Classical Doppler shift explains the Michelson‐Morley null result

Abstract

Here we review Michelson‐Morley's original analysis of their interferometer experiment and discuss its use of optical distance. We derive a formula for transverse Doppler shift from geometric considerations, apply this to the Michelson‐Morley interferometer, and present a phase analysis for the experiment. Furthermore, we present an equation for Doppler shift at a general angle and use this to derive the null phase shift result for round-trip interferometer paths at any arbitrary angle. We do not dispute the validity of the null result, nor the prediction of an arrival-time difference for the transverse and longitudinal arms of the interferometer; rather, we challenge the implicit assumption that an arrival time difference will necessarily result in an observable fringe shift.