Last week, we heard about the tale of the Cuyahoga River -- a river in Ohio that caught on fire multiple times because it was so polluted. The river is now doing much better, but beyond the fact that it’s not on currently fire -- how do we actually know it’s healthier today? That’s when being a water detective really comes in handy. Plus: Our Moment of Um answers the question: "Why do dogs wag their tails?" Today’s episode is sponsored by Vamousse Lice (vamousselice.com) and Roshambo Baby (roshambobaby.com and offer code BRAINS).