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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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav 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 coo Cor Cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg ura uti val var vec Vel ver Ver vie Vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>

Number of Results: 13116 Search : far
Laplace's equation
  هموگش ِ لاپلاس   
hamugeš-e Laplace

Fr.: équation de Laplace   

A → linear differential equation of the second order the solutions of which are important in many fields of science, mainly in electromagnetism, fluid dynamics, and is often used in astronomy. It is expressed by: ∂2V/ ∂x2 + ∂2V/ ∂y2 + ∂2V/ ∂z2 = 0. Laplace's equation can more concisely expressed by: ∇2V = 0. The function V may, for example, be the potential at any point in the electric field where there is no free charge. The general theory of solutions to Laplace's equation is known as potential theory.

Laplace; → equation.

Laplacian
  لاپلاسی   
lâplâsi (#)

Fr.: laplacien   

A differential → operator, denoted ∇2 = ∇.∇, which is the sum of all second partial derivatives of a dependant variable: ∇2≡ ∂2/∂x2 + ∂2/∂y2 + ∂2/∂z2, in Cartesian coordinates. It has numerous applications in several fields of physics and mathematics. Also called Laplace operator.

Named after → Laplace.

large
  بزرگ   
bozorg (#)

Fr.: grand   

Of more than average size, quantity, degree, etc.; of great scope or range.

From O.Fr. large "broad, wide," from L. largus "abundant, copious, plentiful," of unknown origin.

Bozorg "great, large, immense, grand, magnificient;" Mid.Pers. vazurg "great, big, high, lofty;" O.Pers. vazarka- "great;" Av. vazra- "club, mace" (Mod.Pers. gorz "mace"); cf. Skt. vájra- "(Indra's) thunderbolt," vaja- "strength, speed;" L. vigere "be lively, thrive," velox "fast, lively," vegere "to enliven," vigil "watchful, awake;" P.Gmc. *waken (Du. waken; O.H.G. wahhen; Ger. wachen "to be awake;" E. wake); PIE base *weg- "to be strong, be lively."

Large Magellanic Cloud (LMC)
  ابر ِ بزرگ ِ ماژلان   
Abr-e Bozorg-e Magellan (#)

Fr.: Grand Nuage de Magellan   

The larger of the two Magellanic Cloud galaxies visible in the southern hemisphere at about 22 degrees from the South Celestial Pole. It is approximately on the border between the constellations → Dorado and → Mensa in a region of faint stars. The center of the LMC is approximately RA: 5h 23m 35s, dec: -69° 45' 22''. The LMC shines with a total → apparent visual magnitude of approximately zero. It spans an area of the sky about 9 by 11 degrees, corresponding to about 30,000 → light-years across in the longest dimension, for a distance of some 162,000 light-years. It has a visible mass of about one-tenth that of our own Galaxy (1010 Msun). The LMC and its twin, the → Small Magellanic Cloud, are two of our most prominent Galactic neighbors. The LMC is classified as a disrupted → barred spiral galaxy of type SBm, the prototype of a class of → Magellanic spirals. The galaxy is characterized by a prominent offset → stellar bar located near its center with the dominant → spiral arm to the north with two "embryonic" arms situated to the south. The → metallicity in the LMC is known to be lower than in the solar neighborhood by a factor 2 or more. Based on 20 → eclipsing binary systems, the distance to the LMC is measured to one percent precision to be 49.59±0.09 (statistical) ±0.54 (systematic) kpc (Pietrzynski et al., 2019, Nature 567, 200).

large; → Magellanic; → cloud.

large number
  عدد ِ بزرگ   
adad-e bozorg

Fr.: grand nombre   

A → dimensionless number representing the ratio of various → physical constants. For example:
1) The ratio of the → Coulomb force to the → gravitational force for a proton-electron pair (e2/Gmpme), which is of the order of 1040.
2) The age of Universe (T = 10-20 x 109 years) in units of the → elementary time: T/te≅ 1040.
3) The square root of the total number of particles in the Universe ≅ 1040.

large; → number.

large number hypothesis
  انگاره‌ی ِ عددهای ِ بزرگ   
engâre-ye adadhâ-ye bozorg

Fr.: hypothèse des grands nombres   

The idea whereby the coincidence of various → large numbers would bear a profound sense as to the nature of physical laws and the Universe. Dirac suggested that the coincidence seen among various large numbers of different nature is not accidental but must point to a hitherto unknown theory linking the quantum mechanical origin of the Universe to the various cosmological parameters. As a consequence, some of the → fundamental constants cannot remain unchanged for ever. According to Dirac's hypothesis, atomic parameters cannot change with time and hence the → gravitational constant should vary inversely with time (G∝ 1/t). Dirac, P. A. M., 1937, Nature 139, 323; 1938, Proc. R. Soc. A165, 199.

large; → number; → hypothesis.

large Reynolds number flow
  تچان با عدد ِ بزرگ ِ رینولدز   
tacân bâ adad-e bozorg-e Reynolds

Fr.: écoulement à grand nombre de Reynolds   

A turbulent flow in which viscous forces are negligible compared to nonlinear advection terms, which characterize the variation of fluid quantities. The dynamics becomes generally turbulent when the Reynolds number is high enough. However, the critical Reynolds number for that is not universal, and depends in particular on boundary conditions.

large; → Reynolds number; → flow.

large scale
  بزرگ-مرپل   
bozorg-marpel

Fr.: grande échelle   

1) A scale representing measures that significantly override the usual ones of the same kind.
2) In meteorology, a scale in which the curvature of the earth is not negligible.

large; → scale.

Large Synoptic Survey Telescope (LSST)
  تلسکوپ ِ بزرگ ِ هنوینی برای ِ بردید   
teleskop-e bozorg-e hanvini barâye bardid

Fr.: Grand Télescope d'étude synoptique   

Initial name given to → Vera C. Rubin Observatory.

large; → synoptic; → survey; → telescope.

large-scale structure
  ساختار ِ بزرگ-مرپل   
sâxtâr-e bozorg-marpel

Fr.: structure à grandes échelles   

The distribution of galaxies and other forms of mass on large distance scales, covering hundreds of millions of → light-years.

large; → scale; → structure.

Larissa
  لریسا   
Larissa (#)

Fr.: Larissa   

The fifth of Neptune's known satellites. It orbits 73,600 km from Neptune and is a non spherical object about 208 × 178 km in size. It was discovered using NASA's Voyager 2 mission in 1989.

In Gk. mythology, Larissa is a princess of Argos (in central Greece) who, according to some, bore Poseidon three sons: Akhaios, Pelasgos and Pythios (though others gave these eponymous heroes different parents).

Larmor frequency
  بسامد ِ لارمور، فرگی ِ ~   
basâmad-e Larmor (#), feregi-ye ~ (#)

Fr.: fréquence de Larmor   

The frequency of precession of a charged particle describing a circular motion in a plane perpendicular to the magnetic induction in a uniform magnetic field.

Named after Joseph Larmor (1857-1942), an Irish physicist, the first to calculate the rate at which energy is radiated by an accelerated electron, and the first to explain the splitting of spectrum lines by a magnetic field; → frequency.

Larmor radius
  شعاع ِ لارمور   
šoâ'-e Larmor (#)

Fr.: rayon de Larmor   

The radius of the circular motion of a → charged particle moving in a → uniform magnetic field. Same as → gyroradius, → radius of gyration, → cyclotron radius. The Larmor radius (rL) is obtained by equating the → Lorentz force with the → centripetal force: qvB = mv2/rL, which leads to rL = p/(ZeB), where p is → momentum, Z is → atomic number, e is the → electron charge, and B is → magnetic induction. The frequency of this circular motion is known as the → gyrofrequency.

Larmor frequency; → radius.

Larmor's theorem
  فربین ِ لارمور   
farbin-e Larmor

Fr.: théorème de Larmor   

If a system of → charged particles, all having the same ratio of charge to mass (q/m), acted on by their mutual forces, and by a central force toward a common center, is subject in addition to a weak uniform magnetic field (B), its possible motions will be the same as the motions it could perform without the magnetic field, superposed upon a slow → precession of the entire system about the center of force with angular velocity ω = -(q/2mc)B.

Larmor frequency; → theorem.

Larson relation
  بازانش ِ لرسون   
bâzâneš-e Larson

Fr.: relation de Larson   

An → empirical relationship between the internal → velocity dispersion of → molecular clouds and their size. The velocity dispersions are derived from molecular → linewidths, in particular those of → carbon monoxide. It was first established on star forming regions and found to be: σ (km s-1) = 1.10 L (pc)0.38, where σ is the velocity dispersion and L the size. The relation holds for 0.1 ≤ L ≤ 100 pc. More recent set of cloud data yield: σ (km s-1) = L (pc)0.5. This relation indicates that larger molecular clouds have larger internal velocity dispersions. It is usually interpreted as evidence for → turbulence in molecular clouds. Possible sources of interstellar turbulence include the following processes operating at various scales: galactic-scale (→ differential rotation, → infall of extragalactic gas on the galaxy), intermediate-scale (expansion of → supernova remnants, → shocks, → stellar winds from → massive stars), and smaller-scale processes (→ outflows from → young stellar objects).

First derived by Richard B. Larson, American astrophysicist working at Yale University (Larson, 1981, MNRAS 194, 809). See Falgarone et al. (2009, A&A 507, 355) for a recent study; → relation.

Larson-Penston solution
  لویش ِ لرسون-پنستون   
luyeš-e Larson-Penston

Fr.: solution de Larson-Penston   

The analytical solution to the → hydrodynamic equations describing the → collapse of an → isothermal sphere. The Larson-Penston solution is → self-similar for a purely dynamical isothermal collapse with spherical symmetry. It corresponds to the collapse prior to the formation of a → protostar, and thus is suitable for the study of → pre-stellar cores. The Larson-Penston solution was extended by Shu (1977) to obtain a whole family of solutions for this problem.

Named after R. B. Larson (1969, MNRAS 145, 271) and M. V. Penston (1969, MNRAS 144, 425), who simultaneously, but independently, did this study.

laryngeal
  حنجره‌ای   
hanjare-yi (#)

Fr.: laryngé   

1) Of, pertaining to, or located in the larynx.
2) Phonetics: articulated in the larynx (Dictionary.com).

larynx; → -al.

laryngeal consonant
  هم‌آوای ِ حنجره‌ای   
hamâvâ-ye hanjare-yi

Fr.: son laryngé   

A consonant generated in the → larynx with the → vocal cords partly closed and partly vibrating. It is hypothesized that the → Proto-Indo-European language contained some laryngeal consonants (denoted by H).

laryngeal; → consonant.

larynx
  حنجره   
hanjaré (#)

Fr.: larynge   

A muscular and cartilaginous structure lined with mucous membrane at the upper part of the → trachea in humans, in which the → vocal cords are located (Dictionary.com).

From M.Fr. larynx, from M.L. from Gk. larynx (genitive laryngos) "the upper windpipe," probably from laimos "throat," influenced by pharynx "throat, windpipe."

Hanjaré, from Ar. Hanjarah.

laser
  لیزر   
leyzer (#)

Fr.: laser   

1) A device that generates an intense directional beam of → monochromatic and → coherent light by exciting atoms to a higher energy level and causing them to radiate their energy in phase. The high degree of collimation arises from the fact that excited atoms are are situated in a cavity bounded by two parallel front and back mirrors. A first photon stimulates an atom which emits a second photon, and so on thanks to the mirrors. The resulting photons are all identical. They have the same energy which gives them the same color and a unique direction. The first working laser, a pulsed ruby device, was developed by T. Maiman in 1959. See also → gas laser, → stimulated emission; → maser.
2) The light produced in this way.

Acronym for light amplification by stimulated emission of radiation, on pattern of → maser.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav 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 coo Cor Cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg ura uti val var vec Vel ver Ver vie Vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>