David J Taylor wrote:
The flying clock tests were closed loop (I think there's a more
accurate term for the process) where the clock, including both its
initial time error and its frequency offset (rate difference from USNO
or NIST), was well characterized via radio and against a set of
similar clocks prior to take-off. At the end of the trip, the clock
was measured again. The time difference between departure and arrival
was proportionally applied to the measurements taken along the way.
e.g., if the clock was known to be 10ns/day fast during the trip, you
adjust a measurement made on the 3rd day by 30ns. There were lots of
additional statistics applied to improve the measurement results.
John
Thanks, John. Was the measurement down to the nanosecond level?
Cheers,
David
Hi David --
I haven't had a chance to review the article about the 1964 trip, so
don't recall all the details, but I know that the HP advertisement about
the experiment had a tag line that after seventeen days or whatever,
"somewhere along the way we lost a microsecond." So they clearly were
measuring at sub-microsecond levels.
That first experiment was done with HP 5060A cesium standards and there
have been several generations since; the HP 5071A that's been available
since the early 90's is perhaps three orders of magnitude better than
the 5060A.
BTW -- someone cited a paper showing relativistic effects of a
round-the-world flying clock trip in both directions. That, I believe,
was done with the 5071A. Another great experiment -- done by an amateur
time-nut, Tom Van Baak -- took three 5071As on a camping trip up a
mountain in Washington state and verified Einstein's prediction of a
change in clock rate with elevation. Take a look at
http://www.leapsecond.com/great2005/index.htm and be amazed.
John
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