Atmosphere

Based on the Greek term “atmos” = vapour and “sphaira” = ball, the word originally describes the layer of gas surrounding the terrestrial sphere.

Atmosphere means:

1. The layer of air surrounding the earth with the characteristic composition of:

• 78 % nitrogen (N₂)
• 21 % oxygen (O₂)
• 0.9 % argon (Ar)
• 0.04 % carbon dioxide (CO₂)
• Tracer gases
• Variable proportion of water vapour 0 - 40 g water vapour per kg of air.

• “Atmospheric pressure" means the air pressure under normal conditions on the ground. Except on high mountains, it is around 1000 hectopascal [hPa]. 1 Pascal [Pa] is 1 N/m². 

2. The atmospheres of other celestial bodies have completely different compositions and pressures.

3. “Atmosphere” is also understood to mean the gas environment of a chemical or physical process. In a closed room, it can have a completely different composition than in natural atmosphere. In pressure or vacuum chambers, the pressure of the technical atmosphere can differ from the natural atmospheric pressure by the factor of 10^-15 up to several 1,000.

In low-pressure plasma, the atmosphere may consist of any type of process gases. bestehen.