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Index (Q)
QA - QC
QD - QF
QG - QJ
QK - QN
QO - QR
QS - QV
QW - QZ
Moment of truth
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More than 25 million people died in Europe from the bubonic plague (the black death) in five years, from 1347 to 1352. |
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QS - QV
quantum chromodynamics Phys.
Abbreviated as QCD, it is the theoretical description of strong interactions within atomic nuclei (such as quarks), mediated by gluons, the massless boson.
quantum electrodynamics Phys.
Abbreviated as QED, it is a theoretical description of electromagnetic forces in terms of the exchange of photons, the massless boson. For example, whenever two electrons exchange photons, they generate
an electromagnetic force.
quantum mechanics Phys.
A physical theory that describes the behavior of very size such as atoms, that cannot be accounted for, nor manifested in matter of larger in size (as appears in our daily life). Quantum mechanics cannot describe precisely
the state of a system at any one time. Rather, an observable, such as the energy, position or momentum, is described according to its probability distribution. For instance, the position of an electron that surrounds an atomic nucleus
cannot be precisely known at any one time. Instead, the likelihood of its existence at certain positions can be stated according to its probability distribution. The mathematical postulation of the quantum mechanics is the
Schrödinger equation
quantum vacuum Phys.
The sea of short-lived virtual particles that fills the void between visible matter. According to quantum mechanics, empty space is not completely empty but extremely short-lived
pairs of charged particles and antiparticles are continually created and destroyed spontaneously. This quantum phenomena can be detected as an attractive force known as the Casimir effect.
quark Phys.
A hypothetical fundamental particle of no known structural feature with a size estimated to be less than 10-20m and is a
fundamental building block of hadrons. According to the Standard Model theory there are six types of quarks, each having magnitude
charges of 1/3 or 2/3 of the electron charge. For example, proton is made of one up quark of charge 2/3 and two down quark of charge -1/3.
The total sum of the charge gives +1 to proton. The existence of quarks in isolation has never been confirmed experimentally. They always exist in pairs (mesons) or in trios (baryons).
quartz Min.
The most abundant and common mineral of silicon dioxide (silica, SiO2). It is found in any every geological environment and forms a component of almost all rocks, especially igneous rock (granite and quartzite),
metamorphic rocks (gneisses etc.) and sedimentary rocks (sandstone, limestone, etc). It has a hardness of 7 and belongs to the trigonal crystallographic system. Well form crystals can be found in nature with six-sides prisms terminating with six-sided
pyramids. Normal quartz is transparent and colorless (rock crystals), but it can also appear in a variety of colors. For example, purple amethyst, pink rose quartz, gray-brown smoky quartz, yellow-orange citrine, agate, jasper, etc.
The figure shows a milky quartz, which is the cloudy-white variety. Due to its piezoelectric behavior, quartz is used to make oscillators for clocks, watches, radio and radar instruments. It is also as ornaments, glass, glaze and abrasives.
quasar Astron.
A mysterious celestial object that lies at the edge of the Universe that appears star-like in an optical telescope. It is in fact extremely bright and may be an active galactic nucleus that contained a supermassive blackhole
in the center.
quicklime Chem.
A common name of calcium oxide. Also called lime or burnt lime. It is obtained by heating limestone that contains calcium carbonate in a kiln to around 550°C - 900°C.
QS - QV
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