Tuesday, February 20, 2007

Earth

Earth often known as the Earth, Terra, the World or Planet Earth is the third planet away from the Sun, and is the fifth largest planet in the solar system. It is also the largest of its terrestrial system's global planets, making it the largest solid body in the solar system, and it is the only position in the universe known to humans to support life. It as well the densest planet in the lunar system. The Earth was shaped around 4.57 billion years ago and its natural satellite, the Moon, was orbiting it shortly thereafter, around 4.53 billion years ago.

The outer surface is divided into several tectonic plates that gradually travel across the surface over geologic time spans. The interior of the planet remains active, with a thick layer of convicting yet solid layer and an iron core that generates a magnetic field. Its atmospheric conditions have been considerably altered by the presence of life forms, which make an ecological balance that modifies the surface situation. About 71% of the surface is covered in salt-water oceans, and the remaining consists of continents and islands.