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[[File:CMB.png|right|300px|thumb|This image shows the [[temperature]] variations of the early [[universe]]. The different colours represent around 10<sup>-4</sup>K [[temperature]] variation.]]
===Meaning===
The '''cosmic microwave background''' ('''CMB''') is the [[radiation]] left over from the [[Big Bang Theory|big bang]] which comes from all directions in [[space]].
===About The Cosmic Microwave Background===
: The '''CMB''' shows that at some point in the past all the [[matter]] in the [[Universe]] was at roughly the same [[temperature]] everywhere. This shows that the [[Universe]] must have once been very small.