Here's a simple at-home experiment.
Wait until nightfall. Walk outside. And look up.
What do you see?
If you happen to inhabit a major metropolitan city—say Los Angeles—you might see a passing airplane or a spotlight for some distant movie premiere.
What you probably won't see are any of the 400 billion stars populating the night sky.
A new image, generated by Stellarium software, reveals the growing problem of light pollution.
Just how bad has the light pollution problem gotten? Well, if Vincent Van Gogh had been, say, a modern-day Clevelander, he never would have conjured up Starry Night.
Founded in 1988, the International Dark-Sky Association (IDA) is the first organization to call attention to the hazards of light pollution. According to the IDA, light pollution is growing at an annual rate of 4 percent.
At this rate, there will be few dark skies left over the country by the year 2025.
As Treehugger asks: "This is low hanging fruit, why can't we fix this?"