How can the Cosmic Microwave Background  be used as a cosmological tool?

Hello and thank you for your question.

There is a whole field of cosmology built on the discovery and
interpretation of cosmic microwave background radiation.  The
following excerpts provide a good summary answer to your question.

"More than three decades after Penzias and Wilson's discovery, the
significance of their finding remains as great. It provided a new tool
for exploring the early universe.  A few years ago, NASA sent the
Cosmic Microwave Background Explorer (COBE) satellite into orbit to
investigate the cosmic microwave background in great detail. The
principal scientist of the COBE mission, George Smoot, said, 'There is
no doubt that Penzias and Wilson's discovery of the cosmic background
radiation marked a turning point in cosmology.'"
A turning point for cosmology
http://www.bell-labs.com/project/feature/archives/cosmology/

"Early measurements of the cosmic background radiation, emitted from
the hot gases of the young universe, seemed to show that it was nearly
smooth and featureless, with no irregularities that could have spawned
lumpy structures like galaxies. But in 1992, a NASA satellite called
the Cosmic Background Explorer satellite, or COBE, made highly
sensitive measurements of the radiation and saw minute temperature
variations suggesting the existence of so- called acoustic waves
sloshing in the early universe."
Scientists Detect the Traces of the Seeds of Cosmic Structures
http://www.threeeyesofuniverse.org/CoursesPrograms/ScienceCosmos/1.FlaringForth/2-SeedsOfCosmicStructures.html

"The cosmic microwave background (CMB) spectrum is that of a nearly
perfect blackbody with a temperature of 2.725 +/- 0.002 K. This
observation matches the predictions of the hot Big Bang theory
extraordinarily well, and indicates that nearly all of the radiant
energy of the Universe was released within the first year after the
Big Bang."
Cosmic Background Explorer
http://space.gsfc.nasa.gov/astro/cobe/cobe_home.html

Search terms used:
microwave background tool "big bang"

If you find any of this unclear, or if you would like more sources of
information (there are thousands of sites) please let me know via a
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Sincerely,
Google Answers Researcher
Richard-ga

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Clarification of Answer by richard-ga on 07 May 2003 10:03 PDT

Here's a clearer example of the radiation being used as a tool--it
helps support the hypothesis that our universe will expand forever!
(the whole article makes very interesting reading, by the way):

"Cosmologists are the astronomers who try to answer this question.
Recently they have found a new tool: the fossil light from the Big
Bang itself. This light is known as the cosmic microwave background
radiation and it is the oldest light we can see. It is as old as the
Universe itself. By scrutinising the variations in this light (there
are hot spots and cold spots) cosmologists can tell us what will
become of our Universe."
New Evidence for an Infinite Future
http://www.phys.unsw.edu.au/SCHOOL_INFORMATION/MEDIA_ROOM/infinite_cappuccino.html

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Clarification of Answer by richard-ga on 07 May 2003 17:17 PDT

Hello yet again.

Google Researcher mathtalk-ga has brought to my attention an important
recent development where a detailed survey of the background radiation
has been used to further elucidate the structure of the universe.

"The Wilkinson Microwave Anisotropy Probe (WMAP) team has made the
first detailed full-sky map of the oldest light in the universe. It is
a 'baby picture' of the universe."
The First Detailed Full Sky Picture of the Oldest Light in the
Universe.
http://map.gsfc.nasa.gov/m_mm.html