John Wheeler: Why is ice so slick?

Friction from an object moving against a layer of ice makes a layer of water that makes ice slippery.

featured-image

FARGO — Anyone who has ever driven on an icy road or walked on an icy sidewalk or sledded or skied down a hill knows that ice is slippery. However, ice has a solid, crystalline structure, which does not seem like it would be so slippery. It turns out, ice is not that slippery until something moves against it.

The friction of a car tire or a boot, a sled, or a ski for that matter; melts a thin layer of ice and it is this layer of water on top of the ice that encourages objects to glide over the ice, sometimes in an out-of-control manner. A person can stand on ice without danger of falling down. Only when that person tries to walk does the ice become slippery.



The melting and refreezing of this top layer of ice can develop a sheen which can make the thin layer of water on ice even more slippery..