The Earth

The Earth

The first thing to notice about the Earth is the vast quantity of water on its surface. Our oceans hold over a billion cubic kilometers of water. If this water were spread evenly over the surface of the Earth, it would be over two kilometers deep. The next thing to notice about Earth is the nice thick atmosphere, made of nitrogen (78%), oxygen (21%), and argon (0.9%). The high quantities of oxygen are a sure sign of life. In fact, Earth is the only planet we know of that has life on it, though we are by no means sure it is the only planet with life on it. Earth weighs 6X10²⁴kg and has one relatively large Moon. Earth has a mean surface temperature of 15℃ (and rising). The Earth is exactly 1AU from the Sun by definition or 93 million miles. [TB] {EA}