††††Cryogenics is the study of matter at very low temperatures. It includes the study of liquefied gases and effects, such as superconductivity, that occur when materials are very cold.
In 1884, a Scottish scientist, Sir James Dewar became the first person to cool and compress oxygen gas until it became a liquid.
Today the production of oxygen, nitrogen and argon is carried out by separating air at cryogenic temperatures. A number of engineering processes are carried out more rapidly and more cheaply at very low temperatures.
Cryogenics is also used in some kinds of surgery. In eye surgery, for example, a freezing probe is applied to the outside of the eye to repair damage to its sensitive screen, the retina.
