Complotto della Nasa

Dark Shadows

On the next sunny day, step outdoors and look inside your shadow. It's not very dark, is it? Grass, sidewalk, toes--whatever's in there, you can see quite well.
Your shadow's inner light comes from the sky. Molecules in Earth's atmosphere scatter sunlight (blue more than red) in all directions, and some of that light lands in your shadow. Look at your shadowed footprints on fresh sunlit snow: they are blue!
Without the blue sky, your shadow would be eerily dark, like a piece of night following you around. Weird. Yet that's exactly how it is on the Moon.

http://science.nasa.gov/headlines/y2006/03...moonshadows.htm