Re: "quantization"

[Leigh Palmer <palmer@sfu.ca>]

Igal clarifies. First he stated

> > > Well, ANY physical concept is not more than a mental construct

I proposed a physical concept which I claim is not a mental construct:

> > Hmm. Is electrical charge a mental construct? Conservation of
> > charge is also a counterpart of a symmetry of Nature. Charge is,
> > somehow, a different sort of physical quantity than energy. For
> > example, the quantity of charge is independent of the frame from
> > which it is observed; the quantity of energy observed depends
> > upon the observer's frame. Charge is quantized; energy is not.
> > Charge is locally conserved; energy is not even localizable.
> >
> > There are large qualitative differences between the concepts of
> > charge and energy. Charge is substantial; energy is insubstantial.

Igal andswers:

> Whatever charge you mean, electrical or others, their conservation can be
> interpreted as following a symmetry of some additional dimension (which may
> be closed, to provide quantization?).

Note that I said charge conservation is related to a symmetry
(guage invariance of electrodynamics) of Nature. I am aware of it.

> Leigh, let me explain myself.  I
> mentioned my reservation putting ("within the known limits").  Conservation
> of charge is the first question which can be raised (and is discussed in
> the supersymetry theory, I believe), but  AFTER a great success of our
> understanding of the origin for energy, momentum and angular momentum (in
> classical theory) and parity (in quantum theory) to conserve.  The open
> questions regarding all other charges remain, meanwhile, out of a regular
> curriculum, and occupy the minds of theoreticians. All this does not (for
> me and I am quite sure, for the students) spoil the beauty of the emerging
> picture.   Just the opposite, it inspires an appetite for further search
> for this elucidating connection: symmetry - conservation.

I think I don't disagree.

> > I believe that if your claim above is not trivial then it is not
> > correct, either.
>
> I am sorry, Leigh, I do not follow your logic.  I said that
> symmetry-conservation law connection is a discovery of the twenties century
> physics, which has not yet sufficiently used in introductory physics
> courses.  Not more than this.  I did not intend to say anything more.

My reference was to the statement at the beginning of this post:

> > > Well, ANY physical concept is not more than a mental construct

Is this statement a solipsism? I am an objective realist about
some physical concepts, by which I mean, of course, the physical
entity which is conceived. Charge is a real physical entity;
energy is not.

As to the trivial part, of course a concept is a mental construct.
That's why I specified a *physical* concept, meaning that which is
conceived. Energy is not a concept *per se*, but energy is what we
were talking about, was it not?

> > > (see Dewey's aftermail quote of Einstein).
> >
> > I'm told Einstein spoke German. I don't recall a German quote
> > following Dewey's signature.
>
> No problem:
>
> "Physical concepts are the free creations of the human mind and
> are not, however it may seem, uniquely determined by the external
> world."--A. Einstein in The Evolution of Physics with L. Infeld,
> 1938.

I have always taken this as a religious statement - by Dewey. He
advocates a view of teaching he calls "constructivism", something
akin to postmodernist science studies, I think. Science studies
extremists believe that all physical law is constructed by human
thought (e.g. conservation of charge is a human mental construct)
and I have imagined that Dewey means to suggest that Einstein
held this opinion. It is unclear to me who said this, and in what
language it was said. Is this a statement from Einstein? Did it,
perhaps, occur in the context of a paragraph?

Einstein was not into solipsism.

Leigh

           "We cannot learn everything from general
            principles; there may be exceptions."