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Pogson's ratio vâbar-e Pogson Fr.: rapport de Pogson The constant 2.512, which is the 5th → root of 100 (2.512^{5} = 100); the ratio between two successive stellar → magnitudes. → Pogson's relation; → ratio. |
Pogson's relation bâzâneš-e Pogson Fr.: relation de Pogson The equation that expresses the → magnitude
→ difference between
two objects in terms of the → logarithm of the
→ flux → ratio: Named after Norman Robert Pogson (1829-1891), the English astronomer, who introduced the magnitude scale in 1856; → relation. |
Poincaré recurrence theorem farbin-e bâzâmad-e Poincaré Fr.: théorème de récurrence de Poincaré In an → isolated system, any initial state will occur again in the course of the → evolution of the system over a sufficiently long but finite → time. → Poincaré sphere; → recurrence; → theorem. |
Poincaré sphere kore-ye Poincaré Fr.: sphère de Poincaré A representation that permits an easy visualisation of all different states of → polarization of a vector wave. The equator represents → linear polarization; the north pole corresponds to right-circular and the south pole to left- → circular polarization. Named after Henri Poincaré (1854-1912), French mathematician and theoretical physicist, and a philosopher of science; → sphere. |
Poinsot's motion jonbeš-e Poinsot Fr.: mouvement à la Poinsot The motion of a torque free rotating rigid body in space, in general whose angular velocity vector precesses regularly about the constant angular momentum factor. After Louis Poinsot (1777-1859), French physicist and mathematician. He was the inventor of geometrical mechanics, showing how a system of forces acting on a rigid body could be resolved into a single force and a couple. |
point 1) noqté (#), pandé (#); 2) âmâjidan Fr.: 1) point; 2) pointer 1a) General: A sharp or tapering end, as of a dagger; a projecting part of anything. M.E. point(e); O.Fr. point "dot, mark, place, moment;" L. punctum noun use of neuter p.p. of pungere "to prick, pierce." 1) Noqté, loan from Ar. Pandé, variants in classical dictionaries
pindé, pendé, fand "a point, dot, mole, freckle;" cf. Skt.
prānta- "point, tip, border," from pra "before, forward,"
→ pro-, + ánta- "end, limit, term;"
Pali, panta- "remote, solitary;" Prakrit panta " last;"
Sindhi pandu "border of a garment;" Lahnda pand, pad "end, top of
sugar cane." |
point mass noqté jerm, pandé jerm, jerm-e noqtevâr, ~ pandevâr Fr.: masse ponctuelle A hypothetical object which can be thought of as infinitely small. |
point source noqté xan, pandé xan, xan-e noqtevâr, pande-ye ~ Fr.: source ponctuelle A source of radiation at a great distance from the observer; an ideal source of infinitesimal size. |
point spread function (PSF) karyâ-ye gostareš-e noqté, ~ ~ pandé Fr.: fonction d'étalement du point The two-dimensional intensity distribution about the image of a point source. |
Pointers dorahnemâ Fr.: The two stars that form the front of the Big Dipper's bowl, away from the handle. More specifically, the stars Dubhe (α Ursae Majoris) and Merak (β Ursae Majoris). A line through β to α passes close to the North Star and they are used for finding it. → point + -er. Dorahnemâ, literally "the two guides," from do "two" + rah, râh "way, path" (from Mid.Pers. râh, râs "way, street," also rah, ras "chariot;" from Proto-Iranian *rāθa-; cf. Av. raθa- "chariot;" Skt. rátha- "car, chariot," rathyā- "road;" L. rota "wheel," rotare "to revolve, roll;" Lith. ratas "wheel;" O.H.G. rad; Ger. Rad; Du. rad; O.Ir. roth; PIE *roto- "to run, to turn, to roll") + nemâ agent noun of nemudan "to show" (Mid.Pers. nimūdan, nimây- "to show," from O.Pers./Av. ni- "down; into" (Skt. ni "down," nitaram "downward," Gk. neiothen "from below," cf. E. nether, O.E. niþera, neoþera "down, downward, below, beneath," from P.Gmc. *nitheraz, Du. neder, Ger. nieder; PIE *ni- "down, below") + māy- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum; PIE base *me- "to measure"). |
pointing âmâješ Fr.: pointage The act or process of directing a telescope. → point. Verbal noun of → point. |
pointing model model-e âmâješ Fr.: modèle de pointage A mathematical model that reproduces the diurnal rotation of the Earth and is used to direct a telescope toward a precise position on the sky. |
poise poise Fr.: poise The unit of viscosity in the c.g.s. system, equal to 1 dyne.s/cm^{2}. Symbol: P Poise, from Jean-Louis-Marie Poiseuille (1797-1869), a French physiologist and physician who studied the flow of liquids through tubes and developed a method for measuring blood pressure. |
Poiseuille's law qânun-e Poiseuille Fr.: loi de Poiseuille In fluid dynamics, the law that the rate of flow of a liquid through a horizontal tube of uniform radius is directly proportional to the pressure of the liquid and the fourth power of the radius of the tube and is inversely proportional to the viscosity of the liquid and the length of the tube. Named after Jean-Louis-Marie Poiseuille (1797-1869), a French physiologist and physician who found the law in 1844; → law. |
Poisson distribution vâbâžeš-e Poisson Fr.: distribution de Poisson A → probability function that characterizes → discrete → random events occurring independently of one another within some definite time or space. It may be regarded as an approximation of the → binomial distribution when the number of events becomes large and the probability of success becomes small. The Poisson distribution is expressed by: f(x) = (λ^{x}e^{-λ})/x!, where λ is the mean number of successes in the interval, e is the base of the → natural logarithm, and x is the number of successes we are interested in. Named after Siméon Denis Poisson (1781-1840), French mathematician, who developed the application of Fourier series to physical problems and made major contributions to the theory of probability and to the calculus of variations; → distribution. |
Poisson's equation hamugeš-e Poisson Fr.: équation de Poisson An equation (∇^{2}φ = 4πGρ) which relates the gravitational (or electromagnetic) potential to the mass density (or charge density). → Poisson distribution; → equation. |
polar 1) qotbi; 2) polâr Fr.: 1) polaire; 2) polar 1) Of or pertaining to the pole of any sphere, a magnet, an electric cell, etc. 1) Adj. of → pole. |
polar alignment âxateš-e qotbi Fr.: alignement polaire The process or the state of making a → telescope's → polar axis → parallel to the → Earth's → rotation axis, that is with the → true North or → South → celestial pole. When this is accomplished, the sky's motion can be cancelled out simply by turning the axis (either by hand or with a motor → drive) at the same rate as the rotation of the Earth, but in the opposite direction. |
polar axis âse-ye qotbi (#) Fr.: axe polaire The axis of an → equatorial mounting that is parallel to the Earth's axis, and consequently points to the celestial pole. |
polar bond band-e qotbi Fr.: lien polaire A chemical bond where the electrons are shared unequally between atoms. The atom that is more electronegative will pull the electrons closer to itself. |
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