These effects reach across entire regions of the globe, far outside of cities. Over the past decade biologists have discovered that wasteful nighttime lighting drastically disrupts animals, plants and the ecological relationships that knit the world together. Its impacts are not limited to astronomy, of course.
Not so with light pollution, even though astronomers looking through telescopes may have been the first to really notice it. Species spiraling into oblivion, a few extra parts per million of carbon dioxide in the air, sea life gobbling up microplastics-many of our era's ecological calamities are hard to see with unaided eyes. Intense wildfires linked to global warming (such as one that swept the summit half a year after my visit) may pose more obvious risks to the telescopes there, but the subtle, pernicious effects of ever brighter nights could eventually become an even bigger threat to astronomy. Under skies so filled with stray photons, it takes twice as long to resolve an astronomical target as it typically would, one Kitt Peak astronomer told me a few hours after sunset. For them, the boundary of each glowing dome was a battle line, expanding or shrinking with each skirmish won or lost the imperfect darkness overhead was a testament to local policy and millions of collective actions-or collective shrugs and proliferations of gleaming billboards and streetlights. Over the decades astronomers have taken urgent steps to slow or even reverse its spread. To the south, across the Mexican border, loomed another luminous half-circle from the lights of Nogales.Īll that light is an existential threat to high-grade stargazing on Kitt Peak. A snake of lesser lights-Interstate 10-wriggled out from the glow, winding 100 miles north toward the glare of Phoenix. Tucson was a bright bubble eating the eastern sky and the shoulder of Orion. “Holy crap,” Edwards said, taken aback by the enormous city glow.
As the stars came out, electric lights dotting the landscape below turned on, too, leaving a diminished Milky Way arcing above the brighter civilization. But on this evening last December she stood alongside me in the twilight, watching two worlds collide. At this hour Michelle Edwards, the observatory's associate director, would usually be inside prepping for a night on the telescope. Darkness was falling at Kitt Peak National Observatory outside Tucson, Ariz.
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