Lowell Observatory and the Dark Sky Battle

Percival Lowell chose Flagstaff in eighteen ninety-four for reasons that had nothing to do with the town. He wanted dark skies, dry air, and altitude. Mars was what he was after, specifically evidence of Martian canals, which he believed were irrigation channels built by an intelligent civilization. Flagstaff sat at roughly seven thousand feet, was nearly uninhabited, and had atmospheric conditions that gave exceptional clarity on most nights of the year. He built his observatory on a hill above the pine forest and began watching the sky.

The Mars canals turned out to be optical artifacts. But the observatory he built became one of the most productive research institutions in American astronomy, producing the first reliable measurement of the expanding universe and, eventually, the discovery of Pluto.

Lowell did not anticipate that Flagstaff would grow. By the nineteen eighties, a city of fifty thousand people surrounded the observatory, and light pollution was threatening the sky that had made the site viable. The observatory's astronomers and city officials began negotiating. Flagstaff adopted lighting ordinances restricting upward-facing light and unnecessary illumination. The effort worked well enough that in two thousand one, Flagstaff became the first city in the world to be designated an International Dark Sky City by the International Dark-Sky Association. The designation has since been adopted by dozens of cities worldwide as a model.

The telescope that found Pluto is still in its dome. On clear nights, the sky above Flagstaff is dark enough to see the Milky Way from downtown. Percival Lowell, who chose the location for its darkness, would recognize the sky, though probably not the city beneath it.