Bill Nye hosts this episode of a nine-part series ranking history's biggest scientific breakthroughs, this installment devoted to astronomy. The film moves through discoveries about the cosmos using historical re-creations, archival footage, and visits to research facilities where astronomers do their work today. Nye interviews present-day scientists, including Nobel laureates, who explain how a given finding changed what humans understood about the universe and why it mattered at the time. The tone stays light and explanatory rather than academic, consistent with Nye's television persona, but the structure is straightforward: each discovery gets set up, explained, and placed in context before the episode moves to the next. It sits alongside seven other subject episodes (evolution, earth sciences, medicine, physics, chemistry, genetics and biology) plus a finale ranking the top ten discoveries overall, but this hour stays focused on astronomy alone.