Microwave radiation {cosmic microwave background}| (CMB) {microwave background} {background radiation, microwave} comes from all universe directions. Cosmic microwave background radiation is same visible-light-frequency radiation that was in hot plasma before plasma cooled enough, to 3000 K, for neutral-charge atoms to form, 300,000 years after universe origin, and comes from 13.72 billion light years away.
temperature
At that distance, recession velocity is near light speed, and redshift divides frequency by 1000, so radiation is now microwaves, with effective temperature 2.7 K.
temperature fluctuations
Cosmic-microwave-background temperature varies over space by less than 1 part in 10000. Temperature variations have Gaussian distribution. Temperature fluctuations arose from early-universe in-phase acoustic waves, density differences, and gravity waves. Gravitational waves cause red-shift and blue-shift. Gravitational-wave handedness causes polarization curls. Gravitational lensing affects CMB.
Largest same-temperature structures have one-degree diameter. Temperature variations depend on in-phase acoustic-wave wavelength, such as the largest spatial distance {first Doppler peak}. The four largest spatial distances have same intensity differences {scale-invariance}.
Physical Sciences>Astronomy>Universe>Cosmology>Radiation
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Date Modified: 2022.0224