Re: [LEAPSECS] Leap second status?

From: John Cowan <jcowan_at_REUTERSHEALTH.COM>
Date: Wed, 4 Dec 2002 15:31:04 -0500

Rob Seaman scripsit:

> (Imagine trying to convince your grandparents of the need to switch.)

Well, hey, our grandparents were convinced to switch from LCT to UTC +/-
some number of minutes, to say nothing of DST changes.

> > No, no, the second is a fundamental unit of time duration. It must not
> > be futzed with.
> But redefining the duration of the second is a tool that we've previously
> used for this task.

We have (AFAIU) switched the definition of the second from one mode to
another so as to improve its precision. We have not (AFAIU) adjusted
its value in such a way that low-precision devices would now be flat
wrong as opposed to merely low-precision. In particular, a change of
one part in 10^4 (or even 10^5) has not happened.

(What is the SEM for the best crystal timekeepers?)

> "Simplification" is an interesting concept. Any changes must not only
> simplify the description of the standard - they must simplify the
> operational requirements. "Robustness" is another interesting concept.
> To encourage robust system design, does one sweep technical realities
> under the rug?

Today's technical realities are tomorrow's obsolete constraints.

> The notion of a leap second "freeze" is identical to implementing a
> much larger tolerance on DUT. At some point, it is inevitable that
> future members of this community will decide to resync GMT and UTC.
> This is the same old trade of the latency between leap jumps with
> the amplitude of the jumps. For the SRG to vote "to exclude from
> consideration all redefinition options except freezing the number of
> leap seconds" is misleading.

I agree that eliminating all options except a freeze was tantamount to
saying "Do nothing."

> So - too frequent leap jumps are perceived to be a problem. If we're
> ever going to issue leap jumps at all, so are too *infrequent* jumps.

To me, it's *unpredictable* jumps that are the problem.

> My choice? Fully implement the current standard, such that - when it
> eventually become necessary, many years hence - leap seconds are allowed
> to occur at the end of every month, not just December and June. This
> will keep the size of the jumps small - and will avoid lengthy separations
> between the jumps such that hardware and software engineers will be
> encouraged to address the *actual* technical tradeoffs.

I have no technical difficulty with handling leap seconds at any rate up to
one per minute (after that, I have to change things). But I jib at keeping
a table of every minute, forever, constantly being updated, to keep track
of whether that particular minute contained 60 or 61 seconds, according to
an arbitrary pattern reflecting the rumblings and bumblings of that
more than crappy clock, the rotation of the Earth.

John Cowan
To say that Bilbo's breath was taken away is no description at all.  There are
no words left to express his staggerment, since Men changed the language that
they learned of elves in the days when all the world was wonderful. --The Hobbit
Received on Wed Dec 04 2002 - 12:52:07 PST

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