Why You Don't Fall Through the Floor: The Surprising Science of Solid Objects

Every single solid object you've ever touched—your chair, your desk, your own body—is more than ninety-nine-point-nine-nine-nine percent empty space. It's true. And that fact breaks people's brains every single time. They always ask, "Well, why don't I fall through the floor?" Okay, I'm asking! Why don't I fall through the floor? And this feels connected to what we talked about last week with the speed of light. That was a universal rule. This feels like a rule, too. It IS a rule! And you're right, it's totally connected. The "light" in the speed of light is made of a particle called a photon. That photon is a key player in the big rulebook for...

well, for everything. It's called the Standard Model of Particle Physics. The Standard Model. I've heard that phrase, but it sounds like a car. What is it, really? It's our best map of the absolute smallest things in the universe. It's a list of all the fundamental ingredients and the forces that tell them how to interact. Think of it like a recipe for the cosmos with only a few ingredients. Okay, so what are the ingredients? They fall into two main camps. First, you have the "matter" particles. These are the things that have mass, the stuff you can build with. The two most important types for us are Quarks and Leptons. Quarks. That's a fun word.

Right? And they're the shiest particles of all. You can NEVER find a quark by itself. They're always glued together in groups. To build the protons and neutrons in the nucleus of an atom, you just need two kinds: an "up" quark and a "down" quark. So they're like... ultimate Lego bricks? Exactly! The tiniest Legos. You take two ups and a down, you get a proton. You take two downs and an up, you get a neutron. And with those two things, you can build the core of every atom in existence. Wow. Okay, so that's quarks. What about the other one... leptons? The most famous lepton is the electron. If the nucleus is the heavy, stable center of the atom, the electrons are the restless little things buzzing around the outside.

They're what's responsible for basically all of chemistry—for bonding atoms together to make molecules, to make... us. Okay, so I've got quarks making protons and neutrons in the middle, and I've got electrons—the leptons—buzzing around the outside. That makes an atom. But you said there was another camp. There is. And this one answers your first question—why you don't fall through the floor. These are the "force" particles. The official name is bosons. Bosons. So they're not matter, they're... instructions? They're messengers! They carry the fundamental forces of nature between the matter particles. Remember the photon from our speed of light talk?

Yeah, the particle of light. It's a boson! It carries the electromagnetic force. The electron in your chair is sending out a constant stream of photons to the electrons in your body, and those photons are basically screaming "GET AWAY!" That's the feeling of solidity. It's not stuff touching stuff. It's a force field. Whoa. So the feeling of touch is actually just... repulsion? A force being carried by these little light particles? You got it. The photon is the messenger for the electromagnetic force. There are other bosons for other forces, like the ones that hold the quarks together inside the proton. But for our everyday world, it's all about quarks, electrons, and photons.

So... wait. Let me get this straight. A couple of quarks, an electron, and a messenger particle... that's it? That's the recipe for a star and a tree and a person? That's the mind-blowing part. The entire universe, in all its complexity, is just an unbelievably huge, intricate arrangement of these few tiny things, following the same simple rules. Everything is just a different song played on the same handful of notes. So when I'm looking at my hand... I'm not really seeing something solid. I'm seeing a community of trillions of particles, all held in a delicate dance by invisible messengers. Exactly. You're a universe of particles, looking out at a universe made of the exact same stuff.

And that, I think, is just beautiful.