Asthadi Setyawan in Malang, East Java, Indonesia posted this photo at EarthSky Photo on G+. What you see here is the shadow of a cloud. 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.
We asked Les why it appears that this shadow is on the wrong side of the cloud. It looks from the photo as if the sun and the shadow are both behind the cloud. He told EarthSky:
It only looks that way. The shadow is closer to the camera than the cloud. Rays from the sun 93 million miles [150 million km] away are (nearly) parallel and always downward pointing. The shadows can be through misty or hazy air, or, sometimes, they’re cast on a lower thin layer of cloud that is otherwise invisible.
Thank you, Asthadi, and thank you, Les!