Summary
The Cosmic Microwave Background (CMB) was discovered in 1965 as a pervasive, uniform microwave radiation filling space. Its existence was predicted by Big Bang cosmology and provided decisive empirical confirmation of a hot, dense origin of the universe.
Observation / Fact
Arno Penzias and Robert Wilson detected an unexplained, isotropic microwave signal corresponding to a temperature of approximately 2.7 K, present in all directions and independent of Earth’s motion or local sources.
Why This Is Non-Trivial
The signal precisely matched predictions made decades earlier for residual radiation from an early, hot universe. Competing cosmological models at the time did not predict such a background.
What It Implies
The discovery indicates that the universe underwent a hot, dense early phase, leaving behind observable thermal radiation. This strongly supports a finite beginning rather than a steady or eternal state.
Related
- Expansion of Space
- Blackbody Spectrum Precision