Three Roads to Quantum Gravity
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Three Roads to Quantum Gravity

4.04 of 5 stars 4.04  ·  rating details  ·  1,170 ratings  ·  37 reviews
The Barnes & Noble Review
A detached reporter of science could have provided no more balanced account of the competing theories on quantum gravity than does Lee Smolin, a practicing scientist. His own inclinations are clear, of course, but the reader is left with a sense that the real contribution of this young physicist is not so much the content of the still-nascent t...more
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Published July 4th 2002 by Basic Books (first published December 28th 2000)
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Lee Smolin is one of the most interesting and controversial figures in modern physics. Establishment physicists often call him a maverick or worse. I am one of many laypeople who think that he's telling it like it is, and the mainstream people are full of s...trings.

When he wrote this book, around 1999, I think he was more part of the mainstream. He presents several different approaches to the very difficult problem of unifying gravity and quantum mechanics. It's clear that his heart belongs to...more
a nice, easy intro into quantum gravity for the interested:

This book isn't too bad but I don't think I retain much. the feline analogy and cosmological evolution are cute ideas, and the black hole stuff is fascinating. but much of it is extremely speculative and cryptic rambling. Or maybe I just get more cynical of theoretical physics day by day. That's fine, and at least Lee Smolin acknowledges that it is speculative, but at least don't be so incredibly...more
An Introduction to Loop Quantum Gravity

Since the postulation of theory of relativity (theory of cosmos, which describes the structure of space and time), and quantum mechanics (laws of microcosm, which describes atomic structure, nuclear forces, and nature of basic component of matter); physicists until now have struggled to explain gravity (which is a manifestation of spacetime fabric in presence of matter) in terms of quantum mechanics (quantum gravity). In this book the author attempts to exp...more
Lucas Ventura
Lee Smolin does an excellent job of detailing the current exploration in physics for a quantum theory of gravity. Most of the "physics for non-physicists" books I'd read were a bit dated (In Search of Schrodinger's Cat, A Brief History of Time, etc.), so I'd needed something a bit more contemporary. I found Quantum Gravity to be very informative and enlightening, and what seems to be a very good advanced introduction.
The author gives a very solid and understandable overview of the main avenues o...more
I love Smolin's style of writing. A worthwhile read for those interested in the diversity of the field and the questions being tackled.
Mark Abrams
As a layperson (and closet science geek), I really appreciated the author's straightforward and mostly non-mathematical approach to a difficult and incomplete new theory about quantum gravity. It covers three approaches which include super strings and M theory and black hole thermodynamics, both of which I hadn't really looked into before. It was great fun and I really enjoyed reading this book!

I found this work to be brilliant and very thought-provoking and would highly recommend it to anyone w...more
Overall this was a good read. That said, I think I liked reading Hawkings better back some 20-odd years ago. Of course the scope and the topic is a little different here, and maybe I was just that much more impressionable back then, who knows.

Smolin starts out string, the first few chapters regarding "why we don't ask what's outside the universe" and "why classical logic is unsuitable for cosmology (and real life)" were really great. As you make it further into the book things fall apart a littl...more
Aug 18, 2008 Kev rated it 5 of 5 stars  ·  review of another edition
Recommended to Kev by: Clayton Crockett
I cannot adequately express how amazing this book is. If you are at all interested in physics -- and I am! -- this is a very important one to read. If you read "The Evolution of Physics" & "Relativity: The Special & General Theory" by Einstein, "Chaos" & "Genius" by Gleick & "Feynman's Lost Lecture" by the Goodsteins, then, read this one ... you will be in a position to reevaluate all of the known unviverse as we understand it right now.

I think this one is better by far than Gre...more
Smolin presents a mind-expanding overview of fairly recent (as of 2001, the publication date) efforts to come up with a complete theory of quantum gravity, which would resolve the longstanding discrepancy between the quantum theory of Heisenberg, Bohr and others (which focuses on radiation and matter but is less successful at explaining gravity) and Einstein's general theory of relativity, which addresses gravity quite well. Smolin's "Three Roads" to such a theory are three approaches that have...more
An amazingly lucid book evenly dealing with different approaches to unify quantum mechanics and general relativity in a theory of quantum gravity. Smolin is very straight-forward and presents his ideas in an interesting, provocative and intelligent manner. I've struggled to understand how space can be quantized for three months, and I think I finally have some solid explanations. Smolin also does well with the Holographic Principle, which is about a difficult subject as you can come by in modern...more
This is one of the small list of books that has forever changed my paradigm. Unlike the other ones, I was aware of the paradigm change as it was happening and I could not put this book down.

"...the first principle of cosmology must be 'There is nothing outside the universe' . . . This first principle means that we take the universe to be, by definition, a closed system. It means that the explanation for anything in the universe can involve only other things that also exist in the universe . . ....more
Feb 16, 2009 DJ rated it 4 of 5 stars  ·  review of another edition Recommends it for: any young scientist interested in today's fundamental questions in physics
Shelves: popular-physics
Lee Smolin stormed his way onto my fantasy grandfather list the fateful summer of 2008 when I realized physics and I were more than just a fling. His The Trouble with Physics was a fatherly introduction to the current state of the edges of theoretical physics and I was hooked. Needless to see, I was ecstatic to find "Three Roads to Quantum Gravity" under my Christmas tree this year and devoured it on plane ride to Thailand soon after.

"Three Roads to Quantum Gravity" is Smolin's briefing to the p...more
May 02, 2008 Ethan rated it 4 of 5 stars  ·  review of another edition Recommends it for: nerds
Shelves: memebase
Some sadness. The very first words on the back cover of the paperback edition, after PHYSICS, are:

"The Holy Grail of modern physics is the theory of 'quantum gravity'. It is a search for a view of the Universe that unites two seemingly opposed pillars of modern science..." et cetera. Let's unpack these two sentences. The first mentions the Holy Grail, which I think is not the right analogy for a mathematical description of spacetime. I seem to remember the Holy Grail as the one identified by In...more
this book is so dumbed-down that i seriously considered putting it on the "non-fiction for humans" shelf. the absolute nadir came when he used as his analogy for the superposition principle of quantum mechanics a mouse which, when eaten by a cat, might turn out to be either "tasty" or "yukky". Yukky? Yukky? forget that it's universally spelled "yucky". but he hammers away at his analogy and the reader is subjected to the word "yukky" several times over a few pages.

but thank the lord most of the...more
Bukk Rogers
It's been 10 years since I read Three Roads to Quantum Gravity, so what I have to say about it is minimal. Lee Smolin is probably the best of popular physics writers today, with a very firm grasp of his field of expertise, and an even-handed, detailed treatment of 'competing' models of unifying theories. He's also a refreshingly honest doubter of the superstring hype that pollutes much of pop-physics these days. This book isn't so much a declaration of his preferred "road" to quantum gravity, bu...more
Nick Black
really enjoyable for its details regarding the development of loop quantum gravity; not so good regarding the scientific details. kind of a pop science companion to Schild's Ladder.
Jun 12, 2008 Jim rated it 4 of 5 stars  ·  review of another edition Recommends it for: Quantum Physics enthusiasts
Either I'm getting progressively dumber, or the books I'm reading are getting progressively harder for me to understand. Hopefully it's the latter of the two. I enjoyed this book in principle, however there was a lot that I had trouble understanding. I think I was able to grasp the basic ideas behind most of the theories mentioned, but some of the finer details may have been lost on me.

Still, Smolin does give very detailed explanations for the different versions of String Theory, Loop Quantum Gr...more
While concepts and proofs in cutting edge physics may change radically each month, this book - written about 15 years ago - stands the test of time very well. I especially liked the demonstration about the granularity of space and time.
Steve Alker
Probably one of the most readable books about the extremes of the universe I've come across. I was grabbed by the opening questions "Is space infinitely divisible?" and half a dozen more. he goes on to explore the very small to the very large and to look at the consequences of what we can see, how we can see it and where we are and might be in the universe.

I passed it along to some Christian friends who enjoy advanced science - you might think that a book of superb science, founded in relativity...more
Xiaomin Zu
Lee Smolin is certainly one of the best scientists in this field and probably the only one (at top level) who can also write for general public without annoying experts in this field. As a physicist, I rarely read any science book for general public because of the intentional misconceptions (to aid broader understanding) and misrepresentations (to help generate public interest). However, in today's society, we desperately need more scientists writing more for general public for PR reasons and fo...more
Mark Johnson
I really liked this book because while the author makes no bones about what he believes, he brings together N Theory and Loop Quantum Gravity, as well as the combined view that some adhere to, talking about all three view points without really stating that any one avenue is wrong. He essentially takes that stand that he believes X, but that Y and Z are both possible, and gets into pretty good descriptions of X, Y, and Z concepts. It really made me want to go back to school again!
Mark Gomer
This is a decent (and very non-technical) summary of string theory and loop quantum gravity as they relate to the elusive theory of quantum gravity, but the third road from the title - which includes "less conventional" approaches like Isham et al.'s topos physics and Sorkin's causets - is almost completely ignored.

My favorite bit is from the last chapter:

"We shall have the basic framework of the quantum theory of gravity by 2010, 2015 at the outside."
excellent book on quantum gravity approach. it gives basic ideas which are clear enough to not appear oversimplified, and Smolin has given many great insights on myriad aspects of the theory, such as the need for a cosmological logic, the sociological factors affecting the development of the theory in academia, and troubles that followed its formulation. it's a great book, more so due to it's lack of oversimplification and watering down the theory.
Evan Macbeth
It's a complicated subject, no doubt. And Smolin does his best to make it narratively accessible. That being said, this book is disjointed and a bit impenetrable, not because Smolin doesn't understand the subject matter. He clearly does! But because his explanations of that subject matter don't seem to answer some basic "why?" and "how?" questions.

But then again, I'm not a physicist so I am probably not the best person to judge.
Kam-Yung Soh
An interesting book by Smolin that offers three ways that Quantum Mechanics and Relativity could be combined to produced the unified Quantum Theory of Gravity. All three ways currently give an incomplete view of the Unified Theory and only time will tell if one ever emerges. But the journey is fun, and requires you to rethink the concepts of space, time, information and the connections between events.
A lot of what's covered in the various pop physics books is all the same stuff over and over, but the proposed extensions to contemporary physics explained in this book are nothing I've read anywhere else. I like that it covers string theory realistically, neither treating it as the one true way, nor as being void of value just because it's flawed.
Can a physicist, however brilliant, explain string theory, M-theory and loop quantum gravity to the lay reader in a 240-page book? I don't think so. However, he can boost the reader's self-esteem by giving the reader the impression that he (the reader) understands these three theoretical frameworks.
This book is truly well written and provides a description of the nature of space which invites further thought..."space indeed is not empty! Many of the ideas about space I also have thought of are in this book...perhaps, I'm smarter than I previously have given myself credit for.
Always had a problem understanding time. This book solved that problem.
Loved the book, simply written for someone with an understanding of physics and chemistry. This book brought me up to date with developments since I had ceased to be actively involved in learning science.
Smolin is a champion of reasonable science and the scientific method. A former advocate of String Theory, he has now gone on to propose Quantum Loop Theory as a more likely candidate. Highly recommended for an exploration of this exciting world of 21st-century physics.
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Lee Smolin is a theoretical physicist who has made influential contributions to the search for a unification of physics. He is a founding faculty member of the Perimeter Institute for Theoretical Physics. His previous books include The Trouble with Physics, The Life of the Cosmos and Three Roads to Quantum Gravity.
More about Lee Smolin...
The Trouble with Physics: The Rise of String Theory, the Fall of a Science and What Comes Next The Life of the Cosmos Time Reborn: From the Crisis in Physics to the Future of the Universe Computers And Artificial Intelligence Science, Mind And Cosmos

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