Nutation, in astronomy, a slight wobbling motion of the earth's axis. The causes of nutation are similar to those of the precession of the equinoxes, involving the varying attraction of the moon on the earth's equatorial bulge. However, the period of the motion is only 18.6 years, the same as that of the precession of the moon's nodes, as opposed to the nearly 26,000-year period of the precession of the equinoxes. Nutation was discovered by the English astronomer James Bradley in 1728 but was not explained until 20 years later.
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A stamp depicting the image of Hanaoka Seishu. Hanaoka Seishu (1760-1835), Japanese physician and pioneer of anesthetic surgery. Hanaok... -
In the N and W United States the era of mechanized agriculture began with the invention of such farm machines as the reaper, the cultivator,...
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Fluid Mechanics, physical science dealing with the action of fluids at rest or in motion, and with applications and devices in engineering u...