4 ms·
Another interesting velocity-related conundrum: It’s impossible to measure the one-way speed of light (from a source to a detector) because we have to synchroni
by LudwigNagasena 3y ago
Another interesting velocity-related conundrum: It’s impossible to measure the one-way speed of light (from a source to a detector) because we have to synchronize the clocks somehow, which requires an algorithm based on the speed of light to account for time dilation. We can only measure the two-way speed of light (from a source to a reflector and back).
So, from the standpoint of pure math, isotropy of the speed of light is purely a convention. The argument can only be made based on, so to speak, philosophical reasoning.
- superposeur 3y agoThis is true — I take the upshot of this observation to be that only proper times are ever directly physically measurable. Coordinate times and concepts that rely on them (such as what you call one-way velocity of light) are always merely a bookkeeping device for organizing the results of different proper time measurements and will always entail some amount of arbitrariness. General relativity makes this more explicit: the arbitrariness is that of the choice of coordinates on spacetime, and one can choose any old coordinate system or none at all.