This week we're talking about the mindbending science trying to understand the inner workings of the Universe. Astrophysicist Ethan Siegel returns to discuss the BICEP2 experiment, and its search for the fingerprints of cosmic inflation. And we'll talk to theoretical cosmologist Roberto Trotta about his book "The Edge of the Sky: All You Need to Know about the All-There-Is," which explains the history and concepts of cosmology using the 1,000 most common words in the English language.