Atmosphere
The gaseous or air portion of the physical environment that encircles a planet. In the case of the earth, it is held more or less near the surface by the earth’s gravitational attraction. The divisions of the atmosphere include the troposphere, the stratosphere, the mesosphere, the ionosphere, and the exosphere.
Air
This is considered the mixture of gases that make up the earth’s atmosphere. The principal gases that compose dry air are Nitrogen (N2) at 78.09%, Oxygen (O2) at 20.946%, Argon (A) at 0.93%, and Carbon Dioxide (CO2) at 0.033%. One of the most important constituents of air and most important gases in meteorology is water vapor (H2O).
Environment
The sum total of all the external conditions that effect an organism, community, material, or energy.
Gravitation
The mutual attraction between two masses of matter. The rotation of the earth and the atmosphere modifies this attraction to produce the field of gravity.
Troposphere
The lowest layer of the atmosphere located between the earth’s surface to approximately 11 miles (17 kilometers) into the atmosphere. Characterized by clouds and weather, temperature generally decreases with increasing altitude.
Stratosphere
The layer of the atmosphere located between the troposphere and the mesosphere, characterized by a slight temperature increase and absence of clouds. It extends between 11 and 31 miles (17 to 50 kilometers) above the earth’s surface. It is the location of the earth’s ozone layer.
Mesosphere
The layer of the atmosphere located between the stratosphere and the ionosphere, where temperatures drop rapidly with increasing height. It extends between 31 and 50 miles (17 to 80 kilometers) above the earth’s surface.
Ionosphere
A complex atmospheric zone of ionized gases that extends between 50 and 400 miles (80 to 640 kilometers) above the earth’s surface. It is located between the mesosphere and the exosphere and is included as part of the thermosphere.
Exosphere
This region is considered the very outer limits of the earth’s atmosphere. Its lower boundary is often called the critical level of escape, where gas atoms are so widely spaced that they rarely collide with one another and have individual orbits. It is estimated to be some 400 plus miles (640 kilometers) above the surface.