(cosmology) the cooled remnant of the hot big bang that fills the entire universe and can be observed today with an average temperature of about 2
Electromagnetic radiation, mostly in the microwave range, believed to be the highly redshifted residual effect (see redshift) of the explosion billions of years ago from which, according to the big-bang model, the universe was created. It was discovered by accident in 1964 by Robert W. Wilson and Arno Penzias; its presence supports the predictions of big-bang cosmology