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

Just Posted

(Submitted Photo)
Skeena Voices| Dance, discipline and determination

When Braya Kluss is not dancing, she is a regular 16-year-old teenager… Continue reading

Karl Meyer was an active member of the Thornhill Volunteer Fire Department. (Terrace Professional Firefighters/ Facebook)
VIDEO: First responders parade through town in honour of fallen Thornhill firefighter

Thornhill Volunteer Fire Department’s Karl Meyer was found deceased during June 3 flooding

Suspected methamphetamine and scale seized by police. (Terrace RCMP photo)
Terrace RCMP seize guns, ammo, suspected narcotics

Man released after court appearance

Caledonia Secondary School is the recipient of a $50,000 grant to replace its aging science equipment. (File photo)
Cal snags major grant to modernize science equipment

The $50,000 comes from a pharmaceutical company

Unemployment rate drops in northwestern B.C.

Large improvement since Spring 2020

Canadian Prime Minister Justin Trudeau participates in a plenary session at the G7 Summit in Carbis Bay, England on Friday June 11, 2021. THE CANADIAN PRESS/Adrian Wyld
Canada donating 13M surplus COVID-19 vaccine doses to poor countries

Trudeau says the government will pay for 87 million shots to be distributed to poor countries

Montreal Canadiens goaltender Carey Price (31) is scored on by Vegas Golden Knights defenseman Alec Martinez, not pictured, during the second period in Game 1 of an NHL hockey Stanley Cup semifinal playoff series Monday, June 14, 2021, in Las Vegas. (AP Photo/John Locher)
Habs fall 4-1 to Vegas Golden Knights in Game 1 of NHL semifinal series

Match was Montreal’s first game outside of Canada in 2021

Kelowna-Lake Country MLA Norm Letnick, assistant deputy speaker at the B.C. legislature, presides over committee discussions. The legislature is completing its delayed spring session this week, with most MLAs participating by video conference. (Hansard TV)
B.C.’s daily COVID-19 infections dip below 100 over weekend

Only 68 new cases recorded Monday, four additional deaths

The BC Ferries website went down for a short while Monday morning following a provincial announcement that recreational travel between health authorities can resume Tuesday. (Black Press Media file photo)
BC Ferries’ website crashes in wake of provincial reopening announcement

Website back up now, recreational travel between health regions to resume as of Tuesday

The Kamloops Indian Residential School is photographed using a drone in Kamloops, B.C., Monday, June, 14, 2021. The remains of 215 children were discovered buried near the former school earlier this month. THE CANADIAN PRESS/Jonathan Hayward
Communities grapple with what to do with former residential and day schools

Some tear them down as a tool to help healing, others repurpose them as tools for moving forward

FILE – Provincial health officer Dr. Bonnie Henry talks about B.C.’s plan to restart the province during a press conference at Legislature in Victoria, Tuesday, May 25, 2021. THE CANADIAN PRESS/Chad Hipolito
B.C. watching U.K.’s COVID struggles but don’t think province will see similar pitfalls

Studies show that one dose of vaccine is only 33 per cent effective in preventing B.1.617.2 spread

RCMP Const. Shelby Patton is shown in this undated handout photo. RCMP say that Patton was hit by an allegedly stolen truck that he had pulled over on Saturday morning in Wolseley, east of Regina. THE CANADIAN PRESS/HO, RCMP
Pair charged in Saskatchewan Mountie’s death make first court appearance

Const. Shelby Patton was hit by an allegedly stolen truck that he had pulled over Saturday morning

David and Collet Stephan leave for a break during an appeal hearing in Calgary on Thursday, March 9, 2017. THE CANADIAN PRESS/Todd Korol
Appeal Court rejects stay for Alberta couple facing third trial in son’s death

Pair accused in their earlier trials of not seeking medical attention for their son sooner

Highway notices like this come down effective June 14. Public health restrictions on non-essential travel and commercial operation have hit local businesses in every corner of B.C. (B.C. government)
Province-wide travel back on in B.C.’s COVID-19 restart plan

Gathering changes include up to 50 people for outdoor events

Most Read