Atmosphere of Earth

The atmosphere of Earth is the layer of gas around the Earth that is held in place by gravity. The atmosphere of Earth consists of mainly nitrogen and oxygen gas.

Constituents
Dry air (ignoring water vapor) consists of:
 * 78.09% nitrogen
 * 20.95% oxygen
 * 0.93% argon
 * 0.039% carbon dioxide
 * Other gasses in trace amounts.

These numbers are consistent when the water vapor is removed from the air. The amount of water vapor varies considerably depending on the weather, but it averages around 1%.

Air with 1% water vapor (the average) consists of:
 * 77.31% nitrogen
 * 20.74% oxygen
 * 1% water vapor
 * 0.92% argon
 * 0.039% carbon dioxide
 * Other gasses in trace amounts.