Super-Kamiokande
The general weirdness of neutrinos—such as how they pass right through most matter without interacting with it at all—has driven scientists to construct experiments that try to measure them. Super-Kamiokande is a vat containing 50,000 tons of water. It sits beneath Japan’s Mount Ikeno and is lined with detectors that turn minute flashes of light into signals read into computers. Like other giant-vat-of-stuff experiments, it lies in wait for its target particles—in this case, neutrinos from the Sun, from deep space, or produced at the Japan Proton Accelerator Research Complex 186 miles away. Super-K is most famous for discovering neutrinos’ identity-switching behavior, called neutrino oscillations, and recently made headlines for a measurement hinting at the fact that neutrinos could differ from their antiparticle partners, which scientists think is a prerequisite for explaining why the universe contains more matter than antimatter.
