librational, adj.
/luy bray"sheuhn/, n. Astron.
a real or apparent oscillatory motion, esp. of the moon.
[1595-1605; < L libration- (s. of libratio) a balancing. See LIBRATE, -ION]

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      in astronomy, an oscillation, apparent or real, of a satellite, such as the Moon, the surface of which may as a consequence be seen from different angles at different times from one point on its primary body.

      The latitudinal libration of the Moon occurs because its axis is tilted slightly, relative to the plane of its orbit around the Earth; this makes the Moon's north and south poles apparently alternate in tipping slightly toward the Earth as the Moon moves through its orbit. The Moon's longitudinal libration (a back and forth turning, a “headshaking” motion) results from its moving at slightly different speeds at different points in its orbit (in accord with Kepler's second law).

      These and other small librations allow about 59 percent of the Moon's surface to be seen from Earth, though it presents nearly the same face to the Earth at all times.

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Universalium. 2010.

Look at other dictionaries:

  • libration — [ librasjɔ̃ ] n. f. • 1547; lat. libratio ♦ Astron. Balancement apparent (d un astre, et spécialement de la Lune). « un capteur optique de la position angulaire du Soleil pour étudier la libration de Phobos » (Sciences et Avenir, 1988). ●… …   Encyclopédie Universelle

  • Libration — Libration: Die animierte Simulation zeigt den Anblick des Mondes über den Zeitraum von 27 Tagen, was einem täglichen Foto des Erdtrabanten in allen Mondphasen von Neu über Vollmond bis Neumond entspricht. Daneben ist auch seine Winkel und… …   Deutsch Wikipedia

  • Libration — Li*bra tion (l[ i]*br[=a] sh[u^]n), n. [L. libratio: cf. F. libration.] 1. The act or state of librating. Jer. Taylor. [1913 Webster] 2. (Astron.) A real or apparent libratory motion, like that of a balance before coming to rest. [1913 Webster]… …   The Collaborative International Dictionary of English

  • Libration — (vom lat.), das Schwanken, namentlich das Schwanken des Mondes, s.d …   Pierer's Universal-Lexikon

  • Libration — (lat.), das scheinbare Schwanken des Mondes, wird erzeugt durch dessen ungleichförmige Bewegung in seiner elliptischen Bahn und durch deren Neigung zur Erdbahn; sie bewirkt, daß man statt der Hälfte nahezu 4/7 der Mondoberfläche beobachten kann …   Kleines Konversations-Lexikon

  • Libration — Libration, s. Mond …   Herders Conversations-Lexikon

  • libration — [lī brā′shən] n. [L libratio] 1. the act of librating 2. Astron. a slight rocking motion of the moon which allows 59% of the moon s surface to be visible from the earth libratory [lī′brə tôr΄ē] adj …   English World dictionary

  • Libration — This article is about astronomical observations. For molecular motion, see Libration (molecule). Not to be confused with Liberation, Libation, or Vibration. Simulated views of the Moon over one month, demo …   Wikipedia

  • Libration — Cette animation montre un ensemble de vues simulées de la Lune sur une période d un mois, comme si une photographie avait été prise chaque jour à la même heure. Elle permet de mettre en évidence le phénomène de libration lunaire. En astronomie,… …   Wikipédia en Français

  • Libration — Li|bra|ti|on auch: Lib|ra|ti|on 〈f. 20〉 Schwankung des Mondkörpers um die mittlere Lage [<lat. libratio „das Abwägen, Schwingen“; zu librare „wägen, schwingen“] * * * Li|b|ra|ti|on, die; , en [lat. libratio = das Wägen, zu: librare = wägen]… …   Universal-Lexikon

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