I wanted to understand the issue of measuring the one-way speed of light in a bit more depth. I have seen this subject pop up in a few recent threads, however as my questions were mostly off-topic, I thought I should start a new thread rather than continue to hijack others. I also need to say that I in no way want to debunk SR, I am just trying to understand some of the fundamental principles in more detail. I should also say that I don’t have a background in physics and am still learning the math part, so please forgive if my approach is sometimes elementary! As I understand it, we do not currently have a way to measure the one-way speed of light that is in keeping with the principles of SR. So if we could measure the one-way speed of light, it would dis-prove SR. So the one-way speed of light is currently assumed to be the same in all directions, but we can’t validate that for certain. So I wanted to understand if the issue is: a) SR does not allow for the one-way speed of light to be measured (Due to the clock synchronisation issue) and that's that. OR b) We just don’t have a way of testing if light travels at different speeds in different directions. I saw points a) and b) as being subtly different. That is that the first point is about measuring a speed and the second point is about measuring a difference. My thinking is that if it was about just about proving that there is not a difference, then maybe that helps eliminate the clock synchronisation issue. So I was actually thinking of a thought experiment that might be able to show there is no difference, but I wanted to understand the issue in a bit more depth before I make a fool of myself again!