  The thoughts expressed in this article are based on remarks made by J\"urgen
Ehlers at the Albert-Einstein-Institut, Golm, Germany in July 2007. The main
objective of this article is to demonstrate, in terms of plausible
order-of-magnitude estimates for geometrical scalars, the relevance of spatial
curvature in realistic models of the Universe that describe the dynamics of
structure formation since the epoch of matter-radiation decoupling. We
introduce these estimates with a commentary on the use of a quasi-Newtonian
metric form in this context.
