ABSTRACT

This chapter looks at that the models based on the Robertson–Walker metric predict that, in addition to the redshifting of its light, all physical processes in a source at redshift z are observed to be slowed down, that is they are time dilated, by a factor. The Friedmann, Lemaître, Robertson–Walker (FLRW) models give people a relationship between the apparent magnitude, m, and the redshift, z, of a 'standard candle' source. The probability of a quasar being lensed by a galaxy along its line of sight depends on which cosmological model is assumed. The chapter investigates how the number of galaxies in a region of the sky depends on the redshift of the galaxies. It shows that the inflationary hypothesis provides a mechanism and it also provides a natural resolution of the flatness problem. The early recollapse of the Universe in the absence of a fine-tuning of the density parameter provides an alternative expression of the flatness problem.