The weblog of Matthew Walker: MatthewWalker.net.nz, Otautahi, Aotearoa / Christchurch, New Zealand  
  • Monday, 28 July 2003

    • Fun with contrails

      This morning there was thin high cloud and the sun was low in the sky. An aeroplane was crossing the sky directly away from the sun leaving a long white contrail. The contrail was casting a thin blue shadow across the other half of the sky. It looked just like this:


      O - - - - ----------->=========== = = = =

      Where O is the sun, - is the contrail, > is the plane, and = is the shadow. So yes the plane was flying directly along the shadow of its own contrail, which was turning from blue to white like a giant zipper.

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