What is at the centre of the Earth?

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Professor Kei Hirose has recreated the conditions found at the Earth's core in his laboratory at the SPring-8 synchrotron near Osaka, Japan.

A sample of the material thought to make up the Earth's core, iron-nickel alloy, was subjected to three million times atmospheric pressure and heated to about 4,500C, resulting in the rapid growth of crystals.

Horizon: The Core is on BBC Two at 21:00 BST on Wednesday 31 August. Watch more clips or catch up afterwards via iPlayer.