Another great map I found this week describes the spatial pattern of light pollution across the US (there are also maps for other countries available online). This map was described in an article in The Week magazine. The US map below shows the amount of light pollution across the US. The areas in green are the limit of where the Milky Way can be seen. While a lot of the Southeast is affected by light pollution, there are still some areas where skies are dark enough to view the spectacular Milky Way, although the West is much better due to drier conditions and less cloud cover as well as less cities. The second image shows the change in light pollution over time. If current trends continue, we will no longer be able to see the Milky Way in most of the eastern half of the country by 2025.
What impact does the light have on our health? Environmental Health Perspectives newsletter describes some of the adverse affects of having too much light at night, when our eyes and brains need to rest. Of course, there are many other impacts on ecosystems as well, including the well-documented confusion it causes sea turtles when they come ashore to lay their eggs.