In the following web page with imbedded video, play and stop the video at the 30 second mark (the video is about 1/3 of the way down the following link). http://blogs.scientificamerican.com...the-best-video-of-earth-from-space-ever-made/ Why does there appear to be a thin shell of light at an altitude of about 37 miles above Earth (look on the left and not the right side where the aurora is active, measurements taken off computer monitor). Why is it a relatively thin shell of light? What powers the light? Thanks for any pointers!