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Topic: Cosmic microwave background


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CMB

In the News (Mon 20 Nov 17)

  
  Cosmic microwave background radiation - Wikipedia, the free encyclopedia
In cosmology, the cosmic microwave background radiation (CMB) is a form of electromagnetic radiation discovered in 1964 that radiates throughout the universe in the microwave range.
The period after the emission of the CMB and the observation of the first stars is semi-humorously referred to by cosmologists as the dark age, and is a period which is under intense study by astronomers.
The CMB was predicted by George Gamow, Ralph Alpher, and Robert Hermann in the 1940s and was accidentally discovered in 1964 by Arno Penzias and Robert Woodrow Wilson, who received a Nobel Prize in Physics in 1978 for this discovery.
en.wikipedia.org /wiki/Cosmic_microwave_background   (1938 words)

  
 Cosmic microwave background radiation - Wikipedia, the free encyclopedia   (Site not responding. Last check: 2007-11-07)
The cosmic microwave background radiation (CMB) is a form of electromagnetic radiation that fills the whole of the universe.
The interpretation of the CMB was a very controversial issue in the 1960s with some proponents of the steady state theory arguing that the CMB was the result of scattered starlight from distant galaxies.
Of these experiments, the Cosmic Background Explorer (COBE) satellite that was flown in 1989-1996 is probably the most famous and which made the first detection of the large scale anisotropies (other than the dipole).
www.hartselle.us /project/wikipedia/index.php/Cosmic_microwave_background_radiation   (1625 words)

  
 Cosmic microwave background radiation   (Site not responding. Last check: 2007-11-07)
The Cosmic Microwave Background Radiation is a form of electromagnetic radiation that fills the whole of the universe.
One of the microwave background's most salient features is a high degree of isotropy.
In addition, the Sachs-Wolfe effect causes photons from the Cosmic microwave background to be gravitationally redshifted.
www.sciencedaily.com /encyclopedia/cosmic_microwave_background_radiation   (1075 words)

  
 The Cosmic Microwave Background Radiation
The surface z=1000 is sometimes called the cosmic photosphere, in comparison with the photosphere (apparent surface) of the Sun.
It is the surface from which the cosmic background photons last scattered before coming to us.
Usually the features of the Universe and the CMB are interpreted in the context of a cosmological model - The Big Bang - which is derived from general cosmological principles and observations.
aether.lbl.gov /www/science/cmb.html   (827 words)

  
 WMAP Cosmology 101: Cosmic Microwave Background
The existence of the CMB radiation was first predicted by George Gamow in 1948, and by Ralph Alpher and Robert Herman in 1950.
In addition to this cosmic microwave background radiation, the early universe was filled with hot hydrogen gas with a density of about 1000 atoms per cubic centimeter.
The behavior of CMB photons moving through the early universe is analogous to the propagation of optical light through the Earth's atmosphere.
map.gsfc.nasa.gov /m_uni/uni_101bbtest3.html   (1150 words)

  
 The Cosmic Background Radiation
If the Earth moves with respect to the microwave background, it will be blue shifted to a higher effective temperature in the direction of the Earth's motion and red shifted to a lower effective temperature in the direction opposite the Earth's motion.
The cosmic background radiation (sometimes called the CBR), is the afterglow of the big bang, cooled to a faint whisper in the microwave spectrum by the expansion of the Universe for 15 billion years (which causes the radiation originally produced in the big bang to redshift to longer wavelengths).
First, when we look at the microwave background coming from widely separated parts of the sky it can be shown that these regions are too separated to have been able to communicate with each other even with signals travelling at light velocity.
csep10.phys.utk.edu /astr162/lect/cosmology/cbr.html   (660 words)

  
 Cosmology - Penzias and Wilson's Discovery is One of the Century's Key Advances   (Site not responding. Last check: 2007-11-07)
The discovery in 1963 by Arno Penzias and Robert Wilson of the cosmic microwave background of the Big Bang set the seal of approval on the theory, and brought cosmology to the forefront as a scientific discipline.
The cosmic microwave background hails from the earliest observable event in the history of the universe, some 300,000 years after its birth.
Although the original temperature of the cosmic microwave background was much higher, the expansion of the universe has cooled it to its present value of 2.7 degrees Kelvin.
www.bell-labs.com /project/feature/archives/cosmology   (981 words)

  
 Physics Today July 2001
The microwave background comes to us directly from the moment, some 400 000 years after the Big Bang, when the cosmos first became cool enough to be transparent.
If one maps the CMB temperature of a patch of sky with sufficient sensitivity and angular resolution, the spherical-harmonic power spectrum should exhibit the first few acoustic peaks (see figure 2).
The CMB observations are particularly sensitive to this sum.
www.physicstoday.org /pt/vol-54/iss-7/p16.html   (1673 words)

  
 Cosmic microwave background radiation - FreeEncyclopedia   (Site not responding. Last check: 2007-11-07)
The CBR was predicted by George Gamow, Ralph Alpher, and Robert Hermann in the 1940s and was accidentally discovered in the 1950s by Penzias and Wilson, who received a Nobel Prize for this discovery.
Since the cosmic microwave radiation is rather difficult to observe with ground-based instruments, CMB research makes increasing use of air and space-borne experiments.
Probably still the most famous of these is the Cosmic Background Explorer (COBE) satellite that was flown in 1989-1996, which made the first detection of anisotropies (other than the dipole).
openproxy.ath.cx /co/Cosmic_microwave_background_radiation.html   (464 words)

  
 Physics Today Online - July 2000   (Site not responding. Last check: 2007-11-07)
The CMB is thought to be the vestigial light from the first moments of clarity when the cosmos had finally cooled down enough, some half a million years after the Big Bang, for the opaque universal plasma of ions and electrons to coalesce into a transparent gas of neutral hydrogen and helium.
The temperature fluctuations of the CMB are imprints of the point-to-point density fluctuations of the cosmos at the "moment of last scattering." Hotter than average points on the CMB signify regions of above-average mass density.
Both are microwave telescopes that scan the sky and focus the radiation onto an array of bolometers sensitive to different frequency bands.
www.aip.org /pt/vol-53/iss-7/p17.html   (1961 words)

  
 Cosmology
The uniformity of the background radiation is evidence for the cosmological principle.
This background radiation is interpreted to be the relic of the early universe.
Notice that the background appears completely uniform at a temperature of 2.728 K. The colors for the temperatures range from blue for 2.724 K to red for 2.732 K. The double-lobe pattern shows the doppler effect from the motion of the Sun with respect to the background radiation.
www.astronomynotes.com /cosmolgy/s5.htm   (1289 words)

  
 Cosmic Microwave Background   (Site not responding. Last check: 2007-11-07)
In 1964 two astronomers were studying microwave signals from space and noticed that there was a constant background signal coming from all points in space.
This background is (nearly) uniform in intensity across the sky.
The big bang model theoretically predicts that such background radiation would be present in the universe today some 12 or so billion years after the initial big bang.
theoryx5.uwinnipeg.ca /mod_tech/node218.html   (89 words)

  
 Cosmic Microwave Background Activity
This is the spectrum of the cosmic microwave background as measured with the FIRAS instrument on NASA's Cosmic Background Explorer (COBE) satellite in the early 1990s.
By carefully measuring the peak of the intensity spectrum as a function of frequency and applying Wien's displacement law, the temperature of the CMB today is T = 2.725 +/- 0.001 K. Use this law to calculate the peak wavelength (in cm) and the peak frequency (in GHz) of the CMB.
Today, 14 billion years after recombination, the surface of last scattering is 14 billion light years away, the intervening space is transparent and nearly empty, and the cosmic background has been redshifted into the microwave (radio) portion of the electromagnetic spectrum.
geology.wcupa.edu /mgagne/ess355/cmb-lab1.html   (1179 words)

  
 Cosmology: A Research Briefing
The cosmic microwave background radiation (CMBR), discovered in 1964, is a telltale remnant of the early universe.
The illustration on the cover of this report is the resulting COBE map of the intensity of microwave radiation arriving from various directions in the sky.
However, variants of the Big Bang theory, such as theories involving cosmic strings (discontinuities in the structure of space), predict that important clues to the universe's history might be embedded in the CMBR at these angular scales.
www.nap.edu /readingroom/books/cosmology/2.html   (2628 words)

  
 SPACE.com -- About WMAP and the Cosmic Microwave Background
In fact, the CMB started out as something else, and because the universe has been expanding all along, the radiation's wavelengths were stretched over time to the microwave range.
The CMB carries an imprint of the last scattering that occurred as it emerged from the fog.
The CMB was predicted to exist in 1948 by George Gamow.
www.space.com /scienceastronomy/map_mission_basics_030211.html   (1008 words)

  
 Cosmic Microwave Background.   (Site not responding. Last check: 2007-11-07)
Interest in the Cosmic Microwave Background and its anisotropies is continuing.
The Jodrell Bank CMB experiments on Tenerife have located the first individual hot and cold features with a series of beam-switching observations exploring scales of 5 to 15 degree at 10, 15, and 33 GHz.
In the Tenerife results, the rms amplitude of the structure is 54 micro K. Measurement of the 1.4-GHz absolute temperature of the CMB with a ground-based radiometer has yielded a value of 2.65 K. observations of a low-background region of sky at high galactic latitude has revealed significant anisotropy on degree angular scales.
www.astrosmo.unam.mx /IAU_Com40/c40rpt97/node72.html   (304 words)

  
 Astronomy & Space
The Cosmic Microwave Background Radiation Peter D. Burns Department of Physics and Astronomy University of Manchester Manchester Summer 1999 Introduction The cosmic microwave background (CMB) is the thermal afterglow of the Big Bang.
Microwave Background Astronomy ASTROPHYSICS A significant fraction of the Astrophysics Group is involved in work on the Cosmic Microwave Background, both experimental and theorectical.
The cosmic microwave background spectrum was measured with a precision of 0.005%, the background was found to have intrin
groups.msn.com /AstronomySpace/mapmission.msnw   (720 words)

  
 Cosmic Microwave Background
So as a result of the continual expansion of the universe, the light waves of this radiation have stretched out to longer wavelengths which today exist in the microwave region of the electromagnetic spectrum (which is why we call it the Cosmic "Microwave" Background).
This is a picture of an anisotropy map taken by the Cosmic Microwave Background Explorer (COBE).
Astronomers and physicists suspected that the Cosmic Microwave Background might display very slight fluctuations in temperature, but this data could not be accurately recorded until the flight of COBE because it was the first satellite experiment to gather information from outer space, where all of the background noise from water vapor could be eliminated.
cmb.physics.wisc.edu /tutorial/cmb.html   (1431 words)

  
 Cosmic Microwave Background Group at Jodrell Bank Observatory   (Site not responding. Last check: 2007-11-07)
The Cosmic Microwave Background is the very first light, giving us a snapshot of the Universe as it was just 400,000 years after the Big Bang.
Jodrell Bank has been a centre for the study of the CMB since the mid 1980's, and is currently a major participant in two world-leading initiatives to map the CMB: the Very Small Array and the Planck Spacecraft.
Direct observations of the CMB are supplemented by theoretical work and by study of microwave emission from our own Galaxy that appears in the foreground of the CMB and has to be modelled and subtracted.
www.jb.man.ac.uk /research/cmb   (325 words)

  
 Cosmic Microwave Background - FAQs   (Site not responding. Last check: 2007-11-07)
Microwaves are the name given to radiation between the infra-red and radio region, with wavelengths typically in the 1mm to 10cm range.
The basic point is that the spectrum of the CMB is remarkably close to the theoretical spectrum of what is known as a "flbody", which means an object in "thermal equilibrium".
Hence the CMB spectrum is essentially incontrovertible evidence that the Universe experienced a "hot Big Bang" stage (that's not to say that we understand the initial instant, just that we know the Universe used to be very hot and dense and has been expanding ever since).
www.astro.ubc.ca /people/scott/faq_basic.html   (1466 words)

  
 Footprints of Creation
In 1989, an instrument aboard the Cosmic Background Explorer (COBE) satellite measured the cosmic background radiation with unprecedented accuracy.
COBE measured a cosmic background radiation spectrum that fits perfectly with the predicted flbody spectrum at 2.735 degrees Kelvin.
Until 1992, the cosmic background radiation was thought to vary by no more than one part in 10,000.
archive.ncsa.uiuc.edu /Cyberia/Cosmos/Footprints.html   (791 words)

  
 Martin White: Current Research Interests
Our models can simultaneously match the microwave background fluctuations which trace the universe 300,000yr after the big bang, the nearby distribution of galaxies, the distribution of mass revealed by gravitational lensing and the structure seen in the spectra of distant quasars.
The Cosmic Microwave Background gives a snapshot of the universe (plus some processing) corresponding to when the universe was about 300,000 years old.
Since any model of structure formation must explain both the tiny ripples in the Cosmic Microwave Background temperature across the sky, and the large-scale structures we see in the universe today, the combination of these two probes is especially powerful.
astron.berkeley.edu /~mwhite/myresearch.html   (2031 words)

  
 New Scientist Breaking News - Sharp new portrait of the infant Universe
The cosmic image, unveiled on Tuesday, was taken by the Microwave Anisotropy Probe (MAP) spacecraft during a 12-month scan of the entire sky.
MAP is the successor to NASA's Cosmic Microwave Background Explorer (COBE), which recorded the relic radiation across the whole sky for the first time in 1992.
The spacecraft was recently renamed as the Wilkinson Microwave Anisotropy Probe in honour of cosmologist David Wilkinson of Princeton University who died in September 2002.
www.newscientist.com /article.ns?id=dn3375   (660 words)

  
 Microwaves
The longer microwaves, those closer to a foot in length, are the waves which heat our food in a microwave oven.
Microwaves are good for transmitting information from one place to another because microwave energy can penetrate haze, light rain and snow, clouds, and smoke.
The image above is a Cosmic Background Explorer (COBE) image of the cosmic microwave background, the pink and blue colors showing the tiny fluctuations in it.
imagers.gsfc.nasa.gov /ems/micro.html   (472 words)

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