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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 free-free emission   گسیل ِ آزاد-آزاد   gosil-e âzâd-âzâd (#)Fr.: emission libre-libre   → Electromagnetic radiation produced in a → plasma by → free electrons scattering off → ions without being captured. The electrons are free before the interaction and remain free afterward.→ free; → emission. frequency to wavelength conversion   هاگرد ِ بسامد به موج-طول   hâgard-e basâmad bé mowj-tulFr.: conversion fréquence / longueur d'onde   Deriving the → wavelength of an undulatory phenomenon from its → frequency, and vice versa. 1) For → electromagnetic waves: λ = c / f, where λ is the wavelength, c is the → speed of light in → meters per second and f the frequency in → hertz. It can be written as: λ (m) = 2.998 × 108 / f (Hz). 2) For → sound waves: λ = C / f, where C is the → sound speed. For air at temperature 0°C, λ (m) = 332 / f (Hz).→ frequency; → wavelength; → conversion. Fresnel diffraction   پراش ِ فرنل   parâš-e Fresnel (#)Fr.: diffraction de Fresnel   The diffraction effects obtained when either the source of light or observing screen, or both, are at a finite distance from diffracting aperture or obstacle. → Fraunhofer diffraction.Named after Jean Augustin Fresnel (1788-1827), French physicist, a key figure in establishing the wave theory of light. His earlier work on interference was carried out in ignorance of that of Thomas Young (1773-1829), English physician and physicist, but later they corresponded and were allies; → diffraction. Fresnel equation   هموگش ِ فرنل   hamugeš-e FresnelFr.: équation de Fresnel   For an electromagnetic wave incident upon the interface between two media with different indices of refraction, one of a set of equations that give the → reflection coefficient and → transmission coefficient at the optical interface. These coefficients depend on the polarization degree of the incident wave. 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. 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. 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. Frontier Fields   میدانهای ِ مرزی   Meydânhâ-ye MarziFr.: Champs frontialers   An observing project using the → Hubble Space Telescope (HST) and the → Spitzer Space Telescope to obtain deep images for cosmological studies. The Frontier Fields combines the power of HST and Spitzer with the natural gravitational telescopes of massive high-magnification clusters of galaxies to produce the deepest observations of clusters and their lensed galaxies ever obtained. Six clusters (Abell 2744, MACSJ0416.1-2403, MACSJ0717.5+3745, MACSJ1149.5+2223, Abell S1063, and Abell 370) were selected based on their lensing strength, sky darkness, Galactic extinction, parallel field suitability, accessibility to ground-based facilities, HST, Spitzer and JWST observability, and preexisting ancillary data. (Lotz et al., 2016, arxiv/1605.06567 and references therein).→ frontier; → field. FU Orionis object   بر‌آخت ِ FU شکارگر   barâxt-e FU ŠekârgarFr.: 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 micro Moon   ریز پرمانگ، ~ پرماه   riz pormâng, ~ pormâhFr.: pleine lune d'apogée   Same as → apogee full Moon.→ full; → micro-; → Moon. full moon   پرمانگ، پرماه   pormâng, pormâh (#)Fr.: pleine lune   1) The moon at → opposition, when it appears as a round disk to an observer on the Earth because the illuminated side is toward him. 2) The phase when the → age of the moon, measured from → new moon, is 14.5 days.→ full; → moon.Pormâh, from Mid.Pers. purrmâh, from Av. pərənô.manha- "full moon" (cf. Skt. pūrná-mās-); → full; → moon. full super Moon   ابر پرمانگ، ابر پرماه   abar pormâng, abar pormâhFr.: pleine lune de périgée   Same as → perigee full Moon.→ full; → super-; → Moon. function   کریا   karyâFr.: fonction   A mathematical rule between two sets which assigns to each element of the first exactly one element of the second, as the expression y = axb.From M.Fr. fonction, from O.Fr. function, from L. functio (gen. functionis) "performance, execution," from functus, p.p. of fungor "to perform, execute."Karyâ, from Av. kairya- "function;" cf. Mod.Pers. Laki karyâ "done," Awromâni kiriyây, kiria "to be done," from kar- "to do" (Mod.Pers. 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 kwer- "to do, to make") + -ya suffix of verbal adjectives and nouns (e.g. išya- "desirable," jivya- "living, fresh," haiθya- "true," maidya- "middle," dadya- "grain"); cf. Skt. kāryá- "work, duty, performance." functional   ۱) کریایی؛ ۲) کریال   1) karyâyi; 2) karyâlFr.: 1) fonctionnel; 2) fonctionnelle   1) Math.: Of, relating to, or affecting a function. 2) A → function that associates a → real number or → complex number to a function or a → set of functions. A functional can be considered as a function of a set of several infinite and continuous → variables.→ function; → -al. fundamental constant   پایای ِ بنیادین   pâyâ-ye bonyâdin (#)Fr.: constante fondamentale   A physical constant that cannot be expressed in terms of other constants of nature, such as the charge of the electron.→ fundamental; → constant. fundamental interaction   اندرژیرش ِ بنیادین   andaržireš-e bonyâdinFr.: interaction fondamentale   Any of the four interactions in nature between bodies of matter and that are mediated by one or more particles. Also called the → fundamental force. In order of decreasing strength, the four fundamental interactions are the → strong interaction, the → electromagnetic interaction, the → weak interaction, and the → gravitational interaction. fusion   ۱، ۲، ۳) ایوش؛ ۳) گداز   1, 2, 3) iveš; 3) godâz (#)Fr.: fusion   1) The act or process of fusing; the state of being → fused; that which is fused; the result of fusing. 2) A → nuclear reaction between atomic nuclei (→ nucleus) as a result of which a heavier nucleus is formed and a large quantity of → nuclear energy is released. → proton-proton chain, → CNO cycle, → nucleosynthesis. 3) Change of the → state of a → substance from → solid to → liquid which occurs at a definite → temperature at a given applied → pressure. Same as melting.From M.Fr. fusion, from L. fusionem, from fusus, p.p. of fundere "to pour, melt."Verbal noun form of → fuse. future light cone   مخروط ِ نوری ِ آینده   maxrut-e nuri-ye âyandé (#)Fr.: cône de lumière futur   The set of all points in a → space-time diagram that are reached by signals travelling from a specified point at the speed of light.→ future; → light; → cone.