[time-nuts] Pendulums & Atomic Clocks & Gravity

Tom Van Baak tvb at LeapSecond.com
Sat May 26 17:02:36 EDT 2007

>> Gravity also effects atomic clocks, see: http://www.leapsecond.com/great2005/
>> and this puts a limit on what can be done with any atomic clock that's on
>> Earth.  "g" will always have minor fluctuations (noise) due to all sorts of
>> things like the Sun, Moon, planets, asteroids, earthquakes, etc.  It's still a
>> direct "g" effect called red shift like (U2 Gˆ’ U1)/c2, where the Us are
>> gravitational potentials, only smaller by c squared.
>Mostly Sun (

Sorry, that posting got cut off. See the full reply that followed.

> Effects due to Sun and Moon are about the same.  Run the
> numbers using g=GM/r^2.


I think what Brooke is talking about are changes in g due
to tides (an effect that makes pendulum clocks unstable in
the 7th or 8th decimal place). So the simple "g" formula
above doesn't apply. Instead one must use the "delta g", or
tidal formula, as in dg = GM2R/d^3.

Check the web for references to gravity and tides, or read
the paper on tides and pendulum clocks Brooke mentioned:

Another nice one is: Myths about Gravity and Tides


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