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Glossary Q

Quantum chromodynamics (QCD)
Is the physical theory describing one
of the fundamental forces, the strong interaction. It was first
proposed in the early 1970s by Frank Wilczek and Dieter Gross.
Quantum electrodynamics (QED)
Is a quantum field theory of electromagnetism.
QED describes all phenomena exhibited by charged point particles,
such as electrons and positrons, and the particles of light (photons),
interacting by electromagnetism
The smallest discrete amount of any quantity
(plural: quanta). The word comes from the Latin for quantity.
Electric charges comes in fixed multiples of a basic unit, the
quantum of charge.
Name Charge Mass (MeV)
Up +2/3 4
Down -1/3 8
Charm +2/3 1500
Strange -1/3 150
Top (Truth) +2/3 176,000
Bottom (Beauty) -1/3 4,700

Quantum mechanics or quantum physics

Is a physical theory formulated in the
first half of the twentieth century which successfully describes
the behavior of matter at small distance scales. It is in contrast
to classical mechanics which deals with larger scales.
Quarks are one of the two families of
particles thought to be elemental and indivisible (the other
being the leptons). Quarks never exist alone but only in
groups. Quarks are differentiated from leptons, the other
family of elemental particles, by electric charge. [more]
A quasar (from quasi-stellar radio source)
is an astronomical object that looks like a star in optical telescopes
(i.e. it is a point source), but has a very high redshift. The
general consensus is that this high redshift is cosmological,
the result of Hubble’s law and that their redshift indicates that
they are typically very distant from Earth; we observe them as
they were several billions of years ago. [more]
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