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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Correlation between large-scale galaxy structure and CMB fluctuations?

During a relatively non-technical astronomy seminar the other day, the speaker displayed the famous WMAP full-sky image as an aid to describing what the CMB is, the scale of its fluctuations, etc. ...
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How can we detect cosmic background radiation?

From what I understand, CMB is the left over radiation from the Big Bang. As all matter, including the Earth, was made during the Big Bang and then as the universe expanded that matter/energy got ...
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How does the Cosmic Microwave Background give us information about the Big Bang?

I was reading about CMB after this new breakthrough last week and I could not figure this out. The CMB did not exist before the epoch of Last Scattering. They were just photons which were formed at ...
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Immediately after the Big Bang, was the universe in a state of extremely low or extremely high entropy?

Phase space theory suggests that the largest course-graining region, $p$, in a phase space, $P$, is the point in the phase space with the highest entropy. As such, it is in thermal equilibrium with ...
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What are the implications of the possibility that the BICEP2 results are caused by a self ordering scalar field transition?

I've found this interesting paper that mentions another possible way to interpret the recent BICEP2 results, and that hadn't been ruled out yet 1. As interesting as the possibility that the BICEP2 ...
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66 views

The gravity waves from the big bang? How can we know?

The latest news says that scientists detected gravitational waves from the Big Bang. My question is how do they know the waves originated in the big bang verses any number of supernovae and or ...
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114 views

What does BICEP2's results tell us about gravitation waves and quantum gravity?

The BICEP2 results, unless I am mistaken, are a measurement of CMB polarization, i.e. photon polarization. That is, taken at face value they say nothing about gravity directly. Now, we can start to ...
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What's the $\ell$ in the Bicep2 paper mean?

The BICEP experiment's recent announcement included the preprint of their paper, BICEP2 I: Detection of $B$-mode polarization at degree angular scales. BICEP2 Collaboration. To be submitted. ...
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CMB curly B-modes and dark matter

I raised a question a while ago regarding weak gravitational lensing of galaxies and the CMB. With all the fuzz with the BICEP2 data, I think it is time to raise even more questions about this amazing ...
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97 views

How big of an area of the sky is the BICEP2 survey?

So here is the BICEP2 picture: How big is that? How much of the sky? Say, compared to this picture of the CMB by Planck:
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38 views

Is Λ-CDM and no inflaton field compatible with the observed value of the scalar spectral index?

From the cosmic microwave background, one can extract the scalar spectral index $n_s$. It is measured to be smaller than 1 by several standard deviations. Wikipedia says that it is a parameter of the ...
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What do the names “E mode” and “B mode” mean? Where do they come from?

This has been bugging me a bit since the BICEP announcement, but if there are any resources that answer my question in a simple way, they've been buried in a slew of over-technical or over-popularized ...
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BICEP2 and string theory

Can anybody elaborate on the implications of the BICEP2 result for string theory? The discussion here What experiment would disprove string theory? suggests that refuting string theory is rather ...
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Connection between BAO und CMB Spectrum

I have a problem understanding the connection between the accoustic peaks in the CMB spectrum and the baryon oscillation picture. On the one hand it is stated, that the odd accoustic peaks (1,3,5..) ...
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143 views

BICEP2 experiments

How was the polarization experimentally measured in the BICEP2 experiments and why did they look specifically at B-modes? Why is it implying the existence of gravitational waves and the need to ...
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202 views

What do the BICEP2 results mean for string gas cosmology and the ekpyrotic universe?

The imprint of gravitational waves created shortly after the big bang may offer direct evidence for inflation theory, according to a discovery by the BICEP2 experiment at the South Pole and released ...
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What experiments compete with BICEP 2, and when are their results expected?

The recent results of the BICEP 2 experiment published on March 17th 2014, has generated a lot of media attention, with the general consensus being that "this is a major discovery" perhaps leading to ...
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What do the line segments on the BICEP2 B-mode polarization map mean?

The first image of BICEP2 visuals shows the "BICEP2 B-mode Signal", described as follows: Gravitational waves from inflation generate a faint but distinctive twisting pattern in the ...
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What was the major discovery on gravitational waves made March 17th, 2014, in the BICEP2 experiment?

The Harvard-Smithsonian Centre for Astrophysics held a press conference today to announce a major discovery relating to gravitational waves. What was their announcement, and what are the implications? ...
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Meaning of $k$ in Sachs-Wolfe formula for angular power spectrum

I've seen the formula for the angular power spectrum of the CMB written as $$C_\ell = \frac2\pi \int\left|\Theta_\ell(k) \right|^2 k^2dk, $$ where $\Theta_\ell(k)$ is the temperature contrast at a ...
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why does the CMB change so slowly

If anisotropies of the CMB originated from "quantum fluctuations of matter in a very tiny space that expanded to the size of the observable universe we see today" (quote from Wikipedia) would they ...
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CMB radiation and holography

If in principle someone have the exact data of the CMB of our universe and unlimited computability power, to what extent it is possible to determine how the universe should look like? Does it fully ...
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Did Penzias and Wilson need such a large horn antenna to discover the CMB?

Penzias and Wilson discovered the 2.7K Cosmic Microwave Background (CMB) Radiation using a 6 meter horn antenna, along with a cryogenic low-noise detector measuring at 4 GHz: ...
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Angles in cosmology

We have several definitions of distances in cosmology. Take angular diameter distance. $$d_A = a(t)\int \frac{dt}{a(t)}\;.$$ If an object has proper length $L$ then the angle $\theta$ it is seen at ...
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Where is radiation density in the Planck 2013 results?

I've been looking at the Planck 2013 cosmological parameters paper, trying to update my toy cosmology simulator with the most recent data. Most of the interesting values such as $H_0$, $\Omega_m$, ...
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Is it reasonable to assume that de Sitter temperature will stop growing when it reaches equilibrium with the temperature of CMB?

Is it reasonable to assume that de Sitter temperature will stop growing when it reaches equilibrium with the temperature of CMB? Currently the de Sitter temperature (the temperature of the Universe's ...
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What is the de Sitter temperature as of now?

It is claimed that de Sitter temperature is $$T=\frac{1}{2\pi}H,$$ where $H$ is the Hubble constant. I presume it is expressed in natural units with which I am not familiar. So what it will be in ...
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What speed should have an alone planet to have a habitable zone due to relic radiation?

What speed should have an alone planet to have a habitable zone due to relic radiation, without any star involvement? How much time the planet will be able to remain in the habitable zone before the ...
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Temperature of relic radiation and thermal equilibrium

The temperature or relic radiation is 2.7 K. Does it mean that any flying body sufficiently far from any stars will reach this temperature? As I understand it, you can warm up water with sufficient ...
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Temperature of thermally isolated space region

If we thermally isolate a region in space, say using a hypothetical material of $0$ conductivity, and measure the region's temperature, will it be 2.7K?
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76 views

Weak gravitational lensing multispectral, multibackground correlations

My understanding of weak gravitational lensing is that it assumes random alignment distribution of galaxies in order to estimate statistical shear and convergences, which are used to estimate matter ...
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111 views

Could there have been two “Big Bangs”?

A couple of years ago, I remember seeing a documentary on the big bang theory. The theory presented was that to explain the cosmic microwave background radiation, there needed to have been two big ...
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22 views

Would the microwave background radiation have an “observer effect” on all systems in the universe due to its permeation?

Or more specifically, does the CMB radiation have an observer effect on us in our local system due to gravitational lensing? Acknowledging this effect, if any would be nearly negligible I have an ...
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What are the different ways to measure the spatial curvature of the universe?

Just what the question asks. Assuming the Friedmann-Rovertson-Walker (FRW) metric, what measurements can be performed to determine the spatial curvature of the universe.
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How Does Cosmology Constrain the Number of Neutrino Species?

I know that based upon theories of structure formation cosmologists can constrain the sum of the masses of neutrinos - if neutrinos were too light or too heavy it would simply change the power ...
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Are there any programs or codes widely used for computing spherical multipole expansion, especially for CMB?

I have data of coordinates and values of a part of sky, and I'm supposed to calculate multipole expansion, change some components between some $\ell$s, and finally calculate back to values. The ...
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superhorizon mode and cmb

During the period of inflation, perturbations went out of the Hubble horizon (Hubble radius, R = 1/aH) because the Hubble radius was decreasing during that time. After inflation, the Hubble radius ...
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169 views

How far away is Cosmic Background Radiation? [duplicate]

I've been reading about Cosmic Background Radiation (CMBR) lately. My understanding so far is that this is the "Noise"/"Flash" from the big bang. Assuming that information is correct, how far away ...
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108 views

CMBR temperature over time?

How has CMBR temperature dropped as function of time? A graph would be nice, but I'd be happy with times (age of universe) when it cooled enough to not be visible to human eye, became room temperature ...
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Does the Cosmic Microwave Background obey $\sigma T^4$?

The fact that the CMB has a temperature of 2.7 degrees Kelvin is well publicized, but I have a harder time finding a measure of the wattage per unit area. The Wikipedia article on the CMB is totally ...
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what is the radial extent of the last scattering “shell”?

At CMB recombination (z=1090), what is the radial extent of the last scattering "shell"? a) Delta(z) = .... b) Delta(comoving angular distance)= ....Mpc The WMAP first-year parameters give Delta(z) ...
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Are there multiple ways to determine the redshift of the CMB experimentally?

I know that by using Boltzmann equation and all that one can calculate that photons become decoupled around T~3000K and because temperature scales as T~1/a we can determine that the redshift of the ...
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Spread and direction of the cosmic background radiation

Something I can never understand is that where the cosmic background radiation spreads? If I know well, the cosmic background radiation is actually the light of the Big Bang. If it happened exactly ...
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441 views

Recent Planck probe results: how unexpected?

The data from the Planck probe's observations are in, and according to the European Space Agency they show a "hemispheric asymmetry in the cosmic microwave background (CMB)". Quote: an asymmetry ...
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Causal structure of the inflationary multiverse

In the multiverse as it is described by eternal inflation, it is not clear to me what is its causal structure and in particular if the bubble-universes are causally connected. We start from a ...
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Cosmological triangle with PLANCK results

Is there an updated version of the cosmological triangle with recent PLANCK results included?
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49 views

CMB anisotropies and tightly coupled limit

Sorry if this is a technical question. I am studying the origin of CMB anisotropies and the tightly coupled limit of the Boltzmann equations. We have a fluid composed of ionized electrons and photons. ...
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314 views

How the CMB anisotropy is linked to the existence of cold dark matter and dark energy?

After the data from the cosmic microwave background has been collected by WMAP or Planck, what types of analysis is needed to conduct in order to deduce the cold dark matter density and the ...
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Why cosmic background radiation is not ether?

why cosmic background radiation is not ether? I mean it's everywhere and it' a radiation then we can measure Doppler effect by moving with a velocity.
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What does Planck/WMAP/COBE actually measure when studying the CMB?

I have been reading a lot about Cosmological experiments such as Planck or WMAP that aim to investigate the CMB's power spectrum. I am unclear though as to what theses sky surveys actually measure, is ...