What is Earth’s atmosphere? Earth is surrounded by its atmosphere, which is the body of air or gases that protects the planet and enables life. The three major constituents are nitrogen, oxygen, and argon. Earth’s atmosphere has five distinct layers. Let's look at each, from closest to farthest from the Earth. Troposphere The layer of the atmosphere closest to the Earth is the troposphere. It begins at the surface of the Earth and extends out to about 12 km. This layer is known as the lower atmosphere. It's where weather happens and contains the air humans breathe. The temperature of the troposphere decreases with height. Stratosphere Above the troposphere is the stratosphere. This layer is where the ozone layer exists and scientists send weather balloons. Jets fly in the lower stratosphere to avoid turbulence in the troposphere. Temperature rises within the stratosphere but still remains well below freezing. Ozone layer The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. Mesosphere The layer, where the air is especially thin and molecules are great distances apart is the mesosphere. Temperatures in the mesosphere reach a low of -90°C. Meteors burn up in this layer. The stratosphere and the mesosphere are known as the middle atmospheres. Thermosphere The thermosphere rises several hundred kolimeters above the Earth's surface. Temperature is very much affected by the Sun here. Temperature increases with height and can rise to as high as 2000ºC. Nonetheless, the air would feel cold because the hot molecules are so far apart. Kármán line The Kármán line is based on physical reality in the sense that it roughly marks the altitude where traditional aircraft can no longer effectively fly. Exosphere The exosphere has very few atmospheric molecules, which can escape into space. Some scientists disagree that the exosphere is a part of the atmosphere and instead classify it actually as a part of outer space. There is no clear upper boundary, as in other layers. Exobase The lower boundary of the exosphere is called the exobase. It is also called the 'critical altitude' as this is the altitude where barometric conditions no longer apply. Atmospheric temperature becomes nearly a constant above this altitude. If you've enjoyed this video don't forget to like and I would like to say to the viewers who actually subcribed: Thank you!