Cosmic Microwave Background Measured: Debate Over Its Existence May Now End

The NASA WMAP project has been dedicated for five years to making a full-sky map of the cosmic microwave background of the universe, which is left over from the first moments of the universe's beginning. It has now been successfully measured by Wilkinson Microwave Anisotropy Probe (WMAP) and the debate over its existence seems likely to be put to rest. succeeded.

As the universe expanded in its earliest epochs, light lost energy in the expansion and was reduced to microwaves, which are the weakest waves at the right-hand side of the linearly presented electromagnetic spectrum. This means that the wave length frequencies of microwaves are very slow and very stretched out. They are not the rapidly occurring and compact wave lengths found at the visible and near-infrared frequencies in the middle of the electromagnetic spectrum. These microwaves, residues of light, are the background, or "backlight," of the universe, the cosmic microwave background, and are detectable by WMAP.

Microwaves are invisible, but if image contrast is corrected, they can be rendered observable and, more importantly, measurable. An animation showing how observations in visible light can be manipulated to yield observations in invisible microwave remnant light is available from through this hyperlink to NASA (WMV movie).

WMAP is located in space at the L2 spot beyond Earth and follows Earth in its orbit around the Sun. The three stand in a line: Sun--Earth--WMAP. As WMAP orbits the Sun, in company with Earth, it makes a full sky map every 6 months. WMAP has a fast spin around the spacecraft axis, rotating every 2.2 minutes, and a slow precession spin of 1 hour upon the Sun-WMAP line, which is within 0.1* of the Sun-Earth line. The combinations of this triple rotation--2.2.minute spin, 1 hour precession, daily solar orbit--allows for full sky mapping coverage, including coverage of the north and south ecliptic poles, every 6 months for the duration of the mission. The yield of multiple full sky maps provides dependable stability and consistency of data. A full explanation is available through this link to NASA.

In 2003, WMAP returned early results showing that (1) the universe is composed of a large percent of dark energy (see image) and (2) the microwaves can be traced back to a 13.7 billion year starting point, giving us our closest measurement of the age of the universe (see image).

What are the current breakthroughs currently being announced from WMAP's data?

The first is that the early universe was composed of 10% neutrinos, those elusive particles that metamorphosize from one variety to another in mid-flight and hurtle through us and all parts of the universe, including lead, at a rate near the speed of light.

It has been theorized that due to the amount of helium in the present state of the universe, it must have at one time contained a larger quantity of neutrinos than there are now. WMAP's measurements show that this theory is correct and that whereas today, neutrinos measure less than 1%, in the early universe neutrinos measured at 10% of the universe. This confirms, with 99.5 % confidence, the existence of the hypothesized "cosmic neutrino background," which would have effected the development of the universe and therefore the characteristics of the microwave background as is evidenced in the analysis of WMAP data.

The second is that the end of the cosmic "dark ages," when the first star began to shine, came when the universe was about 400 million years old and lasted for another half a billion years. How do they know this? The glow from new stars created a fog of electrons in the gases surrounding those stars that scattered microwaves. The first presence of this fog and scattering of microwaves are measurable because electromagnetic microwaves created mechanical sound waves during their scattering, thus creating the first imprint of sound in the universe at about the 400 million year mark. The first sound peak (see image) was followed by two smaller sound peaks that represented the subsequent harmonic overtones (the second of which is significant in the analysis for neutrinos).

The third breakthrough provided by WMAP is that measurable constraints can now be placed on the primary period in the formation of the universe called "inflation," a time during which the particles and energy rapidly expanded and possibly created ripples (like waves over a lake) in the fabric of space. Since WMAP can now offer accurate measurements of the condition of the early universe, some of the hypotheses about this inflation can now discarded while others are supported.

As Gary Hinshaw of NASA's Goddard Space Flight Center in Greenbelt, Maryland, said, "We are living in an extraordinary time. Ours is the first generation in human history to make such detailed and far-reaching measurements of our universe."

References & Further Reading:

http://www.jhu.edu/news_info/news/home08/mar08/bennett.html

http://wmap.gsfc.nasa.gov/mission/observatory_scan.html

http://www.pschweigerphysics.com/waves.html

http://map.gsfc.nasa.gov/news/index.html