Download ➾ Quantum Space: Loop Quantum Gravity and the Search for the Structure of Space, Time, and the Universe Author Jim Baggott –

Today We Are Blessed With Two Extraordinarily Successful Theories Of Physics The First Is Albert Einstein S General Theory Of Relativity, Which Describes The Large Scale Behaviour Of Matter In A Curved Spacetime This Theory Is The Basis For The Standard Model Of Big Bang Cosmology The Discovery Of Gravitational Waves At The LIGO Observatory In The US And Then Virgo, In Italy Is Only The Most Recent Of This Theory S Many Triumphs The Second Is Quantum Mechanics This Theory Describes The Properties And Behaviour Of Matter And Radiation At Their Smallest Scales It Is The Basis For The Standard Model Of Particle Physics, Which Builds Up All The Visible Constituents Of The Universe Out Of Collections Of Quarks, Electrons And Force Carrying Particles Such As Photons The Discovery Of The Higgs Boson At CERN In Geneva Is Only The Most Recent Of This Theory S Many Triumphs But, While They Are Both Highly Successful, These Two Structures Leave A Lot Of Important Questions Unanswered They Are Also Based On Two Different Interpretations Of Space And Time, And Are Therefore Fundamentally Incompatible We Have Two Descriptions But, As Far As We Know, We Ve Only Ever Had One Universe What We Need Is A Quantum Theory Of Gravity Approaches To Formulating Such A Theory Have Primarily Followed Two Paths One Leads To String Theory, Which Has For Long Been Fashionable, And About Which Much Has Been Written But String Theory Has Become Mired In Problems In This Book, Jim Baggott Describes Jim Baggott is perhaps my favourite science writer due to the way he takes my favourite subject particle physics and writes about its history and theories in a way that makes it accessible to those of us who are science graduates but have not worked in this field.One of the main dichotomies in recent times is the fact that the theory of general relativity and quantum theory are based on different assumptions and so can t, at this point in time, be fully reconciled Here, Baggott tells the history of Loop Quantum Gravity and how the theories behind this have been developed Whilst LQG is still in its infancy in terms of being accepted by the wider scientific community, as a valid alternative to the increasingly unuseful string theory, I expect it to grow in popularity something which, presumably, Baggott is presaging here.As a guide to the basics and history of the subject, it s excellent, and has taught me a lot the book should be of huge interest to anybody with an interest in quantum mechanics, and is one that I will be returning to. No dislikes whatsoever I found it very helpful for clarification of thinking about the basis of reality, especially time. There s no doubt that Jim Baggott is one of the best popular science writers currently active He specialises in taking really difficult topics and giving a in depth look at them than most of his peers The majority of the time he achieves with a fluid writing style that remains easily readable, though inevitably there are some aspects that are difficult for the readers to get their heads around and this is certainly true of his latest title Quantum Space, which takes on loop quantum gravity.As Baggott points out, you could easily think that string theory was the only game in town when it comes to the ultimate challenge in physics, finding a way to unify the currently incompatible general theory of relativity and quantum theory Between them, these two behemoths of twentieth century physics underlie the vast bulk of physics very well but they simply can t be put together String theory and its big brother M theory, which as Baggott points out, is not actually a theory at all but simply a conjecture has had much written about it But the main alternative theory, loop quantum gravity has had far less coverage As I mentioned in another review and Baggott also picks this up , in one whole book on gravity, loop quantum gravity is only mentioning in an endnote Yet in many ways, loop quantum gravity has a lot going for it than string theory.One major strand of Quantum Space is a biography of two key players in the field Lee Smolin and Carlo Rovelli, both good writers for the general public in their own right, but neither has been able to come close to what Baggott does in trying to make the ideas of loop quantum gravity accessible at a deeper level than a summary, hand waving description It s also the first complete and approachable account I ve seen of how both approaches to a quantum theory of gravity were derived The only downside of the way it s structured is that I think if you re going to be comfortable with the level of detail Baggott gives, you probably don t need the first 100 pages or so giving background on quantum theory and general relativity.My only real concern apart from that unnecessary opening material, which makes the book a little too long for my tastes, is that there could have been unpacking of how loop quantum gravity represents reality the jump from the introduction of spin networks to anything resembling a theory that can be applied to a real world where things happen is overwhelming I had to resort to the much valued advice of one of my supervisors at university who said Don t worry if it doesn t all make sense, just keep on with it and hopefully it will all come together It almost all did all come together, but I was left with a nagging doubt that I couldn t really grasp the foundation of the whole idea.As well as coming out of reading this book with significantly respect for Rovelli whose popular science writing I find flowery and overrated , I feel that Baggott has done a huge favour for anyone who really wants to understand modern theoretical physics, giving a much better understanding of this fascinating attempt to deal with a central requirement to explain the workings of our universe It s a triumph.