Elon Musk's ideas aren't enough to turn humanity into an multi-planet species

I admit it: I'm an optimist. I wanted Elon Musk to show me a strong Mars plan with real finances and real life-support design. I was hoping he'd talked some of his billionaire friends into financing this Mars dream. I wanted the dream to be real.

Optimists, of course, are frequently disappointed, which is why we're often mistaken for cynics. And so, listening to Musk talk about a ticket to Mars that costs less than $200,000 — the median price of a house in America — I must say: I was disappointed. That number doesn’t square with what is likely to be the enormous cost of making Mars habitable for humans.

Optimists are frequently disappointed I should have realized earlier, when Musk was talking about restaurants in his spaceship, that...