Light pollution—the needless shining of bright lights into the night sky—has robbed whole generations of the chance to see nature on its largest scale. It is estimated that as many as eighty percent of all the people alive today have never even glimpsed the Milky Way. (When a massive power outage struck southern California in the 1990s, Los Angeles residents reportedly called 911 to express alarm about strange clouds hovering overhead; they were seeing the Milky Way for the first time.)
The problem is not lighting in itself, but the billions of dollars worth of energy wasted each year by spilling light into the sky rather than confining it to the ground where it is needed.