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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 428
Fresnel rhomb
  لوزی‌وار ِ فرنل   
lowzivâr-ye Fresnel

Fr.: parallélépipède de Fresnel   

A piece of special glass in the form of an oblique → parallelepiped so cut that a ray of light entering one of its faces at right angles shall emerge at right angles at the opposite face, after undergoing two internal reflections. It is a type of → quarter-wave retarder used to produce a → circularly polarized light from a → plane polarized light, or the reverse.

Fresnel diffraction; → rhombus.

Fresnel's biprism
  دومنشور ِ فرنل   
domanšur-e Fresnel (#)

Fr.: biprisme de Fresnel   

An optical element consisting of two small angle → prisms, joined together at their bases, used to produce two → coherent sources. The thin double prism refracts the light from a source into two overlapping beams, which produce → interference fringes. With this experiment Fresnel was able to produce interference without relying upon → diffraction to bring the interfering beams together.

Fresnel diffraction; → bi-; → prism.

Fresnel's mirrors
  آینه‌های ِ فرنل   
âyenehâ-ye Fresnel (#)

Fr.: miroirs de Fresnel   

Two plane mirrors, fitted side by side at a small angle, used to create two mutually → coherent sources in a famous → interference experiment first suggested by A. Fresnel. A point source reflected at the mirrors appears as a pair of → virtual light sources, positioned close together, which interfere with each other due to their → coherence. This arrangement removes the problem that two separate light sources do not produce observable interference on account of their incoherence. Same as Fresnel's double mirror. See also → Fresnel's biprism, → Lloyd's mirror.

Fresnel diffraction; → mirror.

friction
  مالش   
mâleš (#)

Fr.: frottement   

The resisting force offered by one body to the relative motion of another body in contact with the first.

From L. frictionem "a rubbing, rubbing down," from fricare "to rub."

Mâleš, verbal noun of mâlidan "to rub," from, variants parmâs "contact, touching," marz "frontier, border, boundary," Mid.Pers. mâlitan, muštan "to rub, sweep;" Av. marəz- "to rub, wipe," marəza- "border, district;" PIE base *merg- "boundary, border;" cf. L. margo "edge" (Fr. marge "margin"); P.Gmc. *marko; Ger. Mark; E. mark, margin.

Fried parameter
  پارامون ِ فرید   
pârâmun-e Fried

Fr.: paramètre de Fried   

One of the parameters that characterize atmospheric → seeing. It is the diameter of the largest aperture that can be used before → turbulence starts to degrade the image quality. As the turbulence gets stronger, the Fried parameter, denoted r0, becomes smaller. The Fried parameter is wavelength dependent: r0 ∝ λ6/5. On best astronomical mountain tops it ranges between 20 and 30 cm for λ = 5000 A.

Named after David L. Fried, who defined the parameter 10 1966; → parameter.

Friedmann equation
  هموگش ِ فریدمن   
hamugeš-e Friedmann

Fr.: équation de Friedmann   

An equation that expresses energy conservation in an → expanding Universe. It is formally derived from → Einstein's field equations of → general relativity by requiring the Universe to be everywhere → homogeneous and → isotropic. It is expressed by H2(t) = (8πG)/(3c2)ε(t) - (kc2)/R2(t), where H(t) is the → Hubble parameter, G is the → gravitational constant, c is the → speed of light, ε(t) is the → energy density, k is the → curvature of space-time, and R(t) is the → cosmic scale factor. See also → Big Bang, → accelerating Universe. See also → Friedmann-Lemaitre Universe.

Named after the Russian mathematician and physical scientist Aleksandr Aleksandrovich Friedmann (1888-1925), who was the first to formulate an → expanding Universe based on Einstein's theory of → general relativity ; → equation.

Friedmann-Lemaitre Universe
  گیتی ِ فریدمن-لو‌متر   
giti-ye Friedmann-Lemaître

Fr.: univers Friedmann-Lemaître   

One of the first → cosmological models to incorporate Einstein's → general relativity, predicting that → galaxies should be → receding from each other due to → cosmic expansion.

Friedmann equation; Georges Edouard Lemaître (1894-1966), a Belgian cosmologist and priest who proposed a first sketch of the → Big Bang theory; → universe.

frigid
  سجن   
sajan (#)

Fr.: glacial, froid, glacé, frigide   

Very cold in temperature.

From Latin frigidus "cold, chill, cool," from stem of frigere "be cold;" related to noun frigus "cold, coldness, frost," from PIE root *srig- "cold;" cf. Gk. rhigos "cold, frost."

Sajan "very cold," variants šaja,, sajâm, šajad, Oss. I. syjyn/syd, D. sujun/sud "to freeze," Yaghnobi ši-, Yazghulami šed/šiy- "to freeze," Shughni šitô , Sariqoli š(i)tu "cold, ice." Proto-Ir. *saiH-/siH- "to freeze." Skt. syā- "to freeze, coagulate, become rigid."

fringe
  فریز   
fariz (#)

Fr.: frange   

1) One of the alternating bright or dark bands produced by → interference or → diffraction.
2) Wavy patterns due to the layered structure of → CCDs. These interference effects are prominent when emission lines such as the night-sky emissions are present.

From M.E. frenge, from O.Fr. frange, from V.L. *frimbia, metathesis of L. fimbriæ "fibers, threads, fringe," of uncertain origin.

Fariz, contraction of farâviz "fringe, lace, edging," from far-, par-, variant pirâ- "around, about" (Mid.Pers. pêrâ; O.Pers. pariy "around, about," Av. pairi "around, over;" Skt. pari; Indo-Iranian *pari- "around;" PIE base *per- "through, across, beyond;" cf. Gk. peri "around, about, beyond;" L. per "through") + âviz "anything suspended; a place where things are hung up; a border, margin," from âvixtan, âvizidan "to hang, suspend;" Mid.Pers. âwextan "to hang;" Av. vij- "to shake, swing," frauuaēγa- "swinging forward;" cf. Skt. vej- "to dart up or back, move up;" Proto-Iranian *uij- "to shake, swing."

front
  رو، پیشان   
ru, pišân

Fr.: face, front   

1) The part or side of anything that faces forward. → ionization front.
2) Meteo.: A narrow zone of transition between air masses of contrasting density, that is, air masses of different temperature or different water vapor concentration or both.
3) The side of the → planispheric astrolabe that displays the → limb of the → mater, the → tympanum, the → rete, and, in some models, the → rule. By setting the front, i.e., by rotating the rete around the mater, one can depict the appearance of the heavens as determined by observation in order to obtain a time value from the instrument. Alternatively, by configuring the rete for a given day, one can perform several astronomical computations such as the rising, culmination, and setting of the Sun, Moon, planets, and stars (online museo galileo, VirtualMuseum).

From O.Fr. front "forehead, brow," from L. frontem "forehead," perhaps lit. "that which projects," from PIE *bhront-, from base *bhren- "to project, stand out."

Pišân, from pišâni "front, forehead," from piš "before; in front," from Mid.Pers. pêš "before, earlier;" O.Pers. paišiya "before; in the presence of" + -ân suffix of place and time.
Ru "face," → surface.

front-end
  پیش-ته   
piš-tah

Fr.:   

A device containing a radio-frequency amplifier and associated cryogenic systems, routers, and converters (mixers), whose input is the voltage from a receptor and whose output is an intermediate-frequency signal. → back-end.

front + end, from O.E. ende, from P.Gmc. *andja, originally "the opposite side," from PIE *antjo "end, boundary," from base *anta-/*anti- "opposite, in front of, before."

Piš-tah, from piš, → front, + tah "end;" Mid.Pers. tah "bottom." The origin of this term is not clear. It may be related to Gk. tenagos "bottom, swamp," Latvian tigas "depth;" PIE *tenegos "water bottom."

frontier
  مرز   
marz (#)

Fr.: frontière   

A border between two countries.
A line of division between different or opposed things.
The farthermost limits of knowledge or achievement in a particular subject.

From O.Fr. fronter, from front "forehead, brow," → front.

Marz, from Mid.Pers. marz "boundary;" Av. marəza- "border, district," marəz- "to rub, wipe;" Mod.Pers. parmâs "contact, touching" (→ contact), mâl-, mâlidan "to rub;" PIE base *merg- "boundary, border;" cf. L. margo "edge" (Fr. marge "margin"); P.Gmc. *marko; Ger. Mark; E. mark, margin.

frost
  بشمه   
bašmé (#)

Fr.: givre, gelée   

Ice crystals that are formed by deposition of water vapor on a relatively cold surface.
The condition that exists when the temperature of the earth's surface and earthbound objects fall below freezing.

O.E. forst, frost "a freezing, becoming frozen, extreme cold," from P.Gmc. *frusta- (cf. O.H.G. frost, Du. vorst), related to freosan "to freeze."

Bašmé, from bašm "hoar-frost; dew," variants bažm, bašk, pašak "frost; dew," may be related to (štiyâni, Qomi dialects) bašand, vašand, vašan "rain" (vašan-sâl "rainy year"), (Lori, Laki) vašt "rain shower," (Gurâni) wašt, wišani "rain" (Tâti Karingâni) vurasten "to rain;" Av. -varšta- "rain," aiwi-varšta- "rained upon;" Skt. vars- "to rain," varsá- "rain;" M.Irish frass "rain shower, torrent;" Gk. eérse "dew," oureo "to urinate."

Froude number
  عدد ِ فرود   
adad-e Froude

Fr.: nombre de Froude   

A → dimensionless number that gives the ratio of local acceleration to gravitational acceleration in the vertical.

Named after William Froude (1810-1879), English engineer.

frozen
  یخ‌بسته، رچیده   
yax basté, rocidé

Fr.: gelé   

1) Turned into or covered with ice. → frozen water.
2) Attached or → fixed so as to be immovable. → frozen magnetic field line.

Past participle of → freeze.

frozen magnetic field line
  خط ِ میدان ِ مغناتیسی ِ یخ‌بسته، ~ ~ ~ رچیده   
xatt-e meydân-e meqnâtisi-ye yax basté, ~ ~ ~ rocidé

Fr.: ligne de champ magnétique gelée   

A → magnetic field line in a → fluid when the motion of the fluid carries the magnetic field along with it.

Frozen, p.p. of → freeze; → magnetic; → line.

frozen water
  آب ِ یخ‌بسته، ~ رچیده   
âb-e yax basté, âb-e rocidé

Fr.: eau gelée   

Turned into or covered with → ice. See also: → water ice.

Past participle of → freeze.

FU Orionis object
  بر‌آخت ِ FU شکارگر   
barâxt-e FU Šekârgar

Fr.: objet FU Orionis   

A member of a class of → pre-main sequence stars that experience dramatic changes in magnitude and → spectral type. During an outburst the luminosity of such an object can increase by several orders of magnitude on short time-scales (few months to few years). The phenomenon is explained by abrupt mass transfer from an → accretion disk to a young, low mass → T Tauri star (accretion rates 10-4 to 10-3 solar masses per year). → EX Lupi; → Z CMa.

F and U, alphabet letters; Orionis, → Orion; → object.

full
  پر   
por (#)

Fr.: plein   

Completely filled; containing all that can be held; complete; entire; maximum.

O.E. full "completely, full," from P.Gmc. *fullaz (cf. O.Fris. ful, O.N. fullr, O.H.G. fol, Ger. voll), akin to Pers. por, as below.

Por "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- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full.

full micro Moon
  ریز پرمانگ، ~ پرماه   
riz pormâng, ~ pormâh

Fr.: pleine lune d'apogée   

Same as → apogee full Moon.

full; → micro-; → Moon.

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