How Crazy Is Elon Musk's Mission to Mars?

Yesterday, billionaire tech entrepreneur and noted late guy Elon Musk unveiled his hotly-anticipated plan to send humans to live --and die --on Mars. And not just a few humans: a lot of them. In a talk that wavered between overreaching science fair presentation and straight-up science fiction, Musk described sending fleets of spacecraft, each packed hundreds of colonists, to live on a dusty, airless wasteland that we're apparently going to fix up with nuclear reactors and artificial magnetic fie...