[time-nuts] Re: UTC - A Cautionary Tale
Rob Seaman
seaman at noao.edu
Sat Jul 16 11:20:53 EDT 2005
On Jul 16, 2005, at 12:07 AM, Poul-Henning Kamp wrote:
> No, you can not tell me today how many seconds between now and
> 2010-01-01 00:00:00 UTC and that is the whole problem.
That is *part* of the problem - a part that is intrinsic to living
within a non-inertial reference frame. Folks who need interval time
such as you describe should use TAI.
> The entire point here is to make UTC be a usable timescale without
> having to put all military personal, all civil servants, all school
> teachers, all emergency response personel and all programmers
> through a reeducation.
UTC is a usable timescale - in fact, it conveys two usable
timescales: TAI for interval time and an approximation of UTn for
time-of-day. In point of fact it conveys TAI with at least two
orders of magnitude higher precision than UTn - it is already more of
a TAI standard than a UTn standard. All of the people you describe
expect civil time to be responsive to the rotation of the Earth, few
care about leap seconds one way or another. Most clocks are, and
will continue to be, unaffected by leap seconds since they are
embedded in systems that require resetting more frequently than the
secular drift can build up. Most clocks and users of clocks are
deeply affected, however, by the underlying nature of the civil
timescale. Try to "reeducate" the public to understand that each day
will no longer begin and end at midnight - that the prime meridian is
drifting out to sea - that "atomic" clocks (with all the 20th century
baggage of that word) are more important than mother Earth. The
"leap second deauthorization proposal" is not only a naive technical
"solution", it is astoundingly bad public relations for the precision
timing community. Having castrated the world's clocks, should the
PTC expect new funding to be forthcoming to clean up the mess they've
created?
Those clocks and systems and projects and people that *are* affected
by leap seconds should have implemented the civil time standard that
was in effect when the clocks were designed and built. A
professional builds to spec even if he has a philosophical
disagreement with it. The real issue here is that the "medium-
precision" timing community built lots of clocks and clock-like
systems without ever bothering to investigate the underlying issues
of timekeeping. The clocks aren't built to spec, because nobody read
the specification. It was the ITU's responsibility to promulgate the
UTC specification. Are we now to trust them when they want to
abandon it?
There will be no need to reeducate anybody if the civil time standard
is left unchanged. Part of what is going on, however, is the simple
and inevitable *education* of technical personnel whose projects have
run afoul of previously unexamined real-world constraints.
Rob Seaman
National Optical Astronomy Observatory
More information about the time-nuts
mailing list