A science documentary from the Spark catalog that uses violent cosmic energy as its throughline: black holes tearing apart matter, the nuclear furnaces burning at the core of giant stars, and the volcanic pressure building inside planets. Rather than treating space as an empty void, the film frames it as a series of engines, each one converting raw energy into the structures that hold the universe together, from stellar cores to planetary interiors. The camera and narration move between these scales, using visualizations and expository narration typical of the genre to explain how a star's furnace differs from a planet's molten core, and how black holes represent the most extreme version of the same physics. The question in the title runs underneath the whole hour: if energy transformation never stops, where does the observable universe actually stop being space and start being something else. It plays as a survey piece, built for viewers who want the big picture of cosmic mechanics rather than a single narrow case study.