The term "Microwave Background Radiation" refers to electromagnetic radiation that is left over from the early universe, shortly after the Big Bang. This type of radiation fills the entire universe and has a temperature of about 2.7 Kelvin (-270°C or -454°F). It was first discovered in 1964 by Arno Penzias and Robert Wilson who were awarded the Nobel Prize for their discovery.
The microwave background radiation is considered to be one of the most important pieces of evidence supporting the Big Bang theory, as it provides a snapshot of the universe when it was only about 380,000 years old. The radiation comes from the time when the universe was still very hot and dense, and the electrons and protons had combined to form neutral hydrogen atoms. This allowed photons to travel freely through space without being scattered by charged particles.
Today, scientists study the microwave background radiation using powerful telescopes in order to learn more about the early universe and its evolution over time. The data collected from these observations has helped to confirm many of the predictions made by the Big Bang theory, and continues to provide valuable insights into the nature of our universe.