The atmosphere is the stratified gaseous layer that surrounds, by the force of gravity, the Earth, a celestial body or any other body. It is formed from two Greek words: ἀτμός (atm), which means ‘steam’, ‘air’, and σφαῖρα (sfaira), ‘sphere’.
The Earth’s atmosphere is composed of a set of gases, among which nitrogen (78%) and oxygen (21%) stand out, with the remaining percentage (barely 1%) being distributed by carbon dioxide, noble gases , water vapor and ozone.
The function of the atmosphere is to be a protective shield against the hostility of outer space: it maintains temperatures within tolerable extremes, protects us from ultraviolet rays and meteorites, and contains nothing more and nothing less than the indispensable oxygen. In short, the atmosphere creates favorable conditions for life on Earth.
The term is also often used to refer to a certain social situation: “My boyfriend created a romantic atmosphere to ask me to marry,” or: “An atmosphere of violence reigns in the country .” For example, in Cuba it is said that an “atmosphere has formed” when an unpleasant situation has been created.
In the field of Physics, the atmosphere is a unit of measurement that is equivalent to the pressure or tension exerted by the atmosphere at sea level. Its value is equal to the pressure of a column of mercury 760 mm high.
In Literature, atmosphere can also refer to the narrative procedures that a writer applies to generate a certain perception about the environment where a story is developed . A master of narrative atmospheres is the American storyteller Raymond Carver.
Layers of the atmosphere
We can subdivide the Earth’s atmosphere into different layers, taking into account its particular characteristics.
First, we find the troposphere, which is where we all live and, therefore, the closest to our planet. In this layer the highest density of gases is located, and in it the meteorological phenomena take place, such as rains and clouds. Its height varies between 11 and 18 km.
The stratosphere, on the other hand, reaches about 50 km high. There we find the ozone layer or ozone atmosphere, whose function is to protect us from the sun’s ultraviolet radiation.
Then, at an approximate height of 80 km, we run into the mesosphere . In this area, the temperature may decrease, as the altitude increases, to -90°C.
For its part, the thermosphere or ionosphere reaches up to 500 km high. This is where meteorites disintegrate. In addition, it is an excellent conductor of electricity, which facilitates radio and television wave transmissions. Its temperatures can range from -70°C to 1,500°C.
Finally, the exosphere starts from 500 km high onwards. It is the area furthest from Earth and, therefore, where we find the least concentration of gases. It is our border with outer space.