An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < -ti Tam Tay tel ten ter The the the the thi thr tid tig tin tol tor tot tra tra tra tra tri tri Tro tsu tur two Typ > >>

Number of Results: 569
toluen (#)

Fr.: toluène   

A colorless, flammable liquid, insoluble in water and soluble in alcohol and ether, used as a solvent and in the manufacture of other organic chemicals and explosives. Chemical formula C6H5CH3. Same as methylbenzene and phenylmethane. See also → trinitrotoluene.

From tolu, from the older name toluol, which refers to tolu balsam, an aromatic extract from the tropical Colombian tree Myroxylon balsamum, from which it was first isolated, + -ene suffix used to form names of unsaturated hydrocarbons, from Gk. -ene denoting origin or source.


Fr.: tomographie   

Any of several techniques, such as → Doppler tomography, for constructing a spatial distribution of physical quantity given measurements that are essentially line-integrals ("projections") through the distribution. Most famously, in medical tomography, the absorption of X-rays by a specimen is directly related to the line integral to make detailed images of a predetermined plane section of a solid object while blurring out the images of other planes.

From Gk. tomo- combining form of tomos "a cut, section, slice" tome "cutting" + → -graphy.

Borešnegâri, from boreš "section, slice, cutting," from boridan "to cut" (Mid.Pers. britan, brinitan "to cut off;" Av. brī- "to shave, shear," brin-; cf. Skt. bhrī- "to hurt, injure," bhrinanti "they hurt") + -negâri, → -graphy.

ton (#)

Fr.: tonne   

A → metric unit of → mass, equal to 1000 → kilograms.

M.E. tunne unit of weight or capacity (cf. O.Fris. tunne, M.Du. tonne, O.H.G. tunna, Ger. tonne), also found in M.L. tunna and O.Fr. tonne, perhaps from a Celtic source.

ton (#)

Fr.: son   

A musical sound of definite pitch, consisting of several relatively simple constituents called partial tones, the lowest of which is called the fundamental tone and the others harmonics or overtones.

M.E., from O.Fr. ton, from L. tonus "a sound, tone, accent," literally "stretching," from Gk. tonos "vocal pitch, raising of voice," related to teinein "to stretch," cognate with Pers. tanidan "to spin, weave," → tension.

Ton, loan from Fr., as above.

Toomre criterion
  سنجیدار ِ تومره   
sanjidâr-e Toomre

Fr.: critère d'Ostriker-Peebles   

A criterion for the stability of the disk of a → spiral galaxy. It is expressed by the → Toomre parameter.

Toomre criterion; → criterion.

Toomre length
  درازای ِ تومره   
derâzâ-ye Toomre

Fr.: longueur de Toomre   

The scale beyond which for a thin, rotating disk, rotation stabilizes self-gravitational contraction. The Toomre length is given by: λT = 4π2GΣ / κ2, where G is the → gravitational constant, Σ is the mass → surface density, and κ is the → epicyclic frequency (Toomre 1964, ApJ 139, 1217).

Toomre parameter; → length.

Toomre parameter
  پارامون ِ تومره   
pârâmun-e Toomre

Fr.: paramètre de Toomre   

A quantity that measures the stability of a differentially rotating disk of matter against → gravitational collapse. It is expressed by the relation: Q = csκ / πGΣ, where cs is the → sound speed, κ the → epicyclic frequency, G the → gravitational constant, and Σ the → surface density. The disk is linearly stable for Q > 1 and linearly unstable for Q < 1.

After Alar Toomre (1936-), an American astrophysicist of Estonian origin, professor of mathematics at the Massachusetts Institute of Technology; → parameter.

toothed-wheel experiment
  آزمایش ِ چرخ ِ دندانه‌دار   
âzmâyeš-e carx-e dandâne-dâr

Fr.: expérience de la roue dentée   

The experiment which provided the first accurate measurement of the speed of light. The experiment, conducted by the French physicist Armand H. L. Fizeau (1819-1896) in 1849, used a rotating wheel containing 720 teeth. The function of the wheel was to cut a light beam into short pulses and to measure the time required for these pulses to travel to a distant mirror and back (17.34 km). The round-trip time for each pulse could be calculated to be about 1/18,000 sec, which yielded the value of 315,300 km/sec for the speed of light. Leon Foucault (1819-1868) improved on Fizeau's method by replacing the cogwheel with a rotating mirror. Foucault's estimate, published in 1862, was 298,000 km/s.

From tooth; M.E.; O.E. toth (cf. O.S., Dan., Swed., Du. tand, O.N. tönn, O.Fris. toth, O.H.G. zand, Ger. Zahn, Goth. tunthus), cognate with Pers. dandân, as below; → wheel; → experiment.

Âzmâyeš, → experiment; carxwheel; dandâne-dâr "toothed," from dandân "tooth," Mid.Pers. dandân; Av. dantan-; cf. Skt. dánta-; Gk. odontos; L. dens (Fr. dent); Lith. dantis, O.Ir. det, Welsh dent; PIE base *dont-/*dent- "tooth."

bâlâ (#)

Fr.: sommet, du haut, haut   

The highest point or part. The higher end of anything on a slope.

M.E., O.E. top "summit, crest, tuft;" cf. O.N. toppr "tuft of hair," O.Fris. top "tuft," O.Du. topp, Du. top, O.H.G. zopf "end, tip, tuft of hair," Ger. Zopf "tuft of hair."

Bâlâ "up, above, high, elevated, height" (variants boland "high, tall, elevated, sublime," borz "height, magnitude" (it occurs also in the name of the mountain chain Alborz), Laki dialect berg "hill, mountain;" Mid.Pers. buland "high;" O.Pers. baršan- "height;" Av. barəz- "high, mount," barezan- "height;" cf. Skt. bhrant- "high;" L. fortis "strong" (Fr. and E. force); O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg; PIE base *bhergh- "high."

top-down structure formation
  دیسش ِ ساختار از بالا به پایین   
diseš-e sâxtâr az bâlâ bé pâyin

Fr.: formation des structures du haut vers le bas   

A cosmological model of → structure formation in which larger structures, such as galaxy → superclusters or perhaps even the vast → filaments and → voids, form earlier and then they fragment into smaller structures such as individual galaxies. Opposite of → bottom-up structure formation.

top; → down; → structure; → formation.

top-heavy IMF
   IMF ِ بالا-سنگین   
IMF-e bâlâ-sangin


A star formation process in which → massive stars form more abundantly than that predicted by standard models, whereby the top end of the → initial mass function is significantly flatter than the canonical → Salpeter slope.

top; → heavy; → initial mass function.

topocentric coordinates
  هماراهای ِ جا-مرکزی   
hamârâhâ-ye jâ-markazi

Fr.: coordonées topocentriques   

A coordinate system that uses the observer's location as its central reference point. Usually, the difference in the position of an object in the sky measured using topocentric and geocentric coordinates is very small because most celestial objects are so far away. However, for nearby objects this is not true. The Sun, for example, may appear displaced as much as eight arcseconds from its geocentric position, and the Moon by as much as one degree.

Topocentric, from topo- combining form of Gk. topos "place" + centric, from → center; → coordinate.

Hamârâhâ, → coordinate; jâ-markazi "topocentric," from "place" (from Mid.Pers. giyâg "place;" O.Pers. ā-vahana- "place, village;" Av. vah- "to dwell, stay," vanhaiti "he dwells, stays;" Skt. vásati "he dwells;" Gk. aesa (nukta) "to pass (the night);" Ossetic wat "room; bed; place;" Tokharian B wäs- "to stay, wait;" PIE base ues- "to stay, live, spend the night") + markazi, of, pertaining to markaz, → center.

  توپوشناختی، توپوشناسیک   
topošenâxti, topošenâsik

Fr.: topologique   

Of or relating to → topology.

topology; → -ic; → -al

topological defect
  آک ِ توپوشناختی، ~ توپوشناسیک   
âk-e topošenâxti, ~ topošenâsik

Fr.: défaut topologique   

In → cosmological models, a stable configuration of → matter formed when the → early Universe underwent → phase transitions during which fundamental symmetries were broken. There are a number of possible types of defects, such as domain walls, → cosmic strings, → magnetic monopoles, and → texture s. Same as → cosmic defect.

topological; → defect.

topological space
  فضای ِ توپوشناختی   
fazâ-ye topošenâxti

Fr.: espace topologique   

A set X together with a collection of open subsets T that satisfies the three following conditions: 1) The empty set Ø and X are in T. 2) The intersection of a finite number of sets in T is also in T. 3) The union of an arbitrary number of sets in T is also in T.

topological; → space.


Fr.: topologie   

The study of the properties of geometric figures that remain invariant under certain transformations, as bending or stretching. A circle is topologically equivalent to an ellipse (into which it can be deformed by stretching) and a sphere is equivalent to an ellipsoid.

From topo- combining form of Gk. topos "place" + → -logy.

Topošenâsi, from topo-, loan from Gk., as above, + šenâsi-logy.

âhir (#)

Fr.: torche   

A light to be carried in the hand, consisting of some combustible substance, as resinous wood, or of twisted flax or the like soaked with tallow or other flammable substance, ignited at the upper end (

M.E. torche, from O.Fr. torche "torch," originally "twisted thing," then "torch formed of twisted tow dipped in wax," probably from V.L. *torca, alteration of L.L. torqua, from torquere "to twist," → torque.

Âhir, from Kurd. âhir "torch," variant of âzar, → fire.

Torino scale
  مرپل ِ تورین   
marpel-e Turin

Fr.: échelle de Turin   

A scale used to assess the threat posed by the → impact of a → near-Earth object (NEO). It considers the impact energy as well as the probability of impact. It is designed to communicate to the public the risk associated with a NEO in more qualitative form than the → Palermo scale. The → impact hazard is expressed by a number between 0 and 10 depending on the probability that an impact will occur and the kinetic energy of the potential → impactor. The extent of damage ranges from inconsequential (0) to catastrophic (10). The scale is color-coded such that white = no consequence; green = meriting careful monitoring; yellow = meriting concern; orange = threatening events; red = impact is certain.

Named for Torino, because the scale was adopted by that city in Italy in 1999; → scale.

  پیچ-توف، توفان ِ پیچنده   
pic-tuf, tufân-e picandé

Fr.: tornade   

A mass of rotating air with high wind speeds at its center. It is produced in a very severe thunderstorm and appears as a funnel cloud extending from the base of a Cumulonimbus to the ground.

Tornado, metathesis from Sp tronada "thunderstorm," from tronar "to thunder," from L. tonare "to thunder," → thunder.

Pic-tuf, from pic present stem of picidan "to twist, entwine, coil" (Mid.Pers. pecidan "to twist, entwine") + tuf short for tufân, → storm.
Tufân-e picandé, from tufânstorm + picandé agant noun/adj. of picidan

cambarvâr (#)

Fr.: toroïde   

A surface of revolution obtained by rotating a closed plane curve about an axis parallel to the plane which does not intersect the curve. The simplest toroid is the → torus. The solid enclosed by such a surface.

From tor-, from → torus + → -oid.

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