Tesla and SpaceX founder Elon Musk raised eyebrows this week by proposing the Hyperloop, a solar-powered tube that would shuttle passengers between Los Angeles to San Francisco at speeds of up to 800 mph. The idea sounds crazy, and probably won't pan out, but it's still pleasing to see an innovator like Musk giving his imagination free rein, writes John Pavlus. "Yes, ideas are cheap. But where else are we supposed to start?" he asks.