Ganymede (Jupiter III)
The seventh and largest of → Jupiter's known satellites. This → Galilean satellite has a diameter of 5270 km, slightly larger than Mercury, a mass about 1.48 × 1023 kg (about 2 Earth Moons); an → orbital period of 7.155 days, and an → eccentricity of e = 0.0015. It was discovered by Galileo and Marius in 1610. The mean → surface temperature of Ganymede is -160 °C. It is the only moon known to have a → magnetosphere.
In Gk. mythology, Ganymedes, a unusually beautiful prince of Troy who was abducted to Olympus by Zeus and made the cup-bearer of the gods.
Fr.: division, lacune, trou
An empty space or interval; interruption in continuity; a break or opening, as in a fence, wall. → Encke gap.
Gap, from O.N. gap "chasm," related to gapa "to gape."
Gâf, variant kâf "split, slit," stem of kâftan, kâvidan "to split; to dig," Mid./Mod.Pers. škâf- škâftan "to split, burst," Proto-Iranian *kap-, *kaf- "to split;" cf. Gk. skaptein "to dig;" L. cabere "to scratch, scrape," P.Gmc. *skabanan (Goth. skaban; Ger. schaben; E. shave). PIE base *(s)kep- "to cut, to scrape, to hack."
Fr.: étoile Grenat
A variable → red supergiant star of → spectral type M2 Ia in the → constellation → Cepheus. Also called → Mu Cephei. Its → apparent magnitude is usually about 4.5 and varies from 3.6 to 5.1. It is also a → triple star.
Garnet "a deep-red color," from the more or less transparent, usually red, silicate mineral that has a vitreous luster. So named by William Herschel from its unusual deep reddish tint. From O.Fr. grenat "garnet," from M.L. granatum, originally an adj., "of dark red color," probably abstracted from pomegranate, from M.L. pomum granatum "apple with many seeds," from pome "apple, fruit" + grenate "having grains."
Nârsang, from nâr, from anâr "pomegranate," from Mid.Pers. anâr "pomegranate" + sang, → stone.
A substance whose physical state is such that it always occupies the whole of the space in which it is contained.
Gas, from Du. gas, probably from Gk. khaos "empty space," → chaos. The term gas was coined by the Belgian physician Jean-Baptiste van Helmont (1579-1644) to designate aerial spirits.
Gâz, loanword from Fr.
pâyâ-ye gâzhâ (#)
Fr.: constante des gaz parfaits
Fr.: équation des gaz
An equation that links the pressure and volume of a quantity of gas with the absolute temperature. For a gram-molecule of a perfect gas, PV = RT, where P = pressure, V = volume, T = absolute temperature, and R = the gas constant.
qulpeykar-e gâzi (#)
Fr.: géante gazeuse
A → giant planet composed mainly of → hydrogen and → helium with → traces of → water, → methane, → ammonia, and other hydrogen compounds. Gas giants have a small rocky or metallic core. The core would be at high temperatures (as high as 20,000 K) and extreme pressures. There are four gas giants in our solar system: → Jupiter, → Saturn, → Uranus, and → Neptune. Another category of gas giants is → ice giants. Ice giants are also composed of small amounts of hydrogen and helium. However, they have high levels of what are called "ices." These ices include methane, water, and ammonia.
Fr.: laser à gaz
A kind of laser where the lasing medium is a gas or a mixture of gases that can be excited with an electric discharge. The first gas laser to operate successfully was built by A. Javan and William R. Bennette at the Bell Telephone Laboratories. This laser used a mixture of helium and neon as the active medium and produced a continuous beam rather than a series of pulses. This laser operated in the infrared region of the spectrum at 1.15 micrometres. A few years later Kumar Patel developed the CO2 laser.
Fr.: mélange de gaz
An aggregate of several different kinds of gases which do not react chemically under the conditions being considered. A gas mixture constitutes a homogeneous thermodynamical system.
Fr.: queue de gaz
Fr.: galaxie pauvre en gaz
Fr.: galaxie riche en gaz
A galaxy, usually young, which has a relatively important gas content.
vâbar-e gâz bé qobâr
Fr.: rapport gaz/poussière
The mass ratio of gas to dust. It amounts to approximately 100 in the → interstellar medium, but may vary in → molecular clouds and → circumstellar disks due to dust → grain evaporation, → dust settling, → condensation of gas, etc. The gas-to-dust ratio depends on the → metallicity. It is larger in galaxies with lower metallicity.
1) Existing in the → state of a gas.
Fr.: nébuleuse gazeuse
(n.) gaz; (v.) gaz kardan
1) (n.) A standard of measure or measurement, size, or quantity.
From Fr. jauge "gauging rod," perhaps from Frankish galga "rod, pole for measuring;" cf. O.N. gelgja "pole, perch;" O.H.G. galgo; Lith. zalga "pole, perch;" Arm. dzalk "pole;" E. gallows; see below.
Gaz "a yard for measuring cloth; a length of 24 finger-breadths, or six hands; the tamarisk-tree," from Mid.Pers. gaz "tamarisk," may be of the same origin as gauge. In verbal form with kardan "to do, to make" (Mid.Pers. kardan; O.Pers./Av. kar- "to do, make, build;" Av. kərənaoiti "he makes;" cf. Skt. kr- "to do, to make," krnoti "he makes, he does," karoti "he makes, he does," karma "act, deed;" PIE base kwer- "to do, to make").
Fr.: boson de jauge
A class of elementary particles that includes the gluon, photon, W+, W-, and Z0 particles, each having an integral spin.
goruh-e gaz (#)
Fr.: groupe de jauge
The mathematical group associated with a particular set of gauge transformations.
Fr.: invariance de jauge
The invariance of any field theory under gauge transformation.
Fr.: symétrie de jauge
A principle underlying the quantum-mechanical description of the three non-gravitational forces. It allows a system to behave in the same way even though it has undergone various transformations. The earliest physical theory which had a gauge symmetry was Maxwell's electrodynamics.