On Thu 2006-06-01T06:25:39 -0700, Tom Van Baak hath writ: > > UT1 et al are not really measures of time, but of angle (of Terran > > rotation). > > To some degree yes, but don't they also include minor > corrections (polar motion, longitude, etc.) and so at one > level they already depart from raw angle measurement > and instead are trying to act like clocks?
Yes. It is ironic that UT1 and UT2 were introduced in hopes of getting timeservices worldwide to finally start broadcasting time signals that agreed, but that because the observatories feeding the data to the broadcasters would not abandon the self-inconsistent values for their "conventional longitudes" (c.f. Janssen and Newcomb at the 1884 IMC) the signals did not start to agree until coordinated cesium clocks were in use. -- Steve Allen <[EMAIL PROTECTED]> WGS-84 (GPS) UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99858 University of California Voice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m