Models of galactic colonization implicitly assume that the important objects out in space are stable, middle-aged, G2-type stars such as the Sun and watery planets such as Earth. But who knows where a civilization much older than ours would choose to live? Even if Earth-like conditions are necessary for the genesis and early evolution of life, once a civilization is technologically advanced and can construct a habitat for itself it might not want to remain on the surface of a planet orbiting a commonplace star. We tend to think ETCs would love to get their hands (tentacles, feelers, whatever)
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