Bryce Canyon » A hush falls over a crowd of stargazers as they lean in, tilt their heads up toward the heavens and listen to the tragic tale of Callisto, a virgin seduced by Zeus and transformed into a bear as punishment.

People travel here from around the world -- not just to explore the magical red spires of the canyon -- but to savor the night skies.

It's no wonder. A single glance can sweep in a breathtaking 7,500 stars.

But even Bryce Canyon isn't immune from a growing scourge that threatens this view. Visitors now can detect a little bit of a glow in the horizon -- lights from the nearby small towns of Tropic and Panguitch but also larger cities -- as far as St. George and even Las Vegas.

"We're losing 10 percent of the sky, and it's noticeable and a cause for concern," said Chad Moore, National Park Service night sky program manager. "It hasn't yet taken away from the enthusiasm of those who come to see the night sky, but it is a warning of how things will be."

Endangered » "Light pollution is outpacing population growth," Moore said. "Virtually all dark skies are considered threatened."

The likelihood of a person born today actually seeing the Milky Way is less than 50 percent, and many astronomers -- both professional and amateur -- grieve for the lost experience of seeing galaxies, constellations and deep-sky objects such as the Swan Nebula.

It's not just the views that are being lost -- but the whole sense of discovery and lore that are part of the stargazing experience.

"People like to hear the stories of the constellations. It's a legacy that's being lost, and we're trying to bring attention to the things that are jeopardizing it," said Don Brown, cofounder of Utah Skies, an amateur astronomy Web site that advocates against light pollution. "When you measure the degradation of the night sky, each year it's getting worse, and every night is a reminder. We're closing the doors to the oldest classroom the world has ever had."

One particularly ironic contributor to the problem: Salt Lake City's Clark Planetarium.

Each night, upward-facing lights shoot into the night sky, meaning no one can actually see real stars from the planetarium and instead must see images of them in the dome and IMAX theaters inside the building. The Boyer Co. , which manages the building, has control of the planetarium's outside lighting, much to the annoyance of planetarium director Seth Jarvis.

"When we talked to the project's designers, we said we didn't want to contribute to light pollution -- for heaven's sake, we're a planetarium," Jarvis said. "But we weighed the pros and cons, and sometimes you don't get a la carte, you get no substitutions. We're not proud of that."

Light's hazards » While some worry about losing familiarity with the stars, others are starting to point out other hazards of light pollution.

Studies have shown that light pollution can increase the risk of breast and large intestine cancers as well as the risk of premature reproductive system aging in women, according to a collaborative study coauthored by the Pertov Scientific Research Institute of Oncology. Light at night interrupts a person's ability to produce melatonin, a hormone that affects the endocrine system and prevents cancer growth. When melatonin isn't produced, cancer becomes more prevalent. Women usually are hit harder as they are more sensitive to light at night than men, the study said. The problem is big enough that the World Health Organization has listed shift work to its list of possible carcinogens.

Light pollution is also deeply impacting wildlife.

In Florida, sea turtle hatchlings head toward the brightest light source after emerging from their eggs. Traditionally, that has been the horizon with the sun or moon shining down. Now, many coastal Florida cities are brighter than their natural counterparts, and the turtles become disoriented. The problem is a key reason that all sea turtles in Florida are either classified as threatened or endangered.

In Utah, Great Horned Owls may meet a similar fate. The owls' feathers make them nearly silent when stalking prey, but the number of lights in once-rural areas are making it increasingly difficult for owls to hunt.

"Mice aren't exactly smart, but when they see an owl-shaped shadow cross over them, they know to run," said Kevin Poe, a ranger at Bryce Canyon National Park.

When the owls can't find food anymore, their owlets starve. The numbers of Great Horned Owls dipped in 1987 and has declined slightly since, said Greg Butcher, director of Bird Conservation at National Audubon Society. He says the owls have been able to adapt to urbanized areas, but that a loss of habitat, invasive species and possibly light pollution could be contributing to their decline, though he hasn't seen studies on the effects of light pollution on the owls.

While animals are suffering, the quality and amount of astronomical research is, too. Astronomers are forced to remote areas such as Chile and Hawaii to get proper views of deep-space objects, and time at such observatories is becoming increasingly difficult and more costly.

"I'm so used to the fact that you have to go away to do research -- it's all I've ever known," said J. Ward Moody, professor of physics and astronomy at Brigham Young University. "But if we did not have to go huge distances to see dark skies, the whole profession would be much easier to do and much less expensive."

Solutions » Some local counties and cities, including Summit and Bountiful, have instituted policies mandating more downward-pointing, less-intrusive lighting.

Brian Jolley, an amateur astrophotographer who lives in Bountiful, appreciates his hometown's ordinances limiting light trespass, but he is still irked when some of the local car dealerships aim spotlights into the night sky. He's taken photographs of the glaring skyglow caused by lights shining upward in his hometown and along the Wasatch Front.

"It's getting worse all the time," he said. "People just need to be use more common sense with their lighting."

Alan Fawcett, planning director for Heber City, says he has policies in place to keep the town's "country charm."

"We would like to keep our skies a little darker a little longer so we can enjoy the stars and moon," he said.

But not everyone thinks that's a bright idea.

State Sen. Ron Allen attempted to pass a resolution urging light pollution prevention in 2003. The bill never made it past committee.

Now, with soaring energy prices, dark-sky advocates are hopeful others will realize the economic impact of light pollution -- potentially billions of dollars.

However, a lit sign or billboard can be the difference between running a successful or failing business, said Kirk Brimley, past president of the Utah Sign Association and special services manager for Young Electric Sign Company.

Lighting technology has come a long way since Brimley entered the sign business more than 60 years ago. Businesses have responded to most community concerns by having less obtrusive signage.

"We try to be sensitive to anything that might create problems for anyone," he said. "But a city without lights doesn't work."

Urban vs. rural » In 2004, as the Boyer Co. finished its Redstone development in Park City, Utah Skies led a group of citizens concerned that the development bordered the Swaner Nature Preserve. They worried about the impact it would have on the 40 wildlife species that lived there.

Boyer responded, adding shielding to the lights to direct it downward at what they called a "substantial cost."

But, according to Scott Verhaaren, a partner in Boyer Co., the company only has met resistance to bright lights in Park City and Heber City.

"Light pollution issues don't come up in big urban areas," he said.

But big urban areas seem to be encroaching on even the most rural skies. At Great Basin National Park, the sky is tinged with lights from Salt Lake City, 200 miles away.

The only two patches of pristinely dark sky left are Natural Bridges National Monument and Capitol Reef National Park, Moore said, and he's fighting hard to protect them.

"Our nighttime scenery can be just as much of a draw as the daytime scenery," Moore said. "Utah is fortunate to have those skies and it's the perfect time to protect them. It's easy to make small changes to make sure that in 50 years, Utah has the same quality of night skies."

smcfarland@sltrib.com