Curling is a mystery – every object on earth slid along a surface and rotated clockwise curls in a anti-clockwise direction and those rotated anti-clockwise curl clockwise -except curling stones. Scientists have been asking why do stones curl in this way and so far there is no consensus. Differing theories have been proposed and rather than one being wrong and one right it is likely that a combination of all are nearer the truth.
Theory 1: The ice is “pebbled”. Curling sheets are not flat, they consist of many tiny bumps over which the stone travels. The rotation is caused by the stone catching on the pebbles causing it to turn with the rotation.
• Theory 2. When the curling stone is slid along the ice, the pressure on the from of the stone is higher on the front than the back. This friction may warm the ice and create a layer of water that reduces the friction on the front end and increase the friction on the back causing the stone to travel with its rotation.
• Theory 3. Curling stones don’t have a flat bottom to slide on, instead there is a thing ring under to stone on which they slide. That ring is thought to scratch the ice and create marks running in the direction of the curl. The valleys then guide the other bumps on the back half of the stone, and curl the stone.