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Article: Earth Science: Earth in Space
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- The New York Public Library Science Desk Reference
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Earth Science: Earth in Space
Rotation
The Earth rotates around a central axis, approximately
identified by the North and South Poles. The Earth's axis
tilts 23° 27' (23.5°) away from a line perpendicular to the
plane of its orbit. One complete rotation of the Earth on
its axis results in a day. A mean solar day lasts 24 hours,
which is the average of all apparent solar days in the
orbital year; the mean sidereal day is 23 hours, 56 minutes,
and 4.091 seconds; this is the time required for a star to
go from one spot to the same spot in the sky (for more
information on days, months, and years, see Chapter 3, "Time").
There are variations in the ...