Lars Onsager (November 27, 1903 – October 5, 1976)[1] was a Norwegian American physical chemist and theoretical physicist.

After completing secondary school in Oslo, he attended the Norwegian Institute of Technology (NTH) in Trondheim, graduating as a chemical engineer in 1925.

[7] On leaving JHU, he accepted a position (involving the teaching of statistical mechanics to graduate students in chemistry) at Brown University in Providence, Rhode Island, where it became clear that he was no better at teaching advanced students than freshmen, but he made significant contributions to statistical mechanics and thermodynamics.

His graduate student Raymond Fuoss worked under him and eventually joined him on the Yale chemistry faculty.

[8] His research at Brown was concerned mainly with the effects on diffusion of temperature gradients, and produced the Onsager reciprocal relations, a set of equations published in 1929 and, in an expanded form, in 1931, in statistical mechanics whose importance went unrecognized for many years.

However, their value became apparent during the decades following World War II, and by 1968 they were considered important enough to gain Onsager that year's Nobel Prize in Chemistry.

[10] At Yale, he had been hired as a postdoctoral fellow, but it was discovered that he had never received a Ph.D.[3] While he had submitted an outline of his work in reciprocal relations to the Norwegian Institute of Technology, they had decided it was too incomplete to qualify as a doctoral dissertation.

He was told that he could submit one of his published papers to the Yale faculty as a dissertation, but insisted on doing a new research project instead.

His dissertation laid the mathematical background for his interpretation of deviations from Ohm's law in weak electrolytes.

[8] During the late 1930s, Onsager researched the dipole theory of dielectrics, making improvements for another topic that had been studied by Peter Debye.

In what is widely considered a tour de force of mathematical physics, he obtained the exact solution for the two dimensional Ising model in zero field in 1944.

[16] In 1945, Onsager was naturalized as an American citizen, and the same year he was awarded the title of J. Willard Gibbs Professor of Theoretical Chemistry.

[23] The solution involved generalized quaternion algebra and the theory of elliptic functions, which he learned from A Course of Modern Analysis.

When Onsager's wife Gretel died in 1991 and was buried there, his children added an asterisk after "Nobel Laureate" and "*etc."

In 1997 his sons and daughter donated his scientific works and professional belongings to NTNU (before 1996 NTH) in Trondheim, Norway as his alma mater.