Join the Arnold Arboretum for a lecture by science journalist Kelly Beatty. Light pollution, simply put, is any unnecessary or excessive outdoor illumination. Sadly, it’s become a pervasive and ugly consequence of modern 24/7 society. Light pollution robs us of the night sky’s beauty, negatively affects the ecosystem, and creates an in-your-face waste of energy. But a new mindset and new technology are poised to slow—and perhaps reverse—this bane of modern life.