SpaceX CEO Elon Musk made a splash at the International Astronautical Conference in Mexico with his plans for an Interplanetary Transport System, along with a disturbingly inspirational ultimatum:

“There are really two fundamental paths. One path is we stay on Earth forever and there will be some eventual extinction event. . . . The alternative is to become a space-faring civilization and a multi-planet species, which, I hope you would agree, that is the right way to go.”

Unless we slip the surly bonds of Earth, humankind is doomed. The only alternative -- the right thing to do -- is to...