Gliese 581 is a red dwarf 20 light years away in the constellation Libra, identified over 40 years ago by German astronomer Wilhelm Gliese, and this film uses it as the test case for whether the galaxy is full of life or Earth is a lucky accident. Narrated by Edward Norton, it explains why dim M-class stars like Gliese 581 were long ignored by planet hunters (a habitable planet would have to orbit dangerously close for warmth) and how new precision instruments and supercomputers are finally reading their planets. The film traces the underlying argument back through history: Carl Sagan's case for a universe brimming with life, Copernicus and Galileo dismantling Earth's supposed centrality, against Aristotle, Ptolemy, and the modern Rare Earth hypothesis that treats Earth's mix of water, rocky density, and stable orbit as a fluke. It also lays out the Habitable Zone concept in practical terms, the band around a star where water stays liquid, and asks whether Earth even qualifies as a good model for finding another one.