Submitted by JarasM t3_100snke in askscience
teejay89656 t1_j2mybd7 wrote
Reply to comment by Aseyhe in Is any "movement" visible in the fluctuations of the CMB over time, or does it appear static? by JarasM
How did all the light scatter at the same time? All photons in the CMB just bounced off a particle somewhere and haven’t touched any particles since?
Aseyhe t1_j2n195x wrote
What happened is that the universe cooled enough that all of the free protons and electrons condensed into neutral hydrogen. Neutral atoms interact with light much more weakly than do free electric charges, so this process made the universe transparent to light.
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