In the 3rd episode of Wonders of the Universe by Brian Cox (see below) there was the mention of cloud chambers. These chambers have allowed scientists to see the paths of ionising particles since 1912 (it is a chamber filled with supersaturated alcohol). These particles can also be affected by magnetic fields; the positive and negative particles curve in opposite ways to each other.
The particles that are seen in these cloud chambers do not come from the earth - they are travelling at a much too high speed with too much energy to come from such a close source.
Cosmic rays are most commonly protons. By travelling the paths of unaffected gamma rays (given off when protons collide with other protons) it can be seen that the high-speed protons originate from the two largest supernova remnants in the Milky Way. As these high speed protons collide with slower protons, it releases a neutral pion, instantaneously decaying into two gamma rays, having lower energy than normal gamma rays, therefore not showing up in the energy spectrum, making the discovery of the origin of the cosmic rays harder to trace. However, there are still questions regarding the MAIN causation of these rays.
Alice
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