Curling Quandary: Why Stones Curl the "Wrong" Way

Brian Handwerk
for National Geographic News
February 23, 2006

Canadian physicists may have answered a question that's been around for curling's entire 500-year history: Why does a curling stone curl in a direction that seems contrary to the laws of physics?

Interest in curling is enjoying a growth spurt, highlighted by this winter's Olympic competition in Turin, Italy.

Tomorrow Canada battles Finland in the men's gold-medal game, while the United States men's team goes for a first ever curling medal in a bronze matchup against Great Britain.

But even with increased attention to the sport, many athletes and fans have been largely unaware of one of curling's biggest quandaries.

In the modern version of this ancient Scottish game, competitors slide 42-pound (19-kilogram) "stones" or "rocks" down a clean sheet of ice. Each team hopes to place its own stones closest to the center of a bull's-eye target known as the house.

Spin is a crucial part of every shot. Olympic curlers generally try to spin the stone the same way each time—three rotations from the start of a shot to its finish.

"The spin actually makes the stone go to a specific spot," said Shawn Rojeski, a member of the U.S. Olympic Curling Team from Chisholm, Minnesota.

"When we put the spin on it, one way or the other, we're more or less guiding in which direction we want the rock to go.

"If you were to throw the rock with no spin, it would be nearly impossible, and it would be hard to control where it goes," he continued. "Any little feature on the ice would make the rock change direction."

Sliding Surprise

But when University of Northern British Columbia physicist Mark Shegelski took up the game, he noticed that the spinning stone curled, or moved to one side, in a counterintuitive direction as it slid down the ice.

Shegelski often demonstrates the problem to curlers after a game.

Continued on Next Page >>




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