Re: The Electron

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

At 21:44 -0500 11/10/03, J. Green wrote:
> When I mentioned the "some guy's theory" bit, I was principally thinking of
> the Pauli exclusion principle, which is not much of an answer for me, since
> the proof is that "he said it".

Not so. Pauli's exclusion principle follows from the proper QM
calculations. It can be proven, but it isn't all that easy to do. The
book by Icke I mentioned deals extensively with this subject. In
particular, it deals with why the integer-spin particles behave
differently from the half-integer spin ones, and gives some insight
into why the Pauli principle has to apply to Fermions but not to
Bosons.

>   I'm not so much concerned with something I
> can draw on a piece of paper as much as something I can imagine.

As Jack pointed out, there are lots of QM things that we just can't
visualize--they have no classical analog. About all we can say about
the electrons around a free atom is that they are there, and each one
has its own unique set of quantum numbers. But it doesn't mean much
to ask about their specific location, or to identify which electron
is which. They all look alike and they don't wear their quantum
numbers on their sleeves.

For example, if you do an elastic scattering experiment of electrons
on hydrogen atoms, you send a beam of electrons into a cloud of
hydrogen atoms and you get electrons coming out at various angles. If
you look at just one electron, say you reduce the incident flux of
electrons until there is just one going in at a time, and one coming
out at a time. You cannot tell whether the electron that comes out is
the same one that went in, or the original atomic electron, and the
one that entered took its place around the nucleus. It's even so that
if you do the quantum theoretical calculation of the scattering and
don't take into account the possibility that the electrons exchange
places sometimes, you get answers that don't agree with experiment.
But you never know when it happens and when it doesn't, only that
sometimes is does.

>   If it is
> indeed a string, how does it explain what we do know about it?

I'll leave this to others.

>  I think it
> would be best to separate what is "KNOWN" about electrons (wich I admit
> could be an endless argument in itself) and what the questions are.

Well, there are some numbers which haven't changed much in several
decades, so they can probably be called as "known" as anything: mass,
charge, spin, magnetic dipole moment, and a few others. The questions
are much less well defined. "What is an electron?" is probably way
too vague to lead to any sort of useful answer. "How does it behave?"
is better, but quickly leads us into the quantum quagmire, and we
realize that about all we can say about it is what the QM/QED
equations tell us, and we can't draw many pictures. "How does it
interact with matter?" may be even better. QED can give us a pretty
good handle on that. For instance, we now know that the electron
interacts with the "vacuum" and that has something to do with why we
see it as we do--that is, "dressed." Maybe string theory will do even
better at some time.

>   We talk
> about things as if they ARE as the models say they are, when we really don't
> know what is really going on.

We will *never* know what is *really* going on. All we have are our
models, which we test and modify as the data lead us. For some
insight into this I suggest Martin Krieger's book "Doing Physics: How
Physicists Take Hold of the World" (Indiana Univ. Press, 1992, ISBN:
0-253-33123-4).

When someone asks questions like "What is an electron?" probably the
best thing we can tell them is that we don't understand the current
theories of physics well enough to be able to give a really good
answer to a question like that. After all QED is not yet a hundred
years old. There were aspects of Newton's theories that weren't well
understood for more than 100 years after he published them. I suspect
that these may be even harder questions than the ones that puzzled
Newtonian scholars for so long.

Hugh
--

Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

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