Re: [LEAPSECS] Defining our terms (was Re: [LEAPSECS] Longer leap second notice)

From: Steve Allen <sla_at_UCOLICK.ORG>
Date: Fri, 6 Jan 2006 16:07:21 -0800

On Sat 2006-01-07T00:32:44 +0100, Poul-Henning Kamp hath writ:
> Owned by BIPM / Metre Convention

This is indisputably agreed to be true since the demise of the BIH.
I know of no endorsement for the use of TAI outside of metrological

> UTC(time) = TAI(time) + Leap(time)
> Owned by ITU.
> IERS evaluates Leap(time) according ITU definition

Not quite. The endorsement for the usage of UTC comes from CGPM,
and that is predicated on the existence of leap seconds.

But in the original agreement, UTC and TAI were defined solely by the
BIH according to the rules of the CCIR. Both the BIH and the CCIR are
defunct. TAI was transferred from BIH to the BIPM. Determination of
the UTC offset was transferred from BIH to IERS. But IERS is not
a single entity, it is an ensemble of entities.

The branch of the IERS responsible for the UTC offset currently
asserts that it is still following the UTC rules from the CCIR before
there was an IERS.

At the beginning of 1984 and at the beginning of 2003 the branches of
the IERS responsible for UT1 followed new IAU recommendations and
changed the rules by which UT1 is calculated. The current version
of UT1 has a notably different flavor and long-term purpose than
the version of UT1 which was in place when UTC with leap seconds
was originally defined by the CCIR.

The whole scheme works now because there is still consensus about
the way in which the original agreements are to be interpreted.
It remains to be seen whether the gentleman's agreements which hold
this whole scheme together will tolerate a non-consensual arrangement.

> Now tell me why you think Leap seconds are so important again.

In a word, I offer psychology.

Steve Allen                 <>                WGS-84 (GPS)
UCO/Lick Observatory        Natural Sciences II, Room 165    Lat  +36.99858
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Received on Fri Jan 06 2006 - 16:07:43 PST

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