Re: "4/3 Problem" Resolution (fwd), comment on

["John S. Denker" <jsd@MONMOUTH.COM>]

I wrote:
> >2) It is not generally true that v.E is related to div(A).

Then at 08:35 AM 5/16/01 -0700, David Rutherford wrote:

> In my original post, I showed that it definitely is. Here is my derivation
>
> -div(A) = v.(-grad(phi))/c^2 = v.E/c^2
>
> I've used the same reasoning that Feynman used to derive curl(A)=vxE/c^2,
> for constant v and E=-grad(phi) (d(A)/dt=0). If you accept Feynman's
> derivation you _must_ accept mine.

Well, actually, Mr. Rutherford has not followed Feynman's reasoning.  He
has only pushed some symbols around in patterns superficially analogous to
Feynman's calculation.

Feymnan invoked the Maxwell equations (among others).  The Maxwell
equations make certain statements about the behavior of curl(A).  There are
no corresponding equations governing the behavior of div(A).

You can make up additional equations if you want, but there is no
theoretical or experimental justification for doing so.

Arguing that div(A) must behave analogously to curl(A) is like building a
wooden mockup of a radio, and expecting it to behave like the original.

 http://www.physics.brocku.ca/etc/cargo_cult_science.html


> >   3b) It turns out that div(A) is not observable.
>
> I would be if anybody chose to try to observe it. Which they haven't.

And how are they supposed to observe it?
 -- Using the Lorentz force law?   I don't think so!
 -- Using the Aharonov-Bohm effect?  I don't think so!

  http://www.sp.phy.cam.ac.uk/SPWeb/research/AB.html