A team of Antarctic scientists has just verified the existence of cosmic neutrinos — tiny, energetic particles that might hail from far reaches of the Milky Way and beyond. And these ghostly little flecks of matter could hold the key to some of the deepest mysteries of the cosmos. High-energy cosmic neutrinos are thought to be produced by some of the universe’s most violent agents, including black holes, supernovae, and the energetic cores of galaxies. Unchanged as they zip across space and time, these particles may represent something of an intergalactic breadcrumb trail, pointing us in the direction of any...