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: 13048 Search : far
free system
  راژمان ِ آزاد   
râžmân-e âzâd

Fr.: système libre   

A → mechanical system if all of its constituent particles or bodies can occupy arbitrary points in space or have arbitrary velocities. Otherwise, it is called a → constrained system.

free; → system.

free-bound emission
  گسیل ِ آزاد-بندیده   
gosil-e âzâd-bandidé

Fr.: émission libre-liée   

The radiation emitted when a → free electron is captured by an → ion. See also: → free-free emission; → bound-free transition.

free; → bound; → emission.

free-fall time
  زمان ِ افت ِ آزاد   
zamân-e oft-e âzâd

Fr.: temps de chute libre   

The characteristic time it would take a body to collapse under its own → gravitational attraction, if no other forces existed to oppose the collapse. It is given by: tff = (3π/32 ρ0 G)1/2, where ρ0 denotes the initial density and G the → gravitational constant. Free-fall time is independent of the starting radius. Also known as → dynamical time scale.

free fall; → time.

free-floating objects
  بر‌آخت‌های ِ شناور   
barâxthâ-ye šenâvar

Fr.: objets flottants   

A population of → substellar objects which are not bound to stars; they are detected in young star clusters. Their masses, estimated from their fluxes, is several Jupiter masses, lower than those of → brown dwarfs. Their formation is not yet explained. Among the envisaged possibilities: 1) These objects form like stars, from protostellar core collapse and subsequent accretion; 2) they form as low-mass members of small groups, and are ejected from the group; 3) they form like planets within circumstellar disks of higher-mass objects, but are ejected either due to internal dynamics or external interactions.

free; floating, from M.E. float, from O.E. flotian "to float" (cf. O.N. flota, M.Du. vloten); → object.

Barâxt, → object; šenâvar "that swims, floats," from šenâ "swimming;" Mid.Pers. šnâz "swim," šnâzidan "to swim;" Av. snā- "to wash, swim;" cf. Skt. snā- "to bathe, to wash;" L. nare, natare "to swim" (Fr. nage, nager, natation; Sp.nadar, natacion).

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.

freedom
  آزادی   
âzâdi (#)

Fr.: liberté   

The state of being free or at liberty.

From M.E. fredom, from O.E. freodom, from freo "free; noble, joyful," → free.

Âzâdi "freedom," noun from âzâd, → free.

Freeman's law
  قانون ِ فریمن   
qânun-e Freeman

Fr.: loi de Freeman   

A statistical finding about "normal" → spiral galaxies, whereby there is an upper limit on the mean central → surface brightness of disks. This value is constant for different spiral types, amounting to 21.65 ± 0.30 mag arcsec2 in the B band.

Named after K. C. Freeman (1970, Ap.J. 160, 811); → law.

freeze
  ۱) یخ بستن؛ ۲) رچیدن   
1) yax bastan; 2) rocidan

Fr.: geler   

1) To change from the liquid to the solid state by loss of heat; become hardened into ice.
2) Become hardened into a solid body. → coagulate.

Freeze, from O.E. freosan "turn to ice," from P.Gmc. *freusanan (cf. O.H.G. friosan, Ger. frieren "to freeze"), from *freus-, from PIE base *preus- "to freeze" also "to burn" (cf. Skt. pruśva- "hoar-frost, ice;" L. pruina "hoar-frost," Skt. pruśta- "burnt;" Albanian prus "burning coals;" L. pruna "a live coal").

1) Yax bastan, from yax "ice" + bastan "to bind, shut; to congeal, coagulate." The first component yax, from Av. aexa- "ice, frost," isav-, isu- "icy, chilly," cf. Sarikoli (Pamir dialect) īš "cold," P.Gmc. *isa- (O.N. iss, O.Fris. is, Du. ijs, Ger. Eis). The second component bastan, from Mid.Pers. bastan/vastan "to bind, shut;" Av./O.Pers. band- "to bind, fetter," banda- "band, tie" (cf. Skt. bandh- "to bind, tie, fasten;" PIE *bhendh- "to bind;" Ger. binden; E. bind). 2) Rocidan, → coagulate.

freezing
  ۱) یخ‌بست؛ ۲) رچش   
1) yaxbast; 2) roceš

Fr.: gel, congélation   

1) The phase transition of a substance passing from the liquid to the solid state; the opposite of → fusion. In meteorology, the freezing of water.
2) Solidification.

Verbal noun from → freeze.

freezing point
  نقطه‌ی ِ یخ‌بست   
noqte-ye yaxbast

Fr.: point de congélation   

1) The temperature at which a liquid of specified composition changes into a solid under a specified pressure.
2) The temperature at which the liquid and solid phases of a substance of specified composition coexist in equilibrium.

freezing; → point.

French Republican Calendar
  گاهشمار ِ جمهوری ِ فرانسه   
gâhšomâr-e jomhuri-ye Farâncé

Fr.: Calendrier républicain, Calendrier révolutionnaire français   

A calendar composed by Fabre d'Eglantine and others during the French Revolution which divided the year into 12 months of 30 days each, with five odd days called → Sansculottides. The year started at → autumnal equinox and the months were: Vendémiaire (Vintage), Brumaire (Fog), Frimaire (Frost), Nivôse (Snow), Pluviôse (Rain), Ventôse (Wind), Germinal (Buds), Floréal (Flowers), Prairial (Meadows), Messidor (Harvest), Termidor (Heat), Fructidor (Fruits). The week consisted of 10 days, and was called a Décade; each 10th day of Décade (called Décadi) was a day of rest. The calendar was used by the French government for about 12 years, from late 1793 to 1805, when it was suppressed by Napoleon.

M.E. Frensh, French, O.E. Frencisc "of the Franks," from Frank; republican, from republic, from Fr. république, from L. respublica, from res publica "public interest, the state," from res "affair, matter, thing" + publica, feminine of publicus "public;" → calendar.

frequency
  بسامد، فرگی   
basâmad (#), feregi (#)

Fr.: fréquence   

The number of complete oscillations per unit time of a vibrating system. The reciprocal of the → period, T.

From L. frequentia "assembly, multitude, crowd."

Basâmad, from bas "many, much" (Mid.Pers. vas "many, much;" O.Pers. vasiy "at will, greatly, utterly;" Av. varəmi "I wish," vasô, vasə "at one's pleasure or will," from vas- "to will, desire, wish") + âmad past stem of âmadan "to occur, to come, to become" (Mid.Pers. âmatan; O.Pers. gam- "to come; to go," Av. gam- "to come; to go," jamaiti "goes;" Proto-Iranian *āgmatani; Skt. gamati "goes;" Gk. bainein "to go, walk, step;" L. venire "to come;" Tocharian A käm- "to come;" O.H.G. queman "to come;" E. come; PIE root *gwem- "to go, come").
Feregi, from feré "much, more; increase; priority," farâ(vân) "abundant," Mid.Pers. frêh "more, much;" O.Pers. fra- "before, forth;" Av. frā, fərrā "forth, forward;" PIE base *pro-; cf. L. pro "on behalf of, in place of, before, for;" Gk. pro- "before, in front of."

frequency band
  باند ِ بسامد   
bând-e basâmad

Fr.: bande de fréquence   

A range of frequencies that is continuous between two specified limits, selected from a more extended range of frequencies.

frequency; → band.

frequency drift
  دلک ِ بسامد   
delek-e basâmad

Fr.: dérive de fréquence   

An undesired progressive change in an oscillator's frequency with time.

frequency; → drift.

frequency shift
  کیب ِ بسامد   
kib-e basâmad

Fr.: décalage de fréquence   

The change in the frequency of a wave motion due to the → Doppler effect.

frequency; → shift.

frequency spectrum
  بیناب ِ بسامد   
binâb-e basâmad

Fr.: spectre de fréquence   

A graphical display of the intensity of radiation or energy versus frequency.

frequency; → spectrum.

frequency switching
  دگربانی ِ بسامد   
degarbâni-ye basâmad

Fr.: permutation de fréquence   

A mode of observation in radio astronomy in which the telescope remains at a fixed position and data is accumulated while the center of the receiver passband is switched between signal and offset frequencies. Data accumulated at the offset frequency is subtracted from the signal frequency data before storage as a frequency switched scan. → beam switching.

frequency; → switching.

frequency to wavelength conversion
  هاگرد ِ بسامد به موج-طول   
hâgard-e basâmad bé mowj-tul

Fr.: 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 Fresnel

Fr.: 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.

Fresnel diffraction; → equation.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara Arc ari Arr ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit cla clo clo clu Coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg hyp ice ide ima Ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per per pha phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>