Earth

History: In ancient imes the earth was thought to be at the center of the solar system. This theory was developed by the second century astronomer Ptolemly, and was called the Ptolemaic system. This was accepted until 1543 when Copernicus devised his heliocentric theory in which the sun was at the center of the solar system and the earth orbited around the sun. Ancients also thought of the earth as flat, consisting of an island, Europe, surrounded by an endless river.

Description: Earth is one of the four terrestrial planets; it is small, rocky, and possesses a thin atmosphere. The earth's mass consists of layers, a solid inner core, surrounded by a liquid outer core, a amntle, and a crust. Scientists believe that 200 million years ago earth had one giant land mass, called pangea. Over the eons, plate tectonics have seperated the land into the continents we know today. The planets atmosphere, oceans, and moderate temperature are all conditions that allowed for life to evolve on earth.

Satellites:
The Moon

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