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Heres a program from our archives.TORNADO-- ModelAmbience: Tornado ModelTornadoes are one of nature's most destructive forces and they're more common in the United States than any other place in the world. I'm Jim Metzner, and this is the Pulse of the Planet.The sounds we're listening to are coming from a model of a tornado-like vortex inside a large tank filled with water. This twister-in-a-tank is helping scientists learn more about the way tornadoes form and how they change over time.Alfred Bedard is an adjunct professor at the University of Colorado. Bedard: What we have is a cylinder that's transparent and we can pull the water out of the bottom of it with a pump and then we inject it around the sides of the cylinder and that creates a background rotation which we then concentrate just like a skater pulls in their arms and spins faster-- the same thing happens in this tank. The water spins faster and faster as we pull it in. And eventually you see a funnel appear at the top of the tank and it comes down to the ground, and then it starts to make a very loud noise, and that's one of the sounds that we're studying in the tank.By learning about the sounds produced by tornadoes, scientists may someday be able to actually detect them coming from great distances. Bedard: We're hoping that what we're doing here in the laboratory will help us understand what nature is doing with a real tornado. It's very difficult to do a census on such a dynamic and transient kind of thing, and such a dangerous thing to measure.This archival program is part of our thirtieth anniversary celebration. If you want hear more, check out our podcast. Im Jim Metzner and this is the Pulse of the Planet.