[time-nuts] Primary Time Standards
lists at rtty.us
Thu Jul 14 16:56:29 UTC 2011
One would assume that mean sea level / 1 G would be the standard reference
point for the "official" Cs transition. I've never seen anybody pull out a
gravity meter to set up their Cs though. I suspect that NIST has at least
done the math.
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Mike S
Sent: Thursday, July 14, 2011 6:26 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Primary Time Standards
At 10:26 PM 7/13/2011, Jim Palfreyman wrote...
>But why is it that Caesium Clocks and Hydrogen Masers have an
Cs defines the second, but only at the physically impossible
temperature of absolute zero. Relativistic effects make it so the
second is a different length at different altitudes.
So, when one wants to track global "mean" time, individual clocks need
Which brings up another question - what altitude (=geoid?) is TAI
defined for? I don't know enough about general relativity, but think
the latitude would make a difference, too?
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