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

Take a thin, light non-stick frying pan and heat it up, then let it cool. Do the same with a heavy cast iron pan and you’ll find the heavy cast iron holds heat for a lot longer.

Same thing with Earth. It’s very big and heavy, and the core is under immense pressure. It’s cooling, just very slowly.