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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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.
"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.
I'm supposed to take any of this seriously?
Time runs both forwards and backwards at the same time, while it also doesn't run at all and stands still. The Universe was created at the time of the Big Bang but is continuously experiencing little "Big Bangs" at the same time, which is flowing both forwards and backwards at the same "time" while also standing still.
"Dark energy" is all around us but undetectible except for theory. Since our theories can't be wrong it must exist and we just have to find it. That will explain why the Universe is expanding in a fashion that we can't explain and how time runs both forwards and backwards at the same time.
I'm going back to be now, my dreams have more coherence than this.
Not when I wrote the reply, since I had been searching on that darned word in search engines looking for that web page. The first time, however. . .
Also, while you're here: are you related to A.Pole?
Not that I know of. But hey, if you ever want to know what "The People" are thinking, just ask me, T.P.Pole. I got so sick last election cycle of the media saying "The American People" want this and "The People" want that, that I decided to prove them wrong.
Time is the ordering of cause and effect. The effect can't precede the cause.
Just remember...In comedy timing is everything.
A $2 billion dollar study on why water is wet!
The article isn't clear but I think they want to say that local entropy is increasing (this is measurable) but in an infinite universe, the total would be infinite. But, maybe the authors meant something else entirely.
Are you sure it isn't the other way around. If event A always preceeds event B, then we call A the cause, and B the effect. The concept of causa efficiens works this way. But if A and B always occur together, one could choose to call the earlier the cause or just call the cause the earlier (were there some non-temporal method of determining cause.)
LOL
That's good!
OlBlue, you were reading my mind...
Better check with AlGore. He may have been involved with the Big Bang ;)
I think that's about it, at least as I read it. Measurable local increase in entropy. There's no limit, in principle, to how far the BB might continue to expand, thus in a universe of ever-increasing volume, entropy would approach the infinite.
God did it.
time is simply the movent of an object in space. if nothing moved, there would be no time. And, since and object cannot move in two directions at the same time, time only goes in one direction. forward.
The motion you refer to is just a sequence of events. "Time" is the duration of a sequence of events, as measured against another sequence used as a standard -- usually something astronomical, such as the rotation of the earth.
I wish!!!! LOL
Molecules?
Because otherwise, poop would fly up our butt.
(For more details read, Phillip K. Dick's "Counterclock World" (one of his few stories not made into a movie yet))
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