Playoff season is almost here again, and the physics department is celebrating. Alain Haché, a physics professor in New Brunswick and a U of T grad, recently returned to his alma mater to give a lecture to an enthusiastic crowd of physics professors and students about physics and hockey. Haché has just published a book called The Physics of Hockey, which uses general-level physics to explain various hockey phenomena. Describing his lack of success in appearing on Hockey Night in Canada to promote the book, Haché wondered aloud about Don Cherry’s degree of interest in physics. One audience member had a different theory about Cherry’s lack of enthusiasm for the book: “He can’t read.”
Haché began by explaining why ice hockey is possible at all: the minuscule amount of friction between the ice and the steel of the skate blade. In fact, the friction between the ice and ice skate is comparable to the amount of friction in a knee joint that resists bending your knee.
The reasons for this are actually pretty sophisticated. While people used to think the low friction was attributable to pressure or friction of the skate on the ice, which would heat up and melt the ice a little bit, it is actually an inherent property of the ice itself. Using an atomic force microscope, scientists have discovered a thin layer that coats the ice below. This layer is in an intermediate stage between a liquid and a solid, where the water molecules are randomly scattered. This narrow strip moves easily, reducing friction. If this layer didn’t exist, Haché said, the ice’s coefficient of friction would be roughly 120 times higher than it is, about equal to that of concrete.
Haché also discussed bodily collisions between players. After working out the kinetic energy of the average hockey player, he calculated that the maximum force in a head-on collision would be about 30 times the force of gravity—comparable to crashing a car at 50 km/h while wearing a seat belt.
The point of this kind of modelling, according to Haché, is to connect physics to the “real world” and make it more accessible to a general audience. Popularizing science is new territory for him; Haché made the national news in January by sending electrical pulses at three times the speed of light through cables. While he continues his optics research, The Physics of Hockey has made the science bestsellers list. The book will soon be translated into Finnish.
