It is approximately 4000ï¿½C at the centre of the Earth. To put this in context:
The centre of the Sun is approximately 15 millionï¿½C
The surface of the Sun is 5500ï¿½C
Iron melts at 1535ï¿½C (when at atmospheric pressure)
Water boils at 100ï¿½C (when at atmospheric pressure)
Human skin is comfortable with temperatures up to about 60ï¿½C
The highest temperature recorded on the Earth's surface is 58ï¿½C (Libya 1922)
It is not possible to directly measure the temperature at the centre of the Earth and four thousand degrees is nothing more than our most well-established piece of guesswork to date. Most modern calculations rely on the fact that we believe the inner core to be made up of iron and nickel that is just about at melting point. It is under a lot of pressure, which prevents it from melting, even at such high temperatures. There is also a lot of evidence regarding how the outer core of the Earth convects and that helps to establish the temperature. However, recently British scientists have suggested that the temperature of the Earth's core may in fact be as high as the surface of the Sun, so the question is still open.
Sally Riordan, M.A., Management Consultant, London
'As long as men are free to ask what they must; free to say what they think; free to think what they will; freedom can never be lost and science can never regress. '