Re: [LEAPSECS] more media coverage

From: Ed Davies <>
Date: Thu, 26 Jun 2003 12:13:49 +0100

Steve Allen wrote:
> The Guardian

I thought this was, generally, a quite good article but that the
comments about aircraft navigation system's timescales were a
bit overblown. GPS is just one of the inputs that the navigation
systems use. The main ones are usually the INS, inertial
navigation system, and DME, distance measuring equipment. I'd
have thought that GPS receivers would output UTC and that the
rest of the systems would work with either their own internal
clocks or UTC as required. I'll check this with various people
in the industry (pilots and engineers).

Meanwhile, this article also reminded me of a question that
has been lurking in my mind for a while. We haven't had a leap
second for a while even though:

  1. The Earth has already slowed down enough, on average, to
     need a leap second every year or two.

  2. The usual tidal effects, etc, have presumably still been
     busy slowing it down further.

So, something has been speeding the Earth up for a while. As
this article says - it's not really known what this effect is.
My question: does anybody have a feeling as to whether this
effect is likely to "unwind" at some point resulting in a
faster than normal string of leap seconds? Could we get to
leap seconds more often than once every six months any time

Received on Thu Jun 26 2003 - 04:25:23 PDT

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