Cosmic microwave background radiation is the faint glow of radiation that fills the universe and is believed to be leftover heat from the early stages of the Big Bang. It is considered one of the primary pieces of evidence supporting the Big Bang Theory.
The cosmic microwave background radiation, also known as the Penzias-Wilson radiation, was discovered by Arno Penzias and Robert Wilson in 1965. This discovery earned Penzias and Wilson the Nobel Prize in Physics in 1978.