Introduction.—The ether drift experiments heretofore performed seem to have proven the reality of the Lorentz-Fitzgerald contraction, but the explanation of the negative results requires nothing further. The experiment forming the subject of this paper is designed to detect ether drift or to confirm the time transformation between relatively moving systems, which is an essential part of the theory of relativity.

Theory.—Assuming Huyghen's principle and the Lorentz-Fitzgerald contraction it can be shown that the paths of light rays relative to a system are unaffected by its motion or orientation in the medium transmitting the light. The relative phases of two homogeneous beams superposed under large retardation are unaffected by the orientation but not by the velocity of the system. The effect sought in this experiment depends on the velocity change due to the alternate adding and subtracting of the earth's orbital motion and that of the solar system as a whole.

Apparatus and Method.—A delicate optical system is used in which a half-shade analyzer measures the variation with change of phase of component beams, of the position of the plane of polarization of a beam resulting from the superposition of two oppositely circularly polarized ones. The change manifests itself as an unbalancing of a uniform photometric field. The smallest effect to be expected according to the classical ether theory is shown to be several times the least detectable with the experimental arrangements, so that conclusive evidence for or against the relativity principle should be obtained.

• Received 1 February 1922

DOI:https://doi.org/10.1103/PhysRev.20.26