Antimatter


In the late 1920s a British physicist was trying to work out mathematics of the electron's wave nature and came to the conclusion that the it should be possible for the electron to have to two energy states and therefore be both positive and negative. He hoped that the opposite particle would be the proton but found in his computations that the opposite particle had to be identical in every property except for the charge. In 1930, he published his ideas but there was no scientific evidence of such a particle, yet. He proved mathematically that if an electron and its anti-particle were to meet their waves would cancel and they should undergo mutual annihilation. Conservation of charge would therefore be conserved but what about conservation of mass? This would be conserved through a release of gamma rays with energy that is directly related to the mass of the electron counterpart thought Einstein's E=mc˛.

The first scientific evidence of these ideas were to be demonstrated two years later by an American named Carl David Anderson. In the beginning of the twentieth century physicist were doing research into charge and electricity and were finding that their electroscopes were losing their charge over time. The found that if near a radioactive source they would lose this charge faster. Now radiation is everywhere on the earth, it's even in the soil, so these physicist would take their electroscopes out to sea and yet they still lost their charge. Then, in 1911, the Physicist Victor Franz Hess of Austria took an electroscope up in a hot air balloon to see if a difference in altitude would have an effect and it did. He found over the course of ten trips that the higher the altitude the faster the charge was lost. It therefore was reasoned that there was radiation, powerful radiation, coming to Earth from space. This radiation became known as Cosmic Rays. Through the work of American Robert Millikan, Thomas Johnson, and an Italian Bruno Rossi, working independently, it was found that these cosmic rays were positively charges particles. These particles were extremely energetic, coming from the Sun and other stars, and very difficult to work with in terms of experiments.

Anderson's experiment was to attempt to study these cosmic rays using a cloud chamber in a strong magnetic field. He found that even with this magnetic field the cosmic rays were moving too fast for it to have any appreciable effect. To solve this problem he put a lead plate in the cloud chamber with the idea that the cosmic rays were energetic enough to travel through it but would be slowed down by it. What he found was, when he looked at the cloud chamber when the experiment was done, that he had the track of an electron but with an opposite (positive) charge. He had discovered the Positron. For this he and Hess were awarded the Nobel Prize in 1936.

Later it was found that some positrons were created when alpha particle would strike lead but by far the best source was an atom that had an excess of protons. In order to reach a more stable state the proton would break down into a neutron and a positive Beta particle (a positron).

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