mystery of walking of water solved

No, walking on water is not a miracle, at least not for the small insects known as water striders. But even for striders, the ability has remained mysterious — until now. John W. M. Bush and his colleagues from the Massachusetts Institute of Technology report in the August 7 Nature that they have solved the mystery. Michael Dickinson of the California Institute of Technology writes in a related article, “Much of animal locomotion distills down to a simple application of Newton’s third law: to move forwards, animals must push something backwards.” It was long thought that striders pushed forward off tiny surface waves they created with their long, thin legs. But, even though baby water striders didn’t have enough strength in their legs to generate these waves, they were still able to walk on water. So how do they do it? Using high-speed video and particle-tracking studies to analyze the insects’ movements, the MIT researchers found that water striders’ legs create swirling whirlpools below the surface that propel the insect forward. MIT being MIT, the team also built a robotic version of the insect, named Robostrider, which walks on water, too.

This news brief appeared in the Random Data column of the Boston Globe’s Health/Science section on 8/12/2003.