Was the CMB emitted at the same time as visible light at 379,000 yrs after the BB ? Was this a one time event ? If headed away from us, how does it measure the age of the universe?

  • $\begingroup$ What does "the same as" mean in your question? I ask because of course microwaves and visible light are not the same frequency, but I cannot guess what other "same"ness you are asking about. $\endgroup$
    – Lee Mosher
    Sep 25, 2022 at 17:18
  • $\begingroup$ The CMB is blackbody radiation. It was visible when it was originally released, but it's now redshifted to the microwave band because of expansion. Its original color was approximately $$\Large{\color{#ffb46b}■}$$ $\endgroup$
    – PM 2Ring
    Sep 26, 2022 at 0:01
  • $\begingroup$ "If headed away from us" What do you mean? You can't see light that's heading away from you. The CMB was released everywhere (over a relatively short time span), heading in every direction. $\endgroup$
    – PM 2Ring
    Sep 26, 2022 at 5:18


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