This illustration shows a neutrino interacting with ordinary matter and releasing a muon. The muon moves very rapidly, leaving the telltale blue glow of Cherenkov radiation. The most energetic neutrino ever observed was detected by the muon it created. Its energy was so great that researchers think it may have been an elusive cosmogenic neutron. Credit: Nicolle R. Fuller/NSF/IceCube In the exotic world of particle physics, neutrinos may be the most mysterious members. They rarely interact with other matter, have almost no mass, and have no electrical charge. These characteristics make them extremely difficult to study. Even detecting them requires specialized facilities in deep caves, in thick Antarctic ice, or on the ocean floor. One of the foremost neutrino detectors is called KM3NeT , which stands for the Cubic Kilometer Neutrino Telescope. It's on the seafloor in the Mediterranean, and in February 2023, it detected the most energetic neutron ever observed.…