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How are cosmic microwave background radiation and the cosmic neutrino background different?
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Cosmic microwave background
A full-sky map produced by the Wilkinson Microwave Anisotropy Probe (WMAP) showing cosmic background radiation, a very uniform glow of microwaves emitted by the infant universe more than 13 billion years ago. Color differences indicate tiny fluctuations in the intensity of the radiation, a result of tiny variations in the density of matter in the early universe. According to inflation theory, these irregularities were the “seeds” that became the galaxies. WMAP's data support the big bang and inflation models, and cosmic microwave background is at the farthest limits of the observable universe.
The cosmic microwave background (CMB) and the cosmic neutrino background (CNB) are both relic signatures of the early big bang, but they differ fundamentally in their physical nature and interaction with matter.12
- Nature of Radiation: The cosmic microwave background consists of electromagnetic radiation that fills the universe. In contrast, the cosmic neutrino background is composed of low-energy neutrinos.21
- Decoupling Time: The CNB formed when the universe was approximately one second old, at which point neutrinos ceased interacting with ordinary matter. The CMB represents a later stage of the universe's evolution, originating as the universe cooled sufficiently for photons to travel freely.12
- Detection: Because neutrinos interact only weakly with matter and do not emit electromagnetic radiation, they are extremely difficult to detect directly. The CMB, however, is readily observable as microwave radiation, and its fluctuations have been mapped in great detail by missions like the Wilkinson Microwave Anisotropy Probe.13