Do You See the Light?

Over at According To Hoyt the other day, a commenter linked to a NASA composite image of the Western Hemisphere at night.

Image Credit: NASA Earth Observatory image by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA's Goddard Space Flight Center

I find it interesting how distinct and obvious some of the metropolitan areas are. The Salt Lake City and Denver-Colorado Springs areas are little vertical splashes of light among a sea of dark, while Saint Louis and Kansas City stand out as larger bright spots among a bunch of smaller bright spots. Chicago and Dallas-Fort Worth are large splotches. The Northeast Corridor cities, on the other hand, kind of run together - but the near-straight horizontal splash that is Long Island makes it possible to pick NYC out of the mess. 

Map above blown up with captions added by me

You can also see how quickly the light falls off as you get a bit west of about 96 degrees west.  Between about 96 and 103 degrees west (it varies a bit), the population density drops off.  With the decline in population density comes a similar decline in density of the road network and the lights.  This is where the land transitions from the wetter, more fertile lands that support many types of crops, to the drier lands more suitable for ranching and grains.  This is the area once known generations earlier as the Great American Desert, though it is not really.

And I think that's all I shall touch on tonight.  Good night, world!