Alright, I'll take a couple of shots at it, but you really didn't give us enough of a clue. There are quite a few things to notice on this image:

1. The American Midwest has almost a "grid" of cities, almost undoubtedly arising from proximity to grain elevators. Transport cost of grain would drive the development of towns at some interval.

2. Most of the lights are near water, with the earliest developed coastlines a solid outline of lights: the Nile, Italy's coast (the whole Med, really). Not a big surprise, since that's where the population centers are because that's how people used to get around. Actually, come to think of it, why is the Nile a solid white line?

3. You can see some of the settlement routes of lands by light density, particularly in Russia and N America.

4. The North Slope appears to have more candlepower than the rest of Alaska.

5. Humans are practically dripping off of this little spherical rock.

6. Outdoor folks in the continental US can give up on their silly ideas that they go to any "wilderness" areas.

7. Disease, poverty, infant mortality, short life expectancy and probably bad smell are inversely correllated to candlepower (again, no big suprise, since this is basically an "infrastructure map").

My best guess: what the hell is up with the Nile River?

Jim