Quantum mechanics supposes that many universes exist, undetectable to each other, except through the narrow port hole of quantum mechanical experiments. Science, as opposed to technology, does violence to the common sense.
Middle World – the scale at which we live. We cannot navigate the world of atoms, and we cannot grasp the notions of the large world, moving at speeds of light. Our middle world makes us sensitive to the forces of gravity, but not so much to surface tension – a small insect would reverse this distinction.
Do rocks contain empty spaces? For us, no, because we live in this middle range world – but for neutrinos, if they had a brain and consciousness, would for sure perceive a rock to have empty space.
Each creature has a brain that has been customized to their surroundings. It works as it needs to.
For us, we have a limit to what we can understand, and also a limit to what we can even dream up and imagine. The universe, most likely, contains things which we simply cannot understand, because we cannot even imagine them.
(Part of TED a day for June)