4 ideas
Rees is a young miner in the Belt, a community that extracts iron from the cores of burnt-out stars. He travels to the Raft, the political center built by descendants of a stranded human starship's crew, and learns enough physics there to see that the nebula their civilization depends on is running out of gas and approaching collapse.
Raising the gravitational constant a billion times shrinks and speeds up the scale of astrophysics. Life becomes possible only in the thin outskirts of a gas nebula, where survivors can use orbital mechanics directly with trees, ropes and their own bodies.
On the Raft, scientific understanding is held by a privileged caste, while the laborers who meet physical reality every day are kept uneducated. A civilization therefore sleepwalks toward collapse until someone crosses the class line that separates data from theory.
Generations after a crash, descendants keep the remnants and terms of their ancestors' starship, but understanding has decayed into custom, rank and myth. Read this way, a society's sacred objects and titles are often fossils of functional knowledge whose purpose has been forgotten. Recovering that purpose means treating inherited tradition as a technical record to decode rather than an authority to obey.