Cycles of Time: An Extraordinary New View of the Universe

by Roger Penrose

we see that the surface of last scattering , (decoupling; see §2.2) occurs much too close to the Big-Bang 3-surface for effects that are seen from our vantage point to be more than about 2° apart in the sky ever to have been in causal contact. This assumes that all such correlations arise from processes occurring after the Big Bang, and the different points of are in fact completely uncorrelated. Inflation is able to achieve such correlations because the ‘inflationary phase’ increases the separation between and in a conformal diagram,[3.82] so that much larger angles seen from our vantage point are brought into causal contact;