The ocean of air which surrounds our planet presses down upon us with a force of about 15 pounds per square inch. With an increase in elevation the air thins out and pressure declines. The first seven miles forms the weather envelope known as the Troposphere.
The next layer, the ten-mile-thick Stratosphere, is used by high-flying jet planes. Temperatures drop to -80 F. and oxygen is needed to survive.
At a height of 30 miles there is a poorly defined but important ozone layer known as the Chemosphere. It screens out harmful ultraviolet rays of the sun.
The next layer of rarified air is the Ionosphere, which extends up to 300 miles above the earth. There are four levels of ionization, or accumulations of electrically charges air molecules. The Ionosphere acts as a mirror to reflect radio waves for long-distance transmission. The aurora borealis also forms in this area.
Above 300 miles is the Exosphere. Here the air becomes quite rarified and temperatures reach 3000 F.
Beyond 1,000 miles is found the Magnetosphere, where high-energy atomic particles from the sun are trapped in the earth's magnetic field. The outer limit of this hazardous radiation belt, first mapped by Dr. James Van Allen, appears to be 40,000 miles. Beyond lies outer space, with fluctuating magnetic fields and solar winds that are still to be charted.
To learn more about our solar system, try our java version of the HAMMOND SPACE INFOGRAPH. A Hammond product of the early sixties, meets technology of the nineties.
Visit our Sun Clock/Moon Phase page. This java applet was developed by Martin Minow, who has allowed us to use it for your edification and enjoyment.
(1-2 minute load time for both applets)
What is Space? 
on their channel three.
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