On Tue, 2 Jan 2007, Rob Seaman wrote:

> Daniel R. Tobias replies to Poul-Henning Kamp:
> >> Has anybody calculated how much energy is required to change
> >> the Earths rotation fast enough to make this rule relevant ?
> >
> > Superman could do it.  Or perhaps he could nudge the Earth's rotation
> > just enough to make the length of a mean solar day exactly equal
> > 86,400 SI seconds.
> Only briefly.  Consider the LOD plots from http://www.ucolick.org/
> ~sla/leapsecs/dutc.html.  The Earth wobbles like a top, varying its
> speed even if tidal slowing is ignored.
> Actually, rather than being merely a troublemaker, the Moon serves to
> stabilize the Earth's orientation.  The "Rare Earth Hypothesis" makes
> a strong case that a large Moon and other unlikely processes such as
> continental drift are required for multicellular life to evolve, in
> addition to the more familiar issues of a high system "metal" content
> and a stable planetary orbit at a distance permitting liquid water.
> Without the Moon, the Earth could nod through large angles, lying on
> its side or perhaps even rotating retrograde every few million
> years.  Try making sense of timekeeping under such circumstances.
> Rob Seaman

Hang on a minute, statistically planets in the Solar System do not have a
large moon and yet are "upright"; for example Mars comes very close to the
conditions required to generate a leapseconds email exploder.


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