Cmb Definition and 252 Threads

cosmology strings vs loops How well does string cosmology account for inflation, CMB, gravitational waves, evolution classically using FRW metric? does string cosmology offer either qualitative or quantitative predictions? This paper addresses these in the loop framework...

An article on news.discovery.com titled, "The Universe is Precisely 13.75 Billion Years Old" on Feb. 4 says: "The amount of CMB radiation spotted near clusters of galaxies is greater than expected. According to [cosmological] theory, CMB photons should interact with these clusters, getting...

hello, I am interested in calculating the size of the anisotropies of the CMB to make the comparison with the observed angle through the WMAP satellite. I found an article on the physics of microwave background anisotropies and which explains all the different physical processes that occur...

I went to wikipedia to look up decoupling and ended up getting a pretty crappy result "In physical cosmology, the term decoupling is often used for the moment during recombination when the rate of Compton scattering became slower than the expansion of the universe. At that moment, photons...

Question Estimate the current number of cosmic microwave background (CMB) photons there are now, per cubic meter, given that the mean photon energy of a blackbody distribution is about 2.70kT. Method http://en.wikipedia.org/wiki/Planck_function" gives the energy density (i.e. energy per...

My question is regarding when the the CMB was created. I understand that it is predicted to have been "when the universe cooled to about 3,000K". However, might it have been possible that different areas of the universe reached that temperature and decoupled a little earlier than others? This...

During the interval from t = 380,000 yr (CMB last surface) to the present, if the Universe were exclusively matter at critical density, the scale factor [1+z] would be proportional to t to the 2/3 power. Note that [13.7 Gyr/380,000 yr] raised to the power 2/3 corresponds to [1+z] = 1090. This of...

Cosmic Microwave Background radiation is coming to us from about 13.7 billion light years away... is that correct? The reason its coming from 13.7 billion ly away is because the universe is 13.7 billion years old... is that correct? so when the universe was only 12 billion years old the...

Which textbook does contain some accessible details of the calculation of the temperature of CMB? Thx!

How does one convert measurements in radio astronomical terms to temperature (Kelvin)? Specifically: Penzias & Wilson's measurement of CMB was "excess temperature at 4080 Mc/s." HOW does this yield a "value of about 3.5 degrees Kelvin higher than expected?" Basically, how do you get from...

CMB fluctuations and large scale fluctuations nowadays do not match ? The CMB dark matter density fluctuations for big scales is d_rho/rho~ 10^-5 and lower. The scale factor increased ~ 1000 times from last scattering to now. Linear perturbation theory predicts that the density fluctuations...

I've heard it said that it is impossible to determine an objects absolute velocity, all one can do is find it relative to some other object... but, if the CMB is everywhere, why could you not just measure the doppler shift in all directions, and adjust your velocity so the CMB has no doppler...

Good day. I've been reading and reviewing the posts and linked references on this forum for about 3 weeks now (enjoying the heck out of the exchanges BTW) and have assimilated much of the information (I think). I am trying to understand how it fits together and several questions remain. This...

Does anyone know where I can find numbers (or how to derive) the CMB flux density (W/m^2)? I'm only really interested in our present cosmological time, so a solution may assume the CMB to be at a constant temperature.

The size of bouncing lumps of charged particles, DM and photons in the primordial universe is supposed to be around 220,000 lyr (= sound horizon since the acoustic speed is approx 0.6c). If we then calculate the angle A subtended at Earth by a lump of this size W, some 13.8 Glyr away D (back at...

Smoot et. al. have measure a dipole (as well as higher order anisotropies) in the cosmic microwave background. This has been interpreted as our motion through the universe. so how do we know that the dipole is due to our motion through space and not the anisotropic expansion of space? the...

I've looked quite a bit on this forum and also elsewhere online and I cannot really find any information on my inquiry. If this is a double post please delete and send me in the right direction. Now I may be totally off on my thought process, but as I understand it the CMB first started off...

Does the CMB allow special "almost" rest frames to be defined? In this sense, use a rocket to put yourself in a frame of reference such that in this frame observations of the CMB would average to zero (average over photon momentum) over your celestial sphere. In such a rest frame is the total...

Hi, Am I right when I say that the cosmic microwave background is a picture of the radiation left from recombination but that the picture (from COBE or WMAP) that we see today is not exactly the same as it was then due to the redshifting of the radiation particles. The flucuations that we see...

Why do we require a background-free theory when we have such a convenient and universal cosmic microwave background map?

How do astronomers "look" at historic CMB? I have a few question regarding CMB (Cosmic Microwave Background): I am confused, when I look at this is this a 360 degree view or a normal one sided view? As recent study that shown the universe is flat, do astronomer did consider at which...

From Olbers' paradox, the night sky is dark because the universe is finite in age, so some stars' light hasn't had time to reach us. BUT, we see the CMB which occurred some 13 billion years ago (14 billion maybe?) So, if light from the cmb has had time to reach us, shouldn't every object's light...

Are the particles that comprise the CMB in the shape of a "shell" so that all of these particles are very far from our Solar System, or are they in the form of a solid "ball" so that they are evenly distributed throughout our Observable Universe in which case some would be located right here...

Hi, I am trying to get some confirmation of a few facts about how CMB underwrites the current cosmological model. I actually have a few questions on this topic, but will first try my luck with an issue I believe described in terms of a blackbody radiator, which is then said to explain how the...

I heard that dark matter could be the CMB mass corresponding, but I am not satisfied from that. What about this?

Maybe someone could help me on a technical detail and the WMAP (the latest "five years" results). On this website (and several others too), you can find some very nice textures of the CMB from the WMAP study : http://lambda.gsfc.nasa.gov/product/map/current/sos/ Then, they say (read the WMAP...

Could we expect that temperature of CMB decreases or increases? Could we suppose that we are in a contracting universe?

Is it possible to relate the hypothesized dark energy of the universe with the CMB wavelength?

While I think I understand the general principle behind CMB and blackbody radiation, I am trying to understand whether it directly supports the current assumptions about age and size of the universe. Therefore, I was hoping that some members of this forum might be able to clarify what basic...

What will happen when the CMB will raise the zero?

Joao Magueijo. Cosmologist at London Imperial, and Perimeter Institute. Three introductory lectures on the CMB observation and interpretation The first talk is a light intro to the technology, the software that does the mapping, and the analysis that derives the power spectrum (what...

Lyman Page is a senior observational cosmologist who publishes in good company like with Charles Bennett, Joanna Dunkley, David Spergel and Ned Wright. He and an associate have a new idea about getting information from the CMB http://arxiv.org/abs/0706.3908 to me it seems conceptually novel...

On a sheet of paper draw four concentric circles, one outside the other. Fill the innermost circle with dots. This is the CMB photons at the point in time when they were scattered throughout the early universe and first became liberated from the spreading dense matter cloud that scattered...

What is the peak frequency of the Cosmic Microwave Background? Using Wien's Displacement (#1) and then converting the wavelength of frequency (#2), I get 282 GHz. #1. 0.0028977685 / 2.728 = 0.00106223185483871 Meters (1 millimeter) #2. 299792458 / 0.00106223185483871 =...

How to understand that the cosmic microwave background (CMB) can define a cosmological frame? Cheers!

How do they measure the CMB temperature? Aren't they just some radiation?

Hey, Was reading how the CMB is ~2.75 Kelvin, while the Neutrino BG is ~2 Kelvin. Clearly this means that neutrino transparency occurred before photon transparency did in the early evolution of the universe. My question is why? Does is have anything to do with neutron-to-proton decay...

Consider two farmes of reference moving relative each other. In one of the frames the CMD is fully isotropic, i.e., it looks the same in all directions. In the other frame however, the CMD should be red shifted in one direction and blue shifted in the other direction. Thus, the first frame can...

I'm not sure how it is derived. Do we follow this order? 1. Temperature at last scattering/recombination/decoupling (3000 K) 2. Measuring the temperature of the CMB (~3K) 3. 3000K/~3K = 1100 4. z=1100 5. t(z) Or this order? 1. Assume Big Bang and Inflation 2. Determine Volume and Pressure 3...

The Local Groups motion relative to the CMB is said to be around 700 km/s. I would have thought there would be no motion relative to the rest frame of the CMB, and instead expected it to be at a constant distance regardless of motion. Do we have to factor in the speed at which the CMB is...

http://arxiv.org/abs/astro-ph/0601307 Cosmic Microwave Background Mini-Review Douglas Scott, George Smoot 8 pages, 2005 partial update for the 2006 edition of "The Review of Particle Physics", available on the PDG WWW pages at http://pdg.lbl.gov/ "A compact overview of the status of...

Ok, I'm reading up on the Cosmic Microwave background radiation guys. And I'm at a part that confuses me (actually i kinda don't understand the whole thing, but I'm trying) regarding the uniformity or isotropy. If someone can put this in a simpler form so that i can understand it easier i'd...

Would the power spectrum of the CMB tell you whether the cosmological principle is correct? Ack, I was going to try to explain my reasoning, but it doesn't really count as reasoning. :redface: I guess I was wondering what the CMB power spectrum tells you. If it's complicated, nevermind; I'm...

A paper just came out this month that makes it more certain that the Cosmic Microwave map will have to be revised, with even less quadrupole and octopole power. http://www.arxiv.org/abs/astro-ph/0508047/ On the large-angle anomalies of the microwave sky I opened a thread on this paper in...

Does anyone here know of any good books or sites that describe the CMB in a comprehensive way? I want to learn more about it, because I find it very interesting, but most of what I've found is just snippets here and there, or descriptions that either take for granted that I know a lot about...

This may seem like a silly question, but it has me puzzled. Theory tells us that as space expands then photons (and I guess all form of energy?) in that space are red-shifted, ie their wavelength increases, ie they lose energy. The most obvious example of this is the CMB, which consists of...

Here is the latest entry in the CMB anisotropy derby: The Multipole Vectors of WMAP, and their frames and invariants http://arxiv.org/abs/astro-ph/0502574 The authors, Land and Magueijo, are prominent among the more active researchers in this arena. They apply an apparently more...

Recently, several groups have endeavored to experimentally map the large-scale structure of the Universe with the Sloan Survey being the most ambitious. At the same time, we've been able to map the cosmic microwave background to 10^-6 degrees. I believe these two maps agree but I'm confused...

Hello folks, I'm new to this fine forum and wondered if anyone here knows which present or future spacecraft (perhaps even balloon borne mission?) are capable of discriminating the effects of the strongly blue shifted gravitational spectrum that should be evident in the CMB as the Ekpyrotic...

Dated as of today: http://arxiv.org/abs/astro-ph/0401070 What do you think guys? :)