Don't forget the gravitational title forces of the moon and the sun combined that stretch and cool the earth also Generate heat within the planet
Example, take a plastic spoon or something like that and start to slowly bend it – bend it back and forth slowly so it doesn't break and it will slowly start to get soft and as it gets soft , bend it back faster and faster until it actually gets hot enough to cause a first real 1st° burn in the spot that's been bending the most
If we didn't have the moon, we would've ended up like Mars. Mars does not have any real moons to speak – it has two large asteroids. If Mars had a moon similar to ours, it would've kept the center of the planet Liquid and hot, which would have It's magnetic field and prevented the atmosphere from being blown away by solar winds....
Mars once had a huge ocean and an atmosphere but then lost it… And the only way to lose that is to lose your magnetic field… And the only way to lose that is for the core of the planet to cool
The amount of radioactivity based on the materials in our plan earth are not enough to keep our plan as warm and hot as it has been underneath the crust