How do quarks stay trapped inside protons and neutrons?

Quarks remain trapped because the strong force behaves very differently from gravity or electricity. As quarks move farther apart, the energy in the gluon field increases rather than decreases, making separation increasingly difficult. At some point, it becomes energetically easier to create new quark-antiquark pairs than to isolate one quark. This is known as color confinement, a central feature of quantum chromodynamics. Protons and neutrons are therefore stable bound states of three quarks, while other combinations can exist only briefly in high-energy experiments.