Longman Dictionary of Contemporary English
n. (context physics English) fundamental particle; any of the subatomic particles that does not consist of other, smaller particles; the gauge bosons, leptons and quarks.
n. a particle that is less complex than an atom; regarded as constituents of all matter [syn: fundamental particle, subatomic particle]
In particle physics, an elementary particle or fundamental particle is a -->particle whose substructure is unknown, thus it is unknown whether it is composed of other particles. Known elementary particles include the fundamental fermions ( quarks, leptons, antiquarks, and antileptons), which generally are "matter particles" and " antimatter particles", as well as the fundamental bosons ( gauge bosons and the Higgs boson), which generally are "force particles" that mediate interactions among fermions. A particle containing two or more elementary particles is a composite particle.
Everyday matter is composed of atoms, once presumed to be matter's elementary particles—atom meaning "unable to cut" in Greek—although the atom's existence remained controversial until about 1910, as some leading physicists regarded molecules as mathematical illusions, and matter as ultimately composed of energy. Soon, subatomic constituents of the atom were identified. As the 1930s opened, the electron and the proton had been observed, along with the photon, the particle of electromagnetic radiation. At that time, the recent advent of quantum mechanics was radically altering the conception of particles, as a single particle could seemingly span a field as would a wave, a paradox still eluding satisfactory explanation.
Via quantum theory, protons and neutrons were found to contain quarks— up quarks and down quarks—now considered elementary particles. And within a molecule, the electron's three degrees of freedom ( charge, spin, orbital) can separate via wavefunction into three quasiparticles ( holon, spinon, orbiton). Yet a free electron—which, not orbiting an atomic nucleus, lacks orbital motion—appears unsplittable and remains regarded as an elementary particle.
Around 1980, an elementary particle's status as indeed elementary—an ultimate constituent of substance—was mostly discarded for a more practical outlook, embodied in particle physics' Standard Model, science's most experimentally successful theory. Many elaborations upon and theories beyond the Standard Model, including the extremely popular supersymmetry, double the number of elementary particles by hypothesizing that each known particle associates with a "shadow" partner far more massive, although all such superpartners remain undiscovered. Meanwhile, an elementary boson mediating gravitation—the graviton—remains hypothetical.
Usage examples of "elementary particle".
An elementary particle would be stuck with a constant wormhole length, fixed at the moment of its creation, but a traversable wormhole would be free to tunnel its way into detours of arbitrary size.
The father was the late Luis Alvarez, a physicist who had won the 1968 Nobel Prize for his contributions to elementary particle physics.
There is, we are told, an infinite hierarchy of universes, so that an elementary particle, such as an electron, in our universe would, if penetrated, reveal itself to be an entire closed universe.
Consider the grand idea that our Universe and everything in it is just an elementary particle - an electron, say - in a much bigger Cosmos.
If there is an elementary particle, or wavicle, of thought, a faster-than-light one like the tachyon might be a good candidate for the honor.
But some years ago a Muscovite called Boris Mikhailovitch Rusakov discovered a new kind of elementary particle.
And an elementary particle, an electron perhaps, would be able to move at random between any two points of that object, without a time lapse.
Its structure is still fearfully complex for an elementary particle: a twelve-thousand-two-hundred-ton spacecraft, loaded with instruments, its hull windowless and very smoothly contoured.