The Earth

At about 93 million miles from the Sun lies the orbit of our planet Earth. Earth is the largest of the terrestrial planets and the only planet known to support life.

The Earth has an atmosphere which consists of 78% nitrogen, 21% oxygen and 1% argon and other gases [1] and water oceans which cover 71% of the Earth's surface [2].

The Earth has only one natural satellite, the Moon (or Luna) but has thousands of artificial satellites and on a clear night many of these can be seen just by looking up into the night sky. An artificial satellite may look like a faint dot moving between the stars or may appear as bright as the planet Venus in the case of the International Space Station.
Earth, The Blue Planet, is our home but observation of the Earth as a whole can of course only be acheived by leaving it's surface. There is one way however we can observe the Earth's disc and that is by viewing a lunar eclipse. This is because we are seeing the Earth's shadow pass over the surface of the Moon.


[2] Atlas of the Skies - ISBN 1-84406-011-X