Before the Big Bang...?

Question

What would happen if someone went back in time to BEFORE the big bang?

I mean sure, the Big Bang alledgedly created space and time and such, but in order to create said big bang, wouldn't there have had to be time and space before it to make the explosion?

Answer 1

I'm happy to see that all the physicists are busy doing other things...

Here's your reading assignment:

The Whole Shebang
Timothy Ferris

Answer 2

Nobody knows.

Nobody knows because gravity can't be expressed in terms of any other force. There are 5 fundamental forces in the universe, electricity, magnetism, the weak nucleur force, the strong nucleur force and gravity. Electricity and magnetism are easily interchangable and can even be equated to nucleur forces. This all breaks down with gravity. When the universe began, all 5 forces were united into a single force. Because gravity remains distinct from the other forces, nobody knows what happened at the precise instant the universe began expanding.

String theory is an attempt to unite all 5 forces, but it has not really solved the problem exactly. It suggests there are 11 dimensions in the universe and they exist next to each other. One theory states the 3 dimensional expansion of this universe was caused by a collision of two of the dimensional planes. The point of contact created all the energy and matter present in the universe today. A fundamental law of physics is the amount of matter and energy in the universe is constant and is neither created nor destroyed. It is spreading into "empty space". Space is defined to be the distance between two objects and the universe is entering a region where there is no matter or energy of any kind. The matter will probably all decay to energy and everything will eventually become radio waves with infinitly long wavelenghts.

Answer 3

The big-bang was not an 'explosion' in the usual sense of the word. It was the coming into being of an unimagineable amount of energy. It was the existence of this energy which caused spacetime to form (to contain it) and a great deal of that energy became mass during the first few seconds, thus creating massenergy. The exact reason(s) that all of the other dimensions of hyperspace didn't 'unroll' (as did massenergy and spacetime) but remained detectable only at the Planck level, is one of the deeper mysteries of the big bang.

Doug

Answer 4

(1) The Big bang was NOT an explosion. It's just a made-up name for the beginning of time and space. It might be better to call it the "Big Beginning".

(2) There is no time before the BB. It is the beginning of time.

(3) The BB was not "created". It just "is".

Answer 5

If you believe in Big Bang then you should also believe that there is no 'before Big Bang'...

everything including time came out of Big Bang...

Answer 6

There would be nothing ...like nowhere to go and nothing to stand on!

This may have been the start of space and time as we understand it ...and even matter as we know it. Now if we could jump out of this dimension somehow.

Answer 7

There is no such this as the Big Bang. Just a scientific way of saying : "Screw Religion".

Answer 8

You have pinpointed one of the problems (sorry, unsolved mystery) of the big bang theory.

Answer 9

The Universe has ALWAYS been and it will FOREVER be.

Answer 10

Few schoolchildren have failed to frustrate their parents with questions of this sort. It often starts with puzzlement over whether space "goes on forever," or where humans came from, or how the planet Earth formed. In the end, the line of questioning always seems to get back to the ultimate origin of things: the big bang. "But what caused that?"

Presto

Children grow up with an intuitive sense of cause and effect. Events in the physical world aren't supposed to "just happen." Something makes them happen. Even when the rabbit appears convincingly from the hat, trickery is suspected. So could the entire universe simply pop into existence, magically, for no actual reason at all?

This simple, schoolchild query has exercised the intellects of generations of philosophers, scientists, and theologians. Many have avoided it as an impenetrable mystery. Others have tried to define it away. Most have got themselves into an awful tangle just thinking about it.
The problem, at rock bottom, is this: If nothing happens without a cause, then something must have caused the universe to appear. But then we are faced with the inevitable question of what caused that something. And so on in an infinite regress. Some people simply proclaim that God created the universe, but children always want to know who created God, and that line of questioning gets uncomfortably difficult.

One evasive tactic is to claim that the universe didn't have a beginning, that it has existed for all eternity. Unfortunately, there are many scientific reasons why this obvious idea is unsound. For starters, given an infinite amount of time, anything that can happen will already have happened, for if a physical process is likely to occur with a certain nonzero probability-however small-then given an infinite amount of time the process must occur, with probability one. By now, the universe should have reached some sort of final state in which all possible physical processes have run their course. Furthermore, you don't explain the existence of the universe by asserting that it has always existed. That is rather like saying that nobody wrote the Bible: it was. just copied from earlier versions. Quite apart from all this, there is very good evidence that the universe did come into existence in a big bang, about fifteen billion years ago. The effects of that primeval explosion are clearly detectable today-in the fact that the universe is still expanding, and is filled with an afterglow of radiant heat.

So we are faced with the problem of what happened beforehand to trigger the big bang. Journalists love to taunt scientists with this question when they complain about the money being spent on science. Actually, the answer (in my opinion) was spotted a long time ago, by one Augustine of Hippo, a Christian saint who lived in the fifth century. In those days before science, cosmology was a branch of theology, and the taunt came not from journalists, but from pagans: "What was God doing before he made the universe?" they asked. "Busy creating Hell for the likes of you!" was the standard reply.

But Augustine was more subtle. The world, he claimed, was made "not in time, but simultaneously with time." In other words, the origin of the universe-what we now call the big bang-was not simply the sudden appearance of matter in an eternally preexisting void, but the coming into being of time itself. Time began with the cosmic origin. There was no "before," no endless ocean of time for a god, or a physical process, to wear itself out in infinite preparation.

Remarkably, modern science has arrived at more or less the same conclusion as Augustine, based on what we now know about the nature of space, time, and gravitation. It was Albert Einstein who taught us that time and space are not merely an immutable arena in which the great cosmic drama is acted out, but are part of the cast-part of the physical universe. As physical entities, time and space can change- suffer distortions-as a result of gravitational processes. Gravitational theory predicts that under the extreme conditions that prevailed in the early universe, space and time may have been so distorted that there existed a boundary, or "singularity," at which the distortion of space-time was infinite, and therefore through which space and time cannot have continued. Thus, physics predicts that time was indeed bounded in the past as Augustine claimed. It did not stretch back for all eternity.

If the big bang was the beginning of time itself, then any discussion about what happened before the big bang, or what caused it-in the usual sense of physical causation-is simply meaningless. Unfortunately, many children, and adults, too, regard this answer as disingenuous. There must be more to it than that, they object.

Indeed there is. After all, why should time suddenly "switch on"? What explanation can be given for such a singular event? Until recently, it seemed that any explanation of the initial "singularity" that marked the origin of time would have to lie beyond the scope of science. However, it all depends on what is meant by "explanation." As I remarked, all children have a good idea of the notion of cause and effect, and usually an explanation of an event entails finding something that caused it. It turns out, however, that there are physical events which do not have well-defined causes in the manner of the everyday world. These events belong to a weird branch of scientific inquiry called quantum physics.

Mostly, quantum events occur at the atomic level; we don't experience them in daily life. On the scale of atoms and molecules, the usual commonsense rules of cause and effect are suspended. The rule of law is replaced by a sort of anarchy or chaos, and things happen spontaneously-for no particular reason. Particles of matter may simply pop into existence without warning, and then equally abruptly disappear again. Or a particle in one place may suddenly materialize in another place, or reverse its direction of motion. Again, these are real effects occurring on an atomic scale, and they can be demonstrated experimentally.

A typical quantum process is the decay of a radioactive nucleus. If you ask why a given nucleus decayed at one particular moment rather than some other, there is no answer. The event "just happened" at that moment, that's all. You cannot predict these occurrences. All you can do is give the probability-there is a fifty-fifty chance that a given nucleus will decay in, say, one hour. This uncertainty is not simply a result of our ignorance of all the little forces and influences that try to make the nucleus decay; it is inherent in nature itself, a basic part of quantum reality.

The lesson of quantum physics is this: Something that "just happens" need not actually violate the laws of physics. The abrupt and uncaused appearance of something can occur within the scope of scientific law, once quantum laws have been taken into account. Nature apparently has the capacity for genuine spontaneity.
It is, of course, a big step from the spontaneous and uncaused appearance of a subatomic particle-something that is routinely observed in particle accelerators-to the spontaneous and uncaused appearance of the universe. But the loophole is there. If, as astronomers believe, the primeval universe was compressed to a very small size, then quantum effects must have once been important on a cosmic scale. Even if we don't have a precise idea of exactly what took place at the beginning, we can at least see that the origin of the universe from nothing need not be unlawful or unnatural or unscientific. In short, it need not have been a supernatural event.

Inevitably, scientists will not be content to leave it at that. We would like to flesh out the details of this profound concept. There is even a subject devoted to it, called quantum cosmology. Two famous quantum cosmologists, James Hartle and Stephen Hawking, came up with a clever idea that goes back to Einstein. Einstein not only found that space and time are part of the physical universe; he also found that they are linked in a very intimate way. In fact, space on its own and time on its own are no longer properly valid concepts. Instead, we must deal with a unified "space-time" continuum. Space has three dimensions, and time has one, so space-time is a four-dimensional continuum.

In spite of the space-time linkage, however, space is space and time is time under almost all circumstances. Whatever space-time distortions gravitation may produce, they never turn space into time or time into space. An exception arises, though, when quantum effects are taken into account. That all-important intrinsic uncertainty that afflicts quantum systems can be applied to space-time, too. In this case, the uncertainty can, under special circumstances, affect the identities of space and time. For a very, very brief duration, it is possible for time and space to merge in identity, for time to become, so to speak, spacelike-just another dimension of space.

The spatialization of time is not something abrupt; it is a continuous process. Viewed in reverse as the temporalization of (one dimension of) space, it implies that time can emerge out of space in a continuous process. (By continuous, I mean that the timelike quality of a dimension, as opposed to its spacelike quality, is not an all-or-nothing affair; there are shades in between. This vague statement can be made quite precise mathematically.)

The essence of the Hartle-Hawking idea is that the big bang was not the abrupt switching on of time at some singular first moment, but the emergence of time from space in an ultrarapid but nevertheless continuous manner. On a human time scale, the big bang was very much a sudden, explosive origin of space, time, and matter. But look very, very closely at that first tiny fraction of a second and you find that there was no precise and sudden beginning at all. So here we have a theory of the origin of the universe that seems to say two contradictory things: First, time did not always exist; and second, there was no first moment of time. Such are the oddities of quantum physics.

Even with these further details thrown in, many people feel cheated. They want to ask why these weird things happened, why there is a universe, and why this universe. Perhaps science cannot answer such questions. Science is good at telling us how, but not so good on the why. Maybe there isn't a why. To wonder why is very human, but perhaps there is no answer in human terms to such deep questions of existence. Or perhaps there is, but we are looking at the problem in the wrong way.

Well, I didn't promise to provide the answers to life, the universe, and everything, but I have at least given a plausible answer to the question I started out with: What happened before the big bang?
The answer is: Nothing.

PAUL DAVIES is a theoretical physicist and professor of natural philosophy at the University of Adelaide. He has published over one hundred research papers in the fields of cosmology, gravitation, and quantum field theory, with particular emphasis on black holes and the origin of the universe. He is also interested in the nature of time, high-energy particle physics, the foundations of quantum mechanics, and the theory of complex systems. He runs a research group in quantum gravity which is currently investigating superstrings, cosmic strings, higher-dimensional black holes, and quantum cosmology. Davies is well known as an author, broadcaster, and public lecturer. He has written over twenty books, ranging from specialist textbooks to popular books for the general public. Among his better-known works are God and the New Physics; Superforce; The Cosmic Blueprint; and The Mind God. His most recent books are The Last Three Minutes and It's About Time. He was described by the Washington Times as "the best science writer on either side of the Atlantic." He likes to focus on the deep questions of existence, such as how the universe came into existence and how it will end, the nature of human consciousness, the possibility of time travel, the relationship between physics and biology, the status of the laws of physics, and the interface of science and religion.



Another ans.



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?"

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.

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.