Light pollution occurs when light from anthropogenic (man-made) sources is emitted in excess — at the wrong time, intensity direction, or color temperature.
The sources of this abnormal type of pollution are primarily lighting installations that are poorly designed, defectively constructed, and poorly operated.
Why should we stop pointing lights into the sky?
One of the negative effects of this phenomenon is the continuing deterioration of conditions for astronomical observations. The more light that enters the atmosphere, the less light from space the research instruments can record.
However, it is not necessary to refer to science to demonstrate the disastrous impact of light pollution. The length of the day (the part of the day illuminated by the sun’s rays) is crucial to the activation of flowering processes and the growing time of individual plant species.
Changes caused by anthropogenic light also affect the animal world. Some can be disoriented, limited in their activity, disrupting relationships within a species, but also interspecies balance. Other animals in a brighter environment may do better, such as improving hunting efficiency and lengthening hunting time, which may benefit representatives of specific species. However, in the bigger picture, it disrupts the balance of existing ecosystems. An adequate term has already emerged in science – the ecological niche of the light night. 
Humans are the main victims
The Milky Way belt in the night sky is invisible to more than ⅓ of humanity, including around 60 percent of the citizens of European countries and nearly 80 percent of North American territories. According to studies, only 1 percent of the inhabitants of these two continents live under a light pollution-free sky. 
In many urban areas, it is impossible to observe even a lone star at night. This and the above information point to the cultural aspect of light pollution – the view of the night sky for many of us is almost exotic.
Above all, however, human health suffers because of the never-falling night. Problems affect the human psyche – statistics from the most illuminated areas indicate a higher percentage of people with concentration disorders and depression. Defects also impact the physiological sphere – the biological clock and diurnal rhythm are disrupted, closely followed by sleep disorders and consequent disturbances in metabolic processes. 
Night sky over Poland is getting “dirtier”. First such report
The Light Pollution in Poland report prepared by the Light Pollution Think Tank (LPTT) provides a diagnosis of the degree of light pollution in Poland in 2022 and is the first study of its kind. The LPTT is an organization that brings together scientists affiliated with the such as the Cracow University of Technology, the University of Wrocław or the Space Research Institute of the Polish Academy of Sciences.
The conclusions of the report are as clear as they are alarming. According to the authors, the phenomenon of light pollution is widespread in Poland and is constantly growing. Based on data collected in 2022, the night sky across the country was on average 147 percent brighter than the natural sky. In some cities, the same value reaches several thousand percent.
Satellite observation was only possible with cloudless skies. Depending on the location, this was from 30 to as many as 120 nights over the course of a year.
Tackling the problem is hampered by the fact that light pollution is not defined as a threat in Polish law and there is no state institution to monitor the phenomenon.
The year 2022, which the report describes, was the brightest in the history of measurements to date. To indicate trends and possible future scenarios, the scientists analyzed data from the VIIRS instrument. It is a device mounted on the NASA-administered Suomi NPP satellite, which has been operating in orbit since 2012.
The graphs up to 2019 show a strong upward trend, which broke down with the outbreak of the pandemic. The reversal of the downward trend came in 2021, and 2022 not only equalled the highest rates of 2019, but also surpassed them. 
Fig 1. Brightness of night lights in the Polish territory in 2012-2022. Prepared by the Light Pollution Think Tank based on observations of the VIIRS instrument of the SNPP satellite, LPTT 2023.
Researchers associated with the LPTT have adopted an upward light emission index known as the ‘sum of lights’ (SOL) to numerically describe the value of lights. This is the area sum of the radiance values in a given territory, calculated for the whole country and all Polish municipalities. The said radiance is a physical quantity defining the intensity of the light of a given area in space, which is measured by the VIIRS from a distance of almost 900 km.
Nothing shines like a greenhouse
In 2022, only 5 municipalities “produced” as much as 10 percent of the total number of lights for the entire area of Poland. The undisputed leader is, of course, Warsaw (nearly 4 percent), followed by Łódź, Kraków, Gdańsk, and Poznań. Compared to the national average, the sum of lights in the capital was almost 100 times higher than in the average Polish municipality.
In addition to urban agglomerations, road junctions are responsible for much of the light pollution, but no individual objects radiate as much light into the sky as greenhouses.
The brightest places in Poland in 2022 were:
- Goczałkowice-Zdrój (Śląskie Voivodship);
- Brzezie (Małopolskie Voivodship);
- Boguchwała (Podkarpackie Voivodship);
- Mączniaki (Wielkopolskie Voivodship);
- Nowe Izdebno (Mazowieckie Voivodship).
Greenhouse facilities have been located in these localities (the report gives exact geographical coordinates). Each of them emits more light into the sky than even the brightest point in Poland located within city limits – they shine brighter than Defilade Square in Warsaw. 
What can we do? Rescue plan for the night sky over Poland
The report’s creators believe that an effective fight against excessive artificial lighting requires changes in Poland’s legal regulations. At the moment, there are no proper definitions, and there are no specified light emission standards.
Several documents address the issue of light pollution in one way or another, including a decree of the Minister of Infrastructure describing lighting standards for public roads. However, their purpose is not to protect the night sky, but safety and visibility for traffic participants.
However, all guidelines appearing in the national legislation are not mandatory; rather, they are guidelines and recommendations, but failure to enforce them is not fraught with consequences.
Currently, countering excessive light is the domain of grassroots initiatives and some local governments. These are yielding results, but only at the local level and at an insufficient pace.
Some solutions have been developed around the world to reduce light pollution without sacrificing occupant comfort and visibility, one widespread example being flat shades over streetlamps. Significant funds for such initiatives are allocated by Australia, among others, but examples can also be found much closer to Poland. In the first months of last year, a relevant regulation was signed by the Czech environment minister. 
However, a real change and improvement of the situation will be possible only after the adaptation of Polish law with a simultaneous increase in public awareness of the negative effects of light pollution. 
 Edroga.pl, Light also pollutes the environment, https://edroga.pl/ochrona-srodowiska/swiatlo-tez-zanieczyszcza-srodowisko-060214988, (accessed on 10.01.2024)
 Falchi F., The new world atlas of artificial night sky brightness, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4928945/, (accessed on 11.01.2024)
 Light pollution in Poland. Report 2023., Light Pollution Think Tank (2023), Published by the Space Research Center of the Polish Academy of Sciences, Warsaw, www.lptt.org.pl
 Radio Prague International, New rules on light pollution take effect in Czechia, https://english.radio.cz/new-rules-light-pollution-take-effect-czechia-8776532, (accessed on 17.01.2024)