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Airdate: Sep 13, 2010
Scientist: Christopher Viney

Maple Seed Drop - How it Works

Maple Seed Drop - How it Works
Scientists are baffled by the way in which a maple seed spins to the ground to slow the rate of its descent.

Transcript:

CV: What do you notice on that drop?
OD: The tiny one fell slower but the big one did slow down right before it hit the ground

JM: Fifth-grader Olivia Smith Donovan is dropping maple seeds and watching them twirl to the floor. Maple seeds were the inspiration for Olivia's winning idea in last year's Kids' Science Challenge. Now she's working with University of California engineer Christopher Viney to design a device that could be used to drop relief supplies from an airplane, using the aerodynamics of a falling maple seed. I'm Jim Metzner and this is the Pulse of the Planet.

CV: When a maple seed falls from the tree, it starts to rotate. It's sort of like a Frisbee in the way that it spins and, by spinning, it also slows down as it falls. So, really, the spinning is a way to transfer some of the energy that would normally be converted into speed. Some of that energy's turned into rotation, and that helps break the fall of the seed so it gives it time to be caught by the breeze and blown somewhere, you know, to grow a new tree. Now, of course, if we could do this with something heavier, then the breeze wouldn't be blowing it all over the place, but, again, hopefully, it would break the fall of something that you wanted to land gently. So, a water bottle that would go splat and break on the ground, hopefully, would arrive at a speed that didn't cause the water bottle to break.

JM: Interestingly enough, scientists still don't understand why a maple seed falls the way it does.

CV: People can observe it, they can see that when it falls, it spins, and that slows down the rate of fall. But what exactly is about the maple seed that causes it to spin, and what would-if you wanted to copy that and build on it, what would optimize the rate of spin so that it falls as slowly as possible? People don't really know much about that.

JM: We'll hear more about maple seed experiments in future programs. Next month we launch a new Kids' Science Challenge, our free nationwide competition for 3rd to 6th graders. Check out kidsciencechallenge.com.

Pulse of the Planet is made possible by the National Science Foundation. I'm Jim Metzner.