Why Doesn't Your Butt Fall Through The Chair? : 13.7: Cosmos And Culture One of the strangest and least appreciated discoveries of modern physics is that solid matter is — to put it bluntly — a big lie, says astrophysicist Adam Frank.
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Why Doesn't Your Butt Fall Through The Chair?

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Why Doesn't Your Butt Fall Through The Chair?

Why Doesn't Your Butt Fall Through The Chair?

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AUDIE CORNISH, HOST:

Space, the final frontier - not so fast says NPR blogger Adam Frank. He's also an astrophysicist, and he offers this food for thought. There's plenty of space right here on Earth. In fact, you're sitting on it.

ADAM FRANK, BYLINE: One of the strangest and least appreciated discoveries of modern physics is that solid matter is - to put it bluntly - a big fat lie. Consider for a moment the chair your rear end is resting on right now. It's made of a squillion atoms, right? And since it's a solid, all those chair atoms are packed tightly together like a vast collection of marbles in a box, right? And it's all those tightly packed atoms that are keeping your butt in the chair balanced against the force of gravity, right? Well, actually, no - atoms aren't marbles.

Remember, every atom has two components. There's the nucleus at the center, made of protons and neutrons, and then there's a bunch of electrons whizzing around that nucleus. Now, in high school they showed you diagrams of atoms that made the nucleus look like its own bunch of tightly packed marbles with some marble-like electrons orbiting a little ways out, but that ain't an atom. To see what I'm talking about, we need to consider just two numbers. First, an atom's nucleus is only a few femtometers across. And what is a femtometer you ask? It's about a thousand million millionth of a meter. Yeah, I know, that's super tiny. But now let's think about where the whizzing electrons are relative to the atom's nucleus. The electrons zoom around about one-ten-billionth of a meter away from their nuclear core. That's 100,000 times the width of the nucleus - or, in other words, if the nucleus was a beach ball in midtown Manhattan, then the electron would live in an apartment in Philly.

So what's the takeaway here? Atoms are mostly empty space. And as atoms goes, so goes your chair. It's just empty space, too. The image you had of solid matter as tightly packed marbles - nope, not even close. So if atoms are nothing but deserts of empty space, how does your backside even know the chair is there? Well, the answer is as simple as it is weird. It's all about forces. And in this case, they really are with you. The electrons and the nuclei are constantly interacting through the force of electromagnetism. Each interaction is carried out through the jolting exchange of a particle of pure energy called a photon. And each photon swap equals a force, a tiny push or pull exerted across the vast emptiness. And that, along with some other quantum weirdness, is really what's keeping the stuff we call your tush from drifting through the stuff we call your chair.

So the truth of solid matter is there is no solid matter. Everything you think of as solid - tables, chairs, a '69 cherry red Ford Mustang, your kid's noggin - none of it is really solid. Instead, there are only rapid-fire bursts of pure energy carrying forces between impossibly small flecks of somethingness. And all of it is lost in an atomic void nearly as empty as interstellar space. Think about that the next time you plop your tuchus down in a chair.

CORNISH: Adam Frank is a professor of astrophysics at the University of Rochester.

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