At school, his primary interest was literature - he wanted to study Greek - but the path to science developed in his final year after taking chemistry and physics courses.

Danish physicist, Niels Bohr, had founded the Institute for Theoretical Physics at the University of Copenhagen which became the World centre of quantum-physics studies.

During this period, he met key personalities who developed quantum mechanics - and their classically-established elders - with whom he was to maintain connexions throughout his career, including Bohr, Albert Einstein, Erwin Schrödinger, Werner Heisenberg, Wolfgang Pauli, John von Neumann, Leo Szilard and Fritz London.

[6][7][8][9][10] In 1924, he joined the University of Chicago, with the encouragement of Henry Gale (an avowed experimental physicist); this was initially under a second NRC fellowship, before employment as a research associate from 1926.

"[11] He received a Guggenheim Fellowship for a year from September 1927, nominally with Schrödinger, who was at the University of Zurich, although he spent a good deal of this time in Berlin.

Before 1949, he and other physicists such as Hans Bethe, Enrico Fermi, Edward Teller, Lothar Nordheim and von Neumann worked a few months per year at Los Alamos National Laboratory.