Lorentz, Poincaré, and Einstein: Rethinking Doppler, Aberration, and the Fresnel Drag

This paper examines Lorentz's 1895 derivations of the classical Doppler formula and Fresnel drag, Einstein's 1905 derivation of the relativistic Doppler effect and aberration, and Einstein's 1907 kinematical route to the exact velocity composition law from which Fresnel drag is obtained as a low-velocity limit. Einstein acknowledged that he had read Lorentz's "Versuch" well before 1905. In 1907, Einstein identified Lorentz's "Versuch" as a crucial precursor to relativity. In that work, Lorentz had already invoked local time to derive Fresnel's drag coefficient from Maxwell's equations. There is a genuine "family resemblance" between Lorentz's and Einstein's treatments in that both preserve the phase of a plane wave under transformation. Yet I demonstrate that this resemblance is only formal. I also discuss the absence of the relativistic Doppler and aberration laws in Poincaré's Dynamics of the Electron.