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The netX network controller family (based on ASICs ), developed by Hilscher Gesellschaft für Systemautomation mbH, is a solution for implementing all proven Fieldbus and Real-Time Ethernet systems. It was the first Multi-Protocol ASIC which combines Real-Time-Ethernet and Fieldbus System in one solution. The Multiprotocol functionality is done over a flexible cpu sub system called XC. Through exchanging some microcode the XC is able to realize beside others a PROFINET IRT Switch, EtherCAT Slave, Ethernet Powerlink HUB, PROFIBUS , CAN bus , CC-Link Industrial Networks Interface.
The Multiplex Matrix is a set of PINs which could be configured freely with peripheral functions. Options are CAN, UART, SPI, I2C, GPIOs**, PIOs and SYNC Trigger.
The GPIOs from Hilscher are able to generate Interrupts, could count level or flags, or could be connected to a timer unit to auto generate a PWM. The Resolution of the PWM is normally 10ns. In some netX ASICS is a dedicated Motion unit with a resolution if 1ns is available. | https://en.wikipedia.org/wiki/Hilscher_netx_network_controller |
The Hilsenhoff Biotic Index (HBI) is a quantitative method of evaluating the abundance of arthropod fauna in stream ecosystems as a measurement of estimating water quality based on the predetermined pollution tolerances of the observed taxa. This biotic index was created by William Hilsenhoff in 1977 to measure the effects of oxygen depletion in Wisconsin streams resulting from organic or nutrient pollution. [ 1 ]
The collection sample should contain 100+ arthropods. A tolerance value of 0 to 10 is assigned to each arthropod species (or genera ) based on its known prevalence in stream habitats with varying states of detritus contamination. A highly tolerant species would receive a value of 10, while a species collected only in unaltered streams with high water quality would receive a value of 0. [ 2 ] [ 3 ] The sum products of the number of individuals in each species (or genera) multiplied by the tolerance of the species is divided by the total number of specimens in the sample to determine the HBI value.
H B I = Σ ( n i a i ) N {\displaystyle HBI={\frac {\Sigma (n_{i}a_{i})}{N}}} ;
where n = number of specimens in taxa; a = tolerance value of taxa; N = total number of specimens in the sample.
Precautions should be taken to account for confounding variables , such as the effects of dominant species over-abundance, seasonal temperature stress, [ 4 ] and water currents. Limiting the collection of individuals from each species to a maximum of 10 (10-Max BI) has been shown to minimize the effects of these phenomena on the True BI. [ 2 ]
The biotic index is then ranked for water quality and degree of organic pollution, as follows:
This statistics -related article is a stub . You can help Wikipedia by expanding it .
This arthropod -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Hilsenhoff_Biotic_Index |
Hilton's law , espoused by John Hilton in a series of medical lectures given in 1860–1862, [ 1 ] is the observation that in the study of anatomy , the nerve supplying the muscles extending directly across and acting at a given joint not only supplies the muscle, but also innervates the joint and the skin overlying the muscle. [ 2 ] [ 3 ] [ 4 ] [ 5 ] This law remains applicable to anatomy. [ 6 ]
For example, the musculocutaneous nerve supplies the elbow joint of humans with pain and proprioception fibres. It also supplies Coracobrachialis , biceps brachii , brachialis , and the forearm skin close to the insertion of each of those muscles. Hilton's law arises as a result of the embryological development of humans (or indeed other animals). Hilton based his law upon his extensive anatomical knowledge and clinical experiences. As with most British surgeons of his day (1805–1878), he intensely studied anatomy.
The knee joint is supplied by branches from femoral nerve , sciatic nerve , and obturator nerve because all the three nerves are supplying the muscles moving the joint. These nerves not only innervate the muscles, but also the fibrous capsule, ligaments, and synovial membrane of the knee joint. [ 7 ]
Hilton's law is described above. Similar observations can be made, to extend the theory; often a nerve will supply both the muscles and skin relating to a particular joint. The observation often holds true in reverse - that is to say, a nerve that supplies skin or a muscle will often supply the applicable joint. | https://en.wikipedia.org/wiki/Hilton's_law |
In human anatomy, the hilum ( / ˈ h aɪ l ə m / ; pl. : hila ), sometimes formerly called a hilus ( / ˈ h aɪ l ə s / ; pl. : hili ), is a depression or fissure where structures such as blood vessels and nerves enter an organ . Examples include: | https://en.wikipedia.org/wiki/Hilum_(anatomy) |
Himanshu Pandya is an Indian professor and academic at Botany Department Gujarat University , Ahmedabad , Gujarat , India . [ 1 ] He earned a MSc and PhD in botany and areas of specialization In vivo and In vitro studies on physiological and biochemical parameters on Gladiolus , Chrysanthemum and Lily . [ 2 ] [ 3 ]
Pandya taught for 27 years. He is also a professor and Head of the Department of Biochemistry and Forensic Science. [ citation needed ] His research focused on horticulture, plant biotechnology, plant physiology, plant biochemistry, bioinformatics, climate change and impacts management, forensic science, and biochemistry. [ citation needed ]
From 2005 - 2017 he was a Professor in the Department of Botany, Bioinformatics and Climate Change Impacts Management.
In 2017 he became Vice Chancellor of the Gujarat University. [ citation needed ]
This article about an educator is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Himanshu_Pandya |
Hin recombinase is a 21kD protein composed of 198 amino acids that is found in the bacteria Salmonella . Hin belongs to the serine recombinase family (B2) of DNA invertases in which it relies on the active site serine to initiate DNA cleavage and recombination. The related protein, gamma-delta resolvase shares high similarity to Hin, of which much structural work has been done, including structures bound to DNA and reaction intermediates . Hin functions to invert a 900 base pair ( bp ) DNA segment within the salmonella genome that contains a promoter for downstream flagellar genes, fljA and fljB. Inversion of the intervening DNA alternates the direction of the promoter and thereby alternates expression of the flagellar genes. This is advantageous to the bacterium as a means of escape from the host immune response .
Hin functions by binding to two 26bp imperfect inverted repeat sequences as a homodimer . These hin binding sites flank the invertible segment which not only encodes the Hin gene itself, but also contains an enhancer element to which the bacterial Fis proteins binds with nanomolar affinity. Four molecules of Fis bind to this site as a homodimers and are required for the recombination reaction to proceed.
The initial reaction requires binding of Hin and Fis to their respective DNA sequences and assemble into a higher-order nucleoprotein complex with branched plectonemic supercoils with the aid of the DNA bending protein HU. At this point, it is believed that the Fis protein modulates subtle contacts to activate the reaction, possibly through direct interactions with the Hin protein. Activation of the 4 catalytic serine residues within the Hin tetramer make a 2-bp double stranded DNA break and forms a covalent reaction intermediate. The DNA cleavage event also requires the divalent metal cation magnesium . A large conformational change reveals a large hydrophobic interface that allows for subunit rotation which may be driven by superhelical torsion within the protein-DNA complex. After this 180° rotation, Hin returns to its native conformation and re-ligates the cleaved DNA, without the aid of high energy cofactors and without the loss of any DNA. | https://en.wikipedia.org/wiki/Hin_recombinase |
Hindgut fermentation is a digestive process seen in monogastric herbivores (animals with a simple, single-chambered stomach ). Cellulose is digested with the aid of symbiotic microbes including bacteria , archaea , and eukaryotes . [ 1 ] The microbial fermentation occurs in the digestive organs that follow the small intestine : the cecum and large intestine . Examples of hindgut fermenters include proboscideans and large odd-toed ungulates such as horses and rhinos , as well as small animals such as rodents , rabbits and koalas . [ 2 ]
In contrast, foregut fermentation is the form of cellulose digestion seen in ruminants such as cattle which have a four-chambered stomach, [ 3 ] as well as in sloths , macropodids , some monkeys , and one bird, the hoatzin . [ 4 ]
Hindgut fermenters generally have a cecum and large intestine that are much larger and more complex than those of a foregut or midgut fermenter. [ 5 ] Research on small cecum fermenters such as flying squirrels , rabbits and lemurs has revealed these mammals to have a GI tract about 10-13 times the length of their body. [ 6 ] This is due to the high intake of fiber and other hard to digest compounds that are characteristic to the diet of monogastric herbivores. [ 7 ]
Easily digestible food is processed in the gastrointestinal tract & expelled as regular feces. But in order to get nutrients out of hard to digest fiber, some smaller hindgut fermenters, like lagomorphs (rabbits, hares, pikas), ferment fiber in the cecum (at the small and large intestine junction) and then expel the contents as cecotropes , which are reingested ( cecotrophy ). The cecotropes are then absorbed in the small intestine to utilize the nutrients. [ 7 ]
This process is also beneficial in allowing for restoration of the microflora population, or gut flora . These microbes are found in the gastrointestinal tract and can act as protective agents that strengthen the immune system . Small hindgut fermenters have the ability to expel their microflora, which is useful during the acts of hibernation , estivation and torpor .
While foregut fermentation is generally considered more efficient, and monogastric animals cannot digest cellulose as efficiently as ruminants, [ 5 ] hindgut fermentation allows animals to consume small amounts of low-quality forage all day long and thus survive in conditions where ruminants might not be able to obtain nutrition adequate for their needs. While ruminants require a good deal of time resting between meals, hindgut fermenters are able to take in smaller meals more frequently, allowing them to eat and move more readily. [ 8 ] The large hindgut fermenters are bulk feeders: they ingest large quantities of low-nutrient food, which they process more rapidly than would be possible for a similarly sized foregut fermenter. The main food in that category is grass, and grassland grazers move over long distances to take advantage of the growth phases of grass in different regions. [ 9 ]
The ability to process food more rapidly than foregut fermenters gives hindgut fermenters an advantage at very large body size, as they are able to accommodate significantly larger food intakes. The largest extant and prehistoric megaherbivores , elephants and indricotheres (a type of rhino), respectively, have been hindgut fermenters. [ 10 ] Study of the rates of evolution of larger maximum body mass in different terrestrial mammalian groups has shown that the fastest growth in body mass over time occurred in hindgut fermenters ( perissodactyls , rodents and proboscids ). [ 11 ]
Hindgut fermenters are subdivided into two groups based on the relative size of various digestive organs in relationship to the rest of the system: colonic fermenters tend to be larger species such as horses, and cecal fermenters are smaller animals such as rabbits and rodents. [ 2 ] However, in spite of the terminology, colonic fermenters such as horses make extensive use of the cecum to break down cellulose. [ 12 ] [ 13 ] Also, colonic fermenters typically have a proportionally longer large intestine than small intestine, whereas cecal fermenters have a considerably enlarged cecum compared to the rest of the digestive tract.
In addition to mammals, several insects are also hindgut fermenters, the best studied of which are the termites , which are characterised by an enlarged "paunch" of the hindgut that also houses the bulk of the gut microbiota. [ 14 ] Digestion of wood particles in lower termites is accomplished inside the phagosomes of gut flagellates, but in the flagellate-free higher termites, this appears to be accomplished by fibre-associated bacteria. [ 15 ] | https://en.wikipedia.org/wiki/Hindgut_fermentation |
The Hindmarsh–Rose model of neuronal activity is aimed to study the spiking -bursting behavior of the membrane potential observed in experiments made with a single neuron. The relevant variable is the membrane potential, x ( t ), which is written in dimensionless units . There are two more variables, y ( t ) and z ( t ), which take into account the transport of ions across the membrane through the ion channels . The transport of sodium and potassium ions is made through fast ion channels and its rate is measured by y ( t ), which is called the spiking variable. z ( t ) corresponds to an adaptation current, which is incremented at every spike, leading to a decrease in the firing rate. Then, the Hindmarsh–Rose model has the mathematical form of a system of three nonlinear ordinary differential equations on the dimensionless dynamical variables x ( t ), y ( t ), and z ( t ). They read:
where
The model has eight parameters: a , b , c , d , r , s , x R and I . It is common to fix some of them and let the others be control parameters. Usually the parameter I , which means the current that enters the neuron, is taken as a control parameter. Other control parameters used often in the literature are a , b , c , d , or r , the first four modeling the working of the fast ion channels and the last one the slow ion channels, respectively. Frequently, the parameters held fixed are s = 4 and x R = -8/5. When a , b , c , d are fixed the values given are a = 1, b = 3, c = 1, and d = 5. The parameter r governs the time scale of the neural adaptation and is something of the order of 10 −3 , and I ranges between −10 and 10.
The third state equation:
allows a great variety of dynamic behaviors of the membrane potential, described by variable x, including unpredictable behavior, which is referred to as chaotic dynamics . This makes the Hindmarsh–Rose model relatively simple and provides a good qualitative description of the many different patterns that are observed empirically.
This biophysics -related article is a stub . You can help Wikipedia by expanding it .
This chaos theory -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Hindmarsh–Rose_model |
Hindsight optimisation ( HOP ) is a computer science technique used in artificial intelligence for analysis of actions which have stochastic results. HOP is used in combination with a deterministic planner. By creating sample results for each of the possible actions from the given state (i.e. determinising the actions), and using the deterministic planner to analyse those sample results, HOP allows an estimate of the actual action.
This artificial intelligence -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Hindsight_optimization |
Like many Indo-Aryan languages , Hindustani ( Hindi and Urdu ) has a decimal numeral system that is contracted to the extent that nearly every number 1–99 is irregular, and needs to be memorized as a separate numeral. [ 1 ]
Numbers from 100 up are more regular. There are numerals for 100, sau ; 1,000, hazār ; and successive multiples by 100 of 1000: lākh (lakh) 100,000 (10 5 ), karoṛ (crore) 1,00,00,000 (10 7 ), arab 1,00,00,00,000 (10 9 , billion), kharab 1,00,00,00,00,000 (10 11 ), nīl 1,00,00,00,00,00,000 (10 13 ), padma 1,00,00,00,00,00,00,000 (10 15 , quadrillion). (See Indian numbering system .) Lakh and crore are common enough to have entered Indian English .
For number 0, Modern Standard Hindi is more inclined towards śūnya (a Sanskrit tatsama ) and Standard Urdu is more inclined towards sifr (borrowed from Arabic), while the native tadbhava -form is sunnā in Hindustani. Sometimes the ardha-tatsama form śūn is also used (semi-learned borrowing). Colloquially in Hinglish / Urdish , it is simply referred as jīro / zīro (from English zero ).
In writing Hindi, numbers are usually represented using Devanagari numeral signs , while in Urdu the signs employed are those of a modified Eastern Arabic numeral system . | https://en.wikipedia.org/wiki/Hindustani_numerals |
The Hindu–Arabic numeral system (also known as the Indo-Arabic numeral system , [ 1 ] Hindu numeral system , and Arabic numeral system ) [ 2 ] [ note 1 ] is a positional base-ten numeral system for representing integers ; its extension to non-integers is the decimal numeral system , which is presently the most common numeral system.
The system was invented between the 1st and 4th centuries by Indian mathematicians . By the 9th century, the system was adopted by Arabic mathematicians who extended it to include fractions . It became more widely known through the writings in Arabic of the Persian mathematician Al-Khwārizmī [ 3 ] ( On the Calculation with Hindu Numerals , c. 825 ) and Arab mathematician Al-Kindi ( On the Use of the Hindu Numerals , c. 830 ). The system had spread to medieval Europe by the High Middle Ages , notably following Fibonacci 's 13th century Liber Abaci ; until the evolution of the printing press in the 15th century, use of the system in Europe was mainly confined to Northern Italy . [ 4 ]
It is based upon ten glyphs representing the numbers from zero to nine, and allows representing any natural number by a unique sequence of these glyphs. The symbols (glyphs) used to represent the system are in principle independent of the system itself. The glyphs in actual use are descended from Brahmi numerals and have split into various typographical variants since the Middle Ages .
These symbol sets can be divided into three main families: Western Arabic numerals used in the Greater Maghreb and in Europe ; Eastern Arabic numerals used in the Middle East ; and the Indian numerals in various scripts used in the Indian subcontinent .
Sometime around 600 CE, a change began in the writing of dates in the Brāhmī -derived scripts of India and Southeast Asia, transforming from an additive system with separate numerals for numbers of different magnitudes to a positional place-value system with a single set of glyphs for 1–9 and a dot for zero, gradually displacing additive expressions of numerals over the following several centuries. [ 5 ]
When this system was adopted and extended by medieval Arabs and Persians, they called it al-ḥisāb al-hindī ("Indian arithmetic"). These numerals were gradually adopted in Europe starting around the 10th century, probably transmitted by Arab merchants; [ 6 ] medieval and Renaissance European mathematicians generally recognized them as Indian in origin, [ 7 ] however a few influential sources credited them to the Arabs, and they eventually came to be generally known as "Arabic numerals" in Europe. [ 8 ] According to some sources, this number system may have originated in Chinese Shang numerals (1200 BCE), which was also a decimal positional numeral system. [ 9 ]
The Hindu–Arabic system is designed for positional notation in a decimal system. In a more developed form, positional notation also uses a decimal marker (at first a mark over the ones digit but now more commonly a decimal point or a decimal comma which separates the ones place from the tenths place), and also a symbol for "these digits recur ad infinitum ". In modern usage, this latter symbol is usually a vinculum (a horizontal line placed over the repeating digits). In this more developed form, the numeral system can symbolize any rational number using only 13 symbols (the ten digits, decimal marker, vinculum, and a prepended minus sign to indicate a negative number ).
Although generally found in text written with the Arabic abjad ("alphabet"), which is written right-to-left, numbers written with these numerals place the most-significant digit to the left, so they read from left to right (though digits are not always said in order from most to least significant [ 10 ] ). The requisite changes in reading direction are found in text that mixes left-to-right writing systems with right-to-left systems.
Various symbol sets are used to represent numbers in the Hindu–Arabic numeral system, most of which developed from the Brahmi numerals .
The symbols used to represent the system have split into various typographical variants since the Middle Ages , arranged in three main groups:
The Brahmi numerals at the basis of the system predate the Common Era . They replaced the earlier Kharosthi numerals used since the 4th century BCE. Brahmi and Kharosthi numerals were used alongside one another in the Maurya Empire period, both appearing on the 3rd century BCE edicts of Ashoka . [ 11 ]
Buddhist inscriptions from around 300 BCE use the symbols that became 1, 4, and 6. One century later, their use of the symbols that became 2, 4, 6, 7, and 9 was recorded. These Brahmi numerals are the ancestors of the Hindu–Arabic glyphs 1 to 9, but they were not used as a positional system with a zero , and there were rather [ clarification needed ] separate numerals for each of the tens (10, 20, 30, etc.).
The actual numeral system, including positional notation and use of zero, is in principle independent of the glyphs used, and significantly younger than the Brahmi numerals.
The place-value system is used in the Bakhshali manuscript , the earliest leaves being radiocarbon dated to the period 224–383 CE. [ 12 ] The development of the positional decimal system takes its origins in [ clarification needed ] Indian mathematics during the Gupta period . Around 500, the astronomer Aryabhata uses the word kha ("emptiness") to mark "zero" in tabular arrangements of digits. The 7th century Brahmasphuta Siddhanta contains a comparatively advanced understanding of the mathematical role of zero . The Sanskrit translation of the lost 5th century Prakrit Jaina cosmological text Lokavibhaga may preserve an early instance of the positional use of zero. [ 13 ]
The first dated and undisputed inscription showing the use of a symbol for zero appears on a stone inscription found at the Chaturbhuja Temple at Gwalior in India, dated 876 CE. [ 14 ]
These Indian developments were taken up in Islamic mathematics in the 8th century, as recorded in al-Qifti 's Chronology of the scholars (early 13th century). [ 15 ]
In 10th century Islamic mathematics , the system was extended to include fractions, as recorded in a treatise by Abbasid Caliphate mathematician Abu'l-Hasan al-Uqlidisi , who was the first to describe positional decimal fractions. [ 16 ] According to J. L. Berggren, the Muslims were the first to represent numbers as we do since they were the ones who initially extended this system of numeration to represent parts of the unit by decimal fractions, something that the Hindus did not accomplish. Thus, we refer to the system as "Hindu–Arabic" rather appropriately. [ 17 ] [ 18 ]
The numeral system came to be known to both the Persian mathematician Khwarizmi , who wrote a book, On the Calculation with Hindu Numerals in about 825 CE, and the Arab mathematician Al-Kindi , who wrote a book, On the Use of the Hindu Numerals ( كتاب في استعمال العداد الهندي [ kitāb fī isti'māl al-'adād al-hindī ]) around 830 CE. Persian scientist Kushyar Gilani who wrote Kitab fi usul hisab al-hind ( Principles of Hindu Reckoning ) is one of the oldest surviving manuscripts using the Hindu numerals. [ 19 ] These books are principally responsible for the diffusion of the Hindu system of numeration throughout the Islamic world and ultimately also to Europe.
In Christian Europe, the first mention and representation of Hindu–Arabic numerals (from one to nine, without zero), is in the Codex Vigilanus (aka Albeldensis ), an illuminated compilation of various historical documents from the Visigothic period in Spain , written in the year 976 CE by three monks of the Riojan monastery of San Martín de Albelda . Between 967 and 969 CE, Gerbert of Aurillac discovered and studied Arab science in the Catalan abbeys. Later he obtained from these places the book De multiplicatione et divisione ( On multiplication and division ). After becoming Pope Sylvester II in the year 999 CE, he introduced a new model of abacus , the so-called Abacus of Gerbert , by adopting tokens representing Hindu–Arabic numerals, from one to nine.
Leonardo Fibonacci brought this system to Europe. His book Liber Abaci introduced Modus Indorum (the method of the Indians), today known as Hindu–Arabic numeral system or base-10 positional notation, the use of zero, and the decimal place system to the Latin world. The numeral system came to be called "Arabic" by the Europeans. It was used in European mathematics from the 12th century, and entered common use from the 15th century to replace Roman numerals . [ 20 ] [ 21 ]
The familiar shape of the Western Arabic glyphs as now used with the Latin alphabet (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) are the product of the late 15th to early 16th century, when they entered early typesetting . Muslim scientists used the Babylonian numeral system , and merchants used the Abjad numerals , a system similar to the Greek numeral system and the Hebrew numeral system . Similarly, Fibonacci's introduction of the system to Europe was restricted to learned circles. The credit for first establishing widespread understanding and usage of the decimal positional notation among the general population goes to Adam Ries , an author of the German Renaissance , whose 1522 Rechenung auff der linihen und federn (Calculating on the Lines and with a Quill) was targeted at the apprentices of businessmen and craftsmen.
The '〇' is used to write zero in Suzhou numerals , which is the only surviving variation of the rod numeral system. The Mathematical Treatise in Nine Sections , written by Qin Jiushao in 1247, is the oldest surviving Chinese mathematical text to use the character ‘〇’ for zero. [ 22 ]
The origin of using the character '〇' to represent zero is unknown. Gautama Siddha introduced Hindu numerals with zero in 718 CE, but Chinese mathematicians did not find them useful, as they already had the decimal positional counting rods . [ 23 ] [ 24 ] Some historians suggest that the use of '〇' for zero was influenced by Indian numerals imported by Gautama, [ 24 ] but Gautama’s numeral system represented zero with a dot rather than a hollow circle, similar to the Bakhshali manuscript . [ 25 ]
An alternative hypothesis proposes that the use of '〇' to represent zero arose from a modification of the Chinese text space filler "□", making its resemblance to Indian numeral systems purely coincidental. Others think that the Indians acquired the symbol '〇' from China, because it resembles a Confucian philosophical symbol for "nothing". [ 23 ]
Chinese and Japanese finally adopted the Hindu–Arabic numerals in the 19th century, abandoning counting rods.
The "Western Arabic" numerals as they were in common use in Europe since the Baroque period have secondarily found worldwide use together with the Latin alphabet , and even significantly beyond the contemporary spread of the Latin alphabet , intruding into the writing systems in regions where other variants of the Hindu–Arabic numerals had been in use, but also in conjunction with Chinese and Japanese writing (see Chinese numerals , Japanese numerals ). | https://en.wikipedia.org/wiki/Hindu–Arabic_numeral_system |
In geometry , a hinged dissection , also known as a swing-hinged dissection or Dudeney dissection , [ 1 ] is a kind of geometric dissection in which all of the pieces are connected into a chain by "hinged" points, such that the rearrangement from one figure to another can be carried out by swinging the chain continuously, without severing any of the connections. [ 2 ] Typically, it is assumed that the pieces are allowed to overlap in the folding and unfolding process; [ 3 ] this is sometimes called the "wobbly-hinged" model of hinged dissection. [ 4 ]
The concept of hinged dissections was popularised by the author of mathematical puzzles , Henry Dudeney . He introduced the famous hinged dissection of a square into a triangle (pictured) in his 1907 book The Canterbury Puzzles . [ 5 ] The Wallace–Bolyai–Gerwien theorem , first proven in 1807, states that any two equal-area polygons must have a common dissection. However, the question of whether two such polygons must also share a hinged dissection remained open until 2007, when Erik Demaine et al. proved that there must always exist such a hinged dissection, and provided a constructive algorithm to produce them. [ 4 ] [ 6 ] [ 7 ] This proof holds even under the assumption that the pieces may not overlap while swinging, and can be generalised to any pair of three-dimensional figures which have a common dissection (see Hilbert's third problem ). [ 6 ] [ 8 ] In three dimensions, however, the pieces are not guaranteed to swing without overlap. [ 9 ]
Other types of "hinges" have been considered in the context of dissections. A twist-hinge dissection is one which use a three-dimensional "hinge" which is placed on the edges of pieces rather than their vertices, allowing them to be "flipped" three-dimensionally. [ 10 ] [ 11 ] As of 2002, the question of whether any two polygons must have a common twist-hinged dissection remains unsolved. [ 12 ] | https://en.wikipedia.org/wiki/Hinged_dissection |
Hinode ( / ˈ h iː n oʊ d eɪ / ; Japanese : ひので , IPA: [çinode] , Sunrise), formerly Solar-B , is a Japan Aerospace Exploration Agency Solar mission with United States and United Kingdom collaboration. It is the follow-up to the Yohkoh (Solar-A) mission and it was launched on the final flight of the M-V rocket from Uchinoura Space Center , Japan on 22 September 2006 at 21:36 UTC (23 September, 06:36 JST ). Initial orbit was perigee height 280 km, apogee height 686 km, inclination 98.3 degrees. Then the satellite maneuvered to the quasi-circular Sun-synchronous orbit over the day/night terminator , which allows near-continuous observation of the Sun. On 28 October 2006, the probe's instruments captured their first images.
The data from Hinode are being downloaded to the Norwegian , terrestrial Svalsat station, operated by Kongsberg a few kilometres west of Longyearbyen , Svalbard . From there, data is transmitted by Telenor through a fibre-optic network to mainland Norway at Harstad , and on to data users in North America, Europe and Japan.
Hinode was planned as a three-year mission to explore the magnetic fields of the Sun. It consists of a coordinated set of optical, extreme ultraviolet (EUV), and x-ray instruments to investigate the interaction between the Sun's magnetic field and its corona. The result will be an improved understanding of the mechanisms that power the solar atmosphere and drive solar eruptions. The EUV imaging spectrometer (EIS) was built by a consortium led by the Mullard Space Science Laboratory ( MSSL ) in the UK . [ 3 ] NASA , the space agency of the United States, was involved with three science instrument components: the Focal Plane Package (FPP), the X-Ray Telescope (XRT), and the Extreme Ultraviolet Imaging Spectrometer (EIS) and shares operations support for science planning and instrument command generation. [ 4 ]
As of March 2024 [update] , the operation is planned to continue until 2033. [ 5 ]
Hinode carries three main instruments to study the Sun .
A 0.5 meter Gregorian optical telescope with an angular resolution of about 0.2 arcsecond over the field of view of about 400 x 400 arcsec. At the SOT focal plane , the Focal Plane Package (FPP) built by the Lockheed Martin Solar and Astrophysics Laboratory in Palo Alto, California consists of three optical instruments: the Broadband Filter Imager (BFI) which produces images of the solar photosphere and chromosphere in six wide-band interference filters; the Narrowband Filter Imager (NFI) which is a tunable Lyot-type birefringent filter capable of producing magnetogram and dopplergram images of the solar surface; and the Spectropolarimeter (SP) which produces the most sensitive vector magnetograph maps of the photosphere to date.
The FPP also includes a Correlation Tracker (CT) which locks onto solar granulation to stabilize the SOT images to a fraction of an arcsecond . The spatial resolution of the SOT is a factor of 5 improvement over previous space-based solar telescopes (e.g., the MDI instrument on the SOHO ).
A modified Wolter I telescope design that uses grazing incidence optics to image the solar corona 's hottest components (0.5 to 10 Million K) with an angular resolution consistent with 1 arcsec pixels at the CCD. The telescope has an imaging field of view of 34 arcminutes. It is capable of capturing an image of the full sun when pointed at the center of the solar disk. The telescope was designed and built by Smithsonian Astrophysical Observatory (SAO), which, with the Harvard College Observatory (HCO) form the Harvard-Smithsonian Center for Astrophysics (CfA). The camera was developed by NAOJ and JAXA .
A normal incidence extreme ultraviolet (EUV) spectrometer that obtains spatially resolved spectra in two wavelength bands: 17.0–21.2 and 24.6–29.2 nm. [ 6 ] Spatial resolution is around 2 arcsec, and the field of view is up to 560 x 512 arcsec 2 . The emission lines in the EIS wavelength bands are emitted at temperatures ranging from 50,000 K to 20 million K. EIS is used to identify the physical processes involved in heating the solar corona . | https://en.wikipedia.org/wiki/Hinode_(satellite) |
The Hinsberg oxindole synthesis is a method of preparing oxindoles from the bisulfite additions of glyoxal . [ 1 ] [ 2 ] It is named after its inventor Oscar Hinsberg . [ 3 ] [ 4 ] [ 5 ] | https://en.wikipedia.org/wiki/Hinsberg_oxindole_synthesis |
The Hinsberg reaction is a chemical test for the detection of primary, secondary and tertiary amines . The reaction was first described by Oscar Hinsberg in 1890. [ 1 ] [ 2 ] In this test, the amine is shaken well with the Hinsberg reagent ( benzenesulfonyl chloride ) in the presence of aqueous alkali (either KOH or NaOH). A primary amine will form a soluble sulfonamide salt. Acidification of this salt then precipitates the sulfonamide of the primary amine. A secondary amine in the same reaction will directly form an insoluble sulfonamide. A tertiary amine will not react with the original reagent (benzene sulfonyl chloride) and will remain insoluble. After adding dilute acid this insoluble amine is converted to a soluble ammonium salt . In this way the reaction can distinguish between the three types of amines. [ 3 ]
Tertiary amines are able to react with benzenesulfonyl chloride under a variety of conditions; the test described above is not absolute. The Hinsberg test for amines is valid only when reaction speed, concentration, temperature, and solubility are taken into account. [ 4 ]
Amines serve as nucleophiles in attacking the sulfonyl chloride electrophile , displacing chloride. The sulfonamides resulting from primary and secondary amines are poorly soluble and precipitate as solids from solution.
For primary amines (R' = H), the initially formed sulfonamide is deprotonated by base to give a water-soluble sulfonamide salt (Na[PhSO 2 NR]).
Tertiary amines promote hydrolysis of the sulfonyl chloride functional group , which affords water-soluble sulfonate salts. | https://en.wikipedia.org/wiki/Hinsberg_reaction |
In mathematical logic, a Hintikka set is a set of logical formulas whose elements satisfy the following properties:
The exact meaning of "conjuctive-type" and "disjunctive-type" is defined by the method of semantic tableaux .
Hintikka sets arise when attempting to prove completeness of propositional logic using semantic tableaux . They are named after Jaakko Hintikka .
In a semantic tableau for propositional logic , Hintikka sets can be defined using uniform notation for propositional tableaux . The elements of a propositional Hintikka set S satisfy the following conditions: [ 1 ]
If a set S is a Hintikka set, then S is satisfiable . | https://en.wikipedia.org/wiki/Hintikka_set |
HipChat was a web service for internal private online chat and instant messaging . As well as one-on-one and group/topic chat, it also featured cloud-based file storage , video calling, searchable message-history and inline-image viewing. The software was available to download onto computers running Windows , Mac or Linux , as well as Android and iOS smartphones and tablets . [ 1 ] [ 2 ] Since 2014, HipChat used a freemium model, as much of the service was free with some additional features requiring organizations to pay per month. [ 3 ] HipChat was launched in 2010 and acquired by Atlassian in 2012. In September 2017, Atlassian replaced the cloud-based HipChat with a new cloud product called Stride , with HipChat continuing on as the client-hosted HipChat Data Center. [ 4 ]
In July 2018, Atlassian announced a partnership with Slack under which Slack would acquire the codebase and related IP assets of HipChat and Stride from Atlassian . [ 5 ] Following this, HipChat and Stride customers were migrated to the Slack group collaboration platform in a transition that was completed by February 2019. [ 5 ] [ 6 ]
HipChat was founded by Chris Rivers, Garret Heaton, and Pete Curley, who studied together at Rensselaer Polytechnic Institute (RPI) and also created HipCal and Plaxo Pulse . They launched the first HipChat beta on December 13, 2009. [ 7 ] [ 8 ]
HipChat was made available to the public starting January 25, 2010. [ 9 ] [ 10 ] [ 1 ]
On March 22, 2010, HipChat launched a web chat beta which allowed users to chat via the browser in addition to the existing Windows, Mac and Linux client. [ 11 ] HipChat's web client came out of beta and SMS chat support was added on April 16, 2010. [ 12 ] On May 12, 2010, HipChat unveiled its official API . [ 13 ] HipChat is mainly written in PHP and Python using the Twisted software framework , but uses other third-party services. [ 14 ] [ 15 ]
On July 19, 2010, the team moved into an office in Sunnyvale, California . [ 16 ] Co-founder Pete Curley announced that HipChat had secured $100,000 in funding on August 10, 2010. [ 17 ] [ 18 ] This round of seed funding allowed the company to start advertising and cover operational costs. [ 19 ]
HipChat launched their iOS app on March 4, 2011, and their Android app on June 2, 2011. [ 20 ] [ 21 ]
On March 7, 2012, Atlassian , which had been using the service internally, announced it had acquired HipChat. [ 22 ]
On April 24, 2017, HipChat experienced a hacking incident in which user info, messages, and content were accessed. [ 23 ]
On May 11, 2017, Atlassian announced HipChat Data Center, a self-hosted enterprise chat tool. [ 24 ]
On September 7, 2017, Atlassian discontinued the cloud-based HipChat, replacing it with HipChat's successor, called Stride , which offered additional features to enhance efficiency of collaboration. [ 25 ] The client-hosted HipChat Data Center continued to be supported.
On July 26, 2018, Atlassian announced that HipChat and Stride would be discontinued February 15, 2019, and that it had reached a deal to sell their intellectual property to Slack . [ 26 ] Slack will pay an undisclosed amount over three years to assume the user bases of the services, and Atlassian will take a minority investment in Slack. The companies also announced a commitment to work on integration of Slack with Atlassian services. [ 27 ] [ 4 ]
The primary features of HipChat were chat rooms, one-on-one messaging, searchable chat history, image sharing, 5 GB of file storage, and SMS messaging for one-on-one conversations. A premium version added video calling, screen sharing , unlimited file storage, history retention controls, and a virtual machine version allowed HipChat to run within corporate firewalls. [ 3 ] [ 28 ] A guest access mode allowed users outside of the organization to join a group chat via a shareable URL . Inline GIF playback and custom emoticons were also available. [ 29 ] [ 30 ] [ 31 ] The product was available as a mobile client, a web client and a downloadable native application. [ 32 ]
HipChat Data Center was Atlassian's self-hosted team communication offering. [ 33 ]
In addition to integration with Atlassian's other products, HipChat integrated with services such as GitHub , MailChimp and Heroku . [ 34 ] To allow for more third-party integrations to be added, HipChat featured a REST interface with several language-specific implementations. [ 35 ]
Administrators were able to access 1-to-1 chat histories if the customer's company policies permitted viewing of employee communications. [ 36 ] | https://en.wikipedia.org/wiki/HipChat |
The Greek astronomer Hipparchus introduced three cycles that have been named after him in later literature.
Hipparchus proposed a correction to the 76-year-long Callippic cycle , which itself was proposed as a correction to the 19-year-long Metonic cycle . He may have published it in the book "On the Length of the Year" (Περὶ ἐνιαυσίου μεγέθους), which has since been lost.
From solstice observations, Hipparchus found that the tropical year is about 1 ⁄ 300 of a day shorter than the 365 + 1 ⁄ 4 days that Calippus used (see Almagest III.1). So he proposed to make a 1-day correction after 4 Calippic cycles, i.e. 304 years = 3,760 lunations = 111,035 days.
This is a very close approximation for an integer number of lunations in an integer number of days (with an error of only 0.014 days). However, it is in fact 1.37 days longer than 304 tropical years. The mean tropical year is actually about 1 ⁄ 128 day (11 minutes 15 seconds) shorter than the Julian calendar year of 365 + 1 ⁄ 4 days. These differences cannot be corrected with any cycle that is a multiple of the 19-year cycle of 235 lunations; it is an accumulation of the mismatch between years and months in the basic Metonic cycle, and the lunar months need to be shifted systematically by a day with respect to the solar year ( i.e. the Metonic cycle itself needs to be corrected) after every 228 years. [ citation needed ]
Indeed, from the values of the tropical year (365.2421896698 days) and the synodic month (29.530588853) cited in the respective articles of Wikipedia, it follows that the length of 228=12×19 tropical years is about 83,275.22 days, shorter than the length of 12×235 synodic months—namely about 83,276.26 days—by one day plus about one hour. In fact, an even better correction would be two days every 437 years, rather than one day every 228 years. The length of 437=23×19 tropical years (about 159,610.837 days) is shorter than that of 23×235 synodic months (about 159,612.833 days) by almost exactly two days, up to only six minutes.
The durations between the equinoxes (and solstices) are not equal, and will cycle around each other [ clarification needed ] over millennia. There are additional subtle and some imperfectly understood rates of change in both the lunar and solar cycles. The values above (such as the tropical year) depend upon the chosen zero point of the tropical year (such as the March equinox or some other astronomical date), which deviate by minutes per year.
An eclipse cycle constructed by Hipparchus is described in Ptolemy 's Almagest IV.2:
For from the observations he set out he [Hipparchus] shows that the smallest constant interval defining an ecliptic period in which the number of months and the amount of [lunar] motion is always the same, is 126007 days plus 1 equinoctial hour. In this interval he finds comprised 4267 months, 4573 complete returns in anomaly , and 4612 revolutions on the ecliptic less about 7½° which is the amount by which the sun’s motion falls short of 345 revolutions (here too the revolution of sun and moon is taken with respect to the fixed stars). (Hence, dividing the above number of days by the 4267 months, he finds the mean length of the [synodic] month as approximately 29;31,50,8,20 days).
Actually, dividing 126007 days and one hour by 4267 would give 29;31,50,8,9 in sexagesimal , whereas 29;31,50,8,20 was already used in Babylonian astronomy , possibly found by Kidinnu in the fourth century BC . This period is a multiple of a Babylonians unit of time equal to one eighteenth of a minute ( 3 + 1 / 3 seconds), which in sexagesimal is 0;0,0,8,20 days. (The true length of the month, 29.53058885 days, comes to 29;31,50,7,12 in sexagesimal, so the Babylonian value was correct to the nearest 3 + 1 / 3 -second unit.)
Ptolemy points out that if one divides this cycle by 17, one obtains a whole number of synodic months (251) and a whole number of anomalistic months (269):
But if one were to look for the number of months [which always cover the same time-interval], not between two lunar eclipses, but merely between one conjunction or opposition and another syzygy of the same type, he would find an even smaller integer number of months containing a return in anomaly, by dividing the above numbers by 17 (which is their only common factor). This produces 251 months and 269 returns in anomaly.
Franz Xaver Kugler in his Die Babylonische Mondrechnung claimed that the Chaldaeans could have known about this cycle of 251 months, because it falls out of their system of calculating the speed of the moon, seen in a tablet from around 100 BC. [ 2 ] In their system, the speed of the moon at new moon varies in a zigzag, with a period of one full moon cycle , changing by 36 arc minutes each month over a span of 251 arc minutes (see graph), and this implies that after 251 months the pattern repeats, and 269 anomalistic months will have gone by.
So it is possible that Hipparchus constructed his 345-year cycle by multiplying this 20-year cycle by 17 so as to closely match an integer number of synodic months (4,267), anomalistic months (4,573), years (345), and days (a bit over 126,007). It is also close to a half-integer number of draconic months (4,630.53...), making it an eclipse period. By comparing his own eclipse observations with Babylonian records from 345 years earlier, he could verify the accuracy of the various periods that the Chaldean astronomers used. [ citation needed ]
The Hipparchic eclipse cycle is made up of 25 inex minus 21 saros periods. There are only three or four eclipses in a series of eclipses separated by Hipparchic cycles. For example, the solar eclipse of August 21, 2017 was preceded by one in 1672 and will be followed by one in 2362, but there are none before or after these. [ 3 ]
It corresponds to:
There are other eclipse intervals that also have the properties desired by Hipparchus, for example an interval of 81.2 years (four of the 251-month cycles, or 19 inex minus 26 saros) which is even closer to a whole number of anomalistic months (1076.00056), and almost equally close to a half-integer number of draconic months (1089.5366). The "tritrix" eclipse cycle, [ 4 ] consisting of 1743 synodic months, 1891.496 draconic months, or 1867.9970 anomalistic months (140.925 years, equivalent to 3 inex plus 3 saros) is about as accurate as the interval of Hipparchus in terms of anomalistic months, but repeats many more times, around 20. An exceptionally accurate eclipse cycle from this point of view is one of 1154.5 years (43 inex minus 5 saros), which is much closer to a whole number of anomalistic months (15303.00005) than the interval of Hipparchus. At the solar eclipse of October 17, 1781, the moon had an anomaly of 0°, [ 5 ] and similar eclipses have occurred every 1054.5 years for more than 4000 years and will continue at least 13,000 more years. [ 6 ]
The period of Hipparchus is also accurate in the sense of always having the same length to within an hour. This is due to the fact that it is close to a whole number of anomalistic years as well as to a whole number of anomalistic months. Its average length is actually 126007.023 days, half an hour less than what Ptolemy says. This is equivalent to 345 Julian years minus 4.227 days (implying that in the Gregorian calendar the date usually goes back by just one or two days, sometimes by three), which is only about 8 days less than 345 anomalistic years. There are few eclipse periods that are so constant – the semester for example (six synodic months) can vary by a day in each direction.
Ptolemy says that Hipparchus also came up with a period of 5458 synodic months, equal to 5923 draconic months (441.3 years). This is called the Hipparchian Period, and more recently the Babylonian Period, but the latter is a misnomer as there is no evidence that the Babylonians were aware of it. [ 4 ] It is equivalent to 14 inex plus 2 saros periods and therefore repeats many more times than the 345-year cycle. The solar eclipse of July 11, 2010 , for example, is the latest in a series that has been going for more than 13,000 years and will continue for more than 8000 more. [ 6 ] | https://en.wikipedia.org/wiki/Hipparchic_cycle |
Hipparcos was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry , the accurate measurement of the positions and distances of celestial objects on the sky. [ 3 ] This permitted the first high-precision measurements of the intrinsic brightnesses , proper motions , and parallaxes of stars, enabling better calculations of their distance and tangential velocity . When combined with radial velocity measurements from spectroscopy , astrophysicists were able to finally measure all six quantities needed to determine the motion of stars. The resulting Hipparcos Catalogue , [ 4 ] a high-precision catalogue of more than 118,200 stars, was published in 1997. The lower-precision Tycho Catalogue of more than a million stars was published at the same time, while the enhanced Tycho-2 Catalogue of 2.5 million stars was published in 2000. Hipparcos ' follow-up mission, Gaia , was launched in 2013.
The word "Hipparcos" is an acronym for HIgh Precision PARallax COllecting Satellite and also a reference to the ancient Greek astronomer Hipparchus of Nicaea, who is noted for applications of trigonometry to astronomy and his discovery of the precession of the equinoxes .
By the second half of the 20th century, the accurate measurement of star positions from the ground was running into essentially insurmountable barriers to improvements in accuracy, especially for large-angle measurements and systematic terms. Problems were dominated by the effects of the Earth 's atmosphere , but were compounded by complex optical terms, thermal and gravitational instrument flexures, and the absence of all-sky visibility. A formal proposal to make these exacting observations from space was first put forward in 1967. [ 5 ]
The mission was originally proposed to the French space agency CNES , which considered it too complex and expensive for a single national programme and recommended that it be proposed in a multinational context. Its acceptance within the European Space Agency 's scientific programme, in 1980, was the result of a lengthy process of study and lobbying . The underlying scientific motivation was to determine the physical properties of the stars through the measurement of their distances and space motions, and thus to place theoretical studies of stellar structure and evolution, and studies of galactic structure and kinematics, on a more secure empirical basis. Observationally, the objective was to provide the positions, parallaxes , and annual proper motions for some 100,000 stars with an unprecedented accuracy of 0.002 arcseconds , a target in practice eventually surpassed by a factor of two. The name of the space telescope, "Hipparcos", was an acronym for High Precision Parallax Collecting Satellite , and it also reflected the name of the ancient Greek astronomer Hipparchus , who is considered the founder of trigonometry and the discoverer of the precession of the equinoxes (due to the Earth wobbling on its axis).
The spacecraft carried a single all-reflective, eccentric Schmidt telescope , with an aperture of 29 cm (11 in). A special beam-combining mirror superimposed two fields of view, 58° apart, into the common focal plane. This complex mirror consisted of two mirrors tilted in opposite directions, each occupying half of the rectangular entrance pupil, and providing an unvignetted field of view of about 1° × 1°. The telescope used a system of grids, at the focal surface, composed of 2688 alternate opaque and transparent bands, with a period of 1.208 arc-sec (8.2 micrometre). Behind this grid system, an image dissector tube ( photomultiplier type detector) with a sensitive field of view of about 38-arc-sec diameter converted the modulated light into a sequence of photon counts (with a sampling frequency of 1200 Hz ) from which the phase of the entire pulse train from a star could be derived. The apparent angle between two stars in the combined fields of view, modulo the grid period, was obtained from the phase difference of the two star pulse trains. Originally targeting the observation of some 100,000 stars, with an astrometric accuracy of about 0.002 arc-sec, the final Hipparcos Catalogue comprised nearly 120,000 stars [ 6 ] : xiii with a median accuracy of slightly better than 0.001 arc-sec (1 milliarc-sec). [ 6 ] : 3
An additional photomultiplier system viewed a beam splitter in the optical path and was used as a star mapper. Its purpose was to monitor and determine the satellite attitude, and in the process, to gather photometric and astrometric data of all stars down to about 11th magnitude. These measurements were made in two broad bands approximately corresponding to B and V in the (Johnson) UBV photometric system . The positions of these latter stars were to be determined to a precision of 0.03 arc-sec, which is a factor of 25 less than the main mission stars. Originally targeting the observation of around 400,000 stars, the resulting Tycho Catalogue comprised just over 1 million stars, with a subsequent analysis extending this to the Tycho-2 Catalogue of about 2.5 million stars.
The attitude of the spacecraft about its center of gravity was controlled to scan the celestial sphere in a regular precessional motion maintaining a constant inclination between the spin axis and the direction to the Sun. The spacecraft spun around its Z-axis at the rate of 11.25 revolutions/day (168.75 arc-sec/s) at an angle of 43° to the Sun . The Z-axis rotated about the Sun-satellite line at 6.4 revolutions/year. [ 7 ]
The spacecraft consisted of two platforms and six vertical panels, all made of aluminum honeycomb. The solar array consisted of three deployable sections, generating around 300 W in total. Two S-band antennas were located on the top and bottom of the spacecraft, providing an omni-directional downlink data rate of 24 kbit/s . An attitude and orbit-control subsystem (comprising 5- newton hydrazine thrusters for course manoeuvres, 20-millinewton cold gas thrusters for attitude control, and gyroscopes for attitude determination) ensured correct dynamic attitude control and determination during the operational lifetime.
Some key features of the observations were as follows: [ 8 ]
The Hipparcos satellite was financed and managed under the overall authority of the European Space Agency (ESA). The main industrial contractors were Matra Marconi Space (now EADS Astrium ) and Alenia Spazio (now Thales Alenia Space ).
Other hardware components were supplied as follows:
Groups from the Institut d'Astrophysique in Liège , Belgium and the Laboratoire d'Astronomie Spatiale in Marseille , France, contributed optical performance, calibration, and alignment test procedures; Captec in Dublin , Ireland, and Logica in London contributed to the on-board software and calibration.
The Hipparcos satellite was launched (with the direct broadcast satellite TV-Sat 2 as co-passenger) on an Ariane 4 launch vehicle , flight V33, from Centre Spatial Guyanais , Kourou , French Guiana, on 8 August 1989. It was launched into a geostationary transfer orbit (GTO), but the Mage-2 apogee kick motor failed to fire, and the intended geostationary orbit was never achieved. However, with the addition of further ground stations, in addition to ESA operations control centre at European Space Operations Centre (ESOC) in Germany, the satellite was successfully operated in GTO for almost 3.5 years. All of the original mission goals were, eventually, exceeded.
Including an estimate for the scientific activities related to the satellite observations and data processing, the Hipparcos mission cost about €600 million (in year 2000 economic conditions), and its execution involved some 200 European scientists and more than 2,000 individuals in European industry.
The satellite observations relied on a pre-defined list of target stars. Stars were observed as the satellite rotated, by a sensitive region of the image dissector tube detector. This pre-defined star list formed the Hipparcos Input Catalogue (HIC): each star in the final Hipparcos Catalogue was contained in the Input Catalogue. [ 9 ] The Input Catalogue was compiled by the INCA Consortium over the period 1982–1989, finalised pre-launch, and published both digitally and in printed form. [ 10 ]
Although fully superseded by the satellite results, it nevertheless includes supplemental information on multiple system components as well as compilations of radial velocities and spectral types which, not observed by the satellite, were not included in the published Hipparcos Catalogue .
Constraints on total observing time, and on the uniformity of stars across the celestial sphere for satellite operations and data analysis, led to an Input Catalogue of some 118,000 stars. It merged
two components: first, a survey of around 58,000 objects as complete as possible to the following limiting magnitudes:
V<7.9 + 1.1sin|b| for spectral types earlier than G5, and
V<7.3 + 1.1sin|b| for spectral types later than G5 (b is the Galactic latitude). Stars constituting this survey are flagged in the Hipparcos Catalogue .
The second component comprised additional stars selected according to their scientific interest, with none fainter than about magnitude V=13 mag. These were selected from around 200 scientific proposals submitted on the basis of an Invitation for Proposals issued by ESA in 1982, and prioritised by the Scientific Proposal Selection Committee in consultation with the Input Catalogue Consortium. This selection had to balance 'a priori' scientific interest, and the observing programme's limiting magnitude, total observing time, and sky uniformity constraints.
For the main mission results, the data analysis was carried out by two independent scientific teams, NDAC and FAST, together comprising some 100 astronomers and scientists, mostly from European (ESA-member state) institutes. The analyses, proceeding from nearly 1000 Gbit of satellite data acquired over 3.5 years, incorporated a comprehensive system of cross-checking and validation, and is described in detail in the published catalogue.
A detailed optical calibration model was included to map the transformation from sky to instrumental coordinates. Its adequacy could be verified by the detailed measurement residuals. The Earth's orbit, and the satellite's orbit with respect to the Earth , were essential for describing the location of the observer at each epoch of observation, and were supplied by an appropriate Earth ephemeris combined with accurate satellite ranging. Corrections due to special relativity ( stellar aberration ) made use of the corresponding satellite velocity. Modifications due to general relativistic light bending were significant (4 milliarc-sec at 90° to the ecliptic) and corrected for deterministically assuming γ=1 in the PPN formalism . Residuals were examined to establish limits on any deviations from this general relativistic value, and no significant discrepancies were found.
The satellite observations essentially yielded highly accurate relative positions of stars with respect to each other, throughout the measurement period (1989–1993). In the absence of direct observations of extragalactic sources (apart from marginal observations of quasar 3C 273 ) the resulting rigid reference frame was transformed to an inertial frame of reference linked to extragalactic sources. This allows surveys at different wavelengths to be directly correlated with the Hipparcos stars, and ensures that the catalogue proper motions are, as far as possible, kinematically non-rotating. The determination of the relevant three solid-body rotation angles, and the three time-dependent rotation rates, was conducted and completed in advance of the catalogue publication. This resulted in an accurate but indirect link to an inertial, extragalactic, reference frame. [ 11 ]
A variety of methods to establish this reference frame link before catalogue publication were included and appropriately weighted: interferometric observations of radio stars by VLBI networks, MERLIN and Very Large Array (VLA); observations of quasars relative to Hipparcos stars using charge-coupled device (CCD), photographic plates, and the Hubble Space Telescope ; photographic programmes to determine stellar proper motions with respect to extragalactic objects (Bonn, Kiev, Lick, Potsdam, Yale/San Juan); and comparison of Earth rotation parameters obtained by Very-long-baseline interferometry (VLBI) and by ground-based optical observations of Hipparcos stars. Although very different in terms of instruments, observational methods and objects involved, the various techniques generally agreed to within 10 milliarc-sec in the orientation and 1 milliarc-sec/year in the rotation of the system. From appropriate weighting, the coordinate axes defined by the published catalogue are believed to be aligned with the extragalactic radio frame to within ±0.6 milliarc-sec at the epoch J1991.25, and non-rotating with respect to distant extragalactic objects to within ±0.25 milliarc-sec/yr. [ 8 ] : 10
The Hipparcos and Tycho Catalogues were then constructed such that the resulting Hipparcos celestial reference frame (HCRF) coincides, to within observational uncertainties, with the International Celestial Reference Frame (ICRF), and representing the best estimates at the time of the catalogue completion (in 1996). The HCRF is thus a materialisation of the International Celestial Reference System (ICRS) in the optical domain. It extends and improves the J2000 ( FK5 ) system, retaining approximately the global orientation of that system but without its regional errors. [ 8 ] : 10
Whilst of enormous astronomical importance, double stars and multiple stars provided considerable complications to the observations (due to the finite size and profile of the detector's sensitive field of view) and to the data analysis. The data processing classified the astrometric solutions as follows:
If a binary star has a long orbital period such that non-linear motions of the photocentre were insignificant over the short (3-year) measurement duration, the binary nature of the star would pass unrecognised by Hipparcos , but could show as a Hipparcos proper motion discrepant compared to those established from long temporal baseline proper motion programmes on ground. Higher-order photocentric motions could be represented by a 7-parameter, or even 9-parameter model fit (compared to the standard 5-parameter model), and typically such models could be enhanced in complexity until suitable fits were obtained. A complete orbit, requiring 7 elements, was determined for 45 systems. Orbital periods close to one year can become degenerate with the parallax, resulting in unreliable solutions for both. Triple or higher-order systems provided further challenges to the data processing.
The highest accuracy photometric data were provided as a by-product of the main mission astrometric observations. They were made in a broad-band visible light passband , specific to Hipparcos , and designated H p . [ 12 ] The median photometric precision, for H p <9 magnitude, was 0.0015 magnitude , with typically 110 distinct observations per star throughout the 3.5-year observation period. As part of the data reduction and catalogue production, new variables were identified and designated with appropriate variable star designations . Variable stars were classified as periodic or unsolved variables; the former were published with estimates of their period, variability amplitude, and variability type. In total some 11,597 variable objects were detected, of which 8,237 were newly classified as variable. There are, for example, 273 Cepheid variables , 186 RR Lyrae variables , 108 Delta Scuti variables , and 917 eclipsing binary stars . The star mapper observations, constituting the Tycho (and Tycho-2) Catalogue, provided two colours, roughly B and V in the Johnson UBV photometric system , important for spectral classification and effective temperature determination.
Classical astrometry concerns only motions in the plane of the sky and ignores the star's radial velocity , i.e. its space motion along the line-of-sight. Whilst critical for an understanding of stellar kinematics, and hence population dynamics, its effect is generally imperceptible to astrometric measurements (in the plane of the sky), and therefore it is generally ignored in large-scale astrometric surveys. In practice, it can be measured as a Doppler shift of the spectral lines. More strictly, however, the radial velocity does enter a rigorous astrometric formulation. Specifically, a space velocity along the line-of-sight means that the transformation from tangential linear velocity to (angular) proper motion is a function of time. The resulting effect of secular or perspective acceleration is the interpretation of a transverse acceleration actually arising from a purely linear space velocity with a significant radial component, with the positional effect proportional to the product of the parallax, the proper motion, and the radial velocity. At the accuracy levels of Hipparcos it is of (marginal) importance only for the nearest stars with the largest radial velocities and proper motions, but was accounted for in the 21 cases for which the accumulated positional effect over two years exceeds 0.1 milliarc-sec. Radial velocities for Hipparcos Catalogue stars, to the extent that they are presently known from independent ground-based surveys, can be found from the astronomical database of the Centre de données astronomiques de Strasbourg .
The absence of reliable distances for the majority of stars means that the angular measurements made, astrometrically, in the plane of the sky, cannot generally be converted into true space velocities in the plane of the sky. For this reason, astrometry characterises the transverse motions of stars in angular measure (e.g. arcsec per year) rather than in km/s or equivalent. Similarly, the typical absence of reliable radial velocities means that the transverse space motion (when known) is, in any case, only a component of the complete, three-dimensional, space velocity.
The final Hipparcos Catalogue was the result of the critical comparison and merging of the two (NDAC and FAST consortia) analyses, and contains 118,218 entries (stars or multiple stars), corresponding to an average of some three stars per square degree over the entire sky. [ 13 ] Median precision of the five astrometric parameters (Hp<9 magnitude) exceeded the original mission goals, and are between 0.6 and 1.0 mas. Some 20,000 distances were determined to better than 10%, and 50,000 to better than 20%. The inferred ratio of external to standard errors is ≈1.0–1.2, and estimated systematic errors are below 0.1 mas. The number of solved or suspected double or multiple stars is 23,882. [ 14 ] Photometric observations yielded multi-epoch photometry with a mean number of 110 observations per star, and a median photometric precision (Hp<9 magnitude) of 0.0015 magnitude, with 11,597 entries were identified as variable or possibly-variable. [ 15 ]
For the star mapper results, the data analysis was carried out by the Tycho Data Analysis Consortium (TDAC). The Tycho Catalogue comprises more than one million stars with 20–30 milliarc-sec astrometry and two-colour (B and V band) photometry. [ 16 ]
The final Hipparcos and Tycho Catalogues were completed in August 1996. The catalogues were published by European Space Agency (ESA) on behalf of the scientific teams in June 1997. [ 17 ]
A more extensive analysis of the star mapper (Tycho) data extracted additional faint stars from the data stream. Combined with old photographic plate observations made several decades earlier as part of the Astrographic Catalogue programme, the Tycho-2 Catalogue of more than 2.5 million stars (and fully superseding the original Tycho Catalogue) was published in 2000. [ 18 ]
The Hipparcos and Tycho-1 Catalogues were used to create the Millennium Star Atlas : an all-sky atlas of one million stars to visual magnitude 11. Some 10,000 nonstellar objects are also included to complement the catalogue data. [ 19 ]
Between 1997 and 2007, investigations into subtle effects in the satellite attitude and instrument calibration continued. A number of effects in the data that had not been fully accounted for were studied, such as scan-phase discontinuities and micrometeoroid-induced attitude jumps. A re-reduction of the associated steps of the analysis was eventually undertaken. [ 20 ]
This has led to improved astrometric accuracies for stars brighter than Hp=9.0 magnitude, reaching a factor of about three for the brightest stars (Hp<4.5 magnitude), while also underlining the conclusion that the Hipparcos Catalogue as originally published is generally reliable within the quoted accuracies.
All catalogue data are available online from the Centre de données astronomiques de Strasbourg .
The Hipparcos results have affected a very broad range of astronomical research, which can be classified into three major themes:
Associated with these major themes, Hipparcos has provided results in topics as diverse as Solar System science, including mass determinations of asteroids, Earth's rotation and Chandler wobble ; the internal structure of white dwarfs ; the masses of brown dwarfs ; the characterisation of extra-solar planets and their host stars; the height of the Sun above the Galactic mid-plane; the age of the Universe ; the stellar initial mass function and star formation rates; and strategies for the search for extraterrestrial intelligence . The high-precision multi-epoch photometry has been used to measure variability and stellar pulsations in many classes of objects. The Hipparcos and Tycho catalogues are now routinely used to point ground-based telescopes, navigate space missions, and drive public planetaria.
Since 1997, several thousand scientific papers have been published making use of the Hipparcos and Tycho catalogues. A detailed review of the Hipparcos scientific literature between 1997 and 2007 was published in 2009, [ 21 ] and a popular account of the project in 2010. [ 3 ] Some examples of notable results include (listed chronologically):
One controversial result has been the derived proximity, at about 120 parsecs, of the Pleiades cluster, established both from the original catalogue [ 48 ] as well as from the revised analysis. [ 20 ] This has been contested by various other recent work, placing the mean cluster distance at around 130 parsecs. [ 49 ] [ 50 ] [ 51 ] [ 52 ]
According to a 2012 paper, the anomaly was due to the use of a weighted mean when there is a correlation between distances and distance errors for stars in clusters. It is resolved by using an unweighted mean. There is no systematic bias in the Hipparcos data when it comes to star clusters. [ 53 ]
In August 2014, the discrepancy between the cluster distance of 120.2 ± 1.5 parsecs (pc) as measured by Hipparcos and the distance of 133.5 ± 1.2 pc derived with other techniques was confirmed by parallax measurements made using VLBI , [ 54 ] which gave 136.2 ± 1.2 pc , the most accurate and precise distance yet presented for the cluster.
Another distance debate set-off by Hipparcos is for the distance to the star Polaris.
Hipparcos data is recently being used together with Gaia data. Especially the comparison of the proper motion of stars from both spacecraft is being used to search for hidden binary companions. [ 55 ] [ 56 ] Hipparcos-Gaia data is also used to measure the dynamical mass of known binaries, such as substellar companions. [ 57 ] Hipparcos-Gaia data was used to measure the mass of the exoplanet Beta Pictoris b and is sometimes used to study other long-period exoplanets , such as HR 5183 b . [ 58 ] [ 59 ] | https://en.wikipedia.org/wiki/Hipparcos |
The Hippo signaling pathway , also known as the Salvador-Warts-Hippo ( SWH ) pathway , is a signaling pathway that controls organ size in animals through the regulation of cell proliferation and apoptosis . The pathway takes its name from one of its key signaling components—the protein kinase Hippo (Hpo). Mutations in this gene lead to tissue overgrowth, or a " hippopotamus "-like phenotype .
A fundamental question in developmental biology is how an organ knows to stop growing after reaching a particular size. Organ growth relies on several processes occurring at the cellular level, including cell division and programmed cell death (or apoptosis). The Hippo signaling pathway is involved in restraining cell proliferation and promoting apoptosis. As many cancers are marked by unchecked cell division, this signaling pathway has become increasingly significant in the study of human cancer . [ 1 ] The Hippo pathway also has a critical role in stem cell and tissue specific progenitor cell self-renewal and expansion. [ 2 ]
The Hippo signaling pathway appears to be highly conserved . While most of the Hippo pathway components were identified in the fruit fly ( Drosophila melanogaster ) using mosaic genetic screens , orthologs to these components (genes that are related through speciation events and thus tend to retain the same function in different species ) have subsequently been found in mammals . Thus, the delineation of the pathway in Drosophila has helped to identify many genes that function as oncogenes or tumor suppressors in mammals.
The Hippo pathway consists of a core kinase cascade in which Hpo phosphorylates (Drosophila) the protein kinase Warts (Wts). [ 3 ] [ 4 ] Hpo (MST1/2 in mammals) is a member of the Ste-20 family of protein kinases. This highly conserved group of serine/threonine kinases regulates several cellular processes, including cell proliferation, apoptosis, and various stress responses. [ 5 ] Once phosphorylated, Wts ( LATS1 /2 in mammals) becomes active. Misshapen (Msn, MAP4K4/6/7 in mammals) and Happyhour (Hppy, MAP4K1/2/3/5 in mammals) act in parallel to Hpo to activate Wts. [ 6 ] [ 7 ] [ 8 ] Wts is a nuclear DBF-2-related kinase. These kinases are known regulators of cell cycle progression, growth, and development. [ 9 ] Two proteins are known to facilitate the activation of Wts: Salvador (Sav) and Mob as tumor suppressor (Mats). Sav ( SAV1 in mammals) is a WW domain -containing protein, meaning that this protein contains a sequence of amino acids in which a tryptophan and an invariant proline are highly conserved. [ 10 ] Hpo can bind to and phosphorylate Sav, which may function as a scaffold protein because this Hpo-Sav interaction promotes phosphorylation of Wts. [ 11 ] Hpo can also phosphorylate and activate Mats (MOBKL1A/B in mammals), which allows Mats to associate with and strengthen the kinase activity of Wts. [ 12 ]
Activated Wts can then go on to phosphorylate and inactivate the transcriptional coactivator Yorkie (Yki). Yki is unable to bind DNA by itself. In its active state, Yki binds to the transcription factor Scalloped (Sd), and the Yki-Sd complex becomes localized to the nucleus. This allows for the expression of several genes that promote organ growth, such as cyclin E , which promotes cell cycle progression, and diap1 ( Drosophila inhibitor of apoptosis protein-1), which, as its name suggests, prevents apoptosis. [ 13 ] Yki also activates expression of the bantam microRNA , a positive growth regulator that specifically affects cell number. [ 14 ] [ 15 ] Thus, the inactivation of Yki by Wts inhibits growth through the transcriptional repression of these pro-growth regulators. By phosphorylating Yki at serine 168, Wts promotes the association of Yki with 14-3-3 proteins , which help to anchor Yki in the cytoplasm and prevent its transport to the nucleus. In mammals, the two Yki orthologs are Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif ( WWTR1, also known as TAZ ). [ 16 ] When activated, YAP and TAZ can bind to several transcription factors including p73 , Runx2 and several TEADs. [ 17 ] YAP regulates the expression of Hoxa1 and Hoxc13 in mouse and human epithelial cells in vivo and in vitro. [ 18 ]
The upstream regulators of the core Hpo/Wts kinase cascade include the transmembrane protein Fat and several membrane-associated proteins. As an atypical cadherin , Fat (FAT1-4 in mammals) may function as a receptor, though an extracellular ligand has not been positively identified. The GPI -anchored cell surface protein glypican-3 (GPC3) is known to interact with Fat1 in human liver cancer. [ 19 ] GPC3 is also shown to modulate Yap signaling in liver cancer. [ 20 ] While Fat is known to bind to another atypical cadherin, Dachsous (Ds), during tissue patterning, [ 21 ] it is unclear what role Ds has in regulating tissue growth. Nevertheless, Fat is recognized as an upstream regulator of the Hpo pathway. Fat activates Hpo through the apical protein Expanded (Ex; FRMD6/Willin in mammals). Ex interacts with two other apically-localized proteins, Kibra ( KIBRA in mammals) and Merlin (Mer; NF2 in mammals), to form the Kibra-Ex-Mer (KEM) complex. Both Ex and Mer are FERM domain -containing proteins, while Kibra, like Sav, is a WW domain-containing protein. [ 22 ] The KEM complex physically interacts with the Hpo kinase cascade, thereby localizing the core kinase cascade to the plasma membrane for activation. [ 23 ] Fat may also regulate Wts independently of Ex/Hpo, through the inhibition of the unconventional myosin Dachs. Normally, Dachs can bind to and promote the degradation of Wts. [ 24 ]
In fruitfly, the Hippo signaling pathway involves a kinase cascade involving the Salvador (Sav), Warts (Wts) and Hippo (Hpo) protein kinases . [ 25 ] Many of the genes involved in the Hippo signaling pathway are recognized as tumor suppressors , while Yki/YAP/TAZ is identified as an oncogene . YAP/TAZ can reprogram cancer cells into cancer stem cells . [ 26 ] YAP has been found to be elevated in some human cancers, including breast cancer , colorectal cancer , and liver cancer . [ 27 ] [ 28 ] [ 29 ] This may be explained by YAP’s recently defined role in overcoming contact inhibition , a fundamental growth control property of normal cells in vitro and in vivo , in which proliferation stops after cells reach confluence [ 30 ] (in culture) or occupy maximum available space inside the body and touch one another. This property is typically lost in cancerous cells, allowing them to proliferate in an uncontrolled manner. [ 31 ] In fact, YAP overexpression antagonizes contact inhibition. [ 32 ]
Many of the pathway components recognized as tumor suppressor genes are mutated in human cancers. For example, mutations in Fat4 have been found in breast cancer, [ 33 ] while NF2 is mutated in familial and sporadic schwannomas . [ 34 ] Additionally, several human cancer cell lines invoke mutations of the SAV1 and MOBK1B proteins. [ 35 ] [ 36 ] However, recent research by Marc Kirschner and Taran Gujral has demonstrated that Hippo pathway components may play a more nuanced role in cancer than previously thought. Hippo pathway inactivation enhanced the effect of 15 FDA-approved oncology drugs by promoting chemo-retention. [ 37 ] In another study, the Hippo pathway kinases LATS1/2 were found to suppress cancer immunity in mice. [ 38 ] Not all studies, however, support a role for Hippo signaling in promoting carcinogenesis. In hepatocellular carcinoma , for instance, it was suggesting that AXIN1 mutations would provoke Hippo signaling pathway activation, fostering the cancer development, but a recent study demonstrated that such an effect cannot be detected. [ 39 ] Thus the exact role of Hippo signaling in the cancer process awaits further elucidation.
Two venture-backed oncology startups, Vivace Therapeutics and the General Biotechnologies subsidiary Nivien Therapeutics, are actively developing kinase inhibitors targeting the Hippo pathway. [ 40 ]
The heart is the first organ formed during mammalian development. A properly sized and functional heart is vital throughout the entire lifespan. Loss of cardiomyocytes because of injury or diseases leads to heart failure, which is a major cause of human morbidity and mortality. Unfortunately, regenerative potential of the adult heart is limited. The Hippo pathway is a recently identified signaling cascade that plays an evolutionarily conserved role in organ size control by inhibiting cell proliferation, promoting apoptosis, regulating fates of stem/progenitor cells, and in some circumstances, limiting cell size. Research indicates a key role of this pathway in regulation of cardiomyocyte proliferation and heart size. Inactivation of the Hippo pathway or activation of its downstream effector, the Yes-associated protein transcription coactivator, improves cardiac regeneration. Several known upstream signals of the Hippo pathway such as mechanical stress, G-protein-coupled receptor signaling, and oxidative stress are known to play critical roles in cardiac physiology. In addition, Yes-associated protein has been shown to regulate cardiomyocyte fate through multiple transcriptional mechanisms. [ 41 ] [ 42 ] [ 43 ]
Note that Hippo TAZ protein is often confused with the gene TAZ, which is unrelated to the Hippo pathway. The gene TAZ produces the protein tafazzin. The official gene name for the Hippo TAZ protein is WWTR1. Also, the official names for MST1 and MST2 are STK4 and STK3, respectively. All databases for bioinformatics use the official gene symbols, and commercial sources for PCR primers or siRNA also go by the official gene names. | https://en.wikipedia.org/wiki/Hippo_signaling_pathway |
A Hippocratic Oath for scientists is an oath similar to the Hippocratic Oath for medical professionals, adapted for scientists. Multiple varieties of such an oath have been proposed. Joseph Rotblat has suggested that an oath would help make new scientists aware of their social and moral responsibilities; [ 1 ] opponents, however, have pointed to the "very serious risks for the scientific community" posed by an oath, particularly the possibility that it might be used to shut down certain avenues of research, such as stem cells . [ 2 ]
The idea of an oath has been proposed by various prominent members of the scientific community, including Karl Popper , Joseph Rotblat and John Sulston . Research by the American Association for the Advancement of Science (AAAS) identified sixteen different oaths for scientists or engineers proposed during the 20th century, most after 1970. [ 2 ]
Popper, Rotblat and Sulston were all primarily concerned with the ethical implications of scientific advances, in particular for Popper and Rotblat the development of the atomic bomb , and believed that scientist, like medics, should have an oath that compelled them to " first do no harm ". Popper said: "Formerly the pure scientist or the pure scholar had only one responsibility beyond those which everybody has; that is, to search for the truth. … This happy situation belongs to the past." [ 3 ] Rotblat similarly stated: "Scientists can no longer claim that their work has nothing to do with the welfare of the individual or with state policies." He also attacked the attitude that the only obligation of a scientist is to make their results known, the use made of these results being the public's business, saying: "This amoral attitude is in my opinion actually immoral, because it eschews personal responsibility for the likely consequences of one's actions." [ 1 ] Sulston was more concerned with rising public distrust of scientists and conflicts of interest brought about by the exploitation of research for profit. The stated intention of his oath was "both to require qualified scientists to cause no harm and to be wholly truthful in their public pronouncements, and also to protect them from discrimination by employers who might prefer them to be economical with the truth." [ 4 ]
The concept of an oath, rather than a more detailed code of conduct , has been opposed by Ray Spier, Professor of Science and Engineering Ethics at the University of Surrey , UK, who stated that "Oaths are not the way ahead". [ 4 ] Other objections raised at a AAAS meeting on the topic in 2000 included that an oath would simply make scientists look good without changing behaviour, that an oath could be used to suppress research, that some scientists would refuse to swear any oath as a matter of principle, that an oath would be ineffective, that creation of knowledge is separate from how it is used, and that the scientific community could never agree on the content of an oath. The meeting concluded that: "There was a broadly shared consensus that a tolerant (but not patronizing) attitude should be taken towards those developing oaths, but that an oath posed very serious risks for the scientific community which could not be ignored." [ 2 ] Nobel laureate Jean-Marie Lehn has said "The first aim of scientific research is to increase knowledge for understanding. Knowledge is then available to mankind for use, namely to progress as well as to help prevent disease and suffering. Any knowledge can be misused. I do not see the need for an oath". [ 5 ]
Some of the propositions are outlined below.
In 1968, the philosopher Karl Popper gave a talk on "The Moral Responsibility of the Scientist" at the International Congress on Philosophy in Vienna, in which he suggested "an undertaking analogous to the Hippocratic oath". In his analysis he noted that the original oath had three sections: the apprentice's obligation to their teacher; the obligation to carry on the high tradition of their art, preserve its high standards, and pass these standards on to their own students; and the obligation to help the suffering and preserve their confidentiality. He also noted that it was an apprentice's oath, as distinct from a graduation oath. Based on this, he proposed a three-section oath for students, rearranged from the Hippocratic oath to give professional responsibility to further the growth of knowledge; the student , who owes respect to others engaged in science and loyalty to teachers; and the overriding loyalty owed to humanity as a whole. [ 3 ]
The idea of a Hippocratic Oath for scientists was raised again by Joseph Rotblat in his acceptance speech for the Nobel Peace Prize in 1995, [ 6 ] who later expanded on the idea, endorsing the formulation of the Student Pugwash Group: [ 1 ]
I promise to work for a better world, where science and technology are used in socially responsible ways. I will not use my education for any purpose intended to harm human beings or the environment. Throughout my career, I will consider the ethical implications of my work before I take action. While the demands placed upon me may be great, I sign this declaration because I recognize that individual responsibility is the first step on the path to peace.
In 2001, in the scientific journal Biochemical Journal , Nobel laureate John Sulston proposed that "For individual scientists, it may be helpful to have a clear professional code of conduct – a Hippocratic oath as it were". This path would enable scientists to declare their intention "to cause no harm and to be wholly truthful in their public pronouncements", and would also serve to protect them from unethical employers. The concept of an oath was opposed by Ray Spiers of the University of Surrey , an expert on scientific ethics who was preparing a 20-point code of conduct at the time. [ 4 ]
In 2007, the UK government's chief scientific advisor, David King , presented a "Universal Ethical Code for Scientists" at the British Association 's Festival of Science in York. Despite being a code rather than an oath, this was widely reported as a Hippocratic oath for scientists. [ 7 ] [ 8 ] [ 9 ] In contrast to the earlier oaths, King's code was not only intended to meet the public demand that "scientific developments are ethical and serve the wider public good" but also to address public confidence in the integrity of science, which had been shaken by the disgrace of cloning pioneer Hwang Woo-suk and by other research-fraud scandals. [ 10 ]
Work on the code started in 2005, following a meeting of G8 science ministers and advisors. It was supported by the Royal Society in its response to a public consultation on the draft code in 2006, where they said it would help whistleblowers and the promotion of science in schools. [ 11 ]
The code has seven principles, divided into three sections: [ 12 ]
Rigour
Respect
Responsibility | https://en.wikipedia.org/wiki/Hippocratic_Oath_for_scientists |
In mathematics, Hiptmair–Xu (HX) preconditioners [ 1 ] are preconditioners for solving H ( curl ) {\displaystyle H(\operatorname {curl} )} and H ( div ) {\displaystyle H(\operatorname {div} )} problems based on the auxiliary space preconditioning framework. [ 2 ] An important ingredient in the derivation of HX preconditioners in two and three dimensions is the so-called regular decomposition, which decomposes a Sobolev space function into a component of higher regularity and a scalar or vector potential. The key to the success of HX preconditioners is the discrete version of this decomposition, which is also known as HX decomposition. The discrete decomposition decomposes a discrete Sobolev space function into a discrete component of higher regularity, a discrete scale or vector potential, and a high-frequency component.
HX preconditioners have been used for accelerating a wide variety of solution techniques, thanks to their highly scalable parallel implementations, and are known as AMS [ 3 ] and ADS [ 4 ] precondition. HX preconditioner was identified by the U.S. Department of Energy as one of the top ten breakthroughs in computational science [ 5 ] in recent years. Researchers from Sandia, Los Alamos, and Lawrence Livermore National Labs use this algorithm for modeling fusion with magnetohydrodynamic equations. [ 6 ] Moreover, this approach will also be instrumental in developing optimal iterative methods in structural mechanics, electrodynamics, and modeling of complex flows.
Consider the following H ( curl ) {\displaystyle H(\operatorname {curl} )} problem: Find u ∈ H h ( curl ) {\displaystyle u\in H_{h}(\operatorname {curl} )} such that
( curl u , curl v ) + τ ( u , v ) = ( f , v ) , ∀ v ∈ H h ( curl ) , {\displaystyle (\operatorname {curl} ~u,\operatorname {curl} ~v)+\tau (u,v)=(f,v),\quad \forall v\in H_{h}(\operatorname {curl} ),} with τ > 0 {\displaystyle \tau >0} .
The corresponding matrix form is
A curl u = f . {\displaystyle A_{\operatorname {curl} }u=f.}
The HX preconditioner for H ( curl ) {\displaystyle H(\operatorname {curl} )} problem is defined as
B curl = S curl + Π h curl A v g r a d − 1 ( Π h curl ) T + grad A grad − 1 ( grad ) T , {\displaystyle B_{\operatorname {curl} }=S_{\operatorname {curl} }+\Pi _{h}^{\operatorname {curl} }\,A_{vgrad}^{-1}\,(\Pi _{h}^{\operatorname {curl} })^{T}+\operatorname {grad} \,A_{\operatorname {grad} }^{-1}\,(\operatorname {grad} )^{T},}
where S curl {\displaystyle S_{\operatorname {curl} }} is a smoother (e.g., Jacobi smoother, Gauss–Seidel smoother), Π h curl {\displaystyle \Pi _{h}^{\operatorname {curl} }} is the canonical interpolation operator for H h ( curl ) {\displaystyle H_{h}(\operatorname {curl} )} space, A v g r a d {\displaystyle A_{vgrad}} is the matrix representation of discrete vector Laplacian defined on [ H h ( grad ) ] n {\displaystyle [H_{h}(\operatorname {grad} )]^{n}} , g r a d {\displaystyle grad} is the discrete gradient operator, and A grad {\displaystyle A_{\operatorname {grad} }} is the matrix representation of the discrete scalar Laplacian defined on H h ( grad ) {\displaystyle H_{h}(\operatorname {grad} )} . Based on auxiliary space preconditioning framework, one can show that
κ ( B curl A curl ) ≤ C , {\displaystyle \kappa (B_{\operatorname {curl} }A_{\operatorname {curl} })\leq C,}
where κ ( A ) {\displaystyle \kappa (A)} denotes the condition number of matrix A {\displaystyle A} .
In practice, inverting A v g r a d {\displaystyle A_{vgrad}} and A g r a d {\displaystyle A_{grad}} might be expensive, especially for large scale problems. Therefore, we can replace their inversion by spectrally equivalent approximations, B v g r a d {\displaystyle B_{vgrad}} and B grad {\displaystyle B_{\operatorname {grad} }} , respectively. And the HX preconditioner for H ( curl ) {\displaystyle H(\operatorname {curl} )} becomes B curl = S curl + Π h curl B v g r a d ( Π h curl ) T + grad B grad ( grad ) T . {\displaystyle B_{\operatorname {curl} }=S_{\operatorname {curl} }+\Pi _{h}^{\operatorname {curl} }\,B_{vgrad}\,(\Pi _{h}^{\operatorname {curl} })^{T}+\operatorname {grad} B_{\operatorname {grad} }(\operatorname {grad} )^{T}.}
Consider the following H ( div ) {\displaystyle H(\operatorname {div} )} problem: Find u ∈ H h ( div ) {\displaystyle u\in H_{h}(\operatorname {div} )}
( div u , div v ) + τ ( u , v ) = ( f , v ) , ∀ v ∈ H h ( div ) , {\displaystyle (\operatorname {div} \,u,\operatorname {div} \,v)+\tau (u,v)=(f,v),\quad \forall v\in H_{h}(\operatorname {div} ),} with τ > 0 {\displaystyle \tau >0} .
The corresponding matrix form is
A div u = f . {\displaystyle A_{\operatorname {div} }\,u=f.}
The HX preconditioner for H ( div ) {\displaystyle H(\operatorname {div} )} problem is defined as
B div = S div + Π h div A v g r a d − 1 ( Π h div ) T + curl A curl − 1 ( curl ) T , {\displaystyle B_{\operatorname {div} }=S_{\operatorname {div} }+\Pi _{h}^{\operatorname {div} }\,A_{vgrad}^{-1}\,(\Pi _{h}^{\operatorname {div} })^{T}+\operatorname {curl} \,A_{\operatorname {curl} }^{-1}\,(\operatorname {curl} )^{T},}
where S div {\displaystyle S_{\operatorname {div} }} is a smoother (e.g., Jacobi smoother, Gauss–Seidel smoother), Π h div {\displaystyle \Pi _{h}^{\operatorname {div} }} is the canonical interpolation operator for H ( div ) {\displaystyle H(\operatorname {div} )} space, A v g r a d {\displaystyle A_{vgrad}} is the matrix representation of discrete vector Laplacian defined on [ H h ( grad ) ] n {\displaystyle [H_{h}(\operatorname {grad} )]^{n}} , and curl {\displaystyle \operatorname {curl} } is the discrete curl operator.
Based on the auxiliary space preconditioning framework, one can show that
κ ( B div A div ) ≤ C . {\displaystyle \kappa (B_{\operatorname {div} }A_{\operatorname {div} })\leq C.}
For A curl − 1 {\displaystyle A_{\operatorname {curl} }^{-1}} in the definition of B div {\displaystyle B_{\operatorname {div} }} , we can replace it by the HX preconditioner for H ( curl ) {\displaystyle H(\operatorname {curl} )} problem, e.g., B curl {\displaystyle B_{\operatorname {curl} }} , since they are spectrally equivalent. Moreover, inverting A v g r a d {\displaystyle A_{vgrad}} might be expensive and we can replace it by a spectrally equivalent approximations B v g r a d {\displaystyle B_{vgrad}} . These leads to the following practical HX preconditioner for H ( div ) {\displaystyle H(\operatorname {div} )} problem,
B div = S div + Π h div B v g r a d ( Π h div ) T + curl B curl ( curl ) T = S div + Π h div B v g r a d ( Π h div ) T + curl S curl ( curl ) T + curl Π h curl B v g r a d ( Π h curl ) T ( curl ) T . {\displaystyle B_{\operatorname {div} }=S_{\operatorname {div} }+\Pi _{h}^{\operatorname {div} }B_{vgrad}(\Pi _{h}^{\operatorname {div} })^{T}+\operatorname {curl} B_{\operatorname {curl} }(\operatorname {curl} )^{T}=S_{\operatorname {div} }+\Pi _{h}^{\operatorname {div} }B_{vgrad}(\Pi _{h}^{\operatorname {div} })^{T}+\operatorname {curl} S_{\operatorname {curl} }(\operatorname {curl} )^{T}+\operatorname {curl} \Pi _{h}^{\operatorname {curl} }B_{vgrad}(\Pi _{h}^{\operatorname {curl} })^{T}(\operatorname {curl} )^{T}.}
The derivation of HX preconditioners is based on the discrete regular decompositions for H h ( curl ) {\displaystyle H_{h}(\operatorname {curl} )} and H h ( div ) {\displaystyle H_{h}(\operatorname {div} )} , for the completeness, let us briefly recall them.
Theorem: [Discrete regular decomposition for H h ( curl ) {\displaystyle H_{h}(\operatorname {curl} )} ]
Let Ω {\displaystyle \Omega } be a simply connected bounded domain. For any function v h ∈ H h ( curl Ω ) {\displaystyle v_{h}\in H_{h}(\operatorname {curl} \Omega )} , there exists a vector v ~ h ∈ H h ( curl Ω ) {\displaystyle {\tilde {v}}_{h}\in H_{h}(\operatorname {curl} \Omega )} , ψ h ∈ [ H h ( grad Ω ) ] 3 {\displaystyle \psi _{h}\in [H_{h}(\operatorname {grad} \Omega )]^{3}} , p h ∈ H h ( grad Ω ) {\displaystyle p_{h}\in H_{h}(\operatorname {grad} \Omega )} , such that v h = v ~ h + Π h curl ψ h + grad p h {\displaystyle v_{h}={\tilde {v}}_{h}+\Pi _{h}^{\operatorname {curl} }\psi _{h}+\operatorname {grad} p_{h}} and ‖ h − 1 v ~ h ‖ + ‖ ψ h ‖ 1 + ‖ p h ‖ 1 ≲ ‖ v h ‖ H ( curl ) {\displaystyle \Vert h^{-1}{\tilde {v}}_{h}\Vert +\Vert \psi _{h}\Vert _{1}+\Vert p_{h}\Vert _{1}\lesssim \Vert v_{h}\Vert _{H(\operatorname {curl} )}}
Theorem: [Discrete regular decomposition for H h ( div ) {\displaystyle H_{h}(\operatorname {div} )} ]
Let Ω {\displaystyle \Omega } be a simply connected bounded domain. For any function v h ∈ H h ( div Ω ) {\displaystyle v_{h}\in H_{h}(\operatorname {div} \Omega )} , there exists a vector v ~ h ∈ H h ( div Ω ) {\displaystyle {\widetilde {v}}_{h}\in H_{h}(\operatorname {div} \Omega )} , ψ h ∈ [ H h ( grad Ω ) ] 3 , {\displaystyle \psi _{h}\in [H_{h}(\operatorname {grad} \Omega )]^{3},} w h ∈ H h ( curl Ω ) , {\displaystyle w_{h}\in H_{h}(\operatorname {curl} \Omega ),} such that v h = v ~ h + Π h div ψ h + curl w h , {\displaystyle v_{h}={\widetilde {v}}_{h}+\Pi _{h}^{\operatorname {div} }\psi _{h}+\operatorname {curl} \,w_{h},} and ‖ h − 1 v ~ h ‖ + ‖ ψ h ‖ 1 + ‖ w h ‖ 1 ≲ ‖ v h ‖ H ( div ) {\displaystyle \Vert h^{-1}{\widetilde {v}}_{h}\Vert +\Vert \psi _{h}\Vert _{1}+\Vert w_{h}\Vert _{1}\lesssim \Vert v_{h}\Vert _{H(\operatorname {div} )}}
Based on the above discrete regular decompositions, together with the auxiliary space preconditioning framework, we can derive the HX preconditioners for H ( curl ) {\displaystyle H(\operatorname {curl} )} and H ( div ) {\displaystyle H(\operatorname {div} )} problems as shown before. | https://en.wikipedia.org/wiki/Hiptmair–Xu_preconditioner |
The Hirao coupling (also called the Hirao reaction or the Hirao cross-coupling ) is the chemical reaction involving the palladium - catalyzed cross-coupling of a dialkyl phosphite and an aryl halide to form a phosphonate . [ 1 ] [ 2 ] [ 3 ] This reaction is named after Toshikazu Hirao and is related to the Michaelis–Arbuzov reaction . In contrast to the classic Michaelis–Arbuzov reaction, which is limited to alkyl phosphonates, the Hirao coupling can also deliver aryl phosphonates.
This chemical reaction article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Hirao_coupling |
In mathematics , especially in the study of infinite groups , the Hirsch–Plotkin radical is a subgroup describing the normal locally nilpotent subgroups of the group. It was named by Gruenberg (1961) after Kurt Hirsch and Boris I. Plotkin, who proved that the join of normal locally nilpotent subgroups is locally nilpotent; this fact is the key ingredient in its construction. [ 1 ] [ 2 ] [ 3 ]
The Hirsch–Plotkin radical is defined as the subgroup generated by the union of the normal locally nilpotent subgroups (that is, those normal subgroups such that every finitely generated subgroup is nilpotent). The Hirsch–Plotkin radical is itself a locally nilpotent normal subgroup, so is the unique largest such. [ 4 ] In a finite group, the Hirsch–Plotkin radical coincides with the Fitting subgroup but for
infinite groups the two subgroups can differ. [ 5 ] The subgroup generated by the union of infinitely many normal nilpotent subgroups need not itself be nilpotent, [ 6 ] so the Fitting subgroup must be modified in this case. [ 7 ]
This algebra -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Hirsch–Plotkin_radical |
A polyhistidine-tag , best known by the trademarked name His-tag , is an amino acid motif in proteins that typically consists of at least six histidine ( His ) residues, often at the N- or C-terminus of the protein. It is also known as a hexa histidine-tag , 6xHis-tag , or His6 tag . The tag was invented by Roche , [ 1 ] although the use of histidines and its vectors are distributed by Qiagen . Various purification kits for histidine-tagged proteins are commercially available from multiple companies. [ 2 ]
The total number of histidine residues may vary in the tag from as low as two, to as high as 10 or more His residues. N- or C-terminal His-tags may also be followed or preceded, respectively, by a suitable amino acid sequence that facilitates removal of the polyhistidine-tag using endopeptidases . This extra sequence is not necessary if exopeptidases are used to remove N-terminal His-tags (e.g., Qiagen TAGZyme). Furthermore, exopeptidase cleavage may solve the unspecific cleavage observed when using endoprotease-based tag removal. Polyhistidine-tags are often used for affinity purification of genetically modified proteins.
Proteins can coordinate metal ions on their surface and it is possible to separate proteins using chromatography by making use of the difference in their affinity to metal ions. This is termed as immobilized metal ion affinity chromatography (IMAC), as originally introduced in 1975 under the name metal chelate affinity chromatography. [ 3 ] Subsequent studies have revealed that among amino acids constituting proteins, histidine is strongly involved in the coordination complex with metal ions. [ 4 ] Therefore, if a number of histidines are added to the end of the protein, the affinity of the protein for the metal ion is increased and this can be exploited to selectively isolate the protein of interest. When a protein with a His-tag is brought into contact with a carrier on which a metal ion such as nickel is immobilized, the histidine residue chelates the metal ion and binds to the carrier. Since other proteins do not bind to the carrier or bind only very weakly, they can be removed by washing the carrier with an appropriate buffer. The poly-histidine tagged protein can then be recovered by eluting it off the resin. [ 5 ]
Polyhistidine tags most commonly consist of six histidine residues. Tags with up to twelve histidine residues or dual tags attached via short linker are not uncommon though and may improve purification results by enhancing binding to the affinity resin, allowing for increased stringency of washing and separation from endogenous proteins. [ 6 ] [ 7 ] [ 8 ] The tag can be added to a gene of interest using methods common to most purification tags . The most basic method is to subclone the gene of interest into a vector containing a polyhistidine tag sequence. Many vectors for use with various expression systems are available with polyhistidine tags in a variety of positions and with differing protease cleavage sites, other tags etc . [ 9 ] However, if an appropriate vector is unavailable or the tag needs to be inserted at a location other than the proteins N- or C-terminus, the gene of interest can be either directly synthesised containing a polyhistidine tag sequence or various methods based on PCR can be used to add the tag to a gene. A common approach is to add the coding sequence for the polyhistidine tag to the PCR primers as an overhang. [ 10 ] [ 11 ]
Most commonly, a polyhistidine tag is fused at the N-terminus or C-terminus of a protein and is attached via a short flexible linker, which may contain a protease cleavage site. [ 10 ] [ 9 ] Less commonly, tags can be added at both the N- and C-termini or inserted at an intermediate part of a protein, such as within an exposed loop. [ 12 ] [ 8 ] The choice of tag position depends on the properties of each protein and the chosen purification strategy; it may be necessary to test multiple constructs with the tag at different positions. [ 6 ] [ 10 ] Although polyhistidine tags are considered to typically not alter the properties of a protein, it has been demonstrated that addition of the tag can cause unwanted effects, such as influencing the protein's oligomeric state. [ 13 ]
Various carrier matrices bound to a solid resin support are on the market and these can be subsequently charged with a metal cation. Derivatives of iminodiacetic acid (IDA) and nitrilotriacetic acid (NTA) are most frequently used for this purpose, with differing matrices having certain advantages and disadvantages for various applications. [ 14 ]
Several metal cations have high affinities for imidazole, the functional group of the His-tag. Divalent cation M 2+ (M = Mn, Fe, Co, Ni, Cu, Zn etc ) transition metal imidazole complexes are most frequently used for this purpose. The choice of cation is generally a compromise between binding capacity and purity. Nickel is often used as it offers a good balance between these factors, while cobalt can be used when it is desired to increase the purity of purification as it has less affinity for endogenous proteins; binding capacity however is lower compared with nickel. [ 14 ] [ 10 ]
In order to elute His-tagged protein from the carrier there are several potential methods, which can be used in combination if necessary. In order to avoid denaturation of proteins, it is generally desirable to use as mild a method as possible.
For releasing the His-tagged protein from the carrier, a compound is used that has a structure similar to the His-tag and which also forms a coordination complex with the immobilized metal ions. Such a compound added to the His-tagged protein on the carrier competes with the protein for the immobilized metal ions. The compound added at high concentration replaces virtually all carrier-bound protein which is thus eluted from the carrier. Imidazole is the side chain of histidine and is typically used at a concentration of 150 - 500 mM for elution. Histidine or histamine can also be used.
When the pH decreases, the histidine residue is protonated and can no longer coordinate the metal tag, allowing the protein to be eluted. When nickel is used as the metal ion, it is eluted at around pH 4 and cobalt at around pH 6.
When a strong chelating agent such as EDTA is added, the protein is detached from the carrier because the metal ion immobilized on the carrier is lost.
Polyhistidine-tags are often used for affinity purification of polyhistidine-tagged recombinant proteins expressed in Escherichia coli or other expression systems. Typically, cells are harvested via centrifugation and the resulting cell pellet lysed either by physical means or by means of detergents and enzymes such as lysozyme or any combination of these. At this stage, the lysate contains the recombinant protein among many endogenous proteins originating from the host cells. The lysate is exposed to affinity resin bound to a carrier matrix coupled with a divalent cation, either by direct addition of resin (batch binding) or by passing over a resin bed in a column format. The resin is then washed with buffer to remove proteins that do not specifically interact with bound cation and the protein of interest is eluted off the resin using buffer containing a high concentration of imidazole or a lowered pH. The purity and amount of protein can be assessed by methods such SDS-PAGE and Western blotting . [ 14 ] [ 10 ] [ 15 ]
Affinity purification using a polyhistidine-tag usually results in relatively pure protein. Protein purity can be improved by the addition of a low (20-40 mM) concentration of imidazole to the binding and/or wash buffers. However, depending on the requirements of the downstream application, further purification steps using methods such as ion exchange or size exclusion chromatography may be required. IMAC resins typically retain several prominent endogenous proteins as impurities. In E. coli for instance, a prominent example is FKBP-type peptidyl prolyl isomerase, which appears around 25 kDa on SDS-PAGE . These impurities can be eliminated using additional purification steps or by expressing the recombinant protein in a deficient strain of cells. Alternatively, cobalt charged IMAC resins which have less affinity for endogenous proteins can be used. [ 16 ] [ 10 ] [ 14 ] [ 17 ]
Polyhistidine-tagging can be used to detect protein-protein interactions in the same way as a pull-down assay. Polyhistidine tagging has several advantages over other tags commonly used for pull-down assays, including its small size, few naturally occurring proteins binding to the carrier matrices and the increased stability of the carrier matrix over monoclonal antibody matrices. [ 18 ]
Hexahistadine CyDye tags have been developed, which use nickel covalent coordination to EDTA groups attached to fluorophores in order to create dyes that attach to the polyhistidine tag. This technique has been shown to be useful for following protein migration and trafficking and may be effective for measuring distance via Förster resonance energy transfer . [ 19 ]
A polyfluorohistidine tag has been reported for use in in vitro translation systems. [ 20 ] In this system, an expanded genetic code is used in which histidine is replaced by 4-fluorohistidine. The fluorinated analog is incorporated into peptides via the relaxed substrate specificity of histidine-tRNA ligase and lowers the overall pK a of the tag. This allows for the selective enrichment of polyfluorohistidine tagged peptides in the presence of complex mixtures of traditional polyhistidine tags by altering the pH of the wash buffers. [ citation needed ]
The polyhistidine-tag can also be used for detecting a protein via anti-polyhistidine-tag antibodies , which can be useful for subcellular localization , ELISA , western blotting and other immuno-analytical methods. Alternatively, in-gel staining of SDS-PAGE or native-PAGE gels with fluorescent probes bearing metal ions can be used for detection of a polyhistidine tagged protein. [ 21 ]
The HQ tag has alternating histidine and glutamine (HQHQHQ).
The HN tag has alternating histidine and asparagine (HNHNHNHNHNHN) and is more likely to be presented on the protein surface than Histidine-only tags. The HN tag binds to the immobilized metal ion more efficiently than the His tag. [ 22 ]
The HAT tag is a peptide tag (KDHLIHNVHKEEHAHAHNK) derived from chicken lactate dehydrogenase , and is more likely to be a soluble protein with no bias in charge distribution compared to the His tag. [ 23 ] The arrangement of histidines in the HAT tag allows high accessibility compared to the His tag, and it binds efficiently to the immobilized metal ion. | https://en.wikipedia.org/wiki/His-tag |
The Museum of Science & Industry (Tampa) honors a Hispanic scientist every year since 2001. [ 1 ] MOSI awards a Scientist every year to provide role models for the diverse youth of the Tampa Bay area. [ 2 ]
The 2001 honoree was Dr. Alejandro Acevedo-Gutierrez, a Marine Biologist from Mexico.
The 2002 honoree was Fernando "Frank" Caldeiro , a NASA Astronaut from Argentina.
The 2003 honoree was Dr. Mario Molina , a Nobel Laureate in Chemistry from Mexico.
Dr. Antiona Coello Novello was the 2004 honoree, and she was the U.S. Surgeon General from 1990 to 1993. She is originally from Puerto Rico.
Dr. Edmond Yunis was the 2005 honoree, and he is an Immunologist from Colombia.
The 2006 honoree was Dr. Ines Cifuentes , a Seismologist from England, Ecuador, and America.
Dr. Louis A. Martin-Vega is an Industrial Engineer from America and Puerto Rico, and he was the 2007 honoree.
The 2008 honoree was Dr. Lydia Villa-Komaroff , a Molecular Biologist from America and Mexico.
Dr. Nils Diaz , the former chair of the U.S. Nuclear Regulatory Commission, was the 2009 honoree, and he is from Cuba.
Dr. Dan Arvizu , the 2010 honoree, is the Director and Chief Executive of the U.S. Department of Energy's National Renewable Energy Laboratory, and he is from Mexico.
Dr. Cristian Samper , Director of the Smithsonian Institution's National Museum of Natural History, was the 2011 honoree, and he is from Colombia.
Dr. Nora Volkow , the Director of the National Institute on Drug Abuse (NIDA) at the National Institutes of Health, was the 2012 honoree, and she is originally from Mexico.
Dr. Raul Cuero , Inventor and Microbiologist, is the 2013 honoree, and he is from Colombia
. [ 3 ]
Dr. Rafael L. Bras , Civil Engineer, Puerto Rico.
Prize expanded to include an Early Career Honoree: Dr. Ana Maria Rey , Physicist, Colombia.
Dr. Modesto Alex Maidique , Electrical Engineer, Cuba.
Early Career Honoree: Dr. Miguel Morales Silva, Physicist, Puerto Rico.
Dr. Adriana Ocampo , Planetary Geologist, USA. [ 4 ] | https://en.wikipedia.org/wiki/Hispanic_Scientist_of_the_Year_Award |
Histaminergic means "working on the histamine system", and histaminic means "related to histamine ". [ 1 ]
A histaminergic agent (or drug ) is a chemical which functions to directly modulate the histamine system in the body or brain. Examples include histamine receptor agonists and histamine receptor antagonists (or antihistamines). Subdivisions of histamine antagonists include H 1 receptor antagonists , H 2 receptor antagonists , and H 3 receptor antagonists . [ 2 ]
This drug article relating to the nervous system is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Histaminergic |
Histatins are histidine -rich (cationic) antimicrobial proteins found in saliva . [ 1 ] Histatin's involvement in antimicrobial activities makes histatin part of the innate immune system . [ 2 ]
Histatin was first discovered (isolated) in 1988, with functions that's responsible in keeping homeostasis inside the oral cavity, helping in the formation of pellicles, and assist in bonding of metal ions. [ 3 ]
The structure of histatin is unique depending on whether the protein of interest is histatin 1, 3 or 5. Nonetheless, histatins mainly possess a cationic (positive) charge due to the primary structure consisting mostly of basic amino acids. An amino acid that is crucial to histatin's function is histidine. Studies show that the removal of histidine (especially in histatin 5) resulted in reduction of antifungal activity. [ 4 ]
Histatins are antimicrobial and antifungal proteins, and have been found to play a role in wound-closure. [ 5 ] [ 6 ] A significant source of histatins is found in the serous fluid secreted by Ebner's glands , salivary glands at the back of the tongue, and produced by acinus cells. [ 7 ] Here they offer some early defense against incoming microbes. [ 8 ]
The three major histatins are 1, 3, and 5, which contains 38, 32, and 24 amino acids, respectively. Histatin 2 is a degradation product of histatin 1, and all other histatins are degradation products of Histatin 3 through the process of post-translational proteolysis of the HTN3 gene product. [ 9 ] Therefore there are only two genes, HTN1 and HTN3 .
The N-terminus of Histatin 5 allows it to bind with metals, and this can result in the production of reactive oxygen species . [ 3 ]
Histatins disrupt the fungal plasma membrane, resulting in release of the intracellular content of the fungal cell. [ 7 ] They also inhibit the growth of yeast , by binding to the potassium transporter and facilitating in the loss of azole - resistant species. [ 10 ]
The antifungal properties of histatins have been seen with fungi such as Candida glabrata , Candida krusei , Saccharomyces cerevisiae , and Cryptococcus neoformans . [ 11 ]
Histatins also precipitate tannins from solution, thus preventing alimentary adsorption. [ 12 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Histatin |
Histidine-tryptophan-ketoglutarate , or Custodiol HTK solution, is a high-flow, low- potassium preservation solution used for organ transplantation . The solution was initially developed by Hans-Jürgen Bretschneider. [ 1 ]
HTK solution is intended for perfusion and flushing of donor liver, kidney, heart, lung and pancreas prior to removal from the donor and for preserving these organs during hypothermic storage and transport to the recipient. HTK solution is based on the principle of inactivating organ function by withdrawal of extracellular sodium and calcium , together with intensive buffering of the extracellular space by means of histidine /histidine hydrochloride, so as to prolong the period during which the organs will tolerate interruption of oxygenated blood . The composition of HTK is similar to that of intracellular fluid. All of the components of HTK occur naturally in the body. The osmolarity of HTK is 310 mOsm/L.
HTK (branded as Custodiol® by Essential Pharmaceuticals LLC), has been presented by industry to surgeons as an alternative solution that exceeds other cardioplegias in myocardial protection during cardiac surgery. [ 2 ] This claim relies on the single-dose administration of HTK compared with other multidose cardioplegias (MDC), sparing time in the adjustment of equipment during cardioplegia re-administration, allowing greater time to operate and thus a decreased CPB duration. [ 3 ] Other benefits include a lower concentration of sodium, calcium, and potassium compared with other cardioplegias with cardiac arrest arising from the deprivation of sodium. [ 4 ] Finally, histidine is thought to aid buffering, mannitol and tryptophan to improve membrane stability, and ketoglutarate to help ATP production during reperfusion. [ 5 ]
A 2021 meta-analysis demonstrated no statistical advantage of HTK over blood or other crystalloid cardioplegias during adult cardiac surgery. The only practical advantage of HTK, therefore, is the single-dose administration compared to multi-dose requirements of blood and other crystalloid cardioplegia. [ 6 ]
1. 510(k) Summary. Custodiol HTK Solution Common/Classification Name: Isolated Kidney Perfusion and Transport System and Accessories, 21 CFR 876.5880; Franz Kohler. Prepared December 14, 2004. https://www.fda.gov/cdrh/pdf4/K043461.pdf
2. Ringe B., et al. Safety and efficacy of living donor liver preservation with HTK solution. Transplant Proc. 2005;37:316–319.
3. Agarawal A., et al. Follow-up experience using histidine-tryptophan-ketoglutarate solution in clinical pancreas transplantation Transplant Proc. 2005;37:3523–3526.
4. Pokorny H., et al.: Histidine-tryptophan-ketoglutarate solution for organ preservation in human liver transplantation — a prospective multi-centre observation study. Transpl Int. 2004;17:256-60.
5. de Boer J., et al.: Eurotransplant randomized multicenter kidney graft preservation study comparing HTK with UW and Euro-Collins. Transpl lnt. 1999;12:447-453.
6. Hesse U.J., et al.: Organ preservation with HTK and UW solution . Pabst Sci. Publishers, D-49525 Lengerich, 1999.
7. Hatano E., et al.: Hepatic preservation with histidine-tryptophan-ketoglutarate solution in living related and cadaveric liver transplantation. Clin Sci. 1997;93:81-88. | https://en.wikipedia.org/wiki/Histidine-tryptophan-ketoglutarate |
Histidine methyl ester ( HME ) is an irreversible histidine decarboxylase inhibitor. [ 1 ] [ 2 ] [ 3 ] It is the methyl ester of histidine .
This article about an ester is a stub . You can help Wikipedia by expanding it .
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Histidine_methyl_ester |
Histidine phosphotransfer domains and histidine phosphotransferases (both often abbreviated HPt ) are protein domains involved in the "phosphorelay" form of two-component regulatory systems . These proteins possess a phosphorylatable histidine residue and are responsible for transferring a phosphoryl group from an aspartate residue on an intermediate "receiver" domain , typically part of a hybrid histidine kinase , to an aspartate on a final response regulator .
In orthodox two-component signaling, a histidine kinase protein autophosphorylates on a histidine residue in response to an extracellular signal, and the phosphoryl group is subsequently transferred to an aspartate residue on the receiver domain of a response regulator . In phosphorelays, the "hybrid" histidine kinase contains an internal aspartate-containing receiver domain to which the phosphoryl group is transferred, after which an HPt protein containing a phosphorylatable histidine receives the phosphoryl group and finally transfers it to the response regulator. The relay system thus progresses in the order His-Asp-His-Asp, with the second His contributed by Hpt. [ 3 ] [ 4 ] [ 5 ] In some cases, a phosphorelay system is constructed from four separate proteins rather than a hybrid histidine kinase with an internal receiver domain, and in other examples both the receiver and the HPt domains are present in the histidine kinase polypeptide chain. [ 6 ] : 198 A census of two-component system domain architecture found that HPt domains in bacteria are more common as domains of larger proteins than they are as individual proteins. [ 4 ]
The increased complexity of the phosphorelay system compared to orthodox two-component signaling provides additional opportunities for regulation and improves the specificity of the response. [ 6 ] : 192 [ 7 ] Although there is very little cross-talk between orthodox two-component systems, phosphorelays allow more complex signaling pathways; examples include a bifurcated pathway with multiple downstream outputs, as in the case of the Caulobacter crescentus ChpT HPt involved in cell cycle regulation, [ 2 ] or, alternatively, pathways in which more than one histidine kinase controls a single response regulator, such as the sporulation pathway in Bacillus subtilis , which can give rise to complex temporal variations. [ 8 ] In some known cases, there is an additional form of regulation in phosphohistidine phosphatase enzymes that act on HPt, such as the Escherichia coli protein SixA which targets ArcB . [ 6 ] : 206
The histidine phosphotransfer function can be carried out by proteins with at least two different architectures, both composed of a four-helix bundle but differing in the way the bundle is assembled. Most structurally characterized HPt proteins, such as the Hpt domain from the Escherichia coli protein ArcB and the Saccharomyces cerevisiae protein Ypd1 , form the bundle as monomers. [ 5 ] [ 2 ] In the less common type, such as the Bacillus subtilis sporulation factor Spo0B or the Caulobacter crescentus protein ChpT , the bundle is assembled as a protein dimer , with similarity to the structure of histidine kinases. [ 7 ] [ 2 ] Monomeric HPt domains possess only one phosphorylatable histidine residue and interact with one response regulator, whereas dimers have two phosphorylation sites and can interact with two response regulators at the same time. Monomeric HPt domains have no enzymatic activity of their own and act purely as phosphate shuttles, [ 10 ] [ 4 ] while the dimeric Spo0B is catalytic; its phosphotransfer rate to the recipient response regulator is dramatically accelerated compared to histidine phosphate. [ 11 ] Despite possessing a second domain with some similarity to ATPase domains, dimeric HPt proteins have not been shown to bind or hydrolyze ATP and lack key residues present in other ATPases. [ 2 ]
The monomeric and dimeric forms do not have detectable sequence similarity and are most likely not evolutionarily related; they are instead examples of convergent evolution . [ 2 ] Although dimeric HPts likely originate from degenerate histidine kinases, it is possible that monomeric HPts have a number of distinct origins, as there are few evolutionary constraints on the structure. [ 3 ]
In bacteria , where two-component signaling is extremely common, about 25% of known histidine kinases are of the hybrid type. Two-component systems are much rarer in archaea and eukaryotes , and occur in lower eukaryotes and in plants but not in metazoans . Among known examples, most if not all eukaryotic two-component systems are hybrid kinase phosphorelays. [ 3 ]
A bioinformatic census of bacterial genomes found large variations in the number of (monomeric) HPt domains identified in different bacterial phyla , with some genomes encoding no HPts at all. Relative to the number of histidine kinase and response regulators present in a genome, eukaryotes have more identifiable HPt domains than bacteria. [ 12 ] In fungi , the genomic inventory of HPt proteins varies, with filamentous fungi generally possessing more HPt proteins than yeasts ; only one is encoded in the well-characterized Saccharomyces cerevisiae genome. Plants generally have more than one HPt, but fewer HPts than response regulators. [ 4 ] [ 10 ] | https://en.wikipedia.org/wiki/Histidine_phosphotransfer_domain |
A histiocyte is a vertebrate cell that is part of the mononuclear phagocyte system (also known as the reticuloendothelial system or lymphoreticular system). The mononuclear phagocytic system is part of the organism's immune system . The histiocyte is a tissue macrophage [ 1 ] or a dendritic cell [ 2 ] ( histio , diminutive of histo , meaning tissue , and cyte , meaning cell ). Part of their job is to clear out neutrophils once they've reached the end of their lifespan.
Histiocytes are derived from the bone marrow by multiplication from a stem cell . The derived cells migrate from the bone marrow to the blood as monocytes . They circulate through the body and enter various organs, where they undergo differentiation into histiocytes, which are part of the mononuclear phagocytic system (MPS).
However, the term histiocyte has been used for multiple purposes in the past, and some cells called "histocytes" do not appear to derive from monocytic-macrophage lines. [ 3 ] The term Histiocyte can also simply refer to a cell from monocyte origin outside the blood system, such as in a tissue (as in rheumatoid arthritis as palisading histiocytes surrounding fibrinoid necrosis of rheumatoid nodules).
Some sources consider Langerhans cell derivatives to be histiocytes. [ 4 ] The Langerhans cell histiocytosis embeds this interpretation into its name.
Histiocytes have common histological and immunophenotypical characteristics (demonstrated by immunostains ). Their cytoplasm is eosinophilic and contains variable amounts of lysosomes . They bear membrane receptors for opsonins , such as IgG and the fragment C3b of complement. They express LCAs ( leucocyte common antigens ) CD45 , CD14 , CD33 , and CD4 (also expressed by T helper cells ).
These histiocytes are part of the immune system by way of two distinct functions: phagocytosis and antigen presentation . Phagocytosis is the main process of macrophages and antigen presentation the main property of dendritic cells (so called because of their star-like cytoplasmic processes).
Macrophages and dendritic cells are derived from common bone marrow precursor cells that have undergone different differentiation (as histiocytes) under the influence of various environmental (tissue location) and growth factors such as GM-CSF, TNF and IL-4. The various categories of histiocytes are distinguishable by their morphology , phenotype , and size.
A subset of cells differentiates into Langerhans cells ; this maturation occurs in the squamous epithelium , lymph nodes , spleen , and bronchiolar epithelium . Langerhans cells are antigen-presenting cells but have undergone further differentiation. Skin Langerhans cells express CD1a, as do cortical thymocytes (cells of the cortex of the thymus gland). They also express S-100, and their cytoplasm contains tennis-racket like ultra-structural inclusions called Birbeck granules .
Histiocytoses describe neoplasias wherein the proliferative cell is the histiocyte. The most common histiocyte disorders are Langerhans' cell histiocytosis and haemophagocytic lymphohistiocytosis . [ 5 ] | https://en.wikipedia.org/wiki/Histiocyte |
Histogenesis is the formation of different tissues from undifferentiated cells . [ 1 ] These cells are constituents of three primary germ layers , the endoderm , mesoderm , and ectoderm . The science of the microscopic structures of the tissues formed within histogenesis is termed histology .
A germ layer is a collection of cells formed during animal embryogenesis . Germ layers are typically pronounced within vertebrate organisms; however, animals more complex than sponges ( eumetazoans and agnotozoans ) produce two or three primary tissue layers. Animals with radial symmetry , such as cnidarians , produce two layers, called the ectoderm and endoderm . They are diploblastic . Animals with bilateral symmetry produce a third layer in-between called mesoderm , making them triploblastic . Germ layers will eventually give rise to all of an animal's or mammal's tissues and organs through a process called organogenesis .
The endoderm is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the archenteron form the inner layer of the gastrula , which develops into the endoderm . Initially, the endoderm consists of flattened cells, which subsequently become columnar...
The mesoderm germ layer forms in the embryos of animals and mammals more complex than cnidarians , making them triploblastic . During gastrulation , some of the cells migrating inward to form the endoderm form an additional layer between the endoderm and the ectoderm . A theory suggests that this key innovation evolved hundreds of millions of years ago and led to the evolution of nearly all large, complex animals. The formation of a mesoderm led to the formation of a coelom . Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks.
The ectoderm is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers .
The proceeding graph represents the products produced by the three germ layers. | https://en.wikipedia.org/wiki/Histogenesis |
Histology , [ help 1 ] also known as microscopic anatomy or microanatomy , [ 1 ] is the branch of biology that studies the microscopic anatomy of biological tissues . [ 2 ] [ 3 ] [ 4 ] [ 5 ] Histology is the microscopic counterpart to gross anatomy , which looks at larger structures visible without a microscope . [ 5 ] [ 6 ] Although one may divide microscopic anatomy into organology , the study of organs, histology , the study of tissues, and cytology , the study of cells , modern usage places all of these topics under the field of histology. [ 5 ] In medicine , histopathology is the branch of histology that includes the microscopic identification and study of diseased tissue. [ 5 ] [ 6 ] In the field of paleontology , the term paleohistology refers to the histology of fossil organisms. [ 7 ] [ 8 ]
There are four basic types of animal tissues: muscle tissue , nervous tissue , connective tissue , and epithelial tissue . [ 5 ] [ 9 ] All animal tissues are considered to be subtypes of these four principal tissue types (for example, blood is classified as connective tissue, since the blood cells are suspended in an extracellular matrix , the plasma ). [ 9 ]
For plants, the study of their tissues falls under the field of plant anatomy , with the following four main types:
Histopathology is the branch of histology that includes the microscopic identification and study of diseased tissue. [ 5 ] [ 6 ] It is an important part of anatomical pathology and surgical pathology , as accurate diagnosis of cancer and other diseases often requires histopathological examination of tissue samples. [ 10 ] Trained physicians, frequently licensed pathologists , perform histopathological examination and provide diagnostic information based on their observations.
The field of histology that includes the preparation of tissues for microscopic examination is known as histotechnology. Job titles for the trained personnel who prepare histological specimens for examination are numerous and include histotechnicians, histotechnologists, [ 11 ] histology technicians and technologists, medical laboratory technicians , and biomedical scientists .
Most histological samples need preparation before microscopic observation; these methods depend on the specimen and method of observation. [ 9 ]
Chemical fixatives are used to preserve and maintain the structure of tissues and cells; fixation also hardens tissues which aids in cutting the thin sections of tissue needed for observation under the microscope. [ 5 ] [ 12 ] Fixatives generally preserve tissues (and cells) by irreversibly cross-linking proteins. [ 12 ] The most widely used fixative for light microscopy is 10% neutral buffered formalin , or NBF (4% formaldehyde in phosphate buffered saline ). [ 13 ] [ 12 ] [ 9 ]
For electron microscopy, the most commonly used fixative is glutaraldehyde , usually as a 2.5% solution in phosphate buffered saline . [ 9 ] Other fixatives used for electron microscopy are osmium tetroxide or uranyl acetate . [ 9 ]
The main action of these aldehyde fixatives is to cross-link amino groups in proteins through the formation of methylene bridges ( −CH 2 − ), in the case of formaldehyde, or by C 5 H 10 cross-links in the case of glutaraldehyde. This process, while preserving the structural integrity of the cells and tissue can damage the biological functionality of proteins, particularly enzymes .
Formalin fixation leads to degradation of mRNA, miRNA, and DNA as well as denaturation and modification of proteins in tissues. However, extraction and analysis of nucleic acids and proteins from formalin-fixed, paraffin-embedded tissues is possible using appropriate protocols. [ 14 ] [ 15 ]
Selection is the choice of relevant tissue in cases where it is not necessary to put the entire original tissue mass through further processing. The remainder may remain fixed in case it needs to be examined at a later time.
Trimming is the cutting of tissue samples in order to expose the relevant surfaces for later sectioning. It also creates tissue samples of appropriate size to fit into cassettes. [ 16 ]
Tissues are embedded in a harder medium both as a support and to allow the cutting of thin tissue slices. [ 9 ] [ 5 ] In general, water must first be removed from tissues (dehydration) and replaced with a medium that either solidifies directly, or with an intermediary fluid (clearing) that is miscible with the embedding media. [ 12 ]
For light microscopy, paraffin wax is the most frequently used embedding material. [ 12 ] [ 13 ] Paraffin is immiscible with water, the main constituent of biological tissue, so it must first be removed in a series of dehydration steps. [ 12 ] Samples are transferred through a series of progressively more concentrated ethanol baths, up to 100% ethanol to remove remaining traces of water. [ 9 ] [ 12 ] Dehydration is followed by a clearing agent (typically xylene [ 13 ] although other environmental safe substitutes are in use [ 13 ] ) which removes the alcohol and is miscible with the wax, finally melted paraffin wax is added to replace the xylene and infiltrate the tissue. [ 9 ] In most histology, or histopathology laboratories the dehydration, clearing, and wax infiltration are carried out in tissue processors which automate this process. [ 13 ] Once infiltrated in paraffin, tissues are oriented in molds which are filled with wax; once positioned, the wax is cooled, solidifying the block and tissue. [ 13 ] [ 12 ]
Paraffin wax does not always provide a sufficiently hard matrix for cutting very thin sections (which are especially important for electron microscopy). [ 12 ] Paraffin wax may also be too soft in relation to the tissue, the heat of the melted wax may alter the tissue in undesirable ways, or the dehydrating or clearing chemicals may harm the tissue. [ 12 ] Alternatives to paraffin wax include, epoxy , acrylic , agar , gelatin , celloidin , and other types of waxes. [ 12 ] [ 17 ]
In electron microscopy epoxy resins are the most commonly employed embedding media, [ 9 ] but acrylic resins are also used, particularly where immunohistochemistry is required.
For tissues to be cut in a frozen state, tissues are placed in a water-based embedding medium. Pre-frozen tissues are placed into molds with the liquid embedding material, usually a water-based glycol, OCT , TBS , Cryogen, or resin, which is then frozen to form hardened blocks.
For light microscopy, a knife mounted in a microtome is used to cut tissue sections (typically between 5-15 micrometers thick) which are mounted on a glass microscope slide . [ 9 ] For transmission electron microscopy (TEM), a diamond or glass knife mounted in an ultramicrotome is used to cut between 50 and 150 nanometer thick tissue sections. [ 9 ]
A limited number of manufacturers are recognized for their production of microtomes, including vibrating microtomes commonly referred to as vibratomes , primarily for research and clinical studies. Additionally, Leica Biosystems is known for its production of products related to light microscopy in the context of research and clinical studies. [ 18 ]
Biological tissue has little inherent contrast in either the light or electron microscope. [ 17 ] Staining is employed to give both contrast to the tissue as well as highlighting particular features of interest. When the stain is used to target a specific chemical component of the tissue (and not the general structure), the term histochemistry is used. [ 9 ]
Hematoxylin and eosin ( H&E stain ) is one of the most commonly used stains in histology to show the general structure of the tissue. [ 9 ] [ 19 ] Hematoxylin stains cell nuclei blue; eosin, an acidic dye, stains the cytoplasm and other tissues in different stains of pink. [ 9 ] [ 12 ]
In contrast to H&E, which is used as a general stain, there are many techniques that more selectively stain cells, cellular components, and specific substances. [ 12 ] A commonly performed histochemical technique that targets a specific chemical is the Perls' Prussian blue reaction, used to demonstrate iron deposits [ 12 ] in diseases like hemochromatosis . The Nissl method for Nissl substance and Golgi's method (and related silver stains ) are useful in identifying neurons are other examples of more specific stains. [ 12 ]
In historadiography , a slide (sometimes stained histochemically) is X-rayed. More commonly, autoradiography is used in visualizing the locations to which a radioactive substance has been transported within the body, such as cells in S phase (undergoing DNA replication ) which incorporate tritiated thymidine , or sites to which radiolabeled nucleic acid probes bind in in situ hybridization . For autoradiography on a microscopic level, the slide is typically dipped into liquid nuclear tract emulsion, which dries to form the exposure film. Individual silver grains in the film are visualized with dark field microscopy .
Recently, antibodies have been used to specifically visualize proteins, carbohydrates, and lipids. This process is called immunohistochemistry , or when the stain is a fluorescent molecule, immunofluorescence . This technique has greatly increased the ability to identify categories of cells under a microscope. Other advanced techniques, such as nonradioactive in situ hybridization, can be combined with immunochemistry to identify specific DNA or RNA molecules with fluorescent probes or tags that can be used for immunofluorescence and enzyme-linked fluorescence amplification (especially alkaline phosphatase and tyramide signal amplification). Fluorescence microscopy and confocal microscopy are used to detect fluorescent signals with good intracellular detail.
For electron microscopy heavy metals are typically used to stain tissue sections. [ 9 ] Uranyl acetate and lead citrate are commonly used to impart contrast to tissue in the electron microscope. [ 9 ]
Similar to the frozen section procedure employed in medicine, cryosectioning is a method to rapidly freeze, cut, and mount sections of tissue for histology. The tissue is usually sectioned on a cryostat or freezing microtome. [ 12 ] The frozen sections are mounted on a glass slide and may be stained to enhance the contrast between different tissues. Unfixed frozen sections can be used for studies requiring enzyme localization in tissues and cells. Tissue fixation is required for certain procedures such as antibody-linked immunofluorescence staining. Frozen sections are often prepared during surgical removal of tumors to allow rapid identification of tumor margins, as in Mohs surgery , or determination of tumor malignancy, when a tumor is discovered incidentally during surgery.
Ultramicrotomy is a method of preparing extremely thin sections for transmission electron microscope (TEM) analysis. Tissues are commonly embedded in epoxy or other plastic resin. [ 9 ] Very thin sections (less than 0.1 micrometer in thickness) are cut using diamond or glass knives on an ultramicrotome . [ 12 ]
Artifacts are structures or features in tissue that interfere with normal histological examination. Artifacts interfere with histology by changing the tissues appearance and hiding structures. Tissue processing artifacts can include pigments formed by fixatives, [ 12 ] shrinkage, washing out of cellular components, color changes in different tissues types and alterations of the structures in the tissue. An example is mercury pigment left behind after using Zenker's fixative to fix a section. [ 12 ] Formalin fixation can also leave a brown to black pigment under acidic conditions. [ 12 ]
In the 17th century the Italian Marcello Malpighi used microscopes to study tiny biological entities; some regard him as the founder of the fields of histology and microscopic pathology. [ 20 ] [ 21 ] Malpighi analyzed several parts of the organs of bats, frogs and other animals under the microscope. While studying the structure of the lung, Malpighi noticed its membranous alveoli and the hair-like connections between veins and arteries, which he named capillaries. His discovery established how the oxygen breathed in enters the blood stream and serves the body. [ 22 ]
In the 19th century histology was an academic discipline in its own right. The French anatomist Xavier Bichat introduced the concept of tissue in anatomy in 1801, [ 23 ] and the term "histology" ( German : Histologie ), coined to denote the "study of tissues", first appeared in a book by Karl Meyer in 1819. [ 24 ] [ 25 ] [ 20 ] Bichat described twenty-one human tissues, which can be subsumed under the four categories currently accepted by histologists. [ 26 ] The usage of illustrations in histology, deemed as useless by Bichat, was promoted by Jean Cruveilhier . [ 27 ] [ when? ]
In the early 1830s Purkynĕ invented a microtome with high precision. [ 25 ]
During the 19th century many fixation techniques were developed by Adolph Hannover (solutions of chromates and chromic acid ), Franz Schulze and Max Schultze ( osmic acid ), Alexander Butlerov ( formaldehyde ) and Benedikt Stilling ( freezing ). [ 25 ]
Mounting techniques were developed by Rudolf Heidenhain (1824–1898), who introduced gum Arabic ; Salomon Stricker (1834–1898), who advocated a mixture of wax and oil; and Andrew Pritchard (1804–1884) who, in 1832, used a gum/ isinglass mixture. In the same year, Canada balsam appeared on the scene, and in 1869 Edwin Klebs (1834–1913) reported that he had for some years embedded his specimens in paraffin. [ 28 ]
The 1906 Nobel Prize in Physiology or Medicine was awarded to histologists Camillo Golgi and Santiago Ramon y Cajal . They had conflicting interpretations of the neural structure of the brain based on differing interpretations of the same images. Ramón y Cajal won the prize for his correct theory, and Golgi for the silver-staining technique that he invented to make it possible. [ 29 ]
There is interest in developing techniques for in vivo histology (predominantly using MRI ), which would enable doctors to non-invasively gather information about healthy and diseased tissues in living patients, rather than from fixed tissue samples. [ 30 ] [ 31 ] [ 32 ] [ 33 ] | https://en.wikipedia.org/wiki/Histology |
Histone acetylation and deacetylation are the processes by which the lysine residues within the N-terminal tail protruding from the histone core of the nucleosome are acetylated and deacetylated as part of gene regulation .
Histone acetylation and deacetylation are essential parts of gene regulation . These reactions are typically catalysed by enzymes with " histone acetyltransferase " (HAT) or " histone deacetylase " (HDAC) activity. Acetylation is the process where an acetyl functional group is transferred from one molecule (in this case, acetyl coenzyme A ) to another. Deacetylation is simply the reverse reaction where an acetyl group is removed from a molecule.
Acetylated histones , octameric proteins that organize chromatin into nucleosomes , the basic structural unit of the chromosomes and ultimately higher order structures, represent a type of epigenetic marker within chromatin . Acetylation removes the positive charge on the histones, thereby decreasing the interaction of the N termini of histones with the negatively charged phosphate groups of DNA . As a consequence, the condensed chromatin is transformed into a more relaxed structure that is associated with greater levels of gene transcription . This relaxation can be reversed by deacetylation catalyzed by HDAC activity. Relaxed, transcriptionally active DNA is referred to as euchromatin . More condensed (tightly packed) DNA is referred to as heterochromatin . Condensation can be brought about by processes including deacetylation and methylation. [ 1 ]
Nucleosomes are portions of double-stranded DNA (dsDNA) that are wrapped around protein complexes called histone cores. These histone cores are composed of 8 subunits, two each of H2A , H2B , H3 and H4 histones. This protein complex forms a cylindrical shape that dsDNA wraps around with approximately 147 base pairs. Nucleosomes are formed as a beginning step for DNA compaction that also contributes to structural support as well as serves functional roles. [ 2 ] These functional roles are contributed by the tails of the histone subunits. The histone tails insert themselves in the minor grooves of the DNA and extend through the double helix, [ 1 ] which leaves them open for modifications involved in transcriptional activation. [ 3 ] Acetylation has been closely associated with increases in transcriptional activation while deacetylation has been linked with transcriptional deactivation. These reactions occur post-translation and are reversible. [ 3 ]
The mechanism for acetylation and deacetylation takes place on the NH 3 + groups of lysine amino acid residues. These residues are located on the tails of histones that make up the nucleosome of packaged dsDNA. The process is aided by factors known as histone acetyltransferases (HATs). HAT molecules facilitate the transfer of an acetyl group from a molecule of acetyl-coenzyme A (Acetyl-CoA) to the NH 3 + group on lysine. When a lysine is to be deacetylated, factors known as histone deacetylases (HDACs) catalyze the removal of the acetyl group with a molecule of H 2 O. [ 3 ] [ 4 ]
Acetylation has the effect of changing the overall charge of the histone tail from positive to neutral. Nucleosome formation is dependent on the positive charges of the H4 histones and the negative charge on the surface of H2A histone fold domains. Acetylation of the histone tails disrupts this association, leading to weaker binding of the nucleosomal components. [ 1 ] By doing this, the DNA is more accessible and leads to more transcription factors being able to reach the DNA. Thus, acetylation of histones is known to increase the expression of genes through transcription activation. Deacetylation performed by HDAC molecules has the opposite effect. By deacetylating the histone tails, the DNA becomes more tightly wrapped around the histone cores, making it harder for transcription factors to bind to the DNA. This leads to decreased levels of gene expression and is known as gene silencing. [ 5 ] [ 6 ] [ 7 ]
Acetylated histones, the octomeric protein cores of nucleosomes, represent a type of epigenetic marker within chromatin. Studies have shown that one modification has the tendency to influence whether another modification will take place. Modifications of histones can not only cause secondary structural changes at their specific points, but can cause many structural changes in distant locations which inevitably affects function. [ 8 ] As the chromosome is replicated, the modifications that exist on the parental chromosomes are handed down to daughter chromosomes. The modifications, as part of their function, can recruit enzymes for their particular function and can contribute to the continuation of modifications and their effects after replication has taken place. [ 1 ] It has been shown that, even past one replication, expression of genes may still be affected many cell generations later. A study showed that, upon inhibition of HDAC enzymes by Trichostatin A, genes inserted next to centric heterochromatin showed increased expression. Many cell generations later, in the absence of the inhibitor, the increased gene expression was still expressed, showing modifications can be carried through many replication processes such as mitosis and meiosis. [ 8 ]
Histone Acetyltransferases, also known as HATs, are a family of enzymes that acetylate the histone tails of the nucleosome. This, and other modifications, are expressed based on the varying states of the cellular environment. [ 2 ] Many proteins with acetylating abilities have been documented and, after a time, were categorized based on sequence similarities between them. These similarities are high among members of a family, but members from different families show very little resemblance. [ 9 ] Some of the major families identified so far are as follows.
General Control Non-Derepressible 5 (Gcn5) –related N-Acetyltransferases (GNATs) is one of the many studied families with acetylation abilities. [ 10 ] This superfamily includes the factors Gcn5 which is included in the SAGA, SLIK, STAGA, ADA, and A2 complexes, Gcn5L, p300/CREB-binding protein associated factor (PCAF) , Elp3 , HPA2 and HAT1 . [ 10 ] [ 11 ] Major features of the GNAT family include HAT domains approximately 160 residues in length and a conserved bromodomain that has been found to be an acetyl-lysine targeting motif. [ 9 ] Gcn5 has been shown to acetylate substrates when it is part of a complex. [ 11 ] Recombinant Gcn5 has been found to be involved in the acetylation of the H3 histones of the nucleosome. [ 2 ] [ 11 ] To a lesser extent, it has been found to also acetylate H2B and H4 histones when involved with other complexes. [ 2 ] [ 3 ] [ 11 ] PCAF has the ability to act as a HAT protein and acetylate histones, it can acetylate non-histone proteins related to transcription, as well as act as a coactivator in many processes including myogenesis , nuclear-receptor -mediated activation and growth-factor -signaled activation. Elp3 has the ability to acetylate all histone subunits and also shows involvement in the RNA polymerase II holoenzyme. [ 2 ]
MOZ (Monocytic Leukemia Zinc Finger Protein), Ybf2/Sas3, Sas2 and Tip60 (Tat Interacting Protein) all make up MYST, another well known family that exhibits acetylating capabilities. This family includes Sas3, essential SAS-related acetyltransferase (Esa1), Sas2, Tip60, MOF, MOZ, MORF, and HBO1. The members of this family have multiple functions, not only with activating and silencing genes, but also affect development and have implications in human diseases. [ 11 ] Sas2 and Sas3 are involved in transcription silencing, MOZ and TIF2 are involved with the formation of leukemic transclocation products while MOF is involved in dosage compensation in Drosophila . MOF also influences spermatogenesis in mice as it is involved in the expansion of H2AX phosphorylation during the leptotene to pachytene stages of meiosis . [ 12 ] HAT domains for this family are approximately 250 residues which include cysteine-rich, zinc binding domains as well as N-terminal chromodomains. The MYST proteins Esa1, Sas2 and Sas3 are found in yeast, MOF is found in Drosophila and mice while Tip60, MOZ, MORF, and HBO1 are found in humans. [ 9 ] Tip60 has roles in the regulation of gene transcription, HBO has been found to impact the DNA replication process, MORF is able to acetylate free histones (especially H3 and H4) as well as nucleosomal histones. [ 2 ]
Adenoviral E1A-associated protein of 300kDa (p300) and the CREB-binding protein (CBP) make up the next family of HATs. [ 10 ] This family of HATs contain HAT domains that are approximately 500 residues long and contain bromodomains as well as three cysteine-histidine rich domains that help with protein interactions. [ 9 ] These HATs are known to acetylate all of the histone subunits in the nucleosome. They also have the ability to acetylate and mediate non-histone proteins involved in transcription and are also involved in the cell-cycle , differentiation and apoptosis . [ 2 ]
There are other proteins that have acetylating abilities but differ in structure to the previously mentioned families. One HAT is called steroid receptor coactivator 1 (SRC1) , which has a HAT domain located at the C-terminus end of the protein along with a basic helix-loop-helix and PAS A and PAS B domains with a LXXLL receptor interacting motif in the middle. Another is ATF-2 which contains a transcriptional activation (ACT) domain and a basic zipper DNA-binding (bZip) domain with a HAT domain in-between. The last is TAFII250 which has a Kinase domain at the N-terminus region, two bromodomains located at the C-terminus region and a HAT domain located in-between. [ 13 ]
There are a total of four classes that categorize Histone Deacetylases (HDACs). Class I includes HDACs 1 , 2 , 3 , and 8 . Class II is divided into two subgroups, Class IIA and Class IIB. Class IIA includes HDACs 4 , 5 , 7 , and 9 while Class IIB includes HDACs 6 and 10 . Class III contains the Sirtuins and Class IV contains only HDAC11 . [ 5 ] [ 6 ] Classes of HDAC proteins are divided and grouped together based on the comparison to the sequence homologies of Rpd3, Hos1 and Hos2 for Class I HDACs, HDA1 and Hos3 for the Class II HDACs and the sirtuins for Class III HDACs. [ 6 ]
HDAC1 & HDAC2 are in the first class of HDACs are most closely related to one another. [ 5 ] [ 6 ] By analyzing the overall sequences of both HDACs, their similarity was found to be approximately 82% homologous. [ 5 ] These enzymes have been found to be inactive when isolated which led to the conclusion that they must be incorporated with cofactors in order to activate their deacetylase abilities. [ 5 ] There are three major protein complexes that HDAC 1 & 2 may incorporate themselves into. These complexes include Sin3 (named after its characteristic protein mSin3A ), Nucleosome Remodelling and Deacetylating complex (NuRD) , and Co-REST . [ 5 ] [ 6 ] The Sin3 complex and the NuRD complex both contain HDACs 1 and 2, the Rb-associated protein 48 (RbAp48) and RbAp46 which make up the core of each complex. [ 2 ] [ 6 ] Other complexes may be needed though in order to initiate the maximum amount of available activity possible. HDACs 1 and 2 can also bind directly to DNA binding proteins such as Yin and Yang 1 (YY1) , Rb binding protein 1 and Sp1 . [ 5 ] HDACs 1 and 2 have been found to express regulatory roles in key cell cycle genes including p21 . [ 6 ]
Activity of these HDACs can be affected by phosphorylation . An increased amount of phosphorylation ( hyperphosphorylation ) leads to increased deacetylase activity, but degrades complex formation between HDACs 1 and 2 and between HDAC1 and mSin3A/YY1. A lower than normal amount of phosphorylation (hypophosphorylation) leads to a decrease in the amount of deacetylase activity, but increases the amount of complex formation. Mutation studies found that major phosphorylation happens at residues Ser 421 and Ser 423 . Indeed, when these residues were mutated, a drastic reduction was seen in the amount of deacetylation activity. [ 5 ] This difference in the state of phosphorylation is a way of keeping an optimal level of phosphorylation to ensure there is no over or under expression of deacetylation. HDACs 1 and 2 have been found only exclusively in the nucleus . [ 2 ] [ 6 ] In HDAC1 knockout (KO) mice , mice were found to die during embryogenesis and showed a drastic reduction in the production but increased expression of Cyclin-Dependent Kinase Inhibitors (CDKIs) p21 and p27 . Not even upregulation of the other Class I HDACs could compensate for the loss of HDAC1. This inability to recover from HDAC1 KO leads researchers to believe that there are both functional uniqueness to each HDAC as well as regulatory cross-talk between factors. [ 6 ]
HDAC3 has been found to be most closely related to HDAC8. HDAC3 contains a non-conserved region in the C-terminal region that was found to be required for transcriptional repression as well as its deacetylase activity. It also contains two regions, one called a Nuclear Localization Signal (NLS) as well as a Nuclear Export Signal (NES) . The NLS functions as a signal for nuclear action while an NES functions with HDACs that perform work outside of the nucleus. A presence of both signals for HDAC3 suggests it travels between the nucleus and the cytoplasm . [ 5 ] HDAC3 has even been found to interact with the plasma membrane . [ 6 ] Silencing Mediator for Retinoic Acid and Thyroid Hormone (SMRT) receptors and Nuclear Receptor Co-Repressor (N-CoR) factors must be utilized by HDAC3 in order to activate it. [ 5 ] [ 6 ] Upon doing so, it gains the ability to co-precipitate with HDACs 4, 5, and 7. HDAC3 can also be found complexed together with HDAC-related protein (HDRP). [ 5 ] HDACs 1 and 3 have been found to mediate Rb-RbAp48 interactions which suggests that it functions in cell cycle progression. [ 5 ] [ 6 ] HDAC3 also shows involvement in stem cell self-renewal and a transcription independent role in mitosis . [ 6 ]
HDAC8 has been found to be most similar to HDAC3. Its major feature is its catalytic domain which contains an NLS region in the center. Two transcripts of this HDAC have been found which include a 2.0kb transcript and a 2.4kb transcript. [ 5 ] Unlike the other HDAC molecules, when purified, this HDAC showed to be enzymatically active. [ 6 ] At this point, due to its recent discovery, it is not yet known if it is regulated by co-repressor protein complexes. Northern blots have revealed that different tissue types show varying degrees of HDAC8 expression [ 5 ] but has been observed in smooth muscles and is thought to contribute to contractility. [ 6 ]
The Class IIA HDACs includes HDAC4 , HDAC5 , HDAC7 and HDAC9 . HDACs 4 and 5 have been found to most closely resemble each other while HDAC7 maintains a resemblance to both of them. There have been three discovered variants of HDAC9 including HDAC9a, HDAC9b and HDAC9c/HDRP, while more have been suspected. The variants of HDAC9 have been found to have similarities to the rest of the Class IIA HDACs. For HDAC9, the splicing variants can be seen as a way of creating a "fine-tuned mechanism" for differentiation expression levels in the cell. Different cell types may take advantage and utilize different isoforms of the HDAC9 enzyme allowing for different forms of regulation. HDACs 4, 5 and 7 have their catalytic domains located in the C-terminus along with an NLS region while HDAC9 has its catalytic domain located in the N-terminus. However, the HDAC9 variant HDAC9c/HDRP lacks a catalytic domain but has a 50% similarity to the N-terminus of HDACs 4 and 5. [ 5 ]
For HDACs 4, 5 and 7, conserved binding domains have been discovered that bind for C-terminal binding protein (CtBP) , myocyte enhancer factor 2 (MEF2) and 14-3-3 . [ 5 ] [ 6 ] All three HDACs work to repress the myogenic transcription factor MEF2 which an essential role in muscle differentiation as a DNA binding transcription factor. Binding of HDACs to MEF2 inhibits muscle differentiation, which can be reversed by action of Ca 2+ /calmodulin-dependent kinase (CaMK) which works to dissociate the HDAC/MEF2 complex by phosphorylating the HDAC portion. [ 5 ] They have been seen to be involved in cellular hypertrophy in muscle control differentiation as well as cellular hypertrophy in muscle and cartilage tissues. [ 6 ] HDACs 5 and 7 have been shown to work in opposition to HDAC4 during muscle differentiation regulation so as to keep a proper level of expression. There has been evidence that these HDACs also interact with HDAC3 as a co-recruitment factor to the SMRT/ N-CoR factors in the nucleus. Absence of the HDAC3 enzyme has shown to lead to inactivity which makes researchers believe that HDACs 4, 5 and 7 help the incorporation of DNA-binding recruiters for the HDAC3-containing HDAC complexes located in the nucleus. [ 5 ] When HDAC4 is knocked out in mice, they suffer from a pronounced chondrocyte hypertrophy and die due to extreme ossification . HDAC7 has been shown to suppress Nur77 -dependent apoptosis . This interaction leads to a role in clonal expansion of T cells . HDAC9 KO mice are shown to suffer from cardiac hypertrophy which is exacerbated in mice that are double KO for HDACs 9 and 5. [ 6 ]
The Class IIB HDACs include HDAC6 and HDAC10 . These two HDACs are most closely related to each other in overall sequence. However, HDAC6's catalytic domain is most similar to HDAC9. [ 5 ] A unique feature of HDAC6 is that it contains two catalytic domains in tandem of one another. [ 5 ] [ 6 ] Another unique feature of HDAC6 is the HDAC6-, SP3 , and Brap2-related zinc finger motif (HUB) domain in the C-terminus which shows some functions related to ubiquitination , meaning this HDAC is prone to degradation. [ 5 ] HDAC10 has two catalytic domains as well. One active domain is located in the N-terminus and a putative catalytic domain is located in the C-terminus [ 5 ] [ 6 ] along with an NES domain. [ 5 ] Two putative Rb-binding domains have also been found on HDAC10 which shows it may have roles in the regulation of the cell cycle. Two variants of HDAC10 have been found, both having slight differences in length. HDAC6 is the only HDAC to be shown to act on tubulin , acting as a tubulin deacetylase which helps in the regulation of microtubule-dependent cell motility . It is mostly found in the cytoplasm but has been known to be found in the nucleus, complexed together with HDAC11. HDAC10 has been seen to act on HDACs 1, 2, 3 (or SMRT), 4, 5 and 7. Some evidence has been shown that it may have small interactions with HDAC6 as well. This leads researchers to believe that HDAC10 may function more as a recruiter rather than a factor for deacetylation. However, experiments conducted with HDAC10 did indeed show deacetylation activity. [ 5 ]
HDAC11 has been shown to be related to HDACs 3 and 8, but its overall sequence is quite different from the other HDACs, leading it to be in its own category. [ 5 ] [ 6 ] HDAC11 has a catalytic domain located in its N-terminus. It has not been found incorporated in any HDAC complexes such as Nurd or SMRT which means it may have a special function unique to itself. It has been found that HDAC11 remains mainly in the nucleus. [ 5 ]
The discovery of histone acetylation causing changes in transcription activity can be traced back to the work of Vicent Allfrey and colleagues in 1964. [ 14 ] The group hypothesized that histone proteins modified by acetyl groups added negative charges to the positive lysines, and thus, reduced the interaction between DNA and histones . [ 15 ] Histone modification is now considered a major regulatory mechanism that is involved in many different stages of genetic functions. [ 16 ] Our current understanding is that acetylated lysine residues on histone tails is associated with transcriptional activation. In turn, deacetylated histones are associated with transcriptional repression. In addition, negative correlations have been found between several histone acetylation marks. [ 17 ]
The regulatory mechanism is thought to be twofold. Lysine is an amino acid with a positive charge when unmodified. Lysines on the amino terminal tails of histones have a tendency to weaken the chromatin's overall structure. Addition of an acetyl group, which carries a negative charge, effectively removes the positive charge and hence, reduces the interaction between the histone tail and the nucleosome . [ 18 ] This opens up the usually tightly packed nucleosome and allows transcription machinery to come into contact with the DNA template, leading to gene transcription . [ 1 ] : 242 Repression of gene transcription is achieved by the reverse of this mechanism. The acetyl group is removed by one of the HDAC enzymes during deacetylation, allowing histones to interact with DNA more tightly to form compacted nucleosome assembly. This increase in the rigid structure prevents the incorporation of transcriptional machinery, effectively silencing gene transcription.
Another implication of histone acetylation is to provide a platform for protein binding. As a posttranslational modification , the acetylation of histones can attract proteins to elongated chromatin that has been marked by acetyl groups. It has been hypothesized that the histone tails offer recognition sites that attract proteins responsible for transcriptional activation. [ 19 ] Unlike histone core proteins, histone tails are not part of the nucleosome core and are exposed to protein interaction. A model proposed that the acetylation of H3 histones activates gene transcription by attracting other transcription related complexes. Therefore, the acetyl mark provides a site for protein recognition where transcription factors interact with the acetylated histone tails via their bromodomain . [ 20 ]
The Histone code hypothesis suggests the idea that patterns of post-translational modifications on histones, collectively, can direct specific cellular functions. [ 21 ] Chemical modifications of histone proteins often occur on particular amino acids. This specific addition of single or multiple modifications on histone cores can be interpreted by transcription factors and complexes which leads to functional implications. This process is facilitated by enzymes such as HATs and HDACs that add or remove modifications on histones, and transcription factors that process and "read" the modification codes. The outcome can be activation of transcription or repression of a gene. For example, the combination of acetylation and phosphorylation have synergistic effects on the chromosomes overall structural condensation level and, hence, induces transcription activation of immediate early gene . [ 22 ]
Experiments investigating acetylation patterns of H4 histones suggested that these modification patterns are collectively maintained in mitosis and meiosis in order to modify long-term gene expression. [ 8 ] The acetylation pattern is regulated by HAT and HADC enzymes and, in turn, sets the local chromatin structure. In this way, acetylation patterns are transmitted and interconnected with protein binding ability and functions in subsequent cell generation.
The bromodomain is a motif that is responsible for acetylated lysine recognition on histones by nucleosome remodelling proteins. Posttranslational modifications of N- and C-terminal histone tails attracts various transcription initiation factors that contain bromodomains, including human transcriptional coactivator PCAF , TAF1 , GCN5 and CREB-binding protein (CBP), to the promoter and have a significance in regulating gene expression. [ 23 ] Structural analysis of transcription factors has shown that highly conserved bromodomains are essential for protein to bind to acetylated lysine. This suggests that specific histone site acetylation has a regulatory role in gene transcriptional activation. [ 24 ]
Gene expression is regulated by histone acetylation and deacetylation, and this regulation is also applicable to inflammatory genes. Inflammatory lung diseases are characterized by expression of specific inflammatory genes such as NF-κB and AP-1 transcription factor . Treatments with corticosteroids and theophylline for inflammatory lung diseases interfere with HAT/HDAC activity to turn off inflammatory genes. [ 25 ]
Specifically, gene expression data demonstrated increased activity of HAT and decreased level of HDAC activity in patients with Asthma . [ 26 ] Patients with chronic obstructive pulmonary disease showed there is an overall decrease in HDAC activity with unchanged levels of HAT activity. [ 27 ] Results have shown that there is an important role for HAT/HDAC activity balance in inflammatory lung diseases and provided insights on possible therapeutic targets. [ 28 ]
Due to the regulatory role during transcription of epigenetic modifications in genes, it is not surprising that changes in epigenetic markers, such as acetylation, can contribute to cancer development. HDACs expression and activity in tumor cells is very different from normal cells. The overexpression and increased activity of HDACs has been shown to be characteristic of tumorigenesis and metastasis , suggesting an important regulatory role of histone deacetylation on the expression of tumor suppressor genes. [ 29 ] One of the examples is the regulation role of histone acetylation/deacetylation in P300 and CBP, both of which contribute to oncogenesis . [ 30 ]
Approved in 2006 by the U.S. Food and Drug Administration (FDA), Vorinostat represents a new category for anticancer drugs that are in development. Vorinostat targets histone acetylation mechanisms and can effectively inhibit abnormal chromatin remodeling in cancerous cells. Targets of Vorinostat includes HDAC1 , HDAC2 , HDAC3 and HDAC6 . [ 31 ] [ 32 ]
Carbon source availability is reflected in histone acetylation in cancer. Glucose and glutamine are the major carbon sources of most mammalian cells, and glucose metabolism is closely related to histone acetylation and deacetylation. Glucose availability affects the intracellular pool of acetyl-CoA, a central metabolic intermediate that is also the acetyl donor in histone acetylation. Glucose is converted to acetyl-CoA by the pyruvate dehydrogenase complex (PDC), which produces acetyl-CoA from glucose-derived pyruvate; and by adenosine triphosphate-citrate lyase (ACLY), which generates acetyl-CoA from glucose-derived citrate. PDC and ACLY activity depend on glucose availability, which thereby influences histone acetylation and consequently modulates gene expression and cell cycle progression. Dysregulation of ACLY and PDC contributes to metabolic reprogramming and promotes the development of multiple cancers. At the same time, glucose metabolism maintains the NAD+/NADH ratio, and NAD+ participates in SIRT-mediated histone deacetylation. SIRT enzyme activity is altered in various malignancies, and inhibiting SIRT6, a histone deacetylase that acts on acetylated H3K9 and H3K56, promotes tumorigenesis. SIRT7, which deacetylates H3K18 and thereby represses transcription of target genes, is activated in cancer to stabilize cells in the transformed state. Nutrients appear to modulate SIRT activity. For example, long-chain fatty acids activate the deacetylase function of SIRT6, and this may affect histone acetylation. [ 33 ]
Epigenetic modifications of histone tails in specific regions of the brain are of central importance in addictions , and much of the work on addiction has focused on histone acetylation. [ 34 ] [ 35 ] [ 36 ] Once particular epigenetic alterations occur, they appear to be long lasting "molecular scars" that may account for the persistence of addictions. [ 34 ] [ 37 ]
Cigarette smokers (about 21% of the US population [ 38 ] ) are usually addicted to nicotine . [ 39 ] After 7 days of nicotine treatment of mice, acetylation of both histone H3 and histone H4 was increased at the FosB promoter in the nucleus accumbens of the brain, causing 61% increase in FosB expression. [ 40 ] This would also increase expression of the splice variant Delta FosB . In the nucleus accumbens of the brain, Delta FosB functions as a "sustained molecular switch" and "master control protein" in the development of an addiction . [ 41 ] [ 42 ]
About 7% of the US population is addicted to alcohol . In rats exposed to alcohol for up to 5 days, there was an increase in histone 3 lysine 9 acetylation in the pronociceptin promoter in the brain amygdala complex. This acetylation is an activating mark for pronociceptin. The nociceptin/nociceptin opioid receptor system is involved in the reinforcing or conditioning effects of alcohol. [ 43 ]
Cocaine addiction occurs in about 0.5% of the US population. Repeated cocaine administration in mice induces hyperacetylation of histone 3 (H3) or histone 4 (H4) at 1,696 genes in one brain "reward" region [the nucleus accumbens (NAc)] and deacetylation at 206 genes. [ 44 ] [ 45 ] At least 45 genes, shown in previous studies to be upregulated in the NAc of mice after chronic cocaine exposure, were found to be associated with hyperacetylation of H3 or H4. Many of these individual genes are directly related to aspects of addiction associated with cocaine exposure. [ 45 ] [ 46 ]
In rodent models, many agents causing addiction, including tobacco smoke products, [ 47 ] alcohol, [ 48 ] cocaine, [ 49 ] heroin [ 50 ] and methamphetamine, [ 51 ] [ 52 ] cause DNA damage in the brain. During repair of DNA damages some individual repair events may alter the acetylations of histones at the sites of damage, or cause other epigenetic alterations, and thus leave an epigenetic scar on chromatin . [ 37 ] Such epigenetic scars likely contribute to the persistent epigenetic changes found in addictions.
In 2013, 22.7 million persons aged 12 or older needed treatment for an illicit drug or alcohol use problem (8.6 percent of persons aged 12 or older). [ 38 ]
Suggested by the idea that the structure of chromatin can be modified to allow or deny access of transcription activators , regulatory functions of histone acetylation and deacetylation can have implications with genes that cause other diseases. Studies on histone modifications may reveal many novel therapeutic targets.
Based on different cardiac hypertrophy models, it has been demonstrated that cardiac stress can result in gene expression changes and alter cardiac function. [ 53 ] These changes are mediated through HATs/HDACs posttranslational modification signaling. HDAC inhibitor trichostatin A was reported to reduce stress induced cardiomyocyte autophagy . [ 54 ] Studies on p300 and CREB-binding protein linked cardiac hypertrophy with cellular HAT activity suggesting an essential role of histone acetylation status with hypertrophy responsive genes such as GATA4 , SRF , and MEF2 . [ 55 ] [ 56 ] [ 57 ] [ 58 ]
Epigenetic modifications also play a role in neurological disorders. Deregulation of histones modification are found to be responsible for deregulated gene expression and hence associated with neurological and psychological disorders, such as Schizophrenia [ 59 ] and Huntington disease . [ 60 ] Current studies indicate that inhibitors of the HDAC family have therapeutic benefits in a wide range of neurological and psychiatric disorders. [ 61 ] Many neurological disorders only affect specific brain regions; therefore, understanding of the specificity of HDACs is still required for further investigations for improved treatments. | https://en.wikipedia.org/wiki/Histone_acetylation_and_deacetylation |
The histone fold is a structural motif located near the C-terminus of histone proteins, characterized by three alpha helices separated by two loops. This motif facilitates the formation of heterodimers , which subsequently assemble into a histone octamer , playing a crucial role in the packaging of DNA into nucleosomes within chromatin . [ 1 ] This fold is an ancient and highly conserved structural motif, essential for DNA compaction and regulation across a wide range of species.
The histone fold motif was first discovered in TATA box -binding protein-associated factors, which play a key role in transcription . [ 1 ]
The histone fold is typically around 70 amino acids long and is characterized by three alpha helices connected by two short, unstructured loops. [ 2 ] In the absence of DNA, core histones assemble into head-to-tail intermediates. For instance, H3 and H4 first form heterodimers, which then combine to form a tetramer. Similarly, H2A and H2B form heterodimers. [ 3 ] These interactions occur through hydrophobic "handshake" interactions between histone fold domains. [ 4 ]
Histones H4 and H2A can form internucleosomal contacts that, when acetylated , enable ionic interactions between peptides. These interactions can alter the surrounding internucleosomal contacts, leading to chromatin opening and increased accessibility for transcription. [ 5 ]
The histone fold plays a crucial role in nucleosome formation by mediating interactions between histones. The largest interface surfaces are found in the heterotypic dimer interactions of H3-H4 and H2A-H2B. These interactions are primarily mediated by the "handshake" motif between histone fold domains. Additionally, the H2A structure has a unique loop modification at its interface, contributing to its distinct role in transcriptional activation. [ citation needed ]
The histone fold is thought to have evolved from ancestral peptide sets that formed helix-strand-helix motifs. These peptides are believed to have originated from ancient fragments, which may be precursors to the modern H3-H4 tetramer found in eukaryotes. Notably, archaeal single-chain histones, similar to eukaryotic histones, are found in the bacterium Aquifex aeolicus , suggesting a shared ancestry between eukaryotes and archaea, with possible lateral gene transfers to bacteria. [ 2 ]
Studies on species like Drosophila have revealed variations in the histone fold motif, particularly in the subunits of transcription initiation factors. These proteins contain histone-like structures, which show that the histone fold motif can also be found in non-histone proteins involved in protein-protein and protein-DNA interactions. [ 4 ] | https://en.wikipedia.org/wiki/Histone_fold |
Histone methylation is a process by which methyl groups are transferred to amino acids of histone proteins that make up nucleosomes , which the DNA double helix wraps around to form chromosomes . Methylation of histones can either increase or decrease transcription of genes, depending on which amino acids in the histones are methylated, and how many methyl groups are attached. Methylation events that weaken chemical attractions between histone tails and DNA increase transcription because they enable the DNA to uncoil from nucleosomes so that transcription factor proteins and RNA polymerase can access the DNA. This process is critical for the regulation of gene expression that allows different cells to express different genes.
Histone methylation, as a mechanism for modifying chromatin structure is associated with stimulation of neural pathways known to be important for formation of long-term memories and learning. [ 1 ] Histone methylation is crucial for almost all phases of animal embryonic development . [ 2 ]
Animal models have shown methylation and other epigenetic regulation mechanisms to be associated with conditions of aging, neurodegenerative diseases , and intellectual disability [ 1 ] ( Rubinstein–Taybi syndrome , X-linked intellectual disability ). [ 3 ] Misregulation of H3K4, H3K27, and H4K20 are associated with cancers . [ 4 ] This modification alters the properties of the nucleosome and affects its interactions with other proteins, particularly in regards to gene transcription processes.
The fundamental unit of chromatin , called a nucleosome , contains DNA wound around a protein octamer . This octamer consists of two copies each of four histone proteins: H2A , H2B , H3 , and H4 . Each one of these proteins has a tail extension, and these tails are the targets of nucleosome modification by methylation. DNA activation or inactivation is largely dependent on the specific tail residue methylated and its degree of methylation. Histones can be methylated on lysine (K) and arginine (R) residues only, but methylation is most commonly observed on lysine residues of histone tails H3 and H4. [ 7 ] The tail end furthest from the nucleosome core is the N-terminal (residues are numbered starting at this end). Common sites of methylation associated with gene activation include H3K4, H3K48, and H3K79. Common sites for gene inactivation include H3K9 and H3K27. [ 8 ] Studies of these sites have found that methylation of histone tails at different residues serve as markers for the recruitment of various proteins or protein complexes that serve to regulate chromatin activation or inactivation.
Lysine and arginine residues both contain amino groups, which confer basic and hydrophobic characteristics. Lysine is able to be mono-, di-, or trimethylated with a methyl group replacing each hydrogen of its NH3+ group. With a free NH2 and NH2+ group, arginine is able to be mono- or dimethylated. This dimethylation can occur asymmetrically on the NH2 group or symmetrically with one methylation on each group. [ 9 ] Each addition of a methyl group on each residue requires a specific set of protein enzymes with various substrates and cofactors. Generally, methylation of an arginine residue requires a complex including protein arginine methyltransferase (PRMT) while lysine requires a specific histone methyltransferase (HMT), usually containing an evolutionarily conserved SET domain. [ 10 ]
Different degrees of residue methylation can confer different functions, as exemplified in the methylation of the commonly studied H4K20 residue. Monomethylated H4K20 ( H4K20me 1) is involved in the compaction of chromatin and therefore transcriptional repression. However, H4K20me2 is vital in the repair of damaged DNA. When dimethylated, the residue provides a platform for the binding of protein 53BP1 involved in the repair of double-stranded DNA breaks by non-homologous end joining. H4K20me3 is observed to be concentrated in heterochromatin and reductions in this trimethylation are observed in cancer progression. Therefore, H4K20me3 serves an additional role in chromatin repression. [ 10 ] Repair of DNA double-stranded breaks in chromatin also occurs by homologous recombination and also involves histone methylation ( H3K9me3 ) to facilitate access of the repair enzymes to the sites of damage. [ 11 ]
The genome is tightly condensed into chromatin, which needs to be loosened for transcription to occur. In order to halt the transcription of a gene the DNA must be wound tighter. This can be done by modifying histones at certain sites by methylation. Histone methyltransferases are enzymes which transfer methyl groups from S-Adenosyl methionine (SAM) onto the lysine or arginine residues of the H3 and H4 histones. There are instances of the core globular domains of histones being methylated as well.
The histone methyltransferases are specific to either lysine or arginine. The lysine-specific transferases are further broken down into whether or not they have a SET domain or a non-SET domain. These domains specify exactly how the enzyme catalyzes the transfer of the methyl from SAM to the transfer protein and further to the histone residue. [ 12 ] The methyltransferases can add 1-3 methyls on the target residues.
These methyls that are added to the histones act to regulate transcription by blocking or encouraging DNA access to transcription factors. In this way the integrity of the genome and epigenetic inheritance of genes are under the control of the actions of histone methyltransferases. Histone methylation is key in distinguishing the integrity of the genome and the genes that are expressed by cells, thus giving the cells their identities.
Methylated histones can either repress or activate transcription. [ 12 ] For example, while H3K4me2 , H3K4me3 , and H3K79me3 are generally associated with transcriptional activity, whereas H3K9me2 , H3K9me3 , H3K27me2 , H3K27me3 , and H4K20me3 are associated with transcriptional repression. [ 13 ]
Modifications made on the histone have an effect on the genes that are expressed in a cell and this is the case when methyls are added to the histone residues by the histone methyltransferases. [ 14 ] Histone methylation plays an important role on the assembly of the heterochromatin mechanism and the maintenance of gene boundaries between genes that are transcribed and those that aren’t. These changes are passed down to progeny and can be affected by the environment that the cells are subject to. Epigenetic alterations are reversible meaning that they can be targets for therapy.
The activities of histone methyltransferases are offset by the activity of histone demethylases. This allows for the switching on or off of transcription by reversing pre-existing modifications. It is necessary for the activities of both histone methyltransferases and histone demethylases to be regulated tightly. Misregulation of either can lead to gene expression that leads to increased susceptibility to disease. Many cancers arise from the inappropriate epigenetic effects of misregulated methylation. [ 15 ] However, because these processes are at times reversible, there is interest in utilizing their activities in concert with anti-cancer therapies. [ 15 ]
In female organisms, a sperm containing an X chromosome fertilizes the egg, giving the embryo two copies of the X chromosome. Females, however, do not initially require both copies of the X chromosome as it would only double the amount of protein products transcribed as shown by the hypothesis of dosage compensation. The paternal X chromosome is quickly inactivated during the first few divisions. [ 16 ] This inactive X chromosome (Xi) is packed into an incredibly tight form of chromatin called heterochromatin . [ 17 ] This packing occurs due to the methylation of the different lysine residues that help form different histones. In humans X inactivation is a random process, that is mediated by the non-coding RNA XIST. [ 18 ]
Although methylation of lysine residues occurs on many different histones, the most characteristic of Xi occurs on the ninth lysine of the third histone (H3K9). While a single methylation of this region allows for the genes bound to remain transcriptionally active, [ 19 ] in heterochromatin this lysine residue is often methylated twice or three times, H3K9me2 or H3K9me3 respectively, to ensure that the DNA bound is inactive. More recent research has shown that H3K27me3 and H4K20me1 are also common in early embryos. Other methylation markings associated with transcriptionally active areas of DNA, H3K4me2 and H3K4me3, are missing from the Xi chromosome along with many acetylation markings. Although it was known that certain Xi histone methylation markings stayed relatively constant between species, it has recently been discovered that different organisms and even different cells within a single organism can have different markings for their X inactivation. [ 20 ] Through histone methylation, there is genetic imprinting , so that the same X homolog stays inactivated through chromosome replications and cell divisions.
Due to the fact that histone methylation regulates much of what genes become transcribed, even slight changes to the methylation patterns can have dire effects on the organism. Mutations that occur to increase and decrease methylation have great changes on gene regulation, while mutations to enzymes such as methyltransferase and demethyltransferase can completely alter which proteins are transcribed in a given cell. Over methylation of a chromosome can cause certain genes that are necessary for normal cell function, to become inactivated. In a certain yeast strain, Saccharomyces cerevisiae , a mutation that causes three lysine residues on the third histone, H3K4, H3K36, and H3K79, to become methylated causes a delay in the mitotic cell cycle, as many genes required for this progression are inactivated. This extreme mutation leads to the death of the organism. It has been discovered that the deletion of genes that will eventually allow for the production of histone methyltransferase allows this organism to live as its lysine residues are not methylated. [ 21 ]
In recent years it has come to the attention of researchers that many types of cancer are caused largely due to epigenetic factors. Cancer can be caused in a variety of ways due to differential methylation of histones. Since the discovery of oncogenes as well as tumor suppressor genes it has been known that a large factor of causing and repressing cancer is within our own genome. If areas around oncogenes become unmethylated these cancer-causing genes have the potential to be transcribed at an alarming rate. Opposite of this is the methylation of tumor suppressor genes. In cases where the areas around these genes were highly methylated, the tumor suppressor gene was not active and therefore cancer was more likely to occur. These changes in methylation pattern are often due to mutations in methyltransferase and demethyltransferase. [ 22 ] Other types of mutations in proteins such as isocitrate dehydrogenase 1 (IDH1) and isocitrate dehydrogenase 2 (IDH2) can cause the inactivation of histone demethyltransferase which in turn can lead to a variety of cancers, gliomas and leukemias, depending on in which cells the mutation occurs. [ 23 ]
In one-carbon metabolism, the amino acids glycine and serine are converted via the folate and methionine cycles to nucleotide precursors and SAM. Multiple nutrients fuel one-carbon metabolism, including glucose , serine, glycine, and threonine . High levels of the methyl donor SAM influence histone methylation, which may explain how high SAM levels prevent malignant transformation. [ 24 ] | https://en.wikipedia.org/wiki/Histone_methylation |
Histone methyltransferases ( HMT ) are histone-modifying enzymes (e.g., histone-lysine N-methyltransferases and histone-arginine N-methyltransferases), that catalyze the transfer of one, two, or three methyl groups to lysine and arginine residues of histone proteins . The attachment of methyl groups occurs predominantly at specific lysine or arginine residues on histones H3 and H4. [ 1 ] Two major types of histone methyltranferases exist, lysine-specific (which can be SET ( S u(var)3-9, E nhancer of Zeste, T rithorax) domain containing or non-SET domain containing) and arginine-specific. [ 2 ] [ 3 ] [ 4 ] In both types of histone methyltransferases, S-Adenosyl methionine (SAM) serves as a cofactor and methyl donor group. [ 1 ] [ 5 ] [ 6 ] [ 7 ] The genomic DNA of eukaryotes associates with histones to form chromatin . [ 8 ] The level of chromatin compaction depends heavily on histone methylation and other post-translational modifications of histones. [ 9 ] Histone methylation is a principal epigenetic modification of chromatin [ 9 ] that determines gene expression, genomic stability, stem cell maturation, cell lineage development, genetic imprinting, DNA methylation, and cell mitosis. [ 2 ]
The class of lysine-specific histone methyltransferases is subdivided into SET domain-containing and non-SET domain-containing. As indicated by their monikers, these differ in the presence of a SET domain, which is a type of protein domain.
Human genes encoding proteins with histone methyltransferase activity include:
The structures involved in methyltransferase activity are the SET domain (composed of approximately 130 amino acids), the pre-SET, and the post-SET domains. The pre-SET and post-SET domains flank the SET domain on either side. The pre-SET region contains cysteine residues that form triangular zinc clusters, tightly binding the zinc atoms and stabilizing the structure. The SET domain itself contains a catalytic core rich in β-strands that, in turn, make up several regions of β-sheets. Often, the β-strands found in the pre-SET domain will form β-sheets with the β-strands of the SET domain, leading to slight variations to the SET domain structure. These small changes alter the target residue site specificity for methylation and allow the SET domain methyltransferases to target many different residues. This interplay between the pre-SET domain and the catalytic core is critical for enzyme function. [ 1 ]
In order for the reaction to proceed, S-Adenosyl methionine (SAM) and the lysine residue of the substrate histone tail must first be bound and properly oriented in the catalytic pocket of the SET domain. Next, a nearby tyrosine residue deprotonates the ε-amino group of the lysine residue. [ 10 ] The lysine chain then makes a nucleophilic attack on the methyl group on the sulfur atom of the SAM molecule, transferring the methyl group to the lysine side chain.
Instead of SET, non-SET domain-containing histone methyltransferase utilizes the enzyme Dot1. Unlike the SET domain, which targets the lysine tail region of the histone, Dot1 methylates a lysine residue in the globular core of the histone, and is the only enzyme known to do so. [ 1 ] A possible homolog of Dot1 was found in archaea which shows the ability to methylate archaeal histone-like protein in recent studies.
The N terminal of Dot1 contains the active site. A loop serving as the binding site for SAM links the N-terminal and the C-terminal domains of the Dot1 catalytic domain. The C-terminal is important for the substrate specificity and binding of Dot1 because the region carries a positive charge, allowing for a favorable interaction with the negatively charged backbone of DNA. [ 11 ] Due to structural constraints, Dot1 is only able to methylate histone H3.
There are three different types of protein arginine methyltransferases (PRMTs) and three types of methylation that can occur at arginine residues on histone tails. The first type of PRMTs ( PRMT1 , PRMT3 , CARM1 ⧸PRMT4, and Rmt1⧸Hmt1) produce monomethylarginine and asymmetric dimethylarginine (Rme2a). [ 12 ] [ 13 ] [ 14 ] The second type (JBP1⧸ PRMT5 ) produces monomethyl or symmetric dimethylarginine (Rme2s). [ 5 ] The third type (PRMT7) produces only monomethylated arginine. [ 15 ] The differences in methylation patterns of PRMTs arise from restrictions in the arginine binding pocket. [ 5 ]
The catalytic domain of PRMTs consists of a SAM binding domain and substrate binding domain (about 310 amino acids in total). [ 5 ] [ 6 ] [ 7 ] Each PRMT has a unique N-terminal region and a catalytic core. The arginine residue and SAM must be correctly oriented within the binding pocket. SAM is secured inside the pocket by a hydrophobic interaction between an adenine ring and a phenyl ring of a phenylalanine. [ 7 ]
A glutamate on a nearby loop interacts with nitrogens on the target arginine residue. This interaction redistributes the positive charge and leads to the deprotonation of one nitrogen group, [ 16 ] which can then make a nucleophilic attack on the methyl group of SAM. Differences between the two types of PRMTs determine the next methylation step: either catalyzing the dimethylation of one nitrogen or allowing the symmetric methylation of both groups. [ 5 ] However, in both cases the proton stripped from the nitrogen is dispersed through a histidine–aspartate proton relay system and released into the surrounding matrix. [ 17 ]
Histone methylation plays an important role in epigenetic gene regulation . Methylated histones can either repress or activate transcription as different experimental findings suggest, depending on the site of methylation. For example, it is likely that the methylation of lysine 9 on histone H3 (H3K9me3) in the promoter region of genes prevents excessive expression of these genes and, therefore, delays cell cycle transition and/or proliferation. [ 18 ] In contrast, methylation of histone residues H3K4, H3K36, and H3K79 is associated with transcriptionally active euchromatin. [ 2 ]
Depending on the site and symmetry of methylation, methylated arginines are considered activating (histone H4R3me2a, H3R2me2s, H3R17me2a, H3R26me2a) or repressive (H3R2me2a, H3R8me2a, H3R8me2s, H4R3me2s) histone marks. [ 15 ] Generally, the effect of a histone methyltransferase on gene expression strongly depends on which histone residue it methylates. See Histone#Chromatin regulation .
Abnormal expression or activity of methylation-regulating enzymes has been noted in some types of human cancers, suggesting associations between histone methylation and malignant transformation of cells or formation of tumors. [ 18 ] In recent years, epigenetic modification of the histone proteins, especially the methylation of the histone H3, in cancer development has been an area of emerging research. It is now generally accepted that in addition to genetic aberrations, cancer can be initiated by epigenetic changes in which gene expression is altered without genomic abnormalities. These epigenetic changes include loss or gain of methylations in both DNA and histone proteins. [ 18 ]
There is not yet compelling evidence that suggests cancers develop purely by abnormalities in histone methylation or its signaling pathways, however they may be a contributing factor. For example, down-regulation of methylation of lysine 9 on histone 3 (H3K9me3) has been observed in several types of human cancer (such as colorectal cancer, ovarian cancer, and lung cancer), which arise from either the deficiency of H3K9 methyltransferases or elevated activity or expression of H3K9 demethylases. [ 18 ] [ 19 ] [ 20 ]
The methylation of histone lysine has an important role in choosing the pathway for repairing DNA double-strand breaks . [ 21 ] As an example, tri-methylated H3K36 is required for homologous recombinational repair, while dimethylated H4K20 can recruit the 53BP1 protein for repair by the pathway of non-homologous end joining .
Histone methyltransferase may be able to be used as biomarkers for the diagnosis and prognosis of cancers. Additionally, many questions still remain about the function and regulation of histone methyltransferases in malignant transformation of cells, carcinogenesis of the tissue, and tumorigenesis. [ 18 ] | https://en.wikipedia.org/wiki/Histone_methyltransferase |
In molecular biology , a histone octamer is the eight-protein complex found at the center of a nucleosome core particle . It consists of two copies of each of the four core histone proteins ( H2A , H2B , H3 , and H4 ). The octamer assembles when a tetramer , containing two copies of H3 and two of H4, complexes with two H2A/H2B dimers. Each histone has both an N-terminal tail and a C-terminal histone-fold. Each of these key components interacts with DNA in its own way through a series of weak interactions, including hydrogen bonds and salt bridges . These interactions keep the DNA and the histone octamer loosely associated, and ultimately allow the two to re-position or to separate entirely.
Histone post-translational modifications were first identified and listed as having a potential regulatory role on the synthesis of RNA in 1964. [ 1 ] Since then, over several decades, chromatin theory has evolved. Chromatin subunit models as well as the notion of the nucleosome were established in 1973 and 1974, respectively. [ 2 ] Richmond and his research group has been able to elucidate the crystal structure of the histone octamer with DNA wrapped up around it at a resolution of 7 Å in 1984. [ 3 ] The structure of the octameric core complex was revisited seven years later and a resolution of 3.1 Å was elucidated for its crystal at a high salt concentration. Though sequence similarity is low between the core histones, each of the four have a repeated element consisting of a helix-loop-helix called the histone fold motif. [ 4 ] Furthermore, the details of protein-protein and protein-DNA interactions were fine-tuned by X-ray crystallography studies at 2.8 and 1.9 Å, respectively, in the 2000s. [ 5 ]
Core histones are four proteins called H2A, H2B, H3 and H4 and they are all found in equal parts in the cell. All four of the core histone amino acid sequences contain between 20 and 24% of lysine and arginine and the size or the protein ranges between 11400 and 15400 daltons, making them relatively small, yet highly positively charged proteins. [ 6 ] High content of positively charged amino acids allow them to closely associate with negatively charged DNA . Heterodimers, or histone-only intermediates are formed from histone-fold domains. The formation of histone only-intermediates proceeds when core histones are paired into the interlocked crescent shape quasi-symmetric heterodimer. Each histone fold domain is composed of 3 α-helix regions that are separated by disordered loops. The histone fold domain is responsible for formation of head-to-tail heterodimers of two histones: H2A-H2B and H3-H4. However, H3 and H4 histones first form a heterodimer and then in turn the heterodimer dimerizes to form a tetramer (H3-H4) 2 . [ 7 ] The heterodimer formation is based on the interaction of hydrophobic amino acid residue interactions between the two proteins. [ 7 ]
Quasi symmetry allows the heterodimer to be superimposed on itself by a 180 degree rotation around this symmetry axis. As a result of the rotation, two ends of histones involved in DNA binding of the crescent shape H3-H4 are equivalent, yet they organize different stretches of DNA. The H2A-H2B dimer also folds similarly. The (H3-H4) 2 tetramer is wrapped with DNA around it as a first step of nucleosome formation. Then two H2A-H2B dimers are connected to the DNA-(H3-H4) 2 complex to form a nucleosome. [ 8 ]
Each of the four core histones, in addition to their histone-fold domains, also contain flexible, unstructured extensions called histone “tails”. [ 9 ] Treatment of nucleosomes with protease trypsin indicates that after histone tails are removed, DNA is able to stay tightly bound to the nucleosome. [ 6 ] Histone tails are subject to a wide array of modifications which includes phosphorylation , acetylation , and methylation of serine, lysine and arginine residues. [ 6 ]
The nucleosome core particle is the most basic form of DNA compaction in eukaryotes . Nucleosomes consist of a histone octamer surrounded by 146 base pairs of DNA wrapped in a superhelical manner. [ 10 ] In addition to compacting the DNA, the histone octamer plays a key role in the transcription of the DNA surrounding it. The histone octamer interacts with the DNA through both its core histone folds and N-terminal tails. The histone fold interacts chemically and physically with the DNA's minor groove . Studies have found that the histones interact more favorably with A : T enriched regions than G : C enriched regions in the minor grooves. [ 6 ] The N-terminal tails do not interact with a specific region of DNA but rather stabilize and guide the DNA wrapped around the octamer. The interactions between the histone octamer and DNA, however, are not permanent. The two can be separated quite easily and often are during replication and transcription . Specific remodeling proteins are constantly altering the chromatin structure by breaking the bonds between the DNA and nucleosome.
Histones are composed of mostly positively charged amino acid residues such as lysine and arginine . The positive charges allow them to closely associate with the negatively charged DNA through electrostatic interactions. Neutralizing the charges in the DNA allows it to become more tightly packed. [ 6 ]
The histone-fold domains’ interaction with the minor groove accounts for the majority of the interactions in the nucleosome. [ 11 ] As the DNA wraps around the histone octamer, it exposes its minor groove to the histone octamer at 14 distinct locations. At these sites, the two interact through a series of weak, non-covalent bonds. The main source of bonds comes from hydrogen bonds, both direct and water-mediated. [ 10 ] The histone-fold hydrogen bonds with both phosphodiester backbone and the A:T rich bases. In these interactions, the histone fold binds to the oxygen atoms and hydroxyl side chains, respectively. [ 11 ] Together these sites have a total of about 40 hydrogen bonds, most of which are from the backbone interactions. [ 6 ] Additionally, 10 out of the 14 times that the minor groove faces the histone fold, an arginine side chain from the histone fold is inserted into the minor groove. The other four times, the arginine comes from a tail region of the histone. [ 11 ]
As mentioned above the histone tails have been shown to directly interact with the DNA of the nucleosome. Each histone in the octamer has an N-terminal tail that protrudes from the histone core. The tails play roles both in inter and intra nucleosomal interactions that ultimately influence gene access. [ 12 ] Histones are positively charged molecules which allow a tighter bonding to the negatively charged DNA molecule. Reducing the positive charge of histone proteins reduces the strength of binding between the histone and DNA, making it more open to gene transcription (expression). [ 12 ] Moreover, these flexible units direct DNA wrapping in a left-handed manner around the histone octamer during nucleosome formation. [ 6 ] Once the DNA is bound the tails continue to interact with the DNA. The parts of the tail closest to the DNA hydrogen bond and strengthen the DNA's association with the octamer; the parts of the tail furthest away from the DNA, however, work in a very different manner. Cellular enzymes modify the amino acids in the distal sections of the tail to influence the accessibility of the DNA. The tails have also been implicated in the stabilization of 30-nm fibers. Research has shown removing certain tails prevents the nucleosomes from forming properly and a general failure to produce chromatin fiber. [ 12 ] In all, these associations protect the nucleosomal DNA from the external environment but also lower their accessibility to cellular replication and transcriptional machinery.
In order to access the nucleosomal DNA, the bonds between it and the histone octamer must be broken. This change takes place periodically in the cell as specific regions are transcribed, and it happens genome-wide during replication. Remodeling proteins work in three distinct ways: they can slide the DNA along the surface of the octamer, replace the one histone dimer with a variant, or remove the histone octamer entirely. No matter the method, in order to modify the nucleosomes, the remodeling complexes require energy from ATP hydrolysis to drive their actions.
Of the three techniques, sliding is the most common and least extreme. [ 13 ] The basic premise of the technique is to free up a region of DNA that the histone octamer would normally tightly bind. While the technique is not well defined, the most prominent hypothesis is that the sliding is done in an “inchworm” fashion. In this method, using ATP as an energy source, the translocase domain of the nucleosome-remodeling complex detaches a small region of DNA from the histone octamer. This “wave” of DNA, spontaneously breaking and remaking the hydrogen bonds as it goes, then propagates down the nucleosomal DNA until it reaches the last binding site with the histone octamer. Once the wave reaches the end of the histone octamer the excess that was once at the edge is extended into the region of linker DNA. In total, one round of this method moves the histone octamer several base pairs in a particular direction—away from the direction the “wave” propagated. [ 6 ] [ 14 ]
Numerous reports show a link between age-related diseases, birth defects, and several types of cancer with disruption of certain histone post translational modifications. Studies have identified that N- and C-terminal tails are main targets for acetylation, methylation, ubiquitination and phosphorylation. [ 15 ] New evidence is pointing to several modifications within the histone core. Research is turning towards deciphering the role of these histone core modifications at the histone-DNA interface in the chromatin. p300 and cAMP response element-binding protein ( CBP ) possess histone acetyltransferase activity. p300 and CBP are the most promiscuous histone acetyltransferase enzymes acetylating all four core histones on multiple residues. [ 16 ] Lysine 18 and Lysine 27 on H3 were the only histone acetylation sites reduced upon CBP and p300 depletion in mouse embryonic fibroblasts. [ 17 ] Also, CBP and p300 knockout mice have an open neural tube defect and therefore die before birth. p300−/− embryos exhibit defective development of the heart. CBP+/− mice display growth retardation, craniofacial abnormalities, hematological malignancies, which are not observed in mice with p300+/−. [ 18 ] Mutations of both p300 have been reported in human tumors such as colorectal, gastric, breast, ovarian, lung, and pancreatic carcinomas. Also, activation or localization of two histone acetyltransferases can be oncogenic. | https://en.wikipedia.org/wiki/Histone_octamer |
Histopathology (compound of three Greek words: ἱστός histos 'tissue', πάθος pathos 'suffering', and -λογία -logia 'study of') is the microscopic examination of tissue in order to study the manifestations of disease . Specifically, in clinical medicine, histopathology refers to the examination of a biopsy or surgical specimen by a pathologist , after the specimen has been processed and histological sections have been placed onto glass slides. In contrast, cytopathology examines free cells or tissue micro-fragments (as "cell blocks
").
Histopathological examination of tissues starts with surgery , biopsy , or autopsy . The tissue is removed from the body or plant , and then, often following expert dissection in the fresh state, placed in a fixative which stabilizes the tissues to prevent decay . The most common fixative is 10% neutral buffered formalin (corresponding to 3.7% w/v formaldehyde in neutral buffered water, such as phosphate buffered saline ).
The tissue is then prepared for viewing under a microscope using either chemical fixation or frozen section.
If a large sample is provided e.g. from a surgical procedure then a pathologist looks at the tissue sample and selects the part most likely to yield a useful and accurate diagnosis - this part is removed for examination in a process commonly known as grossing or cut up. Larger samples are cut to correctly situate their anatomical structures in the cassette. Certain specimens (especially biopsies) can undergo agar pre-embedding to assure correct tissue orientation in cassette & then in the block & then on the diagnostic microscopy slide. This is then placed into a plastic cassette for most of the rest of the process. [ citation needed ]
In addition to formalin, other chemical fixatives have been used. But, with the advent of immunohistochemistry (IHC) staining and diagnostic molecular pathology testing on these specimen samples, formalin has become the standard chemical fixative in human diagnostic histopathology. Fixation times for very small specimens are shorter, and standards exist in human diagnostic histopathology.
Water is removed from the sample in successive stages by the use of increasing concentrations of alcohol . [ 1 ] Xylene is used in the last dehydration phase instead of alcohol - this is because the wax used in the next stage is soluble in xylene where it is not in alcohol allowing wax to permeate (infiltrate) the specimen. [ 1 ] This process is generally automated and done overnight. The wax infiltrated specimen is then transferred to an individual specimen embedding (usually metal) container. Finally, molten wax is introduced around the specimen in the container and cooled to solidification so as to embed it in the wax block. [ 1 ] This process is needed to provide a properly oriented sample sturdy enough for obtaining a thin microtome section(s) for the slide.
Once the wax embedded block is finished, sections will be cut from it and usually placed to float on a water bath surface which spreads the section out. This is usually done by hand and is a skilled job (histotechnologist) with the lab personnel making choices about which parts of the specimen microtome wax ribbon to place on slides. A number of slides will usually be prepared from different levels throughout the block. After this the thin section mounted slide is stained and a protective cover slip is mounted on it. For common stains, an automatic process is normally used; but rarely used stains are often done by hand. [ 1 ]
An initial evaluation of a suspected lymphoma is to make a "touch prep" wherein a glass slide is lightly pressed against excised lymphoid tissue, and subsequently stained (usually H&E stain ) for evaluation under light microscopy .
The second method of histology processing is called frozen section processing. This is a highly technical scientific method performed by a trained histoscientist. In this method, the tissue is frozen and sliced thinly using a microtome mounted in a below-freezing refrigeration device called the cryostat . The thin frozen sections are mounted on a glass slide, fixed immediately & briefly in liquid fixative, and stained using the similar staining techniques as traditional wax embedded sections. The advantages of this method is rapid processing time, less equipment requirement, and less need for ventilation in the laboratory. The disadvantage is the poor quality of the final slide. It is used in intra-operative pathology for determinations that might help in choosing the next step in surgery during that surgical session (for example, to preliminarily determine clearness of the resection margin of a tumor during surgery).
This can be done to slides processed by the chemical fixation or frozen section slides. To see the tissue under a microscope, the sections are stained with one or more pigments . The aim of staining is to reveal cellular components; counterstains are used to provide contrast.
The most commonly used stain in histology is a combination of hematoxylin and eosin (often abbreviated H&E). Hematoxylin is used to stain nuclei blue , while eosin stains the cytoplasm and the extracellular connective tissue matrix of most cells pink . There are hundreds of various other techniques which have been used to selectively stain cells. Other compounds used to color tissue sections include safranin , Oil Red O , congo red , silver salts and artificial dyes. Histochemistry refers to the science of using chemical reactions between laboratory chemicals and components within tissue. A commonly performed histochemical technique is the Perls' Prussian blue reaction, used to demonstrate iron deposits in diseases like Hemochromatosis . [ 2 ]
Recently, antibodies have been used to stain particular proteins , lipids and carbohydrates . Called immunohistochemistry , this technique has greatly increased the ability to specifically identify categories of cells under a microscope. Other advanced techniques include in situ hybridization to identify specific DNA or RNA molecules. These antibody staining methods often require the use of frozen section histology. These procedures above are also carried out in the laboratory under scrutiny and precision by a trained specialist medical laboratory scientist (a histoscientist). Digital cameras are increasingly used to capture histopathological images.
The histological slides are examined under a microscope by a pathologist , a medically qualified specialist who has completed a recognised training program. This medical diagnosis is formulated as a pathology report describing the histological findings and the opinion of the pathologist. In the case of cancer , this represents the tissue diagnosis required for most treatment protocols. In the removal of cancer , the pathologist will indicate whether the surgical margin is cleared, or is involved (residual cancer is left behind). This is done using either the bread loafing or CCPDMA method of processing. Microscopic visual artifacts can potentially cause misdiagnosis of samples. Scanning of slides allows for various methods of digital pathology , including the application of artificial intelligence for interpretation.
Following are examples of general features of suspicious findings that can be appreciated from low to high magnification on histopathology:
Major histopathologic architectural patterns include:
Major nuclear patterns include: | https://en.wikipedia.org/wiki/Histopathology |
The Historical Metallurgy Society is a British learned society providing an international forum for exchange of information and research in historical metallurgy . It was founded as the Historical Metallurgy Group in 1963. All aspects of the history of metals and associated materials are covered from prehistory to the present, from processes and production through technology and economics to archaeology and conservation. [ 1 ]
The Historical Metallurgy Society origins were partly a response to the damage and destruction of many historically important metallurgical sites. Conservation, research and protection remain important parts of the society’s role.
Each year the society holds a two-day conference (usually in the United Kingdom ) with a program of papers covering a particular area of metallurgical interest. In addition to this, it also runs other day meetings.
The Historical Metallurgy Society publishes Historical Metallurgy an internationally recognised peer-reviewed journal, published annually in two parts. The society also issues a newsletter The Crucible three times a year, and has published edited collections based on the papers given at several of its conferences in an Occasional Papers series.
The Historical Metallurgy Society is a company limited by guarantee (no. 1442508) and a registered charity (no. 279314). | https://en.wikipedia.org/wiki/Historical_Metallurgy_Society |
Historical astronomy is the science of analysing historic astronomical data. The American Astronomical Society (AAS), established 1899, states that its Historical Astronomy Division "...shall exist for the purpose of advancing interest in topics relating to the historical nature of astronomy. By historical astronomy we include the history of astronomy ; what has come to be known as archaeoastronomy ; and the application of historical records to modern astrophysical problems." [1] Historical and ancient observations are used to track theoretically long term trends, such as eclipse patterns and the velocity of nebular clouds. [2] Conversely, using known and well documented phenomenological activity, historical astronomers apply computer models to verify the validity of ancient observations, as well as dating such observations and documents which would otherwise be unknown.
This astronomy -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Historical_astronomy |
Historical dynamics broadly includes the scientific modeling of history . This might also be termed computer modeling of history, historical simulation, or simulation of history - allowing for an extensive range of techniques in simulation and estimation. Historical dynamics does not exist as a separate science, but there are individual efforts such as long range planning, population modeling , economic forecasting , demographics , global modeling , country modeling , regional planning , urban planning and many others in the general categories of computer modeling , planning , forecasting , and simulations .
Some examples of "large" history where historical dynamics simulations would be helpful include; global history , large structures, histories of empires , long duration history, philosophy of history , Eurasian history , comparative history , long-range environmental history , world systems theory , non-Western political and economic development, and historical demography .
With the rise of technologies like wikis, and internet-wide search engines, some historical and social data can be mined to constrain models of history and society. Data from social media sites, and busy sites, can be mined for human patterns of action. These can provide more and more realistic behavioral models for individuals and groups of any size. Agent-based models and microsimulations of human behavior can be embedded in larger historical simulations. Related subfields are behavioral economics and human behavioral ecology .
In every sector of human activity, there are extensive databases for transportation data , urban development , health statistics , education data , social data , economic data —along with many projections. See Category:economic databases , Category:statistical data sets , Category:social statistics data , Category:social statistics and Category:statistics .
Some examples of database activity include Asian Development Bank statistics, [ 2 ] World Bank data, [ 3 ] and the International Monetary Fund data. [ 4 ]
Time series analysis and econometrics are well established fields for the analysis of trends and forecasting ; but, survey data and microdatasets can also be used in forecasts and simulations.
The United Nations [ 5 ] and other organizations routinely project the population of individual countries and regions of the world decades into the future. These demographic models are used by other organizations for projecting demand for services in all sectors of each economy.
Each country often has their corresponding modeling groups for each of these major sectors. These can be grouped in separate articles according to sector. Groups include government departments, international aid agencies , as well as nonprofit and non-governmental organizations .
A broad class of models used for economic and social modeling of countries and sectors are the Computable general equilibrium (CGE) model - also called applied general equilibrium models. In the context of time based simulations and policy analysis, see dynamic stochastic general equilibrium models.
Partly because of the controversy over global climate change , there is an extensive network of global climate models, [ 8 ] [ 9 ] and related social and economic models. These seek to estimate, not only the change in climate and its physical effects, but also the impact on human society and the natural environment. See global economic models , social model , microsimulation , climate model , global climate models , and general circulation model .
The relationship between the environment and society is examined through environmental social science . human ecology , political ecology , and ecology , in general, can be areas where computer and mathematical modeling over time can be relevant to historical simulation.
Web-based historical simulations, simulations of history , interactive historical simulations, are increasingly popular for entertainment and educational purposes. [ 10 ] The field is expanding rapidly and no central index seems to be available. Another example is [ 11 ]
Several computer games allow players to interact with the game to model societies over time. The Civilization (series) is one example. Others include Age of Empires , Rise of Nations , Spore , Colonization , Alpha Centauri , Call to Power , and CivCity: Rome . A longer list of games in historical context, which might include degrees of simulation, are found at Category:Video games with historical settings .
Military simulation is a well-developed field and increasingly accessible on the internet.
Computer models for simulating society fall under artificial society , social simulation , computational sociology , computational social science , and mathematical sociology . There is an interdisciplinary Journal of Artificial Societies and Social Simulation for computer simulation of social processes. [ 12 ] The European Social Simulation Association promotes social simulation research in Europe; it is the publisher of JASSS. [ 13 ] There is a corresponding Computational Social Science Society of the Americas ., [ 14 ] and a Pan-Asian Association for Agent-based Approach in Social Systems Sciences. [ 15 ] PAAA lists some related Japanese associations. [ 16 ]
The SimSoc ( Simulated Society tool) is in its fifth edition.
There has been extensive research in urban planning , environmental planning and related fields: regional planning , land-use planning , transportation planning , urban studies , and regional science . Journals for these fields are listed at List of planning journals .
SimCity is a game for simulations of artificial cities. It has spawned a range of "sim" games. The planning groups try to simulate changes in real cities. The game groups allow experiments with artificial cities. And the two are merging in such efforts as Vizicities [ 17 ]
The profiling of industries is well developed, and most industries make forecasts and plans. See industrial history , history of steel , history of mining , history of construction , history of the petroleum industry , and many other histories of specific industries. See cyclical industrial dynamics for modeling of industries in the sense of "historical dynamics of industries". Some related terms are industrial planning , history of industry , industrial evolution , technology change , and technology forecasting . An example of "history friendly" industrial models. [ 18 ] from the journal, Industrial and Corporate Change. [ 19 ]
Economy-wide models must take into account the interactions between industry and the rest of the economy. See Input–output model , economic planning , and social accounting matrix for some relevant techniques.
Many of the techniques from futures studies are applicable to historical dynamics. Whether projecting forward from a point in the past to the present for validation studies, or projecting backwards from the present into the past - many of the techniques are useful. Likewise, simulations of the past, or alternative pasts, provide a groundwork of techniques for futures studies. | https://en.wikipedia.org/wiki/Historical_dynamics |
Historical ecology is a research program that focuses on the interactions between humans and their environment over long-term periods of time, typically over the course of centuries. [ 1 ] In order to carry out this work, historical ecologists synthesize long-series data collected by practitioners in diverse fields. [ 2 ] Rather than concentrating on one specific event, historical ecology aims to study and understand this interaction across both time and space in order to gain a full understanding of its cumulative effects. Through this interplay, humans both adapt to and shape the environment, continuously contributing to landscape transformation. Historical ecologists recognize that humans have had world-wide influences, impact landscape in dissimilar ways which increase or decrease species diversity, and that a holistic perspective is critical to be able to understand that system. [ 3 ]
Piecing together landscapes requires a sometimes difficult union between natural and social sciences , close attention to geographic and temporal scales, a knowledge of the range of human ecological complexity, and the presentation of findings in a way that is useful to researchers in many fields. [ 4 ] Those tasks require theory and methods drawn from geography , biology , ecology , history , sociology , anthropology , and other disciplines. Common methods include historical research, climatological reconstructions, plant and animal surveys, archaeological excavations, ethnographic interviews , and landscape reconstructions. [ 2 ]
The discipline has several sites of origins by researchers who shared a common interest in the problem of ecology and history, but with a diversity of approaches. [ 2 ] Edward Smith Deevey, Jr. used the term in the 1960s [ 5 ] to describe a methodology that had been in long development. [ 6 ] Deevey wished to bring together the practices of "general ecology" which was studied in an experimental laboratory, with a "historical ecology" which relied on evidence collected through fieldwork. For example, Deevey used radiocarbon dating to reconcile biologists’ successions of plants and animals with the sequences of material culture and sites discovered by archaeologists. [ 7 ]
In the 1980s, members of the history department at the University of Arkansas at Little Rock organized a lecture series entitled "Historical Ecology: Essays on Environment and Social Change" [ 8 ] The authors noted the public's concerns with pollution and dwindling natural resources, and they began a dialogue between researchers with specialties which spanned the social sciences. The papers highlighted the importance of understanding social and political structures, personal identities, perceptions of nature, and the multiplicity of solutions for environmental problems. [ 9 ]
The emergence of historical ecology as a coherent discipline was driven by a number of long-term research projects in historical ecology of tropical, temperate and arctic environments:
E.S. Deevey's Historical Ecology of the Maya Project (1973-1984) was carried out by archaeologists and biologists who combined data from lake sediments, settlement patterns, and material from excavations in the central Petén District of Guatemala to refute the hypotheses that a collapse of Mayan urban areas was instigated by faltering food production. [ 10 ]
Carole L. Crumley's Burgundian Landscape Project (1974–present) is carried out by a multidisciplinary research team aimed at identifying the multiple factors which have contributed to the long-term durability of the agricultural economy of Burgundy, France . [ 11 ]
Thomas H. McGovern's Inuit-Norse Project (1976–present) uses archaeology, environmental reconstruction, and textual analysis to examine the changing ecology of Nordic colonizers and indigenous peoples in Greenland , Iceland , Faeroes , and Shetland . [ 12 ]
In recent years the approaches to historical ecology have been expanded to include coastal and marine environments:
Stellwagen Bank National Marine Sanctuary Project (1984–present) examines Massachusetts , USA cod fishing in the 17th through 19th centuries through historical records. [ 13 ]
Florida Keys Coral Reef Eco-region Project (1990–present) researchers at the Scripps Institute of Oceanography are examining archival records including natural history descriptions, maps and charts, family and personal papers, and state and colonial records in order to understand the impact of over-fishing and habitat loss in the Florida Keys , USA which contains the third largest coral reef in the world.
Monterey Bay National Marine Sanctuary Historical Ecology (2008–present) seeks to collect relevant historical data on fishing, whaling, and trade of the furs of aquatic animals in order form a baseline for environmental restorations of the California , USA coast. [ 14 ]
Historical ecology is interdisciplinary in principle; at the same time, it borrows heavily from the rich intellectual history of environmental anthropology . Western scholars have known since the time of Plato that the history of environmental changes cannot be separated from human history. Several ideas have been used to describe human interaction with the environment, the first of which is the concept of the Great Chain of Being , or inherent design in nature. In this, all forms of life are ordered, with Humanity as the highest being, due to its knowledge and ability to modify nature. This lends to the concept of another nature, a manmade nature, which involves design or modification by humans, as opposed to design inherent in nature. [ 15 ]
Interest in environmental transformation continued to increase in the 18th, 19th, and 20th centuries, resulting in a series of new intellectual approaches. One of these approaches was environmental determinism , developed by geographer Friedrich Ratzel . This view held that it is not social conditions, but environmental conditions, which determine the culture of a population. Ratzsel also viewed humans as restricted by nature, for their behaviors are limited to and defined by their environment. A later approach was the historical viewpoint of Franz Boas which refuted environmental determinism, claiming that it is not nature, but specifics of history, that shape human cultures. This approach recognized that although the environment may place limitations on societies, every environment will impact each culture differently. Julian Steward 's cultural ecology is considered a fusion of environmental determinism and Boas' historical approach. Steward felt it was neither nature nor culture that had the most impact on a population, but instead, the mode of subsistence used in a given environment.
Anthropologist Roy Rappaport introduced the field of ecological anthropology in a deliberate attempt to move away from cultural ecology. Studies in ecological anthropology borrow heavily from the natural sciences, in particular, the concept of the ecosystem from systems ecology . In this approach, also called systems theory, ecosystems are seen as self-regulating, and as returning to a state of equilibrium. This theory views human populations as static and as acting in harmony with the environment. [ 16 ]
The revisions of anthropologist Eric Wolf and others are especially pertinent to the development of historical ecology. These revisions and related critiques of environmental anthropology undertook to take into account the temporal and spatial dimensions of history and cultures, rather than continuing to view populations as static. These critiques led to the development of historical ecology by revealing the need to consider the historical, cultural, and evolutionary nature of landscapes and societies. Thus, historical ecology as a research program developed to allow for the examination of all types of societies, simple or complex, and their interactions with the environment over space and time .
In historical ecology, the landscape is defined as an area of interaction between human culture and the non-human environment. The landscape is a perpetually changing, physical manifestation of history. [ 17 ] Historical ecology revises the notion of the ecosystem and replaces it with the landscape. While an ecosystem is static and cyclic, a landscape is historical. While the ecosystem concept views the environment as always trying to return to a state of equilibrium, the landscape concept considers "landscape transformation" to be a process of evolution. Landscapes do not return to a state of equilibrium, but are palimpsests of successive disturbances over time. [ 16 ] The use of "landscape" instead of "ecosystem" as the core unit of analysis lies at the heart of historical ecology.
Various individuals and schools of thought have informed the idea of the landscape as historical ecologists conceive of it. The Old English words landskift , landscipe or landscaef refer to environments that have been altered by humans. [ 18 ] [ 19 ] [ 20 ] As this etymology demonstrates, landscapes have been conceived of as related to human culture since at least the 5th century CE. Cultural and historical geographers have had a more recent influence. They adopted this idea from nineteenth-century German architects, gardeners, and landscape painters in Europe, Australia, and North America. [ 21 ] Landscapes are not only physical objects, but also "forms of knowledge". [ 22 ] Landscapes have cultural meanings, for example, the sacredness in many cultures of burial grounds. This recognition of landscapes as forms of knowledge is central to historical ecology, which studies landscapes from an anthropocentric perspective. [ 16 ]
The idea of the cultural landscape is directly attributed to American geographer Carl Sauer . Sauer's theories developed as a critique of environmental determinism, which was a popular theory in the early twentieth century. Sauer's pioneering 1925 paper "The Morphology of Landscape" is now fundamental to many disciplines and defines the domain. In this, the term landscape is used in a geographical sense to mean an arbitrarily selected section of reality; morphology means the conceptual and methodological processes for altering it. Hence to Sauer, wherever humans lived and impacted the environment, landscapes with determinate histories resulted. [ 23 ]
The perception of the landscape in historical ecology differs from other disciplines, such as landscape ecology . Landscape ecologists often attribute the depletion of biodiversity to human disturbance. Historical ecologists recognize that this is not always true. These changes are due to multiple factors that contribute to the ever-changing landscape. Landscape ecology still focuses on areas defined as ecosystems. [ 24 ] In this, the ecosystem perpetually returns to a state of equilibrium. In contrast, historical ecologists view the landscape as perpetually changing. Landscape ecologists view noncyclical human events and natural disasters as external influences, while historical ecologists view disturbances as an integral part of the landscape's history. It is this integration of the concept of disturbance and history that allows for landscape to be viewed as palimpsests , representing successive layers of change, rather than as static entities.
Historical ecologists recognize that landscapes undergo continuous alteration over time and these modifications are part of that landscape's history. Historical ecology recognizes that there is a primary and a secondary succession that occurs in the landscape. These successions should be understood without a preconceived bias against humanity. Landscape transformations are ecological successions driven by human impacts. Primary landscape transformations occur when human activity results in a complete turnover of species and major substrate modifications in certain habitats while secondary landscape transformations involve human-induced changes in species proportions. The stages of landscape transformation demonstrate the history of a landscape. These stages can be brought on by humans or natural causes. [ 16 ] Parts of the Amazon rainforest exhibit different stages of landscape transformation such as the impact of indigenous slash-and-burn horticulture on plant species compositions . Such landscape transformation does not inherently reduce biodiversity or harm the environment. There are many cases in which human-mediated disturbance increases biodiversity as landscapes transform over time.
Historical ecology challenges the very notion of a pristine landscape, such as virgin rainforests. [ 16 ] The idea that the landscape of the New World was uninhabited and unchanged by those groups that did inhabit it was fundamental to the justifications of colonialism. [ 25 ] Thus, perceptions of landscape have profound consequences on the histories of societies and their interactions with the environment. [ 26 ] All landscapes have been altered by various organisms and mechanisms prior to human existence on Earth. Humans have always transformed the landscapes they inhabit, however, and today there are no landscapes on Earth that have not been affected by humans in some way. [ 16 ]
Human alterations have occurred in different phases, including the period prior to industrialization . These changes have been studied through the archeological record of modern humans and their history. The evidence that classless societies, like foragers and trekkers, were able to change a landscape was a breakthrough in historical ecology and anthropology as a whole. [ 16 ] Using an approach that combines history, ecology, and anthropology, a landscape's history can be observed and deduced through the traces of the various mechanisms that have altered it, anthropogenic or otherwise. Understanding the unique nature of every landscape, in addition to relations among landscapes, and the forms which comprise the landscape, is key to understanding historical ecology. [ 27 ]
Homo sapiens have interacted with the environment throughout history, generating a long-lasting influence on landscapes worldwide. Humans sometimes actively change their landscapes, while at other times their actions alter landscapes through secondary effects. These changes are called human-mediated disturbances, and are effected through various mechanisms. These mechanisms vary; they may be detrimental in some cases, but advantageous in others. [ 23 ]
Both destructive and at times constructive, anthropogenic fire is the most immediately visible human-mediated disturbance, and without it, many landscapes would become denatured. [ 28 ] Humans have practiced controlled burns of forests globally for thousands of years, shaping landscapes in order to better fit their needs. They burned vegetation and forests to create space for crops, sometimes resulting in higher levels of species diversity. Today, in the absence of indigenous populations who once practiced controlled burns (most notably in North America and Australia ), naturally ignited wildfires have increased. In addition, there has been destabilization of "ecosystem after ecosystem, and there is good documentation to suggest fire exclusion by Europeans has led to floral and faunal extinctions." [ 23 ]
Biological invasions and the spread of pathogens and diseases are two mechanisms that spread both inadvertently and purposefully. Biological invasions begin with introductions of foreign species or biota into an already existing environment. They can be spread by stowaways on ships or even as weapons in warfare. [ 24 ] In some cases a new species may wreak havoc on a landscape, causing the loss of native species and destruction of the landscape. In other cases, the new species may fill a previously empty niche, and play a positive role. The spread of new pathogens, viruses, and diseases rarely have any positive effects; new pathogens and viruses sometimes destroy populations lacking immunities to those diseases. Some pathogens have the ability to transfer from one species to another, and may be spread as a secondary effect of a biological invasion.
Other mechanisms of human-mediated disturbances include water management and soil management . In Mediterranean Europe, these have been recognized as ways of landscape alteration since the Roman Empire . Cicero noted that through fertilization, irrigation, and other activities, humans had essentially created a second world. [ 16 ] At present, fertilization yields larger, more productive harvests of crops, but also has had adverse effects on many landscapes, such as decreasing the diversity of plant species and adding pollutants to soils.
Anthropogenic fire is a mechanism of human-mediated disturbance, defined within historical ecology as a means of altering the landscape in a way that better suits human needs. [ 3 ] The most common form of anthropogenic fire is controlled burns, or broadcast burning, which people have employed for thousands of years. Forest fires and burning tend to carry negative connotations, yet controlled burns can have a favorable impact on landscape diversity, formation, and protection.
Broadcast burning alters the biota of a landscape. The immediate effect of a forest fire is a decrease in diversity. This negative impact associated with broadcast burning, however, is only temporary. Cycles of burning will allow the landscape to gradually increase in diversity. The time required for this change is dependent on the intensity, frequency, timing, and size of the controlled burns. After a few cycles, however, diversity increases. The adaptation to fire has shaped many of Earth's landscapes.
In addition to fostering diversity, controlled burns have helped change landscapes. These changes can range from grasslands to woodlands, from prairies or forest-steppes, to scrubland to forest. Whatever the case, these transformations increase diversity and engender landscapes more suitable to human needs, creating patches rich in utilitarian and natural resources. [ 16 ]
In addition to increasing diversity of landscapes, broadcast burning can militate against catastrophic wildfires. Forest fires gained a negative connotation because of cultural references to uncontrolled fires that take lives and destroy homes and properties. Controlled burns can decrease the risk of wildfires through the regular burning of undergrowth that would otherwise fuel rampant burning. Broadcast burning has helped to fireproof landscapes by burning off undergrowth and using up potential fuel, leaving little or no chance for a wildfire to be sparked by lightning. [ 3 ]
Of all of the mechanisms of human-mediated disturbances, anthropogenic fire has become one of great interest to ecologists, geographers, soil scientists, and anthropologists alike. By studying the effects of anthropogenic fires, anthropologists have been able to identify landscape uses and requirements of past cultures. Ecologists became interested in the study of anthropogenic fire as to utilize methods from previous cultures to develop policies for regular burning. Geographers and soil scientists are interested in the utility of anthropic soils caused by burning in the past. The interest in anthropogenic fire came about in the wake of the Industrial Revolution . This time period included a mass migration from rural to urban areas, which decreased controlled burning in the countryside. This led to an increase in the frequency and strength of wildfires, thus initiating a need to develop proper prevention methods. [ 23 ] Historical ecology focuses on the impact on landscapes through human-mediated disturbances, once such being anthropogenic fire. It is a fusion of ecological, geographical, anthropological, and pedological interests.
Biological invasions are composed of exotic biota that enter a landscape and replace species with which they share similarities in structure and ecological function. Because they multiply and grow quickly, invasive species can eliminate or greatly reduce existing flora and fauna by various mechanisms, such as direct competitive exclusion. Invasive species typically spread at a faster rate when they have no natural predators or when they fill an empty niche. These invasions often occur in a historical context and are classified as a type of human-mediated disturbance called human-mediated invasions.
Invasive species can be transported intentionally or accidentally. Many invasive species originate in shipping areas from where they are unintentionally transported to their new location. Sometimes human populations intentionally introduce species into new landscapes to serve various purposes, ranging from decoration to erosion control. These species can later become invasive and dramatically modify the landscape. It is important to note that not all exotic species are invasive; in fact, the majority of newly introduced species never become invasive. [ 16 ] Humans have on their migrations through the ages taken along plants of agricultural and medicinal value, so that the modern distribution of such favored species is a clear mapping of the routes they have traveled and the places they have settled.
One example of an invasive species that has had a significant impact on the landscape is the gypsy moth ( Lymantria dispar ). The foliage-feeding gypsy moth is originally from temperate Eurasia ; it was intentionally brought to the United States by an entomologist in 1869. Many specimens escaped from captivity and have since changed the ecology of deciduous and coniferous forests in North America by defoliation. This has led not only to the loss of wildlife habitat, but also other forest services, such as carbon sequestration and nutrient cycling. After its initial introduction, the continued accidental transport of its larvae across North America has contributed to its population explosion. [ 29 ]
Regardless of the medium of introduction, biological invasions have a considerable effect on the landscape. The goal of eliminating invasive species is not new; Plato wrote about the benefits of biotic and landscape diversity centuries ago. However, the notion of eliminating invasive species is difficult to define because there is no canonical length of time that a species must exist in a specific environment until it is no longer classified as invasive. European forestry defines plants as being archetypes if they existed in Europe before 1500 and neophytes if they arrived after 1500. This classification is still arbitrary and some species have unknown origins while others have become such key components of their landscape that they are best understood as keystone species. As a result, their removal would have an enormous impact on the landscape, but not necessarily cause a return to conditions that existed before the invasion.
A clear relationship between nature and people is expressed through human disease. Infectious disease can thus be seen as another example of human-mediated disturbance as humans are hosts for infectious diseases. Historically, evidence of epidemic diseases is associated with the beginnings of agriculture and sedentary communities. Previously, human populations were too small and mobile for most infections to become established as chronic diseases . Permanent settlements, due to agriculture, allowed for more inter-community interaction, enabling infections to develop as specifically human pathogens. [ 30 ]
Holistic and interdisciplinary approaches to the study of human disease have revealed a reciprocal relationship between humans and parasites. The variety of parasites found within the human body often reflects the diversity of the environment in which that individual resides. For instance, Bushmen and Australian Aborigines have half as many intestinal parasites as African and Malaysian hunter-gatherers living in a species-rich tropical rainforest. Infectious diseases can be either chronic or acute, and epidemic or endemic, impacting the population in any given community to different extents. Thus, human-mediated disturbance can either increase or decrease species diversity in a landscape, causing a corresponding change in pathogenic diversity . [ 30 ]
Historical ecologists postulate that landscape transformations have occurred throughout history, even before the dawn of western civilization . Human-mediated disturbances are predated by soil erosion and animals damming waterways which contributed to waterway transformations. Landscapes , in turn, were altered by waterway transformation. [ 31 ] Historical ecology views the effects of human-mediated disturbances on waterway transformation as both subtle and drastic occurrences. Waterways have been modified by humans through the building of irrigation canals, expanding or narrowing waterways, and multiple other adjustments done for agricultural or transportation usage.
The evidence for past and present agricultural use of wetlands in Mesoamerica suggests an evolutionary sequence of landscape and waterway alteration. [ 32 ] Pre-Columbian , indigenous agriculturalists developed capabilities with which to raise crops under a wide range of ecological conditions, giving rise to a multiplicity of altered, cultivated landscapes. The effects of waterway transformation were particularly evident in Mesoamerica, where agricultural practices ranged from swiddening to multicropped hydraulically transformed wetlands. [ 33 ]
Historical ecologists view the Amazon basin landscape as cultural and embodying social labor. The Amazon River has been altered by the local population for crop growth and water transportation. Previous research failed to account for human interaction with the Amazon landscape. Recent research, however, has demonstrated that the landscape has been manipulated by its indigenous population over time. The continual, natural shifting of rivers, however, often masked the human disturbances in the course of rivers. As a result, the indigenous populations in the Amazon are often overlooked for their ability to alter the land and the river. [ 34 ]
However, waterway transformation has been successfully identified in the Amazon landscape. Clark Erickson observes that pre-Hispanic savanna peoples of the Bolivian Amazon built an anthropogenic landscape through the construction of raised fields, large settlement mounds, and earthen causeways. Erickson, on the basis of location, form, patterning, associations and ethnographic analogy, identified a particular form of earthwork, the zigzag structure, as fish weirs in the savanna of Baures , Bolivia. The artificial zigzag structures were raised from the adjacent savanna and served as a means to harvest the fish who used them to migrate and spawn. [ 35 ]
Further evidence of waterway transformation is found in Igarapé Guariba in Brazil. It is an area in the Amazon basin where people have intervened in nature to change rivers and streams with dramatic results. Researcher Hugh Raffles notes that British naturalists Henry Walter Bates and Alfred Russel Wallace noted waterway transformation as they sailed through a canal close to the town of Igarapé-Miri in 1848. Archival materials identifies that it had been dug out by slaves. In his studies he notes an abundance of documentary and anecdotal evidence which supports landscape transformation by the manipulation of waterways. Transformation continues in more recent times as noted when in 1961, a group of villagers from Igarapé Guariba cut a canal about two miles (3 km) long across fields thick with tall papyrus grass and into dense tropical rain forest. The narrow canal and the stream that flowed into it have since formed a full-fledged river more than six hundred yards wide at its mouth, and the landscape in this part of the northern Brazilian state of Amapá was dramatically transformed. [ 34 ] In this case, an area of swampy grassland became a lake, easing access to a rich area of forest. [ 36 ]
In general, with an increase in global population growth, comes an increase in the anthropogenic transformation of waterways. The Sumerians had created extensive irrigations by 4000 BC. As the population increased in the 3,000 years of agriculture, the ditches and canals increased in number. By the early 1900s, ditching, dredging, and diking had become common practice. This led to an increase in erosion which impacted the landscapes. [ 37 ] Human activities have affected the natural role of rivers and its communal value. These changes in waterways have impacted the floodplains, natural tidal patterns, and the surrounding land. [ 38 ]
The importance of understanding such transformation is it provides a more accurate understanding to long-standing popular and academic insights of the Amazon, as well as other ecological settings, as places where indigenous populations have dealt with the forces of nature . Ecological landscapes have been portrayed as an environment , not a society . Recent studies supported by historical ecologists, however, understand that ecological landscape like the Amazon are biocultural, rather than simply natural and provide for a greater understanding of anthropogenic transformation of both waterways and landscapes . [ 34 ]
Soil management , or direct human interaction with the soil, is another mechanism of anthropogenic change studied by historical ecologists. Soil management can take place through rearranging soils, altering drainage patterns, and building large earthen formations. Consistent with the basic premises of historical ecology, it is recognized that anthropogenic soil management practices can have both positive and negative effects on local biodiversity . Some agricultural practices have led to organically and chemically impoverished soils. In the North American Midwest, industrial agriculture has led to a loss in topsoil . Salinization of the Euphrates River has occurred due to ancient Mesopotamian irrigation, and detrimental amounts of zinc have been deposited in the New Caliber River of Nigeria. [ 39 ] Elsewhere, soil management practices may not have any effect on soil fertility. The iconic mounds of the Hopewell Indians built in the Ohio River valley likely served a religious or ceremonial purpose, and show little evidence of changing soil fertility in the landscape.
The case of soil management in the Neotropics (including the Amazon) is a classic example of beneficial results of human-mediated disturbance. In this area, prehistoric peoples altered the texture and chemical composition of natural soils. The altered black and brown earths, known as Amazon Dark Earths, or Terra preta , are actually much more fertile than unaltered surrounding soils. [ 39 ] Furthermore, the increased soil fertility improves the results of agriculture. Terra preta is characterized by the presence of charcoal in high concentrations, along with pottery shards and organic residues from plants, animal bones, and feces. It is also shows increased levels of nutrients such as nitrogen, phosphorus, calcium, zinc, and manganese; along with high levels of microorganic activity. [ 40 ] It is now accepted that these soils are a product of a labor-intensive technique termed slash-and-char . In contrast to the commonly known slash-and-burn technique, this uses a lower temperature burn that produces more charcoal than ashes. Research shows these soils were created by human activity between 9000 and 2500 years ago. Contemporary local farmers actively seek out and sell this dark earth, which covers around 10% of the Amazon basin. Harvesting Terra preta does not deplete it however, for it has the ability to regenerate at the rate of one centimeter per year by sequestering more carbon. [ 41 ]
Interest in and the study of Amazon dark earths was advanced with the work of Wim Sombroek. Sombroek's interest in soil fertility came from his childhood. He was born in the Netherlands and lived through the Dutch famine of 1944. His family subsided on a small plot of land that had been maintained and improved for generations. Sombroek's father, in turn, improved the land by sowing it with the ash and cinders from their home. Sombroek came across Terra preta in the 1950s and it reminded him of the soil from his childhood, inspiring him to study it further. Soil biologist from the University of Kansas William W. Woods is also a major figure in Terra preta research. Woods has made several key discoveries and his comprehensive bibliography on the subject doubles in size every decade. [ 42 ]
Globally, forests are well known for having greater biodiversity than nearby savannas or grasslands. Thus, the creation of ‘forest islands’ in multiple locations can be considered a positive result of human activity. This is evident in the otherwise uniform savannas of Guinea and central Brazil that are punctured by scattered clumps of trees. [ 43 ] These clumps are the result of generations of intense resource management. Earth works and mounds formed by humans, such as the Ibibate mound complex in the Llanos de Mojos in Bolivia, are examples of built environments that have undergone landscape transformation and provide habitats for a greater number of species than the surrounding wetland areas. [ 41 ] The forest islands in the Bolivian Amazon not only increase the local plant species diversity, but also enhance subsistence possibilities for the local people.
Historical ecology involves an understanding of multiple fields of study such as archaeology and cultural history as well as ecological processes, species diversity, natural variability, and the impact of human-mediated disturbances. Having a broad understanding of landscapes allows historical ecology to be applied to various disciplines. Studying past relationships between humans and landscapes can successfully aid land managers by helping develop holistic, environmentally rational, and historically accurate plans of action. As summarized in the postulates of historical ecology, humans play significant roles in the creation and destruction of landscapes as well as in ecosystem function. Through experience, many indigenous societies learned how to effectively alter their landscapes and biotic distributions. Modern societies, seeking to curtail the magnitude of their effects on the landscape, can use historical ecology to promote sustainability by learning from the past. Farmers in the Amazon region, for example, now utilize nutrient-rich terra preta to increase crop yields [ 44 ] much like the indigenous societies that lived long before them.
Historical ecology can also aid in the goals of other fields of study. Conservation biology recognizes different types of land management processes, each attempting to maintain the landscape and biota in their present form. Restoration ecology restores sites to former function, structure, and components of biological diversity through active modification of the landscapes. Reclamation deals with shifting a degraded ecosystem back toward a higher value or use, but not necessarily to its original state. Replacement of an ecosystem would create an entirely new one. Revegetation involves new additions of biota into a landscape, not limited to the original inhabitants of an area. [ 45 ] Each method can be enriched by the application of historical ecology and the past knowledge it supplies. The interdisciplinary nature of historical ecology would permit conservation biologists to create more effective and efficient landscape improvements. Reclamation and revegetation can use a historical perspective to determine what biota will be able to sustain large populations without threatening native biota of the landscape.
A tropical forest in particular needs to be studied extensively because it is a highly diverse, heterogeneous setting. Historical ecology can use archaeological sites within this setting to study past successes and failures of indigenous peoples. The use of swidden fires in Laos is an example of historical ecology as used by current land managers in policy-making. Swidden fires were originally considered a source of habitat degradation. This conclusion led the Laos government to discourage farmers from using swidden fires as a farming technique. However, recent research has found that swidden fires were practiced historically in Laos and were not, in fact, the source of degradation. Similar research revealed that habitat degradation originated from a population increase after the Vietnam War. The greater volume of people compelled the government to put pressure on farmers for increased agricultural production. [ 46 ] Land managers no longer automatically eliminate the use of swidden fires, but rather the number of swidden fires that are set for government-sponsored agricultural purposes.
The San Francisco Estuary Institute also uses historical ecology to study human impacts on the California landscape to guide environmental management. [ 47 ] [ 48 ] A study of the wetlands of Elkhorn Slough near Monterey, California , sought to enhance conservation and restoration activities. By using historical data such as maps, charts, and aerial photographs, researchers were able to trace habitat change to built structures that had negatively altered the tidal flow into the estuaries dating from the early 1900s. [ 49 ] The study further suggested using techniques that "imitate the complex structure of natural tidal wetlands and maintain connectivity with intact wetland habitats as well as with adjoining subtidal and upland habitats." | https://en.wikipedia.org/wiki/Historical_ecology |
Historical models of the Solar System first appeared during prehistoric periods and remain updated to this day. The models of the Solar System throughout history were first represented in the early form of cave markings and drawings, calendars and astronomical symbols. Then books and written records became the main source of information that expressed the way the people of the time thought of the Solar System.
New models of the Solar System are usually built on previous models, thus, the early models are kept track of by intellectuals in astronomy, an extended progress from trying to perfect the geocentric model eventually using the heliocentric model of the Solar System. The use of the Solar System model began as a resource to signify particular periods during the year as well as a navigation tool which was exploited by many leaders from the past.
Astronomers and great thinkers of the past were able to record observations and attempt to formulate a model that accurately interprets the recordings. This scientific method of deriving a model of the Solar System is what enabled progress towards more accurate models to have a better understanding of the Solar System that civilization is located within
The Nebra Sky Disc is a bronze dish with symbols that are interpreted generally as the Sun or full moon , a lunar crescent , and stars (including a cluster of seven stars interpreted as the Pleiades ). The disc has been attributed to a site in present-day Germany near Nebra , [ 1 ] Saxony-Anhalt , and was originally dated by archaeologists to c. 1600 BCE , based on the provenance provided by the looters who found it. [ 2 ] Researchers initially suggested the disc is an artefact from the Bronze Age Unetice culture , although a later dating to the Iron Age has also been proposed. [ 3 ] [ 2 ]
The ancient Hebrews, like all the ancient peoples of the Near East, believed the sky was a solid dome with the Sun , Moon , planets and stars embedded in it. [ 4 ] In biblical cosmology , the firmament is the vast solid dome created by God during his creation of the world to divide the primal sea into upper and lower portions so that the dry land could appear. [ 5 ] [ 6 ]
Babylonians thought the universe revolved around heaven and Earth. [ 7 ] They used methodological observations of the patterns of planets and stars movements to predict future possibilities such as eclipses . [ 8 ] Babylonians were able to make use of periodic appearances of the Moon to generate a time source - a calendar. This was developed as the appearance of the full moon was visible every month. [ 9 ] The 12 months came about by dividing the ecliptic into 12 equal segments of 30 degrees and were given zodiacal constellation names which were later used by the Greeks. [ 10 ]
The Chinese had multiple theories of the structure of the universe. [ 11 ] The first theory is the Gaitian (celestial lid) theory, mentioned in an old mathematical text called Zhou bei suan jing in 100 BCE, in which the Earth is within the heaven, where the heaven acts as a dome or a lid. The second theory is the Huntian (Celestial sphere) theory during 100 BCE. [ 11 ] This theory claims that the Earth floats on the water that the Heaven contains, which was accepted as the default theory until 200 AD. [ 11 ] The Xuanye (Ubiquitous darkness) theory attempts to simplify the structure by implying that the Sun, Moon and the stars are just a highly dense vapour that floats freely in space with no periodic motion. [ 12 ]
Since 600 BCE, Greek thinkers noticed the periodic fashion of the Solar System (then regarded as the "whole universe ") but, like their contemporaries, they were puzzled about the forward and retrograde motion of the planets, the "wanderer stars", long taken as heavenly deities . Many theories were announced during this period, mostly purely speculative, but progressively supported by geometry . [ 13 ]
Thales of Miletus alleged to have predicted the solar eclipse of 586 BCE . [ 14 ] Around 475 BCE, Parmenides claimed that the universe is spherical and moonlight is a reflection of sunlight. [ 13 ] Shortly after, circa 450 BCE, Anaxagoras was the first philosopher to consider the Sun as a huge object (larger than the land of Peloponnesus [ 15 ] ), and consequently, to realize how far from Earth it might be. He also suggested that the Moon is rocky , thus opaque , and closer to the Earth than the Sun, giving a correct explanation of eclipses. [ 16 ] To him, comets are formed by collisions of planets and that the motion of planets is controlled by the nous (mind). [ 13 ]
Anaximander , around 560 BCE, was the first to conceive a mechanical model of the world. In his model, the Earth floats very still in the centre of the infinite, not supported by anything. [ 17 ] Its curious shape is that of a cylinder [ 18 ] with a height one-third of its diameter. The flat top forms the inhabited world, which is surrounded by a circular oceanic mass.
At the origin, after the separation of hot and cold, a ball of flame appeared that surrounded Earth like bark on a tree. This ball broke apart to form the rest of the Universe. It resembled a system of hollow concentric wheels, filled with fire, with the rims pierced by holes like those of a flute. Consequently, the Sun was the fire that one could see through a hole the same size as the Earth on the farthest wheel, and an eclipse corresponded with the occlusion of that hole. The diameter of the solar wheel was twenty-seven times that of the Earth (or twenty-eight, depending on the sources) [ 19 ] and the lunar wheel, whose fire was less intense, eighteen (or nineteen) times. Its hole could change shape, thus explaining lunar phases . The stars and the planets, located closer, [ 20 ] followed the same model. [ 21 ]
Anaximander was the first philosopher to present a system where the celestial bodies turned at different distances.
Around 400 BCE, Pythagoras' students believed the motion of planets is caused by an out-of-sight "fire" at the centre of the universe (not the Sun) that powers them, and Sun and Earth orbit that Central Fire at different distances. The Earth's inhabited side is always opposite to the Central Fire, rendering it invisible to people. So, the Earth rotates around itself synchronously with a daily orbit around that Central Fire, while the Sun revolves it yearly in a higher orbit. That way, the inhabited side of Earth faces the Sun once every 24 hours. They also claimed that the Moon and the planets orbit the Earth. [ 23 ] This model is usually attributed to Philolaus .
This model is the first one that depicts a moving Earth, simultaneously self-rotating and orbiting around an external point (but not around the Sun), thus not being geocentrical, contrary to common intuition .
Due to philosophical concerns about the number 10 (a " perfect number " for the Pythagorians), they also added a tenth "hidden body" or Counter-Earth ( Antichthon ), always in the opposite side of the invisible Central Fire and therefore also invisible from Earth. [ 24 ]
Around 360 BCE when Plato wrote in his Timaeus his idea to account for the motions. He claimed that circles and spheres were the preferred shape of the universe and that the Earth was at the centre and the stars forming the outermost shell, followed by planets, the Sun and the Moon. [ 25 ] This is the so-called geocentric model .
In Plato's cosmogony , [ 26 ] the demiurge gave the primacy to the motion of Sameness and left it undivided; but he divided the motion of Difference in six parts, to have seven unequal circles. He prescribed these circles to move in opposite directions, three of them with equal speeds, the others with unequal speeds, but always in proportion. These circles are the orbits of the heavenly bodies: the three moving at equal speeds are the Sun, Venus and Mercury, while the four moving at unequal speeds are the Moon, Mars, Jupiter and Saturn. [ 27 ] [ 28 ] The complicated pattern of these movements is bound to be repeated again after a period called a 'complete' or 'perfect' year . [ 29 ]
So, Plato arranged these celestial orbs in the order (outwards from the center): Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, and fixed stars , with the fixed stars located on the celestial sphere . However, this did not suffice to explain the observed planetary motion.
Eudoxus of Cnidus , student of Plato in around 380 BCE, introduced a technique to describe the motion of the planets called the method of exhaustion . [ 30 ] Eudoxus reasoned that since the distances of the stars, the Moon, the Sun and all known planets do not appear to be changing, they are fixed in a sphere in which the bodies move around the sphere but with a constant radius and the Earth is at the centre of the sphere. [ 31 ] To explain the complexity of the movements of the planets, Eudoxus thought they move as if they were attached to a number of concentrical, invisible spheres , every of them rotating around its own and different axis and at different paces. [ 32 ]
Eudoxus’ model had twenty-seven homocentric spheres with each sphere explaining a type of observable motion for each celestial object. Eudoxus assigns one sphere for the fixed stars which is supposed to explain their daily movement. He assigns three spheres to both the Sun and the Moon with the first sphere moving in the same manner as the sphere of the fixed stars. The second sphere explains the movement of the Sun and the Moon on the ecliptic plane. The third sphere was supposed to move on a “latitudinally inclined” circle and explain the latitudinal motion of the Sun and the Moon in the cosmos. Four spheres were assigned to Mercury, Venus, Mars, Jupiter, and Saturn, the only known planets at that time. The first and second spheres of the planets moved exactly like the first two spheres of the Sun and the Moon. According to Simplicius , the third and fourth sphere of the planets were supposed to move in a way that created a curve known as a hippopede . The hippopede was a way to try and explain the retrograde motions of planets.
Eudoxus emphasised that this is a purely mathematical construct of the model in the sense that the spheres of each celestial body do not exist, it just shows the possible positions of the bodies. [ 33 ]
Around 350 BCE Aristotle , in his chief cosmological treatise De Caelo (On the Heavens) , modified Eudoxus' model by supposing the spheres were material and crystalline. He was able to articulate the spheres for most planets, however, the spheres for Jupiter and Saturn crossed each other. Aristotle solved this complication by introducing an unrolled sphere in between, increasing the number of spheres needed well above Eudoxus'. Historians are unsure about how many spheres Aristotle thought there were in the cosmos with theories ranging from 43 up to 55. [ 34 ]
Aristotle also tried to determine whether the Earth moves and concluded that all the celestial bodies fall towards Earth by natural tendency and since Earth is the centre of that tendency, it is stationary. [ 35 ]
By 330 BCE, Heraclides of Pontus said that the rotation of the Earth on its axis, from west to east, once every 24 hours, explained the apparent daily motion of the celestial sphere . Simplicius says that Heraclides proposed that the irregular movements of the planets can be explained if the Earth moves while the Sun stays still, [ 36 ] but these statements are disputed. [ 37 ]
Around 280 BCE, Aristarchus of Samos offers the first definite discussion of the possibility of a heliocentric cosmos , [ 38 ] and uses the size of the Earth's shadow on the Moon to estimate the Moon's orbital radius at 60 Earth radii, and its physical radius as one-third that of the Earth. He made an inaccurate attempt to measure the distance to the Sun, but sufficient to assert that the Sun is bigger than Earth and it is further away than the Moon. So the minor body, the Earth, must orbit the major one, the Sun, and not the opposite. [ 39 ]
Following the heliocentric ideas of Aristarcus (but not explicitly supporting them), around 250 BCE Archimedes in his work The Sand Reckoner computes the diameter of the universe centered around the Sun to be about 10 14 stadia (in modern units, about 2 light years , 18.93 × 10 12 km , 11.76 × 10 12 mi ). [ 40 ]
In Archimedes' own words:
His [Aristarchus'] hypotheses are that the fixed stars and the Sun remain unmoved, that the Earth revolves about the Sun on the circumference of a circle, the Sun lying in the middle of the orbit, and that the sphere of fixed stars, situated about the same center as the Sun, is so great that the circle in which he supposes the Earth to revolve bears such a proportion to the distance of the fixed stars as the center of the sphere bears to its surface. [ 41 ]
However, Aristarchus' views were not widely adopted, and the geocentric notion will remain for centuries.
Around 210 BCE, Apollonius of Perga shows the equivalence of two descriptions of the apparent retrograde planet motions (assuming the geocentric model), one using eccentrics and another deferent and epicycles . [ 42 ] The latter will be a key feature for future models. The epicycle is described as a small orbit within a greater one, called the deferent : as a planet orbits the Earth, it also orbits the original orbit, so its trajectory resembles an epitrochoid , as shown in the illustration at left. This could explain how the planet seems to move as viewed from Earth.
In the following century, measures of sizes and distances of the Earth and the Moon are improved. Around 200 BCE Eratosthenes determines that the radius of the Earth is roughly 6,400 km. [ 43 ] Circa 150 BCE Hipparchus uses parallax to determine that the distance to the Moon is roughly 380,000 km. [ 44 ]
The work of Hipparchus about the Earth-Moon system was so accurate that he could forecast solar and lunar eclipses for the next six centuries. Also, he discovers the precession of the equinoxes , and compiles a star catalog of about 850 entries. [ 45 ]
During the period 127 to 141 AD, Ptolemy deduced that the Earth is spherical based on the fact that not everyone records the solar eclipse at the same time and that observers from the North can not see the Southern stars. [ 46 ] Ptolemy attempted to resolve the Planetary motion dilemma in which the observations were not consistent with the perfect circular orbits of the bodies. Ptolemy adopted the Apollonius' epicycles as solution. [ 47 ] Ptolemy emphasised that the epicycle motion does not apply to the Sun. His main contribution to the model was the equant points. He also re-arranged the heavenly spheres in a different order than Plato did (from Earth outward): Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn and fixed stars, following a long astrological tradition and the decreasing orbital periods.
Ptolemy's work Almagest cemented the geocentric model in the West, and it remained the most authoritative text on astronomy for more than 1,500 years. His methods were accurate enough to keep them largely undisputed. [ 48 ]
Around 420 AD Martianus Capella describes a modified geocentric model, in which the Earth is at rest in the center of the universe and circled by the Moon, the Sun, three planets and the stars, while Mercury and Venus circle the Sun. [ 49 ] His model was not widely accepted, despite his authority; he was one of the earliest developers of the system of the seven liberal arts , the trivium ( grammar , logic , and rhetoric ) and the quadrivium ( arithmetic , geometry , music , astronomy ), that structured early medieval education. [ 50 ] Nonetheless, his single encyclopedic work, De nuptiis Philologiae et Mercurii ("On the Marriage of Philology and Mercury"), also called De septem disciplinis ("On the seven disciplines") was read, taught, and commented upon throughout the early Middle Ages and shaped European education during the early medieval period and the Carolingian Renaissance . [ 51 ]
This model implies some knowledge about the transits of Mercury and Venus in front of the Sun, [ 52 ] and the fact they pass also behind it periodically, which cannot be explained with Ptolemy's model. [ 53 ] But it is unclear how that knowledge could be achieved by that times, due to the difficult to see these transits at naked eye; [ 54 ] indeed, there is no evidence that any ancient culture knew of the transits.
Alternatively, as seen from Earth, Mercury never departs from the Sun, neither East nor West, more than 28° [ 55 ] and Venus no more than 47°, [ 56 ] facts both known from antiquity that also could not be explained by Ptolemy. So it could be inferred that they orbit the Sun, and hence, there should be these transits.
The Islamic golden age period in Baghdad , picking off from Ptolemy's work, had more accurate measurements taken followed by interpretations. In 1021 A.D, Ibn Al Haytham adjusted Ptolemy's geocentric model to his specialty in optics in his book Al-shukuk 'ata Batlamyus which translates to "Doubts about Ptolemy". [ 57 ] Ibn al-Haytham claimed that the epicycles Ptolemy introduced are inclined planes, not in a flat motion which settled further conflicting disputes. [ 58 ] However, Ibn Al Haytham agreed with the Earth being in the centre of the Solar System at a fixed position. [ 59 ]
Nasir al-Din, during the 13th century, was able to combine two possible methods for a planet to orbit and as a result, derived a rotational aspect of planets within their orbits. [ 60 ] Copernicus arrived to the same conclusion in the 16th century. [ 57 ] Ibn al-Shatir , during the 14th century, in an attempt to resolve Ptolemy's inconsistent lunar theory, applied a double epicycle model to the Moon which reduced the predicted displacement of the Moon from the Earth. [ 61 ] Copernicus also arrived at the same conclusion in the 16th century. [ 62 ]
In 1051, Shen Kua , a Chinese scholar in applied mathematics , rejected the circular planetary motion. He substituted it with a different motion described by the term ‘willow-leaf’. This is when a planet has a circular orbit but then it encounters another small circular orbit within or outside the original orbit and then returns to its original orbit which is demonstrated by the figure on the right. [ 63 ]
During the 16th century Nicholas Copernicus , in reflecting on Ptolemy and Aristotle's interpretations of the Solar System, believed that all the orbits of the planets and Moon must be a perfect uniform circular motion despite the observations showing the complex retrograde motion. [ 64 ] Copernicus introduced a new model which was consistent with the observations and allowed for perfect circular motion. This is known as the Heliocentric model where the Sun is placed at the centre of the universe (hence, the Solar System) and the Earth is, like all the other planets, orbiting it. The heliocentric model also resolved the varying brightness of planets problem. [ 65 ] Copernicus also supported the spherical Earth theory with the idea that nature prefers spherical limits which are seen in the Moon, the Sun, and also the orbits of planets. [ 66 ] Copernicus furthermore believed that the universe had a spherical limit. [ 66 ] Copernicus contributed further to practical Astronomy by producing advanced techniques of observations [ 67 ] and measurements and providing instructional procedure. [ 68 ]
The heliocentric model implies that the Earth is also a planet, the third from the Sun after Mercury and Venus, and before Mars, Jupiter and Saturn. And also implicitly, that planets are "worlds", like Earth is, not "stars". But the Moon still orbits the Earth.
The heliocentric model was not immediately adopted. Conservatism along to numerous observational, philosophical and religious concerns prevented it for more than a century.
In 1588, Tycho Brahe publishes his own Tychonic system , a blend between the Ptolemy's classical geocentric model and Copernicus' heliocentric model, in which the Sun and the Moon revolve around the Earth, in the center of universe, and all other planets revolve around the Sun. [ 69 ] It was an attempt to conciliate his religious beliefs with heliocentrism. This was the so-called geoheliocentric model, and it was adopted by some astronomers during the geocentrism vs heliocentrism disputes.
In 1609, Johannes Kepler , an advocate of the heliocentric model, using his patron Tycho Brahe's accurate measurements, noticed the inconsistency of a heliocentric model where the Sun is exactly in the centre. Instead Kepler developed a more accurate and consistent model where the Sun is located not in the centre but at one of the two foci of an elliptic orbit . [ 70 ]
Kepler derived the three laws of planetary motion which changed the model of the Solar System and the orbital path of planets. These three laws of planetary motion are:
In modern notation,
where a is the radius of the orbit, T is the period, G is the gravitational constant and M is the mass of the Sun . The third law explains the periods that occur during the year which relates the distance between the Earth and the Sun. [ 74 ]
Along with unprecedent accuracy, the Keplerian model also allows put the Solar System into scale. If a reliable measure between planetary bodies would be taken, the whole size of the system could be computed. By this time, the Solar System started to be conceived as something smaller than the rest of the universe. (Yet, up to 1596 Kepler himself still believed in the sphere of fixed stars , as it was illustrated in his book Mysterium Cosmopgraphicum .)
With the help of the telescope providing a closer look into the sky, Galileo Galilei proved the most part of the heliocentric model of the Solar System. Galileo observed the phases of Venus 's appearance with the telescope and was able to confirm Kepler's first law of planetary motion and Copernicus's heliocentric model, of which Galileo was an advocate. [ 75 ] Galileo claimed that the Solar System is not only made up of the Sun, the Moon and the planets but also comets. [ 76 ] By observing movements around Jupiter, Galileo initially thought that these were the actions of stars. [ 77 ] However, after a week of observing, he noticed changes in the patterns of motion in which he concluded that they are moons, four moons . [ 77 ]
Shortly after, it was proved by Kepler himself that the Jupiter's moons move around the planet the same way planets orbit the Sun, thus making Kepler's laws universal. [ 78 ]
After all these theories, people still did not know what made the planets orbit the Sun, nor why the Moon tracks the Earth. Until the 17th century when Isaac Newton introduced The Law of Universal Gravitation . He claimed that between any two masses, there is an attractive force between them proportional to the inverse of the distance squared. [ 79 ]
where m 1 is the mass of the Sun and m 2 is the mass of the planet, G is the gravitational constant and r is the distance between them. [ 80 ] This theory was able to calculate the force on each planet by the Sun, which consequently, explained the planets elliptical motion. [ 81 ]
The term " Solar System " entered the English language by 1704, when John Locke used it to refer to the Sun, planets, and comets as a whole. [ 82 ] By then it had been established beyond doubt that planets are other worlds, and stars are other distant suns, so the whole Solar System is actually only a small part of an immensely large universe, and definitively something distinct.
In 1672 Jean Richer and Giovanni Domenico Cassini measure the astronomical unit (AU), the mean distance Earth-Sun, to be about 138,370,000 km, [ 83 ] (later refined by others up to the current value of 149,597,870 km). This gave for first time ever a well estimated size of the then known Solar System (that is, up to Saturn), following the scale derived from Kepler's third law.
In 1798 Henry Cavendish accurately measures the gravitational constant in the laboratory , which allows the mass of the Earth to be derived thru Newton's law of universal gravitation, and hence the masses of all bodies in the Solar System. [ 84 ]
Telescopic observations found new moons around Jupiter and Saturn , as well as an impressive ring system around the latter.
In 1705 Edmond Halley asserted that the comet of 1682 is periodical with a highly elongated elliptical orbit around the Sun, and predicts its return in 1757. [ 85 ] Johann Palitzsch observed in 1758 the return of the comet that Halley had anticipated. [ 86 ] The interference of Jupiter's orbit had slowed the return by 618 days. Parisian astronomer La Caille suggests it should be named "Halley's Comet". [ 87 ] Comets became a popular target for astronomers, and were recognized as members of the Solar System.
In 1766 Johann Titius found a numeric progression for planetary distances, published in 1772 by Johann Bode , the so-called Titius-Bode rule. [ 88 ]
When in 1781 William Herschel discovered a new planet, Uranus , [ 89 ] it was found it lies at a distance beyond Saturn that approximately matches that predicted by the Titius-Bode rule.
That rule observed a gap between Mars and Jupiter void of any known planet. In 1801 Giuseppe Piazzi discovered Ceres , a body that filled the gap and was regarded as a new planet, [ 90 ] and in 1802 Heinrich Wilhelm Olbers discovered Pallas , at roughly the same distance to the Sun than Ceres. [ 91 ] He proposed that the two objects were the remnants of a destroyed planet , [ 92 ] and predicted that more of these pieces would be found.
Due their star-like apparience, William Herschel suggested Ceres and Pallas, and similar objects if found, be placed into a separate category, named asteroids , although they were still counted among the planets for some decades. [ 93 ] In 1804 Karl Ludwig Harding discovered the asteroid Juno , [ 94 ] and in 1807 Olbers discovered the asteroid Vesta . [ 95 ] In 1845 Karl Ludwig Hencke discovered a fifth body between Mars and Jupiter, Astraea , [ 96 ] and in 1849 Annibale de Gasparis discovers the asteroid Hygiea , the fourth largest asteroid in the Solar System by both volume and mass. [ 97 ] As new objects of that kind were found there at an accelerating rate, counting them among the planets became increasingly cumbersome. Eventually, they were dropped from the planet list (as first suggested by Alexander von Humboldt in the early 1850s) and Herschel's coinage, "asteroids", gradually came into common use. [ 98 ] Since then, the region they occupy between Mars and Jupiter is known as the asteroid belt .
Alexis Bouvard detected irregularities in the orbit of Uranus in 1821. [ 99 ] Later, between 1845 and 1846, John Adams and Urbain Le Verrier separately predicted the existence and location of a new planet from irregularities in the orbit of Uranus. [ 100 ] This new planet was finally found by Johann Galle and eventually named Neptune , following the predicted position gave to him by Le Verrier. This fact marked the climax of the Newtonian mechanics applied to astronomy, but the Neptune's orbit does not fit with the Titius-Bode rule, so it has been deprecated from then on.
Eventually, new moons were discovered also around Uranus starting in 1787 by Herschel, [ 101 ] around Neptune starting in 1846 by William Lassell [ 102 ] and around Mars in 1877 by Asaph Hall . [ 103 ]
In 1919 Arthur Stanley Eddington uses a solar eclipse to successfully test Albert Einstein 's General Theory of Relativity , [ 104 ] which in turn explains the observed irregularities in the orbital motion of Mercury, [ 105 ] and disproves the existence of the hypothesized inner planet Vulcan .
General Theory of Relativity supersedes Newton's celestial mechanics. Instead of forces of attraction, gravity is seen as a bend of the tissue of the continuum space-time produced by the bodies' masses.
Clyde Tombaugh discovered Pluto in 1930. [ 106 ] It was regarded for decades as the ninth planet of the Solar System. In 1978 James Christy discovers Charon , the large moon of Pluto. [ 107 ]
In 1950 Jan Oort suggested the presence of a cometary reservoir in the outer limits of the Solar System, the Oort cloud , [ 108 ] and in 1951 Gerard Kuiper argued for an annular reservoir of comets between 40 and 100 astronomical units from the Sun having formed early in the Solar System's evolution, but he did not think that such a belt still existed today. [ 109 ] Decades later, this region was named after him, the Kuiper belt .
New asteroid populations were discovered, as Trojans since 1906 by Max Wolf , [ 110 ] and Centaurs since 1977 by Charles Kowal , [ 111 ] among many other .
From 1957 on, technology allowed for direct space exploration of the Solar System's bodies. To date, all their known main bodies have been visited at least once by robotic spacecraft , providing firsthand scientific data and closeup imaging. In some instances, robotic probes and rovers have landed on satellites, planets, asteroids and comets. And even some samples have been returned.
The Sun is a lone, G-type main-sequence star inside the galaxy of the Milky Way , surrounded by eight major planets orbiting the star by the influence of gravity, most of them with a cohort of satellites, or moons , orbiting them. The biggest planets also have rings , consisting of a multitude of tiny solid objects and dust.
The planets are, in order of distance from the Sun: Mercury , Venus , Earth , Mars , Jupiter , Saturn , Uranus and Neptune .
There are three main belts of minor bodies:
The biggest of these minor bodies are regarded as dwarf planets : Ceres in the asteroid belt, and Pluto , Eris , Haumea , Makemake , Gonggong , Quaoar , Sedna , and Orcus (along with other candidates ) in the Kuiper belt.
{{
Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each arrow ( → ) may be read as "within" or "part of". | https://en.wikipedia.org/wiki/Historical_models_of_the_Solar_System |
Computer-aided design is the use of computers to aid in the creation, modification, analysis, or optimization of a design. Designers have used computers for calculations since their invention. [ 1 ] [ 2 ] [ 3 ] [ 4 ] CAD software was popularized and innovated in the 1960s, although various developments were made between the mid-1940s and 1950s. Digital computers were used in power system analysis or optimization as early as proto-" Whirlwind " in 1949 . Circuit [ 5 ] design theory or power network methodology was algebraic , symbolic , and often vector -based.
Between the mid-1940s and 1950s, various developments were made in computer software . Some of these developments include servo-motors controlled by generated pulse (1949), a digital computer with built-in operations to automatically coordinate transforms to compute radar related vectors (1951), and the graphic mathematical process of forming a shape with a digital machine tool (1952). [ 6 ]
In 1953, MIT researcher Douglas T. Ross saw the "interactive display equipment" being used by radar operators, believing it would be exactly what his SAGE -related data reduction group needed. Ross and the other researchers from the Massachusetts Institute of Technology Lincoln Laboratory were the sole users of the complex display systems installed for the pre-SAGE Cape Cod system. Ross claimed in an interview that they "used it for their own personal workstation." [ 7 ] The designers of these early computers built utility programs to ensure programmers could debug software, using flowcharts on a display scope, with logical switches that could be opened and closed during the debugging session. They found that they could create electronic symbols and geometric figures to create simple circuit diagrams and flowcharts. [ 8 ] These programs also enabled objects to be reproduced at will; it also was possible to change their orientation, linkage ( flux , mechanical , lexical scoping ), or scale. This presented numerous possibilities to them.
Ross coined the term computer-aided design (CAD) in 1959. [ 9 ] [ 10 ]
The invention of the 3D CAD/CAM is often attributed to French engineer Pierre Bézier ( Arts et Métiers ParisTech , Renault). Between 1966 and 1968, after his mathematical work concerning surfaces, he developed UNISURF to ease the design of parts and tools for the automotive industry. UNISURF then became the working base for the following generations of CAD software.
In parallel, French carmaker Citroen had developed its design system SPAC (system de programmatic automatique Citroen) as part of its CAD/CAM solution SADUSCA (aid systems for the defining and the machining of bodywork surfaces), both based on the 1959 mathematical works of Paul de Casteljau . In 1968, it used an IBM 360-40, then 360-65 for batch jobs, but already had a graphical interface with an IBM 2250 prototype. [ 11 ] [ 12 ]
However, CAD may have been in use earlier at Boeing , having been used to help design the outer surface of Boeing's 727 airplane (which rolled out in 1962). [ 13 ] Based on his human factors cockpit drawings, William Fetter from Boeing coined the term "computer graphic" in 1960. [ 14 ] A computer graphics department was established in 1962, and by 1965 had begun to make movies by computer. [ 13 ]
In the 1960s, technological developments in the industries of aircraft, automotive, industrial control, and electronics provided advancements in the fields of three-dimensional surface construction, NC programming, and design analysis. Most of these developments were independent of one another and often not published until much later. Some of the mathematical description work on curves was developed in the early 1940s by Robert Issac Newton. [ citation needed ] In his 1957 novel The Door into Summer , Robert A. Heinlein hinted at the possibility of a robotic Drafting Dan . However, more substantial work on polynomial curves and sculptured surface was done by mathematician Paul de Casteljau from Citroen ; Pierre Bézier from Renault; Steven Anson Coons from MIT; James Ferguson from Boeing ; Carl de Boor , George David Birkhoff and Garibedian from GM in the 1960s; and W. Gordon and R. Riesenfeld from GM in the 1970s.
The development of the Sketchpad system at MIT [ 15 ] [ 16 ] by Ivan Sutherland , who later created a graphics technology company with David Evans , was a turning point. [ 15 ] The distinctive feature of Sketchpad was that it allowed a human to interact with a computer graphically; the design can be fed into the computer by drawing on a cathode ray tube (CRT) computer display (monitor) with a light pen . In effect, this feature of Sketchpad was a prototype for a graphical user interface , an indispensable feature of modern CAD. In 1963, under doctoral adviser Claude Shannon , Sutherland presented his PhD thesis paper, Sketchpad: A Man-Machine Graphical Communication System , at a Joint Computer Conference . In his paper, he said: [ 17 ]
For drawings where motion of the drawing or analysis of a drawn problem is of value to the user, Sketchpad excels. For highly repetitive drawings or drawings where accuracy is required, Sketchpad is sufficiently faster than conventional techniques to be worthwhile. For drawings which merely communicate with shops, it is probably better to use conventional paper and pencil.
Over time, efforts would be directed toward the goal of having the designers' drawings communicate not just with shops, but also with the shop tool itself; however, it was a long time before this goal was achieved.
The first commercial applications of CAD were in large companies within the automotive and aerospace industries, as well as in electronics. This was because only large corporations could afford the computers capable of performing the necessary calculations. Notable company projects included a joint project between Patrick J. Hanratty from GM and Sam Matsa, Doug Ross's MIT APT research assistant from IBM , to develop a prototype system for design engineers, DAC-1 (Design Augmented by Computer) 1964, Lockheed projects, Bell GRAPHIC 1, and Renault .
One of the most influential events in the development of CAD was the founding of Manufacturing and Consulting Services Inc. (MCS) in 1971 by Patrick J. Hanratty , [ 18 ] who wrote the system Automated Drafting And Machining (ADAM), but more importantly supplied code to companies such as McDonnell Douglas ( Unigraphics ), Computervision ( CADDS ), Calma , Gerber , Autotrol, and Control Data .
As computers became more affordable, the application of CAD gradually expanded into new areas. The development of CAD software for personal desktop computers was the impetus for almost universal application in all areas of construction.
Other notable events in the 1960s and 1970s include the foundation of CAD systems United Computing , Intergraph , IBM , and Intergraph IGDS in 1974 (which led to Bentley Systems MicroStation in 1984), as well as the Applicon in 1969 and commercial CAD systems from Japanese manufacturers Seiko and Zuken during the 1970s. [ 19 ]
CAD implementations have evolved dramatically since this early development. Initially, with 3D in the 1970s, CAD was typically limited to producing drawings similar to hand-drafted drawings. Advances in programming and computer hardware, [ 20 ] [ 21 ] most notably solid modeling in the 1980s, have allowed more versatile applications of computers in design activities.
In 1981, the key products were the solid modeling packages— Romulus (ShapeData) and Uni-Solid (Unigraphics) based on PADL-2—and the surface modeler CATIA ( Dassault Systèmes ). Autodesk was founded in 1982 by John Walker, which led to the two-dimensional system AutoCAD . [ 22 ] The next milestone was the release of Pro/ENGINEER in 1987, which heralded greater usage of feature-based modeling methods and parametric linking of the parameters of features; this marked the introduction of parametric modeling . [ 23 ]
Also important to the development of CAD was the development in the late 1980s and early 1990s of B-rep solid modeling kernels (engines for manipulating geometrically and topologically consistent 3D objects), Parasolid (ShapeData), and ACIS (Spatial Technology Inc.). These developments were inspired by the work of Ian Braid. This subsequently led to the release of mid-range packages such as SolidWorks and TriSpective (later known as IRONCAD ) in 1995, Solid Edge (then Intergraph ) in 1996, and Autodesk Inventor in 1999. Between 1992-1998 Robert McNeel & Associates develop, based in the OPENNURBS Kernel, the 3D CAD Application called Rhinoceros 3D. An independent geometric modeling kernel has been evolving in Russia since the 1990s. [ 24 ]
Availability of free and open-source CAD software and high costs of advanced and 3D CAD software may restrain the growth of the CAD software market. [ 25 ] Free and open-source CAD software packages include FreeCAD , [ 26 ] [ 27 ] [ 28 ] BRL-CAD developed for the US Army, [ 29 ] [ 30 ] QCAD Community Edition , [ 31 ] LibreCAD [ 32 ] and others. [ 33 ]
CAD software: | https://en.wikipedia.org/wiki/History_of_CAD_software |
This article covers the History of CP/CMS — the historical context in which the IBM time-sharing virtual machine operating system was built.
CP/CMS development occurred in a complex political and technical milieu .
Historical notes , below, provides supporting quotes and citations from first-hand observers.
The seminal first-generation time-sharing system was CTSS , first demonstrated at MIT in 1961 and in production use from 1964 to 1974. [ 1 ] It paved the way for Multics , CP/CMS , and all other time-sharing environments. Time-sharing concepts were first articulated in the late 50s, particularly as a way to meet the needs of scientific computing . At the time, computers were primarily used for batch processing — where jobs were submitted on punch cards, and run in sequence. Time-sharing let users interact directly with a computer, so that calculation and simulation results could be seen immediately.
Scientific users quickly embraced the concept of time-sharing, and pressured computer vendors such as IBM for improved time-sharing capabilities. MIT researchers spearheaded this effort, launching Project MAC , which was intended to develop the next generation of time-sharing technology and which would ultimately build Multics, an extremely feature-rich time-sharing system that would later inspire the initial development of UNIX . [ 2 ] This high-profile team of leading computer scientists formed very specific technical recommendations and requirements, seeking an appropriate hardware platform for their new system. The technical problems were awesome. Most early time-sharing systems sidestepped these problems by giving users new or modified languages, such as Dartmouth BASIC , which were accessed through interpreters or restricted execution contexts. But the Project MAC vision was for shared, unrestricted access to general-purpose computing.
Along with other vendors, IBM submitted a proposal to Project MAC. However, IBM's proposal was not well received: To IBM's surprise, MIT chose General Electric as the Multics system vendor. The fallout from this event led directly to CP/CMS.
In the early 60s, IBM was struggling to define its technical direction. The company had identified a problem with its past computer offerings: incompatibility between the many IBM products and product lines. Each new product family, and each new generation of technology, forced customers to wrestle with an entirely new set of technical specifications. IBM products incorporated a wide variety of processor designs, memory architectures, instruction sets, input/output strategies, etc. This was not, of course, unique to IBM. All computer vendors seemed to begin each new system with a "clean sheet" design. IBM saw this as both a problem and an opportunity. The cost of software migration was an increasing barrier to hardware sales. Customers could not afford to upgrade their computers, and IBM wanted to change this.
IBM embarked on a very risky undertaking: the System/360 . This product line was intended to replace IBM's diverse earlier offerings, including the IBM 7000 series, the canceled IBM 8000 series, the IBM 1130 series, and various other specialized machines used for scientific and other applications. The System/360 would span an unprecedented range of processing power, memory size, device support, and cost; and more important, it was based on a pledge of backward compatibility , such that any customer could move software to a new system without modification. In today's world of standard interfaces and portable systems, this may not seem such a radical goal; but at the time, it was revolutionary. Before System/360, each computer model often had its own specific devices and programs that could not be used with other systems. Buying a bigger CPU also meant buying new printers, card readers, tape drives, etc. In addition, customers would have to rewrite their programs to run on the new CPU, something customers often balked at. With the S/360, IBM wanted to offer a huge range of computer systems, all sharing a single processor architecture, instruction set, I/O interface, and operating system. Customers would be able to "mix and match" to meet current needs; and they could confidently upgrade their systems in the future, without the need to rewrite all their software applications. IBM's focus remained on its traditional customer base: large organizations doing administrative and business data processing.
At the start of the System/360 project, IBM did not fully appreciate the amount of risk involved. System/360 ultimately gave IBM total dominance over the computer industry; but at first, it nearly put IBM out of business. IBM took on one of the largest and most ambitious engineering projects in history, and in the process discovered diseconomies of scale and the mythical man-month . Extensive literature on the period, such as that by Fred Brooks , illustrate the pitfalls.
It was during the period of System/360 panic that Project MAC asked IBM to provide computers with extensive time-sharing capabilities. This was not the direction the System/360 project was going. Time-sharing wasn't seen as important to IBM's main customer base; batch processing was key. Moreover, time-sharing was new ground. Many of the concepts involved, such as virtual memory , remained unproven. For example: At the time, nobody could explain why the troubled Manchester/Ferranti Atlas virtual memory "didn't work". [ 3 ] [ a ] This was later explained as due to thrashing , based on CP/CMS and M44/44X research. As a result, IBM's System/360 announcement in April 1964 did not include key elements sought by the time-sharing advocates, particularly virtual memory capabilities. Project MAC researchers were crushed and angered by this decision. The System/360 design team met with Project MAC researchers, and listened to their objections; but IBM chose another path.
In February 1964, at the height of these events, IBM had launched its Cambridge Scientific Center (CSC), headed by Norm Rassmussen . CSC was to serve as the link between MIT researchers and the IBM labs, and was located in the same building with Project MAC. IBM fully expected to win the Project MAC competition, and to retain its perceived lead in scientific computing and time-sharing.
One of CSC's first projects was to submit IBM's Project MAC proposal. IBM had received intelligence that MIT was leaning toward the GE proposal, which was for a modified 600-series computer with virtual memory hardware and other enhancements; this would eventually become the GE 645 . IBM proposed a modified S/360 that would include a virtual memory device called the "Blaauw Box" – a component that had been designed for, but not included in, the S/360. The MIT team rejected IBM's proposal. The modified S/360 was seen as too different from the rest of the S/360 line; MIT did not want to use a customized or special-purpose computer for MULTICS , but sought hardware that would be widely available. GE was prepared to make a large commitment to time-sharing, while IBM was seen as obstructive. Bell Laboratories, another important IBM customer, soon made the same decision, and rejected the S/360 for time-sharing.
The loss of Project MAC was devastating for CSC, which essentially lost its reason for existence. Rasmussen remained committed to time-sharing, and wanted to earn back the confidence of MIT and other researchers. To do this, he made a bold decision: The now-idle CSC team would build a time-sharing operating system for the S/360. Robert Creasy left Project MAC to lead the CSC team, which promptly began work on what was to become CP-40 , the first successful virtual machine operating system based on fully virtualized hardware. [ 4 ]
IBM's loss of Project MAC and Bell Laboratories caused repercussions elsewhere at IBM.
CSC soon submitted a successful proposal to MIT's Lincoln Laboratory for a S/360-67, marking an improvement in IBM's credibility at MIT. By committing to a "real" time-sharing product, rather than a customized RPQ system, IBM was showing the kind of commitment MIT found with GE.
CSC also continued work on CP-40, ostensibly to provide research input to the S/360-67 team — but also because the CSC team had grown skeptical about the TSS project, which faced a very aggressive schedule and lofty goals. Since a S/360-67 would not be available to CSC for some time, the team conceived an ingenious stopgap measure: building their own virtual-memory S/360. They designed a set of custom hardware and microcode changes that could be implemented on a S/360-40, providing a comparable platform capable of supporting CP-40's virtual machine architecture. Actual CP-40 and CMS development began in mid 1965, even before the arrival of their modified S/360-40. First production use of CP-40 was in January 1967.
The TSS project, in the meantime, was running late and struggling with problems. CSC personnel became increasingly convinced that CP/CMS was the correct architecture for S/360 time-sharing.
In September 1966, CSC staff began the conversion of CP-40 and CMS to run on the S/360-67. CP-67 was a significant reimplementation of CP-40; Varian reports that the design was "generalized substantially, to allow a variable number of virtual machines, with larger virtual memories", that new data structures replaced "the control blocks describing the virtual machines [which] had been a hard-coded part of the nucleus ", that CP-67 added "the concept of free storage, so that control blocks could be allocated dynamically", and that "the inter-module linkage was also reworked, and the code was made re-entrant." Since CSC's -67 would not arrive for some time, CSC further modified the microcode on its own customized S/360-40 to simulate the S/360-67 – particularly its different approach to virtual memory. [ 5 ] CSC repeatedly and successfully used simulation to work around the absence of hardware: when waiting for its modified S/360-40, for its S/360-67, and later for the first S/370 prototypes. This can be seen as a logical outgrowth of "virtual machine" thinking. During this period, early testing of CP-67 was also done at sites where S/360-67 hardware was available – notably IBM's Yorktown Heights lab and MIT's Lincoln Laboratory .
Observers of CP-67 at Lincoln Labs, already frustrated with severe TSS problems, were very impressed by CP-67. They insisted that IBM provide them a copy of CP/CMS. According to Varian, this demand "rocked the whole company", which had invested so heavily in TSS. However, because the site was so critical, IBM complied. Varian and others speculate that this chain of events could have been "engineered" by Rasmussen, as a "subterfuge" to motivate IBM's continued funding CSC's work on the "counter-strategic" CP/CMS, which he "was told several times to kill". [ 6 ]
By April 1967 – just a few months after CP-40 went into production – CP/CMS was already in daily use at Lincoln Labs. Lincoln Lab personnel worked closely with CSC in improving CP/CMS. They "began enhancing CP and CMS as soon as they were delivered. The Lincoln and Cambridge people worked together closely and exchanged code on a regular basis", beginning a tradition of code sharing and mutual support that would continue for years. At around the same time, Union Carbide , another influential IBM customer, followed the same path – deciding to run CP/CMS, to send personnel to work with CSC, and to contribute to the CP/CMS development effort. [ 7 ]
CP-40, CP-67, and CMS were essentially research systems at the time, built away from IBM's mainstream product organizations, with active involvement of outside researchers. Experimenting was both an important goal and a constant activity. Robert Creasy , the CP-40 project leader, later wrote:
The design of CP/CMS [was] by a small and varied software research and development group for its own use and support… [and] for experimenting with time-sharing system design.... Schedules and budgets, plans and performance goals did not have to be met.… We also expected to redo the system at least once after we got it going. For most of the group, it was meant to be a learning experience. Efficiency was specifically excluded as a software design goal, although it was always considered. We did not know if the system would be of practical use.... In January, 1965, after starting work on the system, it became apparent from presentations to outside groups that the system would be controversial. [ 8 ]
TSS, in the meantime, described by Varian as an "elegant and very ambitious system," was exhibiting "serious stability and performance problems, for it had been snatched from its nest too young." [ 9 ] In February 1968, at the time of SHARE 30, there were eighteen S/360-67 sites attempting to run TSS. During the conference, IBM announced via "blue letter" that TSS was being decommitted — a great blow to the time-sharing community. This decision would be temporarily reversed, and TSS would not be scrapped until 1971. [ b ] However, CP/CMS soon began gaining attention as a viable alternative.
At the time of the S/360-67, software was "bundled" into computer hardware purchases; see "IBM's unbundling of software and services" . In particular, IBM operating systems were available without additional charge to IBM customers. CP/CMS was unusual in that it was delivered as unsupported Type-III software in source code form – meaning that CP/CMS sites ran an unsupported operating system. The need for self-support and community support helped lead to the creation of a strong S/360-67 and CP/CMS user communities, precursors to the open source movement.
In the summer of 1970, the CP/CMS team had begun work on a System/370 version of CP/CMS; this would become VM/370 . CP-370 proved vital to the S/370 project, by providing a usable simulation of a S/370 on S/360-67 hardware – a reprise of CSC's earlier hardware simulation strategies. This approach enabled S/370 development and testing before S/370 hardware was available. A shortage of prototype S/370s was causing critical delays for the MVS project, in particular. This remarkable technical feat transformed MVS development, won an award for the CP-370 developers, and probably rescued the CP project from extinction, despite aggressive efforts to cancel the project.
August 1972 marked the end of CP/CMS, with IBM's "System/370 Advanced Function" announcement. This included: the new S/370-158 and -168; address relocation hardware on all S/370s; and four new operating systems: DOS/VS (DOS with virtual storage), OS/VS1 (OS/MFT with virtual storage), OS/VS2 (OS/MVT with virtual storage, which would grow into SVS and MVS), and VM/370 — the re-implemented CP/CMS. By this time the VM and CP/CMS development team had swelled to 110 people, including documenters. VM/370 was now a real IBM system, no longer part of the IBM Type-III Library. Source code distribution continued for several releases, however; see CP/CMS as free software for details.
In 1968, the principals of a small consulting firm in Connecticut called Computer Software Systems had the audacious idea of leasing an IBM System/360-67 to run CP/CMS and reselling computer time. It was audacious because IBM would not typically lease its $50–100K/month systems to a two-person startup. The third and fourth employees were Dick Orenstein , one of the authors of CTSS , and Dick Bayles , from CSC – the primary architect of CP-67. Other key hires from the CP/CMS world included Harold Feinleib , Mike Field , and Robert Jesurum (Bob Jay) .
By late November 1968, having persuaded IBM to accept the order (no small feat) and secured initial funding, CSS took delivery on their first S/360-67. They began selling time in December 1968.
CSS quickly discovered that, by selling every available virtual machine minute at published prices, they could barely take in enough revenue to pay the machine lease. A whirlwind development program followed, ramping up CP/CMS performance to the point where it could be resold profitably. This began a fork of CP/CMS source code that evolved independently for some fifteen years. This operating system was soon renamed VP/CSS ; the company went public, and was renamed National CSS .
Although VP/CSS shared much with its CP/CMS parent and its VM/370 sibling, it diverged from them in many important ways. For business reasons, the system had to run at a profit; and its users, if frustrated, could stop paying at any time simply by hanging up the phone. These forces gave a high priority to factors affecting performance, usability, and customer support. VP/CSS soon became known for routinely supporting two to three times as many interactive users as on comparable VM systems.
Early NCSS enhancements involved such areas as page migration, dispatching, file system, device support, and efficient fast-path hypervisor functions accessed via the diagnose (DIAG) instruction. Later features included a packet-switched network , FILEDEF-level ( pipe ) interprocess/intermachine communication, and database integration. Similar features also appeared in the VM implementation. Ultimately, the NCSS development team rivaled the size of IBM's, implementing a wide array of features. The VP/CSS platform remained in use through at least the mid-80s. NCSS was acquired by Dun & Bradstreet in 1979; renamed DBCS (Dun & Bradstreet Computer Services); increased its focus on the NOMAD product; changed its business strategy to embrace VM and other platforms; and in the process discontinued support and development of VP/CSS, probably the last non-VM fork of CP/CMS.
Interactive Data Corporation (IDC) followed a plan similar to that of National CSS , selling time-sharing services based on the CP/CMS platform. Its focus at the time was in financial services. Varian reports that IDC had "several" S/360-67 systems running CP/CMS and one of IBM's "first relocating S/370", presumably referring to the S/370-145 of 1971, with the first DAT box; but perhaps to the systems announced in 1972 with the "System/370 Advanced Function" announcement, including the S/370-158 and -168. [ 10 ]
[Further details and citations are sought on the history of IDC and CP/CMS time-sharing.]
The following notes provide brief quotes, primarily from Pugh and Varian [see references], illustrating the development context of CP/CMS. Direct quotes rather than paraphrases are provided here, because the authors' perspectives color their interpretations.
Background information
Citations | https://en.wikipedia.org/wiki/History_of_CP/CMS |
This page details the history of the programming language and software product Delphi .
Delphi evolved from Borland's Turbo Pascal for Windows , itself an evolution with Windows support from Borland's Turbo Pascal and Borland Pascal with Objects, fast 16-bit native-code MS-DOS compilers with their own sophisticated integrated development environment (IDE) and textual user interface toolkit for DOS ( Turbo Vision ). Early Turbo Pascal (for MS-DOS) was written in a dialect of the Pascal programming language ; in later versions support for objects was added, and it was named Object Pascal .
Delphi was originally one of many codenames of a pre-release development tool project at Borland . Borland developer Danny Thorpe suggested the Delphi codename in reference to the Oracle at Delphi . One of the design goals of the product was to provide database connectivity to programmers as a key feature and a popular database package at the time was Oracle database ; hence, "If you want to talk to [the] Oracle, go to Delphi".
As development continued towards the first release, the Delphi codename gained popularity among the development team and beta testing group. However, the Borland marketing leadership preferred a functional product name over an iconic name and made preparations to release the product under the name Borland AppBuilder.
Shortly before the release of the Borland product in 1995, Novell AppBuilder was released, leaving Borland in need of a new product name. After multiple debates and market research surveys, the Delphi codename became the Delphi product name. [ 1 ]
Delphi (later known as Delphi 1) was released in 1995 for the 16-bit Windows 3.1 , and was an early example of what became known as Rapid Application Development (RAD) tools. Delphi 1 features included:
Delphi 2, released in 1996, supported 32-bit Windows environments and bundled with Delphi 1 to retain 16-bit Windows 3.1 application development. New Quickreport components replacing Borland ReportSmith. Delphi 2 also introduced:
Delphi 3, released in 1997, added:
Inprise Delphi 4, released in 1998, completely overhauled the editor and became dockable. It was the last version shipped with Delphi 1 for 16-bit programming. New features included:
Borland Delphi 5 was released in 1999 and improved upon Delphi 4 by adding:
Shipped in 2001, Delphi 6 supported both Linux (using the name Kylix ) and Windows for the first time and offered a cross-platform alternative to the VCL known as CLX. Delphi 6 also added:
Delphi 7, released in August 2002, added support for:
Used by more Delphi developers than any other single version, Delphi 7 is one of the most successful IDEs created by Borland. Its stability, speed, and low hardware requirements led to active use through 2020.
Delphi 8 (Borland Developer Studio 2.0), released December 2003, was a .NET -only release that compiled Delphi Object Pascal code into .NET CIL . The IDE changed to a docked interface (called Galileo ) similar to Microsoft's Visual Studio.NET. Delphi 8 was highly criticized [ by whom? ] for its low quality and its inability to create native applications (Win32 API/x86 code). The inability to generate native applications is only applicable to this release; the capability would be restored in the next release.
The next version, Delphi 2005 (Delphi 9, also Borland Developer Studio 3.0), included the Win32 and .NET development in a single IDE, reiterating Borland's commitment to Win32 developers. Delphi 2005 included:
Delphi 2005 was widely criticized [ 2 ] for its bugs; both Delphi 8 and Delphi 2005 had stability problems when shipped, which were only partially resolved in service packs. CLX support was dropped for new applications from this release onwards.
In late 2005 Delphi 2006 (Delphi 10, also Borland Developer Studio 4.0) was released combining development of C# and Delphi.NET, Delphi Win32 and C++ (Preview when it was shipped but stabilized in Update 1) into a single IDE. It was much more stable than Delphi 8 or Delphi 2005 when shipped, and improved further with the release of two updates and several hotfixes. Delphi 2006 included:
On September 6, 2006, The Developer Tools Group (the working name of the not yet spun off company) of Borland Software Corporation released single-language editions of Borland Developer Studio 2006, bringing back the Turbo name. The Turbo product set included Turbo Delphi for Win32, Turbo Delphi for .NET, Turbo C++, and Turbo C#. There were two variants of each edition: Explorer , a free downloadable flavor, and a Professional flavor, priced at US$899 for new users and US$399 for upgrades, which opened access to thousands of third-party components. Unlike earlier Personal editions of Delphi, Explorer editions could be used for commercial development.
On February 8, 2006, Borland announced that it was looking for a buyer for its IDE and database line of products, including Delphi, to concentrate on its ALM line. Instead of selling it, Borland transferred the development tools group to an independent, wholly owned subsidiary company named CodeGear on November 14, 2006.
Delphi 2007 (Delphi 11), the first version by CodeGear, was released on March 16, 2007. The Win32 personality was released first, before the .NET personality of Delphi 2007 based on .NET Framework 2.0 was released as part of the CodeGear RAD Studio 2007 product. For the first time, Delphi could be downloaded from the internet and activated with a license key. New features included:
Delphi 2007 also dropped a few features:
Internationalized versions of Delphi 2007 shipped simultaneously in English, French, German and Japanese. RAD Studio 2007 (code named Highlander), which included .NET and C++Builder development, was released on September 5, 2007.
The CodeGear era produced an IDE targeting PHP development despite the word "Delphi" in the product name. Delphi for PHP was a VCL-like PHP framework that enabled the same Rapid Application Development methodology for PHP as in ASP.NET Web Form. Versions 1.0 and 2.0 were released in March 2007 and April 2008 respectively. The IDE would later evolve into RadPHP after CodeGear's acquisition by Embarcadero.
Borland sold CodeGear to Embarcadero Technologies in 2008. Embarcadero retained the CodeGear division created by Borland to identify its tool and database offerings but identified its own database tools under the DatabaseGear name.
Delphi 2009 (Delphi 12, code named Tiburón), added many new features:
Delphi 2009 dropped support for .NET development, [ 4 ] replaced by the Delphi Prism developed by RemObjects Software .
Delphi 2010 (code-named Weaver, aka Delphi 14; there was no version 13), was released on August 25, 2009, and is the second Unicode release of Delphi. It included:
Delphi XE (aka Delphi 2011, [ 7 ] code named Fulcrum), was released on August 30, 2010, and improved upon the development environment and language with:
On January 27, 2011, Embarcadero announced the availability of a new Starter Edition that gives independent developers, students and micro businesses a slightly reduced feature set [ 8 ] for a price less than a quarter of that of the next-cheapest version. This Starter edition is based upon Delphi XE with update 1.
On September 1, 2011, Embarcadero released RAD Studio XE2 (code-named Pulsar), which included Delphi XE2, C++Builder , Embarcadero Prism XE2 (Version 5.0 later upgraded to XE2.5 Version 5.1) which was rebranded from Delphi Prism and RadPHP XE2 (Version 4.0). Delphi XE2 included:
Embarcadero said that Linux operating system support "is being considered for the roadmap", as is Android , and that they are "committed to ... FireMonkey. ... expect regular and frequent updates to FireMonkey". Pre-2013 versions only supported iOS platform development with Xcode 4.2.1 and lower, OS X version 10.7 and lower, and iOS SDK 4.3 and earlier.
On September 4, 2012, Embarcadero released RAD Studio XE3, which included Delphi XE3, C++Builder, Embarcadero Prism XE3 (Version 5.2) and HTML5 Builder XE3 (Version 5.0) which was upgraded and rebranded from RadPHP. Delphi XE3 added:
On April 22, 2013, Embarcadero released RAD Studio XE4, which included Delphi XE4, and C++Builder but dropped Embarcadero Prism and HTML5 Builder. XE4 included the following changes:
On September 12, 2013, Embarcadero released RAD Studio XE5, which included Delphi XE5 and C++Builder. It added:
On April 15, 2014, Embarcadero released RAD Studio XE6, which included Delphi XE6 and C++Builder. It allows developers to create natively compiled apps for all platforms for desktop, mobile, and wearable devices like Google Glass, with a single C++ or Object Pascal (Delphi) codebase. RAD Studio XE6 added:
On September 2, 2014, Embarcadero released RAD Studio XE7, which included Delphi XE7 and C++Builder. Its biggest development enabled Delphi/Object Pascal and C++ developers to extend existing Windows applications and build apps that connect desktop and mobile devices with gadgets, cloud services, and enterprise data and API by compiling FMX projects for both desktop and mobile devices. XE7 also included:
On April 7, 2015, Embarcadero released RAD Studio XE8, which included Delphi XE8 and C++Builder. XE8 added the following tools:
On August 31, 2015, Embarcadero released RAD Studio 10 Seattle, which included Delphi and C++Builder. Seattle included:
In October 2015, Embarcadero was purchased by Idera Software . Idera continues to run the developer tools division under the Embarcadero brand.
On April 20, 2016, Embarcadero released RAD Studio 10.1 Berlin, which included Delphi and C++Builder, both generating native code for the 32- and 64-bit Windows platforms, OSX, iOS and Android (ARM, MIPS and X86 processors). Delphi 10.1 Berlin introduced:
Released September 2016, Update 1 added:
Released December 2016, Update 2 included:
On March 22, 2017, Embarcadero released RAD Studio 10.2 Tokyo, adding:
Released August 2017, Update 1 included:
Released December 2017, Update 2 included:
Released March 2018, Update 3 included:
On July 18, 2018, Embarcadero released Community Edition for free download. Commercial use limited to earning no more than US$ 5,000. Similar to Professional, but library source code and VCL/FMX components are more limited.
On November 21, 2018, Embarcadero released RAD Studio 10.3 Rio. This release had many improvements, including:
Released February 2019, Update 1 included:
Released July 2019, Update 2 and included:
Released November 2019, Update 3 included:
On May 26, 2020, Embarcadero released RAD Studio 10.4 Sydney with new features such as:
Released September 2020, Update 1 included:
Released February 24, 2021, Update 2 included:
On September 9, 2021, Embarcadero released RAD Studio 11 Alexandria with new features including:
On March 15, 2022, Embarcadero released RAD Studio 11.1 with new features including:
Released September 5, 2022, Update 2 included:
Released February 27, 2023, Update 3 included:
On November 7, 2023, Embarcadero released RAD Studio 12 Athens with new features. [ citation needed ]
Released April 4, 2024 included:
Released September 13, 2024 included: | https://en.wikipedia.org/wiki/History_of_Delphi_(software) |
DuPont de Nemours, Inc. , commonly shortened to DuPont , is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours . The company played a major role in the development of the U.S. state of Delaware and first arose as a major supplier of gunpowder. DuPont developed many polymers such as Vespel , neoprene , nylon , Corian , Teflon , Mylar , Kapton , Kevlar , Zemdrain, M5 fiber , Nomex , Tyvek , Sorona , Corfam and Lycra in the 20th century, and its scientists developed many chemicals, most notably Freon ( chlorofluorocarbons ), for the refrigerant industry. It also developed synthetic pigments and paints including ChromaFlair .
In 2015, DuPont and the Dow Chemical Company agreed to a reorganization plan in which the two companies would merge and split into three. As a merged entity, DuPont simultaneously acquired Dow and renamed itself to DowDuPont on August 31, 2017, and after 18 months spun off the merged entity's material science divisions into a new corporate entity bearing Dow Chemical's name and agribusiness divisions into the newly created Corteva ; DowDuPont reverted its name to DuPont and kept the specialty products divisions. Prior to the spinoffs it was the world's largest chemical company in terms of sales. The merger has been reported to be worth an estimated $130 billion. [ 2 ] [ 3 ] [ 4 ] The present DuPont, as prior to the merger, is headquartered in Wilmington, Delaware , in the state where it is incorporated . [ 5 ] [ 3 ] [ 4 ] [ 6 ] [ 7 ]
DuPont was founded in 1802 by Éleuthère Irénée du Pont , using capital raised in France and gunpowder machinery imported from France. He started the company at the Eleutherian Mills , on the Brandywine Creek , near Wilmington, Delaware , two years after du Pont and his family left France to escape the French Revolution and religious persecution against Huguenot Protestants. The company began as a manufacturer of gunpowder, as du Pont noticed that the industry in North America was lagging behind Europe. The company grew quickly, and by the mid-19th century had become the largest supplier of preppy gunpowder to the United States military , supplying one-third to one-half the powder used by the Union Army during the American Civil War . The Eleutherian Mills site is now a museum and a National Historic Landmark . [ 9 ] [ 10 ]
DuPont continued to expand, moving into the production of dynamite and smokeless powder . In 1902, DuPont's president, Eugene du Pont , died, and the surviving partners sold the company to three great-grandsons of the original founder. Charles Lee Reese was appointed as director and the company began centralizing their research departments. [ 11 ] The company subsequently purchased several smaller chemical companies; in 1912 these actions generated government scrutiny under the Sherman Antitrust Act . The courts declared that the company's dominance of the explosives business constituted a monopoly and ordered divestment . The court ruling resulted in the creation of the Hercules Powder Company (later Hercules Inc. and now part of Ashland Inc. ) and the Atlas Powder Company (purchased by Imperial Chemical Industries (ICI) and now part of AkzoNobel ). [ 12 ] At the time of divestment, DuPont retained the single-base nitrocellulose powders, while Hercules held the double-base powders combining nitrocellulose and nitroglycerine . DuPont subsequently developed the Improved Military Rifle (IMR) line of smokeless powders . [ 13 ]
In 1910, DuPont published a brochure entitled "Farming with Dynamite". The pamphlet was instructional, outlining the benefits to using their dynamite products on stumps and various other obstacles that would be easier to remove with dynamite as opposed to other more conventional and inefficient means. [ 14 ]
DuPont also established two of the first industrial laboratories in the United States, where they began the work on cellulose chemistry, lacquers and other non-explosive products. DuPont Central Research was established at the DuPont Experimental Station , across the Brandywine Creek from the original powder mills.
In 1914, Pierre S. du Pont invested in the fledgling automobile industry, buying stock in General Motors (GM). The following year he was invited to be on GM's board of directors and would eventually be appointed the company's chairman. The DuPont company would assist the struggling automobile company further with a $25 million purchase of GM stock ($777,055,921 in 2024 dollars [ 15 ] ). In 1920, Pierre S. du Pont was elected president of General Motors. Under du Pont's leadership, GM became the number one automobile company in the world. However, in 1957, because of DuPont's influence within GM, further action under the Clayton Antitrust Act forced DuPont to divest its shares of General Motors.
In 1920, the E.I. du Pont de Nemours & Company formed a joint venture with the French textile company Comptoir des Textiles Artificiels (CTA) to produce artificial silk or viscose at the new Yerkes plant in Buffalo, New York . [ 16 ]
This material had been around for several decades, with British, French, and Germany companies competing for sales primarily in Europe and American Viscose dominating the U.S. market. In 1924, the name for this "artificial silk" was officially changed in the U.S. to Rayon , although the term viscose continued to be used in Europe.
In 1923, the two companies formed a second joint venture to produce Cellophane at same the site in the U.S. DuPont bought the French interests in both companies in March 1928. [ 16 ]
Throughout the 1920s, DuPont continued its emphasis on materials science , hiring Wallace Carothers to work on polymers in 1928. Carothers invented neoprene , a synthetic rubber ; [ 17 ] the first polyester super polymer ; and, in 1935, nylon .
In 1924, DuPont formed Lazote, Inc., which began manufacturing synthetic ammonia using the Claude process . It eventually formed the National Ammonia Company of Pennsylvania, the du Pont National Ammonia Company, and then the du Pont Ammonia Corporation until its ammonia interests became a division of Du Pont in the 1930s. [ 18 ]
In 1930, General Motors and DuPont formed Kinetic Chemicals to produce Freon . Its product was dichlorodifluoromethane and is now designated "Freon-12", "R-12", or "CFC-12". The number after the R is a refrigerant class number developed by DuPont to systematically identify single halogenated hydrocarbons , as well as other refrigerants besides halocarbons.
DuPont introduced phenothiazine as an insecticide in 1935. [ 19 ]
The invention of Teflon followed a few years later and has since been proven responsible for health problems in those exposed to the chemical through manufacturing and home use. [ 20 ]
DuPont ranked 15th among United States corporations in the value of wartime production contracts. [ 21 ] As the inventor and manufacturer of nylon , DuPont helped produce the raw materials for parachutes , powder bags, [ 22 ] and tires . [ 23 ]
DuPont also played a major role in the Manhattan Project in 1943, designing, building and operating the Hanford plutonium producing plant in Hanford, Washington . In 1950 DuPont also agreed to build the Savannah River Plant in South Carolina as part of the effort to create a hydrogen bomb .
DuPont was one of an estimated 150 American companies that provided Nazi Germany with patents, technology and material resources that proved crucial to the German war effort . DuPont maintained business connections with various corporations in the Third Reich from 1933 until 1943 when all of DuPont's assets in Germany were seized by the Nazi government along with those of all other American companies. Irénée du Pont , a descendant of Éleuthère Irénée du Pont and the president of the company during the buildup to World War II, was also a financial supporter of Nazi Führer Adolf Hitler and keenly followed Hitler since the 1920s. [ 24 ] [ 25 ]
After the war, DuPont continued its emphasis on new materials, developing Mylar , Dacron , Orlon , and Lycra in the 1950s, and Tyvek , Nomex , Qiana , Corfam , and Corian in the 1960s.
DuPont has been the key company behind the development of modern body armor . In the Second World War , DuPont's ballistic nylon was used by Britain 's Royal Air Force to make flak jackets . With the development of Kevlar in the 1960s, DuPont began tests to see if it could resist a lead bullet. This research would ultimately lead to the bullet-resistant vests that are used by police and military units.
In 1962, DuPont applied for a patent on the explosion welding process, which was granted on June 23, 1964, under US Patent 3,137,937[123] and resulted in the use of the Detaclad trademark to describe the process. On July 22, 1996, Dynamic Materials Corporation completed the acquisition of DuPont's Detaclad operations for a purchase price of $5,321,850 (or about $10.34 million today).
In 1981, DuPont acquired Conoco Inc. , a major American oil and gas producing company, which gave it a secure source of petroleum feedstocks needed for the manufacturing of many of its fiber and plastics products. The acquisition, which made DuPont one of the top ten U.S.-based petroleum and natural gas producers and refiners, came about after a bidding war with the giant distillery Seagram Company Ltd. Seagram became DuPont's largest single shareholder, with four seats on the board of directors. On April 6, 1995, after being approached by Seagram Chief Executive Officer Edgar Bronfman Jr. , DuPont announced a deal in which the company would buy back all the shares owned by Seagram. [ 26 ]
In 1999, DuPont spun off Conoco and sold all of its shares. Conoco later merged with Phillips Petroleum Company .
DuPont acquired the Pioneer Hi-Bred agricultural seed company in 1999.
DuPont ranked 86th in the Fortune 500 on the strength of nearly $36 billion in revenues, $4.848 billion in profits in 2013. [ 27 ] In April 2014, Forbes ranked DuPont 171st on its Global 2000, the listing of the world's top public companies. [ 28 ]
During this time, DuPont businesses were organized into the following five categories, known as marketing "platforms": Electronic and Communication Technologies, Performance Materials, Coatings and Color Technologies, Safety and Protection, and Agriculture and Nutrition. The agriculture division, DuPont Pioneer , made and sold hybrid seed and genetically modified seed , some of which produces genetically modified food . Genes engineered into their products included LibertyLink , which provides resistance to Bayer's Ignite Herbicide /Liberty herbicides; the Herculex I Insect Protection gene, which provides protection against various insects; the Herculex RW insect protection trait, which provides protection against other insects; the YieldGard Corn Borer gene, which provides resistance to another set of insects; and the Roundup Ready Corn 2 trait that provides crop resistance against glyphosate herbicides. [ 29 ]
DuPont had 150 research and development facilities located in China, Brazil, India, Germany, and Switzerland, with an average investment of $2 billion annually in a diverse range of technologies for many markets including agriculture, genetic traits, biofuels , automotive, construction, electronics, chemicals, and industrial materials. [ 30 ]
In October 2001, the company sold its pharmaceutical business to Bristol Myers Squibb for $7.798 billion. [ 31 ]
In 2002, the company sold the Clysar business to Bemis Company for $143 million. [ 32 ]
In 2004, the company sold its textiles business, which included some of its best-known brands such as Lycra ( Spandex ), Dacron polyester, Orlon acrylic, Antron nylon and Thermolite, to Koch Industries . [ 33 ]
In May 2007 the $2.1 million DuPont Nature Center at Mispillion Harbor Reserve, a wildlife observatory and interpretive center on the Delaware Bay near Milford, Delaware was opened to enhance the beauty and integrity of the Delaware Estuary. The facility is state-owned and operated by the Delaware Department of Natural Resources and Environmental Control (DNREC). [ 34 ] [ 35 ]
In 2010, DuPont Pioneer received approval to market Plenish soybeans, which contain "the highest oleic acid content of any commercial soybean product, at more than 75 percent. Plenish has no trans fat, 20 percent less saturated fat than regular soybean oil, and is a more stable oil with greater flexibility in food and industrial applications." [ 36 ] Plenish is genetically engineered to "block the formation of enzymes that continue the cascade downstream from oleic acid (that produces saturated fats), resulting in an accumulation of the desirable monounsaturated acid." [ 37 ]
In 2011, DuPont was the largest producer of titanium dioxide in the world, primarily provided as a white pigment used in the paper industry . [ 38 ]
On January 9, 2011, DuPont announced that it had reached an agreement to buy Danish company Danisco for US$6.3 billion. On May 16, 2011, DuPont announced that its tender offer for Danisco had been successful and that it would proceed to redeem the remaining shares and delist the company. [ 39 ]
On May 1, 2012, DuPont announced that it had acquired from Bunge full ownership of the Solae joint venture, a soy-based ingredients company. DuPont previously owned 72 percent of the joint venture while Bunge owned the remaining 28 percent. [ 40 ]
In February 2013, DuPont Performance Coatings was sold to the Carlyle Group and rebranded as Axalta Coating Systems . [ 41 ]
In October 2013, DuPont announced that it was planning to spin off its Performance Chemicals business into a new publicly traded company in mid-2015. [ 42 ] The company filed its initial Form 10 with the SEC in December 2014 and announced that the new company would be called The Chemours Company . [ 43 ] The spin-off to DuPont shareholders was completed on July 1, 2015, and Chemours stock began trading on the New York Stock Exchange on the same date. DuPont then focused on production of GMO seeds, materials for solar panels , and alternatives to fossil fuels. [ 44 ] Responsibility for the cleanup of 171 former DuPont sites, which DuPont says will cost between $295 million and $945 million, was transferred to Chemours. [ 45 ]
In October 2015, DuPont sold the Neoprene chloroprene rubber business to Denka Performance Elastomers, a joint venture of Denka and Mitsui .
On December 11, 2015, DuPont announced a merger with Dow Chemical Company, in an all-stock transaction. The combined company, DowDuPont, had an estimated value of $130 billion, being equally held by both companies’ shareholders, while also maintaining its two headquarters. The merger of the two largest U.S. chemical companies closed on August 31, 2017. [ 3 ] [ 4 ] [ 46 ]
Both companies' boards of directors decided that following the merger DowDuPont would pursue a separation into three independent, publicly traded companies: an agriculture, a materials science, and a specialty products company.
Advisory Committees were established for each of the businesses. DuPont CEO Ed Breen would lead the Agriculture and Specialty Products Committees, and Dow CEO Andrew Liveris would lead the Materials Science Committee. These Committees were intended to oversee their respective businesses, and would work with both CEOs on the scheduled separation of the businesses’ standalone entities. [ 51 ] Announced in February 2018, DowDuPont's agriculture division is named Corteva Agriscience, its materials science division is named Dow, and its specialty products division is named DuPont. [ 6 ] In March 2018, it was announced that Jeff Fettig would become executive chairman of DowDuPont on July 1, 2018, and Jim Fitterling would become CEO of Dow Chemical on April 1, 2018. [ 52 ] In October 2018, the company's agricultural unit recorded a $4.6 billion loss in the third quarter after lowering its long-term sales and profits targets. [ 53 ]
In 2019, DuPont completed its spin off from DowDuPont [ 54 ] and the company adapted its marketing and branding in order to establish a new identity that is "fundamentally different" from DowDuPont. The company published a list of sustainability commitments to be achieved by 2030. [ 55 ]
In February 2020, DuPont announced that it is bringing back Edward D. Breen as its CEO after removing former Chief Executive Marc Doyle and CFO Jeanmarie Desmond less than a year after they assumed their roles. Lori D. Koch, previously head of investor relations, assumed the CFO position. [ 56 ]
In November 2021, DuPont announced that it intended to acquire Rogers Corporation in a deal valued at $5.2 billion. [ 57 ] While the deal had been approved by many other regulatory agencies, due to Chinese regulators prolonging the review, DuPont decided on November 1, 2022, to walk away from the deal. DuPont paid Rogers a termination fee of US$162.5 million. [ 58 ] [ 59 ]
In May 2024, DuPont announced it would split into three publicly traded companies, separating its electronics and water businesses while continuing as a diversified industrial firm. CFO Lori Koch was named CEO effective 1 June 2024, as current CEO Ed Breen transitioned to executive chairman. The split is expected to be completed in 18 to 24 months. [ 60 ] On January 17, 2025, DuPont shelved its plans to spin-off its water division which would be retained within DuPont. [ 61 ]
The company's corporate headquarters and experimental station were located in Wilmington, Delaware . The company's manufacturing, processing, marketing, and research and development facilities, as well as regional purchasing offices and distribution centers were located throughout the world. [ 63 ] Major manufacturing sites included the Spruance plant near Richmond, Virginia , (currently the company's largest plant), the Washington Works site in Washington, West Virginia , the Mobile Manufacturing Center (MMC) in Axis, Alabama , the Bayport plant near Houston , Texas, the Mechelen site in Belgium , and the Changshu site in China. [ 64 ] Other locations included the Yerkes Plant on the Niagara River at Tonawanda, New York , the Sabine River Works Plant in Orange, Texas , and the Parlin Site in Sayreville, New Jersey . The facilities in Vadodara , Gujarat and Hyderabad , Telangana in India constituted the DuPont Services Center and DuPont Knowledge Center respectively.
In 2017, the European Commission opened a probe to assess whether the proposed merger of DuPont with Dow Chemical was in line with the EU's respective regulations. The Commission investigated whether the deal reduced competition in areas such as crop protection, seeds and petrochemicals. [ 65 ] The closing date for the merger was repeatedly delayed due to these regulatory inquiries. [ 66 ] [ 67 ]
Ed Breen said the companies were negotiating possible divestitures in their pesticide operations to win approval for the deal. As part of their EU counterproposal, the companies offered to dispose of a portion of DuPont's crop protection business and associated R&D, as well as Dow's acrylic acid copolymers and ionomers businesses. [ 68 ] [ 69 ]
The remedy submission in turn delayed the commission's review deadline to April 4, 2017. The intended spins of the company businesses were expected to occur about 18 months after closing. [ 69 ] According to the Financial Times , the merger was "on track for approval in March" 2017. [ 70 ] Dow Chemical and DuPont postponed the planned deadline during late March, as they struck an $1.6 billion asset swap with FMC Corporation in order to win the antitrust clearances. DuPont acquired the corporation's health and nutrition business, while selling its herbicide and insecticide properties. [ 71 ] [ 72 ]
The European Commission conditionally approved the merger as of April, 2017, although the decision was said to consist of over a thousand pages and was expected to take several months to be released publicly. As part of the approval, Dow must also sell off two acrylic acid co-polymers manufacturing facilities in Spain and the US. China conditionally cleared the merger in May, 2017. [ 73 ] [ 72 ] [ 74 ]
According to former United States Secretary of Agriculture during the Clinton administration, Dan Glickman , and former Governor of Nebraska , Mike Johanns , by creating a single, independent, U.S.-based and – owned pure agriculture company, Dow and DuPont would be able to compete against their still larger global peers. [ 75 ] The merger was not opposed by competition authorities around the world due to the view that it did not have noticeable impact on the global seed markets. [ 76 ]
On the other hand, if Monsanto and Bayer , the 1st and 3rd largest biotech and seed firms, together with Dow and DuPont being the 4th and 5th largest biotechnology and seed companies in the world respectively, both went through with the mergers, the so-called "Big Six" (including Syngenta and BASF [ 77 ] ) in the industry would control 63 percent of the global seed market and 76 percent of the global agriculture chemical market. They would also control 95 percent of corn, soybeans, and cotton traits in the US. Both duopolies would become the "big two" industry dominators.
DuPont has been awarded the National Medal of Technology four times: first in 1990, for its invention of "high-performance man-made polymers such as nylon, neoprene rubber , " Teflon " fluorocarbon resin, and a wide spectrum of new fibers, films, and engineering plastics"; the second in 2002 "for policy and technology leadership in the phaseout and replacement of chlorofluorocarbons ". DuPont scientist George Levitt was honored with the medal in 1993 for the development of sulfonylurea herbicides . In 1996, DuPont scientist Stephanie Kwolek was recognized for the discovery and development of Kevlar . In the 1980s, Dr. Jacob Lahijani, Senior Chemist at DuPont, invented Kevlar 149 and was highlighted in the "Innovation: Agent of Change. [ 78 ] Kevlar 149 is used in armor, belts, hoses, composite structures, cable sheathing, gaskets, brake pads, clutch linings, friction pads, slot insulation , phase barrier insulation, and interturn insulation. [ 79 ] Following the DuPont and Dow merger and subsequent spinoff, this product line remained with DuPont. [ 79 ]
On the company's 200th anniversary in 2002, it was presented with the Honor Award by the National Building Museum in recognition of DuPont's "products that directly influence the construction and design process in the building industry." [ 80 ]
In 2005, BusinessWeek magazine, in conjunction with the Climate Group, ranked DuPont as the best-practice leader in cutting their carbon gas emissions. DuPont reduced its greenhouse gas emissions by more than 65 percent from the 1990 levels while using 7 percent less energy and producing 30 percent more product. [ 81 ] [ 82 ]
In 2012 DuPont was named to the Carbon Disclosure Project Global 500 Leadership Index. Inclusion is based on company performance on sustainability metrics, emissions reduction goals, and environmental performance transparency. [ 83 ] In 2014 DuPont was the top scoring company in the chemical sector according to CDP, with a score of "A" or "B" in every evaluation area except for supply chain management. [ 84 ]
DuPont was part of Global Climate Coalition , a group that lobbied against taking action on climate change. [ 85 ] DuPont has been criticized for its activities in Cancer Alley and blamed for emitting chloroprene, and has been connected by some to anecdotes of "illnesses and ailment" as told by residents of Cancer Alley. [ 86 ]
In 2010, researchers at the Political Economy Research Institute of the University of Massachusetts Amherst ranked DuPont as the fourth-largest corporate source of air pollution in the United States . [ 87 ] DuPont released a statement that 2012 total releases and transfers were 13% lower than 2011 levels, and 70% lower than 1987 levels. [ 88 ] Data from the U.S. Environmental Protection Agency (EPA)'s Toxic Release Inventory database included in the Political Economy Research Institute studies likewise show a reduction in DuPont's emissions from 12.4 million pounds of air releases and 22.4 million pounds of toxic incinerator transfers in 2006 [ 89 ] to 10.94 million pounds and 22.0 million pounds, respectively, in 2010. Over the same period, the Political Economy Research Institutes Toxic score for DuPont increased from 122,426 to 7,086,303. [ 90 ]
One of DuPont's facilities was listed No. 4 on the Mother Jones top 20 polluters of 2010, legally discharging over 5,000,000 pounds (2,300,000 kg) of toxic chemicals into New Jersey and Delaware waterways. [ 91 ] In 2016, Carneys Point Township, New Jersey , where the facility is located, initiated a $1.1 billion lawsuit against the corporation, accusing it of divesting an unprofitable company without first remediating the property as required by law. [ 92 ]
Between 2007 and 2014 there were 34 accidents resulting in toxic releases at DuPont plants across the U.S., with a total of eight fatalities. [ 93 ] Four employees died of suffocation in a Houston, Texas, accident involving leakage of nearly 24,000 pounds (11,000 kg) of methyl mercaptan. [ 94 ] As a result, the company became the largest of the 450 businesses placed into the Occupational Safety and Health Administration 's "severe violator program" in July 2015. The program was established for companies OSHA says have repeatedly failed to address safety infractions. [ 95 ] [ 96 ]
DuPont was fined over $3 million for environmental violations in 2018. [ 97 ] In 2019, DuPont led the Toxic 100 Water Polluters Index . [ 98 ]
Pioneer Hi-Bred , a DuPont subsidiary until 2019, manufactures genetically modified seeds, other tools, and agricultural technologies used to increase crop yield. In 2019, DowDuPont spun off its agricultural unit, which included Pioneer Hi-Bred, as an independent public company under the name Corteva . [ 99 ]
Dupont, along with Frigidaire and General Motors, was a part of a collaborative effort to find a replacement for toxic refrigerants in the 1920s, resulting in the invention of chlorofluorocarbons (CFCs) by Thomas Midgley in 1928. [ 100 ] CFCs are ozone -depleting chemicals that were used primarily in aerosol sprays and refrigerants . DuPont was the largest CFC producer in the world with a 25 percent market share in the 1980s, totaling $600 million in annual sales. [ 101 ]
In 1974, responding to public concern about the safety of CFCs, [ 102 ] DuPont promised to stop production of CFCs should they be proven to be harmful to the ozone layer. However, after the discovery of grave ozone depletion in 1986, DuPont, as a member of the industry group Alliance for Responsible CFC Policy, lobbied against regulations of CFCs. By 1989, it reversed course after calculating that it would profit from production of other chemicals used to replace CFCs. [ 103 ]
In February 1988, United States Senator Max Baucus , along with two other senators, wrote to DuPont reminding the company of its pledge. The Los Angeles Times reported that the letter was "generally regarded as an embarrassment for DuPont, which prides itself on its reputation as an environmentally conscious company." [ 101 ] The company responded with a strongly worded letter that the available evidence did not support a need to dramatically reduce CFC production and calling the proposal "unwarranted and counterproductive". [ 104 ]
On March 14 of the same year, scientists from the National Aeronautics and Space Agency announced the results of a study demonstrating a 2.3% decline in mid-latitude ozone levels between 1969 and 1986, along with evidence tying the decline to CFCs in the upper atmosphere. [ 105 ] On March 24, DuPont reversed its position, calling the NASA results "important new information" and announcing that it would phase out CFC production. The company further called for worldwide controls on CFC production and for additional countries to ratify the Montreal Protocol . DuPont's change of policy was widely praised by environmentalists. [ 106 ] In 2003, DuPont was awarded the National Medal of Technology , recognizing the company as the leader in developing CFC replacements. [ 107 ]
In 1999, attorney Robert Bilott filed a lawsuit against DuPont, alleging its chemical waste ( perfluorooctanoic acid or PFOA, also known as C8) fouled the property of a cattle rancher in Parkersburg, West Virginia . A subsequent class action lawsuit in 2004 alleged DuPont's actions led to widespread water contamination in West Virginia and Ohio and contributed to high rates of cancers and other health problems. PFOA-contaminated drinking water led to increased levels of the compound in the bodies of residents who lived in the surrounding area. A court-appointed C8 Science Panel investigated "whether or not there is a probable link between C8 exposure and disease in the community." [ 108 ] In 2011, the panel concluded that there is a probable link between PFOA and kidney cancer , testicular cancer , thyroid disease , high cholesterol , pre-eclampsia and ulcerative colitis . [ 109 ]
Unlike other persistent organic pollutants, PFOA persists indefinitely and is completely resistant to bio-degradation, remaining toxic. The only way to reduce levels in the body is by physical elimination rather than degradation. [ 110 ] In 2014, the International Agency for Research on Cancer designated PFOA as "possibly carcinogenic" in humans. [ 111 ] DuPont agreed to sharply reduce its output of PFOA, [ 112 ] and was one of eight companies to sign on with the EPA's 2010/2015 PFOA Stewardship Program. The agreement called for the reduction of "facility emissions and product content of PFOA and related chemicals on a global basis by 95 percent by 2010 and to work toward eliminating emissions and product content of these chemicals by 2015." [ 113 ] DuPont phased out PFOA entirely in 2013.
In October 2015, one Ohio resident was awarded $1.6 million when a jury found that her kidney cancer was caused by PFOA in drinking water. In December 2016, $2 million was awarded when a jury found it caused the plaintiff's testicular cancer and awarded punitive damages of $10.5 million. [ 114 ] This was the third case where a jury found DuPont liable for injuries resulting from exposure to PFOA in drinking water sources. According to the co-lead counselor, internal documents revealed during trial showed DuPont had known of a link between PFOA and cancers since 1997. DuPont maintained it has always handled PFOA "reasonably and responsibly" based on the information they, and industry regulators, had available during its use. However, the jury concluded that DuPont did not act to prevent harm or inform the public, despite the information available. [ 115 ] In 2017, DuPont settled 3,550 personal injury claims related to the Parkersburg, West Virginia contamination for $671 million. [ 116 ] [ 117 ] [ 118 ]
The 2019 film Dark Waters is based on the 2016 New York Times Magazine article "The Lawyer Who Became DuPont's Worst Nightmare" by Nathaniel Rich about Bilott. [ 119 ] [ 120 ] An account of the investigation and case was first publicized in the book Stain-Resistant, Nonstick, Waterproof and Lethal: The Hidden Dangers of C8 (2007) by Callie Lyons, a Mid-Ohio Valley journalist who covered the controversy as it was unfolding. [ 121 ] Parts of the pollution and coverup story were also reported by Mariah Blake, whose 2015 article "Welcome to Beautiful Parkersburg, West Virginia" was a National Magazine Award finalist, [ 122 ] and Sharon Lerner , whose series "Bad Chemistry" ran in The Intercept . [ 123 ] [ 124 ] Bilott wrote a memoir, Exposure , published in 2019, detailing his 20-year legal battle against DuPont. [ 125 ] [ 126 ]
DuPont also paid $16.5 million in fines to the Environmental Protection Agency over releases of PFOA from their facility in Washington, West Virginia . [ 127 ] [ 128 ] Water contamination in the Netherlands and links to cancer are also being investigated. [ 129 ]
On November 10, 2022, the state of California announced it had filled suit against both DuPont and 3M for their manufacturing of persistent organic pollutants following multi-year probes into both companies. According to CNN, a DuPont spokesperson claimed DuPont has never manufactured PFOA, PFOS , nor firefighting foam , and said the state's claims are meritless. [ 130 ]
In October 2010 DuPont began marketing a herbicide called Imprelis , for control of certain plants in turf areas. DuPont voluntarily pulled Imprelis from the market in August 2011 before the EPA issued a mandatory stop-sale order on Imprelis after being alerted of numerous reports from golf courses to nurseries that the product was suspected of injuring and, in some cases, killing trees. Norway spruce, white pines and honey locust proved to be among the species of trees that were susceptible. [ 131 ] [ 132 ]
In 2005, the company pleaded guilty to fixing prices of chemicals and products that used neoprene , a synthetic rubber, resulting in an $84 million fine. [ 133 ]
In 2023, DuPont pled guilty for criminal negligence for its role in a poisonous gas leak that killed four workers and injured others at a Houston-area plant on November 15, 2014. 24,000 pounds of methyl mercaptan was released, and travelled downwind into surrounding areas. The company was ordered to pay a $12 million fine, and donate an additional $4 million to the National Fish and Wildlife Foundation . [ 134 ] [ 135 ] | https://en.wikipedia.org/wiki/History_of_DuPont |
The history of IBM mainframe operating systems is significant within the history of mainframe operating systems , because of IBM 's long-standing position as the world's largest hardware supplier of mainframe computers . IBM mainframes run operating systems supplied by IBM and by third parties.
The operating systems on early IBM mainframes have seldom been very innovative, except for TSS/360 and the virtual machine systems beginning with CP-67 . But the company's well-known reputation for preferring proven technology has generally given potential users the confidence to adopt new IBM systems fairly quickly. IBM's current mainframe operating systems, z/OS , z/VM , z/VSE , and z/TPF , are backward compatible successors to those introduced in the 1960s.
IBM was slow to introduce operating systems. General Motors produced General Motors OS in 1955 and GM-NAA I/O in 1956 for use on its own IBM computers; and in 1962 Burroughs Corporation released MCP and General Electric introduced GECOS , in both cases for use by their customers. [ 1 ] [ 2 ]
The first operating systems for IBM computers were written in the mid-1950s by IBM customers with very expensive machines at US$2,000,000 (equivalent to about $23,000,000 in 2024), which had sat idle while operators set up jobs manually, and so they wanted a mechanism for maintaining a queue of jobs. [ 3 ]
These operating systems run only on a few processor models and are suitable only for scientific and engineering calculations. Other IBM computers or other applications function without operating systems. But one of IBM's smaller computers, the IBM 650 , introduced a feature which later became part of OS/360 , where if processing is interrupted by a "random processing error" (hardware glitch), the machine automatically resumes from the last checkpoint instead of requiring the operators to restart the job manually from the beginning. [ 4 ]
General Motors Research division produced GM-NAA I/O for its IBM 701 in 1956 (from a prototype, GM Operating System, developed in 1955), and updated it for the 701's successor. In 1960 the IBM user association SHARE took it over and produced an updated version, SHARE Operating System . [ 3 ]
Finally IBM took over the project and supplied an enhanced version called IBSYS with the IBM 7090 and IBM 7094 computers. IBSYS required 8 tape drives —fewer if one or more disk drives are present. Its main components are a card -based Job Control language, which is the main user interface; compilers for FORTRAN and COBOL ; an assembler ; and various utilities including a sort program. [ 5 ] [ 6 ]
In 1958, the University of Michigan Executive System adapted GM-NAA I/O to produce UMES , which was better suited to the large number of small jobs created by students. UMES was used until 1967 when it was replaced by the MTS timesharing system. [ 7 ]
Bell Labs produced BESYS (sometimes referred to as BELLMON) and used it until the mid-1960s. Bell also made it available to others without charge or formal technical support. [ 8 ] [ 3 ]
Before IBSYS, IBM produced for its IBM 709 , 7090 and 7094 computers a tape-based operating system whose sole purpose was to compile FORTRAN programs. In fact, FMS and the FORTRAN compiler were on the same tape. [ 9 ] [ 10 ]
MIT 's Fernando Corbató produced the first experimental time-sharing systems, such as CTSS , from 1957 to the early 1960s, using slightly modified IBM 709 , [ 11 ] [ 12 ] IBM 7090 , [ 11 ] [ 12 ] and IBM 7094 [ 12 ] mainframes; these systems were based on a proposal by John McCarthy . [ 13 ] [ 14 ] In the 1960s IBM's own laboratories created experimental time-sharing systems, using standard mainframes with hardware and microcode modifications to support virtual memory : IBM M44/44X in the early 1960s; CP-40 from 1964 to 1967; CP-67 from 1967 to 1972. The company even released CP-67 without warranty or technical support to several large customers from 1968 to 1972. CP-40 and CP-67 used modified System/360 CPUs , but the M44/44X was based on the IBM 7044 , an earlier generation of CPU which was very different internally. [ 15 ] [ 16 ] [ 17 ]
These experimental systems were too late to be incorporated into the System/360 series which IBM announced in 1964 but encouraged the company to add virtual memory and virtual machine capabilities to its System/370 mainframes and their operating systems in 1972: [ 15 ]
In 1968 a consulting firm called Computer Software Systems used the released version of CP-67 to set up a commercial time-sharing service. The company's technical team included 2 recruits from MIT (see CTSS above), Dick Orenstein and Harold Feinleib. As it grew, the company renamed itself National CSS and modified the software to increase the number of paying users it could support until the system was sufficiently different that it warranted a new name, VP/CSS . VP/CSS was the delivery mechanism for National CSS' services until the early 1980s, when it switched to IBM's VM/370 (see below). [ 19 ] [ 20 ]
Universities produced three other S/360 time-sharing operating systems in the late 1960s:
Up to the early 1960s, IBM's low-end and high-end systems were incompatible, so programs could not easily be transferred from one to another, and the systems often used completely different peripherals such as disk drives. [ 25 ] IBM concluded that these factors were increasing its design and production costs for both hardware and software to a level that was unsustainable, and were reducing sales by deterring customers from upgrading. So in 1964, the company announced System/360 , a new range of computers which all used the same peripherals and most of which could run the same programs. [ 26 ]
IBM originally intended that System/360 should have only one batch-oriented operating system, OS/360. There are at least two accounts of why IBM later decided it should also produce a simpler batch-oriented operating system, DOS/360 :
System/360's operating systems were more complex than previous IBM operating systems for several reasons, including: [ 28 ]
This made the development of OS/360 and other System/360 software one of the largest software projects anyone had attempted, and IBM soon ran into trouble, with huge time and cost overruns and large numbers of bugs . [ 28 ] These problems were only magnified because to develop and test System/360 operating systems on real hardware, IBM first had to develop Basic Programming Support/360 (BPS/360). [ 29 ] BPS was used to develop the tools needed to develop DOS/360 and OS/360, as well as the first versions of tools it would supply with these operating systems – compilers for FORTRAN and COBOL , utilities including Sort , and above all the assembler it needed to build all the other software. [ 30 ]
IBM's competitors took advantage of the delays in OS/360 and the System/360 to announce systems aimed at what they thought were the most vulnerable parts of IBM's market. To prevent sales of System/360 from collapsing, IBM released four stop-gap operating systems: [ 26 ]
When IBM announced the S/360-67 it also announced a timesharing operating system, TSS/360 , that would use the new virtual memory capabilities of the 360/67. TSS/360 was late and early releases were slow and unreliable. By this time the alternative operating system CP-67 , developed by IBM's Cambridge Scientific Center , was running well enough for IBM to offer it "without warranty" as a timesharing facility for a few large customers. [ 32 ] CP-67 would go on to become VM/370 and eventually z/VM . IBM ultimately offered three releases of a TSS/370 PRPQ as a migration path for its TSS/360 customers, and then dropped it.
The traumas of producing the System/360 operating systems gave a boost to the emerging discipline of software engineering , the attempt to apply scientific principles to the development of software, and the management of software projects . Frederick P. Brooks , who was a senior project manager for the whole System/360 project and then was given specific responsibility for OS/360 (which was already long overdue), wrote an acclaimed book, The Mythical Man-Month , based on the problems encountered and lessons learned during the project, two of which were: [ 33 ]
While OS/360 was the preferred operating system for the higher-end System/360 machines, DOS/360 was the usual operating system for the less powerful machines. It provided a set of utility programs , a macro assembler , and compilers for FORTRAN and COBOL . Support for RPG [ 34 ] [ 35 ] came later, and eventually a PL/I subset. And it supported a useful range of file organizations with access methods to help in using them:
Sequential and ISAM files could store either fixed-length or variable-length records, and all types could occupy more than one disk volume.
DOS/360 also offered BTAM , a data communications facility that was primitive and hard to use by today's standards. But BTAM could communicate with almost any type of terminal, which was a big advantage at a time when there was hardly any standardization of communications protocols.
But DOS/360 had significant limitations compared with OS/360 , which was used to control most larger System/360 machines:
IBM expected that DOS/360 users would soon upgrade to OS/360, but despite its limitations, DOS/360 became the world's most widely used operating system because:
DOS/360 ran well on the System/360 processors which medium-sized organizations could afford, and it was better than the "operating systems" these customers had before. As a result, its descendant z/VSE is still widely used today, as of 2005. [ 27 ]
OS/360 included multiple levels of support, a single API, and much shared code. PCP was a stop-gap version that could run only one program at a time, but MFT (" Multiprogramming with a Fixed number of Tasks") and MVT (" Multiprogramming with a Variable number of Tasks") were used until at least the late 1970s, a good five years after their successors had been launched. [ 38 ] It is unclear whether the divisions among PCP, MFT and MVT arose because MVT required too much memory to be usable on mid-range machines or because IBM needed to release a multiprogramming version of OS (MFT) as soon as possible.
PCP, MFT, and MVT had different approaches to managing memory (see below), but provided very similar facilities:
Experience indicated that it was not advisable to install OS/360 on systems with less than 256 KB of memory, [ 30 ] which was a common limitation in the 1960s.
When installing MFT , customers would specify up to four partitions of memory with fixed boundaries, in which application programs could be run simultaneously. [ 39 ] MFT Version II (MFT-II) raised the limit to 52.
MVT was considerably larger and more complex than MFT and therefore was used on the most powerful System/360 CPUs. It treated all memory not used by the operating system as a single pool from which contiguous "regions" could be allocated as required by an indefinite number of simultaneous application programs. This scheme was more flexible than MFT's and in principle used memory more efficiently, but was liable to fragmentation – after a while one could find that, although there was enough spare memory in total to run a program, it was divided into separate chunks none of which was large enough. [ 31 ] : 372–373
In 1971 the Time Sharing Option (TSO) for use with MVT was added. TSO became widely used for program development because it provided: an editor, debuggers for some of the programming languages used on System/360, and the ability to submit batch jobs, be notified of their completion, and view the results without waiting for printed reports. TSO communicated with terminals by using TCAM ( Telecommunications Access Method ), which eventually replaced the earlier Queued Telecommunications Access Method (QTAM). TCAM's name suggests that IBM hoped it would become the standard access method for data communications, but in fact, TCAM was used almost entirely for TSO and was largely superseded by VTAM from the late 1970s onwards.
System/360's hardware and operating systems were designed for processing batch jobs which in extreme cases might run for hours. As a result, they were unsuitable for transaction processing , in which there are thousands of units of work per day and each takes between 30 seconds and a very few minutes. In 1968 IBM released IMS to handle transaction processing, and in 1969 it released CICS , a simpler transaction processing system which a group of IBM's staff had developed for a customer. IMS was only available for OS/360 and its successors, but CICS was also available for DOS/360 and its successors. [ 40 ] [ 41 ] For many years this type of product was known as a "TP (teleprocessing) monitor". Strictly speaking TP monitors were not operating system components but application programs which managed other application programs. In the 1970s and 1980s, several third-party TP monitors competed with CICS (notably COM-PLETE, DATACOM/DC, ENVIRON/1, INTERCOMM, SHADOW II, TASK/MASTER and WESTI), but IBM gradually improved CICS to the point where most customers abandoned the alternatives. [ 42 ] [ 43 ]
In the 1950s airlines were expanding rapidly but this growth was held back by the difficulty of handling thousands of bookings manually (using card files). In 1957 IBM signed a development contract with American Airlines for the development of a computerized reservations system, which became known as SABRE . The first experimental system went live in 1960 and the system took over all booking functions in 1964 – in both cases using IBM 7090 mainframes. In the early 1960s IBM undertook similar projects for other airlines and soon decided to produce a single standard booking system, PARS , to run on System/360 computers.
In SABRE and early versions of PARS there was no separation between the application and operating system components of the software, but in 1968 IBM divided it into PARS (application) and ACP (operating system). Later versions of ACP were named ACP / TPF and then TPF (Transaction Processing Facility) as non-airline businesses adopted this operating system for handling large volumes of online transactions. The latest version is z/TPF .
IBM developed ACP and its successors because: in the mid-1960s IBM's standard operating systems ( DOS/360 and OS/360 ) were batch -oriented and could not handle large numbers of short transactions quickly enough; even its transaction monitors IMS and CICS , which run under the control of standard general-purpose operating systems, are not fast enough for handling reservations on hundreds of flights from thousands of travel agents.
The last "public domain" version of ACP, hence its last "free" version, was ACP 9.2, which was distributed on a single mini-reel with an accompanying manual set (about two dozen manuals, which occupied perhaps 48 lineal inches of shelf space) and which could be restored to IBM 3340 disk drives and which would, thereby, provide a fully functional ACP system.
ACP 9.2 was intended, primarily, for bank cards like MasterCard and other financial applications, but it could also be utilized for airline reservation systems, too, as by this time ACP had become a more general-purpose OS.
ACP had by then incorporated a hypervisor module (CHYR) which supported a virtual OS (usually VS1 , but possibly also VS2 ) as a guest, with which program development or file maintenance could be accomplished concurrently with the online functions.
In some instances, production work was run under VS2 under the hypervisor, including, possibly, IMS DB.
The Model 20 was labeled as part of the System/360 range because it could be connected to some of the same peripherals, but it was a 16-bit machine and not entirely program-compatible with other members of the System/360 range. Three operating systems were developed by IBM's labs in Germany, for different 360/20 configurations; DPS—with disks (minimum memory required: 12 KB); TPS—no disk but with tapes (minimum memory required: 8 KB); and CPS—punched-card-based (minimum memory required: 4 KB). [ 44 ] These had no direct successors since IBM introduced the System/3 range of small business computers in 1969 and System/3 had a different internal design from the 360/20 and different peripherals from IBM's mainframes.
The 360/44 is another processor that uses the System/360 peripherals but has a modified instruction set. It was designed for scientific computation using floating point numbers, such as geological or meteorological analyses. Because of the internal differences and the specialized type of work for which it was designed, the 360/44 has its own operating system, PS/44. [ 45 ] An optional feature allows a System/360 emulator to run in hidden storage and implement the missing instructions in order to run OS/360. The 360/44 and PS/44 have no direct successors.
System/370 was announced in 1970 with essentially the same facilities as System/360 but with about 4 times the processor speeds of similarly-priced System/360 CPUs. [ 46 ] Then in 1972 IBM announced "System/370 Advanced Functions", of which the main item was that future sales of System/370 would include virtual memory capability and this could also be retro-fitted to existing System/370 CPUs. Hence IBM also committed to delivering enhanced operating systems which could support the use of virtual memory. [ 47 ] [ 48 ]
Most of the new operating systems are distinguished from their predecessors by the presence of "/VS" in their names. "VS" stands for "Virtual Storage". IBM avoided the term "virtual memory", allegedly because the word "memory" might be interpreted to imply that IBM computers could forget things.
All modern IBM mainframe operating systems except z/TPF are descendants of those included in the "System/370 Advanced Functions" announcement – z/TPF is a descendant of ACP , the system which IBM initially developed to support high-volume airline reservations applications.
DOS/VS is the successor to DOS/360 , and offers similar facilities, with the addition of virtual memory. In addition to virtual memory DOS/VS provided other enhancements:
DOS/VS was followed by significant upgrades: DOS/VSE and VSE/SP (1980s), VSE/ESA (1991), and z/VSE (2005). [ 49 ] [ 50 ]
OS/VS1 succeeded MFT , with similar facilities, and adding virtual memory. [ 31 ] IBM released fairly minor enhancements of OS/VS1 until 1983, and in 1984 announced that there would be no more. OS/VS1 and TSS/370 are the only IBM [ 51 ] System/370 operating systems that do not have modern descendants.
The Special Real Time Operating System (SRTOS), Programming RPQ Z06751, is a variant of OS/VS1 extended to support real-time computing . It was targeted at such industries as electric utility energy management and oil refinery applications. [ 52 ]
OS/VS2 Release 1 ( SVS ) is a replacement for MVT with virtual memory. There are many changes, but it retains the overall structure of MVT.
In 1974 IBM released what it described as OS/VS2 Release 2 but which is a major rewrite that was upwards-compatible with the earlier OS/VS2 SVS. The new system's most noticeable feature is support for multiple virtual address spaces. Different applications thought they were using the same range of virtual addresses, but the new system's virtual memory facilities mapped these to different ranges of real memory addresses. [ 31 ] As a result, the new system rapidly became known as " MVS " (Multiple Virtual Storages), the original OS/VS2 became known as "SVS" (Single Virtual Storage). IBM itself accepted this terminology and labelled MVS's successors "MVS/...". [ 53 ]
The other distinctive features of MVS are: its main catalog must be a VSAM catalog; it supports "tightly-coupled multiprocessing" (2 or more CPUs share the same memory and copy of the operating system); it includes a System Resources Manager (renamed Workload Manager in later versions) which allows users to load additional work on to the system without reducing the performance of high-priority jobs.
IBM has released several MVS upgrades: MVS/SE , MVS/SP Version 1, MVS/XA (1981), MVS/ESA (1985), OS/390 (1996) and currently z/OS (2001). [ 54 ]
VM/370 combines a virtual machine facility with a single-user system called Conversational Monitor System (CMS); this combination provides time-sharing by allowing each user to run a copy of CMS on a virtual machine. This combination was a direct descendant of CP/CMS . [ 55 ] The virtual machine facility was often used for testing new software while normal production work continues on another virtual machine, and the CMS timesharing system was widely used for program development. [ 56 ]
VM/370 was followed by a series of upgrades: VM/SEPP ("Systems Extensions Program Product "), VM/BSEPP ("Basic Systems Extensions Program Product"), VM/SP (System Product), VM/SP HPO ("High Performance Option"), VM/XA MA ("Extended Architecture Migration Aid"), VM/XA SF ("Extended Architecture System Facility"), VM/XA SP ("Extended Architecture System Product"), VM/ESA ("Enterprise Systems Architecture"), and z/VM . IBM also produced optional microcode assists for VM and successors, to speed up the hypervisor 's emulation of privileged instructions (those which only operating systems can use) on behalf of "guest" operating systems. As part of 370/Extended Architecture, IBM added the Start Interpretive Execution (SIE) instruction [ 57 ] to allow a further speedup of the CP hypervisor. [ 58 ] | https://en.wikipedia.org/wiki/History_of_IBM_mainframe_operating_systems |
Linux began in 1991 as a personal project by Finnish student Linus Torvalds to create a new free operating system kernel. The resulting Linux kernel has been marked by constant growth throughout its history. Since the initial release of its source code in 1991, it has grown from a small number of C files under a license prohibiting commercial distribution to the 4.15 version in 2018 with more than 23.3 million lines of source code, not counting comments, [ 1 ] under the GNU General Public License v2 with a syscall exception meaning anything that uses the kernel via system calls are not subject to the GNU GPL. [ 2 ] : 7 [ 3 ] [ 4 ]
After AT&T had dropped out of the Multics project, the Unix operating system was conceived and implemented by Ken Thompson and Dennis Ritchie (both of AT&T Bell Laboratories ) in 1969 and first released in 1970. Later they rewrote it in a new programming language, C , to make it portable. The availability and portability of Unix caused it to be widely adopted, copied and modified by academic institutions and businesses.
In 1977, the Berkeley Software Distribution (BSD) was developed by the Computer Systems Research Group (CSRG) from UC Berkeley , based on the 6th edition of Unix and UNIX/32V ( 7th edition ) from AT&T. Since BSD contained Unix code that AT&T owned, AT&T filed a lawsuit ( USL v. BSDi ) in the early 1990s against the University of California. This strongly limited the development and adoption of BSD. [ 5 ] [ 6 ]
Onyx Systems began selling early microcomputer-based Unix workstations in 1980. Later, Sun Microsystems , founded as a spin-off of a student project at Stanford University , also began selling Unix-based desktop workstations in 1982. While Sun workstations did not utilize commodity PC hardware like Linux was later developed for, it represented the first successful commercial attempt at distributing a primarily single-user microcomputer that ran a Unix operating system. [ 7 ] [ 8 ]
In 1983, Richard Stallman started the GNU Project with the goal of creating a free UNIX-like operating system. [ 9 ] As part of this work, he wrote the GNU General Public License (GPL). By the early 1990s, there was almost enough available software to create a full operating system. However, the GNU kernel, called Hurd , failed to attract enough development effort, leaving GNU incomplete. [ citation needed ]
In 1985, Intel released the 80386 , the first x86 microprocessor with a 32-bit instruction set and a memory management unit with paging . [ 10 ]
In 1986, Maurice J. Bach, of AT&T Bell Labs, published The Design of the UNIX Operating System . [ 11 ] This definitive description principally covered the System V Release 2 kernel, with some new features from Release 3 and BSD.
In 1987, MINIX , a Unix-like system intended for academic use, was released by Andrew S. Tanenbaum to exemplify the principles conveyed in his textbook , Operating Systems: Design and Implementation . While source code for the system was available, modification and redistribution were restricted. In addition, MINIX's 16-bit design was not well adapted to the 32-bit features of the increasingly cheap and popular Intel 386 architecture for personal computers. In the early nineties a commercial UNIX operating system for Intel 386 PCs was too expensive for private users. [ 12 ]
These factors and the lack of a widely adopted, free kernel provided the impetus for Torvalds' starting his project. He has stated that if either the GNU Hurd or 386BSD kernels had been available at the time, he likely would not have written his own. [ 13 ] [ 14 ]
In 1991, while studying computer science at University of Helsinki , Linus Torvalds began a project that later became the Linux kernel . He wrote the program specifically for the hardware he was using and independent of an operating system because he wanted to use the functions of his new PC with an 80386 processor. Development was done on MINIX using the GNU C Compiler .
On 3 July 1991, in an effort to implement Unix system calls in his project, Linus Torvalds attempted to obtain a digital copy of the POSIX standards documentation with a request to the comp.os.minix newsgroup . [ 15 ] He was not successful in finding the POSIX documentation, so Torvalds initially resorted to determining system calls from SunOS documentation owned by the university for use in operating its Sun Microsystems server. He also learned some system calls from Tanenbaum's MINIX text that was a part of the Unix course.
As Torvalds wrote in his book Just for Fun , [ 16 ] he eventually ended up writing an operating system kernel. On 25 August 1991, he (at age 21) announced this system in another posting to the comp.os.minix newsgroup: [ 17 ]
Hello everybody out there using minix -
I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones. This has been brewing since april, and is starting to get ready. I'd like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of the file-system (due to practical reasons) among other things).
I've currently ported bash(1.08) and gcc(1.40) , and things seem to work. This implies that I'll get something practical within a few months, and I'd like to know what features most people would want. Any suggestions are welcome, but I won't promise I'll implement them :-)
Linus (torvalds@kruuna.helsinki.fi)
PS. Yes - it's free of any minix code, and it has a multi-threaded fs. It is NOT portable (uses 386 task switching etc), and it probably never will support anything other than AT-harddisks, as that's all I have :-(.
According to Torvalds, Linux began to gain importance in 1992 after the X Window System was ported to Linux by Orest Zborowski , which allowed Linux to support a GUI for the first time. [ 16 ]
Linus Torvalds had wanted to call his invention Freax, a portmanteau of "free", "freak", and "x" (as an allusion to Unix). During the start of his work on the system, he stored the files under the name "Freax" for about half of a year. Torvalds had already considered the name "Linux", but initially dismissed it as too egotistical. [ 16 ]
In order to facilitate development, the files were uploaded to the FTP server (ftp.funet.fi) of FUNET in September 1991. Ari Lemmke at Helsinki University of Technology (HUT), who was one of the volunteer administrators for the FTP server at the time, did not think that "Freax" was a good name. Therefore, he named the project "Linux" on the server without consulting Torvalds. [ 16 ] Later, however, Torvalds consented to "Linux".
To demonstrate how the word "Linux" should be pronounced ( [ˈliːnɵks] ), Torvalds included an audio guide ( listen ⓘ ) with the kernel source code. [ 19 ]
Torvalds first published the Linux kernel under its own licence, [ 20 ] which had a restriction on commercial activity.
The software to use with the kernel was software developed as part of the GNU project licensed under the GNU General Public License, a free software license. The first release of the Linux kernel, Linux 0.01, included a binary of GNU's Bash shell. [ 21 ]
In the "Notes for linux release 0.01", Torvalds lists the GNU software that is required to run Linux: [ 21 ]
Sadly, a kernel by itself gets you nowhere. To get a working system you need a shell, compilers, a library etc. These are separate parts and may be under a stricter (or even looser) copyright. Most of the tools used with linux are GNU software and are under the GNU copyleft . These tools aren't in the distribution - ask me (or GNU) for more info. [ 21 ]
In 1992, he suggested releasing the kernel under the GNU General Public License. He first announced this decision in the release notes of version 0.12. [ 22 ] In the middle of December 1992 he published version 0.99 using the GNU GPL. [ 23 ] Linux and GNU developers worked to integrate GNU components with Linux to make a fully functional and free operating system. [ 24 ] Torvalds has stated, "making Linux GPLed was definitely the best thing I ever did." [ 25 ]
Around 2000, Torvalds clarified that the Linux kernel uses the GPLv2 license, without the common "or later clause". [ 3 ] [ 4 ]
After years of draft discussions, the GPLv3 was released in 2007; however, Torvalds and the majority of kernel developers decided against adopting the new license. [ 26 ] [ 27 ] [ 28 ]
The designation "Linux" was initially used by Torvalds only for the Linux kernel. The kernel was, however, frequently used together with other software, especially that of the GNU project. This quickly became the most popular adoption of GNU software. In June 1994 in GNU's Bulletin, Linux was referred to as a "free UNIX clone", and the Debian project began calling its product Debian GNU/Linux . In May 1996, Richard Stallman published the editor Emacs 19.31, in which the type of system was renamed from Linux to Lignux. This spelling was intended to refer specifically to the combination of GNU and Linux, but this was soon abandoned in favor of "GNU/Linux". [ 29 ]
This name garnered varying reactions. The GNU and Debian projects use the name, although most people simply use the term "Linux" to refer to the combination. [ 30 ]
Torvalds announced in 1996 that there would be a mascot for Linux, a penguin. This was because when they were about to select the mascot, Torvalds mentioned he was bitten by a little penguin ( Eudyptula minor ) on a visit to the National Zoo & Aquarium in Canberra, Australia. Larry Ewing provided the original draft of today's well known mascot based on this description. The name Tux was suggested by James Hughes as derivative of Torvalds' UniX , along with being short for tuxedo , a type of suit with color similar to that of a penguin. [ 16 ] : 138
The largest part of the work on Linux is performed by the community: the thousands of programmers around the world that use Linux and send their suggested improvements to the maintainers. Various companies have also helped not only with the development of the kernels, but also with the writing of the body of auxiliary software, which is distributed with Linux. As of February 2015, over 80% of Linux kernel developers are paid. [ 2 ] : 11
It is released both by organized projects such as Debian, and by projects connected directly with companies such as Fedora and openSUSE . The members of the respective projects meet at various conferences and fairs, in order to exchange ideas. One of the largest of these fairs is the LinuxTag in Germany, where about 10,000 people assemble annually to discuss Linux and the projects associated with it. [ citation needed ]
The Open Source Development Lab (OSDL) was created in the year 2000, and is an independent nonprofit organization which pursues the goal of optimizing Linux for employment in data centers and in the carrier range. It served as sponsored working premises for Linus Torvalds and also for Andrew Morton (until the middle of 2006 when Morton transferred to Google). Torvalds worked full-time on behalf of OSDL, developing the Linux kernels.
On 22 January 2007, OSDL and the Free Standards Group merged to form The Linux Foundation , narrowing their respective focuses to that of promoting Linux in competition with Microsoft Windows . [ 31 ] [ 32 ] As of 2015, Torvalds remains with the Linux Foundation as a Fellow. [ 33 ]
Despite being freely available, companies profit from Linux. These companies, many of which are also members of the Linux Foundation, invest substantial resources into the advancement and development of Linux, in order to make it suited for various application areas. This includes hardware donations for driver developers, cash donations for people who develop Linux software, and the employment of Linux programmers at the company. Some examples are Dell , IBM , and Hewlett-Packard , which validate, use and sell Linux on their own servers, and Red Hat (now part of IBM) and SUSE , which maintain their own enterprise distributions. Likewise, Digia supports Linux by the development and LGPL licensing of the Qt toolkit , which makes the development of KDE possible, and by employing some of the X and KDE developers.
KDE was the first advanced desktop environment (version 1.0 released in July 1998), but it was controversial due to the then-proprietary Qt toolkit used. [ 34 ] GNOME was developed as an alternative due to licensing questions. [ 34 ] The two use a different underlying toolkit and thus involve different programming, and are sponsored by two different groups, German nonprofit KDE e.V. and the United States nonprofit GNOME Foundation .
As of April 2007, one journalist estimated that KDE had 65% of market share versus 26% for GNOME. [ 34 ] In January 2008, KDE 4 was released prematurely with bugs, driving some users to GNOME. [ 35 ] GNOME 3 , released in April 2011, was called an "unholy mess" by Linus Torvalds due to its controversial design changes . [ 36 ]
Dissatisfaction with GNOME 3 led to a fork, Cinnamon , which is developed primarily by Linux Mint developer Clement LeFebvre. This restores the more traditional desktop environment with marginal improvements.
The relatively well-funded distribution, Ubuntu , designed (and released in June 2011) another user interface called Unity which is radically different from the conventional desktop environment and has been criticized as having various flaws [ 37 ] and lacking configurability. [ 38 ] The motivation was a single desktop environment for desktops and tablets, [ citation needed ] although as of November 2012 Unity has yet to be used widely in tablets. However, the smartphone and tablet version of Ubuntu and its Unity interface was unveiled by Canonical Ltd in January 2013. In April 2017, Canonical canceled the phone-based Ubuntu Touch project entirely in order to focus on IoT projects such as Ubuntu Core . [ 39 ] In April 2017, Canonical dropped Unity and began to use GNOME for the Ubuntu releases from 17.10 onward. [ 40 ]
In 1992, Andrew S. Tanenbaum, recognized computer scientist and author of the Minix microkernel system, wrote a Usenet article on the newsgroup comp.os.minix with the title "Linux is obsolete", [ 41 ] which marked the beginning of a famous debate about the structure of the then-recent Linux kernel. Among the most significant criticisms were that:
Tanenbaum's prediction that Linux would become outdated within a few years and replaced by GNU Hurd (which he considered to be more modern) proved incorrect. Linux has been ported to all major platforms and its open development model has led to an exemplary pace of development. In contrast, GNU Hurd has not yet reached the level of stability that would allow it to be used on a production server. [ 45 ] His dismissal of the Intel line of 386 processors as 'weird' has also proven short-sighted, as the x86 series of processors and the Intel Corporation would later become near ubiquitous in personal computers and servers .
In his unpublished book Samizdat , Kenneth Brown claims that Torvalds illegally copied code from MINIX. In May 2004, these claims were refuted by Tanenbaum, the author of MINIX: [ 46 ]
[Brown] wanted to go on about the ownership issue, but he was also trying to avoid telling me what his real purpose was, so he didn't phrase his questions very well. Finally he asked me if I thought Linus wrote Linux. I said that to the best of my knowledge, Linus wrote the whole kernel himself, but after it was released, other people began improving the kernel, which was very primitive initially, and adding new software to the system—essentially the same development model as MINIX. Then he began to focus on this, with questions like: "Didn't he steal pieces of MINIX without permission." I told him that MINIX had clearly had a huge influence on Linux in many ways, from the layout of the file system to the names in the source tree, but I didn't think Linus had used any of my code.
The book's claims, methodology and references were seriously questioned and in the end it was never released and was delisted from the distributor's site.
Although Torvalds has said that Microsoft's feeling threatened by Linux in the past was of no consequence to him, the Microsoft and Linux camps had a number of antagonistic interactions between 1997 and 2001. This became quite clear for the first time in 1998, when the first Halloween document was brought to light by Eric S. Raymond . This was a short essay by a Microsoft developer that sought to lay out the threats posed to Microsoft by free software and identified strategies to counter these perceived threats. [ 47 ] It went on to include a comparison between Windows NT Server and Linux called "Linux Myths" on Microsoft's website in October 1999. [ 48 ]
Competition entered a new phase in the beginning of 2004, when Microsoft published results from customer case studies evaluating the use of Windows vs. Linux under the name "Get the Facts" on its own web page. Based on inquiries, research analysts, and some Microsoft sponsored investigations, the case studies claimed that enterprise use of Linux on servers compared unfavorably to the use of Windows in terms of reliability, security, and total cost of ownership . [ 49 ]
In response, commercial Linux distributors produced their own studies, surveys and testimonials to counter Microsoft's campaign. Novell 's web-based campaign at the end of 2004 was entitled "Unbending the truth" and sought to outline the advantages as well as dispelling the widely publicized legal liabilities of Linux deployment (particularly in light of the SCO v IBM case ). Novell particularly referenced the Microsoft studies in many points. IBM also published a series of studies under the title "The Linux at IBM competitive advantage" to again parry Microsoft's campaign. Red Hat had a campaign called "Truth Happens" aimed at letting the performance of the product speak for itself, rather than advertising the product by studies. [ citation needed ]
In the autumn of 2006, Novell and Microsoft announced an agreement to co-operate on software interoperability and patent protection. [ 50 ] This included an agreement that customers of either Novell or Microsoft may not be sued by the other company for patent infringement. This patent protection was also expanded to non-commercial free software developers. The last part was criticized because it only included non-commercial free software developers.
In July 2009, Microsoft submitted 22,000 lines of source code to the Linux kernel under the GPLV2 license in order to better support being a guest for Windows Virtual PC / Hyper-V , which were subsequently accepted. Although this has been referred to as "a historic move" and as a possible bellwether of an improvement in Microsoft's corporate attitudes toward Linux and open-source software, the decision was not altogether altruistic, as it promised to lead to significant competitive advantages for Microsoft and avoided legal action against Microsoft. Microsoft was actually compelled to make the code contribution when Vyatta principal engineer and Linux contributor Stephen Hemminger discovered that Microsoft had incorporated a Hyper-V network driver, with GPL-licensed open source components, statically linked to closed-source binaries in contravention of the GPL licence. Microsoft contributed the drivers to rectify the licence violation, although the company attempted to portray it as a charitable act, rather than one to avoid legal action against it. In the past Microsoft had termed Linux a "cancer" and "communist". [ 51 ] [ 52 ] [ 53 ] [ 54 ] [ 55 ]
By 2011, Microsoft had become the 17th largest contributor to the Linux kernel. [ 56 ] As of February 2015, Microsoft was no longer among the top 30 contributing sponsor companies. [ 2 ] : 10–12
The Windows Azure project was announced in 2008 and renamed to Microsoft Azure . It incorporates Linux as part of its suite of server-based software applications. In August 2018, SUSE created a Linux kernel specifically tailored to the cloud computing applications under the Microsoft Azure project umbrella. Speaking about the kernel port, a Microsoft representative said "The new Azure-tuned kernel allows those customers to quickly take advantage of new Azure services such as Accelerated Networking with SR-IOV." [ 57 ]
In recent years, Torvalds has expressed a neutral to friendly attitude towards Microsoft following the company's new embrace of open source software and collaboration with the Linux community. "The whole anti-Microsoft thing was sometimes funny as a joke, but not really." said Torvalds in an interview with ZDNet. "Today, they're actually much friendlier. I talk to Microsoft engineers at various conferences, and I feel like, yes, they have changed, and the engineers are happy. And they're like really happy working on Linux. So I completely dismissed all the anti-Microsoft stuff." [ 58 ]
In May 2023, Microsoft publicly released their Azure Linux distribution. [ 59 ]
In March 2003, the SCO Group accused IBM of violating their copyright on UNIX by transferring code from UNIX to Linux. SCO claims ownership of the copyrights on UNIX and a lawsuit was filed against IBM. Red Hat has counter-sued and SCO has since filed other related lawsuits. At the same time as their lawsuit, SCO began selling Linux licenses to users who did not want to risk a possible complaint on the part of SCO. Since Novell also claimed the copyrights to UNIX, it filed suit against SCO.
In early 2007, SCO filed the specific details of a purported copyright infringement. Despite previous claims that SCO was the rightful copyright holder of 1 million lines of code, they specified only 326 lines of code, most of which were uncopyrightable. [ 60 ] In August 2007, the court in the Novell case ruled that SCO did not actually hold the Unix copyrights, to begin with, [ 61 ] though the Tenth Circuit Court of Appeals ruled in August 2009 that the question of who held the copyright properly remained for a jury to answer. [ 62 ] The jury case was decided on 30 March 2010 in Novell's favour. [ 63 ]
SCO has since filed for bankruptcy . [ 64 ]
In 1994 and 1995, several people from different countries attempted to register the name "Linux" as a trademark. Thereupon requests for royalty payments were issued to several Linux companies, a step with which many developers and users of Linux did not agree. Linus Torvalds clamped down on these companies with help from Linux International and was granted the trademark to the name, which he transferred to Linux International. Protection of the trademark was later administered by a dedicated foundation, the non-profit Linux Mark Institute . In 2000, Linus Torvalds specified the basic rules for the assignment of the licenses. This means that anyone who offers a product or a service with the name Linux must possess a license for it, which can be obtained through a unique purchase.
In June 2005, a new controversy developed over the use of royalties generated from the use of the Linux trademark. The Linux Mark Institute, which represents Linus Torvalds' rights, announced a price increase from 500 to 5,000 dollars for the use of the name. This step was justified as being needed to cover the rising costs of trademark protection.
In response to this increase, the community became displeased, which is why Linus Torvalds made an announcement on 21 August 2005, in order to dissolve the misunderstandings. In an e-mail he described the current situation as well as the background in detail and also dealt with the question of who had to pay license costs:
[...] And let's repeat: somebody who doesn't want to protect that name would never do this. You can call anything "MyLinux", but the downside is that you may have somebody else who did protect himself come along and send you a cease-and-desist letter. Or, if the name ends up showing up in a trademark search that LMI needs to do every once in a while just to protect the trademark (another legal requirement for trademarks), LMI itself might have to send you a cease-and-desist-or-sublicense it letter.
At which point you either rename it to something else, or you sublicense it. See? It's all about whether you need the protection or not, not about whether LMI wants the money or not.
[...] Finally, just to make it clear: not only do I not get a cent of the trademark money, but even LMI (who actually administers the mark) has so far historically always lost money on it. That's not a way to sustain a trademark, so they're trying to at least become self-sufficient, but so far I can tell that lawyers fees to give that protection that commercial companies want have been higher than the license fees. Even pro bono lawyers charge for the time of their costs and paralegals etc.
The Linux Mark Institute has since begun to offer a free, perpetual worldwide sublicense. [ 66 ] | https://en.wikipedia.org/wiki/History_of_Linux |
Microsoft Flight Simulator began as a set of articles on computer graphics, written by Bruce Artwick throughout 1976, about flight simulation using 3-D graphics. When the editor of the magazine told Artwick that subscribers were interested in purchasing such a program, Artwick founded Sublogic Corporation to commercialize his ideas. At first the new company sold flight simulators through mail order, but that changed in January 1979 with the release of Flight Simulator (FS) for the Apple II . [ 1 ] They soon followed this up with versions for other systems and from there it evolved into a long-running series of computer flight simulators.
In 1984, Amiga Corporation asked Artwick to port Flight Simulator for its forthcoming computer, but Commodore's purchase of Amiga temporarily ended the relationship. Sublogic instead finished a Macintosh version, released by Microsoft, then resumed work on the Amiga and Atari ST versions. [ 2 ] Although still called Flight Simulator II , the Amiga and Atari ST versions compare favorably with Microsoft Flight Simulator 3.0. Notable features included a windowing system allowing multiple simultaneous 3d views - including exterior views of the aircraft itself - and (on the Amiga and Atari ST) modem play.
Info gave the Amiga version five out of five, describing it as the "finest incarnation". Praising the "superb" graphics, the magazine advised to "BEGIN your game collection with this one!" [ 3 ]
In 1984, Microsoft released their version 2 for IBM PCs. This version made small improvements to the original version, including the graphics and a more precise simulation in general. It added joystick and mouse input, as well as support for RGB monitors (4-color CGA graphics ), the IBM PCjr , and (in later versions) Hercules graphics , and LCD displays for laptops. The new simulator expanded the scenery coverage to include a model of the entire United States, although the airports were limited to the same areas as in Flight Simulator 1 .
Over the next year or two, compatibility with Sublogic Scenery Disks was provided, gradually covering the whole U.S. (including Hawaii), Japan, and part of Europe.
Microsoft Flight Simulator 3 improved the flight experience by adding additional aircraft and airports to the simulated area found in Flight Simulator 2 , as well as improved high-res ( EGA ) graphics, and other features lifted from the Amiga/ST versions.
The three simulated aircraft were the Gates Learjet 25 , Cessna Skylane , and Sopwith Camel . Flight Simulator 3 also allowed the user to customize the display; multiple windows, each displaying one of several views, could be positioned and sized on the screen. The supported views included the instrument and control panel, a map view, and various external camera angles.
This version included a program to convert the old series of Sublogic Scenery Disks into scenery files (known as SCN files), which could then be copied to the FS3 directory, allowing the user to expand the FS world.
Version 4 followed in 1989, and brought several improvements over Flight Simulator 3 . These included improved aircraft models, random weather patterns, a new sailplane , and dynamic scenery (non-interactive air and ground traffic on and near airports moving along static prerecorded paths). The basic version of FS4 was available for Macintosh computers in 1991. Like FS3, this version included an upgraded converter for the old Sublogic Scenery Disks into SCN files.
A large series of add-on products were produced for FS4 between 1989 and 1993. First from Microsoft and the Bruce Artwick Organization (BAO) came the Aircraft and Scenery Designer (ASD) integration module. This allowed FS4 users to build custom scenery units known as SC1 files which could be used within FS4 and traded with other users. Also, with the provided Aircraft Designer Module, the user could select one of two basic type aircraft frames (prop or jet) and customize flight envelope details and visual aspects. ASD provided additional aircraft including a Boeing 747 with a custom dash/cockpit (which required running in 640 × 350 resolution).
Mallard Software and BAO released the Sound, Graphics, and Aircraft Upgrade (SGA), which added digital and synth sound capability (on compatible hardware) to FS4. A variety of high resolution modes also became available for specific types of higher end video cards and chipsets, thus supplying running resolutions up to 800 × 600. As with ASD, the SGA upgrade also came with some additional aircraft designed by BAO, including an Ultra-light.
Another addition was known as the Aircraft Adventure Factory (AAF), which had two components. The first, the Aircraft Factory, was a Windows-based program allowing custom design aircraft shapes to be used within FS4 utilizing a CAD-type interface, supported by various sub menu and listing options. Once the shape was created and colors assigned to the various pieces, it could be tied to an existing saved flight model as was designed in the Aircraft Designer module. The other component of AAF was the Adventure module. Using a simple language, a user could design and compile a script that could access such things as aircraft position, airspeed, altitude, and aircraft flight characteristics.
Other add-on products (most published by Mallard Software) included: The Scenery Enhancement Edition (SEE4), which further enhanced SC1 files and allowed for AF objects to be used as static objects within SEE4; Pilots Power Tools (PPT), which greatly eased the management of the many aircraft and scenery files available; and finally, a variety of new primary scenery areas created by MicroScene, including Hawaii (MS-1), Tahiti (MS-2), Grand Canyon (MS-3), and Japan (MS-4). Scenery files produced by Sublogic could also be used with FS4, including Sublogic's final USA East and West scenery collections.
Flight Simulator 5.0 is the first version of the series to use textures. This allowed FS5 to achieve a much higher degree of realism than the previous flat-shaded simulators. This also made all add-on scenery and aircraft for the previous versions obsolete, as they would look out of place.
The bundled scenery was expanded (now including parts of Europe). Improvements were made to the included aircraft models, the weather system's realism, and artificial intelligence. The coordinate system introduced in Flight Simulator 1 was revamped, and the scenery format was migrated from the old SCN/SC1 to the new and more complex BGL format.
More noticeable improvements included the use of digital audio for sound effects, custom cockpits for each aircraft (previous versions had one cockpit that was slightly modified to fit various aircraft), and better graphics.
It took about a year for add-on developers to get to grips with the new engine, but when they did they were not only able to release scenery, but also tools like Flightshop that made it feasible for users to design new objects.
In 1995, Flight Simulator 5.1 was introduced, adding the ability to handle scenery libraries including wide use of satellite imagery, faster performance, and a barrage of weather effects: storms, 3D clouds, and fog became true-to-life elements in the Flight Simulator world. This edition was also the first version that was released on CD-ROM and the last for DOS. This was released in June 1995.
In the fall of 1995, with the release of the Flight shop program, nearly any aircraft could be built. The French program "Airport" was also available for free which allowed users to build airports (FS5.1 only had 250 Worldwide) and other designers were doing custom aircraft cockpit panels. This all made for a huge amount of "freeware" to be released to be downloaded and added to the FS5.1 simulator. Forums such as CompuServe, Avsim, and Flightsim.com acted as libraries for uploads and discussion.
In November 1995, Microsoft acquired the Bruce Artwick Organization (BAO), Ltd from Bruce Artwick . Employees were moved to Redmond, WA, and development of Microsoft Flight Simulator continued.
With the release of Windows 95 , a new version (6.0) was developed for that platform. Although this was essentially just a port from the DOS version (FS5.1), it did feature a vastly improved frame-rate, better haze, and additional aircraft, including the Extra 300 aerobatic aircraft.
Instead of using the version number in the title, Microsoft instead called it " Flight Simulator for Windows 95 " to advertise the change in operating system. It is often abbreviated as "FS95" or "FSW95".
This was the first version released after the purchase of BAO by Microsoft, and after having physically relocated development of the BAO development staff to Microsoft's primary campus in Redmond, Washington. The BAO team was integrated with other non-BAO Microsoft staff, such as project management, testing, and artwork.
Additional scenery included major airports outside Europe and the US for the first time.
Flight Simulator 98 (version 6.1), abbreviated as FS98, is generally regarded as a "service release", offering minor improvements, with a few notable exceptions: The simulator now also featured a helicopter (the Bell 206B III JetRanger ), as well as a generally improved interface for adding additional aircraft, sceneries, and sounds.
Other new "out of the box" aircraft included a revised Cessna 182 with a photorealistic instrument panel and updated flight model. The primary rationale for updating the 182 was Cessna 's return to manufacturing that model in the late 1990s. The Learjet Model 45 business jet was also included, replacing the aging Learjet 35 from earlier versions. The Dynamic Scenery models were also vastly improved. One of the most noticeable improvements in this version was the ability to have independent panels and sounds for every aircraft.
A major expansion of the in-box scenery was also included in this release, including approximately 45 detailed cities (many located outside the United States, some of which had been included in separate scenery enhancement packs), as well as an increase in the modeled airports to over 3000 worldwide, compared with the approximately 300 in earlier versions. This major increase in scenery production was attributable partially to inclusion of the content from previous standalone scenery packs, as well as new contributions by MicroScene, a company in San Ramon, California who had developed several scenery expansions released by Microsoft.
This release also included support for the Microsoft SideWinder Pro Force Feedback joystick, which allowed the player to receive some sensory input from simulated trim forces on the aircraft controls.
This was the first version to take advantage of 3D-graphic cards, through Microsoft's DirectX technology. With such combination of hardware and software, FS98 not only achieved better performance, but also implemented better haze/visibility effects, "virtual cockpit" views, texture filtering, and sunrise/sunset effects.
By November 1997, Flight Simulator 98 had shipped one million units, following its September launch. [ 5 ] [ 6 ] It received a "Gold" award from the Verband der Unterhaltungssoftware Deutschland (VUD) in August 1998, [ 7 ] for sales of at least 100,000 units across Germany, Austria, and Switzerland. [ 8 ] The VUD raised it to "Platinum" status, indicating 200,000 sales, by November. [ 9 ]
Flight Simulator 2000 (version 7.0), abbreviated as FS2000, was released as a major improvement over the previous versions, and was also offered in two versions: One version for "normal" users, and one "pro" version with additional aircraft. Although many users had high expectations when this version arrived, many were disappointed when they found out that the simulator demanded high-end hardware; the minimum requirements were only a Pentium 166 MHz computer, although 400–500 MHz computer was deemed necessary to have an even framerate. [ 10 ] However, even on a high-end system, stuttering framerate was a problem, especially when performing sharp turns in graphically dense areas. Also, the visual damage effects introduced in FS5 were disabled, and continued to be unavailable in versions after FS2000. While the visual damage effects were still in the game, Microsoft disabled them through the game's configuration files. Users can re-enable the damage effects through modifications. FS2000 also introduced computer controlled aircraft in some airports.
This version also introduced 3D elevation, making it possible to adjust the elevation for the scenery grids, thus making most of the previous scenery obsolete (as it didn't support this feature). A GPS was also added, enabling an even more realistic operation of the simulator. FS2000 also upgraded its dynamic scenery, with more detailed models and AI that allowed aircraft to yield to other aircraft to avoid incursions while taxiing.
FS2000 included an improved weather system, which featured precipitation for the first time in the form of either snow or rain, as well as other new features such as the ability to download real-world weather.
New aircraft in FS2000 included the supersonic Aerospatiale-BAC Concorde (prominently featured on both editions' box covers) and the Boeing 777 which had recently entered service at the time.
An often overlooked, but highly significant milestone in Flight Simulator 2000 , was the addition of over 17,000 new airports, for a total exceeding 20,000 worldwide, as well as worldwide navigational aid coverage. This greatly expanded the utility of the product in simulating long international flights as well as instrument-based flight relying on radio navigation aids. Some of these airports, along with additional objects such as radio towers and other "hazard" structures, were built from publicly available U.S. government databases. Others, particularly the larger commercial airports with detailed apron and taxiway structures, were built from detailed information in Jeppesen 's proprietary database, one of the primary commercial suppliers of worldwide aviation navigation data.
In combination, these new data sources in Flight Simulator allowed the franchise to claim the inclusion of virtually every documented airport and navigational aid in the world, as well as allowing implementation of the new GPS feature. As was the case with FS98, scenery development using these new data sources in FS2000 was outsourced to MicroScene in San Ramon, working with the core development team at Microsoft.
The air traffic control system first featured in Flight Simulator 2002 was originally scheduled for inclusion in this version, but eventually postponed due to performance issues.
Microsoft Flight Simulator 2000 was the last of the Flight Simulator series to support the Windows 95 and Windows NT 4.0 operating systems.
Flight Simulator 2002 (version 8.0), abbreviated as FS2002, improved vastly over previous versions. In addition to improved graphics, FS2002 introduced air traffic control (ATC) and artificial intelligence (AI) aircraft enabling users to fly alongside computer-controlled aircraft and communicate with airports. An option for a target framerate was added, enabling a cap on the framerate to reduce stutter while performing texture loading and other maintenance tasks. In addition, the 3D Virtual Cockpit feature from FS98 was re-added in a vastly improved form, creating in effect a view of the cockpit from the viewpoint of a real pilot. The external view also featured an inertia effect, inducing an illusion of movement in a realistic physical environment. The simulation runs smoother than Flight Simulator 2000 , even on comparable hardware. A free copy of Fighter Ace 2 was also included with the software.
Flight Simulator 2004: A Century of Flight (version 9.0), also known as FS9 or FS2004, was shipped with several historical aircraft such as the Wright Flyer , Ford Tri-Motor , and the Douglas DC-3 to commemorate the 100th anniversary of the Wright Brothers ' first flight. The program included an improved weather engine that provided true three-dimensional clouds and true localized weather conditions for the first time. [ 11 ] The engine also allowed users to download weather information from actual weather stations , allowing the simulator to synchronize the weather with the real world. Other enhancements from the previous version included better ATC communications, GPS equipment , interactive virtual cockpits, and more variety in autogen such as barns, street lights, silos, etc. This version was the first to include worldwide taxiway signs by default.
Flight Simulator 2004 is also the last version to include and feature Meigs Field as its default airport. The airport was closed on March 30, 2003, and the airport was removed in the subsequent releases. It is also the last version to support Windows 98/9x series of operating systems.
Flight Simulator X (version 10.0), abbreviated as FSX, is the tenth edition in the Flight Simulator franchise. It features new aircraft, improved multiplayer support, including the ability for two players to fly a single plane, and players to occupy a control tower available in the Deluxe Edition, and improved scenery with higher resolution ground textures.
FSX includes fewer aircraft than FS2004, but incorporates new aircraft such as the Airbus A321 , Maule Orion , Boeing 737-800 (replacing the aging Boeing 737-400 ), Beechcraft King Air and Bombardier CRJ700 . The expansion pack, named Acceleration , was released later, which includes new missions, aircraft, and other updates. The Deluxe edition of Flight Simulator X includes the Software Development Kit (SDK), which contains an object placer, allowing the game's autogen and full scenery library to be used in missions or add-on scenery. Finally, the ability to operate the control surfaces of aircraft with the mouse was reintroduced after it was removed in FS2002.
Previous versions did not allow great circle navigation at latitudes higher than 60 degrees (north or south), and at around 75-80 degrees north–south it became impossible to "fly" closer to the poles, whichever compass heading was followed. This problem is solved in FSX. Users may now navigate through any great circle as well as "fly" across both the Arctic and Antarctic . This version also adds the option to have a transparent panel.
FSX is the first of the series to be released exclusively on DVD-ROM due to space constraints. This is also the first in the series that calls for the preparing process known as activating . Through the internet or a phone a hardware number is generated, and a corresponding code is then used to lock the DVD to one single computer only. It also requires a significantly more powerful computer to run smoothly, even on low graphical settings. Users have reported that the game is "CPU-bound" - a powerful processor is generally more helpful in increasing performance than a powerful graphics card.
Meigs Field in Chicago was removed following its sudden destruction in 2003, [ 12 ] while Kai Tak Airport in Hong Kong, which had closed in 1998, remained.
FSX is the last version of Microsoft Flight Simulator to support Windows XP, Vista, 7, 8, and 8.1 as Microsoft Flight Simulator (2020) only works on Windows 10 and 11.
Microsoft released their first expansion pack for Flight Simulator in years, called Flight Simulator X: Acceleration , to the US market on October 23, 2007, and released to the Australian market on November 1, 2007. Unlike the base game, which is rated E, Acceleration is rated E10+ in the US.
Acceleration introduces new features, including multiplayer air racing, new missions, and three all-new aircraft, the F/A-18A Hornet , EH-101 helicopter, and P-51D Mustang . In many product reviews, users complained of multiple bugs in the initial release of the pack. One of the bugs, that occurs only in the Standard Edition, is the Maule Air Orion aircraft used in the mission has missing gauges and other problems, as it is a Deluxe Version-only aircraft.
The new scenery enhancements cover Berlin, Istanbul, Cape Canaveral, and Edwards Air Force Base, providing high accuracy both in the underlying photo texture (60 cm/pixel) and in the detail given to the 3D objects.
Flight Simulator X: Acceleration can take advantage of Windows Vista, Windows 7, and DirectX 10 as well.
The expansion pack includes code from both service packs, thus installing them is unnecessary.
On 9 July 2014, Dovetail Games announced a licensing agreement with Microsoft to distribute Microsoft Flight Simulator X: Steam Edition [ 13 ] and to develop further products based on Microsoft's technology for the entertainment market.
Dovetail released Microsoft Flight Simulator X: Steam Edition on 18 December 2014. It is a re-release of Flight Simulator X: Gold Edition , which includes the Deluxe and Acceleration packs and both Service Packs. It includes "all standard Steam functionality", and replaces the GameSpy multiplayer system with Steam's multiplayer system. [ 14 ]
While FSX: Steam Edition remains on sale, Dovetail also released a new flight simulation franchise, Flight Sim World . The company originally planned to bring this game to market in 2015. [ 15 ] However, the program became available in 2017. In April 2018, Flight Sim World development was closed, and sales ended in May 2018. [ 16 ]
The latest entry to the series was first revealed in June 2019, at Microsoft's E3 2019 conference. Soon after the announcement, Microsoft Studios made available to the public its Microsoft Flight Simulator Insider Program webpage, where participants could subscribe to news, offer feedback, access a private forum, and be eligible to participate in Alpha and Beta releases of the game. [ 17 ]
Flight Simulator (2020) features significantly more scenery detail, accurately modelling virtually every part of the world. The simulation also includes vastly more sophisticated aircraft, with nearly complete simulations of aircraft systems, overhead panels and flight management computers (FMCs) in commercial jet airliners; features which were highly incomplete in previous versions.
The new Flight Simulator is powered by satellite data and Azure AI. It features high fidelity shadow generation and reflections on aircraft surfaces, busy airports with animated vehicles and people, complex cloud formations, defined shorelines and water bodies, realistic precipitation effects on the aircraft's windshield, and very detailed terrain generation with a vast amount of autogenerated scenery.
The official website for the game states: "Microsoft Flight Simulator is the next generation of one of the most beloved simulation franchises. From light planes to wide-body jets, fly highly detailed and stunning aircraft in an incredibly realistic world. Create your flight plan and fly anywhere on the planet. Enjoy flying day or night and face realistic, challenging weather conditions." [ 18 ]
The game was released for Windows on August 18, 2020, through Xbox Game Pass and Steam on PC. Microsoft Flight Simulator 2020 was released on Xbox Series S/X on July 27, 2021.
On June 11, 2023, Microsoft announced Flight Simulator 2024, releasing a 2-minute announcement trailer on Twitter during Xbox Showcase.
Some of the new features are real world aviation scenarios, such as skydiving operations, aerial firefighting, and executive transport missions.
The game released on November 19, 2024. Many players faced issues loading the game on launch day, causing the game to a receive an "Overwhelmingly Negative" rating on Steam after its release. [ 19 ]
On August 17, 2010, Microsoft announced a new flight simulator, Microsoft Flight , designed to replace the Microsoft Flight Simulator series. [ 20 ] New to Flight is Games for Windows – Live integration, replacing the GameSpy client which was used in previous installments.
An add-on market place was implemented as well, offering some additional scenery packs and aircraft as downloadable content (DLC). The new version was aimed at current flight simulator fans, as well as novice players. However, Flight has a different internal architecture and operational philosophy, and is not compatible with the previous Flight Simulator series.
Some users and critics such as Flying Magazine were disappointed with the product, the main issue being that the product is a game , rather than a simulator , [ 21 ] to attract a casual audience rather than enthusiasts who would want a more realistic experience. [ 22 ]
On July 25, 2012, Microsoft announced it had cancelled further development of Microsoft Flight , stating that this was part of "the natural ebb and flow" of application management. The company stated it will continue to support the community and offer Flight as a free download, but closed down all further development of the product on 26 July 2012. [ 23 ]
In 2009, Lockheed Martin announced that they had negotiated with Microsoft to purchase the intellectual property and including source code for Microsoft ESP which was the commercial-use version of Flight Simulator X SP2. In 2010 Lockheed announced that the new product based upon the ESP source code would be called Prepar3D . Lockheed has hired members of the original ACES Studios team to continue development of the product. Most Flight Simulator X addons as well as the default FSX aircraft work in Prepar3D without any adjustment since Prepar3D is kept backward compatible. The first version was released on 1 November 2010.
In May 2017, Dovetail Games announced Flight Sim World , based on the codebase of Flight Simulator X , and released later that month. [ 24 ] Only a year later, on April 23, 2018, Dovetail announced end of development of Flight Sim World and the end of sales effective May 15, 2018. [ 25 ]
In 1989, Video Games & Computer Entertainment reported that Flight Simulator was "unquestionably the most popular computer game in the world, with nearly two million copies sold." [ 26 ] | https://en.wikipedia.org/wiki/History_of_Microsoft_Flight_Simulator |
This is a history of the various versions of Microsoft Office , consisting of a bundle of several different applications which changed over time. This table only includes final releases and not pre-release or beta software. It also does not list the history of the constituent standalone applications which were released much earlier starting with Word in 1983, Excel in 1985, and PowerPoint in 1987.
Microsoft Office 2000 Personal was an additional SKU, solely designed for the Japanese market, that included Word 2000, Excel 2000 and Outlook 2000. [ 26 ] This compilation would later become widespread as Microsoft Office 2003 Basic.
As with previous versions, Office 2016 is made available in several distinct editions aimed towards different markets. All traditional editions of Microsoft Office 2016 contain Word , Excel , PowerPoint and OneNote and are licensed for use on one computer. [ 56 ] [ 57 ] The installation of retail channels of Office 2016 is Click-To-Run (C2R), however volume licensing channels Office 2016 are using traditional Microsoft Installer (MSI).
Five traditional editions of Office 2016 were released for Windows:
For a comparison chart for the new version of Office, Microsoft 365, click here .
Three traditional editions of Office 2016 were released for Mac: | https://en.wikipedia.org/wiki/History_of_Microsoft_Office |
The history of Microsoft SQL Server begins with the first Microsoft SQL Server database product – SQL Server v1.0, a 16-bit relational database for the OS/2 operating system, released in 1989.
On June 12, 1988, Microsoft joined Ashton-Tate and Sybase to create a variant of Sybase SQL Server for IBM OS/2 (then developed jointly with Microsoft), which was released the following year. [ 1 ] This was the first version of Microsoft SQL Server, and served as Microsoft's entry to the enterprise-level database market, competing against Oracle , IBM, Informix, Ingres and later, Sybase. SQL Server 4.2 was shipped in 1992, bundled with OS/2 version 1.3, followed by version 4.21 for Windows NT , released alongside Windows NT 3.1. SQL Server 6.0 was the first version designed for NT, and did not include any direction from Sybase.
About the time Windows NT was released in July 1993, Sybase and Microsoft parted ways and each pursued its own design and marketing schemes. Microsoft negotiated exclusive rights to all versions of SQL Server written for Microsoft operating systems. (In 1996 Sybase changed the name of its product to Adaptive Server Enterprise to avoid confusion with Microsoft SQL Server.) Until 1994, Microsoft's SQL Server carried three Sybase copyright notices as an indication of its origin.
SQL Server 7.0 was a major rewrite (using C++) of the older Sybase engine, which was coded in C. Data pages were enlarged from 2k bytes to 8k bytes. Extents thereby grew from 16k bytes to 64k bytes. User Mode Scheduling (UMS) was introduced to handle SQL Server threads better than Windows preemptive multi-threading, also adding support for fibers (lightweight threads, introduced in NT 4.0, which are used to avoid context switching [ 2 ] ). SQL Server 7.0 also introduced a multi-dimensional database product called SQL OLAP Services (which became Analysis Services in SQL Server 2000).
SQL Server 7.0 would be the last version to run on the DEC Alpha platform. Although there were pre-release versions of SQL 2000 (as well as Windows 2000) compiled for Alpha, these were canceled and were never commercially released. Mainstream support ended on December 31, 2005, and extended support ended on January 11, 2011.
SQL Server 2000 included more modifications and extensions to the Sybase code base, adding support for the IA-64 architecture (now out of "mainstream" support [ 3 ] ). By SQL Server 2005 the legacy Sybase code had been completely rewritten. [ 4 ]
Since the release of SQL Server 2000, advances have been made in performance, the client IDE tools, and several complementary systems that are packaged with SQL Server 2005. These include:
SQL Server 2000 also introduced many T-SQL language enhancements, such as table variables, user-defined functions, indexed views, INSTEAD OF triggers, cascading referential constraints and some basic XML support. [ 5 ] [ 6 ]
With the release of Service Pack 3, Microsoft also released the first 64-bit version of the SQL Server for the Itanium IA-64 platform (not to be confused with the x86-64 platform). Only the SQL Server relational engine and SQL Agent were ported to Itanium at this time. Client tools, such as SQL Server Management Studio, were still 32-bit x86 programs. The first release of SQL IA-64 was version 8.00.760, with a build date of February 6, 2003.
Mainstream support ended on April 8, 2008, and extended support ended on April 9, 2013.
SQL Server 2005 (formerly codenamed "Yukon") was released in November 2005, introducing native support for x64 systems and updates to Reporting Services, Analysis Services & Integration Services. [ 7 ] It included native support for managing XML data, in addition to relational data . For this purpose, it defined an xml data type that could be used either as a data type in database columns or as literals in queries. XML columns can be associated with XSD schemas; XML data being stored is verified against the schema. XML data is queried using XQuery ; SQL Server 2005 added some extensions to the T-SQL language to allow embedding XQuery queries in T-SQL. It also defines a new extension to XQuery, called XML DML, that allows query-based modifications to XML data. SQL Server 2005 also allows a database server to be exposed over web services using Tabular Data Stream (TDS) packets encapsulated within SOAP requests. When the data is accessed over web services, results are returned as XML. [ 8 ]
Common Language Runtime (CLR) integration was introduced with this version, enabling one to write SQL code as Managed Code by the CLR. For relational data, T-SQL has been augmented with error handling features (try/catch) and support for recursive queries with CTEs (Common Table Expressions). SQL Server 2005 has also been enhanced with new indexing algorithms, syntax and better error recovery systems. Data pages are checksummed for better error resiliency, and optimistic concurrency support has been added for better performance. Permissions and access control have been made more granular and the query processor handles concurrent execution of queries in a more efficient way. Partitions on tables and indexes are supported natively, so scaling out a database onto a cluster is easier. SQL CLR was introduced with SQL Server 2005 to let it integrate with the .NET Framework. [ 9 ]
SQL Server 2005 introduced:
Service Pack 1 (SP1) was released on April 18, 2006, adding Database Mirroring, a high availability option that provides redundancy and failover capabilities at the database level [ 12 ] (Database Mirroring was included in the RTM release of SQL Server 2005, but it was not enabled by default, being supported for evaluation purposes [ citation needed ] ). Failover can be manual or automatic; automatic failover requires a witness partner and an operating mode of synchronous (also known as high-safety or full safety). [ 13 ] Service Pack 2 released on February 19, 2007, Service Pack 3 was released on December 15, 2008, and SQL Server 2005 Service Pack 4 released on December 13, 2010.
Mainstream support for SQL Server 2005 ended on April 12, 2011, and Extended support for SQL Server 2005 ended on April 12, 2016.
SQL Server 2008 (formerly codenamed "Katmai") [ 14 ] [ 15 ] was released on August 6, 2008, announced to the SQL Server Special Interest Group at the ESRI 2008 User's Conference on August 6, 2008, by Ed Katibah (Spatial Program Manager at Microsoft), and aims to make data management self-tuning , self organizing, and self maintaining with the development of SQL Server Always On technologies, to provide near-zero downtime. SQL Server 2008 also includes support for structured and semi-structured data, including digital media formats for pictures, audio, video and other multimedia data. In current versions, such multimedia data can be stored as BLOBs (binary large objects), but they are generic bitstreams. Intrinsic awareness of multimedia data will allow specialized functions to be performed on them. According to Paul Flessner , senior Vice President of Server Applications at Microsoft, SQL Server 2008 can be a data storage backend for different varieties of data: XML, email, time/calendar, file, document, spatial, etc. as well as perform search, query, analysis, sharing, and synchronization across all data types. [ 15 ]
Other new data types include specialized date and time types and a Spatial data type for location-dependent data. [ 16 ] Better support for unstructured and semi-structured data is provided using the new FILESTREAM [ 17 ] data type, which can be used to reference any file stored on the file system. [ 18 ] Structured data and metadata about the file is stored in SQL Server database, whereas the unstructured component is stored in the file system. Such files can be accessed both via Win32 file handling APIs as well as via SQL Server using T-SQL ; doing the latter accesses the file data as a BLOB. Backing up and restoring the database backs up or restores the referenced files as well. [ 19 ] SQL Server 2008 also natively supports hierarchical data, and includes T-SQL constructs to directly deal with them, without using recursive queries. [ 19 ]
The full-text search functionality has been integrated with the database engine. According to a Microsoft technical article, this simplifies management and improves performance. [ 20 ]
Spatial data will be stored in two types. A "Flat Earth" (GEOMETRY or planar) data type represents geospatial data which has been projected from its native, spherical, coordinate system into a plane. A "Round Earth" data type (GEOGRAPHY) uses an ellipsoidal model in which the Earth is defined as a single continuous entity which does not suffer from the singularities such as the international dateline, poles, or map projection zone "edges". Approximately 70 methods are available to represent spatial operations for the Open Geospatial Consortium Simple Features for SQL , Version 1.1. [ 21 ]
SQL Server includes better compression features, which also helps in improving scalability. [ 22 ] It enhanced the indexing algorithms and introduced the notion of filtered indexes. It also includes Resource Governor that allows reserving resources for certain users or workflows. It also includes capabilities for transparent encryption of data (TDE) as well as compression of backups. [ 17 ] SQL Server 2008 supports the ADO.NET Entity Framework and the reporting tools, replication, and data definition will be built around the Entity Data Model . [ 23 ] SQL Server Reporting Services will gain charting capabilities from the integration of the data visualization products from Dundas Data Visualization, Inc. , which was acquired by Microsoft. [ 24 ] On the management side, SQL Server 2008 includes the Declarative Management Framework which allows configuring policies and constraints, on the entire database or certain tables, declaratively. [ 16 ] The version of SQL Server Management Studio included with SQL Server 2008 supports IntelliSense for SQL queries against a SQL Server 2008 Database Engine. [ 25 ] SQL Server 2008 also makes the databases available via Windows PowerShell providers and management functionality available as Cmdlets , so that the server and all the running instances can be managed from Windows PowerShell . [ 26 ]
The final SQL Server 2008 service pack (10.00.6000, Service Pack 4) was released on September 30, 2014. [ 27 ]
SQL Server 2008 had mainstream support until July 8, 2014, and extended support until July 9, 2019. [ 28 ] Volume licensed Standard, Web, Enterprise, Workgroup and Datacenter editions of SQL Server 2008 are eligible for the Extended Security Updates program. [ 29 ] The first term of yearly installment ended on July 14, 2020, the second term ended on July 13, 2021, and the third term ended on July 12, 2022. [ 30 ] [ 31 ] Those volume licensed editions rehosted on Microsoft Azure automatically received ESUs until July 11, 2023. [ 32 ] [ 33 ] [ 34 ] [ 35 ]
SQL Server 2008 R2 (10.50.1600.1, formerly codenamed "Kilimanjaro") was announced at TechEd 2009, and was released to manufacturing on April 21, 2010. [ 36 ] SQL Server 2008 R2 introduced several new features and services: [ 37 ]
Service Pack 1 (10.50.2500) was released on July 11, 2011, [ 40 ] Service Pack 2 (10.50.4000) was released on July 26, 2012 [ 41 ] and the final service pack, Service Pack 3 (10.50.6000), was released on September 26, 2014. [ 42 ]
SQL Server 2008 R2 is the last version of SQL Server to run on Itanium (IA-64) systems, with extended support for SQL Server on Itanium continuing until 2018. [ 43 ]
SQL Server 2008 R2 had mainstream support until July 8, 2014, and extended support until July 9, 2019. [ 44 ] Volume licensed Standard, Enterprise, Datacenter and Embedded editions of SQL Server 2008 R2 are eligible for the Extended Security Updates program. [ 29 ] The first term of yearly installment ended on July 14, 2020, the second term ended on July 13, 2021, and the third term ended on July 12, 2022. [ 30 ] [ 31 ] Volume-licensed editions rehosted on Microsoft Azure automatically received ESUs until July 11, 2023. [ 32 ]
At the 2011 Professional Association for SQL Server (PASS) summit on October 11, Microsoft announced another major version of SQL Server, SQL Server 2012 (codenamed "Denali"). The final version was released to manufacturing on March 6, 2012. [ 45 ] SQL Server 2012 Service Pack 1 was released to manufacturing on November 7, 2012, Service Pack 2 was released to manufacturing on June 10, 2014, Service Pack 3 was released to manufacturing on December 1, 2015, and Service Pack 4 was released to manufacturing on October 5, 2017.
It was announced to be the last version to natively support OLE DB and instead to prefer ODBC for native connectivity. [ 46 ]
SQL Server 2012's new features and enhancements include Always On SQL Server Failover Cluster Instances and Availability Groups which provides a set of options to improve database availability, [ 47 ] Contained Databases which simplify the moving of databases between instances, new and modified Dynamic Management Views and Functions, [ 48 ] programmability enhancements including new spatial features, [ 49 ] metadata discovery, sequence objects and the THROW statement, [ 50 ] performance enhancements such as ColumnStore Indexes as well as improvements to OnLine and partition level operations and security enhancements including provisioning during setup, new permissions, improved role management, and default schema assignment for groups. [ 51 ] [ 52 ]
SQL Server 2012 had mainstream support until July 11, 2017, and extended support until July 12, 2022. [ 53 ] [ 32 ] All volume licensed editions of SQL Server 2012 are eligible for the Extended Security Updates program. [ 29 ] The first term of yearly installment ended on July 11, 2023, the second term ended on, 2024, and the third and final term will end on July 8, 2025. [ 33 ] [ 31 ] Those volume licensed editions rehosted on Microsoft Azure automatically receive ESUs until July 8, 2025. [ 35 ] [ 34 ]
SQL Server 2014 was released to manufacturing on March 18, 2014, and released to the general public on April 1, 2014, and the build number was 12.0.2000.8 at release. [ 54 ] Until November 2013 there were two CTP revisions, CTP1 and CTP2. [ 55 ] SQL Server 2014 provides a new in-memory capability for tables that can fit entirely in memory (also known as Hekaton ). Whilst small tables may be entirely resident in memory in all versions of SQL Server, they also may reside on disk, so work is involved in reserving RAM , writing evicted pages to disk, loading new pages from disk, locking the pages in RAM while they are being operated on, and many other tasks. By treating a table as guaranteed to be entirely resident in memory much of the 'plumbing' of disk-based databases can be avoided. [ 56 ]
For disk-based SQL Server applications, it also provides the SSD Buffer Pool Extension, which can improve performance by cache between RAM and spinning media.
SQL Server 2014 also enhances the Always On (HADR) solution by increasing the readable secondaries count and sustaining read operations upon secondary-primary disconnections, and it provides new hybrid disaster recovery and backup solutions with Microsoft Azure, enabling customers to use existing skills with the on-premises version of SQL Server to take advantage of Microsoft's global datacenters. In addition, it takes advantage of new Windows Server 2012 and Windows Server 2012 R2 capabilities for database application scalability in a physical or virtual environment.
Microsoft provides three versions of SQL Server 2014 for downloading: the one that runs on Microsoft Azure , the SQL Server 2014 CAB, and SQL Server 2014 ISO. [ 57 ]
SQL Server 2014 SP1, consisting primarily of bugfixes, was released on May 15, 2015. [ 58 ]
SQL Server 2014 is the last version available for x86/IA-32 systems [ 59 ] and the final version supported on Windows Server 2008 R2 . [ 60 ]
SQL Server 2014 had mainstream support until July 9, 2019, and extended support until July 9, 2024. [ 61 ] All volume licensed editions of SQL Server 2014 are eligible for the Extended Security Updates program. [ 29 ] [ 62 ] The first term of yearly installment will end on July 8, 2025, the second term will end on July 14, 2026, and the third and final term will end on July 12, 2027. [ 31 ] Those volume licensed editions rehosted on Microsoft Azure automatically receive ESUs until July 12, 2027.
The official General Availability (GA) release date for SQL Server 2016 (13.0.1601.5) was June 1, 2016, with SQL Server 2016 being the first version to only support x64 processors [ 59 ] and the last to have the Service Packs updating mechanism. Service Pack 1 was released on November 16, 2016, Service Pack 2 (13.2.5026) was released on April 24, 2018 and Service Pack 3 was released on September 15, 2021.
Microsoft launched SQL Server 2017 on October 2, 2017, along with support for Linux . [ 63 ] [ 64 ] This is the final release supporting Windows Server 2012 and 2012 R2 . [ 65 ] [ 66 ]
Microsoft launched SQL Server 2019 (15.x) on November 4, 2019. SQL Server 2019 introduces Big Data Clusters for SQL Server. It also provides additional capability and improvements for the SQL Server database engine, SQL Server Analysis Services, SQL Server Machine Learning Services, SQL Server on Linux, and SQL Server Master Data Services. [ 67 ]
Microsoft launched SQL Server 2022 on November 16, 2022. [ 68 ] [ unreliable source? ] However, customers purchasing via OEM , and Services Provider License Agreement (SPLA) had to purchase SQL Server 2022 starting January 2023. [ 69 ] | https://en.wikipedia.org/wiki/History_of_Microsoft_SQL_Server |
The first version of Microsoft Word was developed by Charles Simonyi and Richard Brodie , former Xerox programmers hired by Bill Gates and Paul Allen in 1981. Both programmers worked on Xerox Bravo , the first WYSIWYG (What You See Is What You Get) word processor . The first Word version, Word 1.0, was released in October 1983 for Xenix , MS-DOS , and IBM ; it was followed by four very similar versions that were not very successful. The first Windows version was released in 1989, with a slightly improved interface. When Windows 3.0 was released in 1990, Word became a huge commercial success. Word for Windows 1.0 was followed by Word 2.0 in 1991 and Word 6.0 in 1993. Then it was renamed to Word 95 and Word 97, Word 2000 and Word for Office XP (to follow Windows commercial names). With the release of Word 2003, the numbering was again year-based. Since then, Windows versions include Word 2007, Word 2010, Word 2013, Word 2016, and most recently, Word for Office 365.
In 1986, an agreement between Atari and Microsoft brought Word to the Atari ST . [ 2 ] The Atari ST version was a translation of Word 1.05 for the Apple Macintosh; however, it was released under the name Microsoft Write (the name of the word processor included with Windows during the 1980s and early 1990s). [ 3 ] [ 4 ] Unlike other versions of Word, the Atari version was a one-time release with no future updates or revisions. The release of Microsoft Write in 1988 was one of two major PC applications to be released for the Atari ST (the other application being WordPerfect).
In 2014, the source code for Word for Windows version 1.1a was made available to the Computer History Museum and the public for educational purposes. [ 5 ] [ 6 ]
The first Microsoft Word was released in 1983 as Multi-Tool Word at the same time as the first Microsoft Mouse . Costing $395, [ 7 ] it featured graphics video mode and mouse support in a WYSIWYG interface. It could run in text mode or graphics mode but the visual difference between the two was minor. In graphics mode, the document and interface were rendered in a fixed font size monospace character grid with italic, bold and underline features that were not available in text mode. It had support for style sheets in separate files (.STY).
The first version of Word was a 16-bit PC DOS/MS-DOS application. A Macintosh 68000 version named Word 1.0 was released in 1985 and a Microsoft Windows version was released in 1989. The three products shared the same Microsoft Word name, the same version numbers but were very different products built on different code bases. Three product lines co-existed: Word 1.0 to Word 5.1a [ 8 ] for Macintosh, Word 1.0 to Word 2.0 for Windows and Word 1.0 to Word 5.5 for DOS.
Word 1.1 for DOS was released in 1984 and added the Print Merge support, equivalent to the Mail Merge feature in newer Word systems.
Word 2.0 for DOS was released in 1985 and featured Extended Graphics Adapter (EGA) support.
Word 3.0 for DOS was released in 1986.
Word 4.0 for DOS was released in 1987 and added support for revision marks (equivalent to the Track Changes feature in more recent Word versions), search/replace by style and macros stored as keystroke sequences. [ 9 ]
Word 5.0 for DOS, released in 1989, added support for bookmarks, cross-references and conditions and loops in macros, remaining backwards compatible with Word 3.0 macros. The macro language differed from the WinWord 1.0 WordBasic macro language.
Word 5.5 for DOS, released in 1990, significantly changed the user interface, with popup menus and dialog boxes. Even in graphics mode, these graphical user interface (GUI) elements got the monospace ASCII art look and feel found in text mode programs like Microsoft QuickBasic.
Word 6.0 for DOS, the last Word for DOS version, was released in 1993, at the same time as Word 6.0 for Windows (16-bit) and Word 6.0 for Macintosh. Although Macintosh and Windows versions shared the same code base, the Word for DOS was different. The Word 6.0 for DOS macro language was compatible with the Word 3.x-5.x macro language while Word 6.0 for Windows and Word 6.0 for Macintosh inherited WordBasic from the Word 1.0/2.0 for Windows code base. The DOS and Windows versions of Word 6.0 had different file formats.
The first version of Word for Windows was released in November 1989 at a price of USD $ 498, but was not very popular as Windows users still comprised a minority of the market. [ 10 ] The next year, Windows 3.0 debuted, followed shortly afterwards by WinWord 1.1, which was updated for the new OS. The failure of WordPerfect to produce a Windows version proved a fatal mistake. The following year, in 1991, WinWord 2.0 was released which had further improvements and finally solidified Word's marketplace dominance. WinWord 6.0 came out in 1993 and was designed for the newly released Windows 3.1 . [ 11 ]
The early versions of Word also included copy protection mechanisms that tried to detect debuggers , and if one was found, it produced the message "The tree of evil bears bitter fruit. Only the Shadow knows. Now trashing program disk." and performed a zero seek on the floppy disk (but did not delete its contents). [ 12 ] [ 13 ] [ 14 ]
After MacWrite , Word for Macintosh never had any serious rivals, although programs such as Nisus Writer provided features such as non-continuous selection, which were not added until Word 2002 in Office XP .
Word 5.1 for the Macintosh, released in 1992, was a very popular word processor , owing to its elegance, relative ease of use and feature set. However, version 6.0 for the Macintosh, released in 1994, was widely derided, unlike the Windows version. It was the first version of Word based on a common code base between the Windows and Mac versions; many accused the Mac version of being slow, clumsy and memory intensive.
With the release of Word 6.0 in 1993 Microsoft again attempted to synchronize the version numbers and coordinate product naming across platforms; this time across the three versions for DOS, Macintosh, and Windows (where the previous version was Word for Windows 2.0). There may have also been thought given to matching the current version 6.0 of WordPerfect for DOS and Windows, Word's major competitor. However, this wound up being the last version of Word for DOS. In addition, subsequent versions of Word were no longer referred to by version number, and were instead named after the year of their release (e.g. Word 95 for Windows, synchronizing its name with Windows 95, and Word 98 for Macintosh), once again breaking the synchronization.
When Microsoft became aware of the Year 2000 problem , it released the entire DOS port of Microsoft Word 5.5 instead of getting people to pay for the update. As of March 2024, it is still available for download from Microsoft's web site. [ 15 ]
Word 6.0 was the second attempt to develop a common code base version of Word. The first, code-named Pyramid, had been an attempt to completely rewrite the existing product. It was abandoned when Chris Peters replaced Jeff Raikes as the general manager of the Word group [ 16 ] and determined it would take the development team too long to rewrite and then catch up with all the new capabilities that could have been added in the same time without a rewrite. Therefore, Word 6.0 for Windows and Macintosh were both derived from Word 2.0 for Windows code base. The Word 3.0 to 5.0 for Windows version numbers were skipped (outside of DBCS locales) in order to keep the version numbers consistent between Macintosh and Windows versions. Supporters of Pyramid claimed that it would have been faster, smaller, and more stable than the product that was eventually released for Macintosh, and which was compiled using a beta version of Visual C++ 2.0 that targets the Macintosh, so many optimizations have to be turned off (the version 4.2.1 of Office is compiled using the final version), and sometimes use the Windows API simulation library included. [ 17 ] Pyramid would have been truly cross-platform, with machine-independent application code and a small mediation layer between the application and the operating system .
More recent versions of Word for Macintosh are no longer ported versions of Word for Windows.
Later versions of Word have more capabilities than merely word processing. The drawing tool allows simple desktop publishing operations, such as adding graphics to documents.
In 1986, Atari announced an agreement with Microsoft to bring Microsoft Write to the Atari ST . [ 18 ] The agreement was first teased by Compute! 's Atari ST Disk & Magazine in October 1986 (the premier issue) via the rumors & gossip section reporting, "Mum's The Word: At this writing, Atari is expected to soon announce a major software deal with a big-name software company--one of the biggest, in fact. If the deal goes through, it should turn a lot of heads and gain new respect for Atari and the ST. Even the Macintosh and IBM people will be impressed. Sorry, but we promised not to reveal any more about this one." [ 19 ]
Atari ST User ’s Mike Cowley commented on the enthusiasm within the industry regarding the agreement between Atari and Microsoft writing, “It is not just the provision of the package that is being seen as a coup by Atari, but the fact that it carries with it an endorsement for the ST from such a powerful company. “You could compare it with a blessing from the Pope”, observed one industry pundit.” [ 20 ] ST-Log ’s D.F. Scott offered a thoughtful insight on the impact of the agreement, “Superior or mediocre (Microsoft Word), Atari has scored a victory in acquiring Microsoft's assistance. There's only one microcomputer I can name, to date, which has thrived without being somehow shaped by the hand of Bill Gates at Microsoft, and it is the ST. That should be an indication of the machine's strength-it has independence, not "compatibility." [ 21 ]
For the 1988 holiday shopping season, STart magazine reported Atari bundling Microsoft Write with a couple of their Atari ST packages including an Atari Mega ST 2 package (Atari SLM804 laser printer, Microsoft Write, The Terminal Emulator, and VIP Professional) for $2995 and an Atari 520STFM monochrome package (Arrakis Scholastic Series package, Atari Planetarium, Battlezone, Microsoft Write, and Missile Command) for $699. [ 22 ]
Microsoft Write for the Atari ST retailed at $129.95 and is one of two high-profile PC word processors that were released on the Atari platform. The other application is WordPerfect . Getting Microsoft Word and WordPerfect on the Atari ST platform was considered a big win for Atari as during the ST era Atari (reemerging from the " Video Game Crash of 1983 " as a Fortune 500 [ 23 ] public company ) was trying to downplay their videogames image and reimagine itself as a serious business computer brand as it competed against the PC and Macintosh markets. Leonard Tramiel (Vice President Of Software Development) boasted of Microsoft and WordPerfect Corporation's involvement on the Atari ST platform saying, "You don't get much bigger names than those." [ 24 ] STart would declare, “The two most talked-about programs under development are Microsoft Write and WordPerfect.” [ 25 ]
Microsoft Write also featured a "Help Screen" tool to help a user explore the advanced features of the word processor. STart praised the help screen feature stating that “Write's online help screens are a significant aid: their form and presentation should be seriously studied by other ST developers. Each help screen doesn't just list the commands, it actually explains how to use the program in easily understood language.” [ 26 ]
STart ' s Ian Chadwick wrote, "To put Write into perspective, it is basically a decent GEM-based word processor, but at a price that puts it above most of its competitors." [ 27 ] Writing in Antic , Gregg Pearlman commented, "You could call Write a "full-featured" word processor. It's GEM-based and it can (but doesn't have to) run under GDOS. It can use any of several fonts in a WYSIWYG format. It has a search-and-replace feature as well as cut-and-paste, and a visible (non-editable) copy buffer called the Clipboard." [ 28 ] Atari ST User described Microsoft Write in their ST User Software Buyer’s Guide as, “Easy-to-use GDOS document processor. Very reminiscent of the Macintosh in places.” [ 29 ] Atari Explorer's John Jainschigg wrote, "All in all, Microsoft Write is a powerful, flexible, and genuinely easy-to-use word processor appropriate for business, professional, and academic writing." [ 30 ]
In 1990 Atari ST User would reminisce about the 1986 agreement milestone that brought Word to the Atari ST writing, "Four Years Ago: Atari announces that US software giant Microsoft, is to produce an ST version of their Macintosh document processor, Microsoft Word. The ST package, to be called Microsoft Write, was said at the time to signify the ST's arrival as a serious business tool." [ 31 ]
Word 95 was released as part of Office 95 and was numbered 7.0, consistently with all Office components. It ran exclusively on the Win32 platform, but otherwise had few new features. The file format did not change.
Word 97 had the same general operating performance as later versions such as Word 2000. This was the first copy of Word featuring the Office Assistant , "Clippit", which was an animated helper used in all Office programs. This was a takeover from the earlier launched concept in Microsoft Bob . Word 97 introduced the macro programming language Visual Basic for Applications (VBA) which remains in use in Word 2016.
Word 98 for the Macintosh gained many features of Word 97, and was bundled with the Macintosh Office 98 package. Document compatibility reached parity with Office 97 and Word on the Mac became a viable business alternative to its Windows counterpart. Unfortunately, Word on the Mac in this and later releases also became vulnerable to future macro viruses that could compromise Word (and Excel) documents, leading to the only situation where viruses could be cross-platform. A Windows version of this was only bundled with the Japanese/Korean Microsoft Office 97 Powered By Word 98 and could not be purchased separately. It was then released in the same period as well.
Word 2001 was bundled with the Macintosh Office for that platform, acquiring most, if not all, of the feature set of Word 2000. Released in October 2000, Word 2001 was also sold as an individual product. The Macintosh version, Word X, released in 2001, was the first version to run natively on (and required) Mac OS X .
Word 2002 was bundled with Office XP and was released in 2001. It had many of the same features as Word 2000, but had a major new feature called the 'Task Panes', which gave quicker information and control to a lot of features that were before only available in modal dialog boxes. One of the key advertising strategies for the software was the removal of the Office Assistant in favor of a new help system, although it was simply disabled by default.
Microsoft Office 2003 is an office suite developed and distributed by Microsoft for its Windows operating system. Office 2003 was released to manufacturing on August 19, 2003, and was later released to retail on October 21, 2003. It was the successor to Office XP and the predecessor to Office 2007.
A new Macintosh version of Office was released in May 2004. Substantial cleanup of the various applications (Word, Excel, PowerPoint) and feature parity with Office 2003 (for Microsoft Windows ) created a very usable release. Microsoft released patches through the years to eliminate most known macro vulnerabilities from this version. While Apple released Pages and the open source community created NeoOffice, Word remains the most widely used word processor on the Macintosh. Office 2004 for Mac is a version of Microsoft Office developed for Mac OS X. It is equivalent to Office 2003 for Windows. The software was originally written for PowerPC Macs, so Macs with Intel CPUs must run the program under Mac OS X's Rosetta emulation layer.
Also: Stable release: v11.6.6 / December 13, 2011; 7 years ago
The release includes numerous changes, including a new XML-based file format, a redesigned interface, an integrated equation editor and bibliographic management. Additionally, an XML data bag was introduced, accessible via the object model and file format, called Custom XML – this can be used in conjunction with a new feature called Content Controls to implement structured documents. It also has contextual tabs, which are functionality specific only to the object with focus, and many other features like Live Preview (which enables you to view the document without making any permanent changes), Mini Toolbar, Super-tooltips, Quick Access toolbar, SmartArt, etc.
Word 2007 uses a new file format called docx. Word 2000–2003 users on Windows systems can install a free add-on called the "Microsoft Office Compatibility Pack" to be able to open, edit, and save the new Word 2007 files. [ 32 ] Alternatively, Word 2007 can save to the old doc format of Word 97–2003. [ 33 ] [ 34 ]
Word 2008 was released on January 15, 2008. It includes some new features from Word 2007, such as a ribbon-like feature that can be used to select page layouts and insert custom diagrams and images. Word 2008 also features native support for the new Office Open XML format, although the old doc format can be set as a default. [ 35 ] Microsoft Office 2008 for Mac is a version of the Microsoft Office productivity suite for Mac OS X. It supersedes Office 2004 for Mac and is the Mac OS X equivalent of Office 2007. Office 2008 was developed by Microsoft's Macintosh Business Unit and released on January 15, 2008.
Microsoft Office 2010 is a version of the Microsoft Office productivity suite for Microsoft Windows. Office 2010 was released to manufacturing on April 15, 2010, and was later made available for retail and online purchase on June 15, 2010. It is the successor to Office 2007 and the predecessor to Office 2013.
The release of Word 2013 has brought Word a cleaner look and this version focuses further on Cloud Computing with documents being saved automatically to OneDrive (previously Skydrive). If enabled, documents and settings roam with the user. Other notable features are a new read mode which allows for horizontal scrolling of pages in columns, a bookmark to find where the user left off reading their document and opening PDF documents in Word just like Word content. The version released for the Windows 8 operating system is modified for use with a touchscreen and on tablets. It is the first version of Word to not run on Windows XP or Windows Vista . [ 36 ]
On July 9, 2015, Microsoft Word 2016 was released. Features include the tell me, share and faster shape formatting options. Other useful features include realtime collaboration, which allows users to store documents on Share Point or OneDrive, as well as an improved version history and a smart lookup tool. As usual, several editions of the program were released, including one for home and one for business.
Word 2019 added support for Scalable Vector Graphics , Microsoft Translator , and LaTeX , as well as expanded drawing functionality. [ 37 ]
Word 2021 was released in October 2021. As of early 2024, the latest version was 2312 (build 17126.20132).
Word 2024 is expected to be released in the second half of 2024. [ 38 ]
Microsoft Office 365 is a free/paid subscription plan for the classic Office applications. | https://en.wikipedia.org/wiki/History_of_Microsoft_Word |
The History of Modern Biomedicine Research Group ( HoMBRG ) is an academic organisation specialising in recording and publishing the oral history of twentieth and twenty-first century biomedicine . It was established in 1990 as the Wellcome Trust's History of Twentieth Century Medicine Group , [ 1 ] and reconstituted in October 2010 as part of the School of History [ 2 ] at Queen Mary University of London . [ 3 ] [ 4 ] [ 5 ]
The project originated as The Wellcome Trust 's History of Twentieth Century Medicine Group, and later functioned as the Academic Unit of the Wellcome Institute for the History of Medicine. It was originally established at the Royal College of Physicians in 1990 and comprised Sir Christopher Booth (the Harveian Librarian) and Professor Tilli Tansey . [ 6 ] Its purpose was to devise ways of stimulating historians, scientists & clinicians to discuss, preserve and write the history of recent biomedicine. The Group's activities were originally overseen by a Programme Committee, which included professional historians of medicine, practising scientists and clinicians. [ 7 ] From 2000 to 2010 it was a constituent part of the Wellcome Trust Centre for the History of Medicine at University College London. In October 2010 it moved to the School of History, Queen Mary's University, London. In 2011 the Group received a Strategic Award from the Wellcome Trust to embark upon a new project, "Makers of Modern Biomedicine". [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ]
An archive of oral and written history, plus videoed interviews, has been compiled by the HoMBRG and consists of three projects: Witness Seminars, Today's Neuroscience, Tomorrow's History and SAD at 30. All material and documentation related to the project is deposited with the Wellcome Library. The resultant publications are open access, [ 13 ] and made freely available online via the HoMBRG website, a partnership with the Medical Heritage Library , [ 14 ] and iTunes. [ 15 ]
The topics covered by the archive fall broadly into five themes: clinical genetics , [ 16 ] neuroscience , global health and infectious diseases , medical technologies and ethics of research and practice.
Resources from the archive are online at The History of Modern Biomedicine Archive [ 17 ] and the internet archive [ 18 ]
The Group's 'Today's Neuroscience, Tomorrow's History' initiative (2006–2008) was funded by a Wellcome Trust Public Engagement grant. It recorded interviews on three themes, neuropharmacology , psychiatry / neuropsychology , and neuroimaging , with twelve neuroscientists, including Geoffrey Burnstock , Salvador Moncada , Michael Rutter and Uta Frith . [ 19 ]
A series of witness seminars began in 1993, with regular meetings being held, about four per year. These recorded the voices of those who have contributed, in diverse ways, to the development of modern biomedicine , using oral history methodology. The aim is to make the series widely available for education, research and outreach purposes. [ 20 ] [ 21 ] [ 22 ] [ 23 ] [ 24 ] The results are published online, [ 25 ] with most edited transcripts appearing within 18 months. [ 20 ]
Witness Seminar participants have included Usama Abdulla , Thomas Brown , Professor Dugald Cameron , Professor Stuart Campbell , John Fleming , Professor John MacVicar , Professor Peter Wells , Dr James Willocks , Sir Douglas Black , Sir John Gray , Sir Raymond Hoffenberg , Dr Sheila Howarth , Professor Peter Lachmann , Sir Patrick Nairne , Professor Sir Stanley Peart , Dr Peter Williams and Professor Anthony PM Coxon . [ 26 ]
Each witness seminar is transcribed and published by HoMBRG. [ 27 ] Recent volumes have been edited by E M Jones, C Overy and E M Tansey. As of May 2017 [update] there are 62 Volumes. [ 28 ] Titles include The Development of Brain Banks , Narrative Medicine ; Migraine ; The National Survey of Sexual Attitudes and Lifestyles ; [ 29 ] and The Avon Longitudinal Study of Parents and Children (ALSPAC) [ 30 ] The publication of these works are often referred to by specialists in their fields of medical practice. [ 31 ]
The first two volumes were reviewed in Journal of the Royal Society of Medicine in 1999, with the comment, "Few books are so intellectually stimulating or uplifting." [ 32 ] Reviewing the series in the British Medical Journal in 2002, medical historian Irvine Loudon wrote, "This is oral history at its best...all the volumes make compulsive reading...they are, primarily, important historical records [ 33 ]
In 2014 a seminar, chaired by Professor Sir Brian Follett, with Norman Rosenthal and Alfred Lewy , entitled 'The Recent History of Seasonal Affective Disorder (SAD): 30 Years of SAD' was undertaken on the topic of Seasonal Affective Disorder. [ 34 ] This resulted in a number of podcasts, [ 15 ] and Volume 51 of the Witness Seminar publications. [ 35 ]
In 2015 the Group began producing oral history interviews with notable scientists and clinicians. This material is made freely available on YouTube (in the case of video interviews) and the Group's website, as are the transcripts of both audio and video interviews. [ 36 ]
As the HoMBRG project came to an end, a Wikimedian in Residence was engaged, to create Wikidata records for the publications and those people interviewed in them. [ 37 ] | https://en.wikipedia.org/wiki/History_of_Modern_Biomedicine_Research_Group |
The Portable Document Format (PDF) was created by Adobe Systems , introduced at the Windows and OS/2 Conference in January 1993 and remained a proprietary format until it was released as an open standard in 2008. Since then, it has been under the control of an International Organization for Standardization (ISO) committee of industry experts.
Development of PDF began in 1991 when Adobe's co-founder John Warnock wrote a paper for a project then code-named Camelot, in which he proposed the creation of a simplified version of Adobe's PostScript format called Interchange PostScript (IPS). [ 1 ] Unlike traditional PostScript, which was tightly focused on rendering print jobs to output devices, IPS would be optimized for displaying pages to any screen and any platform. [ 1 ]
PDF was developed to share documents, including text formatting and inline images, among computer users of disparate platforms who may not have access to mutually-compatible application software . [ 2 ] It was created by a research and development team called Camelot, [ 3 ] which was personally led by Warnock himself. PDF was one of a number of competing electronic document formats in that era such as DjVu , Envoy , Common Ground Digital Paper, Farallon Replica and traditional PostScript itself. In those early years before the rise of the World Wide Web and HTML documents, PDF was popular mainly in desktop publishing workflows .
PDF's adoption in the early days of the format's history was slow. [ 4 ] Indeed, the Adobe Board of Directors attempted to cancel the development of the format, as they could see little demand for it. [ 5 ] Adobe Acrobat , Adobe's suite for reading and creating PDF files, was not freely available; early versions of PDF had no support for external hyperlinks, reducing its usefulness on the Internet; the larger size of a PDF document compared to plain text required longer download times over the slower modems common at the time; and rendering PDF files was slow on the less powerful machines of the day.
Adobe distributed its Adobe Reader (now Acrobat Reader) program free of charge from version 2.0 onwards, [ 6 ] and continued supporting the original PDF, which eventually became the de facto standard for fixed-format electronic documents. [ 7 ]
In 2008 Adobe Systems' PDF Reference 1.7 became ISO 32000:1:2008. Thereafter, further development of PDF (including PDF 2.0) is conducted by ISO's TC 171 SC 2 WG 8 with the participation of Adobe Systems and other subject matter experts.
From 1993 to 2006 Adobe Systems changed the PDF specification several times to add new features. Various aspects of Adobe's Extension Levels published after 2006 were accepted into working drafts of ISO 32000-2 (PDF 2.0), but developers are cautioned that Adobe's Extensions are not part of the PDF standard. [ 8 ]
Adobe declared that it is not producing a PDF 1.8 Reference. Future versions of the PDF Specification will be produced by ISO technical committees. However, Adobe published documents specifying what proprietary extended features for PDF, beyond ISO 32000-1 (PDF 1.7), are supported in its newly released products. This makes use of the extensibility features of PDF as documented in ISO 32000–1 in Annex E. [ 21 ]
The specifications for PDF are backward inclusive. The PDF 1.7 specification includes all of the functionality previously documented in the Adobe PDF Specifications for versions 1.0 through 1.6. Where Adobe removed certain features of PDF from their standard, they are not contained in ISO 32000-1 [ 9 ] either. Some features are marked as deprecated.
On January 29, 2007, Adobe announced that it would release the full Portable Document Format 1.7 specification to the American National Standards Institute (ANSI) and the Enterprise Content Management Association (AIIM), for the purpose of publication by the International Organization for Standardization (ISO). [ 32 ] By virtue of this change, ISO produces versions of the PDF specification beyond 1.7, and Adobe will be only one of the ISO technical committee members. [ 21 ]
ISO standards for "full function PDF" [ 32 ] are published under the formal number ISO 32000. Full function PDF specification means that it is not only a subset of Adobe PDF specification; in the case of ISO 32000-1 the full function PDF includes everything defined in Adobe's PDF 1.7 specification. However, Adobe later published extensions that are not part of the ISO standard. [ 21 ] There are also proprietary functions in the PDF specification, that are only referenced as external specifications. [ 33 ] [ 34 ] These were eliminated in PDF 2.0, which includes no proprietary technology.
(ISO 32000-1:2008) [ 21 ]
(ISO 32000-2:2017) [ 37 ]
(ISO 32000-2:2020) [ 39 ] [ 40 ]
PDF documents conforming to ISO 32000-1 carry the PDF version number 1.7. Documents containing Adobe extended features still carry the PDF base version number 1.7 but also contain an indication of which extension was followed during document creation. [ 21 ]
PDF documents conforming to ISO 32000-2 carry the PDF version number 2.0, and are known to developers as "PDF 2.0 documents".
The final revised documentation for PDF 1.7 was approved by ISO Technical Committee 171 in January 2008 and published as ISO 32000-1:2008 on July 1, 2008, and titled Document management – Portable document format – Part 1: PDF 1.7 .
ISO 32000-1:2008 is the first ISO standard for full function PDF. The previous ISO PDF standards (PDF/A, PDF/X, etc.) are subsets intended for more specialized uses. ISO 32000-1 includes all of the functionality previously documented in the Adobe PDF Specifications for versions 1.0 through 1.7. Adobe removed certain features of PDF from previous versions; these features are not contained in PDF 1.7 either. [ 9 ]
The ISO 32000-1 document was prepared by Adobe Systems Incorporated based upon PDF Reference, sixth edition, Adobe Portable Document Format version 1.7, November 2006 . It was reviewed, edited and adopted under a special fast-track procedure, by ISO Technical Committee 171 (ISO/TC 171), Document management application, Subcommittee SC 2, Application issues , in parallel with its approval by the ISO member bodies.
According to the ISO PDF standard abstract: [ 42 ]
ISO 32000-1:2008 specifies a digital form for representing electronic documents to enable users to exchange and view electronic documents independent of the environment they were created in or the environment they are viewed or printed in. It is intended for the developer of software that creates PDF files (conforming writers), software that reads existing PDF files and interprets their contents for display and interaction (conforming readers) and PDF products that read and/or write PDF files for a variety of other purposes (conforming products).
Some proprietary specifications under the control of Adobe Systems (e.g. Adobe Acrobat JavaScript or XML Forms Architecture) are in the normative references of ISO 32000-1 and are indispensable for the application of ISO 32000-1. [ 32 ]
A new version of the PDF specification, ISO 32000-2 (PDF 2.0) was published by ISO's TC 171 SC 2 WG 8 Committee in July, 2017. [ 43 ]
The goals of the ISO committee developing PDF 2.0 include evolutionary enhancement and refinement of the PDF language, deprecation of features that are no longer used (e.g. Form XObject names), and standardization of Adobe proprietary specifications (e.g. Adobe JavaScript, Rich Text). [ 34 ] [ 44 ]
Known in PDF syntax terms as "PDF-2.0", ISO 32000-2 is the first update to the PDF specification developed entirely within the ISO Committee process (TC 171 SC 2 WG 8). Interested parties resident in TC 171 Member or Observer countries and wishing to participate should contact their country's Member Body or the secretary of TC 171 SC 2. [ 45 ] Members of the PDF Association may review and comment on drafts via that organization's Category A liaison with ISO TC 171 SC 2. [ 46 ]
In December 2020, the second edition of PDF 2.0, ISO 32000-2:2020, was published, including clarifications, corrections and critical updates to normative references. [ 47 ] ISO 32000-2 does not include any proprietary technologies as normative references. [ 40 ]
On April 5, 2023, the PDF Association and its sponsors, Adobe, Apryse and Foxit, made ISO 32000-2 available at no cost. [ 48 ]
Formed in 2008 to curate the PDF Reference as an ISO Standard, ISO TC 171 SC 2 Working Group 8 typically meets twice a year, with members from fifteen or more countries attending in person. Attendance is also possible via conference call.
Since 1995, Adobe participated in some of the working groups that create technical specifications for publication by ISO and cooperated within the ISO process on specialized subsets of PDF standards for specific industries and purposes (e.g. PDF/X or PDF/A). [ 32 ] The purpose of specialized subsets of the full PDF specification is to remove those functions that are not needed or can be problematic for specific purposes and to require some usage of functions that are only optional (not mandatory) in the full PDF specification.
The following specialized subsets of PDF specification has been standardized as ISO standards (or are in standardization process): [ 9 ] [ 49 ] [ 50 ] [ 51 ]
The PDF Association published a subset of PDF 2.0 called PDF/raster 1.0 in 2017. [ 53 ] PDF/raster is intended for storing, transporting and exchanging multi-page raster-image documents, especially scanned documents. | https://en.wikipedia.org/wiki/History_of_PDF |
History of Programming Languages ( HOPL ) is an infrequent ACM SIGPLAN conference. It has been held in 1978, 1993, 2007, and 2021.
HOPL I was held June 1–3, 1978 in Los Angeles, California . [ 1 ] Jean E. Sammet was both the general and program committee chair. John A. N. Lee was the administrative chair. Richard L. Wexelblat was the proceedings chair. Grace Hopper gave the keynote speech. [ 2 ] From Sammet's introduction: The HOPL Conference "is intended to consider the technical factors which influenced the development of certain selected programming languages." The languages and presentations in the first HOPL were by invitation of the program committee. The invited languages must have been created and in use by 1967. They also must have remained in use in 1977. Finally, they must have had considerable influence on the field of computing.
The papers and presentations went through extensive review by the program committee (and revisions by the authors), far beyond the norm for conferences and commensurate with some of the best journals in the field. [ citation needed ]
Preprints of the proceedings were published in SIGPLAN Notices . [ 3 ] The final proceedings, including transcripts of question and answer sessions, was published as a book titled History of Programming Languages . [ 4 ]
HOPL II was held April 20–23, 1993 in Cambridge, Massachusetts . [ 1 ] John A. N. Lee was the conference chair and Sammet again was the program chair. In contrast to HOPL I, HOPL II included both invited papers and papers submitted in response to an open call. The scope also expanded. Where HOPL I had only papers on the early history of languages, HOPL II solicited contributions on:
The submitted and invited languages must have been documented by 1982. They also must have been in use or taught by 1985.
As in HOPL I, there was a rigorous multi-stage review and revision process. [ citation needed ]
Preprints of the proceedings were published in SIGPLAN Notices . [ 5 ] The final proceedings, including copies of the presentations and transcripts of question and answer sessions, was published as the book titled History of Programming Languages II . [ 6 ]
HOPL III was held June 9–10, 2007 in San Diego, California . [ 1 ] Brent Hailpern and Barbara G. Ryder were the conference co-chairs. HOPL III had an open call for participation and asked for papers on either the early history or the evolution of programming languages. The languages must have come into existence before 1996 and been widely used since 1998, either commercially or within a specific domain. Research languages that had a great influence on subsequent languages were also candidates for submission.
As with HOPL I and HOPL II, the papers were managed with a multiple stage review/revision process.
The HOPL III languages can be broadly categorized into five classes (or paradigms ): Object-oriented ( Modula-2 , Oberon , C++ , Self , Emerald , BETA ), Functional ( Haskell ), Scripting ( AppleScript , Lua ), Reactive ( Erlang , Statecharts ), and Parallel ( ZPL , High Performance Fortran ). Each HOPL III paper describes the perspective of the creators of the language.
HOPL IV was held virtually on June 20–22, 2021 (it was postponed from 2020 due to the COVID-19 pandemic ). The conference co-chairs were Guy L. Steele Jr. and Richard P. Gabriel . The languages covered in this conference had to be widely adopted by 2011. [ 7 ] | https://en.wikipedia.org/wiki/History_of_Programming_Languages_(conference) |
The programming language Python was conceived in the late 1980s, [ 1 ] and its implementation was started in December 1989 [ 2 ] by Guido van Rossum at CWI in the Netherlands as a successor to ABC capable of exception handling and interfacing with the Amoeba operating system . [ 3 ] Van Rossum was Python's principal author and had a central role in deciding the direction of Python (as reflected in the title given to him by the Python community, Benevolent Dictator for Life (BDFL) [ 4 ] [ 5 ] ) until stepping down as leader on July 12, 2018. [ 6 ] Python was named after the BBC TV show Monty Python's Flying Circus . [ 7 ]
Python 2.0 was released on October 16, 2000, with many major new features, such as list comprehensions , cycle-detecting garbage collector (in addition to reference counting ) and reference counting , for memory management and support for Unicode , along with a change to the development process itself, with a shift to a more transparent and community-backed process. [ 8 ]
Python 3.0, a major, backwards-incompatible release, was released on December 3, 2008 [ 9 ] after a long period of testing. Many of its major features were also backported to the backwards-compatible Python versions 2.6 and 2.7 [ 10 ] until support for Python 2 finally ceased at the beginning of 2020 . Releases of Python 3 include the 2to3 utility, which automates the translation of Python 2 code to Python 3. [ 11 ]
Van Rossum first published the code (for Python version 0.9.1) to alt.sources in February 1991. [ 12 ] [ 13 ] Several features of the language were already present at this stage, among them classes with inheritance , exception handling, functions, and various core datatypes such as list , dict , and str . The initial release also contained a module system borrowed from Modula-3 ; Van Rossum describes the module as "one of Python's major programming units". [ 1 ] Python's exception model also resembled Modula-3's, with the addition of an else clause. [ 3 ] In 1994 comp.lang.python , the primary discussion forum for Python, was formed. [ 1 ]
Python reached version 1.0 in January 1994. The major new features included in this release were the functional programming tools lambda , map , filter and reduce . Van Rossum stated that "Python acquired lambda, reduce(), filter() and map(), courtesy of a Lisp hacker who missed them and submitted working patches ". [ 14 ]
The last version released while Van Rossum was at CWI was Python 1.2. In 1995, Van Rossum continued his work on Python at the Corporation for National Research Initiatives (CNRI) in Reston , Virginia from where he released several versions.
By version 1.4, Python had acquired several new features. Notable among these are the Modula-3 inspired keyword arguments (which are also similar to Common Lisp 's keyword arguments) and built-in support for complex numbers . Also included is a basic form of data hiding by name mangling , though this is easily bypassed. [ 15 ]
During Van Rossum's stay at CNRI, he launched the Computer Programming for Everybody (CP4E) initiative, intending to make programming more accessible to more people, with a basic "literacy" in programming languages, similar to the basic English literacy and mathematics skills required by most employers. Python served a central role in this: because of its focus on clean syntax, it was already suitable, and CP4E's goals bore similarities to its predecessor, ABC. The project was funded by DARPA . [ 16 ] As of 2007 [update] , the CP4E project is inactive, and while Python attempts to be easily learnable and not too arcane in its syntax and semantics, outreach to non-programmers is not an active concern. [ 17 ]
In 2000, the Python core development team moved to BeOpen.com [ 18 ] to form the BeOpen PythonLabs team. [ 19 ] [ 20 ] CNRI requested that a version 1.6 be released, summarizing Python's development up to the point at which the development team left CNRI. Consequently, the release schedules for 1.6 and 2.0 had a significant amount of overlap. [ 8 ] Python 2.0 was the only release from BeOpen.com. After Python 2.0 was released by BeOpen.com, Guido van Rossum and the other PythonLabs developers joined Digital Creations .
The Python 1.6 release included a new CNRI license that was substantially longer than the CWI license that had been used for earlier releases. The new license included a clause stating that the license was governed by the laws of the State of Virginia . The Free Software Foundation argued that the choice-of-law clause was incompatible with the GNU General Public License . BeOpen, CNRI and the FSF negotiated a change to Python's free-software license that would make it GPL-compatible. Python 1.6.1 is essentially the same as Python 1.6, with a few minor bug fixes, and with the new GPL-compatible license. [ 21 ]
Python 2.0, released October 2000, [ 8 ] introduced list comprehensions , a feature borrowed from the functional programming languages SETL and Haskell . Python's syntax for this construct is very similar to Haskell's, apart from Haskell's preference for punctuation characters and Python's preference for alphabetic keywords. Python 2.0 also introduced a garbage collector able to collect reference cycles. [ 8 ]
Python 2.1 was close to Python 1.6.1, as well as Python 2.0. Its license was renamed Python Software Foundation License . All code, documentation and specifications added, from the time of Python 2.1's alpha release on, is owned by the Python Software Foundation (PSF), a nonprofit organization formed in 2001, modeled after the Apache Software Foundation . [ 21 ] The release included a change to the language specification to support nested scopes, like other statically scoped languages. [ 22 ] (The feature was turned off by default, and not required, until Python 2.2.)
Python 2.2 was released in December 2001; [ 23 ] a major innovation was the unification of Python's types (types written in C ) and classes (types written in Python) into one hierarchy. This single unification made Python's object model purely and consistently object oriented. [ 24 ] Also added were generators which were inspired by Icon . [ 25 ]
Python 2.5 was released in September 2006 [ 26 ] and introduced the with statement, which encloses a code block within a context manager (for example, acquiring a lock before the block of code is run and releasing the lock afterwards, or opening a file and then closing it), allowing resource acquisition is initialization (RAII)-like behavior and replacing a common try/finally idiom. [ 27 ]
Python 2.6 was released to coincide with Python 3.0, and included some features from that release, as well as a "warnings" mode that highlighted the use of features that were removed in Python 3.0. [ 28 ] [ 10 ] Similarly, Python 2.7 coincided with and included features from Python 3.1, [ 29 ] which was released on June 26, 2009.
Parallel 2.x and 3.x releases then ceased, and Python 2.7 was the last release in the 2.x series. [ 30 ] In November 2014, it was announced that Python 2.7 would be supported until 2020, but users were encouraged to move to Python 3 as soon as possible. [ 31 ] Python 2.7 support ended on January 1, 2020, along with code freeze of 2.7 development branch. A final release, 2.7.18, occurred on April 20, 2020, and included fixes for critical bugs and release blockers. [ 32 ] This marked the end-of-life of Python 2. [ 33 ]
Python 3.0 (also called "Python 3000" or "Py3K") was released on December 3, 2008. [ 9 ] It was designed to rectify fundamental design flaws in the language – the changes required could not be implemented while retaining full backwards compatibility with the 2.x series, which necessitated a new major version number. The guiding principle of Python 3 was: "reduce feature duplication by removing old ways of doing things". [ 34 ]
Python 3.0 was developed with the same philosophy as in prior versions. However, as Python had accumulated new and redundant ways to program the same task, Python 3.0 had an emphasis on removing duplicative constructs and modules, in keeping with the Zen of Python : "There should be one— and preferably only one —obvious way to do it".
Nonetheless, Python 3.0 remained a multi-paradigm language . Coders could still follow object-oriented , structured , and functional programming paradigms, among others, but within such broad choices, the details were intended to be more obvious in Python 3.0 than they were in Python 2.x.
Python 3.0 broke backward compatibility, and much Python 2 code does not run unmodified on Python 3. [ 35 ] Python's dynamic typing combined with the plans to change the semantics of certain methods of dictionaries, for example, made perfect mechanical translation from Python 2.x to Python 3.0 very difficult. A tool called " 2to3 " does the parts of translation that can be done automatically. At this, 2to3 appeared to be fairly successful, though an early review noted that there were aspects of translation that such a tool would never be able to handle. [ 36 ] Prior to the roll-out of Python 3, projects requiring compatibility with both the 2.x and 3.x series were recommended to have one source (for the 2.x series), and produce releases for the Python 3.x platform using 2to3 . Edits to the Python 3.x code were discouraged for so long as the code needed to run on Python 2.x. [ 10 ] This is no longer recommended; as of 2012 the preferred approach was to create a single code base that can run under both Python 2 and 3 using compatibility modules. [ 37 ]
Some of the major changes included for Python 3.0 were:
Subsequent releases in the Python 3.x series have included additional, substantial new features; all ongoing development of the language is done in the 3.x series.
Releases before numbered versions:
Table notes: | https://en.wikipedia.org/wiki/History_of_Python |
RISC OS , the computer operating system developed by Acorn Computers for their ARM -based Acorn Archimedes range, was originally released in 1987 as Arthur 0.20 , and soon followed by Arthur 0.30 , and Arthur 1.20 . The next version, Arthur 2 , became RISC OS 2 and was completed in September 1988 and made available in April 1989. RISC OS 3 was released with the very earliest version of the A5000 in 1991 and contained a series of new features. By 1996 RISC OS had been shipped on over 500,000 systems. [ 1 ]
RISC OS 4 was released by RISCOS Ltd (ROL) in July 1999, based on the continued development of OS 3.8 . ROL had in March 1999 licensed the rights to RISC OS from Element 14 (the renamed Acorn) and eventually from the new owner, Pace Micro Technology . According to the company, over 6,400 copies of OS 4.02 on ROM were sold up until production was ceased in mid-2005.
RISC OS Select was launched in May 2001 by ROL. This is a subscription scheme allowing users access to the latest OS updates. These upgrades are released as soft-loadable ROM images , separate to the ROM where the boot OS is stored, and are loaded at boot time. Select 1 was shipped in May 2002, with Select 2 following in November 2002 and the final release of Select 3 in June 2004. ROL released the ROM based OS 4.39 the same month, dubbed RISC OS Adjust as a play on the RISC OS GUI convention of calling the three mouse buttons 'Select', 'Menu' and 'Adjust'. ROL sold its 500th Adjust ROM in early 2006.
RISC OS 5 was released in October 2002 on Castle Technology 's Acorn clone Iyonix PC . OS 5 is a separate evolution based upon the NCOS work done by Pace for set-top boxes . In October 2006, Castle announced a source sharing license plan for elements of OS 5 . This Shared Source Initiative (SSI) is managed by RISC OS Open Ltd (ROOL). RISC OS 5 has since been released under a fully free and open source Apache 2.0 license , while the older no longer maintained RISC OS 6 has not.
RISC OS Six was also announced in October 2006 by ROL. This is the next generation of their stream of the operating system. The first product to be launched under the name was the continuation of the Select scheme, Select 4 . A beta-version of OS 6 , Preview 1 ( Select 4i1 ), was available in 2007 as a free download to all subscribers to the Select scheme, while in April 2009 the final release of Select 5 was shipped. The latest release of RISC OS from ROL is Select 6i1 , shipped in December 2009.
The OS was designed in the United Kingdom by Acorn for the 32-bit ARM based Acorn Archimedes , and released in its first version in 1987, as the Arthur operating system.
The first public release of the OS was Arthur 1.20 in June 1987. [ 2 ]
It was bundled with a desktop graphical user interface (GUI), which mostly comprises assembly language software modules, [ citation needed ] and the Desktop module itself being written in BBC BASIC . [ 3 ] It features a colour-scheme typically described as " technicolor ". [ 4 ]
The graphical desktop runs on top of a command-line driven operating system which owes much to Acorn's earlier MOS operating system for its BBC Micro range of 8-bit microcomputers. [ 5 ]
Arthur, as originally conceived, was intended to deliver similar functionality to the operating system for the BBC Master series of computers, MOS , as a reaction to the fact that a more advanced operating system research project ( ARX ) would not be ready in time for the Archimedes . [ 5 ]
The Arthur project team, led by Paul Fellows, was given just five months to develop it entirely from the ground up—with the directive "just make it like the BBC micro". It was intended as a stop-gap until the operating system which Acorn had under development ( ARX ) could be completed. However, the latter was delayed time and again, and was eventually dropped when it became apparent that the Arthur development could be extended to have a window manager and full desktop environment. Also, it was small enough to run on the first 512K machines with only a floppy disc, whereas ARX required 4 megabytes and a hard drive. [ citation needed ]
The OS development was carried out using a prototype ARM-based system connected to a BBC computer, before moving onto the prototype Acorn Archimedes the A500. [ 6 ]
Arthur was not a multitasking operating system, but offered support for adding application-level cooperative multitasking . [ 7 ] No other version of the operating system was released externally, but internally the development of the desktop and window management continued, with the addition of a cooperative multitasking system, implemented by Neil Raine, which used the memory management hardware to swap-out one task, and bring in another between call-and-return from the Wimp_Poll call that applications were obliged to make to get messages under the desktop. Reminiscent of a similar technique employed by MultiFinder on the Apple Macintosh , [ 8 ] this transformed a single-application-at-a-time system into one that could operate a full multi-tasking desktop. This transformation took place at version 1.6 though it was not made public until released, with the name change from Arthur to RISC OS, as version 2.0. [ 9 ]
Most software made for Arthur 1.2 can be run under RISC OS 2 and later because, underneath the desktop, the original Arthur OS core, API interfaces and modular structures remain as the heart of all versions. (A few titles will not work, however, because they used undocumented features, side effects or in a few cases APIs that became deprecated). [ original research? ]
In 2011, Business Insider listed Arthur as one of ten "operating systems that time forgot". [ 10 ]
RISC OS was a rapid development of Arthur 1.2 after the failure of the ARX project. [ 5 ] Given growing dissatisfaction with various bugs and limitations with Arthur, testing of what was then known as Arthur 2 was apparently ongoing during 1988 with selected software houses. [ 11 ]
At this stage, Computer Concepts, who had been prolific developers for the BBC Micro and who had begun software development for the Archimedes, had already initiated a rival operating system project, Impulse, to support their own applications (including the desktop publishing application that would eventually become Impression ), stating that Arthur did not meet the "hundreds of requirements" involved including "true multi-tasking". [ 12 ] Such an operating system was to be offered free of charge with the planned application packages, [ 11 ] but with the release of RISC OS and Computer Concepts acknowledging that RISC OS "overcomes the old problems with Arthur", the applications were to be able to run under either RISC OS or Impulse. [ 13 ] Impression was eventually released as a RISC OS application. [ 14 ]
Ultimately, Arthur 2 was renamed to RISC OS , and was first sold as RISC OS 2.00 in April 1989. [ 15 ]
The operating system implements co-operative multitasking with some limitations but is not multi-threaded . It uses the ADFS file system for both floppy and hard disc access. It ran from a 512 KB set of ROMs . The WIMP interface offers all the standard features and fixes many of the bugs that had hindered Arthur. It lacks virtual memory and extensive memory protection (applications are protected from each other, but many functions have to be implemented as 'modules' which have full access to the memory). At the time of release, the main advantage of the OS was its ROM; it booted very quickly and while it was easy to crash, it was impossible to permanently break the OS from software. Its high performance was due to much of the system being written in ARM assembly language . [ citation needed ]
The OS was designed with users in mind, rather than OS designers. [ 16 ] It is organised as a relatively small kernel which defines a standard software interface to which extension modules are required to conform. Much of the system's functionality is implemented in modules coded in the ROM, though these can be supplanted by more evolved versions loaded into RAM . Among the kernel facilities are a general mechanism, named the callback handler, which allows a supervisor module to perform process multiplexing. This facility is used by a module forming part of the standard editor program to provide a terminal emulator window for console applications. The same approach made it possible for advanced users to implement modules giving RISC OS the ability to do pre-emptive multitasking . [ citation needed ]
A slightly updated version, RISC OS 2.01 , was released later to support the ARM3 processor, larger memory capacities, and the VGA and SVGA modes provided by the Acorn Archimedes 540 and Acorn R225/R260. [ 17 ]
RISC OS 3 introduced a number of new features, [ 18 ] including multitasking Filer operations, applications and fonts in ROM, no limit on number of open windows, ability to move windows off screen, safe shutdown , the Pinboard , grouping of icon bar icons, up to 128 tasks, native ability to read MS-DOS format discs and use named hard discs. Improved configuration was also included, by way of multiple windows to change the settings. [ 18 ]
RISC OS 3.00 was released with the very earliest version of the A5000 in 1991; it is almost four times the size of RISC OS 2 and runs from a 2 MB ROM. It improves multitasking and also places some of the more popular base applications in the ROM. RISC OS 3.00 had several bugs and was replaced by RISC OS 3.1 a few months later; the upgraded ROMs were supplied for the cost of postage.
RISC OS 3.1 was released later and sold built into the A3010, A3020, A4000, A4 and later A5000 models. It was also made available as replacement ROMs for the A5000 and earlier Archimedes machines (this is the last RISC OS version suitable for those machines). Three variants were released: RISC OS 3.10 the base version, RISC OS 3.11 which included a slight update that fixes some serial port issues and RISC OS 3.19 which was a German translation.
RISC OS 3.50 was sold from 1994 with the first Risc PCs . Due to the very different hardware architecture of the Risc PC , including an ARM 6 processor, 16- and 24-bit colour and a different IO chip (IOMD), RISC OS 3.50 was not made available for the older Archimedes and A Series ARM2 and 3 machines. RISC OS 3.5 was somewhat shoehorned into the 2 MB footprint, and moved the ROM applications of RISC OS 3.1 onto the hard drive; this proved so unpopular that they were later moved back into ROM. This version introduced issues of backward compatibility , particularly with games .
RISC OS 3.60 followed in 1995. The OS features much improved hard disk access and its networking was enhanced to include TCP/IP as standard in addition to Acorn's existing proprietary Econet system. The hardware support was also improved; Risc PCs could now use ARM7 processors. Acorn's A7000 machine with its ARM7500 processor was also supported. RISC OS 3.6 was twice the size of RISC OS 3.5, shipping on 4 MB in two ROM chips; components that had been moved onto disk in 3.5 (the standard application suite and networking) were now moved back into ROM. [ 19 ]
RISC OS 3.70 was released in 1996. The primary changes in the OS was support for the StrongARM processor that was made available as an upgrade for the Risc PC . This required extensive code changes due to StrongARM's split data and instruction cache ( Harvard architecture ) and 32-bit interrupt modes.
RISC OS 3.71 is a small update released to support the hardware in the Acorn A7000+ with its ARM7500FE processor. The FE offered hardware support for floating point mathematics, which until then was usually emulated in one of the RISC OS Software modules).
RISC OS 3.60 also formed the foundation of NCOS , as shipped in the Acorn NetChannel NCs . [ 20 ]
Acorn officially halted work in all areas except set-top boxes in January 1999 and the company was renamed Element 14 [ 21 ] (the 14th element of the periodic table being silicon ) with a new goal to become purely a Silicon design business (like the previous very successful spin off of ARM from Acorn in 1990). RISC OS development was halted during the development of OS 4.0 for the RiscPC 2 (" Phoebe 2100 "), whose completion was also cancelled. A beta version, OS 3.8 ("Ursula") for the original RiscPC, had previously been released to developers. The project code names of Phoebe (for the hardware), Ursula (for the software) and Chandler (for the graphics processor chip) were taken from the names of characters in the TV series Friends (Phoebe and Ursula were twin sisters in the series).
This led to a number of rescue efforts to try to keep the Acorn desktop computer business alive. Acorn held discussions with many interested parties, and eventually agreed to exclusively licence RISC OS to RISCOS Ltd, which was formed from a consortium of dealers, developers and end-users. Pace purchased the rights to use and develop NCOS.
There were also a number of projects to bring the advantages of the RISC Operating System to other platforms by the creation of the ROX Desktop to provide a RISC OS-like interface on Unix and Linux systems. The separate work by RISC OS Ltd and Pace resulted in a code fork . This continued after the subsequent licensing agreement with Castle Technology, causing much community debate at the time. [ 22 ] The debate remains ongoing in 2011.
In March 1999, a new company called RISCOS Ltd was founded. They licensed the rights to RISC OS from Element 14 (and eventually from the new owner, Pace Micro Technology ) [ 23 ] and continued the development of OS 3.8, releasing it as RISC OS 4 in July 1999. [ 24 ]
Whilst the hardware support for Phoebe was not needed, the core improvements to RISC OS 3.80 could be finished and released. They included:
According to the company, over 6,400 copies of RISC OS 4.02 on ROM were sold up until production was ceased in mid-2005. [ 31 ]
During 1999 and 2000, RISCOS Ltd also released versions of RISC OS 4 to support several additional hardware platforms, the MicroDigital Mico , [ 32 ] MicroDigital Omega , RiscStation R7500 [ 33 ] and the Castle Kinetic RiscPC. [ 34 ] In 2003 a version of RISC OS 4 was released with support for the Millipede Graphics AlphaLock podule. [ 35 ]
RISC OS 4 is also available for various hardware emulators for other operating systems. In September 2003 VirtualAcorn released the commercial emulator VirtualRPC which included a copy of RISC OS 4.02. [ 36 ] In December 2008 RISCOS Ltd made 4.02 available for non-commercial emulators for £5 in a product called Virtually Free. [ 37 ]
In May 2001, the company launched RISC OS Select , a subscription scheme allowing users access to the latest OS updates. These upgrades are released as soft-loadable ROM images , separate to the ROM where the boot OS is stored, and are loaded at boot time. [ 38 ] By providing soft-loads, physical ROM costs are eliminated and updates are able to be delivered with accelerated speed and frequency. [ 39 ] It has also allowed the company to subsidise the retail price of ROM releases, which are generally a culmination of the last few Select upgrades with a few extra minor changes. [ citation needed ]
In May 2002 the final release of Select 1 was shipped that included; [ 40 ]
In November 2002, the final release of Select 2 was shipped [ 41 ] that included; [ 42 ]
In June 2004 the final release of Select 3 was shipped [ 41 ] that included: [ 43 ]
Also in June 2004, RISCOS Ltd released the ROM based version 4.39, [ 44 ] being dubbed RISC OS Adjust . (The name was a play on the RISC OS GUI convention of calling the three mouse buttons 'Select', 'Menu' and 'Adjust'.) RISCOS Ltd sold its 500th Adjust ROM in early 2006. [ 45 ] Features introduced in 4.39 include user customization of the graphical user interface. [ 46 ]
Further release under the Select scheme were made under the RISC OS Six branding, mentioned below.
The A9home, released in 2006, uses RISC OS version 4.42 Adjust 32 . This was developed by RISCOS Ltd and supports 32-bit addressing modes found on later ARM architectures.
In October 2006, shortly after Castle Technology announced the Shared Source Initiative, RISCOS Ltd announced RISC OS Six, the next generation of their stream of the operating system. [ 47 ]
The first product to be launched under the RISC OS Six name, was the continuation of the Select scheme, Select 4. [ citation needed ] A beta-version of RISC OS 6, Preview 1 (Select 4i1), was available in 2007 as a free download [ 48 ] to all subscribers to the Select scheme, both present subscribers and those whose subscription was renewed after 30 May 2004 but has since lapsed.
RISC OS Six brought portability, stability and internal structure improvements, including full 26/32-bit neutrality. It is now highly modularised, with legacy and hardware specific features abstracted, and other code separated for easier future maintenance and development. [ 49 ] Teletext support, device interrupt handler, software-based graphics operations, the real-time clock, the mouse pointer, CMOS RAM support, and hardware timer support have been abstracted out of the kernel and into their own separate modules. [ 49 ] Legacy components, like the VIDC driver, and obsolete functionality for the BBC Micro have been abstracted too. [ 49 ] AIF and transient utility executable checking has been introduced also to protect against rogue software, while graphics acceleration modules may be provided for the SM501 graphics chip in the A9home and for ViewFinder AGP podule cards . [ 50 ] In April 2008 the final release of Select 4 was shipped that included: [ 51 ]
Select 4 releases are initially compatible with only Acorn Risc PC and A7000 machines. [ citation needed ] RiscStation R7500, MicroDigital Omega and Mico computers will not officially be supported, as the company does not have test machines available and requires proprietary software code to which they do not have the rights. [ 52 ] Lack of detailed technical information about the MicroDigital Omega has also been cited as being another reason why support of that hardware is difficult. [ citation needed ]
In April 2009 the final release of Select 5 was shipped [ 47 ] that included: [ 53 ]
The final release of RISC OS from RISCOS Ltd was Select 6i1, shipped in December 2009, it includes; [ 54 ]
RISC OS 5 is a separate evolution by Castle Technology Ltd based upon work done by Pace for their NCOS based set top boxes. RISC OS 5 was written to support Castle's Iyonix PC Acorn-compatible, which runs on the Intel XScale ARM processor. Although a wealth of software has now been updated, a few older applications can only be run on RISC OS 5 via an emulator called Aemulor, since the ARMv5 XScale processor does not support 26-bit addressing modes. Likewise, RISC OS 5 itself had to be ported to run properly on the new CPU, and abstraction of the graphics and other hardware interfaces created, to allow it, for example, to use standard graphics cards, instead of Acorn's own VIDC chip.
In July 2003, Castle Technology Ltd bought the head licence for RISC OS from Pace Micro. [ 55 ] [ 56 ]
In October 2006, Castle Technology Ltd announced a plan to release elements of RISC OS 5 under a source sharing license. The Shared Source Initiative (SSI) was a joint venture between Castle and RISC OS Open Limited (ROOL), a newly formed software development company, which aimed to accelerate development and encourage uptake of the OS. Under the custom dual license, released source was freely available and could be modified and redistributed without royalty for non-commercial use, while commercial usage incurred a per-unit license fee to Castle.
The SSI made phased releases of source code, starting in May 2007. [ 57 ] By October 2008, enough source was released to build an almost complete Iyonix ROM image. [ 58 ] By late 2011, it was possible to build complete ROM images from the published sources; with the full source code available as tarballs , CVS , or a web interface to the CVS archive.
In October 2018, the rights to RISC OS 5 were acquired by RISC OS Developments, and re-licensed under the Apache 2.0 license. [ 59 ] ROOL continues to maintain the source tree and co-ordinates an international developer community on a non-profit basis to support and encourage development.
Prebuilt images are available, as both stable releases and development " nightly builds ". [ 60 ]
Ports of RISC OS 5 are available for the A7000/A7000+ , RiscPC , RPCemu , the OMAP3 BeagleBoard and derivatives , OMAP4 PandaBoard and PandaBoard ES, OMAP5 IGEPv5 and UEVM5432, AM5728 Titanium, the Raspberry Pi , and the XScale Iyonix. [ 60 ] | https://en.wikipedia.org/wiki/History_of_RISC_OS |
Numerous key discoveries in biology have emerged from studies of RNA (ribonucleic acid), including seminal work in the fields of biochemistry , genetics , microbiology , molecular biology , molecular evolution , and structural biology . As of 2010, 30 scientists have been awarded Nobel Prizes for experimental work that includes studies of RNA. Specific discoveries of high biological significance are discussed in this article.
For related information, see the articles on History of molecular biology and History of genetics . For background information, see the articles on RNA and nucleic acids .
When first studied in the early 1900s, the chemical and biological differences between RNA and DNA were not apparent, and they were named after the materials from which they were isolated; RNA was initially known as " yeast nucleic acid" and DNA was " thymus nucleic acid". [ 1 ] Using diagnostic chemical tests, carbohydrate chemists showed that the two nucleic acids contained different sugars , whereupon the common name for RNA became "ribose nucleic acid". Other early biochemical studies showed that RNA was readily broken down at high pH , while DNA was stable (although denatured) in alkali . Nucleoside composition analysis showed first that RNA contained similar nucleobases to DNA, with uracil instead of thymine , and that RNA contained a number of minor nucleobase components, e.g. small amounts of pseudouridine and dimethylguanine . [ 2 ]
In 1933, while studying virgin sea urchin eggs, Jean Brachet suggested that DNA is found in the cell nucleus and that RNA is present exclusively in the cytoplasm . At the time, "yeast nucleic acid" (RNA) was thought to occur only in plants, while "thymus nucleic acid" (DNA) only in animals. The latter was thought to be a tetramer , with the function of buffering cellular pH . [ 3 ] [ 4 ] During the 1930s, Joachim Hämmerling conducted experiments with Acetabularia in which he began to distinguish the contributions of the nucleus and the cytoplasm substances (later discovered to be DNA and messenger RNA (mRNA), respectively) to cell morphogenesis and development . [ 5 ] [ 6 ]
The concept of messenger RNA emerged during the late 1950s, and is associated with Crick 's description of his " central dogma of molecular biology ", which asserted that DNA led to the formation of RNA, which in turn led to the synthesis of proteins . During the early 1960s, sophisticated genetic analysis of mutations in the lac operon of E. coli and in the rII locus of bacteriophage T4 were instrumental in defining the nature of both messenger RNA and the genetic code . The short-lived nature of bacterial RNAs, together with the highly complex nature of the cellular mRNA population, made the biochemical isolation of mRNA very challenging. This problem was overcome in the 1960s by the use of reticulocytes in vertebrates, [ 7 ] which produce large quantities of mRNA that are highly enriched in RNA encoding alpha- and beta-globin (the two major protein chains of hemoglobin ). [ 8 ] The first direct experimental evidence for the existence of mRNA was provided by such a hemoglobin synthesizing system. [ 9 ]
In the 1950s, results of labeling experiments in rat liver showed that radioactive amino acids were found to be associated with "microsomes" (later redefined as ribosomes ) very rapidly after administration, and before they became widely incorporated into cellular proteins. Ribosomes were first visualized using electron microscopy , and their ribonucleoprotein components were identified by biophysical methods, chiefly sedimentation analysis within ultracentrifuges capable of generating very high accelerations (equivalent to hundreds of thousands times gravity ). Polysomes (multiple ribosomes moving along a single mRNA molecule) were identified in the early 1960s, and their study led to an understanding of how ribosomes read the mRNA in a 5′ to 3′ direction , [ 10 ] generating proteins as they do so. [ 11 ]
Biochemical fractionation experiments showed that radioactive amino acids were rapidly incorporated into small RNA molecules that remained soluble under conditions where larger RNA-containing particles would precipitate . These molecules were termed soluble (sRNA) and were later renamed transfer RNA ( tRNA ). Subsequent studies showed that (i) every cell has multiple species of tRNA, each of which is associated with a single specific amino acid, (ii) that there are a matching set of enzymes responsible for linking tRNAs with the correct amino acids, and (iii) that tRNA anticodon sequences form a specific decoding interaction with mRNA codons . [ 12 ]
The genetic code consists of the translation of particular nucleotide sequences in mRNA to specific amino acid sequences in proteins (polypeptides). The ability to work out the genetic code emerged from the convergence of three different areas of study: (i) new methods to generate synthetic RNA molecules of defined composition to serve as artificial mRNAs, (ii) development of in vitro translation systems that could be used to translate the synthetic mRNAs into protein, and (iii) experimental and theoretical genetic work which established that the code was written in three letter "words" ( codons ). Today, our understanding of the genetic code permits the prediction of the amino sequence of the protein products of the tens of thousands of genes whose sequences are being determined in genome studies. [ 13 ]
The biochemical purification and characterization of RNA polymerase from the bacterium Escherichia coli ( E. coli ) enabled the understanding of the mechanisms through which RNA polymerase initiates and terminates transcription , and how those processes are regulated to regulate gene expression (i.e. turning genes on and off). Following the isolation of E. coli RNA polymerase, the three RNA polymerases of the eukaryotic nucleus were identified, as well as those associated with viruses and organelles. Studies of transcription also led to the identification of many protein factors that influence transcription, including repressors, activators and enhancers. The availability of purified preparations of RNA polymerase permitted investigators to develop a wide range of novel methods for studying RNA in the test tube, and led directly to many of the subsequent key discoveries in RNA biology. [ 14 ]
Although determining the sequence of proteins was becoming somewhat routine, methods for sequencing of nucleic acids were not available until the mid-1960s. In this seminal work, a specific tRNA was purified in substantial quantities, and then sliced into overlapping fragments using a variety of ribonucleases . Analysis of the detailed nucleotide composition of each fragment provided the information necessary to deduce the sequence of the tRNA. Today, the sequence analysis of much larger nucleic acid molecules is highly automated and much faster. [ 15 ]
Additional tRNA molecules were purified and sequenced. The first comparative sequence analysis was done and revealed that the sequences varied through evolution in such a way that all of the tRNAs could fold into very similar secondary structures (two-dimensional structures) and had identical sequences at numerous positions (e.g. CCA at the 3′ end). The radial four-arm structure of tRNA molecules is termed the " cloverleaf structure ", and results from the evolution of sequences with common ancestry and common biological function. Since the discovery of the tRNA cloverleaf, comparative analysis of numerous other homologous RNA molecules has led to the identification of common sequences and folding patterns. [ 16 ]
The 3569-nucleotide sequence of all of the genes of the RNA bacteriophage MS2 was determined by a large team of researchers over several years, and was reported in a series of scientific papers. These results enabled the analysis of the first complete genome, albeit an extremely tiny one by modern standards. Several surprising features were identified, including genes that partially overlap one another and the first clues that different organisms might have slightly different codon usage patterns. [ 17 ]
Retroviruses were shown to have a single-stranded RNA genome and to replicate via a DNA intermediate, the reverse of the usual DNA-to-RNA transcription pathway. They encode a RNA-dependent DNA polymerase ( reverse transcriptase ) that is essential for this process. Some retroviruses can cause diseases, including several that are associated with cancer, and HIV-1 which causes AIDS. Reverse transcriptase has been widely used as an experimental tool for the analysis of RNA molecules in the laboratory, in particular the conversion of RNA molecules into DNA prior to molecular cloning and/or polymerase chain reaction (PCR). [ 18 ]
Biochemical and genetic analyses showed that the enzyme systems that replicate viral RNA molecules (reverse transcriptases and RNA replicases ) lack molecular proofreading (3′ to 5′ exonuclease) activity, and that RNA sequences do not benefit from extensive repair systems analogous to those that exist for maintaining and repairing DNA sequences. Consequently, RNA genomes appear to be subject to significantly higher mutation rates than DNA genomes. For example, mutations in HIV-1 that lead to the emergence of viral mutants that are insensitive to antiviral drugs are common, and constitute a major clinical challenge. [ 19 ]
Analysis of ribosomal RNA sequences from a large number of organisms demonstrated that all extant forms of life on Earth share common structural and sequence features of the ribosomal RNA, reflecting a common ancestry . Mapping the similarities and differences among rRNA molecules from different sources provides clear and quantitative information about the phylogenetic (i.e. evolutionary) relationships among organisms. Analysis of rRNA molecules led to the identification of a third major kingdom of organisms, the archaea , in addition to the prokaryotes and eukaryotes . [ 20 ]
Molecular analysis of mRNA molecules showed that, following transcription, mRNAs have non-DNA-encoded nucleotides added to both their 5′ and 3′ ends (guanosine caps and poly-A, respectively). Enzymes were also identified that add and maintain the universal CCA sequence on the 3′ end of tRNA molecules. These events are among the first discovered examples of RNA processing , a complex series of reactions that are needed to convert RNA primary transcripts into biologically active RNA molecules. [ 21 ]
Small nuclear RNA molecules (snRNAs) were identified in the eukaryotic nucleus using immunological studies with autoimmune antibodies , which bind to small nuclear ribonucleoprotein complexes (snRNPs; complexes of the snRNA and protein). Subsequent biochemical, genetic, and phylogenetic studies established that many of these molecules play key roles in essential RNA processing reactions within the nucleus and nucleolus , including RNA splicing , polyadenylation , and the maturation of ribosomal RNAs . [ 22 ]
The detailed three-dimensional structure of tRNA molecules was determined using X-ray crystallography , and revealed highly complex, compact three dimensional structures consisting of tertiary interactions laid upon the basic cloverleaf secondary structure. Key features of tRNA tertiary structure include the coaxial stacking of adjacent helices and non-Watson-Crick interactions among nucleotides within the apical loops. Additional crystallographic studies showed that a wide range of RNA molecules (including ribozymes , riboswitches and ribosomal RNA ) also fold into specific structures containing a variety of 3D structural motifs. The ability of RNA molecules to adopt specific tertiary structures is essential for their biological activity, and results from the single-stranded nature of RNA. In many ways, RNA folding is more highly analogous to the folding of proteins rather than to the highly repetitive folded structure of the DNA double helix. [ 12 ]
Analysis of mature eukaryotic messenger RNA molecules showed that they are often much smaller than the DNA sequences that encode them. The genes were shown to be discontinuous, composed of sequences that are not present in the final mature RNA ( introns ), located between sequences that are retained in the mature RNA ( exons ). Introns were shown to be removed after transcription through a process termed RNA splicing . Splicing of RNA transcripts requires a highly precise and coordinated sequence of molecular events, consisting of (a) definition of boundaries between exons and introns, (b) RNA strand cleavage at exactly those sites, and (c) covalent linking (ligation) of the RNA exons in the correct order. The discovery of discontinuous genes and RNA splicing was entirely unexpected by the community of RNA biologists, and stands as one of the most shocking findings in molecular biology research. [ 23 ]
The great majority of protein-coding genes encoded within the nucleus of metazoan cells contain multiple introns . In many cases, these introns were shown to be processed in more than one pattern, thus generating a family of related mRNAs that differ, for example, by the inclusion or exclusion of particular exons. The result of alternative splicing is that a single gene can encode a number of different protein isoforms that can exhibit a variety of (usually related) biological functions. Indeed, most of the proteins encoded by the human genome are generated by alternative splicing. [ 24 ]
An experimental system was developed in which an intron-containing rRNA precursor from the nucleus of the ciliated protozoan Tetrahymena could be spliced in vitro . Subsequent biochemical analysis shows that this group I intron was self-splicing; that is, the precursor RNA is capable of carrying out the complete splicing reaction in the absence of proteins. In separate work, the RNA component of the bacterial enzyme ribonuclease P (a ribonucleoprotein complex) was shown to catalyze its tRNA-processing reaction in the absence of proteins. These experiments represented landmarks in RNA biology, since they revealed that RNA could play an active role in cellular processes, by catalyzing specific biochemical reactions. Before these discoveries, it was believed that biological catalysis was solely the realm of protein enzymes . [ 25 ] [ 26 ]
The discovery of catalytic RNA ( ribozymes ) showed that RNA could both encode genetic information (like DNA) and catalyze specific biochemical reactions (like protein enzymes ). This realization led to the RNA World Hypothesis , a proposal that RNA may have played a critical role in prebiotic evolution at a time before the molecules with more specialized functions (DNA and proteins) came to dominate biological information coding and catalysis. Although it is not possible for us to know the course of prebiotic evolution with any certainty, the presence of functional RNA molecules with common ancestry in all modern-day life forms is a strong argument that RNA was widely present at the time of the last common ancestor . [ 27 ]
Some self-splicing introns can spread through a population of organisms by "homing", inserting copies of themselves into genes at sites that previously lacked an intron. Because they are self-splicing (that is, they remove themselves at the RNA level from genes into which they have inserted), these sequences represent transposons that are genetically silent, i.e. they do not interfere with the expression of the gene into which they become inserted. These introns can be regarded as examples of selfish DNA . Some mobile introns encode homing endonucleases , enzymes that initiate the homing process by specifically cleaving double-stranded DNA at or near the intron-insertion site of alleles lacking an intron. Mobile introns are frequently members of either the group I or group II families of self-splicing introns. [ 28 ]
Introns are removed from nuclear pre-mRNAs by spliceosomes , large ribonucleoprotein complexes made up of snRNA and protein molecules whose composition and molecular interactions change during the course of the RNA splicing reactions. Spliceosomes assemble on and around splice sites (the boundaries between introns and exons in the unspliced pre-mRNA) in mRNA precursors and use RNA-RNA interactions to identify critical nucleotide sequences and, probably, to catalyze the splicing reactions. Nuclear pre-mRNA introns and spliceosome-associated snRNAs show similar structural features to self-splicing group II introns. In addition, the splicing pathway of nuclear pre-mRNA introns and group II introns shares a similar reaction pathway. These similarities have led to the hypothesis that these molecules may share a common ancestor. [ 29 ]
Messenger RNA precursors from a wide range of organisms can be edited before being translated into protein. In this process, non-encoded nucleotides may be inserted into specific sites in the RNA, and encoded nucleotides may be removed or replaced. RNA editing was first discovered within the mitochondria of kinetoplastid protozoans, where it has been shown to be extensive. [ 30 ] For example, some protein-coding genes encode fewer than 50% of the nucleotides found within the mature, translated mRNA. Other RNA editing events are found in mammals, plants, bacteria and viruses. These latter editing events involve fewer nucleotide modifications, insertions and deletions than the events within kinetoplast DNA, but still have high biological significance for gene expression and its regulation. [ 31 ]
Telomerase is an enzyme that is present in all eukaryotic nuclei which serves to maintain the ends of the linear DNA in the linear chromosomes of the eukaryotic nucleus, through the addition of terminal sequences that are lost in each round of DNA replication ( telomeres ). Before telomerase was identified, its activity was predicted on the basis of a molecular understanding of DNA replication, which indicated that the DNA polymerases known at that time could not replicate the 3′ end of a linear chromosome, due to the absence of a template strand. Telomerase was shown to be a ribonucleoprotein enzyme that contains an RNA component that serves as a template strand , and a protein component that has reverse transcriptase activity and adds nucleotides to the chromosome ends using the internal RNA template. [ 32 ]
For years, scientists had worked to identify which protein(s) within the ribosome were responsible for peptidyl transferase function during translation , because the covalent linking of amino acids represents one of the most central chemical reactions in all of biology. Careful biochemical studies showed that extensively-deproteinized large ribosomal subunits could still catalyze peptide bond formation, thereby implying that the sought-after activity might lie within ribosomal RNA rather than ribosomal proteins. Structural biologists, using X-ray crystallography , localized the peptidyl transferase center of the ribosome to a highly- conserved region of the large subunit ribosomal RNA (rRNA) that is located at the place within the ribosome where the amino-acid-bearing ends of tRNA bind, and where no proteins are present. These studies led to the conclusion that the ribosome is a ribozyme . The rRNA sequences that make up the ribosomal active site represent some of the most highly conserved sequences in the biological world. Together, these observations indicate that peptide bond formation catalyzed by RNA was a feature of the last common ancestor of all known forms of life. [ 33 ]
Experimental methods were invented that allowed investigators to use large, diverse populations of RNA molecules to carry out in vitro molecular experiments that utilized powerful selective replication strategies used by geneticists, and which amount to evolution in the test tube. These experiments have been described using different names, the most common of which are "combinatorial selection", "in vitro selection", and SELEX (for Systematic Evolution of Ligands by Exponential Enrichment ). These experiments have been used for isolating RNA molecules with a wide range of properties, from binding to particular proteins, to catalyzing particular reactions, to binding low molecular weight organic ligands . They have equal applicability to elucidating interactions and mechanisms that are known properties of naturally occurring RNA molecules to isolating RNA molecules with biochemical properties that are not known in nature. In developing in vitro selection technology for RNA, laboratory systems for synthesizing complex populations of RNA molecules were established, and used in conjunction with the selection of molecules with user-specified biochemical activities, and in vitro schemes for RNA replication. These steps can be viewed as (a) mutation , (b) selection, and (c) replication . Together, then, these three processes enable in vitro molecular evolution . [ 34 ]
Transposable genetic elements (transposons) are found which can replicate via transcription into an RNA intermediate which is subsequently converted to DNA by reverse transcriptase. These sequences, many of which are likely related to retroviruses, constitute much of the DNA of the eukaryotic nucleus, especially so in plants. Genomic sequencing shows that retrotransposons make up 36% of the human genome and over half of the genome of major cereal crops (wheat and maize). [ 35 ]
Segments of RNA, typically embedded within the 5′-untranslated region of a vast number of bacterial mRNA molecules, have a profound effect on gene expression through a previously-undiscovered mechanism that does not involve the participation of proteins. In many cases, riboswitches change their folded structure in response to environmental conditions (e.g. ambient temperature or concentrations of specific metabolites ), and the structural change controls the translation or stability of the mRNA in which the riboswitch is embedded. In this way, gene expression can be dramatically regulated at the post-transcriptional level. [ 36 ]
Another previously unknown mechanism by which RNA molecules are involved in genetic regulation was discovered in the 1990s. Small RNA molecules termed microRNA (miRNA) and small interfering RNA (siRNA) are abundant in eukaryotic cells and exert post-transcriptional control over mRNA expression. They function by binding to specific sites within the mRNA and inducing cleavage of the mRNA via a specific silencing-associated RNA degradation pathway. [ 37 ]
In addition to their well-established roles in translation and splicing, members of noncoding RNA (ncRNA) families have recently been found to function in genome defense and chromosome inactivation. For example, piwi-interacting RNAs (piRNAs) prevent genome instability in germ line cells, while Xist (X-inactive-specific-transcript) is essential for X-chromosome inactivation in mammals. [ 38 ] | https://en.wikipedia.org/wiki/History_of_RNA_biology |
History of Science and Technology is a biannual peer-reviewed academic journal covering the history of science and technology . It is published by State University of Infrastructure and Technologies (Ukraine) and was established in 2011.
The journal is abstracted and indexed in Scopus and the Emerging Sources Citation Index .
This article about a history of science journal is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about academic journals . Further suggestions might be found on the article's talk page . | https://en.wikipedia.org/wiki/History_of_Science_and_Technology_(journal) |
Sinhala language software for computers have been present since the late 1980s [ 1 ] (Samanala written in C) but no standard character representation system was put in place which resulted in proprietary character representation systems and fonts. In the wake of this CINTEC (Computer and Information Technology Council of Sri Lanka) introduced Sinhala within the UNICODE (16‑bit character technology) standard. ICTA concluded the work started by CINTEC for approving and standardizing Sinhala Unicode in Sri Lanka. [ 2 ]
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It is a Unicode font developed by Microsoft , designed to accurately represent Sinhala characters on digital platforms. Iskoola Pota is widely utilized in various digital applications, including word processing software, web design, and mobile devices, to enable Sinhala speakers to communicate effectively in their native language online. Its clear and legible design makes it a popular choice for both professional and personal use, contributing to the preservation and promotion of the Sinhala language in the digital age. [ 9 ]
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The history of scientific thought about the formation and evolution of the Solar System began with the Copernican Revolution . The first recorded use of the term " Solar System " dates from 1704. [ 1 ] [ 2 ] Since the seventeenth century, philosophers and scientists have been forming hypotheses concerning the origins of the Solar System and the Moon and attempting to predict how the Solar System would change in the future. René Descartes was the first to hypothesize on the beginning of the Solar System; however, more scientists joined the discussion in the eighteenth century, forming the groundwork for later hypotheses on the topic. Later, particularly in the twentieth century, a variety of hypotheses began to build up, including the now–commonly accepted nebular hypothesis .
Meanwhile, hypotheses explaining the evolution of the Sun originated in the nineteenth century, especially as scientists began to understand how stars in general functioned. In contrast, hypotheses attempting to explain the origin of the Moon have been circulating for centuries, although all of the widely accepted hypotheses were proven false by the Apollo missions in the mid-twentieth century. Following Apollo, in 1984, the giant impact hypothesis was composed, replacing the already-disproven binary accretion model as the most common explanation for the formation of the Moon. [ 3 ]
The most widely accepted model of planetary formation is known as the nebular hypothesis . This model posits that, 4.6 billion years ago, the Solar System was formed by the gravitational collapse of a giant molecular cloud spanning several light-years . Many stars , including the Sun , were formed within this collapsing cloud. The gas that formed the Solar System was slightly more massive than the Sun itself. Most of the mass concentrated in the center, forming the Sun, and the rest of the mass flattened into a protoplanetary disk , out of which all of the current planets , moons , asteroids , and other celestial bodies in the Solar System formed.
French philosopher and mathematician René Descartes was the first to propose a model for the origin of the Solar System in his book The World , written from 1629 to 1633. In his view, the universe was filled with vortices of swirling particles, and both the Sun and planets had condensed from a large vortex that had contracted, which he thought could explain the circular motion of the planets. However, this was before the knowledge of Newton's theory of gravity , which explains that matter does not behave in this way. [ 4 ]
The vortex model of 1944, [ 4 ] formulated by the German physicist and philosopher Carl Friedrich von Weizsäcker , hearkens back to the Cartesian model by involving a pattern of turbulence-induced eddies in a Laplacian nebular disc. In Weizsäcker's model, a combination of the clockwise rotation of each vortex and the anti-clockwise rotation of the whole system could lead to individual elements moving around the central mass in Keplerian orbits , reducing energy dissipation due to overall motion. However, material would be colliding at a high relative velocity in the inter-vortex boundaries and, in these regions, small roller-bearing eddies would coalesce to give annular condensations. This hypothesis was much criticized, as turbulence is a phenomenon associated with disorder and would not spontaneously produce the highly ordered structure required by the hypothesis. It also does not provide a solution to the angular momentum problem or explain lunar formation and other very basic characteristics of the Solar System. [ 5 ]
This model was modified [ 4 ] in 1948 by Dutch theoretical physicist Dirk Ter Haar , who hypothesized that regular eddies were discarded and replaced by random turbulence, which would lead to a very thick nebula where gravitational instability would not occur. He concluded the planets must have formed by accretion, and explained the compositional difference between the planets as resulting from the temperature difference between the inner and outer regions, the former being hotter and the latter being cooler, so only refractories (non-volatiles) condensed in the inner region. A major difficulty was that, in this supposition, turbulent dissipation took place over the course of a single millennium, which did not give enough time for planets to form.
The nebular hypothesis was first proposed in 1734 by Swedish scientist Emanuel Swedenborg [ 6 ] and later expanded upon by Prussian philosopher Immanuel Kant in 1755. A similar hypothesis was independently formulated by the Frenchman Pierre-Simon Laplace in 1796. [ 7 ]
In 1749, Georges-Louis Leclerc, Comte de Buffon conceived the idea that the planets were formed when a comet collided with the Sun, sending matter out to form the planets. However, Pierre-Simon Laplace refuted this idea in 1796, stating that any planets formed in such a way would eventually crash into the Sun. Laplace felt that the near-circular orbits of the planets were a necessary consequence of their formation. [ 8 ] Today, comets are known to be far too small to have created the Solar System in this way. [ 8 ]
In 1755, Immanuel Kant speculated that observed nebulae could be regions of star and planet formation. In 1796, Laplace elaborated by arguing that the nebula collapsed into a star, and, as it did so, the remaining material gradually spun outward into a flat disc, which then formed planets. [ 8 ]
However plausible it may appear at first sight, the nebular hypothesis still faces the obstacle of angular momentum ; if the Sun had indeed formed from the collapse of such a cloud, the planets should be rotating far more slowly. The Sun, though it contains almost 99.9 percent of the system's mass, contains just 1 percent of its angular momentum, [ 9 ] meaning that the Sun should be spinning much more rapidly.
Attempts to resolve the angular momentum problem led to the temporary abandonment of the nebular hypothesis in favor of a return to "two-body" hypotheses. [ 8 ] For several decades, many astronomers preferred the tidal or near-collision hypothesis put forward by James Jeans in 1917, in which the approach of some other star to the Sun ultimately formed the solar system. This near-miss would have drawn large amounts of matter out of the Sun and the other star by their mutual tidal forces , which could have then condensed into planets. [ 8 ] In 1929, astronomer Harold Jeffreys countered that such a near-collision was massively unlikely. [ 8 ] American astronomer Henry Norris Russell also objected to the hypothesis by showing that it ran into problems with angular momentum for the outer planets, with the planets struggling to avoid being reabsorbed by the Sun. [ 10 ]
In 1900, Forest Moulton showed that the nebular hypothesis was inconsistent with observations because of the angular momentum. Moulton and Chamberlin in 1904 originated the planetesimal hypothesis . [ 11 ] Along with many astronomers of the time, they came to believe the pictures of "spiral nebulas" from the Lick Observatory were direct evidence of the formation of planetary systems , which later turned out to be galaxies.
Moulton and Chamberlin suggested that a star had passed close to the Sun early in its life, causing tidal bulges, and that this, along with the internal process that leads to solar prominences, resulted in the ejection of filaments of matter from both stars. While most of the material would have fallen back, part of it would remain in orbit. The filaments cooled into numerous, tiny, solid planetesimals and a few larger protoplanets . This model received favorable support for about 3 decades, but passed out of favor by the late '30s and was discarded in the '40s due to the realization it was incompatible with the angular momentum of Jupiter. A part of the hypothesis, planetesimal accretion, was retained. [ 4 ]
In 1937 and 1940, Raymond Lyttleton postulated that a companion star to the Sun collided with a passing star. [ 4 ] Such a scenario had already been suggested and rejected by Henry Russell in 1935, though it may have been more likely assuming the Sun was born in an open cluster , where stellar collisions are common. Lyttleton showed that terrestrial planets were too small to condense on their own and suggested that one very large proto-planet broke in two because of rotational instability, forming Jupiter and Saturn, with a connecting filament from which the other planets formed. A later model, from 1940 and 1941, involved a triple star system, a binary plus the Sun, in which the binary merged and later split because of rotational instability and escaped from the system, leaving a filament that formed between them to be captured by the Sun. Objections of Lyman Spitzer apply to this model also. [ clarification needed ]
In 1954, 1975, and 1978, [ 12 ] Swedish astrophysicist Hannes Alfvén included electromagnetic effects in equations of particle motions, and angular momentum distribution and compositional differences were explained. In 1954, he first proposed the band structure, in which he distinguished an A-cloud, containing mostly helium with some solid-particle impurities ("meteor rain"), a B-cloud with mostly carbon, a C-cloud having mainly hydrogen, and a D-cloud made mainly of silicon and iron. Impurities in the A-cloud formed Mars and the Moon (later captured by Earth), impurities in the B-cloud collapsed to form the outer planets, the C-cloud condensed into Mercury, Venus, Earth, the asteroid belt, moons of Jupiter, and Saturn's rings, while Pluto, Triton, the outer satellites of Saturn, the moons of Uranus, the Kuiper Belt, and the Oort cloud formed from the D-cloud.
In 1943, Soviet astronomer Otto Schmidt proposed that the Sun, in its present form, passed through a dense interstellar cloud and emerged enveloped in a cloud of dust and gas, from which the planets eventually formed. This solved the angular momentum problem by assuming that the Sun's slow rotation was peculiar to it and that the planets did not form at the same time as the Sun. [ 8 ] Extensions of the model, together forming the Russian school, include Gurevich and Lebedinsky in 1950, Safronov in 1967 and 1969, Ruskol in 1981 Safronov and Vityazeff in 1985, and Safronov and Ruskol in 1994, among others [ 4 ] However, this hypothesis was severely dented by Victor Safronov , who showed that the amount of time required to form the planets from such a diffuse envelope would far exceed the Solar System's determined age. [ 8 ]
Ray Lyttleton modified the hypothesis by showing that a third body was not necessary and proposing that a mechanism of line accretion, as described by Bondi and Hoyle in 1944, enabled cloud material to be captured by the star (Williams and Cremin, 1968, loc. cit.).
In Hoyle's 1944 model, [ 4 ] the Sun's companion star went nova with ejected material captured by the Sun and planets forming from this material. In a version a year later, it [ clarification needed ] was a supernova. In 1955, he proposed a similar system to Laplace, and again proposed the idea with more mathematical detail in 1960. Hoyle's model differs from Laplace's in that a magnetic torque occurred between the disk and the Sun, which came into effect immediately; otherwise, more and more matter would have been ejected, resulting in a massive planetary system exceeding the size of the existing one and comparable to the Sun. The torque caused a magnetic coupling and acted to transfer angular momentum from the Sun to the disk. The magnetic field strength would have to have been 1 gauss. The existence of torque depended on magnetic lines of force being frozen into the disk, a consequence of a well-known magnetohydrodynamic (MHD) theorem on frozen-in lines of force. As the solar condensation temperature when the disk was ejected could not be much more than 1,000 K (730 °C; 1,340 °F), numerous refractories must have been solid, probably as fine smoke particles, which would have grown with condensation and accretion. These particles would have been swept out with the disk only if their diameter at the Earth's orbit was less than 1 meter, so as the disk moved outward, a subsidiary disk consisting of only refractories remained behind, where the terrestrial planets would form. The model agrees with the mass and composition of the planets and angular momentum distribution provided the magnetic coupling. However, it does not explain twinning, the low mass of Mars and Mercury, and the planetoid belts. Alfvén formulated the concept of frozen-in magnetic field lines.
Gerard Kuiper in 1944 [ 4 ] argued, like Ter Haar, that regular eddies would be impossible and postulated that large gravitational instabilities might occur in the solar nebula, forming condensations. In this, the solar nebula could be either co-genetic with the Sun or captured by it. Density distribution would determine what could form, a planetary system or a stellar companion. The two types of planets were assumed to have resulted from the Roche limit. No explanation was offered for the Sun's slow rotation, which Kuiper saw as a larger G-star problem.
In Fred Whipple 's 1948 scenario, [ 4 ] a smoke cloud about 60,000 AU in diameter and with 1 solar mass ( M ☉ ) contracted and produced the Sun. It had a negligible angular momentum, thus accounting for the Sun's similar property. This smoke cloud captured a smaller one with a large angular momentum. The collapse time for the large smoke and gas nebula is about 100 million years, and the rate was slow at first, increasing in later stages. The planets condensed from small clouds developed in or captured by the second cloud. The orbits would be nearly circular because accretion would reduce eccentricity due to the influence of the resisting medium, and orbital orientations would be similar because of the size of the small cloud and the common direction of the motions. The protoplanets might have heated up to such high degrees that the more volatile compounds would have been lost, and the orbital velocity decreased with increasing distance so that the terrestrial planets would have been more affected. However, this scenario was weak in that practically all the final regularities are introduced as a prior assumption, and quantitative calculations did not support most of the hypothesizing. For these reasons, it did not gain wide acceptance.
American chemist Harold Urey , who founded cosmochemistry , put forward a scenario [ 4 ] in 1951, 1952, 1956, and 1966 based largely on meteorites. His model also used Chandrasekhar's stability equations and obtained density distribution in the gas and dust disk surrounding the primitive Sun. To explain that volatile elements like mercury could be retained by the terrestrial planets, he postulated a moderately thick gas and dust halo shielding the planets from the Sun. To form diamonds, pure carbon crystals, moon-sized objects, and gas spheres that became gravitationally unstable would have to form in the disk, with the gas and dust dissipating at a later stage. Pressure fell as gas was lost and diamonds were converted to graphite, while the gas became illuminated by the Sun. Under these conditions, considerable ionization would be present, and the gas would be accelerated by magnetic fields, hence the angular momentum could be transferred from the Sun. Urey postulated that these lunar-size bodies were destroyed by collisions, with the gas dissipating, leaving behind solids collected at the core, with the resulting smaller fragments pushed far out into space and the larger fragments staying behind and accreting into planets. He suggested the Moon was such a surviving core.
In 1960, 1963, and 1978, [ 13 ] W. H. McCrea proposed the protoplanet hypothesis, in which the Sun and planets individually coalesced from matter within the same cloud, with the smaller planets later captured by the Sun's larger gravity. [ 8 ] It includes fission in a protoplanetary nebula and excludes a solar nebula. Agglomerations of floccules, which are presumed to compose the supersonic turbulence assumed to occur in the interstellar material from which stars are born, formed the Sun and protoplanets, the latter splitting to form planets. The two portions could not remain gravitationally bound to each other at a mass ratio of at least 8 to 1, and for inner planets, went into independent orbits, while for outer planets, one portion exited the Solar System. The inner protoplanets were Venus-Mercury and Earth-Mars. The moons of the greater planets were formed from "droplets" in the neck connecting the two portions of the dividing protoplanet. These droplets could account for some asteroids. Terrestrial planets would have no major moons, which does not account for the Moon . The hypothesis also predicts certain observations, such as the similar angular velocity of Mars and Earth with similar rotation periods and axial tilts. In this scheme, there are six principal planets: two terrestrial, Venus and Earth; two major, Jupiter and Saturn; and two outer, Uranus and Neptune, along with three lesser planets: Mercury, Mars, and Pluto.
This hypothesis has some problems, such as failing to explain the fact that the planets all orbit the Sun in the same direction with relatively low eccentricity, which would appear highly unlikely if they were each individually captured. [ 8 ]
In American astronomer Alastair G. W. Cameron 's hypothesis from 1962 and 1963, [ 4 ] the protosun, with a mass of about 1–2 Suns and a diameter of around 100,000 AU, was gravitationally unstable, collapsed, and broke into smaller subunits. The magnetic field was around 1/100,000 gauss. During the collapse, the magnetic lines of force were twisted. The collapse was fast and occurred due to the dissociation of hydrogen molecules, followed by the ionization of hydrogen and the double ionization of helium. Angular momentum led to rotational instability, which produced a Laplacean disk. At this stage, radiation removed excess energy, the disk would cool over a relatively short period of about 1 million years, and the condensation into what Whipple calls cometismals took place. Aggregation of these cometismals produced giant planets, which in turn produced disks during their formation, which evolved into lunar systems. The formation of terrestrial planets, comets, and asteroids involved disintegration, heating, melting, and solidification. Cameron also formulated the giant-impact hypothesis for the origin of the Moon.
The capture hypothesis, proposed by Michael Mark Woolfson in 1964, posits that the Solar System formed from tidal interactions between the Sun and a low-density protostar . The Sun's gravity would have drawn material from the diffuse atmosphere of the protostar, which would then have collapsed to form the planets. [ 14 ]
As captured planets would have initially eccentric orbits, Dormand and Woolfson [ 15 ] [ 16 ] proposed the possibility of a collision. They hypothesized that a filament was thrown out by a passing protostar and was captured by the Sun, resulting in the formation of planets. In this idea, there were 6 original planets, corresponding to 6 point-masses in the filament, with planets A and B , the two innermost, colliding. A , at 200 Earth masses, was ejected out of the Solar System, while B , estimated to be 25 Earth masses, split into Earth and Venus. Mercury is also a fragment of B . Mars and the Moon are escaped moons of A . Pluto is either a fragment from the collision [ 15 ] or a former moon of Neptune sent into a heliocentric orbit by Triton, another of A 's former satellites, which formed Charon from tidal disruption of Pluto. The collision also formed the asteroid belt and Oort's cloud. [ 17 ]
Jeans, in 1931, divided the various models into two groups: those where the material for planet formation came from the Sun, and those where it did not and may be concurrent or consecutive. [ 4 ]
In 1963, William McCrea divided them into another two groups: those that relate the formation of the planets to the formation of the Sun and those where it is independent of the formation of the Sun, where the planets form after the Sun becomes a normal star. [ 4 ]
Ter Haar and Cameron [ 18 ] distinguished between those hypotheses that consider a closed system, which is a development of the Sun and possibly a solar envelope, that starts with a protosun rather than the Sun itself, and state that Belot calls these hypotheses monistic; and those that consider an open system, which is where there is an interaction between the Sun and some foreign body that is supposed to have been the first step in the developments leading to the planetary system, and state that Belot calls these hypotheses dualistic.
Hervé Reeves' classification [ 19 ] also categorized them as co-genetic with the Sun or not, but also considered their formation from altered or unaltered stellar and interstellar material. He also recognized four groups: models based on the solar nebula, originated by Swedenborg, Kant, and Laplace in the 1700s; hypotheses proposing a cloud captured from interstellar space, major proponents being Alfvén and Gustaf Arrhenius in 1978; the binary hypotheses which propose that a sister star somehow disintegrated and a portion of its dissipating material was captured by the Sun, with the principal hypothesizer being Lyttleton in the 1940s; and the close-approach filament ideas of Jeans, Jeffreys, and Woolfson and Dormand.
Iwan P. Williams and Alan William Cremin [ 4 ] split the models between two categories: those that regard the origin and formation of the planets as being essentially related to the Sun, with the two formation processes taking place concurrently or consecutively, and those that regard the formation of the planets as being independent of the formation process of the Sun, the planets forming after the Sun becomes a normal star. The latter category has 2 subcategories: models where the material for the formation of the planets is extracted either from the Sun or another star, and models where the material is acquired from interstellar space. They conclude that the best models are Hoyle's magnetic coupling and McCrea's floccules.
Woolfson [ 20 ] recognized monistic models, which included Laplace, Descartes, Kant, and Weizsäcker, and dualistic models, which included Buffon, Chamberlin-Moulton, Jeans, Jeffreys, and Schmidt-Lyttleton.
In 1978, astronomer Andrew J. R. Prentice revived the Laplacian nebular model in his Modern Laplacian Theory by suggesting that the angular momentum problem could be resolved by drag created by dust grains in the original disc, which slowed down rotation in the centre. [ 8 ] [ 21 ] Prentice also suggested that the young Sun transferred some angular momentum to the protoplanetary disc and planetesimals through supersonic ejections understood to occur in T Tauri stars. [ 8 ] [ 22 ] However, his contention that such formation would occur in toruses or rings has been questioned, as any such rings would disperse before collapsing into planets. [ 8 ]
The birth of the modern, widely accepted hypothesis of planetary formation, the Solar Nebular Disk Model (SNDM), can be traced to the works of Soviet astronomer Victor Safronov . [ 23 ] His book Evolution of the protoplanetary cloud and formation of the Earth and the planets , [ 24 ] which was translated to English in 1972, had a long-lasting effect on how scientists thought about the formation of the planets. [ 25 ] In this book, almost all major problems of the planetary formation process were formulated, and some of them were solved. Safronov's ideas were further developed in the works of George Wetherill , who discovered runaway accretion. [ 8 ] By the early 1980s, the nebular hypothesis in the form of SNDM had come back into favor, led by two major discoveries in astronomy. First, several young stars, such as Beta Pictoris , were found to be surrounded by discs of cool dust, much as was predicted by the nebular hypothesis. Second, the Infrared Astronomical Satellite , launched in 1983, observed that many stars had an excess of infrared radiation that could be explained if they were orbited by discs of cooler material.
While the broad picture of the nebular hypothesis is widely accepted, [ 26 ] many of the details are not well understood and continue to be refined.
The refined nebular model was developed entirely on observations of the Solar System because it was the only one known until the mid-1990s. It was not confidently assumed to be widely applicable to other planetary systems , although scientists were anxious to test the nebular model by finding protoplanetary discs or even planets around other stars. [ 27 ] As of August 30, 2013, the discovery of 941 extrasolar planets [ 28 ] has turned up many surprises, and the nebular model must be revised to account for these discovered planetary systems, or new models considered.
Among the extrasolar planets discovered to date are planets the size of Jupiter or larger, but that possess very short orbital periods of only a few hours. Such planets would have to orbit very closely to their stars, so closely that their atmospheres would be gradually stripped away by solar radiation. [ 29 ] [ 30 ] There is no consensus on how to explain these so-called hot Jupiters , but one leading idea is that of planetary migration , similar to the process which is thought to have moved Uranus and Neptune to their current, distant orbit. Possible processes that cause the migration include orbital friction while the protoplanetary disk is still full of hydrogen and helium gas [ 31 ] and exchange of angular momentum between giant planets and the particles in the protoplanetary disc. [ 32 ] [ 33 ] [ 34 ]
One other problem is the detailed features of the planets. The solar nebula hypothesis predicts that all planets will form exactly in the ecliptic plane. Instead, the orbits of the classical planets have various small inclinations with respect to the ecliptic. Furthermore, for the gas giants, it is predicted that their rotations and moon systems will not be inclined with respect to the ecliptic plane. However, most gas giants have substantial axial tilts with respect to the ecliptic, with Uranus having a 98° tilt. [ 35 ] The Moon being relatively large with respect to the Earth and other moons in irregular orbits with respect to their planet is yet another issue. It is now believed these observations are explained by events that happened after the initial formation of the Solar System. [ 36 ]
Attempts to isolate the physical source of the Sun's energy, and thus determine when and how it might ultimately run out, began in the 19th century.
In the 19th century, the prevailing scientific view on the source of the Sun's heat was that it was generated by gravitational contraction . In the 1840s, astronomers J. R. Mayer and J. J. Waterson first proposed that the Sun's massive weight would cause it to collapse in on itself, generating heat. Both Hermann von Helmholtz and Lord Kelvin expounded upon this idea in 1854, suggesting that heat may also be produced by the impact of meteors on the Sun's surface. [ 37 ] Theories at the time suggested that stars evolved moving down the main sequence of the Hertzsprung-Russell diagram , starting as diffuse red supergiants before contracting and heating to become blue main-sequence stars , then even further down to red dwarfs before finally ending up as cool, dense black dwarfs . However, the Sun only has enough gravitational potential energy to power its luminosity by this mechanism for about 30 million years—far less than the age of the Earth. (This collapse time is known as the Kelvin–Helmholtz timescale .) [ 38 ]
Albert Einstein 's development of the theory of relativity in 1905 led to the understanding that nuclear reactions could create new elements from smaller precursors with the loss of energy. In his treatise Stars and Atoms , Arthur Eddington suggested that pressures and temperatures within stars were great enough for hydrogen nuclei to fuse into helium, a process which could produce the massive amounts of energy required to power the Sun. [ 37 ] In 1935, Eddington went further and suggested that other elements might also form within stars. [ 39 ] Spectral evidence collected after 1945 showed that the distribution of the commonest chemical elements, such as carbon , hydrogen, oxygen , nitrogen , neon , and iron , was fairly uniform across the galaxy, suggesting that these elements had a common origin. [ 39 ] Numerous anomalies in the proportions hinted at an underlying mechanism for creation. For example, lead has a higher atomic weight than gold , but is far more common; besides, hydrogen and helium (elements 1 and 2) are virtually ubiquitous, yet lithium and beryllium (elements 3 and 4) are extremely rare. [ 39 ]
While the unusual spectra of red giant stars had been known since the 19th century, [ 40 ] it was George Gamow who, in the 1940s, first understood that they were stars of roughly solar mass that had run out of hydrogen in their cores and had resorted to burning the hydrogen in their outer shells. [ citation needed ] This allowed Martin Schwarzschild to draw the connection between red giants and the finite lifespans of stars. It is now understood that red giants are stars in the last stages of their life cycles.
Fred Hoyle noted that, even while the distribution of elements was fairly uniform, different stars had varying amounts of each element. To Hoyle, this indicated that they must have originated within the stars themselves. The abundance of elements peaked around the atomic number for iron, an element that could only have been formed under intense pressures and temperatures. Hoyle concluded that iron must have formed within giant stars. [ 39 ] From this, in 1945 and 1946, Hoyle constructed the final stages of a star's life cycle. As the star dies, it collapses under its weight, leading to a stratified chain of fusion reactions: carbon-12 fuses with helium to form oxygen-16, oxygen-16 fuses with helium to produce neon-20, and so on up to iron. [ 41 ] There was, however, no known method by which carbon-12 could be produced. Isotopes of beryllium produced via fusion were too unstable to form carbon, and for three helium atoms to form carbon-12 was so unlikely as to have been impossible over the age of the Universe. However, in 1952, physicist Ed Salpeter showed that a short enough time existed between the formation and the decay of the beryllium isotope that another helium had a small chance to form carbon, but only if their combined mass/energy amounts were equal to that of carbon-12. Hoyle, employing the anthropic principle , showed that it must be so, since he himself was made of carbon, and he existed. When the matter/energy level of carbon-12 was finally determined, it was found to be within a few percent of Hoyle's prediction. [ 42 ]
The first white dwarf discovered was in the triple star system of 40 Eridani , which contains the relatively bright main sequence star 40 Eridani A , orbited at a distance by the closer binary system of the white dwarf 40 Eridani B and the main sequence red dwarf 40 Eridani C . The pair 40 Eridani B/C was discovered by William Herschel on January 31, 1783; [ 43 ] , p. 73 it was again observed by Friedrich Georg Wilhelm Struve in 1825 and by Otto Wilhelm von Struve in 1851. [ 44 ] [ 45 ] In 1910, Henry Norris Russell , Edward Charles Pickering , and Williamina Fleming discovered that, despite being a dim star, 40 Eridani B was of spectral type A, or white. [ 46 ]
White dwarfs were found to be extremely dense soon after their discovery. If a star is in a binary system, as is the case for Sirius B and 40 Eridani B, it is possible to estimate its mass from observations of the binary orbit. This was done for Sirius B by 1910, [ 47 ] yielding a mass estimate of 0.94 M ☉ (a more modern estimate being 1.00 M ☉ ). [ 48 ] Since hotter bodies radiate more than colder ones, a star's surface brightness can be estimated from its effective surface temperature , and hence from its spectrum . If the star's distance is known, its overall luminosity can also be estimated. A comparison of the two figures yields the star's radius. Reasoning of this sort led to the realization, puzzling to astronomers at the time, that Sirius B and 40 Eridani B must be very dense. For example, when Ernst Öpik estimated the density of some visual binary stars in 1916, he found that 40 Eridani B had a density of over 25,000 times the Sun's, which was so high that he called it "impossible". [ 49 ]
Such densities are possible because white dwarf material is not composed of atoms bound by chemical bonds , but rather consists of a plasma of unbound nuclei and electrons . There is therefore no obstacle to placing nuclei closer to each other than electron orbitals —the regions occupied by electrons bound to an atom—would normally allow. [ 50 ] Eddington, however, wondered what would happen when this plasma cooled and the energy which kept the atoms ionized was no longer present. [ 51 ] This paradox was resolved by R. H. Fowler in 1926 by an application of newly devised quantum mechanics . Since electrons obey the Pauli exclusion principle , no two electrons can occupy the same state , and they must obey Fermi–Dirac statistics , also introduced in 1926 to determine the statistical distribution of particles that satisfies the Pauli exclusion principle. [ 52 ] At zero temperature, therefore, electrons could not all occupy the lowest-energy, or ground , state; some of them had to occupy higher-energy states, forming a band of lowest-available energy states, the Fermi sea . This state of the electrons, called degenerate , meant that a white dwarf could cool to zero temperature and still possess high energy.
Planetary nebulae are generally faint objects, and none are visible to the naked eye . The first planetary nebula discovered was the Dumbbell Nebula in the constellation of Vulpecula , observed by Charles Messier in 1764 and listed as M27 in his catalogue of nebulous objects. To early observers with low-resolution telescopes, M27 and subsequently discovered planetary nebulae somewhat resembled the gas giants, and William Herschel , the discoverer of Uranus , eventually coined the term 'planetary nebula' for them, although, as we now know, they are very different from planets.
The central stars of planetary nebulae are very hot. Their luminosity , though, is very low, implying that they must be very small. A star can collapse to such a small size only once it has exhausted all its nuclear fuel, so planetary nebulae came to be understood as a final stage of stellar evolution. Spectroscopic observations show that all planetary nebulae are expanding, and so the idea arose that planetary nebulae were caused by a star's outer layers being thrown into space at the end of its life.
Over the centuries, many scientific hypotheses have been put forward concerning the origin of Earth's Moon. One of the earliest was the so-called binary accretion model , which concluded that the Moon accreted from material in orbit around the Earth leftover from its formation. Another, the fission model , was developed by George Darwin (son of Charles Darwin ), who noted that, as the Moon is gradually receding from the Earth at a rate of about 4 cm per year, so at one point in the distant past, it must have been part of the Earth but was flung outward by the momentum of Earth's then–much faster rotation. This hypothesis is also supported by the fact that the Moon's density, while less than Earth's, is about equal to that of Earth's rocky mantle , suggesting that, unlike the Earth, it lacks a dense iron core. A third hypothesis, known as the capture model , suggested that the Moon was an independently orbiting body that had been snared into orbit by Earth's gravity. [ 3 ]
The existing hypotheses were all refuted by the Apollo lunar missions in the late 1960s and early 1970s, which introduced a stream of new scientific evidence, specifically concerning the Moon's composition, age, and history. These lines of evidence contradict many predictions made by these earlier models. [ 3 ] The rocks brought back from the Moon showed a marked decrease in water relative to rocks elsewhere in the Solar System and evidence of an ocean of magma early in its history, indicating that its formation must have produced a great deal of energy. Also, oxygen isotopes in lunar rocks showed a marked similarity to those on Earth, suggesting that they formed at a similar location in the solar nebula. The capture model fails to explain the similarity in these isotopes (if the Moon had originated in another part of the Solar System, those isotopes would have been different), while the co-accretion model cannot adequately explain the loss of water (if the Moon formed similarly to the Earth, the amount of water trapped in its mineral structure would also be roughly similar). Conversely, the fission model, while it can account for the similarity in chemical composition and the lack of iron in the Moon, cannot adequately explain its high orbital inclination and, in particular, the large amount of angular momentum in the Earth–Moon system, more than any other planet–satellite pair in the Solar System. [ 3 ]
For many years after Apollo, the binary accretion model was settled on as the best hypothesis for explaining the Moon's origins, even though it was known to be flawed. Then, at a conference in Kona, Hawaii in 1984, a compromise model was composed that accounted for all of the observed discrepancies. Originally formulated by two independent research groups in 1976, the giant impact model supposed that a massive planetary object the size of Mars had collided with Earth early in its history. The impact would have melted Earth's crust, and the other planet's heavy core would have sunk inward and merged with Earth's. The superheated vapor produced by the impact would have risen into orbit around the planet, coalescing into the Moon. This explained the lack of water, as the vapor cloud was too hot for water to condense; the similarity in composition, since the Moon had formed from part of the Earth; the lower density, since the Moon had formed from the Earth's crust and mantle, rather than its core; and the Moon's unusual orbit, since an oblique strike would have imparted a massive amount of angular momentum to the Earth–Moon system. [ 3 ]
The giant impact model has been criticized for being too explanatory, since it can be expanded to explain any future discoveries and, as such, is unfalsifiable. Many also claim that much of the material from the impactor would have ended up in the Moon, meaning that the isotope levels would be different, but they are not. In addition, while some volatile compounds such as water are absent from the Moon's crust, many others, such as manganese , are not. [ 3 ]
While the co-accretion and capture models are not currently accepted as valid explanations for the existence of the Moon, they have been employed to explain the formation of other natural satellites in the Solar System. Jupiter 's Galilean satellites are believed to have formed via co-accretion, [ 53 ] while the Solar System's irregular satellites , such as Triton , are all believed to have been captured. [ 54 ]
Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each arrow ( → ) may be read as "within" or "part of". | https://en.wikipedia.org/wiki/History_of_Solar_System_formation_and_evolution_hypotheses |
Algebra can essentially be considered as doing computations similar to those of arithmetic but with non-numerical mathematical objects. However, until the 19th century, algebra consisted essentially of the theory of equations . For example, the fundamental theorem of algebra belongs to the theory of equations and is not, nowadays, considered as belonging to algebra (in fact, every proof must use the completeness of the real numbers , which is not an algebraic property).
This article describes the history of the theory of equations, referred to in this article as "algebra", from the origins to the emergence of algebra as a separate area of mathematics .
The word "algebra" is derived from the Arabic word الجبر al-jabr , and this comes from the treatise written in the year 830 by the medieval Persian mathematician, Al-Khwārizmī , whose Arabic title, Kitāb al-muḫtaṣar fī ḥisāb al-ğabr wa-l-muqābala , can be translated as The Compendious Book on Calculation by Completion and Balancing . The treatise provided for the systematic solution of linear and quadratic equations . According to one history, "[i]t is not certain just what the terms al-jabr and muqabalah mean, but the usual interpretation is similar to that implied in the previous translation. The word 'al-jabr' presumably meant something like 'restoration' or 'completion' and seems to refer to the transposition of subtracted terms to the other side of an equation; the word 'muqabalah' is said to refer to 'reduction' or 'balancing'—that is, the cancellation of like terms on opposite sides of the equation. Arabic influence in Spain long after the time of al-Khwarizmi is found in Don Quixote , where the word 'algebrista' is used for a bone-setter, that is, a 'restorer'." [ 1 ] The term is used by al-Khwarizmi to describe the operations that he introduced, " reduction " and "balancing", referring to the transposition of subtracted terms to the other side of an equation, that is, the cancellation of like terms on opposite sides of the equation. [ 2 ]
Algebra did not always make use of the symbolism that is now ubiquitous in mathematics; instead, it went through three distinct stages. The stages in the development of symbolic algebra are approximately as follows: [ 3 ]
As important as the use or lack of symbolism in algebra was the degree of the equations that were addressed. Quadratic equations played an important role in early algebra; and throughout most of history, until the early modern period, all quadratic equations were classified as belonging to one of three categories.
where p {\displaystyle p} and q {\displaystyle q} are positive.
This trichotomy comes about because quadratic equations of the form x 2 + p x + q = 0 {\displaystyle x^{2}+px+q=0} , with p {\displaystyle p} and q {\displaystyle q} positive, have no positive roots . [ 4 ]
In between the rhetorical and syncopated stages of symbolic algebra, a geometric constructive algebra was developed by classical Greek and Vedic Indian mathematicians in which algebraic equations were solved through geometry. For instance, an equation of the form x 2 = A {\displaystyle x^{2}=A} was solved by finding the side of a square of area A . {\displaystyle A.}
In addition to the three stages of expressing algebraic ideas, some authors recognized four conceptual stages in the development of algebra that occurred alongside the changes in expression. These four stages were as follows: [ 5 ]
The origins of algebra can be traced to the ancient Babylonians , [ 6 ] who developed a positional number system that greatly aided them in solving their rhetorical algebraic equations. The Babylonians were not interested in exact solutions, but rather approximations, and so they would commonly use linear interpolation to approximate intermediate values. [ 7 ] One of the most famous tablets is the Plimpton 322 tablet , created around 1900–1600 BC, which gives a table of Pythagorean triples and represents some of the most advanced mathematics prior to Greek mathematics. [ 8 ]
Babylonian algebra was much more advanced than the Egyptian algebra of the time; whereas the Egyptians were mainly concerned with linear equations the Babylonians were more concerned with quadratic and cubic equations . [ 7 ] The Babylonians had developed flexible algebraic operations with which they were able to add equals to equals and multiply both sides of an equation by like quantities so as to eliminate fractions and factors. [ 7 ] They were familiar with many simple forms of factoring , [ 7 ] three-term quadratic equations with positive roots, [ 9 ] and many cubic equations, [ 10 ] although it is not known if they were able to reduce the general cubic equation. [ 10 ]
Ancient Egyptian algebra dealt mainly with linear equations while the Babylonians found these equations too elementary, and developed mathematics to a higher level than the Egyptians. [ 7 ]
The Rhind Papyrus, also known as the Ahmes Papyrus, is an ancient Egyptian papyrus written c. 1650 BC by Ahmes, who transcribed it from an earlier work that he dated to between 2000 and 1800 BC. [ 11 ] It is the most extensive ancient Egyptian mathematical document known to historians. [ 12 ] The Rhind Papyrus contains problems where linear equations of the form x + a x = b {\displaystyle x+ax=b} and x + a x + b x = c {\displaystyle x+ax+bx=c} are solved, where a , b , {\displaystyle a,b,} and c {\displaystyle c} are known and x , {\displaystyle x,} which is referred to as "aha" or heap, is the unknown. [ 13 ] The solutions were possibly, but not likely, arrived at by using the "method of false position", or regula falsi , where first a specific value is substituted into the left hand side of the equation, then the required arithmetic calculations are done, thirdly the result is compared to the right hand side of the equation, and finally the correct answer is found through the use of proportions. In some of the problems the author "checks" his solution, thereby writing one of the earliest known simple proofs. [ 13 ]
It is sometimes alleged that the Greeks had no algebra, but this is disputed. [ 15 ] By the time of Plato , Greek mathematics had undergone a drastic change. The Greeks created a geometric algebra where terms were represented by sides of geometric objects, [ 16 ] usually lines, that had letters associated with them, [ 17 ] and with this new form of algebra they were able to find solutions to equations by using a process that they invented, known as "the application of areas". [ 16 ] "The application of areas" is only a part of geometric algebra and it is thoroughly covered in Euclid 's Elements .
An example of geometric algebra would be solving the linear equation a x = b c . {\displaystyle ax=bc.} The ancient Greeks would solve this equation by looking at it as an equality of areas rather than as an equality between the ratios a : b {\displaystyle a:b} and c : x . {\displaystyle c:x.} The Greeks would construct a rectangle with sides of length b {\displaystyle b} and c , {\displaystyle c,} then extend a side of the rectangle to length a , {\displaystyle a,} and finally they would complete the extended rectangle so as to find the side of the rectangle that is the solution. [ 16 ]
Iamblichus in Introductio arithmatica says that Thymaridas (c. 400 BC – c. 350 BC) worked with simultaneous linear equations. [ 18 ] In particular, he created the then famous rule that was known as the "bloom of Thymaridas" or as the "flower of Thymaridas", which states that:
If the sum of n {\displaystyle n} quantities be given, and also the sum of every pair containing a particular quantity, then this particular quantity is equal to 1 / ( n − 2 ) {\displaystyle 1/(n-2)} of the difference between the sums of these pairs and the first given sum. [ 19 ]
or using modern notation, the solution of the following system of n {\displaystyle n} linear equations in n {\displaystyle n} unknowns, [ 18 ]
x + x 1 + x 2 + ⋯ + x n − 1 = s {\displaystyle x+x_{1}+x_{2}+\cdots +x_{n-1}=s} x + x 1 = m 1 {\displaystyle x+x_{1}=m_{1}} x + x 2 = m 2 {\displaystyle x+x_{2}=m_{2}} ⋮ {\displaystyle \vdots } x + x n − 1 = m n − 1 {\displaystyle x+x_{n-1}=m_{n-1}}
is,
x = ( m 1 + m 2 + . . . + m n − 1 ) − s n − 2 = ( ∑ i = 1 n − 1 m i ) − s n − 2 . {\displaystyle x={\cfrac {(m_{1}+m_{2}+...+m_{n-1})-s}{n-2}}={\cfrac {(\sum _{i=1}^{n-1}m_{i})-s}{n-2}}.}
Iamblichus goes on to describe how some systems of linear equations that are not in this form can be placed into this form. [ 18 ]
Euclid ( Greek : Εὐκλείδης ) was a Greek mathematician who flourished in Alexandria , Egypt , almost certainly during the reign of Ptolemy I (323–283 BC). [ 20 ] [ 21 ] Neither the year nor place of his birth [ 20 ] have been established, nor the circumstances of his death.
Euclid is regarded as the "father of geometry ". His Elements is the most successful textbook in the history of mathematics . [ 20 ] Although he is one of the most famous mathematicians in history there are no new discoveries attributed to him; rather he is remembered for his great explanatory skills. [ 22 ] The Elements is not, as is sometimes thought, a collection of all Greek mathematical knowledge to its date; rather, it is an elementary introduction to it. [ 23 ]
The geometric work of the Greeks, typified in Euclid's Elements , provided the framework for generalizing formulae beyond the solution of particular problems into more general systems of stating and solving equations.
Book II of the Elements contains fourteen propositions, which in Euclid's time were extremely significant for doing geometric algebra. These propositions and their results are the geometric equivalents of our modern symbolic algebra and trigonometry. [ 15 ] Today, using modern symbolic algebra, we let symbols represent known and unknown magnitudes (i.e. numbers) and then apply algebraic operations on them, while in Euclid's time magnitudes were viewed as line segments and then results were deduced using the axioms or theorems of geometry. [ 15 ]
Many basic laws of addition and multiplication are included or proved geometrically in the Elements . For instance, proposition 1 of Book II states:
But this is nothing more than the geometric version of the (left) distributive law , a ( b + c + d ) = a b + a c + a d {\displaystyle a(b+c+d)=ab+ac+ad} ; and in Books V and VII of the Elements the commutative and associative laws for multiplication are demonstrated. [ 15 ]
Many basic equations were also proved geometrically. For instance, proposition 5 in Book II proves that a 2 − b 2 = ( a + b ) ( a − b ) , {\displaystyle a^{2}-b^{2}=(a+b)(a-b),} [ 24 ] and proposition 4 in Book II proves that ( a + b ) 2 = a 2 + 2 a b + b 2 . {\displaystyle (a+b)^{2}=a^{2}+2ab+b^{2}.} [ 15 ]
Furthermore, there are also geometric solutions given to many equations. For instance, proposition 6 of Book II gives the solution to the quadratic equation a x + x 2 = b 2 , {\displaystyle ax+x^{2}=b^{2},} and proposition 11 of Book II gives a solution to a x + x 2 = a 2 . {\displaystyle ax+x^{2}=a^{2}.} [ 25 ]
Data is a work written by Euclid for use at the schools of Alexandria and it was meant to be used as a companion volume to the first six books of the Elements . The book contains some fifteen definitions and ninety-five statements, of which there are about two dozen statements that serve as algebraic rules or formulas. [ 26 ] Some of these statements are geometric equivalents to solutions of quadratic equations. [ 26 ] For instance, Data contains the solutions to the equations d x 2 − a d x + b 2 c = 0 {\displaystyle dx^{2}-adx+b^{2}c=0} and the familiar Babylonian equation x y = a 2 , x ± y = b . {\displaystyle xy=a^{2},x\pm y=b.} [ 26 ]
A conic section is a curve that results from the intersection of a cone with a plane . There are three primary types of conic sections: ellipses (including circles ), parabolas , and hyperbolas . The conic sections are reputed to have been discovered by Menaechmus [ 27 ] (c. 380 BC – c. 320 BC) and since dealing with conic sections is equivalent to dealing with their respective equations, they played geometric roles equivalent to cubic equations and other higher order equations.
Menaechmus knew that in a parabola, the equation y 2 = l x {\displaystyle y^{2}=lx} holds, where l {\displaystyle l} is a constant called the latus rectum , although he was not aware of the fact that any equation in two unknowns determines a curve. [ 28 ] He apparently derived these properties of conic sections and others as well. Using this information it was now possible to find a solution to the problem of the duplication of the cube by solving for the points at which two parabolas intersect, a solution equivalent to solving a cubic equation. [ 28 ]
We are informed by Eutocius that the method he used to solve the cubic equation was due to Dionysodorus (250 BC – 190 BC). Dionysodorus solved the cubic by means of the intersection of a rectangular hyperbola and a parabola. This was related to a problem in Archimedes ' On the Sphere and Cylinder . Conic sections would be studied and used for thousands of years by Greek, and later Islamic and European, mathematicians. In particular Apollonius of Perga 's famous Conics deals with conic sections, among other topics.
Chinese mathematics dates to at least 300 BC with the Zhoubi Suanjing , generally considered to be one of the oldest Chinese mathematical documents. [ 29 ]
Chiu-chang suan-shu or The Nine Chapters on the Mathematical Art , written around 250 BC, is one of the most influential of all Chinese math books and it is composed of some 246 problems. Chapter eight deals with solving determinate and indeterminate simultaneous linear equations using positive and negative numbers, with one problem dealing with solving four equations in five unknowns. [ 29 ]
Ts'e-yuan hai-ching , or Sea-Mirror of the Circle Measurements , is a collection of some 170 problems written by Li Zhi (or Li Ye) (1192 – 1279 AD). He used fan fa , or Horner's method , to solve equations of degree as high as six, although he did not describe his method of solving equations. [ 30 ]
Shu-shu chiu-chang , or Mathematical Treatise in Nine Sections , was written by the wealthy governor and minister Ch'in Chiu-shao (c. 1202 – c. 1261). With the introduction of a method for solving simultaneous congruences , now called the Chinese remainder theorem , it marks the high point in Chinese indeterminate analysis [ clarification needed ] . [ 30 ]
The earliest known magic squares appeared in China. [ 31 ] In Nine Chapters the author solves a system of simultaneous linear equations by placing the coefficients and constant terms of the linear equations into a magic square (i.e. a matrix) and performing column reducing operations on the magic square. [ 31 ] The earliest known magic squares of order greater than three are attributed to Yang Hui (fl. c. 1261 – 1275), who worked with magic squares of order as high as ten. [ 32 ]
Ssy-yüan yü-chien 《四元玉鑒》, or Precious Mirror of the Four Elements , was written by Chu Shih-chieh in 1303 and it marks the peak in the development of Chinese algebra. The four elements , called heaven, earth, man and matter, represented the four unknown quantities in his algebraic equations. The Ssy-yüan yü-chien deals with simultaneous equations and with equations of degrees as high as fourteen. The author uses the method of fan fa , today called Horner's method , to solve these equations. [ 33 ]
The Precious Mirror opens with a diagram of the arithmetic triangle ( Pascal's triangle ) using a round zero symbol, but Chu Shih-chieh denies credit for it. A similar triangle appears in Yang Hui's work, but without the zero symbol. [ 34 ]
There are many summation equations given without proof in the Precious mirror . A few of the summations are: [ 34 ]
Diophantus was a Hellenistic mathematician who lived c. 250 AD, but the uncertainty of this date is so great that it may be off by more than a century. He is known for having written Arithmetica , a treatise that was originally thirteen books but of which only the first six have survived. [ 35 ] Arithmetica is the earliest extant work present that solve arithmetic problems by algebra. Diophantus however did not invent the method of algebra, which existed before him. [ 36 ] Algebra was practiced and diffused orally by practitioners, with Diophantus picking up techniques to solve problems in arithmetic. [ 37 ]
In modern algebra a polynomial is a linear combination of variable x that is built of exponentiation, scalar multiplication, addition, and subtraction. The algebra of Diophantus, similar to medieval arabic algebra is an aggregation of objects of different types with no operations present [ 38 ]
For example, in Diophantus a polynomial "6 4 ′ inverse Powers, 25 Powers lacking 9 units", which in modern notation is 6 1 4 x − 1 + 25 x 2 − 9 {\displaystyle 6{\tfrac {1}{4}}x^{-1}+25x^{2}-9} is a collection of 6 1 4 {\displaystyle 6{\tfrac {1}{4}}} object of one kind with 25 object of second kind which lack 9 objects of third kind with no operation present. [ 39 ]
Similar to medieval Arabic algebra Diophantus uses three stages to solve a problem by Algebra:
1) An unknown is named and an equation is set up
2) An equation is simplified to a standard form( al-jabr and al-muqābala in arabic)
3) Simplified equation is solved [ 40 ]
Diophantus does not give a classification of equations in six types like Al-Khwarizmi in extant parts of Arithmetica. He does say that he would give solution to three terms equations later, so this part of the work is possibly just lost [ 37 ]
In Arithmetica , Diophantus is the first to use symbols for unknown numbers as well as abbreviations for powers of numbers, relationships, and operations; [ 41 ] thus he used what is now known as syncopated algebra. The main difference between Diophantine syncopated algebra and modern algebraic notation is that the former lacked special symbols for operations, relations, and exponentials. [ 42 ]
So, for example, what we would write as
which can be rewritten as
would be written in Diophantus's syncopated notation as
where the symbols represent the following: [ 43 ] [ 44 ]
Unlike in modern notation, the coefficients come after the variables and that addition is represented by the juxtaposition of terms. A literal symbol-for-symbol translation of Diophantus's syncopated equation into a modern symbolic equation would be the following: [ 43 ]
where to clarify, if the modern parentheses and plus are used then the above equation can be rewritten as: [ 43 ]
However the distinction between "rhetorical algebra", "syncopated algebra" and "symbolic algebra" is considered outdated by Jeffrey Oaks and Jean Christianidis. The problems were solved on dust-board using some notation, while in books solution were written in "rhetorical style". [ 45 ]
Arithmetica also makes use of the identities: [ 46 ]
The Indian mathematicians were active in studying about number systems. The earliest known Indian mathematical documents are dated to around the middle of the first millennium BC (around the 6th century BC). [ 47 ]
The recurring themes in Indian mathematics are, among others, determinate and indeterminate linear and quadratic equations, simple mensuration, and Pythagorean triples. [ 48 ]
Aryabhata (476–550) was an Indian mathematician who authored Aryabhatiya . In it he gave the rules, [ 49 ]
and
Brahmagupta (fl. 628) was an Indian mathematician who authored Brahma Sphuta Siddhanta . In his work Brahmagupta solves the general quadratic equation for both positive and negative roots. [ 50 ] In indeterminate analysis Brahmagupta gives the Pythagorean triads m , 1 2 ( m 2 n − n ) , {\displaystyle m,{\frac {1}{2}}\left({m^{2} \over n}-n\right),} 1 2 ( m 2 n + n ) , {\displaystyle {\frac {1}{2}}\left({m^{2} \over n}+n\right),} but this is a modified form of an old Babylonian rule that Brahmagupta may have been familiar with. [ 51 ] He was the first to give a general solution to the linear Diophantine equation a x + b y = c , {\displaystyle ax+by=c,} where a , b , {\displaystyle a,b,} and c {\displaystyle c} are integers . Unlike Diophantus who only gave one solution to an indeterminate equation, Brahmagupta gave all integer solutions; but that Brahmagupta used some of the same examples as Diophantus has led some historians to consider the possibility of a Greek influence on Brahmagupta's work, or at least a common Babylonian source. [ 52 ]
Like the algebra of Diophantus, the algebra of Brahmagupta was syncopated. Addition was indicated by placing the numbers side by side, subtraction by placing a dot over the subtrahend, and division by placing the divisor below the dividend, similar to our modern notation but without the bar. Multiplication, evolution, and unknown quantities were represented by abbreviations of appropriate terms. [ 52 ] The extent of Greek influence on this syncopation, if any, is not known and it is possible that both Greek and Indian syncopation may be derived from a common Babylonian source. [ 52 ]
Bhāskara II (1114 – c. 1185) was the leading mathematician of the 12th century. In Algebra, he gave the general solution of Pell's equation . [ 52 ] He is the author of Lilavati and Vija-Ganita , which contain problems dealing with determinate and indeterminate linear and quadratic equations, and Pythagorean triples [ 48 ] and he fails to distinguish between exact and approximate statements. [ 53 ] Many of the problems in Lilavati and Vija-Ganita are derived from other Hindu sources, and so Bhaskara is at his best in dealing with indeterminate analysis. [ 53 ]
Bhaskara uses the initial symbols of the names for colors as the symbols of unknown variables. So, for example, what we would write today as
Bhaskara would have written as
where ya indicates the first syllable of the word for black , and ru is taken from the word species . The dots over the numbers indicate subtraction.
The first century of the Islamic Arab Empire saw almost no scientific or mathematical achievements since the Arabs, with their newly conquered empire, had not yet gained any intellectual drive and research in other parts of the world had faded. In the second half of the 8th century, Islam had a cultural awakening, and research in mathematics and the sciences increased. [ 54 ] The Muslim Abbasid caliph al-Mamun (809–833) is said to have had a dream where Aristotle appeared to him, and as a consequence al-Mamun ordered that Arabic translation be made of as many Greek works as possible, including Ptolemy's Almagest and Euclid's Elements . Greek works would be given to the Muslims by the Byzantine Empire in exchange for treaties, as the two empires held an uneasy peace. [ 54 ] Many of these Greek works were translated by Thabit ibn Qurra (826–901), who translated books written by Euclid, Archimedes, Apollonius, Ptolemy, and Eutocius. [ 55 ]
Arabic mathematicians established algebra as an independent discipline, and gave it the name "algebra" ( al-jabr ). They were the first to teach algebra in an elementary form and for its own sake. [ 56 ] There are three theories about the origins of Arabic Algebra. The first emphasizes Hindu influence, the second emphasizes Mesopotamian or Persian-Syriac influence and the third emphasizes Greek influence. Many scholars believe that it is the result of a combination of all three sources. [ 57 ]
Throughout their time in power, the Arabs used a fully rhetorical algebra, where often even the numbers were spelled out in words. The Arabs would eventually replace spelled out numbers (e.g. twenty-two) with Arabic numerals (e.g. 22), but the Arabs did not adopt or develop a syncopated or symbolic algebra [ 55 ] until the work of Ibn al-Banna , who developed a symbolic algebra in the 13th century, followed by Abū al-Hasan ibn Alī al-Qalasādī in the 15th century.
The Muslim [ 58 ] Persian mathematician Muhammad ibn Mūsā al-Khwārizmī , described as the father [ 59 ] [ 60 ] [ 61 ] or founder [ 62 ] [ 63 ] of algebra , was a faculty member of the " House of Wisdom " ( Bait al-Hikma ) in Baghdad, which was established by Al-Mamun. Al-Khwarizmi, who died around 850 AD, wrote more than half a dozen mathematical and astronomical works. [ 54 ] One of al-Khwarizmi's most famous books is entitled Al-jabr wa'l muqabalah or The Compendious Book on Calculation by Completion and Balancing , and it gives an exhaustive account of solving polynomials up to the second degree . [ 64 ] The book also introduced the fundamental concept of " reduction " and "balancing", referring to the transposition of subtracted terms to the other side of an equation, that is, the cancellation of like terms on opposite sides of the equation. This is the operation which Al-Khwarizmi originally described as al-jabr . [ 65 ] The name "algebra" comes from the " al-jabr " in the title of his book.
R. Rashed and Angela Armstrong write:
"Al-Khwarizmi's text can be seen to be distinct not only from the Babylonian tablets , but also from Diophantus ' Arithmetica . It no longer concerns a series of problems to be resolved, but an exposition which starts with primitive terms in which the combinations must give all possible prototypes for equations, which henceforward explicitly constitute the true object of study. On the other hand, the idea of an equation for its own sake appears from the beginning and, one could say, in a generic manner, insofar as it does not simply emerge in the course of solving a problem, but is specifically called on to define an infinite class of problems." [ 66 ]
Al-Jabr is divided into six chapters, each of which deals with a different type of formula. The first chapter of Al-Jabr deals with equations whose squares equal its roots ( a x 2 = b x ) , {\displaystyle \left(ax^{2}=bx\right),} the second chapter deals with squares equal to number ( a x 2 = c ) , {\displaystyle \left(ax^{2}=c\right),} the third chapter deals with roots equal to a number ( b x = c ) , {\displaystyle \left(bx=c\right),} the fourth chapter deals with squares and roots equal a number ( a x 2 + b x = c ) , {\displaystyle \left(ax^{2}+bx=c\right),} the fifth chapter deals with squares and number equal roots ( a x 2 + c = b x ) , {\displaystyle \left(ax^{2}+c=bx\right),} and the sixth and final chapter deals with roots and number equal to squares ( b x + c = a x 2 ) . {\displaystyle \left(bx+c=ax^{2}\right).} [ 67 ]
In Al-Jabr , al-Khwarizmi uses geometric proofs, [ 17 ] he does not recognize the root x = 0 , {\displaystyle x=0,} [ 67 ] and he only deals with positive roots. [ 68 ] He also recognizes that the discriminant must be positive and described the method of completing the square , though he does not justify the procedure. [ 69 ] The Greek influence is shown by Al-Jabr' s geometric foundations [ 57 ] [ 70 ] and by one problem taken from Heron. [ 71 ] He makes use of lettered diagrams but all of the coefficients in all of his equations are specific numbers since he had no way of expressing with parameters what he could express geometrically; although generality of method is intended. [ 17 ]
Al-Khwarizmi most likely did not know of Diophantus's Arithmetica , [ 72 ] which became known to the Arabs sometime before the 10th century. [ 73 ] And even though al-Khwarizmi most likely knew of Brahmagupta's work, Al-Jabr is fully rhetorical with the numbers even being spelled out in words. [ 72 ] So, for example, what we would write as
Diophantus would have written as [ 74 ]
And al-Khwarizmi would have written as [ 74 ]
'Abd al-Hamīd ibn Turk authored a manuscript entitled Logical Necessities in Mixed Equations , which is very similar to al-Khwarzimi's Al-Jabr and was published at around the same time as, or even possibly earlier than, Al-Jabr . [ 73 ] The manuscript gives exactly the same geometric demonstration as is found in Al-Jabr , and in one case the same example as found in Al-Jabr , and even goes beyond Al-Jabr by giving a geometric proof that if the discriminant is negative then the quadratic equation has no solution. [ 73 ] The similarity between these two works has led some historians to conclude that Arabic algebra may have been well developed by the time of al-Khwarizmi and 'Abd al-Hamid. [ 73 ]
Arabic mathematicians treated irrational numbers as algebraic objects. [ 75 ] The Egyptian mathematician Abū Kāmil Shujā ibn Aslam (c. 850–930) was the first to accept irrational numbers in the form of a square root or fourth root as solutions to quadratic equations or as coefficients in an equation. [ 76 ] He was also the first to solve three non-linear simultaneous equations with three unknown variables . [ 77 ]
Al-Karaji (953–1029), also known as Al-Karkhi, was the successor of Abū al-Wafā' al-Būzjānī (940–998) and he discovered the first numerical solution to equations of the form a x 2 n + b x n = c . {\displaystyle ax^{2n}+bx^{n}=c.} [ 78 ] Al-Karaji only considered positive roots. [ 78 ] He is also regarded as the first person to free algebra from geometrical operations and replace them with the type of arithmetic operations which are at the core of algebra today. His work on algebra and polynomials gave the rules for arithmetic operations to manipulate polynomials. The historian of mathematics F. Woepcke, in Extrait du Fakhri, traité d'Algèbre par Abou Bekr Mohammed Ben Alhacan Alkarkhi ( Paris , 1853), praised Al-Karaji for being "the first who introduced the theory of algebraic calculus". Stemming from this, Al-Karaji investigated binomial coefficients and Pascal's triangle . [ 79 ]
Omar Khayyám (c. 1050 – 1123) wrote a book on Algebra that went beyond Al-Jabr to include equations of the third degree. [ 80 ] Omar Khayyám provided both arithmetic and geometric solutions for quadratic equations, but he only gave geometric solutions for general cubic equations since he mistakenly believed that arithmetic solutions were impossible. [ 80 ] His method of solving cubic equations by using intersecting conics had been used by Menaechmus , Archimedes , and Ibn al-Haytham (Alhazen) , but Omar Khayyám generalized the method to cover all cubic equations with positive roots. [ 80 ] He only considered positive roots and he did not go past the third degree. [ 80 ] He also saw a strong relationship between geometry and algebra. [ 80 ]
In the 12th century, Sharaf al-Dīn al-Tūsī (1135–1213) wrote the Al-Mu'adalat ( Treatise on Equations ), which dealt with eight types of cubic equations with positive solutions and five types of cubic equations which may not have positive solutions. He used what would later be known as the " Ruffini - Horner method" to numerically approximate the root of a cubic equation. He also developed the concepts of the maxima and minima of curves in order to solve cubic equations which may not have positive solutions. [ 81 ] He understood the importance of the discriminant of the cubic equation and used an early version of Cardano's formula [ 82 ] to find algebraic solutions to certain types of cubic equations. Some scholars, such as Roshdi Rashed, argue that Sharaf al-Din discovered the derivative of cubic polynomials and realized its significance, while other scholars connect his solution to the ideas of Euclid and Archimedes. [ 83 ]
Sharaf al-Din also developed the concept of a function . [ 84 ] In his analysis of the equation x 3 + d = b x 2 {\displaystyle x^{3}+d=bx^{2}} for example, he begins by changing the equation's form to x 2 ( b − x ) = d {\displaystyle x^{2}(b-x)=d} . He then states that the question of whether the equation has a solution depends on whether or not the "function" on the left side reaches the value d {\displaystyle d} . To determine this, he finds a maximum value for the function. He proves that the maximum value occurs when x = 2 b 3 {\displaystyle \textstyle x={\frac {2b}{3}}} , which gives the functional value 4 b 3 27 {\displaystyle \textstyle {\frac {4b^{3}}{27}}} . Sharaf al-Din then states that if this value is less than d {\displaystyle d} , there are no positive solutions; if it is equal to d {\displaystyle d} , then there is one solution at x = 2 b 3 {\displaystyle \textstyle x={\frac {2b}{3}}} ; and if it is greater than d {\displaystyle d} , then there are two solutions, one between 0 {\displaystyle 0} and 2 b 3 {\displaystyle \textstyle {\frac {2b}{3}}} and one between 2 b 3 {\displaystyle \textstyle {\frac {2b}{3}}} and b {\displaystyle b} . [ 85 ]
In the early 15th century, Jamshīd al-Kāshī developed an early form of Newton's method to numerically solve the equation x P − N = 0 {\displaystyle x^{P}-N=0} to find roots of N {\displaystyle N} . [ 86 ] Al-Kāshī also developed decimal fractions and claimed to have discovered it himself. However, J. Lennart Berggrenn notes that he was mistaken, as decimal fractions were first used five centuries before him by the Baghdadi mathematician Abu'l-Hasan al-Uqlidisi as early as the 10th century. [ 77 ]
Al-Hassār , a mathematician from Morocco specializing in Islamic inheritance jurisprudence during the 12th century, developed the modern symbolic mathematical notation for fractions , where the numerator and denominator are separated by a horizontal bar. This same fractional notation appeared soon after in the work of Fibonacci in the 13th century. [ 87 ] [ failed verification ]
Abū al-Hasan ibn Alī al-Qalasādī (1412–1486) was the last major medieval Arab algebraist, who made the first attempt at creating an algebraic notation since Ibn al-Banna two centuries earlier, who was himself the first to make such an attempt since Diophantus and Brahmagupta in ancient times. [ 88 ] The syncopated notations of his predecessors, however, lacked symbols for mathematical operations . [ 42 ] Al-Qalasadi "took the first steps toward the introduction of algebraic symbolism by using letters in place of numbers" [ 88 ] and by "using short Arabic words, or just their initial letters, as mathematical symbols." [ 88 ]
Just as the death of Hypatia signals the close of the Library of Alexandria as a mathematical center, so does the death of Boethius signal the end of mathematics in the Western Roman Empire . Although there was some work being done at Athens , it came to a close when in 529 the Byzantine emperor Justinian closed the pagan philosophical schools. The year 529 is now taken to be the beginning of the medieval period. Scholars fled the West towards the more hospitable East, particularly towards Persia , where they found haven under King Chosroes and established what might be termed an "Athenian Academy in Exile". [ 89 ] Under a treaty with Justinian, Chosroes would eventually return the scholars to the Eastern Empire . During the Dark Ages, European mathematics was at its nadir with mathematical research consisting mainly of commentaries on ancient treatises; and most of this research was centered in the Byzantine Empire . The end of the medieval period is set as the fall of Constantinople to the Turks in 1453.
The 12th century saw a flood of translations from Arabic into Latin and by the 13th century, European mathematics was beginning to rival the mathematics of other lands. In the 13th century, the solution of a cubic equation by Fibonacci is representative of the beginning of a revival in European algebra.
As the Islamic world was declining after the 15th century, the European world was ascending. And it is here that algebra was further developed.
Modern notation for arithmetic operations was introduced between the end of the 15th century and the beginning of the 16th century by Johannes Widmann and Michael Stifel . At the end of 16th century, François Viète introduced symbols, now called variables , for representing indeterminate or unknown numbers. This created a new algebra consisting of computing with symbolic expressions as if they were numbers.
Another key event in the further development of algebra was the general algebraic solution of the cubic and quartic equations , developed in the mid-16th century. The idea of a determinant was developed by Japanese mathematician Kowa Seki in the 17th century, followed by Gottfried Leibniz ten years later, for the purpose of solving systems of simultaneous linear equations using matrices . Gabriel Cramer also did some work on matrices and determinants in the 18th century.
By tradition, the first unknown variable in an algebraic problem is nowadays represented by the symbol x {\displaystyle {\mathit {x}}} and if there is a second or a third unknown, then these are labeled y {\displaystyle {\mathit {y}}} and z {\displaystyle {\mathit {z}}} respectively. Algebraic x {\displaystyle x} is conventionally printed in italic type to distinguish it from the sign of multiplication.
Mathematical historians [ 90 ] generally agree that the use of x {\displaystyle x} in algebra was introduced by René Descartes and was first published in his treatise La Géométrie (1637). [ 91 ] [ 92 ] In that work, he used letters from the beginning of the alphabet ( a , b , c , … ) {\displaystyle (a,b,c,\ldots )} for known quantities, and letters from the end of the alphabet ( z , y , x , … ) {\displaystyle (z,y,x,\ldots )} for unknowns. [ 93 ] It has been suggested that he later settled on x {\displaystyle x} (in place of z {\displaystyle z} ) for the first unknown because of its relatively greater abundance in the French and Latin typographical fonts of the time. [ 94 ]
Three alternative theories of the origin of algebraic x {\displaystyle x} were suggested in the 19th century: (1) a symbol used by German algebraists and thought to be derived from a cursive letter r , {\displaystyle r,} mistaken for x {\displaystyle x} ; [ 95 ] (2) the numeral 1 with oblique strikethrough ; [ 96 ] and (3) an Arabic/Spanish source (see below). But the Swiss-American historian of mathematics Florian Cajori examined these and found all three lacking in concrete evidence; Cajori credited Descartes as the originator, and described his x , y , {\displaystyle x,y,} and z {\displaystyle z} as "free from tradition[,] and their choice purely arbitrary." [ 97 ]
Nevertheless, the Hispano-Arabic hypothesis continues to have a presence in popular culture today. [ 98 ] It is the claim that algebraic x {\displaystyle x} is the abbreviation of a supposed loanword from Arabic in Old Spanish. The theory originated in 1884 with the German orientalist Paul de Lagarde , shortly after he published his edition of a 1505 Spanish/Arabic bilingual glossary [ 99 ] in which Spanish cosa ("thing") was paired with its Arabic equivalent, شىء ( shay ʔ ), transcribed as xei . (The "sh" sound in Old Spanish was routinely spelled x . {\displaystyle x.} ) Evidently Lagarde was aware that Arab mathematicians, in the "rhetorical" stage of algebra's development, often used that word to represent the unknown quantity. He surmised that "nothing could be more natural" ("Nichts war also natürlicher...") than for the initial of the Arabic word— romanized as the Old Spanish x {\displaystyle x} —to be adopted for use in algebra. [ 100 ] A later reader reinterpreted Lagarde's conjecture as having "proven" the point. [ 101 ] Lagarde was unaware that early Spanish mathematicians used, not a transcription of the Arabic word, but rather its translation in their own language, "cosa". [ 102 ] There is no instance of xei or similar forms in several compiled historical vocabularies of Spanish. [ 103 ] [ 104 ]
Although the mathematical notion of function was implicit in trigonometric and logarithmic tables , which existed in his day, Gottfried Leibniz was the first, in 1692 and 1694, to employ it explicitly, to denote any of several geometric concepts derived from a curve, such as abscissa , ordinate , tangent , chord , and the perpendicular . [ 105 ] In the 18th century, "function" lost these geometrical associations.
Leibniz realized that the coefficients of a system of linear equations could be arranged into an array, now called a matrix , which can be manipulated to find the solution of the system, if any. This method was later called Gaussian elimination . Leibniz also discovered Boolean algebra and symbolic logic , also relevant to algebra.
The ability to do algebra is a skill cultivated in mathematics education . As explained by Andrew Warwick, Cambridge University students in the early 19th century practiced "mixed mathematics", [ 106 ] doing exercises based on physical variables such as space, time, and weight. Over time the association of variables with physical quantities faded away as mathematical technique grew. Eventually mathematics was concerned completely with abstract polynomials , complex numbers , hypercomplex numbers and other concepts. Application to physical situations was then called applied mathematics or mathematical physics , and the field of mathematics expanded to include abstract algebra . For instance, the issue of constructible numbers showed some mathematical limitations, and the field of Galois theory was developed.
The title of "the father of algebra" is frequently credited to the Persian mathematician Al-Khwarizmi , [ 107 ] [ 108 ] [ 109 ] supported by historians of mathematics , such as Carl Benjamin Boyer , [ 107 ] Solomon Gandz and Bartel Leendert van der Waerden . [ 110 ] However, the point is debatable and the title is sometimes credited to the Hellenistic mathematician Diophantus . [ 107 ] [ 111 ] Those who support Diophantus point to the algebra found in Al-Jabr being more elementary than the algebra found in Arithmetica , and Arithmetica being syncopated while Al-Jabr is fully rhetorical. [ 107 ] However, the mathematics historian Kurt Vogel argues against Diophantus holding this title, [ 112 ] as his mathematics was not much more algebraic than that of the ancient Babylonians . [ 113 ]
Those who support Al-Khwarizmi point to the fact that he gave an exhaustive explanation for the algebraic solution of quadratic equations with positive roots, [ 114 ] and was the first to teach algebra in an elementary form and for its own sake, whereas Diophantus was primarily concerned with the theory of numbers . [ 56 ] Al-Khwarizmi also introduced the fundamental concept of "reduction" and "balancing" (which he originally used the term al-jabr to refer to), referring to the transposition of subtracted terms to the other side of an equation, that is, the cancellation of like terms on opposite sides of the equation. [ 65 ] Other supporters of Al-Khwarizmi point to his algebra no longer being concerned "with a series of problems to be resolved, but an exposition which starts with primitive terms in which the combinations must give all possible prototypes for equations, which henceforward explicitly constitute the true object of study." They also point to his treatment of an equation for its own sake and "in a generic manner, insofar as it does not simply emerge in the course of solving a problem, but is specifically called on to define an infinite class of problems". [ 66 ] Victor J. Katz regards Al-Jabr as the first true algebra text that is still extant. [ 115 ]
According to Jeffrey Oaks and Jean Christianidis neither Diophantus nor Al-Khwarizmi should be called "father of algebra". [ 116 ] [ 117 ] Pre-modern algebra was developed and used by merchants and surveyors as part of what Jens Høyrup called "subscientific" tradition. Diophantus used this method of algebra in his book, in particular for indeterminate problems, while Al-Khwarizmi wrote one of the first books in Arabic about this method. [ 37 ] | https://en.wikipedia.org/wiki/History_of_algebra |
An arcade video game is an arcade game where the player's inputs from the game's controllers are processed through electronic or computerized components and displayed to a video device, typically a monitor, all contained within an enclosed arcade cabinet . Arcade video games are often installed alongside other arcade games such as pinball and redemption games at amusement arcades . Up until the late 1990s, arcade video games were the largest [ 1 ] and most technologically advanced [ 2 ] [ 3 ] sector of the video game industry .
The first arcade game, Computer Space , was created by Nolan Bushnell and Ted Dabney , the founders of Atari, Inc. , and released in 1971; the company followed on its success the next year with Pong . The industry grew modestly until the release of Taito 's Space Invaders in 1978 and Namco 's Pac-Man in 1980, creating a golden age of arcade video games that lasted through about 1983. At this point, saturation of the market with arcade games led to a rapid decline in both the arcade game market and arcades to support them. The arcade market began recovering in the mid-1980s, with the help of software conversion kits, new genres such as beat 'em ups , and advanced motion simulator cabinets. There was a resurgence in the early 1990s, with the birth of the fighting game genre with Capcom 's Street Fighter II in 1991 and the emergence of 3D graphics , before arcades began declining in the West during the late 1990s. After several traditional companies closed or migrated to other fields (especially in the West), arcades lost much of their relevance in the West, but have continued to remained popular in Eastern and Southeastern Asia .
Since the early 20th century, skee ball and other pin-based games had been a popular arcade game. The first pinball machines had been introduced in the 1930s but gained a reputation as games of chance and had been banned from many venues from the 1940s through the 1960s. Instead, newer coin-operated electro-mechanical games (EM games), classified as games of skill took their place in amusement arcades by the 1960s. [ 4 ]
Following the arrival of Sega 's EM game Periscope (1966), the arcade industry was experiencing a "technological renaissance" driven by "audio-visual" EM novelty games, establishing the arcades as a healthy environment for the introduction of commercial video games in the early 1970s. [ 5 ] In the late 1960s, a college student Nolan Bushnell had a part-time job at an arcade where he became familiar with EM games through watching customers play and helping to maintain the machinery, while learning how it worked and developing his understanding of how the game business operates. [ 6 ]
While early video games running on computers had been developed as far back as 1950, the first video game to spread beyond a single computer installation, Spacewar! , was developed by students and staff at MIT on a PDP-1 mainframe computer in 1962. As the group that developed it migrated across the country to other schools, they took Spacewar! ' s source code to run on other mainframe machines at those schools. It inspired two different groups to attempt to develop a coin-operated version of the game. [ 7 ]
Around 1970, Nolan Bushnell was invited by a colleague to see Spacewar! running on Stanford University 's PDP-6 computer. Bushnell got the idea of recreating the game on a smaller computer, a Data General Nova , connected to multiple coin-operated terminals. He and fellow Ampex employee Ted Dabney , under the company name Syzygy, worked with Nutting Associates to create Computer Space , the first commercial arcade game, with location tests in August 1971 and production starting in November. [ 4 ] More than 1300 units of the game were sold, and while not as large of a hit game as hoped, it proved the potential for the coin-operated computer game. [ 4 ] At Stanford University , students Bill Pitts and Hugh Tuck used a PDP-11 mainframe to build two prototypes of Galaxy Game , which they demonstrated at the university starting in November 1971, but were unable to turn into a commercial game. [ 7 ]
Bushnell got the idea for his next game after seeing a demonstration of a table tennis game on the Magnavox Odyssey , the first home video game console that was based on the designs of Ralph H. Baer . Deciding to go on their own, Bushnell and Dabney left Nutting and reformed their company as Atari Inc. , and brought on Allan Alcorn to help design an arcade game based on the Odyssey game. After a well-received trial run of a demo unit at Andy Capp's Tavern in San Jose, California in August 1972, [ 8 ] Pong was first released in limited numbers in November 1972 with a wider release by March 1973. Pong was highly successful, with each machine earning over US$40 a day, far greater than most other coin-operated machine at the time. [ 4 ]
With Pong 's success, numerous other coin-operated manufacturers, most who were making electro-mechanical games and pinball machines, attempted to capitalize on the success of arcade games; such companies included Bally Manufacturing , Midway Manufacturing , and Williams Electronics , as well as Japanese companies Taito and Sega . Most took to trying to copy the games that Atari had already made with small alterations, leading to a wave of clones . Bushnell, having failed to patent on the idea, considered these competitors "jackals" but rather than seeking legal action, continued to have Atari devise new games. Separately, Magnavox and Sanders Associates , through which Baer had developed the basics of the Odyssey, sued Atari, among the other manufacturers, for patent violations of the basic patents behind the electronic game concepts. Bushnell opted to settle out of court, negotiating for perpetual licensing rights to Baer's patents for Atari as part of the settlement fee, which allowed Atari to pursue the development of additional arcade games and bringing Pong in a home console form, while Magnavox continued legal against the other manufacturers. It is estimated that Magnavox collected over US$100 million in awards and settlements from these suits over the Baer patents. [ 9 ]
By the end of 1974, more than fifteen companies, both in the United States and Japan, were in the development of arcade games. [ 4 ] A key milestone was the introduction of microprocessor technology to arcade games with Midway's Gun Fight (an adaptation of Taito's Western Gun as released in Japan), which could be programmed more directly rather than relying on the complex interaction of integrated circuitry (IC) chips. [ 4 ]
Video games were still considered to be adult entertainment at this point, and treated as with pinball machines as games of skill, "For Amusement Only", and placed in locations that children would likely not be at such as bar and lounges. However, the same stigma that pinball machines had seen in the prior decades became to appear for video games. Notably, the release of Death Race in 1976, which involved driving over gremlins on screen, drew criticism in the United States for being too violent, and created the first major debate on violence and video games . [ 4 ] [ 10 ]
After the "paddle game" trend came to an end around 1975, the arcade video game industry entered a period of stagnation in the "post paddle game era" over the next several years up until 1977. [ 11 ]
In 1978, Taito released Space Invaders , first in Japan, followed by its North American release. [ 4 ] Among its novel gameplay features that drove its popularity, the game was the first to maintain a persistent high score . [ 12 ] and though simplistic, used an interactive audio system that increased with the pace of the game. [ 13 ] The game was extremely popular in both regions. In Japan, specialty arcades were established that featured only Space Invaders machines, and Taito estimated that they had sold over 100,000 machines in the country alone by the end of 1978, [ 14 ] while in the United States, over 60,000 machines had been sold by 1980. [ 15 ] The game was considered the best-selling video game and highest-grossing "entertainment product" of its time. [ 16 ] Many arcade games since then have been based on "the multiple life , progressively difficult level paradigm" established by Space Invaders . [ 17 ]
Space Invaders led to a string of popular arcade games over the next five years that are considered the "Golden Years" for arcade games. Among these titles include: [ 4 ]
Of these, Pac-Man had an even larger impact on popular culture when it arrived in 1980; the game itself was popular but people took to Pac-Man as a mascot, leading to merchandise and an animated series of the same name in 1982. The game also inspired the Gold-certified song " Pac-Man Fever " by Buckner & Garcia . [ 4 ] Pac-Man sold about 400,000 cabinets overall by 1982. [ 18 ] Donkey Kong was also significant as not only being the first recognized platform game but also bringing a cute, more fantastical concept that was well-founded in Japanese culture but new to Western regions, compared to prior arcade games. Western audiences became accustomed to this level of abstraction, making later Japanese-made arcade games and titles for the Nintendo Entertainment System easily accepted by these players. [ 19 ]
These games, along with numerous others, created video game arcades around the world. The construction boom of shopping malls in the United States during the 1970s and 1980s gave rise to dedicated arcade storefronts such as Craig Singer's Tilt Arcades . [ 20 ] Other arcades were featured in bowling alleys and skating rinks, as well as standalone facilities, such as Bushnell's chain of Chuck E. Cheese pizzerias and arcades. [ 4 ] Time reported in January 1982 that there were over 13,000 arcades in the United States, with the most popular machines bringing in over $400 in profit each day. [ 4 ] Twin Galaxies , an arcade opened by Walter Day in Ottumwa, Iowa , became known for tracking the high scores of many these top video games, and in 1982, Life featured the arcade, Day, and several of the top players at the time in a cover story, bringing the idea of a professional video game player to public consciousness. [ 21 ] [ 4 ] The formation of video game tournaments around arcade games in the 1980s was the predecessor of modern esports . [ 22 ]
Arcade machines also found their way into any area where they could be placed and would be able to draw children or young adults, such as supermarkets and drug stores. [ 4 ] The Golden Age was also buoyed by the growing home console market which had just entered the second generation with the introduction of game cartridges . Atari had been able to license Space Invaders for the Atari 2600 which became the system's killer application . [ 4 ] Similarly, Coleco beat Atari in licensing Donkey Kong from Nintendo, and among other ports, included their conversion of the game as a pack-in for the ColecoVision , which helped to boost sales of the console and compete against the Atari 2600. [ 23 ] Licensing of arcade hits became a major business for the home markets, which in turn spurred further growth in the arcade field. [ 4 ] By 1981, the US arcade game market had an estimated value of $8 billion . [ 24 ]
Jonathan Greenberg of Forbes predicted in early 1981 that Japanese companies would eventually dominate the North American video game industry, as American video game companies were increasingly licensing products from Japanese companies, who in turn were opening up North American branches. [ 25 ] By 1982–1983, Japanese manufacturers had captured a large share of the North American arcade market, which Gene Lipkin of Data East USA partly attributed to Japanese companies having more finances to invest in new ideas. [ 26 ]
Though 1982 was recognized as the height of success of the video game arcade, many in the industry knew the success could not last too long. Walter Day had commented in 1982 that there were "too many arcades" by that point for what was really needed. [ 4 ] Additionally, players required novelty and new games, and thus required older games to be discontinued and replaced with new ones, but not all new games were as successful as those at the height of the Golden Age. Knowing that players were seeking more challenge, game manufacturers designed the newer games to be harder, but this caused less-skilled mainstream players to be turned away. [ 4 ]
Coupled with this was an increased pressure on possible harmful impacts of video games on children. Arcades had taken steps to make their venues as "family fun centers" alleviate some concerns, but parents and activists still saw video games as potentially addictive and leading to aggressive behavior. The U.S. Surgeon General C. Everett Koop spoke in November 1982 about the potential addiction of video game by young children, as part general moral concerns around youth in the early 1980s. These fears not only affected video game arcades, but other places where youth would normally be able to hang out without adult supervision such as shopping malls and skating rinks. There were also reports of increased crime associated with arcades due to lack of adult supervision. Many cities and towns implemented bans on arcades or limiting businesses to only a few machines by the mid-1980s. [ 4 ] [ 20 ] Several of these bans were challenged by arcade owners on First Amendment grounds, asserting video games merits protection as an art form , but the bulk of these cases ruled against arcades, favoring local regulations that were limiting conduct rather than restricting speech. [ 27 ] Further impacting the arcades, the rising popularity of home consoles threatened the arcades, since players did not have to repeatedly spend money to play at arcades when they could play at home. But with the 1983 video game crash which drastically affected the home console market, the arcade market also felt its impact as it was already waning from oversaturation, loss of players, and the moral concerns over video games, all stressed by the early 1980s recession . [ 4 ]
Arcade games became relatively dormant in the United States for a while, declining from the peak financial success of the golden age. [ 4 ] The US arcade industry had declined from a peak of $8.9 billion in 1982 down to $4.5 billion in 1984. [ 28 ] The US arcade video game market was sluggish in 1984, but Sega president Hayao Nakayama was confident that good games "can surely be sold in the U.S. market, if done adequately." Sega announced plans to open a new US subsidiary for early 1985, which Game Machine magazine predicted would "most probably enliven" the American video game business. [ 29 ] Despite the downturn in 1984, John Lotz of Betson Pacific Distributing predicted that another arcade boom could potentially happen by the early 1990s. [ 30 ]
The arcade industry began recovering in 1985 and made a comeback by 1986, [ 31 ] with the arcade industry experiencing several years of growth during the late 1980s. [ 11 ] A major factor in its recovery was the arrival of software conversion kit systems, such as Sega 's Convert-a-Game system, the Atari System 1 , and the Nintendo VS. System , the latter being the Western world's introduction to the Famicom (NES) hardware in 1984, prior to the official release of the NES console; the success of the VS. System in arcades was instrumental to the release and success of the NES in North America. [ 32 ] Other major factors that helped revive arcades were the arrival of popular martial arts action games (including fighting games such as Karate Champ and Yie Ar Kung-Fu , and beat 'em ups such as Kung-Fu Master and Renegade ), [ 31 ] advanced motion simulator games [ 31 ] (such as Sega's "taikan" games including Hang-On , Space Harrier and Out Run ), [ 33 ] [ 11 ] and the resurgence of sports video games (such as Track & Field , Punch-Out and Tehkan World Cup ). [ 34 ]
By 1985, the arcade industry was largely dominated by Japanese manufacturers, with the number of American manufacturers having declined. [ 35 ] [ 36 ] By 1988, annual US arcade video game revenue had increased to $5,500,000,000 (equivalent to $14,600,000,000 in 2024). [ 37 ] However, competition from new home consoles , like the Nintendo Entertainment System (NES) that had revitalized the home video game industry, were drawing players away from the arcades. [ 4 ] After the NES took off in North America, home consoles kept many children at home and under parental supervision, keeping them away from arcades. [ 20 ] The US arcade video game market experienced another decline from 1989. [ 31 ] [ 38 ] RePlay magazine partly attributed the decline to the rise of home consoles following the success of the NES. [ 39 ] In Japan, on the other hand, the arcade market grew while home video game sales declined. [ 40 ] Overall, the worldwide arcade market continued to grow, remaining larger than the console market. [ 1 ]
Various technological advances were made in arcades during this era. Sega's Hang-On , designed by Yu Suzuki and running on the Sega Space Harrier hardware, was the first of Sega's 16-bit " Super Scaler " arcade system boards that pushed pseudo-3D sprite-scaling at high frame rates . [ 41 ] [ 42 ] Hang-On also used a motion-controlled arcade cabinet that included a mounted motorbike -like control unit on a hydraulic system, which the player used to control the game by tilting their body to the left or right, two decades before motion controls became popular on consoles. This game began the "taikan" ("body sensation") trend, the use of motion simulator arcade cabinets in many arcade games of the late 1980s, such as Sega's Space Harrier (1985), Out Run (1986) and After Burner (1987). [ 43 ] SNK also launched its Neo Geo line in 1990 to try to bridge the arcade and home console gap. The launch consisted of the Neo Geo Multi Video System (MVS) arcade system and the Neo Geo Advanced Entertainment System (AES). Both units shared the same game cartridges, with the MVS able to support up to six different games at the same time selectable by the player. Further, players could use a memory card to transfer save game information from the MVS to their home AES and back. [ 44 ] Arcade systems dedicated to flat-shaded 3D polygon graphics also began emerging, with the Namco System 21 used for Winning Run (1988) and the related Atari Games hardware for Hard Drivin' (1989), [ 45 ] as well as the Taito Air System used for amateur flight simulations such as Top Landing (1988) and Air Inferno (1990). [ 46 ] [ 47 ]
One format of arcade video games that briefly expanded during this period were quiz-style or trivia-based arcade games. Besides the other avenues of technical advances, the hardware for arcade machines had shrunk small enough that the core electronics could be fitted into cocktail-style cabinets or half-height bartop or countertop versions, making them ideal for placement in more adult venues. Coupled with waning interest in traditional arcade games due to the 1983 video game crash and the rising popularity of the board game Trivial Pursuit first introduced in 1981, several manufacturers turned to quiz style games to be sold to bars in these smaller formats, including more risque titles. Manufacturers also saw similar opportunities to promote these games for family-oriented entertainment and potential use as educational tools. The rush of arcade-based trivia games waned around 1986 as the general interest in trivia waned, but arcades and other entertainment businesses managed to find ways to keep trivia-style games going within arcades since, often based on multiplayer trivia challenges played out on multiple screens. These trivia games also influenced the creation of trivia games on consoles and computers such as the You Don't Know Jack series of games and Trivia HQ . [ 48 ]
Arcade games gained a resurgence with the introduction of Street Fighter II by Capcom in 1991. The original Street Fighter in 1987 had already introduced a fighting game game format that allowed two players to challenge each other, but the characters were generic combatants. Street Fighter II introduced modern elements to the genre and created the fundamental one-on-one fighting game template, featuring numerous characters with backgrounds and personalities to select from and a wide range of special moves to use. [ 4 ] Street Fighter II sold more than 200,000 cabinets worldwide, [ 49 ] and drew other arcade manufacturers to make similar fighting games, [ 4 ] including Mortal Kombat in 1992, Virtua Fighter in 1993, and Tekken in 1994. [ 4 ] The period was referred to as a "boom" [ 50 ] or "renaissance" for the arcade industry, [ 4 ] [ 51 ] with the success of Street Fighter II drawing comparisons to that of arcade golden age blockbusters Space Invaders and Pac-Man . [ 52 ] [ 51 ]
By 1993, arcade games in the United States were generating an annual revenue of $7,000,000,000 (equivalent to $15,200,000,000 in 2024), larger than both the home video game market ( $6 billion ) as well as the film box office market ( $5 billion ). [ 53 ] Worldwide arcade video game revenue also maintained its lead over consoles. [ 1 ] In 1993, Electronic Games noted that when "historians look back at the world of coin-op during the early 1990s, one of the defining highlights of the video game art form will undoubtedly focus on fighting/martial arts themes" which it described as "the backbone of the industry" at the time. [ 54 ] Mortal Kombat , however, led to further controversy over violence in video games due to its gruesome-looking finishing moves. When the game was ported to home consoles in 1993, it led to U.S. Congressional hearings on violence in video games, which resulted in the formation of the Entertainment Software Ratings Board (ESRB) in 1994 to avoid government oversight in video games. [ 4 ] Despite this, fighting games remained the dominant style of game in arcades through the 1990s.
Another factor that contributed to the arcade "renaissance" was increasingly realistic games, [ 51 ] notably the "3D Revolution" where arcade games made the transition from 2D and pseudo-3D graphics to true real-time 3D polygon graphics , [ 55 ] [ 56 ] largely driven by a technological arms race rivalry between Sega and Namco . [ 57 ] [ 58 ] The Namco System 21 which was originally developed for racing games in the late 1980s was adapted by Namco for new 3D action games in the early 1990s, such as the rail shooters Galaxian 3 (1990) and Solvalou (1991). [ 55 ] Sega responded with the Sega Model 1 , [ 57 ] which further popularized 3D polygons with Sega AM2 games including Virtua Racing (1992) and the fighting game Virtua Fighter (1993), [ 59 ] [ 56 ] which popularized 3D polygon human characters. [ 60 ] Namco then responded with the Namco System 22 , [ 57 ] capable of 3D polygon texture mapping and Gouraud shading , used for Ridge Racer (1993). [ 61 ] The Sega Model 2 took it further with 3D polygon texture filtering , used by 1994 for racers such as Daytona USA , [ 62 ] fighting games such as Virtua Fighter 2 , [ 63 ] and light gun shooters such as Virtua Cop . [ 64 ] [ 65 ] Namco responded with 3D fighters such as Tekken (1994) and 3D light gun shooters such as Time Crisis (1995), [ 55 ] the latter running on the Super System 22 . [ 57 ]
Other arcade manufacturers were also manufacturing 3D arcade hardware by this time, including Midway, Konami , and Taito , [ 66 ] as well as Mesa Logic with light gun shooter Area 51 (1995). [ 67 ] The new, more realistic 3D games gained considerable popularity in arcades, especially in more family-family fun centers. [ 50 ] [ 51 ] Virtual reality (VR) also began appearing in arcades during the early 1990s. The Amusement & Music Operators Association (AMOA) in the United States held its second largest AMOA show ever in 1994, after the 1982 AMOA show. [ 68 ]
Around the mid-1990s, the fifth-generation home consoles, Sega Saturn , PlayStation , and Nintendo 64 , also began offering true 3D graphics, along with improved sound and better 2D graphics than the previous fourth generation of video game consoles . By 1995, personal computers followed, with 3D accelerator cards. While arcade systems such as the Sega Model 3 remained considerably more advanced than home systems in the late 1990s, [ 2 ] [ 3 ] the technological advantage that arcade games had, in their ability to customize and use the latest graphics and sound chips, slowly began narrowing, and the convenience of home games eventually caused a decline in arcade gaming. Sega 's sixth generation console, the Dreamcast , could produce 3D graphics comparable to the Sega NAOMI arcade system in 1998, after which Sega produced more powerful arcade systems such as the Sega NAOMI Multiboard and Sega Hikaru in 1999 and the Sega NAOMI 2 in 2000, before Sega eventually stopped manufacturing expensive proprietary arcade system boards, with their subsequent arcade boards being based on more affordable commercial console or PC components.
During the late 1990s, arcade video games declined, while console games overtook arcade video games for the first time around 1997–1998. Up until then, the arcade video game market had larger revenue than consoles. [ 1 ] In 1997, Konami began releasing a number of music-based games that used unique peripherals to control the game in time to music, including Beatmania and GuitarFreaks , culminating in the 1998 release of Dance Dance Revolution ( DDR ) in Japan, a new style of arcade game that used a dance pad and required players to tap their feet on appropriate squares on the pad in time to notes on screen in synchronization to popular music. DDR later released in the West in 1999, and while it did not enjoy the same popularity in Japan initially, it led the trend of rhythm games in arcades. [ 4 ]
Worldwide arcade video game revenue stabilized in the early 2000s after years of declining revenue in the late 1990s, during which time it had been surpassed in revenue by the console, handheld and PC game industries. [ 1 ] Arcade video games continue to be a thriving industry in Eastern Asian countries such as Japan and China, where arcades are widespread across the region. [ 69 ]
Since the 2000s, arcade games and arcades in the United States have generally had to continue as niche markets to adapt to remain profitable, competition against the allure of home consoles. Most arcades were unable to sustain on operating arcade games alone, and have since added back redemption systems for prizes along with non-arcade games for these, such as Dave & Busters . [ 4 ] Arcade games were developed to try to create experiences that could not be had via home consoles, such as motion simulator games, but their expense and space required was difficult to justify over more traditional games. [ 70 ] The US market has experienced a slight resurgence, with the number of video game arcades across the nation increasing from 2,500 in 2003 to 3,500 in 2008, though this is significantly less than the 10,000 arcades in the early 1980s. As of 2009, a successful arcade game usually sells around 4000 to 6000 units worldwide. [ 71 ] Since around 2018, arcades specializing in virtual reality games have also become popular, allowing players to experience these games without the hardware investment in VR headsets. [ 72 ]
The relative simplicity yet solid gameplay of many of these early games has inspired a new generation of fans who can play them on mobile phones or with emulators such as MAME . Some classic arcade games are reappearing in commercial settings, such as Namco's Ms. Pac-Man/Galaga: Class of 1981 two-in-one game, [ 73 ] or integrated directly into controller hardware (joysticks) with replaceable flash drives storing game ROMs . Arcade classics have also been reappearing as mobile games , with Pac-Man in particular selling over 30 million downloads in the United States by 2010. [ 74 ] Arcade classics also began to appear on replica multi-game arcade machines for home users, using emulation on modern hardware. [ 75 ]
In the Japanese gaming industry, arcades have remained popular since the 2000s. Much of the consistent popularity and growing industry is due to several factors such as support for continued innovation and that developers of machines own the arcades. Additionally, Japan arcade machines are notably more unique as to US machines, where Japanese arcades can offer experiences that players could not get at home. This is constant throughout Japanese arcade history. [ 76 ] As of 2009, out of Japan's US$20 billion gaming market, US$6 billion of that amount is generated from arcades, which represent the largest sector of the Japanese video game market, followed by home console games and mobile games at US$3.5 billion and US$2 billion, respectively. [ 77 ] According to in 2005, arcade ownership and operation accounted for a majority of Namco 's for example. [ 78 ] With considerable withdrawal from the arcade market from companies such as Capcom , Sega became the strongest player in the arcade market with 60% marketshare in 2006. [ 79 ] Despite the global decline of arcades, Japanese companies hit record revenue for three consecutive years during this period. [ 80 ] However, due to the country's economic recession , the Japanese arcade industry has also been steadily declining, from ¥ 702.9 billion (US$8.7 billion) in 2007 to ¥504.3 billion (US$6.2 billion) in 2010. [ 81 ] In 2013, estimation of revenue is ¥470 billion. [ 81 ]
The layout of an arcade in Japan greatly differs from an arcade in America. The arcades of Japan are multi-floor complexes (often taking up entire buildings), split into sections by game types. On the ground level the arcade typically hosts physically demanding games that draw crowds of onlookers, like music rhythm games. Another floor is often a maze of multi-player games and battle simulators. These multi-player games often have online connectivity tracking rankings and reputation of each player; top players are revered and respected in arcades. The top floor of the arcade is typically for rewards where Players can trade credits or tickets for prizes. [ 82 ]
In the Japanese market, network and card features introduced by Virtua Fighter 4 and World Club Champion Football , and novelty cabinets such as Gundam Pod machines have caused revitalizations in arcade profitability in Japan. The reason for the continued popularity of arcades in comparison to the west, are heavy population density and an infrastructure similar to casino facilities.
Former rivals in the Japanese arcade industry, Konami , Taito , Bandai Namco Entertainment and Sega , collaborated during the period. [ 83 ] Approaching the end of the 2010s, the typical business of the Japanese arcade shifted further as arcade video games were less predominant, accounting for only 13% of revenue in arcades in 2017, while redemption games like claw crane machines were the most popular. By 2019, only about four thousand arcades remained in Japan, down from the height of 22,000 in 1989. [ 84 ]
The impact of the COVID-19 pandemic from March 2020 onward on arcades financially harmed many arcades that were still operating. In Japan, arcades did not qualify for funding to recover from lost revenue from the Japanese government. In the wake of the pandemic, several long-standing arcades were forced to close; notably, Sega sold off most of its arcade business. [ 84 ] Financial analysis firm Teikoku Databank reported in 2024 that they estimated that over 8000 arcades had closed in the previous decade, with arcade games being shifted away in favor of redemption games. [ 85 ] Large game companies view the remaining arcade businesses "as a rapidly sinking ship", and regard future investment in arcade titles as "fruitless". The decline was experienced strongly among gambling oriented games such as Pachislot. [ 86 ] A UK arcade owner described a similar situation there, saying that "All arcades are either closed or suffering hardships." [ 87 ] | https://en.wikipedia.org/wiki/History_of_arcade_video_games |
The history of artificial intelligence ( AI ) began in antiquity , with myths, stories, and rumors of artificial beings endowed with intelligence or consciousness by master craftsmen. The study of logic and formal reasoning from antiquity to the present led directly to the invention of the programmable digital computer in the 1940s, a machine based on abstract mathematical reasoning. This device and the ideas behind it inspired scientists to begin discussing the possibility of building an electronic brain .
The field of AI research was founded at a workshop held on the campus of Dartmouth College in 1956. [ 1 ] Attendees of the workshop became the leaders of AI research for decades. Many of them predicted that machines as intelligent as humans would exist within a generation. The U.S. government provided millions of dollars with the hope of making this vision come true. [ 2 ]
Eventually, it became obvious that researchers had grossly underestimated the difficulty of this feat. [ 3 ] In 1974, criticism from James Lighthill and pressure from the U.S.A. Congress led the U.S. and British Governments to stop funding undirected research into artificial intelligence. Seven years later, a visionary initiative by the Japanese Government and the success of expert systems reinvigorated investment in AI, and by the late 1980s, the industry had grown into a billion-dollar enterprise. However, investors' enthusiasm waned in the 1990s, and the field was criticized in the press and avoided by industry (a period known as an " AI winter "). Nevertheless, research and funding continued to grow under other names.
In the early 2000s, machine learning was applied to a wide range of problems in academia and industry. The success was due to the availability of powerful computer hardware, the collection of immense data sets, and the application of solid mathematical methods. Soon after, deep learning proved to be a breakthrough technology, eclipsing all other methods. The transformer architecture debuted in 2017 and was used to produce impressive generative AI applications, amongst other use cases.
Investment in AI boomed in the 2020s. The recent AI boom, initiated by the development of transformer architecture, led to the rapid scaling and public releases of large language models (LLMs) like ChatGPT . These models exhibit human-like traits of knowledge, attention, and creativity, and have been integrated into various sectors, fueling exponential investment in AI. However, concerns about the potential risks and ethical implications of advanced AI have also emerged, prompting debate about the future of AI and its impact on society.
In Greek mythology , Talos was a creature made of bronze who acted as guardian for the island of Crete . He would throw boulders at the ships of invaders and would complete 3 circuits around the island's perimeter daily. [ 4 ] According to pseudo-Apollodorus ' Bibliotheke , Hephaestus forged Talos with the aid of a cyclops and presented the automaton as a gift to Minos . [ 5 ] In the Argonautica , Jason and the Argonauts defeated Talos by removing a plug near his foot, causing the vital ichor to flow out from his body and rendering him lifeless. [ 6 ]
Pygmalion was a legendary king and sculptor of Greek mythology, famously represented in Ovid 's Metamorphoses . In the 10th book of Ovid's narrative poem, Pygmalion becomes disgusted with women when he witnesses the way in which the Propoetides prostitute themselves. Despite this, he makes offerings at the temple of Venus asking the goddess to bring to him a woman just like a statue he carved. [ 7 ]
In Of the Nature of Things , the Swiss alchemist Paracelsus describes a procedure that he claims can fabricate an "artificial man". By placing the "sperm of a man" in horse dung, and feeding it the "Arcanum of Mans blood" after 40 days, the concoction will become a living infant. [ 8 ]
The earliest written account regarding golem-making is found in the writings of Eleazar ben Judah of Worms in the early 13th century. [ 9 ] During the Middle Ages, it was believed that the animation of a Golem could be achieved by insertion of a piece of paper with any of God's names on it, into the mouth of the clay figure. [ 10 ] Unlike legendary automata like Brazen Heads , [ 11 ] a Golem was unable to speak. [ 12 ]
Takwin , the artificial creation of life, was a frequent topic of Ismaili alchemical manuscripts, especially those attributed to Jabir ibn Hayyan . Islamic alchemists attempted to create a broad range of life through their work, ranging from plants to animals. [ 13 ]
In Faust: The Second Part of the Tragedy by Johann Wolfgang von Goethe , an alchemically fabricated homunculus , destined to live forever in the flask in which he was made, endeavors to be born into a full human body. Upon the initiation of this transformation, however, the flask shatters and the homunculus dies. [ 14 ]
By the 19th century, ideas about artificial men and thinking machines became a popular theme in fiction. Notable works like Mary Shelley 's Frankenstein and Karel Čapek 's R.U.R. (Rossum's Universal Robots) [ 15 ] explored the concept of artificial life. Speculative essays, such as Samuel Butler 's " Darwin among the Machines ", [ 16 ] and Edgar Allan Poe's " Maelzel's Chess Player " [ 17 ] reflected society's growing interest in machines with artificial intelligence. AI remains a common topic in science fiction today. [ 18 ]
Realistic humanoid automata were built by craftsman from many civilizations, including Yan Shi , [ 19 ] Hero of Alexandria , [ 20 ] Al-Jazari , [ 21 ] Haroun al-Rashid , [ 22 ] Jacques de Vaucanson , [ 23 ] [ 24 ] Leonardo Torres y Quevedo , [ 25 ] Pierre Jaquet-Droz and Wolfgang von Kempelen . [ 26 ] [ 27 ]
The oldest known automata were the sacred statues of ancient Egypt and Greece . [ 28 ] [ 29 ] The faithful believed that craftsman had imbued these figures with very real minds, capable of wisdom and emotion— Hermes Trismegistus wrote that "by discovering the true nature of the gods, man has been able to reproduce it". [ 30 ] English scholar Alexander Neckham asserted that the Ancient Roman poet Virgil had built a palace with automaton statues. [ 31 ]
During the early modern period, these legendary automata were said to possess the magical ability to answer questions put to them. The late medieval alchemist and proto-Protestant Roger Bacon was purported to have fabricated a brazen head , having developed a legend of having been a wizard. [ 32 ] [ 33 ] These legends were similar to the Norse myth of the Head of Mímir . According to legend, Mímir was known for his intellect and wisdom, and was beheaded in the Æsir-Vanir War . Odin is said to have "embalmed" the head with herbs and spoke incantations over it such that Mímir's head remained able to speak wisdom to Odin. Odin then kept the head near him for counsel. [ 34 ]
Artificial intelligence is based on the assumption that the process of human thought can be mechanized. The study of mechanical—or "formal"—reasoning has a long history. Chinese , Indian and Greek philosophers all developed structured methods of formal deduction by the first millennium BCE. Their ideas were developed over the centuries by philosophers such as Aristotle (who gave a formal analysis of the syllogism ), [ 35 ] Euclid (whose Elements was a model of formal reasoning), al-Khwārizmī (who developed algebra and gave his name to the word algorithm ) and European scholastic philosophers such as William of Ockham and Duns Scotus . [ 36 ]
Spanish philosopher Ramon Llull (1232–1315) developed several logical machines devoted to the production of knowledge by logical means; [ 37 ] [ 38 ] Llull described his machines as mechanical entities that could combine basic and undeniable truths by simple logical operations, produced by the machine by mechanical meanings, in such ways as to produce all the possible knowledge. [ 39 ] Llull's work had a great influence on Gottfried Leibniz , who redeveloped his ideas. [ 40 ]
In the 17th century, Leibniz , Thomas Hobbes and René Descartes explored the possibility that all rational thought could be made as systematic as algebra or geometry. [ 41 ] Hobbes famously wrote in Leviathan : "For reason ... is nothing but reckoning , that is adding and subtracting". [ 42 ] Leibniz envisioned a universal language of reasoning, the characteristica universalis , which would reduce argumentation to calculation so that "there would be no more need of disputation between two philosophers than between two accountants. For it would suffice to take their pencils in hand, down to their slates, and to say each other (with a friend as witness, if they liked): Let us calculate ." [ 43 ] These philosophers had begun to articulate the physical symbol system hypothesis that would become the guiding faith of AI research.
The study of mathematical logic provided the essential breakthrough that made artificial intelligence seem plausible. The foundations had been set by such works as Boole 's The Laws of Thought and Frege 's Begriffsschrift . [ 44 ] Building on Frege 's system, Russell and Whitehead presented a formal treatment of the foundations of mathematics in their masterpiece, the Principia Mathematica in 1913. Inspired by Russell 's success, David Hilbert challenged mathematicians of the 1920s and 30s to answer this fundamental question: "can all of mathematical reasoning be formalized?" [ 36 ] His question was answered by Gödel 's incompleteness proof , [ 45 ] Turing 's machine [ 45 ] and Church 's Lambda calculus . [ a ]
Their answer was surprising in two ways. First, they proved that there were, in fact, limits to what mathematical logic could accomplish. But second (and more important for AI) their work suggested that, within these limits, any form of mathematical reasoning could be mechanized. The Church-Turing thesis implied that a mechanical device, shuffling symbols as simple as 0 and 1 , could imitate any conceivable process of mathematical deduction. [ 45 ] The key insight was the Turing machine —a simple theoretical construct that captured the essence of abstract symbol manipulation. [ 48 ] This invention would inspire a handful of scientists to begin discussing the possibility of thinking machines.
Calculating machines were designed or built in antiquity and throughout history by many people, including Gottfried Leibniz , [ 38 ] [ 49 ] Joseph Marie Jacquard , [ 50 ] Charles Babbage , [ 50 ] [ 51 ] Percy Ludgate , [ 52 ] Leonardo Torres Quevedo , [ 53 ] Vannevar Bush , [ 54 ] and others. Ada Lovelace speculated that Babbage's machine was "a thinking or ... reasoning machine", but warned "It is desirable to guard against the possibility of exaggerated ideas that arise as to the powers" of the machine. [ 55 ] [ 56 ]
The first modern computers were the massive machines of the Second World War (such as Konrad Zuse 's Z3 , Alan Turing 's Heath Robinson and Colossus , Atanasoff and Berry 's ABC and ENIAC at the University of Pennsylvania ). [ 57 ] ENIAC was based on the theoretical foundation laid by Alan Turing and developed by John von Neumann , [ 58 ] and proved to be the most influential. [ 57 ]
The earliest research into thinking machines was inspired by a confluence of ideas that became prevalent in the late 1930s, 1940s, and early 1950s. Recent research in neurology had shown that the brain was an electrical network of neurons that fired in all-or-nothing pulses. Norbert Wiener 's cybernetics described control and stability in electrical networks. Claude Shannon 's information theory described digital signals (i.e., all-or-nothing signals). Alan Turing 's theory of computation showed that any form of computation could be described digitally. The close relationship between these ideas suggested that it might be possible to construct an "electronic brain".
In the 1940s and 50s, a handful of scientists from a variety of fields (mathematics, psychology, engineering, economics and political science) explored several research directions that would be vital to later AI research. [ 59 ] Alan Turing was among the first people to seriously investigate the theoretical possibility of "machine intelligence". [ 60 ] The field of " artificial intelligence research " was founded as an academic discipline in 1956. [ 61 ]
In 1950 Turing published a landmark paper " Computing Machinery and Intelligence ", in which he speculated about the possibility of creating machines that think. [ 63 ] [ b ] In the paper, he noted that "thinking" is difficult to define and devised his famous Turing Test : If a machine could carry on a conversation (over a teleprinter ) that was indistinguishable from a conversation with a human being, then it was reasonable to say that the machine was "thinking". [ 64 ] This simplified version of the problem allowed Turing to argue convincingly that a "thinking machine" was at least plausible and the paper answered all the most common objections to the proposition. [ 65 ] The Turing Test was the first serious proposal in the philosophy of artificial intelligence .
Donald Hebb was a Canadian psychologist whose work laid the foundation for modern neuroscience, particularly in understanding learning, memory, and neural plasticity. His most influential book, The Organization of Behavior (1949), introduced the concept of Hebbian learning, often summarized as "cells that fire together wire together." [ 66 ]
Hebb began formulating the foundational ideas for this book in the early 1940s, particularly during his time at the Yerkes Laboratories of Primate Biology from 1942 to 1947. He made extensive notes between June 1944 and March 1945 and sent a complete draft to his mentor Karl Lashley in 1946. The manuscript for The Organization of Behavior wasn’t published until 1949. The delay was due to various factors, including World War II and shifts in academic focus. By the time it was published, several of his peers had already published related ideas, making Hebb’s work seem less groundbreaking at first glance. However, his synthesis of psychological and neurophysiological principles became a cornerstone of neuroscience and machine learning. [ 67 ] [ 68 ]
Walter Pitts and Warren McCulloch analyzed networks of idealized artificial neurons and showed how they might perform simple logical functions in 1943. They were the first to describe what later researchers would call a neural network . [ 69 ] The paper was influenced by Turing's paper ' On Computable Numbers ' from 1936 using similar two-state boolean 'neurons', but was the first to apply it to neuronal function. [ 60 ] One of the students inspired by Pitts and McCulloch was Marvin Minsky who was a 24-year-old graduate student at the time. In 1951 Minsky and Dean Edmonds built the first neural net machine, the SNARC . [ 70 ] Minsky would later become one of the most important leaders and innovators in AI.
Experimental robots such as W. Grey Walter 's turtles and the Johns Hopkins Beast , were built in the 1950s. These machines did not use computers, digital electronics or symbolic reasoning; they were controlled entirely by analog circuitry. [ 71 ]
In 1951, using the Ferranti Mark 1 machine of the University of Manchester , Christopher Strachey wrote a checkers program [ 72 ] and Dietrich Prinz wrote one for chess. [ 73 ] Arthur Samuel 's checkers program, the subject of his 1959 paper "Some Studies in Machine Learning Using the Game of Checkers", eventually achieved sufficient skill to challenge a respectable amateur. [ 74 ] Samuel's program was among the first uses of what would later be called machine learning . [ 75 ] Game AI would continue to be used as a measure of progress in AI throughout its history.
When access to digital computers became possible in the mid-fifties, a few scientists instinctively recognized that a machine that could manipulate numbers could also manipulate symbols and that the manipulation of symbols could well be the essence of human thought. This was a new approach to creating thinking machines. [ 76 ] [ 77 ]
In 1955, Allen Newell and future Nobel Laureate Herbert A. Simon created the " Logic Theorist ", with help from J. C. Shaw . The program would eventually prove 38 of the first 52 theorems in Russell and Whitehead's Principia Mathematica , and find new and more elegant proofs for some. [ 78 ] Simon said that they had "solved the venerable mind/body problem , explaining how a system composed of matter can have the properties of mind." [ 79 ] [ c ] The symbolic reasoning paradigm they introduced would dominate AI research and funding until the middle 90s, as well as inspire the cognitive revolution .
The Dartmouth workshop of 1956 was a pivotal event that marked the formal inception of AI as an academic discipline. [ 61 ] It was organized by Marvin Minsky and John McCarthy , with the support of two senior scientists Claude Shannon and Nathan Rochester of IBM . The proposal for the conference stated they intended to test the assertion that "every aspect of learning or any other feature of intelligence can be so precisely described that a machine can be made to simulate it". [ 80 ] [ d ] The term "Artificial Intelligence" was introduced by John McCarthy at the workshop. [ e ] The participants included Ray Solomonoff , Oliver Selfridge , Trenchard More , Arthur Samuel , Allen Newell and Herbert A. Simon , all of whom would create important programs during the first decades of AI research. [ 86 ] [ f ] At the workshop Newell and Simon debuted the "Logic Theorist". [ 87 ] The workshop was the moment that AI gained its name, its mission, its first major success and its key players, and is widely considered the birth of AI. [ g ]
In the autumn of 1956, Newell and Simon also presented the Logic Theorist at a meeting of the Special Interest Group in Information Theory at the Massachusetts Institute of Technology (MIT). At the same meeting, Noam Chomsky discussed his generative grammar , and George Miller described his landmark paper " The Magical Number Seven, Plus or Minus Two ". Miller wrote "I left the symposium with a conviction, more intuitive than rational, that experimental psychology, theoretical linguistics, and the computer simulation of cognitive processes were all pieces from a larger whole." [ 89 ] [ 57 ]
This meeting was the beginning of the " cognitive revolution "—an interdisciplinary paradigm shift in psychology, philosophy, computer science and neuroscience. It inspired the creation of the sub-fields of symbolic artificial intelligence , generative linguistics , cognitive science , cognitive psychology , cognitive neuroscience and the philosophical schools of computationalism and functionalism . All these fields used related tools to model the mind and results discovered in one field were relevant to the others.
The cognitive approach allowed researchers to consider "mental objects" like thoughts, plans, goals, facts or memories, often analyzed using high level symbols in functional networks. These objects had been forbidden as "unobservable" by earlier paradigms such as behaviorism . [ h ] Symbolic mental objects would become the major focus of AI research and funding for the next several decades.
The programs developed in the years after the Dartmouth Workshop were, to most people, simply "astonishing": [ i ] computers were solving algebra word problems, proving theorems in geometry and learning to speak English. Few at the time would have believed that such "intelligent" behavior by machines was possible at all. [ 93 ] [ 94 ] [ 92 ] Researchers expressed an intense optimism in private and in print, predicting that a fully intelligent machine would be built in less than 20 years. [ 95 ] Government agencies like the Defense Advanced Research Projects Agency (DARPA, then known as "ARPA") poured money into the field. [ 96 ] Artificial Intelligence laboratories were set up at a number of British and US universities in the latter 1950s and early 1960s. [ 60 ]
There were many successful programs and new directions in the late 50s and 1960s. Among the most influential were these:
Many early AI programs used the same basic algorithm . To achieve some goal (like winning a game or proving a theorem), they proceeded step by step towards it (by making a move or a deduction) as if searching through a maze, backtracking whenever they reached a dead end. [ 97 ] The principal difficulty was that, for many problems, the number of possible paths through the "maze" was astronomical (a situation known as a " combinatorial explosion "). Researchers would reduce the search space by using heuristics that would eliminate paths that were unlikely to lead to a solution. [ 98 ]
Newell and Simon tried to capture a general version of this algorithm in a program called the " General Problem Solver ". [ 99 ] [ 100 ] Other "searching" programs were able to accomplish impressive tasks like solving problems in geometry and algebra, such as Herbert Gelernter 's Geometry Theorem Prover (1958) [ 101 ] and Symbolic Automatic Integrator (SAINT), written by Minsky's student James Slagle in 1961. [ 102 ] [ 103 ] Other programs searched through goals and subgoals to plan actions , like the STRIPS system developed at Stanford to control the behavior of the robot Shakey . [ 104 ]
An important goal of AI research is to allow computers to communicate in natural languages like English. An early success was Daniel Bobrow 's program STUDENT , which could solve high school algebra word problems. [ 105 ]
A semantic net represents concepts (e.g. "house", "door") as nodes, and relations among concepts as links between the nodes (e.g. "has-a"). The first AI program to use a semantic net was written by Ross Quillian [ 106 ] and the most successful (and controversial) version was Roger Schank 's Conceptual dependency theory . [ 107 ]
Joseph Weizenbaum 's ELIZA could carry out conversations that were so realistic that users occasionally were fooled into thinking they were communicating with a human being and not a computer program (see ELIZA effect ). But in fact, ELIZA simply gave a canned response or repeated back what was said to it, rephrasing its response with a few grammar rules. ELIZA was the first chatbot . [ 108 ] [ 109 ]
In the late 60s, Marvin Minsky and Seymour Papert of the MIT AI Laboratory proposed that AI research should focus on artificially simple situations known as micro-worlds. [ j ] They pointed out that in successful sciences like physics, basic principles were often best understood using simplified models like frictionless planes or perfectly rigid bodies. Much of the research focused on a " blocks world ," which consists of colored blocks of various shapes and sizes arrayed on a flat surface. [ 110 ]
This paradigm led to innovative work in machine vision by Gerald Sussman , Adolfo Guzman, David Waltz (who invented " constraint propagation "), and especially Patrick Winston . At the same time, Minsky and Papert built a robot arm that could stack blocks, bringing the blocks world to life. Terry Winograd 's SHRDLU could communicate in ordinary English sentences about the micro-world, plan operations and execute them. [ 110 ]
In the 1960s funding was primarily directed towards laboratories researching symbolic AI , however several people still pursued research in neural networks.
The perceptron , a single-layer neural network was introduced in 1958 by Frank Rosenblatt [ 111 ] (who had been a schoolmate of Marvin Minsky at the Bronx High School of Science ). [ 112 ] Like most AI researchers, he was optimistic about their power, predicting that a perceptron "may eventually be able to learn, make decisions, and translate languages." [ 113 ] Rosenblatt was primarily funded by Office of Naval Research . [ 114 ]
Bernard Widrow and his student Ted Hoff built ADALINE (1960) and MADALINE (1962), which had up to 1000 adjustable weights. [ 115 ] [ 116 ] A group at Stanford Research Institute led by Charles A. Rosen and Alfred E. (Ted) Brain built two neural network machines named MINOS I (1960) and II (1963), mainly funded by U.S. Army Signal Corps . MINOS II [ 117 ] had 6600 adjustable weights, [ 118 ] and was controlled with an SDS 910 computer in a configuration named MINOS III (1968), which could classify symbols on army maps, and recognize hand-printed characters on Fortran coding sheets . [ 119 ] [ 120 ] Most of neural network research during this early period involved building and using bespoke hardware, rather than simulation on digital computers. [ k ]
However, partly due to lack of results and partly due to competition from symbolic AI research, the MINOS project ran out of funding in 1966. Rosenblatt failed to secure continued funding in the 1960s. [ 121 ] In 1969, research came to a sudden halt with the publication of Minsky and Papert's 1969 book Perceptrons . [ 122 ] It suggested that there were severe limitations to what perceptrons could do and that Rosenblatt's predictions had been grossly exaggerated. The effect of the book was that virtually no research was funded in connectionism for 10 years. [ 123 ] The competition for government funding ended with the victory of symbolic AI approaches over neural networks. [ 120 ] [ 121 ]
Minsky (who had worked on SNARC ) became a staunch objector to pure connectionist AI. Widrow (who had worked on ADALINE ) turned to adaptive signal processing. The SRI group (which worked on MINOS) turned to symbolic AI and robotics. [ 120 ] [ 121 ]
The main problem was the inability to train multilayered networks (versions of backpropagation had already been used in other fields but it was unknown to these researchers). [ 124 ] [ 123 ] The AI community became aware of backpropogation in the 80s, [ 125 ] and, in the 21st century, neural networks would become enormously successful, fulfilling all of Rosenblatt's optimistic predictions. Rosenblatt did not live to see this, however, as he died in a boating accident in 1971. [ 126 ]
The first generation of AI researchers made these predictions about their work:
In June 1963, MIT received a $2.2 million grant from the newly created Advanced Research Projects Agency (ARPA, later known as DARPA ). The money was used to fund project MAC which subsumed the "AI Group" founded by Minsky and McCarthy five years earlier. DARPA continued to provide $3 million each year until the 70s. [ 133 ] DARPA made similar grants to Newell and Simon's program at Carnegie Mellon University and to Stanford University 's AI Lab , founded by John McCarthy in 1963. [ 134 ] Another important AI laboratory was established at Edinburgh University by Donald Michie in 1965. [ 135 ] These four institutions would continue to be the main centers of AI research and funding in academia for many years. [ 136 ] [ m ]
The money was given with few strings attached: J. C. R. Licklider , then the director of ARPA, believed that his organization should "fund people, not projects!" and allowed researchers to pursue whatever directions might interest them. [ 138 ] This created a freewheeling atmosphere at MIT that gave birth to the hacker culture , [ 139 ] but this "hands off" approach did not last.
In the 1970s, AI was subject to critiques and financial setbacks. AI researchers had failed to appreciate the difficulty of the problems they faced. Their tremendous optimism had raised public expectations impossibly high, and when the promised results failed to materialize, funding targeted at AI was severely reduced. [ 140 ] The lack of success indicated the techniques being used by AI researchers at the time were insufficient to achieve their goals. [ 141 ] [ 142 ]
These setbacks did not affect the growth and progress of the field, however. The funding cuts only impacted a handful of major laboratories [ 143 ] and the critiques were largely ignored. [ 144 ] General public interest in the field continued to grow, [ 143 ] the number of researchers increased dramatically, [ 143 ] and new ideas were explored in logic programming , commonsense reasoning and many other areas. Historian Thomas Haigh argued in 2023 that there was no winter, [ 143 ] and AI researcher Nils Nilsson described this period as the most "exciting" time to work in AI. [ 145 ]
In the early seventies, the capabilities of AI programs were limited. Even the most impressive could only handle trivial versions of the problems they were supposed to solve; [ n ] all the programs were, in some sense, "toys". [ 147 ] AI researchers had begun to run into several limits that would be only conquered decades later, and others that still stymie the field in the 2020s:
The agencies which funded AI research, such as the British government , DARPA and the National Research Council (NRC) became frustrated with the lack of progress and eventually cut off almost all funding for undirected AI research. The pattern began in 1966 when the Automatic Language Processing Advisory Committee (ALPAC) report criticized machine translation efforts. After spending $20 million, the NRC ended all support. [ 157 ] In 1973, the Lighthill report on the state of AI research in the UK criticized the failure of AI to achieve its "grandiose objectives" and led to the dismantling of AI research in that country. [ 158 ] (The report specifically mentioned the combinatorial explosion problem as a reason for AI's failings.) [ 142 ] [ 146 ] [ s ] DARPA was deeply disappointed with researchers working on the Speech Understanding Research program at CMU and canceled an annual grant of $3 million. [ 160 ] [ t ]
Hans Moravec blamed the crisis on the unrealistic predictions of his colleagues. "Many researchers were caught up in a web of increasing exaggeration." [ 161 ] [ u ] However, there was another issue: since the passage of the Mansfield Amendment in 1969, DARPA had been under increasing pressure to fund "mission-oriented direct research, rather than basic undirected research". Funding for the creative, freewheeling exploration that had gone on in the 60s would not come from DARPA, which instead directed money at specific projects with clear objectives, such as autonomous tanks and battle management systems. [ 162 ] [ v ]
The major laboratories (MIT, Stanford, CMU and Edinburgh) had been receiving generous support from their governments, and when it was withdrawn, these were the only places that were seriously impacted by the budget cuts. The thousands of researchers outside these institutions and the many more thousands that were joining the field were unaffected. [ 143 ]
Several philosophers had strong objections to the claims being made by AI researchers. One of the earliest was John Lucas , who argued that Gödel's incompleteness theorem showed that a formal system (such as a computer program) could never see the truth of certain statements, while a human being could. [ 164 ] Hubert Dreyfus ridiculed the broken promises of the 1960s and critiqued the assumptions of AI, arguing that human reasoning actually involved very little "symbol processing" and a great deal of embodied , instinctive , unconscious " know how ". [ w ] [ 166 ] John Searle 's Chinese Room argument, presented in 1980, attempted to show that a program could not be said to "understand" the symbols that it uses (a quality called " intentionality "). If the symbols have no meaning for the machine, Searle argued, then the machine can not be described as "thinking". [ 167 ]
These critiques were not taken seriously by AI researchers. Problems like intractability and commonsense knowledge seemed much more immediate and serious. It was unclear what difference " know how " or " intentionality " made to an actual computer program. MIT's Minsky said of Dreyfus and Searle "they misunderstand, and should be ignored." [ 168 ] Dreyfus, who also taught at MIT , was given a cold shoulder: he later said that AI researchers "dared not be seen having lunch with me." [ 169 ] Joseph Weizenbaum , the author of ELIZA , was also an outspoken critic of Dreyfus' positions, but he "deliberately made it plain that [his AI colleagues' treatment of Dreyfus] was not the way to treat a human being," [ x ] and was unprofessional and childish. [ 171 ]
Weizenbaum began to have serious ethical doubts about AI when Kenneth Colby wrote a "computer program which can conduct psychotherapeutic dialogue" based on ELIZA. [ 172 ] [ 173 ] [ y ] Weizenbaum was disturbed that Colby saw a mindless program as a serious therapeutic tool. A feud began, and the situation was not helped when Colby did not credit Weizenbaum for his contribution to the program. In 1976, Weizenbaum published Computer Power and Human Reason which argued that the misuse of artificial intelligence has the potential to devalue human life. [ 175 ]
Logic was introduced into AI research as early as 1958, by John McCarthy in his Advice Taker proposal. [ 176 ] [ 101 ] In 1963, J. Alan Robinson had discovered a simple method to implement deduction on computers, the resolution and unification algorithm. [ 101 ] However, straightforward implementations, like those attempted by McCarthy and his students in the late 1960s, were especially intractable: the programs required astronomical numbers of steps to prove simple theorems. [ 176 ] [ 177 ] A more fruitful approach to logic was developed in the 1970s by Robert Kowalski at the University of Edinburgh , and soon this led to the collaboration with French researchers Alain Colmerauer and Philippe Roussel [ fr ] who created the successful logic programming language Prolog . [ 178 ] Prolog uses a subset of logic ( Horn clauses , closely related to " rules " and " production rules ") that permit tractable computation. Rules would continue to be influential, providing a foundation for Edward Feigenbaum 's expert systems and the continuing work by Allen Newell and Herbert A. Simon that would lead to Soar and their unified theories of cognition . [ 179 ]
Critics of the logical approach noted, as Dreyfus had, that human beings rarely used logic when they solved problems. Experiments by psychologists like Peter Wason , Eleanor Rosch , Amos Tversky , Daniel Kahneman and others provided proof. [ z ] McCarthy responded that what people do is irrelevant. He argued that what is really needed are machines that can solve problems—not machines that think as people do. [ aa ]
Among the critics of McCarthy's approach were his colleagues across the country at MIT . Marvin Minsky , Seymour Papert and Roger Schank were trying to solve problems like "story understanding" and "object recognition" that required a machine to think like a person. In order to use ordinary concepts like "chair" or "restaurant" they had to make all the same illogical assumptions that people normally made. Unfortunately, imprecise concepts like these are hard to represent in logic. MIT chose instead to focus on writing programs that solved a given task without using high-level abstract definitions or general theories of cognition, and measured performance by iterative testing, rather than arguments from first principles. Schank described their "anti-logic" approaches as scruffy , as opposed to the neat paradigm used by McCarthy , Kowalski , Feigenbaum , Newell and Simon . [ 180 ] [ ab ]
In 1975, in a seminal paper, Minsky noted that many of his fellow researchers were using the same kind of tool: a framework that captures all our common sense assumptions about something. For example, if we use the concept of a bird, there is a constellation of facts that immediately come to mind: we might assume that it flies, eats worms and so on (none of which are true for all birds). Minsky associated these assumptions with the general category and they could be inherited by the frames for subcategories and individuals, or over-ridden as necessary. He called these structures frames . Schank used a version of frames he called " scripts " to successfully answer questions about short stories in English. [ 181 ] Frames would eventually be widely used in software engineering under the name object-oriented programming .
The logicians rose to the challenge. Pat Hayes claimed that "most of 'frames' is just a new syntax for parts of first-order logic." But he noted that "there are one or two apparently minor details which give a lot of trouble, however, especially defaults". [ 182 ]
Ray Reiter admitted that "conventional logics, such as first-order
logic, lack the expressive power to adequately represent the knowledge required for reasoning by default". [ 183 ] He proposed augmenting first-order logic with a closed world assumption that a conclusion holds (by default) if its contrary cannot be shown. He showed how such an assumption corresponds to the common sense assumption made in reasoning with frames. He also showed that it has its "procedural equivalent" as negation as failure in Prolog . The closed world assumption, as formulated by Reiter, "is not a first-order notion. (It is a meta notion.)" [ 183 ] However, Keith Clark showed that negation as finite failure can be understood as reasoning implicitly with definitions in first-order logic including a unique name assumption that different terms denote different individuals. [ 184 ]
During the late 1970s and throughout the 1980s, a variety of logics and extensions of first-order logic were developed both for negation as failure in logic programming and for default reasoning more generally. Collectively, these logics have become known as non-monotonic logics .
In the 1980s, a form of AI program called " expert systems " was adopted by corporations around the world and knowledge became the focus of mainstream AI research. Governments provided substantial funding, such as Japan's fifth generation computer project and the U.S. Strategic Computing Initiative . "Overall, the AI industry boomed from a few million dollars in 1980 to billions of dollars in 1988." [ 125 ]
An expert system is a program that answers questions or solves problems about a specific domain of knowledge, using logical rules that are derived from the knowledge of experts. [ 185 ] The earliest examples were developed by Edward Feigenbaum and his students. Dendral , begun in 1965, identified compounds from spectrometer readings. [ 186 ] [ 123 ] MYCIN , developed in 1972, diagnosed infectious blood diseases. [ 125 ] They demonstrated the feasibility of the approach.
Expert systems restricted themselves to a small domain of specific knowledge (thus avoiding the commonsense knowledge problem) [ 123 ] and their simple design made it relatively easy for programs to be built and then modified once they were in place. All in all, the programs proved to be useful : something that AI had not been able to achieve up to this point. [ 187 ]
In 1980, an expert system called R1 was completed at CMU for the Digital Equipment Corporation . It was an enormous success: it was saving the company 40 million dollars annually by 1986. [ 188 ] Corporations around the world began to develop and deploy expert systems and by 1985 they were spending over a billion dollars on AI, most of it to in-house AI departments. [ 189 ] An industry grew up to support them, including hardware companies like Symbolics and Lisp Machines and software companies such as IntelliCorp and Aion . [ 190 ]
In 1981, the Japanese Ministry of International Trade and Industry set aside $850 million for the Fifth generation computer project. Their objectives were to write programs and build machines that could carry on conversations, translate languages, interpret pictures, and reason like human beings. [ 191 ] Much to the chagrin of scruffies , they initially chose Prolog as the primary computer language for the project. [ 192 ]
Other countries responded with new programs of their own. The UK began the £350 million Alvey project. [ 193 ] A consortium of American companies formed the Microelectronics and Computer Technology Corporation (or "MCC") to fund large scale projects in AI and information technology. [ 194 ] [ 193 ] DARPA responded as well, founding the Strategic Computing Initiative and tripling its investment in AI between 1984 and 1988. [ 195 ] [ 196 ]
The power of expert systems came from the expert knowledge they contained. They were part of a new direction in AI research that had been gaining ground throughout the 70s. "AI researchers were beginning to suspect—reluctantly, for it violated the scientific canon of parsimony —that intelligence might very well be based on the ability to use large amounts of diverse knowledge in different ways," [ 197 ] writes Pamela McCorduck . "[T]he great lesson from the 1970s was that intelligent behavior depended very much on dealing with knowledge, sometimes quite detailed knowledge, of a domain where a given task lay". [ 198 ] Knowledge based systems and knowledge engineering became a major focus of AI research in the 1980s. [ 199 ] It was hoped that vast databases would solve the commonsense knowledge problem and provide the support that commonsense reasoning required.
In the 1980s some researchers attempted to attack the commonsense knowledge problem directly, by creating a massive database that would contain all the mundane facts that the average person knows. Douglas Lenat , who started a database called Cyc , argued that there is no shortcut ― the only way for machines to know the meaning of human concepts is to teach them, one concept at a time, by hand. [ 200 ]
Although symbolic knowledge representation and logical reasoning produced useful applications in the 80s and received massive amounts of funding, it was still unable to solve problems in perception , robotics , learning and common sense . A small number of scientists and engineers began to doubt that the symbolic approach would ever be sufficient for these tasks and developed other approaches, such as " connectionism ", robotics , "soft" computing and reinforcement learning . Nils Nilsson called these approaches "sub-symbolic".
In 1982, physicist John Hopfield was able to prove that a form of neural network (now called a " Hopfield net ") could learn and process information, and provably converges after enough time under any fixed condition. It was a breakthrough, as it was previously thought that nonlinear networks would, in general, evolve chaotically. [ 201 ] Around the same time, Geoffrey Hinton and David Rumelhart popularized a method for training neural networks called " backpropagation ". [ ac ] These two developments helped to revive the exploration of artificial neural networks . [ 125 ] [ 202 ]
Neural networks, along with several other similar models, received widespread attention after the 1986 publication of the Parallel Distributed Processing , a two volume collection of papers edited by Rumelhart and psychologist James McClelland . The new field was christened " connectionism " and there was a considerable debate between advocates of symbolic AI and the "connectionists". [ 125 ] Hinton called symbols the " luminous aether of AI" – that is, an unworkable and misleading model of intelligence. [ 125 ] This was a direct attack on the principles that inspired the cognitive revolution .
Neural networks started to advance state of the art in some specialist areas such as protein structure prediction. Following pioneering work from Terry Sejnowski [ 203 ] , cascading multilayer perceptrons such as PhD [ 204 ] and PsiPred [ 205 ] reached near-theoretical maximum accuracy in predicting secondary structure.
In 1990, Yann LeCun at Bell Labs used convolutional neural networks to recognize handwritten digits. The system was used widely in 90s, reading zip codes and personal checks. This was the first genuinely useful application of neural networks. [ 206 ] [ 207 ]
Rodney Brooks , Hans Moravec and others argued that, in order to show real intelligence, a machine needs to have a body — it needs to perceive, move, survive and deal with the world. [ 208 ] Sensorimotor skills are essential to higher level skills such as commonsense reasoning . They can't be efficiently implemented using abstract symbolic reasoning, so AI should solve the problems of perception, mobility, manipulation and survival without using symbolic representation at all. These robotics researchers advocated building intelligence "from the bottom up". [ ad ]
A precursor to this idea was David Marr , who had come to MIT in the late 1970s from a successful background in theoretical neuroscience to lead the group studying vision . He rejected all symbolic approaches ( both McCarthy's logic and Minsky 's frames), arguing that AI needed to understand the physical machinery of vision from the bottom up before any symbolic processing took place. (Marr's work would be cut short by leukemia in 1980.) [ 210 ]
In his 1990 paper "Elephants Don't Play Chess," [ 211 ] robotics researcher Brooks took direct aim at the physical symbol system hypothesis , arguing that symbols are not always necessary since "the world is its own best model. It is always exactly up to date. It always has every detail there is to be known. The trick is to sense it appropriately and often enough." [ 212 ]
In the 1980s and 1990s, many cognitive scientists also rejected the symbol processing model of the mind and argued that the body was essential for reasoning, a theory called the " embodied mind thesis". [ 213 ]
Soft computing uses methods that work with incomplete and imprecise information. They do not attempt to give precise, logical answers, but give results that are only "probably" correct. This allowed them to solve problems that precise symbolic methods could not handle. Press accounts often claimed these tools could "think like a human". [ 214 ] [ 215 ]
Judea Pearl 's Probabilistic Reasoning in Intelligent Systems: Networks of Plausible Inference , an influential 1988 book [ 216 ] brought probability and decision theory into AI. [ 217 ] Fuzzy logic , developed by Lofti Zadeh in the 60s, began to be more widely used in AI and robotics. Evolutionary computation and artificial neural networks also handle imprecise information, and are classified as "soft". In the 90s and early 2000s many other soft computing tools were developed and put into use, including Bayesian networks , [ 217 ] hidden Markov models , [ 217 ] information theory and stochastic modeling . These tools in turn depended on advanced mathematical techniques such as classical optimization . For a time in the 1990s and early 2000s, these soft tools were studied by a subfield of AI called " computational intelligence ". [ 218 ]
Reinforcement learning [ 219 ] gives an agent a reward every time it performs a desired action well, and may give negative rewards (or "punishments") when it performs poorly. It was described in the first half of the twentieth century by psychologists using animal models, such as Thorndike , [ 220 ] [ 221 ] Pavlov [ 222 ] and Skinner . [ 223 ] In the 1950s, Alan Turing [ 221 ] [ 224 ] and Arthur Samuel [ 221 ] foresaw the role of reinforcement learning in AI.
A successful and influential research program was led by Richard Sutton and Andrew Barto beginning 1972. Their collaboration revolutionized the study of reinforcement learning and decision making over the four decades. [ 225 ] [ 226 ] In 1988, Sutton described machine learning in terms of decision theory (i.e., the Markov decision process ). This gave the subject a solid theoretical foundation and access to a large body of theoretical results developed in the field of operations research . [ 226 ]
Also in 1988, Sutton and Barto developed the " temporal difference " (TD) learning algorithm, where the agent is rewarded only when its predictions about the future show improvement. It significantly outperformed previous algorithms. [ 227 ] TD-learning was used by Gerald Tesauro in 1992 in the program TD-Gammon , which played backgammon as well as the best human players. The program learned the game by playing against itself with zero prior knowledge. [ 228 ] In an interesting case of interdisciplinary convergence, neurologists discovered in 1997 that the dopamine reward system in brains also uses a version of the TD-learning algorithm. [ 229 ] [ 230 ] [ 231 ] TD learning would be become highly influential in the 21st century, used in both AlphaGo and AlphaZero . [ 232 ]
The business community's fascination with AI rose and fell in the 1980s in the classic pattern of an economic bubble . As dozens of companies failed, the perception in the business world was that the technology was not viable. [ 233 ] The damage to AI's reputation would last into the 21st century. Inside the field there was little agreement on the reasons for AI's failure to fulfill the dream of human level intelligence that had captured the imagination of the world in the 1960s. Together, all these factors helped to fragment AI into competing subfields focused on particular problems or approaches, sometimes even under new names that disguised the tarnished pedigree of "artificial intelligence". [ 234 ]
Over the next 20 years, AI consistently delivered working solutions to specific isolated problems. By the late 1990s, it was being used throughout the technology industry, although somewhat behind the scenes. The success was due to increasing computer power , by collaboration with other fields (such as mathematical optimization and statistics ) and using the highest standards of scientific accountability. By 2000, AI had achieved some of its oldest goals. The field was both more cautious and more successful than it had ever been.
The term " AI winter " was coined by researchers who had survived the funding cuts of 1974 when they became concerned that enthusiasm for expert systems had spiraled out of control and that disappointment would certainly follow. [ ae ] Their fears were well founded: in the late 1980s and early 1990s, AI suffered a series of financial setbacks. [ 125 ]
The first indication of a change in weather was the sudden collapse of the market for specialized AI hardware in 1987. Desktop computers from Apple and IBM had been steadily gaining speed and power and in 1987 they became more powerful than the more expensive Lisp machines made by Symbolics and others. There was no longer a good reason to buy them. An entire industry worth half a billion dollars was demolished overnight. [ 236 ]
Eventually the earliest successful expert systems, such as XCON , proved too expensive to maintain. They were difficult to update, they could not learn, and they were " brittle " (i.e., they could make grotesque mistakes when given unusual inputs). Expert systems proved useful, but only in a few special contexts. [ 237 ]
In the late 1980s, the Strategic Computing Initiative cut funding to AI "deeply and brutally". New leadership at DARPA had decided that AI was not "the next wave" and directed funds towards projects that seemed more likely to produce immediate results. [ 238 ]
By 1991, the impressive list of goals penned in 1981 for Japan's Fifth Generation Project had not been met. Indeed, some of them, like "carry on a casual conversation" would not be accomplished for another 40 years. As with other AI projects, expectations had run much higher than what was actually possible. [ 239 ] [ af ]
Over 300 AI companies had shut down, gone bankrupt, or been acquired by the end of 1993, effectively ending the first commercial wave of AI. [ 241 ] In 1994, HP Newquist stated in The Brain Makers that "The immediate future of artificial intelligence—in its commercial form—seems to rest in part on the continued success of neural networks." [ 241 ]
In the 1990s, algorithms originally developed by AI researchers began to appear as parts of larger systems. AI had solved a lot of very difficult problems [ ag ] and their solutions proved to be useful throughout the technology industry, [ 242 ] [ 243 ] such as data mining , industrial robotics , logistics, speech recognition , [ 244 ] banking software, [ 245 ] medical diagnosis [ 245 ] and Google 's search engine. [ 246 ] [ 247 ]
The field of AI received little or no credit for these successes in the 1990s and early 2000s. Many of AI's greatest innovations have been reduced to the status of just another item in the tool chest of computer science. [ 248 ] Nick Bostrom explains: "A lot of cutting edge AI has filtered into general applications, often without being called AI because once something becomes useful enough and common enough it's not labeled AI anymore." [ 245 ]
Many researchers in AI in the 1990s deliberately called their work by other names, such as informatics , knowledge-based systems , "cognitive systems" or computational intelligence . In part, this may have been because they considered their field to be fundamentally different from AI, but also the new names help to procure funding. [ 244 ] [ 249 ] [ 250 ] In the commercial world at least, the failed promises of the AI Winter continued to haunt AI research into the 2000s, as the New York Times reported in 2005: "Computer scientists and software engineers avoided the term artificial intelligence for fear of being viewed as wild-eyed dreamers." [ 251 ]
AI researchers began to develop and use sophisticated mathematical tools more than they ever had in the past. [ 252 ] [ 253 ] Most of the new directions in AI relied heavily on mathematical models, including artificial neural networks , probabilistic reasoning , soft computing and reinforcement learning . In the 90s and 2000s, many other highly mathematical tools were adapted for AI. These tools were applied to machine learning, perception and mobility.
There was a widespread realization that many of the problems that AI needed to solve were already being worked on by researchers in fields like statistics , mathematics , electrical engineering , economics or operations research . The shared mathematical language allowed both a higher level of collaboration with more established and successful fields and the achievement of results which were measurable and provable; AI had become a more rigorous "scientific" discipline.
Another key reason for the success in the 90s was that AI researchers focussed on specific problems with verifiable solutions (an approach later derided as narrow AI ). This provided useful tools in the present, rather than speculation about the future.
A new paradigm called " intelligent agents " became widely accepted during the 1990s. [ 254 ] [ 255 ] [ ah ] Although earlier researchers had proposed modular "divide and conquer" approaches to AI, [ ai ] the intelligent agent did not reach its modern form until Judea Pearl , Allen Newell , Leslie P. Kaelbling , and others brought concepts from decision theory and economics into the study of AI. [ 256 ] When the economist's definition of a rational agent was married to computer science 's definition of an object or module , the intelligent agent paradigm was complete.
An intelligent agent is a system that perceives its environment and takes actions which maximize its chances of success. By this definition, simple programs that solve specific problems are "intelligent agents", as are human beings and organizations of human beings, such as firms . The intelligent agent paradigm defines AI research as "the study of intelligent agents". [ aj ] This is a generalization of some earlier definitions of AI: it goes beyond studying human intelligence; it studies all kinds of intelligence.
The paradigm gave researchers license to study isolated problems and to disagree about methods, but still retain hope that their work could be combined into an agent architecture that would be capable of general intelligence. [ 257 ]
On May 11, 1997, Deep Blue became the first computer chess-playing system to beat a reigning world chess champion, Garry Kasparov . [ 258 ] In 2005, a Stanford robot won the DARPA Grand Challenge by driving autonomously for 131 miles along an unrehearsed desert trail. Two years later, a team from CMU won the DARPA Urban Challenge by autonomously navigating 55 miles in an urban environment while responding to traffic hazards and adhering to traffic laws. [ 259 ]
These successes were not due to some revolutionary new paradigm, but mostly on the tedious application of engineering skill and on the tremendous increase in the speed and capacity of computers by the 90s. [ ak ] In fact, Deep Blue's computer was 10 million times faster than the Ferranti Mark 1 that Christopher Strachey taught to play chess in 1951. [ al ] This dramatic increase is measured by Moore's law , which predicts that the speed and memory capacity of computers doubles every two years. The fundamental problem of "raw computer power" was slowly being overcome.
In the first decades of the 21st century, access to large amounts of data (known as " big data "), cheaper and faster computers and advanced machine learning techniques were successfully applied to many problems throughout the economy. A turning point was the success of deep learning around 2012 which improved the performance of machine learning on many tasks, including image and video processing, text analysis, and speech recognition. [ 261 ] Investment in AI increased along with its capabilities, and by 2016, the market for AI-related products, hardware, and software reached more than $8 billion, and the New York Times reported that interest in AI had reached a "frenzy". [ 262 ]
In 2002, Ben Goertzel and others became concerned that AI had largely abandoned its original goal of producing versatile, fully intelligent machines, and argued in favor of more direct research into artificial general intelligence . By the mid-2010s several companies and institutions had been founded to pursue Artificial General Intelligence (AGI), such as OpenAI and Google 's DeepMind . During the same period, new insights into superintelligence raised concerns that AI was an existential threat . The risks and unintended consequences of AI technology became an area of serious academic research after 2016.
The success of machine learning in the 2000s depended on the availability of vast amounts of training data and faster computers. [ 263 ] Russell and Norvig wrote that the "improvement in performance obtained by increasing the size of the data set by two or three orders of magnitude outweighs any improvement that can be made by tweaking the algorithm." [ 206 ] Geoffrey Hinton recalled that back in the 90s, the problem was that "our labeled datasets were thousands of times too small. [And] our computers were millions of times too slow." [ 264 ] This was no longer true by 2010.
The most useful data in the 2000s came from curated, labeled data sets created specifically for machine learning and AI. In 2007, a group at UMass Amherst released Labeled Faces in the Wild , an annotated set of images of faces that was widely used to train and test face recognition systems for the next several decades. [ 265 ] Fei-Fei Li developed ImageNet , a database of three million images captioned by volunteers using the Amazon Mechanical Turk . Released in 2009, it was a useful body of training data and a benchmark for testing for the next generation of image processing systems. [ 266 ] [ 206 ] Google released word2vec in 2013 as an open source resource. It used large amounts of data text scraped from the internet and word embedding to create a numeric vector to represent each word. Users were surprised at how well it was able to capture word meanings, for example, ordinary vector addition would give equivalences like China + River = Yangtze, London-England+France = Paris. [ 267 ] This database in particular would be essential for the development of large language models in the late 2010s.
The explosive growth of the internet gave machine learning programs access to billions of pages of text and images that could be scraped . And, for specific problems, large privately held databases contained the relevant data. McKinsey Global Institute reported that "by 2009, nearly all sectors in the US economy had at least an average of 200 terabytes of stored data". [ 268 ] This collection of information was known in the 2000s as big data .
In a Jeopardy! exhibition match in February 2011, IBM 's question answering system Watson defeated the two best Jeopardy! champions, Brad Rutter and Ken Jennings , by a significant margin. [ 269 ] Watson's expertise would have been impossible without the information available on the internet. [ 206 ]
In 2012, AlexNet , a deep learning model, [ am ] developed by Alex Krizhevsky , won the ImageNet Large Scale Visual Recognition Challenge , with significantly fewer errors than the second-place winner. [ 271 ] [ 206 ] Krizhevsky worked with Geoffrey Hinton at the University of Toronto . [ an ] This was a turning point in machine learning: over the next few years dozens of other approaches to image recognition were abandoned in favor of deep learning . [ 263 ]
Deep learning uses a multi-layer perceptron . Although this architecture has been known since the 60s, getting it to work requires powerful hardware and large amounts of training data. [ 272 ] Before these became
available, improving performance of image processing systems required hand-crafted ad hoc features that were difficult to implement. [ 272 ] Deep learning was simpler and more general. [ ao ]
Deep learning was applied to dozens of problems over the next few years (such as speech recognition, machine translation, medical diagnosis, and game playing). In every case it showed enormous gains in performance. [ 263 ] Investment and interest in AI boomed as a result. [ 263 ]
It became fashionable in the 2000s to begin talking about the future of AI again and several popular books considered the possibility of superintelligent machines and what they might mean for human society. Some of this was optimistic (such as Ray Kurzweil 's The Singularity is Near ), but others warned that a sufficiently powerful AI was existential threat to humanity, such as Nick Bostrom and Eliezer Yudkowsky . [ 273 ] The topic became widely covered in the press and many leading intellectuals and politicians commented on the issue.
AI programs in the 21st century are defined by their goals – the specific measures that they are designed to optimize. Nick Bostrom 's influential 2005 book Superintelligence argued that, if one isn't careful about defining these goals, the machine may cause harm to humanity in the process of achieving a goal. Stuart J. Russell used the example of an intelligent robot that kills its owner to prevent it from being unplugged, reasoning "you can't fetch the coffee if you're dead". [ 274 ] (This problem is known by the technical term " instrumental convergence ".) The solution is to align the machine's goal function with the goals of its owner and humanity in general. Thus, the problem of mitigating the risks and unintended consequences of AI became known as "the value alignment problem" or AI alignment . [ 275 ]
At the same time, machine learning systems had begun to have disturbing unintended consequences. Cathy O'Neil explained how statistical algorithms had been among the causes of the 2008 economic crash , [ 276 ] Julia Angwin of ProPublica argued that the COMPAS system used by the criminal justice system exhibited racial bias under some measures, [ 277 ] [ ap ] others showed that many machine learning systems exhibited some form of racial bias , [ 279 ] and there were many other examples of dangerous outcomes that had resulted from machine learning systems. [ aq ]
In 2016, the election of Donald Trump and the controversy over the COMPAS system illuminated several problems with the current technological infrastructure, including misinformation, social media algorithms designed to maximize engagement, the misuse of personal data and the trustworthiness of predictive models. [ 280 ] Issues of fairness and unintended consequences became significantly more popular at AI conferences, publications vastly increased, funding became available, and many researchers re-focussed their careers on these issues. The value alignment problem became a serious field of academic study. [ 281 ] [ ar ]
In the early 2000s, several researchers became concerned that mainstream AI was too focused on "measurable performance in specific applications" [ 283 ] (known as " narrow AI ") and had abandoned AI's original goal of creating versatile, fully intelligent machines. An early critic was Nils Nilsson in 1995, and similar opinions were published by AI elder statesmen John McCarthy, Marvin Minsky, and Patrick Winston in 2007–2009. Minsky organized a symposium on "human-level AI" in 2004. [ 283 ] Ben Goertzel adopted the term " artificial general intelligence " for the new sub-field, founding a journal and holding conferences beginning in 2008. [ 284 ] The new field grew rapidly, buoyed by the continuing success of artificial neural networks and the hope that it was the key to AGI.
Several competing companies, laboratories and foundations were founded to develop AGI in the 2010s. DeepMind was founded in 2010 by three English scientists, Demis Hassabis , Shane Legg and Mustafa Suleyman , with funding from Peter Thiel and later Elon Musk . The founders and financiers were deeply concerned about AI safety and the existential risk of AI . DeepMind's founders had a personal connection with Yudkowsky and Musk was among those who was actively raising the alarm. [ 285 ] Hassabis was both worried about the dangers of AGI and optimistic about its power; he hoped they could "solve AI, then solve everything else." [ 286 ] The New York Times wrote in 2023 "At the heart of this competition is a brain-stretching paradox. The people who say they are most worried about AI are among the most determined to create it and enjoy its riches. They have justified their ambition with their strong belief that they alone can keep AI from endangering Earth." [ 285 ]
In 2012, Geoffrey Hinton (who been leading neural network research since the 80s) was approached by Baidu , which wanted to hire him and all his students for an enormous sum. Hinton decided to hold an auction and, at a Lake Tahoe AI conference, they sold themselves to Google for a price of $44 million. Hassabis took notice and sold DeepMind to Google in 2014, on the condition that it would not accept military contracts and would be overseen by an ethics board. [ 285 ]
Larry Page of Google, unlike Musk and Hassabis, was an optimist about the future of AI. Musk and Paige became embroiled in an argument about the risk of AGI at Musk's 2015 birthday party. They had been friends for decades but stopped speaking to each other shortly afterwards. Musk attended the one and only meeting of the DeepMind's ethics board, where it became clear that Google was uninterested in mitigating the harm of AGI. Frustrated by his lack of influence he founded OpenAI in 2015, enlisting Sam Altman to run it and hiring top scientists. OpenAI began as a non-profit, "free from the economic incentives that were driving Google and other corporations." [ 285 ] Musk became frustrated again and left the company in 2018. OpenAI turned to Microsoft for continued financial support and Altman and OpenAI formed a for-profit version of the company with more than $1 billion in financing. [ 285 ]
In 2021, Dario Amodei and 14 other scientists left OpenAI over concerns that the company was putting profits above safety. They formed Anthropic , which soon had $6 billion in financing from Microsoft and Google. [ 285 ]
The AI boom started with the initial development of key architectures and algorithms such as the transformer architecture in 2017, leading to the scaling and development of large language models exhibiting human-like traits of knowledge, attention and creativity. The new AI era began since 2020, with the public release of scaled large language models (LLMs) such as ChatGPT . [ 288 ]
In 2017, the transformer architecture was proposed by Google researchers. It exploits an attention mechanism and became widely used in large language models. [ 289 ]
Large language models , based on the transformer, were developed by AGI companies: OpenAI released GPT-3 in 2020, and DeepMind released Gato in 2022. These are foundation models : they are trained on vast quantities of unlabeled data and can be adapted to a wide range of downstream tasks. [ citation needed ]
These models can discuss a huge number of topics and display general knowledge. The question naturally arises: are these models an example of artificial general intelligence ? Bill Gates was skeptical of the new technology and the hype that surrounded AGI. However, Altman presented him with a live demo of ChatGPT4 passing an advanced biology test. Gates was convinced. [ 285 ] In 2023, Microsoft Research tested the model with a large variety of tasks, and concluded that "it could reasonably be viewed as an early (yet still incomplete) version of an artificial general intelligence (AGI) system". [ 290 ]
In 2024, OpenAI o3 , a type of advanced reasoning model developed by OpenAI was announced. On the Abstraction and Reasoning Corpus for Artificial General Intelligence (ARC-AGI) benchmark developed by François Chollet in 2019, the model achieved an unofficial score of 87.5% on the semi-private test, surpassing the typical human score of 84%. The benchmark is supposed to be a necessary, but not sufficient test for AGI. Speaking of the benchmark, Chollet has said "You’ll know AGI is here when the exercise of creating tasks that are easy for regular humans but hard for AI becomes simply impossible." [ 291 ]
Investment in AI grew exponentially after 2020, with venture capital funding for generative AI companies increasing dramatically. Total AI investments rose from $18 billion in 2014 to $119 billion in 2021, with generative AI accounting for approximately 30% of investments by 2023. [ 292 ] According to metrics from 2017 to 2021, the United States outranked the rest of the world in terms of venture capital funding , number of startups , and AI patents granted. [ 293 ] The commercial AI scene became dominated by American Big Tech companies, whose investments in this area surpassed those from U.S.-based venture capitalists . [ 294 ] OpenAI 's valuation reached $86 billion by early 2024, [ 295 ] while NVIDIA 's market capitalization surpassed $3.3 trillion by mid-2024, making it the world's largest company by market capitalization as the demand for AI-capable GPUs surged. [ 296 ]
15.ai , launched in March 2020 [ 297 ] by an anonymous MIT researcher, [ 298 ] [ 299 ] was one of the earliest examples of generative AI gaining widespread public attention during the initial stages of the AI boom. [ 300 ] The free web application demonstrated the ability to clone character voices using neural networks with minimal training data, requiring as little as 15 seconds of audio to reproduce a voice—a capability later corroborated by OpenAI in 2024. [ 301 ] The service went viral on social media platforms in early 2021, [ 302 ] [ 303 ] allowing users to generate speech for characters from popular media franchises, and became particularly notable for its pioneering role in popularizing AI voice synthesis for creative content and memes . [ 304 ]
Contemporary AI systems are now becoming human-competitive at general tasks, and we must ask ourselves: Should we let machines flood our information channels with propaganda and untruth? Should we automate away all the jobs, including the fulfilling ones? Should we develop nonhuman minds that might eventually outnumber, outsmart, obsolete and replace us? Should we risk loss of control of our civilization? Such decisions must not be delegated to unelected tech leaders. Powerful AI systems should be developed only once we are confident that their effects will be positive and their risks will be manageable. This confidence must be well justified and increase with the magnitude of a system’s potential effects. OpenAI’s recent statement regarding artificial general intelligence, states that "At some point, it may be important to get independent review before starting to train future systems, and for the most advanced efforts to agree to limit the rate of growth of compute used for creating new models." We agree. That point is now.
Therefore, we call on all AI labs to immediately pause for at least 6 months the training of AI systems more powerful than GPT-4 . This pause should be public and verifiable, and include all key actors. If such a pause cannot be enacted quickly, governments should step in and institute a moratorium.
ChatGPT was launched on November 30, 2022, marking a pivotal moment in artificial intelligence's public adoption. Within days of its release it went viral, gaining over 100 million users in two months and becoming the fastest-growing consumer software application in history. [ 306 ] The chatbot's ability to engage in human-like conversations, write code, and generate creative content captured public imagination and led to rapid adoption across various sectors including education , business , and research. [ 307 ] ChatGPT's success prompted unprecedented responses from major technology companies— Google declared a "code red" and rapidly launched Gemini (formerly known as Google Bard), while Microsoft incorporated the technology into Bing Chat . [ 308 ]
The rapid adoption of these AI technologies sparked intense debate about their implications. Notable AI researchers and industry leaders voiced both optimism and concern about the accelerating pace of development. In March 2023, over 20,000 signatories, including computer scientist Yoshua Bengio , Elon Musk , and Apple co-founder Steve Wozniak , signed an open letter calling for a pause in advanced AI development , citing " profound risks to society and humanity ." [ 309 ] However, other prominent researchers like Juergen Schmidhuber took a more optimistic view, emphasizing that the majority of AI research aims to make "human lives longer and healthier and easier." [ 310 ]
By mid-2024, however, the financial sector began to scrutinize AI companies more closely, particularly questioning their capacity to produce a return on investment commensurate with their massive valuations. Some prominent investors raised concerns about market expectations becoming disconnected from fundamental business realities. Jeremy Grantham , co-founder of GMO LLC , warned investors to "be quite careful" and drew parallels to previous technology-driven market bubbles. [ 311 ] Similarly, Jeffrey Gundlach , CEO of DoubleLine Capital , explicitly compared the AI boom to the dot-com bubble of the late 1990s, suggesting that investor enthusiasm might be outpacing realistic near-term capabilities and revenue potential. [ 312 ] These concerns were amplified by the substantial market capitalizations of AI-focused companies, many of which had yet to demonstrate sustainable profitability models.
In March 2024, Anthropic released the Claude 3 family of large language models, including Claude 3 Haiku, Sonnet, and Opus. [ 313 ] The models demonstrated significant improvements in capabilities across various benchmarks, with Claude 3 Opus notably outperforming leading models from OpenAI and Google. [ 314 ] In June 2024, Anthropic released Claude 3.5 Sonnet, which demonstrated improved performance compared to the larger Claude 3 Opus, particularly in areas such as coding, multistep workflows, and image analysis. [ 315 ]
In 2024, the Royal Swedish Academy of Sciences awarded Nobel Prizes in recognition of groundbreaking contributions to artificial intelligence . The recipients included:
In January 2025, OpenAI announced a new AI, ChatGPT-Gov, which would be specifically designed for US government agencies to use securely. [ 317 ] Open AI said that agencies could utilize ChatGPT Gov on a Microsoft Azure cloud or Azure Government cloud, "on top of Microsoft’s Azure’s OpenAI Service." OpenAI's announcement stated that "Self-hosting ChatGPT Gov enables agencies to more easily manage their own security, privacy, and compliance requirements, such as stringent cybersecurity frameworks (IL5, CJIS, ITAR, FedRAMP High). Additionally, we believe this infrastructure will expedite internal authorization of OpenAI’s tools for the handling of non-public sensitive data." [ 317 ]
In January 2025, a significant development in AI infrastructure investment occurred with the formation of Stargate LLC . The joint venture, created by OpenAI , SoftBank , Oracle , and MGX , announced plans to invest US$500 billion in AI infrastructure across the United States by 2029, starting with US$100 billion. The venture was formally announced by U.S. President Donald Trump on January 21, 2025, with SoftBank CEO Masayoshi Son appointed as chairman. [ 318 ] [ 319 ]
. | https://en.wikipedia.org/wiki/History_of_artificial_intelligence |
Astrological belief in relation between celestial observations and terrestrial events have influenced various aspects of human history, including world-views, language and many elements of culture . It has been argued that astrology began as a study as soon as human beings made conscious attempts to measure, record, and predict seasonal changes by reference to astronomical cycles. [ 1 ]
Early evidence of such practices appears as markings on bones and cave walls, which show that the lunar cycle was being noted as early as 25,000 years ago; the first step towards recording the Moon's influence upon tides and rivers, and towards organizing a communal calendar. [ 2 ] With the Neolithic Revolution new needs were also being met by the increasing knowledge of constellations, whose appearances in the night-time sky change with the seasons, thus allowing the rising of particular star-groups to herald annual floods or seasonal activities. [ 3 ] By the 3rd millennium BCE , widespread civilisations had developed sophisticated understanding of celestial cycles, and are believed to have consciously oriented their temples to create alignment with the heliacal risings of the stars. [ 4 ]
There is scattered evidence to suggest that the oldest known astrological references are copies of texts made during this period, particularly in Mesopotamia . Two, from the Venus tablet of Ammisaduqa (compiled in Babylon round 1700 BC) are reported to have been made during the reign of king Sargon of Akkad (2334–2279 BC). [ 5 ] Another, showing an early use of electional astrology , is ascribed to the reign of the Sumerian ruler Gudea of Lagash (c. 2144–2124 BC). However, there is controversy over whether they were genuinely recorded at the time or merely ascribed to ancient rulers by posterity. The oldest undisputed evidence of the use of astrology as an integrated system of knowledge is attributed to records that emerge from the first dynasty of Mesopotamia (1950–1651 BC). [ 6 ]
Among West Eurasian peoples, the earliest evidence for astrology dates from the 3rd millennium BC, with roots in calendrical systems used to predict seasonal shifts and to interpret celestial cycles as signs of divine communications. [ 7 ] Until the 17th century, astrology was considered a scholarly tradition, and it helped drive the development of astronomy . It was commonly accepted in political and cultural circles, and some of its concepts were used in other traditional studies, such as alchemy , meteorology and medicine . [ 8 ] By the end of the 17th century, emerging scientific concepts in astronomy, such as heliocentrism , undermined the theoretical basis of astrology, which subsequently lost its academic standing and became regarded as a pseudoscience . Empirical scientific investigation has shown that predictions based on these systems are not accurate. [ 9 ] : 85, [ 10 ] : 424
In the 20th century, astrology gained broader consumer popularity through the influence of regular mass media products, such as newspaper horoscopes. [ 11 ]
Babylonian astrology is the earliest recorded organized system of astrology, arising in the 2nd millennium BC. [ 12 ] There is speculation that astrology of some form appeared in the Sumerian period in the 3rd millennium BC, but the isolated references to ancient celestial omens dated to this period are not considered sufficient evidence to demonstrate an integrated theory of astrology. [ 13 ] The history of scholarly celestial divination is therefore generally reported to begin with late Old Babylonian texts ( c. 1800 BC ), continuing through the Middle Babylonian and Middle Assyrian periods ( c. 1200 BC ). [ 14 ]
By the 16th century BC the extensive employment of omen-based astrology can be evidenced in the compilation of a comprehensive reference work known as Enuma Anu Enlil . Its contents consisted of 70 cuneiform tablets comprising 7,000 celestial omens. Texts from this time also refer to an oral tradition – the origin and content of which can only be speculated upon. [ 15 ] At this time Babylonian astrology was solely mundane, concerned with the prediction of weather and political matters, and prior to the 7th century BC the practitioners' understanding of astronomy was fairly rudimentary. Astrological symbols likely represented seasonal tasks, and were used as a yearly almanac of listed activities to remind a community to do things appropriate to the season or weather (such as symbols representing times for harvesting, gathering shell-fish, fishing by net or line, sowing crops, collecting or managing water reserves, hunting, and seasonal tasks critical in ensuring the survival of children and young animals for the larger group). By the 4th century, their mathematical methods had progressed enough to calculate future planetary positions with reasonable accuracy, at which point extensive ephemerides began to appear. [ 16 ]
Babylonian astrology developed within the context of divination . A collection of 32 tablets with inscribed liver models , dating from about 1875 BC, are the oldest known detailed texts of Babylonian divination, and these demonstrate the same interpretational format as that employed in celestial omen analysis. [ 17 ] Blemishes and marks found on the liver of the sacrificial animal were interpreted as symbolic signs which presented messages from the gods to the king.
The gods were also believed to present themselves in the celestial images of the planets or stars with whom they were associated. Evil celestial omens attached to any particular planet were therefore seen as indications of dissatisfaction or disturbance of the god that planet represented. [ 18 ] Such indications were met with attempts to appease the god and find manageable ways by which the god's expression could be realised without significant harm to the king and his nation. An astronomical report to the king Esarhaddon concerning a lunar eclipse of January 673 BC shows how the ritualistic use of substitute kings, or substitute events, combined an unquestioning belief in magic and omens with a purely mechanical view that the astrological event must have some kind of correlate within the natural world:
... In the beginning of the year a flood will come and break the dikes. When the Moon has made the eclipse, the king, my lord, should write to me. As a substitute for the king, I will cut through a dike, here in Babylonia, in the middle of the night. No one will know about it. [ 19 ]
Ulla Koch-Westenholz, in her 1995 book Mesopotamian Astrology , argues that this ambivalence between a theistic and mechanic worldview defines the Babylonian concept of celestial divination as one which, despite its heavy reliance on magic, remains free of implications of targeted punishment with the purpose of revenge, and so "shares some of the defining traits of modern science: it is objective and value-free, it operates according to known rules, and its data are considered universally valid and can be looked up in written tabulations". [ 20 ] Koch-Westenholz also establishes the most important distinction between ancient Babylonian astrology and other divinatory disciplines as being that the former was originally exclusively concerned with mundane astrology, being geographically oriented and specifically applied to countries, cities and nations, and almost wholly concerned with the welfare of the state and the king as the governing head of the nation. [ 21 ] Mundane astrology is therefore known to be one of the oldest branches of astrology. [ 22 ] It was only with the gradual emergence of horoscopic astrology , from the 6th century BC, that astrology developed the techniques and practice of natal astrology . [ 23 ] [ 24 ]
In 525 BC Egypt was conquered by the Persians so there is likely to have been some Mesopotamian influence on Egyptian astrology. Arguing in favour of this, historian Tamsyn Barton gives an example of what appears to be Mesopotamian influence on the Egyptian zodiac , which shared two signs – the Balance and the Scorpion, as evidenced in the Dendera Zodiac (in the Greek version the Balance was known as the Scorpion's Claws). [ 25 ]
After the occupation by Alexander the Great in 332 BC, Egypt came under Hellenistic rule and influence. The city of Alexandria was founded by Alexander after the conquest and during the 3rd and 2nd centuries BC, the Ptolemaic scholars of Alexandria were prolific writers. It was in Ptolemaic Alexandria that Babylonian astrology was mixed with the Egyptian tradition of Decanic astrology to create Horoscopic astrology . This contained the Babylonian zodiac with its system of planetary exaltations , the triplicities of the signs and the importance of eclipses. Along with this it incorporated the Egyptian concept of dividing the zodiac into thirty-six decans of ten degrees each, with an emphasis on the rising decan, the Greek system of planetary Gods, sign rulership and four elements . [ 26 ]
The decans were a system of time measurement according to the constellations. They were led by the constellation Sothis or Sirius. The risings of the decans in the night were used to divide the night into 'hours'. The rising of a constellation just before sunrise (its heliacal rising) was considered the last hour of the night. Over the course of the year, each constellation rose just before sunrise for ten days. When they became part of the astrology of the Hellenistic Age, each decan was associated with ten degrees of the zodiac. Texts from the 2nd century BC list predictions relating to the positions of planets in zodiac signs at the time of the rising of certain decans, particularly Sothis. [ 27 ] The earliest Zodiac found in Egypt dates to the 1st century BC, the Dendera Zodiac .
Particularly important in the development of horoscopic astrology was the Greco-Roman astrologer and astronomer Ptolemy , who lived in Alexandria during Roman Egypt . Ptolemy's work the Tetrabiblos laid the basis of the Western astrological tradition, and as a source of later reference is said to have "enjoyed almost the authority of a Bible among the astrological writers of a thousand years or more". [ 28 ] It was one of the first astrological texts to be circulated in Medieval [ 29 ] Europe after being translated from Arabic into Latin by Plato of Tivoli (Tiburtinus) in Spain, 1138. [ 30 ]
According to Firmicus Maternus (4th century), the system of horoscopic astrology was given early on to an Egyptian pharaoh named Nechepso and his priest Petosiris . [ 31 ] The Hermetic texts were also put together during this period and Clement of Alexandria , writing in the Roman era , demonstrates the degree to which astrologers were expected to have knowledge of the texts in his description of Egyptian sacred rites:
This is principally shown by their sacred ceremonial. For first advances the Singer, bearing some one of the symbols of music. For they say that he must learn two of the books of Hermes, the one of which contains the hymns of the gods, the second the regulations for the king's life. And after the Singer advances the Astrologer, with a horologe in his hand, and a palm, the symbols of astrology. He must have the astrological books of Hermes, which are four in number, always in his mouth. [ 32 ]
The conquest of Asia by Alexander the Great exposed the Greeks to the cultures and cosmological ideas of Syria , Babylon, Persia and central Asia. Greek overtook cuneiform script as the international language of intellectual communication and part of this process was the transmission of astrology from cuneiform to Greek. [ 33 ] Sometime around 280 BC, Berossus , a priest of Bel from Babylon, moved to the Greek island of Kos in order to teach astrology and Babylonian culture to the Greeks. With this, what historian Nicholas Campion calls, "the innovative energy" in astrology moved west to the Hellenistic world of Greece and Egypt. [ 34 ] According to Campion, the astrology that arrived from the Eastern World was marked by its complexity, with different forms of astrology emerging. By the 1st century BC two varieties of astrology were in existence, one that required the reading of horoscopes in order to establish precise details about the past, present and future; the other being theurgic (literally meaning 'god-work'), which emphasised the soul's ascent to the stars. While they were not mutually exclusive, the former sought information about the life, while the latter was concerned with personal transformation, where astrology served as a form of dialogue with the Divine . [ 35 ]
As with much else, Greek influence played a crucial role in the transmission of astrological theory to Rome . [ 36 ] However, our earliest references to demonstrate its arrival in Rome reveal its initial influence upon the lower orders of society, [ 36 ] and display concern about uncritical recourse to the ideas of Babylonian 'star-gazers'. [ 37 ] Among the Greeks and Romans , Babylonia (also known as Chaldea ) became so identified with astrology that 'Chaldean wisdom' came to be a common synonym for divination using planets and stars. [ 38 ]
The first definite reference to astrology comes from the work of the orator Cato , who in 160 BC composed a treatise warning farm overseers against consulting with Chaldeans. [ 39 ] The 2nd-century Roman poet Juvenal , in his satirical attack on the habits of Roman women, also complains about the pervasive influence of Chaldeans, despite their lowly social status, saying "Still more trusted are the Chaldaeans; every word uttered by the astrologer they will believe has come from Hammon's fountain, ... nowadays no astrologer has credit unless he has been imprisoned in some distant camp, with chains clanking on either arm". [ 40 ]
One of the first astrologers to bring Hermetic astrology to Rome was Thrasyllus , who, in the first century AD, acted as the astrologer for the emperor Tiberius . [ 36 ] Tiberius was the first emperor reported to have had a court astrologer, [ 41 ] although his predecessor Augustus had also used astrology to help legitimise his Imperial rights. [ 42 ] In the second century AD, the astrologer Claudius Ptolemy was so obsessed with getting horoscopes accurate that he began the first attempt to make an accurate world map (maps before this were more relativistic or allegorical) so that he could chart the relationship between the person's birthplace and the heavenly bodies. While doing so, he coined the term "geography". [ 43 ]
Even though some use of astrology by the emperors appears to have happened, there was also a prohibition on astrology to a certain extent as well. In the 1st century AD, Publius Rufus Anteius was accused of the crime of funding the banished astrologer Pammenes, and requesting his own horoscope and that of then emperor Nero . For this crime, Nero forced Anteius to commit suicide. At this time, astrology was likely to result in charges of magic and treason. [ 44 ]
Cicero 's De divinatione (44 BC), which rejects astrology and other allegedly divinatory techniques, is a fruitful historical source for the conception of scientificity in Roman classical Antiquity. [ 45 ] The Pyrrhonist philosopher Sextus Empiricus compiled the ancient arguments against astrology in his book Against the Astrologers. [ 46 ]
Astrology was taken up enthusiastically by Islamic scholars following the collapse of Alexandria to the Arabs in the 7th century, and the founding of the Abbasid empire in the 8th century. The second Abbasid caliph , Al Mansur (754–775) founded the city of Baghdad to act as a centre of learning, and included in its design a library-translation centre known as Bayt al-Hikma 'Storehouse of Wisdom', which continued to receive development from his heirs and was to provide a major impetus for Arabic translations of Hellenistic astrological texts. [ 48 ] The early translators included the Persian Jewish astrologer Mashallah , who helped to elect the time for the foundation of Baghdad, [ 49 ] and Sahl ibn Bishr (a.k.a. Zael ), whose texts were directly influential upon later European astrologers such as Guido Bonatti in the 13th century, and William Lilly in the 17th century. [ 50 ] Knowledge of Arabic texts started to become imported into Europe during the Latin translations of the 12th century .
In the 9th century, Persian astrologer Albumasar was thought to be one of the greatest astrologer at that time. His practical manuals for training astrologers profoundly influenced Muslim intellectual history and, through translations, that of western Europe and Byzantium In the 10th century. [ 51 ] [ 52 ] Albumasar's Introductorium in Astronomiam was one of the most important sources for the recovery of Aristotle for medieval European scholars. [ 53 ] Another was the Persian mathematician, astronomer, astrologer and geographer Al Khwarizmi . The Arabs greatly increased the knowledge of astronomy, and many of the star names that are commonly known today, such as Aldebaran , Altair , Betelgeuse , Rigel and Vega retain the legacy of their language. They also developed the list of Hellenistic lots to the extent that they became historically known as Arabic parts , for which reason it is often wrongly claimed that the Arabic astrologers invented their use, whereas they are clearly known to have been an important feature of Hellenistic astrology .
During the advance of Islamic science some of the practices of astrology were refuted on theological grounds by astronomers such as Al-Farabi (Alpharabius), Ibn al-Haytham (Alhazen) and Avicenna . Their criticisms argued that the methods of astrologers were conjectural rather than empirical , and conflicted with orthodox religious views of Islamic scholars through the suggestion that the Will of God can be precisely known and predicted in advance. [ 54 ] Such refutations mainly concerned 'judicial branches' (such as horary astrology ), rather than the more 'natural branches' such as medical and meteorological astrology, these being seen as part of the natural sciences of the time.
For example, Avicenna's 'Refutation against astrology' Resāla fī ebṭāl aḥkām al-nojūm , argues against the practice of astrology while supporting the principle of planets acting as the agents of divine causation which express God's absolute power over creation. Avicenna considered that the movement of the planets influenced life on earth in a deterministic way, but argued against the capability of determining the exact influence of the stars. [ 55 ] In essence, Avicenna did not refute the essential dogma of astrology, but denied our ability to understand it to the extent that precise and fatalistic predictions could be made from it. [ 56 ]
While astrology in the East flourished following the break up of the Roman world, with Indian, Persian and Islamic influences coming together and undergoing intellectual review through an active investment in translation projects, Western astrology in the same period had become "fragmented and unsophisticated ... partly due to the loss of Greek scientific astronomy and partly due to condemnations by the Church." [ 57 ] Translations of Arabic works into Latin started to make their way to Spain by the late 10th century, and in the 12th century the transmission of astrological works from Arabia to Europe "acquired great impetus". [ 57 ]
By the 13th century astrology had become a part of everyday medical practice in Europe. Doctors combined Galenic medicine (inherited from the Greek physiologist Galen - AD 129–216) with studies of the stars. By the end of the 1500s, physicians across Europe were required by law to calculate the position of the Moon before carrying out complicated medical procedures, such as surgery or bleeding. [ 58 ]
Influential works of the 13th century include those of the British monk Johannes de Sacrobosco ( c. 1195–1256) and the Italian astrologer Guido Bonatti from Forlì (Italy). Bonatti served the communal governments of Florence , Siena and Forlì and acted as advisor to Frederick II, Holy Roman Emperor . His astrological text-book Liber Astronomiae ('Book of Astronomy'), written around 1277, was reputed to be "the most important astrological work produced in Latin in the 13th century". [ 59 ] Dante Alighieri immortalised Bonatti in his Divine Comedy (early 14th century) by placing him in the eighth Circle of Hell, a place where those who would divine the future are forced to have their heads turned around (to look backwards instead of forwards). [ 60 ]
In medieval Europe , a university education was divided into seven distinct areas, each represented by a particular planet and known as the seven liberal arts . Dante attributed these arts to the planets. As the arts were seen as operating in ascending order, so were the planets in decreasing order of planetary speed: grammar was assigned to the Moon, the quickest moving celestial body, dialectic was assigned to Mercury, rhetoric to Venus, music to the Sun, arithmetic to Mars, geometry to Jupiter and astrology/ astronomy to the slowest moving body, Saturn. [ 61 ]
Medieval writers used astrological symbolism in their literary themes. For example, Dante's Divine Comedy builds varied references to planetary associations within his described architecture of Hell , Purgatory and Paradise , (such as the seven layers of Purgatory's mountain purging the seven cardinal sins that correspond to astrology's seven classical planets ). [ 62 ] Similar astrological allegories and planetary themes are pursued through the works of Geoffrey Chaucer . [ 63 ]
Chaucer's astrological passages are particularly frequent and knowledge of astrological basics is often assumed through his work. He knew enough of his period's astrology and astronomy to write a Treatise on the Astrolabe for his son. He pinpoints the early spring season of the Canterbury Tales in the opening verses of the prologue by noting that the Sun "hath in the Ram his halfe cours yronne". [ 64 ] He makes the Wife of Bath refer to "sturdy hardiness" as an attribute of Mars , and associates Mercury with "clerkes". [ 65 ] In the early modern period, astrological references are also to be found in the works of William Shakespeare [ 66 ] and John Milton .
One of the earliest English astrologers to leave details of his practice was Richard Trewythian (b. 1393). His notebook demonstrates that he had a wide range of clients, from all walks of life, and indicates that engagement with astrology in 15th-century England was not confined to those within learned, theological or political circles. [ 67 ]
During the Renaissance, court astrologers would complement their use of horoscopes with astronomical observations and discoveries. Many individuals now credited with having overturned the old astrological order, such as Tycho Brahe , Galileo Galilei and Johannes Kepler , were themselves practicing astrologers. [ 68 ]
At the end of the Renaissance the confidence placed in astrology diminished, with the breakdown of Aristotelian Physics and rejection of the distinction between the celestial and sublunar realms , which had historically acted as the foundation of astrological theory. Keith Thomas writes that although heliocentrism is consistent with astrology theory, 16th and 17th century astronomical advances meant that "the world could no longer be envisaged as a compact inter-locking organism; it was now a mechanism of infinite dimensions, from which the hierarchical subordination of earth to heaven had irrefutably disappeared". [ 69 ] Initially, amongst the astronomers of the time, "scarcely anyone attempted a serious refutation in the light of the new principles" and in fact astronomers "were reluctant to give up the emotional satisfaction provided by a coherent and interrelated universe". By the 18th century the intellectual investment which had previously maintained astrology's standing was largely abandoned. [ 69 ] Historian of science Ann Geneva writes:
Astrology in seventeenth century England was not a science. It was not a Religion. It was not magic. Nor was it astronomy, mathematics, puritanism, neo Platism, psychology, meteorology, alchemy or witchcraft. It used some of these as tools; it held tenets in common with others; and some people were adept at several of these skills. But in the final analysis it was only itself: a unique divinatory and prognostic art embodying centuries of accreted methodology and tradition. [ 70 ]
The earliest recorded use of astrology in India is recorded during the Vedic period . Astrology, or jyotiṣa is listed as a Vedanga , or branch of the Vedas of the Vedic religion . The only work of this class to have survived is the Vedanga Jyotisha , which contains rules for tracking the motions of the sun and the moon in the context of a five-year intercalation cycle. The date of this work is uncertain, as its late style of language and composition, consistent with the last centuries BC, albeit pre- Mauryan , conflicts with some internal evidence of a much earlier date in the 2nd millennium BC. [ 71 ] [ 72 ] Indian astronomy and astrology developed together. The earliest treatise on Jyotisha, the Bhrigu Samhita , was compiled by the sage Bhrigu during the Vedic era . The sage Bhirgu is also called the 'Father of Hindu Astrology', and is one of the venerated Saptarishi or seven Vedic sages. The Saptarishis are also symbolized by the seven main stars in the Ursa Major constellation. [ citation needed ]
The documented history of Jyotisha in the subsequent newer sense of modern horoscopic astrology is associated with the interaction of Indian and Hellenistic cultures through the Greco-Bactrian and Indo-Greek Kingdoms. [ 73 ] The oldest surviving treatises, such as the Yavanajataka or the Brihat-Samhita , date to the early centuries AD. The oldest astrological treatise in Sanskrit is the Yavanajataka ("Sayings of the Greeks"), a versification by Sphujidhvaja in 269/270 AD of a now lost translation of a Greek treatise by Yavanesvara during the 2nd century AD under the patronage of the Indo-Scythian king Rudradaman I of the Western Satraps . [ 74 ]
Written on pages of tree bark, the Samhita (Compilation) is said to contain five million horoscopes comprising all who have lived in the past or will live in the future. The first named authors writing treatises on astronomy are from the 5th century AD, the date when the classical period of Indian astronomy can be said to begin. Besides the theories of Aryabhata in the Aryabhatiya and the lost Arya-siddhānta , there is the Pancha-Siddhāntika of Varahamihira .
The Chinese astrological system is based on native astronomy and calendars , and its significant development is tied to that of native astronomy , which came to flourish during the Han dynasty (2nd century BC – 2nd century AD). [ 75 ]
Chinese astrology has a close relation with Chinese philosophy (theory of three harmonies: heaven, earth and water) and uses the principles of yin and yang , and concepts that are not found in Western astrology, such as the wu xing teachings, the 10 Celestial stems , the 12 Earthly Branches , the lunisolar calendar (moon calendar and sun calendar), and the time calculation after year, month, day and shichen (時辰).
Astrology was traditionally regarded highly in China, and Confucius is said to have treated astrology with respect saying: "Heaven sends down its good or evil symbols and wise men act accordingly". [ 76 ] The 60-year cycle combining the five elements with the twelve animal signs of the zodiac has been documented in China since at least the time of the Shang (Shing or Yin) dynasty (c. 1766 BC – c. 1050 BC). Oracle bones have been found dating from that period with the date according to the 60-year cycle inscribed on them, along with the name of the diviner and the topic being divined. Astrologer Tsou Yen lived around 300 BC, and wrote: "When some new dynasty is going to arise, heaven exhibits auspicious signs for the people".
There is debate as to whether the Babylonian astrology influenced early development of Chinese astrology. [ 77 ] Later in the 6th century, the translation of the Mahāsaṃnipāta Sūtra brought the Babylonian system to China. Though it did not displace Chinese astrology, it was referenced in several poems. [ 78 ]
The calendars of Pre-Columbian Mesoamerica are based upon a system which had been in common use throughout the region, dating back to at least the 6th century BC. The earliest calendars were employed by peoples such as the Zapotecs and Olmecs , and later by such peoples as the Maya , Mixtec and Aztecs . Although the Mesoamerican calendar did not originate with the Maya, their subsequent extensions and refinements to it were the most sophisticated. Along with those of the Aztecs, the Maya calendars are the best-documented and most completely understood.
The distinctive Mayan calendar used two main systems, one plotting the solar year of 360 days, which governed the planting of crops and other domestic matters; the other called the Tzolkin of 260 days, which governed ritual use. Each was linked to an elaborate astrological system to cover every facet of life. On the fifth day after the birth of a boy, the Mayan astrologer-priests would cast his horoscope to see what his profession was to be: soldier, priest, civil servant or sacrificial victim. [ 76 ] A 584-day Venus cycle was also maintained, which tracked the appearance and conjunctions of Venus . Venus was seen as a generally inauspicious and baleful influence, and Mayan rulers often planned the beginning of warfare to coincide with when Venus rose. There is evidence that the Maya also tracked the movements of Mercury, Mars and Jupiter, and possessed a zodiac of some kind. The Mayan name for the constellation Scorpio was also 'scorpion', while the name of the constellation Gemini was 'peccary'. There is some evidence for other constellations being named after various beasts. [ 79 ] The most famous Mayan astrological observatory still intact is the Caracol observatory in the ancient Mayan city of Chichen Itza in modern-day Mexico .
The Aztec calendar shares the same basic structure as the Mayan calendar , with two main cycles of 360 days and 260 days. The 260-day calendar was called Tonalpohualli and was used primarily for divinatory purposes. Like the Mayan calendar, these two cycles formed a 52-year 'century', sometimes called the Calendar Round . | https://en.wikipedia.org/wiki/History_of_astrology |
The history of astronomy focuses on the contributions civilizations have made to further their understanding of the universe beyond earth's atmosphere. [ 1 ] Astronomy is one of the oldest natural sciences , achieving a high level of success in the second half of the first millennium. Astronomy has origins in the religious , mythological , cosmological , calendrical, and astrological beliefs and practices of prehistory. Early astronomical records date back to the Babylonians around 1000 BCE. There is also astronomical evidence of interest from early Chinese, Central American and North European cultures. [ 2 ]
Astronomy was used by early cultures for a variety of reasons. These include timekeeping, navigation , spiritual and religious practices, and agricultural planning. Ancient astronomers used their observations to chart the skies in an effort to learn about the workings of the universe. During the Renaissance Period, revolutionary ideas emerged about astronomy. One such idea was contributed in 1593 by Polish astronomer Nicolaus Copernicus , who developed a heliocentric model that depicted the planets orbiting the sun. This was the start of the Copernican Revolution , [ 3 ] with the invention of the telescope in 1608 playing a key part.
The success of astronomy, compared to other sciences, was achieved because of several reasons. Astronomy was the first science to have a mathematical foundation and have sophisticated procedures such as using armillary spheres and quadrants. This provided a solid base for collecting and verifying data. [ 4 ] [ 5 ] Throughout the years, astronomy has broadened into multiple subfields such as astrophysics , observational astronomy , theoretical astronomy , and astrobiology . [ 6 ]
Early cultures identified celestial objects with gods and spirits. [ 7 ] They related these objects (and their movements) to phenomena such as rain , drought , seasons , and tides . It is generally believed that the first astronomers were priests who understood celestial objects and events to be manifestations of the divine , hence the connection to what is now called astrology . A 32,500-year-old carved ivory mammoth tusk could contain the oldest known star chart (resembling the constellation Orion ). [ 8 ] It has also been suggested that drawings on the wall of the Lascaux caves in France dating from 33,000 to 10,000 years ago could be a graphical representation of the Pleiades , the Summer Triangle , and the Northern Crown . [ 9 ] [ 10 ] Ancient structures with possibly astronomical alignments (such as Stonehenge ) probably fulfilled astronomical, religious , and social functions .
Calendars of the world have often been set by observations of the Sun and Moon (marking the day , month , and year ) and were important to agricultural societies, in which the harvest depended on planting at the correct time of year. The nearly full moon was also the only lighting for night-time travel into city markets. [ 11 ]
The common modern calendar is based on the Roman calendar . Although originally a lunar calendar , it broke the traditional link of the month to the phases of the Moon and divided the year into twelve almost-equal months, that mostly alternated between thirty and thirty-one days. Julius Caesar instigated calendar reform in 46 BC and introduced what is now called the Julian calendar , based upon the 365 + 1 ⁄ 4 day year length originally proposed by the 4th century BC Greek astronomer Callippus .
Ancient astronomical artifacts have been found throughout Europe . The artifacts demonstrate that Neolithic and Bronze Age Europeans had a sophisticated knowledge of mathematics and astronomy.
Among the discoveries are:
The origins of astronomy can be found in Mesopotamia , the "land between the rivers" Tigris and Euphrates , where the ancient kingdoms of Sumer , Assyria , and Babylonia were located. A form of writing known as cuneiform emerged among the Sumerians around 3500–3000 BC. Our knowledge of Sumerian astronomy is indirect, via the earliest Babylonian star catalogues dating from about 1200 BC. The fact that many star names appear in Sumerian suggests a continuity reaching into the Early Bronze Age. Astral theology , which gave planetary gods an important role in Mesopotamian mythology and religion , began with the Sumerians . They also used a sexagesimal (base 60) place-value number system, which simplified the task of recording very large and very small numbers. The modern practice of dividing a circle into 360 degrees , or an hour into 60 minutes, began with the Sumerians. For more information, see the articles on Babylonian numerals and mathematics .
Mesopotamia is worldwide the place of the earliest known astronomer and poet by name: Enheduanna , Akkadian high priestess to the lunar deity Nanna/Sin and princess, daughter of Sargon the Great ( c. 2334 – c. 2279 BCE). She had the Moon tracked in her chambers and wrote poems about her divine Moon. [ 26 ]
Classical sources frequently use the term Chaldeans for the astronomers of Mesopotamia, who were originally a people , before being identified with priest-scribes specializing in astrology and other forms of divination .
The first evidence of recognition that astronomical phenomena are periodic and of the application of mathematics to their prediction is Babylonian. Tablets dating back to the Old Babylonian period document the application of mathematics to the variation in the length of daylight over a solar year. Centuries of Babylonian observations of celestial phenomena are recorded in the series of cuneiform tablets known as the Enūma Anu Enlil . The oldest significant astronomical text that we possess is Tablet 63 of the Enūma Anu Enlil , the Venus tablet of Ammi-saduqa , which lists the first and last visible risings of Venus over a period of about 21 years and is the earliest evidence that the phenomena of a planet were recognized as periodic. The MUL.APIN contains catalogues of stars and constellations as well as schemes for predicting heliacal risings and the settings of the planets, lengths of daylight measured by a water clock , gnomon , shadows, and intercalations . The Babylonian GU text arranges stars in 'strings' that lie along declination circles and thus measure right-ascensions or time-intervals, and also employs the stars of the zenith, which are also separated by given right-ascensional differences. [ 27 ]
A significant increase in the quality and frequency of Babylonian observations appeared during the reign of Nabonassar (747–733 BC). The systematic records of ominous phenomena in Babylonian astronomical diaries that began at this time allowed for the discovery of a repeating 18-year cycle of lunar eclipses , for example. The Greek astronomer Ptolemy later used Nabonassar's reign to fix the beginning of an era, since he felt that the earliest usable observations began at this time.
The last stages in the development of Babylonian astronomy took place during the time of the Seleucid Empire (323–60 BC). In the 3rd century BC, astronomers began to use "goal-year texts" to predict the motions of the planets. These texts compiled records of past observations to find repeating occurrences of ominous phenomena for each planet. About the same time, or shortly afterwards, astronomers created mathematical models that allowed them to predict these phenomena directly, without consulting records. A notable Babylonian astronomer from this time was Seleucus of Seleucia , who was a supporter of the heliocentric model .
Babylonian astronomy was the basis for much of what was done in Greek and Hellenistic astronomy , in classical Indian astronomy , in Sassanian Iran, in Byzantium, in Syria, in Islamic astronomy , in Central Asia, and in Western Europe. [ 28 ]
Astronomy in the Indian subcontinent dates back to the period of Indus Valley Civilisation during 3rd millennium BC, when it was used to create calendars. [ 29 ] As the Indus Valley civilization did not leave behind written documents, the oldest extant Indian astronomical text is the Vedanga Jyotisha , dating from the Vedic period . [ 30 ] The Vedanga Jyotisha is attributed to Lagadha and has an internal date of approximately 1350 BC, and describes rules for tracking the motions of the Sun and the Moon for the purposes of ritual. It is available in two recensions, one belonging to the Rig Veda, and the other to the Yajur Veda. According to the Vedanga Jyotisha, in a yuga or "era", there are 5 solar years, 67 lunar sidereal cycles, 1,830 days, 1,835 sidereal days, and 62 synodic months. During the sixth century, astronomy was influenced by the Greek and Byzantine astronomical traditions. [ 29 ] [ 31 ] [ 32 ]
Aryabhata (476–550), in his magnum opus Aryabhatiya (499), propounded a computational system based on a planetary model in which the Earth was taken to be spinning on its axis and the periods of the planets were given with respect to the Sun. He accurately calculated many astronomical constants, such as the periods of the planets, times of the solar and lunar eclipses , and the instantaneous motion of the Moon. [ 33 ] [ 34 ] [ page needed ] Early followers of Aryabhata's model included Varāhamihira , Brahmagupta , and Bhāskara II .
Astronomy was advanced during the Shunga Empire , and many star catalogues were produced during this time. The Shunga period is known [ according to whom? ] as the "Golden age of astronomy in India".
It saw the development of calculations for the motions and places of various planets, their rising and setting, conjunctions , and the calculation of eclipses.
By the sixth century, Indian astronomers believed that comets were celestial bodies that re-appeared periodically. This was the view expressed in the sixth century by the astronomers Varahamihira and Bhadrabahu. The tenth-century astronomer Bhattotpala listed the names and estimated periods of certain comets, but it is not known how these figures were calculated or how accurate they were. [ 35 ]
The Ancient Greeks developed astronomy, which they treated as a branch of mathematics, to a highly sophisticated level. The first geometrical, three-dimensional models to explain the apparent motion of the planets were developed in the 4th century BC by Eudoxus of Cnidus and Callippus of Cyzicus . Their models were based on nested homocentric spheres centered upon the Earth. Their younger contemporary Heraclides Ponticus proposed that the Earth rotates around its axis.
A different approach to celestial phenomena was taken by natural philosophers such as Plato and Aristotle . They were less concerned with developing mathematical predictive models than with developing an explanation of the reasons for the motions of the Cosmos. In his Timaeus , Plato described the universe as a spherical body divided into circles carrying the planets and governed according to harmonic intervals by a world soul . [ 36 ] Aristotle, drawing on the mathematical model of Eudoxus, proposed that the universe was made of a complex system of concentric spheres , whose circular motions combined to carry the planets around the Earth. [ 37 ] This basic cosmological model prevailed, in various forms, until the 16th century.
In the 3rd century BC Aristarchus of Samos was the first to suggest a heliocentric system, although only fragmentary descriptions of his idea survive. [ 38 ] Eratosthenes estimated the circumference of the Earth with great accuracy (see also: history of geodesy ). [ 39 ]
Greek geometrical astronomy developed away from the model of concentric spheres to employ more complex models in which an eccentric circle would carry around a smaller circle, called an epicycle which in turn carried around a planet. The first such model is attributed to Apollonius of Perga and further developments in it were carried out in the 2nd century BC by Hipparchus of Nicea . Hipparchus made a number of other contributions, including the first measurement of precession and the compilation of the first star catalog in which he proposed our modern system of apparent magnitudes .
The Antikythera mechanism , an ancient Greek astronomical observational device for calculating the movements of the Sun and the Moon, possibly the planets, dates from about 150–100 BC, and was the first ancestor of an astronomical computer . It was discovered in an ancient shipwreck off the Greek island of Antikythera , between Kythera and Crete . The device became famous for its use of a differential gear , previously believed to have been invented in the 16th century, and the miniaturization and complexity of its parts, comparable to a clock made in the 18th century. The original mechanism is displayed in the Bronze collection of the National Archaeological Museum of Athens , accompanied by a replica.
Depending on the historian's viewpoint, the acme or corruption [ citation needed ] [ dubious – discuss ] of Classical physical astronomy is seen with Ptolemy , a Greco-Roman astronomer from Alexandria of Egypt, who wrote the classic comprehensive presentation of geocentric astronomy, the Megale Syntaxis (Great Synthesis), better known by its Arabic title Almagest , which had a lasting effect on astronomy up to the Renaissance . In his Planetary Hypotheses , Ptolemy ventured into the realm of cosmology, developing a physical model of his geometric system, in a universe many times smaller than the more realistic conception of Aristarchus of Samos four centuries earlier.
The precise orientation of the Egyptian pyramids affords a lasting demonstration of the high degree of technical skill in watching the heavens attained in the 3rd millennium BC. It has been shown the Pyramids were aligned towards the pole star , which, because of the precession of the equinoxes , was at that time Thuban , a faint star in the constellation of Draco . [ 40 ] Evaluation of the site of the temple of Amun-Re at Karnak , taking into account the change over time of the obliquity of the ecliptic , has shown that the Great Temple was aligned on the rising of the midwinter Sun. [ 41 ] The length of the corridor down which sunlight would travel would have limited illumination at other times of the year. The Egyptians also found the position of Sirius (the dog star), who they believed was Anubis, their jackal-headed god, moving through the heavens. Its position was critical to their civilisation as when it rose heliacal in the east before sunrise it foretold the flooding of the Nile. It is also the origin of the phrase "dog days of summer". [ 42 ]
Astronomy played a considerable part in religious matters for fixing the dates of festivals and determining the hours of the night . The titles of several temple books are preserved recording the movements and phases of the Sun , Moon , and stars . The rising of Sirius ( Egyptian : Sopdet, Greek : Sothis) at the beginning of the inundation was a particularly important point to fix in the yearly calendar.
Writing in the Roman era , Clement of Alexandria gives some idea of the importance of astronomical observations to the sacred rites:
And after the Singer advances the Astrologer (ὡροσκόπος), with a horologium (ὡρολόγιον) in his hand, and a palm (φοίνιξ), the symbols of astrology . He must know by heart the Hermetic astrological books, which are four in number. Of these, one is about the arrangement of the fixed stars that are visible; one on the positions of the Sun and Moon and five planets; one on the conjunctions and phases of the Sun and Moon; and one concerns their risings. [ 43 ]
The Astrologer's instruments ( horologium and palm ) are a plumb line and sighting instrument [ clarification needed ] . They have been identified with two inscribed objects in the Berlin Museum ; a short handle from which a plumb line was hung, and a palm branch with a sight-slit in the broader end. The latter was held close to the eye, the former in the other hand, perhaps at arm's length. The "Hermetic" books which Clement refers to are the Egyptian theological texts, which probably have nothing to do with Hellenistic Hermetism . [ 44 ]
From the tables of stars on the ceiling of the tombs of Rameses VI and Rameses IX it seems that for fixing the hours of the night a man seated on the ground faced the Astrologer in such a position that the line of observation of the pole star passed over the middle of his head. On the different days of the year each hour was determined by a fixed star culminating or nearly culminating in it, and the position of these stars at the time is given in the tables as in the centre, on the left eye, on the right shoulder, etc. According to the texts, in founding or rebuilding temples the north axis was determined by the same apparatus, and we may conclude that it was the usual one for astronomical observations. In careful hands it might give results of a high degree of accuracy.
The astronomy of East Asia began in China . Solar term was completed in Warring States period . The knowledge of Chinese astronomy was introduced into East Asia.
Astronomy in China has a long history. Detailed records of astronomical observations were kept from about the 6th century BC, until the introduction of Western astronomy and the telescope in the 17th century. Chinese astronomers were able to precisely predict eclipses.
Much of early Chinese astronomy was for the purpose of timekeeping. The Chinese used a lunisolar calendar, but because the cycles of the Sun and the Moon are different, astronomers often prepared new calendars and made observations for that purpose.
Astrological divination was also an important part of astronomy. Astronomers took careful note of "guest stars" ( Chinese : 客星 ; pinyin : kèxīng ; lit. 'guest star') which suddenly appeared among the fixed stars . They were the first to record a supernova, in the Astrological Annals of the Houhanshu in 185 AD. Also, the supernova that created the Crab Nebula in 1054 is an example of a "guest star" observed by Chinese astronomers, although it was not recorded by their European contemporaries. Ancient astronomical records of phenomena like supernovae and comets are sometimes used in modern astronomical studies.
The world's first star catalogue was made by Gan De , a Chinese astronomer , in the 4th century BC.
Maya astronomical codices include detailed tables for calculating phases of the Moon , the recurrence of eclipses, and the appearance and disappearance of Venus as morning and evening star . The Maya based their calendrics in the carefully calculated cycles of the Pleiades , the Sun , the Moon , Venus , Jupiter , Saturn , Mars , and also they had a precise description of the eclipses as depicted in the Dresden Codex , as well as the ecliptic or zodiac, and the Milky Way was crucial in their Cosmology. [ 45 ] A number of important Maya structures are believed to have been oriented toward the extreme risings and settings of Venus. To the ancient Maya, Venus was the patron of war and many recorded battles are believed to have been timed to the motions of this planet. Mars is also mentioned in preserved astronomical codices and early mythology . [ 46 ]
Although the Maya calendar was not tied to the Sun, John Teeple has proposed that the Maya calculated the solar year to somewhat greater accuracy than the Gregorian calendar . [ 47 ] Both astronomy and an intricate numerological scheme for the measurement of time were vitally important components of Maya religion .
The Maya believed that the Earth was the center of all things, and that the stars, moons, and planets were gods. They believed that their movements were the gods traveling between the Earth and other celestial destinations. Many key events in Maya culture were timed around celestial events, in the belief that certain gods would be present. [ 48 ]
The Arabic and the Persian world under Islam had become highly cultured, and many important works of knowledge from Greek astronomy , Indian astronomy , and Persian astronomy were translated into Arabic, which were then used and stored in libraries throughout the area. An important contribution by Islamic astronomers was their emphasis on observational astronomy . [ 49 ] This led to the emergence of the first astronomical observatories in the Muslim world by the early 9th century. [ 50 ] [ 51 ] Zij star catalogues were produced at these observatories.
In the ninth century, Persian astrologer Albumasar was thought to be one of the greatest astrologer at that time. His practical manuals for training astrologers profoundly influenced Muslim intellectual history and, through translations, that of western Europe and Byzantium In the 10th century, [ 52 ] Albumasar's "Introduction" was one of the most important sources for the recovery of Aristotle for medieval European scholars. [ 53 ] Abd al-Rahman al-Sufi (Azophi) carried out observations on the stars and described their positions, magnitudes , brightness, and colour and drawings for each constellation in his Book of Fixed Stars . He also gave the first descriptions and pictures of "A Little Cloud" now known as the Andromeda Galaxy . He mentions it as lying before the mouth of a Big Fish, an Arabic constellation . This "cloud" was apparently commonly known to the Isfahan astronomers, very probably before 905 AD. [ 54 ] The first recorded mention of the Large Magellanic Cloud was also given by al-Sufi. [ 55 ] [ 56 ] In 1006, Ali ibn Ridwan observed SN 1006 , the brightest supernova in recorded history, and left a detailed description of the temporary star.
In the late tenth century, a huge observatory was built near Tehran , Iran , by the astronomer Abu-Mahmud al-Khujandi who observed a series of meridian transits of the Sun, which allowed him to calculate the tilt of the Earth's axis relative to the Sun. He noted that measurements by earlier (Indian, then Greek) astronomers had found higher values for this angle, possible evidence that the axial tilt is not constant but was in fact decreasing. [ 57 ] [ 58 ] In 11th-century Persia, Omar Khayyám compiled many tables and performed a reformation of the calendar that was more accurate than the Julian and came close to the Gregorian .
Other Muslim advances in astronomy included the collection and correction of previous astronomical data, resolving significant problems in the Ptolemaic model , the development of the universal latitude-independent astrolabe by Arzachel , [ 59 ] the invention of numerous other astronomical instruments, Ja'far Muhammad ibn Mūsā ibn Shākir 's belief that the heavenly bodies and celestial spheres were subject to the same physical laws as Earth , [ 60 ] and the introduction of empirical testing by Ibn al-Shatir , who produced the first model of lunar motion which matched physical observations. [ 61 ]
Natural philosophy (particularly Aristotelian physics ) was separated from astronomy by Ibn al-Haytham (Alhazen) in the 11th century, by Ibn al-Shatir in the 14th century, [ 62 ] and Qushji in the 15th century. [ 63 ]
Bhāskara II (1114–1185) was the head of the astronomical observatory at Ujjain, continuing the mathematical tradition of Brahmagupta. He wrote the Siddhantasiromani which consists of two parts: Goladhyaya (sphere) and Grahaganita (mathematics of the planets). He also calculated the time taken for the Sun to orbit the Earth to nine decimal places. The Buddhist University of Nalanda at the time offered formal courses in astronomical studies.
Other important astronomers from India include Madhava of Sangamagrama , Nilakantha Somayaji and Jyeshtadeva , who were members of the Kerala school of astronomy and mathematics from the 14th century to the 16th century. Nilakantha Somayaji, in his Aryabhatiyabhasya , a commentary on Aryabhata's Aryabhatiya , developed his own computational system for a partially heliocentric planetary model, in which Mercury, Venus, Mars , Jupiter and Saturn orbit the Sun , which in turn orbits the Earth , similar to the Tychonic system later proposed by Tycho Brahe in the late 16th century. Nilakantha's system, however, was mathematically more efficient than the Tychonic system, due to correctly taking into account the equation of the centre and latitudinal motion of Mercury and Venus. Most astronomers of the Kerala school of astronomy and mathematics who followed him accepted his planetary model. [ 64 ] [ 65 ]
After the significant contributions of Greek scholars to the development of astronomy, it entered a relatively static era in Western Europe from the Roman era through the 12th century. This lack of progress has led some astronomers to assert that nothing happened in Western European astronomy during the Middle Ages. [ 66 ] Recent investigations, however, have revealed a more complex picture of the study and teaching of astronomy in the period from the 4th to the 16th centuries. [ 67 ]
Western Europe entered the Middle Ages with great difficulties that affected the continent's intellectual production. The advanced astronomical treatises of classical antiquity were written in Greek , and with the decline of knowledge of that language, only simplified summaries and practical texts were available for study. The most influential writers to pass on this ancient tradition in Latin were Macrobius , Pliny , Martianus Capella , and Calcidius . [ 68 ] In the 6th century Bishop Gregory of Tours noted that he had learned his astronomy from reading Martianus Capella, and went on to employ this rudimentary astronomy to describe a method by which monks could determine the time of prayer at night by watching the stars. [ 69 ]
In the 7th century the English monk Bede of Jarrow published an influential text, On the Reckoning of Time , providing churchmen with the practical astronomical knowledge needed to compute the proper date of Easter using a procedure called the computus . This text remained an important element of the education of clergy from the 7th century until well after the rise of the Universities in the 12th century . [ 70 ]
The range of surviving ancient Roman writings on astronomy and the teachings of Bede and his followers began to be studied in earnest during the revival of learning sponsored by the emperor Charlemagne . [ 71 ] By the 9th century rudimentary techniques for calculating the position of the planets were circulating in Western Europe; medieval scholars recognized their flaws, but texts describing these techniques continued to be copied, reflecting an interest in the motions of the planets and in their astrological significance. [ 72 ]
Building on this astronomical background, in the 10th century European scholars such as Gerbert of Aurillac began to travel to Spain and Sicily to seek out learning which they had heard existed in the Arabic-speaking world. There they first encountered various practical astronomical techniques concerning the calendar and timekeeping, most notably those dealing with the astrolabe . Soon scholars such as Hermann of Reichenau were writing texts in Latin on the uses and construction of the astrolabe and others, such as Walcher of Malvern , were using the astrolabe to observe the time of eclipses in order to test the validity of computistical tables. [ 73 ]
By the 12th century, scholars were traveling to Spain and Sicily to seek out more advanced astronomical and astrological texts, which they translated into Latin from Arabic and Greek to further enrich the astronomical knowledge of Western Europe. The arrival of these new texts coincided with the rise of the universities in medieval Europe, in which they soon found a home. [ 74 ] Reflecting the introduction of astronomy into the universities, John of Sacrobosco wrote a series of influential introductory astronomy textbooks: the Sphere , a Computus, a text on the Quadrant , and another on Calculation. [ 75 ]
In the 14th century, Nicole Oresme , later bishop of Liseux, showed that neither the scriptural texts nor the physical arguments advanced against the movement of the Earth were demonstrative and adduced the argument of simplicity for the theory that the Earth moves, and not the heavens. However, he concluded "everyone maintains, and I think myself, that the heavens do move and not the earth: For God hath established the world which shall not be moved." [ 76 ] In the 15th century, Cardinal Nicholas of Cusa suggested in some of his scientific writings that the Earth revolved around the Sun, and that each star is itself a distant sun.
During the renaissance period, astronomy began to undergo a revolution in thought known as the Copernican Revolution , which gets the name from the astronomer Nicolaus Copernicus , who proposed a heliocentric system, in which the planets revolved around the Sun and not the Earth. His De revolutionibus orbium coelestium was published in 1543. [ 77 ] While in the long term this was a very controversial claim, in the very beginning it only brought minor controversy. [ 77 ] The theory became the dominant view because many figures, most notably Galileo Galilei , Johannes Kepler and Isaac Newton championed and improved upon the work. Other figures also aided this new model despite not believing the overall theory, like Tycho Brahe , with his well-known observations. [ 78 ]
Brahe, a Danish noble, was an essential astronomer in this period. [ 78 ] He came on the astronomical scene with the publication of De nova stella , in which he disproved conventional wisdom on the supernova SN 1572 [ 78 ] (As bright as Venus at its peak, SN 1572 later became invisible to the naked eye, disproving the Aristotelian doctrine of the immutability of the heavens.) [ 79 ] [ 80 ] He also created the Tychonic system , where the Sun and Moon and the stars revolve around the Earth, but the other five planets revolve around the Sun. This system blended the mathematical benefits of the Copernican system with the "physical benefits" of the Ptolemaic system. [ 81 ] This was one of the systems people believed in when they did not accept heliocentrism, but could no longer accept the Ptolemaic system. [ 81 ] He is most known for his highly accurate observations of the stars and the planets. Later he moved to Prague and continued his work. In Prague he was at work on the Rudolphine Tables , that were not finished until after his death. [ 82 ] The Rudolphine Tables was a star map designed to be more accurate than either the Alfonsine tables , made in the 1300s, and the Prutenic Tables , which were inaccurate. [ 82 ] He was assisted at this time by his assistant Johannes Kepler, who would later use his observations to finish Brahe's works and for his theories as well. [ 82 ]
After the death of Brahe, Kepler was deemed his successor and was given the job of completing Brahe's uncompleted works, like the Rudolphine Tables. [ 82 ] He completed the Rudolphine Tables in 1624, although it was not published for several years. [ 82 ] Like many other figures of this era, he was subject to religious and political troubles, like the Thirty Years' War , which led to chaos that almost destroyed some of his works. Kepler was, however, the first to attempt to derive mathematical predictions of celestial motions from assumed physical causes. He discovered the three Kepler's laws of planetary motion that now carry his name, those laws being as follows:
With these laws, he managed to improve upon the existing heliocentric model. The first two were published in 1609. Kepler's contributions improved upon the overall system, giving it more credibility because it adequately explained events and could cause more reliable predictions. Before this, the Copernican model was just as unreliable as the Ptolemaic model. This improvement came because Kepler realized the orbits were not perfect circles, but ellipses.
The invention of the telescope in 1608 revolutionized the study of astronomy. Galileo Galilei was among the first to use a telescope [ 84 ] to observe the sky, after constructing a 20x refractor telescope. [ 85 ] He discovered the four largest moons of Jupiter in 1610, which are now collectively known as the Galilean moons , in his honor. [ 86 ] This discovery was the first known observation of satellites orbiting another planet. [ 86 ] He also found that the Moon had craters and observed, and correctly explained sunspots, and that Venus exhibited a full set of phases resembling lunar phases. [ 87 ] Galileo argued that these facts demonstrated incompatibility with the Ptolemaic model, which could not explain the phenomenon and would even contradict it. [ 87 ] With Jupiter's moons, he demonstrated that the Earth does not have to have everything orbiting it and that other bodies could orbit another planet, such as the Earth orbiting the Sun. [ 86 ] In the Ptolemaic system the celestial bodies were supposed to be perfect so such objects should not have craters or sunspots. [ 88 ] The phases of Venus could only happen in the event that Venus orbits around the Sun, which did not happen in the Ptolemaic system. He, as the most famous example, had to face challenges from church officials, more specifically the Roman Inquisition . [ 89 ] They accused him of heresy because these beliefs went against the teachings of the Roman Catholic Church and were challenging the Catholic church's authority when it was at its weakest. [ 89 ] While he was able to avoid punishment for a little while he was eventually tried and pled guilty to heresy in 1633. [ 89 ] Although this came at some expense, his book was banned, and he was put under house arrest until he died in 1642. [ 90 ]
Sir Isaac Newton developed further ties between physics and astronomy through his law of universal gravitation . Realizing that the same force that attracts objects to the surface of the Earth held the Moon in orbit around the Earth, Newton was able to explain – in one theoretical framework – all known gravitational phenomena. In his Philosophiæ Naturalis Principia Mathematica , he derived Kepler's laws from first principles. Those first principles are as follows:
Thus while Kepler explained how the planets moved, Newton accurately managed to explain why the planets moved the way they do. Newton's theoretical developments laid many of the foundations of modern physics.
Outside of England, Newton's theory took some time to become established. René Descartes ' theory of vortices held sway in France, and Christiaan Huygens , Gottfried Wilhelm Leibniz and Jacques Cassini accepted only parts of Newton's system, preferring their own philosophies. Voltaire published a popular account in 1738. [ 92 ] In 1748, the French Academy of Sciences offered a reward for solving the question of the perturbations of Jupiter and Saturn, which was eventually done by Euler and Lagrange . Laplace completed the theory of the planets, publishing from 1798 to 1825. The early origins of the solar nebular model of planetary formation had begun.
Edmond Halley succeeded John Flamsteed as Astronomer Royal in England and succeeded in predicting the return of the comet that bears his name in 1758. William Herschel found the first new planet, Uranus , to be observed in modern times in 1781. The gap between the planets Mars and Jupiter disclosed by the Titius–Bode law was filled by the discovery of the asteroids Ceres and Pallas in 1801 and 1802 with many more following.
At first, astronomical thought in America was based on Aristotelian philosophy , [ 93 ] but interest in the new astronomy began to appear in Almanacs as early as 1659. [ 94 ]
Cosmic pluralism is the name given to the idea that the stars are distant suns, perhaps with their own planetary systems.
Ideas in this direction were expressed in antiquity, by Anaxagoras and by Aristarchus of Samos , but did not find mainstream acceptance. The first astronomer of the European Renaissance to suggest that the stars were distant suns was Giordano Bruno in his De l'infinito universo et mondi (1584). This idea, together with a belief in intelligent extraterrestrial life, was among the charges brought against him by the Inquisition.
The idea became mainstream in the later 17th century, especially following the publication of Conversations on the Plurality of Worlds by Bernard Le Bovier de Fontenelle (1686), and by the early 18th century it was the default working assumptions in stellar astronomy.
The Italian astronomer Geminiano Montanari recorded observing variations in luminosity of the star Algol in 1667. Edmond Halley published the first measurements of the proper motion of a pair of nearby "fixed" stars, demonstrating that they had changed positions since the time of the ancient Greek astronomers Ptolemy and Hipparchus. William Herschel was the first astronomer to attempt to determine the distribution of stars in the sky. During the 1780s, he established a series of gauges in 600 directions and counted the stars observed along each line of sight. From this he deduced that the number of stars steadily increased toward one side of the sky, in the direction of the Milky Way core . His son John Herschel repeated this study in the southern hemisphere and found a corresponding increase in the same direction. [ 95 ] In addition to his other accomplishments, William Herschel is noted for his discovery that some stars do not merely lie along the same line of sight, but are physical companions that form binary star systems. [ 96 ]
Pre-photography, data recording of astronomical data was limited by the human eye. In 1840, John W. Draper , a chemist, created the earliest known astronomical photograph of the Moon. And by the late 19th century thousands of photographic plates of images of planets, stars, and galaxies were created. Most photography had lower quantum efficiency (i.e. captured less of the incident photons) than human eyes but had the advantage of long integration times (100 ms for the human eye compared to hours for photos). This vastly increased the data available to astronomers, which led to the rise of human computers , famously the Harvard Computers , to track and analyze the data.
Scientists began discovering forms of light which were invisible to the naked eye: X-rays , gamma rays , radio waves , microwaves , ultraviolet radiation , and infrared radiation . This had a major impact on astronomy, spawning the fields of infrared astronomy , radio astronomy , x-ray astronomy and finally gamma-ray astronomy . With the advent of spectroscopy it was proven that other stars were similar to the Sun, but with a range of temperatures , masses and sizes.
The science of stellar spectroscopy was pioneered by Joseph von Fraunhofer and Angelo Secchi . By comparing the spectra of stars such as Sirius to the Sun, they found differences in the strength and number of their absorption lines —the dark lines in stellar spectra caused by the atmosphere's absorption of specific frequencies. In 1865, Secchi began classifying stars into spectral types . [ 97 ] The first evidence of helium was observed on August 18, 1868, as a bright yellow spectral line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun. The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India.
The first direct measurement of the distance to a star ( 61 Cygni at 11.4 light-years ) was made in 1838 by Friedrich Bessel using the parallax technique. Parallax measurements demonstrated the vast separation of the stars in the heavens. [ citation needed ] Observation of double stars gained increasing importance during the 19th century. In 1834, Friedrich Bessel observed changes in the proper motion of the star Sirius and inferred a hidden companion. Edward Pickering discovered the first spectroscopic binary in 1899 when he observed the periodic splitting of the spectral lines of the star Mizar in a 104-day period. Detailed observations of many binary star systems were collected by astronomers such as Friedrich Georg Wilhelm von Struve and S. W. Burnham , allowing the masses of stars to be determined from the computation of orbital elements . The first solution to the problem of deriving an orbit of binary stars from telescope observations was made by Felix Savary in 1827. [ 98 ] In 1847, Maria Mitchell discovered a comet using a telescope.
With the accumulation of large sets of astronomical data, teams like the Harvard Computers rose in prominence which led to many female astronomers, previously relegated as assistants to male astronomers, gaining recognition in the field. The United States Naval Observatory (USNO) and other astronomy research institutions hired human "computers" , who performed the tedious calculations while scientists performed research requiring more background knowledge. [ 99 ] A number of discoveries in this period were originally noted by the women "computers" and reported to their supervisors. Henrietta Swan Leavitt discovered the cepheid variable star period-luminosity relation which she further developed into a method of measuring distance outside of the Solar System.
A veteran of the Harvard Computers, Annie J. Cannon developed the modern version of the stellar classification scheme in during the early 1900s (O B A F G K M, based on color and temperature), manually classifying more stars in a lifetime than anyone else (around 350,000). [ 100 ] [ 101 ] The twentieth century saw increasingly rapid advances in the scientific study of stars. Karl Schwarzschild discovered that the color of a star and, hence, its temperature, could be determined by comparing the visual magnitude against the photographic magnitude . The development of the photoelectric photometer allowed precise measurements of magnitude at multiple wavelength intervals. In 1921 Albert A. Michelson made the first measurements of a stellar diameter using an interferometer on the Hooker telescope at Mount Wilson Observatory . [ 102 ]
Important theoretical work on the physical structure of stars occurred during the first decades of the twentieth century. In 1913, the Hertzsprung–Russell diagram was developed, propelling the astrophysical study of stars.
In Potsdam in 1906, the Danish astronomer Ejnar Hertzsprung published the first plots of color versus luminosity for these stars. These plots showed a prominent and continuous sequence of stars, which he named the Main Sequence.
At Princeton University , Henry Norris Russell plotted the spectral types of these stars against their absolute magnitude, and found that dwarf stars followed a distinct relationship. This allowed the real brightness of a dwarf star to be predicted with reasonable accuracy.
Successful models were developed to explain the interiors of stars and stellar evolution. Cecilia Payne-Gaposchkin first proposed that stars were made primarily of hydrogen and helium in her 1925 doctoral thesis. [ 103 ] The spectra of stars were further understood through advances in quantum physics . This allowed the chemical composition of the stellar atmosphere to be determined. [ 104 ] As evolutionary models of stars were developed during the 1930s, Bengt Strömgren introduced the term Hertzsprung–Russell diagram to denote a luminosity-spectral class diagram.
A refined scheme for stellar classification was published in 1943 by William Wilson Morgan and Philip Childs Keenan .
The existence of our galaxy , the Milky Way , as a separate group of stars was only proven in the 20th century, along with the existence of "external" galaxies, and soon after, the expansion of the universe seen in the recession of most galaxies from us. The " Great Debate " between Harlow Shapley and Heber Curtis , in the 1920s, concerned the nature of the Milky Way, spiral nebulae, and the dimensions of the universe. [ 105 ]
With the advent of quantum physics , spectroscopy was further refined.
The Sun was found to be part of a galaxy made up of more than 10 10 stars (10 billion stars). The existence of other galaxies, one of the matters of the great debate , was settled by Edwin Hubble , who identified the Andromeda nebula as a different galaxy, and many others at large distances and receding, moving away from our galaxy.
Physical cosmology , a discipline that has a large intersection with astronomy, made huge advances during the 20th century, with the model of the hot Big Bang heavily supported by the evidence provided by astronomy and physics, such as the redshifts of very distant galaxies and radio sources, the cosmic microwave background radiation , Hubble's law and cosmological abundances of elements . | https://en.wikipedia.org/wiki/History_of_astronomy |
Attachment theory , originating in the work of John Bowlby , is a psychological , evolutionary and ethological theory that provides a descriptive and explanatory framework for understanding interpersonal relationships between human beings.
In order to formulate a comprehensive theory of the nature of early attachments, Bowlby explored a range of fields including evolution by natural selection, object relations theory ( psychoanalysis ), control systems theory , evolutionary biology and the fields of ethology and cognitive psychology . [ 1 ] There were some preliminary papers from 1958 onwards but the full theory is published in the trilogy Attachment and Loss , 1969- 82. Although in the early days Bowlby was criticised by academic psychologists and ostracised by the psychoanalytic community, [ 2 ] attachment theory has become the dominant approach to understanding early social development and given rise to a great surge of empirical research into the formation of children's close relationships. [ 3 ]
In infants, behavior associated with attachment is primarily a process of proximity seeking to an identified attachment figure in situations of perceived distress or alarm, for the purpose of survival. Infants become attached to adults who are sensitive and responsive in social interactions with the infant, and who remain as consistent caregivers for some months during the period from about six months to two years of age. During the later part of this period, children begin to use attachment figures (familiar people) as a secure base to explore from and return to. Parental responses lead to the development of patterns of attachment which in turn lead to 'internal working models' which will guide the individual's feelings, thoughts, and expectations in later relationships. [ 4 ] Separation anxiety or grief following serious loss are normal and natural responses in an attached infant.
The human infant is considered by attachment theorists to have a need for a secure relationship with adult caregivers, without which normal social and emotional development will not occur. However, different relationship experiences can lead to different developmental outcomes. Mary Ainsworth developed a theory of a number of attachment patterns or "styles" in infants in which distinct characteristics were identified; these were secure attachment, avoidant attachment, anxious attachment and, later, disorganized attachment. In addition to care-seeking by children, peer relationships of all ages, romantic and sexual attraction, and responses to the care needs of infants or sick or elderly adults may be construed as including some components of attachment behavior.
A theory of attachment is a framework of ideas that attempt to explain attachment, the almost universal human tendency to prefer certain familiar companions over other people, especially when ill, injured, or distressed. [ 5 ] Historically, certain social preferences, like those of parents for their children, were explained by reference to instinct, or the moral worth of the individual. [ 6 ]
The concept of infants' emotional attachment to caregivers has been known anecdotally for hundreds of years. Most early observers focused on the anxiety displayed by infants and toddlers when threatened with separation from a familiar caregiver. [ 6 ] [ 7 ] Psychological theories about attachment were suggested from the late nineteenth century onward. [ 8 ] Freudian theory attempted a systematic consideration of infant attachment and attributed the infant's attempts to stay near the familiar person to motivation learned through feeding experiences and gratification of libidinal drives . In the 1930s, the British developmentalist Ian Suttie put forward the suggestion that the child's need for affection was a primary one, not based on hunger or other physical gratifications. [ 9 ] A third theory prevalent at the time of Bowlby's development of attachment theory was "dependency". This approach posited that infants were dependent on adult caregivers but that dependency was, or should be outgrown as the individual matured. Such an approach perceived attachment behaviour in older children as regressive whereas within attachment theory older children and adults remain attached and indeed a secure attachment is associated with independent exploratory behaviour rather than dependence. [ 10 ] William Blatz , a Canadian psychologist and teacher of Bowlby's colleague Mary Ainsworth, was among the first to stress the need for security as a normal part of personality at all ages, as well as normality of the use of others as a secure base and the importance of social relationships for other aspects of development. [ 11 ]
Current attachment theory focuses on social experiences in early childhood as the source of attachment in childhood and in later life. [ 12 ] Attachment theory was developed by Bowlby as a consequence of his dissatisfaction with existing theories of early relationships. [ 13 ]
Bowlby was influenced by the beginnings of the object relations school of psychoanalysis and in particular, Melanie Klein , although he profoundly disagreed with the psychoanalytic belief then prevalent that saw infants' responses as relating to their internal fantasy life rather than to real life events. As Bowlby began to formulate his concept of attachment, he was influenced by case studies by Levy, Powdermaker, Lowrey, Bender and Goldfarb. [ 14 ] An example is the one by David Levy that associated an adopted child's lack of social emotion to her early emotional deprivation. [ 15 ] Bowlby himself was interested in the role played in delinquency by poor early relationships, and explored this in a study of young thieves. [ 16 ] Bowlby's contemporary René Spitz proposed that " psychotoxic " results were brought about by inappropriate experiences of early care. [ 17 ] A strong influence was the work of James and Joyce Robertson who filmed the effects of separation on children in hospital. They and Bowlby collaborated in making the 1952 documentary film A Two-Year Old Goes to the Hospital illustrating the impact of loss and suffering experienced by young children separated from their primary caretakers. This film was instrumental in a campaign to alter hospital restrictions on visiting by parents. [ 18 ]
In his 1951 monograph for the World Health Organization , Maternal Care and Mental Health , Bowlby put forward the hypothesis that "the infant and young child should experience a warm, intimate, and continuous relationship with his mother (or permanent mother substitute) in which both find satisfaction and enjoyment" and that not to do so may have significant and irreversible mental health consequences. This proposition was both influential in terms of the effect on the institutional care of children, and highly controversial. [ 19 ] There was limited empirical data at the time and no comprehensive theory to account for such a conclusion. [ 20 ]
Following the publication of Maternal Care and Mental Health , Bowlby sought new understanding from such fields as evolutionary biology, ethology, developmental psychology, cognitive science and control systems theory and drew upon them to formulate the innovative proposition that the mechanisms underlying an infants tie emerged as a result of evolutionary pressure. [ 13 ] He realised that he had to develop a new theory of motivation and behaviour control, built on up-to-date science rather than the outdated psychic energy model espoused by Freud. [ 8 ] Bowlby expressed himself as having made good the "deficiencies of the data and the lack of theory to link alleged cause and effect" in "Maternal Care and Mental Health" in his later work "Attachment and Loss" published between 1969 and 1980. [ 21 ]
Bowlby's first official representations were carried out for the relationship theory in three very controversial lectures in 1957 by the British Psychoanalytical Society in London. [ 22 ] The formal origin of attachment theory can be traced to the publication of two 1958 papers, one being Bowlby's The Nature of the Child's Tie to his Mother , in which the precursory concepts of "attachment" were introduced, and Harry Harlow 's The Nature of Love , based on the results of experiments which showed, approximately, that infant rhesus monkeys spent more time with soft mother-like dummies that offered no food than they did with dummies that provided a food source but were less pleasant to the touch. [ 23 ] [ 24 ] [ 25 ] [ 26 ] Bowlby followed this up with two more papers, Separation Anxiety (1960a), and Grief and Mourning in Infancy and Early Childhood (1960b). [ 27 ] [ 28 ] At about the same time, Bowlby's former colleague, Mary Ainsworth was completing extensive observational studies on the nature of infant attachments in Uganda with Bowlby's ethological theories in mind. Mary Ainsworth's innovative methodology and comprehensive observational studies informed much of the theory, expanded its concepts and enabled some of its tenets to be empirically tested. [ 29 ] Attachment theory was finally presented in 1969 in Attachment the first volume of the Attachment and Loss trilogy. [ 30 ] The second and third volumes, Separation: Anxiety and Anger and Loss: Sadness and Depression followed in 1972 and 1980 respectively. [ 31 ] [ 32 ] Attachment was revised in 1982 to incorporate more recent research. [ 33 ]
Bowlby's attention was first drawn to ethology when he read Lorenz 's 1952 publication in draft form although Lorenz had published much earlier work. [ 34 ] Soon after this he encountered the work of Tinbergen , [ 35 ] and began to collaborate with Robert Hinde . [ 36 ] [ 37 ] In 1953 he stated "the time is ripe for a unification of psychoanalytic concepts with those of ethology, and to pursue the rich vein of research which this union suggests". [ 38 ]
Konrad Lorenz had examined the phenomenon of " imprinting " and felt that it might have some parallels to human attachment. Imprinting, a behavior characteristic of some birds and a very few mammals, involves rapid learning of recognition by a young bird or animal exposed to a conspecific or an object or organism that behaves suitably. The learning is possible only within a limited age period, known as a critical period. This rapid learning and development of familiarity with an animate or inanimate object is accompanied by a tendency to stay close to the object and to follow when it moves; the young creature is said to have been imprinted on the object when this occurs. As the imprinted bird or animal reaches reproductive maturity, its courtship behavior is directed toward objects that resemble the imprinting object. Bowlby's attachment concepts later included the ideas that attachment involves learning from experience during a limited age period, and that the learning that occurs during that time influences adult behavior. However, he did not apply the imprinting concept in its entirety to human attachment, nor assume that human development was as simple as that of birds. He did, however, consider that attachment behavior was best explained as instinctive in nature, an approach that does not rule out the effect of experience, but that stresses the readiness the young child brings to social interactions. [ 39 ] Some of Lorenz's work had been done years before Bowlby formulated his ideas, and indeed some ideas characteristic of ethology were already discussed among psychoanalysts some time before the presentation of attachment theory. [ 40 ]
Bowlby's view of attachment was also influenced by psychoanalytical concepts and the earlier work of psychoanalysts. In particular he was influenced by observations of young children separated from familiar caregivers, as provided during World War II by Anna Freud and her colleague Dorothy Burlingham. [ 41 ]
Observations of separated children's grief by René Spitz were another important factor in the development of attachment theory. [ 42 ] However, Bowlby rejected psychoanalytical explanations for early infant bonds. He rejected both Freudian " drive-theory ", which he called the Cupboard Love theory of relationships, and early object-relations theory as both in his view failed to see the attachment as a psychological bond in its own right rather than an instinct derived from feeding or sexuality. [ 43 ] Thinking in terms of primary attachment and neo-darwinism, Bowlby identified as what he saw as fundamental flaws in psychoanalysis, namely the overemphasis of internal dangers at the expense of external threat, and the picture of the development of personality via linear "phases" with " regression " to fixed points accounting for psychological illness. Instead he posited that several lines of development were possible, the outcome of which depended on the interaction between the organism and the environment. In attachment this would mean that although a developing child has a propensity to form attachments, the nature of those attachments depends on the environment to which the child is exposed. [ 44 ]
The important concept of the internal working model of social relationships was adopted by Bowlby from the work of the philosopher Kenneth Craik , [ 45 ] who had noted the adaptiveness of the ability of thought to predict events, and stressed the survival value of and natural selection for this ability. According to Craik, prediction occurs when a "small-scale model" consisting of brain events is used to represent not only the external environment, but the individual's own possible actions. This model allows a person to mentally try out alternatives and to use knowledge of the past in responding to the present and future. At about the same time that Bowlby was applying Craik's ideas to the study of attachment, other psychologists were using these concepts in discussion of adult perception and cognition. [ 46 ]
The theory of control systems (cybernetics), developing during the 1930s and '40s, influenced Bowlby's thinking. [ 47 ] The young child's need for proximity to the attachment figure was seen as balancing homeostatically with the need for exploration. The actual distance maintained would be greater or less as the balance of needs changed; for example, the approach of a stranger, or an injury, would cause the child to seek proximity when a moment before he had been exploring at a distance.
Behaviour analysts have constructed models of attachment. Such models are based on the importance of contingent relationships. Behaviour analytic models have received support from research. [ 48 ] and meta-analytic reviews. [ 49 ]
Although research on attachment behaviors continued after Bowlby's death in 1990, there was a period of time when attachment theory was considered to have run its course. Some authors argued that attachment should not be seen as a trait (lasting characteristic of the individual), but instead should be regarded as an organizing principle with varying behaviors resulting from contextual factors. [ 50 ] Related later research looked at cross-cultural differences in attachment, and concluded that there should be re-evaluation of the assumption that attachment is expressed identically in all humans. [ 51 ] In a recent study conducted in Sapporo , Behrens, et al., 2007 found attachment distributions consistent with global norms using the six-year Main & Cassidy scoring system for attachment classification. [ 52 ] [ 53 ]
Interest in attachment theory continued, and the theory was later extended to adult romantic relationships by Cindy Hazan and Phillip Shaver. [ 54 ] [ 55 ] [ 56 ] Peter Fonagy and Mary Target have attempted to bring attachment theory and psychoanalysis into a closer relationship by way of such aspects of cognitive science as mentalization, the ability to estimate what the beliefs or intentions of another person may be. [ 47 ] A "natural experiment" has permitted extensive study of attachment issues, as researchers have followed the thousands of Romanian orphans who were adopted into Western families after the end of Nicolae Ceauşescu 's regime. The English and Romanian Adoptees Study Team, led by Michael Rutter , has followed some of the children into their teens, attempting to unravel the effects of poor attachment, adoption and new relationships, and the physical and medical problems associated with their early lives. Studies on the Romanian adoptees, whose initial conditions were shocking, have in fact yielded reason for optimism. Many of the children have developed quite well, and the researchers have noted that separation from familiar people is only one of many factors that help to determine the quality of development. [ 57 ]
Neuroscientific studies are examining the physiological underpinnings of observable attachment style, such as vagal tone which influences capacities for intimacy, [ 58 ] stress response which influences threat reactivity (Lupien, McEwan, Gunnar & Heim, 2009), [ 59 ] as well as neuroendocrinology such as oxytocin. [ 60 ] [ 61 ] These types of studies underscore the fact that attachment is an embodied capacity not only a cognitive one.
Some authors have noted the connection of attachment theory with Western family and child care patterns characteristic of Bowlby's time. The implication of this connection is that attachment-related experiences (and perhaps attachment itself) may alter as young children's experience of care change historically. For example, changes in attitudes toward female sexuality have greatly increased the numbers of children living with their never-married mothers and being cared for outside the home while the mothers work.
This social change, in addition to increasing abortion rates, has also made it more difficult for childless people to adopt infants in their own countries, and has increased the number of older-child adoptions and adoptions from third-world sources. Adoptions and births to same-sex couples have increased in number and even gained some legal protection, compared to their status in Bowlby's time. [ 62 ]
One focus of attachment research has been on the difficulties of children whose attachment history was poor, including those with extensive non-parental child care experiences. Concern with the effects of child care was intense during the so-called "day care wars" of the late 20th century, during which the deleterious effects of day care were stressed. [ 63 ] As a beneficial result of this controversy, training of child care professionals has come to stress attachment issues and the need for relationship-building through techniques such as assignment of a child to a specific care provider. Although only high-quality child care settings are likely to follow through on these considerations, nevertheless a larger number of infants in child care receive attachment-friendly care than was the case in the past, and emotional development of children in nonparental care may be different today than it was in the 1980s or in Bowlby's time. [ 64 ]
Finally, any critique of attachment theory needs to consider how the theory has connected with changes in other psychological theories. Research on attachment issues has begun to include concepts related to behaviour genetics and to the study of temperament (constitutional factors in personality), but it is unusual for popular presentations of attachment theory to include these. Importantly, some researchers and theorists have begun to connect attachment with the study of mentalization or Theory of Mind , the capacity that allows human beings to guess with some accuracy what thoughts, emotions, and intentions lie behind behaviours as subtle as facial expression or eye movement. [ 65 ] The connection of theory of mind with the internal working model of social relationships may open a new area of study and lead to alterations in attachment theory. [ 66 ]
The maternal deprivation hypothesis, attachment theory's precursor, was enormously controversial. Ten years after the publication of the hypothesis, Ainsworth listed nine concerns that she felt were the chief points of controversy. [ 67 ] Ainsworth separated the three dimensions of maternal deprivation into lack of maternal care, distortion of maternal care and discontinuity of maternal care. She analysed the dozens of studies undertaken in the field and concluded that the basic assertions of the maternal deprivation hypothesis were sound although the controversy continued. [ 68 ] As the formulation of attachment theory progressed, critics commented on empirical support for the theory and for the possible alternative explanations for results of empirical research. [ 69 ] Wootton questioned the suggestion that early attachment history (as it would now be called) had a lifelong impact. [ 70 ]
In 1957 found the young relationship theory in the DDR ( East Germany ) by an essay of James Robertson in the Zeitschrift für ärztliche Fortbildung (magazine for a medical further education) and Eva Schmidt-Kolmer carried out some journal extracts from Bowlby's essay Maternal Care and mental Health for WHO. [ 71 ] In the following period it came to extensive comparative development psychological in the DDR at the end of the fifties. Examinations between family-bound babies and small children, day and week hayracks-as well as Institution children. The findings could do with regard to the morbidity for the family-bound children, the physical and emotional development as well as adaption disturbances at change of environment. After the construction of the Berlin Wall 1961 it didn't come to any additional publications in the DDR Relationship theory and comparative investigations with family-bound children. The previous ones Research results weren't published further and got like the relationship theory into oblivion in the DDR in the subsequent years. [ 72 ]
In the 1970s, problems with the emphasis on attachment as a trait (a stable characteristic of an individual) rather than as a type of behaviour with important organising functions and outcomes, led some authors to consider that "attachment (as implying anything but infant-adult interaction) [may be said to have] outlived its usefulness as a developmental construct..." and that attachment behaviours were best understood in terms of their functions in the child's life. [ 50 ] Children may achieve a given function, such as a sense of security, in many different ways and the various but functionally comparable behaviours should be categorized as related to each other. This way of thinking saw the secure base concept (the organisation of exploration of an unfamiliar situation around returns to a familiar person) as "central to the logic and coherence of attachment theory and to its status as an organizational construct." [ 73 ] Similarly, Thompson pointed out that "other features of early parent-child relationships that develop concurrently with attachment security, including negotiating conflict and establishing cooperation, also must be considered in understanding the legacy of early attachments." [ 74 ]
From an early point in the development of attachment theory, there was criticism of the theory's lack of congruence with the various branches of psychoanalysis. Like other members of the British object-relations group, Bowlby rejected Melanie Klein 's views that considered the infant to have certain mental capacities at birth and to continue to develop emotionally on the basis of fantasy rather than of real experiences. But Bowlby also withdrew from the object-relations approach (exemplified, for example, by Anna Freud), as he abandoned the "drive theory" assumptions in favor of a set of automatic, instinctual behaviour systems that included attachment. Bowlby's decisions left him open to criticism from well-established thinkers working on problems similar to those he addressed. [ 75 ] [ 76 ] [ 77 ] Bowlby was effectively ostracized from the psychoanalytic community. [ 2 ] More recently some psychoanalysts have sought to reconcile the two theories in the form of attachment-based psychotherapy , a therapeutic approach.
Ethologists expressed concern about the adequacy of some of the research on which attachment theory was based, particularly the generalisation to humans from animal studies. [ 78 ] [ 79 ] Schur, discussing Bowlby's use of ethological concepts (pre-1960) commented that these concepts as used in attachment theory had not kept up with changes in ethology itself. [ 80 ]
Ethologists and others writing in the 1960s and 1970s questioned the types of behaviour used as indications of attachment, and offered alternative approaches. For example, crying on separation from a familiar person was suggested as an index of attachment. [ 81 ] Observational studies of young children in natural settings also provided behaviours that might be considered to indicate attachment; for example, staying within a predictable distance of the mother without effort on her part and picking up small objects and bringing them to the mother, but usually not other adults. [ 82 ] Although ethological work tended to be in agreement with Bowlby, work like that just described led to the conclusion that "[w]e appear to disagree with Bowlby and Ainsworth on some of the details of the child's interactions with its mother and other people". Some ethologists pressed for further observational data, arguing that psychologists "are still writing as if there is a real entity which is 'attachment', existing over and above the observable measures." [ 83 ]
Robert Hinde expressed concern with the use of the word "attachment" to imply that it was an intervening variable or a hypothesised internal mechanism rather than a data term. He suggested that confusion about the meaning of attachment theory terms "could lead to the 'instinct fallacy' of postulating a mechanism isomorphous with the behaviours, and then using that as an explanation for the behaviour". However, Hinde considered "attachment behaviour system" to be an appropriate term of theory language which did not offer the same problems "because it refers to postulated control systems that determine the relations between different kinds of behaviour." [ 84 ]
Bowlby's reliance on Piaget 's theory of cognitive development gave rise to questions about object permanence (the ability to remember an object that is temporarily absent) and its connection to early attachment behaviours, and about the fact that the infant's ability to discriminate strangers and react to the mother's absence seems to occur some months earlier than Piaget suggested would be cognitively possible. [ 85 ] More recently, it has been noted that the understanding of mental representation has advanced so much since Bowlby's day that present views can be far more specific than those of Bowlby's time. [ 86 ]
In 1969, Gewirtz discussed how mother and child could provide each other with positive reinforcement experiences through their mutual attention and therefore learn to stay close together; this explanation would make it unnecessary to posit innate human characteristics fostering attachment. [ 87 ] Learning theory saw attachment as a remnant of dependency and the quality of attachment as merely a response to the caregivers cues. Behaviourists saw behaviours such as crying as a random activity that meant nothing until reinforced by a caregivers response therefore frequent responses would result in more crying. To attachment theorists, crying is an inborn attachment behaviour to which the caregiver must respond if the infant is to develop emotional security. Conscientious responses produce security which enhances autonomy and results in less crying. Ainsworth's research in Baltimore supported the attachment theorists view. [ 88 ] In the last decade, behaviour analysts have constructed models of attachment based on the importance of contingent relationships. These behaviour analytic models have received some support from research [ 48 ] and meta-analytic reviews. [ 49 ]
There has been critical discussion of conclusions drawn from clinical and observational work, and whether or not they actually support tenets of attachment theory. For example, Skuse based criticism of a basic tenet of attachment theory on the work of Anna Freud with children from Theresienstadt, who apparently developed relatively normally in spite of serious deprivation during their early years. This discussion concluded from Freud's case and from some other studies of extreme deprivation that there is an excellent prognosis for children with this background, unless there are biological or genetic risk factors. [ 89 ] The psychoanalyst Margaret Mahler interpreted ambivalent or aggressive behaviour of toddlers toward their mothers as a normal part of development, not as evidence of poor attachment history. [ 90 ]
Some of Bowlby's interpretations of the data reported by James Robertson were eventually rejected by the researcher, who reported data from 13 young children who were cared for in ideal circumstances during separation from their mothers. Robertson noted, "...Bowlby acknowledges that he draws mainly upon James Robertson's institutional data. But in developing his grief and mourning theory, Bowlby, without adducing non-institutional data, has generalized Robertson's concept of protest, despair and denial beyond the context from which it was derived. He asserts that these are the usual responses of young children to separation from the mother regardless of circumstance..."; however, of the 13 separated children who received good care, none showed protest and despair, but "coped with separation from the mother when cared for in conditions from which the adverse factors which complicate institutional studies were absent". [ 91 ] In the second volume of the trilogy, Separation , published two years later, Bowlby acknowledged that Robertsons foster study had caused him to modify his views on the traumatic consequences of separation in which insufficient weight was given to the influence of skilled care from a familiar substitute. [ 92 ]
Some authors have questioned the idea of attachment patterns, thought to be measured by techniques like the Strange Situation Protocol. Such techniques yield a taxonomy of categories considered to represent qualitative difference in attachment relationships (for example, secure attachment versus avoidant). However, a categorical model is not necessarily the best representation of individual difference in attachment. An examination of data from 1139 15-month-olds showed that variation was continuous rather than falling into natural groupings. [ 93 ] This criticism introduces important questions for attachment typologies and the mechanisms behind apparent types, but in fact has relatively little relevance for attachment theory itself, which "neither requires nor predicts discrete patterns of attachment." [ 94 ] As was noted above, ethologists have suggested other behavioural measures that may be of greater importance than Strange Situation behaviour.
Following the argument made in the 1970s that attachment should not be seen as a trait (lasting characteristic of the individual), but instead should be regarded as an organising principle with varying behaviours resulting from contextual factors, [ 50 ] later research looked at cross-cultural differences in attachment, and concluded that there should be re-evaluation of the assumption that attachment is expressed identically in all humans. [ 51 ] Various studies appeared to show cultural differences but a 2007 study conducted in Sapporo in Japan found attachment distributions consistent with global norms using the six-year Main & Cassidy scoring system for attachment classification. [ 52 ] [ 53 ]
Recent critics such as J. R. Harris , Steven Pinker and Jerome Kagan are generally concerned with the concept of infant determinism ( Nature versus nurture ) and stress the possible effects of later experience on personality. [ 95 ] [ 96 ] [ 97 ] Building on the earlier work on temperament of Stella Chess , Kagan rejected almost every assumption on which attachment theory etiology was based, arguing that heredity was far more important than the transient effects of early environment, for example a child with an inherent difficult temperament would not illicit sensitive behavioural responses from their care giver. The debate spawned considerable research and analysis of data from the growing number of longitudinal studies. [ 98 ] Subsequent research has not bourne out Kagan's argument and broadly demonstrates that it is the caregivers' behaviours that form the child's attachment style although how this style is expressed may differ with temperament. [ 99 ]
Harris and Pinker have put forward the notion that the influence of parents has been much exaggerated and that socialisation takes place primarily in peer groups, although H. Rudolph Schaffer concludes that parents and peers fulfill different functions and have distinctive roles in children's development. [ 100 ] Concern about attachment theory has been raised with regard to the fact that infants often have multiple relationships, within the family as well as in child care settings, and that the dyadic model characteristic of attachment theory cannot address the complexity of real-life social experiences. [ 101 ] | https://en.wikipedia.org/wiki/History_of_attachment_theory |
The history of biochemistry can be said to have started with the ancient Greeks who were interested in the composition and processes of life, although biochemistry as a specific scientific discipline has its beginning around the early 19th century. [ 1 ] Some argued that the beginning of biochemistry may have been the discovery of the first enzyme , diastase (today called amylase ), in 1833 by Anselme Payen , [ 2 ] while others considered Eduard Buchner 's first demonstration of a complex biochemical process alcoholic fermentation in cell-free extracts to be the birth of biochemistry. [ 3 ] [ 4 ] Some might also point to the influential work of Justus von Liebig from 1842, Animal chemistry, or, Organic chemistry in its applications to physiology and pathology , which presented a chemical theory of metabolism, [ 1 ] or even earlier to the 18th century studies on fermentation and respiration by Antoine Lavoisier . [ 5 ] [ 6 ]
The term biochemistry itself is derived from the combining form bio- , meaning 'life', and chemistry . The word is first recorded in English in 1848, [ 7 ] while in 1877, Felix Hoppe-Seyler used the term ( Biochemie in German) in the foreword to the first issue of Zeitschrift für Physiologische Chemie (Journal of Physiological Chemistry) as a synonym for physiological chemistry and argued for the setting up of institutes dedicate to its studies. [ 8 ] [ 9 ] Nevertheless, several sources cite German chemist Carl Neuberg as having coined the term for the new discipline in 1903, [ 10 ] [ 11 ] and some credit it to Franz Hofmeister . [ 12 ]
The subject of study in biochemistry is the chemical processes in living organisms, and its history involves the discovery and understanding of the complex components of life and the elucidation of pathways of biochemical processes. Much of biochemistry deals with the structures and functions of cellular components such as proteins, carbohydrates, lipids, nucleic acids and other biomolecules; their metabolic pathways and flow of chemical energy through metabolism; how biological molecules give rise to the processes that occur within living cells; it also focuses on the biochemical processes involved in the control of information flow through biochemical signalling, and how they relate to the functioning of whole organisms. Over the last 40 years [ as of? ] the field has had success in explaining living processes such that now almost all areas of the life sciences from botany to medicine are engaged in biochemical research.
Among the vast number of different biomolecules, many are complex and large molecules (called polymers), which are composed of similar repeating subunits (called monomers). Each class of polymeric biomolecule has a different set of subunit types. For example, a protein is a polymer whose subunits are selected from a set of twenty or more amino acids, carbohydrates are formed from sugars known as monosaccharides, oligosaccharides, and polysaccharides, lipids are formed from fatty acids and glycerols, and nucleic acids are formed from nucleotides. Biochemistry studies the chemical properties of important biological molecules, like proteins, and in particular the chemistry of enzyme-catalyzed reactions. The biochemistry of cell metabolism and the endocrine system has been extensively described. Other areas of biochemistry include the genetic code (DNA, RNA), protein synthesis , cell membrane transport , and signal transduction .
In a sense, the study of biochemistry can be considered to have started in ancient times, for example when biology first began to interest society—as the ancient Chinese developed a system of medicine based on yin and yang , and also the five phases , [ 13 ] which both resulted from alchemical and biological interests. Its beginning in the ancient Indian culture was linked to an interest in medicine, as they developed the concept of three humors that were similar to the Greeks' four humours (see humorism ). They also delved into the interest of bodies being composed of tissues . The ancient Greeks' conception of biochemistry was linked with their ideas on matter and disease, where good health was thought to come from a balance of the four elements and four humors in the human body. [ 14 ] As in the majority of early sciences, the Islamic world contributed significantly to early biological advancements as well as alchemical advancements; especially with the introduction of clinical trials and clinical pharmacology presented in Avicenna 's The Canon of Medicine . [ 15 ] On the side of chemistry, early advancements were heavily attributed to exploration of alchemical interests but also included: metallurgy , the scientific method , and early theories of atomism . In more recent times, the study of chemistry was marked by milestones such as the development of Mendeleev's periodic table , Dalton's atomic model , and the conservation of mass theory. This last mention has the most importance of the three due to the fact that this law intertwines chemistry with thermodynamics in an intercalated manner.
As early as the late 18th century and early 19th century, the digestion of meat by stomach secretions [ 16 ] and the conversion of starch to sugars by plant extracts and saliva were known. However, the mechanism by which this occurred had not been identified. [ 17 ]
In the 19th century, when studying the fermentation of sugar to alcohol by yeast , Louis Pasteur concluded that this fermentation was catalyzed by a vital force contained within the yeast cells called ferments , which he thought functioned only within living organisms. He wrote that "alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells." [ 18 ]
In 1833 Anselme Payen discovered the first enzyme , diastase , [ 19 ] and in 1878 German physiologist Wilhelm Kühne (1837–1900) coined the term enzyme , which comes from Greek ενζυμον 'in leaven', to describe this process. The word enzyme was used later to refer to nonliving substances such as pepsin , and the word ferment was used to refer to chemical activity produced by living organisms.
In 1897 Eduard Buchner began to study the ability of yeast extracts to ferment sugar despite the absence of living yeast cells. In a series of experiments at the University of Berlin , he found that the sugar was fermented even when there were no living yeast cells in the mixture. [ 20 ] He named the enzyme that brought about the fermentation of sucrose zymase . [ 21 ] In 1907 he received the Nobel Prize in Chemistry "for his biochemical research and his discovery of cell-free fermentation". Following Buchner's example; enzymes are usually named according to the reaction they carry out. Typically the suffix -ase is added to the name of the substrate ( e.g. , lactase is the enzyme that cleaves lactose ) or the type of reaction ( e.g. , DNA polymerase forms DNA polymers).
Having shown that enzymes could function outside a living cell, the next step was to determine their biochemical nature. Many early workers noted that enzymatic activity was associated with proteins, but several scientists (such as Nobel laureate Richard Willstätter ) argued that proteins were merely carriers for the true enzymes and that proteins per se were incapable of catalysis. However, in 1926, James B. Sumner showed that the enzyme urease was a pure protein and crystallized it; Sumner did likewise for the enzyme catalase in 1937. The conclusion that pure proteins can be enzymes was definitively proved by Northrop and Stanley , who worked on the digestive enzymes pepsin (1930), trypsin, and chymotrypsin. These three scientists were awarded the 1946 Nobel Prize in Chemistry. [ 22 ]
This discovery, that enzymes could be crystallized, meant that scientists eventually could solve their structures by x-ray crystallography . This was first done for lysozyme , an enzyme found in tears, saliva, and egg whites that digests the coating of some bacteria; the structure was solved by a group led by David Chilton Phillips and published in 1965. [ 23 ] This high-resolution structure of lysozyme marked the beginning of the field of structural biology and the effort to understand how enzymes work at an atomic level of detail.
The term metabolism is derived from the Greek Μεταβολισμός – Metabolismos for 'change', or 'overthrow'. [ 24 ] The history of the scientific study of metabolism spans 800 years. The earliest of all metabolic studies began during the early thirteenth century (1213–1288) by a Muslim scholar from Damascus named Ibn al-Nafis . al-Nafis stated in his most well-known work Theologus Autodidactus that "that body and all its parts are in a continuous state of dissolution and nourishment, so they are inevitably undergoing permanent change." [ 25 ] Although al-Nafis was the first documented physician to have an interest in biochemical concepts, the first controlled experiments in human metabolism were published by Santorio Santorio in 1614 in his book Ars de statica medecina . [ 26 ] This book describes how he weighed himself before and after eating, sleeping, working, sex, fasting, drinking, and excreting. He found that most of the food he took in was lost through what he called " insensible perspiration ".
One of the most prolific of these modern biochemists was Hans Krebs who made huge contributions to the study of metabolism. [ 27 ] Krebs was a student of extremely important Otto Warburg , and wrote a biography of Warburg by that title in which he presents Warburg as being educated to do for biological chemistry what Fischer did for organic chemistry. Which he did. Krebs discovered the urea cycle and later, working with Hans Kornberg , the citric acid cycle and the glyoxylate cycle. [ 28 ] [ 29 ] [ 30 ] These discoveries led to Krebs being awarded the Nobel Prize in physiology in 1953, [ 31 ] which was shared with the German biochemist Fritz Albert Lipmann who also codiscovered the essential cofactor coenzyme A .
In 1960, the biochemist Robert K. Crane revealed his discovery of the sodium-glucose cotransport as the mechanism for intestinal glucose absorption. [ 32 ] This was the very first proposal of a coupling between the fluxes of an ion and a substrate that has been seen as sparking a revolution in biology. This discovery, however, would not have been possible if it were not for the discovery of the molecule glucose 's structure and chemical makeup. These discoveries are largely attributed to the German chemist Emil Fischer who received the Nobel Prize in chemistry nearly 60 years earlier. [ 33 ]
Since metabolism focuses on the breaking down (catabolic processes) of molecules and the building of larger molecules from these particles (anabolic processes), the use of glucose and its involvement in the formation of adenosine triphosphate (ATP) is fundamental to this understanding. The most frequent type of glycolysis found in the body is the type that follows the Embden-Meyerhof-Parnas (EMP) Pathway, which was discovered by Gustav Embden , Otto Meyerhof , and Jakob Karol Parnas . These three men discovered that glycolysis is a strongly determinant process for the efficiency and production of the human body. The significance of the pathway shown in the adjacent image is that by identifying the individual steps in this process doctors and researchers are able to pinpoint sites of metabolic malfunctions such as pyruvate kinase deficiency that can lead to severe anemia. This is most important because cells, and therefore organisms, are not capable of surviving without proper functioning metabolic pathways.
Since then, biochemistry has advanced, especially since the mid-20th century, with the development of new techniques such as chromatography , X-ray diffraction , NMR spectroscopy , radioisotopic labelling , electron microscopy and molecular dynamics simulations. These techniques allowed for the discovery and detailed analysis of many molecules and metabolic pathways of the cell , such as glycolysis and the Krebs cycle (citric acid cycle). The example of an NMR instrument shows that some of these instruments, such as the HWB-NMR, can be very large in size and can cost anywhere from a few thousand dollars to millions of dollars ($16 million for the one shown here).
Polymerase chain reaction (PCR) is the primary gene amplification technique that has revolutionized modern biochemistry. Polymerase chain reaction was developed by Kary Mullis in 1983. [ 34 ] There are four steps to a proper polymerase chain reaction: 1) denaturation 2) extension 3) insertion (of gene to be expressed) and finally 4) amplification of the inserted gene. These steps with simple illustrative examples of this process can be seen in the image below and to the right of this section. This technique allows for the copy of a single gene to be amplified into hundreds or even millions of copies and has become a cornerstone in the protocol for any biochemist that wishes to work with bacteria and gene expression. PCR is not only used for gene expression research but is also capable of aiding laboratories in diagnosing certain diseases such a lymphomas , some types of leukemia , and other malignant diseases that can sometimes puzzle doctors. Without polymerase chain reaction development, there are many advancements in the field of bacterial study and protein expression study that would not have come to fruition. [ 35 ] The development of the theory and process of polymerase chain reaction is essential but the invention of the thermal cycler is equally as important because the process would not be possible without this instrument. This is yet another testament to the fact that the advancement of technology is just as crucial to sciences such as biochemistry as is the painstaking research that leads to the development of theoretical concepts. | https://en.wikipedia.org/wiki/History_of_biochemistry |
Before the 20th century , the use of biological agents took three major forms:
In the 20th century , sophisticated bacteriological and virological techniques allowed the production of significant stockpiles of weaponized bio-agents :
The earliest documented incident of the intention to use biological weapons is possibly recorded in Hittite texts of 1500–1200 BC, in which victims of tularemia were driven into enemy lands, causing an epidemic. [ 1 ] Although the Assyrians knew of ergot , a parasitic fungus of rye which produces ergotism when ingested, there is no evidence that they poisoned enemy wells with the fungus, as has been claimed.
According to Homer's epic poems about the legendary Trojan War , the Iliad and the Odyssey , spears and arrows were tipped with poison. During the First Sacred War in Greece , in about 590 BC, Athens and the Amphictionic League poisoned the water supply of the besieged town of Kirrha (near Delphi ) with the toxic plant hellebore . [ 2 ] According to Herodotus , during the 4th century BC Scythian archers dipped their arrow tips into decomposing cadavers of humans and snakes [ 3 ] or in blood mixed with manure, [ 4 ] supposedly making them contaminated with dangerous bacterial agents like Clostridium perfringens and Clostridium tetani , and snake venom . [ 5 ]
In a naval battle against King Eumenes of Pergamon in 184 BC, Hannibal of Carthage had clay pots filled with venomous snakes and instructed his sailors to throw them onto the decks of enemy ships. [ 6 ] The Roman commander Manius Aquillius poisoned the wells of besieged enemy cities in about 130 BC. In about AD 198, the Parthian city of Hatra (near Mosul , Iraq) repulsed the Roman army led by Septimius Severus by hurling clay pots filled with live scorpions at them. [ 7 ] Like Scythian archers, Roman soldiers dipped their swords into excrements and cadavers too — victims were commonly infected by tetanus as result. [ 8 ]
The use of bees as guided biological weapons was described in Byzantine written sources, such as Tactica of Emperor Leo VI the Wise in the chapter On Naval Warfare. [ 9 ]
There are numerous other instances of the use of plant toxins, venoms, and other poisonous substances to create biological weapons in antiquity. [ 10 ]
The Mongol Empire established commercial and political connections between the Eastern and Western areas of the world, through the most mobile army ever seen. The armies, composed of the most rapidly moving travelers who had ever moved between the steppes of East Asia (where bubonic plague was and remains endemic among small rodents), managed to keep the chain of infection without a break until they reached, and infected, peoples and rodents who had never encountered it. The ensuing Black Death may have killed up to 25 million total, including China and roughly a third of the population of Europe and in the next decades, changing the course of Asian and European history.
Biologicals were extensively used in many parts of Africa from the sixteenth century AD, most of the time in the form of poisoned arrows, or powder spread on the war front as well as poisoning of horses and water supply of the enemy forces. [ 11 ] [ 12 ] In Borgu, there were specific mixtures to kill, hypnotize, make the enemy bold, and to act as an antidote against the poison of the enemy as well. The creation of biologicals was reserved for a specific and professional class of medicine-men. [ 12 ] In South Sudan, the people of the Koalit Hills kept their country free of Arab invasions by using tsetse flies as a weapon of war. [ 13 ] Several accounts can give an idea of the efficiency of the biologicals. For example, Mockley-Ferryman in 1892 commented on the Dahomean invasion of Borgu, stating that "their (Borgawa) poisoned arrows enabled them to hold their own with the forces of Dahomey notwithstanding the latter's muskets." [ 12 ] The same scenario happened to Portuguese raiders in Senegambia when they were defeated by Mali's Gambian forces, and to John Hawkins in Sierra Leone where he lost a number of his men to poisoned arrows. [ 14 ]
During the Middle Ages , victims of the bubonic plague were used for biological attacks, often by flinging fomites such as infected corpses and excrement over castle walls using catapults . Bodies would be tied along with cannonballs and shot towards the city area. In 1346, during the siege of Caffa (now Feodossia , Crimea) the attacking Tartar Forces (subjugated by the Mongol Empire under Genghis Khan more than a century earlier), used the bodies of Mongol warriors of the Golden Horde who had died of plague, as weapons. It has been speculated that this operation may have been responsible for the advent of the Black Death in Europe. At the time, the attackers thought that the stench was enough to kill them, though it was the disease that was deadly. [ 15 ] [ 16 ] (However in recent years, some scholarship and research has cast doubt on the use of trebuchets to hurl corpses due to factors such as the size of trebuchets and how close they would have to be constructed due to the hilly landscape in Caffa.) [ 17 ]
At the siege of Thun-l'Évêque in 1340, during the Hundred Years' War , the attackers catapulted decomposing animals into the besieged area. [ 18 ]
In 1422, during the siege of Karlstein Castle in Bohemia , Hussite attackers used catapults to throw dead (but not plague-infected) bodies and 2000 carriage-loads of dung over the walls. [ 19 ]
English Longbowmen usually did not draw their arrows from a quiver ; rather, they stuck their arrows into the ground in front of them. This allowed them to nock the arrows faster and the dirt and soil was likely to stick to the arrowheads, thus making the wounds much more likely to become infected . [ citation needed ]
The last known incident of using plague corpses for biological warfare may have occurred in 1710, when Russian forces attacked Swedish troops by flinging plague-infected corpses over the city walls of Reval (Tallinn) (although this is disputed). [ 20 ] [ 21 ] [ 22 ] However, during the 1785 siege of La Calle , Tunisian forces flung diseased clothing into the city. [ 19 ]
During Pontiac's Rebellion , in June 1763 a group of Native Americans laid siege to British-held Fort Pitt . During a parley in the middle of the siege on June 24, Captain Simeon Ecuyer gave representatives of the besieging Delawares , including Turtleheart , two blankets and a handkerchief enclosed in small metal boxes that had been exposed to smallpox, in an attempt to spread the disease to the besieging Native warriors in order to end the siege. [ 23 ] William Trent , the trader turned militia commander who had come up with the plan, sent an invoice to the British colonial authorities in North America indicating that the purpose of giving the blankets was "to Convey the Smallpox to the Indians." The invoice was approved by General Thomas Gage , then serving as Commander-in-Chief, North America . [ 24 ] A reported outbreak that began the spring before left as many as one hundred Native Americans dead in Ohio Country from 1763 to 1764. It is not clear whether the smallpox was a result of the Fort Pitt incident or the virus was already present among the Delaware people as outbreaks happened on their own every dozen or so years [ 25 ] and the delegates were met again later and seemingly had not contracted smallpox. [ 26 ] [ 27 ] [ 28 ] Trade and combat also provided ample opportunity for transmission of the disease. [ 29 ]
A month later, Colonel Henry Bouquet , who was leading a relief attempt towards Fort Pitt, wrote to his superior Sir Jeffery Amherst to discuss the possibility of using smallpox-infested blankets to spread smallpox amongst Natives. Amherst wrote to Bouquet that: "Could it not be contrived to send the small pox among the disaffected tribes of Indians? We must on this occasion use every stratagem in our power to reduce them." Bouquet replied in a latter, writing that "I will try to inocculate [ sic ] the Indians by means of Blankets that may fall in their hands, taking care however not to get the disease myself. As it is pity to oppose good men against them, I wish we could make use of the Spaniard's Method, and hunt them with English Dogs. Supported by Rangers, and some Light Horse, who would I think effectively extirpate or remove that Vermine." After receiving Bouquet's response, Amherst wrote back to him, stating that "You will Do well to try to Innoculate [ sic ] the Indians by means of Blankets, as well as to try Every other method that can serve to Extirpate this Execrable Race. I should be very glad your Scheme for Hunting them Down by Dogs could take Effect, but England is at too great a Distance to think of that at present." [ citation needed ]
Many Aboriginal Australians have claimed that smallpox outbreaks in Australia were a deliberate result of European colonisation , [ 30 ] though this possibility has only been raised by historians from the 1980s onwards, when Noel Butlin suggested "there are some possibilities that... disease could have been used deliberately as an exterminating agent." [ 31 ]
In 1997, scholar David Day claimed there "remains considerable circumstantial evidence to suggest that officers other than Phillip , or perhaps convicts or soldiers... deliberately spread smallpox among aborigines", [ 32 ] and in 2000, John Lambert argued that "strong circumstantial evidence suggests the smallpox epidemic which ravaged Aborigines in 1789, may have resulted from deliberate infection." [ 33 ]
Judy Campbell argued in 2002 that it is highly improbable that the First Fleet was the source of the epidemic as "smallpox had not occurred in any members of the First Fleet"; the only possible source of infection from the Fleet being exposure to variolous matter imported for the purposes of inoculation against smallpox. Campbell argued that, while there has been considerable speculation about a hypothetical exposure to the First Fleet's variolous matter, there was no evidence that Aboriginal people were ever actually exposed to it. She pointed to regular contact between fishing fleets from the Indonesia archipelago, where smallpox was always present , and Aboriginal people in Australia's North as a more likely source for the introduction of smallpox. She notes that while these fishermen are generally referred to as 'Macassans', referring to the port of Macassar on the island of Sulawesi from which most of the fishermen originated, "some travelled from islands as distant as New Guinea". She noted that there is little disagreement that the smallpox epidemic of the 1860s was contracted from Macassan fishermen and spread through the Aboriginal population by Aborigines fleeing outbreaks and also via their traditional social, kinship and trading networks. She argued that the 1789–90 epidemic followed the same pattern. [ 34 ]
These claims are controversial as it is argued that any smallpox virus brought to New South Wales probably would have been sterilised by heat and humidity encountered during the voyage of the First Fleet from England and incapable of biological warfare. However, in 2007, Christopher Warren demonstrated that any smallpox which might have been carried onboard the First Fleet may have been still viable upon landing in Australia. [ 35 ] Since them, some scholars have argued that smallpox in Australia was deliberately spread by the inhabitants of the British penal colony at Port Jackson in 1789. [ 36 ] [ 37 ]
In 2013, Warren reviewed the issue and argued that smallpox did not spread across Australia before 1824 and showed that there was no smallpox at Macassar that could have caused the outbreak at Sydney. Warren, however, did not address the issue of persons who joined the Macassan fleet from other islands and from parts of Sulawesi other than the port of Macassar. Warren concluded that the British were "the most likely candidates to have released smallpox" near Sydney Cove in 1789. Warren proposed that the British had no choice as they were confronted with dire circumstances when, among other factors, they ran out of ammunition for their muskets; he also used Aboriginal oral tradition and archaeological records from indigenous gravesites to analyse the cause and effect of the spread of smallpox in 1789. [ 38 ]
Prior to the publication of Warren's article (2013), a professor of physiology John Carmody argued that the epidemic was an outbreak of chickenpox which took a drastic toll on an Aboriginal population without immunological resistance. [ 39 ] With regard to how smallpox might have reached the Sydney region, Carmody said: "There is absolutely no evidence to support any of the theories and some of them are fanciful and far-fetched." [ 40 ] [ 41 ] Warren argued against the chickenpox theory at endnote 3 of Smallpox at Sydney Cove – Who, When, Why? . [ 42 ] However, in a 2014 joint paper on historic Aboriginal demography, Carmody and the Australian National University's Boyd Hunter argued that the recorded behavior of the epidemic ruled out smallpox and indicated chickenpox . [ 43 ]
By the turn of the 20th century, advances in microbiology had made thinking about "germ warfare" part of the zeitgeist . Jack London , in his short story '" Yah! Yah! Yah! "' (1909), described a punitive European expedition to a South Pacific island deliberately exposing the Polynesian population to measles, of which many of them died. London wrote another science fiction tale the following year, " The Unparalleled Invasion " (1910), in which the Western nations wipe out all of China with a biological attack.
During the First World War (1914–1918), the German Empire made some early attempts at anti-agriculture biological warfare. Those attempts were made by special sabotage group headed by Rudolf Nadolny . Using diplomatic pouches and couriers, the German General Staff supplied small teams of saboteurs in the Russian Duchy of Finland , and in the then-neutral countries of Romania , the United States , and Argentina . [ 44 ] In Finland, saboteurs mounted on reindeer placed ampoules of anthrax in stables of Russian horses in 1916. [ 45 ] Anthrax was also supplied to the German military attaché in Bucharest , as was glanders , which was employed against livestock destined for Allied service. German intelligence officer and US citizen Anton Casimir Dilger established a secret lab in the basement of his sister's home in Chevy Chase, Maryland , that produced glanders which was used to infect livestock in ports and inland collection points including, at least, Newport News , Norfolk , Baltimore , and New York City , and probably St. Louis and Covington, Kentucky . In Argentina, German agents also employed glanders in the port of Buenos Aires and also tried to ruin wheat harvests with a destructive fungus. Also, Germany itself became a victim of similar attacks — horses bound for Germany were infected with Burkholderia by French operatives in Switzerland. [ 46 ]
The Geneva Protocol of 1925 prohibited the use of chemical weapons and biological weapons among signatory states in international armed conflicts, but said nothing about experimentation, production, storage, or transfer; later treaties did cover these aspects. Twentieth-century advances in microbiology enabled the first pure-culture biological agents to be developed by World War II.
In the interwar period, little research was done in biological warfare in both Britain and the United States at first. In the United Kingdom the preoccupation was mainly in withstanding the anticipated conventional bombing attacks that would be unleashed in the event of war with Germany . As tensions increased, Sir Frederick Banting began lobbying the British government to establish a research program into the research and development of biological weapons to effectively deter the Germans from launching a biological attack. Banting proposed a number of innovative schemes for the dissemination of pathogens, including aerial-spray attacks and germs distributed through the mail system.
With the onset of hostilities, the Ministry of Supply finally established a biological weapons programme at Porton Down , headed by the microbiologist Paul Fildes . The research was championed by Winston Churchill and soon tularemia , anthrax , brucellosis , and botulism toxins had been effectively weaponized. In particular, Gruinard Island in Scotland, during a series of extensive tests, was contaminated with anthrax for the next 48 years. Although Britain never offensively used the biological weapons it developed, its program was the first to successfully weaponize a variety of deadly pathogens and bring them into industrial production. [ 47 ] Other nations, notably France and Japan , had begun their own biological-weapons programs. [ 48 ]
When the United States entered the war, mounting British pressure for the creation of a similar research program for an Allied pooling of resources led to the creation of a large industrial complex at Fort Detrick, Maryland in 1942 under the direction of George W. Merck . [ 49 ] The biological and chemical weapons developed during that period were tested at the Dugway Proving Grounds in Utah . Soon there were facilities for the mass production of anthrax spores, brucellosis , and botulism toxins, although the war was over before these weapons could be of much operational use. [ 50 ]
However, the most notorious program of the period was run by the secret Imperial Japanese Army Unit 731 during the war , based at Pingfan in Manchuria and commanded by Lieutenant General Shirō Ishii . This unit did research on BW, conducted often fatal human experiments on prisoners, and produced biological weapons for combat use. [ 51 ] Although the Japanese effort lacked the technological sophistication of the American or British programs, it far outstripped them in its widespread application and indiscriminate brutality. Biological weapons were used against both Chinese soldiers and civilians in several military campaigns. Three veterans of Unit 731 testified in a 1989 interview to the Asahi Shimbun that they contaminated the Horustein river with typhoid near the Soviet troops during the Battle of Khalkhin Gol . [ 52 ] In 1940, the Imperial Japanese Army Air Force bombed Ningbo with ceramic bombs full of fleas carrying the bubonic plague. [ 53 ] A film showing this operation was seen by the imperial princes Tsuneyoshi Takeda and Takahito Mikasa during a screening made by mastermind Shirō Ishii. [ 54 ] During the Khabarovsk War Crime Trials the accused, such as Major General Kiyashi Kawashima, testified that as early as 1941 some 40 members of Unit 731 air-dropped plague-contaminated fleas on Changde . These operations caused epidemic plague outbreaks. [ 55 ]
Many of these operations were ineffective due to inefficient delivery systems, using disease-bearing insects rather than dispersing the agent as a bioaerosol cloud. [ 51 ]
Ban Shigeo, a technician at the Japanese Army 's 9th Technical Research Institute, left an account of the activities at the Institute which was published in "The Truth About the Army Noborito Institute". [ 56 ] Ban included an account of his trip to Nanking in 1941 to participate in the testing of poisons on Chinese prisoners. [ 56 ] His testimony tied the Noborito Institute to the infamous Unit 731, which participated in biomedical research. [ 56 ]
During the final months of World War II, Japan planned to utilize plague as a biological weapon against U.S. civilians in San Diego , California , during Operation Cherry Blossoms at Night . They hoped that it would kill tens of thousands of U.S. civilians and thereby dissuade America from attacking Japan. The plan was set to launch on September 22, 1945, at night, but it never came into fruition due to Japan's surrender on August 15, 1945. [ 57 ]
When the war ended, the US Army quietly enlisted certain members of Noborito in its efforts against the communist camp in the early years of the Cold War. [ 56 ] The head of Unit 731, Shirō Ishii , was granted immunity from war crimes prosecution in exchange for providing information to the United States on the Unit's activities. [ 58 ] Allegations were made that a "chemical section" of a US clandestine unit hidden within Yokosuka naval base was operational during the Korean War , and then worked on unspecified projects inside the United States from 1955 to 1959, before returning to Japan to enter the private sector. [ 56 ] [ 59 ]
Some of the Unit 731 personnel were imprisoned by the Soviets [ citation needed ] , and may have been a potential source of information on Japanese weaponization.
Considerable research into BW was undertaken throughout the Cold War era by the US, UK and USSR, and probably other major nations as well, although it is generally believed that such weapons were never used.
In Britain, the 1950s saw the weaponization of plague , brucellosis , tularemia and later equine encephalomyelitis and vaccinia viruses . Trial tests at sea were carried out including Operation Cauldron off Stornoway in 1952. The programme was cancelled in 1956, when the British government unilaterally renounced the use of biological and chemical weapons.
The United States initiated its weaponization efforts with disease vectors in 1953, focused on Plague-fleas, EEE-mosquitoes, and yellow fever – mosquitoes (OJ-AP). [ citation needed ] However, US medical scientists in occupied Japan undertook extensive research on insect vectors, with the assistance of former Unit 731 staff, as early as 1946. [ 58 ]
The United States Army Chemical Corps then initiated a crash program to weaponize anthrax (N) in the E61 1/2-lb hour-glass bomblet. Though the program was successful in meeting its development goals, the lack of validation on the infectivity of anthrax stalled standardization. [ citation needed ] The United States Air Force was also unsatisfied with the operational qualities of the M114/US bursting bomblet and labeled it an interim item until the Chemical Corps could deliver a superior weapon. [ citation needed ]
Around 1950 the Chemical Corps also initiated a program to weaponize tularemia (UL). Shortly after the E61/N failed to make standardization, tularemia was standardized in the 3.4" M143 bursting spherical bomblet . This was intended for delivery by the MGM-29 Sergeant missile warhead and could produce 50% infection over a 7-square-mile (18 km 2 ) area. [ 60 ] Although tularemia is treatable by antibiotics, treatment does not shorten the course of the disease. US conscientious objectors were used as consenting test subjects for tularemia in a program known as Operation Whitecoat . [ 61 ] There were also many unpublicized tests carried out in public places with bio-agent simulants during the Cold War. [ 62 ]
In addition to the use of bursting bomblets for creating biological aerosols, the Chemical Corps started investigating aerosol-generating bomblets in the 1950s. The E99 was the first workable design, but was too complex to be manufactured. By the late 1950s the 4.5" E120 spraying spherical bomblet was developed; a B-47 bomber with a SUU-24/A dispenser could infect 50% or more of the population of a 16-square-mile (41 km 2 ) area with tularemia with the E120. [ 63 ] The E120 was later superseded by dry-type agents.
Dry-type biologicals resemble talcum powder, and can be disseminated as aerosols using gas expulsion devices instead of a burster or complex sprayer. [ citation needed ] The Chemical Corps developed Flettner rotor bomblets and later triangular bomblets for wider coverage due to improved glide angles over Magnus-lift spherical bomblets. [ 64 ] Weapons of this type were in advanced development by the time the program ended. [ 64 ]
From January 1962, Rocky Mountain Arsenal "grew, purified and biodemilitarized" plant pathogen Wheat Stem Rust (Agent TX), Puccinia graminis, var. tritici, for the Air Force biological anti-crop program. TX-treated grain was grown at the Arsenal from 1962–1968 in Sections 23–26. Unprocessed TX was also transported from Beale AFB for purification, storage, and disposal. [ 65 ] Trichothecenes Mycotoxin is a toxin that can be extracted from Wheat Stem Rust and Rice Blast and can kill or incapacitate depending on the concentration used. The "red mold disease" of wheat and barley in Japan is prevalent in the region that faces the Pacific Ocean. Toxic trichothecenes, including nivalenol, deoxynivalenol, and monoace tylnivalenol (fusarenon- X) from Fusarium nivale, can be isolated from moldy grains. In the suburbs of Tokyo, an illness similar to "red mold disease" was described in an outbreak of a food borne disease, as a result of the consumption of Fusarium- infected rice. Ingestion of moldy grains that are contaminated with trichothecenes has been associated with mycotoxicosis. [ 66 ]
Although there is no evidence that biological weapons were used by the United States, China and North Korea accused the US of large-scale field testing of BW against them during the Korean War (1950–1953). At the time of the Korean War the United States had only weaponized one agent, brucellosis ("Agent US"), which is caused by Brucella suis . The original weaponized form used the M114 bursting bomblet in M33 cluster bombs. While the specific form of the biological bomb was classified until some years after the Korean War, in the various exhibits of biological weapons that Korea alleged were dropped on their country nothing resembled an M114 bomblet . There were ceramic containers that had some similarity to Japanese weapons used against the Chinese in World War II, developed by Unit 731. [ 51 ] [ 67 ]
Cuba also accused the United States of spreading human and animal disease on their island nation. [ 68 ] [ 69 ]
During the 1948 1947–1949 Palestine war , International Red Cross reports raised suspicion that the Israeli Haganah militia had released Salmonella typhi bacteria into the water supply for the city of Acre , causing an outbreak of typhoid among the inhabitants. Egyptian troops later claimed to have captured disguised Haganah soldiers near wells in Gaza , whom they executed for allegedly attempting another attack. Israel denies these allegations. [ 70 ] [ 71 ]
In mid-1969, the UK and the Warsaw Pact, separately, introduced proposals to the UN to ban biological weapons, which would lead to the signing of the Biological and Toxin Weapons Convention in 1972. United States President Richard Nixon signed an executive order in November 1969, which stopped production of biological weapons in the United States and allowed only scientific research of lethal biological agents and defensive measures such as immunization and biosafety . The biological munition stockpiles were destroyed, and approximately 2,200 researchers became redundant. [ 72 ]
Special munitions for the United States Special Forces and the CIA and the Big Five Weapons for the military were destroyed in accordance with Nixon's executive order to end the offensive program. The CIA maintained its collection of biologicals well into 1975 when it became the subject of the senate Church Committee .
The Biological and Toxin Weapons Convention was signed by the US, UK, USSR and other nations, as a ban on "development, production and stockpiling of microbes or their poisonous products except in amounts necessary for protective and peaceful research" in 1972. The convention bound its signatories to a far more stringent set of regulations than had been envisioned by the 1925 Geneva Protocols. By 1996, 137 countries had signed the treaty; however it is believed that since the signing of the Convention the number of countries capable of producing such weapons has increased.
The Soviet Union continued research and production of offensive biological weapons in a program called Biopreparat , despite having signed the convention. The United States had no solid proof of this program until Vladimir Pasechnik defected in 1989, and Kanatjan Alibekov , the first deputy director of Biopreparat defected in 1992. Pathogens developed by the organization would be used in open-air trials. It is known that Vozrozhdeniye Island, located in the Aral Sea, was used as a testing site. [ 73 ] In 1971, such testing led to the accidental aerosol release of smallpox over the Aral Sea and a subsequent smallpox epidemic. [ 74 ]
During the closing stages of the Rhodesian Bush War , the Rhodesian government resorted to use chemical and biological warfare agents. Watercourses at several sites inside the Mozambique border were deliberately contaminated with cholera . These biological attacks had little overall impact on the fighting capability of ZANLA , but resulted in at least 809 recorded deaths of insurgents. It also caused considerable distress to the local population. The Rhodesians also experimented with several other pathogens and toxins for use in their counterinsurgency. [ 75 ]
After the 1991 Persian Gulf War , Iraq admitted to the United Nations inspection team to having produced 19,000 liters of concentrated botulinum toxin, of which approximately 10,000 L were loaded into military weapons; the 19,000 liters have never been fully accounted for. This is approximately three times the amount needed to kill the entire current human population by inhalation, [ 76 ] although in practice it would be impossible to distribute it so efficiently, and, unless it is protected from oxygen, it deteriorates in storage. [ 77 ]
According to the U.S. Congress Office of Technology Assessment eight countries were generally reported as having undeclared offensive biological warfare programs in 1995: China , Iran , Iraq , Israel , Libya , North Korea , Syria and Taiwan . Five countries had admitted to having had offensive weapon or development programs in the past: United States , Russia , France , the United Kingdom , and Canada . [ 78 ] Offensive BW programs in Iraq were dismantled by Coalition Forces and the UN after the first Gulf War (1990–91), although an Iraqi military BW program was covertly maintained in defiance of international agreements until it was apparently abandoned during 1995 and 1996. [ 79 ]
On September 18, 2001, and for a few days thereafter, several letters were received by members of the U.S. Congress and American media outlets which contained intentionally prepared anthrax spores; the attack sickened at least 22 people of whom five died. The identity of the bioterrorist remains unknown, although in 2008 authorities stated that Bruce Ivins was likely the perpetrator. (See 2001 anthrax attacks .)
Suspicions of an ongoing Iraqi biological warfare program were not substantiated in the wake of the March 2003 invasion of that country . Later that year, however, Muammar Gaddafi was persuaded to terminate Libya 's biological warfare program. In 2008, according to a U.S. Congressional Research Service report, China , Cuba , Egypt , Iran , Israel , North Korea , Russia , Syria and Taiwan are considered, with varying degrees of certainty, to have some biologicalwarfare capability. [ 80 ] According to the same 2008 report by the U.S. Congressional Research Service , "Developments in biotechnology , including genetic engineering , may
produce a wide variety of live agents and toxins that are difficult to
detect and counter; and new chemical warfare agents and mixtures of chemical weapons and
biowarfare agents are being developed . . . Countries are using the natural overlap between weapons and
civilian applications of chemical and biological materials to conceal
chemical weapon and bioweapon production." By 2011, 165 countries had officially joined the BWC and pledged to disavow biological weapons. [ 81 ] | https://en.wikipedia.org/wiki/History_of_biological_warfare |
Biotechnology is the application of scientific and engineering principles to the processing of materials by biological agents to provide goods and services. [ 1 ] From its inception, biotechnology has maintained a close relationship with society. Although now most often associated with the development of drugs , historically biotechnology has been principally associated with food, addressing such issues as malnutrition and famine . The history of biotechnology begins with zymotechnology , [ 2 ] which commenced with a focus on brewing techniques for beer. By World War I, however, zymotechnology would expand to tackle larger industrial issues, and the potential of industrial fermentation gave rise to biotechnology. However, both the single-cell protein and gasohol projects failed to progress due to varying issues including public resistance, a changing economic scene, and shifts in political power.
Yet the formation of a new field, genetic engineering , would soon bring biotechnology to the forefront of science in society, and the intimate relationship between the scientific community, the public, and the government would ensue. These debates gained exposure in 1975 at the Asilomar Conference , where Joshua Lederberg was the most outspoken supporter for this emerging field in biotechnology. By as early as 1978, with the development of synthetic human insulin , Lederberg's claims would prove valid, and the biotechnology industry grew rapidly. Each new scientific advance became a media event designed to capture public support, and by the 1980s, biotechnology grew into a promising real industry. In 1988, only five proteins from genetically engineered cells had been approved as drugs by the United States Food and Drug Administration (FDA), but this number would skyrocket to over 125 by the end of the 1990s.
The field of genetic engineering remains a heated topic of discussion in today's society with the advent of gene therapy , stem cell research , cloning , and genetically modified food . While it seems only natural nowadays to link pharmaceutical drugs as solutions to health and societal problems, this relationship of biotechnology serving social needs began centuries ago.
Biotechnology arose from the field of zymotechnology or zymurgy, which began as a search for a better understanding of industrial fermentation, particularly beer. Beer was an important industrial, and not just social, commodity. In late 19th-century Germany, brewing contributed as much to the gross national product as steel, and taxes on alcohol proved to be significant sources of revenue to the government. [ 3 ] In the 1860s, institutes and remunerative consultancies were dedicated to the technology of brewing. The most famous was the private Carlsberg Institute, founded in 1875, which employed Emil Christian Hansen, who pioneered the pure yeast process for the reliable production of consistent beer. Less well known were private consultancies that advised the brewing industry. One of these, the Zymotechnic Institute, was established in Chicago by the German-born chemist John Ewald Siebel.
The heyday and expansion of zymotechnology came in World War I in response to industrial needs to support the war. Max Delbrück grew yeast on an immense scale during the war to meet 60 percent of Germany's animal feed needs. [ 3 ] Compounds of another fermentation product, lactic acid , made up for a lack of hydraulic fluid, glycerol . On the Allied side the Russian chemist Chaim Weizmann used starch to eliminate Britain's shortage of acetone , a key raw material for cordite , by fermenting maize to acetone. [ 4 ] The industrial potential of fermentation was outgrowing its traditional home in brewing, and "zymotechnology" soon gave way to "biotechnology."
With food shortages spreading and resources fading, some dreamed of a new industrial solution. The Hungarian Károly Ereky coined the word "biotechnology" in Hungary during 1919 to describe a technology based on converting raw materials into a more useful product. He built a slaughterhouse for a thousand pigs and also a fattening farm with space for 50,000 pigs, raising over 100,000 pigs a year. The enterprise was enormous, becoming one of the largest and most profitable meat and fat operations in the world. In a book entitled Biotechnologie , Ereky further developed a theme that would be reiterated through the 20th century: biotechnology could provide solutions to societal crises, such as food and energy shortages. For Ereky, the term "biotechnologie" indicated the process by which raw materials could be biologically upgraded into socially useful products. [ 5 ]
This catchword spread quickly after the First World War, as "biotechnology" entered German dictionaries and was taken up abroad by business-hungry private consultancies as far away as the United States. In Chicago, for example, the coming of prohibition at the end of World War I encouraged biological industries to create opportunities for new fermentation products, in particular a market for nonalcoholic drinks. Emil Siebel, the son of the founder of the Zymotechnic Institute, broke away from his father's company to establish his own called the "Bureau of Biotechnology," which specifically offered expertise in fermented nonalcoholic drinks. [ 1 ]
The belief that the needs of an industrial society could be met by fermenting agricultural waste was an important ingredient of the "chemurgic movement." [ 5 ] Fermentation-based processes generated products of ever-growing utility. In the 1940s, penicillin was the most dramatic. While it was discovered in England, it was produced industrially in the U.S. using a deep fermentation process originally developed in Peoria, Illinois. [ 6 ] The enormous profits and the public expectations penicillin engendered caused a radical shift in the standing of the pharmaceutical industry. Doctors used the phrase "miracle drug", and the historian of its wartime use, David Adams, has suggested that to the public penicillin represented the perfect health that went together with the car and the dream house of wartime American advertising. [ 3 ] Beginning in the 1950s, fermentation technology also became advanced enough to produce steroids on industrially significant scales. [ 7 ] Of particular importance was the improved semisynthesis of cortisone which simplified the old 31 step synthesis to 11 steps. [ 8 ] This advance was estimated to reduce the cost of the drug by 70%, making the medicine inexpensive and available. [ 9 ] Today biotechnology still plays a central role in the production of these compounds and likely will for years to come. [ 10 ] [ 11 ]
Even greater expectations of biotechnology were raised during the 1960s by a process that grew single-cell protein. When the so-called protein gap threatened world hunger, producing food locally by growing it from waste seemed to offer a solution. It was the possibilities of growing microorganisms on oil that captured the imagination of scientists, policy makers, and commerce. [ 1 ] Major companies such as BP staked their futures on it. In 1962, BP built a pilot plant at Cap de Lavera in Southern France to publicize its product, Toprina. [ 1 ] Initial research work at Lavera was done by Alfred Champagnat, [ 12 ] In 1963, construction started on BP's second pilot plant at the Grangemouth Refinery in Scotland. [ 12 ]
As there was no well-accepted term to describe the new foods, in 1966 the term " single-cell protein " (SCP) was coined at MIT to provide an acceptable and exciting new title, avoiding the unpleasant connotations of microbial or bacterial. [ 1 ]
The "food from oil" idea became quite popular by the 1970s, when facilities for growing yeast fed by n- paraffins were built in a number of countries. The Soviets were particularly enthusiastic, opening large "BVK" ( belkovo-vitaminny kontsentrat , i.e., "protein-vitamin concentrate") plants next to their oil refineries in Kstovo (1973) [ 13 ] [ 14 ] and Kirishi (1974). [ citation needed ]
By the late 1970s, however, the cultural climate had completely changed, as the growth in SCP interest had taken place against a shifting economic and cultural scene (136). First, the price of oil rose catastrophically in 1974, so that its cost per barrel was five times greater than it had been two years earlier. Second, despite continuing hunger around the world, anticipated demand also began to shift from humans to animals. The program had begun with the vision of growing food for Third World people, yet the product was instead launched as an animal food for the developed world. The rapidly rising demand for animal feed made that market appear economically more attractive. The ultimate downfall of the SCP project, however, came from public resistance. [ 1 ]
This was particularly vocal in Japan, where production came closest to fruition. For all their enthusiasm for innovation and traditional interest in microbiologically produced foods, the Japanese were the first to ban the production of single-cell proteins. The Japanese ultimately were unable to separate the idea of their new "natural" foods from the far from natural connotation of oil. [ 1 ] These arguments were made against a background of suspicion of heavy industry in which anxiety over minute traces of petroleum was expressed. Thus, public resistance to an unnatural product led to the end of the SCP project as an attempt to solve world hunger.
Also, in 1989 in the USSR, the public environmental concerns made the government decide to close down (or convert to different technologies) all 8 paraffin-fed-yeast plants that the Soviet Ministry of Microbiological Industry had by that time. [ citation needed ]
In the late 1970s, biotechnology offered another possible solution to a societal crisis. The escalation in the price of oil in 1974 increased the cost of the Western world's energy tenfold. [ 1 ] In response, the U.S. government promoted the production of gasohol , gasoline with 10 percent alcohol added, as an answer to the energy crisis. [ 3 ] In 1979, when the Soviet Union sent troops to Afghanistan, the Carter administration cut off its supplies to agricultural produce in retaliation, creating a surplus of agriculture in the U.S. As a result, fermenting the agricultural surpluses to synthesize fuel seemed to be an economical solution to the shortage of oil threatened by the Iran–Iraq War . Before the new direction could be taken, however, the political wind changed again: the Reagan administration came to power in January 1981 and, with the declining oil prices of the 1980s, ended support for the gasohol industry before it was born. [ 1 ]
Biotechnology seemed to be the solution for major social problems, including world hunger and energy crises. In the 1960s, radical measures would be needed to meet world starvation, and biotechnology seemed to provide an answer. However, the solutions proved to be too expensive and socially unacceptable, and solving world hunger through SCP food was dismissed. In the 1970s, the food crisis was succeeded by the energy crisis, and here too, biotechnology seemed to provide an answer. But once again, costs proved prohibitive as oil prices slumped in the 1980s. Thus, in practice, the implications of biotechnology were not fully realized in these situations. But this would soon change with the rise of genetic engineering .
The origins of biotechnology culminated with the birth of genetic engineering . There were two key events that have come to be seen as scientific breakthroughs beginning the era that would unite genetics with biotechnology. One was the 1953 discovery of the structure of DNA , by Watson and Crick, and the other was the 1973 discovery by Cohen and Boyer of a recombinant DNA technique by which a section of DNA was cut from the plasmid of an E. coli bacterium and transferred into the DNA of another. [ 15 ] This approach could, in principle, enable bacteria to adopt the genes and produce proteins of other organisms, including humans. Popularly referred to as "genetic engineering," it came to be defined as the basis of new biotechnology.
Genetic engineering proved to be a topic that thrust biotechnology into the public scene, and the interaction between scientists, politicians, and the public defined the work that was accomplished in this area. Technical developments during this time were revolutionary and at times frightening. In December 1967, the first heart transplant by Christiaan Barnard reminded the public that the physical identity of a person was becoming increasingly problematic. While poetic imagination had always seen the heart at the center of the soul, now there was the prospect of individuals being defined by other people's hearts. [ 1 ] During the same month, Arthur Kornberg announced that he had managed to biochemically replicate a viral gene. "Life had been synthesized," said the head of the National Institutes of Health. [ 1 ] Genetic engineering was now on the scientific agenda, as it was becoming possible to identify genetic characteristics with diseases such as beta thalassemia and sickle-cell anemia .
Responses to scientific achievements were colored by cultural skepticism. Scientists and their expertise were looked upon with suspicion. In 1968, an immensely popular work, The Biological Time Bomb , was written by the British journalist Gordon Rattray Taylor. The author's preface saw Kornberg's discovery of replicating a viral gene as a route to lethal doomsday bugs. The publisher's blurb for the book warned that within ten years, "You may marry a semi-artificial man or woman…choose your children's sex…tune out pain…change your memories…and live to be 150 if the scientific revolution doesn’t destroy us first." [ 1 ] The book ended with a chapter called "The Future – If Any." While it is rare for current science to be represented in the movies, in this period of " Star Trek ", science fiction and science fact seemed to be converging. " Cloning " became a popular word in the media. Woody Allen satirized the cloning of a person from a nose in his 1973 movie Sleeper , and cloning Adolf Hitler from surviving cells was the theme of the 1976 novel by Ira Levin , The Boys from Brazil . [ 1 ]
In response to these public concerns, scientists, industry, and governments increasingly linked the power of recombinant DNA to the immensely practical functions that biotechnology promised. One of the key scientific figures that attempted to highlight the promising aspects of genetic engineering was Joshua Lederberg , a Stanford professor and Nobel laureate . While in the 1960s "genetic engineering" described eugenics and work involving the manipulation of the human genome , Lederberg stressed research that would involve microbes instead. [ 1 ] Lederberg emphasized the importance of focusing on curing living people. Lederberg's 1963 paper, "Biological Future of Man" suggested that, while molecular biology might one day make it possible to change the human genotype, "what we have overlooked is euphenics , the engineering of human development." [ 1 ] Lederberg constructed the word "euphenics" to emphasize changing the phenotype after conception rather than the genotype which would affect future generations.
With the discovery of recombinant DNA by Cohen and Boyer in 1973, the idea that genetic engineering would have major human and societal consequences was born. In July 1974, a group of eminent molecular biologists headed by Paul Berg wrote to Science suggesting that the consequences of this work were so potentially destructive that there should be a pause until its implications had been thought through. [ 1 ] This suggestion was explored at a meeting in February 1975 at California's Monterey Peninsula, forever immortalized by the location, Asilomar . Its historic outcome was an unprecedented call for a halt in research until it could be regulated in such a way that the public need not be anxious, and it led to a 16-month moratorium until National Institutes of Health (NIH) guidelines were established.
Joshua Lederberg was the leading exception in emphasizing, as he had for years, the potential benefits. At Asilomar , in an atmosphere favoring control and regulation, he circulated a paper countering the pessimism and fears of misuses with the benefits conferred by successful use. He described "an early chance for a technology of untold importance for diagnostic and therapeutic medicine: the ready production of an unlimited variety of human proteins . Analogous applications may be foreseen in fermentation process for cheaply manufacturing essential nutrients, and in the improvement of microbes for the production of antibiotics and of special industrial chemicals." [ 1 ] In June 1976, the 16-month moratorium on research expired with the Director's Advisory Committee (DAC) publication of the NIH guidelines of good practice. They defined the risks of certain kinds of experiments and the appropriate physical conditions for their pursuit, as well as a list of things too dangerous to perform at all. Moreover, modified organisms were not to be tested outside the confines of a laboratory or allowed into the environment. [ 15 ]
Atypical as Lederberg was at Asilomar, his optimistic vision of genetic engineering would soon lead to the development of the biotechnology industry. Over the next two years, as public concern over the dangers of recombinant DNA research grew, so too did interest in its technical and practical applications. Curing genetic diseases remained in the realms of science fiction, but it appeared that producing human simple proteins could be good business. Insulin , one of the smaller, best characterized and understood proteins, had been used in treating type 1 diabetes for a half century. It had been extracted from animals in a chemically slightly different form from the human product. Yet, if one could produce synthetic human insulin , one could meet an existing demand with a product whose approval would be relatively easy to obtain from regulators. In the period 1975 to 1977, synthetic "human" insulin represented the aspirations for new products that could be made with the new biotechnology. Microbial production of synthetic human insulin was finally announced in September 1978 and was produced by a startup company, Genentech . [ 16 ] Although that company did not commercialize the product themselves, instead, it licensed the production method to Eli Lilly and Company . 1978 also saw the first application for a patent on a gene, the gene which produces human growth hormone , by the University of California , thus introducing the legal principle that genes could be patented. Since that filing, 20% of the more than 20,000 to 25,000 genes mapped in the human DNA have been patented. [ 17 ]
The radical shift in the connotation of "genetic engineering" from an emphasis on the inherited characteristics of people to the commercial production of proteins and therapeutic drugs was nurtured by Joshua Lederberg. His broad concerns since the 1960s had been stimulated by enthusiasm for science and its potential medical benefits. Countering calls for strict regulation, he expressed a vision of potential utility. Against a belief that new techniques would entail unmentionable and uncontrollable consequences for humanity and the environment, a growing consensus on the economic value of recombinant DNA emerged. [ citation needed ]
The MOSFET invented at Bell Labs between 1955 and 1960, [ 18 ] [ 19 ] [ 20 ] [ 21 ] [ 22 ] [ 23 ] Two years later, L.C. Clark and C. Lyons invented the biosensor in 1962. [ 24 ] Biosensor MOSFETs (BioFETs) were later developed, and they have since been widely used to measure physical , chemical , biological and environmental parameters. [ 25 ]
The first BioFET was the ion-sensitive field-effect transistor (ISFET), invented by Piet Bergveld for electrochemical and biological applications in 1970. [ 26 ] [ 27 ] the adsorption FET (ADFET) was patented by P.F. Cox in 1974, and a hydrogen -sensitive MOSFET was demonstrated by I. Lundstrom, M.S. Shivaraman, C.S. Svenson and L. Lundkvist in 1975. [ 25 ] The ISFET is a special type of MOSFET with a gate at a certain distance, [ 25 ] and where the metal gate is replaced by an ion -sensitive membrane , electrolyte solution and reference electrode . [ 28 ] The ISFET is widely used in biomedical applications, such as the detection of DNA hybridization , biomarker detection from blood , antibody detection, glucose measurement, pH sensing, and genetic technology . [ 28 ]
By the mid-1980s, other BioFETs had been developed, including the gas sensor FET (GASFET), pressure sensor FET (PRESSFET), chemical field-effect transistor (ChemFET), reference ISFET (REFET), enzyme-modified FET (ENFET) and immunologically modified FET (IMFET). [ 25 ] By the early 2000s, BioFETs such as the DNA field-effect transistor (DNAFET), gene-modified FET (GenFET) and cell-potential BioFET (CPFET) had been developed. [ 28 ]
With ancestral roots in industrial microbiology that date back centuries, the new biotechnology industry grew rapidly beginning in the mid-1970s. Each new scientific advance became a media event designed to capture investment confidence and public support. [ 16 ] Although market expectations and social benefits of new products were frequently overstated, many people were prepared to see genetic engineering as the next great advance in technological progress. By the 1980s, biotechnology characterized a nascent real industry, providing titles for emerging trade organizations such as the Biotechnology Industry Organization (BIO).
The main focus of attention after insulin were the potential profit makers in the pharmaceutical industry: human growth hormone and what promised to be a miraculous cure for viral diseases, interferon . Cancer was a central target in the 1970s because increasingly the disease was linked to viruses. [ 15 ] By 1980, a new company, Biogen , had produced interferon through recombinant DNA. The emergence of interferon and the possibility of curing cancer raised money in the community for research and increased the enthusiasm of an otherwise uncertain and tentative society. Moreover, to the 1970s plight of cancer was added AIDS in the 1980s, offering an enormous potential market for a successful therapy, and more immediately, a market for diagnostic tests based on monoclonal antibodies. [ 29 ] By 1988, only five proteins from genetically engineered cells had been approved as drugs by the United States Food and Drug Administration (FDA): synthetic insulin , human growth hormone , hepatitis B vaccine , alpha-interferon , and tissue plasminogen activator (TPa), for lysis of blood clots. By the end of the 1990s, however, 125 more genetically engineered drugs would be approved. [ 29 ]
The Great Recession led to several changes in the way the biotechnology industry was financed and organized. First, it led to a decline in overall financial investment in the sector, globally; and second, in some countries like the UK it led to a shift from business strategies focused on going for an initial public offering (IPO) to seeking a trade sale instead. [ 30 ] By 2011, financial investment in the biotechnology industry started to improve again and by 2014 the global market capitalization reached $1 trillion. [ 30 ]
Genetic engineering also reached the agricultural front as well. There was tremendous progress since the market introduction of the genetically engineered Flavr Savr tomato in 1994. [ 29 ] Ernst and Young reported that in 1998, 30% of the U.S. soybean crop was expected to be from genetically engineered seeds. In 1998, about 30% of the US cotton and corn crops were also expected to be products of genetic engineering . [ 29 ]
Genetic engineering in biotechnology stimulated hopes for both therapeutic proteins, drugs and biological organisms themselves, such as seeds, pesticides, engineered yeasts, and modified human cells for treating genetic diseases. From the perspective of its commercial promoters, scientific breakthroughs, industrial commitment, and official support were finally coming together, and biotechnology became a normal part of business. No longer were the proponents for the economic and technological significance of biotechnology the iconoclasts. [ 1 ] Their message had finally become accepted and incorporated into the policies of governments and industry.
According to Burrill and Company, an industry investment bank, over $350 billion has been invested in biotech since the emergence of the industry, and global revenues rose from $23 billion in 2000 to more than $50 billion in 2005. The greatest growth has been in Latin America but all regions of the world have shown strong growth trends. By 2007 and into 2008, though, a downturn in the fortunes of biotech emerged, at least in the United Kingdom, as the result of declining investment in the face of failure of biotech pipelines to deliver and a consequent downturn in return on investment. [ 31 ] | https://en.wikipedia.org/wiki/History_of_biotechnology |
Bitcoin is a cryptocurrency , a digital asset that uses cryptography to control its creation and management rather than relying on central authorities . [ 1 ] Originally designed as a medium of exchange , Bitcoin is now primarily regarded as a store of value . The history of bitcoin started with its invention and implementation by Satoshi Nakamoto , who integrated many existing ideas from the cryptography community. Over the course of bitcoin's history, it has undergone rapid growth to become a significant store of value both on- and offline. From the mid-2010s, some businesses began accepting bitcoin in addition to traditional currencies. [ 2 ]
Prior to the release of bitcoin, there were a number of digital cash technologies, starting with the issuer-based ecash protocols of David Chaum and Stefan Brands . [ 3 ] [ 4 ] [ 5 ] The idea that solutions to computational puzzles could have some value was first proposed by cryptographers Cynthia Dwork and Moni Naor in 1992. [ 6 ]
12 years prior to creating Bitcoin the NSA published the white paper "How To Make A Mint: The Cryptography of Anonymous Electronic Cash" [ 7 ]
The idea was independently rediscovered by Adam Back who developed hashcash , a proof-of-work scheme for spam control in 1997. [ 8 ] The first proposals for distributed digital scarcity-based cryptocurrencies were Wei Dai 's b-money [ 9 ] and Nick Szabo 's bit gold . [ 10 ] [ 11 ] Hal Finney developed reusable proof of work (RPOW) using hashcash as proof of work algorithm. [ 12 ]
In the bit gold proposal which proposed a collectible market-based mechanism for inflation control, Nick Szabo also investigated some additional aspects including a Byzantine fault-tolerant agreement protocol based on quorum addresses to store and transfer the chained proof-of-work solutions, which was vulnerable to Sybil attacks, though. [ 11 ]
On 18 August 2008, the domain name bitcoin.org was registered. [ 13 ] Later that year, on 31 October, a link to a paper authored by Satoshi Nakamoto titled Bitcoin: A Peer-to-Peer Electronic Cash System [ 14 ] was posted to a cryptography mailing list. [ 15 ] This paper detailed methods of using a peer-to-peer network to generate what was described as "a system for electronic transactions without relying on trust". [ 16 ] [ 17 ] [ 18 ] On 3 January 2009, the bitcoin network came into existence with Satoshi Nakamoto mining the genesis block of bitcoin (block number 0), which had a reward of 50 bitcoins. [ 16 ] [ 19 ] Embedded in the genesis block was the text:
The Times 03/Jan/2009 Chancellor on brink of second bailout for banks [ 20 ]
The text refers to a headline in The Times published on 3 January 2009. [ 21 ] This note has been interpreted as both a timestamp of the genesis date and a derisive comment on the instability caused by fractional-reserve banking . [ 22 ] : 18
The first open source bitcoin client was released on 9 January 2009, hosted at SourceForge . [ 23 ] [ 24 ]
One of the first supporters, adopters, contributors to bitcoin and receiver of the first bitcoin transaction was programmer Hal Finney . Finney downloaded the bitcoin software the day it was released, and received 10 bitcoins from Nakamoto in the world's first bitcoin transaction on 12 January 2009 (block 170). [ 25 ] [ 26 ] Other early supporters were Wei Dai , creator of bitcoin predecessor b-money , and Nick Szabo , creator of bitcoin predecessor bit gold . [ 16 ] One of the first miners included James Howells , who subsequently lost thousands of Bitcoin to a landfill in Newport . [ 27 ] [ 28 ]
In the early days, Nakamoto is estimated to have mined 1 million bitcoins. [ 29 ] Before disappearing from any involvement in bitcoin, Nakamoto in a sense handed over the reins to developer Gavin Andresen , who then became the bitcoin lead developer at the Bitcoin Foundation , the 'anarchic' bitcoin community's closest thing to an official public face. [ 30 ]
"Satoshi Nakamoto" is presumed to be a pseudonym for the person or people who designed the original bitcoin protocol in 2007 then released the whitepaper in 2008 and finally launched the network in 2009. Nakamoto was responsible for creating the majority of the official bitcoin software and was active in making modifications and posting technical information on the bitcoin forum. [ 16 ] There has been much speculation as to the identity of Satoshi Nakamoto with suspects including Dai, Szabo, and Finney – and accompanying denials. [ 31 ] [ 32 ] The possibility that Satoshi Nakamoto was a computer collective in the European financial sector has also been discussed. [ 33 ]
Investigations into the real identity of Satoshi Nakamoto were attempted by The New Yorker and Fast Company . The New Yorker's investigation brought up at least two possible candidates: Michael Clear and Vili Lehdonvirta . Fast Company' s investigation brought up circumstantial evidence linking an encryption patent application filed by Neal King, Vladimir Oksman and Charles Bry on 15 August 2008, and the bitcoin.org domain name which was registered 72 hours later. The patent application ( #20100042841 ) contained networking and encryption technologies similar to bitcoin's, and textual analysis revealed that the phrase "... computationally impractical to reverse" appeared in both the patent application and bitcoin's whitepaper. [ 14 ] All three inventors explicitly denied being Satoshi Nakamoto. [ 34 ] [ 35 ]
In May 2013, Ted Nelson speculated that Japanese mathematician Shinichi Mochizuki is Satoshi Nakamoto. [ 36 ] Later in 2013 the Israeli researchers Dorit Ron and Adi Shamir pointed to Silk Road-linked Ross William Ulbricht as the possible person behind the cover. The two researchers based their suspicion on an analysis of the network of bitcoin transactions. [ 37 ] These allegations were contested [ 38 ] and Ron and Shamir later retracted their claim. [ 39 ]
Nakamoto's involvement with bitcoin does not appear to extend past mid-2010. [ 16 ] In April 2011, Nakamoto communicated with a bitcoin contributor, saying that he had "moved on to other things". [ 20 ]
Stefan Thomas, a Swiss coder and active community member, graphed the time stamps for each of Nakamoto's 500-plus bitcoin forum posts; the resulting chart showed a steep decline to almost no posts between the hours of 5 a.m. and 11 a.m. Greenwich Mean Time . Because this pattern held true even on Saturdays and Sundays, it suggested that Nakamoto was asleep at this time, and the hours of 5 a.m. to 11 a.m. GMT are midnight to 6 a.m. Eastern Standard Time (North American Eastern Standard Time). Other clues suggested that Nakamoto was British: A newspaper headline he had encoded in the genesis block came from the UK-published newspaper The Times , and both his forum posts and his comments in the bitcoin source code used British English spellings, such as "optimise" and "colour". [ 16 ]
An Internet search by an anonymous blogger of texts similar in writing to the bitcoin whitepaper suggests Nick Szabo 's "bit gold" articles as having a similar author. [ 31 ] Nick denied being Satoshi, and stated his official opinion on Satoshi and bitcoin in a May 2011 article. [ 40 ]
In a March 2014 article in Newsweek , journalist Leah McGrath Goodman doxed Dorian S. Nakamoto of Temple City, California , saying that Satoshi Nakamoto is the man's birth name . Her methods and conclusion drew widespread criticism. [ 41 ] [ 42 ]
In June 2016, the London Review of Books published a piece by Andrew O'Hagan about Nakamoto. [ 43 ]
After a May 2020 YouTube documentary pointed to Adam Back as the creator of bitcoin, [ 44 ] widespread discussion ensued. The real identity of Satoshi Nakamoto still remains a matter of dispute.
The first notable retail transaction involving physical goods was paid on May 22, 2010, by exchanging 10,000 mined BTC for two pizzas delivered from a Papa John’s in Jacksonville, Florida . Laszlo Hanyecz, who lives in Jacksonville, created a thread in an online forum offering the bitcoins for anyone who could order him two pizzas. Jeremy Sturdivant, a user from England accepted the offer and ordered the pizzas to his home. The 10,000 Bitcoins were worth about $40 USD at the time. This event would mark May 22 as the Bitcoin Pizza Day for crypto-fans. [ 16 ] [ 45 ] At the time, a transaction's value was typically negotiated on the Bitcoin forum. [ citation needed ]
On 6 August 2010, a major vulnerability in the bitcoin protocol was spotted. While the protocol did verify that a transaction's outputs never exceeded its inputs, a transaction whose outputs summed to more than 2 64 {\displaystyle 2^{64}} would overflow , permitting the transaction author to create arbitrary amounts of bitcoin. [ 46 ] [ 47 ] On 15 August, the vulnerability was exploited; a single transaction spent 0.5 bitcoin to send just over 92 billion bitcoins ( 2 63 {\displaystyle 2^{63}} satoshis) to each of two different addresses on the network. Within hours, the transaction was spotted, the bug was fixed, and the blockchain was forked by miners using an updated version of the bitcoin protocol. [ 48 ] Since the blockchain was forked below the problematic transaction, the transaction no longer appears in the blockchain used by the Bitcoin network today. This was the only major security flaw found and exploited in bitcoin's history. [ 46 ] [ 47 ] [ 49 ]
Based on bitcoin's open-source code, other cryptocurrencies started to emerge. [ 50 ]
The Electronic Frontier Foundation , a non-profit group, started accepting bitcoins in January 2011, [ 51 ] then stopped accepting them in June 2011, citing concerns about a lack of legal precedent about new currency systems. [ 52 ] The EFF's decision was reversed on 17 May 2013 when they resumed accepting bitcoin. [ 53 ]
In May 2011, bitcoin payment processor, BitPay was founded to provide mobile checkout services to companies wanting to accept bitcoins as a form of payment.
In June 2011, WikiLeaks [ 54 ] and other organizations began to accept bitcoins for donations.
In January 2012, bitcoin was featured as the main subject within a fictionalized trial on the CBS legal drama The Good Wife in the third-season episode " Bitcoin for Dummies ". The host of CNBC 's Mad Money , Jim Cramer , played himself in a courtroom scene where he testifies that he does not consider bitcoin a true currency, saying, "There's no central bank to regulate it; it's digital and functions completely peer to peer". [ 55 ]
In September 2012, the Bitcoin Foundation was launched to "accelerate the global growth of bitcoin through standardization, protection, and promotion of the open source protocol". The founders were Gavin Andresen , Jon Matonis, Mark Karpelès , Charlie Shrem , and Peter Vessenes. [ citation needed ]
In October 2012, BitPay reported having over 1,000 merchants accepting bitcoin under its payment processing service. [ 56 ] In November 2012, WordPress started accepting bitcoins. [ 57 ]
In February 2013, the exchange Coinbase reported selling US$1 million worth of bitcoins in a single month at over $22 per bitcoin. [ 58 ] The Internet Archive announced that it was ready to accept donations as bitcoins and that it intends to give employees the option to receive portions of their salaries in bitcoin currency. [ 59 ]
In Charles Stross 's 2013 science fiction novel Neptune's Brood , the universal interstellar payment system is known as "bitcoin" and operates using cryptography. [ 60 ] Stross later blogged that the reference was intentional, saying "I wrote Neptune's Brood in 2011. Bitcoin was obscure back then, and I figured had just enough name recognition to be a useful term for an interstellar currency: it'd clue people in that it was a networked digital currency." [ 61 ]
In March, the bitcoin transaction log, called the blockchain, temporarily split into two independent chains with differing rules on how transactions were accepted. For six hours two bitcoin networks operated at the same time, each with its own version of the transaction history. The core developers called for a temporary halt to transactions, sparking a sharp sell-off. [ 62 ] Normal operation was restored when the majority of the network downgraded to version 0.7 of the bitcoin software. [ 62 ] The Mt. Gox exchange briefly halted bitcoin deposits and the exchange rate briefly dipped by 23% to $37 as the event occurred [ 63 ] [ 64 ] before recovering to previous level of approximately $48 in the following hours. [ 65 ] In the US , the Financial Crimes Enforcement Network (FinCEN) established regulatory guidelines for "decentralized virtual currencies" such as bitcoin, classifying American bitcoin miners who sell their generated bitcoins as Money Service Businesses (or MSBs), that may be subject to registration and other legal obligations. [ 66 ] [ 67 ] [ 68 ]
In April, payment processors BitInstant and Mt. Gox experienced processing delays due to insufficient capacity [ 69 ] resulting in the bitcoin exchange rate dropping from $266 to $76 before returning to $160 within six hours. [ 70 ] Bitcoin gained greater recognition when services such as OkCupid and Foodler began accepting it for payment. [ 71 ] In April 2013, Eric Posner , a law professor at the University of Chicago , stated that "a real Ponzi scheme takes fraud; bitcoin, by contrast, seems more like a collective delusion." [ 72 ]
On 15 May 2013, the US authorities seized accounts associated with Mt. Gox after discovering that it had not registered as a money transmitter with FinCEN in the US. [ 73 ] [ 74 ]
On 17 May 2013, it was reported that BitInstant processed approximately 30 percent of the money going into and out of bitcoin, and in April alone facilitated 30,000 transactions, [ 75 ]
On 23 June 2013, it was reported that the US Drug Enforcement Administration listed 11.02 bitcoins as a seized asset in a United States Department of Justice seizure notice pursuant to 21 U.S.C. § 881. This was the first time a government agency was reported to have seized bitcoin. [ 76 ] [ 77 ]
In July 2013, a project began in Kenya linking bitcoin with M-Pesa , a popular mobile payments system, in an experiment designed to spur innovative payments in Africa. [ 78 ] During the same month the Foreign Exchange Administration and Policy Department in Thailand stated that bitcoin lacks any legal framework and would therefore be illegal, which effectively banned trading on bitcoin exchanges in the country. [ 79 ] [ 80 ]
On 6 August 2013, Federal Judge Amos Mazzant of the Eastern District of Texas of the Fifth Circuit ruled that bitcoins are "a currency or a form of money" (specifically securities as defined by Federal Securities Laws), and as such were subject to the court's jurisdiction, [ 81 ] [ 82 ] and Germany's Finance Ministry subsumed bitcoins under the term "unit of account" – a financial instrument – though not as e-money or a functional currency, a classification nonetheless having legal and tax implications. [ 83 ]
In September 2013, Chinese Govt. banned financial institution from trading in Bitcoin fearing a risk of money laundering. [ 84 ]
In October 2013, the FBI seized roughly 26,000 BTC from website Silk Road during the arrest of alleged owner Ross William Ulbricht . [ 85 ] [ 86 ] [ 87 ] Two companies, Robocoin and Bitcoiniacs launched the world's first bitcoin ATM on 29 October 2013 in Vancouver , BC , Canada , allowing clients to sell or purchase bitcoin currency at a downtown coffee shop. [ 88 ] [ 89 ] [ 90 ] Chinese internet giant Baidu had allowed clients of website security services to pay with bitcoins. [ 91 ]
In November 2013, the University of Nicosia announced that it would be accepting bitcoin as payment for tuition fees, with the university's chief financial officer calling it the "gold of tomorrow". [ 92 ] During November 2013, the China-based bitcoin exchange BTC China overtook the Japan-based Mt. Gox and the Europe-based Bitstamp to become the largest bitcoin trading exchange by trade volume. [ 93 ]
In December 2013, Overstock.com [ 94 ] announced plans to accept bitcoin in the second half of 2014.
On 5 December 2013, the People's Bank of China prohibited Chinese financial institutions from using bitcoins. [ 95 ] After the announcement, the value of bitcoins dropped, [ 96 ] and Baidu no longer accepted bitcoins for certain services. [ 97 ] Buying real-world goods with any virtual currency had been illegal in China since at least 2009. [ 98 ]
On 4 December 2013, Alan Greenspan referred to it as a "bubble". [ 99 ]
In January 2014, Zynga [ 100 ] announced it was testing bitcoin for purchasing in-game assets in seven of its games. That same month, The D Las Vegas Casino Hotel and Golden Gate Hotel & Casino properties in downtown Las Vegas announced they would also begin accepting bitcoin, according to an article by USA Today . The article also stated the currency would be accepted in five locations, including the front desk and certain restaurants. [ 101 ] The network rate exceeded 10 petahash/sec. TigerDirect [ 102 ] and Overstock.com [ 103 ] started accepting bitcoin.
The same month, an operator of a U.S. bitcoin exchange, Robert Faiella better known as Charlie Shrem , was arrested for money laundering. [ 104 ]
In early February 2014, one of the largest bitcoin exchanges, Mt. Gox , [ 105 ] suspended withdrawals citing technical issues. [ 106 ] By the end of the month, Mt. Gox had filed for bankruptcy protection in Japan amid reports that 744,000 bitcoins had been stolen. [ 107 ] Months before the filing, the popularity of Mt. Gox had waned as users experienced difficulties withdrawing funds. [ 108 ]
In June 2014, the network exceeded 100 petahash/sec. [ citation needed ] On 18 June 2014, it was announced that bitcoin payment service provider BitPay would become the new sponsor of St. Petersburg Bowl under a two-year deal, renamed the Bitcoin St. Petersburg Bowl. Bitcoin was to be accepted for ticket and concession sales at the game as part of the sponsorship, and the sponsorship itself was also paid for using bitcoin. [ 109 ]
In July 2014, Newegg and Dell [ 110 ] started accepting bitcoin.
In September 2014, TeraExchange, LLC, received approval from the U.S. Commodity Futures Trading Commission "CFTC" to begin listing an over-the-counter swap product based on the price of a bitcoin. The CFTC swap product approval marks the first time a U.S. regulatory agency approved a bitcoin financial product. [ 111 ]
In December 2014, Microsoft began to accept bitcoin to buy Xbox games and Windows software. [ 112 ]
In 2014, several light-hearted songs celebrating bitcoin such as the "Ode to Satoshi" [ 113 ] were released. [ 114 ]
A documentary film, The Rise and Rise of Bitcoin , was released in 2014, featuring interviews with bitcoin users such as a computer programmer and a drug dealer. [ 115 ]
On 13 March 2014, Warren Buffett called bitcoin a "mirage". [ 116 ]
In January 2015, Coinbase raised US$75 million as part of a Series C funding round, smashing the previous record for a bitcoin company. Less than one year after the collapse of Mt. Gox, United Kingdom-based exchange Bitstamp announced that their exchange would be taken offline while they investigate a hack which resulted in about 19,000 bitcoins (equivalent to roughly US$5 million at that time) being stolen from their hot wallet. [ 117 ] The exchange remained offline for several days amid speculation that customers had lost their funds. Bitstamp resumed trading on 9 January after increasing security measures and assuring customers that their account balances would not be impacted. [ 118 ]
In February 2015, the number of merchants accepting bitcoin exceeded 100,000. [ 119 ]
In 2015, the MAK ( Museum of Applied Arts, Vienna ) became the first museum to acquire art using bitcoin, when it purchased the screensaver "Event listeners" [ 120 ] of van den Dorpel. [ 121 ]
In September 2015, the establishment of the peer-reviewed academic journal Ledger ( ISSN 2379-5980 ) was announced. It covers studies of cryptocurrencies and related technologies, and is published by the University of Pittsburgh . [ 122 ] The journal encourages authors to digitally sign a file hash of submitted papers, which will then be timestamped into the bitcoin blockchain. Authors are also asked to include a personal bitcoin address in the first page of their papers. [ 123 ] [ 124 ]
In October 2015, a proposal was submitted to the Unicode Consortium to add a code point for the bitcoin symbol. [ 125 ]
In January 2016, the network rate exceeded 1 exahash /sec. [ citation needed ]
In March 2016, the Cabinet of Japan recognized virtual currencies like bitcoin as having a function similar to real money. [ 126 ] Bidorbuy , the largest South African online marketplace, launched bitcoin payments for both buyers and sellers. [ 127 ]
In July 2016, researchers published a paper showing that by November 2013 bitcoin commerce was no longer driven by "sin" activities but instead by legitimate enterprises. [ 128 ]
In July 2016, the CheckSequenceVerify soft fork activated. [ 129 ]
In August 2016, a major bitcoin exchange, Bitfinex , was hacked and nearly 120,000 BTC (around $60m) was stolen. [ 130 ]
In November 2016, the Swiss Railway operator SBB (CFF) upgraded all their automated ticket machines so that bitcoin could be bought from them using the scanner on the ticket machine to scan the bitcoin address on a phone app. [ 131 ]
Bitcoin generates more academic interest year after year; the number of Google Scholar articles published mentioning bitcoin grew from 83 in 2009, to 424 in 2012, and 3580 in 2016. Also, the academic journal Ledger published its first issue. It is edited by Peter Rizun.
The number of businesses accepting bitcoin continued to increase. In January 2017, NHK reported the number of online stores accepting bitcoin in Japan had increased 4.6 times over the past year. [ 132 ] BitPay CEO Stephen Pair declared the company's transaction rate grew 3× from January 2016 to February 2017, and explained usage of bitcoin is growing in B2B supply chain payments. [ 133 ]
Bitcoin gains more legitimacy among lawmakers and legacy financial companies. For example, Japan passed a law to accept bitcoin as a legal payment method, [ 134 ] and Russia has announced that it will legalize the use of cryptocurrencies such as bitcoin. [ 135 ]
Exchange trading volumes continue to increase. For the 6-month period ending March 2017, Mexican exchange Bitso saw trading volume increase 1500%. [ citation needed ] Between January and May 2017 Poloniex saw an increase of more than 600% active traders online and regularly processed 640% more transactions. [ 136 ]
In June 2017, the bitcoin symbol was encoded in Unicode version 10.0 at position U+20BF (₿) in the Currency Symbols block . [ 137 ]
Up until July 2017, bitcoin users maintained a common set of rules for the cryptocurrency. [ 138 ] On 1 August 2017 bitcoin split into two derivative digital currencies, the bitcoin (BTC) chain with 1 MB blocksize limit and the Bitcoin Cash (BCH) chain with 8 MB blocksize limit. The split has been called the Bitcoin Cash hard fork . [ 139 ]
On 6 December 2017 the software marketplace Steam announced that it would no longer accept bitcoin as payment for its products, citing slow transactions speeds, price volatility, and high fees for transactions. [ 140 ]
On 22 January 2018, South Korea brought in a regulation that requires all the bitcoin traders to reveal their identity, thus putting a ban on anonymous trading of bitcoins. [ 141 ]
On 24 January 2018, the online payment firm Stripe announced that it would phase out its support for bitcoin payments by late April 2018, citing declining demand, rising fees and longer transaction times as the reasons. [ 142 ]
On 25 January 2018, George Soros referred to bitcoin as a bubble. [ 143 ]
In May 2018, the United States Department of Justice investigated bitcoin traders for possible price manipulation , [ 144 ] focusing on practices like spoofing and wash trades . [ 145 ] The investigation, which involved key exchanges like Bitstamp , Coinbase , and Kraken , led to subpoenas from the Commodity Futures Trading Commission after these exchanges failed to comply with information requests. [ 146 ]
In October 2018, Nelson Saiers installed a 9-foot inflatable rat covered with bitcoin references and code in front of the Federal Reserve as a homage to Satoshi Nakamoto and protests in New York City. [ 147 ] [ 148 ]
The dawn of 2019 found Bitcoin trading below the $4000 mark after a difficult year for the global crypto market. It climbed to just over $12,000 in July before. [ 149 ]
On 2 July 2020, the Swiss company 21Shares started to quote a set of bitcoin exchange-traded products (ETP) on the Xetra trading system of the Deutsche Boerse. [ 150 ]
On 1 September 2020, the Wiener Börse [ clarification needed ] listed its first 21 titles denominated in cryptocurrencies like bitcoin, including the services of real-time quotation and securities settlement . [ 151 ]
On 3 September 2020, the Frankfurt Stock Exchange admitted in its Regulated Market the quotation of the first bitcoin exchange-traded note (ETN), centrally cleared via Eurex Clearing . [ 152 ] [ 153 ]
In October 2020, PayPal announced that it would allow its users to buy and sell bitcoin on its platform, although not to deposit or withdraw bitcoins. [ 154 ]
On 19 January 2021, Elon Musk placed the handle #Bitcoin in his Twitter profile, tweeting "In retrospect, it was inevitable", which caused the price to briefly rise about $5,000 in an hour to $37,299. [ 155 ] On 25 January 2021, Microstrategy announced that it continued to buy bitcoin and as of the same date it had holdings of ₿70,784 worth $2.38 billion. [ 156 ] On 8 February 2021 Tesla's announcement of a bitcoin purchase of US$1.5 billion and the plan to start accepting bitcoin as payment for vehicles, pushed the bitcoin price to $44,141. [ 157 ] On 18 February 2021, Elon Musk stated that "owning bitcoin was only a little better than holding conventional cash, but that the slight difference made it a better asset to hold". [ 158 ] After 49 days of accepting the digital currency, Tesla reversed course on 12 May 2021, saying they would no longer take bitcoin due to concerns that "mining" the cryptocurrency was contributing to the consumption of fossil fuels and climate change. [ 159 ] The decision resulted in the price of bitcoin dropping around 12% on 13 May. [ 160 ] During a July bitcoin conference, Musk suggested Tesla could possibly help bitcoin miners switch to renewable energy in the future and also stated at the same conference that if bitcoin mining reaches, and trends above 50 percent renewable energy usage, that "Tesla would resume accepting bitcoin." The price for bitcoin rose after this announcement. [ 161 ]
From February 2021, the Swiss canton of Zug allows for tax payments in bitcoin and other cryptocurrencies. [ 162 ]
In May 2021, Tesla suspends Bitcoin payments due to environmental concerns, causing a significant market reaction. [ 163 ]
On 1 June 2021, El Salvador President Nayib Bukele announced his plans to adopt bitcoin as legal tender ; this would render El Salvador the world's first country to do so. [ 164 ]
On June 7, 2021, United States Justice Department recovered $2.3 million worth of bitcoin paid by Colonial Pipeline to a criminal cyber group in cyber-security ransom. [ 165 ] [ 166 ]
On 8 June 2021, at the initiative of the president, pro-government deputies in the Legislative Assembly of El Salvador voted legislation— Ley Bitcoin or the Bitcoin Law —to make Bitcoin legal tender in the country alongside the US Dollar . [ 167 ] [ 168 ]
On April 22, 2022, its price fell back down below $40,000. [ 169 ] It further dropped to as low as $26,970 in May after the collapse of Terra-Luna and its sister stablecoin, UST, in addition to a shedding of tech stocks. [ 170 ] On 18 June, Bitcoin dropped below $18,000, to trade at levels beneath its 2017 highs. [ 171 ] [ 172 ]
In May 2022, following a vote by Wikipedia editors the previous month, the Wikimedia Foundation announced it would stop accepting donations in bitcoin or other cryptocurrencies—eight years after it had first started taking contributions in bitcoin. [ 173 ] [ 174 ]
In 2023, ordinals, non-fungible tokens (NFTs) on Bitcoin, went live. [ 175 ]
In 2024, Bitcoin continued its strong development with many important events. [ 176 ] [ 177 ] One of the highlights was the approval of Bitcoin-holding ETF funds, helping to increase investment properties, and diversify stocks.
On December 4th, 2024, Bitcoin price reached 103,332.30
USD. [ 178 ] [ 179 ] [ 180 ] With a market capitalization of ~1,906,373,771,469 USD. [ 176 ] Bitcoin accounted for 55.2% of the total value of the cryptocurrency market on November 11, 2024. [ 181 ]
Among the factors which may have contributed to this rise were the European sovereign-debt crisis – particularly the 2012–2013 Cypriot financial crisis – statements by FinCEN improving the currency's legal standing, and rising media and Internet interest. [ 182 ] [ 183 ] [ 184 ] [ 185 ]
Until 2013, almost all market with bitcoins were in United States dollars (US$). [ 186 ]
As the market valuation of the total stock of bitcoins approached US$1 billion, some commentators called bitcoin prices a bubble . [ 187 ] [ 188 ] [ 189 ] In early April 2013, the price per bitcoin dropped from $266 to around $50 and then rose to around $100. Over two weeks starting late June 2013 the price dropped steadily to $70. The price began to recover, peaking once again on 1 October at $140. On 2 October, The Silk Road was seized by the FBI . This seizure caused a flash crash to $110. The price quickly rebounded, returning to $200 several weeks later. [ 190 ] The latest run went from $200 on 3 November to $900 on 18 November. [ 191 ] Bitcoin passed US$1,000 on 28 November 2013 at Mt. Gox. [ citation needed ]
A fork , referring to a blockchain, is defined variously as a blockchain split into two paths forward, or as a change of protocol rules. Accidental forks on the bitcoin network regularly occur as part of the mining process. They happen when two miners find a block at a similar point in time. As a result, the network briefly forks. This fork is subsequently resolved by the software which automatically chooses the longest chain, thereby orphaning the extra blocks added to the shorter chain (that were dropped by the longer chain).
On 12 March 2013, a bitcoin miner running version 0.8.0 of the bitcoin software created a large block that was considered invalid in version 0.7 (due to an undiscovered inconsistency between the two versions).
This created a split or "fork" in the blockchain since computers with the recent version of the software accepted the invalid block and continued to build on the diverging chain, whereas older versions of the software rejected it and continued extending the blockchain without the offending block.
This split resulted in two separate transaction logs being formed without clear consensus, which allowed for the same funds to be spent differently on each chain. In response, the Mt. Gox exchange temporarily halted bitcoin deposits. [ 236 ] The exchange rate fell 23% to $37 on the Mt. Gox exchange but rose most of the way back to its prior level of $48. [ 63 ] [ 64 ]
Miners resolved the split by downgrading to version 0.7, putting them back on track with the canonical blockchain.
User funds largely remained unaffected and were available when network consensus was restored. [ 237 ] The network reached consensus and continued to operate as normal a few hours after the split. [ 238 ]
Two significant forks took place in August. One, Bitcoin Cash , is a hard fork off the main chain in opposition to the other, which is a soft fork to implement Segregated Witness .
On 18 March 2013, the Financial Crimes Enforcement Network (or FinCEN), a bureau of the United States Department of the Treasury , issued a report regarding centralized and decentralized "virtual currencies" and their legal status within " money services business " (MSB) and Bank Secrecy Act regulations. [ 68 ] [ 74 ] It classified digital currencies and other digital payment systems such as bitcoin as " virtual currencies " because they are not legal tender under any sovereign jurisdiction . FinCEN cleared American users of bitcoin of legal obligations [ 74 ] by saying, "A user of virtual currency is not an MSB under FinCEN's regulations and therefore is not subject to MSB registration, reporting, and recordkeeping regulations." However, it held that American entities who generate "virtual currency" such as bitcoins are money transmitters or MSBs if they sell their generated currency for national currency : "...a person that creates units of convertible virtual currency and sells those units to another person for real currency or its equivalent is engaged in transmission to another location and is a money transmitter." This specifically extends to "miners" of the bitcoin currency who may have to register as MSBs and abide by the legal requirements of being a money transmitter if they sell their generated bitcoins for national currency and are within the United States. [ 66 ] Since FinCEN issued this guidance, dozens of virtual currency exchangers and administrators have registered with FinCEN, and FinCEN is receiving an increasing number of suspicious activity reports (SARs) from these entities. [ 239 ]
Additionally, FinCEN claimed regulation over American entities that manage bitcoins in a payment processor setting or as an exchanger: "In addition, a person is an exchanger and a money transmitter if the person accepts such de-centralized convertible virtual currency from one person and transmits it to another person as part of the acceptance and transfer of currency, funds, or other value that substitutes for currency." [ 67 ] [ 68 ]
In summary, FinCEN's decision would require bitcoin exchanges where bitcoins are traded for traditional currencies to disclose large transactions and suspicious activity, comply with money laundering regulations, and collect information about their customers as traditional financial institutions are required to do. [ 74 ] [ 240 ]
Jennifer Shasky Calvery, the director of FinCEN said, "Virtual currencies are subject to the same rules as other currencies. ... Basic money-services business rules apply here." [ 74 ]
In its October 2012 study, Virtual currency schemes , the European Central Bank concluded that the growth of virtual currencies will continue, and, given the currencies' inherent price instability, lack of close regulation, and risk of illegal uses by anonymous users, the Bank warned that periodic examination of developments would be necessary to reassess risks. [ 241 ]
In 2013, the U.S. Treasury extended its anti-money laundering regulations to processors of bitcoin transactions. [ 242 ] [ 243 ]
In June 2013, Bitcoin Foundation board member Jon Matonis wrote in Forbes that he received a warning letter from the California Department of Financial Institutions accusing the foundation of unlicensed money transmission. Matonis denied that the foundation is engaged in money transmission and said he viewed the case as "an opportunity to educate state regulators." [ 244 ]
In late July 2013, the industry group Committee for the Establishment of the Digital Asset Transfer Authority began to form to set best practices and standards, to work with regulators and policymakers to adapt existing currency requirements to digital currency technology and business models and develop risk management standards. [ 245 ]
In 2014, the U.S. Securities and Exchange Commission filed an administrative action against Erik T. Voorhees, for violating Securities Act Section 5 for publicly offering unregistered interests in two bitcoin websites in exchange for bitcoins. [ 246 ]
By December 2017, bitcoin futures contracts began to be offered, and the US Chicago Board Options Exchange (CBOE) was formally settling the futures daily. [ 247 ] [ 248 ] By 2019, multiple trading companies were offering services around bitcoin futures. [ 249 ]
A bitcoin faucet was a website or software app that dispensed rewards in the form of bitcoin for visitors to claim in exchange for completing a captcha or task as described by the website. There have also been faucets that dispense other cryptocurrencies . The first example was called "The Bitcoin Faucet" and was developed by Gavin Andresen in 2010. [ 250 ] It originally gave out five bitcoins per person.
The rewards were dispensed at regular time intervals as rewards for completing simple tasks such as captcha completion, or as prizes from simple games. The amount of bitcoin would typically fluctuate according to the cash value of bitcoin. Some faucets also had random larger rewards. To reduce mining fees , faucets saved up these small individual payments in their own ledgers , which would be dispersed as larger payment to a user's bitcoin address . [ 251 ]
Because bitcoin transactions are irreversible and there have been many faucets, they have been targets for hackers interested in acquiring bitcoins through theft or exploitation. Advertisements were the main income source of bitcoin faucets, with the potential reward in cryptocurrency intended to incentivize traffic. Some ad networks have also paid directly in bitcoin. Faucets typically have a low profit margin. Some faucets have also made money by mining cryptocurrencies in the background, using the user's CPU. [ citation needed ]
Bitcoins can be stored in a bitcoin cryptocurrency wallet . Theft of bitcoin has been documented on numerous occasions. At other times, bitcoin exchanges have shut down, taking their clients' bitcoins with them. A Wired study published April 2013 showed that 45 percent of bitcoin exchanges end up closing. [ 252 ]
On 19 June 2011, a security breach of the Mt. Gox bitcoin exchange caused the nominal price of a bitcoin to fraudulently drop to one cent on the Mt. Gox exchange, after a hacker used credentials from a Mt. Gox auditor's compromised computer illegally to transfer a large number of bitcoins to himself. They used the exchange's software to sell them all nominally, creating a massive "ask" order at any price. Within minutes, the price reverted to its correct user-traded value. [ 253 ] [ 254 ] [ 255 ] [ 256 ] [ 257 ] [ 258 ] Accounts with the equivalent of more than US$8,750,000 were affected. [ 255 ]
In July 2011, the operator of Bitomat, the third-largest bitcoin exchange, announced that he had lost access to his wallet.dat file with about 17,000 bitcoins (roughly equivalent to US$220,000 at that time). He announced that he would sell the service for the missing amount, aiming to use funds from the sale to refund his customers. [ 259 ]
In August 2011, MyBitcoin, a now defunct bitcoin transaction processor, declared that it was hacked, which caused it to be shut down, paying 49% on customer deposits, leaving more than 78,000 bitcoins (equivalent to roughly US$800,000 at that time) unaccounted for. [ 260 ] [ 261 ]
In early August 2012, a lawsuit was filed in San Francisco court against Bitcoinica – a bitcoin trading venue – claiming about US$460,000 from the company. Bitcoinica was hacked twice in 2012, which led to allegations that the venue neglected the safety of customers' money and cheated them out of withdrawal requests. [ 262 ] [ 263 ]
In late August 2012, an operation titled Bitcoin Savings and Trust was shut down by the owner, leaving around US$5.6 million in bitcoin-based debts; this led to allegations that the operation was a Ponzi scheme . [ 264 ] [ 265 ] [ 266 ] In September 2012, the U.S. Securities and Exchange Commission had reportedly started an investigation on the case. [ 267 ]
In September 2012, Bitfloor, a bitcoin exchange, also reported being hacked, with 24,000 bitcoins (worth about US$250,000) stolen. As a result, Bitfloor suspended operations. [ 268 ] [ 269 ] The same month, Bitfloor resumed operations; its founder said that he reported the theft to FBI, and that he plans to repay the victims, though the time frame for repayment is unclear. [ 270 ]
On 3 April 2013, Instawallet, a web-based wallet provider, was hacked, [ 271 ] resulting in the theft of over 35,000 bitcoins [ 272 ] which were valued at US$129.90 per bitcoin at the time, or nearly $4.6 million in total. As a result, Instawallet suspended operations. [ 271 ]
On 11 August 2013, the Bitcoin Foundation announced that a bug in a pseudorandom number generator within the Android operating system had been exploited to steal from wallets generated by Android apps; fixes were provided 13 August 2013. [ 273 ]
In October 2013, Inputs.io, an Australian-based bitcoin wallet provider was hacked with a loss of 4100 bitcoins, worth over A$1 million at time of theft. The service was run by the operator TradeFortress. Coinchat, the associated bitcoin chat room, was taken over by a new admin. [ 274 ]
On 26 October 2013, a Hong Kong–based bitcoin trading platform owned by Global Bond Limited (GBL) vanished with 30 million yuan (US$5 million) from 500 investors. [ 275 ]
Mt. Gox , the Japan-based exchange that in 2013 handled 70% of all worldwide bitcoin traffic, declared bankruptcy in February 2014, with bitcoins worth about $390 million missing, for unclear reasons. The CEO was eventually arrested and charged with embezzlement. [ 276 ]
On 3 March 2014, Flexcoin announced it was closing its doors because of a hack attack that took place the day before. [ 277 ] [ 278 ] [ 279 ] In a statement that once occupied their homepage they announced on 3 March 2014 that "As Flexcoin does not have the resources, assets, or otherwise to come back from this loss [the hack], we are closing our doors immediately." [ 280 ] Users can no longer log into the site.
Chinese cryptocurrency exchange Bter lost $2.1 million in BTC in February 2015.
The Slovenian exchange Bitstamp lost bitcoin worth $5.1 million to a hack in January 2015.
The US-based exchange Cryptsy declared bankruptcy in January 2016, ostensibly because of a 2014 hacking incident; the court-appointed receiver later alleged that Cryptsy's CEO had stolen $3.3 million.
In August 2016, hackers stole some $72 million in customer bitcoin from the Hong Kong–based exchange Bitfinex . [ 281 ]
In December 2017, hackers stole 4,700 bitcoins from NiceHash, a platform that allowed users to sell hashing power. [ 282 ] The value of the stolen bitcoins totaled about $80 million at the time. [ 283 ]
On 19 December 2017, Yapian, a company that owns the Youbit cryptocurrency exchange in South Korea, filed for bankruptcy following a hack, the second in eight months. [ 284 ]
On 11 November 2022 FTX filed for bankruptcy with an estimated $8 billion missing in customer funds.
In 2012, the Cryptocurrency Legal Advocacy Group (CLAG) stressed the importance for taxpayers to determine whether taxes are due on a bitcoin-related transaction based on whether one has experienced a " realization event": when a taxpayer has provided a service in exchange for bitcoins, a realization event has probably occurred and any gain or loss would likely be calculated using fair market values for the service provided." [ 285 ]
In August 2013, the German Finance Ministry characterized bitcoin as a unit of account , [ 83 ] [ 286 ] usable in multilateral clearing circles and subject to capital gains tax if held less than one year. [ 286 ]
On 5 December 2013, the People's Bank of China announced in a press release regarding bitcoin regulation that whilst individuals in China are permitted to freely trade and exchange bitcoins as a commodity, it is prohibited for Chinese financial banks to operate using bitcoins or for bitcoins to be used as legal tender currency, and that entities dealing with bitcoins must track and report suspicious activity to prevent money laundering. [ 287 ] The value of bitcoin dropped on various exchanges between 11 and 20 percent following the regulation announcement, before rebounding upward again. [ 288 ]
Bitcoin's blockchain can be loaded with arbitrary data. In 2018 researchers from RWTH Aachen University and Goethe University identified 1,600 files added to the blockchain, 59 of which included links to unlawful images of child exploitation, politically sensitive content, or privacy violations. "Our analysis shows that certain content, e.g. illegal pornography, can render the mere possession of a blockchain illegal." [ 289 ]
Interpol also sent out an alert in 2015 saying that "the design of the blockchain means there is the possibility of malware being injected and permanently hosted with no methods currently available to wipe this data". [ 290 ] | https://en.wikipedia.org/wiki/History_of_bitcoin |
Calculus , originally called infinitesimal calculus, is a mathematical discipline focused on limits , continuity , derivatives , integrals , and infinite series . Many elements of calculus appeared in ancient Greece, then in China and the Middle East, and still later again in medieval Europe and in India. Infinitesimal calculus was developed in the late 17th century by Isaac Newton and Gottfried Wilhelm Leibniz independently of each other. An argument over priority led to the Leibniz–Newton calculus controversy which continued until the death of Leibniz in 1716. The development of calculus and its uses within the sciences have continued to the present.
In mathematics education , calculus denotes courses of elementary mathematical analysis , which are mainly devoted to the study of functions and limits. The word calculus is Latin for "small pebble" (the diminutive of calx , meaning "stone"), a meaning which still persists in medicine . Because such pebbles were used for counting out distances, [ 1 ] tallying votes, and doing abacus arithmetic, the word came to mean a method of computation. In this sense, it was used in English at least as early as 1672, several years prior to the publications of Leibniz and Newton. [ 2 ]
In addition to the differential calculus and integral calculus, the term is also used widely for naming specific methods of calculation. Examples of this include propositional calculus in logic, the calculus of variations in mathematics, process calculus in computing, and the felicific calculus in philosophy.
The ancient period introduced some of the ideas that led to integral calculus, but does not seem to have developed these ideas in a rigorous and systematic way. Calculations of volumes and areas, one goal of integral calculus, can be found in the Egyptian Moscow papyrus ( c. 1820 BC ), but the formulas are only given for concrete numbers, some are only approximately true, and they are not derived by deductive reasoning. [ 3 ] Babylonians may have discovered the trapezoidal rule while doing astronomical observations of Jupiter . [ 4 ] [ 5 ]
From the age of Greek mathematics , Eudoxus (c. 408–355 BC) used the method of exhaustion , which foreshadows the concept of the limit, to calculate areas and volumes, while Archimedes (c. 287–212 BC) developed this idea further , inventing heuristics which resemble the methods of integral calculus. [ 6 ] Greek mathematicians are also credited with a significant use of infinitesimals . Democritus is the first person recorded to consider seriously the division of objects into an infinite number of cross-sections, but his inability to rationalize discrete cross-sections with a cone's smooth slope prevented him from accepting the idea. At approximately the same time, Zeno of Elea discredited infinitesimals further by his articulation of the paradoxes which they seemingly create.
Archimedes developed this method further, while also inventing heuristic methods which resemble modern day concepts somewhat in his The Quadrature of the Parabola , The Method , and On the Sphere and Cylinder . [ 7 ] It should not be thought that infinitesimals were put on a rigorous footing during this time, however. Only when it was supplemented by a proper geometric proof would Greek mathematicians accept a proposition as true. It was not until the 17th century that the method was formalized by Cavalieri as the method of Indivisibles and eventually incorporated by Newton into a general framework of integral calculus . Archimedes was the first to find the tangent to a curve other than a circle, in a method akin to differential calculus. While studying the spiral, he separated a point's motion into two components, one radial motion component and one circular motion component, and then continued to add the two component motions together, thereby finding the tangent to the curve. [ 8 ]
The method of exhaustion was independently invented in China by Liu Hui in the 4th century AD in order to find the area of a circle. [ 9 ] In the 5th century, Zu Chongzhi established a method that would later be called Cavalieri's principle to find the volume of a sphere . [ 10 ]
In the Middle East, Hasan Ibn al-Haytham , Latinized as Alhazen ( c. 965 – c. 1040 AD) derived a formula for the sum of fourth powers . He determined the equations to calculate the area enclosed by the curve represented by y = x k {\displaystyle y=x^{k}} (which translates to the integral ∫ x k d x {\displaystyle \int x^{k}\,dx} in contemporary notation), for any given non-negative integer value of k {\displaystyle k} . [ 11 ] He used the results to carry out what would now be called an integration , where the formulas for the sums of integral squares and fourth powers allowed him to calculate the volume of a paraboloid . [ 12 ] Roshdi Rashed has argued that the 12th century mathematician Sharaf al-Dīn al-Tūsī must have used the derivative of cubic polynomials in his Treatise on Equations . Rashed's conclusion has been contested by other scholars, who argue that he could have obtained his results by other methods which do not require the derivative of the function to be known. [ 13 ]
Evidence suggests Bhāskara II was acquainted with some ideas of differential calculus. [ 14 ] Bhāskara also goes deeper into the 'differential calculus' and suggests the differential coefficient vanishes at an extremum value of the function, indicating knowledge of the concept of ' infinitesimals '. [ 15 ] There is evidence of an early form of Rolle's theorem in his work, though it was stated without a modern formal proof. [ 16 ] [ 17 ] In his astronomical work, Bhāskara gives a result that looks like a precursor to infinitesimal methods: if x ≈ y {\displaystyle x\approx y} then sin ( y ) − sin ( x ) ≈ ( y − x ) cos ( y ) {\displaystyle \sin(y)-\sin(x)\approx (y-x)\cos(y)} . This leads to the derivative of the sine function, although he did not develop the notion of a derivative. [ 18 ]
Some ideas on calculus later appeared in Indian mathematics, at the Kerala school of astronomy and mathematics . [ 12 ] Madhava of Sangamagrama in the 14th century, and later mathematicians of the Kerala school, stated components of calculus such as the Taylor series and infinite series approximations. [ 19 ] They considered series equivalent to the Maclaurin expansions of sin ( x ) {\displaystyle \sin(x)} , cos ( x ) {\displaystyle \cos(x)} , and arctan ( x ) {\displaystyle \arctan(x)} more than two hundred years before they were studied in Europe. But they did not combine many differing ideas under the two unifying themes of the derivative and the integral , show the connection between the two, and turn calculus into the powerful problem-solving tool we have today. [ 12 ]
The mathematical study of continuity was revived in the 14th century by the Oxford Calculators and French collaborators such as Nicole Oresme . They proved the "Merton mean speed theorem ": that a uniformly accelerated body travels the same distance as a body with uniform speed whose speed is half the final velocity of the accelerated body. [ 20 ]
Johannes Kepler 's work Stereometrica Doliorum published in 1615 formed the basis of integral calculus. [ 21 ] Kepler developed a method to calculate the area of an ellipse by adding up the lengths of many radii drawn from a focus of the ellipse. [ 22 ]
A significant work was a treatise inspired by Kepler's methods [ 22 ] published in 1635 by Bonaventura Cavalieri on his method of indivisibles . He argued that volumes and areas should be computed as the sums of the volumes and areas of infinitesimally thin cross-sections. He discovered Cavalieri's quadrature formula which gave the area under the curves x n of higher degree. This had previously been computed in a similar way for the parabola by Archimedes in The Method , but this treatise is believed to have been lost in the 13th century, and was only rediscovered in the early 20th century, and so would have been unknown to Cavalieri. Cavalieri's work was not well respected since his methods could lead to erroneous results, and the infinitesimal quantities he introduced were disreputable at first.
Torricelli extended Cavalieri's work to other curves such as the cycloid , and then the formula was generalized to fractional and negative powers by Wallis in 1656. In a 1659 treatise, Fermat is credited with an ingenious trick for evaluating the integral of any power function directly. [ 23 ] Fermat also obtained a technique for finding the centers of gravity of various plane and solid figures, which influenced further work in quadrature.
In the 17th century, European mathematicians Isaac Barrow , René Descartes , Pierre de Fermat , Blaise Pascal , John Wallis and others discussed the idea of a derivative . In particular, in Methodus ad disquirendam maximam et minima and in De tangentibus linearum curvarum distributed in 1636, Fermat introduced the concept of adequality , which represented equality up to an infinitesimal error term. [ 24 ] This method could be used to determine the maxima, minima, and tangents to various curves and was closely related to differentiation. [ 25 ]
Isaac Newton would later write that his own early ideas about calculus came directly from "Fermat's way of drawing tangents." [ 26 ]
The formal study of calculus brought together Cavalieri's infinitesimals with the calculus of finite differences developed in Europe at around the same time, and Fermat's adequality. The combination was achieved by John Wallis , Isaac Barrow , and James Gregory , the latter two proving predecessors to the second fundamental theorem of calculus around 1670. [ 27 ] [ 28 ]
James Gregory , influenced by Fermat's contributions both to tangency and to quadrature, was then able to prove a restricted version of the second fundamental theorem of calculus, that integrals can be computed using any of a function's antiderivatives. [ 29 ] [ 30 ]
The first full proof of the fundamental theorem of calculus was given by Isaac Barrow . [ 31 ] : p.61 when arc ME ~ arc NH at point of tangency F fig.26 [ 32 ]
One prerequisite to the establishment of a calculus of functions of a real variable involved finding an antiderivative for the rational function f ( x ) = 1 x . {\displaystyle f(x)\ =\ {\frac {1}{x}}.} This problem can be phrased as quadrature of the rectangular hyperbola xy = 1. In 1647 Gregoire de Saint-Vincent noted that the required function F satisfied F ( s t ) = F ( s ) + F ( t ) , {\displaystyle F(st)=F(s)+F(t),} so that a geometric sequence became, under F , an arithmetic sequence . A. A. de Sarasa associated this feature with contemporary algorithms called logarithms that economized arithmetic by rendering multiplications into additions. So F was first known as the hyperbolic logarithm . After Euler exploited e = 2.71828..., and F was identified as the inverse function of the exponential function , it became the natural logarithm , satisfying d F d x = 1 x . {\displaystyle {\frac {dF}{dx}}\ =\ {\frac {1}{x}}.}
The first proof of Rolle's theorem was given by Michel Rolle in 1691 using methods developed by the Dutch mathematician Johann van Waveren Hudde . [ 33 ] The mean value theorem in its modern form was stated by Bernard Bolzano and Augustin-Louis Cauchy (1789–1857) also after the founding of modern calculus. Important contributions were made by Barrow, Huygens , and many others.
Barrow has been credited by some authors as having invented calculus, however, Swiss mathematician Florian Cajori notes that while Barrow did work out a set of "geometric theorems suggesting to us constructions by which we can find lines, areas and volumes whose magnitudes are ordinarily found by the analytical processes of the calculus", he did not create "what by common agreement of mathematicians has been designated by the term differential and integral calculus", and further notes that "Two processes yielding equivalent results are not necessarily the same". Cajori finishes with stating that "The invention belongs rightly belongs to Newton and Leibniz". [ 34 ]
Before Newton and Leibniz , the word "calculus" referred to any body of mathematics, but in the following years, "calculus" became a popular term for a field of mathematics based upon their insights. [ 35 ] Newton and Leibniz, building on this work, independently developed the surrounding theory of infinitesimal calculus in the late 17th century. Also, Leibniz did a great deal of work with developing consistent and useful notation and concepts. Newton provided some of the most important applications to physics, especially of integral calculus .
By the middle of the 17th century, European mathematics had changed its primary repository of knowledge. In comparison to the last century which maintained Hellenistic mathematics as the starting point for research, Newton, Leibniz and their contemporaries increasingly looked towards the works of more modern thinkers. [ 36 ]
Newton came to calculus as part of his investigations in physics and geometry . He viewed calculus as the scientific description of the generation of motion and magnitudes . In comparison, Leibniz focused on the tangent problem and came to believe that calculus was a metaphysical explanation of change. Importantly, the core of their insight was the formalization of the inverse properties between the integral and the differential of a function . This insight had been anticipated by their predecessors, but they were the first to conceive calculus as a system in which new rhetoric and descriptive terms were created. [ 37 ]
Newton completed no definitive publication formalizing his fluxional calculus; rather, many of his mathematical discoveries were transmitted through correspondence, smaller papers or as embedded aspects in his other definitive compilations, such as the Principia and Opticks . Newton would begin his mathematical training as the chosen heir of Isaac Barrow in Cambridge . His aptitude was recognized early and he quickly learned the current theories. By 1664 Newton had made his first important contribution by advancing the binomial theorem , which he had extended to include fractional and negative exponents . Newton succeeded in expanding the applicability of the binomial theorem by applying the algebra of finite quantities in an analysis of infinite series . He showed a willingness to view infinite series not only as approximate devices, but also as alternative forms of expressing a term. [ 38 ]
Newton's formulated his calculus between the years 1664 to 1666, [ 39 ] [ 40 ] [ 41 ] later describing them as, "the prime of my age for invention and minded mathematics and [natural] philosophy more than at any time since." A manuscript dated May 20, 1665 showed that Newton "had already developed the calculus to the point where he could compute the tangent and the curvature at any point of a continuous curve." [ 42 ] It was during his plague-induced isolation that the first written conception of fluxionary calculus was recorded in the unpublished De Analysi per Aequationes Numero Terminorum Infinitas . In this paper, he determined the area under a curve by first calculating a momentary rate of change and then extrapolating the total area. He began by reasoning about an indefinitely small triangle whose area is a function of x and y . He then reasoned that the infinitesimal increase in the abscissa will create a new formula where x = x + o (importantly, o is the letter, not the digit 0). He then recalculated the area with the aid of the binomial theorem, removed all quantities containing the letter o and re-formed an algebraic expression for the area. Significantly, Newton would then "blot out" the quantities containing o because terms "multiplied by it will be nothing in respect to the rest".
At this point Newton had begun to realize the central property of inversion. He had created an expression for the area under a curve by considering a momentary increase at a point. In effect, the fundamental theorem of calculus was built into his calculations. While his new formulation offered incredible potential, Newton was well aware of its logical limitations at the time. He admits that "errors are not to be disregarded in mathematics, no matter how small" and that what he had achieved was "shortly explained rather than accurately demonstrated".
In an effort to give calculus a more rigorous explication and framework, Newton compiled in 1671 the Methodus Fluxionum et Serierum Infinitarum . In this book, Newton's strict empiricism shaped and defined his fluxional calculus. He exploited instantaneous motion and infinitesimals informally. He used math as a methodological tool to explain the physical world. The base of Newton's revised calculus became continuity; as such he redefined his calculations in terms of continual flowing motion. For Newton, variable magnitudes are not aggregates of infinitesimal elements, but are generated by the indisputable fact of motion. As with many of his works, Newton delayed publication. Methodus Fluxionum was not published until 1736. [ 43 ]
Newton attempted to avoid the use of the infinitesimal by forming calculations based on ratios of changes. In the Methodus Fluxionum he defined the rate of generated change as a fluxion , which he represented by a dotted letter, and the quantity generated he defined as a fluent . For example, if x {\displaystyle {x}} and y {\displaystyle {y}} are fluents, then x ˙ {\displaystyle {\dot {x}}} and y ˙ {\displaystyle {\dot {y}}} are their respective fluxions. This revised calculus of ratios continued to be developed and was maturely stated in the 1676 text De Quadratura Curvarum where Newton came to define the present day derivative as the ultimate ratio of change, which he defined as the ratio between evanescent increments (the ratio of fluxions) purely at the moment in question. Essentially, the ultimate ratio is the ratio as the increments vanish into nothingness. Importantly, Newton explained the existence of the ultimate ratio by appealing to motion: [ 44 ]
For by the ultimate velocity is meant that, with which the body is moved, neither before it arrives at its last place, when the motion ceases nor after but at the very instant when it arrives... the ultimate ratio of evanescent quantities is to be understood, the ratio of quantities not before they vanish, not after, but with which they vanish
Newton developed his fluxional calculus in an attempt to evade the informal use of infinitesimals in his calculations.
Historian A. Rupert Hall noted Newton's rapid development of calculus in comparison to contemporaries, stating that Newton "well before 1690 . . . had reached roughly the point in the development of the calculus that Leibniz, the two Bernoullis, L’Hospital, Hermann and others had by joint efforts reached in print by the early 1700s". [ 45 ]
While Newton began development of his fluxional calculus in 1665–1666 his findings did not become widely circulated until later. In the intervening years Leibniz also strove to create his calculus. In comparison to Newton who came to math at an early age, Leibniz began his rigorous math studies with a mature intellect. He was a polymath , and his intellectual interests and achievements involved metaphysics , law , economics , politics , logic , and mathematics . In order to understand Leibniz's reasoning in calculus his background should be kept in mind. Particularly, his metaphysics which described the universe as a Monadology , and his plans of creating a precise formal logic whereby, "a general method in which all truths of the reason would be reduced to a kind of calculation". [ 46 ]
In 1672, Leibniz met the mathematician Huygens who convinced Leibniz to dedicate significant time to the study of mathematics. By 1673 he had progressed to reading Pascal 's Traité des sinus du quart de cercle and it was during his largely autodidactic research that Leibniz said "a light turned on". Like Newton, Leibniz saw the tangent as a ratio but declared it as simply the ratio between ordinates and abscissas . He continued this reasoning to argue that the integral was in fact the sum of the ordinates for infinitesimal intervals in the abscissa; in effect, the sum of an infinite number of rectangles. From these definitions the inverse relationship or differential became clear and Leibniz quickly realized the potential to form a whole new system of mathematics. Where Newton over the course of his career used several approaches in addition to an approach using infinitesimals , Leibniz made this the cornerstone of his notation and calculus. [ 47 ] [ 48 ]
In the manuscripts of 25 October to 11 November 1675, Leibniz recorded his discoveries and experiments with various forms of notation. He was acutely aware of the notational terms used and his earlier plans to form a precise logical symbolism became evident. Eventually, Leibniz denoted the infinitesimal increments of abscissas and ordinates dx and dy , and the summation of infinitely many infinitesimally thin rectangles as a long s (∫ ), which became the present integral symbol ∫ {\displaystyle \scriptstyle \int } .
While Leibniz's notation is used by modern mathematics, his logical base was different from our current one. Leibniz embraced infinitesimals and wrote extensively so as, "not to make of the infinitely small a mystery, as had Pascal." [ 49 ] According to Gilles Deleuze , Leibniz's zeroes "are nothings, but they are not absolute nothings, they are nothings respectively" (quoting Leibniz' text "Justification of the calculus of infinitesimals by the calculus of ordinary algebra"). [ 50 ] Alternatively, he defines them as, "less than any given quantity". For Leibniz, the world was an aggregate of infinitesimal points and the lack of scientific proof for their existence did not trouble him. Infinitesimals to Leibniz were ideal quantities of a different type from appreciable numbers. The truth of continuity was proven by existence itself. For Leibniz the principle of continuity and thus the validity of his calculus was assured. Three hundred years after Leibniz's work, Abraham Robinson showed that using infinitesimal quantities in calculus could be given a solid foundation. [ 51 ]
The rise of calculus stands out as a unique moment in mathematics. Calculus is the mathematics of motion and change, and as such, its invention required the creation of a new mathematical system. Importantly, Newton and Leibniz did not create the same calculus and they did not conceive of modern calculus. While they were both involved in the process of creating a mathematical system to deal with variable quantities their elementary base was different. For Newton, change was a variable quantity over time and for Leibniz it was the difference ranging over a sequence of infinitely close values. Notably, the descriptive terms each system created to describe change was different.
Historically, there was much debate over whether it was Newton or Leibniz who first "invented" calculus. This argument, the Leibniz and Newton calculus controversy , involving Leibniz, who was German, and the Englishman Newton, led to a rift in the European mathematical community lasting over a century. Leibniz was the first to publish his investigations; however, it is well established that Newton had started his work several years prior to Leibniz and had already developed a theory of tangents by the time Leibniz became interested in the question.
It is not known how much this may have influenced Leibniz. The initial accusations were made by students and supporters of the two great scientists at the turn of the century, but after 1711 both of them became personally involved, accusing each other of plagiarism .
The priority dispute had an effect of separating English-speaking mathematicians from those in continental Europe for many years. Only in the 1820s, due to the efforts of the Analytical Society , did Leibnizian analytical calculus become accepted in England. Today, both Newton and Leibniz are given credit for independently developing the basics of calculus. It is Leibniz, however, who is credited with giving the new discipline the name it is known by today: "calculus". Newton's name for it was "the science of fluents and fluxions ".
While neither of the two offered convincing logical foundations for their calculus according to mathematician Carl B. Boyer , Newton came the closest, with his best attempt coming in Principia , where he described his idea of "prime and ultimate ratios" and came extraordinarily close to the limit , and his ratio of velocities corresponded to a single real number , which would not be fully defined until the late nineteenth century. [ 52 ] On the other hand, the calculus of Leibniz was from a "logical point of view, distinctly inferior to that of Newton, for it never transcended the view of d y d x {\displaystyle {\frac {dy}{dx}}} as a quotient of infinitely small changes or differences in y and x ." [ 52 ] However, heuristically, it was a success, despite being a "failure" from a logical point of view. [ 52 ]
The work of both Newton and Leibniz is reflected in the notation used today. Newton introduced the notation f ˙ {\displaystyle {\dot {f}}} for the derivative of a function f . [ 53 ] Leibniz introduced the symbol ∫ {\displaystyle \int } for the integral and wrote the derivative of a function y of the variable x as d y d x {\displaystyle {\frac {dy}{dx}}} , both of which are still in use.
Since the time of Leibniz and Newton, many mathematicians have contributed to the continuing development of calculus. One of the first and most complete works on both infinitesimal and integral calculus was written in 1748 by Maria Gaetana Agnesi . [ 54 ] [ 55 ]
The calculus of variations began with the work of Isaac Newton , such as with Newton's minimal resistance problem , [ 56 ] which Newton formulated and solved in 1685, and later published in his Principia in 1687, [ 57 ] and which was the first problem in the field to be formulated and correctly solved, and was one of the most difficult problems tackled by variational methods prior to the twentieth century. [ 57 ] [ 58 ] [ 59 ] It was followed by the brachistochrone curve problem of Johann Bernoulli (1696), which Bernoulli solved, using the principle of least time, but not the calculus of variations, whereas Newton did to solve it in 1697, thus he pioneered the field with his work on the two problems. [ 59 ] The problem was similar to one raised by Galileo Galilei in 1638, but he did not solve the problem explicity nor did he use the methods based on calculus. [ 58 ] It immediately occupied the attention of Jakob Bernoulli but Leonhard Euler first elaborated the subject. His contributions began in 1733, and his Elementa Calculi Variationum gave to the science its name. Joseph Louis Lagrange contributed extensively to the theory, and Adrien-Marie Legendre (1786) laid down a method, not entirely satisfactory, for the discrimination of maxima and minima. To this discrimination Brunacci (1810), Carl Friedrich Gauss (1829), Siméon Denis Poisson (1831), Mikhail Vasilievich Ostrogradsky (1834), and Carl Gustav Jacob Jacobi (1837) have been among the contributors. An important general work is that of Sarrus (1842) which was condensed and improved by Augustin Louis Cauchy (1844). Other valuable treatises and memoirs have been written by Strauch (1849), Jellett (1850), Otto Hesse (1857), Alfred Clebsch (1858), and Carll (1885), but perhaps the most important work of the century is that of Karl Weierstrass . His course on the theory may be asserted to be the first to place calculus on a firm and rigorous foundation.
Antoine Arbogast (1800) was the first to separate the symbol of operation from that of quantity in a differential equation. Francois-Joseph Servois (1814) seems to have been the first to give correct rules on the subject. Charles James Hargreave (1848) applied these methods in his memoir on differential equations, and George Boole freely employed them. Hermann Grassmann and Hermann Hankel made great use of the theory, the former in studying equations , the latter in his theory of complex numbers .
Niels Henrik Abel seems to have been the first to consider in a general way the question as to what differential equations can be integrated in a finite form by the aid of ordinary functions, an investigation extended by Liouville . Cauchy early undertook the general theory of determining definite integrals , and the subject has been prominent during the 19th century. Frullani integrals , David Bierens de Haan 's work on the theory and his elaborate tables, Lejeune Dirichlet 's lectures embodied in Meyer 's treatise, and numerous memoirs of Legendre , Poisson , Plana , Raabe , Sohncke , Schlömilch , Elliott , Leudesdorf and Kronecker are among the noteworthy contributions.
Eulerian integrals were first studied by Euler and afterwards investigated by Legendre, by whom they were classed as Eulerian integrals of the first and second species, as follows:
although these were not the exact forms of Euler's study.
If n is a positive integer :
but the integral converges for all positive real n {\displaystyle n} and defines an analytic continuation of the factorial function to all of the complex plane except for poles at zero and the negative integers. To it Legendre assigned the symbol Γ {\displaystyle \Gamma } , and it is now called the gamma function . Besides being analytic over positive reals R + {\displaystyle \mathbb {R} ^{+}} , Γ {\displaystyle \Gamma } also enjoys the uniquely defining property that log Γ {\displaystyle \log \Gamma } is convex , which aesthetically justifies this analytic continuation of the factorial function over any other analytic continuation. To the subject Lejeune Dirichlet has contributed an important theorem (Liouville, 1839), which has been elaborated by Liouville , Catalan , Leslie Ellis , and others. Raabe (1843–44), Bauer (1859), and Gudermann (1845) have written about the evaluation of Γ ( x ) {\displaystyle \Gamma (x)} and log Γ ( x ) {\displaystyle \log \Gamma (x)} . Legendre's great table appeared in 1816.
The application of the infinitesimal calculus to problems in physics and astronomy was contemporary with the origin of the science. All through the 18th century these applications were multiplied, until at its close Laplace and Lagrange had brought the whole range of the study of forces into the realm of analysis. To Lagrange (1773) we owe the introduction of the theory of the potential into dynamics, although the name " potential function " and the fundamental memoir of the subject are due to Green (1827, printed in 1828). The name " potential " is due to Gauss (1840), and the distinction between potential and potential function to Clausius . With its development are connected the names of Lejeune Dirichlet , Riemann , von Neumann , Heine , Kronecker , Lipschitz , Christoffel , Kirchhoff , Beltrami , and many of the leading physicists of the century.
It is impossible in this article to enter into the great variety of other applications of analysis to physical problems. Among them are the investigations of Euler on vibrating chords; Sophie Germain on elastic membranes; Poisson, Lamé , Saint-Venant , and Clebsch on the elasticity of three-dimensional bodies; Fourier on heat diffusion; Fresnel on light ; Maxwell , Helmholtz , and Hertz on electricity ; Hansen, Hill, and Gyldén on astronomy ; Maxwell on spherical harmonics ; Lord Rayleigh on acoustics ; and the contributions of Lejeune Dirichlet, Weber , Kirchhoff , F. Neumann , Lord Kelvin , Clausius , Bjerknes , MacCullagh , and Fuhrmann to physics in general. The labors of Helmholtz should be especially mentioned, since he contributed to the theories of dynamics, electricity, etc., and brought his great analytical powers to bear on the fundamental axioms of mechanics as well as on those of pure mathematics.
Furthermore, infinitesimal calculus was introduced into the social sciences, starting with Neoclassical economics . Today, it is a valuable tool in mainstream economics. | https://en.wikipedia.org/wiki/History_of_calculus |
Cell theory has its origins in seventeenth century microscopy observations , but it was nearly two hundred years before a complete cell membrane theory was developed to explain what separates cells from the outside world. By the 19th century it was accepted that some form of semi-permeable barrier must exist around a cell. Studies of the action of anesthetic molecules led to the theory that this barrier might be made of some sort of fat ( lipid ), but the structure was still unknown. A series of pioneering experiments in 1925 indicated that this barrier membrane consisted of two molecular layers of lipids—a lipid bilayer . New tools over the next few decades confirmed this theory, but controversy remained regarding the role of proteins in the cell membrane. Eventually the fluid mosaic model was composed in which proteins “float” in a fluid lipid bilayer "sea". Although simplistic and incomplete, this model is still widely referenced today.
Since the invention of the microscope in the seventeenth century it has been known that plant and animal tissue is composed of cells : the cell was discovered by Robert Hooke . The plant cell wall was easily visible even with these early microscopes but no similar barrier was visible on animal cells, though it stood to reason that one must exist. By the mid 19th century, this question was being actively investigated and Moritz Traube noted that this outer layer must be semipermeable to allow transport of ions. [ 1 ] Traube had no direct evidence for the composition of this film, though, and incorrectly asserted that it was formed by an interfacial reaction of the cell protoplasm with the extracellular fluid. [ 2 ]
The lipid nature of the cell membrane was first correctly intuited by Georg Hermann Quincke in 1888 , who noted that a cell generally forms a spherical shape in water and, when broken in half, forms two smaller spheres. The only other known material to exhibit this behavior was oil. He also noted that a thin film of oil behaves as a semipermeable membrane, precisely as predicted. [ 3 ] Based on these observations, Quincke asserted that the cell membrane comprised a fluid layer of fat less than 100 nm thick. [ 4 ] This theory was further extended by evidence from the study of anesthetics. Hans Horst Meyer and Ernest Overton independently noticed that the chemicals which act as general anesthetics are also those soluble in both water and oil. They interpreted this as meaning that to pass the cell membrane a molecule must be at least sparingly soluble in oil, their “lipoid theory of narcosis.” Based on this evidence and further experiments, they concluded that the cell membrane might be made of lecithin ( phosphatidylcholine ) and cholesterol . [ 5 ] One of the early criticisms of this theory was that it included no mechanism for energy-dependent selective transport. [ 6 ] This “flaw” remained unanswered for nearly half a century until the discovery that specialized molecules called integral membrane proteins can act as ion transportation pumps.
Thus, by the early twentieth century the chemical, but not the structural nature of the cell membrane was known. Two experiments in 1924 laid the groundwork to fill in this gap. By measuring the capacitance of erythrocyte solutions Fricke determined that the cell membrane was 3.3 nm thick. [ 7 ] Although the results of this experiment were accurate, Fricke misinterpreted the data to mean that the cell membrane is a single molecular layer. Because the polar lipid headgroups are fully hydrated, they do not show up in a capacitance measurement meaning that this experiment actually measured the thickness of the hydrocarbon core, not the whole bilayer . Gorter and Grendel approached the problem from a different perspective, performing a solvent extraction of erythrocyte lipids and spreading the resulting material as a monolayer on a Langmuir-Blodgett trough . When they compared the area of the monolayer to the surface area of the cells, they found a ratio of two to one. [ 8 ] Later analyses of this experiment showed several problems including an incorrect monolayer pressure, incomplete lipid extraction and a miscalculation of cell surface area. [ 9 ] In spite of these issues the fundamental conclusion- that the cell membrane is a lipid bilayer- was correct.
A decade later, Davson and Danielli proposed a modification to this concept. In their model, the lipid bilayer was coated on either side with a layer of globular proteins . [ 10 ] According to their view, this protein coat had no particular structure and was simply formed by adsorption from solution. Their theory was also incorrect in that it ascribed the barrier properties of the membrane to electrostatic repulsion from the protein layer rather than the energetic cost of crossing the hydrophobic core. A more direct investigation of the membrane was made possible through the use of electron microscopy in the late 1950s. After staining with heavy metal labels, Sjöstrand et al. noted two thin dark bands separated by a light region, [ 11 ] which they incorrectly interpreted as a single molecular layer of protein. A more accurate interpretation was made by J. David Robertson, who determined that the dark electron-dense bands were the headgroups and associated proteins of two apposed lipid monolayers. [ 12 ] [ 13 ] In this body of work, Robertson put forward the concept of the “unit membrane.” This was the first time the bilayer structure had been universally assigned to all cell membranes as well as organelle membranes.
The idea of a semipermeable membrane , a barrier that is permeable to solvent but impermeable to solute molecules was developed at about the same time. The term osmosis originated in 1827 and its importance to physiological phenomena realized, but it was not until 1877 when the botanist Wilhelm Pfeffer proposed the membrane theory of cell physiology . In this view, the cell was seen to be enclosed by a thin surface, the plasma membrane , and cell water and solutes such as a potassium ion existed in a physical state like that of a dilute solution . In 1889, Hamburger used hemolysis of erythrocytes to determine the permeability of various solutes. By measuring the time required for the cells to swell past their elastic limit, the rate at which solutes entered the cells could be estimated by the accompanying change in cell volume. He also found that there was an apparent nonsolvent volume of about 50% in red blood cells and later showed that this includes water of hydration in addition to the protein and other nonsolvent components of the cells. Ernest Overton (a distant cousin of Charles Darwin) first proposed the concept of a lipid (oil) plasma membrane in 1899. The major weakness of the lipid membrane was the lack of an explanation of the high permeability to water, so Nathansohn (1904) proposed the mosaic theory. In this view, the membrane is not a pure lipid layer, but a mosaic of areas with lipid and areas with semipermeable gel. Ruhland refined the mosaic theory to include pores to allow additional passage of small molecules. Since membranes are generally less permeable to anions , Leonor Michaelis concluded that ions are adsorbed to the walls of the pores, changing the permeability of the pores to ions by electrostatic repulsion . Michaelis demonstrated the membrane potential (1926) and proposed that it was related to the distribution of ions across the membrane. [ 14 ] Harvey and James Danielli (1939) proposed a lipid bilayer membrane covered on each side with a layer of protein to account for measurements of surface tension. In 1941 Boyle & Conway showed that the membrane of resting frog muscle was permeable to both K+ and Cl-, but apparently not to Na+, so the idea of electrical charges in the pores was unnecessary since a single critical pore size explained the permeability to K+, H+, and Cl- as well as the impermeability to Na+, Ca+, and Mg++.
With the development of radioactive tracers , it was shown that cells are not impermeable to Na+. This was difficult to explain with the membrane barrier theory, so the sodium pump was proposed to continually remove Na+ as it permeates cells. This drove the concept that cells are in a state of dynamic equilibrium , constantly using energy to maintain ion gradients . In 1935, Karl Lohmann discovered ATP and its role as a source of energy for cells, so the concept of a metabolically-driven sodium pump was proposed.
The tremendous success of Hodgkin , Huxley , and Katz in the development of the membrane theory of cellular membrane potentials , with differential equations that modeled the phenomena correctly, provided even more support for the membrane pump hypothesis.
The modern view of the plasma membrane is of a fluid lipid bilayer that has protein components embedded within it. The structure of the membrane is now known in great detail, including 3D models of many of the hundreds of different proteins that are bound to the membrane.
These major developments in cell physiology placed the membrane theory in a position of dominance.
Around the same time the development of the first model membrane, the painted bilayer, allowed direct investigation of the properties of a simple artificial bilayer. By “painting” a reconstituted lipid solution across an aperture, Mueller and Rudin were able to determine that the resulting bilayer exhibited lateral fluidity, high electrical resistance and self-healing in response to puncture. [ 15 ] This form of model bilayer soon became known as a “BLM” although from the beginning the meaning of this acronym has been ambiguous. As early as 1966, BLM was used to mean either “black lipid membrane” or "bimolecular lipid membrane". [ 16 ] [ 17 ]
This same lateral fluidity was first demonstrated conclusively on the cell surface by Frye and Edidin in 1970. They fused two cells labeled with different membrane-bound fluorescent tags and watched as the two dye populations mixed. [ 18 ] The results of this experiment were key in the development of the "fluid mosaic" model of the cell membrane by Singer and Nicolson in 1972. [ 19 ] According to this model, biological membranes are composed largely of bare lipid bilayer with proteins penetrating either half way or all the way through the membrane. These proteins are visualized as freely floating within a completely liquid bilayer. This was not the first proposal of a heterogeneous membrane structure. Indeed, as early as 1904 Nathansohn proposed a “mosaic” of water permeable and impermeable regions. [ 20 ] But the fluid mosaic model was the first to correctly incorporate fluidity, membrane channels and multiple modes of protein/bilayer coupling into one theory.
Continued research has revealed some shortcomings and simplifications in the original theory. [ 21 ] For instance, channel proteins are described as having a continuous water channel through their center, which is now known to be generally untrue (an exception being nuclear pore complexes, which have a 9 nm open water channel). [ 22 ] Also, free diffusion on the cell surface is often limited to areas a few tens of nanometers across. These limits to lateral fluidity are due to cytoskeleton anchors, lipid phase separation and aggregated protein structures. Contemporary studies also indicate that much less of the plasma membrane is “bare” lipid than previously thought and in fact much of the cell surface may be protein-associated. In spite of these limitations, the fluid mosaic model remains a popular and often referenced general notion for the structure of biological membranes.
The modern mainstream consensus model of cellular membranes is based on the fluid-mosaic model that envisions a lipid bilayer separating the inside from the outside of cells with associated ion channels, pumps and transporters giving rise to the permeability processes of cells. Alternative hypotheses were developed in the past that have largely been rejected. One of these opposing concepts developed in the 1980's within the context of studies on osmosis , permeability, and electrical properties of cells was that of Gilbert Ling . [ 23 ] The modern idea holds that these properties all belonged to the plasma membrane whereas Ling's view was that the protoplasm was responsible for these properties.
As support for the lipid bilayer membrane theory grew, this alternative concept was developed which denied the importance of the lipid bilayer membrane. In 1916, Procter & Wilson demonstrated that gels, which do not have a semipermeable membrane , swelled in dilute solutions . Loeb (1920) also studied gelatin extensively, with and without a membrane, showing that more of the properties attributed to the plasma membrane could be duplicated in gels without a membrane. In particular, he found that an electrical potential difference between the gelatin and the outside medium could be developed, based on the H+ concentration.
Some criticisms of the membrane theory developed in the 1930s, based on observations such as the ability of some cells to swell and increase their surface area by a factor of 1000 (as in adipose tissue ). A lipid layer cannot stretch to that extent without becoming a patchwork (thereby losing its barrier properties). Such criticisms stimulated continued studies on protoplasm as the principal agent determining cell permeability properties. In 1938, Fischer and Suer proposed that water in the protoplasm is not free but in a chemically combined form, and that the protoplasm represents a combination of protein, salt and water. They demonstrated the basic similarity between swelling in living tissues and the swelling of gelatin and fibrin gels. Dimitri Nasonov (1944) viewed proteins as the central components responsible for many properties of the cell, including electrical properties.
By the 1940s, the bulk phase theories were not as well developed as the membrane theories and were largely rejected. In 1941, Brooks & Brooks published a monograph The Permeability of Living Cells , which rejects the bulk phase theories. [ 24 ] | https://en.wikipedia.org/wiki/History_of_cell_membrane_theory |
Chemical engineering is a discipline that was developed out of those practicing "industrial chemistry" in the late 19th century. Before the Industrial Revolution (18th century), industrial chemicals and other consumer products such as soap were mainly produced through batch processing . Batch processing is labour-intensive and individuals mix predetermined amounts of ingredients in a vessel, heat, cool or pressurize the mixture for a predetermined length of time. The product may then be isolated, purified and tested to achieve a saleable product. Batch processes are still performed today on higher value products, such as pharmaceutical intermediates, specialty and formulated products such as perfumes and paints, or in food manufacture such as pure maple syrups, where a profit can still be made despite batch methods being slower and inefficient in terms of labour and equipment usage. Due to the application of Chemical Engineering techniques during manufacturing process development, larger volume chemicals are now produced through continuous "assembly line" chemical processes . The Industrial Revolution was when a shift from batch to more continuous processing began to occur. Today commodity chemicals and petrochemicals are predominantly made using continuous manufacturing processes whereas speciality chemicals , fine chemicals and pharmaceuticals are made using batch processes.
The Industrial Revolution led to an unprecedented escalation in demand, both with regard to quantity and quality, for bulk chemicals such as soda ash . [ 1 ] This meant two things: one, the size of the activity and the efficiency of operation had to be enlarged, and two, serious alternatives to batch processing, such as continuous operation, had to be examined.
Industrial chemistry was being practiced in the 1800s, and its study at British universities began with the publication by Friedrich Ludwig Knapp , Edmund Ronalds and Thomas Richardson of the important book Chemical Technology in 1848. [ 2 ] By the 1880s the engineering elements required to control chemical processes were being recognized as a distinct professional activity. Chemical engineering was first established as a profession in the United Kingdom after the first chemical engineering course was given at the University of Manchester in 1887 by George E. Davis in the form of twelve lectures covering various aspects of industrial chemical practice. [ 3 ] As a consequence George E. Davis is regarded as the world's first chemical engineer. Today, chemical engineering is a highly regarded profession. Chemical engineers with experience can become licensed Professional Engineers in the United States, aided by the National Society of Professional Engineers , or gain "Chartered" chemical-engineer status through the UK-based Institution of Chemical Engineers .
In 1880, the first attempt was made to form a Society of Chemical Engineers in London. This eventually resulted in the formation of the Society of Chemical Industry in 1881. The American Institute of Chemical Engineers (AIChE) was founded in 1908, and the UK Institution of Chemical Engineers (IChemE) in 1922. [ 4 ] These both now have substantial international membership. Some other countries now have chemical engineering societies or sections within chemical or engineering societies, but the AIChE, IChemE and IiChE remain the major ones in numbers and international spread: they are both open to suitably qualified professionals or students of chemical engineering anywhere in the world.
For the other established branches of engineering, there were ready associations in the public's mind: Mechanical Engineering meant machines, Electrical Engineering meant circuitry, and Civil Engineering meant structures. Chemical engineering came to mean chemicals production .
Arthur Dehon Little is credited with the approach chemical engineers to this day take: process-oriented rather than product-oriented analysis and design. The concept of unit operations was developed to emphasize the underlying similarity among seemingly different chemical productions. For example, the principles are the same whether one is concerned about separating alcohol from water in a fermenter, or separating gasoline from diesel in a refinery, as long as the basis of separation is generation of a vapor of a different composition from the liquid. Therefore, such separation processes can be studied together as a unit operation, in this case called distillation .
In the early part of the last century, a parallel concept called Unit Processes was used to classify reactive processes. Thus oxidations , reductions , alkylations , etc. formed separate unit processes and were studied as such. This was natural considering the close affinity of chemical engineering to industrial chemistry at its inception. Gradually however, the subject of chemical reaction engineering has largely replaced the unit process concept. This subject looks at the entire body of chemical reactions as having a personality of its own, independent of the particular chemical species or chemical bonds involved. The latter does contribute to this personality in no small measure, but to design and operate chemical reactors, a knowledge of characteristics such as rate behaviour , thermodynamics , single or multiphase nature, etc. are more important. The emergence of chemical reaction engineering as a discipline signaled the severance of the umbilical cord connecting chemical engineering to industrial chemistry and cemented the unique character of the discipline. | https://en.wikipedia.org/wiki/History_of_chemical_engineering |
Chemical weapons have been a part of warfare in most societies for centuries. [ 1 ] However, their usage has been extremely controversial since the 20th century. [ 2 ]
Ancient Greek myths about Heracles poisoning his arrows with the venom of the Hydra monster are the earliest references to toxic weapons in western literature. Homer's epics, the Iliad and the Odyssey , allude to poisoned arrows used by both sides in the legendary Trojan War ( Bronze Age Greece). [ 3 ]
Some of the earliest surviving references to toxic warfare appear in the Indian epics Ramayana and Mahabharata . [ 4 ] The " Laws of Manu ," a Hindu treatise on statecraft (c. 400 BC) forbids the use of poison and fire arrows, but advises poisoning food and water. Kautilya 's " Arthashastra ", a statecraft manual of the same era, contains hundreds of recipes for creating poison weapons, toxic smokes, and other chemical weapons. Ancient Greek historians recount that Alexander the Great encountered poison arrows and fire incendiaries in India at the Indus basin in the 4th century BC. [ 3 ]
Arsenical smokes were known to the Chinese as far back as c. 1000 BC [ 5 ] and Sun Tzu 's " Art of War " (c. 200 BC) advises the use of incendiary weapons . In the second century BC, writings of the Mohist sect in China describe the use of bellows to pump smoke from burning balls of toxic plants and vegetables into tunnels being dug by a besieging army. Other Chinese writings dating around the same period contain hundreds of recipes for the production of poisonous or irritating smokes for use in war along with numerous accounts of their use. These accounts describe an arsenic -containing "soul-hunting fog", and the use of finely divided lime dispersed into the air to suppress a peasant revolt in 178 AD. [ citation needed ]
The earliest recorded use of gas warfare in the West dates back to the fifth century BC, during the Peloponnesian War between Athens and Sparta . Spartan forces besieging an Athenian city placed a lighted mixture of wood, pitch, and sulfur under the walls hoping that the noxious smoke would incapacitate the Athenians, so that they would not be able to resist the assault that followed. Sparta was not alone in its use of unconventional tactics in ancient Greece; Solon of Athens is said to have used hellebore roots to poison the water in an aqueduct leading from the River Pleistos around 590 BC during the siege of Kirrha . [ 3 ]
The earliest archaeological evidence of gas warfare is during the Roman–Persian wars . Research carried out on the collapsed tunnels at Dura-Europos in Syria suggests that during the siege of the town in the third century AD, the Sasanians used bitumen and sulfur crystals to get it burning. When ignited, the materials gave off dense clouds of choking sulfur dioxide gases which killed 19 Roman soldiers and a single Sassanian, purported to be the fire-tender, in a matter of two minutes. [ 6 ] [ 7 ] [ 8 ] [ 9 ]
Quicklime may have been used in medieval naval warfare, including to use of "lime-mortars" to throw it at enemy ships. [ 10 ] Scottish historian David Hume , in his work The History of England , recounted how during the reign of Henry III of England the English navy destroyed an invading French fleet by attacking it with quicklime. [ 11 ]
In the late 15th century, Spanish conquistadors encountered a rudimentary type of chemical warfare on the island of Hispaniola . The Taíno threw gourds filled with ashes and ground hot peppers at the Spaniards to create a blinding smoke screen before launching their attack. [ 12 ]
The natives of the Pernambuco province used pepper smoke during sieges; they would wait till the wind was blowing towards the enemy, and light a bonfire filled with peppers. [ 13 ]
Leonardo da Vinci proposed the use of a powder of sulfide, arsenic and verdigris in the 15th century:
It is unknown whether this powder was ever actually used.
In the 17th century during sieges , armies attempted to start fires by launching incendiary shells filled with sulfur , tallow , rosin , turpentine , saltpeter , and/or antimony . Even when fires were not started, the resulting smoke and fumes provided a considerable distraction. Although their primary function was never abandoned, a variety of fills for shells were developed to maximize the effects of the smoke.
In 1672, during his siege of the city of Groningen , Christoph Bernhard von Galen , the Bishop of Münster , employed several different explosive and incendiary devices, some of which had a fill that included belladonna , intended to produce toxic fumes. Just three years later, August 27, 1675, the French and the Holy Roman Empire concluded the Strasbourg Agreement , which included an article banning the use of "perfidious and odious" toxic devices. [ citation needed ]
Pirate Captain Thompson used "vast numbers of powder flasks, grenade shells, and stinkpots" to defeat two pirate-hunters sent by the Governor of Jamaica in 1721. [ 14 ]
The Qing dynasty used stinkpots in naval operations. [ 15 ] Those earthenware incendiary weapons were in part filled with sulphur, gunpowder, nails, and shot, while the other part was filled with noxious materials designed to emanate a highly unpleasant and suffocating smell to its enemies when ignited. [ 15 ] During the War of 1812 , the Royal Navy used stinkpots in a bombardment of Stonington, Connecticut on 9 August 1814. [ 16 ]
The modern notion of chemical warfare emerged from the mid-19th century, with the development of modern chemistry and associated industries . The first recorded modern proposal for the use of chemical warfare was made by Lyon Playfair , Secretary of the Science and Art Department , in 1854 during the Crimean War . He proposed a cacodyl cyanide artillery shell for use against enemy ships as way to solve the stalemate during the siege of Sevastopol . The proposal was backed by Admiral Thomas Cochrane of the Royal Navy . It was considered by the Prime Minister, Lord Palmerston , but the British Ordnance Department rejected the proposal as "as bad a mode of warfare as poisoning the wells of the enemy." Playfair's response was used to justify chemical warfare into the next century: [ 17 ]
Later, during the American Civil War , New York school teacher John Doughty proposed the offensive use of chlorine gas, delivered by filling a 10- inch (254 millimeter) artillery shell with two to three quarts (1.89–2.84 liters ) of liquid chlorine, which could produce many cubic feet of chlorine gas. Doughty's plan was apparently never acted on, as it was probably [ 18 ] presented to Brigadier General James Wolfe Ripley , Chief of Ordnance. [ clarification needed ]
In March 1868, during the War of Triple Alliance , the Paraguayan troops threw lit tubes full of asphixiating mixtures in their attempt to board Brazilian ironclads with canoes. The attack failed since the tubes were easily put out by the defenders. [ 19 ]
A general concern over the use of poison gas manifested itself in 1899 at the Hague Conference with a proposal prohibiting shells filled with asphyxiating gas. The proposal was passed, despite a single dissenting vote from the United States. The American representative, Navy Captain Alfred Thayer Mahan , justified voting against the measure on the grounds that "the inventiveness of Americans should not be restricted in the development of new weapons." [ 20 ]
The French were the first to use chemical weapons during the First World War, using the tear gases ethyl bromoacetate and chloroacetone . They likely did not realize that effects might be more serious under wartime conditions than in riot control . It is also likely that their use of tear gas escalated to the use of poisonous gases. [ 21 ]
The Hague Declaration of 1899 and the Hague Convention of 1907 prohibit the firing of any projectiles "the sole object of which is the diffusion of asphyxiating or deleterious gases." [ 22 ] Germany exploited this loophole by opening canisters filled with poison gas into the wind and letting it carry it towards the enemy lines, instead of launching it in artillery rounds. One of Germany's earliest uses of chemical weapons occurred on October 27, 1914, when shells containing the irritant dianisidine chlorosulfonate were fired at British troops near Neuve-Chapelle , France. [ 5 ] Germany used another irritant, xylyl bromide , in artillery shells that were fired in January 1915 at the Russians near Bolimów , in present-day Poland. [ 23 ] The first full-scale deployment of deadly chemical warfare agents during World War I was at the Second Battle of Ypres , on April 22, 1915, when the Germans attacked French, Canadian and Algerian troops with chlorine gas released from canisters and carried by the wind towards the Allied trenches. [ 24 ] [ 25 ] [ 26 ] [ 27 ]
A total 50,965 tons of pulmonary, lachrymatory, and vesicant agents were deployed by both sides of the conflict, including chlorine , phosgene , and mustard gas . Historians have reached a wide range of estimates on gas casualties, ranging from 500k to 1.3 million casualties directly caused by chemical warfare agents during the course of the war. A minimum of around 1300 civilians were injured due to the use of the weapons, and at least around 4000 were injured during weapon production. [ 28 ]
World War I-era chemical ammunition is still found, unexploded, at former battle, storage, or test sites and poses an ongoing threat to inhabitants of Belgium, France and other countries. [ 29 ] Camp American University where American chemical weapons were developed and later buried, has undergone 20 years of remediation efforts. [ 30 ] [ 31 ]
After the war, the most common method of disposal of chemical weapons was to dump them into the nearest large body of water. [ 32 ] As many as 65,000 tons of chemical warfare agents may have been dumped in the Baltic Sea alone; agents dumped in that sea included mustard gas , phosgene, lewisite (β-chlorovinyldichloroarsine), adamsite (diphenylaminechloroarsine), Clark I (diphenylchloroarsine) and Clark II (diphenylcyanoarsine). [ 33 ] [ 34 ] [ 35 ] Over time the containers corrode, and the chemicals leaked out. On the sea floor, at low temperatures, mustard gas tends to form lumps within a "skin" of chemical byproducts. These lumps can wash onto shore, where they look like chunks of waxy yellowish clay. They are extremely toxic, but the effects may not be immediately apparent. [ 32 ]
During the interwar period , chemical agents were occasionally used to subdue populations and suppress rebellion. In 1925, 16 of the world's major nations signed the Geneva Protocol , thereby pledging never to use chemical weapons in interstate warfare again. Notably, while the United States delegation under presidential authority signed the Protocol, it was not ratified until 1975. The Protocol does not ban the development or production of chemical weapons nor it applies to non-international armed conflicts.
It has been alleged that the British used chemical weapons in Mesopotamia during the Iraqi revolt of 1920. Noam Chomsky claimed that Winston Churchill at the time was keen on chemical weapons, suggesting they be used "against recalcitrant Arabs as an experiment", and that he stated to be "strongly in favour of using poisoned gas against uncivilised tribes". [ 36 ] [ 37 ]
According to some historians, including Geoff Simons and Charles Townshend , the British used chemical weapons in the conflict, [ 38 ] [ 39 ] while according to Lawrence James and Niall Ferguson the weapons were agreed by Churchill but eventually not used; [ 40 ] [ 41 ] R.M. Douglas of Colgate University also observed that Churchill's statement had served to convince observers of the existence of weapons of mass destruction which were not actually there. [ 42 ]
Lenin's Soviet government employed poison gas in 1921 during the Tambov Rebellion . An order signed by military commanders Tukhachevsky and Vladimir Antonov-Ovseyenko stipulated, "The forests where the bandits are hiding are to be cleared by the use of poison gas. This must be carefully calculated, so that the layer of gas penetrates the forests and kills everyone hiding there." [ 43 ] [ 44 ]
In the 1930s, the Soviet Union used mustard gas deployed from planes against Basmachi rebels in Central Asia . [ 45 ]
During the Soviet invasion of Xinjiang in 1934, Ma Zhongying 's New 36th Division put up a fierce resistance at the Battle of Dawan Cheng , but was forced to retreat after Soviets delivered mustard gas from planes. [ 46 ]
A chemical arms race developed during the Warlord Era . The first chemical weapons were imported by a minor Hunan warlord, who bought two small cases of "gas-producing shells" in August 1921. Marshal Cao Kun , approached a British-owned chemical company in Tianjin in 1923; he attempted to order gas bombs, but as far as is known they turned down his proposal. In 1925, Zhang Zuolin had a chemical plant built in Mukden and hired German and Russian experts to produce chlorine, phosgene and mustard gas, in the same year Feng Yuxiang also set up a ‘special arsenal’ to produce chemical weapons designed by Soviet and German experts. All of these efforts appear to have failed. There was one reported incident of chemical warfare when Zhang Zuolin's aircraft dropped gas bombs’ on the forces of Wu Peifu ; who branded the use of these bombs as inhumane. [ 47 ]
Combined Spanish and French forces dropped mustard gas bombs against Berber rebels and civilians during the Rif War in Spanish Morocco (1921–1927). These attacks marked the first widespread employment of gas warfare in the post-WWI era. [ 48 ] The Spanish army indiscriminately used phosgene , diphosgene , chloropicrin and mustard gas against civilian populations, markets and rivers. [ 49 ] [ 50 ] Although Spain signed the Geneva Protocol in 1925, it only prohibited the use of chemical and biological weapons in international conflicts, instead of non-international conflicts like the Rif War. [ 50 ]
In a telegram sent by the High Commissioner of Spanish Morocco Dámaso Berenguer on August 12, 1921, to the Spanish minister of War, Berenguer stated: "I have been obstinately resistant to the use of suffocating gases against these indigenous peoples but after what they have done, and of their treacherous and deceptive conduct, I have to use them with true joy." [ 51 ]
According to military aviation general Hidalgo de Cisneros in his autobiographical book Cambio de rumbo , [ 52 ] he was the first warfighter to drop a 100-kilogram mustard gas bomb from his Farman F60 Goliath aircraft in the summer of 1924. [ 53 ] About 127 fighters and bombers flew in the campaign, dropping around 1,680 bombs each day. [ 54 ] The mustard gas bombs were brought from the stockpiles of Germany and delivered to Melilla before being carried on Farman F60 Goliath airplanes. [ 55 ] Historian Juan Pando has been the only Spanish historian to have confirmed the usage of mustard gas starting in 1923. [ 51 ] Spanish newspaper La Correspondencia de España published an article called Cartas de un soldado ( Letters of a soldier ) on August 16, 1923, which backed the usage of mustard gas. [ 56 ]
Some have cited the chemical weapons used in the region as the main reason for the widespread occurrence of cancer among the population. [ 57 ] In 2007, the Catalan party of the Republican Left ( Esquerra Republicana de Catalunya ) passed a bill to the Spanish Congress of Deputies requesting Spain to acknowledge the "systematic" use of chemical weapons against the population of the Rif mountains; [ 58 ] however, the bill was rejected by 33 votes from the governing Socialist Labor Party and the opposition right-wing Popular Party . [ 59 ]
Italy used mustard gas and other "gruesome measures" against Senussi forces in Libya (see Pacification of Libya , Italian colonization of Libya ). [ 60 ] Poison gas was used against the Libyans as early as January 1928 [ 61 ] The Italians dropped mustard gas from the air. [ 62 ]
Beginning in October 1935 and continuing into the following months, Fascist Italy used mustard gas against the Ethiopians during the Second Italo-Abyssinian War in violation of the Geneva Protocol. Italian general Rodolfo Graziani first ordered the use of chemical weapons at Gorrahei against the forces of Ras Nasibu . [ 63 ] Benito Mussolini personally authorized Graziani to use chemical weapons. [ 64 ] Chemical weapons dropped by warplane "proved to be very effective" and was used "on a massive scale against civilians and troops, as well as to contaminate fields and water supplies." [ 65 ] Among the most intense chemical bombardment by the Italian Air Force in Ethiopia occurred in February and March 1936, although "gas warfare continued, with varying intensity, until March 1939." [ 64 ] J. F. C. Fuller , who was present in Ethiopia during the conflict, stated that mustard gas "was the decisive tactical factor in the war." [ 66 ] Some estimate that up to one-third of Ethiopian casualties of the war were caused by chemical weapons. [ 67 ]
The Italians' deployment of mustard gas prompted international criticism. [ 63 ] [ 66 ] In April 1936, British Prime Minister Stanley Baldwin told Parliament: "If a great European nation, in spite of having given its signature to the Geneva Protocol against the use of such gases, employs them in Africa, what guarantee have we that they may not be used in Europe?" [ 66 ] [ 68 ] Mussolini initially denied the use of chemical weapons; later, Mussolini and Italian government sought to justify their use as lawful retaliation for Ethiopian atrocities. [ 63 ] [ 64 ] [ 66 ]
After the liberation of Ethiopia in 1941 , Ethiopia repeatedly but unsuccessfully sought to prosecute Italian war criminals. The Allied powers excluded Ethiopia from the United Nations War Crimes Commission (established in 1942) because the Allies feared that Ethiopia would seek to prosecute Italian commander Pietro Badoglio , who had ordered the use of chemical gas in the Second Italo-Ethiopian War but later "became a valuable ally against the Axis powers" after the fall of the Fascist regime in Italy , serving as a senior officer in the Italian Co-belligerent Army . [ 63 ] In 1946, Ethiopians ruler Haile Selassie again sought "to prosecute senior Italian officials who had sanctioned the use of chemical weapons and had committed other war crimes such as torturing and executing Ethiopian prisoners and citizens during the Italian-Ethiopian War." [ 63 ] These attempts failed, in large part because the Western Allies wished to avoid alienating the Italian government at a time when Italy was seen as key to containing the Soviet Union. [ 63 ]
Following World War II, the Italian government denied that Italy had ever used chemical weapons in Africa; only in 1995 did Italy formally acknowledge that it had used chemical weapons in colonial wars. [ 69 ]
Shortly after the end of World War I , Germany's General Staff enthusiastically pursued a recapture of their preeminent position in chemical warfare. In 1923, Hans von Seeckt pointed the way, by suggesting that German poison gas research move in the direction of delivery by aircraft in support of mobile warfare. Also in 1923, at the behest of the German army , poison gas expert Dr. Hugo Stoltzenberg negotiated with the USSR to build a huge chemical weapons plant at Trotsk, on the Volga river.
Collaboration between Germany and the Soviet Union in poison gas research continued on and off through the 1920s. In 1924, German officers debated the use of poison gas versus non-lethal chemical weapons against civilians.
Chemical warfare was revolutionized by Nazi Germany 's discovery of the nerve agents tabun (in 1937) and sarin (in 1939) by Gerhard Schrader , a chemist of IG Farben .
IG Farben was Germany's premier poison gas manufacturer during World War II , so the weaponization of these agents cannot be considered accidental. [ 70 ] Both were turned over to the German Army Weapons Office prior to the outbreak of the war.
The nerve agent soman was later discovered by Nobel Prize laureate Richard Kuhn and his collaborator Konrad Henkel at the Kaiser Wilhelm Institute for Medical Research in Heidelberg in the spring of 1944. [ 71 ] [ 72 ] The Germans developed and manufactured large quantities of several agents, but chemical warfare was not extensively used by either side. Chemical troops were set up (in Germany since 1934) and delivery technology was actively developed.
Despite the 1899 Hague Declaration IV, 2 – Declaration on the Use of Projectiles the Object of Which is the Diffusion of Asphyxiating or Deleterious Gases , [ 73 ] Article 23 (a) of the 1907 Hague Convention IV – The Laws and Customs of War on Land , [ 74 ] and a resolution adopted against Japan by the League of Nations on May 14, 1938, the Imperial Japanese Army frequently used chemical weapons. Because of fear of retaliation, however, those weapons were never used against Westerners, but against other Asians judged "inferior" by imperial propaganda. According to historians Yoshiaki Yoshimi and Kentaro Awaya, gas weapons, such as tear gas, were used only sporadically in 1937 but in early 1938, the Imperial Japanese Army began full-scale use of sneeze and nausea gas (red), and from mid-1939, used mustard gas (yellow) against both Kuomintang and Communist Chinese troops. [ 75 ]
According to historians Yoshiaki Yoshimi and Seiya Matsuno, the chemical weapons were authorized by specific orders given by Emperor Hirohito himself, transmitted by the chief of staff of the army . For example, the Emperor authorized the use of toxic gas on 375 separate occasions during the Battle of Wuhan from August to October 1938. [ 76 ] They were also profusely used during the invasion of Changde . Those orders were transmitted either by Prince Kan'in Kotohito or General Hajime Sugiyama . [ 77 ] The Imperial Japanese Army had used mustard gas and the US-developed (CWS-1918) blister agent lewisite against Chinese troops and guerrillas. Experiments involving chemical weapons were conducted on live prisoners ( Unit 731 and Unit 516 ).
The Japanese also carried chemical weapons as they swept through Southeast Asia towards Australia. Some of these items were captured and analyzed by the Allies. Historian Geoff Plunkett has recorded how Australia covertly imported 1,000,000 chemical weapons from the United Kingdom from 1942 onwards and stored them in many storage depots around the country, including three tunnels in the Blue Mountains to the west of Sydney. They were to be used as a retaliatory measure if the Japanese first used chemical weapons. [ 78 ] Buried chemical weapons have been recovered at Marrangaroo and Columboola. [ 79 ] [ 80 ]
During the Holocaust , a genocide perpetrated by Nazi Germany, millions of Jews, Romani, Slavs, homosexuals, people with disabilities, and other victims were gassed with carbon monoxide and hydrogen cyanide (including Zyklon B ). [ 81 ] [ 82 ] This remains the deadliest use of poison gas in history. [ 81 ] Nevertheless, the Nazis did not extensively use chemical weapons in combat, [ 81 ] [ 82 ] at least not against the Western Allies, [ 83 ] despite maintaining an active chemical weapons program in which the Nazis used concentration camp prisoners as forced labor to secretly manufacture tabun , a nerve gas, and experimented upon concentration camp victims to test the effects of the gas. [ 81 ] Otto Ambros of IG Farben was a chief chemical-weapons expert for the Nazis. [ 81 ] [ 84 ]
The Nazis' decision to avoid the use of chemical weapons on the battlefield has been variously attributed to a lack of technical ability in the German chemical weapons program and fears that the Allies would retaliate with their own chemical weapons. [ 83 ] It also has been speculated to have arisen from Adolf Hitler 's experiences as a soldier in the German army during World War I , where he was injured by a British mustard gas attack in 1918. [ 85 ] After the Battle of Stalingrad , Joseph Goebbels , Robert Ley , and Martin Bormann urged Hitler to approve the use of tabun and other chemical weapons to slow the Soviet advance . At a May 1943 meeting in the Wolf's Lair , however, Hitler was told by Ambros that Germany had 45,000 tons of chemical gas stockpiled, but that the Allies likely had far more. Hitler responded by suddenly leaving the room and ordering production of tabun and sarin to be doubled, but "fearing some rogue officer would use them and spark Allied retaliation, he ordered that no chemical weapons be transported to the Russian front." [ 81 ] After the Allied invasion of Italy , the Germans rapidly moved to remove or destroy both German and Italian chemical-weapon stockpiles, "for the same reason that Hitler had ordered them pulled from the Russian front—they feared that local commanders would use them and trigger Allied chemical retaliation." [ 81 ]
Stanley P. Lovell, deputy director for Research and Development of the Office of Strategic Services, reports in his book Of Spies and Stratagems that the Allies knew the Germans had quantities of Gas Blau available for use in the defense of the Atlantic Wall . The use of nerve gas on the Normandy beachhead would have seriously impeded the Allies and possibly caused the invasion to fail altogether. He submitted the question "Why was nerve gas not used in Normandy ?" to be asked of Hermann Göring during his interrogation after the war had ended. Göring answered that the reason was that the Wehrmacht was dependent upon horse-drawn transport to move supplies to their combat units, and had never been able to devise a gas mask horses could tolerate; the versions they developed would not pass enough pure air to allow the horses to pull a cart. Thus, gas was of no use to the German Army under most conditions. [ 86 ]
The Nazis did use chemical weapons in combat on several occasions along the Black Sea , notably in Sevastopol , where they used toxic smoke to force Soviet resistance fighters out of caverns below the city, in violation of the 1925 Geneva Protocol . [ 87 ] The Nazis also used asphyxiating gas in the catacombs of Odessa in November 1941, following their capture of the city , and in late May 1942 during the Battle of the Kerch Peninsula in eastern Crimea . [ 87 ] Victor Israelyan, a Soviet ambassador, reported that the latter incident was perpetrated by the Wehrmacht's Chemical Forces and organized by a special detail of SS troops with the help of a field engineer battalion. Chemical Forces General Ochsner reported to German command in June 1942 that a chemical unit had taken part in the battle. [ 88 ] After the battle in mid-May 1942, roughly 3,000 Red Army soldiers and Soviet civilians not evacuated by sea were besieged in a series of caves and tunnels in the nearby Adzhimushkay quarry . After holding out for approximately three months, "poison gas was released into the tunnels, killing all but a few score of the Soviet defenders." [ 89 ] Thousands of those killed around Adzhimushkay were documented to have been killed by asphyxiation from gas. [ 88 ]
In February 1943, German troops stationed in Kuban received a telegram: "Russians might have to be cleared out of the mountain range with gas." [ 90 ] The troops also received two wagons of toxin antidotes. [ 90 ]
The Western Allies did not use chemical weapons during the Second World War. The British planned to use mustard gas and phosgene to help repel a German invasion in 1940–1941, [ 91 ] [ 92 ] and had there been an invasion may have also deployed it against German cities. [ 93 ] General Alan Brooke , Commander-in-Chief, Home Forces , in command of British anti-invasion preparations of the Second World War said that he " ...had every intention of using sprayed mustard gas on the beaches " in an annotation in his diary. [ 94 ] The British manufactured mustard, chlorine , lewisite , phosgene and Paris Green and stored them at airfields and depots for use on the beaches. [ 93 ]
The mustard gas stockpile was enlarged in 1942–1943 for possible use by RAF Bomber Command against German cities, and in 1944 for possible retaliatory use if German forces used chemical weapons against the D-Day landings . [ 91 ]
Winston Churchill , the British Prime Minister , issued a memorandum advocating a chemical strike on German cities using poison gas and possibly anthrax . Although the idea was rejected, it has provoked debate. [ 95 ] In July 1944, fearing that rocket attacks on London would get even worse, and saying he would only use chemical weapons if it were "life or death for us" or would "shorten the war by a year", [ 96 ] Churchill wrote a secret memorandum asking his military chiefs to "think very seriously over this question of using poison gas." He stated "it is absurd to consider morality on this topic when everybody used it in the last war without a word of complaint..."
The Joint Planning Staff, however, advised against the use of gas because it would inevitably provoke Germany to retaliate with gas. They argued that this would be to the Allies' disadvantage in France both for military reasons and because it might "seriously impair our relations with the civilian population when it became generally known that chemical warfare was first employed by us." [ 97 ]
In 1945, the U.S. Army 's Chemical Warfare Service standardized improved chemical warfare rockets intended for the new M9 and M9A1 " Bazooka " launchers, adopting the M26 Gas Rocket, a cyanogen chloride (CK)-filled warhead for the 2.36-in rocket launcher. [ 98 ] CK, a deadly blood agent, was capable of penetrating the protective filter barriers in some gas masks, [ 99 ] and was seen as an effective agent against Japanese forces (particularly those hiding in caves or bunkers), whose gas masks lacked the impregnants that would provide protection against the chemical reaction of CK. [ 98 ] [ 100 ] [ 101 ] While stockpiled in US inventory, the CK rocket was never deployed or issued to combat personnel. [ 98 ]
On the night of December 2, 1943, German Ju 88 bombers attacked the port of Bari in Southern Italy, sinking several American ships—among them the SS John Harvey , which was carrying mustard gas intended for use in retaliation by the Allies if German forces initiated gas warfare. The presence of the gas was highly classified, and authorities ashore had no knowledge of it, which increased the number of fatalities since physicians, who had no idea that they were dealing with the effects of mustard gas, prescribed treatment improper for those suffering from exposure and immersion.
The whole affair was kept secret at the time and for many years after the war. According to the U.S. military account, "Sixty-nine deaths were attributed in whole or in part to the mustard gas, most of them American merchant seamen" [ 102 ] out of 628 mustard gas military casualties. [ 103 ]
The large number of civilian casualties among the Italian population was not recorded. Part of the confusion and controversy derives from the fact that the German attack was highly destructive and lethal in itself, also apart from the accidental additional effects of the gas (the attack was nicknamed "The Little Pearl Harbor"), and attribution of the causes of death between the gas and other causes is far from easy. [ 104 ] [ 105 ]
Rick Atkinson , in his book The Day of Battle, describes the intelligence that prompted Allied leaders to deploy mustard gas to Italy. This included Italian intelligence that Adolf Hitler had threatened to use gas against Italy if the state changed sides, and prisoner of war interrogations suggesting that preparations were being made to use a "new, egregiously potent gas" if the war turned decisively against Germany. Atkinson concludes, "No commander in 1943 could be cavalier about a manifest threat by Germany to use gas."
After World War II , the Allies recovered German artillery shells containing the three German nerve agents of the day (tabun, sarin, and soman), prompting further research into nerve agents by all of the former Allies.
Although the threat of global thermonuclear war was foremost in the minds of most during the Cold War , both the Soviet and Western governments put enormous resources into developing chemical and biological weapons .
In the late 1940s and early 1950s, British postwar chemical weapons research was based at the Porton Down facility. Research was aimed at providing Britain with the means to arm itself with a modern nerve-agent-based capability and to develop specific means of defense against these agents.
Ranajit Ghosh, a chemist at the Plant Protection Laboratories of Imperial Chemical Industries was investigating a class of organophosphate compounds (organophosphate esters of substituted aminoethanethiols), [ 106 ] for use as a pesticide . In 1954, ICI put one of them on the market under the trade name Amiton . It was subsequently withdrawn, as it was too toxic for safe use.
The toxicity did not go unnoticed, and samples of it were sent to the research facility at Porton Down for evaluation. After the evaluation was complete, several members of this class of compounds were developed into a new group of much more lethal nerve agents, the V agents. The best-known of these is probably VX , assigned the UK Rainbow Code Purple Possum , with the Russian V-Agent coming a close second (Amiton is largely forgotten as VG). [ 107 ]
On the defensive side, there were years of difficult work to develop the means of prophylaxis, therapy, rapid detection and identification, decontamination and more effective protection of the body against nerve agents, capable of exerting effects through the skin, the eyes and respiratory tract.
Tests were carried out on servicemen to determine the effects of nerve agents on human subjects, with one recorded death due to a nerve gas experiment. There have been persistent allegations of unethical human experimentation at Porton Down, such as those relating to the death of Leading Aircraftman Ronald Maddison , aged 20, in 1953. Maddison was taking part in sarin nerve agent toxicity tests. Sarin was dripped onto his arm and he died shortly afterwards. [ 108 ]
In the 1950s, the Chemical Defence Experimental Establishment became involved with the development of CS , a riot control agent, and took an increasing role in trauma and wound ballistics work. Both these facets of Porton Down's work had become more important because of the situation in Northern Ireland. [ 109 ]
In the early 1950s, nerve agents such as sarin were produced— about 20 tons were made from 1954 until 1956. CDE Nancekuke was an important factory for stockpiling chemical weapons. Small amounts of VX were produced there, mainly for laboratory test purposes, but also to validate plant designs and optimise chemical processes for potential mass production. However, full-scale mass production of VX agent never took place, with the 1956 decision to end the UK's offensive chemical weapons programme. [ 110 ] In the late 1950s, the chemical weapons production plant at Nancekuke was mothballed, but was maintained through the 1960s and 1970s in a state whereby production of chemical weapons could easily re-commence if required. [ 110 ]
In 1952, the U.S. Army patented a process for the "Preparation of Toxic Ricin ", publishing a method of producing this powerful toxin . In 1958 the British government traded their VX technology with the United States in exchange for information on thermonuclear weapons [ citation needed ] . By 1961 the U.S. was producing large amounts of VX and performing its own nerve agent research. This research produced at least three more agents; the four agents ( VE , VG , VM , VX ) are collectively known as the "V-Series" class of nerve agents.
Between 1951 and 1969, Dugway Proving Ground was the site of testing for various chemical and biological agents, including an open-air aerodynamic dissemination test in 1968 that accidentally killed, on neighboring farms, approximately 6,400 sheep by an unspecified nerve agent . [ 111 ]
From 1962 to 1973, the Department of Defense planned 134 tests under Project 112 , a chemical and biological weapons "vulnerability-testing program." In 2002, the Pentagon admitted for the first time that some of tests used real chemical and biological weapons, not just harmless simulants. [ 112 ]
Specifically under Project SHAD , 37 secret tests were conducted in California, Alaska, Florida, Hawaii, Maryland, and Utah. Land tests in Alaska and Hawaii used artillery shells filled with sarin and VX , while Navy trials off the coasts of Florida, California and Hawaii tested the ability of ships and crew to perform under biological and chemical warfare, without the crew's knowledge. The code name for the sea tests was Project Shipboard Hazard and Defense—"SHAD" for short. [ 112 ]
In October 2002, the Senate Armed Forces Subcommittee on Personnel held hearings as the controversial news broke that chemical agents had been tested on thousands of American military personnel. The hearings were chaired by Senator Max Cleland , former VA administrator and Vietnam War veteran.
In December 2001, the United States Department of Health and Human Services , Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), and National Personal Protective Technology Laboratory (NPPTL), along with the U.S. Army Research, Development and Engineering Command (RDECOM), Edgewood Chemical and Biological Center (ECBC), and the U.S. Department of Commerce National Institute of Standards and Technology (NIST) published the first of six technical performance standards and test procedures designed to evaluate and certify respirators intended for use by civilian emergency responders to a chemical, biological, radiological, or nuclear weapon release, detonation, or terrorism incident.
To date NIOSH/NPPTL has published six new respirator performance standards based on a tiered approach that relies on traditional industrial respirator certification policy, next-generation emergency response respirator performance requirements, and special live chemical warfare agent testing requirements of the classes of respirators identified to offer respiratory protection against chemical, biological, radiological, and nuclear (CBRN) agent inhalation hazards. These CBRN respirators are commonly known as open-circuit self-contained breathing apparatus (CBRN SCBA), air-purifying respirator (CBRN APR), air-purifying escape respirator (CBRN APER), self-contained escape respirator (CBRN SCER) and loose- or tight-fitting powered air-purifying respirators (CBRN PAPR).
Due to the secrecy of the Soviet Union's government, very little information was available about the direction and progress of the Soviet chemical weapons until relatively recently. After the fall of the Soviet Union , Russian chemist Vil Mirzayanov published articles revealing illegal chemical weapons experimentation in Russia.
In 1993, Mirzayanov was imprisoned and fired from his job at the State Research Institute of Organic Chemistry and Technology, where he had worked for 26 years. In March 1994, after a major campaign by U.S. scientists on his behalf, Mirzayanov was released. [ 113 ]
Among the information related by Vil Mirzayanov was the direction of Soviet research into the development of even more toxic nerve agents, which saw most of its success during the mid-1980s. Several highly toxic agents were developed during this period; the only unclassified information regarding these agents is that they are known in the open literature only as " Foliant " agents (named after the program under which they were developed) and by various code designations, such as A-230 and A-232. [ 114 ]
According to Mirzayanov, the Soviets also developed weapons that were safer to handle, leading to the development of binary weapons , in which precursors for the nerve agents are mixed in a munition to produce the agent just prior to its use. Because the precursors are generally significantly less hazardous than the agents themselves, this technique makes handling and transporting the munitions a great deal simpler.
Additionally, precursors to the agents are usually much easier to stabilize than the agents themselves, so this technique also made it possible to increase the shelf life of the agents a great deal. During the 1980s and 1990s, binary versions of several Soviet agents were developed and designated " Novichok " agents (after the Russian word for "newcomer"). [ 115 ] Together with Lev Fedorov, he told the secret Novichok story exposed in the newspaper The Moscow News . [ 116 ]
The first attack of the North Yemen Civil War took place on June 8, 1963, against Kawma, a village of about 100 inhabitants in northern Yemen, killing about seven people and damaging the eyes and lungs of 25 others. This incident is considered to have been experimental, and the bombs were described as "home-made, amateurish and relatively ineffective". The Egyptian authorities suggested that the reported incidents were probably caused by napalm , not gas.
There were no reports of gas during 1964, and only a few were reported in 1965. The reports grew more frequent in late 1966. On December 11, 1966, fifteen gas bombs killed two people and injured thirty-five. On January 5, 1967, the biggest gas attack came against the village of Kitaf, causing 270 casualties, including 140 fatalities. The target may have been Prince Hassan bin Yahya, who had installed his headquarters nearby. The Egyptian government denied using poison gas, and alleged that Britain and the US were using the reports as psychological warfare against Egypt. On February 12, 1967, it said it would welcome a UN investigation. On March 1, U Thant , the then Secretary-General of the United Nations , said he was "powerless" to deal with the matter.
On May 10, 1967, the twin villages of Gahar and Gadafa in Wadi Hirran, where Prince Mohamed bin Mohsin was in command, were gas bombed, killing at least seventy-five. The Red Cross was alerted and on June 2, 1967, it issued a statement in Geneva expressing concern. The Institute of Forensic Medicine at the University of Berne made a statement, based on a Red Cross report, that the gas was likely to have been halogenous derivatives—phosgene, mustard gas, lewisite, chloride or cyanogen bromide.
Evidence points to a top-secret Rhodesian program in the 1970s to use organophosphate pesticides and heavy metal rodenticides to contaminate clothing as well as food and beverages. The contaminated items were covertly introduced into insurgent supply chains. Hundreds of insurgent deaths were reported, although the actual death toll likely rose over 1,000. [ 117 ]
During the Cuban intervention in Angola , United Nations toxicologists certified that residue from both VX and sarin nerve agents had been discovered in plants, water, and soil where Cuban units were conducting operations against National Union for the Total Independence of Angola (UNITA) insurgents. [ 118 ] In 1985, UNITA made the first of several claims that their forces were the target of chemical weapons, specifically organophosphates . The following year guerrillas reported being bombarded with an unidentified greenish-yellow agent on three separate occasions. Depending on the length and intensity of exposure, victims suffered blindness or death. The toxin was also observed to have killed plant life. [ 119 ] Shortly afterwards, UNITA also sighted strikes carried out with a brown agent which it claimed resembled mustard gas . [ 120 ] As early as 1984 a research team dispatched by the University of Ghent had examined patients in UNITA field hospitals showing signs of exposure to nerve agents, although it found no evidence of mustard gas. [ 121 ]
The UN first accused Cuba of deploying chemical weapons against Angolan civilians and partisans in 1988. [ 118 ] Wouter Basson later disclosed that South African military intelligence had long verified the use of unidentified chemical weapons on Angolan soil; this was to provide the impetus for their own biological warfare programme, Project Coast . [ 118 ] During the Battle of Cuito Cuanavale , South African troops then fighting in Angola were issued with gas masks and ordered to rehearse chemical weapons drills. Although the status of its own chemical weapons program remained uncertain, South Africa also deceptively bombarded Cuban and Angolan units with colored smoke in an attempt to induce hysteria or mass panic. [ 120 ] According to Defence Minister Magnus Malan , this would force the Cubans to share the inconvenience of having to take preventative measures such as donning NBC suits , which would cut combat effectiveness in half. The tactic was effective: beginning in early 1988 Cuban units posted to Angola were issued with full protective gear in anticipation of a South African chemical strike. [ 120 ]
On October 29, 1988, personnel attached to Angola's 59 Brigade, accompanied by six Soviet military advisors, reported being struck with chemical weapons on the banks of the Mianei River. [ 122 ] The attack occurred shortly after one in the afternoon. Four Angolan soldiers lost consciousness while the others complained of violent headaches and nausea. That November the Angolan representative to the UN accused South Africa of employing poison gas near Cuito Cuanavale for the first time. [ 122 ]
Technically, the reported employment of tear gas by Argentine forces during the 1982 invasion of the Falkland Islands constitutes chemical warfare. [ 123 ] However, the tear gas grenades were employed as nonlethal weapons to avoid British casualties. The barrack buildings the weapons were used on proved to be deserted in any case. The British claim that more lethal, but legally justifiable as they are not considered chemical weapons under the Chemical Weapons Convention , white phosphorus grenades were used. [ 124 ]
There were reports of chemical weapons being used by Soviet forces during the Soviet–Afghan War , sometimes against civilians. [ 125 ] [ 126 ]
There is some evidence suggesting that Vietnamese troops used phosgene gas against Cambodian resistance forces in Thailand during the 1984–1985 dry-season offensive on the Thai-Cambodian border. [ 127 ] [ 128 ] [ 129 ]
Chemical weapons employed by Saddam Hussein killed and injured numerous Iranians and Iraqi Kurds . According to Iraqi documents, assistance in developing chemical weapons was obtained from firms in many countries, including the United States, West Germany , the Netherlands , the United Kingdom, and France . [ 130 ]
About 100,000 Iranian soldiers were victims of Iraq's chemical attacks. Many were hit by mustard gas. The official estimate does not include the civilian population contaminated in bordering towns or the children and relatives of veterans, many of whom have developed blood, lung and skin complications, according to the Organization for Veterans. Nerve gas agents killed about 20,000 Iranian soldiers immediately, according to official reports. Of the 80,000 survivors, some 5,000 seek medical treatment regularly and about 1,000 are still hospitalized with severe, chronic conditions. [ 131 ] [ 132 ] [ 133 ]
According to the Foreign Policy , the "Iraqis used mustard gas and sarin prior to four major offensives in early 1988 that relied on U.S. satellite imagery, maps, and other intelligence. ... According to recently declassified CIA documents and interviews with former intelligence officials like Francona, the U.S. had firm evidence of Iraqi chemical attacks beginning in 1983." [ 134 ] [ 135 ]
In March 1988, the Iraqi Kurdish town of Halabja was exposed to multiple chemical agents dropped from warplanes; these "may have included mustard gas , the nerve agents sarin, tabun and VX and possibly cyanide." [ 136 ] Between 3,200 and 5,000 people were killed, and between 7,000 and 10,000 were injured. [ 136 ] Some reports indicated that three-quarters of them were women and children. [ 136 ] The preponderance of the evidence indicates that Iraq was responsible for the attack. [ 136 ]
The U.S. Department of Defense and Central Intelligence Agency 's longstanding official position is that Iraqi forces under Saddam Hussein did not use chemical weapons during the Persian Gulf War in 1991. In a memorandum in 1994 to veterans of the war, Defense Secretary William J. Perry and General John M. Shalikashvili , the chairman of the Joint Chiefs of Staff , wrote that "There is no evidence, classified or unclassified, that indicates that chemical or biological weapons were used in the Persian Gulf." [ 137 ]
However, chemical weapons expert Jonathan B. Tucker , writing in the Nonproliferation Review in 1997, determined that although "[t]he absence of severe chemical injuries or fatalities among Coalition forces makes it clear that no large-scale Iraqi employment of chemical weapons occurred," an array of "circumstantial evidence from a variety of sources suggests that Iraq deployed chemical weapons into the Kuwait Theater of Operations (KTO)—the area including Kuwait and Iraq south of the 31st Parallel , where the ground war was fought—and engaged in sporadic chemical warfare against Coalition forces." [ 137 ] In addition to intercepts of Iraqi military communications and publicly available reporting:
Other sources of evidence for sporadic Iraqi chemical warfare include U.S. intelligence reports on the presence of Iraqi chemical weapons in the KTO; military log entries describing the discovery by U.S. units of chemical munitions in Iraqi bunkers during and after the ground war; incidents in which troops reported acute symptoms of toxic chemical exposure; and credible detections of chemical-warfare agents by Czech, French, and American forces. [ 137 ]
Nerve agents (specifically, tabun, sarin, and cyclosarin) and blister agents (specifically, sulfur-mustard and lewisite) were detected at Iraqi sites. [ 137 ]
The threat itself of gas warfare had a major effect on Israel , which was not part of the coalition forces led by the US. Israel was attacked with 39 scud missiles, most of which were knocked down in the air above their targets by Patriot missiles developed by Raytheon together with Israel, and supplied by the US. Sirens warned of the attacks approximately 10 minutes before their expected arrival, and Israelis donned gas masks and entered sealed "safe" rooms, over a period 5 weeks. Babies were issued special gas-safe cribs, and religious men were issued gas masks that allowed them to preserve their beards. [ 138 ] [ 139 ] [ 140 ]
In 2014, tapes from Saddam Hussain's archives revealed that Saddam had given orders to use gas against Israel as a last resort if his military communications with the army were cut off. [ 141 ]
In 2015, The New York Times published an article about the declassified report of operation Avarice in 2005 in which over 400 chemical weapons including many rockets and missiles from the Iran-Iraq war period were recovered and subsequently destroyed by the CIA. [ 142 ] Many other stockpiles, estimated by UNSCOM up to 600 metric tons of chemical weapons, were known to have existed and even admitted by Saddam's regime, but claimed by them to have been destroyed. These have never been found but are believed to still exist. [ 143 ] [ 144 ]
During Operation Iraqi Freedom , American service members who demolished or handled older explosive ordnance may have been exposed to blister agents (mustard agent) or nerve agents (sarin). [ 145 ] According to The New York Times , "In all, American troops secretly reported finding roughly 5,000 chemical warheads, shells or aviation bombs, according to interviews with dozens of participants, Iraqi and American officials, and heavily redacted intelligence documents obtained under the Freedom of Information Act." [ 146 ] Among these, over 2,400 nerve-agent rockets were found in summer 2006 at Camp Taji , a former Iraqi Republican Guard compound. "These weapons were not part of an active arsenal"; "they were remnants from an Iraqi program in the 1980s during the Iran-Iraq war". [ 146 ]
Sarin, mustard gas, and chlorine have been used during the conflict. Numerous casualties led to an international reaction, especially the 2013 Ghouta attacks . A UN fact-finding mission was requested to investigate alleged chemical weapons attacks. In four cases the UN inspectors confirmed use of sarin gas. [ 147 ] In August 2016, a confidential report by the United Nations and the OPCW explicitly blamed the Syrian military of Bashar al-Assad for dropping chemical weapons (chlorine bombs) on the towns of Talmenes in April 2014 and Sarmin in March 2015 and ISIS for using sulfur mustard on the town of Marea in August 2015. [ 148 ] In 2016, Jaysh al-Islam rebel group had used chlorine gas or other agents against Kurdish militia and civilians in the Sheikh Maqsood neighborhood of Aleppo. [ 149 ]
Many countries, including the United States and the European Union have accused the Syrian government of conducting several chemical attacks. Following the 2013 Ghouta attacks and international pressure, Syria acceded to the Chemical Weapons Convention and the destruction of Syria's chemical weapons began. In 2015 the UN mission disclosed previously undeclared traces of sarin compounds [ disputed – discuss ] in a "military research site". [ 150 ] After the April 2017 Khan Shaykhun chemical attack , the United States launched its first attack against Syrian government forces. On 14 April 2018, the United States, France and the United Kingdom carried out a series of joint military strikes against multiple government sites in Syria, including the Barzah scientific research centre , after a chemical attack in Douma .
Russians have used tear gas against Ukrainian forces. [ 151 ] It has been done by having a drone drop a grenade with K-51 aerosol CS gas in it. [ 152 ] As of March 2024, Ukrainian forces reported an increase of Russian drones dropping “grenades with suffocating and tear gas”. 371 Cases of gas usage was reported over the past month, an increase of 90 incidents was recorded compared to February. Compared to Ukrainian soldiers are receiving training to deal with such attacks but lack modern gas masks. Old Soviet issued masks are “ineffective” and soldiers are having to crowd fund newer masks. Tear Gas or Captir Spray is banned under the Chemical Weapons Convention [ 153 ] [ 154 ]
For many terrorist organizations, chemical weapons might be considered an ideal choice for a mode of attack, if they are available: they are cheap, relatively accessible, and easy to transport. A skilled chemist can readily synthesize most chemical agents if the precursors are available.
In July 1974, a group calling themselves the Aliens of America successfully firebombed the houses of a judge, two police commissioners, and one of the commissioner's cars, burned down two apartment buildings, and bombed the Pan Am Terminal at Los Angeles International Airport , killing three people and injuring eight. The organization, which turned out to be a single resident alien named Muharem Kurbegovic , claimed to have developed and possessed a supply of sarin, as well as four unique nerve agents named AA1, AA2, AA3, and AA4S. Although no agents were found at the time Kurbegovic was arrested in August 1974, he had reportedly acquired "all but one" of the ingredients required to produce a nerve agent. A search of his apartment turned up a variety of materials, including precursors for phosgene and a drum containing 25 pounds of sodium cyanide . [ 155 ]
The first successful use of chemical agents by terrorists against a general civilian population was on June 27, 1994, when Aum Shinrikyo , an apocalyptic group based in Japan that believed it necessary to destroy the planet, released sarin gas in Matsumoto, Japan , killing eight and harming 200. The following year, Aum Shinrikyo released sarin into the Tokyo subway system killing 12 and injuring over 5,000.
On December 29, 1999, four days after Russian forces began an assault of Grozny, Chechen terrorists exploded two chlorine tanks in the town. Because of the wind conditions, no Russian soldiers were injured. [ 156 ]
Following the September 11 attacks on the U.S. cities of New York City and Washington, D.C. , the organization Al-Qaeda responsible for the attacks announced that they were attempting to acquire radiological, biological, and chemical weapons. This threat was lent a great deal of credibility when a large archive of videotapes was obtained by the cable television network CNN in August 2002 showing, among other things, the killing of three dogs by an apparent nerve agent. [ 157 ]
In an anti-terrorist attack on October 26, 2002, Russian special forces used a chemical agent (presumably KOLOKOL-1 , an aerosolized fentanyl derivative), as a precursor to an assault on Chechen terrorists, which ended the Moscow theater hostage crisis . All 42 of the terrorists and 120 out of 850 hostages were killed during the raid. Although the use of the chemical agent was justified as a means of selectively targeting terrorists, it killed over 100 hostages.
In early 2007, multiple terrorist bombings had been reported in Iraq using chlorine gas. These attacks wounded or sickened more than 350 people. Reportedly the bombers were affiliated with Al-Qaeda in Iraq, [ 158 ] and they have used bombs of various sizes up to chlorine tanker trucks. [ 159 ] United Nations Secretary-General Ban Ki-moon condemned the attacks as "clearly intended to cause panic and instability in the country." [ 160 ]
The Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or other Gases, and the Bacteriological Methods of Warfare , or the Geneva Protocol, is an international treaty which prohibits the use of chemical and biological weapons between signatory nations in international armed conflicts. Signed into international law at Geneva on June 17, 1925, and entered into force on February 8, 1928, this treaty states that chemical and biological weapons are "justly condemned by the general opinion of the civilised world." [ 161 ]
The most recent arms control agreement in international law , the Convention of the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction , or the Chemical Weapons Convention, outlaws the production, stockpiling, and use of chemical weapons. It is administered by the Organisation for the Prohibition of Chemical Weapons (OPCW), an intergovernmental organisation based in The Hague . [ 162 ] | https://en.wikipedia.org/wiki/History_of_chemical_warfare |
The history of chromatography spans from the mid-19th century to the 21st. Chromatography , literally "color writing", [ 1 ] was used—and named— in the first decade of the 20th century, primarily for the separation of plant pigments such as chlorophyll (which is green) and carotenoids (which are orange and yellow). New forms of chromatography developed in the 1930s and 1940s made the technique useful for a wide range of separation processes and chemical analysis tasks, especially in biochemistry .
The earliest use of chromatography—passing a mixture through an inert material to create separation of the solution components based on differential adsorption —is sometimes attributed to German chemist Friedlieb Ferdinand Runge , who in 1855 described the use of paper to analyze dyes . Runge dropped spots of different inorganic chemicals onto circles of filter paper already impregnated with another chemical, and reactions between the different chemicals created unique color patterns. [ 2 ] According to historical analysis of L. S. Ettre , however, Runge's work had "nothing to do with chromatography" (and instead should be considered a precursor of chemical spot tests such as the Schiff test ). [ 3 ]
In the 1860s, Christian Friedrich Schönbein and his student Friedrich Goppelsroeder published the first attempts to study the different rates at which different substances move through filter paper. [ 4 ] [ 5 ] [ 6 ] Schönbein, who thought capillary action (rather than adsorption) was responsible for the movement, called the technique capillary analysis , and Goppelsroeder spent much of his career using capillary analysis to test the movement rates of a wide variety of substances. Unlike modern paper chromatography, capillary analysis used reservoirs of the substance being analyzed, creating overlapping zones of the solution components rather than separate points or bands. [ 7 ] [ 8 ]
Work on capillary analysis continued, but without much technical development, well into the 20th century. The first significant advances over Goppelsroeder's methods came with the work of Raphael E. Liesegang : in 1927, he placed filter strips in closed containers with atmospheres saturated by solvents, and in 1943 he began using discrete spots of sample adsorbed to filter paper, dipped in pure solvent to achieve separation. [ 9 ] [ 10 ] [ 11 ] This method, essentially identical to modern paper chromatography, was published just before the independent—and far more influential—work of Archer Martin and his collaborators that inaugurated the widespread use of paper chromatography. [ 12 ]
In 1897, the American chemist David Talbot Day (1859–1915), then serving with the U.S. Geological Survey, observed that crude petroleum generated bands of color as it seeped upwards through finely divided clay or limestone. [ 13 ] In 1900, he reported his findings at the First International Petroleum Congress in Paris, where they created a sensation. [ 14 ] [ 15 ]
The first true chromatography is usually attributed to the Russian-Italian botanist Mikhail Tsvet . Tsvet applied his observations with filter paper extraction to the new methods of column fractionation that had been developed in the 1890s for separating the components of petroleum . He used a liquid-adsorption column containing calcium carbonate to separate yellow, orange, and green plant pigments (what are known today as xanthophylls , carotenes , and chlorophylls , respectively). The method was described on December 30, 1901, at the 11th Congress of Naturalists and Doctors (XI съезд естествоиспытателей и врачей) in Saint Petersburg . The first printed description was in 1903, in the Proceedings of the Warsaw Society of Naturalists, section of biology. He first used the term chromatography in print in 1906 in his two papers about chlorophyll in the German botanical journal, Berichte der Deutschen Botanischen Gesellschaft . In 1907 he demonstrated his chromatograph for the German Botanical Society. Mikhail's surname "Цвет" means "color" in Russian, so there is the possibility that his naming the procedure chromatography (literally "color writing") was a way that he could make sure that he, a commoner in Tsarist Russia, could be immortalized. [ citation needed ]
In a 1903 lecture (published in 1905), Tsvet also described using filter paper to approximate the properties of living plant fibers in his experiments on plant pigments—a precursor to paper chromatography . He found that he could extract some pigments (such as orange carotenes and yellow xanthophylls ) from leaves with non-polar solvents , but others (such as chlorophyll ) required polar solvents . He reasoned that chlorophyll was held to the plant tissue by adsorption , and that stronger solvents were necessary to overcome the adsorption. To test this, he applied dissolved pigments to filter paper, allowed the solvent to evaporate, then applied different solvents to see which could extract the pigments from the filter paper. He found the same pattern as from leaf extractions: carotene could be extracted from filter paper using non-polar solvents, but chlorophyll required polar solvents. [ 16 ]
Tsvet's work saw little use until the 1930s. [ 17 ]
Chromatography methods changed little after Tsvet's work until the explosion of mid-20th century research in new techniques, particularly thanks to the work of Archer John Porter Martin and Richard Laurence Millington Synge . By "the marrying of two techniques, that of chromatography and that of countercurrent solvent extraction", [ 18 ] Martin and Synge developed partition chromatography to separate chemicals with only slight differences in partition coefficients between two liquid solvents. [ 19 ] Martin, who had previously been working in vitamin chemistry (including attempts to purify vitamin E ), began collaborating with Synge in 1938, brought his experience with equipment design to Synge's project of separating amino acids . After unsuccessful experiments with complex countercurrent extraction machines and liquid-liquid chromatography methods where the liquids move in opposite directions, [ 20 ] Martin hit on the idea of using silica gel in columns to hold water stationary while an organic solvent flows through the column. Martin and Synge demonstrated the potential of the methods by separating amino acids marked in the column by the addition of methyl red . [ 21 ] In a series of publications beginning in 1941, they described increasingly powerful methods of separating amino acids and other organic chemicals. [ 22 ]
In pursuit of better and easier methods of identifying the amino acid constituents of peptides, Martin and Synge turned to other chromatography media as well. A short abstract in 1943 followed by a detailed article in 1944 described the use of filter paper as the stationary phase for performing chromatography on amino acids: paper chromatography . [ 23 ] By 1947, Martin, Synge and their collaborators had applied this method (along with Fred Sanger's reagent for identifying N-terminal residues) to determine the pentapeptide sequence of Gramicidin S . These and related paper chromatography methods were also foundational to Fred Sanger 's effort to determine the amino acid sequence of insulin . [ 24 ]
Martin, in collaboration with Anthony T. James , went on to develop gas chromatography [ 25 ] (GC; the principles of which Martin and Synge had predicted in their landmark 1941 paper) beginning in 1949. In 1952, during his lecture for the Nobel Prize in Chemistry (shared with Synge, for their earlier chromatography work), Martin announced the successful separation of a wide variety of natural compounds by gas chromatography. Previously, Erika Cremer had laid the theoretical basis of GC in 1944 and Austrian chemist Fritz Prior, under the direction of Erika Cremer, constructed in 1947 the first prototype of a gas chromatograph [ 26 ] and achieved separating oxygen and carbon dioxide , in 1947 during his Ph.D. research. [ 27 ]
The ease and efficiency of gas chromatography for separating organic chemicals spurred the rapid adoption of the method, as well as the rapid development of new detection methods for analyzing the output. The thermal conductivity detector , described in 1954 by N. H. Ray, was the foundation for several other methods: the flame ionization detector was described by J. Harley, W. Nel, and V. Pretorius in 1958, [ 28 ] and James Lovelock introduced the electron capture detector that year as well. Others introduced mass spectrometers to gas chromatography in the late 1950s. [ 29 ]
The work of Martin and Synge also set the stage for high performance liquid chromatography , suggesting that small sorbent particles and pressure could produce fast liquid chromatography techniques. This became widely practical by the late 1960s (and the method was used to separate amino acids as early as 1960). [ 30 ]
The first developments in thin layer chromatography occurred in the 1940s, and techniques advanced rapidly in the 1950s after the introduction of relatively large plates and relatively stable materials for sorbent layers. [ 31 ]
In 1987 Pedro Cuatrecasas and Meir Wilchek were awarded the Wolf Prize in Medicine for the invention and development of affinity chromatography and its applications to biomedical sciences. [ citation needed ] | https://en.wikipedia.org/wiki/History_of_chromatography |
In physics, mechanics is the study of objects, their interaction, and motion; classical mechanics is mechanics limited to non-relativistic and non-quantum approximations. Most of the techniques of classical mechanics were developed before 1900 so the term classical mechanics refers to that historical era as well as the approximations. Other fields of physics that were developed in the same era, that use the same approximations, and are also considered "classical" include thermodynamics (see history of thermodynamics ) and electromagnetism (see history of electromagnetism ).
The critical historical event in classical mechanics was the publication by Isaac Newton of his laws of motion and his associated development of the mathematical techniques of calculus in 1678. Analytic tools of mechanics grew through the next two centuries, including the development of Hamiltonian mechanics and the action principles , concepts critical to the development of quantum mechanics and of relativity .
Chaos theory is a subfield of classical mechanics that was developed in its modern form in the 20th century.
The ancient Greek philosophers , Aristotle in particular, were among the first to propose that abstract principles govern nature. Aristotle argued, in On the Heavens , that terrestrial bodies rise or fall to their "natural place" and stated as a law the correct approximation that an object's speed of fall is proportional to its weight and inversely proportional to the density of the fluid it is falling through. [ 1 ] Aristotle believed in logic and observation but it would be more than eighteen hundred years before Francis Bacon would first develop the scientific method of experimentation, which he called a vexation of nature . [ 2 ]
Aristotle saw a distinction between "natural motion" and "forced motion", and he believed that 'in a void' i.e. vacuum , a body at rest will remain at rest [ 3 ] and a body in motion will continue to have the same motion. [ 4 ] In this way, Aristotle was the first to approach something similar to the law of inertia. However, he believed a vacuum would be impossible because the surrounding air would rush in to fill it immediately. He also believed that an object would stop moving in an unnatural direction once the applied forces were removed. Later Aristotelians developed an elaborate explanation for why an arrow continues to fly through the air after it has left the bow, proposing that an arrow creates a vacuum in its wake, into which air rushes, pushing it from behind. Aristotle's beliefs were influenced by Plato's teachings on the perfection of the circular uniform motions of the heavens. As a result, he conceived of a natural order in which the motions of the heavens were necessarily perfect, in contrast to the terrestrial world of changing elements, where individuals come to be and pass away.
There is another tradition that goes back to the ancient Greeks where mathematics is used to analyze bodies at rest or in motion, which may found as early as the work of some Pythagoreans . Other examples of this tradition include Euclid ( On the Balance ), Archimedes ( On the Equilibrium of Planes , On Floating Bodies ), and Hero ( Mechanica ). Later, Islamic and Byzantine scholars built on these works, and these ultimately were reintroduced or became available to the West in the 12th century and again during the Renaissance .
Persian Islamic polymath Ibn Sīnā published his theory of motion in The Book of Healing (1020). He said that an impetus is imparted to a projectile by the thrower, and viewed it as persistent, requiring external forces such as air resistance to dissipate it. [ 5 ] [ 6 ] [ 7 ] Ibn Sina made distinction between 'force' and 'inclination' (called "mayl"), and argued that an object gained mayl when the object is in opposition to its natural motion. So he concluded that continuation of motion is attributed to the inclination that is transferred to the object, and that object will be in motion until the mayl is spent. He also claimed that projectile in a vacuum would not stop unless it is acted upon. This conception of motion is consistent with Newton's first law of motion, inertia. Which states that an object in motion will stay in motion unless it is acted on by an external force. [ 8 ]
In the 12th century, Hibat Allah Abu'l-Barakat al-Baghdaadi adopted and modified Avicenna's theory on projectile motion . In his Kitab al-Mu'tabar , Abu'l-Barakat stated that the mover imparts a violent inclination ( mayl qasri ) on the moved and that this diminishes as the moving object distances itself from the mover. [ 9 ] According to Shlomo Pines , al-Baghdaadi's theory of motion was "the oldest negation of Aristotle 's fundamental dynamic law [namely, that a constant force produces a uniform motion], [and is thus an] anticipation in a vague fashion of the fundamental law of classical mechanics [namely, that a force applied continuously produces acceleration]." [ 10 ]
In the 14th century, French priest Jean Buridan developed the theory of impetus , with possible influence by Ibn Sina. [ 11 ] Albert , Bishop of Halberstadt , developed the theory further.
Nicole Oresme , one of Oxford Calculators at Merton College, Oxford , provided the mean speed theorem using geometrical arguments. [ 12 ]
Galileo Galilei 's development of the telescope and his observations further challenged the idea that the heavens were made from a perfect, unchanging substance. Adopting Copernicus 's heliocentric hypothesis, Galileo believed the Earth was the same as other planets. Though the reality of the famous Tower of Pisa experiment is disputed, he did carry out quantitative experiments by rolling balls on an inclined plane ; his correct theory of accelerated motion was apparently derived from the results of the experiments. [ 13 ] Galileo also found that a body dropped vertically hits the ground at the same time as a body projected horizontally, so an Earth rotating uniformly will still have objects falling to the ground under gravity. More significantly, it asserted that uniform motion is indistinguishable from rest , and so forms the basis of the theory of relativity. Except with respect to the acceptance of Copernican astronomy, Galileo's direct influence on science in the 17th century outside Italy was probably not very great. Although his influence on educated laymen both in Italy and abroad was considerable, among university professors, except for a few who were his own pupils, it was negligible. [ 14 ] [ 15 ]
Christiaan Huygens was the foremost mathematician and physicist in Western Europe. He formulated the conservation law for elastic collisions, produced the first theorems of centripetal force, and developed the dynamical theory of oscillating systems. He also made improvements to the telescope, discovered Saturn's moon Titan , and invented the pendulum clock. [ 16 ]
Isaac Newton was the first to unify the three laws of motion (the law of inertia, his second law mentioned above, and the law of action and reaction), and to prove that these laws govern both earthly and celestial objects in 1687 in his treatise Philosophiæ Naturalis Principia Mathematica . Newton and most of his contemporaries hoped that classical mechanics would be able to explain all entities, including (in the form of geometric optics) light.
Newton also developed the calculus which is necessary to perform the mathematical calculations involved in classical mechanics. However it was Gottfried Leibniz who, independently of Newton, developed a calculus with the notation of the derivative and integral which are used to this day. Classical mechanics retains Newton's dot notation for time derivatives.
Leonhard Euler extended Newton's laws of motion from particles to rigid bodies with two additional laws . Working with solid materials under forces leads to deformations that can be quantified. The idea was articulated by Euler (1727), and in 1782 Giordano Riccati began to determine elasticity of some materials, followed by Thomas Young . Simeon Poisson expanded study to the third dimension with the Poisson ratio . Gabriel Lamé drew on the study for assuring stability of structures and introduced the Lamé parameters . [ 17 ] These coefficients established linear elasticity theory and started the field of continuum mechanics .
After Newton, re-formulations progressively allowed solutions to a far greater number of problems. The first was constructed in 1788 by Joseph Louis Lagrange , an Italian - French mathematician . In Lagrangian mechanics the solution uses the path of least action and follows the calculus of variations . William Rowan Hamilton re-formulated Lagrangian mechanics in 1833, resulting in Hamiltonian mechanics . In addition to the solutions of important problems in classical physics, these techniques form the basis for quantum mechanics : Lagrangian methods evolved in to the path integral formulation and the Schrödinger equation builds Hamiltonian mechanics.
In the middle of the 19th century, Hamilton could claim classical mechanics as at the center of attention among scholars:
"The theoretical development of the laws of motion of bodies is a problem of such interest and importance that it has engaged the attention of all the eminent mathematicians since the invention of the dynamics as a mathematical science by Galileo, and especially since the wonderful extension which was given to that science by Newton."
In the 1880s, while studying the three-body problem , Henri Poincaré found that there can be orbits that are nonperiodic, and yet not forever increasing nor approaching a fixed point. [ 19 ] [ 20 ] [ 21 ] In 1898, Jacques Hadamard published an influential study of the chaotic motion of a free particle gliding frictionlessly on a surface of constant negative curvature, called Hadamard's billiards . [ 22 ] Hadamard was able to show that all trajectories are unstable, in that all particle trajectories diverge exponentially from one another, with a positive Lyapunov exponent .
These developments led in the 20th century to the development of chaos theory .
Although classical mechanics is largely compatible with other " classical physics " theories such as classical electrodynamics and thermodynamics , some difficulties were discovered in the late 19th century that could only be resolved by modern physics. When combined with classical thermodynamics, classical mechanics leads to the Gibbs paradox in which entropy is not a well-defined quantity. As experiments reached the atomic level, classical mechanics failed to explain, even approximately, such basic things as the energy levels and sizes of atoms. The effort at resolving these problems led to the development of quantum mechanics. Action at a distance was still a problem for electromagnetism and Newton's law of universal gravitation , these were temporary explained using aether theories . Similarly, the different behaviour of classical electromagnetism and classical mechanics under velocity transformations led to the Albert Einstein 's special relativity .
At the beginning of the 20th century quantum mechanics (1900) and relativistic mechanics (1905) were discovered. This development indicated that classical mechanics was just an approximation of these two theories.
The theory of relativity , introduced by Einstein, would later also include general relativity (1915) that would rewrite gravitational interactions in terms of the curvature of spacetime . Relativistic mechanics recovers Newtonian mechanics and Newton's gravitational law when the speeds involved are much smaller than the speed of light and masses involved are smaller than stellar objects.
Quantum mechanics describing atomic and sub-atomic phenomena was also updated in the 1915 to quantum field theory , that would lead to the Standard Model of elementary particles and elementary interactions like electromagnetism, the strong interaction and the weak interaction . Quantum mechanics recovers classical mechanics at the macroscopic scale in the presence of decoherence .
The unification of general relativity and quantum field theory into a quantum gravity theory is still an open problem in physics .
Emmy Noether proved the Noether's theorem in 1918 relating symmetries and conservation laws , it applies to all realms of physics including classical mechanics. [ 23 ]
Following the introduction of general relativity, Élie Cartan in 1923 derived Newtonian gravitation from Einstein field equations . This led to Newton–Cartan theory , where classical gravitation can be treated using a geometric formulation of spacetime. [ 24 ]
In the 1930s, inspired by quantum mechanics, Bernard Koopman and John von Neumann made some links between Hilbert spaces , wavefunctions and classical mechanics. This discovery led to the development of Koopman–von Neumann classical mechanics . [ 25 ]
In 1954, Andrey Kolmogorov revisited the work of Poincaré. He considered the problem of whether or not a small perturbation of a conservative dynamical system resulted in a quasiperiodic orbit in celestial mechanics. The same problem was worked by Jürgen Moser and later by Vladimir Arnold , leading to the Kolmogorov–Arnold–Moser theorem and KAM theory. [ 26 ]
Meteorologist Edward Norton Lorenz is often credited as rediscovering the field of chaos theory. [ 26 ] About 1961, he discovered that his weather calculations were sensitive to the significant figures in the initial conditions. He later developed the theory of Lorenz system . [ 26 ] In 1971, David Ruelle coined the term strange attractor to describe these systems. [ 26 ] The term "chaos theory" was finally coined in 1975 by James A. Yorke . [ 26 ] | https://en.wikipedia.org/wiki/History_of_classical_mechanics |
The mathematical field of combinatorics was studied to varying degrees in numerous ancient societies . Its study in Europe dates to the work of Leonardo Fibonacci in the 13th century AD, which introduced Arabian and Indian ideas to the continent. It has continued to be studied in the modern era .
The earliest recorded use of combinatorial techniques comes from problem 79 of the Rhind papyrus , which dates to the 16th century BC. The problem concerns a certain geometric series , and has similarities to Fibonacci's problem of counting the number of compositions of 1s and 2s that sum to a given total. [ 1 ]
In Greece, Plutarch wrote that Xenocrates of Chalcedon (396–314 BC) discovered the number of different syllables possible in the Greek language . This would have been the first attempt on record to solve a difficult problem in permutations and combinations . [ 2 ] The claim, however, is implausible: this is one of the few mentions of combinatorics in Greece , and the number they found, 1.002 × 10 12 , seems too round to be more than a guess. [ 3 ] [ 4 ]
Later, an argument between Chrysippus (3rd century BC) and Hipparchus (2nd century BC) of a rather delicate enumerative problem, which was later shown to be related to Schröder–Hipparchus numbers , is mentioned. [ 5 ] [ 6 ] There is also evidence that in the Ostomachion , Archimedes (3rd century BC) considered the configurations of a tiling puzzle , [ 7 ] while some combinatorial interests may have been present in lost works of Apollonius . [ 8 ] [ 9 ]
In India , the Bhagavati Sutra had the first mention of a combinatorics problem; the problem asked how many possible combinations of tastes were possible from selecting tastes in ones, twos, threes, etc. from a selection of six different tastes ( sweet , pungent , astringent , sour, salt , and bitter). The Bhagavati is also the first text to mention the choose function . [ 10 ] In the second century BC, Pingala included an enumeration problem in the Chanda Sutra (also Chandahsutra) which asked how many ways a six-syllable meter could be made from short and long notes. [ 11 ] [ 12 ] Pingala found the number of meters that had n {\displaystyle n} long notes and k {\displaystyle k} short notes; this is equivalent to finding the binomial coefficients .
The ideas of the Bhagavati were generalized by the Indian mathematician Mahavira in 850 AD, and Pingala's work on prosody was expanded by Bhāskara II [ 10 ] [ 13 ] and Hemacandra in 1100 AD. Bhaskara was the first known person to find the generalised choice function , although Brahmagupta may have known earlier. [ 1 ] Hemacandra asked how many meters existed of a certain length if a long note was considered to be twice as long as a short note, which is equivalent to finding the Fibonacci numbers . [ 11 ]
The ancient Chinese book of divination I Ching describes a hexagram as a permutation with repetitions of six lines where each line can be one of two states: solid or dashed . In describing hexagrams in this fashion they determine that there are 2 6 = 64 {\displaystyle 2^{6}=64} possible hexagrams. A Chinese monk also may have counted the number of configurations to a game similar to Go around 700 AD. [ 3 ] Although China had relatively few advancements in enumerative combinatorics, around 100 AD they solved the Lo Shu Square which is the combinatorial design problem of the normal magic square of order three. [ 1 ] [ 14 ] Magic squares remained an interest of China, and they began to generalize their original 3 × 3 {\displaystyle 3\times 3} square between 900 and 1300 AD. China corresponded with the Middle East about this problem in the 13th century. [ 1 ] The Middle East also learned about binomial coefficients from Indian work and found the connection to polynomial expansion . [ 15 ] The work of Hindus influenced Arabs as seen in the work of al-Khalil ibn Ahmad who considered the possible arrangements of letters to form syllables . His calculations show an understanding of permutations and combinations . In a passage from the work of Arab mathematician Umar al-Khayyami that dates to around 1100, it is corroborated that the Hindus had knowledge of binomial coefficients, but also that their methods reached the middle east.
Abū Bakr ibn Muḥammad ibn al Ḥusayn Al-Karaji (c. 953–1029) wrote on the binomial theorem and Pascal's triangle . In a now lost work known only from subsequent quotation by al-Samaw'al , Al-Karaji introduced the idea of argument by mathematical induction .
The philosopher and astronomer Rabbi Abraham ibn Ezra (c. 1140) counted the permutations with repetitions in vocalization of Divine Name . [ 16 ] He also established the symmetry of binomial coefficients , while a closed formula was obtained later by the talmudist and mathematician Levi ben Gerson (better known as Gersonides), in 1321. [ 17 ] The arithmetical triangle—a graphical diagram showing relationships among the binomial coefficients — was presented by mathematicians in treatises dating as far back as the 10th century, and would eventually become known as Pascal's triangle . Later, in 17th century England, campanology provided examples of what is now known as Hamiltonian cycles in certain Cayley graphs on permutations . [ 18 ]
Combinatorics came to Europe in the 13th century through mathematicians Leonardo Fibonacci and Jordanus de Nemore . Fibonacci's Liber Abaci introduced many of the Arabian and Indian ideas to Europe, including that of the Fibonacci numbers . [ 19 ] Jordanus was the first person to arrange the binomial coefficients in a triangle , as he did in proposition 70 of De Arithmetica . This was also done in the Middle East in 1265, and China around 1300. [ 1 ] Today, this triangle is known as Pascal's triangle .
Pascal 's contribution to the triangle that bears his name comes from his work on formal proofs about it, and the connections he made between Pascal's triangle and probability . [ 1 ] From a letter Leibniz sent to Daniel Bernoulli we learn that Leibniz was formally studying the mathematical theory of partitions in the 17th century, although no formal work was published. Together with Leibniz, Pascal published De Arte Combinatoria in 1666 which was reprinted later. [ 20 ] Pascal and Leibniz are considered the founders of modern combinatorics. [ 21 ]
Both Pascal and Leibniz understood that the binomial expansion was equivalent to the choice function . The notion that algebra and combinatorics corresponded was expanded by De Moivre , who found the expansion of a multinomial . [ 22 ] De Moivre also found the formula for derangements using the principle of principle of inclusion–exclusion , [ 1 ] a method different from Nikolaus Bernoulli , who had found it previously. [ 23 ] [ 24 ] De Moivre also managed to approximate the binomial coefficients and factorial , and found a closed form for the Fibonacci numbers by inventing generating functions . [ 25 ] [ 26 ]
In the 18th century, Euler worked on problems of combinatorics, and several problems of probability which are linked to combinatorics. Problems Euler worked on include the Knights tour , Graeco-Latin square , Eulerian numbers , and others. To solve the Seven Bridges of Königsberg problem he invented graph theory , which also led to the formation of topology . Finally, he broke ground with partitions by the use of generating functions . [ 27 ]
In the 19th century, the subject of partially ordered sets and lattice theory originated in the work of Dedekind , Peirce , and Schröder . However, it was Garrett Birkhoff 's seminal work in his book Lattice Theory published in 1967, [ 28 ] and the work of John von Neumann that truly established the subjects. [ 29 ] In the 1930s, Hall (1936) and Weisner (1935) independently stated the general Möbius inversion formula . [ 30 ] In 1964, Gian-Carlo Rota's On the Foundations of Combinatorial Theory I. Theory of Möbius Functions introduced poset and lattice theory as theories in Combinatorics. [ 29 ] Richard P. Stanley has had a big impact in contemporary combinatorics for his work in matroid theory , [ 31 ] for introducing Zeta polynomials, [ 32 ] for explicitly defining Eulerian posets , [ 33 ] developing the theory of binomial posets along with Rota and Peter Doubilet, [ 34 ] and more. Paul Erdős made seminal contributions to combinatorics throughout the century, winning the Wolf prize in-part for these contributions. [ 35 ] | https://en.wikipedia.org/wiki/History_of_combinatorics |
The history of X-ray computed tomography (CT) traces back to Wilhelm Conrad Röntgen’s discovery of X-ray radiation in 1895 and its rapid adoption in medical diagnostics. While X-ray radiography achieved tremendous success in the early 1900s, it had a significant limitation: projection-based imaging lacked depth information, which is crucial for many diagnostic tasks. To overcome this, additional X-ray projections from different angles were needed. The challenge was both mathematically and experimentally addressed by multiple scientists and engineers working independently across the globe. The breakthrough finally came in the 1970s with the work of Godfrey Hounsfield , when advancements in computing power and the development of commercial CT scanners made routine diagnostic applications possible.
Early attempts to overcome the superimposition of structures inherent to projectional radiography involved methods in which the X-ray source and the detecting film moved simultaneously along specific trajectories. These techniques were based on principles of projective geometry, allowing a particular plane (or slice) to be “focused” during exposure while structures above and below the plane were blurred. This approach became known as planography or focal plane tomography . Key contributors to its development included the French physician André Bocage, Italian radiologist Alessandro Vallebona, and Dutch radiologist Bernard George Ziedses des Plantes. [ 1 ]
In 1961, neurologist William Oldendorf proposed a notable approach to imaging structures inside the skull. He developed an experimental setup using a pencil beam and a rotating sample with slow linear motion perpendicular to the beam axis. This allowed him to record variations in radiodensity within a test sample containing aluminum and iron nails arranged concentrically around the center, mimicking the structure of a skull. [ 2 ] Oldendorf’s method can be considered a form of focal point tomography, as it sampled points on a specific line or trajectory, while objects outside the center of rotation appeared blurred. In 1963, he was granted a U.S. patent for a "Radiant energy apparatus for investigating selected areas of interior objects obscured by dense material." [ 3 ] In recognition of his contributions, he shared the 1975 Lasker Award with Godfrey Hounsfield.
These early tomographic methods, relying solely on mechanical techniques, continued to evolve throughout the mid-20th century, steadily producing sharper images and allowing for greater control over the thickness of the examined cross-section. This progress was driven by the development of more complex, multidirectional devices capable of moving in multiple planes and achieving more effective blurring of out-of-focus structures. [ 1 ] However, despite these advancements in focal plane tomography, its ability to image soft tissue remained highly limited due to poor contrast.
To reliably solve the problem of X-ray passage through a plane at various angles, it was necessary to formulate an integral equation that accounted for the setup’s geometry. Given the line integrals of a function f ( x , y ) {\displaystyle f(x,y)} along multiple lines within the x y {\displaystyle xy} -plane, the goal was to reconstruct the original function f ( x , y ) {\displaystyle f(x,y)} . This kind of problem was solved by Johann Radon in 1917 who worked on integral transforms without having a certain practical application in mind. [ 4 ] He became the eponym of the Radon transform and also provided its inverse solution needed for the image reconstruction.
In 1957, Soviet scientists Semyon I. Tetelbaum and Boris I. Korenblum were the first to propose reconstructing the linear attenuation coefficient µ in a slice using angular radiographs. [ 6 ] [ 5 ] In their paper "О методе получения объемных изображений при помощи рентгеновского излучения" ("About a Method of Obtaining Volumetric Images by Means of X-Ray Radiation") [ 6 ] they formulated the underlying integral equation and proposed a solution—without being aware of Radon's earlier work. As a practical implementation, they also proposed a collimated fan-beam setup, in which a narrow line was recorded on film while the sample’s rotation was synchronized with the film’s orthogonal movement relative to the imaging plane, recording what is today known as a sinogram directly onto the film. [ 6 ] [ 5 ] Additionally, they described an analog computing device, utilizing hardware available in the 1950s, capable of performing the reconstruction and displaying the results on a TV screen. [ 5 ] They estimated that a 100 × 100 pixel matrix could be reconstructed in five minutes using an analog computing device with a frequency bandwidth of up to 1 MHz.
In his paper, Tetelbaum also proposed performing scans using different wavelength ranges (i.e., spectra of different energies) and utilizing the dependence of µ on energy to obtain a "colored image, which could provide, e.g. in medicine, additional diagnostic possibilities. " [ 6 ] According to their 1958 paper, such a device was under construction in their laboratory at the Kiev Polytechnic Institute . [ 5 ] However, no experimental results were published after 1958, likely due to the unexpected death of Tetelbaum in November of that year. Since their papers were written in Russian and published in Soviet scientific journals, they remained largely unknown in the West.
Meanwhile, Allan M. Cormack , a South African physicist working in the Radiology Department at the University of Cape Town , was also interested in obtaining cross-sections of the absorption coefficient of the body to optimize radiotherapy treatments. He described his motivation as follows:
“As I was working in the Radiology Department I could not help noticing the way in which X-ray radiotherapy treatments were planned. I was horrified by what I saw, even though it was as good as anything in the world, because all planning was based on the absorption of radiation by homogeneous matter approximating human tissue, and no account was taken of the differences in absorption between, say, bone, muscle and lung tissue. It struck me that what was needed was a set of maps of absorption coefficient for many sections of the body before one could more accurately plan therapy treatments. It occurred to me that these maps might be interesting in themselves, but I had no idea how interesting they would turn out to be.” [ 7 ]
He formulated the underlying integral equation and searched for its solutions in the mathematical literature. However, unable to find any references to Radon’s work, he solved the problem independently and designed an experiment to validate his tomographic approach. The setup utilized a collimated 60 C o {\displaystyle ^{60}\mathrm {Co} } gamma source and a Geiger counter , with both the source and detector moving linearly and scanning the sample with a pencil beam. For simplicity, he chose a sample consisting of a cylinder made of aluminum, encircled by a ring of wood, arranged symmetrically around the center of rotation. Due to this point symmetry, the recorded intensity pattern remained identical at all angles, making it sufficient to acquire data from just one angle to determine the linear attenuation coefficient within a plane of the sample. The results demonstrated a good agreement between the experimentally acquired data and the theoretical calculations. He published his results in two papers in 1963 [ 8 ] and 1964, [ 9 ] but received no feedback and chose not to pursue the project further until he learned about Hounsfield’s work in 1972.
In the late 1960s, British electrical engineer Godfrey N. Hounsfield , who was employed by EMI and had led the development of Britain’s first commercially available all-transistor computer ( EMIDEC 1100 ), began exploring aspects of pattern recognition . Since EMI had nearly doubled its profits from The Beatles ' record sales, it began investing a substantial amount of money into funding bold and innovative research ideas. In 1967, Hounsfield was given the opportunity to work on his own project and proposed tackling the tomographic problem, drawing inspiration from his earlier radar research. Instead of detecting patterns in the periphery using radar, he wondered whether it would be possible to detect objects inside a structure by sending beams through it from different angles. [ 10 ]
With additional funding from the UK Government Department of Health and Social Security, Hounsfield began developing a pencil beam scanner similar to Cormack’s setup, using an Americium gamma source. Early successful measurements on samples such as bottles, water-filled jars, and pieces of metal and plastic took up to nine days to complete, acquiring 28,000 data points, which then required over two hours to process on a high-speed computer. [ 10 ] Unlike his predecessors, Hounsfield had access to significant computing power and applied an algebraic reconstruction technique , using the Kaczmarz method from numerical algebra. Encouraged by the promising results, he justified the investment in an X-ray tube, a generator, and more sensitive crystal detectors, which soon enabled a significant reduction in measuring time. In 1968, the first promising scans of bovine brain samples were obtained, where white and grey matter could be clearly differentiated. [ 10 ] In the same year, UK Patent No. 1283915 for " A Method of and Apparatus for Examination of a Body by Radiation such as X or Gamma Radiation " [ 11 ] was granted to Hounsfield .
When reaching out to radiologists at leading hospitals, Hounsfield was met with widespread indifference, and his proposals were often dismissed as unfeasible or of little practical value. However, he found a key collaborator in James Ambrose, a neuroradiologist at Atkinson Morley Hospital in London, after convincing him with an impressive image of a brain sample containing a tumor—supplied by Ambrose for a test scan. Over the following year, Hounsfield adapted his scanner for clinical in vivo application, designing it to keep the patient’s head static while a rotating gantry moved the X-ray source and detector around it. The scanner was installed at Atkinson Morley Hospital, and on October 1, 1971, the first patient—a woman with a suspected brain tumor—was successfully examined. Over the following weeks, they successfully diagnosed brain diseases in several patients, aiding in surgical planning. When Ambrose presented these groundbreaking images at the British Institute of Radiology's Annual Congress in 1972, the conference participants were stunned. The clarity of the brain scans, revealing lesions, tumors, and hemorrhages, dispelled any skepticism and marked the beginning of a new era in radiology.
Hounsfield described the method, scanner design, and operation in his landmark 1973 paper, [ 12 ] where he also introduced radiodensity units to which the reconstructed images were calibrated. Later, the eponymous Hounsfield scale was established, defining water as 0 HU and air as -1000 HU. For the introduction of computer tomography, the Nobel Prize in Physiology or Medicine was awarded jointly to Allan M. Cormack and Godfrey N. Hounsfield in 1979. The Nobel Committee stated in its announcement: “It is no exaggeration to state that no other method within x-ray diagnostics within such a short period of time has led to such remarkable advances in research and in a multitude of applications.” [ 13 ]
After the public presentation of the first results in 1972 and the enthusiastic reception by the radiological community, several companies around the world began developing their own CT systems. Just five years later, no fewer than 17 companies were already active on the global market, offering commercial CT scanners. [ 14 ] Progress was driven by innovations in various fields, including X-ray tube optimization, detector development, faster data processing, and advanced reconstruction algorithms. These technological advancements defined the different “generations” of CT scanners, ranging from the first to the fifth generation. In the long term, however, fan-beam CT devices using the rotate-rotate approach—known as third-generation scanners—have proven to be the most practical. Thanks to innovations such as rotating anode tubes, helical scanning, and slip ring technology , they continue to dominate the market today. Scanners with these new developments have occasionally been classified as 6th generation by their manufacturers for marketing purposes, but the term has not become generally accepted.
In first-generation CT scanners—such as Hounsfield’s EMI Mark I design—the X-ray tube, typically operated at 120 kVp and 32 mA, emitted a narrow pencil beam aimed at a two-element detector (acquiring two 13 mm slices simultaneously), which consisted of sodium iodide (NaI) scintillators coupled to photomultiplier tubes . [ 13 ] Both the tube and the detector moved linearly across the patient at a fixed gantry angle. After each traverse, during which 160 data points (two rows of 80 measurements at 1.5 mm intervals) were collected, the system rotated by 1° around the center of the bore and repeated the process, ultimately acquiring 180 projections within five minutes. The detector required gain and offset calibration at the beginning of each linear pass. [ 13 ]
The patient’s head was enclosed in a thick rubber sleeve inside a box filled with water. This "water bag" adapted the dynamic range of the X-ray signal, minimized beam hardening effects, and provided a consistent reference point for calibration of CT numbers and starting point for iterative image reconstruction. [ 13 ] The 28,800 data points collected for two slices were stored on magnetic disks.
The EMI scanner was equipped with a Data General Nova 820 minicomputer featuring 32 KB of memory and a dual-sided 2.5 MB hard drive . The reconstructed images had a matrix of 80 × 80 pixels and a dynamic range from –500 to +500, with water defined as 0. Three types of image output were available: a numerical printout of reconstructed values, a digital grayscale display with 10 intensity levels (with adjustable windowing), and a Polaroid photograph of the screen. A typical patient examination was scheduled for 60 to 120 minutes and included 8 to 12 images of 13 mm slice thickness captured via Polaroid. [ 13 ]
Devices of this generation were primarily dedicated cranial scanners, designed exclusively for imaging the head. In 1974, Robert Ledley developed the first whole-body CT scanner at Georgetown University Medical Center in Washington, D.C.—the Automatic Computerized Transverse Axial (ACTA) scanner. While conceptually similar to the EMI Mark I , the ACTA scanner offered a larger axial field of view of 48 cm and produced images with a matrix of 160 × 160 pixels. [ 15 ] Imaging body parts other than the head presented particular challenges due to motion artifacts caused by breathing and the heartbeat. To address this issue, it was necessary to significantly reduce the scan time.
Companies that offered 1st generation CT scanners include EMI ( Mark 1 , 1972), DISCO ( ACTA 0100 , later sold to Pfizer ), Siemens ( Siretom , 1974), GE ( CT-N ), NS ( Neuroscan CT/N ), Ohio Nuclear/ Technicare ( Delta 25, Delta 50 ) and CGR (Compagnie générale de radiologie, Densitome ). [ 13 ]
To achieve faster scan speeds, the narrow pencil X-ray beam was expanded into a fan-shaped beam and paired with multiple detectors—often more than ten. This configuration enabled the system to sample the object along several lines simultaneously, significantly reducing the number of rotations required for image reconstruction, though the translate-rotate protocol was still employed. For instance, EMI’s second-generation CT 5000 series, introduced in 1975, featured 30 detectors spanning over 10°, which reduced scanning time to just 20 seconds per slice—fast enough to image certain body parts during a single breath-hold. [ 13 ]
The rapidly growing market soon attracted serious competitors to EMI, including Siemens, Hitachi, GE, and several smaller manufacturers, many of whom introduced first- and second-generation scanners. While some of the smaller entrants brought innovative designs to the table, they often struggled to produce large numbers of reliable systems. A notable newcomer was Ohio Nuclear (later Technicare ), which launched its successful Delta Scan series. This system offered a 256 × 256 image matrix, a two-minute scan time, and advanced, user-friendly software. Demand was so strong that, at the 1975 RSNA conference, customers placed $50,000 deposits simply to reserve a spot in the delivery queue. [ 13 ]
Although second-generation systems offered substantial improvements in scan speed, the translate-rotate method still imposed a lower limit of around 20 seconds per slice. For many clinical applications, even faster scanning was necessary—prompting the move toward eliminating the translate motion entirely.
The use of a wide fan beam to illuminate the entire field of view was a logical advancement, first envisioned by Tetelbaum and Korenblum in 1958 [ 5 ] and later by Hounsfield in his early project proposal at EMI in 1968, [ 13 ] as well as in his patents. To accommodate this configuration, a larger detector array was arranged in a curved arc along the gantry, enabling it to capture the full width of the fan beam. As a result, a translational movement was no longer necessary to acquire a complete projection, giving rise to the "rotate-rotate" system—where both the X-ray tube and the detector array rotate around the patient.
In 1973, David Chesler, a scientist at Massachusetts General Hospital who had previously conducted pioneering work in positron emission tomography (PET), secured funding from the National Institutes of Health (NIH) to develop a CT body scanner utilizing a fan-beam design. His system aimed for a scan time of 5 seconds and featured filtered back-projection reconstruction, a bow-tie filter to reduce beam-hardening artifacts, and quarter-offset alignment to minimize aliasing. [ 13 ] Compact detector designs based on Xenon ionization chambers were pivotal to the advancement of third-generation CT scanners.
Driven by the urgent need for faster CT scanning, the NIH and the National Cancer Institute (NCI) offered a $1 million award for the most promising proposal to develop a high-speed, whole-body CT scanner in late 1974. This led to intense competition and sparked the formation of several collaborations between academic institutions and industry. Competing manufacturers crafted ambitious R&D strategies, which they were required to submit along with their proposals. [ 13 ]
Pioneering work in detector development was conducted by Douglas P. Boyd [ 17 ] at Stanford University, as well as N. R. Whetten and J. M. Houston [ 18 ] at GE. In these systems, Xenon gas was compressed within chambers to pressures of 20–30 atmospheres. The chambers contained bias and signal electrodes designed to collect electrons generated by xenon ionization events resulting from X-ray absorption. With cell depths of several centimeters, these detectors achieved detective quantum efficiencies of around 50% for the X-ray spectra used. [ 13 ] They also demonstrated superior stability and linearity compared to earlier technologies and the electrodes simultaneously served as anti-scatter grids. Most third-generation CT systems adopted xenon ionization chambers in combination with pulsed X-ray sources, which helped reduce motion blur and offered improved control over radiation dose. [ 13 ]
One notable example is the V360-3 CT system introduced by Varian Associates in 1976. It featured a 301-channel ionization chamber, a pulsed X-ray source, and a continuously rotating gantry enabled by early slip-ring technology—allowing for a scan time of just 3 seconds per slice. [ 13 ] An alternative detector concept was introduced by Siemens in its 1977 Somatom system, which featured an array of cesium iodide (CsI) scintillators coupled to photodiodes and a rotation time of 4 seconds. [ 13 ] Notable innovations included a high-heat-capacity X-ray tube and fast image reconstruction, with filtered backprojection initiated during the scan itself.
While third-generation systems brought significant improvements in scan speed, they also introduced new challenges—most notably, ring artifacts. These arose from calibration drifts in individual detector channels during the scan, as calibration could only be performed before or after imaging, when the patient was not in the beam. Another issue was aliasing artifacts, caused by the lack of crosstalk between detector channels. These occurred when projections contained periodic features at or below the spatial sampling limit defined by the Nyquist frequency of the detector array. [ 13 ]
One of the central questions of the time was whether these problems could be addressed through technological advancements within the rotate-rotate architecture, or whether an alternative scanning approach would be required. While alternative designs were already in development in the late 1970s and gained traction in the 1980s and 1990s, the third-generation concept ultimately returned to dominance and remains the foundation of modern CT scanner design today.
Prominent manufacturers of third-generation CT systems included GE, Siemens, Varian, Searle, CGR, Artronix, Elscint, Philips, Toshiba, Hitachi, Shimadzu , and others.
Parallel to the development of third-generation CT systems, alternative approaches aimed at reducing mechanical complexity and avoiding moving parts. Specifically, designs using static detector arrays that spanned the entire gantry circumference were explored. In these systems, only the X-ray source rotated, leading to what became known as the rotate-static or fourth-generation architecture.
One prominent pioneer of this approach was Sadek Hilal at Columbia-Presbyterian Medical Center , who won the 1974 NIH/NCI RFP competition, receiving a $1 million grant to develop a high-speed CT scanner. [ 13 ] Collaborating with American Science and Engineering (AS&E), the team pursued a design using bismuth germanate (BGO) detectors coupled to photomultipliers. This new approach eliminated detector calibration issues and got rid of ring artifacts since a single detector cell now measured radiation coming from different fan angles depending on the X-ray source position. In 1977, AS&E introduced their fourth-generation scanner, featuring 600 detector cells, a 512 × 512 image matrix, 5-second scan times, and sub-millimeter in-plane resolution—a major leap forward at the time. [ 13 ] However, the NIH funding of the project led to an intellectual property dispute, and AS&E’s attempt to obtain an exclusive license raised concerns about public interest. As a result, no patents were ultimately granted to AS&E. Meanwhile, other companies adopted similar fourth-generation designs, rapidly advancing the technology and reducing scan times to as little as 1 second.
Although the new design resolved the issue of ring artifacts, it introduced other challenges—most notably, a relatively high skin radiation dose due to the X-ray source being positioned closer to the patient, and a reduction in image quality caused by increased in-plane scatter, which could not be effectively eliminated using a focused anti-scatter grid as in third-generation systems. [ 13 ] Additionally, the greater detector coverage led to significantly higher costs. While various innovative attempts were made to address these issues, they ultimately failed to outperform systems based on the rotate-rotate principle and were gradually phased out by the late 1990s.
Electron Beam CT (EBCT) , another major innovation in CT imaging sought to eliminate mechanically moving parts entirely by employing both a static detector array and a static X-ray source. This was achieved using a large semi-circular tungsten anode made of multiple arcs, across which an electron beam was electronically swept. One such system, the Imatron C-100, was developed by Douglas P. Boyd at the University of California, San Francisco , and introduced in 1981, offering an unprecedented temporal resolution of 33–100 ms. [ 19 ]
The scanner featured an electron gun and magnetic beam deflection system, similar to those in cathode-ray tubes (CRTs), allowing the electron beam to be rapidly steered across multiple 6-foot circular tungsten anode arcs—four in the initial system—covering 210°. The entire electron path was contained within a vacuum chamber, resulting in a large physical footprint, particularly on one side of the gantry. The upper part of the system was equipped with two rows of detectors, comprising 432 scintillator-photodiode elements also spanning 210°, designed to capture the X-ray fan beam generated by the rapidly moving focal spot. With four anode tracks and two detector rows, the system could generate eight image slices in under 1s. [ 13 ]
This design was specifically optimized for cardiac imaging , as the heart's rapid motion makes it highly susceptible to motion artifacts. It enabled advanced applications such as coronary calcium scoring and other heart-related diagnostics. [ 13 ] EBCT was also used for pediatric imaging, where patients often struggle with breath-holding or remaining still during scans. Only much later did modern CT systems, with multi-detector and dual-source technology, achieve comparable temporal resolution, eventually displacing EBCT from the market. Its decline was due to several limitations: a large footprint, limited versatility for general imaging, high acquisition and maintenance costs, and lower spatial resolution compared to newer technologies.
Until the late 1980s, CT scans were performed exclusively in axial mode, where the patient table advanced in small increments after each full 360° rotation of the gantry around the patient. In 1990, continuous gantry rotation became possible with the introduction of slip-ring technology , eliminating the need to reverse the gantry after every rotation. [ 20 ] This advancement enabled the first attempts at continuously moving the patient table during scanning for faster data acquisition. Because the X-ray tube and detectors then moved along a helical path relative to the patient, the method became known as helical or spiral CT . [ 20 ] However, this new acquisition mode introduced motion artifacts that made image reconstruction more challenging.
In 1989, German physicist Willi A. Kalender from Siemens developed a Z-interpolation algorithm that successfully eliminated these artifacts and implemented it in the Somatom Plus scanner. [ 21 ] Within two years, other major CT manufacturers adopted the technique, and helical scanning became the new standard in CT imaging.
Starting in the 1990s, CT detector technology transitioned from xenon ionization chambers to solid-state detectors. These new detectors used powdered scintillators (such as Gd₂O₂S ) coupled with photodiodes to convert light into electrical signals. This advancement offered significantly higher quantum efficiency (>90%) and enabled more compact designs with improved spatial resolution. In 1992, Elscint introduced the CT-Twin scanner, which used a solid-state detector capable of acquiring two slices simultaneously. This innovation was soon adopted by other manufacturers, leading to a rapid increase in the number of simultaneously acquired slices: four in 1998, 16 in 2001, 64 in 2006, and up to 256–640 slices in today's state-of-the-art systems. Modern scanners now cover up to 16 cm of anatomy in a single rotation, allowing complete heart imaging without moving the table. [ 20 ]
The combination of helical scanning and multi-slice technology enabled the acquisition of very thin slices, ultimately making isotropic voxel reconstruction possible. This means that anatomical data can now be viewed from any angle without distortion ( multiplanar reconstruction ), allowing the extraction, analysis, and visualization of accurate 3D models of the scanned structures. [ 20 ] These capabilities have significantly improved surgical planning in fields such as neurology , orthopedics , and cardiology , and have also enabled more advanced calculations in radiotherapy planning .
For specialized applications—such as differentiating materials with similar Hounsfield Unit (HU) values, tracking contrast agents , or reducing metal artifacts—it is beneficial to acquire scans at different X-ray energies. Leading CT manufacturers have developed techniques to achieve this dual-energy acquisition within a single scan.
In 2005, Siemens introduced the SOMATOM Definition , a scanner equipped with two X-ray tubes and two detectors mounted 90° apart on the gantry, each operating at different energies. [ 22 ] This configuration not only enables dual-energy imaging but also delivers significantly higher X-ray flux, which is especially advantageous for cardiac imaging, achieving a temporal resolution of approximately 75 ms and resolving the heartbeat with minimal motion artifacts. [ 23 ]
Other manufacturers, such as GE with Revolution CT and Canon with Aquilion ONE GENESIS , employ rapid kVp switching technology, allowing their detectors to separate and process both high- and low-energy data. [ 24 ] Philips, in contrast, uses a dual-layer detector system (e.g. IQon Spectral CT ) where the top layer captures mostly low-energy photons and the bottom layer detects more high-energy photons, enabling spectral differentiation at the detector level. [ 24 ]
The acquisition of dual-energy data proves useful in clinical applications such as detecting uric acid versus calcium kidney stones , characterizing pulmonary embolism with iodine maps, and improving lesion conspicuity in liver imaging through virtual non-contrast and material decomposition.
The latest advancement in CT detector technology is the development of photon-counting detectors . These systems use semiconductor materials such as cadmium telluride (CdTe) to directly convert absorbed X-ray photons into electrical charges, with the signal strength proportional to the energy of the photon. CdTe is composed of high atomic number elements, making it highly effective at absorbing X-rays and offering excellent detection efficiency. Its relatively large bandgap of 1.5 eV also allows operation at room temperature with minimal thermal noise. [ 20 ]
When an X-ray photon is absorbed in the CdTe crystal via the photoelectric effect , its energy is transferred to an electron, which then ionizes atoms and generates electron-hole pairs . Charge collection electrodes separate these charges, and after amplification, the resulting signal is sorted into energy bins based on pulse height. This enables every photon to be individually counted and classified by energy at each pixel. As a result, photon-counting CT reaches an even better performance than dual-energy CT at material decomposition, and improves overall signal-to-noise ratio and dose efficiency. [ 20 ]
In 2021 Siemens Healthineers introduced the first photon-counting CT scanner NAEOTOM Alpha equipped with two Vectron X-ray tubes and two QuantaMax detector arrays acquiring 144 slices (6cm collimation width) with a gantry rotation time down to 0.25s. [ 25 ] Other manufacturers have respective scanners in development and clinical testing. One notable system is the nu:view brest-CT scanner from the company AB-CT which also uses a CdTe photon-counting detector and has been in clinical use across Europe since 2017. [ 26 ]
Unlike conventional CT scanners, cone beam CT (CBCT) utilizes the entire conical X-ray beam to acquire projection data and typically employs large flat panel detectors with pixel sizes ranging from 50 to 200 µm—similar to those used in chest radiography or fluoroscopy . Accordingly, CBCT systems use different acquisition protocols and cone beam reconstruction algorithms. The first systems entered the market in the late 1990s, such as the NewTom 9000 by QR S.R.L. in 1998, initially designed for dentomaxillofacial imaging . [ 27 ] Since then, CBCT has gained popularity in orthopedic and veterinary medicine , interventional radiology , and surgical applications. Today, C-arm systems are CBCT-capable and have become powerful tools for intraoperative imaging, dental and ENT procedures, radiation therapy planning, and beyond. [ 27 ]
Dedicated cone beam CT systems have also been developed for non-destructive testing , industrial applications, and research since the mid-1980s. [ 28 ] Unlike medical CBCT, these systems typically rotate the sample while keeping the source and detector stationary. Longer scan times and higher radiation doses are generally acceptable in such settings, allowing for much higher spatial resolutions. These systems can achieve resolutions better than 100 µm ( microCT or µCT) and, in some special cases, even below 1 µm ( nanoCT ), making them ideal for material science , precision engineering , and biological research. [ 28 ] | https://en.wikipedia.org/wiki/History_of_computed_tomography |
The history of computer animation began as early as the 1940s and 1950s, when people began to experiment with computer graphics – most notably by John Whitney . It was only by the early 1960s when digital computers had become widely established, that new avenues for innovative computer graphics blossomed. Initially, uses were mainly for scientific, engineering and other research purposes, but artistic experimentation began to make its appearance by the mid-1960s – most notably by Dr. Thomas Calvert. By the mid-1970s, many such efforts were beginning to enter into public media. Much computer graphics at this time involved 2-D imagery, though increasingly as computer power improved, efforts to achieve 3-D realism became the emphasis. By the late 1980s, photo-realistic 3-D was beginning to appear in film movies, and by mid-1990s had developed to the point where 3-D animation could be used for entire feature film production.
John Whitney Sr. (1917–1995) was an American animator, composer and inventor, widely considered to be one of the fathers of computer animation. [ 1 ] In the 1940s and 1950s, he and his brother James created a series of experimental films made with a custom-built device based on old anti-aircraft analog computers ( Kerrison Predictors ) connected by servomechanisms to control the motion of lights and lit objects – the first example of motion control photography . One of Whitney's best known works from this early period was the animated title sequence from Alfred Hitchcock 's 1958 film Vertigo , [ 2 ] which he collaborated on with graphic designer Saul Bass . In 1960, Whitney established his company Motion Graphics Inc, which largely focused on producing titles for film and television, while continuing further experimental works. In 1968, his pioneering motion control model photography was used on Stanley Kubrick 's film 2001: A Space Odyssey , and also for the slit-scan photography technique used in the film's "Star Gate" finale.
One of the first programmable digital computers was SEAC (the Standards Eastern Automatic Computer), which entered service in 1950 at the National Bureau of Standards (NBS) in Maryland, USA. [ 3 ] [ 4 ] In 1957, computer pioneer Russell Kirsch and his team unveiled a drum scanner for SEAC, to "trace variations of intensity over the surfaces of photographs", and so doing made the first digital image by scanning a photograph. The image, picturing Kirsch's three-month-old son, consisted of just 176×176 pixels . They used the computer to extract line drawings, count objects, recognize types of characters and display digital images on an oscilloscope screen. This breakthrough can be seen as the forerunner of all subsequent computer imaging, and recognising the importance of this first digital photograph, Life magazine in 2003 credited this image as one of the "100 Photographs That Changed the World". [ 5 ] [ 6 ]
In 1960, a 49-second vector animation of a car traveling down a planned highway was created at the Swedish Royal Institute of Technology on the BESK computer. The consulting firm Nordisk ADB, which was a provider of software for the Royal Swedish Road and Water Construction Agency realized that they had all the coordinates to be able to draw perspective from the driver's seat for a motorway from Stockholm towards Nacka. In front of a specially designed digital oscilloscope with a resolution of about 1 megapixel a 35 mm camera with an extended magazine was mounted on a specially made stand. The camera was automatically controlled by the computer, which sent a signal to the camera when a new image was fed on the oscilloscope. It took an image every twenty meters (yards) of the virtual path. The result of this was a fictional journey on the virtual highway at a speed of 110 km/h (70 mph). The short animation was broadcast on November 9, 1961, at primetime in the national television newscast Aktuellt. [ 7 ] [ 8 ]
Bell Labs in Murray Hill, New Jersey, was a leading research contributor in computer graphics, computer animation and electronic music from its beginnings in the early 1960s. Initially, researchers were interested in what the computer could be made to do, but the results of the visual work produced by the computer during this period established people like Edward Zajac, Michael Noll and Ken Knowlton as pioneering computer artists.
Edward Zajac produced one of the first computer generated films at Bell Labs in 1963, titled A Two Gyro Gravity Gradient attitude control System , which demonstrated that a satellite could be stabilized to always have a side facing the Earth as it orbited. [ 9 ]
Ken Knowlton developed the Beflix (Bell Flicks) animation system in 1963, which was used to produce dozens of artistic films by artists Stan VanDerBeek , Knowlton and Lillian Schwartz . [ 10 ] Instead of raw programming, Beflix worked using simple "graphic primitives", like draw a line, copy a region, fill an area, zoom an area, and the like.
In 1965, Michael Noll created computer-generated stereographic 3-D movies, including a ballet of stick figures moving on a stage. [ 11 ] Some movies also showed four-dimensional hyper-objects projected to three dimensions. [ 12 ] Around 1967, Noll used the 4-D animation technique to produce computer-animated title sequences for the commercial film short Incredible Machine (produced by Bell Labs) and the TV special The Unexplained (produced by Walt DeFaria). [ 13 ] Many projects in other fields were also undertaken at this time.
In the 1960s, William Fetter was a graphic designer for Boeing at Wichita , and was credited with coining the phrase "Computer Graphics" to describe what he was doing at Boeing at the time (though Fetter himself credited this to colleague Verne Hudson). [ 14 ] [ 15 ] Fetter's work included the 1964 development of ergonomic descriptions of the human body that are both accurate and adaptable to different environments, and this resulted in the first 3-D animated wire-frame figures. [ 16 ] [ 17 ] Such human figures became one of the most iconic images of the early history of computer graphics, and often were referred to as the "Boeing Man". Fetter died in 2002.
Ivan Sutherland is considered by many to be the creator of Interactive Computer Graphics, and an internet pioneer. He worked at the Lincoln Laboratory at MIT ( Massachusetts Institute of Technology ) in 1962, where he developed a program called Sketchpad I , which allowed the user to interact directly with the image on the screen. This was the first graphical user interface , and is considered one of the most influential computer programs an individual has ever written. [ 18 ]
Utah was a major center for computer animation in this period. The computer science faculty was founded by David Evans in 1965, and many of the basic techniques of 3-D computer graphics were developed here in the early 1970s with ARPA funding ( Advanced Research Projects Agency ). Research results included Gouraud, Phong, and Blinn shading, texture mapping, hidden surface algorithms, curved surface subdivision , real-time line-drawing and raster image display hardware, and early virtual reality work. [ 19 ] In the words of Robert Rivlin in his 1986 book The Algorithmic Image: Graphic Visions of the Computer Age , "almost every influential person in the modern computer-graphics community either passed through the University of Utah or came into contact with it in some way". [ 20 ]
In the mid-1960s, one of the most difficult problems in computer graphics was the "hidden-line" problem – how to render a 3D model while properly removing the lines that should not be visible to the observer. [ 21 ] One of the first successful approaches to this was published at the 1967 Fall Joint Computer Conference by Chris Wylie, David Evans, and Gordon Romney, and demonstrated shaded 3D objects such as cubes and tetrahedra . [ 22 ] An improved version of this algorithm was demonstrated in 1968, including shaded renderings of 3D text, spheres, and buildings. [ 23 ]
A shaded 3D computer animation of a colored Soma cube exploding into pieces was created at the University of Utah as part of Gordon Romney's 1969 PhD dissertation, along with shaded renderings of 3D text, 3D graphs, trucks, ships, and buildings. [ 24 ] This paper also coined the term "rendering" in reference to computer drawings of 3D objects. Another 3D shading algorithm was implemented by John Warnock for his 1969 dissertation. [ 25 ]
A truly real-time shading algorithm was developed by Gary Watkins for his 1970 PhD dissertation, and was the basis of the Gouraud shading technique, developed the following year. [ 26 ] [ 27 ] Robert Mahl's 1970 dissertation at the University of Utah described smooth shading of quadric surfaces . [ 28 ]
Further innovations in shaded 3D graphics at the University of Utah included a more realistic shading technique by Bui Tuong Phong for his dissertation in 1973 and texture mapping by Edwin Catmull for his 1974 dissertation. [ 29 ] [ 30 ]
Around 1972, a virtual reality headset known as the "Sorcerer's Apprentice" became operational at the University of Utah, which used head tracking and a device similar to MIT 's Lincoln Wand to track the user's hand in 3D space. [ 31 ] This headset, like Ivan Sutherland's "Sword of Damocles" , was capable of simple, unshaded wireframe 3D graphics; however, the Sorcerer's Apprentice added the capability to create and manipulate 3D objects in real-time through the hand tracking device, termed the "wand". Commands to be performed by the 3D wand could be chosen by pointing the wand at a physical wall chart. [ 32 ]
An important innovation in computer animation at the University of Utah was the creation of the program "KEYFRAME", which would allow a user to pose and keyframe a rigged humanoid 3D character, create walk cycles and other movements, lip-sync the character, all using a mouse -based graphical interface , and then render a shaded animation of the rigged character performing the walk cycle, hand movement, or other animation. This program, as well as one for creating a 3D animation of a football match, were created by Barry Wessler for his 1973 PhD dissertation. [ 33 ] The capabilities of the "KEYFRAME" program were demonstrated in a short film, Not Just Reality , which featured walk cycles, lip syncing, facial expressions, and further movement of a shaded humanoid 3D character. [ 34 ]
In 1968, Ivan Sutherland teamed up with David Evans to found the company Evans & Sutherland —both were professors in the Computer Science Department at the University of Utah, and the company was formed to produce new hardware designed to run the systems being developed in the University. Many such algorithms have later resulted in the generation of significant hardware implementation, including the Geometry Engine , the Head-mounted display , the Frame buffer , and Flight simulators . [ 35 ] Most of the employees were active or former students, and included Jim Clark, who started Silicon Graphics in 1981, Ed Catmull , co-founder of Pixar in 1979, and John Warnock of Adobe Systems in 1982.
In 1968, a group of Soviet physicists and mathematicians with N. Konstantinov as its head created a mathematical model for the motion of a cat. On a BESM-4 computer they devised a programme for solving the ordinary differential equations for this model. The Computer printed hundreds of frames on paper using alphabet symbols that were later filmed in sequence thus creating the first computer animation of a character, a walking cat. [ 36 ] [ 37 ]
Charles Csuri , an artist at The Ohio State University (OSU), started experimenting with the application of computer graphics to art in 1963. His efforts resulted in a prominent CGI research laboratory that received funding from the National Science Foundation and other government and private agencies. The work at OSU revolved around animation languages, complex modeling environments, user-centric interfaces, human and creature motion descriptions, and other areas of interest to the discipline. [ 38 ] [ 39 ] [ 40 ]
In July 1968, the arts journal Studio International published a special issue titled Cybernetic Serendipity – The Computer and the Arts , which catalogued a comprehensive collection of items and examples of work being done in the field of computer art in organisations all over the world, and shown in exhibitions in London, UK, San Francisco, CA. and Washington, DC. [ 41 ] [ 42 ] This marked a milestone in the development of the medium, and was considered by many to be of widespread influence and inspiration. Apart from all the examples mentioned above, two other particularly well known iconic images from this include Chaos to Order [ 43 ] by Charles Csuri (often referred to as the Hummingbird ), created at Ohio State University in 1967, [ 44 ] and Running Cola is Africa [ 45 ] by Masao Komura and Koji Fujino created at the Computer Technique Group, Japan, also in 1967. [ 46 ]
The first machine to achieve widespread public attention in the media was Scanimate , an analog computer animation system designed and built by Lee Harrison of the Computer Image Corporation in Denver. From around 1969 onward, Scanimate systems were used to produce much of the video-based animation seen on television in commercials, show titles, and other graphics. It could create animations in real time , a great advantage over digital systems at the time. [ 47 ] American animation studio Hanna-Barbera experimented with using Scanimate to create an early form of digital cutout style . A clip of artists using the machine to manipulate scanned images of Scooby-Doo characters, scaling and warping the artwork to simulate animation, is available at the Internet Archive . [ 48 ]
The National Film Board of Canada , already a world center for animation art, also began experimentation with computer techniques in 1969. [ 49 ] Most well-known of the early pioneers with this was artist Peter Foldes , who completed Metadata in 1971. This film comprised drawings animated by gradually changing from one image to the next, a technique known as "interpolating" (also known as "inbetweening" or "morphing"), which also featured in a number of earlier art examples during the 1960s. [ 50 ] In 1974, Foldes completed Hunger / La Faim , which was one of the first films to show solid filled (raster scanned) rendering, and was awarded the Jury Prize in the short film category at 1974 Cannes Film Festival , as well as an Academy Award nomination. Foldes and the National Film Board of Canada employed pioneering keyframe computer technology developed at the National Research Council of Canada (NRC) by scientist Nestor Burtnyk in 1969. Burtnyk and his collaborator Marceli Wein received the Academy Award in 1997 in recognition of their role in the field. [ 51 ] The NRC team also contributed high-profile animation sequences to the celebrated BBC documentary series The Ascent of Man (1973). [ 52 ]
The Atlas Computer Laboratory near Oxford was for many years a major facility for computer animation in Britain. [ 53 ] The first entertainment cartoon made was The Flexipede , by Tony Pritchett, which was first shown publicly at the Cybernetic Serendipity exhibition in 1968. [ 54 ] Artist Colin Emmett and animator Alan Kitching first developed solid filled colour rendering in 1972, notably for the title animation for the BBC 's The Burke Special TV program.
In 1973, Kitching went on to develop a software called "Antics", which allowed users to create animation without needing any programming. [ 55 ] [ 56 ] The package was broadly based on conventional "cel" (celluloid) techniques, but with a wide range of tools including camera and graphics effects, interpolation ("inbetweening"/"morphing"), use of skeleton figures and grid overlays. Any number of drawings or cels could be animated at once by "choreographing" them in limitless ways using various types of "movements". At the time, only black & white plotter output was available, but Antics was able to produce full-color output by using the Technicolor Three-strip Process. Hence the name Antics was coined as an acronym for AN imated T echnicolor- I mage C omputer S ystem. [ 57 ] Antics was used for many animation works, including the first complete documentary movie Finite Elements , made for the Atlas Lab itself in 1975. [ 58 ]
The first feature film to use digital image processing was the 1973 film Westworld , a science-fiction film written and directed by novelist Michael Crichton , in which humanoid robots live amongst the humans. [ 59 ] John Whitney, Jr., and Gary Demos at Information International, Inc. digitally processed motion picture photography to appear pixelized to portray the Gunslinger android's point of view . The cinegraphic block portraiture was accomplished using the Technicolor Three-strip Process to color-separate each frame of the source images, then scanning them to convert into rectangular blocks according to its tone values, and finally outputting the result back to film. The process was covered in the American Cinematographer article "Behind the scenes of Westworld". [ 60 ]
Sam Matsa whose background in graphics started with the APT project at MIT with Doug Ross and Andy Van Dam petitioned Association for Computing Machinery (ACM) to form SIGGRAPH (Special Interest Committee on Computer Graphics), the forerunner of ACM SIGGRAPH in 1967. [ 61 ] In 1974, the first SIGGRAPH conference on computer graphics opened. This annual conference soon became the dominant venue for presenting innovations in the field. [ 62 ] [ 63 ]
The first use of 3-D wireframe imagery in mainstream cinema was in the sequel to Westworld , Futureworld (1976), directed by Richard T. Heffron. This featured a computer-generated hand and face created by University of Utah graduate students Edwin Catmull and Fred Parke which had initially appeared in their 1972 experimental short A Computer Animated Hand . [ 64 ] The same film also featured snippets from 1974 experimental short Faces and Body Parts . The Academy Award -winning 1975 short animated film Great , about the life of the Victorian engineer Isambard Kingdom Brunel , contains a brief sequence of a rotating wireframe model of Brunel's final project, the iron steam ship SS Great Eastern .The third film to use this technology was Star Wars (1977), written and directed by George Lucas , with wireframe imagery in the scenes with the Death Star plans, the targeting computers in the X-wing fighters, and the Millennium Falcon spacecraft.
The Walt Disney film The Black Hole (1979, directed by Gary Nelson) used wireframe rendering to depict the titular black hole, using equipment from Disney's engineers. In the same year, the science-fiction horror film Alien , directed by Ridley Scott , also used wire-frame model graphics, in this case to render the navigation monitors in the spaceship. The footage was produced by Colin Emmett at the Atlas Computer Laboratory. [ 65 ]
Although Lawrence Livermore Labs in California is mainly known as a centre for high-level research in science, it continued producing significant advances in computer animation throughout this period. Notably, Nelson Max, who joined the Lab in 1971, and whose 1976 film Turning a sphere inside out is regarded as one of the classic early films in the medium (International Film Bureau, Chicago, 1976). [ 66 ] He also produced a series of "realistic-looking" molecular model animations that served to demonstrate the future role of CGI ( Computer-generated imagery ) in scientific visualization. His research interests focused on realism in nature images, molecular graphics, computer animation, and 3D scientific visualization. He later served as computer graphics director for the Fujitsu pavilions at Expo 85 and 90 in Japan. [ 67 ] [ 68 ]
In 1974, Alex Schure, a wealthy New York entrepreneur, established the Computer Graphics Laboratory (CGL) at the New York Institute of Technology (NYIT). He put together the most sophisticated studio of the time, with state of the art computers, film and graphic equipment, and hired top technology experts and artists to run it – Ed Catmull , Malcolm Blanchard, Fred Parke and others all from Utah, plus others from around the country including Ralph Guggenheim , Alvy Ray Smith and Ed Emshwiller . During the late 1970s, the staff made numerous innovative contributions to image rendering techniques, and produced many influential software, including the animation program Tween , the paint program Paint , and the animation program SoftCel . Several videos from NYIT become quite famous: Sunstone , by Ed Emshwiller , Inside a Quark , by Ned Greene, and The Works . The latter, written by Lance Williams , was begun in 1978, and was intended to be the first full-length CGI film, but it was never completed, though a trailer for it was shown at SIGGRAPH 1982. In these years, many people regarded NYIT CGI Lab as the top computer animation research and development group in the world. [ 69 ] [ 70 ]
The quality of NYIT's work attracted the attention of George Lucas, who was interested in developing a CGI visual effects facility at his company Lucasfilm . In 1979, he recruited the top talent from NYIT, including Catmull, Smith and Guggenheim to start his division, which later spun off as Pixar , founded in 1986 with funding by Apple Inc. co-founder Steve Jobs .
The framebuffer or framestore is a graphics screen configured with a memory buffer that contains data for a complete screen image. Typically, it is a rectangular array ( raster ) of pixels , and the number of pixels in the width and the height is its "resolution". Color values stored in the pixels can be from 1-bit (monochrome), to 24-bit (true color, 8-bits each for RGB —Red, Green, & Blue), or also 32-bit, with an extra 8-bits used as a transparency mask ( alpha channel ). Before the framebuffer, graphics displays were all vector-based , tracing straight lines from one co-ordinate to another. In 1948, the Manchester Baby computer used a Williams tube , where the 1-bit display was also the memory. An early (perhaps first known) example of a framebuffer was designed in 1969 by A. Michael Noll at Bell Labs , [ 71 ] This early system had just 2-bits, giving it 4 levels of gray scale. A later design had color, using more bits. [ 72 ] [ 73 ] Laurie Spiegel implemented a simple paint program at Bell Labs to allow users to "paint" directly on the framebuffer.
The development of MOS memory ( metal–oxide–semiconductor memory) integrated-circuit chips, particularly high-density DRAM (dynamic random-access memory ) chips with at least 1 kb memory, made it practical to create a digital memory system with framebuffers capable of holding a standard-definition (SD) video image. [ 74 ] [ 75 ] This led to the development of the SuperPaint system by Richard Shoup at Xerox PARC during 1972–1973. [ 74 ] It used a framebuffer displaying 640×480 pixels (standard NTSC video resolution) with eight-bit depth (256 colors). The SuperPaint software contained all the essential elements of later paint packages, allowing the user to paint and modify pixels, using a palette of tools and effects, and thereby making it the first complete computer hardware and software solution for painting and editing images. Shoup also experimented with modifying the output signal using color tables, to allow the system to produce a wider variety of colors than the limited 8-bit range it contained. This scheme would later become commonplace in computer framebuffers. The SuperPaint framebuffer could also be used to capture input images from video. [ 76 ] [ 77 ]
The first commercial framebuffer was produced in 1974 by Evans & Sutherland . It cost about $15,000, with a resolution of 512 by 512 pixels in 8-bit grayscale color, and sold well to graphics researchers without the resources to build their own framebuffer. [ 78 ] A little later, NYIT created the first full-color 24-bit RGB framebuffer by using three of the Evans & Sutherland framebuffers linked together as one device by a minicomputer. Many of the "firsts" that happened at NYIT were based on the development of this first raster graphics system. [ 69 ]
In 1975, the UK company Quantel , founded in 1973 by Peter Michael, [ 79 ] produced the first commercial full-color broadcast framebuffer, the Quantel DFS 3000. It was first used in TV coverage of the 1976 Montreal Olympics to generate a picture-in-picture inset of the Olympic flaming torch while the rest of the picture featured the runner entering the stadium. Framebuffer technology provided the cornerstone for the future development of digital television products. [ 80 ]
By the late 1970s, it became possible for personal computers (such as the Apple II ) to contain low-color framebuffers. However, it was not until the 1980s that a real revolution in the field was seen, and framebuffers capable of holding a standard video image were incorporated into standalone workstations. By the 1990s, framebuffers eventually became the standard for all personal computers.
At this time, a major step forward to the goal of increased realism in 3-D animation came with the development of " fractals ". The term was coined in 1975 by mathematician Benoit Mandelbrot , who used it to extend the theoretical concept of fractional dimensions to geometric patterns in nature, and published in English translation of his book Fractals: Form, Chance and Dimension in 1977. [ 81 ] [ 82 ]
In 1979–80, the first film using fractals to generate the graphics was made by Loren Carpenter of Boeing. Titled Vol Libre , it showed a flight over a fractal landscape, and was presented at SIGGRAPH 1980. [ 83 ] Carpenter was subsequently hired by Pixar to create the fractal planet in the Genesis Effect sequence of Star Trek II: The Wrath of Khan in June 1982. [ 84 ]
Bob Holzman of NASA 's Jet Propulsion Laboratory in California established JPL's Computer Graphics Lab in 1977 as a group with technology expertise in visualizing data being returned from NASA missions. On the advice of Ivan Sutherland, Holzman hired a graduate student from Utah named Jim Blinn . [ 85 ] [ 86 ] Blinn had worked with imaging techniques at Utah, and developed them into a system for NASA's visualization tasks. He produced a series of widely seen "fly-by" simulations, including the Voyager , Pioneer and Galileo spacecraft fly-bys of Jupiter, Saturn and their moons. He also worked with Carl Sagan , creating animations for his Cosmos: A Personal Voyage TV series. Blinn developed many influential new modelling techniques, and wrote papers on them for the IEEE (Institute of Electrical and Electronics Engineers), in their journal Computer Graphics and Applications . Some of these included environment mapping, improved highlight modelling, "blobby" modelling, simulation of wrinkled surfaces, and simulation of butts and dusty surfaces.
Later in the 1980s, Blinn developed CGI animations for an Annenberg/CPB TV series, The Mechanical Universe , which consisted of over 500 scenes for 52 half-hour programs describing physics and mathematics concepts for college students. This he followed with production of another series devoted to mathematical concepts, called Project Mathematics! . [ 87 ]
Motion control photography is a technique that uses a computer to record (or specify) the exact motion of a film camera during a shot, so that the motion can be precisely duplicated again, or alternatively on another computer, and combined with the movement of other sources, such as CGI elements. Early forms of motion control go back to John Whitney 's 1968 work on 2001: A Space Odyssey , and the effects on the 1977 film Star Wars Episode IV: A New Hope , by George Lucas ' newly created company Industrial Light & Magic in California (ILM). ILM created a digitally controlled camera known as the Dykstraflex , which performed complex and repeatable motions around stationary spaceship models, enabling separately filmed elements (spaceships, backgrounds, etc.) to be coordinated more accurately with one another. However, neither of these was actually computer-based—Dykstraflex was essentially a custom-built hard-wired collection of knobs and switches. [ 88 ] The first commercial computer-based motion control and CGI system was developed in 1981 in the UK by Moving Picture Company designer Bill Mather . [ 89 ]
3D computer graphics software began appearing for home computers in the late 1970s. The earliest known example is 3D Art Graphics , a set of 3D computer graphics effects, written by Kazumasa Mitazawa and released in June 1978 for the Apple II . [ 90 ] [ 91 ]
Silicon Graphics , Inc (SGI) was a manufacturer of high-performance computer hardware and software, founded in 1981 by Jim Clark . His idea, called the Geometry Engine , was to create a series of components in a VLSI processor that would accomplish the main operations required in image synthesis—the matrix transforms, clipping, and the scaling operations that provided the transformation to view space. Clark attempted to shop his design around to computer companies, and finding no takers, he and colleagues at Stanford University , California, started their own company, Silicon Graphics. [ 92 ]
SGI's first product (1984) was the IRIS (Integrated Raster Imaging System). It used the 8 MHz M68000 processor with up to 2 MB memory, a custom 1024×1024 frame buffer, and the Geometry Engine to give the workstation its impressive image generation power. Its initial market was 3D graphics display terminals, but SGI's products, strategies and market positions evolved significantly over time, and for many years were a favoured choice for CGI companies in film, TV, and other fields. [ 93 ]
In 1981, Quantel released the " Paintbox ", the first broadcast-quality turnkey system designed for creation and composition of television video and graphics. Its design emphasized the studio workflow efficiency required for live news production. Essentially, it was a framebuffer packaged with innovative user software, and it rapidly found applications in news, weather, station promos, commercials, and the like. Although it was essentially a design tool for still images, it was also sometimes used for frame-by-frame animations. Following its initial launch, it revolutionised the production of television graphics, and some Paintboxes are still in use today due to their image quality, and versatility. [ 94 ]
This was followed in 1982 by the Quantel Mirage , or DVM8000/1 "Digital Video Manipulator", a digital real-time video effects processor. This was based on Quantel's own hardware, plus a Hewlett-Packard computer for custom program effects. It was capable of warping a live video stream by texture mapping it onto an arbitrary three-dimensional shape, around which the viewer could freely rotate or zoom in real-time. It could also interpolate, or morph, between two different shapes. It was considered the first real-time 3D video effects processor, and the progenitor of subsequent DVE (Digital video effect) machines. In 1985, Quantel went on to produce "Harry", the first all-digital non-linear editing and effects compositing system. [ 95 ]
In 1982, Japan's Osaka University developed the LINKS-1 Computer Graphics System , a supercomputer that used up to 257 Zilog Z8001 microprocessors , used for rendering realistic 3D computer graphics . According to the Information Processing Society of Japan: "The core of 3D image rendering is calculating the luminance of each pixel making up a rendered surface from the given viewpoint, light source , and object position. The LINKS-1 system was developed to realize an image rendering methodology in which each pixel could be parallel processed independently using ray tracing . By developing a new software methodology specifically for high-speed image rendering, LINKS-1 was able to rapidly render highly realistic images." It was "used to create the world's first 3D planetarium -like video of the entire heavens that was made completely with computer graphics. The video was presented at the Fujitsu pavilion at the 1985 International Exposition in Tsukuba ." [ 96 ] The LINKS-1 was the world's most powerful computer, as of 1984. [ 97 ]
In the '80s, University of Montreal was at the front run of Computer Animation with three successful short 3-D animated films with 3-D characters.
In 1983, Philippe Bergeron, Nadia Magnenat Thalmann , and Daniel Thalmann directed Dream Flight , considered as the first 3-D generated film telling a story. The film was completely programmed using the MIRA graphical language, [ 98 ] an extension of the Pascal programming language based on Abstract Graphical Data Types . [ 99 ] The film got several awards and was shown at the SIGGRAPH '83 Film Show.
In 1985, Pierre Lachapelle, Philippe Bergeron, Pierre Robidoux and Daniel Langlois directed Tony de Peltrie , which shows the first animated human character to express emotion through facial expressions and body movements, which touched the feelings of the audience. [ 100 ] [ 101 ] Tony de Peltrie premiered as the closing film of SIGGRAPH '85.
In 1987, the Engineering Institute of Canada celebrated its 100th anniversary. A major event, sponsored by Bell Canada and Northern Telecom (now Nortel ), was planned for the Place des Arts in Montreal. For this event, Nadia Magnenat Thalmann and Daniel Thalmann simulated Marilyn Monroe and Humphrey Bogart meeting in a café in the old town section of Montreal. The short movie, called Rendez-vous in Montreal [ 102 ] was shown in numerous festivals and TV channels all over the world.
The Sun Microsystems company was founded in 1982 by Andy Bechtolsheim with other fellow graduate students at Stanford University . Bechtolsheim originally designed the SUN computer as a personal CAD workstation for the Stanford University Network (hence the acronym "SUN"). It was designed around the Motorola 68000 processor with the Unix operating system and virtual memory, and, like SGI, had an embedded frame buffer. [ 103 ] Later developments included computer servers and workstations built on its own RISC-based processor architecture and a suite of software products such as the Solaris operating system, and the Java platform. By the '90s, Sun workstations were popular for rendering in 3-D CGI filmmaking—for example, Disney - Pixar 's 1995 movie Toy Story used a render farm of 117 Sun workstations. [ 104 ] Sun was a proponent of open systems in general and Unix in particular, and a major contributor to open source software . [ 105 ]
The NFB's French-language animation studio founded its Centre d'animatique in 1980, at a cost of $1 million CAD, with a team of six computer graphics specialists. The unit was initially tasked with creating stereoscopic CGI sequences for the NFB's 3-D IMAX film Transitions for Expo 86 . Staff at the Centre d'animatique included Daniel Langlois , who left in 1986 to form Softimage . [ 106 ] [ 107 ]
Also in 1982, the first complete turnkey system designed specifically for creating broadcast-standard animation was produced by the Japanese company Nippon Univac Kaisha ("NUK", later merged with Burroughs ), and incorporated the Antics 2-D computer animation software developed by Alan Kitching from his earlier versions. The configuration was based on the VAX 11/780 computer, linked to a Bosch 1-inch VTR, via NUK's own framebuffer. This framebuffer also showed realtime instant replays of animated vector sequences ("line test"), though finished full-color recording would take many seconds per frame. [ 108 ] [ 109 ] [ 110 ] The full system was successfully sold to broadcasters and animation production companies across Japan. Later in the '80s, Kitching developed versions of Antics for SGI and Apple Mac platforms, and these achieved a wider global distribution. [ 111 ]
The first cinema feature movie to make extensive use of solid 3-D CGI was Walt Disney 's Tron , directed by Steven Lisberger , in 1982. The film is celebrated as a milestone in the industry, though less than twenty minutes of this animation were actually used—mainly the scenes that show digital "terrain", or include vehicles such as Light Cycles , tanks and ships. To create the CGI scenes, Disney turned to the four leading computer graphics firms of the day: Information International Inc , Robert Abel and Associates (both in California), MAGI , and Digital Effects (both in New York). Each worked on a separate aspect of the movie, without any particular collaboration. [ 112 ] Tron was a box office success, grossing $33 million on a budget of $17 million. [ 113 ]
In 1984, Tron was followed by The Last Starfighter , a Universal Pictures / Lorimar production, directed by Nick Castle , and was one of cinema's earliest films to use extensive CGI to depict its many starships, environments and battle scenes. This was a great step forward compared with other films of the day, such as Return of the Jedi , which still used conventional physical models. [ 114 ] The computer graphics for the film were designed by artist Ron Cobb , and rendered by Digital Productions on a Cray X-MP supercomputer. A total of 27 minutes of finished CGI footage was produced—considered an enormous quantity at the time. The company estimated that using computer animation required only half the time, and one half to one third the cost of traditional visual effects. [ 115 ] The movie was a financial success, earning over $28 million on an estimated budget of $15 million. [ 116 ]
The terms inbetweening and morphing are often used interchangeably, and signify the creating of a sequence of images where one image transforms gradually into another image smoothly by small steps. Graphically, an early example would be Charles Philipon 's famous 1831 caricature of French King Louis Philippe turning into a pear (metamorphosis). [ 117 ] " Inbetweening " (AKA "tweening") is a term specifically coined for traditional animation technique, an early example being in E.G.Lutz's 1920 book Animated Cartoons . [ 118 ] In computer animation, inbetweening was used from the beginning (e.g., John Whitney in the '50s, Charles Csuri and Masao Komura in the '60s). [ 41 ] These pioneering examples were vector-based, comprising only outline drawings (as was also usual in conventional animation technique), and would often be described mathematically as " interpolation ". Inbetweening with solid-filled colors appeared in the early '70s, (e.g., Alan Kitching's Antics at Atlas Lab , 1973, [ 57 ] and Peter Foldes ' La Faim at NFBC , 1974 [ 50 ] ), but these were still entirely vector-based.
The term "morphing" did not become current until the late '80s, when it specifically applied to computer inbetweening with photographic images—for example, to make one face transform smoothly into another. The technique uses grids (or "meshes") overlaid on the images, to delineate the shape of key features (eyes, nose, mouth, etc.). Morphing then inbetweens one mesh to the next, and uses the resulting mesh to distort the image and simultaneously dissolve one to another, thereby preserving a coherent internal structure throughout. Thus, several different digital techniques come together in morphing. [ 119 ] Computer distortion of photographic images was first done by NASA , in the mid-1960s, to align Landsat and Skylab satellite images with each other. Texture mapping , which applies a photographic image to a 3D surface in another image, was first defined by Jim Blinn and Martin Newell in 1976. A 1980 paper by Ed Catmull and Alvy Ray Smith on geometric transformations, introduced a mesh-warping algorithm. [ 120 ] The earliest full demonstration of morphing was at the 1982 SIGGRAPH conference, where Tom Brigham of NYIT presented a short film sequence in which a woman transformed, or "morphed", into a lynx.
The first cinema movie to use morphing was Ron Howard 's 1988 fantasy film Willow , where the main character, Willow, uses a magic wand to transform animal to animal to animal and finally, to a sorceress.
With 3-D CGI , the inbetweening of photo-realistic computer models can also produce results similar to morphing, though technically, it is an entirely different process (but is nevertheless often also referred to as "morphing"). An early example is Nelson Max's 1977 film Turning a sphere inside out . [ 67 ] The first cinema feature film to use this technique was the 1986 Star Trek IV: The Voyage Home , directed by Leonard Nimoy , with visual effects by George Lucas 's company Industrial Light & Magic (ILM). The movie includes a dream sequence where the crew travel back in time, and images of their faces transform into one another. To create it, ILM employed a new 3D scanning technology developed by Cyberware to digitize the cast members' heads, and used the resulting data for the computer models. Because each head model had the same number of key points, transforming one character into another was a relatively simple inbetweening. [ 121 ]
In 1989 James Cameron 's underwater action movie The Abyss was released. This was one of the first cinema movies to include photo-realistic CGI integrated seamlessly into live-action scenes. A five-minute sequence featuring an animated tentacle or "pseudopod" was created by ILM, who designed a program to produce surface waves of differing sizes and kinetic properties for the pseudopod, including reflection, refraction and a morphing sequence. Although short, this successful blend of CGI and live-action is widely considered a milestone in setting the direction for further future development in the field. [ 122 ]
The Great Mouse Detective (1986) was the first Disney film to extensively use computer animation, a fact that Disney used to promote the film during marketing. CGI was used during a two-minute climax scene on the Big Ben , inspired by a similar climax scene in Hayao Miyazaki 's The Castle of Cagliostro (1979). The Great Mouse Detective , in turn, paved the way for the Disney Renaissance . [ 123 ] [ 124 ]
The late 1980s saw another milestone in computer animation, this time in 2-D: the development of Disney 's " Computer Animation Production System ", known as "CAPS/ink & paint". This was a custom collection of software, scanners and networked workstations developed by The Walt Disney Company in collaboration with Pixar . Its purpose was to computerize the ink-and-paint and post-production processes of traditionally animated films, to allow more efficient and sophisticated post-production by making the practice of hand-painting cels obsolete. The animators' drawings and background paintings are scanned into the computer, and animation drawings are inked and painted by digital artists. The drawings and backgrounds are then combined, using software that allows for camera movements, multiplane effects, and other techniques—including compositing with 3-D image material. The system's first feature film use was in The Little Mermaid (1989), for the "farewell rainbow" scene near the end, but the first full-scale use was for The Rescuers Down Under (1990), which therefore became the first traditionally animated film to be entirely produced on computer—or indeed, the first 100% digital feature film of any kind ever produced. [ 125 ] [ 126 ]
The 1980s saw the appearance of many notable new commercial software products:
The decade saw some of the first computer-animated television series. For example Quarxs , created by media artist Maurice Benayoun and comic book artist François Schuiten , was an early example of a CGI series based on a real screenplay and not animated solely for demonstrative purposes. [ 135 ] VeggieTales , an American Christian media , is also one of the first computer-animated series. Phil Vischer came up with the idea for VeggieTales while testing animation software as a medium for children's videos in the early 1990s.
The 1990s began with much of CGI technology now sufficiently developed to allow a major expansion into film and TV production. 1991 is widely considered the "breakout year", with two major box-office successes, both making heavy use of CGI.
The first of these was James Cameron 's movie Terminator 2: Judgment Day , [ 136 ] and was the one that first brought CGI to widespread public attention. The technique was used to animate the two "Terminator" robots. The "T-1000" robot was given a "mimetic poly-alloy" (liquid metal) structure, which enabled this shapeshifting character to morph into almost anything it touched. Most of the key Terminator effects were provided by Industrial Light & Magic , and this film was the most ambitious CGI project since the 1982 film Tron . [ 137 ]
The other was Disney 's Beauty and the Beast , [ 138 ] the second traditional 2-D animated film to be entirely made using CAPS . The system also allowed easier combination of hand-drawn art with 3-D CGI material, notably in the "waltz sequence", where Belle and Beast dance through a computer-generated ballroom as the camera " dollies " around them in simulated 3-D space. [ 139 ] Notably, Beauty and the Beast was the first animated film ever to be nominated for a Best Picture Academy Award. [ 140 ]
Another significant step came in 1993, with Steven Spielberg 's Jurassic Park , [ 141 ] where 3-D CGI dinosaurs were integrated with life-sized animatronic counterparts. The CGI animals were created by ILM, and in a test scene to make a direct comparison of both techniques, Spielberg chose the CGI. Also watching was George Lucas who remarked "a major gap had been crossed, and things were never going to be the same." [ 142 ] [ 143 ] [ 144 ]
Flocking is the behavior exhibited when a group of birds (or other animals) move together in a flock. A mathematical model of flocking behavior was first simulated on a computer in 1986 by Craig Reynolds , and soon found its use in animation, beginning with Stanley and Stella in: Breaking the Ice . Jurassic Park notably featured flocking, and brought it to widespread attention by mentioning it in the actual script [ citation needed ] . Other early uses were the flocking bats in Tim Burton 's Batman Returns (1992), and the wildebeest stampede in Disney 's The Lion King (1994). [ 145 ]
With improving hardware, lower costs, and an ever-increasing range of software tools, CGI techniques were soon rapidly taken up in both film and television production.
In 1993, J. Michael Straczynski 's Babylon 5 became the first major television series to use CGI as the primary method for their visual effects (rather than using hand-built models), followed later the same year by Rockne S. O'Bannon 's SeaQuest DSV .
Also the same year, the French company Studio Fantome produced the first full-length completely computer-animated TV series, Insektors (26×13'), [ 146 ] [ 147 ] though they also produced an even earlier all 3-D short series, Geometric Fables (50 x 5') in 1991. [ 148 ] A little later, in 1994, the Canadian TV CGI series ReBoot (48×23') was aired, produced by Mainframe Entertainment and Alliance Atlantis Communications , two companies that also created Beast Wars: Transformers which was released 2 years after ReBoot. [ 149 ]
In 1995, there came the first fully computer-animated feature film, Disney - Pixar 's Toy Story , which was a huge commercial success. [ 150 ] This film was directed by John Lasseter , a co-founder of Pixar, and former Disney animator, who started at Pixar with short movies such as Luxo Jr. (1986), Red's Dream (1987), and Tin Toy (1988), which was also the first computer-generated animated short film to win an Academy Award. Then, after some long negotiations between Disney and Pixar, a partnership deal was agreed in 1991 with the aim of producing a full feature movie, and Toy Story was the result. [ 151 ]
The following years saw a greatly increased uptake of digital animation techniques, with many new studios going into production, and existing companies making a transition from traditional techniques to CGI. Between 1995 and 2005 in the US, the average effects budget for a wide-release feature film leapt from $5 million to $40 million. According to Hutch Parker, President of Production at 20th Century Fox , as of 2005 [update] , "50 percent of feature films have significant effects. They're a character in the movie." However, CGI has made up for the expenditures by grossing over 20% more than their real-life counterparts, and by the early 2000s, computer-generated imagery had become the dominant form of special effects. [ 152 ]
Warner Bros ' 1999 The Iron Giant was the first traditionally-animated feature to have a major character, the title character, to be fully CGI. [ 153 ]
Motion-capture , or "Mo-cap" , records the movement of external objects or people, and has applications for medicine, sports, robotics, and the military, as well as for animation in film, TV and games. The earliest example would be in 1878, with the pioneering photographic work of Eadweard Muybridge on human and animal locomotion, which is still a source for animators today. [ 154 ] Before computer graphics, capturing movements to use in animation would be done using Rotoscoping , where the motion of an actor was filmed, then the film used as a guide for the frame-by-frame motion of a hand-drawn animated character. The first example of this was Max Fleischer 's Out of the Inkwell series in 1915, and a more recent notable example is the 1978 Ralph Bakshi 2-D animated movie The Lord of the Rings .
Computer-based motion-capture started as a photogrammetric analysis tool in biomechanics research in the 1970s and 1980s. [ 155 ] A performer wears markers near each joint to identify the motion by the positions or angles between the markers. Many different types of markers can be used—lights, reflective markers, LEDs, infra-red, inertial, mechanical, or wireless RF—and may be worn as a form of suit, or attached direct to a performer's body. Some systems include details of face and fingers to capture subtle expressions, and such is often referred to as " performance-capture ". The computer records the data from the markers, and uses it to animate digital character models in 2-D or 3-D computer animation, and in some cases this can include camera movement as well. In the 1990s, these techniques became widely used for visual effects.
Video games also began to use motion-capture to animate in-game characters. As early as 1988, an early form of motion-capture was used to animate the 2-D main character of the Martech video game Vixen , which was performed by model Corinne Russell . [ 156 ] Motion-capture was later notably used to animate the 3-D character models in the Sega Model 2 arcade game Virtua Fighter 2 in 1994. [ 157 ] In 1995, examples included the Atari Jaguar CD-based game Highlander: The Last of the MacLeods , [ 158 ] [ 159 ] and the arcade fighting game Soul Edge , which was the first video game to use passive optical motion-capture technology. [ 160 ]
Another breakthrough where a cinema film used motion-capture was creating hundreds of digital characters for the film Titanic in 1997. The technique was used extensively in 1999 to create Jar-Jar Binks and other digital characters in Star Wars: Episode I – The Phantom Menace .
Match moving (also known as motion tracking or camera tracking ), although related to motion capture, is a completely different technique. Instead of using special cameras and sensors to record the motion of subjects, match moving works with pre-existing live-action footage, and uses computer software alone to track specific points in the scene through multiple frames, and thereby allow the insertion of CGI elements into the shot with correct position, scale, orientation, and motion relative to the existing material. The terms are used loosely to describe several different methods of extracting subject or camera motion information from a motion picture. The technique can be 2D or 3D, and can also include matching for camera movements. The earliest commercial software examples being 3D-Equalizer from Science.D.Visions [ 161 ] and rastrack from Hammerhead Productions, [ 162 ] both starting mid-90s.
The first step is identifying suitable features that the software tracking algorithm can lock onto and follow. Typically, features are chosen because they are bright or dark spots, edges or corners, or a facial feature—depending on the particular tracking algorithm being used. When a feature is tracked it becomes a series of 2-D coordinates that represent the position of the feature across the series of frames. Such tracks can be used immediately for 2-D motion tracking, or then be used to calculate 3-D information. In 3-D tracking, a process known as "calibration" derives the motion of the camera from the inverse-projection of the 2-D paths, and from this a "reconstruction" process is used to recreate the photographed subject from the tracked data, and also any camera movement. This then allows an identical virtual camera to be moved in a 3-D animation program, so that new animated elements can be composited back into the original live-action shot in perfectly matched perspective. [ 163 ]
In the 1990s, the technology progressed to the point that it became possible to include virtual stunt doubles. Camera tracking software was refined to allow increasingly complex visual effects developments that were previously impossible. Computer-generated extras also became used extensively in crowd scenes with advanced flocking and crowd simulation software. Being mainly software-based, match moving has become increasingly affordable as computers become cheaper and more powerful. It has become an essential visual effects tool and is even used providing effects in live television broadcasts. [ 164 ]
In television, a virtual studio , or virtual set , is a studio that allows the real-time combination of people or other real objects and computer generated environments and objects in a seamless manner. It requires that the 3-D CGI environment is automatically locked to follow any movements of the live camera and lens precisely. The essence of such system is that it uses some form of camera tracking to create a live stream of data describing the exact camera movement, plus some realtime CGI rendering software that uses the camera tracking data and generates a synthetic image of the virtual set exactly linked to the camera motion. Both streams are then combined with a video mixer, typically using chroma key . Such virtual sets became common in TV programs in the 1990s, with the first practical system of this kind being the Synthevision virtual studio developed by the Japanese broadcasting corporation NHK (Nippon Hoso Kyokai) in 1991, and first used in their science special, Nano-space . [ 165 ] [ 166 ] Virtual studio techniques are also used in filmmaking, but this medium does not have the same requirement to operate entirely in realtime. Motion control or camera tracking can be used separately to generate the CGI elements later, and then combine with the live-action as a post-production process. However, by the 2000s, computer power had improved sufficiently to allow many virtual film sets to be generated in realtime, as in TV, so it was unnecessary to composite anything in post-production.
Machinima uses realtime 3-D computer graphics rendering engines to create a cinematic production. Most often, video games machines are used for this. The Academy of Machinima Arts & Sciences (AMAS), a non-profit organization formed 2002, and dedicated to promoting machinima, defines machinima as "animated filmmaking within a real-time virtual 3-D environment". AMAS recognizes exemplary productions through awards given at its annual [ 167 ] [ 168 ] The practice of using graphics engines from video games arose from the animated software introductions of the '80s " demoscene ", Disney Interactive Studios ' 1992 video game Stunt Island , and '90s recordings of gameplay in first-person shooter video games, such as id Software 's Doom and Quake . Machinima Film Festival. Machinima-based artists are sometimes called machinimists or machinimators.
There were many developments, mergers and deals in the 3-D software industry in the '90s and later.
In 2000, a team led by Paul Debevec managed to adequately capture (and simulate) the reflectance field over the human face using the simplest of light stages . [ 183 ] which was the last missing piece of the puzzle to make digital look-alikes of known actors.
The first mainstream cinema film fully made with motion-capture was the 2001 Japanese-American Final Fantasy: The Spirits Within directed by Hironobu Sakaguchi , which was also the first to use photorealistic CGI characters. [ 184 ] The film was not a box-office success. [ 185 ] Some commentators have suggested this may be partly because the lead CGI characters had facial features that fell into the " uncanny valley ". [ 186 ] In 2002, Peter Jackson's The Lord of the Rings: The Two Towers was the first feature film to use a realtime motion-capture system, which allowed the actions of actor Andy Serkis to be fed direct into the 3-D CGI model of Gollum as it was being performed. [ 187 ]
Motion capture is seen by many as replacing the skills of the animator, and lacking the animator's ability to create exaggerated movements that are impossible to perform live. The end credits of Pixar 's film Ratatouille (2007) carry a stamp certifying it as "100% Pure Animation — No Motion Capture!" However, proponents point out that the technique usually includes a good deal of adjustment work by animators as well. Nevertheless, in 2010, the US Film Academy ( AMPAS ) announced that motion-capture films will no longer be considered eligible for "Best Animated Feature Film" Oscars, stating "Motion capture by itself is not an animation technique." [ 188 ] [ 189 ]
The early 2000s saw the advent of fully virtual cinematography with its audience debut considered to be in the 2003 films The Matrix Reloaded and The Matrix Revolutions with its digital look-alikes so convincing that it is often impossible to know if some image is a human imaged with a camera or a digital look-alike shot with a simulation of a camera. The scenes built and imaged within virtual cinematography are the "Burly brawl" and the end showdown between Neo and Agent Smith . With conventional cinematographic methods the burly brawl would have been prohibitively time-consuming to make with years of compositing required for a scene of few minutes. Also a human actor could not have been used for the end showdown in Matrix Revolutions: Agent Smith's cheekbone gets punched in by Neo leaving the digital look-alike naturally unhurt.
In SIGGRAPH 2013 Activision and USC presented a real-time digital face look-alike of "Ira" using the USC light stage X by Ghosh et al. for both reflectance field and motion capture. [ 190 ] [ 191 ] The result, both precomputed and real-time rendered with the state-of-the-art Graphics processing unit : Digital Ira , [ 190 ] looks fairly realistic. Techniques previously confined to high-end virtual cinematography systems are rapidly moving into the video games and leisure applications .
New developments in computer animation technologies are reported each year in the United States at SIGGRAPH , the largest annual conference on computer graphics and interactive techniques, and also at Eurographics , and at other conferences around the world. [ 192 ] | https://en.wikipedia.org/wiki/History_of_computer_animation |
This article describes the history of computer hardware in Bulgaria . At its peak, Bulgaria supplied 40% of the computers in the socialist economic union COMECON. [ 1 ] The electronics industry employed 300,000 workers, and it generated 8 billion rubles a year. Since the democratic changes in 1989 and the subsequent chaotic political and economic conditions, the once blooming Bulgarian computer industry almost completely disintegrated.
In the 1980s, Bulgaria manufactured computers according to an agreement within the COMECON :
IZOT series and ES EVM series (abbreviation from Edinnaya Sistema Elektronno Vichislitelnih Machin, or Unified Computer System — created in 1969 by USSR, Bulgaria, Hungary, GDR, Poland and Czechoslovakia).
For example, the Pravetz-8M featured two processors (primary: Bulgarian-made clone of 6502 , designated SM630 at 1.018 MHz, secondary: Z80A at 4 MHz), 64 KB DRAM and 16 KB EPROM.
The largest computer factory was some 60 km (37 mi) from Sofia , in Pravetz . Another big facility was the plant "Electronika" in Sofia. Smaller plants throughout the country produced monitors and peripherals, notably DZU ( Diskovi Zapametyavashti Ustroistva — Disk Memory Devices) — Stara Zagora made hard disks for mainframes and personal computers. | https://en.wikipedia.org/wiki/History_of_computer_hardware_in_Bulgaria |
The history of computer science began long before the modern discipline of computer science , usually appearing in forms like mathematics or physics . Developments in previous centuries alluded to the discipline that we now know as computer science. [ 1 ] This progression, from mechanical inventions and mathematical theories towards modern computer concepts and machines , led to the development of a major academic field , massive technological advancement across the Western world , and the basis of massive worldwide trade and culture. [ 2 ]
The earliest known tool for use in computation was the abacus , developed in the period between 2700 and 2300 BCE in Sumer . [ 3 ] The Sumerians' abacus consisted of a table of successive columns which delimited the successive orders of magnitude of their sexagesimal number system. [ 4 ] : 11 Its original style of usage was by lines drawn in sand with pebbles. Abaci of a more modern design are still used as calculation tools today, such as the Chinese abacus . [ 5 ]
In the 5th century BC in ancient India , the grammarian Pāṇini formulated the grammar of Sanskrit in 3959 rules known as the Ashtadhyayi which was highly systematized and technical. Panini used metarules, transformations and recursions . [ 6 ]
The Antikythera mechanism is believed to be an early mechanical analog computer. [ 7 ] It was designed to calculate astronomical positions. It was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete , and has been dated to circa 100 BC. [ 7 ]
Mechanical analog computer devices appeared again a thousand years later in the medieval Islamic world . They were developed by Muslim astronomers , such as the mechanical geared astrolabe by Abū Rayhān al-Bīrūnī , [ 8 ] and the torquetum by Jabir ibn Aflah . [ 9 ] According to Simon Singh , Muslim mathematicians also made important advances in cryptography , such as the development of cryptanalysis and frequency analysis by Alkindus . [ 10 ] [ 11 ] Programmable machines were also invented by Muslim engineers , such as the automatic flute player by the Banū Mūsā brothers. [ 12 ]
Technological artifacts of similar complexity appeared in 14th century Europe , with mechanical astronomical clocks . [ 13 ]
When John Napier discovered logarithms for computational purposes in the early 17th century, [ 14 ] there followed a period of considerable progress by inventors and scientists in making calculating tools. In 1623 Wilhelm Schickard designed the calculating machine as a commission for Johannes Kepler which he named the Calculating Clock, but abandoned the project, when the prototype he had started building was destroyed by a fire in 1624. [ 15 ] Around 1640, Blaise Pascal , a leading French mathematician, constructed a mechanical adding device based on a design described by Greek mathematician Hero of Alexandria . [ 16 ] Then in 1672 Gottfried Wilhelm Leibniz invented the Stepped Reckoner which he completed in 1694. [ 17 ]
In 1837 Charles Babbage first described his Analytical Engine which is accepted as the first design for a modern computer. The analytical engine had expandable memory, an arithmetic unit, and logic processing capabilities that enabled it to interpret a programming language with loops and conditional branching. Although never built, the design has been studied extensively and is understood to be Turing equivalent . The analytical engine would have had a memory capacity of less than 1 kilobyte of memory and a clock speed of less than 10 Hertz . [ 18 ]
Considerable advancement in mathematics and electronics theory was required before the first modern computers could be designed.
In 1702, Gottfried Wilhelm Leibniz developed logic in a formal, mathematical sense with his writings on the binary numeral system. Leibniz simplified the binary system and articulated logical properties such as conjunction, disjunction, negation, identity, inclusion, and the empty set. [ 20 ] He anticipated Lagrangian interpolation and algorithmic information theory . His calculus ratiocinator anticipated aspects of the universal Turing machine . In 1961, Norbert Wiener suggested that Leibniz should be considered the patron saint of cybernetics . [ 21 ] Wiener is quoted with "Indeed, the general idea of a computing machine is nothing but a mechanization of Leibniz's Calculus Ratiocinator." [ 22 ] But it took more than a century before George Boole published his Boolean algebra in 1854 with a complete system that allowed computational processes to be mathematically modeled. [ 23 ]
By this time, the first mechanical devices driven by a binary pattern had been invented. The Industrial Revolution had driven forward the mechanization of many tasks, and this included weaving . Punched cards controlled Joseph Marie Jacquard 's loom in 1801, where a hole punched in the card indicated a binary one and an unpunched spot indicated a binary zero . Jacquard's loom was far from being a computer, but it did illustrate that machines could be driven by binary systems and stored binary information. [ 23 ]
Charles Babbage is often regarded as one of the first pioneers of computing. Beginning in the 1810s, Babbage had a vision of mechanically computing numbers and tables. Putting this into reality, Babbage designed a calculator to compute numbers up to 8 decimal points long. Continuing with the success of this idea, Babbage worked to develop a machine that could compute numbers with up to 20 decimal places. By the 1830s, Babbage had devised a plan to develop a machine that could use punched cards to perform arithmetical operations. The machine would store numbers in memory units, and there would be a form of sequential control. This means that one operation would be carried out before another in such a way that the machine would produce an answer and not fail. This machine was to be known as the "Analytical Engine", which was the first true representation of what is the modern computer. [ 24 ]
Ada Lovelace (Augusta Ada Byron) is credited as the pioneer of computer programming and is regarded as a mathematical genius. Lovelace began working with Charles Babbage as an assistant while Babbage was working on his "Analytical Engine", the first mechanical computer. [ 25 ] During her work with Babbage, Ada Lovelace became the designer of the first computer algorithm, which could compute Bernoulli numbers , [ 26 ] although this is arguable as Charles was the first to design the difference engine and consequently its corresponding difference based algorithms, making him the first computer algorithm designer. Moreover, Lovelace's work with Babbage resulted in her prediction of future computers to not only perform mathematical calculations but also manipulate symbols, mathematical or not. [ 27 ] While she was never able to see the results of her work, as the "Analytical Engine" was not created in her lifetime, her efforts in later years, beginning in the 1840s, did not go unnoticed. [ 28 ]
Following Babbage, although at first unaware of his earlier work, was Percy Ludgate , a clerk to a corn merchant in Dublin, Ireland. He independently designed a programmable mechanical computer, which he described in a work that was published in 1909. [ 29 ] [ 30 ]
Two other inventors, Leonardo Torres Quevedo and Vannevar Bush , also did follow on research based on Babbage's work. In his Essays on Automatics (1914), Torres designed an analytical electromechanical machine that was controlled by a read-only program and introduced the idea of floating-point arithmetic . [ 31 ] [ 32 ] [ 33 ] In 1920, to celebrate the 100th anniversary of the invention of the arithmometer , he presented in Paris the Electromechanical Arithmometer , which consisted of an arithmetic unit connected to a (possibly remote) typewriter, on which commands could be typed and the results printed automatically. [ 34 ] Bush's paper Instrumental Analysis (1936) discussed using existing IBM punch card machines to implement Babbage's design. In the same year he started the Rapid Arithmetical Machine project to investigate the problems of constructing an electronic digital computer. [ 35 ]
In an 1886 letter, Charles Sanders Peirce described how logical operations could be carried out by electrical switching circuits. [ 36 ] During 1880–81 he showed that NOR gates alone (or alternatively NAND gates alone ) can be used to reproduce the functions of all the other logic gates , but this work on it was unpublished until 1933. [ 37 ] The first published proof was by Henry M. Sheffer in 1913, so the NAND logical operation is sometimes called Sheffer stroke ; the logical NOR is sometimes called Peirce's arrow . [ 38 ] Consequently, these gates are sometimes called universal logic gates . [ 39 ]
Eventually, vacuum tubes replaced relays for logic operations. Lee De Forest 's modification, in 1907, of the Fleming valve can be used as a logic gate. Ludwig Wittgenstein introduced a version of the 16-row truth table as proposition 5.101 of Tractatus Logico-Philosophicus (1921). Walther Bothe , inventor of the coincidence circuit , got part of the 1954 Nobel Prize in physics, for the first modern electronic AND gate in 1924. Konrad Zuse designed and built electromechanical logic gates for his computer Z1 (from 1935 to 1938).
Up to and during the 1930s, electrical engineers were able to build electronic circuits to solve mathematical and logic problems, but most did so in an ad hoc manner, lacking any theoretical rigor. This changed with switching circuit theory in the 1930s. From 1934 to 1936, Akira Nakashima , Claude Shannon , and Viktor Shetakov published a series of papers showing that the two-valued Boolean algebra , can describe the operation of switching circuits. [ 40 ] [ 41 ] [ 42 ] [ 43 ] This concept, of utilizing the properties of electrical switches to do logic, is the basic concept that underlies all electronic digital computers . Switching circuit theory provided the mathematical foundations and tools for digital system design in almost all areas of modern technology. [ 43 ]
While taking an undergraduate philosophy class, Shannon had been exposed to Boole's work, and recognized that it could be used to arrange electromechanical relays (then used in telephone routing switches) to solve logic problems. His thesis became the foundation of practical digital circuit design when it became widely known among the electrical engineering community during and after World War II. [ 44 ]
Before the 1920s, computers (sometimes computors ) were human clerks that performed computations. They were usually under the lead of a physicist. Many thousands of computers were employed in commerce, government, and research establishments. Many of these clerks who served as human computers were women. [ 45 ] [ 46 ] [ 47 ] [ 48 ] Some performed astronomical calculations for calendars, others ballistic tables for the military. [ 49 ]
After the 1920s, the expression computing machine referred to any machine that performed the work of a human computer, especially those in accordance with effective methods of the Church-Turing thesis . The thesis states that a mathematical method is effective if it could be set out as a list of instructions able to be followed by a human clerk with paper and pencil, for as long as necessary, and without ingenuity or insight.
Machines that computed with continuous values became known as the analog kind. They used machinery that represented continuous numeric quantities, like the angle of a shaft rotation or difference in electrical potential.
Digital machinery, in contrast to analog, were able to render a state of a numeric value and store each individual digit. Digital machinery used difference engines or relays before the invention of faster memory devices.
The phrase computing machine gradually gave way, after the late 1940s, to just computer as the onset of electronic digital machinery became common. These computers were able to perform the calculations that were performed by the previous human clerks.
Since the values stored by digital machines were not bound to physical properties like analog devices, a logical computer, based on digital equipment, was able to do anything that could be described "purely mechanical." The theoretical Turing Machine , created by Alan Turing , is a hypothetical device theorized in order to study the properties of such hardware.
The mathematical foundations of modern computer science began to be laid by Kurt Gödel with his incompleteness theorem (1931). In this theorem, he showed that there were limits to what could be proved and disproved within a formal system . This led to work by Gödel and others to define and describe these formal systems, including concepts such as mu-recursive functions and lambda-definable functions . [ 50 ]
In 1936 Alan Turing and Alonzo Church independently, and also together, introduced the formalization of an algorithm , with limits on what can be computed, and a "purely mechanical" model for computing. [ 51 ] This became the Church–Turing thesis , a hypothesis about the nature of mechanical calculation devices, such as electronic computers. The thesis states that any calculation that is possible can be performed by an algorithm running on a computer, provided that sufficient time and storage space are available. [ 51 ]
In 1936, Alan Turing also published his seminal work on the Turing machines , an abstract digital computing machine which is now simply referred to as the Universal Turing machine . This machine invented the principle of the modern computer and was the birthplace of the stored program concept that almost all modern day computers use. [ 52 ] These hypothetical machines were designed to formally determine, mathematically, what can be computed, taking into account limitations on computing ability. If a Turing machine can complete the task, it is considered Turing computable . [ 53 ]
The Los Alamos physicist Stanley Frankel , has described John von Neumann 's view of the fundamental importance of Turing's 1936 paper, in a letter: [ 52 ]
I know that in or about 1943 or ‘44 von Neumann was well aware of the fundamental importance of Turing's paper of 1936… Von Neumann introduced me to that paper and at his urging I studied it with care. Many people have acclaimed von Neumann as the "father of the computer" (in a modern sense of the term) but I am sure that he would never have made that mistake himself. He might well be called the midwife, perhaps, but he firmly emphasized to me, and to others I am sure, that the fundamental conception is owing to Turing...
Kathleen Booth wrote the first assembly language and designed the assembler and autocode for the Automatic Relay Calculator (ARC) at Birkbeck College, University of London . [ 54 ] She helped design three different machines including the ARC, SEC ( Simple Electronic Computer ), and APE(X)C .
The world's first electronic digital computer, the Atanasoff–Berry computer , was built on the Iowa State campus from 1939 through 1942 by John V. Atanasoff , a professor of physics and mathematics, and Clifford Berry , an engineering graduate student.
In 1941, Konrad Zuse developed the world's first functional program-controlled computer, the Z3 . In 1998, it was shown to be Turing-complete in principle. [ 57 ] [ 58 ] Zuse also developed the S2 computing machine, considered the first process control computer. He founded one of the earliest computer businesses in 1941, producing the Z4 , which became the world's first commercial computer. In 1946, he designed the first high-level programming language , Plankalkül . [ 59 ]
In 1948, the Manchester Baby was completed; it was the world's first electronic digital computer that ran programs stored in its memory, like almost all modern computers. [ 52 ] The influence on Max Newman of Turing's seminal 1936 paper on the Turing Machines and of his logico-mathematical contributions to the project, were both crucial to the successful development of the Baby. [ 52 ]
In 1950, Britain's National Physical Laboratory completed Pilot ACE , a small scale programmable computer, based on Turing's philosophy. With an operating speed of 1 MHz, the Pilot Model ACE was for some time the fastest computer in the world. [ 52 ] [ 60 ] Turing's design for ACE had much in common with today's RISC architectures and it called for a high-speed memory of roughly the same capacity as an early Macintosh computer, which was enormous by the standards of his day. [ 52 ] Had Turing's ACE been built as planned and in full, it would have been in a different league from the other early computers. [ 52 ]
Later in the 1950s, the first operating system , GM-NAA I/O , supporting batch processing to allow jobs to be run with less operator intervention, was developed by General Motors and North American Aviation for the IBM 701 .
In 1969, an experiment was conducted by two research teams at UCLA and Stanford to create a network between 2 computers although the system crashed during the initial attempt to connect to the other computer but was a huge step towards the Internet.
The first actual computer bug was a moth . It was stuck in between the relays on the Harvard Mark II. [ 61 ] While the invention of the term 'bug' is often but erroneously attributed to Grace Hopper , a future rear admiral in the U.S. Navy, who supposedly logged the "bug" on September 9, 1945, most other accounts conflict at least with these details. According to these accounts, the actual date was September 9, 1947 when operators filed this 'incident' — along with the insect and the notation "First actual case of bug being found" (see software bug for details). [ 61 ]
Claude Shannon went on to found the field of information theory with his 1948 paper titled A Mathematical Theory of Communication , which applied probability theory to the problem of how to best encode the information a sender wants to transmit. This work is one of the theoretical foundations for many areas of study, including data compression and cryptography . [ 62 ]
From experiments with anti-aircraft systems that interpreted radar images to detect enemy planes, Norbert Wiener coined the term cybernetics from the Greek word for "steersman." He published "Cybernetics" in 1948, which influenced artificial intelligence . Wiener also compared computation , computing machinery, memory devices, and other cognitive similarities with his analysis of brain waves. [ 63 ]
In 1946, a model for computer architecture was introduced and became known as Von Neumann architecture . Since 1950, the von Neumann model provided uniformity in subsequent computer designs. The von Neumann architecture was considered innovative as it introduced an idea of allowing machine instructions and data to share memory space. [ citation needed ] The von Neumann model is composed of three major parts, the arithmetic logic unit (ALU), the memory, and the instruction processing unit (IPU). In von Neumann machine design, the IPU passes addresses to memory, and memory, in turn, is routed either back to the IPU if an instruction is being fetched or to the ALU if data is being fetched. [ 64 ]
Von Neumann's machine design uses a RISC (Reduced instruction set computing) architecture, [ dubious – discuss ] which means the instruction set uses a total of 21 instructions to perform all tasks. (This is in contrast to CISC, complex instruction set computing , instruction sets which have more instructions from which to choose.) With von Neumann architecture, main memory along with the accumulator (the register that holds the result of logical operations) [ 65 ] are the two memories that are addressed. Operations can be carried out as simple arithmetic (these are performed by the ALU and include addition, subtraction, multiplication and division), conditional branches (these are more commonly seen now as if statements or while loops. The branches serve as go to statements), and logical moves between the different components of the machine, i.e., a move from the accumulator to memory or vice versa. Von Neumann architecture accepts fractions and instructions as data types. Finally, as the von Neumann architecture is a simple one, its register management is also simple. The architecture uses a set of seven registers to manipulate and interpret fetched data and instructions. These registers include the "IR" (instruction register), "IBR" (instruction buffer register), "MQ" (multiplier quotient register), "MAR" (memory address register), and "MDR" (memory data register)." [ 64 ] The architecture also uses a program counter ("PC") to keep track of where in the program the machine is. [ 64 ]
The term artificial intelligence was credited by John McCarthy to explain the research that they were doing for a proposal for the Dartmouth Summer Research . The naming of artificial intelligence also led to the birth of a new field in computer science. [ 66 ] On August 31, 1955, a research project was proposed consisting of John McCarthy, Marvin L. Minsky, Nathaniel Rochester , and Claude E. Shannon . The official project began in 1956 that consisted of several significant parts they felt would help them better understand artificial intelligence's makeup.
McCarthy and his colleagues' ideas behind automatic computers was while a machine is capable of completing a task, then the same should be confirmed with a computer by compiling a program to perform the desired results. They also discovered that the human brain was too complex to replicate, not by the machine itself but by the program. The knowledge to produce a program that sophisticated was not there yet.
The concept behind this was looking at how humans understand our own language and structure of how we form sentences, giving different meaning and rule sets and comparing them to a machine process. The way computers can understand is at a hardware level. This language is written in binary (1s and 0's). This has to be written in a specific format that gives the computer the ruleset to run a particular hardware piece. [ 67 ]
Minsky's process determined how these artificial neural networks could be arranged to have similar qualities to the human brain. However, he could only produce partial results and needed to further the research into this idea.
McCarthy and Shannon's idea behind this theory was to develop a way to use complex problems to determine and measure the machine's efficiency through mathematical theory and computations . [ 68 ] However, they were only to receive partial test results.
The idea behind self-improvement is how a machine would use self-modifying code to make itself smarter. This would allow for a machine to grow in intelligence and increase calculation speeds. [ 69 ] The group believed they could study this if a machine could improve upon the process of completing a task in the abstractions part of their research.
The group thought that research in this category could be broken down into smaller groups. This would consist of sensory and other forms of information about artificial intelligence. Abstractions in computer science can refer to mathematics and programming language. [ 70 ]
Their idea of computational creativity is how the program or a machine can be seen in having similar ways of human thinking. [ 71 ] They wanted to see if a machine could take a piece of incomplete information and improve upon it to fill in the missing details as the human mind can do. If this machine could do this; they needed to think of how did the machine determine the outcome. | https://en.wikipedia.org/wiki/History_of_computer_science |
The history of computing is longer than the history of computing hardware and modern computing technology and includes the history of methods intended for pen and paper or for chalk and slate, with or without the aid of tables.
Digital computing is intimately tied to the representation of numbers . [ 1 ] But long before abstractions like the number arose, there were mathematical concepts to serve the purposes of civilization. These concepts are implicit in concrete practices such as:
Eventually, the concept of numbers became concrete and familiar enough for counting to arise, at times with sing-song mnemonics to teach sequences to others. All known human languages, except the Piraha language , have words for at least the numerals "one" and "two", and even some animals like the blackbird can distinguish a surprising number of items. [ 5 ]
Advances in the numeral system and mathematical notation eventually led to the discovery of mathematical operations such as addition, subtraction, multiplication, division, squaring, square root, and so forth. Eventually, the operations were formalized, and concepts about the operations became understood well enough to be stated formally , and even proven . See, for example, Euclid's algorithm for finding the greatest common divisor of two numbers.
By the High Middle Ages, the positional Hindu–Arabic numeral system had reached Europe , which allowed for the systematic computation of numbers. During this period, the representation of a calculation on paper allowed the calculation of mathematical expressions , and the tabulation of mathematical functions such as the square root and the common logarithm (for use in multiplication and division), and the trigonometric functions . By the time of Isaac Newton 's research, paper or vellum was an important computing resource , and even in our present time, researchers like Enrico Fermi would cover random scraps of paper with calculation, to satisfy their curiosity about an equation. [ 6 ] Even into the period of programmable calculators, Richard Feynman would unhesitatingly compute any steps that overflowed the memory of the calculators, by hand, just to learn the answer; by 1976 Feynman had purchased an HP-25 calculator with a 49 program-step capacity; if a differential equation required more than 49 steps to solve, he could just continue his computation by hand. [ 7 ]
Mathematical statements need not be abstract only; when a statement can be illustrated with actual numbers, the numbers can be communicated and a community can arise. This allows the repeatable, verifiable statements which are the hallmark of mathematics and science. These kinds of statements have existed for thousands of years, and across multiple civilizations, as shown below:
The earliest known tool for use in computation is the Sumerian abacus , and it was thought to have been invented in Babylon c. 2700 –2300 BC. Its original style of usage was by lines drawn in sand with pebbles. [ citation needed ]
In c. 1050 –771 BC, the south-pointing chariot was invented in ancient China . It was the first known geared mechanism to use a differential gear , which was later used in analog computers . The Chinese also invented a more sophisticated abacus from around the 2nd century BC known as the Chinese abacus . [ citation needed ]
In the 3rd century BC, Archimedes used the mechanical principle of balance (see Archimedes Palimpsest § The Method of Mechanical Theorems ) to calculate mathematical problems, such as the number of grains of sand in the universe ( The sand reckoner ), which also required a recursive notation for numbers (e.g., the myriad myriad ).
The Antikythera mechanism is believed to be the earliest known geared computing device. It was designed to calculate astronomical positions. It was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete , and has been dated to circa 100 BC. [ 8 ]
According to Simon Singh , Muslim mathematicians also made important advances in cryptography , such as the development of cryptanalysis and frequency analysis by Alkindus . [ 9 ] [ 10 ] Programmable machines were also invented by Muslim engineers , such as the automatic flute player by the Banū Mūsā brothers . [ 11 ]
During the Middle Ages, several European philosophers made attempts to produce analog computer devices. Influenced by the Arabs and Scholasticism , Majorcan philosopher Ramon Llull (1232–1315) devoted a great part of his life to defining and designing several logical machines that, by combining simple and undeniable philosophical truths, could produce all possible knowledge. These machines were never actually built, as they were more of a thought experiment to produce new knowledge in systematic ways; although they could make simple logical operations, they still needed a human being for the interpretation of results. Moreover, they lacked a versatile architecture, each machine serving only very concrete purposes. Despite this, Llull's work had a strong influence on Gottfried Leibniz (early 18th century), who developed his ideas further and built several calculating tools using them.
The apex of this early era of mechanical computing can be seen in the Difference Engine and its successor the Analytical Engine both by Charles Babbage . Babbage never completed constructing either engine, but in 2002 Doron Swade and a group of other engineers at the Science Museum in London completed Babbage's Difference Engine using only materials that would have been available in the 1840s. [ 12 ] By following Babbage's detailed design they were able to build a functioning engine, allowing historians to say, with some confidence, that if Babbage had been able to complete his Difference Engine it would have worked. [ 13 ] The additionally advanced Analytical Engine combined concepts from his previous work and that of others to create a device that, if constructed as designed, would have possessed many properties of a modern electronic computer, such as an internal "scratch memory" equivalent to RAM , multiple forms of output including a bell, a graph-plotter, and simple printer, and a programmable input-output "hard" memory of punch cards which it could modify as well as read. The key advancement that Babbage's devices possessed beyond those created before him was that each component of the device was independent of the rest of the machine, much like the components of a modern electronic computer. This was a fundamental shift in thought; previous computational devices served only a single purpose but had to be at best disassembled and reconfigured to solve a new problem. Babbage's devices could be reprogrammed to solve new problems by the entry of new data and act upon previous calculations within the same series of instructions. Ada Lovelace took this concept one step further, by creating a program for the Analytical Engine to calculate Bernoulli numbers , a complex calculation requiring a recursive algorithm. This is considered to be the first example of a true computer program, a series of instructions that act upon data not known in full until the program is run.
Following Babbage, although unaware of his earlier work, Percy Ludgate [ 14 ] [ 15 ] in 1909 published the 2nd of the only two designs for mechanical analytical engines in history. [ 16 ] Two other inventors, Leonardo Torres Quevedo [ 17 ] and Vannevar Bush , [ 18 ] also did follow-on research based on Babbage's work. In his Essays on Automatics (1914) Torres presented the design of an electromechanical calculating machine and introduced the idea of Floating-point arithmetic . [ 19 ] [ 20 ] In 1920, to celebrate the 100th anniversary of the invention of the arithmometer , Torres presented in Paris the Electromechanical Arithmometer , an arithmetic unit connected to a remote typewriter, on which commands could be typed and the results printed automatically. [ 21 ] [ 22 ] Bush's paper Instrumental Analysis (1936) discussed using existing IBM punch card machines to implement Babbage's design. In the same year, he started the Rapid Arithmetical Machine project to investigate the problems of constructing an electronic digital computer.
Several examples of analog computation survived into recent times. A planimeter is a device that does integrals, using distance as the analog quantity. Until the 1980s, HVAC systems used air both as the analog quantity and the controlling element. Unlike modern digital computers, analog computers are not very flexible and need to be reconfigured (i.e., reprogrammed) manually to switch them from working on one problem to another. Analog computers had an advantage over early digital computers in that they could be used to solve complex problems using behavioral analogues while the earliest attempts at digital computers were quite limited.
Since computers were rare in this era, the solutions were often hard-coded into paper forms such as nomograms , [ 23 ] which could then produce analog solutions to these problems, such as the distribution of pressures and temperatures in a heating system.
The "brain" [computer] may one day come down to our level [of the common people] and help with our income-tax and book-keeping calculations. But this is speculation and there is no sign of it so far.
In an 1886 letter, Charles Sanders Peirce described how logical operations could be carried out by electrical switching circuits. [ 25 ] During 1880-81 he showed that NOR gates alone (or NAND gates alone ) can be used to reproduce the functions of all the other logic gates , but this work on it was unpublished until 1933. [ 26 ] The first published proof was by Henry M. Sheffer in 1913, so the NAND logical operation is sometimes called Sheffer stroke ; the logical NOR is sometimes called Peirce's arrow . [ 27 ] Consequently, these gates are sometimes called universal logic gates . [ 28 ]
Eventually, vacuum tubes replaced relays for logic operations. Lee De Forest 's modification, in 1907, of the Fleming valve can be used as a logic gate. Ludwig Wittgenstein introduced a version of the 16-row truth table as proposition 5.101 of Tractatus Logico-Philosophicus (1921). Walther Bothe , inventor of the coincidence circuit , got part of the 1954 Nobel Prize in physics, for the first modern electronic AND gate in 1924. Konrad Zuse designed and built electromechanical logic gates for his computer Z1 (from 1935 to 1938).
The first recorded idea of using digital electronics for computing was the 1931 paper "The Use of Thyratrons for High Speed Automatic Counting of Physical Phenomena" by C. E. Wynn-Williams . [ 29 ] From 1934 to 1936, NEC engineer Akira Nakashima , Claude Shannon , and Victor Shestakov published papers introducing switching circuit theory , using digital electronics for Boolean algebraic operations. [ 30 ] [ 31 ] [ 32 ] [ 33 ]
In 1936 Alan Turing published his seminal paper On Computable Numbers, with an Application to the Entscheidungsproblem [ 34 ] in which he modeled computation in terms of a one-dimensional storage tape, leading to the idea of the Universal Turing machine and Turing-complete systems. [ citation needed ]
The first digital electronic computer was developed in the period April 1936 - June 1939, in the IBM Patent Department, Endicott, New York by Arthur Halsey Dickinson. [ 35 ] [ 36 ] [ 37 ] In this computer IBM introduced, a calculating device with a keyboard, processor and electronic output (display). The competitor to IBM was the digital electronic computer NCR3566, developed in NCR, Dayton, Ohio by Joseph Desch and Robert Mumma in the period April 1939 - August 1939. [ 38 ] [ 39 ] The IBM and NCR machines were decimal, executing addition and subtraction in binary position code.
In December 1939 John Atanasoff and Clifford Berry completed their experimental model to prove the concept of the Atanasoff–Berry computer (ABC) which began development in 1937. [ 40 ] This experimental model is binary, executed addition and subtraction in octal binary code and is the first binary digital electronic computing device. The Atanasoff–Berry computer was intended to solve systems of linear equations, though it was not programmable. The computer was never truly completed due to Atanasoff's departure from Iowa State University in 1942 to work for the United States Navy. [ 41 ] [ 42 ] Many people credit ABC with many of the ideas used in later developments during the age of early electronic computing. [ 43 ]
The Z3 computer , built by German inventor Konrad Zuse in 1941, was the first programmable, fully automatic computing machine, but it was not electronic.
During World War II, ballistics computing was done by women, who were hired as "computers." The term computer remained one that referred to mostly women (now seen as "operator") until 1945, after which it took on the modern definition of machinery it presently holds. [ 44 ]
The ENIAC (Electronic Numerical Integrator And Computer) was the first electronic general-purpose computer, announced to the public in 1946. It was Turing-complete, [ 45 ] digital, and capable of being reprogrammed to solve a full range of computing problems. Women implemented the programming for machines like the ENIAC, and men created the hardware. [ 44 ]
The Manchester Baby was the first electronic stored-program computer . It was built at the Victoria University of Manchester by Frederic C. Williams , Tom Kilburn and Geoff Tootill , and ran its first program on 21 June 1948. [ 46 ]
William Shockley , John Bardeen and Walter Brattain at Bell Labs invented the first working transistor , the point-contact transistor , in 1947, followed by the bipolar junction transistor in 1948. [ 47 ] [ 48 ] At the University of Manchester in 1953, a team under the leadership of Tom Kilburn designed and built the first transistorized computer , called the Transistor Computer , a machine using the newly developed transistors instead of valves. [ 49 ] The first stored-program transistor computer was the ETL Mark III, developed by Japan's Electrotechnical Laboratory [ 50 ] [ 51 ] [ 52 ] from 1954 [ 53 ] to 1956. [ 51 ] However, early junction transistors were relatively bulky devices that were difficult to manufacture on a mass-production basis, which limited them to a number of specialized applications. [ 54 ]
In 1954, 95% of computers in service were being used for engineering and scientific purposes. [ 55 ]
The metal–oxide–silicon field-effect transistor (MOSFET), also known as the MOS transistor, was invented at Bell Labs between 1955 and 1960, [ 56 ] [ 57 ] [ 58 ] [ 59 ] [ 60 ] [ 61 ] [ 62 ] It was the first truly compact transistor that could be miniaturised and mass-produced for a wide range of uses. [ 54 ] The MOSFET made it possible to build high-density integrated circuit chips. [ 63 ] [ 64 ] The MOSFET is the most widely used transistor in computers, [ 65 ] [ 66 ] and is the fundamental building block of digital electronics . [ 67 ]
The silicon-gate MOS integrated circuit was developed by Federico Faggin at Fairchild Semiconductor in 1968. [ 68 ] This led to the development of the first single-chip microprocessor , the Intel 4004 . [ 69 ] The Intel 4004 was developed as a single-chip microprocessor from 1969 to 1970, led by Intel's Federico Faggin, Marcian Hoff , and Stanley Mazor , and Busicom's Masatoshi Shima. [ 70 ] The chip was mainly designed and realized by Faggin, with his silicon-gate MOS technology. [ 69 ] The microprocessor led to the microcomputer revolution, with the development of the microcomputer , which would later be called the personal computer (PC).
Most early microprocessors, such as the Intel 8008 and Intel 8080 , were 8-bit . Texas Instruments released the first fully 16-bit microprocessor, the TMS9900 processor, in June 1976. [ 71 ] They used the microprocessor in the TI-99/4 and TI-99/4A computers.
The 1980s brought about significant advances with microprocessors that greatly impacted the fields of engineering and other sciences. The Motorola 68000 microprocessor had a processing speed that was far superior to the other microprocessors being used at the time. Because of this, having a newer, faster microprocessor allowed for the newer microcomputers that came along after to be more efficient in the amount of computing they were able to do. This was evident in the 1983 release of the Apple Lisa . The Lisa was one of the first personal computers with a graphical user interface (GUI) that was sold commercially. It ran on the Motorola 68000 CPU and used both dual floppy disk drives and a 5 MB hard drive for storage. The machine also had 1MB of RAM used for running software from disk without rereading the disk persistently. [ 72 ] After the failure of the Lisa in terms of sales, Apple released its first Macintosh computer, still running on the Motorola 68000 microprocessor, but with only 128KB of RAM, one floppy drive, and no hard drive to lower the price.
In the late 1980s and early 1990s, computers became more useful for personal and work purposes, such as word processing . [ 73 ] In 1989, Apple released the Macintosh Portable , it weighed 7.3 kg (16 lb) and was extremely expensive, costing US$7,300. At launch, it was one of the most powerful laptops available, but due to the price and weight, it was not met with great success and was discontinued only two years later. That same year Intel introduced the Touchstone Delta supercomputer , which had 512 microprocessors. This technological advancement was very significant, as it was used as a model for some of the fastest multi-processor systems in the world. It was even used as a prototype for Caltech researchers, who used the model for projects like real-time processing of satellite images and simulating molecular models for various fields of research.
In terms of supercomputing, the first widely acknowledged supercomputer was the Control Data Corporation (CDC) 6600 [ 74 ] built in 1964 by Seymour Cray . Its maximum speed was 40 MHz or 3 million floating point operations per second ( FLOPS ). The CDC 6600 was replaced by the CDC 7600 in 1969; [ 75 ] although its normal clock speed was not faster than the 6600, the 7600 was still faster due to its peak clock speed, which was approximately 30 times faster than that of the 6600. Although CDC was a leader in supercomputers, their relationship with Seymour Cray (which had already been deteriorating) completely collapsed. In 1972, Cray left CDC and began his own company, Cray Research Inc . [ 76 ] With support from investors in Wall Street, an industry fueled by the Cold War, and without the restrictions he had within CDC, he created the Cray-1 supercomputer. With a clock speed of 80 MHz or 136 megaFLOPS, Cray developed a name for himself in the computing world. By 1982, Cray Research produced the Cray X-MP equipped with multiprocessing and in 1985 released the Cray-2 , which continued with the trend of multiprocessing and clocked at 1.9 gigaFLOPS. Cray Research developed the Cray Y-MP in 1988, however afterward struggled to continue to produce supercomputers. This was largely because the Cold War had ended, and the demand for cutting-edge computing by colleges and the government declined drastically and the demand for microprocessing units increased.
In 1998, David Bader developed the first Linux supercomputer using commodity parts. [ 77 ] While at the University of New Mexico, Bader sought to build a supercomputer running Linux using consumer off-the-shelf parts and a high-speed low-latency interconnection network. The prototype utilized an Alta Technologies "AltaCluster" of eight dual, 333 MHz, Intel Pentium II computers running a modified Linux kernel. Bader ported a significant amount of software to provide Linux support for necessary components as well as code from members of the National Computational Science Alliance (NCSA) to ensure interoperability, as none of it had been run on Linux previously. [ 78 ] Using the successful prototype design, he led the development of "RoadRunner," the first Linux supercomputer for open use by the national science and engineering community via the National Science Foundation's National Technology Grid. RoadRunner was put into production use in April 1999. At the time of its deployment, it was considered one of the 100 fastest supercomputers in the world. [ 78 ] [ 79 ] Though Linux-based clusters using consumer-grade parts, such as Beowulf , existed before the development of Bader's prototype and RoadRunner, they lacked the scalability, bandwidth, and parallel computing capabilities to be considered "true" supercomputers. [ 78 ]
Today, supercomputers are still used by the governments of the world and educational institutions for computations such as simulations of natural disasters, genetic variant searches within a population relating to disease, and more. As of November 2024 [update] , the fastest supercomputer is El Capitan .
Starting with known special cases, the calculation of logarithms and trigonometric functions can be performed by looking up numbers in a mathematical table , and interpolating between known cases. For small enough differences, this linear operation was accurate enough for use in navigation and astronomy in the Age of Exploration . The uses of interpolation have thrived in the past 500 years: by the twentieth century Leslie Comrie and W.J. Eckert systematized the use of interpolation in tables of numbers for punch card calculation.
The numerical solution of differential equations, notably the Navier-Stokes equations was an important stimulus to computing,
with Lewis Fry Richardson 's numerical approach to solving differential equations. The first computerized weather forecast was performed in 1950 by a team composed of American meteorologists Jule Charney , Philip Duncan Thompson , Larry Gates, and Norwegian meteorologist Ragnar Fjørtoft , applied mathematician John von Neumann , and ENIAC programmer Klara Dan von Neumann . [ 80 ] [ 81 ] [ 82 ] To this day, some of the most powerful computer systems on Earth are used for weather forecasts . [ 83 ]
By the late 1960s, computer systems could perform symbolic algebraic manipulations well enough to pass college-level calculus courses. [ citation needed ]
Women are often underrepresented in STEM fields when compared to their male counterparts. [ 84 ] In the modern era before the 1960s, computing was widely seen as "women's work" since it was associated with the operation of tabulating machines and other mechanical office work. [ 85 ] [ 86 ] The accuracy of this association varied from place to place. In America, Margaret Hamilton recalled an environment dominated by men, [ 87 ] while Elsie Shutt recalled surprise at seeing even half of the computer operators at Raytheon were men. [ 88 ] Machine operators in Britain were mostly women into the early 1970s. [ 89 ] As these perceptions changed and computing became a high-status career, the field became more dominated by men. [ 90 ] [ 91 ] [ 92 ] Professor Janet Abbate , in her book Recoding Gender , writes:
Yet women were a significant presence in the early decades of computing. They made up the majority of the first computer programmers during World War II; they held positions of responsibility and influence in the early computer industry; and they were employed in numbers that, while a small minority of the total, compared favorably with women's representation in many other areas of science and engineering. Some female programmers of the 1950s and 1960s would have scoffed at the notion that programming would ever be considered a masculine occupation, yet these women’s experiences and contributions were forgotten all too quickly. [ 93 ]
Some notable examples of women in the history of computing are: | https://en.wikipedia.org/wiki/History_of_computing |
The history of computing hardware spans the developments from early devices used for simple calculations to today's complex computers, encompassing advancements in both analog and digital technology.
The first aids to computation were purely mechanical devices which required the operator to set up the initial values of an elementary arithmetic operation, then manipulate the device to obtain the result. In later stages, computing devices began representing numbers in continuous forms, such as by distance along a scale, rotation of a shaft, or a specific voltage level. Numbers could also be represented in the form of digits, automatically manipulated by a mechanism. Although this approach generally required more complex mechanisms, it greatly increased the precision of results. The development of transistor technology, followed by the invention of integrated circuit chips, led to revolutionary breakthroughs. Transistor-based computers and, later, integrated circuit-based computers enabled digital systems to gradually replace analog systems, increasing both efficiency and processing power. Metal-oxide-semiconductor (MOS) large-scale integration (LSI) then enabled semiconductor memory and the microprocessor , leading to another key breakthrough, the miniaturized personal computer (PC), in the 1970s. The cost of computers gradually became so low that personal computers by the 1990s, and then mobile computers ( smartphones and tablets ) in the 2000s, became ubiquitous.
Devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers . The earliest counting device was probably a form of tally stick . The Lebombo bone from the mountains between Eswatini and South Africa may be the oldest known mathematical artifact. [ 2 ] It dates from 35,000 BCE and consists of 29 distinct notches that were deliberately cut into a baboon 's fibula . [ 3 ] [ 4 ] Later record keeping aids throughout the Fertile Crescent included calculi (clay spheres, cones, etc.) which represented counts of items, probably livestock or grains, sealed in hollow unbaked clay containers. [ b ] [ 6 ] [ c ] The use of counting rods is one example. The abacus was early used for arithmetic tasks. What we now call the Roman abacus was used in Babylonia as early as c. 2700 –2300 BC. Since then, many other forms of reckoning boards or tables have been invented. In a medieval European counting house , a checkered cloth would be placed on a table, and markers moved around on it according to certain rules, as an aid to calculating sums of money.
Several analog computers were constructed in ancient and medieval times to perform astronomical calculations. These included the astrolabe and Antikythera mechanism from the Hellenistic world (c. 150–100 BC). [ 8 ] In Roman Egypt , Hero of Alexandria (c. 10–70 AD) made mechanical devices including automata and a programmable cart . [ 9 ] The steam-powered automatic flute described by the Book of Ingenious Devices (850) by the Persian-Baghdadi Banū Mūsā brothers may have been the first programmable device. [ 10 ]
Other early mechanical devices used to perform one or another type of calculations include the planisphere and other mechanical computing devices invented by Al-Biruni (c. AD 1000); the equatorium and universal latitude-independent astrolabe by Al-Zarqali (c. AD 1015); the astronomical analog computers of other medieval Muslim astronomers and engineers; and the astronomical clock tower of Su Song (1094) during the Song dynasty . The castle clock , a hydropowered mechanical astronomical clock invented by Ismail al-Jazari in 1206, was the first programmable analog computer. [ disputed (for: The cited source doesn't support the claim, and the claim is misleading.) – discuss ] [ 11 ] [ 12 ] [ 13 ] Ramon Llull invented the Lullian Circle: a notional machine for calculating answers to philosophical questions (in this case, to do with Christianity) via logical combinatorics. This idea was taken up by Leibniz centuries later, and is thus one of the founding elements in computing and information science .
Scottish mathematician and physicist John Napier discovered that the multiplication and division of numbers could be performed by the addition and subtraction, respectively, of the logarithms of those numbers. While producing the first logarithmic tables, Napier needed to perform many tedious multiplications. It was at this point that he designed his ' Napier's bones ', an abacus-like device that greatly simplified calculations that involved multiplication and division. [ d ]
Since real numbers can be represented as distances or intervals on a line, the slide rule was invented in the 1620s, shortly after Napier's work, to allow multiplication and division operations to be carried out significantly faster than was previously possible. [ 14 ] Edmund Gunter built a calculating device with a single logarithmic scale at the University of Oxford . His device greatly simplified arithmetic calculations, including multiplication and division. William Oughtred greatly improved this in 1630 with his circular slide rule. He followed this up with the modern slide rule in 1632, essentially a combination of two Gunter rules , held together with the hands. Slide rules were used by generations of engineers and other mathematically involved professional workers, until the invention of the pocket calculator . [ 15 ]
In 1609, Guidobaldo del Monte made a mechanical multiplier to calculate fractions of a degree. Based on a system of four gears, the rotation of an index on one quadrant corresponds to 60 rotations of another index on an opposite quadrant. [ 16 ] Thanks to this machine, errors in the calculation of first, second, third and quarter degrees can be avoided. Guidobaldo is the first to document the use of gears for mechanical calculation.
Wilhelm Schickard , a German polymath , designed a calculating machine in 1623 which combined a mechanized form of Napier's rods with the world's first mechanical adding machine built into the base. Because it made use of a single-tooth gear there were circumstances in which its carry mechanism would jam. [ 17 ] A fire destroyed at least one of the machines in 1624 and it is believed Schickard was too disheartened to build another.
In 1642, while still a teenager, Blaise Pascal started some pioneering work on calculating machines and after three years of effort and 50 prototypes [ 18 ] he invented a mechanical calculator . [ 19 ] [ 20 ] He built twenty of these machines (called Pascal's calculator or Pascaline) in the following ten years. [ 21 ] Nine Pascalines have survived, most of which are on display in European museums. [ e ] A continuing debate exists over whether Schickard or Pascal should be regarded as the "inventor of the mechanical calculator" and the range of issues to be considered is discussed elsewhere. [ 22 ]
Gottfried Wilhelm von Leibniz invented the stepped reckoner and his famous stepped drum mechanism around 1672. He attempted to create a machine that could be used not only for addition and subtraction but would use a moveable carriage to enable multiplication and division. Leibniz once said "It is unworthy of excellent men to lose hours like slaves in the labour of calculation which could safely be relegated to anyone else if machines were used." [ 23 ] However, Leibniz did not incorporate a fully successful carry mechanism. Leibniz also described the binary numeral system , [ 24 ] a central ingredient of all modern computers. However, up to the 1940s, many subsequent designs (including Charles Babbage 's machines of 1822 and even ENIAC of 1945) were based on the decimal system. [ f ]
Around 1820, Charles Xavier Thomas de Colmar created what would over the rest of the century become the first successful, mass-produced mechanical calculator, the Thomas Arithmometer . It could be used to add and subtract, and with a moveable carriage the operator could also multiply, and divide by a process of long multiplication and long division. [ 25 ] It utilised a stepped drum similar in conception to that invented by Leibniz. Mechanical calculators remained in use until the 1970s.
In 1804, French weaver Joseph Marie Jacquard developed a loom in which the pattern being woven was controlled by a paper tape constructed from punched cards . The paper tape could be changed without changing the mechanical design of the loom. This was a landmark achievement in programmability. His machine was an improvement over similar weaving looms. Punched cards were preceded by punch bands, as in the machine proposed by Basile Bouchon . These bands would inspire information recording for automatic pianos and more recently numerical control machine tools.
In the late 1880s, the American Herman Hollerith invented data storage on punched cards that could then be read by a machine. [ 26 ] To process these punched cards, he invented the tabulator and the keypunch machine. His machines used electromechanical relays and counters . [ 27 ] Hollerith's method was used in the 1890 United States census . That census was processed two years faster than the prior census had been. [ 28 ] Hollerith's company eventually became the core of IBM .
By 1920, electromechanical tabulating machines could add, subtract, and print accumulated totals. [ 29 ] Machine functions were directed by inserting dozens of wire jumpers into removable control panels . When the United States instituted Social Security in 1935, IBM punched-card systems were used to process records of 26 million workers. [ 30 ] Punched cards became ubiquitous in industry and government for accounting and administration.
Leslie Comrie 's articles on punched-card methods [ 31 ] and W. J. Eckert 's publication of Punched Card Methods in Scientific Computation in 1940, described punched-card techniques sufficiently advanced to solve some differential equations or perform multiplication and division using floating-point representations, all on punched cards and unit record machines . [ 32 ] Such machines were used during World War II for cryptographic statistical processing, [ 33 ] as well as a vast number of administrative uses. The Astronomical Computing Bureau of Columbia University performed astronomical calculations representing the state of the art in computing . [ 34 ] [ 35 ]
By the 20th century, earlier mechanical calculators, cash registers, accounting machines, and so on were redesigned to use electric motors, with gear position as the representation for the state of a variable. The word "computer" was a job title assigned to primarily women who used these calculators to perform mathematical calculations. [ 36 ] By the 1920s, British scientist Lewis Fry Richardson 's interest in weather prediction led him to propose human computers and numerical analysis to model the weather; to this day, the most powerful computers on Earth are needed to adequately model its weather using the Navier–Stokes equations . [ 37 ]
Companies like Friden , Marchant Calculator and Monroe made desktop mechanical calculators from the 1930s that could add, subtract, multiply and divide. [ 38 ] In 1948, the Curta was introduced by Austrian inventor Curt Herzstark . It was a small, hand-cranked mechanical calculator and as such, a descendant of Gottfried Leibniz 's Stepped Reckoner and Thomas ' Arithmometer .
The world's first all-electronic desktop calculator was the British Bell Punch ANITA , released in 1961. [ 39 ] [ 40 ] It used vacuum tubes , cold-cathode tubes and Dekatrons in its circuits, with 12 cold-cathode "Nixie" tubes for its display. The ANITA sold well since it was the only electronic desktop calculator available, and was silent and quick. The tube technology was superseded in June 1963 by the U.S. manufactured Friden EC-130, which had an all-transistor design, a stack of four 13-digit numbers displayed on a 5-inch (13 cm) CRT , and introduced reverse Polish notation (RPN).
The Industrial Revolution (late 18th to early 19th century) had a significant impact on the evolution of computing hardware, as the era's rapid advancements in machinery and manufacturing laid the groundwork for mechanized and automated computing. Industrial needs for precise, large-scale calculations—especially in fields such as navigation, engineering, and finance—prompted innovations in both design and function, setting the stage for devices like Charles Babbage's difference engine (1822). [ 41 ] [ 42 ] This mechanical device was intended to automate the calculation of polynomial functions and represented one of the earliest applications of computational logic. [ 43 ]
Babbage, often regarded as the "father of the computer," envisioned a fully mechanical system of gears and wheels, powered by steam, capable of handling complex calculations that previously required intensive manual labor. [ 44 ] His difference engine, designed to aid navigational calculations, ultimately led him to conceive the analytical engine in 1833. [ 45 ] This concept, far more advanced than his difference engine, included an arithmetic logic unit , control flow through conditional branching and loops, and integrated memory. [ 46 ] Babbage's plans made his analytical engine the first general-purpose design that could be described as Turing-complete in modern terms. [ 47 ] [ 48 ]
The analytical engine was programmed using punched cards , a method adapted from the Jacquard loom invented by Joseph Marie Jacquard in 1804, which controlled textile patterns with a sequence of punched cards. [ 49 ] These cards became foundational in later computing systems as well. [ 50 ] Babbage's machine would have featured multiple output devices, including a printer, a curve plotter, and even a bell, demonstrating his ambition for versatile computational applications beyond simple arithmetic. [ 51 ]
Ada Lovelace expanded on Babbage's vision by conceptualizing algorithms that could be executed by his machine. [ 52 ] Her notes on the analytical engine, written in the 1840s, are now recognized as the earliest examples of computer programming. [ 53 ] Lovelace saw potential in computers to go beyond numerical calculations, predicting that they might one day generate complex musical compositions or perform tasks like language processing. [ 54 ]
Though Babbage's designs were never fully realized due to technical and financial challenges, they influenced a range of subsequent developments in computing hardware. Notably, in the 1890s, Herman Hollerith adapted the idea of punched cards for automated data processing, which was utilized in the U.S. Census and sped up data tabulation significantly, bridging industrial machinery with data processing. [ 55 ]
The Industrial Revolution's advancements in mechanical systems demonstrated the potential for machines to conduct complex calculations, influencing engineers like Leonardo Torres Quevedo and Vannevar Bush in the early 20th century. Torres Quevedo designed an electromechanical machine with floating-point arithmetic, [ 56 ] while Bush's later work explored electronic digital computing. [ 57 ] By the mid-20th century, these innovations paved the way for the first fully electronic computers. [ 58 ]
In the first half of the 20th century, analog computers were considered by many to be the future of computing. These devices used the continuously changeable aspects of physical phenomena such as electrical , mechanical , or hydraulic quantities to model the problem being solved, in contrast to digital computers that represented varying quantities symbolically, as their numerical values change. As an analog computer does not use discrete values, but rather continuous values, processes cannot be reliably repeated with exact equivalence, as they can with Turing machines . [ 59 ]
The first modern analog computer was a tide-predicting machine , invented by Sir William Thomson , later Lord Kelvin, in 1872. It used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location and was of great utility to navigation in shallow waters. His device was the foundation for further developments in analog computing. [ 60 ]
The differential analyser , a mechanical analog computer designed to solve differential equations by integration using wheel-and-disc mechanisms, was conceptualized in 1876 by James Thomson , the brother of the more famous Lord Kelvin. He explored the possible construction of such calculators, but was stymied by the limited output torque of the ball-and-disk integrators . [ 61 ] In a differential analyzer, the output of one integrator drove the input of the next integrator, or a graphing output.
A notable series of analog calculating machines were developed by Leonardo Torres Quevedo since 1895, including one that was able to compute the roots of arbitrary polynomials of order eight, including the complex ones, with a precision down to thousandths. [ 62 ] [ 63 ] [ 64 ]
An important advance in analog computing was the development of the first fire-control systems for long range ship gunlaying . When gunnery ranges increased dramatically in the late 19th century it was no longer a simple matter of calculating the proper aim point, given the flight times of the shells. Various spotters on board the ship would relay distance measures and observations to a central plotting station. There the fire direction teams fed in the location, speed and direction of the ship and its target, as well as various adjustments for Coriolis effect , weather effects on the air, and other adjustments; the computer would then output a firing solution, which would be fed to the turrets for laying. In 1912, British engineer Arthur Pollen developed the first electrically powered mechanical analogue computer (called at the time the Argo Clock). [ citation needed ] It was used by the Imperial Russian Navy in World War I . [ citation needed ] The alternative Dreyer Table fire control system was fitted to British capital ships by mid-1916.
Mechanical devices were also used to aid the accuracy of aerial bombing . Drift Sight was the first such aid, developed by Harry Wimperis in 1916 for the Royal Naval Air Service ; it measured the wind speed from the air, and used that measurement to calculate the wind's effects on the trajectory of the bombs. The system was later improved with the Course Setting Bomb Sight , and reached a climax with World War II bomb sights, Mark XIV bomb sight ( RAF Bomber Command ) and the Norden [ 65 ] ( United States Army Air Forces ).
The art of mechanical analog computing reached its zenith with the differential analyzer , [ 66 ] built by H. L. Hazen and Vannevar Bush at MIT starting in 1927, which built on the mechanical integrators of James Thomson and the torque amplifiers invented by H. W. Nieman. A dozen of these devices were built before their obsolescence became obvious; the most powerful was constructed at the University of Pennsylvania 's Moore School of Electrical Engineering , where the ENIAC was built.
A fully electronic analog computer was built by Helmut Hölzer in 1942 at Peenemünde Army Research Center . [ 67 ] [ 68 ] [ 69 ]
By the 1950s the success of digital electronic computers had spelled the end for most analog computing machines, but hybrid analog computers , controlled by digital electronics, remained in substantial use into the 1950s and 1960s, and later in some specialized applications.
The principle of the modern computer was first described by computer scientist Alan Turing , who set out the idea in his seminal 1936 paper, [ 70 ] On Computable Numbers . Turing reformulated Kurt Gödel 's 1931 results on the limits of proof and computation, replacing Gödel's universal arithmetic-based formal language with the formal and simple hypothetical devices that became known as Turing machines . He proved that some such machine would be capable of performing any conceivable mathematical computation if it were representable as an algorithm . He went on to prove that there was no solution to the Entscheidungsproblem by first showing that the halting problem for Turing machines is undecidable : in general, it is not possible to decide algorithmically whether a given Turing machine will ever halt.
He also introduced the notion of a "universal machine" (now known as a universal Turing machine ), with the idea that such a machine could perform the tasks of any other machine, or in other words, it is provably capable of computing anything that is computable by executing a program stored on tape, allowing the machine to be programmable. John von Neumann acknowledged that the central concept of the modern computer was due to this paper. [ 71 ] Turing machines are to this day a central object of study in theory of computation . Except for the limitations imposed by their finite memory stores, modern computers are said to be Turing-complete , which is to say, they have algorithm execution capability equivalent to a universal Turing machine .
The era of modern computing began with a flurry of development before and during World War II. Most digital computers built in this period were built with electromechanical – electric switches drove mechanical relays to perform the calculation. These mechanical components had a low operating speed due to their mechanical nature and were eventually superseded by much faster all-electric components, originally using vacuum tubes and later transistors .
The Z2 was one of the earliest examples of an electric operated digital computer built with electromechanical relays and was created by civil engineer Konrad Zuse in 1940 in Germany. It was an improvement on his earlier, mechanical Z1 ; although it used the same mechanical memory , it replaced the arithmetic and control logic with electrical relay circuits. [ 72 ]
In the same year, electro-mechanical devices called bombes were built by British cryptologists to help decipher German Enigma-machine -encrypted secret messages during World War II . The bombe's initial design was created in 1939 at the UK Government Code and Cypher School at Bletchley Park by Alan Turing , [ 73 ] with an important refinement devised in 1940 by Gordon Welchman . [ 74 ] The engineering design and construction was the work of Harold Keen of the British Tabulating Machine Company . It was a substantial development from a device that had been designed in 1938 by Polish Cipher Bureau cryptologist Marian Rejewski , and known as the " cryptologic bomb " ( Polish : "bomba kryptologiczna" ).
In 1941, Zuse followed his earlier machine up with the Z3 , [ 72 ] the world's first working electromechanical programmable , fully automatic digital computer. [ 75 ] The Z3 was built with 2000 relays , implementing a 22- bit word length that operated at a clock frequency of about 5–10 Hz . [ 76 ] Program code and data were stored on punched film . It was quite similar to modern machines in some respects, pioneering numerous advances such as floating-point numbers . Replacement of the hard-to-implement decimal system (used in Charles Babbage 's earlier design) by the simpler binary system meant that Zuse's machines were easier to build and potentially more reliable, given the technologies available at that time. [ 77 ] The Z3 was proven to have been a Turing-complete machine in 1998 by Raúl Rojas . [ 78 ] In two 1936 patent applications, Zuse also anticipated that machine instructions could be stored in the same storage used for data—the key insight of what became known as the von Neumann architecture , first implemented in 1948 in America in the electromechanical IBM SSEC and in Britain in the fully electronic Manchester Baby . [ 79 ]
Zuse suffered setbacks during World War II when some of his machines were destroyed in the course of Allied bombing campaigns. Apparently his work remained largely unknown to engineers in the UK and US until much later, although at least IBM was aware of it as it financed his post-war startup company in 1946 in return for an option on Zuse's patents.
In 1944, the Harvard Mark I was constructed at IBM's Endicott laboratories. [ 80 ] It was a similar general purpose electro-mechanical computer to the Z3, but was not quite Turing-complete.
The term digital was first suggested by George Robert Stibitz and refers to where a signal, such as a voltage, is not used to directly represent a value (as it would be in an analog computer ), but to encode it. In November 1937, Stibitz, then working at Bell Labs (1930–1941), [ 81 ] completed a relay-based calculator he later dubbed the " Model K " (for " k itchen table", on which he had assembled it), which became the first binary adder . [ 82 ] Typically signals have two states – low (usually representing 0) and high (usually representing 1), but sometimes three-valued logic is used, especially in high-density memory. Modern computers generally use binary logic , but many early machines were decimal computers . In these machines, the basic unit of data was the decimal digit, encoded in one of several schemes, including binary-coded decimal or BCD, bi-quinary , excess-3 , and two-out-of-five code .
The mathematical basis of digital computing is Boolean algebra , developed by the British mathematician George Boole in his work The Laws of Thought , published in 1854. His Boolean algebra was further refined in the 1860s by William Jevons and Charles Sanders Peirce , and was first presented systematically by Ernst Schröder and A. N. Whitehead . [ 83 ] In 1879 Gottlob Frege developed the formal approach to logic and proposes the first logic language for logical equations. [ 84 ]
In the 1930s and working independently, American electronic engineer Claude Shannon and Soviet logician Victor Shestakov both showed a one-to-one correspondence between the concepts of Boolean logic and certain electrical circuits, now called logic gates , which are now ubiquitous in digital computers. [ 85 ] They showed that electronic relays and switches can realize the expressions of Boolean algebra . [ 86 ] This thesis essentially founded practical digital circuit design. In addition Shannon's paper gives a correct circuit diagram for a 4 bit digital binary adder. [ 87 ]
Purely electronic circuit elements soon replaced their mechanical and electromechanical equivalents, at the same time that digital calculation replaced analog. Machines such as the Z3 , the Atanasoff–Berry Computer , the Colossus computers , and the ENIAC were built by hand, using circuits containing relays or valves (vacuum tubes), and often used punched cards or punched paper tape for input and as the main (non-volatile) storage medium. [ 88 ]
Engineer Tommy Flowers joined the telecommunications branch of the General Post Office in 1926. While working at the research station in Dollis Hill in the 1930s, he began to explore the possible use of electronics for the telephone exchange . Experimental equipment that he built in 1934 went into operation 5 years later, converting a portion of the telephone exchange network into an electronic data processing system, using thousands of vacuum tubes . [ 60 ]
In the US, in 1940 Arthur Dickinson (IBM) invented the first digital electronic computer. [ 89 ] This calculating device was fully electronic – control, calculations and output (the first electronic display). [ 90 ] John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed the Atanasoff–Berry Computer (ABC) in 1942, [ 91 ] the first binary electronic digital calculating device. [ 92 ] This design was semi-electronic (electro-mechanical control and electronic calculations), and used about 300 vacuum tubes, with capacitors fixed in a mechanically rotating drum for memory. However, its paper card writer/reader was unreliable and the regenerative drum contact system was mechanical. The machine's special-purpose nature and lack of changeable, stored program distinguish it from modern computers. [ 93 ]
Computers whose logic was primarily built using vacuum tubes are now known as first generation computers .
During World War II, British codebreakers at Bletchley Park , 40 miles (64 km) north of London, achieved a number of successes at breaking encrypted enemy military communications. The German encryption machine, Enigma , was first attacked with the help of the electro-mechanical bombes . [ 94 ] They ruled out possible Enigma settings by performing chains of logical deductions implemented electrically. Most possibilities led to a contradiction, and the few remaining could be tested by hand.
The Germans also developed a series of teleprinter encryption systems, quite different from Enigma. The Lorenz SZ 40/42 machine was used for high-level Army communications, code-named "Tunny" by the British. The first intercepts of Lorenz messages began in 1941. As part of an attack on Tunny, Max Newman and his colleagues developed the Heath Robinson , a fixed-function machine to aid in code breaking. [ 95 ] Tommy Flowers , a senior engineer at the Post Office Research Station [ 96 ] was recommended to Max Newman by Alan Turing [ 97 ] and spent eleven months from early February 1943 designing and building the more flexible Colossus computer (which superseded the Heath Robinson ). [ 98 ] [ 99 ] After a functional test in December 1943, Colossus was shipped to Bletchley Park, where it was delivered on 18 January 1944 [ 100 ] and attacked its first message on 5 February. [ 101 ] By the time Germany surrendered in May 1945, there were ten Colossi working at Bletchley Park. [ 102 ]
Colossus was the world's first electronic digital programmable computer . [ 60 ] It used a large number of valves (vacuum tubes). It had paper-tape input and was capable of being configured to perform a variety of Boolean logical operations on its data, [ 103 ] but it was not Turing-complete . Data input to Colossus was by photoelectric reading of a paper tape transcription of the enciphered intercepted message. This was arranged in a continuous loop so that it could be read and re-read multiple times – there being no internal store for the data. The reading mechanism ran at 5,000 characters per second with the paper tape moving at 40 ft/s (12.2 m/s; 27.3 mph). Colossus Mark 1 contained 1500 thermionic valves (tubes), but Mark 2 with 2400 valves and five processors in parallel, was both 5 times faster and simpler to operate than Mark 1, greatly speeding the decoding process. Mark 2 was designed while Mark 1 was being constructed. Allen Coombs took over leadership of the Colossus Mark 2 project when Tommy Flowers moved on to other projects. [ 104 ] The first Mark 2 Colossus became operational on 1 June 1944, just in time for the Allied Invasion of Normandy on D-Day .
Most of the use of Colossus was in determining the start positions of the Tunny rotors for a message, which was called "wheel setting". Colossus included the first-ever use of shift registers and systolic arrays , enabling five simultaneous tests, each involving up to 100 Boolean calculations . This enabled five different possible start positions to be examined for one transit of the paper tape. [ 105 ] As well as wheel setting some later Colossi included mechanisms intended to help determine pin patterns known as "wheel breaking". Both models were programmable using switches and plug panels in a way their predecessors had not been.
Without the use of these machines, the Allies would have been deprived of the very valuable intelligence that was obtained from reading the vast quantity of enciphered high-level telegraphic messages between the German High Command (OKW) and their army commands throughout occupied Europe. Details of their existence, design, and use were kept secret well into the 1970s. Winston Churchill personally issued an order for their destruction into pieces no larger than a man's hand, to keep secret that the British were capable of cracking Lorenz SZ cyphers (from German rotor stream cipher machines) during the oncoming Cold War. Two of the machines were transferred to the newly formed GCHQ and the others were destroyed. As a result, the machines were not included in many histories of computing. [ g ] A reconstructed working copy of one of the Colossus machines is now on display at Bletchley Park.
The ENIAC (Electronic Numerical Integrator and Computer) was the first electronic programmable computer built in the US. Although the ENIAC used similar technology to the Colossi , it was much faster and more flexible and was Turing-complete. Like the Colossi, a "program" on the ENIAC was defined by the states of its patch cables and switches, a far cry from the stored-program electronic machines that came later. Once a program was ready to be run, it had to be mechanically set into the machine with manual resetting of plugs and switches. The programmers of the ENIAC were women who had been trained as mathematicians. [ 107 ]
It combined the high speed of electronics with the ability to be programmed for many complex problems. It could add or subtract 5000 times a second, a thousand times faster than any other machine. It also had modules to multiply, divide, and square root. High-speed memory was limited to 20 words (equivalent to about 80 bytes). Built under the direction of John Mauchly and J. Presper Eckert at the University of Pennsylvania, ENIAC's development and construction lasted from 1943 to full operation at the end of 1945. The machine was huge, weighing 30 tons, using 200 kilowatts of electric power and contained over 18,000 vacuum tubes, 1,500 relays, and hundreds of thousands of resistors, capacitors, and inductors. [ 108 ] One of its major engineering feats was to minimize the effects of tube burnout, which was a common problem in machine reliability at that time. The machine was in almost constant use for the next ten years.
The theoretical basis for the stored-program computer was proposed by Alan Turing in his 1936 paper On Computable Numbers . [ 70 ] Whilst Turing was at Princeton University working on his PhD, John von Neumann got to know him and became intrigued by his concept of a universal computing machine. [ 109 ]
Early computing machines executed the set sequence of steps, known as a ' program ', that could be altered by changing electrical connections using switches or a patch panel (or plugboard ). However, this process of 'reprogramming' was often difficult and time-consuming, requiring engineers to create flowcharts and physically re-wire the machines. [ 110 ] Stored-program computers, by contrast, were designed to store a set of instructions (a program ), in memory – typically the same memory as stored data.
ENIAC inventors John Mauchly and J. Presper Eckert proposed, in August 1944, the construction of a machine called the Electronic Discrete Variable Automatic Computer ( EDVAC ) and design work for it commenced at the University of Pennsylvania 's Moore School of Electrical Engineering , before the ENIAC was fully operational. The design implemented a number of important architectural and logical improvements conceived during the ENIAC's construction, and a high-speed serial-access memory . [ 111 ] However, Eckert and Mauchly left the project and its construction floundered.
In 1945, von Neumann visited the Moore School and wrote notes on what he saw, which he sent to the project. The U.S. Army liaison there had them typed and circulated as the First Draft of a Report on the EDVAC . The draft did not mention Eckert and Mauchly and, despite its incomplete nature and questionable lack of attribution of the sources of some of the ideas, [ 60 ] the computer architecture it outlined became known as the ' von Neumann architecture '.
In 1945, Turing joined the UK National Physical Laboratory and began work on developing an electronic stored-program digital computer. His late-1945 report 'Proposed Electronic Calculator' was the first reasonably detailed specification for such a device. Turing presented a more detailed paper to the National Physical Laboratory (NPL) Executive Committee in March 1946, giving the first substantially complete design of a stored-program computer , a device that was called the Automatic Computing Engine (ACE).
Turing considered that the speed and the size of computer memory were crucial elements, [ 112 ] : p.4 so he proposed a high-speed memory of what would today be called 25 KB , accessed at a speed of 1 MHz . The ACE implemented subroutine calls, whereas the EDVAC did not, and the ACE also used Abbreviated Computer Instructions, an early form of programming language .
The Manchester Baby (Small Scale Experimental Machine, SSEM) was the world's first electronic stored-program computer . It was built at the Victoria University of Manchester by Frederic C. Williams , Tom Kilburn and Geoff Tootill, and ran its first program on 21 June 1948. [ 113 ]
The machine was not intended to be a practical computer but was instead designed as a testbed for the Williams tube , the first random-access digital storage device. [ 114 ] Invented by Freddie Williams and Tom Kilburn [ 115 ] [ 116 ] at the University of Manchester in 1946 and 1947, it was a cathode-ray tube that used an effect called secondary emission to temporarily store electronic binary data , and was used successfully in several early computers.
Described as small and primitive in a 1998 retrospective, the Baby was the first working machine to contain all of the elements essential to a modern electronic computer. [ 117 ] As soon as it had demonstrated the feasibility of its design, a project was initiated at the university to develop the design into a more usable computer, the Manchester Mark 1 . The Mark 1 in turn quickly became the prototype for the Ferranti Mark 1 , the world's first commercially available general-purpose computer. [ 118 ]
The Baby had a 32-bit word length and a memory of 32 words. As it was designed to be the simplest possible stored-program computer, the only arithmetic operations implemented in hardware were subtraction and negation ; other arithmetic operations were implemented in software. The first of three programs written for the machine found the highest proper divisor of 2 18 (262,144), a calculation that was known would take a long time to run—and so prove the computer's reliability—by testing every integer from 2 18 − 1 downwards, as division was implemented by repeated subtraction of the divisor. The program consisted of 17 instructions and ran for 52 minutes before reaching the correct answer of 131,072, after the Baby had performed 3.5 million operations (for an effective CPU speed of 1.1 kIPS ). The successive approximations to the answer were displayed as a pattern of dots on the output CRT which mirrored the pattern held on the Williams tube used for storage.
The SSEM led to the development of the Manchester Mark 1 at the University of Manchester. [ 119 ] Work began in August 1948, and the first version was operational by April 1949; a program written to search for Mersenne primes ran error-free for nine hours on the night of 16/17 June 1949. The machine's successful operation was widely reported in the British press, which used the phrase "electronic brain" in describing it to their readers.
The computer is especially historically significant because of its pioneering inclusion of index registers , an innovation which made it easier for a program to read sequentially through an array of words in memory. Thirty-four patents resulted from the machine's development, and many of the ideas behind its design were incorporated in subsequent commercial products such as the IBM 701 and 702 as well as the Ferranti Mark 1. The chief designers, Frederic C. Williams and Tom Kilburn , concluded from their experiences with the Mark 1 that computers would be used more in scientific roles than in pure mathematics. In 1951 they started development work on Meg , the Mark 1's successor, which would include a floating-point unit .
The other contender for being the first recognizably modern digital stored-program computer [ 120 ] was the EDSAC , [ 121 ] designed and constructed by Maurice Wilkes and his team at the University of Cambridge Mathematical Laboratory in England at the University of Cambridge in 1949. The machine was inspired by John von Neumann 's seminal First Draft of a Report on the EDVAC and was one of the first usefully operational electronic digital stored-program computers. [ h ]
EDSAC ran its first programs on 6 May 1949, when it calculated a table of squares [ 124 ] and a list of prime numbers .The EDSAC also served as the basis for the first commercially applied computer, the LEO I , used by food manufacturing company J. Lyons & Co. Ltd. EDSAC 1 was finally shut down on 11 July 1958, having been superseded by EDSAC 2 which stayed in use until 1965. [ 125 ]
The "brain" [computer] may one day come down to our level [of the common people] and help with our income-tax and book-keeping calculations. But this is speculation and there is no sign of it so far.
ENIAC inventors John Mauchly and J. Presper Eckert proposed the EDVAC 's construction in August 1944, and design work for the EDVAC commenced at the University of Pennsylvania 's Moore School of Electrical Engineering , before the ENIAC was fully operational. The design implemented a number of important architectural and logical improvements conceived during the ENIAC's construction, and a high-speed serial-access memory . [ 111 ] However, Eckert and Mauchly left the project and its construction floundered.
It was finally delivered to the U.S. Army 's Ballistics Research Laboratory at the Aberdeen Proving Ground in August 1949, but due to a number of problems, the computer only began operation in 1951, and then only on a limited basis.
The first commercial electronic computer was the Ferranti Mark 1 , built by Ferranti and delivered to the University of Manchester in February 1951. It was based on the Manchester Mark 1 . The main improvements over the Manchester Mark 1 were in the size of the primary storage (using random access Williams tubes ), secondary storage (using a magnetic drum ), a faster multiplier, and additional instructions. The basic cycle time was 1.2 milliseconds, and a multiplication could be completed in about 2.16 milliseconds. The multiplier used almost a quarter of the machine's 4,050 vacuum tubes (valves). [ 127 ] A second machine was purchased by the University of Toronto , before the design was revised into the Mark 1 Star . At least seven of these later machines were delivered between 1953 and 1957, one of them to Shell labs in Amsterdam. [ 128 ]
In October 1947, the directors of J. Lyons & Company , a British catering company famous for its teashops but with strong interests in new office management techniques, decided to take an active role in promoting the commercial development of computers. The LEO I computer (Lyons Electronic Office) became operational in April 1951 [ 129 ] and ran the world's first regular routine office computer job . On 17 November 1951, the J. Lyons company began weekly operation of a bakery valuations job on the LEO – the first business application to go live on a stored-program computer. [ i ]
In June 1951, the UNIVAC I (Universal Automatic Computer) was delivered to the U.S. Census Bureau . Remington Rand eventually sold 46 machines at more than US$1 million each ($12.1 million as of 2025). [ 130 ] UNIVAC was the first "mass-produced" computer. It used 5,200 vacuum tubes and consumed 125 kW of power. Its primary storage was serial-access mercury delay lines capable of storing 1,000 words of 11 decimal digits plus sign (72-bit words).
In 1952, Compagnie des Machines Bull released the Gamma 3 computer, which became a large success in Europe, eventually selling more than 1,200 units, and the first computer produced in more than 1,000 units. [ 131 ] The Gamma 3 had innovative features for its time including a dual-mode, software switchable, BCD and binary ALU, as well as a hardwired floating-point library for scientific computing. [ 131 ] In its E.T configuration, the Gamma 3 drum memory could fit about 50,000 instructions for a capacity of 16,384 words (around 100 kB), a large amount for the time. [ 131 ]
Compared to the UNIVAC, IBM introduced a smaller, more affordable computer in 1954 that proved very popular. [ j ] [ 133 ] The IBM 650 weighed over 900 kg , the attached power supply weighed around 1350 kg and both were held in separate cabinets of roughly 1.5 × 0.9 × 1.8 m . The system cost US$500,000 [ 134 ] ($5.85 million as of 2025) or could be leased for US$3,500 a month ($40,000 as of 2025). [ 130 ] Its drum memory was originally 2,000 ten-digit words, later expanded to 4,000 words. Memory limitations such as this were to dominate programming for decades afterward. The program instructions were fetched from the spinning drum as the code ran. Efficient execution using drum memory was provided by a combination of hardware architecture – the instruction format included the address of the next instruction – and software: the Symbolic Optimal Assembly Program , SOAP, [ 135 ] assigned instructions to the optimal addresses (to the extent possible by static analysis of the source program). Thus many instructions were, when needed, located in the next row of the drum to be read and additional wait time for drum rotation was reduced.
In 1951, British scientist Maurice Wilkes developed the concept of microprogramming from the realisation that the central processing unit of a computer could be controlled by a miniature, highly specialized computer program in high-speed ROM . Microprogramming allows the base instruction set to be defined or extended by built-in programs (now called firmware or microcode ). [ 136 ] This concept greatly simplified CPU development. He first described this at the University of Manchester Computer Inaugural Conference in 1951, then published in expanded form in IEEE Spectrum in 1955. [ citation needed ]
It was widely used in the CPUs and floating-point units of mainframe and other computers; it was implemented for the first time in EDSAC 2 , [ 137 ] which also used multiple identical "bit slices" to simplify design. Interchangeable, replaceable tube assemblies were used for each bit of the processor. [ k ]
Magnetic drum memories were developed for the US Navy during WW II with the work continuing at Engineering Research Associates (ERA) in 1946 and 1947. ERA, then a part of Univac included a drum memory in its 1103 , announced in February 1953. The first mass-produced computer, the IBM 650 , also announced in 1953 had about 8.5 kilobytes of drum memory.
Magnetic-core memory patented in 1949 [ 139 ] with its first usage demonstrated for the Whirlwind computer in August 1953. [ 140 ] Commercialization followed quickly. Magnetic core was used in peripherals of the IBM 702 delivered in July 1955, and later in the 702 itself. The IBM 704 (1955) and the Ferranti Mercury (1957) used magnetic-core memory. It went on to dominate the field into the 1970s, when it was replaced with semiconductor memory. Magnetic core peaked in volume about 1975 and declined in usage and market share thereafter. [ 141 ]
As late as 1980, PDP-11/45 machines using magnetic-core main memory and drums for swapping were still in use at many of the original UNIX sites.
The bipolar transistor was invented in 1947. From 1955 onward transistors replaced vacuum tubes in computer designs, [ 143 ] giving rise to the "second generation" of computers. Compared to vacuum tubes, transistors have many advantages: they are smaller, and require less power than vacuum tubes, so give off less heat. Silicon junction transistors were much more reliable than vacuum tubes and had longer service life. Transistorized computers could contain tens of thousands of binary logic circuits in a relatively compact space. Transistors greatly reduced computers' size, initial cost, and operating cost . Typically, second-generation computers were composed of large numbers of printed circuit boards such as the IBM Standard Modular System , [ 144 ] each carrying one to four logic gates or flip-flops .
At the University of Manchester , a team under the leadership of Tom Kilburn designed and built a machine using the newly developed transistors instead of valves. Initially the only devices available were germanium point-contact transistors , less reliable than the valves they replaced but which consumed far less power. [ 145 ] Their first transistorized computer , and the first in the world, was operational by 1953 , [ 146 ] and a second version was completed there in April 1955. [ 146 ] The 1955 version used 200 transistors, 1,300 solid-state diodes , and had a power consumption of 150 watts. However, the machine did make use of valves to generate its 125 kHz clock waveforms and in the circuitry to read and write on its magnetic drum memory, so it was not the first completely transistorized computer.
That distinction goes to the Harwell CADET of 1955, [ 147 ] built by the electronics division of the Atomic Energy Research Establishment at Harwell . The design featured a 64-kilobyte magnetic drum memory store with multiple moving heads that had been designed at the National Physical Laboratory, UK . By 1953 this team had transistor circuits operating to read and write on a smaller magnetic drum from the Royal Radar Establishment . The machine used a low clock speed of only 58 kHz to avoid having to use any valves to generate the clock waveforms. [ 148 ] [ 147 ]
CADET used 324-point-contact transistors provided by the UK company Standard Telephones and Cables ; 76 junction transistors were used for the first stage amplifiers for data read from the drum, since point-contact transistors were too noisy. From August 1956, CADET was offering a regular computing service, during which it often executed continuous computing runs of 80 hours or more. [ 149 ] [ 150 ] Problems with the reliability of early batches of point contact and alloyed junction transistors meant that the machine's mean time between failures was about 90 minutes, but this improved once the more reliable bipolar junction transistors became available. [ 151 ]
The Manchester University Transistor Computer's design was adopted by the local engineering firm of Metropolitan-Vickers in their Metrovick 950 , the first commercial transistor computer anywhere. [ 152 ] Six Metrovick 950s were built, the first completed in 1956. They were successfully deployed within various departments of the company and were in use for about five years. [ 146 ] A second generation computer, the IBM 1401 , captured about one third of the world market. IBM installed more than ten thousand 1401s between 1960 and 1964.
Transistorized electronics improved not only the CPU (Central Processing Unit), but also the peripheral devices . The second generation disk data storage units were able to store tens of millions of letters and digits. Next to the fixed disk storage units, connected to the CPU via high-speed data transmission, were removable disk data storage units. A removable disk pack can be easily exchanged with another pack in a few seconds. Even if the removable disks' capacity is smaller than fixed disks, their interchangeability guarantees a nearly unlimited quantity of data close at hand. Magnetic tape provided archival capability for this data, at a lower cost than disk.
Many second-generation CPUs delegated peripheral device communications to a secondary processor. For example, while the communication processor controlled card reading and punching , the main CPU executed calculations and binary branch instructions . One databus would bear data between the main CPU and core memory at the CPU's fetch-execute cycle rate, and other databusses would typically serve the peripheral devices. On the PDP-1 , the core memory's cycle time was 5 microseconds; consequently most arithmetic instructions took 10 microseconds (100,000 operations per second) because most operations took at least two memory cycles; one for the instruction, one for the operand data fetch.
During the second generation remote terminal units (often in the form of Teleprinters like a Friden Flexowriter ) saw greatly increased use. [ l ] Telephone connections provided sufficient speed for early remote terminals and allowed hundreds of kilometers separation between remote-terminals and the computing center. Eventually these stand-alone computer networks would be generalized into an interconnected network of networks —the Internet. [ m ]
The early 1960s saw the advent of supercomputing . The Atlas was a joint development between the University of Manchester , Ferranti , and Plessey , and was first installed at Manchester University and officially commissioned in 1962 as one of the world's first supercomputers – considered to be the most powerful computer in the world at that time. [ 155 ] It was said that whenever Atlas went offline half of the United Kingdom's computer capacity was lost. [ 156 ] It was a second-generation machine, using discrete germanium transistors . Atlas also pioneered the Atlas Supervisor , "considered by many to be the first recognisable modern operating system ". [ 157 ]
In the US, a series of computers at Control Data Corporation (CDC) were designed by Seymour Cray to use innovative designs and parallelism to achieve superior computational peak performance. [ 158 ] The CDC 6600 , released in 1964, is generally considered the first supercomputer. [ 159 ] [ 160 ] The CDC 6600 outperformed its predecessor, the IBM 7030 Stretch , by about a factor of 3. With performance of about 1 megaFLOPS , the CDC 6600 was the world's fastest computer from 1964 to 1969, when it relinquished that status to its successor, the CDC 7600 .
The "third-generation" of digital electronic computers used integrated circuit (IC) chips as the basis of their logic.
The idea of an integrated circuit was conceived by a radar scientist working for the Royal Radar Establishment of the Ministry of Defence , Geoffrey W.A. Dummer .
The first working integrated circuits were invented by Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor . [ 161 ] Kilby recorded his initial ideas concerning the integrated circuit in July 1958, successfully demonstrating the first working integrated example on 12 September 1958. [ 162 ] Kilby's invention was a hybrid integrated circuit (hybrid IC). [ 163 ] It had external wire connections, which made it difficult to mass-produce. [ 164 ]
Noyce came up with his own idea of an integrated circuit half a year after Kilby. [ 165 ] Noyce's invention was a monolithic integrated circuit (IC) chip. [ 166 ] [ 164 ] His chip solved many practical problems that Kilby's had not. Produced at Fairchild Semiconductor, it was made of silicon , whereas Kilby's chip was made of germanium . The basis for Noyce's monolithic IC was Fairchild's planar process , which allowed integrated circuits to be laid out using the same principles as those of printed circuits . The planar process was developed by Noyce's colleague Jean Hoerni in early 1959, based on Mohamed M. Atalla 's work on semiconductor surface passivation by silicon dioxide at Bell Labs in the late 1950s. [ 167 ] [ 168 ] [ 169 ]
Third generation (integrated circuit) computers first appeared in the early 1960s in computers developed for government purposes, and then in commercial computers beginning in the mid-1960s. The first silicon IC computer was the Apollo Guidance Computer or AGC. [ 170 ] Although not the most powerful computer of its time, the extreme constraints on size, mass, and power of the Apollo spacecraft required the AGC to be much smaller and denser than any prior computer, weighing in at only 70 pounds (32 kg). Each lunar landing mission carried two AGCs, one each in the command and lunar ascent modules.
The MOSFET (metal–oxide–semiconductor field-effect transistor, or MOS transistor) was invented by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959. [ 171 ] In addition to data processing, the MOSFET enabled the practical use of MOS transistors as memory cell storage elements, a function previously served by magnetic cores . Semiconductor memory , also known as MOS memory , was cheaper and consumed less power than magnetic-core memory . [ 172 ] MOS random-access memory (RAM), in the form of static RAM (SRAM), was developed by John Schmidt at Fairchild Semiconductor in 1964. [ 172 ] [ 173 ] In 1966, Robert Dennard at the IBM Thomas J. Watson Research Center developed MOS dynamic RAM (DRAM). [ 174 ] In 1967, Dawon Kahng and Simon Sze at Bell Labs developed the floating-gate MOSFET , the basis for MOS non-volatile memory such as EPROM , EEPROM and flash memory . [ 175 ] [ 176 ]
The "fourth-generation" of digital electronic computers used microprocessors as the basis of their logic. The microprocessor has origins in the MOS integrated circuit (MOS IC) chip. [ 177 ] Due to rapid MOSFET scaling , MOS IC chips rapidly increased in complexity at a rate predicted by Moore's law , leading to large-scale integration (LSI) with hundreds of transistors on a single MOS chip by the late 1960s. The application of MOS LSI chips to computing was the basis for the first microprocessors, as engineers began recognizing that a complete computer processor could be contained on a single MOS LSI chip. [ 177 ]
The subject of exactly which device was the first microprocessor is contentious, partly due to lack of agreement on the exact definition of the term "microprocessor". The earliest multi-chip microprocessors were the Four-Phase Systems AL-1 in 1969 and Garrett AiResearch MP944 in 1970, developed with multiple MOS LSI chips. [ 177 ] The first single-chip microprocessor was the Intel 4004 , [ 178 ] developed on a single PMOS LSI chip. [ 177 ] It was designed and realized by Ted Hoff , Federico Faggin , Masatoshi Shima and Stanley Mazor at Intel , and released in 1971. [ n ] Tadashi Sasaki and Masatoshi Shima at Busicom , a calculator manufacturer, had the initial insight that the CPU could be a single MOS LSI chip, supplied by Intel. [ 180 ] [ 178 ]
While the earliest microprocessor ICs literally contained only the processor, i.e. the central processing unit, of a computer, their progressive development naturally led to chips containing most or all of the internal electronic parts of a computer. The integrated circuit in the image on the right, for example, an Intel 8742, is an 8-bit microcontroller that includes a CPU running at 12 MHz, 128 bytes of RAM , 2048 bytes of EPROM , and I/O in the same chip.
During the 1960s, there was considerable overlap between second and third generation technologies. [ o ] IBM implemented its IBM Solid Logic Technology modules in hybrid circuits for the IBM System/360 in 1964. As late as 1975, Sperry Univac continued the manufacture of second-generation machines such as the UNIVAC 494. The Burroughs large systems such as the B5000 were stack machines , which allowed for simpler programming. These pushdown automatons were also implemented in minicomputers and microprocessors later, which influenced programming language design. Minicomputers served as low-cost computer centers for industry, business and universities. [ 181 ] It became possible to simulate analog circuits with the simulation program with integrated circuit emphasis , or SPICE (1971) on minicomputers, one of the programs for electronic design automation ( EDA ). The microprocessor led to the development of microcomputers , small, low-cost computers that could be owned by individuals and small businesses. Microcomputers, the first of which appeared in the 1970s, became ubiquitous in the 1980s and beyond.
While which specific product is considered the first microcomputer system is a matter of debate, one of the earliest is R2E's Micral N ( François Gernelle , André Truong ) launched "early 1973" using the Intel 8008. [ 182 ] The first commercially available microcomputer kit was the Intel 8080 -based Altair 8800 , which was announced in the January 1975 cover article of Popular Electronics . However, the Altair 8800 was an extremely limited system in its initial stages, having only 256 bytes of DRAM in its initial package and no input-output except its toggle switches and LED register display. Despite this, it was initially surprisingly popular, with several hundred sales in the first year, and demand rapidly outstripped supply. Several early third-party vendors such as Cromemco and Processor Technology soon began supplying additional S-100 bus hardware for the Altair 8800.
In April 1975, at the Hannover Fair , Olivetti presented the P6060 , the world's first complete, pre-assembled personal computer system. The central processing unit consisted of two cards, code named PUCE1 and PUCE2, and unlike most other personal computers was built with TTL components rather than a microprocessor. It had one or two 8" floppy disk drives, a 32-character plasma display , 80-column graphical thermal printer , 48 Kbytes of RAM , and BASIC language. It weighed 40 kg (88 lb). As a complete system, this was a significant step from the Altair, though it never achieved the same success. It was in competition with a similar product by IBM that had an external floppy disk drive.
From 1975 to 1977, most microcomputers, such as the MOS Technology KIM-1 , the Altair 8800 , and some versions of the Apple I , were sold as kits for do-it-yourselfers. Pre-assembled systems did not gain much ground until 1977, with the introduction of the Apple II , the Tandy TRS-80 , the first SWTPC computers, and the Commodore PET . Computing has evolved with microcomputer architectures, with features added from their larger brethren, now dominant in most market segments.
A NeXT Computer and its object-oriented development tools and libraries were used by Tim Berners-Lee and Robert Cailliau at CERN to develop the world's first web server software, CERN httpd , and also used to write the first web browser , WorldWideWeb .
Systems as complicated as computers require very high reliability . ENIAC remained on, in continuous operation from 1947 to 1955, for eight years before being shut down. Although a vacuum tube might fail, it would be replaced without bringing down the system. By the simple strategy of never shutting down ENIAC, the failures were dramatically reduced. The vacuum-tube SAGE air-defense computers became remarkably reliable – installed in pairs, one off-line, tubes likely to fail did so when the computer was intentionally run at reduced power to find them. Hot-pluggable hard disks, like the hot-pluggable vacuum tubes of yesteryear, continue the tradition of repair during continuous operation. Semiconductor memories routinely have no errors when they operate, although operating systems like Unix have employed memory tests on start-up to detect failing hardware. Today, the requirement of reliable performance is made even more stringent when server farms are the delivery platform. [ 183 ] Google has managed this by using fault-tolerant software to recover from hardware failures, and is even working on the concept of replacing entire server farms on-the-fly, during a service event. [ 184 ] [ 185 ]
In the 21st century, multi-core CPUs became commercially available. [ 186 ] Content-addressable memory (CAM) [ 187 ] has become inexpensive enough to be used in networking, and is frequently used for on-chip cache memory in modern microprocessors, although no computer system has yet implemented hardware CAMs for use in programming languages. Currently, CAMs (or associative arrays) in software are programming-language-specific. Semiconductor memory cell arrays are very regular structures, and manufacturers prove their processes on them; this allows price reductions on memory products. During the 1980s, CMOS logic gates developed into devices that could be made as fast as other circuit types; computer power consumption could therefore be decreased dramatically. Unlike the continuous current draw of a gate based on other logic types, a CMOS gate only draws significant current, except for leakage, during the 'transition' between logic states. [ 188 ]
CMOS circuits have allowed computing to become a commercial product which is now ubiquitous, embedded in many forms , from greeting cards and telephones to satellites . The thermal design power which is dissipated during operation has become as essential as computing speed of operation. In 2006 servers consumed 1.5% of the total U.S. electricity consumption. [ 189 ] The energy consumption of computer data centers was expected to double to 3% of world consumption by 2011. The SoC (system on a chip) has compressed even more of the integrated circuitry into a single chip; SoCs are enabling phones and PCs to converge into single hand-held wireless mobile devices . [ 190 ]
Quantum computing is an emerging technology in the field of computing. MIT Technology Review reported 10 November 2017 that IBM has created a 50- qubit computer; currently its quantum state lasts 50 microseconds. [ 191 ] Google researchers have been able to extend the 50 microsecond time limit, as reported 14 July 2021 in Nature ; [ 192 ] stability has been extended 100-fold by spreading a single logical qubit over chains of data qubits for quantum error correction . [ 192 ] Physical Review X reported a technique for 'single-gate sensing as a viable readout method for spin qubits' (a singlet-triplet spin state in silicon) on 26 November 2018. [ 193 ] A Google team has succeeded in operating their RF pulse modulator chip at 3 kelvins , simplifying the cryogenics of their 72-qubit computer, which is set up to operate at 0.3 K ; but the readout circuitry and another driver remain to be brought into the cryogenics. [ 194 ] [ p ] See: Quantum supremacy [ 196 ] [ 197 ] Silicon qubit systems have demonstrated entanglement at non-local distances. [ 198 ]
Computing hardware and its software have even become a metaphor for the operation of the universe. [ 199 ]
An indication of the rapidity of development of this field can be inferred from the history of the seminal 1947 article by Burks, Goldstine and von Neumann. [ 200 ] By the time that anyone had time to write anything down, it was obsolete. After 1945, others read John von Neumann's First Draft of a Report on the EDVAC , and immediately started implementing their own systems. To this day, the rapid pace of development has continued, worldwide. [ q ] [ r ] | https://en.wikipedia.org/wiki/History_of_computing_hardware |
The history of computing hardware starting at 1960 is marked by the conversion from vacuum tube to solid-state devices such as transistors and then integrated circuit (IC) chips. Around 1953 to 1959, discrete transistors started being considered sufficiently reliable and economical that they made further vacuum tube computers uncompetitive . Metal–oxide–semiconductor (MOS) large-scale integration (LSI) technology subsequently led to the development of semiconductor memory in the mid-to-late 1960s and then the microprocessor in the early 1970s. This led to primary computer memory moving away from magnetic-core memory devices to solid-state static and dynamic semiconductor memory, which greatly reduced the cost, size, and power consumption of computers. These advances led to the miniaturized personal computer (PC) in the 1970s, starting with home computers and desktop computers , followed by laptops and then mobile computers over the next several decades.
For the purposes of this article, the term "second generation" refers to computers using discrete transistors, even when the vendors referred to them as "third-generation". By 1960 transistorized computers were replacing vacuum tube computers, offering lower cost, higher speeds, and reduced power consumption. The marketplace was dominated by IBM and the seven dwarfs :
Some examples of 1960s second generation computers from those vendors are:
However, some smaller companies made significant contributions. Also, towards the end of the second generation Digital Equipment Corporation (DEC) was a serious contender in the small and medium machine marketplace.
Meanwhile, second-generation computers were also being developed in the USSR as, e.g., the Razdan family of general-purpose digital computers created at the Yerevan Computer Research and Development Institute .
The second-generation computer architectures initially varied; they included character-based decimal computers , sign-magnitude decimal computers with a 10-digit word, sign-magnitude binary computers, and ones' complement binary computers, although Philco, RCA, and Honeywell, for example, had some computers that were character-based binary computers and Digital Equipment Corporation (DEC) and Philco, for example, had two's complement computers. With the advent of the IBM System/360 , two's complement became the norm for new product lines.
The most common word sizes for binary mainframes were 36 and 48 bits, although entry-level and midrange machines used smaller words, e.g., 12 bits , 18 bits , 24 bits , 30 bits . All but the smallest machines had asynchronous I/O channels and interrupts . Typically binary computers with word size up to 36 bits had one instruction per word, binary computers with 48 bits per word had two instructions per word and the CDC 60-bit machines could have two, three, or four instructions per word, depending on the instruction mix; the Burroughs B5000 , B6500/B7500 and B8500 lines are notable exceptions to this.
First-generation computers with data channels (I/O channels) had a basic DMA interface to the channel cable. The second generation saw both simpler, e.g., channels on the CDC 6000 series had no DMA, and more sophisticated designs, e.g., the 7909 on the IBM 7090 had limited computational, conditional branching and interrupt system.
By 1960, magnetic core was the dominant memory technology, although there were still some new machines using drums and delay lines during the 1960s. Magnetic thin film and rod memory were used on some second-generation machines, but advances in core technology meant they remained niche players until semiconductor memory displaced both core and thin film.
In the first generation, word-oriented computers typically had a single accumulator and an extension, referred to as, e.g., Upper and Lower Accumulator, Accumulator and Multiplier-Quotient (MQ) register. In the second generation, it became common for computers to have multiple addressable accumulators. On some computers, e.g., PDP-6 , the same registers served as accumulators and index registers , making them an early example of general-purpose registers .
In the second generation there was considerable development of new address modes , including truncated addressing on, e.g., the Philco TRANSAC S-2000 , the UNIVAC III , and automatic index register incrementing on, e.g., the RCA 601, UNIVAC 1107 , and the GE-600 series . Although index registers were introduced in the first generation under the name B-line , their use became much more common in the second generation. Similarly, indirect addressing became more common in the second generation, either in conjunction with index registers or instead of them. While first-generation computers typically had a small number of index registers or none, several lines of second-generation computers had large numbers of index registers, e.g., Atlas , Bendix G-20 , IBM 7070 .
The first generation had pioneered the use of special facilities for calling subroutines, e.g., TSX on the IBM 709 . In the second generation, such facilities were ubiquitous; some examples are:
The second generation saw the introduction of features intended to support multiprogramming and multiprocessor configurations, including master/slave (supervisor/problem) mode, storage protection keys, limit registers, protection associated with address translation, and atomic instructions .
Second generation supercomputers were substantially faster than most contemporary mainframes. Some of the technologies developed in order to achieve the desired performance are now used in commodity computers.
The mass increase in the use of computers accelerated with Third Generation computers starting around 1966 in the commercial market. These generally relied on early (sub-1000 transistor) integrated circuit technology. The third generation ends with the microprocessor -based fourth generation.
In 1958, Jack Kilby at Texas Instruments invented the hybrid integrated circuit (hybrid IC), [ 1 ] which had external wire connections, making it difficult to mass-produce. [ 2 ] In 1959, Robert Noyce at Fairchild Semiconductor invented the monolithic integrated circuit (IC) chip. [ 3 ] [ 2 ] It was made of silicon , whereas Kilby's chip was made of germanium . The basis for Noyce's monolithic IC was Fairchild's planar process , which allowed integrated circuits to be laid out using the same principles as those of printed circuits . The planar process was developed by Noyce's colleague Jean Hoerni in early 1959, based on the silicon surface passivation and thermal oxidation processes developed by Carl Frosch and Lincoln Derrick in 1955 and 1957. [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ]
Computers using IC chips began to appear in the early 1960s. For example, the 1961 Semiconductor Network Computer (Molecular Electronic Computer, Mol-E-Com), [ 10 ] [ 11 ] [ 12 ] the first monolithic integrated circuit [ 13 ] [ 14 ] [ 15 ] general purpose computer (built for demonstration purposes, programmed to simulate a desk calculator) was built by Texas Instruments for the US Air Force . [ 16 ] [ 17 ] [ 18 ] [ 19 ]
Some of their early uses were in embedded systems , notably used by NASA for the Apollo Guidance Computer , by the military in the LGM-30 Minuteman intercontinental ballistic missile , the Honeywell ALERT airborne computer, [ 20 ] [ 21 ] and in the Central Air Data Computer used for flight control in the US Navy 's F-14A Tomcat fighter jet.
An early commercial use was the 1965 SDS 92 . [ 22 ] [ 23 ] IBM first used ICs in computers for the logic of the System/360 Model 85 shipped in 1969 and then made extensive use of ICs in its System/370 which began shipment in 1971.
The integrated circuit enabled the development of much smaller computers. The minicomputer was a significant innovation in the 1960s and 1970s. It brought computing power to more people, not only through more convenient physical size but also through broadening the computer vendor field. Digital Equipment Corporation became the number two computer company behind IBM with their popular PDP and VAX computer systems. Smaller, affordable hardware also brought about the development of important new operating systems such as Unix .
In November 1966, Hewlett-Packard introduced the 2116A [ 24 ] [ 25 ] minicomputer, one of the first commercial 16-bit computers. It used CTμL (Complementary Transistor MicroLogic) [ 26 ] in integrated circuits from Fairchild Semiconductor . Hewlett-Packard followed this with similar 16-bit computers, such as the 2115A in 1967, [ 27 ] the 2114A in 1968, [ 28 ] and others.
In 1969, Data General introduced the Nova and shipped a total of 50,000 at $8,000 each. The popularity of 16-bit computers, such as the Hewlett-Packard 21xx series and the Data General Nova, led the way toward word lengths that were multiples of the 8-bit byte . The Nova was first to employ medium-scale integration (MSI) circuits from Fairchild Semiconductor, with subsequent models using large-scale integrated (LSI) circuits. Also notable was that the entire central processor was contained on one 15-inch printed circuit board .
Large mainframe computers used ICs to increase storage and processing abilities. The 1965 IBM System/360 mainframe computer family are sometimes called third-generation computers; however, their logic consisted primarily of SLT hybrid circuits , which contained discrete transistors and diodes interconnected on a substrate with printed wires and printed passive components; the S/360 M85 and M91 did use ICs for some of their circuits. IBM's 1971 System/370 used ICs for their logic, and later models used semiconductor memory .
By 1971, the ILLIAC IV supercomputer was the fastest computer in the world, using about a quarter-million small-scale ECL logic gate integrated circuits to make up sixty-four parallel data processors. [ 29 ]
Third-generation computers were offered well into the 1990s; for example the IBM ES9000 9X2 announced April 1994 [ 30 ] used 5,960 ECL chips to make a 10-way processor. [ 31 ] Other third-generation computers offered in the 1990s included the DEC VAX 9000 (1989), built from ECL gate arrays and custom chips, [ 32 ] and the Cray T90 (1995).
Third-generation minicomputers were essentially scaled-down versions of mainframe computers , designed to perform similar tasks but on a smaller and more accessible scale. In contrast, the fourth generation's origins are fundamentally different, as it is based on the microprocessor —a computer processor integrated onto a single large-scale integration (LSI) MOS integrated circuit chip. [ 33 ]
Microprocessor-based computers were originally very limited in their computational ability and speed and were in no way an attempt to downsize the minicomputer. They were addressing an entirely different market.
Processing power and storage capacities have grown beyond all recognition since the 1970s, but the underlying technology has remained basically the same of large-scale integration (LSI) or very-large-scale integration (VLSI) microchips, so it is widely regarded that most of today's computers still belong to the fourth generation.
The microprocessor has origins in the MOS integrated circuit (MOS IC) chip. [ 33 ] The MOS IC was fabricated by Fred Heiman and Steven Hofstein at RCA in 1962. [ 34 ] Due to rapid MOSFET scaling , MOS IC chips rapidly increased in complexity at a rate predicted by Moore's law , leading to large-scale integration (LSI) with hundreds of transistors on a single MOS chip by the late 1960s. The application of MOS LSI chips to computing was the basis for the first microprocessors, as engineers began recognizing that a complete computer processor could be contained on a single MOS LSI chip. [ 33 ]
The earliest multi-chip microprocessors were the Four-Phase Systems AL1 in 1969 and Garrett AiResearch MP944 in 1970, each using several MOS LSI chips. [ 33 ] On November 15, 1971, Intel released the world's first single-chip microprocessor, the 4004 , on a single MOS LSI chip. Its development was led by Federico Faggin , using silicon-gate MOS technology, along with Ted Hoff , Stanley Mazor and Masatoshi Shima . [ 35 ] It was developed for a Japanese calculator company called Busicom as an alternative to hardwired circuitry, but computers were developed around it, with much of their processing abilities provided by one small microprocessor chip. The dynamic RAM (DRAM) chip was based on the MOS DRAM memory cell developed by Robert Dennard of IBM, offering kilobits of memory on one chip. Intel coupled the RAM chip with the microprocessor, allowing fourth generation computers to be smaller and faster than prior computers. The 4004 was only capable of 60,000 instructions per second, but its successors brought ever-growing speed and power to computers, including the Intel 8008, 8080 (used in many computers using the CP/M operating system ), and the 8086/8088 family. (The IBM personal computer (PC) and compatibles use processors that are still backward-compatible with the 8086.) Other producers also made microprocessors which were widely used in microcomputers.
The following table shows a timeline of significant microprocessor development.
The powerful supercomputers of the era were at the other end of the computing spectrum from the microcomputers , and they also used integrated circuit technology. In 1976, the Cray-1 was developed by Seymour Cray , who had left Control Data in 1972 to form his own company. This machine was the first supercomputer to make vector processing practical. It had a characteristic horseshoe shape to speed processing by shortening circuit paths. Vector processing uses one instruction to perform the same operation on many arguments; it has been a fundamental supercomputer processing method ever since. The Cray-1 could calculate 150 million floating-point operations per second (150 megaflops ). 85 were shipped at a price of $5 million each. The Cray-1 had a CPU that was mostly constructed of SSI and MSI ECL ICs.
Computers were generally large, costly systems owned by large institutions before the introduction of the microprocessor in the early 1970s—corporations, universities, government agencies, and the like. Users were experienced specialists who did not usually interact with the machine itself, but instead prepared tasks for the computer on off-line equipment, such as card punches . A number of assignments for the computer would be gathered up and processed in batch mode . After the jobs had completed, users could collect the output printouts and punched cards. In some organizations, it could take hours or days between submitting a job to the computing center and receiving the output.
A more interactive form of computer use developed commercially by the middle 1960s. In a time-sharing system, multiple teleprinter and display terminals let many people share the use of one mainframe computer processor, with the operating system assigning time slices to each user's jobs. This was common in business applications and in science and engineering.
A different model of computer use was foreshadowed by the way in which early, pre-commercial, experimental computers were used, where one user had exclusive use of a processor. [ 36 ] Some of the first computers that might be called "personal" were early minicomputers such as the LINC and PDP-8 , and later on VAX and larger minicomputers from Digital Equipment Corporation (DEC), Data General , Prime Computer , and others. They originated as peripheral processors for mainframe computers, taking on some routine tasks and freeing the processor for computation.
By today's standards, they were physically large (about the size of a refrigerator) and costly (typically tens of thousands of US dollars ), and thus were rarely purchased by individuals. However, they were much smaller, less expensive, and generally simpler to operate than the mainframe computers of the time, and thus affordable by individual laboratories and research projects. Minicomputers largely freed these organizations from the batch processing and bureaucracy of a commercial or university computing center.
In addition, minicomputers were more interactive than mainframes, and soon had their own operating systems . The minicomputer Xerox Alto (1973) was a landmark step in the development of personal computers, because of its graphical user interface , bit-mapped high-resolution screen, large internal and external memory storage, mouse , and special software. [ 37 ]
In the minicomputer ancestors of the modern personal computer, processing was carried out by circuits with large numbers of components arranged on multiple large printed circuit boards . Minicomputers were consequently physically large and expensive to produce compared with later microprocessor systems. After the "computer-on-a-chip" was commercialized, the cost to produce a computer system dropped dramatically. The arithmetic, logic, and control functions that previously occupied several costly circuit boards were now available in one integrated circuit which was very expensive to design but cheap to produce in large quantities. Concurrently, advances in developing solid state memory eliminated the bulky, costly, and power-hungry magnetic-core memory used in prior generations of computers.
In France, the company R2E (Réalisations et Etudes Electroniques) formed by five former engineers of the Intertechnique company, André Truong Trong Thi [ 38 ] [ 39 ] and François Gernelle [ 40 ] introduced in February 1973 a microcomputer, the Micral N based on the Intel 8008 . [ 41 ] Originally, the computer had been designed by Gernelle, Lacombe, Beckmann and Benchitrite for the Institut National de la Recherche Agronomique to automate hygrometric measurements. [ 42 ] [ 43 ] The Micral N cost a fifth of the price of a PDP-8 , about 8500FF ($1300).
The clock of the Intel 8008 was set at 500 kHz, the memory was 16 kilobytes.
A bus, called Pluribus was introduced and allowed connection of up to 14 boards.
Different boards for digital I/O, analog I/O, memory, floppy disk were available from R2E.
The development of the single-chip microprocessor was an enormous catalyst to the popularization of cheap, easy to use, and truly personal computers. The Altair 8800 , introduced in a Popular Electronics magazine article in the January 1975 issue, at the time set a new low price point for a computer, bringing computer ownership to an admittedly select market in the 1970s. This was followed by the IMSAI 8080 computer, with similar abilities and limitations. The Altair and IMSAI were essentially scaled-down minicomputers and were incomplete: to connect a keyboard or teleprinter to them required heavy, expensive "peripherals". These machines both featured a front panel with switches and lights, which communicated with the operator in binary . To program the machine after switching it on the bootstrap loader program had to be entered, without error, in binary, then a paper tape containing a BASIC interpreter loaded from a paper-tape reader. Keying the loader required setting a bank of eight switches up or down and pressing the "load" button, once for each byte of the program, which was typically hundreds of bytes long. The computer could run BASIC programs once the interpreter had been loaded.
The MITS Altair , the first commercially successful microprocessor kit, was featured on the cover of Popular Electronics magazine in January 1975. It was the world's first mass-produced personal computer kit, as well as the first computer to use an Intel 8080 processor. It was a commercial success with 10,000 Altairs being shipped. The Altair also inspired the software development efforts of Paul Allen and his high school friend Bill Gates who developed a BASIC interpreter for the Altair, and then formed Microsoft .
The MITS Altair 8800 effectively created a new industry of microcomputers and computer kits, with many others following, such as a wave of small business computers in the late 1970s based on the Intel 8080, Zilog Z80 and Intel 8085 microprocessor chips. Most ran the CP/M -80 operating system developed by Gary Kildall at Digital Research . CP/M-80 was the first popular microcomputer operating system to be used by many different hardware vendors, and many software packages were written for it, such as WordStar and dBase II.
Many hobbyists during the mid-1970s designed their own systems, with various degrees of success, and sometimes banded together to ease the job. Out of these house meetings, the Homebrew Computer Club developed, where hobbyists met to talk about what they had done, exchange schematics and software, and demonstrate their systems. Many people built or assembled their own computers as per published designs. For example, many thousands of people built the Galaksija home computer later in the early 1980s.
The Altair was influential. It came before Apple Computer , as well as Microsoft which produced and sold the Altair BASIC programming language interpreter, Microsoft's first product. The second generation of microcomputers , those that appeared in the late 1970s, sparked by the unexpected demand for the kit computers at the electronic hobbyist clubs, were usually known as home computers . For business use these systems were less capable and in some ways less versatile than the large business computers of the day. They were designed for fun and educational purposes, not so much for practical use. And although you could use some simple office/productivity applications on them, they were generally used by computer enthusiasts for learning to program and for running computer games, for which the personal computers of the period were less suitable and much too expensive. For the more technical hobbyists home computers were also used for electronically interfacing to external devices, such as controlling model railroads , and other general hobbyist pursuits.
The advent of the microprocessor and solid-state memory made home computing affordable. Early hobby microcomputer systems such as the Altair 8800 and Apple I introduced around 1975 marked the release of low-cost 8-bit processor chips, which had sufficient computing power to be of interest to hobby and experimental users. By 1977 pre-assembled systems such as the Apple II , Commodore PET , and TRS-80 (later dubbed the "1977 Trinity" by Byte Magazine) [ 44 ] began the era of mass-market home computers ; much less effort was required to obtain an operating computer, and applications such as games, word processing, and spreadsheets began to proliferate. Distinct from computers used in homes, small business systems were typically based on CP/M , until IBM introduced the IBM PC , which was quickly adopted. The PC was heavily cloned , leading to mass production and consequent cost reduction throughout the 1980s. This expanded the PC's presence in homes, replacing the home computer category during the 1990s and leading to the current monoculture of architecturally identical personal computers. | https://en.wikipedia.org/wiki/History_of_computing_hardware_(1960s–present) |
The history of Polish computing ( informatics ) began during the Second World War with breaking the Enigma machine code by Polish mathematicians. After World War II, work on Polish computers began. Poles made a significant contribution to both the theory and technique of world computing.
In the State Institute of Mathematics, established in 1948 (from 1952 at the Polish Academy of Sciences), it was decided [ when? ] to start prospective work on the construction of at least one machine comparable to the American ENIAC. For this purpose, the Mathematical Apparatus Group of this Institute ( pol. Grupa Aparatów Matematycznych, GAM ) was established. [ when? ] The first engineering employee of GAM was Leon Łukaszewicz [ pl ] , and shortly after he was joined by his fellow students, Romuald Marczyński and Krystyn Bochenek . Logician and statistician Henryk Greniewski became the head of GAM. There were no resources to build such a computer - neither technical facilities, nor electronic equipment, nor experience. The only chance was given by the enthusiasm and alleged talent of a few newly promoted engineers. [ citation needed ]
Some of the earliest computers created in Poland were the first Odra computers . They were manufactured at the Elwro manufacturing plant in Wrocław , (the brand name comes from the Odra River that flows through the city of Wrocław) and exported to other communist countries. The production started in 1959–1960. The last series of Odra computers—the Odra 1300—consisted of three models: the Odra 1304, 1305, and the 1325. The hardware was developed by Polish teams to run the software for the above machines provided by the British company ICL . The Odra 1300 models were designed to be ICL 1900 compatible.
K-202 was 16-bit minicomputer built by Jacek Karpiński in 1971. It was faster and cheaper than most of the world's production at this time [ citation needed ] , and more advanced than IBM PC released decade later [ citation needed ] , but the mass production was never started because of political reasons and dependence on western parts; it was not compatible with the ES EVM standard.
Produced by Mera-Elzab, Meritum I and II models were created in 1983 and 1985 respectively. Based on U880DA CPU (Zilog Z80 clone), with 16 and 48KB RAM, were based on the TRS-80 computer. They were intended primarily for scientific, engineering and office applications.
Elwro 800 Junior (1986) and Elwro 804 Junior PC (1990) were ZX Spectrum clones intended for schools, and for home use respectively. The 804 model had a 3.5" disk drive built in; the drive was available as an accessory for 800 (the alternative mass storage being a tape recorder). The computers used the Z80A CPU, 64KB RAM and 24KB ROM. The ROM contained either CP/J (a variant of CP/M ) operating system, or Spectrum-compatible BASIC. [ 1 ] [ 2 ]
Mazovia was a Polish clone of IBM PC/XT .
The Polish Information Processing Society (also known as Polish Informatics Society ) is the oldest Polish organization that associates professionals from the computing industry. They act for their environment, as well as the social and economic environment. As part of its statutory activities, the Polish Informatics Society speaks on behalf of the surrounding community in the most important issues related to computerization, is consulted in legislative processes, and conducts certification and appraisal activities. They also organize a series of conferences, meetings and thematic workshops aimed at improving competences and integrating IT specialists. They are also working to increase general digital skills in society. They effectively promote Poland by showing the global successes of their computer scientists and unique digital technology products created in Poland. | https://en.wikipedia.org/wiki/History_of_computing_in_Poland |
This article describes the history of computing in Romania .
The Romanian computers HC family [ ro ] (HC 85, HC 85+, HC 88, HC 90, HC 91 and HC 2000) were clones of the ZX Spectrum produced at ICE Felix from 1985 to 1994. HC 85 was first designed at Institutul Politehnic București by Prof. Dr. Ing. Adrian Petrescu (in laboratory), then redesigned at ICE Felix (in order to be produced at industrial scale). Their operating system was a BASIC interpreter.
aMIC (microcomputer) [ ro ] was a Romanian microcomputer designed by Prof. Adrian Petrescu at Institutul Politehnic București in 1982, later produced at Fabrica de Memorii in Timișoara .
MARICA and the DACICC family ( DACICC-1 and DACICC-200 ) were Romanian computers produced in 1959–1968 at T. Popoviciu Institute of Numerical Analysis, Cluj-Napoca .
Felix PC [ ro ] was a Romanian IBM-PC compatible produced at ICE Felix in 1985–1990.
Felix C [ ro ] was a family of Romanian computers produced by ICE Felix from 1970 to 1978. They were similar to IBM/360; their operating system was SIRIS.
Felix M [ ro ] was a family of Romanian mini and microcomputers in 1975–1984.
CoBra [ ro ] was a Romanian personal computer produced at I.T.C.I Brașov , in 1986.
Independent minicomputer series [ ro ] was a series of Romanian minicomputers, manufactured from 1983 to 1989. They were compatible with DEC-PDP 11–34, running RSX-11M operating system. They were produced at ITC Timișoara, with memory chips also produced in Timișoara. | https://en.wikipedia.org/wiki/History_of_computing_in_Romania |
Ecology is a new science and considered as an important branch of biological science, having only become prominent during the second half of the 20th century. [ 1 ] Ecological thought is derivative of established currents in philosophy, particularly from ethics and politics. [ 2 ]
Its history stems all the way back to the 4th century. One of the first ecologists whose writings survive may have been Aristotle or perhaps his student, Theophrastus , both of whom had interest in many species of animals and plants. Theophrastus described interrelationships between animals and their environment as early as the 4th century BC. [ 3 ] Ecology developed substantially in the 18th and 19th century. It began with Carl Linnaeus and his work with the economy of nature. [ 4 ] Soon after came Alexander von Humboldt and his work with botanical geography. [ 5 ] Alexander von Humboldt and Karl Möbius then contributed with the notion of biocoenosis . Eugenius Warming 's work with ecological plant geography led to the founding of ecology as a discipline. [ 6 ] Charles Darwin 's work also contributed to the science of ecology, and Darwin is often attributed with progressing the discipline more than anyone else in its young history. Ecological thought expanded even more in the early 20th century. [ 7 ] Major contributions included: Eduard Suess ’ and Vladimir Vernadsky 's work with the biosphere, Arthur Tansley 's ecosystem, Charles Elton's Animal Ecology , and Henry Cowles ecological succession. [ 8 ]
Ecology influenced the social sciences and humanities. Human ecology began in the early 20th century and it recognized humans as an ecological factor. Later James Lovelock advanced views on earth as a macro-organism with the Gaia hypothesis . [ 9 ] [ 10 ] Conservation stemmed from the science of ecology. Important figures and movements include Shelford and the ESA, National Environmental Policy act, George Perkins Marsh , Theodore Roosevelt , Stephen A. Forbes , and post- Dust Bowl conservation. Later in the 20th century world governments collaborated on man’s effects on the biosphere and Earth’s environment.
The history of ecology is intertwined with the history of conservation and restoration efforts. [ 11 ] [ 12 ]
In the early Eighteenth century, preceding Carl Linnaeus, two rival schools of thought dominated the growing scientific discipline of ecology. First, Gilbert White a "parson-naturalist" is attributed with developing and endorsing the view of Arcadian ecology . Arcadian ecology advocates for a "simple, humble life for man" and a harmonious relationship with humans and nature. [ 13 ] Opposing the Arcadian view is Francis Bacon's ideology, "imperial ecology". Imperialists work "to establish through the exercise of reason and by hard work, man’s dominance over nature". [ 13 ] Imperial ecologists also believe that man should become a dominant figure over nature and all other organisms as "once enjoyed in the Garden of Eden". [ 13 ] Both views continued their rivalry through the early eighteenth century until Carl Linnaeus's support of imperialism; and in short time due to Linnaeus's popularity, imperial ecology became the dominant view within the discipline.
Carl Linnaeus, a Swedish naturalist, is well known for his work with taxonomy but his ideas helped to lay the groundwork for modern ecology. He developed a two part naming system for classifying plants and animals. Binomial Nomenclature was used to classify, describe, and name different genera and species. The compiled editions of Systema Naturae developed and popularized the naming system for plants and animals in modern biology. Reid suggests "Linnaeus can fairly be regarded as the originator of systematic and ecological studies in biodiversity," due to his naming and classifying of thousands of plant and animal species. Linnaeus also influenced the foundations of Darwinian evolution, he believed that there could be change in or between different species within fixed genera. Linnaeus was also one of the first naturalists to place men in the same category as primates . [ 4 ]
Throughout the 18th and the beginning of the 19th century, the great maritime powers such as Britain, Spain, and Portugal launched many world exploratory expeditions to develop maritime commerce with other countries, and to discover new natural resources, as well as to catalog them. At the beginning of the 18th century, about twenty thousand plant species were known, versus forty thousand at the beginning of the 19th century, and about 300,000 today.
These expeditions were joined by many scientists , including botanists , such as the German explorer Alexander von Humboldt . Humboldt is often considered as father of ecology. He was the first to take on the study of the relationship between organisms and their environment . He exposed the existing relationships between observed plant species and climate , and described vegetation zones using latitude and altitude , a discipline now known as geobotany . Von Humboldt was accompanied on his expedition by the botanist Aimé Bonpland .
In 1856, the Park Grass Experiment was established at the Rothamsted Experimental Station to test the effect of fertilizers and manures on hay yields. This is the longest-running field experiment in the world. [ 5 ]
Alfred Russel Wallace , contemporary and colleague of Darwin, was first to propose a "geography" of animal species. Several authors recognized at the time that species were not independent of each other, and grouped them into plant species, animal species, and later into communities of living beings or biocoenosis . The first use of this term is usually attributed to Karl Möbius in 1877, but already in 1825, the French naturalist Adolphe Dureau de la Malle used the term societé about an assemblage of plant individuals of different species.
While Darwin recognized the role of competition as one among many selective forces, Eugen Warming devised a new discipline that took abiotic factors, that is drought, fire, salt, cold etc., as seriously as biotic factors in the assembly of biotic communities. Biogeography before Warming was largely of descriptive nature – faunistic or floristic. Warming's aim was, through the study of organism (plant) morphology and anatomy , i.e. adaptation, to explain why a species occurred under a certain set of environmental conditions. Moreover, the goal of the new discipline was to explain why species occupying similar habitats, experiencing similar hazards, would solve problems in similar ways, despite often being of widely different phylogenetic descent. Based on his personal observations in Brazilian cerrado , in Denmark , Norwegian Finnmark and Greenland , Warming gave the first university course in ecological plant geography. Based on his lectures, he wrote the book 'Plantesamfund' , which was immediate translated to German, Polish and Russian , later to English as 'Oecology of Plants' . Through its German edition, the book had an immense effect on British and North American scientists like Arthur Tansley , Henry Chandler Cowles and Frederic Clements . [ 6 ]
Thomas Robert Malthus was an influential writer on the subject of population and population limits in the early 19th century. His works were very important in shaping the ways in which Darwin saw the world worked. Malthus wrote:
That the increase of population is necessarily limited by the means of subsistence,
That population does invariably increase when the means of subsistence increase, and,
That the superior power of population is repressed, and the actual population kept equal to the means of subsistence, by misery and vice. [ 14 ]
In An Essay on the Principle of Population Malthus argues for the reining in of rising population through 2 checks: Positive and Preventive checks. The first raising death rates, the later lowers birthing rates. [ 15 ] Malthus also brings forth the idea that the world population will move past the sustainable number of people. [ 16 ] This form of thought still continues to influences debates on birth and marriage rates to this theory brought forth by Malthus. [ 17 ] The essay had a major influence on Charles Darwin and helped him to theories his theory of Natural Selection. [ 18 ] This struggle proposed by Malthusian thought not only influenced the ecological work of Charles Darwin, but helped bring about an economic theory of world of ecology. [ 19 ]
It is often held that the roots of scientific ecology may be traced back to Darwin. [ 20 ] This contention may look convincing at first glance inasmuch as On the Origin of Species is full of observations and proposed mechanisms that clearly fit within the boundaries of modern ecology (e.g. the cat-to-clover chain – an ecological cascade) and because the term ecology was coined in 1866 by a strong proponent of Darwinism, Ernst Haeckel . However, Darwin never used the word in his writings after this year, not even in his most "ecological" writings such as the foreword to the English edition of Hermann Müller 's The Fertilization of Flowers (1883) or in his own treatise of earthworms and mull formation in forest soils ( The formation of vegetable mould through the action of worms , 1881). Moreover, the pioneers founding ecology as a scientific discipline, such as Eugen Warming , A. F. W. Schimper , Gaston Bonnier , F.A. Forel , S.A. Forbes and Karl Möbius , made almost no reference to Darwin's ideas in their works. [ 7 ] This was clearly not out of ignorance or because the works of Darwin were not widespread. Some such as S.A.Forbes studying intricate food webs asked questions as yet unanswered about the instability of food chains that might persist if dominant competitors were not adapted to have self-constraint. [ 21 ] Others focused on the dominant themes at the beginning, concern with the relationship between organism morphology and physiology on one side and environment on the other, mainly abiotic environment, hence environmental selection. Darwin's concept of natural selection on the other hand focused primarily on competition. [ 22 ] The mechanisms other than competition that he described, primarily the divergence of character which can reduce competition and his statement that "struggle" as he used it was metaphorical and thus included environmental selection, were given less emphasis in the Origin than competition. [ 13 ] Despite most portrayals of Darwin conveying him as a non-aggressive recluse who let others fight his battles, Darwin remained all his life a man nearly obsessed with the ideas of competition, struggle and conquest – with all forms of human contact as confrontation. [ 13 ] [ 23 ]
Although there is nothing incorrect in the details presented in the paragraph above, the fact that Darwinism used a particularly ecological view of adaptation and Haeckel's use and definitions of the term were steeped in Darwinism should not be ignored. According to ecologist and historian Robert P. McIntosh, "the relationship of ecology to Darwinian evolution is explicit in the title of the work in which ecology first appeared." [ 24 ] [ 25 ] A more elaborate definition by Haeckel in 1870 is translated on the frontispiece of the influential ecology text known as 'Great Apes' as "… ecology is the study of all those complex interrelations referred to by Darwin as the conditions of the struggle for existence." [ 26 ] [ 24 ] The issues brought up in the above paragraph are covered in more detail in the Early Beginnings section underneath that of History in the Wikipedia page on Ecology.
By the 19th century, ecology blossomed due to new discoveries in chemistry by Lavoisier and de Saussure , notably the nitrogen cycle . After observing the fact that life developed only within strict limits of each compartment that makes up the atmosphere , hydrosphere , and lithosphere , the Austrian geologist Eduard Suess proposed the term biosphere in 1875. Suess proposed the name biosphere for the conditions promoting life, such as those found on Earth , which includes flora , fauna , minerals , matter cycles , et cetera.
In the 1920s Vladimir I. Vernadsky , a Russian geologist who had defected to France, detailed the idea of the biosphere in his work "The biosphere" (1926), and described the fundamental principles of the biogeochemical cycles . He thus redefined the biosphere as the sum of all ecosystems .
First ecological damages were reported in the 18th century, as the multiplication of colonies caused deforestation . Since the 19th century, with the Industrial Revolution , more and more pressing concerns have grown about the impact of human activity on the environment . The term ecologist has been in use since the end of the 19th century.
Over the 19th century, botanical geography and zoogeography combined to form the basis of biogeography . This science, which deals with habitats of species, seeks to explain the reasons for the presence of certain species in a given location.
It was in 1935 that Arthur Tansley , the British ecologist , coined the term ecosystem , the interactive system established between the biocoenosis (the group of living creatures), and their biotope , the environment in which they live. Ecology thus became the science of ecosystems.
Tansley's concept of the ecosystem was adopted by the energetic and influential biology educator Eugene Odum . Along with his brother, Howard T. Odum , Eugene P. Odum wrote a textbook which (starting in 1953) educated more than one generation of biologists and ecologists in North America.
At the turn of the 20th century, Henry Chandler Cowles was one of the founders of the emerging study of "dynamic ecology", through his study of ecological succession at the Indiana Dunes , sand dunes at the southern end of Lake Michigan . Here Cowles found evidence of ecological succession in the vegetation and the soil with relation to age. Cowles was very much aware of the roots of the concept and of his (primordial) predecessors. [ 8 ] Thus, he attributes the first use of the word to the French naturalist Adolphe Dureau de la Malle , who had described the vegetation development after forest clear-felling, and the first comprehensive study of successional processes to the Finnish botanist Ragnar Hult (1881).
20th century English zoologist and ecologist, Charles Elton , is commonly credited as "the father of animal ecology". [ 27 ] Elton influenced by Victor Shelford's Animal Communities in Temperate America began his research on animal ecology as an assistant to his colleague, Julian Huxley, on an ecological survey of the fauna whilst taking part in the 1921 Oxford University Spitsbergen expedition . Elton's most famous studies were conducted during his time as a biological consultant to the Hudson Bay Company to help understand the fluctuations in the company's fur harvests. Elton studied the population fluctuations and dynamics of snowshoe hare, Canadian lynx, and other mammals of the region. Elton is also considered the first to coin the terms, food chain and food cycle in his famous book Animal Ecology . [ 28 ] Elton is also attributed with contributing to disciplines of: invasion ecology, community ecology, and wildlife disease ecology . [ 29 ]
George "G" Evelyn Hutchinson was a 20th-century ecologist who is commonly recognized as the "Father of Modern Ecology". Hutchinson is of English descent but spent most of professional career studying in New Haven, Connecticut at Yale University. Throughout his career, over six decades, Hutchinson contributed to the sciences of limnology, entomology, genetics, biogeochemistry, mathematical theory of population dynamics and many more. [ 30 ] Hutchinson is also attributed as being the first to infuse science with theory within the discipline of ecology. [ 31 ] Hutchinson was also one of the first credited with combining ecology with mathematics. Another major contribution of Hutchinson was his development of the current definition of an organism's "niche" – as he recognized the role of an organism within its community. Finally, along with his great impact within the discipline of ecology throughout his professional years, Hutchinson also left a lasting impact in ecology through his many students he inspired. Foremost among them were Robert H. MacArthur , who received his PhD under Hutchinson, and Raymond L. Lindeman , who finished his PhD dissertation during a fellowship under him. MacArthur became the leader of theoretical ecology and, with E. O. Wilson , developed island biography theory. Raymond Lindeman was instrumental in the development of modern ecosystem science. [ 32 ]
"What is ecology?” was a question that was asked in almost every decade of the 20th century. [ 33 ] Unfortunately, the answer most often was that it was mainly a point of view to be used in other areas of biology and also "soft", like sociology, for example, rather than "hard", like physics. Although autecology (essentially physiological ecology) could progress through the typical scientific method of observation and hypothesis testing, synecology (the study of animal and plant communities) and genecology (evolutionary ecology), for which experimentation was as limited as it was for, say, geology, continued with much the same inductive gathering of data as did natural history studies. [ 34 ] Most often, patterns, present and historical, were used to develop theories having explanatory power, but which had little actual data in support. Darwin's theory, as much as it is a foundation of modern biology, is a prime example.
G. E. Hutchinson, identified above as the "father of modern ecology", through his influence raised the status of much of ecology to that of a rigorous science. By shepherding of Raymond Lindemann's work on the trophic-dynamic concept of ecosystems through the publication process after Lindemann's untimely death, [ 35 ] Hutchinson set the groundwork for what became modern ecosystem science. With his two famous papers in the late1950s, "Closing remarks", [ 36 ] and "Homage to Santa Rosalia", [ 37 ] as they are now known, Hutchinson launched the theoretical ecology which Robert MacArthur championed.
Ecosystem science became rapidly and sensibly associated with the "Big Science"—and obviously "hard" science—of atomic testing and nuclear energy. It was brought in by Stanley Auerbach, who established the Environmental Sciences Division at Oak Ridge National Laboratory, [ 38 ] to trace the routes of radionuclides through the environment, and by the Odum brothers, Howard and Eugene, much of whose early work was supported by the Atomic Energy Commission. [ 39 ] Eugene Odum's textbook, Fundamentals of Ecology , has become something of a bible today. When, in the 1960s, the International Biological Program (IBP) took on an ecosystem character, [ 40 ] ecology, with its foundation in systems science, forever entered the realm of Big Science, with projects having large scopes and big budgets. Just two years after the publication of Silent Spring in 1962, ecosystem ecology was trumpeted as THE science of the environment in a series of articles in a special edition of BioScience . [ 41 ]
Theoretical ecology took a different path to established its legitimacy, especially at eastern universities and certain West Coast campuses. [ 42 ] It was the path of Robert MacArthur, who used simple mathematics in his "Three Influential Papers, [ 43 ] [ 44 ] [ 45 ] also published in the late 1950s, on population and community ecology. Although the simple equations of theoretical ecology at the time, were unsupported by data, they still were still deemed to be "heuristic". They were resisted by a number of traditional ecologists, however, whose complaints of "intellectual censorship" of studies that did not fit into the hypothetico-deductive structure of the new ecology might be seen as evidence of the stature to which the Hutchinson-MacArthur approach had risen by the 1970s. [ 46 ]
MacArthur's untimely death in 1972 was also about the time that postmodernism and the "Science Wars" came to ecology. The names of Kuhn, Wittgenstein, Popper, Lakatos, and Feyerbrend began to enter into arguments in the ecological literature. Darwin's theory of adaptation through natural selection was accused of being tautological. [ 47 ] Questions were raised over whether ecosystems were cybernetic [ 48 ] and whether ecosystem theory was of any use in application to environmental management. [ 49 ] Most vituperative of all was the debate that arose over MacArthur-style ecology.
Matters came to a head after a symposium organized by acolytes of MacArthur in homage to him and a second symposium organized by what was disparagingly called the "Tallahassee Mafia" at Wakulla Springs in Florida. [ 50 ] The homage volume, [ 51 ] published in 1975, had an extensive chapter written by Jared Diamond, who at the time taught kidney physiology at the UCLA School of Medicine, that presented a series of "assembly rules" to explain the patterns of bird species found on island archipelagos, [ 52 ] such as Darwin's famous finches on the Galapagos Islands. The Wakulla conference was organized by a group of dissenters led by Daniel Simberloff and Donald Strong, Jr., who were described by David Quammen in his book as arguing that those patterns "might be nothing more than the faces we see in the moon, in clouds, in Rorschach inkblots". [ 53 ] Their point was that Diamond's work (and that of others) did not fall within the criterion of falsifiability, laid down for science by the philosopher, Karl Popper. A reviewer of the exchanges between the two camps in an issue of Synthese found "images of hand-to-hand combat or a bar-room brawl" coming to mind. [ 54 ] The Florida State group suggested a method that they developed, that of "null" models, [ 55 ] to be used much in the way that all scientists use null hypotheses to verify that their results might not have been obtained merely by chance. [ 56 ] It was most sharply rebuked by Diamond and Michel Gilpin in the symposium volume [ 57 ] and Jonathan Roughgarden in the American Naturalist. [ 58 ]
There was a parallel controversy adding heat to above that became known in conservation circles as SLOSS (Single Large or Several Small reserves). Diamond had also proposed that, according to the theory of island geography developed by MacArthur and E. O. Wilson, [ 59 ] nature preserves should be designed to be as large as possible and maintained as a unified entity. Even cutting a road through a natural area, in Diamond's interpretation of MacArthur and Wilson's theory, would lead to the loss of species, due to the smaller areas of the remaining pieces. [ 60 ] Simberloff, meanwhile, who had defaunated mangrove islands off the Florida coast in his award-winning experimental study under E. O. Wilson and tested the fit of the species-area curve of island biogeography theory to the fauna that returned, [ 61 ] had gathered data that showed quite the opposite: that many smaller fragments together sometimes held more species that the original whole. [ 62 ] It led to considerable vituperation on the pages of Science . [ 33 ]
In the end, in a somewhat Kuhnian fashion, the arguments probably will finally be settled (or not) by the passing of the participants. However, ecology continues apace as a rigorous, even experimental science. Null models, admittedly difficult to perfect, are in use, and, although a leading conservation scientist recently lauded island biogeography theory as "one of the most elegant and important theories in contemporary ecology, towering above thousands of lesser ideas and concept", he nevertheless finds that "the species-area curve is a blunt tool in many contexts" and "now seems simplistic to the point of being cartoonish". [ 63 ]
Human ecology began in the 1920s, through the study of changes in vegetation succession in the city of Chicago . It became a distinct field of study in the 1970s. This marked the first recognition that humans, who had colonized all of the Earth's continents , were a major ecological factor . Humans greatly modify the environment through the development of the habitat (in particular urban planning ), by intensive exploitation activities such as logging and fishing , and as side effects of agriculture , mining , and industry . Besides ecology and biology, this discipline involved many other natural and social sciences, such as anthropology and ethnology , economics , demography , architecture and urban planning , medicine and psychology , and many more. The development of human ecology led to the increasing role of ecological science in the design and management of cities.
In recent years human ecology has been a topic that has interested organizational researchers. Hannan and Freeman ( Population Ecology of Organizations (1977) , American Journal of Sociology) argue that organizations do not only adapt to an environment. Instead it is also the environment that selects or rejects populations of organizations . In any given environment (in equilibrium ) there will only be one form of organization ( isomorphism ). Organizational ecology has been a prominent theory in accounting for diversities of organizations and their changing composition over time.
The Gaia theory , proposed by James Lovelock , in his work Gaia: A New Look at Life on Earth , advanced the view that the Earth should be regarded as a single living macro-organism. In particular, it argued that the ensemble of living organisms has jointly evolved an ability to control the global environment – by influencing major physical parameters as the composition of the atmosphere, the evaporation rate, the chemistry of soils and oceans – so as to maintain conditions favorable to life. The idea has been supported by Lynn Margulis who extended her endosymbiotic theory which suggests that cell organelles originated from free living organisms to the idea that individual organisms of many species could be considered as symbionts within a larger metaphorical "super-organism". [ 98 ]
This vision was largely a sign of the times, in particular the growing perception after the Second World War that human activities such as nuclear energy , industrialization , pollution , and overexploitation of natural resources , fueled by exponential population growth, were threatening to create catastrophes on a planetary scale, and has influenced many in the environmental movement since then.
Environmentalists and other conservationists have used ecology and other sciences (e.g., climatology ) to support their advocacy positions . Environmentalist views are often controversial for political or economic reasons. As a result, some scientific work in ecology directly influences policy and political debate; these in turn often direct ecological research and inquiry. [ 99 ]
The history of ecology, however, should not be conflated with that of environmental thought. Ecology as a modern science traces only from Darwin's publication of Origin of Species and Haeckel's subsequent naming of the science needed to study Darwin's theory. Awareness of humankind's effect on its environment has been traced to Gilbert White in 18th-century Selborne, England. [ 13 ] Awareness of nature and its interactions can be traced back even farther in time. [ 9 ] [ 10 ] Ecology before Darwin, however, is analogous to medicine prior to Pasteur's discovery of the infectious nature of disease. The history is there, but it is only partly relevant.
Neither Darwin nor Haeckel , it is true, did self-avowed ecological studies. The same can be said for researchers in a number of fields who contributed to ecological thought well into the 1940s without avowedly being ecologists. [ 1 ] [ 100 ] Raymond Pearl's population studies are a case in point. [ 101 ] Ecology in subject matter and techniques grew out of studies by botanists and plant geographers in the late 19th and early 20th centuries that paradoxically lacked Darwinian evolutionary perspectives. Until Mendel's studies with peas were rediscovered and melded into the Modern Synthesis, [ 102 ] Darwinism suffered in credibility. Many early plant ecologists had a Lamarckian view of inheritance, as did Darwin, at times. Ecological studies of animals and plants, preferably live and in the field, continued apace however. [ 103 ]
When the Ecological Society of America (ESA) was chartered in 1915, it already had a conservation perspective. [ 104 ] Victor E. Shelford , a leader in the society's formation, had as one of its goals the preservation of the natural areas that were then the objects of study by ecologists, but were in danger of being degraded by human incursion. [ 105 ] Human ecology had also been a visible part of the ESA at its inception, as evident by publications such as: "The Control of Pneumonia and Influenza by the Weather," "An Overlook of the Relations of Dust to Humanity," "The Ecological Relations of the Polar Eskimo," and "City Street Dust and Infectious Diseases," in early pages of Ecology and Ecological Monographs. The ESA's second president, Ellsworth Huntington, was a human ecologist. Stephen Forbes, another early president, called for "humanizing" ecology in 1921, since man was clearly the dominant species on the Earth. [ 106 ]
This auspicious start actually was the first of a series of fitful progressions and reversions by the new science with regard to conservation. Human ecology necessarily focused on man-influenced environments and their practical problems. Ecologists in general, however, were trying to establish ecology as a basic science, one with enough prestige to make inroads into Ivy League faculties. Disturbed environments, it was thought, would not reveal nature's secrets.
Interest in the environment created by the American Dust Bowl produced a flurry of calls in 1935 for ecology to take a look at practical issues. Pioneering ecologist C. C. Adams wanted to return human ecology to the science. [ 107 ] Frederic E. Clements, the dominant plant ecologist of the day, reviewed land use issues leading to the Dust Bowl in terms of his ideas on plant succession and climax. [ 108 ] Paul Sears reached a wide audience with his book, Deserts on the March . [ 109 ] World War II, perhaps, caused the issue to be put aside.
The tension between pure ecology, seeking to understand and explain, and applied ecology, seeking to describe and repair, came to a head after World War II. Adams again tried to push the ESA into applied areas by having it raise an endowment to promote ecology. He predicted that "a great expansion of ecology" was imminent "because of its integrating tendency." [ 110 ] Ecologists, however, were sensitive to the perception that ecology was still not considered a rigorous, quantitative science. Those who pushed for applied studies and active involvement in conservation were once more discreetly rebuffed. Human ecology became subsumed by sociology. It was sociologist Lewis Mumford who brought the ideas of George Perkins Marsh to modern attention in the 1955 conference, "Man’s Role in Changing the Face of the Earth." That prestigious conclave was dominated by social scientists. At it, ecology was accused of "lacking experimental methods" and neglecting "man as an ecological agent." One participant dismissed ecology as "archaic and sterile." [ 111 ] Within the ESA, a frustrated Shelford started the Ecologists' Union when his Committee on Preservation of Natural Conditions ceased to function due to the political infighting over the ESA stance on conservation. [ 104 ] In 1950, the fledgling organization was renamed and incorporated as the Nature Conservancy, a name borrowed from the British government agency for the same purpose.
Two events, however, brought ecology's course back to applied problems. One was the Manhattan Project . It had become the Nuclear Energy Commission after the war. It is now the Department of Energy (DOE). Its ample budget included studies of the impacts of nuclear weapon use and production. That brought ecology to the issue, and it made a "Big Science" of it. [ 13 ] [ 112 ] Ecosystem science, both basic and applied, began to compete with theoretical ecology (then called evolutionary ecology and also mathematical ecology). Eugene Odum , who published a very popular ecology textbook in 1953, became the champion of the ecosystem. In his publications, Odum called for ecology to have an ecosystem and applied focus. [ 113 ]
The second event was the publication of Silent Spring . Rachel Carson's book brought ecology as a word and concept to the public. Her influence was instant. A study committee, prodded by the publication of the book, reported to the ESA that their science was not ready to take on the responsibility being given to it. [ 114 ]
Carson's concept of ecology was very much that of Gene Odum. [ 115 ] As a result, ecosystem science dominated the International Biological Program of the 1960s and 1970s, bringing both money and prestige to ecology. [ 116 ] [ 117 ] Silent Spring was also the impetus for the environmental protection programs that were started in the Kennedy and Johnson administrations and passed into law just before the first Earth Day. Ecologists' input was welcomed. Former ESA President Stanley Cain, for example, was appointed an Assistant Secretary in the Department of the Interior.
The environmental assessment requirement of the 1969 National Environmental Policy Act (NEPA), "legitimized ecology," in the words of one environmental lawyer. [ 118 ] An ESA President called it "an ecological 'Magna Carta.'" [ 119 ] A prominent Canadian ecologist declared it a "boondoggle." [ 120 ] NEPA and similar state statutes, if nothing else, provided much employment for ecologists. Therein was the issue. Neither ecology nor ecologists were ready for the task. Not enough ecologists were available to work on impact assessment, outside of the DOE laboratories, leading to the rise of "instant ecologists," [ 121 ] having dubious credentials and capabilities. Calls began to arise for the professionalization of ecology. Maverick scientist Frank Egler , in particular, devoted his sharp prose to the task. [ 122 ] Again, a schism arose between basic and applied scientists in the ESA, this time exacerbated by the question of environmental advocacy. The controversy, whose history has yet to receive adequate treatment, lasted through the 1970s and 1980s, ending with a voluntary certification process by the ESA, along with lobbying arm in Washington. [ 123 ]
Post-Earth Day, besides questions of advocacy and professionalism, ecology also had to deal with questions having to do with its basic principles. Many of the theoretical principles and methods of both ecosystem science and evolutionary ecology began to show little value in environmental analysis and assessment. [ 124 ] Ecologist, in general, started to question the methods and logic of their science under the pressure of its new notoriety. [ 84 ] [ 125 ] [ 126 ] Meanwhile, personnel with government agencies and environmental advocacy groups were accused of religiously applying dubious principles in their conservation work. [ 127 ] Management of endangered Spotted Owl populations brought the controversy to a head. [ 128 ]
Conservation for ecologists created travails paralleling those nuclear power gave former Manhattan Project scientists. In each case, science had to be reconciled with individual politics, religious beliefs, and worldviews, a difficult process. Some ecologists managed to keep their science separate from their advocacy; others unrepentantly became avowed environmentalists. [ 129 ]
Theodore Roosevelt was interested in nature from a young age. He carried his passion for nature into his political policies. Roosevelt felt it was necessary to preserve the resources of the nation and its environment. In 1902 he created the federal reclamation service, which reclaimed land for agriculture. He also created the Bureau of Forestry. This organization, headed by Gifford Pinchot, was formed to manage and maintain the nations timberlands. [ 130 ] Roosevelt signed the Act for the Preservation of American Antiquities in 1906. This act allowed for him to "declare by public proclamation historic landmarks, historic and prehistoric structures, and other objects of historic and scientific interest that are situated upon lands owned or controlled by the Government of the United States to be national monuments ." Under this act he created up to 18 national monuments. During his presidency, Roosevelt established 51 Federal Bird Reservations , 4 National Game Preserves, 150 National Forests , and 5 National Parks . Overall he protected over 200 million acres of land. [ 131 ]
Ecology became a central part of the World's politics as early as 1971, [ 132 ] UNESCO launched a research program called Man and Biosphere , with the objective of increasing knowledge about the mutual relationship between humans and nature. A few years later it defined the concept of Biosphere Reserve .
In 1972, the United Nations held the first international Conference on the Human Environment in Stockholm , prepared by Rene Dubos and other experts. This conference was the origin of the phrase " Think Globally, Act Locally ". The next major events in ecology were the development of the concept of biosphere and the appearance of terms "biological diversity"—or now more commonly biodiversity —in the 1980s. These terms were developed during the Earth Summit in Rio de Janeiro in 1992, where the concept of the biosphere was recognized by the major international organizations, and risks associated with reductions in biodiversity were publicly acknowledged.
Then, in 1997, the dangers the biosphere was facing were recognized all over the world at the conference leading to the Kyoto Protocol . In particular, this conference highlighted the increasing dangers of the greenhouse effect – related to the increasing concentration of greenhouse gases in the atmosphere, leading to global changes in climate . In Kyoto , most of the world's nations recognized the importance of looking at ecology from a global point of view, on a worldwide scale, and to take into account the impact of humans on the Earth's environment. | https://en.wikipedia.org/wiki/History_of_ecology |
Electrochemistry , a branch of chemistry , went through several changes during its evolution from early principles related to magnets in the early 16th and 17th centuries, to complex theories involving conductivity , electric charge and mathematical methods. The term electrochemistry was used to describe electrical phenomena in the late 19th and 20th centuries. In recent decades, electrochemistry has become an area of current research, including research in batteries and fuel cells , preventing corrosion of metals, the use of electrochemical cells to remove refractory organics and similar contaminants in wastewater electrocoagulation and improving techniques in refining chemicals with electrolysis and electrophoresis .
The 16th century marked the beginning of scientific understanding of electricity and magnetism that culminated with the production of electric power and the Industrial Revolution in the late 19th century.
In the 1550s, English scientist William Gilbert spent 17 years experimenting with magnetism and, to a lesser extent, electricity. For his work on magnets, Gilbert became known as "The Father of Magnetism." His book De Magnete quickly became the standard work throughout Europe on electrical and magnetic phenomena, and made a clear distinction between magnetism and what was then called the "amber effect" (static electricity).
In 1663, German physicist Otto von Guericke created the first electrostatic generator, which produced static electricity by applying friction. The generator was made of a large sulfur ball inside a glass globe, mounted on a shaft. The ball was rotated by means of a crank and a static electric spark was produced when a pad was rubbed against the ball as it rotated. The globe could be removed and used as an electrical source for experiments with electricity. Von Guericke used his generator to show that like charges repelled each other.
In 1709, Francis Hauksbee at the Royal Society in London discovered that by putting a small amount of mercury in the glass of Von Guericke's generator and evacuating the air from it, it would glow whenever the ball built up a charge and his hand was touching the globe. He had created the first gas-discharge lamp .
Between 1729 and 1736, two English scientists, Stephen Gray and Jean Desaguliers , performed a series of experiments which showed that a cork or other object as far away as 800 or 900 feet (245–275 m) could be electrified by connecting it via a charged glass tube to materials such as metal wires or hempen string. They found that other materials, such as silk , would not convey the effect.
By the mid-18th century, French chemist Charles François de Cisternay Du Fay had discovered two forms of static electricity, and that like charges repel each other while unlike charges attract. Du Fay announced that electricity consisted of two fluids: vitreous (from the Latin for "glass"), or positive, electricity; and resinous , or negative, electricity. This was the "two-fluid theory" of electricity, which was opposed by Benjamin Franklin's "one-fluid theory" later in the century.
In 1745, Jean-Antoine Nollet developed a theory of electrical attraction and repulsion that supposed the existence of a continuous flow of electrical matter between charged bodies. Nollet's theory at first gained wide acceptance, but met resistance in 1752 with the translation of Franklin's Experiments and Observations on Electricity into French. Franklin and Nollet debated the nature of electricity, with Franklin supporting action at a distance and two qualitatively opposing types of electricity, and Nollet advocating mechanical action and a single type of electrical fluid. Franklin's argument eventually won and Nollet's theory was abandoned.
In 1748, Nollet invented one of the first electrometers , the electroscope , which showed electric charge using electrostatic attraction and repulsion. Nollet is reputed to be the first to apply the name " Leyden jar " to the first device for storing electricity. Nollet's invention was replaced by Horace-Bénédict de Saussure 's electrometer in 1766.
By the 1740s, William Watson had conducted several experiments to determine the speed of electricity. The general belief at the time was that electricity was faster than sound, but no accurate test had been devised to measure the velocity of a current. Watson, in the fields north of London, laid out a line of wire supported by dry sticks and silk which ran for 12,276 feet (3.7 km). Even at this length, the velocity of electricity seemed instantaneous. Resistance in the wire was also noticed but apparently not fully understood, as Watson related that "we observed again, that although the electrical compositions were very severe to those who held the wires, the report of the Explosion at the prime Conductor was little, in comparison of that which is heard when the Circuit is short." Watson eventually decided not to pursue his electrical experiments, concentrating instead upon his medical career.
By the 1750s, as the study of electricity became popular, efficient ways of producing electricity were sought. The generator developed by Jesse Ramsden was among the first electrostatic generators invented. Electricity produced by such generators was used to treat paralysis, muscle spasms, and to control heart rates. Other medical uses of electricity included filling the body with electricity, drawing sparks from the body, and applying sparks from the generator to the body.
Charles-Augustin de Coulomb developed the law of electrostatic attraction in 1781 as an outgrowth of his attempt to investigate the law of electrical repulsions as stated by Joseph Priestley in England. To this end, he invented a sensitive apparatus to measure the electrical forces involved in Priestley's law. He also established the inverse square law of attraction and repulsion magnetic poles, which became the basis for the mathematical theory of magnetic forces developed by Siméon Denis Poisson . Coulomb wrote seven important works on electricity and magnetism which he submitted to the Académie des Sciences between 1785 and 1791, in which he reported having developed a theory of attraction and repulsion between charged bodies, and went on to search for perfect conductors and dielectrics . He suggested that there was no perfect dielectric, proposing that every substance has a limit, above which it will conduct electricity. The SI unit of charge is called a coulomb in his honour.
In 1789, Franz Aepinus developed a device with the properties of a "condenser" (now known as a capacitor .) The Aepinus condenser was the first capacitor developed after the Leyden jar, and was used to demonstrate conduction and induction . The device was constructed so that the space between two plates could be adjusted, and the glass dielectric separating the two plates could be removed or replaced with other materials.
Despite the gain in knowledge of electrical properties and the building of generators, it was not until the late 18th century that Italian physician and anatomist Luigi Galvani marked the birth of electrochemistry by establishing a bridge between muscular contractions and electricity with his 1791 essay De Viribus Electricitatis in Motu Musculari Commentarius (Commentary on the Effect of Electricity on Muscular Motion), where he proposed a "nerveo-electrical substance" in life forms.
In his essay, Galvani concluded that animal tissue contained a before-unknown innate, vital force, which he termed "animal electricity," which activated muscle when placed between two metal probes. He believed that this was evidence of a new form of electricity, separate from the "natural" form that is produced by lightning and the "artificial" form that is produced by friction (static electricity). He considered the brain to be the most important organ for the secretion of this "electric fluid" and that the nerves conducted the fluid to the muscles. He believed the tissues acted similarly to the outer and inner surfaces of Leyden jars. The flow of this electric fluid provided a stimulus to the muscle fibres.
Galvani's scientific colleagues generally accepted his views, but Alessandro Volta , the outstanding professor of physics at the University of Pavia , was not convinced by the analogy between muscles and Leyden jars. Deciding that the frogs' legs used in Galvani's experiments served only as an electroscope, he held that the contact of dissimilar metals was the true source of stimulation. He referred to the electricity so generated as "metallic electricity" and decided that the muscle, by contracting when touched by metal, resembled the action of an electroscope. Furthermore, Volta claimed that if two dissimilar metals in contact with each other also touched a muscle, agitation would also occur and increase with the dissimilarity of the metals. Galvani refuted this by obtaining muscular action using two pieces of similar metal. Volta's name was later used for the unit of electrical potential, the volt .
In 1800, English chemists William Nicholson and Johann Wilhelm Ritter succeeded in separating water into hydrogen and oxygen by electrolysis . Soon thereafter, Ritter discovered the process of electroplating . He also observed that the amount of metal deposited and the amount of oxygen produced during an electrolytic process depended on the distance between the electrodes . By 1801 Ritter had observed thermoelectric currents, which anticipated the discovery of thermoelectricity by Thomas Johann Seebeck .
In 1802, William Cruickshank designed the first electric battery capable of mass production. Like Volta, Cruickshank arranged square copper plates, which he soldered at their ends, together with plates of zinc of equal size. These plates were placed into a long rectangular wooden box which was sealed with cement. Grooves inside the box held the metal plates in position. The box was then filled with an electrolyte of brine , or watered down acid. This flooded design had the advantage of not drying out with use and provided more energy than Volta's arrangement, which used brine-soaked papers between the plates.
In the quest for a better production of platinum metals, two scientists, William Hyde Wollaston and Smithson Tennant , worked together to design an efficient electrochemical technique to refine or purify platinum. Tennant ended up discovering the elements iridium and osmium . Wollaston's effort, in turn, led him to the discovery of the metals palladium in 1803 and rhodium in 1804.
Wollaston made improvements to the galvanic battery (named after Galvani) in the 1810s. In Wollaston's battery, the wooden box was replaced with an earthenware vessel, and a copper plate was bent into a U-shape, with a single plate of zinc placed in the center of the bent copper. The zinc plate was prevented from making contact with the copper by dowels (pieces) of cork or wood. In his single cell design, the U-shaped copper plate was welded to a horizontal handle for lifting the copper and zinc plates out of the electrolyte when the battery was not in use.
In 1809, Samuel Thomas von Soemmering developed the first telegraph . He used a device with 26 wires (1 wire for each letter of the German alphabet ) terminating in a container of acid. At the sending station, a key, which completed a circuit with a battery, was connected as required to each of the line wires. The passage of current caused the acid to decompose chemically, and the message was read by observing at which of the terminals the bubbles of gas appeared. This is how he was able to send messages, one letter at a time.
Humphry Davy 's work with electrolysis led to conclusion that the production of electricity in simple electrolytic cells resulted from chemical reactions between the electrolyte and the metals, and occurred between substances of opposite charge. He reasoned that the interactions of electric currents with chemicals offered the most likely means of decomposing all substances to their basic elements. These views were explained in 1806 in his lecture On Some Chemical Agencies of Electricity , for which he received the Napoleon Prize from the Institut de France in 1807 (despite the fact that England and France were at war at the time). This work led directly to the isolation of sodium and potassium from their common compounds and of the alkaline earth metals from theirs in 1808.
Hans Christian Ørsted 's discovery of the magnetic effect of electric currents in 1820 was immediately recognised as an important advance, although he left further work on electromagnetism to others. André-Marie Ampère quickly repeated Ørsted's experiment, and formulated them mathematically (which became Ampère's law ) . Ørsted also discovered that not only is a magnetic needle deflected by the electric current, but that the live electric wire is also deflected in a magnetic field, thus laying the foundation for the construction of an electric motor. Ørsted's discovery of piperine , one of the pungent components of pepper, was an important contribution to chemistry, as was his preparation of aluminium in 1825.
During the 1820s, Robert Hare developed the Deflagrator , a form of voltaic battery having large plates used for producing rapid and powerful combustion . A modified form of this apparatus was employed in 1823 in volatilising and fusing carbon . It was with these batteries that the first use of voltaic electricity for blasting under water was made in 1831.
In 1821, the Estonian -German physicist, Thomas Johann Seebeck, demonstrated the electrical potential in the juncture points of two dissimilar metals when there is a temperature difference between the joints. He joined a copper wire with a bismuth wire to form a loop or circuit. Two junctions were formed by connecting the ends of the wires to each other. He then accidentally discovered that if he heated one junction to a high temperature, and the other junction remained at room temperature, a magnetic field was observed around the circuit.
He did not recognise that an electric current was being generated when heat was applied to a bi-metal junction. He used the term "thermomagnetic currents" or "thermomagnetism" to express his discovery. Over the following two years, he reported on his continuing observations to the Prussian Academy of Sciences , where he described his observation as "the magnetic polarization of metals and ores produced by a temperature difference." This Seebeck effect became the basis of the thermocouple , which is still considered the most accurate measurement of temperature today. The converse Peltier effect was seen over a decade later when a current was run through a circuit with two dissimilar metals, resulting in a temperature difference between the metals.
In 1827 German scientist Georg Ohm expressed his law in his famous book Die galvanische Kette, mathematisch bearbeitet (The Galvanic Circuit Investigated Mathematically) in which he gave his complete theory of electricity.
In 1829 Antoine-César Becquerel developed the "constant current" cell, forerunner of the well-known Daniell cell . When this acid-alkali cell was monitored by a galvanometer , current was found to be constant for an hour, the first instance of "constant current". He applied the results of his study of thermoelectricity to the construction of an electric thermometer, and measured the temperatures of the interior of animals, of the soil at different depths, and of the atmosphere at different heights. He helped validate Faraday's laws and conducted extensive investigations on the electroplating of metals with applications for metal finishing and metallurgy . Solar cell technology dates to 1839 when Becquerel observed that shining light on an electrode submerged in a conductive solution would create an electric current.
Michael Faraday began, in 1832, what promised to be a rather tedious attempt to prove that all electricities had precisely the same properties and caused precisely the same effects. The key effect was electrochemical decomposition. Voltaic and electromagnetic electricity posed no problems, but static electricity did. As Faraday delved deeper into the problem, he made two startling discoveries. First, electrical force did not, as had long been supposed, act at a distance upon molecules to cause them to dissociate. It was the passage of electricity through a conducting liquid medium that caused the molecules to dissociate, even when the electricity merely discharged into the air and did not pass through a "pole" or "center of action" in a voltaic cell. Second, the amount of the decomposition was found to be related directly to the amount of electricity passing through the solution.
These findings led Faraday to a new theory of electrochemistry. The electric force, he argued, threw the molecules of a solution into a state of tension. When the force was strong enough to distort the forces that held the molecules together so as to permit the interaction with neighbouring particles, the tension was relieved by the migration of particles along the lines of tension, the different parts of atoms migrating in opposite directions. The amount of electricity that passed, then, was clearly related to the chemical affinities of the substances in solution. These experiments led directly to Faraday's two laws of electrochemistry which state:
William Sturgeon built an electric motor in 1832 and invented the commutator , a ring of metal-bristled brushes which allow the spinning armature to maintain contact with the electric current and changed the alternating current to a pulsating direct current . He also improved the voltaic battery and worked on the theory of thermoelectricity.
Hippolyte Pixii , a French instrument maker, constructed the first dynamo in 1832 and later built a direct current dynamo using the commutator. This was the first practical mechanical generator of electric current that used concepts demonstrated by Faraday.
John Daniell began experiments in 1835 in an attempt to improve the voltaic battery with its problems of being unsteady and a weak source of electric current. His experiments soon led to remarkable results. In 1836, he invented a primary cell in which hydrogen was eliminated in the generation of the electricity. Daniell had solved the problem of polarization . In his laboratory he had learned to alloy the amalgamated zinc of Sturgeon with mercury. His version was the first of the two-fluid class battery and the first battery that produced a constant reliable source of electric current over a long period of time.
William Grove produced the first fuel cell in 1839. He based his experiment on the fact that sending an electric current through water splits the water into its component parts of hydrogen and oxygen. So, Grove tried reversing the reaction—combining hydrogen and oxygen to produce electricity and water. Eventually the term fuel cell was coined in 1889 by Ludwig Mond and Charles Langer , who attempted to build the first practical device using air and industrial coal gas . He also introduced a powerful battery at the annual meeting of the British Association for the Advancement of Science in 1839. Grove's first cell consisted of zinc in diluted sulfuric acid and platinum in concentrated nitric acid , separated by a porous pot. The cell was able to generate about 12 amperes of current at about 1.8 volts. This cell had nearly double the voltage of the first Daniell cell. Grove's nitric acid cell was the favourite battery of the early American telegraph (1840–1860), because it offered strong current output.
As telegraphs became more complex, the need for a constant voltage became critical and the Grove device was limited (as the cell discharged, nitric acid was depleted and voltage was reduced). By the time of the American Civil War , Grove's battery had been replaced by the Daniell battery. In 1841 Robert Bunsen replaced the expensive platinum electrode used in Grove's battery with a carbon electrode. This led to large scale use of the "Bunsen battery" in the production of arc-lighting and in electroplating.
Wilhelm Weber developed, in 1846, the electrodynamometer , in which a current causes a coil suspended within another coil to turn when a current is passed through both. In 1852, Weber defined the absolute unit of electrical resistance (which was named the ohm after Georg Ohm). Weber's name is now used as a unit name to describe magnetic flux , the weber .
German physicist Johann Hittorf concluded that ion movement caused electric current. In 1853 Hittorf noticed that some ions traveled more rapidly than others. This observation led to the concept of transport number, the rate at which particular ions carried the electric current. Hittorf measured the changes in the concentration of electrolysed solutions, computed from these the transport numbers (relative carrying capacities) of many ions, and, in 1869, published his findings governing the migration of ions.
In 1866, Georges Leclanché patented a new battery system, which was immediately successful. Leclanché's original cell was assembled in a porous pot. The positive electrode (the cathode ) consisted of crushed manganese dioxide with a little carbon mixed in. The negative pole ( anode ) was a zinc rod. The cathode was packed into the pot, and a carbon rod was inserted to act as a current collector. The anode and the pot were then immersed in an ammonium chloride solution. The liquid acted as the electrolyte, readily seeping through the porous pot and making contact with the cathode material. Leclanché's "wet" cell became the forerunner to the world's first widely used battery, the zinc-carbon cell.
In 1869 Zénobe Gramme devised his first clean direct current dynamo. His generator featured a ring armature wound with many individual coils of wire.
Svante August Arrhenius published his thesis in 1884, Recherches sur la conductibilité galvanique des électrolytes (Investigations on the galvanic conductivity of electrolytes). From the results of his experiments, the author concluded that electrolytes, when dissolved in water, become to varying degrees split or dissociated into positive and negative ions. The degree to which this dissociation occurred depended above all on the nature of the substance and its concentration in the solution, being more developed the greater the dilution. The ions were supposed to be the carriers of not only the electric current, as in electrolysis, but also of the chemical activity. The relation between the actual number of ions and their number at great dilution (when all the molecules were dissociated) gave a quantity of special interest ("activity constant").
The race for the commercially viable production of aluminium was won in 1886 by Paul Héroult and Charles M. Hall . The problem many researchers had with extracting aluminium was that electrolysis of an aluminium salt dissolved in water yields aluminium hydroxide . Both Hall and Héroult avoided this problem by dissolving aluminium oxide in a new solvent— fused cryolite ( Na 3 Al F 6 ).
Wilhelm Ostwald , 1909 Nobel Laureate , started his experimental work in 1875, with an investigation on the law of mass action of water in relation to the problems of chemical affinity, with special emphasis on electrochemistry and chemical dynamics . In 1894 he gave the first modern definition of a catalyst and turned his attention to catalytic reactions. Ostwald is especially known for his contributions to the field of electrochemistry, including important studies of the electrical conductivity and electrolytic dissociation of organic acids.
Hermann Nernst developed the theory of the electromotive force of the voltaic cell in 1888. He developed methods for measuring dielectric constants and was the first to show that solvents of high dielectric constants promote the ionization of substances. Nernst's early studies in electrochemistry were inspired by Arrhenius' dissociation theory which first recognised the importance of ions in solution. In 1889, Nernst elucidated the theory of galvanic cells by assuming an "electrolytic pressure of dissolution," which forces ions from electrodes into solution and which was opposed to the osmotic pressure of the dissolved ions. He applied the principles of thermodynamics to the chemical reactions proceeding in a battery. In that same year he showed how the characteristics of the current produced could be used to calculate the free energy change in the chemical reaction producing the current. He constructed an equation, known as Nernst Equation , which describes the relation of a battery cell's voltage to its properties.
In 1898 Fritz Haber published his textbook, Electrochemistry: Grundriss der technischen Elektrochemie auf theoretischer Grundlage (The Theoretical Basis of Technical Electrochemistry), which was based on the lectures he gave at Karlsruhe . In the preface to his book he expressed his intention to relate chemical research to industrial processes and in the same year he reported the results of his work on electrolytic oxidation and reduction, in which he showed that definite reduction products can result if the voltage at the cathode is kept constant. In 1898 he explained the reduction of nitrobenzene in stages at the cathode and this became the model for other similar reduction processes.
In 1909, Robert Andrews Millikan began a series of experiments to determine the electric charge carried by a single electron. He began by measuring the course of charged water droplets in an electrical field. The results suggested that the charge on the droplets is a multiple of the elementary electric charge, but the experiment was not accurate enough to be convincing. He obtained more precise results in 1910 with his famous oil-drop experiment in which he replaced water (which tended to evaporate too quickly) with oil.
Jaroslav Heyrovský , a Nobel laureate, eliminated the tedious weighing required by previous analytical techniques, which used the differential precipitation of mercury by measuring drop-time. In the previous method, a voltage was applied to a dropping mercury electrode and a reference electrode was immersed in a test solution. After 50 drops of mercury were collected, they were dried and weighed. The applied voltage was varied and the experiment repeated. Measured weight was plotted versus applied voltage to obtain the curve. In 1921, Heyrovský had the idea of measuring the current flowing through the cell instead of just studying drop-time.
On February 10, 1922, the " polarograph " was born as Heyrovský recorded the current-voltage curve for a solution of 1 mol/L NaOH . Heyrovský correctly interpreted the current increase between −1.9 and −2.0 V as being due to the deposit of Na + ions, forming an amalgam. Shortly thereafter, with his Japanese colleague Masuzo Shikata , he constructed the first instrument for the automatic recording of polarographic curves, which became world-famous later as the polarograph.
In 1923, Johannes Nicolaus Brønsted and Thomas Martin Lowry published essentially the same theory about how acids and bases behave using electrochemical basis.
The International Society of Electrochemistry (ISE) was founded in 1949, and some years later the first sophisticated electrophoretic apparatus was developed in 1937 by Arne Tiselius , who was awarded the 1948 Nobel prize for his work in protein electrophoresis . He developed the "moving boundary," which later would become known as zone electrophoresis , and used it to separate serum proteins in solution. Electrophoresis became widely developed in the 1940s and 1950s when the technique was applied to molecules ranging from the largest proteins to amino acids and even inorganic ions.
During the 1960s and 1970s quantum electrochemistry was developed by Revaz Dogonadze and his pupils. | https://en.wikipedia.org/wiki/History_of_electrochemistry |
The history of electrophoresis for molecular separation and chemical analysis began with the work of Arne Tiselius in 1931, while new separation processes and chemical speciation analysis techniques based on electrophoresis continue to be developed in the 21st century. [ 1 ] Tiselius, with support from the Rockefeller Foundation , developed the Tiselius Apparatus for moving-boundary electrophoresis , which was described in 1937 in the well-known paper "A New Apparatus for Electrophoretic Analysis of Colloidal Mixtures" . [ 2 ]
The method spread slowly until the advent of effective zone electrophoresis methods in the 1940s and 1950s , which used filter paper or gels as supporting media. By the 1960s , increasingly sophisticated gel electrophoresis methods made it possible to separate biological molecules based on minute physical and chemical differences, helping to drive the rise of molecular biology and biochemistry . Gel electrophoresis and related techniques became the basis for a wide range of biochemical methods , such as protein fingerprinting , Southern blot , other blotting procedures, DNA sequencing , and many more. [ 3 ]
Early work with the basic principle of electrophoresis dates to the early 19th century, based on Faraday's laws of electrolysis proposed in the late 18th century and other early electrochemistry . The electrokinetic phenomenon was observed for the first time in 1807 by Russian professors Peter Ivanovich Strakhov and Ferdinand Frederic Reuß at Moscow University , [ 4 ] who noticed that the application of a constant electric field caused clay particles dispersed in water to migrate.
Experiments by Johann Wilhelm Hittorf , Walther Nernst , and Friedrich Kohlrausch to measure the properties and behavior of small ions moving through aqueous solutions under the influence of an electric field led to general mathematical descriptions of the electrochemistry of aqueous solutions. Kohlrausch created equations for varying concentrations of charged particles moving through solution, including sharp moving boundaries of migrating particles. By the beginning of the 20th century, electrochemists had found that such moving boundaries of charged particles could be created with U-shaped glass tubes. [ 5 ]
Methods of optical detection of moving boundaries in liquids had been developed by August Toepler in the 1860s ; Toepler measured the schlieren ( shadows ) or slight variations in optical properties in inhomogeneous solutions. This method combined with the theoretical and experimental methods for creating and analysing charged moving boundaries would form the basis of Tiselius's moving-boundary electrophoresis method. [ 6 ]
The apparatus designed by Arne Tiselius in 1931 enabled a range of new applications of electrophoresis in analyzing chemical mixtures. Its development, significantly funded by the Rockefeller Foundation , was an extension of Tiselius's earlier PhD studies. With more assistance from the Rockefeller Foundation, the expensive Tiselius Apparatus was built at a number of major centers of chemical research.
By the late 1940s, new electrophoresis methods were beginning to address some of the shortcomings of the moving-boundary electrophoresis of the Tiselius Apparatus, which was not capable of completely separating electrophoretically similar compounds. Rather than charged molecules moving freely through solutions, the new methods used solid or gel matrices in new electrophoresis apparatuses to separate compounds into discrete and stable bands or zones. In 1950, Tiselius dubbed these methods " zone electrophoresis ".
Zone electrophoresis found widespread application in biochemistry after Oliver Smithies introduced starch gel as an electrophoretic substrate in 1955. Starch gel (and later polyacrylamide and other gels) enabled the efficient separation of proteins, making it possible with relatively simple technology to analyze complex protein mixtures and identify minute differences in related proteins. [ 7 ]
Despite the development of high-resolution zone electrophoresis methods, the accurate control of parameters such as pore size and stability of polyacrylamide gels was still a major challenge in the 20th century . These technical problems were finally solved in the early 2000s with the introduction of a standardized polymerization time for optimized polyacrylamide gels, making it possible for the first time to fractionate physiological concentrations of highly purified metal ion cofactors and associated proteins in quantitative amounts for structure analysis . [ 8 ]
Since the 1950s, electrophoresis methods have diversified considerably, and new methods and applications are still being developed as affinity electrophoresis , capillary electrophoresis , electroblotting , electrophoretic mobility shift assay , free-flow electrophoresis , isotachophoresis , preparative native PAGE , and pulsed-field gel electrophoresis . [ 8 ] | https://en.wikipedia.org/wiki/History_of_electrophoresis |
The history of email spam reaches back to the mid-1990s, when commercial use of the internet first became possible [ 1 ] [ 2 ] —and marketers and publicists began to test what was possible.
Very soon, email spam was ubiquitous, unavoidable, and repetitive. [ 3 ] This article details significant events in the history of spam, and the efforts made to limit it.
Commercialization of the internet and integration of electronic mail as an accessible means of communication has another face—the influx of unwanted information and mails. As the internet started to gain popularity in the early 1990s, it was quickly recognized as an excellent advertising tool. At practically no cost, a person can use the internet to send an email message to thousands of people. These unsolicited junk electronic mails came to be called 'Spam'. The history of spam is intertwined with the history of electronic mail.
While the linguistic significance of the usage of the word 'spam' is attributed to the British comedy troupe Monty Python in a now legendary sketch from their Flying Circus TV series, in which a group of Vikings sing a chorus of "SPAM, SPAM, SPAM..." at increasing volumes, the historic significance lies in it being adopted to refer to unsolicited commercial electronic mail sent to a large number of addresses, in what was seen as drowning out normal communication on the internet. [ 4 ]
The first known spam electronic mail (although not yet called email), was sent on May 3, 1978 to several hundred users on ARPANET . It was an advertisement for a presentation by Digital Equipment Corporation for their DECSYSTEM-20 products sent by Gary Thuerk, a marketer of theirs. [ 5 ]
The reaction to it was almost universally negative, and for a long time there were no further instances.
The name "spam" was actually first applied, in April 1993, not to an email, but to unwanted postings on Usenet newsgroup network. Richard Depew accidentally posted 200 messages to news.admin.policy and in the aftermath readers of this group were making jokes about the accident, when one person referred to the messages as “spam”, [ 6 ] coining the term that would later be applied to similar incidents over email.
On January 18, 1994, the first large-scale deliberate USENET spam occurred. A message with the subject “Global Alert for All: Jesus is Coming Soon” was cross-posted to every available newsgroup. [ 7 ] [ 8 ] Its controversial message sparked many debates all across USENET.
In April 1994, the first commercial USENET spam arrived. Two lawyers from Phoenix, Canter and Siegel , hired a programmer to post their "Green Card Lottery- Final One?" message to as many newsgroups as possible. [ 8 ] [ 9 ] [ 10 ] What made them different was that they did not hide the fact that they were spammers. They were proud of it, and thought it was great advertising. They even went on to write the book "How to Make a Fortune on the Information Superhighway : Everyone’s Guerrilla Guide to Marketing on the internet and Other On-Line Services". They planned on opening a consulting company to help other people post similar advertisements, but it never took off.
MAPS (" Mail Abuse Prevention System ") was founded in 1996. Dave Rand and Paul Vixie , well known internet software engineers, had started keeping a list of IP addresses which had sent out spam or engaged in other behavior they found objectionable. The list became known as the Real-time Blackhole List ( RBL ). Many network managers wanted to use the RBL to block unwanted email. Thus, Rand and Vixie created a DNS-based distribution scheme which quickly became popular. [ 11 ]
Spam was already becoming a serious concern, leading in late 1997 to the MAPS , which was "blackhole list" to allow mail servers to block mail coming from spam sources.
Others started DNS-based blacklists of open relays.
Alan Hodgson started Dorkslayers in September 1998. By November 1998, he was forced to close, since his upstream BCTel considered the open relay scanning to be abusive. The successor ORBS project was then moved to Alan Brown in New Zealand. [ 12 ]
Al Iverson of Radparker started the RRSS around May 1999. By September 1999, that project was folded into the MAPS group of DNS-based lists as the RSS.
In August 1999, MAPS listed the ORBS mail servers, since the ORBS relay testing was thought to be abusive.
The SpamAssassin spam-filtering system was first uploaded to SourceForge .net on April 20, 2001 by creator Justin Mason.
In May 2000 the ILOVEYOU computer worm travelled by email to tens of millions of Windows personal computers. [ 13 ] Although not spam, its impact highlighted how pervasive email had become.
In June 2001, ORBS was sued in New Zealand, and shortly thereafter closed down (see Open Relay Behavior-modification System#Lawsuits for more details) .
In August 2002, Paul Graham published an influential paper, "A plan for spam", [ 14 ] describing a spam-filtering technique using improved Bayesian filtering [ 15 ] [ 16 ] and variants of this were soon implemented in a number of products. [ 17 ] including server-side email filters, such as DSPAM , SpamAssassin, [ 18 ] and SpamBayes . [ 19 ]
In June 2003, Meng Weng Wong started the SPF-discuss mailing list and posted the very first version of the "Sender Permitted From" proposal, that would later become the Sender Policy Framework , a simple email-validation system designed to detect email spoofing as part of the solution to spam.
The CAN-SPAM Act of 2003 was signed into law by President George W. Bush on December 16, 2003, establishing the United States ' first national standards for the sending of commercial email and requiring the Federal Trade Commission (FTC) to enforce its provisions. The backronym CAN-SPAM derives from the bill's full name: " C ontrolling the A ssault of N on- S olicited P ornography A nd M arketing Act of 2003". It plays on the word "canning" (putting an end to) spam , as in the usual term for unsolicited email of this type; as well as a pun in reference to the canned SPAM food product. The bill was sponsored in Congress by Senators Conrad Burns and Ron Wyden .
In January 2004, Bill Gates of Microsoft announced that "spam will soon be a thing of the past." [ 20 ] [ 21 ] [ 22 ]
In May 2004, Howard Carmack of Buffalo, New York was sentenced to 3½ to 7 years for sending 800 million messages, using stolen identities. In May 2003 he also lost a $16 million civil lawsuit to EarthLink . [ 23 ]
On September 27, 2004, Nicholas Tombros pleaded guilty to charges and became the first spammer to be convicted under the CAN-SPAM Act of 2003 . [ 24 ] He was sentenced in July 2007 to three years' probation, six months' house arrest, and fined $10,000. [ 25 ]
On November 4, 2004, Jeremy Jaynes , rated the 8th-most prolific spammer in the world, according to Spamhaus , was convicted of three felony charges of using servers in Virginia to send thousands of fraudulent emails. The court recommended a sentence of nine years' imprisonment, which was imposed in April 2005 although the start of the sentence was deferred pending appeals. Jaynes claimed to have an income of $750,000 a month from his spamming activities. On February 29, 2008 the Supreme Court of Virginia overturned his conviction. [ 26 ]
On November 8, 2004, Nick Marinellis of Sydney , Australia , was sentenced to 4⅓ to 5¼ years for sending Nigerian 419 emails. [ 27 ]
On December 31, 2004, British authorities arrested Christopher Pierson in Lincolnshire , UK and charged him with malicious communication and causing a public nuisance . On January 3, 2005, he pleaded guilty to sending hoax emails to relatives of people missing following the Asian tsunami disaster.
On July 25, 2005, Russian spammer Vardan Kushnir , who is believed to have spammed every single Russian internet user, was found dead in his Moscow apartment, having suffered numerous blunt-force blows to the head. It is believed that Kushnir's murder was unrelated to his spamming activities. [ 28 ]
On November 1, 2005, David Levi, 29, of Lytham, England was sentenced to four years for conspiracy to defraud by sending emails pretending to be from eBay . His brother Guy Levi, 22, was sentenced to 21 months after pleading guilty to conspiracy to defraud, and four others were each sentenced to six months for money laundering . [ 29 ]
On November 16, 2005, Peter Francis-Macrae of Cambridgeshire , described as Britain 's most prolific spammer, was sentenced to six years in prison. [ 30 ]
In January 2006, James McCalla was ordered to pay $11.2 billion to an ISP in Iowa , U.S. and barred from using the internet for 3 years for sending 280 million email messages. In court, he was not represented by an attorney. [ 31 ]
On June 28, 2006, IronPort released a study which found 80% of spam emails originating from zombie computers . The report also found 55 billion daily spam emails in June 2006, a large increase from 35 billion daily spam emails in June 2005. The study used SenderData which represents 25% of global email traffic and data from over 100,000 ISP's, universities , and corporations .
On August 8, 2006, AOL announced the intention of digging up the garden of the parents of spammer Davis Wolfgang Hawke in search of buried gold and platinum. [ 32 ] AOL had been awarded a US$12.8 million judgment in May 2005 against Hawke, who had gone into hiding. The permission for the search was granted by a judge after AOL proved that the spammer had bought large amounts of gold and platinum. [ 33 ] In July, 2007, AOL decided not to proceed. [ 34 ]
On October 12, 2006, Brian Michael McMullen , 22, of East Pittsburgh, Pennsylvania , U.S., was sentenced to three years' supervised release, five months' home detention and ordered to pay restitution in the amount of $11,848.55 for violating the CAN-SPAM Act of 2003 . [ 35 ]
On October 27, 2006, the Federal Court of Australia fined Clarity1 A$4.5 million (US$3.4 million; euro2.7 million) and its director Wayne Mansfield A$1 million (US$760,000; euro600,000) for sending unsolicited emails in the first conviction under Australia's Spam Act of 2003 . [ 36 ]
In November 2006, Christopher William Smith (aka Chris "Rizler" Smith) was convicted on 9 counts for offenses related to Smith's spamming.
On January 16, 2007, an Azusa, California man was convicted by a jury in United States District Court for the Central District of California in Los Angeles in United States v. Goodin, U.S. District Court, Central District of California, 06-110 , under the CAN-SPAM Act of 2003 (the first conviction under that Act). [ 37 ] He was sentenced to and began serving a 70-month sentence on June 11, 2007. [ 38 ]
On May 30, 2007, notorious spammer Robert Soloway was arrested after having been indicted by a federal grand jury on 35 charges including mail fraud, wire fraud, email fraud, identity theft , and money laundering. [ 39 ] If convicted, he could face decades behind bars. [ 40 ] Bail was initially denied although he was released to a half way house in September. On March 14, 2008, Robert Soloway reached an agreement with federal prosecutors, two weeks before his scheduled trial on 40 charges. Soloway pleaded guilty to three charges - felony mail fraud, fraud in connection with email, and failing to file a 2005 tax return. [ 41 ] In exchange, federal prosecutors dropped all other charges. Soloway faced up to 26 years in prison on the most serious charge, and up to $625,000 total in fines. On 22 July 2008 Robert Soloway was sentenced four years in federal prison . [ 42 ]
On June 25, 2007, two men were each convicted on eight counts including conspiracy, fraud, money laundering, and transportation of obscene materials in U.S. District Court in Phoenix, Arizona . The prosecution is the first of its kind under the CAN-SPAM Act of 2003 , according to a release from the Department of Justice . [ 43 ] One count for each under the act was for falsifying headers, the other was for using domain names registered with false information. The two had been sending millions of hard-core pornography spam emails. [ 44 ] The two men were sentenced to five years in prison and ordered to forfeit US$1.3 million. [ 45 ]
On July 20, 2008, Eddie Davidson "the Spam King" walked away from a federal prison camp in Florence, Colorado . He was subsequently found dead in Arapahoe County, Colorado , after reportedly killing his wife and three-year-old daughter, in an apparent murder-suicide. [ 46 ]
August 19: A survey on Marshal Limited's website (an email and internet content security company) showed that 29% of the 622 respondents had bought something from a spam email. Other studies, one by Forrester Research in 2004, which surveyed 6,000 active Web users, reported 20 percent had bought something from spam, while a 2005 study by Mirapoint and the Radicati Group showed 11%, and 57% indicated that clicking on a link in spam caused them to receive more spam than before. [ 47 ] A 2007 study by Endai Worldwide (an email marketing company) showed 16% had bought something from spam. [ 48 ] In response to the Marshal study, the Download Squad started their own study. With 289 respondents, only 2.1% indicated they had ever bought something from a spam email. [ 49 ]
November 11: McColo , a San Jose, California -based hosting provider identified as hosting spamming organizations, was cut off by its internet providers. It is estimated that McColo hosted the machines responsible for 75 percent of spam sent worldwide. McColo's upstream service was severed on Tuesday, November 11; that same afternoon, organizations tracking spam noted a sharp decrease in the volume being sent; some as much as a half. [ 50 ] | https://en.wikipedia.org/wiki/History_of_email_spam |
Ethical idealism , [ 1 ] which is also referred to by terms such as moral idealism , [ 2 ] [ 3 ] principled idealism , [ 4 ] and other expressions, is a philosophical framework based on holding onto specifically defined ideals in the context of facing various consequences to holding such principles and/or values . Such ideals, which are analyzed during the process of ethical thinking , become applied in practice via a group of specific goals relative to what has been learned over time about morality . As noted by philosopher Norbert Paulo, following ideals in a doctrinaire fashion will "exceed obligations" put on people such that actions "are warranted, but not strictly required." [ 5 ]
With certain philosophical movements throughout history emphasizing various types of moral idealism, such as influences being a part of Christian ethics , Jewish ethics , and Platonist ethics , it relates to human decision making as differing alternatives get compared and contrasted. [ 1 ] [ 3 ] Advocates for ethical idealism, such as the philosopher Nicholas Rescher , have asserted that inherent mental concepts shared in terms of the human condition among multiple peoples have a real, tangible nature due to their influences turning logical thinking into action, particularly by stimulating peoples' sense of motivation . [ 1 ] In contrast, skeptical philosophers, such as Richard Rorty , have argued that the complex course of recorded history has shown that "to do the right thing is largely a matter of luck" and particularly is due to "being born in a certain place and a certain time." [ 3 ]
Debates and discussions held on not just ethical idealism specifically but on the general difficulty of defining goodness versus evilness in an intellectual fashion has become a "great divide in contemporary philosophy". [ 3 ]
A range of different philosophical movements throughout history have emphasized moral idealism, with this including the doctrine influencing Christian ethics , Jewish ethics , and Platonist ethics . This has occurred in the context of an underlying argument about morality in which, as one scholar has put it, certain thinkers have postulated "an underlying sense of right and wrong that is common to all human beings at all times and places". Ongoing debates on whether or not these kinds of inherent mental concepts truly exist have been called a "great divide in contemporary philosophy". [ 3 ]
A framework in the mind based on holding onto specifically defined ideals weighs them in the context of facing various consequences to holding such principles and/or values . An ideal placed under intellectual analysis become applied in practice via a group of specific goals relative to what has been learned over time about moral thinking. As noted by Austrian philosopher Norbert Paulo, following ideals in a doctrinaire fashion will "exceed obligations" put on people such that actions "are warranted, but not strictly required." [ 5 ]
American scholar Nicholas Rescher has stated that metaphysics comes into play when analyzing such a philosophical viewpoint about human thinking given that nature of ideals gives them a particular status as "useful fictions", with this developing in terms of their special existence relative to the broader concept of ethical choice . He has described a worldview coming into focus via logical thinking based on moral idealism that he has defined in depth, remarking that "it [is] rational to strive for the unattainable" and that a "practicality" exists in "seriously pursuing impossible dreams." He interpreted the human condition shared among multiple groups as tied together in a real, tangible fashion due to their mutual influences that've resulted from idealistic ethics, particularly by such ideas stimulating peoples' sense of motivation . [ 1 ]
Writing in his book Ethical Idealism: An Inquiry Into the Nature and Function of Ideals , Rescher specifically argued,
"The 'reality' of an ideal lies not in its substantive realization in some separate domain but in its formative impetus upon human thought and action in this imperfect world. The object at issue with an ideal does not, and cannot, exist as such. What does, however, exist is the idea of such an object. Existing, as it must, in thought alone (in the manner appropriate to ideas), it exerts a powerful[ly] organizing and motivating force on our thinking, providing at once a standard of appraisal and [also] a stimulus to action." [ 1 ]
Other thinkers have asserted that ideals as such constitute things that ought to be said to exist in the real world, having a substance partly to the same extent as human beings and similarly material-based entities . A prominent example of this philosophical take is the ancient Greek intellectual figure of Plato . To him, ideals represented self-contained objects existing in their own domain that humanity discovered through reason rather than invented out of whole cloth for narrow benefit. Thus, while existing in relation to the human mind, ideals still possessed a certain kind of metaphysical independence according to Plato. Labeled later on as an ethical idealist, given his large legacy , Plato saw these applied moral views as significantly influential on one's life course. [ 1 ]
With respect to how exactly human reason should work, American philosopher Ralph Barton Perry defined idealistic morality as being the result of a particular attitude about the act of attaining knowledge itself, writing in his book The Moral Economy ,
"Moral idealism means to interpret life consistently with ethical, scientific, and metaphysical truth. It endeavors to justify the maximum of hope, without compromising or confusing any enlightenment judgement of truth. In this it is, I think, not only consistent with the spirit of a liberal and rational age but also with the primary motive of religion. There can be no religion... without an open and candid mind as well as an indomitable purpose." [ 2 ]
In a keynote speech given in August 2005, American scholar Richard Rorty remarked upon morally idealistic philosophy in the context of strictly specified principles through the lens of his views on applied ethics , asserting to a group of business professionals,
"[I]ndividuals become aware of more alternatives, and therefore wiser, as they grow older. The human race as a whole has become wiser as history has moved along. The source of these new alternatives is the human imagination. It is the ability to come up with new ideas, rather than the ability to get in touch with unchanging essences, that is the engine of moral progress." [ 3 ]
Rorty has argued that the complex course of recorded history has shown that "to do the right thing is largely a matter of luck", with standards of morality being far from broadly universal and instead coming fundamentally from "being born in a certain place and a certain time." He has highlighted the disconnect between intellectual abilities and other elements related to personal character , noting for instance the clarity of vision and rhetorical skill used by historical actors such as those inside of Nazi Germany . In Rorty's opinion, humanity as a whole has advanced at an ethical level due to gradual progress via both technological change and social advancement, which reflects efforts at improving civilization itself. [ 3 ]
German philosopher Immanuel Kant 's particular view of human nature and intellectual inquiry, later summed up as " Kantianism ", stressed the inherent power of logical thinking in terms of moral analysis. Kant's advocacy for the " categorical imperative ", a doctrine through which every individual choice has to be made with the consideration of the decider that it ought to be a universally held maxim, took place in the broader context of his metaphysical views. In Kant's writings, defiance of higher principles was not only wrong in a practical sense but in a fundamentally rational and thus moral sense as well.
All of that has resulted in Kant's intellectual framework being described as a philosophy of moral idealism by later scholars such as Nicholas Rescher. The latter thinker wrote that at a fundamental level Kant had understood that expressing an ideal meant applying "a regulative principle of reason" that commands one's mind to thus use logical thinking in painting a mental landscape "as if certain 'idealized' conditions could be realized". As a matter of working out intellectual concepts, Kant asserted the notion that "ought" implies "can", which as an argument has long attracted controversy and debate among philosophers. [ 1 ]
Works authored by Kant on these overall subjects include the initial publication The Groundwork of the Metaphysics of Morals followed by The Critique of Practical Reason , The Metaphysics of Morals , Anthropology from a Pragmatic Point of View , Religion within the Boundaries of Mere Reason , with those latter commentaries developing the intellectual figure's thinking. Within the pages of Anthropology from a Pragmatic Point of View in particular, the philosopher articulated a vision of people as by their very essence driven by meaningful ethics. Through the lens of Kant's doctrine, no ironclad divide has existed between morality and the natural world , with empirical analysis of human psychology dovetailing with studies of people's ideals.
The philosopher's metaphysics tied closely with his socio-political views and belief in fundamental advancement, such that Kant wrote inside of the pages of the Critique of Pure Reason in detail,
"What the highest level might be at which humanity may have to come to rest, and how great a gulf may still be left between the idea [of perfection] and its realization, are questions which no one can, or ought to answer. For the matter depends upon freedom; and it is in the very nature of freedom to pass beyond any and every specified limit." [ 6 ]
Evaluating Kant's method of turning ideal-based standards into a broader ethical framework in context, scholar Frederick P. Van De Pitte has written about the primacy of rationality to the philosopher, with Pitte remarking,
"Kant realized that man's rational capacity alone is not sufficient to constitute his dignity and elevate him above the brutes. If reason only enables him to do for himself what instinct does for the animal, then it would indicate for man no higher aim or destiny than that of the brute but only a different way of attaining the same end. However, reason is man's most essential attribute because it is the means by which a truly distinctive dimension is made possible for him. Reason, that is, reflective awareness, makes it possible to distinguish between good and bad, and thus morality can be made the ruling purpose of life. Because man can consider an array of possibilities, and which among them is the most desirable, he can strive to make himself and his world into a realization of his ideals." [ 6 ] | https://en.wikipedia.org/wiki/History_of_ethical_idealism |
In computing , floating-point arithmetic ( FP ) is arithmetic on subsets of real numbers formed by a significand (a signed sequence of a fixed number of digits in some base ) multiplied by an integer power of that base.
Numbers of this form are called floating-point numbers . [ 1 ] : 3 [ 2 ] : 10
For example, the number 2469/200 is a floating-point number in base ten with five digits: 2469 / 200 = 12.345 = 12345 ⏟ significand × 10 ⏟ base − 3 ⏞ exponent {\displaystyle 2469/200=12.345=\!\underbrace {12345} _{\text{significand}}\!\times \!\underbrace {10} _{\text{base}}\!\!\!\!\!\!\!\overbrace {{}^{-3}} ^{\text{exponent}}} However, 7716/625 = 12.3456 is not a floating-point number in base ten with five digits—it needs six digits.
The nearest floating-point number with only five digits is 12.346.
And 1/3 = 0.3333… is not a floating-point number in base ten with any finite number of digits.
In practice, most floating-point systems use base two , though base ten ( decimal floating point ) is also common.
Floating-point arithmetic operations, such as addition and division, approximate the corresponding real number arithmetic operations by rounding any result that is not a floating-point number itself to a nearby floating-point number. [ 1 ] : 22 [ 2 ] : 10 For example, in a floating-point arithmetic with five base-ten digits, the sum 12.345 + 1.0001 = 13.3451 might be rounded to 13.345.
The term floating point refers to the fact that the number's radix point can "float" anywhere to the left, right, or between the significant digits of the number. This position is indicated by the exponent, so floating point can be considered a form of scientific notation .
A floating-point system can be used to represent, with a fixed number of digits, numbers of very different orders of magnitude — such as the number of meters between galaxies or between protons in an atom . For this reason, floating-point arithmetic is often used to allow very small and very large real numbers that require fast processing times. The result of this dynamic range is that the numbers that can be represented are not uniformly spaced; the difference between two consecutive representable numbers varies with their exponent. [ 3 ]
Over the years, a variety of floating-point representations have been used in computers. In 1985, the IEEE 754 Standard for Floating-Point Arithmetic was established, and since the 1990s, the most commonly encountered representations are those defined by the IEEE.
The speed of floating-point operations, commonly measured in terms of FLOPS , is an important characteristic of a computer system , especially for applications that involve intensive mathematical calculations.
A floating-point unit (FPU, colloquially a math coprocessor ) is a part of a computer system specially designed to carry out operations on floating-point numbers.
A number representation specifies some way of encoding a number, usually as a string of digits.
There are several mechanisms by which strings of digits can represent numbers. In standard mathematical notation, the digit string can be of any length, and the location of the radix point is indicated by placing an explicit "point" character (dot or comma) there. If the radix point is not specified, then the string implicitly represents an integer and the unstated radix point would be off the right-hand end of the string, next to the least significant digit. In fixed-point systems, a position in the string is specified for the radix point. So a fixed-point scheme might use a string of 8 decimal digits with the decimal point in the middle, whereby "00012345" would represent 0001.2345.
In scientific notation , the given number is scaled by a power of 10 , so that it lies within a specific range—typically between 1 and 10, with the radix point appearing immediately after the first digit. As a power of ten, the scaling factor is then indicated separately at the end of the number. For example, the orbital period of Jupiter 's moon Io is 152,853.5047 seconds, a value that would be represented in standard-form scientific notation as 1.528535047 × 10 5 seconds.
Floating-point representation is similar in concept to scientific notation. Logically, a floating-point number consists of:
To derive the value of the floating-point number, the significand is multiplied by the base raised to the power of the exponent , equivalent to shifting the radix point from its implied position by a number of places equal to the value of the exponent—to the right if the exponent is positive or to the left if the exponent is negative.
Using base-10 (the familiar decimal notation) as an example, the number 152,853.5047 , which has ten decimal digits of precision, is represented as the significand 1,528,535,047 together with 5 as the exponent. To determine the actual value, a decimal point is placed after the first digit of the significand and the result is multiplied by 10 5 to give 1.528535047 × 10 5 , or 152,853.5047 . In storing such a number, the base (10) need not be stored, since it will be the same for the entire range of supported numbers, and can thus be inferred.
Symbolically, this final value is: s b p − 1 × b e , {\displaystyle {\frac {s}{b^{\,p-1}}}\times b^{e},}
where s is the significand (ignoring any implied decimal point), p is the precision (the number of digits in the significand), b is the base (in our example, this is the number ten ), and e is the exponent.
Historically, several number bases have been used for representing floating-point numbers, with base two ( binary ) being the most common, followed by base ten ( decimal floating point ), and other less common varieties, such as base sixteen ( hexadecimal floating point [ 4 ] [ 5 ] [ nb 3 ] ), base eight (octal floating point [ 1 ] [ 5 ] [ 6 ] [ 4 ] [ nb 4 ] ), base four (quaternary floating point [ 7 ] [ 5 ] [ nb 5 ] ), base three ( balanced ternary floating point [ 1 ] ) and even base 256 [ 5 ] [ nb 6 ] and base 65,536 . [ 8 ] [ nb 7 ]
A floating-point number is a rational number , because it can be represented as one integer divided by another; for example 1.45 × 10 3 is (145/100)×1000 or 145,000 /100. The base determines the fractions that can be represented; for instance, 1/5 cannot be represented exactly as a floating-point number using a binary base, but 1/5 can be represented exactly using a decimal base ( 0.2 , or 2 × 10 −1 ). However, 1/3 cannot be represented exactly by either binary (0.010101...) or decimal (0.333...), but in base 3 , it is trivial (0.1 or 1×3 −1 ) . The occasions on which infinite expansions occur depend on the base and its prime factors .
The way in which the significand (including its sign) and exponent are stored in a computer is implementation-dependent. The common IEEE formats are described in detail later and elsewhere, but as an example, in the binary single-precision (32-bit) floating-point representation, p = 24 {\displaystyle p=24} , and so the significand is a string of 24 bits . For instance, the number π 's first 33 bits are: 11001001 00001111 1101101 0 _ 10100010 0. {\displaystyle 11001001\ 00001111\ 1101101{\underline {0}}\ 10100010\ 0.}
In this binary expansion, let us denote the positions from 0 (leftmost bit, or most significant bit) to 32 (rightmost bit). The 24-bit significand will stop at position 23, shown as the underlined bit 0 above. The next bit, at position 24, is called the round bit or rounding bit . It is used to round the 33-bit approximation to the nearest 24-bit number (there are specific rules for halfway values , which is not the case here). This bit, which is 1 in this example, is added to the integer formed by the leftmost 24 bits, yielding: 11001001 00001111 1101101 1 _ . {\displaystyle 11001001\ 00001111\ 1101101{\underline {1}}.}
When this is stored in memory using the IEEE 754 encoding, this becomes the significand s . The significand is assumed to have a binary point to the right of the leftmost bit. So, the binary representation of π is calculated from left-to-right as follows: ( ∑ n = 0 p − 1 bit n × 2 − n ) × 2 e = ( 1 × 2 − 0 + 1 × 2 − 1 + 0 × 2 − 2 + 0 × 2 − 3 + 1 × 2 − 4 + ⋯ + 1 × 2 − 23 ) × 2 1 ≈ 1.57079637 × 2 ≈ 3.1415927 {\displaystyle {\begin{aligned}&\left(\sum _{n=0}^{p-1}{\text{bit}}_{n}\times 2^{-n}\right)\times 2^{e}\\={}&\left(1\times 2^{-0}+1\times 2^{-1}+0\times 2^{-2}+0\times 2^{-3}+1\times 2^{-4}+\cdots +1\times 2^{-23}\right)\times 2^{1}\\\approx {}&1.57079637\times 2\\\approx {}&3.1415927\end{aligned}}}
where p is the precision ( 24 in this example), n is the position of the bit of the significand from the left (starting at 0 and finishing at 23 here) and e is the exponent ( 1 in this example).
It can be required that the most significant digit of the significand of a non-zero number be non-zero (except when the corresponding exponent would be smaller than the minimum one). This process is called normalization . For binary formats (which uses only the digits 0 and 1 ), this non-zero digit is necessarily 1 . Therefore, it does not need to be represented in memory, allowing the format to have one more bit of precision. This rule is variously called the leading bit convention , the implicit bit convention , the hidden bit convention , [ 1 ] or the assumed bit convention .
The floating-point representation is by far the most common way of representing in computers an approximation to real numbers. However, there are alternatives:
In 1914, the Spanish engineer Leonardo Torres Quevedo published Essays on Automatics , [ 9 ] where he designed a special-purpose electromechanical calculator based on Charles Babbage 's analytical engine and described a way to store floating-point numbers in a consistent manner. He stated that numbers will be stored in exponential format as n × 10 m {\displaystyle ^{m}} , and offered three rules by which consistent manipulation of floating-point numbers by machines could be implemented. For Torres, " n will always be the same number of digits (e.g. six), the first digit of n will be of order of tenths, the second of hundredths, etc, and one will write each quantity in the form: n ; m ." The format he proposed shows the need for a fixed-sized significand as is presently used for floating-point data, fixing the location of the decimal point in the significand so that each representation was unique, and how to format such numbers by specifying a syntax to be used that could be entered through a typewriter , as was the case of his Electromechanical Arithmometer in 1920. [ 10 ] [ 11 ] [ 12 ]
In 1938, Konrad Zuse of Berlin completed the Z1 , the first binary, programmable mechanical computer ; [ 13 ] it uses a 24-bit binary floating-point number representation with a 7-bit signed exponent, a 17-bit significand (including one implicit bit), and a sign bit. [ 14 ] The more reliable relay -based Z3 , completed in 1941, has representations for both positive and negative infinities; in particular, it implements defined operations with infinity, such as 1 / ∞ = 0 {\displaystyle ^{1}/_{\infty }=0} , and it stops on undefined operations, such as 0 × ∞ {\displaystyle 0\times \infty } .
Zuse also proposed, but did not complete, carefully rounded floating-point arithmetic that includes ± ∞ {\displaystyle \pm \infty } and NaN representations, anticipating features of the IEEE Standard by four decades. [ 15 ] In contrast, von Neumann recommended against floating-point numbers for the 1951 IAS machine , arguing that fixed-point arithmetic is preferable. [ 15 ]
The first commercial computer with floating-point hardware was Zuse's Z4 computer, designed in 1942–1945. In 1946, Bell Laboratories introduced the Model V , which implemented decimal floating-point numbers . [ 16 ]
The Pilot ACE has binary floating-point arithmetic, and it became operational in 1950 at National Physical Laboratory, UK . Thirty-three were later sold commercially as the English Electric DEUCE . The arithmetic is actually implemented in software, but with a one megahertz clock rate, the speed of floating-point and fixed-point operations in this machine were initially faster than those of many competing computers.
The mass-produced IBM 704 followed in 1954; it introduced the use of a biased exponent . For many decades after that, floating-point hardware was typically an optional feature, and computers that had it were said to be "scientific computers", or to have " scientific computation " (SC) capability (see also Extensions for Scientific Computation (XSC)). It was not until the launch of the Intel i486 in 1989 that general-purpose personal computers had floating-point capability in hardware as a standard feature.
The UNIVAC 1100/2200 series , introduced in 1962, supported two floating-point representations:
The IBM 7094 , also introduced in 1962, supported single-precision and double-precision representations, but with no relation to the UNIVAC's representations. Indeed, in 1964, IBM introduced hexadecimal floating-point representations in its System/360 mainframes; these same representations are still available for use in modern z/Architecture systems. In 1998, IBM implemented IEEE-compatible binary floating-point arithmetic in its mainframes; in 2005, IBM also added IEEE-compatible decimal floating-point arithmetic.
Initially, computers used many different representations for floating-point numbers. The lack of standardization at the mainframe level was an ongoing problem by the early 1970s for those writing and maintaining higher-level source code; these manufacturer floating-point standards differed in the word sizes, the representations, and the rounding behavior and general accuracy of operations. Floating-point compatibility across multiple computing systems was in desperate need of standardization by the early 1980s, leading to the creation of the IEEE 754 standard once the 32-bit (or 64-bit) word had become commonplace. This standard was significantly based on a proposal from Intel, which was designing the i8087 numerical coprocessor; Motorola, which was designing the 68000 around the same time, gave significant input as well.
In 1989, mathematician and computer scientist William Kahan was honored with the Turing Award for being the primary architect behind this proposal; he was aided by his student Jerome Coonen and a visiting professor, Harold Stone . [ 17 ]
Among the x86 innovations are these:
A floating-point number consists of two fixed-point components, whose range depends exclusively on the number of bits or digits in their representation. Whereas components linearly depend on their range, the floating-point range linearly depends on the significand range and exponentially on the range of exponent component, which attaches outstandingly wider range to the number.
On a typical computer system, a double-precision (64-bit) binary floating-point number has a coefficient of 53 bits (including 1 implied bit), an exponent of 11 bits, and 1 sign bit. Since 2 10 = 1024, the complete range of the positive normal floating-point numbers in this format is from 2 −1022 ≈ 2 × 10 −308 to approximately 2 1024 ≈ 2 × 10 308 .
The number of normal floating-point numbers in a system ( B , P , L , U ) where
is 2 ( B − 1 ) ( B P − 1 ) ( U − L + 1 ) {\displaystyle 2\left(B-1\right)\left(B^{P-1}\right)\left(U-L+1\right)} .
There is a smallest positive normal floating-point number,
which has a 1 as the leading digit and 0 for the remaining digits of the significand, and the smallest possible value for the exponent.
There is a largest floating-point number,
which has B − 1 as the value for each digit of the significand and the largest possible value for the exponent.
In addition, there are representable values strictly between −UFL and UFL. Namely, positive and negative zeros , as well as subnormal numbers .
The IEEE standardized the computer representation for binary floating-point numbers in IEEE 754 (a.k.a. IEC 60559) in 1985. This first standard is followed by almost all modern machines. It was revised in 2008 . IBM mainframes support IBM's own hexadecimal floating point format and IEEE 754-2008 decimal floating point in addition to the IEEE 754 binary format. The Cray T90 series had an IEEE version, but the SV1 still uses Cray floating-point format. [ citation needed ]
The standard provides for many closely related formats, differing in only a few details. Five of these formats are called basic formats , and others are termed extended precision formats and extendable precision format . Three formats are especially widely used in computer hardware and languages: [ citation needed ]
Increasing the precision of the floating-point representation generally reduces the amount of accumulated round-off error caused by intermediate calculations. [ 24 ] Other IEEE formats include:
Any integer with absolute value less than 2 24 can be exactly represented in the single-precision format, and any integer with absolute value less than 2 53 can be exactly represented in the double-precision format. Furthermore, a wide range of powers of 2 times such a number can be represented. These properties are sometimes used for purely integer data, to get 53-bit integers on platforms that have double-precision floats but only 32-bit integers.
The standard specifies some special values, and their representation: positive infinity ( +∞ ), negative infinity ( −∞ ), a negative zero (−0) distinct from ordinary ("positive") zero, and "not a number" values ( NaNs ).
Comparison of floating-point numbers, as defined by the IEEE standard, is a bit different from usual integer comparison. Negative and positive zero compare equal, and every NaN compares unequal to every value, including itself. All finite floating-point numbers are strictly smaller than +∞ and strictly greater than −∞ , and they are ordered in the same way as their values (in the set of real numbers).
Floating-point numbers are typically packed into a computer datum as the sign bit, the exponent field, and a field for the significand, from left to right. For the IEEE 754 binary formats (basic and extended) that have extant hardware implementations, they are apportioned as follows:
While the exponent can be positive or negative, in binary formats it is stored as an unsigned number that has a fixed "bias" added to it. Values of all 0s in this field are reserved for the zeros and subnormal numbers ; values of all 1s are reserved for the infinities and NaNs. The exponent range for normal numbers is [−126, 127] for single precision, [−1022, 1023] for double, or [−16382, 16383] for quad. Normal numbers exclude subnormal values, zeros, infinities, and NaNs.
In the IEEE binary interchange formats the leading bit of a normalized significand is not actually stored in the computer datum, since it is always 1. It is called the "hidden" or "implicit" bit. Because of this, the single-precision format actually has a significand with 24 bits of precision, the double-precision format has 53, quad has 113, and octuple has 237.
For example, it was shown above that π, rounded to 24 bits of precision, has:
The sum of the exponent bias (127) and the exponent (1) is 128, so this is represented in the single-precision format as
An example of a layout for 32-bit floating point is
and the 64-bit ("double") layout is similar.
In addition to the widely used IEEE 754 standard formats, other floating-point formats are used, or have been used, in certain domain-specific areas.
By their nature, all numbers expressed in floating-point format are rational numbers with a terminating expansion in the relevant base (for example, a terminating decimal expansion in base-10, or a terminating binary expansion in base-2). Irrational numbers, such as π or 2 {\textstyle {\sqrt {2}}} , or non-terminating rational numbers, must be approximated. The number of digits (or bits) of precision also limits the set of rational numbers that can be represented exactly. For example, the decimal number 123456789 cannot be exactly represented if only eight decimal digits of precision are available (it would be rounded to one of the two straddling representable values, 12345678 × 10 1 or 12345679 × 10 1 ), the same applies to non-terminating digits (. 5 to be rounded to either .55555555 or .55555556).
When a number is represented in some format (such as a character string) which is not a native floating-point representation supported in a computer implementation, then it will require a conversion before it can be used in that implementation. If the number can be represented exactly in the floating-point format then the conversion is exact. If there is not an exact representation then the conversion requires a choice of which floating-point number to use to represent the original value. The representation chosen will have a different value from the original, and the value thus adjusted is called the rounded value .
Whether or not a rational number has a terminating expansion depends on the base. For example, in base-10 the number 1/2 has a terminating expansion (0.5) while the number 1/3 does not (0.333...). In base-2 only rationals with denominators that are powers of 2 (such as 1/2 or 3/16) are terminating. Any rational with a denominator that has a prime factor other than 2 will have an infinite binary expansion. This means that numbers that appear to be short and exact when written in decimal format may need to be approximated when converted to binary floating-point. For example, the decimal number 0.1 is not representable in binary floating-point of any finite precision; the exact binary representation would have a "1100" sequence continuing endlessly:
where, as previously, s is the significand and e is the exponent.
When rounded to 24 bits this becomes
which is actually 0.100000001490116119384765625 in decimal.
As a further example, the real number π , represented in binary as an infinite sequence of bits is
but is
when approximated by rounding to a precision of 24 bits.
In binary single-precision floating-point, this is represented as s = 1.10010010000111111011011 with e = 1.
This has a decimal value of
whereas a more accurate approximation of the true value of π is
The result of rounding differs from the true value by about 0.03 parts per million, and matches the decimal representation of π in the first 7 digits. The difference is the discretization error and is limited by the machine epsilon .
The arithmetical difference between two consecutive representable floating-point numbers which have the same exponent is called a unit in the last place (ULP). For example, if there is no representable number lying between the representable numbers 1.45A70C22 16 and 1.45A70C24 16 , the ULP is 2×16 −8 , or 2 −31 . For numbers with a base-2 exponent part of 0, i.e. numbers with an absolute value higher than or equal to 1 but lower than 2, an ULP is exactly 2 −23 or about 10 −7 in single precision, and exactly 2 −53 or about 10 −16 in double precision. The mandated behavior of IEEE-compliant hardware is that the result be within one-half of a ULP.
Rounding is used when the exact result of a floating-point operation (or a conversion to floating-point format) would need more digits than there are digits in the significand. IEEE 754 requires correct rounding : that is, the rounded result is as if infinitely precise arithmetic was used to compute the value and then rounded (although in implementation only three extra bits are needed to ensure this). There are several different rounding schemes (or rounding modes ). Historically, truncation was the typical approach. Since the introduction of IEEE 754, the default method ( round to nearest, ties to even , sometimes called Banker's Rounding) is more commonly used. This method rounds the ideal (infinitely precise) result of an arithmetic operation to the nearest representable value, and gives that representation as the result. [ nb 8 ] In the case of a tie, the value that would make the significand end in an even digit is chosen. The IEEE 754 standard requires the same rounding to be applied to all fundamental algebraic operations, including square root and conversions, when there is a numeric (non-NaN) result. It means that the results of IEEE 754 operations are completely determined in all bits of the result, except for the representation of NaNs. ("Library" functions such as cosine and log are not mandated.)
Alternative rounding options are also available. IEEE 754 specifies the following rounding modes:
Alternative modes are useful when the amount of error being introduced must be bounded. Applications that require a bounded error are multi-precision floating-point, and interval arithmetic .
The alternative rounding modes are also useful in diagnosing numerical instability: if the results of a subroutine vary substantially between rounding to + and − infinity then it is likely numerically unstable and affected by round-off error. [ 34 ]
Converting a double-precision binary floating-point number to a decimal string is a common operation, but an algorithm producing results that are both accurate and minimal did not appear in print until 1990, with Steele and White's Dragon4. Some of the improvements since then include:
Many modern language runtimes use Grisu3 with a Dragon4 fallback. [ 41 ]
The problem of parsing a decimal string into a binary FP representation is complex, with an accurate parser not appearing until Clinger's 1990 work (implemented in dtoa.c). [ 35 ] Further work has likewise progressed in the direction of faster parsing. [ 42 ]
For ease of presentation and understanding, decimal radix with 7 digit precision will be used in the examples, as in the IEEE 754 decimal32 format. The fundamental principles are the same in any radix or precision, except that normalization is optional (it does not affect the numerical value of the result). Here, s denotes the significand and e denotes the exponent.
A simple method to add floating-point numbers is to first represent them with the same exponent. In the example below, the second number (with the smaller exponent) is shifted right by three digits, and one then proceeds with the usual addition method:
In detail:
This is the true result, the exact sum of the operands. It will be rounded to seven digits and then normalized if necessary. The final result is
The lowest three digits of the second operand (654) are essentially lost. This is round-off error . In extreme cases, the sum of two non-zero numbers may be equal to one of them:
In the above conceptual examples it would appear that a large number of extra digits would need to be provided by the adder to ensure correct rounding; however, for binary addition or subtraction using careful implementation techniques only a guard bit, a rounding bit and one extra sticky bit need to be carried beyond the precision of the operands. [ 43 ] [ 44 ] : 218–220
Another problem of loss of significance occurs when approximations to two nearly equal numbers are subtracted. In the following example e = 5; s = 1.234571 and e = 5; s = 1.234567 are approximations to the rationals 123457.1467 and 123456.659.
The floating-point difference is computed exactly because the numbers are close—the Sterbenz lemma guarantees this, even in case of underflow when gradual underflow is supported. Despite this, the difference of the original numbers is e = −1; s = 4.877000, which differs more than 20% from the difference e = −1; s = 4.000000 of the approximations. In extreme cases, all significant digits of precision can be lost. [ 43 ] [ 45 ] This cancellation illustrates the danger in assuming that all of the digits of a computed result are meaningful. Dealing with the consequences of these errors is a topic in numerical analysis ; see also Accuracy problems .
To multiply, the significands are multiplied while the exponents are added, and the result is rounded and normalized.
Similarly, division is accomplished by subtracting the divisor's exponent from the dividend's exponent, and dividing the dividend's significand by the divisor's significand.
There are no cancellation or absorption problems with multiplication or division, though small errors may accumulate as operations are performed in succession. [ 43 ] In practice, the way these operations are carried out in digital logic can be quite complex (see Booth's multiplication algorithm and Division algorithm ). [ nb 9 ]
Literals for floating-point numbers depend on languages. They typically use e or E to denote scientific notation . The C programming language and the IEEE 754 standard also define a hexadecimal literal syntax with a base-2 exponent instead of 10. In languages like C , when the decimal exponent is omitted, a decimal point is needed to differentiate them from integers. Other languages do not have an integer type (such as JavaScript ), or allow overloading of numeric types (such as Haskell ). In these cases, digit strings such as 123 may also be floating-point literals.
Examples of floating-point literals are:
Floating-point computation in a computer can run into three kinds of problems:
Prior to the IEEE standard, such conditions usually caused the program to terminate, or triggered some kind of trap that the programmer might be able to catch. How this worked was system-dependent, meaning that floating-point programs were not portable . (The term "exception" as used in IEEE 754 is a general term meaning an exceptional condition, which is not necessarily an error, and is a different usage to that typically defined in programming languages such as a C++ or Java, in which an " exception " is an alternative flow of control, closer to what is termed a "trap" in IEEE 754 terminology.)
Here, the required default method of handling exceptions according to IEEE 754 is discussed (the IEEE 754 optional trapping and other "alternate exception handling" modes are not discussed). Arithmetic exceptions are (by default) required to be recorded in "sticky" status flag bits. That they are "sticky" means that they are not reset by the next (arithmetic) operation, but stay set until explicitly reset. The use of "sticky" flags thus allows for testing of exceptional conditions to be delayed until after a full floating-point expression or subroutine: without them exceptional conditions that could not be otherwise ignored would require explicit testing immediately after every floating-point operation. By default, an operation always returns a result according to specification without interrupting computation. For instance, 1/0 returns +∞, while also setting the divide-by-zero flag bit (this default of ∞ is designed to often return a finite result when used in subsequent operations and so be safely ignored).
The original IEEE 754 standard, however, failed to recommend operations to handle such sets of arithmetic exception flag bits. So while these were implemented in hardware, initially programming language implementations typically did not provide a means to access them (apart from assembler). Over time some programming language standards (e.g., C99 /C11 and Fortran) have been updated to specify methods to access and change status flag bits. The 2008 version of the IEEE 754 standard now specifies a few operations for accessing and handling the arithmetic flag bits. The programming model is based on a single thread of execution and use of them by multiple threads has to be handled by a means outside of the standard (e.g. C11 specifies that the flags have thread-local storage ).
IEEE 754 specifies five arithmetic exceptions that are to be recorded in the status flags ("sticky bits"):
The default return value for each of the exceptions is designed to give the correct result in the majority of cases such that the exceptions can be ignored in the majority of codes. inexact returns a correctly rounded result, and underflow returns a value less than or equal to the smallest positive normal number in magnitude and can almost always be ignored. [ 46 ] divide-by-zero returns infinity exactly, which will typically then divide a finite number and so give zero, or else will give an invalid exception subsequently if not, and so can also typically be ignored. For example, the effective resistance of n resistors in parallel (see fig. 1) is given by R tot = 1 / ( 1 / R 1 + 1 / R 2 + ⋯ + 1 / R n ) {\displaystyle R_{\text{tot}}=1/(1/R_{1}+1/R_{2}+\cdots +1/R_{n})} . If a short-circuit develops with R 1 {\displaystyle R_{1}} set to 0, 1 / R 1 {\displaystyle 1/R_{1}} will return +infinity which will give a final R t o t {\displaystyle R_{tot}} of 0, as expected [ 47 ] (see the continued fraction example of IEEE 754 design rationale for another example).
Overflow and invalid exceptions can typically not be ignored, but do not necessarily represent errors: for example, a root-finding routine, as part of its normal operation, may evaluate a passed-in function at values outside of its domain, returning NaN and an invalid exception flag to be ignored until finding a useful start point. [ 46 ]
The fact that floating-point numbers cannot accurately represent all real numbers, and that floating-point operations cannot accurately represent true arithmetic operations, leads to many surprising situations. This is related to the finite precision with which computers generally represent numbers.
For example, the decimal numbers 0.1 and 0.01 cannot be represented exactly as binary floating-point numbers. In the IEEE 754 binary32 format with its 24-bit significand, the result of attempting to square the approximation to 0.1 is neither 0.01 nor the representable number closest to it. The decimal number 0.1 is represented in binary as e = −4 ; s = 110011001100110011001101 , which is
Squaring this number gives
Squaring it with rounding to the 24-bit precision gives
But the representable number closest to 0.01 is
Also, the non-representability of π (and π/2) means that an attempted computation of tan(π/2) will not yield a result of infinity, nor will it even overflow in the usual floating-point formats (assuming an accurate implementation of tan). It is simply not possible for standard floating-point hardware to attempt to compute tan(π/2), because π/2 cannot be represented exactly. This computation in C:
will give a result of 16331239353195370.0. In single precision (using the tanf function), the result will be −22877332.0.
By the same token, an attempted computation of sin(π) will not yield zero. The result will be (approximately) 0.1225 × 10 −15 in double precision, or −0.8742 × 10 −7 in single precision. [ nb 10 ]
While floating-point addition and multiplication are both commutative ( a + b = b + a and a × b = b × a ), they are not necessarily associative . That is, ( a + b ) + c is not necessarily equal to a + ( b + c ) . Using 7-digit significand decimal arithmetic:
They are also not necessarily distributive . That is, ( a + b ) × c may not be the same as a × c + b × c :
In addition to loss of significance, inability to represent numbers such as π and 0.1 exactly, and other slight inaccuracies, the following phenomena may occur:
Q ( h ) = f ( a + h ) − f ( a ) h . {\displaystyle Q(h)={\frac {f(a+h)-f(a)}{h}}.}
Machine precision is a quantity that characterizes the accuracy of a floating-point system, and is used in backward error analysis of floating-point algorithms. It is also known as unit roundoff or machine epsilon . Usually denoted Ε mach , its value depends on the particular rounding being used.
With rounding to zero, E mach = B 1 − P , {\displaystyle \mathrm {E} _{\text{mach}}=B^{1-P},\,} whereas rounding to nearest, E mach = 1 2 B 1 − P , {\displaystyle \mathrm {E} _{\text{mach}}={\tfrac {1}{2}}B^{1-P},} where B is the base of the system and P is the precision of the significand (in base B ).
This is important since it bounds the relative error in representing any non-zero real number x within the normalized range of a floating-point system: | fl ( x ) − x x | ≤ E mach . {\displaystyle \left|{\frac {\operatorname {fl} (x)-x}{x}}\right|\leq \mathrm {E} _{\text{mach}}.}
Backward error analysis, the theory of which was developed and popularized by James H. Wilkinson , can be used to establish that an algorithm implementing a numerical function is numerically stable. [ 52 ] The basic approach is to show that although the calculated result, due to roundoff errors, will not be exactly correct, it is the exact solution to a nearby problem with slightly perturbed input data. If the perturbation required is small, on the order of the uncertainty in the input data, then the results are in some sense as accurate as the data "deserves". The algorithm is then defined as backward stable . Stability is a measure of the sensitivity to rounding errors of a given numerical procedure; by contrast, the condition number of a function for a given problem indicates the inherent sensitivity of the function to small perturbations in its input and is independent of the implementation used to solve the problem. [ 53 ]
As a trivial example, consider a simple expression giving the inner product of (length two) vectors x {\displaystyle x} and y {\displaystyle y} , then fl ( x ⋅ y ) = fl ( fl ( x 1 ⋅ y 1 ) + fl ( x 2 ⋅ y 2 ) ) , where fl ( ) indicates correctly rounded floating-point arithmetic = fl ( ( x 1 ⋅ y 1 ) ( 1 + δ 1 ) + ( x 2 ⋅ y 2 ) ( 1 + δ 2 ) ) , where δ n ≤ E mach , from above = ( ( x 1 ⋅ y 1 ) ( 1 + δ 1 ) + ( x 2 ⋅ y 2 ) ( 1 + δ 2 ) ) ( 1 + δ 3 ) = ( x 1 ⋅ y 1 ) ( 1 + δ 1 ) ( 1 + δ 3 ) + ( x 2 ⋅ y 2 ) ( 1 + δ 2 ) ( 1 + δ 3 ) , {\displaystyle {\begin{aligned}\operatorname {fl} (x\cdot y)&=\operatorname {fl} {\big (}\operatorname {fl} (x_{1}\cdot y_{1})+\operatorname {fl} (x_{2}\cdot y_{2}){\big )},&&{\text{ where }}\operatorname {fl} (){\text{ indicates correctly rounded floating-point arithmetic}}\\&=\operatorname {fl} {\big (}(x_{1}\cdot y_{1})(1+\delta _{1})+(x_{2}\cdot y_{2})(1+\delta _{2}){\big )},&&{\text{ where }}\delta _{n}\leq \mathrm {E} _{\text{mach}},{\text{ from above}}\\&={\big (}(x_{1}\cdot y_{1})(1+\delta _{1})+(x_{2}\cdot y_{2})(1+\delta _{2}){\big )}(1+\delta _{3})\\&=(x_{1}\cdot y_{1})(1+\delta _{1})(1+\delta _{3})+(x_{2}\cdot y_{2})(1+\delta _{2})(1+\delta _{3}),\end{aligned}}} and so fl ( x ⋅ y ) = x ^ ⋅ y ^ , {\displaystyle \operatorname {fl} (x\cdot y)={\hat {x}}\cdot {\hat {y}},}
where
x ^ 1 = x 1 ( 1 + δ 1 ) ; x ^ 2 = x 2 ( 1 + δ 2 ) ; y ^ 1 = y 1 ( 1 + δ 3 ) ; y ^ 2 = y 2 ( 1 + δ 3 ) , {\displaystyle {\begin{aligned}{\hat {x}}_{1}&=x_{1}(1+\delta _{1});&{\hat {x}}_{2}&=x_{2}(1+\delta _{2});\\{\hat {y}}_{1}&=y_{1}(1+\delta _{3});&{\hat {y}}_{2}&=y_{2}(1+\delta _{3}),\\\end{aligned}}}
where
δ n ≤ E mach {\displaystyle \delta _{n}\leq \mathrm {E} _{\text{mach}}}
by definition, which is the sum of two slightly perturbed (on the order of Ε mach ) input data, and so is backward stable. For more realistic examples in numerical linear algebra , see Higham 2002 [ 54 ] and other references below.
Although individual arithmetic operations of IEEE 754 are guaranteed accurate to within half a ULP , more complicated formulae can suffer from larger errors for a variety of reasons. The loss of accuracy can be substantial if a problem or its data are ill-conditioned , meaning that the correct result is hypersensitive to tiny perturbations in its data. However, even functions that are well-conditioned can suffer from large loss of accuracy if an algorithm numerically unstable for that data is used: apparently equivalent formulations of expressions in a programming language can differ markedly in their numerical stability. One approach to remove the risk of such loss of accuracy is the design and analysis of numerically stable algorithms, which is an aim of the branch of mathematics known as numerical analysis . Another approach that can protect against the risk of numerical instabilities is the computation of intermediate (scratch) values in an algorithm at a higher precision than the final result requires, [ 55 ] which can remove, or reduce by orders of magnitude, [ 56 ] such risk: IEEE 754 quadruple precision and extended precision are designed for this purpose when computing at double precision. [ 57 ] [ nb 11 ]
For example, the following algorithm is a direct implementation to compute the function A ( x ) = ( x −1) / (exp( x −1) − 1) which is well-conditioned at 1.0, [ nb 12 ] however it can be shown to be numerically unstable and lose up to half the significant digits carried by the arithmetic when computed near 1.0. [ 58 ]
If, however, intermediate computations are all performed in extended precision (e.g. by setting line [1] to C99 long double ), then up to full precision in the final double result can be maintained. [ nb 13 ] Alternatively, a numerical analysis of the algorithm reveals that if the following non-obvious change to line [2] is made:
then the algorithm becomes numerically stable and can compute to full double precision.
To maintain the properties of such carefully constructed numerically stable programs, careful handling by the compiler is required. Certain "optimizations" that compilers might make (for example, reordering operations) can work against the goals of well-behaved software. There is some controversy about the failings of compilers and language designs in this area: C99 is an example of a language where such optimizations are carefully specified to maintain numerical precision. See the external references at the bottom of this article.
A detailed treatment of the techniques for writing high-quality floating-point software is beyond the scope of this article, and the reader is referred to, [ 54 ] [ 59 ] and the other references at the bottom of this article. Kahan suggests several rules of thumb that can substantially decrease by orders of magnitude [ 59 ] the risk of numerical anomalies, in addition to, or in lieu of, a more careful numerical analysis. These include: as noted above, computing all expressions and intermediate results in the highest precision supported in hardware (a common rule of thumb is to carry twice the precision of the desired result, i.e. compute in double precision for a final single-precision result, or in double extended or quad precision for up to double-precision results [ 60 ] ); and rounding input data and results to only the precision required and supported by the input data (carrying excess precision in the final result beyond that required and supported by the input data can be misleading, increases storage cost and decreases speed, and the excess bits can affect convergence of numerical procedures: [ 61 ] notably, the first form of the iterative example given below converges correctly when using this rule of thumb). Brief descriptions of several additional issues and techniques follow.
As decimal fractions can often not be exactly represented in binary floating-point, such arithmetic is at its best when it is simply being used to measure real-world quantities over a wide range of scales (such as the orbital period of a moon around Saturn or the mass of a proton ), and at its worst when it is expected to model the interactions of quantities expressed as decimal strings that are expected to be exact. [ 56 ] [ 59 ] An example of the latter case is financial calculations. For this reason, financial software tends not to use a binary floating-point number representation. [ 62 ] The "decimal" data type of the C# and Python programming languages, and the decimal formats of the IEEE 754-2008 standard, are designed to avoid the problems of binary floating-point representations when applied to human-entered exact decimal values, and make the arithmetic always behave as expected when numbers are printed in decimal.
Expectations from mathematics may not be realized in the field of floating-point computation. For example, it is known that ( x + y ) ( x − y ) = x 2 − y 2 {\displaystyle (x+y)(x-y)=x^{2}-y^{2}\,} , and that sin 2 θ + cos 2 θ = 1 {\displaystyle \sin ^{2}{\theta }+\cos ^{2}{\theta }=1\,} , however these facts cannot be relied on when the quantities involved are the result of floating-point computation.
The use of the equality test ( if (x==y) ... ) requires care when dealing with floating-point numbers. Even simple expressions like 0.6/0.2-3==0 will, on most computers, fail to be true [ 63 ] (in IEEE 754 double precision, for example, 0.6/0.2 - 3 is approximately equal to −4.440 892 098 500 63 × 10 −16 ). Consequently, such tests are sometimes replaced with "fuzzy" comparisons ( if (abs(x-y) < epsilon) ... , where epsilon is sufficiently small and tailored to the application, such as 1.0E−13). The wisdom of doing this varies greatly, and can require numerical analysis to bound epsilon. [ 54 ] Values derived from the primary data representation and their comparisons should be performed in a wider, extended, precision to minimize the risk of such inconsistencies due to round-off errors. [ 59 ] It is often better to organize the code in such a way that such tests are unnecessary. For example, in computational geometry , exact tests of whether a point lies off or on a line or plane defined by other points can be performed using adaptive precision or exact arithmetic methods. [ 64 ]
Small errors in floating-point arithmetic can grow when mathematical algorithms perform operations an enormous number of times. A few examples are matrix inversion , eigenvector computation, and differential equation solving. These algorithms must be very carefully designed, using numerical approaches such as iterative refinement , if they are to work well. [ 65 ]
Summation of a vector of floating-point values is a basic algorithm in scientific computing , and so an awareness of when loss of significance can occur is essential. For example, if one is adding a very large number of numbers, the individual addends are very small compared with the sum. This can lead to loss of significance. A typical addition would then be something like
The low 3 digits of the addends are effectively lost. Suppose, for example, that one needs to add many numbers, all approximately equal to 3. After 1000 of them have been added, the running sum is about 3000; the lost digits are not regained. The Kahan summation algorithm may be used to reduce the errors. [ 54 ]
Round-off error can affect the convergence and accuracy of iterative numerical procedures. As an example, Archimedes approximated π by calculating the perimeters of polygons inscribing and circumscribing a circle, starting with hexagons, and successively doubling the number of sides. As noted above, computations may be rearranged in a way that is mathematically equivalent but less prone to error ( numerical analysis ). Two forms of the recurrence formula for the circumscribed polygon are: [ citation needed ]
Here is a computation using IEEE "double" (a significand with 53 bits of precision) arithmetic:
While the two forms of the recurrence formula are clearly mathematically equivalent, [ nb 14 ] the first subtracts 1 from a number extremely close to 1, leading to an increasingly problematic loss of significant digits . As the recurrence is applied repeatedly, the accuracy improves at first, but then it deteriorates. It never gets better than about 8 digits, even though 53-bit arithmetic should be capable of about 16 digits of precision. When the second form of the recurrence is used, the value converges to 15 digits of precision.
The aforementioned lack of associativity of floating-point operations in general means that compilers cannot as effectively reorder arithmetic expressions as they could with integer and fixed-point arithmetic, presenting a roadblock in optimizations such as common subexpression elimination and auto- vectorization . [ 66 ] The "fast math" option on many compilers (ICC, GCC, Clang, MSVC...) turns on reassociation along with unsafe assumptions such as a lack of NaN and infinite numbers in IEEE 754. Some compilers also offer more granular options to only turn on reassociation. In either case, the programmer is exposed to many of the precision pitfalls mentioned above for the portion of the program using "fast" math. [ 67 ]
In some compilers (GCC and Clang), turning on "fast" math may cause the program to disable subnormal floats at startup, affecting the floating-point behavior of not only the generated code, but also any program using such code as a library . [ 68 ]
In most Fortran compilers, as allowed by the ISO/IEC 1539-1:2004 Fortran standard, reassociation is the default, with breakage largely prevented by the "protect parens" setting (also on by default). This setting stops the compiler from reassociating beyond the boundaries of parentheses. [ 69 ] Intel Fortran Compiler is a notable outlier. [ 70 ]
A common problem in "fast" math is that subexpressions may not be optimized identically from place to place, leading to unexpected differences. One interpretation of the issue is that "fast" math as implemented currently has a poorly defined semantics. One attempt at formalizing "fast" math optimizations is seen in Icing , a verified compiler. [ 71 ] | https://en.wikipedia.org/wiki/History_of_floating-point_arithmetic |
The history of fluid mechanics is a fundamental strand of the history of physics and engineering . The study of the movement of fluids (liquids and gases) and the forces that act upon them dates back to pre-history. The field has undergone a continuous evolution, driven by human dependence on water, meteorological conditions , and internal biological processes.
The success of early civilizations , can be attributed to developments in the understanding of water dynamics, allowing for the construction of canals and aqueducts for water distribution and farm irrigation, as well as maritime transport. Due to its conceptual complexity, most discoveries in this field relied almost entirely on experiments, at least until the development of advanced understanding of differential equations and computational methods. Significant theoretical contributions were made by notables figures like Archimedes , Johann Bernoulli and his son Daniel Bernoulli , Leonhard Euler , Claude-Louis Navier and Stokes , who developed the fundamental equations to describe fluid mechanics. Advancements in experimentation and computational methods have further propelled the field, leading to practical applications in more specialized industries ranging from aerospace to environmental engineering. Fluid mechanics has also been important for the study of astronomical bodies and the dynamics of galaxies.
A pragmatic, if not scientific, knowledge of fluid flow was exhibited by ancient civilizations, such as in the design of arrows, spears, boats, and particularly hydraulic engineering projects for flood protection, irrigation, drainage, and water supply. [ 1 ] The earliest human civilizations began near the shores of rivers, and consequently coincided with the dawn of hydrology , hydraulics , and hydraulic engineering .
Observations of specific gravity and buoyancy were recorded by ancient Chinese philosophers. In the 4th century BCE Mencius describes the weight of the gold is equivalent to the feathers. In 3rd century CE, Cao Chong describes the story of weighing the elephant by observing displacement of the boats loaded with different weights. [ 2 ]
The fundamental principles of hydrostatics and dynamics were given by Archimedes in his work On Floating Bodies ( Ancient Greek : Περὶ τῶν ὀχουμένων ), around 250 BC. In it, Archimedes develops the law of buoyancy, also known as Archimedes' principle . This principle states that a body immersed in a fluid experiences a buoyant force equal to the weight of the fluid it displaces. [ 3 ] Archimedes maintained that each particle of a fluid mass, when in equilibrium, is equally pressed in every direction; and he inquired into the conditions according to which a solid body floating in a fluid should assume and preserve a position of equilibrium. [ 4 ]
In the Greek school at Alexandria , which flourished under the auspices of the Ptolemies , attempts were made at the construction of hydraulic machinery, and about 120 BC the fountain of compression, the siphon , and the forcing-pump were invented by Ctesibius and Hero . The siphon is a simple instrument; but the forcing-pump is a complicated invention, which could scarcely have been expected in the infancy of hydraulics. It was probably suggested to Ctesibius by the Egyptian wheel or Noria , which was common at that time, and which was a kind of chain pump, consisting of a number of earthen pots carried round by a wheel. In some of these machines the pots have a valve in the bottom which enables them to descend without much resistance, and diminishes greatly the load upon the wheel; and, if we suppose that this valve was introduced so early as the time of Ctesibius, it is not difficult to perceive how such a machine might have led to the invention of the forcing-pump. [ 4 ]
Notwithstanding these inventions of the Alexandrian school, its attention does not seem to have been directed to the motion of fluids; and the first attempt to investigate this subject was made by Sextus Julius Frontinus , inspector of the public fountains at Rome in the reigns of Nerva and Trajan . In his work De aquaeductibus urbis Romae commentarius , he considers the methods which were at that time employed for ascertaining the quantity of water discharged from ajutages (tubes), and the mode of distributing the waters of an aqueduct or a fountain . He remarked that the flow of water from an orifice depends not only on the magnitude of the orifice itself, but also on the height of the water in the reservoir; and that a pipe employed to carry off a portion of water from an aqueduct should, as circumstances required, have a position more or less inclined to the original direction of the current. But as he was unacquainted with the law of the velocities of running water as depending upon the depth of the orifice, the want of precision which appears in his results is not surprising. [ 4 ]
Islamicate scientists , particularly Abu Rayhan Biruni (973–1048) and later Al-Khazini (fl. 1115–1130), were the first to apply experimental scientific methods to fluid mechanics, especially in the field of fluid statics , such as for determining specific weights . They applied the mathematical theories of ratios and infinitesimal techniques, and introduced algebraic and fine calculation techniques into the field of fluid statics. [ 5 ]
Biruni introduced the method of checking tests during experiments and measured the weights of various liquids. He also recorded the differences in weight between freshwater and saline water , and between hot water and cold water. [ citation needed ] During his experiments on fluid mechanics, Biruni invented the conical measure , [ 6 ] in order to find the ratio between the weight of a substance in air and the weight of water displaced. [ citation needed ]
Al-Khazini, in The Book of the Balance of Wisdom (1121), invented a hydrostatic balance . [ 7 ]
In the 9th century, Banū Mūsā brothers' Book of Ingenious Devices described a number of early automatic controls in fluid mechanics. [ 8 ] Two-step level controls for fluids, an early form of discontinuous variable structure controls , was developed by the Banu Musa brothers. [ 9 ] They also described an early feedback controller for fluids. [ 10 ] According to Donald Routledge Hill , the Banu Musa brothers were "masters in the exploitation of small variations" in hydrostatic pressures and in using conical valves as "in-line" components in flow systems, "the first known use of conical valves as automatic controllers." [ 11 ] They also described the use of other valves, including a plug valve , [ 10 ] [ 11 ] float valve [ 10 ] and tap . [ 12 ] : 74–77 The Banu Musa also developed an early fail-safe system where "one can withdraw small quantities of liquid repeatedly, but if one withdraws a large quantity, no further extractions are possible." [ 11 ] The double-concentric siphon and the funnel with bent end for pouring in different liquids, neither of which appear in any earlier Greek works, were also original inventions by the Banu Musa brothers. [ 12 ] : 21 Some of the other mechanisms they described include a float chamber [ 8 ] and an early differential pressure . [ 13 ]
In 1206, Al-Jazari 's Book of Knowledge of Ingenious Mechanical Devices described many hydraulic machines. Of particular importance were his water-raising pumps . The first known use of a crankshaft in a chain pump was in one of al-Jazari's saqiya machines. The concept of minimizing intermittent working is also first implied in one of al-Jazari's saqiya chain pumps, which was for the purpose of maximising the efficiency of the saqiya chain pump. [ 14 ] Al-Jazari also invented a twin-cylinder reciprocating piston suction pump, which included the first suction pipes, suction pumping, double-action pumping, and made early uses of valves and a crankshaft - connecting rod mechanism. This pump is remarkable for three reasons: the first known use of a true suction pipe (which sucks fluids into a partial vacuum ) in a pump, the first application of the double-acting principle, and the conversion of rotary to reciprocating motion , via the crankshaft-connecting rod mechanism. [ 15 ] [ 16 ] [ 17 ]
During the Renaissance , Leonardo da Vinci was well known for his experimental skills. His notes provide precise depictions of various phenomena, including vessels, jets, hydraulic jumps, eddy formation, tides, as well as designs for both low drag (streamlined) and high drag (parachute) configurations. Da Vinci is also credited for formulating the conservation of mass in one-dimensional steady flow. [ 18 ]
In 1586, the Flemish engineer and mathematician Simon Stevin published De Beghinselen des Waterwichts ( Principles on the Weight of Water ), a study of hydrostatics that, among other things, extensively discussed the hydrostatic paradox. [ 19 ]
Benedetto Castelli , and Evangelista Torricelli , two of the disciples of Galileo , applied the discoveries of their master to the science of hydrodynamics. In 1628 Castelli published a small work, Della misura dell' acque correnti , in which he satisfactorily explained several phenomena in the motion of fluids in rivers and canals ; but he committed a great paralogism in supposing the velocity of the water proportional to the depth of the orifice below the surface of the vessel. Torricelli, observing that in a jet where the water rushed through a small ajutage it rose to nearly the same height with the reservoir from which it was supplied, imagined that it ought to move with the same velocity as if it had fallen through that height by the force of gravity , and hence he deduced the proposition that the velocities of liquids are as the square root of the head , apart from the resistance of the air and the friction of the orifice. This theorem was published in 1643, at the end of his treatise De motu gravium projectorum , and it was confirmed by the experiments of Raffaello Magiotti on the quantities of water discharged from different ajutages under different pressures (1648). [ 4 ]
In the hands of Blaise Pascal hydrostatics assumed the dignity of a science, and in a treatise on the equilibrium of liquids ( Sur l’équilibre des liqueurs ), found among his manuscripts after his death and published in 1663, the laws of the equilibrium of liquids were demonstrated in the most simple manner, and amply confirmed by experiments. [ 4 ]
The theorem of Torricelli was employed by many succeeding writers, but particularly by Edme Mariotte (1620–1684), whose Traité du mouvement des eaux , published after his death in the year 1686, is founded on a great variety of well-conducted experiments on the motion of fluids, performed at Versailles and Chantilly . In the discussion of some points he committed considerable mistakes. Others he treated very superficially, and in none of his experiments apparently did he attend to the diminution of efflux arising from the contraction of the liquid vein, when the orifice is merely a perforation in a thin plate; but he appears to have been the first who attempted to ascribe the discrepancy between theory and experiment to the retardation of the water's velocity through friction. His contemporary Domenico Guglielmini (1655–1710), who was inspector of the rivers and canals at Bologna , had ascribed this diminution of velocity in rivers to transverse motions arising from inequalities in their bottom. But as Mariotte observed similar obstructions even in glass pipes where no transverse currents could exist, the cause assigned by Guglielmini seemed destitute of foundation. The French philosopher, therefore, regarded these obstructions as the effects of friction. He supposed that the filaments of water which graze along the sides of the pipe lose a portion of their velocity; that the contiguous filaments, having on this account a greater velocity, rub upon the former, and suffer a diminution of their celerity; and that the other filaments are affected with similar retardations proportional to their distance from the axis of the pipe. In this way the medium velocity of the current may be diminished, and consequently the quantity of water discharged in a given time must, from the effects of friction, be considerably less than that which is computed from theory. [ 4 ]
The effects of friction and viscosity in diminishing the velocity of running water were noticed in the Principia of Sir Isaac Newton , who threw much light upon several branches of hydromechanics. At a time when the Cartesian system of vortices universally prevailed, he found it necessary to investigate that hypothesis, and in the course of his investigations he showed that the velocity of any stratum of the vortex is an arithmetical mean between the velocities of the strata which enclose it; and from this it evidently follows that the velocity of a filament of water moving in a pipe is an arithmetical mean between the velocities of the filaments which surround it. Taking advantage of these results, French engineer Henri Pitot afterwards showed that the retardations arising from friction are inversely as the diameters of the pipes in which the fluid moves. [ 4 ]
The attention of Newton was also directed to the discharge of water from orifices in the bottom of vessels. He supposed a cylindrical vessel full of water to be perforated in its bottom with a small hole by which the water escaped, and the vessel to be supplied with water in such a manner that it always remained full at the same height. He then supposed this cylindrical column of water to be divided into two parts – the first, which he called the "cataract," being an hyperboloid generated by the revolution of an hyperbola of the fifth degree around the axis of the cylinder which should pass through the orifice, and the second the remainder of the water in the cylindrical vessel. He considered the horizontal strata of this hyperboloid as always in motion, while the remainder of the water was in a state of rest, and imagined that there was a kind of cataract in the middle of the fluid. [ 4 ]
When the results of this theory were compared with the quantity of water actually discharged, Newton concluded that the velocity with which the water issued from the orifice was equal to that which a falling body would receive by descending through half the height of water in the reservoir. This conclusion, however, is absolutely irreconcilable with the known fact that jets of water rise nearly to the same height as their reservoirs, and Newton seems to have been aware of this objection. Accordingly, in the second edition of his Principia , which appeared in 1713, he reconsidered his theory. He had discovered a contraction in the vein of fluid ( vena contracta ) which issued from the orifice, and found that, at the distance of about a diameter of the aperture, the section of the vein was contracted in the subduplicate ratio of two to one. He regarded, therefore, the section of the contracted vein as the true orifice from which the discharge of water ought to be deduced, and the velocity of the effluent water as due to the whole height of water in the reservoir; and by this means his theory became more conformable to the results of experience, though still open to serious objections. [ 4 ]
Newton was also the first to investigate the difficult subject of the motion of waves . [ 4 ]
In 1738 Daniel Bernoulli published his book Hydrodynamica . His theory of the motion of fluids, the germ of which was first published in his memoir entitled Theoria nova de motu aquarum per canales quocunque fluentes , communicated to the academy of St Petersburg as early as 1726, was founded on two suppositions, which appeared to him conformable to experience. He supposed that the surface of the fluid, contained in a vessel which is emptying itself by an orifice, remains always horizontal; and, if the fluid mass is conceived to be divided into an infinite number of horizontal strata of the same bulk, that these strata remain contiguous to each other, and that all their points descend vertically, with velocities inversely proportional to their breadth, or to the horizontal sections of the reservoir. In order to determine the motion of each stratum, he employed the principle of the conservatio virium vivarum , and obtained very elegant solutions. But in the absence of a general demonstration of that principle, his results did not command the confidence which they would otherwise have deserved, and it became desirable to have a theory more certain, and depending solely on the fundamental laws of mechanics. Colin Maclaurin and John Bernoulli , who were of this opinion, resolved the problem by more direct methods, the one in his Fluxions , published in 1742, and the other in his Hydraulica nunc primum detecta , et demonstrata directe ex fundamentis pure mechanicis , which forms the fourth volume of his works. The method employed by Maclaurin has been thought not sufficiently rigorous; and that of John Bernoulli is, in the opinion of Lagrange , defective in clearness and precision. [ 4 ]
The theory of Daniel Bernoulli was opposed also by Jean le Rond d'Alembert . When generalizing the theory of pendulums of Jacob Bernoulli he discovered a principle of dynamics so simple and general that it reduced the laws of the motions of bodies to that of their equilibrium . He applied this principle to the motion of fluids, and gave a specimen of its application at the end of his Dynamics in 1743. It was more fully developed in his Traité des fluides , published in 1744, in which he gave simple and elegant solutions of problems relating to the equilibrium and motion of fluids. He made use of the same suppositions as Daniel Bernoulli, though his calculus was established in a very different manner. He considered, at every instant, the actual motion of a stratum as composed of a motion which it had in the preceding instant and of a motion which it had lost; and the laws of equilibrium between the motions lost furnished him with equations representing the motion of the fluid. It remained a desideratum to express by equations the motion of a particle of the fluid in any assigned direction. These equations were found by d'Alembert from two principles – that a rectangular canal, taken in a mass of fluid in equilibrium, is itself in equilibrium, and that a portion of the fluid, in passing from one place to another, preserves the same volume when the fluid is incompressible, or dilates itself according to a given law when the fluid is elastic. His ingenious method, published in 1752, in his Essai sur la résistance des fluides , was brought to perfection in his Opuscules mathématiques , and was adopted by Leonhard Euler . [ 4 ]
The resolution of the questions concerning the motion of fluids was effected by means of Leonhard Euler's partial differential coefficients . This calculus was first applied to the motion of water by d'Alembert, and enabled both him and Euler to represent the theory of fluids in formulae restricted by no particular hypothesis. [ 4 ]
One of the most successful labourers in the science of hydrodynamics at this period was Pierre-Louis-Georges du Buat . Following in the steps of the Abbé Charles Bossut ( Nouvelles Experiences sur la résistance des fluides , 1777), he published, in 1786, a revised edition of his Principes d'hydraulique , which contains a satisfactory theory of the motion of fluids, founded solely upon experiments. Dubuat considered that if water were a perfect fluid, and the channels in which it flowed infinitely smooth, its motion would be continually accelerated, like that of bodies descending in an inclined plane. But as the motion of rivers is not continually accelerated, and soon arrives at a state of uniformity, it is evident that the viscosity of the water, and the friction of the channel in which it descends, must equal the accelerating force. Dubuat, therefore, assumed it as a proposition of fundamental importance that, when water flows in any channel or bed, the accelerating force which obliges it to move is equal to the sum of all the resistances which it meets with, whether they arise from its own viscosity or from the friction of its bed. This principle was employed by him in the first edition of his work, which appeared in 1779. The theory contained in that edition was founded on the experiments of others, but he soon saw that a theory so new, and leading to results so different from the ordinary theory, should be founded on new experiments more direct than the former, and he was employed in the performance of these from 1780 to 1783. The experiments of Bossut were made only on pipes of a moderate declivity, but Dubuat used declivities of every kind, and made his experiments upon channels of various sizes. [ 4 ]
In 1858 Hermann von Helmholtz published his seminal paper "Über Integrale der hydrodynamischen Gleichungen, welche den Wirbelbewegungen entsprechen," in Journal für die reine und angewandte Mathematik , vol. 55, pp. 25–55. So important was the paper that a few years later P. G. Tait published an English translation, "On integrals of the hydrodynamical equations which express vortex motion", in Philosophical Magazine , vol. 33, pp. 485–512 (1867). In his paper Helmholtz established his three "laws of vortex motion" in much the same way one finds them in any advanced textbook of fluid mechanics today. This work established the significance of vorticity to fluid mechanics and science in general.
For the next century or so vortex dynamics matured as a subfield of fluid mechanics, always commanding at least a major chapter in treatises on the subject. Thus, H. Lamb's well known Hydrodynamics (6th ed., 1932) devotes a full chapter to vorticity and vortex dynamics as does G. K. Batchelor's Introduction to Fluid Dynamics (1967). In due course entire treatises were devoted to vortex motion. H. Poincaré's Théorie des Tourbillons (1893), H. Villat's Leçons sur la Théorie des Tourbillons (1930), C. Truesdell's The Kinematics of Vorticity (1954), and P. G. Saffman's Vortex Dynamics (1992) may be mentioned. Early on individual sessions at scientific conferences were devoted to vortices , vortex motion, vortex dynamics and vortex flows. Later, entire meetings were devoted to the subject.
The range of applicability of Helmholtz's work grew to encompass atmospheric and oceanographic flows, to all branches of engineering and applied science and, ultimately, to superfluids (today including Bose–Einstein condensates ). In modern fluid mechanics the role of vortex dynamics in explaining flow phenomena is firmly established. Well known vortices have acquired names and are regularly depicted in the popular media: hurricanes , tornadoes , waterspouts , aircraft trailing vortices (e.g., wingtip vortices ), drainhole vortices (including the bathtub vortex), smoke rings , underwater bubble air rings, cavitation vortices behind ship propellers, and so on. In the technical literature a number of vortices that arise under special conditions also have names: the Kármán vortex street wake behind a bluff body, Taylor vortices between rotating cylinders, Görtler vortices in flow along a curved wall, etc.
The theory of running water was greatly advanced by the researches of Gaspard Riche de Prony (1755–1839). From a collection of the best experiments by previous workers he selected eighty-two (fifty-one on the velocity of water in conduit pipes, and thirty-one on its velocity in open canals); and, discussing these on physical and mechanical principles, he succeeded in drawing up general formulae, which afforded a simple expression for the velocity of running water. [ 4 ]
J. A. Eytelwein of Berlin , who published in 1801 a valuable compendium of hydraulics entitled Handbuch der Mechanik und der Hydraulik , investigated the subject of the discharge of water by compound pipes, the motions of jets and their impulses against plane and oblique surfaces; and he showed theoretically that a water-wheel will have its maximum effect when its circumference moves with half the velocity of the stream. [ 4 ]
JNP Hachette in 1816–1817 published memoirs containing the results of experiments on the spouting of fluids and the discharge of vessels. His object was to measure the contracted part of a fluid vein, to examine the phenomena attendant on additional tubes, and to investigate the form of the fluid vein and the results obtained when different forms of orifices are employed. Extensive experiments on the discharge of water from orifices ( Expériences hydrauliques , Paris, 1832) were conducted under the direction of the French government by J. V. Poncelet (1788–1867) and J. A. Lesbros (1790–1860). [ 4 ]
P. P. Boileau (1811–1891) discussed their results and added experiments of his own ( Traité de la mesure des eaux courantes , Paris, 1854). K. R. Bornemann re-examined all these results with great care, and gave formulae expressing the variation of the coefficients of discharge in different conditions ( Civil Ingénieur, 1880). Julius Weisbach (1806–1871) also made many experimental investigations on the discharge of fluids. [ 4 ]
The experiments of J. B. Francis ( Lowell Hydraulic Experiments , Boston, Mass., 1855) led him to propose variations in the accepted formulae for the discharge over weirs, and a generation later a very complete investigation of this subject was carried out by Henri-Émile Bazin . An elaborate inquiry on the flow of water in pipes and channels was conducted by Henry G. P. Darcy (1803–1858) and continued by Bazin, at the expense of the French government ( Recherches hydrauliques , Paris, 1866). [ 4 ]
German engineers have also devoted special attention to the measurement of the flow in rivers; the Beiträge zur Hydrographie des Königreiches Böhmen (Prague, 1872–1875) of Andreas Rudolf Harlacher contained valuable measurements of this kind, together with a comparison of the experimental results with the formulae of flow that had been proposed up to the date of its publication, and important data were yielded by the gaugings of the Mississippi made for the United States government by Andrew Atkinson Humphreys and Henry Larcom Abbot , by Robert Gordon's gaugings of the Irrawaddy River , and by Allen J. C. Cunningham's experiments on the Ganges canal. [ 20 ] The friction of water, investigated for slow speeds by Coulomb , was measured for higher speeds by William Froude (1810–1879), whose work is of great value in the theory of ship resistance ( Brit. Assoc. Report. , 1869), and stream line motion was studied by Professor Osborne Reynolds and by Professor Henry S. Hele-Shaw . [ 4 ]
In 1904, German scientist Ludwig Prandtl pioneered boundary layer theory. He pointed out that fluids with small viscosity can be divided into a thin viscous layer (boundary layer) near solid surfaces and interfaces, and an outer layer where Bernoulli's principle and Euler equations apply. [ 18 ]
Vortex dynamics is a vibrant subfield of fluid dynamics, commanding attention at major scientific conferences and precipitating workshops and symposia that focus fully on the subject.
A curious diversion in the history of vortex dynamics was the Vortex theory of the atom of William Thomson , later Lord Kelvin . His basic idea was that atoms were to be represented as vortex motions in the ether. This theory predated the quantum theory by several decades and because of the scientific standing of its originator received considerable attention. Many profound insights into vortex dynamics were generated during the pursuit of this theory. Other interesting corollaries were the first counting of simple knots by P. G. Tait , today considered a pioneering effort in graph theory , topology and knot theory . Ultimately, Kelvin's vortex atom was seen to be wrong-headed but the many results in vortex dynamics that it precipitated have stood the test of time. Kelvin himself originated the notion of circulation and proved that in an inviscid fluid circulation around a material contour would be conserved. This result — singled out by Einstein in "Zum hundertjährigen Gedenktag von Lord Kelvins Geburt, Naturwissenschaften, 12 (1924), 601–602," (title translation: "On the 100th Anniversary of Lord Kelvin's Birth"), as one of the most significant results of Kelvin's work provided an early link between fluid dynamics and topology.
The history of vortex dynamics seems particularly rich in discoveries and re-discoveries of important results, because results obtained were entirely forgotten after their discovery and then were re-discovered decades later. Thus, the integrability of the problem of three point vortices on the plane was solved in the 1877 thesis of a young Swiss applied mathematician named Walter Gröbli . In spite of having been written in Göttingen in the general circle of scientists surrounding Helmholtz and Kirchhoff , and in spite of having been mentioned in Kirchhoff's well known lectures on theoretical physics and in other major texts such as Lamb's Hydrodynamics , this solution was largely forgotten. A 1949 paper by the noted applied mathematician J. L. Synge created a brief revival, but Synge's paper was in turn forgotten. A quarter century later a 1975 paper by E. A. Novikov and a 1979 paper by H. Aref on chaotic advection finally brought this important earlier work to light. The subsequent elucidation of chaos in the four-vortex problem, and in the advection of a passive particle by three vortices, made Gröbli's work part of "modern science".
Another example of this kind is the so-called "localized induction approximation" (LIA) for three-dimensional vortex filament motion, which gained favor in the mid-1960s through the work of Arms, Hama, Betchov and others, but turns out to date from the early years of the 20th century in the work of Da Rios, a gifted student of the noted Italian mathematician T. Levi-Civita . Da Rios published his results in several forms but they were never assimilated into the fluid mechanics literature of his time. In 1972 H. Hasimoto used Da Rios' "intrinsic equations" (later re-discovered independently by R. Betchov) to show how the motion of a vortex filament under LIA could be related to the non-linear Schrödinger equation . This immediately made the problem part of "modern science" since it was then realized that vortex filaments can support solitary twist waves of large amplitude.
Using a whole body of mathematical methods (not only those inherited from the antique theory of ratios and infinitesimal techniques, but also the methods of the contemporary algebra and fine calculation techniques), Arabic scientists raised statics to a new, higher level. The classical results of Archimedes in the theory of the centre of gravity were generalized and applied to three-dimensional bodies, the theory of ponderable lever was founded and the 'science of gravity' was created and later further developed in medieval Europe. The phenomena of statics were studied by using the dynamic approach so that two trends – statics and dynamics – turned out to be inter-related within a single science, mechanics. The combination of the dynamic approach with Archimedean hydrostatics gave birth to a direction in science which may be called medieval hydrodynamics. Archimedean statics formed the basis for creating the fundamentals of the science on specific weight. Numerous fine experimental methods were developed for determining the specific weight, which were based, in particular, on the theory of balances and weighing. The classical works of al-Biruni and al-Khazini can by right be considered as the beginning of the application of experimental methods in medieval science. Arabic statics was an essential link in the progress of world science. It played an important part in the prehistory of classical mechanics in medieval Europe. Without it classical mechanics proper could probably not have been created. | https://en.wikipedia.org/wiki/History_of_fluid_mechanics |
The history of gamma-ray [ 1 ] began with the serendipitous detection of a gamma-ray burst (GRB) on July 2, 1967, by the U.S. Vela satellites. After these satellites detected fifteen other GRBs, Ray Klebesadel of the Los Alamos National Laboratory published the first paper on the subject, Observations of Gamma-Ray Bursts of Cosmic Origin . [ 2 ] As more and more research was done on these mysterious events, hundreds of models were developed in an attempt to explain their origins.
Gamma-ray bursts were discovered in the late 1960s by the U.S. Vela nuclear test detection satellites. The Velas were built to detect gamma radiation pulses emitted by nuclear weapon tests in space. The United States suspected that the USSR might attempt to conduct secret nuclear tests after signing the Nuclear Test Ban Treaty in 1963. While most satellites orbited at about 500 miles above Earth's surface, the Vela satellites orbited at an altitude of 65,000 miles. At this height, the satellites orbited above the Van Allen radiation belt , which reduced the noise in the sensors. The extra height also meant that the satellites could detect explosions behind the Moon , a location where the United States government suspected the Soviet Union would try to conceal nuclear weapon tests. The Vela system generally had four satellites operational at any given time such that a gamma-ray signal could be detected at multiple locations. This made it possible to localize the source of the signal to a relatively compact region of space. While these characteristics were incorporated into the Vela system to improve the detection of nuclear weapons, these same characteristics were what made the satellites capable of detecting gamma-ray bursts. [ 3 ]
On July 2, 1967, at 14:19 UTC , the Vela 4 and Vela 3 satellites detected a flash of gamma radiation that were unlike any known nuclear weapons signatures. [ 4 ] Nuclear bombs produce a very brief, intense burst of gamma rays less than one millionth of a second. The radiation then steadily fades as the unstable nuclei decay . The signal detected by the Vela satellites had neither the intense initial flash nor the gradual fading, but instead there were two distinct peaks in the light curve. [ 3 ] Solar flares and new supernovas were the two other possible explanations for the event, but neither had occurred on that day. [ 4 ] Unclear on what had happened, but not considering the matter particularly urgent, the team at the Los Alamos Scientific Laboratory , led by Ray Klebesadel , filed the data away for later investigation.
Vela 5 was launched on May 23, 1969. Because the sensitivity and time resolution on these satellites were significantly more accurate than the instruments on Vela 4, the Los Alamos team expected these new satellites to detect more gamma-ray bursts. Despite an enormous amount of background signals picked up by the new detectors, the research team found twelve events which had not coincided with any solar flares or supernovas. Some of the new detections also showed the same double-peak pattern that had been observed by Vela 4. [ 4 ]
Although their instrumentation offered no improvement over those on Vela 5, the Vela 6 satellites were launched on April 8, 1970, with the intention of determining the direction from which the gamma rays were arriving. The orbits for the Vela 6 satellites were chosen to be as far away from Vela 5 as possible, generally on the order of 10000 kilometers apart. This separation meant that, despite gamma rays traveling at the speed of light , a signal would be detected at slightly different times by different satellites. By analyzing the arrival times, Klebesadel and his team successfully traced sixteen gamma-ray bursts. The random distribution of bursts across the sky made it clear that the bursts were not coming from the Sun, Moon, or other planets in the Solar System . [ 4 ]
In 1973, Ray Klebesadel, Roy Olson, and Ian Strong of the University of California Los Alamos Scientific Laboratory published Observations of Gamma-Ray Bursts of Cosmic Origin , identifying a cosmic source for the previously unexplained observations of gamma-rays. [ 2 ] Shortly thereafter, Klebesadel presented his findings at the 140th meeting of the American Astronomical Society. Although he was interviewed only by The National Enquirer , news of the discovery quickly spread through the scientific community. [ 5 ] Between 1973 and 2001 more than 5300 papers were published on GRBs. [ 6 ]
Shortly after the discovery of gamma-ray bursts, a general consensus arose within the astronomical community that in order to determine what caused them, they would have to be identified with astronomical objects at other wavelengths, particularly visible light, as this approach had been successfully applied to the fields of radio X-ray astronomy . This method would require far more accurate positions of several gamma-ray bursts than the Vela system could provide. [ 7 ] Greater accuracy required the detectors to be spaced farther apart. Instead of launching satellites only into Earth's orbit, it was deemed necessary to spread the detectors throughout the Solar System .
By the end of 1978, the first Inter-Planetary Network ( IPN ) had been completed. In addition to the Vela satellites, the IPN included 5 new space probes: the Russian Prognoz 7 , in orbit around the Earth, the German Helios 2 , in elliptical orbit around the Sun, and NASA 's Pioneer Venus Orbiter , Venera 11 , and Venera 12 , each of which orbited Venus . The research team at the Russian Institute for Space Research in Moscow, led by Kevin Hurley, was able to use the data collected by the IPN to accurately determine the position of gamma-ray bursts with an accuracy of a few minutes of arc . However, even when using the most powerful telescopes available, nothing of interest could be found within the determined regions. [ 8 ]
To explain the existence of gamma-ray bursts, many speculative theories were advanced, most of which posited nearby galactic sources. Little progress was made, however, until the 1991 launch of the Compton Gamma Ray Observatory and its Burst and Transient Source Explorer ( BATSE ) instrument, an extremely sensitive gamma-ray detector. This instrument provided crucial data indicating that GRBs are isotropic (not biased towards any particular direction in space, such as toward the galactic plane or the Galactic Center ). [ 9 ] Because the Milky Way galaxy has a very flat structure, if gamma-ray bursts were to originate from within the Milky Way, they would not be distributed isotropically across the sky, but instead concentrated in the plane of the Milky Way. Although the luminosity of the bursts suggested that they had to be originating within the Milky Way, the distribution provided very strong evidence to the contrary. [ 10 ] [ 11 ]
BATSE data also showed that GRBs fall into two distinct categories: short-duration, hard-spectrum bursts ("short bursts"), and long-duration, soft-spectrum bursts ("long bursts"). [ 12 ] Short bursts are typically less than two seconds in duration and are dominated by higher-energy photons ; long bursts are typically more than two seconds in duration and dominated by lower-energy photons. The separation is not absolute and the populations overlap observationally, but the distinction suggests two different classes of progenitors. However, some believe there is a third type of GRBs. [ 13 ] [ 14 ] [ 15 ] [ 16 ] The three kinds of GRBs are hypothesized to reflect three different origins: mergers of neutron star systems, mergers between white dwarfs and neutron stars, and the collapse of massive stars. [ 17 ]
For decades after the discovery of GRBs, astronomers searched for a counterpart: any astronomical object in positional coincidence with a recently observed burst. Astronomers considered many distinct objects, including white dwarfs , pulsars , supernovae , globular clusters , quasars , Seyfert galaxies , and BL Lac objects . [ 18 ] Researchers specifically looked for objects with unusual properties which might relate to gamma-ray bursts: high proper motion , polarization , orbital brightness modulation, fast time scale flickering, extreme colors, emission lines , or an unusual shape. [ 19 ] From the discovery of GRBs through the 1980s, GRB 790305b [ nb 1 ] was the only event to have been identified with a candidate source object: [ 18 ] nebula N49 in the Large Magellanic Cloud . [ 20 ] All other attempts failed due to poor resolution of the available detectors. The best hope seemed to lie in finding a fainter, fading, longer wavelength emission after the burst itself, the "afterglow" of a GRB. [ 21 ]
As early as 1980, a research group headed by Livio Scarsi at the University of Rome began working on Satellite per Astronomia X , an X-ray astronomy research satellite. The project developed into a collaboration between the Italian Space Agency and the Netherlands Agency for Aerospace Programmes . Though the satellite was originally intended to serve the sole purpose of studying X-rays, Enrico Costa of the Istituto di Astrofisica Spaziale suggested that the satellite's four protective shields could easily serve as gamma-ray burst detectors. [ 22 ] After 10 years of delays and a final cost of approximately $ 350 million, [ 23 ] the satellite, renamed BeppoSAX in honor of Giuseppe Occhialini , [ 24 ] was launched on April 30, 1996. [ 25 ]
In 1983, a team composed of Stan Woosley , Don Lamb, Ed Fenimore , Kevin Hurley, and George Ricker began discussing plans for a new GRB research satellite, the High Energy Transient Explorer ( HETE ). [ 26 ] Although many satellites were already providing data on GRBs, HETE would be the first satellite devoted entirely to GRB research. [ 27 ] The goal was for HETE to be able to localize gamma-ray bursts with much greater accuracy than the BATSE detectors. The team submitted a proposal to NASA in 1986 under which the satellite would be equipped with four gamma ray detectors, an X-ray camera, and four electronic cameras for detecting visible and ultraviolet light. The project was to cost $ 14.5 million, and the launch was originally planned for the summer of 1994. [ 26 ] The Pegasus XL rocket, which launched HETE on November 4, 1996, did not release its two satellites, so the HETE and SAC-B, an Argentinian research satellite also on board, missions were attached to the rocket and unable to direct their solar panels towards the sun, and within one day of the launch, all radio contact with the satellites was lost. [ 28 ] The eventual successor to the mission, HETE 2, was successfully launched on 9 October 2000. It observed its first GRB on 13 February 2001. [ 29 ]
BeppoSAX detected its first gamma-ray burst GRB960720 on July 20, 1996 [ 30 ] from an X-ray burst in one of the two Wide Field Cameras (WFCs), but it was only discovered in the data six weeks later, by a Dutch duty scientist systematically checking WFC-bursts coinciding in time with BATSE-triggers from the same direction. Follow-up radio observations with the Very Large Array by Dale Frail did not find an afterglow at the derived position from the deconvolved data, but a routine procedure for finding gamma-ray bursts with BeppoSAX could be established. This led to the detection of a gamma-ray burst on January 11, 1997, and one of its Wide Field Cameras also detected X-rays at the same moment coinciding with a BATSE-trigger. John Heise , Dutch project scientist for BeppoSAX's WFCs, quickly deconvolved the data from the WFCs using software by Jean in 't Zand , a Dutch former gamma-ray spectroscopist at the Goddard Space Flight Center , and in less than 24 hours, produced a sky position with an accuracy of about 10 arcminutes. [ 31 ] Although this level of accuracy had already been surpassed by the interplanetary networks, they were unable to produce the data as quickly as Heise could. [ 32 ] In the following days, Dale Frail, working with the Very Large Array, detected a single fading radio source within the error box, a BL Lac object . An article was written for Nature stating that this event proved that GRBs originated from active galaxies. However, Jean in 't Zand rewrote the WFC deconvolution software to produce a position with an accuracy of 3 arcminutes, and the BL Lac object was no longer within the reduced error box. Despite BeppoSAX having observed both X-rays and a GRB and the position being known within that same day, the source of the burst was not identified. [ 31 ]
Success for the BeppoSAX team came in February 1997, less than one year after it had been launched. A BeppoSAX WFC detected a gamma-ray burst ( GRB 970228 ), and when the X-ray camera onboard BeppoSAX was pointed towards the direction from which the burst had originated, it detected a fading X-ray emission. Ground-based telescopes later identified a fading optical counterpart as well. [ 33 ] The location of this event having been identified, once the GRB faded, deep imaging was able to identify a faint, very distant host galaxy in the GRB's location. Within only a few weeks the long controversy about the distance scale ended: GRBs were extragalactic events originating inside faint galaxies at enormous distances. [ nb 2 ] By finally establishing the distance scale, characterizing the environments in which GRBs occur, and providing a new window on GRBs both observationally and theoretically, this discovery revolutionized the study of GRBs. [ 34 ]
Two major breakthroughs also occurred with the next event registered by BeppoSAX, GRB 970508 . This event was localized within 4 hours of its discovery, allowing research teams to begin making observations much sooner than any previous burst. By comparing photographs of the error box taken on May 8 and May 9 (the day of the event and the day after), one object was found to have increased in brightness. Between May 10 and May, Charles Steidel recorded the spectrum of the variable object from the W. M. Keck Observatory . Mark Metzger analyzed the spectrum and determined a redshift of z=0.835, placing the burst at a distance of roughly 6 billion light years. This was the first accurate determination of the distance to a GRB, and it further proved that GRBs occur in extremely distant galaxies. [ 35 ]
Prior to the localization of GRB 970228, opinions differed as to whether or not GRBs would emit detectable radio waves. Bohdan Paczyński and James Rhoads published an article in 1993 predicting radio afterglows, but Martin Rees and Peter Mészáros concluded that, due to the vast distances between GRBs and the Earth, any radio waves produced would be too weak to be detected. [ 36 ] Although GRB 970228 was accompanied by an optical afterglow, neither the Very Large Array nor the Westerbork Synthesis Radio Telescope were able to detect a radio afterglow. However, five days after GRB 970508, Dale Frail , working with the Very Large Array in New Mexico , observed radio waves from the afterglow at wavelengths of 3.5 cm, 6 cm, and 21 cm. The total luminosity varied widely from hour to hour, but not simultaneously in all wavelengths. Jeremy Goodman of Princeton University explained the erratic fluctuations as being the result of scintillation caused by vibrations in the Earth's atmosphere, which no longer occurs when the source has an apparent size larger than 3 micro-arcseconds. After several weeks, the luminosity fluctuations had dissipated. Using this piece of information and the distance to the event, it was determined that the source of radio waves had expanded almost at the speed of light . Never before had accurate information been obtained regarding the physical characteristics of a gamma-ray burst explosion. [ 37 ]
Also, because GRB 970508 was observed at many different wavelengths, it was possible to form a very complete spectrum for the event. Ralph Wijers and Titus Galama attempted to calculate various physical properties of the burst, including the total amount of energy in the burst and the density of the surrounding medium. Using an extensive system of equations , they were able to compute these values as 3×10 52 ergs and 30,000 particles per cubic meter, respectively. Although the observation data was not accurate enough for their results to be considered particularly reliable, Wijers and Galama did show that, in principle, it would be possible to determine the physical characters of GRBs based on their spectra. [ 38 ]
The next burst to have its redshift calculated was GRB 971214 with a redshift of 3.42, a distance of roughly 12 billion lightyears from Earth. Using the redshift and the accurate brightness measurements made by both BATSE and BeppoSAX, Shrinivas Kulkarni , who had recorded the redshift at the W. M. Keck Observatory, calculated the amount of energy released by the burst in half a minute to be 3×10 53 ergs, several hundred times more energy than is released by the Sun in 10 billion years. The burst was proclaimed to be the most energetic explosion to have ever occurred since the Big Bang , earning it the nickname Big Bang 2 . This explosion presented a dilemma for GRB theoreticians: either this burst produced more energy than could possibly be explained by any of the existing models, or the burst did not emit energy in all directions, but instead in very narrow beams which happened to have been pointing directly at Earth. While the beaming explanation would reduce the total energy output to a very small fraction of Kulkarni's calculation, it also implies that for every burst observed on Earth, several hundred occur which are not observed because their beams are not pointed towards Earth. [ 39 ]
In November 2019, astronomers reported a notable gamma ray burst explosion, named GRB 190114C , initially detected in January 2019, that, so far, has been determined to have had the highest energy, 1 Tera electron volts (Tev) , ever observed for such a cosmic event. [ 40 ] [ 41 ]
Konus-Wind is flown on board Wind spacecraft. It was launched on 1 November 1994. Experiment consists of two identical gamma ray spectrometers mounted on opposite sites of the spacecraft so all sky is observed. [ 42 ]
INTEGRAL , the European Space Agency 's International Gamma-Ray Astrophysics Laboratory, was launched on October 17, 2002. It is the first observatory capable simultaneously observing objects at gamma ray, X-ray, and visible wavelengths. [ 43 ]
NASA 's Swift satellite launched in November 2004. It combines a sensitive gamma-ray detector with the ability to point on-board X-ray and optical telescopes towards the direction of a new burst in less than one minute after the burst is detected. [ 44 ] Swift's discoveries include the first observations of short burst afterglows and vast amounts of data on the behavior of GRB afterglows at early stages during their evolution, even before the GRB's gamma-ray emission has stopped. The mission has also discovered large X-ray flares appearing within minutes to days after the end of the GRB.
On June 11, 2008 NASA's Gamma-ray Large Area Space Telescope (GLAST), later renamed the Fermi Gamma-ray Space Telescope , was launched. The mission objectives include "crack[ing] the mysteries of the stupendously powerful explosions known as gamma-ray bursts." [ 45 ]
Another gamma-ray burst observation mission is AGILE . Discoveries of GRBs are made as they are detected via the Gamma-ray Burst Coordinates Network so that researchers may promptly focus their instruments on the source of the burst to observe the afterglows. | https://en.wikipedia.org/wiki/History_of_gamma-ray_burst_research |
The history of gasoline started around the invention of internal combustion engines suitable for use in transportation applications. The so-called Otto engines were developed in Germany during the last quarter of the 19th century. The fuel for these early engines was a relatively volatile hydrocarbon obtained from coal gas . With a boiling point near 85 °C (185 °F) ( n -octane boils at 125.62 °C (258.12 °F) [ 1 ] ), it was well-suited for early carburetors (evaporators). The development of a "spray nozzle" carburetor enabled the use of less volatile fuels. Further improvements in engine efficiency were attempted at higher compression ratios , but early attempts were blocked by the premature explosion of fuel, known as knocking .
In 1891, the Shukhov cracking process became the world's first commercial method to break down heavier hydrocarbons in crude oil to increase the percentage of lighter products compared to simple distillation.
The American English word gasoline denotes fuel for automobiles , which common usage shortened to the terms gas , or rarely motor gas and mogas , thus differentiating it from avgas (aviation gasoline), which is fuel for airplanes. English dictionaries, including the Oxford English Dictionary , show that the term gasoline originates from gas plus the chemical suffixes -ole and -ine . [ 3 ] [ 4 ] [ 5 ] However, a blog post at the defunct website Oxford Dictionaries alternatively proposes that the word may have originated from the surname of British businessman John Cassell , who supposedly first marketed the substance. [ a ]
In place of the word gasoline , most Commonwealth countries (except Canada), use the term "petrol", and North Americans more often use "gas" in common parlance, hence the prevalence of the usage gas station in the United States. [ 6 ]
Coined from Medieval Latin , the word petroleum (L. petra , rock + oleum , oil) initially denoted types of mineral oil derived from rocks and stones. [ 7 ] [ 8 ] In Britain, Petrol was a refined mineral oil product marketed as a solvent from the 1870s by the British wholesaler Carless Refining and Marketing Ltd . [ 9 ] When Petrol found a later use as a motor fuel, Frederick Simms , an associate of Gottlieb Daimler , suggested to John Leonard, owner of Carless, that they trademark the word and uppercase spelling Petrol . [ 10 ] The trademark application was refused because petrol had already become an established general term for motor fuel. [ 11 ] Due to the firm's age, [ citation needed ] Carless retained the legal rights to the term and to the uppercase spelling of "Petrol" as the name of a petrochemical product. [ 12 ]
British refiners originally used "motor spirit" as a generic name for the automotive fuel and "aviation spirit" for aviation gasoline . When Carless was denied a trademark on "petrol" in the 1930s, its competitors switched to the more popular name "petrol". However, "motor spirit" had already made its way into laws and regulations, so the term remains in use as a formal name for petrol. [ 13 ] [ 14 ] The term is used most widely in Nigeria, where the largest petroleum companies call their product "premium motor spirit". [ 15 ] Although "petrol" has made inroads into Nigerian English, "premium motor spirit" remains the formal name that is used in scientific publications, government reports, and newspapers. [ 16 ]
Some other languages use variants of gasoline . Gasolina is used in Spanish and Portuguese, and gasorin is used in Japanese. In other languages, the name of the product is derived from the hydrocarbon compound benzene , or more precisely from the class of products called petroleum benzine , such as benzin in German or benzina in Italian; but in Argentina, Uruguay, and Paraguay, the colloquial name nafta is derived from that of the chemical naphtha . [ 17 ]
Some languages, like French and Italian, use the respective words for gasoline to instead indicate diesel fuel . [ 18 ]
Subsequent to the inventions of Daimler, Benz, Otto, and others the growth in the production and consumption of gasoline involved many innovations. One might summarize the timeline in the following way: the first 50 years were focused on the internal combustion engine and on refinery operations and, post 1970, emphasis has been placed on safety and automobile emissions . [ 19 ]
The evolution of gasoline followed the evolution of oil as the dominant source of energy in the industrializing world. Before World War I, Britain was the world's greatest industrial power and depended on its navy to protect the shipping of raw materials from its colonies. Germany was also industrializing and, like Britain, lacked many natural resources which had to be shipped to the home country. By the 1890s, Germany began to pursue a policy of global prominence and began building a navy to compete with Britain's. Coal was the fuel that powered their navies. Though both Britain and Germany had natural coal reserves, new developments in oil as a fuel for ships changed the situation. Coal-powered ships were a tactical weakness because the process of loading coal was slow and dirty and left the ship completely vulnerable to attack, and unreliable supplies of coal at international ports made long-distance voyages impractical. The advantages of petroleum oil soon found the navies of the world converting to oil, but Britain and Germany had very few domestic oil reserves. [ 20 ] Britain eventually solved its naval oil dependence by securing oil from Royal Dutch Shell and the Anglo-Persian Oil Company and this determined from where and of what quality its gasoline would come.
During the early period of gasoline engine development, aircraft were forced to use motor vehicle gasoline since aviation gasoline did not yet exist. These early fuels were termed "straight-run" gasolines and were byproducts from the distillation of a single crude oil to produce kerosene , which was the principal product sought for burning in kerosene lamps . Gasoline production would not surpass kerosene production until 1916. The earliest straight-run gasolines were the result of distilling eastern crude oils and there was no mixing of distillates from different crudes. The composition of these early fuels was unknown, and the quality varied greatly. The engine effects produced by abnormal combustion ( engine knocking and pre-ignition ) due to inferior fuels had not yet been identified, and as a result, there was no rating of gasoline in terms of its resistance to abnormal combustion. The general specification by which early gasolines were measured was that of specific gravity via the Baumé scale and later the volatility (tendency to vaporize) specified in terms of boiling points, which became the primary focuses for gasoline producers. These early eastern crude oil gasolines had relatively high Baumé test results (65 to 80 degrees Baumé) and were called "Pennsylvania high-test" or simply "high-test" gasolines. These were often used in aircraft engines.
By 1910, increased automobile production and the resultant increase in gasoline consumption produced a greater demand for gasoline. Also, the growing electrification of lighting produced a drop in kerosene demand, creating a supply problem. It appeared that the burgeoning oil industry would be trapped into over-producing kerosene and under-producing gasoline since simple distillation could not alter the ratio of the two products from any given crude. The solution appeared in 1911 when the development of the Burton process allowed thermal cracking of crude oils, which increased the percent yield of gasoline from the heavier hydrocarbons. This was combined with the expansion of foreign markets for the export of surplus kerosene which domestic markets no longer needed. These new thermally "cracked" gasolines were believed to have no harmful effects and would be added to straight-run gasolines. There also was the practice of mixing heavy and light distillates to achieve the desired Baumé reading and collectively these were called "blended" gasolines. [ 21 ]
Gradually, volatility gained favor over the Baumé test, though both continued to be used in combination to specify a gasoline. As late as June 1917, Standard Oil (the largest refiner of crude oil in the United States at the time) stated that the most important property of a gasoline was its volatility. [ 22 ] It is estimated that the rating equivalent of these straight-run gasolines varied from 40 to 60 octane and that the "high-test", sometimes referred to as "fighting grade", probably averaged 50 to 65 octane. [ 23 ]
Prior to the United States entry into World War I , the European Allies used fuels derived from crude oils from Borneo , Java , and Sumatra , which gave satisfactory performance in their military aircraft. When the U.S. entered the war in April 1917, the U.S. became the principal supplier of aviation gasoline to the Allies and a decrease in engine performance was noted. [ 24 ] Soon it was realized that motor vehicle fuels were unsatisfactory for aviation, and after the loss of several combat aircraft, attention turned to the quality of the gasolines being used. Later flight tests conducted in 1937 showed that an octane reduction of 13 points (from 100 down to 87 octane) decreased engine performance by 20 percent and increased take-off distance by 45 percent. [ 25 ] If abnormal combustion were to occur, the engine could lose enough power to make getting airborne impossible and a take-off roll became a threat to the pilot and aircraft.
On 2 August 1917, the U.S. Bureau of Mines arranged to study fuels for aircraft in cooperation with the Aviation Section of the U.S. Army Signal Corps and a general survey concluded that no reliable data existed for the proper fuels for aircraft. As a result, flight tests began at Langley, McCook and Wright fields to determine how gasolines performed under various conditions. These tests showed that in certain aircraft, motor vehicle gasolines performed as well as "high-test" but in other types resulted in hot-running engines. It was also found that gasolines from aromatic and naphthenic base crude oils from California, South Texas, and Venezuela resulted in smooth-running engines. These tests resulted in the first government specifications for motor gasolines (aviation gasolines used the same specifications as motor gasolines) in late 1917. [ 26 ]
Engine designers knew that, according to the Otto cycle , power and efficiency increased with compression ratio, but experience with early gasolines during World War I showed that higher compression ratios increased the risk of abnormal combustion, producing lower power, lower efficiency, hot-running engines, and potentially severe engine damage. To compensate for these poor fuels, early engines used low compression ratios, which required relatively large, heavy engines with limited power and efficiency. The Wright brothers ' first gasoline engine used a compression ratio as low as 4.7-to-1, developed only 8.9 kilowatts (12 hp) from 3,290 cubic centimeters (201 cu in), and weighed 82 kilograms (180 lb). [ 27 ] [ 28 ] This was a major concern for aircraft designers and the needs of the aviation industry provoked the search for fuels that could be used in higher-compression engines.
Between 1917 and 1919, the amount of thermally cracked gasoline utilized almost doubled. Also, the use of natural gasoline increased greatly. During this period, many U.S. states established specifications for motor gasoline but none of these agreed and they were unsatisfactory from one standpoint or another. Larger oil refiners began to specify unsaturated material percentage (thermally cracked products caused gumming in both use and storage while unsaturated hydrocarbons are more reactive and tend to combine with impurities leading to gumming). In 1922, the U.S. government published the first specifications for aviation gasolines (two grades were designated as "fighting" and "domestic" and were governed by boiling points, color, sulfur content, and a gum formation test) along with one "motor" grade for automobiles. The gum test essentially eliminated thermally cracked gasoline from aviation usage and thus aviation gasolines reverted to fractionating straight-run naphthas or blending straight-run and highly treated thermally cracked naphthas. This situation persisted until 1929. [ 29 ]
The automobile industry reacted to the increase in thermally cracked gasoline with alarm. Thermal cracking produced large amounts of both mono- and diolefins (unsaturated hydrocarbons), which increased the risk of gumming. [ 30 ] Also, the volatility was decreasing to the point that fuel did not vaporize and was sticking to spark plugs and fouling them, creating hard starting and rough running in winter and sticking to cylinder walls, bypassing the pistons and rings, and going into the crankcase oil. [ 31 ] One journal stated, "on a multi-cylinder engine in a high-priced car we are diluting the oil in the crankcase as much as 40 percent in a 200-mile [320 km] run, as the analysis of the oil in the oil-pan shows". [ 32 ]
Being very unhappy with the consequent reduction in overall gasoline quality, automobile manufacturers suggested imposing a quality standard on the oil suppliers. The oil industry in turn accused the automakers of not doing enough to improve vehicle economy, and the dispute became known within the two industries as "the fuel problem". Animosity grew between the industries, each accusing the other of not doing anything to resolve matters, and their relationship deteriorated. The situation was only resolved when the American Petroleum Institute (API) initiated a conference to address the fuel problem and a cooperative fuel research (CFR) committee was established in 1920, to oversee joint investigative programs and solutions. Apart from representatives of the two industries, the Society of Automotive Engineers (SAE) also played an instrumental role, with the U.S. Bureau of Standards being chosen as an impartial research organization to carry out many of the studies. Initially, all the programs were related to volatility and fuel consumption, ease of starting, crankcase oil dilution, and acceleration. [ 33 ]
With the increased use of thermally cracked gasolines came an increased concern regarding its effects on abnormal combustion, and this led to research for antiknock additives. In the late 1910s, researchers such as A.H. Gibson, Harry Ricardo , Thomas Midgley Jr. , and Thomas Boyd began to investigate abnormal combustion. Beginning in 1916, Charles F. Kettering of General Motors began investigating additives based on two paths, the "high percentage" solution (where large quantities of ethanol were added) and the "low percentage" solution (where only 0.53–1.1 g/L or 0.071–0.147 oz / U.S. gal were needed). The "low percentage" solution ultimately led to the discovery of tetraethyllead (TEL) in December 1921, a product of the research of Midgley and Boyd and the defining component of leaded gasoline. This innovation started a cycle of improvements in fuel efficiency that coincided with the large-scale development of oil refining to provide more products in the boiling range of gasoline. Ethanol could not be patented but TEL could, so Kettering secured a patent for TEL and began promoting it instead of other options.
The dangers of compounds containing lead were well-established by then and Kettering was directly warned by Robert Wilson of MIT, Reid Hunt of Harvard, Yandell Henderson of Yale, and Erik Krause of the University of Potsdam in Germany about its use. Krause had worked on tetraethyllead for many years and called it "a creeping and malicious poison" that had killed a member of his dissertation committee. [ 34 ] [ 35 ] On 27 October 1924, newspaper articles around the nation told of the workers at the Standard Oil refinery near Elizabeth , New Jersey who were producing TEL and were suffering from lead poisoning . By 30 October, the death toll had reached five. [ 35 ] In November, the New Jersey Labor Commission closed the Bayway refinery and a grand jury investigation was started which had resulted in no charges by February 1925. Leaded gasoline sales were banned in New York City, Philadelphia, and New Jersey. General Motors , DuPont , and Standard Oil, who were partners in Ethyl Corporation , the company created to produce TEL, began to argue that there were no alternatives to leaded gasoline that would maintain fuel efficiency and still prevent engine knocking. After several industry-funded flawed studies reported that TEL-treated gasoline was not a public health issue, the controversy subsided. [ 35 ]
In the five years prior to 1929, a great amount of experimentation was conducted on various testing methods for determining fuel resistance to abnormal combustion. It appeared engine knocking was dependent on a wide variety of parameters including compression, ignition timing, cylinder temperature, air-cooled or water-cooled engines, chamber shapes, intake temperatures, lean or rich mixtures, and others. This led to a confusing variety of test engines that gave conflicting results, and no standard rating scale existed. By 1929, it was recognized by most aviation gasoline manufacturers and users that some kind of antiknock rating must be included in government specifications. In 1929, the octane rating scale was adopted, and in 1930, the first octane specification for aviation fuels was established. In the same year, the U.S. Army Air Force specified fuels rated at 87 octane for its aircraft as a result of studies it had conducted. [ 36 ]
During this period, research showed that hydrocarbon structure was important to the antiknocking properties of fuel. Straight-chain paraffins in the boiling range of gasoline had low antiknock qualities while ring-shaped molecules such as aromatic hydrocarbons (for example benzene ) had higher resistance to knocking. [ 37 ] This development led to the search for processes that would produce more of these compounds from crude oils than achieved under straight distillation or thermal cracking. Research by the major refiners led to the development of processes involving isomerization of cheap and abundant butane to isobutane , and alkylation to join isobutane and butylenes to form isomers of octane such as " isooctane ", which became an important component in aviation fuel blending. To further complicate the situation, as engine performance increased, the altitude that aircraft could reach also increased, which resulted in concerns about the fuel freezing. The average temperature decrease is 3.6 °F (2.0 °C) per 300-meter (1,000 ft) increase in altitude, and at 12,000 meters (40,000 ft), the temperature can approach −57 °C (−70 °F). Additives like benzene, with a freezing point of 6 °C (42 °F), would freeze in the gasoline and plug fuel lines. Substituted aromatics such as toluene , xylene , and cumene , combined with limited benzene, solved the problem. [ 38 ]
By 1935, there were seven grades of aviation fuels based on octane rating, two Army grades, four Navy grades, and three commercial grades including the introduction of 100-octane aviation gasoline. By 1937, the Army established 100-octane as the standard fuel for combat aircraft, and to add to the confusion, the government now recognized 14 distinct grades, in addition to 11 others in foreign countries. With some companies required to stock 14 grades of aviation fuel, none of which could be interchanged, the effect on the refiners was negative. The refining industry could not concentrate on large capacity conversion processes for so many grades and a solution had to be found. By 1941, principally through the efforts of the Cooperative Fuel Research Committee, the number of grades for aviation fuels was reduced to three: 73, 91, and 100 octane. [ 39 ]
The development of 100-octane aviation gasoline on an economic scale was due in part to Jimmy Doolittle , who had become Aviation Manager of Shell Oil Company. He convinced Shell to invest in refining capacity to produce 100-octane on a scale that nobody needed since no aircraft existed that required a fuel that nobody made. Some fellow employees would call his effort "Doolittle's million-dollar blunder" but time would prove Doolittle correct. Before this, the Army had considered 100-octane tests using pure octane but at $6.6 per liter ($25/U.S. gal), the price prevented this from happening. In 1929, Stanavo Specification Board Inc. was organized by the Standard Oil companies of California, Indiana, and New Jersey to improve aviation fuels and oils and by 1935 had placed their first 100 octane fuel on the market, Stanavo Ethyl Gasoline 100. It was used by the Army, engine manufacturers and airlines for testing and for air racing and record flights. [ 40 ] By 1936, tests at Wright Field using the new, cheaper alternatives to pure octane proved the value of 100 octane fuel, and both Shell and Standard Oil would win the contract to supply test quantities for the Army. By 1938, the price was down to $0.046 per liter ($0.175/U.S. gal), only $0.0066 ($0.025) more than 87 octane fuel. By the end of WWII, the price would be down to $0.042 per liter ($0.16/U.S. gal). [ 41 ]
In 1937, Eugene Houdry developed the Houdry process of catalytic cracking , which produced a high-octane base stock of gasoline which was superior to the thermally cracked product since it did not contain the high concentration of olefins. [ 21 ] In 1940, there were only 14 Houdry units in operation in the U.S.; by 1943, this had increased to 77, either of the Houdry process or of the Thermofor Catalytic or Fluid Catalyst type. [ 42 ]
The search for fuels with octane ratings above 100 led to the extension of the scale by comparing power output. A fuel designated grade 130 would produce 130 percent as much power in an engine as it would running on pure iso-octane. During WWII, fuels above 100-octane were given two ratings, a rich and a lean mixture, and these would be called 'performance numbers' (PN). 100-octane aviation gasoline would be referred to as 130/100 grade. [ 43 ]
Oil and its byproducts, especially high-octane aviation gasoline, would prove to be a driving concern for how Germany conducted the war. As a result of the lessons of World War I, Germany had stockpiled oil and gasoline for its blitzkrieg offensive and had annexed Austria, adding 18,000 barrels (2,900 m 3 ; 100,000 cu ft) per day of oil production, but this was not sufficient to sustain the planned conquest of Europe. Because captured supplies and oil fields would be necessary to fuel the campaign, the German high command created a special squad of oilfield experts drawn from the ranks of domestic oil industries. They were sent in to put out oilfield fires and get production going again as soon as possible. But capturing oilfields remained an obstacle throughout the war. During the Invasion of Poland , German estimates of gasoline consumption turned out to be vastly too low. Heinz Guderian and his Panzer divisions consumed nearly 2.4 liters per kilometer (1 U.S. gal/mi) of gasoline on the drive to Vienna . When they were engaged in combat across open country, gasoline consumption almost doubled. On the second day of battle, a unit of the XIX Corps was forced to halt when it ran out of gasoline. [ 44 ] One of the major objectives of the Polish invasion was their oil fields but the Soviets invaded and captured 70 percent of the Polish production before the Germans could reach it. Through the German–Soviet Commercial Agreement (1940) , Stalin agreed in vague terms to supply Germany with additional oil equal to that produced by now Soviet-occupied Polish oilfields at Drohobych and Boryslav in exchange for hard coal and steel tubing.
Even after the Nazis conquered the vast territories of Europe, this did not help the gasoline shortage. This area had never been self-sufficient in oil before the war. In 1938, the area that would become Nazi-occupied produced 575,000 barrels (91,400 m 3 ; 3,230,000 cu ft) per day. In 1940, total production under German control amounted to only 234,550 barrels (37,290 m 3 ; 1,316,900 cu ft). [ 45 ] By early 1941 and the depletion of German gasoline reserves, Adolf Hitler saw the invasion of Russia to seize the Polish oil fields and the Russian oil in the Caucasus as the solution to the German gasoline shortage. As early as July 1941, following the 22 June start of Operation Barbarossa , certain Luftwaffe squadrons were forced to curtail ground support missions due to shortages of aviation gasoline. On 9 October, the German quartermaster general estimated that army vehicles were 24,000 barrels (3,800 m 3 ; 130,000 cu ft) short of gasoline requirements. [ 46 ] [ clarification needed (over what time period?) ]
Virtually all of Germany's aviation gasoline came from synthetic oil plants that hydrogenated coals and coal tars. These processes had been developed during the 1930s as an effort to achieve fuel independence. There were two grades of aviation gasoline produced in volume in Germany, the B-4 or blue grade and the C-3 or green grade, which accounted for about two-thirds of all production. B-4 was equivalent to 89-octane and the C-3 was roughly equal to the U.S. 100-octane, though lean mixture was rated around 95-octane and was poorer than the U.S. version. Maximum output achieved in 1943 reached 52,200 barrels (8,300 m 3 ; 293,000 cu ft) a day before the Allies decided to target the synthetic fuel plants. Through captured enemy aircraft and analysis of the gasoline found in them, both the Allies and the Axis powers were aware of the quality of the aviation gasoline being produced and this prompted an octane race to achieve the advantage in aircraft performance. Later in the war, the C-3 grade was improved to where it was equivalent to the U.S. 150 grade (rich mixture rating). [ 47 ]
Japan, like Germany, had almost no domestic oil supply and by the late 1930s, produced only seven percent of its own oil while importing the rest – 80 percent from the U.S.. As Japanese aggression grew in China ( USS Panay incident ) and news reached the American public of Japanese bombing of civilian centers, especially the bombing of Chungking, public opinion began to support a U.S. embargo. A Gallup poll in June 1939 found that 72 percent of the American public supported an embargo on war materials to Japan. This increased tensions between the U.S. and Japan, and it led to the U.S. placing restrictions on exports. In July 1940, the U.S. issued a proclamation that banned the export of 87 octane or higher aviation gasoline to Japan. This ban did not hinder the Japanese as their aircraft could operate with fuels below 87 octane and if needed they could add TEL to increase the octane. As it turned out, Japan bought 550 percent more sub-87 octane aviation gasoline in the five months after the July 1940 ban on higher octane sales. [ 48 ] The possibility of a complete ban of gasoline from America created friction in the Japanese government as to what action to take to secure more supplies from the Dutch East Indies and demanded greater oil exports from the exiled Dutch government after the Battle of the Netherlands . This action prompted the U.S. to move its Pacific fleet from Southern California to Pearl Harbor to help stiffen British resolve to stay in Indochina. With the Japanese invasion of French Indochina in September 1940, came great concerns about the possible Japanese invasion of the Dutch Indies to secure their oil. After the U.S. banned all exports of steel and iron scrap, the next day, Japan signed the Tripartite Pact and this led Washington to fear that a complete U.S. oil embargo would prompt the Japanese to invade the Dutch East Indies. On 16 June 1941 Harold Ickes, who was appointed Petroleum Coordinator for National Defense, stopped a shipment of oil from Philadelphia to Japan in light of the oil shortage on the East coast due to increased exports to Allies. He also telegrammed all oil suppliers on the East coast not to ship any oil to Japan without his permission. President Roosevelt countermanded Ickes's orders telling Ickes that the "I simply have not got enough Navy to go around and every little episode in the Pacific means fewer ships in the Atlantic". [ 49 ] On 25 July 1941, the U.S. froze all Japanese financial assets and licenses would be required for each use of the frozen funds including oil purchases that could produce aviation gasoline. On 28 July 1941, Japan invaded southern Indochina.
The debate inside the Japanese government as to its oil and gasoline situation was leading to invasion of the Dutch East Indies but this would mean war with the U.S., whose Pacific fleet was a threat to their flank. This situation led to the decision to attack the U.S. fleet at Pearl Harbor before proceeding with the Dutch East Indies invasion. On 7 December 1941, Japan attacked Pearl Harbor, and the next day the Netherlands declared war on Japan, which initiated the Dutch East Indies campaign . But the Japanese missed a golden opportunity at Pearl Harbor. "All of the oil for the fleet was in surface tanks at the time of Pearl Harbor", Admiral Chester Nimitz, who became Commander in Chief of the Pacific Fleet, was later to say. "We had about 4 + 1 ⁄ 2 million barrels [0.72 × 10 ^ 6 m 3 ; 25 × 10 ^ 6 cu ft] of oil out there and all of it was vulnerable to .50 caliber bullets. Had the Japanese destroyed the oil," he added, "it would have prolonged the war another two years." [ 50 ]
Early in 1944, William Boyd, president of the American Petroleum Institute and chairman of the Petroleum Industry War Council said: "The Allies may have floated to victory on a wave of oil in World War I, but in this infinitely greater World War II, we are flying to victory on the wings of petroleum". In December 1941 the U.S. had 385,000 oil wells producing 1.6 billion barrels (0.25 × 10 ^ 9 m 3 ; 9.0 × 10 ^ 9 cu ft) barrels of oil a year and 100-octane aviation gasoline capacity was at 40,000 barrels (6,400 m 3 ; 220,000 cu ft) a day. By 1944, the U.S. was producing over 1.5 billion barrels (0.24 × 10 ^ 9 m 3 ; 8.4 × 10 ^ 9 cu ft) a year (67 percent of world production) and the petroleum industry had built 122 new plants for the production of 100-octane aviation gasoline and capacity was over 400,000 barrels (64,000 m 3 ; 2,200,000 cu ft) a day – an increase of more than ten-fold. It was estimated that the U.S. was producing enough 100-octane aviation gasoline to permit the dropping of 16,000 metric tons (18,000 short tons; 16,000 long tons) of bombs on the enemy every day of the year. The record of gasoline consumption by the Army prior to June 1943 was uncoordinated as each supply service of the Army purchased its own petroleum products and no centralized system of control nor records existed. On 1 June 1943, the Army created the Fuels and Lubricants Division of the Quartermaster Corps, and, from their records, they tabulated that the Army (excluding fuels and lubricants for aircraft) purchased over 9.1 billion liters (2.4 × 10 ^ 9 U.S. gal) of gasoline for delivery to overseas theaters between 1 June 1943 through August 1945. That figure does not include gasoline used by the Army inside the U.S. [ 51 ] Motor fuel production had declined from 701 million barrels (111.5 × 10 ^ 6 m 3 ; 3,940 × 10 ^ 6 cu ft)in 1941 down to 208 million barrels (33.1 × 10 ^ 6 m 3 ; 1,170 × 10 ^ 6 cu ft) in 1943. [ 52 ] World War II marked the first time in U.S. history that gasoline was rationed and the government imposed price controls to prevent inflation. Gasoline consumption per automobile declined from 2,860 liters (755 U.S. gal) per year in 1941 down to 2,000 liters (540 U.S. gal)in 1943, with the goal of preserving rubber for tires since the Japanese had cut the U.S. off from over 90 percent of its rubber supply which had come from the Dutch East Indies and the U.S. synthetic rubber industry was in its infancy. Average gasoline prices went from a record low of $0.0337 per liter ($0.1275/U.S. gal) ($0.0486 ($0.1841) with taxes) in 1940 to $0.0383 per liter ($0.1448/U.S. gal) ($0.0542 ($0.2050) with taxes) in 1945. [ 53 ]
Even with the world's largest aviation gasoline production, the U.S. military still found that more was needed. Throughout the duration of the war, aviation gasoline supply was always behind requirements and this impacted training and operations. The reason for this shortage developed before the war even began. The free market did not support the expense of producing 100-octane aviation fuel in large volume, especially during the Great Depression. Iso-octane in the early development stage cost $7.9 per liter ($30/U.S. gal), and, even by 1934, it was still $0.53 per liter ($2/U.S. gal)compared to $0.048 ($0.18) for motor gasoline when the Army decided to experiment with 100-octane for its combat aircraft. Though only three percent of U.S. combat aircraft in 1935 could take full advantage of the higher octane due to low compression ratios, the Army saw that the need for increasing performance warranted the expense and purchased 100,000 gallons. By 1937, the Army established 100-octane as the standard fuel for combat aircraft and by 1939 production was only 20,000 barrels (3,200 m 3 ; 110,000 cu ft) a day. In effect, the U.S. military was the only market for 100-octane aviation gasoline and as war broke out in Europe this created a supply problem that persisted throughout the duration. [ 54 ] [ 55 ]
With the war in Europe a reality in 1939, all predictions of 100-octane consumption were outrunning all possible production. Neither the Army nor the Navy could contract more than six months in advance for fuel and they could not supply the funds for plant expansion. Without a long-term guaranteed market, the petroleum industry would not risk its capital to expand production for a product that only the government would buy. The solution to the expansion of storage, transportation, finances, and production was the creation of the Defense Supplies Corporation on 19 September 1940. The Defense Supplies Corporation would buy, transport and store all aviation gasoline for the Army and Navy at cost plus a carrying fee. [ 56 ]
When the Allied breakout after D-Day found their armies stretching their supply lines to a dangerous point, the makeshift solution was the Red Ball Express . But even this soon was inadequate. The trucks in the convoys had to drive longer distances as the armies advanced and they were consuming a greater percentage of the same gasoline they were trying to deliver. In 1944, General George Patton's Third Army finally stalled just short of the German border after running out of gasoline. The general was so upset at the arrival of a truckload of rations instead of gasoline he was reported to have shouted: "Hell, they send us food, when they know we can fight without food but not without oil." [ 57 ] The solution had to wait for the repairing of the railroad lines and bridges so that the more efficient trains could replace the gasoline-consuming truck convoys.
The development of jet engines burning kerosene-based fuels during WWII for aircraft produced a superior performing propulsion system than internal combustion engines could offer and the U.S. military forces gradually replaced their piston combat aircraft with jet powered planes. This development would essentially remove the military need for ever increasing octane fuels and eliminated government support for the refining industry to pursue the research and production of such exotic and expensive fuels. Commercial aviation was slower to adapt to jet propulsion and until 1958, when the Boeing 707 first entered commercial service, piston powered airliners still relied on aviation gasoline. But commercial aviation had greater economic concerns than the maximum performance that the military could afford. As octane numbers increased so did the cost of gasoline but the incremental increase in efficiency becomes less as compression ratio goes up. This reality set a practical limit to how high compression ratios could increase relative to how expensive the gasoline would become. [ 58 ] Last produced in 1955, the Pratt & Whitney R-4360 Wasp Major was using 115/145 Aviation gasoline and producing 0.046 kilowatts per cubic centimeter (1 hp/cu in) at 6.7 compression ratio (turbo-supercharging would increase this) and 0.45 kilograms (1 lb) of engine weight to produce 0.82 kilowatts (1.1 hp). This compares to the Wright Brothers engine needing almost 7.7 kilograms (17 lb) of engine weight to produce 0.75 kilowatts (1 hp).
The U.S. automobile industry after WWII could not take advantage of the high octane fuels then available. Automobile compression ratios increased from an average of 5.3-to-1 in 1931 to just 6.7-to-1 in 1946. The average octane number of regular-grade motor gasoline increased from 58 to 70 during the same time. Military aircraft were using expensive turbo-supercharged engines that cost at least 10 times as much per horsepower as automobile engines and had to be overhauled every 700 to 1,000 hours. The automobile market could not support such expensive engines. [ 59 ] It would not be until 1957 that the first U.S. automobile manufacturer could mass-produce an engine that would produce one horsepower per cubic inch, the Chevrolet 283 hp/283 cubic inch V-8 engine option in the Corvette. At $485, this was an expensive option that few consumers could afford and would only appeal to the performance-oriented consumer market willing to pay for the premium fuel required. [ 60 ] This engine had an advertised compression ratio of 10.5-to-1 and the 1958 AMA Specifications stated that the octane requirement was 96–100 RON. [ 61 ] At 243 kilograms (535 lb) (1959 with aluminum intake), it took 0.86 kilograms (1.9 lb) of engine weight to make 0.75 kilowatts (1 hp). [ 62 ]
In the 1950s, oil refineries started to focus on high octane fuels, and then detergents were added to gasoline to clean the jets in carburetors. The 1970s witnessed greater attention to the environmental consequences of burning gasoline. These considerations led to the phasing out of TEL and its replacement by other antiknock compounds. Subsequently, low-sulfur gasoline was introduced, in part to preserve the catalysts in modern exhaust systems. [ 19 ] | https://en.wikipedia.org/wiki/History_of_gasoline |
The history of general-purpose CPUs is a continuation of the earlier history of computing hardware .
In the early 1950s, each computer design was unique. There were no upward-compatible machines or computer architectures with multiple, differing implementations. Programs written for one machine would run on no other kind, even other kinds from the same company. This was not a major drawback then because no large body of software had been developed to run on computers, so starting programming from scratch was not seen as a large barrier.
The design freedom of the time was very important because designers were very constrained by the cost of electronics, and only starting to explore how a computer could best be organized. Some of the basic features introduced during this period included index registers (on the Ferranti Mark 1 ), a return address saving instruction ( UNIVAC I ), immediate operands ( IBM 704 ), and detecting invalid operations ( IBM 650 ).
By the end of the 1950s, commercial builders had developed factory-constructed, truck-deliverable computers. The most widely installed computer was the IBM 650 , which used drum memory onto which programs were loaded using either paper punched tape or punched cards . Some very high-end machines also included core memory which provided higher speeds. Hard disks were also starting to grow popular.
A computer is an automatic abacus . The type of number system affects the way it works. In the early 1950s, most computers were built for specific numerical processing tasks, and many machines used decimal numbers as their basic number system; that is, the mathematical functions of the machines worked in base-10 instead of base-2 as is common today. These were not merely binary-coded decimal (BCD). Most machines had ten vacuum tubes per digit in each processor register . Some early Soviet computer designers implemented systems based on ternary logic ; that is, a bit could have three states: +1, 0, or -1, corresponding to positive, zero, or negative voltage.
An early project for the U.S. Air Force , BINAC attempted to make a lightweight, simple computer by using binary arithmetic. It deeply impressed the industry.
As late as 1970, major computer languages were unable to standardize their numeric behavior because decimal computers had groups of users too large to alienate.
Even when designers used a binary system, they still had many odd ideas. Some used sign-magnitude arithmetic (-1 = 10001), or ones' complement (-1 = 11110), rather than modern two's complement arithmetic (-1 = 11111). Most computers used six-bit character sets because they adequately encoded Hollerith punched cards . It was a major revelation to designers of this period to realize that the data word should be a multiple of the character size. They began to design computers with 12-, 24- and 36-bit data words (e.g., see the TX-2 ).
In this era, Grosch's law dominated computer design: computer cost increased as the square of its speed.
One major problem with early computers was that a program for one would work on no others. Computer companies found that their customers had little reason to remain loyal to a given brand, as the next computer they bought would be incompatible anyway. At that point, the only concerns were usually price and performance.
In 1962, IBM tried a new approach to designing computers. The plan was to make a family of computers that could all run the same software, but with different performances, and at different prices. As users' needs grew, they could move up to larger computers, and still keep all of their investment in programs, data and storage media.
To do this, they designed one reference computer named System/360 (S/360). This was a virtual computer, a reference instruction set, and abilities that all machines in the family would support. To provide different classes of machines, each computer in the family would use more or less hardware emulation, and more or less microprogram emulation, to create a machine able to run the full S/360 instruction set .
For instance, a low-end machine could include a very simple processor for low cost. However, this would require the use of a larger microcode emulator to provide the rest of the instruction set, which would slow it down. A high-end machine would use a much more complex processor that could directly process more of the S/360 design, thus running a much simpler and faster emulator.
IBM chose consciously to make the reference instruction set quite complex, and very capable. Even though the computer was complex, its control store holding the microprogram would stay relatively small and could be made with very fast memory. Another important effect was that one instruction could describe quite a complex sequence of operations. Thus the computers would generally have to fetch fewer instructions from the main memory, which could be made slower, smaller and less costly for a given mix of speed and price.
As the S/360 was to be a successor to both scientific machines like the 7090 and data processing machines like the 1401 , it needed a design that could reasonably support all forms of processing. Hence the instruction set was designed to manipulate simple binary numbers, and text, scientific floating-point (similar to the numbers used in a calculator), and the binary-coded decimal arithmetic needed by accounting systems.
Almost all following computers included these innovations in some form. This basic set of features is now called complex instruction set computing [ citation needed ] (CISC, pronounced "sisk"), a term not invented until many years later, when reduced instruction set computing (RISC) began to get market share.
In many CISCs, an instruction could access either registers or memory, usually in several different ways. This made the CISCs easier to program, because a programmer could remember only thirty to a hundred instructions, and a set of three to ten addressing modes rather than thousands of distinct instructions. This was called an orthogonal instruction set . The PDP-11 and Motorola 68000 architecture are examples of nearly orthogonal instruction sets.
There was also the BUNCH ( Burroughs , UNIVAC , NCR , Control Data Corporation , and Honeywell ) that competed against IBM at this time; however, IBM dominated the era with S/360.
The Burroughs Corporation (which later merged with Sperry/Univac to form Unisys ) offered an alternative to S/360 with their Burroughs large systems B5000 series. In 1961, the B5000 had virtual memory, symmetric multiprocessing, a multiprogramming operating system (Master Control Program (MCP)), written in ALGOL 60 , and the industry's first recursive-descent compilers as early as 1964.
The first commercial microprocessor , the binary-coded decimal (BCD) based Intel 4004 , was released by Intel in 1971. [ 1 ] [ 2 ] In March 1972, Intel introduced a microprocessor with an 8-bit architecture, the 8008 , an integrated pMOS logic re-implementation of the transistor–transistor logic (TTL) based Datapoint 2200 CPU.
4004 designers Federico Faggin and Masatoshi Shima went on to design the 8008's successor, the Intel 8080 , a slightly more minicomputer -like microprocessor, largely based on customer feedback on the limited 8008. Much like the 8008, it was used for applications such as terminals, printers, cash registers and industrial robots. However, the more able 8080 also became the original target CPU for an early de facto standard personal computer operating system called CP/M and was used for such demanding control tasks as cruise missiles , and many other uses. Released in 1974, the 8080 became one of the first really widespread microprocessors.
By the mid-1970s, the use of integrated circuits in computers was common. The decade was marked by market upheavals caused by the shrinking price of transistors.
It became possible to put an entire CPU on one printed circuit board. The result was that minicomputers, usually with 16-bit words, and 4K to 64K of memory, became common.
CISCs were believed to be the most powerful types of computers, because their microcode was small and could be stored in very high-speed memory. The CISC architecture also addressed the semantic gap as it was then perceived. This was a defined distance between the machine language, and the higher level programming languages used to program a machine. It was felt that compilers could do a better job with a richer instruction set.
Custom CISCs were commonly constructed using bit slice computer logic such as the AMD 2900 chips, with custom microcode. A bit slice component is a piece of an arithmetic logic unit (ALU), register file or microsequencer. Most bit-slice integrated circuits were 4 bits wide.
By the early 1970s, the 16-bit PDP-11 minicomputer was developed, arguably the most advanced small computer of its day. In the late 1970s, wider-word superminicomputers were introduced, such as the 32-bit VAX .
IBM continued to make large, fast computers. However, the definition of large and fast now meant more than a megabyte of RAM, clock speeds near one megahertz, [ 3 ] [ 4 ] and tens of megabytes of disk drives.
IBM's System 370 was a version of the 360 tweaked to run virtual computing environments. The virtual computer was developed to reduce the chances of an unrecoverable software failure.
The Burroughs large systems (B5000, B6000, B7000) series reached its largest market share. It was a stack computer whose OS was programmed in a dialect of Algol.
All these different developments competed for market share.
The first single-chip 16-bit microprocessor was introduced in 1975. Panafacom , a conglomerate formed by Japanese companies Fujitsu , Fuji Electric , and Matsushita , introduced the MN1610, a commercial 16-bit microprocessor. [ 5 ] [ 6 ] [ 7 ] According to Fujitsu, it was "the world's first 16-bit microcomputer on a single chip". [ 6 ]
The Intel 8080 was the basis for the 16-bit Intel 8086 , which is a direct ancestor to today's ubiquitous x86 family (including Pentium and Intel Core ). Every instruction of the 8080 has a direct equivalent in the large x86 instruction set, although the opcode values are different in the latter.
In the early 1980s, researchers at UC Berkeley and IBM both discovered that most computer language compilers and interpreters used only a small subset of the instructions of complex instruction set computing (CISC). Much of the power of the CPU was being ignored in real-world use. They realized that by making the computer simpler and less orthogonal, they could make it faster and less costly at the same time.
At the same time, CPU calculation became faster in relation to the time for needed memory accesses. Designers also experimented with using large sets of internal registers. The goal was to cache intermediate results in the registers under the control of the compiler. This also reduced the number of addressing modes and orthogonality.
The computer designs based on this theory were called reduced instruction set computing (RISC). RISCs usually had larger numbers of registers, accessed by simpler instructions, with a few instructions specifically to load and store data to memory. The result was a very simple core CPU running at very high speed, supporting the sorts of operations the compilers were using anyway.
A common variant on the RISC design employs the Harvard architecture , versus Von Neumann architecture or stored program architecture common to most other designs. In a Harvard Architecture machine, the program and data occupy separate memory devices and can be accessed simultaneously. In Von Neumann machines, the data and programs are mixed in one memory device, requiring sequential accessing which produces the so-called Von Neumann bottleneck .
One downside to the RISC design was that the programs that run on them tend to be larger. This is because compilers must generate longer sequences of the simpler instructions to perform the same results. Since these instructions must be loaded from memory anyway, the larger code offsets some of the RISC design's fast memory handling.
In the early 1990s, engineers at Japan's Hitachi found ways to compress the reduced instruction sets so they fit in even smaller memory systems than CISCs. Such compression schemes were used for the instruction set of their SuperH series of microprocessors, introduced in 1992. [ 8 ] The SuperH instruction set was later adapted for ARM architecture 's Thumb instruction set. [ 9 ] In applications that do not need to run older binary software, compressed RISCs are growing to dominate sales.
Another approach to RISCs was the minimal instruction set computer (MISC), niladic , or zero-operand instruction set. This approach realized that most space in an instruction was used to identify the operands of the instruction. These machines placed the operands on a push-down (last-in, first out) stack . The instruction set was supplemented with a few instructions to fetch and store memory. Most used simple caching to provide extremely fast RISC machines, with very compact code. Another benefit was that the interrupt latencies were very small, smaller than most CISC machines (a rare trait in RISC machines). The Burroughs large systems architecture used this approach. The B5000 was designed in 1961, long before the term RISC was invented. The architecture puts six 8-bit instructions in a 48-bit word, and was a precursor to very long instruction word (VLIW) design (see below: 1990 to today ).
The Burroughs architecture was one of the inspirations for Charles H. Moore 's programming language Forth , which in turn inspired his later MISC chip designs. For example, his f20 cores had 31 5-bit instructions, which fit four to a 20-bit word.
RISC chips now dominate the market for 32-bit embedded systems. Smaller RISC chips are even growing common in the cost-sensitive 8-bit embedded-system market. The main market for RISC CPUs has been systems that need low power or small size.
Even some CISC processors (based on architectures that were created before RISC grew dominant), such as newer x86 processors, translate instructions internally into a RISC-like instruction set.
These numbers may surprise many, because the market is perceived as desktop computers. x86 designs dominate desktop and notebook computer sales, but such computers are only a tiny fraction of the computers now sold. Most people in industrialised countries own more computers in embedded systems in their car and house, than on their desks.
In the mid-to-late 1980s, designers began using a technique termed instruction pipelining , in which the processor works on multiple instructions in different stages of completion. For example, the processor can retrieve the operands for the next instruction while calculating the result of the current one. Modern CPUs may use over a dozen such stages. (Pipelining was originally developed in the late 1950s by International Business Machines (IBM) on their 7030 (Stretch) mainframe computer.) Minimal instruction set computers (MISC) can execute instructions in one cycle with no need for pipelining.
A similar idea, introduced only a few years later, was to execute multiple instructions in parallel on separate arithmetic logic units (ALUs). Instead of operating on only one instruction at a time, the CPU will look for several similar instructions that do not depend on each other, and execute them in parallel. This approach is called superscalar processor design.
Such methods are limited by the degree of instruction-level parallelism (ILP), the number of non-dependent instructions in the program code. Some programs can run very well on superscalar processors due to their inherent high ILP, notably graphics. However, more general problems have far less ILP, thus lowering the possible speedups from these methods.
Branching is one major culprit. For example, a program may add two numbers and branch to a different code segment if the number is bigger than a third number. In this case, even if the branch operation is sent to the second ALU for processing, it still must wait for the results from the addition. It thus runs no faster than if there was only one ALU. The most common solution for this type of problem is to use a type of branch prediction .
To further the efficiency of multiple functional units which are available in superscalar designs, operand register dependencies were found to be another limiting factor. To minimize these dependencies, out-of-order execution of instructions was introduced. In such a scheme, the instruction results which complete out-of-order must be re-ordered in program order by the processor for the program to be restartable after an exception. Out-of-order execution was the main advance of the computer industry during the 1990s.
A similar concept is speculative execution , where instructions from one direction of a branch (the predicted direction) are executed before the branch direction is known. When the branch direction is known, the predicted direction and the actual direction are compared. If the predicted direction was correct, the speculatively executed instructions and their results are kept; if it was incorrect, these instructions and their results are erased. Speculative execution, coupled with an accurate branch predictor, gives a large performance gain.
These advances, which were originally developed from research for RISC-style designs, allow modern CISC processors to execute twelve or more instructions per clock cycle, when traditional CISC designs could take twelve or more cycles to execute one instruction.
The resulting instruction scheduling logic of these processors is large, complex and difficult to verify. Further, higher complexity needs more transistors, raising power consumption and heat. In these, RISC is superior because the instructions are simpler, have less interdependence, and make superscalar implementations easier. However, as Intel has demonstrated, the concepts can be applied to a complex instruction set computing (CISC) design, given enough time and money.
The instruction scheduling logic that makes a superscalar processor is Boolean logic . In the early 1990s, a significant innovation was to realize that the coordination of a multi-ALU computer could be moved into the compiler , the software that translates a programmer's instructions into machine-level instructions.
This type of computer is called a very long instruction word (VLIW) computer.
Scheduling instructions statically in the compiler (versus scheduling dynamically in the processor) can reduce CPU complexity. This can improve performance, and reduce heat and cost.
Unfortunately, the compiler lacks accurate knowledge of runtime scheduling issues. Merely changing the CPU core frequency multiplier will have an effect on scheduling. Operation of the program, as determined by input data, will have major effects on scheduling. To overcome these severe problems, a VLIW system may be enhanced by adding the normal dynamic scheduling, losing some of the VLIW advantages.
Static scheduling in the compiler also assumes that dynamically generated code will be uncommon. Before the creation of Java and the Java virtual machine , this was true. It was reasonable to assume that slow compiles would only affect software developers. Now, with just-in-time compilation (JIT) virtual machines being used for many languages, slow code generation affects users also.
There were several unsuccessful attempts to commercialize VLIW. The basic problem is that a VLIW computer does not scale to different price and performance points, as a dynamically scheduled computer can. Another issue is that compiler design for VLIW computers is very difficult, and compilers, as of 2005, often emit suboptimal code for these platforms.
Also, VLIW computers optimise for throughput, not low latency, so they were unattractive to engineers designing controllers and other computers embedded in machinery. The embedded systems markets had often pioneered other computer improvements by providing a large market unconcerned about compatibility with older software.
In January 2000, Transmeta Corporation took the novel step of placing a compiler in the central processing unit, and making the compiler translate from a reference byte code (in their case, x86 instructions) to an internal VLIW instruction set. This method combines the hardware simplicity, low power and speed of VLIW RISC with the compact main memory system and software reverse-compatibility provided by popular CISC.
Intel 's Itanium chip is based on what they call an explicitly parallel instruction computing (EPIC) design. This design supposedly provides the VLIW advantage of increased instruction throughput. However, it avoids some of the issues of scaling and complexity, by explicitly providing in each bundle of instructions information concerning their dependencies. This information is calculated by the compiler, as it would be in a VLIW design. The early versions are also backward-compatible with newer x86 software by means of an on-chip emulator mode. Integer performance was disappointing and despite improvements, sales in volume markets continue to be low.
Current [ when? ] designs work best when the computer is running only one program. However, nearly all modern operating systems allow running multiple programs together. For the CPU to change over and do work on another program needs costly context switching . In contrast, multi-threaded CPUs can handle instructions from multiple programs at once.
To do this, such CPUs include several sets of registers. When a context switch occurs, the contents of the working registers are simply copied into one of a set of registers for this purpose.
Such designs often include thousands of registers instead of hundreds as in a typical design. On the downside, registers tend to be somewhat costly in chip space needed to implement them. This chip space might be used otherwise for some other purpose.
Intel calls this technology "hyperthreading" and offers two threads per core in its current Core i3, Core i5, Core i7 and Core i9 Desktop lineup (as well as in its Core i3, Core i5 and Core i7 Mobile lineup), as well as offering up to four threads per core in high-end Xeon Phi processors.
Multi-core CPUs are typically multiple CPU cores on the same die, connected to each other via a shared L2 or L3 cache, an on-die bus , or an on-die crossbar switch . All the CPU cores on the die share interconnect components with which to interface to other processors and the rest of the system. These components may include a front-side bus interface, a memory controller to interface with dynamic random access memory (DRAM), a cache coherent link to other processors, and a non-coherent link to the southbridge and I/O devices. The terms multi-core and microprocessor unit (MPU) have come into general use for one die having multiple CPU cores.
The development of multi-core CPUs was largely driven by the physical and thermal limitations of increasing clock speeds. By distributing computational tasks across several cores, systems can achieve higher performance without proportionally increasing power consumption and heat generation. This parallel processing capability allows modern operating systems to schedule multiple threads concurrently, leading to improved responsiveness and throughput, especially in multi-threaded applications.
Many modern multi-core processors also incorporate simultaneous multithreading (SMT), a technology that allows each physical core to execute multiple threads concurrently. SMT enhances overall efficiency by making better use of the core’s resources during periods of low utilization, thus further optimizing performance without a significant increase in power draw.
In addition to the shared cache and interconnect components mentioned earlier, advanced interconnect technologies have played a crucial role in boosting multi-core performance. Interfaces such as Intel's QuickPath Interconnect (QPI) and AMD's Infinity Fabric have been developed to provide high-bandwidth, low-latency communication channels between cores, memory, and other system components. These innovations reduce data transfer bottlenecks and contribute to a more cohesive and efficient processing environment.
Moreover, the rise of heterogeneous computing has seen the integration of dedicated accelerators, such as GPUs and specialized co-processors, alongside multi-core CPUs. These systems offload specific tasks—like graphics rendering or machine learning computations—from the main CPU cores, allowing for a more balanced and efficient utilization of the overall system resources. This evolution in processor design continues to influence software development, where parallel and concurrent programming models are increasingly adopted to harness the full potential of multi-core architectures. [ 10 ]
One way to work around the Von Neumann bottleneck is to mix a processor and DRAM all on one chip.
Another track of development is to combine reconfigurable logic with a general-purpose CPU. In this scheme, a special computer language compiles fast-running subroutines into a bit-mask to configure the logic. Slower, or less-critical parts of the program can be run by sharing their time on the CPU. This process allows creating devices such as software radios , by using digital signal processing to perform functions usually performed by analog electronics .
As the lines between hardware and software increasingly blur due to progress in design methodology and availability of chips such as field-programmable gate arrays (FPGA) and cheaper production processes, even open source hardware has begun to appear. Loosely knit communities like OpenCores and RISC-V have recently announced fully open CPU architectures such as the OpenRISC which can be readily implemented on FPGAs or in custom produced chips, by anyone, with no license fees, and even established processor makers like Sun Microsystems have released processor designs (e.g., OpenSPARC ) under open-source licenses.
Yet another option is a clockless or asynchronous CPU . Unlike conventional processors, clockless processors have no central clock to coordinate the progress of data through the pipeline. Instead, stages of the CPU are coordinated using logic devices called pipe line controls or FIFO sequencers . Basically, the pipeline controller clocks the next stage of logic when the existing stage is complete. Thus, a central clock is unneeded.
Relative to clocked logic, it may be easier to implement high performance devices in asynchronous logic:
Asynchronous logic proponents believe these abilities would have these benefits:
The biggest disadvantage of the clockless CPU is that most CPU design tools assume a clocked CPU (a synchronous circuit ), so making a clockless CPU (designing an asynchronous circuit ) involves modifying the design tools to handle clockless logic and doing extra testing to ensure the design avoids metastability problems.
Even so, several asynchronous CPUs have been built, including
In theory, an optical computer's components could directly connect through a holographic or phased open-air switching system. This would provide a large increase in effective speed and design flexibility, and a large reduction in cost. Since a computer's connectors are also its most likely failure points, a busless system may be more reliable.
Further, as of 2010, modern processors use 64- or 128-bit logic. Optical wavelength superposition could allow data lanes and logic many orders of magnitude higher than electronics, with no added space or copper wires.
Another long-term option is to use light instead of electricity for digital logic. In theory, this could run about 30% faster and use less power, and allow a direct interface with quantum computing devices. [ citation needed ]
The main problems with this approach are that, for the foreseeable future, electronic computing elements are faster, smaller, cheaper, and more reliable. Such elements are already smaller than some wavelengths of light. Thus, even waveguide-based optical logic may be uneconomic relative to electronic logic. As of 2016, most development effort is for electronic circuitry.
Early experimental work has been done on using ion-based chemical reactions instead of electronic or photonic actions to implement elements of a logic processor.
Relative to conventional register machine or stack machine architecture, yet similar to Intel's Itanium architecture, [ 13 ] a temporal register addressing scheme has been proposed by Ivan Godard and company that is intended to greatly reduce the complexity of CPU hardware (specifically the number of internal registers and the resulting huge multiplexer trees). [ 14 ] While somewhat harder to read and debug than general-purpose register names, it aids understanding to view the belt as a moving conveyor belt where the oldest values drop off the belt and vanish. It is implemented in the Mill architecture. | https://en.wikipedia.org/wiki/History_of_general-purpose_CPUs |
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