© AIP Emilio Segrè Visual Archives, Segrè Collection.

Lars Onsager was a physical chemist and theoretical physicist of Norwegian background who possessed extraordinary mathematical talent and physical insight. In the chemistry community he is perhaps best known for his 1929-31 derivation of what became known as the Onsager reciprocal relations for which he received the Nobel prize in Chemistry in 1968, and for his work on electrolytes, which went considerably beyond the seminal work of Peter Debye. In physics, perhaps, his most outstanding contributions were his 1944 exact solution of the two dimensional Ising model of coupled spins on a lattice, which almost 70 years later still stands as a tour de force of statistical physics; his 1949 work on the quantization of vorticity in superfluid helium, which was largely unrecognized until it was independently reproduced by Feynman two years later; and his 1954 work on de Haas von Alfven measurements of electronic orbits in metals. For recreation, he loved to do difficult mathematical integrals, and once spent almost two years obtaining an analytic solution of an integral that appeared in the Gell-Mann and Brueckner RPA calculation of the correlation energy in metals, one that they had evaluated numerically. He spent the last decades of his career working on understanding the properties of ice, a problem that continues to challenge the best and brightest in chemical physics. (Unit: 8)