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Big Bang and String Theory


mental invalid

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There's a fountain of information on this topic out there, so many possible explanations for what the universe really is, and so many questions. I wish I could know the answer(s) to at least one of these in my lifetime.

 

One thing I've come up with on my own, is that the real "mystery of the universe" is something the human mind can't comprehend. Similar to the way certain animals only see things in black and white, and wouldn't understand the notion of color. Or a how a blind man can't visualize things the way someone with sight does. It's, at least for now, beyond our mental grasp. Some humans, like Einstein & Hawking, have simply come closer to reaching that next level of awareness than others.

 

Try picturing a "new" color. One that doesn't look red, or blue, or green, or yellow, or like anything you've ever seen. Really sit and try to think of one. Or try and picture a sense beyond sight or sound etc.., and what it might feel like. Your brain doesn't know where to begin.

To me, THAT'S the universe. It's something that a person's brain can't fathom without evolving, or at least being awakened a little further beyond its current state of cognizance.

 

Maybe there's infinite universes.

 

Maybe the entire universe is actually a tiny particle of something unbelievably fucking big. And maybe that unbelievably big "thing" is also a particle that makes up something which might even be part of something else.

 

If the universe started as a big bang, or expansion, then what surrounded our little universe before this happened? Was there a space that the universe filled, or was there an endless void of "nothing" reaching off into a distant horizon of even more "nothing"?

 

Who knows. Cool shit to marinate on though.

 

 

 

[This message has been edited by Raels (edited 05-24-2001).]

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Guest imported_El Mamerro

Exactly how I feel, Rael. We could probably come to an understanding that says how we got where we are, but without actually having been present for eternity, we'll never know for sure. One little bit of info to keep you guys thinking:

 

According to string theory, the smallest portion of regular space is the Planck length (which is 10 to the negative 20th power smaller than the size of a proton). If the universe were to be compressed smaller than this size, it would "bounce" back out. I say it in quotation marks because it doesn't exactly bounce... it just begins to retain the same physical properties it had when it was big. This means that there would be absoultely no discernible differences whatsoever between a normal sized universe or a sub-Planck length one. So is our universe really big, or is it really small (under the Planck length)? Are there a lot of mini-universe withing each Planck-sized portion of space that look just like ours?

 

Read "Timeline", by Michael Crichton. He explores the possibility of "time" travel by sending compressed information describing a human being through wormholes in quantum foam into parallel universes that mirror our own, and which are created at every instant in time... so traveling to the past would be actually traveling into a separate universe. Not feasible according to string theory, but kinda feasible with a point-particle description of physics. Pretty dope shit. Beer,

 

El Mamerro

 

PS: Harpo, my SN's Mamerroid. I'll look you up.

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  • 8 months later...
Originally posted by El Mamerro

Rael, I think I read somewhere that there is a possibility the universe ISN'T gonna collapse. If I find the info I'll let you know.

 

That is indeed a very popular theory. It has something to do with the total amount of matter in the universe, like if there's enough matter it will eventually begin to contract, and if there's not enough it will continue expanding forever, in effect putting all our surrounding galaxies farther and farther away. This is called the "runaway universe" theory, I believe, they had a Nova on it a while back. The show actually made it seem like scientists researching the matter were close to the conclusion that our own universe is runaway. I wonder what implications this could have on the thermodynamic arrow of time? Since the universe would never contract, and thusly reverse entropy, would the universe eventually reach a state of complete disorder and stay like that forever?

 

Oh yeah, Mental Invalid, I would appreciate that story as well. My email is Xeroshoe76@hotmail.com

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Couple tidbits:

1.If you're going to talk about the theory that the universe is donut-shaped, don't use the word "donut", use the word "torus" (the scientific term for donut-shaped). It enhances your credibility.

2.There was a theory that maybe matter was being created as fast as it was being destroyed elsewhere, so everything would remain constant. It's called the "steady state theory" and I think it's wack. I believe it exposes a fundamental neurosis in its inventors, namely a fear of change, a desire to have everything comfortably static.

3. I like the donut (sorry, "torus") theory. It's a refreshing alternative to the Big Bang stuff. I always had a big problem with the Hubble Law, which states that the further away a celestial object (galaxy, quasar, etc.) is from us, the faster it is moving away from us. When I first read that, a big red flag went off in my head. Hello, how about an INSTRUMENTATION ERROR that is compounded at greater distances. (If you've ever worked with a divider - a drafting instrument like a compass used to mark off equal distances in succession - you know that the tiniest error early on will be magnified with each step you take with the divider, and if you went a mile you'd be off by many feet.) I never trusted the methods we use to measure huge distances in space to be accurate, so it seems logical that a compounded instrumentation error could be at work in making it look like the Hubble Law is for real.

4. On a related note to #3, I don't believe the speed of light is constant. We've proven that light is affected by strong gravitational sources (or else you could see black holes). So, light traveling enormous distances through space must necessarily suffer drag as it passes near strong gravitational sources. I argue that redshifted light is just "slow" light that has come a long way, and can't tell us exactly where it came from, or rather what has happened to its source since it began the trip. All the experiments I have read about which purport to measure the speed of light utilize "fresh" light that has not traveled a long time from its source, so no discrepancies in its speed are found. I believe Einstein got around this problem by MANDATING that the speed of light be constant, and simply suggesting that space is "curved" instead. I don't buy it and I think that assigning a constant speed to light is a limiting way of conceptualizing the universe, and leads erroneously to the assumption of a Big Bang.

Of course, Einstein and Hawking and other leading minds in cosmology are way smarter than I, and could probably trash my argument in short order. (They would do so with complicated math, and I would be lost quickly, because I don't conceptualize well from math.)

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Originally posted by Cracked Ass

, I don't believe the speed of light is constant.

 

Einstein died a 'lunatic' primarily based on the fact that he couldn't quantify a universal application of Newton's 3rd law. I have always held the notion that the crux was based on the 'constant speed of light' theory...

 

In case any of you upstarts want to tackle Einstein's issue, it basically asks 'why is there no ANTIgravity?'

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well, first we need to quantify 'gravity'... I hope we can all agree that is a force of infinite attraction... therefore, antigravity would be a force of infinite repulsion...here's a little home experiment...

 

think polarity and magnets, if ou combine them one way, the magnets attract each other, the opposite way and they repel... now, take that concept to a universal level... the theory is that all the planets remain in their relative obits due to the constant force of gravity... so... if everything has an equal and opposite reaction, where then is the opposite if gravity? We've discovered black holes, the ultimate statement of gravity, but where are the 'white holes'? Using what Cracked has postulated about 'light drag'...

 

Where then is the force that not only stops, but reverses light... it's an accepted idea that light travels in one direction until halted by a reflective surface. I suggest that light is more akin to AC current, it travels both ways constantly, the alternation being microcosmic and unmeasurable with current devices.

 

Let us never forget that time is the 4th dimension... onward to the 5th!

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OK it's 4AM where I am and I'm fading fast, so pardon my imminent incoherence.

Gravity operates in relationship to size and distance. It's weaker at greater distances and for smaller masses. Perhaps antigravity operates at dissimilar masses and distances than its counterpart. Antigravity could be repulsion at the smallest of levels: that force which prevents matter from shrinking smaller than Planck's Length. It would be a force that doesn't seem apparent or effectual among the more "standard" sizes of things like planets or galaxies.

Of course I'm still foggy on the whole unification thing - strong nuclear, weak nuclear forces, and all that. Another round is called for tomorrow.

Thank you and goodnight.

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dude, but we're fully on the same path... of course, assuming that gravity it duality, then infinite expansion (largeness) can be equal and opposite to an infintessimally small force, it's a balanced view but a view unaccounted for in all of Einstein's theories... and a balance that he could never achieve on paper...

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Guest imported_El Mamerro

One point to quickly clarify something... By the constancy of the speed of light, Einstein didn't mean so much to say that light travels at a constant speed, but that the speed at which it travels is an absolute in the universe. That is, nothing can go faster than the speed of light. But anyways, light hasn't been proven to be able to be speeded up or slowed down, but yes, there are tons of ways yo can fuck with photons to get such results. One particulary neat experiment involved shooting two photons down a path, and placing an obstacle in front of one... Turns out that the photon with an obstacle in its path would arrive faster than the unimpeded one. If you haven't heard of it, I can explain it and it'd make a lot more sense.

 

Second, Super(symmetric)string theory has already provided us with a way to quantify gravity as gravitons, and provided the equations for the vibrating patterns of both the graviton and antigraviton strings (a quantum field theory of gravity). Just like electromagnetic, strong, and weak forces are composed of photons, gluons, and weak gauge bosons respectively, so it is believed that gravitational force should also be particle-based. Antigravity, however, remains elusive and unproven, but if the universe DOES turn out to be supersymmetrical, then it MUST exist. Actually finding the smallest quanta of energy of the feeblest of all the forces has proven to be quite a challenge, and it might be beyond our scope forever. May the discussion continue... beer,

 

El Mamerro

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Alright so I ran into this old chinese man while painting the front of his store, he used to do research work during WWII and has been fucking up my mind with alternative Physics theory. First about all this big bang theory, this guy claims that its not true. Mamerro what you said about the big bang not actually being a bang is on the right track. It is more like a simple expansion of energy. Now what energy and matter is in free space is the real mystery here. What Physics teaches us in the classroom is that energy is the capability to do work and that matter occupies space but these definitions are just engineering tools rather than a helpful way to work out theories.

Another thing is that the universe is not steadily expanding as everyone believes. Based on red shift and blue shift light waves we can observe in some merging universes that there is evidence for contraction as well as expansion. So the universe is very much fluxuating and not in such a static space that we believe.

I started a web site (that is very incomplete) but you can find some original audio samples of this guy explaining elementary Physics and new Physics theory. Enjoy.

http://www.dausone.com

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Originally posted by Cracked Ass

Couple tidbits:

1.If you're going to talk about the theory that the universe is donut-shaped, don't use the word "donut", use the word "torus" (the scientific term for donut-shaped). It enhances your credibility.

 

My old name doesn't work for some reason, but it was me who brought up that statement. I used the word donut because that's how it was explained to me and seemed easy to understand ... wasn't really looking for credibility, I'm not a scientist or anything and just thought it was a pretty cool idea. ;)

 

Also, from what I understand, weren't Einstein's major-yet-unachieved goals to find an explanation for the curved geometry of gravity and the existence of subatomic particles? You guys seem to know more about the subject than me, but I find the shit fascinating. El Mammerro or someone help me out -- what would be a good book about planetary astronomy or Einstein's theories that would make sense to a simpleton such as myself ... ?

 

 

What's up Smart, I'm back near your area -- hit me up on hotmail or somethin'.

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Guest imported_El Mamerro

Alright... I just noticed that it'd be hard as hell to simply explain the experiment in words, so I drew a crappy little diagram to illustrate it a bit:

 

http://newcamp.net/hector/images/diag.jpg'>

 

 

Ok, so here's how it goes... Photons aren't this tiny little dot-particle looking thing; you can't pinpoint a photon's exact location because besides having particle qualities, it has wave qualities, which "spread" its location out. So when you're trying to explain the actual location of the photon, you talk about it existing as a probability wave, that is, an area where it might be located at a certain point in time. In the diagram above, the probability wave of each photon is not-so-cleverly illustrated as a circle with a dot in the middle, poised at the starting line. The dot in the middle of the wave represents the photon's most LIKELY place to be within the probability wave, but keep in mind it can be anywhere in that circle.

 

Now the photon on the right has a big block with a tiny tunnel in the middle standing right in its path. The photon on the left is allowed to proceed unimpeded. You'd think that the photon on the right would finish the race last because of having to struggle through the tiny tunnel, but it happens to be the opposite way.

 

The photons take off, and the one on the right slams against the block. Just like a wave of water, most of that photon's probability wave is deflected by the block (notice the crappier-than-normal circles bouncing backwards), and the amount of probability wave that gets through the tunnel is much smaller than how it started out, but it squeezed through the tunnel at the same speed as the photon on the left, so they're still both tied at the front. Their probability waves arrive at the finish line at the same time, but since the one on the right is much smaller, its entire probability wave goes across the finish line before the other photon's entire probability wave does. That means that no matter where the photons are on their respective probability waves, the one on the right is bound to arrive before the one on the left.

 

Keep in mind this exeriment had to be done thousands and thousands of time and the results averaged out... In a lot of these tries, the photon happened to be in the probability waves that bounced back from the block, and never made it to the finish line... Or the photon on the left happened to be at the very front of its probability wave and crossed the finish line before the one on the right... you get the idea. But over time, the results piled up, and considerably more often than not, the photon on the right beat the one on the left's ass. The experiment has been refined to the point where scientists can "speed up" an photon over 250 times the speed of a normal photon, and this in turn gets misinterpreted in the newspaper as scientists breaking the light barrier.

 

Well, I don't know if this made sense or not, but there it is. Hope you enjoyed it. Beer,

 

El Mamerro

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This is the kind of imprecision in science that annoys me. If you can't decide whether light is a particle or a wave, or something else entirely, you're going to come up with half-assed conclusions for an experiment that tries to build a house out of blocks that aren't even understood. The point of this experiment should be to observe light with and without obstructions, and use the results to try and understand what light is, rather than using a half-assed definition of light to create a half-assed conclusion of how an unknown seems to behave.

Of course, my ire at this approach is symptomatic of a broader dissatisfaction with the mind games of quantum physics, which I think is just applied semantics. Yet it's true about the "black box" problem of very small particles: the better data we obtain about a particle's location or spin, the less we know about the other, which says to me that there are some things in the universe we're not good enough to measure yet. And until we get good enough to measure these things precisely, we have no business postulating anything about the origin of the universe. We need to curtail our ambition to explain everything, and go back to the classroom and the lab and come up with cannier ways to nail down light.

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bump for intelligent life...

 

and cracked..i agree..

many of these observations and experiments are based on theories which can't be proven until we find or invent equipment sophisticated enough to test and measure those theories..

 

just wait a few more years though...

many thought we couldn't clone or map the human genome, especially not so soon, then PCR and craig venteer came along and made the machinery to prove and carry out their experiments..

 

i prefer chemistry and biology over physics because they deal with things that are more tangible...but lets face it...we still can't "see" an atom...is that only a matter of time? possibly..after the advent of the electron micrograph, you never know.

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i say we just say fuck it to all experimentaltion / evolutionary movements and wait for aliens to come and tell us the answers...

 

okay now seriously this topic is right up my alley , and i took both physics 11/12 and read a few books , so i am plenty intelligent enough to comprehende it.....however...

 

"Gravity operates in relationship to size and distance. It's weaker at greater distances and for smaller masses. "

 

isnt gravity a constant force that acts equally on all things , at like -9.8m/s2 ..........?

 

second, i often think that gravity isnt a downward force ( a pull )

but rather a push , while i agree that under this theory all the planets would have come apart and be floating around space , however i saw this old guy on tv who invented a number of simple magnetic and centrfical force experiments that made alot of sense

 

my .O2

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Originally posted by Raels

the real "mystery of the universe" is something the human mind can't comprehend. Similar to the way certain animals only see things in black and white, and wouldn't understand the notion of color. . It's, at least for now, beyond our mental grasp. Some humans, like Einstein & Hawking, have simply come closer to reaching that next level of awareness than others.

 

It's something that a person's brain can't fathom without evolving, or at least being awakened a little further beyond its current state of cognizance.

 

Who knows. Cool shit to marinate on though.

[This message has been edited by Raels (edited 05-24-2001).]

YOU SHOULD REALLY READ " THE CELESTINE PROPHECY " AND ITS SEQUAL(s) , ITS FICTION , HOWEVER IT REALLY REALLY MADE ME THINK OF THE ENTIRE UNIVERSE IN A WHOLE DIFFERENT PERSPECTIVE.

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Originally posted by daus

Alright so I ran into this old chinese man while painting the front of his store, he used to do research work during WWII and has been fucking up my mind with alternative Physics theory. First about all this big bang theory, this guy claims that its not true. Mamerro what you said about the big bang not actually being a bang is on the right track. It is more like a simple expansion of energy. Now what energy and matter is in free space is the real mystery here. What Physics teaches us in the classroom is that energy is the capability to do work and that matter occupies space but these definitions are just engineering tools rather than a helpful way to work out theories.

Another thing is that the universe is not steadily expanding as everyone believes. Based on red shift and blue shift light waves we can observe in some merging universes that there is evidence for contraction as well as expansion. So the universe is very much fluxuating and not in such a static space that we believe.

I started a web site (that is very incomplete) but you can find some original audio samples of this guy explaining elementary Physics and new Physics theory. Enjoy.

http://www.dausone.com

 

wow, that site was badass.

did you make that just for the hell of it?

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...um i noticed a while back that i only posted the link, and some people wanted the article...so here it is, all three pages....dated may 22 2001 from the new york times...sorry its a late or maybe its really just early, and i guess it could just be on time....oh yeah, bump for the cosmos....

 

 

Before the Big Bang, There Was . . . What?

 

By DENNIS OVERBYE

 

 

Expanded Coverage

In Depth: The Nature of the Universe

 

 

 

What was God doing before he created the world? The philosopher and writer (and later saint) Augustine posed the question in his "Confessions" in the fourth century, and then came up with a strikingly modern answer: before God created the world there was no time and thus no "before." To paraphrase Gertrude Stein, there was no "then" then.

 

Until recently no one could attend a lecture on astronomy and ask the modern version of Augustine's question — what happened before the Big Bang? — without receiving the same frustrating answer, courtesy of Albert Einstein's general theory of relativity, which describes how matter and energy bend space and time.

 

If we imagine the universe shrinking backward, like a film in reverse, the density of matter and energy rises toward infinity as we approach the moment of origin. Smoke pours from the computer, and space and time themselves dissolve into a quantum "foam." "Our rulers and our clocks break," explained Dr. Andrei Linde, a cosmologist at Stanford University. "To ask what is before this moment is a self-contradiction."

 

But lately, emboldened by progress in new theories that seek to unite Einstein's lordly realm with the unruly quantum rules that govern subatomic physics — so-called quantum gravity — Dr. Linde and his colleagues have begun to edge their speculations closer and closer to the ultimate moment and, in some cases, beyond it.

 

Some theorists suggest that the Big Bang was not so much a birth as a transition, a "quantum leap" from some formless era of imaginary time, or from nothing at all. Still others are exploring models in which cosmic history begins with a collision with a universe from another dimension.

 

All this theorizing has received a further boost of sorts from recent reports of ripples in a diffuse radio glow in the sky, thought to be the remains of the Big Bang fireball itself. These ripples are consistent with a popular theory, known as inflation, that the universe briefly speeded its expansion under the influence of a violent antigravitational force, when it was only a fraction of a fraction of a nanosecond old. Those ripples thus provide a useful check on theorists' imaginations. Any theory of cosmic origins that does not explain this phenomenon, cosmologists agree, stands little chance of being right.

 

Fortunately or unfortunately, that still leaves room for a lot of possibilities.

 

"If inflation is the dynamite behind the Big Bang, we're still looking for the match," said Dr. Michael Turner, a cosmologist at the University of Chicago. The only thing that all the experts agree on is that no idea works — yet. Dr. Turner likened cosmologists to jazz musicians collecting themes that sound good for a work in progress: "You hear something and you say, oh yeah, we want that in the final piece."

 

One answer to the question of what happened before the Big Bang is that it does not matter because it does not affect the state of our universe today. According to a theory known as eternal inflation, put forward by Dr. Linde in 1986, what we know as the Big Bang was only one out of many in a chain reaction of big bangs by which the universe endlessly reproduces and reinvents itself. "Any particular part of the universe may die, and probably will die," Dr. Linde said, "but the universe as a whole is immortal."

 

Dr. Linde's theory is a modification of the inflation theory that was proposed in 1980 by Dr. Alan Guth, a physicist. He considered what would happen if, as the universe was cooling during its first violently hot moments, an energy field known as the Higgs field, which interacts with particles to give them their masses, was somehow, briefly, unable to release its energy.

 

Space, he concluded, would be suffused with a sort of latent energy that would violently push the universe apart. In an eyeblink the universe would double some 60 times over, until the Higgs field released its energy and filled the outrushing universe with hot particles. Cosmic history would then ensue.

 

Cosmologists like inflation because such a huge outrush would have smoothed any gross irregularities from the primordial cosmos, leaving it homogeneous and geometrically flat. Moreover, it allows the whole cosmos to grow from next to nothing, which caused Dr. Guth to dub the universe "the ultimate free lunch."

 

Subsequent calculations ruled out the Higgs field as the inflating agent, but there are other inflation candidates that would have the same effect. More important, from the pre- Big-Bang perspective, Dr. Linde concluded, one inflationary bubble would sprout another, which in turn would sprout even more. In effect each bubble would be a new big bang, a new universe with different characteristics and perhaps even different dimensions. Our universe would merely be one of them.

 

"If it starts, this process can keep happening forever," Dr. Linde explained. "It can happen now, in some part of the universe."

 

The greater universe envisioned by eternal inflation is so unimaginably large, chaotic and diverse that the question of a beginning to the whole shebang becomes almost irrelevant. For cosmologists like Dr. Guth and Dr. Linde, that is in fact the theory's lure.

 

"Chaotic inflation allows us to explain our world without making such assumptions as the simultaneous creation of the whole universe from nothing," Dr. Linde said in an e-mail message.

 

Questions for Eternity

Trying to Imagine the Nothingness

 

Nevertheless, most cosmologists, including Dr. Guth and Dr. Linde, agree that the universe ultimately must come from somewhere, and that nothing is the leading candidate.

 

As a result, another tune that cosmologists like to hum is quantum theory. According to Heisenberg's uncertainty principle, one of the pillars of this paradoxical world, empty space can never be considered really empty; subatomic particles can flit in and out of existence on energy borrowed from energy fields. Crazy as it sounds, the effects of these quantum fluctuations have been observed in atoms, and similar fluctuations during the inflation are thought to have produced the seeds around which today's galaxies were formed.

 

Could the whole universe likewise be the result of a quantum fluctuation in some sort of primordial or eternal nothingness? Perhaps, as Dr. Turner put it, "Nothing is unstable."

 

The philosophical problems that plague ordinary quantum mechanics are amplified in so-called quantum cosmology. For example, as Dr. Linde points out, there is a chicken- and-egg problem. Which came first: the universe, or the law governing it? Or, as he asks, "If there was no law, how did the universe appear?"

 

 

 

(Page 2 of 3)

 

 

 

One of the earliest attempts to imagine the nothingness that is the source of everything came in 1965 when Dr. John Wheeler and Dr. Bryce DeWitt, now at the University of Texas, wrote down an equation that combined general relativity and quantum theory. Physicists have been arguing about it ever since.

 

The Wheeler-DeWitt equation seems to live in what physicists have dubbed "superspace," a sort of mathematical ensemble of all possible universes, ones that live only five minutes before collapsing into black holes and ones full of red stars that live forever, ones full of life and ones that are empty deserts, ones in which the constants of nature and perhaps even the number of dimensions are different from our own.

 

In ordinary quantum mechanics, an electron can be thought of as spread out over all of space until it is measured and observed to be at some specific location. Likewise, our own universe is similarly spread out over all of superspace until it is somehow observed to have a particular set of qualities and laws. That raises another of the big questions. Since nobody can step outside the universe, who is doing the observing?

 

Dr. Wheeler has suggested that one answer to that question may be simply us, acting through quantum- mechanical acts of observation, a process he calls "genesis by observership."

 

"The past is theory," he once wrote. "It has no existence except in the records of the present. We are participators, at the microscopic level, in making that past, as well as the present and the future." In effect, Dr. Wheeler's answer to Augustine is that we are collectively God and that we are always creating the universe.

 

Another option, favored by many cosmologists, is the so-called many worlds interpretation, which says that all of these possible universes actually do exist. We just happen to inhabit one whose attributes are friendly to our existence.

 

The End of Time

Just Another Card in the Big Deck

 

Yet another puzzle about the Wheeler-DeWitt equation is that it makes no mention of time. In superspace everything happens at once and forever, leading some physicists to question the role of time in the fundamental laws of nature. In his book "The End of Time," published to coincide with the millennium, Dr. Julian Barbour, an independent physicist and Einstein scholar in England, argues that the universe consists of a stack of moments, like the cards in a deck, that can be shuffled and reshuffled arbitrarily to give the illusion of time and history.

 

The Big Bang is just another card in this deck, along with every other moment, forever part of the universe. "Immortality is here," he writes in his book. "Our task is to recognize it."

 

Dr. Carlo Rovelli, a quantum gravity theorist at the University of Pittsburgh, pointed out that the Wheeler- DeWitt equation doesn't mention space either, suggesting that both space and time might turn out to be artifacts of something deeper. "If we take general relativity seriously," he said, "we have to learn to do physics without time, without space, in the fundamental theory."

 

While admitting that they cannot answer these philosophical questions, some theorists have committed pen to paper in attempts to imagine quantum creation mathematical rigor.

 

Dr. Alexander Vilenkin, a physicist at Tufts University in Somerville, Mass., has likened the universe to a bubble in a pot of boiling water. As in water, only bubbles of a certain size will survive and expand, smaller ones collapse. So, in being created, the universe must leap from no size at all — zero radius, "no space and no time" — to a radius large enough for inflation to take over without passing through the in-between sizes, a quantum-mechanical process called "tunneling."

 

Dr. Stephen Hawking, the Cambridge University cosmologist and best-selling author, would eliminate this quantum leap altogether. For the last 20 years he and a series of collaborators have been working on what he calls a "no boundary proposal." The boundary of the universe is that it has no boundary, Dr. Hawking likes to say.

 

One of the keys to Dr. Hawking's approach is to replace time in his equations with a mathematical conceit called imaginary time; this technique is commonly used in calculations regarding black holes and in certain fields of particle physics, but its application to cosmology is controversial.

 

The universe, up to and including its origin, is then represented by a single conical-shaped mathematical object, known as an instanton, that has four spatial dimensions (shaped roughly like a squashed sphere) at the Big Bang end and then shifts into real time and proceeds to inflate. "Actually it sort of bursts and makes an infinite universe," said Dr. Neil Turok, also from Cambridge University. "Everything for all future time is determined, everything is implicit in the instanton."

 

Unfortunately the physical meaning of imaginary time is not clear. Beyond that, the approach produces a universe that is far less dense than the real one.

 

The Faith of Strings

Theorists Bring on the 'Brane' Worlds

 

But any real progress in discerning the details of the leap from eternity into time, cosmologists say, must wait for the formulation of a unified theory of quantum gravity that succeeds in marrying Einstein's general relativity to quantum mechanics — two views of the world, one describing a continuous curved space-time, the other a discontinuous random one — that have been philosophically and mathematically at war for almost a century. Such a theory would be able to deal with the universe during the cauldron of the Big Bang itself, when even space and time, theorists say, have to pay their dues to the uncertainty principle and become fuzzy and discontinuous.

 

In the last few years, many physicists have pinned their hopes for quantum gravity on string theory, an ongoing mathematically labyrinthean effort to portray nature as comprising tiny wiggly strings or membranes vibrating in 10 or 11 dimensions.

 

In principle, string theory can explain all the known (and unknown) forces of nature. In practice, string theorists admit that even their equations are still only approximations, and physicists outside the fold complain that the effects of "stringy physics" happen at such high energies that there is no hope of testing them in today's particle accelerators. So theorists have been venturing into cosmology, partly in the hopes of discovering some effect that can be observed.

 

 

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The Big Bang is an obvious target. A world made of little loops has a minimum size. It cannot shrink beyond the size of the string loops themselves, Dr. Robert Brandenberger, now at Brown, and Dr. Cumrun Vafa, now at Harvard, deduced in 1989. When they used their string equations to imagine space shrinking smaller than a certain size, Dr. Brandenberger said, the universe acted instead as if it were getting larger. "It looks like it is bouncing from a collapsing phase."

 

In this view, the Big Bang is more like a transformation, like the melting of ice to become water, than a birth, explained Dr. Linde, calling it "an interesting idea that should be pursued." Perhaps, he mused, there could be a different form of space and time before the Big Bang. "Maybe the universe is immortal," he said. "Maybe it just changes phase. Is it nothing? Is it a phase transition? These are very close to religious questions."

 

Work by Dr. Brandenberger and Dr. Vafa also explains how it is that we only see 3 of the 9 or 10 spatial dimensions the theory calls for. Early in time the strings, they showed, could wrap around space and strangle most of the spatial dimensions, keeping them from growing.

 

In the last few years, however, string theorists have been galvanized by the discovery that their theory allows for membranes of various dimensions ("branes" in string jargon) as well as strings. Moreover they have begun to explore the possibility that at least one of the extra dimensions could be as large as a millimeter, which is gigantic in string physics. In this new cosmology, our world is a three-dimensional island, or brane floating in a five- dimensional space, like a leaf in a fish tank. Other branes might be floating nearby. Particles like quarks and electrons and forces like electromagnetism are stuck to the brane, but gravity is not, and thus the brane worlds can exert gravitational pulls on each other.

 

"A fraction of a millimeter from you is another universe," said Dr. Linde. "It might be there. It might be the determining factor of the universe in which you live."

 

Worlds in Collision

A New Possibility Is Introduced

 

That other universe could bring about creation itself, according to several recent theories. One of them, called branefall, was developed in 1998 by Dr. Georgi Dvali of New York University and Dr. Henry Tye, from Cornell. In it the universe emerges from its state of quantum formlessness as a tangle of strings and cold empty membranes stuck together. If, however, there is a gap between the branes at some point, the physicists said, they will begin to fall together.

 

Each brane, Dr. Dvali said, will experience the looming gravitational field of the other as an energy field in its own three-dimensional space and will begin to inflate rapidly, doubling its size more than a thousand times in the period it takes for the branes to fall together. "If there is at least one region where the branes are parallel, those regions will start an enormous expansion while other regions will collapse and shrink," Dr. Dvali said.

 

When the branes finally collide, their energy is released and the universe heats up, filling with matter and heat, as in the standard Big Bang.

 

This spring four physicists proposed a different kind of brane clash that they say could do away with inflation, the polestar of Big Bang theorizing for 20 years, altogether. Dr. Paul Steinhardt, one of the fathers of inflation, and his student Justin Khoury, both of Princeton, Dr. Burt Ovrut of the University of Pennsylvania and Dr. Turok call it the ekpyrotic universe, after the Greek word "ekpyrosis," which denotes the fiery death and rebirth of the world in Stoic philosophy.

 

The ekpyrotic process begins far in the indefinite past with a pair of flat empty branes sitting parallel to each other in a warped five-dimensional space — a situation they say that represents the simplest solution of Einstein's equations in an advanced version of string theory. The authors count it as a point in their favor that they have not assumed any extra effects that do not already exist in that theory. "Hence we are proposing a potentially realistic model of cosmology," they wrote in their paper.

 

The two branes, which form the walls of the fifth dimension, could have popped out of nothingness as a quantum fluctuation in the even more distant past and then drifted apart.

 

At some point, perhaps when the branes had reached a critical distance apart, the story goes, a third brane could have peeled off the other brane and begun falling toward ours. During its long journey, quantum fluctuations would ripple the drifting brane's surface, and those would imprint the seeds of future galaxies all across our own brane at the moment of collision. Dr. Steinhardt offered the theory at an astronomical conference in Baltimore in April.

 

In the subsequent weeks the ekpyrotic universe has been much discussed. Some cosmologists, particularly Dr. Linde, have argued that in requiring perfectly flat and parallel branes the ekpyrotic universe required too much fine-tuning.

 

In a critique Dr. Linde and his co- authors suggested a modification they called the "pyrotechnic universe."

 

Dr. Steinhardt admitted that the ekpyrotic model started from a very specific condition, but that it was a logical one. The point, he said, was to see if the universe could begin in a long-lived quasi-stable state "starkly different from inflation." The answer was yes. His co-author, Dr. Turok, pointed out, moreover, that inflation also requires fine-tuning to produce the modern universe, and physicists still don't know what field actually produces it.

 

"Until we have solved quantum gravity and connected string theory to particle physics none of us can claim victory," Dr. Turok said.

 

In the meantime, Augustine sleeps peacefully.

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