Re: CMB Redshift Question (Visible Wavelengths)

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Discussion Overview

The discussion revolves around the redshift of the Cosmic Microwave Background (CMB) and its implications for the age of the universe. Participants explore the relationship between CMB temperature and redshift, questioning the calculations related to the age of the universe at the time of CMB emission.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant suggests that using the formula Tobs = Tem/(1+z) leads to an age of the universe at CMB emission of about 12.5 Myr, which contradicts the commonly accepted 380,000 years.
  • Another participant challenges the initial calculations, stating that redshift does not scale linearly with age, implying that the earlier calculations may be flawed.
  • A participant raises a further concern about the spatial expansion calculations, suggesting a discrepancy in the expected values.
  • There is a claim that if redshift does not scale linearly, then the CMB temperature should not either, questioning the consistency of the formulas used.
  • A later reply asserts that the inconsistency has been resolved, though it is unclear how this conclusion was reached.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus, as there are competing views regarding the calculations and interpretations of redshift and CMB temperature.

Contextual Notes

Participants express uncertainty regarding the linearity of redshift with respect to age and the implications of this on the calculations presented. There are unresolved mathematical steps and assumptions that may affect the conclusions drawn.

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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