Re: [LEAPSECS] Risks of change to UTC

From: Rob Seaman <seaman_at_NOAO.EDU>
Date: Sat, 21 Jan 2006 16:03:04 -0700

On Jan 21, 2006, at 12:03 AM, M. Warner Losh wrote:

> WWV and most of the world's time stations broadcast DUT1. I should
> have added in my last message that some change in the signal format
> would be necessary if the range of DUT1 exceeds 0.9s.

Bearing in mind that the ITU proposal would cease the reporting of DUT1.

> I will note that the profile of high precision time users has
> changed since 1972 when UTC was invented. [...] Should we
> continue to tie our time up in knots because of a tiny minority of
> users?

Am fascinated by the failure of the precision timekeeping community
to perceive six and a half billion souls as "users". Shouldn't
choices related to international/civil/legal/business/historical time
be based on their needs? No matter what the profile of high
precision time users has become - it is that entire community who
comprise a tiny minority.

> How many celestial navigators are there today?

The Apollo astronauts relied on navigation by sextant - celestial
indeed. One expects that future solar system explorers will
carefully continue to carry such fundamental instrumentation -
certainly for emergencies (think Shackleton, not just Magellan), but
also perhaps as an agile and reliable primary resource in their
toolkits. Am not arguing that this has a direct connection to the
matter at hand - but rather that old doesn't mean obsolete.

> Over the next 50 years, these two watches will be well within the
> tolerance of most normal watches.

This interpretation confuses systematic effects (monotonically
diverging timescales) with random errors. Much (one is tempted to
say, "all") experimental science depends on abstracting trends from
noisy data. No matter how large a tolerance one allows, the
diverging meanings of "clock" will eventually exceed it.

> The approximation of civil time will be less than one minute off
> during that time

A useful approximation captures asymptotic or otherwise limiting
behavior. Where there is no limit, there may be an agreement to draw
a line in the sand - but there can be no approximation.

Einstein isn't right and Newton wrong, rather Newton's laws are
correct in the limit - the everyday limit. "High precision time
users" may well place stringent requirements on fundamental
timescales. But civil time requires a common sense everyday
compromise. What this entire "début de siecle" discussion has been
about is whether ignoring the whole question for a few hundred years
is more common sensical than continuing to issue occasional small

> If this is a real issue, the market will take over and produce
> watches that have 'navigation time' and 'civilian time' at the
> touch of a button

The market has not proven itself creative in meeting highly technical
needs. Time and again, the market has converged on significantly
less than ideal solutions - Windows, VHS, internal combustion. If
the "magic hand of the market" is the first law (conservation of
energy) of modern economic theory, the second law (entropy) is the
"tragedy of the commons".

Timekeeping is pervasive in our society, but often invisible. As
with the grand environmental challenges confronting this natal
century, market forces threaten to provide - oh so efficiently
provide - the wrong answers to timekeeping questions.

> Of course, purely mechanical watches have other issues when used on
> a boat.

And yet Harrison found a way around these when he invented the first
chronometers - for the express purpose of being used on ships.

> Stating absolutely that UTC is not broken ignores these other users.

UTC is not broken. We may agree or disagree on whether it meets
various civil or technical timekeeping requirements - but "broken"
would imply that it fails to meet its *own* requirements. UTC is
eminently capable of continuing unchanged for many centuries - and
for millennia more with only slight changes. After that, nothing yet
proposed (except for those danged rubber seconds) is any better (see

It would be the abandonment of leap seconds that would break UTC.
Lobbying to base civil time on some underlying timescale distinct
from UTC would be one thing. Conspiring to emasculate UTC is quite

> GLASNOS is a backup system to GPS that is not subject to DoD's
> selective denial of signal.

Glasnost was Mikhail Gorbachev's policy of encouraging open public
debate, particularly in support of "perestroika" - restructuring - of
the Soviet economy. On the other hand, GLONASS is the Russian Global
Navigation Satelllite System :-) In any event, one suspects that the
Russians (or the FSU, even more so) would object to its being
characterized as a GPS backup.

Rob Seaman
Received on Sat Jan 21 2006 - 15:03:20 PST

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