Summer in Ithaca, New York, is a good time to watch dragonflies. At a glance, you can see that a dragonfly has a prominent head, an elongated body, and two pairs of slender wings extending to each side. As it takes off, the wings appear as a blur. In air, the dragonfly dances in unpredictable steps, hovering briefly then quickly moving to a new location. Just when you think it might stay long enough in the viewfinder of your camera, poof! It is gone. In contrast, an airplane, noisy and powerful, has a more straightforward way of going about its business. Propelled by engines and lifted by wings, it wastes no time in going from one place to another.

Just as people do when they swim or row, planes and insects generate thrust by pushing a fluid. Unless the fluid flow is symmetrical, which is rare in nature, a...

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