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December 28, 2010



Lilliputians would have problems walking as well, with their low weight and short legs. Bodies are in circular motion as they walk. Imagine that your leg is a spoke on a wheel, and your foot is the axle. you plant your foot and your hip moves in an arc from behind your foot to in front of it, where your other foot gets planted and you repeat the motion. It's not awfully hard to calculate maximum walking speed, and it is given by sqrt(gr) where g is the acceleration of gravity and r is the length of the leg. If you want to go faster than this, you'll break into a run; there's a limit to how fast you can walk.

The average human leg is 0.7 m long which means that the average Lilliputian leg is 0.06 m long (that's rounded), and his maximum walking speed is 0.76 m/s or 1.7 mph. Remember, this is walking as fast as he possibly can, not just at a brisk pace. Because of his low weight and short legs, our Lilliputian would probably end up running everywhere (like mice do) or hopping like many small birds. The astronauts on the moon hopped and jumped from place to place because their maximum walking speed (due to low lunar gravity) was about 1 m/s, which was much too slow to get anywhere. But their muscular strength was such that they could jump dramatically longer distances than they could on Earth, much like Gulliver's little friends!

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  • Diane A. Kelly
    Diane Kelly is a Senior Research Fellow at the University of Massachusetts, Amherst, where she studies the neural wiring and mechanical engineering of reproductive systems.
  • James L. Cambias
    Jim Cambias writes science fiction and designs games in the lonely wilderness of Western Massachusetts.