Re: Impacts and ETs

[David Marjanovic <david.marjanovic@gmx.at>]

>  One reason for the rare Earth notion is the supposed
> need for a stabilizing moon. Dinosaurian history
> suggests otherwise. During the Mesozoic, the whole
> world was warm. Since solar declination had relatively
> little effect on temperature, obliquity shifts
> probably wouldn't have either.

I think you've misunderstood this. The idea is that without a large moon the 
Earth would lose balance and tip over at chaotic intervals. Like Mars has 
done -- on Mars there's no evidence of plate tectonics, but plenty of 
glacial features on the equator. Imagine an obliquity shift of 90° that 
takes, I don't know, days, or perhaps centuries, as opposed to one of 20° 
that takes 40,000 years. Just imagine.