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# Three Roads To Quantum Gravity (Science Masters)

by
Lee Smolin

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

...morePaperback

Published
August 16th 2001
by Phoenix
(first published 2000)

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## Community Reviews

(showing 1-30)

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

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

Sep 04, 2007
Rob
rated it
liked it
·
review of another edition

Shelves:
non-fiction-for-egghead-spacealiens

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

but thank the lord most of the ...more

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 ...more

Oct 12, 2007
Jim
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 ...more

Still, Smolin does give very detailed explanations for the different versions of String Theory, Loop Quantum Gr ...more

**DNF!**

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 ...more

But then again, I'm not a physicist so I am probably not the best person to judge.

Apr 19, 2008
DJ
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 ...more

"Three Roads to Quantum Gravity" is Smolin's briefing to the p ...more

"...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 19, 2014
Rama
rated it
really liked it
·
review of another edition

Shelves:
physics,
physical-reality

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

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

Jul 15, 2008
Kev
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 ...more

I think this one is better by far than Gre ...more

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

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 ...more

Aug 24, 2015
Michelle
rated it
really liked it
·
review of another edition

Shelves:
non-fiction,
gcisd-25-book-challenge

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

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 ...more

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 ...more

The author gives a very solid and understandable overview of the main avenues o ...more

Sep 13, 2007
Ethan
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 ...more

"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

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

I found this work to be brilliant and very thought-provoking and would highly recommend it to anyone w ...more

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 ...more

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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.”
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“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'.”
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