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 ...

Sinking in one place leads to plates moving apart in other places. The movement of the plates and the activity inside the Earth, is called the theory of plate tectonics.

Earth is our home planet, and it's the only place in the universe where we know for certain that life exists. Earth formed over 4.5 billion years ago from a swirling cloud of gas and dust squished ...