The cosmic microwave background (CMB) is the electromagnetic radiation in the microwave band which can be observed throughout the whole universe, not connected to any astronomical object. Its spectrum follows a very precise black-body radiation with a temperature of about 2.7 K.

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408 views

Will the CMB eventually recede outside our observable universe?

As I understand it, some billions of years ago, the universe used to be opaque (edge of the sun - orange colored). Due to the expansion of the universe, photons emitted billions of years ago from ...
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23 views

Will CMB images change as technology progresses?

Will cosmic background radiation images change as technology progresses? Will they become more precise, so to speak? I am asking because the images gotten by Planck and WAMP differ greatly. Will the ...
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0answers
18 views

What do the $T, E, B$ in polarization spectra mean?

I was reading about CMB Polarization here. I know that $E$ and $B$ stand for E-mode and B-mode, but what does the $T$ mean? The author states that there are 3 observables: $T, E, B$ and six spectra: ...
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58 views

What would we observe as background on the sky if the big bang had never occurred?

The data we've received so far from satellites such as WMAP paints a near uniform distribution in intensity of the background radiation that we take as evidence that our universe had an origin, and ...
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36 views

I need Resources on CMB Neutrinos

I am doing a research paper for upper level undergrad class on CMB neutrinos (C$\nu$B). I need papers that explain CMB Neutrinos from the ground up like the main theory behind the CMB Neutrinos and ...
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1k views

How do we know that the cosmic background radiation comes from the early universe?

How do we know that the source of the CMB comes from the early universe, and we don't simply observe the rare interstellar or intergalactic dust of 3K temperature?
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1answer
59 views

The CMB and the Hubble comoving radius

I have been thinking on this for a while and i don't get it. My point is, the comoving Hubble radius $(aH)^{-1}$ is the distance at wich the universe expansion begins to be superluminical. In an ...
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49 views

Size of the universe from CMB?

The CMB is almost 13.8 billion light years away in every direction so the diameter of the visible universe as we actually observe it is 27.6 billion light years, twice the distance light traveled over ...
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35 views

How is the first acoustic peak calculated in CMB?

I'm trying to work out the rudiments of the CMB power curve. Looking at the Plank results, we're given the sound horizon at recombination as $\theta = 1.04147\times 10^{-2}$ (radians). So the first ...
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32 views

Is the CMB Cold spot growing or shrinking?

What do we know about the nature of this region of the sky? is that region entirely devoid of galaxies? Could it be a bubble void, and we are simply unable to see the galaxies that are on the ...
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51 views

How will TV Noise look like If we remove the Cosmic Microwave Background?

People have been saying that a small amount of noises you see in the Analog TV is from the CMB and other devices. What if the CMB never existed and the TV never got affected by devices? (Maybe in ...
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2answers
95 views

Why doesn't the Cosmic Microwave Background heat my food like a Microwave?

I know the reason we have a CMB is because the photons don't react with any of the matter in the universe, or the mean distance between interactions for photons generated since decoupling is now the ...
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1answer
50 views

Is the fluctuation pattern of the Cosmic Microwave Background (CMB) identical in every location of the universe?

I know that the Cosmic Microwave Background (CMB) is the leftover radiation from the "surface of last scattering". Let's say an alien civilisation lives on andromeda or further away. Would they see ...
4
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2answers
132 views

How do quantum fluctuations lead to overdense regions in the CMB?

I've read a lot of work about Inflation but yet to find a cogent description where someone explains exactly what 'quantum fluctuations' are and how they led to overdense regions in the CMB. I get the ...
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0answers
32 views

The steady state theory, can it now be falsified on particle physics grounds, in addition to CMB data?

The steady state theory is no longer taken seriously by most physicists and the Big Bang theory is supported by an enormous amount of evidence, especially the CMB data. But from a quick scan through ...
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3answers
111 views

The temperature in space is about 3K, however there are almost no atoms in space. How can there be residual heat?

My understanding is that heat is essentially atomic vibrations. If there are almost no atoms, how can there be residual heat? Also, as I understand in space there is no heat transfer via convection ...
5
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2answers
81 views

Velocity of Solar System relative to CMB

In the book 'An introduction to science of cosmology' by Raine and Thomas, they have two equations $$ \frac{\Delta T}{T} = \frac{v}{c}\cos\theta'\qquad (4.14) $$ $$ T = ...
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388 views

Is the cosmic microwave background radiation red shifted?

My question is. If the cosmic background radiation is red shifted how would you calculate the wavelength at the time it was emitted ?
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42 views

Units of angular power spectrum

I am not sure whether this question might be better suited for crossvalidated or stackoverflow, but I will give it a try here: I have a map of the full sky in in the healpix format, units are $\rm ...
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17 views

Is there a standard of rest in the universe? [duplicate]

If you measure the cosmic background radiation you will find that in any direction it is roughly the same. However, if you were to travel near the speed of light relative to the Earth in a particular ...
3
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2answers
139 views

How do we know that the CMBR is the oldest light?

How do we know that the CMBR is the oldest light which we can see? Is it based just on the facts 1.that waves redshift with expanding space, and 2.predictions of the big bang theory; Or is there a way ...
3
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2answers
42 views

How do we tell the CMB apart from other radiation?

Say I want to observe the CMB and the CMB only. I point my device (telescope in some frequency range) at the sky and start looking. How do I know it should be in the Microwave spectrum? How do I ...
3
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2answers
231 views

Number density of CMB photons?

When we talk about the present-day number density of photons ($n_\gamma\approx 10^8 $ $m^{-3}$) in the universe do we mean the number density of CMB photons? I mean there are other sources of ...
3
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1answer
63 views

What is the mix of ordinary mass vs. ordinary radiating energy in the universe?

I have seen data showing that the estimated mix of dark energy in the universe is 68.3%, the mix of dark matter is 26.8% and the mix of ordinary matter is 4.9%1. However, within "ordinary matter," ...
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0answers
32 views

Best evidence for Big Bang? [duplicate]

Why is the existence of cosmic microwave background regarded as the best evidence of Big Bang (or Big Bang model?)?
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39 views

CMB and Gibbs free energy

I was doing my homework and I have a doubt. I proved that if I have the radiation energy density $$u = \frac{U}{V} $$ and $$P = \frac{1}{3}u $$ Then the Gibbs free energy is 0. But, how can I to ...
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4answers
147 views

Has cosmic microwave background kept a constant frequency?

Has the frequency of CMBR changed at all since the beginning of the universe? Has it always had a microwave frequency or has the frequency increased/decreased over time or is the change due to factors ...
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93 views

Implications of dark matter imprints on Cosmic Microwave Background Radiation?

Looking at this link, CMB Anisotropy, I have two questions regarding the possible creation and properties of dark matter: If dark matter has left it's imprint on the CMB, that to me, would imply ...
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0answers
52 views

Are Cosmic Microwave Background (CMB) photons entangled?

Suppose we'd like to know whether two cosmic microwave background photons emitted from different parts of the sky have any quantum correlation with each other. We could measure polarization of two ...
0
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1answer
74 views

Do we really need inflation for horizon problem?

This is a very fundamental doubt. I think i am missing something in inflation. The inflation theory solves the horizon problem by stating all of the universe started from a very small region in ...
2
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1answer
58 views

Cosmological fluctuations: what is gaussian?

When we are speaking about gaussianity and non-gaussianity in a cosmological context, what is gaussian or non-gaussian in the CMB? What would a non gaussian CMB look like compared to a gaussian one? ...
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1answer
110 views

Particle Horizon and CMB

If particle horizon is the maximum distance we can see presently in the universe, how come we are able to see CMB? CMB is radiation from surface of last scattering happened at t~380k years. Suppose ...
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1answer
159 views

If we go to space why isn't the temperature high? [duplicate]

We know that the temperature in space (which has vacuum) is low. If I go to space will I feel sweaty and hot or chilly? I think I will feel sweaty and hot because the radiation (UV, IR, etc) of the ...
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1answer
84 views

CMB anisotropy, temperature and doppler effect

How would you derive the following equation: $$ T' = T_{CMB} \left( \frac{\sqrt{1-v^2}}{1+v\cos{\theta}} \right) $$ which describes how the temperature of the CMB varies due to the speed $v$ of the ...
5
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2answers
106 views

Would the presence of B-modes in the CMB provide evidence for quantum gravity?

Finding B-modes in the CMB (which aren't due to foreground contamination) would be evidence for gravitational waves, because they cannot be produced by density perturbations (to first order, is my ...
2
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2answers
151 views

Why the CMB has not been dispersed so far?

Imagine you have a box of black body radiation. What happens if you open the box for a long time? It becomes dispersed and no radiation remains in the box. Now, apply this example to the Cosmic ...
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80 views

How do we get the power spectrum through the CMB?

How do we get the power spectrum through observing the CMB?
2
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1answer
194 views

Has the cosmic alignment of Earth and the Solar System been explained (CMB anisotropy)

The Cosmic Microwave Background anisotropy is currently aligning Earth and the Solar System with the largest and earliest structure of the universe. Has this been explained yet? Or are the theories ...
2
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2answers
114 views

What is the process by which the density fluctuations that were detected in the CMB evolved into the first stars?

We can detect very slight fluctuations in the temperature (mass distribution) when the CMB was released (decoupling). It is believed that these fluctuations led to the first stars. However, these ...
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43 views

Energy variations of cosmic background radiation

Has anyone been able to measure a difference in the energy density of Cosmic Background Radiation in a gravity well compared to zero gravity?
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28 views

How is the formation of the first atoms related to the cosmic microwave background? [duplicate]

Common atoms formed when the universe finally got cool enough for electrons to bind with atomic nuclei around the year 380,000. From what I understand this shift in state from plasma to discrete atoms ...
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75 views

Assuming the universe is finite, at some point, CMB should go away, right?

I'm not talking about gradual red-shifting, that happens slowly anyway, but with a universe of finite size, we should actually see Cosmic Background Radiation turn off in a sense, first at a point, ...
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1answer
60 views

What made up the cosmic microwave background and the first stars?

I am trying to figure out how the first stars formed and I'm looking for information on what made up the gas/radiation that they formed from. Most of our evidence for the make up of these formations ...
10
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1answer
339 views

CMB parameter, what's the meaning of the matter power spectrum normalization $\sigma_8$?

Most CMB experiments like WMAP and Planck include a certain cosmological parameter called $\sigma_8$. My understanding is that normalization of the matter power spectrum is not a theoretical ...
1
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1answer
108 views

absorption of cosmic microwave background radiation

My understanding of the CMB radiation is that it comes from everywhere, and goes in every direction. But how can this be the case, when there is a lot of matter in space which could absorb, or for ...
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0answers
25 views

What does velocity relative to CMB mean? [duplicate]

I've see some velocities such as that of the Sun quoted as "relative to the cosmic microwave background"? How is this different to measuring velocities relative to that old, discredited idea, the ...
3
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3answers
135 views

Average temperature of the universe

Is it possible to define some average temperature of the universe? If yes, what fixes this temperature and how t estimate today's temperature? Is it different from the temperature of the black-body ...
1
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1answer
87 views

Confusion with the meaning of CMB

We say that CMB is the radiation leftover from big bang. When we measure the radiations i.e., the flux of photons in a given microwave range (say 0.1cm to 70cm, for example), in deep sky, there are ...
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37 views

Thomson scattering on the elections does not produce any circular polarization?

All references on CMB polarization has this statement as if it is a trivial fact. But I have to admit that I completely don't understand what this sentence is telling us.
3
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1answer
73 views

What are the latest findings on the topology and size of the universe?

The paper G. Aslanyan & A.V. Manohar, The Topology and Size of the Universe from the Cosmic Microwave Background, JCAP 06 (2012) 003, arXiv:1104.0015, uses the 7-year WMAP data. Has any ...