L' Origine du temps: La dernière théorie de Stephen Hawking

by Thomas Hertog

Dans ce livre, Thomas Hertog présente la dernière théorie de Stephen Hawking, dont il a été le plus proche ami et collaborateur : une nouvelle perspective profondément darwinienne sur les origines de l’Univers. Stephen Hawking et Thomas Hertog ont travaillé côte à côte pendant vingt ans sur une nouvelle théorie quantique du cosmos. Poussant leur exploration du Big Bang au plus près des origines ultimes du monde, ils ont identifié un niveau d’évolution plus profond dans lequel les lois physiques elles-mêmes se transforment et se simplifient jusqu’à ce que les particules, les forces et le temps lui-même s’évanouissent. Cette découverte conduit à une idée révolutionnaire : les lois de la physique ne sont pas gravées dans la pierre comme des commandements divins, mais elles naissent et évoluent en même temps que l’univers qu’elles gouvernent, à mesure que celui-ci prend forme. Ce pourrait bien être le plus grand héritage que nous lègue Stephen Hawking. Un bouleversement dans notre façon de penser notre place dans l’ordre du cosmos. Un livre enthousiasmant, profondément neuf, clair et accessible. Thomas Hertog est un cosmologiste mondialement connu. Il a été pendant de nombreuses années le principal collaborateur de Stephen Hawking. Il a obtenu son doctorat à l’Université de Cambridge et est actuellement professeur de physique théorique à l’Université catholique de Louvain, où la théorie du Big Bang a été conçue initialement. 

Genres: Science, Nonfiction, Physics, Astronomy, Audiobook, Philosophy, Space

417 pages, Kindle Edition

First published April 1, 2023

Reviews

[Scottsdale Public Library · Rating 5 out of 5]

Historian David McCullough lamented in a Wall Street interview that the problem with many historians is that they needed to learn to write better. That's a big ask if writing isn't the author's main talent which seems true for many.

For Hertog, his writing is on par with McCullough's. 'Time' is a fabulous history with wonderful McCullough-esque story-telling that brings in the great minds of Hawking and his peers and the long story of Hawking's search for meaning in cosmology.

For all those folks in DC that love science and think that science pops easily out of a laboratory somewhere, they should read what a long and arduous journey with numerous failures and tiny steps forward it is.

Best of all, for all of us armchair cosmologists, Hertog lays out Hawking's newest view of the universe and time that left my head aching in the most pleasant fashion.

I will read the book again in a few months when my imagination has cooled a bit.

What a great book. If I could give it more than five stars, I would. – Tom L.

[Jessaka · Rating 4 out of 5]

I feel as though I have fallen into a black hole. I have no idea what I just read. I know that he said that there are billions of universes out there, but I do not remember if he stated what was at the end of all of the Universes. So I figured it out by myself after thinking about it. Nothing. There is nothing at the end of the universe. Consciousness creates. And when Consciousness desires it creates more universes. And this out of nothing.

[Markus · Rating 4 out of 5]

THE ORIGIN of TIME
By Thomas Hertog


The author Thomas Hertog is a theoretical physicist and longtime friend and team-mate of Stephen Hawking.
In his book "The Origin of Time," Hertog explores the concept of time and how it relates to Darwin's concept of the evolution of life on earth and how it also compares to the Origin of the Univers and Time.
The scientific chapters of the book, representing well two-thirds of it, are lightyears above my knowledge and understanding.
I did however enjoy learning about the historical chronological of cosmology picking up from its early beginnings with Ptolemy, Copernic, Galileo, Kepler Newton, and Einstein. There are many more genial thinkers from there on.
We have here the Who is Who in Cosmology. George Lemaitre, Niels Bohr, Andrei Linde, John Wheeler, Richard Feynman, Paul Dirac, Max Planck, and Gary Gibbons, to mention just a few the list is long.
Then there is the historical chronology of extravagant ideas. From the basic Big Bang to our time, scientists have come up with an open universe with no beginning and no end, a multiverse with as many universes as we have galaxies, with a string theory, and then with the puzzling quantum cosmology, and still further with a holographic universe, with black holes, dark energy, wormholes, and I must be forgetting some.
What I cannot get into my head, Hertog's work challenges the traditional view of time as a linear progression from the past to the future.
Instead, he suggests that time is a complex and dynamic phenomenon that emerges from the quantum behavior of the universe.
How can that be if we are not adding apples to oranges, then you can also say:
Mind over matter, but if you don’t mind it doesn’t matter.

L’Origine du Temps (mon résumé en Français)
Par Thomas Hertog
L'auteur Thomas Hertog est un physicien théoricien et un ami de longue date et coéquipier de Stephen Hawking. Dans son livre "L'Origine du Temps", Hertog explore le concept du temps et sa relation avec le concept darwinien de l'évolution de la vie sur Terre, ainsi que sa comparaison avec l'origine de l'univers et du temps. Les chapitres scientifiques du livre, qui représentent bien les deux tiers de celui-ci, sont à des années-lumière au-dessus de mes connaissances et de ma compréhension.
Cependant, j'ai apprécié apprendre la chronologie historique de la cosmologie, depuis ses débuts avec Ptolémée, Copernic, Galilée, Kepler, Newton et Einstein. Il y a beaucoup d'autres penseurs brillants par la suite. Nous avons ici le Who's Who de la cosmologie. George Lemaître, Niels Bohr, Andrei Linde, John Wheeler, Richard Feynman, Paul Dirac, Max Planck, Gary Gibbons, pour n'en mentionner que quelques-uns, la liste est longue. Ensuite, il y a la chronologie historique des idées extravagantes.
Du Big Bang de base jusqu'à notre époque, les scientifiques ont proposé un univers ouvert sans début ni fin, un multivers avec autant d'univers que nous avons de galaxies, avec une théorie des cordes, et ensuite avec la cosmologie quantique déconcertante, et encore plus avec un univers holographique, avec des trous noirs, de l'énergie sombre, des trous de ver, et j'en oublie sûrement certains.
Ce que je ne parviens pas à comprendre, c'est que le travail de Hertog remet en question la vision traditionnelle du temps comme une progression linéaire du passé vers l'avenir. Au lieu de cela, il suggère que le temps est un phénomène complexe et dynamique qui émerge du comportement quantique de l'univers. Comment cela peut-il être possible si nous ne mélangeons pas les pommes et les oranges.

Die Ursprünge der Zeit (mein Resümee auf Deutsch)
"Die Ursprünge der Zeit" ist eine wissenschaftliche Abhandlung von Thomas Hertog, einem theoretischen Physiker und langjährigen Freund und Kollegen von Stephen Hawking.
Das Buch erforscht das Konzept der Zeit und seine Verbindung zum darwinistischen Konzept der Evolution des Lebens auf der Erde sowie seinen Vergleich mit dem Ursprung des Universums und der Zeit. Der wissenschaftliche Teil des Buches, der etwa zwei Drittel davon ausmacht, geht weit über mein Wissen und Verständnis hinaus.
Allerdings habe ich es genossen, die historische Chronologie der Kosmologie zu lernen, angefangen bei Ptolemäus, Kopernikus, Galilei, Kepler, Newton und Einstein sowie viele weitere brillante Denker. Hier haben wir das Who's Who der Kosmologie. George Lemaître, Niels Bohr, Andrei Linde, John Wheeler, Richard Feynman, Paul Dirac, Max Planck, Gary Gibbons, um nur einige zu nennen - die Liste ist lang.
Dann die historische Chronologie der extravagantesten Ideen.
Vom grundlegenden Urknall bis zur Gegenwart haben Wissenschaftler ein offenes Universum ohne Anfang oder Ende, ein Multiversum mit so vielen Universen wie wir Galaxien haben, mit einer Stringtheorie, und dann mit der verwirrenden quantenkosmologischen Theorie, und noch weiter mit einem holographischen Universum, mit Schwarzen Löchern, Dunkler Energie, Wurmlöchern und so weiter vorgeschlagen - ich vergesse sicherlich einige.
Was ich nicht verstehen kann, ist, dass Hertog‘s Arbeit die traditionelle Vorstellung von Zeit als lineares Fortschreiten von Vergangenheit zu Zukunft in Frage stellt. Stattdessen schlägt er vor, dass Zeit ein komplexes und dynamisches Phänomen ist, das aus dem quantenphysikalischen Verhalten des Universums entsteht. Wie dies möglich sein kann, ohne Äpfel und Birnen zu vermischen, ist mir unverständlich.

[Stany · Rating 5 out of 5]

(This summary is about the Dutch version of the book)

A very interesting book for everyone interested in cosmology and in the latest theories of the origin of the universe. Thomas Hertog, a close collaborator of Stephen Hawking, explains in relatively detailed but clear way their latest top-down cosmology and how it ties in with the current hot topic of holographic theories. Whilst targeted towards a non-technical audience, and as such does not have any mathematics, it remains a complex topic and will stretch the capacity of many readers. To give two examples: Hertog explains how close to the beginning of the universe time changes into space so that the concept of time – and hence of the beginning of the universe – does not make sense. As another example, he explains how gravity in a space-time may be modelled as a quantum field theory on the boundary of that space-time and that time in the universe becomes distance on that surface so that earlier times correspond to particles on the surface that are far away and less entangled. The beginning of time would then correspond to a lack of entanglement, i.e. information. Yes, this is heavy stuff.

What gives the book an additional dimension are the comments on his relationship with Stephen Hawking and the role of the early Leuven cosmologist George Lemaitre.

It is clear that Hertog has thought deeply about this and also about many other topics, not only related to physics. As such he is very much an example of an anti-Cooperian physicist.

[David · Rating 3 out of 5]

An interesting but ultimately frustrating read.

Much of the early part of the book retreads familiar ground for anyone who’s read popular cosmology or quantum gravity books in the last 25 years. There’s the obligatory introduction of general relativity and quantum mechanics, and the now-familiar discussion of the string landscape and eternal inflation leading to thoughts of a multiverse.

But Hertog differs from the standard account in a few ways. The most important difference is his description of the “top-down” cosmology that he, Hawking, and Hartle developed. A second difference is how he tries to connect his cosmology ideas to biology and evolution. A third difference is that he delves much more into the long history of ideas around cosmology and science—it must be said, without tremendous accuracy, but still revealing some interesting things many will be unfamiliar with. I’ll discuss each of these in turn.

Top-down cosmology

What’s new since the books of the 90s is holography, the one angle on quantum gravity that many people feel more confident about. With its roots in the AdS–CFT duality, it has, perhaps, led to some good insights into black holes and the early universe. The top-down cosmology exploits this to develop the idea that the laws of physics themselves are developed by observation (and that time is not fundamental). It’s an interesting idea, but felt a little formless.

I don’t know if Hertog doesn’t develop this idea well just because it’s way too complicated for a popular book, or if he himself doesn’t really quite know what he’s talking about. There are, as he says, “a few layers of craziness still unwrapped” (p. 244). The eternal inflation multiverse idea is pretty easy to understand at an intuitive level, and thus to present to a general audience. Top-down cosmology is not, at least yet.

So Hertog gives a very unsatisfying account of it. The fundamental idea seems to be that the universe is the way it is because it is the way it is. Just an accident, y’all! (And it was the way it was because it is the way it is—“the past is contingent on the present” (p. 202).) There’s no “measure problem” in top-down cosmology because there isn’t even an attempt to gauge statistical likelihood or plausibility, the way there is in multiverse cosmologies. As far as I can tell, top-down cosmology avoids the measure problem only by asserting that there’s no meaning to it and we can’t gauge the probability of things that have already happened.

While Hertog insists that top-down cosmology has far more predictive power than multiverse cosmologies, he has zero examples of this in the book. At least the multiverse had Weinberg’s prediction of a nonzero cosmological constant. Hertog also asserts that the top-down approach has “rendered the anthropic principle obsolete” (p. 200), but it appears to have done so only by asserting that you can’t even ask questions about probability and thus don’t need the anthropic principle. This feels like asserting that you won a game of chess because you knocked down your opponent’s king—and it is meaningless to ask how that happened or whether you followed the rules doing so.

It also seems rather melodramatic to claim that time isn't real just because all the information is holographically encoded on the surface (present). So what? In a deterministic universe Laplace's demon knows the past and future perfectly only by knowing the present, and yet I've never heard anyone claim that time isn't real in a Newtonian cosmos as a result of this.

Biology and Philosophy

Hertog repeatedly tries to make an analogy between top-down cosmology and Darwinian evolution (e.g., p. 260), but this doesn’t actually make sense. There’s no natural selection in top-down cosmology. Hertog is just arguing that things are emergent and accidents can be frozen in place, but that’s not what “Darwinian evolution” means. (Note that multiverse eternal inflation cosmologies have the exact same thing, with different regions dropping out of inflation in very different ways, spontaneous symmetry breaking freezing in place a variety of fundamental constants and so on. But Hertog sharply criticizes such theories. The only difference I can see is that Hertog is arguing the laws of physics themselves are emergent, which is a real difference in approach, but has nothing to do with biological evolution.)

Even if Hertog is trying to analogize descent with selection to the wavefunction branching in Everettian quantum mechanics, that still makes no sense. There is no selective pressure. In Everett’s theory all possibilities are realized in various wavefunction branches.

Given the highly philosophical nature of the top-down cosmology approach, which is arguing for fundamentally revisiting the ways in the physics has worked since physics really began c. 1600, it’s disturbing that Hertog’s knowledge of the philosophy of science appears to start and end with the tired theories of Popperian falsification (p. 30) and Kuhnian paradigms and revolutions (p. 276). There are deep flaws with both. Popper is a good first try, but ultimately unsatisfactory, while Kuhn developed an entire model of repeated paradigm shifts that really only worked with a single historical example of the development of science itself (and even then was oversold).

Hertog also blithely makes claims with no evidence, such as saying “worlds with only two space dimensions… may not provide enough room for complex systems to function” (p. 7). His sole evidence for this is a drawing of a cat trying and failing to eat a bug when it’s two-dimensional. Is he six years old? For a good discussion of the complexity even of an extremely simple deterministic 2-D system (Conway’s Game of Life), see Daniel Dennett’s Freedom Evolves. The Game of Life accommodates a Turing-complete computer (in addition to things that can, quite successfully, eat other things).

Hertog has a tendency to read what he wants into what other people have said. He cites Lemaître as saying that his primeval atom “doesn’t merely represent the beginning of time but a more profound origin that cannot be reached by thought, ‘an inaccessible beginning that stands just before Physics’” (p. 297). Hertog interprets this as Lemaître somehow supporting the Hawking top-down approach, but Lemaître was very famously religious. It seems vastly more plausible that he was invoking a religious origin with this statement. (Hertog also interprets Hawking at the Vatican in 2016 as conciliatory—“there were no more battles with God or the pope to be fought” (p. 259). Really? Hawking was famously irreligious, through the final book that he actually wrote.)

Given this tendency to read into what others have said, it’s concerning that Hertog is attributing so much to Hawking when all we have is Hertog’s word that Hawking’s eyes told him that yes, Hawking agreed with what Hertog was saying.

History

Hertog counts Pythagoras among the pupils of Anaximander (p. 12), when we really have no idea. (Porphyry says that this is true, but he was writing 800 years later.) Hertog says (correctly) that the early Greeks make “little or no effort to test” their ideas about physics, but then claims that “it just didn’t occur to them” (p. 12). Sure, it did. Aristotle famously rejects experimentation because it’s artificial intervention into the world, and he was interested in how the natural world worked. That’s a very valid concern still today in psychology, sociology, field biology, and so on; it just turns out to not be a good approach to physics.

The idea that “the ancients added epicycles onto epicycles in an attempt to rescue the Ptolemaic world model” (p. 164) is not at all true. Ptolemy’s model was extremely accurate, and Copernicus’s no better (and also needed just as many epicycles). Ptolemy’s model also has no epicycles on epicycles (although as realized by Nasir al-Din al-Tusi a millennium after Ptolemy, you could replace the equant with something like an epicycle). By the early 1600s, when Kepler’s ellipses provided a better fit to the data, nobody was arguing for geocentrism by matching the accuracy of Kepler’s model.

On page 37, Hertog says that Einstein cast doubt on the ether’s existence because of experiments showing the constancy of the speed of light. Very famously Einstein claimed to be unaware of the Michelson–Morley experiments (and anything along those lines) when he first developed special relativity, and that he was merely trusting Maxwell’s equations. Scholars have found no reason to disbelieve this account. In sophomore modern physics courses it’s common to present Einstein along with Michelson–Morley, to emphasize the interplay of theory and experiment, but it’s a pedagogical approach, not a history lesson.

In more recent history, Hertog discusses the COBE and Planck observations of the CMB, but weirdly skips entirely over WMAP with no mention at all. On p. 115 he notes that happily Hawking “lived to see the detailed observations of the CMB” released by Planck in 2009. Um, WMAP released theirs in 2003. Hello?

I do appreciate that Hertog delves much more into Lemaître than most readers will be familiar with. He had some very interesting ideas, and is usually underappreciated relative to Hubble.

Conclusion

Hertog seems very dismissive of other people’s ideas. He claims that apart from Hawking and Hartle’s no-boundary proposal (adapted into top-down cosmology), “no viable description of our deepest origins [is] in sight” (p. 101). Really? There are a lot of theories of pre-Big Bang cosmologies (many discussed in Sean Carroll’s From Eternity to Here: The Quest for the Ultimate Theory of Time).

I still found this book worth reading, both for glimpses of what holography might mean for cosmology as well as for the human stories. Just don’t read it assuming that you’re going to get a complete or unbiased picture of the state of cosmological research. And don’t trust any of Hertog’s assertions that he doesn’t cite (and even then I’d follow up with the source).

It’s ironic that for a book that spent all its time arguing for a “worm’s eye view” instead of a “God’s eye view”, Hertog chooses to close with quoting Hawking talking about “when we see the earth from space we see ourselves as a whole; we see the unity and not the divisions” (p. 266). That view, the god’s eye perspective, the “old” bottom-up cosmology, is what most physicists are still trying to do. Hertog disagrees with that. Maybe Hawking did too. Their ideas are worth entertaining, but not without a skeptical eye.

[Mai H.]

Non-fiction November TBR

📱 Thank you to NetGalley and Bantam

[Dennis Christie · Rating 4 out of 5]

A lot of information needs to be processed by my brain while reading this book. First, I am no physicist, but I love being updated on significant discoveries. This book keeps me busy for more than 1 month. I am trying to not rush the reading process as I want to digest all the concepts as much as possible. (I am pretty sure I still miss a lot though).

This book will bring you to the journey to, as the title is, the origin of time. Starting from the Big Bang, the evolution of physical laws, anthropic principles in the multiverse and how Stephen is against that principle (I am on Stephen's side before I read the book, and I am happy to discover that Stephen also shares the same view).

The goal of this book is to inform the reader of his new framework of physics, which bound dynamics, boundary conditions, and observership together into one. In this view, instead of searching for a final theory that describes the law of physics from a bottom-up approach (that is predicting the law of physics in the current time, through the evolutionary process from the beginning of time), he proposes that we should look them from a top-down view (that is tracing the law of physics back in time by our observation). The most remarkable new mindset that he proposes is, inspired by Everett's many world interpretations, our history is somewhat a superposition of multiple histories. We "create" our history by observation.

By this chapter, my brain is already smoking. But then, he continues to explore the concept of the holography principle (especially a duality between quantum mechanics and gravity), to understand the beginning of time itself. That is super interesting, but my mind is already melting. I need to stop reading every 5 or 10 pages, just to digest what is all about.

Anyway, it was an enjoyable journey. Thanks to the author who patiently wrote something that is extremely complicated and high-level concept of physics to be readable by non-physicists like me. Would love to hear more about Stephen's new top-down approach more in the future.

[Sara · Rating 3 out of 5]

چقدر راحت راجع به چیزای به این بزرگی صحبت میکنند.
راجع به تئوری هاوکینگ بود و مثلاً به زبون ساده تری توضیح داده بود. (نمیدونم شاید چون من هیچی راجع بهش نمیدونم به نظرم نمی‌اومد که ساده ترش کرده.)
در کنار توضیح راجع به خود هاوکینگ و تئوری هاش ، توضیحات راجع به بعد های جهان و مدل های جهان و به وجود آمدنش داشت.
فیزیک این مدلی و بررسی های نجومی واقعا برام غیرقابل درکن. یعنی شاید یکم متوجه بشم چی میگن ها، ولی اصلا نمیتونم درک کنم.

[David Nichols · Rating 3 out of 5]

I don’t profess to understand this book any more than I understood BRIEF HISTORY OF TIME, but for my own sake (if no-one else’s) I’d like to jot down a few notes for future reference; perhaps they will show I got some benefit from it:

Until the twentieth century, astronomers and physicists believed the universe was in a steady state, neither growing nor shrinking. Perhaps occasionally burping.

The discovery of redshifted galaxies indicated an expanding universe. Thus, if one were to move back in time, one would find the universe shrinking to a single dense, explosive point. Call it the “Big Bang-o-Plex.”

Stephen Hawking argued (1983 or so) that such a point resembled the singularity within a black hole, a place where time and space became so warped that they resembled the mind of Grant Morrison. Within such a singularity one could not identify a “beginning” point of the universe.

Later Hawking and others determined that the early-universe singularity was more like a great quantum blur, wherein time essentially converted into space. You could walk over to a pub ten years earlier, have a drink or three, walk back to you own era and still have been on the wagon for nine years.

Richard Feynman had something to do with this. Maybe he was the bartender.

Most recently Hawking and Hertog suggested the universe is both a quantum blur and a hologram - it acquires more definition, more intrinsic structure, as its micro-constituent parts pass through various windows of observation.

The “observers,” in this case, need not be humans or even living things, just anything that can collapse a quantum state. Suck it, Wigner.

The mind of God remains inscrutable.

[Stephen · Rating 3 out of 5]

found this book interesting even though some of it went over my head

[Simon De Gussem · Rating 4 out of 5]

Wow. What a brainmelt.

Reading this book was a humbling experience. I think I grasped the fundamentals, maybe just 40%. Just because of that, this was a frustrating read at times. I’d reread certain passages over only to admit: okay, my brain just isn’t wired for this level of abstraction.

There were moments when I wished Hertog had broken things down a bit more, make it a little more foolproof, maybe used some simpler metaphors to guide the way. I’m definitely no physicist, but I do know the basics of quantum mechanics and general relativity, and still I cannot comprehend it... The early chapters were quite manageable, they were like a refresher with some more scientific depth. Then it started to be more mindbending. John Wheeler’s thought experiment showed that observers don’t just observe the universe; they help shape it. “No question, no answer. No observer, no history.” This is just crazy. Wow, there only is history if we look for it?

Then he brought in string theory, and the wild claim that black holes can store their information on a surface, something like 10⁸⁰ gigabytes, which leads to the possibility that the universe itself is a hologram. Euhm?? At that point, I just sat there thinking: what am I reading? I even watched some explainer videos… but I’m not built for this kind of cosmic abstraction, I wish I was though...

Still, I loved it. Hertog really does a fantastic job, making these next-level theories almost graspable.

[Julian Worker · Rating 3 out of 5]

Once upon a time, there was no time, as this book indicates if you wound the universe back to the beginning, time would lose its distinct nature and effectively become space.

The theory also envisages our Universe as a holographic projction.

The story of the personalities behind this theory and how these conclusions were arrived at is fascinating, but I'm not sure how anyone can prove this conclusively.

[lizard · Rating 4 out of 5]

“‘When I hear the words ‘Schrödinger’s cat,��� I reach for my gun,’ [Stephen] once said…” is maybe the funniest line in all my 2025 books so far.

[Marja Coons-Torn · Rating 5 out of 5]

What if you could get inside Stephen Hawkings’ mind after he had written a Brief History of Time. What if you could get a sense of all the theories, the struggles, the incredible speculation that came as big data became a thing.

Thomas Hertog started out as Stephen Hawkins’s graduate student, and became his closest friend and collaborator. He gives us a peek into the man and the scientist he knew.

This book is much more than that also. Hertog is skilled at drawing in the history of physics, even from ancient times. An example: it was interesting to me, as one who has lived through a “plague” (the coronavirus pandemic), that Newton wrote most of his Principia while in isolation from a 17th century plague in England. In fact, he draws not just from the history of physics but from biology and human history in general, with examples. This made the book so much more interesting to me, reminiscent of Hawking’s own book, which I think was one of if not the first book on physics for the reading non-scientific public.

Indeed, the genius of this book is that I, a non-scientist, can read and enjoy it. I think Hertog has accomplished a remarkable feat with On the Origin of Time. The parallel accomplishment is that he humanizes physics with stories of encounters between scientists, in the university setting, in conferences, and in other everyday circumstances.

(DAMTP, the acronym used through Hertog’s book, is the Department of Applied Mathematics and Theoretical Physics at Cambridge University.)

[Sierra]

This is an excellent book for a physics enthusiast - thorough, modern, and fascinating. I hesitate to recommend it for those with only the background of A Brief History of Time, even though it's marketed as a sequel. Hertog's writing is great, but he doesn't have the talent for explaining complex topics to a general audience that Hawking did. This was a great book for where I am in my cosmology journey, with two college physics classes, a textbook to use for references, and background knowledge from a number of other books I've read recently.

ARC provided by NetGalley in exchange for an honest review.

[Thomas Lambe · Rating 5 out of 5]

Many thanks to NetGalley for the ARC of this new work! Wow! This was so good. I love science writing as a genre and this is science writing at its very best. I believe that any student of cosmology will eat this up. This book really makes you think. Hertog and Hawking worked together at Cambridge. This book tells the story of how the universe could have began. Learned so much from this! Highly recommend.

[Neridan · Rating 2 out of 5]

IDK why I picked up another physics book AND listened through all the 12 hours without really understanding anything. A sort of white background noise?

[Michael · Rating 5 out of 5]

Emanuel Bronner born in Germany during 1908, founded Dr. Bronner’s Magic Soap, lived to be 89, was a lover of the exclamation point!! His life purpose wasn’t making soap—it was sharing his life philosophy and mission through his soap. Oftentimes, enlightened human beings end up being ridiculed and Bronner was one of these people.

For no good reason I haven't used his peppermint soap in years. Like many people, on occasion I would read the label on his liquid soap bottles. Perhaps he is best known for 'The Moral ABC of Astronomy’s Eternal All-One-God-Faith Unites the Human Race! Also, 'In all we do, let us be generous, fair & loving to Spaceship Earth and all its inhabitants. For we’re All-One or None! All-One!' Of course, Astronomy is the study of objects and phenomena beyond Earth, while 
cosmology is a branch of astronomy that studies the origin and evolution of the universe. Not exactly the same, but close. Bronner's basic idea is that all lifeforms on Earth, which he called "Spaceship Earth", are connected and should unite in harmony. 

While reading this book about Stephen Hawking and his final thoughts about cosmology, I couldn't help but be reminded about Bronner's often confounding ideas printed with abundant exclamation marks on the labels of his soap bottles. Though, there is no mention in the book about Hawking being aware or influenced by Bronner.

In case you are unaware of the basics regarding Hawking's biography here is a smattering of background information. He was married twice and was father to three children. He is mostly associated with Cambridge and to a lesser extent Caltech in Pasadena. He developed ALS and apparently rarely, if ever complained about his gradually deteriorating physical condition. He died during 2018 at age 76.

Here are some of his general opinions:

a) A super-intelligent AI will be extremely good at accomplishing its goals, and if those goals aren't aligned with ours, we're in trouble.

b) He was concerned about the future emergence of a race of "superhumans" that would be able to design their own evolution.

c) He believed the concept of an afterlife is a fairy story for people afraid of the dark. And also, no one created the universe and no one directs our fate.

d) He was not involved with organized religion, but met with the Pope twice to explain his ideas about cosmology.

f) He advocated for action to prevent climate change. He said, "By denying the evidence for climate change, and pulling out of the Paris Agreement, Donald Trump will cause avoidable environmental damage to our beautiful planet, endangering the natural world, for us and our children."

g) He said, "I deal with tough mathematical questions every day, but please don't ask me to help with Brexit."

h) He was critical of the Israeli government's position on the Israeli–Palestinian conflict, stating that their policy "is likely to lead to disaster."

The book's author, Thomas Hertog, a prominent theoretical physicist in his own right, is a Belgian cosmologist, was a key collaborator of Professor Stephen Hawking especially in the field of cosmic inflation, a branch of the Big Bang theory.

I believe one understanding presented in this book is that the laws of physics, as we currently know them, are emergent or starting to become known. The book links Darwin's concepts of biological evolution to cosmology and physics, in general.

Other concepts discussed in this book include:

a) People and their ideas about evolution, physics, and cosmology do not occur in isolation or are separate from the dynamics and on going change of the universe. The significance of our role as observer is not minor.

b) Quantum entanglement plays an important role in the on going change of the cosmos. Hawking said that things in quantum theory, increasingly being applied to cosmology, have every possible history, each with its own probability. 

c) Hawking in 2006 instigated changing how we view the universe to a Top-Down cosmology perspective (start from present conditions and work towards understanding the past) rather than the dominant, at the time, of the opposite perspective or a Bottom-Up approach.

d) Hawking proposed that a multiverse could exist as a consequence of the inflationary phase of the early universe. Though, he did not specifically endorse the concept of an infinite number of universes.

e) Much like a 3-D hologram emerges from the information encoded on a 2-D surface, our universe's 4-D spacetime could be a holographic projection of a lower-dimensional reality.

f) Hawking and Belgian professor Thomas Hertog theorized that our three-dimensional reality is an illusion. 

g) He theorized that the universe is a four-dimensional membrane in a five-dimensional space, and a small part of a much vaster hidden reality.

h) Consider his famous theory of how black holes die could mean our entire universe is doomed to evaporate.

To conclude, in his final theory, published in the Journal of High Energy Physics after his death, Stephen Hawking suggests that the universe is a hologram. The theory states that all information in the universe is stored on a flat, two-dimensional surface, and our world is projected from that information.

This book makes clear that Stephen Hawking was fun loving, curious, interesting, and well liked by the people who knew him.

[Alex Hughes · Rating 4 out of 5]

Inherent in a book about time you have physics from 1850s-ish metaphysics stuff all the way to like quantum physics like Schrodinger and Bohr and whatnot and then more recently Stephen Hawkins and the core of this book: his final theory. This was really interesting hearing them build this case and try to educate you as a reader on all the philosophy from the past and how different things are wrong and how they’re incrementally disproved and improved upon over time. To be honest, reading this book most of the time was like being high watching TV - I know it's good, I just don't really know what's going on… which is FINE because it's still cool and interesting and the pictures are sick. There’s one pretty fascinating theme and I think it’s summed up well during an argument between Einstein and Schrödinger about observer theory. With schrodingers cat, there's cat in a box and the cats both alive and dead. It's in a quantum zombie state, and when you open the box and look to figure out whether the cats alive or dead, It actually becomes alive OR dead (impossible, but think about it!)… with quantum physics when you observe a particle the act of observing it actually changes what it state is. if you look at the Schrödinger wave function It basically says all these particles travel in these waves that are very smooth moving (how I understand it)and when you observe it — observing it would be like shining laserbeam because that's how we see things — when you hit it with a laserbeam, the impact actually collapses the wave function and the particle isn't on a wave. It's not in multiple positions. It's just a point (think about the double slit experiment!). The whole argument is like OK there's an observer and everything we actually figure out about quantum physics, by nature of observing it, we’ve actually changed… and then the counter to that is like oh well there's all these different branches where observers are branching off in time in their own universes… there's an observer that's one thing and there’s an observer that's in a different state and those observers both see the particle in different ways and the outcome that each sees is the right one for them (because observing the particle actually changes THEM). right. OK. fine. maybe. not convinced. BUT it made me think about Plato and Aristotle: these guys spent their entire lives thinking about physics and how to describe our world and life. They thought we were living in a cave with puppets in front of a fire and the shadows on the wall were what we perceived as reality. We have this innate desire to describe ourselves and even though we know we’re probably wrong (because we can’t even fully explain the quantum particles, but we build theories around them anyway KNOWING that we don’t have unified equations). Someday they’ll look back and have the god equation or whatever it’s called and they’ll be like look at those fools (like I did when I was talking about the cave) but for us now it’s the most crazy complicated thing and the BEST way we can explain our universe even though we can’t know if it’s the RIGHT way (///we know it’s not…).

4/5 stars

[Steve · Rating 5 out of 5]

“On the Origin of Time” is a fascinating and thought-provoking book that delves into the theories of Stephen Hawking, one of the greatest minds in the field of cosmology. Written by Thomas Hertog, a Belgian cosmologist and key collaborator of Professor Hawking, this book explores the latest thinking about the universe and its origins.

The book was written at the request of Stephen Hawking at the end of his life in order to popularize the cosmological theory that they developed together. The thesis of their theory is that the origin of time is the Big Bang and that the laws of physics do not precede the Big Bang, but were born with it. The main hypothesis of their work is that physics laws evolve with time, at least during the very first moment of the Universe and are not transcendent and immutable at the scale of the birth of our Universe as supposed by the theories of Newton and Einstein.

The discovery of Hawking and his PhD student was a total surprise. Quantum theory on the origin of the Universe led to an unexpected quantum theory on the origin of time. Time begins at the Big Bang as it also disappears in black holes. The quantum theory of the Big Bang is closely related to the quantum cosmological theory of black holes, which was Hawking’s main contribution to physics. The main outcome of their work is that physics laws are contingent to emerging phenomena and evolve with them.

The book describes Hawking and Hertog’s top-down approach to Cosmology, utilized to justify what would otherwise be predictive errors in the Hartle-Hawking state (No-boundary Creation) Theory, without the use of the Anthropic Principle or Multiverses. This approach is justified through explorations into quantum superposition and the idea that the past can exist as superpositions until observed in a similar way to the future and present.

The audiobook version is well-narrated and engaging, making complex concepts accessible to a wide audience. It provides a unique insight into Hawking’s final thoughts on cosmology and his collaboration with Hertog.

Overall, “On the Origin of Time” is a must-read for anyone interested in cosmology and the mysteries of our universe. It offers a fresh perspective on some of the most fundamental questions about our existence and provides a fascinating glimpse into the mind of one of history’s greatest thinkers.

[Bjorn · Rating 4 out of 5]

I have a huge amount of respect for people who spend their professional lives in theory. Whether it's physics, mathematics, philosophy or even theology; the idea of spending every hour of your work simply figuring it out, not through practical experimentation but by crunching the numbers, thinking over the contradictions and trying to get to something. Personally I get bored writing an e-mail.

But then, you have to come back and explain it to the ones who haven't spent decades in that rarified air. From what I've read of his, one of Hawking's great talents was his ability (and, I suppose, his necessity) to explain the endlessly complex in terms that people could, at the very least, feel like they understand. Hertog, for all his enthusiasm about the subject, isn't the great communicator. Taking it upon himself to be the executor of Hawking's last will and scientific testament, he wobbles back and forth between writing for physicists and ordinary readers, explaining some things at length and others hardly at all. And above all, I find myself wondering... just how revolutionary is something that does sound as simple and obvious as the aging Hawking's top-down perspective? Yes, he lands in something very likable - a model of the universe where the observer is an inextricable part, one who has to take responsibility for the questions they ask of it - but I honestly can't tell where the math ends and the philosophy begins.

But then, his point is that we're not above all. We are stardust, billion-year-old carbon. I'm sure I don't understand half of this, and that my understanding of half of the rest is shallow at best. But it makes me want to.

[Rick Burcik · Rating 5 out of 5]

Except for the last chapter this is clearly the very best book that I have ever read on the subject of cosmology. It is also one of my favorite books overall. It covers everything from the big bang to blackholes and it propounds Steven Hawkings' last big concept of top-down cosmology. Make certain that you buy and read this book although the last chapter should be considered as optional.

[Jung · Rating 5 out of 5]

**HIGGS BOSON THE GOD PARTICLE **

https://home.cern/science/physics/hig...
https://www.space.com/higgs-boson-god...
https://www.youtube.com/watch?v=0YhJ3...

Cutting-edge science that sounds like fiction.

The best scientists are those who are open-minded and willing to change their views as new evidence presents itself. 

This is important, because even geniuses can be wrong – just like Stephen Hawking started to believe he was about something very important.

In the 1980s, Hawking argued that the rules of physics that govern our universe are immortal and unchanging. But the more he thought about it, the more he began to ask, “Why does it have to be this way?”

In this book, we’ll cover Hawking’s final search for the origins of the rules that control our cosmos. In the process, we’ll be diving into some exhilarating, mind-bending ideas that will stretch the limit of how we typically understand the universe. 

It’s going to be a difficult but rewarding ride, so buckle up and get ready to explore the vast complexity of the cosmos.

-

The Universe – Made for Life

On a dazzling summer's day in 1998, a fresh-faced Thomas Hertog crept into the office of the world's greatest living scientist. As a brilliant graduate student in cosmology – the study of the origin of the universe – Hertog was being sized up by Stephen Hawking as a potential protégé.

Almost completely paralyzed by a rare motor neuron disease, Hawking tapped a clicker with his hand. Gradually, through a computer program and speaker system attached to his wheelchair, synthesized speech emerged. By then, its distinct tone and rhythm had already become permanently associated with Hawking.

What Hawking said next laid the foundation for two decades of collaboration between the men, and the book upon which this current book is based.

Hawking told Hertog that the universe seems beautifully, impeccably designed to harbor life. Which led to this question: Why did our cosmos turn out to be so sympathetic to us?

The further you burrow into the science, the more you realize Hawking had a point: The laws of physics that our universe must obey seem made-to-order for life to grow.

Take gravity. If this fundamental force were just a tiny bit stronger, stars would shine brighter, because the nuclear reactions in their cores rely on compressing hydrogen atoms together to make helium, which gives off light and heat. Greater gravity would intensify this process.

You might think that sunnier days on Earth wouldn't be anything to sniff at, until you realize that all stars would exhaust their fuel much more quickly, and life on any planet wouldn't have a chance to develop before its sun withered and died. 

Also, when the universe was still in its infancy, areas of the cosmos varied slightly in temperature. These variations were only fractions of degrees, but if these had been even marginally bigger, all galaxies would have grown into giant black holes and plunged everything that ever was and would be into eternal darkness. And if these temperature variations had been smaller, no galaxies would have formed at all!

Let's take another example. In the hard code of the universe that we were given, protons and neutrons – the things that make up the nucleus of an atom – weigh different amounts. 

Again, this difference seems trivial: neutrons weigh just 0.1 percent more than protons. But if the universe's code had decided it wanted these weights to be the other way around, with protons weighing more than neutrons, all neutrons would have decayed just moments after the Big Bang. That means no atoms, and therefore no planets, no stars, and no people.

The Stephen Hawking who wrote A Brief History of Time believed that the laws that underpin our universe are unchanging and timeless. No point asking why – they just are.

But as we'll see, he wasn't satisfied with that explanation – or any other current explanation, for that matter.

-

Current Theories Don’t Cut It

Let’s look at how humans have previously tried to explain why the cosmos’ operating manual seems fine-tuned for life. So far, there have been two persuasive views.

The first, and oldest, is the belief in some sort of creative designer: a God, or gods. They set the rules of the game that the universe – and everything in it – must follow. A Christian physicist, for example, might believe that God programmed the unbreakable rule that nothing can move faster than the speed of light. Something as perfect, intricate, and finely balanced as our cosmos must have been designed with life in mind.

The second, newer idea is that our universe is one of an infinite number of universes, all living alongside each other, but mutually inaccessible. In short, we exist within a multiverse. 

Each component member of the multiverse might have completely different laws of physics, and almost all of them would be barren and completely unable to sustain life. But if there's an infinite number of them, once in a while you'll stumble upon a universe that’s like Goldilocks' porridge: just right.

Neither of these explanations satisfied Stephen Hawking, however – and, surprisingly, for the same reason.

Let's wind back the clock a bit. In the twentieth century, a British-Austrian philosopher named Karl Popper tried to define exactly what science is and what it is not. He came up with a powerful, influential, but devilishly simple formulation: Popper simply said that a proper scientific theory must be falsifiable. That means that it must have the potential to be proven wrong through experiments and evidence.

Many people believe in the idea of a creative designer – in fact, it's the most popular explanation for the perfect fit between our universe and life. But it isn't a scientific theory because there's no way of hopping over to the lab, running a few tests, and disproving it. It isn't falsifiable.

The multiverse theory suffers from the same problem. How could we ever test whether there are other universes out there? We can't even see all of our own universe! 

Because nothing can travel faster than the speed of light, we are trapped in a pretty big bubble that scientists call the observable universe. There are places in our cosmos where the light given off by stars hasn't had enough time to reach us, so we can't see them. And that light will never reach us, because the universe is expanding. It's like we're in a dark field with a lantern, and we can't move: we'll never know what’s beyond a certain point.

Hawking surveyed the territory and was deeply discontent. He realized we needed a new theory of our universe's code.

-

What Is the Time?

We're all used to the idea that we live in a three-dimensional world. Up and down, left and right, forward and back: We shop for groceries, drive cars, climb flights of stairs, and fly 30,000 feet in the air to holiday in sunny locales.

But what if we told you there's an extra dimension to our world? A fourth dimension?

This extra dimension was found by a man you might've heard of: Albert Einstein. Well, "found" isn't the right word. The German genius took something present in all our daily lives – and something none of us has enough of – and mathematically proved that it exists as a dimension alongside our three spatial ones. Einstein reinvented time. Think about it: an object doesn't just exist in a location; it also exists at a point in time. 

Following so far? Good, because things are about to get weird.

In 1983, Hawking put forward something called the no-boundary proposal. Winding the history of the universe right back, he found that time didn't exist before the Big Bang. Everything existed as an infinitely tiny, infinitely dense speck in eternity. 

According to the no-boundary proposal, there's no point in asking what came before the Big Bang, because time didn't exist. But a fraction of a second after the Big Bang, our three dimensions of space emerged, and from these three dimensions time popped out as a fourth.

And this is where the magic of Hawking’s new theory – the one at the heart of Hertog’s book – starts to happen.

As we've seen, in A Brief History of Time Hawking wrote that the laws of physics in our universe were fixed and eternal. But after its publication, he began to change his mind. 

Instead, Hawking started to think that these laws evolved with the universe in those crucial moments after the Big Bang. Electromagnetism, gravity, dark matter, and the weight of neutrons – these mutated and evolved, just like how Charles Darwin showed us that animal species mutate and evolve. Toward the end of his life, Hawking began to view physics more and more from the perspective of biology.

Importantly, these evolutions happened in the quantum realm. 

This is complicated stuff, but the best way of thinking about quantum physics is in terms of probabilities. The electron that zips around the nucleus of an atom never has a definite location or weight – it only has probabilities of being at a certain place and weighing a certain amount.

So in the quantum kingdom, where everything is a probability, the laws that govern our universe today were hashed out from a range of infinite possibilities. 

Bizarre, right?

-

Mind-Blowing Top-Down Cosmology

If you're scratching your head after that last section, you're not alone. This is profoundly weird stuff, and far removed from our intuitive methods of understanding – things in this world seem to be completely disconnected from the logic that governs our daily lives. The only thing to do is smile, and marvel at the unfamiliar complexity and magnificence of physics, and the universe in which we find ourselves.

Try to keep this in mind as we muddle our way through these next two sections.

Just now, we said that in quantum physics, nothing has a specific value – only probabilities of being a certain value. But that’s not the whole story.

Once something is measured or observed, it does have a definite value. Let's go back to our electron: before it's measured, there's a 30 percent probability of it being here, and a 67 percent probability of it being there. Once it's measured, though, we know exactly where it is.

As well, in quantum physics there's something called superposition. This is a fancy word for when something has an equal probability of having two different values. Basically, before something is measured, it could technically be in two places at once!

Fixing a value through measurement, and superposition: These two things are important to another mind-bending concept that Hawking and Hertog worked on – one that could revolutionize the study of cosmology altogether.

This is called top-down cosmology, and it's easier to understand once we know that bottom-up cosmology studies the universe as it evolves forward in time. Scientists who do bottom-up cosmology start at the Big Bang and go forward, using scientific theories and evidence to predict what we should see. But bottom-up cosmology turns what we know about time, cause, and effect on its head.

Remember how in quantum physics, the act of observation fixes specific values? Well, if the universe's laws evolved in the quantum realm shortly after the Big Bang, and now there are human scientists measuring and observing those laws, in a strange way we have fixed them by our observation, from a huge range of different possibilities that exist simultaneously as superpositions.

In this view, the past becomes dependent on the present, and human observers have a big role to play in this process. 

-

Weird Science

To complete the tangled, terrifying, yet strangely marvelous collaboration of Hawking and Hertog, we need to explore one final concept: holography.

In the last decade, holography has been all the rage in theoretical physics. In this theory, the universe isn't thought of in terms of atoms and space; it's thought of in terms of information. This makes more sense when we realize that in quantum physics, things don't have values like weight or speed – they exist only as probabilities.

Now, does everyone remember watching Star Wars? When characters communicate with each other from distant planets, eerie computer projections of their bodies spring from flat surfaces near the person they want to talk to. This is what a hologram is – a 3D object being projected from a 2D surface.

So what does a holographic universe mean? Well, it means that we are living in a world containing three spatial dimensions, but that this is just a projection of a universe that contains more dimensions, which we cannot access.

What does any of this have to do with thinking about the universe in terms of information? Answering this is about as hard as science can get, but the essential idea is that we have found evidence that our everyday dimensions are holographic from studying black holes.

At the center of a black hole is something called a singularity – an infinitely dense, infinitely tiny point. Because it's so heavy, a titanic gravitational field surrounds the singularity in the shape of a sphere. Now, if we think of the universe as being made up of information, it makes sense for this sphere to contain a huge amount of information, right?

But when scientists did the math, they found that the information black holes contain isn't equal to their capacity as a sphere – it's equal to their capacity as a circle. What is a sphere represented in two dimensions? You got it, a circle. This provides evidence for the holographic universe theory.

Hawking and Hertog took this, and peered into the beginnings of the universe. They ran some equations, and realized that the no-boundary proposal – which argues that the dimension of time was created moments after the Big Bang from the three spatial dimensions – fits perfectly with the theory that our universe is a hologram containing higher dimensions.

They kept developing this model, and incorporated the idea that the universe consists of bits of information. They kept following this back to the Big Bang, and realized that as you get closer to the beginning of the universe, you begin to run out of bits, like the resolution of a movie getting progressively grainier until … nothing. Before space, and before time.

And with that – congratulations! You've made it through our outlandish journey back to the origin of time!

-

In the final decades of Stephen Hawking’s life, he began to change his mind about how our universe ended up with the laws of physics that govern it. He wasn’t happy with previous explanations because they weren’t falsifiable scientific theories, and so he went back to the drawing board. 

He came up with a theory that our universe is a holographic projection that contains other dimensions that we can’t access, which helped support his theory that the dimension of time sprang out from our three dimensions of space just after the Big Bang. 

It was also in these moments just after the Big Bang that Hawking believed our universe’s laws changed and evolved on the level of quantum physics, and that scientists today, by observing these laws, have fixed them from a range of infinite possibilities just by observing them.

[Porter · Rating 1 out of 5]

This book provides very superficial explanations of some atrophysics concepts and touches on Hawkings life a little bit. The author attributes a lot of ruminating to Hawking that I really don’t think are supportable. There is a lot of self-aggrandizement and hyping up his own importance as Hawking’s right hand and trusty scribe which I doubt he would have been so bold in his claims were Hawking still alive. Really not the book I thought it was going to be. Honestly I am not really sure what the point of this book is other than to try to build up the author’s own image as a “collaborator” of Hawkings which it seems he certainly was not.

[Chad Manske · Rating 4 out of 5]

Stephen Hawking’s final theory dealt with the circumstances of how the perfect conditions for life on planet Earth were created. Delving into quantum physics, space and time, the great physicist and his closest collaborator—author of this new book—tried to peel these concepts back a layer at a time. And the theory they published together is still hotly debated. Interesting side note—Hawking is buried between Newton and Darwin and has a formula inscribed on his tombstone!

[Dolf van der Haven · Rating 4 out of 5]

The latest state of research in cosmology, including (not so) big bang and (not so) black holes is fascinating, but terribly complex. The author, who has worked closely with Stephen Hawking for decades, has a way to make this accessible to lay people, but in the end the theory becomes so abstract that it is hard to correlate it with reality anymore. Great illustrations and wonderful to get closer to Hawking’s mind.

[Doctor Moss · Rating 5 out of 5]

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.

[Dan Trefethen · Rating 4 out of 5]

The author worked with Stephen Hawking for the last twenty years of Dr. Hawking's life, acting as a sounding board to develop out the professor's ideas of the origin of the universe. Dr. Hawking has modified his ideas since he published his runaway bestseller 'A Brief History of Time'. He ended his life in the process of outlining a concept of 'quantum cosmology' that seeks to integrate the known principles of quantum mechanics with the development of the universe as we know it.

As the physics community well know, Dr. Hawking enjoyed turning science underside down with his ideas, from his discovery that black holes 'leak' what came to be known as Hawking radiation, to his most recent ideas about how the universe developed. While hard for a layperson to grasp sometimes, the ideas in this book are mind-expanding and lead the reader to a quiet sense of humility about our place in the world, and the universe that contains it.

[Frank · Rating 5 out of 5]

Zweifelsfrei ein Buch, das man atemlos zu Ende liest, obwohl man - zumindest ich - kaum wird behaupten können, alles auf Anhieb verstanden zu haben. (ich bin ein mathematischer Analphabet und finde es darum schon verdienstvoll, nie das Gefühl gehabt zu haben, gar nicht mehr folgen zu können.) Wichtiger waren für mich jedoch die philosophischen Anregungen aus einer Kosmologie, die versucht, die Physik des Universums aus unseren Beziehungen zu ihm zu entschlüsseln. Der endgültige Ansatz, dessen Genese in dem Buch behandelt wird, schaut nicht mehr "von außen" auf das Universum und auch nicht mehr von seinem spekulativen "Anfang" aus auf den heutigen Zustand, sondern will den Anfang von heute aus erkunden und das Rätsel lösen, warum wir in diesem Universum eine Rolle spielen, warum also die physikalischen Grund- Bedingungen zu biologischen Gesetzmäßigkeiten der Evolution geführt haben, kurz, wie Physik und Biologie einander bedingen und ineinander verschränkt sind.

Im Buch wird die Behauptung stark gemacht, dass die biologische und die kosmologische Evolution keinen separaten, einander gegenüberstehenden Phänomene sind, sondern bloß "zwei äußerst verschiedene Ebenen desselben riesigen Evolutionsbaumes" (S. 350). Alles ist aus der Sicht der Quantenphysik in der universellen Wellenfunktion miteinander vernetzt. Trivialer ausgedrückt: Wir sind wirklich Teil der Natur als Mitwelt und weder deren Aufgipfelung noch etwas, das über oder außerhalb von ihr steht. Dass wir sie manipulieren können, entspricht letzten Endes der Rolle des Experimentators in der Quantenphysik, dem z.B. die Natur des Lichts je nach Frage oder Versuchsanordnung anders erscheint. Auch das eine Manipulation. Dabei ist an der Verquickung von allem mit allem spannend, dass die Gesetze der (biologischen) Evolution auch für die Physik gelten könnten: "Die Meta- Evolution hat darwinistische Züge, mit ihrem Zusammenspiel von Variation und Selektion, das sich in der primordialen Umwelt des jungen Universum entfaltet. Variation tritt auf, weil zufällige Quantensprünge verbreitet kleine und gelegentlich größere Abweichungen von deterministischem Verhalten hervorrufen. Selektion tritt auf, weil einige Abweichungen , insbesondere die größeren, verstärkt und als neue Regeln eingefroren werden, die zur Gestaltung der nachfolgenden Evolution beitragen." (S. 346) Das hat mich interessiert. Wäre es nicht produktiv, die Geschichte bzw. das, was wir dafür halten oder davon zu wissen meinen, nach solchen "frozen accidents" zu durchforschen, um zu verstehen, warum sich die Menschheit eben nicht überall gleichmäßig und gleichförmig entwickelt hat? Den Begriff dafür gibt es schon: "Pfadabhängigkeit". Aber das Ganze ist - scheint mir - noch nicht zum Konzept einer anderen Betrachtung von Globalgeschichte geworden. Hier (und nicht nur hier) kann das vorliegende Buch anregen.

Ich meine, der dichte und auch durch die Verschränkung mit der Lebensleistung Stephen Hawkings interessante und gut lesbare Text, ist bestens geeignet, Interesse für philosophisch- physikalische Fragestellungen zu wecken, die aus der modernen Physik sich ergeben. Für jüngere Leser/innen tut sich darüber hinaus eine Welt auf, die zeigt, dass die Schule selbst ein "frozen accident" in der Lebensgeschichte junger Menschen darstellt. Welche Fragen kann man stellen, damit auch 15- oder 16-jährige verstehen, dass Physik nicht nur in Stein gemeißelte Gesetze, sondern spannende Perspektiven auf Lebensprobleme zu bieten hat? Dazu trägt der am Ende des Buches vorfindliche Bezug auf Hannah Ahrendt bei, die im vorherrschenden Technik- Narrativ der Jugend Tendenzen einer Weltentfremdung ausmachte, die zu korrigieren ist. Technik soll Mitwelt menschenfreundlich gestalten und nicht "Umwelt verändern" und also Mitwelt zerstören. Die von Hertog ausgebreitete Kosmologie weist uns einen Platz innerhalb der Universumsgeschichte an und stimmt, die Rolle des "Beobachters" in der Quantenphysik ernst nehmend, der Erkenntnis zu, dass das, was "wirklich" IST, von den Fragen abhängt, die wir dem SEIN stellen: "Wir sind ein Weg für das Universum, sich selbst zu erkennen." (C. Sagan/ S. 337). Wer Spaß daran hat, diesen Weg nachzuvollziehen und weiterzudenken, dem sei dieser im besten Sinne populärwissenschaftliche Text wärmstens empfohlen.

[Casper Vermeeren · Rating 4 out of 5]

was me beetje kwijt op t einde maar ga er ooit nog les van hebben in Leuven dus hij kan t dan deftig uitleggen