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WMAP Heralds Era of Precision Cosmology


The Wilkinson Microwave Anisotropy Probe (WMAP) has finished its first year of imaging the faint microwave radio emission that pervades the entire sky. This emission is identified as coming from the Universe when it had cooled to a temperature of 3,000 degrees Kelvin, 380,000 years after the Hot Big Bang. The emission originally arose as visible light akin to that of the solar surface, but has since been redshifted by universal expansion to the microwave part of the electromagnetic spectrum.

WMAP's first-year map reveals miniscule irregularities that confirm some of the most important findings in cosmology -- the study of the Universe as a whole. From the mottled emission, WMAP scientists have determined that

* Our Universe is exquisitely "flat" in topology, such that two initially parallel light rays will stay parallel forever. A flat Universe is one of the key predictions of cosmic inflation, a theory that pertains to the very earliest moments of the Universe.

* The Universe and all it contains originated in a Hot Big Bang 13.7 billion years ago.

* The Universe is expanding like a stretchy sheet at a rate of 71 kilometers per second per megaparsec of distance, where one megaparsec equals 3.26 million light-years.

* The matter-energy in the Universe is made up of 4% ordinary matter -- most of which is dark, 23% dark matter of unknown constitution, and 73% dark energy of even more unknown nature.

* The first stars in the Universe were formed less than 200 million years after the Big Bang, less than 1.5% of the total time that has transpired since then.

These far-reaching conclusions are based on the most precise measurements of the cosmic microwave background ever attained. They await confirmation from the additional WMAP data that are accruing, from the European Planck mission that has yet to launch, and from other scientists who may hold different interpretations of the same data.