Friday, February 23, 2007

I Don't Know Why I Go To Extremes

Early reports are that researchers at the University of North Carolina at Chapel Hill have managed to reconcile an intriguing theory with unpleasant reality:

The theory claims to reconcile the notion of a cyclic universe, which expands and contracts for eternity, with the second law of thermodynamics, which seems to imply that the current expansion cannot reverse.

Aum shanti padme hum, I suppose. While it's comforting to think of this old world of ours spinning on forever, and certainly some people find it preferable to a Big Rip or a great final cosmic unraveling, there's no more direct evidence for Rips, cycles, Dark Energy or any of the rest of it than there is for the Flying Spaghetti Monster. We're merely groping for explanations to fill the gaps in our knowledge.

Baum and Frampton's model universe is powered by 'phantom energy' — a hypothetical form of the dark energy that is speeding up the Universe's expansion.

For more rampant if interesting speculation, see The Ultimate Fate of the Universe.


Blogger Mister Spark said...

Published online: 23 February 2007; | doi:10.1038/news070219-4
Universe bounces back from the brink
Cycling cosmos obeys thermodynamics without ripping itself apart.

Philip Ball

It has to be the closest ever shave. Two physicists have proposed that, a fraction of a second before a cataclysm that would destroy space-time itself, the Universe may escape by abruptly collapsing to a virtually empty state that 'resets' it for a fresh cycle of cosmic expansion.

The theory claims to reconcile the notion of a cyclic universe, which expands and contracts for eternity, with the second law of thermodynamics, which seems to imply that the current expansion cannot reverse.

As escape clauses go, this one is jaw-droppingly extravagant. Not only does the turnaround happen less than a thousand-trillion-trillionth (10-27) of a second before a 'Big Rip' in which everything falls apart, but it splits our Universe into countless new and independent ones.

And as the Universe has already gone through an infinite number of cycles, the model predicts an already infinite number of parallel universes, Lauris Baum and Paul Frampton of the University of North Carolina at Chapel Hill report in Physical Review Letters1.

What goes around

Why go to such extremes, rather than just assume that our Universe was produced in a one-off Big Bang that will make it expand for ever? Because, says Frampton, if you work backwards to the Big Bang using standard physics, the equations eventually stop making sense. "The model doesn't work," he says.

In a cyclic universe, says Frampton, physics need not break down.

But a 'bouncing' universe seems to conflict with one of the most fundamental physical principles, the second law of thermodynamics. This states that the entropy of the Universe — a kind of measure of its disorder — must increase. How can you reverse cosmic expansion without reversing this?

Another problem is that most cyclic models show the cycles getting shorter and shorter the further back you go, until you end up with the Big Bang that you set out to avoid.

Baum and Frampton's model universe is powered by 'phantom energy' — a hypothetical form of the dark energy that is speeding up the Universe's expansion.

As the Universe expands, phantom energy increasingly dominates the attractive forces of nature, such as gravity and electromagnetism. Galaxies will drift apart, then stars and planets will disintegrate, then atoms and subatomic particles. Finally, space itself is rent in a Big Rip (see 'Universe can surf the Big Rip'). At this point, says Frampton, "time will stop".

But Baum and Frampton say that a cyclic phantom-energy universe is rescued in the nick of time — without violating the second law.

In their model, the Universe expands to the brink of the Big Rip, when all atoms have disintegrated. At this stage, Frampton says, each atom will have expanded to about the size of the present visible Universe.

So even though the whole Universe has plenty of entropy, a chunk of this empty space has virtually zero entropy: expansion has diluted it almost infinitely.

At this point, the Universe will be a mosaic of causally unconnected patches — expansion will outpace the speed of light, preventing signals travelling between the patches.

In Baum and Frampton's model, 10-27 seconds or less before the Big Rip, everything contracts. The researchers essentially put such a contraction into their model 'by hand', although Frampton says that there are various theoretical reasons why it might occur.

The contraction generates lots of little separate universes from the mosaic of isolated patches. Each has plenty of energy, both dark and ordinary, but no matter and no entropy.

This sudden deflation is followed by rapid inflation, as is thought to have happened in the first instants of the Big Bang, vastly increasing each new universe's size in a fraction of a second.

So if the idea is right, we and everything we can see came from a patch of space lodged somewhere between two subatomic particles in a previous universe — and so on ad infinitum.

Baum and Frampton's is not the only cyclic universe in town. Last year Paul Steinhardt of Princeton University, New Jersey, and Neil Turok at the University of Cambridge, UK, showed that a cyclic model could explain why our Universe seems so 'fine-tuned' to make stars and galaxies - and therefore us2 (see 'Cyclic universe could explain cosmic balancing act').

In Steinhardt and Turok's cyclic universe, dark energy is something other than the destructive phantom energy. Frampton hopes that measurements of the cosmic microwave background radiation — the afterglow of the early Universe — made by the Planck satellite, due to be launched in 2008 by the European Space Agency, will reveal the identity of dark energy.

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Blogger Mister Spark said...

Science Friday: Long Live the Big Rip!
by DarkSyde
Fri Jan 27, 2006 at 04:01:40 AM PST
Rainbows are exquisite apparitions. Hanging immobile on a canvas of turbulent sky, as if an artistic Titan had swung an arc with a hand full of pastel brushes. On an exceptional day, bright and crisp after a heavy rainstorm, one can occasionally observe a magnificent double rainbow, the colors in each arch inverted, nested one on top of the other, suspended cartoon-like high above a glistening landscape. It is a sight to behold.

The old story goes that he who follows the rainbow to the end will find a pot of gold. It is but a legend of course, there is no end to find. Rainbows we now know are an artifact of optics; they're a naturally produced spectra of sunlight, created via millions of raindrop prisms. But spectre is also Latin for ghost. Fittingly then, in the last few months, hidden in the electromagnetic spectra of the most distant and violent stellar objects known, comes a whispered cosmic warning of a growing phantom menace: And the consequences, for stars, planets, and any creatures like ourselves, could be ghastly indeed.

[DR Sean Carroll; Cosmic Variance] This month's provocative results raise an interesting issue: what can we say about our universe's ultimate fate? In the old days (like when I was in grad school) we were told a story that was simple, compelling, and wrong. [But if the new data is accurate] ... all hell breaks loose

Houston we have a BIG problem. There may be something seriously wrong with the Universe: It's going to explode! Images Below

* ::

Just a couple of decades ago, many of the deepest mysteries of space and time were wrapped in a pretty box called the Inflationary Big Bang Model, itself a product of studying those spectral rainbows from distant galaxies. The Big Bang explained why our cosmos is expanding; the Inflationary part covered, among other items, how ripples of matter and energy could arise early on in the infant universe to form the first galaxies and stars. The looming question remaining in cosmology was exactly how fast the universe was growing in size and whether it will end in fire or ice.

In the old paradigm, if the mass of the universe is below a critical magnitude, it will keep growing forever. Our cosmos will end in the Big Freeze: A perpetual state of utter black emptiness and cold. The background temperature will asymptote to absolute zero and such will be the fate of the cosmos to the grim end of time. If it's above that critical mass, one day it will stop expanding and slowly begin to contract. It will grow hotter and denser until the pressure and temperature are unimaginable: The Big Crunch.

The history of our universe in slices of time. Left courtesy Wikipedia: A few fractions of a second after the Big Bang Singularity, the nascent universe undergoes the process of Inflation and then cools until it is transparent to light, eventually assuming its familiar appearance. If the universe continues to expand, it will eventually cool to absolute zero, the stars will finally burn out, and our cosmos will turn black as pitch forever. If the universe stops expanding and then collapses, it will roughly reverse the sequence of events above and end in the Big Crunch. Right courtesy NASA/JPL: The earliest image of the universe captured from the COsmic Background Explorer or COBE, the different colors are precursors to the very first proto-galaxies

But in the 1990s a more precise method of measuring the distance and velocity of galaxies was developed using the husks of once mighty stars as a stellar candle. And when those quantities were calculated for a number of galaxies, cosmologists were in for a big surprise. The universe was expanding alright, but it wasn't slowing down at all; in fact it may be speeding up!

The phenomena was dubbed Dark Energy. Another, even more stunning revelation was soon unveiled, this heretofore unsuspected force accounts for over 2/3 of the mass of the entire universe! What we think of as 'the cosmos', i.e. stars, planets, dust, protons, electrons, light, gravity, and heat, is nothing but a light froth, a mere afterthought of visible substances bubbling on the surface of a deep ocean of invisible Dark Energy.

Now using the brightest, most energetic stellar explosions known, called Silicon Star Hypernova AKA Gamma Ray Bursters, to further measure the rate of change in Dark Energy, cosmologists have found tentative evidence this strange repulsive force is increasing over time. And that's where it gets spooky: At present, this bizarre sort of antigravity works only over vast distances, hundreds of millions of light years or more. But if the mysterious force is increasing, it will become effective over shorter and shorter distances in the future.

Exponential growth is an inexorable process. No matter how humble the beginnings, a phenomenon that is growing exponentially will, sooner or later, reach for infinity. EG: Double a penny once a month and in a few years, you'll be a millionaire. What if Dark Energy is growing slowly, imperceptibly, but relentlessly in this manner?

In that case, over the next fifteen billion years, the galaxies will be pushed apart faster and faster, in fact that's already happening. But as the strange force of repulsion grows in magnitude, individual galaxies will begin to be affected. In the last few millions of years before the final cosmic apocalypse, stars in the outer reaches will begin drifting away from their parent galaxy. Then the gravitational glue holding the galaxies together will fail, whole spirals and elliptical conglomerations will come apart, each of the billions of stars within accelerating away from one another. The effect will build and build and build ... Eventually, the phantom force will over come the pull of stars on their own planets. The earth along with the rest of the solar system will decouple from the sun and each will go their separate ways. And it won't stop there!

Image hosting by Photobucket

The top red curve indicates a universe in which Dark Energy is causing the expansion of the universe to accelerate. There is growing evidence that our universe is following the red curve. For more detail see Cosmic Variance. Diagram courtesy of NASA

Dark Energy will keep growing; first stars and then planets will flatten like spinning pancakes and begin to throw off layer after layer of material. In the final year, the earth unravels in a high speed version of its original formation from space rocks, dust, and gas. Then the rocks, the individual dust grains, the larger molecules of gas, are sheared by the relentless, growing force. In the last few seconds, the very atoms are ripped asunder, the nuclei cut and cut again, reduced to lighter and lighter elements. Individual protons and neutrons are rendered into their constituent quarks and gluons. Perhaps the strings theorized to form the basis of all particles are then stretched and broken, photons, electrons, even theoretical gravitons, are destroyed.

Of particular interest is what might happen to Black Holes. When space is expanding considerably faster than the speed of light, General Relativistic solutions for all kinds of Black Holes are broken.

How long? Based on some estimates of the rate of growth in Dark Energy, in about 20 billion years the universe will be riven to quantum bits and beyond. It's not just matter which will be destroyed: The fabric of space-time itself will be shattered, liberating hitherto unheard of energies whisked away in the escalating, superluminal explosion! The universe would be shredded, not even empty space as we know it would remain: It will be violent, it will be glorious; it will be The End.

And maybe the beginning of a whole new era, one completely alien to our familiar cosmos of matter and energy, space and time. Or maybe it means the end of everything that ever was for all eternity.

If the universe is accelerating, in 20 billion years the fabric of space time may be torn into shards. There would be nothing left, not even empty space. Illustration used with permission, copyright © 1998-2006 Lynette Cook, all rights reserved. Check out more of Lynette's space artwork here, lots of exosolar planets and SETI art. Well worth the look!

What is Dark Energy? An aberration of observational techniques? A Cosmological Constant or a property of space-time, or something entirely new? Could the phantom force be a temporary phase, similar to the initial Cosmic Inflation theorized to have arisen and vanished in the first seconds after the Big Bang? Or is it an unstoppable, growing process? Cosmologists simply don't know the answers at this time.

But it does seem clear that the discovery of evolving Dark Energy, if confirmed, will rank as the most important find in cosmology since Edwin Hubble first measured the Universal Expansion almost eighty years ago. Research into this phenomenon could well lend as much insight into the fundamental physics of our cosmos as when Newton was conked on the head by an apple.

For now, this intriguing and disturbing hypothesis of complete, universal destruction looks like something worth exploring further. And if it holds up, the Big Freeze is comatose, the Big Crunch is dead: Long live The Big Rip!

8:44 PM  
Blogger Mister Spark said...

The Big Rip: New Theory Ends Universe by Shredding Everything
By Robert Roy Britt
Senior Science Writer
posted: 12:04 pm ET
06 March 2003

A rather harrowing new theory about the death of the universe paints a picture of "phantom energy" ripping apart galaxies, stars, planets and eventually every speck of matter in a fantastical end to time.

Scientifically it is just about the most repulsive notion ever conceived.

The speculative but serious cosmology is described as a "pretty fantastic possibility" even by its lead author, Robert Caldwell of Dartmouth University. It explains one possible outcome for solid astronomical observations made in the late 1990s -- that the universe is expanding at an ever-increasing pace, and that something unknown is vacuuming everything outward.

The question Caldwell and his colleagues posed is, what would happen if the rate of acceleration increased?

Their answer is that the eventual, phenomenal pace would overwhelm the normal, trusted effects of gravity right down to the local level. Even the nuclear forces that bind things in the subatomic world will cease to be effective.

"The expansion becomes so fast that it literally rips apart all bound objects," Caldwell explained in a telephone interview. "It rips apart clusters of galaxies. It rips apart stars. It rips apart planets and solar systems. And it eventually rips apart all matter."

He calls it, as you might guess, the Big Rip.

The standard view

Driving the known acceleration of the universe's expansion is a mysterious thing is called dark energy, thought of by scientists as anti-gravity working over large distances.

Conventional wisdom holds that the acceleration will proceed at a constant rate, akin to a car that moves 10 mph faster with each mile traveled. With nothing to cap the acceleration, all galaxies will eventually recede from one another at the speed of light, leaving each galaxy alone in a cold, dark universe within 100 billion years. We would not be able to see any galaxies outside our Milky Way, even with the most powerful telescopes.

That's the conventional view, remarkable as it sounds.

The Big Rip theory has dark energy's prowess increasing with time, until it's an out-of-control phantom energy. Think of our car accelerating an additional 10 mph every half mile, then every hundred yards, then every foot.

Before long, the bumpers are bound to fly off. Sooner or later, our hypothetical engine will come apart, regardless of how much we spend on motor oil.

Countdown to demise

Other theorists who have reviewed the Big Rip theory are not yet sold on the idea. Meanwhile, Caldwell's team has provided a precise countdown to total demise. The projected end is, reassuringly, 20 billion years away. If our species survives the next 19 billion years (and there are serious doubts about this, given our Sun's projected fate) here are some signs that scientists of the future will want to look for.

* A billion years before the end, all galaxies will have receded so far and so fast from our own as to be erased from the sky, as in no longer visible.
* When the Milky Way begins to fly apart, there are 60 million years left.
* Planets in our solar system will start to wing away from the Sun three months before the end of time.
* When Earth explodes, the end is momentarily near.

At this point, there is still a short interval before atoms and even their nuclei break apart. "There's about 30 minutes left," Caldwell said, "But it's not quality time."

And then what? Does the universe recycle itself? Is there something after nothing?

"We're not sure what happens after that," Caldwell says. "On the face of it, it would look like time ends."

The first explosion

Caldwell's study had humble beginnings. He and his colleagues, Marc Kamionkowski and Nevin Weinberg at Caltech, were considering how a sphere of matter collapses under its own weight to form a galaxy. In computer models, they tweaked with the dark energy factor and found that too much of it would actually prevent the sphere from collapsing. In extreme cases, the sphere exploded.

"That was our hint that there was something really unusual going on," Caldwell said.

It wasn't long ago, just before the accelerated expansion was discovered, that many cosmologists believed the universe might reverse course, that normal gravity would win, and that everything would fall back in a Big Crunch. More recently, solid observational data has all but assured the infinite-expansion model and the cold, dark, never-ending end.

The Caldwell group decided there might be a third possibility, leading to their new paper, which has been submitted to the Physical Review.

But there are many unknowns. It is not clear if the dark energy driving expansion is a force not currently described by physics, or if it is merely a different manifestation of gravity over huge distances. The repulsion could be a response to dark matter, unseen stuff that is known to comprise 23 percent of the universe, based on firm observations.

Dark matter has unknown properties, and it may be related to dark energy, Caldwell said. He notes that even Einstein considered that gravity might work repulsively, in a manner consistent with his theory of general relativity.

Dark energy, being quantified only recently, tends to be discussed as some strange new force, in addition to the four fundamental forces: gravity, electromagnetism, and the strong and weak nuclear forces that govern atoms. But the repulsion is possibly just the way gravity behaves in the presence of dark energy, Caldwell said. In that sense, it is not a new force.

Cautious reception

To turn dark energy into destructive phantom energy, Caldwell and his colleagues had to play around with a thing called the cosmological constant, a mathematical fix that Einstein applied to general relativity. Einstein later called it his greatest mistake, when Edwin Hubble found in the 1920s that the universe was expanding (seven decades later, that expansion would be seen accelerating).

The cosmological constant has been recently revived. Attempts to describe dark energy differ in how the density of dark energy varies with time. In some models, the density decreases slowly. For the cosmological constant, the density is a constant. For phantom energy, it must grow with time.

"We considered a more exotic form of dark energy which was more repulsive," as Caldwell explains is.

Abraham Loeb, a theoretician at the Harvard-Smithsonian Center for Astrophysics, has quantified the lonely effects of a forever-expanding universe. Loeb stands by that scenario, but he said Caldwell's idea is nonetheless interesting to explore.

"I think it's a logical possibility," Loeb told But he cautioned that altering the cosmological constant goes against current consensus.

"If I had to place a bet, I would bet in favor of the standard cosmological constant," Loeb said.

Sci-fi to reality

If Caldwell's team is right, cosmology would undergo a revolution. Sci-fi ideas like wormholes and time travel might suddenly enter the realm of hard science. All of this could sort itself out pretty soon, Caldwell believes. Observations over the next few years may actually show whether his phantom energy is possible.

"Who knows if it is right or wrong," Caldwell said of his theory. "I think we'll find out pretty soon."

In fact, recent observations from NASA's WMAP space probe have pinned down the physics of the universe with surprising accuracy. A little wiggle room remains for the cosmological constant. Yet more WMAP data are expected over the next four years. Other missions, including one called the Supernova Acceleration Probe (SNAP), could provide answers, Caldwell said.

Even if the Big Rip is a big bust, there's no guarantee of a pleasant ending.

Alternate final chapter

Paul Steinhardt, a Princeton University physicist, is, like Caldwell and Loeb, no stranger to strange ideas. Steinhardt advocates a cyclical universe, one that has no beginning or end but which instead is constantly starting over again.

Steinhardt theorizes within the generally accepted standards of the cosmological constant. He said the Big Rip is more exotic than most ideas but still conceivable, a projected possible result that is "straightforward and obvious for cosmologists."

Yet there is another entirely different possibility for the final moments of time as we know it.

In a theory put forth two years ago by Steinhardt and his colleagues, our universe is but a membrane, or brane, floating in a five-dimensional space. It is destined to collide dramatically with another brane. The idea, labeled the Ekpyrotic Universe, would replace portions of the Big Bang scenario while sticking to the presently accepted estimates of acceleration.

"Lest you get too optimistic, galaxies are destroyed in a far more violent way," Steinhardt said of the brane scenario. "They are vaporized at the next 'bang' -- the collision between branes so, you either rip them apart or you vaporize them."

8:44 PM  

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