Given that our Earth isn't faring too well, it seems that this is a necessary to make. Besides climate change, Earth has a host of other problems. Overpopulation is the overarching one, and with it comes a depletion of non-renewable resources. I'm not just talking about oil here-we're on track to run out of necessary metals such as zinc and copper in the next century. So an option is always on the table that we begin colonizing other places. Where, when, and how would we do this?