Re: CMB Redshift Question (Visible Wavelengths)

In summary, there was a discussion about the age of the universe based on the formula for CMB temperature and redshift. The earlier thread was closed, prompting a question about the inconsistency between the calculated age of the universe at the emission of CMB and the current age. The calculations were corrected to show that redshift does not scale linearly with age, thus explaining the inconsistency.
  • #1
JArnold
21
3
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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  • #2
  • #3
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.
 
  • #4
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.
 
  • #5
That's fine. But if redshift doesn't scale linearly, neither does CMB "temperature", given by Tobs = Tem/(1+z) in the original thread.
 
  • #6
Right. Inconsistency solved.
 

1. What is CMB redshift?

CMB redshift is the phenomenon where the light from the Cosmic Microwave Background (CMB) radiation is stretched to longer wavelengths, or lower energies, as it travels through the expanding universe. This is due to the expansion of space itself, which causes the wavelength of light to increase over time.

2. How is CMB redshift related to the age of the universe?

The amount of redshift observed in the CMB is directly related to the age of the universe. As the universe expands, the light from the CMB is stretched and the higher the redshift, the older the light is and the farther back in time it originated.

3. Why is studying CMB redshift important in cosmology?

Studying CMB redshift allows scientists to understand the expansion rate of the universe and the distribution of matter within it. It also provides evidence for the Big Bang theory and helps us understand the early stages of the universe.

4. Can CMB redshift be used to measure the distance to objects in the universe?

Yes, CMB redshift can be used as a cosmological standard ruler, meaning it can be used to measure the distance to faraway objects in the universe. By measuring the amount of redshift in the CMB, scientists can calculate the distance to the object and therefore understand the size and structure of the universe.

5. How is CMB redshift different from other types of redshift?

CMB redshift is different from other types of redshift, such as Doppler redshift, because it is not caused by the motion of an object. Instead, it is caused by the expansion of space itself. This means that CMB redshift can be observed in all directions and is isotropic, whereas other types of redshift may only be observed in certain directions.

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