Stability (was Earnshaw's theorem)

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

Bob Sciamanda wrote:

> Ludwik,
> Just to tie a connecting knot . . . you are re-visiting our earlier
> discussion of Earnshaw's theorem.
> > . . .
> > A spherical shell of charge? Hmm, not really! Here the
> > restoring force is zero everwhere. The neutral equilibrium is
> > not the same thing as real equilibrium in the center of a
> > uniformly charged sphere. I suppose that this is not the only
> > way to trap +Q in the center of a structure made from pieces
> > of -Q. What about an oxygen nucleus in the center of a cube
> > made of 8 electrons, one at each corner?
> >
> > The world is made of netral atoms; most atoms are stable.
> > Everything must be in motion to produce stability (which
> > rimes with immobility). Right? What a world !

That Earnshaw's theorem refers to a system which excludes
non-electric forces. Does a "rigid cloud" made from tiny beads
mounted on sticks, depend on other forces? Yes and no, so
to speak. Is it not true that all significant forces keeping this
structure together, including the glue, are electrical? But the
structure is stable, beads do not move with respect to each
other. Is this a paradox?
Ludwik Kowalski