Cosmic rays are high-energy particles originating from outer space that bombard Earth's atmosphere. They are composed of protons, electrons, neutrinos, and atomic nuclei. Primary cosmic rays come from astrophysical sources like supernovae, neutron stars, and black holes. Secondary cosmic rays are produced when primary cosmic rays interact with the Earth's atmosphere. The history of cosmic rays includes their discovery in the late 19th century by Henri Becquerel and Victor Hess, and later work in the early 20th century that established they originate outside the Earth's atmosphere and consist of charged particles. Modern research on cosmic rays includes using extensive air shower arrays and tracking detectors to study their origins and composition.

1. Cosmic Rays Ki Choi Edited by David Osowski