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

it is cooling down. but it’s 1. massive and 2. insulated

think of your hand when it’s cold outside. You can make a fist which will insulate your hand within itself, but it still cools down. now, take a hot rock, and hold it in your fist. Your hand stays warmer longer. The rock will cool down quicker if it isn’t in your hand, and will eventually cool off either way…..

now take that example and increase the size and temperatures into an unimaginably large scale.