Dr. Bill Bottke stops by the show to talk about ancient craters on the Moon and Earth. He tells us about how you can figure out crater ages by looking at the nearby rocks, and how that led him and his colleagues to figure out that the impact rate on Earth changes with time.
Dr. Jeff Rich returns to the show to talk about the night sky. He explains how astronomers used constellations to communicate. He also tells us that anyone can invent their own constellation. In a time when people can create "universes inside a computer," we talk about ways to go outside and experience the cosmos.