If the earth really was just a rock and not a molten ball of goo wouldn't the center of the earth be exceptionally cold nearly as cold as space and the heat transfer would make the surface unlivable?
Part of the reason the earth still has a molten center has to do with its thermal mass. There’s a LOT of rock there, and it hasn’t cooled to the core yet because there is so much mass. Also - if you look at my original post - some theorize that the center of the earth is molten partly because of nuclear energy being released (as I understand it - I’m not that strong on that theory).