What's cosmic microwave background radiation?

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Cosmic microwave background (or CMB) radiation (also known as 3 degree kelvin background radiation) is a very uniform and low energy radiation, emitted in the microwave region of the spectrum, spread throughout our universe. It is a significant proof in favor of the Big Bang Theory of origin of universe. According to the Big Bang Theory, the universe started out some 15 billion years ago from a singularity and has been expanding ever since. If this was to be true, there must be some remnant radiations of such an astronomical event. Cosmic microwave background radiation is that very radiation, thus proving that Big Bang really happened. Arno Penzias and Robert Wilson discovered this radiation in 1965 and were awarded the Nobel Prize in Physics in the year 1978. 

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