This question may not come in the bracket of quantum mechanics but

Aditya3003

This question may not come in the bracket of quantum mechanics but here's the question-
If most of the atom is empty space what gives the illusion of solidity?

gomunkul51

A common answer: electrons repel electrons (EM force)...
A more interesting answer: the electron Degeneracy Pressure.

cepheid

Well, I'm not expert on QM, but I think that these are two distinct effects, and that the first one (Coulomb repulsion) is what is responsible for the "illusion of solidity" in everyday objects. Otherwise, how would you explain the solidity of non-degenerate matter?

Please correct me if I am wrong.

gomunkul51

You are correct, those are distinct. The first one, as I said, was a common answer given by physicists. The second answer is different but more interesting as it may in fact be what stops materials going through each other. I was mealy pointing the OP to the right direction, where he may find a full answer to his question.

*Degeneracy pressure exist in metals and other materials, they don't have to be "degenerate matter" to be affected by it. What makes the later one exceptional is that degeneracy pressure in the dominant force in that matter.

MartinJH

Brian Cox recently hosted a good lecture on Quantum mechanics and covered this quite well I thought.
Here's the lecture, thankfully it was posted on YouTube as it isn't on BBC iPlayer anymore.

http://youtu.be/4f9wcSLs8ZQ

Edit: Also, at one point, it gets very funny with some rude innuendo. What innuendo isn't rude!

gomunkul51

Cool video!
Brian tries to explain elementarily, that the illusion of solidity is caused by electron degeneracy pressure. Option No. 2.