Thanks to citizen scientists around the world, new research shows how light pollution masks the night sky from most of Earth’s population. The scientists' work “shows that 80% of the world and 99% of the U.S. and European populations live under light-polluted skies.”
In an increasingly urbanized world night time light pollution has subtle but serious effects on public health, ecosystems, and long term climate change. Light exposure at night suppresses melatonin levels, disrupting our circadian rhythms and reducing the quality of our sleep. Poor quality sleep can intensify stress, depression and exacerbate medical conditions like diabetes.
In a similar vein light pollution has widespread impacts on local ecosystems. It disorients migrating birds and shifts the balance between predators and their prey. Over the long term, the excess light cast into the night sky represents wasted energy production - and unnecessary carbon emissions.
Light pollution also affects the quality of science. Astronomers have sought ever more remote locations for their observatories to avoid light pollution. Edwin Hubble first measured the Universe’s expansion from the Mount Wilson Observatory north of Los Angeles. The bright lights of Hollywood forced astronomers south to the mountains east of San Diego, but now light pollution limits the science produced at the Palomar Observatory. Amateur astronomers have fewer options. Unless they travel to rural sites away from city lights, they see less and less through their telescopes.
Fortunately amateurs are the very ones documenting the erosion of our night skies. The research paper “The new world atlas of artificial night sky brightness” published in Scientific Advances (open access DOI: 10.1126/sciadv.1600377, arXiv preprint: 1609.01041) consolidates measurements from three international citizen science projects - Globe at Night, Unihedron, and Loss of the Night - as well as specific professional/amateur collaborations in Ireland and Canada. The researchers credit citizen scientists for providing data in “more diverse” locations, especially outside the United States and Europe.
Globe at Night has coordinated volunteer dark sky observation campaigns for the past nine years. Every month before the Moon rises, citizen scientists count the number of stars they see in a constellation. The more light pollution brightens the sky, the fewer stars people see. Participants report back through the Globe at Night website or its smartphone app. Since the project began people in 115 countries have submitted more than 100,000 measurements.
Astronomy instrument maker Unihedron’s Sky Quality Meter lets amateur astronomers measure the quality of the night sky when making their observations. These skywatchers contribute their measurements to the Unihedron Sky Quality Meter Database.
Loss of the Night lets citizen scientists report sky brightness levels from their smartphones. Available on Android-based devices only, the Loss of the Night App asks the users whether they see certain stars in the sky. The project’s scientists will use these ground truth reports to validate sky brightness models based on light-measuring instruments on satellites. The data will also confirm whether the shift to LED-based lighting makes skies darker. Owners of iPhones don’t need to feel left out. An independent group created the Dark Sky Meter app to let people report measurements from iOS devices.
You can see all of the citizen science based sky brightness measurements at the My Sky at Night website. Created by the German researchers behind Loss of the Night, the service consolidates data from all of the citizen science light pollution projects. It displays more than 93,000 measurements in countries around the world (although heavily weighted to North America and Western Europe).
You can help scientists study light pollution’s impacts by going out on a cloudless, moonless night and reporting the sky’s brightness to one of these projects. You can get even more active by supporting organizations like the International Dark-sky Association. The IDA helps communities implement safe and effective lighting policies that reduce light pollution. It also certifies International Dark Sky Places - sanctuaries, reserves, parks, and communities that preserve the darkest skies.
At a time when fewer people can even see the Milky Way span the night sky, shouldn’t we all do what we can to restore a bit of wonder to our lives?