Eur. Phys. J. D (2012) 66: 76
https://doi.org/10.1140/epjd/e2012-20524-8

Regular Article

On measuring the one-way speed of light

Centro de Física Fundamental, Facultad de Ciencias, Universidad de Los Andes, 5101 Mérida, Venezuela

^a e-mail: spavieri@ula.ve

Received: 12 October 2011
Received in final form: 28 November 2011
Published online: 27 March 2012

Abstract

The crucial problem of how to synchronize clocks and measure the one-way speed of light was originally discussed by Poincaré and Einstein. After being neglected for many decades, the Poincaré-Einstein problem of synchronization revived in 1977 with the work of Mansouri and Sexl, by which the one-way speed remains undetermined, allowing for unequal values of the speed of light in opposite directions. We review this problem in the framework of relativistic theories that assume clock-retardation and rod-contraction. We show that, for preferred frame theories, convection or “open” currents yield a magnetic field that depends on the velocity v with respect to the preferred frame S_o. We also outline an experiment, based on Faraday’s law of induction, that can determine the velocity v, identify S_o, and test special relativity versus preferred frame theories. This result resolves the Poincaré-Einstein problem and shows that, in principle, the one-way speed c can be measured.