Few people have heard of light pollution, but it has various inconveniences that affect citizens in their pockets, rest and quality of life. 40 percent of energy costs could be saved if the light were dosed and directed where and when it matters.
What is light pollution?
Light pollution (PL) is the effect produced by misdirected outside light, which is directed upwards, or sideways, rather than illuminating the ground and intended areas. In most cases it results from improperly designed or incorrectly installed lamps and projectors, which emit light beyond their target, without any useful effect. They often even emit light into the clouds. And that light also pays for itself. Many people, in order to be able to sleep, have to close the blinds because the street lamp lets light in through the window, even when it is above that lamp!
In the case of public lighting, we know that it is citizens who pay the bill for wasted energy. Some say that light pollution is inevitable, constituting an indicator of progress and modernity, but this is not true. It is the result of poor planning of lighting systems, not the need for lighting itself, the usefulness of which we have not discussed. The consequences of this immense waste also have other indirect costs: part of this energy comes from thermal power stations, which themselves pollute the environment, which thus have to consume more resources, releasing more carbon dioxide into the atmosphere, which aggravates global warming.
What can be done to improve the situation?
We do not suggest turning off the lights or walking in the dark. It is possible to optimize public lighting while still maintaining good levels of lighting on the ground: where it matters. There are luminaires designed from scratch to minimize light pollution.
To change the current state of chaotic lighting it is necessary for citizens to protest and for municipalities to choose suitable lighting equipment. A more efficient and well-directed light bulb (see figure) can produce the same level of light, consuming much less. Saving 40% is not irrelevant: it's millions of euros a year.
The figure shows the light emission of different types of lamps (light fixtures), where model A is the worst and C is the best. The optimal light beam is that of AREA 1. The beam indicated in AREA 2 is uncomfortable and without relevant lighting; Lighting in AREAS 3 and 4 is inadmissible. In fact, the light beams in areas 2, 3 and 4 should be redirected, by reflection (and refraction), into the optimal area 1.
How to assess light pollution in a location
A good indicator of light pollution in a location is the abundance of stars visible to the naked eye. The more stars you see, the less light pollution. Many young people no longer recognize the stars and constellations. If nothing is done, the tendency will be to make things worse. It is necessary to raise public awareness of the harmful effects of light pollution on the beauty of the night sky, which is a World Heritage Site and one of the greatest wonders we can contemplate.
Text, layout and photography by Guilherme de Almeida
Science in the Regional Press – Ciência Viva
To know more:
Guilherme de Almeida – “O Céu nas Pontas dos Dedos”, 1st Edition, Plátano Editora, 2013.
(book pack+multifunctional celestial planisphere)
Guilherme de Almeida and Pedro Ré — “Observar the Deep Sky” (Chapter 3), Plátano Editora, 2nd Edition, Lisbon, 2003.
See the article more developed e a companion article.
Guilherme de Almeida
Guilherme de Almeida was born in 1950. He has a degree in Physics from the Faculty of Sciences of Lisbon and was a professor of this subject, having included Astronomy in his university education. He gave more than 80 lectures and communications on Astronomy, astronomical observations and physics, in schools, universities and at the Lisbon Astronomical Observatory. It uses telescopes but defends the primacy of knowledge of the sky with the naked eye before the use of observation instruments.
He has written more than 90 articles on Astronomy and Physics. He is the author of eight books: International System of Units; Physics-Mechanical Items and Problems (co-author); Introduction to Astronomy and Astronomical Observations (co-author); Roadmap to Heaven; Observing the Deep Sky (co-author); telescopes; Galileo Galilei; Heaven at Your Fingertips. The work Roteiro do Céu was published in English, under the title “Navigating the Night Sky (Springer Verlag–London). The book Galileo Galilei is also published in Castilian and Catalan.
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