[Dave Lev (OP)]

What is the redshift of the Cosmic Microwave Background (CMB)?

https://thecuriousastronomer.wordpress.com/2015/07/30/what-is-the-redshift-of-the-cosmic-microwave-background-cmb/

"Mark asked how we know the redshift of the CMBR if it has no emission or absorption lines, which is the usual way to determine redshifts of e.g. stars and galaxies."

So, do we all agree that there is no emission or absorption lines in the CMBR and therefore there is no way to extract the redshift value from the CMBR data?

However, our scientists used their understanding about the Big Bang theory in order to calculate the expected CMBR redshift as follow:

1. The requested temp that is needed to for the electrons to finally combine with the protons and form neutral hydrogen. That temp is estimated for 3,000K

"as the Universe expands, the temperature just decreases in inverse proportion to its size. Double the size of the Universe, and the temperature will halve.

When the Universe had cooled to about 3,000K it was cool enough for the electrons to finally combine with the protons and form neutral hydrogen. At this temperature the photons were not energetic enough to ionise any hydrogen atoms, and the electrons had lost enough thermal energy that they too could not ionise electrons bound to protons. Finally, for the first time in the Universe’s history, neutral hydrogen atoms could form."

2. The current CMBR temp:

"so, the blackbody produced at the time of decoupling will have retained its blackbody spectrum through to the current epoch. But, because the Universe has expanded, the peak of the spectrum will have been stretched by the expansion of space (so it is not correct to think of the CMB spectrum as having cooled down, rather than space has expanded and stretched its peak emission to a lower temperature). The peak of a blackbody spectrum is related to its temperature in a very precise way, it is given by Wien’s displacement law,

"In 1990 the FIRAS instrument on the NASA satellite COBE (COsmic Background Explorer) measured the spectrum of the CMB to high precision, and found it to be currently at a temperature of  (as an aside, the spectrum measured by FIRAS was the most perfect blackbody spectrum ever observed in nature)."

3. The redshift formula

"It is thus easy to calculate the current redshift of the CMB, it is given by

z \text{ (redshift)} = \frac{3000}{2.725} = 1100

and “voilà”, that is the redshift of the CMB.  Simples"

Hence, the expected CMBR redshift value based on the BBT calculation should be 1100.
However, we know by now that based on the observed CMBR data it doesn't carry any redshift.

Therefore, do you confirm that there is no correlation between the real redshift based on CMBR data to the expected redshift based on the BBT calculation/Theory?

If so, why our scientists hide this vital information?
Why do they claim that the CMBR redshift is 1100 while this value is totally incorrect based on the real CMBR data?

[evan_au]

CMBR data it doesn't carry any redshift.

The CMBR exhibits a dipole, suggesting a motion of our star in our galaxy of about 600km/sec, relative to the CMBR. https://astronomy.swin.edu.au/cosmos/c/Cosmic+Microwave+Background+Dipole

BBT calculation/Theory?

If this is a subtle way to sneak a New Theory into a mainstream thread, it will be demoted quickly...

[Dave Lev (OP)]

I only ask about the CMBR redshift (1100)

Is it correct that the redshift of the CMBR has no emission or absorption lines?
If there is no redshift in the CMBR data, then do you agree that it is a severe mistake to claim that the redshift of the CMBR is 1100?

[Bored chemist]

"Mark asked how we know the redshift of the CMBR if it has no emission or absorption lines, which is the usual way to determine redshifts of e.g. stars and galaxies."

The only plausible source for radiation with no structure (no lines or bands etc) is the recombination of hydrogen nuclei and electrons. (if you think this is wrong, then please check; if you still think it's wrong, please keep checking)

So, what you seem to be  presenting as a "problem" is, in fact the answer.

Hence, the expected CMBR redshift value based on the BBT calculation should be 1100.
However, we know by now that based on the observed CMBR data it doesn't carry any redshift.

Yes it has.
It has been red shifted from the hard UV down to the microwave region.
How did you get the idea that it was not red shifted?

[Bored chemist]

Is it correct that the redshift of the CMBR has no emission or absorption lines?

No, that's a category error.
A red shift is a number, it is 1100 in this case.
How can  a number have lines?

[Dave Lev (OP)]

Is it correct that the redshift of the CMBR has no emission or absorption lines?

No, that's a category error.
A red shift is a number, it is 1100 in this case.
How can  a number have lines?

There is no error!
https://lco.global/spacebook/light/redshift/
How Do Astronomers Measure Redshift?
The most accurate way to measure redshift is by using spectroscopy. When a beam of white light strikes a triangular prism it is separated into its various components (ROYGBIV). This is known as a spectrum (plural: spectra). Astronomers can look at the spectra created by different elements and compare these with the spectra of stars. If the absorption or emission lines they see in the star's spectra are shifted, they know the object is moving either towards us or away from us."

Therefore, the emission & absorption lines are critical for the redshift measurements.
Do you agree by now that as there is no emission or absorption lines in the CMBR then there is no redshift in the CMBR data?

[Bored chemist]

The most accurate way to measure redshift is by using spectroscopy.

I know.
I'm a spectroscopist.

If the absorption or emission lines they see in the star's spectra are shifted, they know the object is moving either towards us or away from us."

You seem not to have appreciated the importance of the word "if" at the start of that quote or you have failed to recognise that the whole emission spectrum is a very broad "line".

Therefore, the emission & absorption lines are critical for the redshift measurements.

No
All you need to do is look at the peak of the blackbody spectrum.
Indeed, that's all you can look at. It's essentially the only number you get which refers to the wavelength.

Do you agree by now that as there is no emission or absorption lines in the CMBR then there is no redshift in the CMBR data?

No, Of course I don't agree with that.
It is wrong.

You can easily measure the red shift.
We know what the effective temperature is when hydrogen recombines.
And we know what the temperature of the CMBR is.
And the ratio of those gives us the red shift- about 1100. (It's a bit more complicated than that- not every atom has to be ionised; but since you don't even understand the basics, we can leave the complicated bits aside for now).

All you have done here is show that you don't understand what you are trying to talk about.
The same as usual.

[Dave Lev (OP)]

The most accurate way to measure redshift is by using spectroscopy.

Yes, that is clear.

Quote from: Dave Lev on Today at 09:53:26
If the absorption or emission lines they see in the star's spectra are shifted, they know the object is moving either towards us or away from us."

You seem not to have appreciated the importance of the word "if" at the start of that quote or you have failed to recognise that the whole emission spectrum is a very broad "line".

Sorry, even in the following article it is stated:
https://www.thenakedscientists.com/forum/index.php?topic=86083.0#quickreply
"The redshift of the Cosmic Microwave Background (CMB) is not measured, it is calculated."

Quote from: Dave Lev on Today at 09:53:26
Therefore, the emission & absorption lines are critical for the redshift measurements.

No
All you need to do is look at the peak of the blackbody spectrum.
Indeed, that's all you can look at. It's essentially the only number you get which refers to the wavelength.

Now you claim that there is no need for emission & absorption lines.

You can easily measure the red shift.
We know what the effective temperature is when hydrogen recombines.
And we know what the temperature of the CMBR is.
And the ratio of those gives us the red shift- about 1100. (It's a bit more complicated than that- not every atom has to be ionised; but since you don't even understand the basics, we can leave the complicated bits aside for now).

Sorry, this is the same explanation for how to estimate/calculate the redshift based on the BBT understanding which I have already highlighted.
There is no spectroscopy in this explanation.
So, why do you claim: "You can easily measure the red shift." while you do understand that we do not measure it from the CMBR data?

Therefore, do you confirm that we do not measure the redshift value from the CMB radiation data by spectroscopy?

We know what the effective temperature is when hydrogen recombines.

You assume that the hydrogen recombines temp is 3000K.
Can you please prove it?
Even if that value is correct, do you agree that we have calculated the CMBR redshift by the following formula?
 

z \text{ (redshift)} = \frac{3000}{2.725} = 1100

Hence, why do you insist that we measure CMB redshift (by using spectroscopy), while you fully confirm that the redshift is calculated based on the hydrogen recombines idea (without any spectroscopy)?

[Bored chemist]

"The redshift of the Cosmic Microwave Background (CMB) is not measured, it is calculated."

And I told you (roughly) how they calculate it from the thing they measure.

We know what the effective temperature is when hydrogen recombines.
And we know what the temperature of the CMBR is.
And the ratio of those gives us the red shift- about 1100. (It's a bit more complicated than that- not every atom has to be ionised; but since you don't even understand the basics, we can leave the complicated bits aside for now).

Your argument is like saying "he didn't measure the temperature; he measured the length of a thread of mercury".

Now you claim that there is no need for emission & absorption lines.

And again.
I explained this

you have failed to recognise that the whole emission spectrum is a very broad "line".

There is no spectroscopy in this explanation.

Yes there is.
They measure the peak emission wavelength of the CMBR's spectrum.
Why are you arguing about that?

So, why do you claim: "You can easily measure the red shift."

Because we can, and we did. See above.

Therefore, do you confirm that we do not measure the redshift value from the CMB radiation data by spectroscopy?

In reality, we measure the shift using spectroscopy.
It's not my fault that you can't understand it.

You assume that the hydrogen recombines temp is 3000K.

We have measured it.
Even this
https://en.wikipedia.org/wiki/Atomic_hydrogen_welding#:~:text=The%20process%20was%20invented%20by,3400%20to%204000%20%C2%B0C.
Gives you a pretty good estimate.
It's not an assumption.
You just assume that nobody understands it- because you don't understand it.

That's the sort of thing I expect from young children.

Can you please prove it?

I really don't see the point.
Nobody who understands the issues doesn't already know the answer, but see above.

Even if that value is correct, do you agree that we have calculated the CMBR redshift by the following formula?

Yes

Hence, why do you insist that we measure CMB redshift (by using spectroscopy)

Because the temperatures were measured by spectroscopy.
How did you think we did it?
A thermometer on a very long stick?

while you fully confirm that the redshift is calculated based on the hydrogen recombines idea (without any spectroscopy)

Again.
The problem here is that you refuse to pay attention.
Here is the spectroscopy that proves the hydrogen recombination issue.

The only plausible source for radiation with no structure (no lines or bands etc) is the recombination of hydrogen nuclei and electrons.

[Origin]

What is the redshift of the Cosmic Microwave Background (CMB)?

https://thecuriousastronomer.wordpress.com/2015/07/30/what-is-the-redshift-of-the-cosmic-microwave-background-cmb/

"Mark asked how we know the redshift of the CMBR if it has no emission or absorption lines, which is the usual way to determine redshifts of e.g. stars and galaxies."

So, do we all agree that there is no emission or absorption lines in the CMBR and therefore there is no way to extract the redshift value from the CMBR data?

Did you not read the article you supplied??  The article you supplied refutes your conclusion.

[Dave Lev (OP)]

Quote from: Dave Lev on 31/01/2023 15:54:26
You assume that the hydrogen recombines temp is 3000K.

We have measured it.
Even this
https://en.wikipedia.org/wiki/Atomic_hydrogen_welding#:~:text=The%20process%20was%20invented%20by,3400%20to%204000%20%C2%B0C.
Gives you a pretty good estimate.
It's not an assumption.
You just assume that nobody understands it- because you don't understand it.

It is stated:
https://en.wikipedia.org/wiki/Atomic_hydrogen_welding#:~:text=The%20process%20was%20invented%20by,3400%20to%204000%20%C2%B0C
Atomic hydrogen welding (AHW) is an arc welding process that uses an arc between two tungsten electrodes in a shielding atmosphere of hydrogen. The process was invented by Irving Langmuir in the course of his studies of atomic hydrogen. The electric arc efficiently breaks up the hydrogen molecules, which later recombine with tremendous release of heat, reaching temperatures from 3400 to 4000 °C.
The hydrogen gas is normally diatomic (H2), but where the temperatures are over 6,000 °C (10,800 °F) near the arc, the hydrogen breaks down into its atomic form, absorbing a large amount of heat from the arc.
There are several expected temp levels in that "Atomic hydrogen welding" process, but none of them is actually 3000K.
So why the 3000K had been selected?
Why not 3400 °C, 4000 °C or even 6000 °C?
 
Please be aware that the redshift formula is as follow:
Z= (λobserved -λrest) / λrest
We already know that the λrest is equal to the peak in the CMBR (2.75K).
So why we do not use the peak in the "Atomic hydrogen welding" to set the λobserved?
At the maximal level of 6000 °C (or 6273K) the redshift should be about:

Z = (6275 – 2.75) / 2.75 = 2,281

At the minimal level of only 3400 °C (or 3673K) the redshift should be about:

Z = (3673 – 2.75) / 2.75 = 1,334

However, how do we know for sure that the CMBR λobserved is exactly the same as the "Atomic hydrogen welding"?
Don't you agree that the CMBR λobserved means that this is something that we should observe/mesure in the CMBR?
Actually, we can clearly observe galaxies at a very far away distance.
Some of them had been created soon after the recombination process (or "Atomic hydrogen welding").
Today we have very sensitive and advanced observation tools.
Therefore, we should have the technology to detect/observe the CMBR around those far away galaxies.
Do we really observe that the CMBR λobserved over there is as high as expected (based on the age of the early universe)?

Therefore, do you finely confirm that we have never measured the CMBR λobserved?
We only measured the  "Atomic hydrogen welding" temp. However, based on the BBT we had been told that this "Atomic hydrogen welding" temp represents the CMBR λobserved.
Hence, why do you refuse to accept the understanding that the CMBR λobserved is a direct hypothetical idea from the BBT?

How can we claim that the real redshift of the CMBR is exactly 1100?
Why our scientists don't say clearly that based on their understanding about BBT the CMBR λobserved should be 3000K (or 3673K - 6275K)?
Therefore, the CMBR BBT redshift = 1100 (or 1,334 - 2,281), but the real CMBR redshift is unknown as we have never measured the real CMBR λobserved?

[Origin]

Today we have very sensitive and advanced observation tools.
Therefore, we should have the technology to detect/observe the CMBR around those far away galaxies.  Do we really observe that the CMBR λobserved over there is as high as expected (based on the age of the early universe)?

I'm not sure what you are trying to say.  It seems like you are saying the CMBR wavelength we detect around those galaxies should be different than the CMBR wavelength we detect on earth, but that doesn't make any sense.

[Bored chemist]

So why the 3000K had been selected?

(It's a bit more complicated than that- not every atom has to be ionised; but since you don't even understand the basics, we can leave the complicated bits aside for now).

However, how do we know for sure that the CMBR λobserved is exactly the same as the "Atomic hydrogen welding"?

Nobody said they were.
The only person who got close is you.

So why we do not use the peak in the "Atomic hydrogen welding" to set the λobserved?
At the maximal level of 6000 °C (or 6273K) the redshift should be about:

Z = (6275 – 2.75) / 2.75 = 2,281

How can we claim that the real redshift of the CMBR is exactly 1100?

Has anybody actually made that claim, or are you trying to use a straw man argument?

Therefore, do you finely confirm that we have never measured the CMBR λobserved?

We have observed the temperature we observed.
2.72548±0.00057 K.
We have observed the wavelength we observed
 1.063 mm

And you seem, as usual, not to have understood the science.

[Bored chemist]

Z= (λobserved -λrest) / λrest
Z = (6275 – 2.75) / 2.75 = 2,281

Why did you suddenly shift from using wavelengths to temperatures?
Don't you see the problem there?

[Dave Lev (OP)]

We have observed the temperature we observed.
2.72548±0.00057 K.
We have observed the wavelength we observed
 1.063 mm

That is correct.
We have observed the the CMBR wavelength, but we only use the measured peak temperature as the λrest in the redshift formula.
We didn't use any wavelength in the following CMBR redshift formula.
Z= (λobserved -λrest) / λrest
Only the temp of 2.75K had been used.
However, what about the λobserved?

Quote from: Dave Lev on Today at 05:36:48
So why the 3000K had been selected?

(It's a bit more complicated than that- not every atom has to be ionised; but since you don't even understand the basics, we can leave the complicated bits aside for now)

As you clearly understand the basic, would you kindly prove that the REAL CMBR λobserved is 3000K (without using the BBT)?

Z= (λobserved -λrest) / λrest
Z = (6275 – 2.75) / 2.75 = 2,281

Why did you suddenly shift from using wavelengths to temperatures?
Don't you see the problem there?

No, there is no problem?
Why do you calim for wavelengths, while our scientists are using temp in the redshift formula?
Don't you agree that the 2.75K and the 3000K are temperatures?
Therefore, our scientists have assumed that based on the BBT, the temperature of the λobserved should be 3000K.
If you think differently, then please explain.

Today we have very sensitive and advanced observation tools.
Therefore, we should have the technology to detect/observe the CMBR around those far away galaxies.  Do we really observe that the CMBR λobserved over there is as high as expected (based on the age of the early universe)?

I'm not sure what you are trying to say.  It seems like you are saying the CMBR wavelength we detect around those galaxies should be different than the CMBR wavelength we detect on earth, but that doesn't make any sense.

Please look at the following diagram:

https://i.stack.imgur.com/FbcY1.gif
We see that based on the BBT, 12 B years ago, the expected CMBR temp is 15K.

So, in less than 2 billion years the expected CMBR (based on the BBT) had been cooled down from 3000K to 15K.
I couldn't find the expected CMBR temp at 13 B Years ago, but I assume that is should be higher than this 15K.
We clearly see galaxies at a distance of more than 13BLY away.
Those galaxies had been formed more than 13 B years ago.
So, as we see those galaxies, why can't we monitor the ambient-temperature-of-the-universe around those ultra-far away galaxies?
If we would find there the expected ambient-temperature, then it can show us that the assumption that the universe was hotter in its early life time is realistic.
If we don't see the expected higher ambient-temperature , then it proves that the idea that the early universe was hot is not realistic.
In any case, in real science the λobserved must be measured from the ambient-temperature of the Universe itself.
As long as we can't prove this 3000K by real measurements from the Universe, we can't use it in our redshift formula.
It is perfectly ok to claim that the CMBR BBT redshift is 1100 (or 2,281).
However, it is forbidden to claim that this is the real redshift in the CMBR as we can't measure the real ambient-temperature of the Universe at that requested age of the Universe.
Therefore, any scientist that claim that the real CMBR redshift is 1100 mislead himself.

[Origin]

We see that based on the BBT, 12 B years ago, the expected CMBR temp is 15K.

So, in less than 2 billion years the expected CMBR (based on the BBT) had been cooled down from 3000K to 15K.
I couldn't find the expected CMBR temp at 13 B Years ago, but I assume that is should be higher than this 15K.
We clearly see galaxies at a distance of more than 13BLY away.
Those galaxies had been formed more than 13 B years ago.
So, as we see those galaxies, why can't we monitor the ambient-temperature-of-the-universe around those ultra-far away galaxies?

The simple answer is that the photons we see from the galaxy itself are 12 billion years old and the photons we see from the CMBR that were in the vicinity of that galaxy are 13.6 billion years old.

[Dave Lev (OP)]

The simple answer is that the photons we see from the galaxy itself are 12 billion years old and the photons we see from the CMBR that were in the vicinity of that galaxy are 13.6 billion years old.

The simple answer is that our scientists can't prove that the real CMBR λobserved is 3000K.
That value had been set by the BBT.
As long as this value is based on the BBT, then we all must agree that it doesn't reflect the real CMBR redshift!

[evan_au]

The only plausible source for radiation with no structure (no lines or bands etc) is the recombination of hydrogen nuclei and electrons.

As I understand it, a thermal/black-body spectrum can also come from a plasma (in this case composed almost entirely of hydrogen & helium).
- However, a dense plasma is pretty opaque to light, so the light is being continually scattered (thermal equilibrium)
- So you can normally only observe it from the edge
- As far as we know, the universe has no "edge"

The Big Bang theory suggests that as the universe expanded, it cooled and became less dense
- So the peak of the Black Body radiation spectrum shifted to longer wavelengths/lower frequencies
- When the temperature of the universe dropped low enough for the last of the hydrogen protons & electrons to combine into neutral hydrogen atoms, the universe became transparent to all wavelengths up to UV (photons <13 eV)
- So what we now see in the CMBR is the plasma black-body radiation, red-shifted from a temperature of around 3000K to 2.7K
- The formation of atomic hydrogen was not the source of the radiation, but more the "camera shutter" through which we can now see the plasma of the universe's early fireball.

form neutral atoms of mostly hydrogen. Unlike the plasma, these atoms could not scatter thermal radiation by Thomson scattering, and so the universe became transparent

https://en.wikipedia.org/wiki/Cosmic_microwave_background

we should have the technology to detect/observe the CMBR around those far away galaxies.

The galaxies formed after the Big Bang, so there is no CMBR around the galaxies.
- The James Webb IR telescope should give us a better idea of how soon galaxies formed after the Big Bang
- But the highest galactic redshift seen so far is HD1 at z=13.3
(List continually updated at: https://en.wikipedia.org/wiki/List_of_the_most_distant_astronomical_objects  )
- This means that HD1 is far from the "surface of last scattering", which is the source of CMBR at z=1100

There are several expected temp levels in that "Atomic hydrogen welding" process

Hydrogen welding is conducted in hydrogen gas, which has several additional degrees of freedom than the atomic hydrogen which is believed to be the source of the CMBR.

we only use the measured peak temperature as the λrest in the redshift formula

It's true that some earlier studies of CMBR only looked at a fairly narrow range of wavelengths.
But some of the more recent space-based CMBR satellites have measured the spectrum of the CMBR at many wavelengths.
For example, the WMAP probe measured the shape of the CMBR spectrum from 23 GHz to 94 GHz.
https://en.wikipedia.org/wiki/Wilkinson_Microwave_Anisotropy_Probe

[Origin]

I noticed you ignored my response to your claim so I assume you realized your error

As long as this value is based on the BBT, then we all must agree that it doesn't reflect the real CMBR redshift!

No, I don't agree at all. 
It has been explained in this thread and in your own citation how the redshift of the CMBR was calculated, so I am at a loss on how to help you.

[Dave Lev (OP)]

The Big Bang theory suggests that as the universe expanded, it cooled and became less dense
- So the peak of the Black Body radiation spectrum shifted to longer wavelengths/lower frequencies
- When the temperature of the universe dropped low enough for the last of the hydrogen protons & electrons to combine into neutral hydrogen atoms, the universe became transparent to all wavelengths up to UV (photons <13 eV)
- So what we now see in the CMBR is the plasma black-body radiation, red-shifted from a temperature of around 3000K to 2.7K

Thanks
You have just offered the basic explanation of the BBT.
That explanation is very clear to me.
I do not argue about the BBT and I fully understand your explanation why based on the BBT the 3000K had been selected.

This means that HD1 is far from the "surface of last scattering", which is the source of CMBR at z=1100

Sorry, the idea of "surface of last scattering" is based on the BBT idea.
Therefore, the 3000K is a direct outcome from the BBT.
Hence, the 1100 redshift in the CMBR is also a direct outcome from the BBT.
The CMBR by itself has a redshift/blueshift that only indicates about our motion in the local space.
You have already explained it:

The CMBR exhibits a dipole, suggesting a motion of our star in our galaxy of about 600km/sec, relative to the CMBR. https://astronomy.swin.edu.au/cosmos/c/Cosmic+Microwave+Background+Dipole

"This radiation, now called the Cosmic Microwave Background or CMB, has an extremely uniform temperature of 2.725 Kelvin if one accounts for the smooth gradient in its temperature (from 0.0035 Kelvin below average in the direction of the constellation Aquarius, to 0.0035 Kelvin above average in the direction of the constellation Leo) across the sky. It was quickly realised that this dipole was the result of our Galaxy moving at 600 km/sec with respect to the CMB radiation, and it is now known that this reflects the motion of the Local Group of galaxies towards the Great Attractor."

Hydrogen welding is conducted in hydrogen gas, which has several additional degrees of freedom than the atomic hydrogen which is believed to be the source of the CMBR.

It is fully clear that once we believe in the BBT we also believe that the atomic hydrogen idea (at 3000K) is the source of the CMBR.
However, there is no other/direct prof that the CMBR λobserved is 3000K.

- So what we now see in the CMBR is the plasma black-body radiation, red-shifted from a temperature of around 3000K to 2.7K
- The formation of atomic hydrogen was not the source of the radiation, but more the "camera shutter" through which we can now see the plasma of the universe's early fireball.

Do you agree that the 3000K is a direct outcome from the BBT, while we only get the 2.725 Kelvin from the CMBR?
Hence, do you confirm that the λobserved had been set to 3000K as direct outcome from the BBT theory?
If so, why can't we agree that:
The CMBR BBT redshift = 1100
While
The real CMBR redshift only suggesting a motion of our galaxy of about 600km/sec?