Each of these particles, or “nucleons,” is composed of a dense, frothing mess of other particles: quarks, which have mass, and gluons, which do not.
Fascinating! That's some pretty deep nerdery. Is there no end to the enormity of the universe or the incredible tinyness of its components? Are we going to discover someday that quarks and gluons are made from dense, frothing messes of even tinier particles? Is this an Elon Musk simulation?