Superfluidity

1937 Superfluidity

The book of science

Tom Sharp

Pyotr Kapitsa, John F. Allen, Don Misener physics Superfluidity

Superfluidity

Kapitsa, Allen, and Misener cooled liquid helium below 2.17 K and found it became a superfluid— flowing without friction, forming quantized vortices, forming density and temperature waves, flowing against gravity without viscosity, and conducting heat and electricity without resistance.

Second sound

Thermal conduction in a superfluid looks like a sound wave. Instead of slowly diffusing through the liquid, it moves across the liquid in a wave.

Rollin film

A film of superfluid creeps up the side of its container against gravity, without friction, without sticking, and over the top.

The mind

The mind is meta; it models minds, steps back, sees its own reflection, and steps into a mirror. We think we know the mirror surface and its frame, but the mirror is reflected in another mirror.

The history of the discovery of superfluidity in helium has two parts. First, the discovery of superfluidity in liquid helium-4 (a Bose–Einstein condensate) in 1937 by Pyotr Kapitsa, John F. Allen, and Don Misener. Second, the discovery of superfluidity in helium-3 in the 1970s by David Lee, Douglas Osheroff, and Robert Richardson. Unlike helium-4 atoms, which are bosons, helium-3 atoms are fermions, so the explanation for its superfluidity is completely different.

Bosons have an even number of nucleons; fermions have an odd number. For a fermion to become superconducting, each atom must pair up with another, resulting in an even number of nucleons.

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