Quantum Space: Loop Quantum Gravity and the Search for the Structure of Space, Time, and the Universe

Quantum Space takes a look at a less written about physical theory trying to tie together general relativity with quantum mechanics called Loop Quantum Gravity. As a field with a few key pioneers the author spends most of the book following the careers of three men, Smolin, Ashketar and Rovelli, with a focus on Smolin and Rovelli. The book definitely tries to communicate details of the theory to the casual reader and give as intuitive a feel for this esoteric subject as possible, with mixed results.The author is a chemist by training but has a strong history with science for a general audience and I have read his book on quantum theory which I found readable and informative. The author comes with an empirical view of physics and is a skeptical of some of the physics explorations of modern times that seem to be pure mathematical exercises where there are no actual predictions that can be made as the space of solutions seems unbounded. With that skepticism of string theory the author tries to discuss an alternate path to a unified theory, namely loop quantum gravity. The author gives a partial biography of Smolin and Rovelli and describes them as rogue physicists with brilliant flares focused on paving new roads in physics. The author gives the background of their early work and how they met and the early personal bonds formed. The author describes the challenges of a quantum theory of gravity and discusses how quantum field theories treat spacetime as a background vs general relativity which defines the structure of spacetime. The author discusses how loop quantum gravity attempts to quantize space rather than quantize the carrier of force of gravitation and this is a fundamentally different approach. The author gets into details of how the ideas were taken from lattice models from quantum chromodynamics but instead of that being a way to calculate approximate solutions, quantizing space was seen as a way of describing physical space exactly. The author weaves in Penros and spin networks, which turned out to be a way to further improve the model. The author discusses a lot more than just LQG and brings together developments in string theory and how the communities talked or rather didn't communicate. He also brings up works like "Not Even Wrong" to frame what one should be trying to achieve as a physicist. I can't say the book follows a natural path and is always coherent. The author spends time discussing particular issues plaguing all of the theories and then what kinds of solutions are considered and weaves in philosophical issues. The author seems to have strong views on the nature of quantum theory which comes out in his praise for the view of Rovelli but at results are mixed as aspects of loop quantum gravity seem just as metaphysical as string theory currently is. The author seems to be interested in promoting other modern unified theories away from super-symmetric and string theories, but in writing the way he does about loop quantum gravity towards the end, the writing turns out to sound like fantasy as well. In particular the author starts to write about how one could consider the universe as self-selecting itself for the conditions of embedded black hole formation which is not support for his empiricist view of the world.There is a lot in this book on both the history of loop quantum gravity, some of the challenges it has faced in gaining any acceptance and some of the model fixes that have been employed to get it more fully baked. It is not always easy to follow as frontier physical theories require a PhD to actually understand. Nonetheless some information can be gleaned and is a fresh departure from the abundant string theory for the general reader literature. All in all though I think the writing is a bit muddled and whereas author's like Brian Green who are experts in the field they are writing about as well as being a good popular science writer, Jim Baggot is more the latter but not the former and it shows in how he tries to communicate some of the technical details.

I am about 2/3 through this book and it has become a chore to attempt to finish. I was hoping for a book in the league of “The Elegant Universe” as an alternate to string theory, or one written the likes of Plutonium- element 94 the most dangerous element. This is not it. The subject of LQG gets lost in a menutia of random side stories with no substance or connection to the actual science of LQG. Basically a waste of a read if you are looking for some basic science based reading and background science for LQG.

A new book on quantum gravity, and the only book I know to take on the subject of Loop Quantum Gravity in any detail. This alone makes it a gem worth reading. More than that, it is highly readable. I devoured it in a couple of afternoons while travelling. A nice aspect of Baggott's style is that he allows himself to be critical of the orthodoxy from time to time--asking the questions that need to be asked. There has been too much hype around TV-physics these past decades, with the likes of String Theory featuring too prominently, as if it were itself orthodox Truth.The earlier chapters were a standard and rather plain telling of the orthodox views of relativity and quantum mechanics, but less interesting than the later chapters for my part. Later, as he comes to tell the story of Lee Smolin and Carlo Rovelli and their virtual colleague clouds the story gets more interesting. I am a fan of those stories of early quantum theory, as told by Freeman Dyson and Richard Feynman and others. This is a modern story, and we need more of them to inspire young minds to join physics.

The author attempts to explain loop quantum gravity but lost me in a number of areas. Overall I did enjoy the book and would recommend it to those interested in this subject.

Baggott gives an extensive non-mathematical treatment of loop quantum gravity in a clear concise fashion. Also has material not found in Lee Smolin and Rovelli’s respective books on the subject.

I'm just about glad I read this but the experience was like munching slices of bland white bread. The story of Loop Quantum Gravity is told chronologically through the biographies of Lee Smolin and Carlo Rovelli. It's the journey of those who started with General Relativity and tried to quantise spacetime. The nodes and links of LQG are not spacetime quanta, they're precursor objects out of which spacetime, along with its metric field, should emerge in the low-energy limit.This is the fabrication of reality at the Planck scale, way down from observational data. The models are not without interest (especially the cosmological models) and the approach seems to have its compelling moments .. but .. but .. all the nasty things said about the theological or purely mathematical nature of String Theory also apply here, do they not?If you're short of cash you could skip the book and read the Wikipedia article, though you are unlikely to understand it without a total familiarity with GR and QFT. The author had somehow to handwave his way over this cathedral of densely-connected abstractions: the "Quantum Space" reading experience is consequently pretty anaemic.I'm guessing that Baggott wrote this book because, with the continuing decline in the prospects for String Theory, he's become convinced that there's something to Loop Quantum Gravity and wants to raise its profile for a generation of new physicists wondering what on earth they should be devoting their lives to.

Having read the book, I was going to give a great review. I found it readable -- I quite like the interspersing of physics and biography. It presents some pretty hard physics in a very approachable way, which would be accessible to people with almost no physics background -- though maybe it would too difficult if you'd never read anything about quantum mechanics before. The ideas in the book are really exciting, different and well presented.Then I read Lee Smolin's Three Roads to Quantum Gravity, which is extensively quoted (and credited) in this book. It's the same book! Really, all the ideas are the same, and not very much is added.If you like Jim Baggot's other books you'll like this one. There's nothing wrong with it. But I'd recommend reading Three Roads to Quantum Gravity instead, especially as it is about a fifth of the price on Amazon.

A useful but rather plodding summary

No dislikes whatsoever. I found it very helpful for clarification of thinking about the basis of reality, especially time.

Well written interesting book