An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1307
dud (#)

Fr.: fumée   

A mass of tiny particles in the air that rises up from something burning.

M.E., O.E. smoca, related to smeocan "give off smoke;" cf. M.Du. smooc, Du. smook, M.H.G. smouch, Ger. Schmauch; PIE base *smeug(h)- "smoke" (cf. Arm. mux "smoke," Gk. smukho "to burn in a smoldering fire," O.Ir. much, Welsh mwg "smoke").

Dud, from Mid.Pers. dût, dûd "smoke;" Av. dunman- "cloud," duuan- "to fly;" cf. Skt. dhvan- "to smoke;" Hittite tuhhae- "to prouce smoke;" PIE base *dheu- "to blow, reel; smoke, dark."

  ۱) هموار؛ ۲) هموار کردن   
1) hamvâr (#); 2) hamvâr kardan (#)

Fr.: 1) lisse; 2) lisser   

1) Of a curve, free from bumps or abrupt irregularities.
2) To modify a sequential set of numerical data by reducing the differences in magnitude between adjacent values.

O.E. smoð "free from roughness, not harsh," of unknown origin.

Hamvâr "level, equal, an even place or thing," from ham- "same, equally, even; together, with" (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-) + -vâr similarity suffix.

smooth curve
  خم ِ هموار   
xam-e hamvâr

Fr.: courbe lisse   

1) A curve which is free from abrupt fluctuations.
2) A curve if it has tangents at all points and the angle of inclination of the tangent is a continuous function of the arc length.

smooth; → curve.

Smoothed Particle Hydrodynamics (SPH)
  هیدروتوانیک ِ ذره‌های ِ همواریده   
hidrotavânik-e zarrehâ-ye hamvâridé

Fr.: hydrodynamique des particules lissées   

A numerical method for modeling → compressible hydrodynamic flows, which uses particles to simulate a continuous fluid flow. Because the system of hydrodynamical basic equations can be analytically solved only for few exceptional cases, the SPH method provides a numerical algorithm to solve systems of coupled → partial differential equations for continuous field quantities. The main advantage of the method is that it does not require a computational grid to calculate spatial → derivatives and that it is a Lagrangian method, which automatically focuses attention on fluid elements. The equations of motion and continuity are expressed in terms of ordinary differential equations where the body forces become classical forces between particles. This method was first independently developed by Lucy (1977, AJ 82, 1013) and Gingold & Monaghan (1977, MNRAS 181, 375).

Smoothed Particle Hydrodynamics, first used by Gingold & Monaghan (1977); → smooth; → particle; → hydrodynamics.


Fr.: lissage   

The mathematical process that makes a curve smooth.

Verbal noun of → smooth.

smoothing circuit
  برقراه ِ هموارگر   
narqrâh-e hamvârgar

Fr.: circuit atténuateur   

A low-pass filter designed to reduce the amplitude of a ripple while freely passing the direct current obtained from a rectifier or direct-current generator. Also known as smoothing filter.

smoothing; → circuit.

  راب، حلزون   
râb (#), halazun (#)

Fr.: escargot   

A general name for a member of the large group of terrestrial and fresh-water gastropod molluscs which have a coiled shell. → slug.

M.E. snail, snayl(e), O.E. snegel; cognate with M.H.G. snagel, dialectal Ger. Schnegel.

Râb, dialectal Gilaki and Tabari (also see Dehxodâ). Halazun, from Ar.

Snell's law
  قانون ِ اسنل   
qânun-e Snell (#)

Fr.: loi de Snell, loi de Descartes   

The relationship between angles of incidence and refraction for a wave incident on an interface between two media with different indices of refraction. The law states that the ratio of the sine of the → angle of incidence to the sine of the → angle of refraction is a constant: n1/n2 = sinθ2/sinθ1. See also → refractive index. Also known as Descartes' law or the law of refraction.

Named after Dutch mathematician Willebrord Snellius (1580-1626), one of the discoverers of the law; → law.

barf (#)

Fr.: neige   

A precipitation in the form of → ice crystals that falls from clouds when the air temperature is below 0 °C. Snow occurs when → water vapor in the → atmosphere forms directly into ice and completely bypasses the liquid stage of → precipitation. Once an ice crystal has formed, it absorbs up even more water vapor and freezes due to the surrounding atmosphere. The ice crystal then falls down to earth's surface in the form of a → snow crystal, snow → pellet, or more commonly known as the → snowflake. In short, snow formation requires the following conditions: 1) → relative humidity ≥ 100%, 2) → temperature < 0 °C, 3) presence of → condensation nuclei, and 4) → supercooled droplets.

O.E. snaw "snow;" cf. O.S., O.H.G. sneo, O.Fris., M.L.G. sne, M.Du. snee, Du. sneeuw, Ger. Schnee, O.N. snjor, Goth. snaiws "snow;" PIE base *sneigwh- "to snow, snow;" cf. Mid.Pers. snêx, snêxr "snow;" Av. snaēg- "to snow," snaēžaiti "snows;" Skt. snih- "wet;" Gk. nipha "snowflake," neiphei "snows;" L. nix (genitive nivis); O.Ir. snigid "snows;" Lith. sniegas; Rus. snieg'.

Barf "snow," dialectal vafr "snow," var, from Mid.Pers. vafr "snow;" Av. vafra- in jaiwi.vafra- "with deep snow."

snow crystal
  بلور برف   
bolur-e barf

Fr.: cristal de neige   

An → ice crystal forming snow in a → cloud.

snow; → crystal.

snow line
  مرز ِ یخ، یخ-مرز   
marz-e yax, yax-marz

Fr.: limite de glace   

In a → protoplanetary disk, the limit between the regions where water is gaseous and the region where it is cold enough for water to become ice. The core accretion theory predicts that → giant planets form just outside the snow line where they can accrete enough rock and ice to generate a core. Subsequently the core grows into a gas giant like → Jupiter or → Saturn via the → accretion of hydrogen and helium. The snow line location depends on the → luminosity of the central star. For solar system it is about 5 AU, the position of Jupiter. Also known as ice line.

snow; → line.

Marz, → frontier; yax, → ice.


Fr.: congère   

A mound or bank of snow deposited as sloping surfaces and peaks, often behind obstacles and irregularities, due to eddies in the wind field.

snow; → drift.

Barf-rând "snowdrift, drfited snow" from barf, → snow, + rând "driving, drfit; drifted," from rândan "to push, drive, cause to go," causative of raftan "to go, walk, proceed" (present tense stem row-, Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack"); barf-e bâd âvard "snow brought by wind," from barf + bâdwind + âvard, short for âvardé "brought," p.p. of âvardan "to bring; to cause, produce" (Mid.Pers. âwurtan, âvaritan; Av. ābar- "to bring; to possess," from prefix ā- + Av./O.Pers. bar- "to bear, carry," bareθre "to bear (infinitive)," bareθri "a female that bears (children), a mother;" Mod.Pers. bordan "to carry;" Skt. bharati "he carries;" Gk. pherein; L. fero "to carry").

  گلیچ ِ برف، دانه‌ی ِ ~   
golic-e barf, dâne-ye ~

Fr.: flocon de neige   

An agglomeration of many → ice crystals that falls as a unit from a cloud. Snowflakes possess a six-fold symmetry that ultimately derives from the six-fold symmetry of the ice crystal lattice. Typical snowflakes fall at a rate of 1-2 m s-1. The shape of snowflakes is influenced by the → temperature and → humidity of the atmosphere. Snowflakes form in the atmosphere when cold water droplets freeze onto dust particles. Depending on the temperature and humidity of the air where the snowflakes form, the resulting ice crystals will grow into a myriad of different shapes. Snowflakes formed in temperatures below -22 °C consist primarily of simple crystal plates and columns whereas snowflakes with extensive branching patterns are formed in warmer temperatures. Snowflakes are not frozen raindrops. Sometimes raindrops do freeze as they fall, but this is called → sleet. Sleet particles do not have any of the elaborate and symmetrical patterning found in snow crystals.

From → snow + flake, from M.E. akin to O.E. flac- in flacox "flying" (said of arrows), O.N. flakka "to wander," M.Du. vlac "flat, level," M.H.G. vlach, Ger. Flocke "flake."

Golic "snowflake" in dialectal Lori and Laki (originally *geli-ka), variants Laki gal "seed (of millet)," gella "grape berry," Torbat-Heydariyei gella "grape berry," golla "ball, reel," Kurd. kuli, kilole "snowflake," Malâyeri gulu "bead," Qâyeni golle "bead," Qasrâni gella, golla "bead," Tabari gəlilə "bead," Gilaki gudé "ball, bowl, tumour," literary Pers. golulé, goruk "ball;" cf. Skt. guda- "ball, mouthful, lump, tumour;" Pali gula- "ball;" Gk. gloutos "rump;" L. glomus "ball," globus "globe;" Ger. Kugel; E. clot; PIE base *gel- "to make into a ball;" barf, → snow; dâné, → grain.

barfrub (#)

Fr.: chasse-neige   

A piece of equipment mounted on the front of a vehicle for clearing away snow from roads, railroad tracks, etc.

snow + plow, → Plough.

Barfrub, from barf, → snow, + rub, rubidan "to sweep," → scan.

snowplow phase
  فاز ِ برفروب   
fâz-e barfrub

Fr.: phase de chasse-neige   

The third phase in the evolution of a → supernova remnant (SNR) occurring after the → Sedov-Taylor phase when the mass of the swept-up material becomes much larger than the amount of the ejected material. The SNR is surrounded by a cool → shell of accumulated material that is being pushed from behind, similar to what occurs for a snowplow. During this phase, → radiative cooling becomes important and the total energy is no longer conserved. Also called the → radiative phase.

snowplow; → phase.

SNR shell
  پوسته‌ی ِ بازمانده‌ی ِ اَبَر-نوختر   
pustey-e bâzmânde-ye abar-now-axtar

Fr.: coquille de reste de supernova   

A ring-like structure of swept-up → gas and → dust around a → supernova remnant. See also: → free expansion phase, → Sedov-Taylor phase, → snowplow phase.

supernova remnant (SNR); → shell.

Sobolev approximation
  نزدینش ِ سوبولف   
nazdineš-e Sobolev

Fr.: approximation de Sobolev   

A method allowing for a simplified solution to the → radiative transfer equation at frequencies of spectral lines in media moving with a high velocity gradient. This method assumes that the macroscopic velocity gradients are more important than local random variations of thermal line width: dv/dr > vth/l, where dv/dr is the velocity gradient, vth is the thermal broadening of the line, and l the length scale. The Sobolev approximation is only valid if the conditions of the gas do not change over the → Sobolev length. Under the Sobolev approximation, each point in the medium is isolated from other points, and the → radiative transfer problem becomes a local one and therefore much easier to solve.

Named after the Russian astronomer Viktor Viktorovich Sobolev, Moving Envelopes of Stars [in Russian], Leningr. Gos. Univ., Leningrad (1947) [translated by S. Gaposchkin, Harvard Univ. Press, Cambridge, Mass. (1960)]; → approximation.

Sobolev length
  درازای ِ سوبولف   
derâzâ-ye Sobolev

Fr.: longueur de Sobolev   

In the → Sobolev approximation, the length over which the conditions of the gas do not change and the approximation is valid. It is expressed by: ls = vth/(dv/dr), where vth is the thermal line width and (dv/dr) the velocity gradient. In other words, the length over which the profile function of a line is shifted through a distance equal to its own width by the macroscopic velocity gradients that exist in the moving medium.

Sobolev approximation; → length.


Fr.: social   

Of or pertaining to human society.

society; → -al.


Fr.: socialisation   

A continuing process whereby an individual acquires a personal identity and learns the norms, values, behavior, and social skills appropriate to his or her social position (

socialize; → -tion.

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