Q: What is the smallest thing in the universe, how big is it, and what does it do?
—Diego A., age 10.5, Washington
A: When I started researching this question, I thought it would be easy. All we have to do is zoom in, right? People, planets, stars, and everything else in the universe is made out of atoms. Atoms are really small, but they are still made out of other, even smaller, pieces: electrons, protons, and neutrons. Protons and neutrons are made up of even smaller particles called quarks. Electrons, meanwhile, don’t contain any building blocks.OK then, I thought. All we have to do is figure out which one is smaller, a quark or an electron.
For help, I called Lauren Tompkins, a physicist at Stanford University—and quickly realized…