Brian Cox walks through the solar system planet by planet, using the same physics that shapes Earth to explain why its neighbors turned out so differently. Venus gets treated as a cautionary tale, a runaway greenhouse that boiled away any chance of oceans, while the footage moves out to Jupiter's icy moons, where tidal flexing from the giant planet keeps liquid water churning under miles of ice. Cox returns repeatedly to Earth's own extreme environments, from scorched deserts to deep-sea vents, using them as working laboratories for what life might tolerate elsewhere. The film leans on orbital mechanics and thermodynamics rather than speculation to explain each world's fate, pairing CGI flythroughs of planetary surfaces with practical demonstrations back on Earth. Running nearly three hours, it functions as a long-form survey course across Mercury, Venus, Mars, and the outer moons, with Cox's own enthusiasm doing much of the work to keep the physics approachable rather than textbook-dry.