Topic summary
Cosmic microwave background radiation
Extracted from the Wikipedia article Cosmic microwave background.
Features
The cosmic microwave background radiation is an emission of uniform black bodythermal energy coming from all directions. Intensity of the CMB is expressed in kelvin (K), the SI unit of temperature. The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K. Variations in intensity are expressed as variations in temperature. The blackbody temperature uniquely characterizes the intensity of the radiation at all wavelengths; a measured brightness temperature at any wavelength can be converted to a blackbody temperature.