Light pollution sounds fairly harmless, and not like the heavy stuff of air pollution. However, it is a serious problem, and actually refers to the way in which city lights interfere with the visibility of dark skies.
To raise awareness of the problem and to show us what we are missing out on, the Skyglow Project - brainchild of renowned timelapse artists Gavin Heffernan and Harun Mehmedinovic - released the mesmerising timelapse video shown below of dark skies in North America superimposed over urbanscapes in Los Angeles.
But even if you could get away from city lights, the naked eye view isn't quite this spectacular. The video simply reminds us of how beautiful the night sky could be if we weren't destroying it with a combination of wasted light and air pollution. It is also serves as the trailer used for Skyglow's Kickstarter campaign to create a book and DVD exploring the psychological price we are paying for loss of access to the stars, and what can be done to fix it.
Urban air pollution is responsible for around a million deaths a year, whereas light reaching the sky seems harmless by comparison. However, every photon of skyglow we see represents light that has either been shone in the wrong direction, or reflected to where it wasn't needed. The energy wasted in the process costs an estimated $3.3 billion dollars a year and its production is a major contribution to global warming. And the loss of truly dark skies is also thought to be disturbing bird migrations.