A New Cosmological Theory---not the Big Bang but the Big Wreck

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Ho hum

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Instead of a big bang, a big wreck?

By Faye Flam

Philadelphia Inquirer, April 10, 2001

Two universes travel parallel to each other, each unseen by the other, like two ships in the night.

Imagine that they suddenly collide, creating a spectacular explosion and a new universe - our universe.

This new theory of the origin of our universe could be the first in 20 years to seriously rival the standard big bang, according to astronomers and physicists who first heard it at a scientific meeting last week.

Developed by cosmologists and physicists at Princeton University, the University of Pennsylvania, and Cambridge University, the new picture of creation does away with the notion - now almost scientific gospel - that all the billions of galaxies making up our universe sprang from a point smaller than an atom.

Instead, the scientists say, the big bang stemmed from a collision of two universes that had been separated by a "fifth dimension." The impact of the collision would have given the universe the matter and energy we see today.

This theory is generating waves of excitement among cosmologists because it seems consistent with current observations of the heavens and yet proposes a radically different origin.

"It's a very exciting idea," said Mario Livio, director of the Space Telescope Science Institute in Baltimore.

Though some scientists had suggested that the big bang came about as a random event, this new collision theory underscores the idea that genesis was an accident.

At this early stage, however, "the theory has to be raked over by our colleagues," said Penn physicist Burt Ovrut, one of the authors of the new theory.

Princeton astrophysicist Paul Steinhardt presented the new scenario, which he dubbed the Ekpyrotic Universe, at a meeting at the Space Telescope Science Institute. He worked out the details over the last year and a half with Penn's Ovrut, Neil Turok of Cambridge, and Princeton graduate student Justin Khoury.

Steinhardt said he took the name "Ekpyrotic" from the ancient Greek word for conflagration. "Unfortunately, the name 'big bang' was already taken," he quipped, emphasizing, however, that this new collision theory still fits into the general framework of the big bang.

The universe still starts with an explosion of sorts, and it expands outward over 15 billion years, with particles assembling themselves into atoms, and atoms into gas clouds, then galaxies and stars.

What the new theory would replace, he said, was the explanation of how the energy was generated - a key part of the old scenario, known as inflation.

Inflation said that the universe burst forth from a pinpoint, growing faster than the speed of light and generating vast amounts of matter.

Inflation also explained a number of cosmic puzzles, especially the seeming uniformity of space.

"If you go out and look into the sky, you look in one direction, then the other - the universe looks pretty much the same in all directions," said Ovrut. In the early 1980s, Massachusetts Institute of Technology physicist Alan Guth proposed that the uniformity could be explained if the universe expanded very fast from an invisibly tiny point. He named his theory "inflation," after the economic situation of the time.

"I am absolutely thrilled by the mere fact that an alternative to inflation is being suggested," Livio said.

"We'd like to have a backup - a worthy competitor - something in our back pocket in case inflation doesn't work out," said Michael Turner, a cosmologist from the University of Chicago.

Steinhardt, while one of the founders of inflation, wanted to offer another explanation.

To find it, the fast-talking cosmologist looked to a new theory in physics called superstrings, which details the ultimate structure of matter.

He and Turok started mulling over the origin of the universe with superstring theorists, including Penn's Ovrut.

Ovrut - who unlike Steinhardt speaks with non-physicists at half-speed, emphasizing each sentence as though trying to give directions to someone who doesn't speak English - said the team owes its fifth-dimension picture to others, especially Petr Horava of Rutgers University and Ed Witten of the Institute for Advanced Study in Princeton, who five years ago reformulated superstring theory, and, in doing so, changed the vision of the universe.

In Witten and Horava's new physics, our three-dimensional universe (four, counting time) is embedded in a five-dimensional space. Since even these scientists can't visualize a fifth dimension, they think in terms of a two-dimensional analogy, describing the universe as a membrane, or sheet of paper floating in the air.

Out in that wider world of five-dimensional space, other parallel universes can drift, like other sheets of paper lofted in a breeze. The physicists have come to call such parallel worlds membranes, or "branes" for short.

"This is a springboard for our scenario," said Steinhardt.

You start by thinking of our universe as a "brane" floating among other branes. The next step was to consider what would happen if two of these branes slammed together. The branes could be universes like ours, full of matter. But in the simplest possible scenario, they could also contain nothing but empty space - they'd have a kind of tension, said Steinhardt, that could still release energy in a crash.

Steinhardt and his colleagues found that a collision of worlds could create a burst of energy - a big bang - that would lead to particles and light, expanding outward. Rarified areas would become patches of space and denser areas would later congeal into stars and galaxies. In other words, our universe.

No longer does the universe have to start out as an infinitely dense point. "In this scenario, the universe was large when it was created," said Ovrut.

It remains to be seen whether other scientists will shoot the idea down. The team submitted its theory to the journal Physical Review D, though it has not been accepted yet. A version of its paper appeared on an electronic bulletin board on March 30, too recent for other scientists to have spotted any fatal flaws.

But the part of the theory that, to the layman, may seem most farfetched - the notion of an extended fifth dimension of space - has been thoroughly reviewed by the physics community since it was proposed by Witten and Horava about six years ago.

"This is not some flight of fancy," said Ovrut. "This is a question of very deep mathematical consistency."

One reason it's been so hard for competing theories of the origin of the universe to survive is they must be able to conform to a number of high-precision measurements of the structure of the universe.

With such instruments as the Hubble Space Telescope, astronomers have recently measured the patterns made by galaxies across the sky, the exact motions of these galaxies, and the precise mixture of chemical elements in the universe. They've also sampled what they believe is the leftover light from the big bang, now a pervasive microwave hum. This so-called cosmic microwave background is being scrutinized in detail.

"There are so many observations that it's now hard to come up with a new idea that even gets out of the gate," said Turner of the University of Chicago.

Steinhardt and Ovrut don't look at their new idea as a better theory than inflation, only as an alternative whose relative merit will be determined by future observations, particularly the patterns seen in the cosmic microwaves.

If they're right that a collision started our universe, could another brane come out of the fifth dimension and destroy us? It's possible, said Steinhardt. He said in researching the name Ekpyrotic, he found that the Greeks had a theory in which the universe began from a huge fireball and cooled down. "But every now and then the process repeats itself."



-- Lars (larsguy@yahoo.com), April 10, 2001

Answers

Just what we need---more cosmetology.

-- (nemesis@awol.com), April 11, 2001.

Lars,

You'll have to watch how this one plays out. It's easy to make a proposal, much, MUCH more difficult to get it accepted by the community at large.

Even though I'm just a lowly layman, the first question that comes to my mind is, how in the world can they prove this (or, in scientific terms, what test could they possibly arrange for this to disprove it)?

The second is, what happened to the principle of Economy? The simplest theory which fits the observations is to be preferred. (This is one of the biggest problems facing Intelligent Design adherents, by the way, so I'm quite aware of it.[g])

Back in 1998, Andre Linde came up with a similar idea that got all sorts of press. The idea was that there was a master "Mother" universe that "spawned" zillions of other, smaller universes -- ours being just one of them. The same two questions I just asked were what killed his proposal: it couldn't be proven (or falsified, in scientific thinking) and it there were other, simpler explanations that would work just as well.

Do not miss for a moment, either, the PHILOSOPHICAL reason for these alternative proposals: those scientists who choose to reject any idea of a Creator very much despise the Big Bang, with its implied beginning and uniqueness for this universe.

I've been following this closely since 1992, and I can't tell you how many alternatives have been proposed (from plasma models to you name it), only to ultimately be rejected, if not for outright bad science (as was the case with the plasma model from Lerner), under the two principles just mentioned: falsifiabilty and economy.

I can even nitpick this particular proposal. When did the collision occur? How big were the two universes at the time? Why would such a collision spawn a Big Bang, instead of a co-mingling of realms (analogous to what we see when galaxies collide). That this universe began as a small point had been verified by countless experiments, most notably the COBE satellites that measured the cosmic background radiation -- the leftover "noise" from the initial Bang.

As I've told Flint over at my place, you can certainly BELIEVE something like this; I'm not saying you can't. But the operative word is BELIEF.

It is not SCIENCE, and I predict that this proposal will soon die a well-deserved death, same as Lerner's, Linde's, and all the others.

-- Stephen M. Poole (smpoole7@bellsouth.net), April 11, 2001.


One other thought. This article also demonstrates how difficult it is for the media to get things like this straight (which is one reason why Linde got as much press as he did, as did Hawking's "No Boundaries" proposal, even though it was savaged in the literature by his peers).

String theory has actually been around for several years (here's an interesting link: String Theory People). If it pans out, it will address the mathematical problems associated with trying to work with a singularity.

The basic idea is, the Big Bang began as a tiny point, consisting of 6-20 dimensions, filled with energy "strings." As the universe began expanding, all of the excess dimensions folded in on themselves, leaving the 4 dimensions that we're familiar with (height, depth, width and time). THAT much the article got (sortof) right.

String theory could also "unify" all the forces and elemental particles, because it postulates that all of them are just different "energies" (or "states" or "resonances" or whatever) of a given string.

And that's as far as I can explain, because I see the water rising over my head. :)

-- Stephen M. Poole (smpoole7@bellsouth.net), April 12, 2001.


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