How do positively charged protons aggregate in the small volume of an atomic nucleus in apparent contradiction of Coulomb's law that like charges repel? Neutrons in atomic nuclei may increase average distance between protons and partly explain this proton aggregation. Present popular wisdom is that a nuclear force binds protons in atomic nuclei. However, "nuclear force" may be little more than a label for the phenomenon rather than an explanation of it. Based on discoveries of the internal structure of the proton and its real intrinsic spin (Fig. 1) [1] [2] [3] [4], this paper defines a proton cycle network as a foundational principle of nuclear physics.
