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Silver or metallic gray is a color tone resembling gray that is a representation of the color of polished silver.
The visual sensation usually associated with the metal silver is its metallic shine. This cannot be reproduced by a simple solid color because the shiny effect is due to the material's brightness varying w... | Silver (color) | Wikipedia | 503 | 974623 | https://en.wikipedia.org/wiki/Silver%20%28color%29 | Physical sciences | Colors | Physics |
Old silver is a color formulated to resemble tarnished silver.
The first recorded use of old silver as a color name in English was in 1905.
The normalized color coordinates for old silver are identical to battleship gray.
Sonic silver
Sonic silver is a tone of silver included in Metallic FX crayons, specialty crayo... | Silver (color) | Wikipedia | 495 | 974623 | https://en.wikipedia.org/wiki/Silver%20%28color%29 | Physical sciences | Colors | Physics |
Geography
Nevada is referred to as the silver state because of the historically rich silver mines located there, such as the Comstock Lode.
Gerontology
The aging of the baby boomers has been called the "silver tsunami", although this phrase is controversial due to its ageist connotations.
When someone 55 or older g... | Silver (color) | Wikipedia | 431 | 974623 | https://en.wikipedia.org/wiki/Silver%20%28color%29 | Physical sciences | Colors | Physics |
Real estate
The Silverdome, a stadium in Pontiac, Michigan constructed in 1975 for $55,000,000 (about $220,000,000 in 2009 dollars), sold in 2009 for $583,000, symbolizing the collapse of real estate prices in the Detroit metropolitan area due to deindustrialization in the rust belt.
Religion
In Paganism, silver repr... | Silver (color) | Wikipedia | 304 | 974623 | https://en.wikipedia.org/wiki/Silver%20%28color%29 | Physical sciences | Colors | Physics |
Messier 106 (also known as NGC 4258) is an intermediate spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781. M106 is at a distance of about 22 to 25 million light-years away from Earth. M106 contains an active nucleus classified as a Type 2 Seyfert, and the presence of a centr... | Messier 106 | Wikipedia | 462 | 975020 | https://en.wikipedia.org/wiki/Messier%20106 | Physical sciences | Notable galaxies | Astronomy |
Supernovae
Two supernovae have been observed in M106:
SN 1981K (type II, mag. 17) was reported by E. Hummel and verified by Paul Wild by examining archival photos dated 3 November 1981.
SN 2014bc (type II, mag. 14.8) was discovered by the PS1 Science Consortium 3Pi survey on 19 May 2014. | Messier 106 | Wikipedia | 78 | 975020 | https://en.wikipedia.org/wiki/Messier%20106 | Physical sciences | Notable galaxies | Astronomy |
The merit order is a way of ranking available sources of energy, especially electrical generation, based on ascending order of price (which may reflect the order of their short-run marginal costs of production) and sometimes pollution, together with amount of energy that will be generated. In a centralized management s... | Merit order | Wikipedia | 501 | 11730924 | https://en.wikipedia.org/wiki/Merit%20order | Technology | Concepts | null |
A 2013 study estimated the merit order effect of both wind and photovoltaic electricity generation in Germany between the years 2008 and 2012. For each additional GWh of renewables fed into the grid, the price of electricity in the day-ahead market was reduced by 0.11–0.13¢/kWh. The total merit order effect of wind a... | Merit order | Wikipedia | 420 | 11730924 | https://en.wikipedia.org/wiki/Merit%20order | Technology | Concepts | null |
Economic dispatch is the short-term determination of the optimal output of a number of electricity generation facilities, to meet the system load, at the lowest possible cost, subject to transmission and operational constraints. The Economic Dispatch Problem can be solved by specialized computer software which should s... | Merit order | Wikipedia | 480 | 11730924 | https://en.wikipedia.org/wiki/Merit%20order | Technology | Concepts | null |
The power losses depend on the flows in the branches and thus on the net injections as shown in the above equation. However it cannot depend on the injections on all the buses as this would give an over-determined system. Thus one bus is chosen as the Slack bus and is omitted from the variables of the function . The c... | Merit order | Wikipedia | 470 | 11730924 | https://en.wikipedia.org/wiki/Merit%20order | Technology | Concepts | null |
Another notable algorithm combination is used in a real-time emissions tool called Locational Emissions Estimation Methodology (LEEM) that links electric power consumption and the resulting pollutant emissions. The LEEM estimates changes in emissions associated with incremental changes in power demand derived from the ... | Merit order | Wikipedia | 136 | 11730924 | https://en.wikipedia.org/wiki/Merit%20order | Technology | Concepts | null |
In radiometry, radiant flux or radiant power is the radiant energy emitted, reflected, transmitted, or received per unit time, and spectral flux or spectral power is the radiant flux per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of ... | Radiant flux | Wikipedia | 299 | 2970774 | https://en.wikipedia.org/wiki/Radiant%20flux | Physical sciences | Electromagnetic radiation | Physics |
The van Deemter equation in chromatography, named for Jan van Deemter, relates the variance per unit length of a separation column to the linear mobile phase velocity by considering physical, kinetic, and thermodynamic properties of a separation. These properties include pathways within the column, diffusion (axial and... | Van Deemter equation | Wikipedia | 481 | 2971205 | https://en.wikipedia.org/wiki/Van%20Deemter%20equation | Physical sciences | Chromatography | Chemistry |
The form of the Van Deemter equation is such that HETP achieves a minimum value at a particular flow velocity. At this flow rate, the resolving power of the column is maximized, although in practice, the elution time is likely to be impractical. Differentiating the van Deemter equation with respect to velocity, setting... | Van Deemter equation | Wikipedia | 331 | 2971205 | https://en.wikipedia.org/wiki/Van%20Deemter%20equation | Physical sciences | Chromatography | Chemistry |
A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy (also known as the primary galaxy). Satellite galaxies and their constituents are bound to their host galaxy, in the same way that planets within the Solar System a... | Satellite galaxy | Wikipedia | 295 | 2973295 | https://en.wikipedia.org/wiki/Satellite%20galaxy | Physical sciences | Basics_2 | Astronomy |
Satellite galaxies generally lead tumultuous lives due to their chaotic interactions with both the larger host galaxy and other satellites. For example, the host galaxy is capable of disrupting the orbiting satellites via tidal and ram pressure stripping. These environmental effects can remove large amounts of cold gas... | Satellite galaxy | Wikipedia | 242 | 2973295 | https://en.wikipedia.org/wiki/Satellite%20galaxy | Physical sciences | Basics_2 | Astronomy |
Early 20th century
Prior to the 20th century, the notion that galaxies existed beyond the Milky Way was not well established. In fact, the idea was so controversial at the time that it led to what is now heralded as the "Shapley-Curtis Great Debate" aptly named after the astronomers Harlow Shapley and Heber Doust Curt... | Satellite galaxy | Wikipedia | 498 | 2973295 | https://en.wikipedia.org/wiki/Satellite%20galaxy | Physical sciences | Basics_2 | Astronomy |
Motivations to study satellite galaxies
Spectroscopic, photometric and kinematic observations of satellite galaxies have yielded a wealth of information that has been used to study, among other things, the formation and evolution of galaxies, the environmental effects that enhance and diminish the rate of star formati... | Satellite galaxy | Wikipedia | 446 | 2973295 | https://en.wikipedia.org/wiki/Satellite%20galaxy | Physical sciences | Basics_2 | Astronomy |
Transitional types
As a result of minor mergers and environmental effects, some dwarf galaxies are classified as intermediate or transitional type satellite galaxies. For example, Phoenix and LGS3 are classified as intermediate types that appear to be transitioning from dwarf irregulars to dwarf spheroidals. Furthermo... | Satellite galaxy | Wikipedia | 390 | 2973295 | https://en.wikipedia.org/wiki/Satellite%20galaxy | Physical sciences | Basics_2 | Astronomy |
Accumulation of mass in dark matter halos
A crude yet useful method to determine how dark matter halos progressively gain mass through mergers of less massive halos can be explained using the excursion set formalism, also known as the extended Press-Schechter formalism (EPS). Among other things, the EPS formalism can... | Satellite galaxy | Wikipedia | 468 | 2973295 | https://en.wikipedia.org/wiki/Satellite%20galaxy | Physical sciences | Basics_2 | Astronomy |
Halo merger rate
Another utility of the EPS formalism is that it can be used to determine the rate at which a halo of initial mass M merges with a halo with mass between M and M+ΔM. This rate is given by
where , . In general the change in mass, , is the sum of a multitude of minor mergers. Nevertheless, given an infi... | Satellite galaxy | Wikipedia | 495 | 2973295 | https://en.wikipedia.org/wiki/Satellite%20galaxy | Physical sciences | Basics_2 | Astronomy |
Minor merger driven star formation
In 1978, pioneering work involving the measurement of the colors of merger remnants by the astronomers Beatrice Tinsley and Richard Larson gave rise to the notion that mergers enhance star formation. Their observations showed that an anomalous blue color was associated with the merge... | Satellite galaxy | Wikipedia | 348 | 2973295 | https://en.wikipedia.org/wiki/Satellite%20galaxy | Physical sciences | Basics_2 | Astronomy |
The night herons are medium-sized herons, 58–65 cm, in the genera Nycticorax, Nyctanassa, and Gorsachius. The genus name Nycticorax derives from the Greek for "night raven" and refers to the largely nocturnal feeding habits of this group of birds, and the croaking crow-like, almost like a barking sound, call of the bes... | Night heron | Wikipedia | 395 | 2977013 | https://en.wikipedia.org/wiki/Night%20heron | Biology and health sciences | Pelecanimorphae | Animals |
The Hadley cell, also known as the Hadley circulation, is a global-scale tropical atmospheric circulation that features air rising near the equator, flowing poleward near the tropopause at a height of above the Earth's surface, cooling and descending in the subtropics at around 25 degrees latitude, and then returning ... | Hadley cell | Wikipedia | 375 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The Hadley circulation is named after George Hadley, who in 1735 postulated the existence of hemisphere-spanning circulation cells driven by differences in heating to explain the trade winds. Other scientists later developed similar arguments or critiqued Hadley's qualitative theory, providing more rigorous explanation... | Hadley cell | Wikipedia | 435 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The Hadley circulation covers almost half of the Earth's surface area, spanning from roughly the Tropic of Cancer to the Tropic of Capricorn. Vertically, the circulation occupies the entire depth of the troposphere. The Hadley cells comprising the circulation consist of air carried equatorward by the trade winds in the... | Hadley cell | Wikipedia | 396 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
where is the radius of Earth, is the acceleration due to the gravity of Earth, and is the zonally averaged meridional wind at the prescribed latitude and pressure level. The value of gives the integrated meridional mass flux between the specified pressure level and the top of the Earth's atmosphere, with positive v... | Hadley cell | Wikipedia | 370 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The trade winds in the low-latitudes of both Earth's northern and southern hemispheres converge air towards the equator, producing a belt of low atmospheric pressure exhibiting abundant storms and heavy rainfall known as the Intertropical Convergence Zone (ITCZ). This equatorward movement of air near the Earth's surfac... | Hadley cell | Wikipedia | 401 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The ascent of air rises into the upper troposphere to a height of , after which air diverges outward from the ITCZ and towards the poles. The top of the Hadley cell is set by the height of the tropopause as the stable stratosphere above prevents the continued ascent of air. Air arising from the low latitudes has higher... | Hadley cell | Wikipedia | 507 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
where is the difference in potential temperature between the equator and the pole in radiative equilibrium, is the height of the tropopause, is the Earth's rotation rate, and is a reference potential temperature. Other compatible models posit that the width of the Hadley cell may scale with other physical parameter... | Hadley cell | Wikipedia | 463 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
At longer interannual timescales, variations in the Hadley circulation are associated with variations in the El Niño–Southern Oscillation (ENSO), which impacts the positioning of the ascending branch; the response of the circulation to ENSO is non-linear, with a more marked response to El Niño events than La Niña event... | Hadley cell | Wikipedia | 230 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The Hadley cell is an important mechanism by which moisture and energy are transported both between the tropics and subtropics and between the northern and southern hemispheres. However, it is not an efficient transporter of energy due to the opposing flows of the lower and upper branch, with the lower branch transport... | Hadley cell | Wikipedia | 362 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The Hadley circulation may be idealized as a heat engine converting heat energy into mechanical energy. As air moves towards the equator near the Earth's surface, it accumulates entropy from the surface either by direct heating or the flux of sensible or latent heat. In the ascending branch of a Hadley cell, the ascent... | Hadley cell | Wikipedia | 375 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The Hadley circulation also transports planetary angular momentum poleward due to Earth's rotation. Because the trade winds are directed opposite the Earth's rotation, eastward angular momentum is transferred to the atmosphere via frictional interaction between the winds and topography. The Hadley cell then transfers t... | Hadley cell | Wikipedia | 458 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
In the 15th and 16th centuries, observations of maritime weather conditions were of considerable importance to maritime transport. Compilations of these observations showed consistent weather conditions from year to year and significant seasonal variability. The prevalence of dry conditions and weak winds at around 30°... | Hadley cell | Wikipedia | 406 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
Unsatisfied with preceding explanations for the trade winds, George Hadley proposed an alternate mechanism in 1735. Hadley's hypothesis was published in the paper "On the Cause of the General Trade Winds" in Philosophical Transactions of the Royal Society. Like Halley, Hadley's explanation viewed the trade winds as a m... | Hadley cell | Wikipedia | 307 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
Hadley was not widely associated with his theory due to conflation with his older brother, John Hadley, and Halley; his theory failed to gain much traction in the scientific community for over a century due to its unintuitive explanation and the lack of validating observations. Several other natural philosophers indepe... | Hadley cell | Wikipedia | 369 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The work of Gustave Coriolis, William Ferrel, Jean Bernard Foucault, and Henrik Mohn in the 19th century helped establish the Coriolis force as the mechanism for the deflection of winds due to Earth's rotation, emphasizing the conservation of angular momentum in directing flows rather than the conservation of linear mo... | Hadley cell | Wikipedia | 347 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
Hadley's model of the global atmospheric circulation being characterized by hemisphere-wide circulation cells was also challenged by weather observations showing a zone of high pressure in the subtropics and a belt of low pressure at around 60° latitude. This pressure distribution would imply a poleward flow near the s... | Hadley cell | Wikipedia | 296 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The Hadley circulation is one of the most important influences on global climate and planetary habitability, as well as an important transporter of angular momentum, heat, and water vapor. Hadley cells flatten the temperature gradient between the equator and the poles, making the extratropics milder. The global precipi... | Hadley cell | Wikipedia | 456 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
According to the IPCC Sixth Assessment Report (AR6), the Hadley circulation has likely expanded since at least the 1980s in response to climate change, with medium confidence in an accompanying intensification of the circulation. An expansion of the overall circulation poleward by about 0.1°–0.5° latitude per decade si... | Hadley cell | Wikipedia | 460 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
The expansion of the Hadley circulation due to climate change is consistent with the Held–Hou model, which predicts that the latitudinal extent of the circulation is proportional to the square root of the height of the tropopause. Warming of the troposphere raises the tropopause height, enabling the upper poleward bran... | Hadley cell | Wikipedia | 440 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
Projections from climate models indicate that a continued increase in the concentration of greenhouse gas would result in continued widening of the Hadley circulation. However, simulations using historical data suggest that forcing from greenhouse gasses may account for about 0.1° per decade of expansion of the tropics... | Hadley cell | Wikipedia | 432 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
Climate modelling suggests that the shift in the position of the subtropical highs induced by Hadley cell broadening may reduce oceanic upwelling at low latitudes and enhance oceanic upwelling at high latitudes. The expansion of subtropical highs in tandem with the circulation's expansion may also entail a widening of ... | Hadley cell | Wikipedia | 404 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
Venus, which rotates slowly, may have Hadley cells that extend farther poleward than Earth's, spanning from the equator to high latitudes in each of the northern and southern hemispheres. Its broad Hadley circulation would efficiently maintain the nearly isothermal temperature distribution between the planet's pole and... | Hadley cell | Wikipedia | 257 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
Simulations of the Martian atmosphere suggest that a Hadley circulation is also present in Mars' atmosphere, exhibiting a stronger seasonality compared to Earth's Hadley circulation. This greater seasonality results from diminished thermal inertia resulting from the lack of an ocean and the planet's thinner atmosphere.... | Hadley cell | Wikipedia | 474 | 6953458 | https://en.wikipedia.org/wiki/Hadley%20cell | Physical sciences | Atmospheric circulation | null |
A differential equation can be homogeneous in either of two respects.
A first order differential equation is said to be homogeneous if it may be written
where and are homogeneous functions of the same degree of and . In this case, the change of variable leads to an equation of the form
which is easy to solve b... | Homogeneous differential equation | Wikipedia | 511 | 6954092 | https://en.wikipedia.org/wiki/Homogeneous%20differential%20equation | Mathematics | Differential equations | null |
where may be constants, but not all may be zero.
For example, the following linear differential equation is homogeneous:
whereas the following two are inhomogeneous:
The existence of a constant term is a sufficient condition for an equation to be inhomogeneous, as in the above example. | Homogeneous differential equation | Wikipedia | 60 | 6954092 | https://en.wikipedia.org/wiki/Homogeneous%20differential%20equation | Mathematics | Differential equations | null |
Ornithology is a branch of zoology that concerns the study of birds. Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds. It has also been an area with a large contribution made by amateurs in terms of time, resources, and financial support... | Ornithology | Wikipedia | 477 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
Cultures around the world have rich vocabularies related to birds. Traditional bird names are often based on detailed knowledge of the behaviour, with many names being onomatopoeic, and still in use. Traditional knowledge may also involve the use of birds in folk medicine and knowledge of these practices are passed on ... | Ornithology | Wikipedia | 301 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
Aristotle in 350 BC in his History of animals noted the habit of bird migration, moulting, egg laying, and lifespans, as well as compiling a list of 170 different bird species. However, he also introduced and propagated several myths, such as the idea that swallows hibernated in winter, although he noted that cranes mi... | Ornithology | Wikipedia | 230 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
The earliest record of falconry comes from the reign of Sargon II (722–705 BC) in Assyria. Falconry is thought to have made its entry to Europe only after AD 400, brought in from the east after invasions by the Huns and Alans. Starting from the eighth century, numerous Arabic works on the subject and general ornitholog... | Ornithology | Wikipedia | 440 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
Several early German and French scholars compiled old works and conducted new research on birds. These included Guillaume Rondelet, who described his observations in the Mediterranean, and Pierre Belon, who described the fish and birds that he had seen in France and the Levant. Belon's Book of Birds (1555) is a folio v... | Ornithology | Wikipedia | 439 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
In the 17th century, Francis Willughby (1635–1672) and John Ray (1627–1705) created the first major system of bird classification that was based on function and morphology rather than on form or behaviour. Willughby's Ornithologiae libri tres (1676) completed by John Ray is sometimes considered to mark the beginning of... | Ornithology | Wikipedia | 250 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
Towards the late 18th century, Mathurin Jacques Brisson (1723–1806) and Comte de Buffon (1707–1788) began new works on birds. Brisson produced a six-volume work Ornithologie in 1760 and Buffon's included nine volumes (volumes 16–24) on birds Histoire naturelle des oiseaux (1770–1785) in his work on science Histoire na... | Ornithology | Wikipedia | 373 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
The emergence of ornithology as a scientific discipline began in the 18th century, when Mark Catesby published his two-volume Natural History of Carolina, Florida, and the Bahama Islands, a landmark work which included 220 hand-painted engravings and was the basis for many of the species Carl Linnaeus described in the ... | Ornithology | Wikipedia | 312 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
The search for patterns in the variations of birds was attempted by many. Friedrich Wilhelm Joseph Schelling (1775–1854), his student Johann Baptist von Spix (1781–1826), and several others believed that a hidden and innate mathematical order existed in the forms of birds. They believed that a "natural" classification ... | Ornithology | Wikipedia | 482 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
This early idea that the study of living birds was merely recreation held sway until ecological theories became the predominant focus of ornithological studies. The study of birds in their habitats was particularly advanced in Germany with bird ringing stations established as early as 1903. By the 1920s, the Journal fü... | Ornithology | Wikipedia | 472 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
John Hurrell Crook studied the behaviour of weaverbirds and demonstrated the links between ecological conditions, behaviour, and social systems. Principles from economics were introduced to the study of biology by Jerram L. Brown in his work on explaining territorial behaviour. This led to more studies of behaviour tha... | Ornithology | Wikipedia | 502 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
The rise of field guides for the identification of birds was another major innovation. The early guides such as Thomas Bewick's two-volume guide and William Yarrell's three-volume guide were cumbersome, and mainly focused on identifying specimens in the hand. The earliest of the new generation of field guides was prepa... | Ornithology | Wikipedia | 321 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
Organizations were started in many countries, and these grew rapidly in membership, most notable among them being the Royal Society for the Protection of Birds (RSPB) in Britain and the Audubon Society in the US, which started in 1885. Both these organizations were started with the primary objective of conservation. Th... | Ornithology | Wikipedia | 510 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
The use of bird skins to document species has been a standard part of systematic ornithology. Bird skins are prepared by retaining the key bones of the wings, legs, and skull along with the skin and feathers. In the past, they were treated with arsenic to prevent fungal and insect (mostly dermestid) attack. Arsenic, be... | Ornithology | Wikipedia | 456 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
The capture and marking of birds enable detailed studies of life history. Techniques for capturing birds are varied and include the use of bird liming for perching birds, mist nets for woodland birds, cannon netting for open-area flocking birds, the bal-chatri trap for raptors, decoys and funnel traps for water birds.
... | Ornithology | Wikipedia | 418 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
In the laboratory
Many aspects of bird biology are difficult to study in the field. These include the study of behavioural and physiological changes that require a long duration of access to the bird. Nondestructive samples of blood or feathers taken during field studies may be studied in the laboratory. For instance, ... | Ornithology | Wikipedia | 348 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
The entire genome of the domestic fowl (Gallus gallus) was sequenced in 2004, and was followed in 2008 by the genome of the zebra finch (Taeniopygia guttata). Such whole-genome sequencing projects allow for studies on evolutionary processes involved in speciation. Associations between the expression of genes and behav... | Ornithology | Wikipedia | 453 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
The role of some species of birds as pests has been well known, particularly in agriculture. Granivorous birds such as the queleas in Africa are among the most numerous birds in the world, and foraging flocks can cause devastation. Many insectivorous birds are also noted as beneficial in agriculture. Many early studies... | Ornithology | Wikipedia | 379 | 42967 | https://en.wikipedia.org/wiki/Ornithology | Biology and health sciences | Basics_2 | Biology |
Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther a galaxy is from the Earth, the faster it moves away. A galaxy's recessional velocity is typically determined by me... | Hubble's law | Wikipedia | 349 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
Hubble's law is considered the first observational basis for the expansion of the universe, and is one of the pieces of evidence most often cited in support of the Big Bang model. The motion of astronomical objects due solely to this expansion is known as the Hubble flow. It is described by the equation , with the con... | Hubble's law | Wikipedia | 446 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
In 1922, Alexander Friedmann derived his Friedmann equations from Einstein field equations, showing that the universe might expand at a rate calculable by the equations. The parameter used by Friedmann is known today as the scale factor and can be considered as a scale invariant form of the proportionality constant of ... | Hubble's law | Wikipedia | 491 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
The velocities and distances that appear in Hubble's law are not directly measured. The velocities are inferred from the redshift of radiation and distance is inferred from brightness. Hubble sought to correlate brightness with parameter .
Combining his measurements of galaxy distances with Vesto Slipher and Milton H... | Hubble's law | Wikipedia | 511 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
The discovery of the linear relationship between redshift and distance, coupled with a supposed linear relation between recessional velocity and redshift, yields a straightforward mathematical expression for Hubble's law as follows:
where
is the recessional velocity, typically expressed in km/s.
is Hubble's consta... | Hubble's law | Wikipedia | 417 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
Redshift velocity and recessional velocity
Redshift can be measured by determining the wavelength of a known transition, such as hydrogen α-lines for distant quasars, and finding the fractional shift compared to a stationary reference. Thus, redshift is a quantity unambiguously acquired from observation. Care is requi... | Hubble's law | Wikipedia | 491 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
Suppose a galaxy is at distance , and this distance changes with time at a rate . We call this rate of recession the "recession velocity" :
We now define the Hubble constant as
and discover the Hubble law:
From this perspective, Hubble's law is a fundamental relation between (i) the recessional velocity associated w... | Hubble's law | Wikipedia | 469 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
The parameter is commonly called the "Hubble constant", but that is a misnomer since it is constant in space only at a fixed time; it varies with time in nearly all cosmological models, and all observations of far distant objects are also observations into the distant past, when the "constant" had a different value. "... | Hubble's law | Wikipedia | 501 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
In a universe with a deceleration parameter equal to zero, it follows that , where is the time since the Big Bang. A non-zero, time-dependent value of simply requires integration of the Friedmann equations backwards from the present time to the time when the comoving horizon size was zero.
It was long thought that ... | Hubble's law | Wikipedia | 487 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
Occasionally a reference value other than 100 may be chosen, in which case a subscript is presented after to avoid confusion; e.g. denotes , which implies .
This should not be confused with the dimensionless value of Hubble's constant, usually expressed in terms of Planck units, obtained by multiplying by (from d... | Hubble's law | Wikipedia | 510 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
If the dark energy derives from a cosmological constant such as that introduced by Einstein, it can be shown that . The equation then reduces to the last equation in the matter-dominated universe section, with set to zero. In that case the initial dark energy density is given by
If dark energy does not have a consta... | Hubble's law | Wikipedia | 435 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
The Hubble volume is sometimes defined as a volume of the universe with a comoving size of . The exact definition varies: it is sometimes defined as the volume of a sphere with radius , or alternatively, a cube of side . Some cosmologists even use the term Hubble volume to refer to the volume of the observable universe... | Hubble's law | Wikipedia | 487 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
This previously wide variance in estimates was partially resolved with the introduction of the ΛCDM model of the universe in the late 1990s. Incorporating the ΛCDM model, observations of high-redshift clusters at X-ray and microwave wavelengths using the Sunyaev–Zel'dovich effect, measurements of anisotropies in the co... | Hubble's law | Wikipedia | 396 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
The "late universe" or distance ladder measurements typically employ three stages or "rungs". In the first rung distances to Cepheids are determined while trying to reduce luminosity errors from dust and correlations of metallicity with luminosity. The second rung uses
Type Ia supernova, explosions of almost constant ... | Hubble's law | Wikipedia | 472 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
In July 2019, astronomers reported that a new method to determine the Hubble constant, and resolve the discrepancy of earlier methods, has been proposed based on the mergers of pairs of neutron stars, following the detection of the neutron star merger of GW170817, an event known as a dark siren. Their measurement of th... | Hubble's law | Wikipedia | 440 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
Alternatively, it could be that the observations are correct, but some unaccounted-for effect is causing the discrepancy. If the cosmological principle fails (see ), then the existing interpretations of the Hubble constant and the Hubble tension have to be revised, which might resolve the Hubble tension. In particular,... | Hubble's law | Wikipedia | 342 | 42975 | https://en.wikipedia.org/wiki/Hubble%27s%20law | Physical sciences | Physical cosmology | null |
Alternating current (AC) is an electric current that periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the f... | Alternating current | Wikipedia | 454 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
Consequently, power transmitted at a higher voltage requires less loss-producing current than for the same power at a lower voltage. Power is often transmitted at hundreds of kilovolts on pylons, and transformed down to tens of kilovolts to be transmitted on lower level lines, and finally transformed down to 100 V – 24... | Alternating current | Wikipedia | 304 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
Three-phase electrical generation is very common. The simplest way is to use three separate coils in the generator stator, physically offset by an angle of 120° (one-third of a complete 360° phase) to each other. Three current waveforms are produced that are equal in magnitude and 120° out of phase to each other. If co... | Alternating current | Wikipedia | 291 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
For three-phase at utilization voltages a four-wire system is often used. When stepping down three-phase, a transformer with a Delta (3-wire) primary and a Star (4-wire, center-earthed) secondary is often used so there is no need for a neutral on the supply side. For smaller customers (just how small varies by country ... | Alternating current | Wikipedia | 491 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
Low frequency
A low frequency eases the design of electric motors, particularly for hoisting, crushing and rolling applications, and commutator-type traction motors for applications such as railways. However, low frequency also causes noticeable flicker in arc lamps and incandescent light bulbs. The use of lower freque... | Alternating current | Wikipedia | 438 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
At very high frequencies, the current no longer flows in the wire, but effectively flows on the surface of the wire, within a thickness of a few skin depths. The skin depth is the thickness at which the current density is reduced by 63%. Even at relatively low frequencies used for power transmission (50 Hz – 60 Hz), no... | Alternating current | Wikipedia | 471 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
Coaxial cables
Coaxial cables are commonly used at audio frequencies and above for convenience. A coaxial cable has a conductive wire inside a conductive tube, separated by a dielectric layer. The current flowing on the surface of the inner conductor is equal and opposite to the current flowing on the inner surface of... | Alternating current | Wikipedia | 447 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
Fiber optics
At frequencies greater than 200 GHz, waveguide dimensions become impractically small, and the ohmic losses in the waveguide walls become large. Instead, fiber optics, which are a form of dielectric waveguides, can be used. For such frequencies, the concepts of voltages and currents are no longer used.
Fo... | Alternating current | Wikipedia | 463 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
For 230 V AC, the peak voltage is therefore , which is about 325 V, and the peak power is , that is 460 RW. During the course of one cycle (two cycle as the power) the voltage rises from zero to 325 V, the power from zero to 460 RW, and both falls through zero. Next, the voltage descends to reverse direction, -325 V,... | Alternating current | Wikipedia | 467 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
Transformers
The development of the alternating current transformer to change voltage from low to high level and back, allowed generation and consumption at low voltages and transmission, over great distances, at high voltage, with savings in the cost of conductors and energy losses. A bipolar open-core power transfor... | Alternating current | Wikipedia | 411 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
In the autumn of 1884, Károly Zipernowsky, Ottó Bláthy and Miksa Déri (ZBD), three engineers associated with the Ganz Works of Budapest, determined that open-core devices were impractical, as they were incapable of reliably regulating voltage. Bláthy had suggested the use of closed cores, Zipernowsky had suggested the ... | Alternating current | Wikipedia | 448 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
The AC power system was developed and adopted rapidly after 1886. In March of that year, Westinghouse engineer William Stanley, designing a system based on the Gaulard and Gibbs transformer, demonstrated a lighting system in Great Barrington: A Siemens generator's voltage of 500 volts was converted into 3000 volts, an... | Alternating current | Wikipedia | 335 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
The Ames Hydroelectric Generating Plant, constructed in 1890, was among the first hydroelectric alternating current power plants. A long-distance transmission of single-phase electricity from a hydroelectric generating plant in Oregon at Willamette Falls sent power fourteen miles downriver to downtown Portland for stre... | Alternating current | Wikipedia | 490 | 42986 | https://en.wikipedia.org/wiki/Alternating%20current | Physical sciences | Electrical circuits | null |
The sugar glider (Petaurus breviceps) is a small, omnivorous, arboreal, and nocturnal gliding possum. The common name refers to its predilection for sugary foods such as sap and nectar and its ability to glide through the air, much like a flying squirrel. They have very similar habits and appearance to the flying squi... | Sugar glider | Wikipedia | 509 | 42991 | https://en.wikipedia.org/wiki/Sugar%20glider | Biology and health sciences | Diprotodontia | Animals |
The taxonomy of the species is complex, and is still not fully resolved. It was formerly understood to have a wide range across Australia and New Guinea, being the only glider to have this distribution, and to be divided into seven subspecies, with three occurring in Australia and four in New Guinea. This traditional s... | Sugar glider | Wikipedia | 498 | 42991 | https://en.wikipedia.org/wiki/Sugar%20glider | Biology and health sciences | Diprotodontia | Animals |
Distribution and habitat
Sugar gliders are distributed in the coastal forests of southeastern Queensland and most of New South Wales. Their distribution extends to altitudes of 2000m in the eastern ranges. In parts of its range, it may overlap with Krefft's glider (P. notatus).
The sugar glider occurs in sympatry with... | Sugar glider | Wikipedia | 352 | 42991 | https://en.wikipedia.org/wiki/Sugar%20glider | Biology and health sciences | Diprotodontia | Animals |
The fur coat on the sugar glider is thick, soft, and is usually blue-grey; although some have been known to be yellow, tan or (rarely) albino. A black stripe is seen from its nose to midway on its back. Its belly, throat, and chest are cream in colour. Males have four scent glands, located on the forehead, chest, and t... | Sugar glider | Wikipedia | 441 | 42991 | https://en.wikipedia.org/wiki/Sugar%20glider | Biology and health sciences | Diprotodontia | Animals |
Gliding
The sugar glider is one of a number of volplane (gliding) possums in Australia. It glides with the fore- and hind-limbs extended at right angles to the body, with feet flexed upwards. The animal launches itself from a tree, spreading its limbs to expose the gliding membranes. This creates an aerofoil enabling i... | Sugar glider | Wikipedia | 487 | 42991 | https://en.wikipedia.org/wiki/Sugar%20glider | Biology and health sciences | Diprotodontia | Animals |
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