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*'''General Relativity''' (GR) is a theory which explains the laws of motion as viewed from accelerating reference frames and includes a geometric explanation for gravity.  This theory was developed by [[David Hilbert]] and [[Albert Einstein]] as an extension of the postulates of Special Relativity.<ref>"[T]he German mathematician David Hilbert submitted an article containing the correct field equations for general relativity five days before Einstein."[http://nobelprize.org/educational_games/physics/relativity/history-1.html Nobel Prize historical account]</ref> A dramatic but later discredited claim by Sir [[Arthur Eddington]] of experimental proof of General Relativity in 1919 made Einstein a household name.

*'''General Relativity''' (GR) is a theory which explains the laws of motion as viewed from accelerating reference frames and includes a geometric explanation for gravity.  This theory was developed by [[David Hilbert]] and [[Albert Einstein]] as an extension of the postulates of Special Relativity.<ref>"[T]he German mathematician David Hilbert submitted an article containing the correct field equations for general relativity five days before Einstein."[http://nobelprize.org/educational_games/physics/relativity/history-1.html Nobel Prize historical account]</ref> A dramatic but later discredited claim by Sir [[Arthur Eddington]] of experimental proof of General Relativity in 1919 made Einstein a household name.

Relativity has been met with much resistance in the scientific world. To date, a Nobel Prize has never been awarded for relativity. Louis Essen, the man credited with determining the speed of light, wrote many fiery papers against it such as ''The Special Theory of Relativity: A Critical Analysis''.<ref>http://ephysics.fileave.com/physics/Essen/oxford5-essen.pdf</ref> General Relativity also gravely conflicts with [[quantum mechanics]], and although theories like [[string theory]] and [[loop quantum gravity]] have attempted to unify gravity and quantum mechanics, neither has been entirely successful or proven.

Unlike most of physics, the theories of relativity consist of complex mathematical equations relying on several hypotheses. These equations assume that it is forever impossible to attain a velocity faster than the speed of light, a hypothesis that can never be fully tested. By relying on ''assumptions'' about nature rather than ''observations'', the theories of relativity violate [[Isaac Newton]]'s rule against the use of hypotheses: "Hypotheses non fingo" ("I feign no hypotheses)".<ref>http://plato.stanford.edu/entries/newton-philosophy/</ref> Relativity rejects Newton's [[action at a distance]], which is basic to Newtonian gravity and [[quantum mechanics]].  The mathematics of relativity assume no exceptions, yet in the time period immediately following the origin of the universe the relativity equations could not possibly have been valid.

However, [[quantum field theory]] has been an enormously successful realization of both quantum mechanics and special relativity. The [[Standard Model]] of particle physics, a quantum field theory, correctly predicts all observed phenomena observed in particle accelerators and radioactive decays. <ref>http://pdg.lbl.gov/2009/download/rpp-2008-booklet.pdf</ref>

Relativity has been met with much resistance in the scientific world. To date, a Nobel Prize has never been awarded for relativity. Louis Essen, the man credited with determining the speed of light, wrote many fiery papers against it such as ''The Special Theory of Relativity: A Critical Analysis''.<ref>http://ephysics.fileave.com/physics/Essen/oxford5-essen.pdf</ref> Relativity also gravely conflicts with [[quantum mechanics]], and although theories like [[string theory]] and [[quantum field theory]] have attempted to unify relativity and quantum mechanics, neither has been entirely successful or proven.

Unlike [[Newton]]ian physics, in which space and time intervals are each invariant as seen by all observers, in SR the only invariant quantity is a quadratic combination of space and time intervals (x² - c² t²). The (assumed) instantaneous transmission of [[Newton]]ian gravitational effects also contradicts special relativity. This contradiction lead to the modification of [[Newton]]ian gravity, which resulted in General Relativity. 

Unlike [[Newton]]ian physics, in which space and time intervals are each invariant as seen by all observers, in SR the only invariant quantity is a quadratic combination of space and time intervals (x² - c² t²). The (assumed) instantaneous transmission of [[Newton]]ian gravitational effects also contradicts special relativity.

In quantum mechanics, the [[uncertainty principle]] suggests that virtual particles can sometimes travel faster than the speed of light which would violate causality, but "[t]he only known way to resolve this tension involves introducing the idea of antiparticles."<ref>http://nobelprize.org/nobel_prizes/physics/laureates/2004/wilczek-lecture.pdf (p. 102)</ref>  Consequently, in 1928 Paul Dirac derived the Dirac equation, one of the first quantum mechanical equations compatible with special relativity, by which Dirac predicted the existence of antimatter. Four years later, antimatter (the positron) was discovered by Carl Anderson, as successfully predicted by relativistic quantum mechanics.  [[Quantum field theory]], a generalization of quantum mechanics, is fully compatible with special relativity but not with general relativity, and still lacks a vital piece: evidence of the [[graviton]].

In quantum mechanics, the [[uncertainty principle]] suggests that virtual particles can sometimes travel faster than the speed of light which would violate causality, but "[t]he only known way to resolve this tension involves introducing the idea of antiparticles."<ref>http://nobelprize.org/nobel_prizes/physics/laureates/2004/wilczek-lecture.pdf (p. 102)</ref>  Consequently, in 1928 Paul Dirac derived the Dirac equation, one of the first quantum mechanical equations compatible with special relativity, by which Dirac predicted the existence of antimatter. Four years later, antimatter (the positron) was discovered by Carl Anderson, as successfully predicted by relativistic quantum mechanics.  [[Quantum field theory]], a generalization of quantum mechanics, is fully compatible with special relativity but not with general relativity, and still lacks a vital piece: evidence of the [[graviton]].

In layman's terms, these two assumptions can be restated as:

In layman's terms, these two assumptions can be restated as:

# The speed of light is always the same, whether measured in a moving car, or standing on the road.  No matter how an observer is moving, he always gets the same answer for the speed of light.  

# It is impossible ever to transmit information faster than the speed of light.<ref>This assumption is commonly restated in this manner.  For example, a discussion of hypothetical [[tachyons]] talks "about using tachyons to transmit information faster than the speed of light, '''in violation of Special Relativity'''."[http://www.math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html] However, there is some question whether the Theory of Special Relativity really restricts faster-than-light communication of information.</ref>

# The laws of physics are identical, without any variation, in every location throughout the universe.

# The laws of physics are identical, without any variation, in every location throughout the universe.

# The laws of physics are identical, without any variation, no matter how fast something is traveling (in the absence of acceleration).

# The laws of physics are identical, without any variation, no matter how fast something is traveling (in the absence of acceleration).