"The reason we can gracefully glide on an ice-skating rink or clumsily slip on an icy sidewalk is that the surface of ice is coated by a thin watery layer. Scientists generally agree that this lubricating, liquidlike layer is what makes ice slippery. They disagree, though, about why the layer forms. Three main theories about the phenomenon have been debated over the past two centuries. Last year, researchers in Germany put forward a fourth hypothesis that they say solves the puzzle."
"In the mid-1800s, an English engineer named James Thomson suggested that when we step on ice, the pressure we exert melts its surface, making it slippery. Under normal conditions, ice melts when the temperature rises to 0 degrees Celsius (32 degrees Fahrenheit). But pressure lowers its melting point, so that even at lower temperatures, a layer of water might form on the surface. This theoretical relationship between melting point and pressure was experimentally confirmed by Thomson's younger brother William, better known as Lord Kelvin."
A thin watery layer coats ice surfaces and acts as a lubricating, liquidlike film that produces slipperiness. The origin of this surface water remains debated among scientists. Three main theories have been considered over the past two centuries, and researchers in Germany proposed a fourth hypothesis last year. The pressure-melting idea holds that pressure from weight lowers ice's melting point, producing surface water; experimental relations between melting point and pressure were confirmed by Lord Kelvin. Bowden and Hughes calculated that typical human pressures are far too small to cause pressure melting. An alternative theory attributes the water layer to heat generated by friction from sliding objects.
Read at WIRED
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