The dark sky is a natural resource, and too much light is polluting it Premium

A 2016 study reported that a fifth of India’s people experience skyglow that would keep the Milky Way galaxy out of sight.

On December 14, 2022, the district administration of Ladakh designated six hamlets within the Changthang Wildlife Sanctuary a “dark-sky reserve” – an area whose skies were free of light pollution. The designation meant that the reserve had a responsibility to keep the skies dark, particularly for the astronomical observatories located in the area.

When SpaceX’s Starlink constellation of small satellites began to obscure the view of ground-based telescopes around Earth, the idea of the sky as a natural resource capable of being polluted became popular. These incidents also rendered the absence of a global treaty to reduce light pollution more conspicuous.

But while authorities safeguard telescopes’ access to dark skies by actively lowering light pollution around their sites, the night is actually becoming brighter in almost the rest of the world thanks to ‘skyglow’, with significant ecological, health and cultural consequences.

How bad is light pollution?

In a new study, researchers from Germany and the U.S. analysed a global database of what the dimmest star visible from a particular location is; the database had more than 51,000 entries submitted by citizen scientists. They found that non-natural light had increased the brightness of the artificial glow of the night sky, or skyglow, by 9.2-10% every year between 2011 and 2022.

Specifically, they reported that skyglow had brightened around 6.5% over Europe, 10.4% over North America, and 7.7% over the rest of the world.

The finding is significant because it disagrees with satellite-based data, which has indicated that the rate of increase has been around 2% per year. According to the new study, the discrepancy is probably the result of the satellites being unable to ‘sense’ blue light emitted by LEDs and to study light that is emitted parallel to the ground.