NASA's Wilkinson Microwave Anisotropy Probe (WMAP) has taken the best measurement of the age of the Universe to date. According to highly precise observations of microwave radiation observed all over the cosmos, WMAP scientists now have the best estimate yet on the age of the Universe: 13.73 billion years, plus or minus 120 million years (that's an error margin of only 0.87%… not bad really…).
The WMAP mission was sent to the Sun-Earth second Lagrangian point (L2), located approximately 1.5 million km from the surface of the Earth on the night-side (i.e. WMAP is constantly in the shadow of the Earth) in 2001. The reason for this location is the nature of the gravitational stability in the region and the lack of electromagnetic interference from the Sun. Constantly looking out into space, WMAP scans the cosmos with its ultra sensitive microwave receiver, mapping any small variations in the background "temperature" (anisotropy) of the universe. It can detect microwave radiation in the wavelength range of 3.3-13.6 mm (with a corresponding frequency of 90-22 GHz). Warm and cool regions of space are therefore mapped, including the radiation polarity.
This microwave background radiation originates from a very early universe, just 400,000 years after the Big Bang, when the ambient temperature of the universe was about 3,000 K. At this temperature, neutral hydrogen atoms were possible, scattering photons. It is these photons WMAP observes today, only much cooler at 2.7 Kelvin (that's only 2.7 degrees higher than absolute zero, -273.15°C). WMAP constantly observes this cosmic radiation, measuring tiny alterations in temperature and polarity. These measurements refine our understanding about the structure of our universe around the time of the Big Bang and also help us understand the nature of the period of "inflation", in the very beginning of the expansion of the Universe.
It is a matter of exposure for the WMAP mission, the longer it observes the better refined the measurements. After seven years of results-taking, the WMAP mission has tightened the estimate on the age of the Universe down to an error margin of only 120 million years, that's 0.87% of the 13.73 billion years since the Big Bang.
"Everything is tightening up and giving us better and better precision all the time […] It's actually significantly better than previous results. There is all kinds of richness in the data." - Charles L. Bennett, Professor of Physics and Astronomy at Johns Hopkins University.
This will be exciting news to cosmologists as theories on the very beginning of the Universe are developed even further.