[Kryptid]

1. If our distance to the near edge is R1 and the distance to the far edge is 1000R1, do you agree that the expansion impact of 1000R1 should be higher than R1 by 1000? If so, how could it be that we should get the same redshift in both directions?

Since we can't see any visible boundary to the visible universe, the visible universe must have a radius of at least slightly less than R1, The visible universe represents the limits of what we can see, so anything happening more than a distance of R1 away from us simply would not be visible and therefore could not impact our observations.

2. If we are located only one Mpc from the edge, then the impact of the expansion is only 73Km/s. How that speed can set a redshift of 1100?

We're not a mere 1 mega-parsec from the edge. We are about 46 billion light-years from the edge of the visible universe, so we are at least that far from any hypothetical absolute edge of the Universe as well.

Then there is another possibility I realized. Our visible universe could represent such an incredibly small portion of a gigantic (but finite) total universe that any anisotropies in the CMB that are present are too small for us to detect with current technology. It would be like trying to measure the curvature of the Earth with a school ruler.

[Dave Lev (OP)]

1. If our distance to the near edge is R1 and the distance to the far edge is 1000R1, do you agree that the expansion impact of 1000R1 should be higher than R1 by 1000? If so, how could it be that we should get the same redshift in both directions?

Since we can't see any visible boundary to the visible universe, the visible universe must have a radius of at least slightly less than R1, The visible universe represents the limits of what we can see, so anything happening more than a distance of R1 away from us simply would not be visible and therefore could not impact our observations.

The CMB is equidistant in all directions.  It is a shell centered on us.  Any CMB light that originated closer by has already passed by us.  Any further out hasn't got here yet.  Therefore the distance to the edge, in a model that has an edge at all, has zero effect on what is seen.

Sorry, you both don't answer my question.
Space expanding
You have stated that Space expanding in all directions would cause an equal redshift at all locations in the Universe:

Space expanding in all directions would cause an equal redshift at all locations in the Universe.

I wonder how the Space expanding can set the same redsift to different distances and different velocities due to the impact of space expansion.
1. How could it be that we get exactly the same redshift value from the near edge of the universe which is R1 and from the furthest edge which is higher by 1000 times than R1 (without the impact of space expansion)?
2. If we add the impact of space expansion, that it is clear that the edge which is located 1000 times R1 from us will move even further away at higher velocities. That should even make it much more difficult to get the same redshift. So, how can you claim that the space expansion adjust them all to the same level?
3. https://en.wikipedia.org/wiki/List_of_the_most_distant_astronomical_objects
List of the most distant astronomical objects
We see that GN-z11 galaxy is located at a distance of 13.39   billion LY away and its redshift is only z = 11.09.
So, why we get exactly Z = 1400 in the CMB, while for a galaxy that is located at the furthest location (13.39 billion LY)  in our Universe we only get 11.9?
4. If in one side our distance to the edge is only 13.39 billion LY =R1, what do you think should be the CMB redshift?
Do you agree that the radiation amplitude of the furthest galaxy gets to our location at the minimal value (as 1/R^2).
So, if we look directly in this direction we should get radiations from all the galaxies which are located in that line. those galaxies has lower redshift but higher radiation amplitude.
Hence, we should see in the CMB (at the direction of GN-z11 galaxy) the sum of all the radiations from all the galaxies/objects that are located in this direction.
As the furthest galaxy has a minimal radiation amplitude with a redshift of 11.9, while closer galaxies with much more radiation amplitude have a lower redshift (lower even than 1), do you agree that the average redshift should actually be much lower than 11.9. (could it be 2 or even less than 1?).
If so, how could it be that we get a redshift of 1400 in the CMB in all directions? Why not 5 or 11.9?
Do you agree that this redshift value of 1400  is a real enigma for any finite Universe?

[Kryptid]

Sorry, you both don't answer my question.

Yes I did. Anything further away from us than R1 is too far away to see, so it can't impact our observations.

You have stated that Space expanding in all directions would cause an equal redshift at all locations in the Universe:

Yes, but not all radiation that we see has traveled the same distance to reach our telescopes. Radiation that has traveled further would be more redshifted because it has been moving through an expanding space for a longer period of time.

I wonder how the Space expanding can set the same redsift to different distances and different velocities due to the impact of space expansion.

There is a subtle difference that needs to be pointed out. The rate that space is expanding is the same at any given location in the Universe (as far as we can tell, anyway). So the amount of stretching that any given photon experiences over any given measure of time should be the same for every location in the Universe as well. However, what is different is that different photons are given different amounts of time to stretch because some travel further than others before reaching our telescopes (as I explained before). So the redshift we observe is greater for objects of greater distance from us.

1. How could it be that we get exactly the same redshift value from the near edge of the universe which is R1 and from the furthest edge which is higher by 1000 times than R1 (without the impact of space expansion)?

We can't see past R1 so what is happening 1,000 times further away isn't visible to us. I say that we can't see past R1 because the edge of the total Universe must be somewhere outside of the observable universe (otherwise we could detect that edge). So R1 must be at least slightly beyond the edge of the observable universe, putting R1000 just that much further beyond our observation abilities.

2. If we add the impact of space expansion, that it is clear that the edge which is located 1000 times R1 from us will move even further away at higher velocities. That should even make it much more difficult to get the same redshift. So, how can you claim that the space expansion adjust them all to the same level?

Because we can't see past R1 at all.

3. https://en.wikipedia.org/wiki/List_of_the_most_distant_astronomical_objects
List of the most distant astronomical objects
We see that GN-z11 galaxy is located at a distance of 13.39   billion LY away and its redshift is only z = 11.09.
So, why we get exactly Z = 1400 in the CMB, while for a galaxy that is located at the furthest location (13.39 billion LY)  in our Universe we only get 11.9?
4. If in one side our distance to the edge is only 13.39 billion LY =R1, what do you think should be the CMB redshift?
Do you agree that the radiation amplitude of the furthest galaxy gets to our location at the minimal value (as 1/R^2).
So, if we look directly in this direction we should get radiations from all the galaxies which are located in that line. those galaxies has lower redshift but higher radiation amplitude.
Hence, we should see in the CMB (at the direction of GN-z11 galaxy) the sum of all the radiations from all the galaxies/objects that are located in this direction.
As the furthest galaxy has a minimal radiation amplitude with a redshift of 11.9, while closer galaxies with much more radiation amplitude have a lower redshift (lower even than 1), do you agree that the average redshift should actually be much lower than 11.9. (could it be 2 or even less than 1?).
If so, how could it be that we get a redshift of 1400 in the CMB in all directions? Why not 5 or 11.9?
Do you agree that this redshift value of 1400  is a real enigma for any finite Universe?

The reason is because the light from those distant galaxies was emitted when the Universe was relatively old (about 1,000,000,000 years after the Big Bang), whereas the light that would become the CMB was emitted when the Universe first became translucent (only about 379,000 years after the Big Bang). So the CMB has been experiencing redshift for far, far longer than the light from any galaxy has.

[Dave Lev (OP)]

Dear Kryptid

I really don't understand how do you set the contrediction:
In one hand you claim that:

Radiation that has traveled further would be more redshifted because it has been moving through an expanding space for a longer period of time.

Based on this answer it is clear to me that the radiation that has traveled further (from 1000 times R1) would be more redshifted than the radiation that traveled only one R1.
So, how could it be that we get the same radiation from a distance of R1 and 1000 times R1.
I read your following explanation and I still don't understand:
You claim that:

We can't see past R1 so what is happening 1,000 times further away isn't visible to us. I say that we can't see past R1 because the edge of the total Universe must be somewhere outside of the observable universe (otherwise we could detect that edge). So R1 must be at least slightly beyond the edge of the observable universe, putting R1000 just that much further beyond our observation abilities.

So, I agree that R1 represents the nearby edge of our universe and must be at least slightly beyond the edge of the observable universe.
However, we know that on the other side of the Universe, our distance to the edge of the Universe is 1000 times R1. So, why in that direction we don't get higher redshift as the distance is longer by 1000 times?
How it could be that we get a redshift of 1400 if the edge is just slightly beyond the edge of the observable universe or if it 1000 times longer?
Actually, if we get a redshift of 1400 from a far end galaxy, can we calculate/extract the estimated distance to this galaxy?
If so, what is the distance that redshift of 1400 represents?
If we get the same redshift from all directions, why we can't assume that we are located just at the center of the Universe?


 

[Halc]

The visible universe represents the limits of what we can see
...

We are about 46 billion light-years from the edge of the visible universe, so we are at least that far from any hypothetical absolute edge of the Universe as well.

I am going to protest the top statement.  The visible universe represents the current proper distance of the furthest material that could ever have had a causal effect on our current location.  That by no means says we can see that far.  The event horizon is only about a third that distance and anything beyond that cannot have an effect here ever, so that's the absolute limit of how far we can see if we're willing to wait forever.

The light from the CMB is the furthest we can see, and it was emitted a scant ~1.3 million light years (proper distance) from the comoving location corresponding to here.  The journey from there to us/here/now took it considerably further away than that, but no more than say a single digit of BLY away (proper distance again).  That's the furthest we can see, which is well inside the Hubble sphere.  If that light's journey took it to the edge of the universe, it would presumably be affected by that.  We'd see it.  We cannot see any further away than that.
So R1 is not very far at all, no more than 20% of that 46 BLY radius of the 'visible universe'.

To illustrate:

3. https://en.wikipedia.org/wiki/List_of_the_most_distant_astronomical_objects
List of the most distant astronomical objects
We see that GN-z11 galaxy is located at a distance of 13.39   billion LY away and its redshift is only z = 11.09.
So, why we get exactly Z = 1400 in the CMB, while for a galaxy that is located at the furthest location (13.39 billion LY)  in our Universe we only get 11.9?

You will notice a little mark on the collumn where this 13.39 'location' is listed.  It says there that the number has no direct physical significance.  We can't see that far.  The object isn't that far.  The time it took light to get from there to here is not 13.39 billion years in any meaningful frame.  It isn't proper distance.
The CMB is considerably further away than that, yet is not listed as it isn't a distinct galaxy or other object.  And yet the CMB light was emitted only 1.3 million (not billion) light years away.

[Kryptid]

Based on this answer it is clear to me that the radiation that has traveled further (from 1000 times R1) would be more redshifted than the radiation that traveled only one R1.

There hasn't been enough time since the Big Bang for any radiation to travel to that far.

ased on this answer it is clear to me that the radiation that has traveled further (from 1000 times R1) would be more redshifted than the radiation that traveled only one R1.
So, how could it be that we get the same radiation from a distance of R1 and 1000 times R1.

We don't because we can't see any radiation from beyond R1.

So, why in that direction we don't get higher redshift as the distance is longer by 1000 times?

Because we can't see any radiation from beyond R1. How do you possibly expect to measure radiation that hasn't even made it to you?

How it could be that we get a redshift of 1400 if the edge is just slightly beyond the edge of the observable universe or if it 1000 times longer?
Actually, if we get a redshift of 1400 from a far end galaxy, can we calculate/extract the estimated distance to this galaxy?
If so, what is the distance that redshift of 1400 represents?

I don't think there are any galaxies in the observable universe with a redshift anywhere near that high, but you can estimate distances to galaxies based on redshift. I don't know what the equation involved is, though.

If we get the same redshift from all directions, why we can't assume that we are located just at the center of the Universe?

We are located in the center of the observable universe. Since the speed of light is the same in all directions, this means that the distance we can see in all directions is equal. Where this observable universe sits inside the total Universe is unknown.

I am going to protest the top statement.  The visible universe represents the current proper distance of the furthest material that could ever have had a causal effect on our current location.  That by no means says we can see that far.  The event horizon is only about a third that distance and anything beyond that cannot have an effect here ever, so that's the absolute limit of how far we can see if we're willing to wait forever.

The light from the CMB is the furthest we can see, and it was emitted a scant ~1.3 million light years (proper distance) from the comoving location corresponding to here.  The journey from there to us/here/now took it considerably further away than that, but no more than say a single digit of BLY away (proper distance again).  That's the furthest we can see, which is well inside the Hubble sphere.  If that light's journey took it to the edge of the universe, it would presumably be affected by that.  We'd see it.  We cannot see any further away than that.
So R1 is not very far at all, no more than 20% of that 46 BLY radius of the 'visible universe'.

Alright.

[Halc]

I don't think there are any galaxies in the observable universe with a redshift anywhere near that high, but you can estimate distances to galaxies based on redshift. I don't know what the equation involved is, though.

I don't know the equation offhand either, but if you look at the redshift figures for the list of 'furthest galaxies' linked, you notice that the whole list has not much distance variance, but the redshift factor number goes up dramatically for the entries at the top of the list.   The number apparently come from the Lambda-CDM model, a plot (from wiki) appearing here:
https://upload.wikimedia.org/wikipedia/commons/thumb/a/a7/Distance_compared_to_z.png/400px-Distance_compared_to_z.png

Notice that a galaxy at 13.4 GLY (that funny figure that corresponds to nothing physical) plots nicely at 11, and the CMB with z=1100 seems to be 46 GLY away by that measure.
That's contradictory to what I've read about most distant objects since they've measured a quazar at something like 22 GLY away, meaning that object is now that far away, but within our event horizon back when the light reaching us now was first emitted.  So I don't know exactly what is being measured on the vertical axis of that graph.
Notice that the graph levels off at 46 GLY, with z approaching indefinite values as distance approaches the 'size of the visible universe'.  If we could see through the CMB barrier, we'd observer redshifts far greater than 1100.
The red line is the Hubble red shift, and that goes to infinite z at the Hubble radius.

[Dave Lev (OP)]

I don't know the equation offhand either, but if you look at the redshift figures for the list of 'furthest galaxies' linked, you notice that the whole list has not much distance variance, but the redshift factor number goes up dramatically for the entries at the top of the list.   The number apparently come from the Lambda-CDM model, a plot (from wiki) appearing here:
https://upload.wikimedia.org/wikipedia/commons/thumb/a/a7/Distance_compared_to_z.png/400px-Distance_compared_to_z.png
Notice that a galaxy at 13.4 GLY (that funny figure that corresponds to nothing physical) plots nicely at 11, and the CMB with z=1100 seems to be 46 GLY away by that measure.

Thanks Halc
This is very interesting data.
Hence, the CMB with z=1100 seems to be 46 GLY away by that measure!
So, why do you claim that the CMB was emitted only 1.3 million (not billion) light years away.

The CMB is considerably further away than that, yet is not listed as it isn't a distinct galaxy or other object.  And yet the CMB light was emitted only 1.3 million (not billion) light years away.

I really don't understand that contradiction.
You also see the contradiction, but I couldn't understand what do you really mean:

That's contradictory to what I've read about most distant objects since they've measured a quazar at something like 22 GLY away, meaning that object is now that far away, but within our event horizon back when the light reaching us now was first emitted.  So I don't know exactly what is being measured on the vertical axis of that graph.
Notice that the graph levels off at 46 GLY, with z approaching indefinite values as distance approaches the 'size of the visible universe'.  If we could see through the CMB barrier, we'd observer redshifts far greater than 1100.
The red line is the Hubble red shift, and that goes to infinite z at the Hubble radius.

Actually, our scientists claim that the CMB is evidence for the BBT.
So, if the Big bang had been set 13.8 Billion years ago, how could it be that the CMB which is consider as a product of the BBT comes from a distance of 46GLY?
Actually, if we see today a radiation which had been emitted from a distance of 46GLY, don't you think that it proves that our real universe should be much bigger than the estimated size of the observable Universe?
If so, how can we fit that size of the Universe in only 13.8 BY?
Do you think that it could set a contradiction in the BBT?

[Halc]

Hence, the CMB with z=1100 seems to be 46 GLY away by that measure!
So, why do you claim that the CMB was emitted only 1.3 million (not billion) light years away.

Read the post where I said that. The thing 45 GLY away is not the CMB anymore.  It is a collection of galaxies that it has become after 13.8 billion years just like it did here. We cannot see that. We can only see light that is here, now. The CMB that we see is redshifted radiation that was emitted 1.3 million proper LY away, back when the universe was 379,000 years old. It is a perfect shell of uniform radius at any given moment, and hence appears totally uniform to us due to symmetry. The CMB we see is isotropic because we're at the center of it.

The CMB is considerably further away than that, yet is not listed as it isn't a distinct galaxy or other object.  And yet the CMB light was emitted only 1.3 million (not billion) light years away.

I really don't understand that contradiction. You also see the contradiction, but I couldn't understand what do you really mean:

I didn't make any contradiction.  The 'distant' galaxies (or at least the material that would become them) were closer than 1.3 million LY away back at the same time that the CMB light we see now was emitted.  Everything was closer back then.  That's what expansion of space means.

Actually, our scientists claim that the CMB is evidence for the BBT.

Of course.  The BBT predicts it.  Other theories have to find some other way to explain it.

So, if the Big bang had been set 13.8 Billion years ago, how could it be that the CMB which is consider as a product of the BBT comes from a distance of 46GLY?

It doesn't come from that distance.  It comes from 1.3 million LY away.  45GLY is where that material is now, assuming (possibly incorrectly) that the Lambda-CDM model figures its distances that way. 46GLY is even further, but light from there is blocked by the hot plasma of the early universe. I'm not particularly familiar with the Lambda-CDM model, but it is apparently the computation used when asserting the 46 GLY radius of the visible universe.
Remember, I cannot even see the moon right now.  I see some past image of it.  My ability to see into the present is zero.  Light doesn't travel infinitely fast, so I can see nothing in its current state.

Actually, if we see today a radiation which had been emitted from a distance of 46GLY,

We can't.  Light from that far away will not get here ever, even after infinite time.  The event horizon is only ~16GLY away.  Anything beyond that can never be seen.

don't you think that it proves that our real universe should be much bigger than the estimated size of the observable Universe?

It is improbable indeed that the universe is as small as that, but since the furthest we can see (now) is under 10GLY, a hyperspherical universe of radius 1.6GLY would actually look like what we see.  That radius is 30x smaller than 46GLY, but I think perhaps the curvature of such a tight universe might be noticed.

It is an interesting exercise to measure curvature.  Suppose you are on an non-spinning an non-orbiting Earth and you posit Earth is flat and infinite. Your argument seems to be that if it were finite and we were not at the exact center, we'd notice the current of the water as it migrates to the edge and falls off. You do all these calculation showing the improbability of being closer to the center than not. But you never consider a round planet.
How might you measure that? If its a small radius, you might just travel a short ways and notice that the stars have moved, but what if you were confined to one city block?  You can draw a triangle on a parking lot and notice that the angles don't add up to 180 (if you're super accurate with your measurements), but what if the the other angles of the triangle are out of reach?  Such is the difficultly of measuring curvature from one point.

If so, how can we fit that size of the Universe in only 13.8 BY?

I managed to cram it into a ninth that size.  No, I don't propose the universe is that small, but that's about the limit before we'd see an anomaly in the CMB.

Do you think that it could set a contradiction in the BBT?

BBT doesn't assert a finite universe that small, so of course that wouldn't contradict it.  It doesn't assert a finite or infinite universe at all.  If it did, I suppose there would be a stronger opinion of which is correct.

[Dave Lev (OP)]

The 'distant' galaxies (or at least the material that would become them) were closer than 1.3 million LY away back at the same time that the CMB light we see now was emitted.  Everything was closer back then.  That's what expansion of space means.

Thanks
I don't understand how a redshift which we are using for galaxies can't also be used for the CMB?
A redshift is a redshift. It comes as an information in the radiation. It comes from any kind of matter. We can call this matter: dust, Gas cloud, stars, galaxies... (What about CMB radiation from dark matter or dark energy?)
So, if we claim that a radiation from a galaxy with a redshift of 1100 represents a distance of  46GLY, why a radiation which we call CMB with a redshift of 1100 doesn't represents a radiation which had been emitted from a distance of 46GLY?
Few more questions:
1. Do you mean that the whole mass of the Universe were at some point of time at a maximal distance of only 1.3 Million LY from each other?
2. If so, do you agree that there is no way to set an infinite Universe in only 13.8 BY?
3. In this case, why do you claim that we don't know if the universe is finite or infinite. Do you agree that based on the BBT the Universe must be finite? If we will discover that the Universe is infinite, than what do you prefer: a problem with the discovery or a problem with the BBT?
4. If we could eliminate completely the impact of the BBT on the CMB
What is the expected CMB that we should get with regards to Amplitude, Redshift and isotroic?
5. Do we have any idea what is the estimated amplitude degradation in the CMB per one million year?
6. If we could come back to our Universe in one Billion or 10 Billion years from now, then what kind of CMB we might find?
7. Can we extract from the CMB the total mass of the whole Universe?

[evan_au]

I don't understand how a redshift which we are using for galaxies can't also be used for the CMB?

The CMB originated from a soup of hot atomic gas (mostly Hydrogen, some Helium) which had just cooled below 3000K, and become transparent to visible light.

It should not be possible for stars to condense when temperatures are this high, so we don't expect to find galaxies of stars of the same age of the CMB. So the first galaxies (pinwheels of stars) are expected to have a lower redshift than the CMB.

Footnote: Astronomers have seen that the black holes at the core of quasars formed surprisingly early in the early universe, and it is not clear what pulled these supermassive black holes together. It is conceivable that these cores were formed during the Big Bang, started like a giant accretion disk of gas; galaxies of stars later formed around them.

[Halc]

I don't understand how a redshift which we are using for galaxies can't also be used for the CMB?

They don't use a different kind of redshift for different things.  Galaxies are closer, so they're less redshifted, as evan_au points out.  Galaxies are things and have defined distances from us.  The CMB is not a thing or an object and has no distance to us.  It is a single flash of light that occurred everywhere (even here).  It left only the light and no object from which it came.  So there is no meaningful distance to the CMB since there is no CMB to which one might travel.

A redshift is a redshift. It comes as an information in the radiation. It comes from any kind of matter. We can call this matter: dust, Gas cloud, stars, galaxies... (What about CMB radiation from dark matter or dark energy?)

CMB is radiation from normal plasma/hydrogen, not dark anything.  Yes, it is redshifted like anything else that was emitted at a significant distance.

So, if we claim that a radiation from a galaxy with a redshift of 1100 represents a distance of  46GLY, why a radiation which we call CMB with a redshift of 1100 doesn't represents a radiation which had been emitted from a distance of 46GLY?

Nothing that distant can be seen.  It is too far away.  Please read what I said in the prior posts about this.

Few more questions:
1. Do you mean that the whole mass of the Universe were at some point of time at a maximal distance of only 1.3 Million LY from each other?

1.3 MLY is the distance from here that the CMB we see now was emitted.  That was never stated to be the radius of the whole universe at that time.

2. If so, do you agree that there is no way to set an infinite Universe in only 13.8 BY?

No.

3. Do you agree that based on the BBT the Universe must be finite?

No.

4. If we could eliminate completely the impact of the BBT on the CMB
What is the expected CMB that we should get with regards to Amplitude, Redshift and isotroic?

The question makes no sense.  The CMB is the big bang itself we are seeing.  Without the BB, there would be no CMB.

5. Do we have any idea what is the estimated amplitude degradation in the CMB per one million year?

It isn't a fixed value per million years, but is very predictable. I don't know the current rate.  A million years is about a 14000th the age of the universe, so I imagine it will lower the CMB temperature somewhere around the 5th digit in or thereabouts.

6. If we could come back to our Universe in one Billion or 10 Billion years from now, then what kind of CMB we might find?

3000K if you go all the way back to when it was emitted.

7. Can we extract from the CMB the total mass of the whole Universe?

No.  We don't know the size and the CMB is only a temperature of a shell of material at a fixed radius, centered on us.

[Halc]

Here is a good image illustrating all the concepts we're talking about.


The upper graph shows proper distance vs time, and the 'visible universe' is seen to be where the particle horizon crosses the 'now' line (which is defined as the age of the universe for a comoving ('stationary') object).  A comoving object is one for which the universe appears to be isotropic.  The solar system motion varies in the long term, but we're currently about 0.0013c from being comoving.  It's more than twice that when we get to the other side of the galaxy.
The lower graph shows the same thing in comoving coordinates, and the black dotted worldlines are just vertical lines in that view.

The event horizon (orange) delimits events which can never have a causal effect on us here even given infinite time.  The event horizon would not be there if the expansion of the universe was not accelerating.

The Hubble Sphere (purple) is the line where comoving objects are increasing their proper distance from us at light speed.  It would be straight if the expansion of space were not accelerating.

The red line is the light cone and represents what we can see.  Every event (every star in the sky, the moon, the CMB and the beer you're holding) is on that red line.  It seems to go furthest to the right at about 3.5 BY and reaches the 5.5 BLY mark.  That's as far as we can see.  R1 is 5.5 BLY.  If the universe has an edge and looks different there, the red line needs to cross it for us to notice it.

The CMB is on that red line and so low on the chart that you cannot make out how close it is to here.  I figure it to be around 1.3 MLY away, but I did not actually read that number anywhere.  The best way to figure that is to use the lower graph.

The black dotted lines are worldlines for comoving objects, and those within the particle horizon touch the red line, and those outside it do not.  The red line is 'what we see', so this difference defines 'the observable universe'.

You will notice that they don't even bother drawing a line to represent events simultaneous with us in our inertial frame.  I challenge you to plot that.  The inability to do so illustrates why special relativity is special and does not apply to our universe.

[Dave Lev (OP)]

Thanks Halc & Evan_au

I do appreciate the answers.

Let me ask the following:
Is there any way, any evidence, any discovery any issue which could convince you that there is a problem with the BBT?

3000K if you go all the way back to when it was emitted.

If we could travel in time:
If we could verify that at the early days (about 13 Billion years ago) the CMB was exactly as it is today, while also 10 Billion years from now in the future, the CMB is also the same.
What can we learn from that?

The CMB is the big bang itself we are seeing.  Without the BB, there would be no CMB.

Why are you so sure that without the Big bang there is no CMB?
For example:
Thermal emission of dust in the Milky way:
https://irsa.ipac.caltech.edu/applications/DUST/docs/background.html
"The dust temperature varies from 17 K to 21 K, which is modest but does modify the estimate of the dust column by a factor of 5".
So, the Milky Way has a thermal emission.
Let's assume that we could set the whole Milky way in some sort of closed sphere or galactic Oven.
In this case, what would be the thermal radiation amplitude in that galactic oven or closed sphere?
Actually, Oven could be a perfect example:
When the door is closed and we operate the oven, we can get over than 220c in the oven. However, once we open the door, the temp goes immediately down. We can set our hand in the oven and we won't feel that supper high temp.
So, I wonder what might be the "CMB" of the Milky Way if we could set it in some sort of a galactic oven.

[Halc]

Let me ask the following:
Is there any way, any evidence, any discovery any issue which could convince you that there is a problem with the BBT?
...
If we could travel in time:
If we could verify that at the early days (about 13 Billion years ago) the CMB was exactly as it is today, while also 10 Billion years from now in the future, the CMB is also the same.
What can we learn from that?

That would be pretty strong evidence for some sort of steady state theory.  If all the galaxies were younger and closer together 13 BY ago, then the steady state theory would be wrong as well.

Why are you so sure that without the Big bang there is no CMB?.

There is a CMB.  It is an empirical fact.  So another theory that accounts for it (and everything else) is another contender.

For example:
Thermal emission of dust in the Milky way:
https://irsa.ipac.caltech.edu/applications/DUST/docs/background.html.
"The dust temperature varies from 17 K to 21 K, which is modest but does modify the estimate of the dust column by a factor of 5".
So, the Milky Way has a thermal emission..

Sure.  So does the sun.  It looks nothing like the CMB.  The picture at the top of that website looks nothing like the CMB picture.

Let's assume that we could set the whole Milky way in some sort of closed sphere or galactic Oven.
In this case, what would be the thermal radiation amplitude in that galactic oven or closed sphere?.

If you put part of it in a closed sphere like that it would get warm in there and there would be no thermal radiation to the outside because the enclosure would reflect it back in.  Removing the enclosure would be something like opening an oven door, yes.

So, I wonder what might be the "CMB" of the Milky Way if we could set it in some sort of a galactic oven.

It would be the Milky Way light background (MWLB).  It has no thermostat like an oven so it would just keep getting hotter as energy is converted to heat.  The galaxy would also be less massive because the enclosure would prevent any new fuel from getting in, so the temperature seems to depend partly on how much it has when you seal it off, and how long you let it cook.

Concerning the graph I posted:

So, if we claim that a radiation from a galaxy with a redshift of 1100 represents a distance of  46GLY, why a radiation which we call CMB with a redshift of 1100 doesn't represents a radiation which had been emitted from a distance of 46GLY?

Galaxies are objects, and almost all of them are nearly comoving.  Objects have vertical lines in the 2nd graph.  There is a comoving distance to each of them.
The CMB is not an object, and so does not have a vertical line.  It is a horizontal line (it happened everywhere) in either graph, at the T=379,000 mark, which is at the bottom. It doesn't exist now because now isn't year 379,000. What we see now is anything at (not within) the red line.  We can see a galaxy only if the vertical black worldline of the galaxy object intersects the red line.  We can see now the CMB at exactly the one point where the red line intersects the horizontal CMB line, which in the first picture is at about 1.3 million light years.

[Kryptid]

Why are you so sure that without the Big bang there is no CMB?

The CMB is extremely uniform (temperature fluctuations from one place to another amount to a mere + 0.00335 kelvins), which means that it isn't radiation emitted by localized sources like stars or galaxies. It must have been emitted by something that once evenly filled all of space.

[Dave Lev (OP)]

Black Body Radiation:

The CMB is extremely uniform (temperature fluctuations from one place to another amount to a mere + 0.00335 kelvins), which means that it isn't radiation emitted by localized sources like stars or galaxies. It must have been emitted by something that once evenly filled all of space.

Wow
That exactly the message which I was looking for.
You claim that:"It must have been emitted by something that once evenly filled all of space"
I would like to add that: It is emitted by something that filled all of space.
In order to understand that, let's look at the Black body radiation.
https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Map%3A_Physical_Chemistry_(McQuarrie_and_Simon)/01%3A_The_Dawn_of_the_Quantum_Theory/1.1%3A_Blackbody_Radiation_Cannot_Be_Explained_Classically
It is stated clearly:
"A body emits radiation at a given temperature and frequency exactly as well as it absorbs the same radiation"
Therefore:
"Blackbody radiator is any object that is a perfect emitter and a perfect absorber of radiation."
"So how do we construct a perfect absorber in the laboratory? OK, nothing’s perfect, but in 1859 Kirchhoff had a good idea: a small hole in the side of a large box is an excellent absorber, since any radiation that goes through the hole bounces around inside, a lot getting absorbed on each bounce, and has little chance of ever getting out again. So, we can do this in reverse: have an oven with a tiny hole in the side, and presumably the radiation coming out the hole is as good a representation of a perfect emitter as we’re going to find (Figure  1.1.2 )."
They also have used the same idea of Oven as I did: "have an oven with a tiny hole in the side"
So, if I understand it correctly, in order to get from a black body radiation, all/most of the radiation must stay at the object.
However, once we take it out from the "oven", there is no black body radiation any more.
So, Let's go back to the following statement:

It must have been emitted by something that once evenly filled all of space.

Therefore, at the early time the Big bang took all the early available space. Therefore at the first moment the radiation of the Bang was clearly black body.
However, once we start the inflation and the expansion we actually kill any possibility for black body radiation.
As we contradict the basic idea of "perfect absorber of radiation":
"Blackbody radiator is any object that is a perfect emitter and a perfect absorber of radiation"
Therefore I have stated: "It is emitted by something that filled all of space."
So, in order to get the black boday radiation in the CMB, it must also filled all of space today
Therefore, the idea of the inflation and expansion actually contradicts the possibility for black body radiation.
So, the only way to get this black body radiation is by setting the object in an oven (As I have used in my example).
Therefore, let me go back to my example:

Let's assume that we could set the whole Milky way in some sort of closed sphere or galactic Oven.
In this case, what would be the thermal radiation amplitude in that galactic oven or closed sphere?.

If you put part of it in a closed sphere like that it would get warm in there and there would be no thermal radiation to the outside because the enclosure would reflect it back in.  Removing the enclosure would be something like opening an oven door, yes.

So, you agree that we should get some thermal radiation if we put the Milky way at a galactic oven.
I assume that we will also get a black body radiation - as we fulfill the requirement for:
"Blackbody radiator is any object that is a perfect emitter and a perfect absorber of radiation"
I do not claim that it is feasible to set the Milky way in an oven, but I would like you to look at the impact of this hypothetical activity.
Therefore, do you agree that as long as the Milky Way will be in a galactic oven it will create a "CMB" which carry a black body radiation?
Do you also agree that once we open the oven, the black body radiation will be gone forever?
If so, how could it be that we still get a black body radiation from a CMB while the universe expands?
It seems to me that only if there is some envelope to our universe, than this might keep the black body radiation.
However, if the matter in our universe expands to the open infinity space - I really don't see any possibility to keep the black body radiation in the CMB.
Do you agree with that?
Do you agree that (based on hypothetical idea) if the Milky Way is in a galactic oven it can generate black body radiation?

[Kryptid]

However, once we start the inflation and the expansion we actually kill any possibility for black body radiation.

The radiation was emitted well after the inflationary epoch ended.

So, in order to get the black boday radiation in the CMB, it must also filled all of space today

The CMB does fill all of space today.

[Halc]

Wow
That exactly the message which I was looking for.

Strong evidence of usage of the cherry picking fallacy, something I've pointed out before.

[Halc]

It is stated clearly:
"A body emits radiation at a given temperature and frequency exactly as well as it absorbs the same radiation"
Therefore:
"Blackbody radiator is any object that is a perfect emitter and a perfect absorber of radiation."

So, if I understand it correctly, in order to get from a black body radiation, all/most of the radiation must stay at the object.

I know 'understanding correctly' is not your forte, but you just directly contradicted the quote you gave, which says the black body emits as well as it absorbs.  The radiation does not stay at the object.

It must have been emitted by something that once evenly filled all of space.

Therefore, at the early time the Big bang took all the early available space.

It is space.  It doesn't take available space.

Therefore at the first moment the radiation of the Bang was clearly black body.

It isn't an object, so isn't a body at all.  There is nowhere else to send the radiation.  There is no oven or barrier which has an inside and an outside.  That's what is meant by 'everywhere'.

However, once we start the inflation

The start of expansion was 379000 years before, assuming we're talking about the decoupling event that sets up the CMB as we see it.

"Blackbody radiator is any object that is a perfect emitter and a perfect absorber of radiation"
Therefore I have stated: "It is emitted by something that filled all of space."
So, in order to get the black boday radiation in the CMB, it must also filled all of space today

The CMB does fill all of space today. It isn't blackbody radiation because there isn't a body.  Only the light from the thing that happened everywhere remains.  All we detect is the light.  The plasma from which it was emitted is long gone.

If you put part of it in a closed sphere like that it would get warm in there and there would be no thermal radiation to the outside because the enclosure would reflect it back in.  Removing the enclosure would be something like opening an oven door, yes.

So, you agree that we should get some thermal radiation if we put the Milky way at a galactic oven.

See the part I bolded. No, I agreed that you would release pent up thermal radiation if you opened the oven.  Putting it in an oven would serve to block that radiation.  Yes, there would be radiation detected from the inside from the walls of the enclosure.  Perhaps this is what you're asking.

I do not claim that it is feasible to set the Milky way in an oven, but I would like you to look at the impact of this hypothetical activity.
Therefore, do you agree that as long as the Milky Way will be in a galactic oven it will create a "CMB" which carry a black body radiation?

The enclosure is the black body, as viewed from inside?  If it radiates to the outside, is isn't really an enclosure, just a diffuser like frosted glass.  If there was a shell like you describe, it would get hotter in places that receive more radiation than others and the radiation from it would not appear isotropic.  For that, I think the Milky Way would need to be more spherically symmetrical instead of just circularly.
It isn't a model of the CMB because you are modeling a persisting finite object, something that isn't everywhere. Your model has radiation confined to inside an oven, which isn't everywhere.

Do you also agree that once we open the oven, the black body radiation will be gone forever?

No.  Radiation from it would just keep on going unimpeded into space.  Light doesn't stop just because you turned off the source.  It keeps going until it hits something.

If so, how could it be that we still get a black body radiation from a CMB while the universe expands?

The CMB is light, not the stuff from which it came.  We see it because that light is just now finding something to hit.  It isn't black body radiation.  It sort of was before year 379000.

However, if the matter in our universe expands to the open infinity space

No model suggests this.  It is a naive model of the universe as being an object that 'started' at one location instead of everywhere.  Space and time are parts of the universe, not preexisting things in which the universe happened.

- I really don't see any possibility to keep the black body radiation in the CMB.
Do you agree with that?

I never claimed it was black body radiation.  There's no body.  That would be a property of an object, and the universe is not an object, nor is the CMB.