Flat, lightweight rocks like the ones pictured above are favorites for rock skipping. A new study found that heavier rocks can also skim the surface of the water.
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Jeff J. Mitchell/Getty Images
Flat, lightweight rocks like the ones pictured above are favorites for rock skipping. A new study found that heavier rocks can also skim the surface of the water.
Jeff J. Mitchell/Getty Images
When throwing a stone across the water, most people look for ones that are flat and light. Now a new study suggests that heavier, curvier stones can also produce impressive jumps. And these findings won’t just help you up your game, they could be applied to the real world, like helping make planes more efficient.
Ryan Palmer is an applied mathematician at the University of Bristol in the United Kingdom and co-author of the study, published this month in the Royal Society.
He and his colleague created a model to learn how shape and mass affect how objects interact with water. They found that when skipping rocks over a lake, “if you pick something that’s a little bit heavier, you get something called a super elastic response,” Palmer said.
In other words, a heavier object could produce an impressive bounce.
“What happens is that the rock touches the layer of water, and because it’s heavier, it sinks deeper and stays in contact longer,” Palmer said. “This increases the pressure on that rock, which then increases the force lifting it up, and you can get quite a jump on this response.”
Now, Palmer admitted that while you can get quite a jump with heavier stones, they won’t result in as many jumps as with flat ones. The results also depend on the shape of the stone, because too heavy a stone may not work.
“So the bottom line is, for a heavier rock that could sink, if it’s a little bit more curved, it’s more likely to slide,” he said.
However, Palmer and his colleague were studying more than just the physics of jumping stones. Using the mathematical model, they sought to better understand aircraft icing, a phenomenon that occurs when aircraft fly in very cold climates.
Sometimes pools of water form on the wing of an airplane, and airborne ice crystals can appear and sink in that pool or disappear. If they sink, they cause a buildup of ice that can be dangerous.
But if they do slide, Palmer said, “well, it’s very much the same physics and dynamics that you might encounter if you picked up a rock and tried to throw it across a lake.”
Palmer said it’s important to know where the ice might go to better understand if other parts of the aircraft need more protection.
He also insisted that commercial aircraft are safe; Systems are in place to protect them from the dangerous accumulation of ice. His research aims to increase the efficiency of those protections.
“Where we live in this world of climate change and rising fuel costs and things, you really are always looking to be more efficient and therefore you can better design your systems, better protect the aircraft,” he said. “You can cover these weird situations that can happen in an efficient and innovative way.”
And while Palmer searched for practical applications, that wasn’t the only thing he took from his research.
“Since I started this work, it’s become even more compelling to try to skim stones, and in particular to just pick the slightly weirder stones,” he said. “The ones that aren’t necessarily so flat.”
