> Of course, the anthropic principle is in full force. Exactly. For instance, there was a time when Earth didn't have a Moon, which would make collisions more

> Of course, the anthropic principle is in full force. Exactly. For instance, there was a time when Earth didn't have a Moon, which would make collisions more likely. At least one of these collisions seems to have created the Moon. We of course are familiar with the version of Earth that has a Moon; it is unlikely that we would have evolved without that Moon such that we were left thinking "Gee, it would be nice to have a moon.." (http://en.wikipedia.org/wiki/Giant_impact_hypothesis http://en.wikipedia.org/wiki/Giant_impact_hypothesis)