sci.physics.electromag

On Mar 10, 12:02 am, "Timo A. Nieminen"
wrote:

I've come to the conclusion that I really don't understand physics at
all! Maybe you can help me with these concepts:

> The derivation is a matter of algebra, and the algebra doesn't care about
> our interpretation of the symbols in the equation. The modern
> interpretation of the symbols is not the same as Maxwell's, but we end up
> with the same wave equation.

Ah, so physics is all about algebra and observations are irrelevant or
secondary. If the algebra gives the same answer then that represents
reality? Right?

> It is dogma. What would give fields reality? Energy, momentum, AM, for
> starters. How does the energy get from point A to point B? Again, this is
> why radiation, and the energy, momentum, and AM it carries (or the energy,
> momentum, and AM that gets from point A to point B through some other
> means, if you believe that fields don't exist) is central.

Ok, now I'm really confused. somehow algebra transmits energy, M, and
AM? I suppose that if we regard photons as carriers of energy for
example that "explains" it, but aren't photons particles with no mass
(and hence no kinetic energy) and also at the same time are "wave
packets" with waves carrying energy but without any medium to do any
waving?

> Why would they need to be composed of particles? From the QED viewpoint,
> they're composed of photons, but these are hardly particles in the sense
> of the usual usage of the word.

Yes, as I noted above photons have no mass and now you say they aren't
even particles? No Energy, M, or AM there! But they DO carry E, M and
AM! Ah, with nothing real, I am beginning to see why you say it is
maths that carry the energy.

> Of course not. But I also think you can't prove that the fields _aren't_
> real. More on this below.

Well, I was basing that assumption on the definition of mathematics
not being "real" as in having a physical basis in the 3-dimensional
universe. But clearly you've already pointed out that the actions of
the physical universe are solely determined by "algebra" or more
expansively "mathematics" so clearly mathematics is the ONLY basis for
reality in our universe! This turns my mind upside down!

> Re-wind, back-up, and re-read. Consider the electrostatic case. E is
> defined in terms of the force that would act on an ideal test charge. For
> the E field to exist, in the mathematical sense required for it to be used
> in the Maxwell equations - which is all that was claimed above - all that
> is required is that a test charge would experience a force (possibly equal
> to zero) describable as a function of position.

Lessee. Since charges exist based on some mathematics we haven't quite
worked out but presumably are there to give "charge' reality, then the
mathematics of equating an E field with the force on a test charge
makes an E field real! This seems a self-consistent system.

The interesting thing that you already noted is that there are other
formulations of these things which do not use fields at all. This
therefore seems to imply that like so many other things "fields" both
exist and do not exist at the same time. If you are using field
theory they exist and if you are using potentials they don't. Seems
reasonable but it's confusing to me!

> "Is mathematics real" is not the question. There's surely a fuzzy area
> when talking about "real", but I think that if the fields have energy etc,
> they must be physically real. Perhaps fields without energy, momentum, or
> AM can be physically real too, but I think fields with them are physically
> real.

Wait a minute. Now my head really hurts! Since fields have E, M, and
AM they are thus physically real, but when you use the Feynman-Wheeler
formulation they are real but don't exist? This seems like quantum
theory to me, but we are only talking classical physics here!

> This isn't the critical ambiguity. If the energy, momentum, AM, is out
> there in apparently empty space, then something exists there. If these
> quantities mathematically depend only on the fields, then there's a strong
> case to be made that the fields themselves are physically real (or that
> they describe the behaviour of something out there in apparently empty
> space that is physically real).

Lessee. Fields can exist in empty space, but are nevertheless real.
They HAVE to be real because the carry E, M, and AM. Empty space is
void and consists of nothing at all. But on the other hand nothing at
all seems to have properties like impedance and the like. Thus we
have to conclude that since nothing at all has properties and those
properties give rise to fields and those fields transport action, we
are left with the inescapable conclusion that since space consists of
nothing at all, and since mathematics is ALSO nothing at all,
therefore, reality is mathematics! Or stated otherwise, only
mathematics is real! I'm just NEVER going to get what physics is all
about!


> The critical ambiguity is that the conservation laws don't tell us the
> energy density, the momentum density, and the AM density - the
> conservation laws tell us the total energy, the total momentum, and the
> total AM.

So if there is no mathematics to describe energy density does that
mean that it doesn't exist or just that it's "unknowable"? It seems to
me by the above arguments that if the maths (thank you aut.) don't
exist then the whatever it is can't possibly exist either.

> Apart from which, there's always something like field-free
> Feynman-Wheeler.

I mentioned this above. Does this mean that fields are sort of like
inverse QM? They only exist if you are calculating them and if you
don't calculate them they don't exist? This seems to logically follow
to me! Or perhaps it's different and BOTH fields and potentials
actually exist all the time because the maths exist and the act of
calculation has nothing to do with it!!! Yes! I think I'm beginning to
understand this now!

> > Maxwell
> > noted that energy can be transmitted in only TWO ways. One is through
> > the transfer of mass (kinetic) and the other is in the transmission of
> > waves in a medium. In a so-called "field" there is no mass. But lo
> > and behold, modern physics says there is no medium either!!!
>
> The field _is_ the medium, at least mathematically. If fields are real,
> then field is the medium, physically. Modern physics says there is no
> _mechanical_ medium.

So clearly Maxwell missed a very important point. energy can be
transmitted THREE ways! By particles of mass (kinetic), by waves
(needing a medium) and by mathematics (needing nothing at all and
working even in the void). I guess I missed that point too!

> When the maths describes reality well, there's a natural temptation to
> seek correspondence between the mathematical objects and reality. But this
> isn't limited to just mathematical descriptions of reality. Is colour
> real? Is a blue object _really_ "blue"? Look at it in the lovely light of
> a sodium lamp - where is its "blueness"?

Color isn't real? What if I describe a spectrum with maths? Doesn't
that make it real?

> "Explanation"? What is the role of explanation in physics? "Does the model
> of reality describe reality?" is fundamental. Sure explanation can matter
> (e.g., note that it's considered Einstein's special relativity, not
> Lorentz/Poincare's special relativity (except by Whittaker)), but can its
> role be fundamental in a theory known to be a workable approximation only
> (such as classical EM)?

I guess "explanations" or logic outside of mathematical description
clearly doesn't matter and was an error in thinking on my part!
Reasonable cogent systems of thought clearly have no place in physics
unless they are MATHEMATICAL systems! I believe that was my error!
Is this not so?

> "Why" is a question very poorly answered by physics.

No wait! NOW I know what my problem was! I was asking "why" when
physics simply can't provide those kinds of answers!
Oh my! I'm just NEVER going to understand what physics is all about! I
keep trying to be logical and reasonable and keep asking "why" when
physics is about none of those things!

Thanks for explaining how I went wrong though!

(I'm going back to the automobile repair shop now, where things seem
so much more "real" to me! Thanks again!)