# "Aether Drag" in a Transversely Moving Medium

R. V. Jones

## Abstract

A previous measurement of the Fresnel "aether drag" in a transversely moving medium (Jones 1972) has been repeated with improved accuracy to find whether the original Fresnel formula should be modified by a dispersion term as was shown by Lorentz and Zeeman for the longitudinal drag. A formula derived by M.A. Player and by G.L. Rogers gives the transverse displacement of a beam of light passing through a medium of thickness $t$ moving with transverse velocity $\upsilon$ as $\upsilon t(n_{\text{g}}$ - $n_{\phi}^{-1}$)/$c$ rather than $\upsilon t(n_{\text{g}}$ - $n_{\phi}^{-1}$)/$c$ as given by the original Fresnel formula, where $n_{\phi}$ is the phase refractive index and $n$$_{\text{g}}$ is the 'group refractive index.' The present experiment gives results in accordance with the Player-Rogers formula rather than with the Fresnel formula or one in which the group refractive index alone is involved; it parallels what Zeeman found for the longitudinal case. The main improvement in experimental accuracy has come from recognition of errors in the method of calibration by optical micrometry.