ABSTRACT
The current standard models of the universe are the Friedmann-Lemaıˆtre (FL) family of models, based on the Robertson-Walker (RW) spatially homogeneous and isotropic geometries but with a much more complex set of matter constituents than originally envisaged by Friedmann and Lemaıˆtre. It is appropriate then to ask whether the universe is indeed well described by an RW geometry. There is reasonable evidence supporting these models on the largest observable scales, but at smaller scales they are clearly a bad description. Thus a better form of the question is: On what scales and in what domains is the universe’s geometry nearly RW? What are the best-fit RW parameters in the observable domain?
