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March 19, 2015

Going Dark: Earth Hour spreads message about light pollution


“There are few dark places left,” said astronomer Diane Turnshek in a recent talk on campus about local and global efforts to reduce light pollution. “We are going to lose this battle. … What I am trying to do is slow it down.”

Turnshek, a Carnegie Mellon University physics department faculty member, is touting “De-Light Pittsburgh” efforts to raise awareness of light pollution issues.

Increased city lighting has forced changes at Pitt’s Allegheny Observatory, “because the light, especially from the stadiums, is just too bright,” Turnshek said. A telescope there got a new, redder lens in 1995 to filter out the blue light that causes most light pollution problems. “We were lucky because we’re still doing work up there,” she said.

The decline in dark skies has shuttered observatories elsewhere, and lighting from roadways and mining is threatening observations even in the remote Chilean desert — “one of the last places on earth where astronomers could find high, dry desert with dark sky,” Turnshek lamented.

The loss of dark skies is being documented through citizen-science efforts such as and, in which individuals submit their observations of local night sky conditions using smartphones or computers.

Increasingly, people in many urban areas grow up having never seen the Milky Way, she said, noting how during blackouts in Los Angeles people reportedly dialed 911 to express concern about the unfamiliar “weird shimmering cloud” that they saw stretched across the night sky.

“I remember the dark skies, but other people who are young think this is normal. They don’t recognize you should see the Milky Way from wherever you are. You should be able to see stars.”

The ubiquity of artificial light is evident in satellite photos of the Earth. “The whole world is lit up except for North Korea, parts of Africa and parts of Australia,” she said. And a good bit of that light is wasted. Anytime lighting is aimed upward, the earth’s atmosphere scatters it. “It’s escaped light … that’s doing nobody any good,” she said.

Efforts are underway in Pittsburgh to replace thousands of city lights with “full cutoff shielding” fixtures that produce light that’s seen only from below, “lighting what it’s meant to light — the ground,” she said.

Beyond being a bane to astronomers, decreased nighttime darkness confuses wildlife and may have negative effects on human health, Turnshek said.

Low melatonin is associated with higher cancer risk and nighttime light is associated with lower melatonin production, she said. “We don’t know yet that too much light at night is bad for your health,” she said, adding, “It’s going to come out soon, I believe, that too much light at night is a cancer risk.”

In addition, the cost of wasted light is huge.

It takes about one-third of a ton of coal to power a 100-watt light bulb for a year, Turnshek said, adding that the nonprofit Pennsylvania Outdoor Lighting Council estimated that in 2012, the electricity cost of wasted outdoor lighting in the United States was nearly $3.5 billion.

“Turn off your lights. Dim them, put them on timers. Turn them off when it’s not necessary,” Turnshek said. “It’s something people need to think about.”

Aimed at getting people to think about these issues, “De-Light Pittsburgh” will kick off later this month in conjunction with the worldwide observation of Earth Hour 2015.

“Earth Hour is about saving the Earth. It’s about sustainability. It’s about climate change. It’s about doing your part to make this planet a better place to live,” Turnshek said.

Since its inception in Australia in 2007, the annual environmental effort includes a commitment to turn off or dim outdoor signs and unnecessary lighting for one hour in late March. Last year more than 7,000 cities and towns in 162 countries participated, according to the nonprofit group’s website,

This year’s effort will take place on March 28, from 8:30-9:30 p.m. local time. Turnshek said photographers will be poised on Mt. Washington as city lights go out.

“It’s one hour but hopefully it sends a message,” Turnshek said, adding that Earth Hour’s “60+” tagline indicates the lights go off for 60 minutes, “but we keep doing things throughout the whole year.”

Approximately 40 buildings in Downtown and Oakland will go dark, she said, adding that CMU plans to darken the Randy Pausch Bridge, Hunt Library, Hamerschlag Hall, Doherty Hall, the Walking to the Sky sculpture, the East Campus Garage and Mellon Institute.

Dan Marcinko, Pitt’s sustainability coordinator, told the University Times, “We cannot turn off the lights in the buildings due to classes and nighttime cleaning but we make every effort to turn off outside building accent lighting.”

He added that occupancy sensors in many campus buildings turn off lights in unused classrooms and offices automatically.

The Green Building Alliance is encouraging organizations and individuals to post their own local Earth Hour photos using the social media handles #delightpgh, #DeLightPGH, #earthhourpgh or @go_gba.

Details on local Earth Hour efforts, including star parties hosted by the Pittsburgh Amateur Astronomers Association, can be found at

Additional De-Light Pittsburgh activities will involve collaborations with art galleries and a contest to create our Pittsburgh constellation by connecting astronomy-related local map points, Turnshek said.


Humans have an ingrained fear of the dark, Turnshek admitted. And while our cave-dwelling ancestors may have had well-founded fears, today we have cellphone flashlight apps.

“You are never in the dark when you have a phone on you. It is no longer a problem for us,” she said. “You should be able to embrace the dark.”

—Kimberly K. Barlow