All urban stargazers know this and have done since the switch from orange sodium vapor lamps to white LEDs, which emit much more blue light. Now we have a mass of observational evidence.

with the beam-splitter prism diverting light through the camera lens onto two different strips of film at the same time. One ...

Daniela Augenstine, who worked in Berlin's street furniture department, told The Guardian that the east uses sodium-vapor lamps, which are older and produce a yellower light, while the west uses ...