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DaleSpam
#151
Feb25-12, 01:58 PM
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P: 16,965
Quote Quote by Bjarne View Post
I cannot see any other option, - can you ?
Sure, I can see at least 4 ways to compare two distant clocks:

A) Broadcast a reference signal, measure the frequency of the signal locally at each clock
B) Take a reference clock, physically transport it from one clock to the other and measure the rate of the reference locally at each clock
C) Agree on a standard physics experiment as a reference, perform it locally at each clock and measure the time for the experiment
D) Agree on an astronomical reference, and measure the time for the astronomical reference locally

Your suggested measurement of one year with two clocks is an example of D. Your mention of satellites probably refers to A. Mentz114's recent post refers to C, which encapsulates the principle of relativity. I came up with B on my own.

With D and A you will get that the Earth clock and the ISS clock run at different rates. With B and C you will get that the Earth clock and the ISS clock run at the same rates.

The beauty of GR is that it is a single law of physics which explains A, B, C, and D all together.