During a 7 mile hike around Mt. Diablo today, I was asked why, if atoms are 99.9% empty space, things seem solid.
The best answer I could give is that there are two classes of all particles, bosons which can move through each other and fermions which can’t, due to the Pauli Exclusion Principle.
Fermions are the constituents of matter: electrons, protons, neutrons; while bosons are particles that transmit interactions (force carriers), or the constituents of radiation: Photons, the force carriers of the electromagnetic field, W and Z bosons, the force carriers that mediate the weak force and gluons the force carriers underlying the strong force.
This is not an answer, of course. It merely says that we have observed and named minute details of reality.
You might say that it would require infinite energy for two fermions to be in the same place at the same time. Why? Because that’s the nature of fermions.
Clear as mud?
Oh, and if the universe winks out, it will be at the speed of light. You probably won’t feel a thing.