An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1965 Search : ion
geodesic precession
  پیشایان ِ کهین‌رهی   
pišâyân-e kehinrahi

Fr.: précession géodésique   

geodesic precession.

geodesic; → precession

geodetic precession
  پیشایان ِ کهین‌رهی   
pišâyân-e kehinrahi

Fr.: précession géodésique   

A → relativistic effect on the precession motion of a gravitational system due to the → curvature of the → space-time. When a body revolves around a primary, the → rotation axis of the orbiting body follows the curvature of spece-time. Over time the space-time warping causes the spin axis to precess. In the case of the Earth-Moon system, this means a small → direct motion of the → equinox along the → ecliptic, amounting to 1''.915 per century. The geodetic precession is given by: ψg = (3/2) k2 (1 - e) n, where k is the → constant of aberration (in radians), e the → eccentricity of the Earth and n the mean angular orbital motion of the Earth (in arcsec/cy). Also called → Einstein-de Sitter effect and → geodesic precession.

geodetic; → precession

geodetic refraction
  شکست ِ زمین‌سنجیک   
šekast-e zamin-sanjik

Fr.: réfraction géodésique   

The limiting case of → astronomical refraction when the light path is entirely within the Earth's atmosphere.

geodetic; → refraction.

geomagnetic excursion
  زچار ِ زمین‌مغناتی   
zocâr-e zamin-meqnâti

Fr.: excursion géomagnétique   

A geophysical event, distinguished from the → magnetic reversal, in which the Earth's magnetic field departs for a relatively short time from its usual near axial configuration, without establishing a reversed direction. During the excursion the intensity and direction of the Earth's magnetic field undergo drastic changes. Palaeomagnetic measurements have revealed that since the last full reversal the Earth's magnetic field has, for brief intervals, deviated from the behavior expected during "normal" secular variation.

geomagnetic; → excursion.

geometric progression
  فرایازی ِ هندسی   
farâyâsi-e hendesi (#)

Fr.: progression géométrique   

A → sequence in which the ratio of a term to its predecessor is the same for all terms. In general, the nth term has the form ar(n-1), where n is a positive integer, and a and r are nonzero constants; r is called the ratio or common ratio. The sum of the first n terms is given by: Sn = a(1 - rn)/(1 - r). Also called → geometric sequence.

geometric; → progression.

geometrical libration
  رخگرد ِ هندسی   
roxgard-e hendesi (#)

Fr.: libration géométrique   

Libration resulting from changes in the location of the observer with respect to body. More specifically, a lunar libration motion that results from the Earth based observer seeing the Moon from different directions at different times. There are three types of geometrical libration: → libration in longitude, → libration in latitude, and → diurnal libration. See also → physical libration.

geometric; → libration.

geostationary orbit
  مدار ِ زمین‌ایست‌وّر   
madâr-e zamin-istvar

Fr.: orbite géostationnaire   

A satellite orbit in the plane of the Earth's equator and 35,880 km above it, at which distance the satellite's period of rotation matches the Earth's and the satellite always remains fixed in the same spot over the Earth.

Geostationary, from → geo- + → stationary; → orbit.

giant H II region
  ناحیه‌ی ِ II H یِ غولپیکر   
nahiye-ye H II-ye qulpeykar

Fr.: région H II géante   

An → H II region emitting at least 1050 → Lyman continuum photons per second, or about 10 times → Orion nebula. Such an H II region should be powered by at least one O3V star or by at least a dozen → O-type and tens → B-type stars. Our nearest giant H II region is → NGC 3603. Some other Galactic giant H II regions are: → Lagoon Nebula, M17, W31, W51A, and NGC 3576.

giant; → H II; → region.

Gibbs canonical distribution
  واباژش ِ هنجاروار ِ گیبس   
vâbâžeš-e hanjârvâr-e Gibbs

Fr.: distribution canonique de Gibbs   

The probability distribution of the various possible states of a certain → quasi-closed subsystem.

Gibbs free energy; → canonical; → distribution.

Gibbs function
  کریای ِ گیبس   
karyâ-ye Gibbs

Fr.: fonction de Gibbs   

Same as → Gibbs free energy.

Named after Josiah Willard Gibbs (1839-1903), an American physicist who played an important part in the foundation of analytical thermodynamics; → function.

Global Positioning System (GPS)
  راژمان ِ نهش‌داد ِ جهانی   
râžmân-e nehešdâd-e jahâni

Fr.: système de positionnement par satellites   

A coordinate positioning tool, using a combination of satellites that can rapidly and accurately determine the → latitude, → longitude, and the → altitude of a point on or above the Earth's surface. The GPS is based on a constellation of 24 Earth-orbiting satellites at an altitude of about 26,000 km. The system is a direct application of the thories of → special relativity and → general relativity.

global; → positioning; → system.

gnomonic projection
  فراشانش ِ باهویی   
farâšâneš-e bâhu-yi

Fr.: projection gnomonique   

The projection of a spherical surface onto a plane through a point. A gnomonic → map projection displays all great circles as straight lines, and therefore indicates the shortest path between two points. Small circles are projected as conic sections.

gnomon; → -ic; → projection.

Goldschmidt classification
  رده‌بندی ِ گولدسمیت   
radebandi-ye Goldschmidt

Fr.: classification de Goldschmidt   

A → geochemical classification scheme in which → chemical elements on the → periodic table are divided into groups based on their → affinity to form various types of compounds: → lithophile, → chalcophile, → siderophile, and → atmophile. The classification takes into account the positions of the elements in the periodic table, the types of electronic structures of atoms and ions, the specifics of the appearance of an affinity for a particular → anion, and the position of a particular element on the → atomic volume curve.

Developed by Victor Goldschmidt (1888-1947); → classification.

  پداکش، پداک‌دهی، پداک‌گیری   
padâkeš, padâk dehi, padâk giri

Fr.: graduation   

1) Marking the scale of an instrument, e.g. the stem of a thermometer is graduated in degrees.
2) An act of graduating; the state of being graduated.

Verbal noun of → graduate.

grain coagulation
  ماسش ِ دانه   
mâseš-e dâné

Fr.: coagulation des grains   

Sticking together of micron- to centimetre-sized grains occurring in the interstellar and protoplanetary environments to form larger grain agglomerates.

grain; → coagulation.

grain evaporation
  بخارش ِ دانه   
boxâreš-e dâné

Fr.: évaporation des grains   

Conversion of dust grains into smaller grains due to high environmental temperatures.

grain; → evaporation.

grain formation
  دیسش ِ دانه   
diseš-e dâné

Fr.: formation des grains   

The process by which dust grains are assembled or produced.

grain; → formation.


Fr.: granulation   

The mottled appearance of the solar → photosphere, caused by → convective cells, resembling → granules, which rises from the interior of the Sun. Each granule has a mean size of about 1,000 km and an upward velocity of about 0.5 km/sec. Granules are separated by intergranular walls about 400 K colder. They emerge from the fragments of the preceding granules and their lifetimes are about 20 minutes.

From → granule + -ation a combination of -ate and -ion, used to form nouns from stems in -ate.

Dâne-bandi, from dâné, → grain, + bandi verbal noun of bastan, vastan "to bind, shut;" O.Pers./Av. band- "to bind, fetter," banda- "band, tie" (cf. Skt. bandh- "to bind, tie, fasten;" PIE *bhendh- "to bind;" Ger. binden; E. bind).

gerâneš (#)

Fr.: gravitation   

1) The universal phenomenon of attraction between material bodies. → Newton's law of gravitation.
2) The act or process of moving under the influence of this attraction.

Verbal noun of → gravitate.

gerâneši (#)

Fr.: gravitationnel   

Of or relating to or caused by → gravitation.

Adj. of → gravitation.

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