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After the Big Bang, is a fatal contraction inevitable?
 By Richard Stenger for CNN.
(CNN) -- Stanford University researchers theorize that the universe could
experience a cosmic crunch in 10 billion or 20 billion years.
Recent cosmological observations have suggested that the universe will
expand at an increasingly rapid rate for at least 100 billion years and
perhaps enlarge forever.
But according to a new scientific model, the universe will slow its pace
of acceleration and then experience a fatal contraction.
"The universe may be doomed to collapse and disappear. Everything we see
now, and at a much larger distance that we cannot see, will collapse into
a point smaller than a proton," said Andrei Linde, who conducted the
research with Renata Kallosh, his wife and physics colleague at Stanford.
"The standard vision at the moment is that the universe is speeding up, so
we were surprised to find that a collapse could happen with such a short
amount of time," Linde said.
Linde is one of the pioneers of Inflation theory, an increasingly popular
revision of the proposed Big Bang.
First advanced in the 1980s, it suggests that the universe rapidly
inflated into a much larger cosmos only a fraction of a moment after it
began.
Will the universe expand forever and become cool and dark, collapse into
nothingness in a cosmic crunch, or remain in equilibrium between the
forces of gravity and expansion?
Inflationary theory predicts a "flat" universe, or one where the competing
forces pulling and contracting the universe stay balanced.
The debate, by no means settled among cosmologists, hinges on the role of
mysterious and theoretical phenomena known as dark matter and dark energy.
Throw into the mix such notions as string theory, supergravity, extra
dimensions and multiple universes, and the question becomes even more
muddled.
Yet looking at some of the best work in the field of dark energy, Linde
and Kallosh concluded it would change from a positive to a negative force.
Their cosmological model, described in related reports on www.arXiv.org, a
Web site sponsored by the National Science Foundation and Cornell
University, generated another unexpected prediction: the universe,
estimated to be about 14 billion years old, is already middle-aged.
"Physicists have known that dark energy could become negative and the
universe could collapse sometime in the distant future, perhaps a trillion
years," Linde said. "But now we see that we might be not in the beginning,
but in the middle of the life cycle of our universe."
One noted scientist had a lukewarm response to the hypothesis.
"Because their proposal is based on rather specific models and assumptions
and their is no current evidence for it, I would say it logically
possible, but not compelling," said physicist Paul Steinhardt.
The Princeton University professor helped developed an alternative
cosmological theory that proposes that the universe began by colliding
with another universe, with both existing in a higher dimensional medium.
"They are only attempting to explain the evolution of the universe between
now and the collapse, whereas we showed how this can be embedded in a
larger cyclic scenario that leads to an eternal universe," Steinhardt
said.
Linde concedes that the work is raw and that astronomy is an inexact
science at best, and known for continuous revisions. Recalling an ongoing
joke among cosmologists, the Stanford University professor quipped:
"Astrophysicists are always in error but never in doubt."

September 18, 2002.
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