Near-uniform ~2.725 K blackbody radiation filling the universe; relic photons from recombination (~380 000 yr after Big Bang).
Cosmic microwave background
Related concepts
- Big Bang (hot dense early universe)
- ΛCDM concordance model
- Big Bang (hot dense early universe)
- Cosmological inflation
- Recombination (z ≈ 1100)
- CMB polarization (E + B modes)
- Baryon acoustic oscillations
- CMB anisotropy power spectrum
- GZK cutoff: E_th = (m_Δ² − m_p²)/(4·E_CMB) ≈ 5·10¹⁹ eV via p + γ_CMB → Δ⁺ → pπ⁰