WHAT HAPPENED BEFORE THE BIG BANG?
By DENNIS OVERBYE
Like baseball, in which three strikes make an out, three outs on a side make an inning, nine innings make a regular game, the universe makes its own time. There is no outside timekeeper. Space and time are part of the universe, not the other way around, thinkers since Augustine have said, and that is one of the central and haunting lessons of Einstein's general theory of relativity.
In explaining gravity as the "bending" of space-time geometry, Einstein's theory predicted the expansion of the universe, the primal fact of 20th-century astronomy. By imagining the expansion going backward, like a film in reverse, cosmologists have traced the history of the universe credibly back to a millionth of a second after the Big Bang that began it all. But to ask what happened before the Big Bang is a little bit like asking who was on base before the first pitch was thrown out in a game, say between the Yankees and the Red Sox. There was no "then" then.
Still, this has not stopped some theorists with infinity in their eyes from trying to imagine how the universe made its "quantum leap from eternity into time," as the physicist Dr. Sidney Coleman of Harvard once put it. Some physicists speculate that on the other side of the looking glass of Time Zero is another universe going backward in time. Others suggest that creation as we know it is punctuated by an eternal dance of clashing island universes.
In their so-called quantum cosmology, Dr. Stephen Hawking, the Cambridge University physicist and author, and his collaborators envision the universe as a kind of self-contained entity, a crystalline melt of all possibilities existing in "imaginary time." All these will remain just fancy ideas until physicists have married Einstein's gravity to the paradoxical quantum laws that describe behavior of subatomic particles. Such a theory of quantum gravity, scientists agree, is needed to describe the universe when it was so small and dense that even space and time become fuzzy and discontinuous. "Our clocks and our rulers break," as Dr. Andrei Linde, a Stanford cosmologist likes to put it.
At the moment there are two pretenders to the throne of that ultimate theory. One is string theory, the putative "theory of everything," which posits that the ultimate constituents of nature are tiny vibrating strings rather than points. String theorists have scored some striking successes in the study of black holes, in which matter has been compressed to catastrophic densities similar to the Big Bang, but they have made little progress with the Big Bang itself.
String's lesser-known rival, called loop quantum gravity, is the result of applying quantum strictures directly to Einstein's equations. This theory makes no pretensions to explaining anything but gravity and space-time. But recently Dr. Martin Bojowald of the Max Planck Institute for Gravitational Physics in Golm, Germany, found that using the theory he could follow the evolution of the universe back past the alleged beginning point. Instead of having a "zero moment" of infinite density a so-called singularity the universe instead behaved as if it were contracting from an earlier phase, according to the theory, he said. As if the Big Bang were a big bounce.
TSIMTSUN (CONTRACTION OR WITHDRAWAL) "Luria pondered the question of beginnings. How did the process of EMANATION start? If Ein Sof pervaded all space, how was there room for anything other than God to come into being? Elaborating on earlier formulations, Lauria taught that the first divine act was not emanation, but withdral. Ein Sof (the Incomprehensible) withdrew its presence "from itself to itself," withdrawing in all directions away from one point at the center of its infinity, as it were, thereby creating a vacuum. This vacuum served as the site of creation...Into the vacuum Ein Sof emanated a ray of Light (Energy), channeled through vessels (the ten sifirot)...As the emanation proceeded, some of the vessels...shattered. Most of the Light (remained in its original form...while the shattered sparks became trapped in material existence). The human task is to liberate, or raise, these sparks, to restore them to divinity."
In their dreams, theorists of both stripes hope that they will discover that they have been exploring the Janus faces of a single idea, yet unknown, but which might explain how time, space and everything else can be built out of nothing. A prescription for, as the physicist Dr. John Archibald Wheeler of Princeton puts it, "law without law." (THE TAO).
Dr. Wheeler himself, the pre-eminent poet-adventurer in physics, has put forth his own proposal. According to quantum theory's famous uncertainty principle, the properties of a subatomic particle like its momentum or position remain in abeyance, in a sort of fog of possibility until something measures it or hits it. Likewise he has wondered out loud if the universe bootstraps itself into being by the accumulation of billions upon billions of quantum interactions the universe stepping on its own feet, microscopically, and bumbling itself awake. (tch tch). It's a notion he once called "genesis by observership," but now calls "it from bit" to emphasize a proposed connection between quantum mechanics and information theory.
One implication of quantum genesis, if it is correct, is that the notion of the creation of the universe as something far away and long ago must go. "The past is theory," Dr. Wheeler once wrote. "It has no existence except in the records of the present. We are all participators, at the microscopic level, in making that past as well as the present and the future."
If the creation of the universe happens outside time, then it must happen all the time. The Big Bang is here and now, the foundation of every moment. And you are there.
WHAT IS GRAVITY, REALLY?
By DENNIS OVERBYE
Gravity...it's not just a good idea. It's the Law," reads a popular bumper sticker. Gravity is our oldest and most familiar enemy, the force we feel in our bones, the force that will eventually bury us, sagging our organs and pulling us down, but for all its intimacy, it is a mystery. What really is the law?
For most of us it's the one that Isaac Newton proclaimed in 1687 as the rule of the cosmos, describing how (but not why) two objects attract each other with a force proportional to their masses and inversely proportional to the distance between them. But it's been rewritten and physicists expect that it will be rewritten again.
0 1 0 1 0 1 0 1 0 1 = 1 0 1 0 1 0 1 0 1 0
QUANTUM TIME (A GUAGE PARTICLE)
Newton's gravity was replaced by Einstein's general theory of relativity early in the 20th century. Einstein suggested that matter and energy warp space-time the way a heavy sleeper sags a cheap mattress, causing planets, basketballs and light beams to move in curved paths instead of straight lines. General relativity predicted the bending of light, the expansion of the universe and black holes, and has served as the foundation for modern cosmology, but theorists have never presumed that it would be the last word on gravity. For one thing, it is mathematically incompatible with the quantum laws that govern subatomic particles. In order to describe what happens at very small distances or very high energies corresponding to the first moments after the Big Bang, where space and time become discontinuous, general relativity has to be merged with quantum theory, a project that has engrossed the present generation of physicists.
But recently some experts have been wondering out loud if it is time to rewrite Einstein's version of the law as it applies to the other end of the length scale, to very long distances. The motivation comes from the predominance of what is sometimes called "THE DARK SECTOR" in the universe. According to what has recently become a highly celebrated "standard model," ordinary atoms make up only 5 percent of the "stuff" of the cosmos. Some kind of mysterious dark matter, perhaps consisting of elementary particles left over from the Big Bang, makes up 25 percent, while the rest a whopping 70 percent consists of something even more mysterious, known as "dark energy."
He made Darkness his secret place; his pavilions round about him were Dark waters, and thick clouds of the skies...(Psalm 18:11).
Obviously a theory that leaves 95 percent of the universe unexplained is less than a complete triumph.
Neither dark energy nor dark matter has been observed or detected directly. Each has been inferred from its gravitational effects on the tiny fraction of stuff we can see. As a result, some scientists have suggested that what astronomers have discovered in the last 20 years is their own ignorance of gravity. In particular, the discovery, five years ago, that the expansion of the universe is apparently accelerating, under the influence of that dark energy, has occasioned a re-evaluation of the old certainties.
The simplest explanation for dark energy is something called the cosmological constant, first invented by Einstein, a cosmic repulsion caused by the energy residing in empty space. But attempts to calculate this energy have resulted in numbers 1060 bigger than what astronomers have measured so large that the universe would have blown apart before atoms or galaxies could have formed causing theorists to throw up their hands. "I think we are so confused that we should keep an open mind to tinkering with gravity," said Dr. Michael Turner, a cosmologist at the University of Chicago. As a result of all this, physics literature has become peppered with suggestions of ways to change gravity. This fall, given a choice of explanations for dark energy during cosmology workshop at the Kavli Institute for Theoretical Physics in Santa Barbara, Calif., 20 of the 44 participants voted for some variation of "Einstein was wrong."
Some of these proposals take their cue from the science-fiction-sounding string theory, the putative theory of everything, which holds out the possibility that our universe might be a 4-dimensional membrane (or "brane") in an 11-dimensional space. (Allowing for the 11th hidden sefira named Daat)? Most of the vibrating strings that make up the particles and forces of nature in string theory would be stuck to the brane, like the nap on a rug. But the strings responsible for transmitting gravity would be able to drift away or "leak" into the meta-space surrounding the brane as they traveled along it from distant objects, according to a theory set forth in 2000 by Dr. Gia Dvali, Dr. Gregory Gabadadze and Dr. Massimo Porrati of New York University. The effect, they say, would be to make distant galaxies appear as if they were accelerating as they moved away from us.
"The sages of Israel relate: The Almighty created the world in the same manner as a child is formed in its mother's womb. Just as a child begins to grow from its navel and then develops into its full form, so the world began from a central point and then developed in all directions.
The "navel" of the world is Jerusalem (not that Jerusalem in the Middle East), and its core is the great altar in the Holy Temple...
...Within Old Jerusalem rises Mount Moriah upon which stood the Holy Temple (1 Corinthians 3:16-23; 6:14-19)...the shrine of the people of Israel. On the summit lies a big Rock, the Foundation Stone, because the world (the entire Universe) was founded on it. For Isaiah the prophet said: "Thus saith the Lord God: Behold, I lay in Zion for a foundation, a Stone...a costly corner stone of sure foundation." From the Legends of Jerusalem.
Also in a stringy vein is Cardassian expansion, named after the villainous race on "Star Trek," and dreamed up by Dr. Katherine Freese and Dr. Matthew Lewis of the University of Michigan. According to their theory, the universe accelerates as a result of other branes tugging on our own. "One can get an accelerating universe without having any dark energy," Dr. Freese said.
Other theorists are going back and modifying general relativity directly, noting that when he wrote it down Einstein chose the simplest possible equations that would carry out his ideas. But more complicated equations might be necessary. That was the approach taken by Dr. Turner and his colleagues, Dr. Sean Carroll and Dr. Vikram Duvvuri of Chicago, and Dr. Mark Trodden of Syracuse. The result was a universe that would speed up as it got bigger and emptier. That might sound crazy, Dr. Turner said, but not any crazier than the idea 80 years ago that the universe would be expanding.
The model raises as many questions as it answers, but it and others like it are still worth pursuing, Dr. Carroll said. "Something funny is going on when the universe gets to be 10 billion years old," he said, "and none of our current ideas is standing up and declaring itself to be the right answer, so we have to be bold."
The New York Times
SHORTEST DISTANCE IN GRAINY UNIVERSE
IS PLANCK LENGTH
by George Johnson
By measure hath He measured the times, and BY NUMBER hath He numbered the times; and He doth not move nor stir them, until the said measure (pulses) be fulfilled...(2 Esdras 4:37).
Slightly smaller than what Americans quaintly insist on calling half an inch, a centimeter (one hundreth of a meter) is easy enough to see. Divide this small length small length into 10 equal slices and you are looking, or probably squinting at a millimeter (one-thousandth, or 10 to the minus 3 meters).
By the time you divide one of these tiny units into a thousand minuscule microns, you have far exceeded the limits of the finest bifocals.
But in the mind's eye, let the cutting continue, chopping the micron into a thousand nanometers and the nanometers into a thousand picometers, and those in steps of a thousandfold into femtometers, attometers, zeptometers, and yoctometers.
At this point, 10 to the minus 24 meters, about one-billionth the radius of a proton, the roster of convenient Greek names runs out. But go ahead and keep dividing, again and again until you reach a length only a hundred billionth as large as that tiny amount: 10 to the minus 35 meters, or a decimal point followed by 34 zeroes and then a one.
You have finally hit rock bottom: a span called the Planck length, the shortest anything can get. According to recent developments in the quest to devise a "theory of everything," space is not an infinitely divisble continuum. It is not smooth but granular, and the Planck length gives the size of the smallest possible grains.
The time it takes for a light beam to zip across this tiny distance (about 10 to the minus 43 seconds) is called the Planck time, THE SHORTEST POSSIBLE TICK OF AN IMAGINARY CLOCK. Combine these two ideas and the implication is that SPACE AND TIME HAVE A STRUCTURE. What is commonly thought of as the featureless void is built from tiny units, or quanta...
Einstein, Strings and Unity
The hints of graininess come from attempts to unify general relativity, Einstein's theory of gravity, with quantum mechanics, which describe the workings of the three other (known) forces: electro-magnetism and the strong and weak nuclear interactions. The result would be a single framework--sometimes called quantum gravity--that explains all the universes particles and forces.
The most prominent of these unification efforts, superstring theory, and a lesser-known approach called loop quantum gravity, both strongly suggest that space-time has a minute architecture. But just what the void might look like has physicists straining their imaginations.
As Dr. John Baez...put it: "There's alot we don't know about nothing," (about Ein Sof)...
The development of modern atomic theory, in the 19th century, pushed science toward viewing the universe as lumpy instead of smooth, (discontinuous instead of continuous). At the beginning of this century, sentiments swung further in that direction when Max Planck found that even light was emitted in packets. From that unexpected discovery emerged quantum field theory, in which all the forces are carried by tiny particles, or quanta--all, that is, except gravity. (Gravity is transmitted by particles of time).
This force continues to be explained, in entirely different terms, by general relativity: as the warping of a perfectly smooth continuum called space-time. A planet bends the surrounding space-time fabric causing other objects to move toward it like marbles rolling down a hill.
Scientists have long assumed that unification would reveal that gravity, like the other forces, is also quantum in nature, carried by messenger particles called gravitons. But while the other forces can be thought of as acting within an area of space and time, GRAVITY IS SPACE-TIME. Quantizing one is tantamount to quantizing the other...
More recently, physicists have suggested that quarks and everything else are made of...superstrings vibrating in Ten dimensions. At the Planck level, the weave of space-time would be as apparent as when the finest Egyptian cotton is viewed under a magnifying glass, exposing the warp and woof... The New York Times Service.
One Cosmic Question, Too Many Answers
By DENNIS OVERBYE
September 2, 2003
Einstein once wondered aloud whether "God had any choice" in creating the universe. IT WAS HIS FONDEST HOPE THAT THE ANSWER WAS NO. He and subsequent generations of physicists have hoped that at the end of their labors there would be one answer a so-called Theory of Everything that would explain why the details of the world are the way they are and cannot be any other way: why there was a Big Bang, the number of dimensions of space-time, the masses of elementary particles.
For 20 years, physicists have lodged those hopes in string theory, a mathematically labyrinthian effort to portray nature as made up of tiny wriggling strings and membranes, rather than pointlike particles or waves. Once called a piece of 21st-century physics that had fallen into the 20th century by accident, string theory has become one of the hippest fields of science, celebrated in books like the recent best seller "The Elegant Universe," by the Columbia theorist Brian Greene, and the subject of a miniseries on "Nova," coming this fall.
In principle, strings can unite all the forces of nature, including gravity, in a single mathematical framework. But the "stringiness" of nature manifests itself only at energies and temperatures that can be generated in a particle accelerator the size of a small galaxy. As a result, physicists have been left at the mercy of their mathematical imaginations or sifting cosmological data for hints of a clue from God's own particle accelerator, the Big Bang.
The hope was that when all was said and done, there would be only one solution to the theory's tangled equations, one answer corresponding to only one possible universe. But recent progress in string theory paradoxically seems to leave physics further than ever from that dream of a unique answer. Instead of a single answer, the equations of string theory seem to have so many solutions, MILLIONS UPON MILLIONS OF THEM, each describing a logically possible universe, that it may be impossible to tell which one describes our own. (Hmmm, let's see now, how many individual souls are there in the universe)?
In a series of conceptual and technical breakthroughs, a group of theorists at Stanford showed this year that string theory could describe a universe whose expansion was accelerating something that many experts thought impossible. That was no small accomplishment because cosmologists now theorize that some puzzling AND SO FAR UNIDENTIFIED "DARK ENERGY" is wrenching space apart ever more violently. THIS ENERGY SEEMS TO MAKE UP ABOUT 70 PERCENT OF THE COSMOS, according to astronomical observations.
The new calculations suggest that this dark energy cannot last forever, that it will disappear sometime in the far future, according to the researchers, Dr. Shamit Kachru, Dr. Renata Kallosh and Dr. Andrei Linde, all of Stanford, and Dr. Sandip P. Trivedi of the Tata Institute of Fundamental Research in Bombay. But the same calculations confirmed that string theory could have a vast number of solutions, each representing a different universe with slightly different laws of physics. The detailed characteristics of any particular one of these universes the laws that describe the basic forces and particles might be decided BY CHANCE. (Is this like Natural Selection)?
As a result, string theorists and cosmologists are confronted with what Dr. Leonard Susskind of Stanford has called "THE COSMIC LANDSCAPE," A SORT OF METAREALM OF SPACE-TIMES. Contrary to Einstein's hopes, IT MAY BE THAT NEITHER GOD NOR PHYSICS CHOOSES among these possibilities, Dr. Susskind contends. RATHER IT COULD BE LIFE. (God = Life = God)
Only a fraction of the universes in this metarealm would have THE LUCKY BLEND of properties suitable for life, DR. SUSSKIND EXPLAINED. It should be no surprise that we find ourselves in one of these. "We live where we can live," he said.
Dr. Susskind conceded that many colleagues who harbor the Einsteinian dream of predicting everything are appalled by that notion that God plays dice with the laws of physics. Among them is Dr. David Gross, director of the Kavli Institute of Theoretical Physics in Santa Barbara, Calif., who said, "I'm a total Einsteinian with respect to the ultimate goal of science." Physicists should be able to predict all the parameters of nature, Dr. Gross said, adding, "They're not adjustable." But Dr. Max Tegmark, a cosmologist at the University of Pennsylvania, said, "I think this grand dream is basically dying."
Dr. Michael Douglas of Rutgers and the Institute of Advanced Scientific Studies, near Paris, called the plethora of string universes "the Alice's Restaurant" problem. "You can get anything you want at Alice's Restaurant," he said. "Is this a theory of something, very many things or nothing? That's what we're trying to establish."
The Early Hopes: Not Particles, but Strings
The question of whether strings will provide a unique answer to the universe has been hanging over physicists' heads ever since the modern form of string theory made its triumphal emergence in 1984. That year, Dr. John Schwarz of the California Institute of Technology and Dr. Michael Green, now of Cambridge University in England, showed that thinking of elementary particles as little strings instead of points eliminated troublesome mathematical anomalies from theories that sought to combine gravity with subatomic physics.
Even Einstein had failed to unite those disparate and mathematically incompatible realms. But the 1984 calculation raised the hope that physicists had finally found the key to the so-called Theory of Everything. "There was this wild enthusiasm, unbridled enthusiasm, that we paid for later," said Dr. Andrew Strominger, a professor of physics at Harvard.
In 1985, Dr. Strominger, Dr. Edward Witten of the Institute for Advanced Study in Princeton, Dr. Gary T. Horowitz, now at the University of California at Santa Barbara, and Dr. Philip Candelas, now at the University of Texas, published a classic paper showing that it was possible to construct a string theory consistent with the so-called Standard Model that describes particles and forces in our four-dimensional universe.
ONE PROBLEM IS THAT STRING THEORY REQUIRES TEN DIMENSIONSOF SPACE-TIME, WHEREAS WE LIVE IN FOUR. Dr. Strominger remembered being excited when he found a paper by the mathematician Dr. Shing-Tung Yau, now of Harvard and the Chinese University of Hong Kong. It proved a conjecture by Dr. Eugenio Calabi, now retired from the University of Pennsylvania, that the extra dimensions could be curled up in microscopically invisible ways like the loops in a carpet.
0 Dimensions....ONE Force; 1 Dimension...Two Forces; 2 Dimensions....Three Forces; 3 Dimensions...Four Forces; 4 Dimensions....Five Forces.
The paper described only one way this folding could be done. But Dr. Yau soon told the physicists that there were thousands of what are now called Calabi-Yau spaces, each one representing a different solution of the string equations. By the time their paper was finished, "the uniqueness of string theory was certainly already in question," Dr. Strominger said.
That was just the beginning. For each of the thousands of ways of curling the extra dimensions into Calabi-Yau spaces, there were hundreds of variations in details like the sizes of the loops and the way electrical and magnetic fields thread through them. When the variations are taken into account, the number of solutions and the number of possible universes can easily exceed 10100.
The Challenge: A Universe Unfit for Life or Physics?
This bounty of possibilities makes it extremely daunting for scientists who want to test string theory by comparing its predictions to the real world. One telltale clue to the right answer, as well as a huge challenge, developed five years ago when astronomers discovered that the expansion of the universe was apparently accelerating. But until recently, many theorists doubted that strings could produce even one example of an accelerating universe. The reason is that the leading explanation for this behavior is a cosmic repulsion, known as THE COSMOLOGICAL CONSTANT, that results from the properties of empty space itself. It was first invented by Einstein in 1917 as a fudge factor to stabilize the universe and then abandoned by him when astronomers found out that THE UNIVERSE WAS NOT STATIC, BUT EXPANDING (as Human Consciousness itself).
If Einstein's fudge factor is real after all, the universe will continue to expand faster and faster AS SPACE GROWS BIGGER AND BIGGER, producing more and more repulsion.
String theorists did not know how to deal with the cosmological constant. According to quantum mechanics, the weird laws that govern subatomic physics, EMPTY SPACE SHOULD BE FOAMING WITH ENERGY AND PARTICLES THAT WINK IN AND OUT OF EXISTENCE, and their collective effect could produce a repulsive force like Einstein's constant. But the calculations also suggest that this force should be some 1060 times what astronomers have measured; (and) it would have blown the universe apart in its first millisecond, long before atoms, galaxies or humans could form.
Moreover, a permanently accelerating universe would present DEEP CONCEPTUAL PROBLEMS, several physicists pointed out, including Dr. Thomas Banks of Rutgers and the University of California at Santa Cruz, Dr. Willy Fischler of the University of Texas, Dr. Susskind and Dr. Witten. Such a universe WOULD SLOWLY EMPTY ITSELF OF ENERGY AND INFORMATION because most of the galaxies would eventually be flying away so fast that humans could not see them. The observable universe would actually shrink, as if surrounded by a black hole. Life would become impossible, and the usual methods of formulating physics might not apply.
Heaven and earth shall passaway but my Word shall never pass away...
I am the Door
As a result of such arguments, it was widely presumed that a universe that accelerated forever that is, one with a cosmological constant was incompatible with string theory, Dr. Kachru of Stanford said. It was partly to counter such claims, he added, that he and his colleagues were motivated to look for the cosmological constant in the gazillions of possible string universes.
The Hitch A Breakthrough, but a Bleak One
Last winter, Dr. Kachru and his colleagues succeeded in using string theory to construct universes that accelerated, but with a surprising twist. The hitch, in each case, was that the acceleration would be only temporary. It might last an extremely long time, but eventually the dark energy of the cosmological constant would melt away, decaying just in time to avoid the problems of permanent acceleration that string theorists have worried about. The universe would then coast for the rest of eternity.
The work followed on previous work by Dr. Kachru with Dr. Joseph Polchinski of the Santa Barbara Institute and Dr. Steven Giddings of the University of California at Santa Barbara, and by Dr. Polchinski and Dr. Raphael Bousso of the University of California at Berkeley. Part of the reason dark energy decays, explained Dr. Linde of Stanford, is that these solutions describe the four-dimensional universe we observe around us three dimensions of space and one of time WITH THE OTHER SIX CURLED UP SO TIGHTLY that they cannot provide closet space. But it takes energy to keep the extra dimensions confined. "IN THE LONG RUN," HE SAID, THE UNIVERSE DOESN'T WANT TO BE FOUR-DIMENSIONAL. IT WANTS TO BE TEN-DIMENSIONAL."
So sooner or later, the loops will unravel like a tangle of rubber bands, passing through a succession of configurations that take less and less energy to maintain, until finally the other dimensions expand and the cosmological constant is gone. THE DECAY OF THE COSMOLOGICAL CONSTANT WILL BE FATAL, ASTRONOMERS AGREE. At that moment a bubble of 10-dimensional space will sweep out at the speed of light, rearranging physics and the prospects of atoms and planets, not to mention biological creatures. "What it leaves behind," Dr. Susskind said, "it's hard to say. Almost certainly not a livable universe."
The Role of Luck: A Controversial Idea Returns to Stage
The universe is certainly livable now, but why has long been a vexing and polarizing issue. Life as We Know It SEEMS TO REQUIRE AN ALMOST MIRACULOUS JUGGLING OF A FEW ATOMIC AND ASTRONOMICAL PARAMETERS. WAS THE UNIVERSE DESIGNED FOR US? OR DID WE JUST GET LUCKY?
Searching for answers, some theorists have invoked THE SO-CALLED ANTHROPIC PRINCIPLE, which states that our universe has to have laws suitable for life. Otherwise we would not be here to see it. The apparent "fine-tuning" of this universe is simply an artifact of our own existence here as observers, Dr. Brandon Carter, now at the Paris Observatory in Meudon, argued in 1974. The principle fits well with recent theories of the Big Bang that suggest that the universe seen through telescopes is just one in an endless chain of bubble universes that sprout from one another.
If there is just one universe, the fact that it suits us would seem suspiciously lucky. BUT IF THERE ARE MANY UNIVERSES TO CHOOSE FROM, OUR EXISTENCE IS LESS MIRACULOUS. It might be the diversity of string-theory universes that gives this metacosmos a chance at harboring life, Dr. Susskind says.
He likes to portray it as a mountain range, the "cosmic landscape," in which the height of the peaks represents the energy or the cosmological constant of that configuration. The universe is like water rolling around the hills, always seeking a lower state. There are valleys and basins and plateaus where it can rest. But it can spread, plopping like a wave sloshing over the hills from valley to valley, from one configuration of dimensions and fields to another.
As a result, he said, in whatever form it starts, the universe will branch out into other forms. If it keeps sloshing, it will eventually land in a valley with the lucky mix of cosmic constants that allows for galaxies and carbon-based chemistry somewhere. If a small fraction of the subuniverses can support life, then there is a good chance that life will arise somewhere, Dr. Susskind explained. Others caution, however, that IT HAS NOT BEEN PROVED THAT DIFFERENT CLASSES OF UNIVERSES WOULD BE SO CONNECTED. "It could be that there are many disconnected landscapes," explained Dr. Douglas of Rutgers.
Dr. Susskind said that "whether we like it or not," the new findings gave further credence to the anthropic principle and a mathematical framework for how it might work. But such "anthropic thinking" is defeatist to many physicists. "We see this kind of thing happen over and over again as a reaction to difficult problems," Dr. Gross said. "Come up with a grand principle that explains why you're unable to solve the problem." The notion that some problems are unsolvable is discouraging to the younger generation, he said, pointing out that nobody even knows what the final form of string theory will be.
Dr. Witten said he also disliked the anthropic principle. "I continue to hope that we are overlooking or misunderstanding something and that THERE IS ULTIMATELY A MORE UNIQUE ANSWER," he wrote by e-mail.
Dr. Susskind conceded that he had once been on the other side of the question. "I've had myself jerked around by this theory," he said. "When you have to give up your fondest dream for what the theory would do" a reference to the quest for a unique answer "that's a hard thing to swallow."
The Future: Still Listening for Orderly Music
Dr. Strominger of Harvard said the debate on anthropic principle was indicative of the "all-or-nothing psychology" of string theory. "It's not enough to solve some problems," he said. "It has to solve every problem." Theorists have long hoped that all but one of these solutions will eliminate themselves through some mathematical inconsistency or failure to reproduce an essential feature of the universe like the cosmological constant. Dr. Douglas of Rutgers has challenged that hope, saying string theory may have so many solutions that physical measurements can not distinguish among them. Indeed, he pointed out in a recent paper, it has not been proved that string theory does not have an infinite number of solutions. So far, anything seems possible.
Rather than sifting myriad solutions for the one that fits our universe, Dr. Douglas has developed statistical methods to analyze the set of string solutions as a whole TO FIND PATTERNS that will not show up when the solutions are examined one by one. The results could help ascertain which features of this "zoo of possibilities" are more common and which are more rare, and how many solutions really are too many.
"My own philosophy," Dr. Douglas said in an interview, "is that we should do our best to listen to what string theory is trying to tell us. It is smarter than we are."
Dr. Kachru suggested that it might be wishful thinking to expect that a "smoking gun" confirmation of string theory could be found from comparing it to today's universe. THE FULL GLORIES of string theory, he said, MANIFEST THEMSELVES ONLY AT ENERGIES TRILLIONS OF TIMES WHAT EARTHBOUND PARTICLE ACCELERATORS CAN PRODUCE.
Perhaps, he said, theorists should be looking for the smoking gun in the Big Bang. Asked what the smoking-gun question might be, Dr. Kachru laughed and said, "If I knew, I would be working in that field."
2003 The New York Times, Sept.2, 2003
If Paradise is the state of ultimate and perfect symmetry, the history of the Big Bang resembles that of "Paradise lost." For the briefest instant at the origin of Time when all laws of physics were on equal footing, all of nature's elementary particles, heavy and light alike, interacted freely and democratically. The most exotic particles known, or even dreamt of, by man were liberated to participate in this unrestrained interchange...
This idyllic era, however, was doomed to transience. Once the temperature began its inexorable fall, the symmetries were broken. Paradise was irretrievable lost.
One of the most extraordinary things about our universe is that although it often appears, at first sight, to be perfectly symmetric, closer examination invariably reveals that the symmetry is not quite exact. The universe is almost, but not quite uniform over its largest expanses; elementary particles are almost, but not quite the same as those that are their mirror images...We invariably find that the tiny breaches in the perfect pattern we might have expected to find are the cogs of a glittering mechanism at the center of things, and one of the reasons our very existence is possible...
A neutrino, A GHOSTLY SPINNING ELEMENTARY PARTICLE, carries with it not only an uncanny reminder of a time when symmetries were perfect but also clues as to how they came to be broken. For every neutrino that now spins to the Left, there was once, near the "Big Bang," a neutrino that spun to the Right. Around us now, we see only Left-handed neutrinos; their Right-handed partners did not survive the early stages of the universe to emerge into the present era of broken symmetry. It is not only neutrinos that fail to be ambidextrous. Even biological development is a breaking of perfect symmetry. The essential biological molecules, the helical building blocks of Life, are Left-handed spirals. We find only the Left-handed amino acids in living things, never their mirror images. This tale of broken symmetries extends from the beginning of Time to the here and now." The Left Hand of Creation, by John Barrow and Joseph Silk.
Two Universes, both flashing on and off in the same Space, in their own separate measure of Time.