Covers the formation of light elements during the first minutes after the Big Bang.
Big Bang Nucleosynthesis (BBN) is the process that forged the lightest atomic nuclei—deuterium, helium-3, helium-4, and lithium-7—during the first three minutes of cosmic history. This article explains the physics, the timeline, the observational evidence, and why BBN remains a cornerstone of the standard Big Bang model.
Big Bang nucleosynthesis (BBN) is the production of light elements during the first minutes of cosmic time. Its evidence comes from the remarkable agreement between predicted and observed primordial abundances, which also constrains the baryon density and supports the standard hot Big Bang model.
About three minutes after the Big Bang, the universe cooled to roughly a billion degrees, allowing protons and neutrons to fuse into light nuclei. This process, known as Big Bang nucleosynthesis, fixed the primordial hydrogen-to-helium ratio that still dominates the cosmos today.
Primordial helium, forged in the first minutes after the Big Bang, provides a crucial test of the hot Big Bang model. Its measured abundance matches theoretical predictions, reinforcing our understanding of the universe’s origin and evolution.
