Matt Benjamin was growing up in Los Angeles when early one morning a "strange, silvery cloud" appeared in the darkened sky. Or so it was described by callers to local astronomical observatories.

Matt Benjamin was growing up in Los Angeles when early one morning a "strange, silvery cloud" appeared in the darkened sky. Or so it was described by callers to local astronomical observatories.

But Benjamin, because of his family's travels to Idaho, knew what he was seeing on that January morning in 1994: the Milky Way Galaxy. The Northridge earthquake that shook Los Angeles had left large swathes of the metropolitan area without power and lights.

Benjamin, now an astrophysicist in Colorado, returned to Idaho recently, this time to testify. The Idaho Conservation League proposes to seek designation for a dark-sky preserve centred on the area around Ketchum and Sun Valley. Three designated wilderness areas buffer the resort valley. Boise is 240 kilometres away. There's darkness already. But Benjamin, in his testimony before the Blaine County commissioners, called for stiffening efforts to tamp down the lights so that the Milky Way can continue to be seen.

Los Angeles isn't alone in blotting out the Milky Way. A team of scientists reporting in a June 2016 issue of Science Advances found that the Milky Way is not visible to more than one-third of humanity. This includes 60 per cent of Europeans and nearly 80 per cent of North Americans. But even when they can detect the Milky Way in the sky overhead, 99 per cent of the U.S. and European populations live under light-polluted skies.

"In terms of where the dark skies are, east of the Mississippi is gone," says Benjamin, the education programs manager at the Fiske Planetarium at the University of Colorado in Boulder, Colo. "There's nothing left to save, unless you start turning off lights and getting rid of cities."

Even in the American West, the Milky Way can be hard to find in the night sky. What Benjamin calls the light footprint from cities can extend 160 to 240 kilometres in every direction. In Colorado, that footprint easily encompasses Rocky Mountain National Park and mountain towns like Winter Park, Vail, and Breckenridge.

Mountain towns can have problems of their own. Consider Colorado's Summit County, located an hour west of Denver.

"The problem is Denver's footprint covers just such a large area," says Benjamin. "The eastern third of the sky in Dillon and Summit County is largely washed out by the Front Range, and Summit County itself has a large footprint." Too, he adds, snow reflects light, obscuring the Milky Way and many stars for much of the year.

How about the canyon country of the Southwest? Again, problems. Chaco Canyon National Historical Park, where the ancestral Pueblo once thrived, has few lights — but just outside are oil and gas drilling in the New Mexico desert, plus the flames of unwanted gases being burned off. Arches and Canyonlands national parks in Utah have darkness, too, but again, drilling has been occurring outside the borders. For that matter, Moab is not such a small place anymore, Benjamin observes.

In Idaho, the proposal being pushed by the Idaho Conservation League would yield the creation of a dark-sky reserve, the first in the United States and 12th in the world designated by the International Dark-Sky Association.

The association has specified minimum criteria for sky quality and natural darkness: 80 per cent of outdoor lighting must be shielded within five years to prevent it from going into the sky. Within a decade, it must hit 100 per cent.

To achieve that would require the cluster of towns along the Wood River — including Ketchum and Sun Valley, plus Blaine County — to up their game.

"I think we're a lot closer than many of us would have thought," says the Idaho Conservation League's Betsy Mizell.

Both Ketchum and Sun Valley adopted dark-sky laws in the late 1990s. Ketchum's ordinance requires all light fixtures be downcast, restricts light trespass onto neighbouring property, and specifies maximum brightness or luminosity of lights. Regulations are imposed when any new project seeks a new permit.

What's to prevent somebody from loading up with warehouse-type lights at the Lowe's in Twin Falls? Enforcement is complaint driven, said Micah Austin, Ketchum's director of planning and building, in an e-mail response.

"Generally, our community abides by the regulations and there has been little to no pushback," he said.

But compliance? "A recent informal lighting survey conducted by staff showed that a majority of lighting in Ketchum's residential neighbourhoods meets the Dark Sky Ordinance," he said. "Nearly all commercial lighting meets the requirements of the ordinance."

Sun Valley already has an ordinance, too, as well as a local resident, nicknamed Dr. Dark (he's a retired physician), who has been a vocal exponent of the value of unpolluted skies. "He's definitely a champion of dark skies, and recognizes the benefits of human health and tourism and his own personal interests," says Jay Hill, the town's director of community development.

Hill sees several drivers to effect change and further tamp down light pollution. Regulations will be necessary for some. When somebody pulls a permit for a new roof, light fixtures will be on the checklist. Others will respond best to incentives, such as rebates. Others will voluntarily comply with encouragement. Just how much Sun Valley needs to improve its compliance, though, has not yet been determined. In the long nights of this winter, says Hill, Sun Valley hopes to measure compliance.

Neighbouring Ketchum, he adds, has done a good job of using social media and website messaging to advance social acceptance for dark sky protections.

Those advocating dark-sky protections have a variety of arguments.

"We lose our perspective of our place in the universe to light pollution," says Benjamin, the astrophysicist.

There's also evidence that light pollution can impact the health of both people and wildlife by disrupting circadian rhythms. "Many environmentalists, naturalists, and medical researchers consider light pollution to be one of the fastest growing and most pervasive forms of environmental pollution," said a January 2009 article by Ron Chepesiuk in Environmental Health Perspectives. "And a growing body of scientific research suggests that light pollution can have lasting adverse effects on both human and wildlife health."

But there's also an argument that dark skies can drive tourism. Ketchum was once a mining town, then a centre for livestock grazing before becoming a resort when Averill Harriman of the Union Pacific decided in the 1930s that skiing was a way to increase railroad business. Today, if summer and winter tourism are strong, the shoulder seasons could benefit from people drawn to see the Milky Way, says Hill.

That's proven to be the case in Alberta. Jasper, for the last three Octobers, has hosted a dark-sky festival. This year, buffed up with the marquee attraction of Bill "The Science Guy" Nye and George Takei, the actor who played Mr. Sulu in the original Star Trek series, the festival drew 10,000 people over the course of the two weekends.

Can we have it both ways, outdoor lights illuminating our pathways at night without precluding sight of the Milky Way, stars like Polaris, and the constellations that inspired shepherds and civilizations past?

The International Dark-Sky Association advocates best practices, such as outdoor light fixtures that shield lights, preventing light from trespassing skyward (or to neighbours' backyards). Different lighting technologies, such as LED, can help in some cases, although Benjamin says all forms of light have upsides and downsides.

Hawaii, on the big island, may have the best light ordinance. There, measures were drawn up by the city of Hilo to protect the quality of the night sky for the Mauna Kea Observatories. The law mandates that outdoor lighting be shielded and requires that most outdoor lighting must use low-pressure sodium lamps.

Benjamin credits the Arizona mountain town of Flagstaff with having a "toned-down version" of the same night-sky protections.

In advocating for such protections, Benjamin describes a "delicate" conversation with people who fear loss of their freedom. Passing a law does not make it so. Rather, the task is to get people to take ownership of rules. We've largely achieved that with sewage. Unlike 50 years ago, you don't see outhouses over creeks anymore.

It's the most fervent hope of dark-sky enthusiasts that the same thing will occur with light pollution. Still, Benjamin isn't hopeful about places like Colorado, where today's population of 5.3 million is projected to hit 10 million by mid-century. Expanding towns and cities will almost certainly make the Milky Way for coming generations a phenomenon of textbooks and the Internet — except, of course, when the power goes out.