“The truth is, preparing for interstellar travel and then sending out ships filled with colonists is bound to be a job so long, thankless, expensive, and difficult that I suspect that only a religion could do it. A lot of people will find ways to make money from it. That might get things started. But it will take something as essentially human and as essentially irrational as religion to keep them focused and keep it going—for generations if it takes generations. I suspect it will. You see, I have thought about this.”