sci.physics.electromag

On Mar 8, 3:04=A0am, Benj wrote:
> On Mar 7, 7:17 pm, "Timo A. Nieminen" wrote:
>
> > Part the Second
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > The retardation of electromagnetic effects presents a direct challenge t=
o
> > the view of electromagnetism as solely an interaction between charges an=
d
> > currents, with fields merely as a mathematical auxiliary. This is
> > especially the case for radiation.
>
> This is exactly correct! =A0This is what Jefimenko has done in his
> approach and has taken quite a bit of flack for. =A0One problem is that
> a huge amount of problems have been solved using Maxwells equations
> NOT taking retardation into account. =A0

People use spanners as hammers as well. That in not
the fault of the tool maker.

Time-independent Maxwell equations
Time-dependent Maxwell's equations
http://farside.ph.utexas.edu/teaching/em/lectures/lectures.html

> People have become so familiar
> with these that they start to assume that these solutions are absolute
> and correct. =A0As you point out, they are not except in certain special
> cases. =A0And this "approximation" thing gets far worse. =A0In practical
> calculations of electromagnetics it's not only common to ignore
> retardation but to ignore a whole host of other problems as well. =A0You
> do complex caculations only to find oddball results that are summarily
> tossed aside as "non-physical solutions". What in hell is that? =A0Does
> the theory work or does it not? =A0Obviously the "problem" is that we
> are using a model to represent reality and the model is not an exact
> fit. =A0OK. Fine. So long as you KNOW you are doing that. =A0You have
> practical solutions available to all manner of practical problems.
> But the trouble starts in PHILOSOPHY! =A0This is when one starts to
> regard the MODEL as "reality" itself. There is FAR too much of this
> kind of dogma in physics today! =A0And THAT is my point.
>
> > While fields introduce some problems into physics, I believe they resolv=
e
> > more than they introduce. The mathematical convenience is immense. Wheth=
er
> > they are "real" or not, they are certainly useful. The only stance that =
is
> > certain to be properly aligned with reality is agnosticism wrt the reali=
ty
> > of fields or otherwise. However, I'd say that, on balance, it's reasonab=
le
> > to assume that fields exist. This opinion may well be coloured by the
> > practical engineering usefulness of assuming that they exist.
>
> Wow. Major exposition!
>
> Do you see what you've just said here? =A0You've said in essence that
> it's OK to assume fields exist because that mathematics gives me lots
> of practical answers to questions I have and the answers seem
> reasonably close to what I'm measuring! =A0You are saying that physics
> (science) is a religion where the important thing is how you feel
> rather than what is true. =A0If believing in fields gives you comfort
> then, who is to say that you shouldn't do it? =A0Well, I say that
> philosophers say you shouldn't do it. They say that one has to be
> careful in your definitions of what is reality and what is merely a
> model mimicking reality. =A0And to them that difference is fundamental.
> In religion the difference doesn't matter. But science is supposed to
> be tested constantly against observation and if you don't do that then
> it ain't science anymore.

If Jefimenko's equations refers to electrons, we can bring a
positron near it and cause the electron to vanish.
Real things can't vanish can they?

Sue...