Or light. Below you will find a fascinating map from the World Resources Institute, (which is a great website, featuring information on such matters as renewable fresh water resources, literacy rates, and other phenomena that are found at the “intersection of the environment and human needs.”
Here is a description of the map:
“The National Geophysical “city lights” database depicts stable lights and radiance calibrated lights of the world (which includes lights from cities, towns, industrial sites, gas flares, fires, and lightning illuminated clouds). A high concentration of city lights is especially found in industrialized densely populated regions such as western Europe, Japan, and the U.S.. Alternatively, few “city lights” are shown in economically poorer and sparsely populated regions (e.g. central and northern Africa and South America). Moderate “city lights” are found in several densely populated “developing countries” (e.g. India, Indonesia, eastern Brazil, and South Africa). The “city lights” data may be used a proxy for population distribution or infrastructure (e.g. in which it may be assumed that the occurrence of few city lights is correlated with the presence of institutional, political, and industrial infrastructure).”
Clouds, Clocks, and Sitting at Tables 