ar X iv : p hy si cs / 0 51 21 60 v 3 [ ph ys ic s . cl as s - ph ] 6 A ug 2 00 7 Michelson – Morley experiment revisited ∗

The idea of the Michelson–Morley experiment is theoretically reanalyzed. Elementary arguments are put forward to precisely derive the most general allowable form of the directional dependence of the oneway velocity of light. According to XIX-century physics light was supposed to propagate in the aether, a mysterious medium devised especially for this purpose. As light was to travel with respect to the aether with a fixed velocity, an experiment was suggested to detect the dependence of the velocity on the direction in a moving frame of the laboratory on the Earth. The experiment was proposed and the first time performed by Albert Michelson (a Nobel laureate, American physicist born in Poland) [1]. The experiment is continually being repeated, known as the Michelson–Morley (MM) experiment, with ever increasing accuracy and improved technical realization (see, e.g. [2]). The result is always the same, negative, i.e. no dependence of the velocity of light on the direction has been ever detected, at least, this is a generally accepted (but sometimes disputable [3]) conclusion. As a (standard) consequence, the velocity of light is the same in each inertial frame, in any direction, and no aether exists. Strictly speaking, the experimental results are usually translated into the theoretical statement saying that the average velocity of light around any closed path is constant and equal to the universal constant c. According to [4] (see also Chapt. 1.3 in [5]) this bound yields the following directional (angular) dependence of the one-way velocity of light c(θ ) = c 1−λ cosθ , (1) where θ is the angle between the direction of light and “the direction of anisotropy”, and λ is a parameter belonging to the interval from 0 to 1. An elementary theoretical analysis of the actual MM experiments, proposed in this paper, yields a more general solution. Among other things, we show that the negative result of the MM experiments imposes milder constrains on the directional dependence (anisotropy) of the one-way velocity of light. In particular, ∗On the occasion of the World Year of Physics 2oo5.