Жарық жылдамдығының тұрақтылығын түсіндіруге жасалған алғашқы әрекеттер

Early attempt to explain constant speed of light
In the 19th century, the theory of the luminiferous aether as the hypothetical medium for the propagation of light waves was widely discussed. The aether hypothesis arose because physicists of that era could not conceive of light waves propagating without a physical medium in which to do so. When experiments failed to detect the hypothesized luminiferous aether, physicists conceived explanations for the experiments' failure which preserved the hypothetical aether's existence. The aether drag hypothesis proposed that the luminiferous aether is dragged by or entrained within moving matter. According to one version of this hypothesis, no relative motion exists between Earth and aether. According to another version, the Earth does move relative to the aether and the measured speed of light should depend on the speed of this motion ("aether wind"), which should be measurable by instruments at rest on Earth's surface. In 1818, Augustin Jean Fresnel proposed that the aether is partially entrained by matter. In 1845, George Stokes proposed that the aether is completely entrained within or in the vicinity of matter. Although Fresnel's almost stationary theory was apparently confirmed by the Fizeau experiment (1851), Stokes' theory was apparently confirmed by the Michelson–Morley experiment (1881, 1887). Hendrik Lorentz resolved this contradictory situation in his own aether theory, which banished any form of aether dragging. Albert Einstein's special theory of relativity (1905) excludes aether as a mechanical medium.

Fresnel's dragging coefficient was directly confirmed by the Fizeau experiment and its repetitions. In general, with the aid of this coefficient the negative result of all optical aether drift experiments sensitive enough to detect first order effects (such as the experiments of Arago, Fizeau, Hoek, Airy, Mascart) can be explained. The notion of an (almost) stationary aether is also consistent with stellar aberration. However, this theory is considered to be refuted for the following reasons:

Stokes already in 1845 introduced some additional assumptions in order to bring his theory into accord with experimental results. To explain aberration, he assumed that his incompressible aether is irrotational as well, which would give, in connection with his specific model of aether drag, the correct law of aberration.

Another version of Stokes' model was proposed by Theodor des Coudres and Wilhelm Wien (1900). They assumed that aether dragging is proportional to the gravitational mass. That is, the aether is completely dragged by the Earth, and only partially dragged by smaller objects on Earth. And to save Stokes's explanation of aberration, Max Planck (1899) argued in a letter to Lorentz, that the aether might not be incompressible, but condensed by gravitation in the vicinity of Earth, and this would give the conditions needed for the theory of Stokes ("Stokes Planck theory"). When compared with the experiments above, this model can explain the positive results of the experiments of Fizeau and Sagnac, because the small mass of those instruments can only partially (or not at all) drag the aether, and for the same reason it explains the negative result of Lodge's experiments. It is also compatible with Hammar's and Michelson–Morley experiment, as the aether is completely dragged by the large mass of Earth. However, this theory was directly refuted by the Michelson–Gale–Pearson experiment (1925). The great difference of this experiment against the usual Sagnac experiments is the fact that the rotation of Earth itself was measured. If the aether is completely dragged by the Earth's gravitational field, a negative result has to be expected but the result was positive.

Maurice Allais proposed in 1959 an aether hypothesis involving a wind velocity of about 8 km/s, much lower than the standard value of 30 km/s supported by scientists of the nineteenth century, and compatible with the Michelson–Morley and the Dayton Miller experiments, as well as his own experiments regarding the controversial Allais effect unpredictable by general relativity. Despite advocating for the need of another theory of gravity, his hypothesis didn't gain significant traction amongst mainstream scientists.

In modern physics (which is based on the theory of relativity and quantum mechanics), the aether as a "material substance" with a "state of motion" no longer plays any role. So questions concerning a possible "aether drag" are no longer considered meaningful by the scientific community. However, frame dragging as predicted by general relativity, in which rotating masses distort the spacetime metric, causing a precession of the orbit of nearby particles, does exist. But this effect is orders of magnitude weaker than any "aether drag" discussed in this article.