Scientists Warn Reflective Satellites Could Disrupt Global Sleep and Ecosystems
Proposals to deploy reflective mirrors and up to one million additional satellites in low Earth orbit could have far-reaching consequences for human health and ecosystems worldwide, according to leading sleep and circadian rhythm researchers. Presidents of four international scientific societies representing approximately 2,500 researchers from more than thirty countries have raised serious concerns in letters to the United States Federal Communications Commission.
Regulatory Considerations and Corporate Plans
The regulator is currently considering plans by the startup Reflect Orbital to illuminate parts of the Earth at night using reflective satellites, alongside applications from SpaceX that could dramatically expand satellite numbers in low Earth orbit. The proposed scale of orbital deployment would represent a significant alteration of the natural night-time light environment at a planetary scale, stated the presidents of the European Biological Rhythms Society, the Society for Research on Biological Rhythms, the Japanese Society for Chronobiology, and the Canadian Society for Chronobiology.
They emphasized that altering the light-dark cycle could disrupt biological clocks that regulate sleep and hormone secretion in humans and animals, migration in nocturnal species, seasonal cycles in plants, and the rhythms of marine phytoplankton that underpin ocean food webs. The researchers have urged regulators to conduct a comprehensive environmental review and establish limits on satellite reflectivity and cumulative night sky brightness.
Scientific Concerns and Environmental Impact
Professor Charalambos Kyriacou, a geneticist at the University of Leicester and president of the European Biological Rhythms Society, expressed grave concerns: "We're saying, please think before you go through with this, because this could have global implications for things like food security. Plants need the night. You can't just get rid of it."
Reflect Orbital aims to use satellites equipped with large reflective mirrors to redirect sunlight onto areas approximately five to six kilometers wide "on demand," with brightness adjustable from full moon to full noon levels. The company claims the system could extend solar energy production into the evening and provide lighting for construction projects, disaster response, and agriculture, with illumination delivered only to locations approved by local authorities.
SpaceX's Ambitious Satellite Network
Meanwhile, SpaceX has proposed launching up to one million satellites to create a massive solar-powered computing network in orbit designed to run artificial intelligence workloads. The company asserts the system could reduce the energy and cooling demands of terrestrial data centers. However, scientific studies have already demonstrated that the existing number of satellites in orbit has increased diffuse night sky brightness, or sky glow, by roughly ten percent.
Ruskin Hartley, the chief executive and executive director of DarkSky International, a non-profit organization focused on protecting natural night skies, which has also written to the Federal Communications Commission, warned: "While ideas like mirrors on satellites beaming 'sunlight on demand' to Earth or mega-constellations of up to one million satellites for AI data centers may sound like science fiction, these proposals are very real."
Technical Analysis of Night Sky Brightness
Dr. Miroslav Kocifaj of the Slovak Academy of Sciences in Bratislava explained that satellites affect the night sky in two primary ways. Individual satellites can leave streaks in telescope images, while sunlight reflected by satellites and debris brightens the sky overall. His modeling suggests these objects already add between three and eight microcandela per square meter to night sky brightness. By 2035, he predicts this could rise to between five and nineteen microcandela, approaching the threshold astronomers have established for preserving naturally dark skies.
While this additional brightness remains far below that of moonlight, Dr. Kocifaj stated: "What I can say with confidence is that the phenomenon is real, that it is global and cannot be escaped by moving to a more remote location, and that it will increase substantially over the coming decade if current trends in satellite launches and debris generation continue."
Biological Sensitivity to Light Changes
Professor Tami Martino of the University of Guelph, who serves as president of the Canadian Society for Chronobiology, highlighted that when considering impacts on life on Earth, "the real question is not brightness compared to moonlight, but whether biological systems can detect the change."
She elaborated: "Circadian systems are sensitive to light levels far below what humans typically perceive as bright. If the night sky becomes permanently brighter, the consequences could ripple through ecosystems in ways we do not yet fully understand."
Health Implications and Global Concerns
A separate letter from the presidents of the World Sleep Society, European Sleep Research Society, Sleep Health Foundation, Australian Sleep Association, and Australasian Chronobiology Society emphasized that "circadian disruption is not mere inconvenience; it is a physiological mechanism driving major adverse health consequences."
The letter added: "We do not argue against space innovation," stating that altering the night sky should be treated with the same seriousness as other planetary-scale environmental changes, such as climate change and ocean acidification. "The alternation of light and dark is not a trivial background condition. It is one of the oldest organizing principles of life on Earth."
Potential Risks and Future Scenarios
Hartley further warned that as satellite numbers grow, fast-moving artificial objects could become a dominant feature of the night sky. "There could be times and places where satellites outnumber the visible stars," he cautioned. Many birds and some insects navigate using the stars, and the human experience of the night sky could also be profoundly altered.
Reflect Orbital's plans would introduce a new form of light pollution with largely unstudied consequences, including potential public safety risks, Hartley noted. "As these beams move across the landscape, there is the possibility of intense glare or blinding flashes, particularly if systems malfunction or drift off target. These are exactly the kinds of risks that need to be carefully studied, which is why DarkSky is calling for a full environmental review before proposals like this move forward."
Reflect Orbital declined to comment on the concerns raised, while SpaceX did not respond to requests for comment regarding the scientific warnings about their satellite expansion plans.
