The atmosphere, solar energy, and our planet’s magnetic fields combine to support life on Earth. The atmosphere absorbs the energy from the Sun, recycles water and other chemicals, and works with the electrical and magnetic forces to provide a moderate climate. The atmosphere also protects us from high-energy radiation and the frigid vacuum of space.

The envelope of gas surrounding the Earth changes from the ground up. Four distinct layers have been identified using thermal characteristics (temperature changes), chemical composition, movement, and density.

The troposphere starts at the Earth's surface and extends 5 to 9 miles up. Since the troposphere is located at the bottom of the atmosphere, it is the densest part. Temperatures drop rapidly as you climb through the troposphere at an average rate of about 10 degrees Celsius per kilometer. Almost all weather occurs in this part of the atmosphere. The tropopause, a strong temperature inversion, separates the troposphere from the next layer.

The stratosphere starts just above the troposphere and extends to roughly 30 miles high. Compared to the troposphere, this part of the atmosphere is dry and less dense. The temperature in this region increases gradually due to the absorption of ultraviolet radiation. The ozone layer, which absorbs and scatters the solar ultraviolet radiation, is in this layer. Ninety-nine percent of "air" is located in the troposphere and stratosphere. The stratopause separates the stratosphere from the next layer.

The mesosphere starts just above the stratosphere and extends to more than 50 miles high. In this region, the temperatures again fall rapidly with height and can reach nearly 100 degrees Celsius below zero. Chemicals in this layer are in an excited state, as they absorb unfiltered energy from the Sun. The mesopause separates the mesophere from the highest layer in the atmosphere.

The thermosphere starts just above the mesosphere and extends to an astonishing 500 plus miles above the surface of the Earth. Here temperatures go up as you increase in altitude due to the Sun's energy. Temperatures in this region can go as high as 1,700 degrees Celsius! Although the air is extremely thin here, chemical reactions occur much faster than on the surface of the Earth. Finally, at roughly 500 miles up, you begin to run out of gas and into the realm of space.