An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 639
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 (#)

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.


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."


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.


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 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 movement of the hidden brane prior to the collision is under the influence of a potential created by the exchange of appropriate M-theory fields between the branes. The resulting temperature is finite, so the hot Big Bang phase begins without a → singularity. The Universe is homogeneous because the collision and initiation of the Big Bang phase occur nearly simultaneously everywhere. The energetically preferred geometry for the two branes is flat, so their collision produces a flat Big Bang Universe. According to → Einstein's field equations, this means that the total energy density of the Universe is equal to the → critical density. Massive → magnetic monopoles, which are over-abundantly produced in the standard Big Bang theory, are not produced at all in this scenario because the temperature after collision is far too small to produce any of these massive particles. A new version of the model provides the possibility of a cyclic Universe in which the fifth dimension undergoes a cycle of contraction and expansion a number of times, or indefinitely. The Big Bang is therefore not a special event and can happen again and again. Each cycle begins with a Big Bang and ends in a → Big Crunch. At the transition between the Big Crunch and Big Bang, matter and radiation are created, restoring the Universe to the high density required for a new Big Bang phase. In this scenario, the → dark energy that is causing the cosmic acceleration of the Universe today is inter-brane potential energy.
See: 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.

Elara (Jupiter VII)

Fr.: Elara   

The thirteenth known moon of Jupiter, discovered in 1905 by Charles Perrine.

In Gk. mythology, Elara was the mother by Zeus of the giant Tityus.

kešâyand (#)

Fr.: élastique   

Of, pertaining to, or noting a body having the property of → elasticity. See also → elastic collision, → elastic deformation, → elastic limit, → elastic scattering.

From Fr., from Gk. elastos "ductile, flexible," related to elaunein "to strike, beat out."

Kešâyand, from keš stem of kešidan/kašidan "to pull, drag, draw" (Av. karš- "to draw, to plough," karša- "furrow;" cf. Skt. kars-, kársati "to pull, drag, plough," Gk. pelo, pelomai "to be busy, to bustle") + âyand agent form of âmadan "to come; to become," from Mid.Pers. âmatan (O.Pers. gam- "to come; to go," Av. gam- "to come; to go," jamaiti "goes;" O.Iranian *āgmatani; Skt. gamati "goes;" Gk. bainein "to go, walk, step;" L. venire "to come;" Tocharian A käm- "to come;" O.H.G. queman "to come;" E. come; PIE root *gwem- "to go, come").

elastic collision
  همکوبش ِ کشایند   
hamkubš-e kešâyand

Fr.: collision élastique   

A collision between two particles which conserves the total kinetic energy and momentum of the system.

elastic; → collision.

elastic deformation
  وادیسش ِ کشایند   
vâdiseš-e kešâyand

Fr.: déformation élastique   

A deformation of a → solid body in which the change (→ strain) in the relative position of points in the body disappears when the deforming stress is removed. See also → elastic limit.

elastic; → deformation.

elastic limit
  حد ِ کشایند   
hadd-e kešâyand

Fr.: limite d'élasticité, ~ élastique   

The smallest → stress beyond which a → solid body can no longer return to its original shape. The material ceases to obey → Hooke's law. Also called → yield point.

elastic; → limit.

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