Sure, but if we take it as true that light speed is the same in every direction – which is perfectly consistent with everything ever measured – you can measure speed between two endpoints using two atomic clocks and a synchronised experiment, with corrections for the relativistic effect of moving the clocks to the different places
if we take it as true that light speed is the same in every direction
This is the crucial assumption, that to my knowledge hasn’t been proven or disproven. Because the alternative, light goes faster in one particular direction, is also perfectly consistent with everything. And if you’re moving atomic clocks, correcting for time dilations requires you to make assumptions about the one-way speed of light (which we only know from measuring roundtrip times)
Sure, but if we take it as true that light speed is the same in every direction – which is perfectly consistent with everything ever measured – you can measure speed between two endpoints using two atomic clocks and a synchronised experiment, with corrections for the relativistic effect of moving the clocks to the different places
This is the crucial assumption, that to my knowledge hasn’t been proven or disproven. Because the alternative, light goes faster in one particular direction, is also perfectly consistent with everything. And if you’re moving atomic clocks, correcting for time dilations requires you to make assumptions about the one-way speed of light (which we only know from measuring roundtrip times)