Picture an infinitely sprawling stadium with billions of seats, lights blazing, and not a single person in it. That image captures the anxiety behind Enrico Fermi's 1950 lunchtime question, "Where is everybody?" This episode explains why the vastness of space is not a good answer, how self-replicating probes could blanket the Milky Way in a few million years, and why Robin Hanson's 1996 Great Filter argues that something must be stopping life from spreading.

We walk through Hanson's nine evolutionary milestones, from the right star system through the freak cellular merger of endosymbiosis to galactic colonization, and ask the terrifying question of whether the filter is behind us or ahead. Along the way we cover the Martian flatworm thought experiment, Brandon Carter's anthropic bias, Olev Vinn's inherited behavior patterns, the Berserker h ...