Figuring out how the universe works

By Steven Schultz

Princeton NJ -- In 1999, Neta Bahcall and Princeton colleagues Jeremiah Ostriker and Paul Steinhardt published a paper, "The Cosmic Triangle," that put the recent years of astronomical research into sharp focus: The universe, it seemed, was getting really strange.

Neta Bahcall
Not only was the universe expanding, riding out the leftover push of the big bang, it was starting to fly apart at an accelerating pace. But nothing accelerates on its own. Some mysterious energy, the scientists argued, must be building up in the universe and pushing everything apart. While gravity tries to pull everything together, this so-called "dark energy" must have an opposite, repelling effect. Eventually, the scientists concluded, all the familiar matter and energy that constitutes the stars -- and humans -- may dissipate into a vast void of dark energy.

The evidence, which came from several independent sets of observations, seemed fairly strong, but even the authors were skeptical.

"It is a very odd thing," Bahcall said of the dark energy idea. This energy field would be a new piece in the understanding of physics. And yet, if the theory is correct, dark energy has been building strength over the eons and now makes up 70 percent of the universe. "That is why we are not only surprised, but somewhat disturbed by it," Bahcall said. "In 1999, we knew that either the different data sets would continue to converge and confirm each other, or, we speculated, it was more likely that they would just fall apart, because it is such a strange model."

They have not fallen apart. In the last three years, new data have been pouring in from a variety of Earth and satellite-based projects and have come together in a remarkable way to render the picture of an accelerating universe in ever-sharper detail. Measurements that once had margins of error so large they could be made to fit any number of theories are now dramatically refined and allow fewer interpretations. The quality and consistency of these observations has prompted Bahcall and some colleagues to assert that they are approaching an era of "precision cosmology."

This phrase, with its suggestion that consistent answers are also right answers, makes some scientists squirm. Even Bahcall acknowledges that the next piece of data to come in could rattle the whole picture. "Then you have to stop and understand it," she said. "This is the beauty of science -- there is no guarantee that everything will fit together. But in science, with more and better data, the correct answer is finally revealed."

When margins of error are so tight, the arrival of contradictory evidence could be very illuminating, said Bahcall. This possibility is drawing interest from particle physicists and others who are beginning to see the laboratory of the cosmos as an opportunity to test ideas that were once strictly matters of theory or needed impossibly powerful atom smashers.

And that is why -- even though the mystery of dark energy looms large -- it is such an exciting time in cosmology, said Bahcall.

"Frequently reporters ask me: Doesn't it make you feel that we, people here on our planet Earth, are so insignificant in comparison with the vast universe? And what I tell them is it makes me feel exactly the opposite. It makes me feel that people here on this small planet Earth are so incredibly imaginative and innovative and bright that we can figure out how the whole universe works."

Related article
Astrophysicist reaches for the stars and more



February 10, 2003
Vol. 92, No. 15
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Page one
Abraham: U.S. participation in international fusion effort builds on success at PPPL
Astrophysicist reaches for the stars and more
Computer program reveals optimum structure for new composites

Figuring out how the universe works
New P-Rides bus service launched
Science on Saturday lectures offered

Nugent named president of Kenyon
Hargadon chosen to deliver baccalaureate address
New faculty members appointed

Nassau Notes
By the numbers: Campus buildings: additions and subtractions
Calendar of events

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