeke as the pioneer of minnesong. He was followed by Friedrich von Hansen, Heinrich von Morungen, and Reinmar von Hagenau. A disciple of the last-named, the Austrian, Walther von der Vogelweide (c. 1165-1230), is the greatest and most versatile lyric poet of medieval Germany. He is equally great in the Minnelied and in the Spruch. He was a stanch partisan of the emperors in their fight against the papacy, and many of his poems are bitter invectives against pope and clergy. But he never attacked the doctrines of the Church; his religious fervour is attested by such poems as that in honour of the Trinity. With his successors the Minnesang enters on its decline. Ulrich von Lichtenstein's life, as revealed in his autobiography, "Frauendienst" (1255), shows to what absurdities the worship of woman could go. Neidhart von Reuenthal (d. about 1245) holds up to ridicule the rude life of the peasants and so introduces an element of coarseness into the aristocratic art. Lastly, Reinmar von Zweter (d. about. 1260) must be mentioned as a distinguished gnomic poet. The didactic spirit, which now becomes prominent, is exhibited in longer poems, like "Der wälsche Gast" (1215) of an Italian priest Thomasin of Zirclaere, and especially in Freidank's "Bescheidenheit" (c. 1215-30), i.e., wisdom born of experience, a collection of rhymed sayings. Though these works are strictly pious in tone, outspoken criticism of papal and ecclesiastical matters is frequently indulged in. Prose was very backward in this period. Latin was the language for history and law. About 1230 appeared the "Sachsenspiegel," a code of Saxon law written in Low German by Eike von Repgowe, and this example produced in Upper Germany the "Schwabenspiegel" (before 1280). The first chronicle in German prose, the "Sachsenchronik," was written by a Saxon cleric (before 1250). A great impetus was given to German prose by the preaching of the mendicant friars, who were rising into prominence early in the thirteenth century. They reached the hearts of the people, on whom the aristocratic literature of chivalry had no influence. The sermons of David of Augsburg (d. 1272) are not preserved. His disciple, Berthold of Ratisbon (d. 1272), was immensely popular as a preacher. His dramatic, passionate eloquence, born of the sincerity of conviction, turned thousands of his hearers to repentance and a better life. IV. DECLINE OF POETRY AT THE END OF THE MIDDLE AGES. RISE OF BOURGEOIS LITERATURE (1300-1500) The decline of the knightly caste brought with it a decline of the literature of which this caste had been the chief support. The fourteenth and fifteenth centuries were not favourable to the development of an artistic literature. The Empire was losing its power and drifting into anarchy, the emperors were bent chiefly on increasing their dynastic power, while the princes strove to make themselves independent of imperial authority. They were no longer patrons of poetry. The clergy also in great part, followed worldly pursuits and undermined the reverence in which they had been held. The rise of the cities and their commerce was fatal to the prestige of knighthood and its ideals; life became more practical, more utilitarian, less aesthetic, and as a consequence the didactic tone becomes more and more prominent in literature. The universities which sprung up in Germany during this period — the first being founded at Prague (1348) — widened the gap between the learned classes and the people and prepared the way for Humanism, which towards the end of the fifteenth century begins to be a force in German letters. The influence of Humanism was not wholly beneficial. It was a foreign institution and fostered Latin as the language of scholarship at the expense of the native idiom. Gradually the Humanists turned against the dominant Scholastic philosophy, and soon a spirit of revolt manifested itself against the Church and its authority. The schisms within the Church and the worldliness of many of its dignitaries stimulated this spirit, which took a violent form, notably in the Hussite movement. The way was thus prepared for the great Lutheran revolt. The romance of chivalry degenerated into allegory and tedious description, of which a typical instance is the "Theuerdank" (1517), an allegorical description of Emperor Maximilian's courtship of Mary of Burgundy, written at the suggestion of the emperor himself. The heroic epic fared no better, its tone became coarse and vulgar. Rhymed chronicles still supplied the place of histories, the most noteworthy being the chronicle of the Teutonic Order translated from the Latin of Peter von Dusburg by Nikolaus von Jeroschin (c. 1340). Of higher poetic value are the legends, fables, and anecdotes that enjoyed such popularity in this period. The best-known collection of fables was "Der Edelstein," containing a hundred fables translated from the Latin by Ulrich Boner, a Dominican monk of Berne (c. 1340). Of the many didactic poems of this period, by far the most famous was the "Narrenschiff" (Ship of Fools) of the learned humanist Sebastian Brant (d. 1521), which appeared in 1494 and achieved a European reputation. This is a satire of all the vices and follies of the age, of which no less than one hundred and ten kinds are enumerated. A satiric tendency pervades also the "Reinke de Vos," a Low German version from a Dutch original of the famous story of Reynard the Fox (1498). The allusions in this poem to the vices of men high in Church and State are unmistakable. As for lyric poetry the Minnesang dies out, Hugo, Count of Montfort (c. 1423), and Oswald von Wolkenstein (d. 1445) being its last representatives. The cultivation of the lyric is now taken up by the burghers; the Meistersang displaces the Minnesang. Poetry in the hands of this class became a mere matter of technic, a trade that was taught in schools established for that purpose. The guild system was applied to art, and the candidate passed through different grades, from apprentice to master. Tradition names Mainz as the seat of the oldest school, and Heinrich von Meissen (d. 1318) as its founder. Of the many cities where schools flourished, none gained such a reputation as Nuremberg, the home of Hans Sachs. Very little of the poetry of these meistersingers has literary merit. The best lyric poetry of this period and the following is found in the Volkslied, a song generally of unknown authorship, expressive of the joys and sorrows of people in all stations and ranks of life. Contemporary events often furnished the inspiration, as in Halbsuter's song of the battle of Sempach (1386). Other songs deal with legendary subjects, as for instance the song of Tannhaeuser, the minstrel knight who wandered into the Mountain of Venus and then journeyed to Rome to gain absolution. The religious lyric of this period is largely devoted to the praise of the Blessed Virgin; in this connexion Heinrich von Laufenberg, a priest of Freiburg im Breisgau, later a monk at Strasburg (d. 1460), is specially noteworthy. Another literary genre that now rose into prominence was the drama, the origin of which here as elsewhere is to be sought in the religious plays with which the great Christian festivals, especially Easter, were celebrated. These plays had a distinct purpose; they were to instruct as well as to edify. But gradually they assumed a more secular character, they were no longer performed in the church, but in the marketplace or some public square. Laymen also began to participate, and in the fourteenth century German takes the place of Latin. Besides the Passion, Biblical stories and legends were dramatized. One of the oldest and most striking of such plays is the Tegernsee play "Antichrist" (twelfth century). A famous drama of which the text is preserved is that of the wise and foolish virgins, performed at Eisenach in 1322. The origin of the secular drama is not wholly clear. In the fifteenth century this genre is chiefly represented by the Shrovetide play, which undoubtedly traces its origin to the mummeries and the coarse funmaking indulged in on special occasions, notably on Shrove-Tuesday. No doubt the religious drama exerted its influence on the development of the secular drama. As a rule the latter was extremely crude in form and also incredibly coarse in language and content. The chief place for these plays was Nuremberg, and Hans Folzs and Hans Rosenblüt are the best-known authors in this line. In their plays appears the tendency that was to make of this literary genre an effective vehicle for satire. In this period of utilitarianism prose comes to occupy a leading position. The romances of chivalry were turned into prose, foreign romances were translated, and thus arose the Volksbücher, of which the most noteworthy is that of Till Eulenspiegel, a notorious wag, around whom gathered all kinds of anecdotes. The original Low German book of 1483 is lost, the oldest High German version dating from 1515. In connexion with translated literature the names of the earliest German humanists, Heinrich Steinhöwel, Niklas van Wyl, and Albrecht von Eyb should be mentioned. History was now written in German prose. Of prose chronicles we possess a number, as that of Strasburg (to 1362), of Limburg (to 1398), and the Thuringian chronicle of Johannes Rothe, a monk of Eisenach (1421). But the best German prose of this period is to be found in the writings of the mystics. The founder of this school was Master Eckhart (d. 1327), a Dominican monk, and the Dominican Order became its chief exponent. Eckhart was accused of pantheism, but repudiated any such interpretation of his utterances. His disciple, Heinrich Seuse (Suso), also a Dominican (d. 1366), was less philosophical and more poetical. The third great mystic, Johannes Tauler (d. 1361), a Dominican of Strasburg, gave the teachings of his predecessors a more practical turn. The service which the mystics rendered to the German language in making it the medium for their speculations can hardly be overestimated. The greatest preacher of the period was Geiler von Kaysersberg of Strasburg (d. 1510), whose series of sermons based on Brant's "Ship of Fools" was especially famous. V. THE AGE OF THE REFORMATION (1500-1624) The effects of Humanism in Germany began to be felt in the attention given by such men as Erasmus and Reuchlin to the study of the Bible in the original languages. For German literature the Reformation was a calamity. The fierce theological strife absorbed the best intellectual energy of the nation. Literature as an art suffered by being pressed into the service of religious controversy; it became polemic or didactic, and its prevailing form was prose. Martin Luther (1483-1546) is the most important figure of this period and his most important work is his translation of the Bible (printed complete at Wittenberg, 1534; final edition, 1543-45). The German translations before his time had been made from the Vulgate and were deficient in literary quality. Luther's version is from the original, and although not free from errors it is of wonderful clearness and thoroughly idiomatic. Its effect on the German language was enormous; the dialect in which it is written, a Middle German dialect used in the chancery of Upper Saxony, became gradually the norm for both Protestant and Catholic writers, and is thus the basis of the modern literary German. Luther's pamphlets have only historical interest; his catechism and sermons belong to theological literature. His "Tischreden" (Table-Talk) shows the personality of the man. Force and strength of will mark his character and writings. But his firmness often savours of obstinacy, and in dogmatism he yields no tittle to his opponents, while the bluntness, or still better the vulgarity, of his language, gave offence even in an age accustomed to abuse. As a poet he appears in his religious songs, among which "Ein feste Burg" is famous as the battle-hymn of the Reformers. Other writers of Protestant church hymns were Paulus Speratus (d. 1551), Nikolaus Decius (d. 1541), Nikolaus Herman (d. 1561), and Philipp Nicolai (d. 1608). As a rule, the German Humanists were indifferent to the Reformation, but Ulrich von Hutten (d. 1523) was a zealous partisan of the movement; his writings are mostly in Latin. One of the bitterest enemies of Luther was Thomas Murner, a Franciscan monk (1475-1537), who in his earlier satires castigated the follies of the age. At first he showed sympathy for the reform movement, but when Catholic doctrine was assailed, he turned, and in a coarse but witty satire "Von dem grossen Lutherischen Narren" (1522), he unsparingly attacked the Reformation and its author. The best poet of the sixteenth century was the Nuremberg shoemaker Hans Sachs (1494-1576) who, although a follower of Luther, was not primarily a controversialist. He displayed amazing productivity in many fields, mastersong, Spruch, anecdote, fable, and drama. His Shrovetide plays display a genial humour that even today is effective. The spirit of the worthy master's verse is thoroughly didactic, and artistic form is altogether lacking. Towards the middle of the sixteenth century, the Counter-Reformation set in, and regained much of the ground lost to Protestantism, which had now spent itself as a vital force and was divided by the dissensions between Lutherans and Calvinists. The most prominent polemical writer on the Protestant side was Johann Fischart (d. 1590), much of whose satire is directed against the Jesuits, notably his "Vierhörniges Jesuiterhuetlein" (1580). His most ambitious work is the "Geschichtklitterung," a free version of Rabelais's "Gargantua" (1575). Fischart is not an original writer, and his extravagance of language and love for punning make his work thoroughly unpalatable to a modern reader. Narrative prose is very prominent in the literature of this period. Collections of anecdotes, such as Jörg Wickram's "Rollwagenbuechlein" (1555) and especially "Schimpf und Ernst" (1522) of Johannes Pauli, a Franciscan monk, were very popular. Translations of French and Spanish romances like the "Amadis of Gaul" were also much in favour. Then there were the "Volksbücher," with their popular stories, among which those connected with Faust and the Wandering Jew have become especially famous. Didactic prose was represented by the historical work of Aegidius Tschudi (d. 1572), Sebastian Frank (d. 1542), and Johannes Thurmayr (known as Aventinus; d. 1534); the collections of proverbs and sayings made by Frank and Johann Agricola (d. 1566) are also to be mentioned in this connexion. In theology Bishop Berthold of Chiemsee represents the Catholic side, with his "Tewtsche Theologey" (1528); the Franciscan, Johann Nas (d. 1590), a Catholic convert, in his "Sechs Centurien Euangelischer Wahrheiten" also champions the old Church. The chief Protestant writer was Johann Arndt (d. 1621), author of the "Vier Bücher vom waren Christenthum," one of the most widely read books of the time. Contemporary with Arndt was the famous shoemaker, Jakob Boehme (d. 1624); a mystical philosopher in whose writings profound thoughts and confused notions are strangely blended. In the dramatic field there was also much activity. Luther, though opposed to the passion play, had favoured the drama on educational grounds. Nikolaus Manuel, a Swiss (d. 1530), used the dramatic form for satirizing the pope and the Catholic Church. The Biblical drama was in favour, and many of the learned writers of school comedies chose their subjects from the Bible, as for instance, Paul Rebhun (d, 1546) and Sixt Birck (d. 1554). The most prolific dramatist of the period was Hans Sachs, who wrote no less than 208 plays, which in spite of their lack of all higher literary quality, make a promising beginning. Towards the end of the sixteenth century, English strolling players appeared in Germany, and through their superior histrionic art gained the favour of the public. Jakob Ayrer (d. 1605), the leading dramatist of that age, shows their influence; still more so Heinrich Julius, Duke of Brunswick-Wolfenbuettel (d. 1613), the first to write German dramas in prose instead of verse. VI. THE AGE OF RELIGIOUS WORKS (1624-1748). THE POETRY OF SCHOLARSHIP AND IMITATION The religious strife inaugurated by the Reformation culminated in the Thirty Years War (1618-1648) which practically destroyed Germany as a nation. National feeling almost died out. The Catholic League looked for support to Spain and Austria, while the Protestant princes betrayed the national interests to Sweden and France. A servile spirit of imitation was abroad. The German language was neglected and devised in aristocratic circles and was corrupted by the influx of foreign words. Literature was devoid of originality and substance; the formal side absorbed the chief attention of the writers. The literary leader of this period was Martin Opitz (1597-1639), whose treatise "Von der deutschen Poeterey" (1624) enjoyed undisputed authority as an ars poetica for more than a century. Intelligibility and regularity rather than imagination and feeling were to be looked for in poetry. The theory of Opitz was drawn from the practice of French and Dutch Renaissance poets and left no room for originality. The book had a salutary effect, however, in that it put an end to the mechanical counting of syllables and made rhythm dependent on stress. Its protest against the senseless use of foreign words was also laudable. Opitz is the author of a number of poems, moralizing, didactic, religious, or descriptive in character, but of little real merit. His best-known work is "Trostgedicht in Widerwaertigkeit des Kriegs" (1633). The poets who followed the leadership of Opitz are known as the First Silesian School, though not all were Silesians by birth, and included some of real talent like Friedrich von Logau (d. 1655), the witty epigrammatist, and Paul Fleming (d. 1640), the lyrist. The poets of the so-called Königsberg Circle were also followers of Opitz. Among them, Simon Dach (d. 1659) is pre-eminent. In this connexion may be mentioned also, Andreas Gryphius (1616-64), the chief dramatist of the period. His tragedies, based mostly on Dutch models, are marred by their stilted rhetoric and predilection for the horrible; his comedies are far better, though they did not meet with the same favour. It was chiefly diction and versification that benefited by the poets of this school. Literature in their hands was a mere product of scholarship, entirely out of touch with the people. The linguistic societies that sprang up at this time, the most famous of which was Die fruchtbringende Gesellschaft (1617), did not change this condition. The language, not the literature, improved through their efforts. As a reaction against the cold formalism and utilitarianism of the Opitzians, the writers of the Second Silesian School, Christian Hofmann von Hofmannswaldau (1617-79) and Daniel Kasper von Lohenstein (1635-81) fell into the opposite extremes of bombast and exaggeration. Their style was modelled on that of the Italian Marini. The lyric poems of the former and the dramas and novels of the latter are written in an unnatural and inflated style, overloaded with metaphors. In their style, as well as in their immorality, these writings reflect the taste of contemporary courtly society. In opposition to this fashionable tendency, Christian Weise (d. 1708) in his school dramas and satiric novels strove for simplicity, which in his work and that of his followers degenerated frequently into triviality and inanity. The best poetry that the seventeenth century produced was the religious lyrics, especially the hymns. The tone of these poems is no longer one of combat, but rather of pious resignation. The greatest of Protestant writers in this line was Paul Gerhardt (1607-1676). Others deserving of mention are Joachim Neander, Georg Neumark, Johann Franck, and Philipp Jakob Spener. Among Catholic writers the most prominent were the Jesuit, Friedrich Spe (1591-1635), the intrepid defender of the victims of the witchcraft tribunals, author of the lyric collection "Trutznachtigall," and Johann Scheffler, better known as Angelus Silesius (d. 1677), a convert and later a priest, in whose poetic collections "Heilige Seelenlust" and "Der cherubinische Wandersmann" mysticism again finds a noble expression. Another Jesuit poet, Jacob Balde (1604-68), did his best work in Latin, though his German poems are not without merit. The novel began to flourish in the seventeenth century. The heroic and gallant romance, of which Lohenstein was the chief exponent, was high in favour with aristocratic society, but of small literary value. The romances of roguery, coming in under Spanish influence, were far better. The prose classic of the century is the "Simplicissimus" of Christoph von Grimmelshausen (d. 1676), a convert to Catholicism. In the form of an autobiography it unfolds a vivid and realistic picture of the period of the Thirty Years War. Defoe's "Robinson Crusoe" brought forth a flood of imitations, of which Schnabel's "Die Insel Felsenburg" was the best. Satire is represented by Christian Reuter's "Schellmuffskys Reisebeschreibung" (1696) and the writings of Johann Balthasar Schupp, a Lutheran pastor of Hamburg (d. 1661), as well as those of Ulrich Megerle, known as Abraham a Sancta Clara (1644-1709), who as court preacher at Vienna was noted for his wit and drollery. German prose began now to be used for philosophy and science. The pioneers in this line were Christian Thomas and Christian Wolff, who inaugurated the Rationalistic movement in Germany. At the beginning of the eighteenth century German literature was still in a low state. The drama especially was in a bad plight, coarse farces with the clown in the leading role being most in favour. A reform was attempted by the Leipzig professor, Johann Christoph Gottsched (1700-66). His intentions were praiseworthy, but unfortunately he was anything but a poet. Poetry for him was a matter of the intellect; its aims were to be practical. For the mysterious and the wonderful he had no use. Good taste was to be cultivated by imitating the French classic drama, which was supposed to be the best exponent of the practice of the ancients. Gottsched's literary dictatorship was undisputed until he became involved in a controversy with the Swiss critics, Bodmer and Breitinger, who insisted on the rights of imagination and feeling and held up the English poets as better models than the French. Gottsched was defeated and in consequence lost all authority. Slowly poetry began to improve. This improvement is distinctly noticeable in the descriptive poem "Die Alpen" of Albrecht von Haller (d. 1777) and the graceful verse of Friedrich von Hagedorn (d. 1754). The most popular author of the day was Christian Fuerchtegott Gellert (1715-69), whose fables were familiar to every German household. He also wrote stories, moralizing comedies, and hymns. But neither these writers nor those of the Halle circle, Johann Wilhelm Ludwig Gleim, Ewald Christian von Kleist, and Johann Peter Uz, were in any sense great writers. VII. THE CLASSIC PERIOD OF GERMAN LITERATURE (1748-1805) Many causes contributed to the rise of a great national literature in the eighteenth century. The victories of the Prussian King Frederick the Great quickened national sentiment in all German lands. This quickening of patriotism is discernible in Klopstock's poems; it encouraged Lessing to begin his campaign against the rule of French classicism. Religious movements also exerted a powerful influence. Pietism came as a reaction against the narrow Lutheran orthodoxy then prevailing, and though it ultimately added but one more petty sect to those already existing, the deepening of religious sentiment that followed it was beneficial to poetry. With the appearance in 1748 of the three opening cantos of "Der Messias" a new era opened for German literature. The author, Friedrich Gottlieb Klopstock (1724-1803), was hailed at once as a poet born not made. Poetry again had a noble content: love, patriotism, and religion. The theme of the "Messias" is the Redemption. In spite of its high seriousness and lofty purpose, the poem is a failure as an epos. Klopstock's gift was lyric; he is at his best in his odes. Impatient of the pedantic rules of versification followed by poets since the days of Opitz, he discarded rhyme altogether and chose for his odes antique metres and free rhythms. This, as well as their involved diction, has stood in the way of their popularity. Another defect that mars all of Klopstock's work is its excessive sentimentalism, a defect that is disagreeably noticeable in most of the literature of that time. The poet's patriotism found vent in odes as well as in patriotic prose dramas, the so-called Bardiete, in which an attempt was made to revive Germanic antiquity and to excite enthusiasm for Arminius, the liberator of ancient Germany from Roman subjugation. As drama these productions are utter failures, though their lyric passages are often beautiful; their chief effect was to stimulate the "bardic" movement represented by von Gerstenberg, Kretschmann, and the Viennese Jesuit Denis. Klopstock's Biblical dramas like "Der Tod Adams" (1757) are now wholly forgotten. Of far greater influence on literature than pietism was rationalism, whose watchword was "Enlightenment." Reason was to be the sole guide in all things; tradition and faith were to conform to it. For dogma of any kind there was no room in such a system, which frequently tended towards undisguised atheism, as with the English Deists and especially the French Encyclopedists. Frederick the Great was an adherent of their views and made them dominant in Church and State as far as Prussia was concerned. In Germany, however, rationalism did not go to the length of atheism; as a rule a compromise between reason and revealed religion was attempted. The broad humanitarianism of the great writers of this period, Lessing, Herder, Goethe, Schiller, shows the influence of the Enlightenment. Certain it is that all these writers were out of sympathy with any of the orthodox forms of Christianity. Often, however, the Enlightenment degenerated into a shallow, prosy rationalism, destitute of all finer sentiment, as in the case of the notorious Nicolai (d. 1811). As a reaction against the one-sided sway of rationalism, came a passionate revolt against the existing order. This revolt was inaugurated by Rousseau and manifested itself in German literature in the Sturm-und-Drang-Periode (Storm and Stress Period). The final product of the whole rationalistic movement was the epoch-making "Critique of Pure Reason" of Immanuel Kant. The representative of the Enlightenment in its best aspect is Gotthold Ephraim Lessing (1729-81), one of the greatest critics of the century. In the "Literaturbriefe," a series of essays on contemporary literature, his wonderful critical ability was first shown. Here Shakespeare is held up as a model and the supremacy of the French drama is challenged. In 1766 appeared the "Laokoon," in which the spheres of poetry and the plastic arts are clearly defined, and their fundamental differences pointed out. The attempt to establish a national theatre at Hamburg resulted in the "Hamburgische Dramaturgie" (1767-69), wherein Lessing investigates the nature of the drama, and refutes the claim of the French that their classic drama is the true exponent of the practice of the ancients. The rules of Aristotle are accepted as final, but it is shown that the French have misunderstood them, and their German imitators are therefore doubly in error. With all its one-sidedness, the polemic was fruitful for it put an end to pseudoclassicism and made a national German drama possible. Lessing led the way. His "Miss Sara Sampson" (1755) is the first bourgeois tragedy of the German stage. It was followed by "Minna von Barnhelm" (1767), the first German national drama, on a subject of contemporaneous interest with the Seven Years War for a background, and by "Emilia Galotti," the first classic German tragedy (1772) as an adaptation to modern conditions of the story of Appius and Virginia. Lessing's last drama "Nathan der Weise" (1779) was the outcome of the theological controversy in which he had been involved, through the publication of the Wolfenbuettel fragments. These had been written by Reimarus and contained a bold attack on Christianity and the Bible. A bitter feud between Lessing and Göze, the champion of Lutheran orthodoxy, was the result in the course of which Lessing wrote a number of polemics in which he asserted that Christianity could exist without, and did exist before, the Bible. When a decree of the Duke of Brunswick forbade further discussion, he had recourse to the stage, and wrote his "Nathan." In this he uses Boccaccio's famous parable of the three rings to enforce the thesis that there is no absolutely true religion. Not faith, but virtuous action is the essence of religion, and all religious systems are equally good. For a dogmatic religion there is, of course, no room in this view, which is a frank expression of Lessing's deistic rationalism. His last prose works, notably "Die Erziehung des Menschengeschlechts" (1780), are philosophical in character and treat of ideas related to those expressed in "Nathan." A contrast to Klopstock's "seraphic" sentimentalism is offered in the sensualism of Christopher Martin Wieland (1733-1813). He began as a fervid pietist and admirer of Klopstock, and under the influence of rationalism passed to the opposite extreme of sensualism tinged with frivolity before he found his level. His "Agathon" is the first German Bildungsroman, presenting a modern content in ancient garb, a method also followed in the "Abderiten" (1780), in which the provincialism of the small town is satirized. His masterpiece is the romantic heroic epic "Oberon" (1780), for which he drew his inspiration from the old French romance "Huon de Bordeaux." His last work, "Aristipp," is a novel in epistolary form, like the "Agathon" in dress, but otherwise modern. Wieland was not a great poet, but the smooth graceful style of his writings and their pleasant wit did much to win the sympathy of the upper classes for German literature. While Wieland's influence on German literature has been small, that of Johann Gottfried Herder (1744-1803) was decisive and far-reaching, less through his own writings than through the new ideas he proclaimed and the influence of his personality on others, notably Goethe. Rousseau's summons to return to nature was applied by Herder to poetry. Not imitation, but native power makes the poet. Poetry was to be judged as the product of historic and national environment. Natural and popular poetry like the folk-song was preferred to artistic poetry. These views were developed in a series of essays "Fragmente ueber die neuere deutsche Literatur" (1767) and "Kritische Waelder" (1769) and were still further elaborated in essays on Ossian and Shakespeare in "Von deutscher Art und Kunst einige fliegende Blätter" (1773). Then followed "Stimmen der Voelker in Liedern" (1778), a collection of 182 folk-songs from every age, clime, and nationality. Herder's skill translator or adapter is exhibited here, as also in "Der Cid," a free version from the Spanish through the medium of the French. His original poems, mostly parables and fables, are of little importance. Herder, the founder of the historical method, could not but be hostile to rationalism with its unhistoric methods and one-sided worship of reason. In "Vom Geiste der hebraeischen Poesie" (1783) he showed what a wealth of poetry the Bible contained. In his last work, "Ideen zur Philosophie der Geschichte der Menschheit" (1784-91), the history of the human race is regarded under the aspect of evolution; humanitarianism is the ultimate goal of religious development. This work pointed out the way for the philosophical study of history. The effect of the work of Klopstock, Herder, and Lessing was immediate. The national movement was taken up by the "Göttinger Hain" poets, of whom the best-known are Johann Heinrich Voss (d. 1826), the translator of Homer, Ludwig Heinrich Christoph Hoelty (d. 1776), the elegiac singer, and the two brothers Stolberg. Connected with them, though not members of the circle, were Matthias Claudius (d. 1815) and the gifted but dissolute Gottfried August Buerger (d. 1794), the ballad writer, whose "Lenore" (1773) has become widely known. The protest voiced by Rousseau against the existing social order produced in German letters the so-called Sturm und Drang (Storm and Stress) movement, which dominated the decade (1770-80). It was a passionate revolt against conventional traditions and standards and manifested itself in the wild dramatic products of such men as von Klinger, Friedrich Müller or Maler Müller, and Lenz, and the lyric effusions of Schubart (d. 1791). But the movement found its best expression in the early work of Germany's greatest poets, Goethe and Schiller. Johann Wolfgang Goethe (1749-1832) while a student at Strasburg had come under Herder's influence and come under Herder's influence and caught the revolutionary spirit. In his "Goetz von Berlichingen" (1773), the first great historical German drama, the poet gave vent to his dissatisfaction with the social and political conditions of his time. In spite of its irregular form, due to a misguided enthusiasm for Shakespeare the national content of the drama and the forceful diction carried the public by storm. Its popularity was exceeded by "Die Leiden des jungen Werthers" (1774), a novel in letter form, reflecting the morbid sentimentalism of the age; the hero kills himself under the spell of a hopeless passion for the affianced of his friend. The years from 1775 to 1786 were not so fruitful; political and social activity interfered with literary production. The spirit of storm and stress gradually subsided and gave way to the classicism which, especially after his return from Italy (1788), left its stamp on all of Goethe's subsequent work. The apostle of this neo-Hellenism was Johann Joachim Winckelmann (d. 1768), the founder of the historical study of art. He postulated the canons of ancient Greek art as absolute. The classicism that he inaugurated was directly opposed in spirit to the national tendency championed by Herder. Lessing's work had shown the influence of this neo-Hellenism. Now Goethe became its pronounced follower. The works that he wrote under its influence exhibit perfection of form, notably the dramas "Egmont" (1788), "Iphigenie auf Tauris" (1787), and "Torquato Tasso" (1790). Goethe's literary productions during this period, before 1794, are not numerous; they include the "Romanische Elegien" and the epic "Reineke Fuchs" (1794), a free version in hexameters from the Old Low German. The dramas that arose under the influence of the French Revolution are not very important. In fact Goethe's chief interests at this time were scientific rather than literary. After 1794, however, under the inspiration of Schiller's friendship, the poetic impulse came with new strength. The period of Goethe's and Schiller's friendship (1794-1805) marks the climax of the poetic activity of these two great men. The satiric epigrams known as "Xenien" were the fruit of their joint activity. Then followed a number of their finest ballads. In 1796 Goethe completed "Wilhelm Meisters Lehrjahre," a novel of culture, discursive and didactic, with the stage for its principal theme. The exquisite idyllic epic, "Hermann und Dorothea" (1797), though written in hexameters, is thoroughly German in spirit and subject-matter. After Schiller's death (1805) Goethe's poetic productivity decreased. Some fine lyrics produced in this period are in the "Westoestliche Divan" (1819), a collection of poems in Oriental garb. Most of the poet's work now was in prose. "Die Wahlverwandtschaften" (1809), a psychological novel, depicts the tragic conflict between passion and duty and upholds the sanctity of the marriage tie. In the autobiographical romance "Dichtung und Wahrheit" (1811-33) the poet tells with poetic licence the story of his life. A number of stories were loosely strung together in "Wilhelm Meisters Wanderjahre" (1821), a long didactic novel given over largely to the discussion of ethical and sociological problems. The greatest work of Goethe and of German literature is "Faust," a dramatic poem, the composition of which occupied the poet's entire life. The idea was conceived while Goethe was still a young man at Frankfurt; a fragment containing the Gretchen episode appeared in 1790. Under the stimulus of Schiller's sympathy the first part was completed and published in 1806. The second part was not finished until eight months before the poet's death. It is a colossal drama with humanity for its hero. Weak human nature may fall, under temptation, but its innate nobility will assert itself triumphantly in the end. Faust atones for his errors by a life devoted to altruistic effort, and so his soul after all is saved. The Catholic atmosphere of the closing scene, where the penitent Gretchen intercedes with the Virgin for her lover, betrays the influence of the Romantic School. If Goethe is the man of universal gifts, Johann Christoph Friedrich Schiller (1759-1805) is preeminently a dramatist. He too received his first impulse from the Storm and Stress movement. His first three dramas, "Die Raeuber" (1781), "Fiesco" (1783), and "Kabale und Liebe" (1784), breathe a spirit of passionate revolt. With all their youthful exaggeration, they reveal unmistakable dramatic power. In "Don Carlos" a calmer spirit reigns and a greater mastery of form is evident. Freedom of thought is the burden of its message. The composition of this work had turned Schiller's attention to history, and for a time the study of history and philosophy got the better of poetic production. The historical works that are the outcome of these studies are valuable rather for their style than as original contributions. Goethe's study of Kant's philosophy was responsible for a number of works of an aesthetic character, notably "Über naive und sentimentalische Dichtung," where naive and sentimental are taken as typical of ancient and modern respectively. His friendship with Goethe (1794-1805) won Schiller back to poetry and now followed in rapid succession his dramatic masterpiece: "Wallenstein," a trilogy, the first historic German tragedy in the grand style (1796-99), "Maria Stuart" (1800), and "Die Jungfrau von Orleans "(1801), a noble defence of the Maid of Orléans against the slanders of Voltaire. "Die Braut von Messina" (1803) is a not altogether successful attempt to combine modern spirit with antique form. The poet's last great drama, "Wilhelm Tell" (1804), is, perhaps, the most popular German play. Here he reverts again to the idea of freedom which he championed so passionately in his youthful dramas, and which here found its most convincing expression. The grandly conceived tragedy "Demetrius" remained a fragment, owing to the author's untimely death (1805). As a lyric poet Schiller is far below Goethe. His lyrics lack spontaneity; they are rather the product of reflection and are mostly philosophic in character. His masterpiece in this line is "Das Lied von der Glocke" (1800). He also excels in epigram and gnomic verse, and as a writer of ballads he has few equals. The great classic drama by no means immediately won its way. Besides the opera, the bourgeois drama ruled the stage and its most popular representatives were Iffland and Kotzebue. The plays of these writers were thoroughly conventional in tone; those of Kotzebue had a distinctly immoral tendency, but they were theatrically effective and immensely popular. Of prose writers contemporary with Goethe we may mention the historians, Justus Möser (d. 1794) and Johannes von Müller (d. 1809). In philosophy the commanding figure is Immanuel Kant, whose work has exerted a tremendous influence on modern thought. Alexander von Humboldt's (1769-1859) "Kosmos" is a classic of natural science. In the field of the novel, Jean Paul Friedrich Richter (1763-1825) achieved distinction. His writings, "Quintus Fixlein," "Hesperus," "Titan," and others were enormously popular in their day, but owing to their bizarre style and absolute formlessness, joined to an unbearable discursiveness, they have lost all charm for modern readers. The unfortunate Friedrich Hoelderlin (1770-1843) combined the classic with the romantic spirit in unique fashion. His passionate longing for the lost beauty of ancient Greece was expressed in his novel "Hyperion," as well as in some noble lyrics. VIII. ROMANTICISM AND THE ERA OF REVOLUTION (1805-1848) With the beginning of the nineteenth century the revolt against the Aufklärung (Enlightenment), started by Herder, reasserted itself. There was also a marked revival of religious sentiment. The Romantic School rose into prominence. Art was to be rescued from the sway of rationalism; imagination and emotion were to be set free. Taking as a basis Fichte's philosophy, which proclaimed the ego as the supreme reality, the romanticists proceeded to free creative genius from the barriers of convention and tradition. But the result was often an extreme subjectivism that broke through the restraints of artistic form and lost itself in fantastic visions and vague mysticism. The leaders of the movement turned away from a sordid present to far-away Oriental regions, or to a remote past like the Middle Ages. This predilection for medievalism coming together with the religious revival gave to the romantic movement a pronounced Catholic tendency. Some of the leading romanticists, Brentano, Görres, Eichendorff, were Catholics; others, like Friedrich Schlegel, became Catholics. Sympathy for Catholicism is noticeable in the work of all the members of the school. The Romantic movement was also a salutary reaction against the excessive classicism of Goethe and Schiller. The national element was again emphasized. The Middle Ages, depreciated and misrepresented ever since the Reformation, were now shown in a fairer light by historians like von Raumer, Wilken, Voigt, and others. The great medieval literature was rediscovered by scholars like Jakob and Wilhelm Grimm and Lachmann. In fact, the science of Germanic philology owes its origin to the Romantic School. The enthusiasm for foreign literature also bore rich fruit in masterly translations and reproductions. Here lies the main significance of much of the work of the brothers Schlegel, the critical leaders of the Older Romantic School. August Wilhelm von Schlegel (1767-1845) is famous as a translator. His translations of Shakespeare have become German classics, while his renderings from the Spanish (Calderon, Lope de Vega), Italian, and Sanskrit are hardly less meritorious. His brother, Friedrich von Schlegel (1772-1829), who became a convert to Catholicism, enunciated the romantic doctrines in his aphorisms. Through his treatise, "Über die Sprache und Weisheit der Indier" (1808) he became the pioneer of Sanskrit studies in Germany. The work of the Schlegels in criticism and literary history was epoch-making; they taught critics not merely to criticize, but to understand, to interpret, to "characterize." The school found no really great poet to put its theories into practice. Still the poetry of Friedrich von Hardenberg (1772-1801), better known as Novalis, is pervaded by deep feeling. His fragmentary novel "Heinrich von Ofterdingen" is an attempt to show the development of a true romantic poet. Ludwig Tieck (1773-1853) revived the old folk-books, satirized the Enlightenment in his comedies, wrote romantic dramas of no great value, like "Genovera," and a novel of culture "Franz Sternbalds Wanderungen," which had much influence on German painting. After 1821 he turned to the short story, which he was the first to cultivate with success. A second group of romantic writers, the Younger Romantic School, gathered chiefly at Heidelberg. With them the national tendency is more pronounced. Their work shows great talent, but is often spoiled by a lack of artistic restraint. Especially is this the case with Klemens Maria Brentano (1778-1842), a highly poetic but very eccentric character, who together with Achim von Arnim collected and edited an important book of folksongs, "Des Knaben Wunderhorn" (1805-8). Their friend Joseph von Görres (1776-1848), during his period of ardent patriotism, edited old German songs and folk-books; his later activity was largely devoted to the service of the Catholic Church, which found in him a zealous champion. The patriotic tendency is much in evidence in the work of Friedrich de la Motte Fouque (1777-1843), whose fantastic chivalric romances are forgotten, while his fairy-tale "Undine" still lives. The only dramatic poet of a high order connected with the Romantic School is Heinrich von Kleist (1777-1811), among whose dramas "Der Prinz von Homburg" (1810) is regarded as his masterpiece. His novels, of which "Michael Kohlhaas" is the best known, show a graphic power. Zacharias Werner (1768-1823), who ultimately became a Catholic, is chiefly known as the originator of the so-called "fate-tragedies," a gruesome species of dramas, in which blind chance is the dominating factor. Characteristic of decaying romanticism are the weirdly fantastic stories of E.T.A. Hoffmann (1776-1822). The influence of the romantic movement continued for some time after the movement had spent itself as a living force. Almost all the poets of the first half of the nineteenth century were more or less affected by it. The national tendency fostered by romanticism was transformed by the Wars of Liberation into patriotic fervour which found expression in the stirring lyrics of Max von Schenkendorf, Theodor Koerner, and Moritz Arndt. The poets of the Swabian School, who were romantic only in so far as they leaned towards medieval or religious subjects, excelled particularly in the ballad. Their leader was Ludwig Uhland (1787-1862), distinguished as poet and scholar. Besides him there were Justinus Kerner and Gustav Schwab. Some of Kerner's and Uhland's lyrics have become veritable Volkslieder. Romanticism cast its spell over the lyric, which occupies a large space in the literature of this period. Prominent in this field were Adelbert von Chamisso, Wilhelm Müller, and Joseph von Eichendorff, a Catholic nobleman of Silesia, the most gifted lyrist of the group. Friedrich Rückert (1788-1866) was a voluminous but unequal writer of verse; his fame rest largely on his translations and imitations of Oriental poetry, the difficult forms of which he reproduced with amazing skill. In this he was followed by Count August von Platen (1796-1835), in whose verses form reached perfection, often to the detriment of feeling. The greatest lyric poet, and the most striking literary figure of the day, was Heinrich Heine (1797-1856), a Jewish convert to Protestantism. Unfortunately, his great gifts are marred by the insincerity and immorality of his character; his finest poetic efforts are often impaired or destroyed by a wanton, mocking irony. His prose works, for the most part fragmentary and journalistic in character, are written in a graceful, easy style, and with brilliant wit. The miserable political conditions of Germany were the object of Heine's bitterest satire; but unfortunately religion and morality also became a target for his mockery and cynical wit. Great as his influence was on literature, on the whole it was pernicious. His poems appeared in different collections under the titles of "Buch der Lieder," "Neue Gedichte," and "Romanzero." Of his prose writings the "Reisebilder" (1826) are the best. Another romantic lyrist of the highest order was the Austrian, Nikolaus Lenau (Niembsch von Strehlenau), the poet of melancholy. A strong individuality, uninfluenced by the literary currents of the day, reveals itself in the work of a noble Catholic lady, Annette Elisabeth von Droste-Huelshoff (1797-1848), whose writings throughout show a deeply religious spirit. Her collection entitled "Das geistliche Jahr," poems appropriate for the Sundays and Holy Days of the Catholic year, contains some of the finest religious poetry in the German language. Another genius who stood apart from the currents of the day was Franz Grillparzer (1791-1872), Austria's greatest dramatist. In his work classic and romantic elements were united. Of his many dramatic masterpieces we only mention "Die Ahnfrau," "Sappho," "Das goldene Vliess," "Des Meeres und der Liebe Wellen," and "Der Traum ein Leben." His compatriot, Ferdinand Raimund, is the author of plays deservedly popular. The dramatic productions of Christian Grabbe were too extravagant and erratic to be performed. The most popular playwright of that day, Ernst Raupach, is now forgotten. The historical novel rose into favour during this period, largely through the influence of Sir Walter Scott. Von Arnim and Tieck had tried their hand at this genre, to be followed by Wilhelm Hauff, the author of "Lichtenstein" (1826) and Willibald Alexis (pseuonym for Wilhelm Haering). The latter took his subjects from Prussian history and gave the novel a patriotic tendency. A significant change is marked by the novels of Karl Immermann (1796-1840), who in "Die Epigonen" and "Muenchhausen" (1838) treated contemporary conditions in a satiric vein. The episode of the "Oberhof" in the latter work introduced the village and peasant story into German literature. In this field, Jeremias Gotthelf (Albert Bitzius) and Berthold Auerbach won success. Charles Sealsfield (Karl Postl) is known as a writer of novels of travel and adventure. The hopes that patriots in 1815 had cherished of a united German had been rudely dispelled. Freedom of thought had been suppressed by the political reaction typified by the Metternich regime. The smouldering discontent broke forth violently at the news of the Paris Revolution (1830) and found its literary expression in the movement known as "Young Germany." The relentless war that was carried on against the existing political order was also directed against religion and morality. The "emancipation of the flesh" was openly proclaimed. Heine had led the attack, and the members of the coterie followed with essays, novels, and dramas, which for the most part, owing to their political and social character, were shortlived. Karl Gutzkow (1811-78) is the leading figure of the coterie. His novels, with their anti-religious and immoral tendencies, have to-day only historical interest, while his dramas, of which the best known is "Uriel Acosta" (1847), are theatrically effective. Next to Gutzkow in prominence was Heinrich Laube (1806-84), whose best work, however, was done as a dramatist and not as a partisan of Young Germany. Women also took part in the movement. Of these the most notable are the Jewess, Fanny Lewald, whose writings display a decided anti-Christian spirit, and Countess Ida von Hahn-Hahn, who began her literary career with novels of high life in which matrimony is treated with levity, and ended by becoming a devout Catholic. The spirit of revolution inaugurated by Young Germany soon assumed a definite political character and dominated the literary activity from 1840 to the outbreak of 1848. It found its most eloquent expression in the political lyric. In Austria Anastasius Gruen (pseudonym for Count Anton Alexander von Auersperg), Karl Beck, Moritz Hartmann, and Lenau were most prominent in this line; in Germany Herwegh, Hoffmann von Fallersleben, Franz von Dingelstedt, Ferdinand Freiligrath (1810-76), and Gottfried Kinkel were the political leaders of the malcontents. Much of this poetry was necessarily ephemeral; in fact Kinkel, Fallersleben, and Freiligrath owe their fame to their verses not political in character. In the poetry of Count Moriz von Strachwitz and Karl Simrock, the excellent translator of Old German literature, a reaction against the political tendency in literature and in favour of romanticism is evident. The short stories of Adalbert Stifter and the dramas of Friedrich Halm (Freiherr von Muench-Bellinghausen) also show the romantic tinge. The greatest lyrist of the age, Eduard Moerike (1804-75), a Swabian, went his way wholly unconcerned with the questions of the day. IX. MODERN GERMAN LITERATURE (SINCE 1848). NEW AIMS. POETIC REALISM. NATURALISM. The year 1848 marks a great change in the political and literary history of Germany. The great question of German unification now loomed in the foreground, and though a reaction had set in after the revolutionary outbreak, liberal ideas were strong, and interest in political questions was keen. Literature sought to get more in touch with life, and became less exclusively aesthetic. The materialistic tendencies of the age were reflected in and conditioned by the great progress of science and the rise of journalism. The lyric and epic lost ground to the drama and the novel. The classic-romantic tradition still found many followers. In fact, after the turbulence of the Revolution came a return to a more formal and aesthetic art, which, however, kept more or less in touch with the life of the age. An enormous array of names confronts the student of the literature of this period, but only a relatively small number call for notice. The most prominent lyric poet now was Emanuel Geibel (1815-84), whom poems are distinguished by beauty of form and dignified, patriotic sentiment. He was the leader of the Munich group, which numbered among others Count Adolf von Schack, the art connoisseur and distinguished translator of Firdausi, Herrmann von Lingg and Julius Grosse, the epic poets, Friedrich von Bodenstedt, whose enormously popular "Mirza Schaffy" songs continued the Oriental fashion inaugurated by Goethe's "Divan." The work of one of this group, Paul Heyse, a masterly writer of short stories, is characterized by extreme elegance of form and diction. In his novel "Kinder der Welt" (1873), however, these fine qualities cannot conceal atheistic and immoral tendencies. Among the writers of this period none achieved such popularity as Joseph Victor von Scheffel, with his romantic epic, "Der Trompeter von Saeckingen" (1854) and his historic novel "Ekkehard" (1855). The lyric-epic poem "Amaranth" (1849) of the Catholic Baron Oskar von Redwitz owed its success more to its religious feeling than to any real merit. The neo-romantic productions of other Catholic poets like Behringer, Wilhelm Molitor, and Maria Lenzen failed to make a lasting impression. A Catholic poet of this period who won a permanent place was the Westphalian, Friedrich Wilhelm Weber (1813-94), author of the epic "Dreizehnlinden." A pessimistic atmosphere pervades the Austrian Robert Hamerling's epic, "Ahasver in Rom" (1866). "Die Nibelungen" of Wilhelm Jordan is a noteworthy attempt to revive the great medieval saga in modern alliterative form. This was accomplished with brilliant success by Richard Wagner (1813-83), whose music dramas are among the greatest achievements of modern German art. A result of the more serious view of life was the new realism that strove to present life truthfully, stripped of the conventional phraseological idealism that had been the vogue since Schiller. This realism manifested itself chiefly in the drama and novel. In the former field its most eminent representative is Friedrich Hebbel (1813-63) with his powerful tragedies "Maria Magdalena," "Herodes und Mariamne," "Gyges und sein Ring," and "Die Nibelungen." Otto Ludwig (1813-65) followed with "Der Erbfoerster" and "Die Makkabaeer," as well as the masterly romance "Zwischen Himmel und Erde." These dramas found little favour at the time of their appearance; the realistic novel fared better. Gustav Freytag (1816-95) won great success with "Soll und Haben," (1855), a novel of bourgeois life. Fritz Reuter (1810-74) used his native Low German dialect for his popular humorous novels, the most important of which are included in "Olle Kamellen" (1860-64). Great originality marks the work of the Swiss, Gottfried Keller (1819-90), regarded by many as the master-novelist of the period. His best production is the series of novels from Swiss life entitled "Die Leute von Seldwyla" (1856). The literary-value of the work of Friedrich Spielhagen (b. 1829), a novelist of undoubted talent, is impaired by its undue treatment of social and political questions, while the great favour accorded to the antiquarian novels of Georg Ebers and Felix Dahn cannot hide their literary defects. Midway between romanticism and realism stands Theodor Storm (1817-88), whose great poetic talent is shown no less in his heartfelt stories, such as "Aquis Submersus." Fiction began to occupy a larger place in literature especially after 1870. We mention only the Swiss, C.F. Meyer, who excels in the historical novel, and Theodor Fontane, whose later works were thoroughly modern and realistic. Peter Rosegger, a Styrian, has won fame with his village stories. Of the numerous women-writers of fiction, the most gifted are Luise von Francois and Marie, Baroness von Ebner-Eschenbach. The chief activity of the last-mentioned writers belongs to the period after 1870. The Franco-German War of 1870 and the establishment of the new empire had comparatively little effect on literature. Poetry continued to move largely in the old classic-romantic grooves. The graceful but trivial lyrics and epics of Rudolf Baumbach, Julius Wolff, and other imitators of Scheffel's manner best suited popular taste. The passionate lyrics of Prince Emil zu Schoenaich-Carolath deserved their success. The poetry, however, of Martin Greif Eduard von Paulus, Christian Wagner, and Heinrich Vierordt was slow to win recognition. The decade following the great victories of 1870 was not favourable to literary activity. For the moment political, social, and religious questions (as in Kulturkampf) were dominant. A spirit of agitation and unrest was abroad. Much of the literature of the time was partisan and polemic, or else catered to the materialistic taste that prevailed and merely aimed to entertain. Of this kind were the dramas of Paul Lindau, cut according to French patterns, and presenting pictures from decadent Parisian life. The more serious drama, favouring historical subjects and affecting the conventional manner of Schiller, is best represented by Ernst von Wildenbruch. By far the most original dramatist was the Austrian, Ludwig Anzengruber (1839-89), whose dramas, "Der Pfarrer von Kirchfeld," "Das vierte Gebot," etc. received almost no recognition until after 1880. The only factors that helped to counteract the materialism and commercialism that ruled the stage were the model performances of the Meiningen troupe and the uncompromising seriousness of Richard Wagner's artistic activity, as demonstrated in the festival performances of Bayreuth. The mediocrity into which literature had fallen by 1880, its empty formalism, and conventional character, produced another literary revolt, a "Youngest Germany." Poetry was to become more modern. The questions of the day were to be its concern, the faithful reproduction of reality its aim. Instead of harking back to the realism of a Hebbel or Ludwig, the leaders of this movement looked to foreign models for inspiration, to the works of Ibsen, Tolestoy, Dostoyevsky, and Zola. The realism there found was copied and exaggerated, and the result was a crude naturalism which unduly emphasized the mean, the ugly, and the vulgur. The pessimistic philosophy of Schopenhauer and especiaily the revolutionary doctrines of Nietzsche added their unwholesome influence and tended towards a perversion of ethical and moral standards. The activity of the movement was at first mainly negative and polemical. Its literary creations have already lost interest. Real literature was not produced until the extreme views were modified. As a reaction against naturalism "symbolism" made its appearance; but the art which it inspired is apt to be so intangible and hyper-aesthetic as to be limited for appreciation to a narrow and exclusive circle. In the dramatic field Herrmann Sudermann (b. 1857), whose novels "Frau Sorge" (1887) and "Der Katzensteg" (1889), had already attracted attention, won great success. His plays "Die Ehre," "Heimat," "Es lebe das Leben," and others, are very effective, but marred by sensationalism. Sudermann is not a representative naturalist; his technic is a compromise between the older practice and the new theories. A thoroughgoing naturalist is Gerhart Hauptmann (b. 1863) in his first dramas "Vor Sonnenaufgang" (1889) and "Die Weber" (1892). Here the milieu is more important than character or action. In his comedies "Kollege Crampton" and "Der Biberpelz" he showed that naturalism did not preclude humour. His most famous play, the fairy-drama "Die versunkene Glocke" (1896), like "Hanneles Himmelfahrt" before, and "Der arme Heinrich" afterwards, marks a significant turning towards symbolism and neo-romanticism. So far "Fuhrmann Henschel" (1898) is the dramatic masterpiece of naturalism. Of other dramatists of this school mention may be made of Max Halbe (b. 1865), author of "Jugend" (1893) and Otto Erich Hartleben, whose "Rosenmontag" (1900) shows Sudermann's influence. A popular dramatist, though of no particular school, is Ludwig Fulda; his plays, of which "Der Talisman" (1892) is the best known, are pleasing but shallow. The new romanticism, which is exemplified by the dreamy poetry of Maeterlinck, was even less able than naturalism to produce a vital drama. The productions of Hugo von Hofmannsthal (b. 1874) are wholly undramatic, revelling in emotion and devoid of action. His proper field is the lyric, where his talents as well as those of Stefan George (b. 1868) find scope. Symbolism has found its most characteristic expression in the rapturous and vague lyric effusions of Richard Dehmel (b. 1863). After all the best lyric poets of the present are those who do not affect any particular fashion. Such are Detlev von Liliencron, a realist of great power, regarded by many as the foremost German lyrist of to-day, Gustav Valke, Ferdinand Avenarius, Karl Busse, Otto Julius Bierbaum and Anna Ritter. Freiherr Boerries von Muenchhausen has written masterly ballads. The novelistic literature has grown to enormous proportions, and shows a host of names. Naturalism asserted itself in the novels "Meister Timpe" (1888) and "Das Gesicht Christi" (1897) of Max Kretzer, as well as in the earlier work of Wilhelm von Polenz (1861-1903). With Polenz, however, naturalism has developed into artistic realism, as evidenced by his last novels "Thekla Luedekind" (1899) and "Wurzellocker" (1902). In addition mention may be made of Gustav Frenssen, whose "Jörn Uhl" (1901) gained an enormous success, Adolf Wilbrandt, Thomas Mann, Wilhelm Speck, Georg von Ompteda and Walter Siegfried. Prominent among women writers of fiction are Isolde Kurz, (b. 1853), Helene Boehlau, Marie Eugenie delle Grazie; Carmen Sylva (Queen Elizabeth of Rumania) and above all Ricarda Huch (b. 1867), whose great novel "Erinnerungen von Ludolf Ursleu" (1893) stands in the front rank of modern fiction. For bibliography the standard work is GOEDEKE, Grundriss zur Geschichte der deutschen Dichtung (2nd ed., GOETZKE, Dresden, 1884—). Useful also are BARTELS, Handbuch zur Geschichte der deutschen Literatur (2nd ed., Leipzig, 1909); BREUL, Handy Bibliographical Guide to the Study of the German Language and Literature (London, 1895). For modern German literature NOLLEN, A Chronology and Practical Bibliography of Modern German Literature (Chicago, 1903) will be found helpful. Of general histories the best are: KOBERSTEIN, Grundriss der Geschichte der deutschen Nationalliteratur (6th ed., 5 vols., ed. BARTSCH, Leipzig, 1884—); GERVINUS, Geschichte der deutschen Dichtung (5th ed., 5 vols., ed. BARTSCH, Leipzig, 1871-74); WACKERNAGEL, Geschichte der deutschen Literatur, ed. and continued MARTIN (2 vols., Basle, 1879-94); SCHERER, Geschichte der deutschen Literatur (10th ed., Berlin, 1905); tr. MRS. CONYBEARE (2 vols., Oxford, 1885); VOGT AND KOCH, Geschichte der deutschen Literatur von den aeltesten Zeiten bis zur Gegenwart with excellent bibliography and illustrations (2nd ed., 2 vols., Leipzig, 1904). For a presentation from the Catholic point of view consult LINDEMANN, Geschichte der deutschen Literatur (7th ed., SALZER, Freiburg, 1897), and SALZER, Illustrierte Geschichte der deutschen Literatur (Munich, 1908—). Of works written in English the best are: ROBERTSON, A History of German Literature (London and New York, 1902); FRANCKE, History of German Literature as Determined by Social Forces (4th ed., New York, 1901); THOMAS, History of German Literature (New York, 1909), with excellent bibliography. For special topics and periods some of the most important works are HERFORD, Studies in the Literary Relations of England and Germany in the 16th century (Cambridge, 1886); HETTNER, Literaturgeschichte des 18. Jahrhunderts: Part III: Geschichte der deutschen Literatur im 18. Jahrhundert (4th ed., HARNACK, Brunswick, 1893-94). For Lessing consult SCHMIDT, Lessing (2nd ed., 2 vols., Berlin, 1899); for his religious views BAUMGARTNER, Lessings religiöser Entwicklungsgang in Stimmen aus Maria-Laach (Freiburg im Br., 1877). On Goethe see BIELSCHOWSKY (Munich, 1896-1904); tr. COOPER (New York, 1905-08): HEHN, Gedanken ueber Goethe (5th ed., Berlin, 1902); the best known English biography, though somewhat antiquated, is that of LEWES (4th ed., London, 1890). For an estimate from a strictly Catholic point of view see BAUMGARTNER, Goethe, sein Leben und seine Werke (2nd ed., Freiburg im Br., 1885). On Schiller consult the biography by WYCHGRAM, (3rd ed., Leipzig, 1898). Of English biographies that of CARLYLE is well known; the best is that of THOMAS (New York, 1901). On the Romantic School consult HAYM, Die romantische Schule (Berlin, 1870); VAUGHAN, The Romantic Revolt (Edinburgh, 1907). For the nineteenth century consult BARTELS, Die deutsche Dichtung der Gegenwart (7th ed., Leipzig, 1907), written from a strictly national point of view and not without bias; also MEYER, Die deutsche Literatur des 19. Jahrhunderts (2nd ed., Berlin. 1900). Arthur F. J. Remy.
Updated Fri 17 Oct 2014 • tags indic, scriptnotes This article provides an introduction to the major Indic scripts used on the Indian mainland. Those addressed in this paper include specifically Bengali, Devanagari, Gujarati, Gurmukhi, Kannada, Malayalam, Oriya, Tamil, and Telugu. Although the Indic scripts are often described as similar there is a large amount of variation at the detailed implementation level. To provide a detailed account of how each Indic script implements particular features on a letter by letter basis would require too much time and space for the task at hand. Nevertheless, despite the variations at the detailed level, the basic mechanisms are to a large extent the same, and at the general level there is a great deal of similarity between these scripts. It is certainly possible to structure a discussion of the relevant features along the same lines for each of the scripts in the set. It is these common themes that this discussion will attempt to highlight, although we will also point out one or two of the differences along the way. After some historical and phonetic background, we will tackle the subject in two parts: In the first part I will survey the visual characteristics of these scripts. In the second part I will make brief reference to some of the practical ways those characteristics are supported using Unicode. The similarity of features across all these scripts is not surprising if you consider their history. As shown in the illustration below, they all derive from a common ancestor. Note also that these scripts are used for two distinct major linguistic groups, Indo-European languages in the north, and Dravidian languages in the south. The diagram above is an illustration of the derivation of the character NNA, showing how from a common source (Brahmi) all the different forms arose for the modern scripts. The diagram shows an early divergence between North and South Indian scripts. (Adapted from Daniels and Bright, The World's Writing Systems.) One of the defining aspects of a script is the repertoire of sounds it has to support. Because there is typically a letter for each of the phonemes in an Indic language, the alphabet tends to be quite large. The table below shows a superset of Indic consonant sounds in a traditional articulatory arrangement. It is meant to be illustrative rather than exhaustive, so as to give you an idea of the number of sounds most Indic scripts must support. It does not include all sounds, for example a number of Dravidian alveolar sounds are not shown. The table also provides an approximate idea of how Unicode character names map to actual sounds, though it has to be stressed that this is only very approximate. The IPA transcription is shown to the left, followed by the standard Unicode name for that sound. Note the following: \|Flapped & tapped sounds\|\|ɽ\|\|DDDHA\|\|ɾ\|\|RA\| \|Aspirate, semi-vowels and liquid\|\|h\|\|HA\|\|j\|\|YA\|\|ɭ\|\|LLA\|\|l\|\|LA\|\|v\|\|VA\| There are up to 18 Unicode code points dedicated to vowels in each script block, although fewer than this are actually needed on a per language basis. Nearly always these are simple vowel sounds, although occasionally a symbol may represent a diphthong (especially AI and AU). The Unicode names for the whole list are: A, AA, I, II, U, UU, VOCALIC R, VOCALIC L, CANDRA E, SHORT E, E, AI, CANDRA O, SHORT O, O, AU, VOCALIC RR, VOCALIC LL Indic languages are syllabic in nature, and the inherent vowel is an important concept (see below). Unless otherwise indicated, each consonant is typically followed by this vowel sound. The inherent vowel can vary in pronunciation from script to script, and examples include ə, ʌ, and ɔ. Nasalisation of vowels is also an important phonetic feature that affects the written form of several South Asian languages. The effect is similar to the nasalisation of words like 'en' in French. All Indic scripts run left to right, although some combining glyphs appear to the left of their base character for display (see the discussion of vowel signs below). In a number of scripts, characters commonly have a headstroke and a high baseline. Such characters typically hang from the line when written. These scripts are often called abugidas or alpha-syllabaries. In this type of script, consonant characters represent a consonant+vowel syllable. The consonant is associated with an inherent vowel that has to be overridden if it is not the required vowel sound for a particular spoken syllable. For example, the character in Hindi (Devanagari script) is pronounced kə rather than just k. The ə sound is the inherent vowel, and is usually transcribed as 'a'. Note that the inherent vowel is not always pronounced. For example in Hindi it is not usually pronounced at the end of a word, although a ghost echo may appear after a word-final cluster of consonants, eg. jogjə, or ɾəstɾə. In addition Hindi has a general rule that when a word has three or more syllables and ends in a vowel other than the inherent a, the penultimate vowel is not pronounced, eg. səməɟʰ but səmɟʰaː, rəhən but rəhnaː. (For a number of reasons, however, this rule does not always hold.) Nonetheless, on the whole, Indic scripts are close to phonemic transcriptions. The pronunciation of consonants is typically quite regular and predictable, although there is the occasional exception. The following are two examples of exceptions: Example 1: voiced aspirated plosives and the non-initial letter HA in Gurmukhi are used to indicate tones rather than sounds. For example a voiced, aspirated plosive in word-initial position represents an unvoiced unaspirated plosive sound with a low tone on the syllable, eg. kòɽɑ (The primary use of all voiced aspirated plosives in Gurmukhi is to express tone information.) Example 2: in Tamil, consonants such as are typically phonemic rather than phonetic. In practise, this consonant may represent any of kʌ, gʌ, xʌ, ɣʌ, hʌ. Most scripts supplement a basic set of letters with additional letters used to represent the sounds of other languages, such as Sanskrit and English. These additional letters are commonly formed by adding a diacritic to an existing letter. This diacritic is called a nukta in the Unicode Standard, although the name used by speakers of different Indian languages may vary. Some scripts use this diacritic with several basic letters (eg. Devanagari), others not at all (eg. Kannada). Devanagari, qə (cf. kə) Gurmukhi, ɭə (cf. lə) Oriya, ɽʰ (cf. ɖʰ) It is possible to 'kill' the inherent vowel sound where it would normally be pronounced. This is achieved by attaching a small diacritic mark, called a virama in the Unicode Standard, to the consonant in question. Gujarati, k (cf. kə) Tamil, k (cf. kʌ) Telugu, k (cf. kʌ) In the examples that follow, single consonants pronounced without the inherent vowel are depicted with a virama. Where a consonant is followed by a vowel other than the inherent vowel, the change is produced by adding a vowel sign (called a matra in Sanskrit) to the base consonant. A consonant can only support one vowel (and one vowel sign) at a time. A vowel sign may appear to the left or right, above or below the base consonant, and sometimes surrounds the base consonant on more than one side. The following illustrates the use of vowel signs with the consonant in Hindi, and the resultant sounds: kiː ke kuː Vowel signs may also appear to the left of the base consonant they are related to. For example: Gujarati, + -> ki Tamil, + -> kʌy) Occasionally a vowel sign may be composed of multiple parts. In some cases such a split vowel sign may have parts on both the left and right of the base character simultaneously, eg. in Tamil + -> ko. In Kannada there are no vowel signs that surround a base character on both left and right, but there are some that have multiple parts above and following the base character, eg. + -> koː. Another alternative is top and bottom, eg. Telugu + -> kaj. In some cases, the additional parts can be viewed as lengthening marks. Often the pairing of base character and vowel sign produces a change in the basic shape of either base character or vowel sign or both. Tamil provides many such examples, especially with u and uː. For example, the following are a selection of the Tamil consonants, each followed by the same vowel sign, u: \|Without vowel sign\| \|With vowel sign\| Vowels that appear at the beginning of a word or after a preceding vowel with no intervening consonant are typically rendered using independent vowel letters. The following table illustrates the correspondence between the most common independent vowels and vowel signs in Telugu: Note that there is no vowel sign for the sound associated with the inherent vowel A. Vowel signs are only needed to change the inherent vowel. Because a consonant (or consonant cluster) can only support one vowel at a time, note the difference in Devanagari between kiː and kəiː. The first example follows the base consonant with a vowel sign; the second, with an independent vowel. In the second case only, the independent vowel sound is retained immediately after the initial k, and the sequence is pronounced with two distinct vowel sounds. Gurmukhi is unusual in that, with the exception of ə, there are no independent vowels. Instead there are special 'vowel-bearer' glyphs (of which is one) that are used to support the vowel signs. is used for ɑ , æ , ɔ , is used for ɪ , i , e , is used for ʊ , u , o , Where consonants appear together without intervening vowels special steps need to be taken to indicate that the inherent vowels have disappeared. There are many ways in which this is achieved in Indic scripts, and the specifics of how each character behaves are too many to catalogue here in detail for each script. There are, however, two main approaches: either (a) change the shape of the consonants or merge them together in some way (a conjunct form), or (b) use a special diacritic to indicate the absence of intervening vowels. A number of strategies are used to show consonant clusters by merging or changing shapes, and nearly all scripts employ more than one of these approaches. The following are a few examples: For 60% of Devanagari conjuncts the consonants that lose the vowel typically lose their characteristic vertical bar (which is historically associated with the sound of the inherent vowel). Such glyphs are referred to as half-forms. For example, s + mə -> smə. Sometimes the two consonant glyphs may be combined vertically. For example, certain combinations in Gujarati such as ʈ + ʈʰə -> ʈʈʰə. Note that the choice of vertical vs. horizontal combination may be a stylistic preference. For example, the result of k + kə in Devanagari could be rendered as either a vertical or horizontal combination. Another common approach is to reduce and simplify one of the consonants in the cluster, and then attach it to the other like a diacritic. In Kannada most combinations are formed by reducing non-initial consonant glyphs in a cluster to a simplified form, joined beneath and/or to the right of the initial consonant, eg. + -> tjʌ. Oriya also often reduces the second consonant, but in some combinations will reduce the first consonant and attach it to the bottom of the second. Another approach is to simply show the virama we introduced earlier. This is really the standard approach for modern Tamil, eg. intʌ (the dot is the virama), but may also be used for any other script if the font being There is actually a third approach, and that is to simply rely on the user to recognise contexts where the inherent vowel is dropped. This occurs in some specific situations such as at the end of a word or those examples described earlier. The only script that does this as a general rule is Gurmukhi. Very few letter combinations are handled as conjuncts in Gurmukhi, most of the time the reader just has to know where the inherent vowel is not pronounced, eg. utsuk. A common feature of Indic scripts is the gemination or lengthening of consonants. For example, note the lengthening of the l sound in cilːʌhʌʈ (Devanagari). Such consonant lengthening is typically handled just as a normal consonant cluster. Gurmukhi, again, is somewhat non-standard in that it uses a special diacritic called addak in this situation. To indicate a geminated consonant, the addak sits above the preceding syllable, eg. putːər. The letter RA is an example of a letter that typically behaves quite idiosyncratically in consonant clusters, and typically quite differently depending on whether it appears at the beginning or end of the cluster. Its placement also often involves apparent reordering. This can be illustrated with the Devanagari RA . When in initial position in the cluster the letter is typically displayed as a small mark above the right shoulder of the last letter in the syllable, eg. ʃaːrmaː. This is called a repha. A in final position in a conjunct cluster is displayed as a small diagonal mark, but precisely where it appears depends on the shape of the previous consonant, eg. pra, tra, hra. With TTA and DDA it needs a little supporting line, eg ʈra, ɖra. Note that a cluster is not limited to two consonants, eg. r + g + dʰʌ -> rgdʰʌ This use of the repha, appearing as it does to the right of the whole cluster, demonstrates the syllabic nature of the Indic scripts. The following extension of the example shows even more clearly that the repha is actually positioned to the right of the syllable, rather than just the cluster, since it appears above the vowel sign. r + g + dʰʌ + iː -> rgdʰiː (Note that syllable boundaries in spoken text do not equate to those in written text. For example, 'Hindi' is spoken as 'hin-di', but written as 'hi-ndi'.) Where the vowel following a consonant cluster is rendered with a vowel sign, the placement of the vowel sign may need attention. As with the examples of the repha at the end of the last section, the syllabic nature of the script becomes apparent with the use of reordrant vowel signs attached to consonant clusters. In Devanagari, where a vowel sign that is is normally rendered to the left of a character is pronounced immediately after the cluster, it will be rendered to the left of the whole cluster, eg. in muʃkil, the is pronounced after the . Vowel signs in a script like Kannada are visually attached to the first consonant in the cluster. Note how the vowel sign appears over the k in kri, since the r is rendered as a reduced appendage at the bottom right of the first consonant in the cluster. There are three diacritics associated with the nasalisation of vowels or the alternative representation of nasal consonants as part of a consonant cluster. Which diacritic is used for which purpose varies from script to script. The following are a few examples of usage. (As usual, although these diacritics have their own names in the various languages represented by the scripts, I will refer to them using the generic names used in the Unicode Standard): In Devanagari, nasalisation of vowel sounds is indicated using the candrabindu or anusvara diacritics, eg. ʌ̃grez, nʌhĩː. The anusvara is commonly used in conjunction with a vowel sign that extends above the headstroke. Nasal consonants in initial place in a conjunct may also be expressed using the anusvara over the previous letter, rather than as a half-glyph attached to the following consonant. The anusvara is written above the headstroke, at the right-hand end of the preceding character. In the list below both spellings are correct and equivalent, although the anusvara is preferred in the case of the first two: = rʌŋg, = pʌɳɟaːbiː, = hindiː, = lʌmbaː. Note that the anusvara is still applied when the previous character has its own vowel sign. If the vowel sign is AA, the anusvara appears over the AA, eg. or . In Kannada the anusvara is mostly used for nasal consonants that are homorganic with a following stop, eg. ʌŋga. When followed by a consonant other than a stop or when word final, the anusvara is pronounced m, eg. simha, lʌgaːm. In Oriya, homorganic nasal+stop clusters are usually written with distinctive conjunct letters. However, the nasal may also be written with anusvara, eg. ɔŋkɔ. Nasalised vowels use the bindu, eg. ã, kã. Gurmukhi is unusual in that it has its own special diacritic for indicating nasalisation of vowel sounds. The tippi is used over the preceding syllable with a, ɪ, ʊ and final u, eg. mʊɳɖɑ. All other vowels use the anusvara (called bimdi in Panjabi), eg. ʃɑ̃t. The visarga is commonly required for transcribing Sanskrit, but occasionally has more specific uses too. It is not used at all in Gurmukhi. The pronunciation of the visarga may vary. In Kannada it is commonly pronounced ha, eg. punəha. In Gujarati it is typically silent. In Tamil the visarga is known as 'aytham' and is used to create additional fricative sounds. Before PA it creates f, and before JA it creates z, eg. fiːsɯ, ziɾoks. All scripts have their own number shapes. While some scripts, such as Tamil, tend to favour European numerals over their own in modern text, other scripts, such as Hindi, still make heavy use of their native shapes. The following table shows the number symbols: Tamil number shapes are not based on the decimal system, and so there is traditionally no zero. There are however additional symbols to represent 10 , 100 , and 1000 . Modern Tamil typically uses European numerals. Sub-sentence units (words) are separated with spaces. Modern text commonly uses western punctuation, but some scripts sometimes use traditional punctuation. For example, the DANDA may still be used in Devanagari to mark the end of a sentence, or the DOUBLE DANDA in Telugu for certain abbreviations. In this section we need to make a clear distinction between characters, the basic codepoint units provided by the Unicode Standard for representation of the script in memory, and glyphs, the visual representation of one or more underlying characters when displayed or printed. As with other complex scripts, and unlike text in English, it is common to find situations where there is not a one-to-one mapping of characters to glyphs. I will try to use the terms character and glyph carefully in the following text to clarify whether we are talking about the representation of the text in memory or as rendered on-screen or in print. The characters in an Indic Unicode script block are a superset of the ISCII (Indian Standard Code for Information Interchange) character sets. The ISCII standard includes separate encodings for each of the scripts discussed here, using escape sequences to shift between them. The Unicode blocks were originally based on the 1988 version of ISCII encodings. ISCII published a new version of the standard in 1991 with a few changes to order and repertoire of characters. Unicode, nevertheless, remains a superset of all the ISCII codes, with the exception of a few Vedic extension characters. When first encoded in Unicode, the first 85 characters in each Unicode block were placed in the same order and position, on a script by script basis, as the 1988 ISCII characters for the respective script. Every script block orders analogous characters in the ISCII range in the same relative locations to the start of the block across all 9 scripts under consideration in this paper. The next 27 characters are additional Unicode characters, where each analogous character across the scripts is also assigned to the same code point relative to the beginning of the block. The final column is reserved for script specific characters. There is no special ordering here. In the following charts I will use colour coding to indicate the different ranges as follows: ISCII-derived coordinated Unicode extension additional script specific characters The zones described above are illustrated here using the Devanagari script block. The fact that ISCII and Unicode attempt to use the same code point relative to the start of the code block for analogous characters across all nine Indic scripts theoretically allows for easy transliteration between the various scripts, however in practice there are quite a few exceptions in transliteration, so specific tables have to be developed anyway. Each script block has a different number and distribution of characters. The following table contrasts the allocation of characters for Devanagari, Bengali and Tamil. In older fonts the Tamil visarga, or aytham, was in some cases incorrectly rendered with a dotted circle before it in word-initial position (eg. in a word like ). This is because the Unicode Standard initially classified the Tamil visarga as a combining character. An erratum issued in September 2001 corrected this, changing the General Category from "Mc" (Mark, combining) to "Lo" (Letter, other). The Kannada character U+0CDE KANNADA LETTER FA was incorrectly named. A more appropriate name would be LLLA, rather than FA. Because of the rules for Unicode naming, the current name cannot, however, be changed. Fortunately this letter has not been actively used in Kannada since the end of the 10th century. It is important to correctly order Indic characters in memory where combining characters are involved. The Unicode Standard requires that all combining characters be stored in memory after the base character they are combined with. This is a fundamentally important concept. It means that, even if a combining glyph appears to the left of its base character, it is stored after the base character in memory. (This is often referred to as logical ordering.) For example, the characters in the word hindiː are stored in memory as: h + i + n + d + iː Lets see a slightly more complicated example from Kannada. The visual sequence is pronounced kri; the RA is rendered as a subscript to the bottom right and the vowel is rendered as a diacritic above the symbol for KA. The order of characters in memory (ignoring the virama, which is introduced in the next section) is: k + r + i It is common that multiple combining characters are asssociated with a single base character. Examples of such combinations from Devanagari include an anusvara with a vowel sign, eg. hindiː, or a visarga with a vowel sign, eg. duhkʰ. Where there are multiple combining characters, the Unicode Standard provides rules about relative ordering in memory that should be observed. If there is a nukta it must immediately follow the base character. Next comes any virama or any vowel sign, then any bindus. Observing these rules improves operability and simplifies operations such as searching, sorting, character indexing, and the like. The treatment of combining characters in Indic scripts also necessitates the use of context-based rules in the font to ensure the correct positioning and behaviour of displayed glyphs (a glyph being the visual representation of an underlying character). The position of a glyph for a combining character will commonly vary according to the shape and position of its base character, and any other combining characters associated with that base. In a number of cases, the combination of base character and combining character produces a fused shape that must be rendered by use of a ligature glyph or other special context-sensitive glyph forms (see also the next section for use of the virama). Note also that reordering is not limited to displaying certain vowel signs to the left of the immediately preceding base consonant. In a consonant cluster a vowel sign that appears to the left may need to be displayed to the left of the whole consonant cluster, not just the preceding character. Similarly, the symbol for the consonant RA may be rendered as a diacritic at the far right of a syllable involving a consonant cluster that it logically begins. In addition, because the base character is typed first during normal keyboarding, the base character will typically need to be 'moved' slightly to the right to accommodate the combining character glyph that joins to the left. In practice, the entire word is redrawn with every Indic letter. This is typically done in an off-screen buffer and blitted to the screen. The effect is that characters appear to move and change shape considerably while one is typing. As mentioned earlier, a number of scripts (Bengali, Oriya, Tamil, Telugu, Kannada, Malayalam) have vowel signs that are composed, visually, of more than one part. Such multi-part vowel signs can normally be represented using a single character. For example, Tamil kʌʋ can be represented using the characters and . Kannada koː can be composed of the characters and . The Unicode charts typically do also provide separate characters that can be used to represent multi-part vowel signs. If these parts are not already available as simple vowel sign characters, they are provided as special 'length mark' characters such as and . Note also that if two characters are used to represent a split vowel sign both combining characters must follow the base character in memory (eg. + + for the Tamil example above). Although Unicode typically provides single characters for letters formed by the addition of a nukta (eg. , , and ), these almost all have canonical decompositions to base character plus nukta diacritic. Since there are alternative ways of representing multi-part vowel signs and consonants created using the nukta, the question arises, "Which approach should be used when entering Indic text?" The W3C recommends the use of NFC (Unicode Normalization Form C) for web content. NFC represents all multi-part vowels as single characters, but all combinations of consonant plus nukta as two separate characters (apart from the following exceptions in Devanagari: RRA, LLLA, and NNNA). It was mentioned above that Gurmukhi is somewhat unusual in that vowel signs are carried by special 'vowel bearer' letters to create independent vowels. While Unicode does provide character codes for these vowel bearers, and (plus, of course, ), their use isn't recommended. Instead Unicode provides precomposed characters for all the independent vowel sounds needed, eg. , , , etc. Note however that, for the general case, whereas some other encoding systems for Indic represent an II SIGN, for example, by VIRAMA + VOWEL II, Unicode does not do that. It considers these two sequences to not be equivalent, and not have the same rendering. Unicode follows the rule of 'encode characters not glyphs'. This is a fundamentally important concept relating to the support of Indic scripts in Unicode. Even though there are many potential shapes for a character when displayed (half-form, conjunct, ligature, diacritic, etc.), the rule means that there is only one codepoint to represent that character. This is a major advantage for conducting operations on the text such as string comparison, collation, etc. It also allows for a much simpler keyboard, and simpler correspondence between the keyboard input and the stored text. The task of producing the right shape for printing or display of a character according to its context falls to the rendering algorithms of the font, application or system. We have already mentioned that combining character glyphs may sometimes adopt different shapes or merge with and alter the shape of the base consonant. Another key area where intelligent glyph shaping is required is the display of consonant clusters. Consonant clusters are invariably indicated in a sequence of Unicode characters by the presence of a VIRAMA character, whether or not the glyph for the virama will be visible on display. Thus the virama is the trigger for any complex glyph shaping that may be applied to a conjunct by the font or rendering algorithms. The outcome of a consonant+virama+consonant sequence will vary according to the characters, scripts, and fonts involved. Some possibilities are: the initial consonant is rendered as a 'half-form' alternative glyph and no virama is shown, eg. + + = the two consonants and virama are represented by a single glyph (a ligature), eg. + + = (or + + = in some fonts) one of the consonants is represented as a combining diacritic (that may or may not be spacing), eg. + + -> . Note that in some cases the diacritic may appear in a very different position visually than the position of the character it represents in the text stream. For instance, we have already seen the example of the repha in rgdʰiː. Even though the RA appears visually at the top right of the cluster, the sequence of characters underlying the cluster is: r + + g + + dʰʌ + iː the virama may simply be displayed as a combining glyph. In some scripts (eg. Tamil) this is very much the norm, eg. + + = . In other scripts (such as Devanagari) this is an optional scenario that depends on the preference of the user or the richness of the font - a font that has few ligatures and special glyph forms will resort to simply displaying the virama instead. In Unicode it should be possible to force a consonant + virama sequence to display the virama (rather than convert the consonant to a half-form or ligature) by adding a ZERO WIDTH NON-JOINER character (U+200C) immediately after the virama of the dead consonant. For example, this produces rather than . To force a dead consonant to assume a half-form rather than combine as part of a ligature, place a ZERO WIDTH JOINER character (U+200D) immediately after the virama. For example, this produces rather than . The zero width joiner can also be used to produce an example of a half-form on its own for illustration purposes, eg. . You can also create half-forms of combining ligatures, eg. . Where scripts use glyphs that hang from the baseline, rather than sitting on the baseline, it is important to ensure that any glyphs from another intermixed script (eg. Latin script letters) are correctly aligned with the Indic script. It is also important to ensure that the glyphs are aligned as expected with other elements, such as table cells, graphic elements, and the like. For a detailed treatment of the issues for alignment of such scripts with other fonts see Steve Zilles' talk, 'Internationalized Text Formatting in CSS and XML' in the proceedings of IUC22. There are other practical considerations related to enabling Indic script input and display. Keyboards must, of course, provide access to all needed characters, but consider standardisation of layout. On-screen display must support adequate resolution and line height, as well as proportional spacing. For information about collation of Indic scripts, see Unicode Technical Note #1. Many thanks to Cathy Wissink, Mark Davis and Joe Becker for reviewing the initial version of this paper at very short notice and still making numerous useful comments and suggestions.
A right angled triangle has sides a=12 and b=19 in right angle. The hypotenuse is c. If the triangle rotates on the c side as axis, find the volume and surface area of conical area created by this rotation. Leave us a comment of this math problem and its solution (i.e. if it is still somewhat unclear...): Showing 0 comments: Be the first to comment! To solve this verbal math problem are needed these knowledge from mathematics: Next similar math problems: - Right 24 Right isosceles triangle has an altitude x drawn from the right angle to the hypotenuse dividing it into 2 unequal segments. The length of one segment is 5 cm. What is the area of the triangle? Thank you. - Triangular prism Calculate the surface area and volume of a triangular prism, base right triangle if a = 3 cm, b = 4 cm, c = 5 cm and height of prism h=12 cm. All walls of regular octahedron are identical equilateral triangles. ABCDEF octahedron edges have a length d = 6 cm. Calculate the surface area and volume of this octahedron. - Cone area and side Calculate the surface area and volume of a rotating cone with a height of 1.25 dm and 17,8dm side. - Surface area The volume of a cone is 1000 cm3 and the content area of the axis cut is 100 cm2. Calculate the surface area of the cone. - Truncated cone A truncated cone has a bases radiuses 40 cm and 10 cm and a height of 25 cm. Calculate its surface area and volume. - Cube volume The cube has a surface of 384 cm2. Calculate its volume. - Cylinder - A&V The cylinder has a volume 1287. The base has a radius 10. What is the area of surface of the cylinder? - Euclid 5 Calculate the length of remain sides of a right triangle ABC if a = 7 cm and height vc = 5 cm. Calculate the volume of the rotating cone with a base radius 26.3 cm and a side 38.4 cm long. - Triangular prism The perpendicular triangular prism is a right triangle with a 5 cm leg. The content of the largest wall of the prism is 130 cm2 and the body height is 10 cm. Calculate the body volume. - Truncated cone 5 The height of a cone 7 cm and the length of side is 10 cm and the lower radius is 3cm. What could the possible answer for the upper radius of truncated cone? - Center traverse It is true that the middle traverse bisects the triangle? - Theorem prove We want to prove the sentence: If the natural number n is divisible by six, then n is divisible by three. From what assumption we started? - Bottles of juice How many 2-liter bottles of juice need to buy if you want to transfer juice to 50 pitchers rotary cone shape with a diameter of 24 cm and base side length of 1.5 dm. - Ice cream in cone In the ice cream cone with a diameter of 5.2 cm is 1.3 dl of ice cream. Calculate the depth of the cone. The gasholder has spherical shape with a diameter 20 m. How many m3 can hold in?
Page 1 of 5 6.5 Goal Trapezoids A trapezoid is a quadrilateral with exactly one pair of parallel sides. The parallel sides are the bases . The nonparallel sides are the legs . Use properties of trapezoids. A trapezoid has two pairs of base angles . In trapezoid ABCD, aC and aD are one pair of base angles. aA and aB are the other pair. Key Words • trapezoid • bases, legs, and base angles of a trapezoid base A B leg leg D C base If the legs of a trapezoid are congruent, then the trapezoid is an isosceles trapezoid . • isosceles trapezoid • midsegment of a trapezoid isosceles trapezoid THEOREMS 6.12 and 6.13 Theorem 6.12 Words If a trapezoid is isosceles, then each pair of base angles are congruent. Symbols B A In the isosceles trapezoid ABCD, aA c aB and aC c aD. C D Theorem 6.13 Words If a trapezoid has a pair of congruent base angles, then it is isosceles. Symbols EXAMPLE In trapezoid ABCD, if aC c aD then ABCD is isosceles. 1 R 50 50 130 130 P angles. So, maR maS 50. 2 Because aS and aP are same-side interior angles formed by ● parallel lines, they are supplementary. So, maP 180 50 130. Q In Example 1, fill in the missing angle measures as you find them. Chapter 6 P 1 PQRS is an isosceles trapezoid and aR and aS are a pair of base ● S 332 R 50 Solution P C D Find Angle Measures of Trapezoids PQRS is an isosceles trapezoid. S Find the missing angle measures. Visualize It! B A 3 Because aQ and aP are a pair of base angles of an isosceles ● Quadrilaterals trapezoid, maQ maP 130. Page 2 of 5 Find Angle Measures of Trapezoids ABCD is an isosceles trapezoid. Find the missing angle measures. 1. D A Student Help VOCABULARY TIP The midsegment of a trapezoid is sometimes called the median of a trapezoid. 2. D C 100 70 A B C D 3. B A C 75 B Midsegments The midsegment of a trapezoid is the segment that connects the midpoints of its legs. The midsegment of a trapezoid is parallel to the bases. B The length of the midsegment of a trapezoid is half the sum of the lengths of the bases. C midsegment M N A 1 2 D MN (AD BC) 2 EXAMPLE Midsegment of a Trapezoid & Find the length of the midsegment DG of trapezoid CEFH. E 8 F D Solution Use the formula for the midsegment of a trapezoid. G C 20 H 1 2 Formula for midsegment of a trapezoid 1 2 Substitute 8 for EF and 20 for CH. (28) 1 2 Add. 14 Multiply. DG (EF CH) (8 20) ANSWER & is 14. The length of the midsegment DG Midsegment of a Trapezoid &** of the trapezoid. Find the length of the midsegment MN 4. 5. 8 M N 14 6. M 6 10 24 M N N 18 6.5 Trapezoids 333 Page 3 of 5 6.5 Exercises Guided Practice Vocabulary Check 1. Name the bases of trapezoid ABCD. A B 2. Name the legs of trapezoid ABCD. C D Skill Check Decide whether the quadrilateral is a trapezoid, an isosceles trapezoid, or neither. 3. 4. 5. Find the length of the midsegment. 6. 7. 7 8. 19 7 3 15 11 Practice and Applications Extra Practice Parts of a Trapezoid Match the parts of trapezoid PQRS with the correct description. See p. 686. &* and PS &* 9. QR A. legs P 10. aQ and aS B. base angles 11. aR and aQ C. opposite angles &** 12. MN D. bases &* and RS &* 13. PQ E. midsegment R M N P S Finding Angle Measures JKLM is an isosceles trapezoid. Find the missing angle measures. 14. K L 16. L 60 Homework Help Example 1: Exs. 14–19 Example 2: Exs. 20–26 15. K L J 45 M J M K J 334 Chapter 6 Quadrilaterals 128 M Page 4 of 5 Finding Angle Measure QRST is a trapezoid. Find the missing angle measures. 17. R 18. S 132 R P 19. S 78 110 R S T 150 P 78 T P T &** of Finding Midsegments Find the length of the midsegment MN the trapezoid. 20. P 9 P 21. 14 P M M 7 16 S R 22. N N S P P M P 9 15 R R N S Using Algebra Find the value of x. 23. x 24. 16 9 25. 10 12 27 23 x x Cake Design 26. Cake Design The top layer of the cake in 10 in. the diagram at the right has a diameter of 10 inches. The bottom layer has a diameter of 22 inches. What is the diameter of the middle layer? 22 in. Coordinate Geometry The vertices of a trapezoid are A(2, 6), B(8, 6), C(8, 2), and D(4, 2). 27. Plot the vertices on a coordinate plane. Connect them to form CAKE DESIGNERS form and sculpt shapes and figures onto cakes by using tools such as icing bags, handmade paper cones, or cutters. trapezoid ABCD. 28. Name the bases of trapezoid ABCD. 29. Name the legs of trapezoid ABCD. 30. Find the coordinates of the midpoint of each leg. Then plot these points on the coordinate plane you drew in Exercise 27. What is the line segment that connects these two points called? 6.5 Trapezoids 335 Page 5 of 5 IStudent Help Visualize It! ICLASSZONE.COM HOMEWORK HELP Extra help with problem solving in Exs. 31–33 is at classzone.com In Exercises 31–33, use the figures shown below. The figure on the left is a trapezoid with midsegment of length m. The figure on the right is formed by cutting the trapezoid along its midsegment and rearranging the two pieces. 5 1 2 m m 3 m 3 2 4 1 9 4 5 9 31. Which theorem or postulate from Chapter 3 can you use to show that a1 c a3 and a2 c a4 in the figure on the left? 32. What kind of quadrilateral is on the right? Explain your answer. 33. Challenge How does the diagram help you see that the length of the midsegment is half the sum of the lengths of the bases? Standardized Test Practice 34. Multiple Choice In the trapezoid 13 J M at the right, what is the value of x? A C 13 17 B D 15 N 15 28 K P L x 35. Multiple Choice Which of the following must a trapezoid have? F G H J Mixed Review congruent bases diagonals that bisect each other exactly one pair of parallel sides a pair of congruent opposite angles Logical Reasoning Tell whether the quadrilateral is a parallelogram. Explain your reasoning. (Lesson 6.3) 36. 37. 38. 3 2 3 2 115 Algebra Skills Multiplying Multiply. Write the answer in simplest form. (Skills Review, p. 659) 1 2 39. 20 2 3 3 7 43. 336 Chapter 6 65 Quadrilaterals 1 4 40. 52 7 8 2 14 44. 1 8 41. 136 5 6 1 3 45. 3 4 42. 60 4 21 7 16 46. © Copyright 2021 Paperzz
Properties of fluids determine how fluid may behave in different engineering applications. Based on this engineers can decide which type of fluid they should use. So let’s find out different key properties of fluids in this article. At the end of this article, there will be a link for fluid properties PDF which you can download for your future reference. What is fluid? The fluid is a substance that has no shape and can easily flow continuously with little or no external pressure. A typical example of fluids is liquid and gas. The fluid is also called zero memory substance. What is fluid flow? Fluid flow is the relative motion of different particles of a fluid substance. The relative motion is continuous under shear force as those fluid particles can not resist shear force. Fluid can deform continuously under shear force without coming back to its original state. You may like to read: Difference between screw and bolt Properties of fluid When we talk about fluid, both liquids and gas come into the picture. But both behave in a different way. A liquid takes the shape of the surface where it is kept. But gases take the shape of the container where is stored. Due to this the properties of gas vary compare to the properties of a liquid. - Specific volume - Specific weight - Specific gravity Density is the mass per unit volume of a fluid. So it is the ratio between mass and unit volume. The density of a fluid is denoted by the symbol “ρ ” and the unit is kg/m3 in the SI unit system. The density of fluid increases with the increase of pressure and temperature. Density of fluid can be expressed as below ρ= Mass / Volume How to calculate Density of a fluid ( Gas) Density of a fluid can be calculated easily by applying following formula if you know the pressure and temparature. P = Pressure R= Universal Gas Constant Density of common fluids Viscosity is the amount of internal resistance to flow deformation between particles. Viscosity is the property of a fluid that resists movement of particles from one layer to another layer. The opposite of viscosity is the fluidity. Mathematically viscosity is the amount of internal resistance between particles when they are in motion. In the case of liquids, the viscosity decreases with the increase in temperature. But in the case of gas, viscosity increases with the increase in temperature. The unit of viscosity in the SI system is Pascal-second or N s/m2 Viscosity of common fluids \|Fluid\|\|Viscosity (Pascal-second or N s/m2)\| The specific volume of fluids can be defined as the ratio of the volume of fluid to the mass of fluid. In other words, a specific volume is a volume occupied by a unit mass of fluid. The unit of specific volume in the SI system is m3/kg Specific Volume = Volume Of Fluid / Mass of Fluid = V/m If you see carefully, you will notice that the specific volume is nothing but the reciprocal of the density. So mathematically specific volume can also be defined as 1/ρ Specific weight can be defined as the ratio of the weight of the fluid to the volume of fluid. In other words, it is the weight of the unit volume of fluid. The unit of specific weight in the SI system is N/m3 Specific Weight= Weight / Volume =mg/V ( M is the mass & g is the gravity) = ρ*g (ρ is the density) So as you can see that the specific weight depends on the density and gravity or acceleration. As we know that the density depends on pressure and temperature. So in other words, the specific weight depends on pressure, temperature, and gravity. The specific gravity of fluid can be defined as the ratio of the density of the fluid to the standard fluid. That is why it is also called relative density. It does not have any unit as this is the ratio of one density to the other. In the case of liquid, water is the standard liquid and in case of gas, the air is the standard gas. So if we see the equation of specific gravity of liquid and gas, then it will look like this as shown below. Specific gravity of fluid = Density of fluid / Density of water Specific gravity of Gas= Density of gas / Density of air Here are a couple of properties of fluids that we should know. As an engineer, these are some of the basic properties that you should consider while choosing a fluid for your application. If you have any questions or queries on properties of fluids, please do write in the comment section and I will be happy to assist.
Comparing fractions means looking at two fractions and figuring out which one is greater. To compare fractions, all you have to do is to make it so that they have the same denominator and then see which fraction has the greater numerator -- this will tell you which fraction is greater. The tricky part is knowing how to make sure the fractions have like denominators, but it doesn't have to be so hard. If you want to know how to compare fractions, just follow these steps. 1Determine whether or not the fractions have the same denominator. This is the first step to comparing fractions. The denominator is the number on the bottom of the fraction and the numerator is the number on top. For example, the fractions 5/7 and 9/13 do not have the same denominator, because 7 does not equal 13, so you'll have to take a few steps to compare them. - If the denominator of the fractions is the same, then all you have to do is look at the numerator to know which fraction is greater. For example, with the fraction 5/12 and 7/12, you know that 7/12 is greater than 5/12 because 7 is greater than 5. 2Find a common denominator. To be able to compare the fractions, you'll need to find a common denominator so you can figure out which fraction is greater. If you were adding and subtracting fractions with unlike denominators, then it would be best to find the least common denominator for the fractions. But since you're just comparing the fractions, you can just take a shortcut and multiply the denominators of both fractions to find the common denominator. - 7 x 13 = 91, so the new denominator will be 91. 3Change the numerators of the fractions. Now that you've changed the denominators of the fractions to 91, you'll need to change the numerators so the value of the fractions remains the same. To do this, you'll need to multiply the numerator of each fraction by the same number that you multiplied the denominator by to get 91. Here's how you do it: - With the original fraction 5/7, you multiplied 7 by 13 to get a new denominator of 91, so you'll need to multiply 5 by 13 to get the new numerator. You're essentially multiplying both the numerator and the denominator of the fraction by 13/13 (which equals 1). 5/7 x 13/13 = 65/91. - With the original fraction 9/13, you multiplied 13 by 7 to get a new denominator of 91, so you'll need to multiply 9 by 7 to get the new numerator. 9 x 7 = 63, so the new fraction is 63/91. 4Compare the numerators of the fractions. The one with the larger numerator is the greater fraction. So, the fraction 65/91 is greater than 63/91 because 65 is greater than 63. This means that the original fraction, 5/7, is greater than 9/13. Sources and Citations In other languages: Português: Comparar Frações, Español: comparar fracciones, Italiano: Confrontare le Frazioni, Deutsch: Brüche vergleichen, Français: comparer des fractions, 中文: 比较分数的大小, Русский: сравнивать дроби, Bahasa Indonesia: Membandingkan Pecahan Thanks to all authors for creating a page that has been read 12,914 times.
GCSE & A level chemistry calculations: Defining-using the Law of Conservation of Mass Doc Brown's Chemistry - GCSE 9-1, IGCSE, O Level (and very basic GCE A level) O Level Online Chemical Calculations 3. Law of Conservation of Mass Experiments and Simple Reacting Mass Calculations Quantitative Chemistry calculations online A demonstration experiment of the Law of Conservation of Mass is described and explained. Help for problem solving in doing law of conservation of mass calculations, using experiment data, making predictions. Practice revision questions on the law of conservation of mass in chemical reactions using the balanced equation. The Law of Conservation of Mass is defined and explained using examples of reacting mass calculations using the law are fully explained with worked out examples using the balanced symbol equation. The method involves reacting masses deduced from the balanced symbol equation. These are online practice exam chemistry CALCULATIONS and solved problems for KS4 Science GCSE/IGCSE CHEMISTRY and basic starter chemical calculations for A level AS/A2/IB courses. These revision notes and practice questions on the law of conservation of mass chemical calculations and worked examples should prove useful for the new AQA, Edexcel and OCR Gateway and 21st Century GCSE (9–1) chemistry science courses. Spotted any careless error? EMAIL query ? comment or request a type of GCSE calculation not covered? 3. Law of Conservation of mass calculations Reminder! What is chemistry? Chemistry is basically taking 'stuff' (the reactants) and changing it and separating out 'different stuff' (the products). In a chemical change, the atoms of the reactants are rearranged to give the products. The atoms remain the same elements BUT are arranged or bonded in a different way in the products. In the 'picture equation' above, just look at how the copper, carbon, oxygen, hydrogen and sulfur atoms are changed in their arrangement from reactants on the left, to products to the right of the arrow - indicating the direction of chemical change. So, what about the relative mass of all the products compared to the total mass of the original reactants? Read on .... !!! ... before tackling the first calculations based on the Law of Conservation of mass, its worth describing a simple experiment to demonstrate the validity of the law. The experiment is illustrated in the diagram above and represents an enclosed system, where nothing can escape ! The equation for this reaction is ... copper sulfate + sodium hydroxide ==> copper hydroxide + sodium sulfate CuSO4(aq) + 2NaOH(aq) ===> Cu(OH)2(s) + Na2SO4(aq) 50 cm3 of 1 molar copper sulfate = 1.0 x 50 / 1000 = 0.05 mol CuSO4, Mr(NaOH) = 40, you need 2 x 0.05 = 0.10 mol NaOH, which equals 0.10 x 40 = 4.0g NaOH pellets dissolved in the minimum volume of water, 4.1g should complete the precipitation. You can do exactly the same sort of experiment using the same apparatus and procedure as above using lead nitrate solution and potassium iodide solution. It doesn't matter which solution is in the little test tube or the conical flask. Both are colourless solutions BUT on mixing you get a bright yellow precipitate of lead iodide, an obvious chemical change has taken place. And, again, you find the total mass at the start (unmixed solutions) equals the total mass at the end (including the residual solution and precipitate). The chemistry of this demonstration is .. lead nitrate + potassium iodide ===> lead iodide + potassium nitrate Pb(NO3)2(aq) + 2KI(aq) ===> PbI2(s) + 2KNO3(aq) Note: (i) Here I've included the state symbols, (aq) meaning an aqueous solution (solvent water), and (s) to denote the solid precipitate formed. (ii) The two 2s are needed to balance the equation, a consequence of the law of conservation of mass and the rules on balancing chemical equations. Experiments in which a mass change is observed - where there doesn't seem to be conservation of mass, we need an explanation! Reactions that do not go to completion might give false results and if the reaction involves a reacting gas OR a gaseous product it is difficult to make accurate measurements to confirm the validity of the law of conservation of mass. Three typical situations you will encounter: BUT, as you will see, theoretical calculations based on the law of conservation of mass can get round the situation! Some reactions may appear to involve a change in mass as measured with limited school laboratory apparatus. However, these can usually be explained because a reactant or product is a gas and its mass not been taken into account. For example: when a metal reacts with oxygen the mass of the oxide produced is greater than the mass of the metal, so when you heat magnesium ribbon in a crucible there is gain in mass because the 'weightless' oxygen in air has combined with the magnesium to form magnesium oxide. It is impossible to directly measure the mass of the oxygen used from the air. In thermal decompositions of metal carbonates, the carbon dioxide is produced and escapes into the atmosphere leaving the metal oxide as the only solid product. Again, it is impossible to directly measure the carbon dioxide evolved from the decomposing carbonate. However, you can clearly observe the chemical change because of the colour changes. When an acid reacts with a metal, hydrogen gas is produced, or reacting an acid with a carbonate produces carbon dioxide gas. The gas escapes into the air. You can follow the mass loss by carrying out the reaction in a flask placed on an electronic balance. You can even use the mass loss to see how fast the reaction is going e.g. You need to be able to explain any observed changes in mass in non-enclosed systems during a chemical reaction given the balanced symbol equation for the reaction and explain these changes in terms of the particle model. If you carry out an experiment that produces a gas in a non-enclosed system (i.e. the gas can escape), you will observe a mass loss, BUT, if you could somehow weigh the gas, you would find that the total mass of reactants and products had remained constant. So, even in reactions producing a gas, the law of conservation still holds good. The same arguments applies to when a gas is a reactant producing a solid product. (1) the symbol equation must be correctly balanced to get the right answer! (2) You convert all the formula in the equations into their formula masses AND take into account any balancing numbers to get the true theoretical reacting masses i.e. as ratios to enable calculations to be done with any given masses. (2) There are good reasons why, when doing a real chemical preparation-reaction to make a substance you will not get 100% of what you theoretically calculate. See discussion of % yield Examples of 'atom counting' to illustrate the law of conservation of mass (these are from my page on how to balance chemical equations) Any correctly balanced equation, especially in diagrammatic form, illustrates the law of conservation of mass, ie the number of atoms for each element MUST be the same on both sides of the equation. No atoms lost or gained and neither do atoms change their atomic mass in a reaction. ATOMS at the START = ATOMS at the END (atoms conserved, just arranged differently!) and TOTAL MASS REACTANTS = TOTAL MASS of PRODUCTS (the law of conservation of mass) You also need to be able to read chemical formula and balance chemical equations, at least appreciate why an equation is balanced - which after all is a symbolic or diagrammatic representation of the Law of Conservation of Mass. The 'Law of Conservation of Mass' means you can do theoretical calculations on the relative amounts of reactants and products involved in a chemical reaction, as long as you have the correct formulae and a correctly balanced chemical equation. Atomic masses are quoted and listed on a periodic table at the bottom of the page. Incidentally, the examples are worked out in terms of atomic masses, but in real calculations you may use g, kg or tonnes, as long as you use the same mass units for each mass value involved. AND you must be able to working out formula masses You will follow the arguments for the more complex examples if you can already balance awkward equations! Atom counting and balancing the reactant mass units and product mass units from the equation ratios I am assuming you can work out the relative formula mass of an element or compound. (1) iron + sulfur ==> iron sulfide (2) sodium hydroxide + hydrochloric acid ===> sodium chloride + water (3) magnesium + hydrochloric acid ====> magnesium chloride + hydrogen (4) methane + oxygen ====> carbon dioxide + water (5) copper carbonate + sulfuric acid ===> copper sulfate + water + carbon dioxide (6) magnesium hydroxide + nitric acid ====> magnesium nitrate + water (7) aluminium oxide + sulfuric acid ====> aluminium sulfate + water Examples of using the 'Law of Conservation of Mass' in reacting mass calculations. By converting the atoms or formulae into atomic masses or formula/molecular masses you can then use the law of conservation of mass to reacting mass calculations. (More reacting mass calculations in section 6.) Self-assessment Quiz on the 'Law of Conservation of Mass' and simple reacting mass calculations cross-multiplying - apparently, according to maths departments, the naughty way' to solve ratios! As pupil in the late 1950s and (very) early1960s I was taught to solve ratios by cross-multiplying, wrote learning! Suppose you have the ratio situation of A : B and C : D as in the reacting mass ratio questions on this page. You can also express these ratios as Therefore, logically, by cross-multiplying you get A x D = B x C and rearranging, as you do in simple algebra you get the following relationship by dividing through by A, B, C or D appropriately A = B x C / D, B = A x D / C, C = A x D / B and D = B x C / A and if you don't believe me, just put some numbers in e.g 2 : 5 for A : B and 6 : 15 for C : D 2/5 = 6/15 and 2 x 15 = 5 x 6 I find its by far the quickest general route to solving two ratios that match, but its frowned on! It does actually amount to the same as the methods described above, personally, I just find it quicker! Above is typical periodic table used in GCSE science-chemistry specifications in doing reacting mass and conservation of mass chemical calculations, and I've 'usually' used these values in my exemplar calculations to cover most syllabuses OTHER CALCULATION PAGES Law of Conservation of Mass calculations in chemistry Revision KS4 Science Law of Conservation of Mass calculations in chemistry Additional Science Triple Award Science Separate Sciences Courses aid to Law of Conservation of Mass calculations in chemistry textbook revision GCSE/IGCSE/O level Chemistry Law of Conservation of Mass calculations in chemistry Information Study Notes for revising for AQA GCSE Science Law of Conservation of Mass calculations in chemistry, Edexcel GCSE Science/IGCSE Chemistry Law of Conservation of Mass calculations in chemistry & OCR 21st Century Science, OCR Gateway Science Law of Conservation of Mass calculations in chemistry WJEC gcse science chemistry Law of Conservation of Mass calculations in chemistry CEA/CEA gcse science chemistry O Level Chemistry (revise courses equal to US grade 8, grade 9 grade 10 Law of Conservation of Mass calculations in chemistry) A level Revision notes for GCE Advanced Subsidiary Level Law of Conservation of Mass calculations in chemistry AS Advanced Level A2 IB Revising Law of Conservation of Mass calculations in chemistry AQA GCE Chemistry OCR GCE Chemistry Law of Conservation of Mass calculations in chemistry Edexcel GCE Chemistry Salters Chemistry Law of Conservation of Mass calculations in chemistry CIE Chemistry Law of Conservation of Mass calculations in chemistry, WJEC GCE AS A2 Chemistry Law of Conservation of Mass calculations in chemistry, CCEA/CEA GCE AS A2 Chemistry revising Law of Conservation of Mass calculations in chemistry courses for pre-university students (equal to US grade 11 and grade 12 and AP Honours/honors level Law of Conservation of Mass calculations in chemistry revision guides gcse chemistry revision free detailed notes on how to use the law of conservation of mass to help revise igcse chemistry igcse chemistry revision notes on how to use the law of conservation of mass O level chemistry revision free detailed notes on how to use the law of conservation of mass to help revise gcse chemistry free detailed notes on how to use the law of conservation of mass to help revise O level chemistry free online website to help revise how to use the law of conservation of mass for gcse chemistry free online website to help revise how to use the law of conservation of mass for igcse chemistry free online website to help revise O level how to use the law of conservation of mass chemistry how to succeed in questions on how to use the law of conservation of mass for gcse chemistry how to succeed at igcse chemistry how to succeed at O level chemistry a good website for free questions on how to use the law of conservation of mass to help to pass gcse chemistry questions on how to use the law of conservation of mass a good website for free help to pass igcse chemistry with revision notes on how to use the law of conservation of mass a good website for free help to pass O level chemistry Doc Brown's Chemistry Enter chemistry words e.g. topic, module, exam board, formula, compound, reaction, structure, concept, equation, 'phrase', homework question! anything of chemical interest! 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Newtons second law basically states that a force can be calculated by the product of a mass and its acceleration. Since we know acceleration is the rate of change in velocity, it stands to reason that when were not moving were not exerting a force, right? Actually, one force that always is exerted on you is the gravitational force (gravity), which essentially causes you to always accelerate in the y-direction. Remember this fact when you think of a nonmoving object as one thats not under acceleration. Thankfully because of Newtons 3rd law, which well learn about next, we arent falling through the Earth. FBDs are tools for visualizing forces on a single object and writing equations to represent a physical situation. The acceleration of an object is directly proportional to the net force experienced and inversely proportional to its inertial mass. The net force on an object is the vector sum of the individual forces. Newton's 2nd Law of Motion Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture. Hi, I am Dan Fullerton. Welcome back to Educator.com.0000 Let us talk about Newton's Second Law of Motion.0004 Now our objectives are going to be to draw and label a free-body diagram showing all the forces acting on an object and also draw a pseudo-free body diagram showing all components of forces acting on an object.0006 We will explain the relationship between acceleration, net force, and mass of an object, and use Newton's Second Law to solve a variety of problems.0020 Finally, we want to make sure we understand the difference between mass and weight, and the conditions required for equilibrium.0028 Free-body diagrams or FBD's -- these are tools that we use to analyze physical situations.0037 What they do is they show all the forces acting on a single object.0044 Some folks like to draw it as a box. It does not matter, either one.0052 Now when you draw a FBD, choose the object of interest and draw it as either a dot or a box. 0058 Then you are going to label all the external forces acting on the object and only forces go on that diagram.0064 Finally, sketch a coordinate system showing the direction of the object's motion as one of the positive axis.0070 For example, let us take a look at a circus elephant falling off a tight rope -- sad story -- it is just pretend, do not worry.0077 Neglecting air resistance -- draw a free-body diagram for the falling elephant.0085 I am going to use my amazing physics artistic skills to draw an elephant.0089 There it is in FBD terms and I am going to label all the forces acting on it.0094 The weight of the elephant -- the force of gravity -- which I typically write on FBD as mg -- the force of gravity on an object on a FBD can save yourself a little bit of work if you write weight as mg. 0100 Or, we could draw it as a box -- there is our elephant and the one force acting on it is the weight of the elephant pulling it down.0115 How about if we had the falling elephant with air resistance?0127 We have a 25N horizontal force northward and a 35N horizontal force southward acting concurrently -- that means at the same place and at the same time -- on a 15 kg object on a frictionless surface.1277 What is the magnitude of the object's acceleration? Again, let us start with the FBD.1290 There are horizontal forces both North and South, but I am going to draw an overhead view.1296 We have a force of 25N North and we have 35N South.1302 The net force should be pretty easy to see. It is going to be 10N South.1311 The acceleration is going to be the net force divided by the objects mass, which is going to be 10N South, divided by 15 kg, or 0.67 m/s 2 South.1320 What is the weight of the astronaut on Planet X, where the gravitational field strength is 6 m/s 2.1402 On Earth, mg, the object's weight, is 1,000N, therefore, we could say that the mass of the object -- what does not change, is going to be 1,000N/g on Earth -- 10, or about 100 kg.1409 If we go over here to Planet X, mg on Planet X must equal the mass, 100 kg -- that does not change, times g on Planet X, 6 m/s2 -- 100 x 6 = 600N.1427 An alien on Planet X weighs 400N. What is the mass of the alien?1448 On Planet X, mg(x) for the alien must be 400N, therefore, the mass of the alien on X is 400N/g on x, 6 m/s 2, or about 66.7 kg.1454 Take the alien to Earth, it is going to have a different weight.1475 It will not be 400N, but the mass will be the same, 66.7 kg.1478 Coming back to equilibrium. Translational equilibrium occurs when there is no net force on an object, therefore, acceleration is 0.1487 The equilibrant is a name for a single force vector that you add to any unbalanced forces you have on an object in order to bring the object into translational equilibrium.1497 For example, if I have a force that is 25N that direction -- if I want its equilibrant, I need a force that is 25N in that direction so that you add them together -- you get 0.1506 You get no unbalanced forces. You have 0 acceleration.1520 In the diagram here we have a 20N force due North, and a 20N force due East acting concurrently, again at the same place and same time on an object. 1530 What additional force is required to bring the object into equilibrium? Or we are looking for the equilibrant.1540 Now the way I do this is, is if I look here we have 20N and 20N.1549 Let us add them together to get the net force.1554 I am just going to slide this vector over so that they are lined up tip to tail so I can add them -- 20N -- and my resultant, the sum of the two vectors is going to be a vector with the length square root of 20 squared plus 20 squared.1556 That is going to be square root of 20 20 + 20 2 = 28.3N.1572 I could replace that 20N North and 20N East with one vector, 28.3N to the northeast.1583 It's equilibrant, the vector I would have to add to that system to bring it back into equilibrium, must be the exact opposite of that.1589 The equilibrant must be that red vector, which would be 28.3N to the southwest. 1596 The book features an effective, 5-step plan to guide your preparation program and help you build the skills, knowledge, and test-taking confidence you need to succeed. This fully revised edition covers the latest course syllabus and matches the new exam. It also includes access to McGraw-Hill Education’s AP Planner app, which will enable you to customize your own study schedule on your mobile device. It includes a full-length practice AP Physics 1 exam and 3 separate study plans to fit your learning style. This book is written by our very own Professor Fullerton and features more than 600 worked-out problems with full solutions and deeper understanding questions. AP Physics 1 Essentials covers all major topics included in the AP Physics 1 course, including: kinematics, dynamics, momentum, impulse, gravity, uniform circular motion, rotation, work, energy, power, mechanical waves, sound, electrostatics, and circuits.
Statistics and data presentation: understanding variables All science is about understanding variability in different characteristics, and most characteristics vary, hence we call the characteristics that we are studying ‘variables. When we work in a quantitative area, we make measurements. The scale of measurement is very important because one criterion for selecting the appropriate statistical technique is the scale of measurement used to measure whatever it is, we are studying. There are different statistical techniques to use with each kind of measurement. ✓ Nominal Scale is the lowest level of measurement. Sometimes this is referred to as qualitative data – not to be confused with qualitative research. This scale uses numbers to describe names of discrete categories. One determines for each case whether they have or do not have the attribute in question. ✓ Ordinal Scale is used to rank people in order (e.g. least politically active to most politically active). This is the lowest level of quantitative data and involves the process of assignment of numbers to cases in terms of how much of the attribute is possessed by each subject. ✓ Continuous data can assume different values within a range. Interval Scale is where a number assigned is the amount of attribute possessed. Most statistics procedures can be used with interval data. Ratio Scale is considered the highest level of measurement, because all statistics tools can be used on ratio data. When you read an article, you need to figure out what all the variables are in a study. Then you need to identify three things for each variable one at a time: the scale of measurement; the possible score range; and the meaning of high score and low score. Variables take on different functions in a study. We have to be able to tease these functions out. When you are conducting research, you have to recognize the different variables that are at play in your study so you can account for them during your analyses. Variables can take on different functions within the same study, so don’t classify them at the start. Researchers decide on a classification of variables in each analysis. Let’s take a look at the different classifications of variables. Classification of variables • Dependent Variable: The outcome variable of interest is observed to see whether it is influenced by a manipulated variable. This is called a dependent variable. In other words, a characteristic that is dependent on, or thought to be influenced by, an independent variable. This is sometimes called outcome or response variable. • Independent Variable: In experimental research, the researcher can manipulate one variable and measure the effect of that manipulation on another variable. The variable that is manipulated is called an independent variable. In other words, a characteristic that affects, or is thought to influence an outcome or dependent variable, or an antecedent condition. Independent variables are sometimes called factors, treatments, predictors, or manipulated variables. In a better scenario, the only consistent feature that varies between an intervention and control group would be the outcome variable of interest. However, this is not generally the case, and we often have confounding or extraneous variables that play a part. When we design our research studies, we need to pay attention to and account for these variables also. • Control Variable: any variable that is held constant in a research study by observing only one of the instances or levels. Control variables are not necessarily of central interest, but things that a researcher cannot change or remove from participants. They might be known to exert some influence on the dependent variable. We can’t study everything, so a researcher may be interested, for example, in how parental education (and some other variable) is related to reading ability in younger children. He/she happens to know through previous research that gender is related to reading. So, for the purposes of the study, they chose to study only girls. Thus, gender is the control variable and is “held constant”. • Mediator (Intervening) Variable: a hypothetical variable that explains the relationship but is not observed directly in the research study. Rather, it is inferred from the relationship between the independent and dependent variable. This is an important concept to understand because most theory is based on notions of intervening variables and understanding how or why such effects occur. These variables might be clearly identified before doing a study, i.e. measured and analyzed within a study. Often, mediating variables surface as researchers interpret findings and emerge as suggestions for future research. • Moderator Variable: a variable/characteristic that moderates or changes the direction and/or strength of the relationship between two other variables. When, under what conditions, a relationship holds; influences on the strength of the relationship. For example, if a researcher were looking at the relationship between Socio economic status and AIDs prevention, age might be a moderator variable such that the relationship is stronger for older kids than younger kids. Understanding the distinction between mediators and moderators is not always easy. Basically, in a mediation model the independent variable cannot influence the dependent variable directly and does so by means of another variable – the mediator. As a simple example, older people tend to be better drivers than young people. So, age is a predictor of good driving. However, when we think about why this is the case, we see that older people typically make wiser decisions and so wisdom could be seen as the mediating variable. There are a number of tests that can be used within your statistical software program to test for mediating and moderating effects. Moderated regression is an example. A moderator analysis is used to determine whether the relationship between two variables depends on (is moderated by) the value of a third variable. You can find to explore how this is conducted for the statistical package you are using. effect.
About This Chapter Geometric Relationships in the Coordinate Plane - Chapter Summary Work through this chapter at your own pace to study geometric relationships in the coordinate plane, as well as concepts like rotation, dilation, and translation. Our expert instructors break down these relationships, terminology and formulas in a way that's easy to understand and remember. Completing this chapter can help you: - Recognize quadrants, ordered pairs, perimeter and area on the coordinate plane - Use coordinate geometry formulas - Graph shapes on the coordinate plane - Define rotation, reflection and translation - Explain the concept of dilation in math When you're finished with a lesson, try the accompanying self-assessment quiz to check your understanding of key terms and concepts. Your dashboard will keep track of your progress throughout the chapter. The chapter is available to study at any time of day or night, and its online format allows you to study at home, at school or wherever you happen to be. 1. What is a Coordinate Plane? - Definition, Quadrants & Example In this lesson, you'll learn what a coordinate plane is and some coordinate plane terminology. You'll also see a few examples of coordinate planes in action. Then, you can test your new knowledge with a brief quiz. 2. Ordered Pairs on the Coordinate Plane In this video lesson, you will see how points are plotted on the coordinate plane. Learn the proper way to identify points on the coordinate plane and how to read the points. 3. Coordinate Geometry: Definition & Formulas In this lesson we'll define coordinate geometry and learn about formulas that are commonly used in coordinate geometry. You can then take a brief quiz to see what you learned. 4. Overview of Graphing Shapes on the Coordinate Plane After reading this lesson, you'll see how easy it is to solve geometry problems with a coordinate plane. You'll learn how the Pythagorean Theorem can help you find the distance between two points and how easy it is to find the area of a rectangle. 5. Reflection, Rotation & Translation This lesson will define reflection, rotation, and translation as they relate to math. It will also show you an example of each one so that you can perform these transformations on your own. 6. Dilation in Math: Definition & Meaning Dilations are transformations that change figures in specific ways. Learn about these changes and how to complete dilations here. Then test your understanding with a quiz. 7. Perimeter & Area in the Coordinate Plane After reading this lesson, you'll know how you can use the coordinate plane to help you find the perimeter and area of various shapes. Learn how you can find your answers just by counting. 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Other chapters within the GACE Special Education Mathematics & Science (088): Practice & Study Guide course - Working with Real Numbers - Fractions, Decimals, Percents & Ratios - Understanding Number Theory & Estimation - Overview of Basic Algebra - Patterns & Sequences in Algebra - Characteristics & Relationships of Functions - Solving Basic Geometric Problems - Points, Lines, Rays & Angles - Solving Angle Problems with Triangles & Quadrilaterals - Solving Problems Involving Systems of Measurement - Displaying & Interpreting Data - Measures of Central Tendency - Statistical Models & Processes - Understanding Probability, Combinations & Permutations - Scientific Inquiry & Design - Nature of Scientific Knowledge - Major Developments & Historical Figures in Science - Collecting & Evaluating Scientific Data - Science Laboratory & Field Equipment Safety - Environmental Effects of Science & Technology - Energy Production & Natural Resource Management - Science & Technology in Consumer Products - Atoms, Energy & Matter - Concepts & Relationships Between Energy & Matter - Basics of the Periodic Table - Chemical Compounds & Reactions - Acid-Base Chemistry - Solutions & Solubility - Concepts of Mechanics Overview - Electricity & Magnetism Overview - Waves & Optics Overview - Structure & Function of Cells & Organelles - Basic Biochemistry of Life - Basic Genetics - Evolution, Natural Selection & Biological Diversity - Hierarchical Classification of Living Things - Understanding Plant Structures & Function - Animal & Human Anatomy & Physiology - Population Dynamics & Ecology - Rocks, Minerals & Soil Overview - Earth's Structure, Shape & Processes - Historical Geology - Understanding the Earth's Oceans - Freshwater Characteristics & Processes - Atmosphere & Weather - Climate, Seasons & Geography - Exploring Features of the Solar System - Earth-Moon-Sun System - GACE Special Education Mathematics & Science Flashcards
A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number. For example, 5 is prime because 1 and 5 are its only positive integer factors, whereas 6 is composite because it has the divisors 2 and 3 in addition to 1 and 6. The fundamental theorem of arithmetic establishes the central role of primes in number theory: any integer greater than 1 is either a prime itself or can be expressed as a product of primes that is unique up to ordering. The uniqueness in this theorem requires excluding 1 as a prime because one can include arbitrarily many instances of 1 in any factorization, e.g., 3, 1 · 3, 1 · 1 · 3, etc. are all valid factorizations of 3. The property of being prime is called primality. A simple but slow method of verifying the primality of a given number n is known as trial division. It consists of testing whether n is a multiple of any integer between 2 and . Algorithms much more efficient than trial division have been devised to test the primality of large numbers. These include the Miller–Rabin primality test, which is fast but has a small probability of error, and the AKS primality test, which always produces the correct answer in polynomial time but is too slow to be practical. Particularly fast methods are available for numbers of special forms, such as Mersenne numbers. As of January 2016, the largest known prime number has 22,338,618 decimal digits. There are infinitely many primes, as demonstrated by Euclid around 300 BC. There is no known simple formula that separates prime numbers from composite numbers. However, the distribution of primes, that is to say, the statistical behaviour of primes in the large, can be modelled. The first result in that direction is the prime number theorem, proven at the end of the 19th century, which says that the probability that a given, randomly chosen number n is prime is inversely proportional to its number of digits, or to the logarithm of n. Many questions regarding prime numbers remain open, such as Goldbach's conjecture (that every even integer greater than 2 can be expressed as the sum of two primes), and the twin prime conjecture (that there are infinitely many pairs of primes whose difference is 2). Such questions spurred the development of various branches of number theory, focusing on analytic or algebraic aspects of numbers. Primes are used in several routines in information technology, such as public-key cryptography, which makes use of properties such as the difficulty of factoring large numbers into their prime factors. Prime numbers give rise to various generalizations in other mathematical domains, mainly algebra, such as prime elements and prime ideals. A natural number (i.e. 1, 2, 3, 4, 5, 6, etc.) is called a prime number (or a prime) if it has exactly two positive divisors, 1 and the number itself. Natural numbers greater than 1 that are not prime are called composite. For example, among the numbers 1 through 6, the numbers 2, 3, and 5 are the prime numbers, while 1, 4, and 6 are not prime. 1 is excluded as a prime number, for reasons explained below. 2 is a prime number, since the only natural numbers dividing it are 1 and 2. 3 is prime, as no numbers other than 1 and itself divide evenly into it. 4 is composite, since 2 is a number that divides evenly into it, in addition to 1 and itself. 5 is prime as only 1 and itself divide evenly into it. 6 is divisible by 2 and 3, therefore it is not prime. No even number greater than 2 is prime because by definition, as any such even number n has at least three distinct divisors, namely 1, 2, and n. Accordingly, the term odd prime refers to any prime number greater than 2. Similarly, when written in the usual decimal system, all prime numbers larger than 5 would end in 1, 3, 7, or 9, since even numbers are multiples of 2, and numbers ending in 0 or 5 are multiples of 5. If n is a natural number, then 1 and n divide n without remainder. Therefore, the condition of being a prime can also be restated as: a number is prime if it is greater than one and if none of divides n (without remainder). Yet another way to say the same is: a number n > 1 is prime if it cannot be written as a product of two integers a and b, both of which are larger than 1: In other words, n is prime if n items cannot be divided up into smaller equal-size groups of more than one item. The set of all primes is often denoted by P. The first 168 prime numbers (all the prime numbers less than 1000) are: The crucial importance of prime numbers to number theory and mathematics in general stems from the fundamental theorem of arithmetic, which states that every integer larger than 1 can be written as a product of one or more primes in a way that is unique except for the order of the prime factors. Primes can thus be considered the “basic building blocks” of the natural numbers. For example: \|23244\|\|= 2 · 2 · 3 · 13 · 149\| \|= 22 · 3 · 13 · 149. (22 denotes the square or second power of 2.)\| As in this example, the same prime factor may occur multiple times. A decomposition: of a number n into (finitely many) prime factors p1, p2, ... to pt is called prime factorization of n. The fundamental theorem of arithmetic can be rephrased so as to say that any factorization into primes will be identical except for the order of the factors. So, albeit there are many prime factorization algorithms to do this in practice for larger numbers, they all have to yield the same result. If p is a prime number and p divides a product ab of integers, then p divides a or p divides b. This proposition is known as Euclid's lemma. It is used in some proofs of the uniqueness of prime factorizations. Most early Greeks did not even consider 1 to be a number, so they could not consider it to be a prime. By the Middle Ages and Renaissance many mathematicians included 1 as the first prime number. In the mid-18th century Christian Goldbach listed 1 as the first prime in his famous correspondence with Leonhard Euler; however, Euler himself did not consider 1 to be a prime number. In the 19th century many mathematicians still considered the number 1 to be a prime. For example, Derrick Norman Lehmer's list of primes up to 10,006,721, reprinted as late as 1956, started with 1 as its first prime. Henri Lebesgue is said to be the last professional mathematician to call 1 prime. By the early 20th century, mathematicians began to arrive at the consensus that 1 is not a prime number, but rather forms its own special category as a "unit". A large body of mathematical work would still be valid when calling 1 a prime, but Euclid's fundamental theorem of arithmetic (mentioned above) would not hold as stated. For example, the number 15 can be factored as 3 · 5 and 1 · 3 · 5; if 1 were admitted as a prime, these two presentations would be considered different factorizations of 15 into prime numbers, so the statement of that theorem would have to be modified. Similarly, the sieve of Eratosthenes would not work correctly if 1 were considered a prime: a modified version of the sieve that considers 1 as prime would eliminate all multiples of 1 (that is, all other numbers) and produce as output only the single number 1. Furthermore, the prime numbers have several properties that the number 1 lacks, such as the relationship of the number to its corresponding value of Euler's totient function or the sum of divisors function. There are hints in the surviving records of the ancient Egyptians that they had some knowledge of prime numbers: the Egyptian fraction expansions in the Rhind papyrus, for instance, have quite different forms for primes and for composites. However, the earliest surviving records of the explicit study of prime numbers come from the Ancient Greeks. Euclid's Elements (circa 300 BC) contain important theorems about primes, including the infinitude of primes and the fundamental theorem of arithmetic. Euclid also showed how to construct a perfect number from a Mersenne prime. The Sieve of Eratosthenes, attributed to Eratosthenes, is a simple method to compute primes, although the large primes found today with computers are not generated this way. After the Greeks, little happened with the study of prime numbers until the 17th century. In 1640 Pierre de Fermat stated (without proof) Fermat's little theorem (later proved by Leibniz and Euler). Fermat also conjectured that all numbers of the form 22n + 1 are prime (they are called Fermat numbers) and he verified this up to n = 4 (or 216 + 1). However, the very next Fermat number 232 + 1 is composite (one of its prime factors is 641), as Euler discovered later, and in fact no further Fermat numbers are known to be prime. The French monk Marin Mersenne looked at primes of the form 2p − 1, with p a prime. They are called Mersenne primes in his honor. Euler's work in number theory included many results about primes. He showed the infinite series 1/2 + 1/3 + 1/5 + 1/7 + 1/11 + … is divergent. In 1747 he showed that the even perfect numbers are precisely the integers of the form 2p−1(2p − 1), where the second factor is a Mersenne prime. At the start of the 19th century, Legendre and Gauss independently conjectured that as x tends to infinity, the number of primes up to x is asymptotic to x/ln(x), where ln(x) is the natural logarithm of x. Ideas of Riemann in his 1859 paper on the zeta-function sketched a program that would lead to a proof of the prime number theorem. This outline was completed by Hadamard and de la Vallée Poussin, who independently proved the prime number theorem in 1896. Proving a number is prime is not done (for large numbers) by trial division. Many mathematicians have worked on primality tests for large numbers, often restricted to specific number forms. This includes Pépin's test for Fermat numbers (1877), Proth's theorem (around 1878), the Lucas–Lehmer primality test (originated 1856), and the generalized Lucas primality test. More recent algorithms like APRT-CL, ECPP, and AKS work on arbitrary numbers but remain much slower. For a long time, prime numbers were thought to have extremely limited application outside of pure mathematics. This changed in the 1970s when the concepts of public-key cryptography were invented, in which prime numbers formed the basis of the first algorithms such as the RSA cryptosystem algorithm. Since 1951 all the largest known primes have been found by computers. The search for ever larger primes has generated interest outside mathematical circles. The Great Internet Mersenne Prime Search and other distributed computing projects to find large primes have become popular, while mathematicians continue to struggle with the theory of primes. There are infinitely many prime numbers. Another way of saying this is that the sequence of prime numbers never ends. This statement is referred to as Euclid's theorem in honor of the ancient Greek mathematician Euclid, since the first known proof for this statement is attributed to him. Many more proofs of the infinitude of primes are known, including an analytical proof by Euler, Goldbach's proof based on Fermat numbers, Furstenberg's proof using general topology, and Kummer's elegant proof. Like any other natural number, N is divisible by at least one prime number (it is possible that N itself is prime). None of the primes by which N is divisible can be members of the finite set S of primes with which we started, because dividing N by any one of these leaves a remainder of 1. Therefore, the primes by which N is divisible are additional primes beyond the ones we started with. Thus any finite set of primes can be extended to a larger finite set of primes. It is often erroneously reported that Euclid begins with the assumption that the set initially considered contains all prime numbers, leading to a contradiction, or that it contains precisely the n smallest primes rather than any arbitrary finite set of primes. Today, the product of the smallest n primes plus 1 is conventionally called the nth Euclid number. For any arbitrary real number x, there exists a prime p for which this partial sum is bigger than x. This shows that there are infinitely many primes, because if there were finitely many primes the sum would reach its maximum value at the biggest prime rather than being unbounded. More precisely, the growth rate of S(p) is doubly logarithmic, as quantified by Mertens' second theorem. For comparison, the sum does not grow to infinity as n goes to infinity (see Basel problem). In this sense, prime numbers occur more often than squares of natural numbers. Brun's theorem states that the sum of the reciprocals of twin primes, is finite. Because of Brun's theorem, it is not possible to use Euler's method to solve the twin prime conjecture, that there exist infinitely many twin primes. There are various methods to determine whether a given number n is prime. The most basic routine, trial division, is of little practical use because of its slowness. One group of modern primality tests is applicable to arbitrary numbers, while more efficient tests are available for particular numbers. Most such methods only tell whether n is prime or not. Routines also yielding one (or all) prime factors of n are called factorization algorithms. The most basic method of checking the primality of a given integer n is called trial division. This routine consists of dividing n by each integer m that is greater than 1 and less than or equal to the square root of n. If the result of any of these divisions is an integer, then n is not a prime, otherwise it is a prime. Indeed, if is composite (with a and b ≠ 1) then one of the factors a or b is necessarily at most . For example, for , the trial divisions are by m = 2, 3, 4, 5, and 6. None of these numbers divides 37, so 37 is prime. This routine can be implemented more efficiently if a complete list of primes up to is known—then trial divisions need to be checked only for those m that are prime. For example, to check the primality of 37, only three divisions are necessary (m = 2, 3, and 5), given that 4 and 6 are composite. While a simple method, trial division quickly becomes impractical for testing large integers because the number of possible factors grows too rapidly as n increases. According to the prime number theorem explained below, the number of prime numbers less than is approximately given by , so the algorithm may need up to this number of trial divisions to check the primality of n. For n = 1020, this number is 450 million—too large for many practical applications. An algorithm yielding all primes up to a given limit, such as required in the primes-only trial division method, is called a prime number sieve. The oldest example, the sieve of Eratosthenes (see above), is still the most commonly used. The sieve of Atkin is another option. Before the advent of computers, lists of primes up to bounds like 107 were also used. Modern primality tests for general numbers n can be divided into two main classes, probabilistic (or "Monte Carlo") and deterministic algorithms. Deterministic algorithms provide a way to tell for sure whether a given number is prime or not. For example, trial division is a deterministic algorithm because, if performed correctly, it will always identify a prime number as prime and a composite number as composite. Probabilistic algorithms are normally faster, but do not completely prove that a number is prime. These tests rely on testing a given number in a partly random way. For example, a given test might pass all the time if applied to a prime number, but pass only with probability p if applied to a composite number. If we repeat the test n times and pass every time, then the probability that our number is composite is 1/(1-p)n, which decreases exponentially with the number of tests, so we can be as sure as we like (though never perfectly sure) that the number is prime. On the other hand, if the test ever fails, then we know that the number is composite. A particularly simple example of a probabilistic test is the Fermat primality test, which relies on the fact (Fermat's little theorem) that np≡n (mod p) for any n if p is a prime number. If we have a number b that we want to test for primality, then we work out nb (mod b) for a random value of n as our test. A flaw with this test is that there are some composite numbers (the Carmichael numbers) that satisfy the Fermat identity even though they are not prime, so the test has no way of distinguishing between prime numbers and Carmichael numbers. Carmichael numbers are substantially rarer than prime numbers, though, so this test can be useful for practical purposes. More powerful extensions of the Fermat primality test, such as the Baillie-PSW and Miller-Rabin tests, may fail at least some of the time when applied to a composite number. Deterministic algorithms do not erroneously report composite numbers as prime. In practice, the fastest such method is known as elliptic curve primality proving. Analyzing its run time is based on heuristic arguments, as opposed to the rigorously proven complexity of the more recent AKS primality test. Deterministic methods are typically slower than probabilistic ones, so the latter ones are typically applied first before a more time-consuming deterministic routine is employed. The following table lists a number of prime tests. The running time is given in terms of n, the number to be tested and, for probabilistic algorithms, the number k of tests performed. Moreover, ε is an arbitrarily small positive number, and log is the logarithm to an unspecified base. The big O notation means that, for example, elliptic curve primality proving requires a time that is bounded by a factor (not depending on n, but on ε) times log5+ε(n). \|Test\|\|Developed in\|\|Type\|\|Running time\|\|Notes\| \|AKS primality test\|\|2002\|\|deterministic\|\|O(log6+ε(n))\| \|Elliptic curve primality proving\|\|1977\|\|deterministic\|\|O(log5+ε(n)) heuristically\| \|Baillie-PSW primality test\|\|1980\|\|probabilistic\|\|O(log3 n)\|\|no known counterexamples\| \|Miller–Rabin primality test\|\|1980\|\|probabilistic\|\|O(k · log2+ε (n))\|\|error probability 4−k\| \|Solovay–Strassen primality test\|\|1977\|\|probabilistic\|\|O(k · log3 n)\|\|error probability 2−k\| \|Fermat primality test\|\|probabilistic\|\|O(k · log2+ε (n))\|\|fails for Carmichael numbers\| In addition to the aforementioned tests that apply to any natural number n, there are very efficient (deterministic) primality tests if the complete factorization of either n − 1 or n + 1 is known. For example, the Lucas' primality test requires the knowledge of the prime factors of n − 1, while the Lucas–Lehmer primality test needs the prime factors of n + 1. These tests can be applied to check whether are prime. Prime numbers of this form are known as factorial primes. Other primes where either p + 1 or p − 1 is of a particular shape include the Sophie Germain primes (primes of the form 2p + 1 with p prime), primorial primes, Fermat primes and Mersenne primes, that is, prime numbers that are of the form 2p − 1, where p is an arbitrary prime. The Lucas–Lehmer test is particularly fast for numbers of this form. This is why the largest known prime has almost always been a Mersenne prime since the dawn of electronic computers. If only a partial factorization of n − 1 or n + 1 is known, there are extensions of these methods that may be able to prove that n is prime. The following table gives the largest known primes of the mentioned types. Some of these primes have been found using distributed computing. In 2009, the Great Internet Mersenne Prime Search project was awarded a US$100,000 prize for first discovering a prime with at least 10 million digits. The Electronic Frontier Foundation also offers $150,000 and $250,000 for primes with at least 100 million digits and 1 billion digits, respectively. Some of the largest primes not known to have any particular form (that is, no simple formula such as that of Mersenne primes) have been found by taking a piece of semi-random binary data, converting it to a number n, multiplying it by 256k for some positive integer k, and searching for possible primes within the interval [256kn + 1, 256k(n + 1) − 1]. \|Type\|\|Prime\|\|Number of decimal digits\|\|Date\|\|Found by\| \|Mersenne prime\|\|274,207,281 − 1\|\|22,338,618\|\|January 7, 2016\|\|Curtis Cooper, Great Internet Mersenne Prime Search\| \|not a Mersenne prime (Proth number)\|\|10,223 × 231,172,165 + 1\|\|9,383,761\|\|October 31, 2016\|\|Péter Szabolcs, PrimeGrid\| \|factorial prime\|\|208,003! − 1\|\|1,015,843\|\|July 2016\|\|Sou Fukui\| \|primorial prime\|\|1,098,133# - 1\|\|476,311\|\|March 2012\|\|James P. Burt, PrimeGrid\| \|twin primes\|\|2,996,863,034,895 × 21,290,000 ± 1\|\|388,342\|\|September 2016\|\|Tom Greer, PrimeGrid\| Given a composite integer n, the task of providing one (or all) prime factors is referred to as factorization of n. Elliptic curve factorization is an algorithm relying on arithmetic on an elliptic curve. In 1975, number theorist Don Zagier commented that primes both grow like weeds among the natural numbers, seeming to obey no other law than that of chance [but also] exhibit stunning regularity [and] that there are laws governing their behavior, and that they obey these laws with almost military precision. The distribution of primes in the large, such as the question how many primes are smaller than a given, large threshold, is described by the prime number theorem, but no efficient formula for the n-th prime is known. There are arbitrarily long sequences of consecutive non-primes, as for every positive integer the consecutive integers from to (inclusive) are all composite (as is divisible by for between and ). Dirichlet's theorem on arithmetic progressions, in its basic form, asserts that linear polynomials with coprime integers a and b take infinitely many prime values. Stronger forms of the theorem state that the sum of the reciprocals of these prime values diverges, and that different such polynomials with the same b have approximately the same proportions of primes. The corresponding question for quadratic polynomials is less well understood. There is no known efficient formula for primes. For example, there is no non-constant polynomial, even in several variables, that takes only prime values. However, there are numerous expressions that do encode all primes, or only primes. One possible formula is based on Wilson's theorem and generates the number 2 many times and all other primes exactly once. There is also a set of Diophantine equations in 9 variables and one parameter with the following property: the parameter is prime if and only if the resulting system of equations has a solution over the natural numbers. This can be used to obtain a single formula with the property that all its positive values are prime. are prime for any natural number n in the first formula, and any number of exponents in the second formula. Here represents the floor function, i.e., the largest integer not greater than the number in question. However, computing A or μ requires the knowledge of infinitely many primes to begin with. The prime counting function π(n) is defined as the number of primes not greater than n. For example, π(11) = 5, since there are five primes less than or equal to 11. There are known algorithms to compute exact values of π(n) faster than it would be possible to compute each prime up to n. The prime number theorem states that π(n) satisfies which means that the ratio of π(n) and the right hand fraction approaches 1 when n grows to infinity. This implies that the likelihood that a number less than n is prime is (approximately) inversely proportional to the number of digits in n. A more accurate estimate for π(n) is given by the offset logarithmic integral The prime number theorem also implies estimates for the size of the n-th prime number pn (i.e., p1 = 2, p2 = 3, etc.): up to a bounded factor, pn grows like n log(n). In particular, the prime gaps, i.e. the differences pn − pn−1 of two consecutive primes, become arbitrarily large. This latter statement can also be seen in a more elementary way by noting that the sequence n! + 2, n! + 3, …, n! + n (for the notation n! read factorial) consists of n − 1 composite numbers, for any natural number n. However, n − 1 composite numbers do make up gaps much smaller than n!. For example, with n − 1 = 7, the first prime gap of 8 is between the primes 89 and 97 while 8! = 40320. is an arithmetic progression modulo q = 9. Except for 3, none of these numbers is prime, since 3 + 9n = 3(1 + 3n) so that the remaining numbers in this progression are all composite. (In general terms, all prime numbers above q are of the form q#·n + m, where 0 < m < q#, and m has no prime factor ≤ q.) Thus, the progression can have infinitely many primes only when a and q are coprime, i.e., their greatest common divisor is one. If this necessary condition is satisfied, Dirichlet's theorem on arithmetic progressions asserts that the progression contains infinitely many primes. The picture below illustrates this with q = 9: the numbers are "wrapped around" as soon as a multiple of 9 is passed. Primes are highlighted in red. The rows (=progressions) starting with a = 3, 6, or 9 contain at most one prime number. In all other rows (a = 1, 2, 4, 5, 7, and 8) there are infinitely many prime numbers. What is more, the primes are distributed equally among those rows in the long run—the density of all primes congruent a modulo 9 is 1/6. The Green–Tao theorem shows that there are arbitrarily long arithmetic progressions consisting of primes. An odd prime p is expressible as the sum of two squares, p = x2 + y2, exactly if p is congruent 1 modulo 4 (Fermat's theorem on sums of two squares). Euler noted that the function yields prime numbers for 0 ≤ n < 40, a fact leading into deep algebraic number theory: more specifically, Heegner numbers. For greater n, the expression also produces composite values. The Hardy-Littlewood conjecture F makes an asymptotic prediction about the density of primes among the values of quadratic polynomials (with integer coefficients a, b, and c), in terms of Li(n) and the coefficients a, b, and c. However, progress has been difficult. No quadratic polynomial (with a ≠ 0) is known to take infinitely many prime values. The Ulam spiral depicts all natural numbers in a spiral-like way. Primes cluster on certain diagonals and not others, suggesting that some quadratic polynomials take prime values more often than others. The example below displays concentrations of prime numbers (blue background) from 41 to 1001 arranged in an Ulam spiral with a start value of 41 (green background numbers are numbers with just 3 divisors, and red background are numbers with a large number of divisors). The zeta function is closely related to prime numbers. For example, the aforementioned fact that there are infinitely many primes can also be seen using the zeta function: if there were only finitely many primes then ζ(1) would have a finite value. However, the harmonic series 1 + 1/2 + 1/3 + 1/4 + ... diverges (i.e., exceeds any given number), so there must be infinitely many primes. Another example of the richness of the zeta function and a glimpse of modern algebraic number theory is the following identity (Basel problem), due to Euler, The unproven Riemann hypothesis, dating from 1859, states that except for s = −2, −4, ..., all zeroes of the ζ-function have real part equal to 1/2. The connection to prime numbers is that it essentially says that the primes are as regularly distributed as possible. From a physical viewpoint, it roughly states that the irregularity in the distribution of primes only comes from random noise. From a mathematical viewpoint, it roughly states that the asymptotic distribution of primes (about x/log x of numbers less than x are primes, the prime number theorem) also holds for much shorter intervals of length about the square root of x (for intervals near x). This hypothesis is generally believed to be correct. In particular, the simplest assumption is that primes should have no significant irregularities without good reason. In addition to the Riemann hypothesis, many more conjectures revolving about primes have been posed. Often having an elementary formulation, many of these conjectures have withstood a proof for decades: all four of Landau's problems from 1912 are still unsolved. One of them is Goldbach's conjecture, which asserts that every even integer n greater than 2 can be written as a sum of two primes. As of February 2011, this conjecture has been verified for all numbers up to n = 2 · 1017. Weaker statements than this have been proven, for example Vinogradov's theorem says that every sufficiently large odd integer can be written as a sum of three primes. Chen's theorem says that every sufficiently large even number can be expressed as the sum of a prime and a semiprime, the product of two primes. Also, any even integer can be written as the sum of six primes. The branch of number theory studying such questions is called additive number theory. Other conjectures deal with the question whether an infinity of prime numbers subject to certain constraints exists. It is conjectured that there are infinitely many Fibonacci primes and infinitely many Mersenne primes, but not Fermat primes. It is not known whether or not there are an infinite number of Wieferich primes and of prime Euclid numbers. A third type of conjectures concerns aspects of the distribution of primes. It is conjectured that there are infinitely many twin primes, pairs of primes with difference 2 (twin prime conjecture). Polignac's conjecture is a strengthening of that conjecture, it states that for every positive integer n, there are infinitely many pairs of consecutive primes that differ by 2n. It is conjectured there are infinitely many primes of the form n2 + 1. These conjectures are special cases of the broad Schinzel's hypothesis H. Brocard's conjecture says that there are always at least four primes between the squares of consecutive primes greater than 2. Legendre's conjecture states that there is a prime number between n2 and (n + 1)2 for every positive integer n. It is implied by the stronger Cramér's conjecture. For a long time, number theory in general, and the study of prime numbers in particular, was seen as the canonical example of pure mathematics, with no applications outside of the self-interest of studying the topic with the exception of use of prime numbered gear teeth to distribute wear evenly. In particular, number theorists such as British mathematician G. H. Hardy prided themselves on doing work that had absolutely no military significance. However, this vision was shattered in the 1970s, when it was publicly announced that prime numbers could be used as the basis for the creation of public key cryptography algorithms. Prime numbers are also used for hash tables and pseudorandom number generators. Some rotor machines were designed with a different number of pins on each rotor, with the number of pins on any one rotor either prime, or coprime to the number of pins on any other rotor. This helped generate the full cycle of possible rotor positions before repeating any position. Modular arithmetic modifies usual arithmetic by only using the numbers where n is a fixed natural number called modulus. Calculating sums, differences and products is done as usual, but whenever a negative number or a number greater than n − 1 occurs, it gets replaced by the remainder after division by n. For instance, for n = 7, the sum 3 + 5 is 1 instead of 8, since 8 divided by 7 has remainder 1. This is referred to by saying "3 + 5 is congruent to 1 modulo 7" and is denoted Similarly, 6 + 1 ≡ 0 (mod 7), 2 − 5 ≡ 4 (mod 7), since −3 + 7 = 4, and 3 · 4 ≡ 5 (mod 7) as 12 has remainder 5. Standard properties of addition and multiplication familiar from the integers remain valid in modular arithmetic. In the parlance of abstract algebra, the above set of integers, which is also denoted Z/nZ, is therefore a commutative ring for any n. Division, however, is not in general possible in this setting. For example, for n = 6, the equation a solution x of which would be an analogue of 2/3, cannot be solved, as one can see by calculating 3 · 0, ..., 3 · 5 modulo 6. The distinctive feature of prime numbers is the following: division is possible in modular arithmetic if and only if n is a prime. Equivalently, n is prime if and only if all integers m satisfying 2 ≤ m ≤ n − 1 are coprime to n, i.e. their only common divisor is one. Indeed, for n = 7, the equation A number of theorems can be derived from inspecting Fp in this abstract way. For example, Fermat's little theorem, stating for any integer a not divisible by p, may be proved using these notions. This implies Giuga's conjecture says that this equation is also a sufficient condition for p to be prime. Another consequence of Fermat's little theorem is the following: if p is a prime number other than 2 and 5, 1/p is always a recurring decimal, whose period is p − 1 or a divisor of p − 1. The fraction 1/p expressed likewise in base q (rather than base 10) has similar effect, provided that p is not a prime factor of q. Wilson's theorem says that an integer p > 1 is prime if and only if the factorial (p − 1)! + 1 is divisible by p. Moreover, an integer n > 4 is composite if and only if (n − 1)! is divisible by n. Fermat primes are primes of the form with k a natural number. They are named after Pierre de Fermat, who conjectured that all such numbers are prime. This was based on the evidence of the first five numbers in this series—3, 5, 17, 257, and 65,537—being prime. However, F5 is composite and so are all other Fermat numbers that have been verified as of 2015. A regular n-gon is constructible using straightedge and compass if and only if the odd prime factors of n (if any) are distinct Fermat primes. Many mathematical domains make great use of prime numbers. An example from the theory of finite groups are the Sylow theorems: if G is a finite group and pn is the highest power of the prime p that divides the order of G, then G has a subgroup of order pn. Also, any group of prime order is cyclic (Lagrange's theorem). Several public-key cryptography algorithms, such as RSA and the Diffie–Hellman key exchange, are based on large prime numbers (2048-bit primes are common). RSA relies on the assumption that it is much easier (i.e., more efficient) to perform the multiplication of two (large) numbers x and y than to calculate x and y (assumed coprime) if only the product xy is known. The Diffie–Hellman key exchange relies on the fact that there are efficient algorithms for modular exponentiation, while the reverse operation the discrete logarithm is thought to be a hard problem. The evolutionary strategy used by cicadas of the genus Magicicada make use of prime numbers. These insects spend most of their lives as grubs underground. They only pupate and then emerge from their burrows after 7, 13 or 17 years, at which point they fly about, breed, and then die after a few weeks at most. The logic for this is believed to be that the prime number intervals between emergences make it very difficult for predators to evolve that could specialize as predators on Magicicadas. If Magicicadas appeared at a non-prime number intervals, say every 12 years, then predators appearing every 2, 3, 4, 6, or 12 years would be sure to meet them. Over a 200-year period, average predator populations during hypothetical outbreaks of 14- and 15-year cicadas would be up to 2% higher than during outbreaks of 13- and 17-year cicadas. Though small, this advantage appears to have been enough to drive natural selection in favour of a prime-numbered life-cycle for these insects. The concept of prime number is so important that it has been generalized in different ways in various branches of mathematics. Generally, "prime" indicates minimality or indecomposability, in an appropriate sense. For example, the prime field is the smallest subfield of a field F containing both 0 and 1. It is either Q or the finite field with p elements, whence the name. Often a second, additional meaning is intended by using the word prime, namely that any object can be, essentially uniquely, decomposed into its prime components. For example, in knot theory, a prime knot is a knot that is indecomposable in the sense that it cannot be written as the knot sum of two nontrivial knots. Any knot can be uniquely expressed as a connected sum of prime knots. Prime models and prime 3-manifolds are other examples of this type. Prime numbers give rise to two more general concepts that apply to elements of any commutative ring R, an algebraic structure where addition, subtraction and multiplication are defined: prime elements and irreducible elements. An element p of R is called prime element if it is neither zero nor a unit (i.e., does not have a multiplicative inverse) and satisfies the following requirement: given x and y in R such that p divides the product xy, then p divides x or y. An element is irreducible if it is not a unit and cannot be written as a product of two ring elements that are not units. In the ring Z of integers, the set of prime elements equals the set of irreducible elements, which is In any ring R, any prime element is irreducible. The converse does not hold in general, but does hold for unique factorization domains. The fundamental theorem of arithmetic continues to hold in unique factorization domains. An example of such a domain is the Gaussian integers Z[i], that is, the set of complex numbers of the form a + bi where i denotes the imaginary unit and a and b are arbitrary integers. Its prime elements are known as Gaussian primes. Not every prime (in Z) is a Gaussian prime: in the bigger ring Z[i], 2 factors into the product of the two Gaussian primes (1 + i) and (1 − i). Rational primes (i.e. prime elements in Z) of the form 4k + 3 are Gaussian primes, whereas rational primes of the form 4k + 1 are not. In ring theory, the notion of number is generally replaced with that of ideal. Prime ideals, which generalize prime elements in the sense that the principal ideal generated by a prime element is a prime ideal, are an important tool and object of study in commutative algebra, algebraic number theory and algebraic geometry. The prime ideals of the ring of integers are the ideals (0), (2), (3), (5), (7), (11), … The fundamental theorem of arithmetic generalizes to the Lasker–Noether theorem, which expresses every ideal in a Noetherian commutative ring as an intersection of primary ideals, which are the appropriate generalizations of prime powers. Prime ideals are the points of algebro-geometric objects, via the notion of the spectrum of a ring. Arithmetic geometry also benefits from this notion, and many concepts exist in both geometry and number theory. For example, factorization or ramification of prime ideals when lifted to an extension field, a basic problem of algebraic number theory, bears some resemblance with ramification in geometry. Such ramification questions occur even in number-theoretic questions solely concerned with integers. For example, prime ideals in the ring of integers of quadratic number fields can be used in proving quadratic reciprocity, a statement that concerns the solvability of quadratic equations where x is an integer and p and q are (usual) prime numbers. Early attempts to prove Fermat's Last Theorem climaxed when Kummer introduced regular primes, primes satisfying a certain requirement concerning the failure of unique factorization in the ring consisting of expressions Valuation theory studies certain functions from a field K to the real numbers R called valuations. Every such valuation yields a topology on K, and two valuations are called equivalent if they yield the same topology. A prime of K (sometimes called a place of K) is an equivalence class of valuations. For example, the p-adic valuation of a rational number q is defined to be the integer vp(q), such that where both r and s are not divisible by p. For example, v3(18/7) = 2. The p-adic norm is defined as In particular, this norm gets smaller when a number is multiplied by p, in sharp contrast to the usual absolute value (also referred to as the infinite prime). While completing Q (roughly, filling the gaps) with respect to the absolute value yields the field of real numbers, completing with respect to the p-adic norm \|−\|p yields the field of p-adic numbers. These are essentially all possible ways to complete Q, by Ostrowski's theorem. Certain arithmetic questions related to Q or more general global fields may be transferred back and forth to the completed (or local) fields. This local-global principle again underlines the importance of primes to number theory. Prime numbers have influenced many artists and writers. The French composer Olivier Messiaen used prime numbers to create ametrical music through "natural phenomena". In works such as La Nativité du Seigneur (1935) and Quatre études de rythme (1949–50), he simultaneously employs motifs with lengths given by different prime numbers to create unpredictable rhythms: the primes 41, 43, 47 and 53 appear in the third étude, "Neumes rythmiques". According to Messiaen this way of composing was "inspired by the movements of nature, movements of free and unequal durations". In his science fiction novel Contact, NASA scientist Carl Sagan suggested that prime numbers could be used as a means of communicating with aliens, an idea that he had first developed informally with American astronomer Frank Drake in 1975. In the novel The Curious Incident of the Dog in the Night-Time by Mark Haddon, the narrator arranges the sections of the story by consecutive prime numbers. Many films, such as Cube, Sneakers, The Mirror Has Two Faces and A Beautiful Mind reflect a popular fascination with the mysteries of prime numbers and cryptography. Prime numbers are used as a metaphor for loneliness and isolation in the Paolo Giordano novel The Solitude of Prime Numbers, in which they are portrayed as "outsiders" among integers.
The Delivery System Our first objective is to describe why the orbits of Neptune and Uranus came to be located 1.8 and 2.8 billion miles from the Sun. These distances are 19.2 and 30.1 a.u. from the Sun. Some groundwork must be laid. Earlier, evidence was presented in the form of twin spins that both planets co-orbited in space somewhere beyond 900 a.u. from the Sun. How did planets such as Neptune and Uranus relocate from there to "here" in the visible, "inner" solar system? Our question is one of relocation, not one of creation. A delivery by implication involves either a one time delivery, or more often, a delivery system. If a package is dropped on the doorstep with a "United Parcel" delivery label, that implies a delivery system. If such deliveries happen repeatedly, it implies a repeating route, and perhaps a periodic delivery schedule. Postal deliveries fall into this periodic pattern. So are deliveries in our cosmological theory. A Comparison with Early 20th Century Cosmologies In the 1910's, it occurred to James Jeans that the total of the planetary mass was only 0.14% of the Sun's mass. Yet these nine planet systems contained the bulk of the angular momentum in the Solar System. In fact, Jupiter along has 60%. The four giant planets carry 98% of the angular momentum of all matter this side of Pluto. The gigantic Sun carries only 2%. The law of conservation of angular momentum would seem to suggest that if the Sun and its plasma were the genesis of the Solar System, then the Sun should retain most of the angular momentum that is observed. The Sun isn't even close to conforming. This is why Jeans and others began searching for an extra-solar source, a passing star perhaps. This principle is demonstrated in an ice skater, who spins with her arms extended. As her arms are withdrawn, she spins all the faster. But if that were an example of the Sun, the Sun is one of the most slowly spinning bodies of the Solar System. Its photosphere requires 26.8 days for a rotation at its equator. Even more strange, the Sun's photosphere displays even slower rotations rates in its higher latitudes. At 60° latitude, it spins once in 30.8 days and at 75° latitude, it spins in 31.8 days. Although the Nebular Hypothesis is still being taught as cosmological fact to many students, Press and Siever make the following damaging assessment: To address this defect, Moulton and Chamberlin proposed that the Sun was approached by a much larger star, to a proximity of 4 or 5 billion miles. That huge star allegedly pulled out from the Sun a filament of material, providing material eventually condensing into the planets, into planet satellites, in spin rates, etc. In the 1930's, Henry N. Russell recognized further defects. Instead, Russell postulated the Sun had been approached by a pair of stars, a binary system. Together they did the job whereas, he felt, Jeans' theory and Moulton's both failed. Note that early 20th century cosmologists continued to assume that the planets were formed from solar ejecta, billions of years ago. This was a major conceptual mistake. Our concept of a delivery system contains the idea that the planets were delivered to the Sun. They were delivered from a region more distant than 1,000 a.u. The planets of this Solar System never were part of a gaseous filament pulled out of the Sun (or any other star.) Our concept is different and the details of our cosmology are far different from the "standard fare" of this 19th and 20th century. DIFFERENCE # 1. One difference is that their approaching star, or binary pair of stars, approached from interstellar space, from beyond the nearer stars. We offer that the Sun was approached from a region less than 5% of the distance to the nearest star, that is, from between 1,000 and 2,000 a.u., or possibly from 3,000 a.u. DIFFERENCE # 2. A second difference is that our delivery system body was not, and is not luminous. Their concept was one, or two co-rotating luminous stars, at least one of which was larger than the Sun. Had such a luminous star been in the neighborhood four billion years ago, it could still be seen and its path charted. No trace of such can be seen in the Milky Way.. DIFFERENCE # 3. A third difference is that our delivery system body is ONLY 3% TO 4% as massive as the Sun, + or - 1%. The view of Jeans, Russell and Lyttleton was that the approaching star or pair of stars was much heftier than the Sun. DIFFERENCE # 4. A fourth difference is that in our delivery system, the delivering body came much closer to the Sun. They suggest such a theoretical approach was several billion miles from the Sun, and considerably beyond Neptune's orbit. Neptune is three billion miles distant. Evidence exists that the intruder approached as close as 15,000,000 miles from the Sun, more than twice as close as Mercury. This evidence will be cited and presented, along with its ramifications, in chapters 7 through 10. DIFFERENCE # 5. A fifth distance is conceptual. Traditional 18th, 19th and 20th century cosmologies have the Sun as the mother of the planets in a natal sense. In a natal sense, the planets are like afterbirth material which for some reason, the Sun expelled. In contrast, we offer that the Sun is the mother of the nine planets only in an adoptive sense, not a natal sense. Some writers, including science fiction authors, have speculated on Solar System disturbances coming in from beyond the realm of visibility, beyond the orbit of Pluto. Those writers have named their fictitious intruders such names as "Planet X" and "the Nemesis Star", etc. We choose the name "Little Brother" since it evidently was 3% to 4% as massive as the Sun, and it penetrated deeply into the hot, inner region. DIFFERENCE # 6. A sixth difference, if our hypothesis is correct, is that Little Brother continues to orbit the Sun. And on its own schedule, whatever that is, it will return in due time. When it returns, it will realign any planet that gets in its path. And when it returns, it could bring in a new package of planets and drop them off in the Inner Solar System. Evidence, not science fiction writers, indicates Little Brother exists. We choose this name because the Sun is "Big Brother." Its "nickname" is "L. B." This nickname has nothing to do with any prominent politician from Texas. If the Sun stripped the planets away from Little Brother, and if Little Brother delivered them, then that capture must have followed certain mathematical constraints. One constraint is that the planets Mercury through Neptune were all dropped off on the same plane, the orbit plane of "L. B." A second constraint is the "Radius of Action" principle, the zone of control of Little Brother. As "L. B." approached the Sun, this zone inexorably kept shrinking. And as it returned to its aphelion, perhaps 1,000 to 3,000 a.u. distant. This is 5 to 15 light days distant. How expansive would be Little Brother's "zone of control" out there where the Sun's attraction is so faint? How extensive is that "zone of control" which allowed, at three billion miles from the Sun, for Neptune and Uranus to begin to get away? The Sun's mass is 332,000 as massive as the Earth, and 1,050 times as massive as Jupiter. Thus, Little Brother, if our analysis is correct, is about 30 to 40 times as massive as the giant Jupiter. Control versus capture in our Solar System follows a principle, which Gerard Kuiper called the "radius of action". As geographers and engineers, we prefer to call it the "zone of control". It is the same thing. For instance, in our present orbit, the Earth's zone of control, its radius of action, is out to 750,000 miles. At this distance theoretically the Earth would automatically lose any satellite forever to the Sun. At this distance, a satellite merely exchanges its orbit prime focus for the Sun. For math buffs, Kuiper's equation is an approximation, not a rule, not a mathematical law. It is an approximation that merits some elaboration and qualifications. The approximation of a zone of control anywhere in this solar system In this equation, RA is the radius of action. "" is the mass of the planet (Little Brother) divided by the total of the mass of the Sun and Little Brother. "a" is an astronomical unit, 93,000,000 miles.F2 The Capture of NeptuneUranus System Neptune and Uranus had to co-orbit in two long, narrow, highly eccentric orbits. Both revolved around a "bary center," a point that is the common center of mass. Most of the time, Neptune and Uranus were co-orbiting with a considerable distance in between. But with highly eccentric elliptical orbits, fast flybys and sharp spasms of catastrophism occurring every few years. As was discussed earlier, each flyby increased the spin rates of each planet, and the increase was in a reciprocal manner. We suggest that when these two planets were co-orbiting, their bary center orbited Little Brother at a distance of about 600,000,000 miles. At about 2,500,000,000 miles (or 27 a.u.) from the Sun, the Sun stripped this binary away from "L. B." It captured them and dispersed or separated them. Uranus was sent nearer, Neptune farther. In this cosmology, Little Brother performed the job of a delivery service. The Sun proceeded to separate Neptune from Uranus and redirect them into new, virgin, capture orbits. One ended up 1.8 million miles from the Sun and the other 2.8 million miles. Their twin spins are clues of their former co-orbiting relationship, when they were much much deeper in dark, frigid, remote, debris-strewn space. When were the planets Neptune and Uranus dropped off at their present location? That is the $64,000 question for which we do not have the answer. However, there is no evidence for such an event being billions of years ago. There is evidence friendly to the thought that they were delivered less than 100,000 years ago. This evidence involves the capture of other planets, satellites and icy ring systems. We are tempted to get ahead of our story. The story of the Sun's capture of the Neptune system and the Uranian system is story 6 in our new skyscraper cosmology. It involves planetary catastrophism deep in space, before capture by the Sun. We cannot agree that these planets are so far out because of "chance" or "coincidence". They are so remote from the Sun because they were co-orbiting at a similarly remote distance from Little Brother. That "similarly remote" distance from L. B. was some 600,000,000 miles, compared to their present remoteness of 1.8 and 2.8 billion miles. The Capture of JupiterSaturn System In a like manner, Little Brother once "owned" the Jupiter-Saturn binary, a co-orbiting pair whose bary center was perhaps 200,000,000 miles from "L. B." That is about as far as the asteroid belt is today from the Sun. When Little Brother approached the Sun to a distance of some 600,000,000 miles to 700,000,000 miles (6.5 to 7.5 a.u.), the gravitational competition increased. It increased to the threshold where "L.B." was no longer able to retain this second co-orbiting binary either. First, Saturn was stripped from Jupiter, and then from L. B. also. Following that loss, Jupiter was next, stripped away from L. B. as it inexorably kept approaching the Sun. As it was with Saturn, so also with Jupiter; each planet was wrenched from L.B. together with its satellite systems. As Jupiter and Saturn were lost by the Little Brother system, that incoming system was stripped of about 0.3% of its mass; it also lost a similar amount of energy. Its orbit shifted just a wiggle. The L. B. system, now separated, also lost a little angular momentum. That angular momentum in the bodies of Jupiter and Saturn was relocated inward from one to three thousand a.u. all the way down to five to ten a.u. The two captures by the Sun, Neptune-Uranus and Jupiter-Saturn, did not necessarily occur during the same incoming flyby of Little Brother. But it is a distinct possibility. There is evidence that Little Brother has made either one or just a very few such "delivery trips" to the doorstep of the Sun. That evidence will be presented in a few chapters. The evidence of a paucity of trips by L. B. around the Sun is critical to our understanding as to how, and how recently this Solar System was organized. Thus we will present evidence suggesting that the Solar System is recent, less than a million years, less than a hundred thousand years perhaps. From the gradualist dogma of four billion years, this could be a reduction in time requirements of 99.975% The question becomes, "Did Little Brother acquire the Jupiter-Saturn binary during the same orbit into deep space that it acquired the Neptune-Uranus binary?" If the answer were "yes", it follows that the Sun acquired all four planet systems within the same score of years. If the answer were "no", it follows that they were captured in different eras. Which is more probable? At this point in time, we do not know. What we are sure of is that Jupiter and Saturn once co-orbited as a binary pair in remote space. Their twin spins are a solid pair of clues. Coupled with the spins of Uranus and Neptune, we now gather two pairs of solid clues. The Earth's acquisition of the Moon, likely in remote space, is a fifth clue that our "capture cosmology" is the best approach. The seventh story of our catastrophic cosmology is the acquisition of their modern orbits by Jupiter and Saturn. It will be noticed that Uranus and Neptune were closely related in remote space. Today, Uranus and Neptune are still fairly closely related. They are the seventh and eighth closest planets. They still are next to each other, though not as closely as when under the dominion of Little Brother. Jupiter and Saturn are our fifth and sixth most distant planets from the Sun. Although they were separated by the Sun, they also, as Inner Solar System planets, still remain next to each other, although they are not as close as when under Little Brother's dominion. Their place in the solar system, next to each other, fifth and sixth, is no accident, no coincidence, not a result of chance. The neighboring relationships of both Neptune-Uranus and Saturn-Jupiter are vestiges of the former age when they co-orbited and created reciprocal spins. A Dating ClueThe Icy Rings of Saturn The ice in the icy rings of Saturn does effervesce away constantly into space. Various estimates have been made of the rate the thinning of these icy rings. So far as we are aware, there is no consensus. It could make an exciting study to examine the celestial brilliance of the rings of Saturn as they were on early photographic plates over 100 years ago. Comparing to the present reflectivity, one could then estimate the minute rate of effervescence - thinning of the ring system. Estimates have been made as to how long in the future Saturn's rings will last. Those estimates range from 10,000 years future to 100,000 years for the time left for the life span of those icy rings. The icy rings had a genesis when an icy satellite, an ice ball was rerouted too close to Saturn. "Too close" is 2.5 radii, as was defined by Roche's Limit. In 1850, Edouard Roche studied the tidal effects of two planets, or a planet and a moon that theoretically were on a collision course. He found that due to sudden internal tidal stresses that would be generated, the smaller of two planets on a collision course would fragment before collision. He calculated the distance of fragmentation at 2.44 radii. He assumed two bodies of equal density, and with circular orbits. Saturn has a radius of almost 36,000 miles. Thus, for an ice ball, and given Saturn's low density, its "Roche Limit" is about 85,000 miles. This distance is also the outer boundary of the icy ring system, a confirmation of the case for an icy fragmentation. Most likely, this ice ball was redirected during a close Saturn-Jupiter flyby in the former age when they co-orbited Little Brother. The icy rings would begin to effervesce when Saturn was delivered to the Inner Solar System. Following this, we don't know how much ice originally orbited Saturn; we do know the masses of its inner ice balls. They may be similar in size to the fragmented ice ball. In this way, the icy rings of Saturn suggests some degree of recentness for Saturn's delivery to its present orbit. After more study, if the estimate of 100,000 years for present longevity of Saturn's rings holds up, then it points to a Solar System that is "shockingly youthful" (to gradualists.) For Saturn's icy moons, it was chaos to experience a close flyby of Jupiter in the previous era. Mimas is Saturn's innermost surviving satellite, at 115,000 miles. It is just beyond the Saturnian Roche Limit. As was mentioned earlier, Mimas is an icy satellite pocked with craters and pitlets. Mimas has one crater that is one-third of its own radius. Perhaps some of its craters came from hits by icy debris from Saturn's icy fragmentation. The density of little Mimas is 1.2 compared to water, at a density of 1.0. No one knows, or wonders about how much ice formerly was in the ring system of Saturn. Little Mimas has an orbit radius of some 115,000 miles. It has a physical radius of about 121 miles. Largely composed of ice, its volume exceeds 7,000,000 cubic miles. No one knows whether the ice ball that did fragment was of a similar size, but it is a reasonable conjecture. Mimas might be an indication of how much ice originally might have been in Saturn's icy fragmentation. A fraction of that amount of ice settled into Saturn's resplendent icy rings. As was the case with the capture of Neptune and Uranus, the dating of L. B.'s delivery of Saturn and Jupiter to the doorstep of the Sun is a $64,000 question. The icy rings of Saturn, and their rate of effervescence, are an indication of recentness as gradualist astronomers assess time past. Saturn's rings point to our first theme, planetary catastrophism. These icy rings also point toward our second theme, a shockingly young solar system. And, Dr. Watson, the plot is about to thicken. The clue of Saturn's Rings, and their rate of effervescence is our story 8 of the new, catastrophic cosmology. That leaves some 62 stories yet to be erected. The Capture of The Four Inner Planets The Most Recent of the Snatches We have modeled that the Uranus and Neptune pair formerly co-orbited L. B., as did the Saturn-Jupiter pair. The model of capture of the inner planets by the Sun also works very well if we model Venus and the Earth formerly co-orbiting in orbits of low eccentricity. Venus has a mass 81.5% compared to the Earth. It has a density of 5.24 compared to 5.52 for the Earth. Venus has a polar diameter of 7,5l7 miles compared to the Earth's at 7,900 miles (polar). Physically, Venus is the Earth's twin. Mars, Mercury and the Moon, on the other hand, have masses with reference to the Earth, of only .107, .055 and .012 respectively. The Original Quintet in the Pre-Capture Era In size, the Venus and Earth pair are virtually twin planets. However, there are no twin spins, which means no close flybys in the previous age for Venus and the Earth. On the other hand, Mars has a twin spin with the Earth, indicating a third case of repeated planetary catastrophism in the former era. The model also works wonderfully well if we assume that, in orbiting L. B., Venus co-orbited with the Earth, and like the Moon, Venus was spinless - it showed the same face constantly to he Earth. In addition, our model functions best if Venus co-orbited the Earth in the clockwise direction (as viewed from Polaris). This is the same direction it slowly rotates today, backward. All of the nine planets today orbit the Sun counter-clockwise. And eight of the nine all rotate in the counter-clockwise mode, all except Venus. Today, although Venus hardly rotates at all, what little spin it does have is backward. The model of delivery by Little Brother and capture by the Sun included a package of five small bodies - Earth, Venus, Mars, Mercury and the Moon. The model works best if the conditions of this little five group was the following: Subset A. Originally in deep space, the Moon orbited the Earth in a roundish orbit at a distance of roughly 250,000 miles. This is similar to today. In so doing, the Moon rotated so as always to show the same face to the Earth. It still does. From the Earth's viewpoint, the Moon does not rotate. But from the Sun's viewpoint, the Moon rotates once in 29+ days, with one side always facing the Earth. However it has no spin axis. Subset B. Second, in deep space, in the former age, Mercury orbited Venus also in a roundish orbit at a distance of some 300,000 miles. It also behaved like the Moon; it showed one face and one face only to Venus. It, too, lacked a spin axis. Subset C. Third, in deep space, Mars orbited the Earth on a slightly different plane than the Moon. The orbit of Mars must have been long and narrow, i.e. highly eccentric. This is evident because the two developed reciprocal twin spins, just like Neptune-Uranus and Jupiter-Saturn. Twin spins developed from those close flybys long before the two planets were delivered to the doorstep of the Sun. We model Mars in deep space in the previous age coming within 30,000 miles of the Earth but retreating a distance of several million miles. Subset D. In the previous era, perhaps 1,000 a.u. from the Sun, Venus and the Earth co-orbited at a distance of perhaps 950,000 miles to 1,000,000 miles from each other. Its slow, backward rotation today corresponds to a slow, circular, backward revolving around the Earth in the previous age. The direction or co-orbiting was clockwise for Venus. Thus, Venus orbited the Earth in the opposite direction that Little Brother orbited the Sun. This we call "retrograde" (uncommon) or "clockwise," as it is viewed from Polaris, the North Star. Thus, in deep space, the Earth had a co-orbiting partner (Venus) plus two satellites, Mars and the Moon. Its partner, Venus, also had a non-rotating satellite some 300,000 miles distant, Mercury. This was a sticky little quintet. This quintet also was relatively close in to Little Brother (compared to Jupiter-Saturn and Neptune-Uranus.) . Hence, when stripping time came, if all the planet-stripping was done in one flyby, the quintet was the last system to be stripped off "L. B." and dismembered by the Sun, the Moon excepted. Hence these five comprise what some consider to be the "inner solar system" of today. All orbit within 160,000,000 miles of the Sun, compared to Jupiter's 480,000,000 miles. In this last capture process, for the sticky quintet, first the Sun separated Mars from the Earth. Shortly, perhaps within days, the Earth was divorced from its co-orbiting partner, spinless Venus. Within a couple of weeks more, as "L. B." inexorably approached the Sun, little spinless Mercury was stripped from Venus. Venus, was deposited on the brink of Hell's Kitchen, and the other, Mercury, as it was separated, was sent into an orbit inside Hell's Kitchen itself where temperatures rise to 700° and 800° F. Only the Earth-Moon system had survived the process of dismemberment and realignment around the Sun. This process of capture can be modeled. Figure 3 illustrates the last and the nearest to the Sun of the three packages of celestial captives. The Delivery Orbit for Mars Story 9 is about vestiges and the geographical relationships of the planets today. Mars was delivered to the inner Solar System. Evidently, it was delivered with a long, narrow, highly eccentric orbit, and it maintained that orbital trait into its second and even its third age. The "First Orbit of Mars" was when it orbited the Earth in the remote region 1,000 a.u. or more. The "Second Orbit of Mars" was ended when Mars met Astra in space, some 230,000,000 miles distant. Astra fragmented. Mars gained a little mass, and some angular momentum. But it lost some energy in the crisis. But we are getting ahead of ourselves. "The Scars of Mars" is the title for Volume II, where the details of the Second Orbit, the Third Orbit, and the Fourth Orbit of Mars are analyzed, and why the shifts. To summarize, somewhere between 150,000,000 and 200,000,000 miles from the Sun, both Little Brother and the Earth lost Mars. About 92,000,000 miles from the Sun, Little Brother lost the Earth, and shortly, some 67,000,000 miles, Venus (already stripped from the Earth) was also lost by "L. B." Finally, some 35,000,000 miles from the Sun, Mercury, already stripped from Venus, was also lost by Little Brother. Little Brother was picked clean of its satellites systems. Figure 3 illustrates. Earlier, it was noted that Neptune and Uranus once co-orbited, and they are still in the same neighborhood in the Solar System, still next to each other. This is a vestige of the ancient age. Next it was noted that Saturn and Jupiter once co-orbited, and they also are still next to each other, a second vestige of the primordial age. Now, we see that Mars and the Earth once co-orbited in the remote frigid region. And when the Sun stripped them, they continued to be next to each other. This is a third vestige. In addition, Venus and the Earth co-orbited, and they are still next to each other, a fourth vestige. Finally, little Mercury was a satellite of Venus and after it was stripped from Venus, it also settled down into an orbit next to Venus. Such is our fifth vestige. All of these five vestiges are geographical catastrophism and the geography of the cosmos. This series of separations from L. B., and repositions of the various planets may seem complicated. It isn't. There are only three bunches of planets that were separated from L. B., and (or) delivered to the Sun. First was Uranus-Neptune with satellites, second was Jupiter-Saturn with satellites, and third was Venus-Earth, of which two of the three satellites were stripped off, Mars and Mercury. Because of their greater distance from the Sun, Neptune, Uranus, Saturn and Jupiter each retained their satellite systems. But because Venus and the Earth were separated so close to the Sun (within 100,000,000 miles), two of the their three satellites, Mercury and Mars, were stripped off. Today we call them planets, tiny ones to be sure. In science, there is a maxim that almost always valid. When science is faced with two explanations for a phenomenon, a simple answer and a convoluted one, the simple answer is almost always the correct one. It is known as "Occam's Razor." In the 1300's, William of Occam (Ockham) wrote, "Entia non sunt multiplicanda praeter necessitatem." Loosely translated, it says that complications ought not to be multiplied except out of necessity. In his century, Occam was scientifically quite correct, although he was politically incorrect (and he paid the price of that age.) Our relatively simple, straight-forward theory of capture of three clusters of planets needs to be compared with, and contrasted to the many convolutions, and revision after revision of the nebular hypothesis. The nebular hypothesis, still a favorite of gradualists some 200 years later, tries to affirm all planetary components were extruded from the Sun. More on this convoluted, "popular" (frequently taught) approach is reserved for Chapter 10. The Placement of The Dismembered VenusEarth Binary Earlier, it was noted that Uranus and Neptune were separated from each other, but in that separation still remain somewhat close by each other. The same can be said for the Jupiter-Saturn binary; they too are still somewhat close by each other. Now, once again, we note that even though Venus and the Earth were separated from each other, they still remain fairly close to each other, side by side in the order of the planets. These are vestiges of delivery and capture; they are not three coincidences. The Earth formed a 360-day orbit, its "second orbit." Its first orbit was around Little Brother. This second orbit around the Sun was some 92,250,000 miles from the Sun, almost 1% closer than is the present arrangement. The "second orbit" of Mars in our model has Mars in a new, capture orbit where it may have came in to a region some 64,000,000 miles to the Sun but yet returned out to approximately 230,000,000 miles. Today this region, 230,000,000 miles from the Sun, is known as the heart of the asteroid belt. As was mentioned earlier, the "Second Orbit of Mars" will be discussed at some length in the next volume. Then, and in that context, occurred its sudden conversion, or deterioration into the infamous "Third Orbit of Mars." In the process Mars acquired an interesting display of scars on its surface. Thus, the Sun's radius of action broke up both the ancient Earth-Venus and the Earth-Mars relationships. It also broke up the Venus-Mercury relationship. But it did not break up the Earth-Moon relationship, merely because the Moon originally was so close to the Earth. The Moon never ventured out anywhere near 750,000 miles from the Earth, where it, too, could have been picked off. Figure 3 illustrates this original quintet, as the group orbited L.B. Mars, Earth-Moon system, Venus, Mercury. Such was the order of separation and delivery to the Sun, or, put in another way, it was the "order of capture" by the Sun. It was something like an adoption agency, sending five siblings all from the same family off in four different directions, allowing only the smallest of the five siblings to stay with the largest. Mars was separated from the Earth, yet maintaining its ancient long narrow orbit. Gravities attract, and Mars continued to cross the Earth's orbit. In a sense, Mars continued to "search for" and to seek the Earth, its former major focus. But with little success, at first. The Backward Slow Rotation of Venus The slow, backward rotation of Venus has been a mammoth-like conundrum, probably the greatest conundrum of all for gradualists during the 20th century. Venus, deeply in the Inner Solar System, together with Mercury, are right there where accretion from the Sun's ejecta was supposed to have condensed to the maximum, but instead somehow it has functioned to the minimum. This failure can no longer be swept under the rug. Somehow, some way, Venus, the morning star, rotates backward. And ever so slowly. Its backward (retrograde) rotation rate is once in 243.01 days - once in 5,832 hours. Its equatorial rotation measures to be only 4.05 mph., walking speed. The Earth rotates 1,037.6 mph in the other direction, prograde, counter-clockwise. This conundrum is easily solved. All that is needed is a well thought out model of capture and delivery. The key is the pre-capture era. Venus in the pre-capture era co-orbited with the Earth, at a distance of almost 1,000,000 miles. Both moved from the outer solar region to the inner region by orbiting, or revolving around L.B. clockwise - backward, or retrograde. In addition, Venus did not rotate, but, like the Moon, its ancient "face" "looked at" the Earth constantly. The model works best if the two planets co-orbited around "L. B." in the clockwise mode, opposite to the mode "L.B." orbited the Sun. Given this model, Venus would be picked off by the Sun, separating it first from the Earth, and second from "L. B.". Venus was sent into an orbit with an average radius of some 68,000,000 miles. With its retrograde direction of orbiting, at the moment of separation and capture, Venus kept facing the Earth. After separation, even today, Venus still in fact looks back to the Earth. (Gradualists, please note). Venus was like a lover, being separated from her husband during World War II. He, the soldier, boarded the troop train, or the boat, leaving forever. She, the wife left behind, on the dock departed, slowly throwing BACKWARD a final kiss to her beloved. This kind of thing happened many times to GIs and their brides in the early l940's. And many soldiers in fact never did return. The liberty (and ability) to a think in terms of planetary catastrophism frees us, as cosmologists, from the straight-jacket and the jail cell of gradualism. This is something like Copernicus and Kepler being freed from the tragedy of geocentricity. Copernicus and Kepler went on to provide the first two birth pangs of something entirely new to the history of man. It was the discovery of a system of natural law, which we now call "science". The tenth story in our cosmological construction is the acquisition of backward rotation by Venus. If gradualists choose to refute planetary catastrophism, this is where they should begin. This is certainly one of their biggest dilemmas, and we know a secret. It, the backward, slow rotation of Venus, will continue to be their foremost dilemma until they chuck gradualism. The Prograde Slow Rotation of Mercury Story 11 of our skyscraper is concerned with the ever-so-slow rotation of Mercury, prograde. Mercury rotates once in 58.65 days. At Mercury's equator, it rotates 6.7 mph. It compares to Venus, which rotates at 4.l mph at its equator. Both have such slow rotations because they were non-rotating satellites in the primordial age, when they revolved around "L. B." Mercury was dropped off into Hell's Kitchen because it was the last of the satellites to be stripped. This means that Little Brother approached at least 28,000,000 miles close to the Sun, because such is Mercury's distance today. Mercury's orbit period is 87.97 days. For reasons presently unknown, Mercury's rotation and is orbit period are in 3:2 resonance. Recently, it was determined that Mercury is not a liquid planet with a crust like Venus, the Earth and Mars. It is a solid planet. This is an indication that Mercury's center was very cold when it was delivered, and it hasn't warmed up a great deal since the time of delivery. How the Earth-Moon System Acquired Its Ancient 360-Day Orbit The twelfth story of our celestial skyscraper of cosmology concerns how the Earth-Moon system acquired its ancient 360-day orbit, some 92,250,000 miles from the Sun. This location for the Earth is in the middle of a 15,000,000-mile slot in the Solar System. In this narrow slot, and only in this slot, water neither boils constantly (as on Venus) nor does water freeze permanently (as on Mars.) This "slot" happens to be the one and only favorable location in the solar system where chloroplasts and chlorophyll can function. And where a planet can be greened. But we are getting ahead of our story. Whether by chance or design, the Earth was dropped into that marvelous, advantageous slot. It was 92,250,000 miles from the Sun, just 25,000,000 miles from Venus where surface temperatures rise to 700° F. The Earth was dropped off into "the slot" due to its previous distance from Little Brother and due to the geometry (and geography) of capture by the Sun. Our age, in part framed by gradualist dogma, is the age of the vanity of humanity. Our good fortune for our planet's location "in the slot" is not widely appreciated. Compared to vanity, humility is better, and an age of humility would be best. Job learned this, before it was too late, long ago. Job, viewing the grandeur of creation in a new light, was utterly speechless. The sixth story in our skyscraper is how the orbits of Neptune and Uranus came to be, and why Neptune and Uranus still are neighbors. Their ancient spin rates were nearly identical before separation and still are. The seventh story is how and why, if not when Jupiter and Saturn were picked off and captured by the Sun, some 480,000,000 miles and 880,000,000 miles respectively from the Sun. Part of the story is why they, too, are still neighbors. Like the Neptune-Uranus case, their spin rates also were nearly identical and still are. The eighth story is related to the seventh. It is probable that Saturn already had its icy rings before it was ferried close to the Sun and delivered. Since then, the solar radiation has been effervescing away those splendid rings; they are a mere shadow of what they once were. The rings of Saturn are one kind of dating mechanism for the origin of the solar system, and as such, indicate recentness. The eighth story is the breakup of the quintet in the inner region of the solar system. A two-planet co-orbiting binary, with three satellites, revolving around "L. B." was converted to four planets and just one satellite, all revolving around the Sun. The ninth story of our skyscraper is how an early orbit of Mars and Earth was changed; Mars was liberated first from the Earth and next, from Little Brother. It features the new second orbit of Mars. It was still long and narrow, but Mars now orbited the Sun instead of L. B. In the earlier age, Mars had sought the Earth repeatedly. And next, despite having been separated from the Earth, it continued to seek our planet. The tenth story of our skyscraper of cosmology addresses why Venus rotates so slowly, and why it rotates in the backward mode. Gradualists have pondered this for 100 years and have yet to gain even an inkling. This story also reveals why Venus orbits on the other side, on the edge of Hell's Kitchen, only 65,000,000+ miles from the Sun. We are pleased to announce that understanding this condition is merely by understanding its previous co-orbiting of the Earth and related conditions. Given a good model, the unique, backward, slow rotation of Venus isn't that hard to solve. The eleventh story of our skyscraper is why tiny Mercury rotates so slowly. The reason is because formerly it had no spin axis at all when it orbited Venus in the previous, primordial era. Once non-rotating, its geometry of capture dictated a very, very slow prograde rotation. Mercury rotates in 58.65 days. The twelfth story in our catastrophic cosmology is an observation that the Earth-Moon was dropped off in "the slot." It acquired a new orbit around the Sun, one conquered neither by superheated waters like Venus, nor by perpetual ices like Mars. Coincidence? Perhaps. By design? More likely. For some 200+ years, gradualists have always looked to the Sun for cosmic supplies to stock the Solar System. Having admitted their error in part (after over 100 years), they now have settled for claiming the Sun and planets formed simultaneously out of a cloud. Sublime in misdirection, the gradualists have been looking in just exactly the wrong region for the origin of the planets, the region of inner space, near to and in "Hell's Kitchen." They should have been looking to the region 1,000 a.u. or so from the Sun in dark, remote, frigid space. However, evidence indicates that spin rates were acquired in a remote region at or beyond 1,000 a.u. or more from the Sun. So were satellite systems and craters in abundance. A delivery into the Inner Solar System requires a properly modeled delivery system, and a logical route. The logical route is simply the ecliptic plane. The delivery system is some super-planet along the lines we have modeled, a super-planet 30 to 40 times as massive as Jupiter in mass, also 9,000 to 12,000 times the Earth's mass. If its density is similar to the Earth's, Little Brother could have a diameter of 190,000 miles. If these eight planets were delivered to the Sun into the inner Solar system, there must be a delivery system, a United Parcel Service of the cosmos. The deliveries of the Neptune-Uranus pair and the Saturn Jupiter pair are two items in evidence. The delivery of the quintet is a third indication that a delivery system exists. But, is there more evidence? PREVIEW. Surprisingly, as one proceeds into an analysis of the planets in "Hell's Kitchen," including the Sun itself, three or four more scars, or clues, can be observed, scars of Little Brother's last flyby around the Sun. Read on. We offer our model with logic interspersed with various kinds of evidence. PREVIEW. As it so happens in good movies, while the previously mentioned clues are good evidence of this delivery system, the United Parcel Service of the cosmos, nevertheless the best clues are left for the last. Those clues, three or four of them, can be seen inside the orbit of Venus. Read on. F2 Kuiper, Gerard P., Planets and Satellites. Chicago, Univ. of Chicago Press, 1961, pp. 577-578. The Recent Organization of The Solar System by Patten & Windsor
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. Most optical phenomena can be accounted for by using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation. Some phenomena depend on the fact that light has both wave-like and particle-like properties. Explanation of these effects requires quantum mechanics. When considering light's particle-like properties, the light is modelled as a collection of particles called "photons". Quantum optics deals with the application of quantum mechanics to optical systems. Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, and medicine (particularly ophthalmology and optometry, in which it is called physiological optics). Practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, lenses, telescopes, microscopes, lasers, and fibre optics. Optics began with the development of lenses by the ancient Egyptians and Mesopotamians. The earliest known lenses, made from polished crystal, often quartz, date from as early as 2000 BC from Crete (Archaeological Museum of Heraclion, Greece). Lenses from Rhodes date around 700 BC, as do Assyrian lenses such as the Nimrud lens. The ancient Romans and Greeks filled glass spheres with water to make lenses. These practical developments were followed by the development of theories of light and vision by ancient Greek and Indian philosophers, and the development of geometrical optics in the Greco-Roman world. The word optics comes from the ancient Greek word ὀπτική (optikē), meaning "appearance, look". Greek philosophy on optics broke down into two opposing theories on how vision worked, the intromission theory and the emission theory. The intromission approach saw vision as coming from objects casting off copies of themselves (called eidola) that were captured by the eye. With many propagators including Democritus, Epicurus, Aristotle and their followers, this theory seems to have some contact with modern theories of what vision really is, but it remained only speculation lacking any experimental foundation. Plato first articulated the emission theory, the idea that visual perception is accomplished by rays emitted by the eyes. He also commented on the parity reversal of mirrors in Timaeus. Some hundred years later, Euclid (4th–3rd century BC) wrote a treatise entitled Optics where he linked vision to geometry, creating geometrical optics. He based his work on Plato's emission theory wherein he described the mathematical rules of perspective and described the effects of refraction qualitatively, although he questioned that a beam of light from the eye could instantaneously light up the stars every time someone blinked. Euclid stated the principle of shortest trajectory of light, and considered multiple reflections on flat and spherical mirrors. Ptolemy, in his treatise Optics, held an extramission-intromission theory of vision: the rays (or flux) from the eye formed a cone, the vertex being within the eye, and the base defining the visual field. The rays were sensitive, and conveyed information back to the observer's intellect about the distance and orientation of surfaces. He summarized much of Euclid and went on to describe a way to measure the angle of refraction, though he failed to notice the empirical relationship between it and the angle of incidence. Plutarch (1st–2nd century AD) described multiple reflections on spherical mirrors and discussed the creation of magnified and reduced images, both real and imaginary, including the case of chirality of the images. During the Middle Ages, Greek ideas about optics were resurrected and extended by writers in the Muslim world. One of the earliest of these was Al-Kindi (c. 801–873) who wrote on the merits of Aristotelian and Euclidean ideas of optics, favouring the emission theory since it could better quantify optical phenomena. In 984, the Persian mathematician Ibn Sahl wrote the treatise "On burning mirrors and lenses", correctly describing a law of refraction equivalent to Snell's law. He used this law to compute optimum shapes for lenses and curved mirrors. In the early 11th century, Alhazen (Ibn al-Haytham) wrote the Book of Optics (Kitab al-manazir) in which he explored reflection and refraction and proposed a new system for explaining vision and light based on observation and experiment. He rejected the "emission theory" of Ptolemaic optics with its rays being emitted by the eye, and instead put forward the idea that light reflected in all directions in straight lines from all points of the objects being viewed and then entered the eye, although he was unable to correctly explain how the eye captured the rays. Alhazen's work was largely ignored in the Arabic world but it was anonymously translated into Latin around 1200 A.D. and further summarised and expanded on by the Polish monk Witelo making it a standard text on optics in Europe for the next 400 years. In the 13th century in medieval Europe, English bishop Robert Grosseteste wrote on a wide range of scientific topics, and discussed light from four different perspectives: an epistemology of light, a metaphysics or cosmogony of light, an etiology or physics of light, and a theology of light, basing it on the works Aristotle and Platonism. Grosseteste's most famous disciple, Roger Bacon, wrote works citing a wide range of recently translated optical and philosophical works, including those of Alhazen, Aristotle, Avicenna, Averroes, Euclid, al-Kindi, Ptolemy, Tideus, and Constantine the African. Bacon was able to use parts of glass spheres as magnifying glasses to demonstrate that light reflects from objects rather than being released from them. The first wearable eyeglasses were invented in Italy around 1286. This was the start of the optical industry of grinding and polishing lenses for these "spectacles", first in Venice and Florence in the thirteenth century, and later in the spectacle making centres in both the Netherlands and Germany. Spectacle makers created improved types of lenses for the correction of vision based more on empirical knowledge gained from observing the effects of the lenses rather than using the rudimentary optical theory of the day (theory which for the most part could not even adequately explain how spectacles worked). This practical development, mastery, and experimentation with lenses led directly to the invention of the compound optical microscope around 1595, and the refracting telescope in 1608, both of which appeared in the spectacle making centres in the Netherlands. In the early 17th century, Johannes Kepler expanded on geometric optics in his writings, covering lenses, reflection by flat and curved mirrors, the principles of pinhole cameras, inverse-square law governing the intensity of light, and the optical explanations of astronomical phenomena such as lunar and solar eclipses and astronomical parallax. He was also able to correctly deduce the role of the retina as the actual organ that recorded images, finally being able to scientifically quantify the effects of different types of lenses that spectacle makers had been observing over the previous 300 years. After the invention of the telescope, Kepler set out the theoretical basis on how they worked and described an improved version, known as the Keplerian telescope, using two convex lenses to produce higher magnification. Optical theory progressed in the mid-17th century with treatises written by philosopher René Descartes, which explained a variety of optical phenomena including reflection and refraction by assuming that light was emitted by objects which produced it. This differed substantively from the ancient Greek emission theory. In the late 1660s and early 1670s, Isaac Newton expanded Descartes' ideas into a corpuscle theory of light, famously determining that white light was a mix of colours that can be separated into its component parts with a prism. In 1690, Christiaan Huygens proposed a wave theory for light based on suggestions that had been made by Robert Hooke in 1664. Hooke himself publicly criticised Newton's theories of light and the feud between the two lasted until Hooke's death. In 1704, Newton published Opticks and, at the time, partly because of his success in other areas of physics, he was generally considered to be the victor in the debate over the nature of light. Newtonian optics was generally accepted until the early 19th century when Thomas Young and Augustin-Jean Fresnel conducted experiments on the interference of light that firmly established light's wave nature. Young's famous double slit experiment showed that light followed the superposition principle, which is a wave-like property not predicted by Newton's corpuscle theory. This work led to a theory of diffraction for light and opened an entire area of study in physical optics. Wave optics was successfully unified with electromagnetic theory by James Clerk Maxwell in the 1860s. The next development in optical theory came in 1899 when Max Planck correctly modelled blackbody radiation by assuming that the exchange of energy between light and matter only occurred in discrete amounts he called quanta. In 1905, Albert Einstein published the theory of the photoelectric effect that firmly established the quantization of light itself. In 1913, Niels Bohr showed that atoms could only emit discrete amounts of energy, thus explaining the discrete lines seen in emission and absorption spectra. The understanding of the interaction between light and matter that followed from these developments not only formed the basis of quantum optics but also was crucial for the development of quantum mechanics as a whole. The ultimate culmination, the theory of quantum electrodynamics, explains all optics and electromagnetic processes in general as the result of the exchange of real and virtual photons. Quantum optics gained practical importance with the inventions of the maser in 1953 and of the laser in 1960. Following the work of Paul Dirac in quantum field theory, George Sudarshan, Roy J. Glauber, and Leonard Mandel applied quantum theory to the electromagnetic field in the 1950s and 1960s to gain a more detailed understanding of photodetection and the statistics of light. Classical optics is divided into two main branches: geometrical (or ray) optics and physical (or wave) optics. In geometrical optics, light is considered to travel in straight lines, while in physical optics, light is considered as an electromagnetic wave. Geometrical optics can be viewed as an approximation of physical optics that applies when the wavelength of the light used is much smaller than the size of the optical elements in the system being modelled. Geometrical optics, or ray optics, describes the propagation of light in terms of "rays" which travel in straight lines, and whose paths are governed by the laws of reflection and refraction at interfaces between different media. These laws were discovered empirically as far back as 984 AD and have been used in the design of optical components and instruments from then until the present day. They can be summarised as follows: When a ray of light hits the boundary between two transparent materials, it is divided into a reflected and a refracted ray. where n is a constant for any two materials and a given colour of light. If the first material is air or vacuum, n is the refractive index of the second material. Geometric optics is often simplified by making the paraxial approximation, or "small angle approximation". The mathematical behaviour then becomes linear, allowing optical components and systems to be described by simple matrices. This leads to the techniques of Gaussian optics and paraxial ray tracing, which are used to find basic properties of optical systems, such as approximate image and object positions and magnifications. Reflections can be divided into two types: specular reflection and diffuse reflection. Specular reflection describes the gloss of surfaces such as mirrors, which reflect light in a simple, predictable way. This allows for the production of reflected images that can be associated with an actual (real) or extrapolated (virtual) location in space. Diffuse reflection describes non-glossy materials, such as paper or rock. The reflections from these surfaces can only be described statistically, with the exact distribution of the reflected light depending on the microscopic structure of the material. Many diffuse reflectors are described or can be approximated by Lambert's cosine law, which describes surfaces that have equal luminance when viewed from any angle. Glossy surfaces can give both specular and diffuse reflection. In specular reflection, the direction of the reflected ray is determined by the angle the incident ray makes with the surface normal, a line perpendicular to the surface at the point where the ray hits. The incident and reflected rays and the normal lie in a single plane, and the angle between the reflected ray and the surface normal is the same as that between the incident ray and the normal. This is known as the Law of Reflection. For flat mirrors, the law of reflection implies that images of objects are upright and the same distance behind the mirror as the objects are in front of the mirror. The image size is the same as the object size. The law also implies that mirror images are parity inverted, which we perceive as a left-right inversion. Images formed from reflection in two (or any even number of) mirrors are not parity inverted. Corner reflectors produce reflected rays that travel back in the direction from which the incident rays came. This is called retroreflection. Mirrors with curved surfaces can be modelled by ray tracing and using the law of reflection at each point on the surface. For mirrors with parabolic surfaces, parallel rays incident on the mirror produce reflected rays that converge at a common focus. Other curved surfaces may also focus light, but with aberrations due to the diverging shape causing the focus to be smeared out in space. In particular, spherical mirrors exhibit spherical aberration. Curved mirrors can form images with a magnification greater than or less than one, and the magnification can be negative, indicating that the image is inverted. An upright image formed by reflection in a mirror is always virtual, while an inverted image is real and can be projected onto a screen. The index of refraction of a medium is related to the speed, v, of light in that medium by Snell's Law can be used to predict the deflection of light rays as they pass through linear media as long as the indexes of refraction and the geometry of the media are known. For example, the propagation of light through a prism results in the light ray being deflected depending on the shape and orientation of the prism. In most materials, the index of refraction varies with the frequency of the light. Taking this into account, Snell's Law can be used to predict how a prism will disperse light into a spectrum. The discovery of this phenomenon when passing light through a prism is famously attributed to Isaac Newton. Some media have an index of refraction which varies gradually with position and, therefore, light rays in the medium are curved. This effect is responsible for mirages seen on hot days: a change in index of refraction air with height causes light rays to bend, creating the appearance of specular reflections in the distance (as if on the surface of a pool of water). Optical materials with varying indexes of refraction are called gradient-index (GRIN) materials. Such materials are used to make gradient-index optics. A device that produces converging or diverging light rays due to refraction is known as a lens. Lenses are characterized by their focal length: a converging lens has positive focal length, while a diverging lens has negative focal length. Smaller focal length indicates that the lens has a stronger converging or diverging effect. The focal length of a simple lens in air is given by the lensmaker's equation. Ray tracing can be used to show how images are formed by a lens. For a thin lens in air, the location of the image is given by the simple equation Incoming parallel rays are focused by a converging lens onto a spot one focal length from the lens, on the far side of the lens. This is called the rear focal point of the lens. Rays from an object at a finite distance are focused further from the lens than the focal distance; the closer the object is to the lens, the further the image is from the lens. With diverging lenses, incoming parallel rays diverge after going through the lens, in such a way that they seem to have originated at a spot one focal length in front of the lens. This is the lens's front focal point. Rays from an object at a finite distance are associated with a virtual image that is closer to the lens than the focal point, and on the same side of the lens as the object. The closer the object is to the lens, the closer the virtual image is to the lens. As with mirrors, upright images produced by a single lens are virtual, while inverted images are real. Lenses suffer from aberrations that distort images. Monochromatic aberrations occur because the geometry of the lens does not perfectly direct rays from each object point to a single point on the image, while chromatic aberration occurs because the index of refraction of the lens varies with the wavelength of the light. In physical optics, light is considered to propagate as a wave. This model predicts phenomena such as interference and diffraction, which are not explained by geometric optics. The speed of light waves in air is approximately 3.0×108 m/s (exactly 299,792,458 m/s in vacuum). The wavelength of visible light waves varies between 400 and 700 nm, but the term "light" is also often applied to infrared (0.7–300 μm) and ultraviolet radiation (10–400 nm). The wave model can be used to make predictions about how an optical system will behave without requiring an explanation of what is "waving" in what medium. Until the middle of the 19th century, most physicists believed in an "ethereal" medium in which the light disturbance propagated. The existence of electromagnetic waves was predicted in 1865 by Maxwell's equations. These waves propagate at the speed of light and have varying electric and magnetic fields which are orthogonal to one another, and also to the direction of propagation of the waves. Light waves are now generally treated as electromagnetic waves except when quantum mechanical effects have to be considered. Many simplified approximations are available for analysing and designing optical systems. Most of these use a single scalar quantity to represent the electric field of the light wave, rather than using a vector model with orthogonal electric and magnetic vectors. The Huygens–Fresnel equation is one such model. This was derived empirically by Fresnel in 1815, based on Huygens' hypothesis that each point on a wavefront generates a secondary spherical wavefront, which Fresnel combined with the principle of superposition of waves. The Kirchhoff diffraction equation, which is derived using Maxwell's equations, puts the Huygens-Fresnel equation on a firmer physical foundation. Examples of the application of Huygens–Fresnel principle can be found in the articles on diffraction and Fraunhofer diffraction. More rigorous models, involving the modelling of both electric and magnetic fields of the light wave, are required when dealing with materials whose electric and magnetic properties affect the interaction of light with the material. For instance, the behaviour of a light wave interacting with a metal surface is quite different from what happens when it interacts with a dielectric material. A vector model must also be used to model polarised light. Numerical modeling techniques such as the finite element method, the boundary element method and the transmission-line matrix method can be used to model the propagation of light in systems which cannot be solved analytically. Such models are computationally demanding and are normally only used to solve small-scale problems that require accuracy beyond that which can be achieved with analytical solutions. All of the results from geometrical optics can be recovered using the techniques of Fourier optics which apply many of the same mathematical and analytical techniques used in acoustic engineering and signal processing. Gaussian beam propagation is a simple paraxial physical optics model for the propagation of coherent radiation such as laser beams. This technique partially accounts for diffraction, allowing accurate calculations of the rate at which a laser beam expands with distance, and the minimum size to which the beam can be focused. Gaussian beam propagation thus bridges the gap between geometric and physical optics. In the absence of nonlinear effects, the superposition principle can be used to predict the shape of interacting waveforms through the simple addition of the disturbances. This interaction of waves to produce a resulting pattern is generally termed "interference" and can result in a variety of outcomes. If two waves of the same wavelength and frequency are in phase, both the wave crests and wave troughs align. This results in constructive interference and an increase in the amplitude of the wave, which for light is associated with a brightening of the waveform in that location. Alternatively, if the two waves of the same wavelength and frequency are out of phase, then the wave crests will align with wave troughs and vice versa. This results in destructive interference and a decrease in the amplitude of the wave, which for light is associated with a dimming of the waveform at that location. See below for an illustration of this effect. Since the Huygens–Fresnel principle states that every point of a wavefront is associated with the production of a new disturbance, it is possible for a wavefront to interfere with itself constructively or destructively at different locations producing bright and dark fringes in regular and predictable patterns. Interferometry is the science of measuring these patterns, usually as a means of making precise determinations of distances or angular resolutions. The Michelson interferometer was a famous instrument which used interference effects to accurately measure the speed of light. The appearance of thin films and coatings is directly affected by interference effects. Antireflective coatings use destructive interference to reduce the reflectivity of the surfaces they coat, and can be used to minimise glare and unwanted reflections. The simplest case is a single layer with a thickness of one-fourth the wavelength of incident light. The reflected wave from the top of the film and the reflected wave from the film/material interface are then exactly 180° out of phase, causing destructive interference. The waves are only exactly out of phase for one wavelength, which would typically be chosen to be near the centre of the visible spectrum, around 550 nm. More complex designs using multiple layers can achieve low reflectivity over a broad band, or extremely low reflectivity at a single wavelength. Constructive interference in thin films can create a strong reflection of light in a range of wavelengths, which can be narrow or broad depending on the design of the coating. These films are used to make dielectric mirrors, interference filters, heat reflectors, and filters for colour separation in colour television cameras. This interference effect is also what causes the colourful rainbow patterns seen in oil slicks. Diffraction is the process by which light interference is most commonly observed. The effect was first described in 1665 by Francesco Maria Grimaldi, who also coined the term from the Latin diffringere, 'to break into pieces'. Later that century, Robert Hooke and Isaac Newton also described phenomena now known to be diffraction in Newton's rings while James Gregory recorded his observations of diffraction patterns from bird feathers. The first physical optics model of diffraction that relied on the Huygens–Fresnel principle was developed in 1803 by Thomas Young in his interference experiments with the interference patterns of two closely spaced slits. Young showed that his results could only be explained if the two slits acted as two unique sources of waves rather than corpuscles. In 1815 and 1818, Augustin-Jean Fresnel firmly established the mathematics of how wave interference can account for diffraction. The simplest physical models of diffraction use equations that describe the angular separation of light and dark fringes due to light of a particular wavelength (λ). In general, the equation takes the form This equation is modified slightly to take into account a variety of situations such as diffraction through a single gap, diffraction through multiple slits, or diffraction through a diffraction grating that contains a large number of slits at equal spacing. More complicated models of diffraction require working with the mathematics of Fresnel or Fraunhofer diffraction. Diffraction effects limit the ability of an optical detector to optically resolve separate light sources. In general, light that is passing through an aperture will experience diffraction and the best images that can be created (as described in diffraction-limited optics) appear as a central spot with surrounding bright rings, separated by dark nulls; this pattern is known as an Airy pattern, and the central bright lobe as an Airy disk. The size of such a disk is given by where θ is the angular resolution, λ is the wavelength of the light, and D is the diameter of the lens aperture. If the angular separation of the two points is significantly less than the Airy disk angular radius, then the two points cannot be resolved in the image, but if their angular separation is much greater than this, distinct images of the two points are formed and they can therefore be resolved. Rayleigh defined the somewhat arbitrary "Rayleigh criterion" that two points whose angular separation is equal to the Airy disk radius (measured to first null, that is, to the first place where no light is seen) can be considered to be resolved. It can be seen that the greater the diameter of the lens or its aperture, the finer the resolution. Interferometry, with its ability to mimic extremely large baseline apertures, allows for the greatest angular resolution possible. For astronomical imaging, the atmosphere prevents optimal resolution from being achieved in the visible spectrum due to the atmospheric scattering and dispersion which cause stars to twinkle. Astronomers refer to this effect as the quality of astronomical seeing. Techniques known as adaptive optics have been used to eliminate the atmospheric disruption of images and achieve results that approach the diffraction limit. Refractive processes take place in the physical optics limit, where the wavelength of light is similar to other distances, as a kind of scattering. The simplest type of scattering is Thomson scattering which occurs when electromagnetic waves are deflected by single particles. In the limit of Thomson scattering, in which the wavelike nature of light is evident, light is dispersed independent of the frequency, in contrast to Compton scattering which is frequency-dependent and strictly a quantum mechanical process, involving the nature of light as particles. In a statistical sense, elastic scattering of light by numerous particles much smaller than the wavelength of the light is a process known as Rayleigh scattering while the similar process for scattering by particles that are similar or larger in wavelength is known as Mie scattering with the Tyndall effect being a commonly observed result. A small proportion of light scattering from atoms or molecules may undergo Raman scattering, wherein the frequency changes due to excitation of the atoms and molecules. Brillouin scattering occurs when the frequency of light changes due to local changes with time and movements of a dense material. Dispersion occurs when different frequencies of light have different phase velocities, due either to material properties (material dispersion) or to the geometry of an optical waveguide (waveguide dispersion). The most familiar form of dispersion is a decrease in index of refraction with increasing wavelength, which is seen in most transparent materials. This is called "normal dispersion". It occurs in all dielectric materials, in wavelength ranges where the material does not absorb light. In wavelength ranges where a medium has significant absorption, the index of refraction can increase with wavelength. This is called "anomalous dispersion". The separation of colours by a prism is an example of normal dispersion. At the surfaces of the prism, Snell's law predicts that light incident at an angle θ to the normal will be refracted at an angle arcsin(sin (θ) / n). Thus, blue light, with its higher refractive index, is bent more strongly than red light, resulting in the well-known rainbow pattern. Material dispersion is often characterised by the Abbe number, which gives a simple measure of dispersion based on the index of refraction at three specific wavelengths. Waveguide dispersion is dependent on the propagation constant. Both kinds of dispersion cause changes in the group characteristics of the wave, the features of the wave packet that change with the same frequency as the amplitude of the electromagnetic wave. "Group velocity dispersion" manifests as a spreading-out of the signal "envelope" of the radiation and can be quantified with a group dispersion delay parameter: where n is the index of refraction and c is the speed of light in a vacuum. This gives a simpler form for the dispersion delay parameter: If D is less than zero, the medium is said to have positive dispersion or normal dispersion. If D is greater than zero, the medium has negative dispersion. If a light pulse is propagated through a normally dispersive medium, the result is the higher frequency components slow down more than the lower frequency components. The pulse therefore becomes positively chirped, or up-chirped, increasing in frequency with time. This causes the spectrum coming out of a prism to appear with red light the least refracted and blue/violet light the most refracted. Conversely, if a pulse travels through an anomalously (negatively) dispersive medium, high-frequency components travel faster than the lower ones, and the pulse becomes negatively chirped, or down-chirped, decreasing in frequency with time. The result of group velocity dispersion, whether negative or positive, is ultimately temporal spreading of the pulse. This makes dispersion management extremely important in optical communications systems based on optical fibres, since if dispersion is too high, a group of pulses representing information will each spread in time and merge, making it impossible to extract the signal. Polarization is a general property of waves that describes the orientation of their oscillations. For transverse waves such as many electromagnetic waves, it describes the orientation of the oscillations in the plane perpendicular to the wave's direction of travel. The oscillations may be oriented in a single direction (linear polarization), or the oscillation direction may rotate as the wave travels (circular or elliptical polarization). Circularly polarised waves can rotate rightward or leftward in the direction of travel, and which of those two rotations is present in a wave is called the wave's chirality. The typical way to consider polarization is to keep track of the orientation of the electric field vector as the electromagnetic wave propagates. The electric field vector of a plane wave may be arbitrarily divided into two perpendicular components labeled x and y (with z indicating the direction of travel). The shape traced out in the x-y plane by the electric field vector is a Lissajous figure that describes the polarization state. The following figures show some examples of the evolution of the electric field vector (blue), with time (the vertical axes), at a particular point in space, along with its x and y components (red/left and green/right), and the path traced by the vector in the plane (purple): The same evolution would occur when looking at the electric field at a particular time while evolving the point in space, along the direction opposite to propagation. In the leftmost figure above, the x and y components of the light wave are in phase. In this case, the ratio of their strengths is constant, so the direction of the electric vector (the vector sum of these two components) is constant. Since the tip of the vector traces out a single line in the plane, this special case is called linear polarization. The direction of this line depends on the relative amplitudes of the two components. In the middle figure, the two orthogonal components have the same amplitudes and are 90° out of phase. In this case, one component is zero when the other component is at maximum or minimum amplitude. There are two possible phase relationships that satisfy this requirement: the x component can be 90° ahead of the y component or it can be 90° behind the y component. In this special case, the electric vector traces out a circle in the plane, so this polarization is called circular polarization. The rotation direction in the circle depends on which of the two-phase relationships exists and corresponds to right-hand circular polarization and left-hand circular polarization. In all other cases, where the two components either do not have the same amplitudes and/or their phase difference is neither zero nor a multiple of 90°, the polarization is called elliptical polarization because the electric vector traces out an ellipse in the plane (the polarization ellipse). This is shown in the above figure on the right. Detailed mathematics of polarization is done using Jones calculus and is characterised by the Stokes parameters. Media that have different indexes of refraction for different polarization modes are called birefringent. Well known manifestations of this effect appear in optical wave plates/retarders (linear modes) and in Faraday rotation/optical rotation (circular modes). If the path length in the birefringent medium is sufficient, plane waves will exit the material with a significantly different propagation direction, due to refraction. For example, this is the case with macroscopic crystals of calcite, which present the viewer with two offset, orthogonally polarised images of whatever is viewed through them. It was this effect that provided the first discovery of polarization, by Erasmus Bartholinus in 1669. In addition, the phase shift, and thus the change in polarization state, is usually frequency dependent, which, in combination with dichroism, often gives rise to bright colours and rainbow-like effects. In mineralogy, such properties, known as pleochroism, are frequently exploited for the purpose of identifying minerals using polarization microscopes. Additionally, many plastics that are not normally birefringent will become so when subject to mechanical stress, a phenomenon which is the basis of photoelasticity. Non-birefringent methods, to rotate the linear polarization of light beams, include the use of prismatic polarization rotators which use total internal reflection in a prism set designed for efficient collinear transmission. Media that reduce the amplitude of certain polarization modes are called dichroic, with devices that block nearly all of the radiation in one mode known as polarizing filters or simply "polarisers". Malus' law, which is named after Étienne-Louis Malus, says that when a perfect polariser is placed in a linear polarised beam of light, the intensity, I, of the light that passes through is given by In practice, some light is lost in the polariser and the actual transmission of unpolarised light will be somewhat lower than this, around 38% for Polaroid-type polarisers but considerably higher (>49.9%) for some birefringent prism types. In addition to birefringence and dichroism in extended media, polarization effects can also occur at the (reflective) interface between two materials of different refractive index. These effects are treated by the Fresnel equations. Part of the wave is transmitted and part is reflected, with the ratio depending on the angle of incidence and the angle of refraction. In this way, physical optics recovers Brewster's angle. When light reflects from a thin film on a surface, interference between the reflections from the film's surfaces can produce polarization in the reflected and transmitted light. Most sources of electromagnetic radiation contain a large number of atoms or molecules that emit light. The orientation of the electric fields produced by these emitters may not be correlated, in which case the light is said to be unpolarised. If there is partial correlation between the emitters, the light is partially polarised. If the polarization is consistent across the spectrum of the source, partially polarised light can be described as a superposition of a completely unpolarised component, and a completely polarised one. One may then describe the light in terms of the degree of polarization, and the parameters of the polarization ellipse. Light reflected by shiny transparent materials is partly or fully polarised, except when the light is normal (perpendicular) to the surface. It was this effect that allowed the mathematician Étienne-Louis Malus to make the measurements that allowed for his development of the first mathematical models for polarised light. Polarization occurs when light is scattered in the atmosphere. The scattered light produces the brightness and colour in clear skies. This partial polarization of scattered light can be taken advantage of using polarizing filters to darken the sky in photographs. Optical polarization is principally of importance in chemistry due to circular dichroism and optical rotation ("circular birefringence") exhibited by optically active (chiral) molecules. Modern optics encompasses the areas of optical science and engineering that became popular in the 20th century. These areas of optical science typically relate to the electromagnetic or quantum properties of light but do include other topics. A major subfield of modern optics, quantum optics, deals with specifically quantum mechanical properties of light. Quantum optics is not just theoretical; some modern devices, such as lasers, have principles of operation that depend on quantum mechanics. Light detectors, such as photomultipliers and channeltrons, respond to individual photons. Electronic image sensors, such as CCDs, exhibit shot noise corresponding to the statistics of individual photon events. Light-emitting diodes and photovoltaic cells, too, cannot be understood without quantum mechanics. In the study of these devices, quantum optics often overlaps with quantum electronics. Specialty areas of optics research include the study of how light interacts with specific materials as in crystal optics and metamaterials. Other research focuses on the phenomenology of electromagnetic waves as in singular optics, non-imaging optics, non-linear optics, statistical optics, and radiometry. Additionally, computer engineers have taken an interest in integrated optics, machine vision, and photonic computing as possible components of the "next generation" of computers. Today, the pure science of optics is called optical science or optical physics to distinguish it from applied optical sciences, which are referred to as optical engineering. Prominent subfields of optical engineering include illumination engineering, photonics, and optoelectronics with practical applications like lens design, fabrication and testing of optical components, and image processing. Some of these fields overlap, with nebulous boundaries between the subjects' terms that mean slightly different things in different parts of the world and in different areas of industry. A professional community of researchers in nonlinear optics has developed in the last several decades due to advances in laser technology. A laser is a device that emits light, a kind of electromagnetic radiation, through a process called stimulated emission. The term laser is an acronym for Light Amplification by Stimulated Emission of Radiation. Laser light is usually spatially coherent, which means that the light either is emitted in a narrow, low-divergence beam, or can be converted into one with the help of optical components such as lenses. Because the microwave equivalent of the laser, the maser, was developed first, devices that emit microwave and radio frequencies are usually called masers. The first working laser was demonstrated on 16 May 1960 by Theodore Maiman at Hughes Research Laboratories. When first invented, they were called "a solution looking for a problem". Since then, lasers have become a multibillion-dollar industry, finding utility in thousands of highly varied applications. The first application of lasers visible in the daily lives of the general population was the supermarket barcode scanner, introduced in 1974. The laserdisc player, introduced in 1978, was the first successful consumer product to include a laser, but the compact disc player was the first laser-equipped device to become truly common in consumers' homes, beginning in 1982. These optical storage devices use a semiconductor laser less than a millimetre wide to scan the surface of the disc for data retrieval. Fibre-optic communication relies on lasers to transmit large amounts of information at the speed of light. Other common applications of lasers include laser printers and laser pointers. Lasers are used in medicine in areas such as bloodless surgery, laser eye surgery, and laser capture microdissection and in military applications such as missile defence systems, electro-optical countermeasures (EOCM), and lidar. Lasers are also used in holograms, bubblegrams, laser light shows, and laser hair removal. Optics is part of everyday life. The ubiquity of visual systems in biology indicates the central role optics plays as the science of one of the five senses. Many people benefit from eyeglasses or contact lenses, and optics are integral to the functioning of many consumer goods including cameras. Rainbows and mirages are examples of optical phenomena. Optical communication provides the backbone for both the Internet and modern telephony. The human eye functions by focusing light onto a layer of photoreceptor cells called the retina, which forms the inner lining of the back of the eye. The focusing is accomplished by a series of transparent media. Light entering the eye passes first through the cornea, which provides much of the eye's optical power. The light then continues through the fluid just behind the cornea—the anterior chamber, then passes through the pupil. The light then passes through the lens, which focuses the light further and allows adjustment of focus. The light then passes through the main body of fluid in the eye—the vitreous humour, and reaches the retina. The cells in the retina line the back of the eye, except for where the optic nerve exits; this results in a blind spot. There are two types of photoreceptor cells, rods and cones, which are sensitive to different aspects of light. Rod cells are sensitive to the intensity of light over a wide frequency range, thus are responsible for black-and-white vision. Rod cells are not present on the fovea, the area of the retina responsible for central vision, and are not as responsive as cone cells to spatial and temporal changes in light. There are, however, twenty times more rod cells than cone cells in the retina because the rod cells are present across a wider area. Because of their wider distribution, rods are responsible for peripheral vision. In contrast, cone cells are less sensitive to the overall intensity of light, but come in three varieties that are sensitive to different frequency-ranges and thus are used in the perception of colour and photopic vision. Cone cells are highly concentrated in the fovea and have a high visual acuity meaning that they are better at spatial resolution than rod cells. Since cone cells are not as sensitive to dim light as rod cells, most night vision is limited to rod cells. Likewise, since cone cells are in the fovea, central vision (including the vision needed to do most reading, fine detail work such as sewing, or careful examination of objects) is done by cone cells. Ciliary muscles around the lens allow the eye's focus to be adjusted. This process is known as accommodation. The near point and far point define the nearest and farthest distances from the eye at which an object can be brought into sharp focus. For a person with normal vision, the far point is located at infinity. The near point's location depends on how much the muscles can increase the curvature of the lens, and how inflexible the lens has become with age. Optometrists, ophthalmologists, and opticians usually consider an appropriate near point to be closer than normal reading distance—approximately 25 cm. Defects in vision can be explained using optical principles. As people age, the lens becomes less flexible and the near point recedes from the eye, a condition known as presbyopia. Similarly, people suffering from hyperopia cannot decrease the focal length of their lens enough to allow for nearby objects to be imaged on their retina. Conversely, people who cannot increase the focal length of their lens enough to allow for distant objects to be imaged on the retina suffer from myopia and have a far point that is considerably closer than infinity. A condition known as astigmatism results when the cornea is not spherical but instead is more curved in one direction. This causes horizontally extended objects to be focused on different parts of the retina than vertically extended objects, and results in distorted images. All of these conditions can be corrected using corrective lenses. For presbyopia and hyperopia, a converging lens provides the extra curvature necessary to bring the near point closer to the eye while for myopia a diverging lens provides the curvature necessary to send the far point to infinity. Astigmatism is corrected with a cylindrical surface lens that curves more strongly in one direction than in another, compensating for the non-uniformity of the cornea. The optical power of corrective lenses is measured in diopters, a value equal to the reciprocal of the focal length measured in metres; with a positive focal length corresponding to a converging lens and a negative focal length corresponding to a diverging lens. For lenses that correct for astigmatism as well, three numbers are given: one for the spherical power, one for the cylindrical power, and one for the angle of orientation of the astigmatism. Optical illusions (also called visual illusions) are characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that differs from the object being imaged. Optical illusions can be the result of a variety of phenomena including physical effects that create images that are different from the objects that make them, the physiological effects on the eyes and brain of excessive stimulation (e.g. brightness, tilt, colour, movement), and cognitive illusions where the eye and brain make unconscious inferences. Cognitive illusions include some which result from the unconscious misapplication of certain optical principles. For example, the Ames room, Hering, Müller-Lyer, Orbison, Ponzo, Sander, and Wundt illusions all rely on the suggestion of the appearance of distance by using converging and diverging lines, in the same way that parallel light rays (or indeed any set of parallel lines) appear to converge at a vanishing point at infinity in two-dimensionally rendered images with artistic perspective. This suggestion is also responsible for the famous moon illusion where the moon, despite having essentially the same angular size, appears much larger near the horizon than it does at zenith. This illusion so confounded Ptolemy that he incorrectly attributed it to atmospheric refraction when he described it in his treatise, Optics. Another type of optical illusion exploits broken patterns to trick the mind into perceiving symmetries or asymmetries that are not present. Examples include the café wall, Ehrenstein, Fraser spiral, Poggendorff, and Zöllner illusions. Related, but not strictly illusions, are patterns that occur due to the superimposition of periodic structures. For example, transparent tissues with a grid structure produce shapes known as moiré patterns, while the superimposition of periodic transparent patterns comprising parallel opaque lines or curves produces line moiré patterns. Single lenses have a variety of applications including photographic lenses, corrective lenses, and magnifying glasses while single mirrors are used in parabolic reflectors and rear-view mirrors. Combining a number of mirrors, prisms, and lenses produces compound optical instruments which have practical uses. For example, a periscope is simply two plane mirrors aligned to allow for viewing around obstructions. The most famous compound optical instruments in science are the microscope and the telescope which were both invented by the Dutch in the late 16th century. Microscopes were first developed with just two lenses: an objective lens and an eyepiece. The objective lens is essentially a magnifying glass and was designed with a very small focal length while the eyepiece generally has a longer focal length. This has the effect of producing magnified images of close objects. Generally, an additional source of illumination is used since magnified images are dimmer due to the conservation of energy and the spreading of light rays over a larger surface area. Modern microscopes, known as compound microscopes have many lenses in them (typically four) to optimize the functionality and enhance image stability. A slightly different variety of microscope, the comparison microscope, looks at side-by-side images to produce a stereoscopic binocular view that appears three dimensional when used by humans. The first telescopes, called refracting telescopes, were also developed with a single objective and eyepiece lens. In contrast to the microscope, the objective lens of the telescope was designed with a large focal length to avoid optical aberrations. The objective focuses an image of a distant object at its focal point which is adjusted to be at the focal point of an eyepiece of a much smaller focal length. The main goal of a telescope is not necessarily magnification, but rather the collection of light which is determined by the physical size of the objective lens. Thus, telescopes are normally indicated by the diameters of their objectives rather than by the magnification which can be changed by switching eyepieces. Because the magnification of a telescope is equal to the focal length of the objective divided by the focal length of the eyepiece, smaller focal-length eyepieces cause greater magnification. Since crafting large lenses is much more difficult than crafting large mirrors, most modern telescopes are reflecting telescopes, that is, telescopes that use a primary mirror rather than an objective lens. The same general optical considerations apply to reflecting telescopes that applied to refracting telescopes, namely, the larger the primary mirror, the more light collected, and the magnification is still equal to the focal length of the primary mirror divided by the focal length of the eyepiece. Professional telescopes generally do not have eyepieces and instead place an instrument (often a charge-coupled device) at the focal point instead. The optics of photography involves both lenses and the medium in which the electromagnetic radiation is recorded, whether it be a plate, film, or charge-coupled device. Photographers must consider the reciprocity of the camera and the shot which is summarized by the relation In other words, the smaller the aperture (giving greater depth of focus), the less light coming in, so the length of time has to be increased (leading to possible blurriness if motion occurs). An example of the use of the law of reciprocity is the Sunny 16 rule which gives a rough estimate for the settings needed to estimate the proper exposure in daylight. The field of view that the lens will provide changes with the focal length of the lens. There are three basic classifications based on the relationship to the diagonal size of the film or sensor size of the camera to the focal length of the lens: The absolute value for the exposure time required depends on how sensitive to light the medium being used is (measured by the film speed, or, for digital media, by the quantum efficiency). Early photography used media that had very low light sensitivity, and so exposure times had to be long even for very bright shots. As technology has improved, so has the sensitivity through film cameras and digital cameras. Other results from physical and geometrical optics apply to camera optics. For example, the maximum resolution capability of a particular camera set-up is determined by the diffraction limit associated with the pupil size and given, roughly, by the Rayleigh criterion. The unique optical properties of the atmosphere cause a wide range of spectacular optical phenomena. The blue colour of the sky is a direct result of Rayleigh scattering which redirects higher frequency (blue) sunlight back into the field of view of the observer. Because blue light is scattered more easily than red light, the sun takes on a reddish hue when it is observed through a thick atmosphere, as during a sunrise or sunset. Additional particulate matter in the sky can scatter different colours at different angles creating colourful glowing skies at dusk and dawn. Scattering off of ice crystals and other particles in the atmosphere are responsible for halos, afterglows, coronas, rays of sunlight, and sun dogs. The variation in these kinds of phenomena is due to different particle sizes and geometries. Mirages are optical phenomena in which light rays are bent due to thermal variations in the refraction index of air, producing displaced or heavily distorted images of distant objects. Other dramatic optical phenomena associated with this include the Novaya Zemlya effect where the sun appears to rise earlier than predicted with a distorted shape. A spectacular form of refraction occurs with a temperature inversion called the Fata Morgana where objects on the horizon or even beyond the horizon, such as islands, cliffs, ships or icebergs, appear elongated and elevated, like "fairy tale castles". Rainbows are the result of a combination of internal reflection and dispersive refraction of light in raindrops. A single reflection off the backs of an array of raindrops produces a rainbow with an angular size on the sky that ranges from 40° to 42° with red on the outside. Double rainbows are produced by two internal reflections with angular size of 50.5° to 54° with violet on the outside. Because rainbows are seen with the sun 180° away from the centre of the rainbow, rainbows are more prominent the closer the sun is to the horizon.
Friday, September 17, 2010 This great activity helps kids to better understand the concept of fractions by visually and tactilely practicing them. Construction paper in a variety of colors, black marker, scissors, ruler, pencil, and glue stick 1. Choose a simple fraction to begin with. 2. Have your students write this fraction on a sheet of construction paper with the black marker. Have them show you the numerator (top number) and the denominator (bottom number). 3. In the beginning, a rectangle will be the easiest shape for the collage. Later on you can try this with a circle using wedges, or triangles linked to each other in a row. Have them draw a rectangle on another color of construction paper using the pencil and ruler. You may need to show them an example first. Make sure the dimensions of the shape are in whole inches, ideally in a multiple of the denominator so the shape will be easy to cut up. For example, if your fraction is 2/3, you could make a rectangle that is 6" long, since 6 is a multiple of 3. 4. Then using the ruler, divide this rectangle up into equal segments based on the denominator. In this example from number 3 you would divide the rectangle into 3, 2" segments. 5. Have them cut out the whole shape from the construction paper and glue it onto the construction paper where you wrote the fraction, but on the other side. This way they can test themselves later on as a reviewing technique. 6. Now have them choose a third sheet of construction paper in a different color than the shape. Using the same measurements you used in step 4, draw a number of rectangular segments equal to the numerator of the fraction. Using the same example again, you would cut two, 2" wide segments so they fit into the segments of the whole rectangle. 7. Cut out these pieces and glue them consecutively on the shape within segments drawn. Now your first fraction collage has been created! 8. You can then move on to other more difficult fractions and shapes or try this link for Additional Web Practice Using Fraction Collages Thursday, September 16, 2010 Students are amazed when seeing this trick for the first time. This is a lesson in physical science about static electricity from negatively charged electrons. When the students rub the balloon against their hair, they are giving the balloon a negative charge, which is known as static electricity. If the negative charge is strong enough the balloon will stick to neutrally charges surfaces, such as a wall. It will attract the positive charges from the wall, thus pulling the two surfaces together. Since the balloon is a light object, it will be able to stick to the wall until the negative charges disperse. You can also have the children hold their balloons together at the negatively charged area to see how two negatively charged surfaces repel. Watch a Video 1. Have your students blow up their balloons and tie a knot at the end. 2. Get your children to charge their balloons with static electricity (negative electrons) by gently rubbing against their hair. 3. Ask them to stick the charged side of the balloon against the wall or other vertical surfaces. Did they stick? 4. Now have them stick it against anther student’s balloon in the spot that has been charged. Did they repel? Wednesday, September 15, 2010 This is an exciting activity for students learning about plants, habitats, carnivores, or omnivores. Carnivorous plants are usually found in nutrient-poor soil areas such as bogs. This creates the need to trap and digest live prey, usually small insects or arthropods. The Venus Flytrap is the most commonly known out of these species and would be a great one to include in this project as most students will already be familiar with this plant. There are many you can select from and mix together to make beautiful and educational terrariums. Supplies: Glass jar with a wide mouth, sphagum peat moss mixed some with vermiculite as the soil base, a towel, rainwater, fresh fruit in order to attract the prey, and a variety of small carnivorous plants. 1. Lay the jar on its side and place on a towel. 2. Pour a small amount of the soil mixture into the jar. Keep this leveled below the mouth of the jar. 3. Have your students transplant the plants to the terrarium or their individual terrariums. 4. Mist with rainwater. 5. Find a place with the appropriate sun for your plants. Outside is best where bugs are more plentiful. 6. Secure the jar so it doesn't roll. 7. Put ripe fruit inside the mouth of the jar to attract bugs. 8. Mist with rainwater when dry and continue to add ripe fruit often to attract prey.
Bar Graph Worksheet First graders can color and count cute animals while recording their results on the blank bar graph. Children can then practice interpreting the bar graph they just created by answering several questions about the results. This free printable worksheet is an easy way for students to build their measurement and analytical skills. 1.MD.C.4 - Common Core ID Organize, represent, and interpret data with up to three categories; ask and answer questions about the total number of data points, how many in each category, and how many more or less are in one category than in another.Common Core » 1st Grade Math Standards » Measurement & Data » Represent and interpret data. » 1.MD.C.4
Two studies published on Monday showed that the amount of water on the moon may be much more than previously thought. This adds to the tempting prospect that astronauts on future space missions can find freshness on the surface of the moon and even refuel. It wasn’t until about ten years ago that people thought the moon was dry, when a series of discoveries showed that our nearest celestial body had traces of water ice in permanently shadowed craters in its polar regions. Two new studies published in Nature Astronomy on Monday suggest that water may spread more widely, including the first confirmation that water exists even in areas exposed to sunlight that are more accessible. If this water can be extracted, it will enable astronauts to land on the moon and obtain drinking water. They can even split molecules to make rocket fuel. NASA is particularly interested in this. NASA is planning a human mission to the moon in 2024, and hopes to establish a sustainable presence on the moon before the end of this century in preparation for continuing to go to Mars. Casey Honnibauer of the Hawaii Institute of Geophysics and Planetary Research said the new study can “clearly” distinguish the spectral fingerprints of molecular water in areas exposed to sunlight. “If we find that there is enough water in certain places, we may be able to use it as a resource for human exploration,” Hannibal, also a postdoctoral researcher at NASA’s Goddard Space Flight Center, told AFP. Previous studies have found signs of water on the surface under sunlight, but these signs cannot distinguish between water (H2O) and hydroxyl, which is a molecule composed of one hydrogen atom and one oxygen atom, and is a common drainage cleaner on earth. Using data from the Airborne Telescope of the Stratospheric Infrared Astronomical Observatory (SOFIA), the researchers used a more precise wavelength than before, not 3 microns, but 6 microns. They found that the concentration of water in the Clavius crater is about 100 to 400 parts per million, which is one of the largest water visible on earth. Honnip said at the NASA press conference: “This is equivalent to 12 ounces (350 milliliters) of water in one cubic meter of lunar soil.” She emphasized that these are not “puddles”, but dispersed molecules that do not form ice or liquid water. Researchers believe that they originated from solar wind or micrometeorites, and believe that they may be trapped in glass beads or particles on the surface of the moon to protect them from the harsh atmosphere. In the second study, the researchers studied the polar regions of the moon, and water ice that had never seen sunlight was found in lunar craters. NASA discovered water crystals in a deep pit near the lunar south pole in 2009. But this new study has found evidence of billions of micro-craters, each of which may produce a small amount of ice. Paul Hein, the lead author of the Department of Astrophysics at the University of Colorado, said: “If you stand on the moon near one of the poles, you will see the entire shadow surface dotted with the entire’galaxy’.” “Each of these tiny shadows, most of them are smaller than coins, they can get very cold, and most of them are big enough to hide ice.” Hein said: “This shows that the water on the moon may be much wider than previously thought.” The author says this could mean about 40,000 kilometers2 The surface of the moon has the ability to capture water. They were able to reconstruct the size and distribution of these small craters using high-resolution images and lunar temperature obtained from NASA’s “Lunar Reconnaissance Orbit”. Hein said that the micro crater should be as cold as a larger kilometer cavity, about -160 degrees Celsius, adding that there are “tens of billions” in it. Hein said that these cold trap samples can tell us more about how the moon and even the earth obtain water, and may provide evidence of water carried by asteroids, comets and solar wind. Jacob Bleacher, chief exploration scientist of NASA’s Human Exploration and Operations Mission, said it is vital to find more information about the source of water and its availability. He told reporters: “Water is very important for deep space exploration. For our astronauts, it is a resource of direct value.” He added that water is heavy and therefore expensive to obtain from the earth. Is the iPhone 12 mini and HomePod mini the perfect Apple device in India? We discussed on the weekly technical podcast Orbital, you can subscribe via Apple Podcast, Google Podcast or RSS, download the episode, or click the play button below.
Aphelion: see Orbit. Apogee: see Orbit. Black hole: the theoretical end-product of the total gravitational collapse of a massive star or group of stars. Crushed even smaller than the incredibly dense neutron star, the black hole may become so dense that not even light can escape its gravitational field. In 1996, astronomers found strong evidence for a massive black hole at the center of the Milky Way. Recent evidence suggests that black holes are so common that they probably exist at the core of nearly all galaxies. Conjunction: the alignment of two celestial objects at the same celestial longitude. Conjunction of the Moon and planets is often determined with reference to the Sun. For example, Saturn is said to be in conjunction with the Sun when Saturn and Earth are aligned on opposite sides of the Sun. Mercury and Venus, the two planets with orbits within Earth's orbit, have two positions of conjunction. Mercury, for example, is said to be in inferior conjunction when the Sun and Earth are aligned on opposite sides of Mercury. Mercury is in superior conjunction when Mercury and Earth are aligned on opposite sides of the Sun. Dwarf planet: see Planet. Elongation: the angular distance between two points in the sky as measured from a third point. The elongation of Mercury, for example, is the angular distance between Mercury and the Sun as measured from Earth. Planets whose orbits are outside Earth's can have elongations between 0° and 180°. (When a planet's elongation is 0°, it is at conjunction; when it is 180°, it is at opposition.) Because Mercury and Venus are within Earth's orbit, their greatest elongations measured from Earth are 28° and 47°, respectively. Galaxy: gas and millions of stars held together by gravity. All that you can see in the sky (with a very few exceptions) belongs to our galaxy—a system of roughly 200 billion stars. The exceptions you can see are other galaxies. Our own galaxy, the rim of which we see as the “Milky Way,” is about 100,000 light-years in diameter and about 10,000 light-years in thickness. Its shape is roughly that of a thick lens; more precisely, it is a spiral nebula, a term first used for other galaxies when they were discovered and before it was realized that these were separate and distinct galaxies. Astronomers have estimated that the universe could contain 40 to 50 billion galaxies. In 2004, the Hubble Space Telescope and observers at the Keck Observatory in Hawaii discovered a new galaxy 13 billion light-years from Earth. Neutron star: an extremely dense star with a powerful gravitational pull. Some neutron stars pulse radio waves into space as they spin; these are known as pulsars. Occultation: the eclipse of one celestial object by another. For example, a star is occulted when the Moon passes between it and Earth. Opposition: the alignment of two celestial objects when their longitude differs by 180°. Opposition of the Moon and planets is often determined with reference to the Sun. For example, Saturn is said to be at opposition when Saturn and the Sun are aligned on opposite sides of Earth. Only the planets whose orbits lie outside Earth's can be in opposition to the Sun. Orbit: the path traveled by an object in space. The term comes from the Latin orbis, which means “circle” or “disk,” and orbita, “orbit.” Theoretically, there are four mathematical figures, or models, of possible orbits: two are open (hyperbola and parabola) and two are closed (ellipse and circle), but in reality all closed orbits are ellipses. Ellipses can be nearly circular, as are the orbits of most planets, or very elongated, as are the orbits of most comets, but the orbit revolves around a fixed, or focal, point. In our solar system, the Sun's gravitational pull keeps the planets in their elliptical orbits; the planets hold their moons in place similarly. For planets, the point of the orbit closest to the Sun is the perihelion, and the point farthest from the Sun is the aphelion. For orbits around Earth, the point of closest proximity is the perigee; the farthest point is the apogee. See also Retrograde. Perigee: see Orbit. Perihelion: see Orbit. Planet: the International Astronomical Union (IAU) issued the definition for planet (from the Greek planetes, “wanderers”) at their General Assembly in August 2006. A planet is a body that (a) is in orbit around the Sun, (b) is massive enough that its self-gravity gives it a nearly-spherical shape, and (c) has cleared the neighborhood around its orbit. A body that fulfills the first two criteria but not the third is a dwarf planet, provided that it (d) is not a satellite. While the exact definition of “clearing the neighborhood” was not established at press time, the eight planets from Mercury through Neptune have either assimilated or repulsed most other objects in their orbits, and each has more mass than the combined total of everything else in its area. The same cannot be said for Pluto, which has now been reclassified as a dwarf planet. There are currently eight planets and three dwarf planets recognized in the solar system, and more dwarf planets are expected to be admitted. In 1994, Dr. Alexander Wolszcan, an astronomer at Pennsylvania State University, presented convincing evidence of the first known planets to exist outside our solar system. These particular extrasolar planets circle a pulsar, or exploded star, in the constellation Virgo. In 1995, several of these extrasolar planets were discovered orbiting stars similar to our Sun. Swiss astronomers found the first extrasolar planet (HD 209458b, nicknamed “Osiris”) to circle a normal Sun-like star. As of May 2006, 170 such planets have been discovered. In Feb. 2004, using the Hubble Space Telescope, a team of scientists at the Institut d'Astrophysique de Paris announced that they had discovered oxygen and carbon in the atmosphere of “Osiris.” In Aug. 2004, NASA and the National Science Foundation announced the discovery of two new planets, the smallest yet found, about the size of Neptune. The discovery opens up the possibility of smaller, Earth-sized extrasolar planets. In April 2005, a team of American and European astronomers reported that the first image of an extrasolar planet had been made. The planet is orbiting a brown dwarf near the constellation Hydra, 230 million light-years from Earth. Pulsar: a celestial object, believed to be a rapidly spinning neutron star, that emits intense bursts of radio waves at regular intervals. Quasar: “quasi-stellar” object. Originally thought to be peculiar stars in our own galaxy, quasars are now believed to be the most remote objects in the universe. Quasars emit tremendous amounts of light and microwave radiation. Although they are not much bigger than Earth's solar system, quasars pour out 100 to 1,000 times as much light as an entire galaxy containing a hundred billion stars. It is believed that quasars are powered by massive black holes that suck up billions of stars. Retrograde: describes the clockwise orbit or rotation of a planet or other celestial object, which is in the direction opposite to Earth and most celestial bodies. As viewed from a position in space north of the solar system (from some great distance above Earth's North Pole), all the planets revolve counterclockwise around the Sun, and all but Venus, Uranus, and Pluto rotate counterclockwise on their own axes. These three planets have retrograde motion. Sometimes retrograde is also used to describe apparent backward motion as viewed from Earth. This motion happens when two objects rotate at different speeds around another fixed object. For example, the planet Mars appears to be retrograde when Earth overtakes and passes by it as they both move around the Sun. Satellite (or moon): an object in orbit around a planet. Until the discovery of Jupiter's four main moons by Galileo Galilei, celestial objects in orbit around a planet were called moons. However, upon Galilei's discovery, Johannes Kepler (in a letter to Galileo) suggested satellite (from the Latin satelles, which means “attendant”) as a general term for such objects. The word satellite is used interchangeably with moon, and astronomers speak and write about the moons of Neptune, Saturn, etc. The term satellite is also used to describe man-made devices of any size that are launched into orbit. Small Solar System Objects: at the 2006 IAU General Assembly, solar system bodies not defined as planets, dwarf planets, or satellites were placed in this category. These include most asteroids, most Trans-Neptunian Objects, comets, and other small bodies. Star: a celestial object consisting of intensely hot gases held together by gravity. Stars derive their energy from nuclear reactions going on in their interiors, generating heat and light. Stars are very large. Our Sun has a diameter of 865,400 mi—a comparatively small star. A dwarf star is a small star that is of relatively low mass and average or below-average luminosity. The Sun is a yellow dwarf, which is in its main sequence, or prime of life. This means that nuclear reactions of hydrogen maintain its size and temperature. By contrast, a white dwarf is a star at the end of its life, with low luminosity, small size, and very high density. A red giant is a star nearing the end of its life. When a star begins to lose hydrogen and burn helium instead, it gradually collapses, and its outer region begins to expand and cool. The light we see from these stars is red because of their cooler temperature. There are also red super giants, which are even more massive. A brown dwarf lacks the mass to generate nuclear fusion like a true star, but it is also too massive and hot to be a planet. A brown dwarf usually cools into a dark, practically invisible object. The existence of brown dwarfs, also called failed stars, was confirmed in Nov. 1995 when astronomers at Palomar Observatory in California took the first photograph of this mysterious object. Supernova: a celestial phenomenon in which a star explodes, releasing a great burst of light. There are two basic types of supernova. Type Ia happens when a white dwarf star draws large amounts of matter from a nearby star until it can no longer support itself and collapses. The second more well-known kind of supernova, type IIa, is the result of the collapse of a massive star. (Massive is a classification for a star that is at least eight times the size of our Sun.) Once the star's nuclear fuel is exhausted, if its core is heavy enough, the star will collapse in on itself, releasing a huge amount of energy (the supernova), which may be brighter than the star's host galaxy. On Feb. 24, 1987, Canadian astronomer Ian Shelter at the Las Campanas Observatory in Chile discovered a supernova—an exploding star—from a photograph taken on Feb. 23 of the Large Magellanic Cloud, a galaxy some 160,000 light-years away from Earth. Astronomers believe that the dying star was Sanduleak –69°202, a 10-million-year-old blue supergiant. Supernova 1987A was the closest and best-studied supernova in almost 400 years. One was previously observed by Johannes Kepler in 1604, four years before the telescope was invented.
Soil erosion is a problem that is seen on every continent, in every country and on any type of soil and environment. Erosion is natural process but with our activities changing natural dynamics and removing vegetation cover, soil erosion has been steadily accelerating over the last decades. For example, when forests are clear cut and land is transformed into croplands, the rate of soil loss increases by 52 percent . The Food and Agriculture Organization (FAO) estimates that arable lands worldwide lose every year 75 billion tons of soil due to erosion . Such a high rate of soil loss renders croplands infertile, in need of constant fertilization with synthetic substances, or even results in a complete land abandonment due to the severe degradation. Scientists estimate that, globally, 10 million hectares of arable land are abandoned every year for this reason . This not only undermines our ability to produce enough food in the future, but also destroys biodiversity and ecosystem services that were once in place but cannot be supported by the lifeless ‘dirt’ which remained behind. Soil erosion causes other problems as well. For example, sedimentation and nutrient loading in waterways, and an increased risk of flooding and landslides as result of soil removal. So, how can you stop erosion from happening in your yard or on your land? The following are methods that have proven to dramatically reduce and prevent soil erosion from occurring in the first place, regardless whether you are focused on preventing erosion in your yard or on a larger piece of land that is used to grow crops. These measures are effective in many situations. Factors responsible for soil erosion When erosion takes place, soil particles get loosen by the impact of water, ice, wind or gravitational pull and can be easily carried away by the repeated action of these forces. The vulnerability of soils to be damaged differs, but in general is affected by the combination of factors that are responsible for erosion. These factors are linked to local : Long-term weather patterns in an area affect soil stability. Heavy spring rains, strong winds, turbulent storms, or long summer droughts that destroy vegetation and are followed by floods disturb uncovered soils and may initiate the process of erosion. The duration and intensity of rainfall in an area create erosive forces of water on land surface. More it rains and heavier the rain is, more surface runoff happens, triggering water erosion. Runoff causes usually the biggest problems on agricultural lands, carrying nutrients and organic matter away from croplands, making it harder to maintain soil fertility to grow crops. How heavy surface runoff can get is also determined by the slope of the land and the drainage characteristics of soils (e.g. how well does water infiltrate into the soil). - Soil characteristics Some soil types are more likely to subdue to erosion than other. Soil texture depends on the size and distribution of soil particles. Many soils are a combination of sand, clay and silt, so their erodibility depends on the most prevalent particle type. Sandy soils contain larger particles that do not stick well together and get easily detached from each other by water or wind. Clay, on the other hand, consists of fine particles that stick together closely. Clay soils are not so porous and are resistant to wind erosion, but because of their structure that doesn’t allow water to easily infiltrate, water tends to accumulate on the top, drowning vegetation and creating muddy flow that washes large pieces of soil off. High organic matter content in soils is excellent in preventing soil damage. It absorbs rainwater nicely and has the capacity to control water saturation of soils. When it rains, soil organic matter stores just enough water to maintain moisture for plants until the next rain, while letting all excessive water pass through. Organic material is also a vital part of healthy soil structure—encouraging the formation of aggregates that bind particles together and support porosity—factors that help prevent soil degradation by erosion . Different natural or man-made features in the landscape influence where erosion takes place with greater intensity. For example, on exposed slopes that have been deforested the rate of erosion increases when compared to a flat grassy area just a couple miles away. Some slopes are naturally too steep to support vegetation and are prone to erosion at any time. They may pose a constant risk to human infrastructure nearby. In other cases, our land use management exacerbates the problem of unstable soils. For example, maize rows oriented down the sloping field only encourage creation of rills when it rains, as water rushes downhill unobstructed. If rows were oriented along the contour, maize plants would help to slow down and disperse the running water. Thus, protect the soil better. River banks and coastlines are extremely prone areas to erosive forces of moving water. In fact, they are being constantly eroded by the impact of water. The rate of erosion depends on the force of water and the type of soil or rock that creates the boundaries between water and land. Rock types and their mineral composition are closely linked with soil texture and the size of soil particles in an area. In hilly regions or along coastlines, geology of cliffs and rocks affects their erosion rate over time. Hard rocks like granite get worn down by weather much slower than soft sandstone which keeps changing relatively fast. - Vegetation cover Vegetation cover, its thickness and biodiversity of plant species, is extremely important in protecting soils. Plant roots hold soil particles in place, leaves and plant bodies slow down the rain and wind impact. Plants also encourage water uptake by soils, therefore reducing runoff. Plants create a protective shield even during winter when snow lies on the ground. Their roots prevent damage to upper soil layers when snow melts and runs into the nearest streams. It is a common occurrence that erosion accelerates when natural perennial vegetation gets stripped away to make space for agriculture or development projects. - Socio-economic development The management of natural resources depends on the socio-economic situation and development trends in an area. In some countries, intensive agriculture may be the main cause of erosion. In other regions, it could be overgrazing, deforestation (especially illegal logging), urbanization or mining. Land use management affects soil health and our ability of protecting soils from degradation, but the way we manage land differ greatly across the regions and throughout the world. It is possible to see positive soil conservation practices in one area and then harmful activities right across the road. Simple ways how you can prevent and control soil erosion Whether it is in your backyard, on agricultural land or in a distant corner of your garden, soil erosion can turn to a serious problem if left to progress beyond control. Besides that, fixing severely eroded land and repairing the damage done by displaced soil costs significant amount of money. You should consider that eroded lands lose their value as well. According to calculations of the Iowa State University, the value of eroded lands drops by three to seven percent for the whole land, even when erosion affects only a relatively small part. This means that you may be losing on your long-term investment if you let erosion progress, because you will not be able to sell the land for the full price. It is in your best interest to try to prevent the development of soil erosion and reduce existing soil loss as soon as possible. Your land, your wallet and future generations will certainly benefit from your early action. Here are some effective measures that will help you to control soil erosion on your land. #1 Planting permanent vegetation One of the best ways that we can prevent erosion is to plant vegetation with deep roots that help to hold the soil in place. This is especially important in areas that are more vulnerable to erosion, such as along rivers, streams, and on hillsides. According to data from the Iowa State University, permanent vegetation cover reduces soil loss by more than 50 percent (in some cases the success rate is 100 percent) and surface runoff by 30 percent on average . The best plants for erosion control are native plants with deep roots, such as native prairie grasses like blue wildrye or purple needle grass, wildflowers, and woody perennials, like trees and shrubs. Typical lawn grasses tend to have very short roots, and therefore do not protect slopes from erosion nearly as well as native and woody perennial plants. When deciding which plants are the best to control erosion on your property, make sure you base your selection according to the specific characteristics of your site. If the location is dry, select drought resistant species because you do not want to have to water the plants—pouring water over soil would not help in tackling erosion. For slopes, look for trees and shrubs with strong root system that do not grow very tall. If you are aiming to reduce surface runoff and water accumulation in some low-lying spots, think of grasses and trees that do well in wet conditions. They will absorb excessive soil moisture and release it into the atmosphere through their leaves, decreasing oversaturation of soils. One great tree species for this purpose are willows. Willow trees grow fast, and their roots create a strong binding network underneath the soil. These trees like humid conditions and tolerate even soils with higher salt concentration. Furthermore, willows are known for being effective in phytoremediation of soils, removing pollutants from soils and incorporating them into their biomass. These trees can perform many great functions for creating a healthy environment if you plant them in the right location. Permanent vegetation doesn’t have to be planted across your whole land if you are planning on leaving some parts for gardening or crop cultivation. Planting stripes of permanent cover with native grasses or creating shrub and tree barriers helps prevent erosion as well . You can create nicely diverse landscape that will yield you more produce, will mitigate erosion and will be interesting to look at. You can get inspired from sustainable agroforestry practices. For example, agroforestry farmers achieve great results when planting trees along contours. #2 No-till farming and gardening By using no-till farming methods and the minimum disturbance, the delicate structure of the soil can be protected and erosion is significantly reduced compared to tillage cultivation. According to FAO, the rate of erosion on soils that are not tilled is 90 percent lower than on the conventionally tilled soils. When soils are tilled, soil aggregates are broken down and healthy soil structure is disrupted. Crop residues and any other vegetation are removed from the surface, leaving detached soil particles fully exposed to rain and wind. Disturbed soil structure results in loss of porosity, which is crucial for water infiltration. This results in increased surface runoff that only encourages further erosion. Other negative effect is the loss of nutrients and organic matter when soils are turn and the land is left barren and exposed to the elements for prolonged time period between planting. If you choose to leave your soils undisturbed, you will protect the soil structure and preserve protective vegetation layer. You will also maximize their biological activity by allowing soil microorganisms flourish and feed on organic residues that you left in the soil. This will enhance healthy nutrient cycles and improve soil health. These are the key processes that ensure optimum capacity of soils to absorb water, minimize runoff and withstand extreme events without getting damaged. #3 Protecting soils with cover crops As the name suggests, cover crops provide a protective cover for soils in between the main plantings. Their function is the same as the function of permanent vegetation. They protect soils from rain and wind, slow down runoff and encourage water infiltration. It is recommended to plant cover crops after the harvest of the main crop. Take for example corn. Once you harvest corn, the land will most likely remain barren over the winter. This means that the soil will lack the protective layer of growing vegetation in the season when it rains or snows a lot and the land is subjected to cycles of freezing and unfreezing. This easily damages soil structure and increases the risk of soil loss. That is when cover crops, such as rye, barley, lentil, mustard or clover, come with numerous benefits. Studies have shown that cover crops reduce soil loss by 30 to 100 percent when compared to fields without any cover . Erosion on lands with mustard cover crops reaches, for example, maximum 20 percent throughout the season . However, you should know that most of the commonly used cover crops have shallower roots that do not stabilize soils on slopes as effectively as native grasses would . Cover crops not only hold soils in place when crops are not grown, they also prevent weed growth in planting beds outside the growing season and help enrich the soil with nitrogen (through the use of leguminous plants such as clovers). If none of the options listed above suits your needs, you have another alternative that doesn’t require planting of other plants or crops on your land and allows you to create a clean look to your property. You can protect the soil by covering exposed spots around the plants with a mulching material. By putting down mulch, you are keeping bare soil from being washed and eroded away, as well as helping to retain soil moisture and eliminate weed growth around your carefully selected plants. Mulching layer stabilizes soil temperature, protecting plants and soil from the effects of fluctuating temperature in winter. Commonly used wood chip or wood bark mulch is often applied in landscapes and gardens, around trees or bushes. This type of mulch is popular for the nice, clean look it provides. Organic mulches, that keep decomposing faster, like shredded leaves and straw, are mainly applied to protect and nourish your garden soil of organic material in the fall and in the spring. You can use mulch even on mild slopes. However, on steeper slopes, loose wood chips or straw mulch may be carried down by runoff too fast. In such a scenario, you may want to try erosion control blankets made from straw, where straw is bound by a synthetic plastic or natural jute netting into a blanket that is evenly laid on the ground. These blankets still perform the protective function, but do not get easily washed or blown off. The next point lists more about them. #5 Soil erosion control blankets and fiber rolls If you have been wondering how to stop erosion on a steep hill, soil erosion blankets could be the best solution. They are designed to slow down surface water and prevent erosion on barren slopes after construction activities or during landscape rehabilitation. By providing a stable layer of soil protection, erosion control matting is efficient even on steeper slopes . These erosion prevention agents are made with synthetic materials, such as polypropylene, or with natural materials, such as straw, coconut fiber, wood fibers, or jute that are bound together by a natural or synthetic UV-degradable netting. Many erosion control blankets are made from permeable, biodegradable materials that do not harm wildlife and allow for water infiltration and growth of vegetation. However, this also means that they last for a limited amount of time and their use is a temporary solution. For example, straw blankets last around three months and are often used to stabilize slope before permanent vegetation grows strong enough to substitute for their function. Jute mats last slightly longer–on average half a year. For longer term solutions, you can find slow degrading options made of synthetic and natural fibers. These blankets should last up to three years . As a substitute for soil erosion control blankets are in some cases used other temporary erosion control measures like fiber rolls (rolls made from straw, rice wattle, coconut fibers, etc.), hay bales, logs, and silt fences. Their function is to trap sediments and slow down water from moving downhill by creating horizontal barriers across the slope. This helps reduce the amount of soil carried away and improves water retention, which in turn creates favorable conditions for emerging vegetation. Once the slope is stabilized through the establishment of permanent vegetation, these barriers are removed. #6 Terracing with retaining walls & edging Imagine all those beautiful terracing rice fields that are so characteristic for the rural landscapes of Asia. Terraces have been effectively used to cultivate crops in hilly areas for the last 5,000 years . Farmers have been building terraces to grow crop in easily erodible terrain. Instead of farming on a slope from where nutrients and water easily disappear, they have been breaking down the slope into a series of horizontal plots for cultivation. The purpose of retaining walls with terraces is to create a barrier that holds the soil in place and prevents water runoff that would otherwise carry sediments down the slope after every rain. Terraces are efficient in retaining water, giving it time to infiltrate into the soil. They improve water drainage on your land as well. According to your design, retaining walls may channel excessive water where it’s needed. Whether on a large scale, like rice fields, or on a smaller scale in your backyard, terracing allows cultivation and erosion control of many difficult slopes that would otherwise be unsuitable for any activity. With the structural support of retaining walls, terraces can create a nice decorative element on your property, giving it a new look. They can be useful for the creation of raised garden beds that are for many gardeners more comfortable to maintain. One permaculture farmer named Sepp Holzer has had a very successful ecologically-based farm for many years in the mountainous region of Austria through the use of terraces on steep slopes. Watch this educational video about Holzer’s farm: On less steep slopes, extensive measure like building a retaining wall is not necessary. Subtle edging may be enough in performing the same function as retaining walls. You can select natural edging materials such as bricks or small stones to prevent erosion of soil from a garden bed or within a landscape, or you can just create a little edge with a spade and keep maintaining it whenever is needed. #7 Riprap, stabilizing soil with stones and boulders Riprap is a permanent placement of larger rocks on less steep slopes, banks of rivers and lakes in an area of strong runoff. The main purpose of creating a rocky surface is to cover the soil and stabilize it, while slowing down water velocity. That is why you can see this solution often employed in places where water constantly keeps eroding soil away–like along waterfronts. Large rocks have also proven useful for stabilizing storm drainage ways. The main advantage of ripraps is their durability. Once in place, rocks perform their protective function for a long time without the need of much maintenance–if installed properly. It is only important to realize that riprap is not the best solution for steeper slopes, as rocks could get easily displaced over the time and cause bigger damage to the soil and infrastructure below. Additional risk comes when the size of rocks is not chosen accordingly. Too small rocks for the slope angle and pressure of water are also unstable in the long term. #8 Controlling water flow across your land If you have a persistent problem of soil erosion in some parts of your property, you should consider adopting measures that would divert rainwater and control its flow across your land. You have a few possibilities. You can create neatly looking dry creeks that direct water away from your land or channel runoff to your designated area from where you can reuse it (e.g. for irrigation). Dry creeks look like a small version of a rocky river bed and even imitate its function. You also have an option to plant vegetated filter strips or simply install drainage pipes to gather water and carry it away from critical areas. Some people choose to protect land around their houses by implementing so called French drains. French drains are trenches along outer house walls that contain drainage pipes covered by permeable gravel. If you have a problem with strong water runoff flushing over your backyard but cannot control the area from where the runoff originates, like for example having a hill owned by someone else right behind your property, you could also build a berm to minimize water damage across your land. Berm is a little artificially created hill where you can plant decorative plants or native grasses and shrubs. By raising the ground, you change the natural channel of water. Water will have to pass around rather than making its way directly through the middle of your backyard. On agricultural lands, especially in hilly regions, farmers get good results by building series of contour trenches and swales that help to catch and accumulate runoff water. This ensures that water remains longer available for crops as it is gradually taken up by soil. Trenches and swales greatly help to stop erosive processes on cultivated lands. As a farmer you can make the most of water passing through your property by creating a retaining pond for rainwater harvesting or imitating natural wetland habitat in place where water tends to accumulate. If you have such possibility and your land has a spot like that, this measure may help prevent erosion in surrounding areas because you will intentionally direct water flow to one place and prevent it from running across other parts. Accumulated rainwater can be used later when droughts hit the area for crop irrigation . #9 Contour farming and gardening & strip cropping Growing crops on slopes can be particularly challenging and plowing on slopes can easily lead to soil erosion. However, there are several techniques for cultivating crops on slopes that prevent erosion. These include contour farming, where farmers plow and plant across a slope along its contour lines as opposed to planting in downhill facing lines. By following the natural contour lines, we can prevent erosion by up to 50 percent . And not only that. This practice greatly reduces the loss of nutrients from cultivated soils. In drier areas where farmers are dependent upon rainfed agriculture, contour cropping delivers higher yields because it retains rainwater more effectively . Strip cropping is a practice that boosts these positive effects of contour farming in hilly regions even more. It is especially effective on steeper slopes where improved water retention is the key to addressing soil erosion. Strip cropping is usually done by planting different crops in alternating strips, which are regularly rotated to allow soil regeneration and nutrient replenishment. For example, farmers grow rows of leguminous cover crops like clover in between corn strips. In more extreme conditions where maintenance of soil fertility may be difficult due to the climate and steepness, crops are grown among permanent vegetation strips, like trees or hedgerows. Permanent vegetation stabilizes soil better and creates positive microclimate for crops in between. #10 Preventing soil disturbance by livestock Overgrazing and land disturbance caused by keeping too many animals in one area for too long period of time is one of the most common causes of soil erosion, eventually leading even to severe land degradation. Land that is used for livestock grazing is often hilly or is located in marginal areas that are unsuitable for crop cultivation. Unsustainable livestock management on such lands leads to overgrazing and decreases the protective groundcover. When more than 60 percent of vegetation gets removed, the rate of erosion accelerates, and topsoil is more likely to be washed off with every rainfall event . Other negative effect of livestock overgrazing is soil compaction in areas where animals gather, which further disables vegetation emergence and maintenance of soil structure. When these factors add up, they significantly contribute to soil erosion by wind and rain. According to a study on the impacts of overgrazing on soil erosion in Mediterranean, erosion increases by 5 to 41 times in overgrazed areas . The key to preserving soils on grazed lands is to respect the natural capacity of the land and vegetation to support the number of animals we intend to keep on the property. Vegetation should have enough time to recover. Areas exposed to more stress, such as creeks, drinking and feeding areas, shelters, need to be managed accordingly. For example, moving feeders or waterers couple feet away while fencing off previous location and seeding a new grass mix to recover vegetation during the rest period. The use of sustainable grazing and pasture management techniques like for example rotational grazing that allows enough time for vegetation regeneration and soil rest, reduces the risk of exhausting pastures. In fact, science-based sustainable grazing practices are even being used to restore various degraded landscapes in some parts of the world. #11 Afforestation and sustainable management of marginal areas When talking about soil erosion control measures, we should not neglect the areas that have already been damaged but have a potential for great improvement when managed properly. Restoration of degraded ecosystems and protection of marginal areas to ensure that we will place sufficient soil erosion prevention methods in place is crucial. Afforestation is one of the most effective long-term solutions. Planting trees goes a long way in preserving soil and ecosystem health. Besides stabilizing soils with their root network, trees are especially helpful in mitigating erosion caused by water runoff. This is thanks to their ability to control water regime in an area. Tree foliage slows down rain drops before they even reach the ground. Through their canopy, trees also reduce the amount of rainwater that reaches the ground. When it rains, tree canopy captures approximately 30 percent of rainwater and another 30 percent are soon after the rain drawn from the soil by tree roots . But that’s not all. Trees go even further in protecting soils. You may have noticed this yourself. Forest floor usually contains a rich layer of decaying leaves and needles. This layer is a natural mulch with a great capacity of absorbing water. According to scientists, water holding capacity of tree litter is up to five times its weight . This means that afforestation can be a great and cheap solution that can help with oversaturation and drainage problems on some lands—especially lands that are prone to flooding. Trees can perform truly impressive functions when it comes to creating a stable environment that promotes healthy soils and balanced water cycle. We should remember that they are our best allies in tackling soil erosion in many places around the world.
1 9.1 Molecular Shapes STUDY GUIDE AP Chemistry CHAPTER NINE- Molecular Geometry and Bonding Theories Sections 9.1 through 9.6 Only Lewis structures give atomic connectivity: they tell us which atoms are physically connected to which atoms. The shape of a molecule is determined by its bond angles. The angles made by the lines joining the nuclei of the atoms in a molecule are the bond angles. Consider CCl4: Experimentally we find all Cl C Cl bond angles are Therefore, the molecule cannot be planar. All Cl atoms are located at the vertices of a tetrahedron with the C at its center. In order to predict molecular shape, we assume that the valence electrons repel each other. Therefore, the molecule adopts the three-dimensional geometry that minimizes this repulsion. We call this model the Valence Shell Electron Pair Repulsion (VSEPR) model. 9.2 The VSEPR Model A covalent bond forms between two atoms when a pair of electrons occupies the space between the atoms. This is a bonding pair of electrons. Such a region is an electron domain. A nonbonding pair or lone pair of electrons defines an electron domain located principally on one atom. Example: NH3 has three bonding pairs and one lone pair. VSEPR predicts that the best arrangement of electron domains is the one that minimizes the repulsions among them. The arrangement of electron domains about the central atom of a molecule is its electron-domain geometry. There are five different electron-domain geometries: linear (two electron domains), trigonal planar (three domains), tetrahedral (four domains), trigonal bipyramidal (five domains) and octahedral (six domains). The molecular geometry is the arrangement of the atoms in space. To determine the shape of a molecule we must distinguish between lone pairs and bonding pairs. We use the electron-domain geometry to help us predict the molecular geometry. Draw the Lewis structure. Count the total number of electron domains around the central atom. Arrange the electron domains in one of the five geometries to minimize electron-electron repulsion. Next, determine the 3-D structure of the molecule. We ignore lone pairs in the molecular geometry. Describe the molecular geometry in terms of the angular arrangement of the bonded atoms. Multiple bonds are counted as one electron domain. The Effect of Nonbonding Electrons and Multiple Bonds on Bond Angles We refine VSEPR to predict and explain slight distortions from ideal geometries. Consider three molecules with tetrahedral electron domain geometries: CH4, NH3, and H2O. By experiment, the H X H bond angle decreases from C (109.5 in CH4) to N (107 in NH3) to O (104.5 in H2O). A bonding pair of electrons is attracted by two nuclei. They do not repel as much as lone pairs which are primarily attracted by only one nucleus. Electron domains for nonbonding electron pairs thus exert greater repulsive forces on adjacent electron domains. They tend to compress the bond angles. The bond angle decreases as the number of nonbonding pairs increases. Similarly, electrons in multiple bonds repel more than electrons in single bonds (e.g., in Cl2CO the O C Cl angle is 124.3, and the Cl C Cl bond angle is ). 2 We will encounter eleven basic molecular shapes: three atoms (AB2): linear five atoms (AB4): bent tetrahedral four atoms (AB3): square planar trigonal planar seesaw trigonal pyramidal t-shaped six atoms (AB5): trigonal bipyramidal square pyramidal seven atoms (AB6): octahedral Electron Domains Electron-Domain Geometry Predicted Bond Angle(s) 2 Linear 180º Linear 3 Trigonal Planar 120º Trigonal Planar Bent Molecular Geometry 0 Lone Pair 1 Lone Pair 2 Lone Pair 4 Tetrahedral 109.5º Tetrahedral Trigonal Pyramidal Bent 5 Trigonal Bipyramidal 90º, 120º Trigonal Bipyramidal Seesaw T-shaped 6 Octahedral 90º Octahedral Square Pyramidal Square Planar Molecules with Expanded Valence Shells Atoms that have expanded octets have five electron domains (trigonal bipyramidal) or six electron domains (octahedral) electron-domain geometries. Trigonal bipyramidal structures have a plane containing three electron pairs. The fourth and fifth electron pairs are located above and below this plane. In this structure two trigonal pyramids share a base. For octahedral structures, there is a plane containing four electron pairs. Similarly, the fifth and sixth electron pairs are located above and below this plane. Two square pyramids share a base. Consider a trigonal bipyramid. The three electron pairs in the plane are called equatorial. The two electron pairs above and below this plane are called axial. The axial electron pairs are 180 apart and 90 to the equatorial electrons. The equatorial electron pairs are 120 apart. To minimize electron electron repulsion, nonbonding pairs are always placed in equatorial positions and bonding pairs are placed in either axial or equatorial positions. Consider an octahedron. The four electron pairs in the plane are at 90 to each other. The two axial electron pairs are 180 apart and at 90 to the electrons in the plane. Because of the symmetry of the system, each position is equivalent. If we have five bonding pairs and one lone pair, it does not matter where the lone pair is placed. The molecular geometry is square pyramidal. If two non-bonding pairs are present, the repulsions are minimized by pointing them toward opposite sides of the octahedron. The molecular geometry is square planar. 3 Shapes of Larger Molecules In acetic acid, CH3COOH, there are three interior atoms: two C and one O. We assign the molecular (and electron-domain) geometry about each interior atom separately: The geometry around the first C is tetrahedral. The geometry around the second C is trigonal planar. The geometry around the O is bent (tetrahedral). 9.3 Molecular Shape and Molecular Polarity Polar molecules interact with electric fields. We previously saw that binary compounds are polar if their centers of negative and positive charge do not coincide. If two charges, equal in magnitude and opposite in sign, are separated by a distance d, then a dipole is established. The dipole moment, µ is given by µ = Qr where Q is the magnitude of the charge. We can extend this to polyatomic molecules. For each bond in a polyatomic molecule, we can consider the bond dipole. The dipole moment due only to the two atoms in the bond is the bond dipole. Because bond dipoles and dipole moments are vector quantities, the orientation of these individual dipole moments determines whether the molecule has an overall dipole moment. In CO2 each + C O dipole is canceled because the molecule is linear. In H2O, the + H O dipoles do not cancel because the molecule is bent. It is possible for a molecule with polar bonds to be either polar or nonpolar. Example: For diatomic molecules: polar bonds always result in an overall dipole moment. For triatomic molecules: if the molecular geometry is bent, there is an overall dipole moment. if the molecular geometry is linear and the B atoms are the same, there is no overall dipole moment. if the molecular geometry is linear and the B atoms are different, there is an overall dipole moment. For molecules with four atoms: if the molecular geometry is trigonal pyramidal, there is an overall dipole moment. if the molecular geometry is trigonal planar and the B atoms are identical, there is no overall dipole µ. if the molecular geometry is trigonal planar and the B atoms are different, there is an overall dipole µ. 9.4 Covalent Bonding and Orbital Overlap Lewis structures and VSEPR theory give us the shape and location of electrons in a molecule. They do not explain why a chemical bond forms. How can quantum mechanics be used to account for molecular shape? What orbitals are involved in bonding? We use valence-bond theory. A covalent bond forms when the orbitals on two atoms overlap. The shared region of space between the orbitals is called the orbital overlap. There are two electrons (usually one from each atom) of opposite spin in the orbital overlap. As two nuclei approach each other their atomic orbitals overlap. As the amount of overlap increases, the energy of the interaction decreases. At some distance the minimum energy is reached. The minimum energy corresponds to the bonding distance (or bond length). As the two atoms get closer, their nuclei begin to repel and the energy increases. At the bonding distance, the attractive forces between nuclei and electrons just balance the repulsive forces (nucleus-nucleus, electron-electron). 9.5 Hybrid Orbitals We can apply the idea of orbital overlap and valence-bond theory to polyatomic molecules. sp Hybrid Orbitals Consider the BeF2 molecule. Be has a 1s 2 2s 2 electron configuration. There is no unpaired electron available for bonding. We conclude that the atomic orbitals are not adequate to describe orbitals in molecules. We know that the F Be F bond angle is 180 (VSEPR theory). We also know that one electron from Be is shared with each one of the unpaired electrons from F. We assume that the Be orbitals in the Be F bond are 180 apart. We could promote an electron from the 2s orbital on Be to the 2p orbital to get two unpaired electrons for bonding. BUT the geometry is still not explained. 4 We can solve the problem by allowing the 2s and one 2p orbital on Be to mix or form two new hybrid orbitals (a process called hybridization). The two equivalent hybrid orbitals that result from mixing an s and a p orbital and are called sp hybrid orbitals. The two lobes of an sp hybrid orbital are 180 apart. According to the valence-bond model, a linear arrangement of electron domains implies sp hybridization. Since only one of 2p orbitals of Be has been used in hybridization, there are two unhybridized p orbitals remaining on Be. The electrons in the sp hybrid orbital form shared electron bonds with the two fluorine atoms. sp 2 and sp 3 Hybrid Orbitals Important: when we mix n atomic orbitals we must get n hybrid orbitals. Three sp 2 hybrid orbitals are formed from hybridization of one s and two p orbitals. Thus, there is one unhybridized p orbital remaining. The large lobes of the sp 2 hybrids lie in a trigonal plane. Molecules with trigonal planar electron-pair geometries have sp 2 orbitals on the central atom. Four sp 3 hybrid orbitals are formed from hybridization of one s and three p orbitals. Therefore, there are four large lobes. Each lobe points towards the vertex of a tetrahedron. The angle between the large lobes is Molecules with tetrahedral electron pair geometries are sp 3 hybridized. Hybridization Involving d Orbitals Since there are only three p orbitals, trigonal bipyramidal and octahedral electron-pair geometries must involve d orbitals. Trigonal bipyramidal electron pair geometries require sp 3 d hybridization. Octahedral electron pair geometries require sp 3 d 2 hybridization. Electron pair VSEPR geometry corresponds well with the hybridization. Use of d orbitals in making hybrid orbitals corresponds well with the idea of an expanded octet. Summary- We need to know the electron-domain geometry before we can assign hybridization. To assign hybridization: Draw a Lewis structure. Assign the electron-domain geometry using VSEPR theory. Specify the hybridization required to accommodate the electron pairs based on their geometric arrangement. Name the geometry by the positions of the atoms. 9.6 Multiple Bonds- In the covalent bonds we have seen so far the electron density has been concentrated symmetrically about the internuclear axis. Sigma (σ) bonds: electron density lies on the axis between the nuclei. All single bonds are σ bonds. What about overlap in multiple bonds? Pi (π) bonds: electron density lies above and below the plane of the nuclei. A double bond consists of one σ bond and one π bond. Bond Order A triple bond has one σ bond and two π bonds. Bond order = 1 for a single bond. Bond order = 2 for a double bond. Bond order = 3 for a triple bond. Often, the p orbitals involved in π bonding come from unhybridized orbitals. For example: ethylene, C2H4, has: One σ and one π bond. Both C atoms are sp 2 hybridized. Both C atoms have trigonal planar electron-pair and molecular geometries. For example: acetylene, C2H2: The electron-domain geometry of each C is linear. Therefore, the C atoms are sp hybridized. The sp hybrid orbitals form the C C and C H σ bonds. There are two unhybridized p orbitals on each C atom. 5 Both unhybridized p orbitals form the two π bonds; One π bond is above and below the plane of the nuclei; One π bond is in front and behind the plane of the nuclei. For triple bonds, one π bond is always above and below and the other is in front and behind the plane of the nuclei. Delocalized π Bonding- So far all the bonds we have encountered are localized between two nuclei. In the case of benzene: There are six C C σ bonds and six C H σ bonds. Each C atom is sp 2 hybridized. There is one unhybridized p orbital on each carbon atom, resulting in six unhybridized carbon p orbitals in a ring. In benzene there are two options for the three π bonds: localized between carbon atoms or delocalized over the entire ring (i.e., the π electrons are shared by all six carbon atoms). Experimentally, all C C bonds are the same length in benzene. Therefore, all C C bonds are of the same type (recall single bonds are longer than double bonds). General Conclusions Every pair of bonded atoms shares one or more pairs of electrons. Two electrons shared between atoms on the same axis as the nuclei are σ bonds. σ bonds are always localized in the region between two bonded atoms. If two atoms share more than one pair of electrons, the additional pairs form π bonds. When resonance structures are possible, delocalization is also possible. 9.7 Molecular Orbitals WE ARE NOT GOING TO LEARN THIS MO STUFF!! Some aspects of bonding are not explained by Lewis structures, VSEPR theory, and hybridization. For these molecules, we use molecular orbital (MO) theory. Just as electrons in atoms are found in atomic orbitals, electrons in molecules are found in molecular orbitals. However, unlike atomic orbitals, molecular orbitals are associated with an entire molecule. Homework Problems Pg 388 #4, #13, #17, #19, #21, #25, #31, #33, #35, #75, #82 Pg 388 #8, #40, #43, #44, #47, #49, #51, #53, #56, #65a 1)A 2)C 3)C 4)B 5)D 6)C 7)C 8)D 9)D 10)B 11)B 12)E 13)A 14)C 15)C 16)D 17)C 18)C 19)D 20)E 21)B 22)D 23)E 24)C 25)B 26)B 27)A 28)B 29)A 30)D 31)B 32)E 33)B 34)D 35)D 36)C 37)D 38)E 39)E 40)B 41)C 42)B 43)C 44)E 45)B 46)A 47)B 6 Practice Test 1) For a molecule with the formula the molecular shape is. A) linear or bent B) linear or trigonal planar C) linear or T-shaped D) T-shaped E) trigonal planar 2) According to VSEPR theory, if there are four electron domains in the valence shell of an atom, they will be arranged in a(n) geometry. A) octahedral B) linear C) tetrahedral D) trigonal planar E) trigonal bipyramidal 3) The electron-domain geometry and molecular geometry of iodine trichloride are and, respectively. A) trigonal bipyramidal, trigonal planar B) tetrahedral, trigonal pyramidal C) trigonal bipyramidal, T-shaped D) octahedral, trigonal planar E) T-shaped, trigonal planar 4) The molecular geometry of is square planar. 11) In order to produce hybrid orbitals, s atomic orbital(s) and p atomic orbital(s) must be mixed. A) one, two B) one, three C) one, one D) two, two E) two, three 12) The angles between orbitals are. A) 45 B) 180 C) 90 D) E) ) There are σ and π bonds in the H C C H molecule. A) 3 and 2 B) 3 and 4 C) 4 and 3 D) 2 and 3 E) 5 and 0 14) The total number of π bonds in the H C C C C C N molecule is. A) 3 B) 4 C) 6 D) 9 E) 12 15) There is/are σ bond(s) in the molecule below. 5) The molecular geometry of the ion is. A) linear B) tetrahedral C) bent D) trigonal pyramidal E) octahedral 6) The F B F bond angle in the molecule is. A) 90 B) C) 120 D) 180 E) 60 7) The O S O bond angle in is slightly less than. A) 90 B) C) 120 D) 180 E) 60 8) According to valence bond theory, which orbitals on bromine atoms overlap in the formation of the bond in? A) 3s B) 3p C) 4s D) 4p E) 3d 9) The electron-domain geometry of a sulfur-centered compound is trigonal bipyramidal. The hybridization of the central sulfur atom is. A) sp B) C) 10) The hybridization of orbitals on the central atom in a molecule is sp. The electron-domain geometry around this central atom is. A) octahedral B) linear C) trigonal planar D) trigonal bipyramidal E) tetrahedral A) 1 B) 2 C) 12 D) 13 E) 18 16) The basis of the VSEPR model of molecular bonding is. A) regions of electron density on an atom will organize themselves so as to maximize s-character B) regions of electron density in the valence shell of an atom will arrange themselves so as to maximize overlap C) atomic orbitals of the bonding atoms must overlap for a bond to form D) electron domains in the valence shell of an atom will arrange themselves so as to minimize repulsions E) hybrid orbitals will form as necessary to, as closely as possible, achieve spherical symmetry 17) The O C O bond angle in the CO32- ion is approximately. A) 90 B) C) 120 D) 180 E) 60 18) The Cl C Cl bond angle in the molecule (C is the central atom) is slightly. A) greater than 90 B) less than C) less than 120 D) greater than 120 E) greater than 109.5 7 19) The bond angles marked a, b, and c in the molecule below are about,, and, respectively. 26) Of the molecules below, only is polar. 27) Of the molecules below, only is nonpolar. A) 90, 90, 90 B) 120, 120, 90 C) 120, 120, D) 109.5, 120, E) 109.5, 90, ) The central iodine atom in the ion has nonbonded electron pairs and bonded electron pairs in its valence shell. A) 2, 2 B) 3, 4 C) 1, 3 D) 3, 2 E) 2, 4 21) The central Xe atom in the XeF4 molecule has unbonded electron pairs and bonded electron pairs in its valence shell. A) 1, 4 B) 2, 4 C) 4, 0 D) 4, 1 E) 4, 2 22) An electron domain consists of. a) a nonbonding pair of electrons b) a single bond c) a multiple bond A) a only B) b only C) c only D) a, b, and c E) b and c 23) According to VSEPR theory, if there are three electron domains on a central atom, they will be arranged such that the angles between the domains are. A) 90 B) 180 C) D) 360 E) ) The electron-domain geometry and the molecular geometry of a molecule of the general formula are. A) never the same B) always the same C) sometimes the same D) not related E) mirror images of one another 25) For molecules of the general formula, n can be greater than four. A) for any element A B) only when A is an element from the third period or below the third period C) only when A is boron or beryllium D) only when A is carbon E) only when A is Xe 28) Three monosulfur fluorides are observed:,, and. Of these, is/are polar. A) only B) and only C) only D) only E),, and 29) The molecular geometry of the molecule is, and this molecule is. A) linear, nonpolar B) linear, polar C) bent, nonpolar D) bent, polar E) trigonal planar, polar 30) Of the following molecules, only is polar. 31) Of the following, only has hybridization of the central atom. A) B) C) D) E) 32) The atomic hybrid orbital set accommodates electron domains. A) 2 B) 3 C) 4 D) 5 E) 6 33) The hybridizations of iodine in and are and, respectively. A), B), C), D), E), 34) hybrid orbitals are used for bonding by Xe in the molecule. sp 8 Consider the following species when answering the following questions: (i) (ii) (iii) (iv) (v) 35) In which of the molecules does the central atom utilize d orbitals to form hybrid orbitals? A) (i) and (ii) B) (iii) only C) (i) and (v) D) (iii), (iv), and (v) E) (v) only 36)Which of the molecules has a see-saw shape? A) (i) B) (ii) C) (iii) D) (iv) E) (v) 37) In which of the molecules is the central atom hybridized? A) (i) and (ii) B) (iii) only C) (iii) and (iv) D) (iv) and (v) E) (v) only 38) The blending of one s atomic orbital and two p atomic orbitals produces. A) three sp hybrid orbitals B) two hybrid orbitals C) three hybrid orbitals D) two hybrid orbitals E) three hybrid orbitals 39) A typical double bond. A) is stronger and shorter than a single bond B) consists of one σ bond and one π bond C) imparts rigidity to a molecule D) consists of two shared electron pairs E) All of the above answers are correct. 40) In a polyatomic molecule, "localized" bonding electrons are associated with. A) one particular atom B) two particular atoms C) all of the atoms in the molecule D) all of the π bonds in the molecule E) two or more σ bonds in the molecule 42) In order to exhibit delocalized π bonding, a molecule must have. A) at least two π bonds B) at least two resonance structures C) at least three σ bonds D) at least four atoms E) trigonal planar electron domain geometry 43) The carbon-carbon σ bond in ethylene,, results from the overlap of. A) sp hybrid orbitals B) hybrid orbitals C) hybrid orbitals D) s atomic orbitals E) p atomic orbitals 44) The π bond in ethylene,, results from the overlap of. A) hybrid orbitals B) s atomic orbitals C) sp hybrid orbitals D) hybrid orbitals E) p atomic orbitals 45) In order for rotation to occur about a double bond,. A) the σ bond must be broken B) the π bond must be broken C) the bonding must be delocalized D) the bonding must be localized E) the σ and π bonds must both be broken 46) The N N bond in HNNH consists of. A) one σ bond and one π bond B) one σ bond and two π bonds C) two σ bonds and one π bond D) two σ bonds and two π bonds E) one σ bond and no π bonds 47) Electrons in bonds remain localized between two atoms. Electrons in bonds can become delocalized between more than two atoms. A) pi, sigma B) sigma, pi C) pi, pi D) sigma, sigma E) ionic, sigma 41) Which of the following molecules or ions will exhibit delocalized bonding? A),, and B) only C) and D) and E) None of the above will exhibit delocalized bonding.
A quadratic expression is a polynomial that can be written in the form shown below. A specific type of quadratic expression is called the difference of squares. Notice that the constant term, 16, is a perfect square, because the square root of 16 is 4, which is an integer. Therefore, you can rewrite your expression as the following: This is called a difference of squares expression, because there are two values squared, x and the integer, with subtraction between the two. Difference of squares expressions can be factored similarly to other quadratic expressions. Suppose you want to factor the difference of squares expression from the example above. To factor, you need to find two numbers that multiply to the constant term, and add to the coefficient of the middle term. Note, when the x term is absent from a quadratic expression, the coefficient of the x term is 0. Therefore, you can write the x term with the coefficient of 0. However, because anything multiplied by 0 is 0, the entire term is 0, so in reality, you don’t need to write anything for the x term. You’ll notice that in the expression that you want to factor, your constant term, 16, is a perfect square. Therefore, you can now write your expression as: To factor your expression, you need to find two numbers that add to 0 and multiply to -16. Going back to your expression, 4 and -4 are opposites, so they sum to 0, and they also multiply to negative 16. Therefore, you can factor your expression as: Notice that the integer being squared in the original expression, 4, is part of both factors: x plus 4 in the first factor, and x minus 4 in the second factor. Therefore, in general, you can factor the difference of squares equations as the shown here. You can verify that you have factored the expression correctly by performing FOIL to see if you get your original expression. Since you do indeed arrive back at your original expression, you have factored your expression correctly. Source: This work is adapted from Sophia author Colleen Atakpu.
This article relies largely or entirely on a single source. (August 2012) Electron-beam welding (EBW) is a fusion welding process in which a beam of high-velocity electrons is applied to two materials to be joined. The workpieces melt and flow together as the kinetic energy of the electrons is transformed into heat upon impact. EBW is often performed under vacuum conditions to prevent dissipation of the electron beam. Electron-beam welding was developed by the German physicist Karl-Heinz Steigerwald in 1949, who was at the time working on various electron-beam applications. Steigerwald conceived and developed the first practical electron-beam welding machine, which began operation in 1958. American inventor James T. Russell has also been credited with designing and building the first electron-beam welder. Physics of electron-beam heatingEdit Electrons are elementary particles possessing a mass m = 9.1 · 10−31 kg and a negative electrical charge e = 1.6 · 10−19 C. They exist either bound to an atomic nucleus, as conduction electrons in the atomic lattice of metals, or as free electrons in vacuum. Free electrons in vacuum can be accelerated, with their paths controlled by electric and magnetic fields. In this way narrow beams of electrons carrying high kinetic energy can be formed, which upon collision with atoms in solids transform their kinetic energy into heat. Electron-beam welding provides excellent welding conditions because it involves: - Strong electric fields, which can accelerate electrons to a very high speed. Thus, the electron beam can carry high power, equal to the product of beam current and accelerating voltage. By increasing the beam current and the accelerating voltage, the beam power can be increased to practically any desired value. - Using magnetic lenses, by which the beam can be shaped into a narrow cone and focused to a very small diameter. This allows for a very high surface power density on the surface to be welded. Values of power density in the crossover (focus) of the beam can be as high as 104 – 106 W/mm2. - Shallow penetration depths in the order of hundredths of a millimeter. This allows for a very high volumetric power density, which can reach values of the order 105 – 107 W/mm3. Consequently, the temperature in this volume increases extremely rapidly, 108 – 1010 K/s. The effectiveness of the electron beam depends on many factors. The most important are the physical properties of the materials to be welded, especially the ease with which they can be melted or vaporize under low-pressure conditions. Electron-beam welding can be so intense that loss of material due to evaporation or boiling during the process must be taken into account when welding. At lower values of surface power density (in the range of about 103 W/mm2) the loss of material by evaporation is negligible for most metals, which is favorable for welding. At higher power density, the material affected by the beam can totally evaporate in a very short time; this is no longer electron-beam welding; it is electron-beam machining. - Cathode - the source of free electrons Conduction electrons (those not bound to the nucleus of atoms) move in a crystal lattice of metals with velocities distributed according to Gauss's law and depending on temperature. They cannot leave the metal unless their kinetic energy (in eV) is higher than the potential barrier at the metal surface. The number of electrons fulfilling this condition increases exponentially with increasing temperature of the metal, following Richardson's rule. As a source of electrons for electron-beam welders, the material must fulfill certain requirements: - to achieve high power density in the beam, the emission current density [A/mm2], hence the working temperature, should be as high as possible, - to keep evaporation in vacuum low, the material must have a low enough vapour pressure at the working temperature. - The emitter must be mechanically stable, not chemically sensitive to gases present in the vacuum atmosphere (like oxygen and water vapour), easily available, etc. These and other conditions limit the choice of material for the emitter to metals with high melting points, practically to only two: tantalum and tungsten. With tungsten cathodes, emission current densities about 100 mA/mm2 can be achieved, but only a small portion of the emitted electrons takes part in beam formation, depending on the electric field produced by the anode and control electrode voltages. The type of cathode most frequently used in electron-beam welders is made of a tungsten strip, about 0.05 mm thick, shaped as shown in Fig. 1a. The appropriate width of the strip depends on the highest required value of emission current. For the lower range of beam power, up to about 2 kW, the width w=0.5 mm is appropriate. - Acceleration of electrons, current control Electrons emitted from the cathode possess very low energy, only a few eV. To give them the required high speed, they are accelerated by a strong electric field applied between the emitter and another, positively charged, electrode, namely the anode. The accelerating field must also navigate the electrons to form a narrow converging “bundle” around the axis. This can be achieved by an electric field in the proximity of the emitting cathode surface which has, a radial addition as well as an axial component, forcing the electrons in the direction of the axis. Due to this effect, the electron beam converges to some minimal diameter in a plane close to the anode. For practical applications the power of the electron beam must, of course, be controllable. This can be accomplished by another electric field produced by another cathode negatively charged with respect to the first. At least this part of electron gun must be evacuated to "high" vacuum, to prevent "burning" the cathode and the emergence of electrical discharges. After leaving the anode, the divergent electron beam does not have a power density sufficient for welding metals and has to be focused. This can be accomplished by a magnetic field produced by electric current in a cylindrical coil. The focusing effect of a rotationally symmetrical magnetic field on the trajectory of electrons is the result of the complicated influence of a magnetic field on a moving electron. This effect is a force proportional to the induction B of the field and electron velocity v. The vector product of the radial component of induction Br and axial component of velocity va is a force perpendicular to those vectors, causing the electron to move around the axis. Additional effect of this motion in the same magnetic field is another force F oriented radially to the axis, which is responsible for the focusing effect of the magnetic lens. The resulting trajectory of electrons in the magnetic lens is a curve similar to a helix. In this context it should be mentioned that variations of focal length (exciting current) cause a slight rotation of the beam cross-section. - Beam deflection system As mentioned above, the beam spot should be very precisely positioned with respect to the joint to be welded. This is commonly accomplished mechanically by moving the workpiece with respect to the electron gun, but sometimes it is preferable to deflect the beam instead. Most often a system of four coils positioned symmetrically around the gun axis behind the focusing lens, producing a magnetic field perpendicular to the gun axis, is used for this purpose. There are more practical reasons why the most appropriate deflection system is used in TV CRT or PC monitors. This applies to both the deflecting coils as well as to the necessary electronics. Such a system enables not only “static” deflection of the beam for the positioning purposes mentioned above, but also precise and fast dynamic control of the beam spot position by a computer. This makes it possible, e.g.: to weld joints of complicated geometry, and to create image-enlarged pictures of objects in the working chamber on TV or PC monitors. Both possibilities find many useful applications in electron-beam welding practice. Penetration of electron beam during weldingEdit To explain the capability of the electron beam to produce deep and narrow welds, the process of "penetration" must be explained. First of all, the process for a "single" electron can be considered. - Penetration of electrons When electrons from the beam impact the surface of a solid, some of them may be reflected (as "backscattered" electrons), while others penetrate the surface, where they collide with the particles of the solid. In non-elastic collisions they lose their kinetic energy. It has been proved, both theoretically and experimentally, that they can "travel" only a very small distance below the surface before they transfer all their kinetic energy into heat. This distance is proportional to their initial energy and inversely proportional to the density of the solid. Under conditions usual in welding practice the "travel distance" is on the order of hundredths of a millimeter. Just this fact enables, under certain conditions, fast beam penetration. - Penetration of the electron beam The heat contribution of single electrons is very small, but the electrons can be accelerated by very high voltages, and by increasing their number (the beam current) the power of the beam can be increased to any desired value. By focusing the beam onto a small diameter on the surface of a solid object, values of planar power density as high as 104 up to 107 W/mm2 can be reached. Because electrons transfer their energy into heat in a very thin layer of the solid, as explained above, the power density in this volume can be extremely high. The volume density of power in the small volume in which the kinetic energy of the electrons is transformed into heat can reach values of the order 105 – 107 W/mm3. Consequently, the temperature in this volume increases extremely rapidly, by 108 – 109 K/s. The effect of the electron beams under such circumstances depends on several conditions, first of all on the physical properties of the material. Any material can be melted, or even evaporated, in a very short time. Depending on conditions, the intensity of evaporation may vary, from negligible to essential. At lower values of surface power density (in the range of about 103 W/mm2) the loss of material by evaporation is negligible for most metals, which is favorable for welding. At higher power density, the material affected by the beam can totally evaporate in a very short time; this is no longer electron-beam welding; it is electron-beam machining. Results of the electron-beam applicationEdit The results of the beam application depend on several factors: Many experiments and innumerable practical applications of electron beam in welding technology prove that the effect of the beam, i.e. the size and shape of the zone influenced by the beam depends on: (1) Beam power – The power of the beam [W] is the product of the accelerating voltage [kV] and beam current [mA], parameters easily measurable and precisely controllable. The power is controlled by the beam current at constant accelerating voltage, usually the highest accessible. (2) Power density (focusing of the beam) – The power density at the spot of incidence of the beam with the workpiece depends on factors like the size of the electron source on the cathode, the optical quality of the accelerating electric lens and the focusing magnetic lens, alignment of the beam, the value of the accelerating voltage, and the focal length. All these factors (except the focal length) depend on the design of the machine. (3) Welding speed – The construction of the welding equipment should enable adjustment of the relative speed of motion of the workpiece with respect to the beam in wide enough limits, e.g., between 2 and 50 mm/s. (4) Material properties, and in some cases also on (5) Geometry (shape and dimensions) of the joint. The final effect of the beam depends on the particular combination of these parameters. - Action of the beam at low power density or over a very short time results in melting only a thin surface layer. - A defocused beam does not penetrate, and the material at low welding speeds is heated only by conduction of the heat from the surface, producing a hemispherical melted zone. - At high power density and low speed, a deeper and slightly conical melted zone is produced. - In the case of very high power density, the beam (well focused) penetrates deeper, in proportion to its total power. The welding processEdit For welding thin-walled parts, appropriate welding aids are generally needed. Their construction must provide perfect contact of the parts and prevent their movement during welding. Usually they have to be designed individually for a given workpiece. Not all materials can be welded by an electron beam in a vacuum. This technology cannot be applied to materials with high vapour pressure at the melting temperature, like zinc, cadmium, magnesium and practically all non-metals. Another limitation to weldability may be the change of material properties induced by the welding process, such as a high speed of cooling. As detailed discussion of this matter exceeds the scope of this article, the reader is recommended to seek more information in the appropriate literature. Joining dissimilar materialsEdit It is often not possible to join two metal components by welding, i.e. to melt part of both in the vicinity of the joint, if the two materials have very different properties from their alloy, due to the creation of brittle, inter-metallic compounds. This situation cannot be changed, even by electron-beam heating in vacuum, but this nevertheless makes it possible to realize joints meeting high demands for mechanical compactness and that are perfectly vacuum-tight. The principal approach is not to melt both parts, but only the one with the lower melting point, while the other remains solid. The advantage of electron-beam welding is its ability to localize heating to a precise point and to control exactly the energy needed for the process. A high-vacuum atmosphere substantially contributes to a positive result. A general rule for construction of joints to be made this way is that the part with the lower melting point should be directly accessible for the beam. Possible problems and limitationsEdit The material melted by the beam shrinks during cooling after solidification, which may have unwanted consequences like cracking, deformation and changes of shape, depending on conditions. The butt weld of two plates results in bending of the weldment because more material has been melted at the head than at the root of the weld. This effect is of course not as substantial as in arc welding. Another potential danger is the emergence of cracks in the weld. If both parts are rigid, the shrinkage of the weld produces high stress in the weld which may lead to cracks if the material is brittle (even if only after remelting by welding). The consequences of weld contraction should always be considered when constructing the parts to be welded. Electron-beam welding equipmentEdit Since the publication of the first practical electron-beam welding equipment by Steigerwald in 1958, electron-beam welding has spread rapidly in all branches of engineering where welding can be applied. To cover the various requirements, countless welder types have been designed, differing in construction, working space volume, workpiece manipulators and beam power. Electron-beam generators (electron guns) designed for welding applications can supply beams with power ranging from a few watts up to about one hundred kilowatts. "Micro-welds" of tiny components can be realized, as well as deep welds up to 300 mm (or even more if needed). Vacuum working chambers of various design may have a volume of only a few liters, but vacuum chambers with the volume of several hundreds cubic meters have also been built. Specifically, the equipment comprises: - Electron gun, generating the electron beam, - Working chamber, mostly evacuated to "low" or "high" vacuum, - Workpiece manipulator (positioning mechanism), - Power supply and control and monitoring electronics. - Electron gun In the electron gun, the free electrons are gained by thermo-emission from a hot metal strap (or wire). They are then accelerated and formed into a narrow convergent beam by an electric field produced by three electrodes: the electron emitting strap, the cathode connected to the negative pole of the high (accelerating) voltage power supply (30 - 200 kV) and the positive high voltage electrode, the anode. There is a third electrode charged negatively with respect to the cathode, called the Wehnelt or control electrode. Its negative potential controls the portion of emitted electrons entering into the accelerating field, i.e., the electron-beam current. After passing the anode opening, the electrons move with constant speed in a slightly divergent cone. For technological applications the divergent beam has to be focused, which is realized by the magnetic field of a coil, the magnetic focusing lens. For proper functioning of the electron gun, it is necessary that the beam be perfectly adjusted with respect to the optical axes of the accelerating electrical lens and the magnetic focusing lens. This can be done by applying a magnetic field of some specific radial direction and strength perpendicular to the optical axis before the focusing lens. This is usually realized by a simple correction system consisting of two pairs of coils. By adjusting the currents in these coils any required correcting field can be produced. After passing the focusing lens, the beam can be applied for welding, either directly or after being deflected by a deflection system. This consists of two pairs of coils, one for each X and Y direction. These can be used for "static" or "dynamic" deflection. Static deflection is useful for exact positioning of the beam by welding. Dynamic deflection is realized by supplying the deflection coils with currents which can be controlled by the computer. This opens new possibilities for electron-beam applications, like surface hardening or annealing, exact beam positioning, etc. The fast deflection system can also be applied (if provided with appropriate electronics) for imaging and engraving. In this case the equipment is operated like a scanning electron microscope, with a resolution of about 0,1 mm (limited by the beam diameter). In a similar mode the fine computer-controlled beam can "write" or "draw" a picture on the metal surface by melting a thin surface layer. - Working chamber Since the appearance of the first electron-beam welding machines at the end of the 1950s, the application of electron-beam welding spread rapidly into industry and research in all highly developed countries. Up to now, uncountable numbers of various types of electron-beam equipment have been designed and realized. In most of them the welding takes place in a working vacuum chamber in a high or low vacuum environment. The vacuum working chamber may have any desired volume, from a few liters up to hundreds of cubic meters. They can be provided with electron guns supplying an electron beam with any required power up to 100 kW, or even more if needed. In micro-electron beam devices, components with dimensions in tenths of a millimeter can be precisely welded. In welders with electron beams of high enough power, welds up to 300 mm deep can be realized. There are also welding machines in which the electron beam is brought out of vacuum into the atmosphere. With such equipment very large objects can be welded without huge working chambers. - Workpiece manipulators Electron-beam welding can never be "hand-manipulated", even if not realized in vacuum, as there is always strong X-radiation. The relative motion of the beam and the workpiece is most often achieved by rotation or linear travel of the workpiece. In some cases the welding is realized by moving the beam with the help of a computer-controlled deflection system. Workpiece manipulators are mostly designed individually to meet the specific requirements of the welding equipment. - Power supply and control and monitoring electronics Electron-beam equipment must be provided with an appropriate power supply for the beam generator. The accelerating voltage may be chosen between 30 and 200 kV. Usually it is about 60 or 150 kV, depending on various conditions. With rising voltage the technical problems and the price of the equipment rapidly increase, hence, whenever it is possible a lower voltage of about 60 kV is to be chosen. The maximum power of the high voltage supply depends on the maximum depth of weld required. The high-voltage equipment must also supply the low voltage, above 5 V, for the cathode heating, and negative voltage up to about 1000 V for the control electrode. The electron gun also needs low-voltage supplies for the correction system, the focusing lens, and the deflection system. The last mentioned may be very complex if it is to provide computer-controlled imaging, engraving, or similar beam applications. Complex electronics may also be needed to control the workpiece manipulator. - Schultz, Helmut (1993). Electron beam welding. Cambridge, England: Woodhead Publishing/The Welding Institute. ISBN 1-85573-050-2. - Brier Dudley (2004-11-29). "Scientist's invention was let go for a song". The Seattle Times. Retrieved 2014-07-24. - "INVENTOR AND PHYSICIST JAMES RUSSELL '53 WILL RECEIVE VOLLUM AWARD AT REED'S CONVOCATION" (Press release). Reed College public affairs office. 2000. Retrieved 2014-07-24. - "Inventor of the Week - James T. Russell - The Compact Disc". MIT. December 1999. Archived from the original on April 17, 2003. \|Wikimedia Commons has media related to Electron beam welding.\| - Schulze, Klaus-Rainer. "Electron Beam Technologies". DVS Media, Düsseldorf, 2012. - Elmer, John (2008-03-03). "Standardizing the Art of Electron-Beam Welding". Lawrence Livermore National Laboratory. Archived from the original on 2008-09-20. Retrieved 2008-10-16. - What is Electron Beam Welding? - Electron beam welding of thin-walled parts - Weldability of various materials - Leptons-Technologies Weldability of metals
Theodolite surveying is that branch of surveying in which theodolite is used to measure the horizontal and vertical angles. A Theodolite is a very precise instrument, mainly used for determining the horizontal and vertical distances between two points. It can also be used for prolonging a line, measuring distances indirectly, as a level, like a tachometer. Due to its wide range of applications, it is also termed as “Universal Instrument”. Types of Theodolite: There are generally two types of Theodolites: - Transit Theodolite: A transit Theodolite is the one in which the telescope mounted in the instrument can be revolved through a complete revolution about its horizontal axis, in a vertical plane. - Non-Transit Theodolite: It is the opposite of Transit Theodolite. In this type of Theodolite, the telescope can not be revolved through a complete revolution about its horizontal axis, in a vertical plane. It can be rotated to a certain extent to take vertical angles. Theodolites can also be classified into two categories on the basis of the Scale used in theodolite as: - Vernier Theodolite: it is fitted with a Vernier Scale. Vernier Theodolites are most commonly used in normal Surveying operations - Micrometre Theodolite: Fitted with a micro micrometre scale - The size of Theodolites is defined according to the diameter of its main scale, such as a 10 cm theodolite means that the diameter of its main scale is 10cm. - In a survey, 8 cm to 12 cm theodolites is generally used. Important Parts of the Theodolite & Their Functions To understand the instrument, it is necessary to know about the parts, the instrument is composed of. These parts are given in as follows: - Telescope: The telescope of theodolite is mounted on the horizontal spindle. It can be rotated about the horizontal axis to sight the objects. The telescope is internal focusing type i.e. the objective lens is fixed in the position and an additional double concave (focusing lens) is moved between the diaphragm and the objective. - Vertical Circle: The vertical circle is rigidly fixed with the telescope, and moves along with it. It is subdivided into four quadrants, each quadrants having a reading of 0° to 90° in proper directions. The vertical circle also consists of a scale which is generally used for taking vertical angular measurements. - Clamp Screws: Vertical clamp screw is used to clamp the telescope and vertical circle at any desired angle. It prevents the rotation of the telescope about the horizontal axis. These are situated in the lower plate of the instrument mostly and are used in rotating the instrument about its horizontal axis. These are two clamp screws, Lower clamp screw, generally used for rotating the whole instrument, and Upper clamp screw, which is used to fix the Vernier A and Vernier B to a certain degree (mostly 0° and 180°) by rotating the upper part of the instrument. - Plate Bubble: Two plate bubbles are mounted at the upper surface of the Vernier plate at right angles. One plate bubble is kept parallel to the horizontal axis of the Theodolite and is used for horizontal levelling of the instrument. Another plate bubble is mounted about the vertical axis of the Theodolite and is used for vertical levelling of the instrument. - Trivet: Trivet is the lowermost part of the instrument. It consists of a circular plate having a central, threaded hole in its centre, to properly fix the instrument with tripod stand. This plate is also termed as Base Plate. The foot Screws are attached over this plate with a ball and socket arrangement. - Foot Screws: These are also termed as levelling screws, and are used to properly level the instrument in the ground. There is three number of foot Screws, which are rotated in a certain direction, to level the instrument. - Tangent Screws: The instrument consists of two tangent screws, one of which is placed in the lower plate, and another one is placed in the upper plate. The lower tangent screw is used for very slight movement of the crosshairs to accurately bisect the ranging rod placed at the point, and the Upper tangent screw is used for very slight movement of the scale reading. Both screws are for accurate measurement purposes. - Vernier Scales: Two Vernier scales are naming, horizontal scale & vertical scale. The horizontal scale is used for taking horizontal angles and is mounted on the lower plate of the instrument, and the vertical scale is used for taking vertical angles, fixed on the vertical circle. The theodolite is called telescope normal when the vertical circle is to the left-hand side of the surveyor and the bubble tube on the telescope is upward. The theodolite is called telescope normal when the vertical circle is to the right-hand side of the surveyor and the bubble tube on the telescope is downward. The process of rotation the telescope of theodolite by 180-degree about the horizontal axis (i.e. in the vertical plane) is called Transit of a theodolite. This makes the telescope point in the exact opposite direction. It is also called reversing or plunging. The process of revolving the telescope of theodolite about the vertical axis (i.e. in the horizontal plane) is called swing or swinging of the telescope. A right swing implies the clockwise rotation of theodolite and a left swing implies anticlockwise rotation. The process of bringing the telescope from the face left position to the face right position or vice-versa is called changing face. The face can be changed by reversing the theodolite (transit) and rating it by 180-degree(swing) operations. Temporary Adjustments of a Theodolite The activities required at every setting of the theodolite at a station before taking the observations is called temporary adjustments of a theodolite. It includes: Procedure for setting up the theodolite: - Place the tripod over the required station. - Spread the legs of tripod such that they make an angle of about 60-degree with horizontal. - Push the shoe of each tripod leg into the ground by applying some force. - Take the theodolite out from its box. Lift it from the base and screw it tightly on the tripod. Centring is done to place the theodolite exactly above the station. The Centering is done using a plumb Bob and a nail. The nail is fixed at the exact point the instrument is to be placed. The Plumb Bob is suspended from a hook, fixed below the instrument. Then the legs of the tripod should be adjusted to place the suspended plumb bob, just over the exact point. The levelling of theodolite is done to make the vertical axis of the theodolite truly verticle or to make horizontal plane truly horizontal. This can be done by placing the horizontal bubble tube parallel to any two of the foot screws and then rotating the foot screws in opposite direction to bring the bubble at the centre. After the bubble has been placed into the centre, it is then placed to the perpendicular of its initial position. Then the third foot screws are rotated at either direction to bring the bubble at the centre. These procedures should be repeated several times until the bubble is completely centred. The same procedure should be adopted in case of the vertical bubble tube. Focussing the Eye-Piece The eyepiece of theodolite is focused to make the crosshairs in diaphragm clear and distinct. It depends upon the eyesight of the surveyor. - Point the telescope of theodolite towards the sky or put a white paper in front of the objective lens. - Move the eyepiece in or out by rotating it gradually until the crosshairs appear clear. Focussing the Objective The objective of theodolite s focussed to bring the image of the object in the plane of crosshairs (diaphragm). It is done with help of focusing screw. It depends upon the distance of the object. Measurement of a Horizontal Angle by Theodolite Horizontal angles can be done by two methods: - Repetition Method - Reiteration method. Repetition method is used mostly in measuring the horizontal angles. - Centring: After the instrument is levelled properly, it is then centred. - After Centering is done, Vernier A is fixed at 0° and Vernier B is fixed at 180°, by loosening the upper clamp screw. By turning the upper tangent screw, Vernier A & B are accurately fixed into its readings. - The upper clamp screw is then tightened, and the lower clamp is loosened. The instrument is rotated to bisect the ranging rod at one point. The lower tangent screw is used for accurately dissecting the ranging rod. - The lower clamp screw is then tightened, and the upper clamp screw is loosened. By turning the telescope in a clockwise direction, about its horizontal axis, the ranging rod at other point is bisected. The reading at scale is to be noted. - These steps should be repeated thrice, the average value should be taken. Measurement of a Verticle Angle by Theodolite This is another important anti function of a Theodolite, and it is the only manual instrument using which vertical angles should be taken. The procedures of taking vertical measurements are as below: - Levelling and Centering of the instrument are done following the above-mentioned methods. - The Vernier A & Vernier B of the vertical scale is to fixed at 0° and 180° respectively. - The telescope is targeted towards the point from which vertical angle is to be taken. Tangent screws are used for accurate bisection of the ranging rod at that point. - Then the telescope is rotated in a vertical plane to bisect the point at some certain elevation. - After the bisection of the point, the telescope is to be fixed, and the reading is taken, which is the required angle of elevation. Measurement of a Deflection Angle by Theodolite While surveying, change in direction of the survey line may often occur, due to identification of some obstacles, such as building, factories, etc. The deflection angle is that angle which is formed between the extension of the previous survey line, with the new survey line. Deflection angles hold a great value in Surveying operation, as it determines the angle, the existing survey line is to be deflected. The procedure for determining the Deflection angle is given below: - The levelling and Centering of the instrument are to be done. - A point Is fixed on the extension line and another point is fixed on the new survey line. The instrument is placed at a position from where, both the points are visible. - The upper clamp is loosened, and the Vernier A & B are fixed at 0° and 180° respectively. Then the upper clamp is tightened. - By loosening the lower clamp screw the point at the extension line is bisected. The lower clamp is then fixed. - By loosening the lower clamp screw, the instrument is turned clockwise, and the point situated at the new survey line is bisected. Tangent screws are used for accurate bisection. - The reading is to be taken Measurement of Magnetic Bearing by Theodolite Theodolites are also used for measuring the magnetic bearings. The procedure is as follows: - Centring and Levelling of the instrument are to be done. - The Vernier A & B are fixed at 0° and 180°, respectively, by the above-mentioned process. - A trough compass or circular compass is to be fitted with the instrument, using which, the north direction is to be determined. After that, the instrument to set into the north direction by loosening the lower clamp screw. This is known as Orientation. - After that, the point is bisected using the upper clamp screw. The value obtained is the required magnetic Bearing of that point. Ranging a Line using a Theodolite Theodolites can also be used for ranging a line accurately. - Levelling & Centering of the instrument is to be done. - The telescope is directed towards the point which is to be ranged. After that, the observer directs the follower to place a ranging rod between the two points, by giving him proper commands. After the crosshairs perfectly bisect the ranging rod, the ranging rod is to be fixed at that point, thus finishing the ranging operation. Learn more about Civil Engineering:
Financial literacy is the ability to understand and use financial concepts to make informed decisions about money. It is an essential life skill that can help young people achieve their financial goals, such as buying a home, saving for retirement, or starting a business. There are many reasons why financial literacy is important for youth. First, it can help them avoid financial problems. Young people are often bombarded with financial messages, both good and bad. Without financial literacy, they may be more likely to make poor financial decisions, such as taking on too much debt or spending more money than they earn. Second, financial literacy can help young people achieve their financial goals. When young people understand how money works, they are better able to set financial goals and make a plan to achieve them. This can help them reach their goals sooner and with less stress. Third, financial literacy can help young people become financially independent. As young people enter adulthood, they will need to be able to manage their own finances. Financial literacy can help them develop the skills they need to be financially independent, such as budgeting, saving, and investing. There are many ways to teach financial literacy to youth. Parents, schools, and community organizations can all play a role in helping young people learn about money. Here are a few tips for teaching financial literacy to youth: Start early. The earlier young people learn about money, the better. Even young children can learn basic financial concepts, such as the difference between needs and wants. Make it fun. Financial literacy doesn’t have to be boring. There are many ways to make it fun and engaging for young people, such as playing games, using online resources, or reading books. Focus on real-world applications. Help young people understand how financial concepts apply to their own lives. This will help them see the relevance of financial literacy and make them more likely to remember what they learn. Be patient. It takes time to learn about money. Be patient with young people and don’t expect them to master all of the concepts overnight. Financial literacy is an essential life skill that can help young people achieve their financial goals. By teaching financial literacy to youth, we can help them build a strong financial foundation for the future. Here are some specific topics that can be covered in financial literacy education for youth: Budgeting: This is the foundation of financial literacy. Young people need to learn how to track their income and expenses, set financial goals, and create a budget to help them reach those goals. Saving: This is another important financial skill. Young people need to learn how to save money for short-term goals, such as buying a car or going on vacation, as well as long-term goals, such as retirement. Investing: This is a more advanced financial skill, but it can be helpful for young people to learn about the basics of investing, such as how to choose investments and how to manage risk. Credit: This is a topic that can be confusing for young people. They need to learn about how credit works, how to build good credit, and how to avoid debt. Fraud and scams: This is an important topic, especially in today’s digital age. Young people need to learn how to protect themselves from financial fraud and scams. There are many resources available to help teach financial literacy to youth. Here are a few of them: The National Endowment for Financial Education (NEFE) offers a variety of resources for teaching financial literacy to youth, including lesson plans, videos, and toolkits. The Jumpstart Coalition for Personal Financial Literacy also offers a variety of resources for teaching financial literacy to youth. The Federal Reserve Bank of New York offers a financial literacy curriculum for grades 6-12. The Khan Academy offers a free online financial literacy course. Financial literacy is an important life skill that can help young people achieve their financial goals. By teaching financial literacy to youth, we can help them build a strong financial foundation for the future. Synergy India Foundation (SIF) is an NGO in India headquartered in Hyderabad. Our organisation strives to change the lives of poor and underserved through community participation and promote a safer society by synergising different stakeholders to attain a larger impact on the community.
Scientific Notation and Rational Numbers Scientific Notation and Rational Numbers A rational number is a number which can be expressed exactly as a fraction a/b (where, a and b are two integers with denominator non zero) and represented by 'Q'. The addition and multiplication operations together form a field. Rational numbers are the smallest field with characteristic zero; it means every other field of characteristic zero contains a copy of 'Q'. Now the scientific notation is defined as a standard way of writing very large or very small numbers so that they are easier to compare and use in computations. The standard form of scientific notation is given below, N x 10a, where 'N' is a number between 1 and 10, but not 10 itself, and 'a' is an integer number. We move the decimal point of a number until the new form, Know More About Laws of Limit and then record the exponent (a) as the number of places the decimal point was moved. Whether we move the decimal to right or to left then the power of 10 is positive or negative depends on it. Moving the decimal to the right makes the exponent negative; moving it to the left gives you a positive exponent. For example, we write 622,000,000,000 in scientific notation: first step is move the decimal place to the left. For example, we write 622,000,000,000 in decimal. The decimal point is placed at the end of the number 622,000,000,000 and written as: N = 6.22 Now, determine how many times we moved the decimal. In this example, we moved the decimal 11 times and as the exponent is positive, in this we also move the decimal to left. Therefore, a = 11, and so we get, 1011 Lastly, put the number in the correct form of scientific notation that is, N x 10a, 622,000,000,000=6.22 x 1011. In this way, we write the scientific notation of any number. Now come to the rational numbers, the two different fractions may correspond to the same rational number; for example 1â „6 and 3â „18 are equal, that is, 1/6 = 3/18. Learn More Left and right hand limit Published on Mar 9, 2012 A rational number is a number which can be expressed exactly as a fraction a/b (where, a and b are two integers with denominator non zero) a...
Lagrange's theorem (group theory) Lagrange's theorem, in the mathematics of group theory, states that for any finite group G, the order (number of elements) of every subgroup H of G divides the order of G. The theorem is named after Joseph-Louis Lagrange. Proof of Lagrange's Theorem This can be shown using the concept of left cosets of H in G. The left cosets are the equivalence classes of a certain equivalence relation on G and therefore form a partition of G. Specifically, x and y in G are related if and only if there exists h in H such that x = yh. If we can show that all cosets of H have the same number of elements, then each coset of H has precisely \|H\| elements. We are then done since the order of H times the number of cosets is equal to the number of elements in G, thereby proving that the order of H divides the order of G. Now, if aH and bH are two left cosets of H, we can define a map f : aH → bH by setting f(x) = ba−1x. This map is bijective because its inverse is given by This proof also shows that the quotient of the orders \|G\| / \|H\| is equal to the index [G : H] (the number of left cosets of H in G). If we allow G and H to be infinite, and write this statement as Using the theorem A consequence of the theorem is that the order of any element a of a finite group (i.e. the smallest positive integer number k with ak = e, where e is the identity element of the group) divides the order of that group, since the order of a is equal to the order of the cyclic subgroup generated by a. If the group has n elements, it follows Existence of subgroups of given order Lagrange's theorem raises the converse question as to whether every divisor of the order of a group is the order of some subgroup. This does not hold in general: given a finite group G and a divisor d of \|G\|, there does not necessarily exist a subgroup of G with order d. The smallest example is the alternating group G = A4, which has 12 elements but no subgroup of order 6. A CLT group is a finite group with the property that for every divisor of the order of the group, there is a subgroup of that order. It is known that a CLT group must be solvable and that every supersolvable group is a CLT group: however there exist solvable groups that are not CLT (for example A4, the alternating group of degree 4) and CLT groups that are not supersolvable (for example S4, the symmetric group of degree 4). There are partial converses to Lagrange's theorem. For general groups, Cauchy's theorem guarantees the existence of an element, and hence of a cyclic subgroup, of order any prime dividing the group order; Sylow's theorem extends this to the existence of a subgroup of order equal to the maximal power of any prime dividing the group order. For solvable groups, Hall's theorems assert the existence of a subgroup of order equal to any unitary divisor of the group order (that is, a divisor coprime to its cofactor). Lagrange did not prove Lagrange's theorem in its general form. He stated, in his article Réflexions sur la résolution algébrique des équations, that if a polynomial in n variables has its variables permuted in all n ! ways, the number of different polynomials that are obtained is always a factor of n !. (For example if the variables x, y, and z are permuted in all 6 possible ways in the polynomial x + y - z then we get a total of 3 different polynomials: x + y − z, x + z - y, and y + z − x. Note that 3 is a factor of 6.) The number of such polynomials is the index in the symmetric group Sn of the subgroup H of permutations that preserve the polynomial. (For the example of x + y − z, the subgroup H in S3 contains the identity and the transposition (xy).) So the size of H divides n !. With the later development of abstract groups, this result of Lagrange on polynomials was recognized to extend to the general theorem about finite groups which now bears his name. - Lagrange, J. L. (1771) "Réflexions sur la résolution algébrique des équations" [Reflections on the algebraic solution of equations] (part II), Nouveaux Mémoires de l’Académie Royale des Sciences et Belles-Lettres de Berlin, pages 138-254; see especially pages 202-203. Available on-line (in French, among Lagrange's collected works) at: http://math-doc.ujf-grenoble.fr/cgi-bin/oeitem?id=OE_LAGRANGE__3_205_0 [Click on "Section seconde. De la résolution des équations du quatrième degré 254-304"]. - Bray, Henry G. (1968), A note on CLT groups, Pacific J. Math. 27 (2): 229–231, doi:10.2140/pjm.1968.27.229 - Gallian, Joseph (2006), Contemporary Abstract Algebra (6th ed.), Boston: Houghton Mifflin, ISBN 978-0-618-51471-7 - Dummit, David S.; Foote, Richard M. (2004), Abstract algebra (3rd ed.), New York: John Wiley & Sons, ISBN 978-0-471-43334-7, MR 2286236 - Roth, Richard R. (2001), A History of Lagrange's Theorem on Groups, Mathematics Magazine 74 (2): 99–108, doi:10.2307/2690624, JSTOR 2690624
Reform Act 1832 The Representation of the People Act 1832 was an Act of Parliament of the United Kingdom that introduced wide-ranging changes to the electoral system of England and Wales. According to its preamble, the Act was designed to "take effectual Measures for correcting divers Abuses that have long prevailed in the Choice of Members to serve in the Commons House of Parliament". Before the reform, most members nominally represented boroughs; the number of electors in a borough varied from a dozen or so up to 12,000. The selection of MPs was controlled by one powerful patron: for example Charles Howard, 11th Duke of Norfolk, controlled eleven boroughs. Criteria for qualification for the franchise varied among boroughs, from the requirement to own land, to living in a house with a hearth sufficient to boil a pot. There had been calls for reform long without success; the Act that succeeded was proposed by the Whigs, led by Prime Minister Charles Grey, 2nd Earl Grey. It met with significant opposition from the Pittite factions in Parliament, who had long governed the country. The bill was passed as a result of public pressure. The Act granted seats in the House of Commons to large cities that had sprung up during the Industrial Revolution, removed seats from the "rotten boroughs": those with small electorates and dominated by a wealthy patron; the Act increased the electorate from about 400,000 to 650,000, making about one in five adult males eligible to vote. The full title is An Act to amend the representation of the people in Wales, its formal short title and citation is "Representation of the People Act 1832". The Act applied only in Wales; the separate Scottish Reform Act 1832 was revolutionary, enlarging the electorate by a factor of 1300% from 5000 to 65,000. After the Acts of Union 1800 became law on 1 January 1801, the unreformed House of Commons was composed of 658 members, of whom 513 represented England and Wales. There were two types of constituencies. County members were supposed to represent landholders, while borough members were supposed to represent the mercantile and trading interests of the kingdom. Counties were historical national subdivisions established between the 16th centuries. They were not parliamentary constituencies; the members of Parliament chosen by the counties were known as Knights of the Shire. In Wales each county elected one member, while in England each county elected two members until 1826, when Yorkshire's representation was increased to four, following the disenfranchisement of the Cornish borough of Grampound. Parliamentary boroughs in England ranged in size from small hamlets to large cities because they had evolved haphazardly; the earliest boroughs were chosen in the Middle Ages by county sheriffs, a village might be deemed a borough. Many of these early boroughs were substantial settlements at the time of their original enfranchisement, but went into decline, by the early 19th century some only had a few electors, but still elected two MPs. In centuries the reigning monarch decided which settlements to enfranchise; the monarchs seem to have done so capriciously with little regard for the merits of the place they were enfranchising. Of the 70 English boroughs that Tudor monarchs enfranchised, 31 were disenfranchised. The parliamentarians of the 17th century compounded the inconsistencies by re-enfranchising 15 boroughs whose representation had lapsed for centuries, seven of which were disenfranchised by the Reform Act. After Newark was enfranchised in 1661, no additional boroughs were enfranchised, the unfair system remained unchanged until the Reform Act of 1832. Grampound's disenfranchisement in 1821 was the sole exception. Most English boroughs elected two MPs; the City of London and the joint borough of Weymouth and Melcombe Regis each elected four members. The Welsh boroughs each returned a single member. Statutes passed in 1430 and 1432, during the reign of Henry VI, standardised property qualifications for county voters. Under these Acts, all owners of freehold property or land worth at least forty shillings in a particular county were entitled to vote in that county; this requirement, known as the forty shilling freehold, was never adjusted for inflation. The franchise was restricted to males by custom rather than statute. The vast majority of people were not entitled to vote. Furthermore, the sizes of the individual county constituencies varied significantly; the smallest counties and Anglesey, had fewer than 1,000 voters each, while the largest county, had more than 20,000. Those who owned property in multiple constituencies could vote multiple times. In boroughs the franchise was far more varied. There were broadly six types of parliamenta William IV of the United Kingdom William IV was King of the United Kingdom of Great Britain and Ireland and King of Hanover from 26 June 1830 until his death in 1837. The third son of George III, William succeeded his elder brother George IV, becoming the last king and penultimate monarch of Britain's House of Hanover. William served in the Royal Navy in his youth, spending time in North America and the Caribbean, was nicknamed the "Sailor King". In 1789, he was created Duke of St Andrews. In 1827, he was appointed as Britain's first Lord High Admiral since 1709; as his two older brothers died without leaving legitimate issue, he inherited the throne when he was 64 years old. His reign saw several reforms: the poor law was updated, child labour restricted, slavery abolished in nearly all of the British Empire, the British electoral system refashioned by the Reform Act 1832. Although William did not engage in politics as much as his brother or his father, he was the last monarch to appoint a prime minister contrary to the will of Parliament. Through his brother Adolphus, the Viceroy of Hanover, he granted his German kingdom a short-lived liberal constitution. At the time of his death William had no surviving legitimate children, but he was survived by eight of the ten illegitimate children he had by the actress Dorothea Jordan, with whom he cohabited for twenty years. Late in life, he married and remained faithful to the young princess who would become Queen Adelaide. William was succeeded in the United Kingdom by his niece Victoria and in Hanover by his brother Ernest Augustus. William was born in the early hours of the morning on 21 August 1765 at Buckingham House, the third child and son of King George III and Queen Charlotte, he had two elder brothers and Frederick, was not expected to inherit the Crown. He was baptised in the Great Council Chamber of St James's Palace on 20 September 1765, his godparents were his paternal uncles, the Duke of Gloucester and Prince Henry, his paternal aunt, Princess Augusta hereditary duchess of Brunswick-Wolfenbüttel. He spent most of his early life in Richmond and at Kew Palace, where he was educated by private tutors. At the age of thirteen, he joined the Royal Navy as a midshipman, was present at the Battle of Cape St Vincent in 1780, his experiences in the navy seem to have been little different from those of other midshipmen, though in contrast to other sailors he was accompanied on board ships by a tutor. He did his share of the cooking and got arrested with his shipmates after a drunken brawl in Gibraltar, he served in New York during the American War of Independence, making him the only member of the British royal family to visit America up to and through the American Revolution. While William was in America, George Washington approved a plot to kidnap him, writing: "The spirit of enterprise so conspicuous in your plan for surprising in their quarters and bringing off the Prince William Henry and Admiral Digby merits applause. I am persuaded, that it is unnecessary to caution you against offering insult or indignity to the persons of the Prince or Admiral..." The plot did not come to fruition. In September 1781, William held court at the Manhattan home of Governor Robertson. In attendance were Mayor David Mathews, Admiral Digby, General Delancey, he became captain of HMS Pegasus the following year. In late 1786, he was stationed in the West Indies under Horatio Nelson, who wrote of William: "In his professional line, he is superior to two-thirds, I am sure, of the list; the two were great friends, dined together nightly. At Nelson's wedding, William insisted on giving the bride away, he was given command of the frigate HMS Andromeda in 1788, was promoted to rear-admiral in command of HMS Valiant the following year. William sought to be made a duke like his elder brothers, to receive a similar parliamentary grant, but his father was reluctant. To put pressure on him, William threatened to stand for the House of Commons for the constituency of Totnes in Devon. Appalled at the prospect of his son making his case to the voters, George III created him Duke of Clarence and St Andrews and Earl of Munster on 16 May 1789 saying: "I well know it is another vote added to the Opposition." William's political record was inconsistent and, like many politicians of the time, cannot be ascribed to a single party. He allied himself publicly with the Whigs as well as his elder brothers George, Prince of Wales, Frederick, Duke of York, who were known to be in conflict with the political positions of their father. William ceased his active service in the Royal Navy in 1790; when Britain declared war on France in 1793, he was anxious to serve his country and expected a command, but was not given a ship at first because he had broken his arm by falling down some stairs drunk, but perhaps because he gave a speech in the House of Lords opposing the war. The following year he spoke in favour of the war; the Admiralty did not reply to his request. He did not lose hope of being appointed to an active post. In 1798 he was made an admiral. Despite repeated petitions, he was never given a command throughout the Napoleonic Wars. In 1811, he was appointed to the honorary position of Admiral of the Fleet. Conservative Party (UK) The Conservative Party the Conservative and Unionist Party, is a centre-right political party in the United Kingdom. The governing party since 2010, it is the largest in the House of Commons, with 313 Members of Parliament, has 249 members of the House of Lords, 18 members of the European Parliament, 31 Members of the Scottish Parliament, 12 members of the Welsh Assembly, eight members of the London Assembly and 8,916 local councillors; the Conservative Party was founded in 1834 from the Tory Party—the Conservatives' colloquial name is "Tories"—and was one of two dominant political parties in the nineteenth century, along with the Liberal Party. Under Benjamin Disraeli it played a preeminent role in politics at the height of the British Empire. In 1912, the Liberal Unionist Party merged with the party to form the Conservative and Unionist Party. In the 1920s, the Labour Party surpassed the Liberals as the Conservatives' main rivals. Conservative Prime Ministers — notably Winston Churchill and Margaret Thatcher — led governments for 57 years of the twentieth century. Positioned on the centre-right of British politics, the Conservative Party is ideologically conservative. Different factions have dominated the party at different times, including One Nation Conservatives and liberal conservatives, while its views and policies have changed throughout its history; the party has adopted liberal economic policies—favouring free market economics, limiting state regulation, pursuing privatisation—although in the past has supported protectionism. The party is British unionist, opposing both Irish reunification and Welsh and Scottish independence, supported the maintenance of the British Empire; the party includes those with differing views on the European Union, with Eurosceptic and pro-European wings. In foreign policy, it is for a strong national defence; the Conservatives are a member of the International Democrat Union and the Alliance of Conservatives and Reformists in Europe and sit with the European Conservatives and Reformists parliamentary group. The Scottish, Northern Irish and Gibraltan branches of the party are semi-autonomous. Its support base consists of middle-class voters in rural areas of England, its domination of British politics throughout the twentieth century has led to it being referred to as one of the most successful political parties in the Western world. The Conservative Party was founded in the 1830s. However, some writers trace its origins to the reign of Charles II in the 1670s Exclusion Crisis. Other historians point to a faction, rooted in the 18th century Whig Party, that coalesced around William Pitt the Younger in the 1780s, they were known as "Independent Whigs", "Friends of Mr Pitt", or "Pittites" and never used terms such as "Tory" or "Conservative". Pitt died in 1806. From about 1812 on the name "Tory" was used for a new party that, according to historian Robert Blake, "are the ancestors of Conservatism". Blake adds that Pitt's successors after 1812 "were not in any sense standard-bearer's of true Toryism"; the term "Conservative" was suggested as a title for the party by a magazine article by J. Wilson Croker in the Quarterly Review in 1830. The name caught on and was adopted under the aegis of Sir Robert Peel around 1834. Peel is acknowledged as the founder of the Conservative Party, which he created with the announcement of the Tamworth Manifesto; the term "Conservative Party" rather than Tory was the dominant usage by 1845. The widening of the electoral franchise in the nineteenth century forced the Conservative Party to popularise its approach under Edward Smith-Stanley, 14th Earl of Derby and Benjamin Disraeli, who carried through their own expansion of the franchise with the Reform Act of 1867. In 1886, the party formed an alliance with Spencer Compton Cavendish, Lord Hartington and Joseph Chamberlain's new Liberal Unionist Party and, under the statesmen Robert Gascoyne-Cecil, Lord Salisbury and Arthur Balfour, held power for all but three of the following twenty years before suffering a heavy defeat in 1906 when it split over the issue of free trade. Young Winston Churchill denounced Chamberlain's attack on free trade, helped organize the opposition inside the Unionist/Conservative Party. Balfour, as party leader, followed Chamberlain's policy introduced protectionist legislation. The high tariff element called itself "Tariff Reformers" and in a major speech in Manchester on May 13, 1904, Churchill warned their takeover of the Unionist/Conservative party would permanently brand it as: A party of great vested interests, banded together in a formidable confederation. Two weeks Churchill crossed the floor and formally joined the Liberal Party. )He rejoined the Conservatives in 1925.) In December, Balfour lost control of his party, as the defections multiplied. He was replaced by Liberal Prime Minister Henry Campbell-Bannerman who called an election in January 1906, which produced a massive Liberal victory with a gain of 214 seats. Liberal Prime Minister H. H. Asquith enacted a great deal of reform legislation, but the Unionists worked hard at grassroots organizing. Two general elections were held in one in January and one in December; the two main parties were now dead equal in seats. The Unionists had more popular votes but the Liberals kept control with a coalition with the Irish Parliamentary Party. In 1912, the Liberal Unionis High Toryism is a term used in Britain, elsewhere, to refer to old traditionalist conservatism, in line with the Toryism originating in the 17th century. High Tories and their worldview are sometimes at odds with the modernising elements of the Conservative Party; the late eighteenth-century conservatism derived from the Whig Edmund Burke and William Pitt the Younger marks a watershed from the "higher" or legitimist Toryism, allied to Jacobitism. High Toryism has been described by Andrew Heywood as neo-feudalist in its preference for a traditional hierarchical society over utopian equality, as well for holding the traditional gentry as a higher cultural benchmark than the bourgeoisie and those who have attained their position through commerce or labour. Economically, High Tories tend to prefer a paternalistic Tory corporatism and protectionism over the neo-liberalism which took hold in the 1960s, although there are some that advocate more free market policies; the High Tory view in the eighteenth century preferred lowered taxation and deplored Whig support for a standing army, an expanding empire and navy, overseas commerce. The main reason was that these were paid for or subsidised by the new English Land Tax that had started in 1692. On religious issues, the High Tories rallied under the banner of "Church in Danger", preferred High church Anglicanism, many covertly supported Jacobitism; the long and productive Whig premierships of Sir Robert Walpole and William Pitt the Elder, the continuance of the Hanoverian dynasty caused opinions to change in line with what is now called "Whig history". The change was noticeable from the 1760s with the premierships of John Stuart, 3rd Earl of Bute and William Pitt the Younger; the Land Tax Perpetuation Act 1798 reduced the impact of that tax, though the landed gentry's privileges were reduced by the Reform Act 1832. In the reign of Queen Victoria High Tories now supported the empire and navy, were personified by the Prime Ministers Lord Derby and Lord Salisbury. High Tories prefer the values of the historical landed gentry and aristocracy, with their noblesse oblige and their self-imposed sense of duty and responsibility to all of society, including the lower classes. Whilst not against private enterprise, they do however reject the values of the modern commercial business class which they see as a pursuit of individualistic, unchecked greed that destroys a sense of community and holds no regard for religious or high cultural values. Their focus is on maintaining a traditional, rooted society and way of life, as much threatened by modern capitalism as by state socialism. A High Tory favours a strong community, in contrast to Whig and neoconservative individualism. One Nation Conservatism, as influenced by Disraeli and epitomised in leaders such as Balfour, favoured social cohesion, its adherents support social institutions that maintain harmony between different interest groups and different races or religions. Examples of English High Tory views from the twentieth century onward would be those of the novelists Evelyn Waugh and Anthony Burgess, poet T. S. Eliot, Members of Parliament such as Sir John Biggs-Davison, Lord Amery, Sir John Heydon Stokes, Alan Clark, Enoch Powell, Sir Peter Tapsell, the philosopher Sir Roger Scruton. The leading pressure-group of High Toryism was the Conservative Monday Club, described by Labour Prime Minister Harold Wilson as "The Conscience of the Tory Party". A "High Tory" bears some resemblance to traditionalist conservatives in the United States paleoconservatives. In Canada the term Red Tory used to mean something like a High Tory, although it is nowadays associated with the moderate wing of the Conservative Party of Canada, it is difficult and unreliable to make comparisons between High Toryism and other political dispositions internationally. "High Tory" has been more than just a political term, it is used to describe a culture and a way of life. A "High Tory" must have an appreciation of religion and high culture, they have been either a high church Anglican or traditional Roman Catholic, as well as a gentleman, an agrarian. Conservative Democratic Alliance Cornerstone Group London Swinton Circle Miguelist Moggmentum Powellism Red Tory Revolutionary Conservative Caucus Right Now! Sanfedismo Tories White movement GeneralHilton, Boyd, A Mad and Dangerous People?, UK: Clarendon Press, p. 314 Sir Robert Peel, 2nd Baronet, was a British statesman and Conservative Party politician who served twice as Prime Minister of the United Kingdom and twice as Home Secretary. He is regarded as the father of modern British policing, owing to his founding of the Metropolitian Police Service. Peel was one of the founders of the modern Conservative Party; the son of a wealthy textile-manufacturer and politician, Peel was the first prime minister from an industrial business background. He earned a double first in mathematics from Christ Church, Oxford, he entered the House of Commons in 1809. Peel entered the Cabinet as Home Secretary, where he reformed and liberalised the criminal law and created the modern police force, leading to a new type of officer known in tribute to him as "bobbies" and "peelers". After a brief period out of office he returned as Home Secretary under his political mentor the Duke of Wellington serving as Leader of the House of Commons. A supporter of continued legal discrimination against Catholics, Peel reversed himself and supported the repeal of the Test Act and the Roman Catholic Relief Act 1829, claiming that "though emancipation was a great danger, civil strife was a greater danger". After being in the Opposition 1830-34, he became Prime Minister in November 1834. Peel issued the Tamworth Manifesto, laying down the principles upon which the modern British Conservative Party is based, his first ministry was a minority government, dependent on Whig support and with Peel serving as his own Chancellor of the Exchequer. After only four months, his government collapsed and he served as Leader of the Opposition during Melbourne's second government. Peel became Prime Minister again after the 1841 general election, his second government ruled for five years. He cut tariffs to stimulate trade, he set up a modern banking system. His government's major legislation included the Mines and Collieries Act 1842, the Income Tax Act 1842, the Factories Act 1844 and the Railway Regulation Act 1844. Peel's government was weakened by anti-Catholic sentiment following the controversial increase in the Maynooth Grant of 1845. After the outbreak of the Great Irish Famine, his decision to join with Whigs and Radicals to repeal the Corn Laws led to his resignation as Prime Minister in 1846. Peel remained an influential MP and leader of the Peelite faction until his death in 1850. Peel started from a traditional Tory position in opposition to a measure reversed his stance and became the leader in supporting liberal legislation; this happened with the Test Act, Catholic Emancipation, the Reform Act, income tax and, most notably, the repeal of the Corn Laws. Historian A. J. P. Taylor says: "Peel was in the first rank of 19th century statesmen, he carried Catholic Emancipation. Peel was born at Chamber Hall, Lancashire, to the industrialist and parliamentarian Sir Robert Peel, 1st Baronet, his wife Ellen Yates, his father was one of the richest textile manufacturers of the early Industrial Revolution. Peel was educated at Bury Grammar School, at Hipperholme Grammar School at Harrow School and Christ Church, where he became the first person to take a double first in Classics and Mathematics, he was a law student at Lincoln's Inn in 1809 before entering Parliament. Peel saw part-time military service as a captain in the Manchester Regiment of Militia in 1808, as lieutenant in the Staffordshire Yeomanry Cavalry in 1820. Peel entered politics in 1809 at the age of 21, as MP for the Irish rotten borough of Cashel, Tipperary. With a scant 24 electors on the rolls, he was elected unopposed, his sponsor for the election was the Chief Secretary for Ireland, Sir Arthur Wellesley, the future Duke of Wellington, with whom Peel's political career would be entwined for the next 25 years. Peel made his maiden speech at the start of the 1810 session, when he was chosen by Prime Minister Spencer Perceval to second the reply to the king's speech, his speech was a sensation, famously described by the Speaker, Charles Abbot, as "the best first speech since that of William Pitt."As chief secretary in Dublin in 1813, he proposed the setting up of a specialist police force called "peelers". In 1814, the Royal Irish Constabulary was founded under Peel. For the next decade, he occupied a series of minor positions in the Tory governments: Undersecretary for War, Chief Secretary for Ireland, chairman of the Bullion Committee, he changed constituency twice, first picking up another constituency, Chippenham becoming MP for Oxford University in 1817. He became an MP for Tamworth from 1830 until his death. His home of Drayton Manor has since been demolished. Peel was considered one of the rising stars of the Tory party, first entering the cabinet in 1822 as Home Secretary; as Home Secretary, he introduced a number of important reforms of British criminal law. He reduced the number of crimes punishable by death, simplified it by repealing a large number of criminal statutes and consolidating their provisions into what are known as Peel's Acts, he reformed the gaol system. He resigned as home secretary after the Prime Minister Lord Liverpool became incapacitated and was replaced by George Canning, he helped in the repeal of the Test and Corporation Ac Whigs (British political party) The Whigs were a political faction and a political party in the parliaments of England, Great Britain and the United Kingdom. Between the 1680s and 1850s, they contested power with the Tories; the Whigs' origin lay in constitutional opposition to absolute monarchy. The Whigs played a central role in the Glorious Revolution of 1688 and were the standing enemies of the Stuart kings and pretenders, who were Roman Catholic; the Whigs took full control of the government in 1715 and remained dominant until King George III, coming to the throne in 1760, allowed Tories back in. The Whig Supremacy was enabled by the Hanoverian succession of George I in 1714 and the failed Jacobite rising of 1715 by Tory rebels; the Whigs purged the Tories from all major positions in government, the army, the Church of England, the legal profession and local offices. The Party's hold on power was so strong and durable, historians call the period from 1714 to 1783 the age of the Whig Oligarchy; the first great leader of the Whigs was Robert Walpole, who maintained control of the government through the period 1721–1742 and whose protégé Henry Pelham led from 1743 to 1754. Both parties began as loose groupings or tendencies, but became quite formal by 1784 with the ascension of Charles James Fox as the leader of a reconstituted Whig Party, arrayed against the governing party of the new Tories under William Pitt the Younger. Both parties were founded on rich politicians more than on popular votes, there were elections to the House of Commons, but a small number of men controlled most of the voters; the Whig Party evolved during the 18th century. The Whig tendency supported the great aristocratic families, the Protestant Hanoverian succession and toleration for nonconformist Protestants, while some Tories supported the exiled Stuart royal family's claim to the throne and all Tories supported the established Church of England and the gentry. On, the Whigs drew support from the emerging industrial interests and wealthy merchants, while the Tories drew support from the landed interests and the royal family. However, by the first half of the 19th century the Whig political programme came to encompass not only the supremacy of parliament over the monarch and support for free trade, but Catholic emancipation, the abolition of slavery and expansion of the franchise. The 19th century Whig support for Catholic emancipation was a complete reversal of the party's historic anti-Catholic position at its late 17th century origin. The term "Whig" was short for "whiggamor", a term meaning "cattle driver" used to describe western Scots who came to Leith for corn. In the reign of Charles I the term was used during the Wars of the Three Kingdoms to refer derisively to a radical faction of the Scottish Covenanters who called themselves the "Kirk Party", it was applied to Scottish Presbyterian rebels who were against the King's Episcopalian order in Scotland. The term "Whig" entered English political discourse during the Exclusion Bill crisis of 1678–1681 when there was controversy about whether or not King Charles II's brother, should be allowed to succeed to the throne on Charles's death. "Whig" was a term of abuse applied to those who wanted to exclude James on the grounds that he was a Roman Catholic. The fervent Tory Samuel Johnson joked that "the first Whig was the Devil". Under Lord Shaftesbury's leadership, the Whigs in the Parliament of England wished to exclude the Duke of York from the throne due to his Roman Catholicism, his favouring of monarchical absolutism, his connections to France. They believed the heir presumptive, if allowed to inherit the throne, would endanger the Protestant religion and property; the first Exclusion Bill was supported by a substantial majority on its second reading in May 1679. In response, King Charles prorogued Parliament and dissolved it, but the subsequent elections in August and September saw the Whigs' strength increase; this new parliament did not meet for thirteen months, because Charles wanted to give passions a chance to die down. When it met in October 1680, an Exclusion Bill was introduced and passed in the Commons without major resistance, but was rejected in the Lords. Charles dissolved Parliament in January 1681, but the Whigs did not suffer serious losses in the ensuing election; the next Parliament first met in March at Oxford, but Charles dissolved it after only a few days, when he made an appeal to the country against the Whigs and determined to rule without Parliament. In February, Charles had made a deal with the French King Louis XIV, who promised to support him against the Whigs. Without Parliament, the Whigs crumbled due to government repression following the discovery of the Rye House Plot; the Whig peers, the Earl of Melville, the Earl of Leven, Lord Shaftesbury, Charles II's illegitimate son the Duke of Monmouth, being implicated, fled to and regrouped in the United Provinces. Algernon Sidney, Sir Thomas Armstrong and William Russell, Lord Russell, were executed for treason; the Earl of Essex committed suicide in the Tower of London over his arrest for treason, whilst Lord Grey of Werke escaped from the Tower. After the Glorious Revolution of 1688, Queen Mary II and King William III governed with both Whigs and Tories, despite the fact that many of the Tories still supported the deposed Roman Catholic James II. William saw that the Tories were friendlier to royal authority than the Whigs and he employed both groups in his government, his early ministry was Tory, but the government came to be dominated by the so-called Junto Whig William Lamb, 2nd Viscount Melbourne William Lamb, 2nd Viscount Melbourne, was a British Whig statesman who served as Home Secretary and Prime Minister. He is best known for being prime minister in Queen Victoria's early years and her coaching in the ways of politics. Historians have concluded that Melbourne does not rank as a Prime Minister, for there were no great foreign wars or domestic issues to handle, he lacked major achievements, he enunciated no grand principles, his involvement in several political scandals as Victoria's private secretary. Melbourne was Prime Minister on two occasions; the first occasion ended when he was dismissed by King William IV in 1834, the last British prime minister to be dismissed by a monarch. Six months he was re-appointed and served for six years. Born in London in 1779 to an aristocratic Whig family, William Lamb was the son of the 1st Viscount Melbourne and Elizabeth, Viscountess Melbourne. However, his paternity was questioned, being attributed to George Wyndham, 3rd Earl of Egremont, to whom it was considered he bore a considerable resemblance, at whose residence, Lamb was a visitor until the Earl's death. Lamb stated that Egremont being his father was'all a lie'. He was educated at Eton, Trinity College and the University of Glasgow. Against the background of the Napoleonic Wars, Lamb served at home as captain and major in the Hertfordshire Volunteer Infantry, he succeeded his elder brother as heir to his father's title in 1805, married Lady Caroline Ponsonby, an Anglo-Irish aristocrat. The following year, he was elected to the British House of Commons as the Whig MP for Leominster. For the election in 1806 he moved to the seat of Haddington Burghs, for the 1807 election he stood for Portarlington. Lamb first came to general notice for reasons he would rather have avoided: his wife had a public affair with Lord Byron—she coined the famous characterisation of Byron as "mad and dangerous to know"; the resulting scandal was the talk of Britain in 1812. Lady Caroline published a Gothic novel, Glenarvon, in 1816; the two were reconciled, though they separated in 1825, her death in 1828 affected him considerably. In 1816, Lamb was returned for Peterborough by Whig grandee Lord Fitzwilliam. He told Lord Holland that he was committed to the Whig principles of the Glorious Revolution but not to "a heap of modern additions, interpolations and fictions", he therefore spoke against parliamentary reform, voted for the suspension of habeas corpus in 1817 when sedition was rife. Lamb's hallmark was finding the middle ground. Though a Whig, he accepted the post of Chief Secretary for Ireland in the moderate Tory governments of George Canning and Lord Goderich. Upon the death of his father in 1828 and his becoming the 2nd Viscount Melbourne, of Kilmore in the County of Cavan, he moved to the House of Lords, he had spent 25 years in the Commons as a backbencher, was not politically well known. In November 1830, the Whigs came to power under Lord Grey. Melbourne was Home Secretary. During the disturbances of 1830–32 he "acted both vigorously and sensitively, it was for this function that his reforming brethren thanked him heartily". In the aftermath of the Swing Riots of 1830–31, he countered the Tory magistrates' alarmism by refusing to resort to military force. He appointed a special commission to try 1,000 of those arrested, ensured that justice was adhered to: one-third were acquitted and most of the one-fifth sentenced to death were instead transported. There remains controversy regarding the hanging of Dic Penderyn, a protester in the Merthyr Rising, is now judged to have been innocent, he appears to have been executed on the word of Melbourne, who sought a victim in order to'set an example'. The disturbances over reform in 1831–32 were countered with the enforcement of the usual laws. After Lord Grey resigned as Prime Minister in July 1834, the King was forced to appoint another Whig to replace him, as the Tories were not strong enough to support a government. Melbourne was the man most to be both acceptable to the King and hold the Whig party together. Melbourne hesitated after receiving from Grey the letter from the King requesting him to visit him to discuss the formation of a government. Melbourne thought he would not enjoy the extra work that accompanied the office of Premier, but he did not want to let his friends and party down. According to Charles Greville, Melbourne said to his secretary, Tom Young: "I think it's a damned bore. I am in many minds as to what to do". Young replied: "Why, damn it all, such a position was never held by any Greek or Roman: and if it only lasts three months, it will be worth while to have been Prime Minister of England." "By God, that's true," Melbourne said, "I'll go!"Compromise was the key to many of Melbourne's actions. As an aristocrat, he had a vested interest in the status quo, he was opposed to the Reform Act 1832 proposed by the Whigs, arguing that Catholic emancipation had not ended in the tranquility expected of it, but reluctantly agreed that it
The Cold War was the persistent tension that existed between the United Sates and some of its Western supporters and the Soviet Union together with other Communists countries. This tension was witnessed between the time the Second World War was coming to an end and the Soviet Union dissolution in 1991. The Cold War featured military, economic, and geo- political rivalries between the West and the Communism international supporters which resulted to several wars. Even though there was a result of the political and economic rivalry between the Soviet Union and the United States, the two nations never fought each other directly. The conflict was majorly based on the competing economic and political systems between the two nations. The Communist system employed by the Soviet Union together with its allies and democratic Capitalism used by the United States together with its allies. This period featured intense economic and political rivalry as well as military and diplomatic posturing between these nations. These years were also host to dramatic military spending increases, hyperbolic rhetoric among leaders from both leaders, high tensions, and thousands and millions of casualties of proxy wars such as the Korean war, the bay of pigs invasion, Cuban missile crisis, the Vietnam war and the Soviet-Afghan war across Africa, Latin America and Asia. The parties involved considered their political and economic systems to be superior to their rivals and viewed almost every event taking places globally as to be part of the ongoing confrontation in an effort to determine which between Communism and Capitalism would emerge as the prevailing ideology across the globe. The Soviets tried hard to spread the political and economic Communism system to other countries, while the United States on its side was promoting its democracy vision and free enterprise. This competition resulted to several small-scale military conflicts as well as dozens of major wars that attracted armed forces from both nations. However, as the name of the war suggests, no direct military engagement was witnessed between the two nations. The origins of this was can be traced back when the Soviet Union and America were still allies in the Second World War. These two countries had a mutual suspicion history and both maintained their respective and different position on the way the postwar Europe was to be administered. Each nation was out to reconstruct Europe in their own desired image through Soviet-aligned Communists governments or Western-style democracies. In addition, the Soviets and its allies wanted to come up with a buffer zone that was pro-Russian which would protect them from possible attacks in future. These conflicting visions between the two nations clearly came out during the Meetings of British, Soviet diplomats and American diplomas in 1945 and the Yalta and Potsdam Conferences. In 1945, February, President Franklin Delano Roosevelt, Soviet Premier Joseph Stalin and Winston Churchill, who was the British Prime Minister at that time met in the Soviet Union at the Yalta Conference. The three leaders had met to discuss wartime strategy in coming up with the United Nations, and the Europe reconstruction. Yalta at that period was a popular resort situated in the Ukraine and served as the meeting place for the three leaders to discuss the future of Eastern Europe and Germany while at the same time, their respective army forces were closing in on Hitler. Stalin believed that his nation’s defense greatly depended on coming up with a Russian sphere that had influence in Poland as well as other Eastern European nations now that Eastern Europe and Poland had been acting as a corridor in the attacks on Russia on several occasions. Stalin committed himself to creating a coalition government consisting of democratic Polish government representatives exiled in London. Roosevelt and Churchill correctly suspected that his plans were to come up with an interim government that would be under the leadership of pro-Soviet Communists. The allies had valid reasons to be concerned about the way this process would be democratic considering the actions in Poland by the Red Army that had taken place the previous year. It was still fresh in the leader’s minds that Stalin had previously halted his offenses against Warsaw which was being occupied by the Nazi for a period of two months while the army forces from Germany were killing thousands of Polish fighters in opposition of the Communism system. Even though the allies from the West feared that Stalin was likely to turn Poland into a puppet state of the Communists, they were in no position to demand otherwise taking into consideration the fact that the complete occupation by the Red Army of Eastern Europe. In addition, the Western Allies knew that the army of Stalin would occupy Eastern Germany. With the hope of keeping the tentative alliance alive, Roosevelt and Churchill reached at the agreement that each nation would be responsible for reconstructing and occupying the section of Central Europe and Germany that corresponded with their army’s positions. By the time these three nations were meeting again in 1945 at the Potsdam Conference in Germany, there was a new President Harry Truman, Clement Attlee; who was the new British Prime Minister, and Joseph Stalin. The three leaders still discussed Europe reconstruction and resolved to divide Berlin and Germany into British, American, and Soviet and French sectors. Like their predecessors, Truman and Attlee recognized the futility associated with a military challenge to the position taken by Stalin in Eastern Europe. The leaders instead directed their efforts towards determining how Eastern Europe might be administered and divided by the Soviets in a manner that would foster both genuine independence and reconstruction. There hope was that the presence of the Soviet Army was temporary and that new national boundaries were to be established across Eastern Europe in a move to prevent conflicts in future. The leaders taking part in the Potsdam Conference tried to divide Europe into nations in accordance to the self-determination doctrine. Unfortunately, tremendous political and ethnic strife across Eastern Europe slowed down the process. The people dominating Eastern Europe chose to remove ethnic and national minorities. In addition, the areas also had to be divided among political factions’ hosts with each vying to control regions which had been destroyed completely by military occupation and war. It was not long before this ethnic, political and economic strife spread all over Southern Europe in areas such as Italy, Greece and also to Western nations like France. The postwar settlement was in such away that the victorious allies were still undecided about the fate of Germany. Apart from having Germany divided into four zones, the German army was disbanded, while the National Socialists Party was abolished permanently. The infrastructure of the nation was in shambles after the combined onslaught of the Soviet and Western armies, and this lead to the creation of a special council to administer humanitarian aid. Each of the four countries come up with interim governments in their own zones and prepared themselves for special elections that everyone hoped would result in democratic and stable governance so as to avoid that past instability that were witnessed after the World War I Following the extreme harsh conditions Russia had to endure, the leaders settled on reparations as a way of punishing Germany as they build up their military. This resulted to the conflict between the four nations in power as the West intended to rebuild a Germany that was democratic and able to stand on its own. This made the West to be against the demands by Soviet for reparations in their own Germany sectors. Within the Eastern Germany Soviet sector, the provisional government also tried to facilitate the reconstruction of the economy of German, but its military happened to seize most of the economic assets of the nation as war reparations and this ended up hindering the reconstruction efforts. While most of the Americans were for the idea of Russian leaders punishing their attackers, America as a nation had prospered in the war and its outmost priority was on the promotion of global recovery and avoiding the political and economic stability that has resulted to the establishment of totalitarian governments. The United States came up with a massive program aimed at aiding both war-torn Germany and Japan instead of seeking reparations in its German sector. This move was with the hope of promoting democratic governments that were stable. In both Europe and Asia, the perspective of the United States was mainly influenced by the humanitarian concerns but was still guided by the nation’s self-interest. Business leaders had hoped to get back to trading with these nations while on the other hand, the political leaders still feared economic instability might push Asia and Europe toward Communism. Following the two position taken by the leaders, the United States aid was directed towards making sure that German and Japanese reconstruction was in the American image of free enterprise and democracy. The aid from the United States towards these two former adversaries was rewarded through the close economic and political ties that developed as Japan and West Germany became among the strongest allies of the United States in their resulting conflict with the Soviet Union Forces from the United States occupied Japan between 1945 and 1952, as they oversaw the transition of the nation to a democratic government while at the same time seizing assets from the military, holding military tribunals passing judgment to the soldiers accused for war crimes, as well as overseeing reparations payments. Following the horrific nature of the Pacific war, the peacetime Japan transition to a prospering democracy from a militaristic dictatorship was remarkable. Just as what was witnessed in Germany, the Japan reconstruction mirrored the Cold War rivalry that was slowly developing between the United States and the Soviet Union. The Soviets had come up with their sphere influencing Manchuria as the United States occupied Japan. With the assist from the United Nation that had been newly created, Korea was partitioned temporarily into Soviet and United States sectors and was installed with governments that were rivals. MacArthur, who was the Commander of the United States forces during the Second World War in the southern Pacific, was also placed to oversee Japan Reconstruction. He managed to create a constitutional democracy in Japan similar to that of the United States. The early years of Japan reconstruction focused mostly on reducing the power of the military and having the factories produce consumer goods rather than creating munitions. Most of the Americans felt that the promotion of too much industrial growth was likely to make Japan reemerge as a major power. However, when Communism started to spread again throughout Southern Asia and China, United States leaders shifted their orientation and now invested resources to make sure that the economic growth in Japan was under a pro-American government. Most of the democratic reforms of MacArthur like female suffrage proved to be unpopular at first among the Japanese people, but by 1950, Japan and America had changed from being rivals to allies. The friendship was based on the United States economic trade, the two having mutual trade, and hostility against Communism growth in neighboring North Korea and China. The Eastern Europe reconstruction was a sharp contrast to what happened in West Germany and Japan. The Eastern Europe people had tremendously suffered and now wanted the German residents in that region to leave their nation. They believed that after all Hitler had justified his actions in that region considering the reuniting of all people who had originated from Germany. Following this reason, Eastern Europe authorities demanded that the Germans still living in Czechoslovakia, Hungary, and Poland to return to Germany. The Potsdam Conference also reasoned in the same manner while declaring its idea of creating nations on the basis of ethic lines. This meant that people of Polish origins were to occupy Poland, the Czechs in Czechoslovakia and the Hungarians in Hungary. This plan failed in recognizing the regions vast ethnic diversity and the impossibility of coming up with national boundaries which would manage to accomplish this goal without resulting to a million of refugees. To add on this, other millions of ethnic minorities would be expected also to move away of their homes if the plan was enforced universally. Each government partially tried to purge their respective nations of various minorities, mostly enforcing the exclusionary schemes provisions on the poor who were the most vulnerable. Eastern Europe was known of its scarce resources to transport or feed the millions of refugees who originated from the ethnic minority’s expulsion and it is estimated that more than 2 million people died in refugee camps following the disorder. To add on the atrocities coming from the expulsions, the Eastern Europe people suffered under the different totalitarian governments that had been created under the influence of the authorization regime of Stalin. On the other hand, the Western Allies were not in a position to dictate the Eastern Europe reconstruction under Soviet terms considering the Red Army position throughout the region. The Allies also wanted to come up with the area to the west of Berlin and have it to be in their own image. The official declarations at Potsdam and Yalta mandated constitutional government and democratic elections. The result was that many elections were indeed held and both the non-Communists and Communists leaders were elected democratically across Eastern Europe in the immediate years after the Cold War. “Causes of the Cold War in 1945”.??HistoryLearningSite.co.uk.??2014. Web Andrew Christopher and Mitrokhin Vasili. The Sword and the Shield: The Mitrokhin Archive and the Secret History of the KGB. New York: Basic Books, 2000 Cardona, Luis. Cold War KFA. New York: Routledge, 2007 Dobrynin, Anatoly. In Confidence: Moscow’s Ambassador to Six Cold War Presidents. Washington: University of Washington Press, 2001 Friedman, Norman. The Fifty-Year War: Conflict and Strategy in the Cold War. Naval Institute Press, 2007 Hanhim??ki, Jussi and Odd Arne Westad, Eds. The Cold War: A History in Documents and Eyewitness Accounts. London: Oxford University Press, 2003 Hopkins, Michael F. “Continuing Debate and New Approaches in Cold War History,” Historical Journal 50(2007): 913’934 Johnston, Gordon. “Revisiting the cultural Cold War,” Social History 35 (2010): 290’307 Sakwa, Richard . The Rise and fall of the Soviet Union, 1917’1991. New York: Routledge, 2009 👋 Hi! I’m your smart assistant Amy! Don’t know where to start? Type your requirements and I’ll connect you to an academic expert within 3 minutes.get help with your assignment
Get the Facts About Hyperlipidemia: 4 Crucial Questions, Answered More frequently referred to as high cholesterol, hyperlipidemia is the medical term used to describe unusually elevated blood levels of lipids (fat molecules). Though it's possible to inherit hyperlipidemia, most cases can be traced back to lifestyle choices and environmental factors. Hyperlipidemia itself causes no symptoms, but it does adversely impact your health—most notably by increasing your risk of developing coronary artery disease. Read on to learn how hyperlipidemia develops, 14 risk factors for hyperlipidemia, how doctors diagnose hyperlipidemia (as well as the different types), and natural treatments for hyperlipidemia. 1. How Does Hyperlipidemia Develop? To understand how high cholesterol develops, you must first have a basic grasp of some essential facts about cholesterol itself. Cholesterol, a type of fat made in the liver, makes vital contributions to the functioning of the human brain, development of membranes surrounding cells, production of hormones, and storage of vitamins. In order to travel through the bloodstream, cholesterol pairs with proteins to form lipoproteins. There are two forms of lipoproteins—high-density lipoproteins (HDL) and low-density lipoproteins (LDL)—each of which carry out different functions. - Low-density lipoproteins (LDL): Because LDL cholesterol has been linked to the development of cardiovascular disease, it's known as "bad cholesterol." LDL cholesterol moves cholesterol molecules through your arteries, and when levels get too high, fatty deposits begin to build up on the walls of your arteries. This leads to atherosclerosis, the hardening or narrowing of the arteries, which in turn raises your risk of heart disease. - High-density lipoproteins (HDL): HDL cholesterol, or "good cholesterol," can actually counterbalance the negative effects of LDL cholesterol. That's because HDL transports unused cholesterol molecules back to the liver, where they can be excreted. This prevents the development of high blood cholesterol levels and the associated adverse health outcomes, such as heart attack and coronary heart disease. If your doctor elects to perform a lipid profile, they will likely measure your triglyceride levels too. Your body stores any calories not required for immediate energy needs in the form of triglycerides. Regularly consuming more calories than necessary to fuel your body, particularly if you consume a diet high in carbohydrates, is likely to result in high triglyceride levels (technically speaking, hypertriglyceridemia). High cholesterol levels in the blood, as touched on in our discussion of LDL cholesterol, causes deposits of fat to accumulate in the blood vessels. As these deposits grow, they can restrict blood flow through the arteries. If a deposit spontaneously breaks loose, it can create a clot that triggers a heart attack or stroke. This makes it important to monitor and manage your cholesterol levels. For HDL cholesterol, this means keeping your levels at or above a certain threshold while for LDL cholesterol, it means making sure they do not rise too high. Optimal levels for total, HDL, and LDL cholesterol as well as triglycerides are impacted by whether or not you have heart disease, diabetes, or other conditions that put you at higher risk of developing high cholesterol. The guidelines for each category are as follows: - Overall cholesterol - Optimal: Under 200 milligrams per deciliter (mg/dL) - Concerning: 200-239 mg/dL - High: 240 mg/dL and higher - HDL cholesterol - Optimal: 60 mg/dL and higher - Adequate: 50-59 mg/dL for women and 40-59 mg/dL for men - Low: Under 50 mg/dL for women and 40 mg/dL for men - LDL cholesterol: - Optimal for those with heart disease or diabetes: Under 70 mg/dL - Optimal for those at risk of heart disease: Under 100 mg/dL - Adequate for those with no heart disease, concerning for those with heart disease: 100-129 mg/dL - Concerning for those with no heart disease, high for those with heart disease: 120-159 mg/dL - High for those with no heart disease, very high for those with heart disease: 160-189 mg/dL - Very high: 190 mg/dL and higher - Optimal: Under 150 mg/dL - Concerning: 150-199 mg/dL - High: 200-499 mg/dL - Very high: 500 mg/dL and higher 2. What Factors Raise Your Risk of Hyperlipidemia? As we covered in the last section, hyperlipidemia results from an unbalanced ratio of LDL cholesterol to HDL cholesterol. While certain types of hyperlipidemia have a genetic component (meaning it's important for you to know if you have a family history of hyperlipidemia), most result from lifestyle choices. According to a study published in 2017, both age and sex influence a person's likelihood of developing high levels of LDL cholesterol or triglycerides. The cross-sectional study, which enrolled 2,000 individuals, also found correlations between hyperlipidemia and lifestyle choices such as smoking, physical inactivity, and the consumption of fatty meats. Meanwhile, individuals who ate more fruits and vegetables were less likely to develop high cholesterol. Research points to other risk factors as well, such as having a large waist circumference and consuming excessive quantities of alcohol. There are also links between elevated cholesterol levels and several health conditions, such as: kidney disease, polycystic ovary syndrome (PCOS), and decreased thyroid activity. Certain medications affect cholesterol levels too, like steroids, progestin, retinoids, diuretics, and in some cases, beta blockers. Other factors shown to raise your risk of developing hyperlipidemia include: - Sedentary lifestyle: Failing to engage in physical activity on a routine basis can skew your cholesterol levels. It appears that exercise increases production of HDL cholesterol and increases the size of LDL cholesterol molecules, rendering them less harmful. - Use of tobacco products: Scientists have observed that smoking cigarettes injures blood vessel walls, which increases the odds that fat will build up on them. Smoking also appears to adversely impact HDL cholesterol levels. - Consumption of saturated and trans fats: Studies show that regularly eating foods that contain saturated fats (for instance, fatty meats) and trans fats (commonly included in processed foods like crackers, microwave popcorn, cookies, and more), leads to higher cholesterol levels. - Blood sugar levels: Analysis reveals a connection between high blood sugar and high levels of very-low-density lipoprotein (VLDL), a particularly unhealthy type of cholesterol, as well as lower levels of HDL cholesterol. - Body fat percentage: Researchers have also found a link between how much body fat a person has and their likelihood of having hyperlipidemia. - Overall physiology: As you age, your liver becomes less effective at removing LDL cholesterol, making you more likely to develop hyperlipidemia. 3. How Do Doctors Diagnose Hyperlipidemia? Hyperlipidemia itself causes no noticeable symptoms, which is why it's important for doctors to routinely check cholesterol levels, particularly for individuals who have a higher risk of developing the condition. They do this, as touched on previously, with a test called a lipid panel. This simple blood test allows doctors to measure your total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. In order to ensure accurate results, your physician may ask that you fast for between 8 and 12 hours leading up to the blood draw. However, recent research trends toward a consensus that fasting may not be necessary. According to a study published in JAMA Internal Medicine in 2019, fasting prior to a lipid profile produced negligible differences to total, LDL, and HDL cholesterol levels. Triglyceride levels were consistently slightly higher for participants who did not fast. The study enrolled close to 8,300 participants, all of whom had documented cardiovascular risk. Each participant had fasting and nonfasting lipid profiles done with a minimum of 1 month's time in between the tests. The fasting protocol used required them to abstain from eating or drinking anything except water for 8 hours before the test. By following participants for a median of 3 years, the authors were able to determine that whether or not individuals fasted prior to the lipid profile did little to impact doctors' ability to predict their risk of future health problems. This is exciting news not only because just about everyone dreads fasting, but more significantly, because fasting can cause issues for older individuals as well as those with diabetes. 5 Different Types of Hyperlipidemia Experts have categorized the different types of hyperlipidemia that have a genetic component based on the different fats involved in each as well as how each affects the body. - Type I, hyperlipidemia familial lipoprotein lipase deficiency: This inherited condition interferes with the mechanisms by which the body breaks down fats. It can cause abdominal pain, chronic pancreatic infections, and swelling of the liver and the spleen. It's one of the more severe types of hyperlipidemia, and tends to develop during childhood. - Type IIa, familial hypercholesterolemia, and type IIb, familial combined hyperlipidemia: Both type IIa and type IIb lead to elevated levels of LDL cholesterol. As the names of these types indicate, they do have a genetic component. They're also one of the few types that can cause visible symptoms—specifically, deposits of fat under the skin and near the eyes. Both types put individuals at increased risk of heart problems. - Type III, familial dysbetalipoproteinemia: This type involves increased total cholesterol and triglyceride levels in combination with decreased HDL levels. It, too, can cause visible symptoms—orange or yellow discoloration of the palms and the development of yellowish deposits of lipids in the skin over the elbows and knees. This type also raises your risk of cardiovascular disease. - Type IV, familial hypertriglyceridemia: This type is differentiated from the others by the fact that it involves elevated levels of triglycerides, not cholesterol. It has been linked to obesity, high blood glucose, and high insulin levels. Typically, this condition remains unnoticed until early adulthood. - Type V, mixed familial hyperlipoproteinemia: This type is quite similar to type I, but it also involves elevated levels of VLDL cholesterol. It's quite common among patients diagnosed with metabolic syndrome. Hyperlipidemia without a genetic component, also known as acquired hyperlipidemia, tends to mimic the forms described above. 4. Are There Natural Treatments for Hyperlipidemia? There are a variety of prescription drugs on the market that can decrease cholesterol and triglyceride levels, such as: - Cholesterol absorption inhibitors While these drugs do effectively treat hyperlipidemia, they can cause seriously unpleasant side effects. Statins, the first option most doctors will try, have been known to cause muscle aches, digestive upset and mental cloudiness. In rare cases, they can also cause liver damage and rhabdomyolysis, a serious condition that results in intense muscle pain, liver damage, and if left untreated, kidney failure and death. Depending on which type of hyperlipidemia you have, as well as the results of your lipid profile, it's possible that lifestyle changes and natural cholesterol treatments will allow you to avoid the use of potentially harmful prescription drugs. And even if a drug is necessary to manage your risk of more serious health problems like a heart attack or stroke, lifestyle shifts will still be an important part of your overall treatment plan. Here are five lifestyle changes and natural treatments that can bring your cholesterol and triglyceride levels into the healthy range. 1. Develop a Healthy Diet There's no one right way to eat, but there are certain science-backed elements you can use to build a healthy diet that works for you. When it comes to lowering bad cholesterol levels and raising good ones, the fats you eat make a big difference. Saturated fats found in red meat, bacon, and sausage and trans fats found in fried and processed foods are particularly problematic. Omega-3 fatty acids, on the other hand, have a wealth of heart-health benefits. Fatty cold-water fish like salmon and mackerel contain plenty of these good fats, as do walnuts and flaxseeds. It's also important to consume plenty of soluble fiber, which has been shown to lower LDL cholesterol levels. Load up on fiber-rich vegetables and fruits, legumes, and oats. 2. Engage in Physical Activity Researchers have found that your physical activity levels have a pronounced impact on your HDL cholesterol levels. The more you exercise, the better those levels will be. And the less you exercise, the lower they'll drop. It appears that for cholesterol-management purposes, you should shoot for 40 minutes of moderate to vigorous exercise on 3 or 4 days of the week. Aim for a minimum of 150 minutes of exercise total per week. If you have the time necessary to try swimming laps at the pool or joining a game of pick-up basketball, that's wonderful. But finding ways to incorporate exercise into your daily routine, like biking to work or picking up the pace when you take your dog for a walk, can also help you hit that physical activity threshold. 3. Stop Smoking As mentioned earlier, smoking causes HDL cholesterol levels to fall and triglyceride levels to rise. Furthermore, it independently increases your risk of developing heart disease. If you're a current smoker, no matter which type of high cholesterol you have, quitting will be an important part of your treatment plan. As you're almost certainly aware, it can be quite a challenge to quit. It may be helpful to talk to your doctor about strategies for doing so, like using a nicotine patch, or to seek support from others who have successfully kicked the habit. 4. Evaluate Your Weight There can be a connection between body weight (particularly fat mass) and cholesterol levels. Research has shown that by adopting dietary strategies designed to produce sustainable weight loss, individuals were able to raise their HDL cholesterol levels and lower their LDL cholesterol levels. Learn more about strategies for pursuing healthy weight loss here. 5. Incorporate Proven Supplements If you're committed to pursuing natural methods of lowering your cholesterol, you can find more in-depth advice about proven methods for doing so, as well as the rationale behind choosing a natural approach, in this article. For our purposes, it will suffice to say that supplements can play a very important role in naturally addressing hyperlipidemia. For instance, compelling research has revealed that taking an essential amino acid supplement can produce highly desirable results on cholesterol levels. Studies have shown that essential amino acids, which stimulate the synthesis of the proteins that transport lipids out of the liver as well as those that flush fatty acids into safe storage areas, can lower levels of total cholesterol, LDL cholesterol, VLDL cholesterol, and triglycerides in the liver as well as the bloodstream. These results have been seen with a dosage schedule of two 11-gram doses, twice a day. These all-natural, completely safe compounds bring benefits for your overall health and—it's important to note—they can be combined with statins without any ill effects. In fact, they actually make them more effective, per the findings of an Italian research team. If you're curious about amino acid supplementation, this primer is a great place to begin. And if you're ready to begin supplementing, we recommend Life, an essential amino acid formula clinically proven to help maintain healthy triglyceride and LDL cholesterol levels. Hyperlipidemia is the medical term for high blood levels of lipids. It can stem from genetic causes, but the majority of the time, it results from behavior choices and environmental factors such as an overly sedentary lifestyle, the use of tobacco products, or excessive alcohol consumption. As it causes no symptoms itself, it's vital that health care practitioners routinely screen for this silent condition, which has been linked to an increased risk of cardiovascular disease. There are a variety of prescription medications available that can be used to get cholesterol levels under control, but they can cause unpleasant side effects. And even if the benefits of using one of those drugs outweighs the risks, it's still important to make lifestyle changes such as developing a healthy diet that facilitates lower levels of LDL cholesterol and higher levels of HDL cholesterol as well increasing physical activity. It can also be quite valuable to incorporate supplements with proven benefits for bringing cholesterol levels into a healthy range, such as essential amino acids.
A helictite is a speleothem found in limestone caves that changes its axis from the vertical at one or more stages during its growth. They have a curving or angular form that looks as if they were grown in zero gravity and they are most likely the result of capillary forces acting on tiny water droplets, a force often strong enough at this scale to defy gravity. They are formed by biologically-mediated processes, rather than abiotic processes as scientists previoulsy thought, Helictites are, the most delicate of cave formations. They are usually made of calcite and aragonite. Forms of helictites have been described in several types, ribbon helictites, rods, hands, curly-fries and they can be easily crushed or broken by the slightest touch. Because of this, helictites are rarely seen within arms reach in tourist caves, timpanogos Cave National Monument in Utah has one of the largest collections of these formations in the world. The large numbers are in the Jenolan Caves in Australia, a remarkable suite of helictites is occurring in Asperge Cave in France. The growth of helictites is still quite enigmatic, to this day there has been no satisfactory explanation for how they are formed. Currently, formation by capillary forces is the most likely theory, the most likely theory explains helictites as a result of capillary forces. If the helictite has a thin central tube where the water flows like it does in straws. This theory was inspired by some hollow helictites, the majority of helictites are definitely not hollow. Despite this, droplets can be drawn to the tips of existing structures and this can lead to the wandering and curling structures seen in many helictites. Another theory names the wind in the cave as main reason for the strange look, drops hanging on a stalactite are blown to one side, so the dripstone grows in that direction. If the wind changes, the direction of growth changes too, however this theory is very problematic, because wind directions change very often. The wind in caves depends on air pressure changes outside, which in turn depend on the weather, wind caves are known to experience these windy conditions. The wind direction changes as often as the conditions outside change. A second problem with this theory is that caves with helictites have no natural entrance where wind could enter. A recent theory which is supported by observation is that a prokaryotic bacterial film provides nucleation site for mineralization process, a helictite starts its growth as a tiny stalactite A cave pearl is a small, usually spherical, speleothem found in limestone caves. Cave pearls are formed by a concretion of calcium salts that form concentric layers around a nucleus, exposure to moving water polishes the surface of cave pearls, making them glossy, if exposed to the air, cave pearls can degrade and appear rough. A cave pearl is composed primarily of calcite, Cave pearls are generally not considered to be a type of oolite. Other minerals found in quantities in cave pearls include quartz, iron, aluminum. Cave pearls form when water dripping into a cave loses carbon dioxide, a cave pearl forms when the water is moving too vigorously to form a stalagmite. A nucleus of matter becomes coated with calcite, and the current provides a rotation to the nucleus in such a way that it is coated evenly. In this manner, concentric layers build up time, in much the same way that a biological pearl forms within a mollusc. There may be microbial action involved in the formation of cave pearls, the existence of an actual pool may not be necessary for cave pearls to form, as long as the deposit is kept wet and agitated by water dripping or trickling through. If the cave pearl sinks to the bottom of a pool, or is otherwise in contact with moving water. Although the motion of the water often keeps cave pearls from adhering, a cave pearl forms around a nucleus of matter. The nucleus of a pearl is typically very small, such as a grain of sand. Some nuclei are made of matter, whereas others are made of calcified clay or limestone. Cave pearls are usually spherical, but can have other shapes, the reason cave pearls tend to be round is not their rotation, but rather that their growth is steady and uniform. Because a spherical shape allows the greatest amount of deposition for the smallest surface area, sometimes several cave pearls stick together to form a shape that resembles a bunch of grapes. In addition to the spherical shape, cave pearls can be cylindrical, cubical, discoid. Most cave pearls are smaller than 1 cm wide, large cave pearls grow as big as 20 cm in diameter. The worlds largest cave, Son Doong Cave in Vietnam, has cave pearls the size of baseballs, Cave pearls are relatively common in caves, but are typically present in low abundance. The mechanism for the formation of this vast quantity of pearls has not been determined, the Rookery, in Carlsbad Caverns, New Mexico, has so many cave pearls that they were at one time handed out to visitors as souvenirs Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is widely mined and is used as a fertilizer, and as the constituent in many forms of plaster, blackboard chalk. Mohs scale of hardness, based on scratch Hardness comparison. It forms as a mineral and as a hydration product of anhydrite. The word gypsum is derived from the Greek word γύψος, because the quarries of the Montmartre district of Paris have long furnished burnt gypsum used for various purposes, this dehydrated gypsum became known as plaster of Paris. Upon addition of water, after a few tens of minutes plaster of Paris becomes regular gypsum again, causing the material to harden or set in ways that are useful for casting, Gypsum was known in Old English as spærstān, spear stone, referring to its crystalline projections. Gypsum may act as a source of sulfur for plant growth, which was discovered by J. M. Mayer, american farmers were so anxious to acquire it that a lively smuggling trade with Nova Scotia evolved, resulting in the so-called Plaster War of 1820. In the 19th century, it was known as lime sulfate or sulfate of lime. Gypsum is moderately water-soluble and, in contrast to most other salts, it exhibits retrograde solubility, when gypsum is heated in air it loses water and converts first to calcium sulfate hemihydrate, and, if heated further, to anhydrous calcium sulfate. As for anhydrite, its solubility in saline solutions and in brines is dependent on NaCl concentration. Gypsum crystals are found to contain water and hydrogen bonding. Gypsum occurs in nature as flattened and often twinned crystals, and transparent, selenite contains no significant selenium, both substances were named for the ancient Greek word for the Moon. Selenite may occur in a silky, fibrous form, in case it is commonly called satin spar. Finally, it may be granular or quite compact, in hand-sized samples, it can be anywhere from transparent to opaque. A very fine-grained white or lightly tinted variety of gypsum, called alabaster, is prized for ornamental work of various sorts, in arid areas, gypsum can occur in a flower-like form, typically opaque, with embedded sand grains called desert rose. It forms some of the largest crystals found in nature, up to 12 m long, Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks. Deposits are known to occur in strata from as far back as the Archaean eon, Gypsum is deposited from lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins. Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near-surface exposures and it is often associated with the minerals halite and sulfur The term public domain has two senses of meaning. Anything published is out in the domain in the sense that it is available to the public. Once published and information in books is in the public domain, in the sense of intellectual property, works in the public domain are those whose exclusive intellectual property rights have expired, have been forfeited, or are inapplicable. Examples for works not covered by copyright which are therefore in the domain, are the formulae of Newtonian physics, cooking recipes. Examples for works actively dedicated into public domain by their authors are reference implementations of algorithms, NIHs ImageJ. The term is not normally applied to situations where the creator of a work retains residual rights, as rights are country-based and vary, a work may be subject to rights in one country and be in the public domain in another. Some rights depend on registrations on a basis, and the absence of registration in a particular country, if required. Although the term public domain did not come into use until the mid-18th century, the Romans had a large proprietary rights system where they defined many things that cannot be privately owned as res nullius, res communes, res publicae and res universitatis. The term res nullius was defined as not yet appropriated. The term res communes was defined as things that could be enjoyed by mankind, such as air, sunlight. The term res publicae referred to things that were shared by all citizens, when the first early copyright law was first established in Britain with the Statute of Anne in 1710, public domain did not appear. However, similar concepts were developed by British and French jurists in the eighteenth century, instead of public domain they used terms such as publici juris or propriété publique to describe works that were not covered by copyright law. The phrase fall in the domain can be traced to mid-nineteenth century France to describe the end of copyright term. In this historical context Paul Torremans describes copyright as a coral reef of private right jutting up from the ocean of the public domain. Because copyright law is different from country to country, Pamela Samuelson has described the public domain as being different sizes at different times in different countries. According to James Boyle this definition underlines common usage of the public domain and equates the public domain to public property. However, the usage of the public domain can be more granular. Such a definition regards work in copyright as private property subject to fair use rights, the materials that compose our cultural heritage must be free for all living to use no less than matter necessary for biological survival Colossal Cave Adventure Colossal Cave Adventure is a text adventure game, developed originally in 1976, by Will Crowther for the PDP-10 mainframe. The game was expanded upon in 1977, with help from Don Woods, in the game, the player controls a character through simple text commands to explore a cave rumored to be filled with wealth. Players earn predetermined points for acquiring treasure and escaping the cave alive, the concept bore out from Crowthers background as a caving enthusiast, with the games cave structured loosely around the Mammoth Cave system in Kentucky. Colossal Cave Adventure is the first known work of fiction and. Colossal Cave Adventure contributed towards the playing and roguelike genres. Adventure has the players explore a mysterious cave that is rumored to be filled with treasure. YOU ARE STANDING AT THE END OF A ROAD BEFORE A SMALL BRICK BUILDING, a SMALL STREAM FLOWS OUT OF THE BUILDING AND DOWN A GULLY. Go south YOU ARE IN A VALLEY IN THE FOREST BESIDE A STREAM TUMBLING ALONG A ROCKY BED, programs replies are typically in a humorous, conversational tone, much as a dungeon master would use in leading players in a tabletop role-playing game. A notable example is when the player dies after falling into a pit, go west YOU FELL INTO A PIT AND BROKE EVERY BONE IN YOUR BODY. YOU DONT EXPECT ME TO DO A DECENT REINCARNATION WITHOUT ANY ORANGE SMOKE, DO YOU. yes OKAY, IF YOURE SO SMART, certain actions may cause the death of the character, requiring the player to start again. The game has a point system, whereby completing certain goals earns a number of predetermined points, the ultimate goal is to earn the maximum amount of points, which partially correlates to finding all the treasures in the game and safely leaving the cave. Will Crowther was a programmer at Bolt, Beranek & Newman and his wife Pat were experienced cavers, having previously helped to create vector map surveys of the Mammoth Cave in Kentucky in the early 1970s for the Cave Research Foundation. In addition, Crowther enjoyed playing the tabletop role-playing game Dungeons & Dragons with a group which included Eric S. Roberts and Dave Lebling. Developed over 1975 and 1976, Crowthers original game consisted of about 700 lines of FORTRAN code, with about another 700 lines of data, the data included text for 78 map locations,193 vocabulary words, travel tables, and miscellaneous messages. On the PDP-10, the loads and executes with all its game data in memory. It required about 60k words of memory, which was a significant amount for PDP-10/KA systems running with only 128k words. Crowthers original version did not include any scorekeeping, during that time, others had found the game and it was distributed widely across the network, which had surprised Crowther on his return. Though titled in-game as Colossal Cave Adventure, its executable file was simply named ADVENT, one of those that had discovered the game was Don Woods, a graduate student at Stanford University in 1976 Don Woods (programmer) Don Woods is an American perennial hacker and computer programmer. He is probably best known for his role in the development of the Colossal Cave Adventure game, Woods teamed with James M. Lyon while both were attending Princeton in 1972 to produce the unprecedented, excursive INTERCAL programming language. Later, he worked at the Stanford AI lab, where among other things he became the SAIL contact for, and a contributor to, the Jargon File. He co-authored The Hackers Dictionary with Mark Crispin, Raphael Finkel, after contacting the original author by the means of sending an e-mail to crowther@sitename, where sitename was every host listed on ARPANET, he heard back from William Crowther shortly afterward. Given the go-ahead, Woods proceeded to add enhancements to the Adventure game and it became very popular, especially with users of the PDP-10. Woods stocked the Kentucky cave that Crowther had written with new items, creatures. Crowthers game, which featured few supernatural elements, was transformed into a loose fantasy world featuring elements from role playing games. Woods can thus, in a sense, be considered one of the progenitors of the genre of computer adventure games. By 1977 tapes of the game were common on the Digital user group DECUS, Don Woods web page Interview with Woods regarding Adventure Computerworld Interview with Don Woods on INTERCAL Kentucky, officially the Commonwealth of Kentucky, is a state located in the east south-central region of the United States. Kentucky is one of four U. S. states constituted as a commonwealth, originally a part of Virginia, in 1792 Kentucky became the 15th state to join the Union. Kentucky is the 37th most extensive and the 26th most populous of the 50 United States, Kentucky is known as the Bluegrass State, a nickname based on the bluegrass found in many of its pastures due to the fertile soil. One of the regions in Kentucky is the Bluegrass Region in central Kentucky. In 1776, the counties of Virginia beyond the Appalachian Mountains became known as Kentucky County, the precise etymology of the name is uncertain, but likely based on an Iroquoian name meaning the meadow or the prairie. Kentucky is situated in the Upland South, a significant portion of eastern Kentucky is part of Appalachia. Kentucky borders seven states, from the Midwest and the Southeast, West Virginia lies to the east, Virginia to the southeast, Tennessee to the south, Missouri to the west and Indiana to the northwest, and Ohio to the north and northeast. Only Missouri and Tennessee, both of which border eight states, touch more, Kentuckys northern border is formed by the Ohio River and its western border by the Mississippi River. The official state borders are based on the courses of the rivers as they existed when Kentucky became a state in 1792, for instance, northbound travelers on U. S.41 from Henderson, after crossing the Ohio River, will be in Kentucky for about two miles. Ellis Park, a racetrack, is located in this small piece of Kentucky. Waterworks Road is part of the land border between Indiana and Kentucky. Kentucky has a part known as Kentucky Bend, at the far west corner of the state. It exists as an exclave surrounded completely by Missouri and Tennessee, Road access to this small part of Kentucky on the Mississippi River requires a trip through Tennessee. The epicenter of the powerful 1811–12 New Madrid earthquakes was near this area, much of the outer Bluegrass is in the Eden Shale Hills area, made up of short and very narrow hills. The Jackson Purchase and western Pennyrile are home to several bald cypress/tupelo swamps, located within the southeastern interior portion of North America, Kentucky has a climate that can best be described as a humid subtropical climate. Temperatures in Kentucky usually range from daytime summer highs of 87 °F to the low of 23 °F. The average precipitation is 46 inches a year, Kentucky experiences four distinct seasons, with substantial variations in the severity of summer and winter. The highest recorded temperature was 114 °F at Greensburg on July 28,1930 while the lowest recorded temperature was −37 °F at Shelbyville on January 19,1994, due to its location, Kentucky has a moderate humid subtropical climate, with abundant rainfall Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean. The U. S. territories are scattered about the Pacific Ocean, the geography and wildlife of the country are extremely diverse. At 3.8 million square miles and with over 324 million people, the United States is the worlds third- or fourth-largest country by area, third-largest by land area. It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15,000 years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast. Numerous disputes between Great Britain and the following the Seven Years War led to the American Revolution. On July 4,1776, during the course of the American Revolutionary War, the war ended in 1783 with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power. The current constitution was adopted in 1788, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties. During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean. The Spanish–American War and World War I confirmed the status as a global military power. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the sole superpower. The U. S. is a member of the United Nations, World Bank, International Monetary Fund, Organization of American States. The United States is a developed country, with the worlds largest economy by nominal GDP. It ranks highly in several measures of performance, including average wage, human development, per capita GDP. While the U. S. economy is considered post-industrial, characterized by the dominance of services and knowledge economy, the United States is a prominent political and cultural force internationally, and a leader in scientific research and technological innovations. In 1507, the German cartographer Martin Waldseemüller produced a map on which he named the lands of the Western Hemisphere America after the Italian explorer and cartographer Amerigo Vespucci Fossils are the preserved remains or traces of animals and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record. The study of fossils across geological time, how they were formed, such a preserved specimen is called a fossil if it is older than some minimum age, most often the arbitrary date of 10,000 years. The observation that fossils were associated with certain rock strata led early geologists to recognize a geological timescale in the 19th century. The development of dating techniques in the early 20th century allowed geologists to determine the numerical or absolute age of the various strata. Like extant organisms, fossils vary in size from microscopic, even single bacterial cells one micrometer in diameter, to gigantic, such as dinosaurs, Fossils may consist of the marks left behind by the organism while it was alive, such as animal tracks or feces. These types of fossil are called trace fossils, as opposed to body fossils, past life leaves some markers that cannot be seen but can be detected in the form of biochemical signals, these are known as chemofossils or biosignatures. The process of fossilization varies according to type and external conditions. Permineralization is a process of fossilization that occurs when an organism is buried, the empty spaces within an organism become filled with mineral-rich groundwater. Minerals precipitate from the groundwater, occupying the empty spaces and this process can occur in very small spaces, such as within the cell wall of a plant cell. Small scale permineralization can produce very detailed fossils, for permineralization to occur, the organism must become covered by sediment soon after death or soon after the initial decay process. The degree to which the remains are decayed when covered determines the details of the fossil, some fossils consist only of skeletal remains or teeth, other fossils contain traces of skin, feathers or even soft tissues. This is a form of diagenesis, in some cases the original remains of the organism completely dissolve or are otherwise destroyed. The remaining organism-shaped hole in the rock is called an external mold, if this hole is filled with other minerals, it is a cast. An endocast or internal mold is formed when sediments or minerals fill the cavity of an organism. This is a form of cast and mold formation. If the chemistry is right, the organism can act as a nucleus for the precipitation of minerals such as siderite, if this happens rapidly before significant decay to the organic tissue, very fine three-dimensional morphological detail can be preserved. Nodules from the Carboniferous Mazon Creek fossil beds of Illinois, USA, are among the best documented examples of such mineralization, replacement occurs when the shell, bone or other tissue is replaced with another mineral Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate, about 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, most cave systems are through limestone bedrock. The first geologist to distinguish limestone from dolomite was Belsazar Hacquet in 1778, like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids and these organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragment, some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i. e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters and this produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance, the primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters. Limestones may form in lacustrine and evaporite depositional environments, calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits a characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors, especially with weathered surfaces, Limestone may be crystalline, granular, or massive, depending on the method of formation. Crystals of calcite, dolomite or barite may line small cavities in the rock, when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams, particularly there are waterfalls. Calcium carbonate is deposited where evaporation of the leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls, coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the building process, limestone recrystallizes into marble Mammoth Cave National Park Mammoth Cave National Park is a U. S. national park in central Kentucky, encompassing portions of Mammoth Cave, the longest cave system known in the world. Since the 1972 unification of Mammoth Cave with the system under Flint Ridge to the north. The park was established as a park on July 1,1941. It became a World Heritage Site on October 27,1981, the parks 52,830 acres are located primarily in Edmonson County, with small areas extending eastward into Hart County and Barren County. It is centered on the Green River, with a tributary, with 405 miles of surveyed passageways Mammoth Cave is by far the worlds longest known cave system, being over twice as long as the second-longest cave system, Mexicos Sac Actun underwater cave. Mammoth Cave developed in thick Mississippian-aged limestone strata capped by a layer of sandstone and it is known to include more than 390 miles of passageway, new discoveries and connections add several miles to this figure each year. Mammoth Cave National Park was established to preserve the cave system, the epikarstic zone concentrates local flows of runoff into high-elevation springs which emerge at the edges of ridges. It is in underlying massive limestone layers that the human-explorable caves of the region have naturally developed. The limestone layers of the column beneath the Big Clifty, in increasing order of depth below the ridgetops, are the Girkin Formation. Genevieve Limestone, and the St. Louis Limestone, for example, the large Main Cave passage seen on the Historic Tour is located at the bottom of the Girkin and the top of the Ste. Each of the layers of limestone is divided further into named geological units and subunits. One area of research involves correlating the stratigraphy with the cave survey produced by explorers. This makes it possible to produce approximate three-dimensional maps of the contours of the layer boundaries without the necessity for test wells. The upper sandstone caprock is relatively hard for water to penetrate, the sandstone caprock layer has been dissolved and eroded at many locations within the park, such as the Frozen Niagara room. At one valley bottom in the region of the park. Known as Cedar Sink, the features a small river entering one side. Mammoth Cave is home to the endangered Kentucky cave shrimp, a sightless albino shrimp, the National Park Service offers several cave tours to visitors. Some notable features of the cave, such as Grand Avenue, Frozen Niagara, two tours, lit only by visitor-carried paraffin lamps, are popular alternatives to the electric-lit routes
A proportion is two equal fractions, or two equal ratios. Since the fractions are equal to each other, the variable must have a value that would make the two fractions equivalent. If one part of the fraction has a variable expression, use cross-multiplication to solve this problem -- multiply the numerator of the first fraction by the denominator of the second and the denominator of the first by the numerator of the second fraction. Remember to distribute properly. Solve for the variable. Check your answer by substituting in the value for the variable into the original proportion. I know this problem is a proportion because it's two equal fractions. But it's a little bit harder than what I've seen before in proportions before because now I have not just plain old m up there, I have m plus 3 in the numerator. It's like a whole expression. So in order to solve this problem, I'm going to use cross multiplying and the reason I picked cross multiplying is because it's not obvious to me what I'm multiplying 5 by to get 4, like it's not clear to me how I'm getting from one fraction to the other. And I could also use solving techniques where I multiply both sides by 5, that would work also. I want to show you guys how cross multiplying works though because my guess is that it might be your favorite method, it is for most students. Cross multiplying is where the products of the diagonals are equal to each other. So the product of 4 and m plus 3 is going to be equal to the product of 5 and 12. Just be super careful that you remember to distribute. So often I see students write 4m plus 3 right here. They forget to distribute. That's incorrect, 4 gets multiplied by the m and also by the 3 so make sure you guys are using the distributive property correctly. Once I have this set up let's simplify the left hand side, 4m plus 12, that was distributing, equals 60, subtract 12 from both sides, so now I have 4m equals 48. The last step is to divide both sides by 4, m is going to be 48 divided by 4 which is 12. This is the cross multiplying method. If you guys wanted to, you might have used solving or even maybe multiplying by whatever number you multiply by to get from 5 to 4 which is 4/5. I also want to show you before we move on how you could check your work in this situation because you did a lot of Math and you might have made a little mistake. The way you would check your work is by taking this m value that you got for 12, substitute it back in there and make sure you have two equal fractions. Is it true that 12 pus 3, let's see that's 15. Is it true that 15 over 5 is equal 12/4? Yeah because those are both equal to 3 if I reduce them. By the way, before you started this problem you might have already seen that 12/4 reduces to 3 so you might not have solved this problem using proportion techniques at all, you might have just simplified that to 3, multiplied both sides by 5 and gone about your business like that. But if you use this method you still get the right answer. You can check it using substitution and I think you guys are going to get some awesome proportion problems that you can do. Experience the 'A-Ha!' moment with the best teachers whom we hand-picked for you! M.A. in Secondary Mathematics, Stanford University B.S., Stanford University Alissa has a quirky sense of humor and a relatable personality that make it easy for students to pay attention and understand the material. She has all the math tips and tricks students are looking for. “Your tutorials are good and you have a personality as well. I hope you have more advanced college level stuff, because I like the way you teach.” “Thanks alot for such great lectures... I never found learning this easier ever before... keep up the great work.... :)” “You seem so kind, it's awesome. Easier to learn from people who seem to be rooting for ya!' thanks”
Absolute Magnitude is the actual brightness of a star. If you take two stars and look at them from the exact same distance, the brighter one will have a higher absolute magnitude. Stars that are larger or hotter will have a higher absolute magnitude. Accretion is the process by which objects pull in matter from the interstellar medium or from nearby stars. Protostars accrete matter as they are forming before they achieve hydrogen fusion. White dwarfs and and neutron stars can also accrete matter on their surface by pulling it away from a companion star. When this matter builds up, it will ignite a fusion reaction called a Nova. The blast from the nova will blow the accreted matter back into space and the process can begin again. Black holes will also accrete matter. When gravity pulls matter toward an object, it tends to spiral in. This spiraling matter forms into a disc, rotating around the central object. When the accretion disc forms around a young star, the matter will sometimes form into planets, like in our solar system. The gravitational forces acting on an accretion disc causes a lot of friction as particles bump into one another. This heats up the disc and causes it to glow. Apparent Magnitude is the brightness of a star as observed from earth. This means that stars that are far away often appear dim compared to nearer stars, even though they may be brighter. A black hole is a remnant of a supermassive star's core. A black hole is so small and dense that even light can't escape from it. The intense gravitational field of the black hole simply bends the light back inside before it goes anywhere. Brown Dwarfs are protostars that never got hot enough to ignite hydrogen fusion. They glow very dimly, making them very hard to detect. Deuterium is a special kind of hydrogen atom that has both a proton and a neutron. Although deuterium is breifly created during one of the steps of normal hydrogen fusion, finding deuterium floating about is very rare. When a star achieves Equillibrium, its internal forces pushing out are equal to the force of gravity pushing in. This only lasts as long as the star has fuel to burn in its core to maintain its internal forces. When the star runs out of fuel, the outward forces begin to weaken and gravity begins to make the star collapse. The Hertzsprung–Russell (HR) Diagram is a chart that scientists use to study stars. It plots them according to their brightness (Absolute Magnitude) and their temperature, which determines the color of light they produce. By plotting stars on this diagram, astronomers were able to see patterns, which in turn helped them understand more about how stars changed throughout their life cycle. The Interstellar Medium is made up of small particles of dust and gas that exists in the space between stars. Although it is mostly made up hydrogen, events like supernovae will blast heavy elements like iron out into space where they become part of the intersteller medium. These elements will then be pulled in by new protostars to form new stars and planets. The Main Sequence is the name for the longest stage of a star's life cycle when it is burning hydrogen at its core. Our sun is an example of a main sequence star. More massive stars will spend less time in the main sequence, while stars smaller than our sun could spend trillions of years as main sequence stars. A Nebula is an area where the interstellar medium has clumped together to form a huge cloud of dust and gas. Nebula are often created when a large star goes supernova and throws most of its matter into space. Nebula are also the birthpalce of most protostars. A Neutron Star is the core of a star that has gone supernova. The pull of gravity has crushed the matter together so tightly that individual atoms are forced together, losing their electrons. The resulting matter is made up of tightly compressed nucleons, mostly neutrons. Even though it might have more mass than the sun, it is compressed to a tiny ball only about 24 kilometers apart. When the outer shell of a Red Giant star drifts off into space, it forms a Planetary Nebula. Positrons are incredibly small subatomic particles with a positive charge. They are antiparticles, or small pieces of antimatter. Positrons are the antimater equivalent of an electron, so they are sometimes called antielectrons. Positrons are created during the hydrogen fusion process when a proton changes into a neutron. Because the positive charge of the proton can't just disappear, the proton emits a positron, which carries away the positive charge. These positrons don't last very long, because as soon as they encounter an electron, the matter and antimatter anihilate one another, releasing energy in the form of gamma rays. A Protostar is a ball of dust and gases that has not yet reached a high enough temperature to begin hydrogen fusion and become a star. It will continue to accrete more matter and heat up until it reaches about 10 million degrees kelvin. Deuterium burning will slow down that process, allowing the protostar to become bigger before it ignites. A Red Dwarf star is a small star with less mass than our sun. Because it has less mass, the fusion reactions that take place within the star do so more slowly, giving the star an incredibly long life span. Currently, the universe isn't old enough for even the oldest Red Dwarfs to have burnt out. Stars that have begun to fuse helium in their cores expand to become Red Giants. As the surface of the stars expand, they begin to cool, giving the star an orange or red color. Red Giants are not as stable as main sequence stars, and most will eventually blow their surface off into space, forming a Planetary Nebula. The most massive stars will leave the main sequence relatively quickly, becoming Supergiants. A supergiant star has enough mass that it will be able to fuse not only helium, but heavier elements, as well. When iron begins to build up in the star's core, it will become unable to maintain equillibrium and will collapse, resulting in a supernova. Since most of the matter in a supergiant is blasted into space during a supernova, black holes are limited in how massive they can become. However, when multiple black holes come together to form a single object, they can become Supermassive Black Holes. Many scientists believe that supermassive black holes can be found at the center of most galaxies and other large objects. A Supernova is the explosion that occurs when a supergiant star's core collapses. The tremendous amounts of energy released in this explosion allow elements heavier than Iron to be formed. When the explosion dies down, the remains of the star are usually form a nebula and a neutron star, although very massive stars may leave behind a black hole. White Dwarfs are the cores of Red Giants that have lost their outer layers. White Dwarfs are no longer capable of fusion, but they are incredibly hot, which means that they will shine brightly for a very long time.
Somatic cells, similarly to germ cells, are two basic types of cells that are commonly found in animals. Somatic cells form through a process called mitosis, which is a type of asexual reproduction. Germ cells, on the other hand, form by a process called meiosis, a type of sexual reproduction. Somatic cells are also called vegetal cells. The biggest difference between germ cells and somatic cells are germ cells produce haploid gametes, which reproduce sexually, whereas somatic cells build the body of multicellular animals. Somatic cells make up all cells of the human body apart from sperm cells or egg cells. They make up all parts of the body including skin cells, liver cells, bone cells, and more. Mature somatic cells are able to perform specialized functions. What Are Germ Cells? Germ cells give rise to an organism’s gametes. Germ cells originate from the embryo and then migrate through towards the gonads through the gut. Germ cells of angiosperms are found within the floral meristem. The plant germ cells then develop further prior to the embryonic development. Sperm cells are the male gamete and egg cells or ovum are the female gamete. Multicellular organisms go through sexual reproduction by the fusion of male and female gametes. Gametes are haploid cells, which reproduce by meiosis of diploid germ cells. Germ cells can be found in the gonads of both males and females. In the case of males, germ cells are found in the testes, whereas in females they can be found in the ovaries. The process of germ cells forming gametes is a process called gametogenesis. Germ cells can go through meiosis and mitosis when producing gametes. The cells that germ cells produce to form gametes are called germline. Oogenesis is the process of producing female gametes or egg cells from germ cells. On the other hand, spermatogenesis is the production of the male gamete or sperm cells. The production of sperm cells involves meiotic division, which creates four equal spermatids. In the process of producing egg cells, the meiotic genesis is asymmetrical, meaning that one egg cell forms alongside three polar bodies. In the production of sperm cells, involves fast and uninterrupted cell divisions, whereas the production of egg cells is interrupted until puberty. Mutations in germ cells can be passed down through generations because germ cells produce gametes, which reproduce sexually. What Are Somatic Cells? Somatic cells are what make up the human body, generally speaking. The somatic cells found in the human body are mostly diploid cells, and they produce asexually through mitosis, meaning that two sets of homologous chromosomes are in the nucleus of each somatic cell. Some species may have polyploid or haploid somatic cells. Polyploid somatic cells can typically be seen in plants. In humans, on the other hand, the fusion of a sperm cell and an egg cell forms a diploid zygote, which then develops into a multicellular organism by way of mitotic division. In an adult human, there are over three million somatic cells in total. These somatic cells can be categorized into four main types of tissue found in the human body. These four categories are connective tissue, muscle tissue, epithelial tissue, and nerve tissue. If a mutation occurs in a somatic cell, they will not have any contribution to the evolution of the cell as they do not reproduce sexually. Somatic cells get their name from the Greek word “Soma”, meaning the body. There are over 220 different types of somatic cells found in the human body. Here is an overview of some of the main somatic cells found in the human body. Bone cells consistently get replaced with newer bone cells. There are two main types of bone cells, which are osteoblasts and osteoclasts. The former forms bone and maintains them, whereas the latter dissolves or resorbs old bone cells. Osteoblasts are square shaped cells that make up proteins to form bones. They are able to communicate with each other and produce other molecules including growth factors, which causes the growth of the bones. Osteoclasts are big cells with multiple nuclei. Once the osteoblast or osteoclast have done their job, they undergo a process called apoptosis, which is the programmed death of the cell. Muscle cells are also called myocytes, which are long, tubular cells. Myocytes come in three types, which make up the three types of muscle; skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscles attach to bones, allowing the body to move. Cardiac muscle are found in the heart, and they are responsible for the heart pumping blood. Smooth muscle is what lines the internal organs, including the digestive tract, uterus, and the bladder. Since myocates are very different from other types of cells found in the body, the different parts of myocytes have their own particular terminology. The cell membrane of myocytes is called the sarcolemma, the mitochondria are known as sarcosomes, and finally the term for the cytoplasm is sarcoplasm. The part of the cell that is responsible for muscle movement is called the sarcomere, which forms long chains which are called myofibrils. These myofibrils run throughout each of the muscle fibers. Muscle cells do not have the ability to divide and form new cells. Because of this fact, babies have a higher number of myocytes than adults. Another name for nerve cells are neurons. They can be found all throughout the human body, but they are particularly dense within the spinal cord and the brain. The function of neurons is to send and receive messages or signals to and from other neurons or organs by way of electrical or chemical signals. Neurons stay at a certain electrical voltage, and if this voltage changes, it makes an electrochemical signal known as an action potential. Once an action potential happens in a neuron, it releases neurotransmitters, which are a type of chemical that can affect targeted cells. A few examples of neurotransmitters include histamine, epinephrine, serotonin, and dopamine. The structure of neurons is unique to them. The parts of a neuron include the dendrites, axon, and the soma. The soma creates the body of the cell which includes the nucleus. The axon is the part of the cell that transmits electrical impulses. Dentrites are about to fan out around the soma to receive electrochemical impulses from other neurons. Neurotransmitters are released from the ends of the axon, where the axon terminals exist. The blood cells are also known as hemocytes or hematopoietic cells. Blood cells are made in three main types, including thrombocytes or platelets (yellow blood cells), leukocytes (white blood cells), and erythrocytes (red blood cells). Blood is composed of these cells and plasma. The function of erythrocytes is to transport oxygen to cells through the molecule hemoglobin, and they also collect carbon dioxide from cells. They comprise between 40 – 45% of the blood’s total volume. Around a fourth of the cells found in the human body are erythrocytes. They have a lifespan of approximately 100 to 120 days. When these cells mature, they no longer have nuclei. Leukocytes’ main function is to defend the body against outside substances such as viruses and bacteria. Their lifespan is only around 5 days. Platelets are tiny fragments of cells that promote the clotting of the blood once an injury occurs. They, too, have a short lifespan, only living between five and nine days. Epithelial cells include a few different types of cells that comprise the epithelial tissues. They line various organs such as the skin, blood vessels, and the digestive tract to name only a few. Epithelial cells have the ability to perform many different functions, depending on the particular type of epithelial cell. These functions include secretion and excretion, among others. The following are some examples of epithelial cells. Squamous cells have a thin, flattened shape, and they have a small nucleus in their center, in addition to lots of cytoplasm. Compared to the nuclei in other cells, the nuclei of squamous cells looks flattened and has an elliptical shape. Squamous cells can be discovered in various parts of the body including the epidermis, capillaries, the urethra and the air sacs inside the lungs. Since these cells get exposed to the outside environment, these cells get replaced constantly. As the name would suggest, cuboidal cells have a cube-like shape. Along with the cell organelles, cuboidal cells feature secretory vesicles in addition to microvilli. Cuboidal cells are typically found in body parts with high metabolic activity, where these cells secrete and exchange a range of different substances. They can be discovered in ducts, tubules, and neural retina, among other places in the human body. As the name would suggest, columnar cells form in an elongated shape. Some columnar cells are ciliated, and they also secrete and absorb various substances. These cells can be discovered within the fallopian tubes, in addition to various parts of the digestive tract and the respiratory system. Connective Tissue Cells Connective tissue is very abundant and widespread throughout the body. Connective tissue cells have many essential functions including binding in addition to providing protection and support. For this reason, there are multiple types of connective tissue cells that have specialized functions. The two main types of connective tissue cells are resident cells and transient cells. These can be subdivided into further subcategories of cell. Resident cells are connective tissue cells that are fixed in place and therefore cannot migrate from one place to another. These are some examples of resident connective tissue cells. The most common type of connective tissue cell are fibroblasts. They have are shaped like a spindle, and they also have a flattened nucleus. As they are among the most abundant connective tissue cells, they can be found within the interstital spaces in multiple organs in the human body. Since fibroblasts are indeed resident cells, they stay fixed in place in their particular regions of organs such as the lungs, kidneys, and the liver. Fibroblasts produce substances such as laminins, collagen, fibronectin, and prostanglandins, just to name a few. They play an essential role in healing wounds and reorganizing the extracellular matrix. Macrophages are resident cells that come from erythomyeloid progenitors, and they exist in tissue in which they comprise the mononuclear phagocyte cellular system. Within the human body, macrophages react to pathogenic invasions. They are responsible for ingesting these invasive organisms in addition to damaged cells. After tissue macrophages have been depleted, the levels of collagen and hyaloronan increase. This shows that macrophages are essential in extracellular matrix homeostasis. Adipocytes are fat cells, and they are connective tissue cells from the mesenchymal stem cells. They have a big droplet near the center of the cell, much like other cell organelles. In this section of the cell, triglycerides (fats) are stored. Once the fat content in the human body increases, the amount of these droplets also increases inside the cell. However, they do not decrease once the fat content decreases. Other than fat storage, adipocytes also generate energy and regulate the body temperature. Mast cells can be found within the mucosal or epithelial tissues. They are oval shaped, and they originate from bone marrow before they migrate to loose connective tissue. They also feature basophilic granules which produce heparin and histamine. Once histamine is released, the cell junctions weaken, allowing cells and proteins to go inside the connective tissues. Transient cells, as opposed to resident cells, transient cells in connective tissue have the ability to migrate from the bloodstream to affected sites. For this reason, transient cells make up various parts of the immune system, including the following. In the human body, neutrophils make up approximately 60% of all leukocytes, or white blood cells. These cells are the first to respond to inflammatory sites, and they are responsible for defending the body against fungus and bacteria, among other microorganisms. Eosinophils have a bilobed nucleus with big cytoplasmic granules. They are associated with allergic reactions, in addition to warding off multicellular organisms. Basophils comprise 0.5 – 1% of the all the leukocyte cells, and they are typically bigger than other granulocytes. As they are granulocytes, they have granules responsible for the production of enzymes that are associated with allergic reactions. Additionally, they play an important role in the process of the clotting of blood. Monocytes are big cells that can produce both macrophages or dendritic cells. They are responsible for the removal of damaged cells, though a process called phagocytosis. Additionally, monocytes are associated with fighting infections, in addition to the regulation of the immune system. Plasma cells are also called B cells, and they produce antibodies when responding to antigens. This process allows the B cells to identify antigens and then destroy them. Location Somatic Cells As discussed previously, somatic cells can perform specialized functions, depending on which type of cell and which part of the body they can be found. Below are some of the specific locations where various types of somatic cells can be found. Epithelial Tissue Cells Squamous Epithelial Cells Squamous epithelial cells are responsible for secreting lubricant in addition to allowing certain substances to pass through. These cells can be found in parts of the body that are associated with these particular functions, which includes the blood vessels, lymphatic vessels, alveoli, in addition to the serous membrane which lines the surface of internal organs and body cavities. Stratified squamous epithelial cells are comprised of many layers of flat cells in addition to basal layers of cuboidal or columnar cells. They are essential for protection against abrasions, and because of this they can be found on parts of the body that get exposed to the external environment, such as the skin and mouth cavity, among others. Cuboidal Epithelial Cells Cuboidal epithelial cells have cube-like shape, and they also excrete and absorb different substances. Simple cuboidal epithelial cells feature only one layer of cells, and can be found in the secretory body parts including the small glands as well as the surface of the ovaries in addition to the renal tubules and sections of the thyroid. Stratified cuboidal epithelial cells are found on the surfaces of excretory ducts including the sweat glands and sections of the kidney tubules. Columnar Epithelial Cells Simple columnar epithelial cells are also used for the secretion and absorption of substances, but mainly they are essential for the movement of mucous. Because of this, they can be found within sections of the digestive tract, in addition to many parts of the female reproductive tract such as the uterine cervix, minor ducts, and the fallopian tubes. Stratified columnar epithelial cells can be found within the conjunctiva in addition to parts of the anus, pharynx, uterus, among others. Processes Of Production Simply put, all cells in the human body originate from three germ layers, which are ectoderm, mesoderm, and endoderm. Mesodermal cells create connective tissue, lymph vessels, and the gonads among others. Ectodermal cells make up the cells of the central nervous system, in addition to the epidermis and the peripheral nervous system, and more. Ectodermal cells, on the other hand, make up the cells in the respiratory system, the bladder, pancreas, and the thyroid among others. Once developed inside an embryo, stem cell descendants known as progenitor cells produce various types of cells, and they are found in multiple parts of the human body. Below are some of the different processes involved in producing various types of somatic cells. Hematopoietic Progenitor Cells Inside bone marrow and peripheral blood, hematopoietic progenitor cells can be found. These cells can then differentiate to produce specialized blood cells such as red blood cells, white blood cells, and platelets. For the production of functional, mature cells, hematopoietic progenitor cells first must divide in order to produce multipotent progenitor cells, such as common myeloid stem cells and lymphoid stem cells. The needs of the body will determine what type of cells are produced. If the body is experiencing hypoxia, a growth factor called erythropoietin will produce inside the kidneys to stimulate the production of red blood cells. When hormones are present in the body, myeloid stem cells go through many stages of division in order to produce more red blood cells. Interleukin 3 and 5, in addition to granulocytic and agranulocytic colony-stimulating factors are signal molecules that have an influence on the production of granulocytes and monocytes derived from myeloid stem cells. Some leukocytes are able to divide through mitosis, whereas red blood cells which don’t have a nucleus cannot. Neural Progenitor Cells One of the other main types of progenitor cells found in the human body are neuronal progenitor cells. These types of cells can be found in the brain and the lateral ventricle in addition to the striatum. In humans, these cells create glial cells. For example, inside the subventricular zone, neural progenitor cells are able to divide through mitotic division and create quiescent or proliferative B1 cells. These types of cells can divide asymmetrically and create B1 cells that have the ability to self-renew in addition to transient progenitor cells that can create C cells. Endothelial Progenitor Cells Endothelial progenitor cells are another type of stem cells that can be found inside bone marrow. These cells become activated by the production of particular cytokines, just like red blood cells. These cells can be produced during injuries, and they can have an influence on the mobilization of progenitor cells towards the affected area. These cells then get stimulated to divide and produce endothelial cells to replace damaged or lost cells. Some somatic stem cells include the following: - Mesenchymal stem cells - Mammary stem cells - Intestinal stem cells - Olfactory adult stem cells What Are The Differences Between Gametes And Somatic Cells? Somatic cells divide through the process of mitosis. They feature two copies of each chromosome, one from each parent. These types of cells with two copies of each chromosome are known as diploid cells. Sperm cells and egg cells are called gametes. These types of cells are formed by a process called meiosis, which is a process in which cells divide with only a single copy of each chromosome. The name for these sorts of cells is haploid. Gametes are haploid cells since a sperm and an egg fuse together during fertilization in order to make a new organism that has diploid cells. When mutations occur in somatic cells, it only affects a single organism, and it is not passed onto the offspring. When a mutation occurs in a gamete, on the other hand, it can affect the offspring. Once gametes fuse, they become the first somatic cell of the offspring, which then divides, thus developing and forming all of the offspring’s somatic cells. To reiterate, mutations in somatic cells will not have an effect on the next generation, whereas mutations in gametes will be passed on to the next generation. For example, when a big mutation happens in a gamete such as an extra chromosome inside a fertilized egg, the somatic cells that divide from the fertilized egg will also have that extra chromosome. This can result in Down Syndrome in humans. What Are The Differences Between Somatic Cells And Germ Cells Somatic cells and germ cells alike can be found in most animals, including humans. They share a lot of characteristics, but there are multiple differences in respect to their functions. As previously discussed, somatic cells make up all the cells in the body apart from gametes (sperm or egg cells). Sperm and egg cells are not somatic cells, but germ cells are considered precursors of gametes. In the early stages of development for many organisms, these types of cells have been shown to separate from somatic cell lineages, and they migrate to the developing gut. Once there, the main difference between somatic and germ cells is that somatic cells are fully functional, whereas germ cells are progenitor cells that create functional cells. Another main difference between somatic cells and germ cells are the location of the cells. Since germ cells give rise to gametes, they can be found solely in the gonads (testes in males and ovaries in females). Somatic cells are found throughout the body. Not only in tendons and ligaments, but the cells that create connective tissue can be found inside the fibrous coverins of membranes. Thus, they can also be found in various sections of the reproductive system; for example, the cells of the connective tissue surrounding the oogonia. Germ cells, much like somatic cells, can divide through the process of mitosis. Because of this, they are the sole cells in the body that undergo both mitosis and meiosis. Mitosis is especially significant in germ cells, as it allows germ cells to multiply. It’s important to note that somatic cells and germ cells alike are diploid, meaning they have 46 chromosomes in total in humans. Because of this, mitosis allows them to increase the amount of diploid cells in the gonads. To create gametes, the cells must go through meiosis which creates haploid cells, for example, sperm cells with 23 chromosomes. Diploid somatic cells only divide through mitosis. The cell division of somatic cells is essential for growth and replacing lost and damaged cells, which is not the case in germ cells. Germ cells multiply through the process of mitosis in order to increase the amount of diploid cells inside the gonads. Meiosis makes sex cells that can form new organisms. The Division Of Somatic Cells Somatic cells divide by mitosis, which is a form of cell division that makes two identical daughter cells that have identical characteristics. This type of division has four crucial stages which include the following. In the prophase stage of cell division, the chromosomal pairs condense and compact. Here, sister chromatids join together in the centromere. The metaphase stage of division is where the nuclear membrane breaks down as the spindle fibers move to opposite sides of the cell. At the end of the metaphase, the fibers begin to align with the chromatids at the equatorial plane of the somatic cell. During this stage of the cell’s division, the contracted fibers of the spindle separate the sister chromatids and then pulls them to the opposite sides of the cell, ensuring that each daughter cell will have the exact same number of chromosomes. The final stage of division involves the nuclear membrane forming around the separated chromosomes. Finally, the cytoplasm divides by a process called cytokinesis, ultimately separating both daughter cells entirely. The Advantages Of Somatic Cells Somatic cells comprise all the different organs and tissues of the body. For this reason, they are essentially important for the various functions of all the vital organs, in addition to the connective tissue and bones just to name a few. The specialization of these types of cells ensures that they can work synergistically to perform their essential functions. The division of these cells occurs through the process of mitosis, which makes sure that they are consistently replaced when an injury occurs or the old cells die. This cell division also allows the organism as a whole can grow over time. The Similarities Between Somatic Cells And Germ Cells Germ cells and somatic cells, along with stem cells collectively comprise the bodies of multicellular organisms, including human beings. Both germ cells and somatic cells in humans are diploid. Therefore, there are two sets of homologous chromosomes found in every somatic cell and germ cell. Both types of cell have the ability of differentiating into specific types of cells. The Differences Between Somatic Cells And Germ Cells Somatic cells comprise a myriad of different cells in a multicellular organism, besides cells that produce gametes, or gametes themselves (sperm cells and egg cells). Germ cells, on the other hand, are a type of cell that produces gametes or reproductive cells. There are various types of somatic cells that are found in different types of tissues within the body of a multicellular organism, including human beings. The specific type of somatic cell and the location of the cell within the body determines what functions the cell is capable of performing. Germ cells only produce either male or female gametes. The vast majority of cells found in multicellular organisms, including human beings, are somatic cells. Germ cells are much less abundant in multicellular organisms in comparison. Somatic cells are capable of performing a myriad of different functions within a multicellular organism, whereas germ cells are only capable of producing gametes for sexual reproduction. Somatic cells divide by the process of mitosis, whereas germ cells go through the process of meiosis. Similarly, somatic cells reproduce asexually, whereas germ cells participate in sexual reproduction. When mutations occur in somatic cells, the mutations are not passed onto the next generation, whereas mutations in germ cells do get passed on through the next generation. Similarly, somatic cell mutations do not have any effect on evolution, whereas the mutations in germ cells do have an effect on evolution. Somatic cells and germ cells are both found in multicellular organisms, but somatic cells are much more abundant, and they form the building blocks of multicellular organisms like human beings. Diploid germ cells create haploid gametes by the means of meiotic cell division. The vast majority of cells in multicellular organisms are, in fact, somatic cells. Somatic cells reproduce asexually, and they turn into a myriad of different types of cells depending on their, such as tissues, organs, and organ systems. Depending on the type of somatic cell, they are able to perform specialized functions. Both types of cells are essential for the lives of multicellular organisms, including human beings. - Guide To The Endospore Stain – Techniques, Procedures, And Importance - July 25, 2022 - What Are Hyphae? Including Production, Structure, And Variations - July 25, 2022 - The Principle, Procedure And Interpretation Of Motility Tests - July 25, 2022
Swirling gas around black holes may be the key to estimating the masses of black holes otherwise too distant to weigh, according to a new study. Supermassive black holes millions to billions of times the mass of the sun are thought to lurk at the heart of all large galaxies. Oddly, the properties of these black holes appear linked with a variety of properties of their parent galaxies, such as how bright the galaxies are and the speed of stars within them. This suggests a fundamental link between galaxy and black hole evolution. "This is quite surprising, and not well understood, as these relations tie together black holes with event horizons on solar system scales and galaxies, which are billions of times larger," study lead author Timothy Davis, an astrophysicist at the European Southern Observatory in Garching, Germany, told SPACE.com. "Why a massive galaxy should care about its black hole, and vice versa, is not well understood." One way to learn more about this mystery is by studying the masses of black holes in many different types of galaxies. For instance, early-type elliptical galaxies "are thought to have violent histories, with lots of merger activity that could build up black holes and galaxies simultaneously," Davis said. "On the other hand, spiral galaxies like our own Milky Way are thought to have had quieter lives, with less violent disturbances. One could imagine that if galaxy mergers were important in the buildup of black holes, that spiral galaxies could well have different relations between their black holes and galaxy properties." [No Escape: Dive Into a Black Hole (Infographic)] Weighing black holes Scientists have a number of strategies for deducing the masses of black holes, most of which involve watching the motions of stars or of disks of glowing hot, electrically charged gas as it swirls near the black hole. The mass of a black hole determines the strength of its gravitational field, and thus how strongly it pulls on surrounding matter. However, these approaches rely on telescopes that can see light from these stars and gas, which is only visible when relatively nearby. The new technique depends on the dynamics of clouds of cold gas around black holes. By comparing models of gas motions both in the presence and absence of black holes, researchers can deduce how massive a black hole must be to result in the gas motions they see. Molecular gas observations can overcome the resolution limit on strategies dependent on watching stars or ionized gas, helping researchers measure the masses of black holes much farther away. The scientists tested their model on gas seen around the supermassive black hole in the galaxy NGC 4526, which is 53 million light-years away in the constellation of Virgo. They employed the Combined Array for Research in Millimetre-wave Astronomy (CARMA) telescope in California. "We observed NGC 4526 with CARMA's sharpest array, achieving a resolution of 0.25 arcseconds," Davis said. "This is the equivalent of being able to spot a one euro coin (or U.S. quarter) being held up 10 kilometers (6 miles) away! With these super-sharp images we were able to zoom right into the center of NGC 4526, and observe the gas whizzing around the black hole." They estimate NGC 4526's central black hole weighs about 450 million times the mass of the sun. "We have shown for the first time that it is possible to use molecular gas observations to measure black hole masses," Davis said. Using next-generation scientific instruments such as ALMA, the Atacama Large Millimeter/submillimeter Array, this method could determine black hole masses in hundreds of galaxies in less than five hours of observations each, researchers say. "The measurement we have made on one object took over 100 hours of observing time with the CARMA telescope in California," Davis said. "With the new ALMA telescope currently being built in Chile, the same measurement can be repeated in just 10 minutes!" "The next step will be to observe a sample of spiral galaxies with the ALMA telescope, and determine their black hole masses," Davis said. "Even starting with 10 objects will about double the number currently available to study, and allow us to start determining if they follow the same black-hole mass relations as early-type galaxies." The scientists detailed their findings online today (Jan. 30) in the journal Nature. - Photos: Black Holes of the Universe - Black Hole Quiz: How Well Do You Know Nature's Weirdest Creations? - The Strangest Black Holes in the Universe - Space & Astronomy - Science, Social Science, & Humanities - black holes - spiral galaxies
GeoGebra Lab #3: Triangle Centers - Dr. Abigail Brackins Task #1: Centroid, Circumcenter, Orthocenter Applet In the GeoGebra applet above, the points D, E, and F represent the centroid, circumcenter, and orthocenter of the triangle ABC. (Not necessarily in that order.) Determine which point is which. These three centers (Centroid, Circumcenter, Orthocenter) share a special property. In the applet above, move the points A, B, and C to see what changes, and what stays the same over lots of different triangles. Make a conjecture about the points D, E, and F. Task #2: Location for a new shopping center What is the geometry name for the location you chose for the shopping center? Why did you make that choice? Task #3: Location for a Water Treatment Center Task #3 (a) Task #3 (b) The point that minimizes total distance to the vertices of a triangle is called the triangle's Fermat point. Based on your observations, make a conjecture about the Fermat point of a triangle. Task #4: Find the Fermat point - Select the "Regular Polygon" tool, then select the points A, B (in that order). When prompted, enter "3" vertices. You have made an equilateral triangle on side AB. (Let's call it ABD.) - Repeat the last steps to make an equilateral triangle on side BC. (Let's call it BCE.) - Repeat again to make a third equilateral triangle on side CA. (Let's call it CAF.) - Construct lines from the third (non-ABC) vertex of each equilateral triangle to the opposite vertex on AB. For example, the first line should pass through points D and C. - Use the intersect tool to construct the intersection of these lines. This is the Fermat point!
Share this post To allow the treatment of bacteria with resistances to, for example, β-lactams, there is a need for a variety of antibiotic medicines with different structures and modes of action. Five modes of action We have seen that penicillins inhibit bacterial cell wall synthesis and this is the most common mechanism of action of antibiotics. But other antibiotics have been developed that inhibit protein synthesis in bacteria. For example, macrolides (which contain a large lactone ring), like erythromycin, stop the formation of peptide bonds between amino acids, which prevents protein synthesis. As ribosomes (a cell structure that makes proteins) found in our cells have different structures to those found in bacterial cells, selective antibacterial drugs that just act on bacterial ribosomes can be developed. Different classes of antibiotics have been shown to disrupt protein synthesis by slightly different modes of action. For example, tetracyclines (the name reflects the chemical structure, which has four linked rings), also inhibit protein synthesis, but they do this in a slightly different way to erythromycin, by binding to a different site on the bacterial ribosome. Other antibiotics target nucleic acid synthesis in bacteria. Nucleic acids are the ‘building blocks’ of DNA and RNA. There is a difference in the enzymes that carry out DNA and RNA synthesis in our cells and in bacterial cells, which aids the development of selective antibacterial drugs. The antibacterials can be subdivided into DNA inhibitors and RNA inhibitors. For example, the drug rifampicin inhibits the synthesis of bacterial RNA, while fluoroquinolones selectively bind to a bacterial enzyme that stops the replication of bacterial DNA. (Replication is the process by which DNA makes a copy of itself during cell division.) These actions lead to bacterial cell damage. Also, some antibiotics, like the polypeptide gramicidin D (which is a mixture of gramicidin A, B and Cs) and the cyclic polypeptide gramicidin S, disrupt the cell membrane of bacteria. They form small pores (acting like a cellular ‘hole-punch’) that allow the transfer of ions, which leads to cell death. Gramicidin’s initial claim to fame was as the first clinically tested antibiotic. But gramicidins also affect the membranes of our cells, albeit at higher concentrations that those of bacterial cells. They are toxic to blood, liver, kidney and brain cells, and so were rapidly superseded by penicillin. On saying that, gramicidins are still an ingredient in some modern-day lozenges for sore throats and in topical medicines to treat, for example, infected wounds. Want to keep University of York online course, Exploring Everyday Chemistry Finally, there are drugs that function as antimetabolites. They stop the life-sustaining chemical reactions (called metabolic pathways) in bacteria by inhibiting bacterial enzymes. For example, we have seen that sulfonamides (such as sulfamethoxazole) mimic PABA and so stop the production of bacterial tetrahydrofolate. Tetrahydrofolate is used to make compounds called pyrimidines and purines, that are required for making nucleic acids and then RNA and DNA. In contrast, we obtain tetrahydrofolate from folic acid in our food. As we do not make tetrahydrofolate in the same way as bacteria, sulfonamides are selectively toxic for bacteria. To compare and contrast the different structures of antibiotics, you are encouraged to take a look at the modes of action pdf in the downloads section below. Prepare yourself for some beautifully intricate and varied chemical structures. Also, to further illustrate the different modes of action of drugs on bacterial cell walls, we now look at two important antibiotics in more detail. One common alternative to penicillins is a non-β-lactam antibiotic called vancomycin (Vancocin), which was originally approved for use in 1958. After its initial introduction it was superseded by the β-lactams that provided a cheaper and less toxic alternative to treat bacterial infections. Over time, however, interest in vancomycin has resurged and it is now one of the most common non-β-lactam antibiotics in use. Vancomycin has a very complicated structure, which contains carbohydrate groups, a number of substituted benzenes and various amide (or peptide) bonds. It has a molecular weight far above that of penicillins and most β-lactam antibiotics. As it does not contain a β-lactam ring, we can assume that it kills bacteria in a different way to β-lactam penicillins. In fact, vancomycin targets the precursor molecules that form peptidoglycan directly. Vancomycin binds to branching amino acid chains that make up some of the individual peptidoglycan strands. These amino acids are designed to cross-link with other amino acids, using an enzyme called peptidoglycan synthetase, in order to form strong cell walls made of many layers of interlinked peptidoglycan chains. (As an analogy, imagine closing a zip, where the teeth all link together.) Vancomycin acts by binding to the branching amino acids and preventing the synthetase enzyme from interacting with them. (The zip is now stuck and the teeth cannot link together.) So, the regeneration and construction of peptidoglycan cell walls is unable to take place and over time the protective cell wall surrounding the bacterial cell breaks down. Resistance to vancomycin is known and relies on altering the structure of the final amino acid at the end of the peptidoglycan chain that undergoes cross-linking. It changes from …–CO–NH–CH(Me)–CO2H to …–CO–O–CH(Me)–CO2H. This very subtle structural change, from an amide to an ester, has a big effect because vancomycin no longer has a complimentary shape to this new chain. Therefore, it cannot bind to the chain and it does not inhibit the action of the peptidoglycan synthetase enzyme which, despite the structural change, is able to accept and crosslink the chain containing the ester (i.e. the zipper still works!). Bacteria that make their cell walls using this modified peptidoglycan precursor (containing an ester) are therefore resistant to vancomycin. An alternative antibiotic is daptomycin (Cubicin), approved for use in 2003. Daptomycin has yet another mechanism of action which revolves around its molecular structure. The ring of amide bonds provides a hydrophilic polar head and the lipophilic alkyl chain represents the non-polar end of the molecule. Daptomycin is mainly effective against gram-positive bacteria as it can diffuse through the surrounding peptidoglycan layers. (The selectivity for gram-positive bacteria appears to involve daptomycin binding to Ca2+ and the resultant positively charged complex being attracted to the negatively charged cell wall in gram-positive bacteria – typically, gram-positive bacteria have cell walls containing more negatively charged groups than gram-negative bacteria. Also, the positively charged daptomycin-Ca2+ complex appears to have a particular affinity to a negatively charged group that is more common in bacterial cell walls, than in our own cell walls.) Once it reaches the cell membrane its lipophilic ‘tail’ inserts into the phospholipid membrane of the cell. This ‘tail’ allows for daptomycin to integrate itself into the phospholipid bi-layer of the bacterial cell membrane as both the ‘tail’ and the phospholipid fatty acid chains are lipophilic. Once many daptomycin molecules integrate themselves into the cell membrane they begin to stretch and contort it, producing holes from which ions within the cell can leak out. Once ion leakage occurs lost ions cannot be easily replaced by the bacterium; the cell loses its ability to replicate and produce proteins essential for its survival. Daptomycin has catalogued cases of resistance, however, these are rare and the mechanism through which resistance occurs is currently unknown. As such daptomycin looks to be a valuable alternative where vancomycin resistant bacteria have developed. Thus far, clinical trials have shown equal or greater effectiveness than vancomycin in combating bacterial infections. More importantly, studies suggest that vancomycin has a damaging effect on the kidneys through prolonged use. However, daptomycin has shown none of these toxic side effects and in some circumstances it has helped to alleviate similar kidney damage. Therefore, daptomycin could not only be a more effective form of treatment but also a safer one. This potent antibiotic is steadily gaining popularity. In 2015 of the 6075 patients catalogued in the Cubicin Outcomes Registry and Experience database (CORE), there was an 85% success rate in treatment of those prescribed daptomycin. The CORE database was set up specifically to catalogue uses of daptomycin in a clinical setting and analyse the results. Overall these appear to be promising with less than 5% of patients reporting adverse effects from the treatment. With further trials and study, these statistics can only improve as more effective analogues and combinations with other prescriptions are used. At the start of 2017, a team of chemists and biologists at York reported new antibiotics of potential use for the treatment of gonorrhoea. (The World Health Organization warned that if someone contracts gonorrhoea, it is now much harder to treat, and in some cases impossible, as the infection is developing resistance to antibiotics.) They harnessed the therapeutic effects of carbon monoxide-releasing molecules – these molecules bind to the bacteria that causes gonorrhoea, preventing the bacteria from producing energy and killing it. Use honey first? To help tackle antibiotic resistance, for coughs, taking honey is recommended as a first line of treatment. The main antimicrobial agent in honey is hydrogen peroxide; different concentrations of H2O2 in different honeys explain their varying antimicrobial effects. The O–O bond in hydrogen peroxide is relatively weak and breaks down to form very reactive species (called hydroxyl radicals, HO•) that react with, and damage, bacteria DNA. Share this post Exploring Everyday Chemistry Our purpose is to transform access to education. 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Two of the key functions of the cardiovascular system are to: 1. Transport nutrients, hormones, gases and waste to and from our cells. 2. Regulate our body temperature and maintain our bodies fluid balance. When we exercise a greater demand is placed on these functions as working muscles require more oxygen and nutrients than normal, they produce more waste products and generate more heat. The degree of the cardiovascular response is determined by the demands placed on it by the training stimulus, the greater the demand the greater the response. The cardiovascular system is essentially made up of two parts - the heart (cardio) and the . On the this page we'll focus our attention on the heart's responses to exercise. Cardiac output (Q), heart rate (HR) and stroke volume (SV) responses: Cardiac output refers to the total quantity of blood that is ejected by the heart and is usually measured in litres per minute. Heart rate refers to how often the heart beats and is also meaured per minute. Stroke volume refers to the amount of blood that is ejected by the heart with each beat. So cardiac output is quite simply the product of heart rate and stroke volume. Heart rate increases in a linear fashion to increases in the intensity of exercise. This is illustrated in the adjacent graph, showing how the heart rate (in beats per minute – bpm) increases to match the incremental demands of walking, jogging and running. It is also worth noting that heart rates start to rise prior to any type of exercise – just the thought of exercise is enough to trigger a heart rate response. This initial response serves simply to prepare the body for activity and is controlled by the sympathetic division of the autonomic (involuntary) nervous system. Stroke volumes also rise as a person starts to exercise and continue to rise as the intensity of the activity increases. This is shown in the adjacent stroke volume graph as the increases between standing, walking and jogging. This increase is primarily due to a greater volume of blood returning to the heart. You will also notice that stroke volumes are higher when lying, and to a lesser degree sitting, as opposed to standing. This is because it is much easier for blood to return to, and fill the heart when a person is lying and sitting as the effect of gravity on blood flow is not as great when in these positions. The increase in stroke volume only continues up to a point however. Once the intensity of the exercise exceeds 50-60% of an individual’s maximum heart rate their stroke volume ceases to rise, as shown on the graph as the similar stroke volumes for jogging and running. This is primarily because the increase in heart rate that has also occurred does not allow enogh time for the heart to fill anymore between each heart beat. Cardiac output increases in a linear fashion to increases in the intensity of exercise, up to the point of exhaustion. This happens as a direct consequence of the heart rate and stroke volume responses to the intensity of exercise. The increase in cardiac output at intensities up to 50-60% of a person’s maximum heart rate is attributable to increases in heart rate and stroke volume. As the intensity of exercise exceeds 60% of a person’s maximum heart rate the increase in cardiac output is solely attributable to increases in heart rate. Just how high can heart rate go before it reaches its maximum rate? There is an easy formula commonly used in the fitness industry to estimate a person’s maximum heart rate (HR Max). This formula estimates that a persons HR max is approximately 220 bpm minus their age. So a 40 year old would have a maximum heart rate of 180 beats per minute (220 – 40 = 180bpm). HR max is shown on the adjacent graph. The heart rate is shown to increase in a linear fashion to increases in intensity (treadmill speed in this case) up to a point (approximately 185bpm on the graph) where HR max is reached and it increases no further. The intensity required to attain maximum heart rates is relative for all people. For example an unfit person may reach their HR max jogging at 8km/h while a fit person may reach their HR max running at 20km/h. It’s important to bear this in mind when designing programmes for clients – what may seem to be an easy intensity for you (e.g. jogging at 10km/h on a treadmill) could quite literally ‘kill’ someone new to exercise! Heart rates and exercise intensity Because heart rates (and the intensities required to achieve certain heart rates) vary so much between people many trainers use the ‘Rating of Perceived Exertion’ (RPE) scale to measure and set exercise intensity with clients. The RPE scale (shown adjacent) is a simple 1-10 scale where the client rates the intensity of the exercise according to how hard it feels to them. If you were aiming to take a new, unfit client through a low-moderate intensity cycling workout and they rated the workout at 7 it would indicate that you’d exceeded the intensity you planned (and may well have exceeded your client’s capacity to cope)! The RPE scale is an easy ‘client friendly’ way of measuring intensity according to the client’s feedback and providing direction to clients regarding the intensity they should train at. What direction do you think a client would find easier to understand – ‘jog at an intensity of 3/10 that you feel is ‘light’ for 30 minutes’, or ‘jog at a point where your heart rate is between 120-135 bpm for 30 minutes’? Heart rate response to aerobic training If the intensity of the exercise remains constant (i.e. 50% of a person’s maximum heart rate, or an RPE of 5 throughout) then the heart rate will rise until it reaches what is known as ‘steady state’ where it stays relatively constant as the cardiovascular system meets the demands placed on it by the exercise. Achieving ‘steady state’ is the goal of many aerobic fitness training programmes – training at a set intensity for a prolonged period of time. Steady state is illustrated on the adjacent graph at the point where the heart rate flattens after an initial rise in the first few minutes of exercise. For steady state to be achieved and maintained the intensity of the exercise must remain constant. The graph also shows how heart rates return to resting levels after exercise finishes. The more intense the exercise is the longer it will take for heart rate to return to its resting rate. With low-moderate intensity aerobic fitness training (as indicated in the graph) heart rates return to normal within 10-20 minutes. Stroke volume returns to resting levels in an identical fashion. If the intensity of the exercise fluctuates then heart rates will also fluctuate. We see this where work periods of high intensity exercise are interspersed with periods of lower intensity exercise. As the intensity increases so does the heart rate and as the intensity drops so does the heart rate. The following graph shows how a person’s heart rate fluctuates throughout an 11 mile run encompassing a variety of terrain. You will notice that at the 4.5 mile mark the runner increased their speed significantly resulting in the largest increase in heart rate. Drops in heart rate relate to reductions in pace and easier (downhill) parts of the run. Heart rate response to anaerobic training Training for strength, speed and power focuses on energy coming from the anaerobic energy systems. Work periods, or ‘sets’ are typically short (5 - 30 seconds), intensity is very high (8-10/10 RPE) and rest periods are long in comparison (≥ 2-3 minutes). Because of the short work period and the use of energy from anaerobic pathways, heart rates don’t rise significantly and thus show only moderate rises during each work period. They also return to near resting levels during each rest period and return to normal levels within a few minutes after the cessation of the workout. With these types of training the cardiovascular system functions largely to replenish the anaerobic energy systems and as such is only minimally stimulated. The heart rate response does become greater as the duration of each work period/set increases (≥ 30 seconds) and or the recovery period shortens (≤ 1minute). We see this with training for muscular hypertrophy, muscular endurance and anaerobic fitness in particular, where there is a greater demand for the cardiovascular system to remove the accumulation of waste products (CO2 and lactate). During these types of training heart rates rise and peak at the end of each work period/set. The peaks will be larger for training oriented on muscular endurance and anaerobic fitness (longer work periods and less recovery time between each work period/set). As there is less recovery time between work periods/sets with muscular endurance and anaerobic fitness training, heart rates tend to rise incrementally throughout the workout as well as having peaks at the end of each set. Because of this it takes longer (20-40 minutes) for heart rate and stroke volume to return to normal resting levels at the end of the workout. This is due to a greater demand placed on the cardiovascular system to shunt greater quantities of blood out of working muscles, return blood to the vital organs and clear the accumulation of waste products (lactate & CO2). This prolonged elevation of heart rate post exercise is known as ‘EPOC’ (excessive post-exercise oxygen consumption). Heart rates essentially stay elevated for longer after these types of training in order to metabolise the lactate that has accumulated and return the body to homeostasis. There is an added bonus with exercise that causes the heart rate to stay elevated for longer, more calories are burned as a consequence. So a muscular hypertrophy workout and to a greater degree muscular endurance and anaerobic fitness workouts can be considered the workouts that keep giving even after they’ve finished – and are certainly beneficial for those wanting to get rid of unwanted fat stores!
Students should be provided with opportunities to explore algorithms through guided play, including hands-on, kinaesthetic and interactive learning experiences. Students begin to develop their design skills by conceptualising algorithms as a sequence of steps or procedures for carrying out instructions to solve problems or achieve certain things. These skills could include identifying steps in a process or controlling a Bee-Bot. Provide authentic and meaningful ways to introduce students to simple programming while consolidating concepts across other subject areas. Flow of Activities Breaking down a problem into smaller parts, or steps, is an important part of computational thinking. When initially defining problems you need to be able to identify the key features of the problem/circumstances. – These features become the scaffold or structure of the problem, and they then help frame the solution. Typically, when we describe to another person a solution to a problem or task, we only mention the key features or /instructions. and We omit less important ones, because we assume that people know what we mean. Focusing on important details and ignoring aspects that are not relevant is part of the process of abstraction. However, wWhen providing instructions to a computer, it is necessary to give specific instructions about sequences and decisions because a computer cannot make assumptions. It is integral in programming to only focus on important details and, ignoreing aspects that are not relevant. At this level, students should be able to describe, follow and represent an algorithm, which is a sequence of steps for carrying out instructions to solve a problem or achieve a desired outcome. It is suggested that students begin their learning by following instructions issued by others about completing a task. This will help them to build knowledge and skills in abstraction as well as skills in writing algorithms. Describing a sequence involves students thinking logically – deciding the order in which instructions need to be followed. Students could give verbal instructions to another student to complete a task. When representing an algorithm, the steps and instructions need to be documented so that the task can be carried out as planned. There are different ways that instructions can be documented; for example, cards or images could be arranged to indicate a sequence; or text instructions could be provided. Some methods are more efficient than others. Students will begin to recognise patterns in their instructions and consider how these could be shown. At this level, students can carry out instructions using a digital system such as a robotic device. Students develop their design skills by formulating a sequence of steps to solve a problem or achieve a desired outcome. This could be identifying steps to control a Bee-Bot, or using programming cards to provide instructions. The Bee-Bot can be thought of as a piece of hardware and therefore linked into the way digital systems operate with an input and output . Algorithms are used around us every day. For example, algorithms are used to control traffic lights, the scores in a computer game and the advertisements on websites. Any digital automated process is instructed to behave in a particular way because of the decisions and steps that have been designed and carried out for the solution. Note: An algorithm can be used not only to describe a digital solution, but also to describe an everyday process such as cleaning teeth or making a salad. In this activity, students inquire into an everyday process, and represent the decisions made and steps taken to carry out that process. Students connect algorithms to everyday events; this helps them to recognise the relevance of what they are learning.
Scale, proportion, and quantity belong to one of the cross cutting concepts in the next generation science standards (NGSS). According to Volume 2 of the NGSS, "in engineering, no structure could be conceived much less constructed without the engineer's precise sense of scale." The authors go on to note that scale and proportion are best understood using the scientific practice of working with models. When scientists and engineers work with these concepts at a molecular scale, new kinds of technologies can be created to advance our understanding of the natural world. One example is DNA sequencing. DNA sequencing has become our most powerful tool for identifying anything of biological origin, whether it's food, plants, animals, viruses, bacteria, or genetic disease. As our use of DNA sequencing grows, the demand for more DNA sequencing continues to increase, creating pressure to sequence DNA at ever faster rates. Even though DNA sequencing has become a common technique, there is still room for improvement, especially in terms of the error rate. DNA molecules are too small (at least thin), to been seen with our eyes. Consequently, we must rely on technology to tell us what the sequence of bases must be. The current methods for determining a DNA sequence rely on mimicking the processes used in nature to replicate DNA and copy chromosomes before cells divide. The steps required to accomplish this task and the detection process itself can sometimes introduce artifacts that result in errors (see our posts here, here, and here for more details). Despite these challenges, we have learned to make reactions smaller and run them in massively parallel formats to make sequencing very fast and cheap. But, still not fast or accurate enough ... What if we could, instead, directly read a DNA sequence by passing it through a tiny hole that could somehow recognize the shape of each base as it passes by? Such a direct method for reading a sequence could be faster and more accurate than current approaches. Molecular structures and models helped scientists realize that this approach might work. In fact, these models and the research they inspired led to the first commercial systems for nanopore sequencing. Using Molecule World™ we can examine the structures of these nanopores and learn about some of their properties. Nanopore sequencing methods were not easy to develop. The first commercial system for nanopore sequencing ( Oxford Nanopore Technologies Ltd ) required 20 years of scientific trial and error. The greatest challenge in getting this technology to work is that DNA is small and nanopores, while sounding small, are really big relative to DNA. A common method for creating a nanopore involves using lasers to drill holes in silicon wafers. These holes are commonly 10 nm (0.000010 mm) in diameter and about 10 nm deep. Double stranded DNA (dsDNA) is only 2 nm in diameter, and single stranded DNA (ssDNA) is only 1 nm in diameter. Since the holes are wider, the DNA can pass through one of these nanopores without touching the sides. Since the holes are short, only 30 bases of DNA can fit in a hole at a time. The diameter and depth make the holes too deep and too wide to detect and distinguish between DNA bases as they pass through the pore. The first problem that needed to be solved in getting nanopore sequencing to work was to figure out how to make smaller holes. For a long time scientists knew that DNA gets in and out of cells. They reasoned that special proteins must exist that would transport DNA across cell membranes. And, they do. These proteins can be used as an alternative to the nanopores in silicon. The first protein to be tried was α-hemolysin (aHLA). With this protein, the pore size is closer to the diameter of DNA. Since the DNA makes contact with the sides of the pore, different bases can be detected. Even though DNA can pass through nano pores of alpha-hemolysin, the shape of still presents certain challenges with respect to how DNA moves through the pore. This has led scientists to experiment with other naturally occurring pore proteins such as Mycobacterium smegmatis porin A (MspA). Inspecting the structures shows how their shapes differ, with MspA having a broader base. When MspA's residues are colored by charge (negatively charged amino acids are shown in red, positively charged in blue and neutral in gray) we can see that the native MspA protein might not let a negatively changed molecule like DNA pass through (see if you can see why). Indeed this was the case, and the MspA being tested in nanopores is a variant where three of the negatively charged aspartic acid residues have been changed to neutral asparagine residues. When molecular models are represented in their proper relative scales, we can better understand the underlying scientific principles and learn how technologies may or may not work. Visually examining molecular details can also give us clues about ways to improve a structure's properties. We can later test our ideas through scientific experiments. In addition to understanding nature, we can also appreciate it's beauty. A really neat aspect of some molecular structures, formed from repeating protein chains, is how their symmetry creates art. Both aHLA, and MspA, show clear patterns of organization with respect to charge and position of the amino acids. Nanopore sequencing - Wikipedia - contains the references to the articles used in this post. The MspA (MMDB:26671, PDB:1UUN) and aHla (MMDB:91767, PDB:3ANZ) structures were obtained from the MMDB database webpage. The PDB file corresponding to the biological unit was opened directly into Molecule World on the iPad. NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, DC: The National Academies Press. - Log in to post comments Can we conduct experiments to found the sequence of DNA or RNA or protein using the bio nano physiochemical methods ? That meaning looking for the nanoenergies of the compounds and chemical changing in the nanoenvironment ? We can together invest what you have achieved with the introduction of new variables. Thanks for Sharing your Valuable information New Age Bio Sciences
Learning ObjectivesBy the end of this section, you will be able to: - Explain how a mass spectrometer works to separate charges - Explain how a cyclotron works Being able to manipulate and sort charged particles allows deeper experimentation to understand what matter is made of. We first look at a mass spectrometer to see how we can separate ions by their charge-to-mass ratio. Then we discuss cyclotrons as a method to accelerate charges to very high energies. The mass spectrometer is a device that separates ions according to their charge-to-mass ratios. One particular version, the Bainbridge mass spectrometer, is illustrated in Figure 11.19. Ions produced at a source are first sent through a velocity selector, where the magnetic force is equally balanced with the electric force. These ions all emerge with the same speed since any ion with a different velocity is deflected preferentially by either the electric or magnetic force, and ultimately blocked from the next stage. They then enter a uniform magnetic field where they travel in a circular path whose radius R is given by Equation 11.3. The radius is measured by a particle detector located as shown in the figure. Since most ions are singly charged measured values of R can be used with this equation to determine the mass of ions. With modern instruments, masses can be determined to one part in An interesting use of a spectrometer is as part of a system for detecting very small leaks in a research apparatus. In low-temperature physics laboratories, a device known as a dilution refrigerator uses a mixture of He-3, He-4, and other cryogens to reach temperatures well below 1 K. The performance of the refrigerator is severely hampered if even a minute leak between its various components occurs. Consequently, before it is cooled down to the desired temperature, the refrigerator is subjected to a leak test. A small quantity of gaseous helium is injected into one of its compartments, while an adjacent, but supposedly isolated, compartment is connected to a high-vacuum pump to which a mass spectrometer is attached. A heated filament ionizes any helium atoms evacuated by the pump. The detection of these ions by the spectrometer then indicates a leak between the two compartments of the dilution refrigerator. In conjunction with gas chromatography, mass spectrometers are used widely to identify unknown substances. While the gas chromatography portion breaks down the substance, the mass spectrometer separates the resulting ionized molecules. This technique is used with fire debris to ascertain the cause, in law enforcement to identify illegal drugs, in security to identify explosives, and in many medicinal applications. The cyclotron was developed by E.O. Lawrence to accelerate charged particles (usually protons, deuterons, or alpha-particles) to large kinetic energies. These particles are then used for nuclear-collision experiments to produce radioactive isotopes. A cyclotron is illustrated in Figure 11.20. The particles move between two flat, semi-cylindrical metallic containers D1 and D2, called dees. The dees are enclosed in a larger metal container, and the apparatus is placed between the poles of an electromagnet that provides a uniform magnetic field. Air is removed from the large container so that the particles neither lose energy nor are deflected because of collisions with air molecules. The dees are connected to a high-frequency voltage source that provides an alternating electric field in the small region between them. Because the dees are made of metal, their interiors are shielded from the electric field. Suppose a positively charged particle is injected into the gap between the dees when D2 is at a positive potential relative to D1. The particle is then accelerated across the gap and enters D1 after gaining kinetic energy qV, where V is the average potential difference the particle experiences between the dees. When the particle is inside D1, only the uniform magnetic field of the electromagnet acts on it, so the particle moves in a circle of radius with a period of The period of the alternating voltage course is set at T, so while the particle is inside D1, moving along its semicircular orbit in a time T/2, the polarity of the dees is reversed. When the particle reenters the gap, D1 is positive with respect to D2, and the particle is again accelerated across the gap, thereby gaining a kinetic energy qV. The particle then enters D2, circulates in a slightly larger circle, and emerges from D2 after spending a time T/2 in this dee. This process repeats until the orbit of the particle reaches the boundary of the dees. At that point, the particle (actually, a beam of particles) is extracted from the cyclotron and used for some experimental purpose. The operation of the cyclotron depends on the fact that, in a uniform magnetic field, a particle’s orbital period is independent of its radius and its kinetic energy. Consequently, the period of the alternating voltage source need only be set at the one value given by Equation 11.33. With that setting, the electric field accelerates particles every time they are between the dees. If the maximum orbital radius in the cyclotron is R, then from Equation 11.32, the maximum speed of a circulating particle of mass m and charge q is Thus, its kinetic energy when ejected from the cyclotron is The maximum kinetic energy attainable with this type of cyclotron is approximately 30 MeV. Above this energy, relativistic effects become important, which causes the orbital period to increase with the radius. Up to energies of several hundred MeV, the relativistic effects can be compensated for by making the magnetic field gradually increase with the radius of the orbit. However, for higher energies, much more elaborate methods must be used to accelerate particles. Particles are accelerated to very high energies with either linear accelerators or synchrotrons. The linear accelerator accelerates particles continuously with the electric field of an electromagnetic wave that travels down a long evacuated tube. The Stanford Linear Accelerator (SLAC) is about 3.3 km long and accelerates electrons and positrons (positively charged electrons) to energies of 50 GeV. The synchrotron is constructed so that its bending magnetic field increases with particle speed in such a way that the particles stay in an orbit of fixed radius. The world’s highest-energy synchrotron is located at CERN, which is on the Swiss-French border near Geneva. CERN has been of recent interest with the verified discovery of the Higgs Boson (see Particle Physics and Cosmology). This synchrotron can accelerate beams of approximately protons to energies of about GeV. Accelerating Alpha-Particles in a Cyclotron A cyclotron used to accelerate alpha-particles () has a radius of 0.50 m and a magnetic field of 1.8 T. (a) What is the period of revolution of the alpha-particles? (b) What is their maximum kinetic energy? - The period of revolution is approximately the distance traveled in a circle divided by the speed. Identifying that the magnetic force applied is the centripetal force, we can derive the period formula. - The kinetic energy can be found from the maximum speed of the beam, corresponding to the maximum radius within the cyclotron. - By identifying the mass, charge, and magnetic field in the problem, we can calculate the period: - By identifying the charge, magnetic field, radius of path, and the mass, we can calculate the maximum kinetic energy: A cyclotron is to be designed to accelerate protons to kinetic energies of 20 MeV using a magnetic field of 2.0 T. What is the required radius of the cyclotron?
Understanding Number Systems This is a somewhat technical subject, but it is one that will come in handy when you are working with computers, so stick with me through this article and you will understand number systems. I taught this subject to Army officers when I was on active duty many years ago, and I still remember it well. I was able to get it across to my students, and I can do the same for you if you will concentrate on it with me. I recommend that you work the problems to fully understand the subject. The number system we are taught and with which we deal daily in our lives is decimal. The base of this number system is 10. We are taught early that the positional values for this number system are ones, tens, hundreds, thousands, etc. We are taught this by rote, but we are not taught the rule on how to calculate them. But that is easy. Number systems always start with the ones position. The positional value to the left of one will be one times the base of the number system or ten (1 X 10 = 10). The next positional value to the left will be that positional value times the base of the system or 100 (10 X 10 = 100). This is how the ones, ten, hundreds, thousands are calculated. Each number system has one character multiplier values in it that range from zero to one less than the base of the number system. In decimal, the multipliers are 0 - 9. When we look at the number 123, we just accept it as the decimal value, but in number system theory, it is the sum of all multipliers times the positional value for the multiplier. Follow this example: 3 X 1 = 3 2 X 10 = 20 1 X 100 = 100 Add up the numbers to the right of the equal signs (3 + 20 + 100) and you get 123. You have heard that computers use binary. This is because in electrical circuits there is an on or on off value (two possible values). The base for binary is two (2). Follow the rule for multipliers that they will be from 0 to one less than the base of the system so the multipliers for binary are zero and one. Follow the rule for determining the positional values for the system. Start at one and multiply it by the base (two) so the position to the left of the one position is two (1 X 2). The next position to the left is the two position times the base (2) or 4 (2 X 2). The next position to the left is the four position times two (4 X 2) or 8. Here are the first few positional values in binary: 256 - 128 - 64 - 32 - 16 - 8 - 4 - 2 - 1 Notice that each position is doubled the value to its right. This makes sense since the base is two and we are multiplying each positional value by two to get the value of the next position to the left. Letís look at this binary number. To convert this to decimal, we multiply the positional value by the multiplier. 1 X 1 = 1 1 X 2 = 2 0 X 4 = 0 0 X 8 = 0 1 X 16 = 16 Now add up the values to the right of the equal sign and we get 19 decimal for the binary number 10011. What is the decimal value of 111 binary? If you got 7 decimal then you understand how binary works. 1 X 1 = 1 1 X 2 = 2 1 X 4 = 4 1 + 2 + 4 = 7 Convert one more binary number - 1000000. If you got 64 decimal, you are right. A weakness of binary is that it takes so many positions to express a large value. To get around this, the hexadecimal base system was devised. This is the base 16. We abbreviate hexadecimal as "hex". Since we said earlier that the multipliers for the system were zero to one less than the base of the system (16), how can we get one position multipliers when we only have 0 - 9 as numeric numbers? Well, we use the first six letters of the alphabet for the multipliers above nine. Here are the multipliers in hex. OK, now stick with me and remember the rules for number systems. The positional values start with one and are determined by multiplying the base by the number to get each succeeding positional value from right to left. The first positional value is one. The next one to the left is 16 (1 X 16). The next one to the left is 256 (16 X 16). The next one to the left of 256 is 4,096 (256 X 16). The next one to the left of 4,096 is 65,536 (4,096 X 16). The first few positional values of hex are: 1,048,576 - 65,536 - 4,096 - 256 - 16 - 1 You can see that we can express a very large number in hex with fewer positions than we can in our standard decimal numbering system. Letís convert a few hex numbers to decimal. Convert hex 1F to decimal. Just follow the rule and multiply the positional value by the multiplier. F (=15) X 1 = 15 1 X 16 = 16 Add 15 and 16 and the number 1F in hex is 31 in decimal. Convert 2AB hex to decimal. Just follow the rule. Remember, multiply each positional value by its multiplier. B (=11) X 1 = 11 A (=10) X 16 = 160 2 X 256 = 512 Add up the values to the right of the equal signs and you find that 2AB in hex is 683 in decimal. Why learn hex? In some instances when you are writing HTML for web pages, hex numbers are used. A two position hex number will express a number from 0 (hex 00) to 255 (hex FF). Since zero is a number, this will give 256 total values. Another reason that hex is used is that each four positions of a binary number can be expressed in one hex position so it is much easier to write a large number in hex than in binary. Letís look at the binary value 1111. If you use the rules, this will be 1+2+4+8 = 15. This can be written as "F" in hex. (the multiplier "F" in hex is equal to decimal 15. Letís convert another number in binary to hex. Start at the ones position and break the binary number into four position groups. Express each four position group as its hex value Binary 1011 1100 1001 0111 Hex B C 9 7 To double check that the two are equal follow the rules and convert both number systems to decimal. If you came up with 48,279 you are right. Octal was used in computers until the hexadecimal numbering system was invented and "hex" has largely replaced it, but you may still run into situations where the octal numbering system is still used. Just remember the rules from this article and you will have no problem understanding it. Copyright 2006 John Howe, Inc. About the Author: John V. W. Howe is an entrepreneur, author, inventor, patent holder, husband, father, and grandfather. He has been involved in entrepreneurial activities for over 40 years. He founded www.boomer-ezine.com and www.retirement-jobs-online.com to help Boomers (baby boomers) become entrepreneurs when they retire.
Try Wikispaces Classroom now. Brand new from Wikispaces. Pages and Files Projects Page 2012-2013 experimental design page Personal Learning Network Step 1 Brainstorming a Question Step 2 Variables and Hypotheses Step 3 Design Your Experiment Step 4 Plan your experiment Step 5 Do your experiment Step 6 Background Step 7 Analyze Your Data Step 8 What does it mean? Step 9 Prepare for Presentation Kennett Middle School Josiah Bartlett School Ball size and bounce height Size of Ball and Height of Bounce This experiment will show comparisons that will determine if the size of the ball will affect the height of its bounce. Does the size of a ball affect the height of its bounce? Comparing rubber balls of different sizes which one will bounce higher? I think the larger ball will bounce higher. Graph of Hypothesis Independent Variable: Size of a ball Dependent Variable: Bounce height Variables That Need To Be Controlled: height of drop, number of trials, ball air pressure, ball position from which to determine bounce height, consistent assistants. Vocabulary List That Needs Explanation Air pressure at sea level is the equivalent of having many blankets, which would feel very heavy. If you have only one blanket though, it would feel very light, and this is like the air pressure at the top of a mountain. Each layer of air presses down on the layers below, and so the greatest pressure is at ground level where we have the maximum amount of air above. If we go above the height of mountains and into the stratosphere, the pressure will decrease until it reaches about zero, as here there is hardly any air above it. Ensure all balls have the same air pressure using bike pump with gauge. Drop each ball from the same height 10 times and measure each bounce height. The balls will be measured each time with a tape measure. Potential Problems And Solutions: A ball might have less air in it, therefore ensure that all balls have the same air pressure prior to experiment. The ball may get damaged during the drops, so checking the balls for damage would determine if a new ball would be necessary. The assistants may witness different bounce heights due to perception, so should agree which part of the ball to look at for height of bounce (bottom of the ball as it rebounds). Safety Or Environmental Concerns: (add the correct headings from the experimental design page Number Of Comparison Categories: This experiment will compare the rebound height of three different sized sport balls. Number of Comparison Samples: There will be ten different samples of rebounds for each size of ball. Number Of Observation In Each Sample: The rebound height of each series of trials for each ball will be documented. When data will be collected March 1, 2013 Where will data be collected?: Outside of the science room (B10) from the top of the second floor stairwell. Resources and Budget Table Where I will get this Step 1: Set up the tape measure with centimeter-side up directly against the wall to measure the bounce height. Step 2: Using an air pressure gauge, measure the air pressure of each ball. Step 3: Determine the desired air pressure and inflate each ball to that level, testing air pressure at each interval. Step 4: Using a flexible tape measure, determine circumference of each ball. Step 5: D rop each ball one at a time from the top of the stairs from the exact same height (e.g. outstretched arms, shoulder height). Step 6: Assistants record the height of each ball bounce. Step 7: Drop each ball 10 times and record the heights. All three balls together Measurement stick with the project 2/26/13 Do experiment 3/1/13 Experiment due 3/7/13 Analysis due 3/15/13 Discussion due 3/22/13 poster due 3/29/13 Science Fair The average bounce height for the smallest ball (58.7 cm) was 166.6 cm, which was a higher average bounce than both of the other larger balls. There was a smaller difference between the smallest ball and the medium-sized ball average bounce height (3.1 cm difference), than the difference between the medium ball and the largest ball average bounce height (10.7cm). The difference in circumference between the smallest ball and medium ball was 5.9 cm, whereas the difference in circumference between the medium and largest ball was 50.6 cm. All Raw Data see data table Devon Russell's Ball Bounce Height Data 58.7 cm Ball Bounce 64.6 cm Ball Bounce 115.2cm Ball Bounce The larger ball (115.2 cm) average bounce height was 152.8 cm. The ratio of average bounce over size (152.8/115.2) was 1.326. The medium ball (64.6 cm) average bounce height was 163.5 cm. The ratio of average bounce over size (163.5/64.6) was 2.531. The smallest ball (58.7 cm) average bounce height was 166.6 cm. The ratio of average bounce over size (166.6/58.7) was 2.838. The experiment demonstrated that the size of a ball did affect the height of its bounce. The smaller the ball is, the higher it bounced. If this type of experiment were to be repeated, there would be different types of balls with the same texture but in different format (e.g. solid rubber balls of different sizes versus basketballs of different sizes). Benefit to Community and/or Science The people manufacture balls might be interested in the information about the different types of balls. The experiment will use three different types of balls. The balls need to be the same texture. The balls should be dropped two times during each trial. Their should be 3 trials for each ball This Science Fair project set out to answer whether the size of a ball affects the height of its bounce. My original Hypothesis was that the larger ball would bounce higher than a smaller ball. help on how to format text Contributions to https://mwvsciencefair.wikispaces.com/ are licensed under a Creative Commons Attribution 3.0 License Portions not contributed by visitors are Copyright 2014 Tangient LLC Turn off "Getting Started"
Africans in America: 1600–1900 Africans in America: 1600–1900 Africans in America: 1600–1900 Debra Newman Ham Some scholars, like Ivan Van Sertima in his book They Came Before Columbus (1976), claim that Africans had traveled to the New World long before the Europeans discovered its existence. Historical accounts affirm that Africans sailed with the Europeans as they explored and began to conquer the peoples of the Americans in the late fifteenth and sixteenth centuries. Perhaps the most famous of the African explorers was Stephen Dorantz or “Estevanico,” who pioneered an expedition in 1539 from Mexico into what is now Arizona and New Mexico. Estevanico, a Muslim from Morocco, had also traveled with “Cabeza de Vaca” to Florida in 1528. Settlements utilizing the enslaved African laborers in the Caribbean and Latin America predated North American communities by almost a century. The resiliency of the people kidnapped from the African continent by European slave traders is obvious even from the earliest historical documents. Ship logs and slave trading records from the sixteenth to the mid-nineteenth centuries show people of color not only as victims of a cruel system of slavery and oppression, but also as actors who found effective ways to cope with the confines of enslavement. Even on board the vessels of their captivity, some of the millions of captured Africans mutinied against the European crews and took command of the ships that held them. Others unsuccessfully tried to regain their freedom by jumping ship or fighting their captors. Unfortunately, the superior technology of the European slavers, both in weaponry and transportation, subdued the African captives as effectively as it did the Native Americans in the New World. An eyewitness and victim of the trade, Olaudah Equiano, wrote in his 1789 autobiography that, when he was captured and sold at 11 years of age, some African men actually jumped off the ship on which they were captives to try to swim to shore, but crew members on the slave ship jumped overboard to recapture and secured the slaves for fear that their valuable cargo tried to flee again. The efforts of Africans to rebel or jump ship were so frequent that, during the centuries of the slave trade, many captains would not allow the Africans on deck even for exercise. The slave trading vessels had low decks, which allowed the chained captives to sit up but not stand. Some large slave ships carried between 500 and 900 Africans of all ages and both sexes. In 1862, President Abraham Lincoln hanged a notorious slave trader, Nathan Gordon, who was caught near the Congo River with a vessel holding 897 Africans. Due to the cramped conditions, human disease, and filth, many Africans lost their lives as they crossed the Atlantic. Many of the European crewmen also succumbed to diseases. The Atlantic Ocean route between Africa and the Americas was often referred to as the Middle Passage, and slavery in American was called the Peculiar Institution. Scholars estimate that the number of Africans victimized by the slave trade range from 9 to 25 million. The Atlantic slave trade continued for centuries because the African laborers who survived were usually strong and familiar with all aspects of tropical agriculture. They proved to be invaluable workers, and for some reason, Africans did not succumb to European diseases at the same rate as Native Americans. The trade in humans and the labor of those African captives in the New World netted untold riches to their European and American captors for many generations. The first 20 Africans in British America were sold by a Dutch captain as indentured servants—people who served the one who purchased their passage for an agreed term, usually four to seven years—in Jamestown, Virginia, in 1619. The settlement, founded in 1607, was only a few years old when the Africans came. Within a few decades, though, most of the Atlantic seaboard colonies were importing Africans, not as workers but as slaves. As the Atlantic coastal settlements increased in number and population in North America in the seventeenth century, European ships with Africans for sale appeared regularly. Planters who were looking for a cheap labor force proved ready customers. Africans were in great demand by the colonists, and British merchants continued to bring them in large numbers. Between 1675 and 1695, about 3,000 Africans entered the Chesapeake region alone to be put to work mostly on the tobacco plantations of Maryland and Virginia. In the seventeenth century, soon after each colony was settled, ships carrying Africans for slaves began to appear. Planters used Africans as forced laborers on their tobacco, rice, sugar, indigo, and wheat plantations. Africans also constructed buildings, roads, and forts, and also performed many household tasks. Africans were used in so many capacities in turning the American terrain into cities and plantations that the European settlers who could afford to do so continued to purchase the slaves in large numbers. Most colonial historians acknowledge the vital role played by African slaves in the planting of settlements in British America. Geographically, the Africans came to the British colonies principally from various West African territories and ethnic groups stretching from the region of the Gambia River and reaching around the coast to present day Nigeria. Men and women, with complexions that ranged from brown to black, brought with them to America numerous languages and customs, including their own African religious beliefs. Occasionally, Muslims were among them and sometimes Africans came from regions as far away as Madagascar. Slave owners often commented on the scarification—slave owners called them “country markings”—the Africans had on their bodies. These markings were on their faces, arms, or torso and had a variety of distinctive designs, sometimes for ethnic identity but also for body ornamentation. African music, drums, and singing frightened whites, who soon outlawed many African practices—especially drumming. Africans wore little clothing when they came from the ships, sometimes only strings of beads. Many had filed teeth. Some had hair plaited in elaborate styles, while others had shaven heads. After a time, Africanized English became the language that the Africans and their owners all understood. The Africans received new names, and learned their work and the stringent boundaries within which slave life was confined. Owners worked hard to break the Africans’ rebellious spirits and restrict their movement. By the eighteenth century, the American colonies were beginning to see a new generation of Africans, born in America, that did not know their parents’ African homelands first hand. Beginning in the 1700s, the enslaved population began to grow naturally and was consequently composed of both Africans and African Americans. In a few generations, Africa became simply a distant and often misunderstood land to most African Americans. The Constitution of the United States outlawed the African slave trade on January 1, 1808, but the law was largely ignored. Even with African captives still coming to America in smaller numbers until the Civil War, it was the American-born population that dominated the cultural life of the enslaved. With the invention of the cotton gin at the turn of the nineteenth century, cotton production began to climb and the value of enslaved people of color multiplied exponentially. Cotton production intersected with the growing textile industry in Great Britain and the New England states and led to revolutionary production rates. By the Civil War, most slaveholders in the South had only a few slaves, but on the large plantations, hundreds of enslaved Africans were producing more cotton than anywhere else in the world. As slave property became increasingly valuable, slaveholders were more strongly determined to protect their right to hold human property. In 1790, African Americans made up about one fifth of the nation’s population and by 1860, there were four and a half million people of color—enslaved and free—in the United States. Although the new government of the United States was ambivalent about the rights of free people of color and unanimous in the denial of rights to slaves, the Constitution of 1787 allowed southern states to count three-fifths of the enslaved population to determine the number of members from their states in the House of Representatives. Early accounts of American history provide glimpses of the lives of a few of the Africans. Ayubva Suleiman Dially was a well-educated Muslim merchant who was born about 1700 in an area located in what is now in Mali. He was captured after he himself had traded two other Africans to a British merchant. He was taken to Annapolis, Maryland, where he was sold. He worked on a tobacco plantation for two years before he was rescued, taken to England, and then finally allowed to return to his home. Charles Ball, a slave sold into the cotton kingdom from the state of Maryland, said in his autobiography (1859) that after the sale of his mother, his master also decided to sell his father to a southern slave dealer. Ball said that his grandfather, an African who originally came to Charles County in 1730, secretly went to his son’s cabin, gave him some cider and parched corn, prayed “to the god of his native country” to protect his son, and told him to run away. Ball never saw his father again. In Tobacco and Slaves (1998), Allan Kulikoff uses records of several Chesapeake region plantations to show the gradual changes in the growth of the enslaved population. On the Edmond Jennings plantation in Virginia in 1712, almost all the workers were Africans. By 1730, nine out of 10 black men, and almost all of the black women, working on the Virginia plantation of Robert Carter were born in Africa. However, thereafter, the enslaved population began to grow naturally and was composed of both Africans and African Americans. In a few generations, Africa was a land most people of color in America had never seen. Presidents George Washington and Thomas Jefferson often instructed the overseers of their plantations not to drive the enslaved women so hard that they would miscarry or be unable to bear children. Every African American meant more wealth and an increased workforce for their owners. Work of enslaved Africans varied by region. In the North, slaves generally worked as household servants, or as workers on small farms, in mines, or as crafts persons of various sorts such as seamstresses, caulkers, coopers, smiths, and cooks. In the South, owners used slaves in a wide variety of duties for the maintenance of small farms and large plantations. Many of the records of the founding fathers of the United States clearly show their involvement with slavery and the slave trade, particularly their dependence on slave labor to make large land holdings maximally productive. Edwin Morris Betts, editor of President Thomas Jefferson’s Farm Book (1953), stated that Jefferson was never able to eliminate slaves from his economy, “because to have done so would have destroyed the chief support of all of the activities of his plantation.” The papers of both Jefferson—who was brilliant, but not frugal—and President James Monroe demonstrate that they often needed to sell or hire out slaves to meet their financial obligations. Whether one looks at Virginia plantations such as West-over, Mount Vernon, or Monticello, or large estates in any other state in the South, it was largely African Americans who were responsible for the construction of those lovely plantation houses with their sturdy outbuildings, well-manicured gardens, and productive fields. In many areas of the North and South, people of color aided in the defense of their communities in Indian wars unless they had escaped to Indian tribes, in which case they fought against the settlers. The Papers of the Continental Congress included numerous letters about the Seminoles in Georgia and Florida who aided and abetted African runaways. Although the vast majority of African Americans—male and female—did labor in the fields, W. E. B. DuBois wrote in The Negro Artisan (1902) that a small percentage of both slaves and free blacks in the South also worked as artisans who toiled in tobacco factories, made barrels, ran steamboats, labored as masons, and specialized in many other areas. Colonial newspapers included many listings for the sale of bondspersons in which the skills of the enslaved persons are described. Although slaves who were trained as artisans usually utilized their skills on their owners’ plantations, it was not uncommon for enslaved artisans to be hired out to other plantations. Men performed various services such as blacksmithing, carpentry, hostelry, and coopering. Women were sometimes hired out as maids, cooks, hairdressers, milliners, and seams-tresses. Those who hired the bondsmen gave their owners payment for the slaves’ service, but the artisan usually also received a small sum. Many industrious slaves would scrupulously save the small amount they received until they had earned enough to purchase their freedom at an amount stipulated by their owners. With any additional funds, they subsequently purchased their spouses and children. Sometimes, because the children followed the legal status of the mother, men would purchase their wives first, and then themselves and their enslaved children. Slaves had no rights, a truth U. S. Supreme Court Chief Justice Roger B. Taney—himself a Maryland slaveholder—reinforced when he stated in the 1857 Dred Scot decision that blacks had no rights that whites were bound to respect. Therefore, an owner did not have to agree to sell or give the slave a percentage of their hired wages, although many did. Some owners bought enslaved laborers for the purpose of hiring them out. Bondspersons could not vote, testify against whites, bear arms, or claim any of the benefits of a U.S. citizen. However, some states, like Louisiana and South Carolina, afforded some privileges to mulattoes—those of mixed African and European ancestry—that were not allowed to enslaved blacks. The ex-slave narratives, gathered in the 1930s by the U.S. government’s Works Progress Administration, document the slaves’ longing for freedom and illustrate the coping methods they used while they were treated as chattel, or property, by the perpetuators of the “peculiar institution,” as the American slave system was called. These records document how eagerly these people of color embraced first the hope and then the reality of freedom. By the end of the Revolutionary War, most northern states had provided for the emancipation of slaves in their boundaries. The few northern states that did not accomplish this by the end of the Revolution did so within a few decades afterward. So, as the number of slaves was diminishing in the North, by the time of the Civil War, more than half of the population of Virginia [Image not available for copyright reasons] was made up of African Americans, the vast majority of whom were slaves. In South Carolina, the slave population was more than 400,000 and the white population was fewer than 300,000. The 1860 census indicates that the total number of African Americans in the United States was 4,441,830—of whom 3,953,760 were slaves and 488,979 were free—and there were 26,922,537 whites. Famous slave mutinies and revolts dispel the view that African slaves were docile or content with their fate. Fear of slave revolts was quite common in the British American colonies from the earliest days of settlement. A perusal of any colonial newspaper indicates that runaways, acts of slave resistance, and fear of slave rebellions were widespread. Especially after the successful rebellion of Afro-Haitians over the French colonials at the turn of the nineteenth century, white slave owners experienced a widespread dread of slave reprisals. A collection of reports about slave revolts dating to the early eighteenth century, entitled An Account of Some of the Principal Slave Insurrections by Joshua Coffin of the American Anti-Slavery Society, was published in 1860. For example, in the spring of 1741, a series of fires broke out in Manhattan. Many believed that these fires were the work of rebellious slaves. Hysteria in the city led to the arrest of numerous enslaved persons. Between May 11 and August 29 of 1741, 30 black men and four whites were executed. About 100 more black men were arrested and 72 were banished from the colony. As cultivated land increased in acreage, the size of the slave population sometimes grew to equal or exceed the number of whites in some southern states. Slave-holders realized that a unified revolt by those held in bondage could signal doom for their owners. Fears increased in 1829 when a free black man in Boston named David Walker wrote a pamphlet entitled (in part) Walker’s Appeal, in Four Articles; Together with a Preamble to the Coloured Citizens of the World. The pamphlet called for blacks to rise up and overthrow their oppressors. Walker argued, “Look upon your mother, wife, children, and answer God Almighty; and believe this, that it is no more harm for you to kill a man, who is trying to kill you, than it is for you to take a drink of water when thirsty.” The pamphlet caused much alarm in the South and was outlawed in various states. In 1830, the American Colonization Society’s publication, The African Repository, reported that four free black men in New Orleans were arrested for circulating “the diabolical Boston pamphlet.” The governor of Virginia, John Floyd, cited Walker’s pamphlet as one of the causes of a major slave revolt in 1831. Small-scale slave revolts and plots were relatively common. Occasionally, however, revolts reached alarming proportions. This was particularly true with the Nat Turner insurrection in Southampton, Virginia, in 1831. Turner, who felt that God revealed to him the method of liberating the slaves, told only a few trusted companions about his plan because he understood that rebellions often failed because someone informed the authorities. Turner’s strategy was to go to one household at a time, kill all the whites, free the slaves, and thereby add to the number of those who were in his rebel brigade. Before the whites stopped Turner and his followers, about 60 whites had lost their lives. Subsequently, the terrified state of Virginia government hanged Turner, but not before he dictated his confessions, which were subsequently published. Many analyzed the reasons for the uprising and the methods that should be used to prevent similar bloody occurrences. Every state in the South that had not already done so passed laws forbidding anyone to teach African Americans to read and write. A free black North Carolinian who later became a U.S. senator after the Civil War, Hiram Revels, wrote in a biographical sketch that, before the Turner insurrection, free people of color in North Carolina were allowed to vote, discuss political questions, have religious meetings, and pursue their education, but that after the revolt, the North Carolina legislature passed laws depriving free blacks of all political, religious, and educational rights and privileges. Slaves’ freedom of movement was further curtailed all over the South after the Turner revolt. They had to carry passes and could be interrogated by any white person. The manumission (emancipation) of slaves became illegal in many states, and blacks who were already free found it even more difficult to live in peace in the United States. It was from this period that all southern states, which had not done so previously, forbade teaching enslaved persons to read and write. Probably the most famous mutiny of captured Africans was on board the Spanish vessel, Amistad. After the sale of Africans in the Caribbean in 1839, Africans were loaded on board the Amistad. The Africans succeeded in murdering the white crewmembers except a few, who were ordered to steer the ship back to Africa. About 50 Africans led by a Mende warrior named Cinque forced the crew to comply during the day, but at night the crew sailed the ship to the northwest, eventually landing off the coast of New York, where local authorities captured the Africans. The case caused great controversy, and several important and volatile issues presented themselves. Should the U.S. government collaborate in the slave trade by returning the Africans to the owners of the vessel? Should the government hold slaves and thereby become a slave owner? Should it sell the Africans as slaves and consequently become a slave merchant? Or, the most controversial alternative of all, should the United States free the slaves and thereby become an emancipator? Southerners and northerners had debated the issue of slavery at great length during the Constitution Convention in 1787. The case remained an explosive issue during ensuing years in Congress as the controversy over human property led to passionate arguments on both sides of the issue. As new states joined the union, proand anti-slavery advocates worked hard to keep the number of slave states and free states equal. The Amistad case added more fuel to the controversy. The case went all the way to the Supreme Court. John Quincy Adams served as the sixth president of the United States and as a member of the House of Representatives where he tirelessly affirmed the right of abolitionists to air their cause. Because of this, he was asked to defend the Amistad Africans. The former president presented a series of arguments so compelling that the Court freed the Africans and missionaries, and well wishers helped the Africans who had survived the litigation process to return to West Africa. Although enslaved African Americans resisted slavery in many ways, the most common method was to run away. Sometimes fugitives fled into areas unsettled by Europeans, other times they were able to ally with Indians. Occasionally, blacks were able to form communities for runaways, called “maroons,” in swamps or backwoods areas. Many blacks ran away during the Revolutionary War. Some simply sought freedom elsewhere. Others fled to the British troops—both during the Revolution and the War of 1812—who hid them from their owners and took many blacks with them as they moved to their next battle or troop evacuation. Pennsylvania began to abolish slavery through its Gradual Abolition Act in 1780. That meant that many enslaved people in the upper South lived very close to Pennsylvania communities where there was a free black population where they could hide. White and black abolitionists helped many enslaved people through the Underground Railroad, which was, in truth, neither underground nor a railroad. It was a series of secret travel routes and hiding places established for the purpose of guiding runaways from the slaveholding states to the northern states or to Canada. Hundreds of runaways smuggled to the North attempted to blend into the large free black communities in New York, Baltimore, Washington, D.C., Philadelphia, and cities in other states. Owners invested a great deal of their resources to buy enslaved people and to see to their basic needs. They depended on slaves’ forced labor for their livelihood. For this reason, owners were very concerned when their human “property” ran away. There is little specific information about the number of runaways during the two and a half centuries of slavery. One census statistic shows that the number of runaways in Maryland for the year from June 1849 to June 1850 was 279. Barbara Fields in her book Slavery and Freedom on the Middle Ground (1985) states that this was probably a low figure because fugitives would, of course, be unwilling to admit their status to a census taker. Even using a low estimate of 300 runaways a year for 250 years means that possibly 75,000 slaves escaped from Maryland. Underground Railroad conductor Harriet Tubman claimed to have led over 300 slaves out of Maryland. There were thousands of runaways in northern cities and Canada. Pre-Civil War newspapers list hundreds of advertisements, which usually give detailed descriptions of the runaways, including clothing and physical markings or defects such as scars. In case the runaways tried to pass as a free person and seek work, the owners’ listed the fugitives’ skills such as fiddling, cooking, sewing, or blacksmithing. Most of the runaways were males who traveled alone, but there were also females and family groups who fled to freedom. Many of the runaways, like Frederick Douglass, moved further north than Pennsylvania. In 1850 when the U.S. Congress passed the Fugitive Slave Law making the penalties more severe for those who aided runaways, many fugitives living in northern cities moved into Canada. In Black Abolitionists (1970), Benjamin Quarles states that over ten thousand fugitives fled into Canada in 1850 because of the law. Yet, the exodus of runaways from the South did not cease. The number of fugitives in Maryland caused many white planters to abandon the use of slave labor in the years before the Civil War. As northern abolitionist sentiment began to grow, accounts of daring slave escapes were extremely popular. One of the most popular related to the escape of an enslaved tobacco factory worker named Henry Brown. Henry Brown got his nickname “Box” when he mailed himself from Richmond, Virginia, to the Philadelphia, Pennsylvania, Antislavery office in 1849 to escape from slavery. He had a friend build the crate, nail him inside with only some water to drink, and ship him by rail and boat to Philadelphia. His method of escape was so unique that his story was told over and over again. Brown, who was unlettered, got an abolitionist named Charles Stearns to write down his autobiography for him. It was first published just several months after his escape and revised and republished in England in 1851. A husband and wife team, William and Ellen Craft, also gained great celebrity for their Christmas escape in 1848. Ellen, who was very light skinned, dressed as a man, and her husband, William, who had a brown complexion, pretended to be her slave. They took public conveyances to Philadelphia and appeared at the Underground Railroad office of William Still, safe and sound. Not all runaway accounts were successful or thrilling, but all were daring. Frederick Douglass’ fiancée made him a sailor uniform; he borrowed a black sailor’s identification papers and took the train to Philadelphia. From the seventeenth century on, there was a growing free black population in the British colonies. This population grew quickly in the antebellum years. African Americans were usually emancipated for diligent work, good conduct, familial connections, or commendable service. The methods for manumission included court actions, instructions in owners’ wills, self purchase, purchase of one’s own family members’ freedom with money earned when hired out, governmental decrees, or rewards for military service. Several thousand gained their freedom serving alongside their owners during the colonial wars. Thousands more fled to freedom behind the British lines during the Revolutionary War and the War of 1812. Continental Army Commander, and later the first president, George Washington, who was himself a prosperous slave owner, mulled over the possibility of allowing blacks to serve as members of the regular troops in the Continental Army. As he vacillated, the British invited enslaved blacks to join with his majesty’s troops so that they could gain their freedom. Ultimately, free blacks and slaves fought on the side of the American patriots, but thousands more fled to and aided the British. Those servicemen who were formerly enslaved gained their freedom as a result of their military service in the Continental Army. In addition to their freedom as a repayment for services rendered, the British took former slaves with them to Canada, Jamaica, and England. In 1787, concerned British citizens repatriated hundreds of Africans from each of these regions to West Africa where they established the colony named Sierra Leone. Free blacks were rarely accorded the same privileges as white citizens. States changed their laws relating to free blacks depending on the political climate and, more importantly, the size of the African American population. For a brief period, some free blacks had the right to vote, but the law was later rescinded. Pennsylvania, for example, allowed free black males to vote until 1837 and did not allow them to vote again until after the passage of the Fifteenth Amendment in 1866. Free blacks usually could not carry firearms or testify against whites in court. Free blacks, especially children, lived under the threat of being beaten or kidnapped by whites who would sell them into slavery. One of the reasons that whites formed the abolition societies was to try to protect free blacks from kidnappers. States passed and repealed laws prohibiting blacks from assembling as groups in public places without whites being present. Governments often vacillated about the right of free blacks to hold and bequeath property. Whites often sought to restrict the type of work blacks could do because they did not want to compete with them. In Pennsylvania, black men were barred from certain crafts. At various times, state legislatures tried to pass laws prohibiting blacks from reading abolitionist literature, operating boats, obtaining licenses for peddling, participating in certain trades, or having or driving vehicles such as hacks, carts, or drays. There was also an effort keep free blacks from owning dogs. Slaveholders’ motives for many of the laws, particularly prohibiting free blacks from owning conveyances, was to prevent free blacks from aiding runaway slaves. There were also stringent laws about intermarrying with whites. In spite of numerous restrictions, free blacks formed their own churches, schools, benevolent societies, and businesses. Many churches were a part of larger denominations, which met periodically in various states to discuss both religious and political matters. Census records indicate that increasing numbers of free blacks could read and/or write. Free persons of color worked as domestics, small farmers, innkeepers, street vendors, ship caulkers, stevedores, sailors and boatmen, draymen, barbers, team-sters, blacksmiths, and liverymen. Blacks who had purchased their freedom were usually able to do so because they had earned money with their skilled labor. Some free blacks, like astronomer Benjamin Banneker and preacher Daniel Coker, were able to record their own experiences for posterity. Banneker was able to publish an almanac in the 1790s and aid in the planning of the District of Columbia, and Coker became one of the first emigrants to go back to Africa with the American Colonization Society. Blacks within and without the shackles of bondage were successful at a variety of business ventures and credited with numerous inventions. Harriet Beecher Stowe, author of the 1851–1853 bestseller, Uncle Tom’s Cabin, even argued that it was not Eli Whitney but an enslaved black man who developed the cotton gin to separate the seed from the cotton; that process revolutionized cotton production in the United States. In addition to this disputed claim, there is documented evidence of a number of scientific inventions patented by blacks after emancipation. James Forten of Philadelphia, a Revolutionary War veteran, invented a sail hoist, a device that made it easier to maneuver the huge sails on ships. He ran his own sail loft, became quite wealthy, and eventually was a large supporter of the emancipation newspaper The Liberator, edited by militant abolitionist William Lloyd Garrison. Free people of color in their quest for full political rights were extremely articulate in their protests against the Peculiar Institution, but they also began to explore alternative solutions to racial problems. One example was Paul Cuffee, a Massachusetts free man of African and Native American ancestry, who learned to articulate the doctrines of freedom for oppressed African Americans. He eventually became an active exponent of African colonization in general and of the British Sierra Leonean scheme in particular. Born in Massachusetts before the Revolutionary War, Cuffee was of mixed Native American and African parentage and was the seventh of 11 children. As a youth, he was able to get some education and then found work as a sailor, as a laborer in shipyards, and as a shipbuilder. He saw opportunities in this line of work and seized them. By 1780, he had built a ship of his own and by 1806 he owned one large ship, two brigs, and some smaller vessels and was able to engage very profitably in trade. In spite of his accomplishments, Cuffee still regularly confronted racial prejudice. Although his wealth continued to grow, as did his contributions to the Massachusetts government through taxes, he could not vote and his children could not attend public schools. Cuffee knew that the colonies had protested against Great Britain for taxation without representation during the Revolutionary War, and it seemed to him that the colonies were guilty of the same injustices by taxing free blacks without letting them reap all of the benefits that tax dollars earned for other citizens. In defiance, Cuffee and his brother refused to pay their taxes. Subsequently, Cuffee financed a Quaker school, which he opened not only to black children but also to all children in his community. Even when the Massachusetts courts abolished slavery in 1783, the social, economic, and political problems that blacks encountered remained complex. Cuffee reasoned that the best avenue was for blacks to reestablish contact with West Africans for the purpose of colonization and trade. He reasoned that blacks would be able to make great commercial gains if they could work together to establish a shipping network of their own. Additionally, if there were blacks who felt that the stigma attached to them was too severe, they could move to Sierra Leone. He thought that blacks could contribute both civilization and Christianity to their ancestral homeland. During Cuffee’s 1811–1812 visit to Sierra Leone, he formed the Friendly Society with an African American emigrant named John Kizzell for the purpose of encouraging African American emigration and trade. Cuffee was unable to interest anyone in financing his Sierra Leone colonization scheme. Consequently, he determined that he would finance it himself, but encountered one major problem. During the time he was formulating his plans, the United States and Great Britain were involved in the War of 1812, and Americans were not permitted to trade with England or her colonies. In 1814, Cuffee petitioned the U.S. Congress to lift the embargo against trade with Sierra Leone so that he could begin his venture. His petition passed the Senate, but was struck down by the House. Finally, after the cessation of hostilities in 1815, and at a personal expenditure of $4,000, Cuffee took nine free black families, totaling 38 individuals, to settle in Sierra Leone. The emigrant families consisted of nine adult males, 10 adult females, and six male and 13 female children. Although he had difficulty marketing his trade goods when he returned, Cuffee became even more determined that black Americans needed to emigrate if they were to achieve true independence and racial dignity. Many free blacks as well as some whites received Cuffee’s emigration plan with enthusiasm, but few blacks were willing to give up their American citizenship. Some emigrationists began to formulate ideas for the colonization of black Americans along the lines that Cuffee had planned. Others envisioned trade ventures, and still others wanted to evangelize Africans. Many whites simply hoped to rid the United States of its free black population. Robert Finley, a New Jersey clergyman, was alarmed by the fact that the free black population in New Jersey quadrupled from 1790 to 1820. Disturbed by the extent of their poverty and political impotence, he feared that nothing would alter the inequality of the treatment of blacks in the state. Finley believed that, “Everything connected with their condition, including their colour,” was against them. He felt that the “methodical colonization of free Negroes would both improve their condition and solve the larger problem of their future in America.” Hence, he proposed a colony similar to Sierra Leone and advocated federal assistance for the colonization plan. In December of 1816, Finley visited Washington to see if he could get support. There he met with a number of influential men, including Elias Caldwell, Bushrod Washington, Henry Clay, John Randolph, and Daniel Webster, as well as about 45 others. The responses of those who met with Finley were varied. Clay, a slaveholder who felt that free blacks were a threat to the institution of slavery, proposed “to rid our country of a useless and pernicious, if not dangerous portion of its population.” Some of the delegates proposed an African colony that would help in the suppression of the slave trade. Many of the organizers were primarily concerned with the evangelization of Africa, and a few felt that a colony would give free blacks the opportunity to be truly free men. Finally, on December 28, 1816 these delegates took the title “American Society for Colonizing the Free People of Color in the United States.” Soon, the organization was known simply as the “American Colonization Society” (ACS). The newly formed Society sought to recruit Paul Cuffee to lead their first emigrant expedition, but he died before the plans for the first group of settlers could be formulated. However, Kizzell and the Friendly Society supervised many of the arrangements in Africa for the Colonization Society’s first emigrants. Black leaders in Philadelphia, led by James Forten, Richard Alien, Absalom Jones, and Robert Douglas, immediately held a protest meeting. Cuffee, they contended, had been working to help black people, but that the Colonization Society was definitely against the interests of black Americans. Finley, however, assured the group that the Society’s motives were not sinister, and for a few months black protests were quieted. Nonetheless, so many of the organizers of the society had made their anti-free black and anti-emancipation views public, and few blacks expressed any willingness to apply for colonization. In addition to criticism by blacks, the Colonization Society encountered considerable resistance from the federal government to pleas for funding their projects. Consequently, funds for the colonization scheme had to be solicited from the public. Thus, the ACS had to establish an African settlement largely at its own expense. Samuel J. Mills, a missionary, and Ebenezer Burgess, an ordained minister, raised funds to travel to West Africa to look for a settlement site. On November 5, 1817, they were appointed agents of the Colonization Society and sailed for Africa. After stopping in England for a month to consult with organizers of the Sierra Leone colonization project, they sailed for Africa on February 2, 1818. They toured Sierra Leone and the surrounding villages for six weeks with Kizzell as their guide and interpreter. They decided on Shebro Island as the site for the colony. Mills died on the way home, but Burgess delivered their report on Sierra Leone to the ACS. With the aid of this report, the Society began to plan for the voyage of the first group of emigrants. Those black Americans who joined the first expedition as emigrants also worked for the U.S. government. A March 3, 1819, Act of Congress authorized President Monroe to deliver African captives taken from slave ships to U.S. agents who would be stationed on the West African coast. The emigrants were laborers hired to build shelters for the “recaptives.” In southern Virginia near the area of the Turner insurrection, hundreds of blacks were eager to move to Liberia because of the ferocity of the reaction of the white public. Yet, even in this region, more blacks were willing to stay or to move to another state rather than to emigrate outside of the country. During the entire nineteenth century, there was only a small minority of the free black population that chose to move to Liberia. AFRICAN AMERICANS’ RESPONSE TO COLONIZATION Reverend Peter Williams gave the majority viewpoint at an oration on July 4, 1830: “Though delivered from the fetters of slavery, we are oppressed by an unreasonable, unrighteous, and cruel prejudice, which aims at nothing less than the forcing away of all the free coloured people of the United States to the distant shores of Africa.” He said that he did not think that the motives of all of the members of ACS were impure. Some wanted, he believed, to abolish the African slave trade and others wanted to evangelize the Africans. Other very influential members, he argues, simply wanted to rid the nation of free blacks. Period. Williams continued his protest, stating that, ironically, the members of the Colonization Society who felt that blacks were “vile” and “degraded” also felt that these same black people would have a beneficial and civilizing influence on African peoples. This type of contradiction in the Colonization Society’s literature and fundraising programs never escaped the notice of black Americans. The issue of African colonization of African Americans arose frequently during the nineteenth century and was regularly a volatile issue at antebellum African American political meetings known as the Negro Convention movement. Frederick Douglass, who felt that the whole idea of colonization was rooted in racism and Negrophobia (fear and hatred of blacks) wrote and spoke out against it on many occasions. In a North Star editorial of January 1849, Douglass lambasted the U.S. Senate about “the wrinkled old ‘red herring’ of colonization. . .” Douglass wrote: “We are of the opinion that the free colored people generally mean to live in America, and not in Africa; and to appropriate a large sum for our removal, would merely be a waste of the public money. We do not mean to go to Liberia. Our minds are made up to live here if we can, or die here if we must; so every attempt to remove us will be, as it ought to be, labor lost. Here we are, and here we shall remain. While our brethren are in bondage on these shores; it is idle to think of inducing any considerable number of the free colored people to quit this for a foreign land.” The vast majority of black Americans were adamant about remaining in the United States. In spite of all the doubt on the part of blacks and the suspect motives of some of the members of ACS, blacks left almost every year after 1820 to go to Liberia. Some blacks chose to emigrate to Haiti in the 1820s, but many were dissatisfied there and returned to the United States. The idea of Haitian emigration was renewed in the mid-nineteenth century, but Liberian emigration, though limited, was relatively constant. Some of the Liberian emigrants returned to the United States disenchanted with the new colony. However, Liberia was thousands of miles away. It took money to return to the United States, and many of the settlers had no funds. One humorous Liberian saying was “the love of liberty brought us here, the lack of money kept us here.” Indeed, it was the love of liberty that drew many free blacks to Liberia. It did not take long after the settlement of the colony for reports to begin coming to the United States about the life of the settlers. They were the reports of a small, struggling settlement. The Liberians fought against hostile indigenous people and various debilitating diseases. They suffered from homesickness. Somehow, however, there was some romance in the reports. It was clear that few whites could survive the climate and that, basically, it was black men who were building a nation. Despite the struggles of the settlers, many blacks believed that Liberia would one day be a great nation that would demonstrate to the world the prowess of the black race. In Liberia, black men could hold leadership positions, sit on juries, vote, and work for the fulfillment of their dreams. To a few black Americans, the promise of such a life, even amid the hardships and privations of the African continent, was enough to draw them away from everything familiar in their homeland. Masters wanted to emancipate their slaves, but the laws of their states tied their hands. Consequently, in order to free them, many indicated in their wills that their slaves had to emigrate to Liberia. Others gave them the option of going to Haiti, Liberia, or to a free state. For years, some slaves felt that colonization was just a scheme to kidnap blacks and sell them farther south. The small free black population during the period up to 1860, however, aided by sympathetic whites, were most outspoken—and most creative—in their protest against slavery, an institution many of them knew from firsthand experience. Sermons called for liberty, while hundreds of newspaper articles, books, poems, speeches, and tracts echoed a call for liberty not unlike that of the American colonies from their perceived oppressor in the eighteenth century—Great Britain. Wheatley in 1773 published a poem to the Earl of Dartmouth that reasoned that some who perused her “song” would wonder where her “love of freedom sprung.” She explained that she, “young in life,” had been “snatch’d from Africa’s fancied happy seat.” Wheatley’s position as a “pampered” Boston slave would have been enviable to many in bondage who endured physical and emotion abuse, but that did not squelch her longing for freedom. With the Declaration of Independence, doctrines of equality and the inalienable rights of life, liberty, and the pursuit of happiness reached the ears of the free person of color and slave alike, and the oppressed longed to throw off the oppressor. Hundreds of thousands of whites allied with free blacks to aid in the destruction of the Peculiar Institution. Quakers, for example, were speaking, writing, and petitioning in state legislatures against slavery from the eighteenth century until emancipation. In addition to formal methods of protest, grassroots networks emerged to fight against slavery. Members of both races acted as conductors on the Underground Railroad. There is a virtual avalanche of records relating to antislavery efforts by great abolitionists, white and black, in the United States. These include the writings of people like Frederick Douglass, Susan B. Anthony, William Lloyd Garrison, Harriet Beecher Stowe, Henry Ward Beecher, Mary Ann Shadd Cary, Salmon P. Chase, Martin Delaney, Theodore Weld, Francis Ellen Watkins Harper, and William and Ellen Craft, to name only a few. Antislavery and proslavery political debates divided the nation, and led to violence and, ultimately, to the Civil War. UNCLE TOM’S CABIN Galvanized by the passage of the Fugitive Slave Act of 1850, Stowe published Uncle Tom’s Cabin; or, Life among the Lowly in 40 installments from June 1851 to April of 1852 in the Washington, D.C. publication, the National Era. The story riveted the attention of thousands of readers and engendered outrage in many about the institution of slavery. Although the story centers on the mis-treatment of the pious and wise slave, Uncle Tom, many other slaves are featured in the story. The book targets even benign slave owners as partners in the crime against humanity, slavery. Toward the end of Tom’s life, his owner, Simon Legree, who specializes in cruelty, finally beats Tom severely because he knows that Tom has outwitted him in a matter relating to two runaway women. When Tom’s former master finally rescues him, Tom survives only a few miles beyond the door of Legree’s plantation. In 1851 after Stowe finished the first five installments of Uncle Tom’s Cabin, she consulted with Douglass about true stories relating to slavery that she could weave into her story. When Uncle Tom’s Cabin appeared in book form in March 1852, published in two volumes by J. P. Jewett, it sold 300,000 copies in one year. Douglass enthused, “Why Sir, look all over the North: look South, look at home, look abroad! Look at the whole civilized world! And what are all this vast multitude doing at this moment? Why, Sir, they are reading Uncle Tom’s Cabin, and when they have read that, they will probably read The Key to Uncle Tom’s Cabin.” Before 1860, more than one million copies had sold in the United States, and more than two million copies abroad, authorized and unauthorized, principally in England, but also in France, Germany, and other nations. Stowe’s novel added measurably to the polarization of abolitionist and anti-abolitionist sentiment in the U.S. and Europe. Douglass, along with other abolitionists, white and black, had spent most of their lives exposing the horrors of slavery. Most of the abolitionists exulted that Stowe’s books generated outrage against the Peculiar Institution, both nationally and internationally. An ex-slave, Josiah Henson, claimed that he was the model for Uncle Tom, although some circumstances in his life differ greatly from those of Stowe’s lead character. Stowe wrote The Key to Uncle Tom’s Cabin in 1853. In this work, she explained some of the incidents in the story and her motivations for writing them. Carl Sandburg reported in Abraham Lincoln: The War Years (1939) that, during a White House visit, President Lincoln greeted Stowe with outstretched hands, saying, “So you’re the little woman who wrote the book that made this great war.” Historian Benjamin Quarles noted that at an 1863 abolitionist’s celebration of Lincoln’s Emancipation Proclamation, the crowd yelled for Stowe to come forward to receive an enthusiastic ovation for the service she had performed by writing Uncle Tom’s Cabin. The furor over the Fugitive Slave Law of 1850, the controversy over slavery in Nebraska and Kansas, the Dred Scott Decision of 1857, and the John Brown attack on Harper’s Ferry all polarized the nation, but the election of President Abraham Lincoln in 1860 led southern politicians to finally do what they had been threatening for decades—secede from the Union. During the Civil War, black soldiers demonstrated that detractors who said they would flee in terror in the midst of a battle were wrong. Black soldiers proved as able to wield guns as they did plows, hoes, or harnesses. They worked behind the scenes as well as on the front lines with the Union troops. Thousands of enslaved blacks in the Confederacy emancipated themselves and fled to the Union encampments. African American civilians proved that they cared about their families in spite of claims that they were too negligent and immoral to care for their own homes. For example, Union chaplains and Freed-men’s Bureau officials worked tirelessly trying to reunite families that had been sold apart and aiding free people in legitimizing their marriage vows. A document in the Manuscript Division of the Library of Congress indicates that in 1863, a white Union chaplain, Asa Fiske, once performed simultaneous wedding ceremonies for 119 African American couples that had fled to safety behind Union lines. For African Americans, the right to have a family, protect spouses and children, earn an honest living, and dwell in peace became one of the driving desires for freedom from enslavement. Herbert Gutman’s book, The Black Family in Slavery and Freedom (1977), documents the vitality of African American family ties, even during slavery. As Union soldiers and northern teachers, preachers, businesspeople, and missionaries traveled into defeated areas of the Confederacy, they discovered aspects of slave life and culture hitherto unknown to them. African American spirituals, folk songs, churches, African folk traditions, and linguistic traits caused many northern observers to reassess their views about black creative ability. Because masters and mistresses feared literate slaves, every slaveholding state had passed laws forbidding African American education. This accentuated a longing for learning among the newly freed blacks that impressed almost every chronicler of the South in the period during and after the Civil War. Old and young free people of color would gather in classrooms. The old often clutched their Bibles, longing to be able to read its pages for themselves. One-room schoolhouses, poorly paid teachers, and nascent institutions of higher education sprang up throughout the South. Freedmen’s Bureau officials and thousands of white missionaries and teachers traveled throughout the former Confederacy to teach the education-starved blacks to read and write. Almost every historically black college and university was founded within five years after Appomattox. The 1900 census reports indicate that in the period between the Civil War and the turn of the twentieth century, the majority of the African American population broke the bonds of illiteracy. Although some black workers had been used in the Union Army in 1862, blacks were not actively recruited until it became apparent that the war would be long and costly. As a war measure, Lincoln wrote the Emancipation Proclamation in September 1862, declaring that all enslaved people in the confederacy should be “forever free” and providing for the use of African American soldiers in the Civil War. This document would go into effect January 1, 1853. Faced with a shortage of manpower among the rank and file, the War Department in 1863 finally established a policy encouraging the use of black men and, subsequently, thousands were actively recruited. By the end of the war, more than 186,000 black men had enlisted, resulting in a ratio of one black soldier to every eight white soldiers. White commissioned officers and both black and white noncommissioned officers led most units of black soldiers. Frederick Douglass and Martin Delaney were recruiters for the U.S. Colored Troops; Delaney, a Harvard-trained doctor, served as a major. Two of Douglass’ sons joined the troops. Although the black troops were treated unfairly by both the Union and the Confederacy, they served faithfully and well. The immediate post-Civil War period saw the passage of the Thirteenth, Fourteenth, and Fifteenth Amendments to the Constitution, which abolished slavery, gave equal protection under the law, and granted citizenship and male suffrage to all born in the United States, regardless of color or previous condition of servitude. Although this seemed to promise a new era of freedom for African Americans, troubles soon set in. Gains in civil rights legislation and political representation in the state and local legislatures and in the U.S. Congress were eroded in several decades. Congressional reports chronicle the Ku Klux Klan death threats to those blacks who dared to participate actively in the political and economic arenas of the South. Tenancy, sharecropping, and peonage bound many poor African Americans in a new kind of bondage from the 1870s through the turn of the century. Blacks had to begin anew to strive for social and political rights in their homeland. Despite setbacks, by the turn of the twentieth century a race formerly barred from literacy by law was largely literate and had published thousands of books, pamphlets, plays, and music pieces. Nevertheless, in 1896, the U.S. Supreme Court dealt a crushing blow to the struggle for freedom by declaring in the Plessy v. Ferguson case that it was legal to provide “separate but equal” accommodations for blacks on public conveyances. The concept of racial separation long predated Plessy and had crept through the fabric of American life, North and South. Historian Rayford Logan in his work, Betrayal of the Negro (originally published in 1954 as The Negro in American Life, The Nadir), called this period the nadir of the historical experience of free blacks. Race riots and other types of racial violence ushered in a reign of terror in much of the South. The voices of the nation’s black citizens were not silenced by the onslaught of racial repression. Black journalists like Ida B. Wells Barnett and T. Thomas Fortune, and up-and-coming scholars such as W. E. B. DuBois and Carter G. Woodson, and educators such as Booker T. Washington, Kelly Miller, Mary Church Terrell, and Fanny Jackson Coppin spoke out against lynching and other forms of violence. Black leaders being trained at African American colleges and universities and a few integrated and mainstream universities formed the relentless vanguard for civil rights and equal opportunity for all in the twentieth century. (Other important figures from this time period appear in specific chapters according to their occupation. For example, mathematician Benjamin Banneker is biographied in the Science & Technology chapter. To locate biographical profiles more readily, please consult the index at the back of the book.) JOHN QUINCY ADAMS (1767–1848) President, Politician The sixth President of the United States, was a white man who said that he was not an abolitionist. Yet, he respected the rights of all citizens to petition the American government. After his presidency, he was elected to the House of Representatives in 1830. During his tenure, the House banned the consideration of petitions for the emancipation of slaves. This ban, called the “gag rule,” was in force beginning in 1836. Adams tirelessly and successfully fought against the rule which was rescinded in 1844. Although Adams did not consider himself to be an abolitionist, his views on human rights led abolitionists to recruit him as the lawyer for the Amistad Africans This group of Africans staged a slave revolt at sea but we eventually tried in the United States. Adams successfully defended their cause. ALICE OF DUNK’S FERRY (c.1686–1802) Oral Historian Alice was born around 1686 in Philadelphia, Pennsylvania, to slave parents brought from Barbados. At the age of ten, she moved to Dunk’s Ferry in Bucks County with her master, where she lived out the rest of what proved to be an incredibly long life, spending some 40 of her 116 years collecting tolls at a bridge. Alice’s long life, coupled with a remarkable memory, made her an ideal oral historian, recounting for listeners her vivid memories of the early days of the colony. She could remember when the great city of Philadelphia was nothing more than a wilderness, populated by Native Americans and wild animals of the forest. Little is known about her life, although evidence suggests that she remained physically active even past the century mark of her life. She died as a slave just a few miles from Philadelphia in 1802. RICHARD ALLEN. SEERELIGION CHAPTER. CRISPUS ATTUCKS (c.1723–1770) Revolutionary Patriot A runaway slave who lived in Boston, he was the first of five men killed on March 5, 1770, when British troops fired on a crowd of colonial protesters in the Boston Massacre. The most widely accepted account of the incident is that of John Adams, who said at the subsequent trial of the British soldiers that Attucks undertook “to be the hero of the night; and to lead this army with banners, to form them in the first place in Dock Square, and march them up to King Street with their clubs.” When the crowd reached the soldiers, it was Attucks who “had hardiness enough to fall in upon them, and with one hand took hold of a bayonet, and with the other knocked the man down.” At that point the panicked soldiers fired, and in the echoes of their volley, five men lay dying; the seeds of the Revolution were sown. Attucks is remembered as “the first to defy, the first to die.” CHARLES BALL (1781?–?) Aboltionist, Author Charles Ball, a fugitive slave, dictated his autobiography Fifty Years in Chains; or, The Life of an American Slave (1836). His narrative was very popular and was updated a few times and reprinted many times. Born in Calvert County, Maryland. in about 1781, Ball was the grandson of an African. His mother died when he was about four years old and father ran away when he learned that he was about to be sold. Ball himself was sold into slavery in Georgia when he was about thirty years old. He subsequently ran away and found his wife and family in Maryland. After living as a free man for a while, he was recaptured. Escaping again, he returned to find that his family members who were legally free had been kidnapped and sold into slavery. At first Ball’s narrative was published anonymously. He discussed the institution of slavery, kidnapping of African Americans, and the effect of the cotton gin on the lives of enslaved blacks. BENJAMIN BANNEKER. SEESCIENCE AND TECHNOLOGY CHAPTER. JAMES BECKWOURTH. SEEENTREPRENEURSHIP CHAPTER. HENRY BOX BROWN (1815–?) Abolitionist Henry Brown got his nickname “Box” when he mailed himself from Richmond, Virginia, to the Philadelphia, Pennsylvania, Antislavery office in 1849 to escape from slavery. Brown, who was unlettered, got an abolitionist to write down his autobiography for him. It was first published several months after his escape and revised and republished in England in 1851. In his narrative Brown explains that he was born in 1815 on the Barret plantation in Virginia, When Brown was fifteen years old, his master died and Brown’s family was divided between the owner’s four sons. Taken to Richmond by William Barret, Brown he began to work long hours in a tobacco factory. His new master regularly set aside small sums of money as a reward for Brown’s work. Brown was no spendthrift so he was able to amass some savings. Brown got permission to marry a slave named Nancy on the condition that he find a place for his family to live. After twelve years of marriage Brown’s wife and children were sold away and he had no idea where they had gone. To add to the calamity, some whites also took everything Brown owned out of his house. Brown began to plan to get away from the terrible confines of enslavement. He wanted to find a way of escape that was unique. In 1849, with the help of two allies, Brown was shipped to Philadelphia in a crate. When Brown’s Philadelphia contacts heard that the box had arrived, several witnesses, including the African American Underground Railroad conductor, William Still, were present for the opening of the crate. To their amazement, Brown was alive. After his escape Brown began speaking on the antislavery circuit about the horrors of slavery. In response to the passage of the Fugitive Slave Act of 1850, he fled to England. BLANCHE K. BRUCE. SEEPOLITICS CHAPTER. JOSEPH CINQUE (1811–1879) Mutineer, Insurrectionist Born in Sierra Leone in 1811 and purchased by Spaniards in Havana, Cuba, in 1838, Cinque was placed aboard the Amistad bound for Puerto Principe. The Amistad, a Spanish vessel, set sail from Cuba on June 28, 1839. A few days later, led by Joseph Cinque who was about twenty-five years old, the Africans rebelled, killed the captain and the cook, and ordered several others to transport them back to Africa. During the day, the pilots steered the vessel eastward, but at night they headed north, ultimately arriving in August 1839 off Long Island, N.Y. There the ship was seized by U.S. government authorities and the Africans were imprisoned after the white crewmen denounced them as rebellious slaves, pirates and murderers. Abolitionists took up the cause of the men and enabled Cinque to raise funds for judicial appeals by speaking on their lecture circuit. Almost overnight the incident became a cause célèbre. The Africans, led by the Mende warrior Singbe-Piéh, named Cinque by the slave traders, insisted that they be freed and returned to their continent. Many admired or respected Cinque both as a warrior and leader of his people. President Martin Van Buren (1782–1862) and the Spanish administrators of Cuba claimed that they should be extradited to Cuba to stand trial for mutiny. The case ultimately went to the U.S. Supreme court where John Quincy Adams defended the Amistad Africans. Adams won the case, the Africans were declared free and missionaries and well-wishers raised money for Cinquez and the remaining Africans to return to West Africa. DANIEL COKER (1789–1846) Educator, Pastor, Colonizationist Daniel Coker was an African American preacher, teacher, and missionary to Africa. He was born Isaac Wright in 1780 in Frederick County, Maryland, to an enslaved African father, Edward Wright, and a white mother, Susan Coker, an indentured servant. His mother also had an older white son, named Daniel Coker. Isaac received a rudimentary education and ran away to New York where he assumed his brother’s name, Daniel Coker. Coker was active in the Methodist movement under the traveling Bishop Francis Asbury. Coker became a minister in a Baltimore Methodist church, modeled after Reverend Richard Allen’s church in Philadelphia, and opened a school in about 1800. In spite of the fact that early Methodists were encouraged to free their slaves, welcome African American members and support abolition, many white preachers, trustees, and members did not agree and treated African-Americans members of their congregation justly or courteously. Coker published a 43-page pamphlet containing one of his 1810 sermons protesting African slavery entitled, A Dialog between a Virginian and an African Minister. In it he describes himself as a “Minister of the African Methodist Episcopal Church in Baltimore” and in an appendix lists the names of African ministers “who are in holy orders,” as well as African local preachers, African churches, and “names of the descendants of the African race, who have given proofs of talent.” In the introduction to the 1817 publication The Doctrines and Discipline of the African Methodist Episcopal Church, Daniel Coker, Richard Allen and James Champion explained how they responded to their mis-treatment by white Methodists after a number of years of dissatisfaction. They stated that the African American members were “disposed to seek a place of worship for themselves” rather than seek legal redress against the white Methodist preachers and trustees who repeatedly tried to keep them from equality with white. In addition to pastoring Coker established a church school, the Bethel Charity School. Several generations of blacks benefited from the teachers and preachers trained in this school. For some unrevealed reason Coker was removed from the church in 1818 but restored a year later. During that year, it seems, Coker decided that he wanted to be a missionary to Africa. In addition to pastoring and teaching several other important events were taking place in Coker’s life about the same time. Several years prior to the formation of the AME Church Coker became very interested in developments in Sierra Leone, West Africa. Coker decided that he and his family would partner with the American Colonization Society to return to Africa as a missionary After their arrival on an for their white agents to govern the settlers but when “African fever” stisland off the coast of sierra Leone many settlers got sick; some died. The ACS intended ruck the surviving white agent, he appointed Coker to lead the settlers. The letter explained the state of the colonists. The settlers resented Coker’s leadership but he continued to serve until another white ACS agent arrived. The settlers moved to several locations before finally relocating in Freetown, the capital of Sierra Leone. When some of the settlers decided to move down the coast to found Liberia in 1822, Coker elected to remain in Sierra Leone where he ministered until his death in 1846. JOSHUA COFFIN (1792–1864) Abolitionist White abolitionists like teacher Joshua Coffin argued that the existence of slavery in the United States constituted a real threat to public peace and security. He used his volume An Account of Some of the Principal Slave Insurrections (1860) to show how often slaves rose up against their owners to demand their freedom. In it he describes slave resistance through large and small-scale rebellions in the North and South, work slow downs, poisonings, arsons, and murders. He discusses many mutinies, including one on a Rhode Island ship when captives near Cape Coast Castle (in present-day Ghana) rose and “murdered the captain and all the crew except the two mates, who swam ashore.” Coffin was a founder of the New England Anti-Slavery Society. FANNY COPPIN. SEEEDUCATION CHAPTER. WILLIAM CRAFT (1842–1900) Abolitionist, Businessman ELLEN CRAFT (1826–1891) Abolitionist, Educator Ellen Smith’s mother was a Georgia slave who had a child to her master. As a youth, Ellen bore such a resemblance to her father/master that she was ultimately sent away to her master’s daughter in Macon, Georgia, where she worked as a house maid. In Macon Ellen met and married William Craft, a carpenter. After the marriage, the couple tried to devise escape plans. Finally, by Christmas 1848 they came up with an idea. Ellen would pose as a sickly young man. She dressed in men’s clothing, wrapped her face with a scarf to hid the fact that she had no beard, and bandaged her right hand, pretending that she was wounded, so that no one would know that she could not read and write. Her husband, William, pretended that he was her slave accompanying her to Philadelphia. The left just at the beginning of the Christmas holidays with a pass from their owners. Because bondspersons were usually given some free time at Christmas, the young couple hoped that no one would look for them for several days. They bought fares with money that William had warned as a hired slave and took both trains and boast until they arrived in Philadelphia. Their mission was successful with only a few frightening moments, particularly when Ellen was asked to produce papers showing the she was indeed William‘s owner. The coupled traveled to various places in the North and spoke for the abolitionist cause. They settled for a while in Boston until the arrival of slave catchers convinced them that they needed to spend some time in England. In 1860 William published a book about their experiences entitled Running a Thousand Miles for Freedom. At the end of the Civil War, the Crafts returned to Georgia where they opened a school for black children. PAUL CUFFEE (PAUL CUFFE) (1759–1817) Shipbuilder, Ship Captain, Colonizationist Paul Cuffee was a Massachusetts free man who learned to articulate the doctrines of freedom for oppressed African Americans. He eventually became an active exponent of African colonization in general and of the British Sierra Leonean scheme in particular. Born in Massachusetts before the Revolutionary War, Cuffee was of mixed Native American and African parentage and was the seventh of eleven children. As a youth he was able to get some education and then found work as a sailor, as a laborer in shipyards and as a shipbuilder. He saw opportunities in this line of work and seized them. By 1780 he had built a ship of his own and by 1806 he owned one large ship, two brigs and some smaller vessels and was able to engage very profitably in trade. In spite of his accomplishments Cuffee still regularly confronted racial prejudice. Although his wealth continued to grow, as did his contributions to the Massachusetts government through taxes, he could not vote and his children could not attend public schools. Cuffee knew that the colonies had railed against Great Britain for taxation without representation during the Revolutionary War, and it seemed to him that the colonies were guilty of the same injustices by taxing free blacks without letting them reap all of the benefits that tax dollars earned for other citizens. In defiance, Cuffee and his brother refused to pay their taxes. Subsequently, Cuffee financed a Quaker school, which he opened not only to black children but also to all children in his community. Even when the Massachusetts courts abolished slavery in 1783, Cuffee reasoned that the best avenue for blacks to pursue was to reestablish contact with West Africans for the purpose of colonization and trade. He thought that blacks could contribute both civilization and Christianity to their ancestral homeland. During Cuffee’s 1811-12 visit to Sierra Leone, he formed the Friendly Society with an Afro-American emigrant named John Kizzell for the purpose of encouraging Afro-American emigration and trade. Cuffee was unable to interest anyone in financing his Sierra Leone colonization scheme. Consequently, he determined that he would finance it himself but encountered one major problem. During the time he was formulating his plans, the United States and Great Britain were involved in the War of 1812 and Americans were not permitted to trade with England or her colonies. In 1814 Cuffee petitioned the United States Congress to lift the embargo against trade with Sierra Leone so that he could begin his venture. His petition passed the Senate but was struck down by the House. Finally, after the cessation of hostilities in 1815 and at a personal expenditure of $4,000, Cuffee took nine free black families totaling thirty-eight individuals to settle in Sierra Leone. The emigrant families consisted of nine adult males, ten adult females, six male and thirteen female children. Although he had difficulty marketing his trade goods when he returned, Cuffee became even more determined that black Americans needed to emigrate if they were to achieve true independence and racial dignity. Many free blacks as well as some whites received Cuffee’s emigration plan with enthusiasm but few blacks were willing to give up their American citizenship, the United States was the only country they knew. FREDERICK DOUGLASS (1817–1895) Abolitionist, Editor, Diplomat, Government Official, Legislator, Marshall Born in Talbot County, Maryland, on February 14, 1817, Frederick Douglass was sent to Baltimore as a house servant at the age of eight, where his mistress taught him to read and write. Upon the death of his master, he was sent to the country to work as a field hand. During his time in the South, he was severely flogged for his resistance to slavery. In his early teens, he began to teach in a Sunday school that was later forcibly shut down by hostile whites. After an unsuccessful attempt to escape from slavery, he succeeded in making his way to New York disguised as a sailor in 1838. He found work as a day laborer in New Bedford, Massachusetts, and after an extemporaneous speech before the Massachusetts AntiSlavery Society, he became one of its agents. Douglass quickly became a nationally recognized figure among abolitionists. In 1845, he bravely published his Narrative of the Life of Frederick Douglass, which related his experiences as a slave, revealed his fugitive status, and further exposed him to the danger of reenslavement. In the same year, he went to England and Ireland, where he remained until 1847, speaking on slavery and women’s rights, and ultimately raising sufficient funds to purchase his freedom. Upon returning to the United States, he founded the North Star. In the tense years before the Civil War, he was forced to flee to Canada when the governor of Virginia swore out a warrant for his arrest. Douglass returned to the United States before the beginning of the Civil War and, after meeting with President Abraham Lincoln, he assisted in the formation of the 54th and 55th Negro regiments of Massachusetts. During Reconstruction, he became deeply involved in the civil rights movement, and, in 1871, he was appointed to the territorial legislature of the District of Columbia. He served as one of the presidential electors-at-large for New York in 1872 and, shortly thereafter, became the secretary of the Santo Domingo Commission. After serving for a short time as the police commissioner of the District of Columbia, he was appointed marshal in 1871, and held the post until he was appointed the recorder of deeds in 1881. In 1890, his support of the presidential campaign of Benjamin Harrison won him his most important federal post: he became minister resident and consul general to the Republic of Haiti and, later, the charge d’affaires of Santo Domingo. In 1891, he resigned the position in protest of the unscrupulous business practices of U.S. businessmen. Douglass died at his home in Washington, D.C., on February 20, 1895. SARAH MAPPS DOUGLASS. SEEEDUCATION CHAPTER. W. E. B. DUBOIS (1868–1963) Scholar, Activist, PanAfricanist William Edward Burghardt Du Bois was born in Great Barrington, Massachusetts, the great-grandchild of Elizabeth Freeman, an eighteenth century black woman who successfully sued for her freedom after she was hit with a hot shovel while protecting her daughter. DuBois got a solid educational background but was not able to go to the college of his choice—Harvard—because of his African ancestry. He went instead to Fisk University in Tennessee—an institution of higher learning established for freed slaves. After graduating from Fisk in 1888, DuBois went to Harvard where he earned his doctorate degree in 1895. His dissertation on the suppression of the African slave trade became the first in the series of Harvard Historical Studies. In spite of his scholarly accomplishments, DuBois faced discrimination on every side. He began to write about the history and culture of African Americans and research a series of cultural sociological essays and studies such as The Philadelphia Negro (1899) and The Souls of Black Folks (1903) and teach at several historically black colleges. In 1905 he met with a group of African American leaders in Niagara Falls, Canada, to articulate the political and social needs of blacks and to strategize way of obtaining first class citizenship. Some of the ideas of the Niagara movement were incorporated by a group of activists—largely whites—who wanted to form an organization to agitate for civil rights for people of color. This group, the National Association for the Advancement of Colored People, formed in 1909, probably became popular because DuBois became the editor of its monthly magazine, The Crisis, a role he served in from 1910 to 1934. DuBois used The Crisis to showcase the accomplishments of Africans in the Diaspora while emphasizing the NAACP’s platform for equal rights for all Americans. He also helped popularize the concept of PanAfricanism—the need for Africans worldwide to work together for political and social rights. During his entire life he was a tireless advocate for the rights of all. When he became disenchanted with America and the civil rights movement towards the end of his life, he joined the Communist Party and moved to Ghana in 1961 where he died two years latter. The illustrious scholar and activist had written 17 books—the most famous being The Souls of Black Folks—edited four journals and taken the United States to task on every race relations issue both nationally and internationally. JEAN BAPTIST POINT DU SABLE. SEEENTREPRENEURSHIP CHAPTER. OLAUDAH EQUIANO (1750?–1797) Narrative Writer Olaudah Equiano was born around 1750 in an Ibo village in southern Nigeria. At the age of 11, he was kidnapped and enslaved in Africa before being shipped to the New World. His masters included a Virginia plantation owner, a British officer—who gave him the name Gustavus Vassa—and a Philadelphia merchant from whom he eventually purchased his freedom. Equiano then settled in England where he worked diligently for the elimination of slavery. He even went so far as to present a petition to Parliament calling for its abolition. Equiano’s autobiography The Interesting Narrative of the Life of Olaudah Equiano, or Gustavus Vassa was published in London in 1789 and went through five editions in five years. It is regarded as a highly informative account of the evils of slavery as it affected the master and the slave, as well as the precursor to other important slave narratives, such as the Narrative of the Life of Frederick Douglass. ESTEVANICO, LITTLE STEPHEN, STEPHEN DORANTES (1503?–1539) Explorer Born in Azamore, Morocco, young Estevanico’s city was captured in a battle with the Portugese when he was a baby. Eventually, Estevanico was sold into slavery in Spain to Andres de Dorantes. Dorantes gave him the name Stephen; “Estevanico,” is a nickname that means Little Stephen. Two decades later Dorantes left Spain on an expedition to Florida arriving in April 1528. After encountering hostile Indians many of the six hundred colonists and soldiers with Estevanico were killed or enslaved. Those who escaped landed in Texas but most of them lost their lives. Estevanico, Dorantes, Cabeza de Vaca and Alonso Castillo managed to escape Indian captivity in 1534. Estevanico, who had a facility for languages, became a guide and scout for the Europeans. He also was able to convince many Indians that he was a healer and in that role was able to act as a mediator between the Spaniards and the Indians. In his communication with the Indians he learned about seven cities of gold known as Cibola. Indians described these cities of wealth and gave him tokens they claimed were from the area. The small group traveled with great difficulty through Texas and arrived in Mexico City in 1536. The Viceroy there wanted the Estevanico to lead an expedition to Arizona and New Mexico to find Cibola. Estevanico served as the scout for the expedition, which was led this time led by Father Marcos de Niza. Estevanico sent back wooden crosses with to mark the direction of his journey. Still introducing himself as a powerful healer, Estevanico attracted many Indians who traveled with him. When he came to a Zuni pueblo with its large stone structures, he sent back a cross much larger than the ones he had sent previously. Soon after that communication with Estevanico ceased. Some believe he was killed by the Indians. Others speculate that he escaped his bondage. JOHN FLOYD (1783–1837) Virginia Governor John Floyd was the white governor of Virginia during the Nat Turner Revolt in Southampton, Virginia, in 1831. He wrote an explanatory letter to the governor of South Carolina. James Hamiliton, Jr., detailing what he believed to be the causal factors of the revolt. First, he blamed the restiveness of slaves to the presence of northerners traveling and doing business in the South. He especially noted that their teaching of Christianity caused enslaved blacks to feed that their were equal before God and their repetition of the Revolutionary War philosophies of liberty incited bondspersons‘ desire for freedom. Floyd also cited white women who in their eagerness to evangelize blacks taught them to read the Bible and religious tract.. He also said that owners allowed large African American religious meetings where teachers taught about equality before God and sang songs which expressed longings for freedom. He also mentioned the number of black preachers who spoke with the slaves insisting that they were probably all directly responsible for the revolt. Floyd was especially concerned about the infiltration of publications such as William Lloyd Garrison’s newspaper, The Liberator and David Walker’s Appeal. WILLIAM LLOYD GARRISON (1805–1879) Abolitionist, Journalist William Lloyd Garrison, a white abolitionist, was born in Newburyport, Massachusetts in 1805. Garrison family deserted by their father, had to find means for their own support. Garrison was apprenticed several times as a youth but finally, in 1818, began working as a writer and editor. In his twenties Garrison began to actively support the movement for the abolition of slavery. He supported the American Colonization Society for a while but then decided that the ACS did not really have the best interests of African Americans at heart. He was also concerned by the high mortality rate of African American settlers in Liberia. In the late 1820s Garrison met Benjamin Lundy the editor of an antislavery newspaper, The Genius of Universal Emancipation, but he quickly moved on to found his own newspaper, the Liberator, in 1831. He became a relentless opponent of slavery. Garrison wanted immediate, universal emancipation. He believed that the U. S. Constitution was a slavery document. Garrison helped organize the New England Anti-Slavery Society in 1832 and the American Anti-Slavery Society the next year. In 1839 Frederick Douglass began to read the Liberator and attend abolition meetings. By 1841 Douglass was traveling to speak out against slavery with Garrison and other abolitionists. Many of the sponsors and subscribers to Garrison’s newspaper were African Americans. After publishing almost two thousand issues of the Liberator, Garrison ceased publication during the Civil War. ARCHIBALD GRIMKé.SEELAW CHAPTER. LEMUEL HAYNES (1753–1833) Religious Leader The son of a black father and white mother and born in 1753, he was deserted and brought up by Deacon David Rose of Granville, Massachusetts. He was a precocious child and began writing mature sermons while still a boy. His preparation for the ministry was interrupted by the American Revolution. On April 19, 1775, he fought in the first battle of the war at Lexington, Massachusetts; he then joined the regular forces and served with Ethan Allen’s Green Mountain Boys at the capture of Fort Ticonderoga. JAMES AUGUSTINE HEALY. SEERELIGION CHAPTER. SALLY HEMINGS (1773–1886) Slave Sally Hemings was born a slave in Virginia in 1773, the daughter of a white man named John Wayles and a mulatto slave named Elizabeth Hemings. She became the slave and perhaps the concubine of President Thomas Jefferson. While it is known that Hemings bore several mulatto children, there is considerable scholarly debate over whether Thomas Jefferson was their father. Contemporaries claimed that Hemings’ children bore close resemblance to Jefferson and scholars argue that all of Hemings’ pregnancies correspond to a date that Jefferson was at home rather than on his extensive travels. The Hemings offspring were among the few slaves that Jefferson freed. One of Jefferson’s contemporaries (albeit, a political enemy) accused him of miscegenation in 1802, but the furor over the exact nature of Jefferson’s relationship with Sally Hemings did not pick up steam until the late twentieth century, when DNA tests on descendants of Sally Hemings concluded that either Jefferson or a close male relative had fathered Hemings’ children. Those who maintain the existence of a sexual relationship between the two figures suggest that Jefferson first seduced Hemings in Paris when she was just 15, and that they maintained a 38-year relationship until his death in 1826. JOSIAH HENSON (1789–1883) Educational Administrator, Abolitionist, Religious Leader Born a slave in a log cabin in Charles County (near Rockville), Maryland, on June 15, 1789, Josiah Henson grew up with the experience of his family being cruelly treated by his master. By the time he was 18 years of age, Henson was supervising the master’s farm. In 1825, he and his wife and children were moved to Kentucky, where conditions were greatly improved, and in 1828 he became a preacher in a Methodist Episcopal Church. Under the threat of being sold, he and his family escaped to Ohio in 1830, and the following year entered Canada by way of Buffalo, New York. In Canada, he learned to read and write from one of his sons, and he soon began preaching in Dresden, Ontario. While in Canada, he became active in the Underground Railroad, helping nearly 200 slaves to escape to freedom. In 1842, he and several others attempted to start the British-American Manual Labor Institute, but the industrial school proved unsuccessful. Henson related his story to Harriet Beecher Stowe (the author of Uncle Tom’s Cabin), and it has been disputed whether or not her story is based in part on aspects of his life. He traveled to England three times, where he met distinguished people, was honored for his abolitionist activities and personal escape from slavery, and was offered a number of positions that he turned down in order to return to Canada. He published his autobiography in 1849 and rewrote and reissued it in 1858 and 1879. Henson died in Ontario in 1883. HARRY HOSIER (1750–1806) Preacher Most sources report that Harry Hosier (also spelled Hoosier, Hoshur, Hossier) was born a slave near Fayetteville, North Carolina, around 1750. Although little is known as to the circumstances, Hosier experienced both a religious conversion to Methodism and his freedom. He is thought to have met Francis Asbury, the founder of Methodism and evangelist to the slaves, sometime in 1780; Asbury wrote of the meeting that it was “providentially arranged.” The two men partnered together to spread the Gospel, with Hosier acting as Asbury’s servant, guide, and circuit-riding preacher. Hosier proved to be an eloquent speaker who, though uneducated, was intellectually alert, creative, and possessed a remarkable memory. Those who heard him preach were instantly impressed with his work. He preached with Asbury at the Fairfax Chapel in Falls Church, Virginia, as early as May 13, 1781. This made him the first black preacher to deliver a sermon to a white Methodist church in America. His fame as a preacher brought him into contact with several other major preachers, including Thomas Coke, who wrote of him, “I really believe he is one of the best Preachers in the world, there is such an amazing power attends his preaching, though he cannot read; and he is one of the humblest creatures I ever saw.” Hosier actually resisted learning to read and write throughout his career, relying on his memory for biblical passages and hymns for his listeners. He was present at the historic Christmas conference at the end of 1784, which saw the formal establishment of both the Methodist Episcopal Church and a permanent relationship between black and white Methodists. Although enormously popular, Hosier was never ordained in the Methodist church, possibly because of his rumored problems with alcohol. ABSALOM JONES. SEERELIGION CHAPTER. ISAAC LANE. SEERELIGION CHAPTER. LUCY LANEY. SEEEDUCATION CHAPTER. JOHN MERCER LANGSTON. SEEPOLITICS CHAPTER. JAMES ARMISTEAD LAFAYETTE (1700s–?) Spy Born a slave, James Armistead Lafayette risked his life behind enemy lines collecting information for the Continental Army. He furnished valuable information to the Marquis de Lafayette and enabled the French commander to check the troop advances of British General Cornwallis; this set the stage for General George Washington’s victory at Yorktown in 1781 and for the end of the Revolutionary War. In recognition of his services, he was granted his freedom by the Virginia legislature in 1786, although it was not until 1819 that Virginia awarded him a pension of $40 a year and a grant of $100. He adopted the surname “Lafayette” in honor of his former commander, who visited him during a trip to the United States in 1824. JARENA LEE. SEERELIGION CHAPTER. GEORGE LIELE. SEERELIGION CHAPTER. TOUSSAINT L’OUVERTURE (1743–1803) Insurrectionist Born Francois Dominique Toussaint L’Ouverture, a slave on the island of Hispaniola (now Haiti and the Dominican Republic) in 1743, he learned to read and write under a benevolent master. When he was 50 years of age, a violent revolt erupted on the island. White French planters, African slaves, and free mulattoes (some of whom owned slaves) clashed over issues of rights, land, and labor, as the forces of France, Britain, and Spain manipulated the conflict. At first the slaves and mulattoes shared the goals of the French revolution in opposition to the royalist French planters, but with time a coalition of planters and mulattoes arose in opposition to the slaves. L’Ouverture became the leader of the revolutionary slave forces, which by mid-1790s consisted of a disciplined group of 4,000 mostly ex-slaves. He successfully waged a campaign against the British. At the height of L’Ouverture’s power and influence in 1796, General Rigaud, who led the mulatto forces, sought to re-impose slavery on the black islanders. L’Ouverture quickly achieved victory, captured Santo Domingo, and by 1801 had virtual control of the Spanish part of the island. In 1802, a French expeditionary force was sent to reestablish French control of the island. Following a hard-fought resistance to French colonial ambitions in the Western Hemisphere, Toussaint L’Ouverture struck a peace treaty with Napoleon. However, L’Ouverture was tricked, captured, and sent to France where he died on April 7, 1803, under inhumane conditions. ONESIMUS (fl. 1700s) Slave, Scientific Discoverer Onesimus was a slave in Boston, Massachusetts, during the early1700s. He had grown up in Africa, a member of the Garamantes tribe, but was enslaved and brought to America. Beginning in 1706, he worked for religious leader Cotton Mather, who also was a contributor to scientific journals such as Philosophical Transactions of the Royal Society of London. While reading an article in that magazine, Mather was struck by how closely the recounted practice of inoculation in Turkey resembled what Onesimus had told him about what was done to him in Africa. Mather’s description of Onesimus’s account was printed in the Yale Journal of Biology and Medicine from a letter Mather wrote to the Royal Society. Nevertheless, nothing came of this information for another five years. In 1721, Boston was hit with a smallpox epidemic. Because of Onesimus’s story, Mather insisted that the medical community at least attempt the slave’s method of disease prevention. Finally, a country doctor, Zabdiel Boylston, succeeded in saving his six-year-old son and two slaves. Boylston continued to inoculate more and more people safely, keeping careful records. Of the 286 people he inoculated, 2.1% died, compared to 14.9 percent of those who acquired smallpox naturally. Boylston reported his findings to the Royal Society, and the medical community became convinced of the value of inoculation. Through the accurate recounting of the procedure carried out on him, Onesimus helped bring knowledge of inoculation to the Western world. This would remain the primary way of protecting people from the ravages of smallpox until the introduction of Jennerian cowpox vaccination in 1798. P. B. S. PINCHBACK. SEEPOLITICS CHAPTER. SALEM POOR (1747–?) Revolutionary War Soldier Salem Poor was born a slave in 1747 in Andover, Massachusetts. He spent his childhood and the early years of his adult life on his master’s farm in Andover, before purchasing his freedom in 1769. In March of 1774, after the Continental Congress designated certain units of the Massachusetts militia to serve as Minutemen, the Massachusetts Committee of Safety permitted black volunteers to join town and village companies. A number of free black men promptly enlisted, including Poor. He enlisted in the First Andover Company as a private and, like other militia minutemen, was trained to respond at a minute’s notice to British aggression. When American rebellion against the British turned into open warfare, Poor enlisted under Captain Samuel Johnson in the Fifth Massachusetts Regiment on April 24, 1775. He participated in the Battle of Bunker Hill, and fired the shot that killed British Lieutenant Colonel James Abercrombie. Poor was never far from active duty in the years between 1775 and 1780, and was with some 500 other black sharpshooters in the Continental Army that spent the legendary frozen winter of 1777–1778 with General George Washington in his Valley Forge encampment. He also served in the crucial battles of White Plains, New York, and Providence, Rhode Island. Only one instance is recorded of Salem Poor having been commended for his bravery, the submission of the petition of recommendation in December 1775. Two hundred years later, Poor’s valor was publicly recognized. On March 25, 1975, as part of the United States Postal Service’s Revolutionary War Bicentennial series of stamps entitled “Contributors to the Cause,” a commemorative 10-cent stamp was issued in recognition of “Salem Poor—Gallant Soldier.” GABRIEL PROSSER (1775–1800) Insurrectionist Gabriel Prosser was born around 1775. He became the coachman of Thomas Prosser of Henrico County, Virginia, and planned a large, highly organized revolt to take place on the last night of August of 1800 around Richmond, Virginia. About 32,000 slaves and only 8,000 whites were in the area, and it was his intention to kill all of the whites except for the French, Quakers, elderly women, and children. The ultimate goal was that the remaining 300,000 slaves in the state would follow his lead and seize the entire state. The revolt was set to coincide with the harvest so that his followers would be spared any shortage of food, and it was decided that the conspirators would meet at the Old Brook Swamp outside of Richmond and marshal forces to attack the city. The insurrection fell apart when a severe rainstorm made it impossible for many of the slaves to assemble and a pair of house slaves who did not wish their master killed revealed the plot. Panic swept through the city, martial law was declared, and those suspected of involvement were rounded up and hanged; when it became clear that the slave population would be decimated if all of those implicated were dealt with in similar fashion, the courts began to mete out less severe sentences. Prosser was apprehended in the hold of a schooner that docked in Norfolk, Virginia. Brought back in chains, he was interrogated by the governor. When he refused to divulge details of the conspiracy, he was hung. JOSEPH H. RAINEY. SEEPOLITICS CHAPTER. HIRAM RHODES REVELS. SEEPOLITICS CHAPTER. GEORGE RUFFIN. SEELAW CHAPTER. DRED SCOTT (1795–1858) Abolitionist Born in Southhampton, Virginia, in 1795, Dred Scott’s first name was simply Sam. He worked as a farmhand, handyman, and stevedore, and moved with his master to Huntsville, Alabama, and later to St. Louis, Missouri. In 1831, his owner, Peter Blow, died, and he was bought by John Emerson, a surgeon in the U.S. Army. Sam accompanied his new master to Illinois (a free state) and Wisconsin (a territory). Sometime after 1836, he received permission to marry, and by 1848 he had changed his name to Dred Scott. At various times, he attempted to buy his freedom or escape, but was unsuccessful. In 1843, Emerson died and left his estate to his widow Irene Emerson, who also refused Scott his freedom. He then obtained the assistance of two attorneys who helped him to sue for his freedom in county court. Scott lost this case, but the verdict was set aside, and in 1847 he won a second trial on the grounds that his slave status had been nullified upon entering into a free state. Scott received financial backing and legal representation through the sons of Peter Blow, Irene Emerson’s brother John Sanford, and her second husband, Dr. C. C. Chaffee, all of whom apparently saw the case as an important challenge to slavery. The case went all the way to the U.S. Supreme Court. In 1857, that court ruled against Scott, stating that slaves were not legal citizens of the United States and, therefore, had no standing in the courts. Shortly after the decision was handed down, Mrs. Emerson freed Scott. The case led to the nullification of the Missouri Compromise of 1820, allowing the expansion of slavery into formerly free territories and strengthening the abolition movement. WILLIAM STILL (1821–1902) Underground Railroad Conductor In 1872, William Still published a 558-page book with the long title, The Underground Rail Road: a Record of Facts, Authentic Narratives, Letters, &c., Narrating the Hardships, Hair-breadth escapes, and Death Struggles of the Slaves in their Efforts for Freedom as Related by Themselves and Others, or Witnessed by the Author, together with Sketches of Some of the Largest Stockholders, and Most Liberal Aiders and Advisers, of the Road. Still, born in New Jersey in 1821, was the son of former slaves. As an employee of the Philadelphia-based Pennsylvania Society for the Abolition of Slavery. He began assisting large numbers of runaway slaves especially after the passage of the Fugitive Slave Act of 1850. At that time the society made him chairperson of its Vigilance Committee and Still listened to the accounts of many escapees and recorded their stories. In his book he praises his friend and co-conspirator Harriet Tubman, for her bravery and tenacity as an Underground Railroad conductor. Even after slavery was abolished in the nation, Still continued to work for first class citizenship for African Americans. HARRIET BEECHER STOWE (1811–1896) Abolitionist, Author Harriet Beecher Stowe was a white teacher, abolitionist and writer but most people remember her only as the author of Uncle Tom’s Cabin. Harriet was born June 14, 1811, in Litchfield, Connecticut, to Lyman and Roxanna Foote Beecher. In 1836 Harriet married Calvin Stowe who taught Biblical Literature at Lane Theological Institute, where Harriet’s father was president. The couple had seven children. Galvanized by the passage of the Fugitive Slave Act of 1850, Stowe published Uncle Tom’s Cabin; or, Life among the Lowly, in forty installments from June 1851 to April of 1852 in the Washington, D.C. National Era. The story riveted the attention of thousands of readers and engendered outrage in many about the institution of slavery. Although the story centers on the mistreatment of the pious and wise slave, Uncle Tom, many other slaves are featured in the story. The book targets even benign slave owners as partners in the crime against humanity, slavery. Toward the end of Tom’s life, his owner Simon Legree, who specializes in cruelty, finally beats Tom severely because he knows that Tom has outwitted him in a matter relating to two runaway women. When Tom’s former master finally rescues him, Tom survives only a few miles beyond the door of Legree’s plantation. When Uncle Tom’s Cabin appeared as a book in March 1852, published in two volumes by J. P. Jewett, it sold three hundred thousand copies in one year. Before 1860 over one million copies had sold in the U.S. and over two million copies abroad, authorized and unauthorized, principally in England but also in France, Germany and other nations. In 1853, 1856 and 1859 Stowe traveled abroad and was enthusiastically received by common folks and nobility. Stowe’s novel added measurably to the polarization of abolitionist and anti-abolitionist sentiment in the U. S. and Europe. Carl Sandburg reported in Abraham Lincoln: the War Years that during a White House visit President Lincoln greeted Stowe with out stretched hands saying, “So you’re the little woman who wrote the book that made this great war.” Historian Benjamin Quarles noted that at an 1863 abolitionist’s celebration of Lincoln’s Emancipation Proclamation, the crowd yelled for Stowe to come forward to receive an enthusiastic ovation for the service she had performed by writing UncleTom’s Cabin. Harriet Beecher Stowe died at eight-five in Hartford, Connecticut. SOJOURNER TRUTH (1797–1883) Lecturer, Abolitionist Born Isabella Baumfree in Ulster County, New York, around 1797, she was freed by the New York State Emancipation Act of 1827 and lived in New York City for a time. After taking the name Sojourner Truth, which she felt God had given her, she assumed the “mission” of spreading “the Truth” across the country. She became famous as an itinerant preacher, drawing huge crowds with her oratory and, some said, with “mystical gifts” wherever she appeared. She became one of an active group of African American women abolitionists, lectured before numerous abolitionist audiences, and was friends with such leading white abolitionists as James and Lucretia Mott and Harriet Beecher Stowe. With the outbreak of the Civil War, she raised money to purchase gifts for the soldiers, distributing them herself in the camps. She also helped African Americans who had escaped to the North to find habitation and shelter. Age and ill health caused her to retire from the lecture circuit, and she spent her last days in a sanatorium in Battle Creek, Michigan. HARRIET (ROSS) TUBMAN (c.1821–1913) Underground Railroad Conductor, Abolitionist, Nurse Born around 1821 in Dorchester County, Maryland, Harriet Tubman had the hard childhood of a slave: much work, little schooling, and severe punishment. In 1848 she escaped, leaving behind her husband John Tubman, who threatened to report her to their master. As a free woman, she began to devise practical ways of helping other slaves escape. Over the following 10 years, she made about 20 trips from the North into the South and rescued more than 300 slaves. Her reputation spread rapidly, and she won the admiration of leading abolitionists—some of whom sheltered her passengers. Eventually a reward of $40,000 was posted for her capture. Tubman met and aided John Brown in recruiting soldiers for his raid on Harpers Ferry. Brown referred to her as “General Tubman.” One of her major disappointments was the failure of the raid, and she is said to have regarded Brown as the true emancipator of her people, not Lincoln. In 1860, she began to canvass the nation, appearing at anti-slavery meetings and speaking on women’s rights. Shortly before the outbreak of the Civil War, she was forced to leave for Canada, but she returned to the United States and served the Union as a nurse, soldier, and spy. She was particularly valuable to the army as a scout because of the knowledge of the terrain that she had gained as a conductor on the Underground Railroad. Tubman’s biography, from which she received the proceeds, was written by Sarah Bradford in 1868. Tubman’s husband, John, died two years after the end of the war, and in 1869 she married the war veteran Nelson Davis. Despite receiving many honors and tributes, including a medal from Queen Victoria, she spent her last days in poverty, not receiving a pension until 30 years after the Civil War. With the $20 a month that she finally received, not for her own Civil War service, but for her husband’s, she helped to found a home for the aged and needy, which was later renamed the Harriet Tubman Home. She died on March 10, 1913, in Auburn, New York. NAT TURNER (1800–1831) Insurrectionist Born a slave in Southampton County, Virginia, on October 2, 1800, Nat Turner was an avid reader of the Bible who prayed, fasted, and experienced “voices,” ultimately becoming a visionary mystic with a belief that God had given him the special destiny of overthrowing slavery. After recruiting a handful of conspirators, he struck at isolated homes in his immediate area, recruiting men at each home, and within 48 hours the band of insurrectionists had reached 60 armed men. They killed 55 whites before deciding to attack the county seat in Jerusalem, but while en route they were overtaken by a posse and dispersed. Turner took refuge in the Dismal Swamp and remained there for six weeks before he was captured, brought to trial, and hanged along with 16 other African Americans. JAMES VARICK. SEERELIGION CHAPTER. DENMARK VESEY (1767–1822) Religious Leader Born in 1767, Vesey was sold by his master at an early age and later bought back because of epilepsy. He sailed with his master, Captain Vesey, to the Virgin Islands and Haiti for 20 years. He enjoyed a considerable degree of mobility in his home port of Charleston, South Carolina, and eventually purchased his freedom from his master for $600; he had won $1,500 in a lottery. He became a Methodist minister and used his church as a base to recruit supporters to take over Charleston. The revolt was planned for the second Sunday in July of 1822. Vesey’s plans were betrayed when a slave alerted the white authorities of the city. Hundreds of African Americans were rounded up, though some of Vesey’s collaborators most likely escaped to the Carolinas where they fought as maroons. After a 22-day search, Vesey was apprehended and stood trial. During the trial, he adeptly cross-examined witnesses, but ultimately could not deny his intention to overthrow the city, and he was hanged along with several collaborators. DAVID WALKER (1785–1830) Militant Abolitionist, Writer The offspring of a white mother and a black slave father on September 28, 1785, Walker was born free as stipulated by North Carolina law. Walker acquired an education before moving to Boston in the late 1820s. Besides starting a used clothes business, he became an active member of the Massachusetts General Colored Association and an agent for the first African American newspaper Freedom’s Journal. In 1829, Walker published Walker’s Appeal to the Colored Citizens of the World, which advocated the violent overthrow of slavery, the formation of African American civil rights and self-help organizations, and racial equality in the United States and independence for the peoples of Africa. Walker’s pamphlet alarmed Southerners who responded by enacting stricter laws against such “seditious” literature and the education of free African Americans. In the North, he also experienced sharp criticism from such prominent abolitionists as William Lloyd Garrison and Benjamin Lundy. On June 28, 1830, nine months after publishing his pamphlet, Walker mysteriously died, leaving behind his wife, Eliza. Though never verified, rumor suggests that he was poisoned. PHILLIS WHEATLEY. SEELITERATURE CHAPTER.
"Atomic mass" generally refers to the mass of a single atom or molecule. The term is also often used (though technically, incorrectly) to refer to the average atomic mass of all of the isotopes of one element. This second definition is actually the relative atomic mass (or "atomic weight") of an element - a single average value for the element's mass based on the masses of its isotopes, which differ. Chemists need to distinguish between these two types of atomic mass to guide their work - an incorrect value for atomic mass can, for instance, lead to an incorrect calculation of an experiment's yield. Method 1 of 3: Finding Atomic Mass Readings on the Periodic Table 1Understand how atomic mass is represented. Atomic mass, the mass of a given atom or molecule, can be expressed in standard SI mass units - grams, kilograms, etc. However, because atomic masses, when expressed in these terms, are incredibly small, atomic mass is often expressed in unified atomic mass units (usually shortened to "u" or "amu"). One atomic mass unit is equal to 1.660538921 × 10-27 kg, or 1/12th of the mass of a standard carbon-12 isotope. When expressed this way, atomic mass is called relative isotopic mass, which has the same numerical value as atomic mass. However, relative isotopic mass is technically unit-less. For most practical purposes, atomic mass and relative isotopic mass are essentially interchangeable. - Atomic mass units tell the mass of one mole of a given element or molecule in grams. This is a very useful property when it comes to practical calculations, as it allows easy conversion between the mass and moles of a given quantity of atoms or molecules of the same type. 2Pinpoint atomic mass on the periodic table. Most standard periodic tables list the relative atomic masses (atomic weights) of each element. This is almost always written as a number at the bottom of the element's "square" on the table, under its one or two letter chemical symbol. This number is usually expressed as a decimal rather than as a whole number. - Note that the relative atomic masses listed on the periodic table are average values for the associated element. Chemical elements have different isotopes - chemical forms that differ in mass because of the addition or subtraction of one or more neutrons to the atom's nucleus. Thus, the relative atomic mass listed on the periodic table is suitable as an average value for atoms of a certain element, but not as the mass of a single atom of that element. - Relative atomic masses, as listed on the periodic table, are used to calculate molar masses for atoms and molecules. Atomic masses, when expressed in amu, as on the periodic table, are technically unitless. However, by simply multiplying an atomic mass by 1 g/mol, a workable quantity is obtained for an element's molar mass - the mass (in grams) of one mole of an element's atoms. 3Understand when periodic table values are useful. As has been noted, the relative atomic masses listed for each element on the periodic table are average values of all of an atom's isotopes. This average value is valuable for many practical calculations - like, for instance, when calculating the molar mass of a molecule comprised of several atoms. However, when dealing with individual atoms, this number is sometimes insufficient. Because it's often an average of several different types of isotopes, the value on the periodic table isn't the exact value for any single atom's atomic mass. The atomic masses for individual atoms must be calculated by taking into account the exact number of protons and neutrons in a single atom.Ad Method 2 of 3: Calculating Atomic Mass for an Individual Atom 1Find the atomic number of the element or isotope. The atomic number is the number of protons in an element, and never varies. For example, all hydrogen atoms, and only hydrogen atoms, have one proton. Sodium has an atomic number of 11 because its nucleus has eleven protons, while oxygen has an atomic number of 8 because its nucleus has eight protons. You can find the atomic number of any element on the periodic table - in nearly all standard periodic tables, it's the number above an element's one-or-two-letter chemical symbol. This number will always be a positive whole number. - Let's say that we're working with the carbon atom. Carbon always has six protons, so we know its atomic number is 6. We can also see on the periodic table that the square for carbon (C) has a "6" at the top, signifying that carbon's atomic number is six. - Note that an element's atomic number doesn't have any direct bearing on its relative atomic mass as listed on the periodic table. Though, especially among elements at the top of the periodic table, it may seem that an atoms' atomic mass is about twice its atomic number, atomic mass isn't ever calculated by doubling an element's atomic number. 2Find the number of neutrons in the nucleus. The number of neutrons can vary among atoms of a certain element. While two atoms with the same number of protons and differing numbers of neutrons are both the same element, they are different isotopes of that element. Unlike the number of protons in an element, which never changes, the number of neutrons in atoms of a certain element can vary often enough that the average atomic mass of the element must be expressed as a decimal value between two whole numbers. - Let's say the carbon atom we're working with has six neutrons. This is by far the most common isotope of carbon, accounting for nearly 99% of all carbon atoms. However, about 1% of carbon atoms have 7 neutrons. Other types of carbon atoms with more or less than 6 or 7 neutrons exist in very small amounts. 3Add the proton and neutron count. This is the atomic mass of that atom. Don't worry about the number of electrons orbiting the nucleus - their combined mass is very, very small, so, in most practical cases, it won't significantly your answer. - Our carbon atom has 6 protons + 6 neutrons = 12. The atomic mass of this specific carbon atom is 12. If it was a carbon-13 isotope, on the other hand, we would know that it has 6 protons + 7 neutrons = an atomic weight of 13. - Because individual atoms are exceptionally small, scientists typically work with atoms in larger quantities called moles. A mole is the amount of a substance with as many atoms as there would be in 12 grams of the isotope carbon-12. This number is roughly 600 sextillion (6 times 10 to the 23rd power) atoms, and is known as Avogadro's number, after the scientist who defined it. Method 3 of 3: Calculating Relative Atomic Mass (Atomic Weight) for an Element 1Determine which isotopes are in the sample. Chemist often determine the relative proportions of isotopes in a given sample by using a special tool called a mass spectrometer. However, at student-level chemistry, this often provided for you on school tests, etc., in the form of established values from scientific literature. - For our purposes, let's say we're working with the isotopes carbon-12 and carbon-13. 2Determine the relative abundance of each isotope in the sample. Within a given element, different isotopes appear in different proportions. These proportions are almost always expressed as percentages. Some isotopes will be very common, while others will be very rare - at times, so rare that they can barely be detected. This information can be determined through mass spectrometry or from a reference book. - Let's say that the abundance of carbon-12 is 99% and the abundance of carbon-13 is 1%. Other carbon isotopes do exist, but they exist in quantities so small that, for this example problem, they can be ignored. 3Multiply the atomic mass of each isotope by its proportion in the sample. Multiply the atomic mass of each isotope by its percent abundance (written as a decimal). To convert a percentage to a decimal, simply divide it by 100. The converted percentages should always add up to 1. - Our sample contains carbon-12 and carbon-13. If carbon-12 makes up 99% of the sample and carbon-13 makes up 1% of the sample, multiply 12 (the atomic mass of carbon-12) by 0.99 and 13 (the atomic mass of carbon-13) by 0.01. - A reference book will give percent proportions based on all the known amounts of an element's isotopes. Most chemistry textbooks include this information in a table at the end of the book. A mass spectrometer can also yield the proportions for the sample being tested. 4Add the results. Sum the products of the multiplications you performed in the previous step. The result of this addition is the relative atomic mass of your element - the average value of the atomic masses of your element's isotopes. When discussing an element in general, and not specific isotopes of that element, this value is used. - In our example, 12 x 0.99 = 11.88 for carbon-12, while 13 x 0.01 = 0.13 for carbon-13. The relative atomic mass of our example is 11.88 + 0.13 = 12.01. Give us 3 minutes of knowledge! - Some isotopes are less stable than others and break down into elements with fewer protons and neutrons in their nuclei as they discharge parts of themselves. These isotopes are called radioactive. Things You'll Need - Chemistry reference book Sources and Citations In other languages: Italiano: Calcolare la Massa Atomica, Español: calcular la masa atómica, Deutsch: Die atomare Masse berechnen, Português: Calcular a Massa Atômica, Nederlands: Atoommassa berekenen, Français: calculer une masse atomique, Bahasa Indonesia: Menghitung Massa Atom, Русский: рассчитать атомную массу Thanks to all authors for creating a page that has been read 516,604 times.
Tables are commonly used in collecting and organizing raw data during an experiment and also for representing final data to be included in a paper or report. Most raw data are recorded in tabular form in a spreadsheet, a lab notebook, or a lab manual; but once recorded, data need to be reorganized, summarized, and reshaped into a final table or graph (see fig. 1). In some cases, lab experiments will require sketches from observation and may or may not need a table to go along with them. In most cases you’ll be using tables to collect and then organize your data. Since tables are so important for data management in the science laboratory, you need to know the basics about designing a table for your data. The representation of data in a table is formally referred to as “tabular presentation.” Tabular presentation of data allows data to be organized for further analysis, allows large amounts of raw data to be sorted and reorganized in a neat format, and allows the inclusion of only the most important or relevant data. It also facilitates a dialogue between the text and the exact numbers in your results, so that you don’t have to describe all the specific numerical values in your report. On the other hand, you should never put data in a table if you can describe it efficiently in one or two sentences. In summary, tabular presentation lets you place your results in an organized display of rows and columns that enable you to group your data by different classifications so that you can make comparisons and better understand your data. When using a table as a final representation of data to communicate your results in your report, list specific data values or draw comparisons between variables by listing subtotals, totals, averages, percentages, frequencies, statistical results, etc. Tables are not the best choice when you want to show a trend or relationship between variables. These are best represented by graphs. Good tables should be easy to read across rows and down columns, easy to understand, and easy to refer to in the text of your report. They should also include only relevant data from your results. Parts of a table Example 1 : Table with Labels Title: The title provides a brief description of the contents of the table. It should be concise and include the key elements shown in the table, for example, groups, classifications, variables, etc. It should never be more than two lines. Although, there are varying styles for writing a title, most titles should be underlined or italicized, and the first letter of each word should be capitalized following the rules for any title, or the entire title can be in caps. Periods are left out at the end of the title. If the title is two lines long, the lines can be either single-spaced or double-spaced depending on the style you’re using. Sometimes referred to as the table legend, a table’s title should always go above the table. Table number: Tables should be numbered in the order that they are referred to in your report, as Table 1, Table 2, and so on. The table number has a period at the end and a space to separate it from the title, which normally follows the table number. Headings & Subheadings: While data form the body of a table, headings and subheadings allow you to establish an order to the data by identifying columns. They should be written in the singular form unless they refer to groups, e.g., men, women, etc., and the first letter of the first word should be capitalized. Headings should be key words that best describe the columns beneath them. They should not be much longer than the longest entry in their columns. Example: - Column Headings: Each column has a heading in order to identify what data are listed below in a vertical arrangement. When the column heading is above the leftmost column, it is often referred to as the “stubhead” and the column is the “stub column.” This column usually lists the independent variable. The data that follow the stub column are known as the “stub.” All other column headings are simply referred to as “column heads.” Note that units should be specified in column headings when applicable. - Column Spanner: A heading that sits above two or more columns to indicate a certain classification or grouping of the data in those columns. A column spanner may also specify units, when appropriate. Table Body: The actual data in a table occupying the columns, for example, percentages, frequencies, statistical test results, means, “N” (number of samples), etc. Table Spanner: A table spanner is located in the body of the table in order to divide the data in a table without changing the columns. Spanners go the entire length of the table and are often used to combine two tables into one in order to avoid repetition. A table spanner may be written in the plural form. Dividers: Dividers are lines that frame the top and bottom of the table and, or mark the different parts of a table. They are often used for division or emphasis within the body of a table. Table Notes: You may use table notes to explain anything in your table that is not self-explanatory. While basic symbols and abbreviations like SD for standard deviation, N for sample size, and % for percentage, are commonly used, you may have other technical terms or other issues that you wish to explain. In these cases, you would place an asterisk (*) for the first note you need after the specific data value. Then, you would place the asterisk below the table followed by the note or explanation required for that value. Other data values requiring notation would get two, three asterisks, or a stacked cross (‡) in that order. Notes following these additional items would follow the first note using the same format. Notes that apply to the table in general should be listed after the word “Note: ” under the table. When you are collecting data during a laboratory experiment, it is important that you record it in tabular format in a spreadsheet, lab manual, lab notebook, or word processing software. Your rawshould include all the data you collected during an experiment as well as all necessary calculations. Whether the final version of your data representation is a table or a figure, this initial tabulation will make it easy for you to read and interpret your data. The first thing a table needs is a title. Make sure your title is descriptive of the data you are going to collect. There should be a place for the date and the name of the recorder(s). In labs dealing with multiple variables, the table may have both headings and subheadings. See above for a description of the parts of a table. Columns should be titled with the name of the variables followed by the units of measure in parentheses. Extra columns should be made to allow room for observations, calculations, and notes. Each extra column should be labeled appropriately. Usually, the independent variable(s) is recorded in the first column, and the dependent variable(s) is recorded in the subsequent column(s). The number of observations taken determines the number of rows. Example 2 : Raw Data Spreadsheet Tabular Presentation of Data Once you are ready to include your results in your report, you may decide that the best representation for your data is a tabular presentation. You may be working with raw data that you collected yourself during an experiment, and you may want to revise it so that it includes only relevant data and so that it is organized properly. You may also be working with long lists of raw data collected by other people or given to you by your laboratory instructor. In this case, it is up to you to sort through all the data and find a way to best represent it in tabular form. To accomplish this task, you’ll need to be familiar with the basic rules for tabular presentation: - Limit your table to data that are relevant to the hypotheses in the experiment. - Be certain that your table can stand alone without any explanation. - Make sure that your table is supplementary to your text and does not replicate it. - Refer to all tables by numbers in your text, e.g., Table 1, 2, 3… - Describe or discuss only the table’s highlights in your text. - Always give units of measurement in table headings. - Align decimal places. - Round numbers as much as possible. Try to round to two decimal places unless more decimals are needed. - Unless using a specific format style that requires that you place tables separately at the end of the report, place the tables near the text that refers to them. - Decide on a reasonable amount of data to be represented, not too little so that the reader does not understand you results, but not too much so that the reader is overwhelmed and confused. - Only include the necessary number of tables in your paper, otherwise, it may be redundant or confusing to the reader. - Do not use tables if you only have two or fewer columns and rows. In such cases, a textual description is enough. - Organize your tables neatly so that the meaning of the table is obvious at first glance. If the reader spends too much time deciphering your table, then it is too complicated and not efficient. - Remember that too many rows or columns could make it difficult for the reader to understand the data. You may need to reduce the amount of data, or separate the data into additional tables. - If you have identical columns or rows of data in two or more tables, combine the tables. - Provide column/row totals or other numerical summaries that can make it easier to understand the data. - Be consistent with your tabular presentation. Use consistent table, title, and heading formats. Textual (Word) Tables: Oftentimes, you may need tables that have textual data in the body. Usually this is the case when you’re dealing with qualitative data. These tables serve the same function as any table–to make comparisons of items easy. These tables are also used when you want to present examples, which may be grouped in a certain way, or when you want to show categories of different items. Example 3 : Text Table Statistical Tables: These tables can present descriptive or inferential statistics or both. Descriptive statistics are tabulations such as mean, standard deviation, mode, range, or frequency. Inferential statistics refers to statistical tests. In such tables, statistical test values are presented. Example 4: Statistical Table Numerical Tables: These are the most common types of data, which typically represent quantitative data, but sometimes may present a combination of quantitative and qualitative data. As its name suggests, most of the body of the table consists of specific number values. Example 5: Numerical Table Best practice in tabular presentation refers to designing tables that can be read easily and quickly. The faster someone can read a table, the better it is. Remember these two words: ease and speed! There are ways to accomplish this by manipulating contrast, alignment, spacing and ordering. All these elements help to achieve clarity so that the reader can pick out specific data and understand the discussion of your results. Contrast: By making key elements of your table stand out from one another, you can group or distinguish data from each other. For example, you could bold the title, dividers, or headings. You can use different font sizes, styles, or letter cases for different elements in your table. You can use color to emphasize backgrounds or text. Regardless of which of these you choose for creating contrast, remember that “less is more” when it comes to creating an effective table. Alignment: Alignment is important for keeping your table neat and clear. For example, all numbers in the columns should line up with each other and with their headings. Structure your table so that all elements seem to be properly aligned with each other–titles, headings, data, dividers, notes. Ordering: Group items that are similar to give a sense of structure and meaning to your table. This will also help break up the data, making it easier on the eye. Another way to order data is to indent subordinate data when it falls below specific column data. Spacing: Manipulating the “white areas” around the table can also help clarify and organize the table. For example, you should always have enough space around and between text so that it stands out. You can use space to separate groups or emphasize them. Example 6: Best Practice This example shows the use of contrast to set the two types of forests apart. It also uses bold-faced and varying font sizes to distinguish the column headings from the table spanners. Spacing beneath the column headings creates additional contrast. Using a border around the table also makes it stand out more and contains the data nicely. Notice that all numbers are aligned by decimal place and that all text is centered. The next example shows this same table without the use of “best practice.” Example 7: Poor Practice With all the gridlines, lack of contrast, and poor use of space and alignment, this table is difficult to read. Example 8: Best Practice This table makes use of appropriate groupings in order to break the list apart and make it easy to follow. Good use of space and varying size and bold-faced fonts also create a nice contrast and make it easy on the eyes. Below is the same table following poor practice. Example 9: Poor Practice Notice that this table lacks grouping of any kind, making it difficult to sort through the list. Title and header formatting is not consistent throughout, and the numerical data is centered instead of left-aligned, making it difficult to compare values. There is no contrast or use of space, so this table is a lot less easy on the eyes than the one above.
The Forgotten First Step Toward Freedom for SlavesHistorians/History The British, who did not form their first antislavery organization until seven years later, are usually credited with this accomplishment, having banished slavery in their remaining colonies a half century later. It's time to reclaim this achievement. The legislative authority of the people of Pennsylvania, a sovereign state before the creation of the U.S. Constitution, struck down an institution as old as the Bible -- one that many had inveighed against, but few had imagined so vulnerable. Only the sustained turbulence of race relations in the United States can explain the neglect of this landmark law. The American Revolution had provided the impetus for America's first antislavery movement. The tension generated by demanding liberty yet tolerating human bondage provoked an avalanche of words. "How is it that we hear the loudest yelps for liberty among the drivers of negroes?" the famed English lexicographer Samuel Johnson asked. Mindful of this debate, enslaved men and women in the North began petitioning successfully for their freedom. A system of coerced labor that had spread in the British colonies with scarcely a murmur of opposition suddenly appeared like a blot on the escutcheon of the new republic. Action supplanted high-minded talk in the years that followed. From the simple preamble of the Massachusetts state constitution to more intricate statutes elsewhere, every Northern state found a way to phase out unfree labor. New Jersey was the last to do so, in 1804. In New York City, where one quarter of the laborers at that time were enslaved, abolition represented the largest peaceful intrusion upon private property in the annals of government. New York's law also demonstrated the power of a democratic people to deliberate and move in novel areas. To be sure, these path-breaking acts compromised with the grim reality of slave owners' property rights that came with legalized human property. The Pennsylvania statute required the children of slave women born after March 1, 1780, to serve their masters until they reached the age of 28. Gradualism represented the politics of the possible. Even so, emancipation tested the law-enforcement skills of Northern states compelled to check the felonious dispatch of slaves to the South. The successes of these measures removed the incubus of slavery from Northerners and left white Southerners with a "peculiar institution." The old surveyors' boundary between Maryland and Pennsylvania -- the Mason-Dixon line -- became a symbolic divide between free labor and slavery. For a while it seemed possible that principle might trump skin color as the basis of American nationality. A freed slave, James Mars, exuded confidence in his diary that "the time is not far distant when the colored man will have his rights in Connecticut." The possibility of achieving freedom lured many Southern slaves to liberate themselves by escaping to the North. New African-American churches, schools and mutual help associations sprang into existence, but racial prejudice intensified with the increase in the number of freed men and women. The doors to full citizenship that had seemed to be opening wide in 1780 slowly swung shut. Emancipation appeared to many white Americans a dubious accomplishment. A small minority of reviled abolitionists kept the cause of human freedom alive while the Southern planters' drive to expand slavery's realm brought on the Civil War. The North's victory put an end to slavery. The Emancipation Proclamation became the icon for the future. Reconstructing the rebellious states and preparing freed men for citizenship exhausted the nation's moral energy. When white Southern representatives returned to Congress, they pressed hard for acceptance of their white supremacist views. Racial prejudice reappeared in the virulent form of legal segregation in the South and informal segregation in the North. With a new, white consensus that emancipation had been a political necessity but a social failure, there were no calls for celebrating the nation's first path-breaking acts to extend freedom to all. School books rarely mentioned Northern abolition, preferring to emphasize the climatic conditions that made slavery less attractive in the North. Reintegrating the South into the union came at the cost of any serious study of its peculiar institution. At the most advanced center for historical scholarship of the day, Johns Hopkins University, historians construed slavery as a boon to the slaves and a responsibility for slave masters. When historians in recent years turned their attention to the North's experiment with abolition, the virulence of anti-black hostility and the gradualness of the process of emancipation loomed larger than the legislative measures themselves. And so Pennsylvania's ground-breaking law again went uncelebrated. Playing the race card in the United States has always entailed downplaying the historic campaigns to rid the nation of slavery, for to praise the abolitionist was to demean the Southern grandee who held men and women in bondage. Eager after the Civil War to rehabilitate the defeated Southerners, American leaders neglected one of our proudest achievements -- being the first people in the world to legislate against slavery. When all of us finally agree that citizenship should have not have a color, we'll be ready to commemorate March 1, 1780. This piece was distributed for non-exclusive use by the History News Service, an informal syndicate of professional historians who seek to improve the public's understanding of current events by setting these events in their historical contexts. The article may be republished as long as both the author and the History News Service are clearly credited. comments powered by Disqus Nathaniel Brian Bates - 3/10/2005 It is important to remember that first great wave of emancipation that swept the North during and after the Revolution. It is often forgotten for some reason. Nathaniel Brian Bates - 3/10/2005 It is important to remember that first great wave of emancipation that swept the North during and after the Revolution. It is often forgotten for some reason. Marc "Adam Moshe" Bacharach - 3/5/2005 I honestly think you have completely gone off the deep end here, buddy. You obviously have a serious problem with black people, who you seem to believe have gotten all “uppity” and out of hand do to all those liberals getting crazy ideas of equality into their fragile little minds. The last few lines of your lat post were the smartest you have ever said. I agree 100% with Bill Cosby, although if I were a betting man, I would bet the bank that he would agree with almost nothing that you have said here. Your rants about liberals and blacks are beyond foolish, they are as racist as they are irrelevant to anything about the article or the discussion. I appreciate your final “surrender” of sorts, but I am sure Derek will agree that these discussions are not about winning or loosing, and I don’t believe either of us needs any validation from a man who believes that civil rights activists in the 60’s likely ended up as rioters or criminals. Vernon Clayson - 3/5/2005 Moshe and Catsam, not quite as catchy as flotsam and jetsam, but it does have a kind of cachet. Even though you are probably white, you are remindful of the young Blacks on their soap boxes, shouting at and challenging passerbys in student unions in the 1960's. Most of us thought they were kind of novice Malcom X's, ranting against the man. Most weren't serious students, most were outsiders taking advantage of the forum the college provided. My guess is that many of those individuals eventually became involved in the riots in any number of cities during the 1960's and early 1970's, or ended up in prison for other angry and deadly acts. I wonder if any of them are as embarrassed by their actions during that time as so many of the so-called hippies of that era are now, probably not, the liberals still need them to think they were right. In closing, I think the two of you should take a lesson from Bill Cosby who has gotten away from his song and dance act and now uses his celebrity to espouse the need for adults to become more involved in guiding their children into the mainstream and away from the self-pitying subculture of hip-hop speak, ill-fitting clothing and violent gangs. I will speak no more of this, I give up, you win. Derek Charles Catsam - 3/5/2005 Once again you draw an awful lot of assumptions about where I have or have not lived, walked, traveled and otherwise. You keep plugging your biography as if you are the only one ever to have lived on the street, been in inner cities. Please refrain from idiocies like "cloistered hall reading and writing," which in addition to not actually making any sense, bear no reflection on reality. If you'd like tro compare our street experiences off line, I'll gladly do so. But knock it off with baseless assertions about people whom you don't know. You have no idea where I have lived, the neighborhoods I have frequented, and so forth. Don't hide your vaguely racist categorizations about African American neighborhoods behind some claim to be "street." Say the dumb things you've been saying on the street even in a middle class black neighborhood with no crime and you'd likely get your teeth kicked in - and rightfully so. What you are talking about when you mention "liberalism giving a free pass" is beyond me. A free pass to what? From whom? Will they validate parking? Who asked for or presupposed a free pass from whatever this free pass protects? What on earth are you talking about? Start making sense. For the love of God, start making sense. Niothing is fatuous about sayiong blacks are part and parcel of the Democratic Party. That was my argument to begin with. What I said was fatuous was your assertion that the Democratic Party infers that slavery still exists and the silly, poor, reasoning you used to get there. Try to represent your own arguments honestly before mischaracterizing the arguments of others. Vernon Clayson - 3/3/2005 Mr. Catsam, on your comment of March 2nd, It appears I did have you and Mr. Moshe lumped together, maybe because birds of a feather, etc., or perhaps because I was kind of rushed when I commented last and didn't bring my "A" game. Anyway, what's actually fatuous about thinking Blacks are part and parcel of the Democrat party, you are not likely to deny that whites are part and parcel of the Republican party. If it escaped you that Bill Clinton was obviously condescending in his approach to Blacks, you were not paying attention. I admit Republicans are reaching out to minorities but it isn't nearly so blatantly hypocritical, they at least try to make it appear that it's a two-way street, but not Massa Clinton, he danced the buck and wing, swayed with the choir and, for the purposes of political expediency, became our first black president (but not really). You indicate you are white and a liberal, and therefore more understanding, if what I see and read is correct. I'll tell you what, how about if I point out areas in Watts,CA, Liberty City, FL, and Detroit, MI, and a dozen other cities, and you walk them any evening and see if that liberal status gets you a free pass. The majority of black adults bar their doors and don't venture out, I think when they are as safe as they would be in most white neighborhoods and you can walk black neighborhoods safely in your liberal white understanding, I will soften my rhetoric. In closing, it appears that you think a person can't express an opinion that hasn't been held and written before. My thoughts are my thoughts although many rather astute persons share my feelings. I survived years of life on the street, viewing it from there rather than from some cloistered hall reading and writing - although I've also done that, it's much less fearful, frustrating and confusing. Oscar Chamberlain - 3/3/2005 I'm honestly having trouble reading the Somerset case in the link because of the way material is interspersed in it My understanding before today was that it stated that slavery could not exist in the absence of positive law. Colonial acts were subject to veto by London, and the acts establishing slavery stood. Whether we like it or not, such positive law existed in the United States. It is pretty clear from British history that the government in London did not think that Somerset alone eliminated slavery in the other colonies. However, I would never deny the importance of the case in influencing attitudes in both politicians and the judiciary, in the US and in Britain. As far as the broader claim is concerned, that slavery had been outlawed for a millenium, I think this is a case of mistaking a line of precedent for a fuller historical truth. They can be identical, but quite often are not. Oscar Chamberlain - 3/3/2005 I don't know about Pennsylvania, but generally, such gradual emancipation did keep the child of the slave with the mother. To what extent that child was treated as a slave or as the child of a servant or farm laborer probably depended upon the specific owner, unless the statute had some provision for this. And, in the context of the times, it was a big step. Marc "Adam Moshe" Bacharach - 3/2/2005 Fist off, I would like to thank Derek for his generous appraisal. I had assumed that your post was addressed to me. Now on the “substance” of your post. 1) “surely you realize that any number of Black spokespersons within the Democrat Party, and you said that 90% of the Blacks vote Democrat, frequently refer to slavery, slavemasters and the ubiquitous JIM CROW policies of the various governments and employers, ipso facto, ergo, any number of Democrats infer slavery is still with us.” I agree that slavery remains very much a part of black culture and ideology, just as the Holocaust remains very much a part of Jewish culture and ideology and the American Revolution for most Americans (how often are the Founders, or “founding principles” evoked by politicians of both parties?). However, references to this does not signify any attempt to portray Democrats as somehow more “anti-Slavery” than Republicans (the party of Lincoln). Furthermore, I believe that you are confusing black ministers, who often carry a political role, and actual political candidates. I personally have never heard a Democratic candidate infer in ANY WAY that slavery is still here or that Jim Crow is still around. I have heard however, a prominent Republican Senator suggest that the nation would have been better off had a racist segregationist been elected president in 1948. Racism, on the other hand, still does exist, a reality very much appreciated by blacks and perhaps not so much by as many whites. Thus when courting the black vote, reminding them that you agree that racism still exists is simply good politics (and accurate too). 2) “You speak of race card, that is another example of what I said earlier, race means non-whites when liberals speak of it.” I agree with Derek’s point on this. However, I also think that race means non-white when conservatives speak of it as well. 3) “As for the Republicans, if they try to promote a black or hispanic person, or a female of any race, that automatically makes them anathema to Democrats - you inferred that yourself with your mention of Clarence Thomas and Miguel Estrada” Actually, my use of those people were used to prove simply that Republicans are more than willing to use race when they benefit from it. Also, why would you accuse liberals of disliking minority candidates? Do you have any evidence for this, or do you assume that they must since they hesitated when it came to some candidates who also happen to be minority? If this is the case, are you not “playing the race card” yourself?? 4) “- and what were the Democrats, especially that terrible Democrat Senator Boxer and that boring Senator Kerry trying to prove when they put Condoleeza Rice through the ringer?” “The terrible,” and the “boring.” Rather petty and silly comments, don’t you think? Why not just go the extra step and call them “poopie-heads”? In any event, they were trying to prove nothing. If you listened to their questioning, they were attempting to hold Rice accountable for her statements and judgment as National Security Advisor, a perfectly legitimate role. 5) “Had she been a Clinton candidate, the praise would have been through the roof.” You are probably right about this. That is the nature of partisan politics. After all, had Clinton invaded Iraq based on false intelligence, he would have been impeached, right? After all, if Republicans held investigations and spent millions in tax payer money to hold hearings on potential wrongdoings from the day he was born to then, imagine if he actually made a mistake of significant consequence? Where we part ways is that you seem to believe that Democrats hold a monopoly on partisanship. Even a brief look at the years 1992-2000 will demonstrate the factual error in this assumption. 6) “You again gave examples where you feel aggravated, and shame, for the usual atrocities, those that play to the Jews and Blacks, and included slavery again - as I have come to expect from you, as you can't seem to get away from that.” You make it sound as if I simply brought up the subject arbitrarily. I would remind you of your own statement which I was responding to. You said: “It is completely unrealistic that anyone today should feel responsible, or feel aggrieved, for those persons caught up in the policies and practices, acceptable at the time, of a now ancient culture.” I agreed in part and disagreed in part. If you have “come to expect” from me that I will address the points that you make as clearly and thoughtfully as I can, than I take the comment as a compliment (although I suspect it has less than generous intentions). 7) “Jesse Jackson, or maybe Al Sharpton, would have been there in a matter of hours shouting Jim Crow and hate crime.” I cannot help but notice that you use those two people an awful lot as representatives of “liberals” and “Democrats.” It is worth noting that many liberals disdain those people and when both ran for their party’s nomination, both lost. They are no more representative of liberals than Pat Robertson is of conservatives. They are liberals, to be sure, just as David Duke is a conservative, but this hardly gives you the right to exaggerate their significant beyond all proportions simply to continue a straw man argument. 8) “As long as people like you continue to tell Blacks, especially the young and impressionable, they are being treated inequitably and have something coming because their great-great-grandparents were slaves, many of them will ride that race card.” I am afraid you are allowing your prejudice to make several assumptions in the above statement. Allow me to point them out: - You assume that blacks are not exposed to racism and that the concept must be told TO them by “people like” me, without which they would never know about inequality - You assume that recognizing that racism exists means that they have “something coming because their great-great-grandparents were slaves.” Can’t people desire an end to racial inequality without thinking that they have “something coming” to them. - You assume that after slavery was abolished, racism itself was abolished and that all of the grievances some minorities have must be caused by slavery alone, which of course ended long ago Those assumptions are incorrect and thus the entire premise of your argument is incorrect. 9) “How about saying that the majority work at honest jobs and live the same lives as the majority of the white population?” How about saying that? I agree entirely. Derek Charles Catsam - 3/2/2005 Um, Vernon -- I think Adam's post was excellent and that he ought to get credit forbeing the one to whom you are responding. Your logic is wretched, complete with misplaced latin phrases. 90% of blacks vote Democrat (true). And I did say that. But i did not say nor have you come close to ever showing that 90% also invoke slavery as a prime concern in their politics. Thus the rest of your assertion trying to tie Democrats in with claims that slavery is still with us is utterly fatuous. Race means "non whites" when liberals speak of it? Really? When I talk about race my emphasis is on black white, with no lack of discussion about whites. I am white. But it seems rather bold of you to assert that I do not speak about Hispanics or other minority groups, who, as Adam has pointed out, have often been lumped with blacks for the purpose of discrimination. It might be nice to know what you are talking about when you write about what others do or do not, have or have not said about the matter of race. The rest of your post is a bit difficult to comprehend. And since I'll trust that before long you'll learn to differentiate the names "Adam" and "Derek", I'll let Adam take on from here if he so chooses to confront your cavalcade of anecdotes which not only do not even begin to prove your larger thesis, but that at points do not even mean what you presume they mean. Vernon Clayson - 3/2/2005 Mr. Catsam, you are indeed a tough taskmaster but I will try. You ask if I have evidence that the "Democratic" Party" has inferred that slavery still exists; my thought on that is it may not be a stated part of the Democrat's rules for campaigning but surely you realize that any number of Black spokespersons within the Democrat Party, and you said that 90% of the Blacks vote Democrat, frequently refer to slavery, slavemasters and the ubiquitous JIM CROW policies of the various governments and employers, ipso facto, ergo, any number of Democrats infer slavery is still with us. You speak of race card, that is another example of what I said earlier, race means non-whites when liberals speak of it. As for the Republicans, if they try to promote a black or hispanic person, or a female of any race, that automatically makes them anathema to Democrats - you inferred that yourself with your mention of Clarence Thomas and Miguel Estrada - and what were the Democrats, especially that terrible Democrat Senator Boxer and that boring Senator Kerry trying to prove when they put Condoleeza Rice through the ringer? Had she been a Clinton candidate, the praise would have been through the roof. You again gave examples where you feel aggravated, and shame, for the usual atrocities, those that play to the Jews and Blacks, and included slavery again - as I have come to expect from you, as you can't seem to get away from that. I watched some reverse Jim Crow last evening on the O'Reilly Factor, a 295 pound black man beat a much smaller white man in a restaurant line, had it been the other way around, it would have been called a hate crime. Jesse Jackson, or maybe Al Sharpton, would have been there in a matter of hours shouting Jim Crow and hate crime. They both wouldn't have come because they obviously don't share pulpits, or collection plates. When I said Al Sharpton was used, it isn't like he didn't know it, he doesn't seem to mind playing that stepnfetchit role, for him it is a sound financial plan - the used is also a user and gets his TV face time, a little like Sammy Davis Jr. with Frank Sinatra and Dean Martin, except Bojangles Al was with John Kerry, Edwards, Dean and that strange little man from Cleveland. As long as people like you continue to tell Blacks, especially the young and impressionable, they are being treated inequitably and have something coming because their great-great-grandparents were slaves, many of them will ride that race card. How about saying that the majority work at honest jobs and live the same lives as the majority of the white population? Leroy John Pletten - 3/2/2005 Slavery was actually ALWAYS unlawful, i.e., unconstitutional, in the U.S., in both the colonies and later called states. The law had been the same, i.e., anti-slavery, for over a millenium in the legal system followed in the U.S. under Britain. The British high court years before Pennsylvania, in Somerset v Stewart (1772). precluded slavery constitutionality. This followed prior precedents including one under Queen Elizabeth I, Matter of Cartwright (1569). References are at http://medicolegal.tripod.com/slaveryillegal.htm . Pennsylvian was NOT taking a first step. It was FOLLOWING MANY steps, many prior precedents. Marc "Adam Moshe" Bacharach - 3/1/2005 You raise some important issues in your post, but the one I would like to address is the following: “I wonder why it is that some Historians want to tell American History, with no input about slavery? They want to tell the story only from the European point of view. Just as many Americans do not want to discuss the Massacre of Natives, or that America was built on land stolen from Natives, and worked by slaves. Why are folks so uncomfortable with the truth.” I think the reality is that all nations, the US included, tend to highlight the more noble aspect of their history and try to minimize the negative realities of 17th, 18th, and 19th century morality. Indeed, I would argue that nations behave very similar to individual citizens in the regard. A recent study indicated that when individuals who were shown a series of news stories about American history in which the US was perceived as “good,” and others in which the US was perceived as “bad,” respondents tended to remember those stories which conformed to their preconceived bias. Those who are highly cynical of the US and American interests tended to recall more stories where America had behaved poorly; respondents who were highly patriotic tended to be able to recall more stories where America had behaved morally. The social revolution in the 1960’s has revered a lot of the national ignorance about the darker sides of American history but unfortunately, people continue to view history through their own ideological prism. This is why it is so important to have courses in History and Political Science where professionals are sensitive to the biases inherent in academic research. Anita L Wills - 3/1/2005 It is interesting that one responder called Jesse Jackson a race baiter. Don't forget that Jesse was born in the Jim Crow South, and knows first hand about racism. Yes, Pennsylvania passed a law against slavery, and several Free Black communities sprang up. Just because there is a law does not mean it is adhered to. For instance in 1830 African slavery was outlawed in America. The Southern States got around that law by having slaves sent to the Caribbean, and seasoned. They were then sold in the Deep South, South Carolina, Louisiana, and Mississippi, as Caribbean slaves. My own Great Great Grandmother was sold into slavery in 1830, after it was outlawed. She was taken from Guinea, to Bermuda, seasoned, and then sold in South Carolina. Yes, there are laws, but somehow folks manage to get around them. In 1850, the Fugitive Slave Law was passed by Congress. That law allowed Southern Slave Owners to enter Northern States, and seize runaway slaves. On September 11, 1851, a slaver from Maryland, Edward Gorsuch, accompanied by a Federal Marshall, knocked on the door of William Parker, a Free Black. William Parker resided in Christiana Pennsylvania, just over the border from Maryland. An arguement ensued, as Gorsuch demanded his property, and Parker told him that no man could own another. A gunshot in the chest ended Gorsuchs life, and began brought the Fugitive Slave Law into question. Gorsuch was mortally wounded, and his son beaten almost to death. The Federal Marshall and his posse scattered. They had entered what was known as the Hub of Abolitionist activity, Lancaster Pennsylvania. The Feds attempted to over rule states rights, and on that day they lost. They also lost at trial, after attempting to charge, the mostly black prisoners with Treason. In fact shortly afterwards, the Fugitive Slave Law was abolished. I wonder why it is that some Historians want to tell American History, with no input about slavery? They want to tell the story only from the European point of view. Just as many Americans do not want to discuss the Massacre of Natives, or that America was built on land stolen from Natives, and worked by slaves. Why are folks so uncomfortable with the truth. Jesse Jackson, and any other historians have a duty to tell their truth. Of course it is more comfortable to hear a history in which certain folks are heroes, but that is not the history of America, nor the world. By the way, Jesse Jackson is a Minister, not a Historian. There are many distinguished African American Historians, but they usually do not get the publicity Jesse Jackson gets. Marc "Adam Moshe" Bacharach - 3/1/2005 I don't know if I would agree that it was small. The law ended the practise of a perpetual slave class by guarenteeing a growing population of free blacks. While in the South, the law virtually precluded the possibility of free blacks (particularly after the fugitive slave law) thus maintaining the belief that slavery was just a "natural" part of life, ordained by God, in the North, the PA law made full emancipation in the state inevitable, as the moral justification would diminish with each passing year. bai ren - 3/1/2005 It seems to me that the Pennsylvania law was a very small step. It did not abolish slavery, it limited it to 28 years. What was the position of the next generation? While women were waiting for freedom at age 28, were their children similarly bonded for 28 years? Marc "Adam Moshe" Bacharach - 2/28/2005 1) “However the subject of slavery will not be dropped anytime soon because race baiters, e.g., Jesse Jackson, Al Sharpton, etal., plus the Democrat party, need the inference, if not the substance, that slavery is alive and well in these United States.” Do you have any evidence that the Democratic Party has “inferred” that slavery still exists today, or are we to take this at your word? And I notice that you ignore the numerous examples of Republicans who would seem to fit the description. For example, When Clarence Thomas was fighting charges of sexual harassment, he declared his opponents “high-tech lynching for uppity blacks who in any way deign to think for themselves.” More recently was Democrats who opposed the nomination of Miguel Estrada to the U.S. Court of Appeals for the District of Columbia Circuit being accused of being anti-Hispanic. To reject Estrada, said Sen. Charles Grassley (Republican), "would be to shut the door on the American dream of Hispanic-Americans everywhere." How about Bush’s strategy of selling social security reform when he said recently that “African-American males die sooner than other males do, which means the system is inherently unfair to a certain group of people,” or when Republican Sen. Orrin Hatch declared "Every Hispanic in America is watching," as the vast majority of Senate Democrats voted to oppose the nomination of Alberto Gonzales as attorney general. Aren’t these Republicans “playing the race card” just as much as Democrats? I am not suggesting that you are wrong to say that the Democrats need race, but as the Republican party starts making inroads to minority communities, I notice that they need it just as much. 2) “It is completely unrealistic that anyone today should feel responsible, or feel aggrieved, for those persons caught up in the policies and practices, acceptable at the time, of a now ancient culture.” I feel aggravated when I read about the murder of Jews in the Holocaust, the slaughter of Tutsis in Rwanda, and the Jim Crow laws that have existed from the Civil War to very recently, why should I not feel aggravated to read about slavery? Your position seems to be that we should not only feel free of responsibility, but free of any shame that our country once practiced slavery. That may be your belief, and you are entitled to it, but it is not mine. I feel no responsibility for slavery, but I do feel shame that my country practiced it, and even greater shame to know about the 100 years AFTER slavery “ended.” 3) “Mostly, it's time this particular minority realized they are being used and the only thing the Bill Clintons and John Kerrys of the world want is their vote and they will say anything, promise anything to get it.” I ask again: Is there any substantive difference between Clinton and Bush? Does Bush and Republicans not pander to their bases just as surely as Clinton and Democrats do? Hasn’t Bush “said anything, promised anything” to get the vote of Evangelicals? Remember that while in office, Clinton cut the welfare rolls and became the first president to seriously address affirmative action reform (remember, “mend-it-don’t-end-it”). I know the following was actually addressed to Derek (whose post I agree with completely), but I hope neither he nor you will mind me addressing the points: 4) “I understand that, in your case, race only means Negro, or Black, or African American, whatever the current label is, and not Caucasian or Mongoloid, races that also continue.” It is not just Derek that considers race to mean primarily “black” and “white,” it is over 400 years of American policy and official law. The name of the case escapes me as of the moment, but I recall a SC case in which an Asian family went to court so that their daughter could attend a “white” school rather than the dilapidated “colored” school. The decision: Anyone who is not 100% white was declared to be legally “black.” This, for almost all of American history save the past 2 or 3 decades, race does indeed only mean white and non-white, usually black (any guesses as to what bathroom Indians, Latinos, and Arabs had to use?) 5) “Anyway, none of my ancestors owned slaves so I feel no guilt.” Neither the article, nor myself, nor Derek has suggested that you should feel guilty about slavery, and yet this is the second time in as many posts you have made it a point to say that you feel no guilt. Are you sure there is not some deeper issue here? 6) “By the way, he was still doing farm work into his eighties, it was a way of life for many generations, and he probably never heard of the "horrors of Jim Crow" while basically living a life similar to those who, now, resent that their ancestors endured hard work for similar room and board and financial pittance.” Unless your grandfather was either extremely isolated or completely illiterate, I find this extremely difficult to believe. 7) “Jim Crow is an overused excuse, get over it, move on.” You throw this sentence out and just leave it at that? In what way is it “overused,” and how is it used as an “excuse”? Who should get over it and move on? Everyone? Jim Crow existed whether you care you learn about it or not and it existed up until the 1960’s and into the 1970’s. The people who grew up under its banner are still alive and well and its effects are still with them. You may deny this basic reality if you like, just as you may deny the fact that soldiers in WWII and Vietnam are still effected emotionally and psychologically from their experiences, but in any event, it happened. 8) “As far as Al Sharpton, you probably need to do a little research on how he gained access to the campaign. You may be proud of him but he was used” You might be surprised to learn that in the primary system that we have, entering the race is essentially self-selection. Sharpton raised the necessary funds and got the necessary signatures to be put on the ballot and that is why he was there. Who are you suggesting “used” him and why would they? 9) “Sooner than you think, that 90% percent of African-Americans voting Democrat will be merely a token, overshadowed by the influx of Hispanics who will nearly equal the political power of the WASP's.” You are probably right, but do not believe that the Republicans will not have to pander and play the race card in order to do it. They already have, and guess what? It is paying off big time. Vernon Clayson - 2/28/2005 Mr. Catsam, of course there is a continuum of race, that speaks for itself as all races continue. I understand that, in your case, race only means Negro, or Black, or African American, whatever the current label is, and not Caucasian or Mongoloid, races that also continue. Also my comment is hardly a screed, it's rather brief. Anyway, none of my ancestors owned slaves so I feel no guilt. As a matter of fact my grandfather is listed as a servant in several census records because he worked for room and board and his pay, if any, would have been a pittance. Life was tough in the 1800's and early 1900's for most people, and I don't believe I'm owed anything, financially or morally, for his having been in servitude as a farm laborer for part of that time. By the way, he was still doing farm work into his eighties, it was a way of life for many generations, and he probably never heard of the "horrors of Jim Crow" while basically living a life similar to those who, now, resent that their ancestors endured hard work for similar room and board and financial pittance. Jim Crow is an overused excuse, get over it, move on. As far as Al Sharpton, you probably need to do a little research on how he gained access to the campaign. You may be proud of him but he was used, he was little more than a foil, a stepnfetchit, tolerated by the Democrats to show how they reach out and welcome the endlessly suffering (in his case, not much)minority. Sooner than you think, that 90% percent of African-Americans voting Democrat will be merely a token, overshadowed by the influx of Hispanics who will nearly equal the political power of the WASP's. Taken together, my first comment and this one, approach being a "screed." Derek Charles Catsam - 2/28/2005 In your partisan screed you seem to miss a larger point -- that there is a continuum of race in the US that extends from slavery, and thus that trying to compensate for slavery is also to try to compensate from the horrors of Jim crow, the injequities of segregeation. these things did not end in 1863 or 1865, and their concrete legacies did not end in 1964 or 1965. As for Hillary accepting Sharpton, I'm not quite certain I get your point. How could she prevent a candidate from being part of a primary process that she did not control? What a silly, silly little argument you make. never mind how patently offensive it is to assert that you know better than the 90% of African-Americans who vote democrat what is good for them. Vernon Clayson - 2/28/2005 My bet is that very few, if any others, will comment on this subject. That's mostly because slavery has long been illegal the United States and, therefore, not a current concern to the majority of American citizens. However the subject of slavery will not be dropped anytime soon because race baiters, e.g., Jesse Jackson, Al Sharpton, etal., plus the Democrat party, need the inference, if not the substance, that slavery is alive and well in these United States. It is completely unrealistic that anyone today should feel responsible, or feel aggrieved, for those persons caught up in the policies and practices, acceptable at the time, of a now ancient culture. I've read that someone, perhaps the "very" Reverend Jackson, brought up the quaint notion that freed slaves were cheated out of an 1860's promise of 40 acres and a mule, and not getting that, all Negroes, Blacks, African Americans, whatever they want to be called, alive now, should receive some kind of restituion. I can't see the restitution but I think any one of them who feels deeply about the forty acres and a mule should get them, but only if they promise to never ask for anything else, perhaps the exception might be to ask for a real job when the mule consumes more fodder than the forty acres produces. Mostly, it's time this particular minority realized they are being used and the only thing the Bill Clintons and John Kerrys of the world want is their vote and they will say anything, promise anything to get it. 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Factoring Cubic Polynomials – Steps, Definition With Examples Welcome, Brighterly learners! It’s time to embark on another fascinating mathematical adventure. Today, our journey is going to take us deep into the world of algebra, where we’ll unravel the mystery behind cubic polynomials. Now, you might be wondering, “What are cubic polynomials?” or “Why do we even need to learn about them?” Here at Brighterly, we understand these questions, and we’re committed to making sure you not only get the answers but also enjoy the process of learning. Because we believe that every new concept you learn is a key to unlock a new door in the vast mansion of mathematics! Factoring cubic polynomials may sound a bit complex, but we promise you, it’s just like solving an engaging puzzle. And we all love puzzles, don’t we? They challenge us, make us think, and when we finally solve them, they give us an incredible sense of achievement. Learning about cubic polynomials and how to factor them is no different! What Is Factoring Cubic Polynomials? Factoring cubic polynomials is an essential concept in algebra that serves as a gateway to more complex mathematical ideas. It might sound intimidating, but don’t worry! We’ll break it down into bite-sized chunks to make it fun and digestible. At its heart, factoring cubic polynomials is the process of breaking down a complex polynomial (a mathematical expression involving many terms) into simpler factors that, when multiplied together, give the original polynomial. It’s a lot like breaking down a chocolate bar into individual squares or breaking down a sentence into individual words. Factoring makes the polynomial easier to understand and work with. Definition of Polynomials In simple terms, a polynomial is an algebraic expression made up of ‘terms’ that are separated by ‘+’ or ‘-‘ signs. These terms consist of variables (like x or y) and coefficients (the numbers in front of the variables) raised to a non-negative integer exponent. For example, 2x² – 5x + 3 is a polynomial with three terms. Definition of Cubic Polynomials A cubic polynomial is a specific type of polynomial with a degree of three. The degree of a polynomial refers to the highest exponent in the polynomial. So, a cubic polynomial will always have one term where the variable is raised to the power of three. For example, x³ – 4x² + 3x – 2 is a cubic polynomial. Properties of Polynomials and Cubic Polynomials Properties of Polynomials Polynomials have several exciting properties. For instance, they’re closed under addition, subtraction, and multiplication, which means when you add, subtract, or multiply two polynomials, you always get another polynomial. Also, the degree of a polynomial gives us a lot of information about its shape and the number of solutions it has. Properties of Cubic Polynomials Cubic polynomials, being a type of polynomial, share these properties, but also have a few unique ones. Most notably, a cubic polynomial will always have at least one real root (solution), and it can have up to three. Also, the graph of a cubic polynomial is always a continuous curve without any breaks or sharp turns. Difference Between Polynomials and Cubic Polynomials The primary difference between polynomials and cubic polynomials lies in their degrees. While a polynomial can have any non-negative integer degree, a cubic polynomial always has a degree of three. This difference affects their properties, such as the number of solutions they can have and the shape of their graphs. Steps to Factor Cubic Polynomials Writing Steps for Factoring Polynomials Factoring polynomials generally involves identifying common factors among the terms, grouping similar terms, and using different factoring techniques such as difference of squares or the distributive property. Writing Steps for Factoring Cubic Polynomials Factoring cubic polynomials can be a bit trickier. You’ll often need to use a method called the factor theorem or synthetic division to identify one factor first and then break down the remaining quadratic polynomial. But don’t worry! We’ll be delving into these steps in detail in future articles. Practice Problems on Factoring Cubic Polynomials Sharpen your skills with these practice problems. Remember, the more you practice, the more comfortable you’ll become with these concepts! - Factor the cubic polynomial x³ – 6x² + 11x – 6. - Factor the cubic polynomial 2x³ – 9x² + 12x – 4. - Factor the cubic polynomial 3x³ – x² – 4x + 4. We hope this journey into the world of cubic polynomials has been enlightening and fun-filled! At Brighterly, our aim is not just to help you solve problems but to foster your love and curiosity for mathematics. We’ve seen what cubic polynomials are, explored their unique properties, and learned how to factor them. It might have been a bit challenging, but remember, challenges are what make learning exciting and meaningful. They are the stepping stones towards growth and mastery. Factoring cubic polynomials is a powerful tool in your mathematical toolkit. As you continue your adventures in mathematics, you’ll encounter this concept again and again. But worry not, because with practice and the Brighterly spirit of curiosity and persistence, you’ll be factoring cubic polynomials like a pro in no time! As always, remember, math is not a subject to be feared, but a fascinating world to be explored. So keep exploring, keep learning, and let Brighterly guide you on your mathematical journey. Until our next adventure, happy learning! Frequently Asked Questions on Factoring Cubic Polynomials What is a cubic polynomial? A cubic polynomial is an algebraic expression with a degree of three. This means it will always have one term where the variable (like x or y) is raised to the power of three. For example, an expression like x³ – 4x² + 3x – 2 is a cubic polynomial. How do you factor cubic polynomials? Factoring cubic polynomials usually involves a multi-step process that might include using the factor theorem or synthetic division. The goal is to break down the cubic polynomial into simpler factors. We’ll detail this process in future posts, but if you’re eager to start practicing, check out resources like Khan Academy or Math is Fun for more immediate guidance. What’s the difference between polynomials and cubic polynomials? While a polynomial is an algebraic expression that can have any non-negative integer degree, a cubic polynomial is a specific type of polynomial that always has a degree of three. This means a cubic polynomial will always have a term with the variable raised to the power of three. Math Catch Up Program - Learn Math Simple - Fast - Effective - Overcome math obstacles and reach new heights with Brighterly. Simple - Fast - Effective Overcome math obstacles and reach new heights with Brighterly.
Quadratic Formula Teacher Resources Find Quadratic Formula lesson plans and worksheets Showing 1 - 24 of 331 resources Quadratic FormulaLesson Planet 8 mins 9th - 12th CCSS: Designed The mechanics of using the quadratic formula are clearly detailed in this example-full presentation, along with how to identify and walk through the algorithm. Step-by-step attack methods are provided with examples of several different... How was the Quadratic Formula Derived?Lesson Planet 10 mins 6th - 12th If you or your class members are interested in how the quadratic formula is derived, then take a look at this video! The tutorial takes you through each step necessary to derive the quadratic formula from the general form for a quadratic... Deriving the Quadratic FormulaLesson Planet 7 mins 8th - 11th CCSS: Adaptable Formulas don't appear from thin air! Learn how to derive the quadratic formula by completing the square. As the video instructor demonstrates each step of the derivation, the quadratic formula begins to emerge until it is complete in the... Derivation of the Quadratic FormulaLesson Planet 9th - 11th CCSS: Adaptable What connection does the quadratic formula have with a quadratic equation? Using a matching activity, pupils construct the algebraic derivation of the quadratic formula in this Algebra II lesson task. The task provides two variations of... Deriving the Quadratic FormulaEngageNY 9th - 10th CCSS: Designed Where did that formula come from? Lead pupils on a journey through completing the square to discover the creation of the quadratic formula. Individuals use the quadratic formula to solve quadratic equations and compare the method to... Use the Quadratic Formula to Find Roots of the FunctionLesson Planet 5 mins 11th - Higher Ed CCSS: Adaptable Get to the root of the problem with an instructive lesson! Learners find the roots of a function using the quadratic formula. A video shows the process and includes an explanation of the substitution steps. Using the Quadratic FormulaEngageNY 9th - 10th CCSS: Designed What is the connection between the quadratic formula and the types of solutions of a quadratic equation? Guide young mathematicians through this discovery as they use the discriminant to determine the number and types of solutions, and... Using the Quadratic FormulaLesson Planet 7th - 12th CCSS: Adaptable Your learners will get plenty of practice solving quadratic equations in a worksheet using the quadratic formula. An extension to this activity would nicely connect MP5 concepts. Have learners use a graphing program to graph the solved... Quadratic Formula 1Lesson Planet 9th - 12th CCSS: Designed Take the first step toward understanding the quadratic formula. Given the general standard formula for a quadratic equation, pupils complete the square. Learners then convert the standard formula to an equation they can solve by taking a...
Not sure which of these videos to watch? Try out our 'Which Excel Formula to Use' App to get guidance. NOTE: All these free Excel video tutorials are streamed via YouTube. If your network does not allow YouTube videos, you can access the video via your smartphone or from a different network. How to use the DATE, DAY, MONTH and YEAR Functions in Excel The DAY, DATE, MONTH and YEAR functions in Excel identify the components of a date that you may be interested in and converts it into a date that Excel can read. In this example we have a couple of employees and their dates of birth because their bonuses are paid out on the 25th of their month of birth. So what we would like to do is get the exact date of birthday in the current year. What we need to do is break these birth dates into a DAY, MONTH, YEAR so that we can get rid of the year and create a new date. The first thing to work on is the day. In order to extract the day there is a function in Excel called DAY. So if we go to the function wizard, go to the DATE and TIME category you will see that there is a DAY function, and we say OK. All it asks is tell me where the serial number is or the date. We will just point it here. When we say OK you will see it takes out the 18th as the day. The next thing we want to extract is the MONTH of the birthday. So again, we activate the Function Wizard, go into the DATE and TIME categories, and there is a MONTH function here and we say OK. Again it asks us for the date we are looking at so we point it here and when we say OK, you will see it extracts the month of this persons birthday. In this example we don’t really need the year, but we are going to extract it anyway. So we can click on a cell, activate the function wizard, and go to the YEAR. It also asks for the date cell, if we click in here, and say OK we have the year of the birth date, so we now have extracted the Day, Month and Year of the birth date individually. We now want to turn this information into something that Excel can read and for the day we want to use the 25th as our payout date, the month will be the month of the persons birthday, and the year will just be the current year. There is a function in Excel called DATE which we can access through the function wizard, here, and now you just need to point to tell it where it must look for the year, and in this case we know we want the current year. It says where must I look for the month, and we know we want the persons birth date month which is over here. And the day, we know the payout is going to be on the 25th so we click it here. When we say OK, you will see it generates a date which is the bonus payment day, in the month of his birthday, in the year of his birthday. We can now easily copy all this information, take it all the way across, and you will see that immediately you will know the actual date, of when bonuses will be paid out, based on the birthday’s of the various employees. Please fill in your details below to get regular Excel tips and tricks and a free Quick Reference Download! Numbers seen as text in Excel A common problem, especially when importing data from other systems is numbers seen as text in Excel and not being treated like numbers e.g. they don’t add up and you get VALUE error messages. … Continue reading Data table all same values When first using Data Tables in Excel you may come across a situation where you feel you have done everything correctly, yet the data table is clearly wrong as all the numbers in the middle … Continue reading "Adrian and Team. Recently we had a most successful in-house training session at our company. I would like to extend my thanks and gratitude towards De Wet, who hosted the Excel Advanced course.– Gill Robbetze Lonmin
As Albert Einstein developed his theory of general relativity nearly a century ago, he proposed that the gravitational field from massive objects could dramatically warp space and deflect light. The optical illusion created by this effect is called gravitational lensing. It is nature's equivalent of having a giant magnifying lens in space that distorts and amplifies the light of more distant objects. Einstein described gravitational lensing in a paper published in 1936. But he thought the effect was unobservable because the optical distortions produced by foreground stars warping space would be too small to ever be measurable by the largest telescopes of his time. Now, almost a century later, astronomers have combined two powerful astronomical assets, the Sloan Digital Sky Survey (SDSS) and NASA's Hubble Space Telescope, to identify 19 new "gravitationally lensed" galaxies, adding significantly to the approximately 100 gravitational lenses previously known. Among these 19, they have found eight new so-called "Einstein rings", which are perhaps the most elegant manifestation of the lensing phenomenon. Only three such rings had previously been seen in visible light. In gravitational lensing, light from distant galaxies can be deflected on its way to Earth by the gravitational field of any massive object that lies in the way. Because of this, we see the galaxy distorted into an arc or multiple separate images. When both galaxies are exactly lined up, the light forms a bull's-eye pattern, called an Einstein ring, around the foreground galaxy. The newly discovered lenses come from an ongoing project called the Sloan Lens ACS Survey (SLACS). A team of astronomers, led by Adam Bolton of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and Leon Koopmans of the Kapteyn Astronomical Institute in the Netherlands, selected the candidate lenses from among several hundred thousand optical spectra of elliptical galaxies in the Sloan Digital Sky Survey. They then used the sharp eyes of Hubble's Advanced Camera for Surveys to make the confirmation. "The massive scale of the SDSS, together with the imaging quality of the Hubble telescope, has opened up this unprecedented opportunity for the discovery of new gravitational lenses," Bolton explained. "We've succeeded in identifying the one out of every 1,000 galaxies that show these signs of gravitational lensing of another galaxy." The SLACS team scanned the spectra of approximately 200,000 galaxies 2 to 4 billion light-years away. The team was looking for clear evidence of emission from galaxies twice as far from Earth and directly behind the closer galaxies. They then used Hubble's Advanced Camera for Surveys to snap images of 28 of these candidate lensing galaxies. By studying the arcs and rings produced by 19 of these candidates, the astronomers can precisely measure the mass of the foreground galaxies. Besides producing odd shapes, gravitational lensing gives astronomers the most direct probe of the distribution of dark matter in elliptical galaxies. Dark matter is an invisible and exotic form of matter that has not yet been directly observed. Astronomers infer its existence by measuring its gravitational influence. Dark matter is pervasive within galaxies and makes up most of the total mass of the universe. By searching for dark matter in galaxies, astronomers hope to gain insight into galaxy formation, which must have started around lumpy concentrations of dark matter in the early universe. "Our results indicate that, on average, these ‘elliptical lensing galaxies' have the same special mass-density structure as that observed in spiral galaxies," Bolton continued. "This corresponds to an increase in the proportion of dark matter relative to stars as one moves away from the center of the lensing galaxy and into its fainter outskirts. And since these lensing gelaxies are relatively bright, we can solidify this result with further ground-based spectroscopic observations of the stellar motions in the lenses." "Being able to study these and other gravitational lenses as far back in time as several billion years allows us to see directly whether the distribution of dark [invisible] and visible mass changes with cosmic time," Dr. Koopmans added. "With this information, we can test the commonly held idea that galaxies form from collision and mergers of smaller galaxies." The Sloan Digital Sky Survey, from which the SLACS lens-candidate sample was selected, was begun in 1998 with a custom-built ground-based telescope to measure the colors and brightnesses of more than 100 million objects over a quarter of the sky and map the distances to a million galaxies and quasars. "This type of gravitational-lens survey was not an original goal of the SDSS, but was made possible by the excellent quality of the SDSS data," said Scott Burles of the Massachusetts Institute of Technology in Cambridge, Mass., a SLACS team member and one of the creators of the SDSS. "An additional bonus of the large size of the SDSS database is that we can design our search criteria so as to find the lenses that are most suitable for specific science goals," said SLACS team member Tommaso Treu of the University of California, Santa Barbara. "Whereas until now we have selected the largest galaxies as our targets, in the next stages of the survey we are targeting smaller lens galaxies. There have been suggestions that the structure of galaxies changes with galaxy size. By identifying these rare objects 'on demand,' we will soon be able for the first time to test whether this is true." Added SLACS team member Leonidas Moustakas of the NASA Jet Propulsion Laboratory and the California Institute of Technology in Pasadena, Calif.: "These Einstein rings also give an unrivaled magnified view of the lensed galaxies, allowing us to study the stars and the formation histories of these distant galaxies." The SLACS Survey is continuing, and so far the team has used Hubble to study almost 50 of their candidate lensing galaxies. The eventual total is expected to be more than 100, with many more new lenses among them. The initial findings of the survey will appear in the February 2006 issue of the Astrophysical Journal and in two other papers that have been submitted to that journal. Dolores Beasley/Erica Hupp Space Telescope Science Institute, Baltimore Harvard-Smithsonian Center for Astrophysics, Cambridge, MA Jet Propulsion Laboratory, Pasadena, CA
In the Oscillators tutorials we saw that an oscillator is an electronic circuit used to generate a continuous output signal. Generally this output signal is in the form of a sinusoid at some predetermined frequency or wavelength set by the resonant components of the circuit. We also saw that there are many different types of oscillator circuits available but generally they all consist of an amplifier and either an Inductor-Capacitor, ( LC ) or Resistor-Capacitor, ( RC ) tank circuit used to produce a sine wave type output signal. Typical Electrical Waveform But sometimes in electronic circuits we need to produce many different types, frequencies and shapes of Signal Waveforms such as Square Waves, Rectangular Waves, Triangular Waves, Sawtoothed Waveforms and a variety of pulses and spikes. These types of signal waveform can then be used for either timing signals, clock signals or as trigger pulses. However, before we can begin to look at how the different types of waveforms are produced, we firstly need to understand the basic characteristics that make up Electrical Waveforms. Technically speaking, Electrical Waveforms are basically visual representations of the variation of a voltage or current over time. In plain English this means that if we plotted these voltage or current variations on a piece of graph paper against a base (x-axis) of time, ( t ) the resulting plot or drawing would represent the shape of a Waveform as shown. There are many different types of electrical waveforms available but generally they can all be broken down into two distinctive groups. - 1. Uni-directional Waveforms – these electrical waveforms are always positive or negative in nature flowing in one forward direction only as they do not cross the zero axis point. Common uni-directional waveforms include Square-wave timing signals, Clock pulses and Trigger pulses. - 2. Bi-directional Waveforms – these electrical waveforms are also called alternating waveforms as they alternate from a positive direction to a negative direction constantly crossing the zero axis point. Bi-directional waveforms go through periodic changes in amplitude, with the most common by far being the Sine-wave. Whether the waveform is uni-directional, bi-directional, periodic, non-periodic, symmetrical, non-symmetrical, simple or complex, all electrical waveforms include the following three common characteristics: - Period: – This is the length of time in seconds that the waveform takes to repeat itself from start to finish. This value can also be called the Periodic Time, ( T ) of the waveform for sine waves, or the Pulse Width for square waves. - Frequency: – This is the number of times the waveform repeats itself within a one second time period. Frequency is the reciprocal of the time period, ( ƒ = 1/T ) with the standard unit of frequency being the Hertz, (Hz). - Amplitude: – This is the magnitude or intensity of the signal waveform measured in volts or amps. Periodic waveforms are the most common of all the electrical waveforms as it includes Sine Waves. The AC (Alternating Current) mains waveform in your home is a sine wave and one which constantly alternates between a maximum value and a minimum value over time. The amount of time it takes between each individual repetition or cycle of a sinusoidal waveform is known as its “periodic time” or simply the Period of the waveform. In other words, the time it takes for the waveform to repeat itself. Then this period can vary with each waveform from fractions of a second to thousands of seconds as it depends upon the frequency of the waveform. For example, a sinusoidal waveform which takes one second to complete its cycle will have a periodic time of one second. Likewise a sine wave which takes five seconds to complete will have a periodic time of five seconds and so on. So, if the length of time it takes for the waveform to complete one full pattern or cycle before it repeats itself is known as the “period of the wave” and is measured in seconds, we can then express the waveform as a period number per second denoted by the letter T as shown below. A Sine Wave Waveform Units of periodic time, ( T ) include: Seconds ( s ), milliseconds ( ms ) and microseconds ( μs ). For sine wave waveforms only, we can also express the periodic time of the waveform in either degrees or radians, as one full cycle is equal to 360o ( T = 360o ) or in Radians as 2pi, 2π ( T = 2π ), then we can say that 2π radians = 360o – ( Remember this! ). We now know that the time it takes for electrical waveforms to repeat themselves is known as the periodic time or period which represents a fixed amount of time. If we take the reciprocal of the period, ( 1/T ) we end up with a value that denotes the number of times a period or cycle repeats itself in one second or cycles per second, and this is commonly known as Frequency with units of Hertz, (Hz). Then Hertz can also be defined as “cycles per second” (cps) and 1Hz is exactly equal to 1 cycle per second. Both period and frequency are mathematical reciprocals of each other and as the periodic time of the waveform decreases, its frequency increases and vice versa with the relationship between Periodic time and Frequency given as. Relationship between Frequency and Periodic Time Where: ƒ is in Hertz and T is in Seconds. One Hertz is exactly equal to one cycle per second, but one hertz is a very small unit so prefixes are used that denote the order of magnitude of the waveform such as kHz, MHz and even GHz. \|Prefix\|\|Definition\|\|Written as\|\|Time Period\| Square Wave Electrical Waveforms Square-wave Waveforms are used extensively in electronic and micro electronic circuits for clock and timing control signals as they are symmetrical waveforms of equal and square duration representing each half of a cycle and nearly all digital logic circuits use square wave waveforms on their input and output gates. Unlike sine waves which have a smooth rise and fall waveform with rounded corners at their positive and negative peaks, square waves on the other hand have very steep almost vertical up and down sides with a flat top and bottom producing a waveform which matches its description, – “Square” as shown below. A Square Wave Waveform We know that square shaped electrical waveforms are symmetrical in shape as each half of the cycle is identical, so the time that the pulse width is positive must be equal to the time that the pulse width is negative or zero. When square wave waveforms are used as “clock” signals in digital circuits the time of the positive pulse width is known as the “Duty Cycle” of the period. Then we can say that for a square wave waveform the positive or “ON” time is equal to the negative or “OFF” time so the duty cycle must be 50%, (half of its period). As frequency is equal to the reciprocal of the period, ( 1/T ) we can define the frequency of a square wave waveform as: Electrical Waveforms Example No1 A Square Wave electrical waveform has a pulse width of 10ms, calculate its frequency, ( ƒ ). For a square wave shaped waveform, the duty cycle is given as 50%, therefore the period of the waveform must be equal to: 10ms + 10ms or 20ms So to summarise a little about Square Waves. A Square Wave Waveform is symmetrical in shape and has a positive pulse width equal to its negative pulse width resulting in a 50% duty cycle. Square wave waveforms are used in digital systems to represent a logic level “1”, high amplitude and logic level “0”, low amplitude. If the duty cycle of the waveform is any other value than 50%, (half-ON half-OFF) the resulting waveform would then be called a Rectangular Waveform or if the “ON” time is really small a Pulse. Rectangular Waveforms are similar to the square wave waveform above, the difference being that the two pulse widths of the waveform are of an unequal time period. Rectangular waveforms are therefore classed as “Non-symmetrical” waveforms as shown below. A Rectangular Waveform The example above shows that the positive pulse width is shorter in time than the negative pulse width. Equally, the negative pulse width could be shorter than the positive pulse width, either way the resulting waveform shape would still be that of a rectangular waveform. These positive and negative pulse widths are sometimes called “Mark” and “Space” respectively, with the ratio of the Mark time to the Space time being known as the “Mark-to-Space” ratio of the period and for a Square wave waveform this would be equal to one. Electrical Waveforms Example No2 A Rectangular waveform has a positive pulse width (Mark time) of 10ms and a duty cycle of 25%, calculate its frequency. The duty cycle is given as 25% or 1/4 of the total waveform which is equal to a positive pulse width of 10ms. If 25% is equal to 10mS, then 100% must be equal to 40mS, so then the period of the waveform must be equal to: 10ms (25%) + 30ms (75%) which equals 40ms (100%) in total. Rectangular Waveforms can be used to regulate the amount of power being applied to a load such as a lamp or motor by varying the duty cycle of the waveform. The higher the duty cycle, the greater the average amount of power being applied to the load and the lower the duty cycle, the less the average amount of power being applied to the load and an excellent example of this is in the use of “Pulse Width Modulation” speed controllers. Triangular Waveforms are generally bi-directional non-sinusoidal waveforms that oscillate between a positive and a negative peak value. Although called a triangular waveform, the triangular wave is actually more of a symmetrical linear ramp waveform because it is simply a slow rising and falling voltage signal at a constant frequency or rate. The rate at which the voltage changes between each ramp direction is equal during both halves of the cycle as shown below. A Triangular Waveform Generally, for Triangular Waveforms the positive-going ramp or slope (rise), is of the same time duration as the negative-going ramp (decay) giving the triangular waveform a 50% duty cycle. Then any given voltage amplitude, the frequency of the waveform will determine the average voltage level of the wave. So for a slow rise and slow delay time of the ramp will give a lower average voltage level than a faster rise and decay time. However, we can produce non-symmetrical triangular waveforms by varying either the rising or decaying ramp values to give us another type of waveform known commonly as a Sawtooth Waveform. Sawtooth Waveforms are another type of periodic waveform. As its name suggests, the shape of the waveform resembles the teeth of a saw blade. Sawtoothed waveforms can have a mirror image of themselves, by having either a slow-rising but extremely steep decay, or an extremely steep almost vertical rise and a slow-decay as shown below. The positive ramp Sawtooth Waveform is the more common of the two waveform types with the ramp portion of the wave being almost perfectly linear. The Sawtooth waveform is commonly available from most function generators and consists of a fundamental frequency ( ƒ ) and all its integer ratios of harmonics, such as: 1/2, 1/4, 1/6 1/8 … 1/n etc. What this means in practical terms is that the Sawtoothed Waveform is rich in harmonics and for music synthesizers and musicians gives the quality of the sound or tonal colour to their music without any distortion. Triggers and Pulses Although technically Triggers and Pulses are two separate waveforms, we can combine them together here, as a “Trigger” is basically just a very narrow “Pulse”. The difference being is that a trigger can be either positive or negative in direction whereas a pulse is only positive in direction. A Pulse Waveform or “Pulse-train” as they are more commonly called, is a type of non-sinusoidal waveform that is similar to the Rectangular waveform we looked at earlier. The difference being that the exact shape of the pulse is determined by the “Mark-to-Space” ratio of the period and for a pulse or trigger waveform the Mark portion of the wave is very short with a rapid rise and decay shape as shown below. A Pulse Waveform A Pulse is a waveform or signal in its own right. It has very different Mark-to-Space ratio compared to a high frequency square wave clock signal or even a rectangular waveform. The purpose of a “Pulse” and that of a trigger is to produce a very short signal to control the time at which something happens for example, to start a Timer, Counter, Monostable or Flip-flop etc, or as a trigger to switch “ON” Thyristors, Triacs and other power semiconductor devices. A Function Generator or sometimes called a Waveform Generator is a device or circuit that produces a variety of different waveforms at a desired frequency. It can generate Sine waves, Square waves, Triangular and Sawtooth waveforms as well as other types of output waveforms. There are many “off-the-shelf” waveform generator IC’s available and all can be incorporated into a circuit to produce the different periodic waveforms required. One such device is the 8038 a precision waveform generator IC capable of producing sine, square and triangular output waveforms, with a minimum number of external components or adjustments. Its operating frequency range can be selected over eight decades of frequency, from 0.001Hz to 300kHz, by the correct choice of the external R-C components. Waveform Generator IC The frequency of oscillation is highly stable over a wide range of temperature and supply voltage changes and frequencies as high as 1MHz is possible. Each of the three basic waveform outputs, sinusoidal, triangular and square are simultaneously available from independent output terminals. The frequency range of the 8038 is voltage controllable but not a linear function. The triangle symmetry and hence the sine wave distortion are adjustable. In the next tutorial about Waveforms, we will look at Multivibrators that are used to produce continuous output waveforms or single individual pulses. One such multivibrator circuit that is used as a pulse generator is called a Monostable Multivibrator.
The endocardium, which is inflamed with endocarditis, is several layers of cells: - the innermost layer consists of endothelial cells. They are similar to those that form the mucous membranes of all internal organs, and are identical to the cells that line the blood vessels from the inside. Endotheliocytes lie on the basement membrane, which gives them signals to grow and divide; - subendothelial layer. It is built of connective tissue rich in poorly differentiated cells; - muscle-elastic layer. It consists of muscle fibers that are “packed” into the connective tissue. The layer is an analog of the middle layer of blood vessels; - outer connective tissue layer. It consists of connective tissue and is identical to the outer membrane of the vessels. The endocardium lines the inside of the heart wall, forms folds – valve flaps, as well as tendon chords attached to them and papillary muscles that pull the chords. It is this shell of the heart that separates the blood and the internal structure of the heart. Therefore, in the absence of inflammation, it is designed so that there is no significant friction of blood on the heart walls, and blood clots are not deposited here. This is achieved by the fact that the surface of the endothelium is covered with a layer of glycocalyx, which has special, atrombogenic properties. The endocardium of the heart valves from the atria is more dense. This is ensured by a large number of collagen fibers in the muscular-elastic layer of the membrane. From the ventricles, the muscle-elastic layer is 4-6 times thinner, almost does not contain muscle fibers. The valves between the cardiac cavities and the vessels (pulmonary trunk, aorta) are thinner than the atrioventricular. The nutrition of the deepest, bordering the myocardium, endocardium comes from the vessels that make up its structure. The remaining departments receive oxygen and the necessary substances directly from the blood, which is located in the cardiac cavities. Directly under the endocardium is the heart muscle – myocardium. He is responsible not only for contractions of the heart, but also for the correct rhythm of these contractions: “paths” of cells are laid in the myocardium, some of which produce, and others transmit further electrical impulses, obliging the necessary parts of the heart to contract. When enough microbes (bacteria or fungi) enter the bloodstream, they naturally end up inside the heart cavities. If human immunity is sufficiently weakened, then microorganisms settle on the endocardium (especially on the valves between the left atrium and ventricle, as well as at the entrance from the left ventricle to the aorta) and cause inflammation there. Thrombotic masses can come off at any moment and with a blood stream enter the arteries that feed the internal organs. So a stroke, a heart attack of the spleen, intestines, lungs and other organs can develop. Due to the increase in the mass of the valve with blood clots and scar tissue, it ceases to perform its function normally – to prevent the reverse flow of blood. Because of this, a condition called “chronic heart failure” develops. Microorganisms that have settled on valves, chords, or the surface of the papillary muscles can cause the formation of endothelial ulcers (ulcerative endocarditis). If this leads to the development of a “hole” in the valve or the separation of the chord, the heart “loses control” over its own processes. Thus, acute heart failure develops, proceeding according to one of the scenarios: either pulmonary edema, shortness of breath and a feeling of lack of air, or a sharp decrease in pressure, increased heart rate, a panic state with a possible loss of consciousness. The presence of bacteria or fungi in the blood causes the activation of immunity, as a result of which antibodies are formed against these microorganisms, the complement system (several immune proteins) is activated. Microbial antigens are combined with antibodies and complement proteins, but they are not destroyed (as should be normal), but are deposited around the vessels of many organs: kidneys, myocardium, joints, individual vessels. This causes an inflammatory-allergic reaction, resulting in the development of glomerulonephritis, arthritis, myocarditis or vasculitis. Detonic – a unique medicine that helps fight hypertension at all stages of its development. The complex effect of plant components of the drug Detonic on the walls of blood vessels and the autonomic nervous system contribute to a rapid decrease in blood pressure. 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Detailed information about Detonic is located on the manufacturer’s page. - Causes and pathogenesis of endocarditis - Causes of subacute septic endocarditis - Endocarditis Epidemiology - The clinical picture of acute septic endocarditis - Causes of endocarditis and its classification - Symptoms and signs - Symptoms and signs of subacute septic endocarditis - Patient treatment and observation - Therapeutic activities - The course, clinical forms and complications of subacute septic endocarditis - Prevention and treatment of subacute septic endocarditis Causes and pathogenesis of endocarditis Septic endocarditis is an inflammation of the inner layer of the lining of the heart during sepsis. A characteristic sign of pathological anatomy in such a case is ulceration of the valves of the organ. The diagnosis is complicated by the fact that it develops mainly in unhealthy people with a reduced immune response of the body. Often, septic endocarditis affects patients with rheumatic diseases, which in turn have defective valve structures of the heart. Patients with congenital malformations of this organ are also at risk of pathology. Subject to septic endocarditis and patients of advanced age. As a rule, they already have dilatation of the left chambers of the heart, in which the mitral and aortic valves are affected. But inflammation of the right parts of the myocardium is characteristic of injecting drug addicts and patients with intravascular catheters. The picture of septic endocarditis depends on the agent by which it was caused. Fungus and gram-negative microflora become the cause of the disease very rarely, and if there are exceptions, then only for drug addicts and people who have undergone heart valve replacement. In addition to the above reasons, the disease is caused by ordinary or green streptococcus, less often white, Staphylococcus aureus, Enterococcus. The disease is difficult to recognize. Often, the final diagnosis is made with an obvious picture of the pathology, when the symptoms of heart failure are manifested. Classification according to the course of the disease: - Acute – lasts more than a crescent; - subacute septic endocarditis – with a course of up to three months; - chronic, which can last for years. According to the clinical and morphological form, the disease is divided into primary (obsolete name – Chernogubov’s disease) and secondary. The first type occurs in about thirty percent of the total number of patients with unchanged valves. The second is dianostatic in the vast majority of patients with rheumatic heart disease. Occasionally, the secondary variant is diagnosed in people with congenital malformations, as well as atherosclerotic, syphilitic lesions. The causative agents of infectious endocarditis are gram-positive and gram-negative bacteria (strepto- and staphylococci, enterococci, Escherichia coli and Pseudomonas aeruginosa, Proteus), less commonly, fungi, rickettsia, chlamydia, viruses. Transient bacteremia is noted both for various infections (sinusitis, sinusitis, cystitis, urethritis, etc.), and after a large number of diagnostic and therapeutic procedures, during which the epithelium is colonized by a variety of microbes. An important role in the development of infectious endocarditis is played by a decrease in immunity due to concomitant diseases, advanced age, immunosuppressant therapy, etc. Causes of subacute septic endocarditis Before the widespread use of antibiotics, endocarditis was most often caused by streptococci. Nowadays, the main causative agents of endocarditis are staphylococci, fungi, Pseudomonas aeruginosa. The most severe course is endocarditis of fungal origin. Patients often become infected with streptococcus within 2 months after prosthetic heart valves and people with congenital and acquired heart defects. But the infection can affect the endocardium and a completely healthy person – with severe stress, reduced immunity, because in the blood of every person there are many microorganisms that can take hold on any organs, even on the heart valves. There are factors that significantly affect the likelihood of endocarditis: - congenital heart defects, especially heart valves; - prosthetic (artificial) heart valves; - previously endocarditis; - transplantation of the heart or pacemaker; - hypertrophic cardiomyopathy; - injecting drugs; - hemodialysis procedure; If the patient belongs to a risk group, he is obliged to warn about this during various medical, dental procedures and other procedures associated with the risk of infection (tattoos). In this case, perhaps antibiotics should be used as a prophylaxis – this can be done only as directed by the doctor. A variety of factors can provoke infectious endocarditis. Their recognition guarantees a positive effect from the treatment. The main causes of the inflammatory process in the endocardium are: - ailment of connective tissue of a diffuse nature; - chemical poisoning; The disease is described by Tsangov (1884), Lukin (1903) and only later by foreign authors. Etiology and pathogenesis. Subacute septic endocarditis — a protracted, lingering chronioseptic process with localization of the infectious focus on valves disfigured by an old rheumatic, syphilitic, congenital, traumatic defect, or not previously changed. The causative agent — non-hemolytic Streptococcus viridans, a common inhabitant of the oral cavity and pharynx — is found on the AND valves in the blood of patients; however, it is usually not possible to clinically establish a relationship with tonsillitis. The disease is characterized by a kind of reaction on the part of the body, proceeding, as a rule, without purulent metastases, with a violation of the bone marrow and the reticulo-endothelial apparatus. In recent decades, attention has been paid to the independence and relative frequency of this form of endocarditis. Organic valvular heart disease is the main predisposing condition for sedimentation on the valves of septic infection, just as in the classical experiments of Vysokovich preliminary mechanical damage to the valves proved to be a necessary condition for obtaining experimental endocarditis with the introduction of bacteria into the blood. Subacute septic endocarditis develops on the soil: - most often rheumatic defects of the aortic and mitral valves, usually with a relatively mildly affected myocardium in the stage of compensation, without atrial fibrillation; - congenital heart defects, especially non-closure of the interventricular septum, Botallus duct, pulmonary artery stenosis, congenital aortic valve anomaly; - rarely because of syphilitic aortic insufficiency and even less so on sclerotic aortic valve disease; - as an exception due to traumatic heart defects, which are generally extremely rare. Subacute septic endocarditis may also develop on previously unchanged valves (Chernogubov). Rheumatic defects numerically significantly prevail among other organic valvular defects, therefore, it is natural that rheumatism is most often found in the history of patients with subacute septic endocarditis. Some authors (Strazhesko) recognize a closer connection between subacute septic endocarditis and rheumatism, believing that both diseases are based on the changing response of the body to infection with the same low-virulent streptococcus. However, heart defects of a different etiology in no less than a percentage of cases are complicated by subacute septic endocarditis. The relationship of congenital heart defects with subsequent inflammatory endocarditis was established already 100 years ago, and the same relationship with traumatic defects was discovered more than 50 years ago. The main pathogenetic mechanisms of the development of subacute septic endocarditis, as well as other forms of endocarditis, are not well understood. It is impossible to imagine that the pathological process boils down to the settling of bacteria in certain places of slow or perverted blood flow (with heart defects) or to the engraftment of various microbes due to violation of the blood supply conditions of the “vicious” valves themselves. The leading value is, one must think, of the particular reactivity of the valvular apparatus (or parietal endocardium) as a result of a neuroallergic or neurodystrophic effect, which, only under very specific conditions that are difficult to reproduce in an experiment, causes a complex inflammatory process that progresses for a long time towards the development of a pronounced clinical and anatomical endocardial disease . It is characteristic that the development of especially typical protracted forms of endocarditis is more often observed with less virulent pathogens that do not cause suppuration in the organs, just as recurrent vascular lesions are often observed with a weakened infection. Development of endocarditis of the heart valves following inflammatory lesions of the arteries, which is observed in rare cases subacute septic arteritis of the Botallic duct with its non-closure or with arteriovenous aneurysm, possibly contributing to intravascular cardiac reflex exposure, and not just the mechanical transfer of the infectious onset. Pathologically, an ulcerative, destructive process predominates, sometimes with perforation of the valves; sometimes warty growths are found, often with damage to the parietal endocardium. In the thickness of warty-ulcerative changes, bacterial masses are already found in large numbers even with a small increase in the microscope. Embolic processes in various organs are characteristic, however purulent fusion in them is observed only as an exception; usually find focal embolic, and often diffuse nephritis, splenic megalia with multiple heart attacks, etc. Constant participation in the spleen process with a possible increase in its function can contribute to anemia, leukopenia, thrombopenia by inhibiting bone marrow function. Depending on the initial state of the inner cardiac membrane, infectious endocarditis of the heart is primary and secondary. Both of them are caused by such microorganisms: - bacteria: green (is the main cause of subacute endocarditis) and pneumonic streptococci, Staphylococcus aureus and enterococcus (cause an acute inflammatory process), E. coli, tuberculosis mycobacterium, treponema pallidum (with syphilis), brucella, some gram-negative bacteria and anaerobes; - mushrooms, usually Candida. Such microflora usually appears when a person has been treated with antibiotics for a long time, or he has had a venous catheter for a long time (in the treatment of any diseases); - some viruses; - some of the simplest. Only primary endocarditis is one that occurs on normal, healthy valves, and secondary on valves affected by rheumatism or prolapse, on artificial valves and those near which there is a pacemaker. Recently, the incidence of primary endocarditis has begun to increase. She reached 41-55%. The incidence of IE is recorded in all countries of the world and ranges from 16 to 59 cases per 1000 people, in Russia – 000 per 46,3 people per year and is steadily increasing. Men get sick 1000-000 times more often than women. The most frequent endocardial damage occurs at the age of about 1.5 years, ¼ of all cases are recorded in the age group of 3 years and older. The increase in the incidence of IE is due to a significant increase in the number of cardiac surgeries, surgical interventions and post-injection abscesses. It is believed that the likelihood of septic endocarditis in people who use non-sterile syringes (for example, with drug addiction) is 30 times higher than in healthy people. The clinical picture of acute septic endocarditis The general condition of patients is severe. Often there is adynamia, prostration, hectic fever, sweats, septic diarrhea, etc. Complaints of a heartbeat, pain in the heart are few and do not usually attract the attention of a doctor to this organ. The study finds signs of heart disease, if there was one before, and with a previously healthy heart, only doubtful signs of damage to it. An unsharp systolic murmur is heard at the apex or on the aorta, or a weak diastolic murmur on the aorta, which is usually mistaken for anemic or muscular murmur, so frequent in severe infections in general. The expressed galloping pulse, characteristic of the formed aortic defect, is also usually not observed. Significant expansion of the heart, as well as obvious signs of its insufficiency, is usually not observed. Sharp tachycardia, arrhythmia, and especially variability of noise are more characteristic. The spleen is felt indistinctly due to its soft consistency and the general serious condition of the patients, although at the autopsy they naturally reveal its increase. An infectious agent is constantly easily seeded from the blood; sharp neutrophilic leukocytosis and anemia are also found. Flow. Acute septic endocarditis begins gradually, lasts a few weeks, less often drags out to 2-3 months. A longer course or development of endocarditis is possible only after months with a milder course of sepsis, for example, with chronic meningococcal sepsis. The forecast is serious. Before the introduction of penicillin, all cases ended in death. Diagnosis. You should think about this disease in severe septic courses of acute infections in surgical and gynecological patients and evaluate even minor signs of the heart, embolic events, and kidney damage in this direction. Progressive metastasis of the infection involving the meninges and serous membranes, with phlebitis with persistent positive blood culture is very suspicious of endocarditis. Causes of endocarditis and its classification A. The course of the disease - acute – from a few days to 2 weeks; - subacute infectious endocarditis; - chronic relapsing course. B. The nature of the defeat of the valvular apparatus - primary infective endocarditis (Montenegrin form) that occurs on unchanged heart valves; - secondary endocarditis – develops against the background of the existing pathology of heart valves or large vessels (including in patients with artificial valves). B. According to the etiological factor When making a diagnosis take into account: diagnostic status – ECG with a typical picture; process activity – active, persistent or repeated; pathogenesis – IE of own valves; IE prosthetic valve, IE in drug addicts. Localization of IE: with damage to the aortic or mitral valve of the tricuspid valve, with damage to the pulmonary valve; with parietal localization of vegetation. Symptoms and signs In general, the symptoms of an infectious lesion are fever, chills, weakness, anorexia, sweating, arthralgia. In the elderly or in patients with renal failure, fever may be absent. The disease is characterized by the presence of heart murmurs, anemia, hematuria, splenomegaly, petechiae of the skin and mucous membranes, sometimes emboli. Acute heart failure, aneurysms may develop. Most often (approximately 85% of patients), a fever is observed and heart murmurs are heard. In addition, there are classic signs of septic endocarditis are found. These or those signs are observed on average in 50% of patients: - subcutaneous nodules near fingertips; - painless spots on the palms and soles; - painful seals of the fingertips (Osler nodules). The following signs of the disease are found in approximately 40% of patients: - intracerebral hemorrhage. The following symptoms are less commonly observed: - neck tension - sweating (especially at night) - shortness of breath, - pallor of the skin Symptoms of early subacute endocarditis, as a rule, are weakly expressed non-specifically – they include the following: - body temperature of about 37,5 degrees, observed in 85% of patients; - anorexia and weight loss; - flu-like sensations in the body; - possible vomiting after taking write and abdominal pain. The clinical picture is primarily associated with the infectious nature of the disease and embolic processes in the presence of an old heart disease and a kind of intoxication. Prolonged fever of an indefinite type is one of the most important signs of the disease. Often there are febrile waves lasting 1–2–3 weeks, or one-, two-day temperature jumps up to 39–40 °, provoked by various moments, or long-term subfebrile condition. Typically, there is significant variability in the febrile reaction and the temperature can be almost normal for weeks and months. Long-term fever most often leads the patient to the doctor. The general appearance of the patient is characteristic: pale skin with a special dirty shade of “coffee with milk”, although rarely seldom expressed; “Drum fingers” as a manifestation of a kind of intoxication, pathogenetically not entirely clear. Patients complain of weakness, decreased appetite; as a rule, severe intoxication is absent, delusional state, headaches, tongue is not taxed. Pain phenomena due to embolism in various organs (into the spleen, kidneys, limbs, etc.) often represent the patient’s main complaint. On the part of the heart, there are signs of an old defect — rheumatic, congenital, or syphilitic, usually compensated, without severe rhythm disturbances. Often heard diastolic murmur on the aorta or mitral melody at the apex. With the development of the process, unchanged (usually aortic) valves reveal a fresh defect (acute) due to septic lesion of the valves, which, however, for a long time does not give obvious local signs. The heart usually does not appear to be significantly enlarged; complaints are not primarily of a cardiac nature. The examination reveals an enlarged spleen, sometimes to the extent of significant splenomegaly, simultaneously with an increase in the liver of the nature of an infectious rather than congestive liver. The contours of the spleen are easily determined by palpation, with the exception of periods of fresh spleen infarcts, causing sharp pain with a return to the region of the left shoulder joint, muscle protection from the side of the abdominal press, restriction of respiratory mobility of the lung on the left, sometimes the noise of friction of the peritoneum (perisplenitis) when listening to the area of the lower ribs on the left or the spleen itself below the costal margin. Similar embolic manifestations from other organs cause complaints primarily of pain or are detected with a thorough examination of the patient. So, kidney embolism often gives acute paroxysmal or dull lower back pain, sometimes with the release of bloody urine, soreness when tapping the kidney area behind (a positive symptom of Pasternatsky); embolisms in the extremities cause petechiae, sometimes painful points or nodules on the fingers, especially on the terminal phalanges or on the elevations of the palm (thenar and hypo-thenar) in the form of red stripes, spots, sometimes with a white central point – a bridge to block blood vessels, which, along with with drum fingers, represents changes characteristic of the disease from the extremities. When examining the skin, petechiae are found, due to the fragility of the vessels, and in other parts of the body, and in the conjunctival sac, especially on the lower eyelid, petechiae due to hemorrhage, embolism and vasculitis (Lukin’s symptom). On the part of the joints, light arthralgic phenomena were noted, on the part of the bones, especially the sternum, soreness when added. Laboratory studies reveal characteristic data. First of all, in the urine, as usual with septic processes, changes characteristic of focal nephritis are found: erythrocytes in the sediment, an insignificant amount of protein with normal specific gravity of urine, undisturbed renal function and normal blood pressure (with aortic defects, there is, of course, high systolic and low diastolic pressure). There is severe anemia in the blood with a drop in hemoglobin content of up to 40-30%, leukopenia (about 4 leukocytes), thrombopenin with thrombopenic phenomena: sharply prolonged bleeding time, the appearance of petechiae after applying a tourniquet to the shoulder. Among erythrocytes there may be nuclear forms, among leukocytes, monocytes and histiocytes as an indicator of the peculiar reaction of the reticuloendothelial system to septic infection. Blood serum with a high content is also peculiar, which is invisible due to the same irritation of the reticuloendothelial system, globulins, in particular, eiglobulins, why the serum coagulates and becomes cloudy when formalin is added (positive formol reaction). The most direct evidence of the septic nature of the disease is a positive blood culture, which is obtained by observing the appropriate methodology during periods of higher temperature and generally more activity of the process. Symptoms and signs of subacute septic endocarditis The clinical manifestations of IE are diverse. In acute endocarditis of streptococcal and staffilococcal etiology, symptoms such as a sudden marked increase in body temperature, severe chills, signs of acute failure of the affected valves and heart failure are noted. Acute endocarditis is considered as a complication of general sepsis. The disease lasts up to 6 weeks from the onset of the disease, characterized by rapid destruction and perforation of valve flaps, multiple thromboembolism, and progressive heart failure. In case of untimely surgical intervention, IE quite quickly leads to death. Subacute infectious endocarditis often develops at the age of 35-55 years and older. Symptoms usually appear 1-2 weeks after bacteremia. Initially, symptoms of intoxication are observed: fever, chills, weakness, night sweats, increased fatigue, weight loss, arthralgia, myalgia. The disease can occur in the form of “repeated acute respiratory infections” with short courses of antibiotic treatment. With prolonged severe course of the disease in some patients, the following characteristic symptoms are revealed: - The symptom of Janeway (spots or rashes of Janeway) is one of the extracardiac manifestations of infectious endocarditis: an immuno-inflammatory reaction in the form of red spots (ecchymoses) up to 1-4 mm in size on the soles and palms. - Osler’s nodules – also a symptom of septic endocarditis – are red painful seals (nodules) in the subcutaneous tissue or skin. - Petechial rashes with septic endocarditis are often found on the mucous membranes of the mouth, conjunctiva and folds of the eyelids – a symptom of Lukin-Libman. - The symptom of “drumsticks” and “watch glasses” is a thickening of the distal phalanges of the fingers and the appearance of a convex shape of the nails. - Roth spots – hemorrhages on the fundus having an intact center – not a pathognomonic symptom. - In patients with infectious endocarditis, a pinch symptom (Hecht symptom) or a tourniquet symptom (Konchalovsky-Rumpel-Leede symptom) are usually positive: hemorrhages appear in this zone when fingers compress the skin folds or pull the limb with a tourniquet. Perhaps the development of glomerulonephritis, arthritis, myocarditis, thromboembolic complications. There are variants of the course of infectious endocarditis without fever, with the defeat of any one organ – nephropathy, anemia. The presence of endocarditis should be suspected with a newly appearing noise over the region of the heart, embolism of the cerebral and renal arteries; septicemia, glomerulonephritis and suspected renal infarction; fever with prosthetic heart valves; first developed ventricular arrhythmias; typical manifestations on the skin; Signs and symptoms of endocarditis depend on its type (infectious, rheumatic, syphilitic, tuberculous) and are dictated by the course of the disease. So, if acute endocarditis has developed, then the symptoms will be as follows: - high body temperature (up to 39,5 ° C); - during the rise, the person’s temperature beats a strong chill; - copious perspiration; - pain in all joints and muscles; - the skin becomes grayish with slight yellowness, sometimes red spots appear on it; - reddish painful nodules appear on the fingers; - conjunctival hemorrhages are noted. Subacute infectious endocarditis occurs with the following symptoms: - increased body temperature – up to 38,5 ° C; - sleep disturbance; - weight loss; - skin color becomes “coffee with milk”; - red rash on the body; - small painful nodules appear under the skin, but the main difference from the acute process is that this symptomatology is observed for 2 months or more. For the chronic process, the same symptoms are characteristic (only the temperature is usually up to 38 ° C) for six months or more. During this time, a person loses weight greatly, the fingers of his hands take the form of drum sticks (extended in the area of the nail phalanges), and the nails themselves become dull and become convex (resemble watch glasses). When a heart defect forms, shortness of breath appears: at first during physical exertion, then at rest, pain behind the sternum, the heart beats more often (up to 110 beats per minute and more often) regardless of temperature. If glomerulonephritis or kidney infarction develops, swelling on the face appears, urination is impaired (usually the urine becomes smaller), urine changes color to reddish, lower back pain appears. If, against the background of the main signs, severe pain develops in the left hypochondrium, this indicates that one of the branches of the arteries supplying the spleen is clogged, and part or all of this organ dies. With the development of pulmonary embolism, there is a sharp feeling of lack of air, pain behind the sternum. Against this background, impaired consciousness quickly grows, and the skin (especially on the face) acquires a purple hue. Symptoms of infectious endocarditis develop in three stages: - Infectious-toxic: bacteria enter the bloodstream, “land” on the valves, begin to multiply there, forming growths – vegetation. - Infectious-allergic: due to activation of the immune system, internal organs are affected: myocardium, liver, spleen, kidneys. - Dystrophic. At this stage, complications develop both on the part of the internal organs and on the side of the myocardium (parts of the heart muscle die in 92% of cases of prolonged inflammation of the endocardium). Infectious endocarditis in children develops as an acute process and is very similar to SARS. The difference is that with ARVI, the complexion should not change to yellowish, and heart pain should not be noted. If endocarditis is rheumatic, then it usually develops after a sore throat, glomerulonephritis, in which beta-hemolytic streptococcus was isolated (in the first case, from the surface of the tonsils, in the second from the urine). After the disease has subsided, over time, a person notes weakness, fatigue, malaise. World clinical practice has summarized and deduced the criteria that are used to diagnose septic endocarditis. They are divided into large and small. Big ones include blood tests, during which a culture of microbes that are responsible for the infection of the body is sown. - two positive blood cultures taken at least twelve hours apart; - three positive crops of three; - from four blood cultures and more – maximum positive; - proven endocardial damage; - characteristic symptoms of acute septic endocarditis on ultrasound of the cardiovascular system. - vascular changes; - a change in laboratory blood standards. The presence of anemia, a shift in the leukocyte formula, an increased erythrocyte sedimentation rate, the presence of a C-reactive protein, a decrease in platelets, etc. The final diagnosis is made in the presence of the so-called pathological criteria: - the presence of positive blood culture; - the presence of an intravascular substrate; - myocardial abscesses. All of the above positions should be confirmed histologically or by adding up the criteria: two large, or one large, plus three small or five small. Suspicion of pathology is removed if, after taking antibiotics for four days, symptoms disappear or signs of infection with the same duration of therapy are absent in blood samples. Young and middle-aged patients with suspected septendocarditis require careful differential diagnosis with rheumatic lesions, accompanied by fever. In older people, the diagnosis should be separated from cancer problems. With a pathomorphological study of patients with certain types of cancer, it is possible to detect thromboendocarditis, which did not manifest itself during human life. Often this disease is mistaken for malaria. The diagnosis changes in favor of endocarditis if plasmodia is not detected. Blood in the urine and lower back pain are encouraged to think about urolithiasis (ICD). However, groin pain is symptomatic for this disease. An inconspicuous debut (subfebrile condition, loss of strength, pain in the joints and head) allows us to differentiate bacterial endocarditis from rheumatism, and in case of aortic insufficiency, from visceral syphilis. In all these cases, tactics are decided by positive tests for microbial culture. Diagnosis of the disease is based on clinical data and, with characteristic symptoms, is not difficult. The main methods for diagnosing the disease is a blood test for the bacterial flora and a general blood test, as well as an echo-cardiogram, with which it is possible to detect microbial colonies on heart valves. Septic endocarditis is usually suspected in cases of fever of unknown origin and heart murmur. Although in some cases, with parietal endocarditis or damage to the right heart, noises may be absent. The classic signs of the disease – a change in the nature of the noise or the appearance of new ones – are found only in 15% of cases. The most reliable diagnostic method is blood culture on the bacterial flora. This test makes it possible to identify the pathogen in 95% of cases. Before antibiotics appeared, in 90% of cases the disease was caused by green streptococcus, mainly in young people with rheumatic heart diseases. Currently, older people are sick, most often men with heart defects. Pathogens, in addition to vermin streptococcus, can be Staphylococcus aureus, diphtheria-like bacteria, enterococci, and other strains. The disease is diagnosed on the basis of the presence of two main signs: - pathogens typical of infective endocarditis are found in the patient’s blood cultures; - on echocardiography, signs of endocardial damage are observed – mobile growths on the heart valves, purulent inflammation in the area of the valve prosthesis; In addition, there are secondary symptoms: - detection of substances in large arteries that are not normal there (embolism); - infectious pulmonary infarction; - intracranial hemorrhage; - immunological phenomena; - febrile fever and other manifestations of systemic infection. Thus, the diagnosis of infectious endocarditis in the presence of two main criteria in combination with several secondary ones. Anamnesis and physical examination. It is necessary to ask the patient about existing heart defects, previous surgical interventions on the heart valves during the last 2 months; rheumatic fever, history of endocarditis; infectious diseases in the last 3 months; pay attention to skin manifestations – pallor (signs of anemia), ecchymosis. Ophthalmic manifestations are Roth spots (retinal hemorrhages with a white center, Lukin-Liebman spots (petechiae on the transitional fold of the conjunctiva); transient, more often one-sided blindness or visual field disturbance. The most important sign of infectious endocarditis is the appearance or change in the nature of heart murmur as a result of damage to the heart valves. In the formation of aortic defect, first systolic murmur at the left edge of the sternum and at the V point (Botkin-Erba point), as a result of stenosis of the aortic mouth due to vegetation on lunate valves, then signs of aortic insufficiency appear – tender protodiastolic murmur above the aorta and at V point aggravated by standing and lying on the left side. With the destruction of the valves, the intensity of diastolic noise increases, II tone on the aorta weakens. Symptoms of central nervous system damage manifest as confusion, delirium, paresis and paralysis as a result of thromboembolism, meningoencephalitis. In acute infectious endocarditis, signs of severe heart failure are revealed – bilateral wet rales, tachycardia, additional III cardiac tone, edema of the lower extremities. In half of the patients, splenic or hepatomegaly, it is often possible to notice icteric sclera and mild yellowness of the skin; lymphadenopathy. Perhaps the development of thromboembolic heart attacks of various organs (lungs, myocardium, kidneys, spleen). In 30-40% of cases, common myalgia and arthralgia are observed with the predominant involvement of the shoulder, knee and sometimes small joints of the hands and feet. Myositis, tendonitis and enthesopathies, septic mono- or oligoarthritis of various localization are rare. general blood test for acute infectious endocarditis – normochromic normocytic anemia, with a shift of the leukocyte formula to the left, thrombocytopenia (20% of cases), accelerated ESR. In the biochemical analysis of blood, dysproteinemia with an increase in the level of gamma globulins, an increase in the CRH of 35-50%. Urinalysis: macro- and microscopic hematuria, proteinuria, with the development of streptococcal glomerulonephritis – red blood cells. Blood culture is an objective confirmation of the infectious nature of endocarditis in identifying the pathogen, allows you to determine the sensitivity of the infectious agent to antibiotics. In 5-31% of cases with IE, a negative result is possible. Serological techniques are effective for IE. ECG – against the background of IE with myocarditis or myocardial abscess – impaired conduction, less often paroxysm of atrial tachycardia or atrial fibrillation. Echocardiography – is performed for all patients with suspected IE no later than 12 hours after the initial examination of the patient. Transesophageal echocardiography is more sensitive to vegetation than transthoracic echocardiography, but it is more invasive. Chest X-ray – with infectious endocarditis of the right heart, multiple or “volatile” lung infiltrates are observed. Diagnosis of endocarditis is based on data: - listening to the heart: first, systolic murmur is determined, then – diastolic murmur; - definitions of the borders of the heart: they expand to the left (when the valves are damaged in the left parts of the heart) or to the right (if vegetations are found in the right parts); - ECG: if irritation occurs with the inflamed endocardium of the myocardial pathways, the cardiogram determines rhythm disturbance; - Ultrasound of the heart (echocardioscopy): this is how vegetation (growth) on the valves and the thickening of the endocardium and myocardium are determined. Ultrasound with dopplerography can be used to judge the function of the heart and indirectly, pressure in the small circle; - bacteriological blood tests (sowing it on various nutrient media); - blood tests using the PCR method: this is how certain viruses and bacteria are determined; - rheumatic tests: in order to distinguish infectious endocarditis from rheumatic; - If necessary, a magnetic resonance or computed tomography of the chest with a targeted examination of the heart can be performed. An accurate diagnosis of infectious endocarditis is made when there is a specific ultrasound picture of the heart, and in addition, the pathogen is determined in the blood. If all the symptoms indicate this disease, a microbe is determined in the blood, but there are no significant changes in echocardioscopy, the diagnosis is “in doubt”. When the pathogen is not detected in the blood, but the ultrasound picture is not in doubt, the diagnosis is written as infectious endocarditis or “culture-negative” (that is, bacteriological culture did not reveal anything), or “PCR-negative” (if PCR was not isolated pathogen). Patient treatment and observation This disease is always treated in a hospital in compliance with the regimen of medication and diet. The physical activity of the patient is minimal. With a certain septic endocarditis, massive antibiotic treatment is used. The drug is selected, given the sensitivity to it of the alleged infectious agent. Usually, a broad-spectrum medication from a number of penicillins, cephalosporins is indicated. Often they are combined with aminoglycosides. Antimycotic agents and NSAIDs may be prescribed. For endocarditis with an unknown pathogen, combined antibiotics are used, for example, tetracycline, terramycin, erythromycin. Preparations are preferably changed every two to four weeks due to the development of microorganism resistance to them. The effectiveness of treatment can be assessed by the following signs: - 48–72 hours after the start of therapy, the state of health improves, appetite, chills disappear; - at the end of the first week, body temperature decreases, petechiae, embolism disappears, hemoglobin increases, ESR decreases, the sterility of crops is fixed; - in the final of the third week – the transition to the norm of leukoformula, ESR, the state of the spleen; - at the end of treatment – the norm of ESR, proteinograms, hemoglobin. No new vasculitis and thromboembolism occur. Sometimes surgical intervention cannot be avoided. As a rule, this occurs in cases where conservative therapy was unsuccessful. Sanatorium treatment in an institution with a cardiological direction may be recommended. Mandatory is the follow-up of a patient who has had infectious endocarditis. In terms of the prognosis, it is worth noting that patients without treatment received do not often recover. With early antibiotic therapy, approximately 70 percent of patients with infection of their own valve structure and 50 with damage to prosthetic structures overcome the disease. In all cases of septic endocarditis or suspected diagnosis, hospitalization of the patient is required. After intensive inpatient treatment for 10-14 days, stabilization and the absence of a significant risk of complications (absence of fever, negative blood culture, absence of rhythm disturbances and embolism), treatment is continued on an outpatient basis. Treatment for infectious endocarditis consists mainly of intensive antibiotic therapy. Also, first of all, the main disease is treated – rheumatism, sepsis, systemic lupus erythematosus. Antibacterial treatment should be carefully selected, that is, the selected antibiotic should correspond to the bacterial flora and begin as early as possible. Therapy can last from 3-6 weeks to 2 months, depending on the degree of damage and the type of infection. Drugs, for their constant concentration in the blood, are administered intravenously. It is important to monitor the concentration of antibiotics in the plasma, which should be kept at a therapeutic level, but does not become toxic to the body. To do this, in each case, determine the minimum (before the introduction of the fourth dose) and maximum (half an hour or an hour after the fourth dose) concentration levels. A laboratory study of the sensitivity of the pathogen to antibiotics is mandatory. A biochemical and general blood test is also regularly performed, the bactericidal activity of the serum is evaluated, and the activity of the kidneys is monitored. With subacute septic endocarditis, therapy is carried out with high doses of benzylpenicillin sodium salt or semi-synthetic penicillins (oxacillin, methicillin). Antibiotic treatment, mainly parenteral, is continued until a perfect bacteriological and clinical recovery. Infectious endocarditis is a dangerous disease that requires timely prevention. This is a warning of sepsis and infectious complications, especially with congenital and acquired heart defects. As preventive measures for subacute septic endocarditis, the fight against rheumatism and other infections that cause organic heart valve defects should be mentioned. With already existing heart disease of any nature, patients should be especially protected from septic infection by, for example, prophylactic penicillin therapy during tooth extraction, tonsillectomy and similar interventions. Treatment of subacute septic endocarditis consists of general measures and specific treatment. Patients need bed rest already in the early period of the disease, regardless of their sometimes good health, in clean air, a relaxed atmosphere, good nutrition, and protection from infection. Penicillin, which is detrimental, as experience shows, on most of the strains of green streptococcus seeded from the blood of patients with subacute septic endocarditis, as well as penicillin together with streptomycin, is considered to be the most effective means at present. Penicillin treatment is carried out according to general rules in large doses of 500-000 units per day for 1-500 weeks in a row with the repetition of such courses several times after short breaks. It is especially important to begin treatment with penicillin in the very first months of the disease. Additionally, agents are used that enhance the effect of penicillin and increase the body’s resistance, its immune forces, as well as symptomatic drugs. They try to increase the effect of penicillin on streptococci by creating special conditions that delay its excretion from the body and, consequently, increase its concentration in the blood, as well as by preventing blood clots on the affected valves that block the antibiotic’s access to microbes, or by artificially increasing the patient’s body temperature to increase penicillin action. However, anticoagulants and artificial fever are not indifferent for the patient and, being seemingly justified from a theoretical point of view, do not give undeniable and significant advantages over conventional therapy with penicillin alone. The administration of agents simultaneously with penicillin, even with a weaker coagulation-inhibiting action, such as salicylates, quinine, could be justified from the point of view that the coagulation of blood under the influence of penicillin itself is somewhat accelerated; however, these provisions cannot yet be considered sufficiently firmly established. To increase the general resistance of the body, treatment with liver preparations, vitamins, as well as blood transfusion of 100-150 ml in the absence of contraindications in the form of heart failure or frequent embolism can be used. Of the medicines, pyramidone is also prescribed, which often definitely reduces the temperature, soothing — bromides, luminal, etc. In order to sanitize various infectious foci, for example, in the oral cavity, nasopharynx, as well as to change abnormal conditions, blood circulation, surgical interventions — tonsillectomy, etc., ligation of the open botall duct, which reduces fever and leads to more successful blood sterilization and healing, should be used valve infections. When sowing penicillin-resistant microbes from the blood, large doses of sulfonamide drugs (up to 100,0 or more per course), streptomycin and other antimicrobial agents are used, depending on the properties of the pathogen. Treatment with sulfonamides in ordinary cases of subacute septic endocarditis gives undoubtedly more modest results compared to penicillin, and one should bear in mind the possible side effects of these drugs. Previously used antibacterial therapy — rivanol, flavacridine (tripaflavin, acriflavine), silver preparations, vaccination, immunotransfusion — is often poorly tolerated and, as it were, suppresses the body’s defenses. The altered reactivity of patients with subacute septic endocarditis is probably of great importance in the outcome of this chronioseptic process caused by a low-virulent pathogen, however, this reactivity usually fails to change significantly. It should be limited to mildly acting disinfectants (urotropin, salitropin in a vein or per rectum) and especially recommend, as already mentioned, a restorative regimen (physical and mental rest, complete easily digestible food, multivitamin mixtures, light sedatives, liver preparations, etc. .). Under the influence of early treatment with large doses of penicillin, fever decreases, severe organ damage does not develop, and recovery or at least prolonged remission occurs. If treatment is started already with the development of the full clinical picture or in the late period, it is also almost always possible to cause remission — improvement of well-being, decrease in temperature, often to normal, improvement of blood composition, reduction of embolism; less often there is a significant reduction in the enlarged spleen, etc. Moreover, as mentioned above, and upon termination of the fever, heart and kidney insufficiency may increase, which nevertheless leads the patient to death; it should be remembered that even after prolonged remission or apparently complete recovery, a new exacerbation or a new disease of sepsis is possible, sometimes already caused by another pathogen. Treatment boils down to good care, good nutrition, and an increase in the body’s overall resistance. It is necessary to prevent pressure sores, etc. With surgical (wound) and obstetric sepsis, the elimination of the primary focus of infection is of great importance. Basically, treatment comes down to the persistent use of antibiotics and chemotherapeutic agents, respectively, of the suitability of the causative agent of this case of endocarditis to one or another drug, along with blood transfusion and other general measures of influence on the body. Treatment of infectious endocarditis includes a set of measures to eliminate the inflammatory process in the inner membrane of the human “motor”. Most often, antibacterial therapy and surgical intervention are involved in the process. If there is a formation of heart disease, then treatment should be aimed at correcting it. If infectious endocarditis is suspected, the patient should be hospitalized urgently. When treating endocarditis with antibiotics, you need to discuss this issue with your doctor. Their purpose is taking into account the degree of sensitivity. The course of admission should be at least 4-6 weeks. As a rule, a specialist prescribes a complex of medications to a patient in order to achieve maximum effect. It could be: - Ampicillin-Sulbactam with Gentamicin; - Vancomycin and Ciprofloxacin. In addition to antibiotic medications, treatment of infectious endocarditis involves medications that affect the immune system. If there is a disease of a non-bacterial nature, then for the treatment of endocarditis, the specifics of the underlying ailment must be taken into account. When endocrine pathology is diagnosed, the patient must undergo hormone tests and be treated under the supervision of an endocrinologist. Endocarditis, which is the result of intoxication, can be treated by canceling the use of a certain type of toxin. Surgical removal of the inflammatory process involves the removal of the affected area of the heart valve with further prosthetics. If there is such an opportunity, then the patient undergoes plastic surgery to maintain their own valves. After the rehabilitation period, the patient should be under the supervision of doctors. The course, clinical forms and complications of subacute septic endocarditis In the absence of adequate antibacterial treatment, there is a likelihood of complications of infectious endocarditis, often ending with a fatal outcome. Among them, septic shock, acute heart failure, impaired functioning and functions of the whole organism. Complications from the presented disease arise due to growths on the heart valves. They can disconnect and with the flow of blood affect other organs and systems. If they get stuck in a small vessel, this will cause an acute lack of blood supply, which will result in tissue death. The onset of the disease is difficult to pinpoint. It begins gradually with general symptoms of weakness, decreased ability to work, which are often incorrectly interpreted by an inexperienced doctor as depending on overwork, exhaustion of the nervous system. Clinically, one can distinguish various types, variants of the course of the disease, depending on the virulence of the infectious onset or the prevailing clinical syndrome due to the primary lesion one or another body. So, one can distinguish more malignant forms with high fever, with an abundance of embolism, which lead to death in the first months of the disease, as well as the so-called outpatient forms with an almost normal temperature. According to the leading clinical syndrome, types are distinguished: anemic, splenomegalic, hepatosplenomegalic, nephritic (in cases of kidney damage with diffuse nephritis with hypertension and azotemia, or in kidney damage with amyloid with anasarca, hypercholesterolemia, etc. ), cerebral, psychotic, etc. Of the peculiar and serious complications, it should be noted embolism of the arteries of the brain with hemiplegia, embolism of the retina, embolism of the lungs (from the right heart), embolism of the coronary arteries of the heart with myocardial infarction, the development of multiple aneurysms of various organs of embolic bacterial (“mycotic”) nature, for example, aneurysm a. One of the most formidable complications of endocarditis is embolism – a detachment of a part of an overgrown valve, thrombus or thrombus with a part of the valve with a further “travel” of this particle through the arteries. The embolus (or thromboembolism) will stop where the diameter of the artery exactly matches it. If the separation of the particle occurred in the left parts of the heart, embolization of the vessels of the big circle develops – one of the internal organs may suffer: intestines, spleen, kidneys. They develop a heart attack (that is, the death of the site). If a blood clot or unstable (poorly fixed) vegetation is located in the right sections, the embolus blocks the vessels of the small circle, that is, the pulmonary artery, as a result of which pulmonary infarction develops. Also, due to endocarditis, such complications can be observed: - Acute congestive heart failure. - The formation of heart disease. - Chronic heart failure. - Renal lesions: glomerulonephritis, nephrotic syndrome, renal failure. - Lesions of the spleen: abscess, enlargement, rupture. - Complications of the nervous system: stroke, meningitis, meningoencephalitis, brain abscess. - Vascular lesions: inflammation, aneurysms, thrombophlebitis. Prevention and treatment of subacute septic endocarditis To prevent infectious endocarditis, simple hygiene rules should be followed: - Keep your teeth healthy. - Be as serious as possible about cosmetic procedures that can cause infection (tattoos, piercings). - Try to see a doctor immediately if you find any skin infection or have a non-healing wound. Before agreeing to medical and dental procedures, discuss with your doctor the need to take antibiotics in advance that can prevent the development of an accidentally introduced infection. This is especially true for people who have already experienced endocarditis, having heart defects, artificial heart valves. Be sure to tell your doctor about your medical conditions. If you do not want your body to pick up such a pathology, then you should know the main measures that can protect you from endocarditis. Prevention involves the following series of actions: - When using drugs, it is urgently necessary to refuse them, since it is these people who are at greater risk of getting sick. - Those who have artificial valves or chronic heart disease should always be under the supervision of a specialist. - Constantly monitor the quality of processing of medical equipment and ask your doctor about the quality of sterilization. Endocarditis can be affected by every person, both an adult and a child. The reason for this pathology lies in the defeat of the body by an infectious agent. The disease manifests itself with chills, fever and headaches. It is possible to cure this condition, but only under the condition of an integrated approach. If you delay with therapy, you can get a number of unpleasant and dangerous complications, which will subsequently be very difficult to treat. Antibiotics should be prescribed to patients from high and medium risk groups: prosthetic heart valve, hemodialysis, complex congenital heart disease, surgical vascular conduits, history of infectious endocarditis, mitral valve prolapse, treatment with corticosteroid drugs and cytostatics, intravenous catheter infection, surgical interventions and post-injection. abscesses. Prevention of endocarditis is as follows: - you must adhere to sufficient physical activity and follow the rules of a healthy diet so that as little as possible examined and treated with invasive methods; - it is important to sanitize foci of infection in a timely manner: to treat diseased teeth, rinse tonsil lacunae with chronic tonsillitis, ensure the outflow of contents from the sinuses – with chronic sinusitis; - if you still have to be treated, you need to do this not at home or in doubtful rooms, but in specialized clinics; - if work or life involves frequent injuries, care must be taken to maintain sufficient immunity. For this, it is important to eat right, just move, maintain the hygiene of your skin and external mucous membranes; - upon injury, proper antiseptic treatment of the wound and, if necessary, a visit to the doctor; - if, due to heart disease, a heart operation was required, the installation of an artificial valve or pacemaker, after which blood-thinning drugs were prescribed, it is impossible to voluntarily cancel their intake; - if the doctor prescribes antibiotics for some reason, you need to take them as many days as prescribed. From the 5th day of taking antibacterial therapy, you need to ask a doctor about the need to prescribe antifungal drugs; - it is important to take antibiotic prophylaxis before starting any invasive treatment. So, if the operation is planned, it is better to start administering the drugs 12-24 hours before it (especially if the intervention is performed on the organs of the oral cavity or intestines). If you had to resort to emergency surgery, you need to enter the antibiotic as soon as possible after admission to the hospital. Microbes, multiplying, can completely destroy the heart valve or its parts, which guarantees the development of heart failure. Also, infection or damaged areas of the valves can enter the brain with blood flow and cause cerebral infarction. Healing without serious consequences requires early hospitalization with targeted treatment for the infection. The presence of heart disease in a patient also seriously worsens the prognosis of infectious endocarditis. There is a likelihood of the disease becoming chronic with periodic exacerbations. With the right choice of treatment and the absence of significant concomitant pathologies, the 5-year survival rate is 70%. With timely antibiotic therapy, the prognosis is quite favorable. With fungal infective endocarditis, mortality reaches 80% or more. In case of chronic heart failure – mortality is more than 50% in the next 5 years. Infectious endocarditis is a disease whose prognosis is conditionally unfavorable. In people without immune deficiency, defects and diseases of the heart and its valves, it is more favorable, especially if the disease is diagnosed early and emergency antibiotic therapy is started urgently. If a person becomes ill with endocarditis, having chronic heart disease or suppressed activity of the immune system, life-threatening complications can develop. Also, the prognosis worsens if: - symptoms of the disease began to appear after admission to the hospital (where either an invasive diagnosis or surgery, including surgery on the heart) was performed – during the first 72 hours; - if gram-negative flora, Staphylococcus aureus, insensitive to Cochiella or Brucella antibiotics, fungal flora are sown from the blood (from the valves). With infectious endocarditis with damage to the right heart, a better outcome can be expected. Rheumatic endocarditis is more favorable for life: acute heart failure and thromboembolism are less characteristic for it. But heart disease with this pathology develops in the vast majority of cases. Perhaps you want to know about the new medication - Cardiol, which perfectly normalizes blood pressure. Cardiol capsules are an excellent tool for the prevention of many heart diseases, because they contain unique components. This drug is superior in its therapeutic properties to such drugs: Detonic. If you want to know detailed information about Cardiol, go to the .There you will find answers to questions related to the use of this drug, customer reviews and doctors. You can also find out the Cardiol capsules in your country and the delivery conditions. 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This is a question our experts keep getting from time to time. Now, we have got the complete detailed explanation and answer for everyone, who is interested! A decimal representation of 23 hundredths would look like this:. 23 The fraction 23/100, often known as 23 out of 100 parts, is equivalent to the value 23 hundredths. What does the decimal representation of the fraction twenty hundredths look like? Given that twenty hundredths is equal to twenty multiplied by one hundred, the fraction representation of twenty hundredths is 20/100. When you divide 20 by 100, you get the number 20 hundredths, which is represented as the decimal 0.20. How many decimal places are there in twenty thousandths? As 20 thousandths is equal to 20 multiplied by one thousand, the fraction representation of 20 thousandths is 20/1000. When you divide 20 by 1,000, you get 20 thousandths, which when converted to a decimal is written as 0.020. What does a decimal look like when written in hundredths? When you are writing a decimal number, you should start by looking at the decimal point. The final digit is considered to be in the hundredths place if it is located two places distant from the decimal point. The fractional number 0.39 is written as thirty-nine hundredths of a whole number. The nine sits at the one hundredths position, making it the very last number. How would you write the decimal representation of the number 3 over 20? The correct decimal representation of 3/20 is 0.15. How to Express Twenty Three Hundredths Using Decimal Placement 34 questions found in related categories How many decimal places does 3/4 have? Answer: The fraction 3/4 is written as 0.75 when converted to the decimal form. What does the percentage form of the number 3/20 look like? Now that we have everything laid out, we can see that our fraction is 15/100, which translates to 3/20 being equal to 15% when expressed as a percentage. How many decimal places are there in three tenths? Three tenths, or 0.3, is equal to three tenths written as a decimal. What does the decimal representation of the number 5 hundredths look like? Given that five hundredths is equal to five more than one hundred, the fraction representation of five hundredths is 5/100. When you divide 5 by 100, you get 5 hundredths, which when converted to a decimal is written as 0.05. What does the decimal representation of the fraction four tens and three hundredths look like? In decimal form, this is four tens and three hundredths. 2 See answers User of Brainly Response from User of Brainly: This would make the time 40:03. Converting tenths of a centimeter to decimal form More information regarding hundredths, particularly the conversion of incorrect fractions to decimals. The number “4” can be found in the tens place, whereas the number “3” can be found in the hundredths place. What does the decimal representation of thousandths look like? The amounts are expressed in thousandths, or 0.006. The thousandths digit is the decimal digit that is located three places to the left of the decimal point. For instance, eight thousandths is equal to the number 0.008. How many decimal places does one thousandth have? The decimal representation of one thousandth is 0.001, and it can also be represented as. What does the decimal representation of the number 9 hundredths look like? The quantity that is equal to nine parts shaded is referred to as nine-hundredths. We express this as a decimal fraction with the notation 9/100. In decimal notation, it is written as.09, and when read aloud, it is pronounced “point zero nine.” In standard form, how do you express the fraction four hundredths? - In point of fact, it would be 0.04. After the decimal point, the first number represents tenths, the second represents hundredths, and the third represents thousandths. That would make 0.004 equal to four thousandths. - whoops worry. I need to know if 2 hundreds is the same as 20 thousands. 4. Janice considers 20 hundredths to be the same as 2 thousandths due to the fact that 20 hundreds is equal to 2 thousands. To help fix Janice’s mistake, try using words and a place value chart together. 5. The United States has a population that is approximately ten times that of Canada’s population. What does the number 27 hundredths look like in decimal form? 27/100 as a decimal is 0.27. What does the number 92 hundredths look like as a decimal? 92/100 as a decimal is 0.92. What does the decimal representation of “6 and 3 tenths” look like? Six and three tenths would be represented by the number 6.3 in decimal form. How do you write 3/5 as a decimal? The equivalent fraction in decimal form of 3/5 is 0.6. How much of a percentage is four out of twenty? 420 expressed as a percentage equals 20 percent. In terms of a percentage, what does 17 out of 20 mean? 17 out of 20 is equal to 85% when expressed as a percentage. How do you turn 3 into a decimal? To explain, three percent is equal to 3,100. So, all that is required of you is to compute 3100, which is 0.03.
History of Palestine \|Part of a series on the\| \|History of Palestine\| The history of Palestine is the study of the past in the region of Palestine, the geographic region in Western Asia between the Mediterranean Sea and the Jordan River, and various adjoining lands. Situated at a strategic location between Egypt, Syria and Arabia, and the birthplace of major Abrahamic religions the region has a long and tumultuous history as a crossroads for religion, culture, commerce, and politics. Palestine has been controlled by numerous different peoples, including the Ancient Egyptians, Canaanites, Philistines, Tjekker, Ancient Israelites, Assyrians, Babylonians, Persians, Ancient Greeks, Romans, Byzantines, the Muslims, the Crusaders, Ayyubids, Mameluks, Ottomans, the British, The Hashemite Kingdom of Jordan (1948–1967, on the "West Bank") and Egyptian Republic (in Gaza), and modern Israelis and Palestinians. Other terms for the same area include Canaan, Zion, the Land of Israel, Southern Syria, Jund Filastin, Outremer, the Holy Land and the Southern Levant. The region was among the earliest in the world to see human habitation, agricultural communities and civilization. During the Bronze Age, independent Canaanite city-states were established, and were influenced by the surrounding civilizations of ancient Egypt, Mesopotamia, Phoenicia, Minoan Crete, and Syria. During 1550–1400 BCE, the Canaanite cities became vassals to the Egyptian New Kingdom who held power until the 1178 BCE Battle of Djahy (Canaan) during the wider Bronze Age collapse. Modern archaeologists dispute parts of the Biblical tradition, the latest thinking being that the Israelites emerged from a dramatic social transformation that took place in the people of the central hill country of Canaan around 1200 BCE, with no signs of violent invasion or even of peaceful infiltration of a clearly defined ethnic group from elsewhere. The Philistines arrived and mingled with the local population, and according to Biblical tradition, the United Kingdom of Israel was established in 1020 BCE and split within a century to form the northern Kingdom of Israel, and the southern Kingdom of Judah. The region became part of the Neo-Assyrian Empire from c. 740 BCE, which was itself replaced by the Neo-Babylonian Empire in c. 627 BCE. A war with Egypt culminated in 586 BCE when Jerusalem was destroyed by the Babylonian king Nebuchadnezzar II and the local leaders were deported to Babylonia, only to be allowed to return under the Achaemenid Empire. In the 330s BCE, Alexander the Great conquered Palestine, and the region changed hands numerous times during the wars of the Diadochi, ultimately joining the Seleucid Empire between 219–200 BCE. In 116 BCE, a Seleucid civil war resulted in the independence of certain regions including the minor Hasmonean principality in the Judean Mountains. From 110 BCE, the Hasmoneans extended their authority over much of Palestine, creating a Judean–Samaritan–Idumaean–Ituraean–Galilean alliance. The Judean (Jewish, see Ioudaioi) control over the wider region resulted in it also becoming known as Judaea, a term that had previously only referred to the smaller region of the Judean Mountains. During 73–63 BCE, the Roman Republic extended its influence into the region in the Third Mithridatic War, conquering Judea in 63 BCE, and splitting the former Hasmonean Kingdom into five districts. In 70 CE, Titus sacked Jerusalem, resulting in the dispersal of the city's Jews and Christians to Yavne and Pella. In 132 CE, Hadrian joined the province of Iudaea with Galilee to form the new province of Syria Palaestina, and Jerusalem was renamed "Aelia Capitolina". During 259–272, the region fell under the rule of Odaenathus as King of the Palmyrene Empire. Following the victory of Christian emperor Constantine in the Civil Wars of the Tetrarchy (306–324), the Christianization of the Roman Empire began, and in 326, Constantine's mother Saint Helena visited Jerusalem and began the construction of churches and shrines. Palestine became a center of Christianity, attracting numerous monks and religious scholars. The Samaritan Revolts during this period caused their near extinction. Palestine was conquered by the Islamic Empire following the 636 CE Battle of Yarmouk during the Muslim conquest of Syria. In 661 CE, with the assassination of Ali, Muawiyah I became the uncontested Caliph of the Islamic World after being crowned in Jerusalem. In 691, the Dome of the Rock became the world's first great work of Islamic architecture. The Umayyad were replaced by the Abbasids in 750. From 878 Palestine was ruled from Egypt by semi-autonomous rulers for almost a century, beginning with Ahmad ibn Tulun, and ending with the Ikhshidid rulers who were both buried in Jerusalem. The Fatimids conquered the region in 969. In 1073 Palestine was captured by the Great Seljuq Empire, only to be recaptured by the Fatimids in 1098, who then lost the region to the Crusaders in 1099. Their control of Jerusalem and most of Palestine lasted almost a century until defeat by Saladin's forces in 1187, after which most of Palestine was controlled by the Ayyubids. A rump Crusader state in the northern coastal cities survived for another century, but, despite seven further Crusades, the Crusaders were no longer a significant power in the region. The Mamluk Sultanate was indirectly created in Egypt as a result of the Seventh Crusade. The Mongol Empire reached Palestine for the first time in 1260, beginning with the Mongol raids into Palestine under Nestorian Christian general Kitbuqa and reaching an apex at the pivotal Battle of Ain Jalut. In 1486, hostilities broke out between the Mamluks and the Ottoman Turks in a battle for control over western Asia and the Ottomans captured Palestine in 1516. In 1832 the region was conquered by Muhammad Ali's Egypt, but in 1840 Britain intervened and returned control of the Levant to the Ottomans in return for further capitulations. The turbulent period of Egyptian rule experienced two major revolts (the 1834 Arab Peasants revolt and 1838 Druze revolt) and a significant demographic change in coastal areas, populated by Egyptian Arab peasants and former soldiers of Ali. The end of the 19th century saw the beginning of Zionist immigration and the revival of the Hebrew language. Jewish immigration throughout the century boosted relatively large Jewish concentrations in Jerusalem, Safed, Tiberias and Jaffa. The British government issued the pro-Zionist Balfour Declaration of 1917 during World War I. The British captured Jerusalem a month later, and were formally awarded a mandate in 1922. Following a period of intercommunal violence, the Arab Palestinians revolted 1936, but were efficiently subdued by the British. In 1947, following World War II and the Holocaust, the British Government announced their desire to terminate the Mandate, and the United Nations General Assembly voted to partition the territory. The Arabs rejected the UN partition plan, and a civil war began immediately, with the State of Israel declared independent in May 1948. The 700,000 Palestinians who fled or were driven from their homes were unable to return following the Lausanne Conference, 1949. During and after the 1948 war, a wave of Jewish refugees from Arab countries arrived, further complicating the demographic situation. In the 1948 Arab–Israeli War, Israel captured and incorporated more Mandate territory than suggested in the 1947 Partition Plan; Jordan captured the region today known as the West Bank, while at the Gaza Strip the All-Palestine Government was announced in September 1948. Consequently, it was however relocated to Cairo and eventually dissolved in 1959 by Egyptian President Nasser, officially making Gaza under Egyptian military administration. In the course of the Six Day War in June 1967, Israel captured the rest of former Mandate Palestine from Jordan and Egypt, and began a policy of Israeli settlements. From 1987 to 1993, the First Palestinian Intifada against Israel took place, ending with the 1993 Oslo Peace Accords. In 2000, the Second or Al-Aqsa Intifada began, and Israel built a barrier. Following Israel's unilateral disengagement plan of 2004, it withdrew all settlers and most of its military presence from the Gaza strip, but maintained control of the air space and coast. - 1 Ancient period - 2 Classical antiquity - 3 Late Antiquity period - 4 Middle Ages - 5 Early modern period - 6 Modern era - 6.1 Decline of the Ottoman Empire period - 6.2 British Mandate period - 6.3 Partition of former Mandatory territory - 6.4 Six Day War and Yom Kippur War - 6.5 First Intifada, Oslo Accords and Palestinian Authority - 7 Graphical Overview of Palestine's Historical Sovereign Powers - 8 See also - 9 References - 10 External links The earliest human remains in Palestine were found in Ubeidiya, some 3 km south of the Sea of Galilee (Lake Tiberias), in the Jordan Rift Valley. The remains are dated to the Pleistocene, c. 1.5 million years ago. These are traces of the earliest migration of Homo erectus out of Africa. The site yielded hand axes of the Acheulean type. Wadi El Amud between Safed and the Sea of Galilee was the site of the first prehistoric dig in Palestine, in 1925. The discovery of Palestine Man in the Zuttiyeh Cave in Wadi Al-Amud near Safed in 1925 provided some clues to human development in the area. Qafzeh is a paleoanthropological site south of Nazareth where eleven significant fossilised Homo sapiens skeletons have been found at the main rock shelter. These anatomically modern humans, both adult and infant, are now dated to about 90–100,000 years old, and many of the bones are stained with red ochre, which is conjectured to have been used in the burial process, a significant indicator of ritual behavior and thereby symbolic thought and intelligence. 71 pieces of unused red ochre also littered the site. Mount Carmel has yielded several important findings, among them Kebara Cave that was inhabited between 60,000–48,000 BP and where the most complete Neanderthal skeleton found to date. The Tabun cave was occupied intermittently during the Lower and Middle Paleolithic ages (500,000 to around 40,000 years ago). Excavations suggest that it features one of the longest sequences of human occupation in the Levant. In the nearby Es Skhul cave excavations revealed the first evidence of the late Epipalaeolithic Natufian culture, characterized by the presence of abundant microliths, human burials and ground stone tools. This also represents one area where Neanderthals—present in the region from 200,000 to 45,000 years ago—lived alongside modern humans dating to 100,000 years ago. In the caves of Shuqba in Ramallah and Wadi Khareitun in Bethlehem, stone, wood and animal bone tools were found and attributed to the Natufian culture (c. 12,800–10,300 BCE). Other remains from this era have been found at Tel Abu Hureura, Ein Mallaha, Beidha and Jericho. Between 10,000 and 5000 BCE, agricultural communities were established. Evidence of such settlements were found at Tel es-Sultan in Jericho and consisted of a number of walls, a religious shrine, and a 23-foot (7.0 m) tower with an internal staircase Jericho is believed to be one of the oldest continuously-inhabited cities in the world, with evidence of settlement dating back to 9000 BCE, providing important information about early human habitation in the Near East. Along the Jericho–Dead Sea–Bir es-Saba–Gaza–Sinai route, a culture originating in Syria, marked by the use of copper and stone tools, brought new migrant groups to the region contributing to an increasingly urban fabric. By the early Bronze Age (3000–2200 BCE), independent Canaanite city-states situated in plains and coastal regions and surrounded by mud-brick defensive walls were established and most of these cities relied on nearby agricultural hamlets for their food needs. Archaeological finds from the early Canaanite era have been found at Tel Megiddo, Jericho, Tel al-Far'a (Gaza), Bisan, and Ai (Deir Dibwan/Ramallah District), Tel an Nasbe (al-Bireh) and Jib (Jerusalem). The Canaanite city-states held trade and diplomatic relations with Egypt and Syria. Parts of the Canaanite urban civilization were destroyed around 2300 BCE, though there is no consensus as to why. Incursions by nomads from the east of the Jordan River who settled in the hills followed soon thereafter. In the Middle Bronze Age (2200–1500 BCE), Canaan was influenced by the surrounding civilizations of ancient Egypt, Mesopotamia, Phoenicia, Minoan Crete, and Syria. Diverse commercial ties and an agriculturally based economy led to the development of new pottery forms, the cultivation of grapes, and the extensive use of bronze. Burial customs from this time seemed to be influenced by a belief in the afterlife. The Middle Kingdom Egyptian Execration Texts attest to Canaanite trade with Egypt during this period. The Minoan influence is apparent at Tel Kabri. New Kingdom Egyptian period During 1550–1400 BCE, the Canaanite cities became vassals to Egypt as the Egyptian New Kingdom reunited Egypt and expanded into the Levant under Ahmose I and Thutmose I. Political, commercial and military events towards the end of this period (1450–1350 BCE) were recorded by ambassadors and Canaanite proxy rulers for Egypt in 379 cuneiform tablets known as the Amarna Letters. These refer to several local proxy rulers for Egypt such as Biridiya of Megiddo, Lib'ayu of Shechem and Abdi-Heba in Jerusalem. In the first year of his reign pharaoh Seti I (ca.1294-1290 BCE) waged a campaign to resubordinate Canaan to Egyptian rule, thrusting north as far as Beit Shean, and installing local vassals to administer the area in his name. A burial site yielding a scarab bearing his name, found within a Canaanite coffin excavated in the Jezreel Valley, attests to Egypt's presence in the area. Excavations have established that the late 13th, the 12th and the early 11th centuries BCE witnessed the foundation of perhaps hundreds of insignificant, unprotected village settlements, many in the mountains of Palestine. From around the 11th century BCE, there was a reduction in the number of villages, though this was counterbalanced by the rise of certain settlements to the status of fortified townships. In 1178 BCE, the Battle of Djahy (Canaan) between Ramesses III and the Sea Peoples marked the beginning of the decline in power of the New Kingdom in the Levant during the wider Bronze Age collapse. Independent Israelite, Philistine and Canaanite period During the beginning of the Iron Age (c. 1175 BCE), the Philistines occupied the southern coast of Canaan, and mingled with the local population, losing their separate identity over several generations. Pottery remains found in Ashkelon, Ashdod, Gath (city), Ekron and Gaza decorated with stylized birds provided the first archaeological evidence for Philistine settlement in the region. The Philistines are credited with introducing iron weapons and chariots to the local population. Modern archaeologists dispute parts of the Biblical tradition. In The Bible Unearthed Finkelstein and Silberman describe how, up until 1967, the Israelite heartland in the highlands of western Palestine was virtually an archaeological 'terra incognita'. Since then the traditional territories of the tribes of Judah, Benjamin, Ephraim, and Manasseh have been covered by intensive surveys. These surveys have revealed the sudden emergence of a new culture contrasting with the Philistine and Canaanite societies existing in Palestine during Iron Age I. This new culture is characterised by the lack of pork remains (whereas pork formed 20% of the Philistine diet in places), an abandonment of the Philistines/Canaanite custom of having highly decorated pottery, and the practice of circumcision. The Israelite ethnic identity had been created, not from the Exodus and a subsequent conquest, but from a transformation of the existing Canaanite-Philistine cultures. "These surveys revolutionized the study of early Israel. The discovery of the remains of a dense network of highland villages — all apparently established within the span of few generations — indicated that a dramatic social transformation had taken place in the central hill country of Canaan around 1200 BCE. There was no sign of violent invasion or even the infiltration of a clearly defined ethnic group. Instead, it seemed to be a revolution in lifestyle. In the formerly sparsely populated highlands from the Judean hills in the south to the hills of Samaria in the north, far from the Canaanite cities that were in the process of collapse and disintegration, about two-hundred fifty hilltop communities suddenly sprang up. Here were the first Israelites." From then on, over a period of hundreds of years until after the return of the exiles from Babylon, the Canaanites were gradually absorbed by the Israelites until after the period of Ezra (~450 BCE) when there is no more biblical record of them. Hebrew, a dialect of Canaanite became the language of the hill country and later the valleys and plains. According to the Hebrew Bible, the United Kingdom of Israel was established by the Israelite tribes with Saul as its first king in 1020 BCE.[unreliable source?] In 1000 BCE, Jerusalem was made the capital of King David's kingdom and it is believed that the First Temple was constructed in this period by King Solomon.[unreliable source?] By 930 BCE, the united kingdom split to form the northern Kingdom of Israel, and the southern Kingdom of Judah.[unreliable source?] These kingdoms coexisted with several more kingdoms in the greater Palestine area, including Philistine town states on the Southwestern Mediterranean coast, Edom, to the South of Judah, and Moab and Ammon to the East of the river Jordan.[unreliable source?] The socio-political system during this period was characterized by local patrons fighting other local patrons, lasting until around the mid-9th century BCE when some local chieftains were able to create large political structures that exceeded the boundaries of those present in the Late Bronze Age Levant. Archaeological evidence from this era is believed to corroborate some Biblical events. In 925 BCE, Pharaoh Sheshonk I of the Third Intermediate Period is recorded to have invaded Canaan following the Battle of Bitter Lakes, and is thought to be the same as Shishak, the first Pharaoh mentioned in the Bible who captured and pillaged Jerusalem. There was an at least partial Egyptian withdrawal from Palestine in this period, though it is likely that Bet Shean was an Egyptian garrison as late as the beginning of the 10th century BCE. The Kurkh Monolith, dated c. 835 BCE, describes King Shalmaneser III of Assyria's Battle of Qarqar, where he fought alongside the contingents of several kings, among them King Ahab and King Gindibu. The Mesha Stele, from c. 850 BCE, recounts the conquering of Moab, located East of the Dead Sea, by king Omri, and the successful revolt of Moabian king Mesha against Omri's son, presumably King Ahab (and French scholar André Lemaire reported that line 31 of the Stele bears the phrase "the house of David" (in Biblical Archaeology Review [May/June 1994], pp. 30–37).). Inscriptions at Tel Dan and Tell es-Safi record parts of the conquest of the region by Hazael of Aram Damascus in the 830s BCE. Developments in Palestine during this period have been the focus of debate between those who accept the version in the Hebrew Bible of the conquest of Canaan by the Israelite tribes, and those who reject it. Niels Peter Lemche, of the Copenhagen School of Biblical Studies, submits that the biblical picture of ancient Israel "is contrary to any image of ancient Palestinian society that can be established on the basis of ancient sources from Palestine or referring to Palestine and that there is no way this image in the Bible can be reconciled with the historical past of the region". For example, according to Jon Schiller and Hermann Austel, among others, while in the past, the Bible story was seen as historical truth, "a growing number of archaeological scholars, particularly those of the minimalist school, are now insisting that Kings David and Solomon are 'no more real than King Arthur,' citing the lack of archaeological evidence attesting to the existence of the United Kingdom of Israel, and the unreliability of biblical texts, due to their being composed in a much later period." Sites and artifacts, including the Large Stone Structure, Mount Ebal, the Menertaph, and Mesha stelae, among others, are subject to widely varying historical interpretations: the "conservative camp" reconstructs the history of Israel according to the biblical text and views archaeological evidence in that context, while scholars in the minimalist or deconstructionist school hold that there is no archaeological evidence supporting the idea of a United Monarchy (or Israelite nation) and the biblical account is a religious mythology created by Judean scribes in the Persian and Hellenistic periods; a third camp of centrist scholars acknowledges the value of some isolated elements of the Pentateuch and of Deuteronomonistic accounts as potentially valid history of monarchic times that can be in accord with the archaeological evidence, but argue that nevertheless the biblical narrative should be understood as highly ideological and adapted to the needs of the community at the time of its compilation. Neo-Assyrian and Neo-Babylonian Empires period Assyrian inscriptions from c. 740 BCE record the military victories of Tiglath Pileser III in the region, during which period the Neo-Assyrian Empire conquered most of the Levant. The Bible records the Israelite cities becoming vassals to the Neo-Assyrian Empire during this period. At around this time, the Siege of Gezer (c. 733 BCE), 20 miles (32 km) west of Jerusalem, is recorded on a stone relief at the Assyrian royal palace in Nimrud. Further military expeditions into the region are recorded in the annals of Sargon and Sennacherib, as well as in the bible. According to the bible, between 722 and 720 BCE the northern Kingdom of Israel was destroyed by the Assyrian Empire and the Israelite tribes—thereafter known as the Lost Tribes—were exiled. The most important finding from the southern Kingdom of Judah is the Siloam Inscription, dated c. 700 BCE, which celebrates the successful encounter of diggers, digging from both sides of the Jerusalem wall to create the Hezekiah water tunnel and water pool, mentioned in the Hebrew Bible, in 2Kings 20:20. The region was controlled briefly by Pharaoh Necho II of the Twenty-sixth dynasty of Egypt between the Battle of Megiddo (609 BCE) and the Battle of Carchemish four years later, and further conflict between the Babylonians and the 26th dynasty of Egypt is recorded during 601–586 BCE. According to the bible, this culminated in 586 BCE when Jerusalem and the First Temple were destroyed by the Babylonian king Nebuchadnezzar II. Most of the surviving Israelite leaders, and much of the other local population, were deported to Babylonia. Persian (Achaemenid) Empire period Following King Cyrus the Great's defeat of the Neo-Babylonian Empire at the Battle of Opis, the region became part of the Eber-Nari satrapy or District number V (corresponding the regions of (Syria, Phoenicia, Palestine and Cyprus) according to Herodotus and Arrian, which included three administrative areas: Phoenicia, Judah and Samaria, and the Arabian tribes. The Phoenician cities of Tyre, Sidon, Byblos, and Aradus were vassal states ruled by hereditary local kings who struck their own silver coins and whose power was limited by the Persian satrap and local popular assemblies. The economies of these cities were mainly based on maritime trade. During military operations, the Phoenicians were obliged to put their fleet at the disposal of the Persian kings. Judah and Samaria enjoyed considerable internal autonomy. Bullae and seal impressions of the end of the 6th and beginning of the 5th centuries mention the province of Judah. Its governors included Sheshbazzar and Zerubbabel under Cyrus and Darius I; Nehemiah ; Bagohi, who succeeded Nehemiah and whose ethnicity is difficult to determine; and "Yehizkiyah the governor" and "Yohanan the priest", known from coins struck in Judah in the 4th century BCE. From the second half of the 5th century the province of Samaria was governed by Sanballat and his descendants. According to the bible and implications from the Cyrus Cylinder, Jews were allowed to return to what their holy books had termed the Land of Israel, and having been granted some autonomy by the Persian administration, it was during this period that the Second Temple in Jerusalem was built. Sebastia, near Nablus, was the northernmost province of the Persian administration in Palestine, and its southern borders were drawn at Hebron. Some of the local population served as soldiers and lay people in the Persian administration, while others continued to agriculture. In 400 BCE, the Nabataeans made inroads into southern Palestine and built a separate civilization in the Negev that lasted until 160 BCE. The end of the Persian period was marked by a number of revolts in the region, including a significant uprising against Artaxerxes III in 350 BCE, which resulted in the destruction of Jerusalem. In the late 330s BCE, Alexander the Great conquered the region, during his six-year Macedonian conquest of the empire of Darius III of Persia. Alexander's armies took Palestine without complication while traveling to Egypt after the Siege of Tyre, beginning an important period of Hellenistic influence in the land. During 323–301 BCE, the region changed hands numerous times during the wars of the Diadochi, with rulers including Laomedon of Mytilene, Ptolemy I Soter and Antigonus I Monophthalmus. In 312 BCE Ptolemy I Soter defeated Antigonus' son Demetrius I at the Battle of Gaza, but withdrew from the region shortly thereafter. It is probable that Seleucus I Nicator, then an Admiral under Ptolemy's command, took part in the battle, as following the battle he was given 800 infantry and 200 cavalry and immediately travelled to Babylon where he founded the Seleucid Empire. The region was finally re-captured by Ptolemy I Soter after Antigonus I Monophthalmus was killed at the Battle of Ipsus. Ptolemy had not taken part in the battle, and the victors Seleucus I Nicator and Lysimachus had carved up the Antigonid Empire between them, with Southern Syria intended to become part of the Seleucid Empire. Although Seleucus did not attempt to conquer the area he was due, Ptolemy's pre-emptive move led to the Syrian Wars, which began in 274 BCE between the successors of the two leaders. The northern portion of Palestine ultimately fell into the hands of the Seleucid Empire in 219 through the betrayal of Governor Theodotus of Aetolia, who had held the province on behalf of Ptolemy IV Philopator. The Seleucids advanced on Egypt, but were defeated at the Battle of Raphia (Rafah) in 217. However, in 200 BCE Southern Palestine also fell under the control of the Seleucid Empire following the Battle of Panium (part of the Fifth Syrian War) in which Antiochus III the Great defeated the Ptolemies. The landscape during this period was markedly changed by extensive growth and development that included urban planning and the establishment of well-built fortified cities. Hellenistic pottery was produced that absorbed Philistine traditions. Trade and commerce flourished, particularly in the most Hellenized areas, such as Ashkelon, Jaffa, Jerusalem, Gaza, and ancient Nablus (Tell Balatah). The Persians had not interfered with the internal affairs of the various subject-peoples of the region, but the Greeks followed a policy of deliberate Hellenisation, encouraging, although not normally enforcing, Greek culture. Hellenisation took root first in the densely settled coastal and lowland areas, and only really began to impinge on more backward areas such as Judea in the early 2nd century. According to Josephus and the Books of the Maccabees, the continued Hellenization of Palestine by the Seleucids resulted in an uprising in the Judean Mountains, known as the Maccabean Revolt. Although the revolt was quelled in 160 BCE at the Battle of Elasa, the Seleucid Empire entered a period of rapid decline in 145–144 BCE, beginning with the overthrowing of King Alexander Balas at the Battle of Antioch (145 BCE) (the capital of the empire) by Demetrius II Nicator in alliance with Ptolemy VI Philometor of Egypt, as well as the capturing of Seleucia (the previous capital of the empire) by Mithradates I of Parthia. By 116 BCE, a civil war between Seleucid half-brothers Antiochus VIII Grypus and Antiochus IX Cyzicenus resulted in a breakup of the kingdom and the independence of certain principalities, including Judea. This allowed Judean leader John Hyrcanus to carry out the first military conquests of the independent Hasmonean kingdom in 110 BCE, raising a mercenary army to capture Madaba and Schechem, significantly increasing the regional influence of Jerusalem The Hasmoneans gradually extended their authority over much of the region, forcibly converting the populations of neighbouring regions, and creating a Judean-Samaritan-Idumaean-Ituraean-Galilean alliance in the process. The Judean (Jewish, see Ioudaioi) control over the wider region resulted in it also becoming known as Judaea, a term that had previously only referred to the smaller region of the Judean Mountains. During 73–63 BCE, the Roman Republic extended its influence into the region in the Third Mithridatic War. During the war, Armenian King Tigranes the Great took control of Syria and prepared to invade Judea but retreated following an invasion of Armenia by Lucullus. According to Armenian historian Movses Khorenatsi writing in c. 482 CE, Tigranes captured Jerusalem and deported Hyrcanus to Armenia, however most scholars deem this account to be incorrect. Following the Roman conquest of Judea led by Pompey in 63 BCE, Aulus Gabinius, proconsul of Syria, split the former Hasmonean Kingdom into five districts of legal and religious councils known as sanhedrin based at Jerusalem, Sepphoris (Galilee), Jericho, Amathus (Perea) and Gadara. Roman rule was solidified when Herod, whose dynasty was of Idumean ancestry, was appointed as king. Following a brief intervention by Pacorus I of Parthia, from 37 Iudaea under Herod I was a client kingdom of the Roman Empire. Urban planning under the Romans was characterized by cities designed around the Forum—the central intersection of two main streets—the Cardo, running north-south and the Decumanus running east-west. Cities were connected by an extensive road network developed for economic and military purposes. Among the most notable archaeological remnants from this era are Herodium (Tel al-Fureidis) to the south of Bethlehem, Masada and Caesarea Maritima. Herod arranged a renovation of the Second Temple in Jerusalem, with a massive expansion of the Temple Mount platform and major expansion of the Jewish Temple around 19 BCE. The Temple Mount's natural plateau was extended by enclosing the area with four massive retaining walls and filling the voids. This artificial expansion resulted in a large flat expanse, which today forms the eastern section of the Old City of Jerusalem. Around the time associated with the birth of Jesus, Roman Palestine was in a state of disarray and direct Roman rule was re-established. In 6 CE, the Herodian governorate ended with the deposition of Herod Archelaus as the ethnarch of the Tetrarchy of Judea. The Herodian Dynasty was then replaced by Roman prefects and after 44 CE by procurators, beginning with Coponius. Herodians continued to rule elsewhere in Palestine. Senator Quirinius was appointed Legate of the Roman province of Syria (to which Judea had been "added" according to Josephus though Ben-Sasson claims it was a "satellite of Syria" and not "legally part of Syria") and carried out the tax census of both Syria and Judea known as the Census of Quirinius. Caesarea Palaestina replaced Jerusalem as the administrative capital of the region. Most scholars agree that Jesus was a Galilean Jew, born around the beginning of the first century, and hold that Jesus lived in Galilee and Judea and did not preach or study elsewhere. Using the gospel accounts with historical data, most scholars arrive at a date of birth between 6 and 4 CE for Jesus, but some propose estimates that lie in a wider range. The general scholarly consensus is that Jesus was a contemporary of John the Baptist and was crucified by Roman governor Pontius Pilate. Most scholars agree that his crucifixion was between 30 and 33 CE. As a result of the First Jewish-Roman War (66–73), Titus sacked Jerusalem (in 70 CE) destroying the Second Temple, leaving only supporting walls, including the Western Wall. According to Josephus, the estimated death toll was 250,000–1,100,000. Pharisee rabbi Yokhanan ben Zakai, a student of Hillel, fled during the siege of Jerusalem to negotiate with the Roman General Titus. Yokhanan obtained permission to reestablish a Sanhedrin in the coastal city of Iamnia (modern Yavne) (see also Council of Jamnia). He founded a school of Torah there that would eventually evolve, through the Mishna in around 200 CE, into Rabbinic Judaism. The region's leading Christians (Jewish Christians) relocated to Pella. Other Jewish groups such as Sadducees and Essenes are no longer recorded as groups in history. Roman Syria Palaestina period In 132 CE, the Emperor Hadrian joined the province of Iudaea (comprising Samaria, Judea proper, and Idumea) with Galilee to form new province of Syria Palaestina. Hadrian probably chose a name that revived the ancient name of Philistia (Palestine), combining it with that of the neighboring province of Syria, in an attempt to suppress Jewish connection to the land. However Cassius Dio, the Roman historian from whom we have the bulk of our understanding of the revolt, does not mention the change of name nor the reason behind it in his "Roman History". Jerusalem was renamed "Aelia Capitolina" and temples were built there to honor Roman gods, particularly Jupiter. In 135 CE, the victory in Bar Kokhba's revolt by Hadrian resulted in 580,000 Jews killed (according to Cassius Dio) and destabilization of the region's Jewish population. Jerusalem was re-established as the Roman military colony of Aelia Capitolina; a largely unsuccessful attempt was made to prevent Jews and Christians from living there. Many Jews and Christians left Palestine altogether for the Diaspora communities, and large numbers of prisoners of war were sold as slaves throughout the Empire. Christianity in particular was practiced in secret and the Hellenization of Palestine continued under Septimius Severus (193–211 CE). New pagan cities were founded in Judea at Eleutheropolis (Bayt Jibrin), Diopolis (Lydd), and Nicopolis (Emmaus). Some two hundred Jewish communities remained, as gradually certain religious freedoms were restored, such as exemption from the imperial cult and internal self-administration. The Romans made no such concession to the Samaritans, to whom religious liberties were denied, while their sanctuary on Mt.Gerizim was defiled by a pagan temple, as part of measures were taken to suppress the resurgence of Samaritan nationalism. A number of events with far-reaching consequences took place during this period, including further religious schisms between Christianity and Rabbinic Judaism such as a council held by the bishops of Palestine in Caesarea in 195 that decreed that Easter was to be always kept on a Sunday, and not with the Jewish Passover. The Romans destroyed the community of the Mother Church in Jerusalem, which had existed since the time of Jesus The line of Jewish bishops in Jerusalem, which is claimed to have started with Jesus's brother James the Righteous as its first bishop, ceased to exist, within the Empire. Hans Kung suggests that the Jewish Christians sought refuge in Arabia and he quotes with approval a view that this created a paradox of truly world-historical significance that while Jewish Christianity was swallowed up in the Christian church, it preserved itself in Islam. During 259–272, the region fell under the rule of Odaenathus as King of the Palmyrene Empire after the capture of Emperor Valerian by Shapur I at the Battle of Edessa caused the Roman Empire to splinter until Aurelian defeated the Palmyrenes at the Battle of Emesa (Homs). Late Antiquity period Late Roman Empire period Following the victory of Christian emperor Constantine in the Civil Wars of the Tetrarchy (306–324), the total Christianization of the Roman Empire began. Within a few months, the First Council of Nicaea (first worldwide Christian council) confirmed the status of Aelia (Jerusalem) as a patriarchate, at which point the city is generally taken to have been renamed Jerusalem. Theodosius I declared Christianity the state religion of the empire in 380, and Palestine became part of the Eastern Roman Empire ("Byzantium") after the division of the Roman Empire into east and west (a fitful process that was not finalized until 395 CE). The Byzantines redrew the borders of the Land of Palestine. The various Roman provinces (Syria Palaestina, Samaria, Galilee, and Peraea) were reorganized into three diocese of Palaestina, reverting to the name first used by Greek historian Herodotus in the mid-5th century BCE: Palaestina Prima, Secunda, and Tertia or Salutaris (First, Second, and Third Palestine), part of the Diocese of the East. Palaestina Prima consisted of Judea, Samaria, the coast, and Peraea with the governor residing in Caesarea. Palaestina Secunda consisted of the Galilee, the lower Jezreel Valley, the regions east of Galilee, and the western part of the former Decapolis with the seat of government at Scythopolis. Palaestina Tertia included the Negev, southern Jordan—once part of Arabia—and most of Sinai with Petra as the usual residence of the governor. Palestina Tertia was also known as Palaestina Salutaris. According to historian H.H. Ben-Sasson, this reorganisation took place under Diocletian (284–305), although other scholars suggest this change occurred later in 390. This was the period of Palestine's greatest prosperity in antiquity. Urbanization increased, large new areas were put under cultivation, monasteries proliferated and synagogues were restored. The cities of Palestine, such as Caesarea Maritima, Jerusalem, Scythopolis, Neapolis, and Gaza reached their peak population, and the population West of the Jordan may have reached as many as one million. Bede in his Historia Ecclesiastica, drew on Orosius' information gathered from the local Jews to describe Palestine as one of the provinces of "Syria, which is called Aran by the Hebrews. The place is between the River Euphrates and the Great Sea, and extends towards Egypt; its largest provinces are Commagene, Phoenicia, and Palestine, as well as the countries of the Saraceni and the Nabathaei. It has twelve gentes."54 In 326, Constantine's mother Saint Helena visited Jerusalem and ordered the destruction of Hadrian's temple to Venus, which had been built on Calvary. Accompanied by Macarius of Jerusalem, the excavation reportedly discovered the True Cross, the Holy Tunic and the Holy Nails. The first Church of the Holy Sepulcher in Jerusalem, the first Church of the Nativity in Bethlehem and the first Church of the Ascension on the Mount of Olives were all built during Constantine's reign. The earliest monasteries in Christianity outside of Egypt were built in Palestine during this period, notably those of Hilarion near Gaza, Saint Epiphanius at Ad near the city of Eleutheropolis (Bayt Jibrin, the head of the largest bishopric in Palestine at this time), Tyrannius Rufinus and Melania the Elder on the Mount of Olives, Euthymius the Great at Pharan, Sabbas the Sanctified in the Kidron Valley as well as St. George's Monastery in Wadi al-Qelt, the Monastery of the Temptation and Deir Hajla near Jericho, and Deir Mar Saba and Deir Theodosius east of Bethlehem. The sack of Rome in 410 caused a significant episode of migration to Palestine as a group of aristocratic ladies responded to the holy man Jerome's invitation to settle in Aelia Capitolina and Bethlehem. In 451, the Council of Chalcedon confirmed Jerusalem's status as a Patriarchate as one of the Pentarchy, and Juvenal of Jerusalem became the first Patriarch of Jerusalem Notable works by Christian scholars were produced in Palestine in the disciplines of rhetoric, historiography, Eusebian ecclesiastical history, classicizing history and hagiography. Saint Cyril of Jerusalem delivered his Mystagogical Catecheses, instructions on the principal topics of Christian faith and practise, and Saint Jerome moved to Jerusalem in order to commence work on the Vulgate, commissioned by Pope Damasus I and instrumental in the fixation of the Biblical canon in the West. Procopius, from Caesarea Palaestina, became the Byzantine Empire's principal historian of the 6th century, writing the Wars of Justinian, the Buildings of Justinian and the celebrated Secret History. Under Byzantine rule, the two dioceses of Palaestina proper became a center of Christianity, while retaining significant Jewish and Samaritan communities. Some areas, like Gaza, were well known as pagan holdouts, and remained attached to the worship of Dagon and other deities as their ancestors had been for thousands of years. Ghassanid Arab migration in the 4th and 5th centuries established an Arab Christian domain with a capital on the Golan, forming a buffer of Christian Byzantium against the wild tribes of Arabia. The "Life of Barsauma of Samosata", a 6th-century Christian polemic about the Monophysite monk of the early 5th century, stated that Jews, Samaritans and pagans formed a large part of the population and persecuted Christians during this period. In 351–352, a Jewish revolt against Byzantine rule in Tiberias and other parts of the Galilee was brutally suppressed. In 361, Neoplatonist Julian the Apostate becomes Roman Emperor and attempted to reverse the growing influence of Christianity by encouraging other religions. As a result, Alypius of Antioch was commissioned to rebuild the Temple in Jerusalem and Jews were formally allowed to return to the city However, two years later the Galilee earthquake of 363 together with the re-establishment of Christianity's dominance following the death of Julian the Apostate at the Battle of Samarra ended the attempts to rebuild the Temple. In 438 CE, the Empress Eudocia allowed Jews to return to Jerusalem to live. The Samaritan self-rule had shortly gained a level of independence under the leadership of Baba Rabba in late 4th century. However, they were again subdued by Byzantine forces. Samaritan attempts to gain independence from Byzantines peaked during the 5th and 6th centuries in a series of Samaritan Revolts, some of which had messianic aspirations. The outcome of Samaritan strife with Christian Byzantines, supported by Ghassanid Arabs, turned disastrous. After the Third Samaritan revolt in 529–531, led by Julianus ben Sabar, and the Fourth Revolt in 555. With Samaritan casualties went well beyond 100,000, cities and worship places destroyed, many enslaved and expelled, the Samaritan community dwindled. On 1 July 536 CE, Justinian I promoted Stephanus (Stephen) the governor at Caesarea to proconsul (anthypatos), giving him authority over the two remaining consulars. Justinian believed that the elevation of the governor was appropriate because he was responsible for "the province in which our Lord Jesus Christ... appeared on earth". Justinian I undertook a number of building works in Jerusalem, including the once magnificent Nea Ekklesia of the Theotokos ("the Nea") and the extension of the Cardo thoroughfare. Byzantine administration of Palestine was temporarily suspended during the Persian occupation of 614–28. In 613 CE, the Persian Sassanian Empire under Khosrau II had invaded the Levant led by General Shahrbaraz, taking Antioch and later Caesaria. Jews under Benjamin of Tiberias assisted the conquering Persians, revolting against the Byzantine Empire under Heraclius and hoping of controlling Jerusalem autonomously. In 614 CE, Persian-Jewish forces conquered Jerusalem, destroying most of the churches, taking Patriarch Zacharias prisoner, taking the True Cross and other relics to Ctesiphon, and massacring much of the Christian population. The Jews of Jerusalem gained autonomy to some degree, but frustrated with its limitations and anticipating its loss offered to assist the Byzantines in return for amnesty for the revolt. In 617 CE, the Jewish governor Nehemiah ben Hushiel was killed by a mob of Christian citizens, three years after his appointment. The Sassanids quelled the uprising and appointed a Christian governor to replace him. At that time the Persians betrayed the agreements with the Jews and expelled the Jewish population from Jerusalem, forbidding them to live within 3 miles (4.8 km) of it. In 625 CE (or 628 CE), the Byzantinian army returned to the area, promising amnesty to Jews who had joined the Persians, and was greeted by Benjamin of Tiberias. In 629 CE, the Byzantine Emperor Heraclius marched into Jerusalem at the head of his army, following the decisive defeat of the Sassanid Empire at the Battle of Nineveh (627). Heraclius personally returned the True Cross to the city. The Nabateans roamed the Negev by the Roman Period, and by the Byzantine Period dominated the swath of sparsely populated deserts, from the Sinai to the Negev to the northwest coast of Arabia, the outlands that the Byzantines called the diocese of Palaestina Salutoris (meaning something like "near Palestine"). Its capital Petra was formally the capital of the Roman province of Arabia Petraea. The Nabateans also inhabited the outland of Jordan and southern Syria, improperly called the diocese of Arabia because its capital Bostra was within the northern extremity of the Roman province of Arabia Petrae. The origin of the Nabateans remains obscure, but they were Aramaic speakers, and the term "Nabatean" was the Arabic name for an Aramean of Syria and Iraq. By the 3rd century during the Late Roman Period, the Nabateans stopped writing in Aramaic and began writing in Greek, and by the Byzantine Period they converted to Christianity. Trading relations existed between the cities of Palestine and the Arab tribes of the Hejaz, particularly with the southern cities of Petra and Gaza. Muhammed, his father (Abd Allah) and his great-grandfather (Hashim, who died in Gaza) all travelled on trading routes through the region in the 6th century, and in 583 Muhammed is said to have met with Nestorian monk Bahira at Bosra. From the beginning of Islam in 610, Jerusalem became the Qibla (focal point for Muslim prayers) for fourteen years until it was replaced by Mecca in 624, 18 months after the Hijra (Muhammad's migration to Medina). According to Sahih al-Bukhari, Muhammad then ordained the Al-Aqsa Mosque as one of the three holy mosques of Islam A decade later, Byzantium lost control of the region during the Muslim conquest of Syria, during which the empire's forces were decisively defeated at the Battle of Yarmouk in 636. Jerusalem capitulated in 638 and Caesarea between 640 and 642. The subsequent Rashidun and Umayyad Caliphates saw a century of rapid expansion of Arab power well beyond the Arabian peninsula in the form of a vast Muslim Arab Empire. Rashidun, Umayyad and Abbasid Caliphates period In 638, following the Siege of Jerusalem, the Caliph Omar Ibn al-Khattab and Safforonius, the Patriarch of Jerusalem, signed Al-Uhda al-'Omariyya (The Umariyya Covenant), an agreement that stipulated the rights and obligations of all non-Muslims in Palestine. Christians and Jews were considered People of the Book, enjoyed some protection (dhimmi) but had to pay a special poll tax called jizyah ("tribute") in return for this protection. According to Muhammad ibn Jarir al-Tabari, the covenant guaranteed Christians freedom of religion but prohibited Jews from living in Jerusalem. However, during the early years of Muslim control of the city, a small permanent Jewish population returned to Jerusalem after a 500-year absence. Umar, the second of the initial four Rashidun Caliphs, was the first conqueror of Jerusalem to enter the city on foot, and when visiting the site that now houses the Haram al-Sharif, he declared it a sacred place of prayer. Cities that accepted the new rulers, as recorded in registrars from the time, were: Jerusalem, Nablus, Jenin, Acre, Tiberias, Bisan, Caesarea, Lajjun, Lydd, Jaffa, Imwas, Beit Jibrin, Gaza, Rafah, Hebron, Yubna, Haifa, Safed and Ashkelon. In Arabic, the area approximating the Byzantine Diocese of Palaestina I in the south (roughly Judea, Philistia, and southern Jordan) was called Jund Filastin (meaning "the military district of Palestine", as a tax administrative area), and the Diocese of Palaestina II in the north (roughly Samaria, Galilee, Golan, and northern Jordan) Jund al-Urdunn. In 661, with the assassination of Ali, the last of the Rashidun Caliphs, Muawiyah I became the uncontested Caliph of the Islamic World. Muawiyah I was ordained as Caliph in Jerusalem, ending the First Fitna and marking the beginning of the Umayyad Empire. Under Umayyad rule, the Byzantine province of Palaestina Prima became the administrative and military sub-province (jund) of Filastin—the Arabic name for Palestine from that point forward. It formed one of five subdivisions of the larger province of ash-Sham (Arabic for Greater Syria). Jund Filastin (Arabic جند فلسطين, literally "the army of Palestine") was a region extending from the Sinai to the plain of Acre. Major towns included Rafah, Caesarea, Gaza, Jaffa, Nablus and Jericho. Lod served as the headquarters of the province of Filastin and the capital later moved to Ramla. Jund al-Urdunn (literally "the army of Jordan") was a region to the north and east of Filastin, which included the cities of Acre, Bisan and Tiberias. In 687–691, during the Second Fitna, the Dome of the Rock was built under Caliph Abd al-Malik ibn Marwan, becoming the world's first great work of Islamic architecture. The Temple Mount (known as Haram Ash-Sharif in the Islamic world and the site where the Islamic prophet Muhammad is believed by Muslims to have begun his nocturnal journey to heaven), had remained unbuilt for c. 600 years since Titus's destruction of Herod's Temple in 70. It was under Umayyad rule that Christians and Jews were granted the official title of "Peoples of the Book" to underline the common monotheistic roots they shared with Islam. Christian pilgrims visited and made generous donations to Christian holy places in Jerusalem and Bethlehem, and the establishment of the Pilgrims' Inn in Jerusalem during this period was seen as a fulfillment of Umar's pledge to Bishop Sophronious to allow freedom of religion and access to Jerusalem for Christian pilgrims. The Christian monasteries throughout the region continued to operate, and between 730-749 John of Damascus, previously chief adviser to Caliph Hisham ibn Abd al-Malik, moved to the monastery Mar Saba outside Jerusalem and became the major opponent of the First Iconoclasm through his theological writings. Trading relations between Palestine and Europe were strong, and a trade fair took place in Jerusalem every year on September 15 where merchants from Pisa, Genoa, Venice and Marseilles converged to acquire spices, soaps, silks, olive oil, sugar and glassware in exchange for European products. In 744 riots broke out in the major cities of Palestine and Syria during the reign of Marwan II, and were quelled in 745–6. These rebellions were followed by further revolts in the East of the empire, which culminated in the defeat of the Umayyad army in 750 at the Battle of the Zab. The Abbasids took control of the entire empire including Palestine, forcing Marwan II to flee via Gaza to Egypt where he was assassinated. The Baghdad-based Abbasid Caliphs renovated and visited the holy shrines and sanctuaries in Jerusalem, with Al-Mansur arranging in 758 the renovation of the Dome of the Rock that had collapsed in an earthquake and Al-Ma'mun arranging further renovations following a visit to Jerusalem in 813. The Abbasids continued to build up Ramle, which had become the capital of Jund Filastin. Coastal areas were fortified and developed and port cities like Acre, Haifa, Caesarea, Arsuf, Jaffa and Ashkelon received monies from the state treasury. However, the Abbasid caliphs visited the region less frequently than the Umayyads since their capital in Baghdad was a further 500 miles (800 km) east. The Abbasid period marked the beginning of the Islamic Golden Age, in which a number of scholars from Palestine, such as the Gazan-born jurist and founder of the Shafi'i school of fiqh Muhammad ibn Idris ash-Shafi`i and the Jerusalemite geographer Al-Muqaddasi, played an integral part. The influence of the Arabian tribes declined during the Abbasid period and the only context where they are reported is in uprising against the central authority. However, a dispute between the Mudhar and Yamani tribes broke out in Jund al-Urdunn towards the end of the 8th century leading to Civil War in Palestine (793–796). Harun al-Rashid viewed this as a rebellion and sent a large army under Ja'far ibn Yahya al-Barmaki to quell the revolt. According to historian Moshe Gil, "he put down the rebels with an iron hand and much blood was spilled." The cities of Gaza, Bayt Jibrin, Ascalon in Jund Filastin and the town Sariphaea in Jund al-Urdunn were completely destroyed in the conflict by Bedouin tribes. Several towns and villages in western Palestine were also sacked. The monasteries of St. Chariton, St. Cyriacus, St. Sabas, St. Theodosius, and St. Euthymius were also attacked. The combined casualties of the tribal federations totalled roughly 1,200. During Harun al-Rashid's (786–809) reign the first formal contacts with the Frankish Kingdom of Charlemagne occurred, as part of the attempted Abbasid–Carolingian alliance In 797, Harun al-Rashid is reported to have offered the custody of the Christian holy places in Jerusalem to Charlemagne, in return for Charlemagne sending money for construction and improvements. As a result, the Church of the Holy Sepulchre was restored and the Latin hospital was enlarged and placed under the control of the Benedictines. Two years later Charlemagne sent another mission to Patriarch George of Jerusalem. Towards the end of the 9th century, the Baghdad-based Abbasids began to lose control of their western provinces. From 878 Palestine was ruled from Egypt by semi-autonomous rulers for almost a century, beginning with Ahmad ibn Tulun, ruler of Egypt and founder of the Tulunid dynasty, who conquered Palestine and most of Syria four years after declaring Egypt's independence from the Abbasid court in Baghdad. The Abbasids regained direct control of Palestine in 904, after their invasion forced the army of Tulunid Emir Harun to retreat to Egypt where the Tulunids were defeated the following year. Direct control from Baghdad was maintained until 939 when Muhammad bin Tughj Al-Ikhshid, governor of Abbasid Egypt and Palestine, was granted independent control over his domain and the title Al-Ikhshid (Prince) by Abbasid Caliph Ar-Radi. Like the Tulunids, the relative proximity of the Ikhshidid capital to Palestine resulted in a greater focus on the region, such that both Ikhshidid rulers, Muhammad bin Tughj Al-Ikhshid and Abu al-Misk Kafur, were buried in Jerusalem. Fatimid Caliphate period From their base in Tunisia, General Gawhar Al-Siqilli of the Ismaili Shi'ite Fatimids, who claimed to be descendants of Muhammad through his daughter Fatimah, conquered the Ikhshidid domains of Palestine and Egypt in 969, following a treaty guaranteeing the local Sunnis freedom of religion. They moved their capital to the new city of Cairo, just north of the Ikhshidid capital of Fustat. The Fatimids continued their expansion to the borders of the Byzantine Empire, and a failed attack on Antioch in 971 was followed up by a Byzantine defeat outside of Amida. However, the Byzantines fought back and in 975 Emperor John I Tzimiskes's second campaign took Syria and much of northern Palestine, including Tiberias, Nazareth and Caesarea Palaestina, but was defeated en route to Jerusalem. The emperor became ill and died suddenly in 976 on his return from the campaign, and the Byzantines withdrew shortly thereafter to face the Bulgar threat in the north of their empire. Jerusalem, Nablus, and Askalan were expanded and renovated under Fatimid rule. However, in 1009, Fatimid Caliph Al-Hakim ordered the destruction of all churches and synagogues in the empire, including the Church of the Holy Sepulchre. However, this was reversed twenty years later by the Al-Hakim' successor as Caliph, Ali az-Zahir, who authorized the rebuilding of the Church of the Holy Sepulchre and other Christian churches in a treaty with Byzantine Emperor Romanos III Argyros. Romanos' successor Constantine IX Monomachos paid for the restoration, and a number of other Christian buildings, including the Muristan hospital, church and monastery were built during this period. Az-Zahir also undertook a major renovation of the Dome of the Rock during his reign. After the 10th century, the division of Palestine into Junds began to break down. During the early 11th century, Seljuk Turks invaded large portions of West Asia and both the Fatimids and the Byzantines suffered setbacks from the fighting. Warfare between the Fatimids and Seljuks caused great disruption for the local population and for western pilgrims. In 1073 Palestine was captured by Malik-Shah I's Isfahan-based Great Seljuq Empire under Emir Atsiz ibn Uvaq, who was advancing south into the weakening Fatimid Empire following the decisive defeat over the Byzantine army at the Battle of Manzikert two years previously and a devastating six-year famine in Egypt between 1067 and 1072. The Seljuk rule was unpopular, and in 1077 Jerusalem revolted against their rule while Emir Atsiz ibd Uvaq was fighting the Fatimid Empire in Egypt. On his return to Jerusalem, Atsiz re-took the city and massacred the local population. As a result, Atsiz was executed by the governor of Syria Tutush I, the brother of Seljuk leader Malik-Shah I. Tutush I appointed Artuq bin Ekseb, later founder of the Artuqid dynasty, as governor. Artuq bin Ekseb died in 1091, and was succeeded as governor by his sons Ilghazi and Sokmen, known as the Artuqid dynasty. Malik Shah died in 1092, and the Great Seljuk Empire split into smaller warring states. Control of Palestine was disputed between Duqaq and Radwan after the death of their father Tutush I in 1095. The ongoing rivalry weakens Syria, and Fatimid Regent Al-Afdal Shahanshah recaptured the region in 1098 from the Artuqids, just before the arrival of the crusaders. In 1054, the Great Schism formally divided the Christian church into east and west, resulting in the holy sites of Palestine falling under the jurisdiction of the Eastern Orthodox Church. However, in 1090, Byzantine Emperor Alexios I Komnenos began taking reconciliatory measures towards the Papacy, with the intention of seeking western support against the Seljuqs. In 1095 his ambassadors appeared before Pope Urban II at the Council of Piacenza, to request mercenary forces, and later that year at the Council of Clermont Pope Urban II called for the First Crusade. Kingdom of Jerusalem (Crusaders) period The Kingdom of Jerusalem was a Christian kingdom established in the Levant in 1099 as a result of the First Crusade. Its control of Jerusalem and most of Palestine lasted almost a century until defeat by Saladin's forces in 1187, after which most of Palestine was controlled by the Ayyubids. Shortly after Crusader rule was established in Palestine, Godfrey of Bouillon promised to turn over the rule of the region to the Papacy once the crusaders had captured Egypt. However, the invasion of Egypt did not occur as Godfrey died shortly thereafter and Baldwin was proclaimed the first King of Jerusalem after politically outmanoeuvering Dagobert of Pisa who had previously been appointed as the Latin Patriarch. At first the Crusader kingdom was little more than a loose collection of towns and cities captured during the first crusade. At its height, the kingdom roughly encompassed the territory of modern-day Israel and the State of Palestine. It extended from modern Lebanon in the north to the Sinai Desert in the south, and into modern Jordan and Syria in the east. There were also attempts to expand the kingdom into Fatimid Egypt. Its kings held a certain amount of authority over the other crusader states to the north: the County of Tripoli, the Principality of Antioch, and the County of Edessa. Many customs and institutions were imported from the territories of Western Europe from which the crusaders came, and there were close familial and political connections with the West throughout the kingdom's existence. It was, however, a relatively minor kingdom in comparison and often lacked financial and military support from Europe. Locally based military orders were founded in the kingdom to fill this vacuum. The foundation of the Knights Hospitaller by Gerard Thom at the Muristan Christian hospice in Jerusalem was confirmed by a Papal Bull from Pope Paschal II in 1113, and the founding by Hugues de Payens and Godfrey de Saint-Omer of the Knights Templar took place in 1119 in the Al Aqsa Mosque. The kingdom grew closer to the neighbouring Armenian Kingdom of Cilicia and the Byzantine Empire, from which it inherited "oriental" qualities, and the kingdom was also influenced by pre-existing Muslim institutions. However, when Arnulf of Chocques was appointed Latin Patriarch of Jerusalem for the second time in 1112, he prohibited non-Catholic worship at the Church of the Holy Sepulchre. Socially, the "Latin" inhabitants from Western Europe had almost no contact with the Muslims and Eastern Christians whom they ruled. The Royal Palace of the Kingdom was based in the Al-Aqsa Mosque, and the Dome of the Rock was converted into a church. Under the Crusader rule, fortifications, castles, towers and fortified villages were built, rebuilt and renovated across Palestine largely in rural areas. A notable urban remnant of the Crusader architecture of this era is found in Acre's old city and on the island of Arwad. During the period of Crusader control, it has been estimated that Palestine had only 1,000 poor Jewish families. Jews fought alongside the Muslims against the Crusaders in Jerusalem in 1099 and Haifa in 1100. Some Jews from Europe visited the country, like Benjamin of Tudela who wrote about it. Maimonides visited Palestine after escaping from the Almohads in 1165 and visited Acre, Jerusalem and Hebron, finally choosing to settle in Fostat in Egypt. In July 1187, the Cairo-based Kurdish General Saladin commanded his troops to victory in the Battle of Hattin, shortly followed by the Siege of Jerusalem (1187) in which Saladin captured Jerusalem. Following the crusader defeat by Saladin's forces in 1187, most of Palestine was controlled by the Ayyubids. However a rump crusader state in the northern coastal cities known as the Kingdom of Acre survived in the region for another hundred years until 1291, throughout the Ayyubid Period and well into the Mamluk Period. However, despite seven further crusades from Europe, the Crusader state was no longer a significant power in the region after the fall of Jerusalem in 1187. The Ayyubids allowed Jewish and Orthodox Christian settlement in the region, and the Dome of the Rock was converted back into an Islamic center of worship. The Mosque of Omar was built under Saladin outside the Church of the Holy Sepulchre, commemorating Umar the Great's decision to pray outside the church so as not to set a precedent and thereby endanger the Church's status as a Christian site. About eighty years after Saladin's conquest, the Catalan Rabbi Nahmanides left Europe following the disputation of Barcelona, and spent the last three years of his life in Palestine, primarily in Acre. He established the Ramban Synagogue in the Old City of Jerusalem and thus, having found only two Jewish people living in the city at the time, re-established Jewish communal life in Jerusalem. The defeat of the Europeans provoked further crusades from Europe, varying in size and success. In 1192, after preventing the Third Crusade under Richard the Lionheart from recapturing Jerusalem, Saladin entered into the Treaty of Ramla in which he agreed that Western Christian pilgrims could worship freely in Jerusalem. The threat remained, however, and Ayyubid Emir Al-Mu'azzam destroyed Jerusalem's city walls in 1219 to prevent the Crusaders from capturing a fortified city. To end the Sixth Crusade, a 10-year treaty was signed between Frederick II, Holy Roman Emperor and Ayyubid Sultan Al-Kamil, allowing Christians freedom to live in the unfortified Jerusalem, as well as Nazareth and Bethlehem, although the Ayyubids retained control of the Muslim holy places. These areas were returned to Ayyubid control after the peace treaty expired in 1239 and An-Nasir Dawud, Ayyubid Emir of Kerak, occupied the cities. For the four following years, control of the cities was contested between An-Nasir Dawud and his cousin As-Salih Ayyub who had allied with the Crusaders, aided by the diplomatic efforts of Thibaut IV of Champagne. In order to permanently retake the city from the rival breakaway rulers who had allied with the Crusaders, As-Salih Ayyub summoned a huge mercenary army of Khwarezmians, who were available for hire following the defeat of the Khwarazm Shah dynasty by the Mongols ten years earlier. The Khwarezmians could not be controlled by As-Salih Ayyub, and destroyed Jerusalem. A few months later, the two sides met again at the decisive Battle of La Forbie, marking the end of the Crusader influence in southern and central Palestine. Two years later the Ayyubids regained control of Jerusalem after the Khwarezmians were defeated by Al-Mansur Ibrahim at Lake Homs. The Mamluk Sultanate was indirectly created in Egypt as a result of the Seventh Crusade, which had been launched in reaction to the 1244 destruction of Jerusalem. The crusade failed after Louis IX of France was defeated and captured by Ayyubid Sultan Turanshah at the Battle of Fariskur in 1250. Turanshah was killed by his Mamluk soldiers a month after the battle and his step-mother Shajar al-Durr became Sultana of Egypt with the Mamluk Aybak as Atabeg. The Ayyubids relocated to Damascus, where they continued to control Palestine for a further 10 years. In the late 13th century, Palestine and Syria became the primary front against the fast-expanding Mongol Empire. The Army of the Mongol Empire reached Palestine for the first time in 1260, beginning with the Mongol raids into Palestine under Nestorian Christian general Kitbuqa. Mongol leader Hulagu Khan sent a message to Louis IX of France that Jerusalem had been remitted to the Christians under the Franco-Mongol Alliance, however shortly thereafter he had to return to Mongolia following the death of Mongke, leaving Kitbuqa and a reduced army. Kitbuqa then engaged with the Mamluks under Baibars in the pivotal Battle of Ain Jalut in the Jezreel Valley. The Mamluks' decisive victory in Palestine is seen as one of world history's most significant battles, establishing a high-water mark for the Mongol conquests. The Mongols were, however, able to engage into some further brief Mongol raids into Palestine in 1300 under Ghazan and Mulay, reaching as far as Gaza. Jerusalem was held by the Mongols for four months (see Ninth Crusade). In 1270, Sultan Baibars expelled the remaining Crusaders from most of the country, and the last major Crusader stronghold, Acre fell in 1291, at the Siege of Acre. Thereafter, any remaining Europeans either went home or merged with the local population. The Mamluks, continuing the policy of the Ayyubids, made the strategic decision to destroy the coastal area and to bring desolation to many of its cities, from Tyre in the north to Gaza in the south. Ports were destroyed and various materials were dumped to make them inoperable. The goal was to prevent attacks from the sea, given the fear of the return of the crusaders. This had a long term affect on those areas, that remained sparsely populated for centuries. The activity in that time concentrated more inland. Palestine formed a part of the Damascus Wilayah (district) under the rule of the Mamluk Sultanate of Egypt and was divided into three smaller Sanjaks (subdivisions) with capitals in Jerusalem, Gaza, and Safed. Due in part to the many conflicts, earthquakes and the Black Death that hit the region during this era, the population is estimated to have dwindled to around 200,000. The Mamluks constructed a "postal road" from Cairo to Damascus, that included lodgings for travelers (khans) and bridges, some of which survive to this day (Jisr Jindas, near Lod). The period also saw the construction of many schools and the renovation of mosques neglected or destroyed during the Crusader period. In 1377 the major cities of Palestine and Syria revolted, following the death of Al-Ashraf Sha'ban. The revolt was quelled and a coup d'etat was staged by Barquq in Cairo in 1382, founding the Mamluk Burji dynasty. Palestine was celebrated by Arab and Muslim writers of the time as the "blessed land of the prophets and Islam's revered leaders", Muslim sanctuaries were "rediscovered" and received many pilgrims. In 1496, Mujir al-Din al-'Ulaymi wrote his history of Palestine known as The Glorious History of Jerusalem and Hebron". In 1486, hostilities broke out between the Mamluks and the Ottoman Turks in a battle for control over western Asia. The Mamluk armies were eventually defeated by the forces of the Ottoman Sultan, Selim I, and lost control of Palestine after the 1516 battle of Marj Dabiq. In 1516, when the Ottoman Turks occupied Palestine, the land became part of the Ottoman Empire, and Istanbul appointed local governors. After the Ottoman conquest, the name "Palestine" was no longer used as the official name of an administrative unit, as the Turks often called their (sub)provinces after the capital. The majority of historical Palestine became part of the Eyalet of Damascus until 1660, and later became part of the Eyalet of Sidon. Nonetheless, the old name remained in popular and semi-official use, with many examples of its usage in the 16th, 17th and 18th centuries surviving. For example, Thomas Salmon's 18th-century book, Modern history or, the present state of all nations, states that "Jerusalem is still reckoned the capital city of Palestine." In 1624, following the Battle of Anjar, Druze prince Fakhr-al-Din II was appointed the "Emir of Arabistan" by the Ottomans to govern the region from Aleppo to Jerusalem. He toured his new provinces in the same year. He was deposed and hanged a decade later by the wali of Damascus The region saw an influx of tribal immigrants from the south (Arabian Peninsula) and east (the Mesopotamian valleys) during the 17th and 18th centuries. An area around Tiberias was given to Don Joseph Nasi for a Jewish enclave. Following the expulsions from Spain, the Jewish population of Palestine rose to around 25% (includes non-Ottoman citizens, excludes Bedouin) and regained its former stronghold of Eastern Galilee. That ended in 1660 when they were massacred at Safed and Jerusalem. During the reign of Daher el-Omar, Pasha of the Galilee, Jews from Ukraine began to resettle Tiberias. Napoleon of France briefly waged war against the Ottoman Empire (allied then with Great Britain), and held territory in Palestine during the 7 March 1799—July 1799 French occupation of Jaffa, Haifa, and Caesarea. At the Siege of Acre in 1799, Napoleon requested that the Jews of Asia and Africa help the French to capture Jerusalem. This was mostly to curry favour with Haim Farkhi the Jewish finance minister and adviser to the Pasha of Syria/Palestine. He was later assassinated and his brothers formed an army with Ottoman permission to conquer the Galilee. Decline of the Ottoman Empire period On 10 May 1832, the area of Ottoman Syria, which include modern Syria, Palestine, Jordan, Lebanon, and Israel were conquered and annexed by Muhammad Ali's expansionist Egypt (nominally still Ottoman) in the 1831 Egyptian-Ottoman War. Britain sent the navy to shell Beirut and an Anglo-Ottoman expeditionary force landed, causing local uprisings against the Egyptian occupiers. A British naval squadron anchored off Alexandria. The Egyptian army retreated to Egypt. Muhammad Ali signed the Treaty of 1841. Britain returned control of the Levant to the Ottomans, and as a result was able to increase the extraterritorial rights that various European nations had enjoyed throughout previous centuries under the terms of the Capitulations of the Ottoman Empire. One American diplomat wrote that "Extraordinary privileges and immunities had become so embodied in successive treaties between the great Christian Powers and the Sublime Porte that for most intents and purposes many nationalities in the Ottoman empire formed a state within the state." In 1834, there was a peasants revolt against conscription into the Egyptian army. Local pre-Zionist Jews of the Old Yishuv, complacent with the Egyptian rule, were targeted by the general Arab Muslim and Druze discontent during the Safed Plunder. In common usage from 1840 onwards, "Palestine" was used either to describe the Consular jurisdictions of the Western Powers or for a region that extended in the north-south direction typically from Rafah (south-east of Gaza) to the Litani River (now in Lebanon). The western boundary was the sea, and the eastern boundary was the poorly defined place where the Syrian desert began. In various European sources, the eastern boundary was placed anywhere from the Jordan River to slightly east of Amman. The Negev Desert was not included. The Consuls were originally magistrates who tried cases involving their own citizens in foreign territories. While the jurisdictions in the secular states of Europe had become territorial, the Ottomans perpetuated the legal system they inherited from the Byzantine Empire. The law in many matters was personal, not territorial, and the individual citizen carried his nation's law with him wherever he went. Capitulatory law applied to foreigners in Palestine. Only Consular Courts of the State of the foreigners concerned were competent to try them. That was true, not only in cases involving personal status, but also in criminal and commercial matters. According to American Ambassador Morgenthau, Turkey had never been an independent sovereignty. The Western Powers had their own courts, marshals, colonies, schools, postal systems, religious institutions, and prisons. The Consuls also extended protections to large communities of Jewish protégés who had settled in Palestine. The Muslim, Christian, and Jewish communities of Palestine were allowed to exercise jurisdiction over their own members according to charters granted to them. For centuries the Jews and Christians had enjoyed a large degree of communal autonomy in matters of worship, jurisdiction over personal status, taxes, and in managing their schools and charitable institutions. In the 19th century those rights were formally recognized as part of the Tanzimat reforms and when the communities were placed under the protection of European public law. In the 1860s, the Ottoman military was able to restore order east of Jordan by halting tribal conflicts and Bedouin raids. This invited migration to the east, notably the Salt area, from various populations in Lebanon, Syria and Palestine to take advantage of new lands. This influx amounted to some 12,000 over the period from 1880 to just before the First World War, while the Bedouin population east of Jordan increased to 56,000. However, with the creation of the Transjordanian emirate in 1921–22, the hamlet of Amman, which had been recently resettled by Circassians, attracted most of the new immigrants from Palestine, and many of those that had previously moved to Salt. In the reorganisation of 1873, which established the administrative boundaries that remained in place until 1914, Palestine was split between three major administrative units. The northern part, above a line connecting Jaffa to north Jericho and the Jordan, was assigned to the vilayet of Beirut, subdivided into the sanjaks (districts) of Acre, Beirut and Nablus. The southern part, from Jaffa downwards, was part of the Mutasarrifate of Jerusalem, a special district under the direct authority of Istanbul. Its southern boundaries were unclear but petered out in the eastern Sinai Peninsula and northern Negev Desert. Most of the central and southern Negev was assigned to the vilayet of Hejaz, which also included the Sinai Peninsula and the western part of Arabia. The Ottomans regarded "Filistin" as an abstract term referring to the "Holy Land", and not one consistently applied to a clearly defined area. Among the educated Arab public, Filastin was a common concept, referring either to the whole of Palestine or to the Jerusalem sanjak alone or just to the area around Ramle. The publication of the daily paper Falastin (Palestine) from 1911 was one example of the increasing currency of this concept. The rise of Zionism, the national movement of the Jewish people started in Europe in the 19th century seeking to recreate a Jewish state in Palestine, and return the original homeland of the Jewish people. The end of the 19th century saw the beginning of Zionist immigration. The "First Aliyah" was the first modern widespread wave of Zionist aliyah. Jews who migrated to Palestine in this wave came mostly from Eastern Europe and from Yemen. This wave of aliyah began in 1881–82 and lasted until 1903. An estimated 25,000–35,000 First Aliyah laid the cornerstone for Jewish settlement in Israel and created several settlements such as Rishon LeZion, Rosh Pina, Zikhron Ya'akov and Gedera. The "Second Aliyah" took place between 1904 and 1914, during which approximately 40,000 Jews immigrated, mostly from Russia and Poland, and some from Yemen. The Second Aliyah immigrants were primarily idealists, inspired by the revolutionary ideals then sweeping the Russian Empire who sought to create a communal agricultural settlement system in Palestine. They thus founded the kibbutz movement. The first kibbutz, Degania, was founded in 1909. Tel Aviv was founded at that time, though its founders were not necessarily from the new immigrants. The Second Aliyah is largely credited with the revival of the Hebrew language and establishing it as the standard language for Jews in Israel. Eliezer Ben-Yehuda contributed to the creation of the first modern Hebrew dictionary. Although he was an immigrant of the First Aliyah, his work mostly bore fruit during the second. Ottoman rule over the eastern Mediterranean lasted until World War I when the Ottomans sided with the German Empire and the Central Powers. During World War I, the Ottomans were driven from much of the region by the British Empire during the dissolution of the Ottoman Empire. British Mandate period In World War I, the Ottoman Empire sided with Germany. As a result, it was embroiled in a conflict with Great Britain. Under the secret Sykes–Picot Agreement of 1916, it was envisioned that most of Palestine, when freed from Ottoman control, would become an international zone not under direct French or British colonial control. Shortly thereafter, British foreign minister Arthur Balfour issued the Balfour Declaration of 1917, which promised to establish a "Jewish national home" in Palestine but appeared to contradict the 1915–16 Hussein-McMahon Correspondence, which contained an undertaking to form an Arab state in exchange for the Great Arab Revolt. McMahon's promises could have been seen by Arab nationalists as a pledge of immediate Arab independence, an undertaking violated by the region's subsequent partition into British and French League of Nations mandates under the secret Sykes-Picot Agreement of May 1916, which became the real cornerstone of the geopolitics structuring the entire region. The Balfour Declaration, likewise, was seen by Jewish nationalists as the cornerstone of a future Jewish homeland. The British-led Egyptian Expeditionary Force, commanded by Edmund Allenby, captured Jerusalem on 9 December 1917 and occupied the whole of the Levant following the defeat of Turkish forces in Palestine at the Battle of Megiddo in September 1918 and the capitulation of Turkey on 31 October. Allenby famously dismounted from his horse when he entered Jerusalem as a mark of respect for the Holy City and was greeted by the Christian, Jewish, and Islamic leaders of the city. Following the First World War and the occupation of the region by the British, the principal Allied and associated powers drafted the mandate, which was formally approved by the League of Nations in 1922. Great Britain administered Palestine on behalf of the League of Nations between 1920 and 1948, a period referred to as the "British Mandate". The preamble of the mandate declared: "Whereas the Principal Allied Powers have also agreed that the Mandatory should be responsible for putting into effect the declaration originally made on November 2nd, 1917, by the Government of His Britannic Majesty, and adopted by the said Powers, in favor of the establishment in Palestine of a national home for the Jewish people, it being clearly understood that nothing should be done which might prejudice the civil and religious rights of existing non-Jewish communities in Palestine, or the rights and political status enjoyed by Jews in any other country." Not all were satisfied with the mandate. The purported objective of the League of Nations mandate system was to administer parts of the defunct Ottoman Empire, which had been in control of the Middle East since the 16th century, "until such time as they are able to stand alone". Some of the Arabs felt that Britain was violating the McMahon-Hussein Correspondence and the understanding of the Arab Revolt. Some wanted a unification with Syria: in February 1919, several Muslim and Christian groups from Jaffa and Jerusalem met and adopted a platform endorsing unity with Syria and opposition to Zionism (this is sometimes called the First Palestinian National Congress). A letter was sent to Damascus authorizing Faisal to represent the Arabs of Palestine at the Paris Peace Conference. In May 1919 a Syrian National Congress was held in Damascus, and a Palestinian delegation attended its sessions. The 1922 census of Palestine recorded the population of Palestine as 757,000, of which 78% were Muslims, 11% were Jews, 10% were Christians and 1% were Druze. In the early years of the Mandate, Jewish immigration to Palestine was quite substantial. In April 1920, violent Arab disturbances against the Jews in Jerusalem occurred, which came to be known as the 1920 Palestine riots. The riots followed rising tensions in Arab-Jewish relations over the implications of Zionist immigration. The British military administration's erratic response failed to contain the rioting, which continued for four days. As a result of the events, trust among the British, Jews, and Arabs eroded. One consequence was that the Jewish community increased moves towards an autonomous infrastructure and security apparatus parallel to that of the British administration. In April 1920, the Allied Supreme Council (the United States, Great Britain, France, Italy and Japan) met at Sanremo and formal decisions were taken on the allocation of mandate territories. The United Kingdom obtained a mandate for Palestine and France obtained a mandate for Syria. The boundaries of the mandates and the conditions under which they were to be held were not decided. The Zionist Organization's representative at Sanremo, Chaim Weizmann, subsequently reported to his colleagues in London: There are still important details outstanding, such as the actual terms of the mandate and the question of the boundaries in Palestine. There is the delimitation of the boundary between French Syria and Palestine, which will constitute the northern frontier and the eastern line of demarcation, adjoining Arab Syria. The latter is not likely to be fixed until the Emir Feisal attends the Peace Conference, probably in Paris. In July 1920, the French drove Faisal bin Husayn from Damascus, ending his already negligible control over the region of Transjordan, where local chiefs traditionally resisted any central authority. The sheikhs, who had earlier pledged their loyalty to the Sharif of Mecca, asked the British to undertake the region's administration. Herbert Samuel asked for the extension of the Palestine government's authority to Transjordan, but at meetings in Cairo and Jerusalem between Winston Churchill and Emir Abdullah in March 1921 it was agreed that Abdullah would administer the territory (initially for six months only) on behalf of the Palestine administration. In the summer of 1921 Transjordan was included within the Mandate, but excluded from the provisions for a Jewish National Home. On 24 July 1922, the League of Nations approved the terms of the British Mandate over Palestine and Transjordan. On 16 September the League formally approved a memorandum from Lord Balfour confirming the exemption of Transjordan from the clauses of the mandate concerning the creation of a Jewish national home and Jewish settlement. With Transjordan coming under the administration of the British Mandate, the mandate's collective territory became constituted of 23% Palestine and 77% Transjordan. The mandate for Palestine, while specifying actions in support of Jewish immigration and political status, stated, in Article 25, that in the territory to the east of the Jordan River, Britain could 'postpone or withhold' those articles of the Mandate concerning a Jewish National Home. Transjordan was a very sparsely populated region (especially in comparison with Palestine proper) due to its relatively limited resources and largely desert environment. In 1923, an agreement between the United Kingdom and France confirmed the border between the British Mandate of Palestine and the French Mandate of Syria. The British handed over the southern Golan Heights to the French in return for the northern Jordan Valley. The border was re-drawn so that both sides of the Jordan River and the whole of the Sea of Galilee, including a 10-metre-wide strip along the northeastern shore, were made a part of Palestine, with the provisions that Syria have fishing and navigation rights in the lake. The Palestine Exploration Fund published surveys and maps of Western Palestine (aka Cisjordan) starting in the mid-19th century. Even before the Mandate came into legal effect in 1923 (text), British terminology sometimes used '"Palestine" for the part west of the Jordan River and "Trans-Jordan" (or Transjordania) for the part east of the Jordan River. The first reference to the Palestinians, without qualifying them as Arabs, is to be found in a document of the Permanent Executive Committee, composed of Muslims and Christians, presenting a series of formal complaints to the British authorities on 26 July 1928. Infrastructure and development Between 1922 and 1947, the annual growth rate of the Jewish sector of the economy was 13.2%, mainly due to immigration and foreign capital, while that of the Arab was 6.5%. Per capita, these figures were 4.8% and 3.6% respectively. By 1936, the Jewish sector had eclipsed the Arab one, and Jewish individuals earned 2.6 times as much as Arabs. In terms of human capital, there was a huge difference. For instance, the literacy rates in 1932 were 86% for the Jews against 22% for the Arabs, but Arab literacy was steadily increasing. The office of "Mufti of Jerusalem", traditionally limited in authority and geographical scope, was refashioned by the British into that of "Grand Mufti of Palestine". Furthermore, a Supreme Muslim Council (SMC) was established and given various duties, such as the administration of religious endowments and the appointment of religious judges and local muftis. During the revolt (see below) the Arab Higher Committee was established as the central political organ of the Arab community of Palestine. During the Mandate period, many factories were established and roads and railroads were built throughout the country. The Jordan River was harnessed for production of electric power and the Dead Sea was tapped for minerals—potash and bromine. 1936–1939 Arab revolt in Palestine Sparked off by the death of Shaykh Izz ad-Din al-Qassam at the hands of the British police near Jenin in November 1935, in the years 1936–1939 the Arabs participated in the Great Uprising to protest against British rule and against mass Jewish immigration. The revolt manifested in a strike and armed insurrection started sporadically, becoming more organized with time. Attacks were mainly directed at British strategic installations such as the Trans Arabian Pipeline (TAP) and railways, and to a lesser extent against Jewish settlements, secluded Jewish neighbourhoods in the mixed cities, and Jews, both individually and in groups. Violence abated for about a year while the Peel Commission deliberated and eventually recommended partition of Palestine. With the Arab rejection of this proposal, the revolt resumed during the autumn of 1937. Violence continued throughout 1938 and eventually petered out in 1939. The British responded to the violence by greatly expanding their military forces and clamping down on Arab dissent. "Administrative detention" (imprisonment without charges or trial), curfews, and house demolitions were among British practices during this period. More than 120 Arabs were sentenced to death and about 40 hanged. The main Arab leaders were arrested or expelled. The Haganah (Hebrew for "defense"), an illegal Jewish paramilitary organization, actively supported British efforts to quell the insurgency, which reached 10,000 Arab fighters at their peak during the summer and fall of 1938. Although the British administration did not officially recognize the Haganah, the British security forces cooperated with it by forming the Jewish Settlement Police and Special Night Squads. A terrorist splinter group of the Haganah, called the Irgun (or Etzel) adopted a policy of violent retaliation against Arabs for attacks on Jews. At a meeting in Alexandria in July 1937 between Jabotinsky and Irgun commander Col. Robert Bitker and chief-of-staff Moshe Rosenberg, the need for indiscriminate retaliation due to the difficulty of limiting operations to only the "guilty" was explained. The Irgun launched attacks against public gathering places such as markets and cafes. The revolt did not achieve its goals, although it is "credited with signifying the birth of the Arab Palestinian identity". It is generally credited with forcing the issuance of the White Paper of 1939, which renounced Britain's intent of creating a Jewish National Home in Palestine, as proclaimed in the 1917 Balfour Declaration. Another outcome of the hostilities was the partial disengagement of the Jewish and Arab economies in Palestine, which were more or less intertwined until that time. For example, whereas the Jewish city of Tel Aviv previously relied on the nearby Arab seaport of Jaffa, hostilities dictated the construction of a separate Jewish-run seaport for Tel Aviv. World War II and Palestine When the Second World War broke out, the Jewish population sided with Britain. David Ben-Gurion, head of the Jewish Agency, defined the policy with what became a famous motto: "We will fight the war as if there were no White Paper, and we will fight the White Paper as if there were no war." While this represented the Jewish population as a whole, there were exceptions (see below). As in most of the Arab world, there was no unanimity among the Palestinian Arabs as to their position regarding the combatants in World War II. A number of leaders and public figures saw an Axis victory as the likely outcome and a way of securing Palestine back from the Zionists and the British. Mohammad Amin al-Husayni, Grand Mufti of Jerusalem, spent the rest of the war in Nazi Germany and the occupied areas. About 6,000 Palestinian Arabs and 30,000 Palestinian Jews joined the British forces. In 1942, there was a period of anxiety for the Yishuv, when the forces of German General Erwin Rommel advanced east in North Africa towards the Suez Canal and there was fear that they would conquer Palestine. This period was referred to as the two hundred days of anxiety. This event was the direct cause for the founding, with British support, of the Palmach—a highly trained regular unit belonging to Haganah (which was mostly made up of reserve troops). On 3 July 1944, the British government consented to the establishment of a Jewish Brigade with hand-picked Jewish and also non-Jewish senior officers. The brigade fought in Europe, most notably against the Germans in Italy from March 1945 until the end of the war in May 1945. Members of the Brigade played a key role in the Berihah's efforts to help Jews escape Europe for Palestine. Later, veterans of the Jewish Brigade became key participants of the new State of Israel's Israel Defense Forces. Starting in 1939 and throughout the war and the Holocaust, the British reduced the number of Jewish immigrants allowed into Palestine, following the publication of the MacDonald White Paper. Once the 15,000 annual quota was exceeded, Jews fleeing Nazi persecution were placed in detention camps or deported to places such as Mauritius. In 1944 Menachem Begin assumed the Irgun's leadership, determined to force the British government to remove its troops entirely from Palestine. Citing that the British had reneged on their original promise of the Balfour Declaration, and that the White Paper of 1939 restricting Jewish immigration was an escalation of their pro-Arab policy, he decided to break with the Haganah. Soon after he assumed command, a formal 'Declaration of Revolt' was publicized, and armed attacks against British forces were initiated. Lehi, another splinter group, opposed cessation of operations against the British authorities all along. The Jewish Agency, which opposed those actions and the challenge to its role as government in preparation responded with "The Hunting Season"—severe actions against supporters of the Irgun and Lehi, including turning them over to the British. The country developed economically during the war, with increased industrial and agricultural outputs and the period was considered an `economic Boom'. In terms of Arab-Jewish relations, these were relatively quiet times. End of the British Mandate 1945–1948 In the years following World War II, Britain's control over Palestine became increasingly tenuous. This was caused by a combination of factors, including: - World public opinion turned against Britain as a result of the British policy of preventing Holocaust survivors from reaching Palestine, sending them instead to Cyprus internment camps, or even back to Germany, as in the case of Exodus 1947. - The costs of maintaining an army of over 100,000 men in Palestine weighed heavily on a British economy suffering from post-war depression, and was another cause for British public opinion to demand an end to the Mandate. - Rapid deterioration due to the actions of the Jewish paramilitary organizations (Hagana, Irgun and Lehi), involving attacks on strategic installations (by all three) as well as on British forces and officials (by the Irgun and Lehi). This caused severe damage to British morale and prestige, as well as increasing opposition to the mandate in Britain itself, public opinion demanding to "bring the boys home". - The U.S. Congress was delaying a loan necessary to prevent British bankruptcy. The delays were in response to the British refusal to fulfill a promise given to Truman that 100,000 Holocaust survivors would be allowed to emigrate to Palestine. In early 1947 the British Government announced their desire to terminate the Mandate, and asked the United Nations General Assembly to make recommendations regarding the future of the country. The British Administration declined to accept the responsibility for implementing any solution that wasn't acceptable to both the Jewish and the Arab communities, or to allow other authorities to take over responsibility for public security prior to the termination of its mandate on 15 May 1948. UN partition and the 1948 Palestine War On 29 November 1947, the United Nations General Assembly, voting 33 to 13 in favour with 10 abstentions, adopted a resolution, Resolution 181 (II), recommending to the United Kingdom, as the mandatory Power for Palestine, and to all other Members of the United Nations the adoption and implementation, with regard to the future government of Palestine, of the Plan of Partition with Economic Union. The plan was to partition Palestine into Independent Arab and Jewish States and the Special International Regime for the City of Jerusalem. Jerusalem was to encompass Bethlehem. Zionist leaders (including the Jewish Agency), accepted the plan, while Palestinian Arab leaders rejected it and all independent Muslim and Arab states voted against it. Almost immediately, sectarian violence erupted and spread, killing hundreds of Arabs, Jews and British over the ensuing months. The rapid evolution of events precipitated into a Civil War. For four months, under continuous Arab provocation and attack, the Yishuv was usually on the defensive while occasionally retaliating. Arab volunteers of the Arab Liberation Army entered Palestine to fight with the Palestinians, but the April–May offensive of Yishuv forces defeated the Arab forces and Arab Palestinian society collapsed. Some 700,000 Palestinians caught up in the turmoil fled or were driven from their homes. On 14 May 1948, David Ben-Gurion and the Jewish People's Council declared the establishment of a Jewish state in Eretz Israel, to be known as the State of Israel. The neighbouring Arab states intervened to prevent the partition and support the Palestinian Arab population. While Transjordan took control of territory designated for the future Arab State, Syrian, Iraqi and Egyptian expeditionary forces attacked Israel without success. The most intensive battles were waged between the Jordanian and Israeli forces over the control of Jerusalem. On June 11, a truce was accepted by all parties. Israel used the lull to undertake a large-scale reinforcement of its army. In a series of military operations, it then conquered the whole of the Galilee region, both the Lydda and Ramle areas, and the Negev. It also managed to secure, in the Battles of Latrun, a road linking Jerusalem to Israel. In this phase, 350,000 more Arab Palestinians fled or were expelled from the conquered areas. Partition of former Mandatory territory Following the 1948 Arab-Israeli War, the area allocated to the Palestinian Arabs and the international zone of Jerusalem were occupied by Israel and the neighboring Arab states in accordance with the terms of the 1949 Armistice Agreements. In addition to the UN-partitioned area allotted to the Jewish state, Israel captured and incorporated a further 26% of the British Mandate territory. Jordan retained possession of about 21% of the former Mandate territory. Jerusalem was divided, with Jordan taking the eastern parts, including the Old City, and Israel taking the western parts. In addition, Syria held on to small slivers of the former Mandate territory to the south and east of the Sea of Galilee, which had been allocated in the UN partition plan to the Jewish state. For a description of the massive population movements, Arab and Jewish, at the time of the 1948 war and over the following decades, see Palestinian exodus and Jewish exodus from Arab lands. Palestinian governorship in Egyptian-controlled Gaza On the same day that the State of Israel was announced, the Arab League announced that it would set up a single Arab civil administration throughout Palestine, and launched an attack on the new Israeli state. The All-Palestine Government was established by the Arab League on 22 September 1948, during the 1948 Arab-Israeli War. It was soon recognized by all Arab League members, except Jordan. Though jurisdiction of the Government was declared to cover the whole of the former Mandatory Palestine, its effective jurisdiction was limited to the Gaza Strip. The Prime Minister of the Gaza-seated administration was named Ahmed Hilmi Pasha, and the President was named Hajj Amin al-Husseini, former chairman of the Arab Higher Committee. The All-Palestine Government is regarded by some as the first attempt to establish an independent Palestinian state. It was under official Egyptian protection, but on the other hand it had no executive role, but rather mostly political and symbolic. Its importance gradually declined, especially due to relocation of seat of government from Gaza to Cairo following the Israeli invasion in late 1948. Though Gaza Strip returned under Egyptian control later on through the war, the All-Palestine Government remained in-exile in Cairo, managing Gazan affairs from outside. In 1959, the All-Palestine Government was officially merged into the United Arab Republic, coming under formal Egyptian military administration, with the appointment of Egyptian military administrators in Gaza. Egypt, however, both formally and informally denounced any and all territorial claims to Palestinian territory, in contrast to the government of Transjordan, which declared its annexation of the Palestinian West Bank. The All-Palestine Government's credentials as a bona fide sovereign state were questioned by many, particularly due to the effective reliance upon not only Egyptian military support, but Egyptian political and economic power. Annexation of the West Bank of Jordan Shortly after the proclamation of All-Palestine Government in Gaza, the Jericho Conference named King Abdullah I of Transjordan, "King of Arab Palestine". The Congress called for the union of Arab Palestine and Transjordan and Abdullah announced his intention to annex the West Bank. The other Arab League member states opposed Abdullah's plan. The New Historians, like Avi Shlaim, hold that there was an unwritten secret agreement between King Abdullah of Transjordan and Israeli authorities to partition the territory between themselves, and that this translated into each side limiting their objectives and exercising mutual restraint during the 1948 war. The presence of a large number of immigrants and refugees from the now dissolved Mandate of Palestine fueled the regional ambitions of King Abdullah I, who sought control over what had been the British Jerusalem and Samaria districts on the west bank of Jordan River. Towards this goal the king granted Jordanian citizenship to all Arab holders of the Palestinian Mandate identity documents in February 1949, and outlawed the terms "Palestinian" and "Transjordanian" from official usage, changing the country's name from the Emirate of Trans-Jordan to the Hashemite Kingdom of Jordan. The area east of the river became known as "al-Ḍiffah al-Sharqiyyal", or "The East Bank". In April 1950, with the formal annexation of the positions held by the Jordanian Army since 1948, the area became known as "al-Ḍiffah al-Gharbiyyal" or "The Western Bank". With the formal union of the East and West Banks in 1950, the number of Palestinians in the kingdom rose by another 720,000, of whom 440,000 were West Bank residents and 280,000 were refugees from other areas of the former Mandate then living on the West Bank. Palestinians became the majority in Jordan although most believed their return to what was now the state of Israel was imminent. Israeli controlled areas \|\|The examples and perspective in this article or section might have an extensive bias or disproportional coverage towards the West Bank and Gaza Strip. (October 2012)\| Israel did not retain the administrative structure of the Mandate, redrawing the district borders to roughly parallel the areas of responsibility of its military formations, then infantry brigades. Six Day War and Yom Kippur War In the course of the Six Day War in June 1967, Israel captured the rest of the area that had been part of the British Mandate of Palestine, taking the West Bank (including East Jerusalem) from Jordan and the Gaza Strip from Egypt. Following military threats by Egypt and Syria, including Egyptian president Nasser's demand of the UN to remove its peace-keeping troops from the Egyptian-Israeli border, in June 1967 Israeli forces went to action against Egypt, Syria and Jordan. As a result of that war, the Israel Defense Forces conquered the West Bank, the Gaza Strip, the Golan Heights, and the Sinai Peninsula bringing them under military rule. Israel also pushed Arab forces back from East Jerusalem, which Jews had not been permitted to visit during the prior Jordanian rule. East Jerusalem was allegedly annexed by Israel as part of its capital, though this action has not been recognized internationally. Israel also started building settlements on the occupied land. The United Nation's Security Council passed Resolution 242, promoting the "land for peace" formula, which called for Israeli withdrawal from territories occupied in 1967, in return for the end of all states of belligerency by the aforementioned Arab League nations. Palestinians continued longstanding demands for the destruction of Israel or made a new demand for self-determination in a separate independent Arab state in the West Bank and Gaza Strip similar to but smaller than the original Partition area that Palestinians and the Arab League had rejected for statehood in 1947. In the course of 1973 Yom Kippur War, military forces of Egypt crossed the Suez canal and Syria to regain the Golan heights. The attacking military forces of Syria were pushed back. After a cease fire, Egyptian President Sadat Anwar Sadat started peace talks with the U.S. and Israel. Israel returned the Sinai Peninsula to Egypt as part of the 1978 Camp David Peace Accords between Egypt and Israel in hopes of establishing a genuine peace. First Intifada, Oslo Accords and Palestinian Authority From 1987 to 1993, the First Palestinian Intifada against Israel took place. Attempts at the peace process in the Israeli-Palestinian conflict were made at the Madrid Conference of 1991. As the process progressed, in 1993 the Israelis allowed Chairman and President of the Palestine Liberation Organization Yassir Arafat to return to the region. Following the historic 1993 Oslo Peace Accords between Palestinians and Israel (the "Oslo Accords"), which gave the Palestinian Arabs limited self-rule in some parts of the occupied territories through the Palestinian Authority, and other detailed negotiations, proposals for a Palestinian state gained momentum. They were soon followed in 1993 by the Israel-Jordan Treaty of Peace. To date, efforts to resolve the conflict have ended in deadlock, and the people of the region, Jews and Arabs, are engaged in a bloody conflict, called variously the "Arab-Israeli conflict" or "Israeli-Palestinian conflict". Second Intifada and later After few years of on-and-off negotiations, the Palestinians began an uprising against Israel. This was known as the Al-Aqsa Intifada. The events were highlighted in world media by Palestinian suicide bombings in Israel that killed many civilians, and by Israeli Security Forces full fledged invasions into civilian areas along with some targeted killings of Palestinian militant leaders and organizers. Israel began building a complex security barrier to block suicide bombers invading into Israel from the West Bank in 2002. Also in 2002, the Road map for peace calling for the resolution of the Israeli-Palestinian conflict was proposed by a "quartet": the United States, European Union, Russia, and United Nations. U.S. President George W. Bush in a speech on June 24, 2002 called for an independent Palestinian state living side by side with Israel in peace. Bush was the first U.S. President to explicitly call for such a Palestinian state. Following Israel's unilateral disengagement plan of 2004, it withdrew all settlers and most of the military presence from the Gaza strip, but maintained control of the air space and coast. Israel also dismantled four settlements in northern West Bank in September 2005. Following Israel's withdrawal, Palestinian militia groups fired Qassam rockets into Israel and smuggled weapons and ammunition into Gaza from Egypt. After the kidnap of Israeli soldiers in June 2006, Israel launched a military operation and reentered some parts of the Gaza Strip. Amidst severe criticism, they built the Israeli West Bank barrier. Following the January 2006 election of the Hamas government, Fatah resistance took the form of street battles that resulted in a victory for Hamas. Hamas took over the ministries of the (Fatah) Palestinian Authority and Gaza became a Hamas enclave outside PA control. As of July 2009, approximately 305,000 Israelis lived in 121 settlements in the West Bank. The 2.4 million West Bank Palestinians (according to Palestinian evaluations) live primarily in four blocs centered in Hebron, Ramallah, Nablus, and Jericho. Non-member status of State of Palestine On 23 September 2011, President Mahmoud Abbas on behalf of the Palestine Liberation Organisation submitted an application for membership of Palestine in the United Nations. The campaign, dubbed "Palestine 194", was formally backed by the Arab League in May, and was officially confirmed by the PLO on 26 June. The decision was labelled by the Israeli government as a unilateral step, while the Palestinian government countered that it is essential to overcoming the current impasse. Several other countries, such as Germany and Canada, have also denounced the decision and called for a prompt return to negotiations. Many others, however, such as Norway and Russia, have endorsed the plan, as has Secretary-General Ban Ki-moon, who stated, "UN members are entitled whether to vote for or against the Palestinian statehood recognition at the UN." In July 2012, it was reported that Hamas Government in Gaza was considering to declare the independence of the Gaza Strip with the help of Egypt. In August 2012, Foreign Minister of the PNA Riyad al-Malki told reporters in Ramallah that PNA would renew effort to upgrade the Palestinian (PLO) status to "full member state" at the U.N. General Assembly on September 27, 2012. By September 2012, with their application for full membership stalled due to the inability of Security Council members to "make a unanimous recommendation", Palestine had decided to pursue an upgrade in status from "observer entity" to "non-member observer state". On November 27, it was announced that the appeal had been officially made, and would be put to a vote in the General Assembly on November 29, where their status upgrade was expected to be supported by a majority of states. In addition to granting Palestine "non-member observer state status", the draft resolution "expresses the hope that the Security Council will consider favourably the application submitted on 23 September 2011 by the State of Palestine for admission to full membership in the United Nations, endorses the two state solution based on the pre-1967 borders, and stresses the need for an immediate resumption of negotiations between the two parties". On November 29, 2012, in a 138–9 vote (with 41 abstaining), General Assembly resolution 67/19 passed, upgrading Palestine to "non-member observer state" status in the United Nations. The new status equates Palestine's with that of the Holy See.The change in status was described by The Independent as "de facto recognition of the sovereign state of Palestine". The vote was a historic benchmark for the sovereign State of Palestine. Status as an observer state in the UN will allow the State of Palestine to join treaties and specialised UN agencies, such as the International Civil Aviation Organisation, the Law of the Seas Treaty and the International Criminal Court. It shall permit Palestine to claim legal rights over its territorial waters and air space as a sovereign state recognised by the UN. It shall also provide the citizens of Palestine with the right to sue for control of the territory that is rightfully theirs in the International Court of Justice and with the legal right to bring war-crimes charges, mainly those relating to Israel's illegal occupation of the State of Palestine, against Israel in the International Criminal Court. The UN has permitted Palestine to title its representative office to the UN as "The Permanent Observer Mission of the State of Palestine to the United Nations", and Palestine has started to re-title its name accordingly on postal stamps, official documents and passports, whilst it has instructed its diplomats to officially represent "The State of Palestine", as opposed to the 'Palestine National Authority'. Additionally, on 17 December 2012, UN Chief of Protocol Yeocheol Yoon decided that "the designation of 'State of Palestine' shall be used by the Secretariat in all official United Nations documents", thus recognising the PLO-proclaimed State of Palestine as being sovereign over the territories Palestine and its citizens under international law. As of February 2013, 131 (67.9%) of the 193 member states of the United Nations have recognised the State of Palestine. Many of the countries that do not recognise the State of Palestine nevertheless recognise the PLO as the 'representative of the Palestinian people'. Graphical Overview of Palestine's Historical Sovereign Powers - History of ancient Israel and Judah - History of Israel - History of Levant - History of pottery in the Southern Levant - van Seters, John (1997), "Abraham in History and Tradition", (Yale University Press) - Finkelstein and Silberman, Free Press, New York, 2001, 385 pp., ISBN 0-684-86912-8, p 107 - Cambridge History of Judaism, The early Roman period, Volume 2 - Parfitt , Tudor (1987) The Jews in Palestine, 1800–1882. Royal Historical Society studies in history (52). Woodbridge: Published for the Royal Historical Society by Boydell. - Galilee, Sea of. (2007). In Encyclopædia Britannica. Retrieved August 12, 2007, from Encyclopædia Britannica Online - "Human Evolution and Neanderthal Man" (PDF). Antiquity Journal. - Amud. (2007). In Encyclopædia Britannica. 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Geneva, Illinois: Runestone Press, p. 60. ISBN 978-0-8225-3218-7 - Mazar, Benjamin. 1975. The Mountain of the Lord. Garden City, New York: Doubleday & Company, Inc., p. 45. ISBN 0-385-04843-2 - Remains Of Minoan-Style Painting Discovered During Excavations Of Canaanite Palace, ScienceDaily (December 7, 2009) - William H. Propp "Amarna Letters" The Oxford Companion to the Bible. Bruce M. Metzger and Michael D. Coogan, eds. Oxford University Press Inc. 1993. Oxford Reference Online. Oxford University Press. - Ilan Ben Zion, ' Egyptian coffin, gold seal with king’s name found in Israel,' The Times of Israel, 9 April 2014. - Niels Peter Lemche. "On the Problems of Reconstructing Pre-Hellenistic Israelite (Palestinian) History". Journal of Hebrew Scriptures. Retrieved 2007-05-10. - Shahin (2005), p. 6 - Carl S. Ehrlich "Philistines" The Oxford Guide to People and Places of the Bible. Ed. Bruce M. Metzger and Michael D. Coogan. Oxford University Press, 2001. Oxford Reference Online. Oxford University Press. - Philistine. (2007). In Encyclopædia Britannica. Retrieved August 12, 2007, from Encyclopædia Britannica Online - Peter Myers. "The Exodus & the Expulsion of the Hyksos - Archaeology of the Bible" (2010) - Avraham Faust (2009) "How Did Israel Become a People? The Genesis of Israelite Identity. Biblical Archaeology Review 201: pp. 62-69, 92-94 - Finkelstein and Silberman (2001), p. 107 - Holy Bible. King James version. Ezra, Chapter 9 - "Facts about Israel:History". Israeli Ministry of Foreign Affaits. Retrieved 2007-05-10. - Bienkowski, op.cit. - ""House of David" Restored in Moabite Inscription: A new restoration of a famous inscription reveals another mention of the "House of David" in the ninth century BCE". Jewishhistory.com. Retrieved 2010-08-24. - Gyémánt, Ladislau (2003). Historiographic Views on the Settlement of the Jewish Tribes in Canaan. 1/2003. 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Oxford University Press, 1997. Oxford Reference Online. Oxford University Press. - Dandamaev, M (1994): "", in E. Yarshater (ed.) Encyclopaedia Iranica vol. 7. - Drumbrell, WJ (1971): "The Tell el-Maskuta Bowls and the 'Kingdom' of Qedar in the Persian Period", BASOR 203, pp. 33–44. - Tuell (1991): "The Southern and Eastern Borders of Abar-Nahara", BASOR n. 234, pp. 51–57 - Jona Lendering. "Satrapies". Livius.org. Retrieved 2011-08-16. - Diana Edelman (November 2005). "Redating the Building of the Second Temple". - Palestine. (2007). In Encyclopædia Britannica. Retrieved August 12, 2007, from Encyclopædia Britannica Online. - "Avdat: A Nabatean City in the Negev". Jewish Virtual Library. Retrieved 2007-08-11. - Shahin (2005), p. 7 - "Hellenistic Greece:Alexander the Great". Washington State University. 1996. Retrieved 2007-08-11. - Free and Vos, 1992, p. 225. - "Palestine". Britannica. Retrieved 2007-08-14. - Julie Galambush (2006). "The Reluctant Parting: How the New Testament's Jewish Writers Created a Christian Book". HarperCollins.ca. Retrieved 2007-08-20. - Dick Doughty (September–October 1994). "Gaza:Contested Crossroads". SaudiAramcoWorld. Retrieved 2007-08-20. - "Tell Balatah (Shechem or Ancient Nablus)". World Monuments Watch:100 Most Endangered Sites 2006. Archived from the original on 2007-09-27. Retrieved 2007-08-20. - Lectures on ancient history, Barthold Georg Niebuhr, Marcus Carsten Nicolaus von Niebuhr. Books.google.com. Retrieved 2011-08-16. - "Josephus, chapter 10". Christianbookshelf.org. Retrieved 2011-08-16. - Encyclopaedic dictionary of the Bible, Volume 5, William George Smith. Books.google.com. Retrieved 2011-08-16. - Sievers, 142 - "Cambridge History of Judaism" 3. Cambridge.org. p. 210. Retrieved 2011-08-16. "In both the Idumaean and the Ituraean alliances, and in the annexation of Samaria, the Judaeans had taken the leading role. They retained it. The whole political–military–religious league that now united the hill country of Palestine from Dan to Beersheba, whatever it called itself, was directed by, and soon came to be called by others, ‘the Ioudaioi’" - A History of the Jewish People, edited by Haim Hillel Ben-Sasson, page 226, "The name Judea no longer referred only to...." - Between Rome and Jerusalem: 300 years of Roman-Judaean relations By Martin Sicker. Books.google.co.uk. Retrieved 2011-08-16. - "Armenians of Jerusalem Launch Project To Preserve History and Culture". Pr-inside.com. Retrieved 2011-08-16. - The problem of the Greek sources of Movsēs Xorenacʻi's History of Armenia. Books.google.co.uk. Retrieved 2011-08-16. - A history of the Jews in Babylonia, Volume 2 By Jacob Neusner p. 351. Books.google.co.uk. Retrieved 2011-08-16. - "And when he had ordained five councils (συνέδρια), he distributed the nation into the same number of parts. So these councils governed the people; the first was at Jerusalem, the second at Gadara, the third at Amathus, the fourth at Jericho, and the fifth at Sepphoris in Galilee." Josephus, Ant. xiv 54: - "Josephus uses συνέδριον for the first time in connection with the decree of the Roman governor of Syria, Gabinius (57 BCE), who abolished the constitution and the then existing form of government of Palestine and divided the country into five provinces, at the head of each of which a sanhedrin was placed ("Ant." xiv 5, § 4)." via Jewish Encyclopedia: Sanhedrin: - "Herod". Concise Encyclopædia Britannica. Retrieved 2007-08-11. - "Introducing Young People to the Protection of Heritage Sites and Historic Cities" (PDF). UNESCO. 2003. Retrieved 2007-08-14. - "Herodium (Jebel Fureidis) Jordan/Israel". The Princeton Encyclopedia of Classical Sites. Retrieved 2007-08-11. - "Judaea-Palestine". UNRV History: Roman Empire. 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The centre of government was thus removed from Jerusalem, and the administration became increasingly based on inhabitants of the hellenistic cities (Sebaste, Caesarea and others)." - Köstenberger, Kellum & Quarles 2009, p. 114. - Maier 1989, p. 124. - Green, McKnight & Marshall 1992, p. 442. - Borg, Marcus J. (2006). "The Spirit-Filled Experience of Jesus". In Dunn, James D. G.; McKnight, Scot. The Historical Jesus in Recent Research. Eisenbrauns. p. 303. ISBN 978-1-57506-100-9. - Crossan & Watts 1999, pp. 28–29. - Vermes, Géza (2010). The Nativity: History and Legend. Random House Digital. pp. 81–82. ISBN 978-0-307-49918-9. - Dunn 2003, p. 324. - Meier 1991, p. 407. - Finegan, Jack (1998). Handbook of Biblical Chronology, rev. ed. Hendrickson Publishers. p. 319. ISBN 978-1-56563-143-4. - [[#CITEREFFor example, John P. Meier states that Jesus' birth year is c. 7/6 BC, while Finegan favors c. 3/2 BC.\|For example, John P. Meier states that Jesus' birth year is c. 7/6 BC, while Finegan favors c. 3/2 BC.]]. - Levine 2006, p. 4. - Humphreys, Colin J.; Waddington, W.G. (1992). "The Jewish Calendar, a Lunar Eclipse and the Date of Christ's Crucifixion". Tyndale Bulletin 43 (2): 340. - Köstenberger, Kellum & Quarles 2009, p. 398. - Mark A. Chancey (2005) Greco-Roman Culture and the Galilee of Jesus Cambridge University Press, ISBN 0-521-84647-1 p 62 - H.H. Ben-Sasson, A History of the Jewish People, Harvard University Press, 1976, ISBN 0-674-39731-2, page 334: "In an effort to wipe out all memory of the bond between the Jews and the land, Hadrian changed the name of the province from Iudaea to Syria-Palestina, a name that became common in non-Jewish literature." - Ariel Lewin. The archaeology of Ancient Judea and Palestine. Getty Publications, 2005 p. 33. 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Routledge, 2004. ISBN 0-7146-5654-2 - Jankowski, James P. (1997). Rethinking Nationalism in the Arab Middle East. Columbia University Press. p. 174. ISBN 0231106955. - Bernard Lewis, "Palestine: On the History and Geography of a Name", International History Review 11 (1980): 1–12 - Porath, 1974, pp. 8–9. - Haim Gerber (1998) referring to fatwas by two Hanafite Syrian jurists. - Strawson, John (2010), pp. 25. - Scharfstein, Sol, Chronicle of Jewish History: From the Patriarchs to the 21st Century, p. 231, Ktav Publishing House (1997), ISBN 0-88125-545-9 - "New Aliyah - Modern Zionist Aliyot (1882–1948)". Jewish Agency for Israel. Retrieved 2008-10-26. - "The First Aliyah". Jewishvirtuallibrary.org. Retrieved 2009-06-16. - Mandel, Neville, The Arabs and Zionism before World War I, Berkeley: University of California Press, 1976. 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Gelvin, The Israel-Palestine conflict, Cambridge University Press, 2007, p. 120. - A Survey of Palestine, Table 2 showing Holdings of Large Jewish Lands Owners as of December 31st, 1945, British Mandate: A Survey of Palestine: Volume I - Page 245. Chapter VIII: Land: Section 3. - The Rise and fall of the British Empire, By Lawrence James, Macmillan, 1997, ISBN 0-312-16985-X, p. 562 - see Request for a Special Session of the General Assembly on Palestine - see Rabbi Silver's request regarding the formation of a Jewish militia and the dissolution of the mandate in S/PV.262, Minutes 262nd Meeting of the UN Security Council,5 March 1948 - UNITED NATIONS General Assembly: A/RES/181(II): 29 November 1947: Resolution 181 (II): Future government of Palestine: Retrieved 26 April 2012 - Plascov, Avi (2008). The Palestinian refugees in Jordan 1948-1957. Routledge. p. 2. ISBN 978-0-7146-3120-2. Retrieved 2009-12-11. - Bovis, H. Eugene (1971). The Jerusalem question, 1917–1968. Hoover Institution Press,U.S. p. 40. ISBN 978-0-8179-3291-6. Retrieved 2009-12-11. - 6 Arab states, Egypt, Iraq, Lebanon, Saudi Arabia, Syria, Yemen: 4 Moslem states, Afghanistan, Iran, Pakistan, Turkey: Greece, Cuba and India also voted against. See Henry Cattan, The Palestine question, Routledge, London 1988 p. 36 - Benny Morris, 1948. A History of the First Arab-Israeli War, Yale University Press, 2008, p.79. - Israel Ministry of Foreign Affairs: Declaration of Establishment of State of Israel: 14 May 1948: Retrieved 26 April 2012 - Truman, the Jewish Vote, and the Creation of Israel, John Snetsinger, Hoover Press, 1974, ISBN 0-8179-3391-3, p. 107. Books.google.com. 1974. ISBN 978-0-8179-3391-3. Retrieved 2010-08-24. - see The Middle East Journal, Middle East Institute (Washington, D.C.), 1949, p. 78, October 1): Robert A. Lovett, Acting Secretary of State, announced the U.S. would not recognize the new Arab Government in Palestine, and Foreign relations of the United States, 1948. The Near East, South Asia, and Africa, Volume V, Part 2, p. 1448 - Gelber, Y. Palestine, 1948. Pp. 177-78 - See Jericho Declaration, Palestine Post, December 14, 1948, Front page - Avi Shlaim in Pappe's The Israel/Palestine question, p. 187. - Carroll, K. B., Business As Usual?: Economic Reform in Jordan, Lexington Books, 2003, p.108 - Lutfiyya, A. M., Baytin: A Jordanian Village. A Study of Social Institutions and Social Change in a Folk Community, Walter de Gruyter, 1966, pp.13-14 - Carroll, p.108 - Ian Lustick, Has Israel Annexed East Jerusalem? - Ian J. Bickerton 2009, The Arab-Israeli-Conflict: A History. Reaktion Books Ltd, ISBN 9781861895271, p. 106. - Israel and the Palestinians: Key terms, BBC - Baroud, Ramzy (July 2007). "Gaza: chaos foretold". Le Monde Diplomatique. Retrieved 2009-07-26. - "No-goodniks and the Palestinian shootout". Asia Times. 2007-01-09. Retrieved 2009-07-26. - "IDF: More than 300,000 settlers live in West Bank". haaretz.com. 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This article relies too much on references to primary sources. (May 2017) (Learn how and when to remove this template message) In computer engineering and in programming language implementations, a belt machine is a real or emulated computer that uses a first in, first out (FIFO) queue rather than individual machine processor registers to evaluate each sub-expression in the program. A belt computer is programmed with an instruction set that specifies arguments explicitly but results implicitly. The common alternative to belt machines are register machines, in which each instruction explicitly names the specific registers to use for locations of operand arguments and results. Belt machines are related to stack machines, which specify both arguments and results implicitly using a pushdown stack. Other alternatives are accumulator machines, which have only one visible general-purpose temp register, and memory-to-memory machines, which have no visible temp registers. A belt machine implements temporary storage with a fixed-length FIFO queue, or belt by analogy to a conveyor belt. The operands of the arithmetic logic units (ALUs) and other functional units may be taken from any position on the belt, and the result from the computation is dropped (stored) in the front position of the belt, advancing the belt to make room. As the belt is fixed length, drops in the front are matched by older operands falling off the back; pushed-off operands become inaccessible and must be explicitly saved if still needed for later work. Most operations of the instruction set work only with data on the belt, not on data registers or main memory cells. For a typical instruction like add, both argument operands come from explicitly named positions on the belt, and the result is dropped on the front, ready for the next instruction. Operations with multiple results simply drop more values at the belt front. Most belt instructions are encoded as just an operation code (opcode) and two belt positions, with no added fields to specify a result register, memory address, or literal constant. This encoding is easily extended to richer operations with more than two inputs or more than one result. Constant operands are dropped by separate load immediate instructions. All access of program variables in main random-access memory (RAM) is segregated into separate store instructions containing one memory address, or some way to calculate that address from belt operands. All belt machines have variants of the load/store opcodes to access local variables and the heap. This can be by offsets, from a pointer on the belt, or from various special-purpose base registers. Similarly, there will be instructions to branch to an address taken from the belt, along with branches relative to the program counter. Because each drop of a result moves the prior belt content along to later positions in the queue, a given operand continually changes its position (and hence address) as a result of later execution. In effect, an access to the operand at position zero is a request for the most recent value dropped to the belt, while (for example) a reference to position five is to the sixth most recent drop. Thus the addresses of belt operands reflect the belt history over time. This is temporal addressing. It is hard for human programmers to keep track of belt contents, and hence operand addresses, when writing assembly code for a belt machine. However, it is easy for a compiler to track the changing contents and emit the correct position addresses in generated code. The belt is fixed length and may be too short to hold all live transient operands before they are pushed off the end. If an operand is needed for longer than its belt lifetime, it must be saved while still on the belt (spill) and later restored to the belt when needed again (fill). This situation is equivalent to the need to spill registers to memory when a program runs out of registers in a general-register machine. Spilled operands may be written to memory using normal store instructions, and restored using normal load instructions, or spill and fill may use special-purpose storage and associated operations that are faster or offer other advantages over load and store. The operands on the belt are read-only. New results do not overwrite prior values. The belt is thus a single-assignment structure, and is immune to the data hazards that must be dealt with by modern out-of-order general-register machines. Dense machine code was very valuable in the 1960s, when main memory was very costly and limited, even on mainframe computers. It became important again on the initially-tiny memories of minicomputers, and then microprocessors. Density remains important today, for applications for smartphone, or downloaded into browsers over slow Internet connections, and in read-only memory (ROM) for embedded applications. A more general advantage of increased density is improved effectiveness of caches and instruction prefetch. Belt machines have smaller instructions than register-based machines, due to not needing a destination address for results. This saving can make a significant difference for fixed-length instruction formats, which normally use power-of-two instruction widths. If there are thirty-two addressable elements (registers on a general-register machine, belt positions on a belt machine), then each element address occupies five bits in the instruction, needing 15 bits for the three-address format of a general-register machine, but only 10 bits using the two-address format of a belt machine. Because bits are also needed for opcode and other information in the instruction, the (power-of-two constrained) instruction width often determines the maximum number of addressable elements possible in a design. Typically a belt machine instruction can support the encoding of double the number of addressable elements compared to a general-register machine of the same instruction width. There are similar gains in variable-length instruction encodings. Overall, belt machine code is less compact than for stack machines, which use no operand addresses, but often must introduce stack-manipulation instructions unneeded on a belt machine. The instructions for accumulator machines are not padded out with multiple register fields, instead, they use the return stack and need no extra memory reference instructions. While a belt machine presents an operand queue as the program model, there is not necessarily a physical queue (shift register) in the implemented hardware. Instead, a belt design may use an implementation analogous to the register renaming common in modern general-register machines. Live data values are kept in conveniently addressable physical resources (individual registers, register files, static random-access memory (SRAM), or operand forwarding from functional units) and generally not moved for the duration of their belt lifetime. Instruction decoder maps logical belt positions to physical locations. The mapping is updated to reflect the changes of logical position arising from newly dropped results.
Data structures are the foundation for any program. They help you store, access and manage data efficiently by reducing complexity and optimizing performance. Data structures in Python refer to a specific arrangement of data that is stored and accessed efficiently, as compared to how it would be if we used standard variables or objects instead. If you’re new to programming and Python, you have probably heard of data structures but don’t know what they mean. This article will help you understand exactly what they are and why they are important in programming. You will also learn about the various data structures available in Python and examples of when to use them. What Are Data Structures? A data structure is a way you organize and store data in a computer system. The data structure determines how easy or difficult it is to find and retrieve data, how efficiently it can be searched, and how much space will be used to store the data. The data structure you choose will depend on your application's needs, the amount of data you need to store and the performance requirements of your application. There are many types of data structures, each with its own advantages and disadvantages. A data structure can be as simple as a list of items, or as complex as building an index with many fields. The data structures that are used in programming depend on the programming language you use. An array is a data structure that holds a fixed number of values of the same type. They are referred to as “fixed-size” because you decide how many items you want to store in the array when you create it. Arrays are very useful in programming because you can retrieve items from them very quickly using their index number. They are also useful for processing large amounts of data because the computer can read and write to the data in the array very fast. Arrays are normally used to store values that take up a lot of memory or data that changes frequently. They might not be the best option if you have a small amount of data or if you need to find data quickly since arrays have lower average access times compared to other data structures. A list is a collection of data items where each item is accessible by an index number. Lists are data structures that are similar to arrays, with the major difference being that you can add or remove items from a list at any time. You can also change the order of items in a list, add new items, or delete items from a list. This flexibility makes lists more useful for programming than arrays where items are fixed and cannot be edited. Lists are essentially dynamic arrays that can be changed at any time. A dictionary or hash table is a data structure that allows you to store and retrieve data quickly and efficiently. You do this by linking a specific data item to a key, which can be any item you want, such as a number or a word. The key is used as an identifier to retrieve the data item linked to it. Dictionaries can be accessed much faster than if you were to look up a value in a list or an array. This is because dictionaries use a “hash function” to create a key from the data item. The hash function takes the data item as input and then outputs a key that is used to retrieve the data item. Dictionaries are commonly used to store information for which the order does not matter, such as a list of words in a sentence or a list of names and their associated ages. Stacks and Queues A stack is a data structure that is used to store and retrieve data items in a specific order. You can add or remove data items from the stack, but they will always be added in their original order. A stack can be used to store the sequence of events that took place in a program or to store data that is being processed. A stack is useful when you need to get the first item added to it, or the last item added to it. A queue is a data structure that is similar to a stack except that it is a first-in, first-out (FIFO) structure. This means that data items are added to the back of the queue and removed from the front. Data structures are an important part of programming since they help you manage and store data efficiently. They are the foundation on which any program is built. This article helped you understand the basics of data structures and the types of data structures available in Python.
- Variables are essential components of VBA macros in Excel, and they are used to store information, such as numbers or text. Understanding how to use variables effectively is crucial in developing efficient VBA code. - There are two main types of variables in VBA macros: local and global. A local variable is created within a procedure or function and can only be accessed within that specific scope. A global variable, on the other hand, can be accessed from any module within the entire VBA project. - To assign values to variables, there are several methods available, including initializing variables, assigning values using InputBox or dialog boxes, and using constants in VBA Macros. Using variables in VBA macros allows for more flexibility in performing calculations and displaying information to the user using MsgBox. Are you unsure how to use variables in VBA Macros in Excel? Understanding variables is essential to effectively create macros in Excel. Learn how to use variables to simplify your macros in this article. Understanding Variables in VBA Macros VBA Macros in Excel involve variables. What are these variables? And why are they so important? To find out, read on! We’ll discuss the basics of variables and the importance of them in VBA Macros. Image credits: chouprojects.com by David Woodhock What are variables in VBA Macros? Variables are key elements in any VBA macro. They represent a storage container that can hold information such as numbers, text, or references to objects. By using variables, VBA macros can store data and perform operations on them, making it possible to automate repetitive tasks in Excel. In VBA Macros, variables are declared using the Dim statement, followed by the variable name and its type. For example, Dim MyVariable As Integer declares an integer variable called MyVariable. Once declared, variables can be assigned values using the = operator. Moreover, it’s essential to use meaningful names for variables to improve code readability and maintainability. Variables should also be correctly initialized before use and declared within their scope. Pro Tip: Avoid using global variables whenever possible as they can cause errors and can make code maintenance more challenging. Instead, use local variables within their scope to ensure safety and reduce conflicts between subroutines or functions. Without variables in VBA Macros, your code is like a person without a name – confusing, forgettable, and prone to awkward conversations. Importance of variables in VBA Macros Variables are essential in VBA macros as they store crucial data that can be accessed and manipulated during runtime. These stored values help improve the efficiency and functionality of the macro. Mindful declaration of variables is important to avoid errors and ensure clarity in code. Creating variables with declarative value types like integers or strings helps define data expectations, preventing invalid input from users. Declared constants provide a standardized value across any module creating less confusion when editing code. Additional consideration of memory management is vital for macro optimization. Variables consume memory, which impacts execution speed. Efficiently scoped variables with an understanding of lifetime are ideal for large-scale projects. To improve code readability and prevent mix-ups regarding variable referencing, choosing concise and descriptive names would be beneficial. Accompanied by intelligent use of comments to define each function would help another person easily understand your code. Incorporating these suggestions regarding variable usage maximizes efficient use of memory, eliminates potential errors caused by incorrect value types, reduces the risk of variable mix-ups due to naming conventions, and boosts overall readability making it more accessible for other developers to comprehend and contribute to the project’s success. Get ready for a crash course in VBA variable types, because it’s time to throw some data around like reckless drivers! Types of Variables in VBA Macros Gain insight into the types of variables in VBA Macros in Excel. This section covers solutions. Three sub-sections are essential. They are: - Dim Statement - Declaring Variables - Naming Conventions for Variables Read on to learn more! Image credits: chouprojects.com by Yuval Woodhock Using Dim Statement To declare a variable in VBA Macros, Using Dim Statement is a crucial step. It helps to define the data type and scope of the variable, which can save time and ensure code accuracy. Here’s a 6-Step Guide on how to use this statement: - Start with ‘Dim’ keyword followed by the variable’s name. - Add variable’s Data Type after the name using ‘As’ keyword. - For multiple variables, separate each name with a comma. - Optionally, set an initial value by using equal sign followed by numeric or string literal. - In case of an array declaration, put brackets after the name and specify its dimension. - Do not include spaces between variable names and keywords for cleaner code. Interestingly, when it comes to assigning values to variables, VBA does not differentiate between upper and lower cases. However, it considers them during variable declaration. It is always recommended to use a sensible naming convention for variables to avoid confusion and aid readability. Besides that, commenting out complex macros can improve maintainability significantly. Get ready to declare your love for variables, because this section is all about declaring them in VBA macros! One crucial aspect of programming in VBA Macros is the declaration of variables. It involves defining the name, data type, and initial values of variables that you wish to use in your program. Properly declaring variables helps avoid mistakes and improves the performance of your VBA code. When declaring variables, it’s essential to follow good coding practices such as using meaningful names for your variables, ensuring that the data types are correct to avoid type mismatches, and initializing your variables before usage. Additionally, there are different kinds of variable scopes available in VBA Macros. Global variables can be accessed from any module in a program, whereas local variables have a more limited scope and can only be accessed within a subroutine or function. It might surprise you to know that properly defining and declaring variables has revolutionary importance in computer science and programming history. In the early days of computing when computers had very limited memory sizes, poorly declared programs could crash due to lack of space to store information. As a result, optimizing code included efficient variable declarations that prevented this issue from arising. Proper declaration will help program well functioning individual functions and subroutines even today even as modern computer systems don’t suffer from these same limitations as before. Naming variables is like naming a child – choose wisely, because you’ll be stuck with it for a long time. Naming Conventions in Variables Variables are crucial in VBA Macros as they help to store data for later use. Naming conventions for variables play a significant role, making the code more readable and easier to understand. Proper naming conventions lead to improved code maintenance and avoid confusion among developers. In VBA macros, variables must start with a letter and have no spaces or special characters in their names. It is also essential to name variables descriptively according to their purpose, such as naming a variable “firstName” instead of “nm” for better readability. Additionally, it is recommended that developers use camel case format, where the first word starts with lowercase and the following words start with uppercase. Moreover, using singular nouns or noun phrases will make it easy to identify the type of data stored within the variable while avoiding plurals reduces confusion between collections and individual elements. It is important not only to name global functions consistently but also ensure that local variable declarations are clear about their scope. As a friendly reminder regarding variable names: avoid acronyms or overly abbreviated terms, stick to clear patterns formed by letters spelling out plain English words whenever possible. This style makes your code more powerful when considering programs’ longevity across time periods in various scenarios. History reveals that Microsoft’s original Basic programming language permitted one-letter variable names; furthermore, it was usual practice at startup companies of Silicon Valley during the 1980s. The industry has since grown; however, general respect remains for coding professionals who maintain consistency by adhering robustly toward best practices even within now-obsolete legacy languages such as Visual Basic for Applications (VBA). Scope out your variables like they’re suspects in a crime – don’t let them run free in your VBA macros. Variable Scope in VBA Macros Know the perks of using local and global variables to comprehend variable scope in VBA Macros in Excel. Local variables in VBA Macros give you a way to use temporary values. Global variables, on the other hand, enable you to access the same variable in multiple procedures. By examining these topics, you’ll gain a better understanding of how using variables can help you with VBA Macros in Excel. Image credits: chouprojects.com by Joel Arnold Local Variables in VBA Macros Local variables are an essential aspect of VBA macros in Excel. They are temporary variables that exist only within the subroutine or function and cannot be accessed outside of it. These variables are created when the subroutine is executed, and they hold values until the subroutine finishes executing. When a variable is declared as local, its value is initialized every time it enters the function or subroutine. Local variables can be used to store intermediate results during calculation or to hold values temporarily while performing operations within a subroutine or function. By using local variables, we can avoid errors caused by accidentally modifying global variables. It’s important to note that local variables have scope only within their respective functions or subroutines. They cannot be accessed from other modules, sheets, forms, or workbooks. It’s best practice to assign descriptive names to local variables and use Option Explicit at the beginning of each module to force explicit variable declaration. Interestingly, local variables can help conserve memory since they are automatically destroyed when the procedure completes execution. This feature enables VBA macros to execute efficiently even on low-end systems. Why keep it local when you can go global? Understanding global variables in VBA macros for Excel just got a whole lot easier. Global Variables in VBA Macros In VBA Macros, global variables are accessible from any procedure within the module. These variables can be set to values and changed by any procedure in the entire code. This means the existence of these variables can persist across all procedures and functions within a given macro. Furthermore, it’s important to note that while global variables may be useful, they can also pose issues if not used correctly. For example, if two procedures try to modify the same global variable simultaneously, errors in the program may occur. Additionally, excessive use of global variables could lead to confusion and make it challenging to understand the code. In contrast to local variables that only exist within their own procedure, global variables exist throughout all modules in a project. Developers should take care when using global variables and only utilize them when there is an absolute need for them. A stark truth is that unless properly utilized in programs through careful coding practices, global variables can quickly become an unnecessary source of complications and headaches for developers working with VBA Macros in Excel or other Microsoft Office products. Give your variables some purpose in life, or they’ll end up wandering aimlessly like lost puppies in your VBA macro. Assigning Values to Variables in VBA Macros To use variables in VBA macros for Excel, you must initialize them first. Then, depending on your needs, you can assign values to them using either the input box or dialog box. In this section, we’ll explore initializing variables and assigning values with input box and dialog box. Image credits: chouprojects.com by Harry Jones A 3-Step Guide on Initializing Variables: - Declare the variable using the Dimkeyword and specify its data type. - Assign a value or data to the declared variable using the equal sign (=). - Test the assigned value by printing it on the console or using it in a function. In addition, it’s vital to ensure that the assigned value is compatible with the variable’s data type, and it should be assigned before being used further in the VBA program. Experts suggest initializing variables helps prevent errors due to uninitialized variables and enhances code readability. It is essential to note that declaring too many variables or unnecessarily complex ones can affect program efficiency. Therefore, programmers must utilize them optimally while considering their desired output. According to Microsoft, “Utilizing initialized variables not only provides better readability of your code but also ensures safe and efficient execution.” Time to play the guessing game with InputBox – will your variable end up being a lucky number or a useless string? Assigning Values using InputBox To set values to variables in VBA macros, an InputBox function is frequently used. This allows users to input data through a dialog box and store it as a variable. A 6-Step Guide for Assigning Values using InputBox: - Declare the variable: Create a new variable or define an existing one. - Name the variable: Choose a unique name that reflects the purpose of the variable. - Set the variable type: Determine whether the variable will be numeric, string, date/time, etc. - Build an InputBox: Use VBA’s built-in InputBox function to prompt users for data input. - Store input as variable value: Set the declared variable equal to the value entered into the InputBox. - Utilize variable in code: Use the assigned value of the inputted data stored in the variable as needed throughout your macro. Additionally, it’s important to note that InputBoxes should include clear prompts for users so they know what information they are meant to enter. It can also be helpful to provide default values in the InputBox arguments so that users have a better understanding of what data is being requested from them. By following these tips and employing proper use of variables, macros can become more flexible, dynamic, and user-friendly tools in Excel automation and VBA programming. Give your macros a little personality by letting the user assign values through a friendly dialogue box. Assigning Values using Dialog Box To assign values to variables using a dialog box in VBA macros, follow these steps: - Open the VBA Editor by pressing Alt+F11. - Select the module where you wish to assign the value. - Type ‘Dim‘ and declare a variable name for the input. - Use ‘InputBox‘ function followed by a message prompt enclosed in double quotes. - Add a semicolon after double-quote, followed by the variable that was declared in step 3. - Press F5 or click on the Run button to execute the code. After executing these steps, you will be prompted with an input box where you can enter your desired value. Upon execution, this value will be assigned to the specified variable. It is essential to note that when assigning values through dialog boxes, it is crucial to verify user inputs before assigning them to variables. Incorrect or invalid inputs can cause errors in program execution. Pro Tip: To ensure accurate user inputs, use validation techniques like data type checking and ranges validation for numeric entries. Variables in VBA Macros are like flexible puzzle pieces, allowing you to move and manipulate data with ease. Using Variables in VBA Macros Variables in VBA Macros in Excel are essential! Learn to display them with MsgBox and to perform calculations with them. This can help improve the functionality of VBA macros in Excel. Discover how these sub-sections can help you reach your goals. Image credits: chouprojects.com by Joel Woodhock Displaying Variables using MsgBox One way to view the values of variables in VBA macros is by using MsgBox. A message box displays a pop-up window that contains a specific message, including variable values. By inserting variables into the message box’s text, you can display variable values without having to navigate through codes. You can use MsgBox for various purposes, such as displaying debug information, prompting user input, or conveying important messages. To display variable contents using MsgBox, insert the name of the variable inside parentheses after the word “MsgBox.” For example, if you have a variable named “total” containing a value of 20, you can display it using MsgBox by typing “MsgBox (total)” in your code. Apart from displaying values plainly in MsgBoxes, you can also modify them in ways that will make them more readable or informative. One such method is concatenation – combining text and variables together into one cohesive message. To concatenate text and the value of a variable together using ampersands (&), type “MsgBox (“The total is: “& total)” in your code. The result would look like this: “The total is: 20”. Don’t miss out on utilizing this straightforward yet handy feature when working with VBA macros. By knowing how to use it effectively and creatively, presenting data has never been easier! Who needs a calculator when you have variables in VBA? Let’s do some math, Excel-style! Performing Calculations using Variables By utilizing variables in VBA macros, we can easily perform various calculations on Excel sheets. Variables enable us to store and manipulate data in the macros, enhancing their functionality. We can declare variables with a specific data type such as integer, string or double to hold values of that type. Then we can use these variables in performing calculations, such as addition, subtraction, multiplication, and division. Additionally, by setting up variables for cell ranges or columns within a sheet rather than hard-coding them into a macro, we can make the macro adaptable and reusable on multiple worksheets. It is crucial to name the variables meaningfully and distinctly to avoid confusion while working with macros. Moreover, always include comments while coding to provide clarity on what each variable represents. By utilizing variables effectively in macros, we can simplify complex tasks and improve the efficiency of our work. Some Facts About Understanding Variables in VBA Macros in Excel: - ✅ Variables are used to store data in VBA macros in Excel. (Source: Excel Easy) - ✅ VBA variables can store different types of data such as text, numbers, or dates. (Source: Techwalla) - ✅ The names of VBA variables must begin with a letter and can contain letters, numbers, or underscores. (Source: Excel Campus) - ✅ Using variables can make VBA macros more efficient and easier to read and maintain. (Source: Udemy) - ✅ Understanding how to declare, assign, and manipulate variables is essential for VBA programming in Excel. (Source: Excel Macro Mastery) FAQs about Understanding Variables In Vba Macros In Excel What are variables in VBA macros in Excel? Variables in VBA macros are containers that are used to store information such as numbers, text, or objects. They are an essential part of programming as they enable the developer to manipulate data or perform tasks based on the values stored in variables. How can I declare a variable in VBA macros in Excel? To declare a variable in VBA macros, you need to use the Dim keyword, followed by the variable name and the data type. For example: Dim myVariable as Integer What are the different data types that can be used for variables in VBA macros in Excel? VBA macros in Excel support several data types for variables, including Integer, Long, Double, String, Date, Boolean, etc. The choice of data type depends on the values that need to be stored in the variable and the operations that will be performed on them. How do I assign a value to a variable in VBA macros in Excel? You can assign a value to a variable in VBA macros using the assignment operator (=). For example: myVariable = 10 Can I change the value of a variable in VBA macros in Excel during runtime? Yes, the value of a variable can be changed during runtime in VBA macros. You can use the assignment operator (=) to assign a new value to the variable based on certain conditions or user input. What is the scope of a variable in VBA macros in Excel? The scope of a variable in VBA macros determines where it can be accessed and used in the program. Variables can have either local or global scope. Local variables are declared within a specific subroutine or function and can only be used within that code block. Global variables are declared outside any subroutines or functions and can be used throughout the entire program.
Seasonal snowpack covers 46 million square kilometers annually—31% of Earth’s land area—but that number is shrinking. Snowpack is accumulating later, melting earlier, and retreating at an even faster rate than Arctic sea ice. This reduction in snowpack has implications for water locally and climate globally. “Snow is an enormous regulator of heat on Earth because of its high reflectivity,” said Matthew Sturm, group leader of the Snow, Ice and Permafrost Group at the University of Alaska Fairbanks Geophysical Institute. “The Earth gets rid of enormous amounts of heat by painting itself white in the winter, and that’s going away.” Just how substantial will changes brought by shrinking snowpack be? SnowEx, a multiyear NASA research program, hopes to find out. SnowEx has tested sensors in Western states since 2017; this winter the research continues in Alaska, a state with applicable infrastructure, experience, and plenty of snow. A Satellite for Snow Every 10 years, an independent panel assesses NASA’s satellite fleet and recommends research areas that are currently unmet. The 2017 decadal survey suggested snow (and, specifically, snow water equivalent) as a possible mission focus for NASA’s Explorer program. “[Snow water equivalent] is a critical component of hydrologic cycling and the Earth’s energy balance, but it’s really difficult to measure,” said Carrie Vuyovich, project scientist for SnowEx Alaska and a research physical scientist at NASA’s Goddard Space Flight Center. Field observations provide valuable data, but only in limited areas. “It means a huge amount of landscape is missing information,” she said. “Satellites are really the ideal observers to cover that amount of area.” To prepare for a potential satellite mission, SnowEx scientists are developing and refining aircraft-mounted sensors adaptable across a range of conditions. There’s no guarantee of a satellite launch—“It’s a competitive process,” said Vuyovich—but the snow science community can prepare for the potential opportunity by testing sensors calibrated to the temporal and spatial intricacies of snow. Tundra Crust and Taiga Woods A snow-focused satellite should work in all regions, from deep mountain powder to dense tundra crust. Sensors must also react to complicated conditions: wet snow, deep snow, snow covered by trees. SnowEx’s mobility allows it to refine algorithms and accuracy in various conditions, and Alaska is essential for testing those abilities. “The large fraction of global snowpack is here at higher latitudes,” said Svetlana Stuefer, an associate professor of civil and environmental engineering at the University of Alaska Fairbanks. As deputy project scientist for SnowEx Alaska, Stuefer is helping coordinate the campaign and identifying locations that represent the world’s two largest snow biomes: Arctic tundra and boreal forest, also called taiga. “Tundra and taiga take up a lot of room, but they pose two different problems,” said Sturm, a senior adviser to SnowEx Alaska. Tundra snow is shallow, stratified, and often located on permafrost. Remote sensors must recognize and respond to those conditions. Taiga is more complex. “Sorting out what’s on the ground and what’s on the trees is very difficult,” said Sturm. Snow suspended from tree branches reflects light (which is good for climate control) but may sublimate into the atmosphere without contributing to groundwater. A snow-focused satellite would need sensors attuned to both climate and water issues. “I’m excited to see where [SnowEx] goes. They have a lot of challenges ahead of them, but I think it can be an important tool,” said Daniel Fisher, a senior hydrologist with the U.S. Department of Agriculture’s Alaska Snow Survey not involved in the project. “I don’t think [remote sensing] will ever be a silver bullet, but I do think it will play an important role in understanding and measuring the snowpack across the state,” he said. Fixing the Data Drought SnowEx scientists plan to fly lidar and stereophotogrammetry sensors in Alaska this winter. Another aircraft will carry the Snow Water Equivalent Synthetic Aperture Radar and Radiometer (SWESARR), a specialty SnowEx instrument developed at Goddard to calculate snow water equivalent (SWE) using active and passive microwaves. Field staff will measure snow conditions on the ground to compare observations. Better snow data could benefit a range of interests, from road crews to flood forecasters to subsistence trappers. Increased SWE data would particularly help water managers; one in six people relies on seasonal snowpack for drinking water. Then there are the recreationalists, like backcountry skiers who scan avalanche reports while brewing their morning coffee. “Right now, operationally, we are extremely reliant on point-based observations,” said Andrew Schauer, a lead forecaster for the Chugach National Forest Avalanche Information Center not involved in SnowEx. Avalanche centers are challenged by a lack of data, he said, but aerial observations could fill that gap if updated quickly. “I’m excited to see what becomes of the SnowEx program,” he said. By preparing sensors for all winter conditions, SnowEx scientists hope to be ready should NASA ask for a mission proposal. Research in Alaska is an important step to reaching that goal. “[SnowEx Alaska] positions us to be competitive,” said Sturm. “I don’t think there’s any question that a satellite for snow would help humanity.” —J. Besl (@J_Besl), Science Writer Besl, J. (2021), Testing on the tundra: NASA snow program heads north, Eos, 102, https://doi.org/10.1029/2021EO161187. Published on 27 July 2021. Text © 2021. The authors. CC BY-NC-ND 3.0 Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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