Celestial ephemerides in a NON-expanding universe

<p>This comment refers to "Celestial ephemerides in an expanding universe" by Sergei M. Kopeikin - Phys. Rev. D 86, 064004 (Published 4 September 2012). One point is that the flatness of space-time needs to be explained in greater detail, to avoid confusion with General Relativity's idea of space-time being curved. Another point is that while the expansion of space appeared to be confirmed by Edwin Hubble's 1929 observations, the universe need not be physically expanding at all but could be undergoing a closely related process of topological extension.</p> <p> </p>