Astronomy and Space

Planets and Moons

Is it true that the rotation speed of Earth varies?

The rotation speed is at its maximum in late July and early August and at its minimum in April; the difference in the length of the day is about 0.0012 second. Since about 1900 Earth’s rotation has been slowing at a rate of approximately 1.7 seconds per year. In the geologic past Earth’s rotational period was much faster; days were shorter and there were more days in the year. About 350 million years ago, the year had 400 to 410 days; 280 million years ago, a year was 390 days long.


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