At night, even from 200 miles above the Earth, an astronaut can float over to a window in the International Space Station and see cities in such incredible detail that it's possible to recognize individual streets. Since 2003, when an astronaut figured out how to snap a clear photo of the view from orbit, hundreds of thousands of amazing urban photographs have piled up in archives.
A new website is attempting to find volunteers to identify each of those cities—not just because the shots are beautiful, but because they can help scientists better understand the problem of urban light pollution. Thanks to artificial light, a place like Hong Kong is now 1,000 times brighter than an unlit natural space at night. All of that blinding light is wrecking sleep, harming wildlife, and wasting energy.
Cities at Night was launched by some Spanish astrophysicists who started following an astronaut's Twitter account. "For us his nighttime pictures were like fire for a firefighter—it's pretty, but you must control it," says Alejandro Sanchez from Complutense University of Madrid. "We want to make the nighttime images useful for citizens, journalists, and scientists. And make this beauty accessible—but also make people think about if all this waste of energy is really needed."
The scientists made apps to help volunteers sort through the images, and have already crowdsourced help for almost 1,000 tasks.
Ultimately, they're hoping that blindingly lit cities start taking more steps to dim down. Some solutions are simple—like using shields that direct light down to where it's actually needed, instead of into the sky—and some, like smart streetlights, use more advanced technology to limit light.
All of the options for reducing extra light can also save money and energy. The scientists point out that the costs are much greater than the space travel that made the photos possible.
"Humans spend over $110 billion per year for obsolete lighting that wastes at least 50% of its energy, but we only use $34 billion for space exploration," says Sanchez. "If these images help reduce the waste of energy, we will save several times the money that we spend on exploration."