[LEAPSECS] Violins and sunspots

[Steve Allen]

On Fri 2009-09-25T09:19:25 -0700, Rob Seaman hath writ:

> First, astronomers "at large" continue to use

> UTC widely for almost every conceivable purpose - it is precisely that

> UTC remains a flavor of Universal Time that permits this.


It's much simpler than that.

Since the epoch when central authorities took over time distribution
from the individual observatories (at first by telegraph, later by
radio, now also by internet) everyone has used a broadcast time scale.
The only other option is to buy an atomic chronometer and eschew the
rest of the world, which is basically what interferometers and pulsar
timing do.

We use UTC because that is the internationally approved name for the
broadcast time scale -- the scale which all the broadcasters of
sovereign time scales have agreed to use as a result of their
conformance to ITU-R recommendations.

(In this I gloss over the fact that fear of FCC fines for blue
language caused many US broadcasters to delay their analog
transmissions of hourly time signals even when the only human
voices were their own staff, and this was before the widespread
deployment of digital radio and its inherent buffering delays.
So there is still no option but to use a broadcast time scale,
it's just a matter of how many seconds off one can expect to be.)

The LIDAR community and some geophysics folks have chosen GPS because
that is another broadcast time scale which can be expected to be
available to every measurement system with above-ground components.

--
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