See also:

• NUTATION (from Lat. nutare, to nod)

NUTATION (from See also:

• LAT

Lat. nutare, to nod)  , a revolution of the See also:

• CELESTIAL, OR STELLAR

celestial See also:

• POLE (FAMILY)
• POLE, REGINALD (1500-1558)
• POLE, RICHARD DE LA (d. 1525)
• POLE, WILLIAM (1814—1900)

pole around its mean position, due to inequalities in the See also:

• ACTION

action of the See also:

• SUN
• SUN (0. Eng. sonne, Ger. sonne. Fr. soleil, Lat. sol, Gr. ijXior, from which comes helio- in various English compounds)

sun and See also:

• MOON (a common Teutonic word, cf. Ger. Mond, Du. maan, Dan. maane, &c., and cognate with such Indo-Germanic forms as Gr. µlip, Sans. ma's, Irish mi, &c.; Lat. uses luna, i.e. lucna, the shining one, lucere, to shine, for the moon, but preserves the word i
• MOON, SIR RICHARD, 1ST BARONET (1814-1899)

moon, on an See also:

• EARTH
• EARTH (a word common to Teutonic languages, cf. Ger. Erde, Dutch aarde, Swed. and Dan. jord; outside Teutonic it appears only in the Gr. 'pq'e, on the ground; it has been connected by some etymologists with the Aryan root ar-, to plough, which is seen in
• EARTH, FIGURE OF
• EARTH, FIGURE OF THE

earth of ellipsoidal See also:

• FORM (Lat. forma)

form . When either of these attracting bodies is in the See also:

• PLANE

plane of the See also:

• EQUATOR (Late Lat. aequator, from aequare, to make equal)

equator, it produces no See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change in the direction of the celestial pole . The greater their distance from this plane, the greater the change, for reasons shown in the See also:

• ARTICLE (from Lat. articulus, a joint)

article See also:

• ASTRONOMY (from Gr. &arpov, a star, and v ,usiv, to classify or arrange)

ASTRONOMY (Celestial See also:

• MECHANICS

Mechanics) . The result is a See also:

• MOTION (Lat. motio, from movere, to move)
• MOTION, LAWS OF

motion which can be divided into two components . One of these is the progressive and nearly See also:

• UNIFORM

uniform motion of a fictitious mean pole, called precession (q.v.), and the other a revolution of the true around the mean pole, de-pending on the varying declinations of the sun and moon, and called See also:

• NUTATION (from Lat. nutare, to nod)

nutation . Owing to the revolution of the moon's See also:

• NODE (Lat. nodus, a loop)

node and the inclination of its See also:

• ORBIT (from Lat. orbita, a track, orbis, a wheel)

orbit, this See also:

• BODY

body moves through a wider range of See also:

• DECLINATION (from Lat. declinare, to decline)

declination in some positions of the node than in others . The See also:

• PERIOD
• PERIOD (Gr. irepioSos, a going or way round, circuit, aepi, round, and &Sis, way, road)

period of the revolution of the node is 18.6 years . At one See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

time of this period the limits of its declination are more than 28° See also:

• NORTH
• NORTH, BARONS
• NORTH, MARIANNE (1830—1890)
• NORTH, ROGER (1653-1734)
• NORTH, SIR THOMAS (1535?-16o1?)

north and See also:

• SOUTH
• SOUTH, ROBERT (1634–1716)

south, while, at the opposite point, they are little more than 18° . The result of these periodic changes is that the nutation takes See also:

• PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place nearly in an See also:

• ELLIPSE (adapted from Gr. EXkei 'tc, a deficiency, iXXeirely, to fall behind)

ellipse, differing little from a circle, at a distance of about 9", in a period of about 18.6 years . The motion is not exactly an ellipse, having a See also:

• GREAT

great number of See also:

• MINUTE
• MINUTE (Lat. minutes, small; minuere, to make less)

minute inequalities arising from the See also:

• ELLIPTICITY

ellipticity of the orbits of the sun and moon and their varying declinations . The amount and formulae of nutation from See also:

• YEAR

year to year are given in the Nautical See also:

• ALMANAC

Almanac .