He had become fascinated by Fermis Paradox, named after the Italian American physicist Enrico Fermi, who in a discussion of alien life in the universe said, But where is everyone? Mathematically it seemed logical there were other civilizations, but the lack of any evidence raised the uncomfortable possibility that the Earths human species might be the only example of consciousness. Weve got this delicate candle of consciousness flickering here, and it may be the only instance of consciousness, so its essential we preserve it, Musk says. If we are able to go to other planets, the probable lifespan of human consciousness is going to be far greater than if we are stuck on one planet that could get hit by an asteroid or destroy its civilization.

Elon Musk by Walter Isaacson