Shadow of Contrail

July 11, 2005

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Provided by: Rick Stankiewicz
Summary authors & editors: Rick Stankiewicz

On the morning of May 3rd, 2005, on my way to work, I noticed a dark band running through the a cloud bank over Peterborough, Ontario, Canada. The Sun had been up for about an hour and a half at this point but was hidden from view above the rather solid cloud deck. Due to the linearity of this feature, the first thing that came to mind was a condensation trail (contrail), which would have to have been located between the clouds and the Sun. The shape, size and length were of this darkened feature seemed reasonable for a contrail-related feature. Since the Sun was above the clouds and at the proper angle to illuminate a contrail from above, the cloud bank was in effect acting as a projection screen that I was viewing from below. This was the first time I had seen such a shadow without the contrail itself being visible as well. Initially, this “shadow” appeared quite uniform and stretched nearly from horizon to horizon.

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