Some days, you might feel like a pretty substantial person. Maybe you have a lot of friends, or an important job, or a really big car.
But it might humble you to know that all of those things — your friends, your office, your really big car, you yourself, and everything in this incredible, vast universe — are almost entirely, 99.9999999%, empty space.
Here's the deal: As I previously wrote in a story for the particle physics publication Symmetry, the size of an atom is governed by the average location of its electrons — how much space there is between the nucleus and the atom's amorphous outer shell. Nuclei are around 100,000 times smaller than the atoms they're housed in.
If the nucleus were the size of a peanut, the atom would be about the size of a baseball stadium. If we lost all the dead space inside our atoms, we would each be able to fit into a particle of dust, and the entire human race would fit into the volume of a sugar cube.

So then where does all of our mass come from?