Under a False Moon: The Rise of Space-Based Light Pollution

For billions of years, the celestial sphere has acted as a universal clock and reliable map for life on Earth. As a result, many species have evolved to regulate critical biological, physiological, and behavioral functions by the regular cycles of sunlight, moonlight, and starlight and navigate by recognizable patterns in the sky. These celestial patterns and photocycles are so fundamentally intertwined with life that many species have come to depend on them at a molecular level. Similarly, the use and importance of these celestial signals is widespread across human cultures.

Accelerating human activity in space has the potential to significantly disrupt the natural patterns and cycles that characterize Earth’s celestial sphere. This is not a hypothetical or distant problem, as rapidly decreasing launch costs and accelerating technological innovation are opening outer space to an increasingly diverse array of human activity—including plans to display advertising, art, and other messages from low Earth orbit, as well as space-based climate engineering projects which seek to provide widespread nighttime illumination or solar power from orbit. Many of these proposed use cases would require thousands of space mirrors in low-Earth orbit in order to provide sufficient lighting, with one current proposal calling for 50,000 space mirrors by 2050, with plans to grow that number to 250,000 in the longer term. These space mirrors would be capable of providing additional sunlight up to 3 hours post-twilight and would have widespread impacts on aerial, aquatic, and terrestrial ecosystems, as well as socioeconomic impacts on human societies.

Thus, the rapid commercialization of space and lack of regulatory clarity present an urgent need for comprehensive technical, ethical, and regulatory frameworks, particularly for those spaceflight activities most likely to be realized in the coming years. This poster will explore current and proposed space missions which risk introducing significant light pollution into the celestial sphere and their connections on Earth-bound ecosystems and human cultures.