How old is the universe according to the big-bang model?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Examine the observable universe's place within the whole universe — Cosmology Learn about defining and measuring the observable universe within the “whole” universe.

According to the big-bang model, the universe emerged from a state of extremely high temperature and density approximately 13.8 billion years ago.12

The age of the universe is calculated by determining how long it has been expanding to reach its current size, a process that relies on measuring the Hubble constant—the current rate of expansion—alongside the density of matter and the cosmological constant. While precise values can vary slightly depending on the specific model parameters used, the figure of 13.8 billion years is the widely accepted estimate derived from these cosmological observations.321