Cosmic rays are high-energy particles that originate from outer space and interact with the Earth's atmosphere.

Supernova explosions are the primary source of cosmic rays. When a massive star dies, it explodes and releases a tremendous amount of energy, which accelerates particles to very high energies.

Cosmic rays consist of protons, neutrons, electrons, and other atomic nuclei.

The energy range of cosmic rays extends from 10^12 eV to 10^23 eV.

The flux of cosmic rays at sea level is approximately 1 particle per square meter per second.

Cosmic rays interact with the Earth's atmosphere through collisions, absorption, and deflection.

Air showers are cascades of secondary particles produced by the interaction of cosmic rays with the atmosphere.

Air showers consist of protons, neutrons, electrons, and other atomic nuclei.

Air showers typically have a diameter of a few kilometers.

Cosmic rays can be detected using scintillation detectors, Cherenkov detectors, muon detectors, and other techniques.

Cosmic rays have a wide range of applications, including studying the origin and evolution of the universe, searching for dark matter and other exotic particles, and medical imaging.

The challenges in studying cosmic rays include the low flux of cosmic rays, the high energies of cosmic rays, and the difficulty in distinguishing cosmic rays from other particles.

The future directions in cosmic ray research include searching for ultra-high-energy cosmic rays, studying the composition of cosmic rays at higher energies, and developing new techniques for detecting cosmic rays.

The highest energy cosmic ray ever detected had an energy of 10^20 eV.

The origin of ultra-high-energy cosmic rays is still unknown.