LIBRATION • DICTIONARY ONE.COM • Definition of Libration

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noun

Libration n.

The act or state of librating.

(Astron.) 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.

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Etymology of 'Libration'

Collaborative International Dictionary of English 0.48

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"Libration" Quotes from Famous Books

... which prevail at a distance from shore between the parallels of thirty degrees north and south, whose uniform and invariable action causes a long and constant swell, that exists even in the calmest weather, about the line, towards which its direction tends from either side. This swell or libration of the sea is so prodigiously long, and the sensible effect of its height, of course, so much diminished, that it is not often attended to; the gradual slope engrossing almost the whole horizon when the eye is not very much elevated ...

— The History of Sumatra - Containing An Account Of The Government, Laws, Customs And - Manners Of The Native Inhabitants • William Marsden

... reduction plant on the one side and the convicts' huts and more pretentious houses of the guards on the other. And the choking mists, and the lurid flame behind. The stifling heat, Luke learned, too, that every ninth day, with what they called the libration of Vulcan, there came an equal period of raw and biting cold to replace the heat. As bad or worse, ...

— Vulcan's Workshop • Harl Vincent

Words linked to "Libration" : astronomy, oscillation, variation