[Dave Lev (OP)]

Because there are other circumstances- like being inside a large but finite cold box where the CMBR would be exactly the same.

No!
You have only two options to get the blackbody radiation:
1. Inside an "opaque and non-reflective object" at any finite size.
2. In infinite universe size.

There is no possibility to get it at "inside a large but finite cold box". This is pure imagination.
I have stated:

As we take out the imaginary walls from the infinite cubes in that infinite Universe, we would still get exactly the same CMBR.

However, if the Universe is finite (at any large size) then at any direction that we move, at some point we should get to its end. Without the imaginary walls at that end there will be no BBR. As there are no imaginary walls in our real universe, then there is no way to get the BBR in any size of finite universe.
Is it clear by now?

[Bored chemist]

You have only two options to get the blackbody radiation:
1. Inside an "opaque and non-reflective object" at any finite size.
2. In infinite universe size.

Plain wrong.
The walls of my cellar are whitewashed.
I have moved all the stuff out of it.
And I have a single candle in there. The flame is burning at about 1200 C
What is the colour temperature of the radiation in the room?

OK, do you now see that you have more than 2 ways to get BBR?

Imagine I go outside on a foggy moonless night.
I have that candle with me.
What does the radiation that i can see look like?

What about if it's a foggy night and there are lots of candles  around me- each one too far away to see properly but together lighting up the place.
What does the ambient radiation look like?

Do you see that there are far more than 2 ways to do it.

Now, imagine that you are in a universe which formed about 14 billion years ago as a rapidly expanding hot gas cloud.
Until that gas cooled down enough for atoms to form, it was opaque.
When it cooled down to the point where atoms(etc) started to form it was very hot and emitted radiation that was appropriate for a black body at that temperature (very roughly 2000K).

And imagine that, since then the universe has expanded, stretching that radiation.

What; in that hypothetical universe, would you see in the night sky?

I'm hoping you are not going to take another six months to answer that.
Either you accept that it looks like what we see or you explain what it would look like and why it would be different.

Remember, this is a purely hypothetical universe, so there is no option for saying anything about its age.
I told you it's 14 billion years old.
I told you that it expanded nd so on.
And, since it's my "model" universe those facts are true.
What would you see in the night sky?

[Dave Lev (OP)]

OK, do you now see that you have more than 2 ways to get BBR?

No, No No
The request for BBR is very clear and it was already given to you:
http://astro.ucla.edu/~wright/CMB.html
"In order to make a blackbody spectrum, an object has to be opaque, non-reflective and isothermal."
It is even stated that:
"Thus a star, which is opaque, does not produce a blackbody spectrum because we can see both cooler outer layers and hotter deeper layers."

So let me explain it slowly to you:
"In order to make a blackbody spectrum, an object has to fulfill the following three elements:
1. Opaque
2. Non-reflective
3. Isothermal.

Once that is clear to you let's see your fatal errors:

The walls of my cellar are whitewashed.

The universe has no walls therefore, it can't be considered as a whitewashed cellar.
So, if the Universe had walls around it, then we could call it a cube/sphere/room/cellar with whitewashed wall.
As I have already explained:

we all can agree that in an "opaque and non-reflective object" cube the radiation must be black body.

In this case, it is perfectly ok to assume that inside that cellar the radiation must be black body.
Therefore, if you claim that the Universe is finite and located inside that cellar, than you have to prove that it has whitewashed walls all around it.
As it is quite clear to all of us that there are no walls around the Universe, than the Universe can't be considered as a whitewashed cellar/room.

I have moved all the stuff out of it.
And I have a single candle in there. The flame is burning at about 1200 C
What is the colour temperature of the radiation in the room?

As the Universe has no walls you can't compare it to cellar or room.

Imagine I go outside on a foggy moonless night.
I have that candle with me.
What does the radiation that i can see look like?

What about if it's a foggy night and there are lots of candles  around me- each one too far away to see properly but together lighting up the place.
What does the ambient radiation look like?

Sorry, you have a fatal mistake.
A foggy moonless night can't be considered as opaque, non-reflective and isothermal object.
This is pure imagination.

And imagine that, since then the universe has expanded, stretching that radiation.

Ok Let's continue with you imagination:

And imagine that, since then the universe has expanded, stretching that radiation.
What; in that hypothetical universe, would you see in the night sky?

The answer had been given by our scientists:
"Thus a star, which is opaque, does not produce a blackbody spectrum because we can see both cooler outer layers and hotter deeper layers."
So, even if we wish to believe that at some point in the Universe life it really carried a BBR, it can't hold it any more if it has expanded, stretching that radiation and eliminating the walls around it.
No walls means - No BBR.
So, you can stretch it to any finite size, it won't help without walls.
Just if you expand/stretch the Universe to the infinity you can get the BBR without any need for walls around it.
Is it clear to you by now?

I told you it's 14 billion years old.
I told you that it expanded nd so on.
And, since it's my "model" universe those facts are true.
What would you see in the night sky?

OK.
Do you confirm that a Universe with age of 14BY can't be infinite?
So, if you insist to have a BBR in that imaginary finite Universe which exists in your imaginary model, then you MUST show where are the whitewashed walls of your imaginary cellar' Universe are located.
You set the model, so you also must set the exact locations of those walls.
You have started your first message with:

Plain wrong.
The walls of my cellar are whitewashed.

Therefore, please show the location of those walls.
If you don't know the exact location of those walls, then it's better for you to set your entire model in the garbage of the science history.

[Bored chemist]

"In order to make a blackbody spectrum, an object has to be opaque, non-reflective and isothermal."

No
That is a sufficient, but not a necessary condition
Do you understand the difference?
Do you realise that a tungsten lamp emits a very near blackbody spectrum?
Do you think it's a box with a hole in it.
"All alsatians are dogs" is not the same as "all dogs are alsatians."

A hole in a box will emit BBR but not all BBR emitters are a hole in a box.
The Sun matches BBR quite well. That's how we know how hot the surface is.

"Thus a star, which is opaque, does not produce a blackbody spectrum because we can see both cooler outer layers and hotter deeper layers."

The universe is not, and never was "a star".

No walls means - No BBR.

That is not true.
It does not matter how often you say it; it remains false.
They only need to be "optically thick".

So, if you insist to have a BBR in that imaginary finite Universe which exists in your imaginary model, then you MUST

No, I don't.
I can point out that the entire universe was, at that time opaque.
Everywhere was a "wall" as far as light was concerned.
That's the point you keep missing.
Now, without waiting another 6 months, answer the question.
What would you see in the night sky of that  model universe?

[Dave Lev (OP)]

Quote from: Dave Lev on Today at 05:29:34
"In order to make a blackbody spectrum, an object has to be opaque, non-reflective and isothermal."

No
That is a sufficient, but not a necessary condition
Do you understand the difference?
Do you realise that a tungsten lamp emits a very near blackbody spectrum?
Do you think it's a box with a hole in it.
"All alsatians are dogs" is not the same as "all dogs are alsatians."

How could you reject the clear explanation which had been given by our scientists?
Do you really believe that your understanding is superior as they have no idea about Black Body radiation?
They clearly claim that:
 

http://astro.ucla.edu/~wright/CMB.html
"In order to make a blackbody spectrum, an object has to be opaque, non-reflective and isothermal."

Then, you don't have to argue with me. You have to argue with them.
In any case, as you claim that there is no need for walls in order to get the BBR:

Quote from: Dave Lev on Today at 05:29:34
No walls means - No BBR.
That is not true.
It does not matter how often you say it; it remains false.
They only need to be "optically thick".

Then show the article that could support your unrealistic understanding.
You have started the whole idea of BBR with walls around a cellar and now you end it with that unrealistic idea of "optically thick".
Sorry, that "optically thick" isn't part of the requirement from a BBR as explained clearly by our scientists.

I can point out that the entire universe was, at that time opaque.
Everywhere was a "wall" as far as light was concerned.

"optically thick" can't be considered as a wall.

That's the point you keep missing.

The real point is that you want to have a BBR in a finite universe while it has no walls and it can't carry a BBR.
So, you offer some imagination about walls around a cellar and then you call it "optically thick" while you clearly reject the explanation which had been given by our scientists.
Therefore, if you wish to hold some water in your imaginary theory, then you MUST show the article which explains how an "optically thick" could be considered as a wall for a cellar.
So please show the article that supports your unrealistic understanding/ideas.

[Bored chemist]

"optically thick" can't be considered as a wall.

From a photon's point of view it can be.
No other point of view is relevant.

Then, you don't have to argue with me. You have to argue with them.

No.
The conditions in the early universe are "opaque, non-reflective and isothermal"
So there's no problem.
However, the radiation from a coal fire is still a very good approximation to BBR.
That's a simple fact; feel free to test it.
It's not that I ma arguing with them.
It's that you are arguing against reality.
And the thing is that a candle, a light bulb and a coal fire are not a container with a hole.

Why are you still trying to pretend that they are?

How could you reject the clear explanation which had been given by our scientists?

No.
That is, however, what you are doing in not accepting that the CMB is what is leftover from the BBR of the early universe.

Then show the article that could support your unrealistic understanding.

I don't need an article; look at the Sun, or a candle flame or a fire.
They are all pretty good approximations to BBR.

Sorry, that "optically thick" isn't part of the requirement from a BBR as explained clearly by our scientists.

I am one of our scientists you idiot.
I'm a spectroscopist.
This sort of thing is my day job.

how an "optically thick" could be considered as a wall for a cellar.

You just proved that you don't know what you are talking about
"optically thick" is an adjective, not a noun.
You can't have

an "optically thick"

for the same reason that you can't have a "green striped".

So, rather than posting nonsense, just answer the question.

What would you see in the night sky of that  model universe?

[Dave Lev (OP)]

Quote from: Dave Lev on Today at 18:04:35
Then show the article that could support your unrealistic understanding.

I don't need an article;

As you have failed to offer an article, then it proves that your understanding is clearly unrealistic and there is no need to continue the discussion on this issue.

[Bored chemist]

then it proves that your understanding is clearly unrealistic and there is no need to continue the discussion on this issue.

No
It shows that I recognize there is a real world out there.
You don't need to look at a wiki article; you need to look at reality.
But, since you insist.
Like I said, the light from a tungsten lamp looks like BBR
https://en.wikipedia.org/wiki/Color_temperature#/media/File:Spectral_Power_Distributions.png

What you are dooing is absurd.
You are pretending thet the whole of  science is wrong because I thought you were big enough to check that for yourself.

So, rather than posting nonsense, just answer the question.


Quote from: Bored chemist on Today at 08:36:32
What would you see in the night sky of that  model universe?

[Dave Lev (OP)]

In your following explanation for the early BBR radiation, you are using walls:

I can point out that the entire universe was, at that time opaque.
Everywhere was a "wall" as far as light was concerned.
That's the point you keep missing.

No, I didn't miss this issue.
You actually claim that based on the BBT there were some sort of "walls" all around the early Universe.
That is OK with me as this is your theory and you can set it as you wish.
However, it proves that you do understand that in order to get a BBR in any sort of box/universe you must have walls around it.
Therefore, how can you claim that our current finite universe without walls could still carry a BBR?

Quote from: Dave Lev on Yesterday at 19:50:46
Then it proves that your understanding is clearly unrealistic and there is no need to continue the discussion on this issue.

No
It shows that I recognize there is a real world out there.
You don't need to look at a wiki article; you need to look at reality.
But, since you insist.
Like I said, the light from a tungsten lamp looks like BBR
https://en.wikipedia.org/wiki/Color_temperature#/media/File:Spectral_Power_Distributions.png

Why do you think that this lamp can support your unrealistic ideas about the Universe' BBR?
You have stated that the Universe was never a star:

The universe is not, and never was "a star".

So, how can you now compare the Universe to a lamp?
Sorry, you have totally failed to show how our current finite Universe without any walls around it could carry a BBR.
All your explanations prove that you have to improve your knowledge in black body radiation.
So, please, if you don't have a specific article about the feasibility to get a Black Body radiation in a finite box/universe without walls, then we clearly wasting our time.

[Bored chemist]

Why do you think that this lamp can support your unrealistic ideas about the Universe' BBR?

Because it undermines your irrational objections.

You actually claim that based on the BBT there were some sort of "walls" all around the early Universe.

Where do you think I made that claim?

[Bored chemist]

So, how can you now compare the Universe to a lamp?

I didn't.
I am using the lamp, which emits pretty close to BBR to prove that you are wrong when you say

No walls means - No BBR.

Do you now accept that you are wrong about that?
Do you agree that , as in the cases I have shown, you can get BBR without  needing a box with a hole in it?

[Bored chemist]

Sorry, you have totally failed to show how our current finite Universe without any walls around it could carry a BBR.

I have not yet demonstrated it to you, but that is because you refuse to throw away this mistaken idea you have.

You have only two options to get the blackbody radiation:
1. Inside an "opaque and non-reflective object" at any finite size.
2. In infinite universe size.

In reality, most things emit something fairly close to BBR.

Go and do some research.
You will discover that this misunderstanding of yours is part of the reason you can not understand why your first few lines, posted 6 months ago, are wrong.

And then, maybe we can start to make progress.

[Dave Lev (OP)]

Quote from: Dave Lev on 04/10/2020 19:35:10
You have only two options to get the blackbody radiation:
1. Inside an "opaque and non-reflective object" at any finite size.
2. In infinite universe size.

In reality, most things emit something fairly close to BBR.
Go and do some research.

In reality, you contradict yourself.
If no walls are needed for a finite universe to generate BBR, why did you use the "walls" for the early Universe:
It seems that you have totally got lost. Why don't you read some information about the BBR before you try to explain it to somebody else?
As you couldn't find any relevant article, let me help you with the following:
http://www.astronomy.ohio-state.edu/~ryden/ast162_9/notes39.html
"The Cosmic Microwave Background is a relic of the time when the universe was hot, dense, and opaque."

So, the BBR that we see today in the CMB is due to that early universe when it was hot, dense, and opaque.
However, it is also stated:

"So why, you may well ask, is today's low-density, largely transparent universe filled with blackbody radiation? After all, blackbody radiation is produced by hot, dense, opaque objects. For instance:
The Sun is made of hot, dense, ionized gas.
The Sun is opaque because it is ionized. (Free electrons scatter photons, preventing them from zipping straight through the Sun.)
The Sun emits blackbody radiation.
However, the Big Bang theory states that the universe was once hotter and denser than it is today. If the Big Bang theory is accurate:
The early universe was full of hot, dense, ionized gas.
The early universe was opaque because it was ionized.
The early universe emitted blackbody radiation.
As the universe expanded, however, it became cooler and less dense. About 300,000 years after the start of expansion, the temperature of the universe had cooled to 3000 Kelvin. At this temperature:
Protons and electrons combined to form neutral hydrogen atoms. (This process is known to physicists as recombination.)
The universe, lacking free electrons to scatter the photons, suddenly became transparent.
The liberated photons started streaming freely in all directions.
Thus, the photons in the Cosmic Microwave Background are relics of the early, hot, dense, ionized, opaque universe. They have been traveling through space for over 13 billion years, and hence are sometimes called ``the oldest light in the universe''.

So, our scientists clearly understand the problematic of having a BBR in our current finite Universe without walls.
Therefore, they claim that ONLY the early Universe had emitted BBR.
Hence, the current finite Universe without walls can't generate any BBR. We actually see today the radiation which had been emitted by the early Universe 13 BY ago.

So, let's see if I understand it correctly:
1. The Early universe has got its BBR only when it was opaque due to ionized gas. If I recall it correctly, that Gas had been created when the universe age was about 380 MY.
2. So, the Big bang itself didn't create the BBR in the early Universe. It took it about 380MY until the BBR had popped up when the Universe had created the ionized gas and therefore it was opaque.
3. The meaning of Opaque is also a "walls" around the early Universe as you have already stated:

Quote from: Bored chemist on Yesterday at 08:36:32
I can point out that the entire universe was, at that time opaque.
Everywhere was a "wall" as far as light was concerned.

4. However, after the time of that opaque, (or when those "walls") had gone, the Universe couldn't generate any sort of BBR.
5. Therefore, our scientists claim that:
"the photons in the Cosmic Microwave Background are relics of the early, hot, dense, ionized, opaque universe. They have been traveling through space for over 13 billion years, and hence are sometimes called ``the oldest light in the universe''.

If you agree with all the above, then we can agree on the following:
1. Your understanding that a finite Universe without walls can generate a BBR is absolutely WRONG. It's better for you to read some articles and improve your knowledge before you start argue on something that you totally don't understand.
2. We need to verify if it is feasible to get today the radiation of that specific moment of time in the age of the Universe (380M) when it was opaque. For example, why we don't get today the radiation of the Universe when the Big bang took place (at that moment, it didn't carry a BBR) Or why not from any other age while it wasn't opaque anymore and it couldn't generate any sort of black body radiation?

[Bored chemist]

I am not "lost"
I'm still trying to get you to recognise that your opening few lines in this topic are wrong.
But you never answer a simple question.
It's not that I get lost, that's the problem. The problem is that you refuse to stick to a point. instead, you post stacks of stuff like this
"
"So why, you may well ask, is today's low-density, largely transparent universe filled with blackbody radiation? After all, blackbody radiation is produced by hot, dense, opaque objects. For instance:
The Sun is made of hot, dense, ionized gas.
The Sun is opaque because it is ionized. (Free electrons scatter photons, preventing them from zipping straight through the Sun.)
The Sun emits blackbody radiation.
However, the Big Bang theory states that the universe was once hotter and denser than it is today. If the Big Bang theory is accurate:
The early universe was full of hot, dense, ionized gas.
The early universe was opaque because it was ionized.
The early universe emitted blackbody radiation.
As the universe expanded, however, it became cooler and less dense. About 300,000 years after the start of expansion, the temperature of the universe had cooled to 3000 Kelvin. At this temperature:
Protons and electrons combined to form neutral hydrogen atoms. (This process is known to physicists as recombination.)
The universe, lacking free electrons to scatter the photons, suddenly became transparent.
The liberated photons started streaming freely in all directions.
Thus, the photons in the Cosmic Microwave Background are relics of the early, hot, dense, ionized, opaque universe. They have been traveling through space for over 13 billion years, and hence are sometimes called ``the oldest light in the universe''."
Which I have known for 30 years or more and which can not be relevant, rather than actually answering a simple question.

Normally when people fail to answer a question like that, it's a politician who knows that the answer to the question shows them to be a fool.
Is that the issue here?
Do you actually know that an honest answer to this question will make you look a fool?

Quote from: Bored chemist on Yesterday at 18:27:33
So, rather than posting nonsense, just answer the question.


Quote from: Bored chemist on Today at 08:36:32
What would you see in the night sky of that  model universe?

[Dave Lev (OP)]

Quote from: Bored chemist on Yesterday at 18:27:33
So, rather than posting nonsense, just answer the question.
Quote from: Bored chemist on Today at 08:36:32
What would you see in the night sky of that  model universe?

When we discuss about magnetic field, it was urgent to you to shift the discussion to black body radiation without getting any real conclusions.
Now when we discuss on Black body radiation it is urgent to you to shift it again to night sky
Is it real?
Do you have any interest in real science?
Would you kindly advice what is your real problem man???
What do you want to show?
It is very clear to me that you just wish to show that I don't understand science while based on your messages it is very clear that your knowledge in science is quite poor
So how can you claim that:.

I'm a spectroscopist.

Please, take your time and read some more scientific articles about Night sky, Dark day, worm Moon or any other idea which you might have.
As you clearly don't have any interest in my explanations, I really feel that we are wasting our time.
Good Luck for you!

[Bored chemist]

Now when we discuss on Black body radiation it is urgent to you to shift it again to night sky

The night sky is black body radiation so that isn't a shift, is it?

But, in reality, we have been discussing it for 6 months- it's just that you have refused to talk sensibly.

Quote from: Bored chemist on 28/03/2020 10:44:30
But I predict that Dave isn't even going to address the fact that he was wrong in the first few lines.
I was right.

while based on your messages it is very clear that your knowledge in science is quite poor

OK
So show something where what I said was actually wrong.

Would you kindly advice what is your real problem man???[/quote]
My problem is that you turned up on a discussion forum, but refuse to actually discus things.
When someone raises an objection to your so-called "theory", you ignore it.


But first, stop pretending to be a bad politician, and answer the question.

Quote from: Bored chemist on Yesterday at 20:22:13
Quote from: Bored chemist on Yesterday at 18:27:33
So, rather than posting nonsense, just answer the question.


Quote from: Bored chemist on Today at 08:36:32
What would you see in the night sky of that  model universe?

[Dave Lev (OP)]

I am one of our scientists you idiot.

Sorry
I have no intention to continue the discussion with you.
Please stop posting any message in this thread.

[Bored chemist]

Quote from: Bored chemist on Yesterday at 13:49:31

Quote from: Bored chemist on Yesterday at 20:22:13
Quote from: Bored chemist on Yesterday at 18:27:33
So, rather than posting nonsense, just answer the question.


Quote from: Bored chemist on Today at 08:36:32
What would you see in the night sky of that  model universe?

Sorry
I have no intention to continue the discussion with you.
Please stop posting any message in this thread.

Good to know that you are sorry for cluttering the site with this nonsense.

If you don't want to discuss things then you should not be on a discussion forum; feel free to leave.
I decide whether I post or not.
You don't get a say in the matter; if you don't like that, you shouldn't have signed up to it.

I think that, if there's anyone else still reading this thread, they have realised that you are hopelessly wrong and that you know you are wrong.

That's the only plausible reason for you to repeatedly refuse to answer a simple question.

[Dave Lev (OP)]

Dear Kryptid

I have few questions for you

Please see the following explanation:
http://www.astronomy.ohio-state.edu/~ryden/ast162_9/notes39.html
"Why, however, do we see a Cosmic MICROWAVE Background? At the era of recombination (the time when neutral atoms formed and the universe became transparent), the temperature was T = 3000 Kelvin (about the surface temperature of an M star, such as Betelgeuse). The wavelength of maximum emission was then 970 nanometers, in the infrared. When the universe first became transparent, therefore, observers would have seen a Cosmic INFRARED Background. However, since the era of recombination, the universe has expanded by a factor of 1100, stretching lambdamax from 970 nanometers to 1 millimeter (that is, 1,000,000 nanometers). This is equivalent to cooling the temperature of the Cosmic Background from 3000 Kelvin to 2.725 Kelvin."

What can we learn from that?
1. The radiation of the CMB came from the era of recombination. At that time the temperature of the Cosmic Background was 3000 Kelvin
2. From that time the universe has expanded by a factor of 1100. Therefore, based on the BBT the current temp is 2.725 Kelvin

Let's stop at this stage and try to understand the real meaning of that.
Based on the BBT the space itself is expanding.
Hence, if we go back to the era of recombination the space of the early Universe was very compact.
Let's assume that the radius of that Universe was R.

Please try to help with the following questions:
1. What was there outside the radius R (From R+1 to the Infinity)?
If there was also space (even if it was empty space), then how can we claim that the space is expanding while there is already space outside R up to the infinity?
If there was no space, than what was there?
2. Why do we claim that there are no walls around the expanding space?
Based on the BBT, it is clear that the space itself is expanding. Therefore, if during the era of recombination the radius of the expanded space was R then it is very clear that there must be some sort of walls or barrier between R to R+1. (Otherwise, how could we claim that the space is expanding?)
Therefore, how can we claim that there is no walls around our expanding universe while it is clear that at any given moment there must be a significant difference between the space inside that R to the space or no space outside R (or R+1).
3. Why the Universe should decrease its temp as it expand?
Based on the BBT the space is expanding, while it carries with it the matter that had created by the Big Bang. Therefore, the concentrated matter from that era of recombination isn't moving to cooler space but it is moving with the space. So, it surly become less dense but as the space is expanding and nothing could cool the temp of that matter, why do we assume that the temp of the matter or the CMB should be decreased?
Just as an example - Let's look at our sun. Let's set it in a closed sphere and claim that this is the whole Universe.
Let's also assume that it has a fixed temp in that sphere.
Now, if we expand that sphere, while we verify that nothing from outside could get in and nothing from inside could get out (like conservation of energy). So, why the expansion itself should decrease the temp of the matter? Don't you think that this idea contradicts the conservation of energy law?

[Bored chemist]

If there was no space, than what was there?

Nothing; not even space.

Why do we claim that there are no walls around the expanding space?

Because that would have stopped it expanding.

it is very clear that there must be some sort of walls or barrier between R to R+1.

No.
That's just something you made up.

Therefore, how can we claim that there is no walls around our expanding universe while it is clear that at any given moment there must be a significant difference between the space inside that R to the space or no space outside R (or R+1).

"Six feet from the end of my nose " defines a region, but doesn't need a wall.
So you are simply wrong.

matter, why do we assume that the temp of the matter or the CMB should be decreased?

Because the wavelength increases as the space stretches.
Longer wavelengths correspond to cooler radiation.

How could it not cool down?