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Volume 11: Pages 504-511, 1998

Sagnac Effect: Isotropic Light‐Speed in the Corotating Frame

Robert B. Driscoll

Istituto per la Ricerca di Base, P.O. Box 637, Oakland, California 94604 U.S.A.

The Sagnac effect is treated as consisting of two possible subeffects: (1) that due to the difference between the light‐path lengths of the direct and the retrograde rays in inertial space and (2) that due to the Doppler effect of at least one of Sagnac's reflective surfaces moving in that space. Subeffect (2) is conventionally ignored to obtain the observed fringe shift Δ= 4ωA/(cλ). A new analysis shows that the observed Sagnac effect requires Maxwell's formula for the speed of light c = (με)^−1/2 to be valid only in the uniformly corotating frame but not in the quasi‐inertial frame of the laboratory, so there is no subeffect (1). The Doppler subeffect (2) is the total effect; the Sagnac effect is properly the Doppler‐Sagnac effect.

Keywords: Sagnac effect, Maxwell's speed of light, special relativity, neo‐Ritzian theory, material relativity

Received: January 5, 1996; Published online: December 15, 2008