Bright lights are part of a city's ecosystem. Think of Times Square or the Las Vegas Strip or right outside your bedroom window.
Electric lighting is ubiquitous in most urban and suburban neighborhoods. It's something most people take for granted, but appreciate, since it feels like well-lit streets keep us safer. But what if all this wattage is actually causing harm?
"We're getting brighter and brighter and brighter," warns Paul Bogard, author of the upcoming book, End of Night: Searching for Natural Darkness in an Age of Artificial Light.
Bogard says the developed world's desire to light up the night has gotten out of control.
"Things like gas stations and parking lots are lit now 10 times as bright as they were just 20 years ago," Bogard tells Celeste Headlee, host of weekends on All Things Considered. "It has everything to do with marketing, really. The gas station on the corner has figured out that if they turn up the lights, more people will be attracted to those lights."
And, Bogard says, all that light is having some unintended consequences. For one, it affects our sleeping patterns, he says.
Others say the effects of light pollution are worse.
Richard Stevens, an epidemiologist at the University of Connecticut Health Center, was one of the first to make the connection between bright, artificial light and breast cancer. Stevens' research found that artificial light can disrupt our body clock — and affect our production of melatonin.
"We know for sure that the lighting in the modern world can disrupt our circadian rhythms, and that cannot be good," Stevens tells Headlee.
The French Environment Ministry recently announced that starting this summer, office buildings and storefronts will have to turn off artificial lights between the hours of 1 a.m. and 7 a.m. Major landmarks like the Eiffel Tower will continue to be lit.
Yet Bogard says he hopes Paris will lead a lighting revolution.
"The fact that Paris, the city of lights, is choosing to control their use of light at night is fantastic, and can serve as a model for cities all over the world," he said.
Perhaps, someday soon, we'll get off the subway, look up at the dark city sky, and see the stars of the Milky Way again.