I read a Scientific American article that I’d like to share. It discusses the problems of interstellar colonization.
Basically, since it would take millennia to reach an inhabitable planet – and people live for decades, the ship would need to carry a breeding population, thus being huge and fragile. Huge and fragile because it would be a isolated island population, having to live in a confined space for centuries at least.
I’m not as pessimistic though. I suspect that by the time anyone thinks about sending humans to another planet, other technologies will advance to the point that the crew could either be frozen, or have their minds downloaded into a computer, then uploaded to either an android body or clone. Really, the possibilities are amazing when you talk about centuries from now. It may be that advances in cybernetics and AI will render the need to colonize other livable planets mute and the next stage of human evolution may be the machine.