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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superposition principle
  پروز ِ برهم‌نهش   
parvaz-e barhamneheš

Fr.: principe de superposition   

1) Math.: The principle concerned with homogeneous and non-homogeneous → linear differential equations, stating that two or more solutions to a linear equation or set of linear equations can be added together so that their sum is also a solution.
2) One of the most fundamental principles of → quantum mechanics which distinctly marks the departure from classical concepts. It holds that any linear superposition of → wave functions is also a possible wave function. Simply put, the state of an object is all its possible states simultaneously, as long as we do not look to check. It is the measurement itself that causes the object to be limited to a single possibility. The superposition principle is rooted in the linearity of → Schrödinger's equation. Hence if two solutions of the wave function, ψ1 and ψ2, are known, other solutions, of the form: ψ = a1ψ1 + a2ψ2 also represent possible states of the system.

superposition; → principle.

supersaturation
  ابر-انجالش   
abar-anjâleš

Fr.: super-saturation   

The process whereby the amount of → water vapor in the air exceeds that needed to → saturate. In other words, the condition of air in which the → humidity is above the level required for saturation at a given temperature (i.e. the → relative humidity is greater than 100%). When the temperature drops below freezing, this can lead to a situation where more water vapor is present in the air than the air can hold. At every temperature, there is a maximum amount of water vapor that can be supported in the air. The higher the temperature, the more water vapor can be accommodated. But if the air that is already at 100% relative humidity is cooled then it becomes supersaturated, and this situation is unstable. As a result, the excess water vapor crystallizes out, either into water droplets or directly into ice.

super-; → saturation.

supersonic
  اَبَر-صدایی   
abar-sedâyi

Fr.: supersonique   

Describing a speed that is greater than the → sound speed in the medium concerned. See also → Mach number, → subsonic.

super-; → sonic.

suppression
  نهاوش   
nehâveš

Fr.: suppression   

The act of suppressing; the state of being suppressed. → Compton suppression, → zero suppression.

suppress; → -tion.

supra-Eddington layer
  لایه‌ی ِ ابر-ادینگتونی   
lâye-ye abar-Eddingtoni

Fr.: couche super-eddingtonienne   

In some stellar models, particularly for evolved → massive stars, such as → red supergiants, → Luminous Blue Variables, and → Wolf-Rayet stars, an outermost layer of the stellar envelope where the luminosity might exceed the → Eddington limit. This is due to the → opacity peak produced by the variation in the ionization level of hydrogen in the outer → convective envelope, beneath the surface, of very luminous stars. The opacity peak generates supra-Eddington layers and density inversion. The high opacity decreases the Eddington luminosity in these layers, possibly to fainter levels than the actual stellar luminosity. As a result, the → radiative acceleration exceeds the → gravitational acceleration leading to → mass loss enhancement (see, e.g., A. Maeder, Physics, Formation and Evolution of Rotating Stars, Springer, 2009).

supra-; → Eddington limit; → layer.

supra-horizontal branch star
  ستاره‌ی ِ فراز ِ شاخه‌ی ِ افقی   
setâre-ye farâz-e šâxe-ye ofoqi

Fr.: étoile au-dessus de la branche horizontale   

A member of a rare class of objects found in → globular clusters to lie about one magnitude above and to the blue part of the → horizontal branch. These stars are identified as post → EHB stars on their way from to the → asymptotic giant branch.

supra-; → horizontal; → branch; → star.

surface tension
  تنش ِ رویه‌ای   
taeš-e ruye-yi

Fr.: tension superficielle   

The inward → attraction of the → molecules at the → surface of a → liquid. The reason is that the molecules at the surface do not have other like molecules on all sides of them and consequently they cohere more strongly to those directly associated with them on the surface. Also called surface energy and capillary forces.

surface; → tension.

surjection
  برشانش   
baršâneš

Fr.: surjection   

A mapping f of a set A onto a set B in such a way that every b element of B is the image of at least one element a of A. In other words, for any element b of B, the equation f(a) = b yields at least one solution. Allso called → surjective mapping.

From → sur- + → injection.

suspicion
  برگاسش   
bargâseš

Fr.: suspicion   

1) The state of mind or feeling of one who suspects.
2) An instance of suspecting something or someone (Dictionary.com).

M.E., from suspecioun, from O.Fr. suspicion, sospeçon "mistrust, suspicion," from L.L. suspectionem "mistrust, suspicion, fear," noun of state from past participle stem of L. suspicere "to look up at," → suspect.

Verbal noun from bargâsidan, → suspect.

symmetric relation
  بازانش ِ همامون   
bâzâneš-e hamâmun

Fr.: relation symétrique   

A relation between two quantities such that the first is to the second as the second is to the first. In symbols: a R b = b R a. For example, multiplication is an operation with a symmetric relation between the factors: 5 x 3 = 3 x 5.

symmetric; → relation.

synchrone
  همگام   
hamgâm

Fr.: synchrone   

A line connecting the dust grains in a comet tail that left the nucleus at the same time. → syndyne.

From L. synchronus "simultaneous," from Gk. synchronos "happening at the same time," from → syn- "together" + khronos "time."

Hamzamân, from ham-, → syn- "together" + zamân, → time.

synchronous
  همگام   
hamgâm (#)

Fr.: synchrone   

1) Going on at the same rate and exactly together. Compare → simultaneous.
2) Having the same period and phase of oscillation or cyclic movement.

From L. synchronus "simultaneous," from Gk. synchronos "happening at the same time," from → syn- "together" + khronos "time."

Hamgâm literally "at the same pace," from ham-, → syn-, + gâm "step, pace," Mid.Pers. gâm, O.Pers. gam- "to come; to go," Av. gam- "to come; to go," jamaiti "goes," Mod.Pers. âmadan "to come," Skt. gamati "goes," Gk. bainein "to go, walk, step," L. venire "to come," Tocharian A käm- "to come," O.H.G. queman "to come," E. come; PIE root *gwem- "to go, come."

synchronous orbit
  مدار ِ همگام   
madâr-e hamgâm

Fr.: orbite synchrone   

synchronous rotation.

synchronous; → orbit.

synchronous rotation
  چرخش ِ همگام   
carxeš-e hamgâm (#)

Fr.: rotation synchrone   

Of a body orbiting another, where the orbiting body takes as long to rotate on its axis as it does to make one orbit. Therefore it always keeps the same hemisphere pointed at the body it is orbiting. Both bodies are tidally locked (→ tidal locking). This phenomenon is a natural consequence of → tidal braking. Synchronous rotation is common throughout the → solar system. It is found among the satellites of → Mars (→ Phobos and → Deimos), → Jupiter (most of Jupiter satellites, including the → Galilean Moons) and → Saturn (e.g. → Iapetus). Similarly, → Pluto and its moon → Charon are locked in mutual synchronous rotation, with both of them keeping the same faces towards each other.

synchronous; → rotation.

synchrotron
  سنکروترون   
sankrotron

Fr.: synchrotron   

A type of → accelerator that accelerates charged subatomic particles (generally protons) in a circular path. Unlike → cyclotrons, in which particles follow a spiral path, synchrotrons consist of a single ring-shaped tube through which the particles loop numerous times, guided by precisely synchronized magnetic fields and accelerated at various points in the loop by electric field bursts. See also → synchrotron frequency, → synchrotron radiation.

From synchro- a combining form representing synchronized or synchronous in compound words, from L. synchronus "simultaneous," from Gk. synchronos "happening at the same time," from → syn- "together" + khronos "time" + → -tron.

Sankrotron, from Fr., as above.

synchrotron frequency
  بسامد ِ سینکروترون   
basâmad-e sinkrvtrvn

Fr.: fréquence synchrotron   

The revolution frequency of a → relativistic particle of charge q and mass m in the → uniform magnetic field B of a synchrotron. It is expressed by: fsyn = qB/2πγm, where γ is the → Lorentz factor. This frequency is lower than → cyclotron frequency for a → non-relativistic case.

synchrotron; → frequency.

synchrotron radiation
  تابش ِ سنکروترون   
tâbeš-e sankrotron

Fr.: rayonnement synchrotron   

The electromagnetic radiation emitted by high-energy particles that are moving in magnetic fields, as in a synchrotron particle accelerator. The acceleration of the moving charges causes the particles to emit radiation. Radio galaxies and supernova remnants are intense sources of synchrotron radiation. Characteristics of synchrotron radiation are its high degree of polarization and nonthermal spectrum.

synchrotron; → radiation.

synodic month
  ماه ِ هماگمی   
mâh-e hamâgami

Fr.: mois synodique   

The interval of 29.530 588 days (29d 12h 44m 2.80s), on average, between two successive → new Moons. Same as → lunation.

synodic; → month.

synonym
  همچم   
hamcem

Fr.: synonyme   

Grammar: A word having the same or nearly the same meaning as another in the language. Opposite of → antonym.

From L. synonymum, from Gk. synonymon "word having the same sense as another," from synonymos "having the same name as, synonymous," from → syn- "together, same" + onyma, → name.

Hamcem, from ham-, → syn-, + cem, → meaning.

synthetic division
  بخش ِ هندایشی   
baxš-e handâyeši

Fr.: division synthétique   

A method of dividing a polynomial in the special case of dividing by a linear factor. Synthetic division allows one to do long division problems much quicker. It is related to the → Ruffini-Horner method.

synthetic; → division.

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