OUR cosmos is a huge ocean of mysteries. Every mystery solved brings us one step closer to understanding the world we live. The existence of cosmic rays has baffled scientists for almost a century. Cosmic rays are not really rays! They are, in fact, tiny, charged particles that come from outer space and continuously bombard the Earth from all sides. These particles have very high energy and they travel almost at the speed of light.
There are two types of cosmic rays — primary and secondary. Primary cosmic rays which come from outer space strike the Earth’s atmosphere and cause the atmospheric atoms and molecules to break down and descend to the ground. These particles form secondary cosmic rays.
Secondary cosmic rays collide with more air molecules, producing a cascade shower called ‘air shower’ or ‘Auger shower’ (named after the scientist Pierre Auger, who discovered these showers).
Cosmic rays were first discovered in 1912 by the Austrian-American scientist Victor Hess during a balloon- flight. He found that as he moved higher above the Earth’s surface, the amount of charged radiation detected went on increasing; causing him to conclude that the radiation was coming from space.
In fact, he also went on a similar expedition during a solar eclipse and found that the amount of radiation recorded did not decrease, thereby confirming that the sun was not the source for this radiation.
The term ‘Cosmic Rays’ was coined by Robert Millikan in1925, although, at the time, it was not known what kind of matter was present in the rays.
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