Time Reborn: From the Crisis in Physics to the Future of the Universe

by Lee Smolin

From one of our foremost thinkers and public intellectuals, a radical new view of the nature of time and the cosmos. What is time? This deceptively simple question is the single most important problem facing science as we probe more deeply into the fundamentals of the universe. All of the mysteries physicists and cosmologists face, from the Big Bang to the future of the universe, from the puzzles of quantum physics to the unification of forces and particles, come down to the nature of time. The fact that time is real may seem obvious. You experience it passing every day when you watch clocks tick, bread toast, and children grow. But most physicists, from Newton to Einstein to today's quantum theorists, have seen things differently. The scientific case for time being an illusion is formidable. That is why the consequences of adopting the view that time is real are revolutionary.

Lee Smolin, author of the controversial bestseller The Trouble with Physics, argues that a limited notion of time is holding physics back. It's time for a major revolution in scientific thought. The reality of time could be the key to the next big breakthrough in theoretical physics. What if the laws of physics themselves were not timeless? What if they could evolve? Time Reborn offers a radical new approach to cosmology that embraces the reality of time and opens up a whole new universe of possibilities. There are few ideas that, like our notion of time, shape our thinking about literally everything, with huge implications for physics and beyond, from climate change to the economic crisis. Smolin explains in lively and lucid prose how the true nature of time impacts our world.

Genres: Science, Physics, Nonfiction, Philosophy, Popular Science, History, Astronomy

352 pages, Hardcover

First published April 23, 2013

About the author

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.

Reviews

[Manny · Rating 4 out of 5]

The sense of beauty leads us astray.
- James Joyce, Ulysses

Physics is in a strange state right now. On the surface, things may seem to be going well; the elusive Higgs particle was detected for the first time last year, and there are interesting signs that we may soon discover what dark matter is made of. But on the truly fundamental issues, there has been little progress. Three items in particular stand out. First, our two central theories, quantum mechanics and General Relativity, are each very successful on their own, but not compatible with each other. Second, there is no good explanation for the fact that all the physical constants of our universe appear to be finely tuned to make life possible. Third, and perhaps most embarrassing of all, no one can convincingly explain the presence of an arrow of time.

People have different strategies for dealing with these questions. Here in Geneva, the de facto physics capital of the world, the most common approach is simply to ignore them. T, who's just published some excellent papers in his speciality, is unconcerned when he comes to dinner the other day. "Cosmology isn't physics," he says. "Physics is about things I can put in a teaspoon."

"What about stars?" I ask. I know that some astrophysicists are interested in T's work. T waves away my objections; evidently, he is talking about a fairly large teaspoon. The point he wants to make is that you can't put the whole universe in a teaspoon, even in principle. T isn't worried about questions that have to do with the whole universe. They are none of his business.

I have read several books over the last few years by people who have a different take on these issues. Paul Davies, Martin Rees and Leonard Susskind, for example, argue that there might well be more universes than the one we see around us. Perhaps there could even be an infinite number of them, all with very different properties. In that case, things are not as mysterious as they first appear. Everything imaginable happens in some universe, and in a few of them the numbers have worked out just right to produce the complex, highly structured world we see around us, in which there is a clear progression from past to future.

Some of these people have produced detailed theoretical scenarios explaining how the other universes might have come to be; Susskind's The Cosmic Landscape describes one of the most popular versions. There is, however, the problem that we can't see any direct evidence of these other worlds, and no one is able to suggest experiments that could determine whether or not they exist. As followers of Karl Popper say, it is not clear that the theory is falsifiable. Susskind replies that he is unconcerned by this criticism: he is more worried that people will reject the right theory for nit-picking methodological reasons. But if your theories aren't falsifiable, are you still doing science? Susskind says he is. Other people are less sure. Helge Kragh, the eminent Danish historian of science, has been a particularly vocal critic.

If many physicists are refusing even to think about the fundamental problems and others are addressing them in a way which is often claimed to be contrary to the principles of science, it's reasonable to say that the field is in crisis. Smolin, a cutting-edge theoretician with a broad range of interests, has been telling us this for some time. In his 2006 book, The Trouble with Physics , his emphasis was on sociology: he warned that research was focusing too much on string theory, which quite likely wasn't going to deliver, and argued that an attack on a broader front was required. In his new book, the point of view is more that of philosophy. He wants to reexamine the underlying assumptions and see if they need replacing. He thinks this is necessary: right now, as he puts it, people are trying to market things as science which in fact are radical metaphysical fantasies. To start with, one of his absolute demands is falsifiability.

Two themes in particular dominate the book; one, as the title suggests, is time, and the other is physical law. Smolin argues that there is a deep connection between them. In the picture of science which many scientists use without even reflecting on what they are doing, physical laws are mathematical objects. They do not form part of our everyday existence, but live in an eternal, Platonic world of abstract entities. Yet somehow these abstractions are supposed to be intimately linked to our "real" world. I thought his analysis was insightful, and helps explain why science is so often compared with religion. A scientist who subscribes to the Platonic picture is not in fact that far from being a kind of priest. He probably doesn't believe in God (most scientists don't), but he still claims to be able to mediate between our world and the eternal world of mathematics.

There is a major difference between the world we experience and the Platonic world. For us, things are constantly changing; the eternal world is frozen in a single moment. But this is exactly where science has scored its greatest victory. Starting with Galileo, scientists have found ways to conceptualize time as space. Smolin starts with the trivial example of someone throwing a ball, and considers how this can (apparently) be captured as the parabola the ball follows. The dynamic experience of watching the ball fly through the air is replaced by a static curve, or even better by the equation describing that curve. Newton extended the picture further, and Einstein completed it. Relativity fuses space and time together into the single concept of space-time.

It is all very beautiful, and Smolin, who says his first exposure to real science was reading Einstein, is particularly receptive to its beauty. But, he explains, you just don't seem to be able to progress any further once you accept Einstein's "block-universe" view. He argues that something has gone wrong, and we need to backtrack; from there, he goes on to outline the daring research program that he and his collaborators have been pursuing. First, he wants to put time center stage, and say that it really does exist in its own right. This means doing something we have been taught for a century to believe is wrong, and claiming that an absolute notion of time exists, in other words that there is a universal time according to which it is meaningful for distant events to be simultaneous. Second, and even more heretically, he wants to abolish the special status of physical laws. They will no longer be inhabitants of the Platonic world, but just part of our normal world, subject to change like everything else. He spends rather more than half of the book sketching out this framework in fair detail.

I would like to say that I was immediately attracted by the elegance of the scheme, but that would not be true. I am in fact shocked. It looks ugly, and it is very much at odds with most of the science I know. However, as the great chess master Aron Nimzowitsch used to say, the beauty of a move lies not in its appearance, but in the thought behind it. One of Einstein's basic principles, which led him to General Relativity, was that anything which acts must itself be acted on. In his case, he argued that, since space acts on matter, matter must act on space. At the time, this must have seemed crazy to many people, but now it makes perfect sense. The idea that physical laws are mutable just takes the idea a step further. And if physical laws can change, it is reasonable to argue that time needs to play a more central role; then one can go further, as Smolin does, to talk about how the laws of nature could gradually evolve over time to look like the ones we now see around us.

So I have mixed feelings about the book. My instinctive reaction is that it will probably be shown to be wrong. But that's exactly why it's science: it makes falsifiable predictions. Smolin's main competitor, the multiverse theory, is in no danger of being disproved, since the other universes aren't observable. No wonder it initially seems more attractive. And Smolin evidently knows all the angles. He's not doing this because he likes craziness; he's doing it because he's tried the obvious ideas, and they don't work.

To conclude, the thing I am most struck by in Time Reborn is that it suggests we have reached a boundary in science. Basically, Smolin agrees with our friend T. He says that science, as we know it today, is about things you can put in teaspoons - possibly very large teaspoons, but still teaspoons. If we want to make progress on the issues currently baffling us, which concern the whole universe, we need to figure out a way of doing science that represents a fundamental break with what has gone before.

Maybe it's not possible. Maybe we've come as far as we can, and the remaining questions are simply outside the scope of scientific inquiry. But if they are things that people can understand at all, it seems plausible that the answers will be something like what Smolin presents here; perhaps not specifically this idea, but something equally bold and different. It's fascinating to read a status report from these fearless explorers on the absolute limits of human knowledge.

[BlackOxford · Rating 4 out of 5]

Reviving the Old Traditions

Time Reborn is an erudite, intense, but nonetheless respectful polemic about the fundamental structure of the universe. Its claim, if I understand it correctly, is simple: the first ‘substance’ of the cosmos is not space, energy, or matter but time. Time is not another dimension of space, or an illusion of material consciousness; it is a reality that generates all else that we experience, and indeed beyond that to everything that happens.

I am not qualified to judge whether what Smolin has to say concerns physics or metaphysics, that is whether his view is a scientific hypothesis subject to experimental verification or a existential presumption which is self-verifying once adopted. But what I can note with some confidence is that it is an idea with a long pedigree even though it has been presented historically in very different terms.

In Orphic myth, for example, the progenitor of all the other gods is Chronos, the god of time (not to be confused with Cronos, a mere Titan). Chronos with his daughter Ananke (don���t ask!) split the Primordial Egg from which emerge the other gods and the rest of the cosmos.

Several hundred years later, Plato in the Timaeus would define time as “the moving image of the eternal according to number.”* What he meant by that is certainly debatable but one coherent explanation is that everything else in the creation of The Craftsman (God) is placed within time in order for these things to exist at all. Even for Plato, therefore, time drives existence itself (or is the cradle of existence if one prefers) in a manner not dissimilar to the Chronos myth.

In the biblical Book of Genesis, the first (or Priestly) story of creation was largely composed in the same era as the Orphic myth. In this story, the first creation is Light which is immediately separated from the Darkness, thus generating day and night. These are created before the Sun and the stars. Thus the first day’s divine work is the creation of time, confirming the Greek idea of time as the primordial substance of the universe.

Remarkably, Lee Smolin believes that both the pre-Socratics and the ancient Hebrews had it right: “Nothing transcends time, not even the laws of nature.” From time everything else flows. The implications of this proposition are astounding, and not just for physics.

Among other things, the hypothesis of primordial time means that every so-called truth - scientific, social, logical, theological, physical, spiritual - has a sell-by date attached. There are no eternal truths (presumably even that one is subject to evolution at time’s discretion). If Time Is King then we will never understand it fully because we are contained within it just as the Greeks suspected. And wasn’t even YHWH surprised when his creation didn’t work out as intended (not once but three times), suggesting an established (although possibly unconscious) recognition of divine subservience to time?

Perhaps the potential dominance of time is the real reason behind the religious objections to Darwinian evolution, which Smolin refers to as “the prototype of thinking in time.” What’s offensive to the the evangelicals is perhaps not so much the idea that not all species were created at once, but that God himself evolved, a possibility that Scripture clearly confirms within both the Hebrew Bible and the Christian addendum, as well as in the transition between the two. If Darwin is perceived as a impending spiritual threat by these people, Smolin represents the apocalypse which already has happened.

Smolin is concerned that we don’t take his hypothesis to imply relativism. I don’t understand why. He clearly states that everything about reality is relative to time with no exceptions. The exception he wants to make is actually no exception at all. When he says that…

“Truth can be both time-bound and objective when it’s about objects that exist once they’ve been invented, either by evolution or human thought.”

… isn’t it clear that what he is referring to are only linguistic expressions of a certain type, namely definitions? The principles of mathematics are indeed objective, eternal, and absolute, but only because they are defined the way they are. Such definitions include not only the number 5, for example, but also the species Homo Sapiens and all other linguistic categories. Words are unavoidably defined only by other words. And even these will be periodically re-defined to suit evolving human purposes.

With these views, Smolin echoes those of the great American philosopher, Charles Sanders Peirce (whom he cites). Peirce was the first to propose that the apparent unpredictability of events is not due to insufficient data or observational error but is an inherent feature of the universe. He called it “tychism,” to designate a permanent randomness in cosmic behaviour. Smolin is, therefore, channeling Peirce when he says, “Surprise is inherent in the structure of the world.”

Peirce also provides the logical justification for Smolin’s proffer of hypotheses in a world with changing natural laws. How is it possible to rationally construct guesses about the way the world works if the way the world works is changing? Peirce formulated his principle of “synechism,” a normative (not existential) presumption that there may be some ultimate knowledge toward which scientific inquiry is striving as a continuous method for dealing with discontinuity.

One of the central presumptions of modern science is that the universe wants itself, or at least allows itself, to be known through specialised and expert human inquiry. In Smolin’s way of thinking, this becomes merely a human conceit. The universe is ultimately inscrutable, which should be obvious since, being part of it, we can never observe it in its totality.

This implies that every scientific theory and explanation we create is not simply temporary and corrigible but ultimately fictional. They are stories we tell, probably to make us feel more secure in a world that we know will finally consume us. That some of these stories work better than others shouldn’t distract us from their fundamental character. None have a happy ending.

It may be that the Greek Heraclitus had the enduring key to all inquiry when he suggested not just that “Nature loves to hide,” (as Smolin notes) but also that “Nothing endures except change.” (which he does not). We cannot step into the same stream twice after all.

So to search for stable knowledge in the obscure details of subatomic particles or arcane string theory may not be the most rational strategy of inquiry. Perhaps the most important discoveries are waiting in plain sight and experienced by everyone. Intellectual humility might be the only essential virtue of not just the scientist but the authentic human being, that is, one who doesn’t readily believe his own press.

Perhaps Smolin should keep in mind that Chronos was intentionally confounded in Greek myth with his progeny of decidedly different character, Cronos. Whatever concept of time is eventually agreed by scientists, it too will be as unstable as Chronos according to Smolin’s theory.

* A little clarification is helpful with this definition. For Plato, as for Thomas Aquinas centuries in the future, eternity is not an infinite series of moments but a entirely timeless category. What Plato seems to be saying is that in every moment we have a glimpse of the eternity in which God exists but with an entirely different mode of existence than that which exists in time. It is time, therefore, which allows and simultaneously restricts existence for created beings. It is the metaphysical ocean in which we swim and that provides us existential nourishment. Any prospective entry into the eternal requires an ontological transformation, an extraction from the cradle of time. Creatures are not capable of this on their own, indeed if at all. This seems to me an alternative way of making Smolin’s point that we are not intellectually permitted to think of ourselves outside of time. This is equivalent to presuming either that we do not exist or that we are divine. Also, keep in mind that for Plato numbers are eternal forms. When he says “according to number” he is not assigning numbers to moments but moments to the eternal scale of numbers. The “image” he refers to is one of these eternal forms, numbers. Thus time is not a measure of change. It’s not a measure of anything at all. It is something sui generis, that is, entirely of its own sort. This too is implied by Smolin. Perhaps it might be productive to think of time as a primal force through which change occurs. Just a speculation.

[Trevor · Rating 5 out of 5]

I found this book deeply interesting – but I am going to start by saying a couple of things about my level of expertise in relation to this subject. Mostly, that I have none. I suspect, despite this guy being remarkably clear, that I still only understood about half of what he was saying. My having said this will probably mean someone will say in the comments below ‘This is the sort of review I would expect from someone unable to solve even the simplest form of Schrödinger’s equation, do you even know what a linear partial differential equation that governs the wave function of a quantum-mechanical system is? Why write a review if….’ And there is something to this, as this book is highly controversial, even for those who can solve Schrödinger’s equation.

It is controversial because the author thinks physics (cosmology in particular) is in crisis. I think a world view that needs to create an infinite number of universes that cannot interact with each other just because someone sneezes is probably ‘in crisis’. In fact, crisis probably doesn’t really cover it.

In large part, this book is seeking to make a fundamental shift in how we understand the universe. Like Plato, we like to think that there are timeless laws that govern the universe, and even if we don’t agree so much with his ‘world of forms’, the search for a theory of everything that will explain all aspects of the universe from the big bang until the cold death of the universe is something scientists hope they will one day be able to express in an equation they will be able to fit onto a t-shirt. The author of this book is not convinced that is ever likely to happen.

The main reason why he is so convinced is because, unlike many other physicists, he believes that time is a real and necessary component of the universe, not just some bizarre prejudice attributable to the limitations of human cognition.

When I read ‘A Brief History of Time’ I had thought that time was something physics had come to accept as a taken for granted sort of thing. But then I read ‘The Fabric of the Universe’ and it wasn’t so clear that Hawking’s arguments were as widely accepted as I might have assumed. Basically, for Hawking, time is real because the direction of time is set by entropy and so while there is nothing in the fundamental equations of physics to say time is going forward rather than backward – entropy makes ‘going backward’ essentially impossible.

I was expecting this book to argue something similar – but he doesn’t. His argument is that time is actually the most fundamental aspect of the universe, rather than merely a property of entropy. And he argues this in of Darwinian sense.

I mean this quite literally. He sees the universe as something that ‘evolves’ and that goes not just for the large and small structures of the universe – but also for the laws of the universe too. In fact, he sees the laws as less ‘holy writ’ and more like ‘common law’ – that is, law that is based on precedent. I’m not going to pretend that I understood this part of his argument enough to really explain it, you’ll need to read the book yourself for that, but this then lead to some interesting things on entropy I hadn’t thought about before.

Entropy is why we grow old. It is the idea that things that are in highly ordered states tend, with time, to become highly disordered. One example is a bottle of perfume in a large room. Before you remove the stopper all of the perfume molecules are in the highly ordered state of being inside the bottle. But if you forget to put the stopper back the perfume will slowly evaporate and ‘drowned the sense in odours’ as TSE would say. When all the perfume was in the bottle, you had low entropy – now that the room smells like a brothel, you have high entropy. Time is this arrow from low to high entropy, from order to disorder.

Now, the thing this guy says is that the universe has been around for over ten billion years. That quite a lot of time. So, we should be seeing some of the effects of entropy taking over by now. You know, entropy is basically disorder. So how is that playing out in the universe as a whole? Well, he says that on every scale we are actually seeing structure evolving – that is, the universe seems to be becoming more complex with time, with more structure, rather than becoming more uniform.

At one point he said that galaxies and solar systems are anti-thermodynamic. That is, if you add energy to these systems the planets will move further from the sun, slow down and therefore they will effectively ‘cool down’. And this anti-thermodynamic property has consequences in providing structure to the universe.

The precedent view of the development of laws also has consequences. Not least in that the laws are more likely to be apparently more fixed if what happens is repeated over and over again. So, the quantum states that a hydrogen atom can take, given most of the universe is made up of such atoms, are fairly well set down, whereas there is only one of you in the universe, even if you are a twin, and this is particularly the case if your situatedness in time and space is important for your being – which it inevitably is. This idea of situatedness, he doesn’t actually call it that, but that’s how I will remember it, pervades the book.

And that is the point. Towards the end he stresses the impossibility of recapturing time, of perfectly reliving a moment from the past. This is because each moment is fundamentally different from the last. This is something that I’ve always liked of Pina Bausch’s choreography – that even when it is full of repetition, she says doing the same thing twice is never doing the same thing twice – it always means something different the second and subsequent times.

I think I like this guy’s universe, I think I like it much more than one held together string or full of multiverses where every decision we make creates yet another whole universe where the other choice plays out. But I guess the universe doesn’t really care about my preferences.

[Brian Clegg · Rating 5 out of 5]

As I write this we are a third of the way through 2013 (time is important here) and I can say with hand on heart this is the best popular science book I have read all year.

Lee Smolin’s book is largely accessible (more on this later) and simply mind-boggling in its scope. What he does here is take on time, and specifically the position of time in physics. Even taken as a simple book on time this is brilliant. The fact is, the majority of books that claim to be about time tell you nothing. It’s striking that A Brief History of Time tells us that amongst a list of deep scientific questions that have answers suggested by ‘Recent breakthroughs in physics, made possible in part by fantastic new technologies’, is ‘What is the nature of time?’ But you can search the book from end to end for any suggestion of what time is or how it works. There is plenty on how we observe time, and how interaction with matter can change these observations, but nothing deeper.

Smolin gives what is, for me, the best analysis of the nature of time from a physics viewpoint in a popular science book I have ever seen. He goes on to describe how most physicists consider that ‘time does not exist’, and comes up with an approach where time becomes real in physics. Now I do have one issue with Smolin here. He says that amongst his non-scientific friends ‘the idea that time is an illusion is a… commonplace.’ This is garbage (or at least his friends are non-representative). The vast majority of people who aren’t physicists or philosophers would say ‘Of course time exists.’ However, Smolin sets off to first persuade us it doesn’t, using the most common arguments of current physics, and then to show how this is a mistake.

In fact, I think the reason most people wouldn’t agree is because it isn’t really true that modern physics says time doesn’t exist. What it says is that the idea of time as a moving present that heads from the past into the future isn’t real, and that there are plenty of concepts in physics like natural laws that appear to be outside of time, and so time isn’t as fundamental as people think. Nor, relativity shows us, is it absolute. This isn’t the same as something not existing or being an illusion, and I think the physicists who use this label have spent too much time talking to philosophers. Dogs aren’t fundamental to the laws of physics, but this doesn’t mean they don’t exist.

Nonetheless, current mainstream physics does prefer time to be kept in a box – and this is where Smolin breaks out. He shows us that pretty well all of physics is based on the idea that we are dealing with closed systems, where in reality there is no so such thing – meaning that it is quite possible that pretty well all existing physics is just an approximation. And he comes up with a mechanism where time, something that actually ticks by and has a universal meaning, can exist (though at the expense of space being quite so real as we thought).

In doing this, Smolin will have irritated a whole lot of physicists. Some will simply not agree – any string theorists, for example, would dismiss his loop quantum gravity viewpoint. Many others will simply not be able to cope. Physicists are, on the whole, a fairly conservative bunch (with a small ‘c’) – they aren’t very good at coming with radical shifts in viewpoint like this. Of course this doesn’t make Smolin right, but it is a fascinating bit of speculation.

The book isn’t perfect. Smolin’s writing style is workmanlike, but suffers from too academic a viewpoint – he doesn’t have the common touch. Oddly, it’s not so much that he baffles us with science, but rather he baffles us with labels which don’t have enough science attached. He has a tendency to use terminology and then say effectively ‘but you don’t need to know what that’s all about.’ I think popular science is much better if you avoid the jargon and instead explain what lies beneath. Also he uses really scrappy hand-drawn illustrations that I suspect are supposed to make them look more friendly and approachable, but actually makes them practically incomprehensible.

These are minor moans though. Whether or not you agree with the physics, this is a book to get you thinking, awash with ideas and totally fascinating. It isn’t the easiest popular science book to understand – it is very much of the ‘read each sentence slowly, and some times several times’ school, yet it is a superb contribution to the field that really puts that cat among the pigeons. Three cheers for Lee Smolin who is, for me, apart from lacking that common touch, the nearest thing we have in the present day to the late, great Fred Hoyle.

Review first published on www.popularscience.co.uk and reproduced with permission

[Gendou · Rating 2 out of 5]

There is something essential about the Now which is just outside the realm of science.

Smolin argues that time is real, because he experiences it, as a sequence of moments. He claims this is evidence not accounted for in the standard Newtonian paradigm (i.e. Plato's timeless mathematical world). He lumps both Quantum Mechanics and General Relativity under this paradigm, and, as it happens, ALL mathematical models that have time written down as a coordinate system!

Throughout the book, Smolin employs the Leibniz's Principle of Sufficient Reason, over and over. He doesn't seem to realize that this principle is the undoing of his central argument. This principle states, "For every proposition P, if P is true, then there is a sufficient explanation for why P is true."

Neuroscience provides a sufficient explain, based on the "timeless" physical laws of chemistry, to explain how people experience time as a succession of moments. Namely, time is governed by the firings of brain neurons, regulated by the accumulation and then purging of charged ions called neurotransmitters. This is a type of clock, not unlike any mechanical clock, and gives rise to the subjective experience of the passage of time. No dualism required.

Here in the real world, it is always some time, some present moment. No mathematical object can have this particularity, because, once constructed, mathematical objects are timeless.

Smolin spends much of the book addressing and attempting to dispel the myth that time is an illusion. I see this as him sinking down to a base, impatient philosophy. There is this strange, unscientific view that things are either "real" or "emergent" which plagues physics.

In truth, a thing can be equally real, regardless of wether it happens to be emergent or fundamental. In quantum physics, the word "real" means it observed to happen 100% of the time. In metaphysics, a component of nature is "real" only in context of a theoretical framework. Theories can remain viable, to the point that we accept them as true, but aren't proved true. This is basic science philosophy!

The fact that we can model spacetime as a 4-dimensional, unchanging object in General Relativity doesn't undermine the "reality" of time. It may mean General Relativity isn't easily compatible idea of laws that evolve in time. For example, a new theory might introduce some non-linear effect that makes a 4-dimensional model incomplete. But that doesn't mean the time dimension, in General Relativity, is unreal.

Smolin makes a similar argument about Quantum Mechanics. He says that quantum mechanics is incomplete because it does not model the observer or the whole universe. These are true limitations on Quantum Mechanics, but demanding that nature be described, at once, in totality, by any theory, is unjustified! Smolin throws Quantum Mechanics under the bus to try and support his opinion about time. It isn't convincing.

The main message of this book is that ... time is real and laws evolve.

Smolin has an awesome idea, first printed in his excellent book The Life of the Cosmos. He proposes that the laws of nature evolve by small incremental changes, much like biological evolution. New universes are "born" by the formation of black holes, and they inherit, with small mutation, the laws of nature from their "parent" universe. This is the only example I have seen of true application of the Anthropic Principle.

But this book doesn't propose any different way for the laws to evolve. There are lots of new arguments from Smolin, but they are all squishy, philosophical, and metaphysical nonsense. Metaphysics is important, but Smolin hasn't provided anything new and good here. Just new and bad.

Smolin overviews crackpot stuff like the Hard problem of determinism, Shape Dynamics, Albino Squirrel, the Meta-laws Dilemma, Barbour's "heap of moments", hidden variables in Quantum Mechanics, subjective "qualia", and Boltzmann brains, both of which are fascinating, but ultimately useless. These aren't really worth addressing here, but if anyone's curious about one or more of them, I will happily post details.

He ends the book with an out of place admonition about how humanity should respond to global warming. Kinda lame.

[Nick Wellings · Rating 4 out of 5]

Lee Smolin's 'Perimeter Institute' in Waterloo Canada sounds like a pretty happening place. Bright young things collaborate on foundational issues in a multimillion dollar purpose built building where the researchers demanded and got full length floor to ceiling blackboards*, glassboards, whiteboards, blackboards in the lounge areas, probably even on the coffee machines and in the toilet cubicles too, which is a good thing I suppose because physics is in trouble and these guys need all the scribbling space they can get.


I GOT 99 PROBLEMS...

Physics has deep problems right now. Shove a pacyderm in a room at a physics party and watch them try and skirt round it.

This gentle mammal wears the colours General Relativity and Quantum Mechanics. Physics knows that at the core of its success are two mutually incompatible theories. General Relativity is really good for large scale things like how stars work and how time travel might not be possible and how clocks work under acceleration. Quantum mechanics is great at describing the really small, the submolecular world of the quantum.

Physics has been trying to marry these up into one theory for about seventy years and we haven't got too far.In some ways this is because physicists are clever and generate multiple ideas for a few problems. This is natural part of how science evolves. We're definitely at some kind of boundary, banging our heads on problems that are only slowly yielding to analysis. Enter Lee Smolin.

STRUCTURE:

Part one of Time Reborn has to build the groundwork for his theory and Smolin's presentation of the history of physics is breezy and good and to the point. As mentioned by other reviewers though, some illustrations are a bit poor. (Compare any in Greene's output or even Penrose's own hand drawn illustrations in 'Road to Reality' for example.)

Along the way Smolin uses a few Leibnitz ideas, the identity of indiscernables and the principal of sufficient reason. These are his philosophical primitives and his foundational maxims and he uses them a lot to gauge whether his ideas are right. I don't know enough about Leibnitz to know if PSR has been thoroughly demolished in the analytic turn of philosophy of the 20th Century but the theory of indiscernibles seems pretty irreproachable on a naive take. (Of course I know that philosophers love to puzzle these things out and recognise that again, 20thC logic can rigorise and interrogate a lot of these seemingly common-sensical ideas to show them as specious, groundless or only applicable in certain cases (I.e. non privileged and not admitting loose application to physical theories.) So whether Smolin's application of those rules is logically rigorous, or if his misapplies them is outside my skill area.

Part two explains his theory proper.

THE PROBLEM OF TIME

Crucially for Smolin, the majority of these theories have inherited a Newtonian legacy: They are all time independent or are formulated as if time does not exist. Smolin says this is a big impediment to progression. He doesn't like this. His is an attempt to get back to basics. Let's privilege time, he says, because it solves a lot of problems. To admit that time exists is the most sensible way out for physics.

So: arrow of time? No problem because if physics admits time exists, the arrow of time is not a problem any more. There is no contradiction between the formulas we use which don't need time, and the world we live in, which does.

So too, we don't need to invoke Anthropic Principle.

So too can we make Quantum mechanics less of a probabilistic oddity. However, to do so seems to bring back pernicious problems of non locality and 'spooky action', but Smolin gives us a cute way out of this by suggesting non locality seems true on a global scale but on his geometrically determined spacetime, the building blocks can be both very close and far away. (I find this idea of geometrically constructed space naively and intuitively appealing. I think if anything, God was a geometer before he was a philosopher... Lord knows how well ever prove that these tiny vertices, graphs and quantum nets are right.)

Smolin reminds us that all theories to date are weasly, our best approximations of the world we observe, and even our observations and experiments are calculated to reinforce this. He also has interesting things to say about symmetry as a component of theory (avoid it, he says, as it is a misleading principle). Further a lot of these theories have a lot of explanatory power but no method whereby we can test them, and hence no falsification potential. Bad news if you're concerned for the Truth of your theory.

[For those interested Page 248 is a nice graphic explaining the dilemmas physics faces as Smolin sees it.]


PROBLEMS WITH TIME REBORN

Smolin's project is not without a few issues though.

To privilege Time he must downplay space. He has to work contrary to General Relativity. He suggests space emerges from his 'Graphity' and that its naive appearance to us has misled us to overesteem its place in our physics, but he suggests that toy models of Quantum Graphity can have space as an emergent property. Conveniently he explains how the model can also be shown to generate a universe in the manner of a Big Freeze (geometrogenesis) which also neatly might explain distribution of Cosmic Mirowave Background radiation. (Such emergent spacetimes are not new, most recently Maldacena suggested a 'holographic' model where our world appears on a boundary of a special type of spacetime - the duality of AdS/CFT correspondence - which I think is still arXiv's most cited HEP paper ever.)

To his credit, Smolin acknowledges the above conflict with Relativity. His proposed solution is clever.

On a personal level, see above for my gut reaction against using Liebnitz to discuss 21st Century physics.

Smolin also has cause to suggest a Principle of Precedence to buttress his ideas in QM. This seemed really rickety when given in natural language: the idea is that observed Laws are merely habituated pattern based on past history. However, Smolin does pretty well in the 'Quantum Mechanics and The Liberation Of The Atom' section to suggest that a sum of precedence is all that is a character of natural law: one admits its non-eternalism, in effect one temporalises timeless Law, and in so doing admits a degree of freedom. This is critical because Newtonian determinism can still obtain where necessary and QM can be truly freed from probabilities and sums of histories.

My opinion:

On the whole I liked the book. The prose was solid and only a few times did I have a 'what??' Moment of bafflement. In addition I learned about Quantum Graphity, Kocher and Conway's Free Will theorem and I learnt about Grete Hermann and how she showed von Neumann's objection to hidden variables was based on a hole in his proof and how this pretty monumental thing was ignored for about 40 years till Bell found it again.

Time Reborn is more a rallying call for open minded pursuit of physics, weight given to Smolin's pet ideas naturally. I can't say if they are true or not as I lack the mathematics and physics background to even begin to question anything his team writes. (Therefore its a good thing in a way that the book has not one equation in it as far as I could see. None! Nada! Zip! All the same I did miss this a bit as even I can see some equations are elegant and powerful.)

Naively the ideas in Time Reborn feel more right than say string theory which has been languishing in the doldrums for nearly 30 years now but we still don't know, in the words of Peter Woit if we are 'even wrong'. The answers will be worked on still by the next generation, some of whom are being trained by Perimeter's outreach and engagement team even now, and probably for time to come. Best keep scribblin', kids.




NOTES:

* Smolin semi-jokingly tells us that the researchers petitioned the architects to increase the number of dimensions in the place to maximise interaction by raising the neighbour quotient, the idea being that a guy in the basement interacts less with a girl on the fourth floor, so that the number of well placed researchers next to each other could be optimal. (Ain't maths cool?) Sadly the architects neglected to help but Smolin says they did offer to cover the entire building inside with slate and glass so the guys and girls could scribble like savant-toddlers all over everything.

[Rohan · Rating 5 out of 5]

This book was extremely tough for me to understand. I took almost 45 days to finish this one simply because I wanted to make sure I understand everything that Lee Smolin was talking about. Some of the concepts were too complex for me and took me few days of web research to process. But on the whole, this book was a philosophical experience for me.

Even though it sounds simple, the whole concept of doing 'Physics in a Box' was mind-boggling to me in the initial chapters. As the chapters went by, it was an eye opening experience for someone like me who recently (an year back) found interest in Physics. Before this book, the kind of books I read were almost meant for laymen and they never really presented underlying concepts about which Physicists are actually researching and publishing every year. This book closed that gap for me. Even though I cannot say I understood each and every point mentioned in this book in its entirety, I really did enjoy getting so up close with the Philosophical and Scientific thoughts of a Physicist. The good thing is that Author has a great list of references for almost all the previous research done on various topics presented in this book.

While using (and not using) the concept of time, the Author covers the history of important theories in physics as popularized by Newton, Boltzmann, Leibnitz, Einstein and others and goes on to talk about Inflation, Duality, multiverses, baby universes, loop quantum gravity. Lee Smolin proposes interesting solutions to many of the problems that physics faces today. I personally felt enlightened to know about these particular theories/concepts: Causal Dynamical Triangulations, Quantum Graphity, Spin-Foam Models, Shape Dynamics.

It was amazing to know how speculative the field of Physics has been over the years and how until a cosmological theory is proved wrong by any doable experiment, it is assumed a serious possibility no matter how improbable it might sound.

Some of the most important conclusions and statements in this book are never quite highlighted and this is the only complaint I have. Even this is understandable because the book does talk about lot of them (important things).

This one is a great read. Even though it is difficult to understand at times and even though the writing style is a little too academic and research oriented, 'Time Reborn' is a genuine attempt at trying to popularize the notion of time with respect to Physics and its future.

[Simon Mcleish · Rating 2 out of 5]

Annoyingly poorly argued book about moving beyond current ideas of time in physics, with some interesting ideas. Smolin spends most of the book discussing the "timelessness" of modern physics, both relativity and quantum mechanics, without ever properly defining what he means by the term. It's clearly not whether the theories have a time parameter in them, but it seems in some places to mean that time is treated as a whole, as it is in the "block universe" of relativity, and in others that the laws of physics themselves do not change. Smolin thinks we need to look at changing laws in order to fix some of the problems with these theories, but his ensuing discussion of what form these changes may take is infuriatingly inconsistent and contains logical flaws (there is a particularly glaring one on p.163 of this edition). Sometimes he seems to be envisaging laws changing only at the creation of a new universe (if his earlier ideas about black holes in one universe containing new generations of universes inside them is adopted); at others, he seems to be talking about changes between distant parts of the same universe or over time, again in a single universe. Where was the editor when they were needed?

[Paperclippe · Rating 2 out of 5]

I'm... not so sure about all this.

I'm going to preface this by saying I was completely whacked out on cough syrup thanks to a miserable month-long cold for almost the entire duration of my listening to the audiobook of "Time Reborn," and that may have colored my opinions a bit. Also, a major disclaimer: I am not a scientist by any measure, nor am I mathematically adept beyond a high school level. However, I spend most of my time being a general nerd and have decimated the popular science section of every bookstore and library within a twenty-mile radius of my home, and then some. With that under consideration, let's continue.

First, I do want to say that the reader of the audiobook was amazing. This was one of the first non-fiction and especially scientific audiobooks that I have listened to that, having not been read by its author, still contained a huge amount of personality. The tone of voice and rhythm really made things relatable and easy to follow.

Which makes the fact that I'm really not buying into Mr. Smolin's arguments here all the more notable.

I had previously attempted to read "The Singular Universe and the Reality of Time" coauthored by Lee Smolin and Roberto Mangabeira Unger, which could be considered the "technical" version of this "popular" science book, and found that I just really couldn't get into it. In fact, I never even made it to Smolin's section, because the first half of the book, authored by Unger, contained a lot of assumptions with which I wasn't really willing to get on board. Having now listened to Time Reborn, I wish I'd tried a little harder, if only because then I might have a more cohesive reason as to why I find the arguments in the book so... wishy-washy.

Thus begins the actual review of Time Reborn:

I feel like Lee Smolin might be a bit of a terrible hypocrite. I'm going to state up front that I'm not a believer in string theory, because I find that it tries too hard to be beautiful while simultaneously ignoring the ugly fact that there is absolutely no evidence for - or against - it. It just kind of... is, and is meaningless, and has no real bearing on anything at all. I'm looking at you, Brian Greene. Anyway, it took me until the last 10% of the book to realize - and I think on purpose - that Lee Smolin was basing most of his arguments from a place where string theory is a given. And that's pretty much how the whole book is written. I noticed it at first when he gave a really unclear definition of what the anthropic principle was, defining it in such a way that suited his means, and was not entirely incorrect, but was far from concise and was farther from the definition I'd seen cited in a hundred popular science books before this one. It may have been the cough medicine, but I found his definitions of many things I previously thought I understood more confusing than helpful. He also had the nasty tendency to, whenever the subject broached something technical, either to say that he wouldn't bother getting into that here or would explain it in such highly technical and impenetrable language that it was nigh impossible to understand without a physics dictionary at hand. It felt very much like a magician pulling the wool over the eyes of the unwitting subject. Being at least reasonably well-versed in popular cosmology (which is to say, knowing, if only just, that the rabbit was in the hat the whole time), this felt incredibly dishonest to me, as did the fact that he would dismiss opposing theories like the Boltzmann brains, using "probablies" and "most likelies" and then writing them off, but allowing his own theories to slide through on those same hairs-breadth.

There were some good points in this book, but the specifics of them are completely blotted out by how much I felt like I was being strung along (har har) by someone at a dinner who has a pet project and wants to tell you all about it and who talks over any objections you might raise, if you'll just let him finish. It was so irritating that even the fact that I'm not sure I even disagree with the main premise of this book - that time is real and unidirectional, and not a construct of consciousness, but an active participant in the fundamental structure of the universe - only nets it two stars. Barely. The more I think about it the more I want to take one away, but I'll let it stand for now.

Was it worth a listen? Yes, but only to see the other side, hear them out, and then allow one's self to step back, take a deep breath, and confirm that nope. I'm still not buying it.

[Rama Rao · Rating 2 out of 5]

The cosmic evolution

In this book, physicist Lee Smolin argues that time is a real phenomenon, and suggests that the laws of physics evolved over cosmic timescale, and the current laws came into existence because of cosmological natural selection like biological evolution. One of the principal reason is that this theory avoids the use of anthropic principle which claims that the universe came into existence with current laws that support living systems, but for Lee Smolin, since this idea is not scientifically falsifiable, therefore that it is not scientific. The book is philosophical than physics since it lacks scientific explanations as to why cosmos was born with different laws than we have at present. There are no scientific explanations except for ideas of an imaginative thinker.

There is a conflict between relativity and quantum mechanics with regards to the concept of time. It is measured and malleable in relativity but remains as background (and not an observable) in quantum mechanics. Time emerges mainly from the second law of thermodynamics, a law that is statistical in nature which does not depend on the nature of individual particles but the behavior of a collection of particles. Time is not an irreducible element or concept required to construct physical reality. It is a human construct that differentiates present from our memories of the past.

According to Einstein’s theory of relativity is that there is no absolute time, no absolute space, but everything is relative. This is a block universe, made of four-dimensional space-time (three space and one-time dimensions) structure where time is like space, in that every event has its own coordinates, or address, in spacetime. The malleability of space and time mean that two events occurring far apart might even happen in one order when viewed by one observer, and in the opposite order when viewed by another. Hence, time change really is an illusion according to relativity because there's nothing that's changing; it's all there, past, present, and future. But the laws of quantum physics are symmetric and reversible, hence that time could have moved in a backward direction or in the forward direction. For example, according to the ‘big crunch’ theory, the universe is expanding since its birth, but at some time in future it will stop expanding and starts contracting back in on itself. This will require time to flow backwards, and the cosmos will collapse into a big crunch into its initial state when big bang happened.

Physicists like Sean Carroll, Andreas Albrecht, and John Polkinghorne believes that the flow and direction of time are real but do not claim that it permits the evolution of laws of nature over time. But physicists like Julian Barbour, Max Tegmark, Carlo Rovelli, and philosopher J. M. E. McTaggart are strong proponents of time being an illusion. Lee Smolin considers that space is an illusion and only time is real and paramount to the way the universe evolved to its current state.

[Karl-O]

An interesting talk by Smolin, apparently of the ideas outlined in this book, can be found in this link, with an equally interesting comment by Sean M. Carroll:

http://www.edge.org/conversation/thin...

[Darren · Rating 4 out of 5]

The Controversy

Before I can even begin a review of the book, I do feel that a bit of background must be provided on the scientific context in which this book appears. Smolin is a prominent if controversial figure within the theoretical physics community, well known for work on the cutting edge of our knowledge and promoting that work directly to the general public well before it has become widely accepted within the physics community itself.

Back in the 1990's, he published a work that focused on the idea that the universe (or rather a series of reproducing universes) evolved over time. The basic idea of Smolin's proposal for an evolving universe is that a universe can create other universes through the creation of black holes, meaning that it's highly probable that the universe we're in is one that is optimized for the creation of black holes. As I said, he's controversial!

Then, in 2001, he wrote The Three Roads to Quantum Gravity, which argued that differing approaches to the problem of quantum gravity (string theory, M-Theory, and loop quantum gravity) could work together to come up with an underlying theory of quantum gravity. This was a controversial stance within the physics community because string theory and M-Theory are both highly prominent theories that have been developed and worked on by a large number of scientists over the previous couple of decades ... while loop quantum gravity was an approach which Smolin himself had helped to develop and pioneer, but which had nowhere near the same amount of acceptance within the theoretical physics community. In other words, The Three Roads to Quantum Gravity was seen by some as an attempt to artificially elevate Smolin's own pet theory to equal status with the prevailing approach to quantum gravity, even though many theoretical physicists did not believe it earned that status.

In his 2006 The Trouble With Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next, Smolin goes even further, claiming that the approach at the heart of string theory is fundamentally harming physics itself. In this book, he outlined 5 great problems in theoretical physics which, while still a controversial list, basically hits the mark of a number of things that theoretical physics really can't explain without speculating well beyond the foundation provided by the current evidence. He points out that string theory has failed to solve this problem ... or even to anticipate that some of these problems would arise. Needless to say, for a community that had spent three decades investing time, energy, and resources into developing string theory, this was not a welcome book, and the "string wars" have certainly had some memorable exchanges, even informing romantic breakdowns on television's The Big Bang Theory.

The current book that I'm about to review is just as controversial ... if not moreso. I found it an engaging book and am certainly recommending it, but it should be read with a great deal of care and skepticism. As I will discuss in the review, many aspects of Smolin's approach involves assumptions of his own which are, at best, no more certain than the assumptions he is trying to argue against.

Smolin's "Crisis in Science" Revisited

In Time Reborn: From the Crisis in Physics to the Future of the Universe, theoretical physicist Lee Smolin of Canada's The Perimeter Institute is once again taking a bold new scientific vision directly to the popular audience. This time, he's tackling the notion of time itself. In his stance, the current scientific understanding of time is that time is not "real" and he feels that's a fundamental flaw, one that could be corrected by taking time serious as a real quantity ... in fact, it would in his vision be one of the only real quantities, with the rest of the universe - indeed the very laws of the universe - evolving within time.

What he suggests is that instead of laws of physics that eternal and everlasting, physicists instead treat physics in a more "relational" way, in which they are viewed as dynamic systems of behaviors.

A key point in this is that Smolin himself is candidly honest that he's not presenting such a theory himself (at least not at this time):

"The purpose of this book is to suggest that there is another way. We need to make a clean break and embark on a search for a new kind of theory that can be applied to the whole universe -- a theory that avoids the confusions and paradoxes, answers the unanswerable questions, and generates genuine physical predictions for cosmological observations.

I do not have such a theory, but what I can offer is a set of principles to guide the search for it."

Why does Smolin believe that such a theory is necessary? In part, it is an argument not rooted so much on science itself as on the field of natural philosophy and specifically grounded in the work of philosopher Gottfried Leibniz.

The Principle of Sufficient Reason

Leibniz is well known in scientific circles for having independently developing calculus at the same time that Sir Isaac Newton was also doing so, but Leibniz's body of work as a philosopher is far more well-developed than that. Specifically, he held a belief that all things that happen in the universe have an exact cause. Leibniz was deeply religious, so his stance was basically that God had a reason for every choice he made and that none of these choices could be arbitrary. Smolin does not rely on a divinity for his argument, but he is willing to accept as a fundamental principle that everything that happens has a reason for that thing happening as opposed to something else, and given knowledge of all of the factors going into the result, there would be no other possible outcome.

This of course seems like a perfectly reasonable ... except that the last century's work in quantum physics has drastically challenged this notion. In situations such as the quantum double slit experiment and the EPR Paradox, it really seems as if things happen on the quantum level with a given probability. In the customary formulation of the EPR paradox, for example, when a particle decays into two particles of opposite spin, there is really no way to determine prior to the event which particle will have which spin. The best we can do is estimate the probabilities. And, in our understanding of quantum physics, this isn't just a matter of us missing some information ... there's actually no way to tell which is which.

Smolin rejects this conclusion, insisting that there must be something fundamental that quantum physics has missed. He is a proponent of a hidden variables theory, even though most physicists agree that Bell's Theorem has really ruled out the possibility of any such theory. At least, to date, no one has come up with one that really works.

Cosmological Fallacy

Having embraced Leibniz's stance, Smolin introduces the idea of a cosmological fallacy, which he defines as:

"It remains a great temptation to take a law or principle we can successfully apply to all the world's subsystems and apply it to the universe as a whole. To do so is to commit a fallacy I will call the cosmological fallacy."

Now, this takes some parsing out to really figure this out. First of all, realize that all of cosmology (and astrophysics, for that matter) involves taking results we observe on Earth and extending them to apply to distant parts of the universe. In other words, we basically assume that the physics we observe here on Earth and in our nearby region of space applies equally well to distant regions in space. In other words, our world and region of space are not particularly special. This is a principle called the Copernican principle. Smolin does not seem to be arguing against this practice.

However, the whole reason that we develop these findings on Earth is through testing them with experiments that are carefully controlled, so we know as precisely as we can which influences are caused by which components of the system. This cannot, of course, be done to the universe as a whole. Smolin rightly identifies this as a major problem in cosmology. We have a sample of only one universe, after all.

But what about the multiverse, you ask? Smolin views this as an attempt by physicists to create a hypothetical set of possible universes, so that applying normal methodologies seems valid. But, since we actually can't observe these universes, I admit that it's a highly suspect conclusion.

Smolin's Science

Despite his goal of treating time as "real" in a new way, Smolin is not suggesting that any current scientific evidence is incorrect. In other words, he's not saying that relativity itself is wrong when it talks about the fluid nature of time, only that there might be alternative explanations or theoretical structures which would yield the same correct results as relativity but would be a bit less relativistic in how it talks about time. (He discusses one approach in the book, called shape dynamics, at a very high level.)

My Conclusion

Smolin makes a compelling but not airtight case for problems with the current understanding of time, but repeatedly while reading the book I felt like Smolin was trying to shoehorn the laws of physics into his own preconceptions of what they should be. We certainly have strong intuitions about time and Smolin's approach involves taking those intuitions more seriously than the mathematical results we've found thus far in physics, which have suggested that time is fluid and that the arrow of time itself is an artifact of entropy. I think this would be useful book for those interested in gaining a deeper understanding of the scientific issues related to time, but I really think that it should only be read alongside Sean Carroll's From Eternity to Here: The Quest for the Ultimate Theory of Time, which presents the more general consensus understanding of time within theoretical physics. Reading Smolin's book alone, without a deep understanding of the physics involved, will very possibly lead the reader to thinking that the flaws are more serious and pervasive than they may actually be.

The above review is from: http://physics.about.com/od/physicsbo...

[Randal Samstag · Rating 4 out of 5]

From my blog post on time here:

Smolin’s 2013 book, Time Reborn, covers much the same ground as Adam Frank’s book, About Time, telling the story of why classical physics banished time and (unlike Frank) why it needs to be considered as real. He is in definite opposition to Newton and Einstein’s expulsion of time from physics in their absolute and block universes. He maintains that physics needs to embrace a cosmology that respects the apparent irreversibility of time, the so-called arrow of time.

Just one concept Smolin develops is his question as to why the universe that we live in is so improbable, full of highly ordered things, like stars and us. He makes a distinction between a Leibnizean universe in which the “law of the identity of the indiscernibles” flourishes and a Boltzmanian universe in which everything runs down according to the second law of thermodynamics. His preference for the Leibnizean version for our universe is based on the observation that the second law holds only for closed systems, while the universe in which we live is an open system through which energy flows. This leads him to the conclusion that time is very real and needs to be brought back into physical theory.

Much more could be said about this interesting book. Oh, look, Manny has already said it!

[Adam · Rating 5 out of 5]

A brilliant contrarian argument against much of the ideology (meta-physics) of contemporary theoretical physics, especially computationalism: the notion that "reality is what math feels like," as Max Tegmark famously put it--the neo-Platonic idea that mathematics is the ultimate reality and that the universe is finally a vast computation from a few simple algorithms. Smolin's underlying argument is that by taking mathematical models derived from isolating physical systems under study from their context and relationships, physicists have developed powerful models with elegant mathematics--but because the systems under study aren't really isolated, the models are only approximations. That's why, Smolin goes on to say, time appears simply as one optional parameter in physical calculations based on math that is time-reversible--whereas everyday experience and the Second Law of Thermodynamics tell us that time is both real and irreversible. On this basis Smolin suggests new directions for physics based on hypotheses that might be experimentally testable. A wonderful counter to the also excellent works of Brian Greene and Sean Carroll, exponents of the mainstream view on these issues.

[Troy Blackford · Rating 3 out of 5]

This was an interesting book, but I feel like it makes it quite clear why concepts in physics the author doesn't endorse - namely string theory - are more popular with the public than the ideas expressed here: the ideas presented are frequently impenetrable and the writing seems to jump from topic to topic without making it very clear what is meant. I mean, it would probably help if I understood physics better, but that's precisely what I'm saying: it's been easier for me to at least feel like I am understanding what authors like Brian Greene and Michio Kaku are saying when they discuss their ideas about physics than it was for me to understand Lee Smolin. Still, I'm glad I read this book.

[Ryan Curry · Rating 5 out of 5]

I had been meaning to read this book for quite a while before I finally picked it up. I can confidently say that Lee Smolin is one my favourite authors when it comes to popular topics in physics. He formulates his ideas in a way that I just can't seem to find elsewhere.

I thoroughly enjoyed Time Reborn, and have a lengthy list of other books to investigate thanks to the endnotes and bibliography.

Throughout the book Smolin explores some novel concepts in cosmology and does a very good job bringing everything back to the reality of time.

I think that anyone interested in the notion of time should read this book.

[Forrest · Rating 4 out of 5]

. . . on second thought, maybe Smolin is wrong and existing theories were right all along?

The book's not closed on this one yet.

[David Dinaburg · Rating 4 out of 5]

Tossing off the word “crisis” is enough of a signifier to fulfill the burden of “shocking-subtitle” that most non-fiction carries. The remainder of the subtitle in Time Reborn: From the Crisis in Physics to the Future of the Universe has the potential to be more egregiously hyperbolic but for the fact that most readers are unlikely to be current on the cosmological scuttlebutt. A theoretical physicist or cosmologist would not be having a first encounter these theories in a pop-sci book, so their actual knowledge of a crisis in physics is wasted. Time Reborn is for the layperson, so the subtitle has the air of a marketing catchphrase rather than an impactful phrasing of what is to come. Though, in the case of a short generic like Time Reborn, distinguishment—not significance—may be the goal.

Those burdened by the metaphysical presupposition that the purpose of science is to discover timeless truths represented by timeless mathematical objects might think that eliminating time and so making the universe akin to a mathematical object is a route to scientific cosmology. But it turns out to be the opposite.

The bulk of Time Reborn is a refresher course in physics so that the reader has the basic knowledge to understand how little time figures into modern theoretical physics. In fact, it is actively excluded. To put it back, you need to know—well, everything.

Mathematics entered science as an expression of a belief in the timeless perfection of the heavens. Useful as mathematics has turned out to be, the postulation of timeless mathematical laws is never completely innocent, for it always carries a trace of the metaphysical fantasy of transcendence from our earthly world to one of perfect forms.

What happens is the reader—the one that can be counted on as having almost no basic theoretical understanding—is walked through two thousand years of math and physics and is spit out on the other side completely ready to accept whatever current cosmological theory to which Time Reborn has spent the last 200 pages building. Within the framework of the history presented, the conclusions seems inevitable; it would take a reader that brings in far more outside information than I to feel confident in proclaiming how strong these modern theories of fundamental time are.

What Time Reborn does well is take a dense subject and inject interesting writing and clear vignettes to make physics unintimidating. Not once does the author talk down to the reader, nor needless complicate the subject in an attempt to academia-up the book. The fast-paced historical journey leads right up to the “crisis in physics” to which the seemingly alarmist—but wholly accurate—subtitle refers:

Most of what we know about nature has come from experiments in which we artificially mark off and isolate a phenomenon from the continual whirl of the universe....What Descartes, Galileo, Kepler, and Newton learned to do was to isolate little pieces of the world, examine them, and record the changes in them. They showed us how to display the records of these motions in simple diagrams whose axes represent the positions and times in a way that is frozen and hence amenable to being studied at our leisure.

In much the same way that social variables and personal intangibles have been diminished to fit within a mathematical equation that is computationally friendly, time has been scrubbed out of physics and math so that equations will function. They are approximations of the world, not definites, analogous to the way that the websites you click on are not you the person; within the framework of marketing engines, your clicks are how algorithms interpret—and corporations envision—you. You are become an equation built from tiny fractions of information, smashed together to provide workable—though woefully incomplete—data:

The notion of effective theories subverts some well-worn notions, such as the platitude that simplicity and beauty are hallmarks of truth. Since we don’t know what could be lurking at higher energies, many hypotheses of physics beyond its specified domain are consistent with one or another effective theory. So these effective theories have an intrinsic simplicity, because they have to be consistent with the simplest and most elegant way they could be extended into unknown domains. A large part of the elegance of general relativity and the Standard model is explained by understanding them as effective theories. Their beauty is a consequence of their being effective and approximate. Simplicity and beauty, then, are signs not of truth but of a well-constructed approximate model of a limited domain of phenomena.

Your facebook page—with its photos and multiple-choice dropdown boxes and “It’s Complicated” relationship status—is the simple version of you; the “math” version that computer algorithms can work with to increase their effective marketing. It isn’t really you, just a “well-constructed approximate model of limited domain”. So is there an offline, realworld version of physics that cannot be scaled up from the pageclick-esque data our mathematical formulae currently capture? Time Reborn drops this problem onto the head of quantum mechanics:

Quantum mechanics is not a theory so much as a method for coding how experimenters interrogate microscopic systems. Neither the measuring instruments we use to interact with a quantum system nor the clock we use to measure time can be described in the language of quantum mechanics—nor can we, as observers, be so described. This suggest that to make a valid cosmological theory we will have to give up quantum mechanics and replace it with a theory that can be extended to the whole universe, including ourselves as observers and our measuring instruments and clocks.

You cannot approximate a person en totale simply by extrapolating scraped data, and you cannot extend quantum mechanics from the micro to the macro, let alone to the cosmological.

Seriously. If you only had information about what someone does online, and absolutely no prior experience or knowledge of what a person is, what identity of “personhood” could you build? You almost certainly don’t have enough data points to get it totally right, but even the information you have might lead you to completely wrong theories. Maybe you’d see that someone bought shoes, so you’d assume they had feet. Unless you thought that shoes were, uh, some sort of house—like how a snail uses a shell—and then what would people look like? Assuming you knew what shoes were. Or feet. Or the act of buying. Is the universe a snail? Or bipedal? We can’t know, we just know it orders a bunch of shoes. Not that we know what shoes are.

There are many ways to think about the universe—online shopping analogies notwithstanding—and removing time has been a requirement for higher-level physical equations for centuries:

How could something be the cause of Earth’s motion around the sun if there is a different and equally valid point of view according to which Earth isn’t moving at all? If motion is relative, an observer is free to adopt the point of view that all motion is defined relative to him. To resolve this impasses and be able to speak of causes of motion, Newton proposed that there must be an absolute meaning to position. This was, for him, position with respect to what he called “absolute space.” Newton argued that it was the Earth and not the sun that moved absolutely.

No one has ever seen or detected absolute space. No one has ever measured a position that was not a relative position. So to the extent that the equations of physics refer to position in absolute space, they cannot be connected to experiment. Newton knew this and it didn’t bother him. He was a deeply religious thinker, and absolute space had a theological meaning for him. God saw the world in terms of absolute space, and that was enough for Newton. He would put it even more strongly: Space was one of God’s senses. Things exist in space because they exist in the mind of God.

Einstein did it, too, though without Newton’s piety:

The picture of the history of the universe, taken as one, as a system of events connected by causal relations, is called the block universe The reason for that perhaps peculiar name is that it suggests that what is real is the whole history at once—the allusion is to a block of stone, from which something solid and unchanging can be carved.

The block universe marries space and time. It can be pictured as a kind of spacetime, with three dimensions for space and a fourth for time. An event taking place at a moment of time is represented as a point in spacetime, and the history of a particle is traced by a curve in spacetime called its world line. Thus, time has been completely subsumed by geometry; we say that time has be spatialized or geometricized.

So our understanding of time and space changes to fit the current theories, all of which are simple enough and consistent enough to give physicists workable approximations of the world. But they cannot extend too far backwards, or too far forwards, or too big, or too small, because then things get weird. For example, you jump back to the big bang: everything in the universe is expanding outwards from this one event:

The electromagnetic arrow of time can also be explained by time-asymmetric initial conditions. At the universe’s beginning, there were no electromagnetic waves. Light was produced only later, by the motion of matter. This explains why, when we look around, the images the light carries gives us information about the matter in the universe. If we just went by the laws of electromagnetism, it could be otherwise. The equations of electromagnetism allow the universe to being with light traveling freely. That is, light would have formed directly in the Big Bang rather than being emitted from matter later on. In a universe like that, any images of objects that light carried away from matter would be swamped by the light coming straight from the Big Bang.

In other words, if everything originated in The Big Bang, then light originated there too. And we should all be blasted out by light. All the time. And maybe we are. Maybe our light is different light. But then, why didn’t what we’ve chosen to call light originate in The Big Bang? Light couldn't have begun at The Big Bang, or we'd be buried by it. So the universe changes over time. So it's possible time is more than an arbitrary construction. Got it.

Let’s go the other direction—not the beginning, but the end:

The simplest way to avoid the eternal dead universe would be if the universe had enough density of matter to stop the expansion and cause it to collapse. Matter attracts matter gravitationally, and this slows the expansion, so if there is enough matter the universe will collapse to a final singularity. Or perhaps quantum effects will stop the collapse and “bounce” the universe, turning contraction into expansion leading to a new universe. But there doesn’t seem to be enough matter to reverse the expansion, let alone counteract the tendency of dark energy to accelerate it.

So nobody knows what’s going on outside of our narrow sliver of experience. Time Reborn: Nobody Knows What’s Going On was probably the working title.

“Every experiment is a fight to extract the data you want from the unavoidable presence of noise coming from outside your imperfectly isolated system.” Science has gotten so good at ignoring the noise and working within our limitations that we’re starting to believe that the universe is as simple as the math that approximates it:

Math in reality comes after nature. It has no generative power. Another way to say this is that mathematics conclusions are forced by logical implication, whereas in nature events are generated by causal processes acting in time. This is not the same thing; logical implications can model aspects of causal processes, but they’re not identical to causal processes. Logic is not the mirror of causality.

At the end of Time Reborn, the reader will not have a pet cosmological theory or an answer to why quantum mechanics fails to scale up past the microcosmic level. Whether or not time will be reborn—if the relativities killed it off in the first place—requires an understanding of the many competing theories of time as an concept:

We speak easily of “here” and “there” while believing that near and far objects are equally real. So some philosophers argue that “now” and “the future” are not really very different from “here” and “there”; they all denote a certain perspective that influences what you see around you but does not affect what is real.

Or:

Temperature is like this: Macroscopic bodies have temperatures, but single particles don’t, because the temperature of a body is the average of the energies of the atoms that make it up. Some physicists have proposed that time, like temperature, is meaningful only in the macro world but not relevant at the Planck scale.

It isn’t a failure that Time Reborn doesn’t answer questions; what is important is that the framework in which we do physics, rely on math, and oversimplify the world to fit our algorithms and equations is examined and excoriated as wish fulfillment. The digital age continues to reduce people to numbers and alters the world to fit the lens of self-effacing code; it is increasingly important to avoid a fallacious “natural” justification for mathematical simplicity in attempting to understand the universe, else risk giving credence to a "true" or "pure" mathematical view of markets or web traffic or any other social construct.

The most radical suggestion arising from this direction of thought is the insistence on the reality of the present moment and, beyond that, the principle that all that is real is so in a present moment. To the extent that this is a fruitful idea, physics can no longer be understood as the search for a precisely identical mathematical double of the universe. That dream must be seen now as a metaphysical fantasy that may have inspired generations of theorists but is now blocking the path to further progress.

[Stephane · Rating 4 out of 5]

Lee Smolin
Time Reborn

One of the books I am reading in order to gain a deeper understanding of time.

From what I gather, most physicist think that time does not exist. Lee Smolin, on the other hand, thinks this is wrong. “If you are one of the many who believe that time is an illusion, I aim to change your mind. If you already believe that time is real, I hope to give you better reasons for your belief.” I don’t think I fit in either category; I am not a physicist or a cosmologist, I am merely curious. Like most, I suppose, I instinctively think that time must be real. So I would certainly be receptive to Smolin’s argument.

The first part of the book demonstrates how the perspective of the unreality of time came about. To do so, Smolin charts a wide path, all the way back to the emergence of many modern ideas.

He first explores how the contributions of Descartes, Galileo and Newton made “our conception of nature far more mathematical than before” allowing the laws of motion to be expressed in a timeless format (mathematic), which, in some ways, opened the door to the “mystic” view that a series of numbers representing a motion is more “real” than the motion itself, and thus that this motion could exist outside of time.

Follows the greatest challenge to the existence of time, Einstein’s relativity. Smolin focuses on the concepts of the relativity of simultaneity and block universe, both are an assault on the reality of the present. Considering two events, very far from each other, happening without causal relation, two observers will have different answers to the questions of which one happened first, or whether or not they are simultaneous. And they will be both right. There is no objective simultaneity and space and time are inextricably linked. The logical conclusion is the concept of block universe: reality is the entire history of the universe; in that sense, past, present and future are equally real.

I think I followed the first part reasonably well, but during the second part, where Smolin attempts to demonstrate the reality of time, I became a little lost. This is probably on me, not on him. The way I saw it, Smolin thinks that our basic mistake is to attempt to generalize models that are successful in explaining local phenomenon to the entire universe. In other words, he thinks that the laws describing what happen in small part of the universe do not work as a theory of the universe as a whole. I was not able to fully follow is arguments.

In searching for a new framework, he invokes, Leibniz’s principle of sufficient reason (there is a reason for every state of affair), the principles of the identity of the indiscernible (no separable entities can have all their properties in common), explanatory closure (if I know a and a entails than b is true, than I know b…) and of no unreciprocated action (nothing in the universe can act on something without being acted on). I include them here partly to remember them, partly to show how broad Smolin's path is. He weaves philosophy, cosmology and physic in an argument that I admittedly, as I already stated, I had a hard time to follow, but that supposes that the laws of physics are not timeless, and that time must exist.

There is no shortage of mind-bending ideas and concepts in the book. The evolution of the law of nature is one, the cosmological natural selection, the idea that the Big Bang is a bounce, and that trace of older universes could be found in ours, therefore, the history of the universes can explain our universe, the vision of gravity as a force driving self-organization and complexity… and a lot more!

Smolin concludes rather philosophically, with a brief look at our social and economic systems, by pleading for an integration of scientific disciplines; we have much to gain if we can reconcile the ecology and the economic, the technical and the natural. In fact, perhaps our survival depends on that. He argues that the reality of time can serve as a platform for a new dialogue between the social and natural sciences. In the some ways, the conclusion felt like the introduction of a different book, and it was a little odd, but I liked it.

Also, I agree with him: global problems need global solutions, not just from a territorial standpoint, but also from a knowledge perspective. In other words, we need contributions from all disciplines, and a framework that allows everybody to communicate effectively and to understand each other’s. Indeed, we need all hands on deck to solve complex problems like climate change or wealth distribution. Thinking in time, as Smolin repeats, certainly can’t hurt...

[uosɯɐS · Rating 5 out of 5]

Time is one of the things that originally got me interested in physics:

"So, for many years now, I had been wondering, how can time be considered a dimension if, unlike the other dimensions, we cannot stop or go backwards in it (and therefore the t-axis is non-interchangeable with x- y- z- axes)?" A blog post of mine from October 10, 2009 (my original question dates back at least to 2000).

"Why is it that in the other three dimensions, we can move around more-or-less at will, but in time we seem to be stuck going forward at a generally constant rate? If we were to travel at extreme velocities (close to the speed of light), relativity says we could travel forward in time a bit faster. However, most of us will never have that opportunity. Earth-bound people have aged less than a second compared to astronauts using this method. But who wants to get older? We're all doing that anyway! Traveling backwards in time would be a much greater trick (physicists don't even know if we can do it), and nobody seems to know how to stop themselves in time either.

There are similarities, I think, with gravity. We feel as though we have control of our movements in the standard 3 dimensions, but in fact gravity does limit our up-down movement, also thanks to gravity we are stuck to the Earth, constantly rotating at the same velocities, both about the Earth's axis and about the sun. We don't even feel this movement, but we are actually stuck moving in the current 3 dimensions, as well as time. If you could take a spaceship out of orbit of anything, and just float around in a space suit, then perhaps you could actually be at rest relative to all the reference points I can imagine. However, most of us will never have the opportunity to do that - even astronauts stay in orbit in their missions (so far as I'm aware)." - January 4, 2013

I ended up getting a BS in Physics, and never felt like anything in any of the classes I took addressed this issue. I also read several pop science books about physics, and likewise never felt that anybody else was asking such questions, until I found out about Gödel's solution to the relativity equations that makes time-travel a logically guaranteed possibility. Then I went through a few years of infatuation with all things Gödel, but actually he never really addressed my original questions about time head-on, or if he did I just never got around to reading about that part of his work.

Anyway, it was so exciting to see that I was actually not alone in noticing this problem with time. A whole book devoted to it! That was awesome... I don't know if Smolin is right but I like the way he thinks, willing to question paradigms and thinking in terms of whole classes of theories, rather than just puttering away on some pet approach.

[Sebastian · Rating 4 out of 5]

Lee Smolin has an almost incredible knack for explaining profound and complicated things in a very clear manner, understandable even to dumbkopfs like myself. Furthermore, he seems to be a scientifically well-equipped person pondering truly deep issues in fundamental physics in a manner that seems to avoid some frequent pitfalls that even the smartest guys and gals working in the field seem to tumble into (e.g. assuming a background even in a background-independent theory, assuming a “view from the outside” of the universe even if no such view can exist, etc.). This, in itself, is invaluable and I praise the quantum spinfoam that there are people like him around, and that they are willing to spread the word among laypeople and hobbyist dabblers like me.

However, there is a strong feeling of non-sequitur between his explanations of the problems physics is facing today, and his repeated conclusion that “therefore – time must be fundamentally real”. So I have a weird situation where I’m nodding my head throughout the book, agreeing wholeheartedly with the man, only to start shaking that same head as he inevitably lands onto the same odd conclusion every few chapters. Nevertheless, even if you, like myself, do not agree with that conclusion, there is much to be learned (or at least refreshed) in the discussions of the troubles with the current state of play in physics, and I feel that his general idea of “we have to go back a few steps and reevaluate everything from the ground up” might be the right one to get us out of the rut that physics has been stuck in for a while now.

That being said, I don’t know if this is an obligatory part of popular science books now (first Tegmark, now Smolin), but there is a weird epilogue tacked on that seems to be “Smolin on stuff”, where he rambles on about a bunch of disconnected ideas, very loosely revolving about the topic of the book, but in fact heavily preachy about the future of mankind and the consequences of global warming, economic and political theory, etc. While I generally agree with many, if not most of his points, I’m not sure this is the place to make them – this bit of bait-and-switch at the end has mucked up the general feel of the book enough to actually knock a star off the overall rating.

[Hilmi Uysal · Rating 4 out of 5]

Kitabın orijinal adı “Time Reborn: From the Crisis in Physics to the Future of the Universe”. İlk basımı 2013'de. Okuduğum baskı “Zamanın Yeniden Doğuşu” adıyla TUBİTAK Yayınları’ndan çıkan Türkçe çevirisi. Çevirmen Bilge Tanrıseven de çok başarılı iş çıkarmış.

Birinci bölümde öncelikle klasik fizikteki zaman kavramı açıklanmış. Modern fizikte ise "evrensel zaman" kavramının yanılsamaya indirgenmesinin arkaplanı açıklanmış. Smolin kitabın bu bölümünde çok başarılı bir iş çıkarmış.

ZYD’nin ikinci bölümünde Smolin, iyi bir kozmoloji kuramının önündeki engelin zamanın modern anlayışı olduğunu iddia ediyor. Smolin kozmolojinin bir kriz dönemi yaşadığını söylüyor ve "zaman" kavramının dışlanmayıp tekrar kurama dahil edilmesi gerektiğini savunuyor.

Smolin, "evrensel zaman" kavramını kullanan yeni bir kozmoloji kuramı sunamıyor bu kitapta. Zaten -anladığım kadarıyla- kimsenin henüz böyle bir kuramı yok. Smolin’in bu kitapta yaptığı şey, klasik fiziktekteki gibi bir "evrensel zaman"ın varlığı kabul edilerek yeni kozmoloji kuramlarının gerektiğine yönelik bir öngörüsü olduğunu ilan etmekten ibaret. "Evrensel zaman" kavramını ortadan kaldırmış bulunan modern fizik, Smolin'e göre başarılı bir kozmoloji kuramı inşaa edemeyecek. Fİzikte kozmoloji kuramlarını ilerletmek ve şu an yaşanan krizden çıkmak isteniyorsa, fizikçilerin zamana bakışlarını değiştirmesi gerektiğini iddia ediyor.

Zamanın Yeniden Doğuşu, Lee Smolin'in ilk okuduğum kitabı oldu. Sonuncusu olmayacak sanırım; “Fiziğin Krizi: Sicim Kuramının Yükselişi, Bilimin Düşüşü ve Sonrası” ile devam etmeyi planlıyorum.

[Jafar · Rating 4 out of 5]

I think Smolin has been hanging out with too many theoretical physicists and philosophers who say funny things like: time doesn’t exist, or, time is an illusion. For the rest of us mortals, a thinning hair is enough proof for the reality of time.

Smolin is not happy with the fact that, starting from Newton, time lost its centrality in physics. It simply doesn’t appear in many representations and formulations of the laws of physics. Even when it does, it doesn’t really do anything other than move things along. Physical laws have become like computer algorithms. Output is determined by the input, and time is not really relevant. Relativity tells us that there is no absolute time. Cosmology tells us that time came into existence with the universe and it’s meaningless to talk about time before the Big Bang.

Smolin wants to change physics and put time back at the center. Time, instead of being an obedient servant of the laws that sit outside time, becomes their master. There are a lot of fascinating discussions in the book. You probably won’t be able to make up your mind and take side in the debate, but it’s fascinating nonetheless.

[Jesús · Rating 4 out of 5]

Lee Smolin is a physicist who can write. Even better, he’s a physicist who understands the way that other fields (like philosophy and economics) actually work. I’ve become accustomed to how physicists regularly misunderstand other disciplines, but Smolin is thoughtful and careful. Best of all, he’s unafraid to make bold claims in a book intended for a non-speciallist audience.

This book makes a stark claim that physics has, since the era of the ancient Greeks, been gradually sidelining time in its view of the cosmos. Time, argues Smolin, is not an emergent property of the universe, but a fundamental one. This runs counter to most mainstream physics. While his point might sound like splitting hairs, the difference is enormous in all kinds of ways, and Smolin is great at showing what the consequences are of thinking of time as “emergent” rather than fundamental. He gives us a healthy dose of what it might mean to reincorporate a real quality of time into physics.

I’m sold.

[Kian · Rating 4 out of 5]

Smolin always has its own special assumption like everyone else but what he wants to achive in general seems more noble let's say.

Here he tries to show why time is real and a fundamental element to the reality of the universe and maybe the only one and not a concept which we preceive based on preconditioned illusion of us.

[G.R. Reader · Rating 4 out of 5]

Way to go, Lee! Glad to see your new book is selling well. Okay, not as well as mine, but still pretty good for a physics text.

[Michael Connolly · Rating 5 out of 5]

This is the best science book that I have ever read!

[Sean · Rating 4 out of 5]

Lee Smolin's "Time Reborn" is the most thought-provoking book I've read in some time. Its thesis is that considering time to be "real" opens a path towards resolving the famous conundrums of cosmology and theoretical physics: the conflict between quantum mechanics (QM) and general relativity (GR), and how to think about the universe's initial conditions (whatever that means) and why the laws of physics are however they are (whatever that means). I think he makes a very poor case overall, but his approach has some important merits and he takes you on such a mindblowing ride along the way I'm hesitant to deduct even one star from my rating.

I was intrigued by the book to begin with because it seemed to hold the promise of squaring with some of the biggest philosophical problems that I personally feel plague most of human history's attempts to grapple with ultimate cosmological explanations, from ancient times all through string theory. I want to go into some detail as to how the beginning of the book led me to believe it was being framed in these terms, and this will illuminate what I think these problems are and why I think Smolin ultimately succumbed to them rather than successfully addressing them.

Some quotes Smolin begins with on p. xxv:

"To suppose universal laws of nature capable of being apprehended by the mind and yet having no reason for their special forms, but standing inexplicable and irrational, is hardly a justifiable position. Uniformities are precisely the sort of facts that need to be accounted for...Law is par excellence the thing that wants a reason." (Charles Sanders Pierce)

"You can trace the properties of the present universe back to properties it must have had at its beginning. But you cannot show that these are the only properties that any universe might have had...To state the laws of nature is not to describe or explain all possible histories of all possible universes. Only a relative distinction exists between law-like explanation and the narration of a one-time historical sequence." (Roberto Mangabeira Unger)

Does this hint at where he might be coming from and where he might be going? My personal preference for how to frame what's wrongheaded with the classic approaches to the question of ultimate explanations is that there is a false dichotomy between infinite regress vs. something that begs for an explanation but by definition cannot have one. By infinite regress I mean that each explanation, itself, needs to be explained in terms of some prior (whether historically or foundationally) explanation, and so on forever: turtles all the way down. Atoms are made of baryons, which are made of quarks, which are made of...ad infinitum (this is not a real theory, but it could have been).

The alternative in my false dichotomy would be that instead of attempting to be increasingly and incrementally reductionistic forever, some grand ultimate explanation is instead constructed that is expected to be taken as the last word, but which is so abstract, magical, complex, unnatural, or irreducible that it begs vastly more strongly for an explanation than the thing it was invented to explain in the first place. This too "solves" one problem by merely replacing it, but with an infinitely more intractable one. The classic example of this kind of explanation is God. But my position is also that it could be the laws of physics as often understood. How does a particle know what laws apply to it or how to follow them? What mechanism connects laws with what they act on, and what IS a law, metaphysically? Or how about this ontology: atoms just ARE; or atoms are made of baryons, which are made of quarks, which just are (or are made of strings or branes, which just are). Or it could be math itself. To me, the idea that mathematical objects are metaphysically "real" and separate from physical reality is no less supernatural and mystical than Deism or religious mythologies.

Although time is certainly part of the problem in the infinite regress case (it seems nonsensical as well as explanatorily unhelpful for time to extend forever in the past), we have precedent in biology for how it can play a role in the solution to the dichotomy: in the theory of evolution, a very down-to-earth mechanism (natural selection) makes a reductionistic explanation out of a finite history. Smolin was already famous for proposing "cosmological natural selection", and he discusses this at enough length in this book that I have no desire to read the one dedicated to that. I have, now as before I read "Time Reborn", major doubts about this theory on scientific grounds even though I find it conceptually very appealing, but I began this book predisposed to hope that his focus on time would frame some way to replace eternal laws with some kind of finite historical process, with a deep critique of how Platonism infects science. I was reinforced in this hope by how I read some early statements (which were interspersed with explicit discussion of Platonism):

"We perceive ourselves as living in time, yet we often imagine that the better aspects of our world and ourselves transcend it...Whatever we most admire and look up to -- God, the truths of mathematics, the laws of nature -- is endowed with an existenece that transcends time. We act inside time but judge our actions by timeless standards.
"As a result of this paradox, we live in a state of alienation from what we most value." (p. xiii)

"There's a cheapness at the core of any claim that our universe is ultimately explained by another, more perfect world standing apart from everything we perceive..."
"Our desire for transcendence is at root a religious aspiration...Does the seeking of mathematical knowledge make one a kind of priest, with special access to an extraordinary form of knowledge? Should we simply recognize mathematics for the religious activity it is?...
"It is far more challenging to accept the discipline of having to explain the universe we pereive and experience only in terms of itself." (p. 11)

I realized, the second time through, I had read too many of my own hopes into the early chapters. The quote above doesn't end its sentence there; the next part is "--to explain the real only by the real, and the time-bound only by the time-bound." This seemed laudable to me at first, but later I realized how much I don't feel that escapes my false dichotomy.

Utlimately, the real needs to be explained in terms of neither the real nor the supernal, but of the fuzzy. That which has a reason not in terms of that which also has a reason, nor of that which MUST not have a reason, but of that which doesn't NEED a reason. How do you start with absolutely no assumptions - not even that there is a reality - and by some sequence of developments that begin completely randomly, following no rules whatsoever (such as a rule that says there is or isn't a reality or that things do or do not exist - so why can't they spontaneously "begin" to?), get to a situation in which regularity and definiteness (indeed reality itself) has emerged, and ruts have been gotten stuck in? Time indeed seems to me to be among the first things to need to emerge (maybe THE first), else there is no sequence or change, and so this is why I thought he'd be on to something.

His argument turns out to develop almost an opposite line of thinking, but in doing so sharpened my own ability to articulate it to myself, and I greatly appreciate that. Indeed one of the strengths of his book is the way he identifies his own assumptions and preferences, making it a thrill for me to be able to engage myself with his ideas, and my own related ones, more critically than I otherwise have the intelligence or background for.

So with that "introduction," let me finally jump into the view he actually does promote:

-Time is the "most real aspect of our perception of the world"
-Space is emergent
-The laws of nature are a product of evolution
-The Big Bang is a bounce, and the universe is a state in a succession of bounces
-QM is an approximation to an unknown cosmological theory
(p. 249)

He uses various core principles to guide his approach:

-Leibniz' principle of sufficient reason - "there must be a rational reason for every ...query of the form 'why is the universe like X rather than Y?'" (p. xxvii)
-The principle of the identity of the indiscernibles
-The principle of background independence - that explanations should not be framed in terms of some fixed background such as Newtonian space.

The biggest problem with all this is that Smolin never defines what "real" even means. The whole book deeply questions the nature of reality at the same time that its main thesis is that one of its most mysterious aspects (time) is "real" in, apparently, some sort of self-evident way. Something that's subjective (like my perception of time) is real in at least that sense (i mean, i really experience the perception), but not necessarily any other sense, if you ask me. And in a sense, the subjective is the only reality we have any access to at all. But his case that time is also "global" creates a subjective/objective gap that he never even attempts to bridge.

So what does it mean for time to be real? Does it (can it?) mean the same as for a particle or wave or space to be real? What does "now" mean? What else is real besides time? Anything? Is "realness" graded or absolute? And doesn't the question of whether time is real or not, and whether it is a mathematical abstraction (as in GR and QM) or what, call into question the definition of time itself? And is that separate or not from the question of whether it's real? He casually defines time as change, but I don't feel satisfied that this distinguishes time from anything else in a clear enough way, let alone that it illuminates what it is about time that makes it "real" in Smolin's definition but not in Einstein's.

His only hints as to the answers to any of these questions seem to conflict with each other. "In a Leibnizian universe, time is real, in the sense that no moment of time is like any other" appears on p. 216, and might be the first time he's defined real. I was underwhelmed. But then when he states "But if time is eternal [huh?], each moment repeats an infinite number of times," I have to wonder if "eternal" is a synomym for fake. And the first sensible explanation of what "global time" means waits until p. 190, where he's discussing various "quantum graphity" models for reconciling QM with GR (fascinating stuff here!): "there cannot be a relativity of simultaneity at the deepest level, because everything is connected to everything else". Yet, I note that in these models, time's still relative, just negligibly so: its globalness is a simplification that can be made for mathematical purposes, but not metaphysical ones, and it seems to me he's defining time in terms of space, and only gets simultaneity due to proximity, just as in GR.

The second biggest problem has to do with this thing he has for "principles." For one thing, not only does he use the ones I listed to guide his approach, which is fine, but he invents new ones that somehow - he never explains how - are supposed to actively constrain and act on the universe. The major example is the "principle of precedence" to "explain" how the laws of physics evolve, which is that once something novel happens, it becomes a habit of nature, and so voila we have a law. So he's solving the mysteriousness of laws with something even more mysterious that really just takes the place of laws but in a more vague way such that it's harder to ask the critical questions we had been asking about laws. He goes so far as to discuss meta-law infinite regress avoidance and has interesting ideas about breaking down the distinction between laws and initial conditions, but he doesn't apply any of this to his "principles." He even recognizes the mystery, stating "principles do not act on matter, laws do" (p. 217) but he actually seems to believe the opposite.

So I prefer the standard "symmetry-breaking" hints at how the laws of physics may have emerged. This is actually a fascinating challenge for me after reading Smolin, though, because he argues that the idea that "the more fundamental a theory is, the more symmetries it should have" is "precisely the wrong lesson to draw" (p. 118). He argues from the identity of the indiscernibles that "there can be no fundamental symmetries in nature" (p. 117), and reminded me of the proven mathematical equivalence between symmetries and conservation laws.

A symmetry, in the most general sense, is invariance under transformation: a way by which two states are distinguishable only by the knowledge that some process has led from one to the other (such as rotating a square 90 degrees). An undifferentiated, indeed ill-defined, reality might be perfectly symmetrical in the sense that no transformations result in change; this is the closest thing I can come up with to an "initial condition" that begs no questions. Indeed I conceptualize as a symmetry the notion of reality itself being indistinguishable from nonreality: that symmetry would have to break for existence to even be possible. Yet it's paradoxical (or really, just plain wrong) in this context to include conservation laws among those that have to evolve by symmetry breaking, since each symmetry is equivalent to a conservation law. This supports Smolin's argument, but larger considerations about needing a mechanism for law-emergence that's less vague than the principle of precedence still bias me towards symmetry-breaking.

But going back to the problem with his principles, his major ones seem in serious conflict with his major conclusions. Global time seems to function as a fixed background, and as exempt from the principle of sufficient reason. His advocacy for the hidden variables interpretation of QM conflicts very badly with the principle of the identity of the indiscernibles.

And that's the third-biggest problem: his interpretation of QM. There's a lot of exciting and radical speculation in this book, most of it thrilling, but I think he totally goes off the deep end in chapter 13 where he argues for the hidden variables interpretation. Not because it's crazy or wrong or radical but because it fundamentally undermines a book that's otherwise trying to promote testability in science and demystification of abstract fundamentals. He admits (p. 159) that hidden variables don't predict anything new (and then contradicts this without citing any basis when summarizing the book on p. 241). The implications of hidden variables combined with global time are extremely radical: We should throw out Bohr, Einstein, Newton, and Galileo (p. 162-163, "Aristotle was right": there is a preferred notion of motion and rest - WOW!) for absolutely no other reason than because Smolin wants to posit and describe things that are by definition, even according to him, unobservable, directly or indirectly. All to satisfy the principle of sufficient reason because he thinks it's a shame that QM doesn't.

What's disappointing to me, aside from the blatant hypocrisy of espousing this view after writing a whole book ("The Trouble With Physics") excoriating string theory for being untestable, is that the Copenhagen interpretation's great and unique strength, to me, is precisely that it doesn't NEED to satify the demand for sufficient reason. In my view, which has been only strengthened by reading this book, QM randomness and indeterminateness are the closest things the current laws of physics have to the situation I described above where I wanted to start with no assumptions or regularities and see what emerges. QM already seems to me to lead the way in the direction I thought this book was going to try to go, and yet that's the thing he wants to throw out. The craziest and most initially-unintuitive aspects of QM are, to me, our best clues, not our worst errors.

To be fair to the hidden variables interpretation, this whole scenario seems to suggest that, ironically, there is no preferred (i.e. experimentally distinguishable) interpretation of the data that bears on the question of whether there's a preferred notion of motion and rest (or time). Maybe Smolin's unwittingly arguing that QM itself, apart from its interpretation or any overarching philosophical considerations, is incompatible with the idea that metaphysics can be scientific. I developed a sort of an opinion during my adventure with this book that maybe just as there is wave/particle duality in QM, there are ultimately dualities amongst any possible competing metaphysical interpretations of physics. And maybe this implies that there is no fact of the matter at all as to what reality is; nature itself cannot distinguish itself from what it might have equivalently been. These are the kinds of trippy speculations I was stimulated into concocting and enjoying throughout this book; another one is I wonder if another duality is information vs. physical entities: maybe utlimately reality is information and vice versa. This would satisfyingly collapse the Platonistic distinction between form and matter.

I'm encouraged in this duality speculation by Smolin's discussion of shape dynamics, an alternative interpretation of GR (p. 168) in which it is size that is relative instead of time. He says you can't in principle tell the difference between these two interpretations. But whereas Smolin uses this to justify his notion of global time, I take it as undermining the absoluteness of BOTH time and size, and am dismayed that he just arbitrarily picks one of these interpretations and calls it true. Metaphysics should illuminate possibilities and show compatibilties or incompatibilities, not select among those possibilities; that's science's job, and if science can't do it, then it's a meaningless task.

There is much more I could say about not just his contradictions and bad arguments, but also his discussions of cosmological natural selection, quantum graphity and quantum loop gravity, the emergence of space, the Big Bounce, inflation, the ways many of these ideas are subjectable to experimental test in surprising and interesting ways, the arrow of time, gravity as anti-thermodynamic, the anthropic principle, and the myriad amazing factoids and fascinating speculations that are incidentally embedded through the book, which would be a much better way of convincing you it would be a worthwhile read, but those are all things you can best experience by reading the book, not my summary, so I'll content myself with this already too long review focusing mainly on my own reactions to the fundamental aspects of the book.

Smolin's a good writer; the book is far briefer than, say, Brian Greene's, and denser, more authoritative, more elegant, and with a lot less handholding and cute analogies, in the same league as Hawking's "Brief History of Time" almost.

The big exception to my praise for his literary style is that he repeats his thesis over and over again, beating you over the head with it. He begins one chapter: "Can the universe contain two identical moments of time?" - which is an awesome way to begin a chapter, except that he doesn't really. That's the beginning of the second paragraph. The first one is "in the last chapter, blah blah blah. In this chapter, i will blah blah blah" drudgery, and it's always about how he showed this and demonstrated that, which are stronger statements than are appropriate for his speculations. If he didn't somehow believe he was running a power point presentation instead of writing a book, it would be as good as Hawking's. But look at my rambling review: who am i to talk?

[Allan Olley · Rating 5 out of 5]

This book is an extended exploration of time in physics especially cosmology with a to my mind somewhat controversial thesis. Time has been largely if not wholly excised from modern physics and this is an impediment to physics making progress in fields like cosmology that attempt to understand the universe as a whole.

The first part of the book explores how physics has removed most if not all of time from its description of the world. The innovations of Galileo and Newton described physical phenomenon in terms of timeless mathematical expressions, curves and equations. Already the future and past are described all as a piece of a block with time functioning like space, now is no more an objective quality of a moment then here is an objective quality of a place. Also gone is the sense that the future is not yet fixed and that the past is gone. Smolin then extends his discussion into the picture given by Relativity where one loses even the sense that there could be a single agreed upon present for different observers distant in space and traveling at different rates. Finally there is a speculative theory that attempts to apply quantum mechanics to the whole universe and calls into question whether there is time at all.

In the second half of the book Smolin sets out why he thinks a return to the reality of time. A view where there is an objective meaning and difference about the present moment and the arrow of time (the way the past and future are different and the past flows into the future). He tries to lay out principles for developing a cosmological theory chief among these the concept that we must explain the laws of nature as themselves the result of a process of evolution (change) rather than as fixed timeless mathematical forms. Much of the book is concerned with suggesting how to make sense of that notion. Another principle he returns to is the need for scientific theories to make empirically testable predictions, he finds much modern theorizing bereft of contact with the world in this regard.

In has no fully concrete proposals but gives a few suggestions. For example, he sketches his suggestion that we view are universe as the product of a process by which each black hole is the instance for the generation of a new universes and these universes composition and laws are variations on the universe they arose from. Thus we would expect an ensemble of universes where the properties (laws and initial conditions) that lead to universes with lots of black holes will be common. Since through a kind of cosmological analogy to natural selection those will be the kind favoured to produce lots of successors. This will then suggest probable properties of universe that can be tested for.

Smolin has many other suggestions. He suggests that an approach called shape dynamics allows us to specify a universal present in relativity theory. How theories that suggest how space might have emerged from something more fundamental might suggest a kind of universal time. He talks about how cyclic views of cosmology where the current period of expansion is in fact a bounce back not from a singularity but a previous period of collapse and that the current period of expansion will be followed by another collapse and another bounce and so on in an endless cycle. He also tries to illustrate how he thinks alternatives that he thinks of as timeless are untenable implying multiverses where anything is possible and notions of empirical verification break down because anything can be explained.

In the epilogue Smolin extends his consideration to economic, social and environmental theory and suggests that here to time has been insufficiently payed respect to and needs to be restored. He thinks economics is in the thrall of theories that posit timeless equilibrium rather than looking at the messy interconnected reality and proposes that the reintroduction of the working of what he takes as time will be helpful in understanding what we need to do to confront challenges like global warming.

I find the book engaging and somewhat persuasive in laying out its issues. The proposed solutions are interesting and engaging for their novelty and the passion behind them, however I am not really convinced by Smolin's interpretations of the problems or the solutions.

In terms of the removal of time from physics and the equating of physical reality to abstract mathematical forms. I think in fact time is real and even things like the present are an integral part of actual physical theory. We can not know the future, changes the past, directly effect things that are not presently happening and so on and this is all understandable in terms of physical descriptions like those given by Newton. The fact that in some abstract sense past people and events still exist on the timeless view, is not as Smolin (and apparently some of the people he criticizes) a comfort because the same view that tells me they exist tells me no less definitely that they will remain forever beyond my ability to know, communicate or interact with, I can do them no favours and they can do me no kindnesses.

There are some tricky conceptual issues at play likewise. If only the present exists as Smolin suggests at least once then there could be no meaning to predicting the future or knowing the past. If the past does not exist in the same sense that unicorns do not exist then everything and nothing can be true of it (consider a story where all unicorns are white and another where all are pink, both are equally false or true) and so that past theories predicted present conditions becomes difficult to analyze. If the past does not exist but existed and so what existed was a definite set of events then you can have a closed future (the series presented as having existed) that has all the properties of the present where the future is open, so is what makes the future open or closed really the existence or not of a series of events that follow?

Indeed even mathematics is not quite the timeless realm Smolin suggests, what is more mathematical then that model of a computer the Turing Machine, but many see the Turing machine as exemplifying aspects of time, the famous halting problem says there is no general method to predict the halting of such a machine. Smolin often equates the timelessness of mathematical laws with some transparency by which they imply knowledge of their outcomes, but in fact such descriptions are not always transparent and so to know whether the machine will halt may not exist in principle to our knowledge even if it is in some other it is determined. In some sense even mathematical truths are not intrinsic in their initial description but must be worked through to some other state.

I would also quibble with things like how he sees shape dynamics or the cosmic microwave background radiation as setting a standard of what constitutes the present in relativity. These standards might get everyone to agree on a time standard, but they would not get everyone to agree on seeing distant events as happening in the same reconstructed order.

Likewise I am not sure how is cosmological natural selection of universes generated by black holes would imply a global standard of time as he suggests. At one point he distinguishes between a Leibnizian universe where things are always different, changing and evolving with a Boltzman universe which tends to a stable recurrent equilibrium. However he admits that in a Boltzman world things need never exactly recur. Likewise in his imagined Leibnizian world events might get arbitrarily close to recurring and never actually recurring and meet his strict definition. I think his distinction here is best understood as loose and heuristic. He believes attempts to model the universe as a one where the features we see like the arrow of time are posited as fundamental and dramatically at work will be more fruitful for science then models where those properties are accidental and fading, I wish he had said it that way is all.

Ultimately I think he fails to confront to big tensions in his views of what will work in physics. The first tension is between his view that the future is open (and so unpredictable) on the one hand and the demand that theories are only when they can be tested (and so yield predictable results). Ultimately only that the future is predictable is fully testable, so if Smolin is right either science must fall short of offering a full theory of things (not all that could be predicted will be) or the future is not open. I am not sure the prospect of what Smolin considers as closed future is quite as dire as he does (for reasons already suggested but also for others about the nature of responsibility and free will), but I also don't think this tension is avoidable. There is almost certainly a limit to our knowledge and yet in order to find it we must never stop demanding to know more these impulses are in tension.

The other tension is Smolin's demands for an explanation of why things are the way they are? Why does the universe have a low entropy beginning? why do the laws seem so fine tuned for life? Against this consider his admission that questions like, why is there something rather than nothing? May just not be appropriate questions to ask there could never be an answer. Yet that is just the most general form of the questions about why these improbable initial conditions or laws, that he keeps asking. Again the tension between what it is possible and impossible to know suggests itself and the need to push on what it is possible to know to reach an answer.

Science almost always explains at least some things, it makes some seemingly improbable thing make more sense, but only so long as we are willing to assume other improbable things. If most of the major planets are spaced according to an integer set of distances (the Titus-Bode law) this is improbable but may be made probable by adducing some principle about the gravitational interactions between them, thus the Titus-Bode Law may have evolved, in much the way Smolin wants to imagine the Standard Model of Physics evolved. The question becomes where do we draw a line and say this regularity this fact will not be explained further or do we.

Smolin's book is a challenge to those who think we are at or near the limit of what can be explained by science and certainly provoked me to think about what we can explain and what we should explain with science.

[Blair · Rating 4 out of 5]

Mystics, philosophers, poets and 20th century physicists all agree - time is an illusion. Newton’s laws work equally well with time going backwards, and Einstein showed that time is relative to the motion of the observer. In contrast, this book argues that time is not only real, it is the most fundamental property of the universe. It certainly provides a lot of new ideas to inspire fresh thinking about this subject.

He does a wonderful job of introducing subjects such as thermodynamics or quantum entanglement in a few pages. Unfortunately he did not do the same for basic quantum mechanics or relativity theory. Some readers may be confused or even misled by his statements on these subjects without knowing the proper context.

His philosophical basis begins with the principle of sufficient reason, which declares that there is a rational reason for every choice that nature makes. The more basic assumption of a single objective reality is left unstated. He challenges the notion that there are eternal laws outside the universe that govern it. As the universe by definition includes everything, this concept is self-contradictory.

Instead, any laws must be a part of the universe. These laws emerge from what the universe contains. We have learned that our universe is not eternal and unchanging; it has been expanding from its origin in the Big Bang. In other words, it is evolving. As biological evolution can be seen as the exploration in time by the biosphere, the laws of physics also evolve, and emerge in time. Time is at the heart of this relationship.

He describes normal science as “Physics in a Box”, which is conducting experiments with restricted conditions, isolated from everything else. But he points out that we cannot really create an isolated experiment to test, for example, Newton’s laws, as every particle in the universe affects every other particle, at least through gravitation. A cosmology of the entire universe may involve principles that we cannot detect in that kind of limited environment.

Conservation laws, such as the conservation of energy, are fundamental to physics. We are assured they are connected the assumed symmetries in the universe. But he claims that there can be no fundamental symmetries in nature because they are derived from a study of subsets of the universe, and do not take into account interactions with the rest of an evolving universe. I do not see how this follows; maybe those interactions are also symmetrical. But who knows, maybe total energy is actually increasing in an expanding universe.

Quantum mechanics presents the biggest challenge to our notions of position and causality. He notes that in QM “there are cats that are both alive and dead at the same time, an infinitude of simultaneously existing universes, reality that depends on what is measured or who is observing, particles that signal each other across vast distances at speeds exceeding that of light”. While the theory works in the experiments that we do, he agrees with Einstein that it is incomplete. It provides no physical picture of what is going on, there is no precise outcome, and measurement and observation are built into the theory. It is not really a true theory at all, it is an experimental method, where the choice of experiment affects the results.

Quantum mechanics cannot be taken as universal, because it only applies to the small subsystems we experiment on. He claims it is missing “relational hidden variables” that relate each particle to the rest of the universe. Unlike the “hidden variables” that Einstein proposed in his critique of quantum mechanics, these are non-local, involving the “spooky action at a distance” that Einstein so disliked.

He suggests the principle of precedence to explain quantum behavior, where an event is more likely to happen if it occurred before in the past. The position of an electron is therefore determined by the fact that it is connected with all other electrons in the universe, and when it finds one in the same quantum state it copies its properties, including its relative position. I think it would make more sense to invoke the already existing Pauli exclusion principle, which says that no particles can share the same quantum state. Extend that across the universe, and each electron places itself where no other electron is located. But either system is like entanglement on a bigger scale, and implies some kind of universal simultaneity. He goes further to say Aristotle was right that there is a preferred version of motion and rest. However, this “preferred global time” has a family of observers at each point in space, and depends on the distribution of matter and energy in the universe, not quite what Aristotle had in mind.

To get around a perceived contradiction between universal time and relativity theory, he introduces a variant of relativity called Shape Dynamics. Its main principle is that all that is real in physics is connected with the shapes of objects, and all real change is simply changes in those shapes. The fact that objects seem to have an intrinsic size is an illusion. In exchange for making size relative, we achieve the goal of a single rate at which time flows throughout the universe.

Because he did not introduce relativity theory properly, the reader might get the impression that time flows randomly. Time always flows in the same direction, but at different rates depending on the motion of the observers. More specifically, if I travel on a very fast rocket, when I return to Earth I will be younger than the twin brother I left behind. Does shape dynamics claim that I will be smaller instead?

Let me propose the following thought experiment: When we look into space, we see the stars moving away from us equally in all directions. Either we are in a special place, or the universe itself is expanding and it will look similar from every point in space. If I am in a fast rocket, it will move faster than the stars are moving around on their own. The stars in front of me will be moving toward me, and the ones behind be will be receding. It is obvious that I am the one moving in an absolute sense, rather than the trillions of stars moving relative to me.

Before I begin my rocket journey, my brother and I measure the age of the universe, based on the acceleration of the stars away from us. Lets assume we can do this very accurately. Then I fly off for one year, and return to Earth and find him ten years older. We measure the age of the universe again. I feel it should be one year older, but the result will be ten years older. The universe aged faster than I did. The age does not depend on from where we measure it. I was the one doing the moving, so the Earth measurement should roughly agree with one made from any of the trillions of stars. I could have made this measurement any time during my journey, and observed the universe was aging more quickly than I was. Thus the age of the universe serves as an absolute clock. The universe IS the clock.

Then why do we need all the cute mathematical tricks to conjure up shape dynamics? Einstein did not develop special relativity by tinkering with Newton’s equations. He added a new factor to take into account the constant speed of light. Any advance on relativity will need a new physical concept, not just a refactoring job. The author seems to be trapped in his own physics in a box. Locally, two objects in motion have clocks that run at different speeds relative to one another. On a universal scale there is a constant time.

The basic premise here is that time is constant, and space is emergent. That seems quite reasonable, given that space is expanding from the Big Bang. In discussing the emergence of space, he points out that it appears to have only a few dimensions. This means we have more separation from other objects than if there were more dimensions. Compare a two dimensional neighborhood of houses with a three-dimensional apartment building: more dimensions give you more neighbors.

In the early universe all points in space were connected. If space is quantized, so there are a finite number of points with a certain size. One assumes this size must increase as the universe expands, unless new points are being manufactured. As it cooled, the links required energy so most of them were turned off, and space as we know it emerged. Entanglement involves turning on some of these non-local connections.

My favorite part of the book begins with his great introduction to thermodynamics. He points out that the second law of thermodynamics does not describe the universe as a whole very well. Instead, the universe has a history of increasing complexity. He explains this is because gravity is anti-thermodynamic. It attracts particles to come together, which creates order from disorder. Further, the fact that fusion occurs when there is sufficient mass in a star creates energy. And it is energy flow that drives the creation of complexity and self-organization, which leads to planets with life on them.

This is a great book for stimulating thought on the most universal topic that can exist. He is trying to explain very complex ideas to a non-specialist audience. This difficult task is sometimes done very well, and other times it is hard to follow. I highly recommend it.