Asked by: Amir Montazer, Iran
The Earth, just like all the planets of the solar system (except Mercury), has a rotation axis that is titled with respect to its orbit around the Sun. Astronomers propose that this is due to energetic collisions between the ‘planetessimals’ which eventually coalesced to form the planets, knocking them off the perpendicular orientation they would naturally have. In some cases, Uranus for example (which has a very large axial tilt), it may be the result of a series of such collisions.
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