A new lighting design follows the natural cues of the moon

This article was originally presented on Hakai Magazine, an online publication on science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.

Camilla Rathsach walked along the lichen-covered sand, starting from the lonely village on Denmark’s remote island of Anholt – a point of land just a few kilometers wide in the middle of the Kattegat Strait, which separates mainland Denmark from Sweden. As the 45 streetlights of Anholt Town receded into the distance, moonlit shadows stretched out to hug the dunes. Rathsach looked up, admiring the Milky Way stretching across the sky. Thousands of stars shone. “It’s just amazing,” he says. “Your senses are heightened and you hear the water and feel the fresh air.”

This moment of dark skies was one of many that Rathsach experienced when she visited the island in 2020 for work on her thesis on balancing the need for external lighting and darkness. Growing up in urban areas, Rathsach wasn’t used to how bright moonlit nights could be. And after talking with the islanders, who deeply appreciate the dark sky and navigate with little external light, he realized that artificial lighting could be reduced at night depending on the phase of the moon.

At Aalborg University in Denmark, she collaborated with her supervisor, Mette Hvass, to present a new exterior lighting design for the church in Anholt. Rathsach and Hvass chose the church for their project because it is a central meeting place for the community, but currently has no exterior lights. They thought the lighting would make it easier for people to navigate, but they wanted to keep the welcoming atmosphere of the moonlight.

One of the guiding principles of sustainable lighting design is to start from darkness and add only the minimum amount of light required. Darkness and natural light sources are important to many species, and artificial light can be downright dangerous.

“Lights can attract and disorient seabirds during their flights between colonies and foraging sites at sea,” says Elena Maggi, an ecologist at the University of Pisa in Italy who is not involved in the project. Anholt’s beaches are home to a variety of breeding seabirds, such as gulls and terns, and the island is a staging post for many migratory birds. The waters around the island are also home to seals, cod, herring and seaweed. Although scientists have made progress in understanding the effects of artificial light at night on a range of species, including turtles, birds and even corals, there is still more to learn.

“We still don’t know exactly how artificial light might interact with other disturbances such as noise and chemical pollution, or with ocean warming and acidification due to climate change,” says Maggi.

The scientists’ final design for the church includes path lighting and small spotlights under the window arches, along with facade lighting under the eaves that shine down. To preserve the dark sky, the path lighting would be turned off on bright moonlit nights and the facade lighting would be turned off on dim or bright nights. The window lighting will stay on regardless of the moon phase.

The adaptive lighting cooked up by Camilla Rathsach and Mette Hvass will automatically adjust to the availability of moonlight, automatically modifying the lighting of this church to balance visibility and darkness. The mock-ups show how the church would be lit under moonlight (first) and a full moon (second). Illustrations courtesy of Camilla Rathsach

“The contrast between the cold white moonlight reflecting off the church walls and the warm orange lights in the windows would create a warm, inviting experience,” says Rathsach.

The adaptive moonlight design project is part of a growing effort to balance the need for functional urban lighting with protection from darkness. Recently, the city’s public lights have been replaced with dark-sky-friendly lamps, says Anne Dixgaard, president of Dark Sky Anholt.

Dixgaard also organizes an annual beach walk in Anholt, where sky watchers can learn about the night sky. “People really appreciate the dark sky of Anholt and want to preserve it,” he says.

Rathsach and Hvass are working on Moonlight’s adaptive design project with the hope that it will one day be implemented, but they still have some challenges to overcome. Moonlight is a relatively dim light source, so detecting it using sensors is difficult, and lights should automatically adjust on nights with intermittent cloud cover. However, big initiatives often start with small steps.

“This project is something new and unexpected,” says Maggi. “It’s a very interesting approach to mitigating the negative effects of artificial light at night.”

This article first appeared in Hakai Magazine and is republished here with permission.

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