Where else does the planet get energy from besides the sun?

Answer 1

That is a rather loaded question, because all of the energy has come from the sun. Then with all of the suns that came before it, and before that.

Over the millions and billions of years plants grew on land and in the sea, converting sunlight to sugars, then eaten by animals, converting all of this to stored energy we call hydrocarbons, or now crude, or gas.

The earth has a molten core at its center because it is still generally young. Like anything massive, the heavier elements will sink to the center in this liquid state. There is a bit of iron likely responsible for our magnetic field. Uranium is just about the densest heaviest element that can hold its own stability long enough to last millions of years, This is likely our source of core heat in our planet.