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Trivia retrieved for Superfluids (1 found)

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The state of matter that exists at the coldest temperature, Bose-Einstein Condensate superfluid, defies gravity. It flows up the side of its container, then flows over the edge and down the outside wall before dripping away.

NOTE: This is possible due to superfluids being at such a cold temperature (less than 2.1768K for helium II) that a significant fraction (over 90% in helium II) of the molecules achieve the lowest quantum state of matter while the other fraction of molecules remain as a normal liquid. Molecules in the lowest state achieve zero viscosity status while retaining the property of surface tension. The zero viscosity produces a frictionless state within the superfluid. Thus, as the molecules moves under the influence of adhesion to the container wall (van der Waal attractive forces between molecules of different types), the surface tension of the superfluid that binds molecules together by cohesion (van der Waal attractive forces between molecules of the same types) allows a front of molecules to rise up the side of the container. This is the same way that normal liquids form their meniscus. In normal liquids, the height that the liquid rises up the side of the container depends on how strong the cohesive forces between the liquid molecules are, before gravity eventually stops it. A superfluid, however, will continue to rise due to zero viscosity where the motion continues in a frictionless state without loss of kinetic energy. It is the surface tension, in binding the superfluid molecules, that allows the superfluid to flow in a thin film (about 30nm in helium II) to keep the bulk moving. The zero viscosity allows for the unimpeded distance to be travelled. This is providing that the superfluid moves at speeds below a critical velocity (60m/s for helium II or 20cm/s by another source). Above this velocity, the superfluid properties are lost and it reverts to normal fluid properties. As of now August 2019, only superfluid ⁴He and ³He have been identified and successfully experimented with. Reports of some success with superfluid evidence in hydrogen have been made in 2000 and another more recently by NASA, in the International Space Station in 2018, from atoms of rubidium.

Published on: 13 Feb 2019 2124.
Last updated: 13 Feb 2019 2124.