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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

   Homepage   
   


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

<< < V20 van var veg ven ver vib vio vir vis vol VY > >>

Number of Results: 222
volcanic eruption
  اسدرش ِ آتشفشانی   
osdareš-e âtašfešâni

Fr.: éruption volcanique   

The explosive ejection of superheated matter from a → volcano.

volcanic; → eruption.

volcanic explosivity index (VEI)
  دیشن ِ اسکفتندگی ِ آتشفشانی   
dišan-e oskaftandegi-ye âtašfešâni

Fr.: indice d'explosivité volcanique   

A logarithmic scale, ranging from 1 to 8, used to measure the intensity of volcano eruptions. The VEI is based on several factors: the degree of fragmentation of the volcanic products released by the eruption, the amounts of sulfur-rich gases that form stratospheric aerosols, the volume of the eruptions, their duration, and the height is reached. The largest eruptions (8) produce an amount of bulk volume of ejected → tephra of ~ 1,000 km3.

volcanic; → explosivity; → index.

volcanic vent
  دودکش ِ آتشفشانی   
dudkaš-e âtašfešâni (#)

Fr.: cheminée volcanique   

vent.

volcanic; → vent.

volcano
  آتشفشان   
âtašfešân (#)

Fr.: volcan   

An opening in the Earth's → crust from which → lava, → ash, and hot → gases flow or are → ejected during an → eruption.

From It. vulcano, from L. Vulcanus, → Vulcan.

Âtašfešân, literally "fire disperser, dispersing fire," from âtaš, → fire, + fešân contraction of afšân, from afšândan "to spread, scatter," Mid.Pers. afšân "to spread, to scatter;" ultimately from Proto-Ir. *apašan-, from root *šan- "to shake" (Cheung 2007).

volt
  ولت   
volt (#)

Fr.: volt   

The SI unit of potential difference, defined as the difference of potentials across the ends of a conductor in which a power 1 watt is liberated when a current of 1 ampere flows through it.

In honor of the Italian scientist Alessandro Volta (1745-1827), known for his pioneering work in electricity and the invention of the first battery.

voltage
  ولتاژ   
voltâž (#)

Fr.: voltage, tension   

The electric potential difference expressed in volts.

From → volt.

voltaic
  ولتایی   
voltâyi (#)

Fr.: voltaïque   

Of, relating to electricity or electric currents, especially when produced by chemical action, as in a cell. → photovoltaic detector.

Alessandro Volta (1745-1827), Italian physicist, known for his pioneering work in electricity.

volume
  گنج   
gonj (#)

Fr.: volume   

The amount of space occupied by a three-dimensional object or region of space, expressed in cubic units.

M.E. volum(e), from O.Fr. volume, from L. volumen (genitive voluminis) "roll (as of a manuscript), coil, wreath," from volvere "to turn around, roll."

Gonj "volume," gonjidan "to be contained or held; to hold;" gonjâyeš "capacity, holding, containing;" Mid.Pers. winj- "to be contained;" Proto-Iranian *uiac-/*uic-; cf. Skt. vyac- "to contain, encompass," vyás- "extent, content, extension;" L. uincire "to bind."

volume-limited survey
  بردید با گنج ِ حدمند   
bardid bâ gonj-e hyaddmand

Fr.: relevé limité en volume   

A survey in which the observed objects are contained in a given volume of space.

volume; → limited; → survey.

von Zeipel paradox
  پارادخش ِ فون زایپل   
pârâdxš-e von Zeipel

Fr.: paradoxe de von Zeipel   

A → rotating star cannot simultaneously achieve → hydrostatic equilibrium and → rigid body rotation. The paradox can be solved if → baroclinic flows (essentially a → differential rotation and a → meridional circulation) are included. For a broader view of the subject see: M. Rieutord, 2006, in Stellar Fluid Dynamics and Numerical Simulations: From the Sun to Neutron Stars, ed. M. Rieutord & B. Dubrulle, EAS Publ., 21, 275, arXiv:astro-ph/0608431.

von Zeipel theorem; → paradox.

von Zeipel theorem
  فربین ِ فون زایپل   
farbin-e von Zeipel

Fr.: théorème de von Zeipel   

A theorem that establishes a relation between the → radiative flux at some → colatitude on the surface of a → rotating star and the local → effective gravity (which is a function of the → angular velocity and colatitude). For a rotating star in which → centrifugal forces are not negligible, the → equipotentials where gravity, centrifugal force, and pressure are balanced will no longer be spheres. The theorem states that the radiative flux is proportional to the local effective gravity at the considered colatitude, F(θ) ∝ geff (θ)α, where α is the → gravity darkening coefficient. As a consequence, the stellar surface will not be uniformly bright, because there is a much larger flux and a higher → effective temperature at the pole than at the equator (Teff (θ) ∝ geff (θ)β, where β is the → gravity darkening exponent. In → massive stars this latitudinal dependence of the temperature leads to asymmetric → mass loss and also to enhanced average → mass loss rates. Also called → gravity darkening. See also → von Zeipel paradox; → meridional circulation; → baroclinic instability; → Eddington-Sweet time scale.

Named for Edvard Hugo von Zeipel, Swedish astronomer (1873-1959), who published his work in 1924 (MNRAS 84, 665); → theorem.

von Zeipel's law
  قانون ِ فون زایپل   
qanun-e von Zeipel

Fr.: loi de von Zeipel   

Same as the → von Zeipel theorem.

von Zeipel theorem; → law.

vortex
  گردشار   
gerdšâr (#)

Fr.: vortex   

Meteo.: A whirling mass of water or air.
A pattern of rotation in which the rotation direction rotates by 360° along any path which surrounds the centre of the vortex.

From L. vortex, variant of vertex "whirlpool; whirlwind, an eddy of water, wind, or flame;" from stem of vertere "to turn," cognate with Pers. gardidan, as below.

Gerdšâr (on the model of gerdâb "whirlpool" and gerdbâd "whirlwind"), from gard present stem of gardidan "to turn, to change" (Mid.Pers. vartitan "to change, to turn;" Av. varət- "to turn, revolve;" cf. Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend") + šâr, from šâré, → fluid.

vortical
  گردشاری   
gerdšâri (#)

Fr.: vorticiel   

Of or pertaining to a → vortex.

Adj. from → vortex.

vorticity
  گردشاریگی   
gerdšârigi

Fr.: vorticité   

In fluid mechanics, a measure of the rate of rotational spin in a fluid. Mathematically, vorticity is a vector field defined as the curl of the velocity field: ω = ∇ x v.
Meteo.: The rotation of air around a vertical axis.

From L. vortic-, from → vortex + → -ity.

Gerdšârigi, from gerdšârvortex + -igi, → -ity.

vowel
  خود‌آوا   
xodâvâ (#)

Fr.: voyelle   

A speech sound that is produced as a stream of air that is not obstructed or blocked in any way by the vocal organs, but only modulated by the position of the tongue, lips, etc.

M.E., from O.Fr. vouel, from L. vocalis shortening of littera vocalis, literally "vocal letter," from  → vox "voice," cognate with Pers. âvâ, → phone, vâžé, → word.

Xodâvâ, literally "self-voice," as Ger. Selbstlaut, from xod-, → self-, + âvâ, → phone.

Vulcan
  وولکان   
Vulkân (#)

Fr.: Vulcain   

A hypothetical small planet proposed in the 19-th century to exist in an orbit between Mercury and the Sun. In order to explain some characteristics of Mercury's orbit, the French astronomer Urbain Jean Joseph Le Verrier (1811-1877) hypothesized the presence of another planet, which he named Vulcan. Those particularities of Mercury's orbit were later explained by Albert Einstein's theory of general relativity.

L. Vulcanus in Roman mythology the blacksmith god of fire and volcanoes, a word of Etruscan origin

vulgar
  جرگوار   
jargvâr

Fr.: vulgaire   

1) Characterized by ignorance of or lack of good breeding or taste.
2) Spoken by, or being in the language spoken by, the people generally; vernacular (Dictionary.com).

From L. vulgaris, volgaris "of or pertaining to the common people, common, vulgar, low, mean," from vulgus "the common people, multitude, crowd, throng" (cognates: Skt. varga- "a company, group, section," Pers. jarga, as below, Gk. eilein "to press, throng," Welsh gwala "sufficiency, enough").

Jargvâr, from jarg, jarga, jargé "a group of people, a ring of men or beasts;" cf. Lori, Laki jarga "group, throng," jarra "bundle;" Kurd. jerge, cerge "assembly, club;" + -vâr a suffix denoting "suiting, befitting, resembling, in the manner of, possession."

vulgar fraction
  برخه‌ی ِ همدار   
barxe-ye hamdâr

Fr.: fraction d'entiers   

Same as → common fraction.

M.E., from L. vulgaris, from vulgus "the common people," + -aris, → -ar.

common; → fraction.

Vulpecula
  روباهک   
Rubâhak (#)

Fr.: Petit Renard   

The Little Fox. A faint constellation in the northern hemisphere, at 20h right ascension, +25° declination, between Cygnus and Aquila. Abbreviation: Vul; Genitive: Vulpeculae.

L. Vulpecua, from vulpes "fox," cognate with Pers. rubâh, as below, + diminutive suffix -cula, variant of → -ule.

Rubâhak "little fox," from rubâh

<< < V20 van var veg ven ver vib vio vir vis vol VY > >>