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University of Chicago News Office
Chicago, Illinois

Contact:
Steve Koppes, (773) 702-8366, s-koppes{at}uchicago.edu

Feb. 15, 2003

Once-bizarre concept of extra dimensions 
 showing hints of scientific revolution
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The concept of extra dimensions, dismissed as nonsense even by one of
its earliest proponents nearly nine decades ago, may soon help solve
seemingly unrelated problems in particle physics, cosmology and
gravitational physics, according to a panel of experts who will
assemble from 8:30 a.m. to 11:30 a.m. Feb. 15 (Saturday) at the
American Association for the Advancement of Science annual meeting in
Denver.

"It doesn't happen often that you get a confluence of ideas and
experiments that come together and it's something that obviously would 
change your whole way of looking at the universe," said one of the 
panelists, Joseph Lykken, Professor in Physics at the University of 
Chicago and a scientist at Fermi National Accelerator Laboratory.

Even though scientists lack direct evidence of extra dimensions, "we
have a number of hints from experiments and theoretical ideas that
make us think they're probably out there. That's why we're so excited
about looking for them," Lykken said.

On the theoretical side, string theory, developed over the past two
decades, requires that space-time has extra dimensions if it is to
include gravity. "It's just built into the way that string theory
works," Lykken said. 

Experiments, meanwhile, have produced the standard model of physics to 
describe the most elementary particles and the forces that hold them 
together. Physicists have come to suspect that something is missing 
from the standard model.

"There seems to be more particles and forces than we really need, and
they operate in more complicated ways than they need to," Lykken said. 
But extra dimensions may ultimately help explain these data
complications. 

"That standard model itself may be our biggest hint that there's this
world of extra dimensions," he said. 

New experiments at Fermi National Accelerator Laboratory are producing 
data that just don't fit the standard model, said Maria Spiropulu an 
Enrico Fermi Fellow at the University of Chicago. "We have things in 
the data that leave our mouths hanging," she said.

Whether extra dimensions or some other phenomenon emerges to clarify
these murky data, scientists seem certain that they stand only a few
years away from a scientific revolution.

"What's going on right now in particle physics, gravitational physics
and cosmology is like when quantum mechanics started coming together," 
Spiropulu said. Quantum mechanics, developed in the 1920s, describes 
the physics of objects at the atomic level and dominates the concepts 
of modern physics.

Spiropulu, who organized the AAAS session on the physics of extra
dimensions, spoke at the session along with scientists from Fermi
National Accelerator Laboratory, Harvard University and the
universities of Chicago and Washington.

Another panelist, Sean Carroll, Assistant Professor in Physics at the
University of Chicago, said that extra dimensions could help solve two 
mysteries in cosmology: what were the initial conditions of the
universe and what is the mysterious dark energy that is accelerating
the expansion of the universe.

The idea of an inflationary universe, one that expanded rapidly just
moments after the big bang, has gained wide acceptance among
cosmologists to explain how conditions in the early universe could be
unexpectedly different from what they later came to be. But
inflationary cosmology tells scientists nothing about the initial
conditions of the universe. This is where extra dimensions come in,
even though they might be microscopically small.

"If you had extra dimensions, then when the universe is very small at
early times, the extra dimensions weren't small compared to the rest
of the universe," Carroll said. "They must have played a big role.
What was that role? Could the role have something to do how we
perceive the initial conditions?" 

Extra dimensions may also explain dark energy. Physicists conjecture
that dark energy is governed partly by occurrences in the familiar
four dimensions and partly by occurrences in the extra dimensions,
Carroll explained. 

"There is the tantalizing possibility that a complete change of
perspective makes all of the problems collapse at once," he said.

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