Atmosphere

An atmosphere is a layer of gases surrounding the Earth. The gases are attracted by the gravity. The air has a mass of about 5.15×10^18 kg and contains 78% N, 21% O, 0.9% Ar, 0.039% CO₂ and small amounts of other gases (Ne, He, CH₄, H₂, Kr) including water vapor. The Earth‘s atmosphere consists, from the ground up, of the troposphere, stratosphere, mesosphere, thermosphere (or ionosphere) and exosphere. Three quarters of the atmosphere lies within the troposphere, and the depth of this layer varies between 18 km at the equator and 7 km at the poles. The ozone layer, which absorbs UV energy from the Sun, is located primarily in the stratosphere, at altitudes of 15 to 35 km. The Kármán line, located within the thermosphere at an altitude of 100 km, is commonly used to define the boundary between the Earth's atmosphere and outer space. However, the exosphere can extend from 500 up to 10,000 km above the surface, where it interacts with the planet's magnetosphere. Clouds are mainly formed in troposphere and are divided into several physical forms based on their physical structures and processes of a formation.