He's called it a cross between a Concorde, a rail gun and an air hockey table, but that's pretty much all we know about Elon Musk's mysterious Hyperloop.
The entrepreneur behind Tesla and SpaceX is expected to announce today how he plans to get travelers between L.A. and San Francisco in 30 minutes. Physicists and tinkerers have been coming up with their own ideas about how this futuristic transportation system might work.
Physics professor and Wired magazine blogger Rhett Allain joins the show to break down some of these ideas.
RELATED: Inventor Musk shares plans for high-speed 'Hyperloop' travel (PDF)