From: LARRY KLAES (ljk4_at_msn.com)
Date: Fri Oct 10 2003 - 06:54:27 PDT
Cosmic Soccer Ball? Theory Already Takes Sharp Kicks
October 9, 2003
By DENNIS OVERBYE
In an unusual logjam of contradictory claims, a
revolutionary new model of the universe, as a soccer ball,
arrives on astronomers' desks this morning at least
slightly deflated.
In a paper being published today in the journal Nature, Dr.
Jeffrey Weeks, an independent mathematician in Canton,
N.Y., and his colleagues suggest, based on analysis of maps
of the Big Bang, that space is a kind of 12-sided hall of
mirrors, in which the illusion of infinity is created by
looking out and seeing multiple copies of the same stars.
If the model is correct, Dr. Weeks said, it would rule out
a popular theory of the Big Bang that asserts that our own
observable universe is just a bubble among others in a
realm of vastly larger extent. "It means we can just about
see the whole universe now," Dr. Weeks said.
But other astronomers, including a group led by Dr. David
Spergel of Princeton, said a continuing analysis of the
same data had probably already ruled out the soccer ball
universe. They promised to post their results soon on the
physics Web site arXiv.org/list/astro-ph.
"Weeks and friends are making a dramatic claim, perhaps one
of the biggest science stories of the century," said Dr.
Neil Cornish, a physicist at Montana State University, "but
extraordinary claims require extraordinary support."
For now, the two groups, who have been in intense
communication the last few days, disagree on whether the
soccer ball universe has been refuted. What is amazing
about this debate, they all agree, is that it will actually
be settled soon, underscoring the power of modern data to
resolve issues that were once considered almost
metaphysical.
"This is what got Giordano Bruno burned at the stake," said
Dr. Max Tegmark, a cosmologist at the University of
Pennsylvania. "Is space infinite or not?"
In Nature, Dr. Weeks and his colleagues write: "Since
antiquity, humans have wondered whether our universe is
finite or infinite. Now, after more than two millennia of
speculation, observational data might finally settle this
ancient question." The other authors are Dr. Jean-Pierre
Luminet of Paris Observatory; Dr. Alain Riazueleo of the
French atomic energy center CEA, in Saclay, France; Dr.
Roland Lehoucq of the Paris Observatory and CEA; and Dr.
Jean-Phillippe Uzan of the University of Paris.
The evidence for and against a finite universe resides in a
radio map of the baby universe produced last February by a
NASA satellite, the Wilkinson Microwave Anisotropy Probe.
It shows that 400,000 years after the Big Bang, the event
in which space and time emerged, the universe was laced
with faint waves and ripples, which are the origin of
modern galaxies and other cosmic structures. In an infinite
universe, according to theory, waves of all size should
appear in the sky, but in the Wilkinson data there was a
cutoff: no waves larger than about 60 degrees across
appeared in the sky.
If the universe were a musical instrument, it would be
inexplicably missing its low notes, perhaps, some
cosmologists have suggested, because it is too small to
play them. The universe is finite rather than infinite,
they speculate. Like a violin that cannot produce deep
cello notes, the universe cannot produce waves larger than
itself.
In such a universe, if you went far enough in one
direction, you would find yourself back where you started,
on the other side of the universe, like a cursor
disappearing off the left side of a screen and reappearing
on the right.
One simple example of this is a torus, or a bagel shape,
which is what you get when you wrap the left and right and
top and bottom sides of the screen around so that they
meet.
In the Nature paper, Dr. Weeks and his colleagues propose
that three-dimensional space has 12 sides, like a soccer
ball, or more technically a dodecahedron. This model would
fit with the cutoff of large waves observed in the
Wilkinson satellite data. Each face is "glued" to its
opposite number. (Don't try this at home.) A spaceship
crossing one face or panel of the soccer ball would enter
the other side of the ball. After traveling 74 billion
light-years it would find itself back where it had started.
While the lack of cosmic low notes is suggestive,
cosmologists say there is a definitive test of finite
universes in the Wilkinson map. When the cosmic radiation
intersects the edges of the universe, it would make
identical circles, like a balloon squashed in a box, on
opposite sides of the sky. In the case of a bagel, there
would be two circles in the map, on opposite sides of the
sky. In the case of Dr. Weeks's dodecahedron, there would
be six pairs of circles, each about 35 degrees in diameter.
"This is a much higher bar to clear," Dr. Cornish said.
Dr. Tegmark said: "What's nice is it's so testable. It's
the truth or it's dead. The data is even out there, on the
Internet. It's just a question of sifting through it."
But so far the circles have not showed up.
Earlier this
year, Dr. Tegmark and his wife and colleague Dr. Angelica
Oliveira-Costa, Dr. Mattias Zaldarriago, of Harvard, and
Dr. Andrew Hamilton of the University of Colorado, searched
the Wilkinson data for oppositely matched circles. The
results, they said, ruled out the possibility that the
universe was shaped like a bagel, no doubt disappointing
New Yorkers who would like to have imagined a cosmic
connection with their breakfast.
Dr. Tegmark said that the results also ruled out Dr.
Weeks's dodecahedron. "We ought to have seen those circles
in our study," he said.
Meanwhile, a more thorough analysis of the data, looking
for all possible circles, has been undertaken by Dr.
Spergel, who was part of the original Wilkinson team, Dr.
Cornish, and Dr. Glenn Starkman of Case Western Reserve
University in Cleveland. The study, about two-thirds
complete, had already eliminated many simple models of
so-called "small universes," including a dodecahedron when
the Nature paper hit their desks last week, Dr. Spergel
said.
"No soccer ball, no doughnuts, no bagels," he said.
But Dr. Weeks said there were potential gaps in the circle
search methods. For one thing, if the dodecahedron were
slightly larger, he said, the circles would be smaller and
would not show up in Dr. Spergel's search. But until all
the papers are posted on the archive or published where
everybody can read them, these claims cannot be evaluated.
Dr. Weeks said that astronomers from both teams would join
this fall to test the circle search, using simulated data.
If the models are false, they could be ruled out as early
as November, he said.
Dr. Cornish said that, although it was the scientific
community that would ultimately decide, his team was
confident of its results. "I don't see any wiggle room," he
said.
But because it is such a "truly spectacular claim," he
said, they are planning in the next few days to run a
special test focused on the particular model. The test
could detect very small circles. "We can push it to where
there's no chance," Dr. Cornish said.
The prospects for the finite universe, he added, look
bleak.
The stakes for cosmology, should the soccer ball or some
other variety of small universe prevail, are not small at
all. A small universe, everybody agrees, would present
severe problems for the prevailing theory of the Big Bang,
known as inflation, which posits that the cosmos underwent
a burst of hyperexpansion in its first moments.
Moreover, Dr. Weeks said, a small universe would eliminate
one popular variant of the theory known as eternal
inflation, in which bubble universes give rise to one
another endlessly in what some cosmologists call a
"multiverse."
"This puts the whole universe in view," he explained. "It
wouldn't rule out other universes. There could be others.
They would be totally unrelated, without any contact
between them."
http://www.nytimes.com/2003/10/09/science/09COSM.html?ex=1066793500&ei=1&en=4b4341247d8d7038
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