An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 155 Search : ratio
operational calculus
  افماریکِ آپارشی   
afmârik-e âpâreši

Fr.: calcul opérationnel   

A method of mathematical analysis which in many cases makes it possible to reduce the study of differential operators, pseudo-differential operators and certain types of integral operators, and the solution of equations containing them, to an examination of simpler algebraic problems. It is also known as operational analysis.

operational; → calculus.


Fr.: opérationalisme   

In the philosophy of science, the view that → concepts are defined in terms of measuring operations which determine their applicability. Same as operationism.

operation; → -ism.

optical aberration
  بیراهشِ نوری   
birâheš-e nuri

Fr.: aberration optique   

An imperfection in the imaging properties of a lens or mirror. The main aberrations are → chromatic aberration, → spherical aberration, → coma, → astigmatism, → field curvature, → distortion.

optical; → aberration.

orbital migration
  کوچِ مداری   
kuc-e madâri

Fr.: migration orbitale   

Theoretical prediction according to which a → giant planet, formed in the outer regions of a → protoplanetary disk, could migrate inward by losing → energy and → angular momentum as the result of → gravitational interactions with the remnants of the disk. This orbital migration could explain the presence of giant gaseous Jupiter-like planets (→ hot Jupiters) very close to their host stars.

orbital; → migration.

partition ratio
  وابر ِ پرکش   
vâbar-e parkeš

Fr.: rapport de partition   

The ratio of the → concentration of a → solute in a single definite form in the stationary phase to its concentration in the same form in the other phase at equilibrium.

partition; → ratio.


Fr.: péjoration   

1) Depreciation; a lessening in worth, quality, etc.
2) Semantic change in a word to a lower, less approved, or less respectable meaning.

Verbal noun of → pejorate.

  شید-واپاشی، نور-واپاشی   
šidvâpâši, nurvâpâši

Fr.: photodésintégration   

The process by which atomic nuclei are broken apart into their constituent protons and neutrons by the impact of high energy gamma photons. Photodisintegration takes place during the core collapse phase of a → Type II supernova explosion.

photo- + → disintegration.

  شید-بخارش، نور-بخارش   
šidboxâreš, nurboxâreš

Fr.: photoévaporation   

A process going on in a molecular cloud surface whereby the surface material ionized by ultraviolet photons of neighboring stars is dissipated.

photo- + → evaporation.

photometric calibration
  کبیزش ِ شید-سنجیک، ~ سنور-سنجیک   
kabizeš-e šidsanjik, ~ nursanjik

Fr.: calibration photométrique   

A calibration which converts the measured relative magnitudes into an absolute photometry.

photometric + → calibration.

physical libration
  هلازان ِ فیزیکی، رخگرد ِ ~   
halâzân-e fiziki, roxgard-e ~

Fr.: libration physique   

A real periodic variation in the rotation rate of a celestial object, as distinct from a → geometrical libration. In particular, slight oscillations in the → Moon's rotation caused by the → gravitational attraction of the Earth on the → equatorial bulge of the Moon's near side. The Moon's physical libration is about 0.03° in longitude and about 0.04° in latitude.

physical; → libration.

plane of vibration
  هامن ِ شیوش   
hâmon-e šiveš

Fr.: plan de vibration   

In a → linearly polarized light, a plane perpendicular to the → plane of polarization and containing the direction of propagation of light. It is also the plane containing the direction of propagation and the electric vector (E) of the electromagnetic light wave.

plane; → polarization.

planetary aberration
  بیراهش ِ سیاره‌ای   
birâheš-e sayyâreyi

Fr.: aberration planétaire   

The difference between the true position of a planet and its apparent position, due to the time required for light to travel the distance from the planet to Earth. Correction for planetary aberration is necessary in determining orbits.

planetary; → aberration.

Pogson's ratio
  وابر ِ پوگسون   
vâbar-e Pogson

Fr.: rapport de Pogson   

The constant 2.512, which is the 5th → root of 100 (2.5125 = 100); the ratio between two successive stellar → magnitudes.

Pogson's relation; → ratio.

radial migration
  کوچ ِ شعاعی   
kuc-e šo'â'i

Fr.: migration radiale   

The process whereby a → disk star changes its → galactocentric distance. Radial migration involves → angular momentum transfer, resulting from → resonances created by transient → density waves such as → bars or → spiral arms in → galactic disks. According to → galactic dynamics models, → churning is the main cause of radial migration. Radial migration of stars plays an important role in shaping the properties of galactic disks.

radial; → migration.

radiative acceleration
  شتاب ِ تابشی   
šetâb-e tâbeši

Fr.: accélération radiative   

The acceleration imparted to matter by → radiation pressure.

radiative; → acceleration.

radius of gyration
  شعاع ِ لرش   
šo'â'-e lereš

Fr.: gyrorayon   

Same as → Larmor radius.

radius; → gyration.


Fr.: rapport   

Math.: The quotient of two quantities arrived at by dividing one by the other.

From L. ratio "reckoning, calculation," also "reason," from rat-, p.p. stem of reri "to reckon, calculate," also "think," → reason.
Fr. rapport, back-formation from rapporter "bring back," from → re- "back, again" + apporter "to bring," from L. apportare "to bring," from → ad- "to" + portare "to carry."

Vâbar, on the model of Fr. rapport "bringing back," as above, from vâ- prefix meaning "back to the original place, again," → re-, + bar present stem of bordan "to carry, lead" (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").

  ۱) راینی، راینوار؛ ۲) خردانه، خردمندانه؛ ۳) وابری   
1) râyani, râyanvâr; 2) xeradâné, xeradmandâné; 3) vâbari

Fr.: rationnel   

1) Having or exercising the ability to → reason.
2) Consistent with or based on reason; logical; in accordance with sound reasoning.
3) Math.: Capable of being expressed as a quotient of integers.

M.E. racional, from O.Fr. racionel, from L. rationalis "of or belonging to reason, reasonable," from ratio (genitive rationis) "reckoning, calculation, reason," from rat-, pp. stem of reri "to reckon, calculate; consider, think."

1) Râyani, of or pertaining to râyan, → reason.
2) Xeradâné, xeradmandâné, of or pertaining to xerad "understanding, judgement, intellect, wisdom;" Mid.Pers. xrad "reason, intellect, intelligence, wisdom, understanding;" O.Pers. xraθu- "wisdom;" Av. xratu- "intelligence, undestanding, wisdom; will, purpose, council;" cf. Skt. krátu- "power, will-power;" Gk. kratos "power, strength."
3) vâbari, of or pertaining to vâbar, → ratio.

rational number
  عدد ِ وابری   
'adad-e vâbari

Fr.: nombre rationnel   

Any number that can be expressed as a ratio of two integers, providing the second number is not zero.

rational; → number.


Fr.: raisonnement, exposé raisonné   

1) The fundamental reason or reasons serving to account for something.
2) A statement of reasons.
3) A reasoned exposition of principles (

L. neuter of rationalis.

Râyanâl, from râyan, → reason, + -âl, → -al.

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