The Atmosphere

   The atmosphere of Earth is immensely complicated, it has many layers that are separated by a variety of criteria, and often overlap. The atmosphere is separated into five layers, determined by "temperature" I use quotes because at the higher altitudes, the meaning of the word is a little fuzzy, so in this case I mean the kinetic energy carried by individual particles such as atoms and molecules. The lowest layer is the Troposphere, it is usually between nine and twenty kilometers high, taller at the equator, and shorter at the poles. This layer is heated mostly by heat radiating off the surface of the earth, and as such is warmer at the bottom and cooler at the top. This causes turbulence, and constant vertical mixing. This layer contains eighty percent of the atmosphere by mass, and ends at the Tropopause.
   Just on the other side of the Tropopause is the stratosphere, beginning from the top of the troposphere to a height of about 51 kilometers above sea level, and warmer at the top than at the bottom because of the large amounts of energy absorbed by the ozone layer in the upper stratosphere. because of this temperature gradient, there is little air movement vertically, the Stratosphere ends at the Stratopause.
   Above the Stratopause is the Mesosphere. Here the temperature begins to decrease as you go up again. This layer usually has an upper height of 85 kilometers at the Mesopause.
  Above the Mesosphere is the Thermosphere, here things begin to warm up as you move upwards, features include the "warmest" place near earth, and outer space. In Mesosphere the gasses are so diffuse that they begin to stratify by mass, this begins above the Turbopause which is at about the same height as the Karman Line, the internationally recognized beginning of space, a height of about one hundred kilometers. The International Space Station and many satellites orbit the Earth at this level, even though it is incredibly hot, these structures do not gain much heat because the space between each particle is very great, but they do need to have their orbits boosted as they decay because of atmospheric drag.
   Finally, at the very top of the atmosphere is the Exosphere, here the temperature is constant with altitude. This is just the tiny layer of hydrogen that is barely differentiated from the rest of actual space.
   There are other layers determined by things other than temperature, these layers include, the ozone layer, the Homeosphere, and the Heterosphere, as well as myriad others.