Satellites threaten sleep, ecosystems: scientists sound alarm

The relentless march of space innovation may be coming at a steep cost to life on Earth. A coalition of international scientists is urgently warning that plans to blanket low Earth orbit with reflective mirrors and a staggering million new satellites could disrupt everything from human sleep patterns to the delicate balance of ocean ecosystems – a prospect they say demands immediate and rigorous regulatory scrutiny.

A planetary-scale disruption of darkness

The concerns, voiced in letters to the US Federal Communications Commission (FCC), stem from proposals by Reflect Orbital to use mirrors to beam sunlight onto Earth’s surface, and by SpaceX to deploy a colossal network of satellites intended for AI processing. The sheer scale of these projects represents, as the presidents of four prominent scientific societies put it, “a significant alteration of the natural night-time light Environment at a planetary scale.” These societies, representing over 2,500 researchers across more than 30 countries, aren't merely expressing reservations; they're raising alarms about potentially irreversible damage.

The crux of the issue lies in the disruption of biological rhythms – those fundamental cycles that govern life as we know it. From the sleep-wake patterns of humans to the migration routes of nocturnal animals, from the seasonal cycles of plants to the rhythms of phytoplankton in the ocean, all are intrinsically linked to the natural alternation of light and dark. “The alternation of light … is one of the oldest organizing principles of life on Earth,” notes a stark reminder from the scientists.

Professor Charalambos Kyriacou, president of the European Biological Rhythms Society, puts it bluntly: “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.”

Glare, sky glow, and a dim future

While Reflect Orbital envisions its mirrors providing “sunlight on demand” for construction, disaster relief, and even agriculture, concerns mount about the potential for intense glare and blinding flashes, particularly if these systems malfunction. SpaceX’s proposed mega-constellation, on the other hand, aims to reduce the energy demands of data centers, but at what cost? Ruskin Hartley of DarkSky International points out that the existing number of satellites has already increased diffuse night sky brightness—what he calls “sky glow”—by roughly 10%.

Dr. Miroslav Kocifaj's modelling predicts this brightness could worsen considerably. By 2035, he estimates, the added light from satellites and debris could approach the threshold for preserving naturally dark skies, a threshold that, while still below moonlight, will become increasingly difficult to escape. “What I can say with confidence is that the phenomenon is real, that it is global, and that it will increase substantially over the coming decade if current trends continue,” Kocifaj warns.

But the impact isn't just about brightness. Professor Tami Martino of the University of Guelph emphasizes that even subtle changes in light levels can have profound effects. “Circadian systems are sensitive to light levels far below what humans typically perceive as bright,” she explains, adding that the ripple effects through ecosystems remain largely unknown.

Beyond moonlight: a threat to biological systems

The scientists aren't arguing against space innovation itself, but caution that altering the night sky warrants the same level of scrutiny as climate change or ocean acidification. They stress that disruption of circadian rhythms isn’t simply an inconvenience; it's a physiological mechanism linked to serious health consequences. And as Hartley notes, satellites could soon outnumber visible stars, disrupting navigation for birds and insects and fundamentally altering the human experience of the night sky.

The FCC’s decision on these proposals could reshape our planet's natural rhythms—and the consequences are far more profound than we realize.