An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 215
Weierstrass approximation theorem
  فربین ِ نزدینش ِ وایرشتراس   
farbin-e nazdineš-e Weierstrass

Fr.: théorème d'approximation de Weierstrass   

If a function φ(x) is continuous on a closed interval [a,b], then for every ε > 0 there exists a polynomial P(x) such that |f(x) - P(x)| <ε, for every x in the interval.

After German mathematician Karl Wilhelm Theodor Weierstrass (1815-1897); → approximation; → theorem.

Weierstrass M test
  آزمون ِ M وایرشتراس   
âzmun-e M Weierstrass

Fr.: Weierstrass   

A test for uniform convergence of a sequence of functions. If there exists a series of numbers Σ Mi (summed from n = 1 to ∞), in which Mi≥ Σ |ui(x)| for all x in the interval [a, b] and Σ Mi is convergent, the series ui(x) will be uniformly convergent in that interval.

Weierstrass approximation theorem; M referring to → majorant; → test.

vazn (#)

Fr.: poids   

1) The force of attraction of the Earth on a given mass. → molecular weight; → weightlessness.
2) Statistics: A measure of the relative importance of an item in a statistical population. → weighted mean.
See also: → atomic weight, → counterweight, → mean molecular weight, → molecular weight, → statistical weight, → weight concentration, → weight fraction, → weight of a tensor density, → weight-fraction concentration, → weightlessness.

M.E., from O.E. gewiht, cf. O.N. vætt, O.Fris. wicht, M.Du. gewicht, Ger. Gewicht.

Vazn, loan from Ar. wazn.

weight concentration
  دبزش ِ وزنی   
dabzeš-e vazni

Fr.: concentration en poids   

of a gas included in the composition of a → gas mixture, the ratio of mass of this gas to the mass of the whole mixture. Same as → weight fraction and → weight-fraction concentration.

weight; → concentration.

weight fraction
  برخه‌ی ِ وزنی   
barxe-ye vazni

Fr.: fraction en poids   

Same as → weight concentration.

weight; → fraction.

weight of a tensor density
  وزن ِ چگالی ِ تانسور   
vazn-e cagâli-ye tânsor

Fr.: poids d'une densité de tenseur   

A constant the value of which is characteristic for any given → tensor density.

weight; → tensor; → density.

weight-fraction concentration
  برخه‌ی ِ وزنی ِ دبزش   
barxe-ye vazni-ye dabzeš

Fr.: concentration en poids   

Same as → weight concentration.

weight; → fraction; → concentration.

weighted mean
  میانگین ِ وزنی   
miyângin-e vazni (#)

Fr.: moyenne pondérée   

An mean which is obtained by combining different numbers according to the relative importance of each.

weight; → mean.

bivazni (#)

Fr.: apesanteur   

The phenomenon experienced by a body when there is no force of reaction on it. This happens when the body is in → free fall in a → gravitational field or when the net force on it is zero.

From → weight + -less suffix meaning "without" + -ness a suffix of quality or state.

Bivazni, from bi- "without," → a-, + vazn, → weight, + -i.

Weizsacker formula
  دیسول ِ وایتسکر   
disul-e Weizsäcker

Fr.: formule de Weizsäcker   

A → semiempirical → equation which describes the → binding energy of the → atomic nucleus. It is essentially a nuclear mass formula that provides the total binding energy per → nucleon as the sum of five terms:
Eb = aVA - aSA2/3 - aCZ2/A1/3 - aA(N -Z)2/A + δ(A,Z),
where the terms in the right-hand side of this equation are called the volume term, surface term, Coulomb term, asymmetry term, and pairing term, respectively. A, Z, and N are the number of nucleons, → protons, and → neutrons, respectively (see, e.g., Alexi M. Frolov, 2013, Also called Bethe-Weizacker formula and → semiempirical binding energy formula.

Named after Carl Friedrich von Weizäcker (1912-2007), German physicist, who derived the formula in 1935, Z. für Physik 96, 431; → formula.

  ۱) خوش، خوب؛ ۲) چاه   
1) xoš, xub; 2) câh


1) In a good or satisfactory manner; thoroughly, carefully, or soundly.
2) A hole drilled or bored into the earth to obtain water, petroleum, natural gas, brine, or sulfur (

1) M.E., from O.E. wel(l) (cognates Du. wel, Ger. wohl).
2) M.E. well(e), O.E. wylle, wella, welle (cognates: O.Saxon wallan, O.Fris. walla, O.H.G. wallan, Ger. wallen "to bubble, boil").

1) Xoš "good, well, sweet, fair, lovely," probably related to hu- "good, well," → eu-. Xub, ultimately from Av. huuāpah- "doing good work," → operate.
2) Câh "a well," from Mid.Pers. câh "a well;" Av. cāt- "a well," from kan- "to dig," uskən- "to dig out;" O.Pers. kan- "to dig," akaniya- "it was dug;" Mod.Pers. kandan "to dig;" cf. Skt. khan- "to dig," khanati "he digs," kha- "cavity, hollow, cave, aperture."

well-formed formula (wff)
  دیسول ِ خوش‌دیسه (wff)   
disul-e xošdisé (wff)

Fr.: formule bien formée (FBF)   

A string of → symbols from the alphabet of the → formal language that conforms to the grammar of the formal language. → closed wff, → open wff.

Wff, pronounced whiff; → well; → form; → formula.

well-ordered set
  هنگرد ِ خوش‌رایه   
hangard-e xoš-râyé

Fr.: ensemble bien ordonné   

A set in which every → nonempty → subset has a minimum element.

well; → order; → set.

Werner band
  باند ِ ورنر   
bând-e Werner

Fr.: bande de Werner   

A sequence of → permitted transitions in the → ultraviolet from an → excited state (C) of the → molecular hydrogen (H2) to the electronic → ground state, with ΔE > 12.3 eV and λ ranging from 1160 Å to 1250 Å. When a hydrogen molecule absorbs such a photon, it undergoes a transition from the ground electronic state to the excited state (C). The following rapid → decay creates an → absorption band in that wavelength range. See also → Lyman band; → Lyman-Werner photon.

Named after the Danish physicist Sven Theodor Werner (1898-1984), who discovered the band (S. Werner, 1926, Proc. R. Soc. London Ser. A, 113, 107); → band.

bâxtar (#)

Fr.: ouest   

The direction 90° to the left or 270° to the right of → north.

M.E., O.E. "west" "in or toward the west;" cf. O.N. vestr, O.Fris., M.Du., Du. west, Ger. West; PIE base *wes- (Gk. hesperos, L. vesper "evening, west").

Bâxtar "west;" Mid.Pers. apâxtar "north;" Av. apāxtar "northern."

bâxtari (#)

Fr.: (de l') ouest, occidental   

Lying toward or situated in the west. → greatest western elongation.

Adjective from → west.

western elongation
  درازش ِ باختری   
derâzeš-e bâxtari

Fr.: élongation ouest   

The position of a planet when it is visible in the eastern sky before dawn.

western; → elongation.

xis (#)

Fr.: mouillé   

Consisting of, containing, covered or soaked with water or some other liquid.

O.E. wæt "moist, liquid," related to O.Frisian wēt, O.N. vātr, O.E. wæter "water."

Xis, xês "wet, moist," related to pašang, pašangidan "sprinkle," ultimately from Proto-Ir. *haic- "to pour (out), moisten;" cf. Av. haēc- "to pour (out); to irrigate;" Khotanese häs- "to wet, besprinkle;" Sogd. šync "to pour" (Cheung 2007).

wet merger
  تشک ِ پر گاز   
tašk-e porgâz

Fr.: fusion avec gaz   

A merger between → gas-rich galaxies. Wet mergers may lead to enhanced star formation, trigger → active galactic nuclei, and transform a → disk galaxy into an → elliptical galaxy. The larger the → redshift, the wetter mergers should be.

wet; → merger.

Weyl's principle
  پروز ِ ویل   
parvaz-e Weyl

Fr.: principe de Weyl   

The → world lines of galaxies form in the 4D space-time a bundle of non-intersecting → geodesics orthogonal to a series of space-like hyperstructures (e.g. Narlikar 2002, An Introduction to Cosmology, 3rd Edition, Cambridge Univ. Press). Expressed differently: The world lines of galaxies, or "fundamental particles," form (on average) a space-time filling family of non-intersecting geodesics converging toward the past (Rugh & Zinkernagel, 2010, astro-ph/1006.5848). The statement is sometimes denoted postulate, assumption, or hypothesis. The importance of Weyl's principle is that it asserts that cosmic matter moves according to certain regularity requirements. See also → cosmological principle.

First introduced by the German mathematician Hermann Weyl (1885-1955) in 1923 in his Raum, Zeit, Materie; → principle.

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