Janet Furlong in Culpeper, Virginia captured this beautiful photo of a shadow from a jet contrail (NOT chemtrail), cast on clouds, on November 23, 2013. She said a cold front had moved in that day and that there was a 40% temperature difference that evening from the evening before. As for this contrail shadow, she said her dad had been fascinated by it and asked her to photograph it. Overall, of the sky that evening, Janet wrote:
I could not believe my eyes …
We wondered what light source was creating the shadow and asked an expert, Les Cowley at the great website Atmospheric Optics. On his page about jet contrails, you can see, if you look, that he said:
Contrail shadows sometimes appear counter-intuitive. [They may seem to be cast] by a low altitude bright light shining upwards and casting the contrail shadow on a higher cloud.
The reverse is the case …
In other words, he said, the jet itself and its contrail are always higher up than the shadow, which is cast on clouds below. By email, Les told me:
Contrail shadows often don’t look ‘right’ and seem as if the contrail is below the clouds. But the shadow casters – the sun and moon – always shine downwards so the shadow must be below the contrail.
Like all statements there is an exception! At sunset and sunrise rays can travel very slightly upwards to illuminate the underside of clouds. Under those circumstances however a contrail shadow would be a long way from the contrail.
So he doesn’t think that’s the case here; as usual, he thinks, this shadow is actually below the jet and its contrail. Since there was no moon in the evening sky on November 23, Les also thinks this contrail shadow is caused by the setting sun. He wrote:
From the lighting on the clouds and the appearance of the contrail shadow I would estimate that we are close to sunset and that would also put the contrail as only slightly above the cloud layer.
Thank you, Janet and Les!
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.