Massive space mirrors could be 40 times brighter than the full moon, astronomers warn. 'It will be worse than big cities like London'

Each of the sun-reflecting mirrors proposed by U.S.-based startup Reflect Orbital will appear 40 times brighter than the full moon to observers standing within its beam on Earth, a study has found. The light pollution produced by each of those mirrors would completely wipe out stars from the sky for those underneath them, turning the starry night into an eerie twilight zone.

"It will be worse than big cities like London," Gaspar Bakos, a professor of astrophysics at the University of Princeton and one of the authors of the study, told Space.com. "You would not see any stars if you were in the beam."

Reflect Orbital recently received a license from the U.S. Federal Communications Commission (FCC) to launch a demonstration satellite called EARENDIL-1 into an orbit 373 miles (600 kilometers) above Earth. The spac...