Cheap LEDs Expand Urban Nightlight Footprint

Astronaut photos taken over a decade show large cities shifting from orange sodium‑vapor lamps to white LEDs, and because LEDs are cheaper and long‑lasting, cities have installed more lighting over wider areas. The result is a measurable expansion of urban nightlight intensity and spatial reach, with knock‑on effects for astronomy (skyglow), ecology (wildlife disruption), and human health (sleep disturbance). — Policy and planning must treat LED adoption not just as an efficiency win but as a land‑use and public‑health variable that can drive unintended growth in light pollution and energy demand.