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Contents Black hole A black hole is an astronomical body so compact that its gravity prevents anything, including light, from escaping. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. The boundary of no escape is called the event horizon. In general relativity, a black hole's event horizon seals an object's fate but produces no locally detectable change when crossed. General relativity also predicts that every black hole should have a central singularity, where the curvature of spacetime is infinite. In many ways, a black hole acts like an ideal black body, as it reflects no light. Quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly. Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. In 1916, Karl Schwarzschild found the first modern solution of general relativity that would characterise a black hole. Due to his influential research, the Schwarzschild metric is named after him. David Finkelstein, in 1958, first interpreted Schwarzschild's model as a region of space from which nothing can escape. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were a generic prediction of general relativity. The first black hole known was Cygnus X-1, identified by several researchers independently in 1971. Black holes typically form when massive stars collapse at the end of their life cycle. After a black hole has formed, it can grow by absorbing mass from its surroundings. Supermassive black holes of millions of solar masses may form by absorbing other stars and merging with other black holes, or via direct collapse of gas clouds. There is consensus that supermassive black holes exist in the centres of most galaxies. The presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light. Matter falling toward a black hole can form an accretion disk of infalling plasma, heated by friction and emitting light. In extreme cases, this creates a quasar, some of the brightest objects in the universe. Merging black holes can also be detected by observation of the gravitational waves they emit. If other stars are orbiting a black hole, their orbits can be used to determine the black hole's mass and location. Such observations can be used to exclude possible alternatives such as neutron stars. In this way, astronomers have identified numerous stellar black hole candidates in binary systems and established that the radio source known as Sagittarius A*, at the core of the Milky Way galaxy, contains a supermassive black hole of about 4.3 million solar masses. History The idea of a body so massive that even light could not escape was first proposed in the late 18th century by English astronomer and clergyman John Michell and independently by French scientist Pierre-Simon Laplace. Both scholars proposed very large stars in contrast to the modern concept of an extremely dense object. Michell's idea, in a short part of a letter published in 1784, calculated that a star with the same density but 500 times the radius of the sun would not let any emitted light escape; the surface escape velocity would exceed the speed of light.: 122 Michell correctly hypothesized that such supermassive but non-radiating bodies might be detectable through their gravitational effects on nearby visible bodies. In 1796, Laplace mentioned that a star could be invisible if it were sufficiently large while speculating on the origin of the Solar System in his book Exposition du Système du Monde. Franz Xaver von Zach asked Laplace for a mathematical analysis, which Laplace provided and published in a journal edited by von Zach. In 1905, Albert Einstein showed that the laws of electromagnetism would be invariant under a Lorentz transformation: they would be identical for observers travelling at different velocities relative to each other. This discovery became known as the principle of special relativity. Although the laws of mechanics had already been shown to be invariant, gravity remained yet to be included.: 19 In 1907, Einstein published a paper proposing his equivalence principle, the hypothesis that inertial mass and gravitational mass have a common cause. Using the principle, Einstein predicted the redshift and half of the lensing effect of gravity on light; the full prediction of gravitational lensing required development of general relativity.: 19 By 1915, Einstein refined these ideas into his general theory of relativity, which explained how matter affects spacetime, which in turn affects the motion of other matter. This formed the basis for black hole physics. Only a few months after Einstein published the field equations describing general relativity, astrophysicist Karl Schwarzschild set out to apply the idea to stars. He assumed spherical symmetry with no spin and found a solution to Einstein's equations.: 124 A few months after Schwarzschild, Johannes Droste, a student of Hendrik Lorentz, independently gave the same solution. At a certain radius from the center of the mass, the Schwarzschild solution became singular, meaning that some of the terms in the Einstein equations became infinite. The nature of this radius, which later became known as the Schwarzschild radius, was not understood at the time. Many physicists of the early 20th century were skeptical of the existence of black holes. In a 1926 popular science book, Arthur Eddington critiqued the idea of a star with mass compressed to its Schwarzschild radius as a flaw in the then-poorly-understood theory of general relativity.: 134 In 1939, Einstein himself used his theory of general relativity in an attempt to prove that black holes were impossible. His work relied on increasing pressure or increasing centrifugal force balancing the force of gravity so that the object would not collapse beyond its Schwarzschild radius. He missed the possibility that implosion would drive the system below this critical value.: 135 By the 1920s, astronomers had classified a number of white dwarf stars as too cool and dense to be explained by the gradual cooling of ordinary stars. In 1926, Ralph Fowler showed that quantum-mechanical degeneracy pressure was larger than thermal pressure at these densities.: 145 In 1931, Subrahmanyan Chandrasekhar calculated that a non-rotating body of electron-degenerate matter below a certain limiting mass is stable, and by 1934 he showed that this explained the catalog of white dwarf stars.: 151 When Chandrasekhar announced his results, Eddington pointed out that stars above this limit would radiate until they were sufficiently dense to prevent light from exiting, a conclusion he considered absurd. Eddington and, later, Lev Landau argued that some yet unknown mechanism would stop the collapse. In the 1930s, Fritz Zwicky and Walter Baade studied stellar novae, focusing on exceptionally bright ones they called supernovae. Zwicky promoted the idea that supernovae produced stars with the density of atomic nuclei—neutron stars—but this idea was largely ignored.: 171 In 1939, based on Chandrasekhar's reasoning, J. Robert Oppenheimer and George Volkoff predicted that neutron stars below a certain mass limit, later called the Tolman–Oppenheimer–Volkoff limit, would be stable due to neutron degeneracy pressure. Above that limit, they reasoned that either their model would not apply or that gravitational contraction would not stop.: 380 John Archibald Wheeler and two of his students resolved questions about the model behind the Tolman–Oppenheimer–Volkoff (TOV) limit. Harrison and Wheeler developed the equations of state relating density to pressure for cold matter all the way through electron degeneracy and neutron degeneracy. Masami Wakano and Wheeler then used the equations to compute the equilibrium curve for stars, relating mass to circumference. They found no additional features that would invalidate the TOV limit. This meant that the only thing that could prevent black holes from forming was a dynamic process ejecting sufficient mass from a star as it cooled.: 205 The modern concept of black holes was formulated by Robert Oppenheimer and his student Hartland Snyder in 1939.: 80 In the paper, Oppenheimer and Snyder solved Einstein's equations of general relativity for an idealized imploding star, in a model later called the Oppenheimer–Snyder model, then described the results from far outside the star. The implosion starts as one might expect: the star material rapidly collapses inward. However, as the density of the star increases, gravitational time dilation increases and the collapse, viewed from afar, seems to slow down further and further until the star reaches its Schwarzschild radius, where it appears frozen in time.: 217 In 1958, David Finkelstein identified the Schwarzschild surface as an event horizon, calling it "a perfect unidirectional membrane: causal influences can cross it in only one direction". In this sense, events that occur inside of the black hole cannot affect events that occur outside of the black hole. Finkelstein created a new reference frame to include the point of view of infalling observers.: 103 Finkelstein's new frame of reference allowed events at the surface of an imploding star to be related to events far away. By 1962 the two points of view were reconciled, convincing many skeptics that implosion into a black hole made physical sense.: 226 The era from the mid-1960s to the mid-1970s was the "golden age of black hole research", when general relativity and black holes became mainstream subjects of research.: 258 In this period, more general black hole solutions were found. In 1963, Roy Kerr found the exact solution for a rotating black hole. Two years later, Ezra Newman found the cylindrically symmetric solution for a black hole that is both rotating and electrically charged. In 1967, Werner Israel found that the Schwarzschild solution was the only possible solution for a nonspinning, uncharged black hole, meaning that a Schwarzschild black hole would be defined by its mass alone. Similar identities were later found for Reissner-Nordstrom and Kerr black holes, defined only by their mass and their charge or spin respectively. Together, these findings became known as the no-hair theorem, which states that a stationary black hole is completely described by the three parameters of the Kerr–Newman metric: mass, angular momentum, and electric charge. At first, it was suspected that the strange mathematical singularities found in each of the black hole solutions only appeared due to the assumption that a black hole would be perfectly spherically symmetric, and therefore the singularities would not appear in generic situations where black holes would not necessarily be symmetric. This view was held in particular by Vladimir Belinski, Isaak Khalatnikov, and Evgeny Lifshitz, who tried to prove that no singularities appear in generic solutions, although they would later reverse their positions. However, in 1965, Roger Penrose proved that general relativity without quantum mechanics requires that singularities appear in all black holes. Astronomical observations also made great strides during this era. In 1967, Antony Hewish and Jocelyn Bell Burnell discovered pulsars and by 1969, these were shown to be rapidly rotating neutron stars. Until that time, neutron stars, like black holes, were regarded as just theoretical curiosities, but the discovery of pulsars showed their physical relevance and spurred a further interest in all types of compact objects that might be formed by gravitational collapse. Based on observations in Greenwich and Toronto in the early 1970s, Cygnus X-1, a galactic X-ray source discovered in 1964, became the first astronomical object commonly accepted to be a black hole. Work by James Bardeen, Jacob Bekenstein, Carter, and Hawking in the early 1970s led to the formulation of black hole thermodynamics. These laws describe the behaviour of a black hole in close analogy to the laws of thermodynamics by relating mass to energy, area to entropy, and surface gravity to temperature. The analogy was completed: 442 when Hawking, in 1974, showed that quantum field theory implies that black holes should radiate like a black body with a temperature proportional to the surface gravity of the black hole, predicting the effect now known as Hawking radiation. While Cygnus X-1, a stellar-mass black hole, was generally accepted by the scientific community as a black hole by the end of 1973, it would be decades before a supermassive black hole would gain the same broad recognition. Although, as early as the 1960s, physicists such as Donald Lynden-Bell and Martin Rees had suggested that powerful quasars in the center of galaxies were powered by accreting supermassive black holes, little observational proof existed at the time. However, the Hubble Space Telescope, launched decades later, found that supermassive black holes were not only present in these active galactic nuclei, but that supermassive black holes in the center of galaxies were ubiquitous: Almost every galaxy had a supermassive black hole at its center, many of which were quiescent. In 1999, David Merritt proposed the M–sigma relation, which related the dispersion of the velocity of matter in the center bulge of a galaxy to the mass of the supermassive black hole at its core. Subsequent studies confirmed this correlation. Around the same time, based on telescope observations of the velocities of stars at the center of the Milky Way galaxy, independent work groups led by Andrea Ghez and Reinhard Genzel concluded that the compact radio source in the center of the galaxy, Sagittarius A*, was likely a supermassive black hole. On 11 February 2016, the LIGO Scientific Collaboration and Virgo Collaboration announced the first direct detection of gravitational waves, named GW150914, representing the first observation of a black hole merger. At the time of the merger, the black holes were approximately 1.4 billion light-years away from Earth and had masses of 30 and 35 solar masses.: 6 In 2017, Rainer Weiss, Kip Thorne, and Barry Barish, who had spearheaded the project, were awarded the Nobel Prize in Physics for their work. Since the initial discovery in 2015, hundreds more gravitational waves have been observed by LIGO and another interferometer, Virgo. On 10 April 2019, the first direct image of a black hole and its vicinity was published, following observations made by the Event Horizon Telescope (EHT) in 2017 of the supermassive black hole in Messier 87's galactic centre. In 2022, the Event Horizon Telescope collaboration released an image of the black hole in the center of the Milky Way galaxy, Sagittarius A*; The data had been collected in 2017. In 2020, the Nobel Prize in Physics was awarded for work on black holes. Andrea Ghez and Reinhard Genzel shared one-half for their discovery that Sagittarius A* is a supermassive black hole. Penrose received the other half for his work showing that the mathematics of general relativity requires the formation of black holes. Cosmologists lamented that Hawking's extensive theoretical work on black holes would not be honored since he died in 2018. In December 1967, a student reportedly suggested the phrase black hole at a lecture by John Wheeler; Wheeler adopted the term for its brevity and "advertising value", and Wheeler's stature in the field ensured it quickly caught on, leading some to credit Wheeler with coining the phrase. However, the term was used by others around that time. Science writer Marcia Bartusiak traces the term black hole to physicist Robert H. Dicke, who in the early 1960s reportedly compared the phenomenon to the Black Hole of Calcutta, notorious as a prison where people entered but never left alive. The term was used in print by Life and Science News magazines in 1963, and by science journalist Ann Ewing in her article "'Black Holes' in Space", dated 18 January 1964, which was a report on a meeting of the American Association for the Advancement of Science held in Cleveland, Ohio. Definition A black hole is generally defined as a region of spacetime from which no information-carrying signals or objects can escape. However, verifying an object as a black hole by this definition would require waiting for an infinite time and at an infinite distance from the black hole to verify that indeed, nothing has escaped, and thus cannot be used to identify a physical black hole. Broadly, physicists do not have a precisely-agreed-upon definition of a black hole. Among astrophysicists, a black hole is a compact object with a mass larger than four solar masses. A black hole may also be defined as a reservoir of information: 142 or a region where space is falling inwards faster than the speed of light. Properties The no-hair theorem postulates that, once it achieves a stable condition after formation, a black hole has only three independent physical properties: mass, electric charge, and angular momentum; the black hole is otherwise featureless. If the conjecture is true, any two black holes that share the same values for these properties, or parameters, are indistinguishable from one another. The degree to which the conjecture is true for real black holes is currently an unsolved problem. The simplest static black holes have mass but neither electric charge nor angular momentum. According to Birkhoff's theorem, these Schwarzschild black holes are the only vacuum solution that is spherically symmetric. Solutions describing more general black holes also exist. Non-rotating charged black holes are described by the Reissner–Nordström metric, while the Kerr metric describes a non-charged rotating black hole. The most general stationary black hole solution known is the Kerr–Newman metric, which describes a black hole with both charge and angular momentum. The simplest static black holes have mass but neither electric charge nor angular momentum. Contrary to the popular notion of a black hole "sucking in everything" in its surroundings, from far away, the external gravitational field of a black hole is identical to that of any other body of the same mass. While a black hole can theoretically have any positive mass, the charge and angular momentum are constrained by the mass. The total electric charge Q and the total angular momentum J are expected to satisfy the inequality Q 2 4 π ϵ 0 + c 2 J 2 G M 2 ≤ G M 2 {\displaystyle {\frac {Q^{2}}{4\pi \epsilon _{0}}}+{\frac {c^{2}J^{2}}{GM^{2}}}\leq GM^{2}} for a black hole of mass M. Black holes with the maximum possible charge or spin satisfying this inequality are called extremal black holes. Solutions of Einstein's equations that violate this inequality exist, but they do not possess an event horizon. These are so-called naked singularities that can be observed from the outside. Because these singularities make the universe inherently unpredictable, many physicists believe they could not exist. The weak cosmic censorship hypothesis, proposed by Sir Roger Penrose, rules out the formation of such singularities, when they are created through the gravitational collapse of realistic matter. However, this theory has not yet been proven, and some physicists believe that naked singularities could exist. It is also unknown whether black holes could even become extremal, forming naked singularities, since natural processes counteract increasing spin and charge when a black hole becomes near-extremal. The total mass of a black hole can be estimated by analyzing the motion of objects near the black hole, such as stars or gas. All black holes spin, often fast—One supermassive black hole, GRS 1915+105 has been estimated to spin at over 1,000 revolutions per second. The Milky Way's central black hole Sagittarius A* rotates at about 90% of the maximum rate. The spin rate can be inferred from measurements of atomic spectral lines in the X-ray range. As gas near the black hole plunges inward, high energy X-ray emission from electron-positron pairs illuminates the gas further out, appearing red-shifted due to relativistic effects. Depending on the spin of the black hole, this plunge happens at different radii from the hole, with different degrees of redshift. Astronomers can use the gap between the x-ray emission of the outer disk and the redshifted emission from plunging material to determine the spin of the black hole. A newer way to estimate spin is based on the temperature of gasses accreting onto the black hole. The method requires an independent measurement of the black hole mass and inclination angle of the accretion disk followed by computer modeling. Gravitational waves from coalescing binary black holes can also provide the spin of both progenitor black holes and the merged hole, but such events are rare. A spinning black hole has angular momentum. The supermassive black hole in the center of the Messier 87 (M87) galaxy appears to have an angular momentum very close to the maximum theoretical value. That uncharged limit is J ≤ G M 2 c , {\displaystyle J\leq {\frac {GM^{2}}{c}},} allowing definition of a dimensionless spin magnitude such that 0 ≤ c J G M 2 ≤ 1. {\displaystyle 0\leq {\frac {cJ}{GM^{2}}}\leq 1.} Most black holes are believed to have an approximately neutral charge. For example, Michal Zajaček, Arman Tursunov, Andreas Eckart, and Silke Britzen found the electric charge of Sagittarius A* to be at least ten orders of magnitude below the theoretical maximum. A charged black hole repels other like charges just like any other charged object. If a black hole were to become charged, particles with an opposite sign of charge would be pulled in by the extra electromagnetic force, while particles with the same sign of charge would be repelled, neutralizing the black hole. This effect may not be as strong if the black hole is also spinning. The presence of charge can reduce the diameter of the black hole by up to 38%. The charge Q for a nonspinning black hole is bounded by Q ≤ G M , {\displaystyle Q\leq {\sqrt {G}}M,} where G is the gravitational constant and M is the black hole's mass. Classification Black holes can have a wide range of masses. The minimum mass of a black hole formed by stellar gravitational collapse is governed by the maximum mass of a neutron star and is believed to be approximately two-to-four solar masses. However, theoretical primordial black holes, believed to have formed soon after the Big Bang, could be far smaller, with masses as little as 10−5 grams at formation. These very small black holes are sometimes called micro black holes. Black holes formed by stellar collapse are called stellar black holes. Estimates of their maximum mass at formation vary, but generally range from 10 to 100 solar masses, with higher estimates for black holes progenated by low-metallicity stars. The mass of a black hole formed via a supernova has a lower bound: If the progenitor star is too small, the collapse may be stopped by the degeneracy pressure of the star's constituents, allowing the condensation of matter into an exotic denser state. Degeneracy pressure occurs from the Pauli exclusion principle—Particles will resist being in the same place as each other. Smaller progenitor stars, with masses less than about 8 M☉, will be held together by the degeneracy pressure of electrons and will become a white dwarf. For more massive progenitor stars, electron degeneracy pressure is no longer strong enough to resist the force of gravity and the star will be held together by neutron degeneracy pressure, which can occur at much higher densities, forming a neutron star. If the star is still too massive, even neutron degeneracy pressure will not be able to resist the force of gravity and the star will collapse into a black hole.: 5.8 Stellar black holes can also gain mass via accretion of nearby matter, often from a companion object such as a star. Black holes that are larger than stellar black holes but smaller than supermassive black holes are called intermediate-mass black holes, with masses of approximately 102 to 105 solar masses. These black holes seem to be rarer than their stellar and supermassive counterparts, with relatively few candidates having been observed. Physicists have speculated that such black holes may form from collisions in globular and star clusters or at the center of low-mass galaxies. They may also form as the result of mergers of smaller black holes, with several LIGO observations finding merged black holes within the 110-350 solar mass range. The black holes with the largest masses are called supermassive black holes, with masses more than 106 times that of the Sun. These black holes are believed to exist at the centers of almost every large galaxy, including the Milky Way. Some scientists have proposed a subcategory of even larger black holes, called ultramassive black holes, with masses greater than 109-1010 solar masses. Theoretical models predict that the accretion disc that feeds black holes will be unstable once a black hole reaches 50-100 billion times the mass of the Sun, setting a rough upper limit to black hole mass. Structure While black holes are conceptually invisible sinks of all matter and light, in astronomical settings, their enormous gravity alters the motion of surrounding objects and pulls nearby gas inwards at near-light speed, making the area around black holes the brightest objects in the universe. Some black holes have relativistic jets—thin streams of plasma travelling away from the black hole at more than one-tenth of the speed of light. A small faction of the matter falling towards the black hole gets accelerated away along the hole rotation axis. These jets can extend as far as millions of parsecs from the black hole itself. Black holes of any mass can have jets. However, they are typically observed around spinning black holes with strongly-magnetized accretion disks. Relativistic jets were more common in the early universe, when galaxies and their corresponding supermassive black holes were rapidly gaining mass. All black holes with jets also have an accretion disk, but the jets are usually brighter than the disk. Quasars, typically found in other galaxies, are believed to be supermassive black holes with jets; microquasars are believed to be stellar-mass objects with jets, typically observed in the Milky Way. The mechanism of formation of jets is not yet known, but several options have been proposed. One method proposed to fuel these jets is the Blandford-Znajek process, which suggests that the dragging of magnetic field lines by a black hole's rotation could launch jets of matter into space. The Penrose process, which involves extraction of a black hole's rotational energy, has also been proposed as a potential mechanism of jet propulsion. Due to conservation of angular momentum, gas falling into the gravitational well created by a massive object will typically form a disk-like structure around the object.: 242 As the disk's angular momentum is transferred outward due to internal processes, its matter falls farther inward, converting its gravitational energy into heat and releasing a large flux of x-rays. The temperature of these disks can range from thousands to millions of Kelvin, and temperatures can differ throughout a single accretion disk. Accretion disks can also emit in other parts of the electromagnetic spectrum, depending on the disk's turbulence and magnetization and the black hole's mass and angular momentum. Accretion disks can be defined as geometrically thin or geometrically thick. Geometrically thin disks are mostly confined to the black hole's equatorial plane and have a well-defined edge at the innermost stable circular orbit (ISCO), while geometrically thick disks are supported by internal pressure and temperature and can extend inside the ISCO. Disks with high rates of electron scattering and absorption, appearing bright and opaque, are called optically thick; optically thin disks are more translucent and produce fainter images when viewed from afar. Accretion disks of black holes accreting beyond the Eddington limit are often referred to as polish donuts due to their thick, toroidal shape that resembles that of a donut. Quasar accretion disks are expected to usually appear blue in color. The disk for a stellar black hole, on the other hand, would likely look orange, yellow, or red, with its inner regions being the brightest. Theoretical research suggests that the hotter a disk is, the bluer it should be, although this is not always supported by observations of real astronomical objects. Accretion disk colors may also be altered by the Doppler effect, with the part of the disk travelling towards an observer appearing bluer and brighter and the part of the disk travelling away from the observer appearing redder and dimmer. In Newtonian gravity, test particles can stably orbit at arbitrary distances from a central object. In general relativity, however, there exists a smallest possible radius for which a massive particle can orbit stably. Any infinitesimal inward perturbations to this orbit will lead to the particle spiraling into the black hole, and any outward perturbations will, depending on the energy, cause the particle to spiral in, move to a stable orbit further from the black hole, or escape to infinity. This orbit is called the innermost stable circular orbit, or ISCO. The location of the ISCO depends on the spin of the black hole and the spin of the particle itself. In the case of a Schwarzschild black hole (spin zero) and a particle without spin, the location of the ISCO is: r I S C O = 3 r s = 6 G M c 2 , {\displaystyle r_{\rm {ISCO}}=3\,r_{\text{s}}={\frac {6\,GM}{c^{2}}},} where r I S C O {\displaystyle r_{\rm {_{ISCO}}}} is the radius of the ISCO, r s {\displaystyle r_{\text{s}}} is the Schwarzschild radius of the black hole, G {\displaystyle G} is the gravitational constant, and c {\displaystyle c} is the speed of light. The radius of this orbit changes slightly based on particle spin. For charged black holes, the ISCO moves inwards. For spinning black holes, the ISCO is moved inwards for particles orbiting in the same direction that the black hole is spinning (prograde) and outwards for particles orbiting in the opposite direction (retrograde). For example, the ISCO for a particle orbiting retrograde can be as far out as about 9 r s {\displaystyle 9r_{\text{s}}} , while the ISCO for a particle orbiting prograde can be as close as at the event horizon itself. The photon sphere is a spherical boundary for which photons moving on tangents to that sphere are bent completely around the black hole, possibly orbiting multiple times. Light rays with impact parameters less than the radius of the photon sphere enter the black hole. For Schwarzschild black holes, the photon sphere has a radius 1.5 times the Schwarzschild radius; the radius for non-Schwarzschild black holes is at least 1.5 times the radius of the event horizon. When viewed from a great distance, the photon sphere creates an observable black hole shadow. Since no light emerges from within the black hole, this shadow is the limit for possible observations.: 152 The shadow of colliding black holes should have characteristic warped shapes, allowing scientists to detect black holes that are about to merge. While light can still escape from the photon sphere, any light that crosses the photon sphere on an inbound trajectory will be captured by the black hole. Therefore, any light that reaches an outside observer from the photon sphere must have been emitted by objects between the photon sphere and the event horizon. Light emitted towards the photon sphere may also curve around the black hole and return to the emitter. For a rotating, uncharged black hole, the radius of the photon sphere depends on the spin parameter and whether the photon is orbiting prograde or retrograde. For a photon orbiting prograde, the photon sphere will be 1-3 Schwarzschild radii from the center of the black hole, while for a photon orbiting retrograde, the photon sphere will be between 3-5 Schwarzschild radii from the center of the black hole. The exact location of the photon sphere depends on the magnitude of the black hole's rotation. For a charged, nonrotating black hole, there will only be one photon sphere, and the radius of the photon sphere will decrease for increasing black hole charge. For non-extremal, charged, rotating black holes, there will always be two photon spheres, with the exact radii depending on the parameters of the black hole. Near a rotating black hole, spacetime rotates similar to a vortex. The rotating spacetime will drag any matter and light into rotation around the spinning black hole. This effect of general relativity, called frame dragging, gets stronger closer to the spinning mass. The region of spacetime in which it is impossible to stay still is called the ergosphere. The ergosphere of a black hole is a volume bounded by the black hole's event horizon and the ergosurface, which coincides with the event horizon at the poles but bulges out from it around the equator. Matter and radiation can escape from the ergosphere. Through the Penrose process, objects can emerge from the ergosphere with more energy than they entered with. The extra energy is taken from the rotational energy of the black hole, slowing down the rotation of the black hole.: 268 A variation of the Penrose process in the presence of strong magnetic fields, the Blandford–Znajek process, is considered a likely mechanism for the enormous luminosity and relativistic jets of quasars and other active galactic nuclei. The observable region of spacetime around a black hole closest to its event horizon is called the plunging region. In this area it is no longer possible for free falling matter to follow circular orbits or stop a final descent into the black hole. Instead, it will rapidly plunge toward the black hole at close to the speed of light, growing increasingly hot and producing a characteristic, detectable thermal emission. However, light and radiation emitted from this region can still escape from the black hole's gravitational pull. For a nonspinning, uncharged black hole, the radius of the event horizon, or Schwarzschild radius, is proportional to the mass, M, through r s = 2 G M c 2 ≈ 2.95 M M ⊙ k m , {\displaystyle r_{\mathrm {s} }={\frac {2GM}{c^{2}}}\approx 2.95\,{\frac {M}{M_{\odot }}}~\mathrm {km,} } where rs is the Schwarzschild radius and M☉ is the mass of the Sun.: 124 For a black hole with nonzero spin or electric charge, the radius is smaller,[Note 1] until an extremal black hole could have an event horizon close to r + = G M c 2 , {\displaystyle r_{\mathrm {+} }={\frac {GM}{c^{2}}},} half the radius of a nonspinning, uncharged black hole of the same mass. Since the volume within the Schwarzschild radius increase with the cube of the radius, average density of a black hole inside its Schwarzschild radius is inversely proportional to the square of its mass: supermassive black holes are much less dense than stellar black holes. The average density of a 108 M☉ black hole is comparable to that of water. The defining feature of a black hole is the existence of an event horizon, a boundary in spacetime through which matter and light can pass only inward towards the center of the black hole. Nothing, not even light, can escape from inside the event horizon. The event horizon is referred to as such because if an event occurs within the boundary, information from that event cannot reach or affect an outside observer, making it impossible to determine whether such an event occurred.: 179 For non-rotating black holes, the geometry of the event horizon is precisely spherical, while for rotating black holes, the event horizon is oblate. To a distant observer, a clock near a black hole would appear to tick more slowly than one further from the black hole.: 217 This effect, known as gravitational time dilation, would also cause an object falling into a black hole to appear to slow as it approached the event horizon, never quite reaching the horizon from the perspective of an outside observer.: 218 All processes on this object would appear to slow down, and any light emitted by the object to appear redder and dimmer, an effect known as gravitational redshift. An object falling from half of a Schwarzschild radius above the event horizon would fade away until it could no longer be seen, disappearing from view within one hundredth of a second. It would also appear to flatten onto the black hole, joining all other material that had ever fallen into the hole. On the other hand, an observer falling into a black hole would not notice any of these effects as they cross the event horizon. Their own clocks appear to them to tick normally, and they cross the event horizon after a finite time without noting any singular behaviour. In general relativity, it is impossible to determine the location of the event horizon from local observations, due to Einstein's equivalence principle.: 222 Black holes that are rotating and/or charged have an inner horizon, often called the Cauchy horizon, inside of the black hole. The inner horizon is divided up into two segments: an ingoing section and an outgoing section. At the ingoing section of the Cauchy horizon, radiation and matter that fall into the black hole would build up at the horizon, causing the curvature of spacetime to go to infinity. This would cause an observer falling in to experience tidal forces. This phenomenon is often called mass inflation, since it is associated with a parameter dictating the black hole's internal mass growing exponentially, and the buildup of tidal forces is called the mass-inflation singularity or Cauchy horizon singularity. Some physicists have argued that in realistic black holes, accretion and Hawking radiation would stop mass inflation from occurring. At the outgoing section of the inner horizon, infalling radiation would backscatter off of the black hole's spacetime curvature and travel outward, building up at the outgoing Cauchy horizon. This would cause an infalling observer to experience a gravitational shock wave and tidal forces as the spacetime curvature at the horizon grew to infinity. This buildup of tidal forces is called the shock singularity. Both of these singularities are weak, meaning that an object crossing them would only be deformed a finite amount by tidal forces, even though the spacetime curvature would still be infinite at the singularity. This is as opposed to a strong singularity, where an object hitting the singularity would be stretched and squeezed by an infinite amount. They are also null singularities, meaning that a photon could travel parallel to the them without ever being intercepted. Ignoring quantum effects, every black hole has a singularity inside, points where the curvature of spacetime becomes infinite, and geodesics terminate within a finite proper time.: 205 For a non-rotating black hole, this region takes the shape of a single point; for a rotating black hole it is smeared out to form a ring singularity that lies in the plane of rotation.: 264 In both cases, the singular region has zero volume. All of the mass of the black hole ends up in the singularity.: 252 Since the singularity has nonzero mass in an infinitely small space, it can be thought of as having infinite density. Observers falling into a Schwarzschild black hole (i.e., non-rotating and not charged) cannot avoid being carried into the singularity once they cross the event horizon. As they fall further into the black hole, they will be torn apart by the growing tidal forces in a process sometimes referred to as spaghettification or the noodle effect. Eventually, they will reach the singularity and be crushed into an infinitely small point.: 182 However any perturbations, such as those caused by matter or radiation falling in, would cause space to oscillate chaotically near the singularity. Any matter falling in would experience intense tidal forces rapidly changing in direction, all while being compressed into an increasingly small volume. Alternative forms of general relativity, including addition of some quatum effects, can lead to regular, or nonsingular, black holes without singularities. For example, the fuzzball model, based on string theory, states that black holes are actually made up of quantum microstates and need not have a singularity or an event horizon. The theory of loop quantum gravity proposes that the curvature and density at the center of a black hole is large, but not infinite. Formation Black holes are formed by gravitational collapse of massive stars, either by direct collapse or during a supernova explosion in a process called fallback. Black holes can result from the merger of two neutron stars or a neutron star and a black hole. Other more speculative mechanisms include primordial black holes created from density fluctuations in the early universe, the collapse of dark stars, a hypothetical object powered by annihilation of dark matter, or from hypothetical self-interacting dark matter. Gravitational collapse occurs when an object's internal pressure is insufficient to resist the object's own gravity. At the end of a star's life, it will run out of hydrogen to fuse, and will start fusing more and more massive elements, until it gets to iron. Since the fusion of elements heavier than iron would require more energy than it would release, nuclear fusion ceases. If the iron core of the star is too massive, the star will no longer be able to support itself and will undergo gravitational collapse. While most of the energy released during gravitational collapse is emitted very quickly, an outside observer does not actually see the end of this process. Even though the collapse takes a finite amount of time from the reference frame of infalling matter, a distant observer would see the infalling material slow and halt just above the event horizon, due to gravitational time dilation. Light from the collapsing material takes longer and longer to reach the observer, with the delay growing to infinity as the emitting material reaches the event horizon. Thus the external observer never sees the formation of the event horizon; instead, the collapsing material seems to become dimmer and increasingly red-shifted, eventually fading away. Observations of quasars at redshift z ∼ 7 {\displaystyle z\sim 7} , less than a billion years after the Big Bang, has led to investigations of other ways to form black holes. The accretion process to build supermassive black holes has a limiting rate of mass accumulation and a billion years is not enough time to reach quasar status. One suggestion is direct collapse of nearly pure hydrogen gas (low metalicity) clouds characteristic of the young universe, forming a supermassive star which collapses into a black hole. It has been suggested that seed black holes with typical masses of ~105 M☉ could have formed in this way which then could grow to ~109 M☉. However, the very large amount of gas required for direct collapse is not typically stable to fragmentation to form multiple stars. Thus another approach suggests massive star formation followed by collisions that seed massive black holes which ultimately merge to create a quasar.: 85 A neutron star in a common envelope with a regular star can accrete sufficient material to collapse to a black hole or two neutron stars can merge. These avenues for the formation of black holes are considered relatively rare. In the current epoch of the universe, conditions needed to form black holes are rare and are mostly only found in stars. However, in the early universe, conditions may have allowed for black hole formations via other means. Fluctuations of spacetime soon after the Big Bang may have formed areas that were denser then their surroundings. Initially, these regions would not have been compact enough to form a black hole, but eventually, the curvature of spacetime in the regions become large enough to cause them to collapse into a black hole. Different models for the early universe vary widely in their predictions of the scale of these fluctuations. Various models predict the creation of primordial black holes ranging from a Planck mass (~2.2×10−8 kg) to hundreds of thousands of solar masses. Primordial black holes with masses less than 1015 g would have evaporated by now due to Hawking radiation. Despite the early universe being extremely dense, it did not re-collapse into a black hole during the Big Bang, since the universe was expanding rapidly and did not have the gravitational differential necessary for black hole formation. Models for the gravitational collapse of objects of relatively constant size, such as stars, do not necessarily apply in the same way to rapidly expanding space such as the Big Bang. In principle, black holes could be formed in high-energy particle collisions that achieve sufficient density, although no such events have been detected. These hypothetical micro black holes, which could form from the collision of cosmic rays and Earth's atmosphere or in particle accelerators like the Large Hadron Collider, would not be able to aggregate additional mass. Instead, they would evaporate in about 10−25 seconds, posing no threat to the Earth. Evolution Black holes can also merge with other objects such as stars or even other black holes. This is thought to have been important, especially in the early growth of supermassive black holes, which could have formed from the aggregation of many smaller objects. The process has also been proposed as the origin of some intermediate-mass black holes. Mergers of supermassive black holes may take a long time: As a binary of supermassive black holes approach each other, most nearby stars are ejected, leaving little for the remaining black holes to gravitationally interact with that would allow them to get closer to each other. This phenomenon has been called the final parsec problem, as the distance at which this happens is usually around one parsec. When a black hole accretes matter, the gas in the inner accretion disk orbits at very high speeds because of its proximity to the black hole. The resulting friction heats the inner disk to temperatures at which it emits vast amounts of electromagnetic radiation (mainly X-rays) detectable by telescopes. By the time the matter of the disk reaches the ISCO, between 5.7% and 42% of its mass will have been converted to energy, depending on the black hole's spin. About 90% of this energy is released within about 20 black hole radii. In many cases, accretion disks are accompanied by relativistic jets that are emitted along the black hole's poles, which carry away much of the energy. The mechanism for the creation of these jets is currently not well understood, in part due to insufficient data. Many of the universe's most energetic phenomena have been attributed to the accretion of matter on black holes. Active galactic nuclei and quasars are believed to be the accretion disks of supermassive black holes. X-ray binaries are generally accepted to be binary systems in which one of the two objects is a compact object accreting matter from its companion. Ultraluminous X-ray sources may be the accretion disks of intermediate-mass black holes. At a certain rate of accretion, the outward radiation pressure will become as strong as the inward gravitational force, and the black hole should unable to accrete any faster. This limit is called the Eddington limit. However, many black holes accrete beyond this rate due to their non-spherical geometry or instabilities in the accretion disk. Accretion beyond the limit is called Super-Eddington accretion and may have been commonplace in the early universe. Stars have been observed to get torn apart by tidal forces in the immediate vicinity of supermassive black holes in galaxy nuclei, in what is known as a tidal disruption event (TDE). Some of the material from the disrupted star forms an accretion disk around the black hole, which emits observable electromagnetic radiation. The correlation between the masses of supermassive black holes in the centres of galaxies with the velocity dispersion and mass of stars in their host bulges suggests that the formation of galaxies and the formation of their central black holes are related. Black hole winds from rapid accretion, particularly when the galaxy itself is still accreting matter, can compress gas nearby, accelerating star formation. However, if the winds become too strong, the black hole may blow nearly all of the gas out of the galaxy, quenching star formation. Black hole jets may also energize nearby cavities of plasma and eject low-entropy gas from out of the galactic core, causing gas in galactic centers to be hotter than expected. If Hawking's theory of black hole radiation is correct, then black holes are expected to shrink and evaporate over time as they lose mass by the emission of photons and other particles. The temperature of this thermal spectrum (Hawking temperature) is proportional to the surface gravity of the black hole, which is inversely proportional to the mass. Hence, large black holes emit less radiation than small black holes.: Ch. 9.6 A stellar black hole of 1 M☉ has a Hawking temperature of 62 nanokelvins. This is far less than the 2.7 K temperature of the cosmic microwave background radiation. Stellar-mass or larger black holes receive more mass from the cosmic microwave background than they emit through Hawking radiation and thus will grow instead of shrinking. To have a Hawking temperature larger than 2.7 K (and be able to evaporate), a black hole would need a mass less than the Moon. Such a black hole would have a diameter of less than a tenth of a millimetre. The Hawking radiation for an astrophysical black hole is predicted to be very weak and would thus be exceedingly difficult to detect from Earth. A possible exception is the burst of gamma rays emitted in the last stage of the evaporation of primordial black holes. Searches for such flashes have proven unsuccessful and provide stringent limits on the possibility of existence of low mass primordial black holes, with modern research predicting that primordial black holes must make up less than a fraction of 10−7 of the universe's total mass. NASA's Fermi Gamma-ray Space Telescope, launched in 2008, has searched for these flashes, but has not yet found any. The properties of a black hole are constrained and interrelated by the theories that predict these properties. When based on general relativity, these relationships are called the laws of black hole mechanics. For a black hole that is not still forming or accreting matter, the zeroth law of black hole mechanics states the black hole's surface gravity is constant across the event horizon. The first law relates changes in the black hole's surface area, angular momentum, and charge to changes in its energy. The second law says the surface area of a black hole never decreases on its own. Finally, the third law says that the surface gravity of a black hole is never zero. These laws are mathematical analogs of the laws of thermodynamics. They are not equivalent, however, because, according to general relativity without quantum mechanics, a black hole can never emit radiation, and thus its temperature must always be zero.: 11 Quantum mechanics predicts that a black hole will continuously emit thermal Hawking radiation, and therefore must always have a nonzero temperature. It also predicts that all black holes have entropy which scales with their surface area. When quantum mechanics is accounted for, the laws of black hole mechanics become equivalent to the classical laws of thermodynamics. However, these conclusions are derived without a complete theory of quantum gravity, although many potential theories do predict black holes having entropy and temperature. Thus, the true quantum nature of black hole thermodynamics continues to be debated.: 29 Observational evidence Millions of black holes with around 30 solar masses derived from stellar collapse are expected to exist in the Milky Way. Even a dwarf galaxy like Draco should have hundreds. Only a few of these have been detected. By nature, black holes do not themselves emit any electromagnetic radiation other than the hypothetical Hawking radiation, so astrophysicists searching for black holes must generally rely on indirect observations. The defining characteristic of a black hole is its event horizon. The horizon itself cannot be imaged, so all other possible explanations for these indirect observations must be considered and eliminated before concluding that a black hole has been observed.: 11 The Event Horizon Telescope (EHT) is a global system of radio telescopes capable of directly observing a black hole shadow. The angular resolution of a telescope is based on its aperture and the wavelengths it is observing. Because the angular diameters of Sagittarius A* and Messier 87* in the sky are very small, a single telescope would need to be about the size of the Earth to clearly distinguish their horizons using radio wavelengths. By combining data from several different radio telescopes around the world, the Event Horizon Telescope creates an effective aperture the diameter size of the Earth. The EHT team used imaging algorithms to compute the most probable image from the data in its observations of Sagittarius A* and M87*. Gravitational-wave interferometry can be used to detect merging black holes and other compact objects. In this method, a laser beam is split down two long arms of a tunnel. The laser beams reflect off of mirrors in the tunnels and converge at the intersection of the arms, cancelling each other out. However, when a gravitational wave passes, it warps spacetime, changing the lengths of the arms themselves. Since each laser beam is now travelling a slightly different distance, they do not cancel out and produce a recognizable signal. Analysis of the signal can give scientists information about what caused the gravitational waves. Since gravitational waves are very weak, gravitational-wave observatories such as LIGO must have arms several kilometers long and carefully control for noise from Earth to be able to detect these gravitational waves. Since the first measurements in 2016, multiple gravitational waves from black holes have been detected and analyzed. The proper motions of stars near the centre of the Milky Way provide strong observational evidence that these stars are orbiting a supermassive black hole. Since 1995, astronomers have tracked the motions of 90 stars orbiting an invisible object coincident with the radio source Sagittarius A*. In 1998, by fitting the motions of the stars to Keplerian orbits, the astronomers were able to infer that Sagittarius A* must be a 2.6×106 M☉ object must be contained within a radius of 0.02 light-years. Since then, one of the stars—called S2—has completed a full orbit. From the orbital data, astronomers were able to refine the calculations of the mass of Sagittarius A* to 4.3×106 M☉, with a radius of less than 0.002 light-years. This upper limit radius is larger than the Schwarzschild radius for the estimated mass, so the combination does not prove Sagittarius A* is a black hole. Nevertheless, these observations strongly suggest that the central object is a supermassive black hole as there are no other plausible scenarios for confining so much invisible mass into such a small volume. Additionally, there is some observational evidence that this object might possess an event horizon, a feature unique to black holes. The Event Horizon Telescope image of Sagittarius A*, released in 2022, provided further confirmation that it is indeed a black hole. X-ray binaries are binary systems that emit a majority of their radiation in the X-ray part of the electromagnetic spectrum. These X-ray emissions result when a compact object accretes matter from an ordinary star. The presence of an ordinary star in such a system provides an opportunity for studying the central object and to determine if it might be a black hole. By measuring the orbital period of the binary, the distance to the binary from Earth, and the mass of the companion star, scientists can estimate the mass of the compact object. The Tolman-Oppenheimer-Volkoff limit (TOV limit) dictates the largest mass a nonrotating neutron star can be, and is estimated to be about two solar masses. While a rotating neutron star can be slightly more massive, if the compact object is much more massive than the TOV limit, it cannot be a neutron star and is generally expected to be a black hole. The first strong candidate for a black hole, Cygnus X-1, was discovered in this way by Charles Thomas Bolton, Louise Webster, and Paul Murdin in 1972. Observations of rotation broadening of the optical star reported in 1986 lead to a compact object mass estimate of 16 solar masses, with 7 solar masses as the lower bound. In 2011, this estimate was updated to 14.1±1.0 M☉ for the black hole and 19.2±1.9 M☉ for the optical stellar companion. X-ray binaries can be categorized as either low-mass or high-mass; This classification is based on the mass of the companion star, not the compact object itself. In a class of X-ray binaries called soft X-ray transients, the companion star is of relatively low mass, allowing for more accurate estimates of the black hole mass. These systems actively emit X-rays for only several months once every 10–50 years. During the period of low X-ray emission, called quiescence, the accretion disk is extremely faint, allowing detailed observation of the companion star. Numerous black hole candidates have been measured by this method. Black holes are also sometimes found in binaries with other compact objects, such as white dwarfs, neutron stars, and other black holes. The centre of nearly every galaxy contains a supermassive black hole. The close observational correlation between the mass of this hole and the velocity dispersion of the host galaxy's bulge, known as the M–sigma relation, strongly suggests a connection between the formation of the black hole and that of the galaxy itself. Astronomers use the term active galaxy to describe galaxies with unusual characteristics, such as unusual spectral line emission and very strong radio emission. Theoretical and observational studies have shown that the high levels of activity in the centers of these galaxies, regions called active galactic nuclei (AGN), may be explained by accretion onto supermassive black holes. These AGN consist of a central black hole that may be millions or billions of times more massive than the Sun, a disk of interstellar gas and dust called an accretion disk, and two jets perpendicular to the accretion disk. Although supermassive black holes are expected to be found in most AGN, only some galaxies' nuclei have been more carefully studied in attempts to both identify and measure the actual masses of the central supermassive black hole candidates. Some of the most notable galaxies with supermassive black hole candidates include the Andromeda Galaxy, Messier 32, Messier 87, the Sombrero Galaxy, and the Milky Way itself. Another way black holes can be detected is through observation of effects caused by their strong gravitational field. One such effect is gravitational lensing: The deformation of spacetime around a massive object causes light rays to be deflected, making objects behind them appear distorted. When the lensing object is a black hole, this effect can be strong enough to create multiple images of a star or other luminous source. However, the distance between the lensed images may be too small for contemporary telescopes to resolve—this phenomenon is called microlensing. Instead of seeing two images of a lensed star, astronomers see the star brighten slightly as the black hole moves towards the line of sight between the star and Earth and then return to its normal luminosity as the black hole moves away. The turn of the millennium saw the first 3 candidate detections of black holes in this way, and in January 2022, astronomers reported the first confirmed detection of a microlensing event from an isolated black hole. This was also the first determination of an isolated black hole mass, 7.1±1.3 M☉. Alternatives While there is a strong case for supermassive black holes, the model for stellar-mass black holes assumes of an upper limit for the mass of a neutron star: objects observed to have more mass are assumed to be black holes. However, the properties of extremely dense matter are poorly understood. New exotic phases of matter could allow other kinds of massive objects. Quark stars would be made up of quark matter and supported by quark degeneracy pressure, a form of degeneracy pressure even stronger than neutron degeneracy pressure. This would halt gravitational collapse at a higher mass than for a neutron star. Even stronger stars called electroweak stars would convert quarks in their cores into leptons, providing additional pressure to stop the star from collapsing. If, as some extensions of the Standard Model posit, quarks and leptons are made up of the even-smaller fundamental particles called preons, a very compact star could be supported by preon degeneracy pressure. While none of these hypothetical models can explain all of the observations of stellar black hole candidates, a Q star is the only alternative which could significantly exceed the mass limit for neutron stars and thus provide an alternative for supermassive black holes.: 12 A few theoretical objects have been conjectured to match observations of astronomical black hole candidates identically or near-identically, but which function via a different mechanism. A dark energy star would convert infalling matter into vacuum energy; This vacuum energy would be much larger than the vacuum energy of outside space, exerting outwards pressure and preventing a singularity from forming. A black star would be gravitationally collapsing slowly enough that quantum effects would keep it just on the cusp of fully collapsing into a black hole. A gravastar would consist of a very thin shell and a dark-energy interior providing outward pressure to stop the collapse into a black hole or formation of a singularity; It could even have another gravastar inside, called a 'nestar'. Open questions According to the no-hair theorem, a black hole is defined by only three parameters: its mass, charge, and angular momentum. This seems to mean that all other information about the matter that went into forming the black hole is lost, as there is no way to determine anything about the black hole from outside other than those three parameters. When black holes were thought to persist forever, this information loss was not problematic, as the information can be thought of as existing inside the black hole. However, black holes slowly evaporate by emitting Hawking radiation. This radiation does not appear to carry any additional information about the matter that formed the black hole, meaning that this information is seemingly gone forever. This is called the black hole information paradox. Theoretical studies analyzing the paradox have led to both further paradoxes and new ideas about the intersection of quantum mechanics and general relativity. While there is no consensus on the resolution of the paradox, work on the problem is expected to be important for a theory of quantum gravity.: 126 Observations of faraway galaxies have found that ultraluminous quasars, powered by supermassive black holes, existed in the early universe as far as redshift z ≥ 7 {\displaystyle z\geq 7} . These black holes have been assumed to be the products of the gravitational collapse of large population III stars. However, these stellar remnants were not massive enough to produce the quasars observed at early times without accreting beyond the Eddington limit, the theoretical maximum rate of black hole accretion. Physicists have suggested a variety of different mechanisms by which these supermassive black holes may have formed. It has been proposed that smaller black holes may have also undergone mergers to produce the observed supermassive black holes. It is also possible that they were seeded by direct-collapse black holes, in which a large cloud of hot gas avoids fragmentation that would lead to multiple stars, due to low angular momentum or heating from a nearby galaxy. Given the right circumstances, a single supermassive star forms and collapses directly into a black hole without undergoing typical stellar evolution. Additionally, these supermassive black holes in the early universe may be high-mass primordial black holes, which could have accreted further matter in the centers of galaxies. Finally, certain mechanisms allow black holes to grow faster than the theoretical Eddington limit, such as dense gas in the accretion disk limiting outward radiation pressure that prevents the black hole from accreting. However, the formation of bipolar jets prevent super-Eddington rates. In fiction Black holes have been portrayed in science fiction in a variety of ways. Even before the advent of the term itself, objects with characteristics of black holes appeared in stories such as the 1928 novel The Skylark of Space with its "black Sun" and the "hole in space" in the 1935 short story Starship Invincible. As black holes grew to public recognition in the 1960s and 1970s, they began to be featured in films as well as novels, such as Disney's The Black Hole. Black holes have also been used in works of the 21st century, such as Christopher Nolan's science fiction epic Interstellar. Authors and screenwriters have exploited the relativistic effects of black holes, particularly gravitational time dilation. For example, Interstellar features a black hole planet with a time dilation factor of over 60,000:1, while the 1977 novel Gateway depicts a spaceship approaching but never crossing the event horizon of a black hole from the perspective of an outside observer due to time dilation effects. Black holes have also been appropriated as wormholes or other methods of faster-than-light travel, such as in the 1974 novel The Forever War, where a network of black holes is used for interstellar travel. Additionally, black holes can feature as hazards to spacefarers and planets: A black hole threatens a deep-space outpost in 1978 short story The Black Hole Passes, and a binary black hole dangerously alters the orbit of a planet in the 2018 Netflix reboot of Lost in Space. Notes References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/List_of_rivers_by_length] | [TOKENS: 920] |
Contents List of river systems by length This is a list of the longest rivers on Earth. It includes river systems over 1,000 kilometres (620 mi) in length. Definition of length There are many factors, such as the identification of the source, the identification or the definition of the mouth, and the scale of measurement of the river length between source and mouth, that determine the precise meaning of "river length". As a result, the length measurements of many rivers are only approximations (see also coastline paradox). In particular, there seems to exist disagreement as to whether the Nile or the Amazon is the world's longest river. The Nile has traditionally been considered longer, but in 2007 and 2008 some scientists claimed that the Amazon is longer by measuring the river plus the adjacent Pará estuary and the longest connecting tidal canal. A peer-reviewed article published 2009 in the International Journal of Digital Earth concludes that the Nile is longer. Even when detailed maps are available, the length measurement is not always clear. A river may have multiple channels, or anabranches. The length may depend on whether the center or the edge of the river is measured. It may not be clear how to measure the length through a lake or reservoir. Seasonal and annual changes may alter both rivers and lakes. Other factors that can change the length of a river include cycles of erosion and flooding, dams, levees, and channelization. In addition, the length of meanders can change significantly over time due to natural or artificial cutoffs, when a new channel cuts across a narrow strip of land, bypassing a large river bend. For example, due to 18 cutoffs created between 1766 and 1885, the length of the Mississippi River from Cairo, Illinois, to New Orleans, Louisiana, was reduced by 351 kilometres (218 miles). These points make it difficult, if not impossible, to get an accurate measurement of the length of a river. The varying accuracy and precision also makes it difficult to make length comparisons between different rivers without a degree of uncertainty. There is no strictly agreed upon standard for dealing with the nuances of measuring rivers and as such the true length of a river is not necessarily a single, discrete, correct number, nor is it static. List of river systems longer than 1,000 km For most rivers, different sources provide conflicting information on the length of a river system. The information in different sources is between parentheses. (Heilong Jiang) Missouri River systems that may have existed in the past The Amazon basin formerly drained westwards into the Pacific Ocean, until the Andes rose and reversed the drainage. The Congo basin is completely surrounded by high land, except for its long narrow exit valley past Kinshasa, including waterfalls around Manyanga. That gives the impression that most of the Congo basin was formerly on a much higher land level and that the Congo River was rejuvenated by much of its lower course being removed, likeliest when Africa split from South America when Gondwanaland broke up due to continental drift, and before that, the Congo would likely have flowed into the Amazon, producing a river around 6000 miles or 10,000 km long. This river would have been about 10,000 km (6,200 mi) long, in the last ice age. Its longest headwater was the Selenga river of Mongolia: it drained through ice-dammed lakes and the Aral Sea and the Caspian Sea to the Black Sea. During the last glacial maximum, much of what is now the southern part of the North Sea was land, known to archaeologists as Doggerland. At this time, the Thames, the Meuse, the Scheldt, and the Rhine probably joined before flowing into the sea, in a system known by palaeogeographers as the Loubourg or Lobourg River System. There is some debate as to whether this river would have flowed southwest into what is now the English Channel, or flowed north, emerging into the North Sea close to modern Yorkshire. If the latter hypothesis is true, the Rhine would have attained a length of close to 1,650 kilometres (1,030 mi). The former hypothesis would have produced a shorter river, some 1,400 kilometres (870 mi) in length. Current scientific research favours the former opinion, with the Thames and Rhine meeting in a large lake, the outflow of which was close to the present-day Straits of Dover. See also Notes and references External links |
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[SOURCE: https://en.wikipedia.org/wiki/Prairie] | [TOKENS: 5241] |
Contents Prairie Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the dominant vegetation type. Temperate grassland regions include the Pampas of Argentina, Brazil, and Uruguay, and the steppe of Romania, Ukraine, Russia, and Kazakhstan. Lands typically referred to as "prairie" (a French loan word) tend to be in North America. The term encompasses the lower and mid-latitude of the area referred to as the Interior Plains of Canada, the United States, and Mexico. It includes all of the Great Plains as well as the wetter, hillier land to the east. From west to east, generally the drier expanse of shortgrass prairie gives way to mixed grass prairie and ultimately the richer and wetter soils of the tallgrass prairie. In the U.S., the area is constituted by most or all of the states, from north to south, of North Dakota, South Dakota, Nebraska, Kansas, and Oklahoma, and sizable parts of the states of Montana, Wyoming, Colorado, New Mexico, Texas in the west, and to the east, Minnesota, Wisconsin, Iowa, Missouri, Illinois, and Indiana. The Palouse of Washington and the Central Valley of California are also prairies. The Canadian Prairies occupy vast areas of Manitoba, Saskatchewan, and Alberta. Prairies may contain various lush flora and fauna, often contain rich soil maintained by biodiversity, with a temperate climate and a varied view. Etymology According to Theodore Roosevelt: We have taken into our language the word prairie, because when our backwoodsmen first reached the land [in the Midwest] and saw the great natural meadows of long grass—sights unknown to the gloomy forests wherein they had always dwelt—they knew not what to call them, and borrowed the term already in use among the French inhabitants. Prairie (pronounced [pʁɛʁi]) is the French word for "meadow", formed ultimately from the Latin root word pratum (which has the same meaning). Formation The formation of the Canadian Prairies started with the uplift of the Rocky Mountains near Alberta. The mountains created a rain shadow which resulted in lower precipitation rates downwind. The parent material of most prairie soil was distributed during the last glacial advance that began about 110,000 years ago. The glaciers expanding southward scraped the landscape, picking up geologic material and leveling the terrain. As the glaciers retreated about 10,000 years ago, they deposited this material in the form of till. Wind-based loess deposits also form an important parent material for prairie soils. Tallgrass prairie evolved over tens of thousands of years with the disturbances of grazing and fire. Native ungulates such as bison, elk, and white-tailed deer roamed the expansive, diverse grasslands before European colonization of the Americas. For 10,000-20,000 years, native people used fire annually as a tool to assist in hunting, transportation, and safety. Evidence of ignition sources of fire in the tall grass prairie are overwhelmingly human as opposed to lightning. Humans, and grazing animals, were active participants in the process of prairie formation and the establishment of the diversity of graminoid and forbs species. Fire has the effect on prairies of removing trees, clearing dead plant matter, and changing the availability of certain nutrients in the soil from the ash produced. Fire kills the vascular tissue of trees, but not prairie species, as up to 75% (depending on the species) of the total plant biomass is below the soil surface and will re-grow from its deep (upwards of 20 feet) roots. Without disturbance, trees will encroach on a grassland and cast shade, which suppresses the understory. Prairie and widely spaced oak trees evolved to coexist in the oak savanna ecosystem. Ecology Prairie ecosystems in the United States and Canada are divided into the easternmost tallgrass prairie, the westernmost shortgrass prairie, and the central mixed-grass prairie. Tallgrass prairies receive over 30 inches of rainfall per year, whereas shortgrass prairies are much more arid, receiving only 12 inches or so, and mixed-grass prairies receive intermediate rainfall. Wet, mesic, and dry prairie ecosystems can also form more locally due to soil and terrain characteristics. Wet prairies may form in low-lying areas with poor drainage; dry prairie can be found on uplands or slopes. Dry prairie is the dominant habitat type in the Southern Canadian agricultural and climatic region which is known as Palliser's Triangle. It was once thought to be completely unarable, but is now one of the most important agricultural regions in Canada thanks to advances in irrigation technology. The dominant plant life in prairies consists of grasses, which may include 40 to 60 different grass species. In addition to grasses, prairies can include over 300 species of flowering plants. The Konza Tallgrass Prairie in Kansas hosts 250 species of native plants and provides habitat for 208 birds, 27 mammals, 25 reptiles, and over 3,000 insects. Some of the dominant grasses of prairies are Indian grass, big bluestem, side-oats grama, Canada wildrye, and switchgrass. Prairies are considered to be fire-dependent ecosystems. Regular controlled burning by Native Americans, practices developed through observation of non-anthropogenic fire and its effects, maintained the biodiversity of the prairie, clearing away dead vegetation and preventing trees from shading out the diverse grasses and herbaceous plants. Prairies also depend on the presence of large grazing animals, particularly bison. Bison are important to the prairie ecosystem because they shape and alter the environment by grazing, trampling areas with their hooves, wallowing, and depositing manure. Bison eat more grass than flowering plants, increasing the diversity of plants in the prairie. Cattle are thought to prefer to eat flowering plants over grasses, but it is not known if that is because of inherent differences in the species or because farmed cattle tend to be confined in smaller areas. Bison dung is a vital source of nutrients for prairie soil, spreads seeds, and supports over 1,000 insect species, including specialist dung beetles which cannot subsist on the feces of any other animal. In spite of long recurrent droughts and occasional torrential rains, the grasslands of the Great Plains were not subject to great soil erosion. The root systems of native prairie grasses firmly held the soil in place to prevent run-off of soil. When the plant died, the fungi and bacteria returned its nutrients to the soil. These deep roots also helped native prairie plants reach water in even the driest conditions. Native grasses suffer much less damage from dry conditions than many farm crops currently grown. When the eastern tallgrass prairies were plowed and turned into agricultural lands, the prairie grasses with their strong root systems were destroyed. In combination with severe droughts that resulted in the Dust Bowl, a major ecological disaster in which winds picked up the dry, unprotected prairie soil and formed it into "black blizzards" of airborne dirt that blackened the skies for days at a time across 19 states and forced 400,000 people to abandon the Great Plains ecoregion. The Dust Bowl was a major reason for the Great Depression. Human use Nomadic hunting has been the main human activity on the prairies for the majority of the archaeological record. This once included many now-extinct species of megafauna. After the other extinctions, the main hunted animal on the prairies was the plains bison. Using loud noises and waving large signals, Native peoples would drive bison into fenced pens called buffalo pounds to be killed with bows and arrows or spears, or drive them off a cliff (called a buffalo jump), to kill or injure the bison en masse. The introduction of the horse and the gun greatly expanded the killing power of the plains Natives. That was followed by the policy of indiscriminate killing by European Americans and Canadians for both commercial reasons and to weaken the independence of plains Natives, and caused a dramatic drop in bison numbers from millions to a few hundred in a century's time, and almost caused their extinction. The very dense soil plagued the first European settlers who were using wooden plows, which were more suitable for loose forest soil. On the prairie, the plows bounced around, and the soil stuck to them. This problem was solved in 1837 by an Illinois blacksmith named John Deere who developed a steel moldboard plow that was stronger and cut the roots, making the fertile soils ready for farming. Former grasslands are now among the most productive agricultural lands on Earth. The tallgrass prairie has been converted into one of the most intensive crop producing areas in North America. Less than one tenth of one percent (<0.09%) of the original landcover of the tallgrass prairie biome remains. Much of what persists is in cemetery prairies, railroad rights-of-way, or rocky/sandy/hilly places unsuitable for agriculture. States formerly with landcover in native tallgrass prairie including Iowa, Illinois, Minnesota, Wisconsin, Nebraska, and Missouri have become valued for their highly productive soils and are included in the Corn Belt. As an example of this land use intensity, Illinois and Iowa rank 49th and 50th, out of 50 US states, in total uncultivated land remaining. Drier shortgrass prairies were once used mostly for open-range ranching. With the development of barbed wire in the 1870s and improved irrigation techniques, this region has mostly been converted to cropland and small fenced pastures. In southern Canada, Palliser's Triangle has been changed into one of the most important sources of wheat in the world as a result of improved methods of watering wheat fields (along with the rest of the Southern prairie provinces which also grow wheat, canola and many other grains). Despite those advances in farming technology, the area is still very prone to extended periods of drought, which can be disastrous for the industry if it is significantly prolonged. Research by David Tilman, ecologist at the University of Minnesota, suggests "Biofuels made from high-diversity mixtures of prairie plants can reduce global warming by removing carbon dioxide from the atmosphere. Even when grown on infertile soils, they can provide a substantial portion of global energy needs, and leave fertile land for food production." Unlike corn and soybeans, which are both directly and indirectly major food crops, including livestock feed, prairie grasses are not used for human consumption. Prairie grasses can be grown in infertile soil, eliminating the cost of adding nutrients to the soil. Tilman and his colleagues estimate that prairie grass biofuels would yield 51 percent more energy per acre than ethanol from corn grown on fertile land. Some plants commonly used are lupine, big bluestem (turkey foot), blazing star, switchgrass, and prairie clover. Preservation Because rich and thick topsoil made the land well suited for agricultural use, only 1% of tallgrass prairie remains in the U.S. today. Shortgrass prairie is more abundant. Significant preserved areas of prairie include: Virgin prairie refers to prairie land which has never been plowed. Small virgin prairies exist in the American Midwestern states and in Canada. Restored prairie refers to a prairie that has been reseeded after plowing or other disturbance. A prairie garden is a garden consisting primarily of plants from a prairie. Physiography The originally treeless prairies of the upper Mississippi basin began in Indiana and extended westward and north-westward until they merged with the drier region known as the Great Plains. An eastward extension of the same area, originally tree-covered, extended to central Ohio. Thus, the prairies generally lie between the Ohio and Missouri rivers on the south and the Great Lakes on the north. The prairies are a contribution of the glacial period. They consist of glacial drift deposited unconformably on an underlying rock surface of moderate or small relief. Here, the rocks are an extension of the same stratified Palaeozoic formations already described as occurring in the Appalachian region and around the Great Lakes. They are usually fine-textured limestones and shales lying horizontal. The moderate or small relief they were given by mature preglacial erosion is now buried under the drift. The most significant area of the prairies, from Indiana to North Dakota, consists of till plains, that is, sheets of unstratified drift. The plains are 30, 50 or even 100 ft (up to 30 m) thick covering the underlying rock surface for thousands of square miles except where postglacial stream erosion has locally laid it bare. The plains have an extraordinarily even surface. The till is presumably made in part of preglacial soils, but it is largely composed of rock waste mechanically transported by the creeping ice sheets. Although the crystalline rocks from Canada and some of the more resistant stratified rocks south of the Great Lakes occur as boulders and stones, a great part of the till has been crushed and ground to a clayey texture. The till plains, although sweeping in broad swells of slowly changing altitude, often appear level to the eye with a view stretching to the horizon. Here and there, faint depressions occur, occupied by marshy sloughs or floored with a rich black soil of postglacial origin. Thus, by sub-glacial aggradation, the prairies have been leveled up to a smooth surface, in contrast to the higher and non-glaciated hilly country just to the south. The great ice sheets formed terminal moraines around their border at various stages. However, the morainic belts are of slight relief in comparison to the great area of the ice. They rise gently from the till plains to 50, 100 or more feet. They may be one, two or three miles (5 km) wide and their hilly surface, dotted over with boulders, contains many small lakes in basins or hollows, instead of streams in valleys. The morainic belts are arranged in groups of concentric loops, convex southward, because the ice sheets advanced in lobes along the lowlands of the Great Lakes. Neighboring morainic loops join each other in re-entrants (north-pointing cusps), where two adjacent glacial lobes came together and formed their moraines in largest volume. The moraines are of too small relief to be shown on any maps except of the largest scale. Small as they are, they are the chief relief of the prairie states, and, in association with the nearly imperceptible slopes of the till plains, they determine the course of many streams and rivers, which as a whole are consequent upon the surface form of the glacial deposits. The complexity of the glacial period and its subdivision into several glacial epochs, separated by interglacial epochs of considerable length (certainly longer than the postglacial epoch) has a structural consequence in the superposition of successive till sheets, alternating with non-glacial deposits. It also has a physiographic consequence in the very different amount of normal postglacial erosion suffered by the different parts of the glacial deposits. The southernmost drift sheets, as in southern Iowa and northern Missouri, have lost their initially plain surface and are now maturely dissected into gracefully rolling forms. Here, the valleys of even the small streams are well opened and graded, and marshes and lakes are rare. These sheets are of early Pleistocene origin. Nearer the Great Lakes, the till sheets are trenched only by the narrow valleys of the large streams. Marshy sloughs still occupy the faint depressions in the till plains and the associated moraines have abundant small lakes in their undrained hollows. These drift sheets are of late Pleistocene origin. When the ice sheets extended to the land sloping southward to the Ohio River, Mississippi River and Missouri River, the drift-laden streams flowed freely away from the ice border. As the streams escaped from their subglacial channels, they spread into broader channels and deposited some of their load, and thus aggraded their courses. Local sheets or aprons of gravel and sand are spread more or less abundantly along the outer side of the morainic belts. Long trains of gravel and sands clog the valleys that lead southward from the glaciated to the non-glaciated area. Later, when the ice retreated further and the unloaded streams returned to their earlier degrading habit, they more or less completely scoured out the valley deposits, the remains of which are now seen in terraces on either side of the present flood plains. When the ice of the last glacial epoch had retreated so far that its front border lay on a northward slope, belonging to the drainage area of the Great Lakes, bodies of water accumulated in front of the ice margin, forming glacio-marginal lakes. The lakes were small at first, and each had its own outlet at the lowest depression of land to the south. As the ice melted further back, neighboring lakes became confluent at the level of the lowest outlet of the group. The outflowing streams grew in the same proportion and eroded a broad channel across the height of land and far down stream, while the lake waters built sand reefs or carved shore cliffs along their margin, and laid down sheets of clay on their floors. All of these features are easily recognized in the prairie region. The present site of Chicago was determined by an Indian portage or carry across the low divide between Lake Michigan and the headwaters of the Illinois River. This divide lies on the floor of the former outlet channel of the glacial Lake Michigan. Corresponding outlets are known for Lake Erie, Lake Huron, and Lake Superior. A very large sheet of water, named Lake Agassiz, once overspread a broad till plain in northern Minnesota and North Dakota. The outlet of this glacial lake, called river Warren, eroded a large channel in which the Minnesota River evident today. The Red River of the North flows northward through a plain formerly covered by Lake Agassiz. Certain extraordinary features were produced when the retreat of the ice sheet had progressed so far as to open an eastward outlet for the marginal lakes. This outlet occurred along the depression between the northward slope of the Appalachian plateau in west-central New York and the southward slope of the melting ice sheet. When this eastward outlet came to be lower than the south-westward outlet across the height of land to the Ohio or Mississippi river, the discharge of the marginal lakes was changed from the Mississippi system to the Hudson system. Many well-defined channels, cutting across the north-sloping spurs of the plateau in the neighborhood of Syracuse, New York mark the temporary paths of the ice-bordered outlet river. Successive channels are found at lower and lower levels on the plateau slope, indicating the successive courses taken by the lake outlet as the ice melted further and further back. On some of the channels, deep gorges were eroded heading in temporary cataracts which exceeded Niagara in height but not in breadth. The pools excavated by the plunging waters at the head of the gorges are now occupied by little lakes. The most significant stage in this series of changes occurred when the glacio-marginal lake waters were lowered so that the long escarpment of Niagara limestone was laid bare in western New York. The previously confluent waters were then divided into two lakes. The higher one, Lake Erie, supplied the outflowing Niagara River, which poured its waters down the escarpment to the lower, Lake Ontario. That gave rise to Niagara Falls. Lake Ontario's outlet for a time ran down the Mohawk Valley to the Hudson River. At the higher elevation, it was known as Lake Iroquois. When ice melted from the northeastern end of the lake, it dropped to a lower level, and drained through the St. Lawrence area creating a lower base level for the Niagara River and increasing its erosive capacity. In certain districts, the subglacial till was not spread out in a smooth plain, but accumulated in elliptical mounds, 100–200 feet. high and 0.5 to 1 mile (0.80 to 1.61 kilometres) long with axes parallel to the direction of the ice motion as indicated by striae on the underlying rock floor. These hills are known by the Irish name, drumlins, used for similar hills in north-western Ireland. The most remarkable groups of drumlins occur in western New York, where their number is estimated at over 6,000, and in southern Wisconsin, where it is placed at 5,000. They completely dominate the topography of their districts. A curious deposit of an impalpably fine and unstratified silt, known by the German name bess (or loess), lies on the older drift sheets near the larger river courses of the upper Mississippi basin. It attains a thickness of 20 ft (6.1 m) or more near the rivers and gradually fades away at a distance of ten or more miles (16 or more km) on either side. It contains land shells, and hence cannot be attributed to marine or lacustrine submergence. The best explanation is that, during certain phases of the glacial period, it was carried as dust by the winds from the flood plains of aggrading rivers, and slowly deposited on the neighboring grass-covered plains. The glacial and eolian origin of this sediment is evidenced by the angularity of its grains (a bank of it will stand without slumping for years), whereas, if it had been transported significantly by water, the grains would have been rounded and polished. Loess is parent material for an extremely fertile, but droughty soil. Southwestern Wisconsin and parts of the adjacent states of Illinois, Iowa, and Minnesota are known as the driftless zone, because, although bordered by drift sheets and moraines, it is free from glacial deposits. It must therefore have been a sort of oasis, when the ice sheets from the north advanced past it on the east and west, and joined around its southern border. The reason for this exemption from glaciation is the converse of that for the southward convexity of the morainic loops. While they mark the paths of greatest glacial advance along lowland troughs (lake basins), the driftless zone is a district protected from ice invasion by reason of the obstruction which the highlands of northern Wisconsin and Michigan (part of the Superior upland) offered to glacial advance. The course of the upper Mississippi River is largely consequent upon glacial deposits. Its sources are in the morainic lakes in northern Minnesota. The drift deposits thereabouts are so heavy that the present divides between the drainage basins of Hudson Bay, Lake Superior, and the Gulf of Mexico evidently stand in no very definite relation to the preglacial divides. The course of the Mississippi through Minnesota is largely guided by the form of the drift cover. Several rapids and the Saint Anthony Falls (determining the site of Minneapolis) are signs of immaturity, resulting from superposition through the drift on the under rock. Further south, as far as the entrance of the Ohio River, the Mississippi follows a rock-walled valley 300 to 400 ft (91 to 122 m) deep, with a flood-plain 2 to 4 mi (3.2 to 6.4 km) wide. This valley seems to represent the path of an enlarged early-glacial Mississippi, when much precipitation that is today discharged to Hudson Bay and the Gulf of St. Lawrence was delivered to the Gulf of Mexico, for the curves of the present river are of distinctly smaller radii than the curves of the valley. Lake Pepin (30 mi [48 km] below St. Paul), a picturesque expansion of the river across its flood-plain, is due to the aggradation of the valley floor where the Chippewa River, coming from the northeast, brought an overload of fluvio-glacial drift. Hence, even the father of waters, like so many other rivers in the Northern states, owes many of its features more or less directly to glacial action. The fertility of the prairies is a natural consequence of their origin. During the mechanical transportation of the till, no vegetation was present to remove the minerals essential to plant growth, as is the case in the soils of normally weathered and dissected peneplains. The soil is similar to the Appalachian piedmont which though not exhausted by the primeval forest cover, are by no means so rich as the till sheets of the prairies. Moreover, whatever the rocky understructure, the till soil has been averaged by a thorough mechanical mixture of rock grindings. Hence, the prairies are continuously fertile for scores of miles together. The true prairies were once covered with a rich growth of natural grass and annual flowering plants, but today, they are covered with farms. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Category:Extraterrestrial_life_in_popular_culture] | [TOKENS: 65] |
Category:Extraterrestrial life in popular culture Subcategories This category has the following 26 subcategories, out of 26 total. Pages in category "Extraterrestrial life in popular culture" The following 43 pages are in this category, out of 43 total. This list may not reflect recent changes. |
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[SOURCE: https://en.wikipedia.org/wiki/Horologium_(constellation)] | [TOKENS: 2200] |
Contents Horologium (constellation) Horologium (Latin hōrologium, the pendulum clock, from Greek ὡρολόγιον, lit. 'an instrument for telling the hour') is a constellation of six stars faintly visible in the southern celestial hemisphere. It was first described by the French astronomer Nicolas-Louis de Lacaille in 1756 and visualized by him as a clock with a pendulum and a second hand. In 1922 the constellation was redefined by the International Astronomical Union (IAU) as a region of the celestial sphere containing Lacaille's stars, and has since been an IAU designated constellation. Horologium's associated region is wholly visible to observers south of 23°N. The constellation's brightest star—and the only one brighter than an apparent magnitude of 4—is Alpha Horologii (at 3.85), an aging orange giant star that has swollen to around 11 times the diameter of the Sun. The long-period variable-brightness star, R Horologii (4.7 to 14.3), has one of the largest variations in brightness among all stars in the night sky visible to the unaided eye. Four star systems in the constellation are known to have exoplanets; at least one—Gliese 1061—contains an exoplanet in its habitable zone. History The French astronomer Nicolas-Louis de Lacaille first described the constellation as l'Horloge à pendule & à secondes (Clock with pendulum and seconds hand) in 1756, after he had observed and catalogued almost 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised fourteen new constellations in previously uncharted regions of the southern celestial hemisphere, which were not visible from Europe. All but one honoured scientific instruments, and so symbolised the Age of Enlightenment.[a] The constellation name was Latinised to Horologium in a catalogue and updated chart published posthumously in 1763. The Latin term is ultimately derived from the Ancient Greek ὡρολόγιον, for an instrument for telling the hour. Characteristics Covering a total of 248.9 square degrees or 0.603% of the sky, Horologium ranks 58th in area out of the 88 modern constellations. Its position in the southern celestial hemisphere means the whole constellation is visible to observers south of 23°N.[b] Horologium is bordered by five constellations: Eridanus (the Po river or Nile river), Caelum (the chisel), Reticulum (the reticle), Dorado (the dolphin/swordfish), and Hydrus (the male water snake). The three letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Hor". The official constellation boundaries are defined by a twenty-two-sided polygon (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 02h 12.8m and 04h 20.3m , while the declination coordinates are between −39.64° and −67.04°. Features Horologium has one star brighter than apparent magnitude 4, and 41 stars brighter than or equal to magnitude 6.5.[c] Lacaille charted and designated 11 stars in the constellation, giving them the Bayer designations Alpha (α Hor) through Lambda Horologii (λ Hor) in 1756. In the mid-19th century, English astronomer Francis Baily removed the designations of two—Epsilon and Theta Horologii—as he held they were too faint to warrant naming. He was unable to find a star that corresponded to the coordinates of Lacaille's Beta Horologii. Determining that the coordinates were wrong, he assigned the designation to another star. Kappa Horologii, too, was unable to be verified—although it most likely was the star HD 18292—and the name fell out of use. In 1879, American astronomer Benjamin Apthorp Gould assigned designations to what became Mu and Nu Horologii as he felt they were bright enough to warrant them. At magnitude 3.9, Alpha Horologii is the brightest star in the constellation, located 115 (± 0.5) light-years from Earth. German astronomer Johann Elert Bode depicted it as the pendulum of the clock, while Lacaille made it one of the weights. It is an orange giant star of spectral type K2III that has swollen to around 11 times the diameter of the Sun, having spent much of its life as a white main-sequence star. At an estimated 1.55 times the mass of the Sun, it is radiating 38 times the Sun's luminosity from its photosphere at an effective (surface) temperature of 5,028 K. At magnitude 4.93, Delta Horologii is the second-brightest star in the constellation, and forms a wide optical double with Alpha. Delta itself is a true binary system composed of a white main sequence star of spectral type A5V that is 1.41 times as massive as the Sun with a magnitude of 5.15 and its fainter companion of magnitude 7.29. The system is located 179 (± 4) light-years from the earth. At magnitude 5.0, Beta Horologii is a white giant 63 times as luminous as the Sun with an effective temperature of 8,303 K. It is 312 (± 4) light-years from Earth, and has been little-studied. Lambda Horologii is an ageing yellow-white giant star of spectral type F2III that spins around at 140 km/second, and is hence mildly flattened at its poles (oblate). It is 161 (± 1) light-years from Earth. With a magnitude of 5.24, Nu Horologii is a white main sequence star of spectral type A2V located 169 (± 1) light-years from Earth that is around 1.9 times as massive as the Sun. Estimated to be around 540 million years old, it has a debris disk that appears to have two components: an inner disk is orbiting at a distance of 96+9−37 AU, while an outer disk lies 410+24−96 AU from the star. The estimated mass of the disks is 0.13%±0.07% the mass of the Earth. Horologium has several variable stars. R Horologii is a red giant Mira variable with one of the widest ranges in brightness known of stars in the night sky visible to the unaided eye. It is around 1,000 light-years from Earth. It has a minimum magnitude of 14.3 and a maximum magnitude of 4.7, with a period of approximately 13 months. T and U Horologii are also Mira variables. The Astronomical Society of Southern Africa reported in 2003 that observations of these two stars were needed as data on their light curves was incomplete. TW Horologii is a semiregular variable red giant star that is classified as a carbon star, and is 1,370 (± 70) light-years from Earth. Iota Horologii is a yellow-white dwarf star 1.23 (± 0.12) times as massive and 1.16 (± 0.04) times as wide as the Sun with a spectral type of F8V, 57 (± 0.05) light-years from Earth. Its chemical profile, movement and age indicate it formed within the Hyades cluster but has drifted around 130 light-years away from the other members. It has a planet at least 2.5 times as massive as Jupiter orbiting it every 307 days. HD 27631 is a Sun-like star located 164 (± 0.3) light-years from Earth which was found to have a planet at least 1.45 times as massive as Jupiter that takes 2,208 (± 66) days (six years) to complete an orbit. WASP-120 is a yellow-white main-sequence star around 1.4 times as massive as the Sun with a spectral type of F5V that is estimated to be 2.6 (± 0.5) billion years old. It has a massive planet around 4.85 times the mass of Jupiter that completes its orbit every 3.6 days, and has an estimated surface temperature of 1,880 (± 70) K. With an apparent magnitude of 13.06, Gliese 1061 is a red dwarf of spectral type M5.5V that has 12% of the mass and 15% of the diameter of the Sun, and shines with only 0.17% of its luminosity. Located 12 light-years away from Earth, it is the 20th-closest single star or stellar system to the Sun. In August 2019, it was announced that it had three planets, one of which lay in its habitable zone. Horologium is home to many deep-sky objects, including several globular clusters. NGC 1261 is a globular cluster of magnitude 8, located 53,000 light-years from Earth. It lies 4.7 degrees north-northeast of Mu Horologii. The globular cluster Arp-Madore 1 is the most remote known globular cluster in the Milky Way at a distance of 123.3 kiloparsecs (402,000 light-years) from Earth. NGC 1512 is a barred spiral galaxy 2.1 degrees west-southwest of Alpha Horologii with an apparent magnitude of 10.2. About five arcmin (13.8 kpc) away is the dwarf lenticular galaxy NGC 1510. The two are in the process of a merger which has been going on for 400 million years. The Horologium-Reticulum Supercluster is a galaxy supercluster, second in mass only to the Shapley Supercluster in the local universe (anything within 200 mpc of Earth). It contains over 20 Abell galaxy clusters and covers more than 100 deg2 of the sky, centered roughly at equatorial coordinates α = 03h 19m , δ = 50° 2′. See also Notes References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Geocentric] | [TOKENS: 8931] |
Contents Geocentrism Geocentrism is a superseded astronomical model description of the Universe with Earth at the center. It is also known as the geocentric model, often exemplified specifically by the Ptolemaic system. Under most geocentric models, the Sun, the Moon, stars, and planets all orbit Earth. The geocentric model was the predominant description of the cosmos in many European ancient civilizations, such as those of Aristotle in Classical Greece and Ptolemy in Roman Egypt, as well as during the Islamic Golden Age. Two observations supported the idea that Earth was the center of the Universe. First, from anywhere on Earth, the Sun appears to revolve around Earth once per day. While the Moon and the planets have their own motions, they also appear to revolve around Earth about once per day. The stars appeared to be fixed on a celestial sphere rotating once each day about an axis through the geographical poles of Earth. Second, Earth seems to be unmoving from the perspective of an earthbound observer; it feels solid, stable, and stationary. Ancient Greek, ancient Roman, and medieval philosophers usually combined the geocentric model with a spherical Earth, in contrast to the older flat-Earth model implied in some mythology. However, the Greek astronomer and mathematician Aristarchus of Samos (c. 310 – c. 230 BC) developed a heliocentric model placing all of the then-known planets in their correct order around the Sun. The ancient Greeks believed that the motions of the planets were circular, a view that was not challenged in Western culture until the 17th century, when Johannes Kepler postulated that orbits were heliocentric and elliptical (Kepler's first law of planetary motion). In 1687, Isaac Newton showed that elliptical orbits could be derived from his laws of gravitation. The astronomical predictions of Ptolemy's geocentric model, developed in the 2nd century, served as the basis for preparing astrological and astronomical charts for over 1,500 years. The geocentric model held sway into the early modern age, but from the late 16th century onward, it was gradually superseded by the heliocentric model of Copernicus, Galileo, and Kepler. There was much resistance to the transition between these two theories, since for a long time the geocentric postulate produced more accurate results.[page needed] Additionally some felt that a new, unknown theory could not subvert an accepted consensus for geocentrism. Ancient Greece In the 6th century BC, Anaximander proposed a cosmology in which Earth is shaped like a section of a pillar (a cylinder), held aloft at the center of everything. The Sun, Moon, and planets were holes in invisible wheels which surround Earth, and through those holes, humans could see concealed fire. At around the same time, Pythagoras thought that Earth was a sphere (in accordance with observations of eclipses), but not at the center; he believed that it was in motion around an unseen fire. Later these two concepts were combined, so that most of the educated Greeks from the 4th century BC onwards thought that Earth was a sphere at the center of the universe. In the 4th century BC Plato and his student Aristotle, wrote works based on the geocentric model. According to Plato, the Earth was a sphere, stationary at the center of the universe. The stars and planets were carried around the Earth on spheres or circles, arranged in the order (outwards from the center): Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, fixed stars, with the fixed stars located on the celestial sphere. In his "Myth of Er", a section of the Republic, Plato describes the cosmos as the Spindle of Necessity, attended by the Sirens and turned by the three Fates. Eudoxus of Cnidus, who worked with Plato, developed a less mythical, more mathematical explanation of the planets' motion based on Plato's dictum stating that all phenomena in the heavens can be explained with uniform circular motion. Aristotle elaborated on Eudoxus' system. In the fully developed Aristotelian system, the spherical Earth is at the center of the universe, and all other heavenly bodies are attached to 47–55 transparent, rotating spheres surrounding the Earth, all concentric with it. (The number is so high because several spheres are needed for each planet.) These spheres, known as crystalline spheres, all moved at different uniform speeds to create the revolution of bodies around the Earth. They were composed of an incorruptible substance called aether. Aristotle believed that the Moon was in the innermost sphere and therefore touches the realm of Earth, causing the dark spots (maculae) and the ability to go through lunar phases. He further described his system by explaining the natural tendencies of the terrestrial elements: earth, water, fire, air, as well as celestial aether. His system held that earth was the heaviest element, with the strongest movement towards the center, thus water formed a layer surrounding the sphere of Earth. The tendency of air and fire, on the other hand, was to move upwards, away from the center, with fire being lighter than air. Beyond the layer of fire, were the solid spheres of aether in which the celestial bodies were embedded. They were also entirely composed of aether. Adherence to the geocentric model stemmed largely from several important observations. If the Earth moved, then the apparent angular separations between stars would be expected to change due to a shifted viewpoint. The shapes of the constellations should then change over the course of a year. Since the constellations appeared constant in shape throughout the year, ancient astronomers concluded that either the stars were extremely distant or the Earth was stationary. The Greeks chose the simpler of the two explanations.[citation needed] Stellar parallax was not detected until the 19th century.[citation needed] Another observation used in favor of the geocentric model at the time was the apparent consistency of Venus' luminosity, which implies that it is usually about the same distance from Earth, which in turn is more consistent with geocentrism than heliocentrism. (In fact, Venus' luminous consistency is due to any loss of light caused by its phases being compensated for by an increase in apparent size caused by its varying distance from Earth.) Objectors to heliocentrism noted that terrestrial bodies naturally tend to come to rest as near as possible to the center of the Earth. Further, barring the opportunity to fall closer the center, terrestrial bodies tend not to move unless forced by an outside object, or transformed to a different element by heat or moisture. Atmospheric explanations for many phenomena were preferred because the Eudoxan–Aristotelian model based on perfectly concentric spheres was not intended to explain changes in the brightness of the planets due to a change in distance. Eventually, perfectly concentric spheres were abandoned as it was impossible to develop a sufficiently accurate model under that ideal, with the mathematical methods then available. However, while providing for similar explanations, the later deferent and epicycle model was already flexible enough to accommodate observations. Ancient Indian Before the Kerala astronomers around 1500, Indian astronomy was focused on predicting solar and planetary motions rather than as a model of the cosmos. The earlier astronomers developed two different approaches, one for the Sun and inner planets, Mercury and Venus, and one for the outer planets, Mars, Jupiter, and Saturn. The systems was broadly similar to the Ptolemaic system but more accurate in calculating the planet's latitude. By 1500 Nilakantha Somayaji developed a single approach for all of the planets. Among the ancient Indian astronomers Aryabhata argued for rotation of the Earth, but his system was otherwise geocentric. Ptolemaic model Although the basic tenets of Greek geocentrism were established by the time of Aristotle, the details of his system did not become standard. The Ptolemaic system, written down by the Hellenistic astronomer Claudius Ptolemaeus in the 2nd century AD, finally standardized geocentrism. The key work describing the system only survives via an Arabic translation of a book named Planetary Hypothesis. For over a millennium, European and Islamic astronomers assumed it was the correct cosmological model. Because of its influence, people sometimes wrongly think the Ptolemaic system is identical with the geocentric model. Ptolemy argued that the Earth was a sphere in the center of the universe, from the simple observation that half the stars were above the horizon and half were below the horizon at any time (stars on rotating stellar sphere), and the assumption that the stars were all at some modest distance from the center of the universe. If the Earth were substantially displaced from the center, this division into visible and invisible stars would not be equal.[n 1] In the Ptolemaic system, each planet is moved by a system of two spheres: one called its deferent; the other, its epicycle. The deferent is a circle whose center point, called the eccentric and marked in the diagram with an X, is distant from the Earth. The original purpose of the eccentric was to account for the difference in length of the seasons (northern autumn was about five days shorter than spring during this time period) by placing the Earth away from the center of rotation of the rest of the universe. Another sphere, the epicycle, is embedded inside the deferent sphere and is represented by the smaller dotted line to the right. A given planet then moves around the epicycle at the same time the epicycle moves along the path marked by the deferent. These combined movements cause the given planet to move closer to and further away from the Earth at different points in its orbit, and explained the observation that planets slowed down, stopped, and moved backward in retrograde motion, and then again reversed to resume normal, or prograde, motion. The deferent-and-epicycle model had been used by Greek astronomers for centuries along with the idea of the eccentric (a deferent whose center is slightly away from the Earth), which was even older. In the illustration, the center of the deferent is not the Earth but the spot marked X, making it eccentric (from the Greek ἐκ ec- meaning "from" and κέντρον kentron meaning "center"), from which the spot takes its name. Unfortunately, the system that was available in Ptolemy's time did not quite match observations, even though it was an improvement over Hipparchus' system. Most noticeably the size of a planet's retrograde loop (especially that of Mars) would be smaller, or sometimes larger, than expected, resulting in positional errors of as much as 30 degrees. To alleviate the problem, Ptolemy developed the equant. The equant was a point near the center of a planet's orbit where, if you were to stand there and watch, the center of the planet's epicycle would always appear to move at uniform speed; all other locations would see non-uniform speed, as on the Earth. By using an equant, Ptolemy claimed to keep motion which was uniform and circular, although it departed from the Platonic ideal of uniform circular motion. The resultant system, which eventually came to be widely accepted in the west, seems unwieldy to modern astronomers; each planet required an epicycle revolving on a deferent, offset by an equant which was different for each planet. It predicted various celestial motions, including the beginning and end of retrograde motion, to within a maximum error of 10 degrees, considerably better than without the equant. The model with epicycles is in fact a very good model of an elliptical orbit with low eccentricity. The well-known ellipse shape does not appear to a noticeable extent when the eccentricity is less than 5%, but the offset distance of the "center" (in fact the focus occupied by the Sun) is very noticeable even with low eccentricities as possessed by the planets. To summarize, Ptolemy conceived a system that was compatible with Aristotelian philosophy and succeeded in tracking actual observations and predicting future movement mostly to within the limits of the next 1,000 years of observations. The observed motions and his mechanisms for explaining them include: The geocentric model was eventually replaced by the heliocentric model. Copernican heliocentrism could remove Ptolemy's epicycles because the retrograde motion could be seen to be the result of the combination of the movements and speeds of Earth and planets. Copernicus felt strongly that equants were a violation of Aristotelian purity, and proved that replacement of the equant with a pair of new epicycles was entirely equivalent. Astronomers often continued using the equants instead of the epicycles because the former was easier to calculate, and gave the same result. It has been determined[by whom?] that the Copernican, Ptolemaic and even the Tychonic models provide identical results to identical inputs: they are computationally equivalent. It was not until Kepler demonstrated a physical observation that could show that the physical Sun is directly involved in determining an orbit that a new model was required. The Ptolemaic order of spheres from Earth outward is: Ptolemy did not invent or work out this order, which aligns with the ancient Seven Heavens religious cosmology common to the major Eurasian religious traditions. It also follows the decreasing orbital periods of the Moon, Sun, planets and stars. After the translation movement that included the translation of Almagest from Latin to Arabic, Muslims adopted and refined the geocentric model of Ptolemy, which they believed correlated with the teachings of Islam. Muslim astronomers generally accepted the Ptolemaic system and the geocentric model, but by the 10th century, texts appeared regularly whose subject matter expressed doubts concerning Ptolemy (shukūk). Several Muslim scholars questioned Earth's apparent immobility and centrality within the universe. Some Muslim astronomers believed that Earth rotates around its axis, such as Abu Sa'id al-Sijzi (d. c. 1020). According to al-Biruni, Sijzi invented an astrolabe called al-zūraqī, based upon a belief held by some of his contemporaries "that the motion we see is due to the Earth's movement and not to that of the sky". The prevalence of this belief is further confirmed by a reference from the 13th century that states: According to the geometers [or engineers] (muhandisīn), the Earth is in constant circular motion, and what appears to be the motion of the heavens is actually due to the motion of the Earth and not the stars. Early in the 11th century, Alhazen wrote a scathing critique of Ptolemy's model in his Doubts on Ptolemy (c. 1028), which some have interpreted to imply he was criticizing Ptolemy's geocentrism, but most agree that he was actually criticizing the details of Ptolemy's model rather than his geocentrism. In the 12th century, Arzachel departed from the ancient Greek idea of uniform circular motions by hypothesizing that the planet Mercury moves in an elliptic orbit, while Alpetragius proposed a planetary model that abandoned the equant, epicycle and eccentric mechanisms, though this resulted in a system that was mathematically less accurate. His alternative system spread through most of Europe during the 13th century. Fakhr al-Din al-Razi (1149–1209), in dealing with his conception of physics and the physical world in his Matalib, rejects the Aristotelian and Avicennian notion of the Earth's centrality within the universe, but instead argues that there are "a thousand thousand worlds (alfa alfi 'awalim) beyond this world, such that each one of those worlds be bigger and more massive than this world, as well as having the like of what this world has." To support his theological argument, he cites the Qur'anic verse, "All praise belongs to God, Lord of the Worlds", emphasizing the term "Worlds". The "Maragha Revolution" refers to the Maragha school's revolution against Ptolemaic astronomy. The "Maragha school" was an astronomical tradition beginning in the Maragha observatory and continuing with astronomers from the Damascus mosque and Samarkand observatory. Like their Andalusian predecessors, the Maragha astronomers attempted to solve the equant problem (the circle around whose circumference a planet or the center of an epicycle was conceived to move uniformly) and produce alternative configurations to the Ptolemaic model without abandoning geocentrism. They were more successful than their Andalusian predecessors in producing non-Ptolemaic configurations which eliminated the equant and eccentrics, were more accurate than the Ptolemaic model in numerically predicting planetary positions, and were in better agreement with empirical observations. The most important of the Maragha astronomers included Mo'ayyeduddin Urdi (d. 1266), Nasīr al-Dīn al-Tūsī (1201–1274), Qutb al-Din al-Shirazi (1236–1311), Ibn al-Shatir (1304–1375), Ali Qushji (c. 1474), Al-Birjandi (d. 1525), and Shams al-Din al-Khafri (d. 1550). However, the Maragha school never made the paradigm shift to heliocentrism. The influence of the Maragha school on Copernicus remains speculative, since there is no documentary evidence to prove it. The possibility that Copernicus independently developed the Tusi couple remains open, since no researcher has yet demonstrated that he knew about Tusi's work or that of the Maragha school. Ptolemaic and rival systems Not all Greeks agreed with the geocentric model. The Pythagorean system has already been mentioned; some Pythagoreans believed the Earth to be one of several planets going around a central fire. Hicetas and Ecphantus, two Pythagoreans of the 5th century BC, and Heraclides Ponticus in the 4th century BC, believed that the Earth rotated on its axis but remained at the center of the universe. Such a system still qualifies as geocentric. It was revived in the Middle Ages by Jean Buridan. Heraclides Ponticus was once thought to have proposed that both Venus and Mercury went around the Sun rather than the Earth, but it is now known that he did not. Martianus Capella definitely put Mercury and Venus in orbit around the Sun. Aristarchus of Samos wrote a work, which has not survived, on heliocentrism, saying that the Sun was at the center of the universe, while the Earth and other planets revolved around it. His theory was not popular, and he had one named follower, Seleucus of Seleucia. Epicurus was the most radical. He correctly realized in the 4th century BC that the universe does not have any single center. This theory was widely accepted by the later Epicureans and was notably defended by Lucretius in his poem De rerum natura. In 1543, the geocentric system met its first serious challenge with the publication of Copernicus' De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres), which posited that the Earth and the other planets instead revolved around the Sun. The geocentric system was still held for many years afterwards, as at the time the Copernican system did not offer better predictions than the geocentric system, and it posed problems for both natural philosophy and scripture. The Copernican system was no more accurate than Ptolemy's system, because it still used circular orbits. This was not altered until Johannes Kepler postulated that they were elliptical (Kepler's first law of planetary motion). Tycho Brahe (1545–1601), made more accurate determinations of the positions of planets and stars. He sought the effect of stellar parallax, which would have been empirically verifiable proof of the Earth's motion around the Sun predicted by the Copernican model. Having observed no effect, he rejected the idea of the Earth's motion. Consequently, he introduced a new system, the Tychonic system, in which the Earth was still at the center of the universe, and around it revolved the Sun, but all the other planets revolved around the Sun in a set of epicycles. His model considered both the benefits of the Copernican model and the lack of evidence for the Earth's motion. With the invention of the telescope in 1609, observations made by Galileo Galilei (such as that Jupiter has moons) called into question some of the tenets of geocentrism but did not seriously threaten it. Because he observed dark "spots" on the Moon, craters, he remarked that the moon was not a perfect celestial body as had been previously conceived. This was the first detailed observation by telescope of the Moon's imperfections, which had previously been explained by Aristotle as the Moon being contaminated by Earth and its heavier elements, in contrast to the aether of the higher spheres. Galileo could also see the moons of Jupiter, which he dedicated to Cosimo II de' Medici, and stated that they orbited around Jupiter, not Earth. This was a significant claim as it would mean not only that not everything revolved around Earth as stated in the Ptolemaic model, but also showed a secondary celestial body could orbit a moving celestial body, strengthening the heliocentric argument that a moving Earth could retain the Moon. Galileo's observations were verified by other astronomers of the time period who quickly adopted use of the telescope, including Christoph Scheiner, Johannes Kepler, and Giovan Paulo Lembo. In December 1610, Galileo Galilei used his telescope to observe that Venus showed all phases, just like the Moon. He thought that while this observation was incompatible with the Ptolemaic system, it was a natural consequence of the heliocentric system. However, Ptolemy placed Venus' deferent and epicycle entirely inside the sphere of the Sun (between the Sun and Mercury), but this was arbitrary; he could just as easily have swapped Venus and Mercury and put them on the other side of the Sun, or made any other arrangement of Venus and Mercury, as long as they were always near a line running from the Earth through the Sun, such as placing the center of the Venus epicycle near the Sun. In this case, if the Sun is the source of all the light, under the Ptolemaic system: If Venus is between Earth and the Sun, the phase of Venus must always be crescent or all dark. If Venus is beyond the Sun, the phase of Venus must always be gibbous or full. But Galileo saw Venus at first small and full, and later large and crescent. This showed that with a Ptolemaic cosmology, the Venus epicycle can be neither completely inside nor completely outside of the orbit of the Sun. As a result, Ptolemaics abandoned the idea that the epicycle of Venus was completely inside the Sun, and later 17th-century competition between astronomical cosmologies focused on variations of the Tychonic or Copernican systems. The Galileo affair pitted the geocentric model against the claims of Galileo. In regards to the theological basis for such an argument, two Popes addressed the question of whether the use of phenomenological language would compel one to admit an error in Scripture. Both taught that it would not. Pope Leo XIII wrote: we have to contend against those who, making an evil use of physical science, minutely scrutinize the Sacred Book in order to detect the writers in a mistake, and to take occasion to vilify its contents. ... There can never, indeed, be any real discrepancy between the theologian and the physicist, as long as each confines himself within his own lines, and both are careful, as St. Augustine warns us, "not to make rash assertions, or to assert what is not known as known". If dissension should arise between them, here is the rule also laid down by St. Augustine, for the theologian: "Whatever they can really demonstrate to be true of physical nature, we must show to be capable of reconciliation with our Scriptures; and whatever they assert in their treatises which is contrary to these Scriptures of ours, that is to Catholic faith, we must either prove it as well as we can to be entirely false, or at all events we must, without the smallest hesitation, believe it to be so." To understand how just is the rule here formulated we must remember, first, that the sacred writers, or to speak more accurately, the Holy Ghost "Who spoke by them, did not intend to teach men these things (that is to say, the essential nature of the things of the visible universe), things in no way profitable unto salvation." Hence they did not seek to penetrate the secrets of nature, but rather described and dealt with things in more or less figurative language, or in terms which were commonly used at the time, and which in many instances are in daily use at this day, even by the most eminent men of science. Ordinary speech primarily and properly describes what comes under the senses; and somewhat in the same way the sacred writers-as the Angelic Doctor also reminds us – "went by what sensibly appeared", or put down what God, speaking to men, signified, in the way men could understand and were accustomed to. — Providentissimus Deus 18 Maurice Finocchiaro, author of a book on the Galileo affair, notes that this is "a view of the relationship between biblical interpretation and scientific investigation that corresponds to the one advanced by Galileo in the "Letter to the Grand Duchess Christina". Pope Pius XII repeated his predecessor's teaching: The first and greatest care of Leo XIII was to set forth the teaching on the truth of the Sacred Books and to defend it from attack. Hence with grave words did he proclaim that there is no error whatsoever if the sacred writer, speaking of things of the physical order "went by what sensibly appeared" as the Angelic Doctor says, speaking either "in figurative language, or in terms which were commonly used at the time, and which in many instances are in daily use at this day, even among the most eminent men of science". For "the sacred writers, or to speak more accurately – the words are St. Augustine's – the Holy Spirit, Who spoke by them, did not intend to teach men these things – that is the essential nature of the things of the universe – things in no way profitable to salvation"; which principle "will apply to cognate sciences, and especially to history", that is, by refuting, "in a somewhat similar way the fallacies of the adversaries and defending the historical truth of Sacred Scripture from their attacks". — Divino afflante Spiritu, 3 In 1664, Pope Alexander VII republished the Index Librorum Prohibitorum (List of Prohibited Books) and attached the various decrees connected with those books, including those concerned with heliocentrism. He stated in a papal bull that his purpose in doing so was that "the succession of things done from the beginning might be made known [quo rei ab initio gestae series innotescat]". The position of the curia evolved slowly over the centuries towards permitting the heliocentric view. In 1757, during the papacy of Benedict XIV, the Congregation of the Index withdrew the decree that prohibited all books teaching the Earth's motion, although the Dialogue and a few other books continued to be explicitly included. In 1820, the Congregation of the Holy Office, with the pope's approval, decreed that Catholic astronomer Giuseppe Settele was allowed to treat the Earth's motion as an established fact and removed any obstacle for Catholics to hold to the motion of the Earth: The Assessor of the Holy Office has referred the request of Giuseppe Settele, Professor of Optics and Astronomy at La Sapienza University, regarding permission to publish his work Elements of Astronomy in which he espouses the common opinion of the astronomers of our time regarding the Earth’s daily and yearly motions, to His Holiness through Divine Providence, Pope Pius VII. Previously, His Holiness had referred this request to the Supreme Sacred Congregation and concurrently to the consideration of the Most Eminent and Most Reverend General Cardinal Inquisitor. His Holiness has decreed that no obstacles exist for those who sustain Copernicus' affirmation regarding the Earth's movement in the manner in which it is affirmed today, even by Catholic authors. He has, moreover, suggested the insertion of several notations into this work, aimed at demonstrating that the above mentioned affirmation [of Copernicus], as it has come to be understood, does not present any difficulties; difficulties that existed in times past, prior to the subsequent astronomical observations that have now occurred. [Pope Pius VII] has also recommended that the implementation [of these decisions] be given to the Cardinal Secretary of the Supreme Sacred Congregation and Master of the Sacred Apostolic Palace. He is now appointed the task of bringing to an end any concerns and criticisms regarding the printing of this book, and, at the same time, ensuring that in the future, regarding the publication of such works, permission is sought from the Cardinal Vicar whose signature will not be given without the authorization of the Superior of his Order. In 1822, the Congregation of the Holy Office removed the prohibition on the publication of books treating of the Earth's motion in accordance with modern astronomy and Pope Pius VII ratified the decision: The most excellent [cardinals] have decreed that there must be no denial, by the present or by future Masters of the Sacred Apostolic Palace, of permission to print and to publish works which treat of the mobility of the Earth and of the immobility of the sun, according to the common opinion of modern astronomers, as long as there are no other contrary indications, on the basis of the decrees of the Sacred Congregation of the Index of 1757 and of this Supreme [Holy Office] of 1820; and that those who would show themselves to be reluctant or would disobey, should be forced under punishments at the choice of [this] Sacred Congregation, with derogation of [their] claimed privileges, where necessary. The 1835 edition of the Catholic List of Prohibited Books for the first time omits the Dialogue from the list. In his 1921 papal encyclical, In praeclara summorum, Pope Benedict XV stated that, "though this Earth on which we live may not be the center of the universe as at one time was thought, it was the scene of the original happiness of our first ancestors, witness of their unhappy fall, as too of the Redemption of mankind through the Passion and Death of Jesus Christ". In 1965 the Second Vatican Council stated that, "Consequently, we cannot but deplore certain habits of mind, which are sometimes found too among Christians, which do not sufficiently attend to the rightful independence of science and which, from the arguments and controversies they spark, lead many minds to conclude that faith and science are mutually opposed." The footnote on this statement is to Msgr. Pio Paschini's, Vita e opere di Galileo Galilei, 2 volumes, Vatican Press (1964). Pope John Paul II regretted the treatment that Galileo received, in a speech to the Pontifical Academy of Sciences in 1992. The Pope declared the incident to be based on a "tragic mutual miscomprehension". He further stated: Cardinal Poupard has also reminded us that the sentence of 1633 was not irreformable, and that the debate which had not ceased to evolve thereafter, was closed in 1820 with the imprimatur given to the work of Canon Settele. ... The error of the theologians of the time, when they maintained the centrality of the Earth, was to think that our understanding of the physical world's structure was, in some way, imposed by the literal sense of Sacred Scripture. Let us recall the celebrated saying attributed to Baronius "Spiritui Sancto mentem fuisse nos docere quomodo ad coelum eatur, non quomodo coelum gradiatur". In fact, the Bible does not concern itself with the details of the physical world, the understanding of which is the competence of human experience and reasoning. There exist two realms of knowledge, one which has its source in Revelation and one which reason can discover by its own power. To the latter belong especially the experimental sciences and philosophy. The distinction between the two realms of knowledge ought not to be understood as opposition. Gravitation Johannes Kepler analysed Tycho Brahe's famously accurate observations, and afterwards constructed his three laws in 1609 and 1619, based upon a heliocentric model wherein the planets move in elliptical paths. Using these laws, he was the first astronomer to successfully predict a transit of Venus for the year 1631. The change from circular orbits to elliptical planetary paths dramatically improved the accuracy of celestial observations and predictions. Because the heliocentric model devised by Copernicus was no more accurate than Ptolemy's system, new observations were needed to persuade those who still adhered to the geocentric model. However, Kepler's laws based upon Brahe's data became a problem that geocentrists could not easily overcome. In 1687, Isaac Newton stated the law of universal gravitation, which was described earlier as a hypothesis by Robert Hooke and others. His main achievement was to mathematically derive Kepler's laws of planetary motion from the law of gravitation, thus helping to prove the latter. This introduced gravitation as the force which kept Earth and the planets moving through the universe, and also kept the atmosphere from flying away. The theory of gravity allowed scientists to rapidly construct a plausible heliocentric model for the Solar System. In his Principia, Newton explained his theory of how gravity, previously thought to be a mysterious, unexplained occult force, directed the movements of celestial bodies, and kept the Solar System in working order. His descriptions of centripetal force were a breakthrough in scientific thought, using the newly developed mathematical discipline of differential calculus, finally replacing the previous schools of scientific thought, which had been dominated by Aristotle and Ptolemy. However, the process was gradual. Several empirical tests of Newton's theory, explaining the longer period of oscillation of a pendulum at the equator and the differing size of a degree of latitude, would gradually become available between 1673 and 1738. In addition, stellar aberration was observed by Robert Hooke in 1674, and tested in a series of observations by Jean Picard over a period of ten years, finishing in 1680. However, it was not explained until 1729, when James Bradley provided an approximate explanation in terms of the Earth's revolution about the Sun. In 1838, astronomer Friedrich Wilhelm Bessel measured the parallax of the star 61 Cygni successfully, and disproved Ptolemy's claim that parallax motion did not exist. This finally confirmed the assumptions made by Copernicus, providing accurate, dependable scientific observations, and conclusively displaying how distant stars are from Earth. A geocentric frame is useful for many everyday activities and most laboratory experiments, but is a less appropriate choice for Solar System mechanics and space travel. While a heliocentric frame is most useful in those cases, galactic and extragalactic astronomy is easier if the Sun is treated as neither stationary nor the center of the universe, but rather rotating around the center of the Milky Way Galaxy, while in turn the Milky Way is also not at rest in the cosmic background. Relativity Albert Einstein and Leopold Infeld wrote in The Evolution of Physics (1938): "Can we formulate physical laws so that they are valid for all CS [coordinate systems], not only those moving uniformly, but also those moving quite arbitrarily, relative to each other? If this can be done, our difficulties will be over. We shall then be able to apply the laws of nature to any CS. The struggle, so violent in the early days of science, between the views of Ptolemy and Copernicus would then be quite meaningless. Either CS could be used with equal justification. The two sentences, 'the sun is at rest and the Earth moves', or 'the sun moves and the Earth is at rest', would simply mean two different conventions concerning two different CS. Could we build a real relativistic physics valid in all CS; a physics in which there would be no place for absolute, but only for relative, motion? This is indeed possible!" Despite giving more respectability to the geocentric view than Newtonian physics does, relativity is not geocentric. Rather, relativity states that the Sun, the Earth, the Moon, Jupiter, or any other point for that matter could be chosen as a center of the Solar System with equal validity. Relativity agrees with Newtonian predictions that regardless of whether the Sun or the Earth are chosen arbitrarily as the center of the coordinate system describing the Solar System, the paths of the planets form (roughly) ellipses with respect to the Sun, not the Earth. With respect to the average reference frame of the fixed stars, the planets do indeed move around the Sun, which due to its much larger mass, moves far less than its own diameter and the gravity of which is dominant in determining the orbits of the planets (in other words, the center of mass of the Solar System is near the center of the Sun). The Earth and Moon are much closer to being a binary planet; the center of mass around which they both rotate is still inside the Earth, but is about 4,624 km (2,873 miles) or 72.6% of the Earth's radius away from the center of the Earth (thus closer to the surface than the center).[citation needed] What the principle of relativity points out is that correct mathematical calculations can be made regardless of the reference frame chosen, and these will all agree with each other as to the predictions of actual motions of bodies with respect to each other. It is not necessary to choose the object in the Solar System with the largest gravitational field as the center of the coordinate system in order to predict the motions of planetary bodies, though doing so may make calculations easier to perform or interpret. A geocentric coordinate system can be more convenient when dealing only with bodies mostly influenced by the gravity of the Earth (such as artificial satellites and the Moon), or when calculating what the sky will look like when viewed from Earth (as opposed to an imaginary observer looking down on the entire Solar System, where a different coordinate system might be more convenient).[citation needed] Religious and contemporary adherence to geocentrism The Ptolemaic model held sway into the early modern age; from the late 16th century onward it was gradually replaced as the consensus description by the heliocentric model. Geocentrism as a separate religious belief, however, never completely died out. In the United States between 1870 and 1920, for example, various members of the Lutheran Church–Missouri Synod published articles disparaging Copernican astronomy and promoting geocentrism. However, in the 1902 Theological Quarterly, A. L. Graebner observed that the synod had no doctrinal position on geocentrism, heliocentrism, or any scientific model, unless it were to contradict Scripture. He stated that any possible declarations of geocentrists within the synod did not set the position of the church body as a whole. Articles arguing that geocentrism was the biblical perspective appeared in some early creation science newsletters.[which?] Contemporary advocates for such religious beliefs include Robert Sungenis (author of the 2006 book Galileo Was Wrong and the 2014 pseudo-documentary film The Principle). Most contemporary creationist organizations reject such perspectives.[n 2] A few Orthodox Jewish leaders maintain a geocentric model of the universe and an interpretation of Maimonides to the effect that he ruled that the Earth is orbited by the Sun. The Lubavitcher Rebbe also explained that geocentrism is defensible based on the theory of relativity. While geocentrism is important in Maimonides' calendar calculations, the great majority of Jewish religious scholars, who accept the divinity of the Bible and accept many of his rulings as legally binding, do not believe that the Bible or Maimonides command a belief in geocentrism. There have been some modern Islamic scholars who promoted geocentrism. One of them was Ahmed Raza Khan Barelvi, a Sunni scholar of the Indian subcontinent. He rejected the heliocentric model and wrote a book that explains the movement of the sun, moon and other planets around the Earth. According to a report released in 2014 by the National Science Foundation, 26% of Americans surveyed believe that the Sun revolves around the Earth. Morris Berman quotes a 2006 survey that show currently some 20% of the U.S. population believe that the Sun goes around the Earth (geocentricism) rather than the Earth goes around the Sun (heliocentricism), while a further 9% claimed not to know. Polls conducted by Gallup in the 1990s found that 16% of Germans, 18% of Americans and 19% of Britons hold that the Sun revolves around the Earth. A study conducted in 2005 by Jon D. Miller of Northwestern University, an expert in the public understanding of science and technology, found that about 20%, or one in five, of American adults believe that the Sun orbits the Earth. According to 2011 VTSIOM poll, 32% of Russians believe that the Sun orbits the Earth. Planetariums Many planetariums can switch between heliocentric and geocentric models. In particular, the geocentric model is still used for projecting the celestial sphere and lunar phases in education. Ephemerides Ephemerides (tables of positions) of the sun, which are needed for astronomical and navigational purposes, assume geocentricity for ease of calculation. See also Notes References All Islamic astronomers from Thabit ibn Qurra in the ninth century to Ibn al-Shatir in the fourteenth, and all natural philosophers from al-Kindi to Averroes and later, are known to have accepted ... the Greek picture of the world as consisting of two spheres of which one, the celestial sphere ... concentrically envelops the other. Bibliography External links |
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[SOURCE: https://en.wikipedia.org/wiki/D%C3%BCrer%27s_Rhinoceros] | [TOKENS: 3155] |
Contents Dürer's Rhinoceros Dürer's Rhinoceros is the name commonly given to a woodcut executed by German artist Albrecht Dürer in 1515.[a] Dürer never saw the actual rhinoceros, which was the first living example seen in Europe since Roman times. Instead the image is based on an anonymous written description and brief sketch of an Indian rhinoceros brought to Lisbon in 1515. Later that year, the King of Portugal, Manuel I, sent the animal as a gift for Pope Leo X, but it died in a shipwreck off the coast of Italy. Another live rhinoceros was not seen again in Europe until Abada arrived from India to the court of Sebastian of Portugal in 1577. Dürer's woodcut is not an accurate representation. It depicts an animal with hard plates that cover its body like sheets of armor, with a gorget at the throat, a solid-looking breastplate, and what appear to be rivets along the seams; there is a small twisted horn on its back, scaly legs and saw-like rear quarters. None of these features are present in a real rhinoceros, although the Indian rhinoceros does have deep folds in its skin that can look like armor from a distance. Dürer's woodcut became very popular in Europe and was copied many times in the following three centuries. It was regarded as a true representation of a rhinoceros into the late 18th century, and it has been said of Dürer's woodcut that "probably no animal picture has exerted such a profound influence on the arts". Eventually, it was supplanted by more realistic drawings and paintings, particularly those of Clara the rhinoceros, who toured Europe in the 1740s and 1750s. The rhinoceros On 20 May 1515, an Indian rhinoceros named Ulysses arrived in Lisbon from the Far East. In early 1514, Afonso de Albuquerque, governor of Portuguese India, sent ambassadors to Sultan Muzaffar Shah II, ruler of Cambay (modern Gujarat), to seek permission to build a fort on the island of Diu. The mission returned without an agreement, but diplomatic gifts were exchanged, including the rhinoceros. At that time, the rulers of different countries would occasionally send each other exotic animals to be kept in a menagerie. The rhinoceros was already well accustomed to being kept in captivity. Albuquerque decided to forward the gift, known by its Gujarati name of Genda or Ganda as Durer noted it (in the lower margin of the original drawing now held at the British Museum), and its Indian keeper, named Ocem, to King Manuel I of Portugal. It sailed on the Nossa Senhora da Ajuda, which left Goa in January 1515. The ship and its two companion vessels were loaded with exotic spices, sailed across the Indian Ocean, around the Cape of Good Hope and north through the Atlantic, stopping briefly in Mozambique, Saint Helena and the Azores. After a relatively fast voyage of 120 days, the rhinoceros was finally unloaded in Portugal, near the site where the Manueline Belém Tower was under construction. The tower was later decorated with gargoyles shaped as rhinoceros heads under its corbels. A rhinoceros had not been seen in Europe since Roman times, twelve centuries prior: and was examined by scholars and the curious, and letters describing the fantastic creature were sent to correspondents throughout Europe. The earliest known image of the animal illustrates a poemetto by Florentine Giovanni Giacomo Penni, published in Rome on 13 July 1515, fewer than eight weeks after its arrival in Lisbon. It was housed in King Manuel's menagerie at the Ribeira Palace in Lisbon, separate from his elephants and other large beasts at the Estaus Palace. Manuel arranged a fight with a young elephant from his collection, to test the account by Pliny the Elder that the elephant and the rhinoceros are bitter enemies, but the elephant fled the field in panic before a single blow was struck. Manuel decided to give the rhinoceros as a gift to the Medici Pope Leo X. The King was keen to curry favour with the Pope, to maintain the papal grants of exclusive possession to the new lands that his naval forces had been exploring in the Far East since Vasco da Gama discovered the sea route to India around Africa in 1498. The previous year, the Pope had been very pleased with Manuel's gift of a white elephant, also from India, which the Pope had named Hanno. Together with other precious gifts of silver plate and spices, the rhinoceros, with its new collar of green velvet decorated with flowers, embarked in December 1515 for the voyage from the Tagus to Rome. After resuming its journey, the ship was wrecked in a sudden storm as it passed through the narrows of Porto Venere, north of La Spezia on the coast of Liguria. The rhinoceros, chained and shackled to the deck to keep it under control, was unable to swim to safety and drowned. The carcass of the rhinoceros was recovered near Villefranche, and its hide was returned to Lisbon, where it was stuffed. Some reports say that the mounted skin was sent to Rome, arriving in February 1516, to be exhibited impagliato (Italian for "stuffed with straw"), although such a feat would have challenged 16th-century methods of taxidermy, which were still primitive. If a stuffed rhinoceros did arrive in Rome, its fate remains unknown: it might have been removed to Florence by the Medici or destroyed in the 1527 sack of Rome. In any event, there was not the popular sensation in Rome that the living beast had caused in Lisbon, although a rhinoceros was depicted in contemporary paintings in Rome by Giovanni da Udine and Raphael. Dürer's woodcut Valentim Fernandes, a Moravian merchant and printer, saw the rhinoceros in Lisbon shortly after it arrived and described it in a newsletter sent to the Nuremberg community of merchants in June 1515. The original document in German has not survived, but a transcript in Italian is held in the Biblioteca Nazionale Centrale in Florence. A second letter of unknown authorship was sent from Lisbon to Nuremberg at around the same time, enclosing a sketch by an unknown artist. Dürer – who was acquainted with the Portuguese community of the factory at Antwerp – saw the second letter and sketch in Nuremberg. He made a pen and ink drawing[b] and printed a reversed reflection of it.[c] The German inscription on the woodcut is largely drawing from Pliny's account and reads: On the first of May in the year 1513 AD [sic], the powerful King of Portugal, Manuel of Lisbon, brought such a living animal from India, called the rhinoceros. This is an accurate representation. It is the colour of a speckled tortoise,[d] and is almost entirely covered with thick scales. It is the size of an elephant but has shorter legs and is almost invulnerable. It has a strong pointed horn on the tip of its nose, which it sharpens on stones. It is the mortal enemy of the elephant. The elephant is afraid of the rhinoceros, for, when they meet, the rhinoceros charges with its head between its front legs and rips open the elephant's stomach, against which the elephant is unable to defend itself. The rhinoceros is so well-armed that the elephant cannot harm it. They also say that the rhinoceros is fast, merry and jovial. Dürer's woodcut is not an accurate representation of a rhinoceros. He depicts an animal with hard plates that cover its body like sheets of armour, with a gorget at the throat, a solid-looking breastplate, and rivets along the seams. He places a small twisted horn on its back and gives it scaly legs and saw-like rear quarters. None of these features is present in a real rhinoceros. Glynis Ridley suggested that it is possible that a suit of armour was forged for the rhinoceros's fight against the elephant in Portugal and that the features depicted by Dürer are parts of the armour, however, there is no mention of this in Bedini. Alternatively, Dürer's "armour" may represent the heavy folds of thick skin of an Indian rhinoceros, or, as with the other inaccuracies, may simply be misunderstandings or creative additions by Dürer.[e] Dürer also draws a scaly texture over the body of the animal, including the "armour". This may be Dürer's attempt to reflect the rough and almost hairless hide of the Indian rhinoceros, which has wart-like bumps covering its upper legs and shoulders. On the other hand, his depiction of the texture may represent dermatitis induced by the rhinoceros' close confinement during the four-month journey by ship from India to Portugal. A second woodcut was executed by Hans Burgkmair in Augsburg around the same time as Dürer's. Burgkmair corresponded with merchants in Lisbon and Nuremberg, but it is not clear whether he had access to a letter or sketch as Dürer did, perhaps even Dürer's sources, or saw the animal himself in Portugal. His image is truer to life, omitting Dürer's more fanciful additions and including the shackles and chain used to restrain the rhinoceros. However, Dürer's woodcut is more powerful and eclipsed Burgkmair's in popularity. Only one impression (example) of Burgkmair's image has survived, whereas Dürer's print survives in many impressions. Dürer produced a first edition of his woodcut in 1515. Many further printings followed after Dürer's death in 1528, including two in the 1540s, and two more in the late 16th century. The block passed into the hands of the Amsterdam printer and cartographer Willem Janssen (also called Willem Blaeu amongst other names). By this time the block was very damaged; the border lines were chipped, there were numerous woodworm holes and a pronounced crack had developed through the rhino's legs. Janssen decided to re-issue the block with the addition of a new tone block printed in a variety of colours, olive-green and dark green, as well as blue-grey. The resulting chiaroscuro woodcut, which entirely omitted the text, was published after 1620. There is an example in the British Museum. This was the seventh of the eight editions in all of the print. Despite its errors, the image remained very popular, and was regarded as an accurate representation of a rhinoceros until the late 18th century. Dürer may have anticipated this and deliberately chosen to create a woodcut, rather than a more refined and detailed engraving, as this was cheaper to produce and more copies could be printed. A rhinoceros clearly based on Dürer's woodcut was chosen by Alessandro de' Medici as his emblem in June 1536, with the motto "Non vuelvo sin vencer" (old Spanish for "I shall not return without victory"). A sculpture of a rhinoceros based on Dürer's image was placed at the base of a 70-foot (21 m) high obelisk designed by Jean Goujon and erected in front of the Church of the Sepulchre in the rue Saint-Denis in Paris in 1549 for the royal entry welcoming the arrival of the new King of France, Henry II. A similar rhinoceros, in relief, decorates a panel in one of the bronze west doors of Pisa Cathedral. The rhinoceros was depicted in numerous other paintings and sculptures and became a popular decoration for porcelain. The popularity of the inaccurate Dürer image remained undiminished despite an Indian rhinoceros spending eight years in Madrid from 1580 to 1588 (although a few examples of a print of the Madrid rhinoceros sketched by Philippe Galle in Antwerp in 1586, and derivative works, have survived), and the exhibition of a live rhinoceros in London a century later, from 1684 to 1686, and of a second individual after 1739. The pre-eminent position of Dürer's image and its derivatives declined from the mid 18th century when more live rhinoceroses were brought to Europe, shown to the curious public, and depicted in more accurate representations. Jean-Baptiste Oudry painted a life-size portrait of Clara the rhinoceros in 1749, and George Stubbs painted a large portrait of a rhinoceros in London around 1790. Both of these paintings were more accurate than Dürer's woodcut, and a more realistic conception of the rhinoceros gradually started to displace Dürer's image in the public imagination. In particular, Oudry's painting was the inspiration for a plate in Buffon's encyclopedic Histoire naturelle, which was widely copied. In 1790, James Bruce's travelogue Travels to discover the source of the Nile dismissed Dürer's work as "wonderfully ill-executed in all its parts" and "the origin of all the monstrous forms under which that animal has been painted, ever since". Even so, Bruce's own illustration of the African white rhinoceros, which is noticeably different in appearance to the Indian rhinoceros, still shares conspicuous inaccuracies with Dürer's work. The semiotician Umberto Eco argues (fetching the idea from E.H. Gombrich, Art and Illusion: A Study in the Psychology of Pictorial Representation, 1961) that Dürer's "scales and imbricated plates" became a necessary element of depicting the animal, even to those who might know better, because "they knew that only these conventionalized graphic signs could denote «rhinoceros» to the person interpreting the iconic sign." He also notes that the skin of a rhinoceros is rougher than it visually appears and that such plates and scales portray this non-visual information to a degree. Until the late 1930s, Dürer's image appeared in school textbooks in Germany as a faithful image of the rhinoceros; and it remains a powerful artistic influence. It was one of the inspirations for Salvador Dalí; a reproduction of the woodcut hung in his childhood home and he used the image in several of his works. Sale history Although very popular, few prints have survived and impressions of the first edition are rare. A fine example was sold at Christie's New York in 2013 for $866,500, setting a new auction record for the artist. See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/ICMPv6] | [TOKENS: 791] |
Contents ICMPv6 Internet Control Message Protocol version 6 (ICMPv6) is the implementation of the Internet Control Message Protocol (ICMP) for Internet Protocol version 6 (IPv6). ICMPv6 is an integral part of IPv6 and performs error reporting and diagnostic functions. ICMPv6 has a framework for extensions to implement new features. Several extensions have been published, defining new ICMPv6 message types as well as new options for existing ICMPv6 message types. For example, Neighbor Discovery Protocol (NDP) is a node discovery protocol based on ICMPv6 which replaces and enhances functions of ARP. Secure Neighbor Discovery (SEND) is an extension of NDP with extra security. Multicast Listener Discovery (MLD) is used by IPv6 routers for discovering multicast listeners on a directly attached link, much like Internet Group Management Protocol (IGMP) is used in IPv4. Multicast Router Discovery (MRD) allows the discovery of multicast routers. Message types and formats ICMPv6 messages may be classified as error messages and information messages. ICMPv6 messages are transported by IPv6 packets in which the IPv6 Next Header value for ICMPv6 is set to the value 58. The ICMPv6 message consists of a header and the protocol payload. The header contains only three fields: Type (8 bits), Code (8 bits), and Checksum (16 bits). Control messages are identified by the value in the type field. The code field gives additional context information for the message. Some messages serve the same purpose as the correspondingly named ICMP message types. There are two subtypes of Multicast Listener Query messages: These two subtypes are differentiated by the contents of the Multicast Address field, as described in section 3.6 of RFC 2710 Note that the table above is not comprehensive. The current complete list of assigned ICMPv6 types can be found at this link: IANA: ICMPv6 Parameters. ICMPv6 provides a minimal level of message integrity verification by the inclusion of a 16-bit checksum in its header. The checksum is calculated starting with a pseudo-header of IPv6 header fields according to the IPv6 standard, which consists of the source and destination addresses, the packet length and the next header field, the latter of which is set to the value 58. Following this pseudo header, the checksum is continued with the ICMPv6 message. The checksum computation is performed according to Internet protocol standards using 16-bit ones' complement summation, followed by a final ones' complement of the checksum itself and inserting it into the checksum field. Note that this differs from the way it is calculated for IPv4 in ICMP, but is similar to the calculation done in TCP. The payload of an ICMPv6 message varies according to the type of message being sent. It begins at bit 32 immediately after the header described above. For some messages such as destination unreachable or time exceeded there is no defined message body. Others define a use only for the first four bytes of the body with no other defined content: In the case of NDP messages the first four bytes are either reserved or used for flags/hoplimit. While the rest of the body has unspecified structured data: For a redirect the first bytes of the message body are reserved but not used. This is followed by a Target and destination address. Unspecified options can be attached to the end: Message processing When an ICMPv6 node receives a packet, it must undertake actions that depend on the type of message. The ICMPv6 protocol must limit the number of error messages sent to the same destination to avoid network overloading. For example, if a node continues to forward erroneous packets, ICMP will signal the error to the first packet and then do so periodically, with a fixed minimum period or with a fixed network maximum load. An ICMP error message must never be sent in response to another ICMP error message. References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Johannes_Kepler] | [TOKENS: 13326] |
Contents Johannes Kepler Page version status This is an accepted version of this page Johannes Kepler[a] (27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and music theorist. He is a key figure in the 17th-century Scientific Revolution, best known for his laws of planetary motion, and his books Astronomia nova, Harmonice Mundi, and Epitome Astronomiae Copernicanae. The variety and impact of his work made Kepler one of the founders and fathers of modern astronomy, the scientific method, natural science, and modern science. He has been described as the "father of science fiction" for his novel Somnium. Kepler was a mathematics teacher at a seminary school in Graz, where he became an associate of Prince Hans Ulrich von Eggenberg. Later he became an assistant to the astronomer Tycho Brahe in Prague, and eventually the imperial mathematician to Emperor Rudolf II and his two successors Matthias and Ferdinand II. He also taught mathematics in Linz, and was an adviser to General Wallenstein. Kepler lived in an era when there was no clear distinction between astronomy and astrology, but there was a strong division between astronomy (a branch of mathematics within the liberal arts) and physics (a branch of natural philosophy). Kepler also incorporated religious arguments and reasoning into his work, motivated by the religious conviction and belief that God had created the world according to an intelligible plan that is accessible through the natural light of reason. Kepler described his new astronomy as "celestial physics", as "an excursion into Aristotle's Metaphysics", and as "a supplement to Aristotle's On the Heavens", transforming the ancient tradition of physical cosmology by treating astronomy as part of a universal mathematical physics. Additionally, he did fundamental work in the field of optics, being named the father of modern optics, in particular for his Astronomiae pars optica. He also invented an improved version of the refracting telescope, the Keplerian telescope, which became the foundation of the modern refracting telescope, while also improving on the telescope design by Galileo Galilei, who mentioned Kepler's discoveries in his work. He postulated the Kepler conjecture. Kepler influenced among others Isaac Newton, providing one of the foundations for his theory of universal gravitation. Early life Kepler was born on 27 December 1571, in the Free Imperial City of Weil der Stadt (now part of the Stuttgart Region in the German state of Baden-Württemberg). His parents were Lutheran, but it is presumed that he was baptized a Catholic, as Protestant baptisms were not permitted in Weil at that time. His grandfather, Sebald Kepler, had been Lord Mayor of the city. By the time Johannes was born, the Kepler family fortune was in decline. His father, Heinrich Kepler, earned a precarious living as a mercenary, and he left the family when Johannes was five years old. He was believed to have died in the Eighty Years' War in the Netherlands where, although a Protestant, he was fighting in the Catholic Spanish army. His mother, Katharina Guldenmann, an innkeeper's daughter, was a healer and herbalist. Johannes had six siblings, of which two brothers and one sister survived to adulthood. Born prematurely, he claimed to have been weak and sickly as a child. Nevertheless, he often impressed travelers at his grandfather's inn with his phenomenal mathematical faculty. He was introduced to astronomy at an early age and developed a strong passion for it that would span his entire life. At age six, he observed the Great Comet of 1577, writing that he "was taken by [his] mother to a high place to look at it." In 1580, at age nine, he observed another astronomical event, a lunar eclipse, recording that he remembered being "called outdoors" to see it and that the Moon "appeared quite red". However, childhood smallpox left him with weak vision and crippled hands, limiting his ability in the observational aspects of astronomy. Kepler attended the Grammar School in Weil until 1577, when the family moved to Leonberg in Protestant Württemberg. He attended the elementary German school in Leonberg for a year, and then the Latin Grammar School, where all lessons and books were in Latin. He was then at two monastic schools, from 1584 in Adelberg, and from 1586 at the seminary at Maulbronn. In September 1589, Kepler entered the Tübinger Stift at the University of Tübingen, a seminary which served to prepare Lutheran pastors for Württemberg. There, he studied philosophy under Vitus Müller and theology under Jacob Heerbrand (a student of Philipp Melanchthon at Wittenberg), who also taught Michael Maestlin while he was a student, until he became Chancellor at Tübingen in 1590. He proved himself to be a superb mathematician and earned a reputation as a skillful astrologer, casting horoscopes for fellow students. Under the instruction of Michael Maestlin, Tübingen's professor of mathematics from 1583 to 1631, he learned both the Ptolemaic system and the Copernican system of planetary motion. He became a Copernican at that time. In a student disputation, he defended heliocentrism from both a theoretical and theological perspective, maintaining that the Sun was the principal source of motive power in the universe. Despite his desire to become a minister in the Lutheran church, he was denied ordination because of beliefs contrary to the Formula of Concord, the Lutheran statement of faith which had been adopted in 1577. Near the end of his studies, Kepler was recommended for a position as teacher of mathematics and astronomy at the Protestant school in Graz, in Styria, Inner Austria. He accepted the position in April 1594, at the age of 22. During his time in Graz (1594–1600), he issued many official calendars and prognostications that enhanced his reputation as an astrologer. Although Kepler had mixed feelings about astrology and disparaged many customary practices of astrologers, he believed deeply in a connection between the cosmos and the individual. He eventually published some of the ideas he had entertained while a student in the Mysterium Cosmographicum (1596), published a little over a year after his arrival at Graz. In December 1595, Kepler was introduced to Barbara Müller, a 23-year-old widow (twice over) with a young daughter, Regina Lorenz, and he began courting her. Müller, an heiress to the estates of her late husbands, was also the daughter of a successful mill owner. Her father Jobst initially opposed a marriage. Even though Kepler had inherited his grandfather's nobility, Kepler's poverty made him an unacceptable match. Jobst relented after Kepler completed work on Mysterium, but the engagement nearly fell apart while Kepler was away tending to the details of publication. However, Protestant officials—who had helped set up the match—pressured the Müllers to honor their agreement. Barbara and Johannes were married on 27 April 1597. In the first years of their marriage, the Keplers had two children (Heinrich and Susanna), both of whom died in infancy. In 1602, they had a daughter (Susanna); in 1604, a son (Friedrich); and in 1607, another son (Ludwig). Following the publication of Mysterium and with the blessing of the Graz school inspectors, Kepler began an ambitious program to extend and elaborate his work. He planned four additional books: one on the stationary aspects of the universe (the Sun and the fixed stars); one on the planets and their motions; one on the physical nature of planets and the formation of geographical features (focused especially on Earth); and one on the effects of the heavens on the Earth, to include atmospheric optics, meteorology, and astrology. He also sought the opinions of many of the astronomers to whom he had sent Mysterium, among them Reimarus Ursus (Nicolaus Reimers Bär)—the imperial mathematician to Rudolf II and a bitter rival of Tycho Brahe. Ursus did not reply directly, but republished Kepler's flattering letter to pursue his priority dispute over (what is now called) the Tychonic system with Tycho. Despite this black mark, Tycho also began corresponding with Kepler, starting with a harsh but legitimate critique of Kepler's system; among a host of objections, Tycho took issue with the use of inaccurate numerical data taken from Copernicus. Through their letters, Tycho and Kepler discussed a broad range of astronomical problems, dwelling on lunar phenomena and Copernican theory (particularly its theological viability). But without the significantly more accurate data of Tycho's observatory, Kepler had no way to address many of these issues. Instead, he turned his attention to chronology and "harmony", the numerological relationships among music, mathematics and the physical world, and their astrological consequences. By assuming the Earth to possess a soul (a property he would later invoke to explain how the Sun causes the motion of planets), he established a speculative system connecting astrological aspects and astronomical distances to weather and other earthly phenomena. By 1599, however, he again felt his work limited by the inaccuracy of available data—just as growing religious tension was also threatening his continued employment in Graz. Graz was a largely Protestant, mostly Lutheran, city, while the ruler of Inner Austria was a Catholic Habsburg. In 1578, Duke Charles II had granted considerable privileges to Protestants in the Pacification of Bruck. Charles died in 1590, when his son and heir Ferdinand II was 12 years old. Ferdinand was educated in the Jesuit College and University of Ingolstadt, and became full ruler of Inner Austria in 1596. He travelled to Italy in 1598, and returned with a determination to restore the true Catholic faith and eliminate heresy. Kepler wrote to a friend in June of that year expressing his foreboding for the future. As Ferdinand's biographer Robert L. Bireley wrote, his fears were justified, as the Counter-Reformation gained strength. In September 1598, Ferdinand ordered all Protestant preachers and teachers to leave the country. Kepler was exempted from the decree, but did not feel secure, and looked for alternatives. He learned that Tycho Brahe had been appointed Imperial Mathematician in Prague, and Kepler re-established contact. In December 1599, Tycho invited Kepler to visit him in Prague; on 1 January 1600 (before he even received the invitation), Kepler set off in the hopes that Tycho's patronage could solve his philosophical problems as well as his social and financial ones. On 4 February 1600, Kepler met Tycho Brahe and his assistants Franz Tengnagel and Longomontanus at Benátky nad Jizerou (35 km from Prague), the site where Tycho's new observatory was being constructed. Over the next two months, he stayed as a guest, analyzing some of Tycho's observations of Mars; Tycho guarded his data closely, but was impressed by Kepler's theoretical ideas and soon allowed him more access. Kepler planned to test his theory from Mysterium Cosmographicum based on the Mars data, but he estimated that the work would take up to two years (since he was not allowed to simply copy the data for his own use). With the help of Johannes Jessenius, Kepler attempted to negotiate a more formal employment arrangement with Tycho, but negotiations broke down in an angry argument and Kepler left for Prague on 6 April. Kepler and Tycho soon reconciled and eventually reached an agreement on salary and living arrangements, and in June, Kepler returned home to Graz to collect his family. The situation in Graz made it impossible to return immediately to Brahe; in hopes of continuing his astronomical studies, Kepler sought an appointment as a mathematician to Duke Ferdinand. To that end, Kepler composed an essay—dedicated to Ferdinand—in which he proposed a force-based theory of lunar motion: "In Terra inest virtus, quae Lunam ciet" ("There is a force in the earth which causes the moon to move"). Though the essay did not earn him a place in Ferdinand's court, it did detail a new method for measuring lunar eclipses, which he applied during the 10 July eclipse in Graz. These observations formed the basis of his explorations of the laws of optics that would culminate in Astronomiae Pars Optica. Then on 17 July a new decree was announced, ordering all inhabitants to renounce the Protestant faith or leave the province. This time there was no exception for Kepler, and he and his wife and step-daughter left Graz for Prague on 30 September 1600. Scientific career Once established in Prague, he was supported directly by Tycho, who assigned him to analyzing planetary observations and writing a tract against Tycho's (by then deceased) rival, Ursus. In September, Tycho secured him a commission as a collaborator on the new project he had proposed to the emperor: the Rudolphine Tables that should replace the Prutenic Tables of Erasmus Reinhold. Two days after Tycho's unexpected death on 24 October 1601, Kepler was appointed his successor as the imperial mathematician with the responsibility to complete his unfinished work. The next 11 years as imperial mathematician would be the most productive of his life. Kepler's primary obligation as imperial mathematician was to provide astrological advice to the emperor, Rudolf II. Though Kepler took a dim view of the attempts of contemporary astrologers to precisely predict the future or divine specific events, he had been casting well-received detailed horoscopes for friends, family, and patrons since his time as a student in Tübingen. In addition to horoscopes for allies and foreign leaders, the emperor sought Kepler's advice in times of political trouble. Rudolf was actively interested in the work of many of his court scholars (including numerous alchemists) and kept up with Kepler's work in physical astronomy as well. Officially, the only acceptable religious doctrines in Prague were Catholic and Utraquist, but Kepler's position in the imperial court allowed him to practice his Lutheran faith unhindered. The emperor nominally provided an ample income for his family, but the difficulties of the over-extended imperial treasury meant that actually getting hold of enough money to meet financial obligations was a continual struggle. Partly because of financial troubles, his life at home with Barbara was unpleasant, marred with bickering and bouts of sickness. Court life, however, brought Kepler into contact with other prominent scholars (Johannes Matthäus Wackher von Wackhenfels, Jost Bürgi, David Fabricius, Martin Bachazek, and Johannes Brengger, among others) and astronomical work proceeded rapidly. In October 1604, a bright new evening star (SN 1604) appeared, but Kepler did not believe the rumors until he saw it himself. Kepler began systematically observing the supernova. Astrologically, the end of 1603 marked the beginning of a fiery trigon, the start of the about 800-year cycle of great conjunctions; astrologers associated the two previous such periods with the rise of Charlemagne (c. 800 years earlier) and the birth of Christ (c. 1600 years earlier), and thus expected events of great portent, especially regarding the emperor. It was in this context, as the imperial mathematician and astrologer to the emperor, that Kepler described the new star two years later in his De Stella Nova. In it, Kepler addressed the star's astronomical properties while taking a skeptical approach to the many astrological interpretations then circulating. He noted its fading luminosity, speculated about its origin, and used the lack of observed parallax to argue that it was beyond the planetary orbits, and thus in the sphere of fixed stars, further undermining the doctrine of the immutability of the heavens (the idea accepted since Aristotle that the celestial spheres were perfect and unchanging). The birth of a new star implied the variability of the heavens. Kepler also attached an appendix where he discussed the recent chronology work of the Polish historian Laurentius Suslyga; he calculated that, if Suslyga was correct that accepted timelines were four years behind, then the Star of Bethlehem—analogous to the present new star—would have coincided with the first great conjunction of the earlier 800-year cycle. Over the following years, Kepler attempted (unsuccessfully) to begin a collaboration with Italian astronomer Giovanni Antonio Magini, and dealt with chronology, especially the dating of events in the life of Jesus. Around 1611, Kepler circulated a manuscript of what would eventually be published (posthumously) as Somnium [The Dream]. Part of the purpose of Somnium was to describe what practicing astronomy would be like from the perspective of another planet, to show the feasibility of a non-geocentric system. The manuscript, which disappeared after changing hands several times, described a fantastic trip to the Moon; it was part allegory, part autobiography, and part treatise on interplanetary travel (and is sometimes described as the first work of science fiction). Years later, a distorted version of the story may have instigated the witchcraft trial against his mother, as the mother of the narrator consults a demon to learn the means of space travel. Following her eventual acquittal, Kepler composed 223 footnotes to the story—several times longer than the actual text—which explained the allegorical aspects as well as the considerable scientific content (particularly regarding lunar geography) hidden within the text. Later life During Kepler's time in Prague, religious and political tensions were building up in the Empire, both between Protestants and Catholics, and within the Habsburg dynasty over the isssue of succession. The situation in Prague, a cosmopolitan city, became increasingly difficult, and Kepler considered a move to Württemberg, which he considered his homeland. In 1609 he wrote to the Duke, Johann Frederick, requesting a position in the University of Tübingen. The Duke turned down the request, but sent a present as a token of goodwill. Kepler replied, and in his letter summarised his position on the doctrinal issues that had caused problems in the past. The Duke did not respond to this. Two years later, he tried again, but this time the request was referred to the theological consistory in Stuttgart, who rejected Kepler's request on 25 April 1611, denouncing his Calvinist leanings both in his reservations about the Formula of Concord, and his insistence that Calvinists should, despite disagreements, be considered "brothers in Christ". In 1611, Emperor Rudolf's health was failing, and he was forced to abdicate as King of Bohemia by his brother Matthias. Both sides sought Kepler's astrological advice, an opportunity he used to deliver conciliatory political advice (with little reference to the stars, except in general statements to discourage drastic action). However, it was clear that Kepler's future prospects in the court of Matthias were bleak. Also in that year, Kepler's wife Barbara contracted Hungarian spotted fever and began having seizures. While she was recovering, all three of their children fell sick with smallpox; six-year-old Friedrich died. As well as his approach to Württemberg, Kepler was in contact with Padua. The University of Padua — on the recommendation of the departing Galileo — sought Kepler to fill the mathematics professorship, but Kepler, preferring to keep his family in German territory, instead travelled to Austria to arrange a position as teacher and district mathematician in Linz. However, Barbara relapsed into illness and died shortly after Kepler's return. Postponing the move to Linz, Kepler remained in Prague until Rudolf's death in early 1612, though political upheaval, religious tension, and family tragedy (along with the legal dispute over his wife's estate) prevented him from doing any research. Instead, he pieced together a chronology manuscript, Eclogae Chronicae, from correspondence and earlier work. Upon his succession as Holy Roman Emperor, Matthias re-affirmed Kepler's position (and salary) as imperial mathematician but allowed him to move to Linz. In Linz, Kepler was appointed District Mathematician and teacher in the district school, as well as retaining his position as court mathematician to the Emperor. His first charge was completing the Rudolphine tables, but many other activities claimed his attention before these were completed. The tables were not published until 1627. In Linz, Kepler's difficulties with Lutheran orthodoxy re-surfaced. The Counter-Reformation had not yet had a major impact on Upper Austria. While the ruler was Catholic, the majority of the population were Lutheran and were able to practice their faith. But the pastor of the Lutheran congregation, Daniel Hitzler, refused communion to Kepler on account of his unwillingness to fully endorse the Formula of Concord. The main issue was Kepler's views on the doctrine of ubiquity or Sacramental union, the belief in the real presence of Christ's body and blood in the Eucharist, which Kepler could not accept. Kepler appealed to the Stuttgart Consistory against his exclusion, and this led to a long correspondence. This involved various theologians including Matthias Hafenreffer. Hafenreffer had been a friend, but on this issue sided with the theological authorities. In 1619 his excommunication was finally and unequivocally declared. In July 1612, Kepler met Matthias Bernegger, the humanist scholar and astronomer. Bernegger knew Kepler by reputation, and had sought him out. The two men became friends, and had extensive correspondence for nearly twenty years, although they never met again. Max Caspar described him as "the best and most faithful friend that he ever found". In an early letter to Bernegger, in October 1613, Kepler tells his friend of his forthcoming marriage, and announces the date as "the day of the eclipse of the moon, when the astronomical spirit is in hiding, as I want to rejoice in the festival day". The day was 30 October 1613, and Kepler's second wife was Susanna Reuttinger from nearby Eferding. Following the death of his first wife Barbara, Kepler had considered 11 different matches over two years (a decision process formalized later as the marriage problem). He eventually returned to Reuttinger (the fifth match) who, he wrote, "won me over with love, humble loyalty, economy of household, diligence, and the love she gave the stepchildren". Kepler was now able to bring his children to Linz from Wels, where they had been staying with a relative. The first three children of his marriage to Susanna (Margareta Regina, Katharina, and Sebald) died in childhood. Three more survived into adulthood: Cordula (born 1621); Fridmar (born 1623); and Hildebert (born 1625). According to Kepler's biographers, this was a much happier marriage than his first. In December 1615 Kepler received a letter from his family in Württemberg informing him that his mother Katharina, had been accused of witchcraft earlier that year. Katharina lived in the Protestant town of Leonberg. The initial accusation was made by Ursula Reinbold, who claimed that Katharina had given her a drink that made her ill. As the case became known, more rumours and accusations circulated, and Katharina's family raised an action for slander against the accusers. Kepler vowed to defend his mother, which he did both by despatches sent to the authorities in Leonberg, and by visiting in person. The case dragged in for several years, with Katharina held in prison from 1620-1621. The final stage was held in Tübingen, under the authority of the Duke, where it was determined that she should be questioned under the threat of torture. She refused to confess, saying she trusted to God to bring the truth to light. She was then absolved and discharged, being released on 4 October, 1621. She died about six months later. The process against Kepler's mother, starting soon after his initial excommunication, has been seen as part of an attack by the Lutheran authorites against Kepler himself. Kepler had other difficulties at this time. In 1618 the conflict that would become the Thirty Years' War began with the Bohemian Revolt against Habsburg rule. Ferdinand II, who became Emperor in August 1619, secured the support of Maximilian, Duke of Bavaria against the Bohemians. In July 1620, the Bavarian army entered Linz on the way to Bohemia. This posed a threat to the Protestants of Linz generally, as well as to Kepler, whose sympathies were with the Bohemians, now led by the Protestant Frederick, who had been declared King of Bohemia. Kepler had openly expressed his admiration for Fredericks's father-in-law, James VI and I King of England and Scotland, who he considered an important peacekeeper. He left Linz for Württemberg in September 1620 to defend his mother, taking his family with him as he did not know if he would be able to return. In November of that year the Bohemian forces were defeated at the Battle of White Mountain, and Frederick (the "Winter King") fled into exile. In November 1621, after his mother's release, Kepler did return to Linz. In December, Emperor Ferdinand confirmed him in his position as court mathematician. In 1622 Protestant preachers and schoolmasters were banished from Upper Austria, but Kepler was exempted as he was in Imperial service. He would remain in Linz for another four years, and complete the Rudolphine Tables. During his time in Linz, Kepler published a number of works. The first was a treatise on the year of the year of the birth of Jesus. This was first published in German in 1613; an expanded Latin version was published the following year as De vero anno. In 1613 he was involved with another chronological issue when the Emporer summoned him to Regensburg to take part in deliberations on the calendar. The Gregorian calendar, the one in general use today, had been introduced by authority of Pope Gregory XIII in 1582, and adopted in much of Catholic Europe. The main changes from the Julian calendar which it superseded were to remove three leap tears in every four centuries, to bring the calendar year in close alignment to the solar year, and to insert 10 days to correct the "drift" that had occurred since the Julian calendar was introduced, so that Thursday 4 October 1582 was followed by Friday 15 October 1582. The new calendar was denounced by Protestant authorities as at best an attempt to re-assert Papal authority in Protestant lands, and at worst as the work of the Devil. Kepler supported the new calendar on practical and astronomical grounds, but the reform was not accepted - it would be 1700 before the new calendar was adopted throughout Germany. Kepler's next work was on measurement. Kepler, buying wine for his household in 1613, observed at first hand the standard method of determining the volume of a barrel, by inserting a measuring rod diagonally from the opening to the bottomm of the cask. This led him to an analysis of the volumes of various shaped containers. Finding that no printer in Augsburg was willing to publish a book in Latin, he brought the printer Johannes Plank from Erfurt to Linz. Plank printed Nova stereometria doliorum vinariorum in 1615, the first book to be printed in Linz, at Kepler's own expense. A shortened German version was published the following year. Kepler's next work was his Epitome Astronomia Copernicae, a summary of Copernican theory, published in two volumes in 1618. In the following year, Kepler's work on Comets, De cometis libelli tres, was published in Augsburg. This book included much observational data and calculation, as well as astrological interpretation. Also in 1619 Kepler's Harmonice Mundi was published. This work, aligning heavenly harmonies with musical ones, had a long gestation. Kepler had first drafted an outline in 1599. In 1618, his little daughter Katharina died, and the grieving father put aside the tables, which required peace, and turned to thinking about harmony. In that same year, he discovered what is now referred to as Kepler's Third Law, relating the orbital period of a planet to its distance from the sun. This finding was first stated in the Harmonice. In 1617, while working on the Tables, Kepler first read Naper's work on logarithms, which had been published in 1614. He realised the value of the method for simplifying the many calculations required in the Tables, but was dissatisfied that Napier presented only the method and not the derivation. So he developed the idea from arithmetic principles, and derived his own table from them. These tables had the advantage that they could be used directly on whole numbers and not just on trigonometric functions. This was published as Chilias logarithmorum ad totidem numeros rotundos in 1624. In the same year he completed work on the Rudolphine Tables. There were negotiations with the Brahe family before the work was ready for printing, and then issues with funding and choice of printer, a choice of printer. Kepler favoured Ulm, because the technical requirements of the work could be most readily met there, but the Emperor insisted it be printed in Austria, which in practice meant Linz, so Kepler set about obtaining suitable equipment, type, paper and workmen, travelling to Vienna and Nuremburg. But before work was fully underway, the city of Linz was besieged from June to August 1626 during the Peasant War. Kepler was unharmed, but the house and printing works, which were on the outskirts of the city, were destroyed by fire. As it was now impossible to complete printing in Linz, Kepler asked the Emperor for permission to move to Ulm. This was granted, and he left for Ulm in November, leaving his wife and family in Regensburg. Kepler had already identified a suitable printer in Ulm, his manuscript had not been damaged in the fire, and printing of the Tables soon got under way, and was completed in September 1627. Kepler was now looking for a stable position. The war had been going well for the Empire. The Peasant Uprising had been suppresssed, and the Imperial commanders Wallenstein and Tilly had defeated Protestant forces including the Danish army under King Christian IV, who had come into the war on the Protestant side. Kepler travelled to Prague to present his Tables to the Emperor. He was nervous about his reception, as the rise in Catholic power might make his position difficult. But he received a warm welcome from the Emperor who was very interested in the Tables. Wallenstein was also in Prague at this time, and had recently been granted the Dukedom of Sagan in Silesia. The two men had been in touch before, when Kepler provided a horoscope through an intermediary, and did not meet Wallenstein in person. Wallenstein negotiated with the Emperor, and invited Kepler to take up residence in Sagan. Kepler travelled to Linz to wind up his affairs there, then travelled with his family to Sagan, where he arrived on 20 July 1628. Kepler felt isolated in this North German city with its unfamiliar dialect. He wrote to Bernegger in March 1629: It is loneliness whick makes me oppressed here, far away from the large cities, and letters come and go only slowly, and are causing great expense. In December 1629 Kepler was able to establish a printing press, which published his Ephemerides for the years 1621-1639. The move to Sagan had not solved Kepler's financial problems. He got little assistance from Wallenstein apart from his salary, and the Ephemerides were printed at his own expense. He was still owed considerable sums from the Imperial treasury for work he had done previously, so on 8 October 1630, he set out for Regensburg, hoping to collect at least some of this. However, a few days after reaching Regensburg, he became sick and progressively worsened. Kepler died on 15 November 1630, just over a month after his arrival. He was buried in a Protestant churchyard in Regensburg, which was later completely destroyed during the war. Kepler's belief that God created the cosmos in an orderly fashion caused him to attempt to determine and comprehend the laws that govern the natural world, most profoundly in astronomy. The phrase "I am merely thinking God's thoughts after Him" has been attributed to him, although this is probably a capsulized version of a writing from his hand: Those laws [of nature] are within the grasp of the human mind; God wanted us to recognize them by creating us after his own image so that we could share in his own thoughts. Kepler advocated for tolerance among Christian denominations, for example arguing that Catholics and Lutherans should be able to take communion together. He wrote, "Christ the Lord neither was nor is Lutheran, nor Calvinist, nor Papist." Astronomy Kepler's first major astronomical work was Mysterium Cosmographicum (The Cosmographic Mystery, 1596). Kepler claimed to have had an epiphany on 19 July 1595, while teaching in Graz, demonstrating the periodic conjunction of Saturn and Jupiter in the zodiac: he realized that regular polygons bound one inscribed and one circumscribed circle at definite ratios, which, he reasoned, might be the geometrical basis of the universe. After failing to find a unique arrangement of polygons that fit known astronomical observations (even with extra planets added to the system), Kepler began experimenting with 3-dimensional polyhedra. He found that each of the five Platonic solids could be inscribed and circumscribed by spherical orbs; nesting these solids, each encased in a sphere, within one another would produce six layers, corresponding to the six known planets—Mercury, Venus, Earth, Mars, Jupiter, and Saturn. By ordering the solids selectively—octahedron, icosahedron, dodecahedron, tetrahedron, cube—Kepler found that the spheres could be placed at intervals corresponding to the relative sizes of each planet's path, assuming the planets circle the Sun. Kepler also found a formula relating the size of each planet's orb to the length of its orbital period: from inner to outer planets, the ratio of increase in orbital period is twice the difference in orb radius. Kepler thought the Mysterium had revealed God's geometrical plan for the universe. Much of Kepler's enthusiasm for the Copernican system stemmed from his theological convictions about the connection between the physical and the spiritual; the universe itself was an image of God, with the Sun corresponding to the Father, the stellar sphere to the Son, and the intervening space between them to the Holy Spirit. His first manuscript of Mysterium contained an extensive chapter reconciling heliocentrism with biblical passages that seemed to support geocentrism. With the support of his mentor Michael Maestlin, Kepler received permission from the Tübingen university senate to publish his manuscript, pending removal of the Bible exegesis and the addition of a simpler, more understandable, description of the Copernican system as well as Kepler's new ideas. Mysterium was published late in 1596, and Kepler received his copies and began sending them to prominent astronomers and patrons early in 1597; it was not widely read, but it established Kepler's reputation as a highly skilled astronomer. The effusive dedication, to powerful patrons as well as to the men who controlled his position in Graz, also provided a crucial doorway into the patronage system. In 1621, Kepler published an expanded second edition of Mysterium, half as long again as the first, detailing in footnotes the corrections and improvements he had achieved in the 25 years since its first publication. In terms of impact, the Mysterium can be seen as an important first step in modernizing the theory proposed by Copernicus in his De revolutionibus orbium coelestium. While Copernicus sought to advance a heliocentric system in this book, he resorted to Ptolemaic devices (viz., epicycles and eccentric circles) in order to explain the change in planets' orbital speed, and also continued to use as a point of reference the center of the Earth's orbit rather than that of the Sun "as an aid to calculation and in order not to confuse the reader by diverging too much from Ptolemy." Modern astronomy owes much to Mysterium Cosmographicum, despite flaws in its main thesis, "since it represents the first step in cleansing the Copernican system of the remnants of the Ptolemaic theory still clinging to it." Kepler never abandoned his five solids theory, publishing the second edition of Mysterium in 1621 and affirming his continued belief in the validity of the model. Although he noted that there were discrepancies between the observational data and his model's predictions, he did not think they were large enough to invalidate the theory. The extended line of research that culminated in Astronomia Nova (A New Astronomy)—including the first two laws of planetary motion—began with the analysis, under Tycho's direction, of the orbit of Mars. In this work Kepler introduced the revolutionary concept of planetary orbit, a path of a planet in space resulting from the action of physical causes, distinct from previously held notion of planetary orb (a spherical shell to which planet is attached). As a result of this breakthrough astronomical phenomena came to be seen as being governed by physical laws. Kepler calculated and recalculated various approximations of Mars's orbit using an equant (the mathematical tool that Copernicus had eliminated with his system), eventually creating a model that generally agreed with Tycho's observations to within two arcminutes (the average measurement error). But he was not satisfied with the complex and still slightly inaccurate result; at certain points the model differed from the data by up to eight arcminutes. The wide array of traditional mathematical astronomy methods having failed him, Kepler set about trying to fit an ovoid orbit to the data. In Kepler's religious view of the cosmos, the Sun (a symbol of God the Father) was the source of motive force in the Solar System. As a physical basis, Kepler drew by analogy on William Gilbert's theory of the magnetic soul of the Earth from De Magnete (1600) and on his own work on optics. Kepler supposed that the motive power (or motive species) radiated by the Sun weakens with distance, causing faster or slower motion as planets move closer or farther from it. Using a physical model to derive a trajectory was a major breakthrough. Kepler did not simply assume a circular orbit but attempted to come up with its cause, and did this before discovering the area law Perhaps this assumption entailed a mathematical relationship that would restore astronomical order. Based on measurements of the aphelion and perihelion of the Earth and Mars, he created a formula in which a planet's rate of motion is inversely proportional to its distance from the Sun. Verifying this relationship throughout the orbital cycle required very extensive calculation; to simplify this task, by late 1602 Kepler reformulated the proportion in terms of geometry: planets sweep out equal areas in equal times—his second law of planetary motion. He then set about calculating the entire orbit of Mars, using the geometrical rate law and assuming an egg-shaped ovoid orbit. After approximately 40 failed attempts, in late 1604 he at last hit upon the idea of an ellipse, which he had previously assumed to be too simple a solution for earlier astronomers to have overlooked. Finding that an elliptical orbit fit the Mars data (the Vicarious Hypothesis), Kepler immediately concluded that all planets move in ellipses, with the Sun at one focus—his first law of planetary motion. Because he employed no calculating assistants, he did not extend the mathematical analysis beyond Mars. By the end of the year, he completed the manuscript for Astronomia nova, though it would not be published until 1609 due to legal disputes over the use of Tycho's observations, the property of his heirs. Since completing the Astronomia Nova, Kepler had intended to compose an astronomy textbook that would cover all the fundamentals of heliocentric astronomy. Kepler spent the next several years working on what would become Epitome Astronomiae Copernicanae (Epitome of Copernican Astronomy). Despite its title, which merely hints at heliocentrism, the Epitome is less about Copernicus's work and more about Kepler's own astronomical system. The Epitome contained all three laws of planetary motion and attempted to explain heavenly motions through physical causes. Although it explicitly extended the first two laws of planetary motion (applied to Mars in Astronomia nova) to all the planets as well as the Moon and the Medicean satellites of Jupiter, it did not explain how elliptical orbits could be derived from observational data. Originally intended as an introduction for the uninitiated, Kepler sought to model his Epitome after that of his master Michael Maestlin, who published a well-regarded book explaining the basics of geocentric astronomy to non-experts. Kepler completed the first of three volumes, consisting of Books I–III, by 1615 in the same question-answer format of Maestlin's and have it printed in 1617. However, the banning of Copernican books by the Catholic Church, as well as the start of the Thirty Years' War, meant that publication of the next two volumes would be delayed. In the interim, and to avoid being subject to the ban, Kepler switched the audience of the Epitome from beginners to that of expert astronomers and mathematicians, as the arguments became more and more sophisticated and required advanced mathematics to be understood. The second volume, consisting of Book IV, was published in 1620, followed by the third volume, consisting of Books V–VII, in 1621. In the years following the completion of Astronomia Nova, most of Kepler's research was focused on preparations for the Rudolphine Tables and a comprehensive set of ephemerides (specific predictions of planet and star positions) based on the table, though neither would be completed for many years. Kepler, at last, completed the Rudolphine Tables in 1623, which at the time was considered his major work. However, due to the publishing requirements of the emperor and negotiations with Tycho Brahe's heir, it would not be printed until 1627. Astrology Like Ptolemy, Kepler considered astrology as the counterpart to astronomy, and as being of equal interest and value. However, in the following years, the two subjects drifted apart until astrology was no longer practiced among professional astronomers. Sir Oliver Lodge observed that Kepler was somewhat disdainful of astrology in his own day, as he was "continually attacking and throwing sarcasm at astrology, but it was the only thing for which people would pay him, and on it after a fashion he lived. Nonetheless, Kepler spent a huge amount of time trying to restore astrology on a firmer philosophical footing, composing numerous astrological calendars, more than 800 nativities, and a number of treatises dealing with the subject of astrology proper. In his bid to become imperial astronomer, Kepler wrote De Fundamentis (1601), whose full title can be translated as "On Giving Astrology Sounder Foundations", as a short foreword to one of his yearly almanacs. In this work, Kepler describes the effects of the Sun, Moon, and the planets in terms of their light and their influences upon humors, concluding with Kepler's view that the Earth possesses a soul with some sense of geometry. Stimulated by the geometric convergence of rays formed around it, the world-soul is sentient but not conscious. As a shepherd is pleased by the piping of a flute without understanding the theory of musical harmony, so likewise Earth responds to the angles and aspects made by the heavens but not in a conscious manner. Eclipses are important as omens because the animal faculty of the Earth is violently disturbed by the sudden intermission of light, experiencing something like emotion and persisting in it for some time. Kepler surmises that the Earth has "cycles of humors" as living animals do, and provides as an example: "the highest tides of the sea are said by sailors to return after nineteen years around the same days of the year". (This may refer to the 18.6-year lunar node precession cycle.) Kepler advocates searching for such cycles by gathering observations over a period of many years, "and so far this observation has not been made". Kepler and Helisaeus Roeslin engaged in a series of published attacks and counter-attacks on the importance of astrology after the supernova of 1604; around the same time, physician Philip Feselius published a work dismissing astrology altogether (and Roeslin's work in particular). In response to what Kepler saw as the excesses of astrology, on the one hand, and overzealous rejection of it, on the other, Kepler prepared Tertius Interveniens (1610). Nominally this work—presented to the common patron of Roeslin and Feselius—was a neutral mediation between the feuding scholars (the titled meaning "Third-party interventions"), but it also set out Kepler's general views on the value of astrology, including some hypothesized mechanisms of interaction between planets and individual souls. While Kepler considered most traditional rules and methods of astrology to be the "evil-smelling dung" in which "an industrious hen" scrapes, there was an "occasional grain-seed, indeed, even a pearl or a gold nugget" to be found by the conscientious scientific astrologer. Music Kepler was convinced "that the geometrical things have provided the Creator with the model for decorating the whole world". In Harmonice Mundi (1619), he attempted to explain the proportions of the natural world—particularly the astronomical and astrological aspects—in terms of music.[note 1] The central set of "harmonies" was the musica universalis or "music of the spheres", which had been studied by Pythagoras, Ptolemy and others before Kepler; in fact, soon after publishing Harmonice Mundi, Kepler was embroiled in a priority dispute with Robert Fludd, who had recently published his own harmonic theory. Kepler began by exploring regular polygons and regular solids, including the figures that would come to be known as Kepler's solids. From there, he extended his harmonic analysis to music, meteorology, and astrology; harmony resulted from the tones made by the souls of heavenly bodies—and in the case of astrology, the interaction between those tones and human souls. In the final portion of the work (Book V), Kepler dealt with planetary motions, especially relationships between orbital velocity and orbital distance from the Sun. Similar relationships had been used by other astronomers, but Kepler—with Tycho's data and his own astronomical theories—treated them much more precisely and attached new physical significance to them. Among many other harmonies, Kepler articulated what came to be known as the third law of planetary motion. He tried many combinations until he discovered that (approximately) "The square of the periodic times are to each other as the cubes of the mean distances." Although he gives the date of this epiphany (8 March 1618), he does not give any details about how he arrived at this conclusion. However, the wider significance for planetary dynamics of this purely kinematical law was not realized until the 1660s. When conjoined with Christiaan Huygens' newly discovered law of centrifugal force, it enabled Isaac Newton, Edmund Halley, and perhaps Christopher Wren and Robert Hooke to demonstrate independently that the presumed gravitational attraction between the Sun and its planets decreased with the square of the distance between them. This refuted the traditional assumption of scholastic physics that the power of gravitational attraction remained constant with distance whenever it applied between two bodies, such as was assumed by Kepler and also by Galileo in his mistaken universal law that gravitational fall is uniformly accelerated, and also by Galileo's student Borrelli in his 1666 celestial mechanics. Optics As Kepler slowly continued analyzing Tycho's Mars observations—now available to him in their entirety—and began the slow process of tabulating the Rudolphine Tables, Kepler also picked up the investigation of the laws of optics from his lunar essay of 1600. Both lunar and solar eclipses presented unexplained phenomena, such as unexpected shadow sizes, the red color of a total lunar eclipse, and the reportedly unusual light surrounding a total solar eclipse. Related issues of atmospheric refraction applied to all astronomical observations. Through most of 1603, Kepler paused his other work to focus on optical theory; the resulting manuscript, presented to the emperor on 1 January 1604, was published as Astronomiae Pars Optica (The Optical Part of Astronomy). In it, Kepler described the inverse-square law governing the intensity of light, reflection by flat and curved mirrors, and principles of pinhole cameras, as well as the astronomical implications of optics such as parallax and the apparent sizes of heavenly bodies. He also extended his study of optics to the human eye, and is generally considered by neuroscientists to be the first to recognize that images are projected inverted and reversed by the eye's lens onto the retina. The solution to this dilemma was not of particular importance to Kepler as he did not see it as pertaining to optics, although he did suggest that the image was later corrected "in the hollows of the brain" due to the "activity of the Soul." Today, Astronomiae Pars Optica is generally recognized as the foundation of modern optics (though the law of refraction is conspicuously absent). With respect to the beginnings of projective geometry, Kepler introduced the idea of continuous change of a mathematical entity in this work. He argued that if a focus of a conic section were allowed to move along the line joining the foci, the geometric form would morph or degenerate, one into another. In this way, an ellipse becomes a parabola when a focus moves toward infinity, and when two foci of an ellipse merge into one another, a circle is formed. As the foci of a hyperbola merge into one another, the hyperbola becomes a pair of straight lines. He also assumed that if a straight line is extended to infinity it will meet itself at a single point at infinity, thus having the properties of a large circle. In the first months of 1610, Galileo Galilei—using his powerful new telescope—discovered four satellites orbiting Jupiter. Upon publishing his account as Sidereus Nuncius [Starry Messenger], Galileo sought the opinion of Kepler, in part to bolster the credibility of his observations. Kepler responded enthusiastically with a short published reply, Dissertatio cum Nuncio Sidereo [Conversation with the Starry Messenger]. He endorsed Galileo's observations and offered a range of speculations about the meaning and implications of Galileo's discoveries and telescopic methods, for astronomy and optics as well as cosmology and astrology. Later that year, Kepler published his own telescopic observations of the moons in Narratio de Jovis Satellitibus, providing further support of Galileo. To Kepler's disappointment, however, Galileo never published his reactions (if any) to Astronomia Nova. Kepler also started a theoretical and experimental investigation of telescopic lenses using a telescope borrowed from Duke Ernest of Cologne. The resulting manuscript was completed in September 1610 and published as Dioptrice in 1611. In it, Kepler set out the theoretical basis of double-convex converging lenses and double-concave diverging lenses—and how they are combined to produce a Galilean telescope—as well as the concepts of real vs. virtual images, upright vs. inverted images, and the effects of focal length on magnification and reduction. He also described an improved telescope—now known as the astronomical or Keplerian telescope—in which two convex lenses can produce higher magnification than Galileo's combination of convex and concave lenses. Mathematics and physics As a New Year's gift that year (1611), he also composed for his friend and some-time patron, Baron Wackher von Wackhenfels, a short pamphlet entitled Strena Seu de Nive Sexangula (A New Year's Gift of Hexagonal Snow). In this treatise, he published the first description of the hexagonal symmetry of snowflakes and, extending the discussion into a hypothetical atomistic physical basis for their symmetry, posed what later became known as the Kepler conjecture, a statement about the most efficient arrangement for packing spheres. This important mathematical problem has practical applications in the understanding of crystalline solids; it was formally solved by Thomas Hales in 2017. Kepler wrote the influential mathematical treatise Nova stereometria doliorum vinariorum in 1613, on measuring the volume of containers such as wine barrels, which was published in 1615. Kepler also contributed to the development of infinitesimal methods and numerical analysis, including iterative approximations, infinitesimals, and the early use of logarithms and transcendental equations. Kepler's work on calculating volumes of shapes, and on finding the optimal shape of a wine barrel, were significant steps toward the development of calculus. Simpson's rule, an approximation method used in integral calculus, is known in German as Keplersche Fassregel (Kepler's barrel rule). Legacy Kepler's laws of planetary motion were not immediately accepted. Several major figures such as Galileo and René Descartes completely ignored Kepler's Astronomia nova. Many astronomers, including Kepler's teacher, Michael Maestlin, objected to Kepler's introduction of physics into his astronomy. Some adopted compromise positions. Ismaël Bullialdus accepted elliptical orbits but replaced Kepler's area law with uniform motion in respect to the empty focus of the ellipse, while Seth Ward used an elliptical orbit with motions defined by an equant. Several astronomers tested Kepler's theory, and its various modifications, against astronomical observations. Two transits of Venus and Mercury across the face of the Sun provided sensitive tests of the theory, under circumstances when these planets could not normally be observed. In the case of the transit of Mercury in 1631, Kepler had been extremely uncertain of the parameters for Mercury, and advised observers to look for the transit the day before and after the predicted date. Pierre Gassendi observed the transit on the date predicted, a confirmation of Kepler's prediction. This was the first observation of a transit of Mercury. However, his attempt to observe the transit of Venus just one month later was unsuccessful due to inaccuracies in the Rudolphine Tables. Gassendi did not realize that it was not visible from most of Europe, including Paris. Jeremiah Horrocks, who observed the 1639 Venus transit, had used his own observations to adjust the parameters of the Keplerian model, predicted the transit, and then built apparatus to observe the transit. He remained a firm advocate of the Keplerian model. Epitome of Copernican Astronomy was read by astronomers throughout Europe, and following Kepler's death, it was the main vehicle for spreading Kepler's ideas. In the period 1630–1650, this book was the most widely used astronomy textbook, winning many converts to ellipse-based astronomy. However, few adopted his ideas on the physical basis for celestial motions. In the late 17th century, a number of physical astronomy theories drawing from Kepler's work—notably those of Giovanni Alfonso Borelli and Robert Hooke—began to incorporate attractive forces (though not the quasi-spiritual motive species postulated by Kepler) and the Cartesian concept of inertia. In Principia Mathematica (1687), Isaac Newton derived Kepler's laws of planetary motion from a force-based theory of universal gravitation, a mathematical challenge later known as "solving the Kepler problem". Beyond his role in the historical development of astronomy and natural philosophy, Kepler has loomed large in the philosophy and historiography of science. Kepler and his laws of motion were central to early histories of astronomy such as Jean-Étienne Montucla's 1758 Histoire des mathématiques and Jean-Baptiste Delambre's 1821 Histoire de l'astronomie moderne. These and other histories written from an Enlightenment perspective treated Kepler's metaphysical and religious arguments with skepticism and disapproval, but later Romantic-era natural philosophers viewed these elements as central to his success. William Whewell, in his influential History of the Inductive Sciences of 1837, found Kepler to be the archetype of the inductive scientific genius; in his Philosophy of the Inductive Sciences of 1840, Whewell held Kepler up as the embodiment of the most advanced forms of scientific method. Similarly, Ernst Friedrich Apelt—the first to extensively study Kepler's manuscripts, after their purchase by Catherine the Great—identified Kepler as a key to the "Revolution of the sciences". Apelt, who saw Kepler's mathematics, aesthetic sensibility, physical ideas, and theology as part of a unified system of thought, produced the first extended analysis of Kepler's life and work. Alexandre Koyré's work on Kepler was, after Apelt, the first major milestone in historical interpretations of Kepler's cosmology and its influence. In the 1930s and 1940s, Koyré, and a number of others in the first generation of professional historians of science, described the "Scientific Revolution" as the central event in the history of science, and Kepler as a (perhaps the) central figure in the revolution. Koyré placed Kepler's theorization, rather than his empirical work, at the center of the intellectual transformation from ancient to modern worldviews. Since the 1960s, the volume of historical Kepler scholarship has expanded greatly, including studies of his astrology and meteorology, his geometrical methods, the role of his religious views in his work, his literary and rhetorical methods, his interaction with the broader cultural and philosophical currents of his time, and even his role as an historian of science. Philosophers of science—such as Charles Sanders Peirce, Norwood Russell Hanson, Stephen Toulmin, and Karl Popper—have repeatedly turned to Kepler: examples of incommensurability, analogical reasoning, falsification, and many other philosophical concepts have been found in Kepler's work. Physicist Wolfgang Pauli even used Kepler's priority dispute with Robert Fludd to explore the implications of analytical psychology on scientific investigation. Modern translations of a number of Kepler's books appeared in the late-nineteenth and early-twentieth centuries, the systematic publication of his collected works began in 1937 (and is nearing completion in the early 21st century). An edition in eight volumes, Kepleri Opera omnia, was prepared by Christian Frisch (1807–1881), during 1858 to 1871, on the occasion of Kepler's 300th birthday. Frisch's edition only included Kepler's Latin, with a Latin commentary. A new edition was planned beginning in 1914 by Walther von Dyck (1856–1934). Dyck compiled copies of Kepler's unedited manuscripts, using international diplomatic contacts to convince the Soviet authorities to lend him the manuscripts kept in Leningrad for photographic reproduction. These manuscripts contained several works by Kepler that had not been available to Frisch. Dyck's photographs remain the basis for the modern editions of Kepler's unpublished manuscripts. Max Caspar (1880–1956) published his German translation of Kepler's Mysterium Cosmographicum in 1923. Both Dyck and Caspar were influenced in their interest in Kepler by mathematician Alexander von Brill (1842–1935). Caspar became Dyck's collaborator, succeeding him as project leader in 1934, establishing the Kepler-Kommission in the following year. Assisted by Martha List (1908–1992) and Franz Hammer (1898–1969), Caspar continued editorial work during World War II. Max Caspar also published a biography of Kepler in 1948. The commission was later chaired by Volker Bialas (during 1976–2003) and Ulrich Grigull (during 1984–1999) and Roland Bulirsch (1998–2014). Kepler has acquired a popular image as an icon of scientific modernity and a man before his time; science popularizer Carl Sagan described him as "the first astrophysicist and the last scientific astrologer". The debate over Kepler's place in the Scientific Revolution has produced a wide variety of philosophical and popular treatments. One of the most influential is Arthur Koestler's 1959 book, The Sleepwalkers: A History of Man's Changing Vision of the Universe, in which Kepler is unambiguously the hero (morally and theologically, as well as intellectually) of the revolution. John Banville's well-received historical novel Kepler (1981) explored many of the themes developed in Koestler's non-fiction narrative and in the philosophy of science. A 2004 nonfiction book, Heavenly Intrigue, speculated that Kepler murdered Tycho Brahe to gain access to his data. In 2010 Tycho Brahe was exhumed by a Dutch-Czech team and his bones, teeth and beard where analyzed for mercury. The results conclusively eliminate mercury poisoning as a cause of Brahe's death. In Austria, a silver collector's 10-euro Johannes Kepler silver coin was minted in 2002. The reverse side of the coin has a portrait of Kepler, who spent some time teaching in Graz and the surrounding areas. Kepler was acquainted with Prince Hans Ulrich von Eggenberg personally, and he probably influenced the construction of Eggenberg Castle (the motif of the obverse of the coin). In front of him on the coin is the model of nested spheres and polyhedra from Mysterium Cosmographicum. The German composer Paul Hindemith wrote an opera about Kepler titled Die Harmonie der Welt (1957), and during the prolonged process of its creation he concurrently wrote a symphony of the same name based on the musical ideas he had developed for the opera. Hindemith's work inspired John Rodgers and Willie Ruff of Yale University to create a synthesizer composition based on Kepler's scheme for representing planetary motion with music. Philip Glass wrote an opera called Kepler (2009) based on Kepler's life, with a libretto in German and Latin by Martina Winkel. Directly named for Kepler's contribution to science are: Kepler's laws of planetary motion; Kepler's Supernova SN 1604, which he observed and described; the Kepler–Poinsot polyhedra (a set of geometrical constructions), two of which were described by him; and the Kepler conjecture on sphere packing. Places and entities named in his honor include multiple city streets and squares, several educational institutions, an asteroid, a lunar crater, and a Martian crater. The Kepler space telescope has observed 530,506 stars and detected 2,778 confirmed planets (as of 16 June 2023[update]), many of them named after the telescope and Kepler himself. Works A critical edition of Kepler's collected works (Johannes Kepler Gesammelte Werke, KGW) in 22 volumes is being edited by the Kepler-Kommission (founded 1935) on behalf of the Bayerische Akademie der Wissenschaften. The Kepler-Kommission also publishes Bibliographia Kepleriana (2nd edition List, 1968), a complete bibliography of editions of Kepler's works, with a supplementary volume to the second edition (ed. Hamel 1998). See also Notes References Sources External links |
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Contents Social network 1800s: Martineau · Tocqueville · Marx · Spencer · Le Bon · Ward · Pareto · Tönnies · Veblen · Simmel · Durkheim · Addams · Mead · Weber · Du Bois · Mannheim · Elias A social network is a social structure consisting of a set of social actors (such as individuals or organizations), networks of dyadic ties, and other social interactions between actors. The social network perspective provides a set of methods for analyzing the structure of whole social entities along with a variety of theories explaining the patterns observed in these structures. The study of these structures uses social network analysis to identify local and global patterns, locate influential entities, and examine dynamics of networks. For instance, social network analysis has been used in studying the spread of misinformation on social media platforms or analyzing the influence of key figures in social networks. Social networks and the analysis of them is an inherently interdisciplinary academic field which emerged from social psychology, sociology, statistics, and graph theory. Georg Simmel authored early structural theories in sociology emphasizing the dynamics of triads and "web of group affiliations". Jacob Moreno is credited with developing the first sociograms in the 1930s to study interpersonal relationships. These approaches were mathematically formalized in the 1950s and theories and methods of social networks became pervasive in the social and behavioral sciences by the 1980s. Social network analysis is now one of the major paradigms in contemporary sociology, and is also employed in a number of other social and formal sciences. Together with other complex networks, it forms part of the nascent field of network science. Overview The social network is a theoretical construct useful in the social sciences to study relationships between individuals, groups, organizations, or even entire societies (social units, see differentiation). The term is used to describe a social structure determined by such interactions. The ties through which any given social unit connects represent the convergence of the various social contacts of that unit. This theoretical approach is, necessarily, relational. An axiom of the social network approach to understanding social interaction is that social phenomena should be primarily conceived and investigated through the properties of relations between and within units, instead of the properties of these units themselves. Thus, one common criticism of social network theory is that individual agency is often ignored although this may not be the case in practice (see agent-based modeling). Precisely because many different types of relations, singular or in combination, form these network configurations, network analytics are useful to a broad range of research enterprises. In social science, these fields of study include, but are not limited to anthropology, biology, communication studies, economics, geography, information science, organizational studies, social psychology, sociology, and sociolinguistics. History In the late 1890s, both Émile Durkheim and Ferdinand Tönnies foreshadowed the idea of social networks in their theories and research of social groups. Tönnies argued that social groups can exist as personal and direct social ties that either link individuals who share values and belief (Gemeinschaft, German, commonly translated as "community") or impersonal, formal, and instrumental social links (Gesellschaft, German, commonly translated as "society"). Durkheim gave a non-individualistic explanation of social facts, arguing that social phenomena arise when interacting individuals constitute a reality that can no longer be accounted for in terms of the properties of individual actors. Georg Simmel, writing at the turn of the twentieth century, pointed to the nature of networks and the effect of network size on interaction and examined the likelihood of interaction in loosely knit networks rather than groups. Major developments in the field can be seen in the 1930s by several groups in psychology, anthropology, and mathematics working independently. In psychology, in the 1930s, Jacob L. Moreno began systematic recording and analysis of social interaction in small groups, especially classrooms and work groups (see sociometry). In anthropology, the foundation for social network theory is the theoretical and ethnographic work of Bronislaw Malinowski, Alfred Radcliffe-Brown, and Claude Lévi-Strauss. A group of social anthropologists associated with Max Gluckman and the Manchester School, including John A. Barnes, J. Clyde Mitchell and Elizabeth Bott Spillius, often are credited with performing some of the first fieldwork from which network analyses were performed, investigating community networks in southern Africa, India and the United Kingdom. Concomitantly, British anthropologist S. F. Nadel codified a theory of social structure that was influential in later network analysis. In sociology, the early (1930s) work of Talcott Parsons set the stage for taking a relational approach to understanding social structure. Later, drawing upon Parsons' theory, the work of sociologist Peter Blau provides a strong impetus for analyzing the relational ties of social units with his work on social exchange theory. By the 1970s, a growing number of scholars worked to combine the different tracks and traditions. One group consisted of sociologist Harrison White and his students at the Harvard University Department of Social Relations. Also independently active in the Harvard Social Relations department at the time were Charles Tilly, who focused on networks in political and community sociology and social movements, and Stanley Milgram, who developed the "six degrees of separation" thesis. Mark Granovetter and Barry Wellman are among the former students of White who elaborated and championed the analysis of social networks. Beginning in the late 1990s, social network analysis experienced work by sociologists, political scientists, and physicists such as Duncan J. Watts, Albert-László Barabási, Peter Bearman, Nicholas A. Christakis, James H. Fowler, and others, developing and applying new models and methods to emerging data available about online social networks, as well as "digital traces" regarding face-to-face networks. Levels of analysis In general, social networks are self-organizing, emergent, and complex, such that a globally coherent pattern appears from the local interaction of the elements that make up the system. These patterns become more apparent as network size increases. However, a global network analysis of, for example, all interpersonal relationships in the world is not feasible and is likely to contain so much information as to be uninformative. Practical limitations of computing power, ethics and participant recruitment and payment also limit the scope of a social network analysis. The nuances of a local system may be lost in a large network analysis, hence the quality of information may be more important than its scale for understanding network properties. Thus, social networks are analyzed at the scale relevant to the researcher's theoretical question. Although levels of analysis are not necessarily mutually exclusive, there are three general levels into which networks may fall: micro-level, meso-level, and macro-level. At the micro-level, social network research typically begins with an individual, snowballing as social relationships are traced, or may begin with a small group of individuals in a particular social context. Dyadic level: A dyad is a social relationship between two individuals. Network research on dyads may concentrate on structure of the relationship (e.g. multiplexity, strength), social equality, and tendencies toward reciprocity/mutuality. Triadic level: Add one individual to a dyad, and you have a triad. Research at this level may concentrate on factors such as balance and transitivity, as well as social equality and tendencies toward reciprocity/mutuality. In the balance theory of Fritz Heider the triad is the key to social dynamics. The discord in a rivalrous love triangle is an example of an unbalanced triad, likely to change to a balanced triad by a change in one of the relations. The dynamics of social friendships in society has been modeled by balancing triads. The study is carried forward with the theory of signed graphs. Actor level: The smallest unit of analysis in a social network is an individual in their social setting, i.e., an "actor" or "ego." Egonetwork analysis focuses on network characteristics, such as size, relationship strength, density, centrality, prestige and roles such as isolates, liaisons, and bridges. Such analyses, are most commonly used in the fields of psychology or social psychology, ethnographic kinship analysis or other genealogical studies of relationships between individuals. Subset level: Subset levels of network research problems begin at the micro-level, but may cross over into the meso-level of analysis. Subset level research may focus on distance and reachability, cliques, cohesive subgroups, or other group actions or behavior. In general, meso-level theories begin with a population size that falls between the micro- and macro-levels. However, meso-level may also refer to analyses that are specifically designed to reveal connections between micro- and macro-levels. Meso-level networks are low density and may exhibit causal processes distinct from interpersonal micro-level networks. Organizations: Formal organizations are social groups that distribute tasks for a collective goal. Network research on organizations may focus on either intra-organizational or inter-organizational ties in terms of formal or informal relationships. Intra-organizational networks themselves often contain multiple levels of analysis, especially in larger organizations with multiple branches, franchises or semi-autonomous departments. In these cases, research is often conducted at a work group level and organization level, focusing on the interplay between the two structures. Experiments with networked groups online have documented ways to optimize group-level coordination through diverse interventions, including the addition of autonomous agents to the groups. Randomly distributed networks: Exponential random graph models of social networks became state-of-the-art methods of social network analysis in the 1980s. This framework has the capacity to represent social-structural effects commonly observed in many human social networks, including general degree-based structural effects commonly observed in many human social networks as well as reciprocity and transitivity, and at the node-level, homophily and attribute-based activity and popularity effects, as derived from explicit hypotheses about dependencies among network ties. Parameters are given in terms of the prevalence of small subgraph configurations in the network and can be interpreted as describing the combinations of local social processes from which a given network emerges. These probability models for networks on a given set of actors allow generalization beyond the restrictive dyadic independence assumption of micro-networks, allowing models to be built from theoretical structural foundations of social behavior. Scale-free networks: A scale-free network is a network whose degree distribution follows a power law, at least asymptotically. In network theory a scale-free ideal network is a random network with a degree distribution that unravels the size distribution of social groups. Specific characteristics of scale-free networks vary with the theories and analytical tools used to create them, however, in general, scale-free networks have some common characteristics. One notable characteristic in a scale-free network is the relative commonness of vertices with a degree that greatly exceeds the average. The highest-degree nodes are often called "hubs", and may serve specific purposes in their networks, although this depends greatly on the social context. Another general characteristic of scale-free networks is the clustering coefficient distribution, which decreases as the node degree increases. This distribution also follows a power law. The Barabási model of network evolution shown above is an example of a scale-free network. Rather than tracing interpersonal interactions, macro-level analyses generally trace the outcomes of interactions, such as economic or other resource transfer interactions over a large population. Large-scale networks: Large-scale network is a term somewhat synonymous with "macro-level." It is primarily used in social and behavioral sciences, and in economics. Originally, the term was used extensively in the computer sciences (see large-scale network mapping). Complex networks: Most larger social networks display features of social complexity, which involves substantial non-trivial features of network topology, with patterns of complex connections between elements that are neither purely regular nor purely random (see, complexity science, dynamical system and chaos theory), as do biological, and technological networks. Such complex network features include a heavy tail in the degree distribution, a high clustering coefficient, assortativity or disassortativity among vertices, community structure (see stochastic block model), and hierarchical structure. In the case of agency-directed networks these features also include reciprocity, triad significance profile (TSP, see network motif), and other features. In contrast, many of the mathematical models of networks that have been studied in the past, such as lattices and random graphs, do not show these features. Theoretical links Various theoretical frameworks have been imported for the use of social network analysis. The most prominent of these are Graph theory, Balance theory, Social comparison theory, and more recently, the Social identity approach. Few complete theories have been produced from social network analysis. Two that have are structural role theory and heterophily theory. The basis of Heterophily Theory was the finding in one study that more numerous weak ties can be important in seeking information and innovation, as cliques have a tendency to have more homogeneous opinions as well as share many common traits. This homophilic tendency was the reason for the members of the cliques to be attracted together in the first place. However, being similar, each member of the clique would also know more or less what the other members knew. To find new information or insights, members of the clique will have to look beyond the clique to its other friends and acquaintances. This is what Granovetter called "the strength of weak ties". Structural holes In the context of networks, social capital exists where people have an advantage because of their location in a network. Contacts in a network provide information, opportunities and perspectives that can be beneficial to the central player in the network. Most social structures tend to be characterized by dense clusters of strong connections. Information within these clusters tends to be rather homogeneous and redundant. Non-redundant information is most often obtained through contacts in different clusters. When two separate clusters possess non-redundant information, there is said to be a structural hole between them. Thus, a network that bridges structural holes will provide network benefits that are in some degree additive, rather than overlapping. An ideal network structure has a vine and cluster structure, providing access to many different clusters and structural holes. Networks rich in structural holes are a form of social capital in that they offer information benefits. The main player in a network that bridges structural holes is able to access information from diverse sources and clusters. For example, in business networks, this is beneficial to an individual's career because he is more likely to hear of job openings and opportunities if his network spans a wide range of contacts in different industries/sectors. This concept is similar to Mark Granovetter's theory of weak ties, which rests on the basis that having a broad range of contacts is most effective for job attainment. Structural holes have been widely applied in social network analysis, resulting in applications in a wide range of practical scenarios as well as machine learning-based social prediction. Research clusters Research has used network analysis to examine networks created when artists are exhibited together in museum exhibition. Such networks have been shown to affect an artist's recognition in history and historical narratives, even when controlling for individual accomplishments of the artist. Other work examines how network grouping of artists can affect an individual artist's auction performance. An artist's status has been shown to increase when associated with higher status networks, though this association has diminishing returns over an artist's career. In J.A. Barnes' day, a "community" referred to a specific geographic location and studies of community ties had to do with who talked, associated, traded, and attended church with whom. Today, however, there are extended "online" communities developed through telecommunications devices and social network services. Such devices and services require extensive and ongoing maintenance and analysis, often using network science methods. Community development studies, today, also make extensive use of such methods. Complex networks require methods specific to modelling and interpreting social complexity and complex adaptive systems, including techniques of dynamic network analysis. Mechanisms such as Dual-phase evolution explain how temporal changes in connectivity contribute to the formation of structure in social networks. The study of social networks is being used to examine the nature of interdependencies between actors and the ways in which these are related to outcomes of conflict and cooperation. Areas of study include cooperative behavior among participants in collective actions such as protests; promotion of peaceful behavior, social norms, and public goods within communities through networks of informal governance; the role of social networks in both intrastate conflict and interstate conflict; and social networking among politicians, constituents, and bureaucrats. In criminology and urban sociology, much attention has been paid to the social networks among criminal actors. For example, murders can be seen as a series of exchanges between gangs. Murders can be seen to diffuse outwards from a single source, because weaker gangs cannot afford to kill members of stronger gangs in retaliation, but must commit other violent acts to maintain their reputation for strength. Diffusion of ideas and innovations studies focus on the spread and use of ideas from one actor to another or one culture and another. This line of research seeks to explain why some become "early adopters" of ideas and innovations, and links social network structure with facilitating or impeding the spread of an innovation. A case in point is the social diffusion of linguistic innovation such as neologisms. Experiments and large-scale field trials (e.g., by Nicholas Christakis and collaborators) have shown that cascades of desirable behaviors can be induced in social groups, in settings as diverse as Honduras villages, Indian slums, or in the lab. Still other experiments have documented the experimental induction of social contagion of voting behavior, emotions, risk perception, and commercial products. In demography, the study of social networks has led to new sampling methods for estimating and reaching populations that are hard to enumerate (for example, homeless people or intravenous drug users.) For example, respondent driven sampling is a network-based sampling technique that relies on respondents to a survey recommending further respondents. The field of sociology focuses almost entirely on networks of outcomes of social interactions. More narrowly, economic sociology considers behavioral interactions of individuals and groups through social capital and social "markets". Sociologists, such as Mark Granovetter, have developed core principles about the interactions of social structure, information, ability to punish or reward, and trust that frequently recur in their analyses of political, economic and other institutions. Granovetter examines how social structures and social networks can affect economic outcomes like hiring, price, productivity and innovation and describes sociologists' contributions to analyzing the impact of social structure and networks on the economy. Analysis of social networks is increasingly incorporated into health care analytics, not only in epidemiological studies but also in models of patient communication and education, disease prevention, mental health diagnosis and treatment, and in the study of health care organizations and systems. Human ecology is an interdisciplinary and transdisciplinary study of the relationship between humans and their natural, social, and built environments. The scientific philosophy of human ecology has a diffuse history with connections to geography, sociology, psychology, anthropology, zoology, and natural ecology. In the study of literary systems, network analysis has been applied by Anheier, Gerhards and Romo, De Nooy, Senekal, and Lotker, to study various aspects of how literature functions. The basic premise is that polysystem theory, which has been around since the writings of Even-Zohar, can be integrated with network theory and the relationships between different actors in the literary network, e.g. writers, critics, publishers, literary histories, etc., can be mapped using visualization from SNA. Research studies of formal or informal organization relationships, organizational communication, economics, economic sociology, and other resource transfers. Social networks have also been used to examine how organizations interact with each other, characterizing the many informal connections that link executives together, as well as associations and connections between individual employees at different organizations. Many organizational social network studies focus on teams. Within team network studies, research assesses, for example, the predictors and outcomes of centrality and power, density and centralization of team instrumental and expressive ties, and the role of between-team networks. Intra-organizational networks have been found to affect organizational commitment, organizational identification, interpersonal citizenship behaviour. Social capital is a form of economic and cultural capital in which social networks are central, transactions are marked by reciprocity, trust, and cooperation, and market agents produce goods and services not mainly for themselves, but for a common good. Social capital is split into three dimensions: the structural, the relational and the cognitive dimension. The structural dimension describes how partners interact with each other and which specific partners meet in a social network. Also, the structural dimension of social capital indicates the level of ties among organizations. This dimension is highly connected to the relational dimension which refers to trustworthiness, norms, expectations and identifications of the bonds between partners. The relational dimension explains the nature of these ties which is mainly illustrated by the level of trust accorded to the network of organizations. The cognitive dimension analyses the extent to which organizations share common goals and objectives as a result of their ties and interactions. Social capital is a sociological concept about the value of social relations and the role of cooperation and confidence to achieve positive outcomes. The term refers to the value one can get from their social ties. For example, newly arrived immigrants can make use of their social ties to established migrants to acquire jobs they may otherwise have trouble getting (e.g., because of unfamiliarity with the local language). A positive relationship exists between social capital and the intensity of social network use. In a dynamic framework, higher activity in a network feeds into higher social capital which itself encourages more activity. This particular cluster focuses on brand-image and promotional strategy effectiveness, taking into account the impact of customer participation on sales and brand-image. This is gauged through techniques such as sentiment analysis which rely on mathematical areas of study such as data mining and analytics. This area of research produces vast numbers of commercial applications as the main goal of any study is to understand consumer behaviour and drive sales. In many organizations, members tend to focus their activities inside their own groups, which stifles creativity and restricts opportunities. A player whose network bridges structural holes has an advantage in detecting and developing rewarding opportunities. Such a player can mobilize social capital by acting as a "broker" of information between two clusters that otherwise would not have been in contact, thus providing access to new ideas, opinions and opportunities. British philosopher and political economist John Stuart Mill, writes, "it is hardly possible to overrate the value of placing human beings in contact with persons dissimilar to themselves.... Such communication [is] one of the primary sources of progress." Thus, a player with a network rich in structural holes can add value to an organization through new ideas and opportunities. This in turn, helps an individual's career development and advancement. A social capital broker also reaps control benefits of being the facilitator of information flow between contacts. Full communication with exploratory mindsets and information exchange generated by dynamically alternating positions in a social network promotes creative and deep thinking. In the case of consulting firm Eden McCallum, the founders were able to advance their careers by bridging their connections with former big three consulting firm consultants and mid-size industry firms. By bridging structural holes and mobilizing social capital, players can advance their careers by executing new opportunities between contacts. There has been research that both substantiates and refutes the benefits of information brokerage. A study of high tech Chinese firms by Zhixing Xiao found that the control benefits of structural holes are "dissonant to the dominant firm-wide spirit of cooperation and the information benefits cannot materialize due to the communal sharing values" of such organizations. However, this study only analyzed Chinese firms, which tend to have strong communal sharing values. Information and control benefits of structural holes are still valuable in firms that are not quite as inclusive and cooperative on the firm-wide level. In 2004, Ronald Burt studied 673 managers who ran the supply chain for one of America's largest electronics companies. He found that managers who often discussed issues with other groups were better paid, received more positive job evaluations and were more likely to be promoted. Thus, bridging structural holes can be beneficial to an organization, and in turn, to an individual's career. Computer networks combined with social networking software produce a new medium for social interaction. A relationship over a computerized social networking service can be characterized by context, direction, and strength. The content of a relation refers to the resource that is exchanged. In a computer-mediated communication context, social pairs exchange different kinds of information, including sending a data file or a computer program as well as providing emotional support or arranging a meeting. With the rise of electronic commerce, information exchanged may also correspond to exchanges of money, goods or services in the "real" world. Social network analysis methods have become essential to examining these types of computer mediated communication. In addition, the sheer size and the volatile nature of social media has given rise to new network metrics. A key concern with networks extracted from social media is the lack of robustness of network metrics given missing data. Based on the pattern of homophily, ties between people are most likely to occur between nodes that are most similar to each other, or within neighbourhood segregation, individuals are most likely to inhabit the same regional areas as other individuals who are like them. Therefore, social networks can be used as a tool to measure the degree of segregation or homophily within a social network. Social Networks can both be used to simulate the process of homophily but it can also serve as a measure of level of exposure of different groups to each other within a current social network of individuals in a certain area. See also References Further reading External links |
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Contents Meta Platforms Meta Platforms, Inc. (doing business as Meta) is an American multinational technology company headquartered in Menlo Park, California. Meta owns and operates several prominent social media platforms and communication services, including Facebook, Instagram, WhatsApp, Messenger, Threads and Manus. The company also operates an advertising network for its own sites and third parties; as of 2023[update], advertising accounted for 97.8 percent of its total revenue. Meta has been described as a part of Big Tech, which refers to the largest six tech companies in the United States, Alphabet (Google), Amazon, Apple, Meta (Facebook), Microsoft, and Nvidia, which are also the largest companies in the world by market capitalization. The company was originally established in 2004 as TheFacebook, Inc., and was renamed Facebook, Inc. in 2005. In 2021, it rebranded as Meta Platforms, Inc. to reflect a strategic shift toward developing the metaverse—an interconnected digital ecosystem spanning virtual and augmented reality technologies. In 2023, Meta was ranked 31st on the Forbes Global 2000 list of the world's largest public companies. As of 2022, it was the world's third-largest spender on research and development, with R&D expenses totaling US$35.3 billion. History Facebook filed for an initial public offering (IPO) on January 1, 2012. The preliminary prospectus stated that the company sought to raise $5 billion, had 845 million monthly active users, and a website accruing 2.7 billion likes and comments daily. After the IPO, Zuckerberg would retain 22% of the total shares and 57% of the total voting power in Facebook. Underwriters valued the shares at $38 each, valuing the company at $104 billion, the largest valuation yet for a newly public company. On May 16, one day before the IPO, Facebook announced it would sell 25% more shares than originally planned due to high demand. The IPO raised $16 billion, making it the third-largest in US history (slightly ahead of AT&T Mobility and behind only General Motors and Visa). The stock price left the company with a higher market capitalization than all but a few U.S. corporations—surpassing heavyweights such as Amazon, McDonald's, Disney, and Kraft Foods—and made Zuckerberg's stock worth $19 billion. The New York Times stated that the offering overcame questions about Facebook's difficulties in attracting advertisers to transform the company into a "must-own stock". Jimmy Lee of JPMorgan Chase described it as "the next great blue-chip". Writers at TechCrunch, on the other hand, expressed skepticism, stating, "That's a big multiple to live up to, and Facebook will likely need to add bold new revenue streams to justify the mammoth valuation." Trading in the stock, which began on May 18, was delayed that day due to technical problems with the Nasdaq exchange. The stock struggled to stay above the IPO price for most of the day, forcing underwriters to buy back shares to support the price. At the closing bell, shares were valued at $38.23, only $0.23 above the IPO price and down $3.82 from the opening bell value. The opening was widely described by the financial press as a disappointment. The stock set a new record for trading volume of an IPO. On May 25, 2012, the stock ended its first full week of trading at $31.91, a 16.5% decline. On May 22, 2012, regulators from Wall Street's Financial Industry Regulatory Authority announced that they had begun to investigate whether banks underwriting Facebook had improperly shared information only with select clients rather than the general public. Massachusetts Secretary of State William F. Galvin subpoenaed Morgan Stanley over the same issue. The allegations sparked "fury" among some investors and led to the immediate filing of several lawsuits, one of them a class action suit claiming more than $2.5 billion in losses due to the IPO. Bloomberg estimated that retail investors may have lost approximately $630 million on Facebook stock since its debut. S&P Global Ratings added Facebook to its S&P 500 index on December 21, 2013. On May 2, 2014, Zuckerberg announced that the company would be changing its internal motto from "Move fast and break things" to "Move fast with stable infrastructure". The earlier motto had been described as Zuckerberg's "prime directive to his developers and team" in a 2009 interview in Business Insider, in which he also said, "Unless you are breaking stuff, you are not moving fast enough." In November 2016, Facebook announced the Microsoft Windows client of gaming service Facebook Gameroom, formerly Facebook Games Arcade, at the Unity Technologies developers conference. The client allows Facebook users to play "native" games in addition to its web games. The service was closed in June 2021. Lasso was a short-video sharing app from Facebook similar to TikTok that was launched on iOS and Android in 2018 and was aimed at teenagers. On July 2, 2020, Facebook announced that Lasso would be shutting down on July 10. In 2018, the Oculus lead Jason Rubin sent his 50-page vision document titled "The Metaverse" to Facebook's leadership. In the document, Rubin acknowledged that Facebook's virtual reality business had not caught on as expected, despite the hundreds of millions of dollars spent on content for early adopters. He also urged the company to execute fast and invest heavily in the vision, to shut out HTC, Apple, Google and other competitors in the VR space. Regarding other players' participation in the metaverse vision, he called for the company to build the "metaverse" to prevent their competitors from "being in the VR business in a meaningful way at all". In May 2019, Facebook founded Libra Networks, reportedly to develop their own stablecoin cryptocurrency. Later, it was reported that Libra was being supported by financial companies such as Visa, Mastercard, PayPal and Uber. The consortium of companies was expected to pool in $10 million each to fund the launch of the cryptocurrency coin named Libra. Depending on when it would receive approval from the Swiss Financial Market Supervisory authority to operate as a payments service, the Libra Association had planned to launch a limited format cryptocurrency in 2021. Libra was renamed Diem, before being shut down and sold in January 2022 after backlash from Swiss government regulators and the public. During the COVID-19 pandemic, the use of online services, including Facebook, grew globally. Zuckerberg predicted this would be a "permanent acceleration" that would continue after the pandemic. Facebook hired aggressively, growing from 48,268 employees in March 2020 to more than 87,000 by September 2022. Following a period of intense scrutiny and damaging whistleblower leaks, news started to emerge on October 21, 2021 about Facebook's plan to rebrand the company and change its name. In the Q3 2021 earnings call on October 25, Mark Zuckerberg discussed the ongoing criticism of the company's social services and the way it operates, and pointed to the pivoting efforts to building the metaverse – without mentioning the rebranding and the name change. The metaverse vision and the name change from Facebook, Inc. to Meta Platforms was introduced at Facebook Connect on October 28, 2021. Based on Facebook's PR campaign, the name change reflects the company's shifting long term focus of building the metaverse, a digital extension of the physical world by social media, virtual reality and augmented reality features. "Meta" had been registered as a trademark in the United States in 2018 (after an initial filing in 2015) for marketing, advertising, and computer services, by a Canadian company that provided big data analysis of scientific literature. This company was acquired in 2017 by the Chan Zuckerberg Initiative (CZI), a foundation established by Zuckerberg and his wife, Priscilla Chan, and became one of their projects. Following the rebranding announcement, CZI announced that it had already decided to deprioritize the earlier Meta project, thus it would be transferring its rights to the name to Meta Platforms, and the previous project would end in 2022. Soon after the rebranding, in early February 2022, Meta reported a greater-than-expected decline in profits in the fourth quarter of 2021. It reported no growth in monthly users, and indicated it expected revenue growth to stall. It also expected measures taken by Apple Inc. to protect user privacy to cost it some $10 billion in advertisement revenue, an amount equal to roughly 8% of its revenue for 2021. In meeting with Meta staff the day after earnings were reported, Zuckerberg blamed competition for user attention, particularly from video-based apps such as TikTok. The 27% reduction in the company's share price which occurred in reaction to the news eliminated some $230 billion of value from Meta's market capitalization. Bloomberg described the decline as "an epic rout that, in its sheer scale, is unlike anything Wall Street or Silicon Valley has ever seen". Zuckerberg's net worth fell by as much as $31 billion. Zuckerberg owns 13% of Meta, and the holding makes up the bulk of his wealth. According to published reports by Bloomberg on March 30, 2022, Meta turned over data such as phone numbers, physical addresses, and IP addresses to hackers posing as law enforcement officials using forged documents. The law enforcement requests sometimes included forged signatures of real or fictional officials. When asked about the allegations, a Meta representative said, "We review every data request for legal sufficiency and use advanced systems and processes to validate law enforcement requests and detect abuse." In June 2022, Sheryl Sandberg, the chief operating officer of 14 years, announced she would step down that year. Zuckerberg said that Javier Olivan would replace Sandberg, though in a “more traditional” role. In March 2022, Meta (except Meta-owned WhatsApp) and Instagram were banned in Russia and added to the Russian list of terrorist and extremist organizations for alleged Russophobia and hate speech (up to genocidal calls) amid the ongoing Russian invasion of Ukraine. Meta appealed against the ban, but it was upheld by a Moscow court in June of the same year. Also in March 2022, Meta and Italian eyewear giant Luxottica released Ray-Ban Stories, a series of smartglasses which could play music and take pictures. Meta and Luxottica parent company EssilorLuxottica declined to disclose sales on the line of products as of September 2022, though Meta has expressed satisfaction with its customer feedback. In July 2022, Meta saw its first year-on-year revenue decline when its total revenue slipped by 1% to $28.8bn. Analysts and journalists accredited the loss to its advertising business, which has been limited by Apple's app tracking transparency feature and the number of people who have opted not to be tracked by Meta apps. Zuckerberg also accredited the decline to increasing competition from TikTok. On October 27, 2022, Meta's market value dropped to $268 billion, a loss of around $700 billion compared to 2021, and its shares fell by 24%. It lost its spot among the top 20 US companies by market cap, despite reaching the top 5 in the previous year. In November 2022, Meta laid off 11,000 employees, 13% of its workforce. Zuckerberg said the decision to aggressively increase Meta's investments had been a mistake, as he had wrongly predicted that the surge in e-commerce would last beyond the COVID-19 pandemic. He also attributed the decline to increased competition, a global economic downturn and "ads signal loss". Plans to lay off a further 10,000 employees began in April 2023. The layoffs were part of a general downturn in the technology industry, alongside layoffs by companies including Google, Amazon, Tesla, Snap, Twitter and Lyft. Starting from 2022, Meta scrambled to catch up to other tech companies in adopting specialized artificial intelligence hardware and software. It had been using less expensive CPUs instead of GPUs for AI work, but that approach turned out to be less efficient. The company gifted the Inter-university Consortium for Political and Social Research $1.3 million to finance the Social Media Archive's aim to make their data available to social science research. In 2023, Ireland's Data Protection Commissioner imposed a record EUR 1.2 billion fine on Meta for transferring data from Europe to the United States without adequate protections for EU citizens.: 250 In March 2023, Meta announced a new round of layoffs that would cut 10,000 employees and close 5,000 open positions to make the company more efficient. Meta revenue surpassed analyst expectations for the first quarter of 2023 after announcing that it was increasing its focus on AI. On July 6, Meta launched a new app, Threads, a competitor to Twitter. Meta announced its artificial intelligence model Llama 2 in July 2023, available for commercial use via partnerships with major cloud providers like Microsoft. It was the first project to be unveiled out of Meta's generative AI group after it was set up in February. It would not charge access or usage but instead operate with an open-source model to allow Meta to ascertain what improvements need to be made. Prior to this announcement, Meta said it had no plans to release Llama 2 for commercial use. An earlier version of Llama was released to academics. In August 2023, Meta announced its permanent removal of news content from Facebook and Instagram in Canada due to the Online News Act, which requires Canadian news outlets to be compensated for content shared on its platform. The Online News Act was in effect by year-end, but Meta will not participate in the regulatory process. In October 2023, Zuckerberg said that AI would be Meta's biggest investment area in 2024. Meta finished 2023 as one of the best-performing technology stocks of the year, with its share price up 150 percent. Its stock reached an all-time high in January 2024, bringing Meta within 2% of achieving $1 trillion market capitalization. In November 2023 Meta Platforms launched an ad-free service in Europe, allowing subscribers to opt-out of personal data being collected for targeted advertising. A group of 28 European organizations, including Max Schrems' advocacy group NOYB, the Irish Council for Civil Liberties, Wikimedia Europe, and the Electronic Privacy Information Center, signed a 2024 letter to the European Data Protection Board (EDPB) expressing concern that this subscriber model would undermine privacy protections, specifically GDPR data protection standards. Meta removed the Facebook and Instagram accounts of Iran's Supreme Leader Ali Khamenei in February 2024, citing repeated violations of its Dangerous Organizations & Individuals policy. As of March, Meta was under investigation by the FDA for alleged use of their social media platforms to sell illegal drugs. On 16 May 2024, the European Commission began an investigation into Meta over concerns related to child safety. In May 2023, Iraqi social media influencer Esaa Ahmed-Adnan encountered a troubling issue when Instagram removed his posts, citing false copyright violations despite his content being original and free from copyrighted material. He discovered that extortionists were behind these takedowns, offering to restore his content for $3,000 or provide ongoing protection for $1,000 per month. This scam, exploiting Meta’s rights management tools, became widespread in the Middle East, revealing a gap in Meta’s enforcement in developing regions. An Iraqi nonprofit Tech4Peace’s founder, Aws al-Saadi helped Ahmed-Adnan and others, but the restoration process was slow, leading to significant financial losses for many victims, including prominent figures like Ammar al-Hakim. This situation highlighted Meta’s challenges in balancing global growth with effective content moderation and protection. On 16 September 2024, Meta announced it had banned Russian state media outlets from its platforms worldwide due to concerns about "foreign interference activity." This decision followed allegations that RT and its employees funneled $10 million through shell companies to secretly fund influence campaigns on various social media channels. Meta's actions were part of a broader effort to counter Russian covert influence operations, which had intensified since the invasion. At its 2024 Connect conference, Meta presented Orion, its first pair of augmented reality glasses. Though Orion was originally intended to be sold to consumers, the manufacturing process turned out to be too complex and expensive. Instead, the company pivoted to producing a small number of the glasses to be used internally. On 4 October 2024, Meta announced about its new AI model called Movie Gen, capable of generating realistic video and audio clips based on user prompts. Meta stated it would not release Movie Gen for open development, preferring to collaborate directly with content creators and integrate it into its products by the following year. The model was built using a combination of licensed and publicly available datasets. On October 31, 2024, ProPublica published an investigation into deceptive political advertisement scams that sometimes use hundreds of hijacked profiles and facebook pages run by organized networks of scammers. The authors cited spotty enforcement by Meta as a major reason for the extent of the issue. In November 2024, TechCrunch reported that Meta were considering building a $10bn global underwater cable spanning 25,000 miles. In the same month, Meta closed down 2 million accounts on Facebook and Instagram that were linked to scam centers in Myanmar, Laos, Cambodia, the Philippines, and the United Arab Emirates doing pig butchering scams. In December 2024, Meta announced that, beginning February 2025, they would require advertisers to run ads about financial services in Australia to verify information about who are the beneficiary and the payer in a bid to regulate scams. On December 4, 2024, Meta announced it will invest US$10 billion for its largest AI data center in northeast Louisiana, powered by natural gas facilities. On the 11th of that month, Meta experienced a global outage, impacting accounts on all of their social media and messaging applications. Outage reports from DownDetector reached 70,000+ and 100,000+ within minutes for Instagram and Facebook, respectively. In January 2025, Meta announced plans to roll back its diversity, equity, and inclusion (DEI) initiatives, citing shifts in the "legal and policy landscape" in the United States following the 2024 presidential election. The decision followed reports that CEO Mark Zuckerberg sought to align the company more closely with the incoming Trump administration, including changes to content moderation policies and executive leadership. The new content moderation policies continued to bar insults about a person's intellect or mental illness, but made an exception to allow calling LGBTQ people mentally ill because they are gay or transgender. Later that month, Meta agreed to pay $25 million to settle a 2021 lawsuit brought by Donald Trump for suspending his social media accounts after the January 6 riots. Changes to Meta's moderation policies were controversial among its oversight board, with a significant divide in opinion between the board's US conservatives and its global members. In June 2025, Meta Platforms Inc. has decided to make a multibillion-dollar investment into artificial intelligence startup Scale AI. The financing could exceed $10 billion in value which would make it one of the largest private company funding events of all time. In October 2025, it was announced that Meta would be laying off 600 employees in the artificial intelligence unit to perform better and simpler. They referred to their AI unit as "bloated" and are seeking to trim down the department. This mass layoff is going to impact Meta’s AI infrastructure units, Fundamental Artificial Intelligence Research unit (FAIR) and other product-related positions. Mergers and acquisitions Meta has acquired multiple companies (often identified as talent acquisitions). One of its first major acquisitions was in April 2012, when it acquired Instagram for approximately US$1 billion in cash and stock. In October 2013, Facebook, Inc. acquired Onavo, an Israeli mobile web analytics company. In February 2014, Facebook, Inc. announced it would buy mobile messaging company WhatsApp for US$19 billion in cash and stock. The acquisition was completed on October 6. Later that year, Facebook bought Oculus VR for $2.3 billion in cash and stock, which released its first consumer virtual reality headset in 2016. In late November 2019, Facebook, Inc. announced the acquisition of the game developer Beat Games, responsible for developing one of that year's most popular VR games, Beat Saber. In Late 2022, after Facebook Inc rebranded to Meta Platforms Inc, Oculus was rebranded to Meta Quest. In May 2020, Facebook, Inc. announced it had acquired Giphy for a reported cash price of $400 million. It will be integrated with the Instagram team. However, in August 2021, UK's Competition and Markets Authority (CMA) stated that Facebook, Inc. might have to sell Giphy, after an investigation found that the deal between the two companies would harm competition in display advertising market. Facebook, Inc. was fined $70 million by CMA for deliberately failing to report all information regarding the acquisition and the ongoing antitrust investigation. In October 2022, the CMA ruled for a second time that Meta be required to divest Giphy, stating that Meta already controls half of the advertising in the UK. Meta agreed to the sale, though it stated that it disagrees with the decision itself. In May 2023, Giphy was divested to Shutterstock for $53 million. In November 2020, Facebook, Inc. announced that it planned to purchase the customer-service platform and chatbot specialist startup Kustomer to promote companies to use their platform for business. It has been reported that Kustomer valued at slightly over $1 billion. The deal was closed in February 2022 after regulatory approval. In September 2022, Meta acquired Lofelt, a Berlin-based haptic tech startup. In December 2025, it was announced Meta had acquired the AI-wearables startup, Limitless. In the same month, they also acquired another AI startup, Manus AI, for $2 billion. Manus announced in December that its platform had achieved $100mm in recurring revenue just 8 months after its launch and Meta said it will scale the platform to many other businesses. In January 2026, it was announced Meta proposed acquisition of Manus was undergoing preliminary scrutiny by Chinese regulators. The examination concerns the cross-border transfer of artificial intelligence technology developed in China. Lobbying In 2020, Facebook, Inc. spent $19.7 million on lobbying, hiring 79 lobbyists. In 2019, it had spent $16.7 million on lobbying and had a team of 71 lobbyists, up from $12.6 million and 51 lobbyists in 2018. Facebook was the largest spender of lobbying money among the Big Tech companies in 2020. The lobbying team includes top congressional aide John Branscome, who was hired in September 2021, to help the company fend off threats from Democratic lawmakers and the Biden administration. In December 2024, Meta donated $1 million to the inauguration fund for then-President-elect Donald Trump. In 2025, Meta was listed among the donors funding the construction of the White House State Ballroom. Partnerships February 2026, Meta announced a long-term partnership with Nvidia. Censorship In August 2024, Mark Zuckerberg sent a letter to Jim Jordan indicating that during the COVID-19 pandemic the Biden administration repeatedly asked Meta to limit certain COVID-19 content, including humor and satire, on Facebook and Instagram. In 2016 Meta hired Jordana Cutler, formerly an employee at the Israeli Embassy to the United States, as its policy chief for Israel and the Jewish Diaspora. In this role, Cutler pushed for the censorship of accounts belonging to Students for Justice in Palestine chapters in the United States. Critics have said that Cutler's position gives the Israeli government an undue influence over Meta policy, and that few countries have such high levels of contact with Meta policymakers. Following the election of Donald Trump in 2025, various sources noted possible censorship related to the Democratic Party on Instagram and other Meta platforms. In February 2025, a Meta rep flagged journalist Gil Duran's article and other "critiques of tech industry figures" as spam or sensitive content, limiting their reach. In March 2025, Meta attempted to block former employee Sarah Wynn-Williams from promoting or further distributing her memoir, Careless People, that includes allegations of unaddressed sexual harassment in the workplace by senior executives. The New York Times reports that the arbitration is among Meta's most forcible attempts to repudiate a former employee's account of workplace dynamics. Publisher Macmillan reacted to the ruling by the Emergency International Arbitral Tribunal by stating that it will ignore its provisions. As of 15 March 2025[update], hardback and digital versions of Careless People were being offered for sale by major online retailers. From October 2025, Meta began removing and restricting access for accounts related to LGBTQ, reproductive health and abortion information pages on its platforms. Martha Dimitratou, executive director of Repro Uncensored, called Meta's shadow-banning of these issues "One of the biggest waves of censorship we are seeing". Disinformation concerns Since its inception, Meta has been accused of being a host for fake news and misinformation. In the wake of the 2016 United States presidential election, Zuckerberg began to take steps to eliminate the prevalence of fake news, as the platform had been criticized for its potential influence on the outcome of the election. The company initially partnered with ABC News, the Associated Press, FactCheck.org, Snopes and PolitiFact for its fact-checking initiative; as of 2018, it had over 40 fact-checking partners across the world, including The Weekly Standard. A May 2017 review by The Guardian found that the platform's fact-checking initiatives of partnering with third-party fact-checkers and publicly flagging fake news were regularly ineffective, and appeared to be having minimal impact in some cases. In 2018, journalists working as fact-checkers for the company criticized the partnership, stating that it had produced minimal results and that the company had ignored their concerns. In 2024 Meta's decision to continue to disseminate a falsified video of US president Joe Biden, even after it had been proven to be fake, attracted criticism and concern. In January 2025, Meta ended its use of third-party fact-checkers in favor of a user-run community notes system similar to the one used on X. While Zuckerberg supported these changes, saying that the amount of censorship on the platform was excessive, the decision received criticism by fact-checking institutions, stating that the changes would make it more difficult for users to identify misinformation. Meta also faced criticism for weakening its policies on hate speech that were designed to protect minorities and LGBTQ+ individuals from bullying and discrimination. While moving its content review teams from California to Texas, Meta changed their hateful conduct policy to eliminate restrictions on anti-LGBT and anti-immigrant hate speech, as well as explicitly allowing users to accuse LGBT people of being mentally ill or abnormal based on their sexual orientation or gender identity. In January 2025, Meta faced significant criticism for its role in removing LGBTQ+ content from its platforms, amid its broader efforts to address anti-LGBTQ+ hate speech. The removal of LGBTQ+ themes was noted as part of the wider crackdown on content deemed to violate its community guidelines. Meta's content moderation policies, which were designed to combat harmful speech and protect users from discrimination, inadvertently led to the removal or restriction of LGBTQ+ content, particularly posts highlighting LGBTQ+ identities, support, or political issues. According to reports, LGBTQ+ posts, including those that simply celebrated pride or advocated for LGBTQ+ rights, were flagged and removed for reasons that some critics argue were vague or inconsistently applied. Many LGBTQ+ activists and users on Meta's platforms expressed concern that such actions stifled visibility and expression, potentially isolating LGBTQ+ individuals and communities, especially in spaces that were historically important for outreach and support. Lawsuits Numerous lawsuits have been filed against the company, both when it was known as Facebook, Inc., and as Meta Platforms. In March 2020, the Office of the Australian Information Commissioner (OAIC) sued Facebook, for significant and persistent infringements of the rule on privacy involving the Cambridge Analytica fiasco. Every violation of the Privacy Act is subject to a theoretical cumulative liability of $1.7 million. The OAIC estimated that a total of 311,127 Australians had been exposed. On December 8, 2020, the U.S. Federal Trade Commission and 46 states (excluding Alabama, Georgia, South Carolina, and South Dakota), the District of Columbia and the territory of Guam, launched Federal Trade Commission v. Facebook as an antitrust lawsuit against Facebook. The lawsuit concerns Facebook's acquisition of two competitors—Instagram and WhatsApp—and the ensuing monopolistic situation. FTC alleges that Facebook holds monopolistic power in the U.S. social networking market and seeks to force the company to divest from Instagram and WhatsApp to break up the conglomerate. William Kovacic, a former chairman of the Federal Trade Commission, argued the case will be difficult to win as it would require the government to create a counterfactual argument of an internet where the Facebook-WhatsApp-Instagram entity did not exist, and prove that harmed competition or consumers. In November 2025, it was ruled that Meta did not violate antitrust laws and holds no monopoly in the market. On December 24, 2021, a court in Russia fined Meta for $27 million after the company declined to remove unspecified banned content. The fine was reportedly tied to the company's annual revenue in the country. In May 2022, a lawsuit was filed in Kenya against Meta and its local outsourcing company Sama. Allegedly, Meta has poor working conditions in Kenya for workers moderating Facebook posts. According to the lawsuit, 260 screeners were declared redundant with confusing reasoning. The lawsuit seeks financial compensation and an order that outsourced moderators be given the same health benefits and pay scale as Meta employees. In June 2022, 8 lawsuits were filed across the U.S. over the allege that excessive exposure to platforms including Facebook and Instagram has led to attempted or actual suicides, eating disorders and sleeplessness, among other issues. The litigation follows a former Facebook employee's testimony in Congress that the company refused to take responsibility. The company noted that tools have been developed for parents to keep track of their children's activity on Instagram and set time limits, in addition to Meta's "Take a break" reminders. In addition, the company is providing resources specific to eating disorders as well as developing AI to prevent children under the age of 13 signing up for Facebook or Instagram. In June 2022, Meta settled a lawsuit with the US Department of Justice. The lawsuit, which was filed in 2019, alleged that the company enabled housing discrimination through targeted advertising, as it allowed homeowners and landlords to run housing ads excluding people based on sex, race, religion, and other characteristics. The U.S. Department of Justice stated that this was in violation of the Fair Housing Act. Meta was handed a penalty of $115,054 and given until December 31, 2022, to shadow the algorithm tool. In January 2023, Meta was fined €390 million for violations of the European Union General Data Protection Regulation. In May 2023, the European Data Protection Board fined Meta a record €1.2 billion for breaching European Union data privacy laws by transferring personal data of Facebook users to servers in the U.S. In July 2024, Meta agreed to pay the state of Texas US$1.4 billion to settle a lawsuit brought by Texas Attorney General Ken Paxton accusing the company of collecting users' biometric data without consent, setting a record for the largest privacy-related settlement ever obtained by a state attorney general. In October 2024, Meta Platforms faced lawsuits in Japan from 30 plaintiffs who claimed they were defrauded by fake investment ads on Facebook and Instagram, featuring false celebrity endorsements. The plaintiffs are seeking approximately $2.8 million in damages. In April 2025, the Kenyan High Court ruled that a US$2.4 billion lawsuit in which three plaintiffs claim that Facebook inflamed civil violence in Ethiopia in 2021 could proceed. In April 2025, Meta was fined €200 million ($230 million) for breaking the Digital Markets Act, by imposing a “consent or pay” system that forces users to either allow their personal data to be used to target advertisements, or pay a subscription fee for advertising-free versions of Facebook and Instagram. In late April 2025, a case was filed against Meta in Ghana over the alleged psychological distress experienced by content moderators employed to take down disturbing social media content including depictions of murders, extreme violence and child sexual abuse. Meta moved the moderation service to the Ghanaian capital of Accra after legal issues in the previous location Kenya. The new moderation company is Teleperformance, a multinational corporation with a history of worker's rights violation. Reports suggests the conditions are worse here than in the previous Kenyan location, with many workers afraid of speaking out due to fear of returning to conflict zones. Workers reported developing mental illnesses, attempted suicides, and low pay. In 26 January 2026, a New Mexico state court case was filed, suggesting that Mark Zuckerberg approved allowing minors to access artificial intelligence chatbot companions that safety staffers warned were capable of sexual interactions. In 2020, the company UReputation, which had been involved in several cases concerning the management of digital armies[clarification needed], filed a lawsuit against Facebook, accusing it of unlawfully transmitting personal data to third parties. Legal actions were initiated in Tunisia, France, and the United States. In 2025, the United States District court for the Northern District of Georgia approved a discovery procedure, allowing UReputation to access documents and evidence held by Meta. Structure Meta's key management consists of: As of October 2022[update], Meta had 83,553 employees worldwide. As of June 2024[update], Meta's board consisted of the following directors; Meta Platforms is mainly owned by institutional investors, who hold around 80% of all shares. Insiders control the majority of voting shares. The three largest individual investors in 2024 were Mark Zuckerberg, Sheryl Sandberg and Christopher K. Cox. The largest shareholders in late 2024/early 2025 were: Roger McNamee, an early Facebook investor and Zuckerberg's former mentor, said Facebook had "the most centralized decision-making structure I have ever encountered in a large company". Facebook co-founder Chris Hughes has stated that chief executive officer Mark Zuckerberg has too much power, that the company is now a monopoly, and that, as a result, it should be split into multiple smaller companies. In an op-ed in The New York Times, Hughes said he was concerned that Zuckerberg had surrounded himself with a team that did not challenge him, and that it is the U.S. government's job to hold him accountable and curb his "unchecked power". He also said that "Mark's power is unprecedented and un-American." Several U.S. politicians agreed with Hughes. European Union Commissioner for Competition Margrethe Vestager stated that splitting Facebook should be done only as "a remedy of the very last resort", and that it would not solve Facebook's underlying problems. Revenue Facebook ranked No. 34 in the 2020 Fortune 500 list of the largest United States corporations by revenue, with almost $86 billion in revenue most of it coming from advertising. One analysis of 2017 data determined that the company earned US$20.21 per user from advertising. According to New York, since its rebranding, Meta has reportedly lost $500 billion as a result of new privacy measures put in place by companies such as Apple and Google which prevents Meta from gathering users' data. In February 2015, Facebook announced it had reached two million active advertisers, with most of the gain coming from small businesses. An active advertiser was defined as an entity that had advertised on the Facebook platform in the last 28 days. In March 2016, Facebook announced it had reached three million active advertisers with more than 70% from outside the United States. Prices for advertising follow a variable pricing model based on auctioning ad placements, and potential engagement levels of the advertisement itself. Similar to other online advertising platforms like Google and Twitter, targeting of advertisements is one of the chief merits of digital advertising compared to traditional media. Marketing on Meta is employed through two methods based on the viewing habits, likes and shares, and purchasing data of the audience, namely targeted audiences and "look alike" audiences. The U.S. IRS challenged the valuation Facebook used when it transferred IP from the U.S. to Facebook Ireland (now Meta Platforms Ireland) in 2010 (which Facebook Ireland then revalued higher before charging out), as it was building its double Irish tax structure. The case is ongoing and Meta faces a potential fine of $3–5bn. The U.S. Tax Cuts and Jobs Act of 2017 changed Facebook's global tax calculations. Meta Platforms Ireland is subject to the U.S. GILTI tax of 10.5% on global intangible profits (i.e. Irish profits). On the basis that Meta Platforms Ireland Limited is paying some tax, the effective minimum US tax for Facebook Ireland will be circa 11%. In contrast, Meta Platforms Inc. would incur a special IP tax rate of 13.125% (the FDII rate) if its Irish business relocated to the U.S. Tax relief in the U.S. (21% vs. Irish at the GILTI rate) and accelerated capital expensing, would make this effective U.S. rate around 12%. The insignificance of the U.S./Irish tax difference was demonstrated when Facebook moved 1.5bn non-EU accounts to the U.S. to limit exposure to GDPR. Facilities Users outside of the U.S. and Canada contract with Meta's Irish subsidiary, Meta Platforms Ireland Limited (formerly Facebook Ireland Limited), allowing Meta to avoid US taxes for all users in Europe, Asia, Australia, Africa and South America. Meta is making use of the Double Irish arrangement which allows it to pay 2–3% corporation tax on all international revenue. In 2010, Facebook opened its fourth office, in Hyderabad, India, which houses online advertising and developer support teams and provides support to users and advertisers. In India, Meta is registered as Facebook India Online Services Pvt Ltd. It also has offices or planned sites in Chittagong, Bangladesh; Dublin, Ireland; and Austin, Texas, among other cities. Facebook opened its London headquarters in 2017 in Fitzrovia in central London. Facebook opened an office in Cambridge, Massachusetts in 2018. The offices were initially home to the "Connectivity Lab", a group focused on bringing Internet access to those who do not have access to the Internet. In April 2019, Facebook opened its Taiwan headquarters in Taipei. In March 2022, Meta opened new regional headquarters in Dubai. In September 2023, it was reported that Meta had paid £149m to British Land to break the lease on Triton Square London office. Meta reportedly had another 18 years left on its lease on the site. As of 2023, Facebook operated 21 data centers. It committed to purchase 100% renewable energy and to reduce its greenhouse gas emissions 75% by 2020. Its data center technologies include Fabric Aggregator, a distributed network system that accommodates larger regions and varied traffic patterns. Reception US Representative Alexandria Ocasio-Cortez responded in a tweet to Zuckerberg's announcement about Meta, saying: "Meta as in 'we are a cancer to democracy metastasizing into a global surveillance and propaganda machine for boosting authoritarian regimes and destroying civil society ... for profit!'" Ex-Facebook employee Frances Haugen and whistleblower behind the Facebook Papers responded to the rebranding efforts by expressing doubts about the company's ability to improve while led by Mark Zuckerberg, and urged the chief executive officer to resign. In November 2021, a video published by Inspired by Iceland went viral, in which a Zuckerberg look-alike promoted the Icelandverse, a place of "enhanced actual reality without silly looking headsets". In a December 2021 interview, SpaceX and Tesla chief executive officer Elon Musk said he could not see a compelling use-case for the VR-driven metaverse, adding: "I don't see someone strapping a frigging screen to their face all day." In January 2022, Louise Eccles of The Sunday Times logged into the metaverse with the intention of making a video guide. She wrote: Initially, my experience with the Oculus went well. I attended work meetings as an avatar and tried an exercise class set in the streets of Paris. The headset enabled me to feel the thrill of carving down mountains on a snowboard and the adrenaline rush of climbing a mountain without ropes. Yet switching to the social apps, where you mingle with strangers also using VR headsets, it was at times predatory and vile. Eccles described being sexually harassed by another user, as well as "accents from all over the world, American, Indian, English, Australian, using racist, sexist, homophobic and transphobic language". She also encountered users as young as 7 years old on the platform, despite Oculus headsets being intended for users over 13. See also References External links 37°29′06″N 122°08′54″W / 37.48500°N 122.14833°W / 37.48500; -122.14833 |
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[SOURCE: https://en.wikipedia.org/wiki/OpenAI#cite_ref-reuters-restructure_62-1] | [TOKENS: 8773] |
Contents OpenAI OpenAI is an American artificial intelligence research organization comprising both a non-profit foundation and a controlled for-profit public benefit corporation (PBC), headquartered in San Francisco. It aims to develop "safe and beneficial" artificial general intelligence (AGI), which it defines as "highly autonomous systems that outperform humans at most economically valuable work". OpenAI is widely recognized for its development of the GPT family of large language models, the DALL-E series of text-to-image models, and the Sora series of text-to-video models, which have influenced industry research and commercial applications. Its release of ChatGPT in November 2022 has been credited with catalyzing widespread interest in generative AI. The organization was founded in 2015 in Delaware but evolved a complex corporate structure. As of October 2025, following restructuring approved by California and Delaware regulators, the non-profit OpenAI Foundation holds 26% of the for-profit OpenAI Group PBC, with Microsoft holding 27% and employees/other investors holding 47%. Under its governance arrangements, the OpenAI Foundation holds the authority to appoint the board of the for-profit OpenAI Group PBC, a mechanism designed to align the entity’s strategic direction with the Foundation’s charter. Microsoft previously invested over $13 billion into OpenAI, and provides Azure cloud computing resources. In October 2025, OpenAI conducted a $6.6 billion share sale that valued the company at $500 billion. In 2023 and 2024, OpenAI faced multiple lawsuits for alleged copyright infringement against authors and media companies whose work was used to train some of OpenAI's products. In November 2023, OpenAI's board removed Sam Altman as CEO, citing a lack of confidence in him, but reinstated him five days later following a reconstruction of the board. Throughout 2024, roughly half of then-employed AI safety researchers left OpenAI, citing the company's prominent role in an industry-wide problem. Founding In December 2015, OpenAI was founded as a not for profit organization by Sam Altman, Elon Musk, Ilya Sutskever, Greg Brockman, Trevor Blackwell, Vicki Cheung, Andrej Karpathy, Durk Kingma, John Schulman, Pamela Vagata, and Wojciech Zaremba, with Sam Altman and Elon Musk as the co-chairs. A total of $1 billion in capital was pledged by Sam Altman, Greg Brockman, Elon Musk, Reid Hoffman, Jessica Livingston, Peter Thiel, Amazon Web Services (AWS), and Infosys. However, the actual capital collected significantly lagged pledges. According to company disclosures, only $130 million had been received by 2019. In its founding charter, OpenAI stated an intention to collaborate openly with other institutions by making certain patents and research publicly available, but later restricted access to its most capable models, citing competitive and safety concerns. OpenAI was initially run from Brockman's living room. It was later headquartered at the Pioneer Building in the Mission District, San Francisco. According to OpenAI's charter, its founding mission is "to ensure that artificial general intelligence (AGI)—by which we mean highly autonomous systems that outperform humans at most economically valuable work—benefits all of humanity." Musk and Altman stated in 2015 that they were partly motivated by concerns about AI safety and existential risk from artificial general intelligence. OpenAI stated that "it's hard to fathom how much human-level AI could benefit society", and that it is equally difficult to comprehend "how much it could damage society if built or used incorrectly". The startup also wrote that AI "should be an extension of individual human wills and, in the spirit of liberty, as broadly and evenly distributed as possible", and that "because of AI's surprising history, it's hard to predict when human-level AI might come within reach. When it does, it'll be important to have a leading research institution which can prioritize a good outcome for all over its own self-interest." Co-chair Sam Altman expected a decades-long project that eventually surpasses human intelligence. Brockman met with Yoshua Bengio, one of the "founding fathers" of deep learning, and drew up a list of great AI researchers. Brockman was able to hire nine of them as the first employees in December 2015. OpenAI did not pay AI researchers salaries comparable to those of Facebook or Google. It also did not pay stock options which AI researchers typically get. Nevertheless, OpenAI spent $7 million on its first 52 employees in 2016. OpenAI's potential and mission drew these researchers to the firm; a Google employee said he was willing to leave Google for OpenAI "partly because of the very strong group of people and, to a very large extent, because of its mission." OpenAI co-founder Wojciech Zaremba stated that he turned down "borderline crazy" offers of two to three times his market value to join OpenAI instead. In April 2016, OpenAI released a public beta of "OpenAI Gym", its platform for reinforcement learning research. Nvidia gifted its first DGX-1 supercomputer to OpenAI in August 2016 to help it train larger and more complex AI models with the capability of reducing processing time from six days to two hours. In December 2016, OpenAI released "Universe", a software platform for measuring and training an AI's general intelligence across the world's supply of games, websites, and other applications. Corporate structure In 2019, OpenAI transitioned from non-profit to "capped" for-profit, with the profit being capped at 100 times any investment. According to OpenAI, the capped-profit model allows OpenAI Global, LLC to legally attract investment from venture funds and, in addition, to grant employees stakes in the company. Many top researchers work for Google Brain, DeepMind, or Facebook, which offer equity that a nonprofit would be unable to match. Before the transition, OpenAI was legally required to publicly disclose the compensation of its top employees. The company then distributed equity to its employees and partnered with Microsoft, announcing an investment package of $1 billion into the company. Since then, OpenAI systems have run on an Azure-based supercomputing platform from Microsoft. OpenAI Global, LLC then announced its intention to commercially license its technologies. It planned to spend $1 billion "within five years, and possibly much faster". Altman stated that even a billion dollars may turn out to be insufficient, and that the lab may ultimately need "more capital than any non-profit has ever raised" to achieve artificial general intelligence. The nonprofit, OpenAI, Inc., is the sole controlling shareholder of OpenAI Global, LLC, which, despite being a for-profit company, retains a formal fiduciary responsibility to OpenAI, Inc.'s nonprofit charter. A majority of OpenAI, Inc.'s board is barred from having financial stakes in OpenAI Global, LLC. In addition, minority members with a stake in OpenAI Global, LLC are barred from certain votes due to conflict of interest. Some researchers have argued that OpenAI Global, LLC's switch to for-profit status is inconsistent with OpenAI's claims to be "democratizing" AI. On February 29, 2024, Elon Musk filed a lawsuit against OpenAI and CEO Sam Altman, accusing them of shifting focus from public benefit to profit maximization—a case OpenAI dismissed as "incoherent" and "frivolous," though Musk later revived legal action against Altman and others in August. On April 9, 2024, OpenAI countersued Musk in federal court, alleging that he had engaged in "bad-faith tactics" to slow the company's progress and seize its innovations for his personal benefit. OpenAI also argued that Musk had previously supported the creation of a for-profit structure and had expressed interest in controlling OpenAI himself. The countersuit seeks damages and legal measures to prevent further alleged interference. On February 10, 2025, a consortium of investors led by Elon Musk submitted a $97.4 billion unsolicited bid to buy the nonprofit that controls OpenAI, declaring willingness to match or exceed any better offer. The offer was rejected on 14 February 2025, with OpenAI stating that it was not for sale, but the offer complicated Altman's restructuring plan by suggesting a lower bar for how much the nonprofit should be valued. OpenAI, Inc. was originally designed as a nonprofit in order to ensure that AGI "benefits all of humanity" rather than "the private gain of any person". In 2019, it created OpenAI Global, LLC, a capped-profit subsidiary controlled by the nonprofit. In December 2024, OpenAI proposed a restructuring plan to convert the capped-profit into a Delaware-based public benefit corporation (PBC), and to release it from the control of the nonprofit. The nonprofit would sell its control and other assets, getting equity in return, and would use it to fund and pursue separate charitable projects, including in science and education. OpenAI's leadership described the change as necessary to secure additional investments, and claimed that the nonprofit's founding mission to ensure AGI "benefits all of humanity" would be better fulfilled. The plan has been criticized by former employees. A legal letter named "Not For Private Gain" asked the attorneys general of California and Delaware to intervene, stating that the restructuring is illegal and would remove governance safeguards from the nonprofit and the attorneys general. The letter argues that OpenAI's complex structure was deliberately designed to remain accountable to its mission, without the conflicting pressure of maximizing profits. It contends that the nonprofit is best positioned to advance its mission of ensuring AGI benefits all of humanity by continuing to control OpenAI Global, LLC, whatever the amount of equity that it could get in exchange. PBCs can choose how they balance their mission with profit-making. Controlling shareholders have a large influence on how closely a PBC sticks to its mission. On October 28, 2025, OpenAI announced that it had adopted the new PBC corporate structure after receiving approval from the attorneys general of California and Delaware. Under the new structure, OpenAI's for-profit branch became a public benefit corporation known as OpenAI Group PBC, while the non-profit was renamed to the OpenAI Foundation. The OpenAI Foundation holds a 26% stake in the PBC, while Microsoft holds a 27% stake and the remaining 47% is owned by employees and other investors. All members of the OpenAI Group PBC board of directors will be appointed by the OpenAI Foundation, which can remove them at any time. Members of the Foundation's board will also serve on the for-profit board. The new structure allows the for-profit PBC to raise investor funds like most traditional tech companies, including through an initial public offering, which Altman claimed was the most likely path forward. In January 2023, OpenAI Global, LLC was in talks for funding that would value the company at $29 billion, double its 2021 value. On January 23, 2023, Microsoft announced a new US$10 billion investment in OpenAI Global, LLC over multiple years, partially needed to use Microsoft's cloud-computing service Azure. From September to December, 2023, Microsoft rebranded all variants of its Copilot to Microsoft Copilot, and they added MS-Copilot to many installations of Windows and released Microsoft Copilot mobile apps. Following OpenAI's 2025 restructuring, Microsoft owns a 27% stake in the for-profit OpenAI Group PBC, valued at $135 billion. In a deal announced the same day, OpenAI agreed to purchase $250 billion of Azure services, with Microsoft ceding their right of first refusal over OpenAI's future cloud computing purchases. As part of the deal, OpenAI will continue to share 20% of its revenue with Microsoft until it achieves AGI, which must now be verified by an independent panel of experts. The deal also loosened restrictions on both companies working with third parties, allowing Microsoft to pursue AGI independently and allowing OpenAI to develop products with other companies. In 2017, OpenAI spent $7.9 million, a quarter of its functional expenses, on cloud computing alone. In comparison, DeepMind's total expenses in 2017 were $442 million. In the summer of 2018, training OpenAI's Dota 2 bots required renting 128,000 CPUs and 256 GPUs from Google for multiple weeks. In October 2024, OpenAI completed a $6.6 billion capital raise with a $157 billion valuation including investments from Microsoft, Nvidia, and SoftBank. On January 21, 2025, Donald Trump announced The Stargate Project, a joint venture between OpenAI, Oracle, SoftBank and MGX to build an AI infrastructure system in conjunction with the US government. The project takes its name from OpenAI's existing "Stargate" supercomputer project and is estimated to cost $500 billion. The partners planned to fund the project over the next four years. In July, the United States Department of Defense announced that OpenAI had received a $200 million contract for AI in the military, along with Anthropic, Google, and xAI. In the same month, the company made a deal with the UK Government to use ChatGPT and other AI tools in public services. OpenAI subsequently began a $50 million fund to support nonprofit and community organizations. In April 2025, OpenAI raised $40 billion at a $300 billion post-money valuation, which was the highest-value private technology deal in history. The financing round was led by SoftBank, with other participants including Microsoft, Coatue, Altimeter and Thrive. In July 2025, the company reported annualized revenue of $12 billion. This was an increase from $3.7 billion in 2024, which was driven by ChatGPT subscriptions, which reached 20 million paid subscribers by April 2025, up from 15.5 million at the end of 2024, alongside a rapidly expanding enterprise customer base that grew to five million business users. The company’s cash burn remains high because of the intensive computational costs required to train and operate large language models. It projects an $8 billion operating loss in 2025. OpenAI reports revised long-term spending projections totaling approximately $115 billion through 2029, with annual expenditures projected to escalate significantly, reaching $17 billion in 2026, $35 billion in 2027, and $45 billion in 2028. These expenditures are primarily allocated toward expanding compute infrastructure, developing proprietary AI chips, constructing data centers, and funding intensive model training programs, with more than half of the spending through the end of the decade expected to support research-intensive compute for model training and development. The company's financial strategy prioritizes market expansion and technological advancement over near-term profitability, with OpenAI targeting cash-flow-positive operations by 2029 and projecting revenue of approximately $200 billion by 2030. This aggressive spending trajectory underscores both the enormous capital requirements of scaling cutting-edge AI technology and OpenAI's commitment to maintaining its position as a leader in the artificial intelligence industry. In October 2025, OpenAI completed an employee share sale of up to $10 billion to existing investors which valued the company at $500 billion. The deal values OpenAI as the most valuable privately owned company in the world—surpassing SpaceX as the world's most valuable private company. On November 17, 2023, Sam Altman was removed as CEO when its board of directors (composed of Helen Toner, Ilya Sutskever, Adam D'Angelo and Tasha McCauley) cited a lack of confidence in him. Chief Technology Officer Mira Murati took over as interim CEO. Greg Brockman, the president of OpenAI, was also removed as chairman of the board and resigned from the company's presidency shortly thereafter. Three senior OpenAI researchers subsequently resigned: director of research and GPT-4 lead Jakub Pachocki, head of AI risk Aleksander Mądry, and researcher Szymon Sidor. On November 18, 2023, there were reportedly talks of Altman returning as CEO amid pressure placed upon the board by investors such as Microsoft and Thrive Capital, who objected to Altman's departure. Although Altman himself spoke in favor of returning to OpenAI, he has since stated that he considered starting a new company and bringing former OpenAI employees with him if talks to reinstate him didn't work out. The board members agreed "in principle" to resign if Altman returned. On November 19, 2023, negotiations with Altman to return failed and Murati was replaced by Emmett Shear as interim CEO. The board initially contacted Anthropic CEO Dario Amodei (a former OpenAI executive) about replacing Altman, and proposed a merger of the two companies, but both offers were declined. On November 20, 2023, Microsoft CEO Satya Nadella announced Altman and Brockman would be joining Microsoft to lead a new advanced AI research team, but added that they were still committed to OpenAI despite recent events. Before the partnership with Microsoft was finalized, Altman gave the board another opportunity to negotiate with him. About 738 of OpenAI's 770 employees, including Murati and Sutskever, signed an open letter stating they would quit their jobs and join Microsoft if the board did not rehire Altman and then resign. This prompted OpenAI investors to consider legal action against the board as well. In response, OpenAI management sent an internal memo to employees stating that negotiations with Altman and the board had resumed and would take some time. On November 21, 2023, after continued negotiations, Altman and Brockman returned to the company in their prior roles along with a reconstructed board made up of new members Bret Taylor (as chairman) and Lawrence Summers, with D'Angelo remaining. According to subsequent reporting, shortly before Altman’s firing, some employees raised concerns to the board about how he had handled the safety implications of a recent internal AI capability discovery. On November 29, 2023, OpenAI announced that an anonymous Microsoft employee had joined the board as a non-voting member to observe the company's operations; Microsoft resigned from the board in July 2024. In February 2024, the Securities and Exchange Commission subpoenaed OpenAI's internal communication to determine if Altman's alleged lack of candor misled investors. In 2024, following the temporary removal of Sam Altman and his return, many employees gradually left OpenAI, including most of the original leadership team and a significant number of AI safety researchers. In August 2023, it was announced that OpenAI had acquired the New York-based start-up Global Illumination, a company that deploys AI to develop digital infrastructure and creative tools. In June 2024, OpenAI acquired Multi, a startup focused on remote collaboration. In March 2025, OpenAI reached a deal with CoreWeave to acquire $350 million worth of CoreWeave shares and access to AI infrastructure, in return for $11.9 billion paid over five years. Microsoft was already CoreWeave's biggest customer in 2024. Alongside their other business dealings, OpenAI and Microsoft were renegotiating the terms of their partnership to facilitate a potential future initial public offering by OpenAI, while ensuring Microsoft's continued access to advanced AI models. On May 21, OpenAI announced the $6.5 billion acquisition of io, an AI hardware start-up founded by former Apple designer Jony Ive in 2024. In September 2025, OpenAI agreed to acquire the product testing startup Statsig for $1.1 billion in an all-stock deal and appointed Statsig's founding CEO Vijaye Raji as OpenAI's chief technology officer of applications. The company also announced development of an AI-driven hiring service designed to rival LinkedIn. OpenAI acquired personal finance app Roi in October 2025. In October 2025, OpenAI acquired Software Applications Incorporated, the developer of Sky, a macOS-based natural language interface designed to operate across desktop applications. The Sky team joined OpenAI, and the company announced plans to integrate Sky’s capabilities into ChatGPT. In December 2025, it was announced OpenAI had agreed to acquire Neptune, an AI tooling startup that helps companies track and manage model training, for an undisclosed amount. In January 2026, it was announced OpenAI had acquired healthcare technology startup Torch for approximately $60 million. The acquisition followed the launch of OpenAI’s ChatGPT Health product and was intended to strengthen the company’s medical data and healthcare artificial intelligence capabilities. OpenAI has been criticized for outsourcing the annotation of data sets to Sama, a company based in San Francisco that employed workers in Kenya. These annotations were used to train an AI model to detect toxicity, which could then be used to moderate toxic content, notably from ChatGPT's training data and outputs. However, these pieces of text usually contained detailed descriptions of various types of violence, including sexual violence. The investigation uncovered that OpenAI began sending snippets of data to Sama as early as November 2021. The four Sama employees interviewed by Time described themselves as mentally scarred. OpenAI paid Sama $12.50 per hour of work, and Sama was redistributing the equivalent of between $1.32 and $2.00 per hour post-tax to its annotators. Sama's spokesperson said that the $12.50 was also covering other implicit costs, among which were infrastructure expenses, quality assurance and management. In 2024, OpenAI began collaborating with Broadcom to design a custom AI chip capable of both training and inference, targeted for mass production in 2026 and to be manufactured by TSMC on a 3 nm process node. This initiative intended to reduce OpenAI's dependence on Nvidia GPUs, which are costly and face high demand in the market. In January 2024, Arizona State University purchased ChatGPT Enterprise in OpenAI's first deal with a university. In June 2024, Apple Inc. signed a contract with OpenAI to integrate ChatGPT features into its products as part of its new Apple Intelligence initiative. In June 2025, OpenAI began renting Google Cloud's Tensor Processing Units (TPUs) to support ChatGPT and related services, marking its first meaningful use of non‑Nvidia AI chips. In September 2025, it was revealed that OpenAI signed a contract with Oracle to purchase $300 billion in computing power over the next five years. In September 2025, OpenAI and NVIDIA announced a memorandum of understanding that included a potential deployment of at least 10 gigawatts of NVIDIA systems and a $100 billion investment from NVIDIA in OpenAI. OpenAI expected the negotiations to be completed within weeks. As of January 2026, this has not been realized, and the two sides are rethinking the future of their partnership. In October 2025, OpenAI announced a multi-billion dollar deal with AMD. OpenAI committed to purchasing six gigawatts worth of AMD chips, starting with the MI450. OpenAI will have the option to buy up to 160 million shares of AMD, about 10% of the company, depending on development, performance and share price targets. In December 2025, Disney said it would make a $1 billion investment in OpenAI, and signed a three-year licensing deal that will let users generate videos using Sora—OpenAI's short-form AI video platform. More than 200 Disney, Marvel, Star Wars and Pixar characters will be available to OpenAI users. In early 2026, Amazon entered advanced discussions to invest up to $50 billion in OpenAI as part of a potential artificial intelligence partnership. Under the proposed agreement, OpenAI’s models could be integrated into Amazon’s digital assistant Alexa and other internal projects. OpenAI provides LLMs to the Artificial Intelligence Cyber Challenge and to the Advanced Research Projects Agency for Health. In October 2024, The Intercept revealed that OpenAI's tools are considered "essential" for AFRICOM's mission and included in an "Exception to Fair Opportunity" contractual agreement between the United States Department of Defense and Microsoft. In December 2024, OpenAI said it would partner with defense-tech company Anduril to build drone defense technologies for the United States and its allies. In 2025, OpenAI's Chief Product Officer, Kevin Weil, was commissioned lieutenant colonel in the U.S. Army to join Detachment 201 as senior advisor. In June 2025, the U.S. Department of Defense awarded OpenAI a $200 million one-year contract to develop AI tools for military and national security applications. OpenAI announced a new program, OpenAI for Government, to give federal, state, and local governments access to its models, including ChatGPT. Services In February 2019, GPT-2 was announced, which gained attention for its ability to generate human-like text. In 2020, OpenAI announced GPT-3, a language model trained on large internet datasets. GPT-3 is aimed at natural language answering questions, but it can also translate between languages and coherently generate improvised text. It also announced that an associated API, named the API, would form the heart of its first commercial product. Eleven employees left OpenAI, mostly between December 2020 and January 2021, in order to establish Anthropic. In 2021, OpenAI introduced DALL-E, a specialized deep learning model adept at generating complex digital images from textual descriptions, utilizing a variant of the GPT-3 architecture. In December 2022, OpenAI received widespread media coverage after launching a free preview of ChatGPT, its new AI chatbot based on GPT-3.5. According to OpenAI, the preview received over a million signups within the first five days. According to anonymous sources cited by Reuters in December 2022, OpenAI Global, LLC was projecting $200 million of revenue in 2023 and $1 billion in revenue in 2024. After ChatGPT was launched, Google announced a similar chatbot, Bard, amid internal concerns that ChatGPT could threaten Google’s position as a primary source of online information. On February 7, 2023, Microsoft announced that it was building AI technology based on the same foundation as ChatGPT into Microsoft Bing, Edge, Microsoft 365 and other products. On March 14, 2023, OpenAI released GPT-4, both as an API (with a waitlist) and as a feature of ChatGPT Plus. On November 6, 2023, OpenAI launched GPTs, allowing individuals to create customized versions of ChatGPT for specific purposes, further expanding the possibilities of AI applications across various industries. On November 14, 2023, OpenAI announced they temporarily suspended new sign-ups for ChatGPT Plus due to high demand. Access for newer subscribers re-opened a month later on December 13. In December 2024, the company launched the Sora model. It also launched OpenAI o1, an early reasoning model that was internally codenamed strawberry. Additionally, ChatGPT Pro—a $200/month subscription service offering unlimited o1 access and enhanced voice features—was introduced, and preliminary benchmark results for the upcoming OpenAI o3 models were shared. On January 23, 2025, OpenAI released Operator, an AI agent and web automation tool for accessing websites to execute goals defined by users. The feature was only available to Pro users in the United States. OpenAI released deep research agent, nine days later. It scored a 27% accuracy on the benchmark Humanity's Last Exam (HLE). Altman later stated GPT-4.5 would be the last model without full chain-of-thought reasoning. In July 2025, reports indicated that AI models by both OpenAI and Google DeepMind solved mathematics problems at the level of top-performing students in the International Mathematical Olympiad. OpenAI's large language model was able to achieve gold medal-level performance, reflecting significant progress in AI's reasoning abilities. On October 6, 2025, OpenAI unveiled its Agent Builder platform during the company's DevDay event. The platform includes a visual drag-and-drop interface that lets developers and businesses design, test, and deploy agentic workflows with limited coding. On October 21, 2025, OpenAI introduced ChatGPT Atlas, a browser integrating the ChatGPT assistant directly into web navigation, to compete with existing browsers such as Google Chrome and Apple Safari. On December 11, 2025, OpenAI announced GPT-5.2. This model will be better at creating spreadsheets, building presentations, perceiving images, writing code and understanding long context. On January 27, 2026, OpenAI introduced Prism, a LaTeX-native workspace meant to assist scientists to help with research and writing. The platform utilizes GPT-5.2 as a backend to automate the process of drafting for scientific papers, including features for managing citations, complex equation formatting, and real-time collaborative editing. In March 2023, the company was criticized for disclosing particularly few technical details about products like GPT-4, contradicting its initial commitment to openness and making it harder for independent researchers to replicate its work and develop safeguards. OpenAI cited competitiveness and safety concerns to justify this repudiation. OpenAI's former chief scientist Ilya Sutskever argued in 2023 that open-sourcing increasingly capable models was increasingly risky, and that the safety reasons for not open-sourcing the most potent AI models would become "obvious" in a few years. In September 2025, OpenAI published a study on how people use ChatGPT for everyday tasks. The study found that "non-work tasks" (according to an LLM-based classifier) account for more than 72 percent of all ChatGPT usage, with a minority of overall usage related to business productivity. In July 2023, OpenAI launched the superalignment project, aiming within four years to determine how to align future superintelligent systems. OpenAI promised to dedicate 20% of its computing resources to the project, although the team denied receiving anything close to 20%. OpenAI ended the project in May 2024 after its co-leaders Ilya Sutskever and Jan Leike left the company. In August 2025, OpenAI was criticized after thousands of private ChatGPT conversations were inadvertently exposed to public search engines like Google due to an experimental "share with search engines" feature. The opt-in toggle, intended to allow users to make specific chats discoverable, resulted in some discussions including personal details such as names, locations, and intimate topics appearing in search results when users accidentally enabled it while sharing links. OpenAI announced the feature's permanent removal on August 1, 2025, and the company began coordinating with search providers to remove the exposed content, emphasizing that it was not a security breach but a design flaw that heightened privacy risks. CEO Sam Altman acknowledged the issue in a podcast, noting users often treat ChatGPT as a confidant for deeply personal matters, which amplified concerns about AI handling sensitive data. Management In 2018, Musk resigned from his Board of Directors seat, citing "a potential future conflict [of interest]" with his role as CEO of Tesla due to Tesla's AI development for self-driving cars. OpenAI stated that Musk's financial contributions were below $45 million. On March 3, 2023, Reid Hoffman resigned from his board seat, citing a desire to avoid conflicts of interest with his investments in AI companies via Greylock Partners, and his co-founding of the AI startup Inflection AI. Hoffman remained on the board of Microsoft, a major investor in OpenAI. In May 2024, Chief Scientist Ilya Sutskever resigned and was succeeded by Jakub Pachocki. Co-leader Jan Leike also departed amid concerns over safety and trust. OpenAI then signed deals with Reddit, News Corp, Axios, and Vox Media. Paul Nakasone then joined the board of OpenAI. In August 2024, cofounder John Schulman left OpenAI to join Anthropic, and OpenAI's president Greg Brockman took extended leave until November. In September 2024, CTO Mira Murati left the company. In November 2025, Lawrence Summers resigned from the board of directors. Governance and legal issues In May 2023, Sam Altman, Greg Brockman and Ilya Sutskever posted recommendations for the governance of superintelligence. They stated that superintelligence could happen within the next 10 years, allowing a "dramatically more prosperous future" and that "given the possibility of existential risk, we can't just be reactive". They proposed creating an international watchdog organization similar to IAEA to oversee AI systems above a certain capability threshold, suggesting that relatively weak AI systems on the other side should not be overly regulated. They also called for more technical safety research for superintelligences, and asked for more coordination, for example through governments launching a joint project which "many current efforts become part of". In July 2023, the FTC issued a civil investigative demand to OpenAI to investigate whether the company's data security and privacy practices to develop ChatGPT were unfair or harmed consumers (including by reputational harm) in violation of Section 5 of the Federal Trade Commission Act of 1914. These are typically preliminary investigative matters and are nonpublic, but the FTC's document was leaked. In July 2023, the FTC launched an investigation into OpenAI over allegations that the company scraped public data and published false and defamatory information. They asked OpenAI for comprehensive information about its technology and privacy safeguards, as well as any steps taken to prevent the recurrence of situations in which its chatbot generated false and derogatory content about people. The agency also raised concerns about ‘circular’ spending arrangements—for example, Microsoft extending Azure credits to OpenAI while both companies shared engineering talent—and warned that such structures could negatively affect the public. In September 2024, OpenAI's global affairs chief endorsed the UK's "smart" AI regulation during testimony to a House of Lords committee. In February 2025, OpenAI CEO Sam Altman stated that the company is interested in collaborating with the People's Republic of China, despite regulatory restrictions imposed by the U.S. government. This shift comes in response to the growing influence of the Chinese artificial intelligence company DeepSeek, which has disrupted the AI market with open models, including DeepSeek V3 and DeepSeek R1. Following DeepSeek's market emergence, OpenAI enhanced security protocols to protect proprietary development techniques from industrial espionage. Some industry observers noted similarities between DeepSeek's model distillation approach and OpenAI's methodology, though no formal intellectual property claim was filed. According to Oliver Roberts, in March 2025, the United States had 781 state AI bills or laws. OpenAI advocated for preempting state AI laws with federal laws. According to Scott Kohler, OpenAI has opposed California's AI legislation and suggested that the state bill encroaches on a more competent federal government. Public Citizen opposed a federal preemption on AI and pointed to OpenAI's growth and valuation as evidence that existing state laws have not hampered innovation. Before May 2024, OpenAI required departing employees to sign a lifelong non-disparagement agreement forbidding them from criticizing OpenAI and acknowledging the existence of the agreement. Daniel Kokotajlo, a former employee, publicly stated that he forfeited his vested equity in OpenAI in order to leave without signing the agreement. Sam Altman stated that he was unaware of the equity cancellation provision, and that OpenAI never enforced it to cancel any employee's vested equity. However, leaked documents and emails refute this claim. On May 23, 2024, OpenAI sent a memo releasing former employees from the agreement. OpenAI was sued for copyright infringement by authors Sarah Silverman, Matthew Butterick, Paul Tremblay and Mona Awad in July 2023. In September 2023, 17 authors, including George R. R. Martin, John Grisham, Jodi Picoult and Jonathan Franzen, joined the Authors Guild in filing a class action lawsuit against OpenAI, alleging that the company's technology was illegally using their copyrighted work. The New York Times also sued the company in late December 2023. In May 2024 it was revealed that OpenAI had destroyed its Books1 and Books2 training datasets, which were used in the training of GPT-3, and which the Authors Guild believed to have contained over 100,000 copyrighted books. In 2021, OpenAI developed a speech recognition tool called Whisper. OpenAI used it to transcribe more than one million hours of YouTube videos into text for training GPT-4. The automated transcription of YouTube videos raised concerns within OpenAI employees regarding potential violations of YouTube's terms of service, which prohibit the use of videos for applications independent of the platform, as well as any type of automated access to its videos. Despite these concerns, the project proceeded with notable involvement from OpenAI's president, Greg Brockman. The resulting dataset proved instrumental in training GPT-4. In February 2024, The Intercept as well as Raw Story and Alternate Media Inc. filed lawsuit against OpenAI on copyright litigation ground. The lawsuit is said to have charted a new legal strategy for digital-only publishers to sue OpenAI. On April 30, 2024, eight newspapers filed a lawsuit in the Southern District of New York against OpenAI and Microsoft, claiming illegal harvesting of their copyrighted articles. The suing publications included The Mercury News, The Denver Post, The Orange County Register, St. Paul Pioneer Press, Chicago Tribune, Orlando Sentinel, Sun Sentinel, and New York Daily News. In June 2023, a lawsuit claimed that OpenAI scraped 300 billion words online without consent and without registering as a data broker. It was filed in San Francisco, California, by sixteen anonymous plaintiffs. They also claimed that OpenAI and its partner as well as customer Microsoft continued to unlawfully collect and use personal data from millions of consumers worldwide to train artificial intelligence models. On May 22, 2024, OpenAI entered into an agreement with News Corp to integrate news content from The Wall Street Journal, the New York Post, The Times, and The Sunday Times into its AI platform. Meanwhile, other publications like The New York Times chose to sue OpenAI and Microsoft for copyright infringement over the use of their content to train AI models. In November 2024, a coalition of Canadian news outlets, including the Toronto Star, Metroland Media, Postmedia, The Globe and Mail, The Canadian Press and CBC, sued OpenAI for using their news articles to train its software without permission. In October 2024 during a New York Times interview, Suchir Balaji accused OpenAI of violating copyright law in developing its commercial LLMs which he had helped engineer. He was a likely witness in a major copyright trial against the AI company, and was one of several of its current or former employees named in court filings as potentially having documents relevant to the case. On November 26, 2024, Balaji died by suicide. His death prompted the circulation of conspiracy theories alleging that he had been deliberately silenced. California Congressman Ro Khanna endorsed calls for an investigation. On April 24, 2025, Ziff Davis sued OpenAI in Delaware federal court for copyright infringement. Ziff Davis is known for publications such as ZDNet, PCMag, CNET, IGN and Lifehacker. In April 2023, the EU's European Data Protection Board (EDPB) formed a dedicated task force on ChatGPT "to foster cooperation and to exchange information on possible enforcement actions conducted by data protection authorities" based on the "enforcement action undertaken by the Italian data protection authority against OpenAI about the ChatGPT service". In late April 2024 NOYB filed a complaint with the Austrian Datenschutzbehörde against OpenAI for violating the European General Data Protection Regulation. A text created with ChatGPT gave a false date of birth for a living person without giving the individual the option to see the personal data used in the process. A request to correct the mistake was denied. Additionally, neither the recipients of ChatGPT's work nor the sources used, could be made available, OpenAI claimed. OpenAI was criticized for lifting its ban on using ChatGPT for "military and warfare". Up until January 10, 2024, its "usage policies" included a ban on "activity that has high risk of physical harm, including", specifically, "weapons development" and "military and warfare". Its new policies prohibit "[using] our service to harm yourself or others" and to "develop or use weapons". In August 2025, the parents of a 16-year-old boy who died by suicide filed a wrongful death lawsuit against OpenAI (and CEO Sam Altman), alleging that months of conversations with ChatGPT about mental health and methods of self-harm contributed to their son's death and that safeguards were inadequate for minors. OpenAI expressed condolences and said it was strengthening protections (including updated crisis response behavior and parental controls). Coverage described it as a first-of-its-kind wrongful death case targeting the company's chatbot. The complaint was filed in California state court in San Francisco. In November 2025, the Social Media Victims Law Center and Tech Justice Law Project filed seven lawsuits against OpenAI, of which four lawsuits alleged wrongful death. The suits were filed on behalf of Zane Shamblin, 23, of Texas; Amaurie Lacey, 17, of Georgia; Joshua Enneking, 26, of Florida; and Joe Ceccanti, 48, of Oregon, who each committed suicide after prolonged ChatGPT usage. In December 2025, Stein-Erik Soelberg, who was 56 years old at the time, allegedly murdered his mother Suzanne Adams. In the months prior the paranoid, delusional man often discussed his ideas with ChatGPT. Adam's estate then sued OpenAI claiming that the company shared responsibility due to the risk of chatbot psychosis despite the fact that chatbot psychosis is not a real medical diagnosis. OpenAI responded saying they will make ChatGPT safer for users disconnected from reality. See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Python_(programming_language)#cite_ref-AutoNT-59_67-0] | [TOKENS: 4314] |
Contents Python (programming language) Python is a high-level, general-purpose programming language. Its design philosophy emphasizes code readability with the use of significant indentation. Python is dynamically type-checked and garbage-collected. It supports multiple programming paradigms, including structured (particularly procedural), object-oriented and functional programming. Guido van Rossum began working on Python in the late 1980s as a successor to the ABC programming language. Python 3.0, released in 2008, was a major revision and not completely backward-compatible with earlier versions. Beginning with Python 3.5, capabilities and keywords for typing were added to the language, allowing optional static typing. As of 2026[update], the Python Software Foundation supports Python 3.10, 3.11, 3.12, 3.13, and 3.14, following the project's annual release cycle and five-year support policy. Python 3.15 is currently in the alpha development phase, and the stable release is expected to come out in October 2026. Earlier versions in the 3.x series have reached end-of-life and no longer receive security updates. Python has gained widespread use in the machine learning community. It is widely taught as an introductory programming language. Since 2003, Python has consistently ranked in the top ten of the most popular programming languages in the TIOBE Programming Community Index, which ranks based on searches in 24 platforms. History Python was conceived in the late 1980s by Guido van Rossum at Centrum Wiskunde & Informatica (CWI) in the Netherlands. It was designed as a successor to the ABC programming language, which was inspired by SETL, capable of exception handling and interfacing with the Amoeba operating system. Python implementation began in December 1989. Van Rossum first released it in 1991 as Python 0.9.0. Van Rossum assumed sole responsibility for the project, as the lead developer, until 12 July 2018, when he announced his "permanent vacation" from responsibilities as Python's "benevolent dictator for life" (BDFL); this title was bestowed on him by the Python community to reflect his long-term commitment as the project's chief decision-maker. (He has since come out of retirement and is self-titled "BDFL-emeritus".) In January 2019, active Python core developers elected a five-member Steering Council to lead the project. The name Python derives from the British comedy series Monty Python's Flying Circus. (See § Naming.) Python 2.0 was released on 16 October 2000, featuring many new features such as list comprehensions, cycle-detecting garbage collection, reference counting, and Unicode support. Python 2.7's end-of-life was initially set for 2015, and then postponed to 2020 out of concern that a large body of existing code could not easily be forward-ported to Python 3. It no longer receives security patches or updates. While Python 2.7 and older versions are officially unsupported, a different unofficial Python implementation, PyPy, continues to support Python 2, i.e., "2.7.18+" (plus 3.11), with the plus signifying (at least some) "backported security updates". Python 3.0 was released on 3 December 2008, and was a major revision and not completely backward-compatible with earlier versions, with some new semantics and changed syntax. Python 2.7.18, released in 2020, was the last release of Python 2. Several releases in the Python 3.x series have added new syntax to the language, and made a few (considered very minor) backward-incompatible changes. As of January 2026[update], Python 3.14.3 is the latest stable release. All older 3.x versions had a security update down to Python 3.9.24 then again with 3.9.25, the final version in 3.9 series. Python 3.10 is, since November 2025, the oldest supported branch. Python 3.15 has an alpha released, and Android has an official downloadable executable available for Python 3.14. Releases receive two years of full support followed by three years of security support. Design philosophy and features Python is a multi-paradigm programming language. Object-oriented programming and structured programming are fully supported, and many of their features support functional programming and aspect-oriented programming – including metaprogramming and metaobjects. Many other paradigms are supported via extensions, including design by contract and logic programming. Python is often referred to as a 'glue language' because it is purposely designed to be able to integrate components written in other languages. Python uses dynamic typing and a combination of reference counting and a cycle-detecting garbage collector for memory management. It uses dynamic name resolution (late binding), which binds method and variable names during program execution. Python's design offers some support for functional programming in the "Lisp tradition". It has filter, map, and reduce functions; list comprehensions, dictionaries, sets, and generator expressions. The standard library has two modules (itertools and functools) that implement functional tools borrowed from Haskell and Standard ML. Python's core philosophy is summarized in the Zen of Python (PEP 20) written by Tim Peters, which includes aphorisms such as these: However, Python has received criticism for violating these principles and adding unnecessary language bloat. Responses to these criticisms note that the Zen of Python is a guideline rather than a rule. The addition of some new features had been controversial: Guido van Rossum resigned as Benevolent Dictator for Life after conflict about adding the assignment expression operator in Python 3.8. Nevertheless, rather than building all functionality into its core, Python was designed to be highly extensible via modules. This compact modularity has made it particularly popular as a means of adding programmable interfaces to existing applications. Van Rossum's vision of a small core language with a large standard library and easily extensible interpreter stemmed from his frustrations with ABC, which represented the opposite approach. Python claims to strive for a simpler, less-cluttered syntax and grammar, while giving developers a choice in their coding methodology. Python lacks do .. while loops, which Rossum considered harmful. In contrast to Perl's motto "there is more than one way to do it", Python advocates an approach where "there should be one – and preferably only one – obvious way to do it". In practice, however, Python provides many ways to achieve a given goal. There are at least three ways to format a string literal, with no certainty as to which one a programmer should use. Alex Martelli is a Fellow at the Python Software Foundation and Python book author; he wrote that "To describe something as 'clever' is not considered a compliment in the Python culture." Python's developers typically prioritize readability over performance. For example, they reject patches to non-critical parts of the CPython reference implementation that would offer increases in speed that do not justify the cost of clarity and readability.[failed verification] Execution speed can be improved by moving speed-critical functions to extension modules written in languages such as C, or by using a just-in-time compiler like PyPy. Also, it is possible to transpile to other languages. However, this approach either fails to achieve the expected speed-up, since Python is a very dynamic language, or only a restricted subset of Python is compiled (with potential minor semantic changes). Python is meant to be a fun language to use. This goal is reflected in the name – a tribute to the British comedy group Monty Python – and in playful approaches to some tutorials and reference materials. For instance, some code examples use the terms "spam" and "eggs" (in reference to a Monty Python sketch), rather than the typical terms "foo" and "bar". A common neologism in the Python community is pythonic, which has a broad range of meanings related to program style: Pythonic code may use Python idioms well; be natural or show fluency in the language; or conform with Python's minimalist philosophy and emphasis on readability. Syntax and semantics Python is meant to be an easily readable language. Its formatting is visually uncluttered and often uses English keywords where other languages use punctuation. Unlike many other languages, it does not use curly brackets to delimit blocks, and semicolons after statements are allowed but rarely used. It has fewer syntactic exceptions and special cases than C or Pascal. Python uses whitespace indentation, rather than curly brackets or keywords, to delimit blocks. An increase in indentation comes after certain statements; a decrease in indentation signifies the end of the current block. Thus, the program's visual structure accurately represents its semantic structure. This feature is sometimes termed the off-side rule. Some other languages use indentation this way; but in most, indentation has no semantic meaning. The recommended indent size is four spaces. Python's statements include the following: The assignment statement (=) binds a name as a reference to a separate, dynamically allocated object. Variables may subsequently be rebound at any time to any object. In Python, a variable name is a generic reference holder without a fixed data type; however, it always refers to some object with a type. This is called dynamic typing—in contrast to statically-typed languages, where each variable may contain only a value of a certain type. Python does not support tail call optimization or first-class continuations; according to Van Rossum, the language never will. However, better support for coroutine-like functionality is provided by extending Python's generators. Before 2.5, generators were lazy iterators; data was passed unidirectionally out of the generator. From Python 2.5 on, it is possible to pass data back into a generator function; and from version 3.3, data can be passed through multiple stack levels. Python's expressions include the following: In Python, a distinction between expressions and statements is rigidly enforced, in contrast to languages such as Common Lisp, Scheme, or Ruby. This distinction leads to duplicating some functionality, for example: A statement cannot be part of an expression; because of this restriction, expressions such as list and dict comprehensions (and lambda expressions) cannot contain statements. As a particular case, an assignment statement such as a = 1 cannot be part of the conditional expression of a conditional statement. Python uses duck typing, and it has typed objects but untyped variable names. Type constraints are not checked at definition time; rather, operations on an object may fail at usage time, indicating that the object is not of an appropriate type. Despite being dynamically typed, Python is strongly typed, forbidding operations that are poorly defined (e.g., adding a number and a string) rather than quietly attempting to interpret them. Python allows programmers to define their own types using classes, most often for object-oriented programming. New instances of classes are constructed by calling the class, for example, SpamClass() or EggsClass()); the classes are instances of the metaclass type (which is an instance of itself), thereby allowing metaprogramming and reflection. Before version 3.0, Python had two kinds of classes, both using the same syntax: old-style and new-style. Current Python versions support the semantics of only the new style. Python supports optional type annotations. These annotations are not enforced by the language, but may be used by external tools such as mypy to catch errors. Python includes a module typing including several type names for type annotations. Also, mypy supports a Python compiler called mypyc, which leverages type annotations for optimization. 1.33333 frozenset() Python includes conventional symbols for arithmetic operators (+, -, *, /), the floor-division operator //, and the modulo operator %. (With the modulo operator, a remainder can be negative, e.g., 4 % -3 == -2.) Also, Python offers the ** symbol for exponentiation, e.g. 5**3 == 125 and 9**0.5 == 3.0. Also, it offers the matrix‑multiplication operator @ . These operators work as in traditional mathematics; with the same precedence rules, the infix operators + and - can also be unary, to represent positive and negative numbers respectively. Division between integers produces floating-point results. The behavior of division has changed significantly over time: In Python terms, the / operator represents true division (or simply division), while the // operator represents floor division. Before version 3.0, the / operator represents classic division. Rounding towards negative infinity, though a different method than in most languages, adds consistency to Python. For instance, this rounding implies that the equation (a + b)//b == a//b + 1 is always true. Also, the rounding implies that the equation b*(a//b) + a%b == a is valid for both positive and negative values of a. As expected, the result of a%b lies in the half-open interval [0, b), where b is a positive integer; however, maintaining the validity of the equation requires that the result must lie in the interval (b, 0] when b is negative. Python provides a round function for rounding a float to the nearest integer. For tie-breaking, Python 3 uses the round to even method: round(1.5) and round(2.5) both produce 2. Python versions before 3 used the round-away-from-zero method: round(0.5) is 1.0, and round(-0.5) is −1.0. Python allows Boolean expressions that contain multiple equality relations to be consistent with general usage in mathematics. For example, the expression a < b < c tests whether a is less than b and b is less than c. C-derived languages interpret this expression differently: in C, the expression would first evaluate a < b, resulting in 0 or 1, and that result would then be compared with c. Python uses arbitrary-precision arithmetic for all integer operations. The Decimal type/class in the decimal module provides decimal floating-point numbers to a pre-defined arbitrary precision with several rounding modes. The Fraction class in the fractions module provides arbitrary precision for rational numbers. Due to Python's extensive mathematics library and the third-party library NumPy, the language is frequently used for scientific scripting in tasks such as numerical data processing and manipulation. Functions are created in Python by using the def keyword. A function is defined similarly to how it is called, by first providing the function name and then the required parameters. Here is an example of a function that prints its inputs: To assign a default value to a function parameter in case no actual value is provided at run time, variable-definition syntax can be used inside the function header. Code examples "Hello, World!" program: Program to calculate the factorial of a non-negative integer: Libraries Python's large standard library is commonly cited as one of its greatest strengths. For Internet-facing applications, many standard formats and protocols such as MIME and HTTP are supported. The language includes modules for creating graphical user interfaces, connecting to relational databases, generating pseudorandom numbers, arithmetic with arbitrary-precision decimals, manipulating regular expressions, and unit testing. Some parts of the standard library are covered by specifications—for example, the Web Server Gateway Interface (WSGI) implementation wsgiref follows PEP 333—but most parts are specified by their code, internal documentation, and test suites. However, because most of the standard library is cross-platform Python code, only a few modules must be altered or rewritten for variant implementations. As of 13 March 2025,[update] the Python Package Index (PyPI), the official repository for third-party Python software, contains over 614,339 packages. Development environments Most[which?] Python implementations (including CPython) include a read–eval–print loop (REPL); this permits the environment to function as a command line interpreter, with which users enter statements sequentially and receive results immediately. Also, CPython is bundled with an integrated development environment (IDE) called IDLE, which is oriented toward beginners.[citation needed] Other shells, including IDLE and IPython, add additional capabilities such as improved auto-completion, session-state retention, and syntax highlighting. Standard desktop IDEs include PyCharm, Spyder, and Visual Studio Code; there are web browser-based IDEs, such as the following environments: Implementations CPython is the reference implementation of Python. This implementation is written in C, meeting the C11 standard since version 3.11. Older versions use the C89 standard with several select C99 features, but third-party extensions are not limited to older C versions—e.g., they can be implemented using C11 or C++. CPython compiles Python programs into an intermediate bytecode, which is then executed by a virtual machine. CPython is distributed with a large standard library written in a combination of C and native Python. CPython is available for many platforms, including Windows and most modern Unix-like systems, including macOS (and Apple M1 Macs, since Python 3.9.1, using an experimental installer). Starting with Python 3.9, the Python installer intentionally fails to install on Windows 7 and 8; Windows XP was supported until Python 3.5, with unofficial support for VMS. Platform portability was one of Python's earliest priorities. During development of Python 1 and 2, even OS/2 and Solaris were supported; since that time, support has been dropped for many platforms. All current Python versions (since 3.7) support only operating systems that feature multithreading, by now supporting not nearly as many operating systems (dropping many outdated) than in the past. All alternative implementations have at least slightly different semantics. For example, an alternative may include unordered dictionaries, in contrast to other current Python versions. As another example in the larger Python ecosystem, PyPy does not support the full C Python API. Creating an executable with Python often is done by bundling an entire Python interpreter into the executable, which causes binary sizes to be massive for small programs, yet there exist implementations that are capable of truly compiling Python. Alternative implementations include the following: Stackless Python is a significant fork of CPython that implements microthreads. This implementation uses the call stack differently, thus allowing massively concurrent programs. PyPy also offers a stackless version. Just-in-time Python compilers have been developed, but are now unsupported: There are several compilers/transpilers to high-level object languages; the source language is unrestricted Python, a subset of Python, or a language similar to Python: There are also specialized compilers: Some older projects existed, as well as compilers not designed for use with Python 3.x and related syntax: A performance comparison among various Python implementations, using a non-numerical (combinatorial) workload, was presented at EuroSciPy '13. In addition, Python's performance relative to other programming languages is benchmarked by The Computer Language Benchmarks Game. There are several approaches to optimizing Python performance, despite the inherent slowness of an interpreted language. These approaches include the following strategies or tools: Language Development Python's development is conducted mostly through the Python Enhancement Proposal (PEP) process; this process is the primary mechanism for proposing major new features, collecting community input on issues, and documenting Python design decisions. Python coding style is covered in PEP 8. Outstanding PEPs are reviewed and commented on by the Python community and the steering council. Enhancement of the language corresponds with development of the CPython reference implementation. The mailing list python-dev is the primary forum for the language's development. Specific issues were originally discussed in the Roundup bug tracker hosted by the foundation. In 2022, all issues and discussions were migrated to GitHub. Development originally took place on a self-hosted source-code repository running Mercurial, until Python moved to GitHub in January 2017. CPython's public releases have three types, distinguished by which part of the version number is incremented: Many alpha, beta, and release-candidates are also released as previews and for testing before final releases. Although there is a rough schedule for releases, they are often delayed if the code is not ready yet. Python's development team monitors the state of the code by running a large unit test suite during development. The major academic conference on Python is PyCon. Also, there are special Python mentoring programs, such as PyLadies. Naming Python's name is inspired by the British comedy group Monty Python, whom Python creator Guido van Rossum enjoyed while developing the language. Monty Python references appear frequently in Python code and culture; for example, the metasyntactic variables often used in Python literature are spam and eggs, rather than the traditional foo and bar. Also, the official Python documentation contains various references to Monty Python routines. Python users are sometimes referred to as "Pythonistas". Languages influenced by Python See also Notes References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Data_(computer_science)] | [TOKENS: 4756] |
Contents Digital data Digital data, in information theory and information systems, is information represented as a string of discrete symbols, each of which can take on one of only a finite number of values from some alphabet, such as letters or digits. An example is a text document, which consists of a string of alphanumeric characters. The most common form of digital data in modern information systems is binary data, which is represented by a string of binary digits (bits) each of which can have one of two values, either 0 or 1. Digital data can be contrasted with analog data, which is represented by a value from a continuous range of real numbers. Analog data is transmitted by an analog signal, which not only takes on continuous values but can vary continuously with time, a continuous real-valued function of time. An example is the air pressure variation in a sound wave. Data requires interpretation to become information. In modern (post-1960) computer systems, all data is digital. The word digital comes from the same source as the words digit and digitus (the Latin word for finger), as fingers are often used for counting. Mathematician George Stibitz of Bell Telephone Laboratories used the word digital in reference to the fast electric pulses emitted by a device designed to aim and fire anti-aircraft guns in 1942. The term is most commonly used in computing and electronics, especially where real-world information is converted to binary numeric form as in digital audio and digital photography. Symbol to digital conversion Since symbols (for example, alphanumeric characters) are not continuous, representing symbols digitally is rather simpler than conversion of continuous or analog information to digital. Instead of sampling and quantization as in analog-to-digital conversion, such techniques as polling and encoding are used. A symbol input device usually consists of a group of switches that are polled at regular intervals to see which switches are switched. Data will be lost if, within a single polling interval, two switches are pressed, or a switch is pressed, released, and pressed again. This polling can be done by a specialized processor in the device to prevent burdening the main CPU. When a new symbol has been entered, the device typically sends an interrupt, in a specialized format, so that the CPU can read it. For devices with only a few switches (such as the buttons on a joystick), the status of each can be encoded as bits (usually 0 for released and 1 for pressed) in a single word. This is useful when combinations of key presses are meaningful, and is sometimes used for passing the status of modifier keys on a keyboard (such as shift and control). But it does not scale to support more keys than the number of bits in a single byte or word. Devices with many switches (such as a computer keyboard) usually arrange these switches in a scan matrix, with the individual switches on the intersections of x and y lines. When a switch is pressed, it connects the corresponding x and y lines together. Polling (often called scanning in this case) is done by activating each x line in sequence and detecting which y lines then have a signal, thus which keys are pressed. When the keyboard processor detects that a key has changed state, it sends a signal to the CPU indicating the scan code of the key and its new state. The symbol is then encoded or converted into a number based on the status of modifier keys and the desired character encoding. A custom encoding can be used for a specific application with no loss of data. However, using a standard encoding such as ASCII is problematic if a symbol such as 'ß' needs to be converted but is not in the standard. It is estimated that in the year 1986, less than 1% of the world's technological capacity to store information was digital and in 2007 it was already 94%. The year 2002 is assumed to be the year when humankind was able to store more information in digital than in analog format (the "beginning of the digital age"). States Digital data come in these three states: data at rest, data in transit, and data in use. The confidentiality, integrity, and availability have to be managed during the entire lifecycle from 'birth' to the destruction of the data. Data at rest in information technology means data that is housed physically on computer data storage in any digital form (e.g. cloud storage, file hosting services, databases, data warehouses, spreadsheets, archives, tapes, off-site or cloud backups, mobile devices etc.). Data at rest includes both structured and unstructured data. This type of data is subject to threats from hackers and other malicious threats to gain access to the data digitally or physical theft of the data storage media. To prevent this data from being accessed, modified or stolen, organizations will often employ security protection measures such as password protection, data encryption, or a combination of both. The security options used for this type of data are broadly referred to as data-at-rest protection (DARP). Definitions include: "...all data in computer storage while excluding data that is traversing a network or temporarily residing in computer memory to be read or updated." "...all data in storage but excludes any data that frequently traverses the network or that which resides in temporary memory. Data at rest includes but is not limited to archived data, data which is not accessed or changed frequently, files stored on hard drives, USB thumb drives, files stored on backup tape and disks, and also files stored off-site or on a storage area network (SAN)." While it is generally accepted that archive data (i.e. which never changes), regardless of its storage medium, is data at rest and active data subject to constant or frequent change is data in use. “Inactive data” could be taken to mean data which may change, but infrequently. The imprecise nature of terms such as “constant” and “frequent” means that some stored data cannot be comprehensively defined as either data at rest or in use. These definitions could be taken to assume that Data at Rest is a superset of data in use; however, data in use, subject to frequent change, has distinct processing requirements from data at rest, whether completely static or subject to occasional change. Because of its nature data at rest is of increasing concern to businesses, government agencies and other institutions. Mobile devices are often subject to specific security protocols to protect data at rest from unauthorized access when lost or stolen and there is an increasing recognition that database management systems and file servers should also be considered as at risk; the longer data is left unused in storage, the more likely it might be retrieved by unauthorized individuals outside the network. Data encryption, which prevents data visibility in the event of its unauthorized access or theft, is commonly used to protect data in motion and increasingly promoted for protecting data at rest. The encryption of data at rest should only include strong encryption methods such as AES or RSA. Encrypted data should remain encrypted when access controls such as usernames and password fail. Increasing encryption on multiple levels is recommended. Cryptography can be implemented on the database housing the data and on the physical storage where the databases are stored. Data encryption keys should be updated on a regular basis. Encryption keys should be stored separately from the data. Encryption also enables crypto-shredding at the end of the data or hardware lifecycle. Periodic auditing of sensitive data should be part of policy and should occur on scheduled occurrences. Finally, only store the minimum possible amount of sensitive data. Tokenization is a non-mathematical approach to protecting data at rest that replaces sensitive data with non-sensitive substitutes, referred to as tokens, which have no extrinsic or exploitable meaning or value. This process does not alter the type or length of data, which means it can be processed by legacy systems such as databases that may be sensitive to data length and type. Tokens require significantly less computational resources to process and less storage space in databases than traditionally encrypted data. This is achieved by keeping specific data fully or partially visible for processing and analytics while sensitive information is kept hidden. Lower processing and storage requirements makes tokenization an ideal method of securing data at rest in systems that manage large volumes of data. A further method of preventing unwanted access to data at rest is the use of data federation especially when data is distributed globally (e.g. in off-shore archives). An example of this would be a European organisation which stores its archived data off-site in the US. Under the terms of the USA PATRIOT Act the American authorities can demand access to all data physically stored within its boundaries, even if it includes personal information on European citizens with no connections to the US. Data encryption alone cannot be used to prevent this as the authorities have the right to demand decrypted information. A data federation policy which retains personal citizen information with no foreign connections within its country of origin (separate from information which is either not personal or is relevant to off-shore authorities) is one option to address this concern. However, data stored in foreign countries can be accessed using legislation in the CLOUD Act. Data in use is an information technology term referring to active data which is stored in a non-persistent digital state or volatile memory, typically in computer random-access memory (RAM), CPU caches, or CPU registers. Data in use has also been taken to mean “active data” in the context of being in a database or being manipulated by an application. For example, some enterprise encryption gateway solutions for the cloud claim to encrypt data at rest, data in transit and data in use. Some cloud software as a service (SaaS) providers refer to data in use as any data currently being processed by applications, as the CPU and memory are utilized. Because of its nature, data in use is of increasing concern to businesses, government agencies and other institutions. Data in use, or memory, can contain sensitive data including digital certificates, encryption keys, intellectual property (software algorithms, design data), and personally identifiable information. Compromising data in use enables access to encrypted data at rest and data in motion. For example, someone with access to random access memory can parse that memory to locate the encryption key for data at rest. Once they have obtained that encryption key, they can decrypt encrypted data at rest. Threats to data in use can come in the form of cold boot attacks, malicious hardware devices, rootkits and bootkits. Encryption, which prevents data visibility in the event of its unauthorized access or theft, is commonly used to protect Data in Motion and Data at Rest and increasingly recognized as an optimal method for protecting Data in Use. There have been multiple projects to encrypt memory. Microsoft Xbox systems are designed to provide memory encryption and the company PrivateCore presently has a commercial software product vCage to provide attestation along with full memory encryption for x86 servers. Several papers have been published highlighting the availability of security-enhanced x86 and ARM commodity processors. In that work, an ARM Cortex-A8 processor is used as the substrate on which a full memory encryption solution is built. Process segments (for example, stack, code or heap) can be encrypted individually or in composition. This work marks the first full memory encryption implementation on a mobile general-purpose commodity processor. The system provides both confidentiality and integrity protections of code and data which are encrypted everywhere outside the CPU boundary. For x86 systems, AMD has a Secure Memory Encryption (SME) feature introduced in 2017 with Epyc. Intel has promised to deliver its Total Memory Encryption (TME) feature in an upcoming CPU. Operating system kernel patches such as TRESOR and Loop-Amnesia modify the operating system so that CPU registers can be used to store encryption keys and avoid holding encryption keys in RAM. While this approach is not general purpose and does not protect all data in use, it does protect against cold boot attacks. Encryption keys are held inside the CPU rather than in RAM so that data at rest encryption keys are protected against attacks that might compromise encryption keys in memory. Enclaves enable an “enclave” to be secured with encryption in RAM so that enclave data is encrypted while in RAM but available as clear text inside the CPU and CPU cache. Intel Corporation has introduced the concept of “enclaves” as part of its Software Guard Extensions. Intel revealed an architecture combining software and CPU hardware in technical papers published in 2013. Several cryptographic tools, including secure multi-party computation and homomorphic encryption, allow for the private computation of data on untrusted systems. Data in use could be operated upon while encrypted and never exposed to the system doing the processing. Data in transit, also referred to as data in motion and data in flight, is data en route between source and destination, typically on a computer network. Data in transit can be separated into two categories: information that flows over the public or untrusted network such as the Internet and data that flows in the confines of a private network such as a corporate or enterprise local area network (LAN). In computing Data within a computer, in most cases, moves as parallel data. Data moving to or from a computer, in most cases, moves as serial data. Data sourced from an analog device, such as a temperature sensor, may be converted to digital using an analog-to-digital converter. Data representing quantities, characters, or symbols on which operations are performed by a computer are stored and recorded on magnetic, optical, electronic, or mechanical recording media, and transmitted in the form of digital electrical or optical signals. Data pass in and out of computers via peripheral devices. Physical computer memory elements consist of an address and a byte/word of data storage. Digital data are often stored in relational databases, like tables or SQL databases, and can generally be represented as abstract key/value pairs. Data can be organized in many different types of data structures, including arrays, graphs, and objects. Data structures can store data of many different types, including numbers, strings and even other data structures. Metadata helps translate data to information. Metadata is data about the data. Metadata may be implied, specified or given. Data relating to physical events or processes will have a temporal component. This temporal component may be implied. This is the case when a device such as a temperature logger receives data from a temperature sensor. When the temperature is received it is assumed that the data has a temporal reference of now. So the device records the date, time and temperature together. When the data logger communicates temperatures, it must also report the date and time as metadata for each temperature reading. Fundamentally, computers follow a sequence of instructions they are given in the form of data. A set of instructions to perform a given task (or tasks) is called a program. A program is data in the form of coded instructions to control the operation of a computer or other machine. In the nominal case, the program, as executed by the computer, will consist of machine code. The elements of storage manipulated by the program, but not actually executed by the central processing unit (CPU), are also data. At its most essential, a single datum is a value stored at a specific location. Therefore, it is possible for computer programs to operate on other computer programs, by manipulating their programmatic data. To store data bytes in a file, they have to be serialized in a file format. Typically, programs are stored in special file types, different from those used for other data. Executable files contain programs; all other files are also data files. However, executable files may also contain data used by the program which is built into the program. In particular, some executable files have a data segment, which nominally contains constants and initial values for variables, both of which can be considered data. The line between program and data can become blurry. An interpreter, for example, is a program. The input data to an interpreter is itself a program, just not one expressed in native machine language. In many cases, the interpreted program will be a human-readable text file, which is manipulated with a text editor program. Metaprogramming similarly involves programs manipulating other programs as data. Programs like compilers, linkers, debuggers, program updaters, virus scanners and such use other programs as their data. For example, a user might first instruct the operating system to load a word processor program from one file, and then use the running program to open and edit a document stored in another file. In this example, the document would be considered data. If the word processor also features a spell checker, then the dictionary (word list) for the spell checker would also be considered data. The algorithms used by the spell checker to suggest corrections would be either machine code data or text in some interpretable programming language. In an alternate usage, binary files (which are not human-readable) are sometimes called data as distinguished from human-readable text. The total amount of digital data in 2007 was estimated to be 281 billion gigabytes (281 exabytes). Keys in data provide the context for values. Regardless of the structure of data, there is always a key component present. Keys in data and data-structures are essential for giving meaning to data values. Without a key that is directly or indirectly associated with a value, or collection of values in a structure, the values become meaningless and cease to be data. That is to say, there has to be a key component linked to a value component in order for it to be considered data.[citation needed] Data can be represented in computers in multiple ways, as per the following examples: Random access memory (RAM) holds data that the CPU has direct access to. A CPU may only manipulate data within its processor registers or memory. This is as opposed to data storage, where the CPU must direct the transfer of data between the storage device (disk, tape...) and memory. RAM is an array of linear contiguous locations that a processor may read or write by providing an address for the read or write operation. The processor may operate on any location in memory at any time in any order. In RAM the smallest element of data is the binary bit. The capabilities and limitations of accessing RAM are processor specific. In general main memory is arranged as an array of locations beginning at address 0 (hexadecimal 0). Each location can store usually 8 or 32 bits depending on the computer architecture. Data keys need not be a direct hardware address in memory. Indirect, abstract and logical keys codes can be stored in association with values to form a data structure. Data structures have predetermined offsets (or links or paths) from the start of the structure, in which data values are stored. Therefore, the data key consists of the key to the structure plus the offset (or links or paths) into the structure. When such a structure is repeated, storing variations of the data values and the data keys within the same repeating structure, the result can be considered to resemble a table, in which each element of the repeating structure is considered to be a column and each repetition of the structure is considered as a row of the table. In such an organization of data, the data key is usually a value in one (or a composite of the values in several) of the columns. The tabular view of repeating data structures is only one of many possibilities. Repeating data structures can be organised hierarchically, such that nodes are linked to each other in a cascade of parent-child relationships. Values and potentially more complex data-structures are linked to the nodes. Thus the nodal hierarchy provides the key for addressing the data structures associated with the nodes. This representation can be thought of as an inverted tree. Modern computer operating system file systems are a common example; and XML is another. Data has some inherent features when it is sorted on a key. All the values for subsets of the key appear together. When passing sequentially through groups of the data with the same key, or a subset of the key changes, this is referred to in data processing circles as a break, or a control break. It particularly facilitates the aggregation of data values on subsets of a key. Until the advent of bulk non-volatile memory like flash, persistent data storage was traditionally achieved by writing the data to external block devices like magnetic tape and disk drives. These devices typically seek to a location on the magnetic media and then read or write blocks of data of a predetermined size. In this case, the seek location on the media, is the data key and the blocks are the data values. Early used raw disk data file-systems or disc operating systems reserved contiguous blocks on the disc drive for data files. In those systems, the files could be filled up, running out of data space before all the data had been written to them. Thus much unused data space was reserved unproductively to ensure adequate free space for each file. Later file-systems introduced partitions. They reserved blocks of disc data space for partitions and used the allocated blocks more economically, by dynamically assigning blocks of a partition to a file as needed. To achieve this, the file system had to keep track of which blocks were used or unused by data files in a catalog or file allocation table. Though this made better use of the disc data space, it resulted in fragmentation of files across the disc, and a concomitant performance overhead due additional seek time to read the data. Modern file systems reorganize fragmented files dynamically to optimize file access times. Further developments in file systems resulted in virtualization of disc drives i.e. where a logical drive can be defined as partitions from a number of physical drives. Retrieving a small subset of data from a much larger set may imply inefficiently searching through the data sequentially. Indexes are a way to copy out keys and location addresses from data structures in files, tables and data sets, then organize them using inverted tree structures to reduce the time taken to retrieve a subset of the original data. In order to do this, the key of the subset of data to be retrieved must be known before retrieval begins. The most popular indexes are the B-tree and the dynamic hash key indexing methods. Indexing is overhead for filing and retrieving data. There are other ways of organizing indexes, e.g. sorting the keys and using a binary search algorithm. Object-oriented programming uses two basic concepts for understanding data and software: It is only after instantiation that an object of a specified class exists. After an object's reference is cleared, the object also ceases to exist. The memory locations where the object's data was stored are garbage and are reclassified as unused memory available for reuse. The advent of databases introduced a further layer of abstraction for persistent data storage. Databases use metadata, and a structured query language protocol between client and server systems, communicating over a computer network, using a two phase commit logging system to ensure transactional completeness, when saving data. Modern scalable and high-performance data persistence technologies, such as Apache Hadoop, rely on massively parallel distributed data processing across many commodity computers on a high bandwidth network. In such systems, the data is distributed across multiple computers and therefore any particular computer in the system must be represented in the key of the data, either directly, or indirectly. This enables the differentiation between two identical sets of data, each being processed on a different computer at the same time. See also References Properties of digital information All digital information possesses common properties that distinguish it from analog data with respect to communications: Historical digital systems Even though digital signals are generally associated with the binary electronic digital systems used in modern electronics and computing, digital systems are actually ancient, and need not be binary or electronic. See also References Further reading |
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[SOURCE: https://en.wikipedia.org/wiki/Jewish_medicine] | [TOKENS: 2184] |
Contents Jewish medicine Jewish medicine is medical practice of the Jewish people, including writing in the languages of both Hebrew and Arabic. 28% of Nobel Prize winners in medicine have been Jewish. History There are no extant texts of ancient medicine, as a first subject, of Hebrew origin. There was no medicine distinctly Jewish and instead Jewish practitioners had adopted Greek and later Graeco-Roman knowledge as practice. A text known as the "Book of Remedies" is recorded of in the Babylonian Talmud twice, and the baraita, evidently dating from at least the reign of Hezekiah. Likewise, a text known as Sefer Refuot, which means "book of remedies," is known. However, its composition has been dated roughly to the time of the Byzantine Empire, anywhere from 1,000 and 1,700 years after Hezekiah. The Book of Remedies, the earliest medical text written in Hebrew, to Asaph the Jew, dates to the seventh or eighth century. The text comprises four parts; a story of the transmission of medicine from God to mankind, a medical survey, a Materia medica and a list of medical aphorisms. While there is no knowledge of the writer himself or where the text was written, it circulated widely in Jewish communities during the Medieval period, and it can be assumed that it was of great influence to Jewish practitioners during this time. In the medieval Islamic world, medicine was one of the most prominent and respected professions among Jews. The Cairo Genizah has preserved over 2,500 fragments related to medicine. There is clear evidence of Jewish students training under Muslim physicians, as well as Jewish practitioners serving non-Jewish patients, including in Islamic hospitals. These hospitals, secular in nature and often royal foundations, admitted patients regardless of religious affiliation and allowed non-Muslims to practice medicine within their walls. Jewish medicine saw significant development in al-Andalus (Islamic Spain). From the 10th through early 12th centuries, Jewish physicians were active participants in the region's medical life, sometimes collaborating with Christian and Muslim counterparts. Ḥasday ibn Shaprut, a minister at the court of Caliph Abd al-Rahman III of Córdoba, was involved in translation work. He is known for successfully treating the obesity of Sancho of León, the grandson of the queen of Navarre. 11th-century Toledan qadi Said al-Andalusi later listed him among noteworthy Jewish scientists, describing him as a physician "whose cures were successful and his praise on everyone's lips." Also notable was Jonah ibn Janāḥ, who produced a pharmacological treatise (Kitāb al-Talkhīṣ) listing drugs in multiple languages. His work influenced Jonah ibn Biklārish, who composed a multilingual medical dictionary (Kitāb al-Mustaʿīnī) for the Muslim court in Zaragoza. Joseph ibn 'Aqnīn, possibly born in Barcelona, later moved to Fez, Morocco, where he abridged Galen’s commentary on Hippocrates' Aphorisms, showing the transmission of classical medicine into Jewish scholarship. Prominent Jewish physicians are also attested in North Africa and the Levant. Isaac Israeli (d. c. 955), originally from Faiyum, Egypt, served the Aghlabid and Fatimid courts in Kairouan (in modern Tunisia). He authored influential Arabic treatises on fevers, the pulse, urine, and materia medica, many of which were later translated into Latin and Hebrew. His Kitāb al-Bawl (Book on Urine) was innovative in its physiological analysis and diagnostic use of uroscopy. He also wrote an ethical guide for physicians (Musar ha-Rof'im), emphasizing both moral conduct and bedside manner. In 12th-century Egypt, Maimonides (1138–1204) became the physician to Qadi al-Fadil, chief counsellor to Saladin. He authored a range of medical works in Arabic, including clinical consilia (personalized medical advice) and treatises on preventative care, convalescence, and specific conditions such as asthma, hemorrhoids, and poisoning. His Sharḥ Asmāʾ al-ʿUqqār is a medical glossary listing drug names in Arabic, Greek, Persian, Spanish, Moroccan, Egyptian, and Berber, showing the multilingual environment of Jewish medical scholarship. Maimonides also produced a summary of Galen's works and a commentary on Ḥunayn ibn Ishāq. Another noteworthy physician, Ibn Jumay' (d. c. 1198), served as private doctor to Saladin and wrote both a commentary on Avicenna's Canon of Medicine and a medical encyclopedia (Kitāb al-Irshād) focused on the welfare of body and soul. Though advances were made in gynaecology during the Middle Ages, the texts about gynaecology were written using the masculine form of Hebrew, indicating that gynecological texts were directed towards male doctors, not female midwives. The only mention of midwives in these texts seems to be when direct contact with a woman’s genitalia is necessary; only then do texts specifically mention the women involved in the procedure. In one instance, a text advised the doctor to "order the midwife to massage the orifice of her womb" with the herbs mentioned. Female practitioners contributed significantly both to the practice of medicine inside and outside of Jewish communities, and to the body of medical knowledge in Jewish community and beyond. From the surviving texts, it would seem that the greatest occurrence of female medical practitioners was during the 14th and 15th centuries. While women contributed to the advancement of Jewish medicine during this time, there were still a number of restrictions placed on them by society. No Jew, male or female, was permitted to attend a Christian university. This could be bypassed by taking an examination and acquiring a licentia curandi et practicandi, a license to practice medicine. In at least one case, this examination was specifically directed towards Jews who would work with Christian patients. As a result, the education of these women largely fell to their male relatives. Hava (also known as Hana), a Manoesque woman mentioned for her "medical capacity" in a document dated to the early 1320s, and Virdimura, a Sicilian who obtained her medical license in 1376, were female Jewish practitioners whose direct relatives—Hava's husband and sons, Virdimura's husband—were practitioners as well. Jewish medical practitioners were often educated in Greek, Latin, Arabic, and Hebrew, which gave them access to medical texts that were often inaccessible to their Christian counterparts. Working as physicians, surgeons, and midwives, Jewish women were accepted as medical authorities in Paris, Florence, Naples, and Sicily, among other cities. Sara of St. Gilles, for instance, was a Jewish doctor who admitted a male Christian student, Salvetus de Burgonovo, in fourteenth century France. Shatzmiller believes this is enough evidence to indicate that Sara taught female students as well. Mayrona, a Jewish woman from Manoesque, France, is listed in over forty documents from 1342 as a phisica, or a licensed medical practitioner. Jewish midwives made up a larger percentage of practitioners in some regions than their population would suggest. In the French town of Marseille between 1390 and 1415, there are 24 known Jewish practitioners to 18 Christian ones; this is a shift from the period from 1337 to 1362 where Jewish doctors compromised approximately half of all practitioners in Marseille. Jewish practitioners participated in the exchange of knowledge between Christian and Muslim writers and practitioners. The degree to which Jewish women practiced midwifery in the Middle Ages depended largely on the areas in which they lived. In Iberia, for instance, Jews were well accustomed to a mix of Muslim, Christian, and their own Jewish culture. Along with this came a shared understanding of medicine; Jews living in this area even wrote medicinal texts in Judeo-Arabic (Arabic written in Hebrew letters) rather than standard Hebrew or the local vernacular Here, it was commonplace for Jewish midwives to work alongside Christian and Muslim women. However, Jewish women still faced adversity and discrimination on the basis of both their gender and their religion. This is more clearly demonstrated in Central Europe, where it is difficult to determine if Jewish midwives working for non-Jewish patients was common practice or, instead, the exception rather than the rule. In 1403, Floreta d’Ays, a Jewish midwife from Marseilles, was brought to court under charges of malpractice. This is the first such known case brought against a midwife and, according to Monica Green, an unusual case of anti-Jewish sentiment in an otherwise relatively tolerant town. While the result of the trial is unknown, it's clear that Floreta's non-Christian status played a part in the charges levied against her. Jewish physicians remained active in both clinical and scholarly medicine under the Mamluks. In Egypt, Al-Sadīd al-Dimyāṭī and Faraj Allāh ibn Saghīr, members of a long-serving Karaite family of court doctors, worked under Sultan Al-Nasir Muhammad. In Syria, Asad al-Yahūdī served Mamluk emirs. Earlier, Abū al-Faḍl Ibn Abī al-Bayān directed the Nāṣirī hospital in Cairo and authored a handbook on compound drugs for hospital use (al-Dustūr al-Bīmāristānī), while Abū al-Munā al-Kūhin al-ʿAṭṭār compiled a pharmacist's manual in 1260 (Minhāj al-Dukkān). Jewish medical scholarship also included works like Nuʿmān al-Isrāʾīlī’s commentary on Abū Sahl al-Masīḥī’s Book of the Hundred, and Solomon ibn Yaʿīsh’s philologically rigorous commentary on Ibn Sīnā’s Canon of Medicine. The first organized study of Biblical medicine began during the 17th century. The famous doctor of psychiatry Sigmund Freud was Jewish by birth. Abraham Maslow was born to Russian Jewish parents during 1908. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/URL#cite_ref-rfc7595_19-0] | [TOKENS: 957] |
Contents URL A uniform resource locator (URL), colloquially known as web address, is a reference to a resource on the World Wide Web. A URL specifies the location of a resource on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifier (URI), although many people use the two terms interchangeably.[a] A URL is most commonly used to reference a web page (HTTP/HTTPS) but is also used for file transfer (FTP), email (mailto), database access (JDBC), and many other applications. Most web browsers display the URL of a web page above the page in an address bar. As an example of a web page URL, https://www.example.com/index.html indicates protocol https, hostname www.example.com, and file name index.html. History The Uniform Resource Locator was defined in RFC 1738 in 1994 by Tim Berners-Lee, the inventor of the World Wide Web, and the URI working group of the Internet Engineering Task Force (IETF), as an outcome of collaboration started at the IETF Living Documents birds of a feather session in 1992. The format combines the pre-existing system of domain names (created in 1985) with file path syntax, where slashes are used to separate directory and filenames. Conventions already existed where server names could be prefixed to complete file paths, preceded by a double slash (//). Berners-Lee later expressed regret at the use of dots to separate the parts of the domain name within URIs, wishing he had used slashes throughout, and also said that, given the colon following the first component of a URI, the two slashes before the domain name were unnecessary. Early WorldWideWeb collaborators, including Berners-Lee, originally proposed the use of UDIs: Universal Document Identifiers. An early (1993) draft of the HTML Specification referred to "Universal" Resource Locators. This was dropped some time between June 1994 and October 1994. In his book Weaving the Web, Berners-Lee emphasizes his preference for the original inclusion of "universal" in the expansion rather than the word "uniform", to which it was later changed, and he gives a brief account of the contention that led to the change. Syntax Every HTTP URL conforms to the syntax of a generic URI. The URI generic syntax consists of five components organized hierarchically in order of decreasing significance from left to right:: §3 A component is undefined if it has an associated delimiter and the delimiter does not appear in the URI; the scheme and path components are always defined.: §5.2.1 A component is empty if it has no characters; the scheme component is always non-empty.: §3 The authority component consists of subcomponents: This is represented in a syntax diagram as: The URI comprises: A web browser will usually dereference a URL by performing an HTTP request to the specified host, by default on port number 80. URLs using the https scheme require that requests and responses be made over a secure connection to the website. Internationalized URL Internet users are distributed throughout the world using a wide variety of languages and alphabets, and expect to be able to create URLs in their own local alphabets. An Internationalized Resource Identifier (IRI) is a form of URL that includes Unicode characters. All modern browsers support IRIs. The parts of the URL requiring special treatment for different alphabets are the domain name and path. The domain name in the IRI is known as an Internationalized Domain Name (IDN). Web and Internet software automatically convert the domain name into punycode usable by the Domain Name System; for example, the Chinese URL http://例子.卷筒纸 becomes http://xn--fsqu00a.xn--3lr804guic/. The xn-- indicates that the character was not originally ASCII. The URL path name can also be specified by the user in the local writing system. If not already encoded, it is converted to UTF-8, and any characters not part of the basic URL character set are escaped as hexadecimal using percent-encoding; for example, the Japanese URL http://example.com/引き割り.html becomes http://example.com/%E5%BC%95%E3%81%8D%E5%89%B2%E3%82%8A.html. The target computer decodes the address and displays the page. Protocol-relative URLs Protocol-relative links (PRL), also known as protocol-relative URLs (PRURL), are URLs that have no protocol specified. For example, //example.com will use the protocol of the current page, typically HTTP or HTTPS. See also Notes Citations References External links |
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Contents Thirty-seventh government of Israel The thirty-seventh government of Israel is the current cabinet of Israel, formed on 29 December 2022, following the Knesset election the previous month. The coalition government currently consists of five parties — Likud, Shas, Otzma Yehudit, Religious Zionist Party and New Hope — and is led by Benjamin Netanyahu, who took office as the prime minister of Israel for the sixth time. The government is widely regarded as the most right-wing government in the country's history, and includes far-right politicians. Several of the government's policy proposals have led to controversies, both within Israel and abroad, with the government's attempts at reforming the judiciary leading to a wave of demonstrations across the country. Following the outbreak of the Gaza war, opposition leader Yair Lapid initiated discussions with Netanyahu on the formation of an emergency government. On 11 October 2023, National Unity MKs Benny Gantz, Gadi Eisenkot, Gideon Sa'ar, Hili Tropper, and Yifat Shasha-Biton joined the Security Cabinet of Israel to form an emergency national unity government. Their accession to the Security Cabinet and to the government (as ministers without portfolio) was approved by the Knesset the following day. Gantz, Netanyahu, and Defense Minister Yoav Gallant became part of the newly formed Israeli war cabinet, with Eisenkot and Ron Dermer serving as observers. National Unity left the government in June 2024. New Hope rejoined the government in September. Otzma Yehudit announced on 19 January 2025 that it had withdrawn from the government, which took effect on 21 January, following the cabinet's acceptance of the three-phase Gaza war ceasefire proposal, though it rejoined two months later. United Torah Judaism left the government in July 2025 over dissatisfaction with the government's draft conscription law. Shas left the government several days later, though it remains part of the coalition. Background The right-wing bloc of parties, led by Benjamin Netanyahu, known in Israel as the national camp, won 64 of the 120 seats in the elections for the Knesset, while the coalition led by the incumbent prime minister Yair Lapid won 51 seats. The new majority has been variously described as the most right-wing government in Israeli history, as well as Israel's most religious government. Shortly after the elections, Lapid conceded to Netanyahu, and congratulated him, wishing him luck "for the sake of the Israeli people". On 15 November, the swearing-in ceremony for the newly elected members of the 25th Knesset was held during the opening session. The vote to appoint a new Speaker of the Knesset, which is usually conducted at the opening session, as well as the swearing in of cabinet members were postponed since ongoing coalition negotiations had not yet resulted in agreement on these positions. Government formation Yair Lapid Yesh Atid Benjamin Netanyahu Likud On 3 November 2022, Netanyahu told his aide Yariv Levin to begin informal coalition talks with allied parties, after 97% of the vote was counted. The leader of the Shas party Aryeh Deri met with Yitzhak Goldknopf, the leader of United Torah Judaism and its Agudat Yisrael faction, on 4 November. The two parties agreed to cooperate as members of the next government. The Degel HaTorah faction of United Torah Judaism stated on 5 November that it will maintain its ideological stance about not seeking any ministerial posts, as per the instruction of its spiritual leader Rabbi Gershon Edelstein, but will seek other senior posts like Knesset committee chairmen and deputy ministers. Netanyahu himself started holding talks on 6 November. He first met with Moshe Gafni, the leader of Degel HaTorah, and then with Goldknopf. Meanwhile, the Religious Zionist Party leader Bezalel Smotrich and the leader of its Otzma Yehudit faction Itamar Ben-Gvir pledged that they would not enter the coalition without the other faction. Gafni later met with Smotrich for coalition talks. Smotrich then met with Netanyahu. On 7 November, Netanyahu met with Ben-Gvir who demanded the Ministry of Public Security with expanded powers for himself and the Ministry of Education or Transport and Road Safety for Yitzhak Wasserlauf. A major demand among all of Netanyahu's allies was that the Knesset be allowed to ignore the rulings of the Supreme Court. Netanyahu met with the Noam faction leader and its sole MK Avi Maoz on 8 November after he threatened to boycott the coalition. He demanded complete control of the Western Wall by the Haredi rabbinate and removal of what he considered as anti-Zionist and anti-Jewish content in schoolbooks. President Isaac Herzog began consultations with heads of all the political parties on 9 November after the election results were certified. During the consultations, he expressed his reservations about Ben-Gvir becoming a member in the next government. Shas met with Likud for coalition talks on 10 November. By 11 November, Netanyahu had secured recommendations from 64 MKs, which constituted a majority. He was given the mandate to form the thirty-seventh government of Israel by President Herzog on 13 November. Otzma Yehudit and Noam officially split from Religious Zionism on 20 November as per a pre-election agreement. On 25 November, Otzma Yehudit and Likud signed a coalition agreement, under which Ben-Gvir will assume the newly created position of National Security Minister, whose powers would be more expansive than that of the Minister of Public Security, including overseeing the Israel Police and the Israel Border Police in the West Bank, as well as giving powers to authorities to shoot thieves stealing from military bases. Yitzhak Wasserlauf was given the Ministry for the Development of the Negev and the Galilee with expanded powers to regulate new West Bank settlements, while separating it from the "Periphery" portfolio, which will be given to Shas. The deal also includes giving the Ministry of Heritage to Amihai Eliyahu, separating it from the "Jerusalem Affairs" portfolio, the chairmanship of the Knesset's Public Security Committee to Zvika Fogel and that of the Special Committee for the Israeli Citizens' Fund to Limor Son Har-Melech, the post of Deputy Economic Minister to Almog Cohen, establishment of a national guard, and expansion of mobilization of reservists in the Border Police. Netanyahu and Maoz signed a coalition agreement on 27 November, under which the latter would become a deputy minister, would head an agency on Jewish identity in the Prime Minister's Office, and would also head Nativ, which processes the aliyah from the former Soviet Union. The agency for Jewish identity would have authority over educational content taught outside the regular curriculum in schools, in addition to the department of the Ministry of Education overseeing external teaching and partnerships, which would bring nonofficial organisations permitted to teach and lecture at schools under its purview. Likud signed a coalition agreement with the Religious Zionist Party on 1 December. Under the deal, Smotrich would serve as the Minister of Finance in rotation with Aryeh Deri, and the party will receive the post of a minister within the Ministry of Defense with control over the departments administering settlement and open lands under the Coordinator of Government Activities in the Territories, in addition to another post of a deputy minister. The deal also includes giving the post of Minister of Aliyah and Integration to Ofir Sofer, the newly created National Missions Ministry to Orit Strook, and the chairmanship of the Knesset's Constitution, Law and Justice Committee to Simcha Rothman. Likud and United Torah Judaism signed a coalition agreement on 6 December, to allow request for an extension to the deadline. Under it, the party would receive the Ministry of Construction and Housing, the chairmanship of the Knesset Finance Committee which will be given to Moshe Gafni, the Ministry of Jerusalem and Tradition (which would replace the Ministry of Jerusalem Affairs and Heritage), in addition to several posts of deputy ministers and chairmanships of Knesset committees. Likud also signed a deal with Shas by 8 December, securing interim coalition agreements with all of their allies. Under the deal, Deri will first serve as the Minister of Interior and Health, before rotating posts with Smotrich after two years. The party will also receive the Ministry of Religious Services and Welfare Ministries, as well as posts of deputy ministers in the Ministry of Education and Interior. The vote to replace then-incumbent Knesset speaker Mickey Levy was scheduled for 13 December, after Likud and its allies secured the necessary number of signatures for it. Yariv Levin of Likud was elected as an interim speaker by 64 votes, while his opponents Merav Ben-Ari of Yesh Atid and Ayman Odeh of Hadash received 45 and five votes respectively. Netanyahu asked Herzog for a 14-day extension after the agreement with Shas to finalise the roles his allied parties would play. Herzog on 9 December extended the deadline to 21 December. On that date, Netanyahu informed Herzog that he had succeeded in forming a coalition, with the new government expected to be sworn in by 2 January 2023. The government was sworn in on 29 December 2022. Timeline Israeli law stated that people convicted of crimes cannot serve in the government. An amendment to that law was made in late 2022, known colloquially as the Deri Law, to allow those who had been convicted without prison time to serve. This allowed Deri to be appointed to the cabinet. Shas leader Aryeh Deri was appointed to be Minister of Health, Minister of the Interior, and Vice Prime Minister in December 2022. He was fired in January 2023, following a Supreme Court decision that his appointment was unreasonable, since he had been convicted of fraud, and had promised not to seek government roles through a plea deal. In March 2023, Defence Minister Yoav Gallant called on the government to delay legislation related to the judicial reform. Prime Minister Netanyahu announced that he had been dismissed from his position, leading to the continuation of mass protests across the country (which had started in January in Tel Aviv). Gallant continued to serve as a minister as he had not received formal notice of dismissal, and two weeks later it was announced that Netanyahu had reversed his decision. Public Safety Minister Itamar Ben-Gvir (Otzma Yehudit leader) and Minister of Justice Yariv Levin (Likud) both threatened to resign if the judicial reform was delayed.[better source needed] After the outbreak of the Gaza war, five members of the National Unity party joined the government as ministers without portfolio, with leader Benny Gantz being made a member of the new Israeli war cabinet (along with Netanyahu and Gallant). As the war progressed, minister of national security Itamar Ben-Gvir threatened to leave the government if the war was ended. A month later in mid December, he again threatened to leave if the war did not maintain "full strength". Gideon Sa'ar stated on 16 March that his New Hope party would resign from the government and join the opposition if Prime Minister Benjamin Netanyahu did not appoint him to the Israeli war cabinet. Netanyahu did not do so, resulting in Sa'ar's New Hope party leaving the government nine days later, reducing the size of the coalition from 76 MKs to 72. Ben-Gvir and Bezalel Smotrich, of the National Religious Party–Religious Zionism party, have indicated that they will withdraw their parties from the government if the January 2025 Gaza war ceasefire is adopted, which would bring down the government. Ben-Gvir announced on 5 June that the members of his party would be allowed to vote as they wish, though his party resumed support on 9 June. On 18 May, Gantz set an 8 June deadline for withdrawal from the coalition, which was delayed by a day following the 2024 Nuseirat rescue operation. Gantz and his party left the government on 9 June, giving the government 64 seats in the Knesset. Sa'ar and his New Hope party rejoined the Netanyahu government on 30 September, increasing the number of seats held by the government to 68. The High Court of Justice ruled on 28 March 2024 that yeshiva funds would no longer be available for students who are "eligible for enlistment", effectively allowing ultra-Orthodox Jews to be drafted into the IDF. Attorney general Gali Baharav-Miara indicated on 31 March that the conscription process must begin on 1 April. The court ruled on 25 June that the IDF must begin to draft yeshiva students. Likud announced on 7 July that it would not put forward any legislation after Shas and United Torah Judaism said that they would boycott the plenary session over the lack of legislation dealing with the Haredi draft. The Ultra-Orthodox boycott continued for a second day, with UTJ briefly ending its boycott on 9 July to unsuccessfully vote in favor of a bill which would have weakened the Law of Return. Yuli Edelstein, who was replaced by Boaz Bismuth on the Foreign Affairs and Defense Committee in early August, published a draft version of the conscription law shortly before his ouster. Bismuth cancelled the work on the draft law in September 2025, which Edelstein called "a shame." Bismuth released the official version of the draft law in late November 2025. It weakened penalties for draft evaders, with Edelstein saying it was "the exact opposite" of the bill which he attempted to pass. Members of Otzma Yehudit resigned from the government on 19 January 2025 over the January 2025 Gaza war ceasefire, which took effect on 21 January. The members rejoined in March, following the "resumption" of the war in Gaza. Avi Maoz of the Noam party left the government in March 2025. On 4 June 2025, senior rabbis for United Torah Judaism Dov Lando and Moshe Hillel Hirsch instructed the party's MKs to pass a bill which would dissolve the Knesset. Yesh Atid, Yisrael Beytenu and The Democrats announced that they will "submit a bill" for dissolution on 11 June, with Yesh Atid tabling the bill on 4 June. There were also reports that Shas would vote in favor of Knesset dissolution amidst division within the governing coalition on Haredi conscription. This jeopardized the coalition's majority and would have triggered new elections if the bill passed. The following day, Agudat Yisrael, one of the United Torah Judaism factions, confirmed that it would submit a bill to dissolve the Knesset. Asher Medina, a Shas spokesman, indicated on 9 June that the party would vote in favor of a preliminary bill to dissolve the Knesset. The rabbis of Degel HaTorah instructed the parties' MKs on 12 June 2025 to oppose the dissolution of the Knesset, which was followed by Yuli Edelstein and the Shas and Degel HaTorah parties announcing that a deal had been reached, with "rabbinical leaders" telling their parties to delay the dissolution vote by a week. Shas and Degel HaTorah voted against the dissolution bill, which led to the bill failing its preliminary reading in a vote of 61 against and 53 in favor. MKs Ya'akov Tessler and Moshe Roth of Agudat Yisrael voted in favor of dissolution. Another dissolution bill will be unable to be brought forward for six months. If the bill had passed its preliminary reading, in addition to three more readings, an election would have been held in approximately three months; The Jerusalem Post posited it would have been held in October. Degel HaTorah announced on 14 July 2025 that it would leave the government because members of the party were dissatisfied after viewing the proposed draft bill by Yuli Edelstein regarding Haredi exemptions from the Israeli draft. Several hours later, Agudat Yisrael announced that it would also leave the government. Deputy Transportation Minister Uri Maklev, Moshe Gafni, the head of the Knesset Finance Committee, Ya'akov Asher, the head of the Knesset Interior and Environment Protection Committee and Jerusalem Affairs minister Meir Porush all submitted their resignations, with their resignations taking effect in 48 hours. Sports Minister Ya'akov Tessler and "Special Committee for Public Petitions Chair" Yitzhak Pindrus also submitted resignations. Yisrael Eichler submitted his resignation as the "head of the Knesset Labor and Welfare Committee" the same day. The resignations will leave Netanyahu's government with a 60-seat majority in the Knesset, as Avi Maoz, of the Noam party, left the government in March 2025. Despite Edelstein's ouster in August, a spokesman for UTJ head Yitzhak Goldknopf remarked that it would not change the faction's withdrawal from the government. The religious council for Shas, called the Moetzet Chachmei HaTorah, instructed the party on 16 July to leave the government, but stay in the coalition. The following day, various cabinet ministers submitted their resignations, including "Interior Minister Moshe Arbel, Social Affairs Minister Ya'akov Margi and Religious Services Minister Michael Malchieli." Malchieli reportedly has postponed his resignation so he could attend a 20 July meeting of the panel investigating whether attorney general Gali Baharav-Miara should be dismissed. Deputy Minister of Agriculture Moshe Abutbul, Minister of Health Uriel Buso and Haim Biton, a minister in the Education Ministry, also submitted their resignation letters, while Arbel retracted his resignation letter. The last cabinet member from the party to submit it was Labor Minister Yoav Ben-Tzur. The ministers who resigned will return to the Knesset, replacing MKs Moshe Roth, Yitzhak Pindrus and Eliyahu Baruchi. Members of government Listed below are the current ministers in the government: Principles and priorities According to the agreements signed between Likud and each of its coalition partners, and the incoming government's published guideline principles, its stated priorities are to combat the cost of living, further centralize Orthodox control over the state religious services, pass judicial reforms which include legislation to reduce judicial controls on executive and legislative power, expand settlements in the West Bank, and consider an annexation of the West Bank. Before the vote of confidence in his new government in the Knesset, Netanyahu presented three top priorities for the new government: internal security and governance, halting the nuclear program of Iran, and the development of infrastructure, with a focus on further connecting the center of the country with its periphery. Policies The government's flagship program, centered around reforms in the judicial branch, drew widespread criticism. Critics said it would have negative effects on the separation of powers, the office of the Attorney General, the economy, public health, women and minorities, workers' rights, scientific research, the overall strength of Israel's democracy and its foreign relations. After weeks of public protests on Israel's streets, joined by a growing number of military reservists, Minister of Defense Yoav Gallant spoke against the reform on 25 March, calling for a halt of the legislative process "for the sake of Israel's security". The next day, Netanyahu announced that he would be removed from his post, sparking another wave of protest across Israel and ultimately leading to Netanyahu agreeing to pause the legislation. On 10 April, Netanyahu announced that Gallant would keep his post. On 27 March 2023, after the public protests and general strikes, Netanyahu announced a pause in the reform process to allow for dialogue with opposition parties. However, negotiations aimed at reaching a compromise collapsed in June, and the government resumed its plans to unilaterally pass parts of the legislation. On 24 July 2023, the Knesset passed a bill that curbs the power of the Supreme Court to declare government decisions unreasonable; on 1 January 2024, the Supreme Court struck the bill down. The Knesset passed a "watered-down" version of the judicial reform package in late March 2025 which "changes the composition" of the judicial selection committee. In December 2022 Minister of National Security Itamar Ben-Gvir sought to amend the law that regulates the operations of the Israel Police, such that the ministry will have more direct control of its forces and policies, including its investigative priorities. Attorney General Gali Baharav-Miara objected to the draft proposal, raising concerns that the law would enable the politicization of police work, and the draft was amended to partially address those concerns. Nevertheless, in March 2023 Deputy Attorney General Gil Limon stated that the Attorney General's fears had been realized, referring to several instances of ministerial involvement in the day-to-day work of the otherwise independent police force – statements that were repeated by the Attorney General herself two days later. Separately, Police Commissioner Kobi Shabtai instructed Deputy Commissioners to avoid direct communication with the minister, later stating that "the Israel Police will remain apolitical, and act only according to law". Following appeals by the Association for Civil Rights in Israel and the Movement for Quality Government in Israel, the High Court of Justice instructed Ben-Gvir "to refrain from giving operational directions to the police... [especially] as regards to protests and demonstrations against the government." As talks of halting the judicial reform gained wind during March 2023, Minister of National Security Itamar Ben-Gvir threatened to resign if the legislation implementing the changes was suspended. To appease Ben-Gvir, Prime Minister Netanyahu announced that the government would promote the creation of a new National Guard, to be headed by Ben-Gvir. On 29 March, thousands of Israelis demonstrated in Tel Aviv, Haifa and Jerusalem against this decision. On 1 April, the New York Times quoted Gadeer Nicola, head of the Arab department at the Association for Civil Rights in Israel, as saying "If this thing passes, it will be an imminent danger to the rights of Arab citizens in this country. This will create two separate systems of applying the law. The regular police which will operate against Jewish citizens — and a militarized militia to deal only with Arab citizens." The same day, while speaking on Israel's Channel 13 about those whom he'd like to see enlist in the National Guard, Ben-Gvir specifically mentioned La Familia, the far-right fan club of the Beitar Jerusalem soccer team. On 2 April, Israel's cabinet approved the establishment of a law enforcement body that would operate independently of the police, under Ben-Gvir's authority. According to the decision, the Minister was to establish a committee chaired by the Director General of the Ministry of National Security, with representatives of the ministries of defense, justice and finance, as well as the police and the IDF, to outline the operations of the new organization. The committee's recommendations will be submitted to the government for consideration. Addressing a conference on 4 April, Police Commissioner Kobi Shabtai said that he is not opposed to the establishment of a security body which would answer to the police, but "a separate body? Absolutely not." The police chief said he had warned Ben-Gvir that the establishment of a security body separate from the police is "unnecessary, with extremely high costs that may harm citizens' personal security." During a press conference on 10 April, Prime Minister Netanyahu said, in what has been seen by some news outlets as a concession to the protesters, that "This will not be anyone's militia, it will be a security body, orderly, professional, that will be subordinate to one of the [existing] security bodies." The committee established by the government recommended the government to order the establishment of the National Guard immediately while allocating budgets. The National Guard, under whose command will be a superintendent of the police, will not be subordinate to Ben-Gvir. It will be subordinate to the police commissioner and will be part of Israel Border Police. The Ministry of Defense and Finance opposed the conclusions. The Israeli National Security Council called for further discussion on this. The coalition's efforts to expand the purview of Rabbinical courts; force some organizations, such as hospitals, to enforce certain religious practices; amend the Law Prohibiting Discrimination to allow gender segregation and discrimination on the grounds of religious belief; expand funding for religious causes; and put into law the exemption of yeshiva and kolel students from conscription have drawn criticism. According to the Haaretz op-ed of 7 March 2023, "the current coalition is interested... in modifying the public space so it suits the religious lifestyle. The legal coup is meant to castrate anyone who can prevent it, most of all the HCJ." Several banks and institutional investors, including the Israel Discount Bank and AIG have committed to avoid investing in, or providing credit to any organization that will discriminate against others on ground of religion, race, gender or sexual orientation. A series of technology companies and investment firms including Wiz, Intel Israel, Salesforce and Microsoft Israel Research and Development, have criticized the proposed changes to the Law Prohibiting Discrimination, with Wiz stating that it will require its suppliers to commit to preventing discrimination. Over sixty prominent law firms pledged that they will neither represent, nor do business with discriminating individuals and organizations. Insight Partners, a major private equity fund operating in Israel, released a statement warning against intolerance and any attempt to harm personal liberties. Orit Lahav, chief executive of the women's rights organization Mavoi Satum ("Dead End"), said that "the Rabbinical courts are the most discriminatory institution in the State of Israel... Limiting the HCJ[d] while expanding the jurisdiction of the Rabbinical courts would... cause significant harm to women." Anat Thon Ashkenazy, Director of the Center for Democratic Values and Institutions at the Israel Democracy Institute, said that "almost every part of the reform could harm women... the meaning of an override clause is that even if the court says that the law on gender segregation is illegitimate, is harmful, the Knesset could say 'Okay, we say otherwise'". She added that "there is a very broad institutional framework here, after which there will come legislation that harms women's right and we will have no way of protecting or stopping it." During July 2023, 20 professional medical associations signed a letter of position warning against the ramifications to public health that would result from the exclusion of women from the public sphere. They cited, among others, a rise in prevalence of risk factors for cardiovascular disease, pregnancy-related ailments, psychological distress, and the risk of suicide. On 30 July the Knesset passed an amendment to penal law adding sexual offenses to those offenses whose penalty can be doubled if done on grounds of "nationalistic terrorism, racism or hostility towards a certain community". According to MK Limor Son Har-Melech, the bill is meant to penalize any individual who "[intends to] harm a woman sexually based on her Jewishness". The law was criticized by MK Gilad Kariv as "populist, nationalistic, and dangerous towards the Arab citizens of Israel", and by MK Ahmad Tibi as a "race law", and was objected to by legal advisors at the Ministry of Justice and the Knesset Committee on National Security. Activist Orit Kamir wrote that "the amendment... is neither feminist, equal, nor progressive, but the opposite: it subordinates women's sexuality to the nationalistic, racist patriarchy. It hijacks the Law for Prevention of Sexual Harassment to serve a world view that tags women as sexual objects that personify the nation's honor." Yael Sherer, director of the Lobby to Combat Sexual Violence, criticized the law as being informed by dated ideas about sexual assault, and proposed that MKs "dedicate a session... to give victims of sexual assault an opportunity to come out of the darkness... instead of [submitting] declarative bills that change nothing and are not meant but for grabbing headlines". In Israel, during 2022, 24 women "were murdered because they were women," which was an increase of 50% compared to 2021. A law permitting courts to order men subject to a restraining order following domestic violence offenses to wear electronic tags was drafted during the previous Knesset and had passed its first reading unanimously. On 22 March 2023, the Knesset voted to reject the bill. It had been urged to do so by National Security Minister Itamar Ben-Gvir, who said that the bill was unfair to men. Earlier in the week, Ben-Gvir had blocked the measure from advancing in the ministerial legislative committee. The MKs voting against the bill included Prime Minister Netanyahu. The Association of Families of Murder Victims said that by rejecting the law, National Security Minister Itamar Ben-Gvir "brings joy to violent men and abandons the women threatened with murder… unsupervised restraining orders endanger women's lives even more. They give women the illusion of being protected, and then they are murdered." MK Pnina Tamano-Shata, chairwoman of the Knesset Committee on the Status of Women and Gender Equality, said that "the coalition proved today that it despises women's lives." The NGO Amutat Bat Melech [he], which assists Orthodox and ultra-Orthodox women who suffer from domestic violence, said that: "Rejecting the electronic bracelet bill is disconnected from the terrible reality of seven femicides since the beginning of the year. This is an effective tool of the first degree that could have saved lives and reduced the threat to women suffering from domestic violence. This is a matter of life and death, whose whole purpose is to provide a solution to defend women." The agreement signed by the coalition parties includes the setting up of a committee to draft changes to the Law of Return. Israeli religious parties have long demanded that the "grandchild clause" of the Law of Return be cancelled. This clause grants citizenship to anyone with at least one Jewish grandparent, as long as they do not practice another religion. If the grandchild clause were to be removed from the Law of Return then around 3 million people who are currently eligible for aliyah would no longer be eligible. The heads of the Jewish Agency, the Jewish Federations of North America, the World Zionist Organization and Keren Hayesod sent a joint letter to Prime Minister Netanyahu, expressing their "deep concern" about any changes to the Law of Return, adding that "Any change in the delicate and sensitive status quo on issues such as the Law of Return or conversion could threaten to unravel the ties between us and keep us away from each other." The Executive Council of Australian Jewry and the Zionist Federation of Australia issued a joint statement saying "We… view with deep concern… proposals in relation to religious pluralism and the law of return that risk damaging Israel's… relationship with Diaspora Jewry." On 19 March 2023, Israeli Finance Minister Bezalel Smotrich spoke in Paris at a memorial service for a Likud activist. The lectern at which Smotrich spoke was covered with a flag depicting the 'Greater Land of Israel,' encompassing the whole of Mandatory Palestine, as well as Trans-Jordan. During his speech, Smotrich said that "there's no such thing as Palestinians because there's no such thing as a Palestinian people." He added that the Palestinian people are a fictitious nation invented only to fight the Zionist movement, asking "Is there a Palestinian history or culture? There isn't any." The event received widespread media coverage. On 21 March, a spokesman for the US State Department sharply criticized Smotrich's comments. "The comments, which were delivered at a podium adorned with an inaccurate and provocative map, are offensive, they are deeply concerning, and, candidly, they're dangerous. The Palestinians have a rich history and culture, and the United States greatly values our partnership with the Palestinian people," he said. The Jordanian Foreign Ministry also voiced disapproval: "The Israeli Minister of Finance's use, during his participation in an event held yesterday in Paris, of a map of Israel that includes the borders of the Hashemite Kingdom of Jordan and the occupied Palestinian territories represents a reckless inflammatory act, and a violation of international norms and the Jordanian-Israeli peace treaty." Additionally, a map encompassing Mandatory Palestine and Trans-Jordan with a Jordanian flag on it was placed on a central lectern in the Jordanian Parliament. Jordan's parliament voted to expel the Israeli ambassador. Israel's Ministry of Foreign Affairs released a clarification relating to the matter, stating that "Israel is committed to the 1994 peace agreement with Jordan. There has been no change in the position of the State of Israel, which recognizes the territorial integrity of the Hashemite Kingdom of Jordan". Ahead of a Europe Day event due to take place on 9 May 2023, far-right wing National Security Minister Itamar Ben-Gvir was assigned as a representative of the government and a speaker at the event by the government secretariat, which deals with placing ministers at receptions on the occasion of the national days of the foreign embassies. The European Union requested that Ben-Gvir not attend, but the government did not make changes to the plan. On 8 May, the European delegation to Israel cancelled the reception, stating that: "The EU Delegation to Israel is looking forward to celebrating Europe Day on May 9, as it does every year. Regrettably, this year we have decided to cancel the diplomatic reception, as we do not want to offer a platform to someone whose views contradict the values the European Union stands for. However, the Europe Day cultural event for the Israeli public will be maintained to celebrate with our friends and partners in Israel the strong and constructive bilateral relationship". Israel's Opposition Leader Yair Lapid stated: "Sending Itamar Ben-Gvir to a gathering of EU ambassadors is a serious professional mistake. The government is embarrassing a large group of friendly countries, jeopardizing future votes in international institutions, and damaging our foreign relations. Last year, after a decade of efforts, we succeeded in signing an economic-political agreement with the European Union that will contribute to the Israeli economy and our foreign relations. Why risk it, and for what? Ben-Gvir is not a legitimate person in the international community (and not really in Israel either), and sometimes you have to be both wise and just and simply send someone else". On 23 February 2023, Defense Minister Gallant signed an agreement assigning governmental powers in the West Bank to a body to be headed by Minister Bezalel Smotrich, who will effectively become the governor of the West Bank, controlling almost all areas of life in the area, including planning, building and infrastructure. Israeli governments have hitherto been careful to keep the occupation as a military government. The temporary holding of power by an occupying military force, pending a negotiated settlement, is a principle of international law – an expression of the prohibition against obtaining sovereignty through conquest that was introduced in the wake of World War II. An editorial in Haaretz noted that the assignment of governmental powers in the West Bank to a civilian governor, alongside the plan to expand the dual justice system so that Israeli law will apply fully to settlers in the West Bank, constitutes de jure annexation of the West Bank. On 26 February 2023, following the 2023 Huwara shooting in which two Israelis were killed by an unidentified attacker, hundreds of Israeli settlers attacked the Palestinian town of Huwara and three nearby villages, setting alight hundreds of Palestinian homes (some with people in them), businesses, a school, and numerous vehicles, killing one Palestinian man and injuring 100 others. Bezalel Smotrich subsequently called on Twitter for Huwara to be "wiped out" by the Israeli government. Zvika Fogel MK, of the ultra-nationalist Otzma Yehudit, which forms part of the governing coalition, said that he "looks very favorably upon" the results of the rampage. Members of the coalition proposed an amendment to the Disengagement Law, which would allow Israelis to resettle settlements vacated during the 2005 Israeli disengagement from Gaza and the northern West Bank. The evacuated settlements were considered illegal under international law, according to most countries. The proposal was approved for voting by the Foreign Affairs and Defense Committee on 9 March 2023, while the committee was still waiting for briefing materials from the NSS, IDF, MFA and Shin Bet, and was passed on 21 March. The US has requested clarification from Israeli ambassador Michael Herzog. A US State Department spokesman stated that "The U.S. strongly urges Israel to refrain from allowing the return of settlers to the area covered by the legislation, consistent with both former Prime Minister Sharon and the current Israeli Government's commitment to the United States," noting that the actions represent a clear violation of undertakings given by the Sharon government to the Bush administration in 2005 and Netanyahu's far-right coalition to the Biden administration the previous week. Minister of Communication Shlomo Karhi had initially intended to cut the funding of the Israeli Public Broadcasting Corporation (also known by its blanket branding Kan) by 400 million shekels – roughly half of its total budget – closing several departments, and privatizing content creation. In response, the Director-General of the European Broadcasting Union, Noel Curran, sent two urgent letters to Netanyahu, expressing his concerns and calling on the Israeli government to "safeguard the independence of our Member KAN and ensure it is allowed to operate in a sustainable way, with funding that is both stable, adequate, fair, and transparent." On 25 January 2023, nine journalist organizations representing some of Kan's competitors issued a statement of concern, acknowledging the "important contribution of public broadcasting in creating a worthy, unbiased and non-prejudicial journalistic platform", and noting that "the existence of the [broadcasting] corporation as a substantial public broadcast organization strengthens media as a whole, adding to the competition in the market rather than weakening it." They also expressed their concern that the "real reason" for the proposal was actually "an attempt to silence voices from which... [the Minister] doesn't always draw satisfaction". The same day, hundreds of journalists, actors and filmmakers protested in Tel Aviv. The proposal was eventually put on hold. On 22 February 2023 it was reported that Prime Minister Netanyahu was attempting to appoint his close associate Yossi Shelley as the deputy to the National Statistician — a highly sensitive position in charge of providing accurate data for decision makers. The appointment of Shelley, who did not possess the required qualifications for the role, was withdrawn following publication. In its daily editorial, Haaretz tied this attempt with the judicial reform: "once they take control of the judiciary, law enforcement and public media, they wish to control the state's data base, the dry numerical data it uses to plan its future". Netanyahu also proposed Avi Simhon for the role, and eventually froze all appointments at the Israel Central Bureau of Statistics. Also on 22 February 2023, it was revealed that Yoav Kish, the Minister of Education, was promoting a draft government decision change to the National Library of Israel board of directors which would grant him more power over the institution. In response, the Hebrew University — which owned the library until 2008 – announced that if the draft is accepted, it will withdraw its collections from the library. The university's collections, which according to the university constitute some 80% of the library's collection, include the Agnon archive, the original manuscript of Hatikvah, and the Rothschild Haggadah, the oldest known Haggadah. A group of 300 authors and poets signed an open letter against the move, further noting their objection against "political takeover" of public broadcasting, as well as "any legislation that will castrate the judiciary and damage the democratic foundations of the state of Israel". Several days later, it was reported that a series of donors decided to withhold their donations to the library, totaling some 80 million shekels. On 3 March a petition against the move by 1,500 academics, including Israel Prize laureates, was sent to Kish. The proposal has been seen by some as retribution against Shai Nitzan, the former State Attorney and the library's current rector. On 5 March it was reported that the Legal Advisor to the Ministry of Finance, Asi Messing, was withholding the proposal. According to Messing, the proposal – which was being promoted as part of the Economic Arrangements Law – "was not reviewed... by the qualified personnel in the Ministry of Finance, does not align with any of the common goals of the economic plan, was not agreed to by myself and was not approved by the Attorney General." As of February 2023, the government has been debating several proposals that will significantly weaken the Ministry of Environmental Protection, including reducing the environmental regulation of planning and development and electricity production. One of the main proposals, the transferal of a 3 billion shekel fund meant to finance waste management plants from the Ministry of Environmental Protection to the Ministry of the Interior, was eventually withdrawn. The Minister of Environmental Protection, Idit Silman, has been criticized for using for meeting with climate change denialists, for wasteful and personally-motivated travel on the ministry's expense, for politicizing the role, and for engaging in political activity on the ministry's time. The government has been noted for an unusually high number of dismissals and resignations of senior career civil servants, and for the frequent attempts to replace them with candidates with known political associations, who are often less competent. According to sources, Netanyahu and people in his vicinity are seeking out civil servants who were appointed by the previous government, intent on replacing them with people loyal to him. Governmental nominees for various positions have been criticized for lack of expertise. In addition to the nominee to the position of Deputy National Statistician (see above), the Director General of the Ministry of Finance, Shlomi Heisler; the Director General of the Ministry of Justice, Itamar Donenfeld; and the Director General of Ministry of Transport, Moshe Ben Zaken, have all been criticized for incompetence, lack of familiarity with their Ministries' subject matter, lack of interest in the job, or lack of experience in managing large organizations. It has been reported that in some ministries, senior officials were enacting slowdowns as a means for dealing with the new ministers and director generals. On 28 July the director general of the Ministry of Education resigned, citing as reason the societal "rift". Asaf Zalel, a retired Air Force Brigadier General, was appointed in January. When asked about attempts to appoint his personal friend and attorney to the board of directors of a state-owned company, Minister David Amsalem replied: "that is my job, due to my authority to appoint directors. I put forward people that I know and hold in esteem". Under Minister of Transport Miri Regev, the ministry has either dismissed or lost the heads of the National Public Transport Authority, Israel Airports Authority, National Road Safety Authority, Israel Railways, and several officials in Netivei Israel. The current chair of Netivei Israel is Likud member and Regev associate Yigal Amadi, and the legal counsel is Einav Abuhzira, daughter of a former Likud branch chair. Abuhzira was appointed instead of Elad Berdugo, nephew of Netanyahu surrogate Yaakov Bardugo, after he was disqualified for the role by the Israel Government Companies Authority. In July 2023 the Ministry of Communications, Shlomo Karhi, and the minister in charge of the Israel Government Companies Authority, Dudi Amsalem, deposed the chair of the Israel Postal Company, Michael Vaknin. The chair, who was hired to lead the company's financial recovery after years of operational loss and towards privatization, has gained the support of officials at the Authority and at the Ministry of Finance; nevertheless, the ministers claimed that his performance is inadequate, and nominated in his place Yiftah Ron-Tal, who has known ties to Netanyahu and Smotrich. They also nominated four new directors, two of which have known political associations, and a third who was a witness in Netanyahu's trial. The coalition is allowed to spend a portion of the state's budget on a discretionary basis, meant to coax member parties to reach an agreement on the budget. As of May 2023, the government was pushing an allocation of over 13 billion shekels over two years - almost seven times the amount allocated by the previous government. Most of the funds will be allocated for uses associated with the religious, orthodox and settler communities. The head of the Budget Department at the Ministry of Finance, Yoav Gardos, objected to the allocations, claiming they would exacerbate unemployment in the Orthodox community, which is projected to cost the economy a total of 6.7 trillion shekels in lost produce by 2065. At the onset of the Gaza war and the declaration of a state of national emergency, Minister of Finance Bezalel Smotrich instructed government agencies to continue with the planned distribution of discretionary funds. Corruption During March 2023, the government was promoting an amendment to the Law on Public Service (Gifts) that would allow Netanyahu to receive donations to fund his legal defense. The amendment follows a decision by the High Court of Justice (HCJ) that forced Netanyahu to refund US$270,000 given to him and his wife by his late cousin, Nathan Mileikowsky, for their legal defense. This is in contrast to past statements by Minister of Justice Yariv Levin, who spoke against the possible conflict of interests that can result from such transactions. The bill was opposed by the Attorney General Gali Baharav-Miara, who stressed that it could "create a real opportunity for governmental corruption", and was eventually withdrawn at the end of March. As of March 2023, the coalition was promoting a bill that would prevent judicial review of ministerial appointments. The bill is intended to prevent the HCJ from reviewing the appointment of the twice-convicted chairman of Shas, Aryeh Deri (convicted of bribery, fraud, and breach of trust), to a ministerial position, after his previous appointment was annulled on grounds of unreasonableness. The bill follows on the heels of another amendment, that relaxed the ban on the appointment of convicted criminals, so that Deri - who was handed a suspended sentence after his second conviction - could be appointed. The bill is opposed by the Attorney General, as well as by the Knesset Legal Adviser, Sagit Afik. Israeli law allows for declaring a Prime Minister (as well as several other high-ranking public officials) to be temporarily or permanently incapacitated, but does not specify the conditions which can lead to a declaration of incapacitation. In the case of the Prime Minister, the authority to do so is given to the Attorney General. In March 2023, the coalition advanced a bill that passes this authority from the Attorney General to the government with the approval of the Knesset committee, and clarified that incapacitation can only result from medical or mental conditions. On 3 January 2024, the Supreme Court ruled by a majority of 6 out of 11 that the validity of the law will be postponed to the next Knesset because the bill in its immediate application is a personal law and is intended to serve a distinct personal purpose. Later, the court rejected a petition regarding the definition of Netanyahu as an incapacitated prime minister due to his ongoing trial and conflict of interests. Notes References External links |
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Contents Beth Nimrah Beth-Nimrah or Beth-nimrah (Hebrew: בית נמרה), also called Nimrin and Bethennabris,[citation needed] was an ancient city in Transjordan, which features prominently the history of ancient Israel and Judah. Tell Nimrin has been identified by Nelson Glueck as the last of three sites successively occupied by the ancient city. Etymology Beth Nimrah means 'house of a leopard' in Hebrew, beit meaning 'house' and namer 'leopard' (cf. nimr in Arabic). Later in antiquity, the city took on the name Nimrin, until its demise in the first century CE. In Talmudic literature, it is mentioned as Nimrin or Nimri. The name is preserved in the names Tell Nimrin (for the archaeological mound) and Wadi Nimrin (for the wadi-type valley). Glueck suggests a possible connection between Wadi Nimrin and the biblical "Waters of Nimrim" (Isaiah 15:6 and Jeremiah 48:34), although he identifies "this stream" with Seil en-Numeirah (not clear if he refers by "this stream" to Seil en-Numeirah, or to Jeremiah's "Waters of Nimrim"). Seil en-Numeira is a stream that flows into the Dead Sea at its southern end. Location The city was located in the Jordan Valley, approximately 12 kilometers (7.5 mi) north of the Dead Sea and 16 kilometers (9.9 mi) east of Jericho.[citation needed] Wadi Nimrin, on whose south (left) bank all the three sites identified by Glueck with Beth Nimra are located, marks the northern limit of the Plains of Moab. The ancient city was believed by Glueck to have moved twice in its history, occupying successively three mounds: Tell el-Mustaḥ during the Early Bronze I, Tell Bleibil in Iron Age I-II, and Tell Nimrin in the Roman through to the Early Muslim period, with similar large historical sedentary habitation gaps as those encountered elsewhere across the Jordan Valley. Glueck based his dates on sherds found at the surface and, in the case of Tell el-Mustah and Tell Nimrin, in cuts caused by modern roads. Tell el-Mustah rises south of Wadi Sha'ib (Wadi Shu'ayb in more recent spelling), which is the name of an easterly section of the same wadi which takes on the name Wadi Nimrin when it reaches Tell Nimrin. Tell Bleibil is just across the wadi from Tell el-Mustah, so on the north side of Wadi Sha'ib. Tell el-Mustah stands c. 1.75 km ENE of Tell Nimrin, both being located on the south side of the wadi. The tells of Mustah and Bleibil are in the foothills flanking the plain of Nimrin from the east, while Nimrin is further down the slope. Glueck describes Tell Nimrin in 1943 as being situated very close to the east of the Arab village of Shuneh (now Ash-Shunah al-Janubiyah or South Shuneh). About Tell Nimrin, see also Alexander Ahrens' Wadi Shuʿayb Archaeological Survey (2018). Hebrew Bible It was assigned to the Tribe of Gad (Numbers 32:36). In the Book of Joshua it was said to have belonged formerly to the kingdom of Sihon (Joshua 13:27). History Excavations at Tell Bleibil, the ancient site identified by Glueck as the site of Nimrah during the Iron Age, show that during this period the settlement was enclosed by a massive casemate fortifications over 12 meter high; they were constructed around the late 9th to the early 8th century BCE. Inside the settlement, archaeologists discovered evidence for long-term occupation spanning roughly 250 years, with domestic spaces, storage and grinding installations, loom weights, lamps and cultic objects such as a pillar figurine. Multiple areas feature destruction layer caused by intense fire, indicating the site was destroyed likely in the early 6th century BCE. In the 4th century BCE, the city was settled by Israelites who had returned from the Babylonian exile and marked the furthest extent eastward of Jewish settlement in Transjordan. In c. 65 CE, the village was the site of a fierce battle during the First Jewish–Roman War under Vespasian, which saw the defeat of the town's defenders. The non-combatants were exterminated, the able-bodied fled, the houses were ransacked by the soldiery, and the village set on fire. The town is also mentioned in the Mosaic of Rehob, which was laid sometimes between the late 3rd and the 6th/7th centuries CE. References Bibliography 31°54′32″N 35°38′17″E / 31.909°N 35.638°E / 31.909; 35.638 External links |
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Contents U.S. Interior Highlands The U.S. Interior Highlands is a mountainous region in the Central United States spanning northern and western Arkansas, southern Missouri, eastern Oklahoma, and southern Illinois. The name is designated by the United States Geological Survey to refer to the combined subregions of the Ouachita Mountains south of the Arkansas River and the Ozark Plateaus north of the Arkansas. The U.S. Interior Highlands is one of few mountainous regions between the Appalachians and Rockies. Geography There are three distinct mountain ranges within the U.S. Interior Highlands: The U.S. Interior Highlands is dominated by temperate broadleaf and mixed forests. Three national forests are located here: The Ouachita National Forest in Arkansas and Oklahoma; the Ozark-St. Francis National Forest in Arkansas; and the Mark Twain National Forest in Missouri. Gallery References See also: U.S. Interior Highlands This Oklahoma state location article is a stub. You can help Wikipedia by adding missing information. |
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[SOURCE: https://en.wikipedia.org/wiki/Neighbor_Discovery_Protocol] | [TOKENS: 721] |
Contents Neighbor Discovery Protocol The Neighbor Discovery Protocol (NDP), or simply Neighbor Discovery (ND), is a protocol of the Internet protocol suite used with Internet Protocol Version 6 (IPv6).: §1 It operates at the internet layer of the Internet model, and is responsible for gathering various information required for network communication, including the configuration of local connections and the domain name servers and gateways. The protocol defines five ICMPv6 packet types to perform functions for IPv6 similar to the Address Resolution Protocol (ARP) and Internet Control Message Protocol (ICMP) Router Discovery and Router Redirect protocols for IPv4. It provides many improvements over its IPv4 counterparts.: §3.1 For example, it includes Neighbor Unreachability Detection (NUD), thus improving robustness of packet delivery in the presence of failing routers or links, or mobile nodes. The Inverse Neighbor Discovery (IND) protocol extension allows nodes to determine and advertise an IPv6 address corresponding to a given link-layer address, similar to Inverse ARP for IPv4. The Secure Neighbor Discovery Protocol (SEND), a security extension of NDP, uses Cryptographically Generated Addresses (CGA) and the Resource Public Key Infrastructure (RPKI) to provide an alternative mechanism for securing NDP with a cryptographic method that is independent of IPsec. Neighbor Discovery Proxy (ND Proxy) provides a service similar to IPv4 Proxy ARP and allows bridging multiple network segments within a single subnet prefix when bridging cannot be done at the link layer. Functions NDP defines five ICMPv6 packet types for the purpose of router solicitation, router advertisement, neighbor solicitation, neighbor advertisement, and network redirects. These messages are used to provide the following functionality: IANA maintains a list of all current NDP options as they are published. Example Two computers, A and B are connected to the same local area network with no intervening gateway or router. A has a packet to send to IP address 2001:db8::55 which happens to be the address of B. Before sending the packet to B, A creates a solicited-node multicast address by appending the least-significant 24 bits of B's address to the prefix ff02::1:ff00:0/104, which is ff02::1:ff00:55 and creates a solicited-node multicast MAC address by appending the least-significant 24 bits of B's solicited-node multicast address to the prefix 33:33:FF:xx:xx:xx, which is 33:33:FF:00:00:55. A sends a neighbor solicitation message requesting an answer for 2001:db8::55 (destination ff02::1:ff00:55 IP address and destination 33:33:FF:00:00:55 MAC address), which is accepted by B which is listening on its own solicited-node multicast address on the local network. B responds with a neighbor advertisement message containing its MAC and IP addresses. A receives the response and sends the packet on the link with B's MAC address. Typically, network nodes maintain a lookup cache that associates IP and MAC addresses. In this example, if A had the lookup cached, then it would not need to send the NDP request. Also, when B received the request, it could cache the lookup to A so that if B needs to send a packet to A later, it does not need to use NDP to lookup its MAC address. Finally, when A receives the NDP response, it can cache the lookup for future messages addressed to the same IP address. Messages formats See also References |
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[SOURCE: https://en.wikipedia.org/wiki/George_Stubbs] | [TOKENS: 2988] |
Contents George Stubbs George Stubbs ARA (25 August 1724 – 10 July 1806) was an English painter, best known for his paintings of horses. Self-trained, Stubbs learnt his skills independently from other great artists of the 18th century such as Joshua Reynolds and Thomas Gainsborough. Stubbs' output includes history paintings, but his greatest skill was in painting animals (such as horses, dogs and lions), perhaps influenced by his love and study of anatomy. His series of paintings on the theme of a lion attacking a horse are early and significant examples of the Romantic movement that emerged in the late 18th century. He enjoyed royal patronage. His painting Whistlejacket hangs in the National Gallery, London. Biography Stubbs was born in Liverpool, the son of a currier, or leather-dresser, John Stubbs, and his wife Mary. Information on his life until the age of 35 or so is sparse, relying almost entirely on notes made by Ozias Humphry, a fellow artist and friend; Humphry's informal memoir, which was not intended for publication, was based on a series of private conversations he had with Stubbs around 1794, when Stubbs was 70 years old, and Humphry 52. Stubbs worked at his father's trade until the age of 15 or 16, at which point he told his father that he wished to become a painter. While initially resistant, Stubbs's father (who died not long afterward in 1741), eventually acquiesced in his son's choice of a career path, on the condition that he could find an appropriate mentor. Stubbs subsequently approached the Lancashire painter and engraver Hamlet Winstanley, and was briefly engaged by him in a sort of apprenticeship relationship, probably not more than several weeks in duration. Having initially demonstrated his abilities and agreed to do some copying work, Stubbs had access to and opportunity to study the collection at Knowsley Hall near Liverpool, the estate where Winstanley was then residing; however, he soon left when he came into conflict with the older artist over exactly which pictures he could work on copying. Thereafter, as an artist Stubbs was self-taught. He had had a passion for anatomy from his childhood, and in or around 1744, he moved to York, in the North of England, to pursue his ambition to study the subject under experts. In York, from 1745 to 1753, he worked as a portrait painter, and studied human anatomy under the surgeon Charles Atkinson, at York County Hospital, One of his earliest surviving works is a set of illustrations for a textbook on midwifery by John Burton, Essay towards a Complete New System of Midwifery, published in 1751. In 1754 Stubbs visited Italy. Forty years later he told Ozias Humphry that his motive for going to Italy was, "to convince himself that nature was and is always superior to art whether Greek or Roman, and having renewed this conviction he immediately resolved upon returning home". In 1756 he rented a farmhouse in the village of Horkstow, Lincolnshire, and spent 18 months dissecting horses, assisted by his common-law wife, Mary Spencer. He moved to London in about 1759 and in 1766 published The anatomy of the Horse. The original drawings are now in the collection of the Royal Academy. Even before his book was published, Stubbs's drawings were seen by leading aristocratic patrons, who recognised that his work was more accurate than that of earlier horse painters such as James Seymour, Peter Tillemans and John Wootton. In 1759 Charles Lennox, 3rd Duke of Richmond commissioned three large pictures from him, and his career was soon secure. By 1763 he had produced works for several more dukes and other lords and was able to buy a house in Marylebone, a fashionable part of London, where he lived for the rest of his life. A famous work, Whistlejacket, a painting of the thoroughbred race horse rising on his hind legs, commissioned by Charles Watson-Wentworth, 2nd Marquess of Rockingham, is now in the National Gallery in London. This and two other paintings carried out for Rockingham break with convention in having plain backgrounds. Throughout the 1760s he produced a wide range of individual and group portraits of horses, sometimes accompanied by hounds. He often painted horses with their grooms, whom he always painted as individuals. Meanwhile, he also continued to accept commissions for portraits of people, including some group portraits. From the inaugural Exhibition of 1761 onwards he exhibited at the Society of Artists of Great Britain at Spring Gardens, but in 1775 he switched his allegiance to the recently founded but already more prestigious Royal Academy of Arts. He served as President of the Society of Artists for a year from October 1772, when it was already beset by financial problems and defections to the Royal Academy. Stubbs also painted more exotic animals including lions, tigers, giraffes, monkeys, and rhinoceroses, which he was able to observe in private menageries. His painting of a kangaroo was the first glimpse of this animal for many 18th-century Britons. He became preoccupied with the theme of a wild horse threatened by a lion and produced several variations on this theme. These and other works became well known at the time through engravings of Stubbs's work, which appeared in increasing numbers in the 1770s and 1780s. Stubbs also painted historical pictures, but these are much less well regarded. From the late 1760s he produced some work on enamel. In the 1770s Josiah Wedgwood developed a new and larger type of enamel panel at Stubbs's request. Stubbs hoped to achieve commercial success with his paintings in enamel, but the venture left him in debt. Also in the 1770s he painted single portraits of dogs for the first time, while also receiving an increasing number of commissions to paint hunts with their packs of hounds. He remained active into his old age. In the 1780s he produced a pastoral series called Haymakers and Reapers, and in the early 1790s he enjoyed the patronage of the Prince of Wales, whom he painted on horseback in 1791. His last project, begun in 1795, was A comparative anatomical exposition of the structure of the human body with that of a tiger and a common fowl, fifteen engravings from which appeared between 1804 and 1806. The project was left unfinished upon Stubbs's death. He died at the age of 81 on 10 July 1806 at the home he had lived in since 1763, No.24 Somerset Street, near Portman Square, Marylebone, central London. He was buried on 18 July in the graveyard of St Marylebone Parish Church, now a garden of rest. Stubbs's son George Townley Stubbs was an engraver and printmaker. A lion attacking a horse Stubbs began an informal series of works on the subject of a lion attacking a horse around 1762 or 1763, and he continued to explore and reinterpret the theme in at least 17 images over a period of about 30 years. These paintings are among his most celebrated and influential works.: 90 p. One art historian wrote "The appearance of the monumental picture now in the Mellon Collection [A Lion Attacking a Horse, ca. 1762-63] must be treated as one of the outstanding events in English eighteenth-century art for within the context of painting at that date its singularity as well as its inherent originality is most striking. Not since the publication of Hogarth's Harlot's Progress thirty years before had there occurred such an innovation.": 86 p. The iconic paintings are in fact among the earliest manifestations of Romanticism in painting, predating the work of more familiar masters of the movement such as William Blake, Eugène Delacroix, Francisco Goya, William Turner, and Théodore Géricault, who was known to be an admirer of both horses, and the work of George Stubbs.: 585 p. : 109 p. Jean Clay, professor of art history at the University of Paris, perceptively observed that not only does the energy and terror of the animals foreshadow the spirit of romanticism but, as Stubbs's series progressed, the horror seemed to diffuse and expand throughout the whole of the landscape: "an image that would fertilize the Romantic imagination and come to full flower a half-century later.": 150 p. The series are mostly oil paintings on canvas, but also include examples of enamel on copper, original engravings, and even a relief model in Wedgwood clay. The white horse was painted from one of the Kings Horses in the Royal Mews, secured for the artist by an architect friend, Mr. Payne. Stubbs was able to study a lion in life that was in the menagerie of William Petty, 2nd Earl of Shelburne at Hounslow Heath.: 90 p. The earliest work is a life-size painting of A Lion Attacking a Horse (ca. 1762–63), which was commissioned by the 2nd Marquess of Rockingham and now in the Yale Center for British Art. Art historian Basil Taylor postulated the theme was treated in three distinct episodes: Episode A, a lion prowling at some distance from a terrified horse; Episode B, a lion close to a terrified horse; Episode C a lion on the horse's back biting its flank. Interestingly, Stubbs first painted "Episode C", and it was not until later that he was inspired to go back and paint the moments leading up to the climatic event.: 81–82 p. An anecdote regarding the origin of the subject matter emerged soon after the artist death, originally published in The Sporting Magazine in 1808, and reiterate often for well over a century and a half. Art historian H. W. Janson repeated it "On a visit to North Africa, he had seen a horse killed by a lion; this experience haunted his imagination, and from it he developed a new type of animal picture full of Romantic feeling for the grandeur and violence of nature.": 567 p. However, research published in 1965 produced a rather persuasive argument that Stubbs in fact never traveled to Africa, and the actual inspiration for the painting was an antique sculpture he had seen in a well documented 1754 stay in Rome. The sculpture, Lion Seizing a Horse, in the Palazzo dei Conservatori, Rome, is a restored Roman copy of a Hellenistic original. It has been a celebrated work since the Renaissance, admired by Michelangelo, included in guidebooks of Stubbs's day, and copied any number of times by various artist in marble, bronze, and prints, including an 18th-century marble copy in the collection of Stubbs's patron Henry Blundell, who also acquired one of the paintings by Stubbs.: 90–91 p. Legacy Stubbs remained a secondary figure in British art until the mid-twentieth century. The art historian Basil Taylor and art collector Paul Mellon both championed Stubbs's work. Stubbs's Pumpkin with a Stable-lad was the first painting that Mellon bought in 1936. Basil Taylor was commissioned in 1955 by Pelican Press to write the book Animal Painting in England – From Barlow to Landseer, which included a large segment on Stubbs. In 1959 Mellon and Taylor first met and bonded over their appreciation of Stubbs. This led Mellon to create the Paul Mellon Foundation for British Art (the predecessor of the Paul Mellon Centre for Studies in British Art) with Taylor as the director. Mellon eventually amassed the largest collection of Stubbs paintings in the world which would become a part of his larger collection of British art that would become the Yale Center for British Art in Connecticut, USA. In 1971, Taylor published the seminal catalogue, Stubbs. The record price for a Stubbs painting was set by the sale at auction of Gimcrack on Newmarket Heath, with a Trainer, a Stable-Lad, and a Jockey (1765) at Christie's in London in July 2011 for £22.4 million. It was sold by the Woolavington Collection of sporting art at Cottesbrooke Hall, Northamptonshire; the buyer was unidentified. The Royal Collection of the British royal family holds 16 paintings by Stubbs. Two paintings by Stubbs were bought by the National Maritime Museum in Greenwich, London after a public appeal to raise the £1.5 million required. The two paintings, The Kongouro from New Holland and Portrait of a Large Dog were both painted in 1772. Depicting a kangaroo and a dingo respectively, they are the first depictions of Australian animals in Western art. His work was shown in a retrospective exhibition at the Whitechapel Gallery in London, 27 February – 7 April 1957. Tate Britain, in conjunction with the Yale Center for British Art, organized the largest exhibition ever devoted to Stubbs (up to that time) in 1984, which travelled to New Haven in 1985.: 7 p. Stubbs' work was shown in Stubbs and the Horse, an exhibit co-organized and exhibited at The Kimbell Art Museum, Fort Worth, Texas (exhibited 14 November 2004–6 February 2005), the Walters Art Museum, Baltimore (exhibited 13 March–29 May 2005), and the National Gallery, London (Summer 2005). The exhibition catalog was written by Malcolm Warner and Robin Blake. From 6 April–8 November 2015, the Metropolitan Museum of Art displayed Paintings by George Stubbs from the Yale Center for British Art. In popular culture A fictional painting by Stubbs plays a key role in the Robert Galbraith novel Lethal White. Anthony Jennings' 2024 novel Mister Stubbs explores the painter's early years, focusing on his time in York during Bonnie Prince Charlie's rebellion of 1745, and his mysterious trip to Rome, where Bonnie Prince Charlie's father, the exiled Jacobite James Edward Stuart, had his court. Gallery List of selected artworks In the Tate Gallery See also References Further reading External links |
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[SOURCE: https://en.wikipedia.org/wiki/Hydra_(constellation)] | [TOKENS: 2025] |
Contents Hydra (constellation) Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees, and also the longest at over 100 degrees. Its southern end borders Libra and Centaurus and its northern end borders Cancer. It was included among the 48 constellations listed by the 2nd century astronomer Ptolemy. Commonly represented as a water snake, it straddles the celestial equator. History and mythology The Greek constellation of Hydra is an adaptation of a Babylonian constellation: the MUL.APIN includes a "serpent" constellation (MUL.DINGIR.MUŠ) that loosely corresponds to Hydra. It is one of two Babylonian "serpent" constellations (the other being the origin of the Greek Serpens), a mythological hybrid of serpent, lion and bird. The shape of Hydra resembles a twisting snake, and features as such in some Greek myths. One myth associates it with a water snake that a crow served Apollo in a cup when it was sent to fetch water. Apollo saw through the fraud and angrily cast the crow, cup and snake into the sky. It is also associated with the monster Hydra, with its many heads, killed by Hercules, represented in another constellation. According to legend, if one of the Hydra's heads was cut off, two more would grow in its place. However, Hercules' nephew, Iolaus, seared the necks with a torch to prevent them from growing back and thus enabled Hercules to overcome the Hydra. In Chinese astronomy, the stars that correspond to Hydra are located within the Vermilion Bird and the Azure Dragon. The head of Hydra was collectively known as "Min al Az'al," meaning "belonging to the uninhabited spot" in Arabic. Features Despite its size, Hydra contains only one moderately bright star, Alphard, designated Alpha Hydrae. It is an orange giant of magnitude 2.0, 177 light-years from Earth. Its traditional name means "the solitary one". Beta Hydrae is a blue-white star of magnitude 4.3, 365 light-years from Earth. Gamma Hydrae is a yellow giant of magnitude 3.0, 132 light-years from Earth. Hydra has one bright binary star, Epsilon Hydrae, which is difficult to split in amateur telescopes; it has a period of 1000 years and is 135 light-years from Earth. The primary is a yellow star of magnitude 3.4 and the secondary is a blue star of magnitude 6.7. However, there are several dimmer double stars and binary stars in Hydra. 27 Hydrae is a triple star with two components visible in binoculars and three visible in small amateur telescopes. The primary is a white star of magnitude 4.8, 244 light-years from Earth. The secondary, a binary star, appears in binoculars at magnitude 7.0 but is composed of a magnitude 7 and a magnitude 11 star; it is 202 light-years from Earth. 54 Hydrae is a binary star 99 light-years from Earth, easily divisible in small amateur telescopes. The primary is a yellow star of magnitude 5.3 and the secondary is a purple star of magnitude 7.4. N Hydrae (N Hya) is a pair of stars of magnitudes 5.8 and 5.9. Struve 1270 (Σ1270) consists of a pair of stars, magnitudes 6.4 and 7.4. The other main named star in Hydra is Sigma Hydrae (σ Hydrae), which also has the name of Minchir, from the Arabic for snake's nose. At magnitude 4.54, it is rather dim. The head of the snake corresponds to the Āshleshā Nakshatra, the lunar zodiacal constellation in Indian astronomy. The name of Nakshatra (Ashlesha) became the proper name of Epsilon Hydrae since 1 June 2018 by IAU. Hydra is also home to several variable stars. R Hydrae is a Mira variable star 2000 light-years from Earth; it is one of the brightest Mira variables at its maximum of magnitude 3.5. It has a minimum magnitude of 10 and a period of 390 days. V Hydrae is an unusually vivid red variable star 20,000 light-years from Earth. It varies in magnitude from a minimum of 9.0 to a maximum of 6.6. U Hydrae is a semi-regular variable star with a deep red color, 528 light-years from Earth. It has a minimum magnitude of 6.6 and a maximum magnitude of 4.2; its period is 115 days. Hydra includes GJ 357, an M-type main sequence star located only 31 light-years from the Solar System. This star has three confirmed exoplanets in its orbit, one of which, GJ 357 d, is considered to be a "Super-Earth" within the circumstellar habitable zone. The constellation also contains the radio source Hydra A galaxy as well as nearby WISE 0855−0714 brown dwarf being the closest (sub)stellar object of the constellation. Hydra contains three Messier objects. M83, also known as the Southern Pinwheel Galaxy, is located on the border of Hydra and Centaurus, M68 is a globular cluster near M83, and M48 is an open star cluster in the western end of the serpent. NGC 3242 is a planetary nebula of magnitude 7.5, 1400 light-years from Earth. Discovered in 1785 by William Herschel, it has earned the nickname "Ghost of Jupiter" because of its striking resemblance to the giant planet. Its blue-green disk is visible in small telescopes and its halo is visible in larger instruments. M48 (NGC 2548) is an open cluster that is visible to the naked eye under dark skies. Its shape has been described as "triangular"; this 80-star cluster is unusually large, more than half a degree in diameter, larger than the diameter of the full Moon. There are several globular clusters in Hydra. M68 (NGC 4590) is a globular cluster visible in binoculars and resolvable in medium amateur telescopes. It is 31,000 light-years from Earth and of the 8th magnitude. NGC 5694 is a globular cluster of magnitude 10.2, 105,000 light-years from Earth. Also called "Tombaugh's Globular Cluster", it is a Shapley class VII cluster; the classification indicates that it has intermediate concentration at its nucleus. Though it was discovered as a non-stellar object in 1784 by William Herschel, its status as a globular cluster was not ascertained until 1932, when Clyde Tombaugh looked at photographic plates taken of the region near Pi Hydrae on 12 May 1931. M83 (NGC 5236), the Southern Pinwheel Galaxy, is an 8th magnitude face-on spiral galaxy. It is easily observed in skies south of 40°N latitude, found by using 1, 2, 3, and 4 Centauri as guide stars. It has been host to six supernovae. Large amateur telescopes - above 12 inches aperture - reveal its spiral arms, bar, and small, bright nucleus. In a medium-sized amateur instrument, around 8 inches in aperture, the spiral arms become visible under good conditions. It is not perfectly symmetrical in the eyepiece, rather, the northwest side is flattened and the nucleus has a southwest-to-northeast bar. A smaller sister to the Milky Way, it is a grand design spiral galaxy 40,000 light-years across. There are many other galaxies located in Hydra. NGC 3314, usually delineated as NGC 3314a and NGC 3314b, is a pair of galaxies that appear superimposed, despite the fact that they are not related or interacting in any way. The foreground galaxy, NGC 3314a, is at a distance of 140 million light-years, and is a face-on spiral galaxy. The background galaxy, NGC 3314b, is an oblique spiral galaxy, and has a nucleus that appears reddened because of NGC 3314a's dusty disk. ESO 510-G13 is a warped spiral galaxy located 150 million light-years from Earth. Though most galactic disks are flat because of their rate of rotation, their conformation can be changed, as is the case with this galaxy. Astronomers speculate that this is due to interactions with other galaxies. NGC 5068 may be a member of the M83 group, but its identity is disputed. It has a low surface brightness and has a diameter of 4.5 arcminutes. It is not perfectly circular, rather, it is elliptical and oriented on a west-northwest/east-southeast axis. However, it is of fairly uniform brightness throughout. Another notable galaxy is NGC 4993, an elliptical galaxy which was the source of events GW170817, GRB 170817A and SSS17a from the merger of two neutron stars. The Sigma Hydrids peak on December 6 and are a very active shower. The parent body of the Sigma Hybrids is believed to be Comet Nishimura (C/2023 P1), which was discovered in 2023 by the Japanese astronomical photographer Hideo Nishimura. The Alpha Hydrids are a minor shower that peaks between January 1 and 7. See also References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Ministry_of_Welfare_and_Social_Affairs] | [TOKENS: 229] |
Contents Ministry of Welfare and Social Affairs The Ministry of Welfare and Social Affairs (Hebrew: משרד הרווחה והביטחון החברתי) is the branch of government charged with overseeing employment and ensuring the welfare of the public in Israel and oversee the supply of services. History The ministry was originally divided into two separate ministries – the Labor Ministry and the Welfare Ministry. In 1977 they were united to be the Welfare and Labor Ministry according to the view that labor can lead to welfare. In the term of the second government of Ariel Sharon (2003), the responsibility of work-related issues was transferred to the Industry, Trade and Labor ministry and in 2007 the name was changed to be Welfare and Social Services Ministry. In 2016 it was changed to the current name. List of ministers The Welfare and Social Services Minister of Israel (Hebrew: שר העבודה והרווחה, Sar HaAvoda HaRevaha) is the political head of the ministry and part of the Israeli cabinet. References External links |
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[SOURCE: https://en.wikipedia.org/wiki/Thirty-seventh_government_of_Israel#cite_note-40] | [TOKENS: 9915] |
Contents Thirty-seventh government of Israel The thirty-seventh government of Israel is the current cabinet of Israel, formed on 29 December 2022, following the Knesset election the previous month. The coalition government currently consists of five parties — Likud, Shas, Otzma Yehudit, Religious Zionist Party and New Hope — and is led by Benjamin Netanyahu, who took office as the prime minister of Israel for the sixth time. The government is widely regarded as the most right-wing government in the country's history, and includes far-right politicians. Several of the government's policy proposals have led to controversies, both within Israel and abroad, with the government's attempts at reforming the judiciary leading to a wave of demonstrations across the country. Following the outbreak of the Gaza war, opposition leader Yair Lapid initiated discussions with Netanyahu on the formation of an emergency government. On 11 October 2023, National Unity MKs Benny Gantz, Gadi Eisenkot, Gideon Sa'ar, Hili Tropper, and Yifat Shasha-Biton joined the Security Cabinet of Israel to form an emergency national unity government. Their accession to the Security Cabinet and to the government (as ministers without portfolio) was approved by the Knesset the following day. Gantz, Netanyahu, and Defense Minister Yoav Gallant became part of the newly formed Israeli war cabinet, with Eisenkot and Ron Dermer serving as observers. National Unity left the government in June 2024. New Hope rejoined the government in September. Otzma Yehudit announced on 19 January 2025 that it had withdrawn from the government, which took effect on 21 January, following the cabinet's acceptance of the three-phase Gaza war ceasefire proposal, though it rejoined two months later. United Torah Judaism left the government in July 2025 over dissatisfaction with the government's draft conscription law. Shas left the government several days later, though it remains part of the coalition. Background The right-wing bloc of parties, led by Benjamin Netanyahu, known in Israel as the national camp, won 64 of the 120 seats in the elections for the Knesset, while the coalition led by the incumbent prime minister Yair Lapid won 51 seats. The new majority has been variously described as the most right-wing government in Israeli history, as well as Israel's most religious government. Shortly after the elections, Lapid conceded to Netanyahu, and congratulated him, wishing him luck "for the sake of the Israeli people". On 15 November, the swearing-in ceremony for the newly elected members of the 25th Knesset was held during the opening session. The vote to appoint a new Speaker of the Knesset, which is usually conducted at the opening session, as well as the swearing in of cabinet members were postponed since ongoing coalition negotiations had not yet resulted in agreement on these positions. Government formation Yair Lapid Yesh Atid Benjamin Netanyahu Likud On 3 November 2022, Netanyahu told his aide Yariv Levin to begin informal coalition talks with allied parties, after 97% of the vote was counted. The leader of the Shas party Aryeh Deri met with Yitzhak Goldknopf, the leader of United Torah Judaism and its Agudat Yisrael faction, on 4 November. The two parties agreed to cooperate as members of the next government. The Degel HaTorah faction of United Torah Judaism stated on 5 November that it will maintain its ideological stance about not seeking any ministerial posts, as per the instruction of its spiritual leader Rabbi Gershon Edelstein, but will seek other senior posts like Knesset committee chairmen and deputy ministers. Netanyahu himself started holding talks on 6 November. He first met with Moshe Gafni, the leader of Degel HaTorah, and then with Goldknopf. Meanwhile, the Religious Zionist Party leader Bezalel Smotrich and the leader of its Otzma Yehudit faction Itamar Ben-Gvir pledged that they would not enter the coalition without the other faction. Gafni later met with Smotrich for coalition talks. Smotrich then met with Netanyahu. On 7 November, Netanyahu met with Ben-Gvir who demanded the Ministry of Public Security with expanded powers for himself and the Ministry of Education or Transport and Road Safety for Yitzhak Wasserlauf. A major demand among all of Netanyahu's allies was that the Knesset be allowed to ignore the rulings of the Supreme Court. Netanyahu met with the Noam faction leader and its sole MK Avi Maoz on 8 November after he threatened to boycott the coalition. He demanded complete control of the Western Wall by the Haredi rabbinate and removal of what he considered as anti-Zionist and anti-Jewish content in schoolbooks. President Isaac Herzog began consultations with heads of all the political parties on 9 November after the election results were certified. During the consultations, he expressed his reservations about Ben-Gvir becoming a member in the next government. Shas met with Likud for coalition talks on 10 November. By 11 November, Netanyahu had secured recommendations from 64 MKs, which constituted a majority. He was given the mandate to form the thirty-seventh government of Israel by President Herzog on 13 November. Otzma Yehudit and Noam officially split from Religious Zionism on 20 November as per a pre-election agreement. On 25 November, Otzma Yehudit and Likud signed a coalition agreement, under which Ben-Gvir will assume the newly created position of National Security Minister, whose powers would be more expansive than that of the Minister of Public Security, including overseeing the Israel Police and the Israel Border Police in the West Bank, as well as giving powers to authorities to shoot thieves stealing from military bases. Yitzhak Wasserlauf was given the Ministry for the Development of the Negev and the Galilee with expanded powers to regulate new West Bank settlements, while separating it from the "Periphery" portfolio, which will be given to Shas. The deal also includes giving the Ministry of Heritage to Amihai Eliyahu, separating it from the "Jerusalem Affairs" portfolio, the chairmanship of the Knesset's Public Security Committee to Zvika Fogel and that of the Special Committee for the Israeli Citizens' Fund to Limor Son Har-Melech, the post of Deputy Economic Minister to Almog Cohen, establishment of a national guard, and expansion of mobilization of reservists in the Border Police. Netanyahu and Maoz signed a coalition agreement on 27 November, under which the latter would become a deputy minister, would head an agency on Jewish identity in the Prime Minister's Office, and would also head Nativ, which processes the aliyah from the former Soviet Union. The agency for Jewish identity would have authority over educational content taught outside the regular curriculum in schools, in addition to the department of the Ministry of Education overseeing external teaching and partnerships, which would bring nonofficial organisations permitted to teach and lecture at schools under its purview. Likud signed a coalition agreement with the Religious Zionist Party on 1 December. Under the deal, Smotrich would serve as the Minister of Finance in rotation with Aryeh Deri, and the party will receive the post of a minister within the Ministry of Defense with control over the departments administering settlement and open lands under the Coordinator of Government Activities in the Territories, in addition to another post of a deputy minister. The deal also includes giving the post of Minister of Aliyah and Integration to Ofir Sofer, the newly created National Missions Ministry to Orit Strook, and the chairmanship of the Knesset's Constitution, Law and Justice Committee to Simcha Rothman. Likud and United Torah Judaism signed a coalition agreement on 6 December, to allow request for an extension to the deadline. Under it, the party would receive the Ministry of Construction and Housing, the chairmanship of the Knesset Finance Committee which will be given to Moshe Gafni, the Ministry of Jerusalem and Tradition (which would replace the Ministry of Jerusalem Affairs and Heritage), in addition to several posts of deputy ministers and chairmanships of Knesset committees. Likud also signed a deal with Shas by 8 December, securing interim coalition agreements with all of their allies. Under the deal, Deri will first serve as the Minister of Interior and Health, before rotating posts with Smotrich after two years. The party will also receive the Ministry of Religious Services and Welfare Ministries, as well as posts of deputy ministers in the Ministry of Education and Interior. The vote to replace then-incumbent Knesset speaker Mickey Levy was scheduled for 13 December, after Likud and its allies secured the necessary number of signatures for it. Yariv Levin of Likud was elected as an interim speaker by 64 votes, while his opponents Merav Ben-Ari of Yesh Atid and Ayman Odeh of Hadash received 45 and five votes respectively. Netanyahu asked Herzog for a 14-day extension after the agreement with Shas to finalise the roles his allied parties would play. Herzog on 9 December extended the deadline to 21 December. On that date, Netanyahu informed Herzog that he had succeeded in forming a coalition, with the new government expected to be sworn in by 2 January 2023. The government was sworn in on 29 December 2022. Timeline Israeli law stated that people convicted of crimes cannot serve in the government. An amendment to that law was made in late 2022, known colloquially as the Deri Law, to allow those who had been convicted without prison time to serve. This allowed Deri to be appointed to the cabinet. Shas leader Aryeh Deri was appointed to be Minister of Health, Minister of the Interior, and Vice Prime Minister in December 2022. He was fired in January 2023, following a Supreme Court decision that his appointment was unreasonable, since he had been convicted of fraud, and had promised not to seek government roles through a plea deal. In March 2023, Defence Minister Yoav Gallant called on the government to delay legislation related to the judicial reform. Prime Minister Netanyahu announced that he had been dismissed from his position, leading to the continuation of mass protests across the country (which had started in January in Tel Aviv). Gallant continued to serve as a minister as he had not received formal notice of dismissal, and two weeks later it was announced that Netanyahu had reversed his decision. Public Safety Minister Itamar Ben-Gvir (Otzma Yehudit leader) and Minister of Justice Yariv Levin (Likud) both threatened to resign if the judicial reform was delayed.[better source needed] After the outbreak of the Gaza war, five members of the National Unity party joined the government as ministers without portfolio, with leader Benny Gantz being made a member of the new Israeli war cabinet (along with Netanyahu and Gallant). As the war progressed, minister of national security Itamar Ben-Gvir threatened to leave the government if the war was ended. A month later in mid December, he again threatened to leave if the war did not maintain "full strength". Gideon Sa'ar stated on 16 March that his New Hope party would resign from the government and join the opposition if Prime Minister Benjamin Netanyahu did not appoint him to the Israeli war cabinet. Netanyahu did not do so, resulting in Sa'ar's New Hope party leaving the government nine days later, reducing the size of the coalition from 76 MKs to 72. Ben-Gvir and Bezalel Smotrich, of the National Religious Party–Religious Zionism party, have indicated that they will withdraw their parties from the government if the January 2025 Gaza war ceasefire is adopted, which would bring down the government. Ben-Gvir announced on 5 June that the members of his party would be allowed to vote as they wish, though his party resumed support on 9 June. On 18 May, Gantz set an 8 June deadline for withdrawal from the coalition, which was delayed by a day following the 2024 Nuseirat rescue operation. Gantz and his party left the government on 9 June, giving the government 64 seats in the Knesset. Sa'ar and his New Hope party rejoined the Netanyahu government on 30 September, increasing the number of seats held by the government to 68. The High Court of Justice ruled on 28 March 2024 that yeshiva funds would no longer be available for students who are "eligible for enlistment", effectively allowing ultra-Orthodox Jews to be drafted into the IDF. Attorney general Gali Baharav-Miara indicated on 31 March that the conscription process must begin on 1 April. The court ruled on 25 June that the IDF must begin to draft yeshiva students. Likud announced on 7 July that it would not put forward any legislation after Shas and United Torah Judaism said that they would boycott the plenary session over the lack of legislation dealing with the Haredi draft. The Ultra-Orthodox boycott continued for a second day, with UTJ briefly ending its boycott on 9 July to unsuccessfully vote in favor of a bill which would have weakened the Law of Return. Yuli Edelstein, who was replaced by Boaz Bismuth on the Foreign Affairs and Defense Committee in early August, published a draft version of the conscription law shortly before his ouster. Bismuth cancelled the work on the draft law in September 2025, which Edelstein called "a shame." Bismuth released the official version of the draft law in late November 2025. It weakened penalties for draft evaders, with Edelstein saying it was "the exact opposite" of the bill which he attempted to pass. Members of Otzma Yehudit resigned from the government on 19 January 2025 over the January 2025 Gaza war ceasefire, which took effect on 21 January. The members rejoined in March, following the "resumption" of the war in Gaza. Avi Maoz of the Noam party left the government in March 2025. On 4 June 2025, senior rabbis for United Torah Judaism Dov Lando and Moshe Hillel Hirsch instructed the party's MKs to pass a bill which would dissolve the Knesset. Yesh Atid, Yisrael Beytenu and The Democrats announced that they will "submit a bill" for dissolution on 11 June, with Yesh Atid tabling the bill on 4 June. There were also reports that Shas would vote in favor of Knesset dissolution amidst division within the governing coalition on Haredi conscription. This jeopardized the coalition's majority and would have triggered new elections if the bill passed. The following day, Agudat Yisrael, one of the United Torah Judaism factions, confirmed that it would submit a bill to dissolve the Knesset. Asher Medina, a Shas spokesman, indicated on 9 June that the party would vote in favor of a preliminary bill to dissolve the Knesset. The rabbis of Degel HaTorah instructed the parties' MKs on 12 June 2025 to oppose the dissolution of the Knesset, which was followed by Yuli Edelstein and the Shas and Degel HaTorah parties announcing that a deal had been reached, with "rabbinical leaders" telling their parties to delay the dissolution vote by a week. Shas and Degel HaTorah voted against the dissolution bill, which led to the bill failing its preliminary reading in a vote of 61 against and 53 in favor. MKs Ya'akov Tessler and Moshe Roth of Agudat Yisrael voted in favor of dissolution. Another dissolution bill will be unable to be brought forward for six months. If the bill had passed its preliminary reading, in addition to three more readings, an election would have been held in approximately three months; The Jerusalem Post posited it would have been held in October. Degel HaTorah announced on 14 July 2025 that it would leave the government because members of the party were dissatisfied after viewing the proposed draft bill by Yuli Edelstein regarding Haredi exemptions from the Israeli draft. Several hours later, Agudat Yisrael announced that it would also leave the government. Deputy Transportation Minister Uri Maklev, Moshe Gafni, the head of the Knesset Finance Committee, Ya'akov Asher, the head of the Knesset Interior and Environment Protection Committee and Jerusalem Affairs minister Meir Porush all submitted their resignations, with their resignations taking effect in 48 hours. Sports Minister Ya'akov Tessler and "Special Committee for Public Petitions Chair" Yitzhak Pindrus also submitted resignations. Yisrael Eichler submitted his resignation as the "head of the Knesset Labor and Welfare Committee" the same day. The resignations will leave Netanyahu's government with a 60-seat majority in the Knesset, as Avi Maoz, of the Noam party, left the government in March 2025. Despite Edelstein's ouster in August, a spokesman for UTJ head Yitzhak Goldknopf remarked that it would not change the faction's withdrawal from the government. The religious council for Shas, called the Moetzet Chachmei HaTorah, instructed the party on 16 July to leave the government, but stay in the coalition. The following day, various cabinet ministers submitted their resignations, including "Interior Minister Moshe Arbel, Social Affairs Minister Ya'akov Margi and Religious Services Minister Michael Malchieli." Malchieli reportedly has postponed his resignation so he could attend a 20 July meeting of the panel investigating whether attorney general Gali Baharav-Miara should be dismissed. Deputy Minister of Agriculture Moshe Abutbul, Minister of Health Uriel Buso and Haim Biton, a minister in the Education Ministry, also submitted their resignation letters, while Arbel retracted his resignation letter. The last cabinet member from the party to submit it was Labor Minister Yoav Ben-Tzur. The ministers who resigned will return to the Knesset, replacing MKs Moshe Roth, Yitzhak Pindrus and Eliyahu Baruchi. Members of government Listed below are the current ministers in the government: Principles and priorities According to the agreements signed between Likud and each of its coalition partners, and the incoming government's published guideline principles, its stated priorities are to combat the cost of living, further centralize Orthodox control over the state religious services, pass judicial reforms which include legislation to reduce judicial controls on executive and legislative power, expand settlements in the West Bank, and consider an annexation of the West Bank. Before the vote of confidence in his new government in the Knesset, Netanyahu presented three top priorities for the new government: internal security and governance, halting the nuclear program of Iran, and the development of infrastructure, with a focus on further connecting the center of the country with its periphery. Policies The government's flagship program, centered around reforms in the judicial branch, drew widespread criticism. Critics said it would have negative effects on the separation of powers, the office of the Attorney General, the economy, public health, women and minorities, workers' rights, scientific research, the overall strength of Israel's democracy and its foreign relations. After weeks of public protests on Israel's streets, joined by a growing number of military reservists, Minister of Defense Yoav Gallant spoke against the reform on 25 March, calling for a halt of the legislative process "for the sake of Israel's security". The next day, Netanyahu announced that he would be removed from his post, sparking another wave of protest across Israel and ultimately leading to Netanyahu agreeing to pause the legislation. On 10 April, Netanyahu announced that Gallant would keep his post. On 27 March 2023, after the public protests and general strikes, Netanyahu announced a pause in the reform process to allow for dialogue with opposition parties. However, negotiations aimed at reaching a compromise collapsed in June, and the government resumed its plans to unilaterally pass parts of the legislation. On 24 July 2023, the Knesset passed a bill that curbs the power of the Supreme Court to declare government decisions unreasonable; on 1 January 2024, the Supreme Court struck the bill down. The Knesset passed a "watered-down" version of the judicial reform package in late March 2025 which "changes the composition" of the judicial selection committee. In December 2022 Minister of National Security Itamar Ben-Gvir sought to amend the law that regulates the operations of the Israel Police, such that the ministry will have more direct control of its forces and policies, including its investigative priorities. Attorney General Gali Baharav-Miara objected to the draft proposal, raising concerns that the law would enable the politicization of police work, and the draft was amended to partially address those concerns. Nevertheless, in March 2023 Deputy Attorney General Gil Limon stated that the Attorney General's fears had been realized, referring to several instances of ministerial involvement in the day-to-day work of the otherwise independent police force – statements that were repeated by the Attorney General herself two days later. Separately, Police Commissioner Kobi Shabtai instructed Deputy Commissioners to avoid direct communication with the minister, later stating that "the Israel Police will remain apolitical, and act only according to law". Following appeals by the Association for Civil Rights in Israel and the Movement for Quality Government in Israel, the High Court of Justice instructed Ben-Gvir "to refrain from giving operational directions to the police... [especially] as regards to protests and demonstrations against the government." As talks of halting the judicial reform gained wind during March 2023, Minister of National Security Itamar Ben-Gvir threatened to resign if the legislation implementing the changes was suspended. To appease Ben-Gvir, Prime Minister Netanyahu announced that the government would promote the creation of a new National Guard, to be headed by Ben-Gvir. On 29 March, thousands of Israelis demonstrated in Tel Aviv, Haifa and Jerusalem against this decision. On 1 April, the New York Times quoted Gadeer Nicola, head of the Arab department at the Association for Civil Rights in Israel, as saying "If this thing passes, it will be an imminent danger to the rights of Arab citizens in this country. This will create two separate systems of applying the law. The regular police which will operate against Jewish citizens — and a militarized militia to deal only with Arab citizens." The same day, while speaking on Israel's Channel 13 about those whom he'd like to see enlist in the National Guard, Ben-Gvir specifically mentioned La Familia, the far-right fan club of the Beitar Jerusalem soccer team. On 2 April, Israel's cabinet approved the establishment of a law enforcement body that would operate independently of the police, under Ben-Gvir's authority. According to the decision, the Minister was to establish a committee chaired by the Director General of the Ministry of National Security, with representatives of the ministries of defense, justice and finance, as well as the police and the IDF, to outline the operations of the new organization. The committee's recommendations will be submitted to the government for consideration. Addressing a conference on 4 April, Police Commissioner Kobi Shabtai said that he is not opposed to the establishment of a security body which would answer to the police, but "a separate body? Absolutely not." The police chief said he had warned Ben-Gvir that the establishment of a security body separate from the police is "unnecessary, with extremely high costs that may harm citizens' personal security." During a press conference on 10 April, Prime Minister Netanyahu said, in what has been seen by some news outlets as a concession to the protesters, that "This will not be anyone's militia, it will be a security body, orderly, professional, that will be subordinate to one of the [existing] security bodies." The committee established by the government recommended the government to order the establishment of the National Guard immediately while allocating budgets. The National Guard, under whose command will be a superintendent of the police, will not be subordinate to Ben-Gvir. It will be subordinate to the police commissioner and will be part of Israel Border Police. The Ministry of Defense and Finance opposed the conclusions. The Israeli National Security Council called for further discussion on this. The coalition's efforts to expand the purview of Rabbinical courts; force some organizations, such as hospitals, to enforce certain religious practices; amend the Law Prohibiting Discrimination to allow gender segregation and discrimination on the grounds of religious belief; expand funding for religious causes; and put into law the exemption of yeshiva and kolel students from conscription have drawn criticism. According to the Haaretz op-ed of 7 March 2023, "the current coalition is interested... in modifying the public space so it suits the religious lifestyle. The legal coup is meant to castrate anyone who can prevent it, most of all the HCJ." Several banks and institutional investors, including the Israel Discount Bank and AIG have committed to avoid investing in, or providing credit to any organization that will discriminate against others on ground of religion, race, gender or sexual orientation. A series of technology companies and investment firms including Wiz, Intel Israel, Salesforce and Microsoft Israel Research and Development, have criticized the proposed changes to the Law Prohibiting Discrimination, with Wiz stating that it will require its suppliers to commit to preventing discrimination. Over sixty prominent law firms pledged that they will neither represent, nor do business with discriminating individuals and organizations. Insight Partners, a major private equity fund operating in Israel, released a statement warning against intolerance and any attempt to harm personal liberties. Orit Lahav, chief executive of the women's rights organization Mavoi Satum ("Dead End"), said that "the Rabbinical courts are the most discriminatory institution in the State of Israel... Limiting the HCJ[d] while expanding the jurisdiction of the Rabbinical courts would... cause significant harm to women." Anat Thon Ashkenazy, Director of the Center for Democratic Values and Institutions at the Israel Democracy Institute, said that "almost every part of the reform could harm women... the meaning of an override clause is that even if the court says that the law on gender segregation is illegitimate, is harmful, the Knesset could say 'Okay, we say otherwise'". She added that "there is a very broad institutional framework here, after which there will come legislation that harms women's right and we will have no way of protecting or stopping it." During July 2023, 20 professional medical associations signed a letter of position warning against the ramifications to public health that would result from the exclusion of women from the public sphere. They cited, among others, a rise in prevalence of risk factors for cardiovascular disease, pregnancy-related ailments, psychological distress, and the risk of suicide. On 30 July the Knesset passed an amendment to penal law adding sexual offenses to those offenses whose penalty can be doubled if done on grounds of "nationalistic terrorism, racism or hostility towards a certain community". According to MK Limor Son Har-Melech, the bill is meant to penalize any individual who "[intends to] harm a woman sexually based on her Jewishness". The law was criticized by MK Gilad Kariv as "populist, nationalistic, and dangerous towards the Arab citizens of Israel", and by MK Ahmad Tibi as a "race law", and was objected to by legal advisors at the Ministry of Justice and the Knesset Committee on National Security. Activist Orit Kamir wrote that "the amendment... is neither feminist, equal, nor progressive, but the opposite: it subordinates women's sexuality to the nationalistic, racist patriarchy. It hijacks the Law for Prevention of Sexual Harassment to serve a world view that tags women as sexual objects that personify the nation's honor." Yael Sherer, director of the Lobby to Combat Sexual Violence, criticized the law as being informed by dated ideas about sexual assault, and proposed that MKs "dedicate a session... to give victims of sexual assault an opportunity to come out of the darkness... instead of [submitting] declarative bills that change nothing and are not meant but for grabbing headlines". In Israel, during 2022, 24 women "were murdered because they were women," which was an increase of 50% compared to 2021. A law permitting courts to order men subject to a restraining order following domestic violence offenses to wear electronic tags was drafted during the previous Knesset and had passed its first reading unanimously. On 22 March 2023, the Knesset voted to reject the bill. It had been urged to do so by National Security Minister Itamar Ben-Gvir, who said that the bill was unfair to men. Earlier in the week, Ben-Gvir had blocked the measure from advancing in the ministerial legislative committee. The MKs voting against the bill included Prime Minister Netanyahu. The Association of Families of Murder Victims said that by rejecting the law, National Security Minister Itamar Ben-Gvir "brings joy to violent men and abandons the women threatened with murder… unsupervised restraining orders endanger women's lives even more. They give women the illusion of being protected, and then they are murdered." MK Pnina Tamano-Shata, chairwoman of the Knesset Committee on the Status of Women and Gender Equality, said that "the coalition proved today that it despises women's lives." The NGO Amutat Bat Melech [he], which assists Orthodox and ultra-Orthodox women who suffer from domestic violence, said that: "Rejecting the electronic bracelet bill is disconnected from the terrible reality of seven femicides since the beginning of the year. This is an effective tool of the first degree that could have saved lives and reduced the threat to women suffering from domestic violence. This is a matter of life and death, whose whole purpose is to provide a solution to defend women." The agreement signed by the coalition parties includes the setting up of a committee to draft changes to the Law of Return. Israeli religious parties have long demanded that the "grandchild clause" of the Law of Return be cancelled. This clause grants citizenship to anyone with at least one Jewish grandparent, as long as they do not practice another religion. If the grandchild clause were to be removed from the Law of Return then around 3 million people who are currently eligible for aliyah would no longer be eligible. The heads of the Jewish Agency, the Jewish Federations of North America, the World Zionist Organization and Keren Hayesod sent a joint letter to Prime Minister Netanyahu, expressing their "deep concern" about any changes to the Law of Return, adding that "Any change in the delicate and sensitive status quo on issues such as the Law of Return or conversion could threaten to unravel the ties between us and keep us away from each other." The Executive Council of Australian Jewry and the Zionist Federation of Australia issued a joint statement saying "We… view with deep concern… proposals in relation to religious pluralism and the law of return that risk damaging Israel's… relationship with Diaspora Jewry." On 19 March 2023, Israeli Finance Minister Bezalel Smotrich spoke in Paris at a memorial service for a Likud activist. The lectern at which Smotrich spoke was covered with a flag depicting the 'Greater Land of Israel,' encompassing the whole of Mandatory Palestine, as well as Trans-Jordan. During his speech, Smotrich said that "there's no such thing as Palestinians because there's no such thing as a Palestinian people." He added that the Palestinian people are a fictitious nation invented only to fight the Zionist movement, asking "Is there a Palestinian history or culture? There isn't any." The event received widespread media coverage. On 21 March, a spokesman for the US State Department sharply criticized Smotrich's comments. "The comments, which were delivered at a podium adorned with an inaccurate and provocative map, are offensive, they are deeply concerning, and, candidly, they're dangerous. The Palestinians have a rich history and culture, and the United States greatly values our partnership with the Palestinian people," he said. The Jordanian Foreign Ministry also voiced disapproval: "The Israeli Minister of Finance's use, during his participation in an event held yesterday in Paris, of a map of Israel that includes the borders of the Hashemite Kingdom of Jordan and the occupied Palestinian territories represents a reckless inflammatory act, and a violation of international norms and the Jordanian-Israeli peace treaty." Additionally, a map encompassing Mandatory Palestine and Trans-Jordan with a Jordanian flag on it was placed on a central lectern in the Jordanian Parliament. Jordan's parliament voted to expel the Israeli ambassador. Israel's Ministry of Foreign Affairs released a clarification relating to the matter, stating that "Israel is committed to the 1994 peace agreement with Jordan. There has been no change in the position of the State of Israel, which recognizes the territorial integrity of the Hashemite Kingdom of Jordan". Ahead of a Europe Day event due to take place on 9 May 2023, far-right wing National Security Minister Itamar Ben-Gvir was assigned as a representative of the government and a speaker at the event by the government secretariat, which deals with placing ministers at receptions on the occasion of the national days of the foreign embassies. The European Union requested that Ben-Gvir not attend, but the government did not make changes to the plan. On 8 May, the European delegation to Israel cancelled the reception, stating that: "The EU Delegation to Israel is looking forward to celebrating Europe Day on May 9, as it does every year. Regrettably, this year we have decided to cancel the diplomatic reception, as we do not want to offer a platform to someone whose views contradict the values the European Union stands for. However, the Europe Day cultural event for the Israeli public will be maintained to celebrate with our friends and partners in Israel the strong and constructive bilateral relationship". Israel's Opposition Leader Yair Lapid stated: "Sending Itamar Ben-Gvir to a gathering of EU ambassadors is a serious professional mistake. The government is embarrassing a large group of friendly countries, jeopardizing future votes in international institutions, and damaging our foreign relations. Last year, after a decade of efforts, we succeeded in signing an economic-political agreement with the European Union that will contribute to the Israeli economy and our foreign relations. Why risk it, and for what? Ben-Gvir is not a legitimate person in the international community (and not really in Israel either), and sometimes you have to be both wise and just and simply send someone else". On 23 February 2023, Defense Minister Gallant signed an agreement assigning governmental powers in the West Bank to a body to be headed by Minister Bezalel Smotrich, who will effectively become the governor of the West Bank, controlling almost all areas of life in the area, including planning, building and infrastructure. Israeli governments have hitherto been careful to keep the occupation as a military government. The temporary holding of power by an occupying military force, pending a negotiated settlement, is a principle of international law – an expression of the prohibition against obtaining sovereignty through conquest that was introduced in the wake of World War II. An editorial in Haaretz noted that the assignment of governmental powers in the West Bank to a civilian governor, alongside the plan to expand the dual justice system so that Israeli law will apply fully to settlers in the West Bank, constitutes de jure annexation of the West Bank. On 26 February 2023, following the 2023 Huwara shooting in which two Israelis were killed by an unidentified attacker, hundreds of Israeli settlers attacked the Palestinian town of Huwara and three nearby villages, setting alight hundreds of Palestinian homes (some with people in them), businesses, a school, and numerous vehicles, killing one Palestinian man and injuring 100 others. Bezalel Smotrich subsequently called on Twitter for Huwara to be "wiped out" by the Israeli government. Zvika Fogel MK, of the ultra-nationalist Otzma Yehudit, which forms part of the governing coalition, said that he "looks very favorably upon" the results of the rampage. Members of the coalition proposed an amendment to the Disengagement Law, which would allow Israelis to resettle settlements vacated during the 2005 Israeli disengagement from Gaza and the northern West Bank. The evacuated settlements were considered illegal under international law, according to most countries. The proposal was approved for voting by the Foreign Affairs and Defense Committee on 9 March 2023, while the committee was still waiting for briefing materials from the NSS, IDF, MFA and Shin Bet, and was passed on 21 March. The US has requested clarification from Israeli ambassador Michael Herzog. A US State Department spokesman stated that "The U.S. strongly urges Israel to refrain from allowing the return of settlers to the area covered by the legislation, consistent with both former Prime Minister Sharon and the current Israeli Government's commitment to the United States," noting that the actions represent a clear violation of undertakings given by the Sharon government to the Bush administration in 2005 and Netanyahu's far-right coalition to the Biden administration the previous week. Minister of Communication Shlomo Karhi had initially intended to cut the funding of the Israeli Public Broadcasting Corporation (also known by its blanket branding Kan) by 400 million shekels – roughly half of its total budget – closing several departments, and privatizing content creation. In response, the Director-General of the European Broadcasting Union, Noel Curran, sent two urgent letters to Netanyahu, expressing his concerns and calling on the Israeli government to "safeguard the independence of our Member KAN and ensure it is allowed to operate in a sustainable way, with funding that is both stable, adequate, fair, and transparent." On 25 January 2023, nine journalist organizations representing some of Kan's competitors issued a statement of concern, acknowledging the "important contribution of public broadcasting in creating a worthy, unbiased and non-prejudicial journalistic platform", and noting that "the existence of the [broadcasting] corporation as a substantial public broadcast organization strengthens media as a whole, adding to the competition in the market rather than weakening it." They also expressed their concern that the "real reason" for the proposal was actually "an attempt to silence voices from which... [the Minister] doesn't always draw satisfaction". The same day, hundreds of journalists, actors and filmmakers protested in Tel Aviv. The proposal was eventually put on hold. On 22 February 2023 it was reported that Prime Minister Netanyahu was attempting to appoint his close associate Yossi Shelley as the deputy to the National Statistician — a highly sensitive position in charge of providing accurate data for decision makers. The appointment of Shelley, who did not possess the required qualifications for the role, was withdrawn following publication. In its daily editorial, Haaretz tied this attempt with the judicial reform: "once they take control of the judiciary, law enforcement and public media, they wish to control the state's data base, the dry numerical data it uses to plan its future". Netanyahu also proposed Avi Simhon for the role, and eventually froze all appointments at the Israel Central Bureau of Statistics. Also on 22 February 2023, it was revealed that Yoav Kish, the Minister of Education, was promoting a draft government decision change to the National Library of Israel board of directors which would grant him more power over the institution. In response, the Hebrew University — which owned the library until 2008 – announced that if the draft is accepted, it will withdraw its collections from the library. The university's collections, which according to the university constitute some 80% of the library's collection, include the Agnon archive, the original manuscript of Hatikvah, and the Rothschild Haggadah, the oldest known Haggadah. A group of 300 authors and poets signed an open letter against the move, further noting their objection against "political takeover" of public broadcasting, as well as "any legislation that will castrate the judiciary and damage the democratic foundations of the state of Israel". Several days later, it was reported that a series of donors decided to withhold their donations to the library, totaling some 80 million shekels. On 3 March a petition against the move by 1,500 academics, including Israel Prize laureates, was sent to Kish. The proposal has been seen by some as retribution against Shai Nitzan, the former State Attorney and the library's current rector. On 5 March it was reported that the Legal Advisor to the Ministry of Finance, Asi Messing, was withholding the proposal. According to Messing, the proposal – which was being promoted as part of the Economic Arrangements Law – "was not reviewed... by the qualified personnel in the Ministry of Finance, does not align with any of the common goals of the economic plan, was not agreed to by myself and was not approved by the Attorney General." As of February 2023, the government has been debating several proposals that will significantly weaken the Ministry of Environmental Protection, including reducing the environmental regulation of planning and development and electricity production. One of the main proposals, the transferal of a 3 billion shekel fund meant to finance waste management plants from the Ministry of Environmental Protection to the Ministry of the Interior, was eventually withdrawn. The Minister of Environmental Protection, Idit Silman, has been criticized for using for meeting with climate change denialists, for wasteful and personally-motivated travel on the ministry's expense, for politicizing the role, and for engaging in political activity on the ministry's time. The government has been noted for an unusually high number of dismissals and resignations of senior career civil servants, and for the frequent attempts to replace them with candidates with known political associations, who are often less competent. According to sources, Netanyahu and people in his vicinity are seeking out civil servants who were appointed by the previous government, intent on replacing them with people loyal to him. Governmental nominees for various positions have been criticized for lack of expertise. In addition to the nominee to the position of Deputy National Statistician (see above), the Director General of the Ministry of Finance, Shlomi Heisler; the Director General of the Ministry of Justice, Itamar Donenfeld; and the Director General of Ministry of Transport, Moshe Ben Zaken, have all been criticized for incompetence, lack of familiarity with their Ministries' subject matter, lack of interest in the job, or lack of experience in managing large organizations. It has been reported that in some ministries, senior officials were enacting slowdowns as a means for dealing with the new ministers and director generals. On 28 July the director general of the Ministry of Education resigned, citing as reason the societal "rift". Asaf Zalel, a retired Air Force Brigadier General, was appointed in January. When asked about attempts to appoint his personal friend and attorney to the board of directors of a state-owned company, Minister David Amsalem replied: "that is my job, due to my authority to appoint directors. I put forward people that I know and hold in esteem". Under Minister of Transport Miri Regev, the ministry has either dismissed or lost the heads of the National Public Transport Authority, Israel Airports Authority, National Road Safety Authority, Israel Railways, and several officials in Netivei Israel. The current chair of Netivei Israel is Likud member and Regev associate Yigal Amadi, and the legal counsel is Einav Abuhzira, daughter of a former Likud branch chair. Abuhzira was appointed instead of Elad Berdugo, nephew of Netanyahu surrogate Yaakov Bardugo, after he was disqualified for the role by the Israel Government Companies Authority. In July 2023 the Ministry of Communications, Shlomo Karhi, and the minister in charge of the Israel Government Companies Authority, Dudi Amsalem, deposed the chair of the Israel Postal Company, Michael Vaknin. The chair, who was hired to lead the company's financial recovery after years of operational loss and towards privatization, has gained the support of officials at the Authority and at the Ministry of Finance; nevertheless, the ministers claimed that his performance is inadequate, and nominated in his place Yiftah Ron-Tal, who has known ties to Netanyahu and Smotrich. They also nominated four new directors, two of which have known political associations, and a third who was a witness in Netanyahu's trial. The coalition is allowed to spend a portion of the state's budget on a discretionary basis, meant to coax member parties to reach an agreement on the budget. As of May 2023, the government was pushing an allocation of over 13 billion shekels over two years - almost seven times the amount allocated by the previous government. Most of the funds will be allocated for uses associated with the religious, orthodox and settler communities. The head of the Budget Department at the Ministry of Finance, Yoav Gardos, objected to the allocations, claiming they would exacerbate unemployment in the Orthodox community, which is projected to cost the economy a total of 6.7 trillion shekels in lost produce by 2065. At the onset of the Gaza war and the declaration of a state of national emergency, Minister of Finance Bezalel Smotrich instructed government agencies to continue with the planned distribution of discretionary funds. Corruption During March 2023, the government was promoting an amendment to the Law on Public Service (Gifts) that would allow Netanyahu to receive donations to fund his legal defense. The amendment follows a decision by the High Court of Justice (HCJ) that forced Netanyahu to refund US$270,000 given to him and his wife by his late cousin, Nathan Mileikowsky, for their legal defense. This is in contrast to past statements by Minister of Justice Yariv Levin, who spoke against the possible conflict of interests that can result from such transactions. The bill was opposed by the Attorney General Gali Baharav-Miara, who stressed that it could "create a real opportunity for governmental corruption", and was eventually withdrawn at the end of March. As of March 2023, the coalition was promoting a bill that would prevent judicial review of ministerial appointments. The bill is intended to prevent the HCJ from reviewing the appointment of the twice-convicted chairman of Shas, Aryeh Deri (convicted of bribery, fraud, and breach of trust), to a ministerial position, after his previous appointment was annulled on grounds of unreasonableness. The bill follows on the heels of another amendment, that relaxed the ban on the appointment of convicted criminals, so that Deri - who was handed a suspended sentence after his second conviction - could be appointed. The bill is opposed by the Attorney General, as well as by the Knesset Legal Adviser, Sagit Afik. Israeli law allows for declaring a Prime Minister (as well as several other high-ranking public officials) to be temporarily or permanently incapacitated, but does not specify the conditions which can lead to a declaration of incapacitation. In the case of the Prime Minister, the authority to do so is given to the Attorney General. In March 2023, the coalition advanced a bill that passes this authority from the Attorney General to the government with the approval of the Knesset committee, and clarified that incapacitation can only result from medical or mental conditions. On 3 January 2024, the Supreme Court ruled by a majority of 6 out of 11 that the validity of the law will be postponed to the next Knesset because the bill in its immediate application is a personal law and is intended to serve a distinct personal purpose. Later, the court rejected a petition regarding the definition of Netanyahu as an incapacitated prime minister due to his ongoing trial and conflict of interests. Notes References External links |
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