The Casimir Force is a consequence of zero-point energy  Casimir
Force  What Is The Casimir Force?  If you bring two flat,
parallel metal plates close to one another, you will find that
they are pulled together or pushed apart -- that is, the exert
equal and opposite forces on each other. If the plates are not
at the same electrostatic potential, charges on the surfaces
(charges in a conductor always go to the surface) will either
attract or repel one another depending on whether the plates are
oppositely or similarly charged. This electric force is usually
a strong one, and varies relatively slowly with the distance
between the plates.  If the temperature is above absolute zero,
the electrons in the two plates will be more or less mobile, and
move about randomly. The resulting fluctuations in their density
will give the same effect as a positive or negeative charge,
which will attract or repel electrons in the other plate. This
weak, temperature-dependent force is similar to the van der
Waals forces between