Cosmic rays are streams of high-energy charged tiny particles that constantly enter the atmosphere of the Earth from outer space. They consist mainly of 89% protons, 9% radiations and 2% of heavy nuclei of carbon, nitrogen, oxygen and iron. These are called primary cosmic rays. They travel nearly at the speed of light.
When these tiny particles of primary cosmic rays collide with the nuclei of the air, they produce new particles called secondary cosmic rays. Secondary cosmic ray particles also travel at high speeds. They further collide with other atoms and again create new particles. After several collisions on the way, only very few secondary cosmic ray particles are able to reach the surface of the Earth. Secondary cosmic rays consist mainly of positrons; neutrons, mesons and neutrinos. All these particles are called elementary or fundamental particles.
Where do these cosmic rays originate in space? It is believed that most of the cosmic rays originate in the supernova explosions far beyond our Milky Way and some of them are produced by storms on the Sun and stars of the galaxy. More and more information is being gathered about the origin of these rays.
The small amount of radiation caused by cosmic rays is not enough to harm the Earth. They can do little damage to the human body. These rays have been colliding with the Earth for billions of years and life has been least affected by them. So, it is believed that cosmic rays are harmless. However, there is a possibility that cosmic rays may have a harmful effect on astronauts because the intensity of cosmic rays is far greater in space than on the Earth.
