Superfluidity is a state of matter in which particles move freely without resistance. Superfluids are strange fluids that have very low viscosity and can flow without friction. They are found in both liquids and gases, and they exhibit many unusual properties.
Superfluids were first predicted by Einstein and Lev Landau in the 1930s. They were observed for the first time in helium-4 by Pyotr Kapitsa, John Allen, and Don Misener in 1937. In 2004, superfluidity was observed in ultracold atomic gases for the first time. Since then, there has been much research on these strange fluids.
Some of the most unusual properties of superfluids include the following:
•They can flow up hills: If you place a container of superfluid on a hill, it will start to flow uphill until it reaches the top (this is called the “Meissner effect”). This happens because superfluids are repelled by gravity. •They can tunnel through barriers: If you place a barrier in front of a superfluid, it will tunnel through the barrier (this is called “quantum tunneling”). •They can rotate without dissipating energy: A rotating container of superfluid will continue to rotate forever without losing energy (this is called “superrotation”). •They have zero viscosity: This means that they can flow without any resistance whatsoever. This property makes them ideal for applications such as lubrication or hydraulic fluid.