Early on, dense iron sank out of the magma oceans to form the metallic core, liberating enough gravitational energy to melt the entire planet.

• 更早期的时候，较重的铁自岩浆海中析出下沉，渐渐形成了金属成份的地核，下沉时释放出的重力位能足以把整个地球再次熔融。