Baryogenesis is a theoretical process that aims to explain why the observable universe is made almost entirely of matter, with very little antimatter—a puzzle known as the matter-antimatter asymmetry.
According to current physics, the Big Bang should have produced equal amounts of matter and antimatter. If that had happened, particles and antiparticles would have annihilated each other, leaving behind only radiation. But instead, a tiny excess of matter—about one part in a billion—remained, which went on to form all the stars, planets, and galaxies we see today.
Baryogenesis proposes that in the early universe, certain conditions allowed physical processes to favor matter over antimatter. For this to occur, three key criteria (known as Sakharov conditions) must be satisfied:
- Baryon number violation – processes must exist that can change the number of baryons (like protons and neutrons).
- C-symmetry and CP-symmetry violation – laws of physics must treat matter and antimatter differently.
- Departure from thermal equilibrium – necessary for creating a net imbalance.
While the exact mechanism of baryogenesis is still unknown, several theories exist, including electroweak baryogenesis, leptogenesis, and models involving grand unified theories. Understanding baryogenesis remains one of the most important unsolved problems in cosmology and particle physics.