[LEAPSECS] Schedule for success

Rob Seaman seaman at noao.edu
Wed Dec 31 10:37:37 EST 2008

Poul-Henning Kamp wrote:

> Notice the "near": the 0° meridian no longe passes through the

> transit instrument there.

Steve and Richard have replied with their usual level of precision.
We risk getting lost in the details.

I might just remind folks that one arc second corresponds to 30 meters
on the surface of the Earth. At the equator, that means that one
second of time corresponds to 450 meters. (280m at the latitude of
Greenwich.) It is the ITU that is seeking to move the prime meridian,
by about two-tenths of a mile per year at the equator (accelerating

We've had this discussion before. What might be different this time
is that presumably there must now be some plan among the proponents of
the ITU proposal to deal with the obvious and completely unacceptable
implications. Or is there?

Of the several rather absurd options it appears the one the ITU has
selected, perhaps implicitly, is to throw Greenwich Mean Time under
the bus.

I won't belabor in this message why that is not likely to happen in
practice. But again - there are indeed two different kinds of time,
and if you suppress one kind in one place, it will always pop up again
somewhere else.

In any event, a policy for dealing with the prime meridian should
appear in the ITU proposal. If you think this is a non-issue, it
should be easy to describe, right?

And what precisely does the ITU propose to do should the UK not accept
this plan? We've been gleefully informed that people persist in
identifying UTC with GMT. We've been told that GMT is nothing more
than the timezone of Greenwich. We've also been told that the
intercalary corrections will be managed purely by local authorities
messing with their timezones. What if local authorities have
different ideas about the appropriateness of this?

Greenwich Mean Time is (and will be) reified by nature. UTC is
currently reified by GMT. The ITU seeks to wrench the two definitions
apart, but is implicitly insisting that they remain the same so that
the Greenwich timezone can participate in the inevitable intercalary

The ITU's biggest argument is with itself.


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