The End of Time: The Next Revolution in Physics 1st Edition by Julian Barbour (PDF)

Description

Richard Feynman once quipped that “Time is what happens when nothing else does.” But Julian Barbour disagrees: if nothing happened, if nothing changed, then time would stop. For time is nothing but change. It is change that we perceive occurring all around us, not time. Put simply, time does not exist.In this highly provocative volume, Barbour presents the basic evidence for a timeless universe, and shows why we still experience the world as intensely temporal. It is a book that strikes at the heart of modern physics. It casts doubt on Einstein’s greatest contribution, the spacetime continuum, but also points to the solution of one of the great paradoxes of modern science, the chasm between classical and quantum physics. Indeed, Barbour argues that the holy grail of physicists–the unification of Einstein’s general relativity with quantum mechanics–may well spell the end of time.Barbour writes with remarkable clarity as he ranges from the ancient philosophers Heraclitus and Parmenides, through the giants of science Galileo, Newton, and Einstein, to the work of the contemporary physicists John Wheeler, Roger Penrose, and Steven Hawking. Along the way he treats us to enticing glimpses of some of the mysteries of the universe, and presents intriguing ideas about multiple worlds, time travel, immortality, and, above all, the illusion of motion.The End of Time is a vibrantly written and revolutionary book. It turns our understanding of reality inside-out.

User’s Reviews

Reviews from Amazon users which were colected at the time this book was published on the website:

⭐I bought this book because I think time is no more than a very useful idea that we all share. THIS IS, BY NO MEANS, AN ORIGINAL IDEA. Time is in our minds and language, as well as the minds and language of everyone around us, so often that that makes it near impossible to imagine that it’s nothing more than that. The case is simple, and most people won’t buy it; we prove that time exists because we see endless change and motion. Without those, we wouldn’t need time, and wouldn’t think it exists – if we could think at all, given that thinking is about mental changes, likely related to physical/chemical changes in our brains. But, if we remove the assumption that change/motion is something that happens in time, or, somehow, because of time – just for a moment – (HAH!!) – then how does change/motion PROVE that time exists? The answer is, it simply doesn’t. It’s just change and motion. We compare this change here – say, the physical change and motion that happens in a clock, to just about every other change. How many changes in a clock compared to the change of us moving from one place to another. How many changes we call WORK compared to those clock changes. How many changes on that clock and, by extension, how many days and years – all changes in the Earth’s movement relative to the sun, before our bodies will change.A big reason we believe in that extra something – time – is that we use it endlessly to coordinate our actions (motions and changes) with other people. Acting together is what makes us a very, very powerful species. We use changes in clocks, days, years to act at the same “time”, and in the most effective sequence of actions. That’s why we all talk and think about time so much.I really doubt most people will accept this but, maybe, just consider the idea, because it’s interesting. Notice that what we all perceive, all the…time…is change. Notice that we really don’t have to add the idea of time to that, that we could just stay with change. You’ll still need clocks, because we all need, and want, to act WITH other people. But, again, notice that clocks are about the changes on a dial or on a digital display compared with all the other changes we see around us.Barbour thinks time is an illusion, but he also feels the need to do away with cause and effect. A sequence of changes, a chain of cause and effect, somehow, tells him that time must be real. So, he posits that motion is also an illusion. Things just are, and have no causes, because there’s no motion that could allow a cause to result in an effect. He tries to make the case that motion, and an endless chain of causes and effects, are mental illusions that we all share, very like the illusion that tells us that the Sun revolves around the Earth. For him, a change – any change, can’t precede another change, because that sequence demonstrates time.I don’t think it does. I think it’s all just changes and motion, and that the sequence of causes and effects make a lot more sense than the notion that all motion is an illusion. It makes a lot more sense than the idea that changes exist because our minds work in a way that now sees this whatever, then see it changed, and now changed again. Occam’s razor tells us motion happens, and they happen in sequence, with one motion/change leading to the next.Overall, although I disagree with some very important points that he attempts to make, there’s a lot of scientific ideas and discussion, and it all comes together in a very interesting way.

⭐I enjoyed this book for presenting most of the time-related physics in a single book. As others have pointed out, there’s something “dense” about the visualizations and analogies used to explain the topics, but I found that somewhat useful for forcing me to look at the concepts again with fresh eyes. After reading the book, I think there are probably clearer ways to explain these concepts, and it just seems that J.B. was struggling to say what he means without math.Ultimately, there is very little, if anything, that’s new in this book, and I think the author acknowledges as much through some of the anecdotes of his career as a physicist.o The Minkowski space of General Relativity treats the time dimension as equivalent to the space dimensions.o There is no present moment in physics, or a movement in time. Classical “block time” looks at the universe as a four-dimensional painting, and physics is the study of the relationships between the “swirls” in the painting.o Machian timeless classical physics is over 100 years old.o The Wheeler-DeWitt wavefunction is over configuration space not regular space and is not restricted to configurations with causal continuity. So as far as the quantum mechanical view of the universe, time continuity is not required.o His concept of “best-matching” is already implied in General Relativity, as he points out eventually in the book.o Time Reversal Invariance is nothing new either. There’s no direction of time in physics. The asymmetry (physical arrow of time) only says that the universe has low entropy on the left side, and high-entropy on the right side (or vice-versa if you flip the picture). The universe can be studied from left to right or right to left. As Hawking points out, it’s strange that we think the reverse of our psychological sensation of time is unfamiliar because that is exactly what is happening. And so, Hawking’s famous question, “Why do we remember the past but not the future.”At this point physics does fine without addressing the psychological features of time such as the present moment, its movement, direction, and apparent continuity, but eventually the physics may force the issue as quantum mechanics has already run into the problem of “people”. For example, the Schrodinger and Wheeler-DeWitt equations have no need to drop out of the complex-number plane of superposition and into the real numbers. The physics is fine with the whole universe being in superposition of all the possibilities allowed by the wavefunction over configuration space.But people insist that we never experience superposition, and since observation is an essential part of physics, the observer comes into play. We end up having to force the wave function into a specific instance (observable state), which causes the physics to go into only one of the possible instances of the universe. That’s a serious problem because QM can’t tell us deterministically which one we’ll find ourselves in when we make the measurement. So we have various kinds of quantum uncertainty like “quantum jitters” in the vacuum, etc. In fact, the Bell theorem points out that it is not possible to predict which universe will be measured by certain types of observations.So, I think, Julian Barbour’s book has value in presenting the kind of problems we’ll run into, as QM already has. For example, one of the problems he addresses is preserving causality when the Wheeler-DeWitt wavefunction doesn’t preserve continuity of time, since it’s a probability function over configuration space. He proposes that it’ll probably turn out that the wavefunction allows only universes which do have a continuous causal link between their boundaries (the big bang and whatever is at the other end) since that is the kind of universe that we experience (above microscopic scales). He doesn’t have an explanation though for how or why it would do that.I think the point of the “End of Time” title is that, just as the interpretations of quantum mechanics are there to comfort our perceptions but not necessary to the physics of it, so are our conceptions of time fitting to our perceptions, but not needed to understanding the physics of the universe. At this point, anyway.Overall, I’m glad I trudged through to the end, but mainly because on the physics side (rather than philosophical) there are few books which focus on the unanswered questions of the topic.

⭐This books asks the fascinating question ‘what is time’ and concludes time doesn’t in fact exist. It’s a bold idea and obviously controversial, and thus piqued my interest. However, whether he is correct or not is not something the average reader is going to learn after forging through the 350 odd pages of this book. Probably the best warning is given by the author himself in chapter 2: in explaining the incomprehensible imagery and analogies he uses to explain his idea, he states “it is…an example of a basic notion in physics called configuration space that is normally regarded as too abstract to attempt to explain in books for non-scientists”. And he is absolutely correct! I have a physics degree and have read many books on quantum and particle physics and I could not make head or tail of his explanation of his so-called “triangle-space”, the analogy he uses for his timeless/motionless universe. He says if you can “get your mind round this concept…you will certainly understand a lot of this book”. The problem is understanding configuration space would require a few years of study for anyone, and after all that, you might then understand part of his model for what is a very esoteric concept. Maybe he is right. But there is no way anyone not fully acquainted with these complex mathematical tools is going to be able to decide, even if they are able to get through this book. A shame, as the question itself is fascinating: it’s just this book doesn’t give an understandable answer.

⭐The motivation for this book is the Wheeler-DeWitt equation of quantum gravity, which can be interpreted to say that nothing ever happens, as only static solutions exist.Most physicists think that the Wheeler-DeWitt equation is therefore wrong, or at least flawed, since clearly things do happen. Julian Barbour has taken the opposite approach, of trying to demonstrate that the universe is static — The End of Time.Not only does the universe appear not to be static, but the two great physical frameworks, general relativity and quantum field theory, work on the assumption that space-time is four dimensional; that a change of point of view can rotate spatial dimensions into time and vice versa. Killing time has the effect of also killing the whole of physics as we know it.Julian Barbour’s approach is to describe the state of the universe in a static many-dimensional configuration space, which he calls Platonia. Two points in this space are nearly enough to define dynamics (enough, if you ignore overall velocity and angular momentum). Julian’s idea is that what we think of as time is the fact that points in this configuration space are related to each other. He does not say explicitly, but I guess what he means is that a pair of points define a position and a momentum, hence link to other points, in what we old-fashioned people would call a timeline.To be blunt, I think that Julian Barbour has not really killed off time, but merely renamed it as a relation (he calls it a resonance) between different points in configuration space. Clearly, at a local level, the points must be related in a way that looks like general relativity and quantum field theory, so time looks as if it exists, even if it is not “really time”.All this would be worth doing if it allowed the Wheeler-DeWitt equation to be used to help define how the individual points in the configuration space interact, but I would need to see some actual physics and maths to persuade me that Julian Barbour has made any real progress in this direction.Another aspect of Julian Barbour’s account is that he links the points in his configuration space to the many-worlds interpretation of quantum mechanics. For me, this is the strongest part of his argument. His presentation of many-worlds is clear and well-thought-out. I particularly like the way his mechanism works both ways in time (if I am allowed to use the word). That said, I think the many-worlds ideas are independent of his other ideas. You could have a timeless configuration space with a single path through it, representing what actually happens, rather than his “blue mist” of all the possibilities, and all the theory would work just as well.I enjoyed the book, because of the clarity of the many-worlds explanation, and the discussion of the ideas of Mach and Leibniz. It is good to think about what time means, and this book is an intelligent contribution to the debate, as is The Fabric Of Reality by David Deutsch.But it is publisher’s hype to say that these theories kill off time, and I would need convincing that they take us any nearer to a theory of quantum gravity.

⭐Initially intriguing and fascinating. The book rambles on, describing the history of scientific discovery, philosophy, etc. The reader is then drawn in to the technical complexities of wave functions and beyond into the realm of (outdated) quantum mechanics. Any lay reader who is still able to keep up thus far is in for an anti climax at the painfully drawn out end of this disappointing read.

⭐If you are looking for THE END OF TIME by Julian Barbour DON’T BUY THIS EDITION!!!!!! What you get behind the cover is a (feminist) novel called ‘Herstory’. Herstory may be a very fine book – maybe I will read it when I have finished my (self-set) reading list – BUT IT IS NOT …. THE END OF TIME. I want my money back!!!!!

⭐Julian Barbour, a well-known maverick at conferences, has managed to present his unorthodox views in a balanced and accessible way in this popular treatment. His singular vision ties together the various themes in a startling manner. The theory therein is exciting, disturbing, and invigorating.Somehow a rather complex set of ideas incorporating the canonical approach to quantum gravity, the many worlds interpretation of quantum mechanics, and Barbour’s novel approach regarding configuration space are presented at a level anyone bothered to put the time in (ho ho) can understand. Generally, Barbour is good at laying out ideas in a simple manner, although he does occasionally transition from carefully explaining everything to quickly reeling off some technical sentence or other, albeit only in a minority of cases. He writes equations out in words, with some loss of technical generality, on the other hand. My main minor criticism of the book is his description of the wavefunction as three coloured ‘mists’. Despite my training in QM, I got lost sometimes when trying to remember whether blue represented probability or position and so on.I think the main reason the book works is because Barbour’s theories are themselves usually only describable in qualitative terms anyway, since quite preliminary. I’ve often thought cutting edge ideas are often easier to explain than well-established ones, since often they only exist in qualitative form. And Barbour has a vision, a breathtaking vision, one that incorporates many themes that are now (2012) even ‘hotter’ then they were back in 1999, which I think is the original publication date. Barbour’s approach to QG is fascinating, even if it should prove false.One further minor quibble, however, is that the book is called the end of TIME, and Barbour’s theory is presented as a theory of time (i.e. there isn’t any ‘flow,’ etc.), yet in reality it is an anti-realist position with regard to MOTION and/or real ‘becoming,’ NOT ‘time’ as such. The further independent argument required – that time is reducible to change, motion, etc. – even if plausible, is nowhere satisfactorily provided. The nearest Babrour comes to providing such, in my view, is when he mentions a critique of Ashtekar’s views. (It may be objected that Barbour’s positive arguments for a ‘Machian’ approach incorporate a certain denial of absolute and/or real time, but this requires an argument. Since distinctions such as denying A-series, B-series, or C-series time are not addressed, for example).Incidentally, where Barbour contrasts his MWI with other historical Everettian’s, including Everett, an update would be interesting, since the field has moved on so much since 1999, perhaps partly inspired by Barbour’s book.All in all, this is an accessible and brilliant book, containing one of the most interesting unified views on nature, physics and time ever. If you enjoyed Deutsch’s Fabric of Reality from the late 90s, you’ll probably enjoy this book too. Barbour is careful, perhaps more so than Deutsch, to point out his ideas are unorthodox, in terms of the ‘sociology’ of physics. However, much as in the case of Deutsch, a sizeable and growing minority of physicists are developing ideas that resemble many of those contained in this book.I should note that I find Barbour’s conception of ‘Nows’ or ‘instants’ physically incoherent, but that it took me a long time to work around his many brilliant and subtle arguments contained herein.

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