WILLEM DE SITTER'S EXPERIMENT (REPRODUCTION AND INTERPRETATION)
De Sitter double star experiment — Wikipedia.
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.
Binary Stars as Evidence Against Ritz's Relativity. (Articles by Willem de Sitter)
An Astronomical Proof for the Constancy of the Speed of Light. (Willem de Sitter) (1913)
A Proof of the constancy of the velocity of light. (Willem de Sitter) (1913)
On the constancy of the velocity of light. (Willem de Sitter) (1913)