Born Nov. 27, 1903, in Oslo. Theoretical physicist and physical chemist; of Norwegian nationality.

Onsager graduated from the Norwegian Technical Institute in Trondheim in 1925. Since 1928 he has lived and worked in the USA. He became a professor at Yale University in 1940. His main works deal with theories of irreversible processes, phase transitions, and electrolytes. In 1926 he derived the Onsager equation of electrical conductivity. In 1931, Onsager discovered the principle of the symmetry of kinetic coefficients, which became the basis of the phenomenological thermodynamics of nonequilibrium processes. In 1942 he derived an exact solution of the two-dimensional Ising problem (published 1944). The solution predicts a logarithmic dependence of the specific heat on the temperature near the critical point. Onsager also proposed a theory of quantumized vortices in superfluid helium. He was awarded the Nobel Prize in 1968.