WOW, I guess no one on HN remotely thinks humans and the earth are facing any sort of environmental problems at the moment. All everyone here is talking about is the profit margins and logistics of pulling this preposterous, albeit very cool, idea off. I'm all for adventure, technology, progress, blah blah blah. I am thrilled about the possibilities of space. But realistically I think we as a species need to better undertand ourselves and create better; more sustainable systems on our native plannet before we embalance our natural habit and ecosystem on an intergalactic scale.