Freeman Dyson - How difficult was it to understand Schwinger? (73/157)
Ғылым және технология
To listen to more of Freeman Dyson’s stories, go to the playlist: • Freeman Dyson (Scientist)
Freeman Dyson (1923-2020), who was born in England, moved to Cornell University after graduating from Cambridge University with a BA in Mathematics. He subsequently became a professor and worked on nuclear reactors, solid state physics, ferromagnetism, astrophysics and biology. He published several books and, among other honours, was awarded the Heineman Prize and the Royal Society's Hughes Medal. [Listener: Sam Schweber; date recorded: 1998]
TRANSCRIPT: So in the meantime, going back now a couple of months, there was a meeting of all the leading physicists at Pocono in the spring of '48, where I wasn't invited but there were then all the leading people, Schwinger and Feynman and Bethe and Oppenheimer and Niels Bohr and Rabi and Lamb, all those people were there. And that was where Schwinger then presented his new version of quantum electrodynamics, which was also getting the right answers. Schwinger had in fact been able to calculate the magnetic moment of the electron and get the right answer, which was a great triumph. That was another of the Columbian experiments done by Kusch and Foley, where they measured the magnetic moment of the electron very precisely, and they found that it was not the Dirac value, but differed from the Dirac value by a certain finite amount, which then Schwinger was able to calculate. And then - so that was a big triumph for Schwinger - and his method of calculating was much more conventional. It was essentially just a relativistic version of Hans Bethe's method. It involved things that Schwinger called Green's Functions, which again I found rather incomprehensible, but Schwinger was very obscure when he described the things he was doing. He loved to make the - as Oppenheimer said, most people when they explain something, they're telling you how to do it; but when Schwinger explains something he's telling you that only he can do it! That was roughly the way it was, I mean, so from Schwinger one only had the impression that this was so difficult and so elaborate a way of calculating, only Schwinger could possibly do it. So people were not too happy with that. But then later on Feynman also was able to calculate the electromagnetic moment and he also got the right answer with his completely different method. So that was also very impressive, that both of these methods somehow must be doing the same thing in some fashion, but nobody understood really the connection. So that was the background in which I came to Ann Arbor; and in Ann Arbor in June of '48 I learned the stuff from Schwinger himself. I listened to his lectures in the morning and I spent the afternoons working very hard, just simply going through the Schwinger lectures step by step and really understanding what he'd been saying, which was very hard work because he just had this wonderfully baroque style of lecturing in which everything was dressed up to be as complicated as possible, and the answer somehow came out miraculously at the end. But I managed to figure out what he'd been doing, so what was clear at the end of this was that actually the Green's Functions that Schwinger was using were really the same thing as the commutators in quantum field theory, that in a way what Schwinger was doing was basically quantum field theory, and that was something I knew, because I'd had it from Kemmer, so I was able to translate Schwinger into the language of quantum field theory and that made sense of it. And then the problem remained whether one could connect that with Feynman, whether one could reduce Feynman also to quantum field theory, and that remained a problem after I finished at Ann Arbor. It was clearly the next thing I had to try. And you actually could talk to Schwinger, I mean... I talked with him very well, in a very happy way. I mean Schwinger was actually very friendly to me.
[SS] And very approachable on a one to one..?
Yes. When I had him alone, I mean, all this public performance, this disappeared. He actually told me quite plainly what he was doing. No, he was very pleasant, and I always felt he was really a great gentleman because afterwards I sort of stole his thunder, and he never made any complaints.
Пікірлер: 69
Freeman Dyson is such a brilliant guy. To even understand what Schwinger and Feynman were doing at the time one needed to be on another level.
These Dyson interviews are incredible treasures that afford us a unique insight into the history and some of the conceptual developments of physics. I was privileged enough to take a couple of advanced courses with Schwinger, and Dyson really hit the nail on the head: Schwinger was an immensely generous human being on a one-on-one basis, but he made almost no attempt to make his lectures more comprehensible for the students. Nor did he take fools or mediocrity gladly.
A total gentleman, Mr Dyson.
Fantastic to hear these great physicists talk about the events and people who shaped the modern world both in and outside science. A real treasure. Thank you
I love these videos. thanks
These snippets are really helpful, thanks.
I think it's quite telling, telling about Freeman Dyson, that he got on so well with Schwinger. Because (shall we say) not everyone managed to do this! But Dyson clearly had a high quality, deep, and positive relationship with him. And, Schwinger seems to have felt this and reciprocated with Dyson, basically because of what a wonderful human being Dyson was.
He nailed Schwinger’s style perfectly.
@allybally0021
4 жыл бұрын
A genius but probably not what you want in teaching.
@placebojesus5652
4 ай бұрын
Well to be fair he quoted Oppenheimer for the crucial/essential part “…most people when they explain something, they’re telling you how to do it, but when Schwinger explains something, he’s telling you that only he can do it,” lol and then he pointed out his baroque style of teaching that makes everything as complicated as possible where the answer magically arrives at the end, and then once he finally grasped it he realized it was basically just quantum field theory in different clothes which of course given Dyson’s speciality in field theory ended up being useful to understand and I suppose reconcile with Feynman’s work on quantum chromodynamics/electrodynamics to reach something approximating modern quantum theory.
These two gentlemen were geniuses in their own right. I remember a book I once read, wherein it mentioned that Dyson wanted to learn differential equations over Christmas break, and the one he wanted was in Russian....so he learned Russian ( in a matter of DAYS). It also mentioned that Schwinger routinely solved complicated equations, with both hands on a chalkboard SIMULTANEOUSLY!!!
@toddtrimble2555
6 жыл бұрын
Well, no, I am sure Dyson (despite his acknowledged brilliance) did not learn to speak conversational Russian in a few days. From what I know (speaking as a mathematician), scientific Russian has an unusually large number of loanwords which one may deduce from knowledge of Cyrillic characters, and the more formalized mode expression would allow Dyson to extract what he needed, reading between the lines as it were.
@Divergent_Integral
6 жыл бұрын
I read in Dyson's *Disturbing the Universe* that the book he used to study differential equations was an English one by H. T. H. Piaggio. Probably this one: archive.org/details/DifferentialEquations_91
@edwardjones2202
6 жыл бұрын
John M Definitely a genius...but he didn't learn Russian in a few days...you probably can't even glance and 3000 definitions in a few days and you'd need to inculcate at least 5000 to begin to be competent in a language. What would be easier: learn the basic grammar in a few days and use the dictionary to translate and get the drift...then just ride the rest out on the equations That's my guess! Sorry for plucking numbers out of thin air but you get my drift!
@High_Priest_Jonko
5 жыл бұрын
@kirwi kirwinson It could've been his freshman year
@toddtrimble2555
5 жыл бұрын
@Dirk du Toit Thanks for the information! Of course this doesn't prove that Dyson was speaking conversational Russian after just a few days of study -- and I'd still consider that an unlikely possibility -- although the existence of savants like Daniel Tammet shows the possibility is there.
My wife: Who's he talking about? Me: Julian Schwinger My wife: Julian Schwinger? Me: The one that looks like Vincent Price. My wife: Oh him!
You see if Gell-Man had said exactly the same thing as Dyson is saying here he’d be accused again of colleague-bashing. But Dyson does it with such charm & elegance that everyone walks away feeling happily affirmed.
People with brilliant minds have brilliant memories. I have only ever knowingly met one genius who, with minimum effort, gained a double 1st in Electronics and then went back to his day job with BAe. He had no interest in being brilliant - he just was.
I thought Dirac had it sewed up. His version of the magnetic moment of the Negative Beta particle I believe lead him to the positive Beta particle. All negative states were occupied.
Poor Freeman Dyson. The interviewer is about to collapse his wave function.
Savor every word!
@DavidMcCoul
3 жыл бұрын
Yes!
I have developed an alternate approach relativistic quantum electrodynamics, out of which gravitational phenomenna fall as an isolated essential singularities - thank God for Green´s functions! (Dyson is always such a gentleman.)
@38vocan
Жыл бұрын
Does it work?
@charlesbromberick4247
Жыл бұрын
@@38vocan No, all my breakthroughs fall flat. I´m just not in the class of these men.
@38vocan
Жыл бұрын
@@charlesbromberick4247 Well, at least, I am sure you learned a lot about physics
I wonder did Feynman play any pranks on Schwinger?
@joeaverage2575
4 жыл бұрын
No, he regarded Schwinger as an equal. Feynman didn't play pranks on his equals. Plus, Schwinger kept his distance. Only Schwinger's wife was close to Schwinger, nobody else could get close. Late in life, Feynman said that many times he wanted to interact with Schwinger, but never could.
@edwardjones2202
Жыл бұрын
@@joeaverage2575 he played a prank on Edward Teller at Los Alamos
3:15
Very interesting and worthwhile video.
Do u already read it
Well Greens Functions are all well and good but I'm here to fix my hoover
Feynman and Schwinger already knew they were doing the same thing, and neither cared much about Dyson's proof of that to the rest of physicists. Schwinger was imperturbable, but he had a droll sense of humor. Years later he wrote: "There were visions at large, being proclaimed in a manner somewhat akin to that of the Apostles, who used Greek logic to bring the Hebrew God to the Gentiles." He was having fun with the fact that he and Feynman were Jewish, and Dyson wasn't.
When he laughs.... He looks like the evil old guy from 'monster house '😊......by the way great video
Wikipedia says he was an English-born American, but he seems to me to have a slight German (or similar) accent. Am I the only one who hears that? What accounts for it?
@maxwellsdaemon7
4 жыл бұрын
I am currently browsing Schweber's book "QED and the Men Who Made It" and in the chapter on Dyson, it says he spent three weeks in Germany after WWII, and that the "stay allowed Dyson to perfect his German and to familiarize himself further with German literature and culture."
@faithlesshound5621
4 жыл бұрын
His first wife was Swiss. Also, up to the 1970s, it was a common belief in the UK that a serious physical scientist needed to understand German.
@johnwheatley1550
3 жыл бұрын
It's got nothing to do with spending three weeks in Germany or learning German.. It's just the old 1930's clipped RP accent once prevalent in the UK, that's been Atlanticised by many decades living and working in the USA.
@jimbocho660
2 жыл бұрын
It's a Berkshire countryside accent. Freeman Dyson was a native of the English county of Berkshire.
@us-Bahn
Жыл бұрын
I too thought it sounded German. Wasn’t aware of any of the Berkshire/transatlantic hybrid explanation which makes sense
I have to say, some of this makes me wonder who is more obscure, was it really schwinger or is it the way physicists choose to express the most basic linear operators, with bra and ket notation etc.
I´m theoretical physicist. I suffer studying Dyson theorems
@edwardjones2202
Жыл бұрын
Is he as good as they say?
Why does this guy have two surnames?
@BLUEGENE13
6 жыл бұрын
nah dude, freeman is his first name
@GoodSteveningeverybody
4 жыл бұрын
Named after his uncle who was killed in WW1
@ublade82
Жыл бұрын
@@GoodSteveningeverybody Then it would be Deadman
@brandonclark435
Жыл бұрын
@@GoodSteveningeverybody No, he was named after the actor.
Schwing!
nnn arbor
He always seems jealous of the great physicists.
@edwardjones2202
Жыл бұрын
Where?!? Throughout these interviews he's pretty modest. In a later segment he acknowledges Fermi's genius and says that Fermi made him realise he "wasn't really a physicist"
Dyson still doesn't have deep understanding of Path Integral approach to Quantum Mechanics and Quantum Field Theory.
@Unexpectedthings007
2 жыл бұрын
huh?
@gouranggehlot4896
2 жыл бұрын
You have no understanding of how to keep your mouth shut.