© Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo.
This photograph shows the almost full water tank at the Super-Kamiokande nucleon decay experiment. The experiment, buried deep underground, seeks evidence of proton decay. A decaying proton will emit one or more charged particles, moving with enough energy to create a flash of "Cerenkov light", the visual equivalent of a sonic boom when an electromagnetically charged particle (like an electron) moves through a material faster than light would move through the same material. The Super-Kamiokande experiment is also capable of detecting neutrinos, as we learned in Unit 1. (Unit: 2)