Can One-Way Light Speed be Measured? Comment on E. D. Greaves et al., Am. J. Phys. 77(10), 894-896 (2009)

TL;DR

This paper critiques a previous experiment claiming to measure one-way light speed, explaining the convention dependence of such measurements and clarifying why the experiment's results do not establish an absolute one-way light speed value.

Contribution

It provides a detailed analysis of the convention dependence in measuring one-way light speed and challenges prior claims of an experimental detection of this quantity.

Findings

The experiment's results are consistent with the convention-dependent nature of one-way light speed.

The Romer experiment does not measure a convention-independent one-way light speed.

The paper clarifies misconceptions about measuring one-way light speed.

Abstract

The convention dependence of one-way light speed is explained in a manner accessible to those unaccustomed to the concept. That logic is used to challenge the claim by Greaves et al that their experiment detected one-way light speed. The reason for the result obtained is then presented and followed by an explanation of why the Romer experiment did not measure a convention independent one-way light speed.