The Earth's interior is composed of four layers, three solid and one liquid—not magma but molten metal, nearly as hot as the surface of the sun. The deepest layer is a solid iron ball ...

A new chapter of the Earth's history may be about to be written after boffins discovered evidence there may be another layer ...

You'd be surprised how little we all know about this rock we call home. You might just need these crazy facts about Earth you never learned in school to ace this one. A. Mercury and Mars B.