Re: [LEAPSECS] Comments on Civil Time decision tree

From: Rob Seaman <>
Date: Mon, 26 Sep 2005 12:40:11 -0700

On Sep 26, 2005, at 11:56 AM, Poul-Henning Kamp wrote:

> Again: merely trying to point out that the "only one timescale"
> argument Rob pushes doesn't work.

This misrepresents my position. There are clearly many time scales
for many purposes. One of those purposes is something that might be
referred to as "International Civil Time". It is this civil time
scale that is the key issue for any proposed change to the current
UTC standard. Personally, I am happy to acknowledge that no such
international standard currently exists. Shoehorning UTC into that
role is not a very good fit, at least not if it is asserted that we
must destroy UTC in order to save it.

It is rather clever how UTC manages, through the mechanism of leap
seconds, to transport both Universal Time (Mean Solar Time) and
Atomic Time in one convenient package. The convenience of this
mechanism is being criticized. Either those criticisms are invalid,
in which case the ITU proposal should be rejected - or the criticisms
are valid, in which case it may well make sense to explicitly
separate Atomic Time from Solar Time. Perhaps that is what you mean
by your statement above.

But, in a world with separate time scales for Atomic and Solar Time,
it seems far more likely that any representation of International
Civil Time should be based solely on Solar Time, not on Atomic Time.
For the vast majority of cases, Civil Time clearly "mimics" - and
must continue to mimic - Solar Time. Doesn't it make more sense to
simply reconfirm the wisdom of the ages that Civil Time IS Solar Time?

E pur si muove!

Rob Seaman
National Optical Astronomy Observatory
Received on Mon Sep 26 2005 - 12:41:24 PDT

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