Has the permeability and permittivity of vacuum ever been measured in a vacuum or space?
No, because you can measure the speed of light directly without involving these constants, in the simplest case just by measuring the time it takes for a signal to travel between point A an B.So is all the above correct? Vacuum constants can't be measured? I know they're derived from the speed of light... But wouldn't saying "the vacuum constants can't be measured" be similar to saying "the speed of light can't be measured"?