Even if we are talking about kilometers away from big cities, the sky is getting brighter and brighter due to light pollution.
It is logical that in big cities the visibility of the night sky has been clouded by a large amount of artificial lighting, but the atmosphere acts like a reflective bubble, and the glare of light pollution is spreading around the world, even in the darkest parts of the planet. Wherever seekers of nocturnal landscapes plunged in complete darkness look, they can see the flashes of artificial luminaires, even if we are talking about kilometers away; the sky is getting brighter and brighter.
As early as 1973, astronomer Kurt Riegel had warned that light pollution was rapidly changing the appearance of the night sky. Since then, it has been known that artificial light is capable of profoundly damaging ecosystems, especially when it comes to animal species that use darkness as a means of survival or fireflies.
Today the trend continues dangerously in that direction, according to new research that shows that the night sky is getting brighter at an accelerating rate and much faster than previously thought. It is currently impossible to observe the faintest stars in the night sky, as they are disappearing as light pollution increases.
To reach this conclusion, the researchers used 50,000 citizen scientists from around the world to compare their stargazing with maps of starry skies with varying degrees of light pollution. Physicist Christopher Kyba, of the German Research Center for Geosciences, said the results indicate that the night sky has become approximately 7% to 10% brighter each year in the period from 2011 to 2022.
Kyba and his team explain that the percentage is equivalent to the night sky doubling in brightness in less than eight years and quadrupling in 18 years. Put in context, someone born under a night sky with 250 visible stars would see just over 50 stars in the night sky by the time they reach the age of 18.
Light Pollution Worsened by LEDs
The authors of the researchers suspect that while light pollution was already a problem before the LED era, the introduction of LEDs has worsened the situation.
These types of lights are designed to emit much more powerful brightness than incandescent bulbs with shorter wavelengths. While the increase in light is already a problem per se, the short wavelengths of LEDs have a greater scattering capacity over the atmosphere than conventional lights. The consequence is a large luminous haze that covers the entire planet and prevents the night sky from darkening completely.
Previous estimates based on satellite measurements of planetary light are completely eclipsed by the new results. LEDs are likely the variable that triggered the brightness percentages from 2.2% per year to 7% per year in this latest research because satellites are not capable of detecting wavelengths below 500 nm, and LEDs are short-wave light emitters.
The results lead us toward a reflection on the immeasurable amount of light we use to illuminate every corner of cities. “Looking at the images and videos from the International Space Station of the Earth’s night hemisphere, people are usually only surprised by the ‘beauty’ of the city lights, as if they were lights on a Christmas tree. They do not perceive that these are images of pollution,” said Fabio Falchi and Salvador Bará, physicists and dark sky advocates.
The physicists finish off with a profound analogy that makes us think about the damage we do to the planet in our eagerness to illuminate everything in our path: “It is like admiring the beauty of the rainbow colors produced by gasoline in water and not recognizing that it is chemical pollution.”
Story originally published in Spanish in Ecoosfera