- #1
George Keeling
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- I often see the assertion that clocks show proper time. I don't think ever seen a justification in GR. What is it?
I often see the assertion that clocks show proper time. (E.g. this thread). But I don't think that I have seen a good reason for the assertion in GR. It's not a problem in SR because one can always find a coordinate system that is stationary relative to a clock so, from the metric, ## d\tau=dt##. But in GR you would get ## d\tau=\sqrt{-g_{00}}dt## or worse if the metric were not diagonal. The only reason I can think of to justify the assertion is that ## dt## is different in different coordinate systems and ## d\tau## is not. So it's, sort of, the only sensible choice left. Surely there must be better than this?