[time-nuts] WWV Doppler Shift

[Steve Allen]

On Tue 2018-11-20T19:02:16-0500 Tom Holmes hath writ:
> So if the SI second is specified at sea level, and we know from
> Einstein and TVB's work that going up a mountain changes a clock's
> period, how would the second be affected at the center of the Earth (
> ignore thermal problems, this is a conceptual discussion) where the
> net gravity vector might conceivably zero?  Or for that matter, at a
> Lagrange point in space?  We do have some data from those locations I
> would think.

Note that it is not at sea level, and not at the geoid, but as of
last week the rate is at a defined geopotential value.  This makes
the rate of TAI insensitive to geological timescale changes of
the sea level.  The astronomical time scale TT had adopted this
in 2000.  It took 18 years for the CGPM to do the same for TAI.

Since the formation of earth the material at the center of the earth
has exprienced about two days less proper time than the material at
the surface.

GPS and Galileo and Beidou navigation satellites have onboard atomic
frequency standards.  Their rate is tweaked so that the received
signals at the surface of the earth match the SI second here.

> A second question (no pun intended) is that given the Earth's
> elliptical orbit around the Sun, has there been observed an effect of
> the change in its gravity on atomic clocks?

We all slow down and speed up together, so we here looking at us here
see no effect.  On the other hand, spacecraft tracking, VLBI, pulsar
timing, etc. can measure the effect.

--
Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
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