Text: South Pole tool peeks at universe's birth By Lidia Wasowicz UPI Senior Science Writer From the Science & Technology Desk Published 12/18/2002 6:27 PM View printer-friendly version Astrophysicists Wednesday said they have gleaned more about the dawning of the universe through a radio telescope array perched on the highest, driest, coldest, windiest continent on Earth, in observations that support bizarre theories of an exotic beginning some 14 billion years ago. Getting a clear shot at the skies from a pristine South Pole site, the space watchers set their sights on cosmic microwave background radiation, or CMB, regarded as a leftover of the primordial gruel that nurtured the infant universe. In hopes of honing their understanding of the birth of the cosmos, they homed in on a patch of sky 3.4 degrees across -- about the area enclosed by a thumb and forefinger arched in an "OK" sign at arm's length. For 20 hours a day for 271 days, the scientists in essence turned their sky-hugging telescope into a pair of oversized polarized sunglasses to focus on the pervasive afterglow of a fireball of extremely compact and searing matter that, according to the widely accepted "Big Bang" theory, converted from a dimensionless point into an expanding universe. The team detected for the first time distinctive patterns of minute polarization in the relic radiation predicted by -- and central to -- the theory. The finding caps a quest of more than 30 years by astrophysicists, using increasingly sensitive instruments, to draw out fundamental secrets from radiation thought to have escaped a rapidly cooling universe some 400,000 years after what most scientists define as the moment of creation. "The great story of the current ... results is how precisely, in each of the different aspects that we were able to measure, the polarization of the CMB appears to match the predictions of our current theory," study co-author John Kovac of the University of Chicago told United Press International. "We scientists are apparently stuck with a preposterous universe." It is, by currently favored accounts, a universe brimming with deep, dark secrets, an enigmatic mix of 30 percent of strange "dark matter" that refuses to interact with light; another 65 percent of even more bizarre invisible, thus-far-undetected "dark energy" that seemingly fuels an accelerated expansion of the universe, and a mere 5 percent of the familiar ordinary stuff of stars, planets and living creatures. The theory-vindicating findings point to cosmic radiation as the fading echo of the harbinger of all these elements. The slight polarization detected in a faint radio haze, deemed a relic of the universe's origins, provides the predicted signature of light's last leap from the sizzling, charged cosmic gases as the infant universe cooled sufficiently for atoms to form, astrophysicists said. Most light is unpolarized, its jumbled waves flickering in all directions, be it up and down, from side to side or somewhere in between. When reflected or scattered, as when it bounces off the surface of a lake or the hood of a car, however, a ray of light can become polarized, its waves vibrating in a constant direction. As a familiar example of this effect, polarized sunglasses filter out glare and other reflected light that flickers along a single axis. The cosmic microwave background was polarized by the scattering of cosmic light when it last interacted with matter some 14 billion years ago, theorists attest. If the space sleuths had failed to scrounge up any sign of polarization, astrophysicists would have had to go back to the drawing boards for new interpretations of the extraordinary data compiled in recent years from experiments based on the ground, aboard balloons and in space, said lead author John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy and Astrophysics at Chicago. "Although it has proved the most difficult ... to measure ... the theory said it had to be there, or else everything we thought we understood about the CMB would be in doubt," co-author Erik Leitch told UPI. "We have all breathed a sigh of relief that this critical test was passed." Difficulties facing Earth-bound investigators trying to obtain a snapshot of the baby universe included the extreme faintness of the microwaves and the obstructive water vapor in the atmosphere. In the new study, the investigators met both challenges with the instrument known as DASI, for Degree Angular Scale Interferometer, at the U.S. National Science Foundation's Amundsen-Scott South Pole Station. The telescope consists of a pair of dishes atop an Antarctic ice shelf 2 miles high. Its location is so cold, the water vapor content of the air is nil. Antarctica has recorded temperatures as low as -91 degrees Centigrade (-132 degrees Fahrenheit) and an absolute humidity lower than that of the Sahara Desert. "The emerging picture of the early universe that the DASI results have bolstered our confidence in is, to say the least, pretty strange," co-author Clem Pryke, assistant professor of astronomy and astrophysics at Chicago, told UPI. "The most exciting aspect of that picture is ... that the universe is mostly composed of dark matter and even-more mysterious dark energy," said Carlstrom, who presented some of the initial findings last September to a rapt audience of 200 cosmologists. "It is a mixture of marvel at the continued string of successes the theory has had in explaining our observations of the past few years, and even greater marvel at the unexpected strangeness of the universe that has been revealed." In two reports spanning 25 pages in the Dec. 19 issue of the British journal Nature, the researchers present a dozen different analyses of the data. "Taken together, they show that not only is the polarization signal there at the level predicted by theory, but that the signal also matches the theory in a number of other qualities that we were able to measure," Kovac told UPI. "If this were a police line-up, I think we would have the suspect positively ID'ed." The results reassure cosmologists they are on the right track with their theories of the universe and bespeak the effectiveness of a pioneering technique for stepping back to the very beginning of time, scientists said. "The detection of polarization by DASI at the level predicted by the cosmological standard model is both a remarkable technical achievement and wonderful consistency check for the theory," said Matias Zaldarriaga of New York University, who analyzed the results. "The polarization experiment represents a real leap forward," he told UPI. "So far nobody had come even close to detecting the effect." The study opens the door to pursuing more detailed descriptions of the universe's early years, such as establishing the validity of the seemingly improbable cosmic inflation theory. It proposes the universe underwent a giant growth spurt in a fraction of a second just moments after the Big Bang. "Inflation makes a specific prediction for the polarization of the CMB that, if observed, many would regard as a 'smoking gun' that not only would tell us that inflation happened, but also would start to reveal the details of the process," Pryke told UPI. The telling pattern -- expected to be at least 10 times fainter than the cosmic radiation polarization signal detected by DASI -- eluded the researchers on this go-around. "DASI is the first step, and we hope that as polarization experiments improve, they will get to the point of measuring this signal, hopefully giving direct evidence for the inflation theory," Zaldarriaga told UPI. Learning more about inflation eventually could shed light on the evolution and ultimate end of the universe, scientists said. The publication of the findings comes just days after another team working at the South Pole station reported producing the most detailed images of the early universe ever recorded. The scientists from the University of California, Berkeley, Carnegie Melon University and Case Western Reserve University measured subtle temperature differences in the cosmic radiation. The group used a sensitive new instrument called the Arcminute Cosmology Bolometer Array Receiver to produce high-resolution images of the CMB, revealing the seeds that sprouted into the gargantuan objects typical of the modern-day universe. While the temperature of the background radiation sheds light on the structure of the early universe, polarization will show the speeds at which specific parts of the primordial gas cloud were moving when atoms began forming. Such insights could help astronomers gauge the time span between the Big Bang and the cosmic growth spurt of inflation, scientists said. "The new ACBAR results are fantastic, and are very much complementary to the DASI results in filling out different aspects of our picture of the early universe," Kovac told UPI. http://www.upi.com/view.cfm?StoryID=20021218-123315-8503r

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