t 2:30 a.m. as the light show was peaking, the two men sat on a grassy bluff here in the Wet Mountain Valley of southern Colorado, swaddled in blankets against the chilly mountain air and looking up at the stars in the torrent of the Milky Way. Every few seconds, a tiny chunk of space ice cast off by Comet Swift-Tuttle would blaze through Earth's atmosphere, silently streaking through the darkness.

"There's one!" the men called out.

"And another!"

"I saw that."

Night skies like this one are disappearing across much of the world, nibbled away by the ever-expanding glow of city lights. American skies are no different. Four out of five Americans live in places where they can no longer see the Milky Way.