The structure and composition of the atmosphere

The Earth is surrounded by a blanket of air, which we call the atmosphere. It reaches over 560 kilometers (348 miles) from the surface of the Earth, so we are only able to see what occurs fairly close to the ground. Life on Earth is supported by the atmosphere, solar energy, and our planet's magnetic fields. The atmosphere absorbs the energy from the Sun, recycles water and other chemicals, and works with the electrical and magnetic forces …

…present at extremely low densities. The air we breathe is actually a combination of several gases. Within the first 80 km or so in altitude, the composition is quite constant. This portion is known as the homosphere. Higher in elevation, the concentrations of each gas vary considerably. The gases found within the 80 km are: 78% Nitrogen (N2), 21% Oxygen (O2) and the other 1% is divided within three other gases, argon (A), water (H2O) and Carbon Dioxide (CO2).