Nobel Prize time reminds me that I haven’t yet blogged about one of the most significant omissions from the list of winners in recent years.
George Zweig is a Russian-born American physicist who was one of the two independent inventors of the concept of what are now known as quarks.
Born in Moscow, on 20 May 1937. Zweig’s parents had been born in what is now Poland, but was then part of the Austro-Hungarian Empire, so they were Austrian citizens. Zweig’s father grew up in Vienna, but he and his wife were living in Germany when Hitler came to power in 1933, and left for Russia because they were afraid of being persecuted as Jews. When George was born, they had a choice of giving him Austrian or Russian citizenship, and chose the latter because of the Austrian attitude towards Jews, althouh as Zweig now comments ruefully, “the Russians weren’t perfect either”. In 1937, shortly after George Zweig was born, his parents left Moscow and went back, with the baby, to Vienna to try to persuade his father’s parents to flee from the war that was by then obviously imminent. The older Zweigs refused, and after the Anschluss by which the Nazis took over Austria, in 1938 George Zweig’s parents became increasingly desperate to escape from the coming conflict themselves. They only succeeded because his mother’s brother had left Poland some time before to go to America, and had enough influence to persuade Senator Vandenberg to attach an amendment to a Senate bill, listing 50 people who would be allowed to enter the United States as refugees. The Zweig family were on the list and were among the last refugees from Hitler’s empire to reach the United States before World War 2 began in Europe. Zweig’s paternal grandparents stayed in Austria, and died in Auschwitz in 1943.
Zweig became a citizen of the United States 1942, when his parents were naturalised, but this was never recognised by the Soviet Union, which always claimed him as a Soviet citizen, making it inadvisable for Zweig to travel behind what used to be the Iron Curtain. He studied at the University of Michigan (BSc 1959) and then moved to Caltech, where he completed his PhD in 1963. He had initially started research in experimental physics, working on a high energy experiment at the Bevatron, but became frustrated by the difficulty of getting any meaningful results, and switched to theory, under the guidance of Richard Feynman. Feynman “exerted his influence”, says Zweig, “both through his work and outlook. Solutions to problems were invariably based on simple ideas. Physical insight balanced calculational skill. And work was to be published only when it was correct, important, and fully understood. This was a stern conscience who practiced what he preached.”
During his time as a frustrated experimenter, Zweig had occasionally discussed his work with Murray Gell-Mann, and it was Gell-Mann who suggested that he should seek guidance from Feynman. But in the autumn of 1962, when Zweig was switching from experiment to theory, Gell-Mann departed on an extended visit to MIT (as a visiting lecturer), and Zweig and Gell-Mann did not meet again, or have any communication, until Zweig returned from a visit to CERN almost two years later.
After completing the work for his PhD in 1963, Zweig spent a year working at CERN, in Geneva, where he developed his model of structure within the proton and neutron, which he described in terms of three sub-baryonic particles that he called aces. The same concept was being developed at the same time by Gell-Mann, although neither of them knew of the other’s work; it was Gell-Mann who gave
the entities the name quarks, and managed to make this name stick, even though his proposal was initially much more tentative than Zweig’s.
From a perspective fifty years on from this work, it is hard to appreciate just how audacious this idea was. In the early 1960s, the nucleons were regarded as fundamental and indivisible building blocks of nature (much as atoms had been regarded before the 1890s); the really outrageous requirement of the ace/quark model was that the hypothetical sub-baryonic particles would each have a fractional electric charge, either 1/3 or 2/3 of the magnitude of the charge on an electron.
Some idea of just how outrageous this idea seemed at the time can be gleaned from the extremely cautious way in which Gell-Mann put forward the idea. In a paper published in 1964, he wrote:
It is fun to speculate about the way quarks would behave if they were physical particles of finite mass (instead of purely mathematical entities as they would be in the limit of infinite mass) . . . a search for stable quarks of charge ©1/3 or‹d‹
+2/3 and/or stable diquarks of charge ©2/3 or +1/3 or +4/3 at the highest energy accelerators would help to reassure us of the non-existence of real quarks!
Even Gell-Mann, to judge from this passage, did not believe that quarks were real. He regarded them as a mathematical device to aid calculations, and urged the experimenters to comfort the theorists by proving that quarks were not real, physical particles!
Zweig, with the confidence of youth, had no such inhibitions, and wrote up his ideas in the form of two papers which were circulated as CERN “preprints”. In what is clearly a style strongly influenced by Feynman, Zweig’s papers use graphic visual imagery to put his ideas across, as well as the mathematics. He used geometrical shapes (triangles, circles and squares) to represent his aces, linking them with lines to make the pairs and triplets corresponding to known particles (the way they are now regarded as being held together by the exchange of
gluons). With this powerful imagery, you can see the way aces/quarks combine as easily as a small child can see how to fit a triangular block into a triangular hole, and it is a great pity that the idea was never taken up and used to teach the quark model.
But Zweig soon found that he had made a mistake — not scientifically, but politically. The papers were never formally published, because of the opposition of other scientists to them. In 1981, Zweig recalled that:
The reaction of the theoretical physics community to the ace model was not benign. Getting the CERN report published in the form that I wanted was so difficult that I finally gave up trying. When the physics department of a leading university was considering an appointment for me, their senior theorist, one of
the most respected spokesmen for all of theoretical physics, blocked the appointment at a faculty meeting by passionately arguing that the ace model was the work of a “charlatan”.
By proposing the ace/quark model, which is now regarded as a jewel in the crown of particle physics, Zweig actually damaged his career prospects!
Zweig returned to Caltech in 1964, and became a junior professor there in 1967. He later (in 1983) moved to the Los Alamos National Laboratory, in New Mexico, but remained a Visiting Associate at Caltech. In the late 1960s and early 1970s, Zweig worked on defence projects, and much of this work is still classified. He then took up neurobiology, and through investigating the way the ear transforms sound into a form that is interpreted by the nervous system he discovered a new way to extract information from any kind of signal. This led to the construction of a device called SigniScope, that emulates the mechanical response of the inner ear to sound, and an understanding of how this represents music led to the design of a music synthesiser that was used to create part of the sound track for the first Star Trek movie.
In 1985, Zweig founded a company, Signition, Inc., which developed an improved version of SigniScope to analyse the structure of speech and its relationship to hearing. A third version of the device was developed as a software package to analyse many kinds of signals and images.
To somebody who is not privy to the inner deliberations of the Nobel Committee, it is totally baffling that Zweig’s fruitful theory of fundamental particles, which has now been amply confirmed by experiment and is a cornerstone of the standard model of particle physics, has not been marked by the award of a Nobel Prize.