![]() Cowan (1919 –1974) finally succeeded in detecting neutrinos produced by the Savannah River Reactor in South Carolina. In 1956, after a four-year search, United States physicists F. (This theory, still used for approximate calculations, was only surpassed for more accurate calculations by theories developed in the 1970s.) But did neutrinos really exist? In the 1930s, no experiments to detect them were possible. Italian physicist Enrico Fermi ’s (1901 –1954) 1934 theory of beta decay used the neutrino hypothesis. When neutrons were discovered, the term “neutron ” was taken, so Pauli ’s particle became the neutrino: literally, the little neutral one. Pauli originally called his suggested particle the neutron, as neutrons had not been discovered in 1930. However, he did not publish the idea for another three years. In 1930, the Austrian physicist Wolfgang Pauli (1900 –1958) wrote a letter to a gathering of physicists in T Übingen, Germany, in which he suggested the idea of neutrinos as the particles that carry away the missing energy. ![]() Where did the missing momentum and energy go? According to fundamental laws of physics, the total amounts of both momentum and energy must remain constant. It was observed that the total momentum and energy of the electron and proton after the decay was sometimes less than the initial momentum and energy of the neutron. In beta decay, a neutron decays into a proton by emitting an electron, also termed a beta particle. History In the 1920s, physicists noticed some discrepancies in beta decay experiments. The total number of neutrinos detected on Earth is in accord, as it turns out, with the standard model of the solar core. This shortage was known as the solar neutrino problem, and was only resolved in 2001 by elaborate experiments that proved that the sun is in fact, producing the number of neutrinos predicted by theory, but that some of these neutrinos change type (electron to muon or tau) en route from the core of the sun to detectors on Earth. In 1968, however, when scientists first tried to detect electron-type neutrinos emitted by the sun, they found less than half those expected from the then-current theory of nuclear reactions in the sun. Because their interaction rate is so low, neutrinos produced in the core of the sun fly directly out through the outer layers of the sun and flood surrounding space, providing direct (though hard-to-intercept) information about nuclear reactions in the sun ’s core. ![]() ![]() Neutrinos have no electrical charge and only a tiny mass, usually travel at nearly the speed of light, come in three types -electron neutrinos, muon neutrinos, and tau neutrinos -and barely interact with normal matter. Neutrinos are elusive subatomic particles that result from certain nuclear reactions. ![]()
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