An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 12982 Search : far
Einstein time-scale
  مرپل ِ زمانی ِ اینشتین   
marpel-e zamâni-ye Einstein

Fr.: 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 Einstein

Fr.: 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 Einstein

Fr.: 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 Einstein

Fr.: 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 Sitter

Fr.: effet Einstein-de Sitter   

Same as → geodetic precession.

Einstein-de Sitter Universe; → effect.

Einstein-de Sitter Universe
  گیتی ِ اینشتین-دو سیتر   
giti-ye Einstein-de Sitter

Fr.: Univers Einstein-de Sitter   

The → Friedmann-Lemaitre model of → expanding Universe that only contains matter and in which space is → EuclideanM > 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-Hilbert

Fr.: 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-Rosen

Fr.: paradoxe Einstein-Podolsky-Rosen   

EPR paradox.

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-Rosen

Fr.: 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 Einsteini

Fr.: 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   
ešândan

Fr.: 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   
ešânâk

Fr.: 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 šândaneject + suffix -âk.

ejecta blanket
  پتو‌ی ِ اشاناک   
patu-ye ešânâk

Fr.: 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   
ešâneš

Fr.: éjection   

Act or instance of ejecting; the state of being ejected.

Verbal noun of → eject.

Ekman layer
  لایه‌ی ِ اکمن   
lâye-ye Ekman

Fr.: 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 Ekman

Fr.: 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.

ekpyrotic Universe
  گیتی ِ آتشزاد   
giti-ye âtašzâd

Fr.: Univers ekpyrotique   

A cosmological model in which the → Big Bang is not the beginning of the → Universe, but a transitory phase in a more global scenario. The ekpyrotic Universe model is fundamentally different from the → standard cosmology and offers radically different explanations for the cosmological problems (→ homogeneity, → isotropy, → flatness, → magnetic monopoles, etc.). In this highly speculative model → space-time has five dimensions, four spatial and one temporal. Two three-dimensional → branes, one visible and one hidden, collide following the contraction of the extra dimension. The contraction produces a blue shift effect that converts gravitational energy into brane kinetic energy. Some fraction of this kinetic energy is converted into matter and radiation that can fuel the Big Bang. The resulting temperature is finite, so the hot Big Bang phase begins without a → singularity. Apart from being speculative, this model suffers from several fine tunings (J. Khoury et al. 2001, Phys. Rev. D64, 123522 (hep-th/0103239); P. J. Steinhardt & N. Turok, 2002, Phys. Rev. D65, 126003 (hep-th/0111098), and references therein).

Ekpyrotic is inspired by the ancient Stoic doctrine according to which the world ends in a supreme conflagration, called ekpyrosis, and then reborns from the fire (palingenesis), only to be destroyed again at the end of the new cycle; ekpyrosis, from Gk. ek- "out of," → ex-, + → pyro- combining form of pyr, → fire, + -sis a suffix used to form nouns of action, process, state, condition, such as thesis, analysis, catharsis; → Universe.

Giti, → Universe; âtašzâd, literally "born out of fire," from âtaš, → fire, + zâd "born," from zâdan "to bring forth," → generate.

El Nino
  ال نی‌نیو   
El Ninyo (#)

Fr.: El Niño   

El Niño. A significant warming of the ocean surface over the eastern and central equatorial Pacific that occurs at irregular intervals, generally ranging between two and seven years. El Niño conditions, which are often characterized by "warm events," most often develop after late December during the early months of the year and decay during the following year. → La Nina.

From Sp. El Niño "the child," i.e. "the Christ Child," alluding to the appearance of the current near Christmas. The term was originally applied by fishermen of northern Peru.

<< < -es -iv -ti 21- a p abe abs abs acc acc acc act act ada adi ads aes Age Alb Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app app arc Arg ari art ass ast ast ast atm ato att Aur aut axi azi bac Bal Bar Bar Bay Bec Ber bet bic bij bin bio Bir bla Bla blu blu bol Boo bou bra Bre bro bug C r cal Cal can car Car Cas cat cau cel cen cer Cha cha Cha che chl cir cir cir Cla cli clo clu co- coc coh col col col com com com com com com com com Com con con con con con con con con con con con con Cop Cor cor cor cos cos Cou cou cow cre cri cro cry cur cut Cyg dam dar dat de deb dec dec ded def deg del dem den dep des det dev dia dif dif dig dio Dir dis dis dis dis dis dis div don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ Equ esc eth Eur eve exa exc exe exi exp exp ext ext eye fac fal Far fed fer fer fie fin fir fit fla flo flu fol for for Fou fra fre Fre fro fuz gai Gal Gal gam gas Gau gen gen geo geo geo gia glo gol gra gra gra gra gre gri gui H I hai Ham har Hau hea hec hel hel her HES hie hig his hom hor hot Hub hum Huy hyd hyd hyl hyp ice ide ima imp imp imp inc ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iro irr iso iso ite jel Jou Jup kao Kep kil Kip Kra Lag Lam lan lar las law lea leg Leo lex lig lim lin lin lin lit Loc loc log Lor low lum lun lun Lym mac mag mag mag mag mag mai Mal mar mas mas mat max mea mec meg men mer met met met mic mic Mik min min mis mob mod mol mon moo mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ odd OH Ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai Pan par par par par pas pea pen per per per per Per per pha phl pho pho pho pi pip Pla pla pla pla ple poa pol Pol pol pol pop pos pos pot pra pre pre pre pri pri pri pro pro pro pro pro pro pro Pto pul puz qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel rep res res res res ret Rhe rid rig ris Roe Ros rot rub rut Sag sam sat sca sca Sch sci sea sec sec see sel sem sen ser Sh2 sha shi sho sid sig sim sin Sir ske sli Smo soc sol sol sol sol sol sou spa spa spe spe spe spe sph spi spo Squ sta sta sta sta ste ste ste sto str str str sub sub sub sum sup sup sup sup sur sus sym syn T d tap tec tem ten tes the the the the thi thr tid tim tip ton tor tow tra tra tra tra tri tri tru tub tur two Typ ult un- und uni uni unp upp urg V20 Van var veg vel ver vib vio vir vis Vol Vul wan wat wav WC4 wea wel whi Wil wis WNL wor X-r Yer Z s zer [C > >>