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Re: wave momentum



At 12:44 AM 3/16/99 -0700, Jim Green wrote:
There is no real E/M wave

I wouldn't have said that. By any reasonable definition, EM waves really
exist.

-- we have given up the idea of an aether long ago have we not.

We have indeed. But we needn't throw out the EM baby with the bath-water
(or bath-ether).

Of course I readily admit that action at a distance is not much more "real"

That gets directly at the point. Conservation-at-a-distance is almost as
useless as no conservation at all. It is precisely to ensure *local*
conservation of momentum that we need expressions for the momentum content
of an EM field.

These points (and most of the other issues raised in this thread) are
pretty well covered in _The Feynman Lectures on Physics_ chapter 27, "Field
Energy and Field Momentum".

Cheers --- jsd