Special relativity is a physical theory that plays a fundamental role in the description of all physical phenomena, as long as gravitation is not significant. Many experiments played (and still play) an important role in its development and justification. The strength of the theory lies in its unique ability to correctly predict to high precision the outcome of an extremely diverse range of experiments. Repeats of many of those experiments are still being conducted with steadily increased precision, with modern experiments focusing on effects such as at the Planck scale and in the neutrino sector. Their results are consistent with the predictions of special relativity. Collections of various tests were given by Jakob Laub,

Special relativity

Overview

Eventually, Albert Einstein (1905) drew the conclusion that established theories and facts known at that time only form a logical coherent system when the concepts of space and time are subjected to a fundamental revision. For instance:

  • Maxwell-Lorentz's electrodynamics (independence of the speed of light from the speed of the source),
  • the negative aether drift experiments (no preferred reference frame),
  • Moving magnet and conductor problem (only relative motion is relevant),
  • the Fizeau experiment and the aberration of light (both implying modified velocity addition and no complete aether drag).

The result is special relativity theory, which is based on the constancy of the speed of light in all inertial frames of reference and the principle of relativity. Here, the Lorentz transformation is no longer a mere collection of auxiliary hypotheses but reflects a fundamental Lorentz symmetry and forms the basis of successful theories such as Quantum electrodynamics. There is a large number of possible tests of the predictions and the second postulate: More recent experiments have definitely ruled out the emission model: the earliest were those of Filippas and Fox (1964), using moving sources of gamma rays, and Alväger et al. (1964), which demonstrated that photons did not acquire the speed of the high speed decaying mesons which were their source. In addition, the de Sitter double star experiment (1913) was repeated by Brecher (1977) under consideration of the extinction theorem, ruling out a source dependence as well.

Observations of Gamma-ray bursts also demonstrated that the speed of light is independent of the frequency and energy of the light rays.

One-way speed of light

A series of one-way measurements were undertaken, all of them confirming the isotropy of the speed of light.

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