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. Rob