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Moment of truth
The fastest man-made object that ever leave the Earth is the New Horizon spacecraft, launched in January 2006, and attained a speed of more than 36000 mph.

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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 cosmology Astron.
A specialized field in theoretical physics to study the effect of quantum mechanics on the creation of the universe, especially just after the Big Bang within the Planck time scale. The idea was first introduced by John Wheeler in 1960s who argued that quantum uncertainty prevents the precise determination of singularity at the Big Bang. Instead of starting at a point of infinite curvature of space time, where space and time are precisely at zero, the quantum effects actually smear out the individual identities of space and time at or near the Planck time after Big Bang.

The study is an attempt to explain the cosmic origin within the realm of science, comlying with the laws of physics everywhere within the universe. Nevertheless, quantum cosmology is still regarded as a speculation, rather than an established subject area and is considered as a sub-branch of quantum gravity.

quantum mechanics Phys.
A physical theory that describes the behavior of very small 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.
quartz mineral 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.

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