Hi,
On 05/29/2017 09:56 AM, Poul-Henning Kamp wrote:
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In message <cagp4rdnjxgfwgqubokfdugec90-dp2a2cnsdwypx8vs_btb...@mail.gmail.com>
, Michael Wouters writes:
The effect you're looking for depends on a comparison of two different
kinds of atomic clocks eg Cs vs H-maser so the maser comparison presumably
will be a null measurement.
It would have to be between clocks where the clock-atoms have very
different masses (for instance Cs vs. H) but it would *also* have to
be clocks where the clock-photons have very different energy.
So the best setup would be H-maser Cs or Rb foundtain and an trapped
ion optical clock.
Since any physicists at NIST will be keenly aware of the Nobel
Prize dangling in front of any competently measured effect, I think
we can trust them to be on the ball :-)
Somewhat south of NIST Boulder is the USNO backup clock at Shriever
Airforce base, just next to the GPS Master Clock. USNO has rubidium
fountains and hydrogen masers there, and some cesiums. If there would be
any significant effect, I'm sure USNO would also look at it, and also
compare to its Washington DC set of clocks.
Honestly, I'm sceptical that there is very much going on there. We have
three orbital masses that will almost align, but they almost align on a
regular basis, it's just that the shadow of the moon just don't hit the
earth very often. The graviational pull of moon, sun and earth keeps
adding continuously so we should already be able to measure these
individual effects separately and not only when it happens to occur at
the same time.
What we can expect is the effect of the shadow, which can potentially
affect the ionspheric TEC delay and for that matter temperature of
troposphere and thus delay there, and that way cause our measurements to
get skewed. This has however nothing to do with the clocks itself.
Humans is a bit too occupied by alignment in the sky. While a nice show,
I'm not to impressed about its scientific significance in this case.
There is things to learn from most perturbations sure, but as always,
some reasoning to sort out what we could expect is always good.
Cheers,
Magnus
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