What if the best way to explore the galaxy is to launch one ship that builds copies of itself? This episode unpacks von Neumann probes, from John von Neumann's insight that exponential replication beats launching fleets, to Robert Freitas's 1980 engineering study that adapted the Daedalus starship with a 443 ton seed factory spending 500 years building its industrial base. We also cover Olivia Borgue and Andreas Hein's more feasible 70 percent self-replicating design that brings microchips from home, and Anders Sandberg and Stuart Armstrong's scenario of dismantling Mercury to build a Dyson swarm and launch probes in 32 years.

At 10 percent light speed such machines could fill the Milky Way in about half a million years, which is why Frank Tipler argued in 1981 that their absence proves we are alone. Carl Sagan and William Newman countered  ...