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: 417
forbidden emission line
  خط ِ گسیلی ِ بژکم   
xat-e gosili-ye bažkam

Fr.: raie d'émission interdite   

A → forbidden line in → emission.

forbidden; → emission; → line.

forbidden line
  خط ِ بژکم   
xatt-e bažkam

Fr.: raie interdite   

A spectral line emitted by atoms undergoing energy transitions not normally allowed by the → selection rules of → quantum mechanics. Forbidden emission lines form in low-density interstellar gas and are collisionally excited. They are designated by enclosing in brackets, e.g. [O III] and [N II], O and N representing oxygen and nitrogen atoms respectively.

forbidden; → line.

forbidden transition
  گذرش ِ بژکم   
gozareš-e bažkam

Fr.: transition interdite   

A transition between two quantum mechanical → states that → violates the quantum mechanical → selection rules.

forbidden; → transition.

Forbush decrease
  کاهش ِ فورباش   
kâheš-e Forbush

Fr.: effet Forbush   

A decrease in the Galactic cosmic flux around sunspot maximum as a consequence of Solar flare activity. When sunspots explode, they often hurl massive clouds of hot gas away from the Sun, a phenomenon called → coronal mass ejections (CME). The CMEs contain not only gas but also magnetic fields. So when a CME sweeps past Earth, it also sweeps away many of the electrically-charged cosmic rays.

After Scott E. Forbush, American physicist who studied cosmic rays in the 1930s and 40s; → effect; decrease, from O.Fr. stem of descreistre, from L. decrescere, from → de- "away from" + crescere "to grow."

Kâheš, verbal noun of kâstan, kâhidan "to decrease," from Mid.Pers. kâhitan, kâstan, kâhênitan "to decrease, diminish, lessen;" Av. kasu- "small, little" (Mod.Pers. keh), Proto-Iranian *kas- "to be small, diminish, lessen."

force
  نیرو   
niru (#)

Fr.: force   

1) The cause of a change in motion or shape of a body.
2) A → vector quantity defined by → Newton's second law as the rate of change of → momentum or, equivalently, as the product of → mass and → acceleration. A force is completely specified by giving its magnitude, direction, and point of application. In mechanics, force represents the quantitative measure of the mechanical interaction of material bodies.

From O.Fr. force, from L.L. fortia, from neut. pl. of L. fortis "strong," from forctus, from PIE base *bhergh- "high" (cf. Av. barəz- "high, mount," barezan- "height;" O.Pers. baršan- "height;" Mod.Pers. borz in (the mountain chain) Alborz, and borz "height, magnitude," bâlâ "up, above, high, elevated, height," Lori dialect berg "hill, mountain;" Skt. bhrant- "high;" O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg).

Niru, from Mid.Pers. nêrok, Av. nairya- "manly, male" (cf. Skt. nárya-), from nar- "man, male" (Mid./Mod.Pers. nar- "male," Skt. nár- "male").

force field
  میدان ِ نیرو   
meydân-e niru (#)

Fr.: champ de force   

Same as → field of force.

force; → field.

force multiplier parameter
  پارامون ِ بستاگر ِ نیرو   
pârâmun-e bastâgar-e niru

Fr.: paramètre de multiplicateur de force   

One of the three quantities (k, α, and δ) which are used in the → radiation-driven wind theory to express the radiation pressure due to spectral lines. These coefficients parametrize the radiation acceleration as: grad≅ k(dv/dr)αge, where ge = σeL/4πcR*2 is the radiative acceleration by electron scattering. The parameter k is dependent on the number of lines that produce the radiation pressure. The parameter α depends on the optical depth of the driving lines and varies between 0 (optically thin) and 1 (optically thick). The parameter δ describes the dependence of k on the density with k ≅ ρδ. The velocity law of radiation-driven winds depends on α and δ, but not on k. The → mass loss rate depends on k, α, and δ (Castor et al. 1975, ApJ 195, 157; Lamers et al., 1995, ApJ 455, 269 and references therein).

force; → multiplier; → parameter.

force system
  راژمان ِ نیروها   
râžmân-e niruhâ

Fr.: système de forces   

Any set of forces acting on a → rigid body.

force; → system.

force-free magnetic field
  میدان ِ مغناتیسی ِ بی‌نیرو   
meydân-meqnâtisi-ye bi-niru

Fr.: champ magnétique sans force   

The condition in a plasma when the → Lorentz force is zero, that is when the electric current flows along the magnetic field. Force-free magnetic fields are encountered in astrophysical plasmas with negligible gas pressure. The solar corona is the best available example of such fields in action in a plasma.

force; → free; → magnetic; → field.

forced
  زوری   
zuri (#)

Fr.: forcé   

1) Physics: Caused by an external force. → forced oscillation.
2) General: Subjected to force, compulsory.

Adjective from → force.

Adjective from zur, → strength.

forced flow
  تچان ِ زوری   
tacân-e zuri

Fr.: écoulement forcé   

A fluid flow generated when external forces cause the fluid to flow, for example when a flow is caused by a pump. It contrasts with → free flow.

forced; → flow.

forced oscillation
  نوش ِ زوری   
naveš-e zuri

Fr.: oscillation forcée   

The oscillation of a system or object induced by an external periodic force. See also → free oscillation.

forced; → oscillation.

foreground
  پیش-زمینه   
pišzaminé

Fr.: avant-plan   

The ground or parts situated, or represented as situated, in the front; the portion of a scene or stellar field nearest to the viewer. → background.

From fore, from O.E. fore (prep.) "before, in front of;" (adv.) "before, previously" (cf. O.H.G. fora, Ger. vor, Goth. faiura); from PIE *per-/*pr- (cf. Skt. pura "before, formerly;" Av. paro "before;" Hittite para- "on, forth;" Gk. paros "before," para "from beside, beyond," peri "around, about, toward," pro "before;" L. pro "before, for, instead of," prae "before," per "through, for") + ground, from M.E., from O.E. grund; akin to O.H.G. grunt "ground."

Pišzaminé, from piš- "before; in front," from Mid.Pers. pêš "before, earlier;" O.Pers. paišiya "before; in the presence of" + ziminé "ground," from zamin "earth, ground" → earth.

foreground absorption
  درشم ِ پیش-زمینه   
daršam-e pišzaminé

Fr.: absorption d'avant-plan   

Loss of radiant energy received from an astronomical object due to the presence of absorbing matter situated between the object and observer.

foreground; → absorption.

forest
  جنگل   
jangal (#)

Fr.: forêt   

1) A large tract of land covered with trees and underbrush; woodland (Dictionary.com).
2) In → graph theory, a → graph which contains no → cycles. The connected components of a forest are → trees.

M.E., from O.Fr. forest, probably from L.L. forestis (silva) "the outside woods," from L. foris "outside."

Jangal "a wood, forest, a vast land with plenty of trees;" cf. Skt. jangala- "arid , sparingly grown with trees and plants."

fork
  دوشاخ، دوشاخه؛ چنگال   
došâx, došâxé; cangâl

Fr.: fourche; forchette   

1) An instrument having two or more prongs or tines, for holding, lifting, etc., as an implement for handling food or any of various agricultural tools (dictionary.com).
2) Something resembling or suggesting this in form. → fork mounting.

Fork, from O.E. forca, from L. furca "pitchfork," of uncertain origin; → mounting.

Došâx, došâxé "two-pronged; fork," from do "two" (Mid.Pers. do, Av. dva-, Skt. dvi-, Gk. duo, L. duo, E. two, Ger. zwei, Fr. deux) + šâx "branch; horn," from Mid.Pers. šâk "branch;" cf. Lith. šaka "branch;" O.S. soxa "plough;" Gothic hoha "plough."
Cangâl "claws, fingers," from cang "claws, fingers," + -al, → -al.

fork mounting
  برنشاند ِ دوشاخه   
barnešând-e došâxé

Fr.: monture à fourche   

A type of → equatorial mounting consisting of a two-pronged fork, which forms the → polar axis, with the → telescope pivoted between the prongs of the fork on a → declination axis.

fork; → mounting.

form
  ۱) دیس، دیسه؛ ۲) دیسیدن؛ ۳) دیساندن   
1) dis, disé (#); 2) disidan (#); 3) disândan (#)

Fr.: 1) forme; 2) se former; 3) former   

1) (n.) General: The shape and structure of something as distinguished from its material.
Philosophy: The structure, pattern, organization, or essential nature of anything. Structure or pattern as distinguished from matter.
Logic: The abstract relations of terms in a proposition, and of propositions to one another.
2) (v.intr.) of form.
3) (v.tr.) of form.

From O.Fr. forme, from L. forma "form, mold, shape, case," origin unknown.

1) Dis, disé "form, appearance," variants -diz, -diš (tandis "body form, like a body; effigy;" mâhdis "moon-like;" šabdiz "night color; a horse of dark rusty color;" andiš- "to think, contemplate"), from Mid.Pers. dêsag "form, appearance," dêsidan "to form, build;" Av. daēs- "to show," daēsa- "sign, omen;" cf. Skt. deś- "to show, point out;" PIE *deik- "to show" (cf. Gk. deiknumi "to show," dike "manner, custom;" L. dicere "to utter, say;" O.H.G. zeigon, Ger. zeigen "to show;" O.E. teon "to accuse," tæcan "to teach").
2) and 3) corresponding infintives of dis, as above.

formal
  دیسه‌ای، دیسه‌ور   
diseyi, desevar

Fr.: formel   

1) According to, or following established or prescribed forms, conventions, etc.
2) Math., logic: Of a proof, in strict logical form with a justification for every step.
3) Math., logic: Of a calculation, correct in form; made with strict justification for every step; of or pertaining to manipulation of symbols without regard to their meaning.
4) → formal language.
5) → formal logic.

M.E. formal, formel, from L. formalis, from → form + → -al.

Diseyi, desevar, from dis, → form, + adj. suffixes -i and -var.

formal language
  زبان ِ دیسه‌ور   
zabân-e disevar

Fr.: langage formel   

A language designed for use in situations in which natural language is unsuitable, as for example in → mathematics, → logic, or → computer  → programming. The symbols and formulas of such languages stand in precisely specified syntactic and semantic relations to one another (Dictionary.com).

formal; → language.

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