An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 3079 Search : on
Coulomb interaction
  اندرژیرش ِ کولن   
andaržireš-e Coulomb

Fr.: interaction de Coulomb   

The reciprocal force between two or more → charged particles according to → Coulomb's law.

coulomb; → interaction.

coupling constant
  پایای ِ جفسری   
pâyâ-ye jafsari

Fr.: constante de couplage   

In nuclear physics, a constant that indicates a measure of how strongly two particles interact.

coupling; → constant.

covalent bond
  بند ِ هم ارزا   
band-e ham-arzâ

Fr.: lien covalent   

A chemical bond between two atoms of the same or different elements, in which each atom contributes one electron to be shared in a pair.

Covalent, adj. of → covalence; → bond.

creation
  آفرینش   
âfarinš (#)

Fr.: création   

1) The act of producing or causing to exist.
2) The act of being created. See also → creation operator.

Verbal noun of → create.

creation operator
  آپارگر ِ آفرینش   
âpârgar-e âfarineš

Fr.: opérateur de création   

An operator that acts on the → eigenstate describing the → harmonic oscillator to raise its → energy level by one step. The creation operator is the → Hermitian conjugate operator of the → annihilation operator.

creation; → operator.

creationism
  آفرینش‌باوری   
âfarineš-bâvari

Fr.: créationisme   

The religious belief that considers the account of creation given in Genesis to be a scientific description and rejects the Big Bang theory and the theory of evolution. Creationism is a → pseudoscience. Same as "creation science" and "scientific creationism."

creation; → -ism.

crescent Moon visibility
  دیاری ِ هلال ِ ماه   
diyâri-ye helâl-e mâh

Fr.: visibilité du croissant lunaire   

The first sighting of the → New Moon after its → conjunction with the Sun. Although the date and time of each New Moon can be computed exactly, the visibility of the lunar → crescent as a function of the → Moon's age depends upon many factors and cannot be predicted with certainty. The sighting within one day of New Moon is usually difficult. The crescent at this time is quite thin, has a low surface brightness, and can easily be lost in the → twilight. Generally, the lunar crescent will become visible to suitably-located, experienced observers with good sky conditions about one day after New Moon. However, the time that the crescent actually becomes visible varies from one month to another. The visibility depends on sky conditions and the location, experience, and preparation of the observer. Ignoring atmospheric conditions, the size and brightness of the lunar crescent depend on the → elongation which in turn depends on several factors: 1) The Moon's elongation at New Moon (the elongation of the Moon at New Moon is not necessarily 0). 2) The speed of the Moon in its elliptical orbit. 3) The distance of the Moon, and 4) The observer's location (parallax). The combined effect of the first three factors gives geocentric elongation of the Moon from the Sun at an age of one day which can vary between about 10 and 15 degrees. This large range of possible elongations in the one-day-old Moon is critical (US Naval Observatory).

crescent; → moon; → visibility.

Cretaceous-Paleogene extinction event
  رویداد ِ خاموشی ِ گچاسا-پارینزاد   
ruydâd-e xâmuši-ye Gacâsâ-Pârinzâd

Fr.: extinction Crétacé-Tertiaire   

The → mass extinction event that destroyed the dinosaurs and a majority of other species on Earth approximately 65 million years ago. This event is believed to have been the impact of a 10 km-size → asteroid or → comet nucleus and its aftereffects, including a severe → impact winter. The collision would have released the energy equivalent to 100 million megatonnes (teratonnes) of → TNT, i.e. more than 109 times the energy of the atomic bomb dropped on Hiroshima on August 6, 1945. Same as the → Cretaceous-Tertiary event.

Cretaceous; → Paleogene; → extinction; → event.

criterion
  سنجیدار   
sanjidâr (#)

Fr.: critère   

A standard or rule that can serve as basis for a judgment or decision.

From Gk. kriterion "means for judging, standard," from krites "judge," from krinein "to separate, distinguish, judge." L. cribrum "sieve" *krei- "to sieve, discriminate, distinguish."

Sanjidâr verbal noun from sanjid- past tense stem of sanjidan "to compare; to measure" (Mid.Pers. sanjidan "to weigh," from present tense stem sanj-, Av. θanj- "to draw, pull;" Proto-Iranian *θanj-) + suffix -âr.

critical Bonnor-Ebert mass
  جرم ِ پرژنی ِ بونور-ابرت   
jerm-e paržani-ye Bonnor-Ebert

Fr.: masse critique de Bonnor-Ebert   

The upper value of mass that a → Bonnor-Ebert sphere must have in order that → hydrodynamic equilibrium be maintained. This → critical mass is given by: Mcrit = 1.18 (a4/G3/2)Pext-1/2, where a = (kT/m)1/2 is the isothermal → sound speed inside the sphere, G is the → gravitational constant, and Pext the pressure of the external medium (see, e.g., F. H. Shu, 1977, ApJ 214, 488).

critical; → Bonnor-Ebert mass.

cross correlation
  هم‌باز‌آنش ِ چلیپایی، ~ خاجی   
hamvbâzâneš-e calipâyi, ~ xâji

Fr.: corrélation croisée   

In radio astronomy, the process performed by a → cross correlator or the result of the process.

cross; → correlation.

cross dispersion
  پاشش چلیپایی، ~ خاجی   
pâšeš-e calipâyi, ~ xâji

Fr.: dispersion croisée   

Dispersion of a light beam by using two dispersing elements (grating, grism), one for separating spectral orders, the other for resolving spectral features within an order.

cross; → dispersion.

cross identification
  ایدانش ِ چلیپایی   
idâneš-e calipâyi

Fr.: identification croisée   

The identification of an object in a data base or catalog and matching it with the same object identified in another catalog.

cross; → identification.

cross section
  سکنج‌گاه   
sekanjgâh

Fr.: 1) section plane; 2) section efficace   

1) Math: The intersection of a plane with a geometric figure, usually at right angles to an axis of symmetry.
2) Physics: A quantity that expresses the effective area that a given particle presents as a target to another incident particle, giving a measure of the probability that the incident particle will induce a particular atomic or nuclear reaction. Also called collision cross section. The cross section has the dimensions of a surface. In nuclear and particle physics, the commonly used units for the cross section are the barn and cm2.

In classical mechanics, the cross section for the collision of a point particle with a hard sphere is just be the surface of a section through the middle of the sphere. This explains the name "cross section." → cross; → section.

crystallization
  بلورش   
bolureš

Fr.: cristallisation   

A process by which a homogeneous solution becomes crystal.

Noun from crystallize, → crystal.

Noun from bolur, from verb boluridan "to crystallize" + verbal noun suffix -eš.

cubic equation
  هموگش ِ کابی   
hamugeš-e kâbi

Fr.: équation cubique   

An equation containing unknowns of the third power; the general form: ax3 + bx2 + cx + d = 0.

Cubic, of or pertaining to → cube; → equation.

cubic function
  کریای ِ کابی   
karyâ-ye kâbi

Fr.: fonction cubique   

A function defined by a → polynomial of → degree three. Its generalized form is: f(x) = ax3 + bx2 + cx + d, where a, b, c and d are constants, and a≠ 0.

cubic; → function.

culmination
  بالست   
bâlest

Fr.: culmination   

The act of culminating or the instant at which a celestial object reaches its highest altitude above the horizon by crossing the observer's meridian. → upper culmination; → lower culmination.

Verbal noun of → culminate.

Bâlest, from Mid.Pers. bâlist "culmination point of a star; highest, summit," from bâlây "high" + -ist superlative suffix, Av. barəzišta- "highest," from barəz- "high, mount" (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; PIE base *bhergh- "high") + -išta- superlative suffix (Skt. -istha-, Gk. -istos, O.H.G. -isto, -osto, O.E. -st, -est, -ost).

cumulative distribution function
  کریای ِ واباژش ِ کومشی   
karyâ-ye vâbâžeš-e kumeši

Fr.: fonction de distribution cumulée   

A function that gives the probability that a → random variable X is less than or equal to x, at each possible outcome: F(x) = P(X ≤ x), for -∞ < x < ∞. Same as → distribution function.

cumulative; → distribution; → function.

curvaton
  کورواتون   
kurvaton

Fr.: curvaton   

A hypothetical → scalar field that is used to explain the → primordial curvature perturbation in the Universe. It is generally supposed that the primordial perturbation originates during → inflation, from the → quantum fluctuation of the inflation field. The curvaton model is an attempt to account for the primordial perturbation by a completely different origin, namely the quantum fluctuation during inflation of a light scalar field which is not the assumed slowly-rolling inflation. In this model, the curvaton field is an energetically sub-dominant component during inflation. As the energy density of the Universe drops after inflation, the fraction of this component becomes significant. At this time the curvaton perturbation is converted into an adiabatic curvature perturbation of the Universe. The amplitude of the final perturbation, which should match observations, depends on both how long the curvaton oscillates before it decays, and on the shape of the potential. The first curvaton model was proposed by D. H. Lyth & D.Wands and in 2002 (Physics Letters B524).

From curvat-, from → curvature, + → -on. Although not related, the term curvaton exists in Fr. meaning "small curve" with variants curvatone, courbaton, and corbatone (A. Jal, 1848, Glossaire nautique).

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