Note Note 2 — § 1 THE "SPECIAL" THEORY OF RELATIVITY AS A STEPPING STONE TO THE "GENERAL" THEORY OF RELATIVITY

(p. 5). There are essentially two fundamental optical experiments on which our view of the distinctive significance of the velocity of light in physical nature is founded: Fizeau's experiment concerning the velocity of light in flowing water, and the Michelson-Morley experiment. Aberration, on the other hand, has nothing to do directly with the question whether it is possible to prove by means of optical experiments in the laboratory a motion of the earth relative to the ether. The aberration in the case of stars states merely that the motion of the earth relatively to the star under consideration changes periodically in the course of a year. If, however, we hold the view that an all-pervading ether is the carrier for the propagation of the light, the phenomenon of aberration may be satisfactorily explained only if we assume that this ether does not participate in the motion of the earth.