Sudbury neutrino observatory

The SNO was built 2 km underground, in an operating nickel mine, primarily to observe neutrinos emitted from the core of the sun. Neutrinos, tiny bits of energy, are the most plentiful particle in the universe. Dr. Earle and his team were primarily interested in those created in the centre of the sun, but also looked at neutrinos created by cosmic rays. Naturally occurring background radioactivity from cosmic rays and building materials were the main concern during design and construction of the laboratory, but work exceeded even optimistic expectations and created one of the lowest radioactive locations on earth. The data obtained have answered a 30-year old question: "Why do other experiments see only a third of the expected solar neutrinos?"