Humans have been looking at the night sky since ancient Mesopotamia and Babylon, but artificial light is making it harder to see the stars.
A study published in Nature found that the sky became about 16% brighter between 2014 and 2022. Researchers at the University of Connecticut used NASA satellite data and reported the findings in a USA Today report.
The United States has the brightest night skies on Earth, followed by countries such as China, Canada, India, and Brazil. Lead researcher Zhe Zhu said that instead of simply getting brighter over time, Earth’s night lighting is constantly changing as cities grow and shift.
Light pollution is measured using the Bortle scale, which ranks sky brightness from Class 1 (very dark skies) to Class 9 (extremely bright city skies). Most people in cities like New York and London live under the highest levels, where only the brightest stars and planets are visible.
Scientists warn that excess artificial light can affect sleep by disrupting melatonin, a hormone that helps control the body’s sleep cycle. Some studies also suggest possible links to health risks, including a slightly higher chance of breast cancer from long-term exposure.
Wildlife is affected too. Animals like birds and sea turtles rely on natural light for navigation, but artificial lighting can confuse them. Satellites in orbit also add to the problem by increasing sky brightness and reducing visibility of space.
Even high mountain locations are affected. Photographers report that light pollution can be seen from far away cities, making it harder to capture clear images of the Milky Way. If light pollution continues to rise, fewer people may be able to see a truly dark night sky.
