Fr.: périodogramme de Lomb-Scargle
An algorithm for detecting and characterizing periodic signals in unevenly-sampled data. The Lomb-Scargle periodogram has a particularly wide use within the astronomy community. This method allows efficient computation of a Fourier-like → power spectrum estimator from such unevenly-sampled data, resulting in an intuitive means of determining the period of oscillation (see VanderPlas, 2017, astro-ph/1703.09824 and references therein).
Named after Lomb, N. R. 1976, Ap&SS 39, 447 and Scargle, J. D. 1982, ApJ 263, 835; → periodogram.
M.E. longe, O.E. lang, long, akin to O.H.G., Ger. lang "long," O.N. langr, M.Du. lanc, Goth. laggs "long," L. longus, → longitude.
Derâz "long," Mid.Pers. drâz "long;" O.Pers. darga- "long;" Av. darəga-, darəγa- "long," drājištəm "longest;" cf. Skt. dirghá- "lon (in space and time)."
domdâr-e derâz dowré
Fr.: comète à longue période
vartande-ye derâz dowré
Fr.: variable à longue période
The angular distance on the Earth's surface, measured east or west from the prime meridian at Greenwich to the meridian passing through a position, expressed in degrees (or hours), minutes, and seconds.
L. longitudo "length," from longus "long," cognate with Pers. derâz, as below, Gk. dolikhos "elongated;" O.H.G., Ger. lang, O.N. langr, M.Du. lanc, Goth. laggs "long;" PIE base *dlonghos- "long."
Derežnâ, from derež (Kurdi, Laki), variants darg "length; long, tall" (Zâzâ), darγ (Ossetic), derâz "long" + -nâ noun forming suffix from adjective, as in derâznâ, pah(n)nâ, farâxnâ, tangnâ, tiznâ. The first element from Mid.Pers. drâz "long;" O.Pers. darga- "long;" Av. darəga-, darəγa- "long," drājištəm "longest;" cf. Skt. dirghá- "long (in space and time);" PIE *dlonghos- "long," as above.
longitude of ascending node
derežnâ-ye gereh-e farâzeši
Fr.: longitude du nœud ascendant
One of the → orbital elements used to specify the orbit of an object in space. It is the angle from the reference direction, called the origin of longitude, to the direction of the → ascending node, measured in the reference plane.
Of or pertaining to longitude or length. Extending in the direction of the length.
Adj. of → longitude.
longitudinal magnetic field
meydân-e meqnâtisi-ye derežnâyi
Fr.: champ magnétique longitudinal
1) A → magnetic field whose lines of force
(→ line of force)
run parallel to the long axis of the → magnet.
of a component can be accomplished using the longitudinal field set
up by a → coil or
→ solenoid. It can also be accomplished using
permanent magnets or electromagnets.
Fr.: masse longitudinale
In special relativity theory, the mass of a body when the acceleration is parallel or anti-parallel to velocity: ml = m0 / [1 - (v/c)2]3/2, where m0 is the → rest mass, v is the velocity, and c the → velocity of light. → transverse mass.
Fr.: onde longitudinale
longitudinal Zeeman effect
oskar-e Zeeman-e derežnâyi
Fr.: effet Zeeman longitudinal
The → Zeeman effect when the emitting source is viewed in the direction of the magnetic field. In the normal longitudinal effect, each spectral line is split into two components with frequencies ν ± Δν. The line with the frequency ν - Δν shows left-hand → circular polarization and that with frequency ν + Δν shows right-hand circular polarization. → transverse Zeeman effect.
The act or instance of looking.
Look, from W.Gmc. *lokjan (cf. O.S. lokon, M.Du. loeken, O.H.G. luogen, Ger. dialectal lugen "to look out"), of unknown origin.
Negâh "look," from Mid.Pers. nikâh "look, glance, observation;" Proto-Iranian *ni-kas- "to look down," from ni- "down," → ni- (PIE), + *kas- "to look, appear;" cf. Av. nikā-, nikāta- (in the name of the 15-th nask) "that which is observed," ākas- "to look;" Mid.Pers. âkâh, Mod.Pers. âgâh "aware, knowing;" Skt. kāś- "to become visible, appear;" Ossetic kast/kaesyn "to look."
zamân-e negâh bé gozašté
Fr.: temps de retour en arrière
The time that has elapsed since the light was emitted from a distant object (of → redshift z). Because → light moves at a → constant → speed, it takes a finite time to travel from distant objects. Hence, we "see" distant objects at a point in time in their past. In other words, look-back time is the difference between the age of the Universe now and the age of the Universe at the time the photons were emitted from the object. See also → comoving distance.
Zamân, → time; negâh, → look; gozašté "past, passed" (from gozaštan "to pass, proceed, go on," variant gozâštan "to put, to place, let, allow;" Mid.Pers. widardan, widâštan "to pass, to let pass (by);" O.Pers. vitar- "to pass across," viyatarayam "I put across;" Av. vi-tar- "to pass across," from vi- "apart, away from" (O.Pers. viy- "apart, away;" Av. vi- "apart, away;" cf. Skt. vi- "apart, asunder, away, out;" L. vitare "to avoid, turn aside") + O.Pers./Av. tar- "to cross over").
Anything shaped more or less like a loop, i.e. portion of a cord, ribbon, etc.,
folded or doubled upon itself.
Probably of Celtic origin (cf. Gael. lub "bend," Ir. lubiam), influenced by O.N. hlaup "a leap, run."
Gerdâl, from gerd "round, a circle" (Mid.Pers. girdag "disk, round," from gird/girt "round, all around," Proto-Iranian *gart- "to twist, to wreathe," cf. Skt krt "to twist threads, spin; to wind; to surround;" kata- "a twist of straw," Pali kata- "ring, bracelet," Gk. kartalos "a kind of basket," kyrtos "curved") + → -al.
Fr.: protubérance en boucle
A very bright active prominence in the form of a loop seen in Hα after a rather big flare. Also called "post-flare loops," they connect the feet where the two-ribbon flares were seen. The lifetime of loop prominences is several hours.
1) A person who has authority, control, or power over others; a master, chief, or ruler.
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.
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.
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.
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.
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.