Why is ice so slippery?
Skating on frozen lake (stock image). The answer to the question of why ice is slippery lies in a film of water that is generated by friction, one that is far thinner than expected and much more viscous than usual water through its resemblance to the "snow cones" of crushed ice we drink during the summer. This phenomenon was recently demonstrated by researchers from the CNRS and ENS-PSL, with support from the École polytechnique, in a study that appeared in Physical Review X on 2019, November 4. The "slippery" nature of ice is generally attributed to the formation of a thin layer of liquid water generated by friction, which for instance allows an ice skater to "surf" on top of this liquid film. The properties of this thin layer of water had never been measured: its thickness remained largely unknown, while its properties, and even its very existence, were the subject of debate. What's more, since liquid water is known to be a poor lu