Re: IONS/metals pedagogy

["Bob Sciamanda" <trebor@velocity.net>]

Hi Ludwig,

First, re: Earnshaw - I couldn't find a lot, but his paper was dated
1842.  Scott's E&M text (in a footnote) says Maxwell applied the theorem
to "forces on charged conductors" (article 116 of the Dover edition) I
don't have a copy (Maxwell), do you? I will consult a library copy asap.
I can only suppose that the short-lived raisin pudding Thompson atomic
model had Earnshaw (or its equivalent) in mind.  Scott gives another ref
(which I have yet to see): "Who Was Earnshaw?", AJP 27,418-19 (1959).

Also, read Article 192 of Jeans' book (on Earnshaw) - his final "small
print" note is an interesting speculation on the stability of matter in
spite of Earnshaw!  (I won't comment till you read it for yourself.)

I really don't have any compunction about referring to conclusions "yet
to be proven/studied" in my teaching.  I don't think the logical
structure of our sciences/curricula are (or can be made) linear enough
that this can be avoided.  Certainly this can be abused.  . . . Gotta
run - we'll argue this one later   :)

-Bob


Bob Sciamanda
Physics, Edinboro Univ of PA (ret)
trebor@velocity.net
http://www.velocity.net/~trebor
-----Original Message-----
From: Ludwik Kowalski <kowalskiL@Mail.Montclair.edu>
To: phys-L@atlantis.uwf.edu <phys-L@atlantis.uwf.edu>
Date: Friday, October 09, 1998 8:58 PM
Subject: hold2


> You are saying that only QM can explain stability of electrons on the
> surface of a large metallic sphere. And you are making this acceptable
> by
> referring to those ideas from QM with which many teachers are familiar.
> This is good and useful. I still hope that a classical explanation of
> Fnet
> will be found and accepted. But your position may prevail.
>
> In that case we must address the problem of the sequence of sections
> in an Introductory Physics course. Do we share the idea that explaining
> something today in terms of what will be explained tomorrow is not
> acceptable? Is it possible to teach QM before e&m? How?
>
> By introducing elements of QM in the chapter on gravitation? Or
> should elements of optical spectroscopy be studied before QM? The
> present teaching sequence is based on the assumption that classical
> physics phenomena (those which we select to study in a given course)
> can be explained without modern physics. Are we saying that this is
> not possible?
>
> By the way, how old is Earnshaw's theorem? Was J.J. Thomson
> aware of it when the plum pudding model of atoms was proposed?