An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 726
reduced mass
  جرم ِ بازهازیده   
jerm-e bâhâzidé

Fr.: masse réduite   

The "effective" → inertial mass appearing in the → two-body problem of → Newtonian mechanics. The reduced mass is a quantity which allows the two-body problem to be solved as if it were a one-body problem. For the masses m1 and m2, it is given by the ratio μ = m1m2 / (m1 + m2). The value of μ is generally smaller than m1 and m2. The larger the difference between the two masses, the closer μ will be to the smaller mass. If the particles are of equal mass, μ is half the mass of either.

reduce; → mass.

reduced Planck's constant
  پایای ِ پلانک ِ باز‌هازیده   
pâyâ-ye Planck-e bâzhâzidé

Fr.: constante de Planck réduite   

The Planck's constant divided by 2π and denoted ħ, pronounced h-bar. Also called → Dirac's constant.

Reduced, p.p. of → reduce; → Planck's constant.

reducing agent
  کنشگر ِ بازهازنده   
konešgar-e bâzhâzandé

Fr.: réducteur   

A substance which removes → oxygen from, or adds → hydrogen, to another substance. In the more general sense, one which loses electrons. Also called → reductant.

reduce; → -ing; → agent.

reducing atmosphere
  جوّ ِ باز‌هازنده، هواسپهر ِ ~   
javv-e bâzhâzandé, havâsepehr-e ~

Fr.: atmosphère réductrice   

1) An atmospheric condition in which oxidation is prevented by removal of oxygen and other oxidating gasses or vapours. Usually nitrogen or hydrogen gas is used in order to produce specific effects, e.g. on ceramic wares being fired.
2) An atmosphere of a planet or moon which has a high hydrogen content, either in the form of free hydrogen or hydrogen-containing compounds, such as methane or ammonia. The early atmosphere of Earth is thought to be reducing, dominated by carbon dioxide.

Reducing verbal adj. of → reduce; → atmosphere.


Fr.: réducteur   

Same as → reducing agent.

Agent noun from → reduce.

reductio ad absurdum
  باز‌هازش به یاوه   
bâzhâzeš bé yâvé

Fr.: raisonnement par l'absurde   

Logic, Math.: A method of → reasoning in which one assumes some statement to be → true and from that → assumption proceeds to deduce a logical → absurdity and hence to a conclusion that the original assumption must have been → false.

L. reductio ad absurdum "reduction to absurdity," → reduction; → absurd.


Fr.: réduction   

1) In → data processing, the transformation of data from a "raw" form to some usable form.
2) Chem.: The removal of → oxygen from a substance, or the addition of → hydrogen to it. The term is also used more generally to include any reaction in which an atom gains → electrons.

Verbal noun of → reduce.


Fr.: redondance   

The fact of repeating or duplicity.
That part of the data content that can be dropped without any significant loss of the original information.

From L. redundantia "an overflowing, excess," from redundare "to flow back, overflow, be excessive," from → re- "again" + undare "rise in waves," from unda "a wave."

Afzun-âyi "redundancy, superabounding," from afzun "more, greater; more ample," from afzudan "to add, increase" (Mid.Pers. abzudan "to increase, grow;" O.Pers. abijav- "to increase, add to, promote," from abi-, aiby- "in addition to; to; against" + root jav- "press forward;" Av. gav- "to hasten, drive;" Sk. jav- "to press forward, impel quickly, excite," javate "hastens") + âyi verbal noun of ây- present stem of âmadan "to come, arrive, become" (Av. ay- "to go, to come," aēiti "goes;" O.Pers. aitiy "goes;" Skt. e- "to come near," eti "arrival;" L. ire "to go;" Goth. iddja "went," Lith. eiti "to go;" Rus. idti "to go").

Rees-Sciama effect
  اسکر ِ ریز-سیاما   
oskar-e Rees-Sciama

Fr.: effet de Rees-Sciama   

The → Sachs-Wolfe effect in which the calculations are extended to nonlinear mass concentrations. In the non-linear regime of large-scale → structure formation the → gravitational potential changes with time, and photons climb out of a → potential well slightly different from the one that they fell into. Therefore, nonlinear density fluctuations produce extra evolution of the potentials against the background expansion. On large scales, the nonlinear contribution to the full ISW effect is expected to be dominated by the linear ISW effect in a Universe with → cosmological constant (Seljak, 1996, ApJ 460, 549).

Martin J. Rees (1942-) & Dennis W. Sciama (1926-1999), 1968, Nature 217, 511; → effect.

bâzbordan (#)

Fr.: référer   

1) To direct for information or anything required.
2) To hand over or submit for information, consideration, decision, etc.
3) To have relation; relate.
4) To make reference or allusion (

M.E. referren, from L. referre "to bring back," from → re- "back" + ferre "carry, bear," cognate with Pers. bordan "to carry, bear," as below.

Bâzbordan, literally "to bring back," from bâz "back," → re- + bordan "to carry, bear" (Mid.Pers. burdan, O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive)," Skt. bharati "he carries," Gk. pherein, L. fero "to carry;" PIE base *bher- "to carry").

bâzbord (#)

Fr.: référence   

1) An act or instance of referring.
2) A book, article, or passage to which one is directed.

Verbal noun of → refer.

reference ellipsoid
  بیضی‌وار ِ بازبرد   
beyzivâr-e bâzbord

Fr.: ellipsoïde de référence   

A mathematically defined surface that approximates the Earth's shape, which is basically a sphere "flattened" at its poles. The length of one of the axes at the Equator is chosen so that the ellipsoid coincides at this latitude with the mean sea level. It is the first-order definition of the non-spherical shape of the Earth as an ellipsoid of revolution. To first order, it accounts for over 90% of the → geoid.

reference; → ellipsoid.

reference frame
  چارچوب ِ بازبرد   
cârcub-e bâzbord

Fr.: système de référence   

A set of axes to which positions and motions in a system can be referred. Same as → frame of reference.

reference; → frame.

reference source
  خن ِ بازبرد   
xan-e bâzbord

Fr.: source de référence   

An astronomical source in a field used as a reference for the detection of another object, astrometry, etc.

reference; → source.

  ۱) نازکیدن؛ ۲) نازکیدن   
1) pâludan; 2) nâzokidan

Fr.: raffiner   

1) To bring to a fine or a pure state; free from impurities.
2) To make more fine, subtle, or precise (

re-; → fine.

1) Pâludan "to purify, starin, → filter."
2) Nâzokidan, from nâzok "tender, delicate, subtle, neat," → fine.

  ۱) پالایش؛ ۲) نازکش   
1) pâlâyeš; 2) nâzokeš

Fr.: raffinement   

1) Fineness or elegance of feeling, taste, manners, language, etc.
2) The act or process of refining. the quality or state of being refined.
3) An improved, higher, or extreme form of something.
Math.: A → set whose elements include the elements of a given set (

Verbal noun of → refine.



Any of a series of features occurring in the → light curve of → dwarf novae and → Soft X-ray Transient (SXT)s during → outburst decay. Reflares appear when the surface density Σ behind the cooling front is high enough to reach Σmax. At the radius at which this happens, the disk becomes thermally unstable and a new heating front develops. This front propagates outward like an inside-out outburst, reheating the disk until Σ(R) ≤ Σmin, when cooling can resume. The density in the cold region is depleted as matter is accreted during this process, and the following reflare occurs at smaller radii and have lower amplitudes (G. Dubus et al., 2001, A&A 373, 251).

re-; → flare.

bâztâbidan (#)

Fr.: réfléchir   

To throw or bend back from a surface, specially light, sound, or heat.

M.E. reflecten, from L. reflectere "to bend back," from → re- "back" + flectere "to bend."

Bâztâbidan, from bâz-, → re- + tâbidan, variants tâftan "to shine," tafsidan "to become hot;" Mid.Pers. tâftan "to heat, burn, shine;" taftan "to become hot;" Parthian t'b "to shine;" Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "; to heat, be/become hot; to spoil, injure, damage; to suffer," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "to be warm."


Fr.: réflectance   

1) Same as → reflection factor.
2) Computers: In optical character recognition, the relative value of the ink color compared to the background.

From → reflect + -ance

Bâztâbâyi, verbal noun from adj./agent noun bâztâbâ "reflecting."

reflected ray
  پرتو ِ بازتابیده   
partow-e bâztâbidé (#)

Fr.: rayon réfléchi   

A → light ray that is reflected from a surface.

reflect; → ray.

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