The quarks, antiquarks, and gluons of the standard model have a color charge, in addition to all the other properties like mass and electric charge that other particles and antiparticles possess. All of these particles, to the best we can tell, are truly point-like, and come in three generations. At higher energies, it is possible that still additional types of particles will exist, but they go beyond the Standard Model’s description. (E. SIEGEL / BEYOND THE GALAXY)

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Why are the rest masses of fundamental particles related like this?

When it comes to the nature of matter in the Universe, the Standard Model describes the known elementary particles perfectly well and without exception, at least so far. There are two classes of fundamental particles:

• the fermions, which all possess non-zero rest masses, half-integer spins, and can be charged under the strong, electromagnetic, and weak interactions,
• and the bosons, which can be massive or massless, possess integer spins, and mediate the strong, electromagnetic, and weak interactions.

The fermions come in three generations and are split between the six types of quarks and leptons, while among the bosons, there are no generations, but merely different numbers of them, depending on the nature of the force being mediated. There’s just one boson (the massless photon) for the electromagnetic force, three (the massive W-and-Z bosons) for the weak force, eight (massless gluons), and one (massive) Higgs boson.

All told, the Standard Model provides the framework for all of the known and discovered fundamental particles, but has no way of providing expected values for what masses each particle…