Anthony J. Leggett held his Nobel Lecture December 8, 2003, at Aula Magna, Stockholm University. He was presented by Professor Mats Jonson, Chairman of the Nobel Committee for Physics.

Summary: Helium exists in two stable forms: the normal Helium-4 with two neutrons and two protons, and Helium-3 with one neutron and two protons. The two show very different superconducting properties at very low temperatures. The anomalous superfluidity of Helium-3 is explained using the principles of quantum mechanics. An analogy between ferro-magnets and liquid Helium-3 is used to explain the theory of superfluid Helium-3.