From Eternity to Here: The Quest for the Ultimate Theory of Time by Sean Carroll

Jan 12, 2013 Manny rated it 4 of 5 stars Recommends it for: People interested in the nature of time

Shelves: science, science-fiction, linguistics-and-philosophy

FREE From Eternity to Here COMPATIBILITY TEST

Read through the following dialogue between two people, A and B. Underline all the sentences which you can imagine saying yourself.
____________________________________________

A: What are you thinking?

B: Have you ever wondered why the future is different from the past?

A: What do you mean, different?

B: Well, you can remember the past, but you can't remember the future. Why?

A: Like deja vu?

B: No, not deja vu. Really remembering the future.

A: But the futu...more

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Nov 24, 2011 Tony Heyl rated it 5 of 5 stars

Time is both a simple and yet complicated scientific question. I looked up books about time after seeing one of the Through the Wormhole shows on Science Channel. This is actually a really well put together book. Most of the book is about entropy and the evolution of the universe, so it makes sense that the content itself goes from the very simple to the very complicated, bring you along the way without making you feel like an idiot. The equations and explanations are also done in a way to reall...more

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Nov 18, 2011 David rated it 5 of 5 stars

Shelves: physics

This is a very well-written, and entertaining book on our understanding of the arrow of time. Entropy is a key concept, which deserves (and gets) lots of attention. The second law of thermodynamics states that, in a closed system, entropy can either stay the same or increase--it cannot decrease. Sean Carroll shows why the reversibility of physics at the particle level gives rise to a seeming paradox; if the physics of particles is just as correct with time switched backwards, why can't entropy d...more

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May 30, 2011 Bob Nichols rated it 4 of 5 stars

If I am tracking his argument accurately, Carroll is saying in this book that change, as time, is eternal.

The so-called arrow of time flows one way as energy dissipates from low entropy to high entropy states. The problem in physics that Carroll needs to address is the big bang theory which states that time (space-time) begins with the initial 'bang' and is expanding space-time outward (i.e., not moving into pre-existent space-time; "the universe expands into nothing"). At this point, the curren...more If I am tracking his argument accurately, Carroll is saying in this book that change, as time, is eternal.

The so-called arrow of time flows one way as energy dissipates from low entropy to high entropy states. The problem in physics that Carroll needs to address is the big bang theory which states that time (space-time) begins with the initial 'bang' and is expanding space-time outward (i.e., not moving into pre-existent space-time; "the universe expands into nothing"). At this point, the current theory suggests three scenarios. In one, expansion continues without end. In a second, expansion continues until energy is fully dissipated and a heat death is reached. The third scenario is that the universe is pulled back to it's starting center by the collective force of gravity ('big crunch').

Regarding the thermal equilibrium and heat death scenario, Carrol writes that as there can never be a complete absence of heat, there is a perpetual movement toward entropy (Whether and how this relates to the first law - the conservation of energy - he doesn't say as I recall). He also states that there will always be clumps of matter that re-form over vast scales of time. These become centers of gravity that, in turn, form new planets, stars, galaxies, and clusters of galaxies. This leaves the first scenario, perpetual expansion (which, appropriating Einstein, he calls the "cosmological constant"), as the only one that is consistent with the state of the evidence.

The 'dark horse' for Carroll is the role of dark energy which, he argues, moves the 'arrow of time' from a low entropy (high energy) to high entropy (low energy) state that began with the big bang. Dark energy is responsible for the continued, and accelerated, expansion (like an expanding balloon) of our universe as energy dissipates along the low to high entropy gradient. Given the unevenness of the expansion ("fluctuation"), matter collects and forms mass, and gravity continues to do its job of creating "pocket universes" of which we, in our corner, are one. These, collectively, constitute a "multi-verse" situation where universes somehow (wormholes?) connect to each other and where each go through continuous cycles of collapse and expansion.

Whether this is close to an accurate summary of Carroll, I can't say. Carroll opens one of his chapters with a quote that states that, compared to cosmology, metaphysics is "pedestrian and unimaginative." That characterization seems true with this book and where Carroll takes his reader. In a way, what Carroll presents is an inspirational and even beautiful theory. We, however small, are privileged to be part of this infinitely vast cosmos and to have the capacity to wonder what it is all about.

On the book cover, Brian Green is quoted as saying Carroll's book is "delightful," but that doesn't seem to be the right word. What Carroll is writing about is hard-to-grasp, heady stuff. Depending on the intended audience, the book may have benefited from leaving out more of the mental experiments and focusing on the big picture instead.

Carroll maintains that his book is about time but in a way, this seems to be not really the most interesting part of this book. In the concept of entropy, the universe as we know it moves from states of disequilibrium to (relative) equilibrium, and then back to states of disequilibrium as dark energy recollects itself as matter. Where Carroll sees this as the driving of time one way, a 'power' gradient can be also seen to lie at the heart of the cosmos as it moves from disequilibrium (concentrated energy or power) to equilibrium states (dissipated energy where there is no power). It's interesting to speculate on the parallels with life processes, where disequilibrium as 'survival need' creates action that results in the re-establishment of equilibrium (satisfaction of need), and the operation of human societies where we, as organic matter, seem to operate by this cyclic tension created by relative power differentials.

The way Carroll uses the term entropy is confusing. He consistently refers to high and low entropy and when this is deciphered more, low energy means order, and order means disequilibrium; high entropy means disorder and equilibrium. As one tends to see equilibrium as order and disequilibrium as disorder, and as it's confusing to understand "high entropy/low energy, and low entropy/high energy," the lay reader has to fight his or her way through this hurdle (constant mental gymnastics) throughout the book. Elsewhere, he references an "increase in entropy" and says such things as "Black Holes have entropy," leaving the reader to wonder what happened to "high and low," and wondering if entropy is a static concept rather than a high-to-low energy gradient and process.

It is also not clear what is meant by "order" in entropy. "Order," Carroll writes, involves "a purposeful arrangement of matter" and it is this movement from order to disorder that drives the arrow of time. While we can readily understand life as some form of purposeful arrangement of matter (i.e., a system of parts that works together), understanding a black hole or a big bang situation as 'order' seems to involve, 'simply,' gravitational pull of matter onto itself. If this is true, it becomes harder to understand order here as "a purposeful arrangement" of matter unless, perhaps, it could ever be understood what it is about gravity that enables it to pull matter into itself.
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Jun 28, 2010 Terry rated it 4 of 5 stars

Overview: From Eternity to Here is a survey of the thinking and research into a simple question "why is there an arrow of time?". The simple answer is "because the past has low entropy and the future has high entropy", done. Sean Carroll asks the simple question of "why does the past have low entropy?" and spends the book explain what science, both good and bad, points us to an answer. He discusses the idea of temporal chauvinism that our timeline shouldn't be privileged and that, entropy as an...more Overview: From Eternity to Here is a survey of the thinking and research into a simple question "why is there an arrow of time?". The simple answer is "because the past has low entropy and the future has high entropy", done. Sean Carroll asks the simple question of "why does the past have low entropy?" and spends the book explain what science, both good and bad, points us to an answer. He discusses the idea of temporal chauvinism that our timeline shouldn't be privileged and that, entropy as an explanation, while powerful, has big implications into how we experience a notion of time.

Writing: While I enjoy books on Cosmology and "big physics" most are a fight with the author to figure out what they assume the reader knows. Lawrence Krauss runs into this problem and even Richard Feynmann makes the assumption that once something is explained, however elegantly, it'll never need to be revisited. Sean Carroll makes no such assumption and has a rare gift for issuing timely reminders on what he's talking about. Despite having just read some blob of text on de Sitter space, his next chapter includes a one-liner of "remember de Sitter space has a positive vacuum energy and anti de Sitter space has a negative vacuum energy". Another polite tactic is how he reminds the reader of differences between how experts and laypeople define terms. This popped up when talking about multiverse in the sci-fi sense of realities somehow separated by another dimension and multiverse in the sense of a patch of spacetime that moves together meaning stuff outside of that area will never and can never effect something inside of it.

Organization: Leonard Susskind writes such that he states his theory at the beginning and spends the rest of the book explaining it. Instead, Sean Carroll spends the first 15 chapters explaining the problems that face modern cosmology, one chapter explaining how he answers those problems, and a final one admitting his idea's shortcomings as well as suggesting the leg work required to prove his idea. Normally, the term "humble" applied to a big brain means "quiet arrogance" but not in this case. I think Carroll's genuinely of the opinion that his model is a contender and seems very excited to tell you about it.

Flow: There were a few cases where I had to page back once or twice to remember the idea of the current chapter but the pacing was acceptable except when he dove into the history of statistical mechanics which was 20 pages too long for my taste. This may be because I consider Boltzmann a personal hero but his discussion of boltzmann-lucretius space borders on droning. The first few chapters move slowly but I think this is of necessity; we're simply not used to thinking about time in a strongly analytical manner.

Rating: My five star usually means "I'd recommend it to everyone" which I'd love to grant the book but while being inviting to even the non-enthusiast, without a glossary, better organized footnotes, and a few more reminders, I think people who've not at least been exposed to some big ideas in Cosmology would find the book 400 pages of drivel. Otherwise, it's awesome.(less)

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May 14, 2010 Daniel R. rated it 2 of 5 stars

This book is a through and frequently tedious exploration for a theory of time. Pay close attention to the word "Quest" in the subtitle. This books poses many questions that don't have answers yet and instead focuses on the various theories that currently exist. The book starts with an introduction to possible definitions of what time is, the role of entropy, and the Second Law of Thermodynamics. With that foundation it dives into microscopic constituents, macroscopic systems, and quantum mechan...more

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Feb 21, 2010 Srinivas marked it as to-read

Through John Walker.
So far, I have never completely understood what's all the fuss about the arrow of time is. Well, there is the second law of thermodynamics, and there is entropy and it keeps increasing; seems pretty reasonable given the Universe that we are in. Do we even need to bring in the arrow of time here to explain things? I have no idea as of now.

Mr. Walker finds another 'evidence' in support of his favorite 'we live in a simulation' explanation of the Universe; Given the initial cond...more Through John Walker.
So far, I have never completely understood what's all the fuss about the arrow of time is. Well, there is the second law of thermodynamics, and there is entropy and it keeps increasing; seems pretty reasonable given the Universe that we are in. Do we even need to bring in the arrow of time here to explain things? I have no idea as of now.

Mr. Walker finds another 'evidence' in support of his favorite 'we live in a simulation' explanation of the Universe; Given the initial conditions that existed immediately after the Big bag, apparently the entropy was inexplicably very low. Of course, if the multiverse model is invoked, it's not only plausible but inevitable that one of the Universes would start with a very low entropy. And for sure we would find ourselves scratching our heads in one such universe. But Mr. Walker thinks that 'Ockham's razor' would favor simulation model as an explanation rather than the complicated, seemingly unreasonable multiverse model.

AFAIUI, Hindu philosophy treats life as we experience it as a simulation à la Matrix. Only the soul is real and has true existence. Not that I take any of these things seriously, the idea of the universe as a simulation is very familiar to me from a long time. I came across this proposal several times. There was an HN thread that discussed different possible ways of setting up such a simulation without using humongous resources. I have even considered some possible ways of testing this hypothesis by trying to break down particular components of the 'simulation'. AFAIK, Mr. Walker is the first one to present some not very unreasonable evidence in favor of the simulation model. Not compelling enough to make history though. He always keeps cribbing about scientists turning their backs on the simulation model. IMO, while it is possible that we might be living in a simulation, it's not a solution to the ultimate puzzle of the Universe. If we are indeed in a simulation, the immediate question would be "who had set this simulation up?". What is the universe that being is inhabiting like? how did that come into existence? The very first time I grappled with the origin question in my childhood, I gave up and concluded in despair that we may never get a completely satisfying answer. Because it more or less gets into an infinite recursion without any possible termination in sight; If we find an answer to the how/why question, the answer itself can be subjected to how and why ad infinitum. How did the universe come to existence? Big bang; how did the Big Bang happen? due to quantum fluctuations; how did they happen? .....
Of late, I have new found hope that some day we might even be able to find an ultimate answer to the this riddle; what made me think of this possibility is not the amazing progress mankind has made in understanding the universe; I'm still convinced that the recursion can't be broken by anyone however intelligent he may be, at the current level of human consciousness and the rationality that is afforded by it. I think it's conceivable that evolution is running its course and our brains may acquire a completely new level of 'intelligence' that might be able to see things in such ways that we can't possibly imagine now. Can a monkey even comprehend what it's to have the consciousness that humans have, let alone theorize about it?. The development of our brains to their current status led us to this amazing understanding we have about the universe. That is a huge leap compared to our immediate ancestors on the tree of life. What would another such leap do to our brains?

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Mar 29, 2013 Laura Cowan rated it 4 of 5 stars

Wow, what a big book! Covers everything from the nature of entropy to the possibilities and challenges of creating time loops, the implications about the structure of the universe that are encoded in the fact that time seems to only flow one way, and all the theories in between. Written for the layperson, so I got a lot out of it, but plan to set aside a hefty chunk of time to read this. Unfortunately I got my one and only aha moment for the purposes of my research for my next novel from the fir...more

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Aug 01, 2010 Todd Martin rated it 2 of 5 stars

Shelves: environment-science

Science and journalism are two very different disciplines and require a different set of skill sets. Those with skill in one area may or may not have talent in the other. I’m not sure about Sean Carroll’s skills as a scientist, but I have little praise for his talents as a writer.

Carroll seems incapable of explaining things clearly. He attempts to illustrate points throughout the book with convoluted examples that appear to be intended to confuse rather than illuminate. He even manages to make v...more

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May 25, 2011 Kathryn rated it 5 of 5 stars

Shelves: 2011

This wonderful non-fiction book is full of physics information, but it is designed for people who are non physicists, or anything near scientific. In everyday language (which only occasionally goes above one’s head), the author delves into the question as to why, if classical physics processes are reversible, one can break an egg and scramble it, but one can’t unscramble an egg and turn it back into an unbroken egg. (The footnotes are well worth keeping track of in this book as well; they are ch...more

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Aug 06, 2012 Joe rated it 4 of 5 stars

When I review non-fiction books, I have two basic criteria: 1) is it factual and 2) is it written well?

From Eternity to Here is a well-written book about the theory of time and a skull crusher for non-scientists such as myself. Is it factual? I guess so .. maybe? There are so many competing theories of the Universe that I don't think I could make a solid judgment either way.

Since Carroll takes great pains to point out the conjectural and unproven nature of many of the theories in the book, I tru...more

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Dec 09, 2011 Gregg Sapp rated it 3 of 5 stars

There's a certain circuitous audacity to any scientific conjecture that posits the possible existence of baby universes birthing out of quantum fluctuations in eternal empty space, going through their own inflationary Big Bangs, then proceeding to spawn black holes and galaxies and possibly infinite, life-bearing planets, where finite minds like mine can wonder what's the whole point, anyway. Carroll demonstrates that the passage of time is due to the second law of thermodynamics, which states t...more

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Feb 22, 2013 Roy Klein rated it 5 of 5 stars · review of another edition

The best book covering modern physics and cosmology that I've read to date.

If questions like "what is entropy and how do we know it's always increasing" or "how did scientists come to the idea of a multiverse" interest you, braving through this book will answer these and more questions wholly, with zero math requirements.

Towards the end of my reading the book, I happened upon an article titled "Universe Has Finite Lifespan, Higgs Boson Calculations Suggest". While reading the article, the crucia...more The best book covering modern physics and cosmology that I've read to date.

If questions like "what is entropy and how do we know it's always increasing" or "how did scientists come to the idea of a multiverse" interest you, braving through this book will answer these and more questions wholly, with zero math requirements.

Towards the end of my reading the book, I happened upon an article titled "Universe Has Finite Lifespan, Higgs Boson Calculations Suggest". While reading the article, the crucial concepts mentioned were familiar to me from the book, and I understood what they were talking about and where these ideas come from. It was both a personal triumph and a seal of approval for the quality of the book. I did not waste my time reading this.

The book takes a tour through modern theories and speculations by starting with a few fundamental questions "what is time and why is it moving forward" and "why did the universe start in a very low entropy configuration". Hunting the answers for these questions is the purpose of the book, and the author makes sure you're not lost in increasingly complex explanations along the way.

It's not an easy read, though, even if it does present super complex subjects in laymen's terms. I bought this book for a two-week vacation, and even though I read all the time, it took me 4 more days of reading after the vacation to finish it. The content requires a fair amount of concentration without stop, and the book is rather long.

I did have a few gripes while reading.
The author explains that the universe had a very low entropy configuration in the big bang, but from his description of entropy, it seemed like it actually had high entropy. I was plagued with this question early on and got the answer only about 75% into the book.

The author keeps implying that the next paragraph or chapter will have an answer to the questions that he asks, but they never come. Only towards the end of the book did I feel that I wasn't being made to follow along with a promise that I could never reach.

Finally, expect some lame humor. Most of the times these are charming, geeky jokes that aren't funny but you appreciate the author's trying, but a few of them were flat out annoying. For example, the author says that a "loaf of raisin bread rising in the oven, with each galaxy represented by one of the raisins, is a terrible analogy of the universe". Why? Because: Raisin bread has an edge, it's inside an oven and it smells yummy, unlike the universe.

I nearly stopped reading the book after this, as it came early on in the book and I was worried most of the book would be like this (it's not). It tells me NOTHING about why the analogy is bad. Everything other than the universe has an edge, so every analogy will fail at that, and the two others are obviously ridiculous. I still don't know whether it really is a terrible analogy or not, because the author had to crack another one.

If you know to expect this kind of humor when reading the book, I'm sure it'd irritate you much less than it did me.
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Sep 05, 2010 Jan Strnad rated it 2 of 5 stars · review of another edition

Mainly what I learned from From Eternity to Here is that I will probably never understand Einstein's theory of general relativity or the concept of spacetime or much of anything at all about quantum mechanics.

Sean Carroll does an admirable job of writing about space, time, the universe and everything in a style that is clear and lively. Unfortunately, I still couldn't get my mind around the concepts and claim that they brought me any real understanding.

I learned tidbits such as the fact that GPS...more

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Apr 20, 2011 Devon rated it 2 of 5 stars

In sum: Carroll is concerned that the probability of our observable universe existing is close to nil given our current understanding of physics, which might imply that our understanding is wrong. He is also concerned that the second law of thermodynamics (that entropy always increases) is not time-symmetric, as many people believe the fundamental laws of physics should be.

Carroll brings up and shoots down a number of possible explanations. He moves quickly, making cavalier approximations and dr...more

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Sep 01, 2010 Steve Clason rated it 4 of 5 stars

Shelves: science

Something about the tone of the first few chapters put me off at first and it took me a long time to get back to this book. Once I did get back to it, though, I read it through quickly and eagerly. Carroll's lighthearted and "geekish" style (which may have been what put me off at first) makes pleasant reading of his voluminous background information so that a casual, non-physicist, reader can get up to some kind of speed, at least, on recent (and not-so-recent) developments in cosmology that per...more

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Feb 10, 2013 Paul McNeil rated it 4 of 5 stars

Shelves: nonfiction

Time is really weird. I mean, it just keeps going and going, but we can experience it in such varied ways. Our subjective experience of the next hour can range from complete absence of awareness (hopefully due to sleep sleep) to a seemingly eternal and detail-rich stressfest, but no matter what does or does not happen in that hour, you can't get it back. The arrow of time, unlike most things in the universe, only goes in one irreversible direction. To use a common example, once you melt an ice c...more Time is really weird. I mean, it just keeps going and going, but we can experience it in such varied ways. Our subjective experience of the next hour can range from complete absence of awareness (hopefully due to sleep sleep) to a seemingly eternal and detail-rich stressfest, but no matter what does or does not happen in that hour, you can't get it back. The arrow of time, unlike most things in the universe, only goes in one irreversible direction. To use a common example, once you melt an ice cube in water, you can't reverse the process in any real-world way.

That common example, however, isn't generally used for time- it's used for entropy. The ice cube melts, disorder increases, and you can't go back. The main argument of Sean Carroll's From Eternity to Here: The Quest for the Ultimate Theory of Time is based on that connection- time and entropy move in the same direction (in our universe at least). Carroll begins with a discussion of time and entropy, but as he pieces his argument together, the story is ultimately about the life and ultimate end of the universe itself. He makes this transition rather naturally, and before you know it you've made the leap from definitions of time to a discussion of melting ice cubes and frying eggs, entropy and information theory, black holes, and far-reaching implications of the multiverse. I didn't expect this much cosmology going in, but the way Carroll explains it, I realize it couldn't have been any other way. He also manages to throw in just enough humor to keep things from getting too fry, but make no mistake, this book isn't a breeze to read. But if you're the kind of person who thinks time is weird and fascinating, like me, you'll find the whole experience illuminating.

After reading it, I'm not really any more sure what time is than before, but I can better see how it ties in with the fabric of space, and I have a much deeper understanding of entropy and things like black holes. I majored in biology, so my understanding of physics isn't anything to brag about, but I found I could follow his arguments, and that they seem to add up to a plausible view of entropy, and how it ties in with life, the universe and anything.(less)

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Dec 08, 2012 Bennett Coles rated it 3 of 5 stars · review of another edition

This is a big book that covers a lot of subject matter. It's looking for an ultimate theory of time and it makes big promises at the beginning, but despite hundreds of pages of very detailed explorations of entropy, relativity, quantum mechanics and cosmology, it ultimately falls flat when the author admits that we really don't know enough to answer with certainty the questions of time. This was disappointing mainly because Carroll states rather brazenly at the beginning of the book that all our...more

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Aug 11, 2012 Dan rated it 5 of 5 stars · review of another edition

Hands down the best cosmology book I've read. The book contains very clear summaries of general relativity and quantum physics, but the real agenda here is entropy. I've been able to identify and answer entropic questions in everyday experience while reading this book, and his discussion of both Boltzmann Brains and the information-based solution to Maxwell's Demon thoroughly cleared away the fuzziness in my understanding of those concepts (for now, at least). Carroll is also refreshingly transp...more

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Jan 03, 2013 Mark Schnitzius rated it 4 of 5 stars

Finally made it through, after two renewals from the library... Mostly that's because I'm a slow reader, but also in part due to the challenging subject matter. This is the first cosmology popularization I've read since A Brief History Of Time, and this one I'd have to say is a fair bit more ambitious at least in terms of the amount of content it attempts to convey. Simply put, there was a lot to take in, and I feel like I'm still reeling a bit from it. Modern cosmology is just... freaking weird...more Finally made it through, after two renewals from the library... Mostly that's because I'm a slow reader, but also in part due to the challenging subject matter. This is the first cosmology popularization I've read since A Brief History Of Time, and this one I'd have to say is a fair bit more ambitious at least in terms of the amount of content it attempts to convey. Simply put, there was a lot to take in, and I feel like I'm still reeling a bit from it. Modern cosmology is just... freaking weird, and whatever dilettante physics knowledge I already had didn't really provide a good framework to hang all this new stuff. So my takeaway from this book was probably not all it could have been.

No fault to the author on that; I appreciated the new perspective. I think perhaps that is my takeaway -- not so much what modern cosmologists are thinking, but *how* they are thinking about it, from an entropy-based perspective. Carroll was good about labelling various models as supported by the evidence versus conjecture. Epistemologically, I think some readers may come away doubting a fair bit due to the fact that so much is conjectural, as well as there not being sufficient space for him to lay out the evidence and supporting equations. But with cosmology such a vibrant field, I'm sure there are enough checks and balances in place to assure us that the models espoused in this book are at least on the right track. Which is interesting because it looks like things are only going to get a whole lot weirder. (For example, the non-locality implied by the holographic principle? It's hard to even imagine a final theory of quantum gravity that will account for that.)

The writing style, I will say, never particularly sparkles, but doesn't ever distract. They say good science writing makes the reader feel like a genius; I have to disagree, because I think this was pretty damn good science writing, and it made me feel largely stupid. It's the nature of the subject matter though, and I appreciate Carroll's attempt to educate me about it.(less)

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Dec 27, 2012 Joseph rated it 4 of 5 stars

This book was good, but very dense. I don't think I would have appreciated it without having a pretty hefty background of popular physics book. That said, it was nice to read a book that took a deep dive into topics that usually get glossed over in popular science books. In particular, I learned a lot about both inflation theory and the holographic principle, which were really interesting. I especially appreciated the discussion of the holographic principle, because it seems (after reading the d...more

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May 15, 2012 James rated it 4 of 5 stars

Book is off to a great start. Update: Wow, felt like a cosmology level 400 classroom at times, but very interesting topics on time, space time and the inability to travel backwards in time.

Finished the book in April. Later went bike riding with my 9 yr old. She proceeded to ask what is time travel, how can we go back in time, what are black holes, what are worm holes and a couple other things I was amazed she knew about. I will say that after reading this book, it was easier to break down the co...more

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Oct 17, 2011 Scott Lupo rated it 4 of 5 stars

Shelves: non-fiction

A fun book about theoretical physics and the beginning of time. Sean Carroll does a great job of explaining these often complicated subjects of theoretical physics into everyday language and thought experiments. Much of the book is dedicated to talking about entropy and how to define and measure it. This takes the reader into the Second Law of Thermodynamics, Einstien's Special Theory of Relativity, his General Theory of Relativity, closed timelike curves, quantum mechanics, the arrow of time, t...more

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Aug 09, 2012 Richard rated it 4 of 5 stars Recommends it for: Everyone

Why do we careen relentlessly from the known and static past towards an unknown and seemingly protean future? Physicist Sean Carroll's answer is that every expression of "time's arrow," from the impossibility of unscrambling an egg to the absurdity of remembering the future, is ultimately rooted in the second law of thermodynamics , which tells us that the entropy of any closed system can never decrease. Entropy – essentially a physical measurement, not unlike temperature or length – can be th...more

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Jul 07, 2011 Nicholas rated it 5 of 5 stars

Shelves: favorites, science

Simply the best popular physics book I've ever read. Carroll is amazingly lucid, practical and totally excited about the subject while being conscious of the problems inherent in understanding something that is so fundamental to our existence that we take it for granted: time.

What is time? Does it exist naturally, or is it emergent from some other property of the universe? These are the grand questions that drive From Eternity to Here. In fact, the questions are so grand, and so monumental, Car...more Simply the best popular physics book I've ever read. Carroll is amazingly lucid, practical and totally excited about the subject while being conscious of the problems inherent in understanding something that is so fundamental to our existence that we take it for granted: time.

What is time? Does it exist naturally, or is it emergent from some other property of the universe? These are the grand questions that drive From Eternity to Here. In fact, the questions are so grand, and so monumental, Carroll can't help but comment on the scope of modern physics from classical mechanics and relativity to the absurd realities of quantum mechanics. Within From Eternity the lay reader will find a candid and clear discussion of pretty much anything physics related a non-specialist would want to know (and perhaps a few things you didn't).

The book is divided into roughly four parts - each dealing with an aspect that explains several key features about time. Of primary focus to Carroll is the arrow of time - a fundamental asymmetry in the flow of time. How is it that we can remember the past, but not the future? It sounds like a nonsensical question at first glance, but when you really think about it, there is no logical reason for why it should be so. The first part of the book attempts to nail down what we even mean by time, and to elucidate some of its properties so that we can better understand what it is we're looking for when constructing a theory of time. Next, Carroll takes us on a whirlwind tour of Einstein's theories of relativity and the way that they distort our common sense notion of what time is and how it's supposed to function. In particular, Carroll emphasizes that subjective nature of time, not in the figurative sense we're all used to (This class feels like it's taking forever!), but in a very literal sense through the exploration of light cones and the time bending effects of black holes.

Perhaps the most interesting part of the book follows thereafter. Carroll ties the evolution of time and its direction to the laws of thermodynamics, in particular to statistical mechanic descriptions of the second law: entropy always tends to increase. Here we see asymmetry manifest and perhaps the first clue as to why we perceive time "flowing" in a single direction, or even existing at all. The tendency of any closed system is to always be more and more entropic (here we can insert the word disorganized, but very carefully). In common parlance, any system tends toward the most likely state we should find it in - mostly equilibrium. Think of a box of gas that initially has all of the gas restricted to one side in its initial condition. If we watched such a box over time, what would we find? Most likely, we'd find that in the future, the gas would have dispersed until it reached equilibrium throughout the box, at which point it stops evolving. So goes the universe according to Carroll. For some reason that we're not one hundred percent clear on, the universe just after the Big Bang contained very low entropy. Our experience of change and time rests on the natural working of that system toward a more natural high entropy condition.

The last section is highly speculative, but exciting to think about. Here Carroll expands upon a number of theories about the evolution of the universe, its origins and its ultimate destination. Admittedly, there is little evidence from any of the proposals, but they're all fantastic to think about.

Carroll seems to succeed more than anything in making you feel smaller and more insignificant than you thought possible. This is an impressive feat given the series of substantial widenings in perspective given to us by scientists from Galileo to Hubble. But it's not a bad thing. On the contrary, there's a wonderful sense of order and determinism in the evolution of the universe as presented by Carroll that's mind-blowing to think about. As a reader, you really can't help but be infected by Carroll's own excitement and optimism that science will ultimately unlock even the deepest mysteries of where we came from and where we're going.

Probably not for people who have no concept of physics whatsoever, but if you've read any popular physics books by Greene or Kaku, you'll find that Carroll is much more down to earth. The stuff in the latter section tends toward the esoteric, but it's presented clearly and with as much caution as possible. Pick it up. It's worth your while.(less)

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Dec 15, 2011 Keith rated it 2 of 5 stars

Sean Carroll’s book is not for the faint of heart. It is a dense, complex tour of physics over the past century and a half. While the book is nominally called “The quest for the ultimate theory of time,” it is really about entropy and the Second Law of Thermodynamics (that things go from order to disorder — entropy — and not the opposite way). That law essentially defines the direction of time, and thus, to Carroll, time. (You make eggs into omelets, but you can make omelets into eggs.)

I must ad...more

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May 15, 2010 Kit rated it 4 of 5 stars

I didn't find this as compulsively readable as Brian Greene's physics overviews, but it was a really good running start at a topic as big as cosmology. I had a hard time reading on Kindle because the diagrams showed up on my screen *after* the explanation that you were intended to read while glancing at the diagram, but once I got used to this it wasn't too distracting. The metaphors were helpful, I got lost in the math, and overall I learned something - although I'm not sure how long I'll remem...more

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Jun 07, 2010 Kristin rated it 3 of 5 stars Recommends it for: science geeks and hangers-on

If I could, I would give 5 stars to the first half of this book and 2 to the second. For the first 500 pages or so (in the iBook version), I was enthralled by Carroll's exceptional ability to lay down the fundamentals of physics and cosmology in clear, straightforward language with simple but highly effective illustrations. This book has by far the best description of general relativity (especially the equivalence principle) for the non-physicist that I have ever encountered. His explanation of...more If I could, I would give 5 stars to the first half of this book and 2 to the second. For the first 500 pages or so (in the iBook version), I was enthralled by Carroll's exceptional ability to lay down the fundamentals of physics and cosmology in clear, straightforward language with simple but highly effective illustrations. This book has by far the best description of general relativity (especially the equivalence principle) for the non-physicist that I have ever encountered. His explanation of dark matter and vacuum energy is also brilliant--I was all mixed up on those concepts before I read this book but now I feel I have at least some clarity (though in reality I'm probably as confused as ever). I also loved the discussion on black holes, white holes, and Hawking's black hole radiation. The chapter on quantum mechanics, the collapse of the quantum wave function, and the wave function of the universe (is this stuff for real?), and Miss Kitty is also superb.

However, the book isn't really meant to be an introduction to the fundamentals of physics and cosmology. It is about the arrow of time (i.e., why we experience time as flowing from past to present to future) and the author's view that it connects not only to the origin of our universe but to a much broader cosmology. We're talking multi-verses, baby universes, and all sorts of other wild visions here. Carroll believes that they key to understanding time, the universe, and everything is...entropy. I would try to summarize entropy here but, quite honestly, I'm now terrified at the thought. Carroll spends about 1/3-2/3 of the book explaining and re-explaining it. It all started with some engineers in the 19th century who were determined to build more effective steam engines. But, in this book, entropy's reach extends far, far, FAR beyond that. And, whether you are convinced by Carroll's application of entropy/thermodynamics will determine your final views on this book.

In the end, I wasn't totally convinced. Entropy is a slippery, fuzzy statistical concept, and it seemed to me that Carroll had no trouble defining and re-defining it on a whim to suit his argument. At times, this practice has completely ridiculous and nonsensical consequences (Boltzmann brains, for instance, which the author seems to believe are "out there"). And, I felt that Carroll spent way too much time chasing down dead ends, seemingly for its own sake.

I did, however, find the end game--once we finally got there--to be really intriguing and imaginative. It will be interesting to see if his model--of our universe being one of many "baby universes" that bubbled up from an infinite, static, high-entropy background universe--is ever backed up by real data. What is it they like to say in physics? "Shut up and calculate?" ;-)(less)

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May 30, 2010 John Wunder rated it 4 of 5 stars

The synopsis of this book is a little deceiving: the vast majority of the book is spent discussing various theories in physics, cosmology, and other things most people don't understand in a very understandable way. It's much more about foundational physics questions (to my layman's understanding anyway) than about the nature of "the arrow of time".

It does start out with the question "what is time?", but very quickly this is redefined to mean "what is entropy?" The author continues this reasoning...more

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Nov 09, 2011 Jack rated it 4 of 5 stars

Shelves: non-fiction-math-and-physics

My new favorite pop-physics book. Carroll is a deft and clear writer, and in this book he walks the lay reader through some pretty advanced concepts with remarkably little difficulty. The first big step Carroll takes is in attributing the arrow of time - the difference between past and future in a universe where the underlying particle physics is all time-reversible - to the fact that the observable universe began in a low-entropy state. He then tackles the question this situation raises: Why di...more

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