[ggdG]

FTA:

> [Einstein's General Relativity] tells us that the universe is expanding

Does GR really tell us that though?

The way I understood it, GR's differential equations will produce solutions for many different constraints and initial conditions you throw at them. Including the constraints & conditions informed by astronomical observation.

[layer8]

GR tells us that a homogeneous and isotropic universe either expands or contracts. Besides being the default assumption, our universe also looks quite homogeneous and isotropic at large scales, and definitely looks like it fits the expanding option rather than the contracting one.