We live on Earth, the third rock from the Sun. Earth is the largest terrestrial planet and the fifth largest planet in the Solar System. An ideal distance from the Sun for liquid water, Earth teems with life from its high mountains to its deep oceans. Earth is an exciting and often unpredictable place.
Scientists believe that Earth formed 4.6 billion years ago out of the solar nebula, dust and gas left over from the formation of the Sun. Once the basic elements of the Earth had formed, the Earth began to separate out.
Heavier material like iron sank into the center of the planet forming the core, while lighter material formed the mantle and crust. Meteorites bombarded Earth. Due to the heat present in the Earth, plate tectonics occurred, and they continue to take place today. Many questions are still unanswered about the formation of our planet. (Image Right: Earth, Courtesy of NASA, Apollo 17 crew)
