Sky Mirrors in Orbit Could Light After-Dark Earth, Sparking Astronomers' Alarm

A California startup, Reflect Orbital, proposes a constellation of up to 4,000 sunlit satellites with large mirrors to redirect sunlight toward Earth after sunset for several minutes, testing with the Eärendil-1 demonstration (an ~18-by-18-meter reflector at ~600 km). The system would illuminate targeted areas briefly while in sunlight, potentially extending usable daylight for activities like solar power or night operations; future versions could have much larger mirrors. While the concept could aid nighttime tasks, astronomers warn it could brighten the sky and disrupt observations, worsen light pollution, and increase space debris, making the success of the initial demonstration crucial for determining whether the idea advances.