An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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tidal force
  نیروی ِ کشندی   
niru-ye kešandi (#)

Fr.: force de marée   

The → gravitational force exerted on an extended body as a result of the difference in the strength of gravity between near and far parts of the body. The ocean tides on Earth result from the varying gravitational force of the Moon exerted on the Earth's oceans closest and farthest from the Moon. Tidal force, which is the → gradient of the gravitational force, varies as 1/r3. More specifically, Ftidal = dF/dr = (2GMm)/r3, where M is mass of the → primary body, m is mass of the → secondary body, r is distance between objects, and G the → gravitational constant. The total tidal force experienced across a body is equal to the tidal force (force per unit distance) multiplied by the diameter of that body: Ftt = Ftidal x 2R (provided that radius R is much smaller than r). It is obvious that the tidal force experienced by Earth at Moon's → perigee is larger than that at the → apogee. If the tidal force is stronger than a body's cohesiveness, the body will be disrupted. The minimum distance that a secondary comes to a primary before it is shattered by tidal force is called its → Roche limit. Tidal forces create → tidal heating.

tidal; → force.

tidal friction
  مالش ِ کشندی   
mâleš-e kešandi

Fr.: friction de marées   

The → friction exerted on a → primary body (Earth) because of the → phase lag between the → tides and the → gravitational attraction of the → secondary body (Moon). The Earth's → rotation is faster than the Moon's orbital motion; therefore the Earth's → tidal bulges lead the Moon on its orbit. This has two important effects: The Earth is being pulled slightly "back" from its sense of rotation. So the Earth's rotation slows (by about 1 second every 50,000 years). Moreover, the Moon is being pulled slightly "forward" on its orbit. So it is harder for the Earth to hold it in place, and it moves further away from the Earth (by about 3-4 cm per yr). Tidal friction tends to synchronize the rotation period of a close-in companion with the period of its orbital motion around the primary. → tidal coupling.

tidal; → friction.

tidal heating
  گرمش ِ کشندی   
garmeš-e kešandi

Fr.: chauffage par marées   

The heating of the → interior of a → planet or → satellite due to the → friction caused by → tidal forces. For example, the huge tidal forces by → Jupiter heat its close satellite → Io, making it a seismically very active body.

tidal; → heating.

tidal locking
  قفل‌شد ِ کشندی   
qoflšod-e kešandi

Fr.: verrouillage gravitationnel   

The process whereby the → rotation period of a → primary body becomes identical to the → orbital period of a → secondary body. Tidal locking results from → tidal braking and leads to → synchronous rotation.

tidal; → lock; → -ing.

tidal radius
  شعاع ِ کشندی   
šo'â'-e kešandi

Fr.: rayon de marée   

Same as → Roche limit.

tidal; → radius.

tidal stretching
  درگش ِ کشندی   
dargeš-e kešandi

Fr.: étirement de marée   

The stretching of an object under → tidal force. Tidal stretching results from a difference in the gravitational pull felt on two sides of a body. It is proportional to the inverse cube of the distance to the source of gravity (1/r3). As a consequence, nearby objects, even small ones like the Moon, raise high tides, whereas distant giants like Jupiter do not produce much of an effect.

tidal; → stretching.

tidal stripping
  لُختانش ِ کشندی   
loxtâneš-e kešandi

Fr.: balayage par effet de marées   

The phenomenon whereby gas and stars are ripped out from a gravitationally → bound system, such as a galaxy or → globular cluster, by the action of → tidal forces from an external, more massive object. See also → ram pressure stripping.

tidal; → strip.

tidal tail
  دنباله‌ی ِ کشندی   
donbâle-ye kešandi

Fr.: queue de marée   

A long stream of stars and gas, often in the form of a spectacular tail, thrown off a galaxy when it collides with another galaxy. → interacting galaxies; → merger. Two tidal tails form in each galaxy, and they are more spectacular when the masses of the two galaxies are comparable, and when their relative orbit is in the same sense as the rotation inside each spiral galaxy.

tidal; → tail.

tidally locked
  کشندانه قفل   
kešandâné qofl

Fr.:   

The description of a → system of two bodies undergoing → tidal locking.

tidal; → -ly; → lock.

tidally stripped
  کشندانه لُختانیده   
kešandâne loxtânide

Fr.: balayé par effet de marées   

Describing a → stellar system that has undergone → tidal stripping.

tidal; → -ly; → strip.

tide
  کشند   
kešand (#)

Fr.: marée   

1) The periodic rising and falling of the waters of the ocean and its inlets. The tides result from the → gravitational attraction of the → Moon and → Sun acting upon the rotating → Earth. See also: → ebb tide, → high tide, → low tide, → neap tide, → spring tide, → tidal braking, → tidal bulge, → tidal capture, → tidal coupling, → tidal current, → tidal disruption, → tidal force, → tidal friction, → tidal heating, → tidal locking, → tidal radius, → tidal stretching.
2) → tidal force.

M.E.; O.E. tid "time, hour" (cf. O.S. tid, Du. tijd, O.H.G. zit, Ger. Zeit "time").

Kešand, from Mod./Mid.Pers. kešidan/kašidan "to draw, protract, trail, drag, carry," dialectal Yaqnavi xaš "to draw," Qomi xaš "streak, stria, mark," Lori kerr "line;" Av. karš- "to draw; to plow," karša- "furrow;" Proto-Iranian *kerš-/*xrah- "to draw, plow;" cf. Skt. kars-, kársati "to pull, drag, plow;" Gk. pelo, pelomai "to move, to bustle;" PIE base kwels- "to plow."

tight
  تنگ   
tang (#)

Fr.: serré   

Firmly or closely fixed in place. → compact.

M.E. thight, from O.N. thettr "watertight, close in texture, solid" (cf. second element in O.E. metethiht "stout from eating;" M.H.G. dihte "dense, thick," Ger. dicht "dense, tight," O.H.G. gidigan, Ger. gediegen "genuine, solid, worthy"), from PIE base *tenk- "to become firm, curdle, thicken;" cf. Ir. techt "curdled, coagulated," Lith. tankus "close, tight;" cognate with Pers. tang "tight," as below.

Tang "tight; narrow, straight; tight," also "horse girth, a strap for fastening a load" (Mid.Pers. tang "tight, narrow"), tanjidan "to squeeze, press, pull together;" cf. Skt. tanákti "draws together, contracts;" cognate with E. tight, as above; PIE base *tenk- "to become firm, curdle, thicken."

tight star cluster
  خوشه‌ی ِ ستاره‌ای ِ تنگ   
xuše-ye setâreyi-ye tang

Fr.: amas stellaire serré   

A cluster of stars in which members are closely situated so that high resolution observations are required to distinguish them individually.

tight; → star cluster.

tightly bound binary star system
  راژمان ِ ستاره‌ای ِ درین ِ تنگ بندیده   
râžmân-e setâre-yi-ye dorin-e tang bandide

Fr.: système d'étoiles binaire très lié   

close binary star.

tight; → bound system; → binary star.

tilt
  گرا   
gerâ

Fr.: inclinaison   

Optics: A deviation in the propagation direction of a beam of light. Tilt quantizes the average slope in both the X and Y directions of a → wavefront or phase profile across the pupil of an optical system.

M.E. tylten "to upset, tumble," from tealt "unsteady" (cf. O.N. tyllast "to trip," Swed. tulta "to waddle," Norw. tylta "to walk on tip-toe," M.Du. touteren "to swing").

Gerâ, present stem of gerâyidan "to incline toward; to intend; to make for." Gerâ may be a variant of Mod.Pers. kil "bent, inclined" (k/g and l/r interchanges), from PIE base *klei- "to lean, incline," cognate with L. clinare "to bend" (E. declination, inclination, etc.), Gk. klinein "to cause to slope, slant, incline," Skt. sri- "to lean," O.Pers. θray-, Av. sray- "to lean," P.Gmc. *khlinen (Ger. lehnen, E. lean).

tilt angle
  زاویه‌ی ِ گرا   
zâviye-ye gerâ

Fr.: angle d'inclinaison   

The angle a rocket makes with the vertical as it curves along its trajectory.

tilt; → angle.

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
  درنگ   
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.

<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl ura uti val var vec vel ver Ver vie vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>