The Collaborative International Dictionary
relativity \rel`a*tiv"i*ty\ (-t?v"?-t?), n.
The state of being relative; as, the relativity of a subject.
--Coleridge.One of two theories (also called theory of relativity) proposed by Albert Einstein, the special theory of relativity, or the general theory of relativity. The special theory of relativity or special relativity is based on the proposition that the speed of light is a constant no matter how observed, and is independent of the motion of the observer. From this follows several principles, such as the increase of mass with velocity (which has been confirmed: see relativistic mass equation) and the impossibility of acceleration to a speed greater than that of light; the equivalence of mass and energy, expressed by the famous equation E = mc^ 2; and time dilation, which is the apparent slowing of a clock in a system, as observed by an observer in a system moving relative to the clock. The general theory of relativity is based on the proposition that there is no physical difference between gravitational force and the force produced by acceleration. From this follow several results, of which the bending of light rays in a gravitational field and the equivalence of the inertial and gravitational masses have been verified. The possible existence of black holes (believed by many astronomers to have been adequately proven) is another consequence of the theory.
Wiktionary
n. (context physics English) The generic term for the theories of special relativity and general relativity, two theories in physics developed mainly by http://en.wikipedia.org/wiki/Albert%20Einstein at the beginning of the 20th century from which several important results such as the equivalence of matter and energy and the Einstein field equations are derived.
WordNet
n. (physics) the theory that space and time are relative concepts rather than absolute concepts [syn: relativity, relativity theory, Einstein's theory of relativity]
Wikipedia
The theory of relativity usually encompasses two theories by Albert Einstein: special relativity and general relativity. Concepts introduced by the theories of relativity include spacetime as a unified entity of space and time, relativity of simultaneity, kinematic and gravitational time dilation, and length contraction.
The term "theory of relativity" was based on the expression "relative theory" used in 1906 by Max Planck, who emphasized how the theory uses the principle of relativity. In the discussion section of the same paper, Alfred Bucherer used for the first time the expression "theory of relativity" .
Usage examples of "theory of relativity".
This, however, would be an error--the sort of error that the theory of relativity avoids.
Our conception of gravity is built around Einsteins General Theory of Relativity, which is now a century and a half old but which, within its limits, remains firm.
They've been there in the general theory of relativity for a hundred years or more.
The theory of relativity says that the laws of physics appear the same to observers moving at different speeds.
It is Einstein's special theory of relativity that tells us we can never accelerate any object to move faster than the speed of light.
The special theory of relativity of 1905 was a profound and important piece of work, of course, but as C.
The mere fact, then, that the secondary radiation of muons reaches us is a strong confirmation of Einstein's theory of relativity.
But I know what you mean when you say the Theory of Simultaneity, in the way I know what is meant by the Theory of Relativity.
Because however vast the distances they covered and however slowly time might crawl along for those left behind on earth, Einstein's theory of relativity still holds good.
I hold that the chief achievement of physics in this century is not the theory of relativity or quantum theory, but the recognition that we are still not in touch with ultimate reality.