"We physicists are always checking to see if there is something the matter with the theory. That’s the game, because if there is something the matter, it’s interesting! But so far, we have found nothing wrong with the theory of quantum electrodynamics. It is, therefore, I would say, the jewel of physics—our proudest possession. The theory of quantum electrodynamics is also the prototype for new theories that attempt to explain nuclear phenomena, the things that go on inside the nuclei of atoms. If one were to think of the physical world as a stage, then the actors would be not only electrons, which are outside the nucleus in atoms, but also quarks and gluons and so forth—dozens of kinds of particles—inside the nucleus. And though these “actors” appear quite different from one another, they all act in a certain style—a strange and peculiar style—the “quantum” style. At the end, I’ll tell you a little bit about the nuclear particles. In the meantime, I’m only going to tell you about photons—particles of light—and electrons, to keep it simple. Because it’s the way they act that is important, and the way they act is very interesting."