Cosmic Rays

Cosmic rays are high-energy particles originating from outer space that constantly bombard Earth's atmosphere. Mostly protons and atomic nuclei, they travel at near-light speeds, carrying energies millions of times greater than anything humans can create in laboratories.

When cosmic rays strike the upper atmosphere, they create cascades of secondary particles, including muons that reach Earth's surface. These collisions produce measurable radiation that penetrates deep underground and even into aircraft cabins—airline crews receive notably higher cosmic ray exposure than ground-level workers.

The sources remain partially mysterious. Most originate from supernovae and other violent cosmic events, accelerated by powerful magnetic fields in space. The highest-energy rays—called ultra-high-energy cosmic rays—are rarer and more enigmatic, possibly arriving from supermassive black holes or exotic physics.

Cosmic rays have shaped Earth's history, ionizing the atmosphere and potentially influencing climate and extinction events. They also pose challenges for space exploration and sensitive electronics. Scientists study them through observational astronomy, ground detectors, and satellite instruments like those aboard the International Space Station.

Related

Radiation, Particle Physics, Solar wind, Ionosphere, Space weather