Modern Frisbees don't look much like tins from Bridgeport, Conn.'s, Frisbie Pie Company--the decades-old platters behind the name. But they fly through the air for the same reasons. Both are essentially spinning wings that stay aloft thanks to aerodynamic lift and gyroscopic stability.

Forward flight splits rushing air at the disk's leading edge: half goes over the Frisbee; half goes under. Because that edge is tipped up, the disk deflects the lower airstream downward. As the Frisbee pushes down on the air, the air pushes upward on the Frisbee--a force known as aerodynamic lift. The upper airstream is also deflected downward. Like all viscous fluids, flowing air tends to follow curving surfaces--even when those surfaces bend away from the airstream. The inward bend of the upper airstream is accompanied by a substantial drop in air pressure just above the Frisbee, sucking it upward.

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