THE FINDINGS, detailed Tuesday at a NASA press conference, provide the strongest support to date for the Big Bang theory of the creation of the universe and the related notion that the first seconds were a period of hyperinflation.
The results come from measurements of radiation emitted just after the birth of the universe, before there were any stars.
The snapshot shows the state of the universe about 380,000 years after the Big Bang, when the only electromagnetic radiation around was of the microwave variety. The study of this so-called cosmic microwave background was made using NASA’s space-based Microwave Anisotropy Probe observatory.
The readings were projected to a later, unseen era, revealing that the universe had cooled enough for matter to condense and form the first stars 200 million years after the Big Bang.
“That’s a surprisingly early time for the turn-on of the first stars,” said Charles L. Bennett, principal investigator for MAP at NASA’s Goddard Space Flight Center.
The new data show the universe to be 13.7 billion years old, to within 200 million years, Bennett said. Further, the early universe was 4 percent real matter in the form of atoms, about 23 percent unseen dark matter, and about 73 percent dark energy, a totally unknown and exotic force that causes the universe to accelerate at an ever-faster pace.
Importantly, these figures are in line with other estimates made from data collected in the nearby universe. Bennett and others said the new results now serve as a cornerstone for modern cosmological theory and support its most widely accepted aspects.
Over the past 38 years, scientists' view of the early universe has become clearer and clearer -- starting with ground-based observations (top), moving to the Cosmic Background Explorer (middle), and climaxing with what scientists expected would be the Microwave Anisotropy Probe's view (bottom).
BIRTH OF A BACKGROUND
The cosmic microwave background was unleashed when the early universe had expanded enough to cool and allow atoms to form. Around that time, a dense and impenetrable primordial cloud cleared out. The background radiation escaped. The radiation retains an imprint of the end of that era and hints about what occurred before, much like the patterns on a cloud’s exterior provide clues to its insides.
The microwave radiation has since spread out and cooled, filling the universe. It appears to be of nearly uniform temperature across all of space, but minute variations first detected a decade ago provide the clues needed to help decipher the primordial structure of the universe.
The MAP spacecraft launched June 30, 2001. These are the first findings attributed to it. MAP examines the cosmic microwave background in greater detail than its predecessor, the Cosmic Background Explorer satellite. COBE first discovered the fine variations in the microwave background in 1992. It took about 3 months to get MAP into position, and since then it has been building up the data that led to Tuesday’s long-anticipated announcement.
The temperature of the cosmic microwave background ranges from 2.7251 to 2.7249 degrees Kelvin (a measure of degrees above absolute zero). These tiny variations reflect the earliest lumps and bumps in the universe — seeds for galaxies and stars.
These seeds, then, formed roughly 380,000 years after the Big Bang. Scientists have no observations to tell them what happened next, but here’s what they imagine:
Nodes of matter were connected by long filaments, much like a spider web. Clumps of hydrogen — something like drops on the spider web — developed along the filaments. Each drop had heft, gravity and a random velocity, and eventually they were drawn toward the nodes, where material gathered to generate the first galaxies.
Princeton University’s David Spergel, co-investigator for MAP, said the new findings result from using the MAP data and running them against millions of computer simulations to look for matches of what the composition and geometry must have been like.
“It’s a lot like matching fingerprints,” Spergel said. Once a match is found, then a computer model can be run forward in time to see if things turn out to match up with observations of the modern universe. It’s a bit like taking a baby picture and morphing it into an adult image.
“What we find when we do that is remarkable,” Spergel said. “It all fits.”
‘ASTOUNDED’ BY FINDINGS
John Bahcall of the Institute for Advanced Study in Princeton, N.J., said he was “astounded” by the MAP findings.
Bahcall, who was not involved in the project, said the observations and analysis were so precise that they must be believed.
“We live in an implausible, crazy universe, but one whose defining characteristics we now know,” Bahcall said.
The cosmic microwave background was detected by accident in 1965, by Bell Labs researchers who heard extra noise in a radio receiver they were testing. At the time, Princeton physicist David Wilkinson had been working on a way to detect the radiation. He helped write a scientific paper back then for the Physical Review, describing the implications of the inadvertent discovery.
Wilkinson later helped develop the COBE satellite. He then worked on the MAP project. “Dave was really the father of MAP,” Lyman Page, a MAP team member from Princeton, said late last year. Wilkinson died in September.
NASA announced Tuesday that the observatory had been remained WMAP, or Wilkinson Microwave Anisotropy Probe.
BACK TO BUSINESS
The new results had originally been slated for a press conference last Thursday but were delayed in deference to the shuttle Columbia’s astronauts and their families. By any account, the discoveries represent a remarkable way for NASA to get its science program heading back toward business as usual.
“Before the WMAP results, astronomers and physicists had put together a very implausible picture of our universe,” Bahcall said. “It had a tiny amount of … ordinary matter. It had a modest amount of dark matter, whatever that is. It had an overwhelming amount of dark energy, which is a strange beast. I have to confess I was very skeptical of this picture. But the WMAP results have convinced me.”
He added that every astronomer will remember when they first heard these results.
“The announcement today … represents a right of passage for cosmology from speculation to precision science,” Bahcall said.
Among the more tantalizing of the findings is what appears to be the first observational evidence that, as theorized, the first seconds of the universe involved an extremely rapid inflation. Further, the WMAP data shows that some inflation models can probably be ruled out, while others may work.
Andrei Linde, of Stanford University, developed some of the inflationary models that still seem to work. He had been greatly anticipating the WMAP results and in a telephone interview called them “extremely impressive.”
Linde said inflation had seemed like science fiction when it was first introduced, about 20 years ago.
“We didn’t expect in our lifetimes it would be verified,” Linde said. “Now we hear the basic features of inflationary cosmology fit with observational data.”
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