Ice skating is moving on ice by use of ice skates. It can be done for a variety of reasons, including leisure, traveling, and various sports. Ice skating occurs both on specially prepared indoor and outdoor tracks, as well as on naturally occurring bodies of frozen water such as lakes and rivers.
thumb|300px|'Skating fun' by 17th century Dutch painter Hendrick Avercamp.A study by Federico Formenti of the University of Oxford suggests that the earliest ice skating happened in Southern Finland about 4000 years ago. Originally, skates were merely sharpened flattened of bone strapped to the bottom of the foot. Skaters did not actually skate on the ice, but rather glided on top of it. True skating emerged when a steel blade with sharpened edges was used. Skates now cut into the ice instead of gliding on top of it. Adding edges to ice skates was invented by the Dutch in the 13th or 14th century. These ice skates were made of steel, with sharpened edges on the bottom to aid movement. The construction of modern ice skates has stayed largely the same.
In the Netherlands, ice skating was considered proper for all classes of people to participate in, as shown in many pictures by the Old Masters. James II of England 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, and was soon enjoyed by people from all walks of life. It is said that Queen Victoria got to know her future husband, Prince Albert, better through a series of ice skating trips; meanwhile Fenland agricultural workers became masters of speed skating. However, in other places, participation in ice skating was limited to members of the upper classes. Emperor Rudolf II of the Holy Roman Empire enjoyed ice skating so much he had a large ice carnival constructed in his court in 1610 in order to popularise the sport. King Louis XVI of France brought ice skating to Paris during his reign. Madame de Pompadour, Napoleon I, Napoleon III, and the House of Stuart were, among others, royal and upper class fans of ice skating.
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 while 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.
How the low-friction surface develops is not exactly known, but a large body of knowledge does exist. These are explained below.
Experiments show that ice has a minimum kinetic friction at −7°C (19°F), and many indoor skating rinks set their system to a similar temperature. The low amount of friction actually observed has been difficult for physicists to explain, especially at lower temperatures. On the surface of any body of ice at a temperature above about −20°C (−4°F), there is always a thin film of liquid water, ranging in thickness from only a few molecules to thousands of molecules. This is because an abrupt end to the crystalline structure is not the most entropically favorable possibility. The thickness of this liquid layer depends almost entirely on the temperature of the surface of the ice, with higher temperatures giving a thicker layer. However, skating is possible at temperatures much lower than −20°C, at which temperature there is no naturally occurring film of liquid.
When the blade of an ice skate passes over the ice, the ice undergoes two kinds of changes in its physical state: an increase in pressure, and a change in temperature due to kinetic friction and the heat of melting. Direct measurements show that the heating due to friction is greater than the cooling due to the heat of melting. Although high pressure can cause ice to melt, by lowering its melting point, the pressure required is far greater than that actually produced by ice skates. Frictional heating does lead to an increase in the thickness of the naturally occurring film of liquid, but measurements with an atomic force microscope have found the boundary layer to be too thin to supply the observed reduction in friction .
The first main danger in ice skating is falling on the ice, which is dependent on the quality of the ice surface, the design of the ice skate, and the skill and experience of the skater. While serious injury is rare, a number of (short track) skaters have been paralysed after a fall when they hit the boarding. An additional danger of falling is injury caused by the skater's own metal blades or those of other skaters. Falling can be fatal if a helmet is not worn to protect against serious head trauma.
The second, and more serious, danger is falling through the ice into the freezing water underneath when skating outdoors on a frozen body of water. This can lead to serious injury or death due to shock, hypothermia or drowning. It is often difficult or impossible for skaters to climb out of the water back onto the ice due to the ice repeatedly breaking, the skater being weighed down by skates and thick winter clothing, or the skater becoming disoriented under water. The skater may even not be able to find the hole he fell through. This may result in drowning or hypothermia, but the rapid cooling can also create a state in which someone can be revived up to hours after having fallen in the water.
Major international competitions are sanctioned by the International Skating Union (ISU). These include the Winter Olympic Games, the World Championships, the World Junior Figure Skating Championships, the European Figure Skating Championships, the Four Continents Figure Skating Championships, and the ISU Grand Prix of Figure Skating.
In Frysia, the Netherlands, the Elfstedentocht is a 200 km long race on natural ice around the province, which was held for the first time in 1909 and has by 2008 been held only 15 times because the ice along the entire course has to be thick enough for large groups to skate on. It is expected to become an even more rare event in the future, due to climate change.
A number of recreational activity games can be played on ice.
Synthetic ice uses a hard polymer skating surface that can be set up anywhere in any climate. It does not require water, cold weather, chilling equipment, or maintenance equipment. Major strides in synthetic ice technology have been made in recent years, which have brought synthetic ice surfaces from some manufacturers with skating characteristics that are very close to that of real ice.