WILLEM DE SITTER'S EXPERIMENT (REPRODUCTION AND INTERPRETATION)
Willem de Sitter's argument against Walther Ritz's "Emission theory". According to this theory, light moves at a speed of c with respect to the emitting object. If this were true, light emitted from a star in a double-star system from different parts of the orbital path would travel towards us at different speeds. For certain combinations of orbital speed, distance, and inclination, the "fast" light given off during approach would overtake "slow" light emitted during a recessional part of the star's orbit. Thus Kepler's laws of motion would apparently be violated for a distant observer. Also many bizarre effects would be seen.
This experiment refute the idea that light might travel at a speed that was partially dependent on the velocity of the emitter.