aberrational day number
šomâre-ye ruz-e birâheši
Fr.: nombre de jours d'aberration
A → Besselian day number denoted by C or D.
apparent sidereal day
ruz-e axtari-ye padidâr
Fr.: jour sidéral apparent
apparent solar day
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.
Besselian day number
šomâre-ye ruz-e Besseli
ruz-e gâhšomâri, ~ gâhmâri
Fr.: jour du calendrier
A period of 24 hours, from one midnight to the following midnight.
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.
Fr.: météore de jour
daylight saving time
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 vaqt
Fr.: temps de jour
The time interval when the Sun is above the horizon for a given position.
Ruzhangâm, from ruz→ day + 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."
ruz-e andargâh (#), ~ tarufté (#), ~ dozidé (#)
Fr.: jour épagomène
Same as → epagomena.
Fr.: jour des éphémérides
86,400 → ephemeris seconds.
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.
Fr.: effet Faraday
Same as → Faraday rotation.
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.
Faraday's law of induction
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.
Greenwich sidereal day number
šomâre-ye ruz-e axtari-ye Greenwich
Fr.: nombre du jour sidéral de Greenwich
The integral part of the → Greenwich sidereal date.
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.
1) Sepantruz, from sepant "holy,"
→ heiligenschein, + ruz, → day.
ruz-e žulian (#)
Fr.: jour julien
Same as → Julian date.
Fr.: jour intercalaire
The extra day added to a solar calendar (e.g. Gregorian, Iranian) in a leap year.
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).