Astronauts aboard the International Space Station are snapping photos of Earth at night, and the images are telling a troubling story.
Using the photos, a citizen science project called Cities at Night has discovered that most light-emitting diodes — which are touted for their energy-saving properties — actually make light pollution worse. The changes in some cities are so intense that space station crew members can tell the difference from orbit.
Tech Insider previously reported on Milan, Italy's LED light pollution, and have since received other before-and-after images of major metropolitan cities that have made the switch. We've turned astronauts' photos into animations below. The results are as astonishing as they are mesmerizing.
Milan: 2012 and 2015
Before Milan transitioned to LEDs in 2012, the lighting levels in the surrounding suburbs were about the same as those of the city center.
But by 2015, after the city transitioned to LEDs, illumination levels in the city center were much brighter than those of the suburbs, with a higher amount of blue light:
Los Angeles: 2010 and 2012
Los Angeles also went through a dramatic change in a two-year period.
Mexico City: 2003 and 2011
Seoul: 2011 and 2014
These aren't the only cities affected.
Others around the world have been replacing energy-guzzling streetlights with brighter and whiter energy-saving LEDs. In fact, New York City is now retrofitting all of its 250,000 street lights with LEDs in what the city is calling the biggest project of its type in the country.
But energy savings doesn't necessarily translate to happy city dwellers. In a piece in The New York Times, Brooklyn residents complained about the glaring white light creeping into their homes and eyes, causing many restless nights.
LEDs also worsen light pollution by giving off more blue and green light than the high-pressure sodium lights they normally replace. And this artificial light pollution washes out the night sky and is linked to many negative consequences. Disrupted night and day cycles can confuse nocturnal animals and alter their hunting interactions, migratory patterns, and internal physiology.
It can also mess with our internal clocks. We produce melatonin at night to help us sleep, which is regulated by light and dark cycles. If we're exposed to light at night, this can suppress melatonin levels, leading to sleep disorders or other problems such as headaches, anxiety, and obesity.
Cities at Night is compiling these images to make a Google-Maps-style map of images of Earth at night. If you want to support its research, check out its KickStarter project here.