Synonym for refract could be bend,swing arch or something similar to those words.
It was in ruins and needed reconstruction.
They became sedentary. they started to use agriculture to create a surplus of food and as the need for farmers decreased; different duties emerged and that led to the formation if civilizations.
Answer:
There are 3 main reasons.
1. heat from when the planet formed and accreted, which has not yet been lost.
2. frictional heating, caused by denser core material sinking into the center of the planet.
3. heat from the decay of radioactive elements.
I hope my answer helped!
