Cosmic Rays: High-Energy Visitors From Space

Cosmic rays are high-energy particles that constantly stream into Earth from space.
Most are protons, but they also include heavier nuclei and some electrons.
They travel at nearly the speed of light, carrying enormous energy.
Cosmic rays were first discovered in 1912 by Victor Hess during balloon experiments.
When they hit Earth’s atmosphere, they create cascades of secondary particles.
Many cosmic rays come from supernovae and distant galaxies.
The highest-energy cosmic rays pack more punch than a baseball traveling at 100 mph.
They pose a radiation hazard for astronauts and high-altitude flights.
Cosmic ray studies have led to discoveries like the positron and the muon.
They remain a cosmic mystery, with scientists still tracing their most extreme origins.