What is Cmbr: Definition and 49 Discussions

The cosmic microwave background (CMB, CMBR), in Big Bang cosmology, is electromagnetic radiation which is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space. It is an important source of data on the early universe because it is the oldest electromagnetic radiation in the universe, dating to the epoch of recombination. 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 noise, or glow, almost isotropic, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The accidental discovery of the CMB in 1965 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s, and earned the discoverers the 1978 Nobel Prize in Physics.
CMB is landmark evidence of the Big Bang origin of the universe. When the universe was young, before the formation of stars and planets, it was denser, much hotter, and filled with an opaque fog of hydrogen plasma. As the universe expanded, both the plasma and the radiation filling it grew cooler. When the temperature had dropped enough, protons and electrons combined to form neutral hydrogen atoms. Unlike the plasma, these newly conceived atoms could not scatter the thermal radiation by Thomson scattering, and so the universe became transparent. Cosmologists refer to the time period when neutral atoms first formed as the recombination epoch, and the event shortly afterwards when photons started to travel freely through space is referred to as photon decoupling. The photons that existed at the time of photon decoupling have been propagating ever since, though growing fainter and less energetic, since the expansion of space causes their wavelength to increase over time (and wavelength is inversely proportional to energy according to Planck's relation). This is the source of the alternative term relic radiation. The surface of last scattering refers to the set of points in space at the right distance from us so that we are now receiving photons originally emitted from those points at the time of photon decoupling.

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  1. Ranku

    I CMBR Evidence for Non-Baryonic Dark Matter

    It is said that CMBR indicates that dark matter is non-baryonic. How so?
  2. T

    B What is the recession speed today of the matter which created the CMBR?

    Hello, I am talking to a Quantum Mechanics Physicist friend who is having a hard time accepting some of the Cosmology theories and numbers and I want to be sure that my numbers were correct. 1. Firstly, what is the recession speed, today, of the matter which created the CMBR? I told him that...
  3. pinball1970

    I Distant Galaxy study, dark matter and the CMBR

    The article is pop but there is a paper Pop article https://www.vice.com/en/article/g5vvjw/the-universes-oldest-light-reveals-unprecedented-dark-matter-patterns Paper. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.061301 The language is a little bit click bate, I just wanted...
  4. Vick

    A Peebles Equation for fractional electron density

    I am trying to compute the Peebles equation as found here: I am doing so in Python and the following is my attempt: However, I'm unable to solve it. Either my solver is not enough, or I have wrongly done the function for calculating the Equation. # imports from scipy.optimize import fsolve...
  5. Adrian59

    A Is the CMBR interpretation for dark matter a fudge?

    The likelihood for dark matter appears to be lessening in direct detection and in its utility in explaining astronomical anomalies. With regard to the former, a trio of recent dark matter detection experiments (LUX 2016, PandaX II 2017 and Xenon1t 2018) have all failed to show any non-baryonic...
  6. Ranku

    I CMBR and the expansion history of the Universe

    Does the CMBR contain the imprint of the entire expansion history of the universe or only of the last scattering ?
  7. Ranku

    I CMBR & Flatness: Mapping Universe Flatness?

    Does the mapping of CMBR measure spatial flatness or spacetime flatness of the universe?
  8. Cerenkov

    B Is the Hawking-Hartle Euclidean approach confirmed by CMBR data?

    Hello. I have three questions about a claim made by Stephen Hawking in his book, 'My Brief History' and I would be grateful to receive some help concerning it please. Here is a .pdf version of it...
  9. Bill McKeeman

    B CMBR: Is It Constant or Changing Over Time?

    My question is this: is the CMB constant or might it be changing with time?
  10. Adrian59

    A CMBR anisotropy and cosmic abundances

    What is (are) the original paper(s) relating to the interpretation of the CMBR anisotropy in setting the cosmic abundances? I did pose the same question last year but it got lost in another thread. I had found papers by Hu and Dodelson from 2002, Hu and white from 1996 and Seljak from 1994 as...
  11. G

    I How long will the CMB be detectable?

    The CMB has already stretched from some 3000K to 3K, so 99.9% of all the possible stretching until asymptotically approaching absolute zero. Even if our telescope technology continues improving, with the ongoing expansion there may come a time in the future when the CMB temperature will be so...
  12. P

    I What is the size of the observable universe relative to CMBR

    Reading the Wikipedia article makes my head spin! Somehow the figure https://en.m.wikipedia.org/wiki/File:Observable_universe_logarithmic_illustration.png doesn't seem quite right. I don't understand how the CMBR doesn't define the edge of the universe. If we can see the CMBR that happened near...
  13. alw34

    CMBR, Dark Matter: Unraveling What it Means

    Chalnoth posted this in another discussion: "The cosmic microwave background is almost impossible to explain without dark matter (there is clear evidence of a component of matter that feels pressure, and a component of matter that does not feel pressure, which can only be true if that matter...
  14. R

    Cosmology: Estimating CMBR Horizon Distances & Inflation Size

    Hello everyone! I have found a pretty interesting problem on the internet about cosmology. I'm new into cosmology and I don't know exactly how to solve it... That's why I need a little help. I wrote under the problem text how I would do it.Measurement of the cosmic microwave background...
  15. H

    Anti-matter annihilation and the CMBR

    Recently I watched a lecture on Anti-matter and the Standard Model... ...At one point Dr. Quinn, makes the statement that the CMB is the resulting energy left over from the annihilation of the matter and anti-matter which arose during cosmic inflation (leaving behind only one part in 30 million...
  16. bland

    CMBr & Absolute Motion: A Query

    Why can't the CMBr 'wall' that is as if we were in the middle of a sphere surrounded by it, be used as a reference point for absolute motion in space?
  17. C

    Why is the CMBR visible to us?

    Since the observable universe is expanding, over time, more galaxies should become visible on Earth as their light has had more time to reach us. But galaxies couldn't form until after recombination. So why is the CMB visible if light sources younger than it are not visible yet?
  18. L

    Is there radiation colder than the CMBR?

    Hi, As I understand it, the CMBR presents with a temperature equivalent to approx 2.5k. If a WMAP-type experiment was run to mapa radiation signature at a colder temperature, say 2, or 1.5, or 1 degree, would it find anything? Thanks in advance, Noel.
  19. photonkid

    Temperature of the CMBR

    I've read that the temperature of the CMBR is 2.7 degrees K or so and is much cooler than when it started out, due to the expansion of the universe making the wavelength longer. What is meant by the temperature of the CMBR? How do you measure it? Is it determines purely by the wavelength...
  20. H

    Temperature of CMBR compared to galaxies in general

    I'm curious about how the temperature of the CMBR compares to the light and temperature of galaxies in general. Basically, I'm wondering how 'hot' are galaxies and how do they contribute to the CMBR readings. Does the temperature of galaxies compare on some scale? Do we have to account for...
  21. G

    Can the shape of the universe be inferred from the CMBR?

    Planck CMBR data http://scienceforseniorcitizens.com/wp-content/uploads/2013/03/cosmic-microwave-radiation-google-earth-background1.jpg [Broken] COBE, WMAP, Planck compared to each other http://www.scidacreview.org/0704/images/cmb07.jpg [Broken] Methinks the distribution of the CMBR intensity...
  22. T

    Is it certain that CMBR originates from the 5% of ordinary matter?

    In standard model Cosmology ordinary matter is only 5% of the total mass - energy of content of the Observable Universe. http://en.wikipedia.org/wiki/Dark_energy Since 95% of the mass energy content of the Universe is unknown with uncertain properties, can we really be certain CMBR originates...
  23. E

    Thoughts and questions about the CMBR.

    Recently it occurred to me that my mental image of the CMB radiation, gleaned from a range of popular science books, was probably completely wrong. I set about some thinking. The following notes outline my thoughts so far, and I would appreciate the comments of others more knowledgeable than I...
  24. L

    Is the CMBR a relic from the big bang or an image from background galaxies?

    Some time ago there was a thread which suggested that there was a logic / papers that demonstrated why the the CMBR could not be the result of ligh from background objects / galaxies. Unfortunately, I have not been able to locate the thread or associated material. Is this correct, and could...
  25. N

    Implicit assumption of CMBR?

    Hello, I am sorry. I apologize for my poor English. [ Implicit assumption of CMBR? ] It is not certain whether this kind of experiment has already been conducted. Still, it need be tested whether the wavelength distribution of 3000k radiation cooling down to 2.7K is completely identical to...
  26. J

    CMBR - loss of photon energy?

    the photons emitted during the big bang, now detected as the CMBR, have been red-shifted by a very large degree due to the expansion of the universe since the BB, resulting in much lower photon energy now than when the photons were first emitted. (i hope i have that correct.) since there is...
  27. T

    Which fraction of the observed CMBR signal is due to some foreground contaminant

    One of the major concerns in any Cosmic Microwave Background (CMB) anisotropy analysis is to determine which fraction of the observed signal is due to some foreground contaminant. Two sources of foreground contamination have been firmly identified: the diffuse Galactic emission and unresolved...
  28. DrChinese

    Does CMBR include free photons?

    Broken off from another thread: So here's a simple question for which the answer is not so simple using current theory: Do the photons from the CMBR exist free and independent of observation? Because some people say that photons are mediators of EM force but are otherwise abstractions. For...
  29. P

    What is the rate at which the CMBR is cooling?

    Hello everyone, I have a question regarding the rate of cooling for the CMBR. I understand that the rate of cooling is directly related to the rate of expansion of the universe, but I lack the mathematical prowess necessary to make any use of this. I am specifically trying to determine...
  30. T

    Effect of the Galactic plane on the COBE CMBR measurements

    http://cosmos.lbl.gov/two_four_maps.html http://cosmos.lbl.gov/Images/phys_today_cover_big.gif CMBR dipole anisotropyFrom the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 627±22 km/s...
  31. L

    CMBR anisotropies, FAQ, & universal rotation (kind of)

    There have been many posting (questions and answers) on universal rotation and there is a fine posting with references on the FAQ. Thanks to everyone for these. I don't pretend to understand the detail (especially of the maths), but I do understand most of the principles. However, there is one...
  32. J

    Does the CMBR have a detectable absorption spectrum?

    I posted this http://answers.yahoo.com/question/index;_ylt=AioiPKUALWyrKuH4dGXejba9DH1G;_ylv=3?qid=20110618143816AAgRMyF"on Yahoo Answers yesterday, but it might be too specialized: If I understand correctly, the Cosmic Microwave Background Radiation is a perfect thermal (black-body)...
  33. TrickyDicky

    Cosmic Microwave Background Radiation: A Homogeneous and Isotropic Universe

    does the CMB radiation fill the universe empty space completely homogenously and isotropically?
  34. TrickyDicky

    Blackbody Prediction for CMBR: Alpher, Herman, and Gamow's 1948 Theory

    I know the CMBR temperature was approximately predicted by Alpher ,Herman and Gamow around 1948, but I can't locate a source specifying when and how the blackbody form of the CMBR was predicted. Does anybody have this information? thanks
  35. N

    Could the CMBR have this flaw?

    I was watching through the wormhole and it occurred to me that the probe they sent in space to collect data on the cmbr couldn't do triangulation, meaning we could not test or see if the cmbr actually came from 2 sources of energy. How do we know for sure without testing it if the CMBR didn't...
  36. S

    Complete photonic view like the CMBR version

    Ignoring what we know. I was curious as to if anyone had overlayed all of the spectrum's of light on top of each other in a complete photonic view like the CMBR version, only with a much more varied scale, that being the entire light spectrum. And if so what did this produce? I only ask because...
  37. A

    How exactly can CMBR tell us universe age

    HI Can someone give a good explanation of how we can infer an age of the universe from the CMBR. I was thinking in principle you could get an estimate from determining the rate at which the CMBR is changing, but experimentally that would seem to difficult to observe. Also i guess that assumes...
  38. A

    CMBR uniformity question?

    Current cosmology is based on CMBR and the idea it is remnant from the big bang, I guess we assume it's the same radiation in the whole universe. My question is how do we know the CMBR is not something local to our galaxy let's say? How do we know in another galaxy the CMBR won't be...
  39. nomadreid

    Fractal dimension of CMBR? Cluster distribution?

    I have read speculations that (1) the cosmic microwave background radiation has a fractal distribution (non-integral Hausdorff dimension), and (2) the same might be true of galaxy cluster distribution (although different dimensionality to (1)) Whether or not one or both analyses are...
  40. maverick280857

    How does CMBR differ from ether (SR self study - Question from W. Rindler)

    How does CMBR differ from ether (SR self study -- Question from W. Rindler) Hello everyone First of all, apologies for a previous post which was against forum rules. I was unaware that I had violated the rules by posting a link to a paper that wasn't from a proper peer-reviewed scientific...
  41. 8

    Could the CMBR Be Very Uneven?

    In a recent article in ScienceNews, Ron Cowen states: (quote) Hidden in the peaks and valleys imprinted on the cosmic microwave background — the radiation leftover from the Big Bang — is a wealth of information not only about the early universe but the distribution of matter throughout the...
  42. B

    CMBR - a possible alternative explanation?

    How can we be sure that the Cosmic Microwave Backgound Radiation is a relic of the big bang and not a reflected echo of the sun's solar wind after it's interaction with the heliopause? I ask this because I read an article some years ago which indicated that one of the voyagers had detected a...
  43. D

    CMBR as an absolute reference frame

    I've been reading Singh's Big Bang book, and towards the end he mentions that the CMBR was used to compute the relative speed of the Milky Way Galaxy, roughly 1,000,000 mph. This seems to suggest that the CMBR can be used as an absolute reference frame for any observer in the universe...
  44. N

    CMBR - multiple detections of the same 'spots'?

    COBE first detected the µK components, though the team cautioned against interpreting any particular hot or cold 'spot' as real. Many independent observations of the CMBR have been made since then (Wayne Hu has a nice website which seems to be pretty comprehensive), including the...
  45. N

    Absorption in 'CMBR' wavelengths - observations? processes?

    A read of the COBE and WMAP teams' papers on the methods they used to produce 'contamination-free' maps (or, to remove all 'foregrounds') is exhilarating. However, unless I missed it, these methods largely address emission in the wavelengths of interest (i.e. those which the various...
  46. M

    Can my TV set pick up the CMBR?

    Nice Topic and info Nick! I heard that when you turn your T.V. on and you get that snow or in otherwords no reception that, the T.V. is picking up is acctualy some sort of energy from the Big Bang.. what do you think?
  47. M

    The Physics of CMBR Anisotropies

    This paper is quite clear explaining all-you-ever-wanted-to-know about the CMB anisotropies and related phenomena. So, i will be glad that everybody post here their doubts about the CMB power spectrum, E-mode polarization, tensor modes,... The physics behind the CMB anisotropies is quite...
  48. K

    Dark energy redshifts cmbr photons

    Dark energy waves absorb energy from photons in intergalactic space and the total energy of dark energy increases, increasing the acceleration of the universe. Because the dark energy is quantised when it absorbs energy from a photon it changes to a higher energy quantum state.If a cosmic...
  49. Hydr0matic

    Comparing the CMBR Over Time

    To what extent does the CMBR vary over time ? If I have understood it correctly the intensity variations in http://lambda.gsfc.nasa.gov/product/cobe/cobe_images/cmb_fluctuations_big.gif, are due to the fact that some of this energy turned into matter in the early universe. So in a sense, the...
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