[Communicating science series]
This is a concept often espoused by science popularizers over the decades. Even the background for plot vouchers in some sci-fi adventures. An amazing fact: We and everyday objects around us are mostly empty space!
That’s why superman could walk through walls. That’s why fantasy superheroes can shrink to atomic size, and neutron stars are not much bigger than a small city.
Well, while much used, in this Forbes article Ethan Siegel might say much abused.
Forbes > “You Are Not Mostly Empty Space” by Ethan Siegel, Senior Contributor (Apr 16, 2020).
Maybe we all watched too many Walt Disney shows, eh. “Our Friend the Atom.” The atom was like a tiny tiny solar system. Lots of empty space about the nucleus. Just read about Ernest Rutherford’s famous gold foil experiment (Wiki): “This could be related to putting a grain of sand in the middle of a football field.”
The better way to think about an electron is like a “fog” or a “cloud,” spread throughout the space around an atomic nucleus. When two or more atoms are bound together into a molecule, their electron clouds overlap, and the electron’s extent in space gets even more diffuse.
This is counterintuitive, of course, because we’re so used to thinking of the fundamental constituents of matter in terms of particles. But it’s better to think of them as quanta instead: behaving like particles under high-energy conditions but behaving like waves under low-energy conditions. When we’re dealing with atoms under normal terrestrial conditions, they’re wave-like, with individual quanta occupying large volumes of space all on their own.
… under normal circumstances, like the ones we consistently experience in our own bodies, even an individual electron is spread out over an entire atom or molecule.
Inside your body, you aren’t mostly empty space. You’re mostly a series of electron clouds, all bound together by the quantum rules that govern the entire Universe.
Siegel might be responding to characterizations like in an April 19, 2019, curiosity.com article [no longer available online], “You’re Almost Completely Made Up of Empty Space – When you blow up an atom to 1 million times its size, it’s about the size of a melon … .”
And other articles professing the “atoms are mostly empty space” theory.
But the point is that fields matter, like electron fields. Or, perhaps that such matter fields have space-filling density. Sort of like a “fluid” cloud. Being transparent to alpha rays (as in Rutherford’s model) does not mean that such space is empty. Objects made of glass are transparent to light but resist being crushed because those matter fields push back. The energy in those fields has “mass,” something which our everyday experience associates with space-filling objects.
And of course, the quantum vacuum is not really empty either.