Of all the physics and cosmology I’ve read over the past 7+ years this book stands out as one of the two most interesting, the other being Ruth Kastner’s “Understanding Our Unseen Reality: Solving Quantum Riddles”. Now this is a tough call because I’ve read a lot of great books, But this book inspired not only this review but one of my books, while Kastner’s work manages to actually account for phenomena like “action at a distance” and the paradoxes of the “double slit experiment” without hidden variables or merely explaining them away.
The crucial insight of Singular Universe is that time is not only real but the most fundamental (brute) characteristic of our universe. No other property of our universe (including space) could begin to exist in the absence of time. Impressively, Unger manages to disentangle the “global time” that both authors insist must be real from the temporal insights of Special and General Relativity. Einstein discovered that the measurement of time can only be a local measurement (from within some relative reference frame) but that discovery does not at all preclude a global time for the universe as a whole. In terms of shaking up modern physics, this might be Unger’s greatest contribution. Smolin adds to Unger’s fundamental a rationale accounting for the crystallization of “the cosmological settings”. He has a hypothesis grounded in empirically verified cosmology (black holes) suggesting an answer to the question “why did the cosmological settings come out with the values they have?” I think his rationale is far fetched but in the present community of cosmologists it counts as a strong rational hypothesis.
This is a superb and important book. It is quite long and two books in one, the first by Roberto Unger and the second by Lee Smolin. Both address the same topic, the reality (and fundamentality) of time and the failure of the Newtonian paradigm when applied to the whole universe. Each author takes a different approach to the subject on which, for the most part, there is a wide area of agreement between them and a few differences as concerns some details.
Neither book is “popular science”, but rather both are serious attempts at a novel “natural philosophy” that contributes (or should contribute) to advancing the subject of cosmology by illuminating little considered implications and interpretations of the physical (standard model) and cosmological data we already have.
Unger’s approach is more purely philosophical. He begins straightforwardly enough with the common (in science) metaphysical assumption that only the material universe is real. Although he abjures a strong metaphysics and offers instead what he calls a “proto ontology” that does not attempt to fix the kinds of things there are in the universe for all time, he is nevertheless stuck with this basic materialism and that forces him onto one of two horns of a dilema. The mystery is the extreme unlikeliness of “the settings” that make the universe hospitable to life. Most physicists being philosophically trapped in the “block universe” model of relativistic time (which in effect denies the fundamentality of time by casting time in terms of spatial geometry) have gone over to the multiverse as an (untestable) explanation (along with the “anthropic principle) for the unlikely values of the settings in our universe. From Unger’s viewpoint, the opposite tack, assuming time to be both real and fundamental, and that there is a global “preferred time” (perfectly compatible with relativity given appropriate alterations in what Unger calls its “metaphysical gloss”) which all means that there is nothing in the physical universe that is immune from the effects of time including the laws and settings which change (albeit in this universe phase very slowly) and that instead of multiple universes, the unlikeliness of our settings is explained by our one universe having an indefinite (not eternal) past that has gone through phases having various settings and has just happened, in this phase, to end up with the settings it has. Unger believes that this option, the “indefinite past” and a single universe at a time is better than the multiverse hypothesis because it provides for a causal (although the laws governing causal interactions will be different from phase to phase) continuance between phases. Time and causation entail one another, they are both fundamental in that what ever the laws and settings operative at a given moment happen to be, there is still some sort of causal interaction in time. As difficult as it might be to detect records of past universe phases (that is prior to our own big bang) such detection remains possible and therefore within the scope of science, while non-communicating multiverses that preclude any interaction do not.
Unger covers his ground very well. His approach is to revisit the same questions and issues over and over again like a skeleton on which he lays a little more flesh with each pass. In the end he leaves out two things. He offers no specific explanation for our particular settings this time around, and he fails to address how it is that the laws and settings we measure in our universe phase happen to hold over a range of conditions from the cold of interstellar space to the interior of stars. He admits that in our present “cooled down” universe the laws and settings appear very stable. His failure to offer any explanation for their stability does not detract from the argument that time is real and there is only one universe at a time. He explicitly leaves the rest to Lee Smolin.
Smolin is a physicist writing here as a natural philosopher and he is very good at it. His argument here is a reprise of his book “Time Reborn”. He’s had a few years to chew over these ideas, and I think his more concise treatment here is clearer than it was in that book. Smolin does offer two possibilities for explaining what Unger leaves out. The first is his “principle of precedence” which goes only part of the way, explaining how it is that the settings might get set, but not why they are what they are. The second, his notion of “cosmological natural selection” does actually explain both the settings and to some extent their stability across the wide range of conditions in our present universe. But these explanations rely on two rather speculative ideas.
First, new universes arise from the interior of black holes. The point of the settings and their stability is that these two properties are necessary to produce lots of black holes from massive stars. Such black holes in effect set the parameters of the universes they generate. Our own universe is in fact such a baby universe generated by a black hole in another universe. Second, the range of possible (or likely) settings of the baby universe would be different than those of the parent universe but only and always in a small range. This is what sets up the “natural selection”.. Universes whose properties happen to produce a lot of those kinds of black holes will end up dominating a history of branching universes such that the great majority of them have settings similar to ours just so that they can produce a lot of black holes.
Of course the very idea that universes are born in black holes (or that ours emerged from a black hole) is at present utterly beyond observational science, so this is sheer speculation whose only relation to physics (as distinct say from asserting that “God did it”) is that there is a potential causal chain (no matter what transformation the settings might undergo in between) connecting parent (black hole) to child (new universe). Smolin fails to say why it is that the variation in settings through black holes from massive stars (he explicitly rejects primordial black holes as selectable parents for this reason) should vary by only a little.This property is what makes them selectable. If the settings vary by very much, the outcomes (as far as black hole creation are concerned, not to mention life) will be random and not converge to an optimal type. There is no mention here that the coincidence of these same settings being conducive to life AND black holes is itself something of a mystery. Dr. Smolin spends a small chapter addressing the nature of qualia in consciousness, but he is interested in suggesting an example of precedent-agnostic causation (brain correlates of qualia) and not the coincidence of settings conducive to both black holes and life.
Both men address “the unreasonable effectiveness of mathematics”, and claim, reasonably enough given their history-first foundation, that present mathematics happens to be fit-able to present physics but that the discipline has no magic insight into the nature of every particular event in the history of the universe (Smolin) or into some Platonic structure that is metaphysically prior to actual history taken in aggregate (Unger). This is one of the more fascinating parts of both arguments because both men get to the same place about math in very different ways.
It is unfair to criticize either author for not solving every problem. For both this book is to be the foundation of a natural philosophy, not its completed edifice. Both author’s arguments rest on a foundation of time, causation, and therefore history as being fundamental. The universe is what it is and if we discover structure in its behavior, that structure, mathematically describable regularities, it doesn’t mean those very regularities weren’t different in the past and won’t change in the future. There is every reason to believe they are both onto something here. Smolin’s illustration of how we slip from an observation of causal stability in the present universe to a mistaken notion of absolutely deterministic precedents is illuminating to say the least. All of this above does not do justice to the over-all philosophical integrity of this work. Drs. Unger and Smolin happen to discover in one another kindred spirits as far as this business of the reality and fundamentality of time is concerned. I hope there will be more collaborations between them in the future.