- News Home
5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
- About Us
How to Walk on Water
7 August 2003 (All day)
Water striders have long baffled scientists with their ability to deftly skate atop ponds and rivers. Now a study shows that the delicate insects paddle with their legs to whip up whirlpools that thrust them forward. All without getting even a drop of water on their bodies.
For at least a decade researchers thought that water striders are pushed along by short waves created in their wake as their legs slide around across the water's surface. If this theory were true, baby striders whose legs are too slow to generate waves shouldn't budge. But the infants don't have a problem with water walking, and scientists were left perplexed. This puzzle intrigued John Bush, an applied mathematician at the Massachusetts Institute of Technology.
Bush and colleagues filmed the bugs in a laboratory aquarium using a high-speed video camera. They noticed that the insects shifted their two middle legs in a rowing motion as they danced across the water. When the group then added a blue dye to the water, they saw swirling eddies directly below the creatures' moving legs. The vortex effect was even more obvious when the researchers put small trackable particles into the pool and watched the patterns they made under the striders. Combining these observations with a few mathematical calculations revealed the answer: By paddling and pushing as hard as they could on top of the water without penetrating it, the striders created strong semicircular currents that pushed them forward, the team reports in the 7 August issue of Nature.
To put their theory to the test, the group built an aluminum strider about 10 times the size of a normal strider. Robostrider was able move just like its live counterpart, making swirling whirlpools below its quickly revolving legs without getting wet. The subsurface vortices turn out to have even more momentum than the waves that the adults make in their wake, Bush adds. And even the smallest striders, which can't make waves, can still stir up the semicircular currents, Bush calculates.
"It's a very nice piece of work that contributes a real understanding of what propels these organisms," says Steve Childress, an applied mathematician who studies hydrodynamics and locomotion at New York University.