'Eureka': Alberta researcher puts new spin on curling conundrum

Edward Lozowski may have solved a mystery which has befuddled curlers for generations: What makes rocks curl?

'I've been scratching my head about this one for about four years now'

Alberta skip Kevin Koe throws a rock during a draw against Team Laycock at the 2017 Canadian Olympic curling trials on Sunday. (Justin Tang/The Canadian Press)

Edward Lozowski may have solved a mystery which has befuddled curlers for generations: What makes rocks curl?

Lozowski, a professor emeritus with the faculty of science at the University of Alberta, has done the math and believes he can explain the physics.

After having "scratched down hundreds of pages of equations," Lozowski has created the first mathematical model accurately explaining the phenomenon.

'It's a difficult problem'

"People have been trying to get an answer to this question as to why curling rocks curl for about 100 years," Lozowski said in an interview with CBC Radio's Edmonton AM.

"I've been scratching my head about this one for about four years now.

"I thought I could do it in under a year but it's taken much longer. It's a difficult problem."
Alberta's Kevin Martin inspects a stone before a draw against Quebec at the Canadian Men's Curling championship in Hamilton in 2007. (Canadian Press)

For decades, scientists who bothered to concern themselves with such matters assumed the trademark curl of each rock was caused by ice friction, said Lozowski.

They believed the tiny pebbles on the ice surface caused the rock to curl.

'What curlers call the curl'

"They thought that maybe that ice friction which causes it to stop also causes it to move to one side, which is what curlers call the curl," Lozowski said.

"It turns out nobody, including me, could use ice friction to explain the magnitude of the curl. It moves about five or six feet in a good curling game and it just can't be explained with ice friction."

Lozowski's theory is more complicated. He likens the phenomena to the work of a jammed circular saw.

When the blade of a saw jams and stops rotating, the whole saw starts to pivot. It's the same with curling rocks, he said.

The textured bottom of the rock actually binds to each tiny ice pebble it encounters, and pulls it to the breaking point. When contact with the icy pebble is broken, the rock lurches ahead, and curls.

His research, 'First principles pivot-slide model of the motion of a curling rock: Qualitative and quantitative predictions' was recently published in Cold Regions Science and Technology.

"Scientists in the past have ignored the fact that the rocks slide on pebbled ice, and those turned out to be really essential," he said

"When that running band of granite hits a pebble, it stops rotating momentarily … and starts rotating around the pebble,  and that causes it to pivot."  

"I wish I could say, 'Eureka' "

Each individual encounter lasts a matter of tens of nanoseconds, said Lozowski.

"Every time it encounters a pebble, that motion direction is changed ever so slightly," he said.

"But during the course of a slide, a rock encounters tens of thousands of pebbles so every little encounter changes the direction of motion."

While Lozowski's research explains the mechanics of curling, he said it likely won't give Canadian curlers an edge.

"I wish I could say, 'Eureka, I have come up with a way to make Canadian curlers even better than they are,' which would be hard to do, because of course as everyone knows, Canadian curlers are the top of the world," he said.

"All the parameters have to do with the nature of the ice, and if the ice maker changes them, he changes them for everyone who plays on that ice."