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DanielLC comments on [Transcript] Richard Feynman on Why Questions - Less Wrong
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I don't think his explanation for why a chair pushes back on your hand is quite right, either. I've mostly been told that material solidness comes from the Pauli exclusion principle, not electrostatic repulsion.
I don't know quantum mechanics, so I don't have a good perspective on the problem, but the electrostatic explanation has always seemed lacking to me. The electric charge in a neutral atom is fairly well-approximated by a symmetric sphere of negative charge with a bunch of positive charge at the center, so two atoms shouldn't experience much electrostatic repulsion until their electron clouds overlap. At which point [I've heard] the PEP should dominate the electrostatic force.
Can any physicists or physics students comment?
I have never been taught this in particular, but it seems unlikely that the Pauli exclusion principle could do it. It's a symmetry, not a force.
From what I understand, if you sent two fermions at each other, assuming they don't otherwise repel, they'd just pass through each other. The Pauli principle would merely guarantee that they do so at an anti-node. You'd never find them at the same spot. You also wouldn't find them at any other anti-nodes that appear along their trajectories, or more accurately, their joint trajectory in configuration space, or still more accurately, their joint waveform in configuration space. In any case, their momentum and energy would be completely unaffected by this.
The Pauli principle might be why electrons end up in a pattern in which they repel each other so well, but I don't see what else it can do.
If I'm wrong, please correct me, and send me somewhere where I can read more about how it works.