We’re Thinking About Darkness All Wrong | Harvard Magazine
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Science
June 10, 2026
We’re Thinking About Darkness All Wrong
There’s a growing movement to curb light pollution. It starts on your front porch.
by
Matt Crossman
From The
July-August 2026
Issue
Stars and the Milky Way as seen from Haleakalā National Park on the island of Maui, Hawaii | photograph by Serena Wurmser
The dormant volcano Haleakalā climbs 10,023 feet into the sky, high above Maui and the Pacific Ocean. As it stretches through the clouds, the summit emerges as one of the darkest and clearest places on earth. That makes Haleakalā National Park an ideal setting for Serena Wurmser ’23 to lead astronomy tours.<br>Wurmser’s love for the stars runs deep. She wrote her Harvard admissions essay about the Big Dipper and now spends hours crafting her nighttime talks, mixing science and stories, history and legends. As the end of her tour draws near, she lets quiet drape over her guests, lets them lose themselves in the infinity above Puʻuʻulaʻula—Red Hill—as the summit is known.<br>Finally, she speaks again. “Think about someone you miss,” she tells them. Someone you wish were here. Wherever that person lives or lived, they once looked up at these same stars. “The stars connect us all,” she says.<br>But outside of rarefied locations like the top of a volcano, we are losing that connection. Ninety-nine percent of Americans live under skies dimmed by light pollution. The spread of light is like suburban sprawl, only worse because the light keeps going—up and out—when the suburbs stop. The eastern seaboard from Boston to Washington, D.C., seen from space, is a ribbon of light. On the ground, thousands of lights collectively shine so bright that it never gets truly dark. Sharp stars are fading and dull stars are disappearing. One study published in the journal Science, based on thousands of reports from citizen scientists, suggests the sky is getting 10 percent brighter every year.<br>And light pollution travels far beyond city borders. Las Vegas lights “are the dominant cause of light pollution in Death Valley National Park, 93 miles from the city,” according to DarkSky, an international organization whose mission is “to restore the nighttime environment and protect communities and wildlife from light pollution.”<br>Man-made light reaches even Puʻuʻulaʻula—though admittedly not very much, it is measurable. “It’s pervading natural areas that we would think are undisturbed,” says Avalon Owens ’13, a research fellow at Harvard’s Rowland Institute who has studied the effect of light pollution on fireflies and other bugs.<br>Light has always and forever been a metaphor for good. The Bible says God’s first spoken command created light. The Enlightenment redeemed the Dark Ages. Light stands for knowledge, for clarity, for purity. We can never have too much of any of those.
Serena Wurmser | Photograph courtesy of Serena Wurmser
But when light is a real thing and not a metaphor, too much of it is just that: too much. And light pollution does far more than just make it hard to see stars. There are long-term and wide-ranging health consequences up and down the food chain.<br>Dark is good. Dark works. We need more of it, not less. On top of Haleakalā, in urban parks, in state capitols, in architectural designs of urban landscapes, and in astronomy conferences across the country, Harvard professors, scientists, and graduates are working to make that happen.<br>The dangers of light<br>Light pollution is still a relatively new field of study. Researchers trace the term to an article in Science in 1973, and for years it seemed that only astronomers cared about it. To the extent the public paid attention, the reaction was to shrug and say the astronomers just need to go where it’s darker.<br>Dark sky advocates have a name for this problem or, rather, an acronym: ALAN, which stands for “artificial light at night.” It’s increasingly clear, they say, that many places we think are dark actually aren’t, with far-reaching health consequences for humans and animals.
The Bortle dark sky scale, developed by amateur astronomer John E. Bortle, measures the impact of light pollution at different locations. | image COURTESY OF EUROPEAN SOUTHERN OBSERVATORY
Road glare causes thousands of car accidents every year. A 2024 story in the AMA Journal of Ethics, “We’re All Healthier Under a Starry Sky,” says artificial light at night has “been associated with sleep disturbances, depression, psychiatric disorders, and obesity, with a subsequent increased risk of diabetes.”<br>In 2017, researchers from Harvard and several other institutions released a landmark study that followed 109,672 nurses for 24 years. They separated the women into five groups based on lighting in their home ZIP codes. Women who lived in areas with the highest levels of exposure to ALAN had a 14 percent...