The city dark (La ciudad oscura) de Ian Cheney.

THE CITY DARK chronicles the disappearance of darkness. When filmmaker Ian Cheney moves to New York City and discovers skies almost completely devoid of stars, a simple question -- what do we lose, when we lost the night? -- spawns a journey to America's brightest and darkest corners. Astronomers, cancer researchers, ecologists and philosophers provide glimpses of what is lost in the glare of city lights; blending a humorous, searching tone with poetic footage of the night sky, what unravels is an introduction to the science of the dark, and an exploration of the human relationship to the stars.