• Question: why does the earth rotate (from my mum who is voting to)

    Asked by slmg to David, Helen, Ian, rhysphillips, Sarah on 24 Jun 2011.
    • Photo: Ian van der Linde

      Ian van der Linde answered on 20 Jun 2011:

      The earth spins because the dust cloud from which it was made was spinning, and this motion was preserved due to the law of conservation of angular momentum.

    • Photo: Rhys Phillips

      Rhys Phillips answered on 20 Jun 2011:

      Because of the way it was made – the Earth was made by lots of spinning particles of dust and it keeps spinning because there’s no forces there to stop it.

    • Photo: David Corne

      David Corne answered on 20 Jun 2011:

      … but why was the dust cloud spinning in the first place? This is a good example of the sort of question that computer modelling can help with. I think that if you run lots of simulations of how the planet might have been formed, it always ends up spinning. I reckon because new dust comes along from somewhere, already with momentum that will nudge the growing planet some way or other, and it is extremely unlikely that the effects of the incoming dust will just cancel out, leaving the planet still.

    • Photo: Helen Fletcher

      Helen Fletcher answered on 24 Jun 2011:

      To make it more fun.. like a carousel at the fair!

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