Warped Passages: Unraveling the Mysteries of the Universe’s Hidden Dimensions by Lisa Randall (PDF)

Description

The universe has many secrets. It may hide additional dimensions of space other than the familier three we recognize. There might even be another universe adjacent to ours, invisible and unattainable . . . for now.Warped Passages is a brilliantly readable and altogether exhilarating journey that tracks the arc of discovery from early twentieth-century physics to the razor’s edge of modern scientific theory. One of the world’s leading theoretical physicists, Lisa Randall provides astonishing scientific possibilities that, until recently, were restricted to the realm of science fiction. Unraveling the twisted threads of the most current debates on relativity, quantum mechanics, and gravity, she explores some of the most fundamental questions posed by Nature—taking us into the warped, hidden dimensions underpinning the universe we live in, demystifying the science of the myriad worlds that may exist just beyond our own.

User’s Reviews

Reviews from Amazon users which were colected at the time this book was published on the website:

⭐The hierarchy problem has for quite some time been a burning issue in elementary particle physics. There have been many proposals for solving this problem, some of which are quite exotic if viewed from a commonsense viewpoint. But the interactions of elementary particles are described by quantum physics, the latter of which has never been a theory that conformed to any notion of commonsense. Therefore one should not discount a proposal if it seems strange or alien to customary ways of thinking. The physicists of fifty years ago might be shocked at some of these proposals, but the physicists of the twenty-first century are very comfortable with them. Of course, any idea in physics, to be considered viable, must be confirmed by experiment. When a physical theory does, it does not matter at all how seemingly strange it is.The author of this book has given an interesting discussion of the hierarchy problem for the general reader, and has included the necessary background in elementary particle physics that puts the problem in context. Since the book is written for a general reader, the author refrains from using mathematical language. The conceptual compression involved in using mathematics is therefore lost in the book, but the author tries very hard, and succeeds, in explaining difficult concepts in physics to readers who have a real thirst for understanding them (there are however “math notes” at the end of the book). The author has made original contributions to the understanding the hierarchy problem, and so a good portion of the book is devoted to explaining her ideas on this problem, and those of her collaborators. Her proposals are interesting not only from a theoretical perspective but also because they may be amenable to experimental verification in the next few years. They therefore should not be described as `science fiction’ as was the case in the inside jacket of the book.The author’s solution to the hierarchy problem takes place in the context of brane theory, which is an extension of string theory and which she explains in some detail in the first part of the book. Central to her solution is the existence of a `warped geometry’, which is a particular type of five-dimensional curved geometry that is bounded by two (three-dimensional) branes. On one of these branes, called the `weak brane’, lies the particles of the Standard Model. This geometry is obtained by solving the Einstein field equations with the assumption that there was energy (tension) on the branes and in the bulk. The geometry is anti de Sitter space, a solution of that is well known to those familiar with general relativity. The author also discusses why this spacetime is designated as “warped”. At first glance this may seem an unlikely way of generating the mass hierarchy between the Planck and weak scales, but the author explains how the hierarchy problem can be “automatically solved” by this geometry.It is the probability function of the graviton that is of the greatest interest in the warped spacetime. The shape of this function indicates where the gravitational field is strongest. This is called the `shape of gravity’ by the author, and varies only along the fifth dimension of this spacetime. The probability function of the graviton decreases exponentially as one leaves the `gravity brane’ and heads toward the `weak brane.’ The probability that the graviton is found near the weak brane is thus small, and so its interactions with the particles on the weak brane are suppressed. There is therefore a hierarchy between the observed masses and the Planck scale mass in this spacetime and explains why the gravitational interaction is so weak in the real world (which lies in the weak brane).Interestingly, and this follows from the author’s constructions, the mass of an object will be different depending on where it is along the fifth dimension. Energy and momentum decreases and therefore time and distance increase as one goes from the gravity brane to the weak brane. The mass and energy are rescaled, the amount of rescaling being proportional to the amplitude of the graviton. And as if anticipating objections by an astute reader that such rescalings are arbitrary (objections that would seem appropriate given the fine-tuning that has taken placed in attempting to resolve the hierarchy problem), the author argues that it is simply an issue of the rescaling of the units that are used to measure energy. This rescaling, she argues, solves the hierarchy problem, and even more importantly, predicts observable consequences on energy scales of TeV.But one can object that the author’s solution to the hierarchy problem, based as it is on having two branes that are essentially a fixed distance apart, is a somewhat contrived solution. At first glance it seems to be no better than the elaborate fine-tuning that takes place in the usual strategy on the hierarchy problem. In addition, it might seem improbable that having the branes arranged in this way would survive cosmological evolution. The author counters these objections by pointing out a idea that was proposed by two other researchers. This proposal involved introducing another massive particle in the five-dimensional volume that acts essentially as a spring. The net result was to obtain an equilibrium configuration for the two branes whose separation had the properties asserted by the author. This stable configuration prevented it from being jostled around under cosmological evolution.The author’s proposal up to his point was not really too radical, if one considers the history of higher-dimensional theories. But in the last few pages of the book she does have her Bastille day, proposing for example that the fifth dimension can actually extend indefinitely and a notion of `locally localized gravity.’ In these same pages she even calls into question the utility of the notion of dimension. As evidence, she cites T-duality, mirror symmetry, and matrix theory. In using these examples, she inadvertently beckons the reader to take on some beautiful but esoteric mathematics.

⭐As a short review, if you are interested in the subject of particle physics and extra dimensions, don’t waste your time reading this book. You would be better served by reading the excellent presentations of these topics which can be found on Wikipedia.org.My initial thoughts on this book are well captured by the review by Mr. Joe Kern (2-star review posted on May 15, 2007. (And please see my “comment” to Mr. Kern’s review.)As indicated in my comment to Mr. Kern’s review, I would like to add some additional comments regarding this book.In the first instance, Dr. Randall cannot determine who her audience is. A writer needs to write for an intended audience, and to this end Dr. Randall is a phenomenal failure. She cannot decide if she is trying to introduce the world of particle physics and extra dimensions to the ignorant masses, or if she is trying to sell her personal view of “a warped extra dimension” to her peers, or to producers of a Science Channel program. Certainly the idea of trying to sell her “warped extra dimension” view of the world to the ignorant masses is stupid – we are so ignorant about the subject that we can’t form an opinion one way or the other (and not that it would matter if we could). Perhaps she’s merely trying to become a “celebrity physicist” so that she can appear on The Science Channel (and get some money and some exposure). (And to this latter end, it appears as if she has obtained some limited success.)If Dr. Randall is trying to educate the ignorant masses, she misses the target audience by a factor of ten (or more). She presumes that her readers will include folks who are so adverse to math that they don’t even know the definition of “integer” (see footnote at page 129), or the concept of “inverse proportionality”. I find it hard to believe that anyone who does not know the definition of “integer” would read a book about high-energy particle physics, and dimensions beyond the four we are accustomed to. Randall should anticipate that her target readers have at least some high-school-level familiarity with basic math. Rather, Randall proceeds from the assumption that her audience is math-stupid. But she then goes on to discuss difficult concepts such as symmetry breaking. Give us a break, Dr. Randall. Anyone who can understand “symmetry breaking” should be able to understand some basic mathematical concepts. So presenting a little math in the text is not going to be a wet dishrag on sales of your book.As for advancing her personal agenda (i.e., the “warped fifth dimension”), to date (June 2016) the Large Hadron Collider (“LHC”) has not generated any data that would support her view (as presented in this 2005 book). Perhaps this is due to the limited operational time of the LHC, and the difficulty of obtaining time to conduct experiments using the LHC. At any rate, this book is now irrelevant in light of her 2012 book “Knocking on Heaven’s Door”, which still does not answer the question of whether or not her “warped extra dimension” theory is correct. (And what better way to promote your “rock-n-roll” hipster status than by using a Bob Dylan lyric as a title for your new book?) But wait – in the next year or so we’ll see yet another book by her, and so on and so on. Randall is to celebrity physicists as George Hamilton is to celebrity actors – famous for being famous. She touts the acceptance of her grand mathematical accomplishment by the physics community at pages 435-437, but in the end all she has done is to develop some mathematical models that have yet to be proven by experimentation. Hubris is the word that comes to mind.I would very much like to read a review of this book by a contemporary physicist who does not agree with her approach, or her views. Alas, I suspect that by now Dr. Randall has acquired the celebrity status that exempts her from critical peer review in a generally public forum (such as the Amazon book review forum). While she may be subject to criticism in the world of papers published in obtuse sources such as “Physics Letters A”, she has acquired a saint-like status in the world of popular opinion. Dr. Randall is to women physicists as Hawking is to ALS-affected physicists. Think about it – what has Hawking contributed to the world of physics other than the concept of “Hawking radiation” near the event horizon of a black hole? And what has Randall contributed to the world of physics other than her unproven abstract theory of “warped extra dimensions”? While her math may be good, it is still only math – nothing has been verified by experimental observation. In my opinion Randall is just a loud voice among a chorus of thousands of other physicists. Her best ability is in promoting herself, and not in promoting proven theories of particle physics.My intended next read on this subject is “The Road to Reality – A Complete Guide to the Physical Universe” by Roger Penrose (2004). Penrose spends the first 300 pages of his 1000 page tome in developing the math that is essential to understanding the concepts that follow. So Penrose takes a more realistic approach to the subject than does Randall. Let’s face it – some subjects require a difficult technical background in order to appreciate and understand the subject matter. One cannot understand quantum mechanics in the absence of a mathematical background anymore than one can understand the actions of a pharmaceutical compound in the absence of a biochemical background. The populist “For Idiots” concept that all things can be described in lay-terms (that are accessible to everyone) is a myth. At some point one needs to have the necessary detailed background knowledge, and understanding, in order to appreciate what is going on. And Dr. Randall fails to grasp this concept in her presentation (whatever her objectives may be).Dr. Randall is a phenomenal success at promoting herself, but an absolute failure at promoting the world of physics beyond unproven theoretical conjecture. She is no Einstein (much as she would like to be, or would like us to believe she is).

⭐As someone who took an astrophysics degree in the seventies I have tried to keep up to date with developments in the field, at the level of pop-sci books. However as of the late nineties it seemed that Physics was getting bogged down. After a long Golden-Age of prediction and dicovery the Standard Model and the Big-Bang were threatening to unravel. So the last such book I read was Brian Greene’s

⭐The Elegant Universe: Superstrings, Hidden Dimensions and the Quest for the Ultimate Theory

⭐which I found unsatisfying in that it just made clear that, if I wanted to really understand what was happening, I was going to have to devote time and energy I just didn’t have, to get to grips with some new maths.So, seven years later I thought I’d give this a try and see if I could get some kind of layman’s angle on what was going on these days. The book starts well in reviewing the history of physics. There’s a very concise and to the point description of Relativity and Quantum Mechanics.There’s a description of the Standard Model that I did find useful. I thought I had a fairly good understanding of the Standard Model, but the lady filled in some new areas for me, Electroweak theory and the Higg’s mechanism which led me to a more flexible understanding of particle mass than I had had before. It is as part of this that we find that the toughest question for the Standard Model is what is called the Hierarchy Problem, which is about the huge gap between the world the other three forces and SM particles inhabit, all of which can be probed, just about, with our accelerators, and then the world of the Planck distance down at E10-33 m, sixteen orders of magnitude smaller, which is where gravity becomes strong enough to be comparable with the other forces, and which we can never hope to build accelerators big enough to study directly.We then walk through QED, QCD, symmetry, supersymmetry keeping an eye on how these things might tackle the Hierarchy problem, but that they either fail to solve the problem or yield positive experimental results.We then get a whirlwind tour of String Theory the Super-Strings, and this is where it all gets really new for me. It would appear particle theorists, trying to extend the Standard Model, and String theorists, working on stuff that can never hope to be proven ‘not even wrong’, have enjoyed a synergy over the last few years, and as a result various classes of exotic multi-dimensional theories have emerged which just might yield observable consequences, possibly even turning up in the new LHC collider, when it eventually comes online. All of these theories try to tackle the Hierarchy problem by allowing gravity to be the only force that gets out of the 4D space-time ‘brane on which we and the other forces and SM particles ‘live’, thus allowing its effects to be diffused. It would appear that there a quite lot of recipes for higher dimensional models that allow for the dissipation of 16 order of magnitude, and the number is growing year on year. For this reason there is a whole community of physicists anxiously waiting for the LHC to get down to work, and who are hoping, in addition to finding Higgs particles, which the Standard Model predicts, to find completely new and unexpected particles, or energy deficits, that might lend support to one or other of the competing higher dimensional theories.The book contains a lot of news for someone interested in these things, but it is pretty hard work and not just due to the nature of the material. I know that communicating this stuff to the lay public is a talent in its own right, and I’ve no doubt as to Randell’s sincerity of purpose. However, I found that reading became tougher is I progressed, because I felt myself to be carrying an ever accumulating baggage of questions of elucidation, so that towards the end we were talking so casually in terms of ‘branes’, curvatures, ‘gravitons’, 5-D Black Holes and curled-up, or large, or infinite but invisible extra dimensions, that she might as well heve been talking about sausages. Hence my quirky title for this review.In my opinion, the book is somewhat longer than it needs to be because of frequent repetition of points that are easily grasped. Each chapter is prefixed with a Lewis Caroll like passage intended to provide a metaphor for the material to follow. These become more irritating as the book proceeds, as the metaphors become more strained and eventually plain cryptic.This book is probably the best of its kind around at the moment, and there’s no denying that Randell has tried really hard to explain some mind-bending things, in lay-person terms. But I think there is scope for a presentation of the same material by someone who has a proven track record in popular science writing.Another point to make is that she has definitely perked my interest in the forthcoming results from the LHC.

⭐Easily the best current book for those wanting an authoritative current account of extra dimensions, branes, and the juxtaposition of perspectives and progress in attempting to advance past the Standard Model. Prof. Lisa Randall answered many questions for me in an entertaining read, that hadn’t fully been cleared up by similar publications. Highly recommended.

⭐Excellent book. Really explains aspects of particle physics, the standard model, relativity and quantum physics well. It would be even better if the book was brought up to date with the Large Hadron Collider, the discovery of the Higgs boson and gravity waves.

⭐This book introduces in a clear and concise manner many difficult and advanced concepts. To do this without mathematics is an impressive feat, which Randall seems to have accomplished. I study physics and have just completed my Bachelor degree so I found extremely tedious to read what I already knew as it was repeated again and again in a long string of pretty much identical analogies. If you don’t understand it the first time it’s explained, you might understand it the second, third or even sixth time time it’s explained in a very similar way to the first.This element of irritation aside, the book still gave me useful insight into a world of physics I have but scratched the surface of. I think the target reader is the scientifically interested / scientifically aware person who would like to get into the “juicy bits” of physics without going through the long and winding academic road. For physics or mathematics undergraduates, you can easily skip the first hundred or two hundred pages without missing a thing.

⭐Exelent bookRead like a novel

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