[LEAPSECS] Nit-pick: SI second
phk at phk.freebsd.dk
Mon Feb 7 05:40:54 EST 2011
In message <20110207101736.BA8A780003B at ip-64-139-1-69.sjc.megapath.net>, Hal Mu
>>> That may all be true. But is the SI second a unit of measurement?
>> yes, one that can be reproduced a priori anywhere in the universe that
>> someone has a cesium atom.
>Doesn't it depend upon gravity (aka sea level)? Is that standardized?
The in-force definition of the SI second does not state it explicitly.
The TAI timescale was redefined to be at mean sea level (aka: "MSL"
aka "on the geoid") sometime in the middle of the 1970-ies.
Since TAI is a count of SI seconds, presumably that (de facto) adds
a "at MSL" footnote to the SI definitions.
I don't know the exact wording of the MSL adjustment text, and therefore
it is not clear if the MSL increase from polar icecap
melting will have a measurable impact on TAI. Probably not...
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