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

1) A small platelike body.
2) One of a variety of forms taken on by → snowflakes.
3) A tiny cell occurring in the blood of vertebrates and involved in clotting of the blood. Formerly called thrombocyte.

→ plate; → -let.

1) To inhabit; live in; be the inhabitants of.
2) To furnish with inhabitants, as by colonization (Dictionary.com).

Infinitive, corresponding to → population.

1a) Math.: An unproved → assumption taken as basic in a mathematical system, and from which (in combination with other → postulates) the propositions of the system are derived, or in terms of which the propositions are proved. In modern usage, postulate is synonymous with → axiom.
1b) Physics: A fundamental principle. For example, the two postulates of special relativity of Einstein are: 1) The laws of physical phenomena are the same when studied in terms of two → reference frames moving at a constant velocity relative to each other. 2) The → velocity of light in free space is the same for all observers and is independent of the relative velocity of the source of light and the observer. See also → Planck postulate.
2a) General: To ask, demand, or claim. To claim or assume the existence or truth of, especially as a basis for reasoning or arguing.
2b) Math.: To assume as a postulate.

From L. postulatum "petition, thing requested," noun use of neuter of p.p. of postulare "to ask, request, demand," akin to poscere "to request."

Farâvas (on the model of piš-nahâd "proposition," and farâ-nemudan "to exhibit, expose"), from farâ-, → pro-, + vas. The second component from Av. vas- "to will, desire, wish, long for," vasəmi "I wish," vasna- "will, favor," ušti- "desire, wish, will," vasô, vasə "at one's will;" cf. O.Pers. vasiy "at will, greatly, utterly," vašna- "will, favor;" Mid.Pers. vasnâd "because, on account of." This word is extant in several Modern Iranian dialects: Tabari vessen "to wish, desire," Gilaki vâssan "to wish, desire," vâsti "desire; for, because, on account of;" Kurd. wistin "to desire, wish," Lâri avessa "to desire;" Nâyini vas "to like;" colloquial Tehrâni vâsé "for;" Lori, Malâyeri biza "pregnancy craving;" cognate with Skt. vaś- "to wish, want, desire," váśa- "wish, desire," vasēna "for, because;" Gk. ekon "voluntary;" PIE base *uek- "to wish."

Elongated in the direction of the polar diameter; opposed to → oblate

From L. prolatus, pt.p. of proferre "to bring forward, extend," from → pro- + → oblate.

Kešidé p.p. of Mod./Mid.Pers. kešidan, kašidan "to draw, protract, trail, drag, carry," dialectal Yaqnavi xaš "to draw," Qomi xaš "streak, stria, mark," Lori kerr "line;" Av. karš- "to draw; to plow," karša- "furrow;" Proto-Iranian *kerš-/*xrah- "to draw, plow;" cf. Skt. kars-, kársati "to pull, drag, plow;" Gk. pelo, pelomai "to move, to bustle;" PIE base k^wels- "to plow."

An ellipsoid produced by rotating an ellipse through 360° about its major axis. → oblate spheroid.

→ prolate; → spheroid.

A plane figure bounded by four straight lines.

From L. quadrilater(us) "four-sided," from L. quattuor, → four, + → lateral.

A plate of doubly refracting material cut parallel to the optic axis of the crystal and of such a thickness that a phase difference of 90° is introduced between the ordinary and extraordinary rays for light of a particular wavelength. → half-wave plate.

→ quarter; → wave; → plate.

To control, direct, or adjust by a rule, principle, method, etc.

From L.L. regulatus, p.p. of regulare "to control by rule, direct," from L. regula, cognate with Pers. râst→ right.

Razanidan, verbal form of razan, → rule, cognate with L. regula.

Controlled or governed according to a rule or principle or law.

Past participle of → regulate.

1) (tr.) To find or show a connection between two or more people or things.
2) (intr.) To have a significant connection with or bearing on something.

From O.Fr. relater, from L. relatus literally "carried, brought back," from re- "back, again" + latus "carried, brought," used as p.p. of referre, from re- "back, again" + ferre "carry, bear," cognate with Pers. bordan "to carry, bear" (Mid.Pers. burdan, O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive)," Skt. bharati "he carries," Gk. pherein, L. fero "to carry;" PIE base *bher- "to carry").

Bâzânidan, literally "to bring, lead back," from bâz- "back, again," → re- + ân stem of ânidan "to bring; to lead; to guide," cf. dialectical Kurd. ânin "to bring, to lead to," Tâleši ânân, ânoe "to bring together two edges;" Mid.Pers. ônidan, nidan, nay- "to lead; to bring;" O.Pers. nay- "to lead; to bring" anaya "leads;" Av. nay- "to lead; to bring," naiieiti "leads;" cf. Skt. nī- "to lead," náyati "leads," aorist s. anait.

Connected; associated.

P.p. of → relate.

Same as → wave plate.

→ retardation; → plate.

An almost horizontal region in the → CMB angular power spectrum belonging to a → multipole index 10 ≤ l ≤ 100. This feature is due to the → Sachs-Wolfe effect.

→ Sachs-Wolfe effect; → plateau.

To create a likeness or model of something (a situation, system, or the like).

M.E., from L. simulatus, p.p. of simulare "to imitate," from stem of similis "like;" cognate with Pers. ham "together, with; same, equally, even" (Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- "one and the same," Skt. sama-, Gk. homos-; originally identical with PIE numeral *sam- "one," from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-).

Mânadidan verb from mânand "resembling, like," variant mânestan "to resemble;" Mid.Pers. mânag "like, resembling;" Av. man- "to resemble;" hamânad sâxtan, from hamânand, from ham-, as above, + mânad + sâxtan "to make, build."

A fine-grained rock formed by the metamorphosis of clay, shale, etc., that tends to split along parallel cleavage planes, usually at an angle to the planes of stratification (Dictionary.com).

M.E. sclate, from M.Fr. esclate, feminine of esclat "piece split off," (Fr. éclat) so called because the rock splits easily into thin plates.

Palmé "slate," "a board on which children learn to read," ultimately from Proto-Ir. *parn-, *parm- "feather," PIE *pernom-, *pornos- "feather," → tablet.

The back, muscular (not bony) part of the roof of the → mouth in front of the → pharynx.

→ soft; → palate.

To guess possible answers to a question when there are not enough information to be certain.

Back formation from O.Fr. speculation, from L. speculatus, p.p. of speculari "to watch over, observe," from specula "watch tower," from specere "to look at, regard," cognate with Av. spas- "to attend; to serve," spasiieiti "looks at, perceives;" Pers. sepâs "kindness, thanksgiving;" Skt. spasati "sees;" Gk. skopein "to behold, look, consider," skeptesthai "to look at;" O.H.G. spehhon "to spy;" Ger. spähen "to spy;" PIE *spek- "to look around, observe."

Gâsidan infinitive from gâs, from Av. kas- "to look at, see," with extension of the vowel and change of the last phoneme from k to g, as in and cognate with negâh (Mid.Pers. nikâh), → look, âgâh (Mid.Pers. âkâh) "aware" (→ Space Situational Awareness), pargast "God forbid!," and maybe (Lori, Laki, Torbat-Heydarie-yi) gâs "perhaps," (Shirâzi, Fasâyi) gâsam "maybe;" cf. Skt. kāś- "to become visible, appear;" Gk. tekmor, tekmar "sign, mark;" PIE base *k^wek- "to appear, show."

The observation that the abundance of → lithium (⁷Li) in metal-poor stars is constant regardless of the → effective temperature (> 5500 K) and the → metallicity ([Fe/H] < -2). The Spite plateau is currently interpreted as evidence that the Li observed in → halo population stars is → primordial. Since its discovery, the Spite plateau has been subject to numerous investigations, increasing the number of stars with Li measurements and extending the sample to include ever lower metallicities. Important issues are the existence or not of a significant scatter along the plateau, and the existence or not of atomic diffusion and mixing with deeper stellar zones where Li can be burnt, producing an offset with respect to the → Big Bang → nucleosynthesis abundance. Several recent studies have shown that the Spite plateau exhibits very little, if any, dispersion. There is, however, a discrepancy between recent results and that derived from Big Bang nucleosynthesis, based on the cosmological parameters constrained by the → WMAP measurements.

Named after François and Monique Spite, French astronomers, Paris Observatory, who first discovered this relation (1982, A&A 115, 357); → plateau.

To cause physical activity in something; e.g. → stimulated emission.

Verb from → stimulus.

The process by which an electron, which is already in an excited state (an upper energy level, in contrast to its lowest possible level or "ground state"), can "stimulate" a transition to a lower level, producing a second photon of the same energy. The quantum energy of the incoming photon should be equal to the energy difference between its present level and the lower level. This process forms the basis of both the → laser and → maser. Same as → induced emission.

Stimulated, p.p. of → stimulate; → emission.