Robertson-Walker Metric
•Homogeneous and Isotropic universe is described geometrically by a metric, or line element, in GR, for “pressureless dust”. •A nice webpage about the Friedman equation and the Robertson-Walker Metric: http://www.jb.man.ac.uk/~jpl/cosmo/friedman.html •Textbook (Combes) is alternatively light and heavy on these topics.  Anyway, R-W metric: