Curling for Science

(This 779th Buffalo Sunday News column was first published on March 5, 2006.)

Canadian Tournament Photo by Glen Larson

"Watching curling is about as interesting as watching grass grow."

That comment by one of my grandsons represented the consensus family attitude toward one of the Olympic sporting events televised last week. My offspring are into skiing, one even into snowboarding, so I guess that was to be expected.

I, on the other hand, enjoy watching curling. Yes, it is slow but that week it offered a pleasant contrast to the frantic skiers and bobsledders hurtling down hills. (I add that it is certainly no slower than baseball or golf and it offers more excitement than cross-country skiing.)

Curling is not a new sport. Probably first played in medieval Scotland, it is today most firmly established internationally in Canada. In fact, the oldest active athletic club of any kind in North America is the Royal Montreal Curling Club, founded in 1807.

More important, there is much physics involved in curling. There is the transfer of energy when one of those 40-plus pound granite stones hits another. And there are the strategic billiard-like vector calculations of the players as they determine how best to move their opponent's stones away from and their own nearer the "button" at the center of the target.

In major events like the 2006 Olympics even electronics has invaded the sport. Sensors determine if the curler guides the ball past the so-called "hog line" where it must be released.

What I never understood until now, however, is the sweeping. If you have watched curling, you've seen two players brushing the ice rapidly ahead of the sliding rock, increasing or decreasing their activity according to instructions from the person who started the stone. It didn't seem to me to have any effect on the stone's speed or direction, but I now realize that it does.

I learned that and much else from science (and science fiction) writer Edward Willett's "Curling: Inspirational to Scientists" essay on the web.

It turns out that the sweepers are heating and thus melting the ice surface and that does indeed have an effect on the movement of the stone. The playing area is prepared before a match by spraying fine water droplets called pebble onto the ice. Due to the friction between the stone and pebble, the stone turns to the inside or outside, causing the stone's path to 'curl'; thus the sport's name. The sweepers increase this slippery moist interface.

Willett's essay also led me to the work of a team of materials scientists led by Jane Blackford of Edinburgh University in Scotland. Before the 2002 Olympics Professor Blackford's team was invited by Great Britain's curlers to study their sweeping technique. The scientists invented a device called a sweep ergometer to monitor this effect. Using the results of the study, the British were able to improve their technique and in fact their women won the Gold that year.

I expect that at this point some readers are wondering about the involvement of university researchers in a sport like curling. What next? Scientists on cruise ships studying shuffleboard?

In this case, however, this "trivial" research opened the door to the Blackford team's more significant study of what makes ice slippery. This research is being funded by the United Kingdom's Engineering and Physical Sciences Research Council with support from the auto firm Jaguar and the tire firm Goodyear.

The team has now developed another device, which they have designated a Tribometer. It is used together with a low temperature scanning electron microscope to investigate how different materials such as rubber or metal (or, of course, stone) slip across a sample of ice. Considered are such factors as temperature, object weight, material composition and velocity.

It turns out, for example, that ice interacts differently at different temperatures. At temperatures only slightly below freezing, friction between an object and ice causes melting but that refreezing then causes ice ripples. At lower temperatures, however, the ice doesn't melt, it simply fractures.

Here research aimed at a seemingly insignificant problem in one field has led to important insights in a related area. Our shoes and cars may soon be better equipped to provide traction on ice because scientists first investigated the delightful sport of curling.-- Gerry Rising