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Theory of relativity
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Two-dimensional analogy of space-time distortion described in General Relativity.
The theory of relativity, or simply relativity, refers specifically to two theories: Albert Einstein's special relativity and general relativity.
The term "relativity" was coined by Max Planck in 1908 to emphasize how special relativity (and later, general relativity) uses the principle of relativity.
Contents[hide]
1 Special relativity
2 General relativity
3 References and links
4 External links
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[edit] Special relativity
Main article: Special relativity
Albert Einstein's 1905 paper "On the Electrodynamics of Moving Bodies" introduced the special theory of relativity. Special relativity considers that observers in inertial reference frames, which are in uniform motion relative to one another, cannot perform any experiment to determine which one of them is "stationary". This is actually Galileo's principle of relativity; Einstein's contribution was to explicitly include electromagnetism within this principle, which required that the Galilean transformations be replaced by the Lorentz transformations. The resultant theory has many surprising consequences. In particular, it requires that the speed of light in a vacuum be the same for all these observers, regardless of their motion, or the motion of the source of the light, since the invariance of the speed of light is a consequence of Maxwell's equations of electromagnetism.

[edit] General relativity
Main article: General relativity
General relativity was developed by Einstein in the years 1907 - 1915. General relativity replaces the global Lorentz symmetry of special relativity with a local Lorentz symmetry in the presence of matter. The presence of matter "curves" spacetime, and this curvature affects the path of free particles (and even the path of light). General relativity uses the mathematics of differential geometry and tensors in order to describe gravitation as an effect of the geometry of spacetime. This theory is based on the general principle of relativity, which requires all observers to experience the same laws of physics, not just those moving with uniform speed, hence its name.

[edit] References and links
See the special relativity references and the general relativity references. For information on the silent film produced on this subject, see The Einstein Theory of Relativity.