Residual strong force
So now we know that the strong force binds quarks together because quarks have
color charge. But that still does not explain what holds the nucleus together, since positive
protons repel each other with electromagnetic force,
and protons and neutrons are
So what holds the nucleus together? Huh?
The answer is that, in short, they don't call it the strong force for nothing.
The strong force between the quarks in one proton and the quarks in another proton
is strong enough to overwhelm the repulsive electromagnetic force.
This is called the residual strong interaction, and it is what "glues" the nucleus