How and when were cosmic rays discovered?
In 1912 a scientist named Viktor Hess carried an instrument called an ionization chamber in a balloon to high altitudes. An ionization chamber is a device that records the passage of charged particles. As Hess made his ascent in the balloon, the ionization chamber recorded fewer particles, up to an altitude of 2,000 meters. The interpretation is that some of this ionization is due to the natural radioactivity of the earth, and its influence decreases with altitude. Above 2,000 meters, however, he recorded more particles, and the increase in particles became even more rapid as his balloon reached its maximum altitude of 5,350 meters. Hess correctly guessed that this increase was due to radiation entering the atmosphere from space. On one occasion he rode the balloon during a solar eclipse, and found no decrease in ionization. From this he concluded that the radiation was coming from somewhere other than the sun. We now know that much of this cosmic radiation originates far outside the s
