Product Description

The Holy Grail of modern physics is the search for a 'quantum gravity' view of the universe that unites Einstein's general relativity with quantum theory. Until recently, these two foundational pillars of modern science have seemed incompatible: relativity deals exclusively with the universe at the large scale (planets, solar systems and galaxies), whereas quantum theory is restricted to the domain of the very small (molecules, atoms, electrons). Here, Lee Smolin provides the first accessible overview of current attempts to reconcile these two theories. Written with wit and style, Three Roads to Quantum Gravity touches on some of the deepest questions about the nature of the universe - are space and time continuous or infinitely divisible? Is there a limit to how small things can be? - while speculating on what developments we can expect at the frontiers of physics in the twenty-first century.

Product Details

• Amazon Sales Rank: #359683 in Books
• Published on: 2001-08-16
• Original language: English
• Binding: Paperback
• 240 pages

Amazon.co.uk Review
As footballers talk of the double, or statesmen dream of Middle East peace, so physicists conceive of "Quantum Gravity". This proposed wedding of the two main strands of modern physics in one Grand Unified Theory is at once the scientists' major goal, and ultimate prize.

Rather like the Middle East, however, the problem of Quantum Gravity has usually appeared intractable: reconciling the macrocosmic with the microcosmic being just too tricky. But now comes Lee Smolin, American academic and author of The Life of the Cosmos, to describe, in direct and lucid prose, how that unhappy situation may be changing. Smolin's well-argued thesis is that one day soon we will see tabled, and accepted, a single overarching Theory of Everything.

Not that Smolin finesses the difficulties. As he deftly and firmly guides the reader through the intricacies of relativity, string theory and black hole thermodynamics, among other even more recondite disciplines, some of which might prove a little challenging for the less enthusiastic layman, he takes pains to emphasise the hurdles to be jumped, the knots to be untied. Still, though, his scientific self-belief abides: this impressively confident and self-assured book ends with the ringing words "In the 21st Century Quantum Gravity will be taught to high school students all over the world". --Sean Thomas

About the Author
Lee Smolin is Professor of Physics at the Center for Gravitational Physics and Geometry at Pennsylvania State University. He is a leading contributor to the search of a unification of quantum theory, cosmology and relativity.

Customer Reviews

A brilliant, lucid summary of modern thoughts on gravity
Those who read "A brief history of time" by Hawkings will find this treatise a natural extension to coverage, inter alia, of the ideas on gravity, the discreteness of spacetime, string theory, black holes, the holographic principle, loop quantum gravity, and gravitons. The relationship between modern thinking and Einstein's general relativity, developed with help from Boltzmann, is covered in much detail. Altogether an outstanding account of modern physics applied to cosmology. The mathematics is kept to a minimum, but that does not subtract from the clarity of the work. The book is not for the faint-hearted but is thrilling for those willing to think through the ideas expressed here.

Know something about loop quantum gravity...
This is a book about the quest for the Theory of Everything or the Theory of Quantum Gravity, Holy Grail of physics, the final destination for theoretical physicists all over the world. Quantum gravity is supposedly an all-encompassing theory which will take under it's fold - the present day pillars of physics - the quantum theory(the world of the small) and the general theory of relativity(world of the large).

Lee Smolin guides you to the three roads leading to QG. The first one is Loop Quantum Gravity, which traces its roots from Einstein's general theory of relativity. Amitaba Sen and Abhay Ashtekar were the ones who kick-started the theory by reformulating the general theory of relativity and bringing it mathematically closer to quantum chromodynamics (a quantum theory of the strong forces). Smolin, Carlo Rovelli and others took it over from there and applied quantum theory to Ashtekar's formulations and shaped the theory which came to be known as loop quantum gravity. It says that not only matter and energy is quantized but even space is discrete and quantized and has an atomic structure which makes itself visible at the plank scale. The smallest unit is a loop and the relationships and interactions between loops gives rise to the space-time structure.

The second road is that of superstring theory, which traces it's origin from the quantum theory. Basically it says that matter particles (fermions) and force/messenger particles (bosons) are manifestation of vibrating strings - the most basic units of our universe - the different vibration generating different particles. Here Smolin doesn't seem to do justice in explaining strings and the treatment is rather shallow. Brian Greene's "The Elegant Universe" is a much better introduction to string theory.

The third road is sketchy and more of a philosophical nature which seeks to radically re-evaluate our concepts of space and time.

All in all a good read but it could have been better. Some parts in the book like Smolin's explanations on black hole entropy, black hole temperature and it's relation to event horizon area(finally leading to derivation of quantization of space) is excellent. Readers inquisitive about loop quantum gravity would definitely gain by reading this book.

A sensible framework for Quantum Mechanics & Gravity
The book is a tour de force of what's new in the different approaches in trying to "pin down" such aspects as space-time, gravity, string theories and much else in the physicist's attempts to make sense of the Universe in which we live. We are fortunate that Lee Smolin managed to take time out and present to us in lay person's terms how he and his associates are excited by their loop quantum gravity approach. Fixed background space-times are out and replaced by dynamical event processes. It is interesting that history is coming full circle here as Lee is greatly influenced (as I am) by Roger Penrose's Spin Network approach in actually constructing space-time so to speak. For the casual uninitiated reader { own up !!! ) there will be some totally new ways of viewing the world that should hold you spell-bound. The conviction that there is the Planck limit to space and time and the Bekenstein Bound will always be there to restrict what information is available from systems was well presented and made me whizz off to the numberous web sites Lee suggests for more in-depth information. Yes it is an inspirational book! There is a certain modesty that shines through his work as he is always quick to give credit to his associates and role models within the physics community. For example John Baez is cited several times and rightly so as he has contributed much to the mathematical, topological aspects of QM-gravity and associated material. Lee Smolin is a rare animal so to speak as he admits that he can listen quite freely to String / M-Theorists and yet be quite at home sitting in on QM- Gravity lectures. He has done much to actually bring "insulated groups" together instead of fighting their corner. This book has contributed to promote the breaking down of these barriers. Time (assuming we know what that is!) will be the final arbitur in saying whether the ideas contained within this book are valid. I'm sure that Feynman would have acknowledged that the ideas are not "just plain wrong" but many aspects of Lee's ideas could well progress our understanding.

Thanks Lee / Amazon for the platform

Ken Linney (BSc), Shrewsbury, UK 6/3/01