Light pollution: what is it and how can we mitigate it?

Currently there are adults, young people, adolescents and infants who live in large cities, who have never in their lives been able to observe the Milky Way.

The light of cities eats up that of the stars at an incredible rate.

Observations carried out between 2011 and 2022 by volunteers from around the world through the Globe at Night citizen science platform confirmed that the stars are becoming more difficult to see due to a rapid increase in light pollution.

According to results published in the journal Science, the brightness of the sky has increased by 10.4% each year in North America. This annual increase is equivalent to a doubling of sky brightness in less than 8 years.

What does light pollution mean?

To understand it better, a person who during his childhood could have 250 stars, 18 years later could only appreciate 100 of these celestial bodies, according to the research team’s estimates.

«It seems to me that we have already lost the dark sky and our generation has not had it. A good proportion of people live in urban places and do not see the Milky Way, let alone daily, many people have not seen it in their entire lives, “explains in an interview with Dr. Alberto Carramiñana Alonso, senior researcher at the National Institute of Astrophysics, Optics and Electronics (INAOE).

All of this study confirms the accelerated growth of the problem of light pollution. This phenomenon is defined by the Institute of Astronomy (IA) of the National Autonomous University of Mexico (UNAM) as “the luminous flux from artificial light sources that cause the brightness of the night sky to increase, decreasing the visibility of celestial bodies.” ».

The main source of pollution of this kind is urban lighting, says Dr. Carramiñana. In an attempt to reduce the cost of lighting cities, the type of luminaires has evolved.

We changed from incandescent lamps to sodium vapor luminaires; cheaper and which in turn illuminate the sky less. However, with the advent of LED light, costs are further reduced, but the illumination of the sky increases, explained the INAOE researcher.

In 2007, the United Nations Educational, Scientific and Cultural Organization (UNESCO) recognized the right to dark skies as an implicit right in the conservation of the cultural and natural heritage of future generations, in accordance with the Declaration on the Defense of the Night Sky and the Right to the Light of the Stars.

However, in Mexico (and the world) “people can only experience a truly dark sky by going out into the countryside or into the mountains; increasingly scarce and remote sites”, points out Carramiñana.

For the astrophysicist, one of the first measures to achieve the preservation of dark skies is to “become aware at a social level that this is a problem, but also that there are ways to address it.”

He clarified that as the conversation on the subject expanded, it was easier to present initiatives to decision makers.

What damage does light pollution cause in the environment?

The loss of dark skies has several consequences and go beyond celestial observation. According to information from the IA, this phenomenon has consequences for ecology, energy consumption, cultural heritage, health and even tourism.

For example, the UNAM Institute of Astronomy explained that a significant number of bird species determine when it is time to emigrate based on the number of daylight hours, in addition to the ambient temperature.

Also, some reptiles depend on dark nights to reproduce, as darkness provides protection for young from predators.

What can I do to reduce light pollution?

Make a difference and follow some suggestions from the Institute of Astronomy of the UNAM to take care of the environment and avoid light pollution.

Does this require being enlightened? Use light only where it is absolutely necessary.

Use motion detectors so lights turn on only when needed. You will save up to 90% on your electricity bill.
Use only the amount of light required.

Direct light only where you need it.

If you are only going out into the dark for a moment, chances are you don’t need light to see.

Inform more people. The more people learn about the economic, environmental and astronomical benefits of reducing light pollution, the sooner and better we will see thousands of stars in the sky.