On their birthday: The wisdom of John Wheeler and Oliver Sacks.

A rare and happy coincidence today: The birthdays of both John Archibald Wheeler and Oliver Sacks. Wheeler was one of the most prominent physicists of the twentieth century. Sacks was one of the most prominent medical writers of his time. Both of them were great explorers, the first of the universe beyond and the second of the universe within.

What made both men special, however, was that they transcended mere accomplishment in the traditional genres that they worked in, and in that process they stand as role models for an age that seems so fractured. Wheeler the physicist was also Wheeler the poet and Wheeler the philosopher. Throughout his life he transmitted startling new ideas through eloquent prose that was too radical for academic journals. Most of his important writings made their way to us through talks and books. Sacks the neurologist was far more than a neurologist, and Sacks the writer was much more than a writer. Both Wheeler and Sacks had a transcendent view of humanity and the universe, a view that is well worth taking to heart in our own self-centered times.

Their backgrounds shaped their views and their destiny. John Wheeler grew up in an age when physics was transforming our view of the universe. While he was too young to participate in the genesis of the twin revolutions of relativity and quantum mechanics, he came on stage at the right time to fully implement the revolution in the burgeoning fields of particle and nuclear physics.

After acquiring his PhD, Wheeler went on a fellowship to what was undoubtedly the mecca of physical thought – Niels Bohr’s Institute of Theoretical Physics in Copenhagen. By then Bohr had already become the grand old man of physics. While Einstein was retreating from the forefront of quantum mechanics, not believing that God would play such an inscrutable game of dice, Bohr and his pioneering disciples – Werner Heisenberg, Wolfgang Pauli and Paul Dirac, in particular – were taking the strange results of quantum mechanics at face value and interpreting them for the next generation. Particles that were waves, that superposed with themselves and that could be described only probabilistically, all found a place in Bohr’s agenda.

Bohr was famous for trying to describe physical reality as accurately as possible. This led to his maddening, Delphic utterances where he would go back and forth with a colleague to rework the fine points of his thinking, relentlessly questioning everyone’s reasoning including his own. But the process also illuminated both his passion to understand the world as well as his absolute insistence on precision and honesty. His talks and writings are often covered in a fine mist of interpretive haze, but once you ponder them enough they are wholly illuminating and novel. Bohr’s disciples did their best to spread his Copenhagen gospel throughout the world, and for the large part they succeeded spectacularly. When Wheeler joined Bohr in the mid 1930s, the grand old philosopher of physics was in the middle of his famous arguments with Einstein concerning the nature of reality. The so-called Einstein-Podolsky-Rosen paradox, published in back-to-back papers by Bohr, Einstein and their eponymous colleagues in 1935, was to set the stage for all quantum mechanical quarrels related to meaning and reality for the next half century.

For Wheeler, doing physics with Bohr was like playing ping-pong with an opponent possessing infinite patience. Back and forth the two went; arguing, refining, correcting, Wheeler doing most of the calculating and Bohr doing most of the talking. Wheeler came from the pragmatic American tradition of physics, later called the “shut up and calculate” tradition. While not particularly attuned back then to philosophical disputes, Wheeler rapidly absorbed Bohr’s avuncular, Socratic method of argument and teaching, later using it to create probably the finest school of theoretical physics in the United States during the postwar years. His opinion of Bohr stayed superlative till the end: “You can talk about people like Buddha, Jesus, Moses, Confucius, but the thing that convinced me that such people existed were the conversations with Bohr.”

In 1939, with Bohr as a sure guide, Wheeler made what was practically speaking probably the most important contribution of his career – an explanation of the mechanism of nuclear fission. The paper is a masterful application of both classical and quantum physics, treating the nucleus as an entity poised on the cusp between the quantum and the classical worlds. In the same issue of the Physical Review that published the Wheeler-Bohr paper, another paper appeared, a paper by Robert Oppenheimer and his student Hartland Snyder. In their paper, Oppenheimer and Snyder laid out the details of what we now call black holes. The seminal Oppenheimer-Snyder paper went practically unnoticed; the seminal Wheeler-Bohr paper spread like wildfire. The reason was simple. Both papers were published on the day Germany attacked Poland and started the Second World War. Just eight months before, German scientists had discovered a potentially awesome and explosive source of energy in the nuclear fission of uranium. The discovery and the Wheeler-Bohr paper made it clear to interested observers that weapons of immensely destructive power could now be made. The race was on. As a professor at Princeton University, Wheeler was in the thick of things.

He became an important part of the Manhattan Project, contributing crucial ideas especially to the design of the nuclear reactors that produced plutonium. He had a vested interest in seeing the bomb come to fruition as soon as possible: his brother, Joe, was fighting on the front in Europe. Joe did not know the details of the secret work John was doing, but the two words in his letter to John made his general understanding of Wheeler’s work clear – “Hurry up”, the letter said. Sadly, Joe was killed in Italy before the bomb could be fully developed. His inability to potentially save his brother’s life massively shaped Wheeler’s political views. From then on, while he did not quite embrace weapons of mass destruction with the same enthusiasm as his friend Edward Teller, his opinion was clear: if there was a bigger weapon, the United States should have it first. One of the hallmarks of Wheeler’s life and career was that in spite of his political leanings – his conservatism was in marked contrast to most of his colleagues’ liberal politics – he seems to have remained friends with everyone. Wheeler’s life is a good illustration, especially in these fraught times, of how someone can keep their politics from interfering with their fundamental decency and appreciation of decency in others.

His scientific gifts and political views led Wheeler to work on the hydrogen bomb amidst an environment of Communist hysteria, witch hunts and stripped security clearances. But after he had done his job perfecting thermonuclear weapons, Wheeler returned to his first love – pure physics. During the war, he had teamed up with an immensely promising young man with fire in his mind and a young wife dying in a hospital in Albuquerque. Richard Feynman and John Wheeler couldn’t have been different from each other; one the fast-talking, irreverent kid from New York City, the other a courtly, conservative, Southern-looking gentleman who wore pinstriped suits. And yet their essential honesty and drive to understand physics from the bottom up made them kindred souls. Feynman got his PhD under Wheeler and for the rest of his life loved and admired his mentor; his work with Wheeler also inspired Feynman’s own Nobel Prize winning work in quantum electrodynamics – the strange theory of the interaction between light and matter. Wheeler’s love for teaching and the art of argument he acquired from Bohr crystallized in his interactions with Feynman. It set the stage for the latter half of his life.

Wheeler is one of the very few scientists in history who did breakthrough work in two completely different branches of science. Before the war he had been an explorer of the infinitesimal, but now he made himself an intrepid Marco Polo of the infinitely large. In the 1950s Wheeler plunged headlong into the physics of gravitational collapse, starting out from where Oppenheimer and others had left off. Memorably, he became the man who christened Oppenheimer’s startling brainchildren: in a conference in New York, Wheeler called objects whose gravitational fields were so strong that they could not let even light escape ‘black holes’. Black holes and curved spacetime became the foci of Wheeler’s career. While pursuing this interest he contributed something even more significant: he essentially created the most important school of relativistic investigations in the United States. And combining this new love with his old love, he also created entire subfields of physics that are today engaging the best minds of our time – quantum gravity, quantum information and quantum computing, quantum entanglement and the philosophy of quantum theory.

As a teacher, Wheeler could give Niels Bohr a run for his mentorship. Not just content with supervising the usual flock of graduate students and postdocs, Wheeler took it upon himself to train promising undergraduates in the art of thinking about the physical world. Story after story flourishes of some young mind venturing with trepidation into Wheeler’s office for the first time, only to emerge dazed two or three hours later, staggering under the weight of papers and books and bursting with research ideas. In fact Wheeler supervised more senior research theses at Princeton than any other professor in the department’s history, and for the longest time he taught the freshman physics class: what better way to ignite a passion for physics than by taking a class as a freshman from one of the century’s most brilliant scientific minds? To top it all, he used to sometimes take his students to see a neighborhood resident at the famous address 112 Mercer Street – Albert Einstein. Sitting in Einstein’s room in a circle, the awestruck young minds would watch Wheeler trying to gently convince a perpetually resistant Einstein of the correctness of quantum ideas.

Out of Wheeler’s fertile school emerged some of the most interesting minds of postwar physics research: a very short list includes Jacob Bekenstein who forged startling links between black hole thermodynamics and relativity; Hugh Everett who came up with the many-worlds interpretation of quantum mechanics, an interpretation which flew in the face of Niels Bohr’s Copenhagen Interpretation; Bryce Dewitt with whom Wheeler made the first inroads into the deep realm of quantum gravity; Kip Thorne, gravitational wave pioneer whose dogged efforts finally won him the Nobel Prize last year. With some of these students Wheeler also wrote pioneering textbooks, including a doorstop of a book that has been gracing the shelves of students and professors of relativity like a patron saint since its publication. Very few teachers of theoretical physics equaled Wheeler in his influence and mentorship; certainly in the twentieth century, only Bohr, Arnold Sommerfeld and Max Born come to mind, and among American physicists, only Robert Oppenheimer and his school at Berkeley.

With his students Wheeler worked on some of the most preposterous extensions of nature’s theories that we can imagine: wormholes, quantum gravity, time travel, measurement in quantum theory. He constantly asked his pupils to think of crazy ideas, to extend our most hallowed theories to their breaking point, to think of the whole universe as a child’s playground. His colleagues often thought he was going crazy, but Feynman once corrected them: “Wheeler’s always been crazy”, he reminded everyone. Like his mentor Bohr, Wheeler became a master of the Delphic utterance, the deep philosophical speculation that could result in leaps and bounds in humanity’s understanding of the universe. Here’s one of those utterances: “Individual events. Events beyond law. Events so numerous and so uncoordinated that, flaunting their freedom from formula, they yet fabricate firm form”. The statement is vintage Wheeler; disarming in its ambiguity, deep in its implications, in equal parts physics, philosophy and poetry.

Many of Wheeler’s ideas were collected together in an essay collection titled “At Home in the Universe” which I strongly recommend. These essays showcase his wide-ranging interests and his gift for philosophy and uncommon prose and are full of paradoxes and puzzles. They also illustrate his warm friendship with many of the most famous names in physics including Bohr, Einstein, Fermi and Feynman. Along with “black hole”, he coined many other memorable phrases and statements: “It from Bit”, “Geometrodynamics”, “Mass without Mass”, and “Time is what prevents everything from happening at once”. He always believed that the universe is simpler than stranger, convinced that what is today’s strangeness and paradox will be tomorrow’s simple accepted wisdom.

John Wheeler died at the ripe old age of ninety-six, a legend among scientists. In affectionate tribute to his own way with words, a sixtieth birthday commemoration for him had called his work “Magic without Magic”, an that’s as good a way as any to remember this giant of science. A fitting epitaph? Many to choose from, but his sentiment about it being impossible to understand science without understanding people stands as a testament to his scientific brilliance and fundamental humanity: “No theory of physics that deals only with physics will ever explain physics. I believe that as we go on trying to understand the universe, we are at the same time trying to understand man.”

We come now to Oliver Sacks. Strangely enough, it took me some time to warm up to Sacks’s writing. I read about the man who mistook his wife for a hat, of course, and the patients with anosmia and colorblindness and the famous patients of ‘Awakenings’ who had been trapped in their bodies and then miraculously – albeit temporarily – resurrected. But I always found Sacks’s descriptions a bit too detached and clinical. It was when I read the charming “Uncle Tungsten” that I came to appreciate the man’s wide-ranging interests. But it was his autobiography “On the Move” that really drove home the unquenchable curiosity, intense desire for connecting to life and human beings and sheer love for living in all its guises that permeated Sacks’s being. I was so moved and satiated by the book that I read it again right after reading the last page, and read it a third time a few days later. After this I went back to almost the entirety of Sacks’s oeuvre and enjoyed it. So mea culpa, Dr. Sacks, and thanks for the reeducation.

Like Wheeler Sacks was born to educated parents in London, both of whom were doctors. He clearly acquired his interest in patients, both as medical curiosities and as human beings from his parents. A voracious reader, he had many interests while growing up – Darwin and chemistry were two which he retained throughout his life – and like other Renaissance men found it hard to settle on one. But family background and natural inclination led him to study medicine at Oxford and, finding England too provincial, he shipped to the New World, first to San Francisco and then to New York.

Throughout his life, Sacks’s most distinguishing quality was the sheer passion with which he clung to various activities. These ranged from the admirable to the foolhardy. For instance, Sacks didn’t just “do bodybuilding”, he became obsessed with it to the point of winning a California state championship and risking permanent damage in his muscles. He didn’t just “ride motorcycles”, he would take his charger on eight hundred mile rides to Utah and Arizona over a single weekend. He didn’t just “do drugs”, he flooded his body with amphetamines to the point of almost killing himself. And he didn’t just “practice medicine” or writing, he turned them into an observational art form without precedent. It is this intense desire for a remarkable diversity of people and things that defined Oliver Sacks’s life. And yet Sacks was lonely; as a gay man who repressed his sexuality after a devastating reception from his mother and a series of failed encounters during his bodybuilding days, he refrained from romantic relationships for four decades before finally finding love in his seventies. It was perhaps his own struggle with his identity, combined with recurring maladies like depression and migraines, that made Sacks sympathize so deeply with his patients.

Two things made Sacks wholly unique as a neurological explorer. The writer Andrew Solomon once frankly remarked in a review of one of Sacks’s books that as purely a writer or purely a neurologist, while Sacks was very good, he probably wasn’t in the first rank. But nobody else could straddle the two realms with as much ease, warmth and informed narrative as he could. It was the intersection that made him one of a kind. That and his absolutely transparent, artless style, amply demonstrated in “On the Move”. He was always the first one to admit to follies, mistakes and missed opportunities.

For Sacks his patients were patients second and human beings first. He was one of the first believers in what is today called “neurodiversity”, long before the idea became fashionable. Neurodiversity means the realization that even people with rather extreme neurological conditions show manifestations of characteristics that are present in “normal” human beings. Even when Sacks told us about the most bizarre kind of patients, he saw them as lying on a continuum of human abilities and powers. He saw the basic humanity among patients frozen in space and time when the rest of the world simply saw them as “cases”. And he displayed all this warmth and understanding toward his patients without ever wallowing in the kind of sweet sentimentality that can mark so much medical writing trying to be literature.

Sacks persisted in exploring an astonishing landscape of aspects of the human mind until his last days. Whether it was music or art, mathematics or natural history, he always had something interesting to say. The one exception – and this was certainly a refreshing part of his writing – was politics; as far as I can tell, Sacks was almost wholly apolitical, preferring to focus on the constants of nature and the human mind than the ephemeral foibles of mankind. His columns in the New York Times were always a pleasure, and in his last few – written after he had announced his impending death in a moving piece – he explored topics dear to his heart; Darwin, the periodic table, his intense love of music, his satisfying and strange connection to Judaism as an atheist, and his gratitude for science, friends and the opportunity to be born, thrive and learn in a world full of chaos. In the column announcing the inevitable end he said, “I cannot pretend I am without fear. But my predominant feeling is one of gratitude. I have loved and been loved”.

Why remember John Wheeler and Oliver Sacks today? Because one taught us to look at the universe beyond ourselves, and the other taught us to look within ourselves. Both appealed to the better angels of our nature and to what we have in common rather than what separates us, asking us to constantly stay curious. These lessons seem to be quite relevant to our day and age. Wheeler told us that the laws of physics and the deep mysteries of the universe, even if they may not care about our fragile, bickering world of politics and social strife, beckon each one of us to explore their limits and essence irrespective of our race, nationality or gender. Sacks appealed to our common humanity and told us that deep within the human brain runs a thread that connects all of us on a continuum, independent again of our race, gender, nationality and political preferences. Two messages should stay with us:

Sacks: “Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and adventure.”

Wheeler: “Behind it all is surely an idea so simple, so beautiful, that when we grasp it – in a decade, a century, or a millennium – we will all say to each other, how could it have been otherwise? How could we have been so stupid?”

This is my latest column for 3 Quarks Daily. Image credits: Wheeler, Sacks

Black holes and the curse of beauty: When revolutionary physicists turn conservative

This is my latest monthly column for 3 Quarks Daily.

On September 1, 1939, the leading journal of physics in the United States, Physical Review, carried two remarkable papers. One was by a young professor of physics at Princeton University named John Wheeler and his mentor Niels Bohr. The other was by a young postdoctoral fellow at the University of California, Berkeley, Hartland Snyder, and his mentor, a slightly older professor of physics named J. Robert Oppenheimer.

The first paper described the mechanism of nuclear fission. Fission had been discovered nine months earlier by a team of physicists and chemists working in Berlin and Stockholm who found that bombarding uranium with neutrons could lead to a chain reaction with a startling release of energy. The basic reasons for the large release of energy in the process came from Einstein's famous equation, E = mc², and were understood well. But a lot of questions remained: What was the general theory behind the process? Why did uranium split into two and not more fragments? Under what conditions would a uranium atom split? Would other elements also undergo fission?

Bohr and Wheeler answered many of these questions in their paper. Bohr had already come up with an enduring analogy for understanding the nucleus: that of a liquid drop that wobbles in all directions and is held together by surface tension until an external force that is violent enough tears it apart. But this is a classical view of the uranium nucleus. Niels Bohr had been a pioneer of quantum mechanics. From a quantum mechanical standpoint the uranium nucleus is both a particle and a wave represented as a wavefunction, a mathematical object whose manipulation allows us to calculate properties of the element. In their paper Wheeler and Bohr found that the uranium nucleus is almost perfectly poised on the cusp of classical and quantum mechanics, being described partly as a liquid drop and partly by a wavefunction. At twenty five pages the paper is a tour de force, and it paved the way for understanding many other features of fission that were critical to both peaceful and military uses of atomic energy.

The second paper, by Oppenheimer and Snyder, was not as long; only four pages. But these four pages were monumental in their importance because they described, for the first time in history, what we call black holes. The road to black holes had begun about ten years earlier when a young Indian physicist pondered the fate of white dwarfs on a long voyage by sea to England. At the ripe old age of nineteen, Subrahmanyan Chandrasekhar worked out that white dwarfs wouldn't be able to support themselves against gravity if their mass increased beyond a certain limit. A few years later in 1935, Chandrasekhar had a showdown with Arthur Eddington, one of the most famous astronomers in the world, who could not believe that nature could be so pathological as to permit gravitational collapse. Eddington was a previous revolutionary who had famously tested Einstein's theory of relativity and its prediction of starlight bending in 1919. By 1935 he had turned conservative.

Four years after the Chandrasekhar-Eddington confrontation, Oppenheimer became an instant revolutionary when he worked out the details of gravitational collapse all the way to their logical conclusion. In their short paper he and Snyder demonstrated that a star that has exhausted all its thermonuclear fuel cannot hold itself against its own gravity. When it undergoes gravitational collapse, it would present to the outside world a surface beyond which any falling object will appear to be in perpetual free fall. This surface is what we now call the event horizon; beyond the event horizon even light cannot escape, and time essentially stops flowing for an outside observer.

Curiously enough, the black hole paper by Oppenheimer and Snyder sank like a stone while the Wheeler-Bohr paper on fission gained wide publicity. In retrospect the reason seems clear. On the same day that both papers came out, Germany attacked Poland and started World War 2. The potential importance of fission as a source of violent and destructive energy had not gone unnoticed, and so the Wheeler-Bohr paper was of critical and ominous portent. In addition, the paper was in the field of nuclear physics which had been for a long time the most exciting field of physics. Oppenheimer's paper on the other hand was in general relativity. Einstein had invented general relativity more than twenty years earlier, but it was considered more mathematics than physics in the 1930s. Quantum mechanics and nuclear physics were considered the most promising fields for young physicists to make their mark in; relativity was a backwater.

What is more interesting than the fate of the papers themselves though is the fate of the three principal characters associated with them. In their fate as well as that of others, we can see the differences between revolutionaries and conservatives in physics.

Niels Bohr had pioneered quantum mechanics with his paper on atomic structure in 1913 and since then had been a founding father of the field. He had run an intellectual salon at his institute at Copenhagen which had attracted some of the most original physicists of the century; men like Werner Heisenberg, Wolfgang Pauli and George Gamow. By any definition Bohr had been a true revolutionary. But in his later life he turned conservative, at least in two respects. Firstly, he stubbornly clung to a philosophical interpretation of quantum mechanics called the Copenhagen Interpretation which placed the observer front and center. Bohr and his disciples rejected other approaches to quantum interpretation, including one named the Many Worlds Interpretation pioneered by John Wheeler's student Hugh Everett. Secondly, Bohr could not grasp the revolutionary take on quantum mechanics invented by Richard Feynman called the sum-over-histories approach. In this approach, instead of considering a single trajectory for a quantum particle, you consider all possible trajectories. In 1948, during a talk in front of other famous physicists in which Feynman tried to explain his theory, Bohr essentially hijacked the stage and scolded Feynman for ignoring basic physics principles while Feynman had to humiliatingly stand next to him. In both these cases Bohr was wrong, although the verdict is still out on the philosophical interpretation of quantum mechanics. It seems however that Bohr forgot one of his own maxims: "The opposite of a big truth is also a big truth". For some reason Bohr was unable to accept the opposites of his own big truths. The quantum revolutionary had become an old-fashioned conservative.

John Wheeler, meanwhile, went on to make not just one but two revolutionary contributions to physics. After pioneering nuclear fission theory with Bohr, Wheeler immersed himself in the backwater of general relativity and brought it into the limelight, becoming one of the world's foremost relativists. In the public consciousness, he will probably be most famous for coining the term "black hole". But Wheeler's contributions as an educator were even more important. Just like his own mentor Bohr, he established a school of physics at Princeton that produced some of the foremost physicists in the world; among them Richard Feynman, Kip Thorne and Jakob Bekenstein. Today Wheeler's scientific children and grandchildren occupy many of the major centers of relativity research around the world, and until the end of his long life that remained his proudest accomplishment. Wheeler was a perfect example of a scientist who stayed a revolutionary all his life, coming up with wild ideas and challenging the conventional wisdom.

What about the man who may not have coined the term "black holes" but who actually invented them in that troubled year of 1939? In many ways Oppenheimer's case is the most interesting one, because after publishing that paper he became completely disinterested in relativity and black holes, a conservative who did not think the field had anything new to offer. What is ironic about Oppenheimer is that his paper on black holes is his only contribution to relativity – he was always known for his work in nuclear physics and quantum mechanics after all – and yet today this very minor part of his career is considered to be his most important contribution to science. There are good reasons to believe that had he lived long enough to see the existence of black holes experimentally validated, he would have won a Nobel Prize.

And yet he was utterly oblivious to his creations. Several reasons may have accounted for Oppenheimer's lack of interest. Perhaps the most obvious reason is his leadership of the Manhattan Project and his fame as the father of the atomic bomb and a critical government advisor after the war. He also became the director of the rarefied Institute for Advanced Study and got saddled with administrative duties. It's worth noting that after the war, Oppenheimer co-authored only a single paper on physics, so his lack of research in relativity really reflects his lack of research in general. It's also true that particle physics became the most fashionable field of physics research after the war, and stayed that way for at least two decades. Oppenheimer himself served as a kind of spiritual guide to that field, leading three key postwar conferences that brought together the foremost physicists in the field and inaugurated a new era of research. But it's not that Oppenheimer simply didn't have the time to explore relativity; it's that he was utterly indifferent to developments in the field, including ones that Wheeler was pioneering at the time. The physicist Freeman Dyson recalls how he tried to draw out Oppenheimer and discuss black holes many times after the war, but Oppenheimer always changed the subject. He just did not think black holes or anything to do with them mattered.

In fact the real reason for Oppenheimer's abandonment of black holes is more profound. In his later years, he was afflicted by a disease which I call "fundamentalitis". As described by Dyson, fundamentalitis leads to a belief that only the most basic, fundamental research in physics matters. Only fundamental research should occupy the attention of the best scientists; other work is reserved for second-rate physicists and their graduate students. For Oppenheimer, quantum electrodynamics was fundamental, beta decay was fundamental, mesons were fundamental; black holes were applied physics, worthy of second-rate minds.

Oppenheimer was not the only physicist to be stricken by fundamentalitis. The malady was contagious and in fact had already infected the occupant of the office of the floor below Oppenheimer's – Albert Einstein. Einstein had become disillusioned with quantum mechanics ever since his famous debates with Bohr in the 1920s and his belief that God did not play dice. He continued to be a holdout against quantum mechanics; a sad, isolated, often mocked figure ignoring the field and working on his own misguided unification of relativity and electromagnetism. Oppenheimer himself said with no little degree of scorn that Einstein had turned into a lighthouse, not a beacon. But what is less appreciated is Einstein's complete lack of interest in black holes, which in some sense is even more puzzling considering that black holes are the culmination of his own theory. Einstein thought that black holes were a pathological example of his relativity, rather than a general phenomenon which might showcase deep mysteries of the universe. He also wrongly thought that the angular momentum of the particles in a purported black hole would stabilize its structure at some point; this thinking was very similar to Eddington's rejection of gravitational collapse, essentially based on faith that some law of physics would prevent it from happening.

Unfortunately Einstein was obsessed with the same fundamentalitis that Oppenheimer was, thinking that black holes were too applied while unified field theory was the only thing worth pursuing. Between them, Einstein and Oppenheimer managed to ignore the two most exciting developments in physics – black holes and quantum mechanics – of their lives until the end. Perhaps the biggest irony is that the same black holes that both of them scorned are now yielding some of the most exciting, and yes – fundamental – findings in cosmology, thermodynamics, information theory and computer science. The children are coming back to haunt the ghosts of their parents.

Einstein and Oppenheimer's fundamentalitis points to an even deeper quality of physics that has guided the work of physicists since time immemorial. That quality is beauty, especially mathematical beauty. Perhaps the foremost proponent of mathematical beauty in twentieth century physics was the austere Englishman Paul Dirac. Dirac said that an equation could not be true until it was beautiful, and he had a point. Some of the most important and universal equations in physics are beautiful by way of their concision and universal applicability. Think about E= mc², or Ludwig Boltzmann's equation relating entropy to disorder, S=klnW. Einstein's field equations of general relativity and Dirac's equation of the electron that marries special relativity with quantum mechanics are both prime examples of elegance and deep beauty. Keats famously said that "Beauty is truth and truth is beauty", and Dirac and Einstein seem to have taken his adage to heart.

And yet stories of Dirac and Einstein's quest for beauty are misleading. To begin with, both of them and particularly their disciples seem to have exaggerated the physicists' reliance on beauty as a measure of reality. Einstein may have become enamored of beauty in his later life, but when he developed relativity, he was heavily guided by experiment and stayed very close to the data. He was after all the pioneer of the thought experiment. As a patent clerk in the Swiss patent office at Bern, Einstein gained a deep appreciation for mechanical instrumentation and its power to reveal the secrets of nature. He worked with his friend Leo Szilard on that most practical of gadgets – a refrigerator. His later debates with Bohr on quantum mechanics often featured ingenious thought experiments with devices that he had mentally constructed. In fact Einstein's most profoundly emotional experience came not with a mathematical breakthrough but when he realized that his theory could explain deviations in the perihelion of Mercury, an unsolved problem for a century; this realization left him feeling that "something had snapped" inside him. Einstein's success thus did not arise as much from beauty as from good old-fashioned compliance with experiment. Beauty was a sort of secondary effect, serving as a post-facto rationalization for the correctness of the theory.

Unfortunately Einstein adopted a very different attitude in later years, trying to find a unified field theory that was beautiful rather than true. He started ignoring the experimental data that was being collected by particle physicists around him. We now know that Einstein's goal was fundamentally flawed since it did not include the theory of the strong nuclear force, a theory which took another thirty years to evolve and which could not have progressed without copious experimental data. You cannot come up with a complete theory, beautiful or otherwise, if you simply lack one of the key pieces. Einstein seems to have forgotten a central maxim of doing science, laid down by the sixteenth century natural philosopher Francis Bacon, one of the fathers of the scientific method: "All depends on keeping the eye steadily fixed upon the facts of nature and so receiving their images simply as they are. For God forbid that we should give out a dream of our own imagination for a pattern of the world". In his zeal to make physics beautiful, Einstein ignored the facts of nature and pursued the dreams of his once-awesome imagination.

Perhaps the biggest irony in the story of Einstein and black holes comes from the words of the man who started it all. In 1983, Subrahmanyan Chandrasekhar published a dense and authoritative tome called "The Mathematical Theory of Black Holes" which laid out the complete theory of this fascinating object in all its mathematical glory. In it Chandra (as he was called by his friends) had the following to say:

"In my entire scientific life, extending over forty-five years, the most shattering experience has been the realization that an exact solution of Einstein's equations of general relativity, discovered by the New Zealand mathematician, Roy Kerr, provides the absolutely exact representation of untold numbers of massive black holes that populate the universe. This shuddering before the beautiful, this incredible fact that a discovery motivated by a search after the beautiful in mathematics should find its exact replica in Nature, persuades me to say that beauty is that to which the human mind responds at its deepest and most profound."

Black holes and beauty had come full circle. Far from being a pathological outlier as believed by Einstein and Oppenheimer, they emerged as the epitome of austere mathematical and physical beauty in the cosmos.

Dirac seems to have been guided by beauty to an even greater extent than Einstein, but even there the historical record is ambiguous. When he developed the Dirac equation, he was very closely aware of the experimental results. His biographer Graham Farmelo notes, "Dirac tried one equation after another, discarding each one as soon as it failed to conform to his theoretical principles or to the experimental facts". Beauty may have been a criterion in Dirac's choices, but it was more a way of serving as an additional check rather than a driving force. Unfortunately Dirac did not see it that way. When Richard Feynman and others developed the theory of quantum electrodynamics – a framework that accounts for almost all of physics and chemistry except general relativity - Dirac was completely unenthusiastic about it. This was in spite of quantum electrodynamics agreeing with experiment to a degree unprecedented in the history of physics. When asked why he still had a problem with it, Dirac said it was because the equations were too ugly; he was presumably referring to a procedure called renormalization that got rid of infinities that had plagued the theory for years.

He continued to believe until the end that those ugly equations would somehow metamorphose into beautiful ones; the fact that they worked spectacularly was of secondary importance to him. In that sense beauty and utility were opposed in Dirac's mind. Dirac continued to look for beauty in his equations throughout his life, and this likely kept him from making any contribution that was remotely as important as the Dirac equation. That's a high bar, of course, but it does speak to the failure of beauty as a primary criterion for scientific discovery. Later in his life, Dirac developed a theory of magnetic monopoles and dabbled in finding formulas relating the fundamental constants of nature to each other; to some this was little more than aesthetic numerology. Neither of these ideas has become part of the mainstream of physics.

It was the quest for beauty and the conviction that fundamental ideas were the only ones worth pursuing that turned Einstein and Dirac from young revolutionaries to old conservatives. It also led them to ignore most of the solid progress in physics that was being made around them. The same two people who had let experimental facts serve as the core of their decision making during their youth now behaved as if both experiment and the accompanying theory did not matter.

Yet there is something to be said for making beauty your muse, and ironically this realization comes from the history of the Dirac equation itself. Perhaps the crowning achievement of that equation was to predict the existence of positively charged electrons or positrons. This discovery seemed so alien and unsettled Dirac so much at the beginning that he thought positrons had to be protons; it wasn't until Oppenheimer showed this could not be the case that Dirac started taking the novel prediction seriously. Positrons were finally found by Carl Anderson in 1932, a full three years after Dirac's prediction. This is one of the very few times in history that theory has genuinely predicted a completely novel fact of nature with no experimental basis in the past. Dirac would claim that it was the tightly knit elegance of his equation that logically ordained the existence of positrons, and one would be hard pressed to argue with him. Even today, when experimental evidence is lacking or absent, one has to admit that mathematical beauty is as good a guide to the truth as any other.

Modern theoretical physics has come a long way from the Dirac equation, and experimental evidence and beauty still guide practitioners of the field. Unfortunately physics at the frontiers seems to be unmoored from both these criteria today. The prime example of this is string theory. According to physicist Peter Woit and others, string theory has made no unique, experimentally testable prediction since its inception thirty years ago, and it also seems that its mathematics is unwieldy; while the equations seem to avoid the infinities that Dirac disliked, they also presents no unique, elegant, tightly knit mathematical structure along the lines of the Dirac equation. One wonders what Dirac would have thought of it.

What can today's revolutionaries do to make sure they don't turn conservative in their later years? The answer might come not from a physicist but from a biologist. Charles Darwin, when explaining evolution by natural selection, pointed out a profoundly important fact: "It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change". The principle applies to frogs and butterflies and pandas, and there is no reason why it should not apply to theoretical physicists.

What would it take for the next Dirac or Einstein to make a contribution to physics that equals those of Einstein and Dirac themselves? We do not know the answer, but one lesson that the lives of both these physicists has taught us – through their successes as well as their failures – is to have a flexible mind, to always stay close to the experimental results and most importantly, to be mindful of mathematical beauty while not making it the sole or even dominant criterion to guide your thought processes, especially when an "uglier" theory seems to agree well with experiment. Keep your eye fixed on the facts of nature, not just on the dream of your imagination.

Dear New York Times

You disappoint me

Dear Sir,
I was rather shocked to notice that in your "Notable Deaths of 2008" slide show that included 44 famous people from the arts, medicine, literature, television, politics, cinema, music and journalism, the name of the legendary physicist John Archibald Wheeler was missing. Dr. Wheeler who worked on the Manhattan Project died on April 13, 2008 and was one of the century's greatest scientists and a national treasure. During his long and remarkably productive life in which he worked with Albert Einstein and Niels Bohr, Dr. Wheeler played a key role in shaping American science, education and government policy. While it was heartening to see an obituary of him in the New York Times, I was quite disconcerted to see no mention of him in the Notable Deaths of 2008 Multimedia slide show list. While I understand that such an enumeration cannot be all-inclusive, Dr. Wheeler's stature as an American scientific icon should ensure the inclusion of his name in any short list of famous American people who died in 2008. I sincerely and strongly hope that this omission would be corrected.
Thanking you,
Sincerely,
Ashutosh S. Jogalekar
Atlanta, GA

Wheeler worked on the atomic and hydrogen bombs, served as an advisor to high-profile Presidential scientific committees, mentored brilliant scientists and leaders like Richard Feynman and Kip Thorne, resurrected and pioneered rather neglected relativity research in the 60s, coined the word "black hole", rendered invaluable teaching service at Princeton and Austin and propelled American physics into the first rank. If a list of notable American deaths of 2008 does not include his name, I don't know whose name it should.

When it comes to public exposition of achievement, it seems that popular media sources always give science short shrift in preference to other areas like art and cinema. The rift between the two cultures keeps growing. Science was undoubtedly one of the core foundations of The American Twentieth Century. Now it threatens to slip away from beneath the twenty-first. The country neglects it to its own perilous detriment. John Wheeler would have been unhappy.

Magic without Magic: John Archibald Wheeler (1911-2008)

Image copyright: NNDB, Soylent communications (2008)

When I heard from a friend about John Wheeler's death this morning, I grimaced and actually loudly let out an exclamation of pain and sadness. That's because not only was Wheeler one of the most distinguished physicists of the century but with his demise, the golden era of physics- that which gave us relativity, quantum theory and the atomic age- finally passes into history. The one consolation is that he lived a long and satisfying life, passing away at the ripe age of 96. It was just a few weeks ago that I asked a cousin of mine who did his PhD. at the University of Texas at Austin whether he ever ran into Wheeler there. My cousin who himself is in his fifties said that Wheeler arrived just as he was finishing- after retirement from Princeton university.

Wheeler was the last survivor of that heroic age that changed the world and he worked with some true prima donnas. He was an unusually imaginative physicist who made excursions into exotic realms; particles traveling backwards in time, black holes, time travel. A list of his collaborators and friends includes the scientific superstars of the century- Niels Bohr, Albert Einstein, Enrico Fermi, Edward Teller and Richard Feynman to name a few. To the interested lay public, he would be best known as Richard Feynman's PhD. advisor at Princeton.

Wheeler is famous for many things- mentor to brilliant students, originator of outrageous ideas, coiner of the phrase "black hole", outstanding teacher and writer. My most enduring memory about him is from John Gribbin's biography of Feynman. Gribbin recounts how Wheeler in his pinstriped suits used to look like a conservative banker, a look that belied one of the most creative scientific minds of his time. The fond incident is about the playful rogue Feynman being summoned into Wheeler's office for the first time. In order to underscore the importance of his time, Wheeler laid out an expensive pocket watch in front of Feynman. Feynman who had a congenital aversion to perceived or real pomposity took note of this and during their next meeting, laid out a dirt-cheap watch on the table. After a moment of stunned silence, both professor and student burst into loud laughter, laughter that almost always accentuated their discussions on physics and life thereafter. Feynman and Wheeler together derived a novel approach to quantum mechanics that involved particles radiating backwards in time. Wheeler also initiated the discussion of the notorious sprinkler problem described by Feynman in Surely you're joking Mr. Feynman

John Wheeler was born in Florida to strong-willed and working class parents. After obtaining his PhD. from Johns Hopkins at the age of 21, he joined Princeton in 1938 where he remained all his working life. Princeton in 1938 was a mecca of physics, largely because of the Institute for Advanced Study nearby which housed luminaries like Einstein, John von Neumann and Kurt Godel. Wheeler knew Einstein well and later sometimes used to hold seminars with his students in Einstein's home. As was customary for many during those times, Wheeler also studied with Niels Bohr at his famous institute in Copenhagen. In 1939 Bohr and Wheeler made a lasting contribution to physics- the liquid drop model of nuclear fission. According to this, the nucleus of especially heavy atoms behaves like a liquid drop, with opposing electrostatic repulsive forces and attractive surface tension and strong forces. Shoot an appropriately energetic neutron into an unstable uranium nucleus and it wobbles sufficiently for the repulsive forces to become dominant, causing it to split. The liquid drop model explained fission discovered earlier. The mathematics was surprisingly simple yet remarkably accurate. Bohr was one of Wheeler's most important mentors; in his biography he describes how he used to have marathon sessions with Bohr, with the great man often insisting on walking around the department, tossing choice tidbits to Wheeler ambling at his side. Caught up in the recent heated debate about the philosophical implications of quantum theory, Wheeler argued the nature of reality with both Einstein and Bohr.

When World War 2 began, Wheeler like many physicists was recruited into the Manhattan Project. Because of his wide-ranging intellect and versatility, he was put in charge as scientific consultant to Du Pont, who was building plutonium producing reactors at Hanford in Washington state. There Wheeler tackled and solved an unexpected and very serious problem. As the reactors were transforming uranium 238 into the precious plutonium, the process suddenly shut down. After some time it started up again. Nobody knew what was happening. Wheeler who was the resident expert worked out the strange phenomenon in an all-night session. What was happening was that some of the fission products produced had a big appetite for neutrons and were therefore "poisoning" the chain reaction. After some time when these products had decayed to sufficiently low levels, they would stop eating up the neutrons and the reactor would start again. This was one of the most valuable pieces of information gained during plutonium production. Ironically, the omission of this information in a second edition of a government history of atomic energy released just after the war alerted the Soviets to its importance. Working on the Manhattan Project was also a poignantly personal experience for Wheeler; the bomb could not save his brother Joe who was killed in action in Italy in 1944. Wheeler later also worked with Edward Teller on the hydrogen bomb, a decision about which he was fairly neutral because he thought it was necessary at the time to stand up to the Soviets.

After the war Wheeler embarked on a lifelong quest in a completely different field and became a pioneer in it- general relativity. He took up where Robert Oppenheimer had left off in 1939. Oppenheimer had made a key contribution to twentieth century physics by first describing what we now know as black holes. Strangely and somewhat characteristically, he lost all interest in the field after the war. But Wheeler took it up and reinitiated a bona fide revolution in the application of general relativity to astrophysics. As his most enduring mark, he coined the word "black hole" in the 1960s. Wheeler became the scientific godfather of a host of other physicists who became pioneers in exploring exotic phenomena- black holes, wormholes, time travel, multiple universes. His most successful student in this regard has been Kip Thorne whose wonderful book expounds on the golden age of relativity. Hugh Everett, the tragic genius who invented multiple universes and the Lagrange multipliers method for optimization problems before plunging into paranoia and depression, left behind choice fodder not just for science but for science fiction; parallel universes have been a staple of our collective imagination ever since then. In retrospect, Wheeler followed his mentor and did for astrophysics what Bohr had done for quantum theory- he served as friend, philosopher and guide for a brilliant new generation of physicists.

Wheeler also was known as an outstanding teacher. His mentoring of Feynman is well-known, and he devoted a lot of time and care to teaching and writing. Along with his students Kip Thorne and Charles Misner, Wheeler produced what is surely the bible of general relativity, Gravitation, a mammoth book running more than a thousand pages whose only discouraging feature may be its length. The book has served as advanced introduction to Einstein and beyond for generations of students. Wheeler also co-authored Spacetime Physics, an introduction to special relativity which even I have timidly managed to savor a little during my college days. His own autobiography, Geons, Black Holes and Quantum Foam: A Life in Physics is worth reading for its evocation of a unique time of the last century, as well as for fond anecdotes about great physicists.

But many people will remember Wheeler as a magician. Sitting in his office in his pinstriped suits, Wheeler's mind roamed across the universe straddling everything from the smallest to the largest, exploring far-flung concepts and realms of the unknown. He grappled with the interpretation of quantum mechanics and was an early proponent of the anthropic principle- in John L Casti's magnificent book Paradigms Lost, Casti quotes Wheeler analogizing observer-created reality with the game in which a group of people asks someone else to guess an object they have in mind by asking questions, except that in the modified version of this game, they let the object be created during the process of questioning. With his mentor Bohr's enduring principle of complementarity as a guide, Wheeler produced esoteric ideas that nonetheless questioned the bedrock of reality. Wheeler was entirely at home with such bizarre yet profound concepts that still tug at the heartstrings of physicist-philosophers. Only Wheeler could have introduced paradoxical and yet meaningful phrases like "mass without mass". In celebration of his sixtieth birthday, physicists produced a volume dedicated to him with a title that appropriately captured the essence of his thinking- "magic without magic".

John Wheeler was indeed a magician. He made great contributions to physics, served as its guide for half a century and motivated and taught new generations to wonder at the universe's complexities as much as he did. He was the last torch-bearer of a remarkable age when mankind transformed the most esoteric and revolutionary investigations into the universe into forces that changed the world. He will be sorely missed.