In 2012, Professor Sara B. Pritchard came across an image that stunned her: a map of the world at night, with large swaths of darkness and intense “lightprints” of illumination.

“I realized I hadn’t seen nocturnal maps before – or globes or atlases for that matter,” writes Pritchard, professor of science and technology studies in the College of Arts and Sciences, in the introduction to her new book, “Transforming Night: The History and Science of Light Pollution” (University of Washington Press), published Sept. 22.

In the book, excerpted on Literary Hub, Pritchard charts the increase in artificial light since the development of electric lighting in the late 19th century and how and why scientists came to consider that light as pollution. She describes a massive spike in the amount of artificial light in the 21st century, with light now originating not only from below but also from a proliferation of satellites in Earth’s low orbit. It’s estimated that between 2011 and 2022 light pollution increased by nearly 10% annually.

Pritchard traces the scientific community’s response to artificial illumination – from astronomers bemoaning the obscuring of the cosmos, to conservationists worried about the “pristine” night in parks, to ecologists sounding the alarm about the impact on species and ecosystems. She also describes the rise in remote sensing and the ability to image light pollution from space, as well as the increasing interdisciplinarity of research around artificial light. Of particular importance are emergent environmental justice movements that consider the impact on communities of having too much artificial light or not enough.

The Chronicle spoke with Pritchard about the book.

Question: How has artificial light “transformed night” since the late 19th century?

Answer: Human-made illumination has altered night and associated darkness in at least four ways. It’s gotten both bigger and brighter. Its growth rate has also accelerated since the 19th century, and especially since the early 21st century. Lastly, different lighting technologies produce differently colored light. The recent adoption of light-emitting diodes (LEDs) has made, for instance, many cities’ “lightprint” whiter. Those are the broad, large-scale trends, although there is a lot of nuance at the local level.

Q: How have scientists in different fields approached nocturnal artificial light?

A: Astronomers were the first scientists to raise concerns about artificial light. Given brightening night skies, they chased darkness above to ensure the continued feasibility of ground-based astronomy by pushing into rural and remote areas, resulting in astrocolonialism. Scientists in the remote sensing community unintentionally made anthropogenic illumination on Earth perceptible from space. With a “Black Marble” image to complement Apollo 17’s “Blue Marble,” they eventually framed nocturnal light as a global and planetary issue.

Conservation scientists perceived darkness – the fundamental feature of night – as a kind of wilderness. Ecologists have emphasized the complexity of artificial light, while making clear that “night” is not synonymous with the night sky but is instead an environment in which essential ecological processes take place.

Q: How is light pollution, along with climate change, a defining feature of our era?

A: Artificial light at night is an important, yet inadequately recognized, driver of global environmental change, given its very recent history, growth rate, expanding reach, increasing brightness and the fact that we now have both ground- and space-based anthropogenic illumination. Due to its visual power, nighttime artificial light has become a symbol of the Anthropocene, yet it’s not merely a symbol. I argue it is a defining feature and marker of the Anthropocene, and specifically of what scholars call the Great Acceleration – the rapid and constant transformation of humans’ relationship with the natural world over the last 80 years.

Q: How are light issues related to environmental justice?

A: Both the overabundance of light (light pollution) and the lack of it (light poverty) are matters of justice. Many “dark-sky” activists have understandably focused on the growing problem of light pollution. Scholars have found that excessive artificial light is unequally distributed in the United States and is thus an environmental justice issue.

Yet, as of 2022, roughly one in 10 people worldwide do not have access to electric lighting. Light poverty is also concentrated in some parts of the world, including sub-Saharan Africa. Vivid visible light should not blind us to what its absence means for those communities.

Q: How should scientists and policymakers move forward?

A: Light justice offers the most promising framework. However, there is no easy, single solution. We need better lighting regulations based on the latest human health and environmental research, better lighting technologies that take advantage of new technical capabilities, and to go beyond protecting starry nights to restoring them – not only in distant, remote locales but also in cities and suburbs. In the words of the light justice movement, “everyone deserves good lighting and beneficial darkness.”

Positive change is happening, but we’re facing urgent decisions, given the new space race. If realized, the proposals to launch tens, even hundreds, of thousands of satellites into low-Earth orbit over the next decade will result in space-based light pollution across almost the entire planet. Some of these proposals have already been approved. We are talking about the transformation of night on a truly unprecedented time scale. I don’t think we should let that happen, but it will if we don’t take action now.