Allen, John Frank (1908-2001), a Canadian-born British physicist, was one of the discoverers of superfluidity. Superfluids are fluids that have very low viscosity (resistance to flow), are almost perfect conductors of heat, and display high capillarity (a tendency to move into or out of tiny passageways).
John Allen, known as Jack Allen, was born in Winnipeg, Manitoba, Canada, on May 6, 1908. He graduated from the University of Manitoba in Winnipeg in 1929. At the University of Toronto, he studied superconductivity, an absence of electrical resistance that some substances display at very low temperatures. Allen’s work focused on the superconductive properties of liquid helium.
In 1935, Allen moved to Cambridge University in the United Kingdom, hoping to work on low-temperature physics with the Russian physicist Pyotr Kapitsa. However, Kapitsa was visiting the Soviet Union that year, and the Soviet authorities prevented him from returning to the United Kingdom. Allen therefore pursued his own researches with a Canadian assistant, Donald Misener. On Jan. 8,1938, the British science journal Nature published two articles on a newly discovered property of liquid helium—superfluidity. One of the articles was written by Kapitsa, the other by Allen and Misener.
Later, Allen and another colleague, Harry Jones, discovered the fountain effect, in which superfluid helium flows up a tube and shoots into the air after being exposed to a weak source of heat. The source Allen and Jones used in their original experiment had been a small light that they were using to view the equipment.
Allen was appointed a lecturer at Cambridge in 1944, and in 1947 he became professor of natural philosophy at St. Andrews University in Fife, Scotland. He retained this post until he retired in 1978. He died on April 22, 2001.
See also Helium ; Kapitsa, Pyotr ; Superconductivity .
