Cosmic Rays: High-Energy Particles from Deep Space

Cosmic rays are fast-moving particles, mostly protons, that bombard Earth from space.
They were first discovered in 1912 by Victor Hess during high-altitude balloon flights.
Many originate from exploding stars—supernovae that hurl particles across the galaxy.
The most powerful cosmic rays may come from black holes or distant galaxies.
A single particle can carry the energy of a pitched baseball packed into something microscopic.
When cosmic rays hit Earth’s atmosphere, they create showers of secondary particles.
These showers can be detected by ground-based observatories worldwide.
Cosmic rays pose radiation risks to astronauts and spacecraft electronics.
They help scientists study extreme physics not reproducible on Earth.
The origin of the highest-energy cosmic rays remains one of astronomy’s great mysteries.