Could you dig all the way through the planet?

Learn the science behind digging a giant hole.

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Have you ever dug a hole in your garden or at the beach? Adults love joking that if you keep digging, you'll end up in Australia. In fact, if you tunnelled straight through the middle of the planet, from anywhere in the British Isles, you'd end up in the ocean south of New Zealand.

Inside the planet

However, with just a garden spade it's unlikely that you would get much further than one metre below the surface, where you often hit rock. Earth has three main layers. The outer skin, called the crust, is a layer of light rock. Its thickness compared to the planet's diameter (the distance from one side of a circle or sphere to the other, passing through the centre) is similar to how thick an apple's skin is compared to its diameter. When you dig holes, you are basically making tiny scratches at the very top of this apple skin.

The mantle, which lies beneath the crust, is much thicker, like the flesh of the apple. It's made of strong, heavy rock that flows a few inches per year as hotter rock rises away from the centre and cooler rock sinks toward it. The core, at Earth's centre, is made of very hot metal, in both solid and liquid forms. Temperatures here are between 2,500°C and 5,200°C.