Cosmic radiation refers to high-energy particles that originate from outer space and constantly bombard the Earth. These particles mainly consist of protons, but they can also include heavier atomic nuclei and electrons. When these particles enter the Earth's atmosphere, they collide with atoms, creating secondary particles that can reach the surface. Most cosmic radiation comes from sources like supernovae and black holes, while some is produced by the Sun. Although the Earth's atmosphere and magnetic field provide protection, people at higher altitudes or frequent flyers may receive slightly higher doses of cosmic radiation compared to those at sea level.