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Study: Most people losing sight of stars

A satellite view of Earth's city lights
A satellite view of Earth's city lights  

By Thom Patterson

(CNN) -- It's possible that future generations of children will know the Milky Way only as a candy bar, instead of a wondrous canopy of stars that has guided travelers and inspired poets, philosophers and dreamers for centuries.

That possibility is supported by a new global satellite survey which concludes that artificial lights are increasingly obscuring Earth's view of the Milky Way galaxy. The study says a truly dark, starry sky is unavailable to two-thirds of the world's population, including 99 percent of people in the continental United States and Western Europe.

The survey, conducted by scientists at the University of Padua, Italy, and the U.S. National Oceanic and Atmospheric Administration, measured for the first time how light degrades the view of the stars in specific places around the globe.

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The report describes regions of the world where true night never occurs because it is blocked by lights from neighboring cities and towns.

"The rapid increase in light pollution is one of the most dramatic changes occurring in our natural environment," said a statement released by the Royal Astronomical Society, which published the study. Light pollution "could have unintended impacts on the future of society," it said.

The NOAA's Dr. Chris Elvidge, who participated in the study, said he agrees with its conclusions, but disagrees with the use of the term "light pollution."

"I prefer to call it artificial light brightness," Elvidge said. "Calling it light pollution is making a value judgment," something Elvidge said he tries to avoid as a scientist, although he personally supports a dark sky for viewing starlight. "It would be nice if more people were able to see that panoramic view of the Milky Way," he said. "There arenít that many people who are actively observing the stars."

'A loss of our heritage'

The stars of the Milky Way have long provided the human race with both inspiration and direction, as voyagers learned to navigate by them.

"The stars awaken a certain reverence, because though always present, they are inaccessible," said U.S. philosopher Ralph Waldo Emerson in writings published in 1836.

Elizabeth Alvarez of the Tucson, Arizona-based International Dark-Sky Association, a non-profit environmental group, described how a group of California students responded to a Dark-Sky field study program designed to acquaint them with star-gazing.

"There were 58 respondents," she said. "Forty wrote back that until they did this they had never looked up at the stars before. The most tragic thing was that they ... were 16 and 17 year old students.

"Whether they're going to be poets or physicists, it doesn't matter. To have a generation growing up without seeing the stars would be tragic," she said. "Losing our view of the skies is a loss of our heritage."

Stars vanishing from night sky

As artificial light increases across the Earth's surface, the stars may not only be inaccessible, but invisible altogether. The survey compared U.S. Department of Defense satellite images of the Earth taken during 28 nights in 1996 and 1997.

"It is undoubtedly worse today," said study co-author Pierantonio Cinzano in a written statement.

Professional and amateur astronomers might be expected to be the most vocal opponents of excessive outdoor lighting, but others warn that it can have negative environmental and physical effects, too.

Alvarez said excessive outdoor lighting wastes precious energy resources in addition to blotting out the stars.

"We are wasting energy by pointing light where it doesn't need to go," she said. "We can't afford to do that with our bright lights, creating extra pollutants that we don't have to create. Let's use energy for things that are desperately needed."

Are night lights disrupting sleep?

In addition, the study concluded that 40 percent of the U.S. population and one-tenth of the world's people live in places where it is never dark enough for their eyes to become adapted to night vision.

Alvarez says losing sight of the stars would disrupt human and animal day-night sleep patterns.

Currently six states have legislation limiting the use of outdoor lighting: Arizona, Colorado, Connecticut, Maine, New Mexico and Texas, according to Alvarez .

Elvidge says there are plans to repeat the satellite study in the near future to monitor the progression of artificial light and how it affects starlight on Earth.

If fears that lights will one day completely blot out the stars do come to pass, an inspiring 1849 quotation from U.S. philosopher Henry David Thoreau would likely become both archaic and obsolete: "The stars are distant and unobtrusive, but bright and enduring as our fairest and most memorable experiences."


• National Oceanic and Atmospheric Administration
• International Dark-Sky Association

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