I'm interested phys-l subscribers' explanations, at about the level of
The Feynman Lectures volume I, but with a little more detail than
provided there (in particular, with some information regarding the role
of the nuclei) as to how it is that the floor keeps a person that is
standing on the floor, from falling downward through the floor.
Feynman says:
----------Feynman Lectures on Physics Volume 1, Section 38-4------------
As we walk, our shoes with their masses of atoms push against the floor
with its mass of atoms. In order to squash the atoms closer together,
the electrons would be confined to a smaller space and, by the
uncertainty principle, their momenta would have to be higher on the
average, and that means high energy; the resistance to atomic
compression is a quantum-mechanical effect and not a classical effect.
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.
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It is the fact that the electrons cannot all get on top of each other
that makes tables and everything else solid.
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In this explanation, the interaction between the top of the floor and
the bottom of a shoe is all about the electrons. I would expect that
there might be some rearrangement of the electrons near the surface of
both objects that would allow the ions to get close enough together for
some electrostatic repulsion of positive ions by positive ions. I am
not being critical of Feynman here. I think his goal was to make it
clear to the reader that the explanation for why one does not fall
through the floor is quantum mechanical in nature and he did a great job
at that. I'm just looking for a slightly more complete explanation, at
the same level--one that might also account for why stepping onto the
surface of a pond is so much different when the water is in its liquid
state than it is when the water is in its solid state.