Berlin might be united now, but evidence of its 40-year history of division still remains.
This photo, taken by Commander Chris Hadfield, shows a divided Berlin, with the East appearing orange and the West white. But why?
What used to be East Berlin still utilizes nearly 40,000sodium-vapour lamps, which appear orange, while what used to be West Berlin has upgraded to mercury vapour, fluorescent or LED lamps that appear white.
Sodium-vapour lamps have fallen out of favour since they give off primarily yellow light that inhibitcolour vision in the dark. They also contain mercury, which makes them potentially toxic if broken and difficult to dispose of,and have lifetimesroughly half that of LED bulbs.