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So when we try to understand the nuclear of atoms, there is an interesting puzzle that crops up, which is that protons all have positive electric charge. Now like charges repel via the electromagnetic force, so how do you cram all these protons together inside the nucleus? Why don’t they all repel and fly apart? And the answer is that another force comes into play, a strong nuclear force. And it’s through the communication of that force, via gluons. The gluons in some sense glue the protons together by virtue of the strong nuclear force, outweighing, being stronger than electron magnetic repulsion that these electrons experience. And even inside the protons themselves, we know there are two up quarks and a down quark. The up quarks have the same electromagnetic charge. Why don’t they repel? Same answer, the gluons that are transmitted between the quarks inside the proton glue the quarks together, and in that way keep them from flying apart.
