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 <s...@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 _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs