But they were using high-temperature blue LEDs, which would have bathed the city in a harsh white light. ![]() In 2015, Phoenix began testing the replacement of some of its 100,000 or so old streetlights with LEDs, which the city estimated would save $2.8 million a year in energy bills. Arizona’s Grand Canyon National Park is designated by the IDA as an International Dark Sky Park, and yet, on a clear night, Barentine says, the horizon is stained by the glow of Las Vegas 170 miles away. “You can stand in the middle of downtown Flagstaff and see the Milky Way,” says James Lowenthal, an astronomy professor at Smith College.īut it’s not immune to light pollution. The state is home to four of the 10 IDA-recognized “Dark Sky Communities” in the United States. He pointed to the city of Phoenix, Arizona.Īrizona is a leader in reducing light pollution. Barentine is a program manager for the International Dark-Sky Association (IDA), a nonprofit founded in 1988 to combat light pollution. The effort to darken the skies has expanded to include a focus on LEDs, as well as an attempt to get ahead of the next industry trend.Īt a January workshop at the annual American Astronomical Society (AAS) meeting, astronomer John Barentine sought to share stories of towns and cities that had successfully battled light pollution. In 2016, the American Medical Association issued guidance to minimize blue-rich light, stating that it disrupts circadian rhythms and leads to sleep problems, impaired functioning and other issues.) (Blue lights have also been found to be more harmful to human health than more warmly colored, amber LEDs. But that blue light turns out to be particularly detrimental to astronomers, for the same reason that the daytime sky is blue: Blue light scatters more than any other color. The creation of energy-efficient blue LEDs was so profound that its inventors were awarded the 2014 Nobel Prize in Physics. The higher the temperature, the bluer the color. ![]() Different bulbs emit different colors, which correspond to different temperatures. Many towns and cities are already reexamining their lighting systems as the industry standard shifts from sodium lights to light-emitting diodes, or LEDs, which last longer and use far less energy, providing both cost-saving and environmental benefits. ![]() For their part, astronomers have worked to convince local governments to adopt better lighting ordinances, including requiring the installation of fixtures that prevent light from seeping into the sky. (Meneghini harbors no hard feelings: “I would have made the same decision,” he says.)īeyond being a problem for astronomers, light pollution is also known to harm and kill wildlife, waste energy and cause disease in humans around the globe. “They decided that if they were going to do greater, more detailed and groundbreaking science in astronomy, they would have to move to a dark place in the world,” says Tom Meneghini, the observatory’s executive director. Wilson to build telescopes in Chile instead. In 1983, the Carnegies, who had owned the observatory since its inception, abandoned Mt. ![]() The city light overpowered the photons coming from faint, distant objects, making deep-sky cosmology all but impossible. As the city of Los Angeles grew, so did the reach and brightness of its skyglow, otherwise known as light pollution. Wilson that it was expanding.īut a problem was radiating from below. In 1929, Edwin Hubble revolutionized our understanding of the shape of the universe when he discovered on Mt. More than a mile up in the San Gabriel Mountains in Los Angeles County sits the Mount Wilson Observatory, once one of the cornerstones of groundbreaking astronomy.įounded in 1904, it was twice home to the largest telescope on the planet, first with its 60-inch telescope in 1908, followed by its 100-inch telescope in 1917.
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