Scientists at Utah State University have figured out how to make the perfect skipping stones. The secret was making sure they were made out of a material that had much more give than stone.

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Inspired by a toy called the Water Bouncing Ball, the USU team, led by the Splash Lab’s Tadd Truscott, collaborated with the Naval Undersea Warfare Center to figure out what makes certain moving objects, like balls or stones, walk or skip across water.

“Our approach was playful at first,” said Truscott in a statement. “My son and nephew wanted to see the impact of the elastic spheres in slow motion, so that was also part of the initial motivation. We simply wondered why these toys skip so well. In general, I have always found that childish curiosity often leads to profound discovery.”

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The researchers sent elastic spheres bouncing across tanks of water and captured that motion with high-speed cameras. They found that the best kind of material to make an object bounce over the water isn’t rigid like stone. It’s soft and elastic. They reported their findings in a paper published today in Nature Communications.

As we see in the image, a hard object cuts into the water, scooping out a large section. An elastic ball hits the water, deforms into a disk—shaping itself to be the ideal skipping stone that you would look for on the shore—and skips off the surface of the water.

The team was able not only to find out why elastic objects skips so well, but predict how many skips they could get from a given throw. This could be helpful to create objects meant to skip over a water to a target, like bombs, or to keep water skiers and life raft occupants afloat.

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It can also be used to skip a ball all the way across a lab while a drone videos the entire event.

[Nature Communications, Walking on Water]

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Image: Chris Mabey