# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 lord   خاوند   xâvand (#)Fr.: seigneur   1) A person who has authority, control, or power over others; a master, chief, or ruler. 2) A person who exercises authority from property rights; an owner of land, houses, etc. 3) A feudal superior; the proprietor of a manor (Dictionary.com).M.E. lord, loverd, O.E. hlâford, hlâfweard, literally "loaf-keeper," from hlaf "bread, loaf" + weard "keeper, guardian."Xâvand, contraction of xodâvand "lord, master, god," from xodâ "lord, master," → God, + suffix -vand. Lorentz   لورنتز   LorentzFr.: Lorentz   Contraction of the full name of Hendrik Antoon Lorentz (1853-1928), a Dutch physicist, who made important contribution to physics. He won (with Pieter Zeeman) the Nobel Prize for Physics in 1902 for his theory of electromagnetic radiation, which, confirmed by findings of Zeeman, gave rise to Albert Einstein's special theory of relativity. Lorentz contraction   ترنگش ِ لورنتز   terengeš-e LorentzFr.: contraction de Lorentz   The decrease in the length of a body moving in the direction of its length as measured by an observer situated in that direction. The shortening factor is [1 - (v/c)2]1/2, where v is the relative velocity and c light speed.→ Lorentz; → contraction. Lorentz factor   کروند ِ لورنتز   karvand-e LorentzFr.: facteur de Lorentz   In → special relativity, an important parameter which appears in several equations, including → time dilation, → length contraction, and → relativistic mass. It is defined as γ = 1 / [1 - (v/c)2]1/2 = dt/dτ, where v is the velocity as observed in the reference frame where time t is measured, τ is the proper time, and c the → velocity of light. Same as Lorentz γ factor.→ Lorentz; → factor. Lorentz force   نیروی ِ لورنتز   niru-ye Lorentz (#)Fr.: force de Lorentz   The force acting upon a → charged particle as it moves in a → magnetic field. It is expressed by F = q.v x B, where q is the → electric charge, v is its → velocity, and B the → magnetic induction of the field. This force is perpendicular both to the velocity of the charge and to the magnetic field. The magnitude of the force is F = qvB sinθ, where θ is the angle between the velocity and the magnetic field. This implies that the magnetic force on a stationary charge or a charge moving parallel to the magnetic field is zero. The direction of the force is given by the → right-hand rule.→ Lorentz; → force. 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.