Max von Laue

“ In Zeeman's experiment, the stationary tube with streaming water is replaced by a body moving as a whole with velocity in the direction of one ray and oppositely to the other one. In order to calculate as to how the traversing time for the first ray is influenced by velocity , we conveniently introduce the concept of relative velocity of light relative to the body, related to the reference system fixed to Earth. ”

“ Both experiments are proving, first, that the optical processes are different in a reference system rotating relative to Earth, as in a system fixed to Earth; we are permitted to consider the latter system with sufficient approximation as a valid system in the sense of the restricted relativity theory. Regarding mechanical processes it's known that every experiment concerning centrifugal forces provides the corresponding confirmation (Sagnac's interpretation of his experiment as a confirmation of the existence of an "aether" is not decisive at all) . ”

“ According to equation (1a) for the absolute phase velocity of light relative to the reference system fixed at Earth, the component of the body's velocity perpendicular to the ray direction doesn't matter, but it is only about the velocity parallel to it. 2. If a line has the smallest distance from the rotation axis and if its direction forms with it the angle , then the component of the body's velocity with respect to this direction is equal to in any of the points, where is the angular velocity of the rotation. ”

“ When the apparatus is rotated, there is also a ray circulating from point to the co-moving point in the sense of rotation. The rotation first causes a change of the relative velocity by which the distances are traversed (under reservation of the proof, we calculate as if were constant upon every distance) , but also a change of distance itself due to the displacement of the relative ray path. The total change of the traversing time amounts ”

“ The deepest reason for the independence of the time difference from the refraction index, is shown, however, by the Lorentz transformation. A glass-rod shall be at rest in reference system , its end-surfaces shall have the equations and . At time we send a light wave of sinus-form, from any of these surfaces to the opposite surface. Both phases reach their target at time . Now we relate this process to a system , relative to which has the velocity in the positive -direction. The transformation equation for time reads ”

“ This is the formula stated by Einstein, Zeeman and H. A. Lorentz [12] , which also was essentially confirmed by Zeeman.
Fig. 1 Now we already come quite near to Harress's experiment, when we think of Zeeman's experiment as altered in terms of Fig. 1. Within it, light isn't entering and leaving through two surfaces perpendicular to velocity, but this happens at two surfaces parallel to velocity. The ray coming from is reflected to after its entrance at at one of the end-surfaces of the body, and there it is reflected at the other end-surface to . ”

“ Then the fringe displacement is not proportional to any more, but depends on it in a less simple way. One shall not see a contradiction against it, that we otherwise always considered summands only proportional to . ”