What caused the Big Bang? Are black holes key to interstellar travel? And how close are we to discovering extraterrestrial life? These are some of the big questions that Kelsey Johnson (University of Virginia) covers in her fascinating class, “The Unsolved Mysteries of the Universe.” And: Robin Hanson (George Mason University) has come up with a mathematical model that predicts when us earthlings will encounter an advanced alien civilization. Hint: It won’t happen anytime soon.

Later in the Show: UFO encounters are usually horror stories of abduction and alien implants. But Stephen Finley (Louisiana State University) says many African Americans describe UFO encounters as positive experiences. Plus: Benjamin Zeller (Lake Forest College) recounts the tragic history of Heaven’s Gate, a religious group whose members committed mass suicide in 1997.