An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 105 Search : ring
ringdown
     

Fr.: desexcitation finale   

The last stage of → merger between two → black holes undergoing → inspiral. At the end of the evolution of a → binary black hole system, the black holes get close enough to → merge together into a single, larger black hole (→ black hole merger). The resulting black hole is at first distorted and asymmetric, but in the ringdown process the black hole's vibrations decay due to → gravitational radiation leaving finally a quiescent, spinning black hole.

M.E. ring, from O.E. hringan; akin to O.Norse hringja "to ring;" → down.

ringlet
  حلقک   
halqak

Fr.: annelet   

1) A small ring.
2) Any of the thin or narrow rings that compose the major → Saturn's rings.

ring; → -let.

Saturn's rings
  حلقه‌های ِ کیوان   
halqehâ-ye Keyvân (#)

Fr.: anneaux de Saturne   

A system of rings around Saturn made up of countless small particles, ranging in size from micrometers to meters, that orbit the planet. The ring particles are made almost entirely of → water ice, with some contamination from → dust and other chemicals. The ring system is divided into six major components: D, C, B, A, F, and G rings, listed from inside to outside. But in reality, these major divisions are subdivided into thousands of individual → ringlets. The large gap between the A and B rings is called the Cassini division. Saturn's rings are extraordinarily thin: though they are 250,000 km or more in diameter, they are less than one kilometer thick. → A ring, → B ring, → C ring, → D ring, → F ring, → G ring.

Saturn; → ring.

scattering
  پراکنش   
parâkaneš (#)

Fr.: diffusion   

The process in which the direction of motion of → particles or → waves is changed randomly because of their → interactions (→ collisions) with other particles of the → medium transversed.
Two parameters govern scattering: 1) the wavelength (λ) of the incident radiation, and 2) the size of the scattering particle (r), usually expressed as the nondimensional size parameter, x = 2πr / λ. The size parameter defines three types of scattering:
1) x much less than 1 (or r much smaller than λ), → Rayleigh scattering;
2) x ~ 1 (or rλ), → Mie scattering; and
3) x much larger than 1 (or r much larger than λ), → geometric scattering.
See also: → atmospheric scattering, → backscattering, → Brillouin scattering, → coherent scattering, → Compton scattering, → elastic scattering, → forward scattering, → last scattering, → last scattering surface, → multiple scattering, → noncoherent scattering, → quasi-single-scattering approximation, → Raman scattering, → scattering angle, → scattering coefficient, → scattering of stars, → selective scattering, → single scattering, → spin-flip scattering, → surface of last scattering, → Thomson scattering.
Related terms: → diffraction; → diffusion; → dispersion; → distribution.

Verbal noun of → scatter.

scattering angle
  زاویه‌ی ِ پراکنش   
zâvie-ye parâkaneš

Fr.: angle de diffusion   

The angle between the → incident radiation on a → particle (such as a water droplet in a rainbow) and the scattered radiation (such as the light ray leaving the droplet). Scattering angle is a function of → impact parameter. In other words, The angle along which the change of direction has taken place, irrespective whether radiation is scattered by particles or reflected (refracted) by a surface.

scattering; → angle.

scattering coefficient
  همگر ِ پراکنش   
hamgar-e parâkaneš

Fr.: coefficient de diffusion   

The fraction of light scattered per unit distance in a medium.

scattering; → coefficient.

scattering of stars
  پراکنش ِ ستارگان   
parâkaneš-e setâregân

Fr.: diffusion des étoiles   

The progressive increase of random motions of → disk stars with increasing stellar → ages. While some initial random motion seems likely in the disturbed conditions of disks when the oldest stars formed, the observation is generally attributed to scattering processes. Both massive gas → clumps and → spiral waves are considered as scattering agents (J. A. Sellwood & J. J. Binney, 2002, astro-ph/0203510 and references therein).

scattering; → star.

selective scattering
  پراکنش ِ گزینشی   
parâkaneš-e gozineši

Fr.: diffusion sélective   

A type of scattering that occurs when certain → particles are more effective at scattering a particular → wavelength of light, as in → Rayleigh scattering.

selective; → scattering.

single scattering
  پراکنش ِ تک   
parâkaneš-e tak

Fr.: diffusion unique, ~ simple   

A type of scattering where photons are scattered only once. Single scattering dominates in → optically thin media, since photons have a high probability of exiting the medium (e.g., a thin cloud) before being scattered again.

single; → scattering.

space weathering
  سایند ِ فضایی   
sâyand-e fazâyi

Fr.: altération spatiale   

The slight erosion of Solar System bodies (planets, moons, asteroids) caused by the → solar wind, → cosmic rays, and → micrometeorite bombardments. Space weathering affects the physical and optical properties of the surfaces of these bodies. Understanding this process is therefore important for the interpretation of remotely obtained spectral data, such as space probe photographs of outer Solar System moons.

space; → weathering.

spin-flip scattering
  پراکنش با وارونی ِ اسپین   
parâkaneš bâ vâruni-ye espin

Fr.: diffusion avec renversement du spin   

Quantum mechanics: The scattering of a particle that reverses the spin direction.

spin; flip, from flip-flap; → scattering.

Parâkaneš, → scattering; "with;" vâruni, noun from vârun, → inverse; espin, → spin.

spring
  ۱) بهار؛ ۲) چشمه؛ ۳) فنر   
1) bahâr (#); 2) cešmé (#); 3) fanar (#)

Fr.: 1) printemps; 2) source; 3) ressort   

1) The season that starts when the Sun, during its apparent yearly motion, attains the celestial longitude 0 degree in the Northern Hemisphere and 180 degrees in the Southern Hemisphere. The current length of the spring season, around the year 2000, is about: spring 92.76 days.
2) A surface flow of groundwater which occurs any time the water table intersects the surface. Related concept → source = xan (خن).
3) An elastic device, usually a twisted piece of metal, that returns to its original shape when it is pressed or stretched, used chiefly to exert constant tension or absorb movement.

1) From the verb M.E. springen; O.E. springan "to leap, burst forth, fly up;" the notion is of the "spring of the year," when plants "spring up" cf. Du., Ger. springen.
2) Similarly from the verb, as above, M.E. spring(e); O.E. spring, spryng; cf. O.H.G., Dan., Sw. spring.
3) From the verb spring, as above.

1) Bahâr, from Mid.Pers. wahâr "spring;" O.Pers. vāhara- "spring time," θūra-vāhara- "name of a spring month;" Av. vaηhar "spring;" cf. Skt. vasara- "relating or appearing in the morning;" Gk. ear "spring;" L. uēr "spring," vernus "of spring;" O.N. vār "spring;" Lith. vasara "summer;" O.C.S. vesna "spring."
2) Cešmé "spring, source," from Mid.Pers. cašmag "spring, source," supposed to be related to cašm, cešmeye.
3) Fanar, from Turk fanâr.

spring constant
  پایای ِ فنر   
pâpâ-ye fanar

Fr.: constante de rappel du ressort   

A characteristic of a spring which is defined as the ratio of the force affecting the spring to the displacement caused by the force. In other words, the spring constant is the force applied if the displacement in the spring is unity. It is expressed by the equation k = -F/x (from → Hooke's law), where F = force applied, x = displacement by the spring. The spring constant is usually expressed in Newton per meter (N/m).

spring; → force.

spring tide
  مهکشند   
mehkešand (#)

Fr.: grande marée   

Tide that occurs when the → Earth, the → Sun, and the → Moon are in a line. This happens approximately twice a month, around → new moon and → full moon. In such a condition, known as → syzygy, the tidal force due to the Sun reinforces that due to the Moon. Spring tides have nothing to do with the season spring. The name derives from the meaning "a leap, jump, bound, rise."

Spring "a leap, jump, or bound;" M.E. springen, from spring O.E. springan "to leap, fly up; spread, grow;" cognates: O.N., O.Fris. springa, M.Du. springhen, O.H.G. springan, Ger. springen, from PIE *sprengh-, form *spergh- "to move, hasten, spring" (Skt. sprhayati "desires eagerly," Gk. sperkhesthai "to hurry."

Mehkešandak "high tide," from meh-, → high, + kešand, → tide.

sputtering
  اُسپرانی   
osparâni

Fr.: éjection par collision ionique   

The ejection of charged particles or atoms by a solid or liquid surface which undergoes collision with high-energy ions.

Verbal noun of → sputter.

squaring the circle
  چاروشش ِ پرهون، ~ ِ دایره   
cârušeš-e parhun, ~ dâyeré

Fr.: quadrature du cercle   

Same as → quadrature of the circle

square; → wave.

squaring the square
  چاروشش ِ چاروش   
cârušeš-e câruš

Fr.: quadrature du carré   

The mathematical problem of subdividing a square into a number of smaller squares, all of different sizes.

square; → square.

string
  تار، ریسمان   
târ, rismân

Fr.: corde   

1) General: A thin cord, usually made of twisted fibers, used for fastening, hanging, or tying. Something that resembles string in form or texture.
2) Music: A cord stretched across a musical instrument and vibrated to produce sound.
3) Subatomic string; → string theory.
4) → cosmic string.

M.E. string, streng; O.E. streng "line, cord, thread;" Du. streng,Ger. Strang "rope, cord;" PIE base *strenk- "stiff, tight."

Târ "thread, warp, string" (related to tur "net, fishing net, snare," tâl "thread" (Borujerdi dialect), tân "thread, warp of a web," from tanidan, tan- "to spin, twist, weave;" Mid.Pers. tanitan; Av. tan- to stretch, extend;" cf. Skt. tan- to stretch, extend;" tanoti "stretches," tántra- "warp; essence, main point;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch;" Lith. tiñklas "net, fishing net, snare," Latv. tikls "net;" PIE base *ten- "to stretch").
Rismân "thread, string, cord" variants rasan, ras, ris, razé, rajé, rijé, rešmé, Mid.Pers. rasan, cf. Skt. rajju- "rope, cord," L. restis "cord," Lith. resgis, rekstis "wicker basket," O.L.G. risch; PIE base *rezg- "to plait."

string theory
  نگره‌ی ِ ریسمان   
negare-ye rismân

Fr.: théorie des cordes   

The latest theory of fundamental physics in which the basic entity is a one-dimensional → brane rather than the "zero-dimensional" point of conventional elementary particle physics. The one-dimensional string-like objects exist in the normal four dimensions of → space-time plus additional dimensions, the total dimensions being ten, eleven, or twenty-six depending on the version of the theory. Particles are strings that vibrate in different ways to account for their various properties.

string; → theory.

submarine spring
  چشمه‌ی ِ زیر-دریایی   
cešme-ye zir-daryâ-yi

Fr.: source sous-marine   

Hydrology: A freshwater spring that emerges off the seashore.

submarine; → spring.

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