Re: [LEAPSECS] trading amplitude for scheduling

From: Tom Van Baak <>
Date: Fri, 4 Aug 2006 20:02:57 -0700

> If the SI second were properly tuned to the mean solar day, and the
> secular slowing were eliminated, there would be no need to mess about with
> the civil time scale, because the random accelerations and decelerations
> would cancel out in the long run. Of course, we'd have to tolerate larger
> differences between clock time and terrestrial time, but we'd expect that.

My understanding is that, in addition to astronomical
effects (lunar/solar tides), no small number of geological
and climatological phenomena also contribute to the
instability of the mean solar day. That all the random
accelerations exactly cancel all the random decelerations
in any finite time, short- or long-term, is very unlikely.

If LOD variations were white noise then, yes, a "true"
mean solar day would exist; the longer you average the
more precise you get. I'm guessing a cold, solid-core
planet without an atmosphere or moon(s) would be
closer to this ideal than our dynamic earth.

Received on Fri Aug 04 2006 - 20:04:07 PDT

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