Cosmic background radiation is the electromagnetic radiation having no discernible source. The region where the spectrum is observed determines the origin of the radiation. One of the components is the cosmic microwave background. Cosmic microwave background is the radiation that is left over from the Big Bang and fills up the universe.
Its discovery and the observations are the sources for confirmation of the Big Bang theory. The discovery happened by chance in 1965. Cosmic background radiation says that long time ago, the universe was dominated by the radiation field which was full of extremely high temperature and pressure.
COSMIC MICROWAVE BACKGROUND RADIATION
The CMB or cosmic microwave background radiation is the faint glow of light that fills up the entire universe with uniform intensity. It is considered to be the residual heat created after the Big Bang which has been continuously streaming throughout the space since the last 14 billion years.
Since the dawn of the twentieth century, there have been two monumental changes in the way that the astronomers observe our universe-
1) The universe is extremely large. The 15 billion light years radius of the universe that we can see is just a little tip of all that the universe entails.
2) Light travels at a fixed speed.
CMB is said to be the oldest light that we can ever see. The light had set out on its journey over 14 billion years ago before the existence of the galaxy. That was when the universe wasn’t dark but was full of radiation and elementary particles. After the universe expanded and cooled down, there was the formation of the stars, planets, galaxies etc.
The study of cosmology finds it critical to study the residual radiation since the radiation contains the fossil imprints of the particles from which we can deduce the vital meaning and statistics of the universe like we can catch a criminal by his fingerprint.
After the release of the cosmic background light, billions of years ago, the light was bright and hot like a star but then the expansion of universe took place. The wavelength of the light got stretched within it into the microwave part of the electromagnetic spectrum while the CMB cooled down to its current temperature. The present day temperature of CMB is 2.73 degree above the absolute zero as determined by the radio telescopes.