I began my graduate academic work in physics at Harvard University in 1956. Julian Schwinger had just completed his reformulation of Quantum Field Theory and was preparing to instruct a three-year series of courses. I took a seat fascinated, as did others.
Attending one of [Schwinger’s] formal lectures was comparable to hearing a new major concert by a very great composer, flawlessly performed by the composer himself … The delivery was magisterial, even, carefully worded, irresistible like a mighty river … Crowds of students and more senior people from both Harvard and MIT attended … I felt privileged– and not a little daunted– to witness physics being made by one of its greatest masters. – Walter Kohn, Nobel laureate (“Climbing the Mountain” by J. Mehra and K.A. Milton).
As Schwinger stood at the chalkboard, writing ambidextrously and speaking mellifluously in well-formed sentences, it was as if God Himself was presenting the Ten Commandments. The equations were so elegant that it seemed the entire world couldn’t be created any other way. From the barest of first basic principles, he derived all of QFT, even encompassing gravity. Not only was the mathematics beautiful, but the philosophic idea of a world made of properties of space seemed to me much more satisfying than mysterious particles. I was amazed and pleased to see how all the mysteries of relativity theory and quantum mechanics that I had previously seen so baffling disappeared or were resolved.
Regretably, Schwinger, once considered “the heir-apparent to Einstein’s mantle” by J. Robert Oppenheimer, never brought forth the effect he should have had on the world of physics or rather on the public at large. It is feasible that Schwinger’s very elegance was his undoing.
Julian Schwinger was one of the most important and influential scientists of the twentieth century … Yet even among physicists, recognition of his funda ¬ mental contributions remains limited, in part because his dense formal style ultimately proved less accessible than Feynman’s more intuitive approach. However, the structure of modern theoretical physics would be inconceivable without Schwinger’s manifold insights. His work underlies much of modern physics, the source of which is often unknown even to the practitioners. His legacy lives on not only through his work, but also through his many students, who include leaders in physics and other fields.– “Climbing the Mountain” by J. Mehra and K.A. Milton.
Schwinger is noted generally, if he is noted at all, for solving a calculational problem with QFT referred to as renormalization, for which he shared the 1965 Nobel prize with Sin-Itiro Tomanaga and Richard Feynman. Feynman’s manner, which had no theoretical basis, proved to be easier to work with than Schwinger’s (and Tomanaga’s) field-based approach, and Schwinger’s method was relegated to the archives. It is Feynman’s image, not Schwinger’s, that was enshrined on a postage stamp.
However Schwinger was not content with his renormalization work:
The pressure to account for those [experimental] results had produced a certain theoretical structure that was perfectly adequate for the original task, but demanded simplification and generalization … I needed time to go back to the beginnings of things … My retreat began at Brookhaven National Laboratory in the summer of 1949. It is only human that my first action was one of reaction. Like the silicon chip of more recent years, the Feynman diagram was bringing computation to the masses … But eventually one has to put it all together again, and then the piecemeal approach loses some of its attraction … Quantum field theory must deal with [force] fields and [matter] fields on a fully equivalent footing … Here was my challenge.– from “The Birth of Particle Physics”, ed. by Brown and Hoddeson.
Schwinger’s last version of the theory was published between 1951 and 1954 in a set of five papers entitled “The Theory of Quantized Fields”. I believe that the primary reason why these masterpieces have been overlooked is that many physicists identified them too difficult to understand. (I know one who could not get past the very first page.).
Schwinger went on from there to develop a brand-new method to QFT that he called source theory (and he called its practitioners “sourcerers”), which is also practically unknown.
In addition to these memorable contributions to Quantum Field Theory, Schwinger had other achievements. As a 19-year old graduate student at Columbia University he was the very first to determine the spin of the neutron. In 1957 he found the precise form for the weak field equations before Gell-mann and Feynman. He was the first to propose electroweak unification, for which Sheldon Glashow, Steven Weinberg and Abdus Salam received the 1979 Nobel Prize. And he showed the Higgs mechanism before Peter Higgs, who shared the 2013 Nobel Prize with Francois Englert.
Read the complete article at Fields of Color.