Where does the world get its energy? We use it for our cars, we use it to heat our homes, we use it to make electricity. But where does it come from? Unfortunately, about 90% of our energy comes from dirty, polluting sources. Now the question is, why? Why do we use sources of energy that create cancer-causing sulfur dioxide and release carbon dioxide that warms our planet? Most people would say, “Because it’s cheaper. Powering homes with a coal power plant is cheaper than building a solar farm.” But is it really? When you look at the cost per megawatt, coal is cheaper. But when you look at the costs including pollution, it’s no contest; solar wins in a landslide. The problem is that pollution is released into the air where it is spread around. And so are the negative effects. Increased cancer risk and global warming affect everyone, while the benefits of cheap electricity go to whoever pays for the power plant. Sound familiar? Dirty Energy is yet another example of the Tragedy of the Commons.