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. Last Updated: 07/27/2016

New Images Indicate Universe Is Flat

It's a question that plagued Einstein, and every astrophysicist in his wake: What is the shape of our universe? Is it curved like the top of a ball? Does it open upward like a potato chip? Or is it perfectly flat?

The question is so big, and so mind-boggling, that until recently, it could be attacked only by theorists. But on Wednesday, astronomers released the first detailed images of the infant universe - images providing conclusive evidence that the universe is very nearly flat.

The finding, already being celebrated by cosmologists around the world, provides the first direct evidence for many provocative and sometimes unpopular notions about how the universe formed. The images may one day provide a clear recipe for the still unknown contents of the cosmos and help predict its eventual fate and whether it will one day violently collapse on itself.

"Five years ago, even last year, people were talking about a very curved universe. Our data says no way," said John Ruhl, a physicist at the University of California, Santa Barbara, who was part of the 36-member international team that made the finding.

"This will be reckoned as the turning point when the history books are written," said Michael Turner, an astrophysicist at the University of Chicago. Turner was not involved in the experiment but had been among those arguing for the notion of a flat universe.

Beyond what they may say about the birth and possible death of our universe, the images have stunned physicists simply because they provide the first close-up view at what the universe was like when it was only 300,000 years old and 1,000 times smaller and hotter than it is today.

The observation also provides critical support for a theory called inflation, which postulates that the entire universe arose from an area smaller than an atom during a violent explosion that occurred a fraction of a second after the Big Bang. Theory predicts that such an incredible expansion would stretch out space until it was flat.

When cosmologists say "flat universe" they mean flat in three dimensions, which is "difficult to imagine," said Paolo deBernardis, an astrophysicist at the University of Rome and co-director of the project.

The images were captured using a balloon-borne telescope that endured a 10 1/2-day, 8,000-kilometer flight high over Antarctica, where constant sunshine and stable high-altitude winds can keep balloons aloft for the long periods necessary to collect data. To make its precise measurements, the telescope needed to float above the earth's distorting atmosphere.

During its flight, the telescope detected nearly imperceptible differences in the faint, cold glow of microwave background radiation that pervades the sky. Like a cosmic fossil trove, this primordial light is made up of relic particles of light, or photons, from shortly after the Big Bang some 10 billion to 15 billion years ago.

"We're looking at the oldest photons in the universe, and they're really starting to talk," Ruhl said.

The background radiation was discovered in 1964. Although it was expected to reveal hints about the early universe, it took decades to develop technology that could examine it.

In 1992, the National Aeronautics and Space Administration's COBE, or Cosmic Background Explorer, satellite detected small variations in the radiation across the sky, huge ripples in the fabric of space time. The variations were dubbed the "Face of God" because they were the first evidence of structure from an early universe that started out as a kind of hot cosmic bisque of particles and radiation.

As exciting as the finding was, the images produced by COBE were blurry and indistinct.

The new images, from the telescope dubbed Boomerang, for Balloon Observations of Millimetric Extragalactic Radiation and Geophysics, are 40 times sharper than those obtained by COBE. "Boomerang has for the first time brought these very faint structures into sharp focus," said Andrew Lange, an astrophysicist at the California Institute of Technology and leader of the U.S. portion of the international team.

"It's quite an achievement," said Wayne Hu, an astrophysicist at the Institute for Advanced Study, who wrote an editorial accompanying the new research paper, which appears in Thursday's issue of the journal Nature. "With this data, we've entered an era of precision cosmology."

Once astronomers knew there were wrinkles in the fabric of the universe, the critical question was how large they were. The new report shows they generally cover 1 degree of space in the sky, which is about twice the size of a full moon seen from Earth, and the exact size predicted by models of a flat universe. A curved universe would have meant the light traveling through space was also curved and the wrinkles would have been distorted in size.

"It's undeniably the pattern of a flat universe," Turner said.

The pictures reveal hundreds of complex structures in the universe that are the seeds in which clusters of galaxies formed, Ruhl said. It's thought that all structures we see today were formed by gravitational attraction in areas of slightly different density and temperature in the early universe.

The images, expected to undergo months or years of additional analysis, may also begin to answer other questions about the contents of the universe. There is simply not enough matter to account for the universe depicted by these images. Further computation of the data on supercomputers at the Lawrence Berkeley Laboratory and at the University of Toronto may help prove theories that the universe is also composed of a strange form of dark matter that is yet to be detected and dark energy, an even stranger force that repels gravity and keeps the universe expanding.

And more work must be done before the inflation theory of the early universe is proved, Ruhl said.

Earlier thinking was that a curved universe was would die in a "big crunch'' and a flat universe would face a calmer fate of expanding ever slower and then stopping. However, the addition of the little-understood dark energy means all bets for the fate of the universe are off.

"The fate of the universe is going to take a long time to answer," said Turner. "Luckily, we have at least 200 billion years to chew on that one."