A team of scientists conducted an experiment by changing the brightness of street lights in the city of Tucson, USA, and observing how it
“When sensors and control systemsinstalled throughout the city, it allows you to change the way the city works and then measure the impact that this change has on the environment, even from space, ”he said.
Within 10 days in March and April 2019Tucson officials tweaked the brightness settings for about 14,000 of the city's 19,500 streetlights. Typically, most street lights in a city turn on 90% of the maximum possible illumination and dim to 60% at midnight. During the experiment, the city dimmed the lights up to 30% on some nights and brightened them up to 100% on others.
A street scene in Tucson under a variety of street lighting conditions with the lighting operating at 90% (left) and 30% (right) full power. Credit: Photo by John Barantin.
City lights were observed from an American satelliteSuomi National Polar-orbiting Partnership (NPP), which is famous for its global maps of light at night. The satellite snapped cloudless images of Tucson for four nights during the test and two other nights with "normal" lighting after the test. Comparing the brightness of the city on six different nights, the researchers found that on a typical night, only 20% of the light in Tucson's satellite images comes from streetlights.
According to study co-author Dr. JohnBrentina from the International Dark Sky Association, the results are important for the environment. In a second experiment conducted at the same time, Barentin and his colleagues demonstrated that Tucson's street lighting accounts for no more than 14% of the artificial light in the night sky found at its zenith. This confirmed the assumptions of scientists that other sources of light pollution are responsible for most of the brightness of the sky above the city.
In addition, a unique experiment reducedlight pollution. The results were even visible from space. Of course, only for a few days… However, if city authorities pay attention to the results of the study, human impact on the environment will decrease. After all, light pollution not only interferes with astronomical observations, but also changes the biorhythms of living beings.
“Taken together, these studies show thatin a city with well-designed streetlights, most of the light emission and light pollution comes from other sources, such as illuminated signs, facades or sports grounds, ”emphasizes Barentin. The authors are confident that local and national authorities need to think about more than street lighting in an effort to reduce light pollution.
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