[LEAPSECS] The Debate over UTC and Leap Seconds

[Steve Allen]

On Mon 2010-08-09T19:40:18 -0700, Steve Allen hath writ:

> On Mon 2010-08-09T17:32:47 -0600, M. Warner Losh hath writ:

> > When the law says Mean Solar Time, and there's a number of different

> > ways to compute a mean solar time, which mean solar time is the law of

> > the land?  UT1?  The noisier UT2?  UTC?  They are all approximations

> > of mean solar time with differing degrees of error...  Both UT1 and

> > UT2 have changed how they are computed over the years.  Are the laws

> > specific as to how the mean solar time is computed?



> Laws are rarely so specific, they dare not be lest the legislators be

> continually revising them as a result of changes in commonly accepted

> practice.  Laws usually get no more specific than to refer to a

> particular code book from some trade organization.  The details are

> left to the practitioners, and disputes to judge and jury.


As I review the proceedings of the 1966 CCIR plenary in Oslo I note
that the CCIR was itself not totally prescriptive.  From 1951 through
1970 the relevant CCIR recommendation for broadcast time signals was
number 374.  As of 1966 it was at revision 374-1.  At least one of
the changes was to specify that broadcast signals should be within
100 ms of UT2 (which had not existed until 1956).

The recommendation allows for signals to be "with or without a
fractional offset in carrier frequency", and I expect that was to
allow for the variations in practice between stations using various
technologies.  Most of the rest of the recommendation is basically
codification of the existing practices of the time service bureaus.
That is to say, CCIR was leaving the particulars to the discretion
of the practitioners.

At that date the publications of the BIH indicated that those stations
attempting to track UT2 using a frequency offset were not calling
their broadcasts UT2.  I suspect that is because they knew the
difference between the broadcasts and UT2 was always significant.

In the 1966 proceedings are reports from the many studies then in
progress, and many directives for more studies.  In particular was a
directive to find a way to synchronize all broadcasts to 5 us (a mile
of navigation).

The amount of scholarship, research, and activity indicated by the
1966 proceedings is far beyond anything I've seen WP7A do about UTC.

--
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