Neutrino: Difference between revisions
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|The neutrinos appear to constitute by number of species not less than one quarter of the particles which make the world, and even half of the stable ones. By number of particles in the Universe they are perhaps second only to photons.<br> | |The neutrinos appear to constitute by number of species not less than one quarter of the particles which make the world, and even half of the stable ones. By number of particles in the Universe they are perhaps second only to photons.<br> | ||
<center>— | <center>—Ivan V. Aniĉin, 2005 <ref name=anicin2005>Anicin IV. (2005) [http://arxiv.org/abs/physics/0503172 The Neutrino: Its past present and future]. arXivPhysics/0503172v1. Downloadable PDF. | Author: Faculty of Physics, University of Belgrade.</ref></center> | ||
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At the time of Pauli's postulated existence of the neutrino, physicists had already discovered that atoms, previously thought of as homogeneous and indivisible, consisted of sub-particles, called subatomic particles, specifically, [[proton]]s and [[neutron]]s localized in a center-of-the-atom nucleus, the major location of the atoms' mass, and electrons, by comparison tiny, surrounding the nucleus. The protons each carried a unit of positive electrical charge and the electrons, equal in number to the number of protons, each carried a unit of negative electrical [[charge]], rendering the atom as a whole electrically neutral, inasmuch as the neutron itself carried no electrical charge. | At the time of Pauli's postulated existence of the neutrino, physicists had already discovered that atoms, previously thought of as homogeneous and indivisible, consisted of sub-particles, called subatomic particles, specifically, [[proton]]s and [[neutron]]s localized in a center-of-the-atom nucleus, the major location of the atoms' mass, and electrons, by comparison tiny, surrounding the nucleus. The protons each carried a unit of positive electrical charge and the electrons, equal in number to the number of protons, each carried a unit of negative electrical [[charge]], rendering the atom as a whole electrically neutral, inasmuch as the neutron itself carried no electrical charge. | ||
Revision as of 17:11, 25 October 2010
Based on theoretical considerations, in 1930, the physicist, Wolfgang Pauli (1900-1958),[1] postulated a new fundamental particle of matter, subsequently (1935) named by the physicist, Enrico Fermi (1901-1954),[2] the neutrino ("little neutral one", in Fermi's Italian), an electrically uncharged particle associated with the negatively electrically charged particle, the electron, specifically the electron that is emitted from an unstable atom's nucleus during a certain type of radioactive emission called beta decay. Initially the electron-accompanying neutrino was presumed to have no mass. Physicists subsequently have confirmed the existence of the neutrino and provide evidence that it has a "vanishingly small" but finite mass.
Introduction
| The neutrinos appear to constitute by number of species not less than one quarter of the particles which make the world, and even half of the stable ones. By number of particles in the Universe they are perhaps second only to photons. |
At the time of Pauli's postulated existence of the neutrino, physicists had already discovered that atoms, previously thought of as homogeneous and indivisible, consisted of sub-particles, called subatomic particles, specifically, protons and neutrons localized in a center-of-the-atom nucleus, the major location of the atoms' mass, and electrons, by comparison tiny, surrounding the nucleus. The protons each carried a unit of positive electrical charge and the electrons, equal in number to the number of protons, each carried a unit of negative electrical charge, rendering the atom as a whole electrically neutral, inasmuch as the neutron itself carried no electrical charge.
| Of all the things that make the universe, the commonest and weirdest are neutrinos. Able to travel through the earth like a bullet through a bank of fog, they are so shy that half a century after their discovery we still know less about them than all the other varieties of matter that have ever been seen. |
They had also discovered that the some atoms were unstable, in that their nuclei might emit one or more subatomic particles, a process called radioactivity...
Basing his thinking on the widely accepted law of conservation of energy, Pauli postulated the existence of an electron-associated, presumably massless, neutrino, postulated in order to reconcile the observed discrepancy between the energy carried by an electron emitted from the nucleus during the radioactive process called 'beta decay' — electron energy too small — and the energy change of the nucleus itself, the missing energy, the energy lost by the nucleus during the beta decay process, carried off by the postulated chargeless neutrino particle.[5]
References
- ↑ Biography of Wolfgang Pauli on the Nobel Prize website.
- ↑ Biography of Enrico Fermi on the Nobel Prize website.
- ↑ Anicin IV. (2005) The Neutrino: Its past present and future. arXivPhysics/0503172v1. Downloadable PDF. | Author: Faculty of Physics, University of Belgrade.
- ↑ Close F. (2010) Neutrino. Oxford University Press. ISBN 978-0-19-957459-9. | Author: Professor of Physics, Oxford University.
- ↑ The Story of the Neutrino. NuMI-MINOS Homepage. Fermi National Accelerator Laboratory.