Northwestern University researchers have expressed concern about two proposals currently under review by the Federal Communications Commission (FCC) that could significantly increase artificial light at night. The scientists warn that these projects may disrupt sleep, circadian rhythms, and seasonal biological cycles in humans, animals, and plants.
One proposal comes from startup Reflect Orbital, which plans to use large mirrored satellites to redirect sunlight to Earth during nighttime hours. While the goal is to provide additional illumination for solar farms, experts note that this technology could unintentionally expose entire cities to daylight-level brightness after dark.
A second proposal by SpaceX involves an orbital data center system with up to one million satellites in orbit. The sheer number of satellites has the potential to scatter sunlight across the sky, increasing overall sky brightness at night.
Researchers from Northwestern’s Center for Circadian and Sleep Medicine and Center for Sleep and Circadian Biology (CSCB) have outlined possible negative consequences if artificial illumination at night increases on a global scale.
Martha Hotz Vitaterna, research professor of neurobiology at the Weinberg College of Arts and Sciences and co-director of CSCB, stated: “Earth was turning on its axis — causing night and day — when life began. All life forms are adapted to these cycles. Disruption by light at night threatens the well-being of not only humans but the plants and animals with which we share the planet.”
Fred Turek, Charles and Emma Morrison Professor of Neurobiology at Weinberg and co-director of CSCB, highlighted how changes in nighttime lighting can affect natural seasonal behaviors: “Plants and animals use the length of day to predict and prepare for seasonal changes. Light at night makes the short days of winter seem like the long days of summer. For example, in the 1930s, people observed that London’s streetlights affected birds’ seasonal reproduction. Light pollution at night disrupts vital seasonal rhythms, such as migration, growth or reproduction.”
Kristen Knutson, associate professor of neurology (sleep medicine) and preventive medicine at Northwestern University Feinberg School of Medicine added: “Circadian rhythms are present in all types of organisms, ranging from bacteria to plants to animals, including humans. These rhythms synchronize physiological function to the natural light-dark cycle, which is important for overall well-being. Light at night will disrupt these rhythms, which can impair health and well-being.”
The researchers emphasize that both human health issues—such as disrupted sleep—and broader ecological impacts could result if increased nighttime illumination becomes widespread due to satellite technologies.
