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'''Relativity''' refers to two closely-related theories in [[physics]], and to [[postulate]]s that led to the first [[theory]]. Special relativity (SR) is a theory which describes the laws of motion for non-accelerating bodies traveling at a significant fraction of the [[speed of light]].  As speeds approach zero, Special Relativity tends towards equivalence with [[Newton's Laws of Motion]].  Special Relativity was almost solely developed by [[Albert Einstein]], but had minor contributions from [[Hendrik Lorentz]], [[Henri Poincaré]], and Hermann Minkowski<ref>"German mathematician who developed the geometrical theory of numbers and who made numerous contributions to number theory, mathematical physics, and the theory of relativity." [http://www.britannica.com/eb/article-9052860/Hermann-Minkowski Hermann Minkowski -- Britannica Online Encyclopedia]</ref><ref>[http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Minkowski.html Hermann Minkowski, Biography]</ref>.

'''Relativity''' refers to two closely-related theories in [[physics]].

 

Special relativity (SR) is a theory which describes the laws of motion for non-accelerating bodies traveling at a significant fraction of the [[speed of light]].  As speeds approach zero, Special Relativity tends towards equivalence with [[Newton's Laws of Motion]].  Special Relativity was almost solely developed by [[Albert Einstein]], but had minor contributions from [[Hendrik Lorentz]], [[Henri Poincaré]], and Hermann Minkowski<ref>"German mathematician who developed the geometrical theory of numbers and who made numerous contributions to number theory, mathematical physics, and the theory of relativity." [http://www.britannica.com/eb/article-9052860/Hermann-Minkowski Hermann Minkowski -- Britannica Online Encyclopedia]</ref><ref>[http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Minkowski.html Hermann Minkowski, Biography]</ref>.

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.

Louis Essen, the man credited with determining the speed of light, was a skeptic of relativity. He 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 has been met with much resistance in the scientific world. To date, a Nobel Prize has never been awarded for relativity. And 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> The theory 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.

'''Relativity''' is a mathematical system built on untestable hypotheses.  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 also rejects -- without any experimental evidence -- Newton's [[action at a distance]], which is basic to Newtonian gravity and [[quantum mechanics]].

'''Relativity''' is a mathematical system built on untestable hypotheses.  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 also rejects -- without any experimental evidence -- Newton's [[action at a distance]], which is basic to Newtonian gravity and [[quantum mechanics]].

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.

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.

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. This theory still lacks a vital piece: evidence for its hypothesized [[graviton]].

== Special Relativity ==

== Special Relativity ==