"How much light is too much light? Satellite pictures show our planet as a brightly glowing orb, and in our era of constant illumination, light pollution has become a major issue. The world’s flora and fauna have evolved to operate in the natural cycle of day and night. But in the last 150 years, we have extended our day—and in doing so have forced out the inhabitants of the night and disrupted the circadian rhythms necessary to sustain all living...