[time-nuts] GENIUS by Stephen Hawking (PBS TV), with 5071A cesium clocks

Hal Murray hmurray at megapathdsl.net
Fri May 20 12:35:00 EDT 2016


preilley_454 at comcast.net said:
> I have a question.   I, of small brain, am wondering: if the time
> difference between the top of the mountain and the bottom of the mountain is
> 20 nS over 24  hours could you repeat the same experiment using GPS?    The
> time difference of 20 nS is  measurable using GPS. 

The experiment has already been run.  (is being run?)

The GPS satellites are much higher than any mountain.  Their clocks are 
adjusted so that they will be the right frequency when the signal gets down 
here.  There are actually two corrections, one each for special and general 
relativity.  One is 45 microseconds per day, the other is 7 microseconds per 
day in the other direction.


preilley_454 at comcast.net said:
> The GPS clock must run faster on the mountain top than the GPS at the
> mountain base and yet the two remain synchronized to the satellite
> reference.    Therefore the GPS 1 PPS signal (measurable to a few nS) must
> be wrong in in one of  the local frame references. 

If you adjusted a clock on the mountain top to track GPS, then brought it 
down to the lab at the bottom, it would run at a slightly different frequency.


-- 
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