LAST YEAR, Jim Holt's Why Does the World Exist? introduced readers to an unusual thing: a science book that didn't force an epiphany. Sure, a “proof” near the end purported to give an answer to the book's main question — why there is something rather than nothing — but it wasn’t clear that Holt himself was much convinced by his argument, or that reaching it was really the point. In bouncing from conversations with one fêted philosopher to the next, the comic journey seems to have been its own reward. When the odyssey turns from considerations of loopy logic to mortality, with the death of the author’s mother, the transition reads as a natural intersection between philosophical “nothingness” and its human roots. This was a text designed for people fonder of possibilities than of clear-cut answers, or for readers you’d imagine following, say, the musical aesthetic of Alfred Schnittke, even if it cut against vested sonic interests. Because of Holt’s refusal to exclude any plausible POV, when I read his book it felt more vital than just about any other work of popular cosmology.
Lee Smolin’s new book, Time Reborn, is, well, a different read. For one, Smolin is a scientist; he is a professor at Ontario’s Perimeter Institute — home of the newly built Stephen Hawking building — and, perhaps more importantly, he’s after epiphanies. While Smolin’s last book, The Trouble With Physics, chronicled how the best minds of his generation were destroyed by string theory, his follow-up attempts a more direct goal. “Much of this book,” he writes, “sets out the scientific argument for believing in the reality of time.”
This goal itself is curious because, as Smolin acknowledges, he “used to believe […] in the unreality of time.” Smolin’s followers will remember that in the last chapter of The Life of the Cosmos, his first foray into pop writing,the authorpraises Julian Barbour’s view of the universe as frozen moments of an unchanging present with certain correlations to other moments that we ignorantly label as “past.” What, then, changed Lee Smolin’s mind? The answer is striking, and may be unprecedented in a serious science book:
My initial motivation might best be described in the language not of science but of fatherhood, through the conversations I have had with my young son, especially when I put him to bed at the end of the day. “Daddy,” he asked once as I read to him, “did you have my name when you were my age?” Here was a child awakening to the knowledge that there was a time before him and seeking to connect the short story of his life so far to a longer epic.
A few pages later he notes, “This does not pretend to be an academic book” (though the endnotes promise to provide a “rigorously argued” version sometime in the future). And yet, despite this sentimental anecdote, Smolin insists that such dalliances have not affected his judgment. Although the idea of a universe without time, he allows, may be “horrifying to anyone whose worldview includes a place for free will or human agency,” nota bene: “This is not an argument I will engage here; my case for the reality of time rests purely on science.”
As if to convince us that the author isn’t cheating, Part I (nearly one third of the book) is given over to explanations of why many physicists have asserted that time is not real. It’s an example of what Thomas Kuhn identified a half-century ago as textbook teleology: a heavily edited, streamlined account of science’s stately march toward enlightenment. But if Smolin’s account marches thusly, it is only to show how we arrived at the incorrect conclusion about time, not the correct one. Though we’re presented here with a charming volta in the narrative, it does not quite perform the departure Smolin intends; in fact, the device is probably an all-too-convincing argument in favor of the unreality of time.
Smolin spends a few chapters explaining what he confusingly has chosen to call the “Newtonian paradigm,” a phrase that in other contexts has been used to describe Newton’s Laws, but that encompasses, for Smolin, any model of reality that one could use, given initial conditions (how the parts of the system are positioned and how they’re moving at the beginning) and laws of motion (the rules for how those movements will change in time), to predict any future changes to that system. He’ll eventually challenge the assumptions that neither space nor the laws themselves evolve with time — but not before showing why systems like these, if accepted, can effectively allow time to disappear.
Suppose a system under review includes a clock. If the motions of objects in this system have previously been described with respect to time, why can’t the discussions of “time” be replaced by discussions of relative positions, with everything in the system compared to the positions of the hands on the clock? And if we’re able, at least theoretically, to use the laws of motion to predict the motions of all parts of the system indefinitely into the future, what’s to stop us from conceptualizing these moments as all effectively preexisting, a block universe of foregone conclusions that (for whatever reason) we’re constrained to experience in the present? “The lesson here is as simple as it is terrifying,” Smolin contends. “To the extent that assumptions underlying the Newtonian paradigm are realized in nature, time is inessential and can be removed from the description of the world.”
Introduce relativity, and the situation for temporal realists only gets worse. Smolin offers a fairly de rigueur discussion of the big topics, from special relativity’s observer-dependent definition of “simultaneity” to general relativity’s gravitationally contingent clocks. He takes special pains to emphasize general relativity’s step forward in having established a “self-contained” theory of physics, a theory that doesn’t require the presence of any phenomenon outside of the system to describe events inside of it — making it a theory that can be applied cosmologically, to the entire universe. “But,” he insists, “it still is based on the Newtonian paradigm, as it can be formulated in terms of timeless laws acting on a timeless configuration space.” To cap off the picture of a universe without time, he revisits Julian Barbour’s quantum cosmology, where the probabilities of quantum theory refer to nothing more than the frequencies with which different moments exist in a causally disconnected universe — an infinite array of frozen slices within a static, coexistent present.
All heady stuff, to be sure. But Smolin's reframing the whole of physics as “the Newtonian paradigm” notwithstanding, his book’s real idiosyncrasies occur in Part II, where we’re given the warp and the woof of his argument — and the promise that the primacy of time will be reinstated.
In the first few pages of Part II, Smolin puts cosmology's fundamental paradoxes in his own terms (see him move deftly from its “fallacy” to its “dilemma,” and on to its “challenge”) and asks us to consider Anaximander, the Greek who solved the question of why, if everything seemed to fall downward, the earth itself didn't fall. Anaximander discovered that instead of falling merely downward, objects fell toward the earth, which also explained why the earth, already in its grand position, had no reason to tumble. Smolin claims that Anaximander's realization that local laws might not extend to larger scales is one that modern cosmologists have yet to generalize. “It remains a great temptation,” Smolin writes, “to take a law or principle […] and apply it to the universe as a whole. To do so is to commit a fallacy I will call the cosmological fallacy.” He tells us that although such applications are poorly justified, they remain at the heart of cosmological practice. “But there is only one universe,” he continues, “and one case does not yield sufficient evidence to justify the claim that a particular law of nature applies. This might be called the cosmological dilemma.”
A sanguine scientist might look at this “cosmological dilemma,” shrug, and move onto something else. But Smolin sees the problem as connected, in some obscure way, to the habits of the “Newtonian paradigm”:
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. The invention of a way to surmount this barrier might be called the cosmological challenge.
Claims like “everything in the universe changes” are impossible to prove, but Smolin is a new father; he’s optimistic. And he’s got principles.
First there’s the principle of no isolated systems, which, reasonably enough, asserts that it’s not possible to entirely neutralize outside influences when you consider one of the universe’s smaller subsystems. This principle, along with his second, the principle of explanatory closure (“No chains of explanation can point outside the universe”), aren't wisdom of the ancients so much as they are the rules of the game. The principle of no reciprocated actions (“There should be nothing in the universe that acts on other things without itself being acted upon”), too, if not exactly a scientific necessity, has a pedigree august enough to raise no hackles.
In fact, the author’s fondness for principles is so great that he seems to have given up the subject of time entirely. He asserts that if we’re to “take up the cosmological challenge,” our best hope is to “devise a theory not patterned on the Newtonian paradigm that can be applied to the whole universe without approximation.” The requirements of this “true cosmological theory”? At the very least, it must a) contain what we already know about nature, b) be scientific — that is, have falsifiable consequences, c) answer why the laws of nature have the particular form they do, and d) answer why the universe, at the beginning of time, had the particular initial conditions it did. He insists, too, that this theory would incorporate the “collective wisdom of physics,” as characterized by the work of its “great sages” — Kepler, Leibniz, Einstein, et al.
The principle of sufficient reason, lifted from Leibniz, states that “there should be an answer to any reasonable question we might ask about why the universe has some particular feature,” which only raises more questions: What counts as “reasonable?” And what, in cases involving the entire universe, would constitute something so momentous as an answer? The identity of the indiscernibles (“Two things that have the same relationships with everything else in the universe must actually be the same thing,” also of Leibniz origin) appears less suspect than sufficient reason, but Smolin immediately forces it to a sweeping claim about the nature of physical law. Symmetries, those aspects of physical law that don’t change under some type of shift, undergird virtually every major accomplishment of modern physics — from the general covariance of relativity theory to gauge transformations in the standard model — but apparently these successes are less impressive than centuries-old principles. “Symmetries are common in all the physical theories we know,” Smolin admits. “Yet if Leibniz’s principles are right, they must not be fundamental.” By the next page, he puts this unequivocally:
So the unknown cosmological theory will have neither symmetries nor conservation laws. Some particle physicists, impressed by the success of the Standard Model, like to say that the more fundamental a theory is, the more symmetries it should have. This is precisely the wrong lesson to draw.
To clarify: what’s under discussion here is an unknown cosmological theory. Restated bluntly: this theory doesn’t exist — not even kind of, not even in draft. Such quibbles are left for other minds to discover. But this doesn’t stop Smolin from referring to his unknown theory as though we should take its consequences seriously. Indeed, meditations on Theory X obscure, for a few chapters, what any of this has do with — where were we? — ah, yes, with arguments now for the reality of time.
Compared with the fleet sloop of anti-time Part I, pro-time Part II seems more like a chest of curious notions scattered across the deck of a sinking ship. A string of arguments, some opalescent, some dull, are unlikely to be recovered by future scholars as pearls. Waves crash over the deck and carry the notions away. “Time!” bellows the captain periodically, though it’s increasingly tough to tell if the rudder is directed anywhere near that distant shore. Still, adrift in this topical cluster, I’ll admit that a certain tenderness crept in for me. Many of my favorite pop-sci writers — George Gamow, Rudy Rucker, even Jim Holt — could be counted in the Treasure Chest School, the defining feature of which is the elevation of momentary digressive pleasures over the larger argumentative swoop. Though I don’t recommend this approach to just any writer of science books, the experience of reading such buckshot exposition can be, despite everything, fun.
But excited states must decay, and Time Reborn must rebirth time. For all the assurances that the reinstatement of time is fundamental and will push cosmology forward, the route Smolin suggests looks backward just as often. His position, observe, is delicate: with Part I having established that the normal ways of looking at physics leave no fundamental place for time, reinstating it is a matter of deciding which of the usual physical assumptions he’s willing to jettison. Quantum mechanics is the first to go. “The apparently free, uncaused behavior of individual quantum systems presents a formidable challenge to [the principle of sufficient reason],” Smolin notes. He then wonders, “Could there be a deterministic cosmological theory that gives rise to quantum physics whenever we isolate a subsystem and ignore the rest?”
This leads him to explore one flavor of “hidden-variable” theories, the flavor that that reinstates determinism to quantum mechanics. But this class of theories has a well-known problem: they require motion to be absolute, not relative. The question remains, then, with a century of passed tests for special and general relativity and a half-millennium of relative motion in physics, just how such a proposal will be able to contain what we already know about nature, as per Smolin’s own mandate. Smolin has anticipated this objection, and it leads, as far as I could tell, to the book’s only striking argument in favor of time.
It starts by nailing down the meaning of rest. “The first thing to note,” Smolin writes, “is that the universe is arranged in a way that does indeed pick out a preferred state of rest.” There are two possible ways to find it: you can either adjust your motion so the universe looks, on average, the same in all directions with respect to the speed of receding galaxies, or the same in all directions with respect to the cosmic microwave background’s temperature. “Happily,” Smolin reports, “the two families of preferred observers coincide” — as they should, given that outward-flying galaxies and leftover microwave radiation jointly constitute the strongest evidence we have for the Big Bang model. Finally, from this universal rest-frame, he’s able to introduce shape dynamics, an idea based, intriguingly, on the suggestions of Julian Barbour, time’s greatest living antagonist.
Smolin admits, “This reformulation is just another way to understand general relativity, but it reveals a physically preferred synchronization of clocks throughout the universe.” In effect, the proposal is that the effects of relativity should be understood entirely in terms of stretches and squashes of space, instead of the usual stretch-squash of time:
In a word, in general relativity size is universal and time is relative, whereas in shape dynamics time is universal and size is relative. Remarkably, though, these two theories are equivalent to each other, because you can — by a clever mathematical trick that isn't necessary to go into here — trade the relativity of time for the relativity of size. […] The physical content of the two descriptions will be the same, and any question about an observable quantity will have the same answer.
Got that? General relativity and shape dynamics are equivalent — that is, for all scientific purposes, it could go either way. Still, Smolin takes the possibility as a triumph. “Time,” he crows, “has been rediscovered.”
Observers unconvinced by this reveal could argue that we’ve been shown little more than a nice demo of mathematical flexibility. But pause to consider it: the discovery of a single time variable for the whole universe is something of a theoretical coup. It need not matter that the practical effects of said formulation are probably nil (after all, clocks exist in space and, subject to distortions as ever, will still run fast or slow); the new formalism makes the reality of time just strictly possible — and that’s enough. In light of the doubt Part I casts on this simple possibility, this revamp feels like Part II’s logical climax.
But five more chapters follow, plus an epilogue. Of what? Well, Smolin loops back into Treasure Chest mode, with variably pleasant adventures whose relationships to time range from plausible (“if we embrace the reality of time, we make possible a time-asymmetric physics”) to frankly absurd (“the greatest harm done by the metaphysical view that reality is timeless is through its influence on economics”).
The strangest of Smolin’s further inquiries are tinged by moral hysteria. In one representative passage, he presents dubious arguments — based not on evidence but on principles — that the universe must be finite, since in an infinite universe one would eventually encounter all “things that might have happened”:
This to me is a horrifying prospect. It raises ethical issues, for why should I care about the consequences of the choices I make, if all the other choices are made by other versions of me in other regions of the infinite universe? I can choose to nurture my child in this world, but shouldn’t I care also for the children in other worlds who suffer because of the bad decisions made by my other selves?
A page later, he concludes, “We can avoid the implications of the tragedy of an infinite universe by denying that the universe is infinite in space.” Parishioners in back pews might nod sleepily along, but it’s plain that this is emotional consolation, not rational argument.
The further I ventured into these waters, the more I discovered that Time Reborn is overflowing with so much quasi-spiritual longing, translated into the language of positivist bluster. But where other narrators might have the leeway to admit wishful thinking, Smolin is constrained to genuflect toward evidence, to insist on the purity of his scientific virtues. In late sections, he returns to discussions of the unknown theory — the one true cosmology that explains both the universe and itself — and supposes that eventually there will be meta-laws to explain scientific laws. And why those meta-laws? Will there be meta-meta-laws, or will it just be meta-laws, as it were, all the way down? Smolin labels this the meta-laws dilemma, but happily insists that despite the appearance of “a dead end,” he has “come to believe that it is, instead, a great scientific opportunity,” a “key to the breakthroughs that will allow cosmology and fundamental physics to progress in this century.”
As with the true cosmological theory itself, Smolin is candid about not having a solution to this problem. (Of course; no one does.) “But to ultimately solve the meta-laws dilemma, the dynamics by which laws evolve must be sufficiently different from the laws we’re familiar with so that the Why this meta-law? and Why these initial conditions? questions do not arise.” You can smell St. Anselm around the corner. A century or two ago, Smolin would already have had his answer.
Which brings us back to Jim Holt, whose Why Does the World Exist? is a uniquely vital work of modern pop cosmology because of its willingness to leave unresolved issues unresolved. Midway through Time Reborn, Smolin, too, cops to the importance of unresolved questions: “If we consider that the laws and initial conditions are described by some parameters, there are two distinct parameter fits to the observed data. Observers call this kind of a situation a degeneracy.” The cosmic microwave background, for instance, is explained via a variety of different scenarios — which, in laboratory physics, would be distinguished from one another by further experiments. “But in a case like the CMB,” he writes, “which is the remnant of an event that happened only once, we may never be able to resolve the degeneracy.”
What Smolin won’t admit is that this too is the case with time: it’s a scientific and philosophical degeneracy that probably won’t be resolved. Instead, the book ends with the mystical insistence that “the key is time and the future is open.” Whatever that means, exactly, readers should know better. It’s 2013 — fans of heavy metal are doing the Watusi and the Hustle; ironists are wearing their hearts on their sleeves, on their book bags, and ontologically; open questions remain open. So far as science can tell us, such ideological humility may be the nearest thing to freedom we humans get.