Something Deeply Hidden by Sean Carroll ★★★★★

I was granted an ebook ARC of Something Deeply Hidden by Sean Carroll by the Publisher Dutton on NetGalley to provide a fair and honest review.

See my full review and discussion on my YouTube Channel!


I am beyond grateful to be offered the opportunity to review this book. I just recently finished one of Carroll’s older books, and it is one of my favorites of the year. I know this book is already out. Nevertheless, the copy I was granted expires on the 31st of December, so intend to finish it before then to provide feedback for the copy I received. When I reviewed From Here to Eternity, I tried to review each part of the book. I think the result was a bit of mess; it was also a lot of work. Here, I will stop after each chapter to very briefly summarize his points and to discuss how effective it was as a chapter. Summarizing it will help me get a sense of how well I really understand it. Basically, I’m blogging my entire experience with the book. When I’m done, I’ll summarize my thoughts above my blogging experience (right after this).

Final Thoughts

I absolutely adored this book. I am so grateful to NetGalley for providing me with an e-ARC of this. I didn’t even realize it was already out, and I ended up using the audiobook (also amazing) to read the book. I still am happy I got the ARC because I may not have read it otherwise. I have only just started on NetGalley. I am a fan of Carroll, so I wanted the chance to review his newest book early. Even if it was already out, I may not have read it without the ARC because that was really the biggest motivator (the need to provide a review).

Otherwise, I might have read a different book by him because I was honestly very afraid of this book. The first time I saw the synopsis (prior to finding it on NetGalley), I read quantum mechanics and thought this was not for me. I have never understood it and was unlikely to start trying now. Then, with the added incentive, I decided to give it a try. Dear Sagan am I happy I did. I left this book feeling as though I actually understand quantum mechanics. Then add on the extra benefit of being beyond fascinated, intrigued, and excited by his discussion of Everett’s Many World’s hypothesis. I go in depth in my thoughts on that in my live blogging where I responded after each chapter. I would refer you there,, if you are interested in reading that.

All in all, this book did everything I want from a science book. It challenged my fundamental way of thinking all the while in a clear and structured manner. What’s more, it is one that doesn’t shy away from the tough parts of science while not creating a story that completely hinges on your reader to have an expert level understanding to follow along. I highly recommend this book and Sean Carroll (and his podcast Mindscape). This will probably be one of my top 10 books of the year. 5/5 stars

I will probably do a review on my channel as well, but that will be in a week or so when I have time.

Rating Break Down
Writing Style: 10/10
Content: 10/10
Structure: 10/10
Summary: 9/10
Engagement: 10/10
Enjoyment: 10/10
Comprehension: 8/10
Pacing: 9/10
Desire to Reread: 10/10
Special: 10/10
Final Rating: 4.785/5
Note, each rating is weighted based on personal importance (see blog for more details).

Live Blogging

Started 12/13/19

The book is already out, so I should be okay to quote it. Lastly, I am reading this via the e-arc in conjunction with the audiobook (on Scribd). The audiobook is narrated by Carroll himself, and it is very well done. If you haven’t already, check out his podcast, Mindscape where he gets guests to discuss leading topics in science. I mention that here because the first thing I noticed was how much the audiobook was like listening to this podcast. It feels natural well performed.

Carroll uses the Prologue of this book for a very simple purpose. He is here to talk to us about Quantum Mechanics, but before he does that, he has to make has to make us care. He takes a subject that, I suspect, most people assume is resolved, and explains why what we think we know is wrong. What’s more, he hints at how he intends to make us look at Quantum Mechanics in a brand new way. He does it in a way that highlights how skilled a science communicator he is, and it gets me beyond excited to dig deeper into this book.

Part One: Spooky

Continued 12/14/19

In Chapter 1, His first step is to explain exactly what quantum mechanics tells us, generally speaking, and where it sits within the realm of physics. Basically, it is a foundation chapter. He discusses how quantum mechanics compares to classical mechanics in how we go from a world of concise reality to one of probability. He sums it up as follows: “What we see when we look at the world [through quantum reality] seems to be fundamentally different from what actually is.” Quantum mechanics works similarly to classical; that is, the system is set up and is let to evolve. The difference comes with the act of measuring. The fundamental problem addressed in this chapter is to understand that quantum theory, as it currently exists, doesn’t explain how reality works only that it is how it is.

The concept seems simple enough, and his background feels like a good description of what quantum mechanics is. In Chapter 2, Carroll takes us on a journey to how this all came to be understood. He tries to make his point, stated in Chapter 1, that there is something missing in our understanding. Carroll explains the difference between epistemology which is the state of our knowledge versus ontology which is the state of reality. Essentially, this says there are ways of getting to the result without fully understanding how we got there. I get a little lost as he transitions to thinking about QM in a different manner. He treats the idea of a wave function as reality. where everything is literally a wave and when we observe it as otherwise, we aren’t observing a fact of reality, simply a piece of reality lacking a bigger picture. The impression I get from this is that the problem with QM isn’t an ontological one but an epistemological one.

I can’t pin point exactly how he goes from each point to the next, but I find his explanation overall effective. I’ve never quite understood what it meant to be a wave function. Now I think I do. Waves aren’t just a construct, they are a fact of reality, where reality acts fundamentally different than we perceive it in classical mechanics. That is, the universe is as much in a state of superposition as the quantum particles that make it up. That leads Carroll to the idea of Many Worlds, where many worlds are simply an extension of quantum theory. “The potential for such universes was always there,” and each world is a realization of that each position. This may be the best explanation of the many worlds theory that I’ve ever read (not a cosmologist). What’s more, Carroll doesn’t hold back that this could be wrong, and he takes the time to address other possibilities.

Continued 12/27/19

Chapter 3 felt like an introduction to quantum mechanics. Carroll provides a reader with the history of the science that lead to our current understanding. He concluded by explaining how the scientific community came to the understanding that quantum mechanics is fundamentally probabilistic despite many attempts to assign it a deterministic nature. It was a fine review, but I found myself wondering what the point of it all was until he spelled it out that they never really explored the implications. Overall, I can’t help leaving the chapter unsure what it means to be probabilistic. Ideally, that is the point; I just wish I could, as a reader, have ascertained his point without him spelling it out.

Continued 12/28/19

Carrol is an apt story teller and science communicator. He uses Chapter 4 to explore probabilities, or more specifically, the nature of uncertainty, further. It seems the most important thing to understand is that the wave and uncertainty descriptions are not a broad description that works with gaps of knowledge. The physics that governs this world is fundamentally different than the rules of classical mechanics. I’ve got a background in that area, and it makes sense to me.

Continued 12/30/19

He finishes his discussion by focusing on the nature of what it means to be a wave. It was probably the most difficult material he has covered yet but still easily understood. He gets into a conversation on spin that feels esoteric and a bit over my head. Luckily, he doesn’t leave us stranded. He uses the information to guide us in our understanding. The nature of waves is a confirmed fact. The act of measuring quite literally appears to alter the wave like nature of a “particle.” I think he explains it best but it is fascinating.

Chapter 5 is what feels like, a concise discussion of the nature of entanglement. It is a doozy. I’m here reviewing the material trying to make sense of what Carrol is saying, but I am having a tough time. It seems entanglement is when two electrons share the same spin. The trick is, their spins are in superposition, and they don’t consolidated until measured. The trick is, once one is measured then the other is guaranteed to be measured as such too. What I don’t get is how we know this isn’t a correlation; why must it be an entanglement.

If a photon is used to force particle a into a fixed spin that doesn’t change the spin of what it is entangled to, it only passes that entanglement on to the photon used to change the spin. That suggests a shared dynamical relationship not an intrinsic entanglement. I have to assume there is an independent way of identifying them as entangled.

My initial impression at the start of the chapter was that entanglement is the way the wave function of the universe (or of these two particles) is intertwined. That is more than a coincidental correlation. All that is to say, the chapter is complicated, and I hope it becomes clearer later in the book.

Part 2: Splitting

Chapter 6 was easier to read. It discusses the nature of decoherence and it’s implications on the many worlds hypothesis. I can’t say I left the chapter absolutely convinced, but it was a much more compelling story to read. Now we are getting into the nitty gritty.

Chapter 7 tackles the nature of probability and the effect on the multiverse. I think the first very compelling point was how it doesn’t feel like we live in a multi-world universe, but the same was said about the earth rotating or the earth orbiting the sun. Sometimes, our intuitive senses aren’t enough. I found this chapter immensely fascinating. The nature of probability means all that can happen does happen. Now I’ve heard that before, but I’ve always wondered what the realistic effect is on the macro scale (vs micro/atomic).

If the position or spin of an electron can be in superposition, what difference does that make on the classical physics of the world. I still don’t really know, but one fantastic point Carroll makes is how we can discuss probabilities. Say we do a random number generator our interpretation of that will vary. If we assume the RNG is quantum (which Carroll’s actually is) then a string of 16 spin directions (1/0) will produce a world where every possible line of 1’s and 0’s exists. In that world, Carroll’s use of this list in his discussion would be directly effected by unlikely results like all 1’s or weird patterns. It’s fascinating to think of the different directions his book and life would take in those scenarios. It’s debatable how big of an effect it would have, but it’s a substantial example of a direct influence of these quantum superpositions on the macro world.

Carroll finishes the chapter exploring how we might differentiate between more likely scenarios. This part highlights my biggest problems with the book which my inability to comprehend the more esoteric discussions. That said, Carroll continues to keep us grounded by walking through each piece such that I leave understanding (I think) the points he is trying to make. Unfortunately, I don’t have the time to study what he’s saying to fully appreciate every step along the way.

The fascination continues in Chapter 8 as Carroll begins to attack, head on, the question of whether the Many Worlds perspective is (1) the most logical conclusion and (2) really science. The quintessential simplicity of the theory is that anything else would have to add on or change the laws of quantum mechanics as we understand it. Basically, if you want to deny the existence of an infinite number of worlds, you have to complicate our own. As far as occurs razor is concerned, that just doesn’t work. Then as far as science, it is said that a theory must be falsifiable, and one cannot deny that the law that implies the multi-world perspective is entirely falsifiable simply by disproving the laws of quantum mechanics.

Chapter 9 is dedicated to the opposing theories that have been proposed to counter the Everett Many-Worlds interpretation. I thought it was a great overview and comparison. To be fair, we have multiple theories condensed to one chapter with 2/3 of this book to talk about Everett’s view, but I thought it Carroll did a good job defending against them. Granted, I may struggle to explain this myself without further review.

What we got in Chapter 10 is really what I’ve been waiting for all along. He talks about the implications on us. He delves into the question of free will, consciousness, and whether these quantum processes can really be assumed to extend to the choices we make. He makes a compelling case that it is unlikely that our choices are in fact quantum. That is to say, the processes that govern it are probably not probabilistic. Nevertheless, he talks about opportunities that we might introduce such randomness into our decisions. We can use quantum number generators to help make decisions to ensure multiple versions of our-self, however minor.

My thoughts while reading chapter 10

Now, I came to this revelation last month, and ever since, I’ve been striving to make decisions by it. Right now, I’ve used it to decide which books (or the order by which) I read. This may be minor, but books can have profound effects on us. I can imagine a world where I read one book and not another and it seriously effecting me. This book is a prime example of that. I may expand on this discussion in another post, but I’ll summarize with how exciting I find this all to be. The ability to actively create multiple versions of one’s self is so enthralling to me.

Part 3: Spacetime

Continued 1/28/20

In Chapter 11 Carroll begins to explore what this actually means for reality. That is, where are the other worlds, and how are they connected to us. My understanding is that these states all coexist in the quantum realm, but there is something about our entangled selves that then experience these physical laws for our specific reality given. However, the others can be thought to be there, experiencing reality slightly different. I think he did a good job explaining this. It is still very abstract but overall a good take on how this relates to the greater universe.

Continued 1/31/20

I found Chapter 12 to be a bit esoteric. He seems to be discussing the nature of quantum field theory, and, while interesting, I didn’t understand the point as it relates to the Many Worlds interpretation. I think he was trying to highlight the fundamentally difference between the way reality works in quantum mechanics than in how we perceive reality. That is to say, particles aren’t strictly what we perceive them to be. Perhaps this suggests the same may be true for Many Worlds? It may be that it has nothing to with that and Carroll is branching off into another tangential area of research.

On that note, Chapter 13, the last chapter, is all about quantum gravity. He makes sure to be very clear: this is purely hypothetical. Quantum gravity may be an intriguing idea, but it is not yet on the same level as say even the Many Worlds interpretation which at least is based on an understood scientific idea. I think it did a really good job bringing this section to close. While it is very theoretical and ongoing research, I can better appreciate how chapter 12 was building up to this idea which is essentially that space, and maybe time, is emergent. That is, the nature of entanglement of particles brings space into existence as we perceive it. As such, that might explain why we perceive our world from a different world where the quantum state is a bit different.

Epilogue and Appendix

This was pretty straightforward close to the book. I like that he read the appendix (or selected parts) on the audiobook.

From Eternity to Now by Sean Carroll ★★★★★

11/10/19 Introduction

I choose to read this while I read Time Reborn by Lee Smolin. In my review of that book, I discuss time and my thoughts around it. I was drawn to Smolin’s book because I wanted to understand the concept of the block universe more clearly. I have since learned that Smolin is on the extreme end of experts in cosmology when it comes time, and I came to Carroll for a more “conventional” point of view. I have never read a book by Carroll. Although, I do listen to his podcast, Mindscape, on occasion, and it was this that taught me how great a communicator Carroll is of complex concepts.

That all led me to reading this book, the second book in less than a week that wasn’t on my (very packed) list of books to read this week. That is why I am forcing myself to pace myself with this book. It is split into four parts, and I will stop after each part to discuss my thoughts when I have the time, all the while reading other things in the down time. It isn’t so much a review as it is a review of the topics and my attempt to articulate what I have learned. You can go to each part from the Table of Contents below.

Table of Contents

  1. Time, Experience, and the Universe
  2. Time in Einstein’s Universe
  3. Entropy and Time’s Arrow
  4. From the Kitchen to the Universe

Part 1: Time, Experience, and the Universe

Finished (11/11/19)

Carroll doesn’t spend much time defending the concept of the Block Universe. The entire reason I wanted to read this was summarized in a paragraph. The idea of a block universe versus a single framed (presentism) universe is, Carroll explained, largely accepted. Whether it is exactly true from a philosophical perspective, isn’t what is important. All that matters is that the laws of physics as we understand them are best explained by the block universe. Therefore, it is most sensible to think of it as reality. Forgive me here, and moving forward, as I may mistake what he says, but I will do my best to translate it as well as I can.

Instead, Carroll begins by discussing what time is, from a physicists perspective and the role of entropy in the flow of time. Part of me wants to reread all of this because it is so well explained. It isn’t just fascinating, it is engaging. It seems, based on one read through, that our concept of time and memory are influenced by the tendency of the universe to reach “chaos” (increased entropy). We can’t remember the future because we lack the necessary information to do it. We can create what we perceive as memories because all the possible scenarios (given the information we have, which is limited) that might have happened have condensed down into one single order of events. If we had complete information and cognitive abilities, one could predict the future, essentially remembering it, but we can’t. I find this concept particularly fascinating. It helps us try and understand why things seem to flow from one point to the next.

My fascination will likely fuel a reread because I know how I like to talk about ideas that intrigue me, and I want to do it justice. For years, I’ve held the idea of the block universe from one PBS documentary, but I always feared I misremembered it because of limited understanding. Lucky for me, Carroll makes the learning experience a joy to undertake.

Part 2: Time in Einstein’s Universe

Finished 11/13/19

Staying still in space will increase how much we move through time, but moving through space slows down our movement through time. Light cones of “experience” are all the possible directions life could extend from or to that event. If we consider a single event, we could try and identify all other points at a constant time, or a time where things happen simultaneously with that event, separating the past and future. Carroll explains that with relativity, we can identify the “light cone”, that is all the things that can effect this event, into the events past and future. However, there still exists a piece of the universe outside this events “light cone” which is to say, not a part of this events past or future. Our instinct is to identify far away events that we say happen simultaneously with this event, but this distinction is a matter of personal choice, as Carroll puts it.

I am writing this first bit as I listen to him explain it because I don’t really understand it, and this is my way of taking notes. It seems he is saying, if an event is independent of an event on earth, both now and in the past and future, we can’t correlate the two. Why then, can’t you repeat the process at the boundary of each “light cone” where you can identify simultaneous moments at different corrections of space? Then you could get a precise estimate of the now?

To answer this, I looked for a youtube video to help explain it! This really helps explain why simultaneous actions are subjective. The video begins by considering two observers, A and B. A is stationary, but B is moving. The act of moving, slows down B’s movement through time, relative to A. So while time for A acts normally (straight up), the time axis for B, again relative to A, is slower (tilted).

I think the best way to think about this is with B’s time being like the hypotenuse of a right triangle. Both A and B are moving along their line of time at the same “speed”, but from A’s perspective, the path B is taking is longer than its path (up the side instead of along the hypotenuse). Then, its perception of B is that it is making its way slower than itself.

When we think about it in regards to simultaneity, everything perpendicular to the time axis of A is what it experiences as happening “now” while everything perpendicular to B’s time axis is happening “now”. The problem is, as the video shows, that these lines of “now” do not match. Therefore, the entire idea of now is relative.

As Carroll approaches the end of this part, he begins to discuss time travel and wormholes. However, first he talks about the nature of predictions and the idea of the block universe. In regards to the philosophical debate over the block universe versus only the now existing, he says the following:

There is an interesting philosophical debate over which is the more fruitful version of reality; to a physicist, however, they are pretty much indistinguishable.

Sean Carroll

The laws of physics work like a computer, receiving an input and predicting the future or the past occurrences. In this case, knowing everything about the present means knowing everything about the past, and, by extension, everything about the future. Nevertheless, he makes an important lesson that we make assumptions that seem reasonable using our knowledge of the world, but assumptions can be wrong (if still the best assumption available).

Part 3: Entropy and Time’s Arrow

Finished 11/29/19

I nearly finished this a week ago, but Buzzwordathon came along and took up all my time. I finally got back around to it. I’ve been away from this material, so I may struggle getting back into the material. Luckily, the basic concept here is simple. Carroll suggests we observe the arrow time as a matter of entropy. As we move forward in time, entropy is known to increase. We have information about what we consider the past, but what seperates these “memories” from vague predictions of the future is an understanding that entropy was lower in the past. Of course, this idea was explained in the past. What Carroll does here is do an in depth discussion about entropy to help us understand how it works and why.

Carroll equates the arrow of time to reversibility or more specifically, conservation of information. The trick is so much of our information about the world is broad and what seems irreversible has more to do with our broad scale abilities to interpret it. Let me break this down using a similar example. Entropy, as Carroll describes it, is the tendency of particles to reach an equilibrium state. This notion of states is really a bulk measurement of some substance, say a gas. However, that same process can be tracked by using the precise mechanical information of each individual molecule of gas. In that way, the tendency of this gas towards higher entropy is reversible. Part of this is because entropy is a measurement defined by how we constrain it (energy of a gas, of the world, etc.). In fact, entropy is not entirely restricted to moving to higher states.

The reason entropy increases isn’t a fundamental nature of the world because it needs to be at a higher state. Think of a system like Earth where we have to wonder how such low entropy states could be reached (assuming you would call this low entropy). Of course, that is all explained by energy being inputed to fuel localized increases, further highlighting the nature of how we define our system. The fact is, however, that even though these lower states of entropy exist and are attainable, there are simply a lot less of them. Particles can be thought to change to different levels of entropy randomly, and because there are so many more states of high entropy than low, the system as a whole will tend towards higher entropy.

This concept begot a very interesting (in my opinion) concept by Bohr. Essentially, if we break entropy down to a matter of probability, we might wonder if the low entropy state of the universe was in fact a part of a larger universe that has experienced a brief, random, drop in entropy. What we experience as the observable universe can be thought as what has happened since that drop. It is very unlikely, but given an infinite amount of time, these impossibilities will happen. It raises the question of what time would be like, say during the period of decrease in entropy. Carroll proposes it would seem the same because time isn’t a consequence of the increase in entropy but rather that there is a distinctly different level of entropy in one direction. In the end, Carroll dismisses this idea because it has other problems. Basically, even though our universe is possible, it is apparently more likely that localized drops in entropy would produce intelligent disembodied brains floating in space far more frequently than the series of events that were necessary to lead to us. Assuming we are representative for the average life form in the universe, we can’t accept this idea. There is a lot of unpack here, and I am not doing it justice. Nevertheless it was fascinating.

Carroll then goes on to discuss cause and effect, and I think it is best conveyed with a couple quotes:

Ultimately, our ability to “choose” how to act in the future is a reflection of our ignorance concerning the specific microstate of the universe; if Laplac’es Demon were around, he would know exactly how we are going to act…

We have no trouble believing in a past condition that restricts our current microstate. The microscopic laws of physics draw no distinction between past and future, and the idea that one event “causes” another or that we can “choose” different actions in the future in a way that we can’t in the past is nowhere to be found therein.

Sean Carroll, From Eternity to Here, Page 185

This really relates to the idea of entropy and the state of every particle involved. We have enough information about the “particles” that relate to the past to recognize what lead to what. However, we don’t have the necessary information to constrain what leads to what in the future. We can track certain paths, and even make broad scale predictions, but it is flawed because it is not a complete estimation. Leplace’s demon is a hypothetical observer with complete knowledge.

Personally, I am very much determinist, and this really highlights why. We can look back and see how a causes b, and how said outcomes are out of our control. Why then is it so taboo to suggest c will cause d, thereby constraining what we can and cannot do.

This is where Carroll pivots to consider quantum mechanics. If we suggest reversibility is a question of information, quantum mechanics directly challenges that. I don’t want to get into the finer details, largely because it is hard to understand even if I thought I could convey the meaning. Just rest assure Carroll takes the time to introduce the reader to this concept. Essentially, observing particles creates a random event. Granted, there are equations to constrain how they act (i.e. deterministic), but they are still random. Does quantum mechanics introduce a fundamental arrow of time into the laws of physics? Carroll suggests no. Avoiding the details, he breaks it down to this:

We’re…coarsegraining, just as we did in (classical) statistical mechanics to define macrostates corresponding to various microstates. The information about our entanglement with the messy external environment is analogous to the information about the…molecule(s) in box of gas.

Carroll, From Time to Eternity, page 255

The way I take this to mean is we are looking at a localized region without understanding the finer interactions between it, the outside world, and ourselves. Admittedly, I don’t entirely grasp this idea. It seems that with more information we could better understand how we lead to the collapse of a wave into a precise location. All that was to end with the same basic concept that the laws are reversible on a microscopic scale, and the irreversibility comes from broad scale attempts to constrain it.

Part 4: From the Kitchen to the Multiverse

Finished 11/29/19

Up until now, I’ve tried to provide an in depth (if scattered) overview of each part of this book. My goal has been to understand the material well enough to articulate it. Unfortunately, I am running short on time and energy, so this will be more succinct. Here Carroll digs into cosmological concepts like the big bang and the loss of information with black holes or inflation and dark matter. He tries to answer the question of why the universe started with low entropy because it is the fundamental reason for our perception of time, as he sees it. He spends a great deal of time, here and in past sections, providing the reader with fundamentals, and it is hard not to lose focus. He is walking us through the appropriate science to understand his conclusion, but all the while I’m trying to jump ahead and see what his point is. I advise future readers (possibly myself, of at least this last part) to focus on the details at hand.

I am leaving this last section with a lesser understanding because of my inability to read through this multiple times and take notes as I go. A lot of it goes back to previously discussed topics. It isn’t enough to say the universe is the way it is because it is. We seemingly have an early universe that defies the laws of physics as we now know them. Therefore, he tries to tackle this problem from a number of different approaches. I think that is representative of this book as a whole which has a fairly clear take away but plenty of alternatives to consider. The answer may be a multiverse that produces a number of different beginnings, or perhaps its baby universes that spring up from a higher entropy universe. It might be an a result of inflation.

In his epilogue, he takes time to discuss how he approached the book, but he also takes time to discuss the nature of science and physics like this that is on the edge. Its okay for science to make fart fetched predictions (like a multiverse, which he explains isn’t a theory unto itself), but it must be a part of a larger testable theory. Sometimes, those tests take time to develop. Other times, they fade away. In either case, the process is what is exciting, the act of testing and learning more and more about the nature of time.

Overall, this book was fascinating. It is dense, but part of that comes from the ample review that Carroll so helpfully provides. All of it is accompanied by clear conclusions of his points that should make it easier for the average reader to understand. 4.5/5 stars.

Time Reborn by Lee Smolin ★★★☆☆

Introduction 11/7/19: My thoughts on Time and Space

Roughly 7 or 8 years ago, I began to explore popular books in cosmology. I read Brian Greene’s new novel the Hidden Reality about the notion of multiverses. Fresh out of high school, I left the book with some serious issues about the significance of our lives, but once I got past it, I was inspired to explore the idea of reality and the cosmos further. I bought a Fabric of the Cosmos and the Elegant Universe by Greene. I never got around to reading either of these (yet!), but I watched the adaptation of the Fabric of the Cosmos on PBS.

The idea of time dilatation fundamentally changed my perception of reality. However, it was how he discussed the idea of the past and future that really resonated with me. The idea, as I understood it, was that the past, present and future all exist simultaneously within the confines of Space-Time, where time is an extra dimension.

Think of it like points on a line. The start and finish of the line both exist in space. If I have my finger on the start and then move it to the end of the line, the start doesn’t cease to exist; every point on the line exists simultaneously. Now replace that line with the timeline of your life. You are at some point between the start and finish, and if time is another dimension like space, the start and finish of that line still exist within the universe. Greene gives a good overview of this idea here, in this clip from the PBS adaption of his novel.

A clip from PBS’s the Fabric of the Cosmos about the nature time

I now understand this idea is called the Block Universe or Eternalism. Essentially, all points in time exist simultaneously. I have been thinking about this more of late, and I have wondered if I misunderstood Greene. Rewatching this video, I see this is exactly what he is saying.

What I want to know is why do we assume a block universe? How much of this idea is based in science vs philosphy/metaphysics? I want to understand what the alternative is and why the block universe is either necessary or at least the best hypothesis? I now appreciate how these types of hypotheses are always incomplete. Does the future exist? If this was true, does this disregard the notion of a big rip or pinch (the end of the universe), or can we think of time like space, stretching outward where the past exists as we exist but the future is in the process of being created? I think the latter is my preferred way of thinking.

Unfortunately, I have not earned that conclusion. That is why I’ve decided to try and pursue this further. In Time Reborn, Smolin presents the common arguments for the past and present existing as Greene suggests, and then he claims to use the scientific method to prove it wrong. His goal: demonstrate the past does not exist and neither does the future. There is only the now.

Now, I am reading this because I want to learn, but it’s also a casual read fueled by my fascination of the subject. This is still for fun, not an academic pursuit. Therefore, this isn’t exactly an analysis of his argument. What I hope to do is discuss my thoughts on his arguments, summarizing where possible. I may get things wrong, but in the end, I hope I still leave with a better idea of the subject matter than when I went in.

Update 11/8/19 (42% progress)

I just reached the second part of this work where he moves from explaining the block universe to try and disprove it. I am loving the conversation. I would attribute that more to my interest in the topic than his writing, but that is fine too. The way he is describing relativity is very reference focused. It seems to be suggesting that just because our perceptions of time are altered that does not mean time itself is. To be clear, he has not explicitly said this. Rather, it is something I am wondering. For example, we can look at star in the sky and recognize the light we see was from years ago; it takes time to reach us. That doesn’t mean at this moment the star isn’t outputting new light. Nor does it mean the past is still there. Rather, the past version of the star has only had a delayed effect.

What I am curious about is whether the perceptions Greene highlights in the video above is a matter of perception or is the causality of the two moments linked. Sure, the past can effect the future, but can that alien in the future effect past versions of earth? If not, is it really right to say the past earth exist in some realm of space time. I suspect I am not seeing the full picture, but it is still important to recognize the limits of what we can know and suspect. If a universe where all versions of time exist is indistinguishable from one where it doesn’t exist, is it worth believing? I think that is essentially Occam’s razor, where the simplest answer is usually the best one.

However, it seems as though Somlin is setting up to make an argument of the laws of the universe evolving rather than staying the same. In which case, we can apply the same logic of the simplest answer being the best one. We have yet to see the laws of the universe change, so is it really appropriate to assume they are? I can’t say for sure if I am interpreting this correctly. Although, I am enjoying it immensely.

I did a bit of digging to find other discussions of Somlin’s argument and came across one scientist’s response which I found worth mentioning.

Smolin’s treatment of this topic is, unfortunately, typical: His book does a poor job of distinguishing established results, speculative ideas, and personal opinions.

Steven Carlip, Physics Today 66, 9, 48 (2013);

I think this highlights the issue at large (and many on the edge of science). We need to recognize the firm from the speculative and everything in between. Carlip is actually hesitant to recommend this to the lay reader because it is difficult to distinguish between speculation and actual results. I am no cosmologist, but hopefully I can at least recognize opinion over fact. The problem is my knowledge of the facts is tenuous. Carlip also recommended another book as a better resource: From Eternity to Here: The Quest for the Ultimate Theory of Time by Sean Carroll. I am more familiar with Carroll. He has a great podcast, Mindscape, that invites experts to discuss topics in science, and I find it really easy to follow and very engaging. I’d also like a take on the conventional way of thinking about the topic as opposed to Smolin’s more controversial view.

Finished 11/9/19

It seems Smolin is equating the randomness of quantum mechanics to a possible evolution of the laws of physics. Granted, he doesn’t just say that; he goes in depth to try and demonstrate this. However, it all comes across as stating a bunch of supposed facts then tacking on therefore time exists. It’s probably fair to say that at least part of this is my own inability to understand some of what he is saying. Nevertheless, it still feels like he is reaching into the realm of the unknown to find something to fit to his desired result. He talks about quantum mechanics being inconsistent with relativity, and the difference between relativity of space and time. Unfortunately, it’s hard to connect the dots in any meaningful way.

I am content leaving this book somewhat confused. It is Smolin’s responsibility to adequately translate this to the lay reader. He succeeds in many ways. I think this book has left me with a better sense of the two sides; what he has not done is convince me his radical view is a reasonable one. Science will have unanswered questions. However, that is not justification for a complete overhaul of our perception of reality. Given my lack of expertise, I still want to hear from people more adapt in this field. I mentioned one reviewer earlier, but I have come across one by Sean Carroll as well.

I am not trying to sell Carroll as a better expert than Smolin, but if we are going to discuss such a radical belief we need an unbiased rundown of the problems with the new hypothesis Smolin presents. As Carlip is quoted as saying above, Smolin doesn’t do an sufficient job highlighting where his “facts” being to blur into opinions. He works so hard to prove himself right, but he fails to be critical of his own work.

Extraordinary claims require extraordinary evidence.

Carl Sagan, paraphrasing Laplace’s principle

His hypothesis are “consistent” as he describes it. The lack of experimental demonstration that he critiques his opposition to (such as in string theory) is not really mentioned until the very end of the book. Where science meets philosophy is similarly muddled.

Smolin seems quite content to draw sweeping conclusions from essentially philosophical arguments, which is not how science traditionally works. There are no necessary hypotheses; there are only those that work, and those that fail.

Sean Carroll, on his blog

While my own understanding of the material is limited, I must follow the consensus of the general scientific community. Of course science can be wrong; that doesn’t mean it isn’t the closest to the truth most of the time. As I said earlier, I think this book has given me a good idea of what that is, but it still leaves me wanting to learn more about the traditional way of thinking. I intend to read Carroll’s book mentioned above on time, but for now I’ll mention the brief overview he gives on his blog.

Image featured in Carroll’s blog post on “The Reality of Time

Carroll suggests Smolin is working on a problem we’ve already solved. He suggests everything we know is consistent with the block/eternalism view of the universe, and it doesn’t put the “now” into a special position as we see in Possibilism. This is a good representation of my understanding of this topic. My confusion comes from Carroll suggesting Smolin is pushing the idea of Possibilism when I took it that he was pushing Presentism. Smolin explicitly says, he is asserting the past and future do not exist, only the now. Now I am wondering if my entire perceived understanding of the book is wrong or if it is Carroll who misrepresented Smolin’s position. That just suggest I need a better explanation on the three realms of thought. Hopefully his book will offer that. I also bought Smolin’s follow up this novel (The Singular Universe and the Reality of Time), but I am not sure if I want to read it anymore.

In any case, it is a fascinating read that, if read, likely will need additional readings. I enjoyed the book, but I left it confused in places and dissatisfied. 3.25/5 stars.