Rotate the helium atom with the mouse. Click the nucleus to zoom into the nucleus, click a proton or neutron to enter the world of quarks, and click an electron to zoom into the world of the electron, which “fluctuates” at 1/137 of the speed of light. At every level the main actor is the quantum fluctuation: the size of an atom is set by the fluctuations of its electrons, the size of a nucleus by the fluctuations of its nucleons, and the size of a nucleon by the fluctuations of quarks and gluons, while electrons and quarks themselves remain “points” down to 10−19 m. In ② we line up gravity, electromagnetism, the weak force, and the strong force on a single yardstick (distance and energy); in ③ we keep a ledger of “size” and “fluctuation”; and in ④ we see how the electromagnetic force is carried by the “exchange” of photons between a proton and an electron, and how that differs from pion exchange and from exchange energy. The numbers are values from PDG 2024, CODATA 2022, and papers on lattice QCD and quantum Monte Carlo; sources are given on the explanation page (in Japanese).
Companion page: Explanation — Elementary Particles for Materials Scientists (elementary-particles-derivation.html, in Japanese) | Related: Nuclear Fusion Simulator (in Japanese), Lie Group Simulator | Mochizuki Research Group, Tokyo University of Science