An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی و اخترفیزیک

M. Heydari-Malayeri

Paris Observatory

Introduction

G

G band = bānd-e G     باند ِ G

Fr.: bande G

A conspicuous band of molecular → CH (methylidine) at 4300 Å, which is present in the spectra of late-type G-K stars.

G refers to → G type stars in the spectra of which this feature is strong. → band.

gain = bahré (#)     بهره

Fr.: gain

1) A measure of the amplification of an electronic device, usually expressed as the ratio of output power to input power.
2) → antenna gain.

From M.Fr. gain, from O.Fr. gaaigne, from guaaignier "to obtain," from Germanic *waidanjan "to hunt, plunder," also "to graze, pasture," from P.Gmc. *wartho "hunting ground" (cf. Ger. weide "pasture, pasturage"); PIE base *weiə- "to go after something, strive after."

Bahré, from bahr "part, portion, share, lot;" Av. baxəδra- "portion," from bag- "to attribute, allot," → division.

galactic = kahkešāni (#)     کهکشانی

Fr.: galactique

Of or pertaining to a galaxy.
Usually with capital G, pertaining to our galaxy, the Milky Way.

Adjective of → galaxy.

galactic anticenter = pādmarkaz-e kahkešān     پادمرکز ِ کهکشان

Fr.: anticentre galactique

The point in the Galactic plane that lies directly opposite the Galactic center. It lies in the constellation Auriga at approximately R.A. 05h 46m, Dec. +28° 56'.

→ galactic; → anticenter.

galactic center = markaz-e kahkešān     مرکز ِ کهکشان

Fr.: centre galactique

The innermost regions of a spiral galaxy characterized by high number of stars per unit volume. The center may contain a supermassive black hole.

→ galactic; → center.

galactic cluster = xuše-ye kahkešāni, ~ kahkešānhā     خوشه‌ی ِ کهکشانی، ~ کهکشانها

Fr.: amas galactique

1) Same as → open cluster.
2) same as → clusters of galaxies.

→ galactic; → cluster.

Galactic coordinates = hamārāhā-ye kahkešāni     هماراهای ِ کهکشانی

Fr.: coordonnées galactiques

A system of astronomical coordinates using latitude measured north and south from the Galactic equator and longitude measured from the Galactic center in the sense of increasing right ascension from 0 to 360 degrees. Same as → galactic system.

→ galactic; → coordinates.

galactic disk = gerde-ye kahkešān     گرده‌ی ِ کهکشان

Fr.: disque galactique

The central plane of a spiral galaxy where the spiral arms are found.

→ galactic; → disk.

Galactic equator = hamugār-e kahkešān     هموگار ِ کهکشان

Fr.: équateur galactique

The great circle in the sky defined by the place of the Galactic plane or the Milky Way. At an angle of about 62°, the Galactic equator intersects the celestial equator at two points located in the constellations of Monoceros and Aquila.

→ galactic; → equator.

Galactic habitable zone = zonār-e zistpazir-e kahkešān     زنار ِ زیست‌پذیر ِ کهکشان

Fr.: zone habitable galactique

A region of the Galaxy whose boundaries are set by its calm and safe environment and access to the chemical materials necessary for building terrestrial planets similar to the Earth. → circumstellar habitable zone; → habitable zone.

→ galactic → habitable; → zone.

Galactic halo = hāle-ye kahkešān     هاله‌ی ِ کهکشان

Fr.: halo galactique

A roughly spherical aggregation of globular clusters, as well as the oldest stars and unseen mass that surrounds the Galaxy.

→ galactic → halo.

Galactic latitude = varunā-ye kahkešāni     ورونای ِ کهکشانی

Fr.: latitude galactique

In the Galactic coordinate system, the angle between the line of sight to an object and the Galactic plane. Galactic latitude ranges from +90 degrees to -90 degrees.

→ galactic; → latitude.

Galactic longitude = derežnā-ye kahkešāni     درژنا‌ی ِ کهکشانی

Fr.: longitude galactique

In the Galactic coordinate system, the angle between the Galactic center and the projection of the object on the Galactic plane. Galactic longitude ranges from 0 degrees to 360 degrees.

→ galactic; → longitude.

galactic nucleus = haste-ye kahkešān     هسته‌ی ِ کهکشان

Fr.: noyau de galaxie

A concentration of stars and gas in the innermost region of a galaxy, sometimes extending over thousands of light-years from the center of the galaxy.

→ galactic; → nucleus.

galactic plane = hāmon-e kahkešān     هامن ِ کهکشان

Fr.: plan galactique

The plane in which the disk of a spiral galaxy lies.

→ galactic; → plane.

galactic pole = qotb-e kahkešān     قطب ِ کهکشان

Fr.: pōle galactique

The point on the sky, north or south, at which the galaxy's rotation axis would meet the celestial sphere.

→ galactic; → pole.

Galactic radio noise = nufe-ye rādioi-ye kahkešān     نوفه‌ی ِ رادیویی ِ کهکشان

Fr.: bruit radio de la Galaxie

A diffuse radio signal that originates outside the solar system. It is strongest in the direction of the Galactic plane.

→ galactic; → radio; → noise.

galactic rotation = carxeš-e kahkešān     چرخش ِ کهکشان

Fr.: rotation galactique

The revolving of the gaseous and stellar content of a galaxy around its central nucleus. The rotation is not uniform, but differential. One revolution of the Sun within our own Galaxy takes about 220 million years, or one cosmic year.

→ galactic; → rotation.

galactic structure = sāxtār-e kahkešān     ساختار ِ کهکشان

Fr.: structure galactique

The global shape and the arrangement of the various parts or constituents of a galaxy.

→ galactic; → structure.

Galactic system = rāžmān-e kahkešāni     راژمان ِ کهکشانی

Fr.: systčme galactique

Same as → galactic coordinates.

→ galactic; → system.

Galactic wind = bād-e kahkešāni     باد ِ کهکشانی

Fr.: vent galactique

An outflow of hot gas, analogous to the solar wind, from a galaxy that has recently undergone a high burst of star formation or a merger.

→ galactic; → wind.

Galactic windows = rowzanehā-ye kahkešān     روزنه‌های ِ کهکشان

Fr.: fenźtres galactiques

The regions near the Galactic plane where there is low absorption of light by interstellar clouds so that some external galaxies may be seen through them.

→ galactic; window, literally "wind eye," from O.N. vindauga, from vindr → wind + auga → eye.

Rowzané, from rowzan "window, aperture;" Mid.Pers. rocānak "window," rōšn "light; bright, luminous," from Av. raocana- "bright, shining, radiant," raocah- "light, luminous; daylight," related to Mod.Pers. ruz "day," from Mid.Pers. rōc, O.Pers. raucah-; akin to Skt. rocaná- "bright, shining, roka- "brightness, light;" Gk. leukos "white, clear;" L. lux "light" (also lumen, luna); PIE base *leuk- "light, brightness." The Persian words rowšan "bright, clear," foruq "light," and afruxtan "to light, kindle" also belong to this family, as well as the E. light, Ger. Licht, and Fr. lumičre; kahkešān → galaxy.

Galactic year = sāl-e kahkešāni (#)     سال ِ کهکشانی

Fr.: année galactique

The time taken for the Sun to revolve once around the center of the Milky Way, amounting to about 220 million years.

→ galactic; → year.

galaxy = kahkešān (#)     کهکشان

Fr.: galaxie

1) Generally, a large body of gas, dust, and stars held together by their mutual gravitational attraction. They are grouped into three main categories: spiral galaxies, elliptical galaxies, and irregular galaxies.
2) With capital G, the galaxy to which our Sun belongs; → Milky Way galaxy.

From L.L. galaxias "Milky Way," from Gk. galaxis (adj.), from gala (gen. galaktos) "milk."
In Gk. mythology, Jupiter, hoping to immortalize his infant son Hercules (who was born to a mortal woman), placed the baby on Juno's breast. Her milk spilled up, forming the Milky Way. A painting by Italian artist Jacopo Tintoretto (c. 1518-1594), called "The Origin of the Milky Way," depicts the legend describing how the Milky Way was formed.

Kahkešān, literally "trail of chaff," from kah, kāh "chaff, straw, hay" (Mid.Pers. kāh "chaff, straw;" cf. Pali kattha- "a piece of wood;" Skt. kastha- "stick;" Gk. klados "twig;" O.Ir. caill "wood;" P.Gmc. *khulto-; Ger. Holz "wood;" E. holt; PIE *kldo-) + kešān pr.p. of kešidan/kašidan "to carry, draw, protract, trail, drag" (Mid.Pers. kešidan "to draw, pull;" Av. karš- "to draw; to plow," karša- "furrow;" cf. Skt. kars-, kársati "to pull, drag, plow;" Gk. pelo, pelomai "to move, to bustle;" PIE base k^wels- "to plow").

gale = tondbād (#)     تندباد

Fr.: vent violent

An unusually strong wind.

Gale, from gaile "wind," origin uncertain, perhaps from O.N. gol "breeze," or O.Dan. gal "bad, furious."

Tondbāb "gale," from tond "swift, rapid, brisk; fierce, severe," Mid.Pers. tund "sharp, violent;" Sogdian tund "violent;" cf. Skt. tod- "to thrust, give a push," tudáti "he thrusts;" L. tundere "to thrust, to hit" (Fr. percer, E. pierce, ultimately from L. pertusus, from p.p. of pertundere "to thrust or bore through," from per- + tundere, as explained); PIE base *(s)teud- "to thrust, to beat" + bād → wind.

Galilean Moons = māhhā-ye Gālile-yi     ماه‌های ِ گالیله‌ای

Fr.: lunes galiléennes

Same as → Galilean satellites.

Galilean, of or pertaining to Galileo Galilei (1564-1642), Italian physicist and astronomer; → moon

Galilean relativity = bāzānigi-ye Gālilé     بازانیگی ِ گالیله

Fr.: relativité galiléenne

The principle according to which the fundamental laws of physics are the same in all inertial frames.

After Galileo Galilei (1564-1642), the Italian physicist and astronomer, who first described this principle in 1632; → relativity.

Galilean satellites = bandevārhā-ye Gālile-yi     بنده‌وارها‌ی ِ گالیله‌ای

Fr.: satellites galiléens

The four largest and brightest stallites of Jupiter (Io, Europa, Ganymede, and Callisto).

Galileo, who had discovered them, called them Sidera Medicęa "Medicean Stars" in honor of the Medici family. → Galilean Moons; → satellite.

Galilean transformation = tarādis-e Gālile-yi (#)     ترادیس ِ گالیله‌ای

Fr.: transformation galiléenne

The method of relating a measurement in one reference frame to another moving with a constant velocity with respect to the first within the Newtonian physics.

Galilean, of or pertaining to Galileo Galilei (1564-1642), Italian physicist and astronomer; → transformation.

Galileo's law of falling bodies = qānun-e Gālilé darbāre-ye oft-e jesmhā     قانون ِ گالیله درباره‌ی ِ افت ِ جسم‌ها

Fr.: loi galiléenne de la chute des corps

In the absence of air resistance, any two bodies that are dropped from rest at the same moment will reach the ground at the same time regardless of their mass.

Galileo (1564-1642) was the first to determine, at the start of the seventeenth century, the law of constant acceleration of free-falling bodies. → law; → fall; → body.

gamma = gāmmā     گاما

Fr.: gamma

1) The third letter of the Greek alphabet (γ, Γ).
2) Symbol used to denote the ratio of the principal specific heats C_P/C_V of a gas, where C_P is the specific heat at constant pressure and C_V that measured at constant volume.
3) Unit of magnetic field intensity, equal to 10^-5 gauss.

The third letter of the Gk. alphabet," from Gk. gamma, from Phoenician gimel.

gamma rays = partowhā-ye gāmmā     پرتوها‌ی ِ گاما

Fr.: rayons gamma

An electromagnetic wave with a wavelength in the range of 10^-11 to 10^-8 cm, corresponding to photons with energy from 10⁴ to 10⁷ electron volts. They are the most energetic form of electromagnetic radiation.

→ gamma; → ray.

gamma-ray astronomy = axtaršenāsi-ye partowhā-ye gāmmā     اخترشناسی ِ پرتوها‌ی ِ گاما

Fr.: astronomie en rayons gamma

The study of gamma rays from extraterrestrial sources, especially gamma-ray bursts.

→ gamma rays; → astronomy.

gamma-ray burst (GRB) = belk-e partowhā-ye gāmmā     بلک ِ پرتوها‌ی ِ گاما

Fr.: sursaut de rayons gamma

Intense discharges of soft gamma rays of unknown origin, which range in duration from tenth of a second to tens of seconds and occur from sources widely distributed over the sky. The radio wave afterglow from the burst can last more than a year, making long-term observations of the enigmatic sources possible.

→ gamma rays; → burst.

gamma-ray burster = belkgar-e partow-e gāmmā     بلک‌گر ِ پرتو ِ گاما

Fr.:

The object or phenomenon at the origin of a gamma-ray burst.

→ gamma ray; burster, agent noun from → burst.

Gamow barrier = varqe-ye Gāmof     ورغه‌ی ِ گاموف

Fr.: barričre de Gamow

In nuclear physics, a potential barrier near the surface of the nucleus that inhibits the release of alpha particles.

Gamow, after George Gamow (originally Georgiy Antonovich Gamov), the Ukrainian born theoretical physicist and cosmologist, who discovered quantum tunneling; → barrier.

Gamow peak = setiq-e Gāmof     ستیغ ِ گاموف

Fr.: pic de Gamow

In nuclear fusion, the product of the Maxwell-Boltzmann distribution with the tunnelling probability of the nuclei through their Coulomb barrier. This is the energy region where the reaction is more likely to take place: at higher energies, the number of particles becomes insignificant while at lower energies the tunnelling through the Coulomb barrier makes the reaction improbable.

→ Gamow barrier; → peak.

Ganymede (Jupiter III) = Gānumedes     گانومدس

Fr.: Ganymčde

The seventh and largest of Jupiter's known satellites. Radius 2635 km (slightly larger than Mercury). Mass about 1.65 × 10²⁶ g; period 7.155 days; e = 0.0015. It was discovered by Galileo and Marius in 1610.

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.

gap = gāf (#)     گاف

Fr.: division

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."

Gāf, variant kāf "split, slit," stem of kāftan, kāvidan "to split; to dig," Mid./Mod.Pers. škāf- škāftan "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."

Garnet star = setāre-ye nārsang     ستاره‌ی ِ نارسنگ

Fr.: étoile Grenat

A variable red supergiant (spectral type M 2 Ia) in the constellation Cepheus (µ Cephei). Its 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."

Nārsang, from nār, from anār "pomegranate," from Mid.Pers. anār "pomegranate" + sang → stone.

gas = gāz (#)     گاز

Fr.: gaz

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.

Gāz, loanword from Fr.

gas constant = pāyā-ye gāzhā (#)     پایا‌ی ِ گاز‌ها

Fr.: constante des gaz parfaits

For a given quantity of an ideal gas, the product of its pressure and the volume divided by the absolute temperature (R = PV/T).

→ gas; → constant.

gaseous nebula = miq-e gāzi     میغ ِ گازی

Fr.: nébuleuse gazeuse

An → H II region, a → planetary nebula, or a → supernova remnant.

Gaseous, adj. of → gas; → nebula.

gas equation = hamugeš-e gāz     هموگش ِ گاز

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.

→ gas; → equation.

gas-poor galaxy = kahkešān-e kamgāz     کهکشان ِ کم‌گاز

Fr.: galaxie pauvre en gaz

A galaxy which has a relatively low gas content.

→ gas; poor, from O.Fr. poure (Fr. pauvre), from L. pauper "poor," perhaps a compound of paucus "little" and parare "to get;" → galaxy.

Kahkešān → galaxy; kamgāz, from kam "little, few; deficient, wanting; scarce" (from Mid.Pers. kam "little, small, few;" O.Pers./Av. kamna- "small, few") + gāz → gas.

gas-rich galaxy = kahkešān-e porgāz     کهکشان ِ پرگاز

Fr.: galaxie riche en gaz

A galaxy, usually young, which has a relatively important gas content.

→ gas; rich, from O.E. rice "wealthy, powerful," from P.Gmc. *rikijaz (cf. Du. rijk, Ger. reich "rich"), from PIE base *reg- "move in a straight line," hence, "to direct, rule" (cf. Mod.Pers./Mid.Pers. rāst "right, straight;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" Ger. recht; E. right); → galaxy.

Kahkešān → galaxy; porgāz, from por "charged; much; full" (Mid.Pers. purr "full;" O.Pers. paru- "much, many;" Av. parav-, pauru-, pouru-, from par- "to fill;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru-; Gk. polus; O.E. full) + gāz → gas.

gas tail = donbāle-ye gāzi     دنباله‌ی ِ گازی

Fr.: queue de gaz

The ionized component of a comet's tail, driven nearly straight away from the Sun by the solar wind. Also called ion tail, plasma tail, Type I tail.

→ gas; → tail.

gauge = (n.) gaz; (v.) gaz kardan (#)     گز؛ گز کردن

Fr.: jauge

(n.) A standard of measure or measurement, size, or quantity.
Any of a wide variety of devices or instruments used for measuring a parameter or characteristic of an object, such as its dimension, quantity, or mechanical accuracy.
Physics: One of the family of choices for an electric scalar potential or a magnetic vector potential that satisfies Maxwell's equations.
(v.) To determine the exact dimensions, capacity, quantity, or force of; measure.

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 k^wer- "to do, to make").

gauge boson = bozon-e gaz     بوزون ِ گز

Fr.: boson de jauge

A class of elementary particles that includes the gluon, photon, W⁺, W^-, and Z⁰ particles, each having an integral spin.

→ gauge; → boson.

gauge group = goruh-e gaz (#)     گروه ِ گز

Fr.: groupe de jauge

The mathematical group associated with a particular set of gauge transformations.

→ gauge; → group.

gauge invariance = nāvartāyi-ye gaz     ناورتایی ِ گز

Fr.: invariance de jauge

The invariance of any field theory under gauge transformation.

→ gauge; → invariance.

gauge symmetry = hamāmuni-ye gaz     همامونی ِ گز

Fr.: symétrie de jauge

A principle underlying the quantum-mechanical description of the three nongravitational 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.

→ gauge; → symmetry.

gauge theory = negare-ye gaz (#)     نگره‌ی ِ گز

Fr.: théorie de jauge

A field theory in which it is possible to perform a transformation without altering any measurable physical quantity.

→ gauge; → theory.

gauge transformation = tarādis-e gaz (#)     ترادیس ِ گز

Fr.: transformation de jauge

A change of the fields of a gauge theory that does not change the value of any measurable quantity.

→ gauge; → transformation.

gauging = gazkard     گزکرد

Fr.:

A technique in which the thickness, density, or quantity of a material is determined by the amount of radiation it absorbs.

Gauging, from → gauge + -ing, suffix of nouns formed from verbs, expressing the action of the verb or its result.

Gazkard, from gaz → gauge + kard past stem of kardan "to do, make," → gauge.

Gaunt factor = karvand-e Gaunt     کروند ِ گاؤنت

Fr.: facteur de Gaunt

In the atomic theory of spectral line formation, a quantum mechanical correction factor applied to the absorption coefficient in the transition of an electron from a bound or free state to a free state.

Gaunt, after John Arthur Gaunt (1904-1944), English physicist born in China, who significantly contributed to the calculation of continuous absorption using quantum mechanics; → factor

gauss = gāws (#)     گاؤس

Fr.: gauss

The c.s.g. unit of magnetic flux density (or magnetic induction), equal to 1 maxwell per square centimeter, or 10^-4 tesla.

Named after the German mathematician and physicist Carl Friedrich Gauss (1777-1855).

Gaussian = gausi (#)     گاؤسی

Fr.: gaussien

Of or relating to Carl Friedrich Gauss or his mathematical theories of magnetism, electricity, astronomy, or probability. → Gaussian distribution; → Gaussian profile.

→ gauss.

Gaussian distribution = vābāžeš-e Gawsi (#)     واباژش ِ گاؤسی

Fr.: distribution gaussienne

A theoretical frequency distribution for a set of variable data, usually represented by a bell-shaped curve with a mean at the center of the curve and tail widths proportional to the standard deviation of the data about the mean.

→ Gaussian; → distribution.

Gaussian profile = farāpāl-e Gawsi     فراپال ِ گاؤسی

Fr.: profile gaussien

The shape of a curve representing a normal distribution.

→ Gaussian; → profile.

gegenschein = pādforuq     پادفروغ

Fr.: gegenschein, lueur anti-solaire

A faint glow of light in the night sky seen exactly opposite the Sun. The gegenschein is sunlight back-scattered off millimeter-sized dust particles along the ecliptic. In comparison with zodiacal light (forward-scattered sunlight), which is triangular in shape and found near the horizon, the gegenschein is roughly circular. Same as counterglow.

Gegenschein, from Ger. gegen "counter, opposed to" (O.H.G. gegin, gagan, M.Du. jeghen, E. against, again) + Schein "glow, shine" (M.H.G. schinen, O.H.G. skinan, P.Gmc. *skinanan; E. shine; cf. Mod.Pers. sāyé "shadow;" Mid.Pers. sāyak "shadow;" Av. a-saya- "throwing no shadow;" Skt. chāya- "shadow;" Gk. skia "shade;" Rus. sijat' "to shine;" PIE base *skai- "bright").

Pādfrouq "counterglow," from pād- "agaist, contrary to" (from Mid.Pers. pāt-; O.Pers. paity "agaist, back, opposite to, towards, face to face, in front of;" Av. paiti; cf. Skt. práti "towards, against, again, back, in return, opposite;" Pali pati-; Gk. proti, pros "face to face with, towards, in addition to, near;" PIE *proti) + foruq "light, brightness" (related to rōšan "light; bright, luminous;" ruz "day," afruxtan "to light, kindle;" Mid.Pers. payrog "light, brightness," rošn light; bright," rōc "day;" O.Pers. raucah-; Av. raocana- "bright, shining, radiant," raocah- "light, luminous; daylight;" cf. Skt. rocaná- "bright, shining, roka- "brightness, light;" Gk. leukos "white, clear;" L. lux "light" (also lumen, luna; E. light, Ger. Licht, and Fr. lumičre; PIE base *leuk- "light, brightness").

Gemini (Twins) = dopeykar (#)     دوپیکر

Fr.: Gémeaux

The Twins. A prominent constellation of the northern hemisphere and the third (and northernmost) of the zodiac. It lies south and east of Auriga, west of Cancer, and north and east of Orion, at 7h right ascension and +22° declination. Its brightest stars are Castor and Pollux. Abbreviation: Gem; genetive: Geminorum.

Gemini, from M.E., from L. gemini, plural of geminus "twin; double;" cf. Av. yəma- "twin;" Skt. yamá-, yamala- "twin, paired;" Persian dialects Kermāni jomoli "twin," Qāyeni jamal "twin," Tabari da-cembali "twin;" PIE base *iem- "to hold."

Dopeykar, from do "two" (Mid.Pers. do, Av. dva-; Skt. dvi-; Gk. duo; L. duo ( Fr. deux); E. two; Ger. zwei) + peykar "figure, form, body" (from Mid.Pers. pahikar "picture, image;" from O.Pers. patikara- "picture, (sculpted) likeness," from patiy "against" (Av. paiti; Skt. prati; Gk. poti/proti) + kara- "doer, maker," from kar- "to do, make, build;" Av. kar-; Skr. kr-; cf. Skt. pratikrti- "an image, likeness, model; counterpart").

Geminids = dopeykariyān (#)     دوپیکریان

Fr.: Géminides

A meteor shower that occurs in the first half of December, with its radiant in the constellation of Gemini.

→ Gemini + → -ids.

Gemma = Alfakké (#)     الفکه

Fr.: Alphekka

The brightest star in the constellation Corona Borealis. Same as → Alphekka.

Gemma, from L. gemma "precious stone, jewel," originally "bud," from the root *gen- "to produce", → generate (v.).

Alfakké, → Alphekka.

general = harvin     هروین

Fr.: général

(Adj.) 1) Not limited to one class, field, product, service, etc. 2) Relating to the whole or to the all or most. 3) Dealing with overall characteristics, universal aspects, or important elements. → public (همگان); → total (هماک).

From L. generalis "relating to all, of a whole class," from genus "race, stock, kind," akin to Pers. zādan, Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born;" Mod.Pers. zādan, present stem zā- "to bring forth, give birth" (Mid.Pers. zātan; cf. Skt. jan- "to produce, create; to be born," janati "begets, bears;" Gk. gignomai "to happen, become, be born;" L. gignere "to beget;" PIE base *gen- "to give birth, beget."

Harvin, from Mid.Pers. harvin "all," from har(v) "all, each, every" (Mod.Pers. har "every, all, each, any"); O.Pers. haruva- "whole, all together;" Av. hauruua- "whole, at all, undamaged;" cf. Skt. sárva- "whole, all, every, undivided;" Gk. holos "whole, complete;" L. salvus "whole, safe, healthy," sollus "whole, entire, unbroken;" PIE base *sol- "whole."

generalization = harvinkard, harvineš     هروین‌کرد، هروینش

Fr.: généralisation

The act or process of generalizing; → generalize.
A result of this process; a general statement, proposition, or principle.

Verbal noun of → generalize.

generalize = harvin kardan, harvinidan     هروین کردن، هروینیدن

Fr.: généraliser

To make general, to include under a general term; to reduce to a general form.
To infer or form a general principle, opinion, conclusion, etc. from only a few facts, examples, or the like.

From → general + → -ize, a verb-forming suffix occurring originally in loanwords from Gk. that have entered E. through L. or Fr.

Harvin kardan, compound verb, from harvin → general + 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 k^wer- "to do, to make"); harvinidan, from harvin → general + infinitive suffix -idan.

general precession = pišāyān-e harvin     پیشایان ِ هروین

Fr.: précession générale

The sum of the precessional motions caused by the Moon-Sun system and the planets. → precession.

→ general; → precession.

general relativity = bāzānigi-ye harvin     بازانیگی ِ هروین

Fr.: relativité générale

The theory of gravitation developed by Albert Einstein (1916) that describes the gravitation as the space-time curvature caused by the presence of matter or energy.

→ general; → relativity.

generate (v.) = āzānidan     آزانیدن

Fr.: générer

To bring into existence; create; produce.
Math.: To trace (a figure) by the motion of a point, straight line, or curve.

Generate, from M.E., from L. generatus "produce," p.p. of generare "to bring forth," from gener-, genus "descent, birth," akin to Pers. zādan, Av. zan- "to give birth," as explained below.

Āzānidan, from ā- nuance/strengthening prefix + zān, from Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born;" Mod.Pers. zādan, present stem zā- "to bring foth, give birth" (Mid.Pers. zātan; cf. Skt. jan- "to produce, create; to be born," janati "begets, bears;" Gk. gignomai "to happen, become, be born;" L. gignere "to beget;" PIE base *gen- "to give birth, beget") + -idan infinitive suffix.

generation = āzāneš     آزانش

Fr.: génération

A coming into being.
The production of energy (heat or electricity).

Verbal noun of → generate (v.).

generator = āzāngar     آزانگر

Fr.: générateur

1) A machine for converting one form of energy into another.
2) Germetry: That which creates a line, a surface, a solid by its motion.

From L. generator "producer," from genera(re) → generate (v.) + -tor a suffix forming personal agent nouns from verbs and, less commonly, from nouns.

Āzāngar, from āzān the stem of āzānidan → generate (v.) + -gar suffix of agent nouns, from kar-, kardan "to do, to make" (Mid.Pers. kardan; O.Pers./Av. kar- "to do, make, build," Av. kərənaoiti "makes;" cf. Skt. kr- "to do, to make," krnoti "makes," karma "act, deed;" PIE base k^wer- "to do, to make").

geo- = zamin- (#)     زمین-

Fr.: géo-

A combining form meaning "the earth," used in the formation of compound words.

Geo-, form Gk. ge "earth, land, ground, soil."

Zamin, zami "earth, ground," from Mid.Pers. zamig "earth;" Av. zam- "the earth;" cf. Skt. ksam; Gk. khthōn, khamai "on the ground;" L. homo "earthly being" and humus "the earth" (as in homo sapiens or homicide, humble, humus, exhume); PIE root *dh(e)ghom "earth."

geocentric = zamin-markazi (#)     زمین‌مرکزی

Fr.: géocentrique

Relating to, measured from, or with respect to the center of the Earth.
Having the earth as a center.

From → geo- + → center + -ic an adjective-forming suffix.

geocentric coordinate system = rāžmān-e hamārāhā-ye zamin-markazi     راژمان ِ هماراها‌ی ِ زمین‌مرکزی

Fr.: systčme de coordonnées géocentriques

A coordinate system which has as its origin the center of the Earth.

→ geocentric; → coordinate; → system.

Geocentric Coordinate Time (TCG) = zamān-e hamārā-ye zamin-markazi     زمان ِ همارا‌ی ِ زمین‌مرکزی

Fr.: Temps coordonné géocentrique

The proper time experienced by a clock at rest in a coordinate frame co-moving with the center of the Earth, i.e. a clock that performs exactly the same movements as the Earth but is outside the Earth's gravity well. TCG was defined in 1991 by the International Astronomical Union as one of the replacements for Barycentric Dynamical Time (TDB).

→ geocentric; → coordinate; → time.

geocentric cosmology = keyhān-šenāsi-ye zamin-markazi (#)     کیهان‌شناسی ِ زمین‌مرکزی

Fr.: cosmologie géocentrique

A model of the Universe in which the Earth is centrally located and the Sun, planets, and stars revolve around the Earth.

→ geocentric; → cosmology.

geocorona = zamin-tāj (#)     زمین‌تاج

Fr.: géocouronne

The outermost part of Earth's atmosphere, a tenuous halo of hydrogen and some helium extending out to perhaps 15 Earth radii, which emits Lyman-alpha radiation when it is bombarded by sunlight.

From → geo- + → corona.

geodesic = kehinrah     کهین‌ره

Fr.: géodésique

The shortest distance between two points in space (or space-time). A geodesic on a sphere is an arc of a great circle. In the general theory of relativity, freely falling bodies follow geodesic paths in space-time.

From Fr. géodésique, → geodesy; → -ic.

Kehinrah "shortest path," from kehin, superlative of keh "small, little, slender" (related to kāstan, kāhidan "to decrease, lessen, diminish," from Mid.Pers. kāhitan, kāstan, kāhźnitan "to decrease, diminish, lessen;" Av. kasu- "small, little;" Proto-Iranian *kas- "to be small, diminish, lessen") + rāh "path, way, road" (from Mid.Pers. rāh, rās "way, street," also rah, ras "chariot;" from Proto-Iranian *rāθa-; cf. Av. raθa- "chariot;" Skt. rátha- "car, chariot," rathyā- "road;" L. rota "wheel," rotare "to revolve, roll;" Lith. ratas "wheel;" O.H.G. rad; Ger. Rad; Du. rad; O.Ir. roth; PIE base *roto- "to run, to turn, to roll").

geodesic line = xatt-e kehinrah     خط ِ کهین‌ره

Fr.: ligne géodésique

The shortest line between two points on a surface. Also called → geodesic.

→ geodesic; → line.

geodesy = zamin-sanji (#)     زمین‌سنجی

Fr.: géodésie

The study and measurement of the shape, size, and curvature of the Earth.

From Fr. géodésie, from Gk. geodaisia, from → geo- + dai(ein) "to divide" + -sia, variant of -ia a noun suffix.

Zamin-sanji, from zamin → geo- + sanji, from sanjidan "to measure; to compare," from Mid.Pers. sanjidan "to weigh," from present tense stem sanj-, Av. θanj- "to draw, pull;" Proto-Iranian *θanj-. Other terms from this base in Pers.: lanjidan "to pull up," hanjidan, āhanjidan "to draw out," farhang "education, culture."

geodesy satellite = māhvāre-ye zamin-sanji, ~ zamin-sanjik     ماهواره‌ی ِ زمین‌سنجی، ~ زمین‌سنجیک

Fr.: satellite géodésique

A type of Earth observing satellite used to measure the location of points on Earth's surface with great accuracy. Their observations help determine the exact size and shape of Earth, act as references for mapping, and track movements of Earth's crust.

→ geodesy; → satellite

geodetic precession = pišāyān-e kehinrāhi     پیشایان ِ کهین‌راهی

Fr.: précession géodétique

A relativistic effect on the precession motion of a gravitational system due to the curvature of the space-time. 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. Also called the Einstein-de Sitter effect.

→ geodetic; → precession

geoid = zaminvār (#)     زمین‌وار

Fr.: géoļde

The form of the Earth obtained by taking average sea level surface and extending it across the continents. In other words, the equipotential surface ("mean sea level") of the Earth's gravitational field.

From → geo- + -oid a suffix meaning "resembling, like," used in the formation of adjectives and nouns.

Zaminvār, from zamin → geo- + -vār a suffix meaning "resembling, like," from Mid.Pers. -wār, Av. -vara, -var, cf. Skt. -vara.

geometric = hendesi (#)     هندسی

Fr.: géométrique

Of or pertaining to geometry or to the principles of geometry.

Adj. of → geometry

geometrical libration = roxgard-e hendesi (#)     رخگرد ِ هندسی

Fr.: libration géométrique

A lunar libration motion either in latitude resulting from the inclination of the Moon's orbit with respect to the ecliptic, or in longitude due to the elliptical shape of the Moon's orbit which causes a change in its aspect as seen from the Earth. → libration; → physical libration.

→ geometric; → libration.

geometric optics = nurik-e hendesi, šidik-e ~     نوریک ِ هندسی، شیدیک ِ ~

Fr.: optique géométrique

A branch of physics that deals with reflection and refraction of rays of light without reference to the wave or physical nature of light.

→ geometric; → optics.

geometric progression = farāyāsi-e hendesi (#)     فرایازی ِ هندسی

Fr.: progression géométrique

A sequence in which the ratio of each term to the preceding term is a given constant.

→ geometric; → progression.

geometry = hendesé (#)     هندسه

Fr.: géométrie

The branch of mathematics that deals with the nature of space and the size, shape, and other properties of figures as well as the transformations that preserve these properties.

Fom O.Fr. géométrie, from L. geometria, from Gk. geometria "measurement of earth or land," from → geo- + -metria, from metrein "to measure," → -metry.

Hendesé, Mid.Pers. handāxtan "to measure," Manichean Mid.Pers. hnds- "to measure," Proto-Iranian ham-, → com-, + *das- "to heap, amass;" cf. Ossetic dasun/dast "to heap up;" Arm. loanword dasel "to arrange (a crowd, people)," das "order, arrangement,"

geophysics = zaminfizik (#)     زمین‌فیزیک

Fr.: géophysique

The branch of physics that deals with the Earth and its environment, including meteorology, oceanography, seismology, and geomagnetism.

→ geo-; → physics.

geostationary orbit = madār-e zamin-istvar     مدار ِ زمین‌ایست‌وّر

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.

geosynchronous orbit = madār-e zamin-hamzamān     مدار ِ زمین‌همزمان

Fr.: orbite géosynchrone

A circular orbit around the Earth identical to a geostationary orbit except that the satellite's orbit does not necessarily lie in the Earth's equatorial plane.

Geosynchronous, from → geo- + → synchronous; → orbit.

German mounting = barnešānd-e Ālmāni     برنشاند ِ آلمانی

Fr.: monture allemande

An equatorial mounting in which the declination axis is at the end of the polar axis, which is on top of a pier to raise the telescope to a convenient height.

German, from L. Germanus, maybe of Gaulish (Celtic) origin, perhaps originally meaning "noisy" (cf. O.Ir. garim "to shout") or "neighbor" (cf. O.Ir. gair "neighbor"); → mounting.

Barnešānd → mounting; Ālmāni "German," from Ālmān, from Fr. Allemand "German," from P.Gmc. *Alamanniz, probably meaning "all-man" and denoting a wide alliance of tribes. Alternatively, perhaps meaning "foreign men," cognate with L. alius "the other."

ghost = parhib (#)     پرهیب

Fr.: image fantōme

A faint false image caused by reflection that is sometimes seen in an optical system. In spectroscopy, a false image of a spectral line formed by irregularities in the ruling of diffraction gratings.

Ghost, from O.E. gast "soul, spirit, breath," from P.Gmc. *ghoizdoz (cf. M.Du. gheest, Ger. Geist "spirit, ghost"), from PIE base *ghois- "to be excited, frightened;" cf. Av. zaēša- "horrible, frightful," zōiždišta- "the most loathsome;" Mid./Mod.Pers. zešt "ugly, disgusting;" Goth. usgaisjan "to be afraid;" O.E. gęstan "to frighten."

Parhib "ghost," Pers. word of Xorāsāni dialect.

Ghost Head Nebula = miq-e sar-e parhib     میغ ِ سر ِ پرهیب

Fr.: Nébuleuse de la Tźte de Fantōme

A star forming region in the Large Magellanic Cloud, a satellite of our Galaxy, as pictured by the Hubble Space Telescope. It spans about 50 light-years and contains several young, massive stars.

→ ghost; → head; → nebula

giant = qul, qulpeykar, kalān (#)     غول، غولپیکر، کلان

Fr.: géant

A person or thing of unusually great size, power, importance. In astronomy, e.g. → giant star, → giant branch.

From O.Fr. géant, from V.L. *gagantem, from L. gigas "giant," from Gk. gigas (gen. gigantos), huge and savage monsters, children of Gaia and Uranus, who fought the Olympians but were eventually destroyed by the gods, probably from a pre-Gk. language. The Gk. word was used in Septuagint (the Greek translation of the Jewish Scriptures) to refer to men of great size and strength, hence the expanded use in Western languages.

Qul "an imaginary hideous demon, supposed to devour men and animals," Pers. word probably related to Skt. grábha- "a demon causing diseases, one who seizes," grahila- "possessed by a demon," from grah-, grabh- "to seize, take," graha "seizing, holding, perceiving," Av./O.Pers. grab- "to take, seize;" Mid.Pers. griftan; Mod.Pers. gereftan "to take, seize;" cf. M.L.G. grabben "to grab," from P.Gmc. *grab, E. grab "to take or grasp suddenly;" PIE base *ghrebh- "to seize."
Qulpeykar, from qul, as explained, + peykar "figure, form, body" (from Mid.Pers. pahikar "picture, image;" from O.Pers. patikara- "picture, (sculpted) likeness," from patiy "against" (Av. paiti; Skt. prati; Gk. poti/proti + kara- "doer, maker," from kar- "to do, make, build;" Av. kar-; Skr. kr-; cf. Skt. pratikrti- "an image, likeness, model; counterpart").
Kalān "great, large, big, bulky."

giant branch = šāxe-ye qulān, ~ qulpeykarān (#)     شاخه‌ی ِ غولان، ~ غولپیکران

Fr.: branche des géantes

A conspicuous family of stars in the Hertzsprung-Russell diagram composed of red, evolved stars with large sizes. → giant star.

→ giant; → branch.

giant magnetoresistance (GMR) = meqnāt-istādegi-ye kalān, istādegi-ye meqnātisi-ye ~     مغناط-ایستادگی ِ کلان، ایستادگی ِ مغناطیسی ِ ~

Fr.: magnétorésistance géante

A quantum mechanical phenomenon where the resistance of certain materials drops dramatically upon application of a magnetic field in certain structures composed of alternating layers of magnetic and nonmagnetic metals. The basis of the GMR is the dependence of the electrical resistivity of electrons in a magnetic metal on the direction of the electron spin, either parallel or antiparallel to the magnetic moment of the layers. The 2007 Nobel Prize in physics was awarded to the French physicist Albert Fert (1938-) and German physicist Peter Grünberg (1939-) for the discovery of GMR.

→ giant; magneto- combining form of → magnet; → resistance.

giant molecular cloud (GMC) = abr-e molekuli-ye qulpeykar (#)     ابر ِ مولکولی ِ غولپیکر

Fr.: nuage moléculaire géant

Massive complex of interstellar gas and dust, consisting mostly of molecular hydrogen, that typically stretches over 150 light-years and contains several hundred thousand solar masses. They are the sites of star formation.

→ giant; → molecular; → cloud.

giant planet = sayyāre-ye qulpeykar (#)     سیاره‌ی ِ غولپیکر

Fr.: plančte géante

A planet much more massive than Earth. The solar system has four giant planets: Jupiter, Saturn, Uranus, and Neptune.

→ giant; → planet.

giant star = setāre-ye qulpeykar (#)     ستاره‌ی ِ غولپیکر

Fr.: étoile géante

A high-luminosity star that has evolved off the main sequence and lies above the main sequence on the Hertzsprung-Russell diagram. A member of the → giant branch.

→ giant; → planet.

gibbous = kuž, kužmāh (#)     کوژ، کوژماه

Fr.: gibbeux

An adjective applied to the phase of the Moon (or a planet) when it is more than half full, but less than entirely full.

From L.L. gibbous "hunchbacked," from L. gibbus "hump, hunch;" cf. Mod.Pers. kaž "crooked, bent, being aside;" Skt. kubja- "hump-backed, crooked;" Pali kujja- "bent;" Lith. kupra "hump."

Kuž "humped," Mid.Pers. kōf "hill, mountain; hump" (Mod.Pers. kuh, "mountain"), kōfik "humpbacked," O.Pers. kaufa-, Av. kaofa- "mountain;" māh → moon.

giga- (G) = gigā- (#)     گیگا-

Fr.: giga-

A prefix that is used to represent 10⁹ in the SI system.

From Gk. gigas → giant.

gimbal(s) = doqāb (#)     دوقاب

Fr.: monture ą la Cardan, cardan

1) A support component of a gyroscope, which allows the axis to move freely.
2) A mechanical mounting frame having two mutually perpendicular axes of rotation.

Gimbal, alteration of gemel "twin," from M.E., gemelles, from O.Fr. gemeles (Fr. jumeau, jumelle), from L. gemellus, diminutive of geminus "twin;" cf. Pers. Kermāni dialect jomoli "twin;" → Gemini.

Doqāb, from do "two" (Mid.Pers. do; Av. dva-; cf. Skt. dvi-; Gk. duo; L. duo; O.E. twa; Ger. zwei) + qāb "frame," from Turkish.

glass = šišé (#)     شیشه

Fr.: verre

A noncrystalline, inorganic mixture of various metallic oxides fused by heating with glassifiers such as silica, or boric or phosphoric oxides.

From O.E. glęs, from W.Gmc. *glasam (M.Du. glas, Ger. Glas), from PIE base *gel-/*ghel- "to shine, glitter."

Šišé "glass," origin unknown.

glass blank = gerde-ye šišé     گرده‌ی ِ شیشه

Fr.: disque de verre

A mass of glass ready to be shaped into a telescope mirror. Same as → glass disk.

→ glass; blank, from O.Fr. blanc "white, shining," from Frank. *blank "white, gleaming," of W.Gmc. origin (cf. O.E. blanca "white horse"), from P.Gmc. *blangkaz, from PIE *bhleg- "to shine."

Gerdé → disk; šišé → glass.

glass disk = gerde-ye šišé     گرده‌ی ِ شیشه

Fr.: disque de verre

Same as glass blank.

→ glass; → disk.

glaze = hasar (#)     هَسَر

Fr.: verglas, givre

A coating of ice, generally clear and smooth, formed on exposed objects by the freezing of a film of supercooled water deposited by rain, drizzle, fog, or possibly condensed from supercooled water vapor. Also called glaze ice, verglas, and (especially British) glazed frost.

Glaze, from → glass.

Hasar "ice," probably related to Av. isu- "icy, chilly," aexa- "ice, frost," Mod.Pers. yax "ice;" cf. O.E. is "ice," from P.Gmc. *isa-; Du. ijs, Ger. Eis, E. ice.

glitch = geles     گِلِس

Fr.:

A defect or malfunction in a machine or plan.
A brief or sudden interruption or surge in voltage in an electric circuit.
A sudden change in the rotation period of a pulsar.

Glitch, from Yiddish glitsh "slippery area;" cf. glitshn, Ger. glitschen "to slip, slide."

Geles, from Lori gelese "to fall down, to slide."

globe = guy (#)     گوی

Fr.: globe

A spherical body; sphere.
The planet Earth (usually preceded by the). A sphere on which is depicted a map of the Earth (terrestrial globe) or of the heavens (celestial globe).

M.E. globe, from M.Fr. globe, from L. globus "round body, ball, sphere," cognate with Pers. guy, see below.

Guy "ball, sphere," variants golulé, gullé, goruk, gulu, gudé; cf. Skt. guda- "ball, mouthful, lump, tumour," Pali gula- "ball," Gk. gloutos "rump," L. glomus "ball," globus "globe," Ger. Kugel, E. clot; PIE *gel- "to make into a ball."

globular cluster = xuše-ye guysān (#)     خوشه‌ی ِ گوی‌سان

Fr.: amas globulaire

A spherical star cluster containing 50,000 to 1 million stars. They are generally old and metal-poor.

Globular, from → globule + -ar, variant of → -al; → cluster.

Xušé → cluster; guysān, from guy → globe + -sān "manner, semblance" (variant sun, Mid.Pers. sān "manner, kind," Sogdian šōné "career").

globule = guycé (#)     گویچه

Fr.: globule

Generally, a small spherical mass, especially a small drop of liquid.
A dense spherical cloud of dust that absorbs radiation; → Bok globule.

From → globe + → -ule.

Guycé, fro guy → globe + -cé diminutive suffix, from Mid.Pers. -cak, variants -źžak (as in kanicak "little girl," sangcak "small stone," xōkcak "small pig"), also Mod.Pers. -ak.

glory = šokuh (#)     شکوه

Fr.: gloire

A colored aureole that is visible around the shadow of an observer's head, appearing on top of a cloud situated below the observer. A glory is caused by the same optics as a rainbow plus diffraction. → heiligenschein.

From O.Fr. glorie, from L. gloria "great praise or honor," of uncertain origin.

Šokuh, from Mid.Pers. škōh "magnificience, majesty, dignity; fear."

gluon = gluon     گلوئون

Fr.: gluon

The hypothetical particle, in the → quantum chromodynamics theory, that carries the force between → quarks. There are eight independent types of gluon.

From glue (O.Fr. glu, from L.L. glus "glue," from L. gluten "glue") + → -on.

g mode = tarz-e g, mod-e ~     ترز ِ g، مُد ِ ~

Fr.: mode g

Waves trapped inside stars, whose restoring force is the buoyancy. → oscillation modes; → p mode; → f mode.

g referring to gravity; → mode.

gnomon = bāhu     باهو

Fr.: gnomon

1) A rod oriented in such a way that its shadow, cast by the Sun's rays, shows the hours on a → sundial; a style.
2) A device used in ancient times onsisting of a vertical shaft used to measure the altitude of the Sun and hence to determine the time of day.

From L. gnomon, from Gk. gnomon "carpenter's square, rule; indicator," literally "one who discerns," from gignoskein "to know, think, judge," cognate with L. gnoscere, noscere "to come to know" (Fr. connaītre; Sp. conocer); O.Pers./Av. xšnā- "to know, learn, come to know, recognize;" Mid.Pers. šnāxtan, šnās- "to know, recognize," dānistan "to know;" Mod.Pers. šenāxtan, šenās- "to recognize, to know," dānestan "to know;" Skt. jñā- "to recognize, know," jānāti "he knows;" P.Gmc. *knoeanan; O.E. cnawan, E. know; Rus. znat "to know;" PIE base *gno- "to know."

Bāhu "stick, staff; arm (from the elbow to the shoulder)," related to bāzu "arm," Mid.Pers. bāzūk "arm;" Av. bāzu- "arm;" cf. Skt. bāhu- "arm, forearm," also "the shadow of the gnomon on a sundial; the bar of a chariot pole;" Gk. pechys "forearm, arm, ell;" O.H.G. buog "shoulder;" Ger. Bug "shoulder;" Du. boeg; O.E. bōg, bōh "shoulder, bough;" E. bough " a branch of a tree;" PIE *bhaghu- "arm."

golden number = 'adad-e zarrin (#)     عدد ِ زرّین

Fr.: nombre d'or

The number giving the position of any year in the lunar or → Metonic cycle of about 19 years. Each year has a golden number between 1 and 19. It is found by adding 1 to the given year and dividing by 19; the remainder in the division is the golden number. If there is no remainder the golden number is 19 (e.g., the golden number of 2007 is 13).

Golden, adj. of gold, from O.E. gold, from P.Gmc. *gulth- (cf. O.H.G. gold, Ger. Gold, Du. goud, Dan. guld, Goth. gulž), from PIE base *ghel-/*ghol- "yellow, green;" cf. Mod.Pers. zarr "gold," see below. → number.

'Adad → number.
Zarrin "golden," from zarr "gold;" Mid.Pers. zarr; Av. zaranya-, zarənu- "gold;" O.Pers. daraniya- "gold;" cf. Skt. hiranya- "gold;" also Av. zaray-, zairi- "yellow, green;" Mod.Pers. zard "yellow;" Skt. hari- "yellow, green;" Gk. khloe literally "young green shoot;" L. helvus "yellowish, bay;" Rus. zeltyj "yellow;" P.Gmc. *gelwaz; Du. geel; Ger. gelb; E. yellow.

gossamer ring = halqe-ye tanté     حلقه‌ی ِ تنته

Fr.: anneau ténu

An extremenly faint and broad ring (in fact two rings) of tiny particles around Jupiter lying just outside the main ring.

Gossamer "a film of cobwebs floating in air in calm clear weather; an extremely delicate variety of gauze, used esp. for veils," from M.E. gossomer, from gos "goose" + somer "summer." Possibly first used as name for late, mild autumn, a time when goose was a favorite dish, then transferred to the cobwebs frequent at that time of year; → ring.

Halqé → ring; tanté "cobweb, spider's web," from tanidan "to spin, twist, weave" (Mid.Pers. tanitan; Av. tan- to stretch, extend;" cf. Skt. tan- to spin, stretch;" tanoti "stretches," tantram "loom;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch; PIE base *ten- "to stretch"), Pers. tār "string," tur "fishing net, net, snare," and tāl "thread" (Borujerdi dialect) belong to this family; variants tanta "cobweb," tanadu, tafen, kartané, kārtané, kātené, Pashtu tanistah "cobweb;" cf. Skt. tantu- "cobweb, thread, string."

Gould's Belt = kamarband-e Gould (#)     کمربند ِ گولد

Fr.: ceinture de Gould

A band of hot, young stars (O and B types) and molecular clouds that stretches around the sky. It is tilted by about 20 degrees with respect to the Galactic plane, and has a diameter of about 3000 light-years.

Named after the American astronomer Benjamin A. Gould (1824-1896), who discovered it in 1879 by studying the distribution of the nearest luminous stars in space; → belt.

govern (v.) = faršāyidan     فرشاییدن

Fr.: gouverner

General: To rule over, to exercise authority.
Science: To serve as or constitute a law for, e.g. physical laws governing star formation, the Universe, and so on.
To regulate the speed of (an engine) with a governor.

From O.Fr. governer "to govern," from L. gubernare "to direct, rule, guide," originally "to steer," from Gk. kybernan "to steer or pilot a ship" (the root of cybernetics).

Faršāyidan, from Av. fraxšā(y)- "to establish authority, to deploy lordship," from fra- "forward, forth" (Av. pouruua- "first"; cf. Skt. pūrva- "first," pra- "before, formerly," Gk. pro; L. pro; O.E. fyrst "foremost," superlative of fore, from P.Gmc. *furisto; E. fore) + xšā(y)- "to rule, have power," xšayati "has power, rules," xšāyō "power;" O.Pers. xša- "to rule," pati-xša- "to have lordship over," Xšyāršan- "hero among kings" or "ruling over heroes" the proper name of the Achaemenid emperor Helenized as Xerxes, upari.xšay- "to rule over," xšāyaθiya- "king;" Mid.Pers. šāh "king," pādixšā(y) "ruler; powerful; authorative;" Mod.Pers. šāh "king," pādšāh "protecting lord, emperor, monarch, king," šāyestan "to be worth, suit, fit;" cf. Skt. ksā- "to rule, have power," ksáyati "possesses;" Gk. ktaomai "I acquire," ktema "piece of property;" PIE base *tkeh- "to own, obtain."

governor = faršāgar     فرشاگر

Fr.: régulateur

A regulating device for maintaining uniform speed regardless of changes of load, as by controlling the supply of gas, steam, fuel, etc.

Agent noun from → govern (v.).

graben = foruzamin (#)     فروزمین

Fr.: graben

A block of the Earth's crust, bounded by two normal faults, that has dropped downward in relation to adjacent portions.

Graben, from Ger. Graben "ditch, trench;" O.H.G. graban "ditch," grab "grave, tomb;" Goth. graban "ditch;" P.Gmc. *graban; cf. O.E. gręf "grave, ditch;" E. a grave; PIE base *ghrebh-/*ghrobh- "to dig, to scratch, to scrape."

Foruzamin, from foru- + zamin. The first component foru- "down, downwards; below; beneath;" Mid.Pers. frōt "down, downwards;" O.Pers. fravata "forward, downward;" cf. Skt. pravát- "a sloping path, the slope of a mountain." The second component zamin, variant zami "earth, ground," from Mid.Pers. zamig "earth;" Av. zam- "the earth;" cf. Skt. ksam; Gk. khthōn, khamai "on the ground;" L. homo "earthly being" and humus "the earth" (as in homo sapiens or homicide, humble, humus, exhume); PIE root *dh(e)ghom "earth."

gradient = ziné (#)     زینه

Fr.: gradient

General: Degree of slope
Physics: Change in the value of a quantity (as temperature, pressure) with change in a given variable.
Math.: A differential operator (symbol ∇) that, operating upon a function of several variables, creates a vector whose coordinates are the partial derivatives of the function.

From L. gradient-, gradiens, pr.p. of gradi "to walk, go," from grad- "walk" + -i- thematic vowel + -ent suffix of conjugation.

Ziné "ladder, steps, stair" of unknown origin.

gradual = pāypāy     پای‌پایه

Fr.: graduel

Proceeding, taking place, changing by small degrees.

From M.L. gradualis, from L. gradus "step."

Pāypāyé "step by step," from pāy, pā "foot, step" (Mid.Pers. pād, pāy; Av. pad-; cf. Skt. pat; Gk. pos, gen. podos; L. pes, gen. pedis; P.Gmc. *fot; E. foot; Ger. Fuss; Fr. pied; PIE *pod-/*ped-).

gradual burst = belk-e pāypāyé     بلک ِ پای‌پایه

Fr.: sursaut graduel

A burst that happens gradually, in contrast to a sudden burst.

→ gradual; → burst.

graduation = darajé-bandi (#)     درجه‌بندی

Fr.: graduation

Marking the scale of an instrument, e.g. the stem of a thermometer is graduated in degrees.

From M.E. graduacion, from M.L. graduation-, from graduatus, from graduare, from gradus "step."

Daraje-bandi, from darajé "degree," from Ar. darajat "step, ladder."

grain coagulation = māseš-e dāné     ماسش ِ دانه

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 = boxāreš-e dāné     بخارش ِ دانه

Fr.: évaporation des grains

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

→ grain; → evaporation.

grain formation = diseš-e dāné     دیسش ِ دانه

Fr.: formation des grains

The process by which dust grains are assembled or produced.

→ grain; → formation.

grain growth = ruyeš-e dāné (#)     رویش ِ دانه

Fr.: croissance des grains

The increase of dust grains to micron sizes in the interstellar environments due to various physical processes, for example mutual collisions and accumulation of ice mantles.

→ grain; growth, from grow, from M.E. growen, O.E. growan; cf. Du. groeien, O.H.G. grouwan (from root of grass) + -th a suffix forming nouns of action.

Ruyeš, verbal noun of ruyidan, rostan "to grow," from Mid.Pers. rōditan, rustan "to grow;" Av. raod- "to grow, sprout, shoot," with fra- "to grow up, shoot forth;" cf. Skt. ruh- "to grow, develop, ascend, climb," rohati "grows," rudh- "to grow, sprout, shoot," rodhati "grows."

grain mantle = rupuš-e dāné (#)     روپوش ِ دانه

Fr.: manteau de grain

A layer of icy molecules covering interstellar dust grains.

→ grain; mantle, from O.E. mentel "loose, sleeveless cloak," from L. mantellum "cloak," perhaps from a Celtic source.

Rupuš "overgarment, cloak," from ru "surface, face; aspect; appearance" (Mid.Pers. rōy, rōdh "face;" Av. raoδa- "growth," in plural form "appearance," from raod- "to grow, sprout, shoot;" cf. Skt. róha- "rising, height") + puš "covering, mantle," from pušidan "to cover; to put on" (Mid.Pers. pōšidan, pōš- "to cover; to wear;" cf. Mid.Pers. pōst; Mod.Pers. pust "skin, hide;" O.Pers. pavastā- "thin clay envelope used to protect unbaked clay tablets;" Skt. pavásta- "cover," Proto-Indo-Iranian *pauastā- "cloth").

grain sputtering = osparāni-ye dāné     ا ُسپرانی ِ دانه

Fr.: érosion des grains par pulvérisation

The ejection of atoms from interstellar dust grains due to impact by gas ions, which leads to grain destruction.

→ grain; sputtering, from sputter "to spit with explosive sounds," cognate with Du. sputteren.

Osparāni, verbal noun of osparāndan, from os- "out of, outside," → ex- + parāndan "to eject," transitive of paridan "to fly" (from Mid./Mod.Pers. par(r) "feather, wing," Av. parəna- "feather, wing;" cp. Skt. parna "feather," E. fern; PIE *porno- "feather").

gram = geram (#)     گرم

Fr.: gramme

A unit of mass equal to one thousandth of a kilogram.

From Fr. gramme, from L.L. gramma "small weight," from Gk. gramma "small weight," originally "letter of the alphabet," from stem of graphein "to draw, write."

Geram, loanword from Fr. gramme, as above.

-gram = -negāšt (#)     -نگاشت

Fr.: -gramme

A combining form meaning "something drawn, written" (diagram, spectrogram, oscillogram).

From Gk. -gramma, combining form of gramma "something written or drawn," → graph.

-Negāšt, from negāšt "drawn, written;" p.p. of negāštan, negārdan "to paint, write," → graph.

grand unified theory (GUTs) = negare-ye yegāneš-e bozorg (#)     نگره‌ی ِ یگانش ِ بزرگ

Fr.: théorie de la grande unification

A class of gauge theories that unite the strong, electromagnetic, and weak interactions at high energy. Ultimately, it is hoped that they can be extended to incorporate gravity.

O.Fr. grant, grand, from L. grandis "big, great," also "full-grown;" unified, p.p. of → unify (v.); → theory.

Negāré → theory; yegāneš, verbal noun of yegānestan → unify (v.); bozorg → great.

granulation = dāne-bandi     دانه‌بندی

Fr.: granulation

The mottled appearance of the solar photosphere, caused by convection cells, resembling granules, rising from the interior of the Sun. Each granule has a mean size of about 1000 km and an upward velocity of about 0.5 km/sec.

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

Dāne-bandi, from dāné → 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).

granule = dānul     دانول

Fr.: granule

A tiny grain; a small particle.
One of the convective cells constituting the solar → granulation.

From L.L. granulum "small grain," from → gain + → -ule.

graph = 1) -negār; 2) negāré (#)     ۱) -نگار: ۲) نگاره

Fr.: 1) -graphe; 2) diagramme, graphique, graphe

1) A suffix meaning "drawn, written," specialized in meaning to indicate the instrument rather than the written product of the instrument.
2) A visual representation of data that displays the relationship among variables, usually cast along X and Y axes.

1) A suffix, from Gk. -graphos "(something) drawn or written, one who draws or writes," from graphein "to draw, write."
2) As noun, short for graphic (formula), from L. graphicus "of painting or drawing," from Gk. graphikos "able to draw or paint," from graph(ein) "to draw, write" + -ikos "-ic."

1) As suffix, stem of negārdan, negāštan "to paint, write."
2) Negāré, from negār "picture, figure" (verb negārdan, negāštan "to paint"), from prefix ne-, O.Pers./Av. ni- "down; into" (Skt. ni "down," nitaram "downward;" Gk. neiothen "from below;" cf. E. nether; O.E. nižera, neožera "down, downwards, below, beneath," from P.Gmc. *nitheraz; Du. neder; Ger. nieder; PIE *ni- "down, below") + gār, from kar-, 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 k^wer- "to do, to make").

graphic = negārik     نگاریک

Fr.: graphique

(Adj.) Pertaining to the use of diagrams, graphs, mathematical curves, or the like.
Math.: Pertaining to the determination of values, solution of problems, etc., by direct measurement on diagrams instead of by ordinary calculations.
(n.) A product of the graphic arts, as a drawing or print. A computer-generated image.

→ graph + → ics.

graphite = gerāfit (#)     گرافیت

Fr.: graphite

A crystalline form of carbon present in the interstellar medium.

From Ger. Graphit, from Gk. graph(ein) "to write, draw," → graph + -it a suffix of chemical compounds, equivalent to E. -ite.

-graphy = -negāri (#)     -نگاری

Fr.: -graphie

A combining form denoting a process or form of drawing, writing, representing, recording, describing, etc., or an art or science concerned with such a process: geography; orthography; photography; spectrography.

→ graph.

grating = turi, ~ -e parāš (#)     توری، ~ ِ پراش

Fr.: réseau

Same as → diffraction grating.

M.E. grating, M.L. grata "a grating," variant of crata, from crat-, stem of cratis "wickerwork."

Turi, from tur "fishing net, net, snare," variants tār "thread, warp, string," tāl "thread" (Borujerdi dialect), cognate with tanidan, tan- "to spin, twist, weave" (Mid.Pers. tanitan; Av. tan- to stretch, extend;" Skt. tan- to stretch, extend;" tanoti "stretches," tantram "loom;" tántra- "warp; essence, main point;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch; Lith. tiñklas "net, fishing net, snare," Latv. tikls "net;" PIE base *ten- "to stretch").

grating angle = zāviye-ye turi (#)     زاویه‌ی ِ توری

Fr.: angle de réseau

The angle between the incident optical beam and the normal to the grating. It is the angle to which the grating must be set to place the desired wavelength at the center of the detector.

→ grating; → angle.

grating efficiency = kārāyi-ye turi (#)     کار‌آیی ِ توری

Fr.: efficacité de réseau

The measure of the light intensity diffracted from a grating.

→ grating; → efficiency.

grating groove = šiyār-e turi (#)     شیار ِ توری

Fr.: trait du réseau, sillon ~ ~

One of thousands of long, narrow indentations in the surface of a → diffraction grating.

→ grating; → groove.

gravitate (v.) = gerānidan (#)     گرانیدن

Fr.: graviter

To move or tend to move under the influence of gravitational force.

From L. gravitatus, p.p. of gravitāre, from gravis "heavy," → gravity.

Gerānidan, infinitive of gerān, → gravity.

gravitation = gerāneš (#)     گرانش

Fr.: gravitation

The universal ability of all material bodies to attract each other.

Verbal noun of → gravitate (v.).

gravitational = gerāneši (#)     گرانشی

Fr.: gravitationnel

Of or relating to or caused by gravitation.

Adj. of → gravitation.

gravitational collapse = rombeš-e gerāneši (#)     رمبش ِ گرانشی

Fr.: effondrement gravitationnel

Collapse of a mass of material as a result of the mutual gravitational pull of all its constituents.

→ gravitational; → collapse.

gravitational constant = pāyā-ye gerāneši (#)     پایای ِ گرانشی

Fr.: constante gravitationnelle

A fundamental constant that appears in Newton's law of gravitation. It is the force of attraction between two bodies of unit mass separated by unit distance (G = 6.668 x 10^-8 dyn cm² g^-2).

→ gravitational; → constant.

gravitational contraction = terenješ-e gerāneši     ترنجش ِ گرانشی

Fr.: contraction gravitationnelle

Decrease in the volume of an astronomical object under the action of a dominant, central gravitational force.

→ gravitational; → contraction.

gravitational encounter = ruyāruyi-ye gerāneši     رویارویی ِ گرانشی

Fr.: rencontre gravitationnelle

An encounter in which two moving bodies alter each other's direction and velocity by mutual gravitational attraction.

→ gravitational; → encounter.

gravitational energy = kāruž-e gerāneši     کاروژ ِ گرانشی

Fr.: énergie gravitationnelle

Same as → gravitational potential energy.

→ gravitational; → energy.

gravitational equilibrium = tarāzmandi-ye gerāneši (#)     ترازمندی ِ گرانشی

Fr.: équilibre gravitationnel

The condition in a celestial body when gravitational forces acting on each point are balanced by some outward pressure, such as radiation pressure or electron degeneracy pressure, so that no vertical motion results.

→ gravitational; → equilibrium.

gravitational field = meydān-e gerāneši (#)     میدان ِ گرانشی

Fr.: champ gravitationnel

The region of space in which gravitational attraction exists.

→ gravitational; → field.

gravitational-field theory = negare-ye meydān-e gerāneši (#)     نگره‌ی ِ میدان ِ گرانشی

Fr.: théorie de champ gravitationnel

A theory that treats gravity as a field rather than a force acting at a distance.

→ gravitational; → field.

gravitational force = niru-ye gerāneši (#)     نیروی ِ گرانشی

Fr.: force gravitationnelle

The weakest of the four fundamental forces of nature. Described by Newton's universal theory of gravity, and subsequently by Einstein's general relativity.

→ gravitational; → force.

gravitational instability = nāpāydāri-ye gerāneši (#)     ناپایداری ِ گرانشی

Fr.: instabilité gravitationnelle

The process by which fluctuations in an infinite medium of size greater than a certain length scale (the Jeans length) grow by self-gravitation.

→ gravitational; → instability.

gravitational interaction = andaržireš-e gerāneši     اندرژیرش ِ گرانشی

Fr.: interaction gravitationnelle

Mutual attraction between any two bodies that have mass.

→ gravitational; → interaction.

gravitational lens = adasi-ye gerāneši (#)     عدسی ِ گرانشی

Fr.: lentille gravitationnelle

A concentration of matter, such as a galaxy or a cluster of galaxies, that bends light rays from a background object, resulting in production of multiple images. If the two objects and the Earth are perfectly aligned, the light from the distant object appears as a ring from Earth. This is called an Einstein Ring, since its existence was predicted by Einstein in his theory of General Relativity.

→ gravitational; → lens.

gravitational mass = jerm-e gerāneši (#)     جرم ِ گرانشی

Fr.: masse gravitationnelle

The mass of an object measured using the effect of a gravitational field on the object.

→ gravitational; → mass.

gravitational potential energy = kāruž-e tavande-ye gerāneši     کاروژ ِ تونده‌ی ِ گرانشی

Fr.: énergie potentielle gravitationnelle

Energy that a body can acquire by falling through a gravitational field and that decreases as the kinetic energy increases.

→ gravitational; → potential; → energy.

gravitational radiation = tābeš-e gerāneši (#)     تابش ِ گرانشی

Fr.: rayonnement gravitationnel

According to general relativity, the energy transported by → gravitational waves. Gravitational radiation is to gravity what light is to electromagnetism.

→ gravitational; → radiation.

gravitational redshift = sorxkib-e gerāneši     سرخ‌کیب ِ گرانشی

Fr.: décalage vers le rouge gravitationnel

The change in the wavelength or frequency of electromagnetic radiation in a gravitational field predicted by general relativity.

→ gravitational; → redshift.

gravitational slingshot = falāxan-e gerāneši     فلاخن ِ گرانشی

Fr.: fronde gravitationnelle

Same as → gravity assist.

→ gravitational; slingshot, from sling, from M.E. slyngen, from O.N. slyngva "to sling, fling" + shot, from M.E., from O.E. sc(e)ot, (ge)sceot; cf. Ger. Schoss, Geschoss.

Falāxan "sling;" from Av. fradaxšana- "sling," fradaxšanya- "sling, sling-stone;" → gravitational.

gravitational waves = mowjhā-ye gerāneši (#)     موجهای ِ گرانشی

Fr.: ondes gravitationnelles

Space-time oscillations created by the motion of matter, as predicted by Einstein's general relativity. They are extremely weak even for the most massive objects like supermassive black holes.

→ gravitational; → wave.

gravitino = gerāvitino (#)     گراویتینو

Fr.: gravitino

A hypothetical force-carrying particle predicted by supersymmetry theories. The gravitino's spin would be 1/2; its mass is unknown.

From gravit(on) + (neutr)ino.

graviton = gerāviton (#)     گراویتون

Fr.: graviton

A hypothetical elementary particle associated with the gravitational interactions. This quantum of gravitational radiation is a stable particle, which travels with the speed of light, and has zero rest mass, zero charge, and a spin of ± 2.

From gravit(y) → gravity + → -on a suffix used in the names of subatomic particles.

gravity = gerāni (#)     گرانی

Fr.: gravité

1) The apparent force of gravitation on an object at or near the surface of a star, planet, satellite, etc.
2) Same as gravitation.

From L. gravitatem (nom. gravitas) "weight, heaviness," from gravis "heavy," from PIE base *g^wrə- "heavy" (cf. Mod.Pers. gerān "heavy;" Av. gouru- "heavy;" Skt. guru- "heavy, weighty, venerable;" Gk. baros "weight," barys "heavy;" Goth. kaurus "heavy").

Gerāni, noun of gerān "heavy, ponderous, valuable," from Mid.Pers. garān "heavy, hard, difficult;" Av. gouru- "heavy" (in compounds), from Proto-Iranian *garu-; cognate with gravity, as above.

gravity assist = yāri-ye gerāneši     یاری ِ گرانشی

Fr.: gravidéviation

An important astronautical technique whereby a spacecraft takes up a tiny fraction of the gravitational energy of a planet it is flying by, allowing it to change trajectory and speed. Also known as the slingshot effect or → gravitational slingshot.

→ gravity; assist, from M.Fr. assister "to stand by, help, assist," from L. assistere "assist, stand by," from → ad-"to" + sistere "to cause to stand," from PIE *siste-, from *sta- "to stand" (cognate with Pers. istādan "to stand").

Yāri "assistance, help; friendship," from Mid.Pers. hayyār "helper," hayyārźh "help, aid, assistance," Proto-Itranian *adyāva-bara-, cf. Av. aidū- "helpful, useful."

gray = xākestari (#)     خاکستری

Fr.: gris

(n.) A color between white and black. (adj.) Having a neutral hue.

O.E. gręg, from P.Gmc. *gręwyaz (cf. O.N. grar, O.Fris. gre, Du. graw, Ger. grau).

Xākestari, "ash-colored," from xākestar "ashes," from Mid.Pers. *xākātur, from xāk "earth, dust" + ātur "fire," varaint ātaxš (Mod.Pers. ātaš, āzar, taš), from Av. ātar-, āθr- "fire," singular nominative ātarš-; O.Pers. ātar- "fire;" Av. āθaurvan- "fire priest;" Skt. átharvan- "fire priest;" cf. L. ater "black" ("blackened by fire"); Arm. airem "burns;" Serb. vatra "fire;" PIE base *āter- "fire."

gray atmosphere = javv-e xākestari, havāsepher-e ~ (#)     جّو ِ خاکستری، هواسپهر ِ ~

Fr.: atmosphčre grise

A simplifying assumption in the models of stellar atmosphere, according to which the absorption coefficient has the same value at all wavelengths.

→ gray; → atmosphere.

gray body = jesm-e xākestari (#)     جسم ِ خاکستری

Fr.: corps gris

A hypothetical body which emits radiation at each wavelength in a constant ratio, less than unity, to that emitted by a black body at the same temperature.

→ gray; → body.

grazing incidence = forud-e barsā     فرود ِ برسا

Fr.: incidence rasante

Light striking a surface at an angle almost perpendicular to the normal.

Grazing, from graze (v.) "to touch or rub lightly in passing," perhaps a transferred sense from graze "to feed," via a notion of cropping grass right down to the ground, M.E. grasen, O.E. grasian, from gręs "grass;" → incidence.

Forud → incidence; barsā, adj. from barsāyidan, from bar- "on, upon, up" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + sāyidan, variants sābidan "to bruise, file," pasāvidan "to touch" (Khotanese sauy- "to rub;" Sogdian ps'w- "to touch;" Proto-Iranian *sau- "to rub").

grazing occultation = forupušān-e barsā     فروپوشان ِ برسا

Fr.: occultation rasante

A special type of occultation that occurs when the star appears to pass tangentially on the edge of the Moon. The star grazes the limb of the Moon; hence, the name.

→ grazing incidence; → occultation.

great = bozorg (#)     بزرگ

Fr.: grand

Unusual or considerable in degree, power, intensity, number, etc.

O.E. great "big, coarse, stout," from W.Gmc. *grautaz (cf. Du. groot, Ger. groß "great").

Bozorg "great, large, immense, grand, magnificient;" Mid.Pers. vazurg "great, big, high, lofty;" O.Pers. vazarka- "great;" Av. vazra- "club, mace" (Mod.Pers. gorz "mace"); cf. Skt. vájra- "(Indra's) thunderbolt," vaja- "strength, speed;" L. vigere "be lively, thrive," velox "fast, lively," vegere "to enliven," vigil "watchful, awake;" P.Gmc. *waken (Du. waken; O.H.G. wahhen; Ger. wachen "to be awake;" E. wake); PIE base *weg- "to be strong, be lively."

Great Attractor = darkešande-ye bozorg     درکشنده‌ی ِ بزرگ

Fr.: Grand Attracteur

A hypothesized large concentration of mass (about 10¹⁶ solar masses), some hundred million light years from Earth, in the direction of the Centaurus supercluster, that seems to be affecting the motions of many nearby galaxies by virtue of its gravity.

→ great; → attractor.

great circle = parhun-e bozorg, dāyere-ye ~     پرهون ِ بزرگ، دایره‌ی ِ ~

Fr.: grand cercle

A circle on a sphere whose plane passes through the center of the sphere.

→ great; → circle.

greatest eastern elongation = bozorgtarin derāzeš-e xāvari     بزرگترین درازش ِ خاوری

Fr.: plus grande élongation est

The Geatest → elongation of an inferior planet occurring after sunset.

Greatest, superlative of →great; →eastern; →elongation.

greatest western elongation = bozorgtarin derāzeš-e bāxtari     بزرگترین درازش ِ باختری

Fr.: plus grande élongation ouest

The Geatest → elongation of an inferior planet occurring before sunrise.

Greatest, superlative of → great; → western; → elongation.

Great Red Spot = lakke-ye sorx-e bozorg (#)     لکه‌ی ِ سرخ ِ بزرگ

Fr.: Grande tache rouge

An anticyclonic storm on the planet Jupiter akin to a hurricane on Earth, but it is enormous (three Earths would fit within its boundaries) and it has persisted for at least the 400 years that humans have observed it through telescopes.

→ great; → red; → spot.

Great Rift = cāk-e bozorg     چاک ِ بزرگ

Fr.:

An apparent fissure in the bright clouds of the Milky Way between Cygnus and Sagittarius caused by a series of large, dark, overlapping clouds.

→ great; rift, from M.E., from O.N. ript " to break an agreement" (cf. Dan., Norw. rift "cleavage"), from rifa "to tear."

Cāk "fissure, rupture, cleft, crack."

green = sabz (#)     سبز

Fr.: vert

A color intermediate in the spectrum between yellow and blue (wavelength between 5000 and 5700 Å). The color of most grasses and leaves while growing.

Green, from O.E. grene, related to growan "to grow," from W.Gmc. *gronja- (cf. Dan. grųn, Du. groen, Ger. grün), from PIE base *gro- "to grow." living plants."

Sabz "green," from Mid.Pers. sabz "green, fresh," related to sabzi "grass."

green flash = deraxš-e sabz (#)     درخش ِ سبز

Fr.: rayon vert

A brilliant green color that occasionally appears on the upper limb of the sun as it rises or sets.

→ green; → flsh.

greenhouse effect = oskar-e garmxāné     اُسکر ِ گرمخانه

Fr.: effet de serre

An increase in the Earth's surface temperature as heat energy from sunlight is trapped by the atmosphere. On average, about one third of the solar radiation that hits the Earth is reflected back to space. The Earth's surface becomes warm and emits infrared radiation. The greenhouse gases trap the infrared radiation, thus warming the atmosphere. Without the greenhouse effect the Earth's average global temperature would be -18° Celsius, rather than the present 15° Celsius. However, human activities are causing greenhouse gas levels in the atmosphere to increase.

→ green; house, from O.E. hus "dwelling, shelter, house," from P.Gmc. *khusan (cf. O.N. hus; Du. huis; Ger. Haus); → effect.

Oskar → effect; garmxāné "greenhouse," from garm, adj. of garmā → heat + xāné "house," from Mid.Pers. xānak, xān, xōn; cf. L. cunae "cradle;" Gk. kome "village;" Pers. Aftari dialect kiye "house, home;" PIE base *kei- "bed; to lie, to settle; beloved" (other cognates: P.Gmc. *khaim-; O.E. ham "dwelling, house, village;" E. home; Ger. Heim; L. civis "townsman;" Fr. cité; E. city; Skt. śiva- "auspicious, dear").

greenhouse gases = gāzhā-ye dārā-ye oskar-e garmxāné     گاز‌های ِ دارای ِ اُسکر ِ گرمخانه

Fr.: gaz ą effet de serre

Gases responsible for the greenhouse effect. These gases include: water vapor (H₂O), carbon dioxide (CO₂); methane (CH₄); nitrous oxide (N₂O); chlorofluorocarbons (CF_xCl_x); and tropospheric ozone (O₃).

→ greenhouse effect; → gas.

Gregorian calendar = gāhšomār-e Gregori (#)     گاهشمار ِ گرگوری

Fr.: calendrier grégorien

A solar calendar in which the year length is assumed to be 365.2425 solar days. It is now used as the civil calendar in most countries. The Gregorian Calendar is a revision of the Julian Calendar instituted in a papal bull by Pope Gregory XIII in 1582. The reason for the calendar change was to correct for drift in the dates of signifigant religious observations (primarily Easter) and to prevent further drift in the dates.

Named after Pope Gregory XIII (1502-1585), an Italian, born Ugo Boncompagni, Pope from 1572 to 1585, who ordered the reform of the Julian calendar; → calendar.

Gregorian telescope = durbin-e Gregori, teleskop-e ~ (#)     دوربین ِ گرگوری، تلسکوپ ِ ~

Fr.: télescope de Gregory

A reflecting telescope in which the light rays are reflected from the primary mirror to a concave secondary mirror, from which the light is reflected back to the primary mirror and through the central hole behind the primary mirror. Compare with the → Cassegrain telescope, in which the secondary mirror is convex.

Named after the Scottish mathematician and astronomer James Gregory (1638-1675), who devised the telescope, but did not succeed in constructing it; → telescope.

grinding = sābeš     سابش

Fr.: ébauchage

A first step in making a telescope mirror, which consists of rubbing the glass blank with hard tools (glass, tile, or metal) and abrasive grit to produce a concave form. → figuring; → polishing.

Grinding, verbal noun of grind, from O.E. grindan, forgrindan "destroy by crushing," from P.Gmc. *grindanan (cf. Du. grenden), from PIE *ghrendh- "crushing" (cf. L. frendere "to crush, grind;" Gk. khondros "granule, groats").

Sābeš, verbal noun of sābidan, variants sāyidan, pasāvidan "to touch" (Khotanese sauy- "to rub;" Sogdian ps'w- "to touch;" Proto-Iranian *sau- "to rub").

grism = grism (#)     گریسم

Fr.: grism

An optical dispersing device used in a spectrograph. It is a combination of a prism and a grating, in the sense that the grating is placed side by side to one surface of a small-angle prism.

Grism, from gr(ating) + (pr)ism.

grit = šen (#)     شن

Fr.: grain abrasif

Abrasive particles or granules, classified into predetermined sizes, typically of Silicon Carbide or Aluminum Oxide, used between the mirror and tile tool to grind the glass.

Grit, from O.E. greot "sand, dust, earth, gravel," from P.Gmc. *greutan "tiny particles of crushed rock" (cf. O.S. griot; O.N. grjot "rock, stone;" Ger. Grieß "grit, sand"); PIE base *ghreu- "to rub, pound, crush."

Šen "sand, grit."

groma = gromā     گروما

Fr.: groma

An instrument composed of a vertical staff and a horizontal cross with a plumb line at the end of each arm. It was used in ancient Roman empire to survey straight lines, squares, and rectangles.

From L. groma, gruma, from Gk. → gnomon, possibly through Etruscan.

groove = šiyār (#)     شیار

Fr.: trait, sillon

→ grating groove.

Groove, from O.N. grod "pit," or M.Du. groeve "furrow, ditch," from P.Gmc. *grobo (cf. O.H.G. gruoba "ditch," Goth. groba "pit, cave," O.E. gręf "ditch"), related to grave (n.).

Šiyār "furrow, ploughed ground," from Av. karši-, karša- "furrow," karšuiiā "plowed (land)," related to Mod.Pers. kašidan/kešidan "to carry, draw, protract, trail, drag;" Mid.Pers. kešidan "to draw, pull;" from Av. karš- "to draw; to plow;" cf. Skt. kars-, kársati "to pull, drag, plough," karṣū- "furrow, trench;" Gk. pelo, pelomai "to be in motion, to bustle;" PIE base k^wels- "to plow."

ground = 1) zamin; 2) zaminé (#)     ۱) زمین؛ ۲) زمینه

Fr.: sol, terrain

1) The surface of the Earth; soil.
2) The foundation or basis on which a belief or action rests.

From O.E. grund "foundation, ground, surface of the earth," from P.Gmc. *grundus (cf. Du. grond, Ger. Grund "ground, soil, bottom").

1) Zamin, variant zami "earth, ground," from Mid.Pers. zamig "earth;" Av. zam- "the earth;" cf. Skt. ksam; Gk. khthōn, khamai "on the ground;" L. homo "earthly being" and humus "the earth" (as in homo sapiens or homicide, humble, humus, exhume); PIE root *dh(e)ghom "earth."
2) Zaminé, from zamin + nuance suffix -é.

ground-based observation = nepāheš az zamin     نپاهش از زمین

Fr.: observation au sol

An astronomical observation carried out using a telescope on Earth, as opposed to that from an orbiting satellite.

→ ground; based, adj. of base, from O.Fr. bas, from L. basis "foundation," from Gk. basis "step, pedestal," from bainein "to step;" → observation.

Nepāheš → observation; az "from," → ex-; zamin → ground.

ground state = hālat-e zaminé (#)     حالت ِ زمینه

Fr.: état fondamental

The lowest energy state of an atom, molecule, or ion, when all electrons are in their lowest possible energy levels, i.e. not excited.

→ ground; → state.

group = goruh (#)     گروه

Fr.: groupe

Any collection or assemblage of persons or things; cluster; aggregation. e.g. → local group.
Math.: In general, a system on which one binary operation can be performed, and which satisfies the axioms for closure, associativity, identity, and the axiom for inverses (negatives), but not necessarily the commutative axiom.

From Fr. groupe "cluster, group," from It. gruppo "cluster, packet, knot," likely from P.Gmc. *kruppa "round mass, lump."

Goruh "group," from Mid.Pers. grōh "group, crowd."

group (v.) = 1) goruhāndan; 2) goruhidan     ۱) گروهاندن؛ ۲) گروهیدن

Fr.: 1) grouper; 2) se grouper

1) (v.tr.) To place or associate together in a group.
2) (v.intr.) To be part of a group.

Infinitive from → group.

grouping = goruheš     گروهش

Fr.: groupement

The act or process of uniting into groups.
A collection of things assembled into a group.
The occurence of several astronomical objects, usually of the same category, in a region of the sky.

Verbal noun of → group (v.).

group theory = negareh-ye goruh (#)     نگره‌ی ِ گروه

Fr.: théorie des groupes

A branch of mathematics which studies symmetry, as described in the structures known as groups. This powerful formal method of analyzing abstract and physical systems in which symmetry is present, has a very important use in physics, especially quantum mechanics.

→ group; → theory.

group velocity = tondā-ye goruh     تندای ِ گروه

Fr.: vitesse de groupe

The velocity of a wave packet (consisting of a collection of simple harmonic waves) as a whole. → phase velocity.

→ group; → velocity.

Grus = dornā (#)     دُرنا

Fr.: Grue

The Crane. A constellation in the Southern Hemisphere , located at 22h 30m right ascension, -45° declination. Its brightest star, of magnitude 1.7 and spectral typr B7. Abbreviation: Gru; genitive: Gruis

From L. grus "crane;" akin to Gk. geranos "crane;" Welsh garan; Lith. garnys "heron, stork;" O.E. cran; E. crane. Named by Johann Bayer in 1603.

Dornā "crane," from Turkish, a bird of the family Gruidae.

G-type star = setāre-ye gune-ye G     ستاره‌ی ِ گونه‌ی ِ G

Fr.: étoile de type G

A yellowish star whose surface temprature is about 6000 K and its spectrum is dominated by H and K lines of ionized calcium (Ca II 3968 Å and 3934 Å).

G from the alphabetical sequence of spectral types; → type; → star.

guider = durbin-e rāhbord     دوربین ِ راهبرد

Fr.: lunette guide

Same as → guiding telescope.

guide star = setāre-ye rāhbord     ستاره‌ی ِ راهبرد

Fr.: étoile de guidage

A relatively bright star conveniently located in the field of view used for → guiding.

Guide, from O.Fr. guider "to guide, lead," from Frankish *witan "show the way," from P.Gmc. *wit- "to know" (cf. Ger. weisen "to show, point out," wissen "to know;" O.E. witan "to see"). Cognate with Pers. bin- "to see" (present stem of didan "to see"); Mid.Pers. wyn-; O.Pers. vain- "to see;" Av. vaēn- "to see;" Skt. veda "I know;" Gk. oida "I know," idein "to see;" L. videre "to see;" PIE base *weid- "to know, to see." → star.

Setāré → star; rāhbord, verbal noun of rāhbordan "to guide, conduct," from rāh "way, path" (from Mid.Pers. rāh, rās "way, street," also rah, ras "chariot;" from Proto-Iranian *rāθa-; cf. Av. raθa- "chariot;" Skt. rátha- "car, chariot," rathyā- "road;" L. rota "wheel," rotare "to revolve, roll;" Lith. ratas "wheel;" O.H.G. rad; Ger. Rad; Du. rad; O.Ir. roth; PIE *roto- "to run, to turn, to roll") + bordan "to carry, lead" (Mid.Pers. burdan, O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive)," Skt. bharati "he carries," Gk. pherein, L. fero "to carry;" PIE base *bher- "to carry").

guiding = rāhbord     راهبرد

Fr.: guidage

A technique used in astronomical observations to keep the telescope tracking in pace with the rotational motion of the Earth. Guiding consists of maintaing the image of a stage motionless during the observation.

Verbal noun of guide → guide star.

guiding accuracy = rašmandi-ye rāhbord     رشمندی ِ راهبرد

Fr.: précision du guidage

The accuracy (expressed in arcseconds) with which the telescope follows the rotational motion of the Earth.

→ guiding; → accuracy.

guiding telescope = durbin-e rāhbord     دوربین ِ راهبرد

Fr.: lunette de guidage

A telescope which is attached to a second telescope being used for photographic purposes. The guiding telescope, mounted parallel to the optical axis of the main telescope, is used by the observer to keep the image of a celestial body motionless on a photographic plate.

→ guiding; → telescope.

Guitar nebula = miq-e gitār     میغ ِ گیتار

Fr.: nébuleuse de la Guitare

A nebula resembling a guitar produced by a neutron star, which is travelling at a speed of 1600 km per sec! The neutron star leaves behind a "wake" in the interstellar medium, which just happens to look like a guitar (only at this time, and from our point of view in space). The Guitar Nebula is about 6.5 light years away, in the constellation Cepheus, and occupies about an arc-minute in the sky, corresponding to about 300 years of travel for the neutron star.

Guitar, ultimately from Gk. kithara "cithara," a stringed musical instrument related to the lyre, perhaps from Pers. sehtar "three-stringed," from sé "three" + tār → string. → nebula.

gully = ābkand (#)     آبکند

Fr.: ravin

A trench or ravine worn away by running water in the earth.

Gully, a variant of M.E. golet "water channel," from O.Fr. goulet, dim. of goule "throat, neck," from L. gula; cf. Mod.Pers. galu "throat," geri, geribān "collar," gerivé "low hill," gardan "neck;" Mid.Pers. galōg, griv "throat," gartan "neck," Av. grīvā- "neck;" Skt. gala- "throat, neck," Gk. bora "food;" L. vorare "to devour;" PIE base *g^wer- "to swallow, devour."

Ābkand, literally "dug by water," from āb "water" (Mid.Pers. āb "water;" O. Pers. ap- "water;" Av. ap- "water;" cf. Skt. áp- "water;" Hitt. happa- "water;" PIE āp-, ab- "water, river;" cf. Gk. Apidanos, proper noun, a river in Thessalia; L. amnis "stream, river" (from *abnis); O.Ir. ab "river," O.Prus. ape "stream," Lith. upé "stream;" Latv. upe "brook") + kand, contraction of kandé, p.p. of kandan "to dig" (Mid.Pers. kandan "to dig;" O.Pers. kan- "to dig," akaniya- "it was dug;" Av. kan- "to dig," uskən- "to dig out" (→ ex- for prefix us-); cf. Skt. khan- "to dig," khanati "he digs").

Gum Nebula = miq-e Gām     میغ ِ گام

Fr.: nébuleuse de Gum

An immense emission nebula about 40° across lying toward the southern constellations Vela and Puppis. It contains the Vela pulsar and the Vela X supernova remnant, and seems to be created by an outburst of ionizing radiation that accompanied a supernova explosion.

Named after its discoverer, the Australian astronomer Colin Stanley Gum (1924-1960); → nebula.

Gunn-Peterson effect = oskar-e Gunn-Peterson     ا ُسکر ِ گان-پیترسون

Fr.: effet Gunn-Peterson

The continuum trough observed in the spectra of high redshift quasars (z > 6) at the blue wing of their Lyman-alpha emission line (1216 Å). It is explained by the scattering of the radiation of the quasar by intergalactic neutral hydrogen on the line of sight. Because of the cosmological expansion, the quasar line is redshifted with respect to the continuum trough. The Gunn-Peterson opacity increases rapidly with redshift. It is interpreted as a strong evidence for the reionization of the Univers around z = 6.

After James E. Gunn and Bruce A. Peterson who predicted the effect in 1965; → effect.

gyrate (v.) = leridan     لِریدن

Fr.: tournoyer

To move in a circle or spiral, or around a fixed point; to revolve in or as if in a spiral course. Close concepts: → revolve (گردیدن); → rotate (چرخیدن); → spin (اسپینیدن).

From L. gyratus, p.p. of gyrare "to turn around," from L. gyrus "circle," from Gk. gyros "circle, ring;" PIE base *geu- "to bend, curve."

Leridan, from Lori, Laki lerr "revolving, whirling, turning" (lerr dāye "to make rotate, to stir a liquid," lerese "to rotate, turn"), variant xer "circular, round" (xer dāyen "to make turn"), maybe cognate with Gk. gyros "circle, ring," as above; variants in Mod.Pers. lulé "rolled-up, wound-up; tube," lulé kardan "to roll up, wind up;" Hamadāni lul "spiral, twisted;" Kurd. lūl "curly (of hair)," garda-lūl, ~ lūlān "wind that whirls dust."

gyroscope = lernemā, carxešnemā     لِرنما، چرخش‌نما

Fr.: gyroscope

A device for measuring or maintaining orientation. Consisting of a rotating wheel so mounted that its axis can turn freely in certain or all directions, it is based on the principle of conservation of angular momentum. In physics this is also known as gyroscopic inertia or rigidity in space.

Gyroscope, from gyro-, → gyrate (v.) + → -scope.

Lernemā, from ler → gyrate (v.) + -nemā → -scope; carxešnemā, from carxeš → rotation + -nemā.

gyrofrequency = lerbasāmad     لِربسامد

Fr.: fréquence gyromagnétique

The frequency with which an electron or other charged particle executes spiral gyrations in moving across a magnetic field.

Gyrofrequency, from gyro-, → gyrate (v.) + → frequency.

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Observatoire de Paris LERMA Last updated 05 August 2009