I hope someone here may be able to shed some light on a question I have.. I know that the clocks used in the GPS system have to take into account the effects of relativity.. The question is which is the more important effect.. The velocity of the satellite (special relativity) or the change in the strength of gravitational field (general relativity)?

Thanks in advance

Ockham"s Barber

According to the information in this link, the difference in gravitational strength is more important than the relative velocity. Although both effects are taken into account.

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"A mystic is a person who is puzzled before the obvious but who understands the nonexistent." -- Elbert Hubbard

Indeed, I think it could be argued that the two effects are necessarily of the same order, given that the satellite motion comes from being in orbit, i.e., is necessitated by the presence of gravity. Remember, general relativity isn't something different from special relativity, it's something more-- it's special relativity plus gravity.