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

Same as → weight concentration.

→ weight; → fraction.

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

→ weight; → tensor; → density.

Same as → weight concentration.

→ weight; → fraction; → concentration.

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

→ weight; → mean.

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.

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:
E_b = a_VA - a_SA^2/3 - a_CZ²/A^1/3 - a_A(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, arxiv.org/pdf/1212.6768). 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.

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 (Dictionary.com).

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."

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.

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

→ well; → order; → set.

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.

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."

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

Adjective from → west.

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

→ western; → elongation.

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).

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.

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.

The star δ Canis Majoris, magnitude 1.84. It is an F8 supergiant 1800 light-years away. Among bright stars, Wezen is one of the most distant and luminous. Its luminosity is 50,000 times that of the Sun. Other designations: Alwazn, Wesen, HR 2693, HD 54605.

From Ar. Al-wazn (الوزن) "weight."

Vazn, from Ar. Al-wazn, as above.

1) Any of the larger ocean mammals, excluding the porpoises and dolphins, that breathe through a blowhole on the top of their head and have front flippers, no hind limbs, and a flat horizontal tail.
2) The constellation → Cetus.

M.E., O.E. hwæl, cf. O.S. hwal, O.N. hvalr, Swed. val, M.Du. wal, Du. walvis, O.H.G. wal, Ger. Wal, probably cognate with L. squalus and Pers. vâl, as below.

1) Mod.Pers. vâl, wâl, related to Mid.Pers. kar (mâhig) "whale (fish);" Av. kara- "a mythological fish;" also Mod.Pers. kuli "a kind of fish;" cf. L. squalus "a kind of large sea fish;" PIE (s)k^walo- "a large fish."
2) Pers. nahang originally "crocodile," from Mid.Pers. nihang "crocodile; hippopotamus," ultimately from Proto-Iranian *ni-θanj- "to drag down," since crocodiles drag down their preys underwater and drown them, from ni- "down, below," → ni- (PIE) , + θanj- "to draw, pull" (cf. Pers. farhang; sanjidan, etc.).

An device consisting of four → resistances in series, used to determine the value of an unknown electrical resistance when the other three resistances are known.

Named after Charles Wheatstone (1802-1875), British physicist, who extensively used the circuit (1843) but was not its inventor. Such an arrangement of four resistances was first used by Samuel Hunter Christie (1784-1865) in 1833; → bridge.

1) A solid disk or a rigid circular ring arranged to turn around an axle passed through the center.
2) Anything like a wheel in shape or function.

M.E. whel(e), O.E. hweol, hweogol, from PIE *k(w)e-k(w)lo- "wheel, circle;" cf. Gk. kyklos "circle, wheel;" L.L. cyclus; Mod.Pers. carx "wheel;" Av. caxra- "wheel;" Skt. cakra- "wheel, circle;" Rus. koleso "wheel."

Carx "wheel," akin to wheel, as above.