“There’s something about sitting alone in the dark that reminds you how big the world really is, and how far apart we all are. The stars look like they’re so close, you could reach out and touch them. But you can’t. Sometimes things look a lot closer than they are.” -Kami Garcia
When we consider things like molecules, atoms, or even protons and neutrons, they all have finite, measurable sizes. Yet the fundamental particles that they’re made out of, like quarks, electrons, and gluons, are all inherently points, with no physical size to them at all. Why, then, does every composite particle not only have a size, but some of them, like atoms, grow to be relatively huge almost immediately, even with only a few fundamental particles involved?
From macroscopic scales down to subatomic ones, the sizes of the fundamental particles play only a small role in determining the sizes of composite structures. Image credit: Magdalena Kowalska / CERN / ISOLDE team.
It’s due to three factors that all work together: forces, the quantum properties of the particles themselves, and energy. Since the strong and electromagnetic forces work against each other, quarks and gluons can form finite-sized protons; protons and ...