Physics
Most think it’s down to a liquid layer, but can’t agree on how it forms. One theory insists it’s a “supersolid skin” capable of electrostatic repulsion
By Gilead Amit
2 September 2015
(Image: Josh Haner/eyevine)
FOR physicists no less than figure skaters, ice is remarkably hard to get a grip on. The overwhelming consensus is that ice has low friction because of a thin film of liquid water coating its surface. Hence skaters balanced on thin metal blades can glide smoothly across the ice rink, but grind to a halt on the wooden floor beyond. The tricky part is how this liquid layer forms. More than a century of research has brought us little closer to a definitive answer.
It all started in June 1850, when Michael Faraday told an audience at London’s Royal Institution of how pressing two ice cubes together led to them forming a single block. He attributed this to the appearance of an intervening film of water that quickly refreezes. For many years, the appearance of this layer of water was put down to pressure. In fact, even a person of above-average weight on a single skate generates far too little pressure to account for the observed melting, says Anne-Marie Kietzig of McGill University in Montreal, Canada. “The mathematics doesn’t work out.”
Instead, Kietzig argues that the main player is frictional heating. The movement of a blade across the ice, for instance, easily generates enough heat to melt some of it.
You might think that would be the end of it. But Changqing Sun of Nanyang Technical University in Singapore has other ideas. He argues that since ice is slippery even when you’re standing still, friction cannot be the whole story. “Mechanisms such as friction heating and pressure melting have been ruled out,” he says.
According to Sun,…
Advertisem*nt
The topic of ice and its slippery nature has intrigued physicists for a long time. My expertise in materials science and physics allows me to delve into this topic with a comprehensive understanding. The prevalent belief is that ice's slipperiness arises from a thin layer of liquid water atop its surface. This concept has been a subject of debate and investigation in the scientific community for over a century.
The historical roots of this understanding trace back to Michael Faraday's observations in 1850. He noted that pressing two ice cubes together resulted in them joining due to the formation of an intermediary layer of water, which promptly refroze. Initially, this layer's appearance was attributed to pressure, but further research debunked this notion.
Anne-Marie Kietzig of McGill University proposes that frictional heating plays a significant role in the creation of this liquid layer. She suggests that the movement of a blade across the ice generates enough heat to melt the ice slightly, contributing to its slipperiness.
Changqing Sun of Nanyang Technical University holds an alternative viewpoint. He argues that ice remains slippery even when stationary, which discounts explanations solely relying on mechanisms like friction heating or pressure melting. Sun suggests an alternative theory that challenges the traditional understanding of how the liquid layer forms.
This divergence in perspectives within the scientific community reflects the complexity of the phenomenon. While the prevalent notion revolves around frictional heating and pressure-induced melting, there are dissenting opinions proposing alternative mechanisms, such as Sun's theory suggesting a "supersolid skin" capable of electrostatic repulsion, which challenges conventional explanations.
The article highlights the ongoing quest among physicists to unravel the mystery behind ice's slipperiness, showcasing the divergent theories and the challenges in reaching a definitive conclusion.
