[LEAPSECS] WP7A status and Re: clinical evidence about time and sun

Zefram zefram at fysh.org
Mon Dec 22 08:55:30 EST 2008

Tony Finch wrote:

> The local atomic clocks on the Moon or Mars will not run at the

>same rate as a time signal transmitted from the Earth.

More due to being at high altitude than due to relative motion, I believe.
If you're concerned about local interval time, with a sufficiently heavy
emphasis on "local", TAI or other realisations of TT are inadequate even
on the Earth's surface. Though you'd likely get better time by applying
a calculated frequency offset to TAI than by running your own (isolated)
atomic clock.

TT (roughly: interval time on the geoid) ticks 0.9999999993030709866 s
(exactly) for each second of TCG (roughly: interval time at infinite
altitude). Interval time on the lunar surface, like interval time up
a Terran mountain, ticks at some rate between these two.

A side effect of gravitational time dilation is that (presuming infinite
precision) radio time signals with phase-locked carrier don't actually
transmit on precisely their nominal carrier frequency, as judged
locally at the transmitter. Being above sea level, they transmit on a
fractionally lower frequency. As the signal travels downwards it gets
blue-shifted, so that at sea level it appears as precisely the nominal
frequency. It's the revenge of the rubber seconds.


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