Cosmic Rays
High-energy relativistic atomic nuclei and subatomic particles originating from outer space that strike Earth's atmosphere.
Governing formula
Primary Energies up to 10²⁰ eV (Extreme Relativistic Protons)
SI unit
eV or GeV (Particle Energy)
In depth
Primary cosmic rays consist mainly of high-energy protons (~90%), alpha particles (~9%), and heavy nuclei accelerated by supernova remnants. Collisions with upper atmospheric gas atoms create particle cascades of pions, muons, and neutrinos.
Examples in the real world
Cosmic ray air showers generating background muon radiation detectable at sea level using spark chambers and cloud chambers.