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**Interesting fact of the day**: The speed of light has only been proven to be a constant speed **round trip**. Not the instantaneous speed of light nor the speed of light while heading in a single direction has ever been able to be proven as constant.
In other words, it has never been experimentally disproved that light doesn't, for example, preferentially travel at half the speed of light in one orientation, but instantaneous in another. In fact it may very well be impossible to test the one-way speed of light due to the very consequences of relativity itself.
@freemo @Science This is not correct according to my understanding of physics. Specifically addressing the claim that it is not testable: you could have distance separated sensors send light to each other and see how long it takes. If it takes longer in one direction than the other than the theory that the speed of light is constant would be falsified. Maybe I'm not understanding something, but I believe your claim is false. If I am missing something I'd love to know what.
Yes you are misunderstanding the fundemental problem.. if you do this experiment as you propose it would require both sensors to have synchronized clocks with very high accuracy correct? Synchronizing the clocks would be impossible if the speed of light is asymmetrical without knowing what that asymmetry is ahead of time. Worse yet, the error in synchronizing those clocks due to the asymmetry would be exactly enough to cause the experiment to incorrectly show that the speed of light is the same in both directions.
Ergo, your experiment would not be able to detect asymmetry in the speed of light if it existed.
