‘Green Lightning’ was likely just an optical illusion
Created by a reflection off a camera filter
The internet was stunned recently by the work of Arthur Few, an atmospheric physicist, exposing the green lightning that supposedly exists inside every stormcloud at the Fall meeting of the American Geophysical Union.
Unfortunately, it’s looking like the discovery was nothing more than an optical illusion, caused perhaps by the use of a filter on the front of the camera lens. We were alerted to this possibility by Thomas Hennig, a physicist and hobby photographer who sent us an email explaining what likely happened.
“It’s simply a reflection of the picture on the imager with the front lens protection filter,” he said. “In German it was called Film-Filter-Reflex, but you can’t find this on the web as it disappeared when everything went digital and photographers increasingly discarded UV Filters for their SLR lenses.”
His hypothesis, which is backed up by a cursory glance at the pictures, is that green “ghost” images are created on the opposite side of the image when you have a dark background, cheap UV filter without antireflective coatings, and a very bright object.
“This effect explains the green colour and the symmetry to the image centre,” Hennig added. Here’s the original shot again — you can clearly see the similarity of the “green lightning” to the bolt on the left side of the image.
We were unable to contact the original photographer, Carlos Guittirez to ascertain whether an ultraviolet filter was used to take the shots. However, we were able to speak to Few, who said that he’d had no correspondence with Guittirez and knew no deals about how the shot was taken.
He added: “I am resigned to believe that the image might indeed be an artifact.”
So while most of Few’s conclusions presented at the Fall meeting of the American Geophysical Union are perfectly valid, it looks like green lightning probably isn’t. Science, unfortunately, does get it wrong sometimes. Don’t be sad, though. There’s plenty of other fascinating and colourful things happening in the sky.
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