The stone in Kurt Steiner’s hand is roughly circular, four inches wide, flat on one side and irregularly dimpled on the other, like a petrified chocolate chunk cookie. He handles it with a card dealer’s deftness, searching its surface for divots, notches, ridges—any irregularities that will lend his fingers the purchase they need to clutch it fast. “I like round rocks with just a little bit of something going on around the edge,” says Steiner, who holds the world record for most consecutive skips of a stone. A good grip, he says, is crucial to a high-octane skip; it translates to more speed and a quicker spin, which help stabilize the rock as it rebounds across the water.

Steiner cocks his arm back. Pauses. Holds this stance, like he’s waiting for a starting gun. I’m standing ten feet away from him, on the banks of First Dam in Logan, Utah, when he sends the stone bolting. It spins so fast I can hear it thrum through the air. The sound is all but indistinguishable from the beating of a hummingbird’s wings.

Kurt Steiner, world record holder for most consecutive skips of a stone, skips a rock at a dam in Logan, Utah

WIRED

A fraction of a second later the rock is riffling across the water’s surface. I struggle to tally the skips, which start just a few feet in front of Steiner. The rock attacks the water at so low an angle that the first several bounces occur in rapid succession. I lose count in the high twenties. To me this throw is a revelation. To Steiner it’s a warmup, and he’s already reaching for another rock. Behind us, stacked in tidy rows inside three boxes that Steiner shipped from his home in rural Pennsylvania, are some 200 natural variations of the stone he just threw. Some are round. Some are square-shaped. Others are triangular. Every one of them is finer, flatter, smoother than anything I’ve ever skipped.

They represent a small sliver of Steiner’s personal cache, a collection of more than 10,000 rocks that he replenishes on semiannual pilgrimages to shorelines around the world to select his stones by hand. The nearest source, Lake Erie, where he collects eminently skippable saucers of Devonian shale, is a few hours’ drive from his home. The shale there cleaves naturally into stones of suitable thickness and weight for skipping, and polishes smoother than sandstone, another sedimentary rock. Its main drawback is that its primary ingredients—layers of silt and clay—compress unevenly, so it’s not often Steiner comes upon a piece of shale with perfectly parallel sides. A uniform edge, he says, is the kind of thing you find in Easdale slate. But that’s in Scotland—a much longer trip.

Eighty-eight skips. That’s Steiner’s official record, which he set in 2013 on a lake in Pennsylvania’s Allegheny National Forest. A stone skipper for most of his life, that year he devoted himself to several months of deliberate skip-count practice, which he supplemented with strength training. (His go-to lower-body workout—elite stone skippers derive a lot of power from their legs—is to shoulder a bar loaded with 60 percent of his body weight and perform 100 deep squats in under five minutes.) He estimates there are just two or three people in the world capable of besting his record, not including his longtime friend and rival, former world record holder Russ Byars, who died in 2017.

Steiner (right) met with WIRED in Logan, Utah. There, Utah State University fluid dynamicist Tadd Truscott (left) and his labmates measured the dynamics of this throw to better understand how his rocks rebound so many times—and what the upper limit to stone-skipping might be. Here, Steiner and Truscott discuss the finer points of skipping-stone anatomy.

Robbie Gonzalez

The only thing more astonishing than Steiner’s best all-time skip count is how much room there is for improvement. Theoretical models suggest that if somebody does set a new world record, it could be by a lot. Steiner’s throw tops out at around 50 miles per hour. (His world record skip was calculated at 43 mph.) But fluid dynamicist Tadd Truscott, head of the Splash Lab at Utah State University, says someone with the power of a Major League Baseball pitcher could sidearm a stone as fast as 93 mph, with a spin rate upwards of 3,000 revolutions per minute. “And if you can get there, you’re going to probably get close to 300, 350 skips,” Truscott says.

Yes, 350 skips.

The Splash Lab’s calculations build on research by French physicists Lydéric Bocquet and Christophe Clanet, who published a series of studies on stone skipping in the early aughts, including a 2004 paper in Nature titled “Secrets of successful stone-skipping.” The pair showed that a spinning rock should hit the water at an angle of 20 degrees, to minimize the drag it experiences as it ricochets across the water. Drag reduces velocity, which the stone needs to avoid losing steam and sinking, and the rate of spin, which keeps it from tipping into the water through a phenomenon known as gyroscopic stabilization. They also devised a set of equations for predicting skip number.

To Bocquet and Clanet’s equations the Splash Lab added kinematics data from MLB pitchers. That’s how they got the 350 figure—a theoretical limit even Truscott admits sounds preposterous. “It’s just—is that even possible? Three hundred already just seems ridiculous, right?” he says between outbursts of incredulous laughter.

Truscott and his team recorded high speed footage of Steiner’s skips, including the instant the stone leaves his hand. This allowed them to calculate his throwing speed and the rock’s spin rate upon release.

Splashlab

And yet, the dynamics of Steiner’s throw—which Truscott and his labmates filmed with high-speed cameras—overlap eerily well with the Splash Lab’s model. At 22 miles per hour and 1700 rpm, the model predicts a skip count between 20 and 25. At the Dam, where Truscott’s team recorded him throwing an average of 21 miles per hour and 1750 rpm, Steiner’s skip-count average was around 25. At 43 miles per hour, the speed Steiner threw when he set the world record, Splash Lab’s model projects a stone thrown at 2200 rpm would skip between 75 and 85 times. Steiner’s record-setting stone, you’ll recall, rebounded 88 times.

Still, it’s possible something in the model breaks down at higher numbers. The Splash Lab’s calculations assume a perfectly circular disk of uniform mass, skipping across a flat body of water. But stone skipping competitions permit only natural rocks, and as Steiner puts it: “Mother nature never sees fit to make two of the same thing.” What’s more, he says, even the tiniest ripple can ruin a skip-count record attempt. Which is why Steiner thinks the upper limit for an ideal stone, thrown under ideal conditions, might be closer to 200 skips.

But Steiner rarely bothers to count his own skips. As his next stone dances across the water, he’s much more interested in the rock itself—the consistency with which it powers through the water, the way it rolls and rights itself as it zips through the air, and the pitter patter pattern that it makes just before it plops below the waterline, with only the tiniest splash to mark its passing.


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