KTU researcher: can light pollution be controlled?

Florian Rabitz is a Chief Researcher in the KTU Faculty of Social Sciences, Arts and Humanities. 

Our skies are not what they used to be. Artificial light sources are increasingly making the night brighter. The thousands of satellites that are being launched every year exacerbate this problem by reflecting light. The loss of dark skies is rapidly becoming a major challenge for the global environment but also for space observation.

When human astronomy began in ancient Mesopotamia some five thousand years ago, humans were almost five thousand years away from inventing the light bulb. While we cannot know for sure, the skies over Nineveh, Ur, or Babylon must have been quite different from today. Artificial light sources and reflective space objects, mostly in the form of the satellite mega-constellations that we need for watching Netflix and surfing the internet while on an airplane, increase the brightness of the night sky by about 10% per year.

And things might get worse soon: Commercial operators are exploring the option of launching thousands of reflective mirrors into Low Earth Orbit for redirecting sunlight to the surface to illuminate the night, allowing for 24-hour solar power or enhanced nighttime fisheries.

This is not just an aesthetic issue. The loss of dark skies is increasingly interfering with ecosystems due to the disruption of night-day cycles. Light pollution can change species migration patterns or interfere with the navigation of insects and birds, causing wider ripple effects due to changes in the structure of food webs. The growth cycles of plants and trees can also be negatively affected, for instance by making them bud earlier in the year and thus exposing them to damage from winter temperatures.

Light pollution also interferes with science. Optical telescopes that are used for peaking deep into space have long exposure times that make them susceptible to satellite streaks, essentially long bright lines that crop up on images. But this is not simply a problem of space observation. Light is essentially information: The light that reaches our planet, and that can be observed with ground- or space-based telescopes, can offer insights into the very early stages of our universe. As light pollution increases, this information is getting drowned out. Jointly, artificial lighting and satellite mega-constellations are permanently curtailing what we can learn of the universe.

The problem of light pollution has been gaining some regulatory traction in recent years. Various communities, for instance in parts of Europe, North America, or South America, have adopted rules for limiting night-time illumination. Alternative satellite designs are being explored to reduce reflectivity, with solutions potentially as simple as painting them black.

The International Dark Skies Association is a non-governmental organization that protects and certifies dark sky reserves and similar places. Internationally, the United Nations Committee on the Peaceful Uses of Outer Space has recently begun technical discussions on dark skies, a very welcome step towards potentially devising a robust set of international rules.

Yet it is also clear that the problem of light pollution highlights the need for deeper, structural changes in urban planning and in satellite infrastructures. Glaring urban lights and thousands of roaming SpaceX satellites for permanent connectivity are the creature comforts of modern civilization. But something is being lost in the process.

Florian Rabitz, Inga Popovaitė and Vidas Vilčinskas are researchers at KTU’s Faculty of Social Sciences, Arts and Humanities working on the project “The Transnationalization of Outer Space”, funded by the Research Council of Lithuania (project no. P-MIP-23-234).