• Question: wher did the moon come from

    Asked by zone58 to Austin, Kirsty, Nicola, Nike, Sarah on 19 Jun 2012. This question was also asked by abs10.
    • Photo: Kirsty Ross

      Kirsty Ross answered on 19 Jun 2012:


      There are various theories explaining where the moon came from. All of them have issues, which is why they are theories, but the one that is in the lead at the moment is the giant impact theory

      This theory proposes that the young earth had a massive impact with another Mars-sized object. This object, which has been nick-named Theia, smacked into the earth at around a 45 degree angle and at a relatively slow speed. The iron rich core of Theia sank into the earth, while large quantities of mantle (the crust of the planets) was blown into space. This material from the impact then clumped together to form the moon. This explains why the moon is relatively short of iron compared to the earth. It took around 100 years for the moon to form from the dust that surrounded the two bodies.

      It is thought that Theia may have originally formed at one of the two Lagrange points. These points are where the earth and the sun’s gravity form a balanced point in space. Theia could have grown there quite happily until she grew to about 10% of the young earth’s size. At that point, gravitational tugs from other objects in the solar system could have pulled it out of the Lagrange point and sent it towards earth.

      This is a fantastic video of the early days of the earth that I thought you’d enjoy.

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