Earth is an Inner Terrestrial Planet Size that is about 8,000 miles in diameter and 1 A. Earth may be the most distinctive of all planets because of the life forms we know exist here and the way they use the Suns energy. The Earth is composed of a vast amount of water, mostly in the form of oceans, which make up most of its surface. It also contains a range of gases, of which make it possible for us humans to exist and is a system that exists between plants and animals here. The Earth has three layers to its interior, the inner core, outer core, and mantle. Of these, the outer core is thought to be liquid. Like most of the terrestrial planets at birth, the Earth has been molten and undergone some differentiation allowing the heavy materials which consist mostly of an iron, nickel, and cobalt core making its density five and a half times the density of water. Earth perhaps has the most unique surface with all its various landmasses and water structures. It also has polar caps, volcanoes, and continents that have trees and living organisms moving about on its surface. Much of the tectonic activity on Earth created new landforms and changed other landmasses. The Earth has one of the most resourceful atmospheres because of the way the solar system here picks up water and carries it around the Earth for redistribution. We have a substantial atmosphere that consists mostly of oxygen and nitrogen that helps plants and animals continue to exist so well here on Earth. We also have a "greenhouse effect" that warms our atmosphere and its surface. The Moon is the only satellite known to exist to Earth. The Earth has a superior magnetic field due to a core consisting of iron and nickel. Currently the rotation of the Earth and its Coriolis effect help to construct this pull of the tides from the oceans. The northern lights or lurora Borealis can be seen at various times in a mystifying view of beauty.