We finally have a theory for why curling rocks curl, says B.C. physicist

We finally have a theory for why curling rocks curl, says B.C. physicist

Think you know why a curling rock curls? Think again.

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

“I would say, ‘Hey, hey, before you pour the beer’ — because you have to drink beer after every game of curling, right — ‘before you pour the beer, let me just show you something,’” 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’s fellow curlers would be dumbfounded.

“They were just like ‘How? What’s going on?’ And for them, this was baffling. Why was the drinking glass going the wrong way?” Shegelski said. “But for me, it was the other way around.”

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.

“From a physics point of view, it’s easy to understand the drinking glass,” he said. “It’s harder to understand the curling rock.”

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 — which is why the glass curls to the left.

But with a curling rock, those rules of physics don’t 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 “king of the physics of ice” according to Shegelski. Together, they came up with a theory that could explain the reason behind the unusual movement of curling rocks.

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

“So then I though, well what if you have a whole bunch of brief times where it rotates and changes its direction.”

The concept, which Shegelski and Lozowski dubbed the “pivot-slide model” 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’s not likely to happen.

“We think there are sticky events or pivoting at different points around the rock,” Shegelski explained. “But the bottom line is that pivots on the left side and pivots on the right side cancel each other out.”

Because of the rotation, the movement isn’t “the same left and right,” he continued.

“So as a result you get more pivoting on the right-hand side. That’s what dominates and governs the way it moves.”

For Shegelski, it was a eureka moment, especially now that other experiments have given credence to his and Lozowski’s 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.

“This is why I say these rocks are amazing, the things they do,” Shegelski said. “You’re just looking at this and you’re just shocked.”

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.

“That’s one of the things I love about physics,” Shegelski said. “You think you get it all figured out, and then you try something and it goes exactly opposite to what you expect.

“And then you sit down and you say ‘Why does it do what it just did?’

“And 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 … you would have realized you were going to get this surprising result.”



editor@cloverdalereporter.com

Like us on Facebook and follow us on Twitter

curling

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Elvira D’Angelo, 92, waits to receive her COVID-19 vaccination shot at a clinic in Montreal, Sunday, March 7, 2021, as the COVID-19 pandemic continues in Canada and around the world. THE CANADIAN PRESS/Graham Hughes
110 new cases of COVID-19 in Interior Health

Provincial health officers announced 1,005 new cases throughout B.C.

It costs as little as $7 to charge an EV at home. (Scott Tibballs / The Free Press)
Electric Vehicles a rare sight (in the Kootenays), but change on the way

Electric pickups will increase the appeal of zero-emission vehicles in years to come according to Blair Qualey of the New Car Dealers Association

Linda Krawczyk and her dad Doug Finney enjoyed a ride around beautiful Fernie on Friday thanks to Melanie Wrigglesworth and the local chapter of Cycling Without Age. (Scott Tibballs / The Free Press)
Cycling Without Age goes for its first spin

Doug Finney (86) got to enjoy a ride around Fernie

The Cranbrook Community Forest is good to go for mountain biking. (Scott Tibballs / The Free Press)
Snow’s done, time to hit the trails

South Country trails are good to go

Interior Health nurses administer Pfizer-BioNTech COVID-19 vaccines to seniors and care aids in Kelowna on Tuesday, March 16. (Phil McLachlan/Kelowna Capital News)
69 new cases of COVID-19 in Interior Health

The total number of cases in the region is now at 9,840 since the pandemic began

Rainbow trouts thrashing with life as they’re about to be transferred to the largest lake of their lives, even though it’s pretty small. These rainbows have a blue tinge because they matched the blue of their hatchery pen, but soon they’ll take on the green-browns of their new home at Lookout Lake. (Zoe Ducklow/News Staff)
VIDEO: B.C. lake stocked with hatchery trout to delight of a seniors fishing club

The Cherish Trout Scouts made plans to come back fishing soon

Pall Bearers carrying the coffin of the Duke of Edinburgh, followed by the Prince of Wales, left and Princess Anne, right, into St George’s Chapel for his funeral, at Windsor Castle, in Windsor, England, Saturday April 17, 2021. (Danny Lawson/Pool via AP)
Trudeau announces $200K donation to Duke of Edinburgh award as Prince Philip laid to rest

A tribute to the late prince’s ‘remarkable life and his selfless service,’ the Prime Minister said Saturday

B.C. homeowners are being urged to take steps to prepare for the possibility of a flood by moving equipment and other assets to higher ground. (J.R. Rardon)
‘Entire province faces risk’: B.C. citizens urged to prepare for above-average spring flooding

Larger-than-normal melting snowpack poses a threat to the province as warmer weather touches down

Cannabis bought in British Columbia (Ashley Wadhwani/Black Press Media)
Is it time to start thinking about greener ways to package cannabis?

Packaging suppliers are still figuring eco-friendly and affordable packaging options that fit the mandates of Cannabis Regulations

Vancouver-based Doubleview Gold Corp. is developing claims in an area north of Telegraph Creek that occupies an important place in Tahltan oral histories, said Chad Norman Day, president of the Tahltan Central Government. (THE CANADIAN PRESS/HO)
B.C. Indigenous nation opposes mineral exploration in culturally sensitive area

There’s “no way” the Tahltan would ever support a mine there, says Chad Norman Day, president of its central government

Stz’uminus Elder George Harris, Ladysmith Mayor Aaron Stone, and Stz’uminus Chief Roxanne Harris opened the ceremony. (Cole Schisler photo)
Symbolic red dresses rehung along B.C. highway after vandals tore them down

Leaders from Stz’uminus First Nation and the Town of Ladysmith hung new dresses on Sat. April 17

A Western toadlet crosses the centre line of Elk View Road in Chilliwack on Aug. 26, 2010. A tunnel underneath the road has since been installed to help them migrate cross the road. Saturday, April 24 is Save the Frogs Day. (Jenna Hauck/ Progress File)
Unofficial holidays: Here’s what people are celebrating for the week of April 18 to 24

Save the Frogs Day, Love Your Thighs Day and Scream Day are all coming up this week

Local carpenter Tyler Bohn embarked on a quest to create the East Sooke Treehouse, after seeing people build similar structures on a Discovery Channel show. (East Sooke Treehouse Facebook photo)
PHOTOS: B.C. carpenter builds fort inspired by TV’s ‘Treehouse Masters’

The whimsical structure features a wooden walking path, a loft, kitchen – and is now listed on Airbnb

The Attorney General’s Ministry says certain disputes may now be resolved through either a tribunal or the court system, pending its appeal of a B.C. Supreme Court decision that reduced the tribunal’s jurisdiction. (AP Photo/Mark J. Terrill)
Court of Appeal grants partial stay in ruling on B.C. auto injuries

B.C. trial lawyers challenged legislation brought in to cap minor injury awards and move smaller court disputes to the Civil Resolution Tribunal

Most Read