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: 215
viscosity
  وشکسانی   
vošksâni (#)

Fr.: viscosité   

The property of a → fluid that resists the force tending to cause the fluid to flow. Viscosity may be thought of as the internal → friction of two fluid layers which flow parallel to each other at different speeds. The cause of viscosity is the transport of → momentum by the molecules from one layer to the other. Viscosity is given by η = φ.u.λ.ρ, where φ is a coefficient which depends on the nature of the interaction between the molecules, u is the average velocity of thermal motion of the molecules, λ is the → mean free path, and ρ the → density of the fluid. Also called → dynamic viscosity or → absolute viscosity. See also → kinematic viscosity.

Noun from → viscous; → -ity.

viscous
  وشکسان   
vošksân (#)

Fr.: visqueux   

Having the property of → viscosity. See also: → viscous dissipation, → viscous fluid, → viscous force, → nonviscous.

M.E., from M.Fr. viscous, from L. viscosus "sticky," from viscum "anything sticky; mistletoe."

From vošk "a kind of sticky gum" + -sân suffix of similarity, from sân "way, manner."

viscous dissipation
  افتال ِ وشکسان   
eftâl-e vošksân

Fr.: dissipation visqueuse   

A degradation of → mechanical energy that is irreversibly converted to → thermal energy due to → viscous forces in the → fluid. Viscous dissipation occurs in → turbulent flows.

viscous; → dissipation.

viscous fluid
  شاره‌ی ِ وشکسان   
šârre-ye vošksân (#)

Fr.: fluide visqueux   

A fluid whose viscosity is sufficiently large to make the viscous forces a significant part of the total force field in the fluid.

viscous; → fluid.

viscous force
  نیروی ِ وشکسان   
niru-ye vošksân

Fr.: force visqueuse   

The force per unit volume or per unit mass arising from the action of tangential stresses in a moving → viscous fluid.

viscous; → force.

visibility
  دیاری، پدیداری   
diyâri, padidâri (#)

Fr.: visibilité   

General: The state or fact of being visible.
1) Optics: If the intensity in an interference fringe pattern has the maximum and minimum values Imax and Imin, the visibility is defined by the relation ν = (Imax - Imin) / (Imax + Imin), where 0 ≤ ν ≤ 1. In terms of the intensities of the two interfering waves: ν = 2(I1 . I2)1/2/(I1 + I2).
2) Meteo.: A measure of transparency of the atmosphere. The maximum horizontal distance at which objects can be identified. → turbidity.

visible + → -ity.

visibility function
  کریای ِ دیاری، ~ پدیداری   
karyâ-ye diyâri, ~ padidâri

Fr.: fonction de visibilité   

The Fourier transform of a source's brightness distribution, weighted by the characteristics of the interferometer's antennas.

visibility; → function.

visibility plane
  هامن ِ دیاری، ~ پدیداری   
hâmon-e diyâri, ~ padidâri

Fr.: plan de visibilité   

In interferometry, the projection of a baseline onto the plane normal to the source direction defining a vector in (u,v) space, measured in wavelength units.

visibility; → plane.

visible
  دیار، پدیدار، پیدا   
diyâr (#), padidâr (#), peydâ (#)

Fr.: visible   

1) Capable of being seen by, or perceptible to, the human eye.
2) → visible light.

M.E., from O.Fr. visible, from L. visibilis "that may be seen," from visus, p.p. of videre "to see;" cognate with Pers. bin, present stem of didan "to see" (Mid.Pers. wyn-; O.Pers. vain- "to see;" Av. vaēn- "to see;" cf. Skt. veda "I know;" Gk. oida "I know," idein "to see;" PIE base *weid- "to know, to see").

Diyâr "visible" in several dialects, e.g. štiyâni, Malâyeri, Širâzi, Tabari, related to didan "to see;" Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen."
Padidâr (→ phenomenon) and peydâ are both also related to dā(y)- (with prefixes).

visible horizon
  افق ِ پدیدار، ~ دیار   
ofoq-e padidâr, ~ diyâr

Fr.: horizon apparent   

That line where Earth and sky appear to meet, and the projection of this line upon the celestial sphere. Also known as the apparent horizon.

visible; → horizon.

visible light
  نور ِ دیار، ~ دیدنی   
nur-e diyâr, ~ didani

Fr.: lumière visible   

The portion of the → electromagnetic radiation that can be seen by the human → eye. The → wavelengths extend from about 400 nm (violet) to 750 nm (red). The wavelengths of various colors of the visible spectrum are as follows: → violet: 390-455 nm; → blue: 455-492 nm; → green: 492-577; → yellow: 577-597; → orange: 597-622; → red: 622-780 nm.

visible; → light.

visible spectrum
  بیناب ِ دیار، ~ دیدنی   
binâb-e diyâr, ~ didani

Fr.: spectre visible   

The portion of → electromagnetic spectrum corresponding to → visible light.

visible; → spectrum.

vision
  نگاه، دید   
negâh, did

Fr.: vision   

The act or power of sensing with the eyes. → averted vision; → acuity of vision.

M.E., from O.Fr. vision, from L. visionem (nominative visio) "act of seeing, sight, thing seen," from p.p. stem of videre "to see," cognate with Pers. bin, present stem of didan "to see" (Mid.Pers. wyn-; O.Pers. vain- "to see;" Av. vaēn- "to see;" cf. Skt. veda "I know;" Gk. oida "I know," idein "to see;" PIE base *weid- "to know, to see").

Negâh, "look," from Mid.Pers. nikâh "look, glance, observation;" Proto-Iranian *ni-kas- "to look down," from ni- "down, below," → ni- (PIE), + *kas- "to look, appear;" cf. Av. nikā-, nikāta- (in the name of the 15-th nask) "that which is observed," ākas- "to look;" Mid.Pers. âkâh, Mod.Pers. âgâh "aware, knowing;" Skt. kāś- "to become visible, appear;" Ossetic kast/kaesyn "to look;" did, from didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen").

visual
  دیدی، دیدگانی، دیداری   
didi (#), didgâni (#), didâri (#)

Fr.: visuel   

1) Of or pertaining to seeing or sight.
2) → optical.

M.E., from L.L. visualis "of sight," from L. visus "sight," from visus, .pp. of videre "to see;" cognate with Pers. bin, present stem of didan "to see" (Mid.Pers. wyn-; O.Pers. vain- "to see;" Av. vaēn- "to see;" cf. Skt. veda "I know;" Gk. oida "I know," idein "to see;" PIE base *weid- "to know, to see").

Didi, of or pertaining to did, from didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen"); didgâni, adj. of didgân, plural of didé, did "sight, eye; seen;" didâri, from didâr, from didan.

visual acuity
  تیزنایی ِ دید   
tiznâyi-ye did

Fr.: acuité visuelle   

Same as → acuity of vision.

visual; → acuity.

visual binary
  درین ِ دیدگانی   
dorin-e didgâni

Fr.: binaire visuelle   

A → binary system of stars whose components can be resolved telescopically and which have detectable orbital motion.

visual; → binary.

visual extinction
  خاموشی ِ دیدگانی   
xâmuši-ye didgâni

Fr.: extinction visuelle   

The → extinction in the visual range of the electromagnetic radiation.

visual; → extinction

visual magnitude
  برز ِ دیدگانی   
borz-e didgâni

Fr.: magnitude visuelle   

The → apparent magnitude of a celestial body in the color sensitivity region of the human eye at a wavelength of 5600 Å. Visual magnitude is now essentially synonymous with V magnitude, which is determined photometrically.

visual; → magnitude.

visualization
  چشم‌دید   
cašm-did

Fr.: visualisation   

1) The act of visualizing (→ visualize).
2) The presentation of → information on a → screen.

Verbal noun of → visualize.

Cašm-did, Mid.Pers. cašm-did "visible," Mod.Pers. cašm-didâr by Tusi, in Pers. translation of Sufi's "Book of Fixed Stars," from cašm "eye" (Mid.Pers. cašm, Av. cašman- "eye," ākas- "to look," from prefix ā- + Proto-Iranian *kas- "to look, appear," cf. Skt. cáksus- "seeing") + did past stem of didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen").

visualize
  چشم‌دید کردن   
cašm-did kardan

Fr.: visualiser   

1) To make → visual or → visible.
2) To present → image or → information on a → screen, usually a → computer  → display.

From → visual + → -ize; → visualization.

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