Earth  also referred to as "the Earth", "Planet Earth", "Terra", or "the World", is the third planet from the Sun and the fifth largest planet in the Solar System. It is also the largest of its planetary system's terrestrial planets, making it the largest solid body in the Solar System, and it is the only place in the universe known to humans to support life. It is also the densest planet in the solar system. The Earth was formed around 4.57 billion years agoand its natural satellite, the Moon, was orbiting it shortly thereafter, around 4.53 billion years ago.