An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1318
stochastic process
  فراروند ِ کاتورگین   
farâravand-e kâturgin

Fr.: processus stochastique   

Any process involving a sequence of random variables. The future evolution of a stochastic process is therefore described by probability distributions.

stochastic; → process.

stochastic self-propagating star formation
  دیسش ِ ستارگان با خود-توچش ِ کاتورگین   
diseš-e setâregân bâ xod-tuceš-e kâturgin

Fr.: formation d'étoiles par auto-propagation stochastique   

A mechanism that could be responsible for global → spiral structure in galaxies either by itself or in conjunction with spiral → density waves. In this mechanism, star formation is caused by → supernova-induced → shocks which compress the → interstellar medium. The → massive stars thus formed may, when they explode, induce further → star formation. If conditions are right, the process becomes self-propagating, resulting in agglomerations of young stars and hot gas which are stretched into spiral shaped features by → differential rotation. Merging of small agglomerations into larger ones may then produce large-scale spiral structure over the entire galaxy. The SSPSF model, first suggested by Mueller & Arnett (1976) was developed by Gerola & Seiden (1978). While the → density wave theory postulates that spiral structure is due to a global property of the galaxy, the SSPSF model examines the alternative viewpoint, namely that spiral structure may be induced by more local processes. The two mechanisms are not necessarily mutually exclusive, but they involve very different approaches to the modeling of galaxy evolution. The SSPSF gives a better fit than the density wave theory to the patchy spiral arms found in many spiral galaxies. However, it cannot explain → galactic bars.

stochastic; → self; → propagate; → star; → formation.


Fr.: stoicheiologie   

1) The statement or discussion of the first principles of any science or art (1913 Webster).
2) Logic: The doctrine of the elementary requisites of mere thought (Sir W. Hamilton; 1913 Webster).

stoichiometry, → -logy.


Fr.: stoechiométrique   

1) Of or pertaining to → stoichiometry.
2) Pertaining to or involving substances that are in the exact proportions required for a given reaction.

stoichiometry; → -ic.


Fr.: stoechiométrie   

1) The branch of chemistry that studies chemical processes within the context of the laws of definite proportions and conservation of matter and energy.
2) The study of the quantitative relationships of two or more compounds in a chemical reaction.

From Gk. stoikheion "element, component, principle," Stoikheia "elements" (the title of Euclid's great collection of Gk. mathematics); loaned in Ar. and Pers. (9-th century A.D.) as ustuqus (اسطقس); akin to stoikhos "row, line, verse," steikhein "to go, march;" cf. Skt. stighnoti "rises, steps;" O.H.G. stigan; Ger. steigen; Goth. steigan "to go up, ascend;" O.E. stigan "to climb, go;" Ger. Steig "path;" O.E. stig "narrow path;" PIE base *steigh- "to go, rise, step, walk," + → -metry.

Stoyxiyosanji, from stoyxiyo loan from Gk., as above, + -sanji, → -metry.

stokes (st)
stokes (#)

Fr.: stokes   

The unit of → viscosity in the → cgs system, cm2/s, equal to 10-4 m2/s.

Stokes law.

Stokes law
  قانون ِ استوکس   
qânun-e Stokes (#)

Fr.: loi de Stokes   

1) Fluid mechanics: At low velocities, the frictional force on a spherical body moving through a fluid at constant velocity is equal to 6πaην, where a is the radius of the sphere, η the fluid viscosity, and ν the velocity.
2) Spectroscopy: The wavelength of luminescence excited by radiation is always greater than that of the exciting radiation.

After Sir George Gabriel Stokes (1819-1903), a British mathematician and physicist, who made important contributions to fluid dynamics, optics, and mathematical physics; → law

Stokes parameters
  پارامون‌های ِ استوکس   
pârâmunhâ-ye Stokes

Fr.: paramètres de Stokes   

Four parameters which are needed to fully describe the → polarization state of → electromagnetic radiation. They involve the maximum and minimum intensity, the ellipticity, and the direction of polarization. The four Stokes parameters are traditionally defined as follows:
I ≡ total intensity.
Q ≡ I0 - I90 = difference in intensities between → horizontal and → vertical  → linearly polarized components.
U ≡ I+45 - I-45 = difference in intensities between linearly polarized components oriented at +45° and -45° (or 135°).
V ≡ Ircp - Ilcp = difference in intensities between right and left → circularly polarized polarized components.

Stokes law; → parameter.

sang (#)

Fr.: pierre   

The hard nonmetallic mineral or group of consolidated minerals either in mass or in a fragment of pebble or larger size. See also → rock.

O.E. stan; cf. O.N. steinn, Dan. steen, O.H.G., Ger. Stein; from PIE *stai- "stone," also "to thicken, stiffen" (cf. Skt. styayate "curdles, becomes hard;" Av. stay- "heap;" Gk. stear "fat, tallow," stia, stion "pebble").

Sang "stone, rock;" Mid.Pers. sang; O.Pers. aθanga-; Av. asenga- "stone;" PIE *aken-.

Stone Age
  عصر ِ سنگ   
asr-e sang (#)

Fr.: âge du fer   

A prehistoric period during which the main material used to make tools and weapons was stone. The Stone Age is usually divided into three separate periods (Paleolithic Period, Mesolithic Period, and Neolithic Period) based on the degree of sophistication in the fashioning and use of tools. The Paleolithic time period is by far the longest, beginning some two million years ago and ending around 10,000 BC to coincide with the end of the last ice age (Pleistocene epoch).

stone; → age.

stony meteorite
  شخانه‌ی ِ سنگی   
šaxân-ye sangi

Fr.: météorite pierreuse   

A meteorite composed largely of rock-forming (→ silicate) → minerals. Stony meteorites are the most abundant kind, about 95%, of all meteorites. They are divided into two groups: → chondrites and → achondrites.

stone; → meteorite.

stony-iron meteorite
  شخانه‌ی ِ سنگی-آهنی   
šaxâne-ye sangi-âhani

Fr.: sidérolithe, sidérolite   

Meteorites comprised of roughly equal amounts of → nickel/→ iron and → stone. They are divided into two groups: → pallasites and → mesosiderites. The stony-irons are thought to have formed at the core/mantle boundary of their parent bodies. The stony-irons account for less than 2% of all known meteorites. Also called → siderolite.

stony; → iron; → meteorite.

  ۱) بازداشتن؛ بازداشت؛ ۲) دریچه   
1) bâzdâštan; bâzdâšt (#); 2) daricé; (#)

Fr.: diaphragme   

1) To hinder or prevent the passage of. → stopping power.
2) The diaphragm used in optical instruments to cut off the marginal portions of a beam of light passing through lenses. → field stop; → stop number.

M.E. stoppen (v.), O.E. -stoppian (in forstoppian "to stop up, stifle"); V.L. *stuppare "to stop or stuff with tow or oakum" (cf. It. stoppare, Fr. étouper "to stop with tow"), from L. stuppa "coarse part of flax, tow."

1) Bâzdâštan, bâzdâšt- "to stop, restrain, inhibit, coerce, detain," from bâz-, → re-, + dâštan "to have, hold, maintain, possess," → access.
2) Daricé, literally "small door; window," from dar "door," + -cé diminutive suffix. Dar "door," Mid.Pers. dar, O.Pers. duvara-, Av. dvar-, cf. Skt. dvár-, Gk. thura, L. fores, P.Gmc. *dur-, O.E. duru, E. door, Lith. dvaras "court-yard;" PIE *dhwer-/*dhwor- "door, gate."

stop number
  وابر ِ کانونی   
vâbar-e kânuni

Fr.: rapport focal   

Same as → focal ratio.

stop; → ratio.

Vâbar, → ratio; kânuni, → focal.

stopping power
  توان ِ بازداشت   
tavân-e bâzdâšt

Fr.: pouvoir d'arrêt   

A quantity indicating the extent with which a substance absorbs a → charged particle passing through it. It is the energy lost by a → non-relativistic particle per unit length of its path in the substance.

stop; → power.

  رهاواژ، فکن‌واژ   
rahâ-vâž, fekan-vâž

Fr.: mot vide   

Computers: A very commonly used word that is normally excluded by computer search engines. Stopwords have very little informational content, such as: and, the, of, it, as, may, that, a, an, of, off, etc.

stop; → word.

Rahâ-vâž, literally "free word," from rahâ "free, set free" (O.Pers. rad- "to leave," Skt. rah-, rahati "separates, leaves," Av. razah- "isolation;" PIE *redh-) + vâž, vâžé, → word. Fekan-vâž, literally "dropped word," from fekan present stem of fekandan, afkandan "to throw, cast away;" Mid.Pers. abgandan "to throw;" O.Pers. avakan- "to throw, place on," from Proto-Iranian *kan- "to throw, place, put."

tufân (#)

Fr.: orage   

An atmospheric disturbance with strong winds accompanied by rain, snow, or other precipitation and often by thunder and lightning.
A violent disturbance or upheaval.

M.E, from O.E. storm; cf. O.S., M.L.G., M.Du., Du. storm, O.H.G., Ger. sturm.

Tufân "storm; the roaring of the sea; noise, confused hum of men or animals," Lori tufo, Laki tuf "intense shower accompanied by wind," from tufidan "to roar, raise a tumult."

dâstân (#)

Fr.: conte, histoire   

A narrative, either true or fictitious, in prose or verse, designed to interest, amuse, or instruct the hearer or reader; tale (

M.E. storie, from O.Fr. estorie, estoire "story, chronicle, history," from L.L. storia, shortened from L. historia "history, account, tale, story," → history.

Dâstân "story, fable, romance."


Fr.: traînard   

One who moves along slowly so as to remain some distance behind the person or people in front. → blue straggler.

From straggle "to wander from the proper path, to rove from one's companions," from M.E. straglen "to wander."

Veylân "wanderer, vagabond," of unknown origin, may be related to yalé "turned loose, vagabond, allowed to pasture at liberty, rover," or vel "set free."

râst (#)

Fr.: droit   

Free from a bend, angle, or curve. → straight line.

M.E. streght, straight, from p.p. of strecchen, → stretch.


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