Category: Quantum Field Theory

At the core of every atom lies its nucleus, where protons and neutrons are found. As their names suggest, these two subatomic particles are profoundly different.

• Protons carry positive electric charge, and can attract negatively-charged electrons, making atoms possible.
• Neutrons have no electric charge and are thus electrically neutral, hence their name; they have no impact on the electrons in atoms.

The distinctions extend to their magnetic effects. Both protons and neutrons have a “magnetic moment,” meaning that in a magnetic field, they will point like compasses. But neutrons point in the opposite direction from protons, and less agressively.

Nevertheless, the proton and neutron have almost identical masses, differing by less than two tenths of a percent! If we ignored their electric and magnetic effects, they’d almost be twins. Why are they so different in some ways and so similar in others? What does it reflect about nature?