Willem de Sitter

“ We can thus not avoid the conclusion that a=0, i.e. the velocity of light is independent of the motion of the source. Ritz's theory would force us to assume that the motion of the double stars is governed not by Newton's law, but by a much more complicated law, depending on the star's distance from the earth, which is evidently absurd. ”

“ In the theory of Ritz light emitted by a source moving with velocity u is propagated through space in the direction of the motion of the source with the velocity c+u, c being the velocity of light emitted by a motionless source. In other theories (Lorentz, Einstein ) the velocity of light is always c, independent of the motion of the source. ”

“ Now it is easily seen that the hypothesis of Ritz leads to results which are absolutely inadmissible.
Consider one of the components of a double star, and an observer situated at a great distance Δ. Let at the time t, the projection of the star's velocity in the direction towards the observer be u. ”