Where does this come from, and can I check it?

Relic radiation from 380,000 years after the Big Bang fills all space. The figure is taken from ESA, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

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Yes. It sits on the Space shelf, one of 1,090 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.

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Mondo Knows Facts

The cosmic microwave background is the oldest light in the universe

Relic radiation from 380,000 years after the Big Bang fills all space

The cosmic microwave background radiation is faint glow of thermal radiation filling the observable universe. Originating roughly 380,000 years after the Big Bang when neutral hydrogen atoms first formed, this thermal afterglow offers a snapshot of the young universe stretched into microwave wavelengths.

Where this comes from

ESA

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Tags: cmb, big bang, cosmology

The cosmic microwave background is the oldest light in the universe: the short answers

Where does this come from, and can I check it?: Relic radiation from 380,000 years after the Big Bang fills all space. The figure is taken from ESA, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a space fact?: Yes. It sits on the Space shelf, one of 1,090 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.