Superfluid

Superfluidity is a state of matter in which the matter behaves like a fluid without viscosity and with infinite thermal conductivity. The substance, which looks like a liquid, will flow uncontrollably, and also will be at exactly the same temperature throughout itself. Despite its lack of viscosity, the liquid still has surface tension which allows it to rise up the sides of its container without the normal restrictions of flow. This allows the liquid to "flow" up the the sides of the container and over the top.


These unusual effects are observed when liquids, typically of helium-4 or helium-3, overcome friction in surface interaction at a stage (known as the "lambda point", which is the temperature and pressure, for helium-4) at which the liquid's viscosity becomes zero. Also known as a major facet in the study of quantum hydrodynamics, this effect was discovered by Pyotr Kapitsa, John F. Allen, and Don Misener in 1937 and has been described through phenomenological and microscopic theories. In the 1950s Hall and Vinen performed experiments establishing the existence of quantized vortex lines. In the 1960s, Rayfield and Reif established the existence of quantized vortex rings.

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