An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 104 Search : time
Terrestrial Dynamical Time
  زمان ِ توانیک ِ زمینی   
zamân-e tavânik-e zamini

Fr.: temps dynamique terrestre   

A uniform atomic time scale for apparent geocentric ephemerides defined by a 1979 IAU resolution, which replaced Ephemeris Time. TDT is independent of the variable rotation of the Earth, and the length of the tropical year is defined in days of 86,400 seconds of international atomic time. In 1991 it was replaced by Terrestrial Time.

terrestrial; → dynamical; → time.

Terrestrial Time
  زمان ِ زمینی   
zamân-e zimini

Fr.: temps terrestre   

The modern astronomical standard for the passage of time on the surface of the Earth. It is the → coordinate time scale consistent with the theory of general relativity for an observer on the surface of the Earth. TT was renamed from Terrestrial Dynamical Time (TDT) in 1991. The fundamental unit of TT is the day of 86,400 SI seconds. It is related to the International Atomic Time by the relation: TDT = TAI + 32.184 sec.

terrestrial; → time.

test time
  زمان ِ آزمون   
zamân-e âzmun

Fr.: temps de test   

That part of the working time of a telescope devoted to tests of coupled instruments or the telescope itself.

test; → time.

  زمان، گاه، وقت (وخت)، تامن   
zamân (#), gâh (#), vaqt (vaxt) (#), tâmen

Fr.: temps   

1) A non-spatial sequential relation in which events occur in apparently irreversible succession from the past through the present to the future. → time's arrow.
2) A limited period or interval, as between two successive events.

M.E.; O.E. tima "limited space of time," from P.Gmc. *timon "time" (cf. O.N. timi "time," Swed. timme "an hour"), akin to L. tempus (genitive temporis) "time" (Fr. temps, Sp. tiempo, It. tempo); maybe related to Pers. Tabari tum, tomon, temen "time;" Aftari ton "time."

Zamân "time," from Mid.Pers. zamân, jamân "time," zamânak "period, epoch;" loaned into Aramaic and Ar., loaned into Arm. žam, žamanak "time;" prefixed Sogdian nγm "time, moment, hour;" Proto-Iranian *gām- "to go, to come;" cf. Av. gam- "to come; to go," jamaiti "goes;" O.Pers. gam- "to come; to go;" Mod./Mid.Pers. gâm "step, pace," âmadan "to come;" cf. 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 base *gwem- "to go, come."
Gâh "time; place;" Mid.Pers. gâh, gâs "time;" O.Pers. gāθu-; Av. gātav-, gātu- "place, throne, spot;" cf. Skt. gâtu- "going, motion; free space for moving; place of abode;" PIE *gwem- "to go, come."
Vaqt, pronounced vaxt (وخت), but written vaqt (وقت), is a Pers. word meaning "portion (of time)". Its variants and related words in Mod./Mid.Pers. are: baxt "what is allotted, 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 allotted (luck, fortune)," baxədra- "part, portion," baγa- "master, god," O.Pers. bāji- "tribute, tax," cf. Skt. bhaj- "to share, divide, distribute, apportion," bhájati "divides," bhakta- "allotted; 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."
Tâmen "time," from Tabari temen, tumun, tum "time," pərtəmən "long time;" Lori temen "age, length of life;" Aftari ton; Lâri, Garâši taim "time span" (related to L. tempus?).

time allocation
  تسک ِ زمان، ~ وقت   
tesk-e zamân, ~ vaqt

Fr.: attribution de temps de télescope   

The assignment of telescope time by an expert panel to proposals after evaluating the merits of the observation projects.

time; → allocation.

time constant
  پایای ِ زمانی   
pâyâ-ye zamâni

Fr.: constante de temps   

Th speed of response of a detector, usually measured as 1/(2πν), where ν is the chopping frequency at which the responsivity fails to 1/√2 of its maximum value.

time; → constant.

time delay
derang (#)

Fr.: retard   

1) The amount of time required for a → signal to travel from one point to another in an → electric circuit.
2) → gravitational lensing time delay.

time; → delay.

time delay distance
  اپست ِ درنگ ِ زمانی   
apest-e derang-e zamâni


A distance-like quantity derived from → gravitational lensing time delay. It is given by a combination of three angular diameter distances in a strong lens system: DΔt = (1 + zL)[DA(EL)DA(ES) / DA(LS)], where zL is the → redshift of the → gravitational lens, while DA(EL), DA(ES), and DA(LS) are the angular diameter distances from the Earth to the lens, from the Earth to the source, and from the lens to the source, respectively. As each of the distance is proportional to the inverse of H0, DΔt is proportional to 1/H0.

time; → delay; → distance.

time dilation
  فراخش ِ زمان   
farâeš-e zamân

Fr.: dilatation du temps   

A phenomenon related to special and general relativity.
1) In → special relativity, the apparent shortening of time that occurs at speeds approaching that of light. A clock moving relative to a stationary observer will appear to slow down by a factor √(1- v2/c2), where v is the velocity and c the speed of light. → twins paradox.
2) In → general relativity, a clock in a stronger gravitational field runs more slowly. The dilation factor is given by: √(1- 2GM/rc2), where G is the gravitational constant, M the mass of the object creating the gravitational field, r a radial coordinate of the observer, which is analogous to the classical distance from the center of the object, and c the speed of light.

time; dilation, verbal noun of dilate, from M.E. dilaten, from O.Fr. dilater, from L. dilatare "make wider, enlarge," from → dis- "apart" + latus "wide."

Farâxeš, → dilation; zamân, → time.

time of periapsis passage
  زمان ِ گذر از پیراهباک   
zamân-e gozar az pirâhabâk

Fr.: temps de passage au périapse   

One of the → orbital elements, the time when the → secondary body reaches → periapsis.

time; → periapsis; → passage.

time resolution
  واگشود ِ زمانی   
vâgošud-e zamâni

Fr.: résolution temporelle   

Same → temporal resolution.

time; → resolution.

time reversal
  وارونش ِ زمان   
vâruneš-e zamân

Fr.: renversement du temps   

A transformation operating on time in the equations of motion of a dynamical system in which t is replaced by -t.

time; → reversal.

time scale
  مرپل ِ زمان   
marpel-e zamân

Fr.: échelle de temps   

A measure of duration of a specific process, such as → crossing time, → dynamical time scale, → evolutionary time scale, → Kelvin-Helmholtz time scale, → nuclear time scale, → photon escape time, → relaxation time, → star formation time scale.

time; → scale.

time series
  سری ِ زمانی   
seri-ye zamâni

Fr.: série temporelle   

A → sequence of values of a → variable in successive time order, usually at fixed intervals of time.

time; → series.

time zone
  زنار ِ زمان، زمان-زنار   
zonâr-e zamân, zamân-zonâr

Fr.: fuseau horaire   

Any of the 24 zones on the Earth surface delimited by → meridians at approximately 15° intervals. In each time zone a common standard time is used, and the time is one hour earlier than the zone immediately to the east.

time; → zone.

time's arrow
  پیکان ِ زمان   
peykân-e zamân

Fr.: flèche du temps   

The sequence of all natural processes in which the → entropy increases. In other words, the fact that these processes all move in one direction in time and are → irreversible. The past is distinctly different from the future; things always grow older, never younger.

time; arrow, M.E. arewe, arwe, from O.E. arwan, earh "arrow," from P.Gmc. *arkhwo (cf. Goth. arhwanza), from PIE base *arku- "bow and/or arrow," source of Latin arcus, → arc.

Peykân "arrow," → Sagitta; zamân, → time.


Fr.: genre temps   

Of, pertaining to, or describing an → event belonging to the interior of the → light cone.

time; → like.

timelike interval
  اندروار ِ زمانسان   
andarvâr-e zamânsân

Fr.: intervalle genre temps   

The → space-time interval between two → events if it is real, i.e. ds2 > 0.

timelike; → interval.

zamân-šomâr (#)

Fr.: appareil horaire   

Any mechanical, electric, or electronic device, such as a clock or watch, designed to measure and display the passage of time.

time; → piece.

Zamân-šomâr, literally "time counter," from zamân, → time, + šomâr "counter," from šomârdan "to count," from Mid.Pers. ôšmârtan, ôšmurtan "to reckon, calculate, enumerate, account for," from Av. base (š)mar- "to have in mind, remember, recall," pati-šmar- "to recall; to long for," hišmar-, cf. Skt. smar- "to remember, become aware," smarati "he remembers," L. memor, memoria, Gk. mermera "care," merimna "anxious thought, sorrow," martyr "witness."

transit time
  زمان ِ گذر   
zamân-e gozar

Fr.: temps de passage   

The time interval between the release of an electron at the photocathode and the arrival of an electron at the anode. Transit time is not a single-valued quantity, but has a bell-shaped distribution.

transit; → time.

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