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Cambridge University Science Magazine
For Millenia, people have looked to the stars for navigation and inspiration. Unfortunately, it’s becoming harder to see stars after sunset, as the sky is lit up by ‘sky glow’: a form of light pollution created when artificial light is scattered in the atmosphere. Sky glow is steadily increasing as populations expand and cities become illuminated, but this is difficult to measure because satellites rely on outdated technology which can’t properly account for the increasing use of LEDs over traditional incandescent bulbs.

A recent study, however, has quantified increases in global sky glow using over 50,000 observations made by citizen scientists between 2011-2022. The Globe at Night project asked volunteers to match a set of star maps to the night sky in their location, estimating the ‘naked eye stellar visibility’. The results showed that the decreasing star visibility over the observation period was equivalent to sky glow increasing by up to 10% per year – around 5 times faster than previous satellite estimates.

Sadly, it’s not just future star gazers who are affected by light pollution, as it can seriously impact ecosystems and organisms whose behaviours are intrinsically linked to the cycles of night and day. Migratory birds are attracted to artificial light at night, and can easily become disoriented and end up circling illuminated areas. This leaves them fatigued and can result in them arriving at their migration destination too late, thus missing out on vital resources. Light pollution has also been suggested as an overlooked cause of declining insect populations, as it negatively affects insects’ movement, foraging, and resting patterns. Fortunately, simple changes to technology and light use can prevent these devastating impacts. Scientists and policymakers have suggested shielding artificial lights, using less harmful wavelengths to control scatter, or including sensors or timers to limit light use.

Article by Lizzie Knight.

Artwork by Barbara Neto-Bradley.