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shadow cone maxrut-e sâyé Fr.: cône d'ombre A cone-shaped shadow cast by Earth or the Moon pointing away from the Sun. The dark inner portion of the shadow cone is called the → umbra. The lighter outer portion of the shadow is called the → penumbra. Its extension is called the → antumbra. |
Shannon entropy dargâšt-e Shannon Fr.: entropie de Shannon Claude Elwood Shannon (1916-2001), an American mathematician and pioneer of → information theory; → entropy. |
Shannon's sampling theorem farbin-e nemunân-giri-ye Shannon Fr.: théorème d'échantillonnage de Shannon Same as → sampling theorem. → Shannon entropy; → sampling; → theorem. |
Shapley concentration dabzeš-e Shapley Fr.: concentration de Shapley Same as the → Shapley supercluster. |
shellular rotation carxeš-e puste-yi Fr.: rotation coquillaire A rotation mode in which internal rotation of a star depends essentially on depth and little on latitude: Ω(r,θ) = Ω(r), where r is the mean distance to the stellar center of the considered level surface (or → isobar). This particular mode was introduced by J.-P. Zahn (1992, A&A 265, 115) to simplify the treatment of rotational → mixing, but also on more physical grounds. Indeed differential rotation tends to be smoothed out in latitude through → shear turbulence. See also → von Zeipel theorem; → meridional circulation . Shellular, the structure of this term is not clear; it may be a combination of → shell (referring to star's assumed division in differentially rotating concentric shells) + (circ)ular, → circular. The first bibliographic occurrence of shellular is seemingly in Ghosal & Spiegel (1991, On the Thermonuclear Convection: I. Shellular Instability, Geophys. Astrophys. Fluid Dyn. 61, 161). However, surprisingly the term appears only in the title, and nowhere in the body of the article; → rotation. |
shepherd moon mâng-e cupân Fr.: satellites bergers A → natural satellite in orbit near the edge of a → planetary ring, whose → gravitational force on the ring particles strongly controls the distribution of material within the ring, creating ringlets and density waves within the ring and sharp edges at ring boundaries. Examples include → Saturn's → Prometheus and → Pandora, which shepherd the narrow outer → F ring and the → Uranus satellites → Cordelia and → Ophelia and the epsilon ring. The faster-moving inside satellite accelerates the inner ring particles as it passes them, causing them to spiral out to larger orbits. At the same time the slower-moving outer satellite decelerates the outer ring particles as they pass by, causing them to spiral inward. The result is a narrow, well-defined ring. |
shinbone dorošt-ney Fr.: tibia → tibia. → tibia Doroštney, literally "big reed," from dorošt, → macro-, + ney "reed, cane." |
shock diamond almâs-e toš Fr.: diamant de choc Any of a series of rings/disks that are formed in a jet flow exhausting a → nozzle when there is a huge difference between the exit pressure and the ambient pressure. At sea level, the exhaust pressure might be lower than the thick atmosphere. In contrast, at very high altitudes, the exhaust pressure might be higher than the thin atmosphere. Shock diamonds can appear just as a rocket is taking off, or at high altitudes when it shifts into → supersonic speed. Shock diamonds are also known as Mach diamonds, → Mach disks, Mach rings, doughnut tails, or thrust diamonds. |
shock front pišân-e toš, ~ šok Fr.: front de choc The boundary over which the physical conditions undergo an abrupt change because of a → shock wave. |
sidereal month mâh-e axtari (#) Fr.: mois sidéral The time taken by the Moon to complete one → revolution around the Earth with respect to a background, → fixed star. The average time is 27.321 661 days (27d 7h 43m 11.5s). Same as → lunar sidereal orbital period. |
sidereal revolution period dowre-ye gardeš-e axtari (#) Fr.: période de révolution sidérale The time taken by a planet or satellite to complete one revolution about its primary with respect to stars. For Earth, same as → sidereal year. Sidereal periods of the solar system planets, interms of the sidereal year, are as follows: Mercury 0.240846 (87.9691 days); Venus 0.615 (225 days); Earth 1 (365.25636 solar days); Mars 1.881; Jupiter 11.86; Satrurn 29.46; Uranus 84.01; and Neptune 164.8. That of the Moon is 0.0748 (27.32 days) and for → Sedna 12050. → sidereal; → revolution; → period. |
sidereal rotation period dowre-ye carxeš-e axtari Fr.: période de rotation sidérale The rotation period of a celestial body with respect to fixed stars. For Earth, same as → sidereal day. |
signification nešânâreš Fr.: signification 1) Something that is signified, → meaning, sense. Verbal noun of → signify. |
silicon silisiom (#) Fr.: silicium A non-metallic chemical element; symbol Si. Atomic number 14; atomic weight 28.0855; melting point 1,410°C; boiling point 2,355°C; specific gravity 2.33 at 25°C. It occurs in a combined state in minerals and rocks and constituting more than one fourth of the earth's crust. From silic(a), from L. silex (genitive silicis) "flint, pebble" + -on, as in carbon and boron. Silisiom, from Fr. silicium, from silic(a), as above, + -ium as in magnesium, barium. |
silicon burning suzeš-e silisiom Fr.: combustion du silicium The → nucleosynthetic process taking place in the interior of → massive stars whereby → silicon is transmuted into iron, nickel, and neighboring nuclei collectively called the → iron peak elements. |
similar polygons candbarhâ-ye hamânand Fr.: polygone similaires Polygons that are exactly the same shape, but can be different sizes. |
similarity transformation tarâdiseš-e hamânandi Fr.: transformation de similarité 1) A transformation that preserves angles and changes all distances in the same ratio. → similarity; → transformation. |
simple fraction barxe-ye sâdé Fr.: fraction simple A fraction in which the → numerator and → denominator are positive → integer numbers. Compare → compound fraction. |
simple harmonic motion jonbeš-e hamâhang-e sâdé Fr.: mouvement harmonique The motion of a body subjected to a restraining force which is directly proportional to the displacement from a fixed point in the line of motion. The equation of simple harmonic motion is given by x = A sin(ωt + θ_{0}), where x is the body's displacement from equilibrium position, A is the → amplitude, or the magnitude of harmonic oscillations, ω is the → angular frequency, t is the time elapsed, and θ_{0} is the → initial phase angle. |
simple harmonic oscillator navešgar-e hamâhang-e sâdé Fr.: oscillateur harmonique simple An oscillator whose force is proportional to its extension, according to → Hooke's law. The way the oscillator moves is called → simple harmonic motion. → simple; → harmonic; → oscillator. |
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