Books

Short works

Books : reviews

Lee Smolin.
The Life of the Cosmos.
Weidenfeld and Nicholson. 1997

rating : 2 : great stuff
review : 23 June 2001

In this gem of a book, Smolin describes his quest for a theory of the universe, a cosmological theory that explains why the universe is necessarily large and complex and the way it is. The old Newtonian, clockwork model of the universe is a picture of a cold, inhospitable, essentially sterile place in which life is a fluke, a vastly improbable statistical fluctuation, and in which all is futile, heading inexorably to the inevitable Heat Death. Fortunately it is a false picture, based on a 19th century understanding of physics. Unfortunately, it is also the picture that many believe to be what physics is still telling us. Smolin overthrows the old, showing how the 20th century physical theories of general relativity and quantum mechanics lead to a picture of a vast, vibrant, complex self-organising universe, hospitable to life, growing, and exhibiting ever more variety.

He takes a philosophical approach to describing physical theories. He points out that two of the mainstays of classical physics, reductionism and atomism, are simply incompatible: reductionism works by describing the whole in terms of its parts, whereas the fundamental "atoms" have no parts. Instead, he takes Leibniz' ideas of relative descriptions, and the principle of sufficient reason, very seriously. He shows how general relativity has moved us away from a theory with absolute space and time (implying some absolute, externally-imposed frame of reference) to a description based on the relationships between things, how position, motion, acceleration are relative concepts (hence the name, "relativity"). And he shows how quantum mechanics has moved us away from a theory of individual things acting independently, to one of entangled things all dependent on each other. And the consequences of these two theories seem to point to a universe that is necessarily large and complex.

Smolin starts by showing that the universe we live in appears to be vastly improbable. In particular, because it contains stars. Stars are necessary for life: they synthesise the sufficient variety of chemical elements (and particularly carbon) needed to build sufficiently complex systems, and they provide the long-term thermodynamic gradients needed for stable far-from-equilibrium systems. A universe full of stars is necessarily quite complex (for example, such a universe needs to contain carbon, to cool the interstellar medium sufficiently that stars can be made). Yet the fundamental physical constants need to be tuned astonishingly precisely to allow a universe with stars, and hence with life. Change those constants only very slightly, and there are no stars, and hence no life.

Why do those constants have the very finely-tuned values they do? Coincidence? Smolin says not, and provides a mechanism for giving them the values they have. General relativity predicts singularities; but we don't know, by definition, what happens at a singularity. Quantum mechanics suggests that maybe there was no singularity at the Big Bang, that maybe there are no singularities inside black holes. What if, Smolin speculates, inside black holes, the "singularity" actually produces a whole new universe? And what if the laws of physics (ie the values of the fundamental constants) are slightly different from those in the "parent" universe? Then each new "singularity" (be it a black hole, or the Big Crunch at the end of the universe) produces a universe slightly different from its parent. A form of natural selection can act: the random walk through value space eventually finds universes where black holes are abundant, and such universe generate many more child universes, with similar values of the constants, and hence will come to dominate. Any universe chosen at random will tend to be one that generates many black holes. Such universes are necessarily rather complex, and so are also good for life. A universe where black holes are abundant must have stars (to turn into black holes) and carbon (to help make stars). This is not simply wild speculation. It is proper scientific theory and is testable/falsifiable: it makes predictions that any universe with different values of the fundamental constants has fewer black holes.

This idea explains why the universe we live in is hospitable to life, without having to invoke special pleading such as the anthropic principle. But we have to give up some "neatness" if this idea is correct. If our universe is a result of natural selection by random walk over the space of values of the fundamental constants, these values may not be "simple" -- there may be no reason for the lower order digits to have the precise values they do (a value very close, but differing in all later digits, might also be tuned sufficiently well). [Is there any connection with Chaitin's work on algorithmic information theory here? Might some of the novelty come from the massive amount of information in the infinitely precise, but essentially random, constants? Or are they actually not infinitely precise, given the practical limitations of measuring them with a finite universe?]

Smolin moves on to discuss the consequences of GR and QM in some detail. He explains how GR gradually helped break the ideas of absolute space and time (it took some time, but GR broke free from coordinate systems approaches with the geometrical approach described by Misner, Thorne and Wheeler). He also explains how QM gradually helped break the idea of it being legitimate to talk about single isolated particles. (Again, this did not happen immediately, because early QM tackled descriptions of single particles. It wasn't until multi-particle systems were tackled that quantum entanglement was discovered and fully appreciated.) In order for these theories to make sense, the universe must be sufficiently complex (for example, if every thing is relative, the universe must be complex enough, have enough variety, that the things in it can be distinguished from each other purely in terms of their relationships with each other, not in terms of some non-existent absolute position).

This all leads on to some very deep stuff. In particular, Smolin points out that GR and QM are at best only partial cosmological theories, and so more work is needed. He speculates on what a full cosmological theory might be. And on the way, he packs in numerous little gems (such as the Bekenstein bound: a black hole has an entropy proportional to its surface area; no region of space can have more information than can the largest black hole that can occupy that space; so the maximum amount of information in a region of space grows as the surface area, and not the volume, of that space.) No review could possibly hope to cover the breadth and depth of the topics Smolin explores (for example: his explanation of how Leibniz' philosophy and gauge theories are linked, and his description of the process of continual star production in the spiral arms of galaxies, are a joy to read).

Smolin is careful to distinguish between accepted physical theory, theories that are still currently under development, and more speculative ideas. Some of the more interesting points are the more speculative ones! Nevertheless, this beautifully written and fascinating account, by a leading quantum gravity researcher, is of a universe vastly different, and vastly more interesting, than the one we are used to reading about in more "popular" accounts of physics.

Lee Smolin.
Three Roads to Quantum Gravity.
Weidenfeld and Nicholson. 2000

rating : 2 : great stuff
review : 24 November 2003

Smolin sets out to explain three different routes to a theory of quantum gravity, and how they might all be leading to the same place, and does so brilliantly. The three roads are black hole thermodynamics, loop quantum gravity, and string theory.

He starts with a description of cosmological logic -- that we can only know about events in our past light cones, that different observers have different light cones (so know different things), and these light cones are growing (so we continually know more). Putting together a logic that allows reasoning under these conditions results in a very different world from that painted by an all-knowing Platonic style of logic. But this less absolute logic isn't some wooly NewAge "everything is relative, and so everything is true" idea -- if observers have overlapping light cones, they will agree on what they can deduce about the shared region. It transpires that there is relationship between this kind of logic and something the mathematicians have already come up with: a very hairy branch of Category Theory known as Topos Theory. (Now I think I understand why Kauffman makes a passing reference to Category Theory in his Investigations -- given he has worked with Smolin, he could be referring to these ideas.)

Smolin also discusses in detail the ideas of "background independent" theories -- ones where there is no framework of absolute time and space for particles to move against, but rather ones where space and time themselves are integral, evolving, changing parts of the cosmos, and in which there are no static things, only dynamic processes. He touched on this to some degree in his earlier marvelous book, The Life of the Cosmos, but goes into more detail and explanation here. And it is all explained so clearly -- I was particularly enthralled with the description of the relativity principle link between the well-known radiation emitted at a black hole's event horizon, and the weird Unruh radiation seen by an accelerating observer in empty space.

Loop quantum gravity is a theory about how space and time are constructed, but the resulting universe doesn't appear to have much else in it. String theory, on the other hand, has particles, but it is a background dependent theory. Work is beginning on how these might be two components of the final theory. Black hole thermodynamics links everything together, and seems to be providing a clue about the relationship between thermodynamic entropy and information. We end up with the weirdness of the Bekenstein bound (again, touched on in TLotC, but gone into in more depth here) and the holographic principle.

Interwoven with all this hard science are some great little vignettes -- Smolin is one of the key players in the loop quantum gravity strand. These serve to enliven and enrich the scientific ideas, and illuminate the scientific process, rather than detracting from them with arbitrary personal details, as happens all too often in the less well written popular science accounts. (It is interesting that scientist popularisers write about science, whereas journalist popularisers tend to write about the people. My interests lie with the science -- I can get people stories anywhere.)

There are some incredibly deep ideas here, explained brilliantly. All in all, this is a marvellous book. It contrasts nicely with TLotC, complementing that one's grand scope with some really fundamental hard science, told in a refreshing and comprehensible manner.

Lee Smolin.
The Trouble with Physics: the rise of string theory, the fall of science, and what comes next.
Penguin. 2006

rating : 2.5 : great stuff
review : 25 May 2010

Smolin lays out some problems he has with modern physics. He doesn't mean problematic results; he is talking about problems with the current process of doing physics that have led to an unprecedented stalling of progress over the last 30 years. When he says "physics", he means fundamental physics of gravity, quantum mechanics, and particle physics, and the attempts to come up with a unified theory, based on 30 years of research in string theory. We can see this focus from the start: in chapter 1, he identifies the five "great unsolved problems of theoretical physics":

Problem 1: Combine general relativity and quantum theory into a single theory that can claim to be the complete theory of nature.
Problem 2: Resolve the problems in the foundations of quantum mechanics, either by making sense of the theory as it stands or by inventing a new theory that does make sense.
Problem 3: Determine whether or not the various particles and forces can be unified in a theory that explains them all as manifestations of a single, fundamental entity.
Problem 4: Explain how the values of the free constants in the standard model of particle physics are chosen in nature.
Problem 5: Explain dark matter and dark energy. Or, if they don't exist, determine how and why gravity is modified on large scales. More generally, explain why the constants of the standard model of cosmology, including the dark energy, have the values they do.

He identifies these as the fundamental problems facing modern theoretical physics, and the fact that no progress has been made on them in the 30 years that string theory has held sway. It's not so much that string theory has failed to make progress however; it's the fact that the unprecedented dominance of one school of thought appears to have stifled any progress on alternative approaches that might bear fruit. Smolin himself is a theoretical physicist, a quantum gravity researcher, who has also worked deeply on string theory, so is in an ideal situation of knowing the field from outside, and from within. This gives his critique a lot of credibility.

He starts off with an historical overview of the attempts over the last century or more to unify the various forces of nature, and how this has led to the "standard model" of particle physics, and how gravity somehow never seems to fit. Actually, that last point is not quite true:

p39. In 1914, a Finnish physicist named Gunnar Nordström found that all you had to do to unify gravity with electromagnetism was increase the dimensions of space by one. He wrote the equations that describe electromagnetism in a world with four dimensions of space (and one of time), and out popped gravity. Just by the extra dimension of space, you got a unification of gravity with electromagnetism that was also perfectly consistent with Einstein's special theory of relativity.

Unfortunately, the gravity that popped out was Newtonian gravity, not General Relativity. So that's no good then. (But I am greatly intrigued by the fact that it was Newtonian gravity that popped out. Coincidence? Surely not. So why? Maybe it is "obvious"? Because it is a good approximation? Because the same assumptions underlying Newtonian gravity are there in the approach? Or some other reason? Smolin does not go into this further.)

Despite not answering every single one of my questions(!), there is lots of lovely stuff in here, and very nicely explained. I particularly like the discussion of why physicists like to unify forces (or other general concepts), and what doing so lets you do that you could not do before. It's not intellectual thumb-twiddling: it serves an important and powerful purpose. Smolin works his way from early unifications to some very hairy string theory, keeping a beautifully clear style throughout. Being a physicist, he explains things using other, simpler physical analogies, such as this description of emergent particles:

p132. if you hit one end of a metal bar, a sound wave will travel through it. The frequency at which the metal vibrates is an emergent property, as is the speed that sound travels in the metal. Recall the wave/particle duality of quantum mechanics, which asserts that there is a wave associated with every particle. The reverse is also true: There is a particle associated with every wave, including a particle associated with the sound wave traveling through the metal. It is called a phonon.
    A phonon is not an elementary particle. It is certainly not one of the particles that make up the metal, for it exists only by virtue of the collective motion of huge numbers of the particles that do make up the metal. But a phonon is a particle just the same. It has all the properties of a particle. It has mass, it has momentum, it carries energy. It behaves precisely the way quantum mechanics says a particle should behave. We say that a phonon is an emergent particle.
    Things like this are believed to happen to strings as well. When the interactions are strong, there are many, many strings breaking and joining, and it becomes difficult to follow what happens to each individual string. We then look for some simple emergent properties of large collections of strings --- properties that we can use to understand what is going on. Now comes something really fun. Just as the vibrations of a whole bunch of particles can behave like a simple particle --- a phonon --- a new string can emerge out of the collective motion of large numbers of strings. We can call this an emergent string.
    The behavior of these emergent strings is the exact opposite of that of ordinary strings --- let's call the latter the fundamental strings. The more the fundamental strings interact, the less the emergent strings do. To put this a bit more precisely: If the probability for two fundamental strings to interact is proportional to the string coupling constant g, then in some cases the probability for the emergent strings to interact is proportional to 1/g.
    How do you tell the fundamental strings from the emergent strings? It turns out that you can't --- at least, in some cases. In fact, you can turn the picture around and see the emergent strings as fundamental. This is the fantastic trick of strong-weak duality. It is as if we could look at a metal and see the phonons --- the quantum sound waves --- as fundamental and all the protons, neutrons, and electrons making up the metal as emergent particles made up of phonons.

However, rather than trying to do this for everything, when the going gets too tough, he declines to attempt a bogus explanation, and simply says it's too hard to explain in the space. That's fair enough: this is a pop science book, not a graduate text, after all. Even so, he manages to portray the beauty and excitement of the subject.

After the background explanation to help us understand what string theory explains, or fails to explain, he evaluates its success. The point to remember here is that string theory is about 30 years old now, and never before in theoretical physics has a single approach been employed, to the almost total exclusion of all other approaches, for so long with so little to show for it. Is it fair to evaluate it so soon? Well:

p178. String theory either is or is not the culmination of the scientific revolution that Einstein began in 1905. ...
    One might ask whether it is too early to make such an assessment. But string theory has been under continuous development for more than thirty-five years, and for more than twenty it has captured the attention of many of the brightest scientists in the world. ... there is no precedent in the history of science, since at least the late eighteenth century, for a proposed major theory going more than a decade before either failing or accumulating impressive experimental and theoretical support. Nor is it convincing to point to the experimental difficulties, for two reasons: First, much of the data that string theory was invented to explain already exists, in the values of the constants in the standard models of particle physics and cosmology. Second, while it is true that strings are too small to observe directly, previous theories have almost always quickly led to the invention of new experiments --- experiments that no one would have thought of doing otherwise.

Quite damning. But surely it has given us some partial knowledge? But no. Smolin describes that string theory is actually a whole Vast family of theories. Some of these are known in detail -- they don't work. Some, those that are supposed to give the right answers, are merely conjectured to exist:

p181. ... any evaluation of string theory will necessarily be controversial. If we restrict our attention to the theories that are known to exist --- those that allow us to do actual calculations and make predictions --- we must conclude that string theory has nothing to do with nature, because every single one of these disagrees with experimental data. So the hope that string theory may describe our world rests wholly on a belief in string theories whose existence is only conjectured.

It's as if Newton had come up with a whole family of theories of gravity, with all those that could be worked out predicting square or triangular orbits, and with some others merely conjectured to exist, but if they did, they might give ellipses, and all being mediated by invisible angels that were moving much too fast for us ever to be able to see.

So why all the effort in string theory? Is it because there just are no alternatives? Smolin says no. And it's not just loop quantum gravity notions. He points out several observational anomalies, and several interesting and potentially promising alternative approaches. Of course, they might be completely wrong -- but shouldn't they at least be investigated? (He's not here talking about obviously barking "theories" by fringe lunatics; he's talking about suggestions by serious, but non-mainstream, scientists.)

He starts off with some observations about a length scale defined by the cosmological constant (itself a relatively recent observation, currently "explained" by "dark energy"). This length scale is enormous: comparable to the size of the observable universe. We can use a standard trick in physics to convert this to a different kind of unit, by combining with fundamental constants like the speed of light c. (For example, the Planck length is defined by a combination of the fundamental constants h, G, and c.) R/c is roughly the age of the universe: that is not surprising. But c2/R is an acceleration, a tiny acceleration, and its value is potentially interesting:

p211. The other possibility is that there is no dark matter and Newton's law of gravity breaks down whenever accelerations get as small as the special value of c2/R. In this case, there needs to be a new law that replaces Newton's law in these circumstances. In his 1983 paper, Milgrom proposed such a theory. He called it MOND, for "modified Newtonian dynamics." According to Newton's law of gravity, the acceleration of a body due to a mass decreases in a specific way when you move away from that mass --- that is, by the square of the distance. Milgrom's theory says that Newton's law holds, but only until the acceleration decreases to the magic value of 1.2 x 10-8 cm/sec2. After that point, rather than decreasing with the square of the distance, it decreases only by the distance. Moreover, while normally the Newtonian force is proportional to the mass of the body causing the acceleration times a constant (which is Newton's gravitational constant), MOND says that when the acceleration is very small, the force is proportional to the square root of the mass times Newton's constant.

And the possible Pioneer trajectory anomalies involve a similar acceleration, too. Smolin notes that such observations potentially indicate something completely unexpected by theorists. (And given all the earlier discussion of adding dimensions to get unified theories, I'm amused to note that force decreasing proportional to the distance, rather than distance squared, is what you would expect in a world with only two spatial dimensions.)

Smolin continues with a whistle-stop survey of non-string approaches, including twistors:

p244. ... Roger Penrose has also proposed an approach to quantum spacetime based on the principle that what is really fundamental is relations of causality. His approach is called twistor theory. .... It is based on a reversal of the usual way of seeing events in spacetime. Traditionally, one sees what happens as primary and the relationships between what happens as secondary. Thus the events are real and the causal relations between the events are simply properties of the events. Penrose found that this way of looking at things can be reversed. You can take the elementary causal processes as fundamental and then define events in terms of coincidences between causal processes. ....
    .... In surprising and beautiful ways, many of the basic equations of physics could be rewritten in terms of twistor space. ... Twistor theory partly realizes the idea that spacetime may emerge from another structure. The events of our spacetime turn out to be certain surfaces suspended in the twistor space. The geometry of our spacetime also emerges from structures in twistor space.
    But there are problems with this picture. ... No one yet knows what a quantum twistor space looks like. Whether quantum twistor theory will make sense, and whether spacetime will emerge from it, has yet to be shown.

He also speculates where there may be a fundamental problem underlying our current conceptions, that old bugaboo, time:

p257. ... time is represented as if it were another dimension of space. Motion is frozen, and a whole history of constant motion and change is presented to us as something static and unchanging. ....
    We have to find a way to unfreeze time --- to represent time without turning it into space. I have no idea how to do this. I can't conceive of a mathematics that doesn't represent a world as if it were frozen in eternity. It's terribly hard to represent time, and that's why there's a good chance that this representation is the missing piece.
    One thing is clear: I can't get anywhere thinking about this kind of problem within the confines of string theory. Since string theory is limited to the description of strings and branes moving in fixed-background spacetime geometries, it offers nothing for someone who wants to break new ground thinking about the nature of time or of quantum theory.

Of course, Smolin is interested in quantum gravity, covered very well in his earlier book, Three Roads to Quantum Gravity. Again, he makes the point that a unified theory should be background-independent in order to incorporate gravity. Maybe starting with background-dependent theories (such as string theory) and then hoping to patch it up later just can't work. (After all, Newtonian gravity pops out of Nordstrom's work with EM, yet the move from Newtonian gravity to General Relativity isn't a fix-up, it's a complete paradigm shift. So maybe even if string theory were to "pop out" of some background-dependent theory, it could turn out to be to the "real" theory as Newtonian gravity is to GR. Not good.)

But it's not just a case of building in the "right" background. Maybe, for a truly fundamental theory of space-time, the space (and time?) should emerge from, not be built into, the theory:

p240. Don't start with space, or anything moving in space. Start with something that is purely quantum-mechanical and has, instead of space, some kind of purely quantum structure. If the theory is right, then space must emerge, representing some average properties of the structure --- in the same sense that temperature emerges as a representation of the average motion of atoms.

So this is a great description of the current status of fundamental theoretic physics. And, as has been mentioned before, there's a problem: progress has stalled. But why? That is Smolin's topic for the final part of his book. He stops looking at just the science, and looks at how science is done, the social processes involved. He has a nice take on the philosophy of the scientific method: it's not one simple approach like Popperianism, but rather a collection of approaches that have been developed and honed. And these approaches are domain-dependent: what works well in theoretical physics need not work as well in biology, for example, because the properties of the two domains are quite different: the kinds of regularities the approach exploits are different in different domains, so could benefit from different approaches.

pp298-9. Science was not invented. It evolved over time, as people discovered tools and habits that worked to bring the physical world within the sphere of our understanding. Science, then, is the way it is because of the way nature is --- and because of the way we are.
    ... The successful strategies were discovered over time and are embedded in the practices of the individual sciences.
    Once we understand this, we can identify the features of nature that science exploits. The most important is that nature is relatively stable. In physics and chemistry, it's easy to devise experiments whose results are repeatable. This did not have to be the case; for example, it is less the case in biology and far less in psychology. But in the domains where experiments are repeatable, it is useful to describe nature in terms of laws. Thus, from its beginnings, the practitioners of physics have been interested in discovering general laws. What is at issue here is not whether there actually are fundamental laws; what matters for how we do science is whether there are regularities that we can discover and model, using tools that we can make with our hands.

These scientific approaches do not exploit only the structure of nature. Just as importantly, they have been carefully honed to exploit and compensate for our peculiarities, particularly our ability to fool ourselves.

pp299-300. But if science works because we live in a world of regularities, it works in the particular way it does because of some peculiarities in our own makeup. In particular, we are masters at drawing conclusions from incomplete information. .... We never have enough information to completely justify the conclusions we draw. Being able to act on guesses and hunches, and act confidently when the information we have points somewhere but does not constitute a proof ... is a big part of what makes human beings such a successful species.
    But this ability comes at a heavy price, which is that we easily fool ourselves. ....
    .... And we fool ourselves not only individually but en masse The tendency of a group of human beings to quickly come to believe something that its individual members will later see as obviously false is truly amazing. .... But arriving at a consensus is part of who we are, for it is essential if a band of hunters is to succeed or a tribe is to flee approaching danger.
    For a community to survive, then, there must be mechanisms of correction: elders who curb the impulsiveness of the young because if they have learned anything from their long lives, it is how often they were wrong; the young, who challenge beliefs that have been held obvious and sacred for generations, when those beliefs are no longer apt. Human society has progressed because it has learned to require of its members both rebellion and respect, and because it has discovered social mechanisms that over time balance those qualities.
    I believe that science is one of those mechanisms. It is a way to nurture and encourage the discovery of new knowledge, but more than anything else it is a collection of crafts and practices that, over time, have been shown to be effective in unmasking error. It is our best tool in the constant struggle to overcome our built-in tendency to fool ourselves and fool others.

So, science requires "both rebellion and respect". Smolin's contention is that currently, the rebellion side of the coin is being stifled in theoretical physics. He cites several reasons, but the main one appears to be the ultra-conservative hiring policies in (US) universities. Rebels don't join big established teams researching conventional (here, string theoretic) approaches; rebels have difficulty getting published; so rebels have difficulty getting grants; so rebels don't get tenure. (Smolin points out how, ironically, some of the founder members of string theory were themselves rebels ploughing a lonely furrow, suffering from precisely this conservatism, until string theory took off and they became respected mainstream "overnight".) Smolin makes some eminently sensible suggestions for how to overcome this problem, for how to ensure that a certain proportion (it does not have to be large) of these rebels, or "seers", can get appointed and given the opportunity to flourish. But how to get anyone in a position to do anything about it to listen? Well, the Perimeter Institute for Theoretical Physics in Ontario, where Smolin is now a faculty member, seems to have some of the right ideas. So there is one place that sanity reigns, hopefully.

This is a great book, with clearly-written fascinating science, and thought-provoking discussions on the way science is (or ought to be) done. Although focussed on fundamental physics, some of the latter discussion is much more widely applicable. Recommended.

Lee Smolin.
Time Reborn: from the crisis in physics to the future of the universe.
Penguin. 2013

rating : 2.5 : great stuff
review : 9 January 2016

Nothing seems more real than time passing. We experience life itself as a succession of moments. Yet the consensus in physics, from Newton and Einstein to today’s string theorists, is that time is an illusion and the universe is governed by absolute, timeless laws.

In Time Reborn physicist Lee Smolin calls for a major revolution in scientific thought, insisting we embrace the reality of time. Not only is time real, he argues, it is the most fundamental feature of reality. Time Reborn explains how the true nature of time shapes us, our world and the foundations of our universe.

Physics has a curious relationship with time. Most laws are time-reversible; famous ones that aren’t, like the Second Law of Thermodynamics, are approximate and emergent from underlying reversibility; in relativity a universal time cannot be defined consistently, and instead provides us with a static space-time. It’s almost as if physics doesn’t believe time exists.

Smolin is having none of that. For him, time is the fundamental property of the universe, whatever else may emerge. We are not flies caught in the amber of a static space-time; time itself is real:

[pxiv] The future does not yet exist and is therefore open- We can reasonably infer some predictions, but we cannot predict the future completely. Indeed, the future can produce phenomena that are genuinely novel, in the sense that no knowledge of the past could have anticipated them.

How can he say this, when all the physical theories seem to point in the other direction? His argument is that those theories are local, and cannot be simply extended to apply to the entire universe. Those theories assume that crucial parts of the process must be outside the region they describe:

[pxxiii] All the major theories of physics are about parts of the universe—a radio, a ball in flight, a biological cell, the Earth, a galaxy. When we describe a part of the universe, we leave ourselves and our measuring tools outside the system. We leave out our role in selecting or preparing the system we study. We leave out the references that serve to establish where the system is. Most crucially for our concern with the nature of time, we leave out the clocks by which we measure change in the system.

This is what Smolin dubs the traditional Newtonian paradigm of doing “physics in a box”. It rests on some underlying assumptions:

[p44] We should be aware that this powerful method is based on some powerful assumptions. The first is that the configuration space is timeless. It’s assumed that some method can give the whole set of possible configurations ahead of time—that is, before we watch the actual evolution of the system. The possible configurations do not evolve, they simply are. A second assumption is that the forces, and hence the laws the system is subject to are timeless. They don’t change in time, and they also presumably can be specified ahead of the actual study of the system.

If all the possible states of the system are predefined, and the laws under which the system evolves are predefined, then time does seem to be nothing more than an accounting variable: which of those states the laws say the system is currently occupying. What if the possible states of the entire universe aren’t predefined, because its laws aren’t predefined?

Smolin argues that this Newtonian paradigm, powerful as it is, cannot be extended to provide a theory of the entire universe.

[p97] The universe is an entity different in kind from any of its parts. Nor is it simply the sum of its parts. In physics, all properties of objects in the universe are understood in terms of relationships or interactions with other objects. But the universe is the sum of all those relations and, as such, cannot have properties defined by relations to another, similar entity.

It is not a simple task to make a truly universal theory: one that doesn’t just apply to every part of the universe, but that applies to the whole universe at once.

[p104] The challenge we face when extending science to a theory of the whole universe is that there can be no static part, because everything in the universe changes, and there is nothing outside of it—nothing that can serve as a background against which to measure the motion of the rest.

He also argues that our current theories are approximations: physicists pretend that the system inside their box is an isolated system, unaffected by the rest of the universe, and they go to a lot of experimental effort to make that approximation as good as possible. Good approximations make effective theories, but they are only as good as their assumptions (energy ranges, for example). These approximations inevitably break down whenever a theory is extended to encompass the entirety of the universe.

So the timeless nature of isolated, local, approximate theories cannot be taken to imply that the universe itself is timeless.

Having argued that the laws cannot be extended naively to imply a timeless universe, Smolin also argues that there is no reason to assume that the laws themselves are timeless.

[p121] The notion of timeless laws also violates the relational principle that nothing in the universe acts without being acted on. If you choose to except the laws of nature from this principle, seeing them as something outside the universe, you put them outside the realm of rational explanation. To make laws explicable, we must consider them as much a part of the world as the particles they act on. This brings them into the purview of change and causality. They become explicable only when they participate in the dance of change and mutual influence that makes the world a whole.

Smolin explicitly links this view with his proposal for an evolutionary universe, where a new universe is born in each black hole, with its laws of physics being a mutation of its parent’s laws, as explained in his earlier work, The Life of the Cosmos. Smolin is a Leibniz fan: as well as following Leibniz’ relational view, he uses the Principle of Sufficient Reason: that everything must have a reason or cause, to show that the laws must also have a cause, an explanation. I wonder: do random mutations to the laws of physics obey this principle? (In passing: I was amused to discover that Smolin was introduced to Leibniz’ ideas by Barbour, but has come to rather different conclusions.)

This mutational view does not mean that Smolin thinks the laws, despite being changeable by mutation, are set at the beginning of the universe, and fixed thereafter. He gives an example of how a quantum system might be free to choose a result in a situation for which there is no precedent:

[pp147-8] These two features of quantum systems let us replace the postulation of timeless laws with the hypothesis that a principle of precedence acts in nature to ensure that the future resembles the past. This principle is sufficient to uphold determinism where its needed but implies that nature, when faced with new properties, can evolve new laws to apply to them.
    Here’s a simple illustration of the operation of the principle of precedence in quantum physics: Consider a quantum process in which a system is prepared and then measured, and assume that this process has occurred many times in the past. This gives you a collection of past outcomes of the measurement: X many times the system said yes to a question, and Y many times it said no. The outcome of any future instance of that process is then picked randomly from the collection of the outcomes of past cases. Now suppose that there’s no precedent, because this system has been prepared with a definite value of a genuinely novel property. Then the outcome of the measurement will be free, in the sense that it is not determined by anything in the past.

Smolin suggests that this principle of precedence could be subject to experimentation, by preparing some genuinely novel quantum states, and measuring them. I’m not sure of the scope of the system’s freedom, however. What about all those more advanced alien races who have already done these experiments? Do those set precedents? Also, the second time a measurement is done, there is only a single precedent from which to select randomly; this seems to imply determinism.

I like his idea of explicable evolving laws; although I still wonder, does a random choice fit with the principle of sufficient reason? And I must admit, I’m not sure why these “principles”, of sufficient reason, of precedence, of whatnot, are allowed to be timeless and universal, when nothing else is. He mentions the need for meta-laws, laws to say how the laws change, but doesn’t go into this as deeply as I wanted. Are the meta-laws timeless? If so, why? If not, what governs their change? I didn’t get the answers here: Smolin refers his book with philosopher Unger, The Singular Universe and the Reality of Time; maybe the answers will be there. For the time being, I have a few new ideas for student projects: growing cellular automata or graphs with rules that depend on configurations, and only deciding on the rule when a new configuration is seen.

Smolin finishes up with more social concerns. He explains that our notion of the fundamental laws of nature as being timeless leads to a damaging distinction between the timeless natural (hence good and right being changeless) and the ephemeral artificial (hence bad and wrong being change). Rather, everything changes and evolves, and we should embrace that fact.

[p257] How can we get rid of the conceptual structure of a divided and hierarchical world separating the natural and artificial? To escape this conceptual trap, we need to eliminate the idea that anything is, or can be, timeless. We need to see everything in nature, including ourselves and our technologies, as time-bound and part of a larger, ever evolving system. A world without time is a world with a fixed set of possibilities that cannot be transcended. If, on the other hand, time is real and everything is subject to it, then there is no fixed set of possibilities and no obstacle to the invention of genuinely novel ideas and solutions to problem.

This is a clearly written and thought-provoking book. It makes plain some issues with physics, and its thesis, about time and change, opens up some fascinating possibilities. Well worth the read.

Roberto Mangabeira Unger, Lee Smolin.
The Singular Universe and the Reality of Time: a proposal in natural philosophy.
CUP. 2015