Re: [LEAPSECS] Leap-seconds, the epsilon perspective

From: John Cowan <>
Date: Wed, 29 Jan 2003 06:48:48 -0500 (EST)

Steve Allen scripsit:

> Which is more important...
> for civil time to be counted in SI seconds?
> for civil time to track the rotation of earth smoothly?

IMHO the former.

> Mark's alternative resembles the civil time solution adopted by the
> martian colonists in Kim Stanley Robinson's "Red/Green/Blue Mars"
> trilogy, where the clocks tick SI seconds, but every day at midnight
> they stop for 39.5 minutes of "slip time" to let the planet catch up.

I always thought that was silly. How do you keep experiments running
(not necessarily precision-time ones, just ordinary ones) while your
clock is saying "midnight, midnight, midnight, midnight, ...". And
what about Martian time zones?

> If we have decided that SI seconds are to be used,
> which is more important...
> for civil time to keep noon from drifting?
> for civil time to increase constantly?

The later. Non-monotonic civil time would be a disaster, and we are
very lucky in the current regime that rotation is slowing and not
speeding up.

> Partly because eventually the scheme of turning UTC into a constant
> offset form of TAI requires a leap hour lest our descendants find
> themselves having their midday meal at 18:00 local civil time. This
> sort of pushing the problem off onto our descendants implies that we
> really don't have the right solution, just one that salves some needs
> now.

I think it's utopian to suppose that a "right" solution exists; we are
trying to reconcile the fundamentally irreconcilable. Eventually (a
very long time from now) we *will* have to abandon the 86400 seconds = 1 day
assumption. (I utterly reject any attempt to redefine the SI second.)

> > > I suspect this would account for 99.9% of the world's clocks,
> > > including the clocks inside most computers, VCRs and microwave
> > > ovens; on your wrist; or next to your bed.
> >
> > Hmm. How reasonable is it to expect this to change in future?
> If the future is a world of ubiquitous networking where Bill Gates can
> make every wristwatch and refrigerator magnet into a .NET client, then
> we should very much expect this to change.

Not what I meant. I meant, how reasonable is it to expect to find 10^-8
reliable clocks in ordinary hands in the future? If every clock is
indeed networked (a very unlikely future, I'd say), then of course the
time scale can be arbitrarily futzed with and all clocks will stay in sync.

John Cowan
Please leave your values        |       Check your assumptions.  In fact,
   at the front desk.           |          check your assumptions at the door.
     --sign in Paris hotel      |            --Cordelia Vorkosigan
Received on Wed Jan 29 2003 - 03:49:01 PST

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