By Guy Gugliotta
Washington Post Staff Writer
Friday, March 17, 2006
Scientists said yesterday they have found the best evidence yet supporting the theory that about 13.7 billion years ago, the universe suddenly expanded from the size of a marble to the size of the cosmos in less than a trillionth of a second.
A team of researchers used data collected by a NASA satellite measuring microwave radiation to offer direct, experimental support for the theory of "inflation" put forth 25 years ago -- that the expansion of the universe, commonly known as the "big bang," began with a single burst of repulsive energy acting in a tiny fraction of time. The expansion continues today but at a much slower rate.
"We can measure the sky to tell what powered this expansion," said Goddard Space Flight Center astrophysicist Gary Hinshaw. "It's really amazing, actually. I was in graduate school when the theory was first proposed, and I've been working on it ever since. It's gratifying to see the idea hold up now."
Hinshaw is a member of a team monitoring data from NASA's Wilkinson Microwave Anisotropy Probe, a satellite launched in 2001. The findings were announced yesterday at a Princeton University news conference and will appear in the Astrophysical Journal.
The theory, developed by Alan H. Guth of the Massachusetts Institute of Technology, holds that during the universe's first moments, inflation produced a sudden burst of heat and light that left an afterglow about 400,000 years after the event. The first stars were formed about 400 million years after the big bang.
The original afterglow has been cooled by the universe's expansion until all that is left is a faint microwave "signature."
"You're looking out to the edge of space and time," Hinshaw said in a telephone interview. "It's like trying to see a car's headlights through the fog."
The NASA probe has two imagers 140 degrees apart that take measurements of microwave radiation in space, then image new slices of the heavens as the satellite rotates to a new position. The readings were averaged as they were taken, and by repeating this process every six months, the team built up enough information to see through the fog of time and focus on the early afterglow.
What the team found was a pattern of light and temperature of differing brightness and intensity. "The light is polarized, like when it bounces off the hood of a car," said astrophysicist David Spergel of Princeton. "We measured temperature differences in 2003, but with three years' more data we were also able to measure polarization."
The result is a pattern of fluctuations that Hinshaw compared to a ship bobbing in a short, choppy sea even as it rolls periodically with longer swells. The theory of inflation predicts what the ratio of chop to swell should be, he said, "and the astonishing thing is that it's doing exactly what was predicted."