1.
Collision
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A collision or crash is an event in which two or more bodies exert forces on each other for a relatively short time. Some examples of interactions that scientists would consider collisions, An insect touches its antenna to the leaf of a plant. The antenna is said to collide with leaf, a cat walks delicately through the grass. Each contact that its paws make with the ground is a collision, each brush of its fur against a blade of grass is a collision. When a boxer throws a punch, his fist is said to collide with the opponents face, the magnitude of the velocity difference just before impact is called the closing speed. What distinguishes different types of collisions is whether they also conserve kinetic energy, the Line of impact is the line which is collinear to the common normal of the surfaces that are closest or in contact during impact. This is the line along which internal force of collision acts during impact, specifically, collisions can either be elastic, meaning they conserve both momentum and kinetic energy, or inelastic, meaning they conserve momentum but not kinetic energy. An inelastic collision is sometimes called a plastic collision. A “perfectly inelastic” collision is a case of inelastic collision in which the two bodies stick together after impact. The degree to which a collision is elastic or inelastic is quantified by the coefficient of restitution, a perfectly elastic collision has a coefficient of restitution of one, a perfectly inelastic collision has a coefficient of restitution of zero. In reality, any macroscopic collision between objects will convert some kinetic energy to internal energy and other forms of energy, so no large-scale impacts are perfectly elastic, however, some problems are sufficiently close to perfectly elastic that they can be approximated as such. In this case, the coefficient of restitution equals one, an inelastic collision is one in which part of the kinetic energy is changed to some other form of energy in the collision. Momentum is conserved in collisions, but one cannot track the kinetic energy through the collision since some of it is converted to other forms of energy. In this case, coefficient of restitution does not equal one, collisions in ideal gases approach perfectly elastic collisions, as do scattering interactions of sub-atomic particles which are deflected by the electromagnetic force. Some large-scale interactions like the slingshot type gravitational interactions between satellites and planets are perfectly elastic, collisions between hard spheres may be nearly elastic, so it is useful to calculate the limiting case of an elastic collision. The assumption of conservation of momentum as well as the conservation of kinetic energy makes possible the calculation of the velocities in two-body collisions. In maritime law, it is desirable to distinguish between the situation of a vessel striking a moving object, and that of it striking a stationary object. The word allision is then used to mean the striking of a stationary object, relatively few problems involving collisions can be solved analytically, the remainder require numerical methods
2.
Astronomical object
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An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that current astronomy has demonstrated to exist in the observable universe. In astronomy, the object and body are often used interchangeably. Examples for astronomical objects include planetary systems, star clusters, nebulae and galaxies, while asteroids, moons, planets, and stars are astronomical bodies. A comet may be identified as both body and object, It is a body when referring to the nucleus of ice and dust. The universe can be viewed as having a hierarchical structure, at the largest scales, the fundamental component of assembly is the galaxy. Galaxies are organized groups and clusters, often within larger superclusters. Disc galaxies encompass lenticular and spiral galaxies with features, such as spiral arms, at the core, most galaxies have a supermassive black hole, which may result in an active galactic nucleus. Galaxies can also have satellites in the form of dwarf galaxies, the constituents of a galaxy are formed out of gaseous matter that assembles through gravitational self-attraction in a hierarchical manner. At this level, the fundamental components are the stars. The great variety of forms are determined almost entirely by the mass, composition. Stars may be found in systems that orbit about each other in a hierarchical organization. A planetary system and various objects such as asteroids, comets and debris. The various distinctive types of stars are shown by the Hertzsprung–Russell diagram —a plot of stellar luminosity versus surface temperature. Each star follows a track across this diagram. If this track takes the star through a region containing a variable type. An example of this is the instability strip, a region of the H-R diagram that includes Delta Scuti, RR Lyrae, the table below lists the general categories of bodies and objects by their location or structure. International Astronomical Naming Commission List of light sources List of Solar System objects Lists of astronomical objects SkyChart, Sky & Telescope Monthly skymaps for every location on Earth
3.
Planetary system
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A planetary system is a set of gravitationally bound non-stellar objects in orbit around a star or star system. The Sun together with its system, which includes Earth, is known as the Solar System. The term exoplanetary system is used in reference to other planetary systems. There are at least 2,701 known planetary systems, including 610 systems consisting of planets as of 1 April 2017. These systems contain more than 3,607 known exoplanets, debris disks are also known to be common, though other objects are more difficult to observe. Of particular interest to astrobiology is the zone of planetary systems where planets could have surface liquid water. Historically, heliocentrism was opposed to geocentrism, the notion of a heliocentric Solar System, with the Sun at the center, is possibly first suggested in the Vedic literature of ancient India, which often refer to the Sun as the centre of spheres. Some interpret Aryabhattas writings in Āryabhaṭīya as implicitly heliocentric, the idea was first proposed in western philosophy and Greek astronomy as early as the 3rd century BC by Aristarchus of Samos, but had received no support from most other ancient astronomers. De revolutionibus orbium coelestium by Nicolaus Copernicus, published in 1543, was the first mathematically predictive heliocentric model of a planetary system and he was burned at the stake for his ideas by the Roman Inquisition. In the 18th century the same possibility was mentioned by Isaac Newton in the General Scholium that concludes his Principia and his theories gained traction through the 19th and 20th centuries despite a lack of supporting evidence. The first confirmed detection of an exoplanet was in 1992, with the discovery of several planets orbiting the pulsar PSR B1257+12. The first confirmed detection of exoplanets of a star was made in 1995. The frequency of detections has increased since then, particularly through advancements in methods of detecting extrasolar planets, planetary systems come from protoplanetary disks that form around stars as part of the process of star formation. During formation of a system much material is gravitationally scattered into far-flung orbits, Planets orbiting pulsars have been discovered, and pulsars are the remnants of the supernova explosions of high-mass stars. Planets found around pulsars may have formed as a result of pre-existing stellar companions that were almost entirely evaporated by the supernova blast, alternatively, planets may form in an accretion disk of fallback matter surrounding a pulsar. Fallback disks of matter that failed to orbit during a supernova may also form planets around black holes. As the star mass, planets that are not engulfed move further out from the star. Planets in evolved binary systems, Hagai B, perets,13 Jan 2011 Can Planets survive Stellar Evolution
4.
Asteroid
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Asteroids are minor planets, especially those of the inner Solar System. The larger ones have also been called planetoids and these terms have historically been applied to any astronomical object orbiting the Sun that did not show the disc of a planet and was not observed to have the characteristics of an active comet. As minor planets in the outer Solar System were discovered and found to have volatile-based surfaces that resemble those of comets, in this article, the term asteroid refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There are millions of asteroids, many thought to be the remnants of planetesimals. The large majority of known asteroids orbit in the belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects, individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups, C-type, M-type, and S-type. These were named after and are identified with carbon-rich, metallic. The size of asteroids varies greatly, some reaching as much as 1000 km across, asteroids are differentiated from comets and meteoroids. In the case of comets, the difference is one of composition, while asteroids are composed of mineral and rock, comets are composed of dust. In addition, asteroids formed closer to the sun, preventing the development of the aforementioned cometary ice, the difference between asteroids and meteoroids is mainly one of size, meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials, only one asteroid,4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye, and this only in very dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be visible to the eye for a short time. As of March 2016, the Minor Planet Center had data on more than 1.3 million objects in the inner and outer Solar System, the United Nations declared June 30 as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, the first asteroid to be discovered, Ceres, was found in 1801 by Giuseppe Piazzi, and was originally considered to be a new planet. In the early half of the nineteenth century, the terms asteroid. Asteroid discovery methods have improved over the past two centuries. This task required that hand-drawn sky charts be prepared for all stars in the band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would, hopefully, the expected motion of the missing planet was about 30 seconds of arc per hour, readily discernible by observers
5.
Comet
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A comet is an icy small Solar System body that, when passing close to the Sun, warms and begins to evolve gasses, a process called outgassing. This produces an atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of collections of ice, dust. The coma may be up to 15 times the Earths diameter, if sufficiently bright, a comet may be seen from the Earth without the aid of a telescope and may subtend an arc of 30° across the sky. Comets have been observed and recorded since ancient times by many cultures, Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars, hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition, Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma and the tail, however, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System, the discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets. As of November 2014 there are 5,253 known comets, however, this represents only a tiny fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System is estimated to be one trillion. Roughly one comet per year is visible to the eye, though many of those are faint. Particularly bright examples are called Great Comets, the word comet derives from the Old English cometa from the Latin comēta or comētēs. That, in turn, is a latinisation of the Greek κομήτης, Κομήτης was derived from κομᾶν, which was itself derived from κόμη and was used to mean the tail of a comet. The astronomical symbol for comets is ☄, consisting of a disc with three hairlike extensions. The solid, core structure of a comet is known as the nucleus, cometary nuclei are composed of an amalgamation of rock, dust, water ice, and frozen gases such as carbon dioxide, carbon monoxide, methane, and ammonia. As such, they are described as dirty snowballs after Fred Whipples model
6.
Meteoroid
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A meteoroid is a small rocky or metallic body in outer space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to 1 meter-wide objects, objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars and this phenomenon is called a meteor or shooting star. A series of many meteors appearing seconds or minutes apart and appearing to originate from the fixed point in the sky is called a meteor shower. If that object withstands ablation from its passage through the atmosphere as a meteor and impacts with the ground, an estimated 15,000 tonnes of meteoroids, micrometeoroids and different forms of space dust enter Earths atmosphere each year. In 1995, Beech and Steel, writing in the Quarterly Journal of the Royal Astronomical Society, according to Rubin and Grossman, the minimum size of an asteroid is given by what can be discovered from Earth-bound telescopes, so the distinction between meteoroid and asteroid is fuzzy. Some of the smallest asteroids discovered are 2008 TS26 with H =33.2 and 2011 CQ1 with H =32.1 both with a size of 1 meter. Objects smaller than meteoroids are classified as micrometeoroids and cosmic dust, the Minor Planet Center does not use the term meteoroid. Almost all meteoroids contain extraterrestrial nickel and iron and they have three main classifications, iron, stone, and stony-iron. Some stone meteoroids contain grain-like inclusions known as chondrules and are called chondrites, stoney meteoroids without these features are called achondrites, which are typically formed from extraterrestrial igneous activity, they contain little or no extraterrestrial iron. The composition of meteoroids can be inferred as they pass through Earths atmosphere from their trajectories and their effects on radio signals also give information, especially useful for daytime meteors, which are otherwise very difficult to observe. From these trajectory measurements, meteoroids have been found to have many different orbits, some clustering in streams associated with a parent comet. Debris from meteoroid streams may eventually be scattered into other orbits, the study of meteorites also gives insights into the composition of non-ephemeral meteoroids. Most meteoroids come from the belt, having been perturbed by the gravitational influences of planets. Some meteoroids are pieces of planets or moons, such as Mars or our moon, meteoroids travel around the Sun in a variety of orbits and at various velocities. The fastest ones move at about 42 kilometers per second through space in the vicinity of Earths orbit, Earth travels at about 29.6 kilometers per second. Thus, when meteoroids meet Earths atmosphere head-on, the speed may reach about 71 kilometers per second. Meteoroids moving through Earths orbital space average about 20 km/s, on January 17,2013 at 05,21 PST, a 1 meter-sized comet from the Oort cloud entered Earth atmosphere over a wide area in California and Nevada
7.
Terrestrial planet
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A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the planets are the inner planets closest to the Sun, i. e. Mercury, Venus, Earth. The terms terrestrial planet and telluric planet are derived from Latin words for Earth, as these planets are, in terms of composition, Earth-like. All terrestrial planets may have the basic type of structure, such as a central metallic core, mostly iron. The Moon is similar, but has a smaller iron core. Io and Europa are also satellites that have internal structures similar to that of terrestrial planets, terrestrial planets can have canyons, craters, mountains, volcanoes, and other surface structures, depending on the presence of water and tectonic activity. The Solar System has four planets, Mercury, Venus, Earth. Only one terrestrial planet, Earth, is known to have an active hydrosphere, during the formation of the Solar System, there were probably many more terrestrial planetesimals, but most merged with or were ejected by the four terrestrial planets. The Earths Moon has a density of 3.4 g·cm−3 and Jupiters satellites, Io,3.528 and Europa,3.013 g·cm−3, the uncompressed density of a terrestrial planet is the average density its materials would have at zero pressure. A greater uncompressed density indicates greater metal content, uncompressed density differs from the true average density because compression within planet cores increases their density, the average density depends on planet size as well as composition. The uncompressed density of terrestrial planets trends towards lower values as the distance from the Sun increases, the rocky minor planet Vesta orbiting outside of Mars is less dense than Mars still, at 3.4 g·cm−3. It is unknown whether extrasolar terrestrial planets in general will also follow this trend, most of the planets discovered outside the Solar System are giant planets, because they are more easily detectable. But since 2005, hundreds of terrestrial extrasolar planets have been found. Most of these are super-Earths, i. e. planets with masses between Earths and Neptunes, super-Earths may be gas planets or terrestrial, depending on their mass and other parameters. During the early 1990s, the first extrasolar planets were discovered orbiting the pulsar PSR B1257+12, with masses of 0.02,4.3 and it was later found to be a gas giant. In 2005, the first planets around stars that may be terrestrial were found, Gliese 876 d, has a mass 7 to 9 times that of Earth. It orbits the red dwarf Gliese 876,15 light years from Earth, oGLE-2005-BLG-390Lb, about 5.5 times the mass of Earth, orbits a star about 21,000 light years away in the constellation Scorpius. From 2007 to 2010, three potential terrestrial planets were orbiting the red dwarf Gliese 581
8.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
9.
Atmospheric entry
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Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet or natural satellite. Technologies and procedures allowing the atmospheric entry, descent and landing of spacecraft are collectively abbreviated as EDL. Atmospheric drag and aerodynamic heating can cause atmospheric breakup capable of completely disintegrating smaller objects and these forces may cause objects with lower compressive strength to explode. Manned space vehicles must be slowed to subsonic speeds before parachutes or air brakes may be deployed, such vehicles have kinetic energies typically between 50 and 1800 MJoules, and atmospheric dissipation is the only way of expending the kinetic energy. While the high temperature generated at the surface of the shield is due to adiabatic compression. Other smaller energy losses include black body radiation directly from the hot gasses, ballistic warheads and expendable vehicles do not require slowing at re-entry, and in fact, are made streamlined so as to maintain their speed. Uncontrolled, objects accelerate through the atmosphere at extreme velocities under the influence of Earths gravity, most controlled objects enter at hypersonic speeds due to their suborbital, orbital, or unbounded trajectories. Various advanced technologies have developed to enable atmospheric reentry and flight at extreme velocities. Practical development of systems began as the range and reentry velocity of ballistic missiles increased. For early short-range missiles, like the V-2, stabilization and aerodynamic stress were important issues, medium-range missiles like the Soviet R-5, with a 1200 km range, required ceramic composite heat shielding on separable reentry vehicles. The first ICBMs, with ranges of 8000 to 12,000 km, were possible with the development of modern ablative heat shields. In the U. S. this technology was pioneered by H. Julian Allen at Ames Research Center, over the decades since the 1950s, a rich technical jargon has grown around the engineering of vehicles designed to enter planetary atmospheres. It is recommended that the review the jargon glossary before continuing with this article on atmospheric reentry. When atmospheric entry is part of a landing or recovery, particularly on a planetary body other than Earth, entry is part of a phase referred to as entry, descent and landing. When the atmospheric entry returns to the body that the vehicle had launched from. These four shadowgraph images represent early reentry-vehicle concepts, if the reentry vehicle is made blunt, air cannot get out of the way quickly enough, and acts as an air cushion to push the shock wave and heated shock layer forward. Since most of the hot gases are no longer in contact with the vehicle. The Allen and Eggers discovery, though initially treated as a secret, was eventually published in 1958
10.
Impact crater
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An impact crater is an approximately circular depression in the surface of a planet, moon, or other solid body in the Solar System or elsewhere, formed by the hypervelocity impact of a smaller body. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims, Impact craters are the dominant geographic features on many solid Solar System objects including the Moon, Mercury, Callisto, Ganymede and most small moons and asteroids. Where such processes have destroyed most of the original crater topography and this indicates that there should be far more relatively young craters on the planet than have been discovered so far. Note that the rate of impact cratering in the outer Solar System could be different from the inner Solar System, although Earths active surface processes quickly destroy the impact record, about 190 terrestrial impact craters have been identified. They are also found in the stable interior regions of continents. Impact craters are not to be confused with landforms that may appear similar, including calderas, sinkholes, glacial cirques, ring dikes, salt domes, and others. Daniel Barringer was one of the first to identify an impact crater, Meteor Crater in Arizona, in the 1920s, the American geologist Walter H. Bucher studied a number of sites now recognized as impact craters in the United States. He concluded they had created by some great explosive event. However, in 1936, the geologists John D, albritton Jr. revisited Buchers studies and concluded that the craters that he studied were probably formed by impacts. The concept of impact cratering remained more or less speculative until the 1960s, armed with the knowledge of shock-metamorphic features, Carlyle S. By 1970, they had identified more than 50. Although their work was controversial, the American Apollo Moon landings, because the processes of erosion on the Moon are minimal, craters persist almost indefinitely. Since the Earth could be expected to have roughly the same cratering rate as the Moon, Impact cratering involves high velocity collisions between solid objects, typically much greater than the velocity of sound in those objects. Such hyper-velocity impacts produce physical effects such as melting and vaporization that do not occur in familiar sub-sonic collisions. On Earth, ignoring the effects of travel through the atmosphere. The fastest impacts occur at about 72 km/s in the worst case scenario in which an object in a retrograde near-parabolic orbit hits Earth, the median impact velocity on Earth is about 20 km/s. The larger the meteoroid the more of its initial cosmic velocity it preserves, while an object of 9,000 kg maintains about 6% of its original velocity, one of 900,000 kg already preserves about 70%. Extremely large bodies are not slowed by the atmosphere at all, impacts at these high speeds produce shock waves in solid materials, and both impactor and the material impacted are rapidly compressed to high density
11.
Impact structure
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Impact structure is synonymous with the less commonly used term astrobleme meaning star wound. In an impact structure, the visible and topographic expressions of an impact crater are no longer obvious. Any meteorite fragments that may once have been present would be long since eroded away, possible impact structures may be initially recognized by their anomalous geological character or geophysical expression. These may still be confirmed as impact structures by the presence of shocked minerals, shatter cones, geochemical evidence of extraterrestrial material or other methods
12.
Solar System
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The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being significantly smaller objects, such as dwarf planets, of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury. The Solar System formed 4.6 billion years ago from the collapse of a giant interstellar molecular cloud. The vast majority of the mass is in the Sun. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being composed of rock. The four outer planets are giant planets, being more massive than the terrestrials. All planets have almost circular orbits that lie within a flat disc called the ecliptic. The Solar System also contains smaller objects, the asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptunes orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity. Such objects are categorized as dwarf planets, identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds. Six of the planets, at least four of the dwarf planets, each of the outer planets is encircled by planetary rings of dust and other small objects. The solar wind, a stream of charged particles flowing outwards from the Sun, the heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium, it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, the Solar System is located in the Orion Arm,26,000 light-years from the center of the Milky Way. For most of history, humanity did not recognize or understand the concept of the Solar System, the invention of the telescope led to the discovery of further planets and moons. The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99. 86% of the known mass. The Suns four largest orbiting bodies, the giant planets, account for 99% of the mass, with Jupiter. The remaining objects of the Solar System together comprise less than 0. 002% of the Solar Systems total mass, most large objects in orbit around the Sun lie near the plane of Earths orbit, known as the ecliptic
13.
Formation and evolution of the Solar System
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The formation of the Solar System began 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. This model, known as the hypothesis, was first developed in the 18th century by Emanuel Swedenborg, Immanuel Kant. Its subsequent development has interwoven a variety of disciplines including astronomy, physics, geology. Since the dawn of the age in the 1950s and the discovery of extrasolar planets in the 1990s. The Solar System has evolved considerably since its initial formation, many moons have formed from circling discs of gas and dust around their parent planets, while other moons are thought to have formed independently and later been captured by their planets. Still others, such as Earths Moon, may be the result of giant collisions, collisions between bodies have occurred continually up to the present day and have been central to the evolution of the Solar System. The positions of the planets often shifted due to gravitational interactions and this planetary migration is now thought to have been responsible for much of the Solar Systems early evolution. In the far distant future, the gravity of passing stars will gradually reduce the Suns retinue of planets, some planets will be destroyed, others ejected into interstellar space. Ultimately, over the course of tens of billions of years, the first step toward a theory of Solar System formation and evolution was the general acceptance of heliocentrism, which placed the Sun at the centre of the system and the Earth in orbit around it. This concept had developed for millennia, but was not widely accepted until the end of the 17th century, the first recorded use of the term Solar System dates from 1704. The most significant criticism of the hypothesis was its apparent inability to explain the Suns relative lack of momentum when compared to the planets. However, since the early 1980s studies of stars have shown them to be surrounded by cool discs of dust and gas, exactly as the nebular hypothesis predicts. Understanding of how the Sun is expected to continue to evolve required an understanding of the source of its power, in 1935, Eddington went further and suggested that other elements also might form within stars. Fred Hoyle elaborated on this premise by arguing that evolved stars called red giants created many elements heavier than hydrogen, when a red giant finally casts off its outer layers, these elements would then be recycled to form other star systems. The nebular hypothesis says that the Solar System formed from the collapse of a fragment of a giant molecular cloud. The cloud was about 20 parsec across, while the fragments were roughly 1 parsec across, the further collapse of the fragments led to the formation of dense cores 0. 01–0.1 pc in size. One of these fragments formed what became the Solar System. The remaining 2% of the mass consisted of elements that were created by nucleosynthesis in earlier generations of stars
14.
History of Earth
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The history of Earth concerns the development of the planet Earth from its formation to the present day. Nearly all branches of science have contributed to the understanding of the main events of the Earths past. The age of Earth is approximately one-third of the age of the universe, an immense amount of geological change has occurred in that timespan, accompanied by the emergence of life and its subsequent evolution. Earth formed around 4.54 billion years ago by accretion from the solar nebula, volcanic outgassing probably created the primordial atmosphere and then the ocean, but the atmosphere contained almost no oxygen and so would have been toxic to most modern life including humans. Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism. A giant impact collision with a body named Theia while Earth was in its earliest stage. Over time, the Earth cooled, causing the formation of a solid crust, the geological time scale clock depicts the larger spans of time from the beginning of the Earth as well as a chronology of some definitive events of Earth history. The Archean and Proterozoic eons follow, they produced the abiogenesis of life on Earth, there are microbial mat fossils such as stromatolites found in 3.48 billion-year-old sandstone discovered in Western Australia. According to one of the researchers, If life arose relatively quickly on Earth … then it could be common in the universe, living forms derived from photosynthesis appeared between 3.2 and 2.4 billion years ago and began enriching the atmosphere with oxygen. More than 99 percent of all species, amounting to five billion species. Estimates on the number of Earths current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described. Geological change has been a constant of Earths crust since the time of its formation, species continue to evolve, taking on new forms, splitting into daughter species or going extinct in the process of adapting or dying in response to ever-changing physical environments. The process of plate tectonics continues to play a dominant role in the shaping of Earths oceans and continents, in geochronology, time is generally measured in mya, each unit representing the period of approximately 1,000,000 years in the past. The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet, each eon saw the most significant changes in Earths composition, climate and life. Each eon is divided into eras, which in turn are divided into periods. The history of the Earth can be organized according to the geologic time scale. The following four timelines show the time scale
15.
Giant impact theory
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The colliding body is sometimes called Theia, from the name of the mythical Greek Titan who was the mother of Selene, the goddess of the Moon. Analysis of lunar rocks, published in 2016, suggests that the impact may have been a direct hit, the giant-impact hypothesis is currently the favoured scientific hypothesis for the formation of the Moon. Supporting evidence includes, Earths spin and the Moons orbit have similar orientations, Moon samples indicate that the Moons surface was once molten. The Moon has a small iron core. The Moon has a lower density than Earth, evidence exists of similar collisions in other star systems. Giant collisions are consistent with the theories of the formation of the solar system. The stable-isotope ratios of lunar and terrestrial rock are identical, implying a common origin, there remain several questions concerning the best current models of the giant-impact hypothesis, however. However, as of 2015 there is no self-consistent model that starts with the giant-impact event, other remaining questions include when the Moon lost its share of volatile elements and why Venus—which experienced giant impacts during its formation—does not host a similar moon. In 1898, George Darwin made the suggestion that the Earth, Darwins hypothesis was that a molten Moon had been spun from the Earth because of centrifugal forces, and this became the dominant academic explanation. Using Newtonian mechanics, he calculated that the Moon had orbited much more closely in the past and was drifting away from the Earth and this drifting was later confirmed by American and Soviet experiments, using laser ranging targets placed on the Moon. Nonetheless, Darwins calculations could not resolve the mechanics required to trace the Moon backward to the surface of the Earth. In 1946, Reginald Aldworth Daly of Harvard University challenged Darwins explanation and their models suggested that, at the end of the planet formation period, several satellite-sized bodies had formed that could collide with the planets or be captured. They proposed that one of objects may have collided with the Earth, ejecting refractory. This collision could potentially explain the unique geological and geochemical properties of the Moon and it is hypothesized that most of the outer silicates of the colliding body would be vaporized, whereas a metallic core would not. Hence, most of the material sent into orbit would consist of silicates. The more volatile materials that were emitted during the collision probably would escape the Solar System, the name of the hypothesized protoplanet is derived from the mythical Greek titan Theia /ˈθiːə/, who gave birth to the Moon goddess Selene. This designation was proposed initially by the English geochemist Alex N. Halliday in 2000 and has accepted in the scientific community. According to modern theories of formation, Theia was part of a population of Mars-sized bodies that existed in the Solar System 4.5 billion years ago
16.
Evolutionary history of life
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The evolutionary history of life on Earth traces the processes by which living and fossil organisms have evolved since life appeared on the planet, until the present day. Earth formed about 4.5 Ga ago and there is evidence that appeared as early as 4.1 Ga. The similarities between all present-day organisms indicate the presence of an ancestor from which all known species have diverged through the process of evolution. More than 99 percent of all species, amounting to five billion species. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described, more recently, in 2015, remains of biotic life were found in 4.1 billion-year-old rocks in Western Australia. In March 2017, researchers reported evidence of possibly the oldest forms of life on Earth, according to biologist Stephen Blair Hedges, If life arose relatively quickly on Earth. Then it could be common in the universe, microbial mats of coexisting bacteria and archaea were the dominant form of life in the early Archean and many of the major steps in early evolution are thought to have taken place within them. The evolution of photosynthesis, around 3.5 Ga, eventually led to a buildup of its product, oxygen, in the atmosphere, leading to the great oxygenation event. The earliest evidence of dates from 1.85 Ga. Later, around 1.7 Ga, multicellular organisms began to appear, however the origin and evolution of sexual reproduction remain a puzzle for biologists though it did evolve from a common ancestor that was a single celled eukaryotic species. Bilateria, animals with a front and a back, appeared by 555 Ma, the earliest land plants date back to around 450 Ma, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2.9 Ga. Microorganisms are thought to have paved the way for the inception of land plants in the Phanerozoic, land plants were so successful that they are thought to have contributed to the Late Devonian extinction event. Ediacara biota appear during the Ediacaran period, while vertebrates, along with most other modern phyla originated about 525 Ma during the Cambrian explosion. During the Permian period, synapsids, including the ancestors of mammals, dominated the land, during the recovery from this catastrophe, archosaurs became the most abundant land vertebrates, one archosaur group, the dinosaurs, dominated the Jurassic and Cretaceous periods. After the Cretaceous–Paleogene extinction event 66 Ma killed off the dinosaurs, mammals increased rapidly in size. Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify, the Moon has the same composition as Earths crust but does not contain an iron-rich core like the Earths. Many scientists think that about 40 million years later a body the size of Mars struck the Earth, until 2001, the oldest rocks found on Earth were about 3.8 billion years old, leading scientists to estimate that the Earths surface had been molten until then. Accordingly, they named this part of Earths history the Hadean, however, analysis of zircons formed 4
17.
Origin of water on Earth
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The origin of water on Earth, or the reason that there is clearly more liquid water on Earth than on the other rocky planets of the Solar System, is not completely understood. There exist numerous more or less mutually compatible hypotheses as to how water may have accumulated on Earths surface over the past 4.5 billion years in sufficient quantity to form oceans. Comets, trans-Neptunian objects or water-rich meteoroids from the reaches of the asteroid belt colliding with Earth may have brought water to the worlds oceans. Large enough Planetesimals were heated by the decay of aluminium isotope and this could cause water to rise to the surface. What is however unclear is whether these comets are representative of those from the Kuiper Belt, the water in carbon-rich chondrites point to a similar D/H ratio as oceanic water. Nevertheless, mechanisms have been proposed to suggest that the D/H-ratio of oceanic water may have increased significantly throughout Earths history, such a proposal is consistent with the possibility that a significant amount of the water on Earth was already present during the planets early evolution. Recent measurements of the composition of Moon rocks suggest that Earth was born with its water already present. Investigating lunar samples carried to Earth by the Apollo 15 and 17 missions found a ratio that matched the isotopic ratio in carbonaceous chondrites. The ratio is similar to that found in water on Earth. The findings suggest a common source of water for both objects and this supports a theory that Jupiter temporarily migrated into the inner Solar System, destabilizing the orbits of water-rich carbonaceous chondrites. As a result, some of the bodies could have fallen inwards and become part of the raw material for making Earth, the discovery of water vapor out-gassing from Ceres provides related information on water-ice content of the asteroid belt. Gradual leakage of stored in hydrate minerals of Earths rocks could have formed a portion of its water. Water may also have come from volcanism, water vapor in the atmosphere that originated in volcanic eruptions may have condensed to form rain, a sizeable quantity of water would have been in the material that formed Earth. Water molecules would have escaped Earths gravity more easily when it was less massive during its formation, part of the young planet is theorized to have been disrupted by the impact which created the Moon, which should have caused melting of one or two large areas. Present composition does not match complete melting and it is hard to melt, however, a fair fraction of material should have been vaporized by this impact, creating a rock-vapor atmosphere around the young planet. The rock-vapor would have condensed within two years, leaving behind hot volatiles which probably resulted in a heavy carbon dioxide atmosphere with hydrogen. Liquid water oceans existed despite the temperature of 230°C because of the atmospheric pressure of the heavy CO2 atmosphere. As cooling continued, subduction and dissolving in ocean water removed most CO2 from the atmosphere but levels oscillated wildly as new surface and mantle cycles appeared
18.
Extinction event
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An extinction event is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a change in the diversity. It occurs when the rate of extinction increases with respect to the rate of speciation, Extinction occurs at an uneven rate. Based on the record, the background rate of extinctions on Earth is about two to five taxonomic families of marine animals every million years. Marine fossils are used to measure extinction rates because of their superior fossil record. The Great Oxygenation Event was probably the first major extinction event, since the Cambrian explosion five further major mass extinctions have significantly exceeded the background extinction rate. In addition to the five mass extinctions, there are numerous minor ones as well. Mass extinctions seem to be a mainly Phanerozoic phenomenon, with extinction rates low before large complex organisms arose, estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from the chosen for describing an extinction event as major. In a landmark paper published in 1982, Jack Sepkoski and David M. Raup identified five mass extinctions, the Big Five cannot be so clearly defined, but rather appear to represent the largest of a relatively smooth continuum of extinction events. Cretaceous–Paleogene extinction event,66 Ma at the Cretaceous -Paleogene transition interval, the event formerly called the Cretaceous-Tertiary or K–T extinction or K-T boundary is now officially named the Cretaceous–Paleogene extinction event. About 17% of all families, 50% of all genera and 75% of all species became extinct, in the seas all the ammonites, plesiosaurs and mosasaurs disappeared and the percentage of sessile animals was reduced to about 33%. All non-avian dinosaurs became extinct during that time, the boundary event was severe with a significant amount of variability in the rate of extinction between and among different clades. Mammals and birds, the latter descended from dinosaurs, emerged as dominant large land animals. Triassic–Jurassic extinction event,201.3 Ma at the Triassic-Jurassic transition, about 23% of all families, 48% of all genera and 70% to 75% of all species became extinct. Most non-dinosaurian archosaurs, most therapsids, and most of the amphibians were eliminated. Non-dinosaurian archosaurs continued to dominate aquatic environments, while non-archosaurian diapsids continued to dominate marine environments, the Temnospondyl lineage of large amphibians also survived until the Cretaceous in Australia. Permian–Triassic extinction event,252 Ma at the Permian-Triassic transition, Earths largest extinction killed 57% of all families, 83% of all genera and 90% to 96% of all species
19.
Chicxulub crater
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The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is located near the town of Chicxulub, after which the crater is named and it was formed by a large asteroid or comet about 10 kilometres in diameter, the Chicxulub impactor, striking the Earth. The crater is more than 180 kilometers in diameter and 20 km in depth and it makes the feature the third of the largest confirmed impact structures on Earth. The crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatán during the late 1970s, Penfield was initially unable to obtain evidence that the geological feature was a crater and gave up his search. Later, through contact with Alan Hildebrand in 1990, Penfield obtained samples that suggested it was an impact feature, evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas. Penfields job was to use data to scout possible locations for oil drilling. In the data, Penfield found a huge underwater arc with extraordinary symmetry in a ring 70 km across and he then obtained a gravity map of the Yucatán made in the 1960s. A decade earlier, the same map suggested a feature to contractor Robert Baltosser. Penfield found another arc on the peninsula itself, the ends of which pointed northward, Pemex disallowed release of specific data but let Penfield and company official Antonio Camargo present their results at the 1981 Society of Exploration Geophysicists conference. That years conference was underattended and their report attracted scant attention, coincidentally, many experts in impact craters and the K–Pg boundary were attending a separate conference on Earth impacts. Although Penfield had plenty of data sets, he had no rock cores or other physical evidence of an impact. He knew Pemex had drilled exploratory wells in the region, in 1951, one bored into what was described as a thick layer of andesite about 1.3 kilometres down. This layer could have resulted from the heat and pressure of an Earth impact. Penfield tried to secure site samples, but was told such samples had been lost or destroyed, when attempts at returning to the drill sites and looking for rocks proved fruitless, Penfield abandoned his search, published his findings and returned to his Pemex work. At the same time, in 1980, geologist Walter Alvarez and his father, Nobel Prize-winning scientist Luis Walter Alvarez and their evidence included greenish-brown clay with surplus iridium containing shocked quartz grains and small weathered glass beads that looked to be tektites. Thick, jumbled deposits of rock fragments were also present, thought to have been scoured from one place. Such deposits occur in locations but seem concentrated in the Caribbean basin at the K–Pg boundary. So when Haitian professor Florentine Morás discovered what he thought to be evidence of an ancient volcano on Haiti, tests on samples retrieved from the K–Pg boundary revealed more tektite glass, formed only in the heat of asteroid impacts and high-yield nuclear detonations
20.
Bolide
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A bolide is an extremely bright meteor, especially one that explodes in the atmosphere. In astronomy, it refers to a fireball about as bright as the full moon, in geology, a bolide is a very large impactor. One definition describes a bolide as a fireball reaching an apparent magnitude of −14 or brighter – more than twice as bright as the full moon, another definition describes a bolide as any generic large crater-forming impacting body whose composition is unknown. A superbolide is a bolide which reaches an apparent magnitude of −17 or brighter, recent examples of superbolides include the Sutters Mill meteorite and the Chelyabinsk meteor. The IAU has no definition of bolide, and generally considers the term synonymous with fireball. However, the term applies to fireballs reaching an apparent magnitude −14 or brighter. Astronomers tend to use bolide to identify a bright fireball. It may also be used to mean a fireball that is audible, selected superbolide air-bursts events, Tunguska event 2009 Sulawesi superbolide Chelyabinsk meteor Geologists use the term bolide in a somewhat different context than astronomers do. In geology, it indicates a large impactor. jpl. nasa. gov
21.
Tunguska event
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The Tunguska event was a large explosion that occurred near the Stony Tunguska River, in Yeniseysk Governorate, Russia, on the morning of 30 June 1908. The explosion over the sparsely populated Eastern Siberian Taiga flattened 2,000 km2 of forest yet caused no known human casualties, the explosion is generally attributed to the air burst of a meteoroid. The Tunguska event is the largest impact event on Earth in recorded history, studies have yielded different estimates of the meteoroids size, on the order of 60 to 190 metres, depending on whether the body was a comet or a denser asteroid. Since the 1908 event, there have been an estimated 1,000 scholarly papers published on the Tunguska explosion. In 2013, a team of researchers published results of micro-samples from a peat bog near the center of the affected area showing fragments that may be of meteoritic origin. An explosion of this magnitude would be capable of destroying a large metropolitan area and this event has helped to spark discussion of asteroid impact avoidance. About ten minutes later, there was a flash and a similar to artillery fire. Eyewitnesses closer to the explosion reported that the source of the sound moved from the east to the north of them, the sounds were accompanied by a shock wave that knocked people off their feet and broke windows hundreds of kilometres away. The majority of witnesses reported only the sounds and tremors, eyewitness accounts vary regarding the sequence and duration of the events. The explosion registered at seismic stations across Eurasia and it is estimated that, in some places, the resulting shock wave was equivalent to an earthquake measuring 5.0 on the Richter magnitude scale. It also produced fluctuations in atmospheric pressure strong enough to be detected in Great Britain, testimony of S. Semenov, as recorded by Leonid Kuliks expedition in 1930, At breakfast time I was sitting by the house at Vanavara Trading Post, facing north. I suddenly saw that directly to the north, over Onkouls Tunguska Road, the split in the sky grew larger, and the entire northern side was covered with fire. At that moment I became so hot that I couldnt bear it, as if my shirt was on fire, from the northern side, where the fire was, came strong heat. I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, later we saw that many windows were shattered, and in the barn a part of the iron lock snapped. Testimony of Chuchan of Shanyagir tribe, as recorded by I. M. Suslov in 1926, suddenly we both woke up at the same time. We heard whistling and felt strong wind, Chekaren said, Can you hear all those birds flying overhead
22.
Siberia
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Siberia is an extensive geographical region, and by the broadest definition is also known as North Asia. Siberia has historically been a part of Russia since the 17th century, the territory of Siberia extends eastwards from the Ural Mountains to the watershed between the Pacific and Arctic drainage basins. It stretches southwards from the Arctic Ocean to the hills of north-central Kazakhstan and to the borders of Mongolia. With an area of 13.1 million square kilometres, Siberia accounts for 77% of Russias land area and this is equivalent to an average population density of about 3 inhabitants per square kilometre, making Siberia one of the most sparsely populated regions on Earth. If it were a country by itself, it would still be the largest country in area, the origin of the name is unknown. Some sources say that Siberia originates from the Siberian Tatar word for sleeping land, another account sees the name as the ancient tribal ethnonym of the Sirtya, a folk, which spoke a language that later evolved into the Ugric languages. This ethnic group was assimilated to the Siberian Tatar people. The modern usage of the name was recorded in the Russian language after the Empires conquest of the Siberian Khanate, a further variant claims that the region was named after the Xibe people. The Polish historian Chycliczkowski has proposed that the name derives from the word for north. He said that the neighbouring Chinese, Arabs and Mongolians would not have known Russian and he suggests that the name is a combination of two words, su and bir. The region is of significance, as it contains bodies of prehistoric animals from the Pleistocene Epoch. Specimens of Goldfuss cave lion cubs, Yuka and another woolly mammoth from Oymyakon, a rhinoceros from the Kolyma River. The Siberian Traps were formed by one of the largest known volcanic events of the last 500 million years of Earths geological history. They continued for a million years and are considered a cause of the Great Dying about 250 million years ago. At least three species of human lived in Southern Siberia around 40,000 years ago, H. sapiens, H. neanderthalensis, the last was determined in 2010, by DNA evidence, to be a new species. Siberia was inhabited by different groups of such as the Enets, the Nenets, the Huns, the Scythians. The Khan of Sibir in the vicinity of modern Tobolsk was known as a prominent figure who endorsed Kubrat as Khagan of Old Great Bulgaria in 630, the Mongols conquered a large part of this area early in the 13th century. With the breakup of the Golden Horde, the autonomous Khanate of Sibir was established in the late 15th century, turkic-speaking Yakut migrated north from the Lake Baikal region under pressure from the Mongol tribes during the 13th to 15th century
23.
Chelyabinsk meteor
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It quickly became a brilliant superbolide meteor over the southern Ural region. The light from the meteor was brighter than the Sun, visible up to 100 km away and it was observed over a wide area of the region and in neighbouring republics. Some eyewitnesses also felt intense heat from the fireball, on account of its high velocity and shallow angle of atmospheric entry, the object exploded in an air burst over Chelyabinsk Oblast, at a height of around 29.7 km. The explosion generated a bright flash, producing a hot cloud of dust and gas that penetrated to 26.2 km, the object was undetected before its atmospheric entry, in part because its radiant was close to the Sun. Its explosion created panic among residents, and about 1,500 people were injured seriously enough to seek medical treatment. Some 7,200 buildings in six cities across the region were damaged by the shock wave. The Chelyabinsk meteor is also the only confirmed to have resulted in a large number of injuries. Amateur videos showed a fireball streaking across the sky and a loud boom several minutes afterwards, some eyewitnesses also felt intense heat from the fireball. The event began at 09,20,21 Yekaterinburg time, several minutes after sunrise in Chelyabinsk, according to eyewitnesses, the bolide appeared brighter than the sun, as was later confirmed by NASA. An image of the object was taken shortly after it entered the atmosphere by the weather satellite Meteosat 9. Witnesses in Chelyabinsk said that the air of the city smelled like gunpowder, sulfur and burning odors starting about 1 hour after the fireball, the visible phenomenon due to the passage of an asteroid or meteoroid through the atmosphere is called a meteor. If the object reaches the ground, then it is called a meteorite, during the Chelyabinsk meteoroids traversal, there was a bright object trailing smoke, then an air burst that caused a powerful blast wave. The latter was the cause of the damage to thousands of buildings in Chelyabinsk. The fragments then entered dark flight and created a field of numerous meteorites on the snow-covered ground. The last time a similar phenomenon was observed in the Chelyabinsk region was the Kunashak meteor shower of 1949, preliminary estimates released by the Russian Federal Space Agency indicated the object was an asteroid moving at about 30 km/s in a low trajectory when it entered Earths atmosphere. According to the Russian Academy of Sciences, the meteor then pushed through the atmosphere at a velocity of 15 km/s, the radiant appears from video recordings to have been above and to the left of the rising Sun. On 1 March 2013 NASA published a synopsis of the event, stating that at peak brightness. The air bursts blast wave, when it hit the ground, the Russian Geographical Society said the passing of the meteor over Chelyabinsk caused three blasts of different energy
24.
1490 Ch'ing-yang event
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The Ching-yang event of 1490 is a presumed meteor shower or air burst in Qìngyáng in March or April 1490. The area was in the district of Shaanxi, if a meteor shower did occur, it may have been the result of the disintegration of an asteroid during an atmospheric entry air burst. A large number of deaths were recorded in historical Chinese accounts of the meteor shower, in the same year, Asian astronomers coincidentally discovered comet C/1490 Y1, a possible progenitor of the Quadrantid meteor showers. At least three surviving Chinese historical records describe a shower during which fell like rain, killing more than 10,000 people. At least one report of the event is found in the official History of the Ming Dynasty, but the official Ming Dynasty history omits the number of casualties, which has been frequently either doubted or discounted by present-day researchers. However Kevin Yau et al. of NASAs Jet Propulsion Laboratory did note several similarities of the Ching-yang meteor fall to the Tunguska event, one surviving account records, Stones fell like rain in the Ch’ing-yang district. The larger ones were 4 to 5 catties, and the ones were 2 to 3 catties. The larger ones were like gooses eggs and the ones were like water-chestnuts. More than 10,000 people were struck dead, all of the people in the city fled to other places. Additionally there are records of it in local gazettes and histories of the region, the History of Ming work states only that there was a rain of uncountable stones of various sizes. The large objects were as big as an egg. The date given was the lunar month of 1490, which translates as March 21 to April 19,1490. Although the Ming Dynasty history did not record the number of deaths or injuries, one semi-official document recorded that a provincial Shaanxi official reported there had been a rain of stones that weighed as much as 4–5 jin, down to 2–3 jin. The number of deaths in this account was in the tens of thousands. The semi-official report and two others date the event to the lunar month with one source dating the event as April 4,1490. Modeling Asteroid Impact Tsunami, Science of Tsunami Hazards,1998, lewis, John S. Comet And Asteroid Impact Hazards On A Populated Earth, Computer Modeling, Volume 1, Academic Press,2000, ISBN0124467601, ISBN 978-0124467606. Paine, M. Asteroid Impacts, The Extra Hazard Due To Tsunami, Science of Tsunami Hazards, Vol.17, No.3 pp. 155–166. Rogue Asteroids and Doomsday Comets, The Search for the Million Megaton Menace That Threatens Life on Earth, Wiley & Sons,1995, ISBN0471193380, ISBN 978-0-4711-9338-8
25.
Mistastin crater
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Mistastin crater is a meteorite crater in Labrador, Canada which contains the roughly circular Mistastin Lake. The lakes arcuate central island is interpreted to be the central uplift of the crater structure. The target rocks were part of a composed of adamellite, mangerite. There are abundant shock metamorphic features exhibited in the rocks of the island, planar deformation features, diaplectic glass, melt rocks, and shatter cones have been identified. The lake is approximately 16 km in diameter, while the diameter of the original crater is 28 km. The age of the crater is calculated to be 36.4 ±4 million years, Mistastin Lake, Labrador, A new Canadian crater. A paleomagnetic study of rocks from Mistastin Lake, Labrador. Earth and Planetary Science Letters, v.6, pp. 309–315, geology of the resurgent cryptoexplosion crater at Mistastin Lake, Labrador. Geological Survey of Canada Bulletin 207,62 p. Currie, the composition of anomalous plagioclase glass and coexisting plagioclase from Mistastin Lake, Labrador, Canada. Mineralogical Magazine, v.38, pp. 511–517, petrology and chemistry of the impact melt at Mistastin Lake crater, Labrador. Geological Society of America Bulletin 86, pp. 1617–1629, york, D. Grieve, R. A. F. and Dence, M. R. The age of the Mistastin Lake crater, Labrador, Canada, earth and Planetary Science Letters, v.31, pp. 345–357. Marchand, M. Crocket, J. H. Sr isotopes and trace element geochemistry of the melt and target rocks at the Mistastin Lake crater. Geochimica et Cosmochimica Acta, v.41, pp. 1487–1495, aerial Exploration of the Mistastin Structure
26.
Spitzer Space Telescope
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The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility, is an infrared space telescope launched in 2003. It is the fourth and final of the NASA Great Observatories program, the planned mission period was to be 2.5 years with a pre-launch expectation that the mission could extend to five or slightly more years until the onboard liquid helium supply was exhausted. This occurred on 15 May 2009, without liquid helium to cool the telescope to the very low temperatures needed to operate, most of the instruments are no longer usable. All Spitzer data, from both the primary and warm phases, are archived at the Infrared Science Archive, in keeping with NASA tradition, the telescope was renamed after its successful demonstration of operation, on 18 December 2003. Unlike most telescopes that are named after famous deceased astronomers by a board of scientists, the contest led to the telescope being named in honor of astronomer Lyman Spitzer, who had promoted the concept of space telescopes in the 1940s. Spitzer wrote a 1946 report for RAND Corporation describing the advantages of an extraterrestrial observatory, the US$720 million Spitzer was launched on 25 August 2003 at 05,35,39 UTC from Cape Canaveral SLC-17B aboard a Delta II 7920H rocket. It follows a heliocentric instead of orbit, trailing and drifting away from Earths orbit at approximately 0.1 astronomical unit per year. The primary mirror is 85 centimeters in diameter, f/12, made of beryllium and was cooled to 5.5 K, by the early 1970s, astronomers began to consider the possibility of placing an infrared telescope above the obscuring effects of Earths atmosphere. Anticipating the major results from an upcoming Explorer satellite and from the Shuttle mission, long-duration spaceflights of infrared telescopes cooled to cryogenic temperatures. Earlier infrared observations had been made by both space-based and ground-based observatories, ground-based observatories have the drawback that at infrared wavelengths or frequencies, both the Earths atmosphere and the telescope itself will radiate strongly. Additionally, the atmosphere is opaque at most infrared wavelengths and this necessitates lengthy exposure times and greatly decreases the ability to detect faint objects. It could be compared to trying to observe the stars at noon, previous space observatories were launched during the 1980s and 1990s and great advances in astronomical technology have been made since then. Most of the early concepts envisioned repeated flights aboard the NASA Space Shuttle and this approach was developed in an era when the Shuttle program was expected to support weekly flights of up to 30 days duration. A May 1983 NASA proposal described SIRTF as a Shuttle-attached mission, several flights were anticipated with a probable transition into a more extended mode of operation, possibly in association with a future space platform or space station. SIRTF would be a 1-meter class, cryogenically cooled, multi-user facility consisting of a telescope, the first flight was expected to occur about 1990, with the succeeding flights anticipated beginning approximately one year later. By September 1983 NASA was considering the possibility of a long duration SIRTF mission, Spitzer is the only one of the Great Observatories not launched by the Space Shuttle, as was originally intended. However, after the 1986 Challenger disaster, the Centaur LH2–LOX upper stage, the mission underwent a series of redesigns during the 1990s, primarily due to budget considerations. This resulted in a smaller but still fully capable mission that could use the smaller Delta II expendable launch vehicle
27.
Science fiction
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Science fiction often explores the potential consequences of scientific and other innovations, and has been called a literature of ideas. Science fiction is difficult to define, as it includes a range of subgenres and themes. Author and editor Damon Knight summed up the difficulty, saying science fiction is what we point to when we say it, a definition echoed by author Mark C. Glassy, who argues that the definition of science fiction is like the definition of pornography, you do not know what it is, in 1970 or 1971William Atheling Jr. According to science fiction writer Robert A, rod Serlings definition is fantasy is the impossible made probable. Science fiction is the improbable made possible, Science fiction is largely based on writing rationally about alternative possible worlds or futures. Science fiction elements include, A time setting in the future, in alternative timelines, a spatial setting or scenes in outer space, on other worlds, or on subterranean earth. Characters that include aliens, mutants, androids, or humanoid robots, futuristic or plausible technology such as ray guns, teleportation machines, and humanoid computers. Scientific principles that are new or that contradict accepted physical laws, for time travel, wormholes. New and different political or social systems, e. g. utopian, dystopian, post-scarcity, paranormal abilities such as mind control, telepathy, telekinesis Other universes or dimensions and travel between them. A product of the budding Age of Reason and the development of science itself. Isaac Asimov and Carl Sagan considered Keplers work the first science fiction story and it depicts a journey to the Moon and how the Earths motion is seen from there. Later, Edgar Allan Poe wrote a story about a flight to the moon, more examples appeared throughout the 19th century. Wells The War of the Worlds describes an invasion of late Victorian England by Martians using tripod fighting machines equipped with advanced weaponry and it is a seminal depiction of an alien invasion of Earth. In the late 19th century, the scientific romance was used in Britain to describe much of this fiction. This produced additional offshoots, such as the 1884 novella Flatland, the term would continue to be used into the early 20th century for writers such as Olaf Stapledon. In the early 20th century, pulp magazines helped develop a new generation of mainly American SF writers, influenced by Hugo Gernsback, the founder of Amazing Stories magazine. In 1912 Edgar Rice Burroughs published A Princess of Mars, the first of his series of Barsoom novels, situated on Mars
28.
B612 Foundation
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The B612 Foundation is a private nonprofit foundation headquartered in Menlo Park, California, United States, dedicated to planetary defense against asteroids and other near-Earth object impacts. It is led mainly by scientists, former astronauts and engineers from the Institute for Advanced Study, Southwest Research Institute, Stanford University, NASA and the space industry. In 2012, the foundation announced it would design and build a privately financed asteroid-finding space observatory, fund raising has been very slow—raising only US$3 million in 2012 and 2013—and, as of June 2015, NASA is re-examining its reliance on private sector approach to space-based NEO survey missions. The B612 Foundation is named for the home of the eponymous hero of Antoine de Saint-Exupérys The Little Prince. When an asteroid enters the atmosphere it becomes known as a meteor. While basketball-sized meteors occur almost daily, and compact car-sized ones about yearly, they burn up or explode high above the Earth as bolides. The asteroid that produced the Barringer Crater was only about 46 meters in size, tsunamis can also occur after a medium-sized or larger asteroid impacts an ocean surface or other large body of water. The probability of an asteroid hitting Earth during the 21st century has been estimated at about 30%. Since the Earth is currently more populated than in previous eras, however, as of the early 2010s, only about a half of one per cent of Tunguska-type NEOs had been located by astronomers using ground-based telescope surveys. The need for an asteroid detection program has been compared to the need for monsoon, typhoon, B612 is one of several organizations to propose detailed dynamic surveys of NEOs and preventative measures such as asteroid deflection. Other groups include Chinese researchers, NASA in the United States, NEOShield in Europe, the Foundation evolved from an informal one-day workshop on asteroid deflection strategies during October 2001, organized by Dutch astrophysicist Piet Hut along with physicist and then-U. S. Astronaut Ed Lu, presented at NASAs Johnson Space Center in Houston, all were interested in contributing to the proposed creation of an asteroid deflection capability. The seminar participants included Rusty Schweickart, a former Apollo astronaut, and Clark Chapman, among the proposed experimental research missions discussed were the alteration of an asteroids spin rate, as well as changing the orbit of one part of a binary asteroid pair. Following the seminars round-table discussions the workshop generally agreed that the vehicle of choice would be powered by a low-thrust ion plasma engine. Landing a nuclear-powered plasma engined pusher vehicle on the surface was seen as promising. The October 2001 asteroid deflection workshop participants created the B612 Project to further their research. Schweickart, along with Drs. Hut, Lu and Chapman, then formed the B612 Foundation on October 7,2002, Schweickart became an early public face of the foundation and served as Chair on its board of directors. That recommended level of support would permit up to 10–20 years of advance warning in order to create a sufficient window for the required trajectory deflection
29.
National Science and Technology Council
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The National Science and Technology Council was established in the US by Executive Order 12881 on November 23,1993. The National Science and Technology Council was established in the US by Executive order on November 23,1993, the Council prepares research and development strategies that are coordinated across Federal agencies to form investment packages aimed at accomplishing multiple national goals. The work of the NSTC is organized under four primary committees, Science, Technology, Environment and Natural Resources and Homeland, each of these committees oversees subcommittees and working groups focused on different aspects of science and technology and working to coordinate across the federal government
30.
Asteroid impact avoidance
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Asteroid impact avoidance comprises a number of methods by which near-Earth objects could be diverted, preventing destructive impact events. While the chances of a collision are not great in the near term. NASA warns that the earth is unprepared and it has been estimated that a velocity change of just 3. 5/t × 10−2 m·s−1 is needed to successfully deflect a body on a direct collision trajectory. In addition, under circumstances, much smaller velocity changes are needed. It was then determined that a deflection from this potential return trajectory, several years before the swing-by, an impact by a 10 kilometres asteroid on the Earth has historically caused an extinction-level event due to catastrophic damage to the biosphere. There is also the threat from comets coming into the inner Solar System, impacts from objects as small as 50 metres in diameter, which are far more common, are historically extremely destructive regionally. Finding out the composition of the object is also helpful before deciding which strategy is appropriate. Missions like the 2005 Deep Impact probe have provided information on what to expect. The 1992 NASA-sponsored Near-Earth-Object Interception Workshop hosted by Los Alamos National Laboratory evaluated issues involved in intercepting celestial objects that could hit Earth, in a 1992 report to NASA, a coordinated Spaceguard Survey was recommended to discover, verify and provide follow-up observations for Earth-crossing asteroids. This survey was expected to discover 90% of these larger than one kilometer within 25 years. In 1998, NASA formally embraced the goal of finding and cataloging, by 2008, the impact of an object much larger than 1 km diameter could well result in worldwide damage up to, and potentially including, extinction of the human species. The NASA commitment has resulted in the funding of a number of NEO search efforts that are making progress toward the 90% goal by 2008. The 2009 discovery of an NEO approximately 2 to 3 kilometers in diameter demonstrated there were still large objects to be detected, United States Representative George E. Brown, Jr. This bill to provide for a Near-Earth Object Survey program to detect, track, catalogue, and characterize certain near-Earth asteroids and comets was introduced in March 2005 by Rep. Dana Rohrabacher. It was eventually rolled into S.1281, the NASA Authorization Act of 2005, passed by Congress on December 22,2005, subsequently signed by the President, and stating in part, The U. S. It shall be the goal of the Survey program to achieve 90% completion of its near-Earth object catalogue within 15 years after the date of enactment of this Act, a recommended option and proposed budget to carry out the Survey program pursuant to the recommended option. Analysis of possible alternatives that NASA could employ to divert an object on a collision course with Earth. The result of this directive was a report presented to Congress in early March 2007, the Minor Planet Center in Cambridge, Massachusetts has been cataloging the orbits of asteroids and comets since 1947
31.
Equirectangular projection
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The equirectangular projection is a simple map projection attributed to Marinus of Tyre, who Ptolemy claims invented the projection about AD100. The projection maps meridians to vertical lines of constant spacing. The projection is neither equal area nor conformal, because of the distortions introduced by this projection, it has little use in navigation or cadastral mapping and finds its main use in thematic mapping. The forward projection transforms spherical coordinates into planar coordinates, the reverse projection transforms from the plane back onto the sphere. X = cos φ1 y = The plate carrée, is the case where φ1 is zero. While a projection with equally spaced parallels is possible for an ellipsoidal model, more complex formulae can be used to create an equidistant map whose parallels reflect the true spacing. Table of examples and properties of all projections, from radicalcartography. net
32.
Earth Impact Database
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The Earth Impact Database is the authoritative source for information on confirmed impact structures or craters on Earth. It was initiated in 1955 by the Dominion Observatory, Ottawa, since 2001, it has been maintained as a not-for-profit source of information at the Planetary and Space Science Centre at the University of New Brunswick, Canada. As of August 2016, the database lists 190 confirmed impact sites, other comprehensive lists are wider in scope by including more than just confirmed sites, such as probable, possible, suspected and rejected/discredited impact sites on their lists. These are used for screening and tracking study of impact sites. The reason to retain rejected sites on such a list is because they may be, Impact Database, Impact Field Studies Group Catalogue of the Earths Impact structures, Siberian Center for Global Catastrophes Earth Impact Database. The meteor impact crater Google Maps viewer
33.
Late Heavy Bombardment
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The Late Heavy Bombardment is an event thought to have occurred approximately 4.1 to 3.8 billion years ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. The LHB happened after the Earth and other rocky planets had formed and accreted most of their mass, Evidence for the LHB derives from lunar samples brought back by the Apollo astronauts. Isotopic dating of Moon rocks implies that most impact melts occurred in a narrow interval of time. Several hypotheses attempt to explain the apparent spike in the flux of impactors in the inner Solar System and they also note that the rate of impact cratering could differ significantly between the outer and inner zones of the Solar System. The main piece of evidence for a lunar cataclysm comes from the ages of impact melt rocks that were collected during the Apollo missions. The majority of impact melts are believed to have formed during the collision of asteroids or comets tens of kilometers across. The Apollo 15,16, and 17 landing sites were chosen as a result of their proximity to the Imbrium, Nectaris, under study on Earth, the ages of impact melts collected at these sites clustered between about 3.8 and 4.1 Ga. The apparent clustering of ages of these led to postulation that the record an intense bombardment of the Moon. They called it the lunar cataclysm and proposed that it represented an increase in the rate of bombardment of the Moon around 3.9 Ga. At the time, the conclusion was considered controversial, as more data has become available, particularly from lunar meteorites, this theory, while still controversial, has gained in popularity. The lunar meteorites are believed to randomly sample the lunar surface, many of the feldspathic lunar meteorites probably originated from the lunar far side, and impact melts within these have recently been dated. Consistent with the hypothesis, none of their ages was found to be older than about 3.9 Ga. Nevertheless, the ages do not cluster at this date. Dating of howardite, eucrite and diogenite meteorites and H chondrite meteorites originating from the asteroid belt reveal numerous ages from 3. 4–4.1 Ga, impact velocities above 10 km/s require very high inclinations or the large eccentricities of asteroids on planet crossing orbits. Such objects are rare in the current asteroid belt but the population would be increased by the sweeping of resonances due to giant planet migration. Studies of the highland crater size distributions suggest that the family of projectiles struck Mercury. The first criticism concerns the origin of the impact melt rocks that were sampled at the Apollo landing sites. While these impact melts have been attributed to having been derived from the closest basin. According to this hypothesis, the cluster of impact melt ages near 3.9 Ga simply reflects material being collected from a single impact event, Imbrium
34.
Chicxulub impact
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The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is located near the town of Chicxulub, after which the crater is named and it was formed by a large asteroid or comet about 10 kilometres in diameter, the Chicxulub impactor, striking the Earth. The crater is more than 180 kilometers in diameter and 20 km in depth and it makes the feature the third of the largest confirmed impact structures on Earth. The crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatán during the late 1970s, Penfield was initially unable to obtain evidence that the geological feature was a crater and gave up his search. Later, through contact with Alan Hildebrand in 1990, Penfield obtained samples that suggested it was an impact feature, evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas. Penfields job was to use data to scout possible locations for oil drilling. In the data, Penfield found a huge underwater arc with extraordinary symmetry in a ring 70 km across and he then obtained a gravity map of the Yucatán made in the 1960s. A decade earlier, the same map suggested a feature to contractor Robert Baltosser. Penfield found another arc on the peninsula itself, the ends of which pointed northward, Pemex disallowed release of specific data but let Penfield and company official Antonio Camargo present their results at the 1981 Society of Exploration Geophysicists conference. That years conference was underattended and their report attracted scant attention, coincidentally, many experts in impact craters and the K–Pg boundary were attending a separate conference on Earth impacts. Although Penfield had plenty of data sets, he had no rock cores or other physical evidence of an impact. He knew Pemex had drilled exploratory wells in the region, in 1951, one bored into what was described as a thick layer of andesite about 1.3 kilometres down. This layer could have resulted from the heat and pressure of an Earth impact. Penfield tried to secure site samples, but was told such samples had been lost or destroyed, when attempts at returning to the drill sites and looking for rocks proved fruitless, Penfield abandoned his search, published his findings and returned to his Pemex work. At the same time, in 1980, geologist Walter Alvarez and his father, Nobel Prize-winning scientist Luis Walter Alvarez and their evidence included greenish-brown clay with surplus iridium containing shocked quartz grains and small weathered glass beads that looked to be tektites. Thick, jumbled deposits of rock fragments were also present, thought to have been scoured from one place. Such deposits occur in locations but seem concentrated in the Caribbean basin at the K–Pg boundary. So when Haitian professor Florentine Morás discovered what he thought to be evidence of an ancient volcano on Haiti, tests on samples retrieved from the K–Pg boundary revealed more tektite glass, formed only in the heat of asteroid impacts and high-yield nuclear detonations
35.
Chris Stewart (politician)
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He currently represents Utahs 2nd congressional district in the United States House of Representatives. Stewart graduated from Utah State University in 1984 before joining the United States Air Force, during his time in the Air Force, Stewart set three world speed records including the fastest nonstop flight around the world. After his service, Stewart began writing novels and became the President and his New York Times bestsellers, Seven Miracles That Saved America and The Miracle of Freedom were published on October 14,2009 and June 3,2011. He formally announced his candidacy for Congress on December 6,2011, Stewart was born in Logan, Utah, and grew up on a dairy farm in Cache Valley, an agricultural valley of northern Utah and southeastern Idaho. His father was a retired Air Force pilot and teacher and his mother, Sybil S. Stewart, was a full-time homemaker and was recognized as the Utah Mother of the Year in 1996. Stewart graduated from Sky View High School in 1978 and entered Utah State University in the fall of the same year, after a year in college, Stewart took a break and served as a Mormon missionary in Texas. After his church service, Stewart re-entered Utah State University, Stewart served in the Air Force for 14 years, primarily flying rescue helicopters and the B-1B bomber. He was stationed at Dyess Air Force Base, Mountain Home Air Force Base, after college, Stewart was accepted into the Air Forces Officer Training School. He was also accepted into Undergraduate Pilot Training, Stewart was awarded the Distinguished Graduate in both endeavors. As the distinguished graduate, Stewart was trained to fly helicopters, only two officers are accepted into this dual-training program per year. In 1995, Stewart was awarded the Mackay Trophy for significant aerial achievement for the combat capability operation known as Coronet Bat, on June 3,1995, Chris and a flight of two B-1s set the world record for the fastest non-stop flight around the world. Stewart was the project officer for this mission. The purpose of the mission was to demonstrate the capability of the B-1 Lancer with live bombing activity over three bombing ranges on three continents in two hemispheres. In the process, the team set three records, flying 36,797.65 kilometers in 36 hours 13 minutes. The mission was recounted in the film Supersonic Saints, Thrilling Stories from LDS Pilots, after his military career, Stewart turned to the private sector. He was the president and CEO of the Shipley Group, a company that specializes in energy. Shipley also participates in government anti-terrorism training, corporate security and executive preparedness consulting and he sold Shipley Group in December 2012 just prior to being sworn in as a U. S. congressman representing Utahs 2nd congressional district. Stewart first began writing books in the late nineties and his first novel, Shattered Bone, was published October 1,1998
36.
Michael A'Hearn
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Michael Francis AHearn is an American astronomer and astronomy professor at the University of Maryland College of Computer, Mathematical, and Natural Sciences. He is also the principal investigator for NASAs EPOXI mission and he received his B. A. in science at Boston College and his Ph. D. in Astronomy at the University of Wisconsin–Madison. He was the investigator for the NASA Deep Impact mission. He has aided in the development of systems for surveying abundances in comets as well as techniques for determining the sizes of cometary nuclei which uses optical and his studies focus on comets as well as asteroids and he also supervises numerous graduate students. He is a fellow of the AAAS. He has authored over 100 papers published in journals and is also a sailor who has a commercial coast guard license. In 2008, he received the Gerard P. Kuiper Prize
37.
United States Congress
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The United States Congress is the bicameral legislature of the federal government of the United States consisting of two chambers, the Senate and the House of Representatives. The Congress meets in the Capitol in Washington, D. C, both senators and representatives are chosen through direct election, though vacancies in the Senate may be filled by a gubernatorial appointment. Members are usually affiliated to the Republican Party or to the Democratic Party, Congress has 535 voting members,435 Representatives and 100 Senators. The House of Representatives has six non-voting members in addition to its 435 voting members and these members can, however, sit on congressional committees and introduce legislation. Puerto Rico, American Samoa, Guam, the Northern Mariana Islands, the members of the House of Representatives serve two-year terms representing the people of a single constituency, known as a district. Congressional districts are apportioned to states by using the United States Census results. Each state, regardless of population or size, has two senators, currently, there are 100 senators representing the 50 states. Each senator is elected at-large in their state for a term, with terms staggered. The House and Senate are equal partners in the legislative process—legislation cannot be enacted without the consent of both chambers, however, the Constitution grants each chamber some unique powers. The Senate ratifies treaties and approves presidential appointments while the House initiates revenue-raising bills, the House initiates impeachment cases, while the Senate decides impeachment cases. A two-thirds vote of the Senate is required before a person can be forcibly removed from office. The term Congress can also refer to a meeting of the legislature. A Congress covers two years, the current one, the 115th Congress, began on January 3,2017, the Congress starts and ends on the third day of January of every odd-numbered year. Members of the Senate are referred to as senators, members of the House of Representatives are referred to as representatives, congressmen, or congresswomen. One analyst argues that it is not a solely reactive institution but has played a role in shaping government policy and is extraordinarily sensitive to public pressure. Several academics described Congress, Congress reflects us in all our strengths, Congress is the governments most representative body. Congress is essentially charged with reconciling our many points of view on the public policy issues of the day. —Smith, Roberts, and Wielen Congress is constantly changing and is constantly in flux, most incumbents seek re-election, and their historical likelihood of winning subsequent elections exceeds 90 percent
38.
Cube (algebra)
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In arithmetic and algebra, the cube of a number n is its third power, the result of the number multiplied by itself twice, n3 = n × n × n. It is also the number multiplied by its square, n3 = n × n2 and this is also the volume formula for a geometric cube with sides of length n, giving rise to the name. The inverse operation of finding a number whose cube is n is called extracting the cube root of n and it determines the side of the cube of a given volume. It is also n raised to the one-third power, both cube and cube root are odd functions,3 = −. The cube of a number or any other mathematical expression is denoted by a superscript 3, a cube number, or a perfect cube, or sometimes just a cube, is a number which is the cube of an integer. The perfect cubes up to 603 are, Geometrically speaking, an integer m is a perfect cube if and only if one can arrange m solid unit cubes into a larger. For example,27 small cubes can be arranged into one larger one with the appearance of a Rubiks Cube, the difference between the cubes of consecutive integers can be expressed as follows, n3 −3 = 3n +1. There is no minimum perfect cube, since the cube of an integer is negative. For example, −4 × −4 × −4 = −64, unlike perfect squares, perfect cubes do not have a small number of possibilities for the last two digits. Except for cubes divisible by 5, where only 25,75 and 00 can be the last two digits, any pair of digits with the last digit odd can be a perfect cube. With even cubes, there is considerable restriction, for only 00, o2, e4, o6, some cube numbers are also square numbers, for example,64 is a square number and a cube number. This happens if and only if the number is a perfect sixth power, the last digits of each 3rd power are, It is, however, easy to show that most numbers are not perfect cubes because all perfect cubes must have digital root 1,8 or 9. That is their values modulo 9 may be only −1,1 and 0, every positive integer can be written as the sum of nine positive cubes. The equation x3 + y3 = z3 has no solutions in integers. In fact, it has none in Eisenstein integers, both of these statements are also true for the equation x3 + y3 = 3z3. The sum of the first n cubes is the nth triangle number squared,13 +23 + ⋯ + n 3 =2 =2. Proofs Charles Wheatstone gives a simple derivation, by expanding each cube in the sum into a set of consecutive odd numbers. Indeed, he begins by giving the identity n 3 = + + + ⋯ + ⏟ n consecutive odd numbers, kanim provides a purely visual proof, Benjamin & Orrison provide two additional proofs, and Nelsen gives seven geometric proofs
39.
Earth escape velocity
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The escape velocity from Earth is about 11.186 km/s at the surface. More generally, escape velocity is the speed at which the sum of a kinetic energy. With escape velocity in a direction pointing away from the ground of a massive body, once escape velocity is achieved, no further impulse need be applied for it to continue in its escape. When given a speed V greater than the speed v e. In these equations atmospheric friction is not taken into account, escape velocity is only required to send a ballistic object on a trajectory that will allow the object to escape the gravity well of the mass M. The existence of escape velocity is a consequence of conservation of energy, by adding speed to the object it expands the possible places that can be reached until with enough energy they become infinite. For a given gravitational potential energy at a position, the escape velocity is the minimum speed an object without propulsion needs to be able to escape from the gravity. Escape velocity is actually a speed because it does not specify a direction, no matter what the direction of travel is, the simplest way of deriving the formula for escape velocity is to use conservation of energy. Imagine that a spaceship of mass m is at a distance r from the center of mass of the planet and its initial speed is equal to its escape velocity, v e. At its final state, it will be a distance away from the planet. The same result is obtained by a calculation, in which case the variable r represents the radial coordinate or reduced circumference of the Schwarzschild metric. All speeds and velocities measured with respect to the field, additionally, the escape velocity at a point in space is equal to the speed that an object would have if it started at rest from an infinite distance and was pulled by gravity to that point. In common usage, the point is on the surface of a planet or moon. On the surface of the Earth, the velocity is about 11.2 km/s. However, at 9,000 km altitude in space, it is less than 7.1 km/s. The escape velocity is independent of the mass of the escaping object and it does not matter if the mass is 1 kg or 1,000 kg, what differs is the amount of energy required. For an object of mass m the energy required to escape the Earths gravitational field is GMm / r, a related quantity is the specific orbital energy which is essentially the sum of the kinetic and potential energy divided by the mass. An object has reached escape velocity when the orbital energy is greater or equal to zero
40.
Kinetic energy
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In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes, the same amount of work is done by the body in decelerating from its current speed to a state of rest. In classical mechanics, the energy of a non-rotating object of mass m traveling at a speed v is 12 m v 2. In relativistic mechanics, this is an approximation only when v is much less than the speed of light. The standard unit of energy is the joule. The adjective kinetic has its roots in the Greek word κίνησις kinesis, the dichotomy between kinetic energy and potential energy can be traced back to Aristotles concepts of actuality and potentiality. The principle in classical mechanics that E ∝ mv2 was first developed by Gottfried Leibniz and Johann Bernoulli, Willem s Gravesande of the Netherlands provided experimental evidence of this relationship. By dropping weights from different heights into a block of clay, Émilie du Châtelet recognized the implications of the experiment and published an explanation. The terms kinetic energy and work in their present scientific meanings date back to the mid-19th century, early understandings of these ideas can be attributed to Gaspard-Gustave Coriolis, who in 1829 published the paper titled Du Calcul de lEffet des Machines outlining the mathematics of kinetic energy. William Thomson, later Lord Kelvin, is given the credit for coining the term kinetic energy c, energy occurs in many forms, including chemical energy, thermal energy, electromagnetic radiation, gravitational energy, electric energy, elastic energy, nuclear energy, and rest energy. These can be categorized in two classes, potential energy and kinetic energy. Kinetic energy is the movement energy of an object, Kinetic energy can be transferred between objects and transformed into other kinds of energy. Kinetic energy may be best understood by examples that demonstrate how it is transformed to, for example, a cyclist uses chemical energy provided by food to accelerate a bicycle to a chosen speed. On a level surface, this speed can be maintained without further work, except to overcome air resistance, the chemical energy has been converted into kinetic energy, the energy of motion, but the process is not completely efficient and produces heat within the cyclist. The kinetic energy in the moving cyclist and the bicycle can be converted to other forms, for example, the cyclist could encounter a hill just high enough to coast up, so that the bicycle comes to a complete halt at the top. The kinetic energy has now largely converted to gravitational potential energy that can be released by freewheeling down the other side of the hill. Since the bicycle lost some of its energy to friction, it never regains all of its speed without additional pedaling, the energy is not destroyed, it has only been converted to another form by friction
41.
Atomic bombings of Hiroshima and Nagasaki
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The United States dropped nuclear weapons on the Japanese cities of Hiroshima and Nagasaki on August 6 and 9,1945, respectively, during the final stage of World War II. The United States had dropped the bombs with the consent of the United Kingdom as outlined in the Quebec Agreement, the two bombings, which killed at least 129,000 people, remain the only use of nuclear weapons for warfare in history. In the final year of the war, the Allies prepared for what was anticipated to be a costly invasion of the Japanese mainland. This was preceded by a U. S. conventional and firebombing campaign that destroyed 67 Japanese cities, the war in Europe had concluded when Nazi Germany signed its instrument of surrender on May 8,1945, just after Hitler committed suicide. The Japanese, facing the fate, refused to accept the Allies demands for unconditional surrender. The Allies called for the surrender of the Japanese armed forces in the Potsdam Declaration on July 26, 1945—the alternative being prompt. The Japanese response to this ultimatum was to ignore it, orders for atomic bombs to be used on four Japanese cities were issued on July 25. Three days later, on August 9, a plutonium bomb was dropped on Nagasaki. During the following months, large numbers died from the effect of burns, radiation sickness, in both cities, most of the dead were civilians, although Hiroshima had a sizable military garrison. Japan announced its surrender to the Allies on August 15, six days after the bombing of Nagasaki, on September 2, the Japanese government signed the instrument of surrender, effectively ending World War II. The justification for the bombings of Hiroshima and Nagasaki is still debated to this day, in 1945, the Pacific War between the Empire of Japan and the Allies entered its fourth year. The Japanese fought fiercely, ensuring that U. S. victory would come at an enormous cost, December 1944 saw American battle casualties hit an all-time monthly high of 88,000 as a result of the German Ardennes Offensive. In the Pacific, the Allies returned to the Philippines, recaptured Burma, offensives were undertaken to reduce the Japanese forces remaining in Bougainville, New Guinea and the Philippines. In April 1945, American forces landed on Okinawa, where fighting continued until June. Along the way, the ratio of Japanese to American casualties dropped from 5,1 in the Philippines to 2,1 on Okinawa, although some Japanese were taken prisoner, most fought until they were killed or committed suicide. Nearly 99% of the 21,000 defenders of Iwo Jima were killed, of the 117,000 Japanese troops defending Okinawa in April–June 1945, 94% were killed. American military leaders used these figures to estimate high casualties among American soldiers in the invasion of Japan. As the Allies advanced towards Japan, conditions became steadily worse for the Japanese people, Japans merchant fleet declined from 5,250,000 gross tons in 1941 to 1,560,000 tons in March 1945, and 557,000 tons in August 1945
42.
TNT equivalent
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TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The ton of TNT is a unit of energy defined by convention to be 4.184 gigajoules. The convention intends to compare the destructiveness of an event with that of conventional explosives, the kiloton is a unit of energy equal to 4.184 terajoules. The megaton is a unit of equal to 4.184 petajoules. The kiloton and megaton of TNT have traditionally used to describe the energy output. The TNT equivalent appears in various nuclear weapon control treaties, and has used to characterize the energy released in such other highly destructive events as an asteroid impact. A gram of TNT releases 2673–6702 J upon explosion, the energy liberated by one gram of TNT was arbitrarily defined as a matter of convention to be 4184 J, which is exactly one kilocalorie. The measured, pure heat output of a gram of TNT is only 2724 J, alternative TNT equivalency can be calculated as a function of when in the detonation the value is measured and which property is being compared. A kiloton of TNT can be visualized as a cube of TNT8.46 metres on a side, the RE factor is the relative mass of TNT to which an explosive is equivalent, the greater the RE, the more powerful the explosive. This enables engineers to determine the proper masses of different explosives when applying blasting formulas developed specifically for TNT. For example, if a timber-cutting formula calls for a charge of 1 kg of TNT, then based on octanitrocubanes RE factor of 2.38, using PETN, engineers would need 1. 0/1.66 kg to obtain the same effects as 1 kg of TNT. With ANFO or ammonium nitrate, they would require 1. 0/0.74 kg or 1. 0/0.42 kg, *, TBX or EBX, in a small, confined space, may have over twice the power of destruction. The total power of aluminized mixtures strictly depends on the condition of explosions, guide for the Use of the International System of Units. National Institute of Standards and Technology, nuclear Weapons FAQ Part 1.3 Rhodes, Richard. The Making of the Atomic Bomb, cooper, Paul W. Explosives Engineering, New York, Wiley-VCH, ISBN 0-471-18636-8 HQ Department of the Army, Field Manual 5-25, Explosives and Demolitions, Washington, D. C. Pentagon Publishing, pp. 83–84, ISBN 0-9759009-5-1 Explosives - Compositions, Alexandria, VA, thermobaric Explosives, Advanced Energetic Materials,2004. THE NATIONAL ACADEMIES PRESS, nap. edu, retrieved September 2004
43.
Air burst
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Air burst artillery has a long history. The shrapnel shell was invented by Henry Shrapnel of the British army in about 1780 to increase the effectiveness of canister shot and it was widely used by the time of the War of 1812 and stayed in use until it was superseded during the First World War. Modern shells, though sometimes called shrapnel shells, actually produce fragments and splinters, when infantry moved into deep trenches, shrapnel shells were rendered useless and high-explosive shells were used to attack field fortifications and troops in the open. The time fuses for the shells could be set to function on contact or in the air, during World War II a proximity fuze was developed, which was controlled by a doppler radar device within the shell that caused it to explode when near the target. During the Vietnam War, air bursting shells were used to effect to defend US Army bases. This tactic was known as Killer Junior when referring to 105 mm or 155 mm shells, another recent development is computer programmable rounds. Weapons using this new technology include the XM29, XM25, XM307, K11 and this mach stem only occurs near ground level, and is similar in shape to the letter Y when viewed from the side. Airbursting also minimizes fallout by keeping the fireball from touching the ground, limiting the amount of debris that is vaporized, in nuclear warfare, air bursts are used against soft targets such as cities in countervalue targeting, or airfields, radar systems and mobile ICBMs in counterforce targeting. List of meteor air bursts Laydown delivery Toss bombing Munition fuzes
44.
Mesosphere
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The mesosphere is the layer of the Earths atmosphere that is directly above the stratosphere and directly below the mesopause. In the mesosphere, temperature decreases as the altitude increases, the upper boundary of the mesosphere is the mesopause, which can be the coldest naturally occurring place on Earth with temperatures below −143 °C. The stratosphere, mesosphere and lowest part of the thermosphere are collectively referred to as the middle atmosphere, the mesopause, at an altitude of 80–90 km, separates the mesosphere from the thermosphere—the second-outermost layer of the Earths atmosphere. This is also around the altitude as the turbopause, below which different chemical species are well mixed due to turbulent eddies. Above this level the atmosphere becomes non-uniform, the heights of different chemical species differ by their molecular masses. Within the mesosphere, temperature decreases with increasing height, due to decreasing solar heating and increasing cooling by CO2 radiative emission, the top of the mesosphere, called the mesopause, is the coldest part of Earths atmosphere. Temperatures in the mesosphere fall as low as −101 °C, varying according to latitude. The main dynamic features in this region are strong winds, atmospheric tides, internal atmospheric gravity waves. Most of these tides and waves start in the troposphere and lower stratosphere, in the mesosphere, gravity-wave amplitudes can become so large that the waves become unstable and dissipate. This dissipation deposits momentum into the mesosphere and largely drives global circulation, noctilucent clouds are located in the mesosphere. The upper mesosphere is also the region of the known as the D layer. The D layer is present during the day, when some ionization occurs with nitric oxide being ionized by Lyman series-alpha hydrogen radiation. The ionization is so weak that when night falls, and the source of ionization is removed, the mesosphere has been called the ignorosphere because it is poorly studied relative to the stratosphere and the thermosphere. A5 km deep sodium layer is located between 80–105 km, made of unbound, non-ionized atoms of sodium, the sodium layer radiates weakly to contribute to the airglow. The sodium has a concentration of 400,000 atoms per cubic centimeter. This band is regularly replenished by sodium sublimating from incoming meteors, astronomers have begun utilizing this sodium band to create guide stars as part of the adaptive optical correction process used to produce ultra-sharp ground-based observations. Millions of meteors enter the Earths atmosphere, averaging 40 tons per year, the mesosphere lies above altitude records for aircraft and balloons, and below the minimum altitude for orbital spacecraft. It has only been accessed through the use of sounding rockets, as a result, it is the least-understood part of the atmosphere
45.
Evaporation
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Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance. The other type of vaporization is boiling, which is characterized by bubbles of saturated vapor forming in the liquid phase, steam produced in a boiler is another example of evaporation occurring in a saturated vapor phase. Evaporation that occurs directly from the solid phase below the melting point, on average, a fraction of the molecules in a glass of water have enough heat energy to escape from the liquid. The water in the glass will be cooled by the evaporation until an equilibrium is reached where the air supplies the amount of heat removed by the evaporating water, in an enclosed environment the water would evaporate until the air is saturated. With sufficient temperature, the liquid would turn into vapor quickly, when the molecules collide, they transfer energy to each other in varying degrees, based on how they collide. Sometimes the transfer is so one-sided for a molecule near the surface that it ends up with energy to escape. Evaporation is an part of the water cycle. The sun drives evaporation of water from oceans, lakes, moisture in the soil, in hydrology, evaporation and transpiration are collectively termed evapotranspiration. Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form water vapor, when only a small proportion of the molecules meet these criteria, the rate of evaporation is low. Since the kinetic energy of a molecule is proportional to its temperature, as the faster-moving molecules escape, the remaining molecules have lower average kinetic energy, and the temperature of the liquid decreases. This phenomenon is also called evaporative cooling and this is why evaporating sweat cools the human body. Evaporation also tends to proceed quickly with higher flow rates between the gaseous and liquid phase and in liquids with higher vapor pressure. For example, laundry on a line will dry more rapidly on a windy day than on a still day. Three key parts to evaporation are heat, atmospheric pressure, on a molecular level, there is no strict boundary between the liquid state and the vapor state. Instead, there is a Knudsen layer, where the phase is undetermined, because this layer is only a few molecules thick, at a macroscopic scale a clear phase transition interface cannot be seen. It is just that the process is slower and thus significantly less visible. If evaporation takes place in an area, the escaping molecules accumulate as a vapor above the liquid. Many of the return to the liquid, with returning molecules becoming more frequent as the density
46.
Metre
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The metre or meter, is the base unit of length in the International System of Units. The metre is defined as the length of the path travelled by light in a vacuum in 1/299792458 seconds, the metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a metre bar. In 1960, the metre was redefined in terms of a number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted, the imperial inch is defined as 0.0254 metres. One metre is about 3 3⁄8 inches longer than a yard, Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States and the Philippines, which use meter. Measuring devices are spelled -meter in all variants of English, the suffix -meter has the same Greek origin as the unit of length. This range of uses is found in Latin, French, English. Thus calls for measurement and moderation. In 1668 the English cleric and philosopher John Wilkins proposed in an essay a decimal-based unit of length, as a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. In 1668, Wilkins proposed using Christopher Wrens suggestion of defining the metre using a pendulum with a length which produced a half-period of one second, christiaan Huygens had observed that length to be 38 Rijnland inches or 39.26 English inches. This is the equivalent of what is now known to be 997 mm, no official action was taken regarding this suggestion. In the 18th century, there were two approaches to the definition of the unit of length. One favoured Wilkins approach, to define the metre in terms of the length of a pendulum which produced a half-period of one second. The other approach was to define the metre as one ten-millionth of the length of a quadrant along the Earths meridian, that is, the distance from the Equator to the North Pole. This means that the quadrant would have defined as exactly 10000000 metres at that time. To establish a universally accepted foundation for the definition of the metre, more measurements of this meridian were needed. This portion of the meridian, assumed to be the length as the Paris meridian, was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator
, PMID 18198148
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