English-Thai Dictionary
libration
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Webster's 1828 Dictionary
LIBRATION
n. 1. The act of balancing or state of being balanced; a state of equipoise, with equal weights on both sides of a center.
2. In astronomy, an apparent irregularity of the moon's motions, by which it seems to librate about its axis.
Libration is the balancing motion or trepidation in the firmament, whereby the declination of the sun and the latitude of the stars change from time to time.
3. A balancing or equipoise between extremes.
Webster's 1913 Dictionary
LIBRATION
Li *bra "tion, n. Etym: [L. libratio: cf. F. libration. ]
1. The act or state of librating. Jer. Taylor.
2. (Astron.)
Defn: A real or apparent libratory motion, like that of a balance before coming to rest. Libration of the moon, any one of those small periodical changes in the position of the moon's surface relatively to the earth, in consequence of which narrow portions at opposite limbs become visible or invisible alternately. It receives different names according to the manner in which it takes place; as: (a ) Libration in longitude, that which, depending on the place of the moon in its elliptic orbit, causes small portions near the eastern and western borders alternately to appear and disappear each month. (b ) Libration in latitude, that which depends on the varying position of the moon's axis in respect to the spectator, causing the alternate appearance and disappearance of either pole. (c ) Diurnal or parallactic libration, that which brings into view on the upper limb, at rising and setting, some parts not in the average visible hemisphere.
New American Oxford Dictionary
libration
li bra tion |līˈbrāSHən laɪˈbreɪʃən | ▶noun Astronomy an apparent or real oscillation of the moon, by which parts near the edge of the disc that are often not visible from the earth sometimes come into view. DERIVATIVES li brate |ˈlīˌbrāt |verb ORIGIN early 17th cent. (denoting an oscillating motion, or equilibrium ): from Latin libratio (n- ), from the verb librare, from libra ‘a balance. ’
Oxford Dictionary
libration
libration |lʌɪˈbreɪʃ (ə )n | ▶noun Astronomy an apparent or real oscillation of the moon, by which parts near the edge of the disc that are often not visible from the earth sometimes come into view. DERIVATIVES librate verb ORIGIN early 17th cent. (denoting an oscillating motion, or equilibrium ): from Latin libratio (n- ), from the verb librare, from libra ‘a balance ’.
Duden Dictionary
Libration
Li b ra ti on , Li bra ti on Substantiv, feminin Astronomie , die |Librati o n |lateinisch libratio = das Wägen, zu: librare = wägen auf der Ungleichförmigkeit der Bahnbewegung des Mondes, optischen Effekten o. Ä. beruhende, scheinbare teilweise Drehbewegung des Mondes um die eigene Achse nach beiden Seiten
The Wordsmith Dictionary