the stars that bowl
like forever
is a card
commemorating
the time we cannot hold
Posted on 10/26/2004 7:36:36 PM PDT by ckilmer
Public release date: 26-Oct-2004 [ Print This Article | Close This Window ]
Contact: Steve Koppes skoppes@uchicago.edu 773-702-8366 University of Chicago
Scientists zero in on why time flows in one direction The big bang could be a normal event in the natural evolution of the universe that will happen repeatedly over incredibly vast time scales as the universe expands, empties out and cools off, according to two University of Chicago physicists. "We like to say that the big bang is nothing special in the history of our universe," said Sean Carroll, an Assistant Professor in Physics at the University of Chicago. Carroll and University of Chicago graduate student Jennifer Chen are scheduled to post a paper describing their ideas at http://arxiv.org/ Thursday evening.
Carroll and Chen's research addresses two ambitious questions: why does time flow in only one direction, and could the big bang have arisen from an energy fluctuation in empty space that conforms to the known laws of physics?
The question about the arrow of time has vexed physicists for a century because "for the most part the fundamental laws of physics don't distinguish between past and future. They're time-symmetric," Carroll said.
And closely bound to the issue of time is the concept of entropy, a measure of disorder in the universe. As physicist Ludwig Boltzmann showed a century ago, entropy naturally increases with time. "You can turn an egg into an omelet, but not an omelet into an egg," Carroll said.
But the mystery remains as to why entropy was low in the universe to begin with. The difficulty of that question has long bothered scientists, who most often simply leave it as a puzzle to answer in the future. Carroll and Chen have made an attempt to answer it now.
Previous researchers have approached questions about the big bang with the assumption that entropy in the universe is finite. Carroll and Chen take the opposite approach. "We're postulating that the entropy of the universe is infinite. It could always increase," Chen said.
To successfully explain why the universe looks as it does today, both approaches must accommodate a process called inflation, which is an extension of the big bang theory. Astrophysicists invented inflation theory so that they could explain the universe as it appears today. According to inflation, the universe underwent a period of massive expansion in a fraction of a second after the big bang.
But there's a problem with that scenario: a "skeleton in the closet," Carroll said. To begin inflation, the universe would have encompassed a microscopically tiny patch in an extremely unlikely configuration, not what scientists would expect from a randomly chosen initial condition. Carroll and Chen argue that a generic initial condition is actually likely to resemble cold, empty space-not an obviously favorable starting point for the onset of inflation.
In a universe of finite entropy, some scientists have proposed that a random fluctuation could trigger inflation. This, however, would require the molecules of the universe to fluctuate from a high-entropy state into one of low entropy-a statistical longshot.
"The conditions necessary for inflation are not that easy to start," Carroll said. "There's an argument that it's easier just to have our universe appear from a random fluctuation than to have inflation begin from a random fluctuation."
Carroll and Chen's scenario of infinite entropy is inspired by the finding in 1998 that the universe will expand forever because of a mysterious force called "dark energy." Under these conditions, the natural configuration of the universe is one that is almost empty. "In our current universe, the entropy is growing and the universe is expanding and becoming emptier," Carroll said.
But even empty space has faint traces of energy that fluctuate on the subatomic scale. As suggested previously by Jaume Garriga of Universitat Autonoma de Barcelona and Alexander Vilenkin of Tufts University, these flucuations can generate their own big bangs in tiny areas of the universe, widely separated in time and space. Carroll and Chen extend this idea in dramatic fashion, suggesting that inflation could start "in reverse" in the distant past of our universe, so that time could appear to run backwards (from our perspective) to observers far in our past.
Regardless of the direction they run in, the new universes created in these big bangs will continue the process of increasing entropy. In this never-ending cycle, the universe never achieves equilibrium. If it did achieve equilibrium, nothing would ever happen. There would be no arrow of time.
"There's no state you can go to that is maximal entropy. You can always increase the entropy more by creating a new universe and allowing it to expand and cool off," Carroll explained.
### Images of the authors are available upon request.
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Photons seem to have managed that trick. But they have no sex life.
Yes, well, we "perceive" the earth to be flat, too. I mean, just look around you! Isn't it obvious?
BTTT
Sex-free placemarker
It is possible that of the eleven dimensions, the eleventh thanks to Witten's M-theory, the ones we see are the ones that were affected by gravitational inflation and may constitute a brane.
A physics society would have journals available in specific disciplines such as cosmology. Picking out the articles specific to string theory would be up to the reader, and the math might be rarified for the non-specialist.
No, it isn't obvious. Those of us who have flown (which is most of us) in airplanes have seen the curvature of the earth. Most people see photos from satellites and the space station. The earth doesn't look flat at all.
Besides my point was that our comprehension of time as flowing forward was far more than just a "perception".
We have all kinds of objective evidence that time moves forward which is not only obvious to the simplest of minds but scientifically provable.
That's a point I've been trying to make for a long time.
Tkhat would take all the fun out of it.
The reason you don't have that nickel is because the blade who wrote this 'research' got your taxes.
Well, to some folks who have done the math, time doesn't look flat either. That's the point I was trying to make.
Carrol and Chen must have been enjoying the same gin soaked raisins that Ms. Kerry has been nipping on!
Witten
It is possible that of the eleven dimensions, the eleventh thanks to Witten's M-theory, the ones we see are the ones that were affected by gravitational inflation and may constitute a brane.
//////////////////
Notice your use of the words "possible" and "may"
the blog I mentioned from columbia u math dept before has all real math guys there. I pulled a piece out of a longer post of one of these math guys who from first hand experience recounted the history of string theory people from the theory's inception. so i'm inclined to believe the guy when he says that besides the witten stuff "I think string theory has been an utter disaster for theoretical physics"
from what I've read apparently superstring theory fills some kind of philosophical need similiar to that of aether theory in the 19th century.
but if your point is that theoretical physics is showing the darkness that in the past (like in the late 19th century) has generally preceded a pretty big paradigm shift. Then I would agree.
cognitive dissonance
may be discerned
in the clock face
sign, hung
upon the door
of the little
shop of hours,
closed for lunch
come back yesterday
bring your own flowers.
My point is that math is merely useful, but any correlation to reality lies in procurement of project funding.
The covariant derivative is anticommutative.
-willful suspension of disbelief [Coleridge]
cognitive dissonance
may be discerned
in the clock face
sign, hung
upon the door
of the little
shop of hours,
closed for lunch
come back yesterday
bring your own flowers.
Beautiful. Every time I think I'm the only one who gets it, someone such as you posts such as this.
The name on the forehead of the Harlot was Mystery.
That is the one thing they all are afraid of.
bttt
bttt
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