What you see here is the shadow of a cloud, captured over Las Vegas, Nevada, by Bettina Berg on October 1, 2018. The great sky optics expert Les Cowley – of the website Atmospheric Optics – calls them the inverse of crepuscular rays and notes they can produce dramatic effects. I asked Les about Bettina’s photo, and he wrote:
A remarkable sight.
There is a combination of (1) a low sun, (2) a widespread layer of high cloud and (3) a towering cumulus that just breaks through the cloud layer. The cumulus top is casting its shadow down onto, or along, the cloud layer making the latter dark.
Check Les’ website for a diagram that explains more about cloud shadows here.
Bottom line: Cloud shadow over Las Vegas on October 1, 2018.
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.