# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 spherical geometry   هندسه‌ی ِ کُره‌ای   hendese-ye kore-yiFr.: géométrie sphérique   The branch of geometry that deals with figures on the surface of a sphere (such as the spherical triangle and spherical polygon). It is an example of a non-Euclidean geometry.→ spherical; → geometry. spherical harmonic   هماهنگ ِ کره‌ای   hamâhang-e kore-yiFr.: fonction harmonique sphérique   A solution of some mathematical equations when → spherical polar coordinates are used in investigating physical problems in three dimensions. For example, solutions of → Laplace's equation treated in spherical polar coordinates. Spherical harmonics are ubiquitous in atomic and molecular physics and appear in quantum mechanics as → eigenfunctions of → orbital angular momentum. They are also important in the representation of the gravitational and magnetic fields of planetary bodies, the characterization of the → cosmic microwave background anisotropy, the description of electrical potentials due to charge distributions, and in certain types of fluid motion.The term spherical harmonics was first used by William Thomson (Lord Kelvin) and Peter Guthrie Tait in their 1867 Treatise on Natural Philosophy; → spherical; → harmonic. spherical latitude   ورونای ِ کره‌ای، ~ سپهری   varunâ-ye kore-yi, ~ sepehriFr.: latitude sphérique   The angle between the → normal to a spherical reference surface and the → equatorial plane.→ spherical; → latitude. spherical lens   عدسی ِ کره‌ای   adasi-ye kore-yiFr.: lentille sphérique   A lens with a refractng surface which is a portion of a sphere. Spherical lenses can be of various types: → biconvex, → biconcave, → plano-convex, → plano-concave, → concavo-convex, and → convexo-concave.→ spherical; → lens. spherical mirror   آینه‌ی ِ کره‌ای   âyene-ye kore-yiFr.: miroir sphérique   A mirror whose reflecting surface is a portion of a sphere. Spherical mirrors can be of two types: → concave mirror and → convex mirror.→ spherical; → mirror. spherical polar coordinate   هماراهای ِ کره‌ای ِ قطبی   hamârâhâ-ye kore-yi-ye qotbiFr.: coordonnées sphériques polaires   Same as → spherical coordinates.→ spherical; → polar; → coordinate spherical symmetry   همامونی ِ کُره‌ای   hamâmuni-ye kore-yiFr.: symétrie sphérique   A configuration in which the constituting parts are arranged concentrically around the center of a sphere.→ spherical; → symmetry. spherical triangle   سه‌بر ِ کُره‌ای   sebar-e kore-yiFr.: triangle sphérique   A triangle drawn on the → surface of a → sphere. A spherical triangle, like a plane triangle, may be right, obtuse, acute, equilateral, isosceles, or scalene. The sum of the angles of a spherical triangle is greater than 180° (π) and less than 540° (3π). See also → spherical excess.→ spherical; → triangle. spheroid   کُره‌وار   korevârFr.: sphéroïde   A body that is shaped like a sphere but is not perfectly round, especially an ellipsoid that is generated by revolving an ellipse around one of its axes.→ sphere; → -oid. spheroidal   کره‌وار   korevâr (#)Fr.: sphéroïdal   Shaped like a → spheroid.→ spheroid; → -al. spherule   گویل   guyelFr.: sphérule   Any of many vitrified droplets of rock formed by the solidification of molten meteoritic material that flows off a meteorite during its passage through the Earth's atmosphere. Sizes range typically from 10 to 200 microns."Small sphere," from → sphere + diminutive suffix → -ule.Guyel "small globe," from guy "ball, sphere" (variants golulé, gullé, goruk, gulu, gudé; cf. Skt. guda- "ball, mouthful, lump, tumour," Pali gula- "ball," Gk. gloutos "rump," L. glomus "ball," globus "globe," Ger. Kugel, E. clot; PIE *gel- "to make into a ball") + -el diminutive suffix, → -ule. Spica (α Virginis)   سنبله   Sonbolé (#)Fr.: Spica   The brightest star in the constellation → Virgo, and the 15th brightest star in the night sky. Also known as HD 116658. It is 260 → light-years distant from Earth. A → blue giant, it is a variable → eclipsing binary, with a period of 4.014 days. Both components are → B-type stars, the → primary being a → Beta Cephei variable near to core hydrogen exhaustion (→ spectral type B1 III-IV) and the → secondary a → main sequence star (B2 V). See, e.g., R.S. Schnerr et al., 2010, arXiv:1008.4260.From L. spica "ear of grain," related to spina "thorn," corresponding to Gk. stakhys "grapes."Sonbolé, from sonbol "an ear of corn; a hyacinth," from Ar. sumbul. spicule   سیخک   sixakFr.: spicule   Any of numerous vertical → spikes of → gas visible in the → monochromatic light of certain strong → spectral lines beyond the → Sun's limb. Spicules are short-lived phenomena, corresponding to rising → jets of gas that move upward at about 30km/sec up to 10,000 km and last only about 10 minutes.From L. spiculum "spearhead, arrowhead, bee stinger," from spica "ear of grain" + -ulum, → -ule.Sixak, from six "spur, spit; thorn; any pointed thing." spider vane   پره‌ی ِ تارتن   parre-ye târtanFr.: araignée   One of, usually three or four, diagonal supports that hold the → secondary mirror in a → reflecting telescope. Also called support vane.M.E. spithre, O.E. M.E. spithra, akin to spinnan "to spin;" cf. M.L.G., M.Du., M.H.G., Ger. spinne, Du. spin "spider;" → vane.Parré, → vane; târtan "spider," literally "weaver," composite word of with two cognate elements, the first one târ "thread, warp, string," related to tur "net, fishing net, snare," tâl "thread" (Borujerdi dialect), tân "thread, warp of a web," from the second element tan-, tanidan "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." spike   سیخک   sixak (#)Fr.: pointe   1) A long, pointed → metal  → bar. 2) Physics: A → transient variation in → voltage or → current in an → electric circuit.M.E. spik(e) from O.N. spikr "nail;" akin to M.L.G. spiker "nail."Sixak, from six "spur, spit; thorn; any pointed thing," + -ak a suffix of similarity and nuance. spin   اسپین   espinFr.: spin   1) Mechanics: The rotation of a body about an axis through the body. To cause to turn around rapidly, as on an axis. To revolve or rotate rapidly, 2) Quantum mechanics: See → spin quantum number; → spin angular momentum.M.E. spinnen; O.E. spinnan "to draw out and twist fibers into thread" (cf. O.N., O.Fris. spinna, Dan. spinde, Du. spinnen, O.H.G. spinnan, Ger. spinnen); cognate with Pers. tan-, tanidan "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").Espin, loan from E., as above. spin angular momentum   جنباک ِ زاویه‌ای ِ اسپین   jonbâk-e zâviyeyi-ye espinFr.: moment angulaire de spin   An intrinsic quantum mechanical characteristic of a particle that has no classical counterpart but may loosely be likened to the classical → angular momentum of a particle arising from rotation about its own axis. The magnitude of spin angular momentum is given by the expression S = ħ √ s(s + 1), where s is the → spin quantum number. As an example, the spin of an electron is s = 1/2; this means that its spin angular momentum is (ħ /2) √ 3 or 0.91 x 10-34 J.s. In addition, the projection of an angular momentum onto some defined axis is also quantized, with a z-component Sz = msħ. The only values of ms (magnetic quantum number) are ± 1/2. See also → Stern-Gerlach experiment.→ spin; → angular; → momentum. spin magnetic moment   گشتاور ِ مغناتیسی ِ اسپین   gaštâvar-e meqnâtisi-ye espin (#)Fr.: moment magnétique de spin   The magnetic moment associated with the → spin angular momentum of a charged particle. The direction of the magnetic moment is opposite to the direction of the angular momentum. The magnitude of the magnetic moment is given by: μ = -g(q / 2m)J, where q is the charge, m is the mass, and J the angular momentum. The parameter g is a characteristic of the state of the atom. It would be 1 for a pure orbital moment, or 2 for a spin moment, or some other number in between for a complicated system like an atom. The quantity in the parenthesis for the electron is the → Bohr magneton. The electron spin magnetic moment is important in the → spin-orbit interaction which splits atomic energy levels and gives rise to → fine structure in the spectra of atoms. It is also a factor in the interaction of atom with external fields, → Zeeman effect.→ spin; → magnetic moment. spin quantum number   عدد ِ کو‌آنتومی ِ اسپین   adad-e kuântomi-ye espinFr.: nombre quantique de spin   An integer or half-integer on which the magnitude of a particle's → spin angular momentum depends. It is expressed in units of → Planck's constant divided by 2π. Called also spin, denoted s. The spin of a particle can only have a value that is zero or a multiple of 1/2. Particles with half-integer spins, 1/2, 3/2, 5/2, ..., are → fermions. Particles with integer spin (0, 1, 2, ...) are called → bosons.→ spin; → quantum; → number. spin temperature   دمای ِ اسپین   damâ-ye espinFr.: température de spin   The → excitation temperature of the → hyperfine structure levels of the → neutral hydrogen→ 21-centimeter line.→ spin; → temperature.