Discovery of cosmic microwave background radiation

The 1965 identification by Arno Penzias and Robert Wilson of a pervasive microwave signal, later recognized as relic radiation from the early universe.

Arno Penzias: An American radio astronomer who, with Robert Wilson, identified the cosmic microwave background in 1965. He co-discovered the unexplained microwave signal while working at Bell Laboratories.
Cosmic microwave background: Electromagnetic radiation filling the universe, released when it became transparent about 380,000 years after the Big Bang. The unexplained microwave signal was identified as this relic radiation.
Steady-state theory: A cosmological model in which the universe expands but maintains a constant average density through continuous matter creation. It lacked the hot early phase that made the newly identified background a natural prediction.
Nobel Prize in Physics: An annual international award recognizing outstanding contributions to physics. Penzias and Wilson received the 1978 prize for their discovery of the cosmic microwave background.
Robert Wilson: An American radio astronomer who, with Arno Penzias, identified the cosmic microwave background in 1965. He shared the antenna observations that revealed the persistent background signal.
Big Bang nucleosynthesis: The formation of light atomic nuclei during the first minutes of the universe. Its light-element predictions independently supported the hot early-universe picture that explained the signal.
Big Bang: The cosmological model that describes the universe expanding from an early hot, dense state. The background signal provided powerful observational support for this broader model.
COBE: A NASA satellite mission that measured the cosmic microwave background’s spectrum and large-scale temperature variations. Its measurements confirmed the relic interpretation and revealed small primordial anisotropies.
Holmdel Horn Antenna: A large horn-reflector radio antenna built by Bell Laboratories in Holmdel, New Jersey. Penzias and Wilson detected the excess noise with this antenna.
Recombination (cosmology): The epoch when electrons combined with nuclei, allowing photons to travel freely through the universe. The detected radiation last interacted with matter around this transition.

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