Customer Reviews

Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions

5 star:		(118)
4 star:		(16)
3 star:		(12)
2 star:		(9)
1 star:		(10)

 

 

Prof. Lisa Randall's new book, Warped Passages, is a grand tour of some of the most important recent developments in high-energy physics.

The book is intended for a popular audience, but is also a very interesting read for anybody with a background in theoretical physics (like myself). The first part contains an overview of modern physics - Einstein's theories of relativity, quantum mechanics and the Standard Model of particle physics. The last part concentrates on the idea of extra dimensions beyond the standard four we know about, which can be motivated by string theory and its discovery of the so-called D-branes. Specifically, she explains the work, pioneered by herself, Raman Sundrum and others, on the so-called "braneworld scenarios". Basically, this is the idea that our four dimensional space-time is embedded in some higher dimensional space, usually called the "bulk".

You might think, that extra dimensions are just part of a set of crazy ideas? On the contrary. You should know, that the idea of extra dimensions is actually not at all new. Already in 1884, the original book, "Flatland: A Romance of Many Dimensions" (written by the English mathematician Edwin Abbott) described a world of two-dimensional beings, who only have indirect knowledge of the extra third space-dimension. But, from a mathematical point of view, one can imagine as many dimensions as one wants to. In physics, the story is somewhat different.

In physics, there are basically two distinct ways in which one can add extra dimensions to our four-dimensional universe. Already in the 1920's, Klein suggested that our universe is five-dimensional, where the extra dimension is rolled up in a circle, which is so tiny, that the universe looks four-dimensional at long enough distance-scales. The motivation was to give a unified geometrical description of electromagnetism and gravitation using Einstein's general theory of relativity. However appealing, this theory was destined to fail. Today we know, that there are other forces which should be included in a unified theory: namely the weak and strong nuclear forces. Presently there is only one theory which can possibly do the work, and this is string theory. Perturbative string theory tells us, that our space-time is ten-dimensional, and that the extra six dimensions should be rolled up in a small but complicated shape (which is determined by some mathematical restrictions).

Another way to achieve hidden extra dimensions of space is to suppose, that all normal matter, as well as the light by which we see the world, is confined to a four-dimensional "brane" embedded in a five-dimensional "bulk" - or larger universe. These so-called braneworld theories are the ones of Lisa Randall, Raman Sundrum and others. Warped Passages explains - in excellent style - the logic behind these seemingly fancy ideas.

What I particularly liked about the first part of this book is how Prof. Randall makes people envision extra dimensions. As Randall writes, "we are not physiologically equipped to envision more than three dimensions of space", so it might be difficult for the general reader to comprehend this idea. But, as Prof. Randall also explains, readers need not imagine a dimension only in spatial terms. Here is an example from the book: If you are buying a house, the factors you might consider include its location (specified by three numbers), price (one number), size (one number), and possibly many other things. So, the number of dimensions in your house search simply equals "the number of quantities you find worth investigating".

What Prof. Randall describes in the last part is - in more technical terms - her work with Raman Sundrum on solving the flavor-changing problem, the gaugino mass problem (and other things) that occur in supersymmetric models with the supersymmetry breaking sector on another brane, separated from ours, or in the bulk; the Randall-Sundrum warped geometry with two branes (a so-called "weak-brane", where we are supposed to live, and a "gravity-brane") and the Randall-Sundrum warped geometry with an infinite extra dimension, using so-called AdS geometry.

The main point guiding Randall's research - described in the last part of the book - is the fact that gravity is such a profoundly weak force. Indeed, gravity is the puniest of the fundamental forces governing the matter in the universe, by a huge margin (typically a 10^36 times weaker than the electromagnetic force between two charged particles). Why is this so?

Why this is so, Prof. Randall suggests, is because we live in a universe containing at least one extra dimension beyond those we can perceive. And gravity is weak because it has been "diluted" into this extra space. This is indeed a very simple and persuasive idea. (And also from the point of view of string theory a very compelling idea, with a simple explanation, related to objects in string theory called D-branes - like an infinite string (a 1-brane), a membrane (a 2-brane) etc). But note that Prof. Randall's original models are not inherently string-theoretical; it is just that her models have an elegant and simple interpretation in string theory. So you don't need to know *anything* about string theory to understand this book).

The breakthrough research by Randall and Sundrum proposed that gravity's dilution can be explained in terms of a cosmic configuration featuring two branes - or two infinite planes, separated by a higher dimensional bulk space. Roughly speaking, the "center of gravity" is on the "gravity-brane" - and some gravity leaks out of this brane, through the bulk, and onto the other brane, usually called the "weak-brane", which is where we live, and which contain the Standard Model fields. Later on, Randall and Sundrum found, that their concept is also theoretically consistent with a configuration which includes only one brane. Usually, one would think that Newton's 1/r^2 law of gravitation implies that there are four and only four non-compact dimensions of infinite extend. Randall and Sundrum showed that this is not correct.

The fact that branes are an important part of modern string theory meant that string theorists took an early interest in the Randall-Sundrum models. Furthermore, since Prof. Randall's research did not directly challenge string theory models, the string theory community actually accepted and recognized the profound significance of her work very early on.

One of the long outstanding problems of the Standard Model of particle physics, that braneworlds do provide an interesting answer for, is the "hierarchy problem", or why the weak and Planck scales are so disparate (10^2 GeV compared with 10^19 GeV). In these scenarios, the fundamental gravitational scale is not the Planck scale, but something closer to the weak scale. The conjecture is that gravity is not weak because the Planck scale is so large, but because braneworlds provide various geometrical mechanisms for making the gravitational force much weaker than the others.

All this would of course be pointless speculation unless there was some way for the extra dimensions to manifest themselves. So, can these ideas be experimentally tested? As Prof. Randall explains in detail, the answer is: yes indeed! It is possible that evidence supporting the braneworld models could appear within a decade or so, after the Large Hadron Collider (LHC), currently being built at the particle-physics laboratory CERN, starts operating in 2007. Here the traces of extra dimensions could come from "gravitons" (the fundamental constituents of gravity) moving into the extra dimension(s).

Some versions of the theory even predict that, as a result, small black holes could conceivably be created from the high-speed collisions at the LHC! (but don't worry, the black holes will only exist for about 10^{-26} sec and the Earth will not disáppear into a black hole). If the LHC sees the kinds of effects predicted by these models, be sure that there will be some well-earned Nobel prizes for the people involved in this story.

Let me say a few words about the style of the book. The book's central point - the possible existence of extra dimensions in space - is easy enough to explain; at least if the reader can comprehend the idea, that our universe has more than four space-time dimensions, which might not be easy. However, to motivate the conjecture of higher dimensions, Prof. Randall must first explain the General Theory of Relativity, quantum mechanics and the Standard Model of particle physics, with its zoo of subatomic objects - quarks, leptons, bosons of various sorts - and the details of the forces that act between them. To ensure the convergence of her ideas in the readers mind, she then has to go into more advanced topics such as "quantum field theory", "spontaneous symmetry breaking", the "Higgs potentials" and "supersymmetry". (But all these concepts are explained in much detail).

All this is a prerequisite for being able to properly describe string theory, and Prof. Randall must then proceed to the less understood generalization called 'M-theory' (which is an eleven-dimensional theory containing two-branes and five-branes). Only then can Prof. Randall explain how branes emerge from a jumble of concepts and ideas, that most likely might be unfamiliar to the general reader. But as far as I can judge, she accomplish this tour de force with *much* success. The immanent "problem" with such theories of unification is that one cannot leave anything out and therefore - to be explained and understood - they require background knowledge in virtually all of physics. But I think that Prof. Randall has done a very good job in explaining all the required physics in terms of analogies, simple illustrations and so on.

Finally I would like to stress that this book is *very* different from many of the random popular books about physics because Lisa Randall actually knows what she is talking about And you should know, that Prof. Randall is not by any standards a random person: she has become the most cited high-energy physicist since 1999.

In conclusion, I'll give Warped Passages some more than well-deserved 5 stars.

Lisa Randall is one of the most important and influential theoretical particle physicists working today and this book tells the story of how she came to her most important ideas. The book is full of detail and takes the reader into the minds of the author and her collaborators as they struggle towards the discovery of a new approach to the key problems in particle physics. What I really like is that she takes the time to tell the real story, and not just some oversimplified version.

She is also refreshingly honest. She explains the motivation for her work, but unlike many of our colleagues, she does not oversell. You can think of her as a reliable climbing guide. With her help you can get to the top of a mountain you could not climb yourself. But you never forget about the difficultyies and the risks that both professionals and amateurs take when we try to advance our understanding of the laws of nature.

As a theorist myself, I am aware of how far we are from solving the problems in elementary particle physics thyat Lisa Randall's work addresses. But I am sure we will get there and my optimism is due in no small part to the fact that Lisa and her colleagues are on the case.

The popularization of Cosmology through recent television (PBS's
"Elegant Universe") and cinema ("What the BLEEP Do We Know?")as well as an extant excellent press by actual Cosmologists such as Brian Greene and Stephen Hawking have "softened up" an avid readership for this book. Dr. Randall is "spherically exquisite", to paraphrase Fritz Zwicky: She is perfect from any angle;cutting edge benchwork researcher; top line theorist; most-quoted author; Harvard Professor....PLUS she's a HOTTIE (my son's words). As she walks you through the requisite historical and theoretical building blocks for armchair Cosmology, her clarity is best ever. Her expansion into extradimensional physics verges upon the philosophic, without straying into the "touchy/feely" quasi religious miasma of cult fiction. Elucidating the Multidimensional Brane Theory of Everything is a task she accomplishes with clarity, wit and a mere hint or Feminism (quite appropriate in her male-dominated field). This is a Great Book. I'm giving it to all my colleagues on our Medical Faculty as well as my friends who share my fascination with Physics, but lack the requisite Math. ( Dr. Randall even supplies much of that onerous mathematical work,unburdened in her unique style, which makes the most stygian topic clear as daylight). Brava, Dr. Randall!
Dennis R. Meyer MD, FACP

Lisa Randall is described in the cover notes as the first woman to hold a tenured professorship in the Princeton physics department, the first woman theoretical physicist to gain tenure at MIT, and the first woman theoretical physicist to gain tenure at Harvard. With credentials like those, she obviously knows her physics. So the only real question is, can she write readably on the subject. And I think she can -- mostly. I certainly understand more about modern concepts like string theory, supergravity, and the ideas of 10- and 11-dimensional spacetimes that physicists are using now than I did before reading the book. While some points are still not clear, it is hard to tell whether this is because they are too complex for anyone but a practicing physicist to understand or because Prof. Randall still hasn't explained them thoroughly enough. And I'm willing to give her the benefit of the doubt there.

Her format derives, it seems, from the type of book that George Gamow wrote describing relativity and quantum mechanics using the adventures of the fictional character, Mr. Tompkins. One difference is that, in this book, the story is a relatively minor part and the physics takes up the bulk of the book, the reverse of Gamow's books. In fact, one can probably ignore the story and get most of what Prof. Randall has to say. Though it is somewhat interesting to follow her characters, Icarus and Athena Rushmore (and she obviously chose her characters' names with care; Icarus is a devil-may-care type who dies in an accident while Athena, his younger sister, is the smart one who loves owls! I wonder if Randall intends Athena to represent herself.)

I mostly liked the book; as I say, I don't think I understand _everything_ yet, but I know a lot more than I did before I opened the book. If you have an interest in the subject matter of this book, I recommend that you read it.

Lisa Randall is one of the leading active particle physicists, and her contributions are making history in that field. Her "Warped Passages" is a very lucid description of the latest progress being made by the handful of physicists who can deal with the complexities of that branch of Physics. I have read several of the most recent "pop science" books that try to make very complex ideas accessible to the general public, and Lisa's is by far the best. Not only is the subject absolutely fascinating, her style for presenting it is superb. As an old retired physicist, her book made me wish I had concentrated more in Quantum Field Theory when I was active, but I plan to catch up on the subject as much as possible. Her contributions solved one of the greatest puzzles in contemporary Physics, the hierarchy problem. She also showed that her theory is consistent with unification of the basic forces. And she did so with a 5-dimension theory of the Universe that does not require supersymetry, and is simpler and more elegant than the supersymetric formalism. It uses the concept of branes, first originated in string theory. If when the Large Hadron Collider starts operating, the experimental results vindicate her theory - the right Kaluza-Klein particles or else events with missing energy are found - she is very likely to be awarded a Nobel Prize. However interesting all this may be, I was startled to read for the first time ever, that according to recent theoretical results about duality, space and time may have more fundamental descriptions! This goes far beyond anything any science-fiction writer ever imagined. I am again marveled that the human intellect has gone so far in elucidating some of the most incredibly complex and amazing features of the Universe. One last observation. Although she has made a great and successful effort to make the ideas understandable by the "average Joe", it stands to reason that you will get a lot more from the book, the larger your background in Physics. But whatever the case, my recommendation can only be, READ IT. It's well worth the effort if you have some interest in contemporary ideas in Physics.

There is nothing like the thrill of hearing about the latest developments in a field from a leader in that field, and Lisa Randall is that. This is a book that explains some of the biggest questions in physics today (offering some possible answers, as well), and it is written for the ordinary reader to understand it. Leavened with humor, helpful diagrams, and the perspective of a woman who clearly lives to probe the mysteries of our universe(s), the book is designed to transmit to us her excitement about the discoveries she describes. Short of a brain transplant, she does everything possible to make clear to the non-scientist a host of arcane concepts. The book has a whole different tone from so many of these pop science books that I‚ve picked up and then put down a short time later because I‚m just not getting it. Warped Passages has a down-to-earth (no pun intended), humane, personal feeling to it, even though it‚s chock full of information, so it draws the reader in and makes him or her feel capable of understanding these momentous concepts. Randall actually makes it fun. Which allowed me to feel like I was, indeed, sharing her adventures in extra dimensions with her. Without having to do the math. An excellent read.

I picked up this book expecting to gain some new insights about the bleeding edge of scientific research, string theory, and model-building, but found it unbelievably tedious, self-congratulatory, and self-absorbed. There may be little doubt that author Lisa Randall is a brilliant physicist, but her explanations of the last 100 years of science and her theories are muddled and poorly written. I found myself longing for a writer such as Bill Bryson or Briane Greene to explain half of these theories about extra dimension, branes, bundles, etc.
In addition, one of most annoying features of this book is the way Randall tries to disguise her inability to explain advanced physics in straightforward terms by starting each chapter with a pop culture reference, usually a lyric from a band such as Metallica, as if such a reference will be enough to goose the reader awake and to take interest in the next muddled exposition. She even has footnotes that explain the American term "runway" is translated as "catwalk" in the United Kingdom -- oh, thank you, Ms. Randall, for such elucidation! Why not make this book more interesting and readable with a more engaging style that explains these fascinating theories in a clearer manner?
Science writer John Gribbin panned the book in a Sunday Times of London review: "The principal problem is that Randall is at best a workmanlike writer, and it would be kindest not to draw attention to her worst passages. Like most physicists today, she also has a patchy understanding of the history of her subject, so it is unfortunate that the first half of the book is devoted to a rather laboured introduction to relativity, quantum theory and the attempts to unify the two - all of which have been covered much more entertainingly, and accurately, in many recent popularisations. She also, like all too many scientists desperate to appeal to a wider audience, starts each chapter with a truly dreadful "SciFi" vignette, which serves only to highlight her inadequacies as a writer."
Not to give away the ending, but many of these theories about extra dimensions cannot even be proven unless the universe demonstrates another massive outburst of energy almost equivalent to the Big Bang. Until then, you must take a leap of faith that Randall's claims are scientifically observable.

The last ten years or so have witnessed an upsurge of interest in an old idea: that there are extra dimensions of space, somehow hidden from our view. Lisa Randall's book provides an insider's view of this revolution in our understanding of spacetime, presented in a way that anyone can understand.

Randall herself has been a leader in extending our picture of extra dimensions, authoring (with Raman Sundrum) a paper that Stephen Hawking called "the best paper of the year." Here she starts with an introduction to the very idea of the dimensions of spacetime, followed by a primer on the foundations of relativity and quantum mechanics, before finishing with a compelling account of how ideas from string theory, cosmology, and particle physics came together to offer new scenarios for branes and extra dimensions. Reading this book will teach you a lot of physics, but also give you an idea of how cutting-edge research actually gets done.

A reviewer below complains that the book can be difficult in places. The truth is, physics is difficult, and some of these ideas are truly mind-bending. We can either gloss over them, or take them seriously; Randall's book takes them seriously, providing explanations that are clear and understandable to any non-experts willing to engage with the material. The expert's view given here provides a perspective that simply isn't available anywhere else. As a theoretical physicist myself, I'm very glad to see this book on the market, and hope as many people as possible will read it.

First, let me point out that I am NOT a Physicist but a retired PhD Geologist, who spent much of his career in geological research. My rather modest background in Physics dates to the late `50s and early `60s.

"Warped Passages" seems to have been written for people like me: high interest, limited background. However, I suspect that even PhD Physicists will find it a worthwhile read. And people with even less background than I will find it readable, informative, and enjoyable.

The most amazing thing to me is Dr. Randall's ability to describe extremely complex and counter intuitive concepts in understandable English (no pages of equations here!). And at the same time she doesn't pull any punches in "telling it like it is." Her excellent use of analogies, as well as her clever allegories at the beginning of each chapter, makes this a readable book without a strong technical background. She is clearly a gifted writer.

The first part of the book brings the reader up to date with a review of the past decades of developments in theoretical physics. Then she delves into the area of her own recent and current research: string theory, branes, and extra spatial dimensions. She analyzes both the strengths and weaknesses of her own ideas and those of other researchers. She also lays out how these ideas can be tested within the next few years. I can't wait to read the results.

"Warped Passages" is a "must read" for anyone interested in the world of theoretical physics.

This book started out well, but went down hill quickly. Many chapters after the first are spent on the standard background material which is covered in SO many other books, and--I must say--covered in those books (e.g. Green, Kaku, Davies, Thorne)
better than here. A substantial effort is then put in to bring the reader up to date on the details of particle physics; these
chapters needed an editor! Shame on the editor! These chapters go into such detail and go on for so long. Really kills the book. Then, finally, the author gets to her own work. I liked these chapters but could not help wondering whether one interesting new idea (to solve a problem called the hierarchy
problem) was worthy of a whole book. As the author says, there are other proposals and by the end it felt a little like the tail wagging the dog--one tenative new idea (within the larger framework of string theory and new dimensions) driving a whole book. As an aside, as a woman I was hoping to get fresh insights into physics/science that the many books written by men wouldn't be senstiive to. Alas, beyond a few cliche ideas and catch phrases, there isn't anything of that sort.

In the end, this book could have been half the length and twice as interesting. What a shame.