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Oct19-07, 11:45 PM
P: 1,473
Quote Quote by pervect View Post
The speeds are certainly established by theory, though. And the theory has survived every experimental test thrown at it, to date.

For instance, if Maxwell's equations were wrong, we'd start to see disagreement with experiment, even if that experiment wasn't directly designed to measure some sort of "speed".

Maxwell's equations certainly give us a good reason to expect that electromagnetism, in general, travels at 'c' in the general sense that if you change something "here", it won't have any effect "there" until after a delay of at least c/distance.
Would concur - there is much indirect/consequential evidence of c as the limiting communication velocity - but being the eternal skeptic, I always find myself compelled to comment when absolute assertions are made about propagation rates of fields

I sort of expected Eugene to jump into this thread somewhere as he has written a couple of papers on the subject