[LEAPSECS] Meeting with Wayne Whyte

Michael Deckers michael.deckers at yahoo.com
Tue Feb 1 15:24:06 EST 2011

On 2011-02-01 11:35, Poul-Henning Kamp wrote:

> Thanks to leap-seconds we do not know how long (certain) minutes

> are, until Daniel tells us.

Daniel Gambis does not define certain time units, he just
communicates the difference TAI - UTC as soon as it becomes
known for another six months.

> "UTC is unpredictable" is the core of the problem, and a problem

> that must be solved, either by extending the predictability horizon

> from six months to at least 10 years, or by making UTC predictable.

What currently is unpredictable far into the future is the
difference TAI - UTC. Now the difference TAI - TT is also
unpredictable -- but is that a reason to say that either TAI
or TT is unpredictable, or to redefine one of them?

As far as the civil uses of time scales are concerned, it is actually
UTC rather than TAI that is currently more "predictable": I can
predict with great certainty that I shall attend a group meeting
when UTC will be 2012-01-30 + 09 h, but TAI at that instant is
currently only known with an uncertainty of 1 s.

How could the unpredictable difference TAI - UTC be a
problem if everybody (including every computer) just kept UTC?

Michael Deckers.

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