# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 431
 Fresnel integrals   درستال‌های ِ فرنل   dorostâlhâ-ye FresnelFr.: intégrales de Fresnel   Two integrals that involve quadratic equations in the sine and cosine functions and are defined as: C(x) = ∫ cos (πt2/2) dt and C(y) = ∫ sin (πt2/2) dt, integrated from 0 to x. They are quite frequently used in optics studying → Fresnel diffraction and similar topics. The Fresnel integrals are also used in railway and freeway constructions. These integrals may be evaluated to arbitrary precision using → power series. Alternatively the amplitudes may be found graphically by use of → Cornu's spiral. Fresnel lens   عدسی ِ فرنل   adasi-ye ferenel (#)Fr.: lentille de Fresnel   An optical lens composed of a series of rings of glass so curved that they all have the same focus. It is flat on one side and ridged on the other making it possible that nearly every ray of light from the source be re-directed out on a horizontal path. This design enables the construction of lenses of large aperture and short focal length avoiding thus the large weights and volumes of material which would be required in conventional lenses. The first Fresnel lens, designed for use in a lighthouse on the river Gironde, was installed in France in 1823, and by the 1850s many examples were in use everywhere. Fresnel lenses are most often used in light gathering applications, such as condenser systems or emitter/detector setups. They can also be used as magnifiers and projection lenses. Nowadays, Fresnel lenses made of optical plastics are widely used for various applications.→ Fresnel diffraction; → lens. Fresnel mirror   آینه‌ی ِ فرنل   âyene-ye Fresnel (#)Fr.: miroir de Fresnel   A pair of plane mirrors which are slightly inclined to one another. It is used for producing two coherent images in interference experiments. Fresnel rhomb   لوزی‌وار ِ فرنل   lowzivâr-ye FresnelFr.: 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'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. 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 FriedFr.: 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 FriedmannFr.: 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-LemaîtreFr.: 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, pišânFr.: 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-tahFr.:   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 (Âštiyâni, 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 FroudeFr.: 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, rocidéFr.: 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, ~ ~ ~ rocidéFr.: 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 rocidéFr.: eau gelée   Turned into or covered with → ice. See also: → water ice.Past participle of → freeze.