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Chapter 1

The Bounds of Reality

On Parallel Worlds

If, when I was growing up, my room had been adorned with only a single mirror, my childhood daydreams might have been very different. But it had two. And each morning when I opened the closet to get my clothes, the one built into its door aligned with the one on the wall, creating a seemingly endless series of reflections of anything situated between them. It was mesmerizing. I delighted in seeing image after image populating the parallel glass planes, extending back as far as the eye could discern. All the reflections seemed to move in unison—but that, I knew, was a mere limitation of human perception; at a young age I had learned of light’s finite speed. So in my mind’s eye, I would watch the light’s round-trip journeys. The bob of my head, the sweep of my arm silently echoed between the mirrors, each reflected image nudging the next. Sometimes I would imagine an irreverent me way down the line who refused to fall into place, disrupting the steady progression and creating a new reality that informed the ones that followed. During lulls at school, I would sometimes think about the light I had shed that morning, still endlessly bouncing between the mirrors, and I’d join one of my reflected selves, entering an imaginary parallel world constructed of light and driven by fantasy. It was a safe way to break the rules.

To be sure, reflected images don’t have minds of their own. But these youthful flights of fancy, with their imagined parallel realities, resonate with an increasingly prominent theme in modern science—the possibility of worlds lying beyond the one we know. This book is an exploration of such possibilities, a considered journey through the science of parallel universes.

Universe and Universes

There was a time when “universe” meant “all there is.” Everything. The whole shebang. The notion of more than one universe, more than one everything, would seemingly be a contradiction in terms. Yet a range of theoretical developments has gradually qualified the interpretation of “universe.” To a physicist, the word’s meaning now largely depends on context. Sometimes “universe” still connotes absolutely everything. Sometimes it refers only to those parts of everything that someone such as you or I could, in principle, have access to. Sometimes it’s applied to separate realms, ones that are partly or fully, temporarily or permanently, inaccessible to us; in this sense, the word relegates ours to membership in a large, perhaps infinitely large, collection.

With its hegemony diminished, “universe” has given way to other terms introduced to capture the wider canvas on which the totality of reality may be painted. Parallel worlds or parallel universes or multiple universes or alternate universes or the metaverse, megaverse, or multiverse—they’re all synonymous and they’re all among the words used to embrace not just our universe but a spectrum of others that may be out there.

You’ll notice that the terms are somewhat vague. What exactly constitutes a world or a universe? What criteria distinguish realms that are distinct parts of a single universe from those classified as universes of their own? Perhaps someday our understanding of multiple universes will mature sufficiently for us to have precise answers to these questions. For now, we’ll use the approach famously applied by Justice Potter Stewart in attempting to define pornography. While the U.S. Supreme Court wrestled mightily to delineate a standard, Stewart declared simply and forthrightly, “I know it when I see it.”

In the end, labeling one realm or another a parallel universe is merely a question of language. What matters, what’s at the heart of the subject, is whether there exist realms that challenge convention by suggesting that what we’ve long thought to be the universe is only one component of a far grander, perhaps far stranger, and mostly hidden reality.

During the last half century, science has provided ample ways in which this possibility might be realized.

Varieties of Parallel Universes

A striking fact (it’s in part what propelled me to write this book) is that many of the major developments in fundamental theoretical physics— relativistic physics, quantum physics, cosmological physics, unified physics, computational physics—have led us to consider one or another variety of parallel universe. Indeed, the chapters that follow trace a narrative arc through nine variations on the multiverse theme. Each envisions our universe as part of an unexpectedly larger whole, but the complexion of that whole and the nature of the member universes differ sharply among them. In some, the parallel universes are separated from us by enormous stretches of space or time; in others, they’re hovering millimeters away; in others still, the very notion of their location proves parochial, devoid of meaning. A similar range of possibility is manifest in the laws governing the parallel universes. In some, the laws are the same as in ours; in others, they appear different but have shared a heritage; in others still, the laws are of a form and structure unlike anything we’ve ever encountered. It’s at once humbling and stirring to imagine just how expansive reality may be.

Some of the earliest scientific forays into parallel worlds were initiated in the 1950s by researchers puzzling over aspects of quantum mechanics, a theory developed to explain phenomena taking place in the microscopic realm of atoms and subatomic particles. Quantum mechanics broke the mold of the previous framework, classical mechanics, by establishing that the predictions of science are necessarily probabilistic. We can predict the odds of attaining one outcome, we can predict the odds of another, but we generally can’t predict which will actually happen. This well-known departure from hundreds of years of scientific thought is surprising enough. But there’s a more confounding aspect of quantum theory that receives less attention. After decades of closely studying quantum mechanics, and after having accumulated a wealth of data confirming its probabilistic predictions, no one has been able to explain why only one of the many possible outcomes in any given situation actually happens. When we do experiments, when we examine the world, we all agree that we encounter a single definite reality. Yet, more than a century after the quantum revolution began, there is no consensus among the world’s physicists as to how this basic fact is compatible with the theory’s mathematical expression.

Over the years, this substantial gap in understanding has inspired many creative proposals, but the most startling was among the first. Maybe, that early suggestion went, the familiar notion that any given experiment has one and only one outcome is flawed. The mathematics underlying quantum mechanics—or at least, one perspective on the math— suggests that all possible outcomes happen, each inhabiting its own separate universe. If a quantum calculation predicts that a particle might be here, or it might be there, then in one universe it is here, and in another it is there. And in each such universe, there’s a copy of you witnessing one or the other outcome, thinking—incorrectly—that your reality is the only reality. When you realize that quantum mechanics underlies all physical processes, from the fusing of atoms in the sun to the neural firing that constitutes the stuff of thought, the far-reaching implications of the proposal become apparent. It says that there’s no such thing as a road untraveled. Yet each such road— each reality—is hidden from all others.

This tantalizing Many Worlds approach to quantum mechanics has attracted much interest in recent decades. But investigations have shown that it’s a subtle and thorny framework (as we will discuss in Chapter 8); so, even today, after more than half a century of vetting, the proposal remains controversial. Some quantum practitioners argue that it has already been proven correct, while others claim just as assuredly that the mathematical underpinnings don’t hold together.

What is beyond doubt is that this early version of parallel universes resonated with themes of separate lands or alternative histories that were being explored in literature, television, and film, creative forays that continue today. (My favorites since childhood include The Wizard of Oz, It’s a Wonderful Life, the Star Trek episode “The City on the Edge of Forever,” and, more recently, Sliding Doors and Run Lola Run). Collectively, these and many other works of popular culture have helped integrate the concept of parallel realities into the zeitgeist and are responsible for fueling much public fascination with the topic. But the mathematics of quantum mechanics is only one of numerous ways that a conception of parallel universes emerges from modern physics. In fact, it won’t be the first I’ll discuss.

Instead, in Chapter 2, I’ll begin with a different route to parallel universes, perhaps the simplest route of all. We’ll see that if space extends infinitely far—a proposition that is consistent with all observations and that is part of the cosmological model favored by many physicists and astronomers—then there must be realms out there (likely way out there) where copies of you and me and everything else are enjoying alternate versions of the reality we experience here. Chapter 3 will journey deeper into cosmology: the inflationary theory, an approach that posits an enormous burst of superfast spatial expansion during the universe’s earliest moments, generates its own version of parallel worlds. If inflation is correct, as the most refined astronomical observations suggest, the burst that created our region of space may not have been unique. Instead, right now, inflationary expansion in distant realms may be spawning universe upon universe and may continue to do so for all eternity. What’s more, each of these ballooning universes has its own infinite spatial expanse, and hence contains infinitely many of the parallel worlds explored in Chapter 2.

In Chapter 4, our trek turns to string theory. After a brief review of the basics, I’ll provide a status report on this approach to unifying all of nature’s laws. With that overview, in Chapters 5 and 6 we’ll explore recent developments in string theory that suggest three new kinds of parallel universes. One is string theory’s braneworld scenario, which posits that our universe is one of potentially numerous “slabs” floating in a higher-dimensional space, much like a slice of bread within a grander cosmic loaf. If we’re lucky, it’s an approach that may provide an observable signature at the Large Hadron Collider in Geneva, Switzerland, in the not too distant future. A second variety involves braneworlds that slam into one another, wiping away all they contain and initiating a new, fiery big-bang-like beginning in each. As if two giant hands were clapping, this could happen over and over—branes might collide, bounce apart, attract each other gravitationally, and then collide again, a cyclic process generating universes that are parallel not in space but in time. The third scenario is the string theory “landscape,” founded on the enormous number of possible shapes and sizes for the theory’s required extra spatial dimensions. We’ll see that, when joined with the Inflationary Multiverse, the string landscape suggests a vast collection of universes in which every possible form for the extra dimensions is realized.

In Chapter 6, we’ll focus on how these considerations illuminate one of the most surprising observational results of the last century: space appears to be filled with a uniform diffuse energy, which may well be a version of Einstein’s infamous cosmological constant. Indeed, this observation has inspired much of the recent research on parallel universes, and it’s responsible for one of the most heated debates in decades on the nature of acceptable scientific explanations. Chapter 7 extends this theme by asking, more generally, whether consideration of hidden universes beyond our own can be rightly understood as a branch of science. Can we test these ideas? If we invoke them to solve outstanding problems, have we made progress, or have we merely swept the problems under a conveniently inaccessible cosmic rug? I’ve sought to lay bare the essentials of the clashing perspectives, while ultimately emphasizing my own view that, under certain specific conditions, parallel universes fall unequivocally within the purview of science.

Quantum mechanics, with its Many Worlds version of parallel universes, is the subject of Chapter 8. I’ll briefly remind you of the essential features of quantum mechanics, then focus on the formidable problem just referred to: how to extract definite outcomes from a theory whose basic paradigm allows for mutually contradictory realities to coexist in an amorphous, but mathematically precise, probabilistic haze. I’ll carefully lead you through the reasoning that, in seeking an answer, proposes anchoring quantum reality in its own profusion of parallel worlds.

Chapter 9 takes us yet further into quantum reality, leading to what I consider the strangest version of all parallel universes proposals. It’s a proposal that emerged gradually over thirty years of theoretical studies spearheaded by luminaries including Stephen Hawking, Jacob Bekenstein, Gerardt Hooft, and Leonard Susskind on the quantum properties of black holes. The work culminated in the last decade, with a stunning result from string theory, and it suggests, remarkably, that all we experience is nothing but a holographic projection of processes taking place on some distant surface that surrounds us. You can pinch yourself, and what you feel will be real, but it mirrors a parallel process taking place in a different, distant reality.

Finally, in Chapter 10 the yet more fanciful possibility of artificial

universes takes center stage. The question of whether the laws of physics give us the capacity to create new universes will be our first order of

business. We’ll then turn to universes created not with hardware but

with software—universes that might be simulated on a superadvanced computer—and investigate whether we can be confident that we’re not now living in someone or something else’s simulation. This will lead to the most unrestrained parallel universe proposal, originating in the philosophical community: that every possible reality is realized somewhere in what’s surely the grandest of all multiverses. The discussion naturally unfolds into an inquiry about the role mathematics has in unraveling the mysteries of science and, ultimately, our ability, or lack thereof, to gain an ever-deeper understanding of the expanse of reality.

The Cosmic Order


The subject of parallel universes is highly speculative. No experiment or observation has established that any version of the idea is realized in nature. So my point in writing this book is not to convince you that we’re part of a multiverse. I’m not convinced—and, speaking generally, no one should be convinced—of anything not supported by hard data. That said, I find it both curious and compelling that numerous developments in physics, if followed sufficiently far, bump into some variation on the parallel universe theme. Of particular note, it’s not that physicists are standing ready, multiverse nets in their hands, seeking to snare any passing theory that might be slotted, however awkwardly, into a parallel- universe paradigm. Rather, all of the parallel-universe proposals that we will take seriously emerge unbidden from the mathematics of theories developed to explain conventional data and observations.

My intention, then, is to lay out clearly and concisely the intellectual steps and the chain of theoretical insights that have led physicists, from a range of perspectives, to consider the possibility that ours is one of many universes. I want you to get a sense of how modern scientific investigations— not untethered fantasies like the catoptric musings of my boyhood— naturally suggest this astounding possibility. I want to show you how certain otherwise confounding observations can become eminently understandable within one or another parallel-universe framework; at the same time, I’ll describe the critical unresolved questions that have, as yet, kept this explanatory approach from being fully realized. My aim is that when you leave this book, your sense of what might be— your perspective on how the boundaries of reality may one day be redrawn by scientific developments now under way— will be far more rich and vivid.

Some people recoil at the notion of parallel worlds; as they see it, if we are part of a multiverse, our place and importance in the cosmos are marginalized. My take is different. I don’t find merit in measuring significance by our relative abundance. Rather, what’s gratifying about being human, what’s exciting about being part of the scientific enterprise, is our ability to use analytical thought to bridge vast distances, journeying to outer and inner space and, if some of the ideas we’ll encounter in this book prove correct, perhaps even beyond our universe. For me, it is the depth of our understanding, acquired from our lonely vantage point in the inky black stillness of a cold and forbidding cosmos, that reverberates across the expanse of reality and marks our arrival.

Revue de presse

“Brian Greene has a gift for elucidating big ideas. . . Captures and engages the imagination. . . . It’s exciting and rewarding to read him.” —The New York Times

“A wonderful way to coax your brain into a host of strange and unfamiliar domains.” —The Boston Globe

“Exciting physics, wrapped up in effortless prose. . . . Greene has done it again.” —New Scientist

“If extraterrestrials landed tomorrow and demanded to know what the human mind is capable of accomplishing, we could do worse than to hand them a copy of this book.” —The New York Times Book Review
 
“The multiverse is an idea whose time has come. . . . The book serves well as an introduction . . . and will open up many people’s eyes.” —The Wall Street Journal
 
“Greene takes us down the rabbit hole yet again, this time setting a course for the terra incognita of parallel universes, hidden worlds, alternate realities, holographic projections, and multiverse simulations. Greene likes to drop you into the middle of the action first and then explain the backstory, but he has an elegant knack for anticipating questions and immediately dealing with any confusion or objections.” —The Daily Beast
 
“An accessible and surprisingly witty handbook to parallel universes…. Greene is immensely gifted at finding apt and colorful everyday analogies for the arcane byways of theoretical physics.” —The Toronto Star
 
“Mind-stretching. . . . [The Hidden Reality is] Greene’s impassioned argument ‘for the capacity of mathematics to reveal hidden truths about the workings of the world.’” —The New Yorker
 
“Like [Stephen] Hawking and [Roger] Penrose before him, [Greene] is an author who writes with the confidence and authority of one who . . . has seen the promised land of cosmic truth.” —Bookforum
 
“If you like your science explained rather than asserted, if you like your science writers articulate and intelligible, if you like popular science to make sense, even as it probes the heart of difficult theory, you are going to love The Hidden Reality and its author, Brian Greene.” —New York Journal of Books
 
“Greene’s forte is his amazing ability to give clear, everyday examples to illustrate complicated physical theories.” —The Globe and Mail
 
“Ambitious. . . . Entertaining and well-written. . . . Greene is a keen interpreter.” —The Christian Science Monitor
 
“A lucid, intriguing, and triumphantly understandable state-of-the-art look at the universe.” —Publishers Weekly (starred review)
 
 “With a slew of clever analogies, Greene communicates with uncommon clarity, intuition, and honesty.” —The Oxonian Review
 
“Greene’s success at explaining the patently inexplicable lies in the way he delightfully melds the utterly bizarre and the utterly familiar.” —Providence Journal
 
“Exotic cosmic terrain through which Greene provides expert guidance.” —The Oregonian
 
“Mind-blowing.” —The Sunday Times (London)
 
“Highly rewarding.” —Scotland on Sunday
 
“[Greene] has something fresh and insightful to say about pretty much everything”—ScienceFiction.com
 
“Vast, energetic and complex.” —The Easthampton Star
 
“The best guide available, in this universe at least.”—Science News
 
“Greene’s greatest achievement is that even as you grapple with these allusive concepts, you start falling in love with these mysteries.” —The Express Tribune



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  • Broché: 464 pages
  • Editeur : Vintage; Édition : Reprint (1 novembre 2011)
  • Langue : Anglais
  • ISBN-10: 0307278123
  • ISBN-13: 978-0307278128
  • Dimensions du produit: 13,1 x 2,4 x 20,3 cm
  • Moyenne des commentaires client : 4.3 étoiles sur 5  Voir tous les commentaires (3 commentaires client)
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1 internautes sur 1 ont trouvé ce commentaire utile  Par Cathy Keustermans le 18 septembre 2012
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another good book that makes science accessible for the general public. I was more impressed with the previous book (the elegant universe) as some "ommissions" were made in this one, that made some chapters harder to follow without the background. Especially in the chapters on inflationary theory a few short-circuits are taken (whatever happened to supercooling and false vacuum..?). Fortunately I read some A. Guth before (the inflationary universe - a recommendation!!). Once into string theory, we clearly notice the "home" of Brian Greene and the explanations are very smooth again. Altogether certainly a very interesting read.
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Par Geneste le 31 mai 2014
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Very instructive book where the author presents several possibilities of infinite universes. There are details of interest in particular about the time we evaluate through observation and the reader will learn that in physics today, there exists 73 different fields!
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0 internautes sur 1 ont trouvé ce commentaire utile  Par Michaelis le 15 juin 2013
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Pour moi il s'agit d'un extraordinaire bouquin de science-fiction. Cela m'a absolument passionnée même si certaines explications m'ont sidérée et je suis vraiment sentie dépassée. Je recommande le livre, c'est un must il faut l'avoir lu.
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523 internautes sur 542 ont trouvé ce commentaire utile 
Another masterpiece of science writing from Brian Greene 7 janvier 2011
Par Michael Birman - Publié sur Amazon.com
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Brian Greene's previous books are exemplars of what science writing should be: clear, wide-ranging in discussion and respectful of the intelligence of his audience. The Elegant Universe and The Fabric of the Cosmos are two of my three favorite popular science books. The third, Kip Thorne's Black Holes and Time Warps, is another superb example of science writing at its best. Now Brian Greene has added another masterpiece to the list. Everything that distinguishes Greene's writing style is in evidence in The Hidden Reality. His elegant prose is enjoyable to read. His brilliant ability to explain difficult abstract ideas in everyday language using easily understood examples still amazes me. And his use of vivid word pictures that always seem perfectly matched to the topic he's discussing propels his narrative forward so that the reader is never bored.

Yes The Hidden Reality is more accessible than his previous books. This book seems easier to read and is readily understandable. In his earlier books, I often read a paragraph several times in order to fully comprehend what Greene was attempting to communicate. That is something science and math majors are used to doing when reading textbooks but difficult for those not as scientifically adept. Greene's first two books dealt with Quantum Mechanics, String Theory and Einstein's Special and General Theories of Relativity: vast math-intensive topics that he was able to distill masterfully. The Hidden Reality inhabits a more abstract world, a conceptually challenging world. I quickly found Greene's more casual approach extremely helpful, even comforting, when I felt slightly adrift. The topics he discusses begin with the geometry of the universe: whether it is spherical (or positively curved), flat (with zero curvature) like a tabletop, or negatively curved like a Pringle.

The book devotes considerable time to the critical question of whether the universe is finite or infinite in size, something which has profound scientific and philosophical implications. It is a statistical certainty that in an infinite universe, regions of local space like ours will be endlessly repeated. In other words, assuming an infinite spatial universe with an expanding big-bang beginning, there are only a finite number of possible matter and energy configurations because the amount of energy and matter is finite. But there is an infinite amount of space within which those configurations will play out. Greene uses the example of a friend named Imelda whose passion for clothing has her purchasing 1000 pairs of shoes and 500 dresses. If Imelda is blessed with an infinitely long lifespan then, despite her vast wardrobe, if she changes outfits daily, within 1400 years she will have exhausted all possible new combinations. Imelda will be forced to repeat her sartorial choices. Philosophically, of course, all of that repetition of stars, planets and life's building blocks suggests that there are an infinite number of doppelgangers of each and every one of us. These infinite duplicates of ourselves would inhabit similar worlds that are forever hidden from mutual observation because the speed of light is finite. As Einstein showed in his Special Theory of Relativity, light-speed (300,000 km/sec) is the fastest rate by which information can be communicated. The bottom line: in an infinite universe the overwhelming bulk of reality remains hidden from its inhabitants by vast distances or by parallel dimensions harboring realities of every possible configuration.

In a finite spherical universe, on the other hand, the light from distant objects should ultimately traverse it several times, leading to multiple images of galaxies, for example. This hasn't been observed as yet, suggesting that the universe is either finite but huge or actually infinite in size. Though the size and shape of the universe remain undetermined, scientists when cornered tend to believe its size is infinite. Recent data also suggests that the universe is flat like a tabletop in shape.

Greene discusses all of the current hot topics in cosmology: brane-worlds, the multiverse, the holographic universe, unseen parallel worlds in dimensions separated by millimeters, our universe as a super-advanced computer program, the essentially hidden nature of reality. These are topics that have been discussed in other books but seldom with the passion for communication and clarity of thought that Greene exhibits in this one. The topics here are abstract concepts that exist at the very boundaries of human thought but Greene somehow manages to bring them down to earth. Even if you don't understand everything, the scientific vistas that Greene offers in this superb book are breathtaking in their intellectual beauty. You will find your personal horizons exponentially expanded. The Hidden Reality is replete with excellent illustrations that illuminate the material and are fun to look at. If this kind of science intrigues you then you will love this book. Brian Greene has written another masterpiece in a difficult genre.
234 internautes sur 249 ont trouvé ce commentaire utile 
Difficult- but rewarding. 12 janvier 2011
Par Michael J. Edelman - Publié sur Amazon.com
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Beginning in the 16th Century, physics started to change from a purely scholastic mode of inquiry, in which questions were answered by argument from first principles and ancient authority, into a scientific one, in which observation and mathematical law predominated. With the introduction of Newton's work and his (and Leibniz') invention of the calculus, physics became a modern science, in which mathematics played a key role not only in testing theories, but in predicting phenomena as well. Even so, it was still possible for the non-scientist to understand much of the work of physicists, as it still dealt (for the most part) with laws and phenomena that could be observed, experienced, or at least imagined with the average person.

With the advent of relativity and quantum mechanics in the early 20th century, this all changed. Special Relativity dealt with velocities far beyond that which any human could ever experience. General Relativity dealt with interactions on a cosmic scale. And quantum mechanics dealt with scales far smaller than that which could be experienced or observed- even by physicists. What these new disciplines shared was that they they could only be truly understood by someone conversant with the mathematics involved. Although mass-induced curvature of space (for example) is commonly explained by analogy to a weight on a rubber sheet; that's at best, a weak metaphor. A ball bearing rolling on a rubber sheet is still being pulled down by gravity; it is not tracing a path in curved space that minimizes action.

As modern theories physics have become more complex, more purely mathematical, and further removed from the experience of the perceivable world, the books that attempt to explain things like inflationary cosmologies, string theory and supersymmetry have become increasingly less satisfying. And that brings us to the central failure of almost every popular book on modern physics I've ever read- the inability to actually explain the why and how. After reading countless books by popular authors like Tim Ferris, I realized that although many were, indeed, excellent writers, none of them actually understood the physics they were purporting to explain. At beast, they were simply repeating the metaphors they'd been given. They didn't understand the physics well enough to explain it.

There were a few exceptions- popular books written by actual physicists who also had a particular gift for teaching and explanation. To date, I've only found three who both have a deep understanding of modern physics, and who can convey more than a metaphorical understanding of this to a reasonably intelligent, but non-specialist, reader: Richard Feynman, Alan Guth, and Brian Greene. True, there are other physicists who write popular books, but most aim pretty low. They're satisfied to give a general sort of metaphorical explanation- curved space is like a curved rubber sheet, expansion is like inflating a beach ball, and strings are like... little strings. But Feynman, Guth and Greene each tried to really convey the real science.

The late Richard Feynman is still the master. His lectures- especially "The Character of Physical Law"- did a magnificent job of making clear even such difficult concepts as the quantum explanation of diffraction. Guth's "The Inflationary Universe" does a superb job of explaining topics like tension and negative energy in telling his story of the origins of cosmic inflation theory. And Brian Greene, author of the current volume under discussion, has now produced his third book attempting to explain some very difficult ideas to the lay reader. In "The Hidden Reality", Green tackles string theory, the multiverse, symmetry, group theory, and dozens of other topics, and he does so without resort to any "it's just like..." metaphors. He uses graphic representations when possible, to illustrate mathematical relationships without math when possible (although much of the real math can be found in the appendix.) He explains where and how contemporary cosmological theories originated, and gives the reader a good sense of exactly how we arrived at a position in which physics is largely dominated by untestable theories that make few predictions about the measurable universe- and why this is not necessarily a problem.

Greene is one of the principle authors of modern string theory, and he does a superlative job of conveying, for the lay reader, both the state of string theory, and its genesis. While to fully understand such notions as (say) the role of Calabi-Yu shapes in defining the topology of the multidimensional universe would no doubt require a real familiarity of topology, I think Greene comes as close as possible (or at least as close as I've seen) in conveying to the reader why it is that these shapes play a role in defining space, and how it is that physicists came to propose their existence. His explanation of quantum uncertainly and of Schrodinger's probability wave is probably the best non-mathematical one I've read.

This is not an easy book to read. I went as far as a few calculus courses and a semester of physics back in my undergraduate days, and I found this book fairly hard going. It's not terribly mathematical (except in the appendices) but the concepts are not easy, and there's little if any fluff to be found. This is not the sort of breezy reading found in the typical popular physics book (here's the atom, here's a quark, wasn't that cool?) The reader who attempts to simply skim through without trying to follow Greene's narration and really understand what he's trying to explain will quickly find themselves lost, reading words without a clue of what they mean. I've been reading it for two weeks, attacking a chapter (or part of a chapter) each day, and often backtracking to make sure I understand what Greene is trying to convey. The reader who is prepared to take this approach, and spend a lot of time reading, pausing, think about what they've read, and rereading each section to make sure they really understand what's going on, will find this a very rewarding book.
288 internautes sur 321 ont trouvé ce commentaire utile 
Often lost in the weeds 21 janvier 2011
Par J. A Magill - Publié sur Amazon.com
Format: Relié Commentaire client Vine pour produit gratuit ( De quoi s'agit-il? )
Let me say from the get go, I am a huge Brian Greene fan, having read both his previous books and having found them deeply edifying. Few writers working today possess his ability to take complex material and explain it in ways that the interested layman can digest. When I learned of his new book, I was excited to dive-in.

Unfortunately, for reasons that are not entirely clear to me, "The Hidden Reality" is far more opaque than his previous books. Time and again I found myself rereading a particular section, unable to decipher what he was seeking to explain. This may result from my own short-comings, I suspect that they might just as well arise from those limitations that Greene, from the very beginning, admits bedevils the notion of the "multiverse." Even more so than in String Theory, this topic currently stands at a point of being little more than speculation. Yes, the math creates the possibility that these other realms exist, but no one has to date suggested a method of falsification for this theory, nor does it offer much in the way of testable predictions.

Sometimes when he tries to counter critics, Green proves to be his own worst enemy. Consider a chapter where he argues against those who point out the difficulty of testing the hypothesis of a "muliverse." In reply, Greene points to Einstein's theories and the inability to demonstrate their veracity through experimentation in the early 20th century when they first appeared. However, this ignores the fact that Einstein's theories offered obvious precise predictions that, even if not testable at the time, one could imagine appearing in the near future. Had these predictions not withstood tests, out would have gone the theory. To date, nobody can offer similar predictions through this theory that we are likely to be able to test anytime soon.

The result of these weaknesses is that I found myself often lost in the weeds, left with little more than the point that the math says that these things may be so. I can understand Greene's enthusiasm at the possibility of limitless realities beyond our own, but glorying at the possibility doesn't get me any closer to accepting -- or even understanding -- that these intriguing suggestions might prove real.
51 internautes sur 55 ont trouvé ce commentaire utile 
Perhaps the Most INTERESTING Science Writer Working Today - 5 STARS !!!! 27 janvier 2011
Par Richard of Connecticut - Publié sur Amazon.com
Format: Relié
If you are a Brian Greene fan, then you may have read his previous books The Elegant Universe and the Fabric of the Cosmos, both of which are beautiful reads. In this his latest book, he lends his understanding of the most advanced concepts in physics and astrophysics to bring us into a world that scientists believe exist mathematically, but so far have not been able to substantiate with physical evidence. This book involves a whole slew of scientific disciplines that under normal conditions would be daunting to try to understand. They include:

* String Theory

* Subatomic particles

* Quantum physics

* Parallel worlds

* The Inflationary Universe

* Cyclic Multiverses

Perhaps you have experienced the same problem I have through the years. So many science writers want to impress you with how smart THEY are. They do this by introducing complex terms which I refer to as jargon. They give you mathematics which at one point years ago, you may have understood, but now you have no chance. In this book the author has planned it out thoroughly for the reader. He does this by introducing a topic at the beginning of the chapter, and telling you just what you need to know by way of background. He assumes no mathematical training on behalf of the reader, and teaches by metaphor, and analogy. He does not go off on tangents into areas that are both confusing and complicated. If he feels you need to know much more than what he has given as a preliminary background, he has relegated it to the notes in the back of the book. This is a kind author, and is one of the reasons why his works have sold so well through the years.

Just take a look at a couple of the very intriguing concepts that Greene expands upon in this book:

* Is there more than one universe? If so where are these parallel worlds? Could they be right next to us and we do not realize it because we cannot see them?

* Are they out there at the edge of the known universe?

* What about the concept of multiple universes? They are also known as parallel worlds, multiple universes, alternate universes, or the metaverse, multiverse, and megaverse.

* Depending upon the mathematics you use, we are getting some strange results indicating that what we believe we see is not what is actually going on. Thus the natural, intuitive understanding developed by Einstein did not follow though in Quantum Mechanics. When Quantum Mechanics clearly demonstrated that the scientific predictions are at best probabilistic as opposed to certain, it was earthshaking.

* The mathematics in vogue today is completely at odds with the single definite reality we all see? We're in trouble.

* It now turns out that Einstein when he created the concept of the mathematical constant may in the end be proven right.

There are 322 pages of narrative in this book followed by 30 pages of notes, and then several pages of suggested readings. I think you will love this book. This is an adventure for the reader as the author whisks us along on a journey of the outer limits of our knowledge of the universe. It is completely readable even to the novice science reader. No math required just a fertile imagination and the desired to be entertained intellectually while absorbing a world of wildly interesting information. Good luck, and thank you for reading this review.

Richard C. Stoyeck
17 internautes sur 18 ont trouvé ce commentaire utile 
Don't worry too much about the physics, read the book and enjoy the ride. 27 mars 2011
Par Denys Yeo - Publié sur Amazon.com
Format: Relié Achat vérifié
I am writing this review from the perspective of a person who has some rudimentary knowledge of classical physics, relativity, quantum mechanics and cosmology (and so on). That is I read a lot of books by Physicists who try to make the subject comprehensible. This means that I cannot comment on the accuracy of the physics described in the book or how it might help physicists further understand the subject. On the other hand, if Greene's intention was to write a book that would get readers thinking about the concept of reality, then I think he has succeeded brilliantly. Essentially, he has taken the top end of speculative physics and, in a number of cases, stretched the level of speculation a notch or two. His thinking about the need to do this is sound; unless scientists (and others?) are willing to stretch their thinking into new zones of possibility, progress will not leave our current reality. Once reality was that the universe (whatever that was) revolved around the Earth - the stretch in thinking to view reality in any other way must have been amazing. In a sense, Greene is not asking for anything more than a similar "wrench" in our thinking. So my recommendation is, don't worry too much about the physics, read the book and enjoy the ride.

Denys Yeo
Dunedin, New Zealand
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