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Encyclopedia > Relativistic

Albert Einstein's theory of relativity is a set of two theories in physics: special relativity and general relativity. These theories were conceived in order to explain the fact that electromagnetic waves do not conform to the Newtonian laws for motion. Electromagnetic waves were shown to move at a constant speed, independent of the motion of an observer. The core idea of both theories is that two observers who move relative to each other will measure different time and space intervals for the same events, but the content of physical law will be observed the same by both.

Contents

Special relativity

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 in "absolute motion". The theory postulates that the speed of light in vacuum will be the same for these observers (i.e. an observer invariant speed).


One of the strengths of special relativity is that it can be derived from only a few premises:

  • The speed of light in vacuum is a constant and is equal to 299,792,458 metres per second.
  • The laws of physics are the same for all observers in inertial frames.

General relativity

General relativity was published by Einstein in 1916 (submitted as a series of lectures before the Prussian Academy of Sciences November 25, 1915). However, it must be noted that German mathematician David Hilbert wrote and made public the covariant equations before Einstein. This resulted in not a few accusations of plagiarism against Einstein, but it is probably closer to reality that they both were co-creators of general relativity. The theory gave an introduction of an equation that replaced Newton's law of gravity. It uses the mathematics of differential geometry and tensors in order to describe gravity. This theory considered all observers to be equivalent, not only those moving at a uniform speed. The laws of general relativity are the same for all observers, even if they are accelerated with respect to each other. In general relativity, gravity is no longer a force (as it was in Newton's law of gravity) but is a consequence of the curvature of space-time. General relativity is a geometrical theory which postulates that the presence of mass and energy "curves" spacetime, and this curvature affects the path of free particles (and even the path of light).


See also

External links

  • Probe set to test theory of Relativity - Aug. 07, 2004 (http://www.wired.com/news/space/0,2697,64505,00.html?tw=wn_tophead_1)
  • Living Reviews in Relativity (http://relativity.livingreviews.org/) — An open access, peer-refereed, solely online physics journal publishing invited reviews covering all areas of relativity research.
  • Reflections on Relativity (http://www.mathpages.com/rr/rrtoc.htm) — A complete online course on Relativity.
  • Relativity explained in words of four letters or less (http://www.muppetlabs.com/~breadbox/txt/al.html)
  • Briefing on Einstein's Theory of Relativity (http://www.sysmatrix.net/~kavs/kjs/briefingetr.html) — A terse dose of insight on the subject.
  • Evaluation of Manyfold spacetime short cuts from Relativity (http://tprints.ecs.soton.ac.uk/40/01/Macroscopic_Spacetime_Shortcuts.pdf)
  • Did Einstein cheat? - July 06, 2000 (http://dir.salon.com/people/feature/2000/07/06/einstein/index.html)

  Results from FactBites:
 
Relativist fallacy - Wikipedia, the free encyclopedia (667 words)
The relativist fallacy, also known as the subjectivist fallacy, is a logical fallacy committed, roughly speaking, when one person claims that something may be true for one person but not true for someone else.
There are at least two ways to interpret "the relativist fallacy": either as identical to relativism (generally), or as the ad hoc adoption of a relativist stance purely to defend a controversial position.
On the one hand, those discussions of the relativist fallacy which make the fallacy out to be identical to relativism (e.g., linguistic relativism or cultural relativism) are themselves committing a commonly-identified fallacy of informal logic, namely, begging the question against an earnest, intelligent, logically-competent relativist.
Relativism (18149 words)
Relativistic arguments often begin with plausible, even truistic premises--e.g., that we are culturally and historically situated creatures, that justification cannot go on forever, that we cannot talk without using language or think without using concepts--only to end up with implausible, even inconsistent, conclusions.
On relativistic accounts it typically involves a semantic holism to the effect that the denotations, or at least the meanings in some more general sense, of linguistic expressions are determined by their overall role in a language (theory, form of life, etc.).
Relativistic themes continue to surface, however, in the so-called "strong programme" in the sociology of science and in the new fields of science studies and related areas like cultural studies.
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