The big bang’s ’smoking gun’

By the faint cosmic glow of the oldest known light, physicists say they have found evidence that the universe grew to astounding proportions in less than the blink of an eye.

In that trillionth of a second after the big bang, the universe expanded from the size of a marble to a volume larger than all of observable space through a process known as inflation. At the same time, the seeds were planted for the formation of stars, galaxies, planets and every other object in the universe.

“It’s giving us our first clues about how inflation took place,” said Michael Turner, assistant director for mathematics and physical sciences at the National Science Foundation. “This is absolutely amazing.”

Researchers found this long-sought “smoking gun” evidence by looking at the cosmic microwave background, the oldest light in the universe. The light was produced when the universe was about 300,000 years old — a long time ago, but still hundreds of millennia after inflation had done its work.

Even so, the pattern of light in the cosmic microwave background offers clues about what came before it, just as a fossil tells a paleontologist about long-extinct life. Of special interest to physicists are subtle brightness variations that give images of the microwave background a lumpy appearance.

Physicists presented new measurements of those variations during a news conference Thursday at Princeton University. The measurements were made by a spaceborne instrument called the Wilkinson Microwave Anistropy Probe, or WMAP, launched by NASA in 2001.

“It amazes me that we can say anything at all about what transpired in the first trillionth of a second of the universe,” said Charles Bennett, a Johns Hopkins University physicist who presented the research along with Lyman Page and David Spergel, both of Princeton.

Earlier studies of WMAP data have determined that the universe is 13.7 billion years old, give or take a few hundred thousand years. They have also measured variations in the cosmic microwave background so huge that they stretch across the entire sky. Those earlier observations are strong indicators of inflation, but no smoking gun, said Turner, who was not involved in the research. They represent tiny inhomogeneities — dense spots in the superhot primordial soup that was the universe in the first stages of inflation — blown up to hundreds of light-years in size by the subsequent expansion of the universe.

The new analysis was able to characterize variations in the microwave background over smaller patches of sky — only billions of light-years across compared to hundreds of billions. Due to some weird aspects of quantum physics, those smaller lumps popped into existence during the middle and end of the inflationary process as tiny subatomic particles.

Then they would have expanded with the space they occupied to become of today’s stars and galaxies. Slightly denser than their surroundings, they would have pulled additional material in by gravity, building up into the massive galaxies and superclusters observable today.

“Galaxies are nothing but quantum mechanics writ large across the sky,” said Brian Greene, a Columbia University physicist.

The measurements are scheduled to be published in a future issue of the Astrophysical Journal.

Copyright 2006 The Associated Press.