Cosmic rays are of great interest because there is no protection outside the atmosphere and magnetic field. The energies of the most energetic ultra-high-energy cosmic rays (UHECRs) have been observed to approach 3 × 1020 eV, about 40 million times the energy of particles accelerated by the Large Hadron Collider. At 50 J, the highest-energy ultra-high-energy cosmic rays have energies comparable to the kinetic energy of a baseball. As a result of these discoveries, there has been interest in investigating cosmic rays of even greater energies. Most cosmic rays, however, do not have such extreme energies. The energy distribution of cosmic rays peaks at .
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