Awesome Detectors

SNO
The Sudbury Neutrino Observatory is a collaborative effort among physicists from Canada, the U.K., and the U.S. Using 1,000 tons of so-called heavy water and almost 10,000 photon detectors, they measure the flux, energy, and direction of solar neutrinos, which originate in the sun. SNO, located 6,800 feet underground in an active Ontario nickel mine, can also detect the other two types of neutrinos, muon neutrinos and tau neutrinos. In 2001, just two years after the observatory opened, physicists at SNO solved the 30-year-old mystery of the "missing solar neutrinos." They found that the answer lies not with the sun—where many physicists had suspected that solar neutrinos undergo changes—but with the journey they take from the core of the sun to the Earth.