An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 13176 Search : far
validity
  پای‌مندی   
pâymandi

Fr.: validité   

Logic: Of an argument, whether or not the conclusion follows logically from the premises and the allowable syllogisms of the logical system being used.

Quality noun from → valid.

Valles Marineris
  درّه‌های ِ مارینر   
darrehâ-ye Mariner

Fr.: Valles Marineris   

A system of canyons located just south of the Martian equator. The system is about 4000 km long. The central individual troughs, generally 50 to 100 km wide, merge into a depression as much as 600 km wide. In places the canyon floor reaches a depth of 10 km, 6 to 7 times deeper than the Grand Canyon on Earth.

L. Valles Marineris "Mariner's Valleys," named after the Mars orbiter Mariner 9, which discovered the Martian canyon in 1971-72. → valley.

valley
  درّه   
darré (#)

Fr.: vallée   

A long, narrow region of low land between ranges of mountains, hills, or other high areas, often having a river or stream running along the bottom.

M.E. valeie, valey, from O.Fr. valee "valley," from V.L. *vallata, from L. vallis "valley," of unknown origin.

Darré "valley," from Mid.Pers. dar, darrak "ravine, cleft;" cf. Skt. pradará- "cleft."

value
  ارزش   
arzeš (#)

Fr.: valeur   

Math.: Magnitude; quantity; a numerical quantity assigned to a mathematical symbol.

M.E., from O.Fr. value "worth, value," noun use of feminine p.p. of valoir "be worth," from L. valere "be strong, be well, be of value."

Arzeš, verbal noun of arzidan "to be worth," arzân "worthy; of small value, cheap," arj "esteem, honour, price, worth;" Mid.Pers. arz "value, worth," arzidan "be worth," arzân "valuable;" Av. arəjaiti "is worth," arəja- "valuable," arəg- "to be worth;" cf. Skt. arh- "to be worth, to earn," árhant- "worthy person;" Gk. alphanein "to bring in as profit," alphein "to ear, obtain;" Lith. algà "salary, pay;" PIE base *algwh- "to earn; price, value."

valve
  دریچه، سوپاپ   
daricé, supâp

Fr.: valve, soupape   

Any device that halts or regulates the flow of a fluid through a passage, pipe, etc.

From L. valvae "leaves of a door."

Daricé, leterally "small door, window," → stop. Supâp, loan from Fr. soupape, from O.Fr. sourpape, probably from souspape "a blow under chin," from sous "under," from L. subtus, → sub-, + *pape "jaw," from paper, from L. pap(p)are "to eat."

valve mechanism
  ساز-و-کار ِ سوپاپ   
sâzokâr-e supâp

Fr.: mécanisme de valve   

A mechanism proposed by Eddington to explain → stellar pulsations. Same as the → kappa mechanism. In this analogy the stellar layer acts like a heat engine with radiation taking the role of stream. The expanding and contracting layer acts as the piston, and the opacity of the layer behaves as the valve mechanism (Eddington, 1917, The pulsation theory of → Cepheid variables, The Observatory 40, 290).

valve; → mechanism.

Van Allen belts
  کمربندهای ِ وان آلن   
kamarbandhâ-ye Van Allen

Fr.: ceintures de Van Allen   

The ring-shaped regions of charged particles surrounding the Earth from 1 to 6 Earth radii into space. The charged particles are trapped in by the Earth's magnetic field. The inner belt is between 1.2 and 4.5 Earth radii and contains high-energy electrons and protons which originate mainly from interactions between cosmic rays and the upper atmosphere. The outer belt, located between 4.5 and 6.0 Earth radii, contains lower-energy charged particles mainly coming from the solar wind.

Named after James Van Allen (1914-2006), who discovered the belts in 1958 based on measurements made by Explorer 1, the USA's first successful artificial satellite; → belt.

Van Cittert-Zernike theorem
  فربین ِ فان سیترت-زرنیکه   
van farbin-e Cittert-Zernike

Fr.: théorème de Cittert-Zernike   

In → Young's experiment of → interference with double apertures, if a monochromatic source is a considerable distance from the → aperture plane and aperture separation is small, → fringe visibility from an extended source is proportional to the → Fourier transform of the source's spatial distribution. The transform variable is the angular separation of the aperture-plane sampling points divided by the wavelength. The van Cittert-Zernike Theorem is at the heart of → aperture synthesis.

Developed independently by Dutch physicists Pieter Hendrick van Cittert (1889-1959) in 1934 and Frits Zernike (1888-1966) in 1939; → theorem.

van den Bergh catalogue (vdB)
     
kâtâlog-e van den Bergh

Fr.: catalogue de van den Bergh   

A catalog of → reflection nebulae containing 158 objects. The catalog gives information for all BD and CD stars north of δ = -33 deg which are surrounded by reflection nebulosity visible on both the blue and red prints of the → Palomar Observatory Sky Survey .

van den Bergh, S., 1966, AJ, 71, 990; → catalog

van der Waals equation
  هموگش ِ وان در والس   
hamugeš-e van der Waals

Fr.: équation de van der Waals   

An → equation of state that satisfactorily describes the behavior of → real gass over a wide range of temperatures and pressures. It is derived from considerations based on kinetic theory, taking into account to a first approximation the size of a molecule and the cohesive forces between molecules: (P + a / V2) (V - b) = RT, where P, V, and T are pressure, volume, and temperature and R the gas constant. a and b are characteristic constants for a given substance. For a = b = 0, the van der Waals equation reduces to the characteristic equation of an → ideal gas. See also → Dieterici equation.

Named after Dutch physicist Johannes Diderik van der Waals (1837-1923), Nobel Prize in Physics 1910; → equation.

van der Waals force
  نیروی ِ وان در والس   
niru-ye van der Waals

Fr.: force de van der Waals   

A weak attractive force between neutral atoms and molecules arising from polarization induced in each particle by the presence of other particles. All molecules contain electrically charged particles, and even though the molecule as a whole is electrically neutral there do exist between molecules van der Waals attractive forces of electric origin.

Named after Dutch physicist Johannes Diderik van der Waals (1837-1923), Nobel Prize in Physics 1910; → force.

vanadium
  وانادیوم   
vânâdiom (#)

Fr.: vanadium   

A soft, ductile, silver-grey metal; symbol V. → Atomic number 23; → atomic weight 50.9415; → melting point about 1,890°C; → boiling point 3,380°C; → specific gravity about 6 at 20°C; and → valence +2,+3, +4, or +5. → It is used in various alloys to increase its shock resistance.

Named 1830 by Swedish chemist Nils Gabriel Sefström (1787-1845), from Old Norse Vanadis, epithet of the goddess Freya, + → -ium.

vane
  ۱، ۲) پره؛ ۳) بادنما   
1, 2) parré (#); 3) bâdnemâ (#)

Fr.: 1) aile, pale; 2) barbe; 3) girouette   

1) A blade attached radially to a central axis, as in a windmill, propeller, revolving fin, or the like. → spider vane.
2) → wind vane.
3) The flat part of a bird's → feather.

M.E., from O.E. fana "flag;" cognate with Ger. Fahne "flag," Gothic fana "piece of cloth."

Parré, from parr, → feather.

vanish
  ونیدن   
venidan

Fr.: 1, 2) disparaître, se volatiser; 3) s'en aller   

1) To disappear from sight, especially quickly; become invisible.
2) To disappear by ceasing to exist; come to an end.
3) Math.: To become zero or to tend to zero.

M.E., from O.Fr. esvanir "disappear; cause to disappear," from L. evanescere "disappear, pass away, die out," from → ex- "out" + vanescere "to vanish," from vanus "empty," cognate with O.E. wanian "to lessen," wan "deficient;" O.N. vanta "to lack;" L. vacare "to be empty," vastus "empty, waste;" see below for Iranian cognates.

Venidan, from Kurd. ven "missing; away; absent," cf. Pers. vang "empty, empty-handed, poor;" related to Av. ūna- "deficient, empty," ū- "to be incomplete;" akin to Skt. vā- "to disappear, diminish," ūná- "deficient;" L. vanus "empty," as above.

vanquish
  وانیدن   
vânidan

Fr.: vaincre   

1) To → conquer or subdue by superior force, as in battle.
2) To defeat in any contest or conflict; be victorious over (Dictionary.com).

O.Fr. venquis-, extended stem of veintre "to defeat," from L. vincere "to overcome, conquer."

Vânidan, from Mid.Pers. vânidan "to vanquish, to conquer;" cf. Av. van- "to vanquish, to defeat;" Skt. van- "to win, conquer;" O.E. winnan, E. win, PIE *uen- "to win, conquer."

vapor
  بخار   
boxâr (#)

Fr.: vapeur   

The gaseous form of substances that are normally in liquid or solid form.

M.E. vapour, L. vapor "exhalation, steam, heat," of unknown origin.

Boxâr, loan from Ar. buxâr.

vapor pressure
  فشار ِ بخار   
fešâr-e boxâr

Fr.: pression de vapeur   

The equilibrium pressure of a vapor above its condensed phases (liquid or solid). In other words, the pressure of the vapor resulting from evaporation of a liquid (or solid) above a sample of the liquid (or solid) in a closed container. The vapor pressure varies with the temperature. As the temperature increases its the vapor pressure also increases, and conversely. The temperature at which the vapor pressure is equal to the atmospheric pressure is called the → boiling point. For example, at 20 °C, water would boil at a pressure of about 0.023 atm, or about a fortieth of atmospheric pressure.

vapor; → pressure.

vaporization
  بخارش   
boxâreš

Fr.: vaporisation, évaporation   

The act of vaporizing. The state of being vaporized.
The rapid change of water into steam.

Verbal noun of → vaporize.

vaporize
  ۱) بخاریدن؛ ۲) بخاراندن   
1) boxâridan; 2) boxârândan

Fr.: 1) s'évaporer; 2) évaporer   

1) To become converted into vapor.
2) To cause to change into a vapor.

vapor + → -ize.

variability
  ورتندگی   
vartandegi

Fr.: variabilité   

The quality, state, or degree of being variable or changeable.

Quality noun from → variable.

<< < -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 > >>