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Basic Information |
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Physical Environment > Neutrino |
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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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A neutrino is a particle which has little or no mass (nobody is quite sure) and no electric charge, so it hardly seems like a real particle at all. There are three types of neutrino: the electron neutrino, muon neutrino and tau neutrino. Each of these also has its anti-particle, called an antineutrino. Electron-antineutrinos for example are created during the decay of neutrons via the weak interaction. They are also created in large quantities in the stars.
A key feature of neutrinos is that they hardly interact with other particles at all. Huge numbers of them are created by the Sun. Every second 60 billion neutrinos (mostly from the Sun) pass through every square centimeter on Earth. Yet we do not even notice them. These elusive particles can only be detected in lakes of liquid sunk deep in coal mines. If neutrinos have mass, even if only a little, then because there are so many of them they would weigh more than all the stars in the Universe. But the mass of the neutrino seems to be too small to account for dark matter by a factor of 20. |
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Physical Environment > Neutrino |
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Basic Information |
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