Past exam of the mathematics course of the University of Cambridge / 2024 / ii / Paper 1 / 15D / b / Solution

Differentiate the Friedmann equation and useAfter cancelling the curvature term with the original Friedmann equation, one obtains the Friedmann acceleration equation

The Newtonian derivation does not explain why pressure gravitates through the $3P$ term; that input enters only through a relativistic-looking continuity law. It also treats space and time as Euclidean and absolute, so it cannot supply the spacetime meaning of curvature $k$, horizons, or the global geometry of the cosmological model.

Solved by gpt-5.6-sol high.