| 释义 |
libration|laɪˈbreɪʃən|
[ad. L. lībrātiōn-em, n. of action f. lībrā-re to librate. Cf. F. libration.]
1. a. The action of librating; motion like that of the beam of a balance oscillating upon its pivot; swaying to and fro. b. The state of being balanced or in equipoise; equipoise, balance.
1603Sir C. Heydon Jud. Astrol. xviii. 381 This Thebit..perceiuing the quantitie of the tropike yeare to varie, first inuented the libration of the 8. sphere. 1625N. Carpenter Geog. Del. i. iv. 73 Some others..imagine the Center..of the Earth to be moued vp and down by a certaine motion of Libration. Ibid. ii. vi. 85 This libration or motion of the Water cannot bee caused by the winde or Aire. 1653Jer. Taylor Serm. Gold. Grove, Winter v. 60 The poor bird was beaten back..descending more at every breath of the tempest then it could recover by the libration and frequent weighing of his wings. 1684T. Burnet Th. Earth ii. 51 This must needs make it lose its former poise and libration. 1694W. Holder Harmony (1731) 29 The Librations of the Pendulum. 1728–46Thomson Spring 742 Their pinions still, In loose libration stretched. 1791E. Darwin Bot. Gard. ii. 26 So turns the needle to the pole it loves, With fine librations quivering, as it moves. 1853Kane Grinnell Exp. xlviii. (1856) 446 Others [viz. icebergs] a congeries of rubbish, and illustrating every possible condition of libration. 1874H. R. Reynolds John Bapt. v. iii. 341 A dazzling brightness above the Splendour of the Sun was drawing nearer with gentle librations of its wings.
c. transf. and fig.
1650Anthroposophia Theomagica 92 Such chiming and clinching of words, Antithetall Librations, and Symphonicall rappings. 1659H. More Immort. Soul ii. x. 218 The Libration or Reciprocation of the Spirits in the Tensility of the Muscles. 1659J. Harrington Lawgiving Wks. (1700) 431 Such a libration or poize of Orders. 1659Walker Oratory 97 The short [period] is adverse to Metaphors &c. the long to exact correspondence and libration of its parts. 1670Dryden 2nd Pt. Conq. Granada iii. i. Wks. 1808 IV. 151 The bounds of thy libration here are set. 1840Blackw. Mag. XLVII. 719 The tremulous libration of the equipoise. 1882J. H. Blunt Ref. Ch. Eng. ii. 480 Oxford has its regular periods of theological libration.
2. Astron. A real or apparent motion of an oscillating kind. libration of the moon: an apparent irregularity of the moon's motion which makes it appear to oscillate in such a manner that the parts near the edge of the disk are alternately visible and invisible. (There are three kinds, called libration in latitude, libration in longitude, and diurnal libration or parallactic libration.)
1669J. Flamstead in Phil. Trans. IV. 1109 If the Libration of the Moon be known, the protraction of the Star's way in this Appearance will be facile. 1670Ibid. V. 2061 Doubtless, as there is a certain Libration in the Moon, so 'tis not absurd to me, to hold a kind of Libration in the Earth, from the Annual and Diurnal motion of the same. 1678Norris Coll. Misc. (1699) 181 We are nonplus'd at a thousand Phenomenas in Nature, which if they were not done, we should have thought them absolutely impossible, as for instance the central Libration of the Earth. 1690Leybourn Curs. Math. 754 Now this Libration of the Eccentrick they commonly call the Deviation. 1728tr. Newton's Treat. Syst. World 61 The Moon's libration in longitude. 1804Herschel in Phil. Trans. XCIV. 374 Some small annual variation, or libration of position, which might lead to a discovery of the parallax of the fixed stars. 1812–16J. Smith Panorama Sci. & Art I. 547 Her libration in latitude, is when either of her poles appears to dip a little towards the earth. 1831Brewster Newton (1855) I. vi. 128 Galileo had discovered and explained the diurnal libration, arising from the spectator not viewing the moon from the centre of the earth. 1834M. Somerville Connex. Phys. Sci. ix. (1849) 78 The moon..is liable to librations depending upon the position of the spectator. 1867–77G. F. Chambers Astron. i. vii. 79 When the North Pole [of the Moon] leans towards the earth we see somewhat more of the region surrounding it;..this is known as libration in latitude. 1874Farrar Christ 51 There is one hemisphere of the lunar surface on which in its entirety, no human eye has ever gazed, while at the same time the moon's librations enable us to conjecture of its general character.
†3. Weighing (lit. and fig.). Obs.
1657W. Morice Coena quasi κοινὴ xiii. 185 We..have made libration, what weight the judgment and practice of the ancient Church doth bear. 1667Waterhouse Fire Lond. 48 Prudent libration of what weight they will and will not beare. 1770Emerson (title) Calculation, libration and mensuration, or the arts of reckoning, weighing and measuring.
Hence liˈbrational a., pertaining to (the moon's) libration.
1880Proctor Rough Ways made Smooth 110 Photographs of the moon should be taken in every aspect..of her librational swayings. |