• Question: Why is the centre of the Earth so hot? How did it get that way?

    Asked by lauren777 to David, Helen, Ian, rhysphillips on 23 Jun 2011.
    • Photo: David Corne

      David Corne answered on 22 Jun 2011:

      When you compress something, it heats up a bit. If you ride a bike, you will know this from when you pump up the inner tube. The pump repeatedly compresses the air inside it, and the inner bits of the pump get very hot. When you compress it you are inputting lots of energy, and this gets partly transferred into making the molcules bounce about more wildly, and that’s what heat is. The centre of the Earth is very powerfully compressed by gravity, and all the pressure of billions of tons of Earth pressing in on it. That’s what makes it and keeps it hot.

    • Photo: Rhys Phillips

      Rhys Phillips answered on 22 Jun 2011:

      Because of the huge amount of pressure inside.

    • Photo: Ian van der Linde

      Ian van der Linde answered on 23 Jun 2011:

      There are two stages to this answer: 1. pressure – the weight of all the other layers of the earth being attracted towards the gravitational centre. 2. heat is just vibration – if you force things close together by placing them under pressure, the more they will bounce off each other, making them heat up!

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