Cosmic Rays: Features and Sources

Cosmic rays are invisible, high-energy particles that constantly bombard Earth from all directions.

Most cosmic rays are protons moving at extremely high speeds, but they can be atomic nuclei of any known element. They enter Earth’s atmosphere at velocities of 90 percent the speed of light or more.

The cosmic rays were discovered by Victor Franz Hess , who got interested in a mysterious radiation that scientists had found in the ground and in Earth’s atmosphere. This radiation could change the electric charge on an electroscope even when placed in a sealed container. In  1912 Hess took a series of high-altitude, hot-air balloon flights with an electroscope aboard. He made ten trips at night, and one during a solar eclipse, just to be sure the Sun was not the source of the radiation. Hess found that the higher he went, the stronger the radiation became. This discovery led Hess to conclude that this radiation was coming from outer space. For his work on understanding cosmic rays, Hess received the Nobel Prize in physics in 1936.

Source of Cosmic Rays

A continuous stream of electrically charged particles flows from the Sun; this flow is called the solar wind. So, a fraction of cosmic rays originate from the Sun, but the Sun alone cannot account for the total flux of cosmic rays onto Earth’s surface.

The source for the rest of these cosmic rays remains mysterious. Distant supernova explosions could account for some of them; another possibility is that many cosmic rays are charged particles that have been accelerated to enormous speeds by interstellar magnetic fields.

All of us are being struck by cosmic rays all the time, however, at Earth ordinarily, they have no deleterious effect on our health. If we go beyond Earth’s magnetosphere, cosmic rays can cause potentially more damage to your body’s cells and systems.