Conversation so far:
where does most of earth's energy come from
Most of the energy in the Earth system comes from just a few sources: solar energy, gravity, radioactive decay, and the rotation of the Earth.
what does solar energy drive on earth
Solar energy drives many surface processes such as winds, currents, the hydrologic cycle, and Earth's overall climate system.
what does gravity drive on earth
Gravity makes rivers and other materials flow downhill and creates tides (from the Moon's gravitational pull).

Question: where does the heat in the core come from
Self-contained rewrite: where does the heat in the earth's core come from