Creating a tornado sounds pretty easy, to hear Louis Michaud tell it. All you've got to do, he says, is "produce warm air, give it a spin, and basically have it rise."

He has built machines that do this—and of course, it wasn't quite so easy. With prototype after prototype of his Atmospheric Vortex Engine, the Ontario, Canada-based engineer set out to prove that humans could make their own twisters. He's done so on a small scale, creating narrow, wispy swirls easily dispersed by a strong wind.

To power entire communities, though, it would take a much larger and stronger vortex—30 meters (98 feet) wide and 14 kilometers (8 miles) tall, Michaud says, adding that the force wouldn't be dangerous because