Pittsburgh is getting ready to dim its streetlights, and other cities are showing interest in joining in.
Pittsburgh will become a "dark sky city" this year. It's common for smaller localities in the western U.S., but not for cities of Pittsburgh's size and for cities on the East Coast.
Pittsburgh says it will switch to lower-wattage LED streetlamp light bulbs to reduce light pollution.
"Light pollution severely affects the natural environment pollinators, and bird migration, fireflies," said Diane Turnshek, a special lecturer in the Carnegie Mellon University physics department.
The city also says the move will increase energy efficiency. They expect to replace around 40,000 streetlights, which will reduce overall energy consumption between 40-50%.
"Street lighting is a major component of our electrical bill and of our emissions footprint, and so when we think about those correlations between energy consumption, the types of energy that we're consuming, as well as the amount of reduction, it'll be a pretty significant consumption reduction that we'll see," said Grant Ervin, Pittsburgh's chief resilience officer.
Ervin says the city is also taking equity into account because of the impact that lighting has on neighborhoods.
"What we're really after is, how do you provide the right amount of light and the right place, given the right conditions?" Ervin said. "So, lighting in a business district, for example, should be different than what it is in a residential neighborhood."
"As you go outside the city, there's a ring somewhere outside the city where you can't see the Milky Way inside, but you can see it outside on a clear, dark night when the Milky Way is directly overhead," Turnshek said. "So, I want to see if that ring shrinks, and that means more people will be able to see stars."
Pittsburgh says it's already talking with places like Washington, D.C., the state of Maryland and some southern cities about how to make the switch. Massachusetts has a bill in the state House and Senate to make the state dark-sky friendly.