# 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: 508
 Lorentz invariance   ناورتایی ِ لورنتز   nâvartâyi-ye LorentzFr.: invariance de Lorentz   Of a physical law, invariance with respect to a → Lorentz transformation.→ Lorentz; → invariance. Lorentz resonance   باز‌آوایی ِ لورنتز   bâzâvâyi-ye LorentzFr.: résonance de Lorentz   A repeated electromagnetic force on an electrically charged ring particle, nudging the particle in the same direction and at the same point in its orbit. Lorentz resonances are especially important for tiny ring particles whose charge-to-mass ratio is high and whose orbit periods are a simple integer fraction of the rotational period of the planet's magnetic field (Ellis et al., 2007, Planetary Ring Systems, Springer).→ Lorentz; → resonance. Lorentz transformation   ترادیس ِ لورنتز   tarâdis-e LorentzFr.: transformation de Lorentz   A set of linear equations that expresses the time and space coordinates of one → reference frame in terms of those of another one when one frame moves at a constant velocity with respect to the other. In general, the Lorentz transformation allows a change of the origin of a coordinate system, a rotation around the origin, a reversal of spatial or temporal direction, and a uniform movement along a spatial axis. If the system S'(x',y',z',t') moves at the velocity v with respect to S(x,y,z,t) in the positive direction of the x-axis, the Lorentz transformations will be: x' = γ(x - vt), y' = y, z' = z, t' = γ [t - (vx/c2)], where c is the → velocity of light and γ = [1 - (v/c)2]-1/2. For the special case of velocities much less than c, the Lorentz transformation reduces to → Galilean transformation. Lorentzian profile   فراپال ِ لورنتزی   farâpâl-e LorentziFr.: profil lorentzien   A spectral profile in which the intensity distribution follows a specific mathematical function (Lorentz or Cauchy probability). Compared to the normal or Gaussian profile, Lorentzian has a pointed peak and more important wings.→ Lorentz; → profile. Lorimer burst   بلک ِ لوریمر   belk-e LorimerFr.: sursaut Lorimer, impulsion ~   The first ever discovered → fast radio burst. It was done during a search of archival data from a 1.4-GHz survey of the → Magellanic Clouds using the multi-beam receiver on the 64-m Parkes Radio Telescope in Australia.D. R. Lorimer et al., 2007, Science, 318, 777; → burst. Loschmidt's number   عدد ِ لوشمیت   adad-e LoschmidtFr.: nombre de Loschmidt   The number of molecules in 1 cm3 of an ideal gas (2.687 x 1019 per cm3).Joseph Loschmidt (1821-1895), Austrian physicist. loss   دسترفت   dastraftFr.: perte   In physics, a measure of the energy, mass, or other physical quantities lost in a system, by conversion or external effects.From O.E. los "loss, destruction," from P.Gmc. *lausa, from PIE base *leu- "to loosen, divide, cut apart, untie, separate" (cf. Gk. lyein "to loosen, untie, slacken," lysus "a loosening;" L. luere "to loose, release, atone for;" Skt. lunati "cuts, cuts off," lavitram "sickle;" Pers. las "loose," lâ "slit, cut;" → analysis).Dastraft, literally "gone from hand," from dast "hand" (Mid.Pers. dast; O.Pers. dasta-; Av. zasta-; cf. Skt. hásta-; Gk. kheir; L. praesto "at hand;" Arm. jern "hand;" Lith. pa-žastis "arm-pit;" PIE *ghes-to-) + raft p.p. of raftan "to go, elapse, glide by, depart" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack"). loud   بلند   boland (#)Fr.: fort, sonore, bruillant   High in volume of sound.M.E., O.E. hlud "making noise, sonorous" (cf. M.Du. luut, Du. luid, O.H.G. hlut, Ger. laut "loud"), from PIE *klutos- (cf. Skt. sruta-, Gk. klytos "heard of, celebrated," Arm. lu "known."Boland, → high. loudness   بلندی ِ صدا   bolandi-ye sedâ (#)Fr.: sonie, force   The magnitude of the sensation produced by a sound wave when it reaches the ear. The loudness of a sound depends upon the effective → acoustic pressure and → frequency. The basis of loudness scales is the → Weber-Fechner law.→ loud + → -ness.Bolandi, → height; sedâ, → sound. loudspeaker   بلندگو   bolandgu (#)Fr.: haut-parleur   A device in which electric signals are converted into audible sound.→ loud, + agent noun of speak M.E. speken, O.E. specan, variant of sprecan "to speak" (cf. O.S. sprecan, M.Du. spreken, O.H.G. sprehhan, Ger. sprechen "to speak," O.N. spraki "rumor, report").Bolandgu, from boland, → loud + gu agent noun of goftan "to speak, to say," from Mid.Pers. guftan "to say, tell, utter;" O.Pers. gaub- "to say." low   ۱) کم، که؛ ۲) کوتاه، پایین   1) kam (#), keh (#); 2) kutâh (#), pâyin (#)Fr.: bas, faible   1) Below the average or expected degree, amount, or intensity. Having or containing a relatively small amount. 2) Situated, placed, or occurring not far above the ground, floor, or base. Relatively little in height.From M.E. lah, from O.N. lagr "low," from P.Gmc. *lægaz (cf. O.Fris. lech, Du. laag, Ger. läge "low"), literally "that which is lying flat;" related to E. lie (v.).Kam "little, few; deficient, wanting; scarce," from Mid.Pers. kam "little, small, few," O.Pers./Av. kamna- "small, few." Keh "small, little, slender" (related to kâstan, kâhidan "to decrease, lessen, diminish," from Mid.Pers. kâhitan, kâstan, kâhênitan "to decrease, diminish, lessen;" Av. kasu- "small, little;" Proto-Iranian *kas- "to be small, diminish, lessen"); kutâh, → small; pâyin, → bottom-up structure. low redshift   که‌سرخ‌کیب   keh sorxkibFr.: faible décalage vers le rouge   A redshift characterizing a near-by receding object.→ low; → redshift. low resolution   که‌واگشود   keh vâgošudFr.: faible résolution   The quality of an instrument that lacks sufficient resolution for a specific observation. This is a relative quality, but presently a resolution below about 1 arcsecond.→ low; → resolution. low surface brightness galaxy (LSBG)   کهکشان با درخشندگی ِ رویه‌ای ِ کم   kahkešân bâ deraxšandegi-ye ruye-yi-ye kamFr.: galaxie à faible brillance de surface   A member of a particularly faint population of galaxies with a central → surface brightness below the brightness of the background sky. The central regions of many of them resemble a → dwarf galaxy, but most of the mass is contained in a large gaseous disk of low density that is observable only with long-exposure optical images or at radio wavelengths. Some are as massive as a large → spiral galaxy, for example Malin 1. The proportion of LSBGs relative to normal galaxies is unknown. They may however represent a significant fraction of mass in the Universe. LSBGs are thought to be primitive systems because they have total masses similar to normal galaxies, but have typically converted less than 10% of their gas into stars. Spiral LSBGs do not obey → Freeman's law.→ low; → surface; → brightness; → galaxy. low tide   اوپس، جزر   owpas (#), jazr (#)Fr.: marée basse   The state of the → tide when at its lowest level.→ low; → tide.Owpas, from Persian Gulf dialects, literally "backward water," from ow, variant of âb, → water, + pas "→ back, behind." Jazr, loan from Ar. low water   اوپس، جزر   owpas, jazrFr.: marée basse   Also known as → low tide.→ low; → water. low-energy neutrino   نوترینو‌ی ِ کم‌کاروژ   notrino-ye kamkâružFr.: neutrino faible énergie   A neutrino which is mainly produced in → nuclear processes, such as the ones in the → Sun (→ solar neutrino), or in the center of an exploding → supernova. Such neutrinos are, however, more energetic than those making up the → cosmic neutrino background.→ low; → energy; → neutrino. low-ionization line   خط ِ کم‌یونش   xatt-e kamyoneš (#)Fr.: raie de faible ionisation   A spectral line arising from a transition between atomic levels with an ionization potential below approximately 15 electron-volts.→ low; → ionization; → line. low-ionization nuclear emission-line region   ناحیه‌ی ِ هسته‌ای با خط ِ گسیلی ِ کم‌یونش   nâhiye-ye hasteyi bâ xatt-e gosili-ye kamyoneš (#)Fr.: Noyau de galaxie à raies d'émission de faible ionisation   Same as → LINER.→ low; → ionization; → nuclear; → emission; → line; → region. low-loss fiber   فیبر ِ کم‌دسترفت   fibr-e kamdastraftFr.: fibre à faible perte   Optical fiber that transmits a greater percentage of input light than does high-loss step-index fiber.→ low; → loss; → fiber.