M

Chicken Tracks and Immortality
Every day, about 500 of the world's deepest thinkers log on to a Web site, hosted by the Los Alamos National Laboratory in New Mexico, that is a clearinghouse for scientific papers. Ever since a major breakthrough was posted to the site in 1995, the world's most abstract vision of the order of the universe -- string theory -- has developed rapidly there, and with unprecedented reach.

To the nonscientist, technical papers on string theory look as if a flock of muddy chickens had run a race on them. Written in a strange form of English, the papers' sentences often are broken up by weird number riffs that try to focus ideas when the precision of ordinary language collapses.

Certain types of physicists, however, find these scientific papers to be the epitome of elegance, because these papers unite, in a potentially historic way, previously discordant explanations of how the universe works.

The papers say we live not just in the four dimensions that ordinary mortals sense -- height, width, length, and time -- but in seven more. They say that everything in this 11-dimension universe is made up of very tiny objects that vibrate like violin strings, and throw off (poetically speaking) "notes" that we, trapped in our four-dimensional consciousness, perceive as energy or matter.

The quest to find The Answer -- to draw the heavenly blueprint of the whole universe, from inframicro to ultramacro -- has entranced and consistently frustrated physicists of the post-Einstein era. If string theory's claims are ever validated in the eyes of a Nobel Prize committee, the discoverers of the Theory of Everything will become living gods on Earth. They will very likely become as eternally famous as Einstein, Galileo, Newton, and the very few other scientists whose discoveries changed how the world viewed itself, instantly and forevermore.

Many physicists believe that a variant on string theory -- known, somewhat cryptically, as M -- does in fact unite previously irreconcilable views of the universe into one elegant set of mathematical calculations. In a collective yet highly competitive enterprise, scientists in Russia, India, Europe, Japan, and America -- where Stanford University and the University of California at Berkeley play leading roles -- are furiously trying to expand string theory's reach, and its acceptance as an explanation for the physical universe.

Unfortunately, there is no machine in existence that can prove the string theorists' speculative picture of reality to be true. Such proof may stand out of scientific reach for decades, or forever, but if it ever comes, scientific immortality and Nobel Prizes are almost sure to follow.

Thought Experiments on the Couch
Most days you can find Stanford University physics professor Eva Silverstein, age 28, sitting on a couch in the common room at the department of physics. Down the hall is a battered wood case that looks like it should hold football trophies. It contains, instead, 10 Nobel Prizes for physics; Stanford professors have won five just since 1990. Sunk deep into comfortable leather, the diminutive Silverstein holds forth -- and holds her own -- with the male heavies of string theory.

Whole paragraphs of intense thought tumble off the youthful Silverstein's tongue as her hazel eyes glitter with the sheer fun of doing high-energy theoretical physics. She has a sense of delight, but, make no mistake: She is a contender in the race to find The Answer.

Silverstein is new to Northern California. One of the world's dozen female string theorists, she learned about Einstein's theory of special relativity when she was attending high school in Spokane, Wash. "The fact that time could slow down blew my mind," she recalls.

So it was on to undergraduate work in physics at Harvard University, and then doctoral work at Princeton. Last year, Silverstein landed a $75,000 assistant professorship and a tiny office at the Stanford Linear Accelerator Center in Palo Alto.

She and other polo-shirted theorists sprawl out in their conversation pit, taking turns chalking intricate formulas on a long blackboard and vocalizing what they call "conjectures." Each and every idea could be the key to achieving Nobel status.

One of the regular couch potatoes is another Bay Area newcomer, Stanford physics professor Stephen H. Shenker. Shenker, age 45, is a fairly typical string theorist. Born to a physicist father and a psychologist mother, Shenker also got turned on to relativity in his teens. He self-deprecatingly admits to not having been very good at high school physics -- "Inclined planes bored me silly," he says -- but was knighted as a "genius" by the MacArthur Foundation 13 years ago.

I met Steve in the fourth grade, before he read Einstein's work. Not only was he an invaluable source for arithmetic answers, but he was also good at dodge ball. We've been friends for nearly 40 years, and during that time, he has periodically informed me that this time the physicists have cracked the answer. When the now gray-haired Shenker talks animatedly about the serious adventure of modern physics, I still see a starry-eyed kid plotting how to blow up model airplanes with homemade firecrackers.

The incendiary tendencies of Shenker's adolescence eventually gave way to exploring the cause of much bigger bangs in the universe. But the compulsion to create a commotion lingers -- tempered by the anxieties of adulthood.

As one of the shakers of string theory, Shenker helped create a theory group at New Jersey's Rutgers University in the early 1990s. The group was a bit revolutionary in its approach to collaboration, says Silverstein, who did postdoctoral work with Shenker. "It was kind of like a Quaker meeting," she remembers.

Instead of sitting through "snobby" lectures, Shenker and his colleagues gathered and spoke whatever was on their minds, even when it came out as stream-of-consciousness rambling. Silverstein says that the Rutgers collective approach to thinking is being copied at string theory centers around the world, including Stanford.

The open discourse that has fueled advances in string theory seems, at times, dangerously self-sacrificing. The price of hearing the new ideas of others is to risk having your own new ideas ... appropriated. The art of physics is no longer an individualistic pursuit, as it was for Sir Isaac Newton, or Albert Einstein. Twenty-first-century string theory is a problem-solving game, and to play, group participants need to know a little bit about all the realms of math and physics. Most important, they need to listen to one another.

Listening to the conversation flowing from the Stanford physics couches is anything but relaxing. Trying not to drown in a sea of jargon, at one point I ask what I fervently hope to be an intelligent question. After an embarrassed silence, Shenker takes pity and whispers, "We stopped talking about that an hour ago."

Later, Shenker confides that he was sad to leave the Rutgers theory group, which had significantly advanced the frontiers of string theory. But the world of physics requires cross-pollination of minds, and one of string theory's founders was, and still is, at Stanford.

At age 58, Leonard Susskind claims elder status in the string revolution; he was, after all, a midwife to string theory at its birth in 1969. Neither he nor Shenker has any truck with the scientists who try to popularize their ideas with talk of worm holes and time machines and Star Trek-ian warp drives. But both physicists are eager to translate, into mundane language that the general public might grasp, the sheer natural beauty they have glimpsed through the looking glass of their mathematics. Today, for example, over cheap lunch in a student cafeteria, they are chewing over one of string theory's odder postulations: that black holes exist at both ends of the universe.

In the large -- cosmological -- scale, black holes are ancient stars that have collapsed in on themselves until all of their matter becomes condensed -- so condensed and heavy, in fact, that not even light can escape their massive gravitational fields. All of known physics falls apart at the entrance to a black hole. It is a realm from which no visitor can return -- even in the "thought experiments" that characterize theoretical physics. These type of black holes have been described well enough in the popular press to be known to many nonscientists.

Now, Susskind explains, some of the smallest objects in the universe also are being described as black holes -- black holes so small that they compare to an atom, in the same proportion that an atom would compare to the size of the solar system. In fact, explains the scruffy visionary, tiny black holes may be a basic building block of nature.

In a string-related sort of way.

Stringing the Large to the Small
Twentieth-century physics devoted itself to exploring two great scientific principles: gravity and quantum mechanics. The laws of gravity govern the motion of very large objects, such as planets. The rules of quantum mechanics describe the motion of unimaginably small things: the components of atoms.

Albert Einstein showed that gravity -- acting over tremendous distances -- actually shapes the geometry of the universe. Along the way, Einstein proved that nothing can travel faster than the speed of light, and that time itself slows down as objects approach that 186,000-miles-per-second limit.

But Einstein's theories -- known generally as relativity -- don't work for describing the motion of very small objects moving around each other at extremely small distances. For this type of subatomic calculation, Max Planck invented the science of quantum mechanics during the Roaring '20s. Radio, radiation therapy, and hydrogen bombs are all practical offshoots of quantum mechanics.

Quantum mechanics also injected a systemic uncertainty into the observation of elementary particles, from protons and electrons down to the almost chimerical quarks. To the disgust of Einstein -- who believed in a God-ordered universe -- quantum mechanics was based on probability, on chance. And its rules were not compatible with the rules of Einstein's relativity.

Einstein died still trying to think up the "unified field theory" that could combine the laws of the big with the rules of the ineffably small.

In the late 1960s, government-subsidized physicists were trying to explain the mysterious force that binds together certain particles at the center of the atom called protons. Fragmentary evidence indicated that the protons might themselves result from the movement of infinitesimally small, stringlike objects: little loops of energy that vibrate through 25 dimensions of space. Oops, said the scientists. We can't deal with the four dimensions we already have -- three of space and one of time -- so forget these strange string things.

But a few bold and stringy souls persisted, despite the ridicule of their peers and their assignment to relatively menial jobs. In 1984, John Schwarz, a research associate at the California Institute of Technology, and Michael Green of Cambridge University made crucial discoveries in "superstring" theory.

Advancing the eclectic mathematics that fuels string theory, these intrepid pioneers discerned that what had been perceived as fatal flaws in the theory were actually blessings. To the astonishment of the physics world, a theory of "quantum gravity" was shown to be possible. Creating the unified field theory Einstein had failed to find -- uniting gravity and quantum mechanics -- seemed to be an equation or two away.

Now, Available in Only 10 Dimensions ...
It turns out (at least according to string theory) that when physicists write equations describing reality in the four "normal" dimensions, they only "see" shallow aspects of the vibrating string. But when the universe is mentally modeled in 10 dimensions, more complexity is revealed.

The six "extra" dimensions are minuscule measurements: not much bigger than a string itself. So why are they important?

In each dimension, the vibration of the string emits what may be metaphorized as a musical note. Physically stuck inside four dimensions, we humans experience each harmonically connected note as a different type of elementary particle. For instance, certain vibrations of a string create quarks, which stick together to form the protons at the center of the atom. Other vibrations make photons, the elementary packets of energy that we see as light. To date, physicists can only wet-dream of finding evidence of a graviton, the force-carrying particle of gravity slung off by a string.

String theory continued to evolve during the '80s and early '90s. For a while, science writers hyped it as a Theory of Everything. But millennial expectations of the theory abruptly died when five different -- and incompatible -- string theories appeared.

An embarrassing surfeit of theory had been produced; and nobody knew how to make five inconsistent postulations fit into one elegant theory. The string theorists had uncovered a wealth of circumstantial evidence that could not be accurately backtracked to basic scientific principles. It was as if a crime detective had discovered a gun, blood, and a spent bullet, but could not say what crime had been committed.

Yet another attempt to invent a theory of quantum gravity had flopped, because nobody could tie up all the loose string theories. Disappointed stringies wandered off to plow other fields, until universal hell broke loose in 1995.

M Is For ...
Steve Shenker's colleagues describe him as one of the top five or six string theorists in the world. Shenker talks more modestly about the role he has played in string theory.

In the early years of his career, he studied something called phase transitions, which is what happens when, say, water changes into steam or ice. Study of physical change led directly to string theory, because anything that changes must be made up of smaller things that change. And there are rules governing all change.

"Physics is like chess," says Shenker. "There are rules, and then there are the consequences of using the rules. We study strings to discover what the rules of the game are, the basic principles governing how the universe is allowed to move."

Discovery, for Shenker, occurs as a flash of intuition. He lives and breathes string theory, and every few years a big idea occurs to him, usually in a group setting. But mostly, theorizing is a game of trial and error. Shenker floats his speculations like balloons, and his $200,000-a-year peers shoot at them.

With eyes constantly cocked on the Nobel Prize, physicists have developed an elaborate system of credit apportionment. But more than personal glory is at stake -- program funding, after all, is based on lists of professional accomplishments. Technical papers are full of exact acknowledgements of the slightest remark of one person that inspired even a mildly important thought by another. And although string theory may be the most collective thinking endeavor since the Manhattan Project, each scientist jealousy guards his individual thought-turf. String etiquette frowns on those who would appropriate even a shred of another's intuition without crediting the fount.

Between moments of joyous discovery, Shenker says, he is subject to personal fears and career anxieties of the ordinary corporate variety. Indeed, the search for the Theory of Everything carries enormous, if subtle, stresses and strains. The scientists of the string theory club do not, by and large, discuss personal problems. But the quest to explain the universe has led to divorce, nervous breakdown, even suicide. Once a person performs a mental feat, after all, the world of science expects it to be repeated. A string theorist's nightmare is to become a dandruffed, inspirationless has-been, shuffling around the quad, pitied by freshmen.

In the pantheon of physics, epochal flashes of genius have often occurred to scientists in their 20s. In the past, in fact, it had been thought that a theorist had only until the age of 30 to make a major discovery, or else be considered a failure. But most successful string theorists are well into middle age. This may be due to Shenker's Theorem (as related by the venerable Leonard Susskind), which states that old ideas discarded in decades past will always come back to haunt the string theorists. Hence, older physicists will remember forgotten trivia -- such as Kaluza-Klein supergravity -- that becomes suddenly vibrant.

And then there is "duality." Theories of the unity of opposites are not new, but string theory found a unique application for the concept of duality. And it is in this sphere that Shenker has made some of his largest scientific contributions.

The fact that human life evolved in four large dimensions prohibits humans from directly investigating the universe of the very small. Until now, physicists have extracted clues about subatomic particles by accelerating them to great speeds, running them into one another, and looking at the resulting debris. But strings are so incomprehensibly small that a particle-colliding machine capable of probing their realm would have to be at least the size of the Milky Way galaxy.

So indirect methods of detecting the unfathomable have been invented. Physi-cists have been forced to resort to "thought experiments."

A duality thought experiment might define the behavior of one object in terms of another. For instance, if water poured into a bowl collects first at the lowest point of the bowl, one can reasonably infer -- from this very small model -- that the Earth's vast oceans filled up the deepest valleys first.

String theory reaches back to 19th-century physics, when James Clerk Maxwell showed that electricity and magnetism are dual aspects of the same force -- electromagnetism. Using the precepts of duality, weak natural forces can be shown to mirror strong forces, and visible forces can be related to invisible forces. Seeming opposites can be shown to have the same cause.

The concept of duality led Edward Witten, a physics professor at the world-famous Institute for Advanced Study in Princeton, N.J., and a pivotal figure in modern physics, to invent the first mathematically consistent theory of quantum gravity. This spectacular leap, made public in March 1995, linked the five ugly -- asymmetrical -- string theories into one unified theory, called M-theory. (Michael Duff of Texas A&M University and Paul Townsend of Cambridge University independently made similar discoveries.)

"M" has been variously described as standing for magic, mystery, mother, membrane, and matrix. In other words, it doesn't have a real name because nobody knows what it is named after, but gravity fits M-theory. And so do the equations of quantum mechanics.

M-theory is the most likely candidate for a Theory of Everything, although some stringies seem embarrassed to be making such a grand claim. They qualify their braggadocio with a disclaimer: M is a Theory of Everything That We Already Know. They cannot, however, hide their excitement, and ambitions. Nobody knows what the equations that rule the behavior of the universe will yield in the way of practical application. But there is no doubt whatsoever that lots of fame and money await the anointed discoverers of The Answer.

The nasty particle in the ointment, however, is that M-theory is only a thought experiment. It cannot be proved in the real world. And -- even though it unites gravity and quantum mechanics on paper -- it cannot yet define the basic principles that govern the universe. Nevertheless, it appears to be an amazing achievement of the human mind -- even if the nitty-gritty of the mathematics is veiled from most people's comprehension.

The 11th Dimension
Witten et al. solved the problem of uniting five unruly, 10-dimensional theories by peeping into a higher dimension: the 11th dimension. This was the mathematical equivalent of stepping inside the forest to see the trees. Or, peeling open the tennis ball to reveal the space inside.

When Witten et al. mentally stepped into the 11th dimension, they saw that each of the five previously incompatible string theories share the 11th dimension: a measurement 1 billion trillion times smaller than the atomic nucleus. It had previously been hidden from mental perception because strings wrap themselves around it like a tennis ball -- or inner tube -- wraps around empty space.

When viewing string theory from four-, five-, or 10-dimensional perspectives, it appears to be fragmented. When looked at from inside the littlest, 11th dimension, all the string theories become a whole: M-theory.

Physicists around the world gasped when Witten posted M-theory on the Los Alamos Web site four years ago. The discovery of the 11th dimension unleashed hundreds of new ideas and revelations.

Steve Shenker, Leonard Susskind, Tom Banks, and Willy Fischler were inspired to invent an offshoot of M-theory -- what they call Matrix Theory -- in 1996. Shenker simplifies the discovery by comparing it to a chart in which cities are listed in relation to mileage. To find the miles between two cities you follow the lines inside the matrix to a coordinate. Only, in this case, there are multiple coordinates, because there are multiple dimensions, or multiple ways to measure where and when a string is.

(The theorists carry these matrices around in their heads -- massaging the numbers without benefit of computers. For purposes of discovery, they tend not to use the powerful computers at their command, because machines are stupid; they have no intuition, no art.)

For a short while, Shenker and his collaborators were the toast of the high-energy physics world. Then, a new theory of "p-branes" burst upon the scene. The physicists gasped again.

The newest fad in M-theory says that a string is fashioned from a kind of membrane -- a p-brane -- wrapped around the previously hidden 11th dimension. Nobody is prepared to say what the difference is between a brane and a string, but, it seems that some strings are built from branes that are actually tiny black holes -- that is, black branes.

Is M Real?
Inside her normal four dimensions, Eva Silverstein relaxes by playing soccer, running, and reading fiction -- but not science fiction. Who needs science fiction, she snorts, when you have M-theory?

As she talks strings, words spill out of Silverstein's mouth, but their meanings are not always obvious. She says that she tries to talk shop with her family -- her father is a professor of philosophy at Washington State University -- and they all end up laughing at the absurdity of the communication gap.

But Silverstein is serious about finding a way to experimentally validate M-theory (short of building a galaxy-sized particle collider). She is concerned about symmetry. Indeed, all scientists are stuck on symmetry.

As an example of perfect spatial symmetry, consider a sphere, such as a beach ball. No matter how you rotate it in space, it always looks the same. Now consider a very unsymmetrical object, such as a tree. It looks different from different angles of viewing: It is asymmetrical and, therefore, ugly to a physicist (until reaching symmetries at the molecular level, of course).

Mathematics is moved along by internal symmetry -- by equations that balance. And the symmetry of simple geometrical objects is analogous to a "supersymmetry" between elementary subatomic particles. In a supersymmetric universe, every subatomic particle in existence will have a matching partner called a superpartner. Particle-colliding machines have yet to detect superpartners. But M-theorists claim that when they do spot them -- when machines powerful enough to do so come online sometime in the next decade -- the superpartners will not be exactly symmetrical to their mates. M-theorists desire to find what they call a "broken" symmetry, because according to M-theory the universe is not exactly symmetrical.

Finding these previously unseen, slightly asymmetrical superpartners would partially -- and very indirectly -- validate some of the claims of M-theory.

And how will Silverstein feel if she is the one to "break" supersymmetry? "I feel important when I understand how the world works," she grins.

Egg or Chicken?
Back in the cafeteria, Leonard Susskind and Steve Shenker discuss supersymmetry and p-branes. Three wide-eyed graduate students memorize their every word.

Yet, studied nonchalance seems to be the party line for most string theorists when asked about personal motivation. They do it because it is a puzzle, because it is interesting. A few spout off about the beauty of the universe and knowing the mind of God.

Shenker, a lifelong atheist, is more down to earth. He says that most people are selfish and act only upon material incentive. He also says that most physicists care more about the opinions of the world of science than they care about the opinions of the general public. They seek emotional satisfaction from the approval of their peers -- that incredibly small circle of people who speak M-theory and make awards.

Once admitted to the inner sanctums of the theory groups, a string theorist's material needs are guaranteed -- through academic tenure and a military-scientific umbilical cord -- for life. Most particle physicists receive career-long salaries from the U.S. Departments of Defense and Energy; those grants follow the scientists, no matter where they research. Today's string theorists decry the notion of a "string bomb"; but they have to admit that yesterday's "relativists" did not know that their "pure science" would map the road to nuclear winter. And certainly, the Pentagon and the Energy Department have their collective fingers crossed in hopes that wild-sounding string theories will one day lead to practical military and/or energy-generating devices.

But it is obvious that money is not the main motivation of the string theorists, and practical applications -- military or otherwise -- hold little interest for them. In the self-contained world of extremely talented physicists, it is considered not just fair, but the way of the world to trade insights into the structure of the universe for social privileges.

Whether M-theory is ever "proven," it is no hoax; the alignment of its mathematics with both quantum mechanics and relativity is too elegant for any physicist to ignore. But that does not mean M-theory is intuitive. A recent article in Scientific American put the theory's paradoxical nature this way: "Elementary objects now seem to be made out of the very particles they create."

And not all of Shenker and Susskind's colleagues are thrilled with M-theory. Gerard 't Hooft, a prominent Dutch physicist, complains, "You can't ask anymore what is happening, you have to believe in miraculous outcomes of abstract mathematical procedures." And 't Hooft scoffs at the notion of a Theory of Everything. How can anyone claim to know the answer, he asks, when they don't even know what the question is?

It is possible, the M-theorists admit, that M is a grandly correct theory -- a theory that applies not to our, but to another, universe!

Meanwhile, string theorists tell a joke on themselves: Three stringies have hold of a slimy tube. One is convinced that the tube is a hose connected to a firetruck; another professes it an elephant's trunk; the third swears it is a giant strand of linguine.

A String by Any Other Name ...
Hiroshi Oguri, Ph.D., professor of physics at the University of California at Berkeley, draws a tube on his blackboard. The tube is like a garden hose, he says. And inside the tube, an ant roams. Oguri says that the ant sees two dimensions as it walks around the circular surface inside the tube. But a human being staring at the hose from a block away sees only a one-dimensional line.

Here is the point about discovering our multidimensional universe, says Oguri. It's all about point of view. You can only see so much of the universe inside four dimensions. In order to see the other seven, the observer must take the point of view of the smallest of the small. The 11th dimension is the realm of the mathematical ant -- so small that it can sense the existence of the dimension that everything in the universe is wrapped around.

In the small reaches of the universe -- a million billion billion billionths of a centimeter -- the eternally humming strings join and divide ceaselessly. Tiny black holes eat gaps in loops of string, breaking them, or, sometimes, a pointlike black hole sucks each end of a string into its infinite darkness, thereby cementing the string into a loop.

And it is the nature of that infinite darkness that inspired Oguri, age 36, to turn a "liking" for math into a vocation.

"I learned of death when my grandfather died. I was young. The loneliness and pain of that experience made me desire something of enduring value. I feared transitoriness.

"Nature is unfair. There are disasters. The everyday world is unstable. People cope by finding the laws that govern nature. I do M-theory in the hope of living in a rational universe."

Eva Silverstein is not quite so confident that M-theory is the key to understanding everything. "New approaches open things up, and new barriers arise," she observes. For instance, the discovery of 11 dimensions is already being called into question by a theory of 12 dimensions, 10 of space and two of time.

The theorists are painfully aware that a blast of nature could pull the rug out from under their beautiful theory at any moment. "If one part of the theory is shown to be wrong, it all falls down," says Susskind.

And even if physical reality does not betray them, Shenker, Susskind, Silverstein, and Oguri may never produce a shred of proof that the universe is rational, stable, or fundamentally understandable by the human brain.

Rules of the Game
The universe may well be an infinite series of puzzles within puzzles, forever defying definition. Whether the reality game has overarching rules, or is simply a never-ending stack of imperfections, there is no law ordaining that all must become known to us. It's how you play the game that counts. At Stanford and UC Berkeley, they are playing the game very hard and well. Whether they are playing the right game is another question, the answer to which may have many, many ... dimensions.