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Walking on water without making
waves
Roger Highfield, Science
Editor
(Filed: 12/08/2003)
The secret of how to walk on water is out. A team has
not only discovered how insects called water striders managed it but
has built a mechanical version called Robostrider that can skim
aquatic surfaces.
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The secret of walking on water is out, thanks to the
water strider |
Water striders, which can grow up to eight inches,
have long, hairy legs to keep them afloat on ponds and rivers. But
their ability to walk on water has left researchers perplexed for
the past decade or so.
Many thought that the animals moved forwards by
creating surface waves that carry momentum backwards. This means,
theoretically, that baby striders should be immobile - and yet they
skim along as easily as adults.
Today, in the journal Nature, Dr John Bush and
colleagues of the Massachusetts Institute of Technology reveal the
secrets of their propulsion.
Their legs act like the oars of a rowing boat. A
water strider's legs create swirling vortices that carry momentum
beneath the surface. And it is the rearwards motion of these
vortices, and not the surface waves, that propel them forwards.
Researchers have now built a light-weight, life-sized
replica. Like its inspiration, Robostrider generates tiny waves and
vortices as it moves along. "That was the proof of concept.''
Dr Bush said that humans are too big to exploit the
same mechanism, and instead would have to have "very large
feet".
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