ostorlâb-e sepehri, ~ kore-yi
Fr.: astrolabe sphérique
A type of → astrolabe in which the observer's horizon is drawn on the surface of a globe, mounted with a freely rotating spherical lattice work or 'spider' representing the celestial sphere. The earliest description of the spherical astrolabe dates back to the Iranian astronomer Nayrizi (865-922).
Fr.: astronomie sphérique
The branch of astronomy that is concerned with determining the apparent positions and motions of celestial bodies on the celestial sphere. Same as → positional astronomy.
Fr.: coordonnées sphériques
A coordinate system using an origin (O) and three perpendicular axes (Ox, Oy, Oz), in which the position of a point (P) is given by three numbers (r, θ, φ). The coordinate r is the distance from the origin, θ the angle between the z-axis and the r direction, and φ the angle between the projection of r on the xy-plane and the Ox-axis. The coordinate φ is also called the → azimuthal angle.
fozuni-ye sepehri, ~ kore-yi
Fr.: excès sphérique
The difference between the sum of the three angles of a → spherical triangle and 180° (π radians).
Fr.: 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.
Fr.: 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.
varunâ-ye kore-yi, ~ sepehri
Fr.: latitude sphérique
Fr.: 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.
Fr.: miroir sphérique
spherical polar coordinate
hamârâhâ-ye kore-yi-ye qotbi
Fr.: coordonnées sphériques polaires
Same as → spherical coordinates.
Fr.: symétrie sphérique
A configuration in which the constituting parts are arranged concentrically around the center of a sphere.
Fr.: 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.
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.
Shaped like a → spheroid.
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.
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)
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.
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."
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."
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.
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,
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.