IceCube sees highest-energy neutrino ever found

For more than a century, scientists have known that particles called cosmic rays rain down on the Earth from space. Some of these cosmic rays slam into our atmosphere at energies higher than we could possibly reach in any earthly particle accelerator. It is still a mystery where these particles come from, but it seems that they are from energetic sources outside our galaxy. One suspicion is that they are coming from active galaxies swirling around distant black holes.