Air knowledge
The layer of gases that surrounds the Earth is called atmosphere. The atmosphere in an essential component of life on Earth: besides containing oxygen, it works as a filter for the Sun’s harmful radiations, reflecting them and preventing them from reaching the ground. Moreover, like a “blanket” it traps part of the Sun’s heat, permitting the Earth to have a temperature suitable to the life of plants and animals. This phenomenon is called greenhouse effect. The atmosphere is also the place where the main meteorological phenomena occur (wind, rain, snow, etc.) that summed together constitute the climate. When air moves from one place to another it originates wind. Wind is generated when air moves from a cold area to a warmer one or, to be more precise, from a low pressure zone to a high pressure one. The atmosphere is subdivided into five concentric layers, called spheres, which have a different temperature, density and thickness and are separated by boundaries called pauses.