Core of the Earth

The core is thought to be around 80% iron, though the exact figure is up for debate.

The main evidence for this is the huge amount of iron in the universe around us. It is one of the ten most common elements in our galaxy, and is frequently found in meteorites (隕石).

The constant movement of molten iron creates an electrical current inside the planet, and that in turn generates a magnetic field that reaches far out into space.

The magnetic field helps to shield us from harmful solar radiation. If the core of the Earth wasn't the way it is, there would be no magnetic field, and we would have all sorts of problems to contend with (對付).

http://www.bbc.com/earth/story/20150814-what-is-at-the-centre-of-earth