Re: [LEAPSECS] ideas for new UTC rules

From: Rob Seaman <seaman_at_noao.edu>
Date: Fri, 14 Apr 2006 09:44:22 -0700

On Apr 13, 2006, at 10:41 PM, Steve Allen wrote:

> Today is one of the four days in the year when Newcomb's
> expression for the equation of time has a value of zero.

...and it was Samuel Beckett's hundredth birthday. Leap second as
Godot:

        ESTRAGON:
                And if he doesn't come?
        VLADIMIR:
                We'll come back tomorrow.
        ESTRAGON:
                And then the day after tomorrow.
        VLADIMIR:
                Possibly.
        ESTRAGON:
                And so on.
        VLADIMIR:
                The point isó
        ESTRAGON:
                Until he comes.
        VLADIMIR:
                You're merciless.
        ESTRAGON:
                We came here yesterday.
        VLADIMIR:
                Ah no, there you're mistaken.

> I suspect that this is almost certain to offend everyone.

Ok, I'll bite - you scurrilous traitor!

Yesterday was also Maundy Thursday - the day Judas betrayed (or did
he?) Jesus.

Today, of course, is the anniversary of Lincoln's assassination.

> I would not be surprised to learn that the Time Lords are
> already contemplating a scheme akin to this one.

One suspects the Time Lords have never seriously considered
any option that would preserve leap seconds in any form, to any
tolerance, utilizing any scheduling algorithm - no way no how.

> ======Educate, educate, educate.

...but can you explain your scheme in under 23 seconds?

> The ITU-R should openly publish the UTC specification.

Boy! On this Easter weekend one has to believe that this
would require a miracle second only to the resurrection.

The reality is that the ITU-R "specification" is just a minor
footnote pertaining to obsolete technologies of time signal
transport. One presumes nothing would stop the IERS from
publishing any scheduling algorithm such as you describe.

> The IERS should enter into dialog with the International Virtual
> Observatory Association (IVOA) and the Internet Engineering Task Force
> (IETF) to determine an adequately robust scheme for guaranteeing the
> distribution and availability of the XML documents which give the
> schedule of upcoming leap seconds.

This was indeed one of the notional use cases for VOEvent
(http://www.ivoa.net/Documents/latest/VOEvent.html).

The specification might benefit from dedicated IETF blessed
support for leap second "aware" semantics, but it would be trivial
even using the current standard to represent such a schedule.
The emerging VOEvent transport protocol(s) could certainly
propagate leap seconds as easily as reports of Supernovae,
Gamma Ray Bursts and Earth-killer asteroids.

To hear the detractors talk, a leap second is made to seem as
dire an event as these cosmic catastrophes.

> As the five year prediction scheme goes into effect this will probably
> mean that there will be times when UT1 - UTC exceeds 0.9 seconds, but
> not by very much.

Cannot simultaneously constrain look-ahead and DUT1 tolerance.
Suggest that rather than pick any fixed window, it is sufficient
to define a mechanism and format for reporting the schedule -
whatever it may be at any given time. After all - what if the
state of the art improves enough to permit accurate ten year
predictions?

Simply allow the IERS to announce any number of leap seconds
in advance extending over any time horizon - and yes - occurring
at the end of any month. If predictability is the goal, relaxing
unnecessary constraints is the solution.

Actually - one presumes the IERS currently has the authority to
do both of these things. Have never heard anyone suggest that
the next two leap seconds might not be announced simultaneously.
And the ITU-R has already signed off on the monthly scheduling
of leap seconds - this is the law of the land.

What precisely is stopping us from implementing some variation
of Steve's scheduling algorithm right now, today, this minute?

All in favor, say aye!

> I am still not convinced that there is any need for change. I would
> like to see further examples of why the status quo is not tolerable.

I think even this gives the current "process" too much credit.
There has not been a single cogent example of any negative
consequence of leap seconds described in a convincing and
well characterized fashion. Moaning and moping is not the
same thing as making a coherent argument.

Surely someone could draft a two page white paper describing
to some (any) level whatsoever of technical, scientific, economic
or sociological detail exactly what dreadful things happen to some
particular system in the presence of a leap second? And more to
the point, to provide evidence why we should believe the cure won't
be worse than the disease.

Rob Seaman
National Optical Astronomy Observatory
Received on Fri Apr 14 2006 - 09:44:40 PDT

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