Re: CMB Redshift Question (Visible Wavelengths)

AI Thread Summary
The discussion centers on the calculation of the Cosmic Microwave Background (CMB) temperature and its relation to redshift (z). A participant questions the age of the universe at the emission of the CMB, suggesting it should be about 12.5 million years instead of the commonly accepted 380,000 years. They argue that if the redshift of 1100 is accurate, it implies a current age of about 420 million years, which contradicts established cosmological models. The conversation highlights the complexity of calculating redshift and its non-linear relationship with age and temperature. Ultimately, the participant believes their calculations are correct, pointing to inconsistencies in the understanding of redshift and CMB temperature.
JArnold
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The earlier thread was closed for some reason.

It prompted this question: Given the formula for CMB temperature Tobs = Tem/(1+z) (analogous to the formula for z) it seems the age of the universe at the emission of the CMB would have been about 12.5 Myr (if 13.75 Gyr presently), not 380,000 years:

1101 = 13750/12.5

If 380,000 is correct, then for z to be 1100 the current age would have to be about 420 Myr:

1100 ~ 420/.38

I understand that calculating for z is complicated for large distances, but the same should hold for CMB. So why the inconsistency?
 
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That thread wasn't helpful. I had specific questions, and I believe my calculations were correct. Here's another strange calculation: The spatial expansion between 13,750 Myr and .38 Myr would be 36,184 -- not 1100.
 
You'll find these numbers also in the other thread, and you'll find what they mean.
Your calculations are not correct, as redshift doesn't scale linearly with age.
 
That's fine. But if redshift doesn't scale linearly, neither does CMB "temperature", given by Tobs = Tem/(1+z) in the original thread.
 
Right. Inconsistency solved.
 

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