LXXEDOC

CODEXXL

CODEX XL

The Shroud of Turn. Photo: Cathedral of St. John the Baptist, Turin, Italy / Weeping Virgin Mary

The horizon problem in cosmology describes the paradox that extremely distant regions of the universe, far beyond what light could have traveled since the Big Bang, exhibit remarkably uniform temperatures and other physical properties. This uniformity is evidenced by the cosmic microwave background (CMB), the afterglow of the Big Bang. The standard Big Bang model cannot explain this apparent coincidence, as these regions should not have had time to exchange heat and reach thermal equilibrium. The theory of cosmic inflation, a period of rapid, exponential expansion in the very early universe, offers a solution by proposing that these now-distant regions were once in causal contact and could have interacted to become uniform before being stretched apart.  

Chapter 56