Light Pollution Trial Reveals Key Role of Private Light Sources

The streets and squares of Brno were plunged into darkness for several hours overnight on April 10th, as part of an experiment which aimed to find out more about light pollution in the city. Initial results indicate that regulation of light from private buildings could be the most effective way to reduce light pollution. Photo Credit: Freepik / Illustrative Photo.

Brno, Apr 20 (BD) – In the early hours of the morning on Saturday, April 10th, public lighting throughout Brno was switched off for several hours, in order to find out more about the extent and source of light pollution in the city. Initial results indicate that although public lighting does create light pollution, the regulation of light from private buildings could have a much more significant effect.

“By turning off the streetlights, brightness was reduced by about 45%. It is not much, but we must also consider that public lighting is regulated. It turned out that the amount of night light is more influenced by sources outside of the Brno city administration. We would like to focus on these in the next measurement,” said Petr Baxant from the Faculty of Electrical Engineering and Communication Technologies at the Brno University of Technology (BUT).

The aerial photography taken during the experiment was colored in pseudo-colors, a scale used to measure brightness. The human eye is sensitive to brightness and perceives contrasts in particular. The brightness of a computer monitor or telephone display is in the order of hundreds of candelas – the unit of luminosity of the source – per square meter, while the surface of the full moon has a brightness of about 3500 cd / m². As Baxant pointed out, a bright moon can interfere with the measurement, but the brightness analyzer built by the research team allows the moon and its luminous effect to be replaced by background. Such a measurement would not be possible with a conventional luxmeter.

“Saturday’s attempt was truly unique. We were ready and we managed it. We can now start the next stage of research. The public might think that these are small numbers and may not be interested in the topic. We are probably searching in vain for a truly zero-light background, or rather what the stars and natural light from the planet’s atmosphere create for us. However, we would like to at least get closer to it and find out how we are doing in the Czech Republic and other places on the planet,” said Baxant.

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