| 1 | It may also have a core, as the earth does. | |
| 2 | Internally the earth consists of two parts, a core and a mantle. | |
| 3 | There are three layers: the upper mantle, lower mantle and the core. | |
| 4 | But the effect ripples outward, changing the core's rate of rotation layer by layer. | |
| 5 | When Earth was forming, molten iron sank to its center, creating the planet's core. |