Artificial night lights, increasingly used by humans all over the planet and, above all, in the urbanized areas, not only illuminate the ground and the environment of our base, but send their brightness to the sky. As a result, animals lose on the one hand the darkness of the night and on the other, they see fewer and fewer stars in the sky. But this loss is greater than previously thought and is growing faster, as evidenced by data collected by the Globe At Night platform.

Scientists have so far relied on information sent by artificial satellites from Earth orbit to measure the development of light pollution. The truth is that satellites can measure the light emitted upwards, but they're not able to measure all the wavelengths generated by LED lighting, not even the light emitted horizontally. The change has come when Kyba and his teams have incorporated in their new study the information gathered in their nocturnal observations by science enthusiasts around the world. They have thus come to the conclusion that between 2011 and 2022 the average night sky has become 9.6% brighter worldwide, that is, every eight years the brightness of the sky visible to the human eye doubles.

Science has highlighted that “the advances made in lighting technology during these years have hindered the measurement of light pollution caused by changes in emission spectra. On this occasion, 51,351 people use stargazing at the spectacularity of stars to investigate the glitter change in the skies of the planet between 2011 and 2022. Thus, a decrease in the number of stars visible to the naked eye has been observed by increasing the night brightness from 7% to 10% in the human vision band. This increase is much faster than we could have deduced from satellite observations so far.”

According to previous studies, in recent years light pollution has grown by about 2% each year. These investigations used satellite data around the Earth, that is, from the space where the light was measured that came out of the atmosphere. In the new investigation they have added thousands of observers who have the information obtained upwards. These observations measure the brightness of the sky, increasing the brightness of artificial lighting. Satellites vertically measure light emitted from Earth into space and are blind to the blue component of light. On the contrary, the observation of the brightness of the sky by the voluntary population from the ground also includes the light transmitted horizontally and indirectly, such as the leakage of building facades, electronic screens and windows. And in addition, the human eye perceives light in a wider spectrum than satellites. These factors produce the brightness of the sky and are valid predictors of biological impact. “Like the human eye,” Kyba said, “is sensitive at night at shorter wavelengths, LED lights greatly influence our perception of the brightness of the sky.”

In the last 150 years, man has greatly transformed nature. It is becoming increasingly evident that the loss of night darkness on much of the planet is one of the most profound changes. As stated by the authors of the study of Science, the nature of the night sky today is very different from the times when life and civilization developed, and it is clear that light pollution continues to increase steadily. Christopher Kyba, a researcher at the Geocience Research Centre in Germany and the lead author of the study, states that "At that rate, a person born in a place where 250 stars could be seen will only see 100 by the time he turns 18."