I found an interview with Peter Ward (atheist) and Donald Brownlee (agnostic) discussing astrobiology in Forbes magazine. They were asked about how important plate tectonics are for a planet to be able to support complex life.
Astrobiologists often cite the sheer numbers of stars and galaxies as evidence that complex life elsewhere must surely have evolved somewhere. But is probability enough?
Without a moon, we don’t have any idea of how commonly a planet could have the long-term stability needed for complex life. Until we “get” that, going to the sheer numbers argument is useless. Without that moon-forming collision, we wouldn’t have plate tectonics. Without plate tectonics, we might have microbes but we’d never get to animals.
What about the rarity of earth’s crustal dichotomy of oceans and continents?
If you can’t make granite, you’re not going to have continents. But granite…
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