After a game of curling, physicist Mark Shegelski likes to sit down with his buddies and play a little game.

鈥淚 would say, 鈥楬ey, hey, before you pour the beer鈥� 鈥� because you have to drink beer after every game of curling, right 鈥� 鈥榖efore you pour the beer, let me just show you something,鈥欌�� Shegelski said. He would grab the empty beer glass, turn it upside down and place it on the table.

Pretending like he was concentrating hard, Shegelski would send the glass down the table. As it travelled, the glass would rotate clockwise and move gradually to the left.

It was the exact opposite to how a curling rock would move, and Shegelski鈥檚 fellow curlers would be dumbfounded.

鈥淭hey were just like 鈥楬ow? What鈥檚 going on?鈥� And for them, this was baffling. Why was the drinking glass going the wrong way?鈥� Shegelski said. 鈥淏ut for me, it was the other way around.鈥�

For Shegelski, a physicist that researches quantum mechanics at the University of Northern British Columbia, the curling rock was the mystery. Unlike a drinking glass, which curls (or moves to the side) in the opposite direction that it rotates, a curling rock will curl in the same direction of its rotation.

鈥淔rom a physics point of view, it鈥檚 easy to understand the drinking glass,鈥� he said. 鈥淚t鈥檚 harder to understand the curling rock.鈥�

Easy is a relative term of course, but the basics of drinking-glass physics can be distilled into a few sentences.

As the glass moves forward, friction increases at the front of the glass. Friction is what slows the glass down and brings it to a stop. But the glass is also rotating, moving in a clockwise pattern. Because the front of the glass is moving to the right (and the right side is moving slower because of it), there will be more friction on the left as it pushes against the table.

This means that the place with the most friction on the glass will be the front-left portion 鈥� which is why the glass curls to the left.

But with a curling rock, those rules of physics don鈥檛 seem to apply. Instead of the rock being drawn in the direction of the most friction, it curls away from it.

That perplexed Shegelski as a grad student, and prompted him to dabble in some of the science behind the sport from the late 1990s to the early 2000s. But it was research that was just for fun, and he dropped it for about 10 years.

When he came back to it, he partnered with Edward Lozowski, a physicist at the University of Alberta and the 鈥渒ing of the physics of ice鈥� according to Shegelski. Together, they came up with a theory that could explain the reason behind the unusual movement of curling rocks.

鈥淚 was just thinking, what鈥檚 the easiest way to make the rock go sideways,鈥� Shegelski explained. 鈥淚 thought, if when you shot the rock, suppose it鈥檚 stuck in the right-hand side, and rotated for a bit 鈥� Then suppose that stickiness broke and it slid the rest of the way straight down the ice.鈥�

鈥淪o then I though, well what if you have a whole bunch of brief times where it rotates and changes its direction.鈥�

The concept, which Shegelski and Lozowski dubbed the 鈥減ivot-slide model鈥� uses the bumpiness of curling ice as a key part of the theory. As the curling rock travels and rotates, it will catch on the multitude of bumps covering the ice. Each bump that pulls it to the right will result in the rock curling towards the right.

Of course, it is hypothetically possible the rock could curl to the left using this model, but that鈥檚 not likely to happen.

鈥淲e think there are sticky events or pivoting at different points around the rock,鈥� Shegelski explained. 鈥淏ut the bottom line is that pivots on the left side and pivots on the right side cancel each other out.鈥�

Because of the rotation, the movement isn鈥檛 鈥渢he same left and right,鈥� he continued.

鈥淪o as a result you get more pivoting on the right-hand side. That鈥檚 what dominates and governs the way it moves.鈥�

For Shegelski, it was a eureka moment, especially now that other experiments have given credence to his and Lozowski鈥檚 theory. But there is still more to learn.

Take the distance a rock curls for example. Normally, a rock will curl about a metre as it travels up the ice; this remains true whether it rotates two times or 60 times as it travels. But get the rock to rotate 80 times? Then suddenly the curling rock will move two metres to the right.

In another experiment, Shegelski found that if he shot the rock on hockey ice, and made it rotate quickly while sliding slowly, it would curl in a spiral pattern.

鈥淭his is why I say these rocks are amazing, the things they do,鈥� Shegelski said. 鈥淵ou鈥檙e just looking at this and you鈥檙e just shocked.鈥�

Shegelski and Lozowski will continue to work on the physics of curling, but only in their spare time. They have other research projects after all, and curling rocks will continue to move in mysterious ways, no matter how thoroughly they are researched.

鈥淭hat鈥檚 one of the things I love about physics,鈥� Shegelski said. 鈥淵ou think you get it all figured out, and then you try something and it goes exactly opposite to what you expect.

鈥淎nd then you sit down and you say 鈥榃hy does it do what it just did?鈥�

鈥淎nd by thinking enough, most of the time you can figure out the answer and realize if you really would have thought about it really carefully 鈥� you would have realized you were going to get this surprising result.鈥�

editor@cloverdalereporter.com
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