Carver Mead

Coherent, Concise, and Challenging: For those of us who were fascinated by Feynman's presentation of the vector potential field A, this book is irresistable. Mead tries to build the foundations of electricity and magnetism anew, and does a fascinating job of it.

There is a lot of history and historiography mixed in with this short book, but I myself find that fascinating. If you're interested in how the currents of thought might have eddied, or where key suggestions were missed, or what from Einstein may have been underappreciated, you'll enjoy this side of the book.

All that said, this book is chewy, and does only a mild amount of hand-holding in walking through the math. This is NOT anybody's first book of mathematical physics - but if you have enjoyed reading books by (e.g.) Feynmann, Misner/Thorne/Wheeler, Herb Kroemer, Andy Grove, Morse/Feshbach, Francon, Ichimaru, Khinchin, Papoulis, Polya, Sapriel, and/or Wiener, you're part of the natural audience for this book. If you liked "The Elegant Universe" you may love this book (and find some common themes), but this book is more mathematically demanding. On the other hand this is no mere tome, and does not require more than undergraduate competence.

I would have liked to see more visualization aids - some of the concepts in this formulation lend themselves very well to a visual presentation. I'm going to be rereading this book, and I'm really looking forward to expository textbooks which may follow this line of presentation.

If you're in doubt, buy this - it's challenging, but very broad and brilliant, and is not only about electrodynamics.… (més)

Interesting, but somewhat frustrating. I wish Mead had started by explaining his goal, instead of requiring us to figure it out as we go.

As I understand him, his point is that:
* Electrons are fields not particles (and he makes explicit his disagreement with Feynman on this point
* There is no such thing as collapse of the wave function, there is only decoherence over short (but finite) timescales, driven by interference from the rest of the universe
* There is no such thing as the EM field, what happens is that "effects" from charged particles propagate outward along the line-cone, both forward and backward in time, and interact with what they find along the light-cone --- but there are no independent degrees of freedom associated with the EM field.
* Because you have this backward-in-time propagation of EM effects, you have a constant random kicking of charged particles that gives radiation reaction.

Obviously I am happy with the first point, less happy about the second point, and sceptical about the third point. My scepticism regarding this way of viewing EM comes from a few different things.

First of all, I'm not sure it works in a GR world. It seems to rely on precise balancing of what goes out along both the fwd and bwd light cones, and in a GR world I'm not sure you get that precise balancing.

Second it doesn't seem to be a useful way of looking at the world in the sense that it generalizes. The same idea might, I guess, work for gravity (subject to my curved space-time point), but it doesn't seem like it's going to work for the weak interaction (massive boson field) and I'm not sure if it works for QCD (irreducibly strong interaction rather than free fields plus perturbation).

Third it doesn't seem to deal with my fundamental collapse of the wave function issue which is the example of sending out two photons, testing the state of one, and having the state of the other correlate exactly. (Or maybe it does work because you can propagate stuff backwards in time. I need to find a better explanation of this.)

Fourth it seems like life is going to get very messy trying to explain the thermodynamics of EM fields if you claim they don't exist, that the thermal effects are also part of the fwd/bwd lightcone interaction.

Overall, I think his goal was, like mine, to demystify QFT, and to show that QED can be viewed as sensible rather than a form of magic, but that he approached the problem in a not very useful fashion
* by concentrating on a few classical examples,
* by not explaining his full conceptual framework, and
* by not explaining how his framework covers the rest of QED, let along QFT and the standard model.… (més)