Space mirrors could render night skies daylight, study warns

A study on Reflect Orbital’s proposed sun-reflecting space mirrors finds that observers in the beam would see a light intensity up to 40 times brighter than the full Moon, with the resulting sky glow potentially wiping out stars. If 40,000 mirrors were deployed, the combined brightness could reach 10,000 times the Moon’s, extending visibility and twilight-like brightness up to tens of kilometers away and threatening astronomical observations. The company has FCC permission to test an 18-by-18-meter mirror on the EARENDIL-1 satellite, a move that has drawn objections from astronomers and environmental groups who cite insufficient environmental review and data transparency; Reflect Orbital argues many mirrors would be inactive or placed in remote locations.