2. Early Experiments (Pre-1905)

The Special Theory of Relativity (SR) is a theory invented in 1905 by Einstein to explain several experimental results. Since then it has been found to explain a wide range of experimental results. SR is not a mathematical game or just a hypothesis. SR is a physical theory that has been well tested many times.

A detailed account of the early history of SRT is given in: Arthur L. Miller, Albert Einstein's Special Theory of Relativity: Emergence and early interpretation, Addison Wesley, 1981, ISBN 0-201-04680-6.

When A. Einstein wrote his famous paper: “The Electrodynamics of Moving Bodies” in 1905, he already had experimental support for his new theory: ...Examples of this sort, together with the unsuccessful attempts to discover any motion of the Earth relatively to the “light medium” suggest that the phenomena of electrodynamics as well as of mechanics possess no properties corresponding to the idea of absolute rest. They suggest rather that, as has already been shown to the first order of small quantities, the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good...What was the experimental support for this claim? There were several experiments concerning the electrodynamics of moving bodies that are not very well known today; but Einstein knew of numerous examples. Many of these experiments were reviewed in H.A. Lorentz's important paper “On the influence of the earth's motion on luminiferous phenomena”, Versl. Kon. Akad. Wettensh. Amsterdam, 297 (1886). Lorentz showed that Stokes' theory of light, which assumed complete dragging of the aether at the surface of the Earth and decreased to zero dragging far away, had severe problems with aberration and the results of Arago and Airy.

Bradley, Phil. Trans. 35, no 406 (1728)

Bradley (1727) discovered that the images of stars move in small ellipses. This is explained as aberration due to the Earth's motion around the sun. This is inconsistent with a simple model of light as waves in an aether that is dragged along by the Earth; it is consistent with SR.

Arago, Oevre completes, T.1. pg 107 (1853) (delayed publication of results from 1810)

Examined the expected change in focus of a refracting telescope due to Earth's motion around the sun. This is first order in v/c if one assumes light is fully dragged by the lens. The null result is consistent with SR. Arago's results caused Fresnel to develop his theory of the partial dragging of aether, which was then confirmed by:

Fizeau, Ann. de Chem et de Physique, 3e ser., T.57 pg 385 (1859)

Measured the speed of light in moving materials. The Fresnel drag coefficient is solidly established by experiments, and is consistent with SR to within experimental resolutions.

Hoek, Arch. Neerl. T.3, pg 180 (1868)

Much more accurate version of the basic concept of Arago's experiment, using a terrestrial source and a square (ring) interferometer with one side in water and three in air. The null result is consistent with Arago's result and with Fresnel's drag coefficient, and with SR.

Airy, Proc. Royal Soc. London, V20, pg 35 (1871); V32, pg 121 (1873). Phil. Mag. 43, pg 310 (1872)

Airy tested whether stellar aberration remained unchanged if the telescope was filled with water. It did, in agreement with the prediction of SR.

Kettler, Pogg. Ann., Bd.144, pg 370 (1872); Bd.147, pg 410 and pg 410 (1872). Astr. Und. Theorie, pg 66 (1873)

Interference and polarization experiments similar to Hoek.

Mascart, Ann. de l'Ecole Normale, 2e ser., T.1 pg 210–214 (1872); T.3, pg 376 (1874)

Changes of polarization in the direction of the Earth's motion not observed.

W.C. Roentgen, Annalen der Physik 35 (1888), pg 264

Note that Roentgen describes in this paper an “unsuccessful” experiment, where he tried to measure the velocity of the Earth through the aether (a “primitive” version of the Trouton-Noble experiment).

R. Blondlot, C.R.A.S. 133 (1901), pg 778.H.A. Wilson, Philosph. Transact. Roy. Soc. London 204, 121 (1904)H.A. Wilson, M. Wilson, Philosph. Transact. Roy. Soc. London 89, 99 (1913)

Experiments concerning the so-called Roentgen convection, with a magnetic field (See Sommerfeld Vol. 3, Chapter 4, and von Laue Ch. 1). Blondlot's experiment was an early experiment with μ, ε= 1.

Rayleigh Phil. Mag. (6) 4, pg 678 (1902).Brace Phil. Mag. (6) 7, pg 317 (1904).Phil. Mag. (6) 10, pg 71 (1905); pg 387 (1905)

Experiments concerning the effect of the motion of the Earth on double refraction.

A. Eichenwald, Annalen der Physik 11 (1903), pg 1 and pg 241

Experiments concerning the so-called Roentgen convection, with an electric field (See Sommerfeld Vol. 3, Chapter 4).

See also the experiments of Trouton-Noble, Kaufmann, and Michelson and Morley.