Why is the sky blue? Or any color, for that matter? It's a question that you'd think people have been asking for thousands of years, but it might not be that old at all. The ancient Greek poet Homer never used a word for blue in The Odyssey or The Iliad, because blue is one of the last colors that cultures pick out a word for. In this episode, Joe Hanson, host of It's Okay to Be Smart, will tell you not only why the sky is blue, but why it's red at sunset.