Chicago Tribune: South Pole Telescope To Probe Mystery Of 'Dark Energy'

By Ronald Kotulak, Chicago Tribune science reporter

August 30, 2002

Astronomers from the University of Chicago and four other institutions plan to build a unique telescope at the coldest place on Earth to figure out the biggest mystery in cosmology: Why is the universe, in a sense, falling up?

Funded by a $16.6 million National Science Foundation grant announced Thursday in Washington, the team expects to have the telescope running at the South Pole in four years.

Its mission is to explore a recent discovery that has turned physics on its head. Two years ago astronomers were stunned to find evidence suggesting that the universe is in the grasp of dark energy, a puzzling antigravity force that is causing it to expand at an ever-accelerating rate.

Cosmologists--scientists who ponder the origins of the universe--had thought that the expansion either was constant-- gradually spreading but basically staying the same--or that it was slowing.

If gravity were causing the universe to slow, then it would eventually collapse on itself, ending up in what has been called the Big Crunch. This would be the opposite of the Big Bang theory that the universe came into existence in a gigantic explosion 10 billion to 15 billion years ago.

An accelerating universe, on the other hand, would mean all stars, galaxies and other matter would spread apart so fast and become so diluted that over billions of years the universe would be nothing but a void.

What it comes down to is that scientists know very little about gravity. It used to be clear that gravity was an attraction between bodies, and on Earth that meant things always fell down.

But cosmologists now suspect that on the scale of the universe, gravity, propelled by something they call dark energy, behaves just the opposite. Newton would have been shocked to see an apple fall up.

"We do have antigravity now, but only on this enormous scale," said Bruce Winstein, director of the U. of C.'s Center for Cosmological Studies, where the dark energy telescope was conceived and developed.

One of the most bizarre features is that as the universe expands, it creates more dark energy that pushes the expansion to warp speeds.

"If dark energy really is 70 percent of the whole universe and it behaves the way current theory predicts, then it really is beginning to dominate everything about the universe," said Tony Stark of the Harvard-Smithsonian Center for Astrophysics.

"It will actually turn off the formation of galaxies. From now on there will be very many fewer galaxy clusters formed."

Besides the U. of C. and the Harvard-Smithsonian Center, other institutions collaborating on the project are the University of Illinois at Urbana-Champaign, the University of California at Berkeley and Case Western Reserve University in Cleveland.

The telescope, which will be 26.4 feet in diameter, will function like a huge thermometer measuring differences in temperature in ancient space. The instrument will be able to detect tiny variations-- as little as 10 millionths of a degree--in the Big Bang's leftover heat, which scientists call the cosmic microwave background.

A variation in the temperature in a specific area signifies the presence of a galaxy cluster. That will allow astronomers to count the galaxy clusters in the field. The fewer the number, the greater the evidence that dark energy is at work, forcing galaxies to fly apart so fast that they can't form clusters.

Antarctica was selected as the site for the radiotelescope because the temperature is always cold, which limits the amount of water vapor in the atmosphere. Water vapor blocks the microwave radiation coming from space.

Astronomers will use the telescope to do a census of galaxy clusters that are 5 billion to 7 billion light years from Earth, when the universe was one-third of its present size and galaxies were rapidly forming clusters.

As the microwave radiation travels through these clusters, their dust slightly changes the wavelength of the radiation. The telescope will be sensitive enough to detect these changes, which will tell astronomers how many galaxy clusters inhabit a given amount of the universe at that early time.

Theory predicts that if dark energy is greatly accelerating the universe's expansion, then galaxies will be scattered too far apart to form many clusters. The fewer the clusters, the more powerful the dark energy.

"With the South Pole telescope we can look at when galaxy clusters formed and how they formed," said U. of C.'s John Carlstrom, who heads the project. "That is critically dependent on the nature of dark energy, this elusive component of the universe."

Dark energy is different from another cosmological mystery, dark matter. Dark matter refers to the unseen matter that exerts enough gravity to keep spinning galaxies from flying apart. Scientists are confident they eventually will solve the mystery of dark matter, which is probably tiny ubiquitous particles that have not yet been detected.

Because matter and energy are interchangeable, an observation made by Albert Einstein, it has been estimated that dark matter makes up about 20 percent to 25 percent of the universe's energy and that stars, planets and people make up a mere 3 percent to 5 percent.

The giant's share, 70 percent, is now believed to be the mysterious dark energy.

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