Incoming cosmic ray creates a flash of Askaryan radiation inside the ice. Credit: ARA Collaboration A detector buried deep in Antarctic ice has captured the first experimental evidence of a predicted but never-before-seen phenomenon: radio pulses generated when high-energy cosmic rays slam into the ice sheet and trigger particle cascades inside it. Through results published in Physical Review Letters , astronomers of the Askaryan Radio Array (ARA) Collaboration have validated a key technique, which they hope will eventually allow them to detect some of the rarest and most energetic particles in the universe. Flashes in the ice In 1962, Soviet physicist Gurgen Askaryan predicted that high-energy particles passing through a dense material should produce a distinctive burst of radio waves. When such a particle strikes an atom, it triggers a cascade of secondary particles that sweeps up electrons from the surrounding material, creating a negatively charged shower front that radiates at radio frequencies.…