Cosmological models and misunderstandings about them

Abstract

Advantages of inhomogeneous cosmological models that are exact solutions of Einstein's equations over linearised perturbations of homogeneous models are presented. Examples of effects that can be described in the inhomogeneous ones are given: the non-repeatable light paths, the observed anisotropies in the cosmic microwave background, the redshift drift and the maximum diameter distance. Criticisms of inhomogeneous models that are based on misunderstandings or fallacious reasonings are pointed out and corrected; these include the "weak singularity", the positivity of deceleration "theorem", the "pathology" of redshift behaviour at the "critical point" and the alleged necessity of the bang time to be constant.