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[Music throughout] Immediately after the universe was born, it was too tiny

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and too hot for protons, electrons and even photons to exist.

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Within a second, it had expanded and cooled enough for

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protons and neutrons, collectively called baryons, to form.

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Almost instantly, there was a rapid burst of sound waves triggered by tiny

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variations in this particle soup. Scientists call these waves

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Baryon Acoustic Oscillations. The pressure waves traveled outward

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for 400,000 years until the universe thinned and cooled enough 

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for light to travel through it. The universe became transparent

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and the waves froze in place. Over

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time, the denser regions formed by the waves encouraged more star and galaxy formation

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than other areas. The imprint of those waves expanded

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with the universe, slowly accelerating due to dark energy.

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Today, with our “snapshot” of the universe, there is a 

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slight tendency for galaxies to be separated from each other by a

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distance related to that expanding-ring radius.

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Although difficult to see, it is

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detectable as a slight bump through careful surveys of many galaxies.

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[Music]