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Einstein's field equations 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: G_{μν} = -κ T_{μν}, where G_{μν} is the → Einstein tensor (a function of the → metric tensor), κ is a coupling constant called the → Einstein gravitational constant, and T_{μν} 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: G_{μν} + Λg_{μν} = - κT_{μν}, where Λ is the → cosmological constant. Named after Albert Einstein (1879-1955); → field; → equation. |
Einstein's gravitational constant pâyâ-ye gerâneši-ye Einstein (#) Fr.: constante gravitationnelle d'Einstein The coupling constant appearing in → Einstein's field equations, expressed by: κ = 8πG/c^{4}, where G is the Newtonian → gravitational constant and c the → speed of light. → einstein; → gravitational; → constant. |
Einstein's theory of specific heat 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 oskar-e Einstein-de Sitter Fr.: effet Einstein-de Sitter Same as → geodetic precession. |
Einstein-de Sitter Universe 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 → Euclidean (Ω_{M} > 0, Ω_{R} = 0, Ω_{Λ} = 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 žireš-e Einstein-Hilbert Fr.: action de Einstein-Hilbert In → general relativity, the → action
that yields → Einstein's field equations.
It is expressed by: → Einstein; → Hilbert space; → action. |
Einstein-Podolsky-Rosen paradox 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 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 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 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. |
eject 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 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 šândan→ eject + suffix -âk. |
ejecta blanket 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. |
ejection ešâneš Fr.: éjection Act or instance of ejecting; the state of being ejected. Verbal noun of → eject. |
Ekman layer 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 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 E_{k} = ν/(ΩH^{2}), 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} m^{2}/s are characterized by an Ekman number of about 10^{-4}. → Ekman layer; → number. |
ekpyrotic Universe 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. 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 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) Elârâ 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. |
elastic 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"). |
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