An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 30 Search : day
aberrational day number
  شماره‌ی ِ روز ِ بیراهشی   
šomâre-ye ruz-e birâheši

Fr.: nombre de jours d'aberration   

A → Besselian day number denoted by C or D.

aberration; → -al; → day; → number.

apparent sidereal day
  روز ِ اختری ِ پدیدار   
ruz-e axtari-ye padidâr

Fr.: jour sidéral apparent   

The time interval between two successive → upper transits of the → true equinox of date.

apparent; → sidereal; → day.

apparent solar day
  روز ِ خورشیدی ِ پدیدار   
ruz-e xoršidi-ye padidâr

Fr.: jour solaire vrai   

The duration of one rotation of the Earth on its axis (→ Earth's rotation), with respect to the → apparent Sun. It is measured by successive transits of the apparent Sun over the lower branch of a → meridian.

apparent; → solar day.

Besselian day number
  شماره‌ی ِ روز ِ بسلی   
šomâre-ye ruz-e Besseli


Any of the five quantities denoted by A, B, C, D, and E used in conjunction with → Besselian star constants for the reduction of a star's → mean catalog place to its → apparent place.

Besselian; → day; → number.

calendar day
  روز ِ گاهشماری، ~ گاهماری   
ruz-e gâhšomâri, ~ gâhmâri

Fr.: jour du calendrier   

A period of 24 hours, from one midnight to the following midnight.

calendar; → day.

ruz (#)

Fr.: jour   

The length of time it takes Earth (or a planet) to rotate once on its axis relative to some external reference. The day is measured in several ways, depending on this reference, → sidereal day; → solar day; → mean solar day.

M.E., from O.E. dæg (cf. Ger. Tag, Swedish and Danish dag "day"), from PIE base *dhegh- "to burn." Not related to L. dies "day" (from *dyeu- "to shine," → diurnal), but rather to Av. dag- "to burn," dažaiti "burns," Mod.Pers. dâq "hot," Skt. dah- "to burn," dáhati, Gk. tephra "ash," L. fovere "to boil," Albanian djeg "to burn," Russ. žeč' "to burn," Lith. dagas "hot season," degti "to burn," O.Prus. dagis "summer."

Ruz "day," from Mid.Pers. rôc, O.Pers. raucah-, Av. raocah- "light, luminous; daylight," Skt. roka- "brightness, light," cognate with Gk. leukos "white, clear," L. lux "light" (also lumen, luna), PIE base *leuk- "light, brightness". The Persian words rowšan "bright, clear," foruq "light," and afruxtan "to light, kindle" also belong to this family, as well as the E. light, Ger. Licht, and Fr. lumière.

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."
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."

ruzhangâm (#)

Fr.: temps de jour   

The time interval when the Sun is above the horizon for a given position.

day; → time.

Ruzhangâm, from ruzday + hangâm "time, hour, season," Mid.Pers. hangâm "time, epoch, season," Av. ham-gam- "to meet together," from ham- "together," → com- + gam- "to come; to go," jamaiti "goes," O.Pers. gam- "to come; to go," Mod.Pers. âmadan "to come," Skt. gamati "goes," Gk. bainein "to go, walk, step," L. venire "to come," Tocharian A käm- "to come," O.H.G. queman "to come," E. come; PIE root *gwem- "to go, come."

epagomenal day
  روز ِ اندرگاه، ~ تروفته، ~ دزدیده   
ruz-e andargâh (#), ~ tarufté (#), ~ dozidé (#)

Fr.: jour épagomène   

Same as → epagomena.

epagomena + → -al; → day.

ephemeris day
  روز ِ روزیجی   
ruz-e ruziji

Fr.: jour des éphémérides   

86,400 → ephemeris seconds.

ephemeris; → day.

Faraday cage
  قفس ِ فارادی   
qafas-e Faraday

Fr.: cage de Faraday   

An enclosure made of conducting material, such as wire mesh or metal plates, that shields what it contains from external electric fields. According to → Gauss's theorem, the electric field inside a hollow conductor is nil. In order to demonstrate this, Faraday, in 1836, made a large box covered with wire mesh, and went inside it himself with an → electroscope. Powerful charges were applied to the outside of the box, but he detected no effect inside the cage.

farad; → cage.

Faraday effect
  اسکر ِ فارادی   
oskar-e Faraday

Fr.: effet Faraday   

Same as → Faraday rotation.

farad; → effect.

Faraday rotation
  چرخش ِ فارادی   
carxeš-e Faraday (#)

Fr.: rotation Faraday   

The rotation of the plane of → polarization experienced by a beam of → linearly polarized radiation when the radiation passes through a material containing a magnetic field with a component in the direction of propagation. This effect occurs in → H II regions in which a magnetic field causes a change in the polarized waves passing through. Same as → Faraday effect.

farad; → rotation.

Faraday's law of induction
  قانون ِ درهازش ِ فارادی   
qânun-e darhazeš-e Faraday

Fr.: loi d'induction de Faraday   

The induced → electromotive force in a circuit is equal in magnitude and opposite in sign to the rate of change of the → magnetic flux through the surface bounded by the circuit. Mathematically, it is expressed as: ∇ x E = -∂B/∂t, which is one of the four → Maxwell's equations.

farad; → law; → induction.

Greenwich sidereal day number
  شماره‌ی ِ روز ِ اختری ِ گرینویچ   
šomâre-ye ruz-e axtari-ye Greenwich

Fr.: nombre du jour sidéral de Greenwich   

The integral part of the → Greenwich sidereal date.

Greenwich; → sidereal; → day; → number.

  ۱) سپنت‌روز؛ ۲) آسودروز؛ ۳) آسودگان   
1) sepantruz; 2) âsudruz; 3) âsudgân

Fr.: 1); 2) férié; 3) vacances   

1) A day fixed by law or custom on which ordinary business is suspended in commemoration of some event or in honor of some person.
2) Any day of exemption from work.
3) (in plural form) A period of cessation from work or one of recreation; vacation.

O.E. haligdæg, from halig "holy," → heiligenschein, + dæg, → day.

1) Sepantruz, from sepant "holy," → heiligenschein, + ruz, → day.
2) Âsudruz, from âsud, âsudan "to rest, repose," from Mid.Pers. âsutan, Av. ā- + saē- (saii-) "to lie down, go to sleep;" + ruz, → day.
3) Âsudgân, from âsud, as before, + -gân suffix forming plurals.

Julian day
  روز ِ ژولی‌ین   
ruz-e žulian (#)

Fr.: jour julien   

Same as → Julian date.

Julian date; → day.

leap day
  روز ِ اندرهلی   
ruz-e andarheli

Fr.: jour intercalaire   

The extra day added to a solar calendar (e.g. Gregorian, Iranian) in a leap year.

leap; → day.

lunar day
  روز ِ مانگ، ~ ِ مانگی   
ruz-e mâng, ~ mângi

Fr.: jour lunaire   

The interval between two successive sunrises for an observer standing on the Moon. This is not the rotational period of the Moon, because the Moon-Earth system has moved round the Sun during that period. It is equal to the length of a → synodic month (29.5306 days).

lunar; → day.

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