On February 11, John Denker was kind enough to respond to certain PHYS-L
assertions regarding chemical bonding. As usual, his insights were deep.
He wrote, in part: "The repulsive [intermolecular] force has to do with
kinetic energy, and it's not electrostatic. Think of an uncharged particle
in a box. As you decrease the size of the box, the wavefunctions get more
wiggles per unit length, so their kinetic energy goes up. This causes a
repulsive force, i.e. a pressure on the piston."
I understand what John has said, here. However, I'd sure appreciate
further clarification of a few ideas. Here goes:
Should we really think of (certain) quantum mechanical rules as forces?
For example, does the Pauli exclusion principle describe a true "force"?
[Astronomers say that such a force is able to counteract gravity and
temporarily prevent the collapse of white dwarf stars, no?] Accordingly,
when we speak of the "four forces of nature," are we speaking only of the
non-quantum world?