Artificial light is changing the night on the ground and increasingly in orbit, a Cornell researcher argues in a new book that examines the science, history and uneven effects of light pollution.
Sara Pritchard, a professor of science and technology studies, published “Transforming Night: The History and Science of Light Pollution” on Sept. 22 through the University of Washington Press. The book traces human-made illumination from the spread of electric lighting in the late 19th century to today's LEDs and growing numbers of satellites in low-Earth orbit.
Brighter skies affect science and ecosystems
Pritchard told the Cornell Chronicle that artificial light has grown in reach and brightness, accelerated especially in the early 21st century and changed color as lighting technology evolved. LEDs, for example, have given many cities a whiter nighttime glow, though conditions differ from place to place.
The Chronicle cited an estimate that light pollution increased by nearly 10% annually between 2011 and 2022. That is a broad estimate presented in the book announcement, not a measurement of the Finger Lakes or a forecast that the same rate will continue.
Astronomers were among the first researchers to object to brightening night skies because artificial light interfered with ground-based observation. Pritchard's account also examines how satellite imagery made the global extent of illumination visible, how conservationists framed darkness as a quality to protect and how ecologists study effects on species and ecosystems.
The ecological question is broader than whether people can see stars, she said. Night is an environment in which important biological processes occur, and artificial lighting can alter it even where the sky is not the main concern.
Pritchard began thinking about nighttime maps after seeing one in 2012. Her book considers how scientists came to describe some artificial illumination as pollution and how different disciplines have measured and interpreted the change. It is a historical and scientific synthesis described in an interview, not a newly reported local experiment.
Too much light and too little
Pritchard argues that lighting policy also has an equity dimension. She said excessive light is distributed unevenly in the United States, while some communities lack enough electric lighting for daily needs and safety. The Chronicle noted an estimate that about one in 10 people worldwide lacked access to electric lighting as of 2022, with shortages concentrated in some regions, including sub-Saharan Africa.
That distinction matters to her proposed idea of “light justice”: reducing harmful over-illumination without treating darkness as a universal answer. Better lighting technology, regulations informed by health and environmental research, and efforts to restore dark skies in cities and suburbs as well as remote places are among the directions she identified.
The book also addresses the prospect of much larger satellite constellations. Pritchard warned that proposals for tens or even hundreds of thousands of low-orbit satellites over the next decade could create light pollution visible across much of the planet if realized. Those numbers describe proposals, not satellites already launched, and the source does not quantify a specific effect over Ithaca.
She called for decisions on lighting and satellite deployment before further changes become entrenched. Her assessment is that technology has made night brighter and more complex, but communities still have choices about how much light they use, where they direct it and whose needs the policies serve.
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