[LEAPSECS] Nit-pick: SI second

[Poul-Henning Kamp]

In message <20110207101736.BA8A780003B at ip-64-139-1-69.sjc.megapath.net>, Hal Mu
rray writes:

>>> 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...

(http://www.skepticalscience.com/sea-level-rise-intermediate.htm)


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