What is the Cosmic Microwave Background?

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By Google Arts & Culture

Polarization of the Cosmic Microwave Background (2015-02-05) by ESA/Planck CollaborationNASA

The cosmic microwave background (CMB) is electromagnetic radiation left over from the hottest phases of the early universe. This ‘afterglow’ of the Big Bang fills the entire universe, and it has almost the same characteristics in all directions.

However, satellite observations have revealed tiny irregularities in this radiation. These irregularities reveal information about the very first instants of the Big Bang - so-called 'quantum fluctuations'.

Planck and the Cosmic Microwave Background Artist Concept (2013-10-23) by ESA and the Planck Collaboration - D. DucrosNASA

As the universe grew in size, these tiny fluctuations in temperature expanded to cosmic dimensions.

The Big Bang left a permanent scare in the cosmic background, 5 billion light-years from Earth (2017-12-08)NASA

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