Curling is a deceptively engrossing sport with some unique physics among Winter Olympic events. Athletes slide 19kg granite stones at a target 28 meters away. Along the way, teammates sweep the pebbled ice with brooms, melting it with frictional heating to help the stone slide further. The underside of the stones is concave, so they only touch the ice along a narrow ring. Researchers think roughness in the leading edge of the sliding stone cuts into the ice, leaving scratches that the trailing edge tries to follow. This is what causes the stone’s trajectory to curl. By melting the ice, sweeping also prevents curling, so competitors must know exactly when and how much to sweep. Ice conditions shift throughout a match, and the best players can read the ice to keep their stones where they want them. (Image credit: AP; W. Zhao/GettyImages)
