If you’ve been reading popular physics books for a while, then you know the name Brian Greene. The Columbia University professor is known for a series of popular science books, beginning with 1999’s “The Elegant Universe,” that have brought string theory, the nature of space and time, and the question of parallel universes to a wide audience. With his new book, he casts a much wider net, seemingly positioning himself in the territory claimed by the likes of Steven Pinker and Yuval Noah Harari.
With “Until the End of Time,” Greene is asking Pinker and Harari to hold his beer. The book covers a stunning array of human thought: There’s still plenty of physics, but we find that Greene also has a great deal to say about evolution; the origins of human culture; the dawn of art and music and storytelling and religion; the puzzle of consciousness; the paradox of free will. It’s an ambitious undertaking, to say the least.
It is perfectly reasonable to wonder if Greene — or any author — is to be trusted with such a multi-disciplinary project. Take biology, for example. Why do we need a physicist to tell us about the workings of living organisms? Because underneath the biology there is physics. And yet the laws of nature appear to pull on these two worlds in opposite directions. Physicists tell us that, according to the second law of thermodynamics, entropy — roughly, the amount of disorder in a system — must increase over time. But evolution, which shapes the living world, appears to add to the order and complexity found in nature. Let evolution loose on some organic compounds in a “warm little pond” (to use Darwin’s phrase), wait a few billion years, and before you know it, the autotrophs begin to drool.
And yet biology is beholden to physics. How, then, is a rabbit different from a rock? “Life does not and cannot contravene physical law,” Greene assures us. “Nothing can.” The trick is information. The DNA in the rabbit’s cells encodes instructions that tell those cells, and the molecules within, what to do. It guides them, as a waterslide guides a child’s descent into the pool — though cells and molecules are utterly oblivious to this guidance. “Life,” Greene writes, “is physics orchestrated.”
We, of course, are just as oblivious to this orchestration as the rabbit is (or the cell or the molecule, for that matter). Which means that in our daily lives we tell a different story, a “higher-level story” centered on humans and their interactions, without worrying about our component parts.
This idea — that nature offers hierarchical “levels” of description — is hardly new. Arthur Eddington wrote about it in his 1927 book “The Nature of the Physical World”; Sean Carroll (perhaps Greene’s closest competitor in the world of let’s-tackle-everything physics writing) explored it in some detail in “The Big Picture” and “Something Deeply Hidden.” But where Carroll emphasizes the distinction between the everyday view of reality and the physicist’s view (he says there’s a “yawning chasm between what we see and what really is”), Greene does not privilege one “story” over the other. We are particles; we are people.
Indeed, there is “little to be gained by physicists clamoring that theirs is the most fundamental explanatory framework or from humanists scoffing at the hubris of unbridled reductionism,” Greene writes. Different “levels” require different kinds of explanations, and, with effort, these stories can be woven together “into a finely textured narrative.”
Greene does not privilege our everyday view of reality over the physicist’s: We are particles; we are people.
Mind you, this leads to the sorts of puzzles that have stymied philosophers for thousands of years. Topping the list is the fact that we don’t feel like a bundle of particles blindly conforming to the laws of physics. We seem to be conscious; we seem to have free will. Greene acknowledges that this is “a critical gap in the scientific narrative.” We do not have “a conclusive account of how consciousness manifests a private world of sights and sounds and sensations.”
Some have suggested that it will take a revolution in thought (perhaps including a profound re-thinking of physics) to crack the problem of the mind — but Greene’s hunch is that conventional science will do the trick, and that “we will one day explain consciousness with nothing more than a conventional understanding of the particles constituting matter and the physical laws that govern them.”
And what of free will? Greene, like Carroll, embraces what philosophers call “compatibilism.” This is the notion that you can still make what feel like free choices even though the atoms that make up your brain (and everything else in the universe) are simply responding to the laws of physics. Does that mean that free will is ultimately an illusion? It depends how you look at it. As Greene puts it: “Our choices seem free because we do not witness nature’s laws acting in their most fundamental guise; our senses do not reveal the operation of nature’s laws in the world of particles.”
Greene sees this in a positive light. We don’t have the sort of freedom that would override the laws of physics (he is confident that there can be no such thing), but we still have freedom “to exhibit behaviors — leaping, thinking, imagining, observing, deliberating, explaining, and so on — that are not available to most other collections of particles.”
Some readers may find this a satisfactory account of free will, but it is the one place where I felt shortchanged, as though I had ordered shepherd’s pie and was served only the mashed potato. Granted, we have this wide range of behaviors; we can perform actions that no rock will ever be able to muster. Cool. The only catch is that we don’t get to choose from this palette of possible actions; in some sense, they just happen, and we are merely along for the ride. (Can we still be held accountable for our actions? I once asked another physicist about this: What would happen if, standing accused in a court of law, one defended oneself by saying, “Sorry; my atoms made me do it.” His reply: “No problem. We’ll put your atoms in jail.”)
There is more. Greene presents the history of the universe, from the Big Bang to the present day, followed by a survey of the various ways in which the universe’s long-term future might play out. The most likely scenario, for better or for worse, is the cold, lifeless void that physicists refer to as the “heat death” of the universe. It is, in a nutshell, the second law of thermodynamics’ ultimate end-game. (Greene examines the question of whether “thought” could somehow survive this descent into maximum entropy. Spoiler: probably not.)
Meanwhile, we have our stories. We evolved language, and immediately began spinning tales; we became a species enamored with myths and legends. But why do stories hold such power over us? Because they help us survive: “Minds that acquired this power were minds capable of seeing old problems in a new way. They are minds that would innovate. They are minds that, in time, would control and reshape the world.”
It is in this realm — where he examines language and culture — that Greene is most firmly planted in territory carved out by Pinker. But Greene has one advantage: He has an extraordinarily deep understanding of the layers that lie beneath. And so we learn about “simple” things like stellar evolution, and also controversial ideas like the multiverse and Boltzmann brains, which he handles with a judicious amount of skepticism.
Greene presents the history of the universe, from the Big Bang to the present day, followed by a survey of the various ways in which the universe’s long-term future might play out.
Greene’s biggest challenge — and ours — is to find meaning in a universe governed by unthinking and uncaring physical law. Steven Weinberg put it bluntly in his 1977 book “The First Three Minutes”: “The more the universe seems comprehensible, the more it also seems pointless.” Certainly the human experiment is temporary; one of Greene’s overarching themes is transience and the search for the timeless. We inhabit “a breathtaking if transient present,” Greene writes. By striving to understand the larger cosmos we gain perspective; it shows us “how singular and fleeting the here and now actually is.”
Not everyone will welcome the message, but Greene makes it crystal clear: It’s physics all the way down. “Particles and fields. Physical laws and initial conditions. To the depth of reality we have so far plumbed, there is no evidence for anything else.” And yet we yearn for more. Which means we have to construct our own meaning as best we can. “During our brief moment in the sun, we are tasked with the noble charge of finding our own meaning.”
Books that try to cover so much ground can easily falter. Harari, for example, can seem a little too eager to provoke; some writers seem to be overly keen on fitting the available facts to some preferred, over-arching theory. Greene, happily, does not fall into either of these traps. He is not selling you anything, he is merely relaying a story. But it is the grandest story one can imagine, told by a master storyteller. And look, you’re not going anywhere for a while. Buy this book, and buy Carroll’s “The Big Picture,” and hunker down.