| 释义 |
▪ I. precession|prɪˈsɛʃən|
[ad. late L. præcessiōnem (Boeth.) a going before, n. of action from præcēdĕre to precede. So F. précession (1690 in Hatz.-Darm.).]
¶1. A going forward, advance, procession. (app. in every case an error for procession.)
13..Cursor M. 20697 (Cott.) Gas þan wit fair precessiun [other MSS. pro-] To ierusalem right thoru þe town. c1420Pol. Rel. & L. Poems (1866) 208, iij women I met with precession. 1529Rastell Pastyme, Brit. (1811) 269 The kynge, the quene, and all the lordes, vpon our Lady-day..went a precessyon in Poules.
2. The action or fact of preceding in time, order, or rank; precedence.
a1628F. Grevil Sidney (1652) 232 To assist her in bounding out the Imperial Meeres of all Princes by the ancient precession of Right and power. 1898Allbutt's Syst. Med. V. 1020 Premising that the precession of the two sounds of tension is aortic in the earlier and pulmonic in the later phases of the disease.
3. a. Astron. precession of the equinoxes, often ellipt. precession [æquinoctiorum præcessio (Copernicus): called by Hipparchus and Ptolemy µετάπτωσις mutation]: the earlier occurrence of the equinoxes in each successive sidereal year, due to the retrograde motion of the equinoctial points along the ecliptic, produced by the slow change of direction in space of the earth's axis, which moves so that the pole of the equator describes a circle (approximately: see nutation) around the pole of the ecliptic once in about 25,800 years. Hence commonly used to denote this motion of the equinoctial points, of the earth's axis, or of the celestial pole or equator; also the motion of the earth itself which manifests itself as the precession of the equinoxes.
As a result of the precession, the longitudes, right ascensions, and declinations of all the stars are continually changing, and the signs of the zodiac shift in a retrograde direction along the zodiac, so that they no longer coincide with the constellations from which they were named (cf. the statement s.v. cancer n. 2 b).
lunisolar precession: that part of the precession which is caused by the combined attractions of the moon and sun upon the mass of the earth (the remaining effect being due to the attractions of the other planets).
planetary precession, that part of the precession of the earth's axis caused by the gravitational attraction of the other planets.[a1530Copernicus De Revolution. Orb. Cœlest. (1543) iii. (title) De æquinoctium solstitiorumque anticipatione. Ibid. iii. ii. (heading) Historia observationum comprobantium inæqualem æquinoctiorum conversionumque præcessionem.] 1594Blundevil Exerc. iii. i. xxvii. (1636) 335 Spica Virginis..is found now to be in the eighteenth of Libra, the cause whereof is the precession of the Equinoctiall point or section. 1621Burton Anat. Mel. ii. ii. iii. (1676) 160/1 Whether there be such a precession of the æquinoxes, as Copernicus holds. 1704J. Harris Lex. Techn. I. s.v., The Equinoctial Points, or the common Intersections of the Equator and Ecliptick, do retrocede or move backwards from East to West, about 50 Seconds each Year; and this Motion backwards is by some called the Recession of the Equinox, by others the Retrocession; and the advancing of the Equinoxes forward by this means is called the Precession of them. 1796Burke Regic. Peace i. Wks. VIII. 208, I cannot move with this precession of the equinoxes, which is preparing for us the return of some very old, I am afraid no golden, æra. 1816Playfair Nat. Phil. II. 89 Hipparchus discovered the precession of the equinoxes, by a comparison of his own with more ancient observations. 1863W. Chauvenet Man. Spherical & Pract. Astron. I. xi. 604 The mutual attraction between the planets and the earth tends continually to draw the earth out of the plane in which it is revolving... The planetary precession is, then, the effect of a motion of the ecliptic upon the equator... The planetary precession does not affect the declination of stars, but changes their right ascensions, their longitudes, and their latitudes. 1867Emerson Lett. & Soc. Aims, Progr. Cult. Wks. (Bohn) III. 228 Six hundred years ago, Roger Bacon explained the precession of the equinoxes. 1881Geikie in Nature XXIII. 359/1 The alternate phases of precession, which tend to bring warmer and colder conditions of climate every 10,500 years. 1913S. E. Slocum Theory & Pract. Mech. vii. 430 (heading) Precession of the earth. Ibid., An important case of regular precession is that furnished by the motion of the earth. 1926H. N. Russell et al. Astron. I. v. 141 The motion of the ecliptic pole produces..the planetary precession. 1939Skilling & Richardson Astron. i. 16 Precession does not affect the position of the terrestrial poles upon the earth's surface. 1959R. H. Baker Astron. (ed. 7) ii. 59 The earth's precession is a slow conical movement of the earth's axis around a line joining the ecliptic poles, having a period of about 26,000 years. 1963D. Alter et al. Pictorial Astron. (ed. 2) xlvi. 211/2 This gradual north–south drift of the Southern Cross is a consequence of the precession of the earth, which produces a slow movement of the celestial pole among the stars on a circle with a radius of 23½°. 1971Baker & Fredrick Astron. (ed. 9) ii. 49 It is the lunisolar precession that has been described... Planetary precession is the effect of other planets on the plane of the equator, so that its intersection with the ecliptic shifts slowly towards the east along the celestial equator. The result of the two precessions is the general precession.
b. Physics. Extended to any motion analogous to that of the earth's axis or the earth itself in the precession of the equinoxes; e.g. the slow rotation of the axis of a top spinning rapidly in a sloping position.
1879Thomson & Tait Nat. Phil. I. i. §105 The plane through the instantaneous axis and the axis of the fixed cone passes through the axis of the rolling cone... The motion of the plane containing these axes is called the precession in any such case. 1907Franklin & Macnutt Elements Mech. vii. 149 The torque required to produce precession of a spinning body depends upon the moment of inertia of the body and upon the angular acceleration which is involved in the continual change of direction of the axis of spin. 1942Tee Emm (Air Ministry) June 56/1 He has a directional gyro—and should have some idea as to its rate of precession. 1958Engineering 31 Jan. 132/3 If the weights are moved from one side of the point of balance to the other the direction of precession is reversed. 1962F. I. Ordway et al. Basic Astronautics ix. 372 The antifriction motor..applies an additional torque in the direction of precession to compensate for friction in the bearings.
c. spec. The rotation of the spin axis of a nucleus, electron, etc., about the direction of a magnetic or an electric field.
1927Physical Rev. XXIX. 395 Predicted and observed intensity relations for a number of band spectra are in agreement if we assume that σ is an electronic quantum number which is correlated with a precession about the internuclear axis. 1928H. S. Allen Quantum xvi. 220 As the electron has a magnetic moment, its axis will experience a precession because of the couple due to its motion in the electric field. 1960Dicke & Wittke Introd. Quantum Mech. xii. 195 This torque produces a precession of the spin axis about the direction of the magnetic field; in other words, the particle acts like a gyroscope because of its spin angular momentum. 1965New Scientist 1 July 36/3 This precession will alter the average area that the molecule presents to other molecules. 1973O. Howarth Theory of Spectroscopy i. 14 The existence of precession explains why even a classical particle with a magnetic moment does not immediately align when put in a magnetic field. It precesses instead.
4. Phonetics. Advance in oral position.
1844Crosby Gram. Gr. Lang. i. §29. 17 Such remarkable has been this precession (præcession, going forward) of the vowels in the Greek language, that η, υ, ει, ῃ, οι, and υι, have all lost their distinctive sounds. 1860Haldeman Analyt. Orthogr. xi. 56 Precession (>) is a vowel change from a more open to a closer position of the organs, towards the lips or throat. The term is adopted from Crosby's Greek Grammar. 1870March Anglo-Saxon Gram. 26.
▪ II. precession
obs. erron. f. presession. |