[LEAPSECS] Nit-pick: SI second

Steve Allen sla at ucolick.org
Mon Feb 7 16:54:54 EST 2011

On Mon 2011-02-07T14:39:10 -0700, Warner Losh hath writ:

> >Are you sure you aren't confusing red shift (which has been

> >a known factor since the 60's) with blackbody shift (which

> >only arose in the 90's as clocks hit the 1e-15 level)?


> I may well be confused between the two...

Astronomically-speaking neither one has a relevant effect.

The IAU did not object when BIH/BIPM changed the rate of TAI by 1e-12
on 1977-01-01. Whereas the SI second was based on the ephemeris
second, and the ephemeris second was originally specified to 1e-12,
the effect of the rate change amounts to 0.25 s over the entirety of
written human history. No astronomical observation was ever likely to
distinguish the change.

Steve Allen <sla at ucolick.org> WGS-84 (GPS)
UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99855
University of California Voice: +1 831 459 3046 Lng -122.06015
Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m

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