Keith Nagel wrote:
Hi Stephen,
You write:
Absent quantum mechanics, we could think of the iron atoms as having
electrons "orbiting" around them. If we did that, and if we could get
the orbits to line up in parallel planes, then voila, we would have a
magnet -- the currents in the interior of the domain would cancel (in
their effects) and the result would be as though there were a single
current running around the outer surface.
And we would be completely confused by our resulting experiments.
Orbital electrons contribute a negligible amount to the field of
a ferromagnet. In addition, when we apply an external field
to the system you describe, the result should be a field opposing
the applied field. We measure just the opposite in a ferromagnet,
??? So we do... I guess. Hmmm?
One of these days I've got to learn something about magnets (like,
macroscopic magnets rather than the fields of individual loose
particles). Every time I get into a discussion of them I end up confused.
I agree that the basic newtonian principle that a body in motion
tends to stay in motion is valid, although an macroscopic electrified body
in orbital motion will most definitely radiate EM waves, something
which the electron seems not to do, so orbital type models must be
gross approximations at best.
Right; you need QM to explain that the electron can't radiate once it's
in ground state. (Unless it can go to a sub-ground state à la Mills.)
Appropo of nothing, it was mentioned on PBS that it was the 100th
anniversary of the publishing of Einsteins theory of SR. It was
proclaimed, with a straight face, that Einstein "discovered that
all matter was made up of individual pieces called atoms". Wow.
Someone better not tell Democritus, or Rutherford for that matter.
Soon we won't need a history of science, it will all have been
created by Einstein. Say, did you know Einstein invented the first
cursor?
Well I wish he hadn't -- they're all over sci.physics.relativity, just
cursing up a storm....
Even some perfectly respectable relativity books blithely credit
Einstein with the whole field, lock stock and barrel. You've got to
find a text like the somewhat-incoherent-but-richly-illustrated
"Gravitation" by Misner, Thorne and Wheeler in order to see any kind of
discussion of the background ambience in which Einstein worked. I'm
currently reading Hawking's "Brief History of Time", in which a lot of
space is devoted to the history leading up to relativity, and even there
the contributions of most of Einstein's predecessors gets rather short
shrift (though he does mention Poincaré's independent development of the
guts of SR, apparently completed within a few weeks of Einstein's
publication, which I had not been aware of).
