The Big Bang is a physical theory that describes how the universe expanded from an early state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, the redshift of galaxies and the large-scale structure of the universe. The observed uniformity of the universe, which leads to the horizon and flatness problems, is explained through cosmic inflation: a phase of accelerated expansion during the earliest stages. Detailed measurements of the expansion rate of the universe place the cosmic inflation at an estimated 13.787±0.02 billion years ago, which is considered the age of the universe. A wide range of empirical evidence strongly favors the Big Bang model, which is now widely accepted.