Published online by Cambridge University Press: 01 April 2022
The most recent attempt at factually establishing a “true” value for the oneway velocity of light is shown to be faulty. The proposal consists of two round-trip photons travelling first in vacuo and then through a medium of refractive index n before returning to their common point of origin. It is shown that this proposal, as well as a similar one considered by Salmon (1977), presupposes that the one-way velocities of light are equal to the round-trip value. Furthermore, experiments of this type, involving regions of space with varying refractive indices, cannot “single out” any factual value for the Reichenbach-Grünbaum ∊ factor thus posing no threat to the conventionalist thesis.
I wish to thank Prof. Kathleen Okruhlik, Philip Catton (both of the University of Western Ontario), Dale Tweed (University of Waterloo) and Prof. Michael Redhead (Cambridge University) for inspiration and criticism. Acknowledgment is also due to the Natural Science and Engineering Research Council of Canada from whom I have received financial support.