For thousands of years, humans have been trying to figure out the universe and determine its true extent. And there have been a lot of assumptions and theories. during the 1960s, astronomers became aware of microwave background radiation that was detectable in all directions. Known as the Cosmic Microwave Background (CMB), the existence of this radiation has helped to hone our understanding of how the Universe began.
The cosmic microwave background (CMB, CMBR) is faint electromagnetic radiation that is a remnant from an early stage of the universe, filling all space. It represents the heat leftover from the Big Bang and radiation is most visible in the microwave part of the electromagnetic spectrum hence the name CMB.