Billionaire Elon Musk unveiled plans yesterday for his new Hyperloop transportation system.  It’s supposed to be able to make the trip from Los Angeles to San Francisco in half an hour.  But he’s not planning on actually building it, so for now it’s just a concept.  (It’s basically a train that travels inside a tube, floating on an air cushion and propelled by electric motors.  He says the whole thing can be powered by solar energy, and it will actually generate more energy than it uses.  Top speed is supposed to be 800 miles an hour!