One-Way Speed of Light Measurements without Clock Synchronisation

The 1991 DeWitte double one-way 1st order in v=c experiment successfully measured the anisotropy of the speed of light using clocks at each end of the RF coaxial cables. However Spavieri et al., Physics Letters A (2012), have reported that (i) clock e ects caused by clock transport should be included, and (ii) that this additional e ect cancels the one-way light speed timing e ect, implying that one-way light speed experiments “do not actually lead to the measurement of the one-way speed of light or determination of the absolute velocity of the preferred frame”. Here we explain that the Spavieri et al. derivation makes an assumption that is not always valid: that the propagation is subject to the usual Fresnel drag e ect, which is not the case for RF coaxial cables. As well DeWitte did take account of the clock transport e ect. The Spavieri et al. paper has prompted a clari cation of these issues.