Q&A: General Astronomy and Space Science

Q:
Where did the energy come from that caused the newly created Earth to be in a molten state?

A:
The core of the Earth was heated by two sources of energy: the release of gravitational energy as the material settled into the central core, and radioactive decay of potassium, thorium and uranium. These decays led to heating by energetic particles released in the nuclear fission process. Most of the helium found in the Earth is also a result of this process--helium nuclei are one of the primary products of the fission or spitting of heavy nuclei into two lighter ones.