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As you may have read in our magazine story, "Turning Out the Lights," the night is not the same as it once was. For a dramatic illustration of artificial light, check out our new "Light Pollution" photo gallery.

s a society, we are addicted to artificial light. We illuminate our homes and offices, our roads and car dealerships, our Christmas trees and cell towers, and even the architectural flourishes on buildings and bridges. Artificial light is essential to modern urban life and, as of this year, half the world's population is urban. Yet scientists and medical experts are beginning to recognize darker aspects of lighting the night, including harm to wildlife and human health—not to mention wasteful energy use.

Artificial light also upsets the body's circadian rhythms by altering our brain's production of the hormone melatonin,

Light Pollution: Burning Earth at Both Ends