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Cosmic microwave background
Intermediate
Afterglow of the early universe at 2.7 K.
Uniform 2.725 K blackbody radiation from 380,000 years after the Big Bang when atoms formed and the universe became transparent. Tiny anisotropies (10⁻⁵) seeded galaxies.
Discovered by Penzias and Wilson in 1965.
Part of 'static' on old TVs.
In more detail
The cosmic microwave background is the faint radiation left over from the early universe, when it became transparent about 380,000 years after the Big Bang. It has a near-perfect blackbody spectrum at about 2.7 K.
Real-world uses
- CMB measurements determine the composition and geometry of the universe.
- Satellites such as Planck have mapped tiny temperature fluctuations.
- Cosmologists map the cosmic microwave background to measure the geometry and composition of the universe.
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Frequently asked questions
Why is it called microwave?
Because the expansion has stretched its wavelength into the microwave range.
Who discovered it?
Arno Penzias and Robert Wilson, in 1964, who received the 1978 Nobel Prize.
Why is the background so uniform?
The early universe was almost uniform, and the tiny variations seen in the background seeded the structures we see today.
Related topics in Particle Physics & Cosmology
Hubble's law · Expansion of the universe · Big Bang theory · Big Bang nucleosynthesis · Inflation · Dark matter