The force drops to nothing almost immediately. The Casimir force is closely
related to the zero point field physics I discussed a month or two ago. As
you mentioned previously in this thread it is a quantum mechanical effect.
The measured force is actually the repulsion between
"virtual"(Heisenberg-ish) electrons.
Here is how it works:
Quantum mechanics describes electrons as occupying a probability space as
opposed to having deterministic locations (Heisenberg uncertainty principle
and Schroedinger among others). The probability curve is such that there is
an astronomically small, but finite, probability that one of the electrons
in your body is quite possibly occupying the space in front of me as you
read this.
The Casimir force is a manifestation of these electrons popping up and
disappearing momentarily in space. We are constantly emersed in a sea of
these virtual electrons, but the density increases with proximity to mass.
The more mass, the denser the field. Consider the non-conductive parallel
plates used to demonstrate the Casimir force. You have two plates in very
close proximity to each other. So close, in fact, that the probability of
an electron popping into existence is considerably higher between the plates
than the probability of an electron emerging outside of the two plates. The
probability is higher because at the distances involved, both plates are
generating significant quantities of these virtual electrons due to the
proximity of the space to the plate. The net result is that the
concentration of electrons in the space between the plates is significantly
higher than the concentration on the outside of the plates, due to
significant overlap of the electron density curves. This generates a
repulsive force due to electron interaction between the plates that is
larger than the repulsive force generated on the outside of the plates where
the electron density is less.
Hope this makes sense. If not, I can elaborate.
-James Rogers
jamesr@best.com