eli5 Where does the earth’s core get the energy to generate heat from?

Question

The suns energy is from fusion, fine makes sense.

But the core is a hot spinning liquid metal generating tremendous amounts of heat. Why hasn’t it cooled down? How is it replenishing its energy?

In: Planetary Science

Answer 1

Earth is not generating energy, during its creation a lot of it was “gathered” from collisions, the thing is that a planet is so huge that it would take billions of years to completely cool down, the sun will engulf earth before it happens