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Such rethinking is apparent in recent changes in the New York City skyline, where subtle and complex patterns of light, rather than mere brilliance, have begun to emerge. In part, the new pattern is a return to the old. In 1925 a writer for the New York Times declared that there was

a new city of light and color rising above an old one.... The illuminated towers of Manhattan are fast multiplying and the application of floodlights to their summits has brought about a fascinating aspect of architectural art. If the practice continues the glory of the cloud-hung castles of Camelot will pale before the reality of the illuminated citadels, towers, pinnacled turrets and minarets that even now rise above the city streets.... Crowning [the Standard Oil Building] is a pyramid illuminated by four huge flares, a beacon that is visible for miles at sea.... The Metropolitan Tower, with its red and yellow light clusters and its illuminated clock ... may be read alike by deckhands on East River craft and watchers on the Palisades.

The advent of fluorescent light not only increased the light emanating from skyscrapers; it also changed the appearance of them at night. Once banks of fluorescents on the ceilings of offices remained on all night—long after even the cleaning crews had departed—a skyline shaped by scores of entirely illuminated tall buildings, of which the lit crowns were only a part, emerged: a skyline endlessly photographed and imagined, one that seemed to embody twentieth-century brilliance and electric energy. But in recent years, with the advent of energy-efficient lighting controlled by motion detectors, dimmers, and timers, and with ceiling lights that can be divided into zones, lighting designers can rely on more subtle effects—akin to what seemed marvelous in 1925—to maintain the individual and iconic appearance of any skyscraper. One lighting designer has observed: "The tall tower with the illuminated floors on all night long is probably a thing of the past. You're not relying on the glowing floors to [give] the building presence...[but] on the crown of light." That crown of light may be illuminated by LEDs rather than floods, and it may even be more modest than the lit crowns of the old city.

Dimming and shielding lights not only increases sky darkness but also helps birds, mammals, and insects trying to navigate the night. Although the strategies for alleviating changes in wildlife habitat are complex, since even shielded streetlights can change the habits of bats and insects, the simplest of things can make an enormous difference in mortality rates, especially of birds. Chicago is situated along a major flyway, and during the spring and fall migrations, more than 5 million birds—at least 250 different species—cross the city skies. In past years, at night, many migrants either crashed into the illuminated buildings or circled them until exhausted. Every morning, the managers of Chicago skyscrapers would pick up dead birds by the shovelful from the roofs. Then city planners instituted the voluntary Lights Out Chicago program. They asked building managers to dim or turn off decorative lighting late at night and to minimize the use of bright interior lights during migration season—from mid-March to mid-June, and again from late August to late October. They also encouraged high-rise residents to draw their shades or dim interior lights late in the evening. As a result, bird mortality dropped by an estimated 80 percent.

Granted, in the heart of any major city, the night sky will never be dark, but damping down city and suburban lights to where they were even a few decades ago will bring the dark sky closer to more people. Astronomer John Bortle, creator of the nine-level Bortle scale, which measures light pollution, noted in 2001, "Unfortunately most of today's stargazers have never observed under a truly dark sky, so they lack a frame of reference for gauging local conditions.... Thirty years ago one could find truly dark skies within an hour's drive of major population centers. Today you often