I've been racking my brain (and Googling with every search term I can think of) to remember a word that describes the glow in the sky above a city (actually, any large source of artificial light, but cities are the classic example.)
This phenomenon is obviously quite undesirable for astronomers, and so it's generally called "light pollution"; this is NOT the word I'm looking for. If I recall correctly, the term actually came into use before astronomy (and artificial light) had developed to a point where cityglow was a problem; prior to that time, it would have been seen as a positive thing: a guide on the horizon for lost travelers, a cheerful sign of civilization, etc.
If it's any help at all: 1) the word that is blocking my memory is "albedo", which is also not what I'm looking for but which keeps popping up - so I believe the two words are similar in sound/origin/etc.; 2) I remember my younger self seeing this word and chuckling because it sounded a bit dirty.