Steve Allen sla at ucolick.org
Wed Jan 18 03:34:21 EST 2012

On 2012 Jan 18, at 00:28, Poul-Henning Kamp wrote:

> UTC's semantics is "the timescale we agree to coordinate on", its

More precisely something like this:
"We will coordinate our efforts so as to produce a time scale
which is more suitable for all purposes."

The annals of the CCIR meetings from the 1970s are positively gleeful
as they noted the endorsements and adoptions of the new UTC by
various agencies and governments, but every one of those came along
with words indicating that it was mean solar time.

Even now we still see that, as in
where the words are

TAI is a uniform and stable scale which does not, therefore, keep
in step with the slightly irregular rotation of the Earth. For
public and practical purposes it is necessary to have a scale that,
in the long term, does. Such a scale is Coordinated Universal Time
(UTC), which is identical with TAI except that from time to time a
leap second is added to ensure that, when averaged over a year,
the Sun crosses the Greenwich meridian at noon UTC to within 0.9 s.

The CCIR managed to create a time scale which was suitable for use
as civil time for the next 1000 years, and now they are on the verge
of disavowing their achievement.

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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