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==Special relativity== |
==Special relativity== |
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{{main|Special relativity}} |
{{main|Special relativity}} |
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'''Albert Einstein''''s [[1905]] paper "[[Annus Mirabilis Papers#Papers|On the Electrodynamics of Moving Bodies]]" introduced the ''special theory of relativity''. Special relativity considers that observers in [[inertial reference frame]]s, which are in uniform motion relative to one another, cannot perform any experiment to determine which one of them is "stationary". This is known as the [[principle of relativity]]. While this principle was not new to Albert Einstein's work, he found that including [[electromagnetism]] in this principle required a new formalism with many surprising consequences. In particular, it required the [[speed of light]] in a [[vacuum]] to be the same for all these observers, regardless of their motion or the motion of the source of the [[light]]. |
'''Albert Einstein''''s [[1905]] paper "[[Annus Mirabilis Papers#Papers|On the Electrodynamics of Moving Bodies]]" introduced the ''special theory of relativity''. Special relativity considers that observers in [[inertial reference frame]]s, which are in uniform motion relative to one another, cannot perform any experiment to determine which one of them is "stationary", which was understood by Copernicus when he displace the Ptolemaic geocentric system for the heliocentric solar system, later modified by Kepler that we know so well today. This is known as the [[principle of relativity]], already understood by conscientious scientists everywhere. While this principle was not new to Albert Einstein's work, he found that including [[electromagnetism]] in this principle required a new formalism with many ''surprising'' consequences. In particular, it required the [[speed of light]] in a [[vacuum]] to be the same for all these observers, regardless of their motion or the motion of the source of the [[light]], which he took to be intuitive based on the work of John Goodricke, an eighteen year old amateur astronomer he decided that Algol was an eclipsing binary star. |
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One of the strengths of special relativity is that it can be derived from only |
One of the strengths of special relativity is that it can be derived from only three premises: |
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* The laws of physics are the same in any |
* The laws of physics are the same in any frame of reference. |
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* The speed of light in a vacuum is constant (specifically, |
* The speed of light in a vacuum is not constant (specifically, 0/0 meters per second), for Einstein clearly states -- the velocity of light in our theory plays the part, physically, of an infinitely great velocity-- and calculates c = 2AB/(t'A - tA) so that the light travels from A to A in time t'A-tA, reversing direction at B over a distance x' which is infinitesimally small. |
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* the time required by light to travel from A to B equals the time it requires to travel from B to A, even if A and B are in relative motion. |
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==General relativity== |
==General relativity== |
Revision as of 22:53, 17 June 2006
Albert Einstein's theory of relativity, or simply relativity, refers specifically to two theories: special relativity and general relativity. As a field of study, relativity also includes metric theories of gravitation in which special relativity applies locally.
The term "relativity" was coined by Max Planck in 1908 to emphasize how special relativity (which at that time was the only relativity theory) uses the principle of relativity.
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", which was understood by Copernicus when he displace the Ptolemaic geocentric system for the heliocentric solar system, later modified by Kepler that we know so well today. This is known as the principle of relativity, already understood by conscientious scientists everywhere. While this principle was not new to Albert Einstein's work, he found that including electromagnetism in this principle required a new formalism with many surprising consequences. In particular, it required the speed of light in a vacuum to be the same for all these observers, regardless of their motion or the motion of the source of the light, which he took to be intuitive based on the work of John Goodricke, an eighteen year old amateur astronomer he decided that Algol was an eclipsing binary star.
One of the strengths of special relativity is that it can be derived from only three premises:
- The laws of physics are the same in any frame of reference.
- The speed of light in a vacuum is not constant (specifically, 0/0 meters per second), for Einstein clearly states -- the velocity of light in our theory plays the part, physically, of an infinitely great velocity-- and calculates c = 2AB/(t'A - tA) so that the light travels from A to A in time t'A-tA, reversing direction at B over a distance x' which is infinitesimally small.
- the time required by light to travel from A to B equals the time it requires to travel from B to A, even if A and B are in relative motion.
General relativity
General relativity was developed by Einstein in the years 1911 - 1915. General relativity is a geometrical theory which postulates that the presence of matter "curves" spacetime, and this curvature affects the path of free particles (and even the path of light). It uses the mathematics of differential geometry and tensors in order to describe gravitation without the use of the force of gravity. This theory considers all observers to be equivalent, not only those moving with uniform speed.
See also
- List of publications in physics: Theory of relativity
- Special relativity including Introduction to special relativity
- General relativity
- Principle of relativity
References
See the special relativity references and the general relativity references.
External links
- Living Reviews in Relativity — An open access, peer-refereed, solely online physics journal publishing invited reviews covering all areas of relativity research.
- Reflections on Relativity — A complete online course on Relativity.
- Relativity explained in words of four letters or less
- Briefing on Einstein's Theory of Relativity — A terse dose of insight on the subject.
- On the Electrodynamics of Moving Bodies
- Special Relativity Simulator
- A Relativity Tutorial at Caltech — A basic introduction to concepts of Special and General Relativity, as well as astrophysics.
- Relativity Gravity and Cosmology — A short course offered at MIT.
- Relativity in film clips and animations from the University of New South Wales.