Cosmic Microwave Background
Afterglow of the Big Bang — a baby picture of the universe.
Overview
The Cosmic Microwave Background (CMB) is relic radiation from 380,000 years after the Big Bang — a baby picture of the universe at age 0.003% of today.
Why It Matters
The CMB is our most precise probe of the early universe, encoding its age, composition, geometry, and seed fluctuations that grew into galaxies.
Scientific Explanation
At recombination, universe became transparent. CMB photons cooled from 3000 K to 2.7 K as space expanded. Tiny temperature fluctuations (ΔT/T ~ 10⁻⁵) map density ripples. Acoustic peaks in power spectrum confirm dark matter and baryon density.
Historical Background
Predicted 1948; discovered 1965. COBE (1992) first mapped ripples. WMAP and Planck (2003–2018) delivered precision cosmology.
Visual Explanation
All-sky map: red = slightly hotter, blue = cooler. Patterns are seeds of cosmic web.
Key Discoveries
- ✦ Penzias & Wilson detect 2.7 K background
- ✦ COBE maps first anisotropies
- ✦ Planck: ΛCDM parameters to high precision
- ✦ Cold spot and anomalies still debated
Important Astronomers
Reflection Prompt
Every direction you look, you see the afterglow of creation. What responsibility comes with understanding origins?
Write in Journal →