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Three Roads To Quantum Gravity (Science Masters)

4.11  ·  Rating details ·  4,096 Ratings  ·  66 Reviews
It's difficult, writes Lee Smolin in this lucid overview of modern physics, to talk meaningfully about the big questions of space and time, given the limitations of our technology and perceptions.

It's more difficult still given some of the contradictions and inconsistencies that obtain between quantum theory, which "was invented to explain why atoms are stable and do not

Published August 16th 2001 by Phoenix (first published 2000)
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Dec 01, 2008 rated it really liked it  ·  review of another edition
Shelves: science
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
Oct 16, 2009 rated it it was ok  ·  review of another edition
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
James F
According to Smolin, there are three "roads" currently leading to a theory of quantum gravity: the first road begins from quantum theory and adds relativity (string theory), the second begins from general relativity and adds quantum theory (loop quantum gravity), and the third rejects both and tries to consider the question from first principles. (This third road is basically not discussed, and later in the book the third road becomes thermodynamics of black holes and the "holographic principle" ...more
Since Lee Smolin has been one of the leading figures both in the string theory and in the theory of loop quantum gravity, I hoped this book would clarify some questions I was left with after reading Carlo Rovelli's Reality Is Not What It Seems: The Journey to Quantum Gravity. I think the main reason both the books failed to do the job is the fact that I lack the adequate background to understand what is really meant by ''strings'' and ''loops'' in the two main approaches to quantum gravity. I fi ...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
Bob Nichols
Smolin describes his thinking about how quantum theory (micro level) might be linked to Einstein’s gravitational theory (macro level), to become “a quantum theory of gravity.” His argument is by no means easy for the lay reader to follow, so what follows may not be an accurate rendering.

At the minutest level of reality (spacetime on Planck scale) are strings (“a string is actually made of discrete pieces, called string bits, each of which carries a discrete amount of momentum and energy”). Part
Oct 12, 2007 rated it really liked it  ·  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
Excellent book describing how the routes to quantum gravity work in rather precise but laymen terms. The human elements are also very clearly done. However, there is clear "side" taken in making loop quantum gravity sound "better" than string theory, which from what I know on technical level they are both stuck in equally critical stalemate (maybe I am wrong). But otherwise it is a good exposition, especially when Smolin laid clear the "philosophy" behind doing science - what are our biases, etc ...more

I'm sorry. Even from the (relatively) short part I read it's clear Smolin is a brilliant scientist, but a writer he is not. The writing is just painful, rambling at times. Very little is explained, and what is explained is done so in the most simplistic ways by comparing certain concepts in quantum theory with daily life events that might work had Smolin not drawn it out to the max, making me forget what he was trying to explain in the first place. This book and I, unfortunately, must part w
Carl Stevens
Aug 25, 2014 rated it really liked it  ·  review of another edition
Do you know a similar book with a little more technical detail? This was an excellent popular treatment of quantum gravity and related topics but I have read several popular treatments now and find myself wanting to dust off my old math texts and go a little deeper. So if you know something that would challenge someone with a math background comparable to a math major in his junior year, please let me know.
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.
Ami Iida
May 18, 2015 rated it did not like it  ·  review of another edition
Shelves: physics
There is some description of the physics mistakes clearly.
It is a disqualification as a physics manual.
Oct 04, 2012 rated it really liked it  ·  review of another edition
I love Smolin's style of writing. A worthwhile read for those interested in the diversity of the field and the questions being tackled.
Austin Barselau
Writing about complex topics, not to mention quantum theoretical physics, is tremendously challenging. Distilling dense, abstruse, and highly mathematized information down to the comprehension level of the average reader is a feat in itself. This is why good popular science- writing that can be accessed and enjoyed by that layperson- is scarce. Far too many academics fall prey to the so-called “curse of knowledge,” or the inability of the expert to condense and summarize information to novices. ...more
Apr 19, 2008 rated it really liked it  ·  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
Jul 03, 2007 rated it it was amazing  ·  review of another edition
Shelves: science
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 . . .
Feb 19, 2014 rated it really liked it  ·  review of another edition
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
Jul 15, 2008 rated it it was amazing  ·  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
Jan 28, 2013 rated it liked it  ·  review of another edition
Shelves: philosophy, physics
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
Vicky Chijwani
Oct 08, 2016 rated it really liked it  ·  review of another edition
Shelves: science
A good way to get up to speed on (almost) the latest physics, after you've worked your way through the thicket of relativity and quantum physics. Although I must say, the sheer abstractness of physics today kinda dampens my enthusiasm for the subject.

What follows below is basically terse notes for my future self:

- Why is quantum gravity important? General relativity and quantum mechanics are simply incompatible. GR does not take into account the role of the observer, while QM accepts Newton's vi
To start this review off, I must say that I was impressed with how well this book was written. Being a high school student with no prior knowledge of quantum gravity or quantum mechanics, I was pleased that this book was written in a way that I could actually understand the content and learn from it. Also, Lee Smolin's "Three Roads to Quantum Gravity" not only taught me about today's groundbreaking physics, but has also sparked my interest in pursuing further knowledge in the fields of theoretic ...more
Nov 26, 2010 rated it really liked it  ·  review of another edition
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
Sanjay Varma
Mar 01, 2016 rated it it was ok  ·  review of another edition
Shelves: non-fiction
It's not a bad book. He writes clearly enough. I was able to follow him for half the book.

He introduces a concept that space-time is not continuous but is made up of discrete units. He speculates that each unit of space-time is extremely small and related in size to Planck's constant. And from this idea he goes on to explain several scenarios in which more space-time is spontaneously created. As someone who has enjoyed reading the empirical philosophers like Descartes, Hume, and Kant, whose the
Gaurav EVHS Desale
Divide an inch in two. Now divide each half again, and then repeat the division, over and over. Can you go on for ever, or do the laws of physics eventually get in the way? Is the fabric of space infinitely divisible, or is it ultimately made up of "atoms" - tiny chunks of space that can never be split?
This question may seem almost unanswerable. But as physicist Lee Smolin writes in Three Roads to Quantum Gravity , some of the newest ideas in physics are pointing to a surprising answer: space an
Lucas Ventura
Jan 20, 2014 rated it it was amazing  ·  review of another edition
Shelves: science
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
Sep 13, 2007 rated it really liked it  ·  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
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
Steve Alker
Jan 28, 2012 rated it it was amazing  ·  review of another edition
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
Mark Abrams
Mar 01, 2014 rated it it was amazing  ·  review of another edition
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
Tapani Aulu
Suurinpiirtein yleistajuinen esitys Smolinin omasta silmukkakvanttipainovoimateoriasta, spinvaahdosta ja spinverkosta. Vastakkainasettelu säieteorioiden kanssa on ilmeinen, vaikka Smolin sitä koettaakin piilottaa.

En ollut oikeastaan koskaan ennen lukenut silmukkakvanttipainovoimasta. Liekö syy, että siitä ei ole tullut mitään sitten viimeisen 15 vuoteen, vai omasta lukemattomuudestani? Onko ehdotuksia lisäsmolineiksi?

Niin ja otsikossa puhutaan kolmesta tiestä. Se kolmas liittyee mustien aukkoje
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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.
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“if physics is much simpler to describe under the assumption that space is discrete, rather than continuous, is not this fact itself a strong argument for space being discrete? If so, then might space look, on some very small scale, something like Wilson's lattice.” 1 likes
“Similarly, a law of physics that allows information to be converted into geometry, and vice versa, but gives no account of why, should not survive for long. There must be something deeper and simpler at the root of the equivalence. This raises two profound questions: Is there an atomic structure to the geometry of space and time, so that entropy of the black hole could be understood in exactly the same way that the entropy of matter is understood: as a measure of information about the motion of atoms? When we understand the atomic structure of geometry will it be obvious why the area of a horizon is proportional to the amount of information it hides? These questions have motivated a great deal of research since the mid-1970s. In the next few chapters I shall explain why there is a growing consensus among physicists that the answer to both questions must ne 'yes'.” 0 likes
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