Most people in brightly lit countries probably take for granted that clouds are bright at night, but this is completely unnatural. You can see it better in this pair of photos we published in a later paper (titled "Red is the new black"): https://doi.org/10.1111/j.1365-2966.2012.21559.x

This probably matters a great deal for nocturnal animals, because it's a reversal of an environmental condition that existed during the hundreds of millions of years that life evolved.

@skyglowberlin I teach large university science courses. Hundreds of fairly privileged students in the room. It has been my habit to ask them to raise their hands if they have ever seen the Milky Way.

The results have always been disappointing. Over the past 20 years it has gotten worse and worse. Recently many students don't even know what I mean by the question, and I have to explain what a dark sky looks like.

"Raise your hand if you have ever been awed by a clear dark sky full of countless, countless stars." Always less than 5%.

@jameshowell @skyglowberlin

I first saw the Milky Way in July 2006. I was about 80 km north of Kandahar, Afghanistan. It was absolutely amazing. (I was sleeping in a hole in the ground, so I could just enjoy it until I fell asleep.)

@venya @skyglowberlin I can't beat that story, but I got two stories.

In 2005 outside the refugio just below the summit of Champaqui about 60 km southwest of Córdoba Argentina. Clearest darkest sky I have experienced and golly, the southern hemisphere sky is disorienting. We were far from home.

In 1990 in rural Ohio with two young women who had grown up in Tokyo. They had never seen a non-urban night sky. Parked the car next to a cornfield, told them I had a treat for them. They flew into a blind panic. Screaming, crying, covering their eyes.