University of Chicago astronomers on Sunday released finely detailed measurements of radiation from the birth of the universe, capturing an unprecedented snapshot of acoustic waves rippling from the cataclysm of the Big Bang.
The results provide the strongest observational evidence yet for a central theory of cosmology called inflation, which states that the universe underwent a mind-boggling growth spurt in the first brief instants of creation, experts said.
That rapid expansion immediately after the Big Bang about 14 billion years ago would help explain the structure of the present-day cosmos, which might be much less orderly and inhospitable to life if inflation had not occurred.
Sunday’s announcement also provides a dramatic example of how seemingly impossible theories about the universe’s violent birth finally are getting experimental backing–marking what U. of C. astronomer Michael Turner calls “the golden age of cosmology.”
The snapshot of the early universe was taken in the last year by a U. of C.-operated microwave observatory at the South Pole. The dry and thin atmosphere in Antarctica lets researchers take detailed pictures of the faint background radiation that comes from every part of the sky and that scientists believe is the afterglow of the Big Bang.
Astronomers immediately hailed the findings, which the U. of C. team unveiled Sunday at a meeting of the American Physical Society in Washington. The Chicago group had been in a race with astronomers at the California Institute of Technology, who presented similar findings at the meeting.
“People are going to be talking about these experiments 100 years from now,” said Marc Kamionkowski, a Caltech professor of theoretical physics who was not part of either team. “We all thought this would happen eventually, but I never thought I’d be sitting here in 2001 talking about it.”
“It’s quite a stunning result,” said the U. of C.’s Turner.
What the astronomers saw was the visual fingerprint of vibrations from a time when the whole universe literally rang like a bell.
That ringing came from the Big Bang and the brief but awesome period of cosmic inflation that occurred when the universe was an infinitesimal fraction of a second old. In one tiny instant, many astronomers believe, the universe expanded by a factor greater than all its growth in the 14 billion years since.
Sound from such an event would not carry in the vacuum of space that exists today. But the primordial ringing coursed for thousands of years through the hot plasma that filled the young universe, experts believe.
Ripples from those acoustic waves found their way into the microwave radiation that shot from the young plasma as it cooled, about 400,000 years after the Big Bang. The U. of C. team studied those ripples using a South Pole telescope called the Degree Angular Scale Interferometer, or DASI (pronounced “Daisy”), which detects temperature variations in the background radiation.
A key prediction from the formulas of inflation theory is that ripples in the background radiation should form a distinct pattern of waves–one large peak followed by two smaller ones.
“Just like a musical note has overtones, you should see these other peaks, too,” said John Carlstrom, a U. of C. astronomer who heads the $3 million South Pole observatory.
A simple graph of data that Carlstrom’s team released on Sunday is the first to show the three peaks that inflation theory predicts, experts said.
Although the picture would look unremarkable to most people, astronomers instantly grasped its significance.
“Ah, that’s pretty … that’s amazing,” said Martin White, a professor of astronomy at the Harvard-Smithsonian Center for Astrophysics who examined the data for the first time, during a phone interview late last week.
“Theorists have been saying for 20 years that this would happen,” White said. “To see it actually come true is incredible.”
Theorist Alan Guth of the Massachusetts Institute of Technology first proposed inflation in 1980 as a way of explaining why the universe did not cool down and stop expanding immediately after its creation.
A major implication of the theory that the new findings appear to support is that the largest structures we can see today, such as galaxies and galaxy clusters, spring from the universe’s origin as a speck smaller than an atom. Turner of the U. of C. was one of the first to propose in 1982 that the lumpy distribution of stars and galaxies arose because inflation stretched out the grainy subatomic world to cosmic scales.
“Without inflation there would be no us, because it provides the seeds for all the structure in the universe,” Turner said. “Without it the universe would be contorted, probably filled with black holes, and expanding every which way.”
Last year, a Caltech project called Boomerang peered at the background radiation and found some of the first observational support for inflation theory. But that experiment, which sent a balloon-borne telescope over Antarctica, did not at first find the three peaks that scientists had expected.
New results the Caltech team released on Sunday supported the Chicago group’s findings–ending the latest leg of the two teams’ race to analyze the background radiation with a virtual tie.
“This is a clash of the titans–it’s like the Lakers versus the Bulls in 1991,” said Caltech’s Kamionkowski. “And they’re good friends off the court.”
Now that experimentation is converging with cosmological hypotheses, researchers must sort through the increasingly bizarre implications of their theories.
Inflation theory, for example, implies that the vast universe we can see is just one of an infinite number of bubble universes constantly being born. The new data also support the once-ridiculed notion that our universe is not only expanding, but doing so at an accelerating pace, said the U. of C.’s Turner.
The DASI telescope results confirm earlier calculations that ordinary matter accounts for just 5 percent of the universe. The rest is thought to consist of mysterious dark matter and so-called “dark energy,” which may supply the force behind the universe’s accelerating expansion.
“We’re being pushed toward this picture of an absurd universe, the universe where you say, `Who ordered that?'” Turner said.
