An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 464
Lorentz
  لورنتز   
Lorentz

Fr.: 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 Lorentz

Fr.: 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 Lorentz

Fr.: 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 Lorentz

Fr.: invariance de Lorentz   

Of a physical law, invariance with respect to a → Lorentz transformation.

Lorentz; → invariance.

Lorentz resonance
  باز‌آوایی ِ لورنتز   
bâzâvâyi-ye Lorentz

Fr.: 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 Lorentz

Fr.: 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.

Lorentz; → transformation.

Lorentzian profile
  فراپال ِ لورنتزی   
farâpâl-e Lorentzi

Fr.: 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 Lorimer

Fr.: 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 Loschmidt

Fr.: 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   
dastraft

Fr.: 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," "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 sorxkib

Fr.: faible décalage vers le rouge   

A redshift characterizing a near-by receding object.

low; → redshift.

low resolution
  که‌واگشود   
keh vâgošud

Fr.: 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 kam

Fr.: 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, jazr

Fr.: marée basse   

Also known as → low tide.

low; → water.

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