<p>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?</p>

CC BY-SA 4.0
2022-09-25T17:18:25.850Z
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.
Lee Mosher
CC BY-SA 4.0
2022-09-26T00:01:22.533Z
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  $$\Large{\color{#ffb46b}■}$$
PM 2Ring
CC BY-SA 4.0
2022-09-26T05:18:46.603Z
*"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.
PM 2Ring
<astrophysics><cosmology><cosmic-microwave-background><age>
Cosmic microwave background the same as the first visible light at 379,000 yrs after the Big Bang? How do these measure the age of the universe?
Jack Farley
# Cosmic microwave background the same as the first visible light at 379,000 yrs after the Big Bang? How do these measure the age of the universe?

(Asked by: username_0 on 2022-09-24)

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?

**Tags:** astrophysics, cosmology, cosmic-microwave-background, age

> **Comments:**
> **username_1**: 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.  
> **username_2**: 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  $$\Large{\color{#ffb46b}■}$$  
> **username_2**: *"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.  

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