[time-nuts] FW: Bulletin C number 30

Warner Losh imp at bsdimp.com
Tue Jul 5 15:15:30 EDT 2005

> At 01:05 PM 7/5/2005, Warner Losh wrote...
> >        (2) UTC is an externally imposed requirement.  Our users have
> >            different needs for things, but UTC is a standard, and
> >            we must provide it.

> Well then, the cost argument goes away - it is simply a cost of
> doing business. TAI is also a standard.

Nobody want TAI.  Nobody.  Everything is done in terms of UTC in the
time and frequency business.

> >        (3) It is called UT1 these days.
 Don't be pedantic. The point is that there are organizations which
> depend upon a time coordinate system which is closely linked to
> astronomical time. UTx/xMST, whatever.

I'm sorry, but all the time issues is about being pedantic.  If you
can't be pedantic, you will make mistakes.

The main argument for elimination of leap seconds is that the
astronomy folks that want UT1-UTC < 1s can adapt more cheaply than the
rest of teh world dealing with unpredictable, random leap seconds.  It
is important to know exactly what you are talking about.

> >Why do you refuse to accept the fundamental message I'm telling you,
> >based on my first hand experience:
> >
> >        Leap seconds have a huge cost associated with them, and they
> >        insinuate themselves into many areas one might not naively
> >        have thought of.

> Why do you refuse to recognize that eliminating leap seconds from
> UTC has huge costs to other organizations? If you're required to use
> UTC because of regulation, then your costs are just a part of doing
> business. If you're not supporting the elimination of leap seconds
> from UTC, then your posts have no purpose unless your're just
> looking for a little sympathy.

I could reduce the cost of doing business by eliminating them.  I've
not been arguing for their elimination in this thread.  I've just been
providing data to show that they have a real, unseen cost.  It is my
belief that the cost of everybody doing leap seconds is much higher
than the astronomers just coping with UTC/UT1 drifting apart.

> UTC was specifically intended to follow astronomical time closely,
> that is the only significant way it differs from TAI. That some
> regulators require you to use it is no reason to change it's
> fundamental nature. Work on changing the regulations instead of
> breaking something which is working as intended.

UTC was intended to be a civil time.  It was thought that it would be
best if it followed astronomical time.  Maybe that fundamental thought
is just wrong.

Over the next few hundred years we'll have several problems with leap
seconds.  As the rate of the earth slows, we'll need them more and
more.  Somewhere near 2072 the UTC-GPS offset will overflow 7 bits.
Somewhere in the next hundred years we'll need more leap seconds than
we can do by doing 2 per year.  For long range analysis of these
effects, you can look at
http://www.ucolick.org/~sla/leapsecs/dutc.html to see that there will
be increasing problems with leap seconds as we move forward and the
earth's rotation continues to slow.


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