About the Earth

The Earth is the largest of the inner planets. It has a dense iron-nickel core surrounded by layers of silicate rock. Earth's surface is approximately three eights ( ³/₈ ) land and five eights ( ⁵/₈ ) water, and the lower atmosphere consists of a mixture of nitrogen, oxygen and other gases supplemented by water vapour. With this atmosphere and surface, temperatures usually vary between minus fifty degrees Celcius (-50 °C) and plus forty degrees Celcius (+40 °C), life is possible.