An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 13048 Search : far
stereography
  استریونگاری   
estereyonegâri

Fr.: stétéographie   

The process or art of depicting solid objects on a plane surface.

stereo- + → -graphy

stereoscope
  استریو-نما، برجسته‌نما   
estereyo-namâ, barjaste-namâ

Fr.: stéréoscope   

An optical instrument for viewing an overlapping pair of photographs (or perspective drawings) in order to see a three-dimensional image.

stereo-; → -scope.

sterile
  سترون   
setarvan (#)

Fr.: stérile   

Incapable of producing offspring; not producing offspring (Dictionary.com).

M.Fr. stérile "not producing fruit," from L. sterilis "barren, unproductive, unfruitful," from PIE *ster- "stiff, rigid, firm, strong."

Satarvan, literally "mule-like, resembling a mule," from setar, variant of astar, → mule, + -van similarity and attribution suffix.

sterile neutrino
  نوترینوی ِ سترون   
notrino-ye setarvan

Fr.: neutron stérile   

A hypothetical type of → neutrino which does not participate in the → weak interaction. It would arise only from ordinary neutrinos oscillating into a sterile form (singlet, right handed → helicity). The sterile neutrino is a candidate for the → dark matter. Sterile neutrinos might have been produced in primordial plasma in the → early Universe. The idea of sterile neutrino was first proposed by Bruno Pontecorvo (1967) in a paper which also discussed neutrino oscillations.

sterile; → neutrino.

Stern-Gerlach experiment
  آزمایش ِ اشترن-گرلاخ   
âzmâyeš-e Stern-Gerlach (#)

Fr.: expérience de Stern et Gerlach   

An experiment devised for measuring the → magnetic moment of → silver atoms. A → beam of silver atoms is directed between the → poles of a non-homogeneous → magnetic field. Contrarily to the prediction of the classical theory, the atoms divide into two distinct parts. One half of atoms are deflected up, the other half deflected down. The amount of deflection up or down is exactly of the same magnitude. Whether an individual atom is deflected up or down appears to be random. From a measurement of the → deflection, one can find the strength of the magnetic moment. This experience provides proof that there exist only two permitted orientations, called the → quantization of → spin.

In honor of Otto Stern (1888-1969), German physicist, Nobel laureate in Physics 1943, and Walter Gerlach (1889-1979), German physicist, who carried out the experiment in 1922. They used a beam of silver atoms from a hot oven because they could be readily detected on a photograph emulsion. Moreover, the silver atoms allowed studying the magnetic properties of a single electron because the atoms have a single outer electron; → experiment.

stilb (sb)
  استیلب   
estilb

Fr.: stilb   

Optics: A unit of luminance equal to one candle per square cm.

From Gk. stilbe "lamp."

stimulate
  گوازیدن   
gavâzidan

Fr.: stimuler   

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

Verb from → stimulus.

stimulated emission
  گسیل ِ گوازیده   
gosil-e gavâzidé

Fr.: émission stimulée   

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.

stimulated star formation
  دیسش ِ گوالیده‌ی ِ ستاره   
diseš-e gavâlide-ye setâré

Fr.: formation stimulée d'étoiles   

A process in which a star is not formed spontaneously but is provoked by the action of external forces, such as pressure and shock on a molecular cloud by close-by → massive stars, → supernova explosions, etc. See also → sequential star formation.

Stimulated, p.p. of → stimulate; → star formation.

stimulus
  گواز   
gavâz

Fr.: stimulus   

Something that incites or rouses to action; an incentive.
Physiology: Something that causes a physical response in an organism,

From L. stimulus "goad, spur;" cognate with Pers. tizsharp.

Gavâz "goad, a stick with a pointed end, for driving cattle," Mid.Pers. *gawâz, lowned in Arm. gawazan "goad;" Av. gauuāza- "whip, stick for driving cattle," from gao- "cattle, cow" (→ Bootes) + āza-, from az- "to drive," azaiti "drives;" cf. Skt. aj- "to drive," ájati "drives;" Gk. agein "to lead, guide, drive;" L. agere "to do, set in motion," → act.

Stirling's approximation
  نزدینش ِ استرلینگ   
nazdineš-e Stirling

Fr.: approximation de Stirling   

A mathematical formula yielding an approximate value for → factorial n, when n is large: n! ≅ (2πn)1/2nne-n, where e is the base of → natural logarithm.

Named after James Stirling (1692-1770), a Scottish mathematician; → approximation.

stochastic
  کاتورگین   
kâturgin

Fr.: stochastique   

Involving or containing a random variable or variables. A stochastic variable is neither completely determined nor completely random. A system containing one or more stochastic variables is probabilistically determined.

From Gk. stokhastikos "able to guess, conjecturing," from stokhazesthai "to aim at, guess," from stokhos "a guess, target," literally "pointed stake."

Kâturgin, from kâtur, kâturé, → random + -gin, adj. suffix, contraction of âgin "filled."

stochastic excitation
  بر‌انگیزش ِ کاتورگین   
barangizeš-e kâturgin

Fr.: excitation stochastique   

The mechanism arising from turbulent convection in the → convective zone of stars, which is responsible for the driving of stellar → pulsation modes. In stars cooler than typically ~ 7 500 K (→ F-type stars and cooler), the stochastic excitation occurs in the convection envelope. In massive stars, it may develop either in the → convective core or in the convective layer beneath the → photosphere. Recent studies suggest that in → Be stars stochastic excitation takes place in the convective core. The stochastic waves can transport → angular momentum from the core to the surface. Fast rotation, as in Be stars, amplifies the stochastic excitation.

stochastic; → mode.

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.

stoicheiology
  استویخیوشناسی   
stoyxiyošenâsi

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.

stoichiometric
  استویخیوسنجیک   
stoyxiyosanjik

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.

stoichiometry
  استویخیوسنجی   
stoyxiyosanji

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)
  استوکس   
stokes (#)

Fr.: stokes   

The unit of → viscosity in the → cgs system, cm2 s-1, equal to 10-4 m2 s-1.

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

Stokes friction factor
  کروند ِ مالش ِ استوکس   
karvand-e mâleš-e Stokes

Fr.: facteur de friction de Stokes   

For the translational motion of a spherical body moving in a → viscous fluid, the proportionality factor between the uniform flow velocity far from the sphere and the drag force, provided no-slip boundary condition and small → Reynolds numbers: f = 6πηR, where η is the Reynolds number and R radius of the sphere.

Stokes; → friction; → factor.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara Arc ari Arr ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit cla clo clo clu Coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg hyp ice ide ima Ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per per pha phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>