Transition from opaque universe to release of CMB

[Bill McKeeman]

What is known about how long it took to transition from an opaque universe to the release of the cosmic microwave background?

 

[mfb]

The usual publications about the CMB cover that, chances are good tons of websites will also mention it. The CMB light we see mainly comes from a period of ~20,000 years, about 380,000 years after the big bang.