mike regish writes:

It is not acceleration. It is speed. GPS travels much faster than we do.

No. There are nearly half a dozen relativistic effects that must be
compensated for in the GPS. The nominal clock frequencies, for example, must
be adjusted by slightly less than one part in two billion in order to adjust
for the cumulative relativistic effects.

I doubt we have clocks accurate enough to measure the relativistic effects at
our speeds.

Sure you do ... in your GPS receivers. The adjustments for relativistic
effects are necessary to make the receivers reasonably accurate.

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