Why is it that after all these millions of years, the centre of the Earth is still molten?

Question

Why is it that after all these millions of years, the centre of the Earth is still molten? Why isn’t the energy source exhausted?

Answer 1

This is exactly the problem which was addressed mathematically by the great Victorian physicist Lord Kelvin (1824-1907). He worked out that if the Earth was any more than about 25 million years old, it could not be as hot now as it actually is.

However, he did not know about radioactivity. We now know that radioactive decay in the metal core generates all the heat which we see coming to the surface, and that it should keep the Earth's temperature steady for a few more thousand million years.

Answer 2

Radioactive decay provides the energy to keep the Earth's core molten - without it Earth would have solidified long ago. Our size also has something to do with it - Mars is pretty much made out of the same stuff Earth is, but the interior of Mars is solid, because it's smaller than Earth so it lost its heat faster.

Answer 3

all thes answers are current theories of why the core has not solidified yet. Another is that the core also contains elements that cause it to act like a nuclear reactor, helping to keep it warm. This was just on Natiol Geographic's Naked science yesterday. Go to there web site and there may be a link.

Answer 4

Gravity. The force of all the layers of rock on the earth crushing down on its core keeps it hot. Smaller planets like Mars or Mercury have since cooled, but the Earth's size has kept it very warm.

Answer 5

because the Earth is still very young i suppose, also it renews itself over time..maybe with it renewing itself it keeps the "fire" alive aka its core alive.