Space/Science — HabitableZone

Space/Science » in reply to Wouldn't it be nice

re: Wouldn't it be nice
Andrew — (archived)

I don’t want to be a downer, and I know this is a well hashed argument with no answer, but just because there are many earth-sized planets doesn’t mean that there are many technologically advanced life forms.

1: Earth may be special (for example it underwent a very major collision early on to form the moon-earth system which probably blew away a lot of atmosphere and water).

2:Of the earth-related bodies that we can explore, earth-like life is present at only 1 in 4 of the sites. Mars is too dry and cold (and it now seems probably never supported live even when it was wetter), Venus is a nightmare, Titan is chemically fascinating but terribly cold, and if there is any kind of life there it is of a kind we would find difficult to recognize. One of the most fundamental insights to have come from the space program is how varied is the evolution of the planets and moons, and this is surely only going to expand as we go beyond our system. Earth-related bodies may be very common, but earth-like bodies are going to be much rarer.

3:Add to that the several near-total extinctions we underwent throughout the history of life on earth- it would take only on to have been total and its game over.

4: There is no compelling reason why biological evolution would run the same course that led to human intelligence even if it rerun elsewhere (i.e. Stephen Jay Gould’s argument for the contingency of evolution).

5. Human evolution went through bottlenecks of near extinction (our species being the only one to make it through). Given a drought at the wrong time and place, or a virulent disease, or a large scale eruption etc and our species might easily have gone extinct almost before we got started.

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