Big Bang
The prevailing cosmological model describing the universe as originating from an extremely hot, dense state ~13.8 billion years ago and expanding ever since.
Governing formula
T_universe ≈ 13.787 ± 0.020 billion years
SI unit
Cosmological Epoch (Years)
In depth
Supported by three major observational pillars: Hubble's law of galactic recessional velocities, the ubiquitous 2.725 K Cosmic Microwave Background (CMB) radiation, and primordial light element abundances (Hydrogen, Deuterium, Helium, Lithium) from Big Bang Nucleosynthesis.
Examples in the real world
The 2.725 K Cosmic Microwave Background radiation filling the universe as the cooled remnant radiation of the Big Bang.