An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1234
  کیهان‌شناختی، کیهان‌شناسیک   
keyhânšenâxti, keyhânšenâsik

Fr.: cosmologique   

Pertaining or relating to → cosmology.

cosmology; → -al.

cosmological constant
  پایای ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
pâyâ-ye keyhânšenâsik, ~ keyhânšenâxti

Fr.: constante cosmologique   

A term introduced by Einstein into his gravitational → field equations in order to allow a solution corresponding to a → static Universe. The cosmological constant is physically interpreted as due to the → vacuum energy of quantized fields. See also → dark energy.

cosmological; → constant.

cosmological constant problem
  پراسه‌ی ِ پایای ِ کیهانشناختی   
parâse-ye pâyâ-ye keyhânšenâxti

Fr.: problème de la constante cosmologique   

The impressive discrepancy of about 120 orders of magnitude between the theoretical value of the → cosmological constant and its observed value. → Quantum field theory interprets the cosmological constant as the density of the → vacuum energy. This density can be derived from the maximum energy at which the theory is valid, i.e. the → Planck energy scale (1018 GeV). The theoretical vacuum → energy density is (1018 GeV)4 = (1027 eV)4 = 10112 erg cm-3. On the other hand, the observed vacuum energy density is estimated to be about (10-3 eV)4 = 10-8 erg cm-3. There is, therefore, a discrepancy of about 120 orders of magnitude.

cosmological; → constant; → problem.

cosmological distance
  دورای ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
durâ-ye keyhânšenâsik, ~ keyhânšenâxti

Fr.: distance cosmologique   

The distance to a remote galaxy based on its redshift assuming that the redshift is caused by the → Doppler effect and reflects the general expansion of the Universe.

cosmological; → distance .

cosmological model
  مدل ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
model-e keyhânšenâsik, ~ keyhânšenâxti

Fr.: modèle cosmologique   

A mathematical description of the Universe, based on observation, which tries to explain its current aspect, and to describe its evolution during time.

cosmological; → model.

cosmological principle
  پروز ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
parvaz-e keyhânšenâsik, ~ keyhânšenâxti

Fr.: principe cosmologique   

The → hypothesis that on → large scales the → Universe is → isotropic and → homogeneous, that is, it appears the same at all places and, from any one place, looks the same in all directions. See also → perfect cosmological principle.

Introduced by E.A. Milne in 1933; → cosmological; → principle.

cosmological redshift
  سرخ کیب ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
sorxkib-e keyhânšenâsik, ~ keyhânšenâxti

Fr.: décalage vers le rouge cosmologique, redshift ~   

The → redshift of a remote object (galaxy, quasar, supenova) due to the expansion of the Universe.

cosmological; → redshift.

keyhânšenâsi (#)

Fr.: cosmologie   

The science of the origin, structure, and evolution of the Universe including the origin of galaxies, the chemical elements, and matter.

Cosmology, from → cosmo- + → -logy.

Keyhânšenâsi, from keyhân, → cosmos, + šenâsi, → -logy.

  کیهان نورد، فضا نورد   
keyhânnavard (#), fazânavard (#)

Fr.: cosmonaute, astronaute   

The Russian term for → astronaut.

Cosmonaut, from → cosmo- + naute, from Gk. nautes "sailor," from naus "ship" (cognate with Pers. nâv "ship," Av./O.Pers. *nāv-, O.Pers. nāviyā- "fleet," Skt. nau-, nava- "ship, boat," Gk. naus, neus, L. navis; PIE *nâu- "ship").

keyhân (#)

Fr.: cosmos   

Everything that exists anywhere; → outer space; → Universe.

M.E., from Gk. kosmos "orderly arrangement."

Keyhân "world," variants geyhân, jahân, giti "world, material world, time," Mid.Pers. gêhân, gêtig, Manichean Mid.Pers. gyh "world," Av. gaeθa- "being, world, matter, mankind", gaya- "life, manner of living," root gay- "to live" (present tense jiva-), O.Pers. gaiθā- "live-stock," cognate with Skt. jivah "alive, living," Gk. bios "life," L. vivus "living, alive," vita "life;" PIE base *gweie- "to live" (cf. O.E. cwic, "alive;" O.C.S. zivo "to live;" Lith. gyvas "living, alive;" O.Ir. bethu "life," bith "age;" Welsh byd "world"). The Persian terms zistan "to live," zendé "alive," zendegi "life," and jân "vital spirit, soul" belong to this family.

kotânžânt (#)

Fr.: cotangent   

The → tangent of the complement of an arc or angle; abbreviation cot. If θ is an → acute angle of a → right angle, cot θ = (adjacent side)/(opposite side).

co-; → tangent.

panbé (#)

Fr.: coton   

A soft, usually white fibrous substance like fine wool surrounding the seeds of various tropical and subtropical plants of the mallow family. It is extensively used in making threads, yarns, and fabrics.

M.E. coton, from O.Fr. coton, from O.It. cotone, from Ar. qutn (قطن), perhaps of Egyptian origin.

Panbé "cotton" (dialectal Lori pamma, Kurd. pemû, maybe Tajik, Afqân pakta, pakhta, bakhta, bakta), from Mid.Pers. pambag "cotton," pambagin "made of cotton," perhaps loaned in Gk. bombux "silk, any silk-like fine fiber;" L. bombyx "silk, cotton," L.L. bombax "cotton," hence O.Fr. bombace "cotton, cotton wadding," E. bombast "cotton wool; inflated language."

coudé focus
  کانون ِ آرنج‌وار   
kânun-e ârenjvâr, ~ kudé

Fr.: foyer coudé   

An optical system in which the beam of light from the primary mirror is reflected down through the instrument's polar axis by a path bent like an elbow. Since the focus remains fixed with respect to the earth, light can be analyzed with permanently installed instruments. In addition long focal lengths allow higher spectral dispersions.

From Fr. coudé "elbowed," from coude "elbow," L. cubitus; → focus.

Kânun, → focus; ârenj "elbow," variants âranj, âran, Mid.Pers. âranj, O.Pers. "cubit," Av. arəθnâ- "elbow," Skt. aratni- "elbow," Iranian stem aratan-, araθn-, borrowed from Iranian into General Slavic as aršin "ell" + -vâr suffix denoting "in the manner of; resembling."

Couette flow
  تچان ِ کویءت   
tacân-e Couette

Fr.: écoulement de Couette   

In fluid dynamics, the motion of an → incompressible → laminar flow passing between two parallel plates, when the upper plate is moving with some velocity while the lower one is stationary. The flow is driven owing to the fluid → viscosity and the applied pressure gradient parallel to the plates. See also → Taylor-Couette flow.

Named after Maurice Marie Alfred Couette (1858-1943), a French physicist who dealt mainly with fluid mechanics; → flow

Couette viscometer
  وشک‌سنج ِ کویءت   
vošksanj-e Couette

Fr.: viscosimètre de Couette   

A device consisting of two vertical coaxial cylinders and a fluid filling the volume between the cylinders and used for measuring the viscosity of the fluid. The inner cylinder is stationary while the outer cylinder rotates. The amount of shear stress produced owing to rotation is directly proportional to the viscosity of the fluid.

Couette flow; → viscometer.

Couette-Taylor flow
  تچان ِ کویءت-تیلر   
tacân-e Couette-Taylor

Fr.: écoulement de Couette-Taylor   

In fluid mechanics, the motion of a fluid between two concentric cylinders when one or both of the cylinders rotate.

Couette flow; Geoffrey Ingram Taylor (1886-1975), British physicist; → flow.

coulomb (C)
coulomb (#)

Fr.: coulomb   

The unit of → electric charge in the → mks system, equal to the quantity of charge transferred in one second by a steady current of one → ampere. One coulomb represents a charge of approximately 6.241 506 × 1018 → electrons. Compared with the charge unit in the → cgs system, 1 C = 2.998 × 109 → esu.

Named after the French physicist Charles Augustin de Coulomb (1736-1806), who pioneered research into magnetism and electricity.

Coulomb barrier
  ورغه‌ی ِ کولن   
varqe-ye Coulomb (#)

Fr.: barrière de Coulomb   

The energy barrier due to electrostatic interaction that two nuclei (for example two protons) need to overcome so they can get close enough to undergo nuclear fusion (to form a helium).

coulomb; → barrier.

Coulomb collision
  همکوبش ِ کولن   
hamkubeš-e Coulomb

Fr.: collision coulombienne   

A particle → collision where the dominant force is described by → Coulomb's law. The collision results in deflections of the particles away from their initial paths.

coulomb; → collision.

Coulomb energy
  کاروژ ِ کولن   
kâruž-e Coulomb

Fr.: énergie coulombienne   

The → potential energy from which derives the repulsive electrostatic force between two → charged particles. For example, the Coulomb energy between two protons is e2/r ~ 0.5 MeV, which is small compared with the average → binding energy per particle (~ 8 Mev). However the Coulomb repulsion becomes important for heavy nuclei. The total Coulomb energy of a nucleus is given by: (3/5) Z(Z - 1)e2/R, where Z is the → atomic number, e the charge, and R the nuclear radius. Since R ∝ A1/3 and Z is roughly proportional to A, the Coulomb energy is roughly proportional to A5/3. On the other hand, the total binding energy is proportional to A, which means that the relative importance of the repulsive electrostatic energy increases with increasing mass number as A2/3.

coulomb; → energy.

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