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Our Mathematical Universe: My Quest for the Ultimate Nature of Reality (Anglais) Relié – Séquence inédite, 7 janvier 2014

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Chapter 9

Internal Reality, External Reality and Consensus Reality
Sweet exists by convention, bitter by convention, color by convention; atoms and void [alone] exist in reality.
—Democritus, ca. 400 B.C.
“Nooooo! My suitcase!”
They were already boarding my flight from Boston to Philadelphia,
where I was supposed to help with a BBC documentary about Hugh Everett, when I realized that my hand wasn’t holding a suitcase. I ran back to the security checkpoint.
“Did someone just forget a black roll-on bag here?”
“No,” said the guard.
“But there it is—that’s my suitcase, right there!”
“That’s not a black suitcase,” said the guard. “That’s a teal suitcase.”
Until then, I’d never realized how color-blind I was, and it was quite
humbling to realize that many assumptions I’d previously made about reality—and my wardrobe—were dead wrong. How could I ever trust what my senses told me about the outside world? And if I couldn’t, then how could I hope to ever know anything with certainty about the external reality? After all, everything I know about the outside world and my untrustworthy senses, I’ve learned from my senses. This puts me on the same shaky epistemological footing as a prisoner who’s spent his whole life in solitary confinement, whose only information about the outside world and his untrustworthy prison guard is what his prison guard has told him. More generally, how can I trust what my conscious perceptions tell me about the world if I don’t understand how my mind works?
This basic dilemma has been eloquently explored by philosophers throughout the ages, including titans such as Plato, René Descartes, David Hume and Immanuel Kant. Socrates said: “The only true wisdom is in knowing you know nothing.” So how can we make further progress in our quest to understand reality?
So far in this book, we’ve taken a physics approach to exploring our external physical reality, zooming out to the transgalactic macrocosm and zooming in to the subatomic microcosm, attempting to understand things in terms of their basic building blocks such as elementary particles. However, all we have direct knowledge of are instead qualia, the basic building blocks of our conscious perception,* (* For introductions to the vast literature on consciousness by psychologists, neuroscientists, philosophers and others, I recommend the books about the mind in the “Suggestions for Further Reading” section.) exemplified by the redness of a rose, the sound of a cymbal, the smell of a steak, the taste of a tangerine or the pain of a pinprick. So don’t we also need to understand consciousness before we can fully understand physics? I used to answer “yes,” thinking that we could never figure out the elusive “theory of everything” for our external physical reality without first understanding the distorting mental lens through which we perceive it. But I’ve changed my mind, and in this brief interlude chapter, I want to tell you why.
External Reality and Internal Reality
Perhaps you’re thinking, Okay, Max, but I’m not color-blind. And I’m looking at the external reality right now with my own eyes, and I’d have to be paranoid to think it’s not the way it looks. But please try these simple experiments:
Experiment 1: Turn your head from left to right a few times. Experiment 2: Move your eyes from left to right a few times, without moving your head.
Did you notice how the first time, the external reality appeared to rotate, and the second time, it appeared to stay still, even though your eyeballs rotated both times? This proves that what your mind’s eye is looking at isn’t the external reality, but a reality model stored in your brain! If you looked at the image recorded by a rotating video camera, you’d clearly see it move as it did in Experiment 1. But your eyes are a form of biological video camera, so Experiment 2 shows that your consciousness isn’t directly perceiving the images formed on their retinas. Rather, as neuroscientists have now studied in great detail, the information recorded by your retinas gets processed in highly complex ways and is used to continually update an elaborate model of the outside world that’s stored in your brain. Take another look in front of you, and you’ll see that, thanks to this advanced information processing, your reality model is three-dimensional even though the raw images from your retinas are two-dimensional.
I don’t have a light switch near my bed, so I’ll often take a good look at my bedroom and all the obstacles littering the floor, then turn off the light and walk to my bed. Try it yourself: put down this book, stand up, look around, and then walk a few steps with your eyes closed. Can you “see”/”feel” the objects in the room moving relative to you? That’s your reality model being updated, this time using information from your leg movements rather than from your eyes. Your brain continuously updates its reality model using any useful information it can get hold of, including sound, touch, smell and taste.
Let’s call this reality model your internal reality, because it’s the way you subjectively perceive the external reality from the internal vantage point of your mind. This reality is internal also in the sense that it exists only internally to you: your mind feels as if it’s looking at the outside world, while it’s actually looking only at a reality model inside your head—which in turn is continually tracking what’s outside your brain via elaborate but automatic processes that you’re not consciously aware of.
It’s absolutely crucial that we don’t conflate this internal reality with the external reality that it’s tracking, because the two are very different. My brain’s internal reality is like the dashboard of my car: a convenient summary of the most useful information. Just as my car’s dashboard tells me my speed, fuel level, motor temperature, and other things useful for a driver to be aware of, my brain’s dashboard/reality model tells me my speed and position, my hunger level, the air temperature, highlights of my surroundings and other things useful for the operator of a human body to be aware of.
The Truth, the Whole Truth and Nothing but the Truth
Once my car’s dashboard malfunctioned and sent me to the garage with its “CHECK ENGINE” indicator illuminated even though nothing was wrong. Similarly, there are many ways in which a person’s reality model can malfunction and differ from the true external reality, giving rise to illusions (incorrect perceptions of things that do exist in the external reality), omissions (nonperception of things that do exist in the external reality) and hallucinations (perceptions of things that don’t exist in the external reality). If we swear under oath to tell the truth, the whole truth and nothing but the truth, we should be aware that our perceptions might violate all three with illusions, omissions and hallucinations, respectively.
So metaphorically speaking, the “CHECK ENGINE” incident was my car hallucinating—or experiencing phantom pain. I recently discovered that my car also suffers from an illusion: based on its speedometer reading, it thinks it’s always driving two miles per hour faster than it really is. That’s not bad compared to the vast list of human illusions that cognitive scientists have discovered, which afflict all our senses and distort our internal reality. If your version of this figure is in color rather than black and white, you’ll probably see the lower dot in the left panel as orange and the upper dot as somewhat brown. Figure 9.1 (in the book) shows two examples of optical illusions, where our visual system creates an internal reality different from the external reality. In the external reality, the light from both of them has identical properties, with a wavelength around 600 nanometers. If a spotlight beamed out such light, it would be orange light. What about brown? Have you ever seen a spotlight or a laser pointer produce a brown beam? Well, you never will, because there’s no such thing as brown light! The color brown doesn’t exist in the external reality, but only in your internal reality: it’s simply what you perceive when seeing dim orange light against a darker background.
For fun, I sometimes compare how the same news story is reported online by MSNBC, FOX News, the BBC, Al Jazeera, Pravda and elsewhere. I find that when it comes to telling the truth, the whole truth, and nothing but the truth, it’s the second part that accounts for most of the differences in how they portray reality: what they omit. I think the same holds for our senses: although they can produce hallucinations and illusions, it’s their omissions that account for most of the discrepancy between the internal and external realities. My visual system omitted the information that distinguishes between black and teal suitcases, but even if you’re not color-blind, you’re missing out on the vast majority of the information that light carries. When I was taught in elementary school that all colors of light can be made up by mixing three primary colors red, green, and blue, I thought that this number three told us something fundamental about the external reality. But I was wrong: it teaches us only about the omissions of our visual system. Specifically, it tells us that our retina has three kinds of cone cells, which take the thousands of numbers that can be measured in a spectrum of light (see Figure 2.5 in Chapter 2) and keeps only three numbers, corresponding to the average light intensity across three broad ranges of wavelengths.
Moreover, wavelengths of light outside of the narrow range 400–700 nanometers go completely undetected by our visual system, and it came as quite a shock when human-built detectors revealed that our external reality was vastly richer than we’d realized, teeming with radio waves, microwaves, x-rays, and gamma rays. And vision isn’t the only one of our senses that’s guilty of omissions: we can’t hear the ultrasound chirping of mice, bats and dolphins; we’re oblivious to most faint scents that dominate the olfactory inner reality of dogs, and so on. Although some animal species capture more visual, auditory, olfactory, gustatory or other sensory information than we humans do, they’re all unaware of the sub-atomic realm, the galaxy-spangled cosmos, and the dark energy and dark matter that, as we saw in Chapter 4, makes up 96% of our external reality.
Consensus Reality
In the first two parts of this book, we’ve seen how our physical world can be remarkably well described by mathematical equations, fueling the hope that one day equations can be found for a “theory of everything,” perfectly describing our external reality on all scales. The ultimate triumph of physics would be to start with the external reality from the “bird perspective” of a mathematician studying these equations (which are ideally simple enough to fit on her T-shirt) and to derive from them her internal reality, the way she subjectively perceives it from her “frog perspective” inside the external reality. To accomplish this would clearly require a detailed understanding of how consciousness works, including illusions, omissions, hallucinations and other complications.
However, between the external reality and the internal reality, there’s also a third and intermediate consensus reality, as illustrated in Figure 9.2 (in the book). This is the version of reality that we life-forms here on Earth all agree on: the 3-D positions and motions of macroscopic objects, and other everyday attributes of the world for which we have a shared description in terms of familiar concepts from classical physics. Table 9.1 summarizes these reality descriptions and perspectives and how they’re interrelated.
Each of us has our own personal inner reality, perceived from the subjective perspective of our own position, orientation and state of mind, and distorted by our personal cognitive biases: in your inner reality, dreams are real and the world turns upside down when you stand on your head. In contrast, the consensus reality is shared. When you give your friend driving directions to your place, you do your best to trans- form your description from one involving subjective concepts from your inner reality (such as “here” and “in the direction I’m facing”) to shared concepts from the consensus reality (such as “on 70 Vassar Street” and “north”). Since we scientists need to be precise and quantitative when we refer to our shared consensus reality, we try extra-hard to be objective: we say that light has a “600-nanometer wavelength” instead of “orange color” and that something has “CH3COOC5H11 molecules” instead of “banana flavor.” The consensus reality isn’t free from some shared illusions relative to the external reality, as we’ll elaborate on below: for example, cats, bats and robots also experience the same quantum randomness and relativistic time dilation. However, it’s by definition free from illusions that are unique to biological minds, and therefore decouples from the issue of how our human consciousness works. The internal reality may feel teal deficient to me, black and white to a seal, iridescent to a bird seeing four primary colors, and still more different to a bee seeing polarized light, a bat using sonar, a blind person with keener touch and hearing, or the latest robotic vacuum cleaner, but we all agree on whether the door is open.
This is why I’ve changed my mind: although understanding the detailed nature of human consciousness is a fascinating challenge in its own right, it’s not necessary for a fundamental theory of physics, which need “only” derive the consensus reality from its equations. In other words, what Douglas Adams called “the ultimate question of life, the universe and everything” splits cleanly into two parts that can be tackled separately: the challenge for physics is deriving the consensus reality from the external reality, and the challenge for cognitive science is to derive the internal reality from the consensus reality. These are two great challenges for the third millennium. They’re each daunting in their own right, and I’m relieved that we need not solve them simultaneously.

Chapter 9 is continued in the book…
--Ce texte fait référence à l'édition Broché .

Revue de presse

Brian Greene, physicist, author of The Elegant Universe and The Hidden Reality
Our Mathematical Universe boldly confronts one of the deepest questions at the fertile interface of physics and philosophy: why is mathematics so spectacularly successful at describing the cosmos? Through lively writing and wonderfully accessible explanations, Max Tegmark—one of the world’s leading theoretical physicists—guides the reader to a possible answer, and reveals how, if it’s right, our understanding of reality itself would be radically altered.”

Michio Kaku, author of Physics of the Future 
“Daring, Radical. Innovative. A game changer. If Dr. Tegmark is correct, this represents a paradigm shift in the relationship between physics and mathematics, forcing us to rewrite our textbooks. A must read for anyone deeply concerned about our universe.” 

Ray Kurzweil, author of The Singularity is Near
“Tegmark offers a fresh and fascinating perspective on the fabric of physical reality and life itself. He helps us see ourselves in a cosmic context that highlights the grand opportunities for the future of life in our universe.” 

Prof. Edward Witten, physicist, Fields Medalist & Milner Laureate
“Readers of varied backgrounds will enjoy this book. Almost anyone will find something to learn here, much to ponder, and perhaps something to disagree with.” 

Prof. Andrei Linde, physicist, Gruber & Milner Laureate for development of inflationary cosmology
“This inspirational book written by a true expert presents an explosive mixture of physics, mathematics and philosophy which may alter your views on reality.”

Prof. Mario Livio, astrophysicist, author of Brilliant Blunders and Is God a Mathematician? 
“Galileo famously said that the universe is written in the language of mathematics. Now Max Tegmark says that the universe IS mathematics. You don’t have to necessarily agree, to enjoy this fascinating journey into the nature of reality.”

Prof. Julian Barbour, physicist, author of The End of Time
“Scientists and lay aficionados alike will find Tegmark’s book packed with information and very thought provoking. You may recoil from his thesis, but nearly every page will make you wish you could debate the issues face-to-face with him.”

Prof. Seth Lloyd, Professor of quantum mechanical engineering, MIT, author of Programming the Universe
“In Our Mathematical Universe, renowned cosmologist Max Tegmark takes us on a whirlwind tour of the universe, past, present—and other.  With lucid language and clear examples, Tegmark provides us with the master measure of not only of our cosmos, but of all possible universes.  The universe may be lonely, but it is not alone.”

Prof. David Deutsch, physicist, Dirac Laureate for pioneering quantum computing
“A lucid, engaging account of the various many-universes theories of fundamental physics that are currently being considered, from the multiverse of quantum theory to Tegmark’s own grand vision.”

Amir Alexander, The New York Times
“This is science writing at its best — dynamic, dramatic and accessible. […] ‘Our Mathematical Universe’ is nothing if not impressive. Brilliantly argued and beautifully written, it is never less than thought-provoking about the greatest mysteries of our existence.”

Publishers Weekly (starred review)
“Tegmark offers a fascinating exploration of multiverse theories, each one offering new ways to explain ‘quantum weirdness’ and other mysteries that have plagued physicists, culminating in the idea that our physical world is ‘a giant mathematical object’ shaped by geometry and symmetry. Tegmark’s writing is lucid, enthusiastic, and outright entertaining, a thoroughly accessible discussion leavened with anecdotes and the pure joy of a scientist at work.” 

Bryce Cristensen, Booklist (starred review)
“Lively and lucid, the narrative invites general readers into debates over computer models for brain function, over scientific explanations of consciousness, and over prospects for finding advanced life in other galaxies. Though he reflects soberly on the perils of nuclear war and of hostile artificial intelligence, Tegmark concludes with a bracingly upbeat call for scientifically minded activists who recognize a rare opportunity to make our special planet a force for cosmic progress. An exhilarating adventure for bold readers.” 

Robert Matthews, BBC Focus magazine 
“Max Tegmark is a professor of physics at MIT and a leading expert on theories of the Universe. But he’s also arguably the nearest we have to a successor to Richard Feynman, the bongo-playing, wise-cracking physicist who proved it is possible to be smart, savvy and subversive at the same time. […] now `Mad Max’ has been given the freedom of an entire book. And he hasn't wasted it. Around half of it is a lucid tour d'horizon of what we know about the Universe. The rest is an exhilarating expedition far beyond conventional thinking, in search of the true meaning of reality. Don't be fooled: Tegmark is a very smart physicist, not a hand-waving philosopher, so the going gets tough in parts. But his insights and conclusions are staggering—and perhaps even crazy enough to be true.”

Andrew Liddle, Nature 
“Cosmologist Max Tegmark has written an engaging and accessible book, Our Mathematical Universe, that grapples with this multiverse scenario. He aims initially at the scientifically literate public, but seeks to take us to—and, indeed, beyond—the frontiers of accepted knowledge. […] This is a valuable book, written in a deceptively simple style but not afraid to make significant demands on its readers, especially once the multiverse level gets turned up to four. It is impressive how far Tegmark can carry you until, like a cartoon character running off a cliff, you wonder whether there is anything holding you up.”

Peter Woit, The Wall Street Journal 
Our Mathematical Universe is a fascinating and well-executed dramatic argument from a talented expositor.”

Edward Frenkel, The New York Times Sunday Book Review
"An informative survey of exciting recent developments in astrophysics and quantum theory [...] Tegmark participated in some of these pioneering developments, and he enlivens his story with personal anecdotes. [...] Tegmark does an excellent job explaining this and other puzzles in a way accessible to nonspecialists. Packed with clever metaphors”

Nathan Gelgud, Biographile Nathan Gelgud, Biographile 
“Just a few years ago, the idea of multiple universes was seen as a crackpot idea, not even on the margins of respectability. […] But now, thanks in large part to Tegmark and his pursuit of controversial ideas, the concept of multiple universes (or a multiverse) is considered likely by many experts in the field.[…] Tegmark's clear, engaging prose style can take you down these exciting and unexpected pathways of thought without making you feel lost. [...] in Our Mathematical Universe, we meet a revolutionary cosmology physicist who is hell bent on figuring out if that theory is true, how to prove it, how to use it, and what it means for the world as we know it.”

Clive Cookson, Financial Times
“Today multiple universes are scientifically respectable, thanks to the work of Tegmark as much as anyone. [...] Physics could do with more characters like Tegmark. He combines an imaginative intellect and a charismatic presence with a determination to promote his subject [...] enough will be comprehensible for non-scientific readers to enjoy an amazing ride through the rich landscape of contemporary cosmology. There are many interesting diversions from the main argument, from an assessment of threats to human civilisation (such as a 30 per cent risk of nuclear war) to the chance of intelligent life elsewhere in our galaxy (lower than astrobiologists like to think). Written in a lively and slightly quirky style, it should engage any reader interested in the infinite variety of nature.” 

Mark Buchanan, New Scientist 
“The book is an excellent guide to recent developments in quantum cosmology and the ongoing debate over theories of parallel universes....Perhaps this book is proof that the two personalities needed for science—the speculative and sceptic—can readily exist in one individual.”

Peter Forbes, The Independent 
"In Our Mathematical Universe, Max Tegmark—a distinguished cosmologist—gives a lucid rundown of the current state of knowledge on the origin, present state, and fate of the universe(s). [...] It is immensely illuminating on the reach of current cosmological theories. [...] From time to time, Tegmark engagingly admits that such ideas sound like nonsense, but he makes the crucial point that if a theory makes good predictions you have to follow all of the consequences. [...] His concluding chapter on the risks humanity faces is wise and bracing: he believes we "are alone in our Universe" but are capable of tackling terrible threats from cosmic accidents, or self-induced nuclear or climatic catastrophes. He doesn’t cite poets but his philosophy adds up to an updated 21st-century version of Thomas Hardy's 'If way to the better there be, it exacts a full look at the worst.'"
Giles Whittell, The Times
"mind-bending book about the cosmos" [...] "Tegmark's achievement is to explain what on earth he is talking about in language any reasonably attentive reader will understand. He is a professor at MIT, and clearly a fine teacher as well as thinker. He tackles the big, interrelated questions of cosmology and subatomic physics much more intelligibly than, say, Stephen Hawking." 

Brian Rotman, The Guardian
"Max Tegmark's doorstopper of a book takes aim at three great puzzles: how large is reality? What is everything made of? Why is our universe the way it is? Tegmark, a professor of physics at MIT, writes at the cutting edge of cosmology and quantum theory in friendly and relaxed prose, full of entertaining anecdotes and down-to-earth analogies."

Stephen Hirtle, The Pittsburg Post-Gazette 
"Our Mathematical Universe is a delightful book in which the Swedish-born author, now at MIT, takes readers on a roller coaster ride through cosmology, quantum mechanics, parallel universes, sub-atomic particles and the future of humanity. It is quite an adventure with many time-outs along the way.... Our Mathematical Universe gives keen insight into someone who asks questions for the pure joy of answering them."

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Détails sur le produit

  • Relié: 432 pages
  • Editeur : Knopf (7 janvier 2014)
  • Langue : Anglais
  • ISBN-10: 0307599809
  • ISBN-13: 978-0307599803
  • Dimensions du produit: 16,8 x 4,1 x 24,2 cm
  • Moyenne des commentaires client : 4.7 étoiles sur 5  Voir tous les commentaires (3 commentaires client)
  • Classement des meilleures ventes d'Amazon: 23.149 en Livres anglais et étrangers (Voir les 100 premiers en Livres anglais et étrangers)
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2 internautes sur 2 ont trouvé ce commentaire utile  Par Jean Paul Choquel le 23 juillet 2014
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Ce livre est l'un des plus intelligents que j'ai lus. Des notions complexes, comme la décohérence ou surtout les multivers sont expliquées de façon brillante et très intuitives. Les trois niveaux de la réalité sont aussi bien décrits et aident à appréhender des idées comme l'écoulement du temps.
Bref un livre à lire pour qui veut comprendre l'univers, tel que la science d'aujourd'hui le dévoile.
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1 internautes sur 1 ont trouvé ce commentaire utile  Par Maussy le 10 avril 2014
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Bon resume de nos connaissances en cosmologie .

Par contre, il exige beaucoup de connaissances mathematiques que je n'ai pas
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Ouvrage de référence très complet de Max Tegmark qui va au bout de toutes les théories sur les univers multiples. Lecture passionnante.
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205 internautes sur 221 ont trouvé ce commentaire utile 
Our Mathematical Universe is one of the finest popular science books I've ever read 6 décembre 2013
Par Michael Birman - Publié sur Amazon.com
Format: Relié Commentaire client Vine pour produit gratuit ( De quoi s'agit-il? )
Books that discuss the nature of reality have become a cottage industry lately. Brian Greene, Stephen Hawking, Roger Penrose and now Max Tegmark have all attempted to explain the physicist's view of the ultimate nature of reality to a popular audience. Penrose's book, with its advanced mathematics, is geared towards those with a technical background but the trend has been to simplify the science and make these books anecdotal and gentle. Tegmark seems to have discovered the sweet spot between hard core science and a fun read, using the word "geeky" as a red flag any time a technical detail is about to be broached. His language is reader friendly and easy to understand. Tegmark is a good writer and anyone that has seen him on television (Through the Wormhole, for example) knows that he is funny and well-grounded in popular culture. Our Mathematical Universe is a nearly perfect example of a popularized science book.

Years of reading science books have produced a personal pantheon of the finest I've ever come across. There are several aspects of Tegmark's book that have placed it amongst the three finest popular science books I've ever read. The other two books are Albert Einstein and Leopold Infield's The Evolution of Physics and Kip Thorne's Black Holes and Time Warps: Einstein's Outrageous Legacy (Commonwealth Fund Book Program). The first book, The Evolution of Physics, is still the clearest exposition of classical and (relatively) modern physics ever written, despite its age. It remains the most authoritative, concise and profound discussion of the source of Einstein's world-shattering ideas, and has never been surpassed as a book written by a great scientist for a popular audience. Kip Thorne's book combines personal reminiscence and scientific exposition with an elegance and depth that makes it my choice as the finest modern popularized science book. Thorne proved that you can write about science in an engaging manner without sacrificing either intelligence or necessary relevant technical detail.

The attributes that raise Tegmark's book amongst the very finest in the genre are its engaging writing style, its willingness to discuss technical details about recent trends in cosmology without sacrificing either intelligence or clarity, and its almost subversive depth. Tegmark has a flair for discussing some really knotty topics like the significance of the cosmic microwave background, Einstein's theory of gravitation, the geometry of curved space, mathematically precise cosmology, dark matter and dark energy without losing the reader in a labyrinth of confusing and difficult scientific details. Tegmark teaches without ever being pedantic and he entertains while he clarifies and enlightens. There aren't many science writers who can write about such abstract and craggy subjects as cosmology, multiple multiverse levels, and mathematics as the ultimate nature of physical reality with Tegmark's wit and ease. If you are a fan of reading popularized science books, Our Mathematical Universe is one of the finest I've ever read and definitely worth your consideration.
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Story of Life, the Universe and Everything 2 janvier 2014
Par Paul Moskowitz - Publié sur Amazon.com
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Despite its name, "Our Mathematical Universe" is not a math book. It is an exploration of the nature of our physical reality according to the author's own Mathematical Universe Hypothesis (MUH). However, the MUH has been noted by math fans. For instance, it is the last subject covered in The Math Book by Clifford Pickover.

At the end of the first chapter, Tegmark suggests that if you are a physicist you can skip ahead. I do not recommend this. Tegmark tells his story in a lively manner punctuated by illustrations and personal anecdotes. It is all a good read.

Along the way, we learn that the author has conducted a survey of physicists, repeated over time, about the quantum wave function. Early on, sentiment favors the Copenhagen interpretation. Later, Many Worlds is favored. I fall into that latter group. Tegmark proposes a life-or-death quantum machine-gun test of Many Worlds. I do not think that his test is necessary. The improbable victory of the Mets in game six of the 1986 World Series is sufficient proof for me.

Tegmark says that it is not enough to say that mathematics describes physical reality, but that our physical reality is mathematics. Our conservation laws are expressions of symmetries of the mathematical object that is our (multi)universe. Also, time is just another coordinate in space-time. Its passage is an illusion. I have read that Tegmark sends e-mails to his future selves.

Like many physicists, I believe that the Second Law is perhaps our most important concept. I think that Tegmark should have said more about how the MUH treats entropy.

Finally, Tegmark presents a way to test the MUH. If the universe is not a mathematical object, then physics will reach a dead end in which we can no longer describe reality by mathematics. If the MUH is correct, then we will continue to find mathematical descriptions.

Tegmark is an excellent storyteller. This work is well worth reading and thinking about.
190 internautes sur 231 ont trouvé ce commentaire utile 
A journey through Max Tegmark's roving mind 31 décembre 2013
Par AshJ - Publié sur Amazon.com
Format: Relié Commentaire client Vine pour produit gratuit ( De quoi s'agit-il? )
Max Tegmark's book is a dazzling journey through the farthest reaches of physics, from the very small to the very large. Tegmark's wide-ranging mind leads us through physics spread across an incredible range of scales, from the size of the atomic nucleus to the entire universe. Tegmark does an excellent job of telling us how we know about the details of events like the Big Bang. He has succinct descriptions of the two cornerstones of physics, quantum mechanics and relativity, and describes many of their manifestations ranging from lasers to black holes. The sheer range of phenomena and topics explored by Tegmark in the book is staggering, and for the most part he does a good job explaining technical details like anomalies in the cosmic microwave background and quantum entanglement. There are even chapters on biology including ruminations on quantum effects in the brain and the emergence of biological complexity.

Tegmark's stories are highly personal and his infectious enthusiasm for science shines through, even if the language is often a little too colloquial and gee-whiz (the phrase "Oh no!" punctuates the narrative literally hundreds of times) and even if the author seems to be a little too smitten at times with his own cleverness and late night thinking binges. Another slight issue with the book is that in his quest to cover as much ground as possible, Tegmark often gives short shrift to some important topics; for instance his criticism of Roger Penrose's thoughts on the brain operating by quantum principles is all too brief and does not consider some recent work implicating quantum entanglement in photosynthesis.

Unfortunately these splendid discussions and detours are marred in my opinion by an even bigger problem: Tegmark's analysis of multiple universes. Drawing on the latest theories in physics, mathematics and quantum computing he navigates the myriad and fascinating implications of parallel universes. He also takes a swipe at the very fanciful conjecture that the entire observable universe might simply be a computer simulation in some super-intelligent alien's universe. Unfortunately this is all speculation and currently we don't have any experimental evidence that these wondrous creatures actually exist. In addition many of the ideas seem to only push previous problems under the rug. For instance, so-called "M theory" suffers from the presence of an unimaginable number of possible solutions; in Tegmark and others' world, the answer to this conundrum is to postulate unobservable multiple universes, each one of which can accommodate every one of these solutions. It's like building one unstable structure to support another. Unlike some other treatments of the subject, Tegmark's narrative pays scant attention to discussing the testable implications of these fantastic theories, and one wishes he had expressed more reservations about some of his musings, especially in the absence of experimental evidence. This makes the journey less of science and more of science fiction and philosophy. Now it's perfectly ok to write a book about philosophy, but it's a problem when it's pitched as cutting-edge science.

Ultimately the discussion of multiple universes generates more heat than light and sounds more like the byproduct of a brilliant and feverish imagination than the handiwork of rigorous science constrained by experiment. Speculation, no matter how fascinating and mind-expanding, is not science. Ever since the Renaissance science has been defined by agreement with observation and experiment, and it would be an understatement to say that this commonsense approach has yielded a windfall of scientific discoveries and benefits that the founders of the scientific method wouldn't even have imagined. Even quantum physics with all its paradoxes and counterintuitive implications is ultimately accepted as legitimate science only because of its unprecedented agreement with experiment. In contrast, the founders of modern science would not have recognized fantasy-laden speculations about extra dimensions and multiverses that have been propagated in a decade's worth of popular physics books, of which Tegmark's volume is only the latest incarnation.

It is time we again grounded physics in the real world and lifted a page out of Newton and Bacon's playbook, and it is time that we clearly separated science from philosophy, but Tegmark's book provides little clues regarding how this very important and necessary goal can be achieved.
15 internautes sur 18 ont trouvé ce commentaire utile 
Welcome to Nerd land - The Universe is a Mathematical Structure! 7 février 2014
Par Sam Santhosh - Publié sur Amazon.com
Format: Format Kindle Achat vérifié
I have never been a great fan of Mathematics though I had been always been fascinated with Science. But I often had the foreboding that Mathematics is not only the foundation of everything but is also the only thing that is completely independent of us and our Universe. Now in this thrilling book, Max Tedmark tries to prove that our Universe is just a mathematical structure (though we do not know the equation) and that there will be as many Universes as there are viable Mathematic structures!

Going beyond parallel universes and multiverses, Max takes us through a fascinating journey to the Level 4 of the Mathematical Universe Hypothesis (MUH) in order to understand the ultimate reality of everything. In this journey you will learn a lot of cosmology, physics and maths and Max’s style of storytelling will keep you engrossed throughout. The book can be divided into three parts, with the first one addressing “How big is everything” – from planets to galaxies and Level 1 multiverse to Level IV multiverse. The second part addresses “What is everything made of” – from elementary particles to mathematical structures. And then in the third part, Max brings us to his conclusion that the answers to the first two questions lead to mathematics as the basis of reality.

One good thing about the book is the summary at the end of each chapter which Max calls ‘Bottom Line’. While going through such tough concepts as cosmological inflation, cosmic microwave background, galaxy clustering, dark matter, dark energy, the horizon problem, the flatness problem, level 1 to level IV of parallel universes (and the evidence for each), particle physics, why randomness is an illusion, decoherence, and various aspects of reality, it is great to have a brief summary at the end of each chapter that highlights the important points.

Max’s writing style is very simple and conversational and his ability to mix his personal learning from childhood onwards and the occasional anecdotes makes the book a pleasure to read. But I found it difficult to buy into all the conclusions that the hypothesis leads Max to, especially the need for a parallel universe for every decision branch of every individual! However since he starts from the basic principles and builds up his case explaining the assumptions made at each level and the counter points to his arguments, it is a great example of not only how science should be practiced but also how it should be taught.

The concluding chapter is a call to action. Instead of just remaining in the exalted pedestal of a scientific researcher, Max takes the plunge of becoming an activist and bringing the learning to influence the path society should take. The analogy of Earth as a spaceship with limited resources and in a challenging environment (which can often turn hostile) is very apt. I found his suggestions of managing this spaceship and its inhabitants very positive and admirable and I hope this book will influence a large number of people.
53 internautes sur 69 ont trouvé ce commentaire utile 
But they also laughed at Bozo the Clown 5 mai 2014
Par Tango - Publié sur Amazon.com
Format: Relié
"They laughed at Columbus, they laughed at Fulton, they laughed at the Wright brothers. But they also laughed at Bozo the Clown." -Sagan

The 9 first chapters constitute 50% of the book and provide no new information and no new insights. None. Chapter one was the best in writing style and the least boring. This first half of the book is basically a review of parts of physics (classical and quantum) but the author seems to think he is making important points where I could not find them for example in describing Everett's interpretation of quantum mechanics he uses exclamation points too frequently when what is being stated is already common knowledge (parallel universe and non collapse of wave functions). I found myself saying, yes, come on already what is your point? Give me some insight or even a new reference or some humor for gods sake! But no. The author instead spends too much time describing how he spent nights doing this or that calculation and repeatedly talking about scribbling numbers on napkins over lunch.... I mean what do I care?! Please deliver!

I picked up this book with an open mind knowing what it is about and fully willing to accept radical thoughts and ideas. I think I even forced myself to read all the first 9 chapters just to allow myself to experience any numbing the author may have intentionally engineered to induce acceptance of his subsequent thesis. After 9 painfully boring chapters we finally reach chapter 10 where the author is ready to present his theory that the universe *is* a mathematical structure. His arguments:

1- A complete description of our external reality has no baggage (by baggage the author explains that he means unnecessary human abstractions and concepts)
2- Something that is "baggage free" is therefore a mathematical structure

By baggage the author means human-made concepts and abstractions. He gives the example of a basketball (the concept) as baggage, the less-baggage is the collection of atoms making up the ball and even an atom is a concept of more elemental mathematical properties and constants. He is correct these are human-made abstractions and concepts but I wonder: Won't we always only be able to observe fewer (initially only "mathematical") properties about the most distant (both smallest and biggest) parts of our reality and at the frontiers of our knowledge? Does that mean what we can observe today at the most distant scale is all that exists? Today's "concepts" were yesterdays measurement. When we learn more about quarks and eventually develop their concepts and abstractions, will they (quarks) still *be* just numbers? The "highest resolution" of observation at a given point in time given our technological capability is a moving target so even today's "math truths" will get "baggage" tacked onto them as we learn more. Why is the least useful resolution where we cannot measure well or map correctly or use predictions, why is that supposedly the true nature of reality?

The core book thesis is since the smallest building blocks of reality (quarks inside atoms for example) -according to the author- have only number properties (no smell, or color) then they *are* numbers. AND since we can (the author claims but does not show) describe (all?) higher abstractions and concepts of our reality by those numbers (only?), then our reality with its "baggage" also *is only* numbers!
What a leap! If you think you can buy this, then buy the book.

The author mentions a harsh letter from a reviewer warning him the papers he is submitting are not making sense and the author's reaction is along the lines of "all great minds were ridiculed so I will march on", hence the title of my review.

Abstractions are useful and at some level biology is just chemistry and chemistry is just physics but physics is not math (is physics language?). Additionally even if it were, if you cannot measure reliably at the smallest (quantum) scale, why reduce the bigger scale where we can measure, predict, and make some sense of things to that smaller scale in the first place? If you cannot show me that you can map from that smaller scale to the bigger scale why are we discussing this zoomed-in useless resolution? Why are we confusing math with "least abstract"? Math is a language and can be used to describe any abstraction (I can talk about either proteins or atoms with either math or English). The author seems to think that everything is math but says math is not arithmetic! Dude, if you claim some ratios and equations are fundamental go ahead and claim it is all just addition for a ratio is really division and division is repeated subtraction and subtraction is addition with negative signs. He is not just claiming his select ratios are fundamental, he is claiming reality *is* a "mathematical structure" and the universe (including us) is just a sort of computer simulation!

The author seems to think that if you divide a number such as the mass of the proton by another such as the mass of the electron then that is a fundamental quantity but he also lists 31 other quantities in a table and claims but does not show that everything is reducible to these numbers and thus -he reasons- reality *is* math. One of the constants he lists in that table is "dark energy density". Well, dark energy and dark matter are just fudge factors we invented to explain what we do not know. We observed that the outer galaxies are moving faster than they should (if our laws held true) so instead of saying those laws do not apply everywhere, we invented something called dark matter and dark energy. Something we cannot observe (dark) but supposedly is out there so it can "cause" those stars to move the way we observe! I ask: How can you consider -as the author does- dark energy density to be a core fundamental math number when it is a human abstraction, concept, and invention? Worse, it is a wastebasket made to contain and "explain" discrepancies between reality and our limited present laws. We lobbed all errors of observation inside a fudge factor and the author is claiming it as fundamental!

In summary: The author needs to justify this leap between "a few essential numbers can describe the world", which I am even willing to accept, and the thesis that "reality *is* a mathematical structure". The book promises but does not deliver. I not only feel cheated out of the time and money I spent on this, text, but also am now concerned for my tax dollars that could be funding this or similar work.
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