I have another thread going right now but I don't want you to refer to that thread. I frankly don't understand what is going on in that thread so please answer my question here. Why do you need to measure the speed of light in both directions for an accurate reading? If I am in an inertial frame, and the light goes from mirror A to B in one light second, do I have an accurate description of the speed of light? Am I totally missing the point here?