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Related to neutrino: quark
n. pl. neu·tri·nos
Any of three electrically neutral leptons (the electron neutrino, muon neutrino and tau neutrino—one in each of the three generations of elementary fermions) that have small or very small masses.
[Italian, from neutrino, little neutral one : neutro, neuter, neutral (from Latin neuter, neutr-, neuter; see neuter) + -ino, dimutive suff. (from Latin -īnus, adj. suff.; see -ine1). Coined by Enrico Fermi on the model of Italian neutrone, neutron, taken as the augmentative of Italian neutro.]
n, pl -nos
(General Physics) physics a stable leptonic neutral elementary particle with very small or possibly zero rest mass and spin that travels at the speed of light. Three types exist, associated with the electron, the muon, and the tau particle
[C20: from Italian, diminutive of neutrone neutron]
neu•tri•no(nuˈtri noʊ, nyu-)
n., pl. -nos.
a massless or nearly massless electrically neutral lepton.
[< Italian (1933)]
Any of three electrically neutral subatomic particles that travel at the speed of light. Neutrinos are thought to have a mass that is too close to zero, when they are not moving, to be measured.
Did You Know? Neutrinos were not observed until 1955, roughly a quarter of a century after the physicist Wolfgang Pauli first proposed, on theoretical grounds, that they might exist. Pauli was studying certain radioactive decay processes in which it seemed that energy somehow mysteriously disappeared. He suggested that the energy was carried away by a very small, electrically neutral particle that was not being detected. (He originally wanted to name the particle a neutron but didn't publish the suggestion, and a few years later the particle we now know as the neutron was discovered and named in print. The Italian physicist Enrico Fermi then coined the term neutrino, which means "little neutron" in Italian.) Neutrinos are hard to detect because they interact only very weakly with other forms of matter. Most of the neutrinos that reach the Earth from space pass right through and go out the other side. Even a chunk of iron a few light-years thick would stop only about half of the neutrinos that struck it.