The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos

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The bestselling author of The Elegant Universe and The Fabric of the Cosmos tackles perhaps the most mind-bending question in modern physics and cosmology: Is our universe the only universe?

There was a time when "universe" meant all there is. Everything. Yet, a number of theories are converging on the possibility that our universe may be but one among many parallel universes populating a vast multiverse. Here, Briane Greene, one of our foremost physicists and science writers, ...

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The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos

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The bestselling author of The Elegant Universe and The Fabric of the Cosmos tackles perhaps the most mind-bending question in modern physics and cosmology: Is our universe the only universe?

There was a time when "universe" meant all there is. Everything. Yet, a number of theories are converging on the possibility that our universe may be but one among many parallel universes populating a vast multiverse. Here, Briane Greene, one of our foremost physicists and science writers, takes us on a breathtaking journey to a multiverse comprising an endless series of big bangs, a multiverse with duplicates of every one of us, a multiverse populated by vast sheets of spacetime, a multiverse in which all we consider real are holographic illusions, and even a multiverse made purely of math--and reveals the reality hidden within each.

Using his trademark wit and precision, Greene presents a thrilling survey of cutting-edge physics and confronts the inevitable question: How can fundamental science progress if great swaths of reality lie beyond our reach? The Hidden Reality is a remarkable adventure through a world more vast and strange than anything we could have imagined.

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  • Brian Greene on String Theory
    Brian Greene on String Theory  

Editorial Reviews

Publishers Weekly
"There was a time when ‘universe' meant ‘all there is,'" writes Greene, but soon we may have to redefine that word, along with our own meager understanding of the cosmos. A theoretical physicist and celebrated author, Greene offers intrepid readers another in-depth yet marvelously accessible look inside the perplexing world of modern theoretical physics and cosmology. Greene's book The Elegant Universe explained late 20th-century efforts to find a unified theory of everything, culminating with string theory. But string theory opened up a new can of worms, hinting at the possible existence of multiple universes and other strange entities. The possibility of other universes existing alongside our own like holes in "a gigantic block of Swiss cheese" seems more likely every day. Beginning with relativity theory, the Big Bang, and our expanding universe, Greene introduces first the mind-blowing multiplicity of forms those parallel universes might take, from patchwork quilts or stretchy "branes" to landscapes and holograms riddled with black holes. With his inspired analogies starring everyone from South Park's Eric Cartman to Ms. Pac-Man and a can of Pringles, Greene presents a lucid, intriguing, and triumphantly understandable state-of-the-art look at the universe. Illus. (Feb.)
Kirkus Reviews

An exploration of cutting-edge physics written for intelligent readers willing to pay close attention.

Greene (Physics and Mathematics/Columbia Univ.; The Fabric of the Cosmos: Space, Time, and the Texture of Reality, 2004, etc.) points out that some astronomers believe that our universe is infinite. If so, the focus of his book, parallel universes, follows naturally. Mathematic calculations prove that an infinite universe contains innumerable regions with identical Milky Ways, solar systems and sentient life, plus many more regions differing in minor details. At this level, the existence of parallel universes is fairly simple. Thereafter, it becomes extremely complex. Essential to the current state of our cosmos is a momentary, massive expansion of the universe occurring an instant after the big bang: inflation. Some theorists maintain that this burst of expansion was not a one-time event but continues to occur, producing innumerable, parallel "bubble universes." Near the beginning of the book, Greene pauses to recap string theory, the subject of his previous books. An unproven, complex but widely held system for explaining all forces and matter, it allows for half-a-dozen additional parallel universes such as the Cyclic, Brane and Landscape multiverses. The author makes imaginative use of charts, diagrams, photographs, analogies and anecdotes to describe difficult scientific ideas. His accounts of confirmed phenomena such as relativity, quantum theory and recent revelations in astronomy provide lucid explanations that will satisfy a lay audience. Where he delves into string theory, many readers will struggle, not always successfully.

The latest cosmological discoveries and speculations, directed at a popular audience but definitely not oversimplified.

Timothy Ferris
[Greene's] ultimate goal is to help us think big in more ways than one. "I find it parochial," he writes, "to bound our thinking by the arbitrary limits imposed by where we are, when we are and who we are. Reality transcends these limits, so it's to be expected that sooner or later the search for deep truths will too." 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
Janet Maslin
…Mr. Greene has a gift for elucidating big ideas and knowing that a bombardment of too many small ones might make the armchair physicist implode…It's exciting and rewarding to read him even when the process is a struggle. This book is significantly more difficult than his earlier ones, but it still captures and engages the imagination.
—The New York Times
From the Publisher

“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”—
“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

Library Journal
The idea of parallel universes will be familiar to sf and popular science readers. Delve into the theories that predict a multiverse with Greene, a superstring physicist, best-selling author, and Pulitzer finalist.
The Barnes & Noble Review

From Paul Di Filippo's "THE SPECULATOR" column on The Barnes & Noble Review

The concept of the multiverse -- a plethora of individually infinite universes of every conceivable nature, coexisting yet separated from each other in some fashion -- holds a particular horror for those who fancy that their lives derive meaning and ethical stature only from a sense of self-determined uniqueness. Ontological nausea and revulsion swiftly set in when such a person begins to contemplate billions of his doppelgangers enacting perverse, bizarre, and morally repulsive scenarios imbued with just as much existential gravitas as the one his particular consciousness in this universe experiences and privileges. Such a vision embodies self-betrayals of the most intimate possible nature.

But for those of us who relish the notion of a limitless plenum in which every possible outcome of consciousness, every possible arrangement of matter, every possible set of natural laws, is given concrete expression somewhere -- even though these other universes lie forever beyond our reach -- the concept of the multiverse offers a triumph of the imagination and spirit. No flight of fancy, however wild, is denied existence. Every potential aspect of one's character, suppressed in this universe, finds manifestation elsewhere. Bad fates in this universe are avoided in an infinity of others. And the multiverse settles all perplexing questions of "Why this?" with a simple "Because we see only one thread of an infinite tapestry."

And you cannot really avoid forming a reaction to the notion of a multiverse either -- assuming you respect science -- since almost all contemporary physics accepts and even demands the reality of parallel worlds. Love it or hate it, the multiverse is here to stay.

It's not hard to guess -- in advance of reading Brian Greene's latest survey of the actual physics behind the multiverse, The Hidden Reality -- which side of the emotional fence he comes down on. Having gone to the effort of producing a hypnotically fascinating book-length explication of the concept, Greene is plainly invested deeply in the awesomeness of multiple realities. His enthusiasm and passion for parallel worlds infuses every iota of this ideationally dense yet essentially comprehensible opus.

Greene informs us at the outset that he will explicate nine types of multiverses. (Yes, we are about to encounter a multiverse of multiverses!) The first seven are direct outgrowths of discoveries or theories in modern physics: cosmology, string theory, etc. The final two are more purely conceptual or speculative exercises. So, because the first set requires grounding in several branches of science, Greene devotes plenty of space to topics that are foundational: how gravity works, the Inflationary Big Bang, and so forth. Admirably, he skips the boring and redundant primer level, which so many popular science books continue timidly to include at this late date, but assumes that his readership of interested twenty-first-century laypeople has a solid acquaintance already with the science of the past hundred years. This tactic is much appreciated, and never abused, as any sticky or abstruse points are still treated with appropriate depth in Greene's trademark crystalline prose studded with handy and often amusing metaphors. ("Imagine you work for the notorious film producer Harvey W. Einstein, who has asked you to put out a casting call for the lead in his new indie, Pulp Friction.")

It's impossible for this review to summarize every step of Greene's balletic footwork, by which, like some multi-limbed Asian deity, he dances into being each different theoretical framework that could support multiple universes. Suffice it to say, switching analogies, that his arguments are constructed like classical cathedrals, with intricate arches and buttresses that all uphold the central spire. Sometimes you think he's lost in the details of some sculpted gargoyle, only to realize how essential to the whole structure this particular feature is.

He starts with the simplest of multiverses, the "Quilted" one. In this case, a purely spatial infinity is all that is needed to produce an infinity of timelines, separated merely by lightyears and not other dimensions. He concludes with the "Ultimate" multiverse, a philosophical construct owing much to the speculations of Robert Nozick. In between, we get bubble universes and "branes" and five other mind-boggling ways in which the cosmos we know can be viewed as merely one member of an endless family of possibilities.

Chapter Seven, coming right at the midpoint of the book, is a very useful diversion from propounding new theories, a breather in which Greene examines the controversies surrounding the very notion of a multiverse, and whether these speculations that cannot be tested, observed, or falsified truly adhere to the spirit of science. Coming down staunchly on the side of unfettered yet rigorous hypothesizing (and leaving open the possibility that our descendants will be able someday to verify our flights of scientific fancy), Greene emerges prepped to ascend even greater heights in the second half of the book.

The tension between the two camps -- lovers and haters of the multiverse -- that I described in my opening paragraphs is a constant motif throughout the book, as Greene continually seeks to justify the rewards inherent in accepting "the hidden reality" of the multiverse. His concluding sentences sum up his stance bravely and concisely: "But it's only through fearless engagement that we can learn our own limits. It's only through the rational pursuit of theories, even those that whisk us into strange and unfamiliar domains, that we stand a chance of revealing the expanse of reality."

* * *

Greene namechecks several fictional treatments of multiversal concepts in his opening chapter -- Star Trek's "The City on the Edge of Forever," Borges's "The Garden of Forking Paths," Run Lola Run -- and indeed this concept has received extensive treatment in science fiction and other types of literature, rendering its outlines familiar to even the most casual reader and viewer. The well-developed scientific treatment of parallel worlds in literature goes back at least as far as H. G. Wells, and has received extensive elaboration from writers as diverse as Edmond Hamilton and Fritz Leiber, Robert Silverberg and Keith Laumer.

Curiously enough, one of the most seminal and impactful introductions of the concept occurred in a comic book, the now-classic September 1961 issue of The Flash, with its feature story "Flash of Two Worlds." Scripter Gardner Fox, long-steeped in pulp writing, imported the notion of multiple timelines to the home turf of Superman and Batman (Marvel Comics belatedly followed suit), and an explosion of multiversal narratives ensued, to the point where parent company DC Comics felt obliged to stage Crisis on Infinite Earths some twenty years later, to pare down the proliferation of alternate worlds.

But if one had to pick a single author who has done the most to portray the quirks and potentials of a functioning multiverse, that figure would undeniably be Michael Moorcock. First employing the concept almost five decades ago, Moorcock has since woven nearly all his copious output -- tightly or loosely, as circumstances allow -- into one vast braided multiverse of story. So identified is Moorcock with the multiverse, in fact, that upon his ascent to SFWA Grandmaster, I was able to easily evoke a humorous scenario involving the author and his doppelgangers that any of his readers would instantly recognize. 

Moorcock's latest, Elric: Swords and Roses, is the sixth and concluding installment in his chronicle of the doomed, Byronic, albino swordsman who functions as a kind of template or seed character for so many other antiheroes in the Moorcock multiverse.

We open the omnibus (which also contains a previously unpublished screenplay, a novella, and several essays, as well as pages of artwork) with its core component, a complete novel from 1991, The Revenge of the Rose. Whereas many of Elric's early adventures dealt with the multiverse only implicitly, this late-period outing foregrounds the nature of creation in Moorcock's fiction. The multiverse nearly assumes the role of an actor in the adventure. For beneath the expected inventive sword-and-sorcery decadence (Elric, a woman warrior named Rose, and a poet named Wheldrake are all plucked from their separate timestreams for exploits in a strange world foreign to them all, as Elric hunts for the plot-coupon soul-in-a-box of his dead father), Elric must continually confront the senses-disturbing and mind-shattering -- yet also uplifting -- nature of parallel worlds.

Now Elric was caught up in a kind of intradimensional hurricane, in which a thousand reverses ocurred within his brain at once and he became a thousand other creatures for an instant, and where he lived through more than ten other lives; a fate only minimally different from the one that was familiar to him; and so vast did the multiverse become, so unthinkable, that he began to go mad as he attempted to make sense of just a fraction of what laid siege to his sanity….

But the upside is this vision, as recounted by a seer:

It is our firm belief that we shall one day learn the plan of the entire multiverse and travel at will from Sphere to Sphere, from realm to realm, from world to world, travel through the great clouds of shifting, multicoloured stars, the tumbling planets in all their millions, through galaxies that swarm like gnats in a summer garden, and rivers of light -- glory beyond glory -- pathways of moonbeams between the roaming stars.

And thus, through Moorcock's exuberant prose, is Brian Greene's carefully controlled and channeled mysticism -- the unnamed engine that powers his researches, yet which must be throttled in the name of science and hidden away -- given ultimate lyrical expression.

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Product Details

  • ISBN-13: 9780307265630
  • Publisher: Knopf Doubleday Publishing Group
  • Publication date: 1/25/2011
  • Pages: 370
  • Sales rank: 309,267
  • Product dimensions: 6.40 (w) x 9.30 (h) x 1.60 (d)

Meet the Author

Brian Greene

Brian Greene received his doctorate from Oxford University, where he was a Rhodes Scholar. He is currently a professor of physics and mathematics at Columbia University, and is highly regarded for a number of groundbreaking discoveries in superstring theory. His first book, The Elegant Universe, was a Peabody Award–winning PBS series, a national best seller, and a finalist for the Pulitzer Prize; his second best-selling book, The Fabric of the Cosmos, is also currently in production as a PBS series. He lives in Andes, New York, and New York City.

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Read an Excerpt

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.

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See All Sort by: Showing 1 – 20 of 94 Customer Reviews
  • Posted January 28, 2011

    more from this reviewer

    great book, and answer about nook vs kindle price

    For the love of all that is holy everyone understand this. its not barnes and noble that decides the price of the ebooks, its the publisher!!!! im not kidding. so, complain to the right sources. why the publisher would charge more for the nook is just bad business, i agree, but barnes and noble makes the hardware, not the ebook that it stores. WRITE THE PUBLISHER!!!!!!!!!!!!!! they are freaking out trying to make a buck because they dont want the market dominated by one source, like the music industry (itunes). so before you piss and moan, actually do what youre complaining about........and read.

    9 out of 20 people found this review helpful.

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  • Posted May 10, 2011

    Poor philosophy presented as if science.

    Mr. Greene may or may not be a competent physicist. However, he is a very poor philosopher. His inability, or refusal, to think clearly undermines the potential of his writing. His writing hastens the death or possible suicide of thought. I will mention only a few example glaring errors of thought I found before having to put the book down due to boredom.

    Mr. Green's poor thinking is evident from the beginning. In the first sentence of the first paragraph of the preface of the book, he writes: "If there was any doubt at the turn of the twentieth century, by the turn of the twenty-first, it was a foregone conclusion: when it comes to revealing the true nature of reality, common experience is deceptive." What is a reader supposed to make of such a statement? The reader is presumably a human being. Common experience is experienced by human beings. Human beings exist in a world of touch, smell, sight, sound, etc .. Measured details of the atomic or subatomic structure of reality enter the minds of human beings only by way of instruments human senses can experience. Mr Greene appears to be oblivious to the reality that the individual atoms making up keyboard on which he types are as far away from his direct experiential knowledge as is Alpha Centauri.

    In chapters 1, 2, and 3 he painstaking (painfully) elaborates on a theory that since there are an allegedly an infinite number of universes but only an allegedly finite number of atomic particles and energy states, there must be an infinite number of parallel universes. In other words, there are an infinite number of Mr. Greens. An infinite number of Mr. Greens wrote the book exactly as Mr. Green did in our universe. An infinite number of Mr Greens wrote the book using an "a" instead of an "an" on some random page of the book. An infinite number of Mr. Greens wrote the book placing figure 3 before figure 2. An infinite number of Mr Greens wrote the book without the first sentence in the first paragraph of the preface to the book. Etc ...

    Mr Green seems to believe he knows definitively that infinite number of universes, combined with a finite number of particles and energy states in each universe, requires duplication of the contents of each universe. He makes no mention, for example, of the alleged orientation of the "orbits" of electrons in each atom in the universe. There is no evidence to suggest that orientation of orbits is quantized, and not infinite. Mr. Green simply asserts the lunacy that nothing more is needed than a finite number of particles and energy states to jump to the conclusion that the contents of the universe is duplicated an infinite number of times.

    The book is loaded with useful ideas and explanations. However Mr. Greene seems to be focused on pretending that he can prove that science illustrates that what we know is false or worse, meaningless.

    I am reminded of Galileo. Galileo ran afoul of authorities not for his science, but for his philosophy. Today, there is no risk Mr. Green will be imprisoned for his philosophy. I just wish Mr. Green would stick to science. Or better, he should learn some philosophy.

    4 out of 29 people found this review helpful.

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  • Posted November 25, 2011

    Amazing book, but previous reviews don't seem to understand

    I have been reading theoretical physics since i was 10 years old, and believe that I have the authority to say that this book is accurate, and a great read. However, the concepts outlined take a bit of getting used to. It is very abstract, and if you are new to the field, i suggest reading the elegant universe before this one, as it is a great introduction to theoretical physics.

    3 out of 5 people found this review helpful.

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  • Posted January 15, 2011

    Questions asked

    RE: universe9015's review; I have read Michio Kaku's books and Brian Greene's books - positive comments = fascinating; semi-negative or perhaps less than fully positive = reinforces fundamental questions of how did life start? and why are we here? and where did the "world" begin? and . . . despite the questions asked I will purchase and read Greene's newest pub.

    3 out of 15 people found this review helpful.

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  • Anonymous

    Posted March 18, 2013

    I liked the book, but it was a little advanced for me.  Greene d

    I liked the book, but it was a little advanced for me.  Greene did a good job of *trying* to explain in a way that can be understood by anyone, but  it was still over my head.  I'll try it again some other time.

    2 out of 2 people found this review helpful.

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  • Anonymous

    Posted July 1, 2013

    good book

    Good book good read

    1 out of 1 people found this review helpful.

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  • Posted February 11, 2011

    price is lower

    the price is 9.99 why are people complaining that its more? must be old reviews

    1 out of 7 people found this review helpful.

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  • Posted January 13, 2011

    The book I have not read

    The book that I have not read is the one to READ! We have been exploring our universe as we know it today. We have found out that our universe is expanding and is speeding up in that expansion.

    There are definitely different levels, and dimensions of existence. Multi dementions that can be proven scientifically.

    In ancient writings, they were given to us as a myth. People are trying to explain the visitation of intelligent life from a place or source which they could not understand.

    I will tell you this from personal experience, this is not the only universe. There are an eternity of universes that exist.

    This will include, parallel universes. There is a difference between multi universes, and parallel universes.

    It is a difference between universes and a different dimension of existence.

    As we explore scientifically, spiritually, has soulfully, our place in the scheme of total existence, you will find you must address all of the above.

    I did not read the book. I already know what's in it.

    Im in this universe. This universe is me. I am this universe.

    With the unbreakable connection to this universe, the knowledge of this Universe comes with me and it's in me.

    Read this book. You will find yourself understanding "The Hidden Reality"

    1 out of 38 people found this review helpful.

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  • Anonymous

    Posted November 29, 2012



    0 out of 2 people found this review helpful.

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  • Anonymous

    Posted March 12, 2012

    In any superuniverse there exist 1000 universes

    And there exist many superuniverses, approx. 7 +-0. We have not come close to the edges of our own universe. Oh yes, many other inhabited planets exist in our own universe and the beings of these others have differing brain types. Some older & wiser, some new and beginning. We are not alone! Run fast and take it to the bank. citti 1/0

    0 out of 3 people found this review helpful.

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  • Posted February 2, 2011

    So good I bought it anyway

    I complained about price and still do but Nook is so much better than Kindle I caved. After reading sample I just had to have this one. A great companion to 'From Eternity To Here'. I strongly recommend both.

    0 out of 4 people found this review helpful.

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    Posted February 1, 2011

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    Posted July 8, 2011

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    Posted March 2, 2012

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    Posted January 14, 2012

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    Posted March 19, 2011

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    Posted July 29, 2011

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