CMB Fluctuations

Background... on the Cosmic Microwave Background!

2008-12-04T15:15:00.001-08:00

In 1948, George Gamow wrote a paper talking about the Big Bang Theory and the reactions cause by the Big Bang. He estimated that there would be a great amount of electromagnetic radiation left over from the Big Bang. He was the first to predict the cosmic microwave background radiation (CMB), and predicted that the radiation from the big bang would cool down to microwave radiation after a few billion years. In 1950, Ralph Alpher and Robert Herman joined with George Gamow to continue studying this CMB.

In 1965, Arno Penzias and Robert Wilson were in the Bell Telephone Laboratories in Murray Hill, New Jersey. They were using an ultra-sensitive microwave receiving system to study radio emissions of the Milky Way. They unexpectedly found a background of radio noise that seemed to be coming from outside the galaxy. They then consulted with Robert Dicke (a Princeton physicist) who had theorized that, “if the universe was created according to the Big Bang theory, a background radiation at 3-degree Kelvin would exist throughout the universe.” [Penzias and Wilson actually thought that the excess noise coming from the antenna was from pigeons on the roof. They spent hours searching for the pigeons and realized that they weren’t the source of the excess noise!] Penzias and Wilson shared the Nobel Peace Prize in physics in 1965.

MP3<== click here to listen to the cosmic noise!

NASA launched the COBE satellite on November 18, 1989 to detect and measure cosmic radiation left over from the big bang. The Satellite was equipped with a Diffuse Infrared Background Experiment to search for cosmic background radiation, Differential Microwave Radiometer in order to map cosmic radiation sensitivity, and lastly a Far Infrared Background Spectrophotometer which views the spectrum of the cosmic background radiation against a blackbody. Each provide their own measurements in favor of Gamos, Dicke, Penzias, & Wilson’s assertions.

Sources:

http://map.gsfc.nasa.gov/

http://www.bell-labs.com/project/feature/archives/cosmology/

http://lambda.gsfc.nasa.gov/product/cobe/

What is the Big & how does it factor in?

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The Big Bang Theory is an idea about how the universe came into existence. It is an explanation of what happened during and before the universe became existence. According to the Big Bang theory, 10 to 20 billion years ago, a sudden explosion created the Universe. Ever since this instant, the Universe has been expanding and cooling from the infinite temperatures in which it began.

Why do we speak of the Big Bang so often when we talk about the cosmic microwave background? For the simple reason that discovery of the CMB’s existence has served as possibly the strongest evidence for the Big Bang Theory; the CMB provides the nearest “look” back to the creation of the Universe!

Photons from the Big Bang moved throughout the Universe and became the radiation we know as the cosmic microwave background. As you’ll recall, observations show the cosmic microwave background to be a nearly perfect blackbody with a temperature of approximately 2.72 K. Well, this measurement matches predictions of the Big Bang theory very well. Though, this alone does not support the theory. The fluctuations in the CMB that make it nearly, but not perfectly, uniform need to be taken into consideration.

Sources:

http://lambda.gsfc.nasa.gov/product/cobe/

http://www.astro.ubc.ca/people/scott/cmb_intro.html

Finally, what do these fluctuations mean?

2008-12-04T15:09:00.000-08:00

The CMB is slightly anisotropic. Rather than be uniform everywhere, the CMB is anisotropic by one part in a 1,000. Studies of these variations in the temperature (and therefore density) of the CMB show the distribution of matter and energy in the Universe.

Why is this important? The temperature fluctuations also mark fluctuations in density fluctuations and it is from these fluctuations in density that all cosmic structures that exist today were formed! Images of the cosmic microwave background allow us to “see” areas of greater and lesser density, thereby linking observations of the present day distribution of galaxies to the Big Bang’s model of the Universe’s creation.

Sources:

http://lambda.gsfc.nasa.gov/product/cobe/

http://www.astro.ubc.ca/people/scott/cmb_intro.html

Other great sites!!

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http://csep10.phys.utk.edu/astr162/lect/cosmology/cbr.htm

http://map.gsfc.nasa.gov/universe/bb_cosmo_fluct.html

http://abyss.uoregon.edu/~js/ast123/lectures/lec23.html