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: 71 Search : light
aberration of light
  بیراهش ِ نور   
birâheš-e nur

Fr.: aberration de la lumière   

aberration of starlight

aberration; → light.

aberration of starlight
  بیراهش ِ نور ِ ستاره   
birâheš-e nur-e setâré

Fr.: aberration de la lumière d'étoile   

An apparent displacement in the observed position of a star. It is a result of the finite speed of light combined with the relative motion of the Earth through space. Suppose that you walk through a vertically falling rain with an umbrella over your head. The faster you walk, the further you must lower the umbrella in front of yourself to prevent the rain from striking your face. For starlight to enter a telescope, a similar phenomenon must occur, because the Earth is in motion. The telescope must be tilted in the direction of motion by an angle: tan θ =(v/c), where v the Earth velocity and c the speed of light. The aberration of starlight was discovered by the English astronomer James Bradley (1693-1762) in 1729 by observing → Gamma Draconis. The tilt angle is θ = 20''.50, from which the Earth's orbital speed, 29.80 km s-1, can be deduced, using the above equation. See also → annual aberration; → diurnal aberration; → secular aberration. → Special relativity modifies the classical formula for aberration, predicting results which differ substantially from those of classical physics for objects moving at a substantial fraction of the speed of light; → relativistic aberration.

aberration; → star; → light.

arc of light
  کمان ِ نور   
kamân-e nur

Fr.: arc de lumière   

The apparent angular separation (→ elongation) between the → centers of the → Sun and the → Moon.

arc; → light.

artificial light
  نور ِ ساختگی   
nur-e sâxtegi

Fr.: lumière artificielle   

Any light other than that which proceeds from the heavenly bodies.

artificial; → light.

ashen light
  نور ِ خاکستری   
nur-e xâkestari (#)

Fr.: lumière cendrée   

The faint glow occasionally observed on the unlit area of Venus in its crescent phase. Its cause is not known with certainty, but it might result from bombardment of atmospheric atoms and molecules by energetic particles and radiation, as with terrestrial airglow.

ash; → light.

astronomical twilight
  نیمتاب ِ اخترشناسیک، ~ اخترشناختی   
nimtâb-e axtaršenâsik, ~ axtarsnâxti

Fr.: crépuscule astronomique   

The time between sunset or sunrise and the moment when the Sun's center lies 18° below the horizon. → civil twilight.

astronomical; → twilight.

backscattered light
  نور ِ پس-پراکنده   
nur-e pas-parâkandé

Fr.: lumière rétrodiffusée   

The light that has undergone → backscattering.

backscatter; → backscattering.

ball lightning
  گوی ِ آذرخش   
gu-ye âzaraxš (#)

Fr.: foudre en bulle   

A rare form of lightning occurring as a bright red globe observed floating or moving through the atmosphere close to the ground. It usually is seen shortly before or after, or during, a → thunderstorm. Its duration varies from a few seconds to a few minutes. See also → Saint Elmo's fire.

ball; → lightning.

beam of light
  تابه‌ی ِ نور   
tâbe-ye nur (#)

Fr.: faisceau lumineux   

A relatively large bundle of → rays of light. See also → pencil of light.

beam; → light.

catoptric light
  نور ِ بازتابیک   
nur-e bâztâbik

Fr.: lumière catoptrique   

Light that is reflected from a curved surface mirror.

catoprtics; → light.

circularly polarized light
  نور ِ قطبیده‌ی ِ دایره‌ای   
nur-e qotbide-ye dâyere-yi

Fr.: lumière polarisée circulairement   

Light exhibiting → circular polarization.

circular; → polarized; → light.

civil twilight
  نیمتاب ِ شارین   
nimtâb-e šârin

Fr.: crépuscule civil   

The time between sunset or sunrise and the moment when the Sun's center lies 6° below the horizon. → astronomical twilight.

civil; → twilight.

coasting flight
  پرواز ِ رهارو   
parvâz-e rahârow

Fr.: vol d'accostage   

The unpowered flight of a spacecraft or missile after propulsion cutoff or between the burnout of one stage and the ignition of the next.

Coasting, verbal adjective from → coast; → flight.

coherent light
  نور ِ همدوس   
nur-e hamdus (#)

Fr.: lumière cohérente   

Light waves that have the same wavelength and possess a fixed phase relationship, as in a laser.

coherent; → light.

corpuscular theory of light
  نگره‌ی ِ کرپولی ِ نور   
negare-ye karpuli-ye nur

Fr.: théorie corpusculaire de la lumière   

Newton's theory according to which light is made up of point-like particles without any mass. It failed to explains several phenomena: simultaneous reflection and refraction at a semi-transparent boundary, interference, diffraction and polarization. Moreover, it requested that the speed of light be greater in a denser medium than in a rarer medium; this prediction is contrary to experimental results. In 1924 Louis de Broglie postulated that matter has not only a corpuscular nature but also a wave nature, and subsequent experiments confirmed de Broglie's model.

Corpuscular, adj. from → corpuscle; → theory, → light.

daylight meteor
  شهاب ِ روز   
šahâb-e ruz

Fr.: météore de jour   

A → meteor detected using → radar techniques during daylight or when skies are cloudy.

day; → light; → meteor.

daylight saving time
  وخت ِ نور‌اندوزی، وقت ِ ~   
vaxt-e nur anduzi, vaqt-e ~

Fr.: heure d'été   

A system of adjusting the official local time in some countries in order to provide a better match between the hours of daylight and the active hours of work and school. The "saved" daylight is spent on evening activities which get more daylight, rather than being "wasted" while people sleep past dawn. Although known also as summer time, it includes the spring season and nearly half of autumn.

day; → light; saving, from save, from O.Fr. sauver, from L.L. salvare "to secure," from L. salvus "safe," PIE *solwos, from base *sol- "whole" (cf. O.Pers. haruva-, Av. haurva- "whole, intact," Mod.Pers. har "every, all; any," Skt. sarva- "whole, entire," Gk. holos "whole"); → time.

Vaxt, written vaqtوقت but pronounced vaxtوخت, is a Pers. word meaning "portion (of time)". Its variants and related words in Mod./Mid.Pers. are: baxt "what is alloted, fate, fortune," baxš "portion, part, division," baxšidan, baxtan "to divide, distribute, grant," Av. base bag- "to attribute, allot, distribute," baxš- "to apportion, divide, give to," baxta- "what is alloted (luck, fortune)," baxədra- "part, portion," baγa- "master, god," O.Pers. bāji- "tribute, tax," cf. Skt. bhaj- "to share, divide, distribute, apportion," bhájati "divides," bhakta- "alloted; occupied with; a share; food or a meal, time of eating?," Gk. phagein "to eat (to have a share of food)"; PIE base *bhag- "to share out, apportion."
nurlight.
anduzi, verbal noun of anduxtan "to save; acquire, gather," from Mid.Pers. handôxtan, handôz- "to gain, acquire, amass," from *ham-tuj-, from ham- "together," → com- + *tuj- "to save, gather, (re)pay," cf. Skt. tuj- "to promote, be strong, move quickly."

deflection of light
  واچفت ِ نور   
vâcaft-e nur

Fr.: déflexion de la lumière   

The bending of a light ray under the gravitational effect of a massive body. → deflection angle.

deflection; → light.

diffuse galactic light
  نور ِ کهکشانی ِ پخشیده   
nur-e kahkašâni-ye paxšidé

Fr.: lumière galactique diffuse   

A minor component of galactic light resulting from the diffusion of starlight by → interstellar dust near the → galactic plane.

diffuse; → galactic; → light.

Drummond light
  نور ِ درامن   
nur-e Drummond

Fr.: lumière de Drummond   

A very brilliant white light which is the ignited flame of a mixture of oxygen and hydrogen projected against a block of calcium oxide (lime). Also called limelight. First working version produced by Lieutenant of the Royal Engineers, upon the Ordnance Trigonometrical Survey of Ireland (1826). It was used at night as a substitute for solar light. It was first employed in a theater in 1837 and was in wide use by the 1860s, among which in photography.

Named after Scottish engineer Thomas Drummond (1797-1840); → light.

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