The Science of Curling

It's played in teams of four people, and teams take it in turns to slide eight tones across the ice towards a target, trying to get as close to the centre - called the tee - as possible. The team with the nearest stone to the tee scores a point, and for every other stone nearer the tee than their opponents', they score another point. What makes curling so curious to watch though are the two team members who use brushes to try to control the slide of the stone. Curling is a fascinating interplay of force, friction and momentum, based on the fact that it's easy to slide things on ice. Just like a toboggan or ice skate, the curling rock slides because the pressure it exerts melts the ice beneath it, creating a thin film of water that lubricates its passage. The player's goal is to balance the energy he imparts to the rock with the friction of the rock on the ice, so that friction will win just when the rock is where he wants it to stop. Curling would just be called "sliding," however, if not for the fact that the rocks are made to curl, or curve, as they move down the ice. The stone is a round piece of polished granite, concave on top and bottom. The direction in which the stone curls is very important. A stone rotating in an anticlockwise direction will curl to the left. This is because as the stone travels it tips forward. The pressure of the stone on the ice is greater at the front and causes more melting (momentarily) than the back. Consequently there is a layer of water between the stone and the ice and so less friction at the front of the stone than at the back. And the frantic sweeping? Sweeping the ice just in front of a rock with a broom makes it travel faster and curl less. Sweeping melts the ice a little bit, decreasing friction, and removes any debris that might slow the rock. Read more about science of curling.... or click the picture to see some flash animations on curling.