Peter Bunclark wrote:

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.

I checked the DDA box on my AAS form, but nobody would mistake me for
a dynamical astronomer.  Folks will note that all my arguments focus
on the requirements for civil timekeeping, not on the many, various
and sundry technically distinct scales used for "professional" purposes.

I actually think all the nice folks at the alphabet soup of
international agencies have been doing a swell job of timekeeping
(even given occasional formatting anachronisms associated with
Bulletins C & D, for instance).  Those who are pushing the absurd
notion of leap hours simply need to be protected from themselves.  It
might also be nice if they called on experts in other technical
disciplines to help resolve these issues and to improve time
standards and infrastructure.

In any event, the requirements placed on technical timekeeping tend
to be simpler (if more rigorous) and thus are easier to meet.  Civil
timekeeping is the real challenge - just like creating functioning
legal and electoral systems for the masses, etc.

Your argument on this point is not with me, but with Peter Ward and
Donald Brownlee.  I heartily recommend their book, "Rare Earth:  Why
Complex Life is Uncommon in the Universe".  I was somewhat skeptical
about this, too.  As you point out, upright planets and satellites
appear not to be statistically uncommon.  Perhaps someone who knows
the literature in this area could provide some references?

Also note that the various effects (see the wikipedia "rare earth"
page) aren't separable.  An ocean appears to be needed for plate
tectonics, as may a large moon.  Planets or satellites orbiting near
to their primary will be tidally locked (or in interesting
resonances).  The ocean is of obvious importance to providing an
environment stable enough over the long term to nursemaid complex
organisms, but plate tectonics may be similarly important to buffer
atmospheric CO2 through sequestration via subduction.  The planet
should rotate under its star to provide even illumination and
heating.  Etc.


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