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Earth’s axis is tilted 23½° with respect to the Earth-Sun plane. What factors contribute to its “wobble” over extended periods?

Robert Feingold, Highlands Ranch, Colorado
RELATED TOPICS: SPACE PHYSICS | EARTH
BlueMarble
The “tap” that causes Earth’s axis to precess is gravity from the Sun and Moon and, to a much lesser extent, the planets. Gravity alone, however, won’t do the trick. Earth has a slight equatorial bulge, and it’s this bulge that gets the gravitational tug.

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