Ice skating is counterintuitive: why should a narrow blade make it easier to slide over the ice? The science is surprisingly complex, but unscientific people worked out the practical application a long time ago.
William FitzStephen described how Londoners entertained themselves in freezing conditions in 1173: “Crowds of young men go out to play on the ice. Some of them fit shinbones of cattle on their feet, tying them round their ankles … and are carried along as fast as a flying bird.”
Some of these early bone skates are on display at the Museum of London.
The standard explanation – that the pressure exerted on a small surface area melts the ice creating a slippery layer of water – is only part of the story. Pressure only slightly lowers the melting point, most of the real work is done by frictional heating between blade and ice. This is why skate blades are not mirror-smooth and are engineered to balance glide with grip.
Ice skates were probably originally inspired by how slippery ice is anyway. This is due to yet another effect: a thin, disordered layer of molecules on top of the crystalline ice acts as a “quasi-liquid” and reduces friction. This layer makes it possible to slide on ice all too easily, even without skates.
