What if the big-bang theory is wrong? What if the universe never began and will never end, driven forever to expand in a series of monster explosions and contract every eon or so in a cosmic crunch?

This is from Princeton University physicist Paul Steinhardt, not some fringe resident.

The (but isn't this old hat?) Curtmudgeon

Even though it won't make any difference to any of us, I find a certain comfort in the possibility that the universe may enjoy a rebirth every 30 or so billion years. It's always bugged me thinking about the last star winking out at some distant future time. That was always my excuse for not doing better in school - "it's all gonna end one day anyway, so what difference does it make".

I thought that recent observations strongly point to a universe that will expand forever. It doesn't bug me that the last star will wink out at some point a few hundred billion years in the future. A vast intergalactic civilization made up of whatever species will exist a few hundred billion years from now could conceivably artifically construct red dwarf stars and encase them in Dyson spheres. Hydrogen reserves held in small gas giants in nearby interstellar space would provide the fuel to create future stars when the red dwarf stars die.

Such feats wouldn't even be close to possible with modern technology, but we're talking hundreds of billions of years in the future! It hurts my head to imagine the year 3000, much less A.D. 10¹¹!

Such a civilization could survive for trillions of years after the last of the natural stars have long since burned out.

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If E = MC², why do I have less energy the more mass my body acquires?
That is all.

--Azpod... Formerly known as James Justin

Has anyone here read Stephen Hawking's "A Brief History of Time"? I was under the impression from my reading of this book (a while back, to be sure) that Mr. Hawking proposed almost exactly what was discussed in this article. The universe has a state of maximum density, minimum diameter, and expands out to a state of minimum density, maximum diameter. He went on to say things like not being sure of the arrow of time during the crunch. So what is new about this?

I think tis the season of NASA grants...
Always lots of press releases this time of year [img]/phpBB/images/smiles/icon_smile.gif[/img]

Yes, but even so, eventually all their fuel will run out. It may be trillions of years, but it isn't forever. In an open-ended universe, there will come a time when everything dies. Then all that's left is an empty ever-expanding void. Entropy will triumph in the end.
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David Hall
"Dave... my mind is going... I can feel it... I can feel it."

<font size="-1">(Forgot my sig.)</font>


<font size=-1>[ This Message was edited by: David Hall on 2002-04-26 10:09 ]</font>

Alas, I'm probably the only one who finds this strangely comforting, even freeing. If the above is true, and the universe expands forever, as more and more evidence seems to indicate, then Everything Ends - no amount of wishful thinking, theologizing, or technology can stop that. There comes a moment when It is all Over. Even if the universe contracts and re-bangs, everything is still destroyed. The inevitability of this finality - entropic or crunchy - just sort of makes me smile. I'm not sure why; it just does.

<font size=-1>[ This Message was edited by: odysseus0101 on 2002-04-26 10:07 ]</font>

What's new is that this guy is trying to take the currently observed acceleration into account, and suggest (as I understand it from my admittedly cursory reading) that the "dark energy" may itself have a property that will cause the acceleration to stop and reverse itself, bringing on a big crunch after all. A Brief History of Time was written before the discovery of the acceleration. Me, I think it's a trifle premature to be speculating on the long term properties of dark energy when we don't even know what or even *if* it *is*. There are competing models that don't require dark energy and can still explain the data, so I would say that the jury is still out.

Don

True. I never claimed that civilization could exist indefinitely. However, humans are remarkably imaginative when their existance is threatened. I image whatever intelligent species will exist 100 billion years from now, be they our far distant ancestors or not, will be even more so. Civilization will likely exist long after the last of the natural stars have been reduced to cold cinders. A vast majority of intelligent creatures will likely only know a dark, cold universe completely unlike the relatively bright, warm universe of today.

However, all things must come to an end. That must include life itself.

__________________
If E = MC², why do I have less energy the more mass my body acquires?
That is all.

--Azpod... Formerly known as James Justin

When (as has been theorized) everything eventually becomes positronium (electron/positron pairs at vast distances from each other, eventually to meet and annihilate), I do not think that anything will be around to see it, not even cockroaches (which will probably outlive mankind).

I have read the articles about the rebounding universe and believe that observations of the universe, along with study of the effects of dark matter, dark energy, etc., by cosmologists are much better than computer simulations by cosmologists alone. I do not know how the deceleration which has been calculated from the computer similation will be accomplished, since it is acceleration which is being viewed in the real universe and no end in sight is seen to the acceleration.

Certainly, nobody knows how the universe began (before the Big Bang) and it cannot be discussed, because it cannot be studied. I do not find any problem there. Scientists can make computer simulations, but I do not think that computer simulations can take the place of observation, even if such observation is limited.

ljbrs [img]/phpBB/images/smiles/icon_biggrin.gif[/img] [img]/phpBB/images/smiles/icon_smile.gif[/img] [img]/phpBB/images/smiles/icon_wink.gif[/img] [img]/phpBB/images/smiles/icon_rolleyes.gif[/img] [img]/phpBB/images/smiles/icon_confused.gif[/img]

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"There is in the universe neither center nor circumference." Giordano Bruno Born 1548. Torched 1600.

Oh, great. You mean my ex will out live me. [img]/phpBB/images/smiles/icon_smile.gif[/img]

Evidently, your *ex* does not exist in your life anymore, so your *it* is as good as *gone* -- except when you resurrect your *it* from time to time.

ljbrs [img]/phpBB/images/smiles/icon_biggrin.gif[/img] [img]/phpBB/images/smiles/icon_smile.gif[/img] [img]/phpBB/images/smiles/icon_rolleyes.gif[/img] [img]/phpBB/images/smiles/icon_confused.gif[/img] [img]/phpBB/images/smiles/icon_wink.gif[/img]

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"There is in the universe neither center nor circumference." Giordano Bruno Born 1548. Torched 1600.

Has anyone ever theorized, (and this is completely unprovable or falsifiable -- so no real theory,) that the universe appears to be expanding and accelerating from a primordial maximum density, out from everywhere to a maximum scarcity, but is actually more akin to continuously expanding fractal patterns whose components (we observe) are made up of mirrors of themselves? In other words, "expanding" towards the same patterns where a sense of "scale" is an illusion since all structures on the largest "scale" are the same. Hard to visualize? Another analogy - like a movie camera image whose zoom lens is tracking "away" while simultaneously the camera is moving forward at the same speed, giving the impression of "expansion" without actually "moving". Could the universe be expanding towards a future "big bang like" expansion but on a "larger" scale, so that someone living in the next universe sees their expansion as accelerating away from a seemingly infinite compression. I know this idea is an ill-defined notion. I'm groping to visualize the notion here.)

Just a pre-weekend idle thought. [img]/phpBB/images/smiles/icon_wink.gif[/img]

Chip

<font size=-1>[ This Message was edited by: Chip on 2002-05-03 13:30 ]</font>

Not only will every star one day wink out(if the universe is destined to expand forever), but every black hole will one day evaporate into stray radiation and particles by a process known as Hawking Radiation(Go Stephen Hawking!) as well.

Actually, I just saw him give a talk earlier this week, Monday to be exact on "The Cyclic Universe" which described that theory.

His theory is interesting. I am not quite up to the level of following everything he said (it was a technical talk) but did pick up some interesting tidbidts. The theory involves two three dimensional branes colliding to start a cycle. The branes expand in three dimensions. The three dimensions of space do not contract to start the next cycle. Rather, the branes move toward each other in a fourth dimension. The collision of the branes starts the next cycle. So you would not see everything coming toward you when the universe contracts as in other cyclic universe models.

One problem this solves is the entropy problem. Since 3-D space never contracts, the entropy increases as constantly, even when a new universe is created.

Another thing he claimed is that dark energy is an essential ingredient of this model, rather than some mysterious thing added in to explain a surprising observation.

Please don't ask any real tech questions...but I will try to explain anhything I can [img]/phpBB/images/smiles/icon_smile.gif[/img]

Rob

See some related(or at least semi-related) material here.

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I like the fractals idea. If electrons are only probabilities until observed and observing them changes them (and all the other QM stuff), then maybe the expanding fractal model is worth a few nights of contemplation. Hmmm.... Not saying there is anything there mind you, but worth thinking about.

The hypothesis featured in Curtmudgeon's post was first proposed in a paper that became availabls as a preprint in March 2001, and was formally published the following December: The Ekpyrotic Universe: Colliding Branes and the Origin of the Hot Big Bang, Khoury et al., Physical Review D 64(12): art. no. 123522, December 15, 2001. It is a speculation based on the geometry of space-time peculiar to string theory. It was in the news the moment it hit the preprint page. If nothing else, Steinhardt knows how to market his product.

Remember that what we actually observe is systematic redshifts, which strongly imply an expanding universe. One might even argue that we observe an expanding universe, since it is such an obvious interpretation of the redshift data.

Big Bang cosmology is the theory we use to explain in physical terms, the origin of an expanding universe. The idea that the universe literally began at the bang event is an outcome of being restricted to strictly classical physics (general relativity), which requires a singular (undefined) origin for the universe.

It's no great shakes of Big Bang cosmology is wrong, and in fact it must be wrong at some level, since it is inherently incapable of addressing the origin of the universe. The origin of the universe cannot be understood in terms of classical physics, only a quantum physical approach will do that (or so it is at our current state of knowledge).

The idea that the universe might be the result of a quantum mechanical event was first proposed in 1973 (Is the Universe a Vacuum Fluctuation?, E.P. Tryon, Nature 246: 396-397, 1973). His idea was later made compatible with 4-D special relativity, and a realistic quantum cosmology was born (The creation of the universe as a quantum phenomenon, Brout, Englert & Gunzig, Annals of Physics 115(1): 78-106, 1978). That idea was further developed by marrying it to a Friedmann-Robertson-Walker metric & general relativity (Origin of the Universe as a quantum tunneling event, Atkatz & Pagels, Physical Review D 25(8): 2065-2073, April 15, 1982). The idea that the universe may have begun as a quantum fluctuation on a pre-existing 4-D vacuum remains viable, I think, though not as cosmologically popular as string theory.

The cyclic universe is much different from these old QM ideas. In the cyclic model, the universe is created by the collision of two 5-D "branes", embedded in the 11-D space-time of M-theory. As the branes move apart after colliding, they pull the space between them, and that's what manifests itself to us as an "expansion" (A Cyclic Model of the Universe, Steinhardt & Turok, Science 296(5572): 1436-1439, May 24, 2002; From Big Crunch to Big Bang, J. Khoury et al., Physical Review D 65(8): art. no. 086007, Part B, April 15, 2002; Cosmic Evolution in a Cyclic Universe, Steinhardt & Turok, Physical Review D 65: art. no. 126003, June 15, 2002; The Cyclic Universe: An Informal Introduction, Steinhardt & Turok, published online, April 2002).

The cyclic universe is not without its detractors, with Andre Linde being perhaps its most vocal critic. Inflationary cosmology presupposes some form of quantum mechanical fluctuation as the origin of the universe, with a rapid expansion ("inflation") providing the mechanism to create large scale structure out of the amplified quantum fluctuations. Linde is a leading proponent of inflationary cosmology. On the other hand, the cyclic universe proposes that inflation, itself "unexplained", need not be invoked, but that the speed of expansion is connected to the rate of departure of the branes. Linde does not like the opposition. Of course, he may still be right anyway (Pyrotechnic Universe, Kallosh, Kofman & Linde, Physical Review D 64(12): art. no. 123523, December 15, 2001, it was the paper following the Khoury et al. original; Inflationary Theory versus Ekpyrotic/Cyclic Scenario, Andre Linde, a talk at Stephen Hawking's 60th birthday conference, Cambridge University, Jan. 2002, published online, May 26, 2002).

Paul Steinhardt's webpage has a lot of interesting cyclic universe stuff on it, including The Endless Universe: A Brief Introduction to the Cyclic Universe (for non scientists). Neil Turok's webpage also has some interesting links.

On the matter of the ultimate fate of the universe, try the book Five Ages of the Universe by Adams & Laughlin. It may not be perfect, but it's a good read, and has a lot to say about what happens in a universe that expands forever (which it won't, if Steinhardt & Turok have anything to say about it). Aside from the fact that tiny red dwarf stars can sit on the main sequence for 10^14 years, it takes about 10^20 years for galaxies to "evaporate", 10^1500 years for everything to spontaneously (quantum mechanically) becone iron, and 10^(10^26) or 10^(10^76) years for everything to become Hawking radiating black holes, depending on how you model that last step (Five Ages of the Universe, Fred Adams & Greg Laughlin, Touchstone (Simon & Schuster) 1999; A dying universe - the long term fate and evolution of astrophysical objects, Adams & Laughlin, Reviews of Modern Physics 69(2): 337-372, April 1997; Time without end: Physics and biology in an open universe, Freeman J. Dyson, Reviews of Modern Physics 51(3): 447-460, July 1979).

Hey! Has anybody else heard of the hypothesis that the universe came, not from a black hole, but from a quantum pea(whatever the heck that is [img]/phpBB/images/smiles/icon_confused.gif[/img])? Can anybody who knows more about this give me a clue as to what this might mean? I think I origionally read about it in a science magazine, and I think Stephen Hawking was one of the main founders of this hypothesis too.

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I think the correct spelling is "quantum pee". You see, it's like this... God was drinking a bit too much beer one day, and...

[img]/phpBB/images/smiles/icon_biggrin.gif[/img]

No Donnie, Pi Man really means "quantum beans" which happen to be the same type of beans that Jack bought.

[img]/phpBB/images/smiles/icon_smile.gif[/img]