Ritz remarked that Michelson’s experiment could be explained by assuming that, contrary to the requirements of the electromagnetic theory of light, waves of light were shot out from the luminous source just as bullets are shot out from a gun. With this species of ballistic theory, the speed of the light ray with respect to the observer would be given by the constant speed of the ray with respect to its source, compounded with the relative speed of the observer and source. Now, there is not the slightest doubt that Ritz’s hypothesis affords an explanation of Michelson’s negative result, but, on the other hand, it leads us into serious difficulties when we wish to interpret a number of other experiments, Bucherer’s, for example. This can be understood when we realize that the Ritz hypothesis compels us to deny the existence of the FitzGerald contraction, since were the contraction to subsist in addition to Ritz’s assumption, Michelson’s experiment would no longer yield a negative result. But, as we have said, the FitzGerald contraction permits a very simple explanation of the moving electron’s increase in mass in Bucherer’s experiment. This difficulty would not be insuperable, but still it would constitute an argument adverse to the acceptance of Ritz’s idea. Other experiments which it would be extremely difficult to account for are those connected with the Fresnel convection coefficient, e.g., Fizeau’s experiment. Furthermore, with Ritz’s conception of the velocity of a light wave through the ether being compounded with the velocity of the source, the frequency of light issuing from a source, moving towards us through the ether, would be increased, whereas the wave length would remain unchanged. Now, it so happens that the angle of refraction of a monochromatic light ray passing through a prism depends on the frequency of the incident light, whereas the dispersion caused by a grating depends on the wave length. It should, therefore, be possible to determine whether frequency and wave length truly behaved like independent variables as demanded by Ritz’s hypothesis. Experiments conducted by Stark in 1910 on canal rays disproved Ritz’s anticipations. Subsequently other experiments led to the same results. [Pg 139]