# Special Relativity

Special relativity (SR, also known as the special theory of relativity or STR) is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies".

It extends Galileo's principle of relativity—that all uniform motion is relative, and that there is no absolute and well-defined state of rest (no privileged reference frames)—to account for the constant speed of light—which was previously observed in the Michelson-Morley experiment—and postulates that it holds for all the laws of physics, including both the laws of mechanics and of electrodynamics, whatever they may be.

This theory has a wide range of consequences which have been experimentally verified, including counter-intuitive ones such as length contraction, time dilation and relativity of simultaneity. It has replaced the classical notion of invariant time interval for two events with the notion of invariant space-time interval. Combined with other laws of physics, the two postulates of special relativity predict the equivalence of mass and energy, as expressed in the mass–energy equivalence formula E = mc2, where c is the speed of light in vacuum. The predictions of special relativity agree well with Newtonian mechanics in their common realm of applicability, specifically in experiments in which all velocities are small compared with the speed of light. Special relativity reveals that c is not just the velocity of a certain phenomenon—namely the propagation of electromagnetic radiation (light)—but rather a fundamental feature of the way space and time are unified as spacetime. One of the consequences of the theory is that it is impossible for any particle that has rest mass to be accelerated to the speed of light.

The theory was originally termed "special" because it applied the principle of relativity only to the special case of inertial reference frames, i.e. frames of reference in uniform relative motion with respect to each other. Einstein developed general relativity to apply the principle in the more general case, that is, to any frame so as to handle general coordinate transformations, and that theory includes the effects of gravity.

The term is currently used more generally to refer to any case in which gravitation is not significant. General relativity is the generalization of special relativity to include gravitation. In general relativity, gravity is described using noneuclidean geometry, so that gravitational effects are represented by curvature of spacetime; special relativity is restricted to flat spacetime. Just as the curvature of the earth's surface is not noticeable in everyday life, the curvature of spacetime can be neglected on small scales, so that locally, special relativity is a valid approximation to general relativity. The presence of gravity becomes undetectable in a sufficiently small, free-falling laboratory.

### Other articles related to "special relativity, relativity, special":

Relativistic Mass Distortion - Conservation Versus Invariance of Mass in Special Relativity - The System Invariant Mass Vs. The Individual Rest Masses of Parts of The System
... Again, in special relativity, the rest mass of a system is not required to be equal to the sum of the rest masses of the parts (a situation which would be analogous to gross ... In special relativity, mass is not "converted" to energy, for all types of energy still retain their associated mass ... Neither energy nor invariant mass can be destroyed in special relativity, and each is separately conserved over time in closed systems ...
Special Relativity (alternative Formulations)
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Special Relativity (alternative Formulations) - Very Special Relativity
... Ignoring gravity, experimental bounds seem to suggest that special relativity with its Lorentz symmetry and Poincare symmetry describes spacetime ... can be described as follows The stabilizer of a null vector is the special Euclidean group SE(2), which contains T(2) as the subgroup of parabolic transformations ... Their new symmetry is called Very Special Relativity (VSR) ...
Special Relativity - Relativistic Quantum Mechanics
... Special relativity can be combined with quantum theory to form relativistic quantum mechanics ... It is an unsolved question how general relativity and quantum mechanics can be unified quantum gravitation is an active area in theoretical research ... atomic model explained the fine structure of alkaline atoms by using both special relativity and the preliminary knowledge on quantum mechanics of the time ...
Special Relativity (alternative Formulations) - "Single Postulate" Approaches
... According to some references, the theory of special relativity can be derived from a single postulate the principle of relativity ... For some historical information, see History of special relativity#Spacetime physics and the section "Lorentz transformation without second postulate" for the approaches of Ignatowski and Frank/Rothe ... So, the trio of "principle of relativity+Maxwell+numerical values from experiment" gives special relativity and this should be compared with "principle of relativity+second postulate+Maxwell+numeri ...

### Famous quotes containing the words relativity and/or special:

By an application of the theory of relativity to the taste of readers, to-day in Germany I am called a German man of science, and in England I am represented as a Swiss Jew. If I come to be regarded as a bête noire the descriptions will be reversed, and I shall become a Swiss Jew for the Germans and a German man of science for the English!
Albert Einstein (1879–1955)

For universal love is as special an aspect as carnal love or any of the other kinds: all forms of mental and spiritual activity must be practiced and encouraged equally if the whole affair is to prosper. There is no cutting corners where the life of the soul is concerned....
John Ashbery (b. 1927)