Behind an aeroplane

Contrails behind aeroplanes
Do aircrafts draw large straight lines on our skies so they can better be spotted?

Yes, but it isn't the only reason. In fact these condensation trails are simply composed of very small condensed water droplets frozen by the very low ambient temperatures present at high altitudes: -45°C (-49°F) at 30'000 feet in the atmosphere considered as standard (definition of the International Standard Atmosphere). The fuel is made of hydrogen and carbon atoms. During the combustion process occurring with oxygen inside the jet engine's combustion chamber, water molecules are produced. It's the same principle for mopeds and farm tractors! But with different quantities involved and slightly different atmospheric conditions, straight lines are created and can sometimes live a complete day.

On this picture we see another phenomenon, which is less common and disappears pretty quickly. The trail coming from the top left hand corner contains not only the classical engine caused contrail, but also two materialized vortexes. They are made of rolling air and they are due to a side effect of the lift force produced by our beautiful aircrafts, allowing them to fly. By the way, everybody would be much happier if these vortexes could be avoided! 

These atmospheric trails are responsible for multiple theories and they are also a curious paradox as they contribute at the same time but via two different effects, to the planet surface heating and cooling.

That being said, the more contrails I see, the better I feel!

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