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: 1244
crest
  ستیغ   
setiq (#)

Fr.: crête   

The highest point or upper part of a wave.

From O.Fr. creste "tuft, comb," from L. crista "tuft, plume; rooster's comb."

Setiq "summit; anything standing upright," from O.Pers./Av. sta- "to stand, stand still; set," Mod.Pers. istâdan "to stand" (cf. Skt. sthâ- "to stand," Gk. histemi "put, place, weigh," stasis "a standing still," L. stare "to stand") + adj. suffix -iq, variants -ig, -ik, → -ics.

Cretaceous
  گچاسا   
Gacâsâ

Fr.: Crétacé   

A period of → geologic time which began at the end of the → Jurassic period approximately 145 million years ago and extended to approximately 65 million years ago.

From L. cretaceus, from cret(a) "chalk, clay," + → -aceous, because the geological remains of this period contain heightened chalk deposits.

Gacâsâ, from gac "chalk," Mid.Pers. gac + -âsâ, → -aceous.

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. Same as the → Cretaceous-Tertiary event.

Cretaceous; → Paleogene; → extinction; → event.

Cretaceous-Tertiary event
  رویداد ِ K-T   
ruydâd-e K-T (#)

Fr.: événement K-T   

See → Cretaceous-Paleogene extinction event.

K, representing the "→ Cretaceous period," and T the "→ Tertiary;" → event.

crew
  کرن   
koran

Fr.: équipage, équipe   

A group of persons acting or working together.

M.E. crewe "augmentation, reinforcement, body of soldiers," from M.Fr. crue, from O.Fr. creue "an increase, recruit, military reinforcement," from p.p. of creistre "grow," from L. crescere "grow, arise," → crescent.

Koran, variants korand, korang "a troop, a circle of people" (Dehxodâ).

crime
  بزه   
bazah (#)

Fr.: crime   

An action or an instance of negligence that is deemed injurious to the public welfare or morals or to the interests of the state and that is legally prohibited (Dictionary.com).

M.E., from O.Fr. crimne, from L. crimen "charge, indictment, accusation; offense."

Bazah, from Mid.Pers. bazag "crime, misdeed," bazagkâr "evil-doer," Parthian bzg "evil, wicked."

criminal
  ۱) بزهی؛ ۲) بزه‌کار   
1) bazahi; 2) bazahkâr

Fr.: criminel   

1) Of the nature of or involving crime.
2) A person guilty or convicted of a crime.

L. criminalis, → crime; → -al.

crisis
  پرژنه   
paržané

Fr.: crise   

A decisive stage or turning point in the course of something, especially in a sequence of events or an acute disease.

M.E., from Latinized from of Gk. krisis "turning point in a disease," literally "judgment, selection," from krinein "to separate, decide, judge;cf. " L. cribrum "sieve," crimen "judgment, crime;" → critique.

Paržané, from paržan, present stem of paržanidan "to separate, sift, → critique," + a suffix of relation.

crisp
  توج   
tuj

Fr.: net   

1) Notably sharp, clear-cut, and clear.
2) Noticeably neat (Merriam-Webster.com).

M.E, from O.E., from L. crispus "curled," cognate with Walsh crych "curly."

Tuj (Kurmanji Kurd.) variant of tiz, → sharp.

crisp set
  هنگرد ِ توج   
hangard-e tuj

Fr.: ensemble net   

A classical set that allows only full membership or no membership at all for its elements, as contrasted with a → fuzzy set. Crisp set can be viewed as a restricted case of the more general fuzzy set concept.

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.

critic
  پرژنکار، پرژنگر   
paržankâr, paržangar

Fr.: critique   

A person who judges, evaluates, or criticizes.

M.E., from M.Fr. critique, from L. criticus "a judge, literary critic," → critique.

Paržangar, from paržan present stem of paržanidan, "criticize", → critique, + -kâr, -gar suffixes of agent nouns, → -or.

critical
  پرژنی   
paržani

Fr.: critique   

1) Of or pertaining to → critics or → criticism.
2) Of, relating to, or being a state or level at which a significant change takes place (Dictionary.com).

critic; → -al.

critical angle
  زاویه‌ی ِ پرژنی   
zâviyeh-ye paržani

Fr.: angle critique   

Angle of incidence of light proceeding from a denser medium toward a thinner, at which grazing refraction occurs (angle of refraction 90°).

critical; → angle.

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.

critical density
  چگالی ِ پرژنی   
cagâli-ye paržani

Fr.: densité critique   

1) Cosmology: The average density of matter in the Universe that would be needed to eventually halt the → cosmic expansion. In a spatially → flat Universe, the critical density is expressed by ρc = (3c2/8πG)Ht2, where c is the → speed of light, G is the → gravitational constant, and Ht the → Hubble parameter. The critical density is currently 9.3 × 10-30g cm-3, about 6 hydrogen atoms per cubic meter (for H0 = 70 km s-1 Mpc-1).
2) In → gravitational lensing, the minimum density that would be needed by an intervening object to bend light rays. It is expressed by: Σ = (c2/4πG)(dos/doldls), where c is the speed of light, G is the gravitational constant, dos, dol, and dls represent angular diameter distances between the observer and the source, the observer and the lens, and the lens and the source respectively. It has units of mass per unit solid angle.
3) Radiative processes: The density at which the collisional → de-excitation rate equals the → radiative transition rate. The critical density for level j is given by: nc = Σi < j Aji = Σi ≠ j qji, where Aji is the → Einstein coefficient of → spontaneous emission and qji is the rate for collisional de-excitation of → energy level j, summed over all possible processes. This expression often simplifies to the ratio of two numbers, since in many cases there is a single important path for emission and a dominant collisional de-excitation process. In the low density limit the → emissivity is proportional to the product Ne (electron density) x Ni (ion density), whereas for densities exceeding the critical density, the emissivity is proportional to Ni. Thus, line emission in a nebula occurs most efficiently near the critical density.

critical; → density.

critical mass
  جرم ِ پرژنی   
jerm-e paržani

Fr.: masse critique   

Of a fissile material (235U or 239Pu), the minimum mass needed for a sustained nuclear chain reaction, as in an atomic bomb.

critical; → mass.

critical metallicity
  فلزیگی ِ پرژنی   
felezigi-ye paržani

Fr.: métallicité critique   

The → metallicity of a → star-forming  → molecular cloud when → cooling → rates by → metals dominate the → gravitational  → heating during → protostellar collapse. The minimum → Jeans mass achieved by gravitational → fragmentation depends on the presence/absence of → coolants in the cloud. Since cooling rate in metal lines is more efficient than in primordial molecular lines (H2 and HD), metals favor fragmentation in gas and formation of → low-mass stars.

critical; → metallicity.

critical opalescence
  اپالستی ِ پرژنی   
opâlesti-ye paržani

Fr.: opalescence critique   

The strong → scattering that occurs in a fluid near the → critical point. Large density fluctuations bring about inhomogeneities of all sizes. This results in the scattering of light at all wavelengths giving a milky appearance to the fluid.

critical; → opalescence.

critical velocity
  تندای ِ پرژنی   
tondâ-ye paržani

Fr.: vitesse critique   

1) Velocity of → fluid through a pipe at which the motion changes from → laminar to → turbulent flow.
2) Same as → break-up velocity.

critical; → velocity.

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