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Contrails -- What do we know?

  1. Apr 22, 2017 #1
    I live in the upper Mississippi valley, near the boundary intersection for the states of Wisconsin, Iowa, and Illinois. It is a very rare day that I cannot see several, sometimes many, very high altitude con trails in the sky. The usually progress roughly NE across my area, although this morning they were heading south.

    Are these simply water condensed from the engine combustion processes, or is there some more sinister explanation? Any knowledgeable comments would be much appreciated.
     
  2. jcsd
  3. Apr 22, 2017 #2

    berkeman

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    Staff: Mentor

    This wikipedia article does a pretty good job explaining how contrails are formed:

    https://en.wikipedia.org/wiki/Contrail

    :smile:
     
  4. Apr 22, 2017 #3
    There is nothing remotely sinister about contrails, and yes, they consist of frozen water vapour from jet exhaust.
    If you closely watch a plane flying at altitude you will notice that the trail forms slightly behind the plane.
    The gap is because it takes a while for the exhaust to cool down enough to freeze.
    Sometimes there is no trail because the air is very dry, so the water vapour is assimilated into the air as a gas instead of crystallizing.
    On rare occasions the ice crystals spawn the development of larger cloud systems,
    so they are not always completely benign, but that can hardly be considered as sinister.
     
    Last edited: Apr 22, 2017
  5. Apr 22, 2017 #4

    Borek

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    From what I remember it is more complicated, and part of the explanation calls for combustion products containing small particles that act as nucleation centers.
     
  6. Apr 22, 2017 #5

    davenn

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    @berkeman .... you know where this was heading aye ?

    Dr.D ... if you are indeed a doctor ??, you should know better than to entertain the belief in the crackpot garbage of government instigated mind control etc by use of chemical release in the contrails of jet aircraft

    Dave
     
  7. Apr 22, 2017 #6

    berkeman

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    Your main question has been answered. After some cleanup of some well-meaning posts, this thread closed.
     
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