Baby pictures of universe show it's flat

Balloon takes photos, first of their kind, high over Antarctica

Glimpse just after Big Bang

April 27, 2000|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

WASHINGTON -- An international team of astronomers has captured what are described as the first detailed pictures of our universe in its infancy -- just a few hundred thousand years after the Big Bang, before the formation of the first stars and galaxies.

The cosmic baby photos look something like slices of a blurry cheese pizza.

But they are delighting scientists because they appear to support promising theories about the early physics of the universe and the mechanisms that led to the birth of stars and galaxies like our own.

The images -- snapped by a telescope hung beneath a balloon over Antarctica -- also appear to resolve a fundamental question raised by Albert Einstein about whether space is "curved" or "flat."

The answer: It's flat, or nearly so, which means that two parallel beams of light will stay that way.

"These measurements represent a watershed event in cosmology," said Mark Kamionkowsky, a theoretical astrophysicist at the California Institute of Technology.

The data "open up a path toward scientifically addressing what happened in the first micro-micro-second after the Big Bang," he said.

The team, composed of scientists from Italy, the United Kingdom, Canada and the United States, reported its findings today in the science journal Nature. The U.S. share of the $4 million cost was borne by the National Science Foundation, NASA and the Department of Energy.

The awkwardly named Balloon Observations of Millimetric Extragalactic Radiation and Geophysics ("Boomerang") project got airborne late in 1998.

The Boomerang balloon soared 120,000 feet over Antarctica, carrying a telescope fitted with highly sensitive microwave sensors built at Caltech. The balloon and its cargo circled the South Pole, carried by circumpolar winds. Ten and a half days and 5,000 miles later, the telescope was retrieved near its launch point.

Boomerang scientists were seeking the most detailed image ever of the "cosmic microwave background" radiation.

Discovered in 1964 by radio astronomers, the background radiation is believed to be the faint afterglow from the fireball that filled the universe right after the Big Bang, 12 billion to 15 billion years ago. The radiation seemed to be uniform no matter which way astronomers looked.

In 1991, however, NASA's Cosmic Background Explorer satellite found the first evidence that this background radiation was not uniform. It seemed slightly uneven. But scientists needed more detail.

Boomerang's telescope zoomed in on 3 percent of the sky and found the background radiation mottled by slight but distinct variations in temperature. If human eyes were sensitive to microwave radiation, the pattern would be visible, dominating the sky.

Embryonic universe

Caltech astrophysicist Andrew Lange said the picture, which looks like dollops of cheese sprinkled on dark tomato sauce, is "the first clear image of the embryonic universe."

This microwave image was "imprinted" in the universe, perhaps 500,000 years after the Big Bang. That was when the cosmic fireball cooled enough to became transparent, and light was finally able to emerge. Like a photograph, scientists say, it has remained unchanged ever since.

Cosmologists are finding support in the Boomerang images for a variety of theories about the early universe.

Astrophysicist Paolo deBernardis, of the Universita Roma, said the patches of light and dark -- corresponding to slight variations of temperature -- support theories about the cause of apparent "lumpiness" of the early universe.

Collapse into galaxies

That lumpiness led eventually to the gravitational collapse of gas clouds into the large-scale structures visible to astronomers today -- clusters, superclusters and filaments of galaxies and the empty spaces between them.

Boomerang's findings lend support to "inflationary" theories, describing a rapid "growth spurt" during the Big Bang that rapidly expanded the early universe.

They also help nail down the relative amounts of visible "ordinary" matter (about 5 percent) and invisible "dark" matter in the universe (30 percent) and the so-called "missing" matter and energy (about 65 percent).

The latter includes the still-mysterious "dark" energy that is believed to be accelerating the expansion of the universe.

Finally, scientists said, the sizes of the light and dark patches in the Boomerang images match predictions for a universe is not "curved," but "flat."

Einstein predicted that if there were enough mass and energy in the universe, it would curve space and time, and two beams of light that start out parallel to each other would eventually merge. Boomerang indicates they'll remain parallel forever.

"We can't imagine it either," conceded University of Chicago astrophysicist Michael Turner. But understanding the math helps scientists accept the notion.

The findings also suggest that the universe has too little mass to one day collapse back onto itself in a big crunch.

"We are really demonstrating that it's flat, and we are demonstrating that it will expand forever," said deBernardis.

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