Siobhan Roberts, "A cosmic crisis" (2004)

A cosmic crisis

Does the universe look like a soccer ball? Or is it flat and infinite in  size? If we don't find out soon, we may never know. SIOBHAN ROBERTS  reports on the latest hypothesis

 By SIOBHAN ROBERTS
"Globe and Mail"

 POSTED AT 8:57 AM EDT Saturday, Jul 10, 2004

 It used to be that, once a decade or so, scientists asked, ''What is the  shape of the universe?'' A hypothesis would arise — for example, that the  universe was flat and infinite — followed by a spurt of research, and that  was enough to last us a while on the space-time odometer.

 Since the early 1990s, however, cosmology is where much of the exciting  science has been happening. "We've been looking for the shape of the  universe like Columbus did the shape of the Earth," says Glenn Starkman,  an astrophysicist currently based at the Conseil Européen pour la  recherche nucléaire (CERN) in Geneva  — the home of the world's largest  particle physics laboratory and essentially the centre of the universe for  determining the content of the cosmos when it was a trillionth of a second  old.

But Dr. Starkman, having cut his teeth at the Canadian Institute for  Theoretical Astrophysics at the University of Toronto, is more concerned  with the large-scale properties of the universe. He focuses his research  on the general topology and shape of the cosmos (his regular gig is as a  professor at Case Western Reserve University in Cleveland).

The "crisis" in cosmology these days, according to Dr. Starkman, speaking  only somewhat with tongue in cheek, is that time is running out. "If we don't figure out the shape of the universe soon," he says, "the universe  will hide this secret from us forever."

This is because the research depends on data salvaged from the microwave  background, the echoes of the Big Bang that created the universe in the  first place.

And as Dr. Starkman explains, "Today, the place from which the echoes come  to us is moving away from us faster than the speed of light, which means  we can't receive light from that place any more  — we can no longer see or  learn about that place, never mind any farther away.

"We have enough data now to be able to determine the shape of the universe  if the shortest distance around the universe is less than the distance  across the microwave sphere of the Big Bang. But we do not have enough  data if the universe is any bigger," he says, getting a tad more  technical.

Max Tegmark, an astrophysicist and professor at the University of  Pennsylvania, likens it to trying to figure out the shape of the Earth if  you're not able to see beyond the walls of your bedroom. "Nature has a  censorship where we can only see so far," Dr. Tegmark says. "We can't see  anything from farther than 14 billion light-years. This limits us in what  we can see and what data we can gather."

"The only way we'll have enough data," Dr. Starkman says, "is if the  universe stops behaving as it is now. It might stop its accelerated  expansion, but probably not for many billion years, which doesn't help us  much."

Aside from finding a solution to this problem — what to do when we can no  longer receive the data — Dr. Starkman is also involved in testing the  latest prediction for the shape of the universe (based on that microwave  information).

It was put forth by four Parisian cosmologists and one American  "freelance" geometer (the spokesman for the group), Jeff Weeks from  Canton, N.Y. Dr. Weeks, a 1999 recipient of the MacArthur Fellowship,  known as the "genius prize," and his team proposed that the universe is in  the shape of a 12-sided figure called a dodecahedron.

Greek philosopher Plato guessed nearly 2,400 years ago that the universe  was structured like a dodecahedron.

The Greeks had recently discovered that there were only five regular  polyhedra: the cube, octahedron, tetrahedron, icosahedron and  dodecahedron. Plato, who believed that the properties of matter could best  be understood in terms of mathematical symmetries, assigned the first four  solids to the elements earth, air, fire and water, respectively, and then  proclaimed that the dodecahedron was the shape of the cosmos itself.

Also in ancient Greece, using bare-hands science and the power of their  imaginations, philosophers Leucippus and Democritus had differing ideas;  they envisaged an infinite universe.

Aristotle thought that it was a finite ball, with the Earth at the centre.  His view prevailed and went mostly unchallenged in Western society for  almost 2,000 years, until the invention of the telescope by Galileo in  1608.

In 1917, when Albert Einstein applied his geometrical theory of relativity  to the questions of cosmology, he recycled a three-sphere scenario  previously posited by German mathematician Bernhard Riemann.

All hypotheses, dating from ancient times to today, remain contentious.  But technological advances over the past decade have increased our chances  of actually finding an answer to this age-old question — that is, of  course, if we manage it in time.

Currently, there are three models considered contenders: a spherical  universe, a hyperbolic saddle-shaped universe and the standard and most  widely accepted model, a flat universe, expanding infinitely under the  pressure of an ominous and as yet inexplicable "dark energy."

Things looked hopeful for the dodecahedron hypothesis when its  computer-generated model was compared to reality — that is, the data from  NASA's Wilkinson Microwave Anisotropy Probe. The WMAP was sent to map the  cosmic echo of the Big Bang and provide information about its early  history and scale.

One particularly useful indicator of universe topology is the temperature  fluctuations of radiation emanating from the originating bang. 

Cosmology 101

 There are three main possibilities for the shape of the universe

Sphere
A spherical universe has positive curvature: It is finite in size, but  without boundaries, like a balloon.
 In a so-called closed universe, you could, in principle, fly a spaceship  in one direction and eventually get back to where you started from. A closed universe is also closed in time: It eventually stops expanding,  then contracts in a "Big Crunch." In such a universe, parallel lines eventually converge (e.g. longitudinal 
lines are parallel at the equator, but converge at the poles) and large  triangles have more than 180 degrees.

 Flat
 You can imagine this kind of universe by cutting out a piece of balloon  material and stretching it with your hands. The surface of the material is  flat, not curved, but you can expand and contract it by tugging on either  end. A flat universe is infinite in size, and has no boundaries.  In such a universe, parallel lines are always parallel and triangles  always have 180 degrees.  A flat universe expands forever, but the expansion rate approaches zero.

 Saddle
 Such a universe has negative curvature: It is infinite and unbounded.  In a so-called open universe, parallel lines eventually diverge, and  triangles have less than 180 degrees. An open universe expands forever, with the expansion rate never  approaching zero.

Staff

In an article in Nature magazine, Dr. Weeks and the other members of his  team — Jean-Pierre Luminet of the Paris Observatory, Roland Lehoucq of the  Paris Observatory and CEA/Saclay (Atomic Energy Research Centre), Alain  Riazuelo of CEA/Saclay and Jean-Philippe Uzan of the University of Paris —  explained these fluctuations by comparing them with the sound waves of  musical harmonics.

"A musical note is the sum of a fundamental, a second harmonic, a third  harmonic, and so on," the group's article said. "The relative strengths of  the harmonics — the note's spectrum — determines the tone quality,  distinguishing, say, a sustained middle C played on a flute from the same  note played on a clarinet.

"Analogously, the temperature map on the microwave sky is the sum of  spherical harmonics. The relative strength of the harmonics — the power  spectrum — is a signature of the physics and geometry of the universe."

When the WMAP data arrived in February, 2003, it confirmed the popular  infinite-flat model of the universe, but only in part. All the small and  medium-sized temperature waves were present as predicted, but the model's  broad wavelengths, which would have to exist in such a large and infinite  universe, were much weaker than expected.

One explanation, Dr. Weeks says, is that space simply isn't that big and  thus could never produce such strong large waves in the first place. "A  violin is never going to play the low notes of a cello because a violin's  strings aren't long enough to support such a long sound wave," he says.  "It's the same with the universe. Its waves cannot be larger than space  itself."

However, the behaviour Dr. Weeks predicted for a dodecahedral universe  matched all the WMAP data. The model, nonetheless, is still in limbo.

It is being subjected, by Dr. Starkman and an international medley of  cosmologists, to a "circles-in-the-sky test (the rest of the team is Neil  Cornish, an Australian currently at Montana State but who did his PhD at  the University of Toronto, David Spergel at Princeton University and  Eiichiro Komatsu at the University of Texas at Austin).

If the dodecahedron model is correct, a computer-coded search should be  able to detect six pairs of matching circles across the cosmic horizon —  echoes from the Big Bang vibrating against the 12 faces of the  dodecahedron universe.

"As much as I love the dodecahedron model," Dr. Tegmark says, "I'm not  putting my money on it. Don't get me wrong, I don't have a bias against  the dodecahedron. It's a beautiful idea, it's the cutest Platonic solid —  the cube and the octahedron are a little more pedestrian.

"The most amazing thing of all is that we humans can address these  questions in a scientific way; that these philosophical questions — like,  Is space infinite? -- have become scientific questions."

Though, the end result of these philosophical questions that now have  scientific answers — the so-what? factor — is still philosophical. That  is, the answers mainly just serve to satisfy the age-old and innate human  curiosity, our egocentric pondering about our local place in universal  scheme of existence. There is always the chance, of course, that the  scientific answers will lead to more scientific questions, and then  potentially more answers, but these subsequent questions and answers are  in areas of science that are essentially unfathomable before we find the  initial answers.

Unfortunately, the scientific data does not seem to be there supporting  the dodecahedron, and thus, it has not yet been accepted as an answer. So  far, for example, Dr. Starkman and the team have found no circles (they  calculate that the universe can be no smaller than 78 billion light-years  across, while the dodecahedron idea means the universe measures just 60  billion light-years).

"And it's not just that we haven't found any circles yet," Dr. Starkman  says. "It's that we've looked, and shown that the circles that should be  there — if the universe is a dodecahedron of the size that Weeks and  company said it was — are definitively not there. And they are not hiding  behind the galaxy."

But Dr. Weeks and his team are holding out hope. They speculate that one  explanation for the missing circles is galactic contamination — dust and  hot electrons getting in the way of the WMAP data.

His team is also exploring other options, such as the possibility of a  universe that is finite in some directions and infinite in others. "We  don't want to ignore other possibilities," Dr. Weeks says. "But  personally, I'm not quite ready to declare the circles missing."

One last-ditch possibility, according to a more recent discovery that Dr.  Starkman is involved with (with another international cluster of  cosmologists), is that there is something odd going on, perhaps a  miscalculation, with the WMAP microwave data and its analysis.

The anomaly was that those weaker-than-expected broad-scale fluctuations  on the microwave sky align with themselves in strange ways, and — still  more outrageously — they seem to align with the ecliptic plane, or the  plane of the solar system. This just shouldn't be. What goes on in deep  space and the distant past should not be affected by the path the planets  follow around the sun.

"It's a mystery," Dr. Starkman says. "There seems to be something, I  hesitate to say wrong, but very odd about what's been measured, which if  it is a reflection of the universe, is inconsistent with our present  understanding."

He stumbled upon this anomaly when he was trying to figure out a way to  determine the shape of the universe if it is too big for circles to be  seen.

Which seems to indicate that while the shape of the universe may or may  not be finite and dodecahedral, the search for the shape of the universe  is most definitely circuitous, the astrophysicist chasing our cosmic tail  to infinity.

Siobhan Roberts is a freelance writer based in Toronto.

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