Why can't we walk through walls if atoms are mostly empty space?

An edited photo of a man appearing to walk through a brick wall.

In movies, people phase through walls like ghosts — think Vision from "Avengers" or Harry Potter going through Platform 9¾. It looks effortless. But in the real world, trying that trick would just leave you with a bruised nose and a lot of questions.

One question, for instance, might be why can't we walk through walls? Atoms, which are the building blocks of matter, are mostly empty space. The tiny nucleus — which is about 100,000 times smaller than the whole atom — sits at the center, while the electrons orbit far away. So why do solid objects feel so ... solid?