horisonttiongelman

Horisonttiongelman, a Finnish term, translates to "horizon problem" in English. It is a concept primarily encountered in the context of cosmology and the standard model of the universe, known as the Lambda-CDM model. The horizon problem arises from observations of the cosmic microwave background (CMB) radiation. The CMB is the afterglow of the Big Bang, and it exhibits a remarkably uniform temperature across the entire sky.

The problem lies in explaining how regions of the universe that were causally disconnected at the time of the CMB's emission could have such similar temperatures. In simpler terms, light could not have traveled between these distant regions in the age of the universe up to that point, meaning they could not have exchanged heat to reach thermal equilibrium. Therefore, according to standard Big Bang cosmology without further modification, these regions should have had different temperatures.

The existence of this uniformity suggests that these regions were once in much closer proximity and could have interacted, or that some mechanism actively smoothed out temperature differences. The theory of cosmic inflation is the most widely accepted proposed solution to the horizon problem. Inflation postulates a period of extremely rapid expansion of the universe in its earliest moments. This rapid expansion would have stretched a very small, causally connected region to encompass the entire observable universe, thus explaining the observed uniformity of the CMB. Without inflation, the horizon problem presents a significant challenge to our understanding of the early universe.