A Sky & Telescope Special Online Feature
March 11, 2008
Along the way, researchers have confirmed some key predictions of the "inflationary universe" theory of how the Big Bang itself erupted from a much larger, underlying pre-existence, which could be producing inconceivable numbers of other, separate big-bang universes all the time.
This has become possible not by conventional astronomy, but by analyzing the cosmic microwave background radiation that covers the entire sky. This weak radio glow is literally the white light emitted by the still-white-hot universe as it stood just 380,000 years after the Big Bang. The light has been redshifted down into the microwave part of the spectrum (by a factor of 1,091) by the expansion of space since that time.
Wilkinson Microwave Anisotropy Probe (WMAP). It is mapping the background radiation's temperature and polarization across the entire celestial sphere, and at a wide variety of angular scales: from large (many degrees wide, constellation-size) to nearly as small as the resolution of the human eye.
As time goes on, WMAP has continued to sharpen its picture.
Its first-year data release, in 2003, set milestones in precision cosmology -- among other things, pinning the age of the universe to 13.7 billion years with an uncertainty of just a couple percent, and confirming the existence of the recently discovered "dark energy" that is making the expansion of the universe speed up.
The three-year data release, in 2006, confirmed that the first results were on target, refined the numbers, and put new constraints on how cosmic inflation could have worked during the first 10–32 second or so of the Big Bang. The story of how such things can be found from mere maps of the microwave background (such as the new one pictured at top) is told in the May issue of Sky & Telescope, now at the printer.
The New Big Picture
Just after we sent that issue to press, WMAP's science team released the much-awaited five-year data set, along with their conclusions about what it tells. Once again, the additional data (and better long-term calibration of the instruments) refines the picture significantly — and, as a result, yields new conclusions.
The following results combine the new WMAP data with other recent astronomical clues:
These refinements affect everything else. For instance:
This also means that the universe's stars, planets, and atoms will not all be torn apart in the coming billions of years by a runaway increase in cosmic acceleration, a situation called the Big Rip.
In addition, the three types of neutrinos that exist have masses that can add up to no more that 0.61 electron volt, agreeing with laboratory experiments.
The five-year WMAP results have been issued in seven scientific papers submitted to the Astrophysical Journal.
Also, NASA has put out a popular summary .
"We are living in an extraordinary time," says Gary Hinshaw (NASA/Goddard Space Flight Center). "Ours is the first generation in human history to make such detailed and far-reaching measurements of our universe."