Night is supposed to feel simple. The sun goes down, the world cools off, and our bodies switch gears, even if we are still doomscrolling in bed. Now a growing coalition of sleep and circadian rhythm experts says two satellite proposals in front of US regulators could tamper with that rhythm on a global scale.
In letters to the Federal Communications Commission, presidents of four international chronobiology societies representing about 2,500 researchers from more than 30 countries warn that reflective “space mirrors” and a massive jump in low-Earth orbit satellites could significantly alter the planet’s natural nighttime light environment.
Their conclusion is that the risks are not theoretical, because biology uses the night as a signal, not a backdrop.
What the FCC is reviewing
One proposal comes from Reflect Orbital, a startup pitching “sunlight on demand” by redirecting sunlight from orbit to the ground at night. An FCC public notice describes Earendil-1, a planned demonstration satellite meant to test space-based reflector technology by reflecting sunlight to targeted areas on Earth.
Reflect Orbital has said the system could redirect light to areas roughly 3 to 4 miles wide, with brightness that can be dialed up or down, including “from full moon to full noon”. Outside groups say the scale matters as much as the spotlight, and the Royal Astronomical Society warns a large mirror constellation could brighten the night sky several times over.
The other proposal is from SpaceX. An FCC bureau notice describes SpaceX seeking authority for an “Orbital Data Center system” of up to one million satellites, pitched as a solar-powered computing network in orbit designed to run artificial intelligence workloads.
Why light at night matters in the real world
If a bright streetlight outside your apartment can leave you groggy the next day, imagine a new source of moving light from above the clouds. The researchers argue that changing the natural cycle of light and darkness can disrupt circadian timing in humans and animals, and can also interfere with seasonal timing in ecosystems.
One concern is that nighttime is not “empty time” for nature. Nocturnal animals rely on darkness for navigation and migration, plants cue growth on day length, and marine phytoplankton follow light driven rhythms that underpin ocean food webs.
That is why Charalambos Kyriacou, president of the European Biological Rhythms Society, has urged regulators to slow down and think about food systems as well as sleep. “Plants need the night,” he said, warning that it is not something we can simply delete.
AI’s energy crunch is real, but space is not a free pass
It is not hard to see why companies are tempted to move computing off Earth. Data centers accounted for around 415 terawatt-hours of electricity in 2024, about 1.5% of global electricity use, according to the International Energy Agency (IEA).
The IEA’s projections show why this debate is accelerating. In its “Energy and AI” analysis, the agency projects global data center electricity consumption could roughly double to around 945 TWh by 2030 in its base case, growing far faster than overall electricity demand.
In everyday terms, that pressure shows up in the electric bill and in the scramble to find enough power and cooling for new server farms.
SpaceX frames its orbital data center concept as a way to harness near-constant solar power in space and reduce Earth-side energy and cooling needs. But reporting and analysts have pointed to a long list of hurdles, including costs, repairs, radiation, and the problem of dumping waste heat in a vacuum.
Orbital clutter has a security side, too
Ecology is only part of the picture. A million-satellite proposal would intensify orbital congestion, raising collision and debris risks in the same altitude bands that support many commercial and government missions.
The OECD has warned that debris density can hit a tipping point that triggers cascading collisions, the scenario often described as the Kessler Syndrome.
That matters for everyday services like weather forecasts and GPS directions, but it also touches military and intelligence systems that use low-Earth orbit for communications and missile warning.
Research on dark and quiet skies has noted that national security motivations can drive large constellations, while the resulting growth in the satellite population can also pose threats to national security itself.
Even the mirror idea has a public safety dimension. DarkSky warns that sweeping illumination patterns or glare from space-based mirrors could disrupt night vision and create risks for aircraft operations and for drivers on dark roads.
The missing piece is environmental governance
Right now, the technology is moving faster than the rulebook. Scientists and advocates are asking regulators to treat light from space as an environmental issue and to require deeper review before approvals, including limits on satellite reflectivity and cumulative night sky brightness.
The Royal Astronomical Society has warned that large mirror constellations could make the night sky three to four times brighter, with knock-on effects that could reach nocturnal ecosystems as well as observatories.
Those projections still need independent testing, but the direction of travel is clear, once you alter the night at scale, it is hard to put it back.
For regulators, the question is simple: do we want to commercialize the night before we measure the biological and security costs?
The official statement was published on BioClocks UK.
