On Einstein's aberration experiment

Abstract

Aberration experiment proposed by Einstein to decide between the theories of light. According to Einstein, if light from swift canal rays were focused on a slit and the transmitted rays were made parallel and were then focused on cross hairs, the image of the slit would be shifted when a plane-parallel layer of a dispersing medium such as CS. is placed in the path of the parallel rays, because, due to the motion of the canal rays, the light rays on one side of the beam would have a shorter wave-length than those on the other side and hence, if the ordinary wave theory is correct, the wave front should be rotated. It is here shown, however, that this conclusion is based on a misconception of the behavior of such wave fronts; that the position of the final image is independent of the relative wave-lengths of the different light rays; and that, therefore, no shift is to be expected either according to the wave theory or according to any other theory of light. Hence the experiment cannot help discriminate between the rival theories.