• Question: What makes the earth rotate?

    Asked by saraw1998 to Arttu, Ceri, James_M, Monica, Philip on 13 Jun 2011. This question was also asked by bassmaa123.
    • Photo: James M Monk

      James M Monk answered on 13 Jun 2011:

      The Solar System and the Earth formed from a cloud of gas and dust about 4.5 billion years ago. Gravity caused the cloud to collapse to form the sun and the planets. Conservation of momentum means that whatever angular momentum was held by the initial cloud must still be present in the solar system today. Since the dust cloud was much larger in radius than the Solar System is, as it collapsed to a smaller radius it had to start rotating more quickly in order to maintain angular momentum. So the initial relatively small rotation became larger and is seen in the rotation of the Sun and the planets

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