Why do we perceive objects as solid, despite atoms being mostly empty space?

• A. Because we interact with them; our hands can't pass through rocks
• B. Because empty space is a myth
• C. Because all matter is continuous
• D. Because we cannot sense empty space

Answer: (A)

When we feel solid objects, the boundary where two materials meet is governed by the electromagnetic forces between their atoms. The outer electron clouds of the atoms in your hand and in the rock repel each other strongly as they come close. That repulsive force rises quickly and prevents the atoms from overlapping, so you can’t push your hand through the rock. Your nervous system interprets that resistance as solidity.

Even though atoms are mostly empty space, the surface region where electron clouds meet creates a powerful barrier that stops interpenetration, which is why objects feel solid. The other statements don’t capture this interaction-based reason: empty space isn’t a myth, matter isn’t literally continuous in the sense implied, and we don’t rely on sensing “empty space” to perceive solidity.