The new comprehensive World Atlas of Artificial Night Sky Brightness measures what is called artificial sky glow – reflected light scatter in the atmosphere from the electric lighting below – across the world. Sky glow results from light pollution, or the excess of electric light during the night. As one measure of how far we have come in obliterating the night sky, Falchi and colleagues estimate that, thanks to sky glow, the Milky Way is no longer visible to one-third of humanity, with the most heavily industrialized regions suffering the greatest loss. But the problem with light pollution isn’t just about stargazing. As Falchi and his colleagues point out, it also has effects on environmental and public health.