Lighting patterns

Europe at night. From europemapofeurope.net

¨Pelorat said thoughtfully, ¨Human beings are diurnal in nature, after all. It seems to me that among the very first tasks of a developing technology would be the conversion of night to day. In fact, if a world lacked technology and developed one, you ought to be able to follow the progress of technological development by the increase in light upon the darkened surface. How long would it take, do you suppose, to go from uniform darkness to uniform light?¨

Trevize laughed. ¨You have odd thoughts, but I suppose that comes from being a mythologist. I don´t think a world would ever achive a uniform glow. Night light would follow the pattern of population density, so that the continents would spark in knots and strings. Even Trantor at its height, when it was one huge structure, let light escape that structure only at scattered points.¨

From Foundation´s Edge. By Isaac Asimov. Page 176.USA. 1982