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Does anyone know what Feynman was referring to in this interview which appears at the beginning of The Feynman Tips on Physics? Note that he is referring to something that did not appear in the Feynman lectures.

I didn't like to do the second year, because I didn't think I had great ideas about how to present the second year. I felt that I didn't have a good idea on how to do lectures on electrodynamics. But, you see, in these challenges that had existed before about lectures, they had challenged me to explain relativity, challenged me to explain quantum mechanics, challenged me to explain the relation of mathematics to physics, the conservation of energy. I answered every challenge. But there was one challenge which nobody asked, which I had set myself, because I didn't know how to do it. I've never succeeded yet. Now I think I know how to do it. I haven't done it, but I'll do it someday. And that is this: How would you explain Maxwell's equations? How would you explain the laws of electricity and magnetism to a layman, almost a layman, a very intelligent person, in an hour lecture? How do you do it? I've never solved it. Okay, so give me two hours of lecture. But it should be done in an hour of lecture, somehow -- or two hours.

Anyhow I've now cooked up a much better way of presenting the electrodynamics, a much more original and much more powerful way than is in the book. But at that time I had no new way, and I complained that I had nothing extra to contribute for myself. But they said, "Do it anyway," and they talked me into it, so I did.

Did this approach to teaching electrodynamics appear in any of his later writing?

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I don't know exactly what he is referring to, but one possibility is the QFT way to do it (which for Feynman was essentially a warm up exercise on the way to deriving GR from similar principles). Basically the unique theory of a Lorentz Invariant, charge=0 massless spin 1 particle at low energies is Maxwell's equations. Feynman's way of getting there in his Lectures on Gravitation is to start from conservation of charge and to say that photons couple to matter as $A_\mu J^\mu$ and then by looking at various scattering amplitudes you can end up at the Maxwell Lagrangian. –  Andrew Feb 26 at 10:58
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"which for Feynman was essentially a warm up exercise on the way to deriving GR from similar principles" Can you provide some reference for this? Very curious to hear about it. –  Danu Feb 26 at 11:37
    
may be he is talking about Feynman diagrams –  Hubble07 Feb 26 at 12:42
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2 Answers 2

I am not sure, but maybe this is about Feynman's derivation of the Maxwell equations outlined in Dyson's article http://signallake.com/innovation/DysonMaxwell041989.pdf (Am. J. Phys. 58(3), March 1990, p. 209). However, my impression was that derivation is deficient.

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This is very interesting, but the article you linked to says that derivation was discovered in 1948, whereas the Feynman lectures were delivered in 1961-1963. So Feynman must've been referring to something else in the interview I quoted. –  littleO Feb 26 at 18:22
    
@littleO: As I said, I am not sure –  akhmeteli Feb 26 at 18:37
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It is possible that Feynman was referring to Feynman Diagrams (for which work he received a Nobel Prize). Feynman diagrams offer a graphical representation of particle interactions collectively known as Quantum Electro Dynamics (QED). Feynman's contribution provided a means to analyze quite complex interactions without relying solely on manipulating wave equations or matrices.

As an adjunct analysis device, most theoreticians agree that Feynman diagrams have been quite successful.

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The same remark than for the previous answer [ physics.stackexchange.com/a/100971/16689 ] applies here as well: the Feynman diagrams have been invented long before his lectures. So if he wanted to present the Maxwell equation from the diagram (an interesting program by itself which I'm not sure how to do that) he would have done this already in his lectures. –  FraSchelle Mar 5 at 9:54
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