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Philosopher, Wissenschaftskolleg zu Berlin (Institute for Advanced Study); Author, The Ego Tunnel


John Brockman points out that new technology leads not only to new ways of perceiving ourselves, but also to a process he calls "recreating ourselves." Could this become true in an even deeper and more radical way than through gene-technology? The answer is yes.

It is entirely plausible that we may one day directly control virtual models of our own bodies directly with our brain. In 2007, I first experienced taking control of a computer-generated whole-body model myself. It took place in a virtual reality lab where my own physical motions were filmed by 18 cameras picking up signals from sensors attached to my body. Over the past two years, different research groups in Switzerland, England, Germany and Sweden have demonstrated how, in a passive condition, subjects can consciously identify with the content of a computer-generated virtual body representation, fully re-locating the phenomenal sense of self into an artificial, visual model of their body.

In 2008, in another experiment, we saw that a monkey on a treadmill could control the real-time walking patterns a humanoid robot via a brain-machine interface directly implanted into its brain. The synchronized robot was in Japan, while the poor monkey was located thousands of miles away, in the US. Even after it stopped walking, the monkey was able to sustain locomotion of the synchronized robot for a few minutes—just by using the visual feedback transmitted from Japan plus his own "thoughts" (whatever that may turn out to be).

Now imagine two further steps.

First, we manage to selectively block the high-bandwidth "interoceptive" input into the human self-model—all the gut feelings and the incessant flow of inner body perceptions that anchor the conscious self in the physical body. After all, we already have selective motor control for an artificial body-model and robust phenomenal self-identification via touch and sight. By blocking the internal self-perception of the body, we could be able to suspend the persistent causal link to the physical body.

Second, we develop richer and more complex avatars, virtual agents emulating not only the proprioceptive feedback generated by situated movement, but also certain abstract aspects of ongoing global control itself—new tools, as Brockman would call them. Then suddenly it happens that the functional core process initiating the complex control loop connecting physical and virtual body jumps from the biological brain into the avatar.

I don't believe this will happen tomorrow. I also don't believe that it would change everything. But it would change a lot.

Psychologist, Director, Institute of Cognition and Culture, Queens University, Belfast; Columnist, Scientific American ("Bering in Mind"), Author, Under God's Skin (forthcoming 2010)


What if I were to tell you that God were all in your mind? That God, like a tiny spec floating at the edge of your cornea producing the image of a hazy, out-of-reach orb accompanying your every turn, were in fact an illusion, a psychological blemish etched onto the core cognitive substrate of your brain? It may feel like there is something grander out there…. watching, knowing, caring. Perhaps even judging. But in fact there is only the air you breathe. Consider, briefly, the implications of seeing God this way, as a sort of scratch on our psychological lenses rather than the enigmatic figure out there in the heavenly world most people believe him to be. Subjectively, God would still be present in our lives. In fact rather annoyingly so. As a way of perceiving, he would continue to suffuse our experiences with an elusive meaning and give the sense that the universe is communicating with us in various ways. But objectively, the notion of God as an illusion is a radical and some would say even dangerous idea, since it raises important questions about God as an autonomous, independent agent that lives outside human brain cells.

In fact, the illusion of God is more plausible a notion than some other related thought experiments, such as the possibility that our brains are sitting in an electrified vat somewhere and we're merely living out simulated lives. In contrast to the vat exercise or some other analogy to the science-fiction movie The Matrix, it is rather uncontroversial to say that our species' ability to think about God—even an absent God—is made possible only by our very naturally derived brains. In particular, by virtue of the fact that our brains have evolved over the eons in the unusual manner they have. In philosophical discourse, the idea that God is an illusion would be a scientifically inspired twist on a very ancient debate, since it deals with the nature and veridicality of God's actual being.

That's all very well, you may be thinking. But perhaps God isn't an illusion at all. Rather than a scratch on our psychological lenses, our brain's ability to reason about the supernatural—about such things as purpose, the afterlife, destiny—is in fact God's personal signature on our brains. One can never rule out the possibility that God micro-engineered the evolution of the human brain so that we've come to see him more clearly, a sort of divine Lasik procedure, or a scraping off the bestial glare that clouds the minds of other animals. In fact some scholars, such as psychologists Justin Barrett and Michael Murray, hold something like this "theistic evolution" view in their writings. Yet as a psychological scientist who studies religion, I take explanatory parsimony seriously. After all, parsimony is the basic premise of Occam's Razor, the very cornerstone of all scientific enquiry. Occam's Razor holds that, of two equally plausible theories, science shaves off the extra fat by favoring the one that makes the fewest unnecessary assumptions. And in the natural sciences, the concept of God as a causal force tends to be an unpalatable lump of gristle. Although treating God as an illusion may not be entirely philosophically warranted, therefore, it is in fact a scientifically valid treatment. Because the human brain, like any physical organ, is a product of evolution, and since natural selection works without recourse to intelligent forethought, this mental apparatus of ours evolved to think about God quite without need of the latter's consultation, let alone his being real.

Indeed, the human brain has many such odd quips that systematically alter, obscure, or misrepresent entirely the world outside our heads. That's not a bad thing necessarily; nor does it imply poor adaptive design. You have undoubtedly seen your share of optical illusions before, such as the famous Müller-Lyer image where a set of arrows of equal length with their tails in opposite directions creates the subjective impression that one line is actually longer than the other. You know, factually, the lines are of equal length, yet despite this knowledge your mind does not allow you to perceive the image this way. There are also well-documented social cognitive illusions that you may not be so familiar with. For example, David Bjorklund, a developmental psychologist, reasons that young children's overconfidence in their own abilities keeps them engaging in challenging tasks rather than simply giving up when they fail. Ultimately, with practice and over time, children's actual skills can ironically begin to more closely approximate these earlier, favorably warped self-judgments. Similarly, evolutionary psychologists David Buss and Martie Haselton argue that men's tendency to over-interpret women's smiles as sexual overtures prompts them to pursue courtship tactics more often, sometimes leading to real reproductive opportunities with friendly women.

In other words, from both a well-being and a biological perspective, whether our beliefs about the world 'out there' are true and accurate matters little. Rather, psychologically speaking, it's whether they work for us—or for our genes—that counts. As you read this, cognitive scientists are inching their way towards a more complete understanding of the human mind as a reality-bending prism. What will change everything? The looming consensus among those who take Occam's Razor seriously that the existence of God is a question for psychologists and not physicists.

Founder Director, Ontological-Hysteric Theater; Playwright


The belief that there is anything that will change things, in and of itself stymies, I believe, real change. To believe that anything "will change things" focuses one on the superficial surface of things, which indeed change all the time. Such changes—which have been and will continue to be—create always an orientation of consciousness that focuses always on "the future".

But I propose that the only thing that will in fact 'change everything' is, or would be, the refusal to think about the future. And this, of course, is almost impossible for almost all human beings to do.

Therefore, nothing will change everything.

(I admit that I myself have fallen prey to this unavoidable human tendency, having written "of the future" in these pages, proposing that the internet is now creating, and will radicalized in the future—wide ranging yet depthless "pancake people".)

But if we could "think not" about the future, the present moment would obviously expand and become the full (and very different) universe. One can say "ah, but this is the animal state".

I would answer—no, the animal achieves this automatically, while the human being who achieves this only does so by erecting it on a foundational superstructure which postulates a necessary 'future' (past-based) much as Freud (and others before him) postulated a necessary "unconscious'—out of which the 'conscious' human being emerged.

(I am aware, obviously, that this theme has been engaged by philosophers and mystics down through the ages).

So for a human being to not think about the future would be to become a non-animal inhabiting the pure present (the dream of so called 'avant-guard' art, by the way). And animals do not (apparently) make avant-guard art.

Take John Brockman's offered example of a future event that changes everything—through genetic manipulation "your dog could become your cat" (and by implication, I could become you, etc.)

I say, this changes only the shell. Such alterations and achievements, along with many others similarly imaginable, add but another room onto the "home" inhabited by human beings—who will still spend most of their time "thinking about the future. And nothing, at the deepest level, therefore will ever change a postulated 'everything'—not so long as we keep imagining possible "change" which only reinforces the psychic dwelling of our un-changing selves in a "future" that is always imaginary and beyond us.

Science Writer, Author, Archimedes to Hawking


Many mathematical surveys indicate that the "Proof of the Riemann Hypothesis" is the most important open question in mathematics. The rapid pace of mathematics, along with computer-assisted mathematical proofs and visualizations, leads me to believe that this question will be resolved in my lifetime. Math aficionado John Fry once said that he thought we would have a better chance of finding life on Mars than finding a counterexample for the Riemann Hypothesis.

In the early 1900s, British mathematician Godfrey Harold Hardy sometimes took out a quirky form of life insurance when embarking on ocean voyages. In particular, he would mail a postcard to a colleague on which he would claim to have found the solution of the Riemann Hypothesis. Hardy was never on good terms with God and felt that God would not let him die in a sinking ship while Hardy was in such a revered state, with the world always wondering if he had really solved the famous problem.

The proof of the Riemann Hypothesis involves the zeta function, which can be represented by a complicated-looking curve that is useful in number theory for investigating properties of prime numbers. Written as f(x), the function was originally defined as the infinite sum:


When x = 1, this series has no finite sum. For values of x larger than 1, the series adds up to a finite number. If x is less than 1, the sum is again infinite. The complete zeta function, studied and discussed in the literature, is a more complicated function that is equivalent to this series for values of x greater than 1, but it has finite values for any real or complex number, except for when the real part is equal to one. We know that the function equals zero when x is -2, -4, -6, ... . We also know that the function has an infinite number of zero values for the set of complex numbers, the real part of which is between zero and one—but we do not know exactly for what complex numbers these zeros occur. In 1859, mathematician Georg Bernhard Riemann (1826–1866) conjectured that these zeros occur for those complex numbers the real part of which equals 1/2. Although vast numerical evidence exists that favors this conjecture, it is still unproven

The proof of Riemann's Hypothesis will have profound consequences for the theory of prime numbers and in our understanding of the properties of complex numbers. A generalized version of the Hypothesis, when proven true, will allow mathematicians to solve numerous important mathematical problems. Amazingly, physicists may have found a mysterious connection between quantum physics and number theory through investigations of the Riemann Hypothesis. I do not know if God is a mathematician, but mathematics is the loom upon which God weaves the fabric of the universe.

Today, over 11,000 volunteers around the world are working on the Riemann Hypothesis, using a distributed computer software package at Zetagrid.Net to search for the zeros of the Riemann zeta function. More than 1 billion zeros for the zeta function are calculated every day.

In modern times, mathematics has permeated every field of scientific endeavor and plays an invaluable role in biology, physics, chemistry, economics, sociology, and engineering. Mathematics can be used to help explain the colors of a sunset or the architecture of our brains. Mathematics helps us build supersonic aircraft and roller coasters, simulate the flow of Earth's natural resources, explore subatomic quantum realities, and image faraway galaxies. Mathematics has changed the way we look at the cosmos.

Physicist Paul Dirac once noted that the abstract mathematics we study now gives us a glimpse of physics in the future. In fact, his equations predicted the existence of antimatter, which was subsequently discovered. Similarly, mathematician Nikolai Lobachevsky said that "there is no branch of mathematics, however abstract, which may not someday be applied to the phenomena of the real world."

Psychologist, London School of Economics; Author, Seeing Red


We're easily seduced by the idea that, once the Big One comes, nothing will ever be the same again. But I guess what will surprise—and no doubt frustrate—those who dream of a scientifically-driven new order is how unchangeable, and unmanageable by technology, human lives are.

Imagine if this Edge question had been posed to the citizens of Rome two thousand years ago. Would they have been able to predict the coming of the internet, DNA finger-printing, mind-control, space travel? Of course not. Would that mean they would have failed to spot the technological developments that were destined to change everything? I don't think so. For the fact is nothing has changed everything.

Those Romans, despite their technological privations, led lives remarkably like ours. Bring them into the 21st century and they would of course be amazed by what science has achieved. Yet they would soon discover that beneath the modern wrapping it is business as usual. Politics, crime, love, religion, heroism.. The stuff of human biography. The more it changes, the more it's the same thing.

The one development that really could change everything would be a radical, genetically programmed, alteration of human nature. It hasn't happened in historical times, and I'd bet it won't be happening in the near future either. Cultural and technical innovations can certainly alter the trajectory of individual human lives. But, while human beings continue to reproduce by having sex and each new generation goes back to square one, then every baby begins life with a set of inherited dispositions and instincts that evolved in the technological dark ages.

The Latin poet Horace wrote: "You can drive out nature with a pitchfork, but she will always return". Let's dream, if we like, of revolution. But be prepared for more of the same.

Physicist, Institute of Advanced Studies; Author, The Scientist as Rebel


What will change everything?  What game-changing scientific ideas and developments do you expect to live to see?

Since I am 85, I cannot expect to see any big changes in science during my life-time. I beg permission to change the question to make it more interesting.

What will change everything?  What game-changing scientific ideas and developments do you expect your grandchildren to see?

I assume that some of my grandchildren will be alive for the next 80 years, long enough for neurology to become the dominant game-changing science. I expect that genetics and molecular biology will be dominant for the next fifty years, and after that neurology will have its turn. Neurology will change the game of human life drastically, as soon as we develop the tools to observe and direct the activities of a human brain in detail from the outside.

The essential facts which will make detailed observation or control of a brain possible are the following. Microwave signals travel easily through brain tissue for a few centimeters. The attenuation is small enough, so that signals can be transmitted from the inside and detected on the outside. Small microwave transmitters and receivers have bandwidths of the order of gigahertz, while neurons have bandwidths of the order of kilohertz. A single microwave transmitter inside a brain has enough bandwidth to transmit to the outside the activity of a million neurons. A system of 10^5 tiny transmitters inside a brain with 10^5 receivers outside could observe in detail the activity of an entire human brain with 10^11 neurons. A system of 10^5 transmitters outside with 10^5 receivers inside could control in detail the activity of 10^11 neurons. The microwave signals could be encoded so that each of the 10^11 neurons would be identified by the code of the signal that it transmits or receives.

These physical tools would make possible the practice of "Radiotelepathy", the direct communication of feelings and thoughts from brain to brain. The ancient myth of telepathy, induced by occult and spooky action-at-a-distance, would be replaced by a prosaic kind of telepathy induced by physical tools. To make radiotelepathy possible, we have only to invent two new technologies, first the direct conversion of neural signals into radio signals and vice versa, and second the placement of microscopic radio transmitters and receivers within the tissue of a living brain. I do not have any idea of the way these inventions will be achieved, but I expect them to emerge from the rapid progress of neurology before the twenty-first century is over.

It is easy to imagine radiotelepathy as a powerful instrument of social change, used either for good or for evil purposes. It could be a basis for mutual understanding and peaceful cooperation of humans all over the planet. Or it could be a basis for tyrannical oppression and enforced hatred between one communal society and another. All that we can say for certain is that the opportunities for human experience and understanding would be radically enlarged. A society bonded together by radiotelepathy would be experiencing human life in a totally new way. It will be our grandchildren's task to work out the rules of the game, so that the effects of radiotelepathy remain constructive rather than destructive. It is not too soon for them to begin thinking about the responsibilities that they will inherit. The first rule of the game, which should not be too difficult to translate into law, is that every individual should be guaranteed the ability to switch off radio communication at any time, with or without cause. When the technology of communication becomes more and more intrusive, privacy must be preserved as a basic human right.

Another set of opportunities and responsibilities will arise when radiotelepathy is extended from humans to other animal species. We will then experience directly the joy of a bird flying or a wolf-pack hunting, the pain of a deer hunted or an elephant starved. We will feel in our own flesh the community of life to which we belong.  I cannot help hoping that the sharing of our brains with our fellow-creatures will make us better stewards of our planet.

Novelist; Author, On Chesil Beach


Philip Larkin began a poem with the hypothesis, If I were called in/ To construct a religion/ I should make use of water. Instead of water, I would propose the sun, and the religion I have in mind is a rational affair, with enormous aesthetic possibilities and of great utility.

By nearly all insider and expert accounts, we are or will be at peak oil somewhere between now and the next five years. Even if we did not have profound concerns about climate change, we would need to be looking for different ways to power our civilization. How fortunate we are to have a safe nuclear facility a mere 93 million miles away, and fortunate too that the dispensation of physical laws is such that when a photon strikes a semi-conductor, an electron is released. I hope I live to see the full flourishing of solar technology—photovoltaics or concentrated solar power to superheat steam, or a combination of the two in concentrated photovoltaics. The technologies are unrolling at an exhilarating pace, with input from nanotechnology and artificial photosynthesis. Electric mobility and electricity storage are also part of this new quest. My hope is that architects will be drawn to designing gorgeous arrays and solar towers in the desert—as expressive of our aspirations as Medieval cathedrals once were. We will need new distribution systems too, smart grids—perfect Rooseveltian projects for our hard-pressed times. Could it be possible that in two or three decades we will look back and wonder why we ever thought we had a problem when we are bathed in such beneficent radiant energy?

Psychologist, Research Associate, Harvard University; Author, Alex and Me


Knowledge of exactly how the brain works will change everything. Despite all our technical advances in brain-mapping, we still do not fully understand how the human or nonhuman brain works as a complete organ—e.g., the interconnectedness of the separate areas we are currently mapping. Just as we are beginning to learn that it is not "the" gene that controls what happens in our bodies, but rather the interplay of many genes, proteins, and environmental influences that turn genes on and off, we will learn how the interplay of various neural tissues, the chemicals in our body, environmental influences, and possibly some current unknowns, come together to affect how the brain works…and that will change everything.

We will, for example:

(a) ameliorate diseases in which the brain stops working properly—from diseases involving cognitive deficits such as Alzheimers to those involving issues of physical control such as Parkinsons. We will monitor just when the brain stops functioning optimally and begin interventions much earlier. Age-related senility, with its concomitant problems and societal costs, will cease to exist. If dysfunctions such as autism and schizophrenia are indeed the result of faulty interconnections among many disparate areas, we will 'rewire' the appropriate systems either physically or through targeted drug intervention….similarly for problems such as dyslexia and ADHD;

(b) understand and repair brains susceptible to addictions, or criminality that is based on lack of inhibitory control;

(b) use this knowledge to develop models of brain function for advanced robotics and computers to design 'smart' interactive systems for, e.g., space and ocean exploration or seamless interfaces for, e.g., artificial limbs, vision, and hearing;

(c) determine ways in which human and nonhuman brains function similarly and differently, whether human and nonhuman intelligences are distinctly separate or whether a measureable gradient exists, the extent of any overlap of function, and whether the critical issues involve modules or a constellation of inter-functioning areas that both match and are disparate. For example, we will better understand how human intelligence and language evolved and the extent to which parallel intelligence and communication evolved in nonmammalian evolutionary lines. And how they may still be evolving….

(d) maybe frighteningly, attempt to improve upon the current human brain in an anatomical sense, or, in a much more acceptable manner, determine what forms of teaching and training enable learning to proceed most rapidly, by enhancing appropriate connectivity and memory formation. Different types of intelligence will likely be found to be correlated with particular brain organizational patterns; thus we will identify geniuses of particular sorts more readily and cultivate their abilities.

By truly understanding brain function, and harnessing it most effectively, we will affect everything else in the universe—for better or worse.

Physicist, former President, Weizmann Institute of Science; Author, A View from the Eye of the Storm


Sometimes you make predictions. Sometimes you have wishful thinking. It is a pleasure to indulge in both, by discussing one and the same development which will change the world.

Today's world, its economy, industry, environment, agriculture, energy, health, food, military power, communications, you name it, are all driven by knowledge. The only way to fight poverty, hunger, diseases, natural catastrophes, terrorism, war, and all other evil, is the creation and dissemination of knowledge, i.e. research and education.

Of the six billion people on our planet, at least four billions are not participating in the knowledge revolution. Hundreds of millions are born to illiterate mothers, never drink clean water, have no medical care and never use a phone.

The "buzz words" of distant learning, individualized learning, and all other technology-driven changes in education, remain largely on paper, far from becoming a daily reality in the majority of the world's schools. The hope that affluent areas will provide remote access good education to others has not materialized. The ideas of bringing all of science, art, music and culture to every corner of the world and the creation of schools designed differently, based on individual and group learning, team work, simulations and special aids to special needs—all of these technology enabled goals remain largely unfulfilled.

It is amazing that, after decades of predictions and projections, education, all around the world, has changed so little. Thirty years ago, pundits talked about the thoroughly computerized school. Many had fantasies regarding an entirely different structure of learning, remote from the standard traditional school-class-teacher complex, which has hardly changed in the last century.

It is even more remarkable that no one has made real significant money on applying the information revolution to education. With a captive consumer audience of all school children and teachers in the world, one would think that the money made by eBay, Amazon, Google and Facebook might be dwarfed by the profits of a very clever revolutionary idea regarding education. Yet, no education oriented company is found among the ranks of the web-billionaires.

How come the richest person on the globe is not someone who had a brilliant idea about using technology for bringing education to the billions of school children of the world? I do not know the complete answer to this question. A possible guess is that in other fields you can have "quickies" but not in education. The time scale of education is decades, not quarters. Another possible guess is that, in education, you must mix the energy and creativity of the young with the wisdom and experience of the older, while in other areas, the young can do it fast and without the baggage of the earlier generations.

I am not necessarily bemoaning the fact that no one got into the list of richest people in the world by reforming education. But I do regret that no "game-changing" event has taken place on this front, by exploiting what modern technology is offering.

Four million Singapore citizens have a larger absolute GDP than 130 million Pakistanis. This is not unrelated to all the miseries and problems of Pakistan, from poverty to terror to severe earthquake damage. The only way to change this, in the long run, is education. Nothing better can happen to the world, than better education to such a country. But, relying only on local efforts may take centuries. On the other hand, if Al Qaida can reach other continents from Pakistan by using the web, why can't the world help educate 130 million Pakistanis using better methods?

So, my game-changing hope and prediction is that, finally, something significant will change on this front. The time is ripe. A few novel ideas, aided by technologies that did not exist until recently, and based on humanistic values, on compassion and on true desire to extend help to the uneducated majority of the earth population, can do the trick.

Am I naive, stupid or both? Why do I think that this miracle, predicted for 30 years by many, and impatiently waited for by more, will finally happen in the coming decades?

Here are my clues:

First, a technology-driven globalization is forcing us to see, to recognize and to fear the enormous knowledge gaps between different parts of the world and between segments of society within our countries. It is a major threat to everything that the world has achieved in the last 100 years, including democracy itself. Identifying the problem is an important part of the solution.

Second, the speed and price of data transmission, the advances in software systems, the feasibility of remote video interactions, the price reduction of computers, fancy screens and other gadgets, finally begin to lead to the realization that special tailor-made devices for schools and education are worth designing and producing. Until now, most school computers were business computers used at school and very few special tools were developed exclusively for education. This is beginning to change.

Third, for the first time, the generation that grew up with a computer at home is reaching the teacher ranks. The main obstacle of most education reforms has always been the training of the teachers. This should be much easier now. Just remember the first generation of Americans who grew up in a car-owning family. It makes a significant difference.

Fourth, the web-based social networks in which the children now participate pose a new challenge. The educational system must join them, because it cannot fight them. So the question is not any more: "Will there be a revolution in education?" But "Will the revolution be positive or deadly?" Too many revolutions in history have led to more pain and death than to progress. We must get this one right.

Fifth, a child who comes to school with a 3G phone, iPod or whatever, sending messages to his mother's blackberry and knowing in real time what is happening in the class room of his brother or friend miles or continents away, cannot be taught anything in the same way that I was taught. Has anyone seen lately a slide rule? A logarithmic table? A volume of Pedia other than Wiki?

At this point I could produce long lists of specific ideas which one may try or of small steps which have already been taken, somewhere in the world. But that is a matter for long essays or for a book, not for a short comment. It is unlikely that one or three or ten such ideas will do the job. It will have to be an evolutionary process of many innovations, trial and error, self adjustment, avoiding repetition of past mistakes and, above all, patience. It will also have to include one or more big game-changing elements of the order of magnitude of the influence of Google.

This is a change that will create a livable world for the next generations, both in affluent societies and, especially, in the developing or not-even-yet-developing parts of the world. Its time has definitely come. It will happen and it will, indeed, change everything.

Physicist; Albert Einstein Professor of Science, Princeton University; Coauthor, Endless Universe


One of the sacred principles of physics is that information is never lost. It can be scrambled, encrypted, dissipated and shredded, but never lost. This tenet underlies the second law of thermodynamics and a concept called "unitarity," an essential component of unified theories of particles and forces. Discovering a counterexample or new ways to preserve information could be a real game-changer: one that alters our understanding of the fundamental laws of nature, transforms our concept of space and time, triggers a reconstruction of the history of the universe and leads to new prognostications about its future.

There is a real chance of breakthrough in the foreseeable future as theorists converge on one of the greatest threats to information preservation: black holes. According to Einstein's general theory of relativity, a black hole forms when matter is so concentrated that nothing, not even light, can escape its gravitational field. Any information that passes through the event horizon surrounding the black hole—the "point of no return"—is lost forever to the outside world. Suppose, for example, that Bob pilots a spaceship into the black hole carrying along three books of his choice. It appears that the titles and contents of the three books vanish. Either that or Einstein's general theory of relativity is wrong.

There is nothing shocking about having to correct Einstein's general theory of relativity. It's known to be missing an essential element, quantum physics. Einstein, and generations of theorists since, have sought an improved theory of gravity that incorporates quantum physics in a way that is mathematically and physically consistent. String theory and loop quantum gravity are the most recent attempts.

There is no doubt that quantum physics alters the event horizon and the evolution of a black hole in a fundamental way, as first point out in the work of Jacob Bekenstein, Gary Gibbons and Stephen Hawking in the 1970s. According to quantum physics, matter and energy are composed of discrete chunks known as quanta (such as electrons, quarks and photons) whose position and velocities are undergoing constant random fluctuations. Even empty space—a pure vacuum—is seething with microscopic fluctuations that create and annihilate pairs of quanta and anti-quanta. The seething vacuum just outside the event horizon occasionally produces a pair of quanta, such as an electron-positron duo, in which one escapes and one falls into the black hole. From afar, it appears that the black hole radiates a particle. This phenomenon repeats continuously, producing a spectrum of particles known as "Hawking radiation," whose properties are similar to the "thermal radiation" emitted by a hot body. Very slowly, the black hole radiates away energy and shrinks in mass and size until—well, here is where the story really begins to get interesting.

Thermal radiation only depends on the temperature of the emitting body, providing no other details about the body itself. So, if Hawking radiation is truly thermal, then the information inside the black hole is truly lost . For the last decade, though, leading physicists including Gerard 't Hooft, Leonard Susskind, and Stephen Hawking fiercely debated (and even bet on) the outcome—Susskind refers to the debate as the "black hole war." Aided by new theoretical tools developed by Juan Maldacena and other string theorists, physicists discovered that Hawking radiation is not quite thermal after all! The radiation deviates by a tiny amount from a perfectly thermal signal, and the tiny deviation incorporates information about whatever was inside. The titles of Bob's three books, for example, are not lost forever, although the information dribbles out incredibly slowly and is unimaginably scrambled. Thus, victory was declared in the black hole war.

But it may be an uneasy peace, for there remains the question of what happens to information after it falls into the horizon. This is a reasonable question because, curiously enough, passage through the horizon can be unremarkable (if the black hole is very big). There are no sign posts indicating to Bob that he has passed the point of no return, and his books remain intact. Now suppose Bob scribbles some notes in the margins of his book. What happens to this information?

Here there is a diversity of views. Some suggest that this information, too, is radiated away through the Hawking process and the black hole simply disappears. Some suggest that quantum physics makes the event horizon penetrable so that some information is radiated by the Hawking process but some escapes directly. Yet others suggest that the information is copied; one copy is radiated away and the other strikes the singularity, entering a new section of space-time that is causally disconnected from observers outside the black hole, so the two copies never meet.

Theorists have recently developed a number of new theoretical tools to attack the problem and are hard at work. Although the subject lies in the domain of quantum gravity, the implications for other fields, including my own, cosmology, will be profound. The answer will shape any future formulation of the laws of thermodynamics, quantum gravity and unified field theory. Since scrambling information, a.k.a., the entropy, determines the arrow of time, the results may inform us how time may have first emerged at the cosmic singularity known as the big bang. Or, if it proves possible for copies to bounce from the black hole singularity to a separate piece of space time, the same may apply to an even more famous singularity, the big bang. This would lend support to recent ideas suggesting that the large scale properties of the universe were shaped by events before the big bang and these conditions (a form of information) were transmitted across the cosmic singularity into a new phase of expansion. In fact, if information is forever preserved across singularities, the universe may undergo regularly repeating cycles of big bangs, expansion, and big crunches, forever into the past and into the future. To me, a breakthrough with these kinds of implications would be the ultimate game-changer.

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