Cosmic background radiation

Electromagnetic radiation from the Big Bang Temperature of the cosmic background radiation spectrum based on COBE data: uncorrected (top); corrected for the dipole term due to our peculiar velocity (middle); corrected additionally for contributions from our galaxy (bottom). Cosmic background radiation is electromagnetic radiation that fills all space. The origin of this radiation depends on the region of the spectrum that is observed. One component is the cosmic microwave background. This component is redshifted photons that have freely streamed from an epoch when the Universe became transparent for the first time to radiation. Its discovery and detailed observations of its properties are considered one of the major confirmations of the Big Bang. Background radiation is largely homogeneous and isotropic. A slight detectable anisotropy is present which correlates to galaxy filaments and voids. The discovery (by chance in 1965) of the cosmic background radiation suggests that the early universe was dominated by a radiation field, a field of extremely high temperature and pressure. There is background radiation observed across all wavelength regimes, peaking in microwave range (cosmic