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

Most of the interior heat is latent heat from the formation of the planet, compressing a planets worth of mass generates a lot of heat. The rest is actually generated by the decay of radioactive elements. It’s just hard to shed heat when your only option is to radiate it into space, and there is a relative cold layer on top trapping the heat below