Questions tagged [cmb]

Questions regarding the cosmic microwave background, or CMB, the leftover radiation that is taken by many as proof of the Big Bang.

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How do CMB photons 'gain energy when they pass through normal regions of space with matter' and 'lose energy when they pass through voids'?

The Space.com article Huge Hole Found in the Universe says: The gargantuan hole was found by examining observations made using the Very Large Array (VLA) radio telescope, funded by the National ...
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1answer
109 views

What Is The Maximum Distance Our Finest Instruments Could See When They're Perfected?

Radius of the observable universe is 47.5 billion light years,which means we are seeing things which are about 48 billion light years away. At a rough estimate,at what distance would our finest ...
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How do they know the X-ray and radio intensity really come from a magnetic field bridge between these two clusters of galaxies?

Gizmodo's Astronomers Spot Mysterious, 10-Million-Light-Year-Long Magnetic Field Connecting Two Galaxy Clusters shows the image below, and Space.com's A Weird 'Radio Bridge' 10 Million-Light Years ...
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How are constraints on dark energy improved the most?

Today we have various data available from independent probes to constrain dark energy, i.e. its equation of state $w$. These include Type 1a supernovae, BAO, CMB, large-scale galaxy surveys, etc. Are ...
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40 views

How is the expansion rate of the universe obtained from Baryon Acoustic Oscillations?

I understand that we can measure the sound horizon from the anisotropies in the CMB. Large galaxy surveys today can construct two-point correlation functions, which reveal peaks at distances equal to ...
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How large part of the energy of the electromagnetic radiation in the universe is primordial

As I understand it there can be said to be two "kinds" of electromagnetic radiation filling up the universe. First you have the primordial radiation from a time soon after Big Bang. Then you have "...
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1answer
39 views

Why would atmospheric absorption increase rather than decrease the antenna temperature in Penzias and Wilson's famous CMB observation?

The classic paper A MEASUREMENT OF EXCESS ANTENNA TEMPERATURE AT 4080 Mc/s begins: Measurements of the effective zenith noise temperature of the 20-foot horn-reflector antenna (Crawford, Hogg, and ...
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Motivation for using $\sigma_{8}$?

Press-Schechter formalism allows one to universally quantify the number of massive dark matter halos in a given volume -- The Halo Mass Function. The density contrast is given by the rms mass variance ...
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1answer
53 views

From CMB anisotropy data observed in 1992, did astronomers figure out that the universe should be accelerating before its discovery in 1998?

CMB anisotropy was measured in 1992. I assume that astronomers, then, like now, would have been able to deduce the cosmological constant and things like that from the CMB anisotropy data. Then, from ...
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375 views

Why can we still 'see' the CMB

I read that the CMB were all the photons left free when the universe was cold enough for electrons got bound with protons (recombination) and the photons free in that moment continued traveling in the ...
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Studies of isotropy from different ends of the visible universe?

Have there been studies to compare structures that are 26 billion light years distant (i.e. from one side of the observable universe to the other) to search for faint differences?
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Does the CMB pattern evolve in a human lifetime?

I was thinking, as CMB is a snapshot of a slice of the Universe during recombination, how much the cmb is changing with time ? I mean as we progress in time we look a CMB a bit more faraway each time, ...
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Who discovered the relation between CMB fluctuations and large-scale structure formation?

I haven't been able to find a reference to the first who showed that the small density fluctuations in the cosmic microwave background led to the formation of large scale structure as we know it.
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76 views

What would the CMB look like somewhere else in the universe?

An answer to a question on Worldbuilding.SE opined that if you were suddenly transported an unknown distance and direction away by magic you could use the Cosmic Microwave Background to determine your ...
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How long after the Big Bang would CMB radiation have been between 273 and 373 K?

Cosmic microwave background radiation is 2.7 K today. When would it have been between 0 and 100 C?
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WMAP beam profile

What do people mean by the "beam" profile/model pertaining to WMAP? Search results are all rather packed with jargon. Is there a pictorial /layman explanation of it and how does it affect the data?
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1answer
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Would a future hole in the Cosmic Microwave Background show us the edge of the universe?

If my understanding is correct, the Cosmic Microwave Background always come from our event horizon. By event horizon I mean the edge of the observable universe. If the universe is finite does it mean ...
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221 views

What is the physics of the “spinning dust” contribution to Cosmic Microwave Background measurements?

The lengthy paper Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results mentions "spinning dust" about 51 times. It is a potential contributor to the measured ...
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1answer
81 views

Centre of the singularity that is the big bang [duplicate]

If it's true that the deeper we look into space the further back in time the light is coming from then does that mean that just behind the cosmic background radiation the entire sky is filled with an ...
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1answer
132 views

Does the Earth ever cross the Moon's path with respect to the CMB?

Title says it, really. As I understand, our total peculiar motion with respect to the CMB is 631 (+/-20) km/h, in the direction of 10.5h RA; -24 deg Dec (or rather away from 22.5h RA; +24 deg Dec, ...
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1answer
109 views

Can the diminishing energy of the CMBR be the source of dark energy?

I was just told the CMBR energy diminishes with time. Can it be that the lost energy is somehow transferred to spacetime, causing the expansion to accelerate?
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1answer
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Is the total energy of the CMBR diminishing with time?

Is the total energy of the CMBR diminishing with time? Since it's existence the volume of the Universe (at least the visible part) has grown by a factor three, which is to say, the number of photons ...
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1answer
82 views

Is the CMB the photons that were created at the birth of the atom?

Is the CMB that we see the same, unchanged energy from this moment? Does the radiation of the CMB exist as Photons and are we only witnessing the photons that have not been absorbed or destroyed? Will ...
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Future redshifting and effect on the 'pitch' of CMB radiation

After discovering this question exploring the sound of a blackbody, I started wondering about the sound of the Cosmic Microwave Background radiation from the Big Bang, specifically what the current ...
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3answers
462 views

Are we moving faster than the Cosmic microwave background radiation?

if the Cosmic microwave background radiation is coming towards us in the speed of light and all matter and energy was singular at the big bang, doesn't that mean we somehow moved faster than the speed ...
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163 views

Why is the CMB not simply travelling parallel to us? [closed]

When we look to the distant farthest reaches of the universe we see light that was emitted at the big bang 14 billion years ago. But the universe was tiny back then so that light, which is only ...
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1answer
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Intuitive explanation for why the universe is flat

I went through Prof. Hitoshi Murayama's online lecture where he describes why the universe is flat. One of the evidences for a flat universe is the evenness of CMB radiation on all directions. My ...
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1answer
186 views

Evidence of CMB redshift

Are there any known spectral lines shifted by ~1100? If not, then how certain is mainstream that the CMB has a redshift of ~1100? All I see is a blackbody radiation curve void of spectral lines.
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3answers
1k views

Are we center of universe? [duplicate]

So I just learned that CMB redshift is 1100 regardless where we look (up down left right). According to Hubble's Law that makes it around 46 billion light years away, making it the farthest matter ...
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2answers
154 views

How is it possible that the CMB approaches the earth from all directions?

I presume that the photons from the CMB approach the earth from all directions, otherwise we couldn't detect them with a picture where it is present everywhere in the universe with a tiny anisotropy. ...
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1answer
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How do we know background radiation does not come from undiscovered galaxies?

Each year while observing voids, astronomers discover more and more unexpected galaxies within them. How do we know the cosmic microwave background radiation is not the weak light from distant ...
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1answer
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Problem with denoising the BICEP2 data?

This question pertains to this article which talks about why the BICEP2 measurements of B-mode polarization in Cosmic microwave background radiation turned out to be noise from galactic stardust. They ...
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2answers
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Why can we observe the Cosmic Microwave Background no matter the direction we look?

I often read that the CMB was released from everywhere in the Universe, in every direction. If that statement is true, can someone elaborate what "everywhere in the universe, in every direction" ...
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0answers
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Why is the E-mode polarization spectrum out of phase with the Temperature spectrum?

The E-mode polarization power spectrum of the Cosmic Microwave Background displays the same acoustic peaks that can be seen in the (more famed) temperature power spectrum. However, they are out of ...
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Galaxy Cluster Temperature

I've read once in an article that the temperature of the medium between the galaxy superclusters is extremely high. What does that temperature really mean? particles' velocity? Why is that so? Is ...
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1answer
183 views

Why is the Boomerang Nebula colder than the CMB?

An earlier answer on temperature mentioned that the temp of the CMB is 2.4K and the temp of the Boomerang nebula as 1K. How did the nebula cool faster than the CMB?
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Was the cosmic microwave background (CMB) radiation originally gamma rays?

I believe that sometime after Big Bang the entire universe was filled with high energy particles. Now we fast forward to the present; most of these particles still linger and managed to avoid being ...
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1answer
102 views

What do cosmologists mean when they talk about “the running of the spectral index”?

All I know is that the spectral index is related to the CMB, and that it has to be slightly less than 1 to favor inflation.
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1answer
286 views

Does the cosmic microwave background recede at the speed of light?

Does the cosmic microwave background recede at the speed of light? Is it possible it recedes even faster because of the stretching of space?
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2answers
2k views

Does the cosmic microwave background change over time?

Does the cosmic microwave background pattern change over time? I would assume it is getting "cooler" as in more redshifted as time passes, but I am more interested if the pattern on the background, ...
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1answer
181 views

Is CMB Polarization simply the temperature gradient of the CMB?

Firstly, I have to admit that I don't fully comprehend the concept of "CMB Polarization". When I think of "Polarization", I normally think of the optical definition of polarization, as defined by the ...
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247 views

How can there be anything “beyond” the CMB?

Two things we take, for this purpose, to be axiomatic: The CMB is the oldest thing we can observe directly The cosmological red shift tells us how "old" something we are observing is Yet we also ...
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447 views

How to determine scalar-to-tensor ratio r from CMB polarization spectrum?

CMB polarization spectrum can tell us about the primordial scalar and tensor perturbation. By analyze B and E mode angular spectrum power spectrum and temperature power spectrum we can determine the ...
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1answer
109 views

Formation of Cosmic Microwave Background

It is said that the cosmic microwave radiation (CMB) was formed when the universe was 379,000 years old. How is this calculated?
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Did cosmological inflation occur at speeds greater than $c$?

If cosmological inflation occurred at speeds less than $c$, wouldn't we see the CMB right in front of our noses (or not at all) instead of at 13.7 billion light years? And if it happened faster than $...
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What is CMB radiation doing to the universe?

It is said that due to CMB radiation our universe has been expanding? Firstly what lead the universe to expand? What do scientists mean by dark energy? Will energy convert into matter?
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1answer
158 views

What is the ratio of cosmic microwave background radiation to normal radiation?

I would like to know the ratio of cosmic microwave background radiation to normal radiation in the universe. I am considering cosmic microwave background radiation to include the microwave, and any ...
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How exactly can the hypothetical conformal invariance of the CMB spectrum be established by analyzing tensor modes?

In the introduction of this paper at the top of p11, it is mentioned that a hypothetical enhancement of the scale invariance of the CMB spectrum to conformal invariance could potentially be ...
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Why can primordial tensor perturbations of the CMB be ascribed to gravitational waves?

Why can primordial tensor perturbations of the CMB be ascribed to gravitational waves? Is this attribution unique, or are there other mechanisms that could lead to the excitation of tensor modes? In ...
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1answer
253 views

Do the E and B modes of the CMB polarization have anything to do with electric and magnetic fields?

As explained in this article, as the CMB is created from a vaiable (matter?) density $\kappa$ its gradient $\nabla \kappa = \vec{u}$ can be separated into a gradient and curl part, called the $E$ and $...