Theories of gravitation

The Aristotelian theory of gravity was that all bodies move towards their natural place. For some objects, Aristotle claimed the natural place to be the center of the earth, wherefore they fall towards it. For other objects, the natural place is the heavenly spheres, wherefore gases, steam for example, move away from the center of the earth and towards heaven and to the moon. The speed of this motion was thought to be proportional to the weight of the object. ...more on Wikipedia about "Aristotelian theory of gravity"

In theoretical physics, the Brans-Dicke theory of gravitation (sometimes called the Jordan-Brans-Dicke theory) is a well-known competitor of Einstein's theory of general relativity. The theory was developed by Robert H. Dicke and Carl H. Brans, building upon earlier work of Pascual Jordan. At present, both general relativity and the Brans-Dicke theory are compatible with all well accepted observational and experimental evidence. ...more on Wikipedia about "Brans-Dicke theory"

The chronology protection conjecture is a conjecture by the physicist Professor Stephen Hawking that the laws of physics are such as to prevent time travel (" closed timelike curves") on all but sub-microscopic scales. ...more on Wikipedia about "Chronology protection conjecture"

* Misner, Thorne and Wheeler ("MTW") Gravitation (Freeman, NY, 1973), chapter 39: "Other theories of gravity and the Post-Newtonian approximation" ...more on Wikipedia about "Classical theories of gravitation"

The goal of creating a unified field theory was (and to some extent, still is) most closely identified in the public mind with the name of Albert Einstein. However, Einstein was by no means the only researcher to attempt such unification in the first half of the twentieth century. Unification of gravitation and electromagnetism was an actively pursued by several physicists and mathematicians in the years between the two world wars. ...more on Wikipedia about "Classical unified field theories"

In theoretical physics, composite gravity refers to models that attempted to derive general relativity in a framework where the graviton is constructed as a composite bound state of more elementary particles, usually fermions. ...more on Wikipedia about "Composite gravity"

This is a generic name for gravity theories which are invariant under conformal transformations in the Riemannian geometric sense. Simplest theory in this category has the Weyl tensor square as the Lagrangian, instead of the usual Einstein-Hilbert action. ...more on Wikipedia about "Conformal gravity" The view on shortopedia. shortopedia

In theoretical physics a Coriolis field is the apparent gravitational field felt by a rotating or forcibly- accelerated body. ...more on Wikipedia about "Coriolis field"

In Einstein's general theory of relativity (or other theories that try to support Mach's principle), the democratic principle is the idea that although acceleration forces and rotational forces might appear to let us define some fixed ( absolute) global reference, that this reference is not externally imposed, but is the collective result of the motion and distribution of all matter in the region, and in the surrounding universe. ...more on Wikipedia about "Democratic principle"

In theoretical physics, DGP gravity is a model proposed by Dvali, Gabadadze, and Porrati in 2000 that assumes that a 3-dimensional brane is embedded in a five-dimensional spacetime and addition Einstein-Hilbert term is concentrated near the brane. This assumption makes gravity four-dimensional at short distances and five-dimensional at long distances. The model is popular with the model builders but has resisted embedding into string theory. ...more on Wikipedia about "DGP model"

Einstein-Cartan theory in theoretical physics extends general relativity, to handle spin angular momentum correctly. ...more on Wikipedia about "Einstein-Cartan theory"

In theoretical physics, geometrodynamics generally denotes a program of reformulation and unification which was enthusiastically promoted by John Archibald Wheeler in the 1960s. ...more on Wikipedia about "Geometrodynamics"

:This article is about the physical concept of gravitation. For information on the manga/anime series, see Gravitation (manga) ...more on Wikipedia about "Gravitation"

Gravitational instantons fall into a few classes, such as asymptotically locally Euclidean spaces (ALE spaces), asymptotically locally flat spaces (ALF spaces). There also exist ALG spaces whose name is chosen by induction. ...more on Wikipedia about "Gravitational instanton"

The black ring is a solution of five dimensional general relativity. It inherits its name from the fact that its event horizon is topologically S^1 x S^2. This is in constract to other known black hole solutions in five dimensions which have horizon topology S^3. ...more on Wikipedia about "Higher dimensional Einstein gravity"

Sakharov proposed the idea of induced gravity as an alternative theory of quantum gravity. Basically, his idea is there is no need to quantize the gravitational field. He observed that many condensed matter systems give rise to emergent phenomena which are identical to general relativity quantitatively. Crystal defects can look like torsion, for example. To him, this was not a coincidence. ...more on Wikipedia about "Induced gravity"

In physics, Kaluza-Klein theory (or KK theory, for short) is a model which sought to unify the two fundamental forces of gravitation and electromagnetism. The theory was first published in 1921 and was discovered by the mathematician Theodor Kaluza who extended general relativity to a five-dimensional spacetime. The resulting equations can be separated out into further sets of equations, one of which is equivalent to Einstein field equations, another set equivalent to Maxwell's equations for the electromagnetic field and the final part an extra scalar field now termed the " radion". ...more on Wikipedia about "Kaluza-Klein theory"

When Sir Isaac Newton published his Theory of Universal Gravitation, he noted that he could not propose a mechanism by which it worked. In 1784 Georges-Louis LeSage (1724-1803) of Geneva proposed a simple kinetic theory of gravitation. LeSage extended the speculations of Newton's friend and contemporary Nicolas Fatio de Duillier, who first suggested a similar explanation for gravity in 1690. ...more on Wikipedia about "LeSage gravity"

In theoretical physics, particularly in discussions of gravition theories, a Mach principle is one of several dozen alternative formulations of vague hypothesis first suggested by the physicist and philosopher Ernst Mach in 1893. ...more on Wikipedia about "Mach's principle"

In theoretical physics, massive gravity is a particular generalization of general relativity studied by van Dam and Veltman; and by Zakharov. ...more on Wikipedia about "Massive gravity"

In physics, the modified Newtonian dynamics (MOND) is a burgeoning theory that attempts to explain the galaxy rotation problem by modifying Newton's second law of motion. (The most widely accepted approach to explaining this problem postulates the existence of dark matter.) MOND was proposed in 1983 by Mordehai Milgrom. The central pillar of MOND is the assumption that Newton's Second Law ( $F = ma$ ) is a high-acceleration approximation of a more accurate law that describes all accelerations. The proposed modification would only become relevant when the total acceleration of a body falls significantly below the constant $a_0$ . Consequently, observations of this behavior could never be made on Earth. ...more on Wikipedia about "Modified Newtonian dynamics"

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In theoretical physics, the nonsymmetric gravitational theory (NGT) of J. W. Moffatt is a classical theory of gravitation which tries to explain the mystery of dark matter. ...more on Wikipedia about "Nonsymmetric Gravitational Theory"

In theoretical physics, Nordström's theory of gravitation was an early competitor of general relativity. It was proposed by Gunnar Nordström in 1913. The original version of the theory did not appear very geometric, but in 1914, Albert Einstein and Adrian Fokker showed that it is in fact a metric theory, which turns out to facilitate direct comparison with general relativity. ...more on Wikipedia about "Nordström's theory of gravitation"

Using these assumptions one can construct an effective field theory in low energies for both. In this form the action of general relativity can be written in the form of the Plebanski action which can be constructed using the Palatini action to derive Einstein's field equations of general relativity. ...more on Wikipedia about "Plebanski action"

In theoretical physics, the PPN formalism is an important method facilitating the comparison of classical theories of gravitation with experimental and observation results. PPN is an acronym standing for parameterized post-Newtonian. The method has its germ in work of Arthur Stanley Eddington but only achieved its full power with the work of later researchers during the Golden Age of General Relativity. ...more on Wikipedia about "PPN formalism"

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