Varoluşsal Fizik

by Sabine Hossenfelder, Murat Havzalı (Translator)

Şu an evrenin kökenini açıklayamıyoruz, günün birinde açıklayacağımız da kuşkuludur. Sabine Hossenfelder’e göre kuantum dolanıklığı ve vakum enerjisinin alternatif şifacıların başvurduğu açıklamalar haline gelmesi veya insanların kuantum mekaniği aracılığıyla, ölen büyükannelerinin hâlâ yaşadığına inanması bir rastlantı değildir. Bilim ve dinin kökenleri de soruları da ortaktır:

Nereden geliyoruz?

Nereye gidiyoruz?

Bu soruları yanıtlamaya en yakın bilim alanı fiziktir. Son yüzyılda, fizikçiler hangi tinselci fikirlerin doğa yasalarıyla uyumluluğunu sürdürdüğü konusunda çok şey öğrendiler. Ancak tartışmaların her zaman bilimsel tarafında kalmadılar: Geçmiş varlığını sürdürüyor mu?

Parçacıklar düşünür mü?

Evren bizim için mi yaratıldı?

Bir her şeyin kuramı olacak mı?

Hossenfelder, fizikçilerin bu soruları yanıtlama yolunda ne ölçüde ilerlediğini ve hangi soruların sonsuza dek pekâlâ yanıtsız kalabileceğini ortaya koyuyor.

“Hossenfelder, fizikçi meslektaşlarının çoğunun bilimsel düşüncelerine spekülasyon ve inanç katma konusunda teologlar ve new age mistikler kadar suçlu olduklarını iddia ederek herkesi şaşırtıyor. Ama dünyanın kaygıları ile fiziğin şaşırtıcı karmaşıklığı arasında köprü kurabilen herkes biraz şımartılmayı hak etmiştir.”
The Wall Street Journal

“Bu ayın en eğlenceli kitabının bilim hakkında olmasını beklemiyor olabilirsiniz. Ünlü fizikçi Hossenfelder konusunu iyi açıklamakla kalmıyor; aynı zamanda okurları, bilim ile maneviyat arasında bağlantı kurmaya teşvik ediyor.”
Los Angeles Times

“Okurları alışılagelmiş varsayımların ötesine geçmeye teşvik ediyor ve bunu yaparken de eğlendirmekten geri kalmıyor. Bilimdışı görüşleri bilimsel olanlardan ayırarak, yaşamın büyük sorularını yanıtlamada bilimin sınırlarını belirlemeye yardımcı oluyor.”
Science Magazine

Genres: Science, Nonfiction, Physics, Philosophy, Audiobook, Popular Science, Psychology

256 pages, Paperback

First published August 9, 2022

About the author

Sabine Hossenfelder is an author and theoretical physicist who researches quantum gravity. She is a Research Fellow at the Frankfurt Institute for Advanced Studies where she leads the Analog Systems for Gravity Duals group.

Hossenfelder completed her undergraduate degree in 1997 at Johann Wolfgang Goethe-Universität in Frankfurt am Main. She remained there for a Masters degree under the supervision of Walter Greiner, entitled "Particle Production in Time Dependent Gravitational Fields", which she completed in 2000. Hossenfelder received her doctorate "Black Holes in Large Extra Dimensions" from the same institution in 2003, under the supervision of Horst Stöcker.

Reviews

[Brian Clegg · Rating 5 out of 5]

If I had six stars to give this book, I'd do it. Sabine Hossenfelder's first book for the general public, Lost in Math, showed just how much some aspects of theoretical physics were based on maths-driven speculation. That was arguably one for the science buffs only - but in Existential Physics she takes on questions that really matter to all of us.

Many of these questions hover on the boundary between science and philosophy - but this is no repeat of a book like Hawking and Mlodinow's unimpressive The Grand Design, which attempted to show that we no longer needed philosophy or religion because science can do it all. Rather, Hossenfelder manages to show where science can tell us things we didn't expect... and where it does not give any helpful contribution to answering a question.

Delightfully, these answers are not at all what you might expect. For example, Hossenfelder makes it clear that the various 'how did we get from the Big Bang to here' theories, such as inflation, are really not usefully scientific - because with different parameters the models could predict pretty much anything - while some apparently unscientific ideas aren't actually excluded by science, even if any sensible person would be likely to think them wrong.

The most startling example of this was in an interview Hossenfelder gives with climate scientist Tim Palmer. Each is either atheist or agnostic, yet there is an impressive argument given that it is possible for the idea of creation happening a few thousand years ago to be compatible with all existing science. I stress that neither of them thinks this is true - there is absolutely no evidence to support this idea, but equally science can't say it's untrue. What the interview demonstrates is that those who dismiss other people's beliefs with a sweeping 'science proves it can't be true' don't understand what science can truly prove or disprove. (Read the book if you want to know the ingenious argument that makes a 6,000-year-ago creation scientifically possible.)

Along the way, Hossenfelder explores a whole gamut of big questions - the sort of things that children like to ask us, we ponder on in the long dark teatime of the soul, and philosophers spend their time exploring. But all this is done from a solid, physics-based viewpoint. You'll find coverage of the distinction between past, present and future, the beginning and end of the universe, consciousness, Boltzmann brains, free will and much more. All the way through, Hossenfelder's light, slightly cynical voice makes it feel like a discussion in the pub rather than a lecture.

One comment early on made me laugh out loud - in the preface we read 'physicists are really good at answering questions' - in my long experience of talking to them, most physicists are absolutely terrible at answering questions. This is partly because they often don't understand what the questioner is asking, and partly because they don't know how to frame the answer in a way the questioner can understand. Hossenfelder admits that, like all modern physicists, her worldview is primarily mathematical and as such she finds it difficult to communicate in an accessible way because the maths is often all there is. It's a fair point, though thankfully in this book she mostly succeeds in overcoming that barrier with no mathematics explicitly involved.

The answers Hossenfelder gives to the many questions she covers in the book are put with such conviction and so convincingly, it's easy to get the feeling these are all the 'right' answers. It's important to remember that science doesn't really work like that - apart from anything else, new evidence can always require a change of theory. But bearing in mind she doesn't always agree with many big name physicists, it's a reminder that sometimes even experts in the field can be wrong. As it happens, I mostly agree with Hossenfelder over many of the famous names she mentions - but one of the nice things about a book like this is that you can actually consider your own beliefs and either change them or be prepared to argue back.

One example where I think this applies - I would suggest that Hossenfelder is a touch over-enthusiastic about the application of Occam's razor (without actually using the term). In several cases she suggests that something is not needed because everything observed can be explained without needing the extra something. This is absolutely true, but that doesn't prevent it existing. The simplest explanation is not always the correct one. (To be fair, this is made clear in several cases.)

The big thing that Hossenfelder grasps but many public-facing scientists don't is that there aren't two categories of theory - scientific and unscientific. Instead there are three: scientific, unscientific and ascientific. (Arguably there is a fourth - pre-scientific, where someone holds a theory for which there is not yet evidence, but for which evidence will eventually be found.) While some ideas are downright unscientific because there is good evidence that they are not true, many others are ascientific because there is no evidence for or against them. Where that's the case, Hossenfelder tells us, we are welcome to hold these beliefs, and it's not good for scientists to argue against them. This is especially the case because there are plenty of beliefs held by some scientists (the many worlds hypothesis, for example, or cosmic inflation) which are ascientific.

All in all, both a thought-provoking exploration of questions that are important to most people from a physics viewpoint and a useful counter to scientists who spend too much time on speculative theories with no hope of ever having evidence to back them up. Highly recommended.

[BlackOxford · Rating 3 out of 5]

Stay in Your Lane

Beware of scientists with philosophical aspirations. Particularly if they write well - as does Sabine Hossenfelder. Especially if they have a contrarian reputation in their own discipline - as does Sabine Hossenfelder. Hidden in plain sight within their lucid prose and controversial interpretations, are some really dodgy arguments. This is the problem with Sabine Hossenfelder, even if one agrees with her conclusions - as I almost always do.

Hossenfelder is an unashamed reductionist. For her the ultimate truth about the world lies in some expression in nuclear physics (but certainly not in cosmological physics which is largely useless, untestable speculation). Specifically there is a hierarchy of scientific enquiry: “Chemistry is underpinned by physics, and that is underpinned by mathematics.” In her theory, the lower down the kind of study the more “fundamental” the enquiry. She wants to focus on the

“… areas of physics that study the fundamental laws as the foundations of physics. Everything else emerges from those fundamental laws, roughly in this order: atomic physics, chemistry, materials science, biology, psychology, sociology…More likely, what’s currently fundamental will turn out to be emergent from yet another, deeper level.[*]”

I find it interesting to note that in the above quotes, mathematics is omitted in the second list as the most fundamental of the sciences. The footnote refers to her first book, Lost in Math: How Beauty Leads Physics Astray which perhaps explains this lapse. There she essentially objects to the criteria used in mathematics which produce things like string theory and other untestable constructions. Mathematics, it seems, has an ambiguous place in her hierarchy.

And indeed mathematics is problematic for Hossenfelder’s theory of the world: “…the closer we look at reality, the more slippery it becomes. Our heavy use of mathematics is a major reason.” So for example, she has to recognise that somehow the gears aren’t meshing between the various ‘emergent’ layers: “failure to distinguish the subjective experience of being inside time from the timeless nature of the mathematics we use to describe it.” Yet mathematics sits there at the ultimate foundation of the scientific enterprise.

The reason for Hossenfelder’s confusion and inconsistency is, it seems to me, obvious to everyone except Hossenfelder. She knows that the map of mathematics is not the territory of reality: “…we can’t assign ‘reality’ to any particular formulation of a theory.” In other words, mathematics does not emerge from reality (a Platonist view she rejects explicitly). In fact, if we accept Hossenfelder’s hierarchy of enquiry, mathematics sits not at the bottom but somewhere near the top of the chain. Mathematics, like all language emerges from the biological/sociological. From that position it then produces the rest of the scientific hierarchy. Mathematics, in other words, is indeed fundamental, but not in the way that Hossenfelder proposes.

So under Hossenfelder’s apparently commonsensical, undogmatic prose lies a dogmatism as rigid as any religion. She wants us to believe on faith that while we can’t demonstrably test the connections between the various levels of scientific enquiry - for example, predicting human behaviour on the basis of quantum theory - this is a matter of available technology not scientific principle. And while she knows that no theoretical description of the world can ever capture its reality, she wants us to share her faith that this doesn’t matter at all. Hers is a sort of militant, evangelical agnosticism suggesting that we follow her fearlessly into the void of knowing more and more about less and less. Sorry Sabine.

[Ryan Boissonneault · Rating 3 out of 5]

It’s a telling fact that centuries of progress in modern science has left the big questions of metaphysics ultimately unresolved. Questions like: How did the universe begin, and how will it end? Does God exist? Do we have free will? What is consciousness? How do mind and matter interact?

Existential Physics by physicist Sabine Hossenfelder goes a long way in explaining why this is the case. The short answer is that, as physical phenomena become increasingly smaller and more remote—and therefore outside the reach of observation and measurement—we must increasingly look to mathematics for answers. But, as Hossenfelder notes, oftentimes more than one mathematical model can fit the current facts, and, without the assistance of further experiment or observation, there’s no way to verify whether or not the chosen mathematical model is in fact an accurate depiction of reality.

The upshot is, the theory of the multiverse, for example, turns out to be, in a sense, no more scientific than the assertion that God created the universe 6,000 years ago. The multiverse may be more consistent with current science—and is supported by mathematical models—but the point is that, without the possibility of directly observing it, there is simply no way of confirming we have the right mathematical model, or that some other set of equations suggesting some other theory is in fact correct.

Hossenfelder points out that while it may be fun to talk about computer-simulated universes, multiverses, brains-in-vats, and panpsychism, we should remind ourselves that all of these theories reach far beyond what experimental physics can actually confirm. It doesn’t mean that these theories will never be confirmed, but at the moment, they represent pure speculation. And speculation that is mathematically sophisticated is still, in the end, speculation.

Of course, as Immanuel Kant noted, the human mind is burdened by questions that, due to its limitations, it cannot answer, but that due to its nature it also cannot ignore. And so we will likely continue to speculate beyond the facts, often invoking the mysteries of quantum physics as support for a host of quack theories (and ignoring the fact that the behavior of particles doesn’t translate to the behavior of macroscopic objects). But what this book makes clear is that this type of speculation is not limited to the idiocy of common supernatural beliefs, and that even scientists quite frequently cannot resist engaging in wild speculations. It just so happens that they’re better at math than the rest of us, so it’s harder to call them out on it.

But we should also remember that it’s not just our enthrallment with mathematics that’s the problem. There’s also the problem of how subjective experience seems to resist mathematical/mechanical explanations entirely (see the Mary’s room thought experiment). Hossenfelder does a rather poor job of explaining these deeper philosophical issues, but that’s unfortunately what one would come to expect lately from a scientist venturing into the field of philosophy.

There are additional problems. Hossenfelder appears to exempt her own preferred views from the same level of skepticism she applies to the theories of other scientists. For example, she’s uncomfortable with the idea of multiple universes because there’s no experimental data to confirm it. And yet, she’s perfectly ok with the idea that we could replace each one of our neurons with silicon chips and maintain consciousness. If she took her own advice, however, she might realize that the idea of artificially creating consciousness has the same level of empirical support as the multiverse; that is to say, none.

The bottom line: Take the conclusions found in the book for what they’re worth—one scientist’s views on difficult questions that are far from being resolved anytime soon.

[Jenna ❤ ❀ ❤ · Rating 4 out of 5]

"If physicists don’t step forward and explain what physics says about the human condition, others will jump at the opportunity and abuse our cryptic terminology for the promotion of pseudoscience."

In Existential Physics, theoretical physicist Sabine Hossenfelder delivers an easy-to-understand look at what physics can tell us about life's big questions.... and what it (at this point) can't.

Is "God" compatible with what we know about the universe? Is there such a thing as free will? Is Bostrum's idea of us being a computer simulation a valid idea? Can the universe think?

Ms. Hossenfelder takes us through these and many more questions. I found the book to be very interesting overall but at times was put off by her seeming to take pains not to offend anyone. 

Though she says early on that, "If your belief conflicts with empirically confirmed knowledge, then you are not seeking meaning; you are delusional", I found her to be too lenient when it comes to cultural beliefs.

For instance, making the remark (if memory serves correct) that those whose culture, as opposed to religion (I would say religion is culture), has a young earth creation story shouldn't be told not to believe it because doing so alienates people from careers in STEM.

[Insert scrunched up "hunh?" face]

She writes, "Saying that the world was created six thousand years ago with everything in place is unfalsifiable but also useless." Ergo, don't tell people they can't believe it if it's their cultural belief because it's unfalsifiable. 

So is that teacup revolving around Mercury.  Should we not discourage people from asserting it's there?  And fairies, and unicorns, and santa claus.... 

Aside from that, I found the book to be interesting and one of the easiest to understand physics books I've read. Ms Hossenfelder is both engaging and witty and this was a joy to read. 

Those who enjoy popular science books will likely enjoy this one, especially if you like books that make you think about the Big Questions and revel in awe at what science can tell us.

"Far from taking away wonder, science gives us more to marvel at. It expands our minds."

[Frank · Rating 5 out of 5]

With her popular blog Backreaction and first book Lost in Math, Sabine Hossenfelder has become one of the most prominent commentators on modern physics. Unapologetic in her frank and acerbic — acidulous, even — commentary, she has definite and demonstrative views on physics and physicists. (“I’m not exactly known for being nice,” she admits.) In Existential Physics, she tackles what physics says — and doesn’t say — about the Meaning of It All, including the nature of time, the origin of the universe, the existence of free will, and the “purpose” of existence.

Meaning is not something those of an existential bent often look for in physics. Indeed, physics is mostly seen as taking away meaning, showing us to be smaller and more insignificant in comparison to the larger universe at every turn. Hossenfelder, however, forcefully believes physics does have a lot to say about our place in the universe. Physicists, alas, aren’t much good at communicating that fact, allowing pseudoscience hucksters to co-opt and provide their own “meaning” to what science says, which is a disaster for both physics and the public by cloaking nonsense in the legitimacy of scientific “fact” and leading to confusion and misguided ideas.

As she explores things such as free will and fine-tuning, Hossenfelder is always at pains to distinguish between the scientific, the unscientific, and the “ascientific.” As opposed to the unscientific, the ascientific are concepts and theories that are not, even cannot, be disproved by science. But they also are not and cannot be proved by science, either. They are simply oblivious to proper scientific method. In such cases, Hossenfelder emphasizes that you can believe them, but you cannot prove them true. Take the many-worlds interpretation of quantum mechanics. This idea says that universes branch off with every flip of a coin, every quantum “decision” made, meaning there are infinite copies of you and everyone else. But these universes are totally unobservable. There is no proof, and never will be, that these universes are actually real. The whole many-worlds interpretation can provide no observational proof of its validity. It is functionally identical to many other interpretations, all producing the same testable results and thus no way to prove or disprove their correctness, that do not posit infinite universes. You can therefore believe in an infinite fellowship of yourself, but you can never actually know there is such a fellowship. What use, really, then, she asks, is the whole idea?

My one and only major criticism of the book concerns the interview chapters Hossenfelder intersperses throughout: I wanted them to be longer and more numerous! They’re fascinating discussions with various experts, but all seem to end before they really get going. I was left unsatisfied and craving more.

Admirably frank in her professions of where physics is ignorant, and never claiming that it has all the answers, Hossenfelder nevertheless provides a vigorous argument for its power to illuminate and its relevance to humanity’s search for meaning in the universe. I heartily recommend this book to any who are interested in the Big Questions.

[สฤณี อาชวานันทกุล · Rating 4 out of 5]

หนังสือแนวหนึ่งที่ชอบหาอ่านมากคือหนังสือข้ามศาสตร์ เช่น นักเศรษฐศาสตร์เขียนเรื่องสังคม นักประวัติศาสตร์เขียนเรื่องการเมือง นักรัฐศาสตร์เขียนเรื่องอาหาร เขียนโดยใช้แว่นหรือมุมมองของวิชาชีพตัวเอง ส่วนเล่มนี้นักฟิสิกส์ชาวเยอรมันเขียนถึงคำถามใหญ่ๆ ของปรัชญา เช่น เอกภพถึอกำเนิดอย่างไรและจะสิ้นสุดตรงไหน พระเจ้ามีจริงหรือไม่ มนุษย์มีเจตจำนงเสรีจริงไหม การรู้ตัว (consciousness) มีจริงหรือไม่ จิต (mind) และสสาร (matter) ปฏิสัมพันธ์กันยังไง? ตกลงอดีต ปัจจุบัน และอนาคต แตกต่างกันอย่างไร ฯลฯ

ความประทับใจที่ได้จากการอ่านหนังสือเล่มนี้คือ Sabine Hossenfelder เขียนอย่างรัดกุมและพยายามอธิบายเรื่องยากๆ ให้คนอ่านทั่วไปที่ไม่ได้เป็นนักวิทยาศาสตร์เข้าใจ ผู้เขียนไม่ใช่นักวิทยาศาสตร์บางคนที่บอกว่า วันนี้เราไม่ต้องการศาสนาหรือปรัชญาแล้วเพราะวิทยาศาสตร์ตอบได้ทุกอย่าง สิ่งที่เธอพยายามทำในเล่มนี้คือ ชี้ให้เห็นว่าวิทยาศาสตร์บอกอะไรเราได้บ้างในเรื่องที่เราไม่คาดคิด และคำถามอะไรบ้างที่วิทยาศาสตร์ช่วยเราตอบไม่ได้ ในแง่นี้หนังสือเล่มนี้แยกแยะอย่างชัดเจนกว่าเล่มอื่นๆ (ที่เคยอ่าน) ว่า ทฤษฎีต่างๆ ไม่ได้มีแต่แบบ “เป็นวิทยาศาสตร์” หรือ “ไม่เป็นวิทยาศาสตร์” (unscientific) เท่านั้น แต่ยังมีแบบ “ไม่เกี่ยวกับวิทยาศาสตร์” (ascientific) ด้วย – คือเราไม่มีข้อมูลหลักฐานใดๆ ที่บอกว่ามันจริงหรือไม่จริง ในกรณีเช่นนี้ผู้เขียนบอกว่า เราทุกคนควรเลือกได้เลยว่าอยากเชื่อหรือไม่เชื่อในทฤษฎี และนักวิทยาศาสตร์ก็ไม่ควรมานั่งเถียงว่ามันไม่จริง (บางทฤษฎีที่นักวิทยาศาสตร์หลายคนเชื่อก็เข้าข่าย ascientific เองด้วย อย่างเช่นทฤษฎีโลกคู่ขนานในการตีความควอนตัม (many worlds interpretation)

ประเด็นหนึ่งที่คิดว่าผู้เขียนอธิบายได้อย่างยอดเยี่ยมก็คือ การทำความเข้าใจกับปรากฎการณ์ที่เกิดขึ้นในระดับเล็กจิ๋วมากๆ เกินขอบเขตการรับรู้ของอุปกรณ์ตรวจวัดของเรานั้น จะต้องอาศัยการพึ่งพาคณิตศาสตร์มากกว่าการสังเกต แต่ส่วนใหญ่จะมีแบบจำลองคณิตศาสตร์มากกว่า 1 แบบจำลองที่อธิบายข้อเท็จจริงได้ ดังนั้นถ้าเราไม่อาจทำการทดลองหรือสังเกตได้มากขึ้น เราจะไม่มีทางยืนยันได้เลยว่าแบบจำลองคณิตศาสตร์ที่เราเลือกใช้นั้นสามารถอธิบายสภาพความเป็นจริงได้อย่างเที่ยงตรง

อ่านสนุก ได้ความรู้และแง่คิดมากมาย เขียนในน้ำเสียงเหมือนฟังเพื่อนเล่าให้ฟังมากกว่าฟังการบรรยายในชั้นเรียน ใครที่สนใจความเชื่อมโยงระหว่างวิทยาศาสตร์กับปรัชญา หรืออยากรู้ว่าการค้นพบ ณ พรมแดนล่าสุดของวิทยาศาสตร์ช่วยตอบหรือไม่ตอบคำถามปรัชญาข้อไหนได้บ้าง เล่มนี้ก็ควรอ่านด้วยประการทั้งปวง

[Márcio · Rating 5 out of 5]

Yesterday morning I received a email about a book on quantum leap to help make life better. Well, one more of those "quantum something" that has become so common from the near past on. And if you ask why I am telling you this to introduce my review of Sabine Hossenfelder's book, then, take a chance and read her quite interesting book.

Sabine is a theoretical physicist, who also happens to have a science channel on Youtube, "Science without the gobbledygook" (that is where I learned about her) about popular science. But don't get her wrong, if you believe in "quantum whatever", then she will smash it to bits. Her goal is to try to make clear what is science, what is ascience, what is bad science, and what is pure garbage. And for someone like me who likes to follow science news, reading Existential physics felt like a huge new experience.

Let me explain this. I can easily recall that a bit after New Horizons' flyby of Pluto (which I adored), I started losing my interest in reading and watching scientific news, for there seemed to be a whole bunch of information that didn't fit well, even though my knowledge of Physics and Maths are all so very poor. But I am no stupid guy, and as a curious being, I look forward to at least understanding the concepts underlying what I am reading or watching. No wonder reading Carlo Rovelli's Helgoland with its quick first part and its mystic second half and last part of his book was a very frustrating experience. I learned much more about quantum mechanics while reading Benjamín Labatut's When We Cease to Understand the World. Or Adam Becker's What is real?, who makes it clear that the meaning of quantum physics is not over yet, regardless of the amount of scientific data we have today. And so does Sabine Hossenfelder, who goes for the same line of thinking, that we need to understand quantum even better to make final conclusions.

I always congratulate scientists like Sabine Hossenfelder and Adam Backer!

[David · Rating 4 out of 5]

Strong physics books tend to feel very unedited, since what editor REALLY knows these facts well enough to change any of the wording. Thus you can 'hear' the author very clearly. Dr Hossenfelder has strong, confident opinions that she is not afraid to state here. Her undergraduate degree was math, before going onward into Physics for her PhD.

Her 'no bullshit' approach to describing how our universe works is refreshing, since many popular-science/physics books can diverge into lots of speculation. But you really need to have read multiple other physics books, and even some high-level physics (with strong philosophical language) prior to reading this book. A prime philosophical question drives each chapter:

1. Does the past still exist?
2. How did the universe begin?
- Interview w Tim Palmer: "Is math all there is?"
3. Why doesn't anyone ever get younger?
4. Are you just a bag of atoms?
- Interview with David Deutsch "I knowledge predictable?"
5. Do copies of us exist?
6. Has physics ruled out free will?
- Interview with Roger Penrose: "Is consciousness computable?"
7. Was the universe made for us?
8. Does the universe think?
- Interview with Zeeya Merali: "Can we create a universe?"
9. Are humans predictable?
Epilogue: "What's the purpose of anything anyway?"

Strong philosophical terms (compatibilism, reductionism, etc.) as well as philosophers from the past (Nietzsche, Kant, Matson, Fischer, etc.) are referenced. There is a glossary in the back of the book, but it is not nearly as complete as I wish it would be.

Some random stickies I put in this book...

Putting Max Tegmark (MIT) in his place...
Frankly, I think Tegmark came up with the mathematical universe only to make sure everyone knows he is a seriously weird fellow.
(I like Max. And I like his book Our Mathematical Universe: My Quest for the Ultimate Nature of Reality)

When was the last time your read a physics book that did NOT use entropy to explain the fate of our universe?
The second law of thermodynamics shouldn't be trusted for conclusions about the fate of the universe. Our notion of entropy is based on how we currently perceive the universe; I don't think it's fundamentally correct.

Or, how about questioning Einstein on a concept of the "Now" in time?
The upshot - please forgive me - is that Einstein was wrong. It is possible to describe the human experience of the present moment with the "timeless" mathematics we now use for physical laws; it isn't even difficult. You don't have to give up the standard interpretation of quantum mechanics for it, or change general relativity, or overhaul mathematics. There is no problem of the Now.

I like her referencing physicist Seth Lloyd commenting on Boltzmann brains:
I believe they fail the Monty Python test: Stop that? That's too silly!

One of her strongest statements is on the concept of Free Will. She trusts the physics/science enough to say:
I would just say this means free will does not exist and put the case to rest.

Basically, she advocates 100.00% of every single action you/I/we take is predetermined by science. Ah, but what does 'science' allow?
The future is fixed except for occasional quantum events that we cannot influence.

I am not comfortable with the word "occasional" added to this sentence. Quantum events are constantly happening. Nothingness turning into something/anti-something and then annihilating. The act of 'observing' that collapses wave functions.

Even much later in the book (pg 206 on Human Predictability) she says: In quantum mechanics, the state of a system cannot be perfectly copied without destroying the original system. This no-cloning theorem makes it provably impossible for people to know exactly what is going on inside hyour brain, because if they knew, they'd have changed your brain. Therefore, if any relevant details of your thought are in quantum format, they are "unknowable" and hence unpredictable.

Isn't this statement about unpredictability in conflict with her stance on the lack of free will?
This is my biggest demotion of 1-star in this book.

I really like on pg 159 her love for the principle of least action:
Today I think they don't teach the principle of least action in school because then everybody would go and study physics.

Another partial star-demotion comes again in conflict with her staunch advocacy of the lack of free will, yet summarizing if the universe can think as: a speculative hypothesis, but if it's correct, the universe might have enough rapid-communication channels to be conscious.

This statement is late in the book, and I find most (even the best) physics books tend to get speculative late in the book. But I had already praised her initial attack of topics in this book for her no bull-shit style. Conscious universe starts to sound like the animal house scene where they are smoking weed. Or maybe reference that Monty Python 'too silly' conclusion.

In the section on creating a universe:
Once again, this is because in a quantum theory everything that can happen will happen, eventually.
This is another conflict with her stance on determinism (I think).

Overall score: 4.25

I like her YouTube channel.
Maybe I'll raise my score on this book after I read her Lost in Math: How Beauty Leads Physics Astray book, which I surely will.

[Lee · Rating 3 out of 5]

There’s a lot of Pop science books and articles that feed my love of awe, but many ignore hard science in favor of a good story or push too far into scientific ideas that are good for getting non-scientist audiences (like me) to read their works. This author detests that and has no time for that tomfoolery. I think it’s important to know the hard science without the fluff because I don’t think it’s useful to push misinformation. But damn it’s like reading a catalogue of awesome ideas and being admonished for calling them awesome and cool. Like Werner Herzog making me feel stupid for being amazed by the idea of multiverses.

But I can see why scientists would appreciate this book. The title suggests it would take on the philosophy of existentialism to at least a small degree but there is no serious exploration of the philosophy or its thinkers (Sartre, de Beauvoir, Camus, Heidegger, Husserl, Jaspers, Merleau-Ponty), which is really what I was looking for. Or I guess at least a discussion of how the mathematical principles underpinning physics can be seen in light of the development of existentialism. She admits about halfway through that using language to describe complex mathematical equations is not something she will be indulging her readers with. She would rather let the math do the describing and leave the metaphors and more poetic language to others. And there are of course many others that one can read if what you’re looking for is shots of awe and experiences of the sublime. Alan Lightman, Sagan, Tyson, Holt, etc.

A good mental stretch, though. Her discussion of Entropy was enlightening and I thought the discussion of reductionism (where larger functions can be explained by smaller fundamental functions) informed the discipline of logic in philosophy, so for that I was intrigued. But the tone of the writing was very strict bare and lacked the kind of playful thinking that big awe-inspiring cosmic perspectives can provide.

[Wendelle · Rating 5 out of 5]

Some of Dr. Hossenfelder's responses to the big questions of life, as drawn from her high level of understanding of physics:
1. From special relativity, one learns that if an observer is moving fast enough close to light speed, any 2 events can be observed as simultaneous. Hence one's birth and one's death can be considered synchronous; one's past and one's future observed at the same time. This is consistent with the 'block universe' notion that past, present and future already coexist.

2. Most information, barring quantum measurements and black hole evaporation, are time-reversible: meaning information about stuff, including us, could technically be reconstructed.

3. However, there's an arrow of time that determines stuff moves from low entropy to higher entropy, and the initial state of the universe was low entropy. As ways to get around the unstoppable march towards highest entropy are hopeful speculations: Dr. Penrose
's conformal cyclic cosmology wherein universes are perpetually destroyed and reborn, resetting the entropy levels and the information accumulated; Dr. Sean Carroll's thoughts of a larger multiverses where new pockets of low-entropy universes are being created; Dr. Julian Barbour's belief of a 'Janus point' universe where directions of time change when two universes are born from the same vantage point in time.

4. We don't have free will.
The author repeats several times that "the future is fixed except for occassional quantum events that we cannot influence." She finds compatibilism a sad, dire pursuit. Free will would only be possible if there is strong emergent phenomenon such that a macroscopic event happens independent of underlying microphysics of our cells and neurons, but she says no other instance of this happening has ever been detected, so it's hard to claim it starts now.
We can "still feel we have free will, but know that we are running a sophisticated computation on our neural processor."

5. The existence or lack of existence of God is an ascientific question, one that can be postulated or not postulated but defies the realm of being determined by science.

6. The beginning of the universe is still an open problem

7. Reductionism, or the stance that our behavior is derived directly from our material substrate and its properties and internal interactions, is the most likely explanation for consciousness. What we think is deducible directly from the physical properties of our brain. Postulating the existence of the soul is ascientific-- neither wrong nor right but in Dr. Hossenfelder's view, unnecessary.

8. The idea of a multiverse with infinitely multiple copies of us is, in Dr. Hossenfelder's view, ascientific

9. She finds the simulation hypothesis laughable. She thinks it is difficult to reproduce our natural world, with all its precision, its detail, its multitude of interactions and predictability from the laws of nature, through some underlying computable algorithm. (However she does not address the P NP problem and the implications of the way any NP problem can be transformed to each other).

10. The lack of free will behooves us to approach problems with a consequentialist mindset instead of a moral judgement: someone should be jailed for posing future endangerment to society, based on past acts, not as moral judgement on their character

11.One of the ultimate meanings in life is passing on knowledge to our next generation.

This is a pretty good book to think of big-picture ideas about our existence.

[Makmild · Rating 3 out of 5]

ขอเชิญพบกับนักวิทย์ขี้แซะที่จะมาตอบคำถามเรื่อง existential crisis ของมนุษย์ ไม่ว่าจะเป็นขณะนี้มีอยู่จริงมั้ย มีตัวตนของเราในเอกภพอื่นหรือเปล่า เอกภพเกิดขึ้นมาทำไมแล้วส่งผลต่อเรามั้ย มนุษย์เราถูกกำหนดดวงชะตาไว้แล้วหรือเปล่า มนุษย์มีเจตจำนงเสรีมั้ย จริงหนังสือไม่ได้ไช้คำแบบนี้หรอก มันวิทย์จ๋ากว่านี้ 555555

แล้วตอนต้นมันดูโรแมนติกมากด้วยคำถามที่ว่า “คุณยายของผมยังมีชีวิตอยู่ตามหลักกลศาสตร์ควอนตัม เพียงแต่เธอไม่ได้มีชีวิตอยู่ที่นี่และตอนนี้ ถูกต้องมั้ยครับ” แล้วหลังจากนั้นเราจะโดนหลักวิชาการซัดจนหัวบวม

ข้อดีคือ เขาจะมีสรุปท้ายบทเอาไว้ด้วยเผื่อเราอ่านไม่รู้เรื่อง ข้อเสียคือ เราอ่านสรุปแล้วก็อาจจะยังไม่รู้เรื่องเหมือนเดิม ท้อ

ใดๆ ก็ตาม ความดีงามของเล่มนี้คือการบอกเราอย่างตรงไปตรงมาว่า “ไม่รู้” “ยังให้คำตอบไม่ได้” และ “ตามทฤษฎีแล้วก็อาจจะเป็นไปได้แต่ในทางปฏิบัตินั้น…” เรียกได้ว่าไม่อาจไขคำตอบใดๆ ให้กับชีวิต

[India M. Clamp · Rating 5 out of 5]

Many of the rough and scratchy concepts in this text do not strike one so gently as a warm sheet straight out of the dryer. The transition is one that is inherently abrasive in its innate form. It's perhaps not complimentary as other philosophical texts. The realization is luminous for it does not burn us as a heretic blatantly with loud oppositions, instead it leads us to find answers within the laws of nature.

“According to the currently established laws of nature, the future, the present, and the past all exist in the same way. ... The past, therefore, exists in just the same way as the present. While the situation is not entirely settled, it seems that the laws of nature preserve information entirely, so all the details that make up you and the story of your grandmother's life are immortal.”
---Sabine Hossenfelder

Natural laws may be found to oppose laws not evident in nature e.g. the laws of nature are equally valid for living beings and inanimate matter (Feynman, 1965). Let us look to omnipresence and what can be everywhere at the same precise moment? Another law of physics---that chemistry obeys---is when one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. How is this law relatable to life? How may we use Newton's first law to reconcile?

[Ira (SF Words of Wonder) · Rating 4 out of 5]

Hossenfelder attempts to explain some of the most mind-bending theoretical physics concepts and mostly succeeds. I say mostly because some of these concepts are basically unexplainable at this point, but she is very clear on where the consensus understanding stops. Some of the concepts she goes over are; the block universe, the beginning and end of the universe, what is math, entropy, free will, consciousness, and what is the purpose of anything. Hossenfelder steps the reader though these ideas in a logical manner and uses some great thought experiments. I had some truly ‘ah-ha’ moments reading this and really enjoyed everything about this book even though it bounced around a bit.

[Chris · Rating 1 out of 5]

A disappointing walk down a very narrow path through difficult questions. Sabine Hossenfelder is an eminent physicist, and she is conversant in both speculative theoretical physics and some philosophy, including philosophy of science. She frequently references ideas that compete with her own — and then waves them away with half-hearted appeals to perspicacity or a kind of high-science common sense. All the erudition and scientific capability she displays amounts to fireworks instead of argumentative firepower.

She frequently gets the burden of proof in science all wrong, claiming her own ideas are right (including ones that she admits are unfalsifiable and thus ascientific) because no one has demonstrated the contrary and claiming her own are correct because they may one day be empirically verifiable, if all goes well.

The chapter on free will was perhaps the worst. She does not engage with the growing literature on whether particle physics is itself causally closed, and she waves away the lack of empirical support for causal articulation between particle physics and higher levels of abstraction. I laughed out loud and closed the book when I read this sentence: “I have found that abandoning the idea of free will has changed the way I think about my own thinking.”

In other words, coming to believe that the universe is deterministic…changed…her…thinking. Either this is a pointless tautology, or she believes in free will after all.

[Brian · Rating 4 out of 5]

This is an intriguing and worthwhile read. The author covers a series of big and interesting of topics that relate to physics. Though the jumping off point is the science of physics, Hossenfelder proceeds to give us her opinions on each topic as well as her philosophical thoughts relating to each. Such topics as the nature of time, free will, multiple universes, and many others are examined. I found both the facts, and the author’s opinions to be fascinating.

A few things that I would note about Hossenfelder and the book. The author has a reputation for being controversial, she criticizes some popular physics research as ascientific. Theories and speculation about topics such as multiverses and the origin of the Universe come under question by her. The author’s positions bring about a lot of disagreements; she tends to be a bit blunt and sarcastic. She even admits in the book that she is not always nice. Thus, she often generates strong reactions. She has also taken positions on political and social issues that have brought about personal attacks on her on social media and on review sites.

Despite this, Hossenfelder seems to be a reputable and serious scientist, who also has opinions that are worth reading about. She challenges some scientific practices but also a agrees with mainstream physicists in many other areas. I agreed with some of the opinions expressed here and I also disagreed with some others. I think that a book can still be strong even if I disagree with an author’s opinions. But it is important that an author presents things logically and coherently. Hossenfelder always does that.

For potential readers of this book, I would recommend being up to date on current theories on cosmology, relativity as well as quantum physics. As the author criticizes some theories and trends, it would behoove a potential reader to be up to date on these things before reading this.
Either way, those interested in cosmology, relativity, and quantum physics, as well as philosophical rumination around these sciences, should get a lot out of this book.

[Ali · Rating 5 out of 5]

Existential Physics is a balanced review of current theories where Hossenfolder leverages several existential questions to weed out ascientific speculations. She walks a fine line between science philosophy and religion throughout the book. Overall very thought provoking read but my worry is that quantum healers and the like will use her arguments to support their pseudoscience. Well they will do that anyway but we have enough flat earthers already to deal with. Anyhow I would recommend Michael Shermer’s interview with Hossenfolder on the Skeptics Podcast and some other resources referred in the book and her interviews.

[Miglė · Rating 4 out of 5]

This book is for you if you:
• Like Sabine Hossenfelder and her no-nonsense approach,
• Are confused by pop-science articles announcing 'Multiverse finally confirmed??', just wanting to know what is actually confirmed in the end and what is not,
• Don't mind that some of the deeper philosophical explorations get sacrificed in the aforementioned 'no-nonsense' account.

This book aims to answer what current research can say about the deepest, broadest questions, such as 'Is everything predetermined?', 'Where does consciousness come from?', 'Does free will exist?', as well as clearing up some of the more esoteric ideas: 'Do we live in a computer simulation?', 'Was the universe made for us?', and including very funny interviews with prominent scientists and their more ambitious thoughts (such as the interview with Roger Penrose and his idea that it's wave function collapse that causes consciousness, and not the other way around).

Sabine Hossenfelder is a proponent of the 'block universe' worldview, a reductionist, and a determinist – but the account is so personal that it's not annoying even if you don't subscribe to those views. She doesn't disparage religion, instead labeling it (together with many other ideas) as ascientific – meaning that science can't tell anything about whether God exists or not, and you're free to believe what you will. She does get annoyed by some other theories (like the computer simulation).

The style is very easy to read and really funny at times. I was expecting maybe deeper scientific explanations, and the author's blasé attitude is refreshing and a bit disappointing at times (when discussing wave-particle duality, she says that she doesn't care that much personally because she's only looking at the math, and the math works). On the other hand, I learned about many fun ideas the author deems ascientific, such as Boltzmann brains or Geometrogenesis, and had good fun reading this book.

[Dan Cassino · Rating 3 out of 5]

Most pop science books, especially those centering on the big questions about life, the universe and everything, take an upbeat, positive view of the topics. "Look at this crazy stuff!" they say, "Isn't the universe an amazing place? There's so much we don't know, and here's some ideas about what might be happening!" Think Katie Mack's "The End of Everything." The goal seems to be to highlight some of the theories about how the universe works, and share the excitement that physicist have about what they're discovering, and what they might find next.
Hossenfelder is not interested in that kind of thing, and this is not that kind of book. She's not exactly trying to say that popular, often speculative, models of how the universe works are false, or bad, or wrong, but she is all about getting the hose and spraying them down. "Look," she says repeatedly, "You can believe in all of that speculative nonsense if you like, but it's not science, and doesn't even rise to the level of being wrong, so have fun, but don't kid yourself." Are there billions of universes that we can't observe in a multiverse? Maybe, but if we can't observe them, and they don't interact with our universe, who cares? Does quantum mechanics lead to universal level unpredictability? Sure, but only if you're very, very, tiny, and not even so much then. Could the universe be conscious? Not unless there's a bunch of mechanisms we don't know about. Maybe there's a universe inside every atom! No. No there isn't.
At some points, she's punching down folks who very much deserve it (paging Deeprak Chopra). Other times, she's basically telling physicists to not get in front of the evidence that they actually have, with the suggestion that speculation and poor communication of the limitations of current knowledge wind up empowering the Chopras and Ben Carsons and Andrew Weils who use public confusion for their own unscientific ends.
The result is a book that is well written, informative, and, honestly, not a lot of fun. Kip Thorne and Katie Mack and the like write the books they do because they're interesting and exciting; a book pooh-poohing them, however correct, is never going to be. It's not mean-spirited, it's not a joyless slog - Hossenfelder clearly shares an enthusiasm for physics and cosmology - but it doesn't have the charge that more speculative books often do. As such, it's successful in what it's trying to do, but, I think, less appealing to popular science readers. She also includes a number of interviews with physicists that don't add a lot to the narrative, they're fine, but could easily have been included in the chapters, rather than getting their own short sections.

[Irene · Rating 5 out of 5]

If Sabine Hossenfelder and Carlo Rovelli are ever up for a slumber party, I'll bring the snacks.

This is a philosophy book. It's a physics book in essence, but the line between quantum physics and philosophy seems very thin to me. It's always a nice feeling to read your own opinions put very eloquently in a book, so I had an excellent reading experience.

My only points of contention with Hossenfelder are her insistence on talking about the brain as if it were a computer (I think that, as a concept, it falls short of the brain's complexity), which ties into the issue with scale. She often wants to apply particle physics to psychology, and for the same reason, I think that simplifies how brains work. Which is why we still don't know why there are different rules for particles than for bigger systems.

The unknown unknowns of neuroscience and quantum physics are likely to overlap, but I've somehow reached the same conclusions about free will that she has, through a different path. Looking forward to getting a physical copy of this book so I can re-read it and annotate it.

[James Easterson · Rating 2 out of 5]

Why is I feel like I’ve been bullied after reading this book? Generally I love reading science explainers, especially about physics and Quantum theory, but this did little for me, and the arguments where difficult to follow. Perhaps she is just too advanced in her terminology for me to follow, but I definitely felt an intolerance for other viewpoints than her own including from other physicists. My personal disagreement is with the total deterministic take on the world. Maybe not scientific enough for her but I call shenanigans on that. To me everything is a process, everything is relational, and everything is to some degree probabilistic with parameters. In the current state of cosmology people do look beyond the current bounds of science to find new science. There was a time when it was impossible to know the makeup of the sun and stars. We would never know, but now we do. So we dream, and imagine, tell stories, to look deeper than we have before.

[Raghu Nathan · Rating 5 out of 5]

I enjoy reading Sabine Hossenfelder’s books, blogs and listening to her YouTube channel. She is a German theoretical physicist working in quantum gravity at the Frankfurt Institute for Advanced Studies. I respect her as a courageous, authentic thinker in science. She highlights physics’ trajectory toward accepting theories lacking experimental validation. In theoretical physics, string theory and cosmology have reached an era where theory is unconstrained by empirical data. A large body of particle physicists continues working without worrying about experimental verification. She worries that aesthetic judgment has been driving research in theoretical physics for decades. In this book, her primary goal is to help readers discern established science from belief. She calls herself an “agnostic heathen” and stresses that any search for meaning must respect scientific fact. She warns readers in the preface that confronting the consequences of certain natural laws could be painful. Contemplating the implications concerning free will might disturb some individuals.

In this book, Hossenfelder uses modern physics and the scientific method to explore philosophical, sociological, and religious questions. These questions include life and death, the nature of reality, and the universe’s origin and end. The book organizes itself around nine core questions.
They are:
Does the past still exist, or is it gone and erased forever?
How did the universe begin, and how will it end?
Does the universe think?
Why doesn’t anyone ever get younger?
Are you just a bag of atoms?
Do copies of us exist?
Has physics ruled out free will?
Was the universe made for us?
Are humans predictable?
The book contains Hossenfelder’s analysis of these questions. There are also interviews with eminent thinkers like David Deutsch, Roger Penrose, Tim Palmer and Zeeya Merali to throw more light on some issues. We shall at into some questions in depth here.

Does the past still exist, or is it gone and erased forever?
This question concerning time and existence holds an allure. Hossenfelder accepts the Block Universe theory and hence leans toward the past being real. It is an offshoot of Einstein’s theory of special relativity. The Block Universe theory is a model of spacetime where the past, present, and future all exist together and are equally real. Time is a dimension, and a four-dimensional block of spacetime already contains all events, from beginning to end. There is no privileged “present” moment. Our subjective experience makes the present seem special, but objectively, all moments are equally real. When loved ones or grandparents die, the information regarding them becomes irretrievable, and communication is impossible. However, physics’ mathematics states that the information endures forever within the block universe. Relativity theory suggests that spacetime geometry permanently documents the lives of those who have died. It is like frames in a movie, even though unbelievable.

How did the universe begin? How will it end?
This is a central existential question. Hossenfelder admits we don’t know how the universe began, unlike the common view that the Big Bang started it. She states that all current origin theories are speculative. They are modern creation myths written in the language of mathematics. Regarding the universe’s end, the author says that, extrapolating from known laws of physics, the end of the universe will be ‘dark’. It is because the second law of thermodynamics predicts the increase of entropy and hence energy running out. However, Hossenfelder is skeptical of predictions trillions of years in the future. Current conclusions may prove invalid upon deeper comprehension of gravity and quantum mechanics. In answering this question, Hossenfelder argues that sometimes the only scientific answer is “We don’t know”.

Another question is, ‘Does the Universe think?’
The direct and simple answer would be it does not because of the sheer scale of the universe. The universe is about 90 billion light-years across. A thought’s journey this far would last an eternity. However, there are other views on this question that challenge such skepticism. The panpsychist view is one of them. It holds that all matter is at least minimally conscious. Hossenfelder is skeptical of the suggestion that elementary particles think. Despite this, she regards consciousness as a gradient property. Systems are conscious depending on how much information they process, such as brains doing computation. Consciousness emerges at a certain size and configuration of matter.
In a curious overturn of this argument, Hossenfelder frames her personal motivation for scientific work as contributing to the universe’s self-awareness! When she was young, she asked her mother about the meaning of life. Her mother was a teacher and hence replied It is to pass along knowledge to the next generation. Though Hossenfelder thought it lame then, thirty years later she came to accept the conclusion. She realized that she herself had studied the laws of nature most of her life and still found joy in sharing that knowledge. Many people seek knowledge of our place in the universe. What she is trying to do is aid the universe’s understanding of itself. We are bags of atoms, yet we are also much more than this. So, in her view, science does not rule out an intelligent universe at present.

Do we have free will? Does physics rule it out?
This is a key existential question Hossenfelder tackles in the book using both physics and philosophy. Many believe life is a “garden of forking paths”. Each path represents a potential future, and we decide which one to experience. But the laws of nature function differently. Physics says that the laws of nature are deterministic with a random element from quantum mechanics. This means we cannot influence the future, except for occasional quantum events. So, there is only one path, because quantum effects seldom manifest themselves in the macroscopic world. Whatever happens today results from yesterday. Yesterday originates from the prior week, continuing backward to the Big Bang.
From a philosophical viewpoint also, Hossenfelder feels the concept of free will to be inconsistent and flawed. She invokes Friedrich Nietzsche in support, who said, “For one’s will to be free, nothing else can cause it (it must be an ‘uncaused cause’).” If the will is uncaused, then you did not cause it, which makes it self-contradictory. However, Hossenfelder does not discuss the consequences of this position, which makes concepts like repentance meaningless. Also, our actions would be pre-determined, which would undercut morality.

Other existential questions from physics are whether we live in a simulation and whether there are multiple universes (multiverse). According to Hossenfelder, the simulation hypothesis is speculative. She thinks it’s an example of confusing science with belief, as it makes unobservable claims that are not needed to explain our current universe. It is ascientific. An ascientific idea is one that is “neither true nor false but unprovable” by science in its current state. She acknowledges the prevalence of the idea of us living within the ‘Matrix’. It may even be true, but believing it will make little difference.

She calls the idea of a multiverse also ascientific because these other universes are by definition unobservable and are unnecessary to explain what we can observe in our universe. Promotion of such speculative ideas damages the scientific community’s ability to maintain high standards. She points out these ideas attract a lot of media attention, casting “bad light” on the scientific community. Extending this criticism, Hossenfelder grants that the idea of parallel universes of the ‘many-worlds interpretation of quantum mechanics’ is compatible with what science knows at present. It implies copies of us exist, yet these are unobservable, rendering them superfluous in explaining what one observes in our universe. This makes the idea unscientific.

I find Hossenfelder’s writing style simple to understand and her ability to explain complex ideas impressive. With her informal style, she makes theoretical physics entertaining. Some may see her as opinionated and her criticism of experts as somewhat harsh. But I feel it is necessary to push back against unscientific speculation, even if experts do it. Scientific disciplines are becoming prone to hypes nowadays, as we note in artificial intelligence about AGI, and medical science about making virtual copies of individuals and experimenting with them. In such an intellectual atmosphere, it is heartening to see Hossenfelder devoting attention to presenting the limits of science.

Whether we agree with Hossenfelder or not, we cannot deny that she is a bold thinker, not only in physics but in science overall. I used to doubt whether scientific discussion was possible for the issues raised in this book, as many of them intersect with philosophy and ethics. The author shows how one can keep close to rigorous science and still critique the issues.

This book is vital in today’s society, where everyone claims expertise via online Google searches.

[Ronnie · Rating 3 out of 5]

I appreciate how blunt and straightforward the author is. However, she seems to think that other physicists who use their knowledge to extrapolate possible future findings are not being usefully imaginative or making educated guesses but rather are just bullshitting, and I disagree with that. She does not seem to realize that her own conjectures are only as valid as theirs.

[Jenny Hu · Rating 2 out of 5]

I appreciate the take of answering how science compatible each existential question is- though found the chapters much more fun to read by skipping to the summary first, and digesting the explanation after.

Didn’t totally appreciate the “trust me” prose sprinkled across the entire book, and struggled to separate what is the author’s opinion from what the hard science says.

[Saiful Salihudin · Rating 4 out of 5]

Our dead relatives are still alive somewhere in this universe. Pretty strong start for a book. I love reading (pop) quantum physics and challenge my perception of our reality. Sabine makes physics accessible and comprehensible.

[Sarah · Rating 3 out of 5]

Hossenfelder is a say-it-with-your-whole-chest type of scientist. Equal opportunity for religious and atheist readers alike to be offended. She has no qualms about equating concepts like the multiverse to "religion masquerading as science under the guise of mathematics". She even manages to throw shade at Hawkins before finishing up.
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The quick summary is Hossenfelder's going to war against all theories that cannot be supported by empirical evidence. She doesn't care about the mathematical universe or alternate probability distributions. In her opinion, if we cannot observe the data points, then there is no scientific requirement to explain them. (Ironically made me want to expand my reading on said topics.)
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Overall, an enjoyable read. I'm always appreciative of sass. I liked that the chapters were interspersed with contradicting scientific opinions. Always good to get both sides of the coin.

[Rrrrrron · Rating 2 out of 5]

Half the chapters are mediocre. The author likes to choose a particular definition such as what is “real” or what is “free” in free will or that humans are “predictable” and to pretend that it is based in science rather than her peculiar opinion. It is a tiresome science strategy writing if you are revisiting common pop science themes and her snarkiness doesn’t help. But there are two or three very entertaining chapters.

[Hugh Simonich · Rating 3 out of 5]

My problem is not with the types of questions asked, but the language she used to write the book. She assumes too much that the layperson would know what she is talking about. She gets into the language of physics which, without the proper context, can be very confusing. She needs to add background and possibly remove some parts that don't matter.

[Liedzeit Liedzeit · Rating 2 out of 5]

I liked the previous book by Sabine Hossenfelder and I like her YouTube channel. I think her humour is sometimes out of place and by and large quite predictable. After a while you know exactly what joke she is going to insert next.

Okay, here is a test. I start watching an episode that I have not yet seen. About the end of science. (https://www.youtube.com/watch?v=KW4yB...) I’ll be back in two minutes...

There. She lists all the great questions, that have not been answered. We still do not know what Dark matter consists of. We do not know how life began, what consciousness is, how to become immortal...

What comes next? Right! We still don’t know why socks disappear in washing machines. At 1:49.

This is not very funny. But the point is, it can easily be predicted. And this is one of the themes in this book. You see, there is no free will. The poor woman could not help herself cracking this joke. It was determined right with the Big Bang.

Chapter VI is called “Has physics ruled out Free Will?” And her answer is yes. And she comes back to this in chapter IX under the heading “Are Humans predictable?”

Because I will concentrate on this let me briefly say that I found most of the other existential questions in the book quite uninteresting if not utterly ridiculous, like can the universe think? Or do copies of ourself exist. (I know people do think it is possible or even likely.) And her interviews with famous people like Palmer or Penrose I found embarrassing. The one really good chapter, I think, is about the question “Are you just a bag of Atoms?”.

So back to the question of free will. I am not saying that Free Will does exist, I am only saying that her arguments that it does not are funny, in the pejorative sense of funny.

It starts with her claim that philosophers have a different concept of free will than normal people, i.e. physicist, have. They, philosophers, have offered a heap of definitions of Free Will and that is why she goes on without a definition.

The currently established laws of nature, she says, are deterministic with a random element from quantum mechanics. And then: “This means the future is fixed, except for occasional quantum events that we cannot influence.” (p. 125) This is her mantra. And she will go on repeating that last sentence two dozen times. Which is either her idea of humour or the result of the well-established insight that an untruth will be accepted if repeated often enough. Maybe a mixture of both.

This is a remarkable sentence. The second part contradicts the first and the third has nothing to do with it at all. It is like saying: “This novel is totally boring except for the scenes with Anna Karenina and the Beatles have a new single out.”

What does the fact that we cannot influence quantum events has to do with the question of determinism? If there is a random element does that not mean that it is not deterministic anymore? John Conway’s Life for example is completely deterministic. There is a rule that determines from a given set of cells the position of the cells of the next generation. You can find implementations of Life with a random effect: From time to time there will be a new cell (a mutation) that is created not according to the rules. What does it mean? That it is not deterministic any more. And this means, you cannot predict it anymore. Simple as that.

Science says this: “What you do today follows from the state of the universe yesterday, which follows from the state of the universe last Wednesday, and so on, all the way back to the Big Bang.” (p. 126)

This may very well be the case. Here is the argument of the other side that she quotes: Free will is incompatible with determinism, but free will exists, therefore determinism must be wrong. This, the view of libertarians, is so ridiculous to her mind, that she is not discussing it at all. (Instead she is arguing against compatibilism.) But just as a piece of argument I fail to see why it should be inherently less convincing than her own: Free will is incompatible with determinism, but determinism is real, therefore free will must be an illusion. We have introspection in contrast to the physical laws of the universe as so far established. Both arguments prove exactly nothing.

But there is an argument for the free will case that suggests itself. Whenever I am about to make a decision (whether to raise an arm, say) I bind myself to a double-slit experiment. This one would not usually call a free decision but it seems that all your knowledge of the state of the Big Bang will not make you able to predict my action. Which means, I would think, that determinism is wrong. But Frau Hossenfelder has a counter-argument. Yes, she agrees, you could have “that Universe-Splitter app on your phone–to decide whether or not to take the marshmallow. And I couldn’t predict that decision.” (p. 201) So, determinism is wrong after all? No, she goes on, she could still predict the probability of my making the decision! Wow! It means she could guess. (So can I, the probability is 50%.) Is human behaviour predictable? Yes, because she can predict the probability. In other words, because of determinism, she can predict my action. It is just the case that sometimes her prediction turns out to be wrong!

Here is another argument. Sometimes people want to prove the existence of God by saying that without God everything would be allowed, and people would be lying, raping maniacs. Even if this were true it would only establish that it is a good thing to believe in God’s existence.

But how about a believe in the freedom of will? If people believing in free will act differently from people who do not it should be an indication that free will exists. And that seems to be the case. A lot (if not most) of our actions occur on auto-pilot. But there are people who think they can influence the course of their lives and people who think that whatever they might intend things are happening in a way they cannot truly influence. There is, of course, no clear cut difference but taken as a whole (I am threading on thin ice, maybe) Christian people more or less believe in free will whereas the control group, Muslims, do not. The difference is surely tiny but there is a difference in society. Maybe a better example is Calvinism. Now calvinists believed in predestination. There was nothing they could do. It was God’s decision who would be rescued and who would be damned. No need to do good Deeds. But! There was a loophole. If you were a worldly success that would be a sign that you were redeemed! And what that meant was that people would work harder. The believe changed the way they behaved.

So whereas the believe in God’s existence has nothing to do with his his ontological status, it seems to me that a believe in Free Will actually creates free will. Why should the believe in Free Will evolve? If there is a benefit in the believe in Free Will does this not suggest that there is Free Will?

Not really, of course. It could be determined from the beginning of time that the people believing in Free Will are doing better as a whole. So my argument proves nothing at all. However, this means that the assertion that everything is determined cannot be falsified. And this, to use one of Hossenfelder’s pet words is ascientific.

5/10

[James Docking · Rating 5 out of 5]

A sound discussion of what Physicists can claim as fact rather than conjecture.

[Allen Roberts · Rating 5 out of 5]

I’ve been a fan of the German theoretical physicist Sabine Hossenfelder for quite a while based on her YouTube channel, where she discusses science-related matters with her no-nonsense, Russellian, skeptical, and often funny outlook.

She puts her insight into book form here, as she discusses such questions as: Why does time flow in only one direction? Do copies of us exist in parallel universes? Has physics ruled out free will? Is the universe made for us? Is the universe conscious? What is consciousness?

In this book, she provides a vigorous, compelling defense for evidence-based science—on multiple topics, she is able to delineate what science can tell us, what it can’t, and give some tantalizing glimpses of its future possibilities.

Whether or not you agree with Sabine’s viewpoints, your gray matter will be highly stimulated by engaging with these scientific and philosophical issues. Personally, I’m an unabashed admirer of Sabine. She’s a tough-as-nails empiricist who eschews bullshit, and it’s hard for me to find fault with that stance. Five stars.