Asked by: Maddie Fraser, London
It’s 6,371km (3,959 miles) to the centre of the Earth and the deepest hole ever drilled (the Kola Superdeep Borehole, now welded shut in the image above) was only 12km (7.5 miles) deep. We could try sending a robot probe, but it would not get very far. The pressure in the Earth’s core is more than 3,000 times the pressure at the bottom of our deepest ocean. The temperature is more than 5,000°C. Your poor little tunnelling machine would be crushed to a pea and then cooked to a bubble of gas long before it could get anywhere near Earth’s core.
Image by Rakot13 (Own work) [CC BY-SA 3.0], via Wikimedia Commons