I like his ideas about biological life not being suited to spread throughout the galaxy, that it's going to be mechanical or at least completely engineered. If

I like his ideas about biological life not being suited to spread throughout the galaxy, that it's going to be mechanical or at least completely engineered. If that's the case, why would engineered life ever want to land on a planet? It seems easier to take everything from asteroids and stay near shining stars and away from other gravity wells. Visiting/colonizing planet Earth doesn't make much sense, other than the challenge.