Re: more Japanese gyro-dropping

[Maurice Barnhill <mvb@UDel.Edu>]

William Beaty wrote:
> On Tue, 30 Sep 1997, GARY HEMMINGER wrote:
> ...
> > The Tolman-Stewart experiment (1916) showed that when a
> > conductor is "centrifuged" the electrons in the electron sea shift a
> > bit toward the "bottom of the test tube".   Therefore,  a spinning,
> > conductive top will be slightly negative on its perimeter, and
> > slightly positve at its center, and hence will have a magnetic
> > field.
> > Could this be involved?
>
> Hey, great connection you've uncovered there.  Would a bismuth
> flywheel
> (has positive carriers) behave opposite?  

Not necessarily.  The physics of hole conduction is that real electrons
hop into "empty" states, states not yet occupied by electrons, leaving a
different empty state behind.  The gravitational force will pull the
electrons toward the bottom of the test tube, thus sending the holes
toward the top.  The holes act as if they had a negative gravitational
mass.  However, there are edge effects -- see below.

To answer a question before it occurs, indirect experiments indicate
that positrons (electron-holes) do not act as if they had negative
gravitational and positive inertial mass; they fall down like they
should.  I am not sure what the current accuracy of this statement is
since I have lost track of that area of physics.  


> For that matter, maybe
> various
> flywheel materials would give various results.


This is entirely possible.  In principle the surface dipole layer of a
metal can depend on the state of compression of the metal.  Since a
metal will be more compressed on the bottom than it is at the top, there
can be an induced electric field different from what you would calculate
by assuming that enough electrons accumulate at the bottom to set up an
electric field that prevents the rest of the electrons from falling.
Apparently this effect is negligible, or perhaps is masked by something
else, in copper tubes at low temperatures, but to the best of my
knowledge its size has never been successfully calculated.  The effect
may well be different in different metals.  

In the late 60's, William Fairbank tried to do a direct measurement of
the gravitational force on positrons falling inside a copper tube at
liquid nitrogen temperatures.  L. I. Schiff put me to work on the
electric field inside these tubes that would be induced by gravitational
forces, as a pre-dissertation problem.  I don't think that the problem
is understood yet.  See L. I. Schiff and M. V. Barnhill III, Phys. Rev.
151 (1966), 1067 for our discussion, which is better than a first guess
but less than a definitive answer.

-- 
Maurice Barnhill, mvb@udel.edu                
http://www.physics.udel.edu/~barnhill/          
Physics Dept., University of Delaware, Newark, DE 19716