An anonymous reader writes "European physicists said Tuesday they had sent an elusive particle known as a neutrino on a 730-kilometer (456-mile) trip under the Earth's crust and taken a snapshot of the instant it slammed into lab detectors. In the October 2 event, a neutrino hit one of the 60,000 bricks that had been installed in San Grasso, leaving a tell-tale track of a muon on the film. The experiment is important, say the investigators, as it could help explain one of the biggest mysteries about the Universe — its missing mass. When scientists tot up the mass of all the visible matter in the Universe, they arrive at a total of just 10 percent of what they know to exist. For years, neutrinos were not thought to have any mass, although that theory has been challenged by experiments at Japan's SuperKamioKande lab, which suggested that they may have a mass, albeit a very tiny one."