why do we human discern our world as a metaphysical solid when in fact at a subatomic level it is mostly empty space?
It is probable that our subconscious generate a field of resistance equivalent to psychic energy that create the illusion of a concrete world when in fact it is not.
(1) Imagine everything you see to be mostly made up of empty space.
(2) Imagine that your body is mostly made up of empty space.
(3) Believe the two thing above are undeniable truth.
(4) Practice reaching across a closed door.
A clear glass door are better for practice but are not necessary.