nutation

nutation

[noo-tey-shuhn, nyoo-]
noun
1.
an act or instance of nodding one's head, especially involuntarily or spasmodically.
2.
Botany. spontaneous movements of plant parts during growth.
3.
Astronomy. the periodic oscillation observed in the precession of the earth's axis and the precession of the equinoxes.
4.
Mechanics. the variation of the inclination of the axis of a gyroscope to the vertical.

Origin:
1605–15; < Latin nūtātiōn- (stem of nūtātiō), equivalent to nūtāt(us) (past participle of nūtāre to nod repeatedly; nū- nod + -tā- frequentative suffix + -tus past participle ending) + -iōn- -ion; cf. numen

nutational, adjective
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World English Dictionary
nutation (njuːˈteɪʃən)
 
n
1.  astronomy a periodic variation in the precession of the earth's axis causing the earth's poles to oscillate about their mean position
2.  physics a periodic variation in the uniform precession of the axis of any spinning body, such as a gyroscope, about the horizontal
3.  Also called: circumnutation the spiral growth of a shoot, tendril, or similar plant organ, caused by variation in the growth rate in different parts
4.  the act or an instance of nodding the head
 
[C17: from Latin nutātiō, from nūtāre to nod]
 
nu'tational
 
adj

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American Heritage
Medical Dictionary

nutation nu·ta·tion (nōō-tā'shən, nyōō-)
n.
The act of nodding the head, especially involuntarily.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
nutation   (n-tā'shən)  Pronunciation Key 
  1. A small, cyclic variation of the Earth's axis of rotation with a period of 18.6 years, caused by tidal forces (mostly due to the gravity of the Moon). Nutation is a small and relatively rapid oscillation of the axis superimposed on the larger and much slower oscillation known as precession. Although discovered in 1728 by the British astronomer James Bradley (1693-1762), nutation was not explained until two decades later.

  2. A slight curving or circular movement in a stem, as of a twining plant, caused by irregular growth rates of different parts.


The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

nutation

in astronomy, a small irregularity in the precession of the equinoxes. Precession is the slow, toplike wobbling of the spinning Earth, with a period of about 26,000 years. Nutation (Latin nutare, "to nod") superimposes a small oscillation, with a period of 18.6 years and an amplitude of 9.2 seconds of arc, upon this great slow movement. The cause of nutation lies chiefly in the fact that the plane of the Moon's orbit around the Earth is tilted by about 5 from the plane of the Earth's orbit around the Sun. The Moon's orbital plane precesses around the Earth's in 18.6 years, and the effect of the Moon on the precession of the equinoxes varies with this same period. The British astronomer James Bradley announced his discovery of nutation in 1748.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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