Sagnac and Gravitation
Keywords: Sagnac effect, gravitation, non-Euclidean geometry, ether
The Einstein theory is sometimes incorrectly accused of being unable to explain the Sagnac effect (even for an unclosed path configuration). However, its explanation reveals that it works with the gravitational field as the equivalent of an ether, in which the velocity of light is not constant unless space is distorted into a non-Euclidean geometry so as to force its constancy. Although not wrong in the sense of disagreeing with experimental results, this mathematical formalism is complicated, opaque and unnecessary, for it is easily replaced by very simple mathematics in Euclidean space yielding the same result when it is assumed that the velocity of light is constant with respect to the local gravitational field; this requires no special non-Euclidean space.