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Giving talks on the idea of isotopic spin


Explaining Dave Peaslee's letter
Murray Gell-Mann Scientist
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Dave Peaslee – who had worked with Weisskopf just before me at MIT, he had left MIT by the time I arrived. Dave Peaslee was then at Columbia and he wrote up this idea and why it wouldn't work, but very obscurely; it was not easy to read his letter, but since I had done the same thing I was able to understand his letter. Then I went to the Institute for Advanced Study on a visit in the spring of 1952 on my way to Europe. I had awarded myself the Murray Gell-Mann travelling fellowship to Europe and I was going to pay my first visit to Britain, France, Italy, Spain, and Switzerland. And when I stopped in Princeton, visiting the hospital or there also for a minor surgical procedure, I was invited to give a little talk at the Institute for Advanced Study. Oh no, perhaps I wasn't invited to give a talk. Anyway, I visited–I guess I was in Princeton anyway–and I visited the institute and visited my old colleagues there. And they asked me if I understood what Peaslee's letter was about, because they had read Peaslee's letter and they couldn't understand it. And I said yes, I hadn't read it very thoroughly either, but since I had worked out the same ideas I could explain my ideas, and it was an idea for how the strange particles could be explained but it was an idea that was flawed and I would explain the flaw.

So they hustled me into the conference room and the seminar room and I gave what amounted to a seminar. I described the idea and then I described how…  I was going to describe how electromagnetism would prevent it from working and so on. Well, in fact I did that. I described the idea and I described how electromagnetism would prevent it from working, and then I gave an example. I said, ‘Suppose for example the v one zero’, which is what we later called the lambda, I mean yes, what… what was called the lambda later on–this was in June, or May–May probably, May 1952. And the names lambda and so on weren't given until 1953 at the conference at Bagnères-de-Bigorre–which I didn't attend unfortunately. Anyway, in May 1952 I presented the idea and I told about why electromagnetism would ruin it and then I started to give an example. I said, ‘Suppose the v one zero is a member of a multiplet, and isotopic multiplet with i = 5/2.’ Now of course there's the difficulty that i = 5/2, that's lots of charged states and nobody had observed a great many multiple charge states such as i = 5/2 would have. But I was going to assume that somebody might discover them some day later, and I would still explain how the idea would function and then why it would be ruined by electromagnetism. I had explained it in general and I was now going to explain it in the specific case. However, instead of saying i =l 5/2, I said i = 1 – just a slip of the tongue. But as soon as I said it I realized that if it were i = 1 there would be no problem: there was no way that electromagnetism could convert i = 1 into i = 3/2; whereas it could easily convert i = 5/2 into i = 3/2. And then I went through in my mind as I stood there all the reasons why i = 1 would be thought to be impossible and I couldn't see that any of them held water. So I said ‘I think this is it! I think this is the explanation.‘ Well everybody pooh-poohed it, and they said, ‘Well, we don't understand what you're talking about and this doesn't seem like a very good idea, and this is just a special case and what we have already been saying,’ and so on and so forth. So I didn't pursue it further at that moment.

New York-born physicist Murray Gell-Mann (1929-2019) was known for his creation of the eightfold way, an ordering system for subatomic particles, comparable to the periodic table. His discovery of the omega-minus particle filled a gap in the system, brought the theory wide acceptance and led to Gell-Mann's winning the Nobel Prize in Physics in 1969.

Listeners: Geoffrey West

Geoffrey West is a Staff Member, Fellow, and Program Manager for High Energy Physics at Los Alamos National Laboratory. He is also a member of The Santa Fe Institute. He is a native of England and was educated at Cambridge University (B.A. 1961). He received his Ph.D. from Stanford University in 1966 followed by post-doctoral appointments at Cornell and Harvard Universities. He returned to Stanford as a faculty member in 1970. He left to build and lead the Theoretical High Energy Physics Group at Los Alamos. He has numerous scientific publications including the editing of three books. His primary interest has been in fundamental questions in Physics, especially those concerning the elementary particles and their interactions. His long-term fascination in general scaling phenomena grew out of his work on scaling in quantum chromodynamics and the unification of all forces of nature. In 1996 this evolved into the highly productive collaboration with James Brown and Brian Enquist on the origin of allometric scaling laws in biology and the development of realistic quantitative models that analyse the influence of size on the structural and functional design of organisms.

Tags: MIT, Columbia University, Institute for Advanced Study, Europe, Princeton University, Bagnères-de-Bigorre, Dave Peaslee, Victor Weisskopf

Duration: 4 minutes, 18 seconds

Date story recorded: October 1997

Date story went live: 24 January 2008