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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 664
 Einstein temperature   دمای ِ اینشتین   damâ-ye Einstein (#)Fr.: température d'Einstein   A characteristic parameter occurring in the → Einstein model of → specific heats.→ Einstein; → temperature. Einstein tensor   تانسور ِ اینشتین   tânsor-e Einstein (#)Fr.: tenseur d'Einstein   A mathematical entity describing the → curvature of → space-time in → Einstein's field equations, according to the theory of → general relativity. It is expressed by Gμν = Rμν - (1/2) gμνR, where Rμν is the Ricci tensor, gμν is the → metric tensor, and R the scalar curvature. This tensor is both symmetric and divergence free.Named after Albert Einstein (1879-1955); → tensor. Einstein time-scale   مرپل ِ زمانی ِ اینشتین   marpel-e zamâni-ye EinsteinFr.: échelle de temps d'Einstein   The time during which a → microlensing event occurs. It is given by the equation tE = RE/v, where RE is the → Einstein radius, v is the magnitude of the relative transverse velocity between source and lens projected onto the lens plane. The characteristic time-scale of → microlensing events is about 25 days.→ Einstein; → time-scale. Einstein's elevator   بالابر ِ اینشتین   bâlâbar-e EinsteinFr.: ascenseur d'Einstein   A → thought experiment, involving an elevator, first conceived by Einstein to show the → principle of equivalence. According to this experiment, it is impossible for an observer situated inside a closed elevator to decide if the elevator is being pulled upward by a constant force or is subject to a gravitational field acting downward on a stationary elevator. Einstein used this experiment and the principle of equivalence to deduce the bending of light by the force of gravity.→ einstein; elevator, from L. elevator, agent noun from p.p. stem of elevare "to lift up, raise," from → ex- "out" + levare "lighten, raise," from levis "light" in weight, → lever.Bâlâbar, → lift. Einstein's field equations   هموگش‌های ِ میدان ِ اینشتین   hamugešhâ-ye meydân-e EinsteinFr.: équations de champ d'Einstein   A system of ten non-linear → partial differential equations in the theory of → general relativity which relate the curvature of → space-time with the distribution of matter-energy. They have the form: Gμν = -κ Tμν, where Gμν is the → Einstein tensor (a function of the → metric tensor), κ is a coupling constant called the → Einstein gravitational constant, and Tμν is the → energy-momentum tensor. The field equations mean that the curvature of space-time is due to the distribution of mass-energy in space. A more general form of the field equations proposed by Einstein is: Gμν + Λgμν = - κTμν, where Λ is the → cosmological constant.Named after Albert Einstein (1879-1955); → field; → equation. Einstein's gravitational constant   پایای ِ گرانشی ِ اینشتین   pâyâ-ye gerâneši-ye Einstein (#)Fr.: constante gravitationnelle d'Einstein   The coupling constant appearing in → Einstein's field equations, expressed by: κ = 8πG/c4, where G is the Newtonian → gravitational constant and c the → speed of light.→ einstein; → gravitational; → constant. Einstein's theory of specific heat   نگره‌ی ِ گرمای ِ آبیزه‌ی ِ اینشتین   negare-ye garmâ-ye âbize-ye EinsteinFr.: théorie de la chaleur spécifique d'Einstein   Same as → Einstein model.→ Einstein; → theory; → specific heat. Einstein-de Sitter effect   اسکر ِ اینشتین-دو سیتر   oskar-e Einstein-de SitterFr.: effet Einstein-de Sitter   Same as → geodetic precession. Einstein-de Sitter Universe   گیتی ِ اینشتین-دو سیتر   giti-ye Einstein-de SitterFr.: Univers Einstein-de Sitter   The → Friedmann-Lemaitre model of → expanding Universe that only contains matter and in which space is → Euclidean (ΩM > 0, ΩR = 0, ΩΛ = 0, k = 0). The Universe will expand at a decreasing rate for ever.→ Einstein; de Sitter, after the Dutch mathematician and physicist Willem de Sitter (1872-1934) who worked out the model in 1917; → Universe. Einstein-Hilbert action   ژیرش ِ اینشتین-هیلبرت   žireš-e Einstein-HilbertFr.: action de Einstein-Hilbert   In → general relativity, the → action that yields → Einstein's field equations. It is expressed by: SEH = (1/2κ)∫d4x (-g)1/2R + Sm, where κ ≡ 8πG and Sm is the matter part of the action.→ Einstein; → Hilbert space; → action. Einstein-Podolsky-Rosen paradox   پارادخش ِ اینشتین-پودولسکی-روزن   pârâdaxš-e Einstein-Podolsky-RosenFr.: paradoxe Einstein-Podolsky-Rosen   A. Einstein, B. Podolsky, N. Rosen: "Can quantum-mechanical description of physical reality be considered complete?" Phys. Rev. 41, 777 (15 May 1935); → paradox. Einstein-Rosen bridge   پل ِ اینشتین-روزن   pol-e Einstein-RosenFr.: pont d'Einstein-Rosen   A hypothetical structure that can join two distant regions of → space-time through a tunnel-like shortcut, as predicted by → general relativity. The Einstein-Rosen bridge is based on the → Schwarzschild solution of → Einstein's field equations. It is the simplest type of → wormholes.Albert Einstein & Nathan Rosen (1935, Phys.Rev. 48, 73); → bridge. Einsteinian relativity   بازانیگی ِ اینشتینی   bâzânigi-ye EinsteiniFr.: relativité einsteinienne   The laws of physics are the same in all → inertial reference frames and are invariant under the → Lorentz transformation. The → speed of light is a → physical constant, i.e. it is the same for all observers in uniform motion. Einsteinian relativity is prompted by the → Newton-Maxwell incompatibility. See also: → Galilean relativity, → Newtonian relativity.→ Einstein; → relativity. einsteinium   اینشتینیوم   einsteinium (#)Fr.: einsteinium   A radioactive metallic → transuranium element belonging to the → actinides; symbol Es. → Atomic number 99, → mass number of most stable → isotope 254 (→ half-life 270 days). Eleven isotopes are known. The element was first identified by A. Ghiorso and collaborators in the debris of first hydrogen bomb explosion in 1952.Named after Albert Einstein, → einstein + → -ium. eject   اشاندن   ešândanFr.: éjecter   To throw out material, for example by a massive star through stellar wind, or by a volcano in eruption.From L. ejectus, p.p. of eicere "to throw out," from → ex- "out" + -icere, comb. form of jacere "to throw."Ešândan, from Hamadâni ešândan "to throw out;" Pashto aestal, wištal "to throw, project;" Laki owštan "to throw, to shoot (with bow and arrow);" Lori šane "throwing," šane kerde "to throw;" Av. ah- "to throw," pres. ahya- "throws," asta- "thrown, shot," astar- "thrower, shooter;" cf. Khotanese ah- "to throw, shoot," Skt. as- "to throw, shoot," ásyati "throws," ásana- "throw, shot." ejecta   اشاناک   ešânâkFr.: éjecta   Material, in solid, liquid, or gaseous form, thrown out by a body, especially as a result of → volcanic eruption, → meteoritic impact, or → supernova explosion. See also: → ejecta blanket, → supernova ejecta.Plural of L. ejectus, → eject.Ešânâk "that which is ejected," from šân present stem of šândan→ eject + suffix -âk. ejecta blanket   پتو‌ی ِ اشاناک   patu-ye ešânâkFr.: couverture d'éjecta   Of an → impact crater, the ejecta that after the → impact event settles back to the Earth's surface. The ejecta blanket is thick near the → crater rim and thin outward from the crater.→ ejecta; → blanket. ejection   اشانش   ešânešFr.: éjection   Act or instance of ejecting; the state of being ejected.Verbal noun of → eject. Ekman layer   لایه‌ی ِ اکمن   lâye-ye EkmanFr.: couche d'Ekman   A kind of viscous → boundary layer in a rotating fluid system. Such a layer forms over a flat bottom that exerts a frictional → stress against the flow, bringing the velocity gradually to zero within the layer above the bottom. An Ekman layer occurs also on the fluid surface whenever there is a horizontal frictional stress, for example along ocean surface, when waters are subject to wind stress.Named for Vagn Walfrid Ekman (1874-1954), Swedish oceanographer, who studied the phenomenon originally in his doctoral thesis (1902) and later developed it (1905, 1906); → layer. Ekman number   عدد ِ اکمن   adad-e EkmanFr.: nombre d'Ekman   A → dimensionless quantity that measures the strength of → viscous forces relative to the → Coriolis force in a rotating fluid. It is given by Ek = ν/(ΩH2), where ν is the → kinematic viscosity of the fluid, Ω is the → angular velocity, and H is the depth scale of the motion. The Ekman number is usually used in describing geophysical phenomena in the oceans and atmosphere. Typical geophysical flows, as well as laboratory experiments, yield very small Ekman numbers. For example, in the ocean at mid-latitudes, motions with a viscosity of 10-2 m2/s are characterized by an Ekman number of about 10-4.→ Ekman layer; → number.