In an announcement that has a huge impact on everything from our understanding of the history of the Universe to the structure of the atom, an international team of scientists at Japan's Super Kamiokande Neutrino Observatory say they've discovered that neutrinos do have mass. Neutrinos are infinitesimally small bits of sub-atomic matter. The neutrinos the Japanese detector was looking for are created when high energy cosmic rays bombard Earth's upper atmosphere, creating a cascade of these elusive and highly mysterious particles that spray out in all directions. There are many different kinds of neutrinos, but scientists found half the number of muon neutrinos coming from the other side of the planet than they were expecting. It suggests these particles actually change form or oscillate as they traveled and that could never happen if neutrinos had no mass. This is a very important finding, since it may indicate where all the missing mass in the universe is and may ultimately answer the question of whether the universe will collapse in on itself or continue expanding forever.