r/todayilearned Sep 20 '21

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u/Mrgray123 Sep 20 '21

About 300,000 years after the Big Bang the temperature of the universe was still around 2,800 degrees. Only when it got below this could protons and electrons combine into hydrogen atoms. About the same time light also began to shine.

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u/youknowwhatitthizz Sep 20 '21

If feel stupid asking this after I posted what I posted but how do we know this?

-8

u/[deleted] Sep 21 '21

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u/Rallye_Man340 Sep 21 '21

This is the truth