Superfluidity

Phenomena by which, at sufficiently low temperatures, a fluid can flow with zero viscosityThe degree to which a liquid resists flow.   High-viscosity liquids (e.g., "molasses in winter") resist flow to a great degree. More formally,  viscosity of a fluid is the measure of its resistance to gradual deformation by shear stress or tensile stress. Water has a low kinetic viscosity of 0.6959. Its causes are associated with superconductivityPhenomena by which, at sufficiently low temperatures, a conductor can conduct charge with zero resistance. The current theory for explaining superconductivity is the BCS theory..