What is the actual origin of atomic (nuclear) mass??? In the 1970s people found they could see and explore point-like structures inside the proton itself, using extremely high energy beams of electrons. One would expect to find 3 quarks, 2 ups and a down, plus the gluons that are responsible for holding the quarks inside the proton. However, it was also realized that the strong nuclear force becomes infinitely strong at larger distances, if you try to pull a colored object away from the rest of the system... in other words the binding energy is infinite!
Gluons are massless, while up quarks have a mass of 2 MeV and down quarks have a mass of 4.8 MeV. Yet the mass of a proton is 938 MeV, and the neutron is even more massive (with two downs and an up). The explanation is that 99% of the mass of neutron and proton is due to the field of force that holds it together. Nearly all the momentum of the neutron and proton is also due to this field. The gluons have so much kinetic energy inside the proton and neutron that they are constantly creating virtual pairs of almost any particle, particularly quarks!

M_pc²(938 MeV) = {[2 m_u + m_d]c²] + E} = 8.8 MeV + E! NO "naked color" can exist in nature!



Because the binding energy of systems held together by the strong force is infinite, there are an infinite number of particles similar to the proton and neutron, but more massive... the family is generally called baryons. There are also an infinite number of particles that are bound states of quark and antiquark... the family is generally called mesons.

Experimentally measured potential energy between two quarks... the potential energy goes to infinity as r goes to infinity, so all states are bound states.

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