Re: [LEAPSECS] what should a time standard encompass?

From: John Cowan <>
Date: Tue, 28 Jan 2003 13:13:31 -0500 (EST)

Rob Seaman scripsit:

> 0) Who owns the civil time standards?

The people of the world, as expressed through their various national
and sub-national governments. (In the U.S., the federal government
specifies what time zones exist, but the states decide when and
where to adhere to them.)

> Implicit in the UTC standard is the idea that
> civil time will continue to track the Earth's rotation. (The standard
> actually explicitly states that UTC should be regarded as the general
> equivalent of GMT.) There isn't the slightest notion hidden in the
> standard that this role could be abandoned by simple committee fiat.

Standards were not brought down from Sinai.

> The "users" we serve may, on occasion, be annoyed by leap seconds -
> that does not mean that were they to understand the full implications
> that they themselves would choose to discard this fundamental
> requirement of civil time.

What do you reckon the full implications *to the broader community*, not
to astronomers and navigators, to be?

> Any mandate to reengineer UTC requires
> a far higher level of consensus than other standards discussions,
> a notoriously excruciating process under the best of circumstances.

I agree with that.

> 2) The Keck Observatory estimates that it would cost $110,000 to
> retrofit their systems to support their guess at what the new UTC
> standard might be.

Surely what really matters for observational purposes is LST and various
kinds of dynamical time? UTC is only a retrospective timescale anyhow.

> how this will affect our current GPS, WWV and NTP hardware and software,

GPS is tied to TAI anyway. As for NTP, implementation would be far easier for
it if there were no leap seconds in civil time.

> right?) to geography (disconnect UTC from GMT - what happens to the
> prime meridian?)

Why, nothing. The meridian is a fixed line on the earth, not the places
where GMT = LMT.

> to transportation (have we talked to our friends in
> air traffic control?)

The airline industry cares only about LCT, and would surely be better off
if there were reliably 60 seconds per LCT minute.

> Has anybody even thought
> to ask a lawyer about potential issues? And not Jacoby and Meyers,
> more like Lawrence Tribe.

In common-law countries, at least, fractions of a day (never mind of a
minute) are ignored unless needed to determine the priority of events,
and even then, simultaneous events can be deemed sequential if it seems
useful. For example, an Act of Parliament becomes effective at 0000 GMT
on the day it receives the Royal Assent (with the exception of royal
abdications, which do not become effective until the following 2400).
And when the 1st Duke (I think) of Somewhere and his son were killed in
an air raid during WWII, the son was deemed to have died an unspecified
fraction of a second later, so that his son could inherit the title.

> We've learned that civil time in the U.K.
> is still referenced to GMT (and why wouldn't it be?). Presumably the
> relationship of civil time to UTC in many other countries is also
> cloudy. Should we change the standard before or after figuring out
> this situation? Can the equivalence between UTC and GMT be broken
> before *all* the world's countries sign off on the change? Alternately,
> would neighboring countries really like to return to the days before
> the standard time zones? You would not only have to convince the U.K.
> to support a drifting UTC, you would have to convince them to adopt
> this emasculated standard in preference to one of the last, very
> popular, remnants of the Empire.


> 5) What about cultural and political issues? The international
> climate is incredibly tense. Many religious traditions care deeply
> about calendrical issues and the timing of astronomical events. For
> instance, observatories get frequent requests for lunar and solar
> information from Moslems, Christians and Jews. Is it prudent to
> introduce an obscure change that can be of no possible benefit in
> these calculations - but that just might appear to be a deadly insult
> to a quarter of the world's population? Are politicians from even a
> single country on the globe likely to want to deal with issues like
> these at this point in time?

Surely things were no less tense when UTC became the international standard.

> 6) What about commercial interests? We have a very few projects or
> individuals who appear to be pushing for this change. (Although I'm
> not convinced any of these individuals has even once sent a message to
> this list.) Has anybody asked the manufacturers of commercial telescope,
> navigation, surveying, or - oh yes - timekeeping hardware or software
> what they think about it? (I'm sure that's not a complete list.)

Timekeeping hardware, i.e. clocks, would be a lot simpler if there were
reliably 60 SI seconds per LCT minute.

> What about the related service industries such as planetarium or
> museum education? Millions of amateur astronomers would be able to
> detect the discrepancy between UTC and UT1 after only a few years.

Bully. They might learn something about timekeeping thereby.

> To sum up: the proponents of the notion of abandoning leap seconds
> have some obscure agenda of their own.

What's obscure about it? No secrets here. Forcing civil time to track
the earth's rotation, when 1200 LCT can see the sun halfway up or down the
sky, is overkill and a pain to keep track of. And the list of leap seconds
only gets longer and longer, and fewer and fewer systems possess a fully
up-to-date list.

> This change to the standard
> is a sop to lazy projects who either can't be bothered to use UTC
> correctly - or shouldn't be using UTC at all, but rather, TAI or a
> related timescale like GPS.

I agree. But when LCT is relevant, as is it is 99% of the time, *even to
astronomers* as members of the world community, then why shouldn't it be
straightforward to track it?

> In any event, many of these projects will
> have died a natural death before any change to the UTC standard could
> become a reality.

Civilian timekeeping will not go away. The rotation of the Earth is a lousy
clock, as has been known since before atomic clocks were heard of, when the
standard for the SI second was a fraction of the tropical year.

As I have said before, it was once thought essential that the civil month
track the synodic month, and for some calendars it still does (Hebrew,
Muslim, Chinese are the ones I know about still in active use). But somehow
we learned to deal with the autonomous civil month, even if it meant that
we couldn't tell the day of the month from the phase of the moon or vice versa
any more. So too we learned to deal with the notion that apparent noon isn't
when the clocks strike twelve. The precession of the equinoxes even entered
popular culture (to some extent) forty years ago, with the dawning of the
Age of Aquarius. Can't we cope with this secular shift as well, in the
interest of simplicity for all non-astronomical applications?

Business before pleasure, if not too bloomering long before.
        --Nicholas van Rijn
                John Cowan <>
Received on Tue Jan 28 2003 - 10:14:02 PST

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