Atmosphere (air) is one of the Earth's four spheres, along with litosphere (land), hydrosphere (water) and biosphere (living things).

The atmosphere is a layer of gases surrounding the Earth up to 1,000 kilometers from the surface.  It has five layers or parts according to temperature: exosphere, troposphere, stratosphere, mesosphere, and thermosphere.  

Troposphere is the first layer above the surface up to 16 km and contains half of the Earth's atmosphere.  Weather occurs in this layer. Troposphere contains roughly 80 percent of the mass of the atmosphere. Most commercial airlines fly in troposphere at an altitude of 10 km above the surface.

Stratosphere extends from the tropopause, with an average altitude of 11 to 51 km.  It contains about 19.9  percent of the total mass of the atmosphere. The stratopause is a transition zone that separates stratosphere from mesosphere, at a height of 50 to 55 km.  Jet aircrafts fly in the stratosphere because it is very stable. The ozone layer is contained within the stratosphere.

Mesosphere extends from the stratopause at an altitude of 80 to 85 km.  It is the layer where most meteors burn up while entering the atmosphere. The mesopause, a transition zone at the top of the mesosphere, is the coldest place on Earth and has an average temperature around ?85 °Celsius.

Thermosphere is a layer with auroras with an altitude above 80 km. The International Space Station orbits in this layer. Temperatures in this layer can be as high as 1200°C.

The top of the thermosphere is the bottom of the exosphere, called the exobase. Its height ranges from about 350 to 800 km.  Exosphere is the outermost layer of the atmosphere.  The ionosphere, stretching from 50 to 1,000 km overlaps both the exosphere and the thermosphere.