Eli5: How does the core of the Earth (or any planets) not cool and still give off tons of heat energy? Where is this energy coming from?

Question

Eli5: How does the core of the Earth (or any planets) not cool and still give off tons of heat energy? Where is this energy coming from?

In: 202

Answer 1

I’d say the earths impact with the moon billions of years ago would be the attributing factor for the amount of heat it’s been able to hold in comparison to the other planets that are pretty much dead or dying