Neutrinos are tiny, mass-less particles that interact with matter. Neutrinos are one of the basic particles that make up the universe and are also one of the least understood. Billions of neutrinos pass through our bodies every second. The sun is the main source for neutrinos, although stars, supernovae and nuclear power plants on earth also produce them. The production of neutrinos is through nuclear fusion and decay processes within the cores of the sun and stars. .
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The sun produces over two hundred trillion neutrinos every second, and a supernova blast can unleash 1000 times more neutrinos than our sun will produce in its 10-billion year lifetime. .
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There are four fundamental interactions between the particles. There are strong, electromagnetic, weak and gravitational interactions. The weak interaction allows neutrinos to pass through the earth without any deviation. The neutrino has a distinctive property; its spin is oriented in the direction opposite to its velocity, which is said to be of left helicity. The anti-neutrino is always of right helicity, which is the same direction as the velocity.
Wolfgang Pauli was the first to suggest a solution for the missing energy in nuclear beta decays. He believed it was carried by a neutral particle, which was later named the "neutrino" by Enrico Fermi who received the Nobel Prize in 1938. In 1945 Pauli later received the Nobel Prize for his discovery. In 1951 Fred Reines and Clyde Cowan decided to attempt to detect neutrinos. First they tried to distinguish neutrinos from nuclear explosions. In 1968 the primary experiment to detect neutrinos they used a liquid chlorine target deep underground. The reports showed that less than half the expected neutrinos are observed. This is the origin of the "solar neutrino problem." In 1985 a large water detector is used to look for proton decay. It also detects neutrinos. Today scientists are still searching for techniques to help us learn more about neutrinos.