[tz] [PROPOSED] Cite Rec. ITU-R TF.460-6 for leap seconds

Steve Allen sla at ucolick.org
Thu Jul 4 20:41:13 UTC 2019

On Thu 2019-07-04T12:59:45-0700 Paul Eggert hath writ:
> -  print "# (which measures the true angular orientation of the earth in space)"
> +  print "# (a proxy for Earth's angle in space corrected for polar motion)"

That's a 1950s-lingo explanation from the era when it was not possible
to measure the sub-diurnal variations of earth orientation so it was
still possible to use simple models that were based on the existence
of an axis of rotation relatively fixed to the surface of the earth.
Current measurement precision requires general treatment of total body
angular momentum and crustal angular velocity with a conventional
model that does not match the 1950s notion of polar motion.

The aim is for the current model to be continuous in value and rate
with the reference frame of Newcomb, even though that was neither
inertial nor a long-term measure of mean solar time.

Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
1156 High Street               Voice: +1 831 459 3046         Lng -122.06015
Santa Cruz, CA 95064           https://www.ucolick.org/~sla/  Hgt +250 m

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