Sagnac Effect
The French physicist Georges Sagnac is nowdays frequently cited by the engineers who work on devices such as ring-laser gyroscopes. These systems operate on the principle of the Sagnac effect. It is less known that Sagnac was a strong opponent to the theory of special relativity proposed by Albert Einstein. He set up his experiment to prove the existence of the aether discarded by the Einsteinian relativity. An accurate explanation of the phenomenon was provided by Paul Langevin in 1921.
🗎 The Sagnac effect and its interpretation by Paul Langevin
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Often the null result of the 1887 Michelson-Morley experiment, as well as duplicate experiments at the beginning of the 20th century, are presented as evidence against a universal and absolute frame of reference. Seemingly ignored is the understanding that the failure to reject the null hypothesis, the absence of evidence, is not evidence of absence.
In fact, a 1998 paper by Héctor A. Múnera at Centro Internacional de Física (Bogotá D.C., Colombia) reassesses Michelson and Morley results and may correctly show that the MM experiment (as well as duplicate experiments by others) do indicate the velocities consistent with the combined orbital and rotational velocities of the Earth. This would be evidence of a reference frame stationary with respect to our Solar System.
Despite the null interpretation of their experiment by Michelson and Morley, it is quantitatively shown that the outcomes of the original experiment, and all subsequent repetitions, never were null. Additionally, due to an incorrect inter-session averaging, the non-null results are even larger than reported. Contrary to the received view, Illingworth’s and other repetitions of the experiment were consistent with Miller’s positive results.
The intra-session averages based on velocity
exactly correspond to the range of variation of the projection of orbital speed at the moment and location of the observations.