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Physical Environment > Antimatter |
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This site tells the story of the history of the universe. Click Earlier and Later to follow the story. Note: Many facts have been simplified to make them easier to understand. |
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Particles which are identical to ordinary particles such as protons, electrons and neutrons in every way except one. The antiparticle of the electron, called the positron, has the same cloud-like nature as the electron and same mass, but has a positive electric charge. The antiproton has the same mass as the proton but carries a negative charge. The antineutron has opposite magnetic moment to a neutron.
We never meet these antimatter particles in normal life, and that is a good thing, because when matter meets antimatter they annihilate each other and their matter energy is changed into radiation. Antiparticles are real, however, and can be made in high energy particle accelerators. Some people believe that some regions of the Universe may be made of antimatter. Perhaps whole galaxies might be made of antimatter, separated from normal matter galaxies by vast oceans of empty space? Based on our current understanding of the early events in the Universe, this seems very unlikely. Particles and antiparticles were created close together in the young Universe. Nobody has yet thought of a way they could have been separated into different galaxies. If a space ship came to Earth from some distant galaxy we would not be able to tell whether it was made of antimatter just by looking at it since matter and antimatter look the same. But if it was antimatter it would explode when it tried to land! By adding a positron to an antiproton it is possible to make an antiatom of hydrogen. This was first achieved in 1995 at the European Laboratory for Particle Physics (CERN) by firing antiprotons through a xenon gas jet. Some of the antiprotons hit protons in the xenon nuclei, creating pairs of electrons and positrons. A few of these positrons then stuck to the antiprotons to form antihydrogen. Antiatoms do not last very long on Earth. Each antiatom produced at CERN survived for only about forty-billionths of a second before it met ordinary matter and changed into gamma radiation. |
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Physical Environment > Antimatter |
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Basic Information |
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