> On the Sunday Feynman was up at his usual hour (nine a.m.), and we went down to the physics building, where he gave me another two-hour lecture of miscellaneous discoveries of his. One of these was a deduction of Maxwell’s equations of the electromagnetic field from the basic principles of quantum theory, a thing which baffles everybody including Feynman, because it ought not to be possible.

Physics stackexchange discussion of this [1].

That includes a link to a 2001 paper, "Feynman's derivation of Maxwell equations and extra dimensions" [2].

Here's a paper Dyson wrote about it in 1989 [3].

That was discussed here on HN [4].

[1] https://physics.stackexchange.com/questions/391744/does-feyn...

[2] https://arxiv.org/abs/hep-ph/0106235

[3] http://fermatslibrary.com/s/feynmans-proof-of-the-maxwell-eq...

[4] https://news.ycombinator.com/item?id=11067435

> In the evening I mentioned that there were just two problems for which the finiteness of the theory remained to be established; both problems are well-known and feared by physicists, since many long and difficult papers running to fifty pages and more have been written about them, trying unsuccessfully to make the older theories give sensible answers to them. When I mentioned this fact, Feynman said, “We’ll see about this,” and proceeded to sit down and in two hours, before our eyes, obtain finite and sensible answers to both problems. It was the most amazing piece of lightning calculation I have ever witnessed, and the results prove, apart from some unforeseen complication, the consistency of the whole theory. The two problems were the scattering of light by an electric field, and the scattering of light by light.

> On the third day of the journey a remarkable thing happened; going into a sort of semistupor as one does after forty-eight hours of bus riding, I began to think very hard about physics, and particularly about the rival radiation theories of Schwinger and Feynman. Gradually my thoughts grew more coherent, and before I knew where I was, I had solved the problem that had been in the back of my mind all this year, which was to prove the equivalence of the two theories. Moreover, since each of the two theories is superior in certain features, the proof of equivalence furnished a new form of the Schwinger theory which combines the advantages of both. This piece of work is neither difficult nor particularly clever, but it is undeniably important if nobody else has done it in the meantime. I became quite excited over it when I reached Chicago and sent off a letter to Bethe announcing the triumph. I have not had time yet to write it down properly, but I am intending as soon as possible to write a formal paper and get it published. This is a tremendous piece of luck for me, coming at the time it does. I shall now encounter Oppenheimer with something to say which will interest him, and so I shall hope to gain at once some share of his attention. It is strange the way ideas come when they are needed. I remember it was the same with the idea for my Trinity Fellowship thesis.

> My tremendous luck was to be the only person who had spent six months listening to Feynman expounding his new ideas at Cornell and then spent six weeks listening to Schwinger expounding his new ideas in Ann Arbor. They were both explaining the same experiments, which measure radiation interacting with atoms and electrons. But the two ways of explaining the experiments looked totally different, Feynman drawing little pictures and Schwinger writing down complicated equations. The flash of illumination on the Greyhound bus gave me the connection between the two explanations, allowing me to translate one into the other.

Dyson is obviously brilliant, and I'm sure he's being humble to a fault here, but it's amazing how valuable being in the right place at the right time is. This piece of work brought Dyson to fame:

> Oppenheimer rewarded Dyson with a lifetime appointment at the Institute for Advanced Study, "for proving me wrong", in Oppenheimer's words.[0]

[0] https://en.wikipedia.org/wiki/Freeman_Dyson

I am always amazed by the sheer brainpower at the Manhattan Project. Has that level of talent ever been assembled before or since?

What a marvelous series of letter. I would sure love to have dinner with these people!

I don't know what it is about this website but it constantly makes its Chrome tab freeze up and so scrolling is as painful as walking on LEGOs.

This is fantastic.