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The Scales. An inconspicuous constellation in the southern hemisphere and a sign of the → Zodiac, at 15h 30m right ascension, 15° south declination. Abbreviation: Lib; genitive: Librae.
L. libra "balance," of obscure origin.
Tarâzu "balance, scales," Mid.Pers. tarâzên-, taraênidan "to weigh," Proto-Iranian *tarāz-, from *tarā- "balance, scale" (cf. Skt. tulā- "scales, balance, weight," from tul- "to weigh, make equal in weight, equal," tolayati "weighs, balances," L. tollere "to raise," Gk. talanton "balance, weight," Atlas "the Bearer" of Heaven," Lith. tiltas "bridge;" PIE base telə- "to lift, weigh") + Av. az- "to convey, conduct, drive," azaiti drives" (cf. Skt. aj- "to dive, sling," ájati "drives," ajirá- "agile, quick," Gk. agein "to lead, guide, drive, carry off," L. agere "to do, set in motion, drive," from PIE root *ag- "to drive, move," → act).
halâzân, roxgard (#)
Small oscillations of a → celestial body about its mean position. The term is used mainly to mean the Moon's libration caused by the apparent wobble of the Moon as it orbits the Earth. The Moon always keeps the same side toward the Earth, but due to libration, 59% of the Moon's surface can be seen over a period of time. This results from three kinds of libration working in combination: → libration in longitude, → libration in latitude, and → diurnal libration. See also: → geometrical libration, → physical libration.
L. libration- "a balancing."
Halâzân "to and fro motion, oscillation," literally
"a swing: a seat suspended by ropes on which a person may sit for swinging,"
from Gilaki halâcin "a swing," Ilâmi harazân
"a swing," variants (Dehxodâ) holucin, holu "a swing,"
probably from Proto-Ir. *harz- "to send, to set."
libration in latitude
Fr.: libration en latitude
A tiny oscillating motion of the Moon arising from the fact that the Moon's axis is slightly inclined relative to the Earth's. More specifically, the Moon's polar axis is tilted nearly 7° with respect to the plane of its orbit around Earth. Hence for half of each orbit we see slightly more of the north pole when its tipped toward us, and for the other half we see slightly more of its south pole. Libration in latitude displaces the mean center of the Moon north-south by between 6°.5 and 6°.9.
libration in longitude
Fr.: libration en longitude
A tiny oscillating motion of the → Moon arising from the fact that the Moon's orbit is not a precise circle but rather an → ellipse. Therefore, Moon is sometimes a little closer to the Earth than at other times, and as a result its → orbital velocity varies a bit. Since the Moon's rotation on its own axis is more regular, the difference appears as a slight east-west oscillation. Libration in longitude is the most significant kind of libration. It varies between about 4°.5 and 8°.1 because of gravitational perturbations in the Moon's orbit caused by the Sun.
The condition that distinguishes living organisms from inorganic objects, i.e. non-life, and dead organisms. It is manifested by growth through metabolism, reproduction, and the power of adaptation to environment through changes originating internally.
O.E. life, from P.Gmc. *liba- (cf. O.N. lif "life, body," Du. lijf "body," O.H.G. lib "life," Ger. Leib "body"), properly "continuance, perseverance," from PIE *lip- "to remain, persevere, continue, live;" cf. Gk. liparein "to persist, persevere."
Zist "life, existence," from zistan "to live;" Mid.Pers. zivastan "to live," zivižn "life," zivik, zivandag "alive, living;" O.Pers./Av. gay- "to live," Av. gaya- "life," gaeθâ- "being, world, mankind," jivya-, jva- "aliving, alive;" cf. Skt. jiva- "alive, living;" Gk. bios "life;" L. vivus "living, alive," vita "life;" O.E. cwic "alive;" E. quick; Lith. gyvas "living, alive;" PIE base *gweie- "to live."
In fluid mechanics, the component of aerodynamical force which is perpendicular to the oncoming flow direction. In aeronautics, the perpendicular component of the force of the air against an airplane; the component that is effective in supporting the plane's weight. → drag; → thrust.
M.E. liften, from O.N. lypta "to raise;" cf. M.L.G. lüchten, Du. lichten, Ger. lüften "to lift;" O.E. lyft "heaven, air."
Bâlâbar "lift," from bâlâ "up, above, high, elevated, height" (variants boland "high," borz "height, magnitude" (it occurs also in the name of the mountain chain Alborz), Lori dialect berg "hill, mountain;" Mid.Pers. buland "high;" O.Pers. baršan- "height;" Av. barəz- "high, mount," barezan- "height;" cf. Skt. bhrant- "high;" L. fortis "strong" (Fr. & E. force); O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg); PIE base *bhergh- "high") + bar present stem of bordan "to carry, transport" (Mid.Pers. burdan; O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive);" Skt. bharati "he carries;" Gk. pherein "to carry;" PIE base *bher- "to carry").
1) (n.) nur (#), luž (#); 2) (adj.) sabok (#)
Fr.: 1) lumière; 2) léger
1) That portion of → electromagnetic radiation
visible to the human → eye.
However, other bands of the → electromagnetic spectrum
are also often referred to as different forms of light.
1) O.E. leoht, leht, from W.Gmc. *leukhtam
(cf. O.Fris. liacht, M.Du. lucht, Ger. Licht),
from PIE *leuk- "light, brightness," cognate with Pers.
rowšan "bright, clear," ruz "day,"
rowzan "window, aperture;" foruq "light," and afruxtan
kindle;" Mid.Pers. rôšn "light; bright, luminous,"
rôc "day;" O.Pers. raucah-rocânak "window;" O.Pers. raocah- "light, luminous; daylight;"
Av. raocana- "bright, shining, radiant;"
akin to Skt. rocaná- "bright, shining," roka-
Gk. leukos "white, clear;" L. lux "light" (also lumen, luna);
1) Nur, from Ar.
niyâveš bé rowšanâyi
Fr.: adaptation à la lumière
The reflex adaptation of the eye to bright light, consisting of an increase in the number of functioning cones, accompanied by a decrease in the number of functioning rods; opposed to dark adaptation.
A bright, confusing, and excessive grouping of light sources. Light clutter is a type of → light pollution. It is a general term relating to lights put up everywhere, without regard to what their purpose really is.
maxrut-e nur (#)
Fr.: cône de lumière
The set of all directions in which a light signal can travel toward an event (past light cone) or from an event (future light cone).
nur-xam, xam-e nur
Fr.: courbe de lumière
Fr.: cylindre de lumière
A cylinder of radius cP/(2π) around a → pulsar's spin axis, where P is the pulsar period and c the → speed of light. At this surface, the velocity of a hypothetical object that corotates with the → neutron star would reach the speed of light.
Fr.: déflexion de la lumière
The deviation of a light ray by the gravitational field of a massive body. For example, stellar light passing near the Sun will be deviated by 1''.75 at the Sun's limb.
pažvâk-e nuri (#)
Fr.: écho de lumière
Reflection of light from a stellar outburst by successively more distant clouds of dust surrounding the star. For example, the light echoes from two shells of dust near supernova 1987A, or those of star V838 Mon.
bonpâr-e sabok (#)
Fr.: élément léger
In astrophysics, a chemical element that has an atomic number of one, two, or three, such as hydrogen, helium, and lithium; sometimes also beryllium and boron.
Fr.: colonne lumineuse
An atmospheric optical phenomenon appearing as a vertical shaft of light extending from the Sun or other bright light source during very cold weather. Light pillars or → sun pillars occur when artificial light or sunlight near the horizon is reflected from falling ice crystals associated with thin, high-level clouds. The ice crystals have a hexagonal plate shape and fall with a horizontal orientation, gently rocking from side to side as they fall.
âludegi-ye nuri (#)
Fr.: pollution lumineuse
The inappropriate or excessive use of artificial light. It brightens the sky and has a particularly damaging effect on astronomical observations. More generally, light pollution can have serious environmental consequences for humans, wildlife, and our climate. Types of light pollution include: → glare, → skyglow, → light trespass, and → light clutter.
Fr.: rayon de lumière
An imaginary line directed along the path that the light follows. In other words, light pictured simply in terms of straight lines.
Fr.: lumière intrusive
A type of → light pollution which is light falling where it is not wanted or needed. Light trespass occurs when poorly shielded or poorly aimed fixtures cast light into unwanted areas, such as buildings, neighboring property, and homes. This light is a main contributor to → skyglow which interferes with astronomical instruments.
nur-sâl (#), sâl-e nuri (#)