Variable speed of light with Einstein and stated both speed and direction of light change in a gravity field first published 1923 in English, 1920 in German. Born expressed the magnitude of light speed as the square root of (−"g"/"g") gravity components in general relativity to leave no doubt about his intent. Richard Tolman also agreed with Einstein and expressed the radial speed of light as "dr"/"dt" in a gravity field. where "m" is "MG"/"c" and where natural units are used such that "c" is equal to one. Robert Dicke, in 1957, developed a related VSL theory of gravity. In contrast to Einstein, Dicke
One-way speed of light Thus the measured value of the average one-way speed is dependent on the method used to synchronize the start and finish clocks. This is a matter of convention. The Lorentz transformation is defined such that the one-way speed of light will be measured to be independent of the inertial frame chosen. Some authors such as Mansouri and Sexl (1977) as well as Will (1992) argued that this problem doesn't affect measurements of the isotropy of the one-way speed of light, for instance, due to direction dependent changes relative to a "preferred" (aether) frame Σ. They based their analysis on a