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Re: ITC copped out on UTC again

2012-01-20 09:14:54
Nick Hilliard <nick(_at_)inex(_dot_)ie> wrote:

Your arguments in favour of abolishing leap seconds are all good.  But can
you please do us all a favour and provide a similarly lucid list of reasons
that an apologist would use to say that leap seconds should be kept.

I agree that leap seconds are a horrible bodge that would be best got rid
of. The reasons to keep them mainly revolve around systems that require
UT1, i.e. the angle of rotation of the Earth, and the protocols that
disseminate UT1.

These include:
Astronomical systems
Space and satellite ground stations
Time broadcast standards

Many protocols and software implementations rely on the guarantee that
DUT1 (the difference between UTC and UT1) is less than 0.9s. For instance
many time broadcast formats don't have space for larger values of DUT1.

Many instruments that point at the sky rely on the fact that DUT1 <
0.9s for establishing an initial rough aim.

For more examples see http://futureofutc.org/preprints

At a more philosophical level a lot of people find it difficult to accept
the idea of decoupling time from Earth rotation, to the extent that they
say it is obvious nonsense or foolishness, even though the rate error is
only one second every year or two. However UT1 is slowing down
quadratically, so the time scales will diverge increasingly rapidly.

We can paper over this difference by adjusting time zones every few
hundred years. In fact time zone adjustments will work further into the
future than leap seconds. But speculating about what will happen that far
into the future is foolish.

Numbers for divergence between UTC and TAI:
http://www.ucolick.org/~sla/leapsecs/dutc.html#dutctable

Tony.
-- 
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