Switching from hot, dense incandescent models

 To colder primordial density simulations via diffusion.  The only thing that worried me was the aether.

https://en.m.wikipedia.org/wiki/Friedmann_equations#FLRW_models

As of 2003, the theoretical implications of the various extensions to the FLRW model appear to be well understood, and the goal is to make these consistent with observations from COBE and WMAP.