Showers of subatomic particles caused by cosmic rays rain down on Earth in this artist’s concept. The most energetic cosmic rays are particles blasted into space by supernova remnants, supermassive black holes, or other powerful objects. When they reach Earth, they strike atoms and molecules in the upper atmosphere. That creates cascades of other particles that eventually reach the surface. [Simon Swordy (Univ. Chicago)/NASA]
Find out more in our radio program entitled Cosmic Rays.