Continuing “Joe’s Answer Bag Week”:
I know this is a question that a huuuge amount of scientists ask, but if atoms are something like 98% space, then how come we aren’t falling through the floor, I’ve always believed it was because there can’t be such a thing as ‘nothing’. Vacuums and stuff confuse me, can you explain Mr. Science Man?
First off, Mister Science Man is my father. Just “Science Man” is fine.
You’re totally right, totallyripped. Atoms are mostly empty space. That is, if we look at them like we are taught in books, as tiny electron planets orbiting a nuclear sun containing protons and neutrons. That isn’t an accurate picture of atoms as we know them today, though.
You need to go quantum. Once you’ve made that leap (get it?!), it’s time to change the way you look at electrons. As Brian Cox said in his Night With the Stars special, “Elehctrunz behayve ahs if they wuh waahves”, which roughly translates to “Electrons behave as if they were waves.”
(I’m an expert Brian Cox translator)
Atoms are mostly empty space (electron cloud “edges” are hundreds of thousands of times farther away from the nucleus than the nucleus is across!) because they need room for all the paths and energy levels of those various waves. When new electrons are added to an atom, it requires energy to make those higher waves, which is why electrons always want to go to low energy states.
So why don’t we fall through the ground, like two intersecting streams of sand? When atoms in your feet get very close to atoms in the ground, the Pauli Exclusion Principle (PEP) takes over. Electrons belong to a particular class of particles called fermions (the name isn’t important, though). The PEP says that electrons like the ones in the ground’s atoms and the ones in your feet’s atoms, no matter how close they get, can’t share the exact same “wave spot” (or orbital). Even if they end up bonding, which I hope doesn’t happen to your feet, they have to split their electrons up into compatible spots.
So when feet atoms get close to ground atoms, their electrons say “I was here first" and they exert force to keep each other where they are. (For more)