We can measure the speed from A to B back to A. We can’t measure the speed from A to B directly (without sending something from B back to A wrt speed of light)

We can measure the speed from A to B back to A. We can’t measure the speed from A to B directly (without sending something from B back to A wrt speed of light). https://en.wikipedia.org/wiki/One-way_speed_of_light https://en.wikipedia.org/wiki/One-way_speed_of_light