Re: Gravity and probability clouds, can we measure any effects?

Tiago,

I'm not sure what you mean by "probability clouds of subatomic
particles".  I will consider the electron cloud around the nucleus of
an atom as a specific example.

For atoms in free fall, such as hydrogen atoms in space, the only
gravitational effect on the electron cloud is a tidal force. http://en.wikipedia.org/wiki/Tidal_force
The tidal force will elongate a body in the direction of the
attracting mass and squeeze a body perpendicular to this direction.
However, the tidal force is a manifestation of the difference in the
force of gravity across the extent of the body and for a body as small
as a atom, the tidal force will be negligibly small unless we consider
an extreme gravity environment like a black hole.  Here the enormous
tidal effect is called "Spaghettification". http://en.wikipedia.org/wiki/Spaghettification
For example, the Moon's gravitational force is measurably different
between the side of the Earth nearer the Moon and the side of the
Earth facing away from the Moon.  This difference causes ocean tides.
But you do not experience a tidal force due to the Moon because your
body is small compared with the distance over which the Moon's gravity
changes.

One of the Mad Scientists here at madsci.org thinks that you may be
referring to an effect called "electron sag" proposed in 1966 by the
Stanford theoretical physicist Leonard I. Schiff and his Ph.D. student
Maurice V. Barnhill (now a physics professor) to explain the
experimental result of F. C. Witteborn and W. M. Fairbank that
electrons had no free-fall acceleration inside a copper tube.  Schiff
and Barnhill thought that given a conductor like copper in a
gravitational field, the conduction electrons would sink to the bottom
while the positive ion cores in the crystal lattice (metals like
copper are crystalline) would remain rigidly in place and unaffected
by gravity.  http://prola.aps.org/abstract/PR/v151/i4/p1067_1

The rigidity assumption is not realistic.  Two years later Dessler,
Michel, Rorschach, and Trammel in one paper, and Herring in another,
used an elastic lattice to account for the effect of gravity on the
ion cores and found an effect 100,000 times larger and in the opposite
direction to Schiff and Barnhill.  That is, they said the conduction
electrons should rise to the top of the copper.  In 1969, Schiff
himself said that his own theory could not account for the
Witteborn-Fairbank free fall results. http://prb.aps.org/abstract/PRB/v1/i12/p4649_1

A. J. Dessler et al., Gravitation-Induced Electric Fields in
Conductors, Phys Rev 168, 737, (1968)

Conyers Herring, Gravitation-Induced Electric Field near a Conductor
and its Relation to the Surface-Stress concept, Phys. Rev. 171, 1361
(1968)

So who was right?  Unfortunately, the quantum mechanical description
of macroscopic solid state systems like a large copper pipe in a
gravitational field is very complicated and the experiments to test
the theories are very delicate.  The issue is still not completely
resolved, but "electron sag", abandoned by its creator, is not very
likely.


--Dr. Randall J. Scalise    http://www.physics.smu.edu/scalise