Ice skating

Ice skating is traveling on ice with skates, narrow (and sometimes parabolic) blade-like devices moulded into special boots (or, more primitively, without boots, tied to regular footwear). It is mainly done for recreation and as a sport.

It is possible on canals and lakes, etc. after it has been freezing for some time, and at indoor and outdoor skating tracks and areas with artificial cooling. The skating rink regarded as the world's longest (about 8 kilometres long) is the Rideau Canal located in Ottawa, Ontario, Canada.

In some countries with a temperate climate, e.g. the Netherlands, frozen canals and lakes are fairly rare, but skating is popular where these are encountered.

History

Ice skating is believed to have been started in Sweden over twelve hundred years ago by the Vikings. The runners, made of bones, were ground down until they formed a flat gliding surface, and thongs tied them to the feet. The blades were polished oxen or reindeer bones. These were not very efficient, so they used a long stick to push themselves forward and stay upright. Skates were originally used for transportation over the frozen rivers and later used for fun. Skating has been found to date back to 50 B.C. It was most common to skate where there are long, cold winters especially in places like Scandinavia.

In the 17th century, canal racing on wooden skates with iron blades was popular in the Netherlands. Also in that century, James, the younger son of the British monarch Charles I, came to the Netherlands in exile, and he fell for the sport. When he went back to England, this "new" sport was introduced to the British aristocracy.

In the 18th century, ice skating became known world-wide as a sport and the Dutch created skates with much longer blades.

How it works

Ice skating works because the metal blade at the bottom of the ice skate shoe can glide with very little friction over the surface of the ice. However, slightly leaning the blade over and digging one of its edges into the ice ("rockover and bite") gives skaters the ability to increase friction and control their movement at will. In addition, by choosing to move along curved paths whilst leaning their bodies radially and flexing their knees, skaters can use gravity to control and increase their momentum. They can also create momentum by pushing the blade against the curved track which it cuts into the ice. Skillfully combining these two actions of leaning and pushing - a technique known as "drawing" - results in what looks like effortless and graceful curvilinear flow across the ice.

Research in materials has come up with a number of theories explaining the true nature of skating. The issue is that the precise mechanism by which the low-friction is generated is not fully understood, though a number of plausible theories abound usually involving explanations of air-ice boundary layer water and/or friction generated through the skate bottom.

The boundary layer of water being the cause of slipperiness has been disputed when measurements of the boundary layer water with an atomic force microscope found the boundary layer to be too thin to supply sufficient friction reduction. Nevertheless, a popular theory of this is: Because the molecular structure of ice is a crystalline structure, it turns out that having this structure abruptly stop when it reaches the top of the ice is not the most entropically favorable form. Instead, there is always a thin film of liquid water ranging in thickness from only a few molecules to thousands of molecules on top of the ice. This allows a smoother transition from the structured ice to the completely random structure of the air molecules. The thickness of this liquid layer depends almost entirely on the temperature of the surface of the ice (higher temperatures give a thicker layer), and the liquid layer disappears around −20°C (−4°F). However, skating is still possible at temperatures much lower than −20°C. Experiments show that ice has a minimum of kinetic friction at −7°C (19°F), and many indoor skating rinks set their system to a similar temperature.

History

How it works

External links

See also

Gourt Home::Gourt :: Ice skating

History

How it works

External links

See also