Baryogenesis: The Matter–Antimatter Asymmetry

Early-Universe Conditions

CP-violation asymmetry η 3.0%

Cooling / expansion rate 0.15

Pair-production rate 1.5×

Cosmic State

Pair production active

Temperature T/T₀

1.000

Cosmic time t

0.00

Matter (blue)

Antimatter (red)

Live asymmetry (n_m − n_a) / (n_m + n_a)

0.0%

How it works

In 1967 Andrei Sakharov showed that a universe starting perfectly symmetric can end up made of matter only if three conditions hold at once: baryon-number violation, C and CP violation, and a departure from thermal equilibrium. This sim visualises all three together.

η = (n_B − n_B̄) / n_γ  ≈ 6×10⁻¹⁰  (observed today)
T(t) = T₀ · e^(−k·t)   (adiabatic cooling from expansion)
production: N_matter = N_pairs·(1+η),  N_antimatter = N_pairs

Baryon-number violation — every "spawn" event is allowed to create an extra unpaired matter particle instead of a clean particle/antiparticle pair.
CP violation (η slider) — sets how much more matter than antimatter each spawn event produces, on average, out of pure asymmetry in the underlying decay.
Out-of-equilibrium freeze-out — as T falls (cooling-rate slider), pair production shuts off faster than annihilation can finish. Whatever antimatter hasn't found a partner yet gets annihilated away; the small matter surplus has nowhere left to go and freezes in — exactly what you see settle at the end of every run.

Real relevance: this same freeze-out logic — production stops before the reverse reaction can fully catch up — is why roughly one baryon survives for every ~1.6 billion photons in the observable universe today, instead of nothing surviving at all.

Matter Antimatter Annihilation flash

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.