Far beyond Neptune, past even the icy Kuiper Belt, astronomers believe an enormous, invisible shell of ancient comets surrounds the entire solar system: the Oort Cloud. This episode traces how a Dutch astronomer inferred its existence from comet orbits alone, why it has never been directly observed, how it differs from the closer, flatter Kuiper Belt, and what "the edge of the solar system" actually means once you look closely at the question.

You'll come away understanding what the Oort Cloud is thought to be and how it likely formed, why long-period comets are the key evidence for its existence, the difference between the Kuiper Belt and the Oort Cloud, what the heliopause is and how it differs from the Oort Cloud as a definition of the solar system's edge, and why honest science communication means treating the Oort Cloud as a well-suppo ...