Econstudentlog

Feynman lectures: Quantum electrodynamics

At some point I should probably read his lectures, but I don’t see that happening anytime soon. In the meantime lectures like the ones posted below in this post are good, if imperfect, substitutes: They are very enjoyable to watch. He repeats himself quite a bit; I assume that part of the reason is that this stuff is from before internet lectures became a thing, and there would have been no way for people to learn what he’d said in previous lectures, making it a reasonable strategy for the lecturer to repeat main points made in previous lectures so that newcomers not be completely lost.

The sound is really awful in the beginning of the second lecture especially, but a lot of the stuff covered there is review and the sound problem gets fixed around 17 minutes in. More generally the sound quality varies somewhat and it isn’t that great. Neither is the image quality – it’s quite grainy most of the time and this sometimes makes it hard to see what he’s written/drawn on the blackboard. The last lecture in particular would presumably have been much easier to follow if you could actually tell the differences among the various colours of chalk he’s using. There are also problems in all videos with the image freezing up around the one-hour mark (the sound keeps working, so he’ll talk without you being able to see what he’s doing), but this problem fortunately lasts only a very short while (30 seconds or so). In my opinion minor technical issues such as these really should not keep you from watching these lectures – these are lectures given before I was even born, by a Nobel Prize winning physicist – the fact that you can watch them at all is quite remarkable.

I had fun watching these lectures. Here’s one neat quote from the third lecture: “Now in order to describe both the space and the time pictures, I’m going to make a kind of graph which we call… – which is very handy – if I call it by its name you’ll be frightened so I’m not going to call it by its name.” I couldn’t hold back a brief laugh at that point – I’m sure some of you understand why. Here’s another nice one, related to Eddington‘s work on the coupling constant: “The first idea was by Eddington, and experiments were very crude in those days and the number looked very close to 136, so he proved by pure logic that it had to be 136. Then it turned out that them experiments showed that that was a little wrong, that it was closer to 137, so he found a slight error in the logic and proved [loud laughter in the background] with pure logic that it had to be exactly the integer 137.” There are a lot more of these in the lectures and incidentally if you manage to watch these lectures without at any point feeling a desire to laugh, your sense of humour is most likely very different from mine. I’m sure you’ll have a lot more fun watching these lectures than you’ll have reading articles like this one.

I will emphasize that these lectures are meant for the general public. Knowledge about stuff like vector algebra, modular arithmetic and complex numbers is not required, even though he implicitly covers this kind of stuff in the lectures. He tries very hard to keep things as simple as possible while still dealing with the main ideas; if you’re the least bit curious don’t miss out on this stuff due to some faulty assumption that this stuff is somehow beyond you. Either way you’ll probably have fun watching these lectures, whether or not you understand all of the stuff he covers.

Oh right, the lectures:

(This is the one I talked about with really bad sound in the beginning. The issue is as mentioned resolved approximately 17 minutes in.)

If you like these lectures and haven’t seen his lectures on the character of physical law (which I’ve blogged before), you’ll probably like those as well – you can start here.

March 5, 2014 - Posted by | Lectures, Physics

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