On the Origin of Time: Stephen Hawking's Final Theory

To my surprise, this book is not a glorification of the multiverse concept — Marvel has that turf well-covered these days, yes? — but a thoughtful and considered navigation of the terrifyingly dark and murky waters between Aristotelian absolutism and profligate quantum possibilities. There is, for example, this striking line from the final chapter: "The multiverse evaporates like snow before the sun in quantum cosmology." I had no idea that the thoughts of Hawking and his associates on the multiverse were this nuanced towards the end of his life. I was fascinated to discover that Hawking vacillated from a bottom-up universe early in his life to a top-down universe later. It would have been fascinating to discuss with him the non-binary alternative that he seems never to have considered: the Matryoshka universe, in which different levels of certainty, complexity, and existence exist simultaneously and nested within each other, with the most robust forming the exterior, and the most significant complexity on the interior. And even without stating that, and despite Hertog declaring a top-down only strategy, he and Hawking and their associates nonetheless seem to have considered, perhaps without recognizing it, a decidedly Russian-doll-like concept in quotes like this one: "… there isn't the slightest ontological difference between the fact that Christian religions dominated Western Europe … and the value of the anomalous magnetic moment of the electron in the standard model of particle physics. They are both frozen accidents, just at widely different levels of complexity." It makes sense that the least time-like and most encompassing of Hawking's "frozen accidents" also form the most stable and encompassing of the layers, and perhaps this is why Hawking refers to this as a top-down universe. Just as a frozen alphabet enables communication and the formation of new levels of linguistic complexity, Hawking's earliest frozen accidents become the Standard Model of particle physics, allowing us to see and understand the most distant reaches of the visible universe. Also, a fully emergent universe enables the interplay of particles, space, and time, allowing levels of space to proceed those that we know from a classical perspective, just as some simpler particles, such as quarks, join together into more complex particles such as protons and neutrons. Perhaps a top-down universe versus a Matryoshka universe is more a matter of linguistic connotation and preference. Top-down better conveys the concept of a tree with the diversification of complexity in the higher branches than the more linear implication of nested dolls. On the other hand, top-down has an unfortunate connotation of premeditated design that is not what Hawking intended, yet it comes to mind quickly for anyone reading the phrase. However one describes Hawking's final and more nuanced concept time, this book is a worthy and thought-provoking read.

Beautifully written. The author bravely presents profound cosmological insights in understandable prose without patronizing the reader. The concepts are spell-binding. The interwoven humanity is uplifting. It was a privilege to read this book.

Most books on physics for the layman must include some history; ideas in science are built on the shoulders of historical giants (and a few dwarves). Thomas Hertog does a good job of including the background necessary for his tale without digressing too much. But like all physicists who write such books, his greatest challenge is to translate the Hawking team's work from the language of physics -- complex mathematics -- into language composed of words. He does quite well, I think. I felt there was perhaps a little too much bashing of the Anthropic Principle (AP). In it's simplest form the AP is a tautology: humans cannot find themselves in a universe where the physical laws make it impossible for life to exist, and therefore we see a universe in which the laws are compatible with us. I think Hertog's (and Hawking's) objection to the AP is that, when coupled with a cosmology which posits multiple universes, it appears to make cosmology untestable -- scientifically moot and therefore somewhat useless. I'm not entirely convinced; there have been hypotheses considered similarly untestable which clever investigation has found ways to test experimentally. But others besides Hertog and Hawking have voiced these concerns about the AP and a multiverse, so I can't ding them too much. While most cosmologies start as far back into the origin of our Universe as possible and then find equations to describe how its physics evolved from there, Hawking's idea here is to start with the known physics of our Universe and work backwards to derive a mathematical framework -- a wave function of the Universe -- describing how it began. He calls it a "worm's-eye view" instead of a "god's-eye view", meaning visualizing our Universe from the inside rather than from a god-like "outside". In Hertog's telling, taking the known physical laws as initial parameters for the math gives a different formulation of the wave function than starting with the Big Bang and evolving the equations from there. When worked this way, according to Hertog (and Hawking), the equations end up quite descriptive of our Universe. I'm not at all competent to address the real physics here, though. For laymen such as myself, it's crucial to remember that Hawking, Hertog, and their team worked rigorously inside the mathematical framework of physics. Their proposal had to fit with the math of General Relativity, quantum field theory, etc. It's not just something they dreamed up over pizza and a few beers. At one point Hertog mentions that a photo in the book shows some of their early equations on a blackboard behind Stephen Hawking. I wish he had emphasized the mathematical process more. Overall, it's another interesting and challenging idea from the workshop of Stephen Hawking. I know I've sold "Origin" short in many respects. I only hope I haven't misstated its thesis. Excellent reading to complement "The Origin of Time" would be Brian Greene's "The Hidden Reality", which explains the inflationary multiverse and other cosmological hypotheses. And of course Hawking's "A Brief History of Time", which gives an overview of cosmology, and of Hawking's prior no-boundary proposal. The no-boundary proposal as originally stated by Hawking was disappointing (according to Hertog) because it predicted a universe quite unlike ours; the proposal in "The Origin of Time" works backwards to the no-boundary condition and, as mentioned, appears to give a much better description of our Universe. And for those who don't know deep physics but would like a view into the equations, the indefatigable science author Sean Carroll is writing a trilogy of books to do just that. The first is "Time, Space, and Motion", dealing with classical physics equations from Newton to Einstein; the second (coming in May, 2024) is "Quanta and Fields"; and the third will be "Complexity and Emergence". Keep reading. Incidentally, I bought a paperback copy of "Origin", and got about 2/3 of the way through before the glue in the binding failed. Glued it back together and continued, of course. But disappointing.

Thomas Hertog was a student and then collaborator with Stephen Hawking, working with him right up to Hawking’s death in 2018. This book is a kind of scientific memoir, recounting their thinking together. What makes the book especially interesting is the methodological turn that Hawking and Hertog make, abandoning traditional scientific objectivity. Their approach, in their own terms, flips the perspective from which cosmological theory should be carried out, from that purely objective perspective to an observer-centric, even subjective perspective. There’s more to the book, but I’ll focus on that methodological flip. It’s really the core idea of the book. Hertog starts with a framing question — the question of “fine tuning”. Why and how did the universe produce conditions so well-tuned for the development of life, and, to bring the questions back full circle, of intelligent observers and theorizers of itself? The constants of nature, the strengths of the various forces and other factors, are so finely tuned that even slight variations would have produced a universe empty of galaxies, without the elements of life, or even a universe that would have collapsed upon itself well before galaxies, stars, planets, and life could have developed. Hertog follows a historical path, tracing the history of cosmological thought with an obvious emphasis on what has led to current challenges and stalemates. I appreciated his emphasis on the role of Georges Lemaitre. Lemaitre, a fascinating figure in part because he combined his scientific career with his life as a Catholic priest, was the originator of many core ideas in modern cosmology, including the “primeval atom” (aka “big bang”) and a cosmological model that incorporated the expansion of the universe with a big bang beginning. The current situation in cosmological theory is challenged by the need to merge our best account of gravity, Einstein’s general relativity, with our best account of microreality, quantum theory, to account for the dynamics of the early moments of the universe, the expansion from something like Lemaitre’s primeval atom. The best evidence we have for those earliest moments is the measurement of their energetic remnants, in the cosmic microwave background radiation. Those measurements, the temperature of the remaining energy from the big bang and its minuscule but crucial variations in different directions, provide the best tests we have. Many theoretical proposals and speculations, from the mostly-accepted theory of cosmic inflation to the much more controversial approaches to string theory try to fill the gaps, but nothing has yet passed the tests of mathematical consistency. causal history, and empirical validity. What Hertog and Hawking propose is not a better theory, it’s a different kind of theory, with a different understanding of what science does. The key distinction running through their thoughts is that between “bottom-up” and “top-down” cosmological theories. “Bottom-up” theories are traditional, causality-centered models of how the universe evolved. Within those theories, we run into a big problem, the improbability of our universe (and therefore of us) — the fine-tuning problem. Given that the universe’s history is one of quantum probabilities stacked and networked endlessly together, what kind of universe is likely to have been produced? Not ours, it turns out — specifically the required value for dark energy, governing the strength of the expansion of the universe, would have to be especially and improbably suited to the development of a universe with galaxies like ours, with stars like ours, producing the stable elements we are made of. “Top-down” theories ask a different, even the opposite question. Instead of how the current state of the universe developed from its origin, they ask what history of the universe follows from its current state. This question is, as Hertog says, observer-centric. It starts with the presence of an observer, and asks historical questions leading back from that observer. Thus it traces paths through the past of probabilities realized to a beginning, guided by the current state, as opposed to tracing paths forward from an origin hoping to get where we are now. This is an abandonment of the traditional task of science, to produce an objective account of reality. This approach is tainted by subjectivity, by its starting point with an observer within the reality it attempts to describe. What justifies such a radical methodological reversal? First, there’s the failure of the bottom-up approach. The bottom-up approach fails to explain how we got to the current state. Unless you add multiverse theory and an anthropic principle. Multiverse theory is well motivated by the physics described in bottom-up approaches. I won’t go into details, but the idea is that multiple universes are implied by that physics, not just one, each of those universes realizing different possible values for dark energy. So we have multiple possible universes realized, not just one improbable universe realized. The anthropic principle picks out the universe we observe around us as, necessarily, one of the members of the set of those universes that support the formation of galaxies, stars, and the elements that make us up. It couldn’t be otherwise. But, according to Hertog and Hawking, that anthropic principle has little explanatory value. We are in the type of universe we are in because we couldn’t be in the other ones. You’ll have to let your own thinking settle for you whether that explains anything. The second justification for going top-down in theorizing stems from the picture of reality that quantum mechanics gives us, and particularly the picture given us by a non-standard interpretation of quantum mechanics. Standard interpretations present a picture of an observer conducting experiments that reveal a probabilistic character to the behavior of the particles he observes. The non-standard interpretation (Everettian, named for the physicist who originated it, Hugh Everett) rejects the separation between observer and what she observes — after all, the observer is herself part of the same probabilistic, quantum universe as the particles she observes. She is a quantum phenomenon just as much as the phenomena she observes, and her observations are just as much events in that shared quantum universe as the events she observes. In fact, her observations, the questions she asks and the measurements she takes mix with the particles she observes to produce the results she observes. It’s an observer-relative universe demanding an observer-relative theory. Hertog calls the subjectivity inherent in top-down theorizing “a delicate subjective touch,” saying, “Observers—in this quantum sense—acquire a sort of creative role in cosmic affairs that imbues cosmology with a delicate subjective touch. Observership also introduces a subtle backward-in-time element into cosmological theory, for it is as if the act of observation today retroactively fixes the outcome of the big bang ‘back then.’” Top-down theorizing itself still allows us to ask the question, what do we find when we do follow observations back in time, to the “beginning”? Hertog says that we find no ultimate theory of the universe from beginning to end, a causal story of how the universe came to be and came to be what we see today. That theory would be one that was “of” the universe rather than “in” the universe, and the only theories we can have are theories “in” the universe. In fact, what he claims we find, in the theory that he and Hawking were pursuing at Hawking’s death, was a theory in which what we call the laws of physics themselves evolve, emerging (in my words) as the conditions of sense-making in our theorizing. If you ask what came before what allows us to make sense of the universe, you’re asking a question that can’t be answered. Hertog says, “Our top-down perspective reverses the hierarchy between laws and reality in physics.” I should say that the theoretical framework that Hawking and Hertog were employing at that point is “holographic physics,” which I can’t begin to explain (because I don’t understand it well enough). So I won’t embarrass myself by trying. Hertog doesn’t pull back from his conclusion that there is no final, absolute theory, or to paraphrase him, no Archimedean point outside the universe from which to understand the whole of it. Instead of a final theory, we can construct numerous top-down theories based on different questions and different observations, leading again back to the limit of theorizing withinin rather than from outside of the universe. This is a humanistic turn as well as a turn away from pure objectivity. He cites extensively the remarks of the philosopher Hannah Arendt from a 1963 talk on “The Conquest of Space and the Stature of Man,” in which Arendt emphasizes this recognition that science is the work of scientists within the phenomena they study. Paraphrasing again, knowing is an activity that contributes to the creation of its objects. That to Hertog is the lesson of a thorough attempt at quantum cosmology, incorporating the inextricable role of the observer. Hertog has written a book for a “general audience,” but it’s not one that overly abandons precision and mathematical expression to make its points accessible. This is much more about method than mathematical theory. The fate of what Hertog is talking about here may be unlike how physicists like to think theories are evaluated. It may be rejected on inertial methodological rather than empirical grounds. The practitioners of science may be loathe to give up the idea of an absolute, objectivist theory, and in fact there’s no great movement to rally around “top-down” theorizing as a result of Hertog’s and Hawking’s work. Physicists, including (infamously) Hawking himself, often have strong allergic reactions to what they think of as philosophical thought.

I have read a number of similar books over the years, and this is by far the best one. Not only is it cutting edge, the author knows what he is talking about and knows how to explain it. Very clear cut, but it helps if you have a basic understanding of science and are a visual thinker. Until I read this book, I had problems grasping and accepting some of the new ideas in cosmology until the author explained them logically in a way that made perfect sense. I really loved that some of the new things I was reading in the book agreed with some of my insights which was an immense joy to show to my sons who think their dad is crazy. Buy the hardcover, this one is a keeper that you will want to go back to for reference and review. I believe this book may very well be the zenith of general market cosmology books.

The strength of this book is Hertog’s ability to show how the history of cosmology is tied to the development of relativity and especially quantum physics. I wish that clarity had extended to his major thesis. Instead of the most common way to explain how the universe developed (including the idea of a multiverse), the universe that Hertog argues for is not causally explained in the sense of the interpreter standing outside to explain it but tied into the “observers” themselves affecting the past and the deep connection of this phenomenon with the concept of the universe as a hologram. One of my biggest problems with the book is Hertog’s use of “observer.” He seems to equivocate on the use of the term though I doubt if he actually is. It may be simply lack of clarity in explanation or my lack of background in physics. But he definitely uses the term in a unique way. He cites a couple times the famous double slit experiment in which the wave-particle duality is affected by whether the observer is present or not. He then cites the fascinating experiment suggested by John Wheeler and later carried out– the “delayed choice” experiment – in which the decision to observe is not made until AFTER the photon passes the slits. The result implies that the effect of the observer appears to work backwards in time. Hertog’s point about the origin of the universe and the origin of time is tied to the “observer” affecting the past. As Hertog puts it, the traditional way of viewing the universe’s origin is “bottom-up.” But the perspective in the book, which is his own and Stephen Hawking’s final theory, is a “top-down” understanding. The act of observing affects the reality of the past. The top-down approach bypasses many problems in the traditional causal interpretation. There is a “retrocausality” though “causal” in this context, as in quantum mechanics in general, is not the appropriate term. Hertog’s use of “observer” obviously is much broader than we usually think. My observing the universe did not result in dinosaurs. It has to do, as I understand it, with the presence of observership at the quantum level that somehow creates the time we know and the physical laws themselves and can be traced back to the origin of the universe as we know it. Undoubtedly the math is there. Hawking and Hertog are (and were) brilliant cosmologists and almost no one reading the book is qualified to question their work. But, if Hertog is going to talk about observership somehow forming (and running through) the universe, he needs to spell that critical point out better for the reader who is interested in the issue but who is not a physicist. I may (and probably am) missing something but I just do not understand how the act of observing functioned when there were no observers nor how observership "precedes" or creates time. (It broadens what the term means but how exactly?) Hertog dismisses speculation about a god or some metaphysical entity being the “observer.” But, as fascinating as the idea is, I think a much clearer explanation could be given (if such is possible). So the book for me was mixed. It is an excellent analysis of the history of cosmology and of Steven Hawking’s own journey through different understandings of the universe’s origin. (The view in here is very different than in Hawking’s Brief History of Time.) In places, as another reviewer noted, there are some elements that strike the reader as scientific hero worship. But for me this would be a minor issue if Hertog better spelled out for the reader how a term like “observer,” which is relatively clear in common usage and in the traditional way people understand the two-slit experiment, is used here.

After reading Hawking’s *A Brief History of Time*, and Kipp Thorne’s *Black Holes and Time Warps*, I had the impression that Hawking is not only a great scientist but also a deep philosopher of science. He is a rare breed of scientist who combines solid technical skills with profound insights. He is able to see both the forest and the trees. All this with little “ego” to be seen in his writings or in his followers. Hertog’s book confirms these conclusions. Hertog is a student-cum-fellow of Stephen Hawking. He is an outstanding physicist that knows what he is writing about. The book analyzes how scientific debate is motivated by philosophical positions. In particular, the book explains the journey that Hawking traveled from the position of Einstein to that of Lemaître. I will not summarize these positions so as not to spoil your appetite to read the book! It is an interesting journey that is worth the struggle. The book elegantly weaves scientific theories with the history of science. The style and prose are simple and clear. The discussion of time is subsumed into the discussion of quantum holography. The author emphasizes that spacetime and gravity are “emergent phenomena.” “Holography ingrains a fundamental element of emergence into the very roots of physics—into the fabric of spacetime itself.” According to the author, “Holographic cosmology excises the multiverse like Ockham’s razor.” An important insight is that “there is an upper bound on the amount of information that black holes can store.” In contrast, “multiverse cosmology assumes that our cosmological theories can contain an arbitrarily large amount of information without affecting the cosmos they describe. But holographic cosmology paints a very different picture.” The last chapter is mostly philosophical. The main message is that we ought to be “At Home in the Universe.” This is quite enlightening. But the discussion overall is not as stimulating as the rest of the book. The author probably needs to take another look at that chapter. Overall, despite the many books on black holes, relativity, and quantum physics, this book presents a unique perspective. It also shows the profound value of Hawking’s contributions to modern science and philosophy.

Interesting stuff. A lot of hypotheses without physical evidence. Could be correct, but …..

An excellent exposition of one of the most fascinating and difficult subjects. A worthy successor to Hawking's A Brief History of Time.

Se podría decir que es el último libro de Stephen Hawking ya que le pide al autor en un momento de la investigación que es hora de escribir un libro. Cuenta como es la colaboración que les une para buscar una explicación del origen del universo dando detalles de las reuniones e ideas sobre las que desarrollar la teoría. Básicamente conciben una explicación que ellos llaman de arriba-abajo hasta el principio de todo que incluiría la génesis de las propias leyes físicas. Basada en la hipótesis de no-frontera, predice que el principio del universo llevado tan lejos en el tiempo como es posible se mezclaria con el espacio dentro de una esfera de altas dimensiones, encerrando el universo dentro de la nada. El origen del tiempo en la teoría final de Hawking es todo lo que puede ser contado del pasado. Ideas especulativas para deleite de lectores que les guste la cosmología. Muy interesante.

Came in good condition

Really nice!

I worked my way through this excellent book quite carefully, absorbing as much of the physics as my limited mathematical skills allowed. Nevertheless, I still was able to grasp the concepts (I think) that are presented so well for the layman. The final pages of the book delve more into the philosophy of Hawking’s theory, and I found that part equally fascinating and enlightening. A great book, if you can stick with it and work your way through.