Structure of the Proton

Structure of the Proton

Feynman, Richard P.
Science 183, no. 4125 (1974): 601-610
https://www.jstor.org/stable/1737688

“We have often made great advances in physics by recognizing that the complexity of things at one level is the result of the fact that these things are composed of simpler elements at an- other level. For example, the enormous variety of behavior and character of matter could be understood by sup- posing it made of simpler elements, atoms. Deeper study of the atoms showed that they came in a hundred varieties and themselves had complex properties (like their spectra, for ex- ample). Atoms were then in turn understood as made of two elements, electrons and nuclei (held together by a third, the electromagnetic interaction, represented today as an exchange of photons). Further study suggested that nuclei were themselves complicated but their complexity can be better comprehended if they are imagined to be made of two elements-protons and neutrons. What held them together remained a question, hinting, as Yukawa pointed out, at the existence of still more particles…”

— Richard P. Feynman