PDA

View Full Version : CIBER v.s CMB



Dave Lee
2015-Oct-28, 03:46 PM
I would like to understand the effect of the CIBER on the CMB.
Let start with CIBER:
CIBER - Cosmic Infrared Background Experiment
Based on CIBER we have discovered that half of the stars in the Universe may lie outside galaxies:
https://cosmosmagazine.com/space/lone-stars-half-stars-universe-may-lie-outside-galaxies
"The CIBER experiment suggests up to 50% of stars may lie outside galaxies, which would balance things nicely.
The CIBER measurement represented light from millions of galaxies at once. The team then blacked out all the light coming from known galaxies, leaving the supposedly dark space between. And they found it wasn’t altogether dark. A faint, splotchy background glow remained that they couldn’t account for.
The only explanation was that the extra light must come from stars lying outside of galaxies – too faint to be seen individually but which could be detected by CIBER from their combined signals."
So, based on CIBER the empty space between galaxies isn't dark and empty. It is actually full with lone stars. Never the less: "Because the light from these lone stars is so faint no one knew they were there until now".
With regards to the CMB - cosmic microwave background
https://en.wikipedia.org/wiki/Cosmic_microwave_background
It was assumed the empty space between galaxies is completely dark and empty from any mass:
"With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark. However, a sufficiently sensitive radio telescope shows a faint background glow, almost exactly the same in all directions, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum."
Therefore, as it was assumed that the space between galaxies is completely empty of mass, it was believed that:
"The cosmic microwave background (CMB) is the thermal radiation left over from the time of recombination in Big Bang cosmology"
However, as we know today that the empty space is full of mass, than could it be that the CMB is a direct output of that mass?
If so, why do we still use the CMB as an evidence for the Big Bang?

Hornblower
2015-Oct-28, 04:13 PM
I would like to understand the effect of the CIBER on the CMB.
Let start with CIBER:
CIBER - Cosmic Infrared Background Experiment
Based on CIBER we have discovered that half of the stars in the Universe may lie outside galaxies:
https://cosmosmagazine.com/space/lone-stars-half-stars-universe-may-lie-outside-galaxies
"The CIBER experiment suggests up to 50% of stars may lie outside galaxies, which would balance things nicely.
The CIBER measurement represented light from millions of galaxies at once. The team then blacked out all the light coming from known galaxies, leaving the supposedly dark space between. And they found it wasn’t altogether dark. A faint, splotchy background glow remained that they couldn’t account for.
The only explanation was that the extra light must come from stars lying outside of galaxies – too faint to be seen individually but which could be detected by CIBER from their combined signals."
So, based on CIBER the empty space between galaxies isn't dark and empty. It is actually full with lone stars. Never the less: "Because the light from these lone stars is so faint no one knew they were there until now".
With regards to the CMB - cosmic microwave background
https://en.wikipedia.org/wiki/Cosmic_microwave_background
It was assumed the empty space between galaxies is completely dark and empty from any mass:
"With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark. However, a sufficiently sensitive radio telescope shows a faint background glow, almost exactly the same in all directions, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum."
Therefore, as it was assumed that the space between galaxies is completely empty of mass, it was believed that:
"The cosmic microwave background (CMB) is the thermal radiation left over from the time of recombination in Big Bang cosmology"
However, as we know today that the empty space is full of mass, than could it be that the CMB is a direct output of that mass?
If so, why do we still use the CMB as an evidence for the Big Bang?

I would expect these lone stars in the voids to have the same sort of spectral signatures as the stars in the galaxies. These signatures do not include a virtually perfect 2.7K blackbody curve in the microwave band. The CMB comes from far beyond the galaxies and the respective voids, and is the strongly redshifted glow of diffuse hot gas that was thermalized at the time the recombination occurred and it became transparent.

Fiery Phoenix
2015-Oct-28, 04:31 PM
Yeah, I can't think of any reason as to why intergalactic stars would give off different signatures. Remember they are generally thought to have been formed within galaxies, but were ejected as part of galactic collision processes.

Amber Robot
2015-Oct-28, 05:00 PM
I would like to understand the effect of the CIBER on the CMB.
Let start with CIBER:
CIBER - Cosmic Infrared Background Experiment

The operative word here is "infrared". And in the CMB it is "microwave". These are different bandpasses that give insight into different astrophysical phenomena.

ShinAce
2015-Oct-29, 04:00 AM
The operative word here is "infrared". And in the CMB it is "microwave". These are different bandpasses that give insight into different astrophysical phenomena.

+1. Plus we need to remember that infrared has a wavelength similar to the size of dust grains, while the microwave background peaks in intensity with a wavelength around 1km.

Jeff Root
2015-Oct-29, 05:30 AM
You exaggerate.

By a factor of a million.

You typed "km" instead of "mm". The peak wavelength of
the CMB is about 1.9 mm. The boundary between microwave
and infrared is arbitrarily defined as 1 mm. So it's very close.
A significant chunk of the CMB is in the infrared band.

So ... the IR observed between galaxies must be in addition
to the cosmic background radiation, if they accounted for it
properly. (I didn't check what part of the IR band they were
measuring. It could be and likely is far from the CMB peak.)

-- Jeff, in Minneapolis

ShinAce
2015-Oct-29, 06:53 AM
Sorry, I read 10-3 as 103 when I guesstimated with Wein's law.

Right, peak wavelength for the CMB is on the order of 1mm. Which is larger than dust and doesn't scatter much.

CIBER is observing near 1um, which is near IR. Basically deep red.

Dave Lee
2015-Oct-30, 04:37 AM
What is so unique in the CMB + IR that it should be correlated only for the BB?
Is there any mass or energy at any temperature, distance or activity which could potentially set this kind of radiation? (Including dark mass or dark energy)
Just few examples: Asteroid, Earth, Sun, Star forming aria, Black hole, Pulsar, Quasar, any sort of gas or dust, Supernova, Twin stars, Gravity, Magnetic/Electric energy of any rotating star or BH, Plasma and so on.

korjik
2015-Oct-30, 05:04 AM
What is so unique in the CMB + IR that it should be correlated only for the BB?
Is there any mass or energy at any temperature, distance or activity which could potentially set this kind of radiation? (Including dark mass or dark energy)
Just few examples: Asteroid, Earth, Sun, Star forming aria, Black hole, Pulsar, Quasar, any sort of gas or dust, Supernova, Twin stars, Gravity, Magnetic/Electric energy of any rotating star or BH, Plasma and so on.

The cosmic microwave background is a very nearly featureless background at a single temperature. It is basically the same in any direction we look. This heavily implies that it is the same everywhere in the universe, which implies that it is a remnant from when the universe was small.

The cosmic infrared background is not featureless, it is splotchy. It has lumps and very much isnt the same in any direction. This implies a local (for very loose use of the work local) effect that isnt permeating the universe evenly.

These are two very different effects caused by very different things

Dave Lee
2015-Oct-30, 02:06 PM
The cosmic microwave background is a very nearly featureless background at a single temperature. It is basically the same in any direction we look.


Could it be that the CMB is just a cosmic noise?
https://en.wikipedia.org/wiki/Cosmic_noise
Cosmic Microwave Background Radiation (CMBR) from outer space, discovered by Arno Penzias and Robert Wilson, who later won the Nobel Prize for this discovery, is also a form of cosmic noise."
The description of cosmic noise is as follow:
"Cosmic noise characteristics are similar to those of thermal noise. Cosmic noise is experienced at frequencies above about 15 MHz when highly directional antennas are pointed toward the sun or to certain other regions of the sky such as the center of the Milky Way Galaxy. Celestial objects like Quasars, super dense objects that lie far from Earth, emit electromagnetic waves in its full spectrum including radio waves. We can also hear the fall of a meteorite in a radio receiver; as the falling object burns from friction with the Earth's atmosphere, ionizing surrounding gases, thereby producing radio waves."
If so, how can we get any valid information from this kind of noise?
Our scientists tried to verify some elements of the CMB and got contradicted results as follow:
"On 17 March 2014 it was announced that the BICEP2 instrument had detected the first type of B-modes, consistent with inflation and gravitational waves in the early universe at the level of r = 0.20+0.07−0.05, which is the amount of power present in gravitational waves compared to the amount of power present in other scalar density perturbations in the very early universe. Had this been confirmed it would have provided strong evidence of cosmic inflation and the Big Bang,[64][65][66][67][90][91][92] but on 19 June 2014, considerably lowered confidence in confirming the findings was reported[68][68][70][70][71][71] and on 19 September 2014 new results of the Planck experiment reported that the results of BICEP2 can be fully attributed to cosmic dust.[93][94]"
So, in one verification it supported the inflation theory, but on the following verification it was fully attributed to cosmic dust.
As electronic engineer, I'm well aware about noise in electronic components. For example, if we put a microphone in a complitly close and quite room, and try to increase the sensitivity, we will eventually get the noise. Actually in any object we could find some noise. Therefore, I assume that in any nothing there might be something. In other words, if we scratch the bottom of nothing we might find something.
So, could it be that the CMB is just some sort of a noise? Could it be that it should be there with or without the BB?

Amber Robot
2015-Oct-30, 05:06 PM
So, could it be that the CMB is just some sort of a noise?

One person's noise is another person's signal.

This "noise" is well studied and there are well-developed theories that predict this noise and accurately reproduce this noise to high degrees of precision while still being consistent with many other observables about the universe.

Shaula
2015-Oct-30, 05:23 PM
This "noise" is well studied and there are well-developed theories that predict this noise and accurately reproduce this noise to high degrees of precision while still being consistent with many other observables about the universe.
Worth highlighting that so far no combination of background sources has come close either. Expansion pretty much rules that out.

Dave Lee
2015-Oct-30, 08:11 PM
One person's noise is another person's signal.

This "noise" is well studied and there are well-developed theories that predict this noise and accurately reproduce this noise to high degrees of precision while still being consistent with many other observables about the universe.

So do you claim that the following statement is incorrect?
"Cosmic Microwave Background Radiation (CMBR) from outer space,... is also a form of cosmic noise."

Shaula
2015-Oct-30, 08:19 PM
So do you claim that the following statement is incorrect?
"Cosmic Microwave Background Radiation (CMBR) from outer space,... is also a form of cosmic noise."
As has been said - it depends on the context. If you are not looking for the CMBR then it is noise. Because it is not the signal you are after. If you are studying the CMBR then it is signal.

A more down to earth example would be that if I were searching for web pages about the singer Fish then pages about cod stocks in the North Sea would be noise. If I were interested in fish the creatures then they would be signal.

Hornblower
2015-Oct-30, 08:20 PM
So do you claim that the following statement is incorrect?
"Cosmic Microwave Background Radiation (CMBR) from outer space,... is also a form of cosmic noise."
That depends on what we mean by noise. Saying yes or no as an exercise in semantics does not address the question of where it is coming from or the physical properties of the source.

cjameshuff
2015-Oct-30, 09:33 PM
As Hornblower said...that it is noise in some contexts means nothing about where it came from.

As an electronics engineer, you should be aware that there are many kinds of noise with a wide variety of characteristics. The cosmic microwave background is an essentially perfect 2.7 K black body spectrum. It is not produced by stars or the instrumentation.

Geo Kaplan
2015-Oct-31, 12:07 AM
So do you claim that the following statement is incorrect?
"Cosmic Microwave Background Radiation (CMBR) from outer space,... is also a form of cosmic noise."

As others have pointed out, that statement is too limited to be useful in many situations. There are many, many kinds of noise. What's special about the CMB is its exquisite conformance to a black body spectrum. Other forms of noise do not have that property.

"Armchair cosmologists" who dislike the idea of a big bang often attempt to argue for an alternative source of CMB noise, and begin with a statement similar to the definition you offered. And yes, noise is a form of noise, but that tautology informs very little. The CMB, as I've said, is a very special kind of noise. The near-perfect isotropy of the CMB also implies an extraordinary isotropy of the universe's earliest epoch, and a maintenance of thermal equilibrium to the present day. Ordinary noise does not have these properties.

Dave Lee
2015-Oct-31, 07:06 AM
. And yes, noise is a form of noise, but that tautology informs very little. The CMB, as I've said, is a very special kind of noise.
If I understand your answer correctly:
You agree that the CMB is a noise. However, you claim that it is a very special kind of noise.
So, let me ask you the following question:
Assuming that we are living in a universe without a BB in its history, what should be the expected CMB?
What is the difference between the expected real noise and the current special noise?

Shaula
2015-Oct-31, 09:15 AM
If I understand your answer correctly:
You agree that the CMB is a noise...
Wow, you really do only hear what you want to hear.

The answer to your other question has already been at least partially given. The background in an expanding universe without an early hot dense state should look like a sum over sources at different redshifts. The difference is that the CMBR does not look anything like this - it looks like a nearly pure blackbody spectrum at 2.7K. The tiny deviations from this are consistent with predictions - which are based on an expanding, evolving hot dense state.

Cougar
2015-Oct-31, 03:43 PM
Assuming that we are living in a universe without a BB in its history, what should be the expected CMB?


Without a big bang, there would be no CMB. The CMB essentially confirms the Big Bang theory.

The CMB is not "noise." It contains an abundance of information (https://en.wikipedia.org/wiki/Cosmic_microwave_background#Primary_anisotropy) about our Universe. "Noise" is basically information-free.

Dave Lee
2015-Oct-31, 04:23 PM
Without a big bang, there would be no CMB. The CMB essentially confirms the Big Bang theory.

The CMB is not "noise." It contains an abundance of information (https://en.wikipedia.org/wiki/Cosmic_microwave_background#Primary_anisotropy) about our Universe. "Noise" is basically information-free.

So, the BB is the ultimate single source for the CMB.
It means that there is no natural source (object, mass, galaxy, activity, supernova, energy...) which could generate the CMB.
Do you all agree with that?

antoniseb
2015-Oct-31, 04:58 PM
So, the BB is the ultimate single source for the CMB.
It means that there is no natural source (object, mass, galaxy, activity, supernova, energy...) which could generate the CMB.
Do you all agree with that?
Why do all your posts seem to be asking for some bumper-sticker phrase that is somehow "correct" or that everyone agrees to? In this case I have to ask what you mean by natural if it does not include the big bang?

Shaula
2015-Oct-31, 05:17 PM
So, the BB is the ultimate single source for the CMB.
It means that there is no natural source (object, mass, galaxy, activity, supernova, energy...) which could generate the CMB.
Do you all agree with that?
It is unlikely you will develop a nuanced and detailed understanding of current theory if you insist on reducing everything to simplistic yes or no questions.
Do you all agree with that?

cjameshuff
2015-Oct-31, 06:40 PM
It is unlikely you will develop a nuanced and detailed understanding of current theory if you insist on reducing everything to simplistic yes or no questions.
Do you all agree with that?

Yes.

Dave Lee
2015-Oct-31, 06:45 PM
The Milky Way galaxy is a significant generator for radiation.
http://cmb.physics.wisc.edu/pub/tutorial/cmb.html
"It is important to note that the microwave radiation that reaches us from our galaxy, the Milky Way, and the effect of the rotation of the Earth have been editted out"
"If the effect from th radiation from the Milky Way had been left in, for example, the map you see would have a huge band running straight through the middle of it like on the temperature map below."
So, The Milky way radiation contribute significant amount to the CMB.
It is also stated:
"This map shows temperature changes in the CMB where the effect of the Milky Way in the data has not been removed."
However, how do we know the exact radiation contribution of the Milky Way? Could it be that the radiation is not exactly the same in all directions? Could it be that those spots in the map is a direct affect by our galaxy?
And even much more difficult question:
If the Milky Way generate radiation, what about other similar galaxies? There are billion galaxies in the Universe. Could it be that the CMB is just a reflation of that radiation?
So, do you still believe that the BB is the only source for the CMB?

cjameshuff
2015-Oct-31, 06:56 PM
In particular, Dave Lee, you give the impression of someone who is digging for some statement that will confirm an existing belief. You repeatedly disregard clear answers and keep pushing along with questions that seem designed to trick someone into saying or agreeing with something you will find personally acceptable. You've made me for one very hesitant to ever simply agree with you even if you appear to be correct in some small detail, because it appears you'll just take that and twist it around to mean what you want.

This is not a useful approach to learning. No matter how wrong an idea is, you will always eventually find something that seems to support it.

Shaula
2015-Oct-31, 06:59 PM
If the Milky Way generate radiation, what about other similar galaxies? There are billion galaxies in the Universe. Could it be that the CMB is just a reflation of that radiation?
There are more than a billion galaxies. 100-200 billion is the estimated number in the observable universe.

And no, the CMB is not thought to be down to them. No proposed model fits observations anywhere near as well as the one derived from the Big Bang cosmology.

cjameshuff
2015-Oct-31, 07:00 PM
The Milky Way galaxy is a significant generator for radiation.
http://cmb.physics.wisc.edu/pub/tutorial/cmb.html
"It is important to note that the microwave radiation that reaches us from our galaxy, the Milky Way, and the effect of the rotation of the Earth have been editted out"
"If the effect from th radiation from the Milky Way had been left in, for example, the map you see would have a huge band running straight through the middle of it like on the temperature map below."
So, The Milky way radiation contribute significant amount to the CMB.
It is also stated:
"This map shows temperature changes in the CMB where the effect of the Milky Way in the data has not been removed."
However, how do we know the exact radiation contribution of the Milky Way? Could it be that the radiation is not exactly the same in all directions? Could it be that those spots in the map is a direct affect by our galaxy?
And even much more difficult question:
If the Milky Way generate radiation, what about other similar galaxies? There are billion galaxies in the Universe. Could it be that the CMB is just a reflation of that radiation?
So, do you still believe that the BB is the only source for the CMB?

No, the CMB is not from the galaxies. It is near perfect 2.7 K black body radiation. Galaxies are not 2.7 K black body emitters. You were told this in the very first reply, and also in multiple subsequent posts in this thread.

Geo Kaplan
2015-Oct-31, 08:29 PM
The Milky Way galaxy is a significant generator for radiation.
http://cmb.physics.wisc.edu/pub/tutorial/cmb.html
"It is important to note that the microwave radiation that reaches us from our galaxy, the Milky Way, and the effect of the rotation of the Earth have been editted out"
"If the effect from th radiation from the Milky Way had been left in, for example, the map you see would have a huge band running straight through the middle of it like on the temperature map below."
So, The Milky way radiation contribute significant amount to the CMB.
It is also stated:
"This map shows temperature changes in the CMB where the effect of the Milky Way in the data has not been removed."
However, how do we know the exact radiation contribution of the Milky Way? Could it be that the radiation is not exactly the same in all directions? Could it be that those spots in the map is a direct affect by our galaxy?
And even much more difficult question:
If the Milky Way generate radiation, what about other similar galaxies? There are billion galaxies in the Universe. Could it be that the CMB is just a reflation of that radiation?
So, do you still believe that the BB is the only source for the CMB?

You have been given answers to these questions already.

To repeat: The CMB spectrum is a near-perfect blackbody spectrum. Other noise sources do not have this spectral shape. Plus, no matter where you look, you see the same spectral shape, and the same equivalent temperature. Many attempts have been made over the decades to explain these features without invoking the BB, and all of them have failed.

It is apparent from your repeated dismissal of the answers given that you are not actually interested in mainstream answers. So, instead of continuing to play a coy, tiresome game, just propose your answer (perhaps in ATM) and let us point out the flaws in that proposed alternative.

Swift
2015-Oct-31, 09:59 PM
Dave Lee

Do not use Q&A to advocate non-mainstream ideas. You've been infracted previously for that, if you do it again you will be suspended. You can ask follow-up questions to further your understanding of the mainstream answers, but you may not argue with or dispute the mainstream answers you have been given.

Dave Lee
2015-Nov-01, 09:08 AM
It's not an issue of ATM and I have no intention to promote any sort of new idea.
I assume that I didn't set my question correctly.
So, let me ask it again as follow:
In one hand I got an answer that BB is the only source for the CMB.
In the other hand it is stated clearly in the article (Which I have just found based on your help), that the Milky way is a main generator for microwave radiation.
So I have the following questions:
Is it correct that the Milky way generate this microwave radiation?
Does it mean that every spiral galaxy generate microwave radiation?
If so, how this Microwave radiation from all the galaxies could impact the Cosmic Microwave Background?

However, if you prefer to stop the discussion on this issue – I will not bother you. Just let me know.

Geo Kaplan
2015-Nov-01, 09:26 AM
It's not an issue of ATM and I have no intention to promote any sort of new idea.
I assume that I didn't set my question correctly.
So, let me ask it again as follow:
In one hand I got an answer that BB is the only source for the CMB.
In the other hand it is stated clearly in the article (Which I have just found based on your help), that the Milky way is one of the main generator for microwave radiation.
So I have the following questions:
Is it correct that the Milky way generate this microwave radiation?
If so, how can we explain this contradiction?
Does it mean that every spiral galaxy generate microwave radiation?
If so, how this Microwave radiation from all the galaxies could impact the Cosmic Microwave Background?

However, if you prefer to stop the discussion on this issue – I will not bother you. Just let me know.

You seem intent on ignoring the answers given, Dave Lee, which is why there are suspicions about your motives (your ejection from other fora for relevant reasons intensifies those suspicions here). I'll repeat one last time: Some of the relevant features of the CMB are its near-perfect conformance to a blackbody spectrum and its near-perfect isotropy. There are many sources of radiation, the Milky Way and your microwave oven and cell phone among them. However, they do not possess those relevant features.

If you ask your questions again, I can reach no other conclusion than that you reject the mainstream position.

Dave Lee
2015-Nov-01, 09:29 AM
Thanks
It is clear

antoniseb
2015-Nov-01, 11:58 AM
... Does it mean that every spiral galaxy generate microwave radiation?
If so, how this Microwave radiation from all the galaxies could impact the Cosmic Microwave Background? ...
Thermal radiation from cold dust in galaxies creates microwaves. We consider them foreground microwaves, and there are straightforward methods of subtracting that foreground contribution. In simplistic terms, that method is to look at microwaves that are in a range too short to be the CMB to identify those objects, and then subtract those objects. This s fairly easy to do because the microwave contribution from any galaxy except the Milky Way is tiny compared to the CMB in the CMB frequency range.

Dave Lee
2015-Nov-01, 02:04 PM
Thanks

I must admit that I'm quite confused.
If I continue with this discussion I might be charged for idea against the mainstream.
However, it's clear that I didn't get sufficient answers to my questions
Please also be aware that I might ask more questions based on the answer which I might get..

With regards to your following answer:

Thermal radiation from cold dust in galaxies creates microwaves. We consider them foreground microwaves, and there are straightforward methods of subtracting that foreground contribution.

If I understand it correctly, the cold dust in our galaxy generates the Microwave radiation.
So, how do we know the exact amplitude of this Dust radiation? Can you please direct me to the article which can give me more highlight about this calculation method?
Based on my understanding, the dust is not located evenly in the galaxy. So, could it be that the Microwave radiation isn't evenly in all direction?
How strong is this radiation comparing to the CMB?

Please stop me at any time if you think that I'm asking too much

Shaula
2015-Nov-01, 02:22 PM
If I understand it correctly, the cold dust in our galaxy generates the Microwave radiation.
So, how do we know the exact amplitude of this Dust radiation? Can you please direct me to the article which can give me more highlight about this calculation method?
Based on my understanding, the dust is not located evenly in the galaxy. So, could it be that the Microwave radiation isn't evenly in all direction?
How strong is this radiation comparing to the CMB?

Please stop me at any time if you think that I'm asking too much
The simplest reason (regardless of how much energy the dust is radiating) that this dust is nothing to do with the CMBR is that wherever in the sky we look, once we have corrected for known sources, we see a near perfect, near constant strength black body spectrum. If it were galactic in origin we'd expect to see spatial variations and we would also expect to see frequency shifts corresponding to rotation around the galactic core.

In order to make this dust work you would need a huge cloud of it, all at constant temperature (no matter where in the galaxy it is) that had no spectral properties, did not block starlight (yet still must interact electromagnetically), that is not subject to gravity, that is perfectly stationary with respect to the Milky Way, that cannot be perturbed by any of the other bodies around us and which has some automagical way of maintaining its distribution. Oh - and as a bonus it cannot interact with any other galaxy's version of this cloud, or the ISM. And even if we chose to propose this this wonder-dust as a solution that would not account for the second and third peaks in the spatial correlation spectrum of this radiation.

In short you would need something that makes dark energy and dark matter look like stuff you see every day.

For a good grounding in the processing and modelling techniques used you could try the Planck Collaboration papers I-XXVII. I think most of them can be found on the Caltech website. There is a lot of physics involved in doing this, and a lot of signal processing. If you really want to understand it I'd suggest reading at the very least II, VI and XII - and possibly XVI to see how this leads to the results.

antoniseb
2015-Nov-01, 02:55 PM
Can you please direct me to the article which can give me more highlight about this calculation method?...
I suggest doing a literature search on the Planck mission results and methods. There are thousands of pages, and they can be quite technical, but there are some images and graphs in there that should give you the quick look you seem to desire. One short thing to look for is that the placement of the dust and the microwaves from it are far from uniform, and fairly easy to identify, whereas the CMB, as so many have told you repeatedly is practically uniform in all directions.

Reality Check
2015-Nov-01, 10:00 PM
Could it be that the CMB is just a cosmic noise?
https://en.wikipedia.org/wiki/Cosmic_noise

Not "just" - a "form of cosmic noise" as in that inked Wiki article. Cosmic microwave background (https://en.wikipedia.org/wiki/Cosmic_microwave_background) is a "cosmic noise" with structure, e.g. a perfect blackbody spectrum, a power spectrum with peaks, etc.

Reality Check
2015-Nov-01, 10:03 PM
So, the BB is the ultimate single source for the CMB.
It means that there is no natural source (object, mass, galaxy, activity, supernova, energy...) which could generate the CMB.
Do you all agree with that?
No, Dave Lee.
The BB (expansion of the universe) is not the "ultimate single source for the CMB". The "ultimate single source for the CMB" and the "natural source" of the CMB is all of the matter in the universe.

Reality Check
2015-Nov-01, 10:13 PM
The Milky Way galaxy is a significant generator for radiation.
.
So, do you still believe that the BB is the only source for the CMB?
It would be very ignorant to think that, Dave Lee, because people here can read cosmic microwave background (https://en.wikipedia.org/wiki/Cosmic_microwave_background) and know that it is impossible for the CMB to be radiation from galaxies (e.g. perfect blackbody spectrum).
Knowledgeable people will even learn about how the cosmic microwave background is measured and see that the foreground microwave radiation from the Milky Way and other galaxies (point sources) is removed from the raw measurements.

Reality Check
2015-Nov-01, 10:27 PM
I must admit that I'm quite confused.

Unfortunately Cosmic microwave background - Data reduction and analysis (https://en.wikipedia.org/wiki/Cosmic_microwave_background#Data_reduction_and_ana lysis) does not go into detaisl about the process. Isn't it lucky that Google exists, Dave Lee :D! For example Cosmic Microwave Background Anisotropy (http://www.astro.ucla.edu/~wright/CMB-DT.html) should resolve your confusion.
Astronomers know that the Milky Way emits detectable microwaves. Astronomers know that closer galaxies emit detectable microwaves. So they remove this foreground contamination from CMB data.
CMB Foregrounds (http://space.mit.edu/home/angelica/foreground.html) lists possible sources.

Amber Robot
2015-Nov-02, 08:53 PM
In the other hand it is stated clearly in the article (Which I have just found based on your help), that the Milky way is a main generator for microwave radiation.
So I have the following questions:
Is it correct that the Milky way generate this microwave radiation?

When observing the CMB, this emission from the Milky Way is the "noise" that has to be removed from the CMB signal.

Jeff Root
2015-Nov-02, 11:52 PM
And when observing microwave emission from the Milky Way,
the CMB is noise that has to be removed from the MWMW signal.

-- Jeff, in Minneapolis

Reality Check
2015-Nov-03, 12:09 AM
And when observing microwave emission from the Milky Way,
the CMB is noise that has to be removed from the MWMW signal
You have it the wrong way around, Jeff Root.
The MWMW is the "noise".
The CMB is the signal.
The MWMW noise is foreground contamination that has to be removed to reveal the CMB signal. No one removes the CMB signal from the MWMW "noise".

cjameshuff
2015-Nov-03, 01:13 AM
You have it the wrong way around, Jeff Root.
The MWMW is the "noise".
The CMB is the signal.
The MWMW noise is foreground contamination that has to be removed to reveal the CMB signal. No one removes the CMB signal from the MWMW "noise".

Those who are studying the Milky Way's MW emissions do.

Reality Check
2015-Nov-03, 01:40 AM
Those who are studying the Milky Way's MW emissions do.
It would be interesting if they do, cjameshuff. But I doubt it given the tiny amount that this would change the measurements.
My point was more that the CMB is the topic of the thread. The CMB is the signal to be measured. The Milky Way's MW emissions are "noise" to be removed from that signal.

Reality Check
2015-Nov-03, 01:44 AM
And when observing microwave emission from the Milky Way,
the CMB is noise that has to be removed from the MWMW signal.
Jeff Root: Please back up this assertion with citations from the scientific literature where astronomers measure the Milky Way microwave emission and remove the CMB.

Dave Lee
2015-Nov-03, 06:01 AM
Jeff Root: Please back up this assertion with citations from the scientific literature where astronomers measure the Milky Way microwave emission and remove the CMB.


Let me help you.
In the following article it is stated:
http://www.astro.ucla.edu/~wright/CMB-DT.html

"The angular power spectrum of the anisotropy of the CMB contains information about the formation of the Universe and its current contents. This angular power spectrum is a plot of how much the temperature varies from point to point on the sky (the y-axis variable) vs. the angular frequency ell (the x-axis variable)."

However, if I understand it correctly, this angular power spectrum of the anisotropy of the CMB is a direct outcome from the WMAP.
Which its energy is very small:

"This map shows a range of 0.0005 K from the coldest (blue) to the hottest (red) parts of the sky.
These ovals are all maps of the entire celestial sphere in an equal-area Mollweide projection. The image at right shows a topographical map of the Earth in this projection. Note that there is no part of the Earth that is not included in the oval, and thus there is nothing "outside" the WMAP map. "

Therefore, it seems to me that the WMAP (or the angular power spectrum of the anisotropy of the CMB) should be the signal. The CMB itself is the noise + Milky way radiation + WMAP signal. However, the WAMP amplitude is almost 5,500 times lower than whole CMB. I couldn't find a direct information about the ref between the CMB and the Milky way radiation amplitude. Based on the contrast, it is stated that the the CMB is higher by 2000 with regards to the Milky way radiation. In any case, this radiation could be considered as a noise from the galaxy. Henec, the noise portion in the CMB is more than 99.99..% than the WAMP signal. Therefore the CMB is called special noise.
Do you agree?

antoniseb
2015-Nov-03, 02:12 PM
... the noise portion in the CMB is more than 99.99..% than the WAMP signal. Therefore the CMB is called special noise.
Do you agree?
I'm guessing from the above that by WAMP you mean WMAP, but that perhaps you don't know that WMAP is the name of the probe that measured the anisotropy of the Microwaves (before the Planck probe did it in even more detail). In any case you seem to want to label something as noise, when perhaps it is better to refer to the whole thing as a collection of mixed signals. Now referring to one of the signals as "special noise" is just adding a new but useless pseudo-technical term into the mix. If you are measuring aspects of the Milky Way, the CMB is a signal you are trying to remove. If you are trying to measure the Baryon Acoustic Oscillations from the early universe, the Milky Way's microwaves are what you're trying to remove. If you're trying to measure the age and total energy of the visible universe, then the entire CMB is the signal you're trying to measure. ... so no, I don't agree.

Jeff Root
2015-Nov-03, 05:30 PM
The CMB was noise (unwanted signal) to those who first
discovered it. That noise has characteristics which make
it special (easily distinguishable from other signals by its
precise blackbody spectrum). That's all Geo Kaplan
meant by "special noise".

-- Jeff, in Minneapolis

glappkaeft
2015-Nov-03, 06:55 PM
You have it the wrong way around, Jeff Root.
The MWMW is the "noise".
The CMB is the signal.
The MWMW noise is foreground contamination that has to be removed to reveal the CMB signal. No one removes the CMB signal from the MWMW "noise".


<MrPicky>
If we are trying to be precise with the terminology then they are both signals. The signal is defined as the number of photons detected and the noise is the variance of the detected signal compared with the "true" signal. In this case the signal is a Poisson distributed statistical process so the noise (and thus also also the SNR) is equal to the square root of the signal.
</MrPicky>

Reality Check
2015-Nov-03, 09:16 PM
Let me help you.
By ignoring the question, Dave Lee? That is no help.
WMAP and Planck have measured the anisotropy of the CMB.
WMAP and Planck made measurements. The CMB itself is the WMAP and Planck measurements minus the Milky Way foreground contamination minus point source foreground contamination. There is a long pipeline of analysis of the raw data. See Welcome to Max Tegmark's CMB data analysis center (http://space.mit.edu/home/tegmark/cmb/pipeline.html) for an older description.
The name is Cosmic Microwave Background, not "special noise". That is what you called it.
Geo Kaplan described the CMB as "a very special kind of noise".

Reality Check
2015-Nov-03, 09:22 PM
The CMB was noise (unwanted signal) to those who first
discovered it.
Correct, Jeff Root. The CMB was noise (interference) in the Penzias and Wilson experiment that they wanted to identify and remove (https://en.wikipedia.org/wiki/Discovery_of_cosmic_microwave_background_radiation ).

Amber Robot
2015-Nov-03, 10:59 PM
Correct, Jeff Root. The CMB was noise (interference) in the Penzias and Wilson experiment that they wanted to identify and remove (https://en.wikipedia.org/wiki/Discovery_of_cosmic_microwave_background_radiation ).

The point is that we've learned so much in the past 50 years about the CMB that it is no longer appropriate to call it "noise".

Jeff Root
2015-Nov-04, 02:12 AM
Anything you aren't interested in at the moment is noise.

-- Jeff, in Minneapolis

cjameshuff
2015-Nov-04, 02:21 AM
The point is that we've learned so much in the past 50 years about the CMB that it is no longer appropriate to call it "noise".

As Jeff said, if it isn't the signal you're interested in, it's noise. That is the appropriate technical term, and it has nothing at all to do with how well understood the source of the noise is or how well characterized the noise itself is.

Amber Robot
2015-Nov-04, 06:06 PM
As Jeff said, if it isn't the signal you're interested in, it's noise. That is the appropriate technical term, and it has nothing at all to do with how well understood the source of the noise is or how well characterized the noise itself is.

All I'm saying is that that is not how I hear professional astronomers use the word "noise".

antoniseb
2015-Nov-04, 07:00 PM
As Jeff said, if it isn't the signal you're interested in, it's noise. That is the appropriate technical term, and it has nothing at all to do with how well understood the source of the noise is or how well characterized the noise itself is.
cjameshuff, I don't know if you are chiming in having not read the thread, but a lot of the discussion of "noise" here is in answer to the OP, and his clarification of his meaning on message #10 on the last line. He wants to know if the CMB could be some kind of noise with no specific source. The answer is no, but you and a few other people (e.g. Jeff Root) have gotten caught up in the semantic argument about the many meanings of the word noise, which is only confusing the effort to provide a good answer to the issue.

ShinAce
2015-Nov-04, 07:40 PM
Indeed, the classic definition of noise is 'any unwanted sound'. So when someone in a car next to you is listening to music you don't like, feel free to call it noise. If the person behind you likes that music, they have every right to call it music.

In that sense, the CMB was originally considered a constant source of noise which the engineers could not get rid of. Nowadays, we understand the source of this signal and are very much interested in it. So whether it is noise or not just depends on who you talk to. If you're building a deep space probe that communicates on a 2mm wavelength, then it is noise you need to contend with. If you're interested in studying the universe, it is a diamond in the rough.

None of this changes the origin of the CMB and its significance.

Dave: The power spectrum of the CMB is definitely the more interesting signal, by far. However, this doesn't mean we should just ignore the blackbody spectrum of the CMB. That is quite significant as well. Since we know how 'transparent' hydrogen gas is at various temperatures, the basic temperature of the CMB gives clues about the expansion history of the universe. In cosmology, we had to work out this ionization 'problem'. The professor did gloss over the power spectrum and how much information is encoded into it, but that was too technical to include on our final exam (an undergraduate cosmology course). I miss Dr. Campbell. I was in his class when the BICEP2 result came out. He spent over hald of that lecture just reminiscing about how far we've come since Penzias and Wilson. Plus the tangents about Dicke and Peebles was legendary. That was less than a year ago, but still....good times....good times.

edit: Don't forget that the CMB even gives you information about big bang nucleosynthesis. The way I see the CMB is like this. Imagine you're trying to demolish a stone wall with a 1 pound hammer. Then someone comes along and gives you a 20 pound sledgehammer. That sledgehammer is the CMB.

glappkaeft
2015-Nov-04, 08:33 PM
As Jeff said, if it isn't the signal you're interested in, it's noise. That is the appropriate technical term, and it has nothing at all to do with how well understood the source of the noise is or how well characterized the noise itself is.

No, it is never ever the appropriate technical term, no way no how.

See for instance https://en.wikipedia.org/wiki/Signal_(electrical_engineering) and https://en.wikipedia.org/wiki/Noise_(electronics)

cjameshuff
2015-Nov-04, 10:44 PM
cjameshuff, I don't know if you are chiming in having not read the thread, but a lot of the discussion of "noise" here is in answer to the OP, and his clarification of his meaning on message #10 on the last line. He wants to know if the CMB could be some kind of noise with no specific source. The answer is no, but you and a few other people (e.g. Jeff Root) have gotten caught up in the semantic argument about the many meanings of the word noise, which is only confusing the effort to provide a good answer to the issue.

I've been following this thread from the start, and no, it's not some irrelevant semantic argument. Amber Robot was advocating much the same misunderstanding that Dave Lee had, that whether something is "noise" somehow had something to do with how well-understood that thing is. Mains hum is a frequently encountered type of noise...there isn't much to learn about the cause of a 50/60 Hz inductively or capacitively-coupled sine wave, and no amount of learning will make it anything but noise in most contexts. Nor will the fact that it is noise mean you can't distinguish from other types of noise, or filter it out from the desired signal.

What is noise is dependent on context, is not at all dependent on how well-known the cause is, and noise from different sources often has clearly identifiable characteristics...the narrow bandwidth 50/60 Hz of mains hum, the near perfect 2.7 K blackbody of the CMB, etc. The two articles glappkaeft linked give a good overview.



No, it is never ever the appropriate technical term, no way no how.

See for instance https://en.wikipedia.org/wiki/Signal_(electrical_engineering) and https://en.wikipedia.org/wiki/Noise_(electronics)

If you read those articles, you might be surprised, since they don't actually disagree with me, and the latter specifically calls out cosmic noise, of which the microwave background is one component.

Amber Robot
2015-Nov-04, 11:30 PM
Amber Robot was advocating much the same misunderstanding that Dave Lee had, that whether something is "noise" somehow had something to do with how well-understood that thing is.

I agree that, colloquially, one can call any unwanted signal "noise", hence my "one person's noise is another person's signal" response. Even if that noise is from a well-understood source. However, the word "noise" isn't always used that way in a professional context amongst astronomers. You often hear "background signal" and not "background noise" when things like the atmosphere's infrared emission is discussed, whereas things like readout noise in a CCD amplifier is what I am more likely to think of as "noise".

ShinAce
2015-Nov-05, 02:10 AM
The last project I worked on was a photothermal microscope for gold nanoparticles. Even after using a lock-in amplifier to reject anything that didn't match the laser's modulation frequency, we were ecstatic if we got a SNR over 2 with a single sample.

We'd take turns presenting papers in journal club. It always amazed me how many graduate physics student simply did not know how to recognize various sources of noise. When the prof would probe them and ask how we could improve the SNR, I'd want to face palm every time I heard someone say "maybe use better equipment". It would appear many of them weren't paying attention when our lab instructor drilled us on the Poisson distribution.

Student: "Why is the error in this paper simply the square root of the signal strength?"
Me: "Because we are measuring discrete events, ergo, the Poisson distribution applies."
Student: "Ok"

One week later...lather, rinse, repeat.

Come to think of it. The prof and I rarely used the word 'noise'. We'd often simply talk about the 'background'. Our focus was really the SNR because it was so poor. In that sense, my experience resembles Amber Robot's.

Shaula
2015-Nov-05, 05:47 AM
Come to think of it. The prof and I rarely used the word 'noise'.

Our focus was really the SNR ...

When the prof would probe them and ask how we could improve the SNR ...
So ... what did the N stand for?

slang
2015-Nov-05, 05:56 AM
Whether we think it is relevant or not, Jeff's semantic half-joke response has now become the start of a major thread derail. PLEASE stop this side discussion, and stay focused on OP's questions, as it seems difficult enough to get them answered to his understanding.

Amber Robot
2015-Nov-05, 06:37 AM
Whether we think it is relevant or not, Jeff's semantic half-joke response has now become the start of a major thread derail. PLEASE stop this side discussion, and stay focused on OP's questions, as it seems difficult enough to get them answered to his understanding.

It seemed that the original question had been addressed fairly well in the first page or two of posts. The first post in this thread suggested that since CIBER had found many stars outside of galaxies that there were thus no truly empty lines of sight and that would mean that the CMB might not be from the Big Bang but is from these stars. It was then pointed out that though these stars may be sources in the infrared wavelengths that CIBER observed in they are not significant contributors to the signal at the microwave frequencies the CMB is observed at, especially since the CMB is an exquisitely uniform (spectrally and spatially) signal. It was even pointed out that the microwave signal from the Milky Way galaxy is a "noise source" when observing the CMB and can be removed from the CMB signal through multi-wavelength techniques. Does that not sum up the questions and the mainstream answers?

Then we got sidetracked by the definition of "noise".

slang
2015-Nov-05, 05:45 PM
Then we got sidetracked by the definition of "noise".

Which is a derail (especially since OP indicated that he still has questions), as is commenting on moderator actions in the thread. Please use the report button if you have an issue with any post, including those by moderators.

Jeff Root
2015-Nov-05, 07:21 PM
Dave Lee indicated in post #10 that he may have an odd
understanding of what "noise" is. Amber Robot and others
were addressing that odd understanding. Amber Robot
made a correct but incomplete statement in post #42 which
I completed with my post #43. Reality Check disagreed
with what I said, and cjameshuff then disagreed with
Reality Check.

I agree with cjameshuff: Noise is any unwanted signal.

"Signal", in turn, can mean either whatever you are trying
to detect, or it can mean anything and everything that is
detected, including noise.

It does not mean-- as is often inferred-- an intentional or
artificial source. It seems very likely that Dave Lee's
understanding of what "noise" is is influenced by his
understanding of what "signal" is.

So microwave radiation from the Milky Way is noise if you
are trying to observe the CMB, and CMB is noise if you are
trying to observe microwave radiation from the Milky Way.

Expressing it with the specific case that way avoided going
into the more difficult question of what a "signal" is. That
could come later.

-- Jeff, in Minneapolis

antoniseb
2015-Nov-05, 07:42 PM
I'm going to close this thread. I don't think anyone meant anything malicious here, or even anything that needs defending. But the answer to the OP is there, along with some other stuff about how people mean the word "noise" in certain technical contexts. Yay! Nicely done everyone. Thread closed.