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The earth is the third planet in order from the sun, only Mercury and Venus being nearer; the mean distance from the earth to the sun is c.93 million mi (150 million km).
Rotation and Revolution
The earth rotates from west to east about a line (its axis) that is perpendicular to the plane of the equator and passes through the center of tth and south geographical poles. The period of one complete rotation is a day; the rotation of the earth is responsible for the alternate periods of light and darkness (day and night). The earth revolves about the sun once in a period of a little more than 365 1/4 days (a year). The path of this revolution, the earth's orbit, is an ellipse rather than a circle, and the earth is consequently nearer to the sun in January than it is in July; the difference between its maximum and minimum distances from the sun is c.3 million mi (4.8 million km). This difference is not great enough to affect climate on the earth.
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