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Gr avi ty - W iki pedi a, the fr ee encycl opedi a
Gravity Gravity From Wiki pedia, pedia, the free the free encyclopedia
natural phenomenon by which all things with Gravity or gravitation gravitation is a natural energy are brought brought toward (or g ravitate ravitate toward) one another, including stars, planets, galaxies and even light and sub-atomic and sub-atomic particles. Gravity is responsible for many many of the structures structures in the Universe, by creating spheres of hydrogen hydrogen — where hydrogen fuses fuses under pressure to form stars — and grouping them into galaxies. On Earth, gravity gives weight to physical objects and causes the tides. Gravity has an infinite range, although its effects become increasingly weaker on farther objects. Gravity Gravity is most accurately described by the general theory of relativity Hammer and feather drop: Apollo 15 (pro posed by Albert Einstein Einstein in 1915) in 1915) which which describes gravity not as a astronaut astronaut David Scott on the Moon force force but as a consequence of the curvature of spacetime caused by the enacting the legend of Galileo's uneven distribution of mass/energy; and resulting in gravitational time gravity experiment. (1.38 MB, dilation, where time lapses lapses more slowly slowly in lower (stronger) gravitational ogg/Theora format). potential. However, for most applications, a pplications, gravity is well approximated a pproximated by Newton's law Newton's law of universal gravitation, universal gravitation, which postulates postulates that gravity gravity causes a force where two bodies of mass mass are directly are directly drawn (or 'attracted') to each other according to a mathematical relationship, where the attractive force is proportional to the product of their masses and inversely proportional to the square of the distance between them. This is considered to occur over an infinite range, such that all bodies (with mass) mass) in the unive the universe rse are drawn to each other no matter how far they are apart. Gravity Gravity is the weakest of the four four fundamental interactions of nature. The gravitational attraction is approximately −38 10−38 times the strength of the strong force (i.e. gravity is 38 38 orders orders of magnitude m agnitude weaker), 10−36 times the strength
of the the electromagnetic force, and 10−29 times the strength of strength of the weak force. As a consequence, gravity has a negligibl negligiblee influence on the behavior of subatomic subatomic particles, and plays plays no no role in determining in determining the internal properties of everyday matter (but see quantum gravity). On the other other hand, gravity is the dominant dominant interaction interaction at the macroscopic scale, and is the cause of the formation, shape, and trajectory (orbit) of astronomical bodies. It is responsible for various phenomena observed on Earth and throughout the universe; for example, it causes the Earth and the other planets to orbit the Sun, the Moon Moon to to orbit the Earth, the formation of tides, and the formation and evolution evolution of galaxies, galaxies, stars and the Solar System. In pursuit of ursuit of a theory of everything, the merging of general relativity and quantum mechanics (or quantum field theory) into a more gener al al theory of quantum quantum gravity has become an area of research.
Contents 1 History of gravitational gravitational theory 1.1 Scientific Scientific revolut revolution ion 1.2 Newton's Newton's theory of gravitat gravitation ion 1.3 Equivalence Equivalence principl principlee 1.4 General relativity relativity 1.4.1 Solutions Solutions 1.4.2 Tests 1.5 Gravity Gravity and quantum mechanic mechanicss 2 Specifi Specifics cs 2.1 Earth's Earth's gravity gravity https://en.wi ki pedia.or g/wi ki/Gr avi ty
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2.2 Equations for a falling body near the surface of the Earth 2.3 Gravity and astronomy 2.4 Gravitational radiation 2.5 Speed of gravity Anomalies and discrepancies Alternative theories 4.1 Historical alternative theories 4.2 Modern alternative theories See also Footnotes References Further reading External links
History of gravitational theory Scientific revolution Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and early 17th centuries. In his famous (though possibly apocryphal[1]) experiment dropping balls from the Tower of Pisa, and later with careful measurements of balls rolling down inclines, Galileo showed that gravitational acceleration is the same for all objects. This was a major departure from Aristotle's belief that heavier objects have a higher gravitational acceleration.[2] Galileo postulated air resistance as the reason that objects with less mass may fall slower in an atmosphere. Galileo's work set the stage for the formulation of Newton's theory of gravity.
Newton's theory of gravitation In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. In his own words, "I deduced that the forces which keep the planets in their orbs must [be] reciprocally as the squares of their distances from the centers about which they revolve: and thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the Earth; and found them answer pretty nearly."[3] The equation is the following:
Where F is the force, m1 and m2 are the masses of the objects interacting, r is
Sir Isaac Newton, an English physicist who lived from 1642 to 1727
the distance between the centers of the masses and G is the gravitational constant.
Newton's theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Calculations by both John Couch Adams and Urbain Le Verrier predicted the general position of the planet, and Le Verrier's calculations are what led Johann Gottfried Galle to the discovery of Neptune.
https://en.wikipedia.org/wiki/Gravity
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